Changes in levels of nerve growth factor in nasal secretions after capsaicin inhalation in patients with airway symptoms from scents and chemicals

Intranasal trigeminal function in chronic rhinosinusitis: a review

INTRODUCTION

Chronic rhinosinusitis (CRS) affects 5-12% of the general population with significant effects on quality of life. Chronic inflammation also seems to affect intranasal trigeminal sensitivity.

AREAS COVERED

A systematic literature search was done in Scopus, Web of Science, and PubMed in February 2023. The review addressed intranasal trigeminal function in patients with CRS and summarized current knowledge on trigeminal function as it relates to the symptoms, assessment, and treatment of CRS.

EXPERT OPINION

Olfaction and trigeminal function are synergistic and this interaction may contribute to trigeminal dysfunction in CRS. Aside from anatomic blockage through polypoid mucosal changes, trigeminal dysfunction may affect the perception of nasal obstruction in CRS. Upregulated immune defense mechanisms leading to damage of nerve endings, changes in nerve growth factor release or other mechanisms may be responsible for trigeminal dysfunction in CRS. Since the pathophysiology of trigeminal dysfunction in CRS is poorly understood, current treatment recommendations are directed toward the therapy of CRS as an underlying cause, although the effect of surgery and corticosteroids on trigeminal function remains unclear. A standardized and validated trigeminal test that is accessible and easy to use in clinical settings would be beneficial for future studies.

Characteristics of idiopathic pulmonary fibrosis -associated cough. a case-control study

BACKGROUND

Most patients with idiopathic pulmonary fibrosis (IPF) complain of cough. IPF-associated cough is widely characterized as dry or non-productive. The aim of this study was to compare chronic cough in early stage IPF patients to cough in subjects with chronic cough from a community-based sample and, especially, to investigate whether cough in IPF is less productive than chronic cough in a community-based sample.

METHODS

The IPF cough population consisted of 46 biopsy-confirmed patients who complained of chronic cough. Control population consisted of subjects with chronic cough, gathered by a community-based email survey sent to public service employees and the Finnish Pensioners' Federation. A case-control setting was applied by having four age, gender, and smoking-status matched subjects from the community sample for each IPF cough patient. A cough specific quality of life questionnaire (Leicester Cough Questionnaire (LCQ)) was filled in by all subjects. The LCQ questionnaire contains 19 questions, each question is scored from 1 to 7 and total score from 3 to 21 with a smaller value indicating more severe impairment.

RESULTS

The sputum production frequency, as assessed by LCQ question 2, was 5.0 (3.0-6.0) in the IPF chronic cough population and 5.0 (3.0-6.0) in the community-based chronic cough population (median and interquartile range p= 0.72). The LCQ total score was 14.8 (11.5-18.1) in the IPF chronic cough population and 15.4 (13.0-17.5) in the community-based chronic cough population (p=0.76). The domain impact scores were physical, 4.9 (3.9-6.1) vs. 5.1 (4.5-5.6) (p=0.80); psychological, 4.6 (3.7-5.9) vs. 4.7 (3.9-5.7) (p=0.90); and social, 5.5 (3.7-6.5) vs. 5.5 (4.5-6.3) (p=0.84), respectively. Furthermore, cough response to paint or fumes, cough disturbing sleep, and cough frequency per day did not differ between the groups.

CONCLUSION

Cough in early stage IPF patients was not distinguishable from chronic cough in the community-based population by LCQ. Especially, there was no difference in the self-reported frequency of cough-associated sputum production.

Multiple Chemical Sensitivity: It's time to catch up to the science

Multiple chemical sensitivity (MCS) is a complex medical condition associated with low dose chemical exposures. MCS is characterized by diverse features and common comorbidities, including fibromyalgia, cough hypersensitivity, asthma, and migraine, and stress/anxiety, with which the syndrome shares numerous neurobiological processes and altered functioning within diverse brain regions. Predictive factors linked to MCS comprise genetic influences, gene-environment interactions, oxidative stress, systemic inflammation, cell dysfunction, and psychosocial influences. The development of MCS may be attributed to the sensitization of transient receptor potential (TRP) receptors, notably TRPV1 and TRPA1. Capsaicin inhalation challenge studies demonstrated that TRPV1 sensitization is manifested in MCS, and functional brain imaging studies revealed that TRPV1 and TRPA1 agonists promote brain-region specific neuronal variations. Unfortunately, MCS has often been inappropriately viewed as stemming exclusively from psychological disturbances, which has fostered patients being stigmatized and ostracized, and often being denied accommodation for their disability. Evidence-based education is essential to provide appropriate support and advocacy. Greater recognition of receptor-mediated biological mechanisms should be incorporated in laws, and regulation of environmental exposures.

