German Cockroach Proteases and Protease-Activated Receptor-2 Regulate Chemokine Production and Dendritic Cell Recruitment

Abstract

We recently showed that serine proteases in German cockroach (GC) feces (frass) decreased experimental asthma through the activation of protease-activated receptor (PAR)-2. Since dendritic cells (DCs) play an important role in the initiation of asthma, we queried the role of GC frass proteases in modulating CCL20 (chemokine C-C motif ligand 20) and granulocyte macrophage colony-stimulating factor (GM-CSF) production, factors that regulate pulmonary DCs. A single exposure to GC frass resulted in a rapid, but transient, increase in GM-CSF and a steady increase in CCL20 in the airways of mice. Instillation of protease-depleted GC frass or instillation of GC frass in PAR-2-deficient mice significantly decreased chemokine release. A specific PAR-2-activating peptide was also sufficient to induce CCL20 production. To directly assess the role of the GC frass protease in chemokine release, we enriched the protease from GC frass and confirmed that the protease was sufficient to induce both GM-CSF and CCL20 production in vivo. Primary airway epithelial cells produced both GM-CSF and CCL20 in a protease- and PAR-2-dependent manner. Finally, we show a decreased percentage of myeloid DCs in the lung following allergen exposure in PAR-2-deficient mice compared to wild-type mice. However, there was no difference in GC frass uptake. Our data indicate that, through the activation of PAR-2, allergen-derived proteases are sufficient to induce CCL20 and GM-CSF production in the airways. This leads to increased recruitment and/or differentiation of myeloid DC populations in the lungs and likely plays an important role in the initiation of allergic airway responses.

The role of dendritic cells in asthma

“…This novel pathway of stimulation by HDM allergen led to airway epithelial cell secretion of CCL20, 62 a chemokine crucial for the initial recruitment of DCs to the lung during allergic airway responses. 59 Similar results were demonstrated in asthmatic patients in a study conducted by Pichavant et al 46 Stimulation with the dust mite allergen Der p 1, the major component of Dermatophagoides pteronyssinus, induced increased CCL20 production from bronchial epithelial cells of asthmatic patients sensitized to HDM, leading to increased migration of Langerhans cell precursors, a subpopulation of mDCs that reside at mucosal surfaces. 46 Another mechanism underlying allergen-induced production of CCL20 involves interactions between protease-activated receptors (PARs) expressed on airway epithelial cells and allergen-associated proteases.…”

“…Through the activation of PAR-2, allergen-derived proteases induce both CCL20 and GM-CSF production in the airways, leading to increased recruitment, differentiation, or both of mDC populations in the lungs. 59 IL-1b and TNF. IL-1b and TNF are pleiotropic cytokines that have major roles in initiating inflammatory and innate immune responses.…”

Functional inhibition of PAR2 alleviates allergen‐induced airway hyperresponsiveness and inflammation

“…administered PAR 2 blocking antibody reaches the lungs and binds to cells lining the airways, which we postulate are airway epithelial cells. PAR 2 -mediated activation of epithelial cells releases cytokines that may mediate asthma [17,31,32] and preventing the release of these cytokines may dampen allergic airway inflammation. We have shown here that pro-inflammatory factors that can be produced by the airway epithelium, such as eotaxin, GM-CSF and CXCL1, are decreased following PAR 2 blockade.…”

Tight junctions in pulmonary epithelia during lung inflammation

“…Bacterial and viral infections induce TNF-α, IL-1α, IL-1β, IL-6, IL-8 and IL-18 [21, 77, 101, 115, 143]. In addition, allergic agents such like cationic peptides [21], proteolytic active [12, 29, 58, 59, 68, 117] as well as non-proteolytic allergens [98] induce the release of IL-6, IL-8, granulocyte macrophage colony-stimulating factor (GM-CSF) and monocyte chemotractant protein 1 (MCP-1). The response to proteolytically active allergens involves store-operated Ca 2+ entry in epithelial cells [58, 59], and it should be noted that bacterial exotoxins also activate store-operated Ca 2+ entry [128].…”