Dexamethasone rapidly suppresses IL-33-stimulated mast cell function by blocking transcription factor activity

Mast cells are critical effectors of allergic disease and can be activated by IL-33, a proinflammatory member of the IL-1 cytokine family. IL-33 worsens the pathology of mast cell-mediated diseases, but therapies to antagonize IL-33 are still forthcoming. Because steroids are the mainstay of allergic disease treatment and are well known to suppress mast cell activation by other stimuli, we examined the effects of the steroid dexamethasone on IL-33-mediated mast cell function. We found that dexamethasone potently and rapidly suppressed cytokine production elicited by IL-33 from murine bone marrow-derived and peritoneal mast cells. IL-33 enhances IgE-mediated mast cell cytokine production, an activity that was also antagonized by dexamethasone. These effects were consistent in human mast cells. We additionally observed that IL-33 augmented migration of IgE-sensitized mast cells toward antigen. This enhancing effect was similarly reversed by dexamethasone. Simultaneous addition of dexamethasone with IL-33 had no effect on the phosphorylation of MAP kinases or NFκB p65 subunit; however, dexamethasone antagonized AP-1- and NFκB-mediated transcriptional activity. Intraperitoneal administration of dexamethasone completely abrogated IL-33-mediated peritoneal neutrophil recruitment and prevented plasma IL-6 elevation. These data demonstrate that steroid therapy may be an effective means of antagonizing the effects of IL-33 on mast cells in vitro and in vivo, acting partly by suppressing IL-33-induced NFκB and AP-1 activity.

Dexamethasone suppresses IL-33-mediated mast cell activation (CCR3P.215)

Dexamethasone, a glucocorticosteroid known for its anti-inflammatory and immunosuppressive activities, has been shown to inhibit IgE-mediated mast cell activation. The present research investigates the role of this drug in suppressing IL-33-mediated mast cell activation. IL-33 is a novel cytokine of the IL-1 family that elicits mast cells to produce inflammatory cytokines independently of IgE-FceRI signals. We have found that micromolar concentrations of dexamethasone are capable of suppressing IL-33-mediated cytokine production, regardless of genetic background. Dexamethasone also suppressed IL-33-induced cytokine production in mouse peritoneal mast cells. Inhibition was maximal when dexamethasone was added simultaneously with IL-33. Intracellular staining demonstrated that dexamethasone significantly reduces T1/ST2 expression in mast cells. However, cytokine suppression was shown to be independent of this downregulation of the IL-33 receptor. Thus, dexamethasone is capable of suppressing IL-33-mediated mast cell activation during the innate and adaptive immune responses. Further studies on the mechanism of dexamethasone are necessary for the understanding of those pathways and the development of more effective strategies for the treatment of inflammatory conditions.

Dexamethasone suppresses of IL-33-mediated mast cell activation in vitro and in vivo (HYP4P.314)

Dexamethasone, a synthetic member of the glucocorticoid class of steroid drugs is known for its immunosuppressant and anti-inflammatory effects. Mast cells, critical effectors of allergic disease, can be activated by IL-33, a pro-inflammatory member of the IL-1 family. We found that Dexamethasone potently suppresses IL-33-stimulated cytokine secretion by mouse mast cells. We similarly found that Dexamethasone treatment in vivo reduced IL-33-mediated cytokine production and neutrophil infiltration in the murine peritoneum. We compared the activation status of signaling proteins during IL-33 stimulation, and found that Dexamethasone pretreatment significantly reduced Erk phosphorylation. However, we also observed that Dexamethasone-mediated suppression occurred when it was added simultaneously with IL-33, suggesting that inhibition occurrs even prior to Erk blockade. The effect of Dexamethasone on IL-33 stimulated NFkB-mediated gene transcription is currently under investigation. Our data show that Dexamethasone, a well-established therapy for inflammatory disease, can suppress IL-33-mediated mast cell activation, and may therefore be effective for treating diseases now being attributed to IL-33 effects.

Dexamethasone suppresses IL-33-mediated mast cell activation (HYP3P.409)

Dexamethasone, a potent synthetic member of the glucocorticoid class of steroid drugs is known for its immunosuppressant and anti-inflammatory effects. The present research investigates the role of this anti-allergic drug in suppressing IL-33-mediated mast cell activation. IL-33 is a novel cytokine of IL-1 family, which promotes mast cells to produce inflammatory cytokines independently of IgE-FcεRI signals. Initial studies have shown that micromolar quantities of dexamethasone suppress the production of TNF-α and IL-6 by IL-33-stimulated mast cells. While confirming these results by intracellular staining, it was observed that dexamethasone not only decreases the fraction of cytokine-positive cells but also causes a drop in cytokine production per cell. Although dexamethasone pretreatment resulted in a significant reduction in the IL-33 receptor subunit T1/ST2, this did not correlate with decreased cytokine production. These results demonstrate the ability of dexamethasone to suppress mast cell activation during innate immune responses, and support further work into the mechanisms by which this occurs.

Differential effects of cyclosporine A and TGFβ1 on IgE- versus IL-33-mediated mast cell activation (HYP3P.407)

Cyclosporine A (CsA), a potent calcineurin antagonist and immunosuppressant, is known to inhibit IgE-mediated mast cell activation. The present research investigates the role of this drug in suppressing IL-33-mediated mast cell activation. IL-33 is a novel cytokine of IL-1 family that elicits mast cells to produce inflammatory cytokines independently of IgE-FcεRI signals. We have found that low concentrations of CsA (10nM) are capable of suppressing IgE-mediated cytokine production by 50-80% in mouse bone marrow-derived mast cells. By comparison, IL-33-mediated secretion of TNF, IL-6, and MCP-1 was unaffected by CsA under these conditions. These results were consistent among mast cells derived from C57BL/6, 129Sv, C3H, and A/J mouse strains. We have previously reported that TGFβ1 inhibits IgE-mediated cytokine production. Our current experiments showed that TGFβ1 similarly antagonizes IL-33-induced cytokine secretion, and that CsA does not enhance this effect. These data demonstrate that mast cell activation by IL-33, thought to be a key regulator of innate immunity, is responsive to TGFβ1-mediated suppression, but relatively resistant to CsA effects. Understanding how mast cells are regulated by innate signals will shed light on many inflammatory diseases.