Tryptase Activates the Mitogen-Activated Protein Kinase/Activator Protein-1 Pathway in Human Peripheral Blood Eosinophils, Causing Cytokine Production and Release

Abstract

We have previously shown that mast cells enhance eosinophil survival and activation. In this study we further characterized mast cell activity toward eosinophils. Sonicate of both rat peritoneal mast cells and the human mast cell line 1 (HMC-1) induced a concentration-dependent IL-6 and IL-8 release from human peripheral blood eosinophils (ELISA). HMC-1-induced IL-8 release was significantly reduced by the tryptase inhibitors GW-45 and GW-58 (90 and 87%, respectively, at an optimal concentration) but not by anti-stem cell factor, anti-TNF-α, or anti-IFN-γ neutralizing Abs or by the antihistamine drugs pyrilamine and cimetidine. In a manner similar to HMC-1, human recombinant tryptase induced the expression of mRNA for IL-8 (RT-PCR) and caused IL-8 release from the eosinophils. Addition of cycloheximide, actinomycin D, dexamethasone, PD 98059, curcumin, or SB 202190 completely inhibited the tryptase-induced IL-6 and IL-8 release. In contrast, cyclosporin A had no effect on tryptase-induced IL-8 release. Tryptase caused phosphorylation of extracellular signal-regulated kinases 1 and 2, c-Jun N-terminal kinases 1 and 2, and p38 (Western blot). Tryptase also induced the translocation of c-Jun from the cytosol to the nucleus (confocal microscopy) and enhanced AP-1 binding activity to the DNA (EMSA). Eosinophils were found to express proteinase-activated receptor 2 (FACS). When eosinophils were incubated with tryptase in the presence of anti-proteinase-activated receptor 2 antagonist Abs a significant decrease in the IL-6 and IL-8 release occurred. In summary, we have demonstrated that the preformed mast cell mediator tryptase induces cytokine production and release in human peripheral blood eosinophils by the mitogen-activated protein kinase/AP-1 pathway.

Neuropeptide Release from Dental Pulp Cells by RgpB via Proteinase-Activated Receptor-2 Signaling

“…As found in RgpB-elicited HPC neuropeptides release (Fig. 7, C-F), eosinophil PAR-2 activation by tryptase leads to activation of the MAPKs/AP-1 pathway, causing cytokine release (59). The MAPKs/AP-1 pathway may be linked to PAR-2-mediated releasing events.…”

Eotaxin Selectively Binds Heparin

“…Mast cells and eosinophils are both components of the innate arm of the CD4 ϩ Th2-mediated immune responses, and co-localize in many Th2-mediated inflammatory reactions that occur during allergy and parasitic infections. A number of mast cell-derived mediators has been shown to prime or activate eosinophil responses, whereas eosinophil-derived mediators can also directly affect mast cells responses (41)(42)(43)(44)(45)(46)(47)(48)(49)(50)(51). In fact, mast celldeficient mice develop less eosinophilia than wild-type mice in models of allergic airways disease (AAD) (52).…”

Role of Protease-activated Receptors in the Vascular System

“…We observed that trypsin induced a transient [Ca 2+ ]i elevation mainly due to Ca 2+ release in the vascular endothelial cells (73). PAR-2 was also reported to activate mitogen-activated protein kinase (74)(75)(76), protein-tyrosine phosphatase SHP2 (77) and tyrosine kinase pathways (78), which could contribute to PAR-2-mediated cytokine production (74), mitogenic signaling (77) and mucin secretion in the rat sublingual gland (78).…”