Inhibition of IKK down-regulates antigen plus IgE-induced TNF production by mast cells:: a role for the IKK-IκB-NF-κB 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 epsilon RI, by antigen initiates a cascade of signaling events leading to nuclear factor (NF)-kappa B activation and tumor necrosis factor (TNF) production. Here, we demonstrated that inhibition of inhibitor of kappa B (I kappa B) kinase (IKK) by a peptide IKK inhibitor or by four individual chemical IKK inhibitors including 15-deoxyprostaglandin J(2), 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 alpha but not IKK beta in BMMC. IgE + TNP-induced phosphorylation of IKK alpha was accompanied with phosphorylation and degradation of I kappa B alpha, subsequent NF-kappa B activation, and TNF production. Inhibition of IKK by sulindac decreased IKK alpha phosphorylation, I kappa B alpha phosphorylation and degradation, NF-kappa B activation, and TNF production by BMMC. It is interesting that IgE + TNP stimulation also induced a prominent synthesis of IKK alpha and I kappa B alpha. Inhibition of NF-kappa B activity by pyrrolidine dithiocarbomate (PDTC) blocked IgE + TNP-induced I kappa B alpha synthesis. NF-kappa B activity and TINT production were also inhibited when PDTC was used even after IgE + TNP stimulation, suggesting a potential role for the newly synthesized I kappa B alpha in MC activation. In. addition, IgE + TNP-induced IKK alpha and I kappa B alpha phosphorylation was inhibited by a protein kinase C (PKC) inhibitor Ro 31-8220. Taken together, our results support a role for the IKK-I kappa B-NF-kappa B pathway, which likely involves PKC in IgE-dependent TNF production by MC. Thus, IKK may serve as a new target for the regulation of MC function in allergy.