Nasal levels of nitric oxide as an outcome variable in allergic upper respiratory tract disease: Influence of atopy and hayfever on nNO

Markers of eosinophilic airway inflammation in patients with asthma and allergic rhinitis

Background: Measurement of airway inflammation is an important step to determine phenotype of asthma and allergic rhinitis (AR). Objective: To assess the level of nitric oxide in exhaled air (FeNO), nasal fraction of nitric oxide (nasal NO), their relationship with clinical control and blood eosinophils in patients with steroid-naive mild and moderate asthma and AR. Methods: One hundred forty-seven patients (65 men), ages 26-49.5 years (mean age, 32 years) with AR (n = 81) or AR and concomitant asthma (n = 46) and 20 healthy subjects were included in a single-center cohort study. All the patients underwent spirometry with reversibility test. Control of asthma and AR was assessed by using the Asthma Control Questionnaire and the visual analog scale, respectively. Levels of FeNO and nasal NO were measured by chemiluminescent analyzer, peripheral blood eosinophils were counted by automatic analyzer. Results: The FeNO level was significantly elevated in the patients with asthma and concomitant AR compared with the healthy subjects and was associated with control of both asthma and AR. There was no correlation between nasal NO and control of AR. Receiver operating characteristic analysis revealed that the level of eosinophils of 150 cells/μL may be a cutoff for lower airway eosinophilic inflammation. Blood eosinophils count was unable to distinguish eosinophilic and non-eosinophilic upper airway inflammation. Conclusion: We confirm that FeNO but not nasal NO is a marker of eosinophilic airway inflammation in patients with mild-moderate steroid-naive AR and concomitant asthma. A blood eosinophil level of ≥150 cells/µL may be a simple marker of eosinophilic airway inflammation in patients with asthma. However, its low specificity requires repeated measurements and use in combination with other biomarkers.

Nasal Nitric Oxide in Children: A Review of Current Outreach in Pediatric Respiratory Medicine

Nasal nitric oxide (nNO) is a gas synthesized by the inducible and constitutive NO synthase (NOS) enzyme in the airway cells of the nasal mucosa. Like lung nitric oxide, it is thought to be associated with airway inflammation in various respiratory diseases in children. The aim of our review was to investigate the current state of use of nNO measurement in children. A comprehensive search was conducted using the Web of Science and PubMed databases specifically targeting publications in the English language, with the following keywords: nasal NO, children, allergic rhinitis, chronic rhinosinusitis, acute rhinosinusitis, primary ciliary dyskinesia (PCD), and cystic fibrosis (CF). We describe the use of nNO in pediatric allergic rhinitis, chronic rhinosinusitis, acute rhinosinusitis, PCD, and CF based on the latest literature. nNO is a noninvasive, clinically applicable test for use in pediatric allergic rhinitis, chronic rhinosinusitis, acute rhinosinusitis, PCD, and CF. It can be used as a complementary method in the diagnosis of these respiratory diseases and as a monitoring method for the treatment of allergic rhinitis and acute and chronic rhinosinusitis.

Clinical Applications of Nasal Nitric Oxide in Allergic Rhinitis: A Review of the Literature

Allergic rhinitis, a common allergic disease affecting a significant number of individuals worldwide, is observed in 25% of children and 40% of adults, with its highest occurrence between the ages of 20 and 40. Its pathogenesis, like other allergic diseases, involves innate and adaptive immune responses, characterized by immunologic hypersensitivity to environmental substances. This response is mediated by type 2 immunity. Within type 2 allergic diseases, certain molecules have been identified as clinical biomarkers that contribute to diagnosis, prognosis, and therapy monitoring. Among these biomarkers, nitric oxide has shown to play a key role in various physiological and pathological processes, including neurotransmission, immunity, inflammation, regulation of mucus and cilia, inhibition of microorganisms, and tumor cell growth. Therefore, measurement of nasal nitric oxide has been proposed as an objective method for monitoring airway obstruction and inflammation in different settings (community, hospital, rehabilitation) and in various clinical conditions, including upper airways diseases of the nose and paranasal sinuses. The purpose of this review is to analyze the potential mechanisms contributing to the production of nasal nitric oxide in allergic rhinitis and other related health issues. Additionally, this review aims to identify potential implications for future research, treatment strategies, and long-term management of symptoms.

