Human cystatin SN is an endogenous protease inhibitor that prevents allergic rhinitis.

BACKGROUND: Protease allergens disrupt epithelial barriers to exert their allergenicity. Cystatin SN (encoded by CST1) is an endogenous cysteine protease inhibitor upregulated in nasal epithelia in patients with allergic rhinitis (AR). OBJECTIVE: We sought to investigate the protective effect of human cystatin SN on AR symptoms using pollen-induced AR mouse models. METHODS: We performed an in vitro protease activity assay to evaluate the effect of recombinant human cystatin SN (rhCystatin SN) on Japanese cedar (JC) or ragweed proteases. A human nasal epithelial cell line, RPMI 2650, was used to examine tight junction (TJ) disruption in vitro. Mice were sensitized and nasally challenged with JC or ragweed pollens with or without rhCystatin SN to examine the effect of rhCystatin SN on AR symptoms and the epithelial barrier in vivo. Because mice lack CST1, we generated transgenic (Tg) mice expressing human CST1 under control of its genomic control region (hCST1-Tg mice) to examine the role of cystatin SN in physiologically expressed conditions. RESULTS: rhCystatin SN inhibited JC but not ragweed protease activities and prevented JC-induced but not ragweed-induced TJ disruption in vitro. Exogenous administration of rhCystatin SN ameliorated JC-induced but not ragweed-induced sneezing and nasal TJ disruption in vivo. Furthermore, hCST1-Tg mice showed decreased JC-induced but not ragweed-induced sneezing symptoms and nasal TJ disruption compared with wild-type mice. CONCLUSION: Human cystatin SN suppresses AR symptoms through inhibiting allergen protease activities and protecting the nasal TJ barrier in an allergen-specific manner. We propose that upregulation of nasal endogenous protease inhibitors, including cystatin SN, is a novel therapeutic strategy for protease allergen-induced AR.

Murine allergic rhinitis and nasal Th2 activation are mediated via TSLP- and IL-33-signaling pathways.

Thymic stromal lymphopoietin (TSLP) and IL-33 are epithelium-derived proallergic cytokines that contribute to allergic diseases. Although the involvement of TSLP in allergic rhinitis (AR) is suggested, the exact role of TSLP in AR is poorly understood. Furthermore, the relative contribution of TSLP and IL-33 in nasal allergic responses has not been described. In this study, we examined the roles of TSLP and IL-33 in AR by analyzing acute and chronic AR models. Acute AR mice were intraperitoneally immunized with ragweed, then intranasally challenged with ragweed pollen for four consecutive days. Chronic AR mice were nasally administrated ragweed pollen on consecutive days for 3 weeks. In both models, TSLP receptor (TSLPR)-deficient mice showed defective sneezing responses and reduced serum ragweed-specific IgE levels compared with wild-type (WT) mice. Analyses of bone-marrow chimeric mice demonstrated that hematopoietic cells were responsible for defective sneezing in TSLPR-deficient mice. In addition, FcεRI(+)-cell-specific TSLPR-deficient mice showed partial but significant reduction in sneezing responses. Of note, Th2 activation and nasal eosinophilia were comparable between WT and TSLPR-deficient mice. ST2- and IL-33-deficient mice showed defective Th2 activation and nasal eosinophilia to acute, but not chronic, ragweed exposure. TSLPR and ST2 double-deficient mice showed defective Th2 activation and nasal eosinophilia even after chronic ragweed exposure. These results demonstrate that TSLPR signaling is critical for the early phase response of AR by controlling the IgE-mast-cell/basophil pathway. The IL-33/ST2 pathway is central to nasal Th2 activation during acute allergen exposure, but both TSLPR and ST2 contribute to Th2 responses in chronically allergen-exposed mice.

B cell-intrinsic MyD88 signaling is essential for IgE responses in lungs exposed to pollen allergens.

