TNF-alpha and IL-5 gene induction in IgE plus antigen-stimulated mast cells require common and distinct signaling pathways

Background: Mast cells produce a variety of cytokines and chemokines in a t imely and tightly controlled fashion if stimulated via the Fc epsilon RI. E vidence is accumulating that the transcriptional induction of the correspon ding genes and the release of these mediators are dependent on common and m ediator-specific components of the signal transduction and transcription fa ctor machinery. Methods: We addressed this issue by comparing the effects o f mitogen activated protein (MAP) kinase pathway inhibitors and protein kin ase C (PKC) inhibitors on the induction of TNF-alpha and IL-5 after IgE plu s antigen (Ag) stimulation in CPII mouse mast cells using Western blot anal yses and transient transfections of reporter gene plasmids, Results: TNF-al pha shows a strict dependence on the MAP kinase pathway, while IL-5 is eith er activated by PMA-dependent PKCs or along the MAP kinase pathway. In addi tion, both mediators are sensitive to PKC mu inhibition, suggesting involve ment of this atypical, non-PMA dependent PKC in the overall induction proce ss. Conclusion: While the two cytokines were recently shown to be regulated by a member of the nuclear factor of activated T-cells (NF-AT) transcripti on factor family, activator protein 1 (AP1) was identified as a cofactor at the TNF-alpha promoter while a GATA family member comprised the cofactor a t the IL-5 promoter. This suggests that the differences in requirement for signal transduction cascades are the result of a different usage of NF-AT c ofactors for transcription of each cytokine in mast cells.