Cough Sensitivity to Several External Triggers is Associated with Multiple Non-respiratory Symptoms

PURPOSE

Enhanced responsiveness to external triggers is thought to reflect hypersensitivity of the cough reflex. It may involve an enhanced sensitivity of the afferent nerves in the airways and/or an abnormal processing of the afferent information by the central nervous system (CNS). The CNS processing of cough has been shown to involve the same regions as those in symptom amplification, a phenomenon that often manifests as multiple symptoms. The main purpose of the present study was to define whether the presence of several cough triggers is associated with multiple symptoms.

METHODS

2131 subjects with current cough responding to two email surveys filled in a comprehensive questionnaire about social background, lifestyle, general health, doctors' diagnoses and visits, symptoms, and medication. Multiple symptoms was defined as three or more non-respiratory, non-mental symptoms.

RESULTS

A carefully controlled multiple regression analysis revealed that the number of cough triggers was the only cough characteristic associating with multiple non-respiratory, non-mental symptoms [aOR 1.15 (1.12-1.19) per one trigger, p < 0.001]. Among the 268 subjects with current cough both in the first survey and in the follow-up survey 12 months later, the repeatability of the trigger sum was good with an intraclass correlation coefficient of 0.80 (0.75-0.84).

CONCLUSION

The association between the number of the cough triggers and multiple symptoms suggests that the CNS component of cough hypersensitivity may be a manifestation of non-specific alteration in the CNS interpretation of various body sensations. The number of cough triggers is a repeatable measure of cough sensitivity.

Neurological susceptibility to environmental exposures: pathophysiological mechanisms in neurodegeneration and multiple chemical sensitivity

The World Health Organization lists air pollution as one of the top five risks for developing chronic non-communicable disease, joining tobacco use, harmful use of alcohol, unhealthy diets and physical inactivity. This review focuses on how host defense mechanisms against adverse airborne exposures relate to the probable interacting and overlapping pathophysiological features of neurodegeneration and multiple chemical sensitivity. Significant long-term airborne exposures can contribute to oxidative stress, systemic inflammation, transient receptor subfamily vanilloid 1 (TRPV1) and subfamily ankyrin 1 (TRPA1) upregulation and sensitization, with impacts on olfactory and trigeminal nerve function, and eventual loss of brain mass. The potential for neurologic dysfunction, including decreased cognition, chronic pain and central sensitization related to airborne contaminants, can be magnified by genetic polymorphisms that result in less effective detoxification. Onset of neurodegenerative disorders is subtle, with early loss of brain mass and loss of sense of smell. Onset of MCS may be gradual following long-term low dose airborne exposures, or acute following a recognizable exposure. Upregulation of chemosensitive TRPV1 and TRPA1 polymodal receptors has been observed in patients with neurodegeneration, and chemically sensitive individuals with asthma, migraine and MCS. In people with chemical sensitivity, these receptors are also sensitized, which is defined as a reduction in the threshold and an increase in the magnitude of a response to noxious stimulation. There is likely damage to the olfactory system in neurodegeneration and trigeminal nerve hypersensitivity in MCS, with different effects on olfactory processing. The associations of low vitamin D levels and protein kinase activity seen in neurodegeneration have not been studied in MCS. Table 2 presents a summary of neurodegeneration and MCS, comparing 16 distinctive genetic, pathophysiological and clinical features associated with air pollution exposures. There is significant overlap, suggesting potential comorbidity. Canadian Health Measures Survey data indicates an overlap between neurodegeneration and MCS (p < 0.05) that suggests comorbidity, but the extent of increased susceptibility to the other condition is not established. Nevertheless, the pathways to the development of these conditions likely involve TRPV1 and TRPA1 receptors, and so it is hypothesized that manifestation of neurodegeneration and/or MCS and possibly why there is divergence may be influenced by polymorphisms of these receptors, among other factors.

[Research progress of biomarkers in nasal secretions in endotypes diagnosis and clinical application of chronic rhinosinusitis]

With the development of studies on the endotypes of chronic rhinosinusitis （CRS） and the biomarkers of nasal secretions, the studies of CRS endotypes based on nasal secretion have become more abundant. This paper summarizes the endotypes classification of CRS, the collection methods of nasal secretion and the nasal secretion biomarkers related to the endotypes of CRS, in order to provide a reference for establishing the corresponding endotypes of CRS based on the nasal secretion biomarkers.