Allergen-specific IgE is linked to asthma pathogenesis, but the underlying mechanisms of IgE production in response to allergen exposure are poorly understood. In this article, we show that B cell-intrinsic MyD88 is essential for IgE/IgG1 production evoked by ragweed pollen instilled into lungs. MyD88-deficient mice showed defective IgE/IgG1 production and germinal center responses to lung instillation of ragweed pollen. However, MyD88 was dispensable for dendritic cell activation and Th2 cell development. B cell-specific deletion of MyD88 replicated the defective Ab production observed in MyD88-deficient mice. Although ragweed pollen contains TLR ligands, TLR2/4/9-deficient mice developed normal allergic responses to ragweed pollen. However, anti-IL-1R1 Ab-treated mice and IL-18-deficient mice showed decreased IgE/IgG1 production with normal Th2 development. Furthermore, B cell-specific MyD88-deficient mice showed reduced IgE/IgG1 production in response to lung instillation of OVA together with IL-1α, IL-1ß, or IL-18. Thus, pollen instillation into lungs induces IL-1α/ß and IL-18 production, which activates B cell-intrinsic MyD88 signaling to promote germinal center responses and IgE/IgG1 production.

Nasal sensitization with ragweed pollen induces local-allergic-rhinitis-like symptoms in mice.

Recently, the concept of local allergic rhinitis (LAR) was established, namely rhinitis symptoms with local IgE production and negative serum antigen-specific IgE. However, the natural course of LAR development and the disease pathogenesis is poorly understood. This study investigated the pathophysiology of mice with allergic rhinitis that initially sensitized with ragweed pollen through the nasal route. Mice were nasally administrated ragweed pollen over consecutive days without prior systemic immunization of the allergen. Serial nasal sensitization of ragweed pollen induced an allergen-specific increase in sneezing, eosinophilic infiltration, and the production of local IgE by day 7, but serum antigen-specific IgE was not detected. Th2 cells accumulated in nose and cervical lymph nodes as early as day 3. These symptoms are characteristic of human LAR. Continual nasal exposure of ragweed pollen for 3 weeks resulted in the onset of classical AR with systemic atopy and adversely affected lung inflammation when the allergen was instilled into the lung. Fcer1a(-/-) mice were defective in sneezing but developed normal eosinophilic infiltration. Contrary, Rag2(-/-) mice were defective in both sneezing and eosinophilic infiltration, suggesting that T cells play a central role in the pathogenesis of the disease. These observations demonstrate nasal allergen sensitization to non-atopic individuals can induce LAR. Because local Th2 cell accumulation is the first sign and Th2 cells have a central role in the disease, a T-cell-based approach may aid the diagnosis and treatment of LAR.

A critical role of IL-33 in experimental allergic rhinitis.

BACKGROUND: We reported previously that serum levels of IL-33 are significantly increased in patients with allergic rhinitis (AR). However, very little is known about the role of IL-33 for the development of AR. OBJECTIVE: We thought to develop a novel murine model of ragweed pollen-specific AR and examined the pathologic role for ragweed-induced IL-33 in the development of AR manifestation using IL-33-deficient (il33(-/-)) mice. METHODS: Ragweed-immunized and ragweed-challenged mice were examined for early- and late-phase nasal responses. IL-33 protein expression in the nasal epithelial cells of the AR murine model and patients with AR were assessed by using confocal microscopy. RESULTS: After nasal challenge with ragweed pollen, ragweed-immunized wild-type mice manifested early-phase (sneezing) and late-phase (eosinophilic and basophilic accumulation) responses. In contrast, il33(-/-) and FcεRI(-/-) mice did not have both early- and late-phase AR responses. IL-33 protein was constitutively expressed in the nucleus of nasal epithelial cells and was promptly released into nasal fluids in response to nasal exposure to ragweed pollen. In human subjects we revealed constitutive expression of IL-33 protein in the nasal epithelial cells of healthy control subjects and downregulated expression of IL-33 protein in inflamed nasal epithelial cells of patients with AR. IL-33-stimulated mast cells and basophils contributed to the early- and late-phase AR manifestation through increasing histamine release and production of chemoattractants for eosinophils/basophils, respectively. CONCLUSIONS: Ragweed pollen-driven endogenous IL-33 contributed to the development of AR responses. IL-33 might present an important therapeutic target for the prevention of AR.