Modulation Of Mast Cell Proteainse Activated Receptor Expression And Th2 Cytokines Release By TNF-α

It has been recognized that proteinase activated receptors (PARs), Th2 Cytokines such as interleukin (IL)-4 , IL-6 and IL-13 are involved in the pathogenesis of allergic diseases, and that tumor necrosis factor (TNF)-αplays an important role in allergic inflammation by stimulating mast cells to release both histamine and tryptase. However, little is known of the effect of TNF-αon Th2 cytokines release from mast cells,and also the role of TNF-αin modulating mast cell PAR expression remain unclear. Therefore, we examined potential influence of TNF-αon mast cell PAR expression and Th2 Cytokines release as well as the potential signal transduction pathways of TNF-αinduced IL-4, IL-6 and IL-13 release from mast cell P815.After being challenged, some of P815 cells were treated and analyzed by flowcytometry to detect expression of PARs at protein level, some of cells were treated and analyzed by real time RT-PCR to detect expression of PARs at mRNA level, and the other cells were treated and analyzed by cellular activation of signaling ELISA (CASE) to detect phosphorylation of ERK, Akt,p38 and STAT3, and the cell supernatant were analysed by ELISA to detect the release of IL-4, IL-6 and IL-13.The results showed that TNF-αupregulated P815 mast cell PAR-1, PAR-2, PAR-3 and PAR-4 mRNA expression. TNF-αinduced concentration dependent release of IL-4, IL-6 and IL-13 from P815 cells following both 6 and 16 h incubation. LY294002 abolished TNF-αinduced IL-4, IL-6 and IL-13 release, while PD98059 and U0126 abolished TNF-αinduced IL-4,and IL-6 release, PD98059, U0126 and LY294002 also inhibited TNF-αinduced phosphorylation of ERK and Akt.In conclusion, TNF-αcan modulate mast cell PAR expression and Th2 cytokines release. The TNF-αinduced IL-4, IL-6 and IL-13 release from P815 cells is most likely through activation of Akt and ERK signaling pathways. These findings implicate that TNF-αmay exert proinflammatory activities in allergic inflammation through its ability in alterating the mast cell responsiveness to PAR agonists and induction of Th2 cytokines release from mast cells which would result in more mast cell degranulation. Induction of IL-4, IL-6 and IL-13 release from mast cells by TNF-αalso may further improve the hypothesis of self-amplification mechanism of mast cell degranulation.