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Immunoregulatory actions of T cell PPAR g at the colonic mucosa

ABSTRACT: BACKGROUND: Peroxisome proliferator-activated receptor g (PPAR g) is a nuclear receptor whose activation has been shown to modulate macrophage and epithelial cell-mediated inflammation. The objective of this study was to use a systems approach for investigating the mechanism by which the deletion of PPAR g in T cells modulates the severity of dextran-sodium sulfate (DSS)-induced colitis, immune cell distribution and global gene expression. METHODS: Wild-type (WT) or PPAR g flfl; CD4 Cre+ (CD4cre) mice in a C57BL/6 background were challenged with 2.5% DSS in their drinking water for 0, 2, or 7 days. Mice were scored on disease severity both clinically and histopathologically. Flow cytometry was used to assess lymphocyte and macrophage populations in the blood, spleen, and mesenteric lymph nodes (MLN). Global gene expression in colonic mucosa was profiled using Affymetrix microarrays. RESULTS: Both disease severity and inflammation-related body weight loss were accelerated by the deficiency of PPAR g in T cells. Examination of colon histopathology revealed significantly greater epithelial erosion, leukocyte infiltration, and mucosal thickening in the CD4cre mice on day 7. CD4cre mice had more CD8+ T cells than wt mice and fewer CD4+FoxP3+ regulatory T cells (Treg) and IL10+CD4+ T cells in blood and MLN, respectively. Transcriptomic profiling revealed around 3000 genes being transcriptionally altered as a result of DSS challenge in CD4cre mice. These included up-regulated adhesion molecules on day 7 and proinflammatory cytokines interleukin-6 (IL-6) and IL-1b, and suppressor of cytokine signaling 3 (SOCS-3) mRNA expression. CONCLUSIONS: These findings suggest that T cell PPAR g down-regulates inflammation during DSS colitis by inhibiting colonic expression of inflammatory mediators and increasing MLN Treg.

ORGANISM(S): Mus musculus

PROVIDER: GSE20523 | GEO | 2010/06/21

SECONDARY ACCESSION(S): PRJNA125133

REPOSITORIES: GEO

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Project description:Inflammatory bowel disease (IBD) is a condition characterized by severe intestinal inflammation and immune cell activation. The severity of the disease can be mitigated by compounds which activate peroxisome proliferator-activated receptor gamma (PPAR gamma), a receptor present widely in tissues involved in IBD pathogenesis. Our objective was to assess the affect of macrophage-specific deficiency of PPAR gamma on peripheral and colonic immune populations and colonic gene expression in experimental IBD. Macrophage-specific PPAR gamma-deficient mice (PPAR gamma flfl Lysozyme M Cre+) and control (PPAR gamma flfl Lysozyme M Cre-) littermates were treated with 2.5% dextran sodium sulfate (DSS) for 7 days. Disease activity was recorded daily and immune cell populations in the blood, spleen, mesenteric lymph nodes (MLN), and lamina propria were examined by flow cytometry. Colonic gene expression was assessed by real time PCR and microarray analyses. Our findings show that macrophage PPAR r-deficiency significantly exacerbates DSS inflammation. CD4+CD25+FoxP3+ regulatory T cells (T-regs) were significantly reduced in Cre+ mice, and MLN macrophages and CD40 expression were enhanced. There were significant differences in the number colonic macrophages between Cre+ and Cre- mice, but those from Cre+ mice expressed more CD40, Ly6C, and TLR-4. PPAR r-deficiency also increased the percent of CD8+ T cells in the lamina propria and enhanced colonic interferon gamma expression. Our findings indicate that macrophage PPAR gamma deficiency augments the severity of DSS colitis by reducing peripheral T-regs and increasing colonic macrophage activation and T cell inflammation. RNA from 3 PPAR gamma-deficient mice (PPAR gamma flfl; Lysozyme M Cre+) and 3 control (PPAR gamma flfl; Lysozyme M Cre-) littermates was processed and labeled according to the standard target labeling protocols. The samples were hybridized, stained, and scanned per standard Affymetrix protocols at the Virginia Bioinformatics Institute (VBI) core laboratory on Mouse 430 2.0 expression arrays (Affymetrix Inc., Santa Clara, CA).

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Immunoregulatory actions of T cell PPAR g at the colonic mucosa

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