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P38 MAP kinase signaling is required for the conversion of CD4+CD25- T cells into iTreg.

Huber S, Schrader J, Fritz G, Presser K, Schmitt S, Waisman A, Lüth S, Blessing M, Herkel J, Schramm C - PLoS ONE (2008)

Bottom Line: Inhibition of p38 MAP kinase activity prevented the TGF-beta-dependent conversion of CD4+CD25- T cells into Foxp3+ iTreg in vitro.Of note, the suppressive capacity of nTreg was not affected by inhibiting p38 MAP kinase.Our findings indicate that signaling via p38 MAP kinase seems to be important for the peripheral generation of iTreg; p38 MAP kinase could thus be a therapeutic target to enhance immunity to chronic viral infection or cancer.

View Article: PubMed Central - PubMed

Affiliation: I. Medizinische Klinik, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany.

ABSTRACT
CD4+CD25+ regulatory T cells (Treg) are important mediators of immune tolerance. A subset of Treg can be generated in the periphery by TGF-beta dependent conversion of conventional CD4+CD25- T cells into induced Treg (iTreg). In chronic viral infection or malignancy, such induced iTreg, which limit the depletion of aberrant or infected cells, may be of pathogenic relevance. To identify potential targets for therapeutic intervention, we investigated the TGF-beta signaling in Treg. In contrast to conventional CD4+ T cells, Treg exhibited marked activation of the p38 MAP kinase pathway. Inhibition of p38 MAP kinase activity prevented the TGF-beta-dependent conversion of CD4+CD25- T cells into Foxp3+ iTreg in vitro. Of note, the suppressive capacity of nTreg was not affected by inhibiting p38 MAP kinase. Our findings indicate that signaling via p38 MAP kinase seems to be important for the peripheral generation of iTreg; p38 MAP kinase could thus be a therapeutic target to enhance immunity to chronic viral infection or cancer.

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Western blot analysis of MAP kinase and Smad phosphorylation in CD4+CD25− and CD4+CD25+ T cells (2–4×106 cells).A: Analysis of p38 and ERK2 expression as well as p38 phosphorylation in CD4+CD25− and CD4+CD25+ T cells freshly isolated from spleen of wild type mice or transgenic mice overexpressing a dominant negative TGF-beta type II receptor in T cells. B: Analysis of Smad 2/3, Smad 7, Foxp3, actin, p-Smad 2, p-Smad 3, p-JNK and p-ERK1/2 from CD4+CD25− and CD4+CD25+ T cells freshly isolated from spleen of wild type animals. C: Densitometry and ratio of phosphorylated to unphosphorylated p38 and Smad 2/3 (p<0.05). The experiments were at least repeated three times giving similar results.
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pone-0003302-g001: Western blot analysis of MAP kinase and Smad phosphorylation in CD4+CD25− and CD4+CD25+ T cells (2–4×106 cells).A: Analysis of p38 and ERK2 expression as well as p38 phosphorylation in CD4+CD25− and CD4+CD25+ T cells freshly isolated from spleen of wild type mice or transgenic mice overexpressing a dominant negative TGF-beta type II receptor in T cells. B: Analysis of Smad 2/3, Smad 7, Foxp3, actin, p-Smad 2, p-Smad 3, p-JNK and p-ERK1/2 from CD4+CD25− and CD4+CD25+ T cells freshly isolated from spleen of wild type animals. C: Densitometry and ratio of phosphorylated to unphosphorylated p38 and Smad 2/3 (p<0.05). The experiments were at least repeated three times giving similar results.

Mentions: The amounts of p38 MAP kinase appeared to be similar both in CD4+CD25+ and CD4+CD25− T cells (Figure 1A; WT). However, the phosphorylation of p38 MAP kinase in CD4+CD25+ T cells was strongly increased as compared to CD4+CD25− T cells (Figure 1A; WT). Of note, the phosphorylation of p38 MAP kinase was decreased in transgenic CD4+CD25+ T cells that overexpress a dominant negative TGFbeta type II receptor, indicating at least partial TGF-beta-dependence of the p38 signal (Figure 1A; TG). We did not find any significant differences in the phosphorylation of JNK or ERK between freshly isolated CD4+CD25− and CD4+CD25+ T cells (Figure 1B). As compared to CD4+CD25− T cells, the phosphorylation of Smad 2 and Smad 3 was increased whereas the inhibitory Smad 7 was found to be strongly downregulated in CD4+CD25+ T cells (Figure 1 B+C). In order to adjust for potential differences in the amount of Smad 2- or 3-expression, we determined the ratio of phosphorylated to unphosphorylated protein in four independent experiments, and found that activation of Smad 2 and 3 and of p38 was significantly increased in the CD4+CD25+ T cells, as compared to the CD4+CD25− T cells (Figure 1C).