International consensus statement on allergy and rhinology: Allergic rhinitis - 2023

BACKGROUND

In the 5 years that have passed since the publication of the 2018 International Consensus Statement on Allergy and Rhinology: Allergic Rhinitis (ICAR-Allergic Rhinitis 2018), the literature has expanded substantially. The ICAR-Allergic Rhinitis 2023 update presents 144 individual topics on allergic rhinitis (AR), expanded by over 40 topics from the 2018 document. Originally presented topics from 2018 have also been reviewed and updated. The executive summary highlights key evidence-based findings and recommendation from the full document.

METHODS

ICAR-Allergic Rhinitis 2023 employed established evidence-based review with recommendation (EBRR) methodology to individually evaluate each topic. Stepwise iterative peer review and consensus was performed for each topic. The final document was then collated and includes the results of this work.

RESULTS

ICAR-Allergic Rhinitis 2023 includes 10 major content areas and 144 individual topics related to AR. For a substantial proportion of topics included, an aggregate grade of evidence is presented, which is determined by collating the levels of evidence for each available study identified in the literature. For topics in which a diagnostic or therapeutic intervention is considered, a recommendation summary is presented, which considers the aggregate grade of evidence, benefit, harm, and cost.

CONCLUSION

The ICAR-Allergic Rhinitis 2023 update provides a comprehensive evaluation of AR and the currently available evidence. It is this evidence that contributes to our current knowledge base and recommendations for patient evaluation and treatment.

The Functional Diversity of Nitric Oxide Synthase Isoforms in Human Nose and Paranasal Sinuses: Contrasting Pathophysiological Aspects in Nasal Allergy and Chronic Rhinosinusitis

The human paranasal sinuses are the major source of intrinsic nitric oxide (NO) production in the human airway. NO plays several roles in the maintenance of physiological homeostasis and the regulation of airway inflammation through the expression of three NO synthase (NOS) isoforms. Measuring NO levels can contribute to the diagnosis and assessment of allergic rhinitis (AR) and chronic rhinosinusitis (CRS). In symptomatic AR patients, pro-inflammatory cytokines upregulate the expression of inducible NOS (iNOS) in the inferior turbinate. Excessive amounts of NO cause oxidative damage to cellular components, leading to the deposition of cytotoxic substances. CRS phenotype and endotype classifications have provided insights into modern treatment strategies. Analyses of the production of sinus NO and its metabolites revealed pathobiological diversity that can be exploited for useful biomarkers. Measuring nasal NO based on different NOS activities is a potent tool for specific interventions targeting molecular pathways underlying CRS endotype-specific inflammation. We provide a comprehensive review of the functional diversity of NOS isoforms in the human sinonasal system in relation to these two major nasal disorders' pathologies. The regulatory mechanisms of NOS expression associated with the substrate bioavailability indicate the involvement of both type 1 and type 2 immune responses.

Nasal nitric oxide testing for allergic rhinitis patients: Systematic review and meta-analysis

BACKGROUND

Nasal nitric oxide (nNO) levels in allergic rhinitis (AR), healthy people or nonallergic rhinitis (NAR) have shown contradicting results in previous studies. By meta-analysis, we reviewed studies that measured nNO in AR patients to assess nNO's ability to discriminate AR from healthy people or NAR.

METHODS

We systematically searched PubMed, Cochrane, Embase, Ovid, Web of Science, Wanfang Data, CNKI until December 15, 2020. Differences were expressed as standardized mean differences (SMD) with 95% confidence interval (CI), by random-effects method.

RESULTS

A total of 10 original studies with 561 AR patients, 327 healthy controls, 123 NAR patients were included in the narrative synthesis and 9 studies in the meta-analysis. nNO in AR was significantly increased compared with healthy controls (SMD: 0.989; 95% CI: 0.402, 1.576; p = .001) or NAR (SMD: 0.680; 95% CI: 0.101, 1.259; p = 0.021). However, subgroup analysis based on measuring process and patient characteristics showed that no significant differences were detected in nNO between AR patients with nasal polyps or sinusitis or marked ostial obstruction and healthy controls.

