TNF Increases Expression of IL-4 and PARs in Mast Cells

Tumor necrosis factor (TNF) is a proinflammatory cytokine which has been shown to be actively involved in the pathogenesis of allergic inflammation. However, little is known of the effects of TNF on cytokine secretion and protease activated receptor (PAR) expression in mast cells. In the present study, we examined potential influence of TNF on IL-4 and IL-12 release from P815 cells and PAR expression in P815 cells by using flow cytometry analysis, quantitative real time PCR, ELISA and cellular activation of signaling ELISA (CASE) techniques. The results showed that TNF induced up to 2.7-fold increase in IL-4, but not IL-12 release from P815 cells, and PAR-2 antagonist peptide FSLLRY-NH(2) and PAR-4 antagonist peptide trans-cinnamoyl (tc)-YPGKF-NH(2) did not affect TNF induced IL-4 release. Approximately up to 2.4 and 2.3 fold increases in expression of PAR-2 and PAR-4 were observed when cells were incubated with TNF. Pretreatment of cells with TNF for 60 min enhanced trypsin and tryptase induced PAR-2 expression by 2.4 and 2.3 fold; PAR-3 expression by 1.6 and 1.7 fold and PAR-4 expression by 1.6 and 1.7 fold, respectively. LY294002, an inhibitor PI3K abolished TNF induced IL-4 release and phosphorylation of Akt in P815 cells, indicating Akt cell signalling pathway is involved in the event. In conclusion, TNF can stimulate IL-4 release from mast cells through an Akt cell signalling pathway dependent, but PAR independent mechanism. TNF may serve as a regulator for IL-4 production and PAR expression, and through which participates in the mast cell related inflammation.