Up-date on neuro-immune mechanisms involved in allergic and non-allergic rhinitis

Inflammatory mediators in nasal secretions of patients with nasal polyposis with and without aspirin sensitivity

BACKGROUND

The aim of this cross-sectional study was to compare the levels of inflammatory mediators in nasal secretions in patients with aspirin-exacerbated respiratory disease (AERD) and in those with nasal polyposis (NP) without aspirin-sensitivity and to correlate nasal fluid mediator concentrations with clinical parameters of the disease.

METHODS

A total of 30 patients with AERD, 30 chronic rhinosinusitis (CRS) with NP patients without aspirin sensitivity (CRSwNP), and 30 control subjects without inflammation of the nasal mucosa (C), selected for surgical treatment entered the study. The total nasal symptom score (TNSS), endoscopic score (ES), and Lund-Mackay score (LMS), were evaluated. The concentrations of eosinophil cationic protein (ECP), tryptase, heat shock protein 70 (HSP70), substance P and Clara cell protein 16 (CC16) were determined in nasal secretions.

RESULTS

Higher concentrations of ECP, tryptase, and HSP70 were measured in the AERD patients than in the CRSwNP patients and the C group (p < .001; p < .001, respectively for all mediators). However, levels of CC16 were higher in the C group than in the AERD and CRSwNP groups (p < .001; p < .001, respectively). A positive correlation between the TNSS and CC16 and a negative one between CC16 and tryptase levels were found in the C group. The CRSwNP group showed positive correlations between ECP, HSP70, and tryptase and negative correlations between substance P, ES, and LMS, as well as between CC16 and tryptase levels. In the AERD group, we found a positive correlation between HSP70 and ECP levels and a negative correlation between the TNSS and CC16 concentration.

CONCLUSION

The obtained results indicate the increased production of mediators of eosinophil and mast cell function, and the decreased production of biomarker of respiratory epithelial function in AERD patients. Clinical and biochemical parameters correlate in different ways in the AERD and CRSwNP patients.

Evaluation of substance P and bradykinin levels in nasal secretions of patients with nasal polyposis with and without sensitivity to non‐steroidal anti‐inflammatory drugs

Objective

The role of neurogenic inflammation in pathogenesis of chronic rhinitis is well known. However, very little is known about its importance in pathogenesis of nasal polyposis (NP), especially in form of NP which appears as a part of aspirin‐exacerbated respiratory disease (AERD). The aim of this study was to examine the concentrations of neuropeptides substance P (SP) and bradykinin (BK) in nasal secretions of patients with NP.

Methods

Fourteen patients with NP as a part of AERD with mild persistent asthma, 14 patients with NP without aspirin sensitivity, and 14 control subjects without nasal inflammation (C) entered this cross‐sectional study. Clinical parameters (symptoms, endoscopic, and radiological findings) were assessed. The concentrations of SP and BK were measured in the nasal secretion samples using commercial human enzyme immunoassay kits.

Results

The concentration of SP in nasal secretions was significantly higher in NP patients without aspirin sensitivity and AERD patients compared to controls (p = .022; p < .0001, respectively), but higher in AERD than in non‐AERD patients (p = .018). The level of BK in nasal fluid was higher in non‐AERD and AERD NP patients than in controls (p < .0001; p < .0001, respectively), but also higher in AERD than in non‐AERD patients (p < .0001). We found high positive correlations between BK in nasal fluid and Lund–Mackay computed tomography (CT) score in both non‐AERD and AERD groups of NP patients.

Conclusion

Our results suggest more intense release of SP and BK from the nasal mucosa in patients with AERD than in patients with NP who do not have aspirin sensitivity. The strong correlation between concentration of BK in nasal secretions and CT score suggests that BK in nasal fluid could be used as a marker for disease severity as measured by the Lund–Mackay score.

Involvement of galanin and galanin receptor 2 in a mouse model of allergic rhinitis

BACKGROUND

Allergic rhinitis (AR) is caused by allergic reaction to allergens such as pollen. Galanin (GAL), a neuropeptide that regulates inflammatory processes, is widely expressed in the central and peripheral nervous systems. Although neuropeptides are implicated in arthritis and chemically induced ileitis, their roles in AR remain unclear.