CONCLUSIONS

nNO is a potential indicator for recognizing AR. Nasal polyps, sinusitis and marked ostial obstruction should be considered before nNO is applied to detect AR.

Role of Exhaled Nasal Nitric Oxide in Distinguishing between Chronic Rhinosinusitis with and without Nasal Polyps

Background

Chronic rhinosinusitis (CRS) with nasal polyps (CRSwNP) and CRS without nasal polyps (CRSsNP) nasal polyps is a global health concern. Several clinical biomarkers, such as inhaled carbon monoxide and exhaled nitric oxide (NO), have been studied to assess the presence and degree of inflammation in the airway mucosa.

Objective

To evaluate the clinical application of exhaled nasal NO (nNO) in distinguishing between CRSwNP and CRSsNP in consideration of the atopic status of patients.

Methods

Eighty-eight patients with CRS and 20 healthy volunteers were recruited for this study. The exhaled nNO level was measured by using a hand-held device. Nasal endoscopy (with Lund-Mackay scoring of CRS) and sinus computed tomographies (CT) were used to evaluate the nasal cavity and sinuses of the subjects. Atopic status was confirmed by using skin prick tests (SPTs).

Results

The mean ∓ standard deviation (SD) levels of nNO in patients with CRSsNP were significantly higher than those in patients with CRSwNP (591 ∓ 153 ppb versus 360 ∓ 181 ppb, p <0.001), whereas patients with CRS exhibited lower levels of nNO compared with the control subjects (449 ∓ 204 ppb versus 881 ∓ 161 ppb, p <0.001). Patients with atopy and with and without nasal polyps exhibited significantly higher levels of nNO compared with patients without atopy (atopic CRSsNP versus nonatopic CRSsNP, 734 ∓ 220 ppb versus 503 ∓ 92 ppb [p <0.001]; atopic CRSwNP versus nonatopic CRSwNP, 518 ∓ 161 ppb versus 299 ∓ 150 ppb [p <0.001]). The levels of nNO were negatively correlated with the Lund-Mackay scores in both atopic (r = -0.45; p = 0.016) and nonatopic (r = -0.600; p <0.001) patients with CRS. Receiver operating characteristic curves differentiated patients as CRSwNP, CRSsNP, and healthy controls, and in atopic and nonatopic subgroups, with acceptable sensitivity and specificity (>70 to 90%).

Conclusion

Exhaled nNO levels can be used to distinguish between patients with CRSwNP and patients with CRSsNP. However, the atopic status of the patient influenced the use of nNO as a diagnostic or monitoring biomarker in CRS.

The role of nasal fractional exhaled nitric oxide as an objective parameter independent of nasal airflow resistance in the diagnosis of allergic rhinitis

OBJECTIVE

Patients with allergic rhinitis (AR) show augmented activity of nitric oxide (NO) metabolism, similar to those in bronchial asthma (BA). We hypothesized that measurements of nasal fractional exhaled NO (FeNO) could be used as an objective marker to detect the presence of AR. Our objective was to clarify the influence of nasal airflow resistance (NAR) on nasal FeNO levels through an exhalation maneuver in symptomatic AR patients. We also examined the diagnostic test validity of the mean nasal FeNO level for disease discrimination by means of a receiver operating characteristic (ROC) curve analysis.

METHODS

Fifty-nine untreated perennial AR patients without BA and 60 healthy controls were enrolled in this retrospective cross-sectional study. The subjective symptoms were recorded and the disease severity was classified according to the Japanese guideline for AR. The oral and nasal FeNO measurements were carried out using a handheld electrochemical analyzer according to the ATS/ERS guidelines. NAR was measured using a rhinomanometer by the anterior method.

