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

Abstract

On activation by cross-linking the high-affinity IgE receptor (FcepsilonRI), expression of TNF-alpha, IL-3, IL-5, and IL-13 is induced in human intestinal mast cells. We sought to examine, for the first time, FcepsilonRI signaling in mature human mast cells. 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 FcepsilonRI 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. We found that nuclear factor-kappaB (NF-kappaB), as well as c-Fos and c-Jun, the components of activator protein 1 (AP-1), are activated after FcepsilonRI cross-linking in human intestinal mast cells. Treatment of the cells with specific inhibitors revealed an involvement of NF-kappaB 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 FcepsilonRI cross-linking. 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 FcepsilonRI-mediated cytokine expression. Nuclear factor of activated T cells and NF-kappaB seem to be necessary for the induction of TNF-alpha, IL-3, and IL-13 but are less important for the transcription of IL-5.