Role of activator protein 1, nuclear factor-κB, and nuclear factor of activated T cells in IgE receptor-mediated cytokine expression in mature human mast cells

Abstract

Background: On activation by cross-linking the high-affinity IgE receptor (FcεRI), expression of TNF-α, IL-3, IL-5, and IL-13 is induced in human intestinal mast cells. Objective: We sought to examine, for the first time, FcεRI signaling in mature human mast cells. Methods: Mast cells were isolated from intestinal tissue and cultured in the presence of stem cell factor. The cells were treated with specific inhibitors before stimulation by means of FcεRI cross-linking. Cytokine mRNA expression was analyzed by means of RT-PCR, and activation of signaling molecules was determined by means of immunocytochemistry, RT-PCR, Western blotting, and protein kinase C (PKC) assay. Results: We found that nuclear factor-κB (NF-κB), as well as c-Fos and c-Jun, the components of activator protein 1 (AP-1), are activated after FcεRI cross-linking in human intestinal mast cells. Treatment of the cells with specific inhibitors revealed an involvement of NF-κB and nuclear factor of activated T cells, as well as the necessity of extracellular signal-regulated kinase 1/2 (ERK-1/2), PKC, and AP-1 for the induced cytokine gene expression. Consistently, we found that activation of c-Fos corresponds with the induced cytokine gene expression and that ERK-1/2, an activator of c-Fos, was activated in response to FcεRI cross-linking. Conclusion: Our data on human mast cells show that the activity of ERK-1/2, PKC, and subsequent activation of AP-1 are necessary for the FcεRI-mediated cytokine expression. Nuclear factor of activated T cells and NF-κB seem to be necessary for the induction of TNF-α, IL-3, and IL-13 but are less important for the transcription of IL-5.