RESULTS

The patients in the moderate-to-most severe AR group showed significantly higher levels of oral FeNO compared to the controls. The AR patients in both the mild (n=25) and the moderate-to-most severe (n=34) groups showed significantly higher levels of nasal FeNO compared to the controls (44.1ppb, 54.5ppb, and 26.5ppb, respectively). There was no significant difference in total NAR between the AR patients and the controls. The results of our comparison of nasal FeNO and NAR values of the ipsilateral nasal cavity for each individual indicated no significant correlation between the two-paired parameters. The optimal cut-off point of the mean nasal FeNO level was calculated as 38.5ppb (with 71% sensitivity and 86% specificity) to discriminate the presence of AR.

CONCLUSION

Nasal FeNO measurements can be an objective parameter for the diagnosis and classification of perennial AR in Japanese individuals. Nasal FeNO and NAR appear to be two independent measures that can be used to objectively evaluate nasal functions.

Application of nitric oxide measurements in clinical conditions beyond asthma

Fractional exhaled nitric oxide (FeNO) is a convenient, non-invasive method for the assessment of active, mainly Th2-driven, airway inflammation, which is sensitive to treatment with standard anti-inflammatory therapy. Consequently, FeNO serves as a valued tool to aid diagnosis and monitoring in several asthma phenotypes. More recently, FeNO has been evaluated in several other respiratory, infectious, and/or immunological conditions. In this short review, we provide an overview of several clinical studies and discuss the status of potential applications of NO measurements in clinical conditions beyond asthma.

Comparison of nasal nitric oxide levels between the inferior turbinate surface and the middle meatus in patients with symptomatic allergic rhinitis

BACKGROUND

Because of the anatomical complexity and the high output of the human nose, it has been unclear whether nasal nitric oxide (NO) serves as a reliable marker of allergic rhinitis (AR). We examined whether nasal NO levels in the inferior turbinate (IT) surface and the middle meatus (MM) differ in symptomatic AR patients.

METHODS

We measured fractional exhaled NO (FeNO) and nasal NO in normal subjects (n = 50) and AR patients with mild symptoms (n = 16) or moderate or severe symptoms (n = 27). Nasal NO measurements were obtained using an electrochemical analyzer connected to a catheter and an air-suction pump (flow rate 50mL/sec).

RESULTS

Compared to the normal subjects, the AR patients showed significantly higher nasal FeNO and nasal NO levels in the IT area. No significant difference in the MM area was observed among the three groups. The MM area showed higher NO levels than the IT area in all three groups. The ratio of nasal NO levels of the MM area to the IT area (MM/IT ratio) was significantly lower in the AR groups. The moderate/severe AR patients showed significantly higher nasal NO in the IT area (104.4 vs. 66.2ppb) and lower MM/IT ratios than those in the mild AR patients. The analysis of nasal brushing cells revealed significantly higher eosinophil cationic protein and nitrotyrosine levels in the AR groups.

CONCLUSIONS

Nasal NO assessment in the IT area directly reflects persistent eosinophilic inflammation and may be a valid marker to estimate the severity of AR.

Evaluation of eicosanoids in nasal lavage as biomarkers of inflammation in patients with allergic rhinitis

INTRODUCTION

Cysteinyl leukotrienes (cys-LTs), 8-isoprostane and prostaglandin E2 (PGE2) constitute fundamental mediators in allergic inflammation; therefore we wanted to determine the utility of PGE2, 8-isoprostane and cys-LT levels in nasal lavage as biomarkers of allergic inflammation.

MATERIAL AND METHODS

Twenty-one patients with allergic rhinitis (AR) were included on the basis of a positive history of AR symptoms and positive results of skin prick tests to grass pollen allergens. The main exclusion criteria were: uncontrolled asthma, nasal polyps, respiratory infection, tuberculosis, neoplastic and autoimmune diseases, current smoking and immunotherapy. Both outside the pollen season and at the height of the pollen season, total nasal symptom score (TNS-4) was evaluated and the levels of cys-LTs, 8-isoprostane and PGE2 were measured in nasal lavage fluid (NALF).

