Mitogen-activated Protein (MAP) Kinase Regulates Production of Tumor Necrosis Factor-α and Release of Arachidonic Acid in Mast Cells

Abstract

Aggregation of the high affinity IgE receptor (Fc⑀RI) in a mast cell line resulted in activation of the p42 and the stress-activated p38 mitogen-activated protein (MAP) kinases. Selective inhibition of these respective kinases with PD 098059 and SB 203580 indicated that p42 MAP kinase, but not p38 MAP kinase, contributed to the production of the cytokine, tumor necrosis factor-␣, and the release of arachidonic acid in these cells. Neither kinase, however, was essential for Fc⑀RI-mediated degranulation or constitutive production of tumor growth factor-␤. Studies with SB 203580 and the p38 MAP kinase activator anisomycin also revealed that p38 MAP kinase negatively regulated activation of p42 MAP kinase and the responses mediated by this kinase.Stimulation of mast cells by aggregation of membrane IgE receptors (Fc⑀RI), leads to recruitment of the tyrosine kinase Syk and activation of Syk-dependent signaling cascades (1, 2). These cascades include activation of phospholipase C and sphingosine kinase for mobilization of calcium ions and PKC 1 (3, 4) and the activation of p42 MAP kinase cascade through Ras (2, 5). These cascades lead ultimately to secretion of intracellular granules, a response primarily driven by the increase in [Ca 2ϩ ] i and activation of PKC (6), and a cPLA 2 -mediated release of arachidonic acid. The activation of cPLA 2 is dependent on increase of [Ca 2ϩ ] i and phosphorylation by MAP kinase (2,7,8).Stimulated mast cells also produce a variety of cytokines that include interleukins 1, 3, 4, 5, and 6 as well as TNF␣ and granulocyte-macrophage colony-stimulating factor (9, 10). Typically, increased expression of cytokine mRNA and protein is detectable 30 min to several hours after the addition of stimulant (11). These cytokines, particularly TNF␣, are thought to mediate pathologic inflammatory reactions (10) and protective responses to bacterial infection (12). The production and release of TNF␣ are regulated through signals transduced by calcium and PKC, although there are indications that additional Fc⑀RI-mediated signals may operate for optimal production of TNF␣ in cultured RBL-2H3 mast cells. Compared with antigen, other stimulants are relatively weak inducers of TNF␣ production when doses of stimulants are matched for maximal stimulation of degranulation (13). Also, concentrations of Ro31-7549 that block PKC, secretion of granules, and release of TNF␣ only partially block production of TNF␣ (13).The present objective was to determine whether stimulation of MAP kinases induces additional signals for production of TNF␣. A linkage between these events has not been established in mast cells. Antigen-induced stimulation of p42 MAP kinase coincides with the activation of its upstream regulators, Ras, Raf, and MEK-1 (2, 5), and persists through the period when production of TNF␣ would be most apparent (14). As noted in this paper, however, RBL-2H3 cells also possess the mammalian homologue of the yeast HOG-1 protein kinase, p38 MAP kinase. We have utilized the MEK-1 inhibitor, PD 098059 (15, 16)...

Phospholipase Cγ2 Is Essential for Specific Functions of FcεR and FcγR

“…Previous studies have demonstrated that activation of PKC and elevation of intracellular Ca 2ϩ are sufficient and necessary for the release of these inflammatory mediators from granules (85)(86)(87). By contrast, studies have shown that the MAPKs are not required for the release of these inflammatory mediators, but are involved in the production of arachidonic acid and cytokines (27,33,88). Here we demonstrate that PLC␥2 deficiency partially impaired Ca 2ϩ signals following engagement of the Fc⑀R in mast cells, resulting in a reduced Fc⑀R-mediated release of serotonin, histamine, and arachidonic acid, but had no effect on cytokine transcription.…”

Dual Phase Priming by IL-3 for Leukotriene C4 Generation in Human Basophils: Difference in Characteristics Between Acute and Late Priming Effects

“…We have previously shown that the activation of ERKs follows stimulation of basophils with FMLP or anti-IgE Ab and appears to be responsible for free AA/LTC 4 generation by phosphorylating cPLA 2 , because PD98059 inhibits ERK and cPLA 2 phosphorylation and selectively inhibits LTC 4 release, but not histamine release or IL-4 production, in human basophils (15). A variety of studies in other cell models also suggest that ERKs are responsible for phosphorylating cPLA 2 (31,39,40). The current study shows that treatment by IL-3 or stimulation by C5a results in ERK phosphorylation that is inhibitable by PD98059 (Fig.…”

“…PD98059 is thought to be a specific inhibitor of MEK1/2, the immediately antecedent kinases to the ERKs (15,30,31). This compound is often used to determine the involvement of MEK/ERK activation.…”

Regulation of Rat Basophilic Leukemia-2H3 Mast Cell Secretion by a Constitutive Lyn Kinase Interaction with the High Affinity IgE Receptor (FcεRI)

“…In RBL cells, secretion of newly synthesized LTC 4 and TNF-␣, but not histamine release, requires activation of the MAPK pathway, specifically MEK and ERK-2 (29). We compared Fc⑀RI-stimulated phosphorylation of MEK and ERK-2 between our two Lyn unique domain transfectants and a control transfectant.…”