METHODS

We developed a murine model of AR and generated control, systemic sensitization, mild AR, and severe AR groups. We examined GAL and GAL receptor (GALR) mRNA and protein levels and localization patterns in each group using reverse transcription PCR, western blotting, and immunohistochemical analyses. Additionally, we evaluated the effects of M871, a GALR2 antagonist, on mice with severe AR.

RESULTS

Gal and Galr2 are expressed in nasal mucosa and brain (control) samples from control and AR mice. GAL and GALR2 were expressed at similar levels and localized to ciliated epithelial and submucosal gland cells of the nasal mucosa in all four groups. Intranasal M871 administration significantly reduced the incidence of nose rubbing behaviors and sneezing (p < 0.001 in 30 min, respectively) in severe AR mice relative to that in controls. Mechanistically, we postulate that GALR2 is expressed in B cells, and M871 administration reduces IgE production, as well as the number of B cells in tissues.

CONCLUSIONS

GAL signaling may not change progressively with increasing nasal sensitization, suggesting that this signaling process exacerbates, rather than directly trigger, AR. GAL-GALR2 signaling likely mediates AR development, suggesting that its inhibition represents a novel therapeutic strategy for AR.

Oxidative Stress and Antioxidant Pathway in Allergic Rhinitis

Oxidative stress is the cause and consequence of redox metabolism in various physiological and pathological conditions. Understanding the molecular pathways underlying oxidative stress and the role of antioxidants could serve as the key to helping treat associated diseases. Allergic rhinitis is a condition that deteriorates the daily function and quality of life of afflicted individuals and is associated with a high socioeconomic burden and prevalence. Recent studies have focused on the role of oxidative stress and antioxidants in allergic rhinitis. This review discusses animal and clinical studies on oxidative markers and the potential therapeutic dietary antioxidants for allergic rhinitis.

Inhibition of TRPA1 reduces airway inflammation and hyperresponsiveness in mice with allergic rhinitis

This study was conducted to investigate whether a transient receptor potential ankyrin 1 (TRPA1) antagonist (HC-030031) can reduce airway inflammation and hyperresponsiveness in a murine allergic rhinitis (AR) model. BALB/c mice were sensitized and challenged by ovalbumin (OVA) to induce AR. HC-030031 or vehicle was administrated to mice via intraperitoneal injection prior to OVA challenges. Nose-scratching events, histopathologic alterations of the airways, and bronchial hyperresponsiveness (BHR) were assessed. Differential cells and proinflammatory cytokines in the nasal lavage (NAL) and bronchoalveolar lavage (BAL) fluid were measured. Expressions of TRPA1 in nasal mucosa were examined by immunohistochemistry. TRPA1-expressing vagal neurons were labeled by immunofluorescent staining. HC-030031-treated AR mice had markedly reduced type-2 inflammation in nasal mucosa and ameliorated-nose-scratching events than AR mice received vehicle. HC-030031 treatment also dramatically reduced leucocyte numbers and IL-8 level in the BAL fluid, inhibited lower airway remodeling and fibrosis, and nearly abolished BHR. HC-0300031 treatment significantly inhibited the upregulated number of TRPA1 expressing nasal epithelial cells and TRPA1 expressing sensory neurons, leading to downregulation of SP in both upper and lower airways. Targeting TRPA1 may represent a promising strategy for treating AR and AR-related asthma.

Naso-ocular neuropeptide interactions in allergic rhinoconjunctivitis, rhinitis, and conjunctivitis

Background

Ocular as well as nasal symptoms contribute to allergic response but remain poorly characterized. The aim of this study was to analyze the levels of substance P (SP), vasoactive intestinal peptide (VIP), and calcitonin gene-related peptide (CGRP) in tears and nasal secretions of patients with allergic rhinoconjunctivitis (ARC), allergic rhinitis, and allergic conjunctivitis, while exploring possible mechanisms of naso-ocular interactions.

Methods

A total of 21 patients with ARC, 17 with allergic rhinitis, 13 with allergic conjunctivitis, and 15 healthy controls were enrolled in the study. Nasal secretions and tears were collected. Patient demographics and clinical characteristics were recorded and levels of substance P, VIP, and CGRP were measured.

