SHIP Negatively Regulates IgE + Antigen-Induced IL-6 Production in Mast Cells by Inhibiting NF-κB Activity

Abstract

We demonstrate in this study that IgE + Ag-induced proinflammatory cytokine production is substantially higher in Src homology-2-containing inositol 5′-phosphatase (SHIP)−/− than in SHIP+/+ bone marrow-derived mast cells (BMMCs). Focusing on IL-6, we found that the repression of IL-6 mRNA and protein production in SHIP+/+ BMMCs requires the enzymatic activity of SHIP, because SHIP−/− BMMCs expressing wild-type, but not phosphatase-deficient (D675G), SHIP revert the IgE + Ag-induced increase in IL-6 mRNA and protein down to levels seen in SHIP+/+ BMMCs. Comparing the activation of various signaling pathways to determine which ones might be responsible for the elevated IL-6 production in SHIP−/− BMMCs, we found the phosphatidylinositol 3-kinase/protein kinase B (PKB), extracellular signal-related kinase (Erk), p38, c-Jun N-terminal kinase, and protein kinase C (PKC) pathways are all elevated in IgE + Ag-induced SHIP−/− cells. Moreover, inhibitor studies suggested that all these pathways play an essential role in IL-6 production. Looking downstream, we found that IgE + Ag-induced IL-6 production is dependent on the activity of NF-κB and that IκB phosphorylation/degradation and NF-κB translocation, DNA binding and transactivation are much higher in SHIP−/− BMMCs. Interestingly, using various pathway inhibitors, it appears that the phosphatidylinositol 3-kinase/PKB and PKC pathways elevate IL-6 mRNA synthesis, at least in part, by enhancing the phosphorylation of IκB and NF-κB DNA binding while the Erk and p38 pathways enhance IL-6 mRNA synthesis by increasing the transactivation potential of NF-κB. Taken together, our data are consistent with a model in which SHIP negatively regulates NF-κB activity and IL-6 synthesis by reducing IgE + Ag-induced phosphatidylinositol-3,4,5-trisphosphate levels and thus PKB, PKC, Erk, and p38 activation.

SHIP1 Is a Repressor of Mast Cell Hyperplasia, Cytokine Production, and Allergic Inflammation In Vivo

“…We demonstrated that the increased levels of IL-6 and TNF were due to loss of SHIP1 specifically in mast cells. Because Ship1 Ϫ/Ϫ mast cells produce more IL-6 and TNF than wild-type mast cells upon Fc RI-mediated stimulation in vitro, we suspect that the increased serum levels of these cytokines arose directly from Ship1 Ϫ/Ϫ mast cells via stimulation with endogenous IgE (10). Although the high level of IL-6 in the serum of Ship1 Ϫ/Ϫ mice was previously attributed to macrophages, in this study we demonstrate that Ship1 Ϫ/Ϫ mast cells also contribute to the increased IL-6 levels in vivo (8).…”

“…Although SHIP1 is not required for mast cell differentiation, it functions as a repressor of mast cell degranulation and cytokine secretion in vitro. Specifically, Ship1 Ϫ/Ϫ mast cells exhibit increased degranulation and cytokine secretion compared with Ship1 ϩ/ϩ mast cells in response to IgE crosslinking (6,10). Further, stimulation with stem cell factor (SCF) 4 or IgE without crosslinking Ag induces aberrant degranulation in Ship1 Ϫ/Ϫ but not Ship1 ϩ/ϩ mast cells (6,11).…”

“…Because Ship1 Ϫ/Ϫ mast cells exhibit enhanced degranulation and cytokine secretion in response to Fc RI stimulation and react aberrantly to c-kit stimulation in vitro, we investigated the levels of inflammatory cytokines in the serum of adult Ship1 Ϫ/Ϫ mice (6,10,11). Ship1 Ϫ/Ϫ mouse serum contained significantly increased levels of IL-5, IL-6, and TNF (and a small increase in CCL2) compared with Ship1 ϩ/ϩ controls (Fig.…”

Once Phosphorylated, Tyrosines in Carboxyl Terminus of Protein-tyrosine Kinase Syk Interact with Signaling Proteins, Including TULA-2, a Negative Regulator of Mast Cell Degranulation

“…There are increased Fc⑀RI-induced degranulation, NFB activation, and IL-6 production in BMMC from SHIP-1-deficient mice (35,55). The recruitment of SHIP-1 to the membrane by binding to Syk or the subunit ␤ of Fc⑀RI would allow SHIP-1 to act on its substrate generated by phosphoinositide 3-kinase activation (56).…”

Association of tumor necrosis factor-α –308G>A polymorphism with IgE-mediated allergy to betalactams in an Italian population

“…4 IgE-dependent mast cell activation plays an important role in the development of allergy. The cross-linking of allergen-specific IgE bound to its high-affinity receptor, FceRI, results in a series of molecular events leading to nuclear factor (NF)-kB activation 5,6 and subsequent cytokine production. Many mast cell-derived cytokines, including tumor necrosis factor-a (TNF-a), are regulated by the transcription factor NF-kB.…”