Protease-activated receptor-2 (PAR-2)-modulated tight junctions (TJs) have been suggested to be involved in the pathogenesis of chronic inflammatory diseases. However, immunopathogenesis remains to be investigated among patients with allergic rhinitis (AR). This study sought to investigate the role of PAR-2 in the modulation of epithelial barrier function and the expression of TJs in the nasal mucosa of AR patients. The expression of TJs and PAR-2 of the nasal mucosa in AR patients and control subjects by immunohistochemistry, quantitative real-time polymerase chain reaction (qRT-PCR), and western blotting. In vitro, Primary human nasal epithelial cells (pHNECs) of AR patients were stimulated by Der p1 to analyze the correlation between PAR-2 and TJs expression. Der p1-induced pHNECs were treated with the PAR-2 agonist SLIGRL-NH2 and antagonist FSLLRY-NH2. Fluorescein isothiocyanate–dextran 4 kDa detection was employed as an indicator of epithelial permeability. Lower expression levels of TJs in the nasal epithelium of AR patients were observed in comparison with that in control subjects. The PAR-2 level was markedly increased following treatment with 1,000 ng/mL of Der p1 for 24 hours in a cellular model of AR. The expression of PAR-2 was increased in Der p1-induced pHNECs of AR patients and correlated inversely with zonula occlidens (ZO)-1 and claudin-1. Treatment with Der p1 further downregulated TJs expression and promoted an increased epithelial permeability in Der p1-induced pHNECs. PAR-2 could downregulate the expression of ZO-1 and claudin-1, which is involved in epithelial barrier dysfunction in AR.

Background: The pathogenesis of chronic rhinosinusitis (CRS) is not yet clear. microRNAs are widely involved in a number of physiological and pathological processes, of which microRNA-146a (miR-146a) plays an important role in innate immunity, inflammatory response, and other pathophysiological processes. Mucins (MUCs) are important components of secreted mucus, of which MUC5AC is the major MUC secreted in the normal airway. Objective: This study was performed to examine human neutrophil elastase (HNE)-induced MUC5AC overexpression in CRS via miR-146a. Methods: miR-146a, HNE, epidermal growth factor receptor (EGFR), and MUC5AC expression in the sinonasal mucosa were determined using quantitative real-time polymerase chain reaction (qRT-PCR). EGFR, phosphorylated EGFR (pEGFR), and MUC5AC expression were determined in primary cultures of human nasal epithelial cells (HNECs). We examined the expression of miR-146a, MUC5AC, EGFR, and pEGFR by transfecting HNECs with miR-146a mimics and negative control (NC). Moreover, dual-luciferase reporter gene assays were used to validate EGFR as an hsa-miR-146a target gene. Results: miR-146a was significantly downregulated, and HNE, EGFR, and MUC5AC were upregulated in CRS patients both with and without nasal polyps. In the in vitro cell experiment, MUC5AC was significantly downregulated after use of an EGFR-specific inhibitor (AG1478). Upon addition of miR-146a inhibitor, miR-146a was downregulated, while MUC5AC was upregulated. MUC5AC was suppressed in normal primary HNECs by miR-146a mimic and pEGFR was downregulated. The results of dual-luciferase reporter assays showed that the luciferase activities were markedly inhibited in the pGL3-EGFR-3′ UTR+miR-146a mimic group compared with the pGL3+ miR-146a mimic group, suggesting that EGFR is a target gene for miR-146a. Conclusion: In HNE-induced CRS, miR-146a downregulates the expression of MUC5AC by inhibiting the activation of EGFR, and EGFR is a target gene of miR-146a.

Background: Hypersecretion of mucin 5AC (MUC5AC) is a prominent feature of chronic rhinosinusitis with nasal polyps (CRSwNP) and autophagy plays a pivotal role in this process. TNF receptor-associated factor 6 (TRAF6) functions as a signal transducer in many inflammation diseases, whereas the correlation between TRAF6 and autophagy in CRSwNP remains unclear. Objective: To investigate the role of TRAF6 in the human neutrophil elastase (HNE)-induced autophagy and mucin MUC5AC over-expression in CRSwNP. Methods: Tissue specimens were obtained from control subjects and patients with CRSwNP. The relationships between HNE, TRAF6, autophagy, and MUC5AC were investigated. The effect of TRAF6 on HNE-mediated autophagy and hypersecretion of MUC5AC was assessed by in-vitro culture of HNECs treated with human recombinant HNE. Results: Patients with CRSwNP had more protein expression of HNE, MUC5AC, TRAF6, and light chain (LC3B), and increased levels of Beclin-1(BECN1) and autophagy-related gene 5 (ATG5) in mRNA level. Treatment of nasal epithelial cells with recombinant HNE induced the upregulation of TRAF6, autophagy, and MUC5AC. Alternatively, si-TRAF6 or autophagy inhibitor treatment mitigates the hyperexpression of MUC5AC before incubating with recombinant HNE. Conclusion: HNE promotes autophagy through TRAF6, resulting in hyperexpression of MUC5AC in CRSwNP.

Background: Chronic rhinosinusitis (CRS) is a heterogeneous disease. The pathogenesis of chronic sinusitis is still unclear; however, the nasal cavity and paranasal sinuses are commonly affected by type 2 inflammation, which is caused by Th2 cytokines such as interleukin (IL)-5, IL-4, and IL-13. Previous studies have shown that pendrin promotes local infiltration of neutrophils through the production of human neutrophil elastase (HNE), which is essential for the secretion of mucin 5AC (MUC5AC) in chronic inflammatory diseases of the lower respiratory tract. This study investigated pendrin expression and its relationship to mucin in type 2 inflammation. Methods: A total of 40 patients (10 CRS patients with nasal polyps,10 CRS patients without nasal polyps, and 20 nasal septum deviation patients) were included in this study and were divided into the CRS group and the NC group. A normal nasal mucosa tissue culture model was established in vitro. IL-13 was used to stimulate primary cultures of human nasal epithelial cells (HNECs). Western blot (WB), enzyme-linked immunosorbent assay (ELISA), and quantitative real-time polymerase chain reaction (qRT-PCR) were used to detect the expression of pendrin, MUC5AC, and MUC5B. After transfecting HNECs with siRNA pendrin or negative control (NC), EGF receptor (EGFR), HNE, MUC5AC, and MUC5B expression were analyzed using qRT-PCR, WB, or ELISA in terms of their relationships with pendrin. Pendrin expression in the tissue was also analyzed. Results: After IL-13 stimulation, pendrin, MUC5AC, and MUC5B expression levels were upregulated; the optimal concentration of IL-13 was 50 ng/mL. The expression levels of HNE, EGFR, MUC5AC, and MUC5B were downregulated after transfection with siRNA pendrin-1650. Pendrin expression in the NC group was lower than in the CRS group. Conclusion: IL-13 is implicated in the inflammation of nasal mucosa, and pendrin is closely related to the excessive secretion of mucin. The expression of mucin is downregulated after transfection with siRNA pendrin. There is a positive relationship between pendrin and EFGR/HNE. Moreover, pendrin plays an important role in type 2 inflammation.