Results

SP levels in nasal secretions and tears were significantly higher in the ARC, AR, and AC groups. Similar results were obtained for VIP levels. CGRP levels in tears were also significantly higher in the 3 patient groups. The level of SP was significantly higher in the nasal secretions than in the tears of the ARC, AR, and AC patient groups. The level of VIP was significantly higher in the nasal secretions than in the tears in the ARC and AR groups. The level of CGRP was significantly higher in the nasal secretions than in the tears in the ARC and AC groups. Finally, both of the nasal and tear levels of SP and VIP but not CGRP were positively correlated with the visual analog scale (VAS) score in the patients with ARC.

Conclusion

The results of this study suggested that SP, VIP, and CGRP play important roles in the mechanism of ARC and that nasal neurotransmitters and neuropeptides might have more important roles than those of ocular origin.

Botulinum toxin for chronic rhinitis: A systematic review and meta-analysis

BACKGROUND

Botulinum toxin type A (BTX-A) is a potential treatment for chronic rhinitis. This study aimed to assess the effectiveness and safety of BTX-A in treating patients with chronic rhinitis.

METHODS

Systematic searches of MEDLINE, Scopus, and EMBASE databases were performed. Randomized controlled trials (RCTs) that assessed the efficacy of BTX-A in allergic rhinitis and/or nonallergic rhinitis patients, compared with either placebo or active treatment, were included. The outcomes were total nasal symptom (TNSS), disease-specific quality of life (QOL), and adverse events.

RESULTS

Nine RCTs (340 patients) met the eligibility criteria. Compared with placebo, the ≤ 12-week effects favored BTX-A injection on TNSS (standardized mean difference [SMD] -2.22, 95% confidence interval [CI] -3.27 to -1.17, p < 0.01, four RCTs). Beneficial effects > 12 weeks over placebo (MD -9.69, 95% CI -11.29 to -8.09, p < 0.01, one RCT) were demonstrated up to 24 weeks. However, the benefits were not shown on nasal congestion and individual nasal symptoms. Compared with active comparators (triamcinolone injection, ipratropium bromide, and cetirizine), there was no difference in the < 12-week effect between groups on TNSS. There was no difference between BTX-A and cetirizine on QOL (one RCT). The > 12-week effects on TNSS and individual nasal symptoms favored BTX-A over triamcinolone injection (one RCT). The risk ratio of adverse events favored BTX-A over cetirizine (one RCT).

CONCLUSIONS

BTX-A improved TNSS and QOL in patients with chronic rhinitis. These effects were demonstrated up to 24 weeks post treatment. BTX-A was safe, well tolerated, and may be considered in patients who are refractory to current standard-of-care therapies.

A TRiP Through the Roles of Transient Receptor Potential Cation Channels in Type 2 Upper Airway Inflammation

PURPOSE OF REVIEW

Despite their high prevalence, the pathophysiology of allergic rhinitis (AR) and chronic rhinosinusitis (CRS) remains unclear. Recently, transient receptor potential (TRP) cation channels emerged as important players in type 2 upper airway inflammatory disorders. In this review, we aim to discuss known and yet to be explored roles of TRP channels in the pathophysiology of AR and CRS with nasal polyps.

RECENT FINDINGS

TRP channels participate in a plethora of cellular functions and are expressed on T cells, mast cells, respiratory epithelial cells, and sensory neurons of the upper airways. In chronic upper airway inflammation, TRP vanilloid 1 is mostly studied in relation to nasal hyperreactivity. Several other TRP channels such as TRP vanilloid 4, TRP ankyrin 1, TRP melastatin channels, and TRP canonical channels also have important functions, rendering them potential targets for therapy. The role of TRP channels in type 2 inflammatory upper airway diseases is steadily being uncovered and increasingly recognized. Modulation of TRP channels may offer therapeutic perspectives.

Diagnosis and treatment of non-allergic rhinitis: focus on immunologic mechanisms

INTRODUCTION

Non-allergic rhinitis (NAR) is a heterogeneous nasal disease with high global prevalence. NAR can be subclassified as nonallergic rhinitis with eosinophilia syndrome (NARES), vasomotor rhinitis (VMR), and local allergic rhinitis (LAR). Although the precise factors involved in the etiology of NAR are not clear, there is evidence that immunological factors play an important role in the pathogenesis of NAR. This review provides a comprehensive overview of the immunological and neurogenic mechanisms involved in the diagnosis and treatment of NAR.

