Evidence that enhanced nasal reactivity to bradykinin in patients with symptomatic allergy is mediated by neural reflexes

Touching a Nerve: Neuroimmune Interactions in Asthma

Asthma is an inflammatory airway disease characterized by excessive bronchoconstriction and airway hyperresponsiveness. Airway nerves play a crucial role in regulating these processes. In asthma, interactions between inflammatory cells and nerves result in nerve dysfunction, which worsens airway function. This review discusses new insights regarding the role of airway nerves in healthy lungs and examines how communication between nerves and leukocytes, including eosinophils, mast cells, dendritic cells, and innate lymphoid cells, contributes to nerve dysfunction and the worsening of airway disease. Clinical implications and therapeutic opportunities presented by neuroimmune interactions are also addressed.

Mutual Influence Between Allergic Rhinitis and Sleep: Factors, Mechanisms, and interventions-A Narrative Review

Patients with allergic rhinitis (AR) have a high incidence of sleep disorders, such as insomnia, which can easily exacerbate nasal symptoms. The aggravation of nasal symptoms further promotes the deterioration of sleep disorders, forming a vicious cycle. Severe cases may even trigger psychological and neurological issues, such as anxiety, depression, and cognitive impairment, causing significant distress to patients, making clinical diagnosis and treatment difficult, and increasing costs. Furthermore, satisfactory therapeutics remain lacking. As the pathogenesis of AR-associated sleep disorders is not clear and research is still insufficient, paying attention to and understanding AR-related sleep disorders is crucial in clinical practice. Multiple studies have shown that the most crucial issues in current research on AR and sleep are analyzing the relationship between AR and sleep disorders, searching for the influencing factors, and investigating potential targets for diagnosis and treatment. This review aimed to identify and summarize the results of relevant studies using "AR" and "sleep disorders" as search terms. In addition, we evaluated the correlation between AR and sleep disorders and examined their interaction and potential mechanisms, offering a foundation for additional screening of potential diagnostic biomarkers and therapeutic targets.

Further Understanding of Neuro-Immune Interactions in Allergy: Implications in Pathophysiology and Role in Disease Progression

The complicated interaction between the central and the autonomic (sympathetic, parasympathetic, and enteric) nervous systems on the one hand and the immune system and its components, on the other hand, seems to substantially contribute to allergy pathophysiology, uncovering an under-recognized association that could have diagnostic and therapeutic potentials. Neurons connect directly with and regulate the function of many immune cells, including mast cells, the cells that have a leading role in allergic disorders. Proinflammatory mediators such as cytokines, neurotrophins, chemokines, and neuropeptides are released by immune cells, which stimulate sensory neurons. The release of neurotransmitters and neuropeptides caused by the activation of these neurons directly impacts the functional activity of immune cells and vice versa, playing a decisive role in this communication. Successful application of Pavlovian conditioning in allergic disorders supports the existence of a psychoneuroimmunological interplay in classical allergic hypersensitivity reactions. Activation of neuronal homeostatic reflexes, like sneezing in allergic rhinitis, coughing in allergic asthma, and vomiting in food allergy, offers additional evidence of a neuroimmunological interaction that aims to maintain homeostasis. Dysregulation of this interaction may cause overstimulation of the immune system that will produce profound symptoms and exaggerated hemodynamic responses that will lead to severe allergic pathophysiological events, including anaphylaxis. In this article, we have systematically reviewed and discussed the evidence regarding the role of the neuro-immune interactions in common allergic clinical modalities like allergic rhinitis, chronic rhinosinusitis, allergic asthma, food allergy, atopic dermatitis, and urticaria. It is essential to understand unknown – to most of the immunology and allergy experts – neurological networks that not only physiologically cooperate with the immune system to regulate homeostasis but also pathogenetically interact with more or less known immunological pathways, contribute to what is known as neuroimmunological inflammation, and shift homeostasis to instability and disease clinical expression. This understanding will provide recognition of new allergic phenotypes/endotypes and directions to focus on specialized treatments, as the era of personalized patient-centered medicine, is hastening apace.

Identification and Functional Analysis of Novel Bradykinin-Related Peptides (BRPs) from Skin Secretions of Five Asian Frogs

In recent decades, various types of bioactive substances have been identified from amphibian skin and its secretions. Bradykinin-related peptides (BRPs) are among these compounds that make up the host defence system of amphibians. In the present study, we identified six novel BRPs, amolopkinin-GN1, amolopkinin-RK1, amolopkinin-TR1, amolopkinin-LF1, ranakinin-MS1, and ranakinin-MS2, from five East Asian amphibians, Amolops granulosus, Amolops ricketti, Amolops torrentis, Amolops lifanensis, and Hylarana maosonensis. This is the first report on BRPs in the skin of these species. Physiological assays reveal that these peptides have a contractive effect on the smooth muscle of rat ileum.

International Consensus Statement on Allergy and Rhinology: Allergic Rhinitis

BACKGROUND

Critical examination of the quality and validity of available allergic rhinitis (AR) literature is necessary to improve understanding and to appropriately translate this knowledge to clinical care of the AR patient. To evaluate the existing AR literature, international multidisciplinary experts with an interest in AR have produced the International Consensus statement on Allergy and Rhinology: Allergic Rhinitis (ICAR:AR).

METHODS

Using previously described methodology, specific topics were developed relating to AR. Each topic was assigned a literature review, evidence-based review (EBR), or evidence-based review with recommendations (EBRR) format as dictated by available evidence and purpose within the ICAR:AR document. Following iterative reviews of each topic, the ICAR:AR document was synthesized and reviewed by all authors for consensus.

RESULTS

The ICAR:AR document addresses over 100 individual topics related to AR, including diagnosis, pathophysiology, epidemiology, disease burden, risk factors for the development of AR, allergy testing modalities, treatment, and other conditions/comorbidities associated with AR.

CONCLUSION

This critical review of the AR literature has identified several strengths; providers can be confident that treatment decisions are supported by rigorous studies. However, there are also substantial gaps in the AR literature. These knowledge gaps should be viewed as opportunities for improvement, as often the things that we teach and the medicine that we practice are not based on the best quality evidence. This document aims to highlight the strengths and weaknesses of the AR literature to identify areas for future AR research and improved understanding.

Prostaglandin D2 Modulates Neuronal Excitation of the Trigeminal Ganglion to Augment Allergic Rhinitis in Guinea Pigs

Prostaglandin D2(PGD2) is involved in the pathogenesis of allergic rhinitis. However, the sensory nervous system-mediated contributions of PGD2to the symptoms of allergic rhinitis remain unclear. We investigated the involvement of PGD2in these symptoms and in neuronal excitation by in vivo and ex vivo experiments. In an ovalbumin-induced model of allergic rhinitis in guinea pigs, the number of sneezing, nasal rubbing, and nasal secretion events were assessed after the nasal cavity instillation of PGD2, histamine, or a combination of PGD2and histamine. In situ hybridization for PGD2receptor 1 (DP1) mRNA transcripts and immunohistochemical analysis of histamine H1receptor protein expression in guinea pig trigeminal ganglion (TRG) were performed. The effects of DP1receptor activation on the excitability of TRG neurons to electrical and histamine stimuli were assessed using whole-cell patch-clamp recordings. Histamine induced more sneezing, nasal rubbing, and nasal secretion events than PGD2 PGD2augmented histamine-induced responses, whereas pretreatment with a DP1receptor-selective antagonist completely suppressed PGD2-induced augmentation. DP1receptor mRNA transcripts and H1receptor protein expression could be detected in TRG neurons. Moreover, a DP1receptor agonist caused significant increases in the number of histamine-induced action potentials and depolarization, and reduced the current threshold in small-diameter neurons. Our findings show that PGD2-DP1receptor signaling augments the symptoms of allergic rhinitis via the sensory nervous system by modulating nasal neuronal activation to various stimuli, such as histamine. These findings suggest that DP1receptor antagonist has therapeutic potential for the treatment of allergic rhinitis.

