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The role of peroxisome proliferator-activated receptor γ in immune responses to enteroaggregative Escherichia coli infection.

Philipson CW, Bassaganya-Riera J, Viladomiu M, Pedragosa M, Guerrant RL, Roche JK, Hontecillas R - PLoS ONE (2013)

Bottom Line: At the molecular level, both pharmacological blockade and deletion of PPARγ in T cells resulted in upregulation of TGF-β, IL-6, IL-17 and anti-microbial peptides, enhanced Th17 responses, fewer colonic lesions, faster clearance of EAEC, and improved recovery.The beneficial effects of PPARγ blockade on weight loss and EAEC clearance were abrogated by neutralizing IL-17 in vivo.Our studies provide in vivo evidence supporting the beneficial role of mucosal innate and effector T cell responses on EAEC burden and suggest pharmacological blockade of PPARγ as a novel therapeutic intervention for EAEC infection.

View Article: PubMed Central - PubMed

Affiliation: Nutritional Immunology and Molecular Medicine Laboratory, Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, Virginia, United States of America.

ABSTRACT

Background: Enteroaggregative Escherichia coli (EAEC) is recognized as an emerging cause of persistent diarrhea and enteric disease worldwide. Mucosal immunity towards EAEC infections is incompletely understood due in part to the lack of appropriate animal models. This study presents a new mouse model and investigates the role of peroxisome proliferator-activated receptor gamma (PPARγ) in the modulation of host responses to EAEC in nourished and malnourished mice.

Methods/principal findings: Wild-type and T cell-specific PPARγ C57BL/6 mice were fed protein-deficient diets at weaning and challenged with 5×10(9)cfu EAEC strain JM221 to measure colonic gene expression and immune responses to EAEC. Antigen-specific responses to E. coli antigens were measured in nourished and malnourished mice following infection and demonstrated the immunosuppressive effects of malnutrition at the cellular level. At the molecular level, both pharmacological blockade and deletion of PPARγ in T cells resulted in upregulation of TGF-β, IL-6, IL-17 and anti-microbial peptides, enhanced Th17 responses, fewer colonic lesions, faster clearance of EAEC, and improved recovery. The beneficial effects of PPARγ blockade on weight loss and EAEC clearance were abrogated by neutralizing IL-17 in vivo.

Conclusions: Our studies provide in vivo evidence supporting the beneficial role of mucosal innate and effector T cell responses on EAEC burden and suggest pharmacological blockade of PPARγ as a novel therapeutic intervention for EAEC infection.

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Related in: MedlinePlus

Gene expression suggests a T helper 17 response in mice when peroxisome proliferator-activated receptor γ (PPARγ) is antagonized.Gene expression data from colonic tissue of malnourished C57BL/6 mice was analyzed using quantitative real-time RT-PCR and reported as values normalized to β-actin. IL-6, IL-1β, MCP-1, CCL20, and CXCL1 were quantified at day 5PI (mice per group: n = 10) (A–E) while IL-6, TGF-β, and IL-17 were quantified 14 days PI (n = 10) (F–H). Asterisks indicate values where differences are statistically significant (p<0.05) while bars connect groups where comparisons are made.
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pone-0057812-g003: Gene expression suggests a T helper 17 response in mice when peroxisome proliferator-activated receptor γ (PPARγ) is antagonized.Gene expression data from colonic tissue of malnourished C57BL/6 mice was analyzed using quantitative real-time RT-PCR and reported as values normalized to β-actin. IL-6, IL-1β, MCP-1, CCL20, and CXCL1 were quantified at day 5PI (mice per group: n = 10) (A–E) while IL-6, TGF-β, and IL-17 were quantified 14 days PI (n = 10) (F–H). Asterisks indicate values where differences are statistically significant (p<0.05) while bars connect groups where comparisons are made.

