Mast cell tumor necrosis factor alpha production is regulated by MEK kinases

Mast cells synthesize and secrete specific cytokines and chemokines which play an important role in allergic inflammation. Aggregation of the high-affinity Fc receptor (Fc epsilon RI) for immunoglobulin E (IgE) in MC/9 mouse mast cells stimulates the synthesis and secretion of tumor necrosis factor alpha (TNF-alpha). Fc epsilon RI aggregation activates several sequential protein kinase pathways, leading to increased activity of extracellular signal-regulated kinases (ERKs), c-Jun amino-terminal kinases (JNKs), and the p38 mitogen-activated protein (MAP) kinase, Inhibition of ERKs with the compound PD 098059 bad little effect on Fc epsilon RI-stimulated TNF-alpha production, Aggregation of Fc epsilon RI stimulated MEK kinase 1 (MEKK1) activity, which activates JNK kinase (JNKK), the kinase that phosphorylates and activates JNKs, Expression of activated MEKK1 (Delta MEKK1) in MC/9 cells strongly stimulated JNK activity but only weakly stimulated p38 activity, and it induced a large activation of TNF-alpha promoter-regulated luciferase gene expression, Inhibitory mutant JNK2 expressed in MC/9 cells significantly blunted Fc epsilon RI stimulation of TNF-alpha promoter-driven luciferase expression, Wortmannin, an inhibitor of phosphatidylinositol 3-kinase, diminished Fc epsilon RI-mediated TNF-alpha synthesis, significantly blunted JNK activation and TNF-alpha promoter-driven luciferase expression, and only weakly inhibited p38 kinase activation. inhibition of NF kappa B activation resulting from Delta MEKK1 expression or Fc epsilon RI stimulation did not affect TNF-alpha promoter-driven luciferase expression. Our findings define a MEEK-regulated JNK pathway activated by Fc epsilon RI that regulates TNF-alpha production in mast cells.