Modulation Of Mast Cell Proteinase Activated Receptor Expression And Cytokine Release By GM-CSF And The Potential Signal Transduction Pathways

BACKGROUND: protease activated receptors (PARs), a new subfamily of G protein- coupled receptors, interleukin(IL)-4 and IL-6 are involved in the pathogenesis of allergic diseases, and GM-CSF plays a role in adaptive immune response. However, little is known of the effect of GM-CSF on protease induced cytokine release from mast cells. In the present study, we examined potential influence of GM-CSF on mast cell PARs expression and IL-4 and IL-6 release as well as the potential signal transduction pathways of GM-CSF induced IL-4 and IL-6 release from P815 mast cell.METHOD: After being challenged, some of cells were analyzed by real time RT-PCR to detect expression of PARs at mRNA level, some of P815 cells were analyzed by flowcytometry to detect expression of PARs at protein level, and the others were analyzed by cellular activation of signaling ELISA to detect phosphorylation of ERK, Akt,p38 and STAT3, and the cell supernatant were analysed by ELISA to detect the release of IL-4 and IL-6.RESULTS: We demonstrated that GM-CSF upregulated mast cell PAR-2 expression both at mRNA level and at protein level. GM-CSF upregulated PAR-1 PAR-3 and PAR-4 expression at mRNA level. Modulation of expression of PARs at protein level were blocked by administration of GM- CSF blocking antibody. GM-CSF induced IL-4 and IL-6 release from P815 cells following 16h incubation. PD98059, U0126 and LY294002 not only abolished GM-CSF induced IL-4 and IL-6 release, but also inhibited GM-CSF induced phosphorylation of ERK and Akt.CONCLUSION: GM-CSF can modulate expression of PARs on mast cells and stimulate IL-4 and IL-6 release from mast cells. The action of GM-CSF on induction of cytokine release from P815 cells is most likely through activation of Akt, ERK and STAT3 signaling pathways. Given the supporting data outlined above, it would seem that GM-CSF can stimulate both Th1 and Th2 type responses depending on the conditions in the immune response and inflammation, and which would have a central role in the network.