Project description:Ionizing radiation (IR) not only affects cells that are directly irradiated but also their non-irradiated neighbors, which show responses known as bystander effects. While bystander and direct responses have several common end points including apoptosis and micronucleation, chromatin remodeling and altered levels or activities of regulatory proteins, they can be quantitatively and qualitatively different. The majority of studies of radiation bystander effects have utilized 2-dimensional in vitro systems, but we have recently demonstrated such effects in EPI-200 (Mat-Tek, Ashland, MA), a 3-dimensional tissue model that precisely imitates the structure and function of human epidermis. Global gene expression is a powerful tool for uncovering both fundamental signaling processes and the mechanistic basis of cellular or physiological effects. By exposing only a thin strip across the center of the EPI-200 tissue, we have been able to measure global gene expression responses in bystander cells located at 0.125 and 0.625 um from the irradiation line, in 16h after irradiation. The data were analyzed using BRB-Array Tools (NIH), and further network analysis was performed with IPA (Ingenuity). Significantly responding genes were identified at the both distances. For instance, all sets demonstrated upregulation of two key enzymes of the lipid biosynthesis, UGT1 and PITPNB, and downregulation of proapoptotic proteins: BAX and ARHGEF5. In contrast, several proteins involved in transcriptional repression (CHD6, CHD8 andWRNIP1) were strongly upregulated suggesting a rearrangement in the gene transcription. These changes suggest an activation of bystander mechanisms different from those observed in 2-dimensional cell cultures. Radiation induced gene expression in 3-dimensional tissue model, Epi-200, was measured in 16 hours after exposure to 0.5 Gy of alpha-particles. Three independent experiments were performed for the samples collected at different distances from the irradiation line (125-625 and 625-1125 um) using three tissue fragments per a data point.

Project description:Ionizing radiation (IR) not only affects cells that are directly irradiated but also their non-irradiated neighbors, which show responses known as bystander effects. While bystander and direct responses have several common end points including apoptosis and micronucleation, chromatin remodeling and altered levels or activities of regulatory proteins, they can be quantitatively and qualitatively different. The majority of studies of radiation bystander effects have utilized 2-dimensional in vitro systems, but we have recently demonstrated such effects in EPI-200 (Mat-Tek, Ashland, MA), a 3-dimensional tissue model that precisely imitates the structure and function of human epidermis. Global gene expression is a powerful tool for uncovering both fundamental signaling processes and the mechanistic basis of cellular or physiological effects. By exposing only a thin strip across the center of the EPI-200 tissue, we have been able to measure global gene expression responses in directly irradiated and bystander cells located at 0, 0.25, 0.5, 0.75 and 1mm from the irradiation line. The data were analyzed using BRB-Array Tools (NIH), and further network analysis was performed with IPA (Ingenuity). Significantly responding genes were identified at all distances and included sets common to both direct and bystander responses. For instance, all sets demonstrated upregulation of a major component of the drug metabolism pathway, CYP1B1, and downregulation of MMP1, an enzyme involved in degradation of extracellular matrix. In contrast, PTGS2, a gene strongly implicated in the bystander response was upregulated in directly irradiated tissues, but actually downregulated in bystander cells. This effect may be time dependent, but may also suggest activation of bystander signaling mechanisms different from those observed in 2-dimensional cell cultures. According to network analysis of our results, the genes responding in bystander tissue fell into 5 major categories: cell death, cell communication, cell differentiation, stress response, and response to wounding, suggesting active intracellular communication in bystander tissue. Radiation induced gene expression in 3-dimensional tissue model, Epi-200, was measured at 4 hours after exposure to 0.5 Gy of alpha-particles. Three independent experiments were performed for the samples collected at different distances from the irradiation line (250-500, 500-750 and 750-1000 micrometers) using three tissue fragments per a data point.

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.

Project description:Direct irradiation of 3-dimensional skin model, Epi-200, with alpha-particles led to differential regulation of 166 genes: 16 and 150 genes were differentially expressed at 1 and 16 h postirradiation. Unlike the traditional 2-dimensional in vitro systems, Epi-200 made of the primary cells, epidermal human keratinocytes. It mimics the structure of the human epidermis Global gene expression is a powerful tool for uncovering both fundamental signaling processes and the mechanistic basis of cellular or physiological effects. By comparing irradiated tissues with non-irradiated control, we have been able to measure global gene expression responses and reveal the affected biological pathways and molecular functions. The data were analyzed using BRB-Array Tools (NIH), and further gene ontology analysis was performed with Panther database (Applied Biosystems). Gene ontology analysis of the samples harvested in 16h after exposure showed that irradiation presumably affected the genes involved in cell-cell signaling (15 genes, , p=9.0 x E-04) ion transport (10 genes, p=0.00189) and amino acid metabolism (5 genes, p=0.0258). Among 16 genes differentially expressed in 1h after exposure we found NOTCH2 (ENST00000401649) and methyltransferase AOF1 (KDM1B). In the mammalian cells, NOTCH signaling pathway has a role in differentiation and intracellular communication. Moreover the intercellular domain of NOTCH regulates gene expression acting as a transcription factor. In turn, AOF1 affects the transcription via histone demethylation. Thus, irradiation with alpha-particles caused predominant downregulation of multiple genes in 1 and 16h after exposure. It also suggested that changes in cell metabolism initially affected transcriptional regulation and finally led to the rearrangement in expression of genes playing a role in biosynthesis and ion trafficking. Radiation induced gene expression in 3-dimensional tissue model, Epi-200, was measured in 1 and 16 h hours after exposure to 0.5 Gy of alpha-particles. Three independent experiments were performed using one tissue sample per a data point.

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