Autoimmune diabetes results from a breakdown of self-tolerance that leads to T cell-mediated β-cell destruction. Abnormal maturation and other defects of dendritic cells (DCs) have been associated with the development of diabetes. Evidence is accumulating that self-tolerance can be restored and maintained by semimature DCs induced by GM-CSF. We have investigated whether GM-CSF is a valuable strategy to induce semimature DCs, thereby restoring and sustaining tolerance in NOD mice. We found that treatment of prediabetic NOD mice with GM-CSF provided protection against diabetes. The protection was associated with a marked increase in the number of tolerogenic immature splenic DCs and in the number of Foxp3+CD4+CD25+ regulatory T cells (Tregs). Activated DCs from GM-CSF-protected mice expressed lower levels of MHC class II and CD80/CD86 molecules, produced more IL-10 and were less effective in stimulating diabetogenic CD8+ T cells than DCs of PBS-treated NOD mice. Adoptive transfer experiments showed that splenocytes of GM-CSF-protected mice did not transfer diabetes into NOD.SCID recipients. Depletion of CD11c+ DCs before transfer released diabetogenic T cells from the suppressive effect of CD4+CD25+ Tregs, thereby promoting the development of diabetes. These results indicated that semimature DCs were required for the sustained suppressive function of CD4+CD25+ Tregs that were responsible for maintaining tolerance of diabetogenic T cells in NOD mice.

A growing number of neutrophil-derived cytokines have proven to be crucial to various inflammatory and immune processes in vivo. Whereas C/EBP (CCAAT/enhancer-binding protein) transcription factors are important for neutrophil differentiation from myeloid precursors, we report herein that they also regulate cytokine production in mature neutrophils. All known C/EBP proteins but C/EBP␥ are expressed in neutrophils; most isoforms localize to the nucleus, except for C/EBP␣, which is cytoplasmic. Neutrophil stimulation does not alter the overall levels, cellular distribution, or turnover of C/EBP proteins; it also does not further induce the constitutive DNA-binding activity detected in nuclear extracts, consisting of C/EBP␤ and C/EBP. However, nuclear C/EBP␤ is rapidly phosphorylated upon cell stimulation, suggesting that it can activate cytokine promoters. Indeed, the transactivation of an IL-8 promoter-luciferase construct in a human neutrophil-like cell line was impaired when its C/EBP or NF-B sites were mutated. Overexpression of a C/EBP repressor also impeded IL-8 promoter transactivation, as well as the generation of IL-8, Mip-1␣, and Mip-1␤ in this cellular model, whereas TNF-␣ generation was mostly unaffected. Finally, overexpression of a C/EBP␤ mutant (T235A) as well as chromatin immunoprecipitation assays unveiled an important role for this residue in cytokine induction. This is the first demonstration that C/EBP factors are important regulators of cytokine expression in human neutrophils.

BackgroundSkeletal muscle atrophy is a serious concern for the rehabilitation of patients afflicted by prolonged limb restriction. This debilitating condition is associated with a marked activation of NFκB activity. The ubiquitin-proteasome pathway degrades the NFκB inhibitor IκBα, enabling NFκB to translocate to the nucleus and bind to the target genes that promote muscle atrophy. Although several studies showed that proteasome inhibitors are efficient to reduce atrophy, no studies have demonstrated the ability of these inhibitors to preserve muscle function under catabolic condition.MethodsWe recently developed a new hindlimb immobilization procedure that induces significant skeletal muscle atrophy and used it to show that an inflammatory process characterized by the up-regulation of TNFα, a known activator of the canonical NFκB pathway, is associated with the atrophy. Here, we used this model to investigate the effect of in vivo proteasome inhibition on the muscle integrity by histological approach. TNFα, IL-1, IL-6, MuRF-1 and Atrogin/MAFbx mRNA level were determined by qPCR. Also, a functional measurement of locomotors activity was performed to determine if the treatment can shorten the rehabilitation period following immobilization.ResultsIn the present study, we showed that the proteasome inhibitor MG132 significantly inhibited IκBα degradation thus preventing NFκB activation in vitro. MG132 preserved muscle and myofiber cross-sectional area by downregulating the muscle-specific ubiquitin ligases atrogin-1/MAFbx and MuRF-1 mRNA in vivo. This effect resulted in a diminished rehabilitation period.ConclusionThese finding demonstrate that proteasome inhibitors show potential for the development of pharmacological therapies to prevent muscle atrophy and thus favor muscle rehabilitation.

OBJECTIVE-Autoimmune diabetes in the nonobese diabetic (NOD) mouse model results from a breakdown of T-cell tolerance caused by impaired tolerogenic dendritic cell development and regulatory T-cell (Treg) differentiation. Re-establishment of the Treg pool has been shown to confer T-cell tolerance and protection against diabetes. Here, we have investigated whether murine thymic stromal lymphopoietin (TSLP) re-established tolerogenic function of dendritic cells and induced differentiation and/or expansion of Tregs in NOD mice and protection against diabetes. RESULTS-Our results showed that bone marrow dendritic cells of NOD mice cultured in the presence of TSLP acquired signatures of tolerogenic dendritic cells, such as an absence of production of pro-inflammatory cytokines and a decreased expression of dendritic cell costimulatory molecules (CD80, CD86, and major histocompatibility complex class II) compared with LPS-treated dendritic cells. Furthermore, TSLP-DCs promoted noninflammatory Th2 response and induced the conversion of naïve T-cells into functional CD4 ϩ CD25 ϩ Foxp3 ϩ Tregs. We further showed that subcutaneous injections of TSLP for 6 days or a single intravenous injection of TSLP-DCs protected NOD mice against diabetes. CONCLUSIONS-Our study demonstrates that TSLP re-established a tolerogenic immune response in NOD mice and protects from diabetes, suggesting that TSLP may have a therapeutic potential for the treatment of type 1 diabetes. RESEARCH DESIGN AND METHODS-We

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