AREAS COVERED

This review provides a comprehensive overview of the immunological basis of diagnostic and treatment strategies for NARES, VMR, and LAR. In particular, recently documented molecular and immunological mechanisms of NAR are discussed, which may help to better understand the mechanisms underlying the pathologies of the different endotypes of NAR.

EXPERT OPINION

An increasing number of studies investigating the pathogenesis of NAR suggest that the immunological mechanisms underlying the different subtypes of NAR vary greatly, and are still not fully understood to accurately diagnose these subtypes. Thus, further studies should focus on making diagnosis and treatment of NAR more precise, safe, and effective. A better understanding of the immunological mechanisms involved in NAR should help in the discovery of new diagnostic and treatment strategies.

Bencycloquidium bromide nasal spray is effective and safe for persistent allergic rhinitis: a phase III, multicenter, randomized, double-blinded, placebo-controlled clinical trial

PURPOSE

To investigate the efficacy and safety of bencycloquidium bromide nasal spray (BCQB) in patients with persistent allergic rhinitis (PAR).

METHODS

We enrolled 720 patients from 15 hospitals across China and randomly assigned them into BCQB group or placebo group (90 μg per nostril qid) to receive a 4-week treatment. Visual analog scale (VAS) for rhinorrhea, sneezing, nasal congestion, itching and overall symptoms were recorded by patients every day. Anterior rhinoscopy scoring was completed by doctors on every visit. Adverse events were recorded in detail.

RESULTS

A total of 354 and 351 patients were included in BCQB group and in placebo group. Baseline information was comparable. At the end of the trial, the decrease of VAS for rhinorrhea from baseline was 4.83 ± 2.35 and 2.46 ± 2.34 in BCQB group and placebo group, respectively (P < 0.001). The change ratio from baseline of VAS for rhinorrhea in BCQB group was 72.32%, higher than 31.03% in placebo group (P < 0.001). VAS for other symptoms and overall symptoms also improved significantly in the BCQB group, while no inter-group difference was found in anterior rhinoscopy scoring. The incidence of adverse reaction was similar between the two groups. Most reactions were mild and no severe reactions happened.

CONCLUSION

90 μg BCQB per nostril four times daily is effective and safe in the treatment of rhinorrhea as well as sneezing, nasal congestion and itching for patients with PAR.

RETROSPECTIVELY REGISTERED

ChiCTR2000030924, 2020/3/17.

Prevalence and triggers of self-reported nasal hyperreactivity in adults with asthma

BACKGROUND

Nasal hyperreactivity (NHR) is a common feature of various rhinitis subtypes and represents a novel phenotype of rhinitis. It is being reported in two-thirds of adult rhinitis patients irrespective of the atopic status. Data on the prevalence of NHR in patients with asthma are lacking, as well as the nature of evoking triggers.

METHODS

Postal questionnaires were distributed to an unselected group of asthmatic patients in Leuven (Belgium, n = 190) and completed by 114 patients. In Mexico City (Mexico) and Brasov (Romania), respectively, 97 out of 110 and 80 out of 100 asthmatic patients attending the outpatient clinic completed the questionnaire. Non-asthmatic volunteers were recruited amongst university and hospital co-workers in Leuven (n = 53). The presence of self-reported NHR, the type of triggers evoking nasal and bronchial symptoms, medication use, self-reported allergy, and environmental factors were evaluated.

RESULTS

Overall, 69% of asthma patients reported NHR, with 32% having more than 4 triggers evoking NHR. These triggers included mainly exposure to temperature and humidity changes, cigarette smoke, and strong odours. A higher prevalence of NHR was detected in allergic compared to non-allergic asthma patients (73% vs. 53% p < 0.01). The prevalence of NHR correlated with asthma severity, ranging from 63% (VAS ≤3) to 81% (VAS ≥7). BHR was found more frequently in patients with NHR compared to without NHR (89% vs. 53%, p < 0.0001).

CONCLUSION

NHR represents a clinical phenotype of upper airway disease affecting over two-thirds of asthma patients and correlates with asthma severity. Targeting NHR in patients with asthma is often overlooked and should be reinforced in the future to achieve better symptom control.