Physiological Health and Physical Performance in Multiple Chemical Sensitivity-Described in the General Population

Multiple chemical sensitivity (MCS) is a multifactorial somatic disorder characterized by physical reactions triggered by even extremely low levels of different airborne chemicals. In most individuals with MCS, these reactions have substantial negative impact on social, occupational, and everyday life often including limited or no engagement in physical activities. The aim of this study was to explore associations between MCS and objective measurements of anthropometry, cardiorespiratory health, and physical performance. From the Danish population-based cohort DanFunD counting 9656 participants aged 18–76 years, 1.95% (n = 188) were categorized as MCS individuals (MCS All). Of those 188, 109 participants were subcategorized as having MCS without functional somatic disorders (FSD) (MCS with no comorbid FSD). The remaining study population without any FSD were regarded controls. We used adjusted multiple linear regression analyses to evaluate associations between MCS and anthropometry, cardiorespiratory fitness, and physical performance. Compared with the general population, MCS All had less optimal body composition, increased risk of obesity, impaired cardiorespiratory fitness, and physical performance which was not seen in MCS with no comorbid FSD. MCS individuals may be inhibited to maintain an active lifestyle which can increase risk of obesity and consequently have negatively impact on general health, which may not be the case among MCS with no comorbid FSD.

Multiple Chemical Sensitivity

Multiple Chemical Sensitivity (MCS), a condition also known as Chemical Sensitivity (CS), Chemical Intolerance (CI), Idiopathic Environmental Illness (IEI) and Toxicant Induced Loss of Tolerance (TILT), is an acquired multifactorial syndrome characterized by a recurrent set of debilitating symptoms. The symptoms of this controversial disorder are reported to be induced by environmental chemicals at doses far below those usually harmful to most persons. They involve a large spectrum of organ systems and typically disappear when the environmental chemicals are removed. However, no clear link has emerged among self-reported MCS symptoms and widely accepted objective measures of physiological dysfunction, and no clear dose-response relationship between exposure and symptom reactions has been observed. In addition, the underlying etiology and pathogenic processes of the disorder remain unknown and disputed, although biologic and psychologic hypotheses abound. It is currently debated whether MCS should be considered a clinical entity at all. Nevertheless, in the last few decades MCS has received considerable scientific and governmental attention in light of the many persons reporting this illness. In this review, we provide a general overview of the history, definition, demographics, prevalence, and etiologic challenges in defining and understanding MCS.

Utility of Cough Provocation Tests in Chronic Cough and Respiratory Diseases: A Comprehensive Review and Introduction of New Reference Ranges for the Capsaicin Test

Cough provocation tests (CPTs) are an objective measurement of the sensitivity of the cough reflex arc. However, they are not established in clinical practice because a large variability of response in healthy subjects limits their diagnostic value. There is a paucity of studies that have investigated CPT reference ranges in healthy subjects. This systematic review describes the variability of the responses to CPTs in healthy subjects and factors that influence it. A new analysis of 134 healthy subjects was conducted to create reference ranges for single-breath capsaicin CPT by calculating the interquartile ranges for the provocative concentration of capsaicin to induce 2 and 5 coughs. Female subjects had a more sensitive cough reflex than male counterparts. The ability of CPTs to distinguish various respiratory diseases from healthy subjects was also reviewed. Cough sensitivity was consistently heightened in the following groups: unselected patients with chronic, refractory, or recurrent cough, unexplained chronic cough, gastro-esophageal reflux-associated cough, cough-variant asthma, lower airway symptoms induced by chemical irritants, and fibrotic interstitial lung diseases. In the following groups, hypersensitivity of the cough reflex was present in those individuals whose symptom profile was predominated by cough: asthma, chronic obstructive pulmonary disease (COPD), bronchiectasis, and sarcoidosis. In the following conditions, patients usually cough in order to expectorate mucus from their airways, not because of a hypersensitive cough reflex arc: productive cough, asthma, upper airway cough syndrome, COPD, bronchiectasis, cystic fibrosis, and chronic respiratory infections. CPTs have the potential to identify patients with chronic respiratory symptoms due to cough reflex hypersensitivity, thereby providing a targeted approach for therapy.

