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Adrenergic receptor agonists and antagonists are extensively used as drugs in medicine for a broad spectrum of indications. We examined the consequences of β2-adrenergic stimulation of murine dendritic cells (DCs) on CD4 + T cell activation. We demonstrated in vitro that treatment of LPS-matured DCs with the β2-agonist salbutamol reduced their ability to trigger OT-II T cell proliferation specific for ovalbumin antigen. Salbutamol also induced a decrease in MHC class II molecule expression by DC through Gi protein activation. Co-culture of CD4 + T cells with salbutamol-conditioned mature DC impaired TNFα and IL-6 secretion while preserving IL-10 production by T cells. Using a vaccination protocol in mice, we showed that salbutamol favored IL-10-producing CD4 + T cells. None of these effects was observed when working with β2-adrenoreceptor deficient mice. Finally, we suggest that β2-adrenergic stimulation of DC could be an interesting way to shape CD4 + T cell responses for the purposes of immunotherapy.

Despite widespread usage of β-adrenergic receptor (AR) agonists and antagonists in current clinical practice, our understanding of their interactions with the immune system is surprisingly sparse. Among the AR expressed by dendritic cells (DC), β2-AR can modify in vitro cytokine release upon stimulation. Because DC play a pivotal role in CD8(+) T cell immune responses, we examined the effects of β2-AR stimulation on MHC class I exogenous peptide presentation and cross-presentation capacities. We demonstrate that β2-AR agonist-exposed mature DC display a reduced ability to cross-present protein Ags while retaining their exogenous peptide presentation capability. This effect is mediated through the nonclassical inhibitory G (Gαi/0) protein. Moreover, inhibition of cross-presentation is neither due to reduced costimulatory molecule expression nor Ag uptake, but rather to impaired phagosomal Ag degradation. We observed a crosstalk between the TLR4 and β2-AR transduction pathways at the NF-κB level. In vivo, β2-AR agonist treatment of mice inhibits Ag protein cross-presentation to CD8(+) T cells but preserves their exogenous MHC class I peptide presentation capability. These findings may explain some side effects on the immune system associated with stress or β-agonist treatment and pave the way for the development of new immunomodulatory strategies.

Carbon monoxide (CO) treatment improves pathogenic outcome of autoimmune diseases by promoting tolerance. However, the mechanism behind this protective tolerance is not yet defined. Here, we show in a transgenic mouse model for autoimmune diabetes that ex vivo gaseous CO (gCO)-treated DCs loaded with pancreatic β-cell peptides protect mice from disease. This protection is peptide-restricted, independent of IL-10 secretion by DCs and of CD4(+) T cells. Although no differences were observed in autoreactive CD8(+) T-cell function from gCO-treated versus untreated DC-immunized groups, gCO-treated DCs strongly inhibited accumulation of autoreactive CD8(+) T cells in the pancreas. Interestingly, induction of β1-integrin was curtailed when CD8(+) T cells were primed with gCO-treated DCs, and the capacity of these CD8(+) T cells to lyse isolated islet was dramatically impaired. Thus, immunotherapy using CO-treated DCs appears to be an original strategy to control autoimmune disease., (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Heme oxygenase-1 (HO-1) exerts its functions via the catabolism of heme into carbon monoxide (CO), Fe(2+), and biliverdin, as well as by depletion of free heme. We have recently described that overexpression of HO-1 is associated with the tolerogenic capacity to dendritic cells (DCs) stimulated by LPS. In this study, we demonstrate that treatment of human monocyte-derived DCs with CO blocks TLR3 and 4-induced phenotypic maturation, secretion of proinflammatory cytokines, and alloreactive T cell proliferation, while preserving IL-10 production. Treatment of DCs with biliverdin, bilirubin, and deferoxamine or replenishing intracellular heme stores had no effect on DC maturation. HO-1 and CO inhibited LPS-induced activation of the IFN regulatory factor 3 pathway and their effects were independent of p38, ERK, and JNK MAPK. HO-1 and CO treatment also inhibited mouse DC maturation in vitro and mouse DC immunogenic properties in vivo, as shown by adoptive cell transfer in a transgenic model of induced diabetes. Thus, for the first time, our data show that CO treatment inhibits DC immunogenicity induced by TLR ligands and that blockade of IFN regulatory factor 3 is associated with this effect.

