Project description:The existence of a radiation bystander effect, in which non-irradiated cells respond to signals from irradiated cells, is well established. It raises concerns for the interpretation of risks from exposure to low doses of ionizing radiation. Sparse data exists about the bystander signaling mechanisms and the ability to transmit damaging effects both spatially and temporally. To understand early signaling and cellular changes in bystanders, we have measured global gene expression 30 minutes after direct and bystander exposure to alpha particle in primary human lung fibroblasts. Gene ontology and pathway analyses suggested that the earliest measured changes at 30 minutes after treatment are in cell structure, motility and adhesion categories and a significant number of genes belong to the category of inflammation and cell-to-cell communication. We investigated time course gene expression profiles of matrix metalloproteinases 1 and 3 (MMP1 and MMP3), chemokine ligands 2, 3 and 5 (CXCL2, CXCL3 and CXCL5), interleukins 1a, 1b, 6 and 33 (IL1A, IL1B, IL6 and IL33) growth differentiation factor 15 (GDF15) and superoxide dismutase2 (SOD2) by real time quantitative PCR. These encode proteins involved in cellular signaling via the NFkappaB pathway and time course of mRNA levels revealed an increased response at 30 minutes after irradiation followed by another wave at 4 to 6 hours. We also investigated protein modifications in the AKT-GSK-3 signaling pathway and found that in irradiated cells AKT and GSK3beta are hyper-phosphorylated at 30 minutes and this effect is maintained until 4 hours after exposure. In bystanders there is a similar response with a delay of 30 minutes. In irradiated cells, inactivated GSK3beta led to decreased phosphorylation of beta-catenin. Our results are the first to show that the radiation induced bystander signal can induce a widespread gene expression response as early as 30 minutes after exposure and that these changes are accompanied by protein modification of signaling modules such as AKT and GSK3beta. There are 12 total samples, 4 corresponding biological replicates of IMR90 cells that were not irradiated (control=C), irradiated (alpha=A) and bystander (B), cells were harvested 0.5 hr after treatment

Project description:Radiation affects tissue and cellular integrity at the level of DNA, protein and metabolites of the cell and extracellular space. The effects of radiation are not limited to targeted cells and tissue and radiation induced bystander effects are significant to exposed individuals in accidental or therapeutic situations. These non-targeted effects of radiation have been studied extensively at the low dose range where they appear to have adverse effects on cells and surrounding environments. The requirement of cellular contact and shared fluid media has been established as critical to the bystander effect yet there is not much known about the actual signaling mechanism and its ability to transmit the damaging effect over space and time. Experimental cell types and context within the tissue are also quite important to the nature and extent of this bystander effect and must be considered when drawing parallels at the organismal level. Our approach was to use a genomic level analysis of global mRNA expression in primary lung fibroblast cells to understand the cellular triggers and mechanism of the bystander effect. Gene ontology and pathway analyses suggested that the p53 induced transcriptional response appears muted in bystanders while cytokine and cell signaling mechanisms such as those controlled by NFkB and p38 MAPK are highly active in both populations. We validated a large number of genes that are significantly changed at 4hrs after irradiation in both irradiated and bystander populations. We investigated time course gene expression profiles of cyclooxygenase2 (PTGS2), interleukin 8 (IL8) and BCL2 related protein 2 (BCL2A1), as genes that are involved in cellular signaling via the NFkB pathway, which revealed that there is a dramatic response at 0.5hr after irradiation followed by another wave at 4hr in both populations. The induction of interleukins such as cytokine IL8 and chemokine IL6 at the transcriptional level is both early and amplified and if followed by translation and secretion of these proteins could explain the concerted response seen in bystander cells. Our results are the first to show that there is a significant and distinct global response of cellular signaling genes in bystander cells with some genes showing a response as early as 0.5hr after irradiation which implies a fast moving intercellular signal that leads to a concerted response in the irradiated and bystander populations. Keywords: gene expression fold change There are 12 total samples, 4 corresponding biological replicates of IMR90 cells that were not irradiated (control=C), irradiated (alpha=A) and bystander (B)

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: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.

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