Asthma Bronchiale and Exercise-Induced Bronchoconstriction

Exercising regularly has a wide range of beneficial health effects; in particular, it has been well documented to help in the management of chronic illnesses including asthma. However, in some individuals, exertion can also trigger an exacerbation of asthmatic episodes and subsequent acute attacks of breathlessness, coughing, tightness of the chest and wheezing. This physiological process is called exercise-induced bronchoconstriction (EIB) whereby post-exercise forced expiratory volume in 1 s is reduced by 10-15% from baseline. While EIB is highly prevalent in asthmatics and presents with similar respiratory symptoms, asthma and EIB are not mutually exclusive. The aim of this review is to present a broad overview of both conditions in order to enhance the understanding of the similarities and differences distinguishing them as two separate entities. The pathophysiology and mechanisms underlying asthma are well described with research now focussing on defining phenotypes for targeted management strategies. Conversely, the mechanistic understanding of EIB remains largely under-described. Diagnostic pathways for both are established and similar, as are pharmacologic and non-pharmacologic treatments and management approaches, which have enhanced success with early detection. Given the potential for exacerbation of asthma, exercise avoidance is common but counterproductive as current evidence indicates that it is well tolerated and improves quality of life. Literature supporting the benefit of exercise for EIB sufferers is at present favourable, yet extremely limited; therefore, future research should be directed in this area as well as towards further developing the understanding of the pathophysiology and mechanisms underpinning both EIB and asthma.

Pollen count and presentation of angiotensin-converting enzyme inhibitor-associated angioedema

BACKGROUND

The incidence of angiotensin-converting enzyme (ACE) inhibitor-associated angioedema is increased in patients with seasonal allergies.

OBJECTIVE

We tested the hypothesis that patients with ACE inhibitor-associated angioedema present during months when pollen counts are increased.

METHODS

Cohort analysis examined the month of presentation of ACE inhibitor-associated angioedema and pollen counts in the ambulatory and hospital setting. Patients with ACE inhibitor-associated angioedema were ascertained through (1) an observational study of patients presenting to Vanderbilt University Medical Center, (2) patients presenting to the Marshfield Clinic and participating in the Marshfield Clinic Personalized Medicine Research Project, and (3) patients enrolled in The Ongoing Telmisartan Alone and in Combination with Ramipril Global Endpoint Trial (ONTARGET). Measurements include date of presentation of ACE inhibitor-associated angioedema, population exposure to ACE inhibitor by date, and local pollen counts by date.

RESULTS

At Vanderbilt, the rate of angioedema was significantly associated with tree pollen months (P = .01 from χ(2) test). When separate analyses were conducted in patients with a history of seasonal allergies and patients without, the rate of ACE inhibitor-associated angioedema was increased during tree pollen months only in patients with a history of seasonal allergies (P = .002). In Marshfield, the rate of angioedema was significantly associated with ragweed pollen months (P = .025). In ONTARGET, a positive trend was observed between the ACE inhibitor-associated angioedema rate and grass season, although it was not statistically significant (P = .057).

CONCLUSIONS

Patients with ACE inhibitor-associated angioedema are more likely to present with this adverse drug event during months when pollen counts are increased.

Phenotyping of allergic rhinitis

Allergic rhinitis (AR) is characterized by immune-mediated inflammation of the nasal mucosal lining. Although this chronic disease is not fatal, it is associated with many debilitating symptoms. Like many other chronic diseases, AR has a wide range of clinical aspects, and comorbidities such as asthma, rhinosinusitis, dermatitis, and conjunctivitis may accompany the disease to different degrees. These comorbidities and features determine the clinical phenotypes of AR. Different phenotypes and other characteristics of AR are discussed in this review. It is important for clinicians to be aware of these variable clinical phenotypes of AR to diagnose and treat the disease properly.

Eosinophil recruitment to nasal nerves after allergen challenge in allergic rhinitis

In allergen challenged animal models, eosinophils localize to airway nerves leading to vagally-mediated hyperreactivity. We hypothesized that in allergic rhinitis eosinophils recruited to nasal nerves resulted in neural hyperreactivity. Patients with persistent allergic rhinitis (n=12), seasonal allergic rhinitis (n=7) and controls (n=10) were studied. Inferior nasal turbinate biopsies were obtained before, 8 and 48h after allergen challenge. Eight hours after allergen challenge eosinophils localized to nerves in both rhinitis groups; this was sustained through 48h. Bradykinin challenge, with secretion collection on the contralateral side, was performed to demonstrate nasal nerve reflexes. Twenty fourhours after allergen challenge, bradykinin induced a significant increase in secretions, indicating nasal hyperreactivity. Histological studies showed that nasal nerves expressed both vascular cell adhesion molecule-1 (VCAM-1) and chemokine (C-C motif) ligand 26 (CCL-26). Hence, after allergen challenge eosinophils are recruited and retained at nerves and so may be a mechanism for neural hyperreactivity.

Eosinophil peroxidase induces the expression and function of acid-sensing ion channel-3 in allergic rhinitis: in vitro evidence in cultured epithelial cells

BACKGROUND

Acid-sensing ion channels (ASIC) are a family of acid-activated ligand-gated cation channels. As tissue acidosis is a feature of inflammatory conditions, such as allergic rhinitis (AR), we investigated the expression and function of these channels in AR.

OBJECTIVES

The aim of the study was to assess expression and function of ASIC channels in the nasal mucosa of control and AR subjects.

METHODS

Immunohistochemical localization of ASIC receptors and functional responses to lactic acid application were investigated. In vitro studies on cultured epithelial cells were performed to assess underlying mechanisms of ASIC function.

RESULTS

Lactic acid at pH 7.03 induced a significant rise in nasal fluid secretion that was inhibited by pre-treatment with the ASIC inhibitor amiloride in AR subjects (n = 19). Quantitative PCR on cDNA isolated from nasal biopsies from control and AR subjects demonstrated that ASIC-1 was equally expressed in both populations, but ASIC-3 was significantly more highly expressed in AR (P < 0.02). Immunohistochemistry confirmed significantly higher ASIC-3 protein expression on nasal epithelial cells in AR patients than controls (P < 0.01). Immunoreactivity for EPO+ eosinophils in both nasal epithelium and submucosa was more prominent in AR compared with controls. A mechanism of induction of ASIC-3 expression relevant to AR was suggested by the finding that eosinophil peroxidase (EPO), acting via ERK1/2, induced the expression of ASIC-3 in epithelial cells. Furthermore, using a quantitative functional measure of epithelial cell secretory function in vitro, EPO increased the air-surface liquid depth via an ASIC-dependent chloride secretory pathway.

CONCLUSIONS

This data suggests a possible mechanism for the observed association of eosinophils and rhinorrhoea in AR and is manifested through enhanced ASIC-3 expression.