Chemical intolerance: involvement of brain function and networks after exposure to extrinsic stimuli perceived as hazardous

Background

Chemical intolerance (CI) is a chronic condition characterized by recurring and severe symptoms triggered by exposure to low levels of odorous or pungent substances. The etiology of CI has been a controversial subject for a long time. The aim of this review is to summarize findings on the neurological processing of sensory information during and after exposure to low levels of odorous or pungent substances in individuals with CI, focusing on the brain function and networks.

Methods

Scientific studies on CI published between 2000 and 2019 in academic peer-reviewed journals were systematically searched using medical and scientific literature databases. Only peer-reviewed articles reporting original research from experimental human studies directly associated with CI, and involving related neurological responses or brain imaging after exposure to odorous or pungent substances (i.e., in chemical provocation tests), were considered.

Results

Forty-seven studies were found to be eligible for a full-text review. Twenty-three studies met the selection criteria and were included in this review. Evidence indicated that differences between subjects with CI and healthy controls were observed by brain imaging during and after exposure to odorous or pungent substances. Differences in brain imaging were also observed between initial exposure and after exposure to these substances. Neurological processing of sensory information after exposure to extrinsic stimuli in the limbic system and related cortices were altered in subjects with CI. A previous documentable exposure event was likely to be involved in this alteration.

Conclusions

This review documents consistent evidence for the altered neurological processing of sensory information in individuals with CI. Further neurophysiological research exploring the processing of extrinsic stimuli and cognition of sensation through the limbic system and related cortices in CI, and the appearance of symptoms in individuals with CI, are required.

Spice-Derived Bioactive Ingredients: Potential Agents or Food Adjuvant in the Management of Diabetes Mellitus

Spices possess tremendous therapeutic potential including hypoglycemic action, attributed to their bioactive ingredients. However, there is no study that critically reviewed the hypoglycemic potency, safety and the bioavailability of the spice-derived bioactive ingredients (SDBI). Therefore, the aim of the study was to comprehensively review all published studies regarding the hypoglycemic action of SDBI with the purpose to assess whether the ingredients are potential hypoglycemic agents or adjuvant. Factors considered were concentration/dosages used, the extent of blood glucose reduction, the IC50 values, and the safety concern of the SDBI. From the results, cinnamaldehyde, curcumin, diosgenin, thymoquinone (TQ), and trigonelline were showed the most promising effects and hold future potential as hypoglycemic agents. Conclusively, future studies should focus on improving the tissue and cellular bioavailability of the promising SDBI to achieve greater potency. Additionally, clinical trials and toxicity studies are with these SDBI are warranted.

Approach to chronic cough: the neuropathic basis for cough hypersensitivity syndrome

Chronic cough is a common symptom that can be difficult to manage because associated causes may remain elusive and treatment of any associated cause may not provide relief. Current antitussives have limited efficacy and undesirable side-effects. Patients with chronic cough describe sensory symptoms suggestive of upper airway and laryngeal neural dysfunction, and report cough triggered by low-level physical and chemical stimuli supporting the concept of cough reflex hypersensitivity. Mechanisms underlying peripheral and central augmentation of the afferent cough pathways have been identified. Chronic cough is a neuropathic condition that could be secondary to sensory nerve damage caused by inflammatory, infective and allergic factors. Recent success in the treatment of chronic cough with agents used for treating neuropathic pain such as gabapentin and amitryptiline would also support this concept. Research into neuropathic cough may lead to the discovery of more effective antitussives.

Review of evidence for a toxicological mechanism of idiopathic environmental intolerance

Idiopathic environmental intolerance (IEI) is a medically unexplained disorder characterised by a wide variety of unspecific symptoms in different organ systems and attributed to nontoxic concentrations of chemicals and other environmental factors that are tolerated by the majority of individuals. Both exposure to chemicals and behavioural conditioning are considered as possible contributors to the development of IEI. However, owing to the heterogeneity of the condition, it is difficult to separate the toxicological, physiological and psychological aspects of IEI. Here, we review the evidence for postulated toxicologically mediated mechanisms for IEI. Available data do not support either a classical receptor-mediated or an idiosyncratic toxicological mechanism. Furthermore, if there were convincing evidence for a psychological cause for many patients with IEI, then this would suggest that the priority for the future is the development of psychological treatments for IEI. Finally, we advocate genome wide screening of IEI patients to elucidate genotypic features of the condition.

Cough pharmacotherapy: current and future status

INTRODUCTION

Chronic cough is responsible for a significant illness burden in the community. Refractory cough causes substantial quality-of-life impairment in people with this problem. Neuromodulators for sensory neuropathic cough and new compounds to block transient receptor potential (TRP) receptors hold promise for chronic cough and upper airway hypersensitivity.

