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Abstract: Although nasal hyperreactivity (NHR) is a common feature in patients suffering from allergic and nonallergic rhinitis, it is widely neglected during history taking, underdiagnosed in the majority of patients with rhinitis and rhinosinusitis, not considered as an outcome parameter in clinical trials on novel treatments for rhinitis and rhinosinusitis, and no target for routine treatment. In contrast to the simple nature of diagnosing NHR by a history of nasal symptoms induced by nonspecific exogenous and/or endogenous triggers, quantification is hardly performed in routine clinic given the lack of a simple tool for its diagnosis. So far, limited efforts have been invested into gaining better insight in the underlying pathophysiology of NHR, helping us to explain why some patients with inflammation develop NHR and others not. Of note, environmental and microbial factors have been reported to influence NHR, contributing to the complex nature of understanding the development of NHR. As a consequence of the neglect of NHR as a key clinical feature of rhinitis and chronic rhinosinusitis (CRS), patients with NHR might be suboptimally controlled and/or dissatisfied with current treatment. We here aim to provide a comprehensive overview of current knowledge on the pathophysiology, and the available tools to diagnose and treat NHR. [ABSTRACT FROM AUTHOR]

Abstract: Background: Nasal hyperreactivity (NHR) is an important clinical feature of allergic rhinitis (AR). The efficacy of MP29‐02 (azelastine hydrochloride (AZE) and fluticasone propionate [FP]) nasal spray on local inflammatory mediators and NHR in AR is unknown. We tested if MP29‐02 decreases inflammatory mediators and NHR in AR and if this effect is due to restoration of nasal epithelial barrier function. Methods: A 4‐week double‐blinded placebo‐controlled trial with MP29‐02 treatment was conducted in 28 patients with house dust mite (HDM) AR. The presence of NHR was evaluated by measuring reduction in nasal flow upon cold dry air exposure. The effects of AZE ± FP on barrier integrity and airway inflammation were studied in a murine model of HDM‐induced NHR and on reduced activation of murine sensory neurons and human mast cells. Results: MP29‐02 but not placebo reduced NHR (P < .0001 vs P = .21), levels of substance P (P = .026 vs P = .941), and β‐hexosaminidase (P = .036 vs P = .632) in human nasal secretions. In wild‐type C57BL6 mice, the reduction in β‐hexosaminidase levels (P < .0001) by AZE + FP treatment upon HDM challenge was found in parallel with a decreased transmucosal passage (P = .0012) and completely reversed eosinophilic inflammation (P = .0013). In vitro, repeated applications of AZE + FP desensitized sensory neurons expressing the transient receptor potential channels TRPA1 and TRPV1. AZE + FP reduced MC degranulation to the same extent as AZE alone. Conclusion: MP29‐02 treatment reduces inflammatory mediators and NHR in AR. The effects of AZE + FP on MC degranulation, nasal epithelial barrier integrity, and TRP channels provide novel insights into the pathophysiology of allergic rhinitis. [ABSTRACT FROM AUTHOR]