Recent developments in United airways disease

The nose and lung are both part of the respiratory tract. Often the diseases affecting the nose and/or the bronchi are treated separately. However, in recent years, numerous studies have highlighted the fact that the respiratory system is a single entity and the concept of "united airway disease" has become more and more important. The unity of the respiratory tract is confirmed both from a morphological and from a functional point of view. Nevertheless, this concept is also confirmed for the respiratory immune system, innervation and vascularization interesting all along the tract, from the nose to the bronchioles. When treating rhinitis, it is often necessary to assess the presence of asthma. Patients with sinusitis should be evaluated for a possible concomitant asthma. Conversely, patients with asthma should always be evaluated for possible nasal disease. The medications that treat nasal diseases appear to be useful in improving control of asthma and in reducing bronchial hyperresponsiveness as well. Physicians should always keep these notions in mind, and evaluate and treat respiratory diseases taking into account the unity of the respiratory tract.

What are the primary clinical symptoms of rhinitis and what causes them?

The nose has a limited repertoire of responses regardless of the triggers. These responses primarily serve as a protective mechanism for the lower respiratory tract. Although the nasal reactions to pollens, particles, and pollution may have a beneficial effect for the lower airway, they create symptoms in some individuals that lead to significant morbidity. The symptoms of allergic rhinitis extend far beyond the nose, and the morbidity associated with rhinitis is significant. The nasal symptoms of rhinitis and their causes are the focus of this review.

The link between allergic rhinitis and asthma: the united airways disease

Rhinitis and asthma are often associated and the two disorders interact at various levels. Rhinitis typically precedes the development of asthma and can contribute to unsatisfactory asthma control. The presence and type of asthma is influenced by sensitization, and the duration and severity of allergic rhinitis. Nasal symptoms, airflow and markers of inflammation directly correlate with lower airway involvement. Local tissue factors, such as microbial stimuli and systemic inflammatory mechanisms, play a role in the clinical expression of the allergic airway syndrome. There is increasing evidence that suggests a major involvement of airway epithelial cells in the pathogenesis of both asthma and allergic rhinitis. Even in patients with rhinitis who do not have asthma, subclinical changes in the lower airways and inflammatory mediators can be detected. The pathogenic role of paranasal sinus infections in respiratory allergy has been better elucidated but there remains a need for further research. Treatment of established rhinitis may affect asthma control and could have some impact on airway obstruction, but a direct effect of rhinitis therapy on lower airway inflammation remains to be clearly established.

Reproducibility of nasal allergen challenge in evaluating the efficacy of intranasal corticosteroid treatment

BACKGROUND

Although nasal challenge with allergen has often been used to evaluate the efficacy of therapeutic modalities used for the treatment of allergic rhinitis, the reproducibility of this model in quantitatively evaluating efficacy has not been rigorously examined.

OBJECTIVE

To examine the reproducibility of the suppressive effects of an intranasal corticosteroid on the clinical and biochemical outcomes of a nasal allergen challenge during two identical treatment periods using the same subjects.

METHODS

In a single-blind study, 25 seasonal allergic subjects with positive skin tests to grass or ragweed were studied outside of their pollen season. Subjects underwent a baseline, three-dose allergen challenge. Beginning 1 week later, subjects received two 7-day courses of intranasal beclomethasone (168 microg b.i.d.) separated by a 1-month washout period. Nasal challenges with allergen were performed after each treatment period. The nasal allergic response was evaluated by counting sneezes, recording symptom scores and measuring levels of albumin (an index of vascular permeability), lysozyme (an index of serous glandular secretion) and kinins (proinflammatory peptides) in recovered nasal lavages.

RESULTS

Compared with the baseline challenge, each course of beclomethasone significantly reduced sneezing, symptom scores, albumin and kinins, but not lysozyme. Reproducibility analysis of the net changes from diluent challenge in the two beclomethasone treatment periods, showed the following intraclass correlation coefficients: sneezing (0.92), lysozyme (0.82), symptom scores (0.72), albumin (0.64) and kinins (0.28).

CONCLUSION

We conclude that the nasal challenge model is a reproducible method to evaluate the efficacy of anti-allergic medications. For nasal corticosteroid trials, sneezing, symptom scores and albumin levels are recommended as the most reproducibly suppressive outcome measures.

Cough sensors. V. Pharmacological modulation of cough sensors

Several airway afferent nerve subtypes have been implicated in coughing. These include bronchopulmonary C-fibers, rapidly adapting airway mechanoreceptors and touch-sensitive tracheal Adelta-fibers (also called cough receptors). Although the last two afferent nerve subtypes are primarily sensitive to mechanical stimuli, all can be acted upon by one or more different chemical stimuli. In this review we catalogue the chemical agents that stimulate and/or modulate the activity of the airway afferent nerves involved in cough, and describe the specific mechanisms involved in these effects. In addition, we describe the mechanisms of action of a number of chemical inhibitors of these afferent nerve subtypes, and attempt to relate this information to the regulation of coughing in health and disease.

The effects of the nasal antihistamines olopatadine and azelastine in nasal allergen provocation

BACKGROUND

Olopatadine, an antihistamine used in allergic conjunctivitis, is under development as a nasal preparation for the treatment of allergic rhinitis.

OBJECTIVES

To evaluate the efficacy of olopatadine in suppressing symptoms and biomarkers of the immediate reaction induced by nasal allergen provocation and to compare olopatadine with azelastine in the same model.

METHODS

The study was approved by the Johns Hopkins University institutional review board, and all subjects gave written consent. We studied 20 asymptomatic subjects with seasonal allergic rhinitis. The study had 2 randomized, double-blind, placebo-controlled, crossover phases that evaluated 2 concentrations of olopatadine, 0.1% and 0.2%. In a third exploratory phase, olopatadine, 0.1%, was compared with topical azelastine, 0.1%, in a patient-masked design. Efficacy variables were the allergen-induced sneezes, other clinical symptoms, and the levels of histamine, tryptase, albumin, lysozyme, and cysteinyl-leukotrienes (third study only) in nasal lavage fluids.

RESULTS

Both concentrations of olopatadine produced significant inhibition of all nasal symptoms, compared with placebo. Olopatadine, 0.1%, inhibited lysozyme levels, but olopatadine, 0.2%, inhibited histamine, albumin, and lysozyme. The effects of olopatadine, 0.1%, were comparable to those of azelastine, 0.1%.

CONCLUSIONS

Olopatadine, at 0.1% and 0.2% concentrations, was effective in suppressing allergen-induced nasal symptoms. At 0.2%, olopatadine provided evidence suggestive of inhibition of mast cell degranulation.

Intranasal corticosteroids reduce ocular symptoms associated with allergic rhinitis

OBJECTIVE: Clinical data and recent guidelines support the positive effects of intranasal corticosteroids on allergic rhinitis-associated ocular symptoms. This article reviews the epidemiology and pathophysiology of ocular allergy symptoms and efficacy, tolerability, and potenti mechanisms of action of intranasal corticosteroids in the treatment of this condition.

DATA SOURCES: MEDLINE database.

REVIEW METHODS: A search of pertinent literature identified in vitro, preclinical, and clinical data that involve intranasal corticosteroids in ocular-related studies. Searches that used epidemiology, pathophysiology, drug class and specific agents, and other appropriate search terms were conducted.

RESULTS: Ocular symptoms, common in patients with allergic rhinitis, are associated with reduced quality of life and substantial economic costs. In the conjunctival epithelium, an early, type-1 hypersensitivity reaction occurs after direct allergen exposure. Progression to late-phase response, with recurrence of symptoms and infiltration of inflammatory cells, may occur 4 to 8 hours later and appears to be dose-related. Alteration of nasal ocular reflex pathways may also contribute to ocular symptoms in allergic rhinitis. Clinical data indicate that intranasal corticosteroids significantly reduce total and individual ocular symptoms in subjects with allergic rhinitis. Meta-analyses have found that oral/topical antihistamines are not superior to intranasal corticosteroids in reducing ocular allergy symptoms. Ocular adverse events from intranasal corticosteroids are rare.