International expert consensus on the management of allergic rhinitis (AR) aggravated by air pollutants: Impact of air pollution on patients with AR: Current knowledge and future strategies

Allergic rhinitis affects the quality of life of millions of people worldwide. Air pollution not only causes morbidity, but nearly 3 million people per year die from unhealthy indoor air exposure. Furthermore, allergic rhinitis and air pollution interact. This report summarizes the discussion of an International Expert Consensus on the management of allergic rhinitis aggravated by air pollution. The report begins with a review of indoor and outdoor air pollutants followed by epidemiologic evidence showing the impact of air pollution and climate change on the upper airway and allergic rhinitis. Mechanisms, particularly oxidative stress, potentially explaining the interactions between air pollution and allergic rhinitis are discussed. Treatment for the management of allergic rhinitis aggravated by air pollution primarily involves treating allergic rhinitis by guidelines and reducing exposure to pollutants. Fexofenadine a non-sedating oral antihistamine improves AR symptoms aggravated by air pollution. However, more efficacy studies on other pharmacological therapy of coexisting AR and air pollution are currently lacking.

A Precision Medicine Approach to Rhinitis Evaluation and Management

PURPOSE OF REVIEW

Precision medicine (PM) represents a new paradigm in disease diagnosis, prevention, and treatment. The PM approach focuses on the characterization of different phenotypes and pathogenic pathways in order to allow the selection of specific biomarkers that will be useful in disease management. Rhinitis is a highly prevalent and heterogeneous disease, both in terms of underlying endotypes and clinical presentations. Therefore, to apply the PM principles to the various rhinitis subtypes rise as a meaningful strategy to improve evaluation and treatment.

RECENT FINDINGS

The technology of recombinant allergens has allowed molecular characterization of IgE reactivity of specific individual components of allergenic extracts. Recently published and ongoing clinical trials based on component resolved diagnosis (CRD) bring more precision to allergen immunotherapy for allergic rhinitis. Monoclonal antibodies against various cytokines involved in inflammatory allergic and nonallergic rhinitis endotypes show promissory results.

SUMMARY

Better understanding of pathogenic pathways together with an accurate phenotype classification of patients presented with rhinitis symptoms contributes to point out clinical usefulness of biomarkers and other diagnostic tools, which leads to more accurate environmental control measures, personalized pharmacologic options, and new biological therapy developments.

Determinants of the Nasal Microbiome: Pilot Study of Effects of Intranasal Medication Use

Introduction

A role for bacteria and other microbes has long been suspected in the chronic inflammatory sinonasal diseases. Recent studies utilizing culture-independent, sequence-based identification have demonstrated aberrant shifts in the sinus microbiota of chronic rhinosinusitis subjects, compared with ostensibly healthy controls. Examining how such microbiota shifts occur and the potential for physician-prescribed interventions to influence microbiota dynamics are the topics of the current article.

Methods

The nasal cavity microbiota of 5 subjects was serially examined over an 8-week period using pan-bacterial 16S rRNA gene sequencing. Four of the subjects were administered topical mometasone furoate spray, while 1 subject underwent a mupirocin decolonization procedure in anticipation of orthopedic surgery.

Results

Measures of microbial diversity were unaffected by intranasal treatment in 2 patients and were markedly increased in the remaining 3. The increase in microbial diversity was related to clearance of Moraxella spp. and a simultaneous increase in members of the phylum Actinobacteria. Both effects persisted at least 2 weeks beyond cessation of treatment. Transient changes in the relative abundance of several bacterial genera, including Staphylococcus and Priopionibacteria, were also observed during treatment.

Conclusions

The effects of intranasal steroids on the sinonasal microbiome are poorly understood, despite their widespread use in treating chronic sinonasal inflammatory disorders. In this longitudinal study, administration of intranasal mometasone furoate or mupirocin resulted in shifts in microbial diversity that persisted to some degree following treatment cessation. Further characterization of these effects as well as elucidation of the mechanism(s) underlying these changes is needed.

