Impaired FcεRI-Dependent Gene Expression and Defective Eicosanoid and Cytokine Production as a Consequence of Fyn Deficiency in Mast Cells

Abstract

Fyn kinase is a key contributor in coupling FcεRI to mast cell degranulation. A limited macroarray analysis of FcεRI-induced gene expression suggested potential defects in lipid metabolism, eicosanoid and glutathione metabolism, and cytokine production. Biochemical analysis of these responses revealed that Fyn-deficient mast cells failed to secrete the inflammatory eicosanoid products leukotrienes B4 and C4, the cytokines IL-6 and TNF, and chemokines CCL2 (MCP-1) and CCL4 (MIP-1β). FcεRI-induced generation of arachidonic acid and normal induction of cytokine mRNA were defective. Defects in JNK and p38 MAPK activation were observed, whereas ERK1/2 and cytosolic phospholipase A2 (S505) phosphorylation was normal. Pharmacological studies revealed that JNK activity was associated with generation of arachidonic acid. FcεRI-mediated activation of IκB kinase β and IκBα phosphorylation and degradation was defective resulting in a marked decrease of the nuclear NF-κB DNA binding activity that drives IL-6 and TNF production in mast cells. However, not all cytokine were affected, as IL-13 production and secretion was enhanced. These studies reveal a major positive role for Fyn kinase in multiple mast cell inflammatory responses and demonstrate a selective negative regulatory role for certain cytokines.

Selective Activation of Fyn/PI3K and p38 MAPK Regulates IL-4 Production in BMMC under Nontoxic Stress Condition

“…Our findings are in agreement with several previous studies that demonstrated the involvement of PI3K/p38 activated pathway, Fc RI-induced IL-4 production in the mast cell (23,35). It is known that PI3K regulates the activation of Rac, which, in turn, activates p21-activated kinase resulting in the induction of p38 MAPK and JNK (36).…”

“…It is known that PI3K regulates the activation of Rac, which, in turn, activates p21-activated kinase resulting in the induction of p38 MAPK and JNK (36). Moreover, the Fyn kinase is known to be required for PI3K activation, and Fyn deficiency results in the reduction of both p38 MAPK and JNK activation but not that of ERK (23). Additionally, the importance of MAPKs for Th2 cytokine production has been reported (37).…”

“…Cytokine production in mast cells as a consequence of Fc RI stimulation seems to be primarily driven by Fyn and not Lyn kinase (23,24). In fact, Fc RI-dependent stimulation of IL-4 production was demonstrated to be defective in Fyn-deficient BMMC but not in Lyn deficiency (23)(24)(25) To determine whether Lyn and/or Fyn might be required for H 2 O 2 -induced IL-4 production, we analyzed IL-4 mRNA up-regulation using BMMC from Lyn Ϫ/Ϫ , Fyn Ϫ/Ϫ , and PI3K Ϫ/Ϫ mice.…”

“…In fact, Fc RI-dependent stimulation of IL-4 production was demonstrated to be defective in Fyn-deficient BMMC but not in Lyn deficiency (23)(24)(25) To determine whether Lyn and/or Fyn might be required for H 2 O 2 -induced IL-4 production, we analyzed IL-4 mRNA up-regulation using BMMC from Lyn Ϫ/Ϫ , Fyn Ϫ/Ϫ , and PI3K Ϫ/Ϫ mice. BMMC from wild type, Lyn-, Fyn-, and PI3K-null mice were treated with 10 nM H 2 O 2 for 3 h and then analyzed together with untreated samples for IL-4 mRNA production.…”

“…At 10 nM, H 2 O 2 phosphorylation of p38 MAPK reached levels of ϳ60% of that seen with Fc RI stimulation. Because Fyn kinase was reported to stimulate p38 MAPK phosphorylation (7,23), we investigated whether Lyn or Fyn might be required for p38 MAPK phosphorylation following H 2 O 2 treatment of BMMC deficient in these Src kinases. Fig.…”