CONCLUSION: Intranasal corticosteroids are effective and well-tolerated in the treatment of ocular symptoms associated with allergic rhinitis. Additional studies are needed to better understand the mechanisms underlying the effects of intranasal corticosteroids on ocular symptoms.

Contribution of allergen-specific and nonspecific nasal responses to early-phase and late-phase nasal responses

BACKGROUND

The relative contributions of the allergen-specific early-phase nasal response and nonspecific nasal response and mast cells to the pathophysiology of allergic rhinitis are not well defined.

OBJECTIVES

To determine the contributions of specific reactivity, nonspecific reactivity, and mast cells to the development of early-phase and late-phase responses using a mouse model of allergic rhinitis.

METHODS

Sensitized wild-type and FcvarepsilonRI-deficient (FcvarepsilonRI-/-) mice were exposed to allergen for 3, 5, or 12 days. As indicators of nasal reactivity, respiratory frequency and nasal resistance were monitored.

RESULTS

Sensitized mice exposed to 3 days of nasal allergen challenge showed a nonspecific early-phase response. As the number of allergen exposures increased, there was progressive diminution in nonspecific responses with increased allergen-specific early-phase responses and a late-phase response. Sensitized FcvarepsilonRI-/- mice did not develop nonspecific nasal responses or late-phase responses, but transfer of in vitro-differentiated wild-type mast cells into FcvarepsilonRI-/- mice restored nonspecific early-phase nasal responses but not the late-phase response.

CONCLUSION

These data identify the nonspecific nasal response as a major contributor to the early-phase response, especially during initial allergen exposure, and is dependent on mast cells. Increasing allergen exposure results in increasing allergen-specific responses, converting the nonspecific early-phase response to a late-phase response that is allergen-specific and mast cell-independent.

Objective monitoring of nasal patency and nasal physiology in rhinitis

Nasal obstruction can be monitored objectively by measurement of nasal airflow, as evaluated by nasal peak flow, or as airways resistance/conductance as evaluated by rhinomanometry. Peak flow can be measured during inspiration or expiration. Of these measurements, nasal inspiratory peak flow is the best validated technique for home monitoring in clinical trials. The equipment is portable, relatively inexpensive, and simple to use. One disadvantage, however, is that nasal inspiratory peak flow is influenced by lower airway as well as upper airway function. Rhinomanometry is a more sensitive technique that is specific for nasal measurements. The equipment, however, requires an operator, is more expensive, and is not portable. Thus, it is applicable only for clinic visit measures in clinical trials. Measurements require patient cooperation and coordination, and not all can achieve repeatable results. Thus, this objective measure is best suited to laboratory challenge studies involving smaller numbers of selected volunteers. A nonphysiological measure of nasal patency is acoustic rhinometry. This sonic echo technique measures internal nasal luminal volume and the minimum cross-sectional area. The derivation of these measures from the reflected sound waves requires complex mathematical transformation and makes several theoretical assumptions. Despite this, however, such measures correlate well with the nasal physiological measures, and the nasal volume measures have been shown to relate well to results obtained by imaging techniques such as computed tomography scanning or magnetic resonance imaging. Like rhinomanometry, acoustic rhinometry is not suitable for home monitoring and can be applied only to clinic visit measures or for laboratory nasal challenge monitoring. It has advantages in being easy to use, in requiring little patient cooperation, and in providing repeatable results. In addition to nasal obstruction, allergic rhinitis is recognized to be associated with impaired mucociliary clearance and altered nasal responsiveness. Measures exist for the monitoring of these aspects of nasal dysfunction. Although measures of mucociliary clearance are simple to perform, they have a poor record of reproducibility. Their incorporation into clinical trials is thus questionable, although positive outcomes from therapeutic intervention have been reported. Measures of nasal responsiveness are at present largely confined to research studies investigating disease mechanisms in allergic and nonallergic rhinitis. The techniques are insufficiently standardized to be applied to multicenter clinical trials but could be used in limited-center studies to gain insight into the regulatory effects of different therapeutic modalities.

Contribution of prostaglandin D2 via prostanoid DP receptor to nasal hyperresponsiveness in guinea pigs repeatedly exposed to antigen

We examined the role of prostanoid DP receptor in nasal blockage in an experimental allergic rhinitis model in guinea pigs. Local inhalation of prostaglandin D(2) (PGD(2)) to the nasal cavity resulted in an increase in intranasal pressure in guinea pigs actively sensitized by repeated antigen exposure but not in non-sensitized guinea pigs. Nasal hyperresponsiveness was observed when the guinea pigs were exposed to histamine and U-46619 (11alpha, 9alpha-epoxymethano-PGH(2); a thromboxane (TX) A(2) mimetic) after repeated antigen exposure. S-5751 ((Z)-7-[(1R,2R,3S,5S)-2-(5-hydroxybenzo[b]thiophen-3-ylcarbonylamino)-10-norpinan-3-yl]hept-5-enoic acid), a prostanoid DP receptor antagonist, inhibited not only PGD(2)-induced nasal blockage but also nasal hyperresponsiveness to histamine and U-46619 in sensitized guinea pigs. Combined exposure of the nasal cavity of guinea pigs to an aerosol of PGD(2) with histamine or U-46619 at sub-threshold concentrations synergistically caused a marked increase in intranasal pressure. These responses were significantly suppressed by S-5751. These results suggest that PGD(2) plays a critical role in the increase in intranasal pressure via prostanoid DP receptor, probably through synergistically enhancing the nasal response with other chemical mediators released from mast cells and other inflammatory cells activated by allergens.

Autonomic dysfunction, allergy and the upper airway

PURPOSE OF REVIEW

The autonomic nervous system has been implicated in the pathophysiology of chronic upper airway inflammatory disease for decades. We discuss the most recent literature with regard to autonomic nervous system dysfunction and chronic upper airway disease.

RECENT FINDINGS

Recently, state of the art autonomic nervous system testing has demonstrated autonomic nervous system dysfunction in patients with chronic upper airway inflammatory disease. This dysfunction has been characterized as hypoadrenergic.

SUMMARY

Autonomic nervous system dysfunction likely plays a role in chronic upper airway inflammatory disease. Further investigation may lead to a better understanding of the role of autonomic nervous system dysfunction in these disorders and, hence, opportunities for novel therapeutic modalities.

The impact of comorbid atopic disease on asthma: clinical expression and treatment

Clinically, asthma and allergic rhinitis involve separate regions of the respiratory tract while representing a common underlying inflammatory syndrome. Much evidence supports an epidemiologic association between the diseases, paranasal sinus involvement in both conditions, and parallel relationship in severity and treatment outcomes. Pathophysiologic mechanisms, including immunoglobulin E (IgE)- mediated inflammation, are also shared. Blocking IgE with the recombinant humanized monoclonal antibody omalizumab demonstrated clinical efficacy in patients with upper and lower airway diseases. IgE blockade, leukotriene modulation, and B-cell depletion therapy have all exhibited success in chronic inflammation, reinforcing and expanding the beneficial role of immunomodulation of global mediators.