RESULTS

Natural allergen stimulation resulted in a significant increase of TNS-4 (p < 0.001) and nasal eosinophilia (p < 0.001). The concentration of PGE2 dominated in the NALF outside the pollen season and decreased significantly at the height of natural exposure (p < 0.01). In contrast, lower baseline concentrations of cys-LTs and 8-isoprostane increased significantly upon allergen stimulation (p < 0.05). There was a significant correlation between mean concentration of PGE2 and eosinophil number in NALF (r = 0.67, p = 0.0439).

CONCLUSIONS

The NALF concentrations of cys-LTs and 8-isoprostane change simultaneously with TNS-4 and nasal eosinophilia. However, due to the lack of any significant correlation, their utility as markers of allergic rhinitis should be warily considered. The decrease of PGE2 concentration in NALF which correlated with nasal eosinophilia may participate in escalation of allergic inflammation and needs further evaluation.

Nasal nitric oxide levels do not allow for discrimination between olfactory loss due to various etiologies

OBJECTIVES/HYPOTHESIS

Nasal nitric oxide (NO) and olfactory function are decreased in patients with chronic inflammatory sinonasal disease, suggesting a link between these two parameters. The aim of the study was to investigate nasal NO levels in patients with olfactory dysfunction due to different causes.

STUDY DESIGN

Prospective study in a university clinic setting (tertiary referral center).

METHODS

Posttraumatic (n = 11), idiopathic (n = 13), and sinonasal-related olfactory-impaired patients (n = 55) were compared with healthy subjects (n = 11). Nasal NO levels, olfactory testing (Sniffin' Sticks), and rhinosinusitis questionnaires (Short-Form 36, Sinonasal Outcome Test 22, Rhinosinusitis Disability Index) were obtained.

RESULTS

No significant difference in nasal NO levels were found between the different olfactory dysfunction causes. Nasal NO correlated negatively with age and positively with overall olfactory function, olfactory discrimination, and identification but not with olfactory thresholds. The more nasal symptoms prevailed in the Rhinosinusitis Disability Index, the lower the nasal NO.

CONCLUSIONS

Nasal NO levels do not allow for discrimination between olfactory loss due to various etiologies based on the present data. Nasal NO production seems to decrease with age and also seems to be associated to overall olfactory function and in particular to central nervous system tasks such as olfactory discrimination and identification but not to olfactory thresholds. These findings raise questions about the link and interaction between olfactory function and nasal NO.

Nasal nitric oxide in a random sample of adults and its relationship to sensitization, cat allergen, rhinitis, and ambient nitric oxide

BACKGROUND

There is conflicting evidence whether nasal nitric oxide (NO) is associated with current rhinitis and with other possible predictors. Most studies have been performed in clinical cohorts and there is a lack of studies based on a general population sample. The aim of the present study was to investigate predictors for levels of nasal nitric oxide (NO) in a general population.

METHODS

The population consisted of 357 subjects from Gothenburg participating in the follow-up of the European Respiratory Health Survey in 1999-2001. All subjects completed an extensive respiratory questionnaire. Nasal NO was measured from one nostril at a time with a sampling rate of 50 mL/s for 16 seconds and the nasal NO concentration was determined as the mean value within the plateau phase. Mattress dust samples were collected for cats and mites in a subsample of subjects. Ambient and exhaled NO was also measured. The predictors for nasal NO were analyzed in multiple linear regression models.

RESULTS

There was no relation between the levels of nasal NO and reporting current rhinitis. Nasal NO was significantly increased among those with high levels of IgE against cats and current smokers had significantly lower nasal NO. There was also a positive association between ambient NO and nasal NO. There were no significant associations between nasal NO and sex, age, or height, or between nasal NO and measured levels of cat antigen.

CONCLUSION

In this general population sample we found no relation between current rhinitis and nasal NO levels. There was a clear association between sensitization to cat and nasal NO, but there was no relation to current exposure to cat allergen. Our data support that nasal NO has a limited value in monitoring upper airway inflammation.

