Unknown,Transcriptomics,Genomics,Proteomics

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Expression data from cyclohexamide treated Human Foreskin Fibroblasts (HFFs) infected with type I Toxoplasma gondii and stimulated with interferon gamma.

ABSTRACT: Pre-infection with Toxoplasma parasites inhibits induction of an interferon gamma responsive gene expression program. In this study we aimed to determine what role host negative regulatory proteins that are induced by Toxoplasma infection, such as SOCS-1, have in this inhibition. We used Affymetrix microarrays to analyze host cell transcription after pre-treatment with the protein synthesis inhibitor cyclohexamide (CHX), Toxoplasma infection, and subsequent interferon-gamma stimulation. Human foreskin fibroblasts (HFFs) were left untreated or treated with CHX for 40min. Cells were infected, or not, with type I (RH) Toxoplasma parasites, for one hour, and subsequently stimulated with human IFN-γ for one hour. Total RNA was isolated and hybridized to Affymetrix Human U133A 2.0 gene chips.

ORGANISM(S): Homo sapiens

SUBMITTER: Emily Rosowski

PROVIDER: E-GEOD-34916 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Intracellular pathogens including the apicomplexan and opportunistic parasite Toxoplasma gondii profoundly modify their host cells in order to establish infection. We have shown previously that intracellular T. gondii inhibit up-regulation of regulatory and effector functions in murine macrophages (MΦ) stimulated with interferon (IFN)-γ, which is the cytokine crucial for controlling the parasites’ replication. Using genome-wide transcriptome analysis we show herein that infection with T. gondii leads to global unresponsiveness of murine macrophages to IFN-γ. More than 61% and 89% of the transcripts, which were induced or repressed by IFN-γ in non-infected MΦ, respectively, were not altered after stimulation of T. gondii-infected cells with IFN-γ. These genes are involved in a variety of biological processes, which are mostly but not exclusively related to immune responses. Analyses of the underlying mechanisms revealed that IFN-γ-triggered nuclear translocation of STAT1 still occurred in Toxoplasma-infected MΦ. However, STAT1 bound aberrantly to oligonucleotides containing the IFN-γ-responsive gamma-activated site (GAS) consensus sequence. Conversely, IFN-γ did not induce formation of active GAS-STAT1 complexes in nuclear extracts from infected MΦ. Mass spectrometry of protein complexes bound to GAS oligonucleotides showed that T. gondii-infected MΦ are unable to recruit non-muscle actin to IFN-γ-responsive DNA sequences, which appeared to be independent of stimulation with IFN-γ and of STAT1 binding. IFN-γ-induced recruitment of BRG-1 and acetylation of core histones at the IFN-γ-regulated CIITA promoter IV, but not β-actin was diminished by >90% in Toxoplasma-infected MΦ as compared to non-infected control cells. Remarkably, treatment with histone deacetylase inhibitors restored the ability of infected macrophages to express the IFN-γ regulated genes H2-A/E and CIITA. Taken together, these results indicate that Toxoplasma-infected MΦ are unable to respond to IFN-γ due to disturbed chromatin remodelling, but can be rescued using histone deacetylase inhibitors. Comparison of 4 different RNA pools with a 2-Color-Loop Design including 10 microarrays: [1] T. gondii infected and IFN-gamma treated, [2] T. gondii infected and untreated, [3] Non-infected and IFN-gamma treated, and [4] Non-infected and untreated.

Project description:Interferon-gamma (IFN-gamma) is approved as a drug to treat chronic granulomatous disease and osteopetrosis and is also used in hyperimmunoglobulin E syndromes. These primary immunodeficiencies involve defects in neutrophils/polymorphonuclear cells. Neutrophils mature in the bone marrow and then enter the blood where they quickly undergo apoptotic cell death with a half-life of 5-10 hours. Therefore we reasoned that IFN-gamma might exert its effects on neutrophils via prolonged exposure to cells undergoing maturation toward a terminally differentiated state in the marrow rather than by its brief exposure to short-lived circulating cells. To explore this possibility we made use of PLB-985 cells which are a myeloblast-like myeloid cell line that can be differentiated into a mature, neutrophil-like state by treatment with various agents including DMSO. In initial studies we investigated transcription and protein expression in PLB-985 cells undergoing DMSO-mediated maturation in the presence or absence of IFN-gamma and identified several classes of immunity related genes that were differentially expressed in the presence of the drug and could potentially explain the immune supportive properties of IFN-gamma. Next we explored if the effect of IFN-gamma on expression of these genes is dependent on whether the cells are undergoing maturation; to do this we compared the effects of IFN-gamma on cells cultured with and without DMSO. For a subset of genes the expression level changes caused by IFN-gamma were much greater in maturing cells than non-maturing cells. These findings indicate that developmental changes associated with cell maturation can modulate the effects of IFN-gamma and supports our hypothesis that the effects of the drug on developing neutrophils in the bone marrow may be very different from its effects on mature cells in the blood. We also compared the effects on gene expression of applying IFN-gamma either during DMSO mediated PLB-985 cell maturation or after maturation i.e. IFN-gamma was applied to already mature cells. For some genes we found that IFN-gamma applied to mature cells caused large changes in expression similar to those seen when IFN-gamma was applied during maturation, however for other genes no effect was seen when drug was applied to mature cells but large effects were seen when drug was applied during DMSO treatment. This data suggests that, in the former class of genes, the effects of IFN-gamma application during maturation are largely the result of the effects of the drug on cells approaching full maturity but in the latter class of genes the effects of IFN-gamma only become apparent when it is present throughout maturation. This further supports our hypothesis that the effects of IFN-gamma are modulated by developmental changes associated with cell maturation.

Dataset Information

Expression data from cyclohexamide treated Human Foreskin Fibroblasts (HFFs) infected with type I Toxoplasma gondii and stimulated with interferon gamma.

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