The Allergic Rhinitis and its Impact on Asthma system: a new classification of allergic rhinitis and nasal responsiveness

OBJECTIVES AND HYPOTHESIS

Allergic rhinitis has traditionally been classified into seasonal and perennial rhinitis. However, many subjects with dual sensitisation do not fit neatly into either category. Recently, the Allergic Rhinitis and its Impact on Asthma workshop has proposed a new allergic rhinitis classification, into intermittent and persistent forms. The purpose of the present study was to investigate whether the symptomatic and secretory responsiveness of allergic rhinitis sufferers correlated well with the Allergic Rhinitis and its Impact on Asthma classification, compared with the traditional classification.

STUDY DESIGN

Experimental study.

METHODS

Forty subjects with allergic rhinitis and 13 normal controls underwent a unilateral nasal bradykinin challenge protocol. Symptom scores were recorded and secretion weights measured bilaterally using filter paper disks. The symptomatic and secretory responses of allergic subjects were analysed according to both the traditional and the Allergic Rhinitis and its Impact on Asthma classifications, and the two systems were compared.

RESULTS

For both classification systems, the two groups of allergic subjects were clearly demarcated by secretory responses. However, after classification according to the traditional system, there was a lack of clear demarcation between the groups as regards symptomatic response, whereas clear demarcation of symptomatic responses was seen after using the Allergic Rhinitis and its Impact on Asthma classification.

CONCLUSIONS

In allergic rhinitis subjects, the degree of nasal responsiveness was closely related to their Allergic Rhinitis and its Impact on Asthma classification. Furthermore, this classification was not compromised by the inclusion of subjects with dual sensitisation. Thus, the Allergic Rhinitis and its Impact on Asthma classification may have advantages for future research studies on allergic rhinitis.

Nonallergic rhinitis with eosinophilia syndrome

Nonallergic rhinitis with eosinophilia syndrome (NARES) is a clinical syndrome comprising symptoms consistent with allergic rhinitis in which an absence of atopy has been demonstrated by allergen skin testing, and nasal cytology analysis demonstrates more than 20% eosinophils. Anosmia is a prominent feature not shared with allergic rhinitis. The pathophysiology of NARES is poorly understood, but a key component involves a self-perpetuating, chronic eosinophilic nasal inflammation with development of nasal micropolyposis and polyposis. Mast cells likely play an important role as well. NARES is a risk factor for the development of nasal polyposis and aspirin sensitivity, as well as obstructive sleep apnea. Treatment consists mainly of intranasal corticosteroids with or without the addition of second-generation antihistamines and/or leukotriene-receptor antagonists.

Subjects with non-allergic non-infectious perennial rhinitis do not show nasal hyper-responsiveness to bradykinin

Symptoms in non-allergic non-infectious perennial rhinitis (NANIPER) are characteristically trigged by non-specific irritants. Hyper-responsiveness to cold dry air has been demonstrated in NANIPER. Bradykinin is a peptide involved in allergic inflammation. Neurally mediated hyper-responsiveness to bradykinin has been demonstrated in allergic rhinitis. The purpose of the present study was to investigate whether hyper-responsiveness to bradykinin is present in NANIPER. Normal subjects (n = 13) and subjects with NANIPER (n = 10) were subjected to a nasal bradykinin challenge protocol. Secretory responses were measured using filter paper disks, and congestive responses measured using acoustic rhinometry. Compared to normal subjects, with NANIPER had a greater secretory response to control challenge with Hartman's solution. On the other hand, the normal ipsilateral secretory and congestive response to bradykinin was absent in NANIPER. Subjects with NANIPER did not demonstrate any evidence of reflex responses to bradykinin, and no evidence of nasal hyper-responsiveness to bradykinin. Hyper-responsiveness to bradykinin is absent in NANIPER. These results suggest that autonomic hyporesponsiveness rather than neural hyper-responsiveness may be an important factor in the etiology of NANIPER.

Autonomic function and dysfunction of the nose and sinuses

Patients with inflammatory disorders of the upper airway exhibit varying degrees of ANS dysfunction, including the sympathetic, parasympathetic,and sensory components. Current evidence is insufficient with regard to the exact role of ANS dysfunction and its relationship to these disorders.Thus, the interaction of the ANS and sinonasal inflammation deserves further study.

Induction of nasal hyper-responsiveness by allergen challenge in allergic rhinitis: the role of afferent and efferent nerves

BACKGROUND

Hyper-responsiveness of nasal secretory function and volume changes are features of allergic rhinitis (AR) that are mediated in part by neural mechanisms. The finding of nasal hyper-responsiveness in subjects with AR who are currently symptomatic, but not in those who are currently out of season and asymptomatic, suggests that induction of neural reflexes in allergic subjects occurs as a result of allergic inflammation.

OBJECTIVES

To investigate whether allergen exposure in subjects with asymptomatic seasonal allergic rhinitis (SAR) may lead to induction of neural reflexes, and to investigate the components of the reflexes involved in this induction.

METHODS

Asymptomatic subjects with (out-of-season) SAR underwent a nasal bradykinin challenge, before and 24 h after preceding ipsilateral (n = 11) and contralateral (n = 11) antigen challenge. Challenges were performed and nasal secretions collected using filter paper disks, and changes in nasal minimal cross-sectional area (A(min)) were measured using acoustic rhinometry.

RESULTS

Preceding ipsilateral antigen challenge led to the induction of a contralateral secretory reflex (P = 0.01), which was absent in control experiments (P = 0.34). Ipsilateral secretion weights were also enhanced. Preceding contralateral antigen challenge also induced a contralateral secretory reflex (P = 0.03). Enhancement of the reduction in contralateral A(min) was also seen (P = 0.02). Ipsilateral responses were unchanged.

CONCLUSIONS

Allergen exposure in asymptomatic allergic subjects leads to induction of neural reflexes, resulting in nasal hyper-responsiveness, which persists beyond the resolution of the acute allergic response. Our data suggest that the mechanisms of allergen-induced hyper-responsiveness involve both afferent and efferent components.

Neuropathology in rhinosinusitis

Pathophysiologic differences in neural responses to hypertonic saline (HTS) were investigated in subjects with acute sinusitis (n = 25), subjects with chronic fatigue syndrome (CFS) with nonallergic rhinitis (n = 14), subjects with active allergic rhinitis (AR; n = 17), and normal (n = 20) subjects. Increasing strengths of HTS were sprayed into their nostrils at 5-minute intervals. Sensations of nasal pain, blockage, and drip increased with concentration and were significantly elevated above normal. These parallels suggested activation of similar subsets of afferent neurons. Urea and lysozyme secretion were dose dependent in all groups, suggesting that serous cell exocytosis was one source of urea after neural stimulation. Only AR and normal groups had mucin dose responses and correlations between symptoms and lysozyme secretion (R(2) = 0.12-0.23). The lysozyme dose responses may represent axon responses in these groups. The neurogenic stimulus did not alter albumin (vascular) exudation in any group. Albumin and mucin concentrations were correlated in sinusitis, suggesting that nonneurogenic factors predominated in sinusitis mucous hypersecretion. CFS had neural hypersensitivity (pain) but reduced serous cell secretion. HTS nasal provocations identified significant, unique patterns of neural and mucosal dysregulation in each rhinosinusitis syndrome.

Treatment with intranasal fluticasone propionate significantly improves ocular symptoms in patients with seasonal allergic rhinitis

BACKGROUND

If monotherapy with an intranasal corticosteroid can alleviate both nasal and ocular symptoms of allergic rhinitis, treatment may be simplified and costs may be reduced.