In addition to important regulatory roles in gene expression through RNA interference, it has recently been shown that microRNAs display immune stimulatory effects through direct interaction with receptors of innate immunity of the Toll-like receptor family, aggravating neuronal damage and tumour growth. Yet no evidence exists on consequences of microRNA immune stimulatory actions in the context of an autoimmune disease. Using microRNA analogues, we here show that pancreatic beta cell-derived microRNA sequences induce pro-inflammatory (TNFa, IFNa, IL-12, IL-6) or suppressive (IL-10) cytokine secretion by primary mouse dendritic cells in a sequence-dependent manner. For miR-29b, immune stimulation in RAW264.7 macrophages involved the endosomal Toll-like receptor-7, independently of the canonical RNA interference pathway. In vivo, the systemic delivery of miR-29b activates CD11b+B220− myeloid and CD11b-B220+ plasmacytoid dendritic cells and induces IFNa, TNFa and IL-6 production in the serum of recipient mice. Strikingly, in a murine model of adoptive transfer of autoimmune diabetes, miR-29b reduces the cytolytic activity of transferred effector CD8+ T-cells, insulitis and disease incidence in a single standalone intervention. Endogenous miR-29b, spontaneously released from beta-cells within exosomes, stimulates TNFa secretion from spleen cells isolated from diabetes-prone NOD mice in vitro. Hence, microRNA sequences modulate innate and ongoing adaptive immune responses raising the question of their potential role in the breakdown of tolerance and opening up new applications for microRNA-based immune therapy. [ABSTRACT FROM AUTHOR]

Carbon monoxide (CO) treatment improves pathogenic outcome of autoimmune diseases by promoting tolerance. However, the mechanism behind this protective tolerance is not yet defined. Here, we show in a transgenic mouse model for autoimmune diabetes that ex vivo gaseous CO (gCO)-treated DCs loaded with pancreatic β-cell peptides protect mice from disease. This protection is peptide-restricted, independent of IL-10 secretion by DCs and of CD4+ T cells. Although no differences were observed in autoreactive CD8+ T-cell function from gCO-treated versus untreated DC-immunized groups, gCO-treated DCs strongly inhibited accumulation of autoreactive CD8+ T cells in the pancreas. Interestingly, induction of β1-integrin was curtailed when CD8+ T cells were primed with gCO-treated DCs, and the capacity of these CD8+ T cells to lyse isolated islet was dramatically impaired. Thus, immunotherapy using CO-treated DCs appears to be an original strategy to control autoimmune disease. [ABSTRACT FROM AUTHOR]

Plasmid-DNA gene-gun immunization may be an efficient approach for investigating the role of skin dendritic cells (DCs) in type 1 diabetes (T1D) pathogenesis and the significance of the presentation of peptides that mimic autoantigenic epitopes in aggravating or modulating the autoimmune reaction. Gene-gun immunization has been described as producing longlasting immune responses elicited by skin DCs, especially Langerhans cells (LCs). Therefore, we tested the immune response and diabetes modulation in nonobese diabetic (NOD) mice and in control BALB/c mice, by gene-gun administration of plasmid-DNA encoding (1) human 65 kDa glutamic acid decarboxylase (hGAD65) mimicking the crucial mouse autoantigen GAD65 (similarity of 95.7%) or (2) β-galactosidase (βGAL) as a negative control. Expression of GAD and βGAL in skin of pc-GAD- and pc-LacZ-injected mice, respectively, was confirmed. It was surprising that both pc-LacZ-injected BALB/c and NOD mice exhibited a βGAL-specific Th1 immune response: spleen cells of pc-LacZ mice proliferated specifically to βGAL (P < 10-4) and secreted significant amounts of IFNγ (P < 10-4). pc-LacZ mice also developed a βGAL-specific Th1-related (IgG2a/2c) and Th2-related (IgG1) humoral response. Although pc-GAD BALB/c mice showed Th2-related GAD-specific IgG1 production and a significant secretion of IL4 (P < .03), pc-GAD NOD mice did not generate either an antibody response or a T cell response specific to GAD. Moreover, gene-gun immunization encoding hGAD65 did not clearly modulate diabetes onset in NOD mice. This absence of detectable GAD-specific response may implicate skin DC deficiencies in NOD mice. The gene-gun technique could thus provide an interesting model for studying skin DC abnormalities in NOD mice and their potential implication of presenting mimetic peptides that modulate the autoimmune response in T1D. [ABSTRACT FROM AUTHOR]