AREAS COVERED

The authors examine current evidence on the new concepts of chronic cough that relate to the study of idiopathic/refractory cough, the role of central nervous system control of cough and the role of laryngeal irritability and sensory neuropathy in cough. Compounds in development to block TRP receptors, treatment for a neuropathic disorder with neuromodulators and cough suppression with opioids, especially codeine and morphine, are investigated. Relevant randomized control trials and case reports were identified through a PubMed search of English-language literature referring to these concepts.

EXPERT OPINION

The concept that sensory neuropathic disorder may underlie some cases of chronic cough is useful in characterizing cough, understanding its mechanisms and guiding drug development.

Unexplained chronic cough and vitamin B-12 deficiency

BACKGROUND

Chronic cough is characterized by sensory neuropathy. Vitamin B-12 (cobalamin) deficiency (Cbl-D) causes central and peripheral nervous system damage and has been implicated in sensory neuropathy and autonomic nervous system dysfunction.

OBJECTIVE

We evaluated whether Cbl-D has a role in chronic, unexplained cough.

DESIGN

Laryngeal threshold (histamine concentration that provokes a 25% decrease in the midinspiratory flow), bronchial threshold (histamine concentration that provokes a 20% decrease in the forced expiratory volume in 1 s), and cough threshold (histamine concentration that causes ≥5 coughs) in response to an inhaled histamine were assessed in 42 patients with chronic, unexplained cough [27 Cbl-D patients and 15 patients without Cbl-D (Cbl-N)] before and after intramuscular injections of cobalamin for 2 mo. Laryngeal, bronchial, and cough hyperresponsiveness was diagnosed when histamine concentration thresholds were ≤8 mg/mL. Seven Clb-D and 3 Cbl-N patients underwent an oropharyngeal biopsy before treatment.

RESULTS

Cbl-D patients had a higher prevalence of laryngeal hyperresponsiveness than did Cbl-N patients (92.6% compared with 66.7%; P = 0.03), a thinner oropharyngeal epithelium [133.7 μm (95% CI: 95, 172 μm) compared with 230.8 μm (95% CI: 224, 237 μm); P = 0.002], a lower number of myelinated nerve fibers [2.25/mm(2) (95% CI: 1.8, 2.7/mm(2)) compared with 3.44/mm(2) (95% CI: 3, 3.8/mm(2)); P = 0.05], and a higher immunoreactive score for nerve growth factor (NGF) [6.7 (95% CI: 6, 7.3) compared with 2.8 (95% CI: 2.5, 3.1); P = 0.02]. After cobalamin supplementation, symptoms and laryngeal, bronchial, and cough thresholds were significantly improved in Cbl-D but not in Cbl-N patients.

CONCLUSIONS

This study suggests that Cbl-D may contribute to chronic cough by favoring sensory neuropathy as indicated by laryngeal hyperresponsiveness and increased NGF expression in pharyngeal biopsies of Cbl-D patients. Cbl-D should be considered among factors that sustain chronic cough, particularly when cough triggers cannot be identified.

The airway sensory hyperreactivity syndrome

After exclusion of diverse pulmonary illnesses, the remaining explanations for chronic cough include medication with angiotensin-converting enzyme (ACE) inhibitor, gastroesophageal reflux disease (GERD), and post-nasal drip. Different clinics report shifting frequencies for both the causes of chronic cough and the success of treatment. However, after all evaluations, differential diagnosis still leaves a group of patients with unexplained cough. This unexplained cough is also known as chronic idiopathic cough (CIC), though there are widely varying opinions as to its existence. Among patients previously diagnosed with CIC, a subgroup has been identified with both upper and lower airway symptoms, including cough induced by odours and chemicals, and with increased cough sensitivity to inhaled capsaicin, which is known to stimulate the airway sensory nerves. A suggested explanation for this condition is a hyperreactivity of the sensory nerves of the entire airways, and hence the condition is known as sensory hyperreactivity (SHR). SHR affects more than 6% of the adult population in Sweden. It is a longstanding condition, and is clearly associated with significant social and psychological impacts.