OBJECTIVE

The purpose of this study was to evaluate the efficacy of once-daily fluticasone propionate (FP) aqueous nasal spray 200 microg compared with vehicle placebo and oral loratadine (LOR) 10 mg in reducing ocular symptoms associated with seasonal allergic rhinitis.

METHODS

A total of 471 patients received vehicle placebo, LOR, or FP in this multi-centre, double-blind, double-dummy, randomized study. Patients were > or =12 years old with a history of seasonal allergic rhinitis and a positive skin test for a relevant allergen. During the baseline and treatment periods, patients rated the severity of eye itching, tearing, and redness via visual analogue scales that ranged from 0 (no symptoms) to 100 (most severe symptoms). The three ocular ratings were added to derive the total ocular symptom score (TOSS). Patients with a TOSS > or =120 on at least 4 of the 7 days before the randomization visit were enrolled. The primary outcome was the difference between FP and vehicle placebo in the mean change from baseline in the reflective TOSS overall (averaged over the 28-day treatment period). A difference between FP and vehicle placebo of 25.5 was considered clinically significant.

RESULTS

The overall mean change from baseline in the TOSS was significantly greater in the FP group compared with vehicle placebo (clinically significant difference of 28.8; P<0.001) and compared with LOR (difference of 16.2; P=0.028). Overall mean (SEM) changes were -59.9 (5.4) for the placebo group, -72.5 (5.4) for the LOR group, and -88.7 (5.3) for the FP group. The FP treatment group also showed significantly greater overall mean changes in ocular itching, tearing, and redness compared with vehicle placebo (P<0.001) and compared with LOR (P< or =0.045).

CONCLUSION

Patients treated with intranasal FP had clinically and statistically significant decreases in ocular symptom scores compared with vehicle placebo. Data also suggest that FP reduced ocular symptoms more than or comparable with oral LOR. Patients experiencing ocular symptoms associated with allergic rhinitis may benefit from monotherapy with intranasal FP.

Bronchopulmonary afferent nerves

Vagal afferent nerves are the primary communication pathways between the bronchopulmonary system and the central nervous system. Input from airway afferent nerves to the CNS is integrated in the brainstem and ultimately leads to sensations and various reflex outputs. Afferent nerves innervating the airways can be classified into various distinct phenotypes. However, there is no single classification scheme that takes all features, including conduction velocity, cell body diameter, ganglionic origin, and stimuli to which they respond (modality) into account. At present, bronchopulmonary afferent nerves are typically considered to belong to one of three general categories, namely C-fibres, rapidly adapting stretch receptors (RARs), and slowly adapting stretch receptors (SARs). As our understanding of bronchopulmonary afferent nerves continues to deepen, we are likely to see more sophisticated classification schemes emerge. It is clear that the function of afferent fibres can be substantively influenced by airway inflammation and remodelling. The perturbations and perversions of afferent nerve function that occur during these states almost certainly contributes to many of the signs and symptoms of inflammatory airway disease. A more lucid characterization of bronchopulmonary afferent nerves, and a better understanding of the mechanisms by which these nerves influence pulmonary physiology during health and disease anticipates future research.

H1-receptors: localization and role in airway physiology and in immune functions

Histamine H(1)-receptors are involved in the pathologic processes of allergy. Clinical trials of H(1)-receptor antagonists have demonstrated the efficacy of these agents in reducing the sneezing, pruritus, and rhinorrhea associated with allergic rhinitis. In the lung, H(1)-receptors mediate the bronchoconstrictive effects of histamine and increase vascular permeability, which lead to plasma exudation. H(1)-receptors are present on T cells, B cells, monocytes, and lymphocytes, and stimulation of these receptors induces pro-inflammatory effects. It has been suggested that a signal from the H(1)-receptor contributes to the antigen receptor-mediated signaling pathways that induce proliferative responses and lead to the production of cytokines and antibodies by T cells and B cells, respectively. It would appear, therefore, that the H(1)-receptor has a wider role in inflammatory processes than simply mediating the actions of histamine.

Experimental rhinovirus challenges in adults with mild asthma: response to infection in relation to IgE

BACKGROUND

Although most children and young adults with asthma are atopic, exacerbations of asthma are frequently associated with viral respiratory tract infections, especially those caused by rhinovirus (HRV).

OBJECTIVE

Young atopic adults with mild asthma were evaluated before and during an experimental HRV infection to test the hypothesis that airway inflammation before virus inoculation may be a risk factor for an adverse response to HRV.

METHODS

Experimental HRV infections were evaluated in 16 allergic volunteers with mild asthma and 9 nonatopic control patients (age, 18 to 30 years). Before virus inoculation, each participant was screened with tests for lung function, prick skin tests for sensitization to common aeroallergens, measurements of total serum IgE, and serum neutralizing antibody to rhinovirus-16 (the serotype used for inoculation). The response to infection was monitored for 21 days by using symptom diary cards, tests for lung function, and markers of airway inflammation in nasal washes, blood, and expired air.

RESULTS

During the infection, asthmatic patients had cumulative upper and lower respiratory tract symptom scores that were significantly greater over the course of 21 days than scores from the control patients. At baseline, the asthmatic patients also had increased sensitivity to methacholine and significantly lower values for FEV(1) (percent predicted) than the control patients (geometric mean and intraquartile values: 87% [79% to 91%] for the asthmatic patients and 101% [90% to 104%] for the control patients, P <.03). Among the patients with mild asthma, 6 had levels of total serum IgE that were substantially elevated (range, 371 to 820 IU/mL) compared with 10 who had lower levels (range, 29 to 124 IU/mL). Those with high levels of IgE had significantly greater lower respiratory tract symptom scores during the initial 4 days of the infection than the low IgE group. They also had higher total blood eosinophil counts at baseline, increased eosinophil cationic protein in their nasal washes (>200 ng/mL), and augmented levels of expired nitric oxide at baseline and during peak cold symptoms. In contrast, levels of soluble intracellular adhesion molecule-1 in nasal wash supernatants from the asthmatic patients with high IgE were diminished, both at baseline and during the infection.

CONCLUSIONS

The reduced lung function and increased markers of inflammation observed before virus inoculation in the asthmatic patients who had high levels of total serum IgE may be risk factors for an adverse response to infections with HRV.

Nasal mucosal histamine reactivity among young students and teachers, having no or prolonged exposure to a deteriorated indoor climate

BACKGROUND

In a study performed in the spring of 1995, we found a significantly greater nasal mucosal histamine reactivity among teachers, who had worked for several years in a recently renovated moisture-damaged school, than in those in a control school. In the present study we investigated the students who begun their high-school studies at both schools in the autumn of 1995 and compared them with the teachers as regards mucosal reactivity, atopy and symptoms.

METHODS

Twenty-eight teachers in the target school, 18 teachers in the control school and 45 students from each school underwent a nasal histamine provocation test and a skin-prick test. They also answered a standardized questionnaire.

RESULTS

The teachers in both schools had more marked nasal mucosal histamine reactivity at the lowest provocation concentrations than the students. The histamine provocation curve of the target school teachers had consistently higher values than that of the students (P = 0.0001), but its slope and shape were similar (P = 0.15), while the slope of the provocation curve of the control school teachers was flatter. However, there was only a borderline significance in this respect compared to the students (P = 0.07). Teachers with a dry and crusty appearance of the nasal mucosa on anterior rhinoscopy reacted more strongly to histamine provocation than those without this finding (P = 0.0004). There was a significantly higher frequency of skin-prick test positivity (SPT+) among the students (P = 0.03). There were no significant differences in nasal mucosal histamine reactivity between atopic and non-atopic subjects out of pollen season.

