Inhibition of IKK down-regulates antigen IgE-induced TNF production by mast cells: a role for the IKK-I B-NF- B pathway in IgE-dependent mast cell activation

Mast cells (MC) are major effector cells for allergic diseases. Cross-linking of immunoglobulin E (IgE) and its high-affinity receptor, Fc RI, by antigen initiates a cascade of signaling events leading to nuclear factor (NF)B activation and tumor necrosis factor (TNF) production. Here, we demonstrated that inhibition of inhibitor of B (I B) kinase (IKK) by a peptide IKK inhibitor or by four individual chemical IKK inhibitors including 15-deoxyprostaglandin J2, BMS-345541, SC-514, or sulindac significantly blocked IgE trinitrophenyl (TNP)-induced TNF production by mouse bone marrow-derived MC (BMMC). Moreover, IgE TNP induced a rapid phosphorylation of IKK but not IKK in BMMC. IgE TNP-induced phosphorylation of IKK was accompanied with phosphorylation and degradation of I B , subsequent NFB activation, and TNF production. Inhibition of IKK by sulindac decreased IKK phosphorylation, I B phosphorylation and degradation, NFB activation, and TNF production by BMMC. It is interesting that IgE TNP stimulation also induced a prominent synthesis of IKK and I B . Inhibition of NFB activity by pyrrolidine dithiocarbomate (PDTC) blocked IgE TNP-induced I B synthesis. NFB activity and TNF production were also inhibited when PDTC was used even after IgE TNP stimulation, suggesting a potential role for the newly synthesized I B in MC activation. In addition, IgE TNP-induced IKK and I B phosphorylation was inhibited by a protein kinase C (PKC) inhibitor Ro 31-8220. Taken together, our results support a role for the IKK-I BNFB pathway, which likely involves PKC in IgEdependent TNF production by MC. Thus, IKK may serve as a new target for the regulation of MC function in allergy. J. Leukoc. Biol. 77: 975–983; 2005.