Modulation of sensory nerve function and the cough reflex: understanding disease pathogenesis

To cough is a protective defence mechanism that is vital to remove foreign material and secretions from the airways and which in the normal state serves its function appropriately. Modulation of the cough reflex pathway in disease can lead to inappropriate chronic coughing and an augmented cough response. Chronic cough is a symptom that can present in conjunction with a number of diseases including chronic obstructive pulmonary disease (COPD) and asthma, although often the cause of chronic cough may be unknown. As current treatments for cough have proved to exhibit little efficacy and are largely ineffective, there is a need to develop novel, efficacious and safe antitussive therapies. The underlying mechanisms of the cough reflex are complex and involve a network of events, which are not fully understood. It is accepted that the cough reflex is initiated following activation of airway sensory nerves. Therefore, in the hope of identifying novel antitussives, much research has focused on understanding the neural mechanisms of cough provocation. Experimentally this has been undertaken using chemical or mechanical tussive stimuli in conjunction with animal models of cough and clinical cough assessments. This review will discuss the neural mechanisms involved in the cough, changes that occur under pathophysiological conditions and and how current research may lead to novel therapeutic opportunities for the treatment of cough.

Down-regulation of cough sensitivity after eucapnic dry air provocation in chronic idiopathic cough

Down-regulation of cough sensitivity in humans is rarely discussed in terms other than pharmacological treatment of cough or hypersensitive cough reflex. Chronic cough and increased cough sensitivity could be due to a number of airway and other diseases. When such conditions are excluded, there still remains a group of patients with no evident medical explanation for persistent coughing; such patients are often described as having "chronic idiopathic cough". The aim of this study was to use a standardized eucapnic dry air provocation among patients with chronic idiopathic cough in order to study physiological parameters and measure their possible influence on capsaicin cough sensitivity. Fourteen female patients with chronic idiopathic cough and ten healthy controls underwent a capsaicin inhalation provocation on two occasions. In all patients, irritating environmental factors were known to induce cough and airway symptoms. One of the two capsaicin provocations was preceded by a eucapnic dry air provocation. Number of coughs, spirometry, respiratory rate, pulse rate, end-tidal CO(2), and oxygen saturation by pulse oximetry (PSaO(2)) were registered and compared. The patients showed increased capsaicin sensitivity compared with the control subjects. This sensitivity was decreased when the capsaicin test was preceded by a eucapnic dry air provocation. Before the dry air provocation and after the capsaicin provocations, end-tidal CO(2) was decreased among the patients in comparison with the controls. After dry air provocation, spirometry values remained unchanged. The results suggest that in patients with chronic idiopathic cough, physiological down-regulation of the cough sensitivity is possible with a eucapnic dry air provocation.

Immunoassay-based measurement of clinical biomarkers for monitoring changes in nasal cavity

BACKGROUND

Many drugs for treatment of allergies, migraine headaches, inflammation, and other indications are administered into the nasal cavity providing access to the immune and central nervous systems. One of the concerns for using this route of administration is potential damage to the nasal epithelium and mucosal regions. We assembled a panel of clinical biomarkers that can be used to monitor changes in the nasal epithelium, mucosa, and olfactory regions in preparation for clinical trials involving drugs administered via intranasal route. These biomarkers included albumin, elastase, IL-6, IL-8, lactoferrin, myeloperoxidase and nerve growth factor.

METHODS

Immunoassays were developed and used to measure changes in these biomarkers in nasal lavage samples collected twice daily from 30 assumed-healthy volunteers over a 2-day period. Various statistical methods including analysis of variance (ANOVA), paired t-test and Pearson's product-moment correlation were used to evaluate the data.

RESULTS

Although the basal levels of these biomarkers were varied among subjects, the data show that the concentrations of albumin, elastase and IL-8 were significantly higher in samples collected in the morning compared to samples collected later during the day. Pre-washing nasal cavity prior to collecting nasal lavage samples did alter the measurement of elastase and albumin, but did not influence the levels of the other biomarkers.

CONCLUSIONS

These data show that this panel of biomarkers can be used to monitor changes in the nasal cavity including those affected by diurnal fluctuations. These results also provide useful baseline values and sources of variability for each biomarker that could be used to help design clinical trials.

Mechanisms of increased airway sensitivity to occupational chemicals and odors

PURPOSE OF REVIEW

Airway symptoms induced by chemicals and odors are common problems that are also reported after contact with substances normally regarded as nontoxic. This article reviews current findings and opinions regarding mechanisms of increased airway sensitivity to occupational chemicals and odors.

