The role of T cell PPAR gamma in mice with experimental inflammatory bowel disease.
BACKGROUND
Peroxisome proliferator-activated receptor gamma (PPAR gamma) is a nuclear receptor whose activation has been shown to modulate macrophage and T cell-mediated inflammation. The objective of this study was to investigate the mechanisms by which the deletion of PPAR gamma in T cells modulates immune cell distribution and colonic gene expression and the severity of experimental IBD.


METHODS
PPAR gamma flfl; CD4 Cre+ (CD4cre) or Cre- (WT) mice were challenged with 2.5% dextran sodium sulfate 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
The deficiency of PPAR gamma in T cells accelerated the onset of disease and body weight loss. 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 mRNA expression of adhesion molecules, proinflammatory cytokines interleukin-6 (IL-6) and IL-1beta, and suppressor of cytokine signaling 3 (SOCS-3) on day 7. Gene set enrichment analysis (GSEA) showed that the ribosome and Krebs cycle pathways were downregulated while the apoptosis pathway was upregulated in colons of mice lacking PPAR gamma in T cells.


CONCLUSIONS
The expression of PPAR gamma in T cells is involved in preventing gut inflammation by regulating colonic expression of adhesion molecules and inflammatory mediators at later stages of disease while favoring the recruitment of Treg to the mucosal inductive sites.
Guri
Amir J
AJ
Nutritional Immunology and Molecular Nutrition Laboratory, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA.
Mohapatra
Saroj K
SK
Horne
William T
WT
Hontecillas
Raquel
R
Bassaganya-Riera
Josep
J
D000818:Animals; D017209:Apoptosis; D015496:CD4-Positive T-Lymphocytes / Q000378:metabolism / Q000473:pathology; D018414:CD8-Positive T-Lymphocytes / Q000378:metabolism / Q000473:pathology; D003106:Colon / Q000378:metabolism / Q000473:pathology; D016207:Cytokines / Q000378:metabolism; D016264:Dextran Sulfate / Q000009:adverse effects; D004195:Disease Models, Animal; D018450:Disease Progression; D015212:Inflammatory Bowel Diseases / Q000139:chemically induced / Q000378:metabolism* / Q000473:pathology*; D007413:Intestinal Mucosa / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D047495:PPAR gamma / Q000235:genetics / Q000378:metabolism*; D013601:T-Lymphocytes / Q000378:metabolism* / Q000473:pathology*; D050378:T-Lymphocytes, Regulatory / Q000378:metabolism / Q000473:pathology
D016207:Cytokines; D047495:PPAR gamma; D016264:Dextran Sulfate