P38 MAP kinase signaling is required for the conversion of CD4+CD25- T cells into iTreg.

Huber S, Schrader J, Fritz G, Presser K, Schmitt S, Waisman A, Lüth S, Blessing M, Herkel J, Schramm C - PLoS ONE (2008)

Western blot analysis of MAP kinase and Smad phosphorylation in CD4+CD25− and CD4+CD25+ T cells (2–4×106 cells).A: Analysis of p38 and ERK2 expression as well as p38 phosphorylation in CD4+CD25− and CD4+CD25+ T cells freshly isolated from spleen of wild type mice or transgenic mice overexpressing a dominant negative TGF-beta type II receptor in T cells. B: Analysis of Smad 2/3, Smad 7, Foxp3, actin, p-Smad 2, p-Smad 3, p-JNK and p-ERK1/2 from CD4+CD25− and CD4+CD25+ T cells freshly isolated from spleen of wild type animals. C: Densitometry and ratio of phosphorylated to unphosphorylated p38 and Smad 2/3 (p<0.05). The experiments were at least repeated three times giving similar results.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2553190&req=5

pone-0003302-g001: Western blot analysis of MAP kinase and Smad phosphorylation in CD4+CD25− and CD4+CD25+ T cells (2–4×106 cells).A: Analysis of p38 and ERK2 expression as well as p38 phosphorylation in CD4+CD25− and CD4+CD25+ T cells freshly isolated from spleen of wild type mice or transgenic mice overexpressing a dominant negative TGF-beta type II receptor in T cells. B: Analysis of Smad 2/3, Smad 7, Foxp3, actin, p-Smad 2, p-Smad 3, p-JNK and p-ERK1/2 from CD4+CD25− and CD4+CD25+ T cells freshly isolated from spleen of wild type animals. C: Densitometry and ratio of phosphorylated to unphosphorylated p38 and Smad 2/3 (p<0.05). The experiments were at least repeated three times giving similar results.
Mentions: The amounts of p38 MAP kinase appeared to be similar both in CD4+CD25+ and CD4+CD25− T cells (Figure 1A; WT). However, the phosphorylation of p38 MAP kinase in CD4+CD25+ T cells was strongly increased as compared to CD4+CD25− T cells (Figure 1A; WT). Of note, the phosphorylation of p38 MAP kinase was decreased in transgenic CD4+CD25+ T cells that overexpress a dominant negative TGFbeta type II receptor, indicating at least partial TGF-beta-dependence of the p38 signal (Figure 1A; TG). We did not find any significant differences in the phosphorylation of JNK or ERK between freshly isolated CD4+CD25− and CD4+CD25+ T cells (Figure 1B). As compared to CD4+CD25− T cells, the phosphorylation of Smad 2 and Smad 3 was increased whereas the inhibitory Smad 7 was found to be strongly downregulated in CD4+CD25+ T cells (Figure 1 B+C). In order to adjust for potential differences in the amount of Smad 2- or 3-expression, we determined the ratio of phosphorylated to unphosphorylated protein in four independent experiments, and found that activation of Smad 2 and 3 and of p38 was significantly increased in the CD4+CD25+ T cells, as compared to the CD4+CD25− T cells (Figure 1C).

Bottom Line: Inhibition of p38 MAP kinase activity prevented the TGF-beta-dependent conversion of CD4+CD25- T cells into Foxp3+ iTreg in vitro.Of note, the suppressive capacity of nTreg was not affected by inhibiting p38 MAP kinase.Our findings indicate that signaling via p38 MAP kinase seems to be important for the peripheral generation of iTreg; p38 MAP kinase could thus be a therapeutic target to enhance immunity to chronic viral infection or cancer.

View Article: PubMed Central - PubMed

Affiliation: I. Medizinische Klinik, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany.

ABSTRACT
CD4+CD25+ regulatory T cells (Treg) are important mediators of immune tolerance. A subset of Treg can be generated in the periphery by TGF-beta dependent conversion of conventional CD4+CD25- T cells into induced Treg (iTreg). In chronic viral infection or malignancy, such induced iTreg, which limit the depletion of aberrant or infected cells, may be of pathogenic relevance. To identify potential targets for therapeutic intervention, we investigated the TGF-beta signaling in Treg. In contrast to conventional CD4+ T cells, Treg exhibited marked activation of the p38 MAP kinase pathway. Inhibition of p38 MAP kinase activity prevented the TGF-beta-dependent conversion of CD4+CD25- T cells into Foxp3+ iTreg in vitro. Of note, the suppressive capacity of nTreg was not affected by inhibiting p38 MAP kinase. Our findings indicate that signaling via p38 MAP kinase seems to be important for the peripheral generation of iTreg; p38 MAP kinase could thus be a therapeutic target to enhance immunity to chronic viral infection or cancer.

Show MeSH
Related in: MedlinePlus