RECENT FINDINGS

Individuals exposed to organic solvents during work had more nasal irritation and lower threshold to pyridine odor compared with a nonexposed control group. Six percentage of a general population in Sweden had pronounced airway chemical sensitivity and augmented capsaicin cough sensitivity, known to reflect the sensory nerve reactivity of the airways. The cough sensitivity was associated with changed levels of nerve growth factor in nasal lavage and such patients had longstanding symptoms influencing their working capacity. Positron emission tomography activation studies with several different odorants showed in patients with odor-associated symptoms an odorant-related increase in activation of the anterior cingulate cortex and cuneus-precuneus in comparison with a control group.

SUMMARY

In subgroups of individuals with airway symptoms induced by chemicals and odors, there seems to be a sustainable physiological mechanism behind the reactions. An increased vulnerability to stress cannot be neglected as a confounding factor in some sensitive individuals.

Dyspnea from exercise in cold air is not always asthma

In the absence of other explanations, exercise-induced dyspnea is often labeled as a manifestation of asthma. The aim of this study was to use exercise provocation in cold air among patients with exercise-induced dyspnea, but without any bronchoconstriction, in order to study induced symptoms and different physiological parameters and to measure the possible influence of exercise in cold air on capsaicin cough sensitivity. Eleven patients with exercise-induced dyspnea but no asthma, along with 11 healthy controls, performed a capsaicin inhalation provocation on two occasions. One of these provocations was preceded by an exercise provocation in a cold chamber. Number of coughs, airway symptoms, spirometry, respiratory rate, pulse rate, end-tidal CO(2), and PSaO(2) were registered. During exercise, the patients coughed more than the controls and also had more airway symptoms. After exercise provocation, spirometry values remained unchanged, but capsaicin cough sensitivity was increased and end-tidal CO(2) decreased among the patients, both in comparison to the controls and in comparison to the patients themselves prior to exercise. Exercise-induced dyspnea may be associated with hypocapnia from hyperventilation and increased capsaicin cough sensitivity. The diagnosis of exercise-induced asthma should be questioned when the patient has no signs of bronchoconstriction.

Inhaled ethanol potentiates the cough response to capsaicin in patients with airway sensory hyperreactivity

A suggested explanation for airway symptoms induced by chemicals and scents is sensory hyperreactivity (SHR) of airway mucosal nerves. Patients with SHR have increased cough sensitivity to inhaled capsaicin, mediated by transient receptor potential (TRP) ion channels. In animal experiments, some TRP receptors are potentiated by ethanol, which is why in this study, the aim was to evaluate whether a pre-inhalation of ethanol could influence the capsaicin cough response in patients with SHR. Fifteen patients with SHR and 15 healthy controls were provoked on three occasions with two concentrations of inhaled capsaicin. Before each capsaicin provocation, a pre-inhalation of saline or one of two concentrations of ethanol was given in a double-blind, randomized fashion. The participants reacted in a dose-dependent way with cough on the capsaicin inhalations. Among the patients, but not in the control group, pre-inhalation of ethanol increased the cough response dose-dependently. The results suggest that the pathophysiology of SHR is related to airway mucosal TRP receptors in the sensory nerves. In scented products, the combination of ethanol as a solvent and perfume may augment an airway reaction in sensitive individuals.

Quality of life and capsaicin sensitivity in patients with airway symptoms induced by chemicals and scents: a longitudinal study

OBJECTIVE

It is common in asthma and allergy clinics to see patients presenting with upper and lower airway symptoms that are induced by chemicals and scents and not explained by allergic or asthmatic reactions. Previous studies have shown that these patients often have increased cough sensitivity to inhaled capsaicin; such sensitivity is known to reflect the airway sensory reactivity. The aim of this study was to evaluate the duration of symptoms induced by chemicals and scents and to measure health-related quality of life (HRQL) in patients with chemically induced airway symptoms. We also wished to determine and compare repeatability of the cough response to capsaicin inhalation, and to evaluate the patients' airway sensory reactivity in a long-term perspective.

PARTICIPANTS

Seventeen patients with a history of at least 12 months of airway symptoms induced by chemicals and scents were followed over 5 years with repeated questionnaires, measurements of HRQL, and capsaicin inhalation tests.

RESULTS

The symptoms persisted and did not change significantly over time, and the patients had a reduced HRQL that did not change during the 5-year period. The capsaicin sensitivity was increased at the start of the study, the cough sensitivity was long-lasting, and the repeatability of the capsaicin inhalation test was considered to be good in a long-term perspective.

CONCLUSIONS

Upper and lower airway symptoms induced by chemicals and scents represent an entity of chronic diseases, different from asthma or chronic obstructive pulmonary disease, with persistent symptoms, a reduced HRQL, and unchanged sensory hyperreactivity.