Clara cell protein in nasal lavage fluid and nasal nitric oxide - biomarkers with anti-inflammatory properties in allergic rhinitis

Background

Clara cell protein (CC16) is ascribed a protective and anti-inflammatory role in airway inflammation. Lower levels have been observed in asthmatic subjects as well as in subjects with intermittent allergic rhinitis than in healthy controls. Nasal nitric oxide (nNO) is present in high concentrations in the upper airways, and considered a biomarker with beneficial effects, due to inhibition of bacteria and viruses along with stimulation of ciliary motility. The aim of this study was to evaluate the presumed anti-inflammatory effects of nasal CC16 and nNO in subjects with allergic rhinitis.

Methods

The levels of CC16 in nasal lavage fluids, achieved from subjects with persistent allergic rhinitis (n = 13), intermittent allergic rhinitis in an allergen free interval (n = 5) and healthy controls (n = 7), were analyzed by Western blot. The levels of nNO were measured by the subtraction method using NIOX^®. The occurrences of effector cells in allergic inflammation, i.e. metachromatic cells (MC, mast cells and basophiles) and eosinophils (Eos) were analyzed by light microscopy in samples achieved by nasal brushing.

Results

The levels of CC16 correlated with nNO levels (r² = 0.37; p = 0.02) in allergic subjects.

The levels of both biomarkers showed inverse relationships with MC occurrence, as higher levels of CC16 (p = 0.03) and nNO (p = 0.05) were found in allergic subjects with no demonstrable MC compared to the levels in subjects with demonstrable MC. Similar relationships, but not reaching significance, were observed between the CC16 and nNO levels and Eos occurrence. The levels of CC16 and nNO did not differ between the allergic and the control groups.

Conclusions

The correlation between nasal CC16 and nNO levels in patients with allergic rhinitis, along with an inverse relationship between their levels and the occurrences of MC in allergic inflammation, may indicate that both biomarkers have anti-inflammatory effects by suppression of cell recruitment. The mechanisms behind these observations warrant further analyses.

Nasal nitric oxide and sinonasal disease: a systematic review of published evidence

OBJECTIVE

To critically and systematically review the data available on the sinonasal application of nasal nitric oxide measurement, particularly its use as a diagnostic, prognostic, or treatment effect indicator.

DATA SOURCES

EMBASE 1980 to February 10, 2010; Medline 1950 to February 10, 2010; Cochrane Collaboration database; NHS Evidence Health Information Resources database. Review Methods. The databases were searched using a search strategy designed to include manuscripts relevant both to nitric oxide measurement and sinus or nasal problems. A title search was carried out on these manuscripts to select those relevant to clinical or basic science aspects of nitric oxide measurement. A subsequent abstract search selected those manuscripts concerning the application of nitric oxide measurement to sinonasal problems. The manuscripts selected were subject to a full-text review to extract data sets of nasal nitric oxide readings for different patient groups.

RESULTS

Initially, 1088 manuscripts were selected. A title search found 335 manuscripts of basic scientific or clinical interest. An abstract search found 35 manuscripts directly relating to nitric oxide measurement in sinonasal disease. Full-text analysis produced 20 studies with extractable data on nasal nitric oxide levels in clearly defined patient groups. Studies did not show sufficient homogeneity to enable substantial meta-analysis of aggregated data.

CONCLUSION

Current evidence shows that nasal nitric oxide is not a clinically useful measure for sinonasal disease. Although there is some evidence that sinus surgery is associated with lowered nasal nitric oxide levels, there is no evidence that this is associated with deterioration in sinus health.

Impact of rhinitis on asthma control in children: association with FeNO

BACKGROUND

The prevalence of rhinitis is high and frequently observed in association with asthma. Although the persistence of predisposing factors such as rhinitis is frequently observed in adults, this has not yet been confirmed in children.

AIMS

The aim of this present work is to show the relationship between rhinitis and asthma control in asthmatic children.

METHODS

The authors carried out a cross-sectional study by collecting clinical, spirometric, and fractional exhaled nitric oxide (FeNO) data in children aged from 4 to 17 years.

RESULTS

One hundred seventeen children were included. Asthma control was optimal in 37.6%, suboptimal in 55.5% and poor in 7.3% of cases. A 74.3% of children were atopic and 62.5% had symptoms 34 of rhinitis. Rhinitis was more frequent when control of asthma was worse (p = .0001). Age (p = .002), asthma control (p < .001), atopy (p = .001), and presence of rhinitis (p = .012) were significantly associated with FeNO.

