Unknown,Transcriptomics,Genomics,Proteomics

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Sirt1 targeting promotes Treg function

ABSTRACT: Sirtuin-1 (Sirt1), a class III histone/protein deacetylase is central to cellular metabolism, stress responses and aging, but its contributions to various host immune functions have been little investigated. To study the role of Sirt1 in T-cell functions, we undertook targeted deletions by mating mice with a floxed Sirt1 gene to mice expressing CD4-cre or Foxp3-cre recombinase, respectively. We found that Sirt1 deletion left conventional T-effector cell activation, proliferation and cytokine production largely unaltered. However, Sirt1 targeting promoted the expression and acetylation of Foxp3, a key transcription factor in T-regulatory (Treg) cells, and increased Treg suppressive functions in vitro and in vivo. Consistent with these data, mice with targeted deletions of Sirt1 in either CD4+ T-cells or Foxp3+ Treg cells exhibited prolonged survival of MHC-mismatched cardiac allografts. Allografts in Sirt1 targeted recipients showed long-term preservation of myocardial histology and infiltration by Foxp3+ Treg cells. Comparable results were seen in wild-type allograft recipients treated with Sirt1 inhibitors, such as EX-527 and splitomicin. Hence, Sirt1 may inhibit Treg functions and its targeting may have therapeutic value in autoimmunity and transplantation. RNA from three independent samples from magnetically separated CD4+CD25+ Treg of Sirt1 knock out, compared to wild type (C57BL6) control

ORGANISM(S): Mus musculus

SUBMITTER: Wayne Hancock

PROVIDER: E-GEOD-26425 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Regulatory T (Treg) cells play an important role in the induction and maintenance of peripheral tolerance. Treg cells also suppress a variety of other immune responses, including anti-tumor and alloimmune responses. We have previously reported that tumor-activated Treg cells express granzyme B and that granzyme B is important for Treg cell-mediated suppression of anti-tumor immune responses (GSE13409). Here, we report that allogeneic mismatch also induces the expression of granzyme B. Granzyme B-deficient mice challenged with fully mismatched allogeneic P815 mastocytoma cells have markedly improved survival compared to WT and other granzyme- or perforin-deficient mice, suggesting an immunoregulatory role for granzyme B in this setting. Treg cells harvested from the tumor environment of P815-challenged mice express granzyme B. Treg cells also express granzyme B in vitro during mixed lymphocyte reactions and in vivo in a mouse model of graft-versus-host disease (GVHD). However, in contrast to findings from our previously published tumor model, granzyme B is not required for the suppression of effector T cell (Teff) proliferation in in vitro Treg suppression assays stimulated by either Concanavalin A or allogeneic antigen presenting cells. Additionally, in an ex vivo assay, sort-purified in vivo-activated CD4+Foxp3+ Treg cells from mice with active GVHD -- under conditions known to induce granzyme B expression in Treg cells -- suppressed Teff cell proliferation in a granzyme B-independent manner. Adoptive transfer of naive granzyme B-deficient CD4+CD25+ Treg cells into a mouse model of GVHD rescued hosts from lethatlity equivalently to naive wild-type Treg cells. Serum analysis of GVHD-associated cytokine production in these recipients also demonstrated that Treg cells suppressed production of IL-2, IL-4, IL-5, GM-CSF, and IFN-gamma in a granzyme B-independent manner. In order to determine whether the context in which Treg cells are activated alters the intrinsic properties of Treg cells, we used Foxp3 reporter mice to obtain gene expression profiles of CD4+Foxp3+ Treg cells purifed from naive resting spleens, spleens from mice with acute GVHD, and from ascites fluid of mice challenged intraperitoneally with allogeneic P815 tumor cells. Unsupervised analyses revealed distinct activation signatures of Treg cells among the 3 experimental groups. Taken together, these findings demonstrate that granzyme B is not required for Treg cell-mediated suppression of GVHD, which is in contrast to what we have previously reported for Treg cell function in the setting of tumor challenge. Cell intrinsic differences could partially account for these differential phenotypes. These data also suggest the therapeutic potential of targeting specific Treg cell suppressive functions in order to segregate GVHD and graft-versus-tumor effector functions. Experiment Overall Design: Six replicates of Naive CD4+Foxp3+ Treg cells were purified from resting spleens, five replicates of allogeneic tumor-activated Treg cells and three samples of GVHD-activated Treg cells. Experiment Overall Design: Naive reps 1-3 are controls for the GVHD-activated samples. Experiment Overall Design: Naive reps 4-6 are controls for the Allogeneic tumor-activated samples.

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Sirt1 targeting promotes Treg function

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