TRPV1: a therapeutic target for novel analgesic drugs?

The vanilloid receptor TRPV1 is now recognized as a molecular integrator of painful stimuli ranging from noxious heat to endovanilloids in inflammation. Pharmacological blockade of TRPV1 represents a new strategy in pain relief. TRPV1 antagonists are expected to prevent pain by silencing receptors where pain is generated rather than stopping the propagation of pain, as most-traditional pain killers do. This hypothesis has already being tested in the clinic by administering small molecule TRPV1 antagonists (e.g. GlaxoSmithKline SB-705498) for migraine and dental pain. Paradoxically, in some murine models of chronic pain, TRPV1-deficient mice exhibit more pain-related behavior than their wild-type littermates, indicating that the understanding of TRPV1 in pain is still incomplete. Moreover, there is mounting evidence to suggest the existence of functional TRPV1 both in the brain and in various non-neuronal tissues. The biological role of these receptors remains elusive, but their tissue distribution clearly indicates that they are involved in many more functions than just pain perception. Here, we review the potential therapeutic indications and adverse effects of TRPV1 antagonists.

Role of the upper airways in patients with chronic cough

PURPOSE OF THE REVIEW

Chronic cough can be caused by a number of factors, including infections, rhinosinusitis, asthma and environmental stimuli. This paper reviews recent findings and opinions regarding the role played by the upper airways in chronic cough.

RECENT FINDINGS

Chronic cough has a significant impact on quality of life, which is more pronounced in women. In Western countries, the reported occurrence of rhinosinusitis in patient groups with chronic cough ranges from 8% to 81%. Allergic rhinitis is a risk factor for later development of asthma. In children, bronchiectasis is combined with upper airway abnormalities in the majority of cases. Increased expression of the capsaicin receptor subtype named 'transient receptor potential vanilloid-1', which correlates with capsaicin cough response, has been identified in patients with chronic cough. Patients with airway chemical sensitivity and chronic cough as one symptom have augmented capsaicin cough sensitivity that is related to changed levels of nerve growth factor in nasal lavage.

SUMMARY

Involvement of the upper airways in chronic cough has been confirmed in several studies. However, there are considerable differences between different health centres in the occurrence of rhinosinusitis as a cause of chronic cough. In patients with chronic cough of various causes, a neurochemical alteration in both the upper and the lower airways appears to have taken place, followed by increased cough sensitivity.

Small molecule vanilloid TRPV1 receptor antagonists approaching drug status: can they live up to the expectations?

The cloning of the transient receptor potential vanilloid type-1 (TRPV1) receptor initiated the discovery of potent small molecule antagonists, many of which are in preclinical phase or already undergoing clinical trials. While animal experiments imply a therapeutic value for these compounds as novel analgesic-antiphlogistic drugs, new findings with TRPV1 deficient (trpv1 -/-) mice signal troubles for TRPV1 antagonists as clinical research gains impetus. An emerging concept with important implications for drug development is that TRPV1 may be differentially regulated under physiological and pathological conditions. If so, it is conceivable that such TRPV1 ligands can be synthesized that specifically target TRPV1 in diseased (e.g. inflamed or neoplastic) tissues but spare TRPV1 that subserves its physiological functions in healthy organs. This review explores the current status of this field and seeks an answer to the question how these new discoveries could be factored into TRPV1 drug discovery and development.

The transient receptor potential vanilloid 1: role in airway inflammation and disease

The transient receptor potential vanilloid 1 (TRPV1) is an excitatory cation channel, rather selectively expressed in a subpopulation of nociceptive, primary sensory neurons that promote neurogenic inflammation via neuropeptide release. TRPV1 is activated by noxious temperature, low extracellular pH and diverse lipid derivatives, and is uniquely sensitive to vanilloid molecules, including capsaicin. TRPV1 expression and sensitivity is highly regulated by diverse G protein-coupled and tyrosine kinase receptors. Other exogenous or endogenous chemical agents, including reactive oxygen species, ethanol and hydrogen sulphide sensitize/activate TRPV1. In the airways, TRPV1 agonists cause cough, bronchoconstriction, microvascular leakage, hyperreactivity and hypersecretion. Patients with asthma and chronic obstructive pulmonary disease are more sensitive to the tussive effect of TRPV1 agonists and TRPV1 activation may contribute to respiratory symptoms caused by acidic media present in the airways during asthma exacerbation, gastroesophageal reflux induced asthma or in other conditions. TRPV1 antagonists may be useful in the treatment of these diseases.