Mentions: Mice that received GW9662 (1 µM) treatment expressed significantly higher levels of proinflammatory cytokines in the colon, including IL-1β, IL-6, CXCL1, and MCP-1, when compared to the untreated group at day 5 PI (Figure 3A–C, E). CCL20 was significantly upregulated in both treated and non-treated infected mice compared to uninfected controls. Additionally, GW9662 treated mice expressed significantly higher levels of colonic CCL20 when compared to the untreated infected mice (P<0.0001) (Figure 3D). A significant decrease in IL-10 expression exists in both infected groups at day 5 PI however no significant differences were observed for expression of IL-12p35 and IL-4 (Figure S2 A–C). Proinflammatory cytokine responses in GW9662 treated mice were associated with significantly larger percentages of infiltrating cells to the colonic lamina propria at 5 days post infection. Percentages of CD3+CD4+ T-cells and MHCII+CD11b-CD11c+ DC were significantly higher in GW9662 treated mice while untreated mice experienced higher levels of GR1high+CD11b+ neutrophils. Although no significance in MHCII+F4/80+CD11b+ macrophages was detected between groups, mice treated with GW9662 tended to have higher percentages of this cell phenotype (Figure S3 A–E). Fecal bacterial shedding results demonstrated a significant EAEC burden in infected untreated mice at the peak of infection, 5 days PI, while GW9662 treated mice experienced a mild level of EAEC shedding throughout the duration of infection (Figure 4A). S100A8 and S100A9, proteins that form the antimicrobial peptide complex known as calprotectin, were also significantly upregulated in the colon of mice treated with GW9662 on day 5 PI displaying an enhanced antimicrobial response associated with bacterial clearance (Figure 4B–C). By day 14, calprotectin levels were nearly undetectable in all mice when compared to expression values on day 5 portraying a reduction in antimicrobial responses after the peak of infection (data not shown). Remarkably, by day 14 PI GW9662 treated mice had sustained the stark increase in IL-6 while simultaneously expressing significantly elevated levels of colonic TGF-β and IL-17 further suggesting a Th17 effector response late during infection (Figure 3F–H). Colonic gene expression for IL-10, IL-12p35, and IL-4 revealed no significant differences among groups suggesting that regulatory T cells (Treg), Th1, and Th2 phenotypes were unaffected during infection (Figure S2D–F).


The role of peroxisome proliferator-activated receptor γ in immune responses to enteroaggregative Escherichia coli infection.

Philipson CW, Bassaganya-Riera J, Viladomiu M, Pedragosa M, Guerrant RL, Roche JK, Hontecillas R - PLoS ONE (2013)

Gene expression suggests a T helper 17 response in mice when peroxisome proliferator-activated receptor γ (PPARγ) is antagonized.Gene expression data from colonic tissue of malnourished C57BL/6 mice was analyzed using quantitative real-time RT-PCR and reported as values normalized to β-actin. IL-6, IL-1β, MCP-1, CCL20, and CXCL1 were quantified at day 5PI (mice per group: n = 10) (A–E) while IL-6, TGF-β, and IL-17 were quantified 14 days PI (n = 10) (F–H). Asterisks indicate values where differences are statistically significant (p<0.05) while bars connect groups where comparisons are made.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3585146&req=5

