Protease-activated receptor 2 activation of myeloid dendritic cells regulates allergic airway inflammation

Abstract

BackgroundA common characteristic of allergens is that they contain proteases that can activate protease-activated receptor (PAR-2); however the mechanism by which PAR-2 regulates allergic airway inflammation is unclear.MethodsMice (wild type and PAR-2-deficient) were sensitized using German cockroach (GC) feces (frass), the isolated protease from GC frass, or through adoptive transfer of GC frass-treated bone marrow-derived dendritic cells (BMDC) and measurements of airway inflammation (cellular infiltration, cytokine expression, and mucin production), serum IgE levels and airway hyperresponsiveness (AHR) were assessed. BMDC were cultured, treated with GC frass and assessed for cytokine production. PAR-2 expression on pulmonary mDCs was determined by flow cytometry.ResultsExposure to GC frass induced AHR and airway inflammation in wild type mice; however PAR-2-deficient mice had significantly attenuated responses. To directly investigate the role of the protease, we isolated the protease from GC frass and administered the endotoxin-free protease into the airways of mice in the presence of OVA. GC frass proteases were sufficient to promote the development of AHR, serum IgE, and Th2 cytokine production. PAR-2 expression on mDC was upregulated following GC frass exposure, but the presence of a functional PAR-2 did not alter antigen uptake. To determine if PAR-2 activation led to differential cytokine production, we cultured BMDC in the presence of GM-CSF and treated these cells ex vivo with GC frass. PAR-2-deficient BMDC released significantly less IL-6, IL-23 and TNFα compared to BMDC from wild type mice, suggesting PAR-2 activation was important in Th2/Th17 skewing cytokine production. To determine the role for PAR-2 on mDCs on the initiation of allergic airway inflammation, BMDCs from wild type and PAR-2-deficient mice were treated in the presence or absence of GC frass and then adoptively transferred into the airway of wild type mice. Importantly, GC frass-stimulated wild type BMDCs were sufficient to induce AHR and allergic airway inflammation, while GC frass-stimulated PAR-2-deficient BMDC had attenuated responses.ConclusionsTogether these data suggest an important role for allergen activation of PAR-2 on mDCs in mediating Th2/Th17 cytokine production and allergic airway responses.

Integrated Innate Mechanisms Involved in Airway Allergic Inflammation to the Serine Protease Subtilisin

“…3D). Finally, because both epithelial cells and hematopoietic cells express PAR-2 (27, 35, 36), we generated mixed bone marrow (BM) chimeras that would allow us to examine independently the contribution of different cell types expressing PAR-2. For this, irradiated PAR-2 - / - mice were reconstituted with WT BM (referred as WT BM to PAR-2 - / - ), and vice-versa (PAR-2 - / - BM to WT).…”

The role of dendritic cells in asthma

“…This activation has been shown to induce both allergic airway inflammation and airway hyperresponsiveness in a murine model of cockroach allergy. 67 …”

Allergen-induced IL-6 trans-signaling activates γδ T cells to promote type 2 and type 17 airway inflammation

“…[16][17][18] In contrast to the canonical intraperitoneal ovalbumin/alum model of experimental asthma, which triggers IL-6-dependent T H 2 cytokine responses and eosinophilic inflammation, 15 the HDM and cockroach models promote mixed granulocytic inflammation, with increased type 2 and type 17 cytokine responses in mice. [19][20][21][22] This provided us with a unique opportunity to dissect the role of classical versus IL-6 trans-signaling in the development of mixed granulocytic asthma in response to 2 clinically relevant allergens.…”