CONCLUSIONS

Teachers had a significantly greater mucosal histamine reactivity than the students, whereas the latter had a significantly higher frequency of atopy. These results are compatible with an age-related pattern of mucosal reactivity. A crusty appearance of the nasal mucosa seems to predispose to an increase in histamine reactivity. There were no significant differences according to histamine reactivity between atopic and non-atopic subjects.

Airways hyper-responsiveness to bradykinin and methacholine: effects of inhaled fluticasone

BACKGROUND

Although inhaled corticosteroids are the most effective anti-inflammatory agents available for the treatment of asthma, they have, at best, only modest effects on airways responsiveness to methacholine. Thus, hyper-responsiveness to methacholine is a relatively insensitive monitor of the effectiveness of glucocorticoids in asthmatic subjects.

OBJECTIVE

The study aimed to determine if airways hyper-responsiveness to bradykinin provides a more sensitive index of glucocorticoid responsiveness in asthmatic subjects than does hyper-responsiveness to methacholine.

METHODS

A double-blind, placebo-controlled, parallel group study comparing the effects of inhaled fluticasone (220 micro g twice daily) on responsiveness to the two stimuli in asthmatic subjects who had never previously received corticosteroid therapy. Drug (n = 13) or placebo (n = 12) were administered for 16 weeks. Responsiveness to bradykinin and methacholine was determined at baseline and at 4 week intervals.

RESULTS

Placebo did not alter responsiveness to either stimulus compared to baseline. Fluticasone treatment significantly reduced responsiveness to bradykinin (P < 0.001 by Friedman anova) and methacholine (P = 0.02), but changes in responsiveness to bradykinin were significantly greater than those in methacholine responsiveness (P = 0.002). Bradykinin responsiveness was decreased at all treatment times compared to baseline, while methacholine responsiveness was not decreased until 8 weeks of therapy. When data were analyzed as changes from baseline (DeltaLog PD20), DeltaLog PD20 for methacholine was not different at any time-point between the two treatment groups. By contrast, DeltaLog PD20 for bradykinin was significantly greater in patients receiving fluticasone compared to those on placebo at all but the 16-week treatment time. Ten of 13 subjects receiving fluticasone failed, on at least one post-treatment visit, to show a 20% fall in forced expiratory volume (FEV1), even at the highest dose of bradykinin.

CONCLUSIONS

Airways responsiveness to bradykinin is more profoundly, and more rapidly, reduced by inhaled glucocorticoids than is responsiveness to methacholine. Airways hyper-responsiveness to bradykinin provides a convenient and sensitive monitor of glucocorticoid responsiveness in asthma.

Neurology of allergic inflammation and rhinitis

Afferent nerves, derived from the trigeminal ganglion, and postganglionic autonomic nerves, derived from sympathetic and parasympathetic ganglia expressing many different neurotransmitters, innervate the nose. Reflexes that serve to optimize the air-conditioning function of the nose by altering sinus blood flow, or serve to protect the nasal mucosal surface by mucus secretion, vasodilatation, and sneezing, can be initiated by a variety of stimuli, including allergen, cold air, and chemical irritation. Activation of nasal afferent nerves can also have profound effects on respiration, heart rate, blood pressure, and airway caliber (the diving response). Dysregulation of the nerves in the nose plays an integral role in the pathogenesis of allergic rhinitis. Axon reflexes can precipitate inflammatory responses in the nose, resulting in plasma extravasation and inflammatory cell recruitment, while allergic inflammation can produce neuronal hyper-responsiveness. Targeting the neuronal dysregulation in the nose may be beneficial in treating upper airway disease.

The role of nerves in asthma

Asthma is a syndrome characterized by reversible episodes of wheezing, cough, and sensations of chest tightness and breathlessness. These symptoms are secondary to changes in the activity of the nervous system. The mechanisms by which the nervous system is altered such that the symptoms of asthma occur have not yet been elucidated. Airway inflammation associated with asthma may affect neuronal activity at several points along the neural reflex pathway, including the function of the primary afferent (sensory) nerves, integration within the central nervous system, synaptic transmission within autonomic ganglia, and transmission at the level of the postganglionic neuroeffector junction. We provide a brief overview of these interactions and the relevance they may have to asthma.

Pharmacology of airway afferent nerve activity

Afferent nerves in the airways serve to regulate breathing pattern, cough, and airway autonomic neural tone. Pharmacologic agents that influence afferent nerve activity can be subclassified into compounds that modulate activity by indirect means (e.g. bronchial smooth muscle spasmogens) and those that act directly on the nerves. Directly acting agents affect afferent nerve activity by interacting with various ion channels and receptors within the membrane of the afferent terminals. Whether by direct or indirect means, most compounds that enter the airspace will modify afferent nerve activity, and through this action alter airway physiology.

Thoughts on the pathophysiology of nonallergic rhinitis

Nonallergic noninfectious rhinitis is a diagnosis by exclusion, meaning that a number of poorly defined nasal conditions that have in common allergy and infection as a cause of the rhinitis have been excluded. The etiology of some subgroups of nonallergic noninfectious rhinitis, like nonallergic rhinitis with eosinophilia (NARES) and drug-induced rhinitis, are quite well defined, but in the majority of the patients, the etiology and pathophysiology are unknown. These patients are classified as idiopathic rhinitis patients. A careful determination of the intensity of the symptoms combined with modern diagnostic tools enables us to discriminate idiopathic rhinitis patients from normal controls. This review discusses the possible pathophysicologic mechanisms of nonallergic noninfectious rhinitis, with emphasis on idiopathic rhinitis.

Neurogenic mechanisms in rhinosinusitis

Nasal sensory nerve stimulation leads to sensations of pain and congestion and nociceptive nerve axon response-mediated release of substance P that stimulates glandular secretion as an immediate-acting protective mucosal defense. Recruited parasympathetic reflexes cause submucosal gland secretion via muscarinic M3 receptors. Parasympathetic reflexes, sneezing, and other avoidance behaviors rapidly clear the upper airway of offending agents while protecting the lower airways. Dysfunction contributes to allergic, infectious, and other nonallergic rhinitides and possibly sinusitis. Sympathetic arterial vasoconstriction reduces mucosal blood flow, sinusoidal filling, and mucosal thickness, restoring nasal patency. Loss of sympathetic tone may contribute to some chronic, nonallergic rhinopathies.

Nasal provocation testing: a review

OBJECTIVE

This review focuses on the uses of nasal provocation testing (NPT) for scientific investigations of the mechanisms of allergic and nonallergic rhinitis. It also describes the use of NPT as a diagnostic tool in clinical practice. The indications, contraindications, advantages, and limitations of different techniques for evaluation of nasal responses are reviewed. The paper familiarizes investigators with particulars of different nasal delivery systems, provocation agents, nasal patency measurements, secretion collection, and nasal lavage techniques.

DATA SOURCES

Relevant publications obtained from a literature review.

STUDY SELECTION

Relevant publications on the topics of NPT, allergic, and nonallergic rhinitis were critically evaluated.

RESULTS AND CONCLUSIONS

To date, NPT has been used primarily as a research tool for the investigation of allergic and nonallergic rhinitis with a wide variety of techniques depending on the specific scientific purposes. NPT will continue to provide useful information about the pathogenesis of airway diseases. Standardized nasal provocation testing has the potential to become a more frequently used clinical test in the diagnosis of allergic and occupational rhinitis and for determination of the appropriate and focused therapy.