Endotyping of non-allergic, allergic and mixed rhinitis patients using a broad panel of biomarkers in nasal secretions

Background

Endotyping chronic rhinitis has proven hardest for the subgroup of non-allergic rhinitis (NAR) patients. While IgE-related inflammation is typical for allergic rhinitis (AR), no markers have been found that can be seen to positively identify NAR. A further complication is that AR and NAR might co-exist in patients with mixed rhinitis. As previous studies have considered only a limited number of inflammatory mediators, we wanted to explore whether a wider panel of mediators could help us refine the endotyping in chronic rhinitis patients.

Objective

To endotype chronic rhinitis, and non-allergic rhinitis in particular, with help of molecular or cellular markers.

Method

In this study we included 23 NAR patients without allergen sensitizations and with persistent rhinitis symptoms, 22 pollen sensitized rhinitis patients with seasonal symptoms, 21 mixed rhinitis patients with pollen-related symptoms and persistent symptoms outside of the pollen season, and 23 healthy controls without any symptoms. Nasal secretions were collected outside of pollen season and differences between the endotypes were assessed for a broad range of inflammatory mediators and growths factors using a multiplex ELISA.

Results

Although we were able to identify two new nasal secretion makers (IL-12 and HGF) that were low in mixed and AR patients versus NAR and healthy controls, the most intriguing outcome is that despite investigating 29 general inflammatory mediators and growth factors no clear profile of non-allergic or mixed rhinitis could be found.

Conclusion

Classical inflammatory markers are not able to differentiate between non-allergic or mixed rhinitis patients and healthy controls.

Rapid onset of action and reduced nasal hyperreactivity: new targets in allergic rhinitis management

Background

This article summarizes a EUFOREA symposium, presented during the European Rhinology Research Forum in Brussels (9–10 November 2017; https://www.rhinologyresearch.eu/) which focused on novel pathways and therapeutic approaches in allergic rhinitis (AR).

Main body

AR remains under-diagnosed, under-estimated and under-treated. A key component in understanding the AR landscape has been the realization of a significant mismatch between how physicians instruct AR patients to manage their disease and what AR patients actually do in real life. Data from the Allergy Diary (developed by MACVIA ARIA) showed that AR patients take their medication prn, rapidly switch treatments, often experience poor control, use multiple therapies and stop treatment when symptoms are controlled. Better control of AR may be achievable by using an AR treatment which has a rapid onset of action and which effectively targets breakthrough symptoms. Indeed, AR patients report complete symptom relief, lack of breakthrough symptoms, rapid onset of action, safety and use on an ‘as needed’ basis as key targets for new nasal sprays. MP-AzeFlu comprises intranasal azelastine and fluticasone propionate (FP) in a novel formulation delivered in a single device. It is the first AR treatment to break the 5 min onset of action threshold and provides clinically relevant symptom relief in 15 min, much faster than that noted for FP + oral loratadine. MP-AzeFlu also significantly reduces nasal hyperresponsiveness (NHR) which may be responsible for the breakthrough symptoms frequently reported by AR patients. Mechanisms underlying MP-AzeFlu’s effect include inhibition of mast cell degranulation, stabilization of the mucosal barrier, synergistic inhibition of inflammatory cell recruitment and a unique desensitization of sensory neurons expressing the transient receptor potential A1 and V1 channels.

Conclusion

With the most rapid onset of action and onset of clinically-relevant effect of any AR medication currently available, and proven efficacy in the treatment of NHR, MP-AzeFlu is an AR treatment which provides what patients want, and fits how patients manage their AR in real life.

Non-allergic rhinitis in children: Epidemiological aspects, pathological features, diagnostic methodology and clinical management

Chronic rhinitis is a very common disease, as the prevalence in the general population resulted to be 40%. Allergic rhinitis has been considered to be the most frequent form of chronic rhinitis, as non-allergic rhinitis has been estimated to account for 25%. However, several evidences suggested that non-allergic rhinitis have been underrated, especially in children. In pediatrics, the diagnostic definition of non-allergic rhinitis has been often limited to the exclusion of an allergic sensitization. Actually, local allergic rhinitis has been often misdiagnosed as well as mixed rhinitis has not been recognized in most cases. Nasal cytology is a diagnostic procedure being suitable for routine clinical practice with children and could be a very useful tool to characterize and diagnose non-allergic rhinitis, providing important clues for epidemiological analysis and clinical management.

