Functional inhibition of PAR2 alleviates allergen-induced airway hyperresponsiveness and inflammation.

BACKGROUND: Proteinase-activated receptor 2 (PAR2 ) is a G protein-coupled receptor activated by trypsin-like serine proteinases. PAR2 activation has been associated with inflammation including allergic airway inflammation. We have also shown that PAR2 activation in the airways leads to allergic sensitization. The exact contribution of PAR2 in the development of eosinophilic inflammation and airway hyperresponsiveness (AHR) in sensitized individuals is not clear. OBJECTIVE: To investigate whether functional inhibition of PAR2 during allergen challenge of allergic mice would inhibit allergen-induced AHR and inflammation in mouse models of asthma. METHODS: Mice were sensitized and challenged with ovalbumin (OVA) or cockroach extract (CE). To investigate the role of PAR2 in the development of AHR and airway inflammation, we administered blocking anti-PAR2 antibodies, or a cell permeable peptide inhibitor of PAR2 signalling, pepducin, i.n. before allergen challenges and then assessed AHR and airway inflammation. RESULTS: Administration of anti-PAR2 antibodies significantly inhibited OVA- and CE-induced AHR and airway inflammation. In particular, two anti-PAR2 antibodies, the monoclonal SAM-11 and polyclonal B5, inhibited AHR, airway eosinophilia, the increase of cytokines in the lung tissue and antigen-specific T cell proliferation, but had no effect on antigen-specific IgG and IgE levels. Pepducin was also effective in inhibiting AHR and airway inflammation in an OVA model of allergic airway inflammation. CONCLUSIONS AND CLINICAL RELEVANCE: Functional blockade of PAR2 in the airways during allergen challenge improves allergen-induced AHR and inflammation in mice. Therefore, topical PAR2 blockade in the airways, through anti-PAR2 antibodies or molecules that interrupt PAR2 signalling, has the potential to be used as a therapeutic option in allergic asthma.

Proteinase-activated receptor-2 activation participates in allergic sensitization to house dust mite allergens in a murine model.

BACKGROUND: Many aeroallergens contain proteinase activity and are able to induce allergic sensitization when presented to mucosal surfaces. Some of these allergens activate proteinase-activated receptor-2 (PAR2 ). OBJECTIVE: To determine the role of PAR2 activation in a murine house dust mite (HDM) allergy model. METHODS: We sensitized and challenged PAR2 -deficient mice with HDM, and examined allergic outcomes compared to wild-type animals. To focus on the role of PAR2 in allergic sensitization, we administered a PAR2 blocking antibody to wild-type animals during the sensitization phase and examined the outcomes immediately after sensitization or following subsequent allergen challenge. RESULTS: We found PAR2 -deficient mice sensitized and challenged with HDM failed to develop airway inflammation, did not produce HDM-specific IgG1 and had less IL-4 mRNA in the lungs than wild-type animals. Prevention of PAR2 activation during sensitization in wild-type mice diminished the levels of Th2 mediators, including IL-4, IL-5 and IL-13, in the lungs. Blocking PAR2 during the sensitization phase also led to decreased manifestations of allergic disease, including airway hyperresponsiveness (AHR) and airway inflammation following subsequent allergen challenge. HDM-induced proliferation of splenocytes obtained from animals sensitized in the presence of PAR2 antibody was reduced relative to those that did not receive antibody. The effect of PAR2 blockade could be transferred to naïve mice through splenic CD4(+) T cells from sensitized mice. CONCLUSIONS AND CLINICAL RELEVANCE: PAR2 activation plays a key role during the sensitization phase of our HDM allergy model, leading to increased lung cytokine production and augmented lung reactivity. PAR2 activation is a common mechanism for sensitization to a wide variety of allergens and is therefore a potential pharmacological target to prevent allergy.

Interleukin mRNA changes in mast cells stimulated by TSL-1 antigens.

In this work we analyzed by RT-PCR, the mRNA changes for IL-4, IL-10, TNF and IFN (induced by TSL-1 antigens in a rat mast cell line (HRMC) with mucosal characteristics. The data obtained showed an increase of 65 and 52% in mRNA expression for IL-4 and TNF respectively and a decrease of 59 and 55% in mRNAs for IFN gamma and IL-10. Our results suggest that TSL-1 antigens induce the release from MC of regulatory molecules, such as IL-4 by an IgE independent mechanism. Our data also provides important information related to the ability of MC to participate not only in the effector phase against the infectious agents, but also in the orchestration of the immune response by the host against parasites.