CONCLUSIONS

Our study confirms the strong relationship between upper airways and poor asthma control in the asthmatic child. Symptoms of rhinitis may be partly responsible for the increased fractional exhaled nitric oxide (FeNO) level, independently of the control of asthma. Evaluation of rhinitis should be included to improve assessment of asthma control in children.

Evidence-based recommendations regarding the differential diagnosis and assessment of nasal congestion: using the new GRADE system

Nasal congestion is an important symptom in nasal pathology and can be defined as an objective restriction of nasal cavity airflow because of mucosal pathology and/or increased mucus secretion (excluding anatomical variants). Using the new Grading Recommendations Assessment, Development and Evaluation system, evidence-based recommendations are made that will encompass different clinical questions regarding diagnostic modalities of nasal congestion: (i) their usefulness in assessment of presence and severity of congestion; (ii) their usefulness in assessment of etiological pathology responsible for congestion; and (iii) their usefulness in follow up and treatment effectiveness evaluation of nasal congestion.

Nasal mucosal expression of nitric oxide synthases in patients with allergic rhinitis and its relation to asthma

BACKGROUND

Nitric oxide (NO) has contradictory roles in the pathophysiology of allergic inflammation in both allergic rhinitis (AR) and asthma. Small amounts of NO produced by constitutive NO synthase (NOS) is anti-inflammatory, whereas large amounts produced by inducible NOS (iNOS) are proinflammatory.

OBJECTIVE

To investigate the difference in constitutive endothelial NOS (eNOS) and iNOS expression in nonallergic and allergic mucosa and the possible relation of this to the coexistence of asthma in seasonal AR.

METHODS

Seventeen patients (10 women and 7 men) with seasonal AR and 9 nonallergic patients (5 women and 4 men) with nasal septum deviation were enrolled. Inferior turbinate nasal biopsy specimens were obtained in all. Levels of eNOS and iNOS expressed as immunohistochemical scores (HSCOREs) were determined immunohistochemically from the specimens.

RESULTS

The mean +/- SD HSCOREs for eNOS in patients with seasonal AR were not significantly different from those of the nonallergic controls (1.85 +/- 0.78 vs 1.63 +/- 0.54; P = .12). On the other hand, the mean +/- SD HSCOREs for iNOS were significantly higher in patients with seasonal AR (1.75 +/- 0.75 vs 0.71 +/- 0.6; P = .004). Furthermore, although eNOS expression was not different between seasonal AR patients with and without asthma, the mean +/- SD HSCOREs for iNOS were significantly higher in the patients with asthma (1.93 +/- 0.78 vs 1.65 +/- 0.55; P = .01).

CONCLUSION

Increased expression of iNOS might have a role in the development of allergic inflammation in upper and lower airways and in comorbidity of AR and asthma.

Neural aspects of allergic rhinitis

PURPOSE OF REVIEW

Recent advances have helped to clarify the role of nerves in allergic rhinitis.

RECENT FINDINGS

Mast cell histamine release activates histamine H1 receptors on a subset of nonmyelinated Type C afferent trigeminal neurons to convey the sensation of itch. The itch nerves may be distinct from those responsible for burning pain and the dull ache of congestion. Activation of brain stem centers leads to cognition of nasal pruritus, generation of the systemic sneeze reflex and recruitment of local nasal parasympathetic reflexes. These cholinergic reflexes stimulate M3 muscarinic receptors on the submucosal glands to cause exocytosis and the thick mucous discharge of allergic rhinitis. The importance of these neural pathways is demonstrated by the benefits of antihistamines to block itch and sneeze, and anticholinergic drugs to block glandular secretion. One open question remains the role of mediators of allergic inflammation on the sensitivity and reactivity of afferent neurons and these secretory reflexes.

SUMMARY

The neurology of the nose helps to explain the sensations encountered in allergic rhinitis and opens new frontiers for drug discovery.