Denervation of nasal mucosa induced by posterior nasal neurectomy suppresses nasal secretion, not hypersensitivity, in an allergic rhinitis rat model

The posterior nasal nerve is the dominant source of the parasympathetic, sympathetic, and sensory fibers that innervate the nasal respiratory mucosa. Therefore, a posterior nasal neurectomy (PNN) is thought to induce denervation of the nasal mucosa and relieve the nasal symptoms of allergic rhinitis. However, the underlying mechanisms and therapeutic action of PNN remain unknown. To investigate the impact of PNN-induced denervation of the nasal mucosa on allergic rhinitis, we developed a rat model of PNN and examined the effects of PNN on allergic rhinitis in ovalbumin-sensitized rats. This rat model of PNN was characterized by the depletion of nerve fibers, choline acetyltransferase, and neuropeptides (eg, substance P, calcitonin gene-related peptide, vasoactive intestinal peptide, and neuropeptide Y) in the nasal respiratory mucosa. These animals exhibited nasal gland and goblet cell hypertrophy in the septal mucosa and atrophy of the submucosal gland in the lateral nasal wall, as well as reduced nasal secretion due to deficient acetylcholine synthesis. In an ovalbumin-sensitized model of allergic rhinitis, PNN also induced the depletion of nerve fibers, choline acetyltransferase, and neuropeptides in the nasal mucosa and suppressed nasal secretion. However, PNN did not affect mucosal thickening, eosinophil and mast cell infiltration, interleukin-4 and interferon-γ mRNA expression, and allergic symptoms (ie, sneezing and nasal scratching). These results suggest that the peripheral nerves and corresponding neuropeptides regulate nasal secretion, but not hypersensitivity, in allergic rhinitis, and that allergic rhinitis-related mucosal reactions occur in a highly denervated mucosa after PNN. Posterior nasal neurectomy may be a therapeutic option for the treatment of hyperrhinorrhea, but not allergic rhinitis hypersensitivity.

Capsaicin for Rhinitis

Rhinitis is a multifactorial disease characterized by symptoms of sneezing, rhinorrhea, postnasal drip, and nasal congestion. Non-allergic rhinitis is characterized by rhinitis symptoms without systemic sensitization of infectious etiology. Based on endotypes, we can categorize non-allergic rhinitis into an inflammatory endotype with usually eosinophilic inflammation encompassing at least NARES and LAR and part of the drug induced rhinitis (e.g., aspirin intolerance) and a neurogenic endotype encompassing idiopathic rhinitis, gustatory rhinitis, and rhinitis of the elderly. Patients with idiopathic rhinitis have a higher baseline TRPV1 expression in the nasal mucosa than healthy controls. Capsaicin (8-methyl-N-vanillyl-6-nonenamide) is the active component of chili peppers, plants of the genus Capsicum. Capsaicin is unique among naturally occurring irritant compounds because the initial neuronal excitation evoked by it is followed by a long-lasting refractory period, during which the previously excited neurons are no longer responsive to a broad range of stimuli. Patients with idiopathic rhinitis benefit from intranasal treatment with capsaicin. Expression of TRPV1 is reduced in patients with idiopathic rhinitis after capsaicin treatment. Recently, in a Cochrane review, the effectiveness of capsaicin in the management of idiopathic rhinitis was evaluated and the authors concluded that given that many other options do not work well in non-allergic rhinitis, capsaicin is a reasonable option to try under physician supervision. Capsaicin has not been shown to be effective in allergic rhinitis nor in other forms of non-allergic rhinitis like the inflammatory endotypes or other neurogenic endotypes like rhinitis of the elderly or smoking induced rhinitis.

Rhinitis Subtypes, Endotypes, and Definitions

Rhinitis is often seen as posing a small burden. However, rhinitis is a complex disease that is underpinned by a plethora of different mechanisms and causes. Rhinitis is frequently associated with other comorbid conditions but, by itself, is a source of considerable morbidity for patients and creates a significant financial burden on health systems worldwide. This article approaches this condition from both a phenotypic and mechanistic standpoint, focusing on the complexity of characterizing these subtypes. Developing a clearer demarcation of the currently obscure rhinitis phenotypes and endotypes will substantially improve their future prevention and treatment.