pone-0057812-g003: Gene expression suggests a T helper 17 response in mice when peroxisome proliferator-activated receptor γ (PPARγ) is antagonized.Gene expression data from colonic tissue of malnourished C57BL/6 mice was analyzed using quantitative real-time RT-PCR and reported as values normalized to β-actin. IL-6, IL-1β, MCP-1, CCL20, and CXCL1 were quantified at day 5PI (mice per group: n = 10) (A–E) while IL-6, TGF-β, and IL-17 were quantified 14 days PI (n = 10) (F–H). Asterisks indicate values where differences are statistically significant (p<0.05) while bars connect groups where comparisons are made.
Mentions: Mice that received GW9662 (1 µM) treatment expressed significantly higher levels of proinflammatory cytokines in the colon, including IL-1β, IL-6, CXCL1, and MCP-1, when compared to the untreated group at day 5 PI (Figure 3A–C, E). CCL20 was significantly upregulated in both treated and non-treated infected mice compared to uninfected controls. Additionally, GW9662 treated mice expressed significantly higher levels of colonic CCL20 when compared to the untreated infected mice (P<0.0001) (Figure 3D). A significant decrease in IL-10 expression exists in both infected groups at day 5 PI however no significant differences were observed for expression of IL-12p35 and IL-4 (Figure S2 A–C). Proinflammatory cytokine responses in GW9662 treated mice were associated with significantly larger percentages of infiltrating cells to the colonic lamina propria at 5 days post infection. Percentages of CD3+CD4+ T-cells and MHCII+CD11b-CD11c+ DC were significantly higher in GW9662 treated mice while untreated mice experienced higher levels of GR1high+CD11b+ neutrophils. Although no significance in MHCII+F4/80+CD11b+ macrophages was detected between groups, mice treated with GW9662 tended to have higher percentages of this cell phenotype (Figure S3 A–E). Fecal bacterial shedding results demonstrated a significant EAEC burden in infected untreated mice at the peak of infection, 5 days PI, while GW9662 treated mice experienced a mild level of EAEC shedding throughout the duration of infection (Figure 4A). S100A8 and S100A9, proteins that form the antimicrobial peptide complex known as calprotectin, were also significantly upregulated in the colon of mice treated with GW9662 on day 5 PI displaying an enhanced antimicrobial response associated with bacterial clearance (Figure 4B–C). By day 14, calprotectin levels were nearly undetectable in all mice when compared to expression values on day 5 portraying a reduction in antimicrobial responses after the peak of infection (data not shown). Remarkably, by day 14 PI GW9662 treated mice had sustained the stark increase in IL-6 while simultaneously expressing significantly elevated levels of colonic TGF-β and IL-17 further suggesting a Th17 effector response late during infection (Figure 3F–H). Colonic gene expression for IL-10, IL-12p35, and IL-4 revealed no significant differences among groups suggesting that regulatory T cells (Treg), Th1, and Th2 phenotypes were unaffected during infection (Figure S2D–F).

Bottom Line: At the molecular level, both pharmacological blockade and deletion of PPARγ in T cells resulted in upregulation of TGF-β, IL-6, IL-17 and anti-microbial peptides, enhanced Th17 responses, fewer colonic lesions, faster clearance of EAEC, and improved recovery.The beneficial effects of PPARγ blockade on weight loss and EAEC clearance were abrogated by neutralizing IL-17 in vivo.Our studies provide in vivo evidence supporting the beneficial role of mucosal innate and effector T cell responses on EAEC burden and suggest pharmacological blockade of PPARγ as a novel therapeutic intervention for EAEC infection.

View Article: PubMed Central - PubMed

Affiliation: Nutritional Immunology and Molecular Medicine Laboratory, Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, Virginia, United States of America.

ABSTRACT

Background: Enteroaggregative Escherichia coli (EAEC) is recognized as an emerging cause of persistent diarrhea and enteric disease worldwide. Mucosal immunity towards EAEC infections is incompletely understood due in part to the lack of appropriate animal models. This study presents a new mouse model and investigates the role of peroxisome proliferator-activated receptor gamma (PPARγ) in the modulation of host responses to EAEC in nourished and malnourished mice.

Methods/principal findings: Wild-type and T cell-specific PPARγ C57BL/6 mice were fed protein-deficient diets at weaning and challenged with 5×10(9)cfu EAEC strain JM221 to measure colonic gene expression and immune responses to EAEC. Antigen-specific responses to E. coli antigens were measured in nourished and malnourished mice following infection and demonstrated the immunosuppressive effects of malnutrition at the cellular level. At the molecular level, both pharmacological blockade and deletion of PPARγ in T cells resulted in upregulation of TGF-β, IL-6, IL-17 and anti-microbial peptides, enhanced Th17 responses, fewer colonic lesions, faster clearance of EAEC, and improved recovery. The beneficial effects of PPARγ blockade on weight loss and EAEC clearance were abrogated by neutralizing IL-17 in vivo.

Conclusions: Our studies provide in vivo evidence supporting the beneficial role of mucosal innate and effector T cell responses on EAEC burden and suggest pharmacological blockade of PPARγ as a novel therapeutic intervention for EAEC infection.

Show MeSH
Related in: MedlinePlus