Ion channels in airway afferent neurons

Action potentials initiated at the peripheral terminal of an afferent nerve are conducted to the central nervous system therein causing release of neurotransmitters that excite secondary neurons in the brain stem or spinal cord. Various chemicals, extremes in osmolarity and pH as well as mechanical stimuli are sensed by primary afferent nerves that innervate the airways. The processes leading to excitation of afferent nerve endings, conduction of action potentials along axons, transmitter secretion, and neuronal excitability are regulated by ions flowing through channels in the nerve membrane. Voltage-gated ion channels selective for K+ and Na+ ions allow the generation and conduction of action potentials and along with families of ion channels selective for other ions such as Ca2+ or Cl- are thought to play distinctive roles in regulating neuronal excitability and transmitter secretion. Here we discuss, in general terms, the roles played by various classes of ion channels in the activation, neurotransmitter secretion and excitability of primary afferent neurons.

The nose-lung interaction in allergic rhinitis and asthma: united airways disease

The link between upper and lower respiratory tracts has been repeatedly observed in the past 50 years but only carefully investigated during the past decade. Several clinical and experimental observations suggested the hypothesis of the unity of upper and lower airways (allergic rhinobronchitis or united airways disease). The relationships between rhinitis (and sinusitis) and asthma also include non-epidemiological aspects such as viral infections and bronchial hyperreactivity. The hypotheses have been confirmed by means of epidemiological observations, functional and immunological evidence and, indirectly, by observing the effects of drugs used mainly for rhinitis on asthma symptoms. In this article, therefore, we collected and reviewed the most relevant experimental results available to support the hypothesis for united airways disease and the studies conducted on the possible mechanisms of nose-lung interaction.

Neural integration and allergic disease

Changes in neural activity play a key role in many symptoms of allergic disease, including sneezing, coughing, itching, and ocular irritation, among others. The mechanisms underlying allergen-induced changes in neural activity (reflexes) are largely unknown and under active investigation. Allergic inflammation can affect neural activity on a variety of levels, including at the primary afferent sensory nerve, integrative centers of the central nervous system, autonomic ganglia, and autonomic neuroeffector junction. At the level of the afferent sensory nerve, mediators released after allergen exposure either directly or indirectly increase neuronal firing. At the level of sensory ganglia, which contain cell bodies that innervate a variety of organs, changes in neuronal excitability may lead to a generalization of allergic symptoms. In the central nervous system, where afferent inputs from throughout the body converge, allergic inflammation may be associated with central sensitization, leading to the modulation of the neural reflexes. Finally, at the autonomic ganglia and neuroeffector junction, allergic inflammation appears to be associated with enhanced ganglionic transmission and neurotransmitter release, respectively. Mechanisms by which allergen challenge affects neuronal activity at various levels of the nervous system are reviewed, with a primary emphasis on studies of airway physiologic factors.

Induction by inhibitors of nitric oxide synthase of hyperresponsiveness in the human nasal airway

1. The effects of inhibitors of nitric oxide synthase (NOS) on the responsiveness of the human nasal airway were investigated, by measuring the nasal response to histamine and bradykinin. 2. Repeated intranasal administration of N(G)-nitro-L-arginine methyl ester (L-NAME) or N(G)-monomethyl-L-arginine (L-NMMA), 1 micromol per nostril every 30 min for 6 h, increased the nasal obstruction induced by histamine, 50 - 500 microg, and bradykinin, 200 microg per nostril. A single administration of L-NAME, 1 micromol per nostril did not induce hyperresponsiveness to histamine. 3. Pretreatment with L-arginine, 30 micromol, abolished the hyperresponsiveness to histamine caused by L-NAME, 1 micromol. Pretreatment with N(G)-nitro-D-arginine methyl ester (D-NAME), 1 micromol, did not induce hyperresponsiveness to histamine. 4. Repeated administration of L-NAME, 1 micromol, caused a significant reduction in the amount of nitric oxide measured in the nasal cavity. 5. Neither L-NMMA, 1 micromol, nor L-arginine, 30 micromol, altered the nasal hyperresponsiveness induced by platelet activating factor (PAF), 60 microg. PAF did not alter the levels of nitric oxide in the nasal cavity. 6. The results suggest that inhibition of nitric oxide synthase induces a hyperresponsiveness in the human nasal airway, and that this occurs by a mechanism different from that involved in PAF-induced hyperresponsiveness.

Unique mechanistic features of allergic rhinitis

Symptoms of allergic rhinitis are produced by inflammatory mediators that are released upon activation of mast cells by antigen-IgE interaction. These mediators target the end organs directly or indirectly. Stimulation of sensory nerves by histamine, for example, leads to sneezing, pruritus, rhinorrhea, and nasal congestion. The clinical presentation of allergic rhinitis is also characterized by the phenomenon of hyperresponsiveness to nonallergic stimuli, such as cold air and various irritants. This phenomenon is believed to result from the effect of allergic inflammation on the sensory nerves that supply the upper airway mucosa. Various nonallergic triggers have been shown to act on the nasal mucosa through sensorineural stimulation. In allergic rhinitis, responsiveness to these stimuli is increased compared with the healthy state. A similar phenomenon is observed against such products of the allergic reaction as his-tamine and bradykinin. Also, in allergic rhinitis, stimulation of sensory nerves per se can produce inflammatory changes, a phenomenon known as neurogenic inflammation. The mechanism behind the development of sensorineural hyperresponsiveness and of increased propensity for neurogenic inflammation is unknown. However, evidence exists that the neurotrophin nerve growth factor, which can induce all these changes on sensory nerves, is produced in the human nasal mucosa and found in higher quantities in nasal secretions of patients with perennial allergic rhinitis as compared with healthy control subjects. Also, nerve growth factor is acutely released into nasal fluids after allergen provocation of patients with allergic disease. In patients with asthma of atopic origin, allergic rhinitis is almost ubiquitous. Because the nose is the air conditioner of the respiratory system, its dysfunction may negatively affect the lower airways. In addition to the conditioning of inhaled air, the association between allergic rhinitis and asthma may involve various mechanisms. For example, allergen provocation in the nose of a patient with asthma can lead to reductions in pulmonary function and to increased lower airway responsiveness after several hours. Also, nasal inflammation may propagate through a systemic route to affect the lower airways.

Nerve growth factor expression and release in allergic inflammatory disease of the upper airways

It is well known that allergic airways disease is characterized by inflammation and hyperresponsiveness, but the link between these two conditions has not been elucidated. We have previously shown that in allergic rhinitis, hyperresponsiveness is attributable to increased neural reactivity. We thus hypothesized that nerve growth factor (NGF), which is expressed by inflammatory cells and effects changes that lead to increased neural responsiveness, could be a pivotal mediator in this disease. Using reverse transcription-polymerase chain reaction (RT-PCR), Western immunoblotting, and ELISA to evaluate NGF expression and release, we found that subjects with allergic rhinitis have significantly decreased NGF mRNA in superficial nasal scrapings and significantly higher baseline concentrations of NGF protein in nasal lavage fluids, compared with control subjects. Nasal provocation with allergen significantly increased NGF protein in nasal lavage fluids of subjects with allergic rhinitis, but not of control subjects. The concentrations of NGF protein in nasal lavage fluids were not affected by provocation with the vehicle for allergen or with histamine. These data provide the first evidence of a steady state of dysregulation in mucosal NGF expression and release in allergic rhinitis, and support a role of this neurotrophin in the pathophysiology of allergic inflammatory disease of the human airways.