RESUMO
Immunomodulatory Foxp3+ regulatory T cells (Tregs) form a heterogeneous population consisting of subsets with different activation states, migratory properties and suppressive functions. Recently, expression of the IL-33 receptor ST2 was shown on Tregs in inflammatory settings. Here we report that ST2 expression identifies highly activated Tregs in mice even under homeostatic conditions. ST2+ Tregs preferentially accumulate at non-lymphoid sites, likely mediated by their high expression of several chemokine receptors facilitating tissue homing. ST2+ Tregs exhibit a Th2-biased character, expressing GATA-3 and producing the Th2 cytokines IL-5 and IL-13 -especially in response to IL-33. Yet, IL-33 is dispensable for the generation and maintenance of these cells in vivo. Furthermore, ST2+ Tregs are superior to ST2- Tregs in suppressing CD4+ T cell proliferation in vitro independent of IL-33. This higher suppressive capacity is partially mediated by enhanced production and activation of the anti-inflammatory cytokines IL-10 and TGFß. Thus, ST2 expression identifies a highly activated, strongly suppressive Treg subset preferentially located in non-lymphoid tissues. Here ST2+ Tregs may be well positioned to immediately react to IL-33 alarm signals. Their specific properties may render ST2+ Tregs useful targets for immunomodulatory therapies.
Assuntos
Proteína 1 Semelhante a Receptor de Interleucina-1/imunologia , Interleucina-10/imunologia , Interleucina-33/imunologia , Linfócitos T Reguladores/imunologia , Fator de Crescimento Transformador beta/imunologia , Animais , Linhagem da Célula/imunologia , Proliferação de Células , Fator de Transcrição GATA3/genética , Fator de Transcrição GATA3/imunologia , Regulação da Expressão Gênica , Imunofenotipagem , Proteína 1 Semelhante a Receptor de Interleucina-1/deficiência , Proteína 1 Semelhante a Receptor de Interleucina-1/genética , Interleucina-10/genética , Interleucina-13/genética , Interleucina-13/imunologia , Interleucina-33/genética , Interleucina-5/genética , Interleucina-5/imunologia , Ativação Linfocitária , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Transdução de Sinais , Linfócitos T Reguladores/citologia , Fator de Crescimento Transformador beta/genéticaRESUMO
Repeatedly activated T helper 1 (Th1) cells present during chronic inflammation can efficiently adapt to the inflammatory milieu, for example, by expressing the transcription factor Twist1, which limits the immunopathology caused by Th1 cells. Here, we show that in repeatedly activated murine Th1 cells, Twist1 and T-bet induce expression of microRNA-148a (miR-148a). miR-148a regulates expression of the proapoptotic gene Bim, resulting in a decreased Bim/Bcl2 ratio. Inhibition of miR-148a by antagomirs in repeatedly activated Th1 cells increases the expression of Bim, leading to enhanced apoptosis. Knockdown of Bim expression by siRNA in miR-148a antagomir-treated cells restores viability of the Th1 cells, demonstrating that miR-148a controls survival by regulating Bim expression. Thus, Twist1 and T-bet not only control the differentiation and function of Th1 cells, but also their persistence in chronic inflammation.
Assuntos
Proteínas Reguladoras de Apoptose/genética , Apoptose/genética , Regulação da Expressão Gênica , Proteínas de Membrana/genética , MicroRNAs/fisiologia , Proteínas Nucleares/metabolismo , Proteínas Proto-Oncogênicas/genética , Proteínas com Domínio T/fisiologia , Células Th1/imunologia , Proteína 1 Relacionada a Twist/metabolismo , Animais , Artrite Reumatoide/imunologia , Proteína 11 Semelhante a Bcl-2 , Sobrevivência Celular/imunologia , Células Cultivadas , Humanos , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Camundongos Knockout , MicroRNAs/antagonistas & inibidores , MicroRNAs/genética , Proteínas Nucleares/genética , Interferência de RNA , RNA Interferente Pequeno , Proteínas com Domínio T/genética , Proteína 1 Relacionada a Twist/genéticaRESUMO
BACKGROUND: miRNAs are a class of small non-coding RNAs that regulate gene expression and have critical functions in various biological processes. Hundreds of miRNAs have been identified in mammalian genomes but only a small number of them have been functionally characterized. Recent studies also demonstrate that some miRNAs have important roles in reprogramming somatic cells to induced pluripotent stem cells (iPSCs). METHODS: We screened 52 miRNAs cloned in a piggybac (PB) vector for their roles in reprogramming of mouse embryonic fibroblast cells to iPSCs. To identify targets of miRNAs, we made Dgcr8-deficient embryonic stem (ES) cells and introduced miRNA mimics to these cells, which lack miRNA biogenesis. The direct target genes of miRNA were identified through global gene expression analysis and target validation. RESULTS AND CONCLUSION: We found that over-expressing miR-25 or introducing miR-25 mimics enhanced production of iPSCs. We identified a number of miR-25 candidate gene targets. Of particular interest were two ubiquitin ligases, Wwp2 and Fbxw7, which have been proposed to regulate Oct4, c-Myc and Klf5, respectively. Our findings thus highlight the complex interplay between miRNAs and transcription factors involved in reprogramming, stem cell self-renewal and maintenance of pluripotency.
