Nocturnal airflow obstruction, histamine, and the autonomic central nervous system in children with allergic asthma

Altered metabolites in guinea pigs with allergic asthma after acupoint sticking therapy: New insights from a metabolomics approach

BACKGROUND

Clinical evidence gathered in Chinese communities suggested that acupoint sticking therapy could be an alternative treatment for asthma-related diseases. However, its underlying mechanism is still poorly understood.

AIM/HYPOTHESIS

In this study, we aimed to investigate the mechanism of the anti-inflammatory effect of acupoint sticking application with 'Treatment of Winter Disease in Summer' (TWDS) prescription by using metabolomics.

METHODS

Allergic asthma in guinea pig was sensitized and challenged by ovalbumin (OVA). Histopathological evaluation of the lung tissue was performed by hematoxylin and eosin (H&E) staining and Masson's trichrome staining. The levels of Th2 cytokine and IgE level in serum were measured using enzyme-linked immunoassay (ELISA). The mRNA expression levels of IL-4, IL-5, IL-13 and orosomucoid-like 3 (ORMDL3) were measured using quantitative reverse transcription polymerase chain reaction (RT-qPCR). Proteins of NF-κB signaling pathway were measured using western blot. The serum metabolomics profiles were obtained by using ultra-performance liquid chromatography combined with electrospray ionization quadrupole time-of-flight mass spectrometry (UPLC-ESI-QTOF-MS).

RESULTS

The overall results confirmed that AST with TWDS prescription had a significant protective effect against OVA-induced allergic asthma in guinea pig. This treatment not only attenuated airway inflammation and collagen deposition in the airway, but also decreased the levels of IL-4, IL-5, IL-13 and IgE in serum. In addition, metabolomics results indicated that metabolisms of phospholipid, sphingolipid, purine, amino acid and level of epinephrine were restored back to the normal control level. Moreover, results of the gene expression of ORMDL3 in lung tissues indicated that AST using TWDS could alter the sphingolipid metabolism. Further western blotting analysis also showed that its anti-inflammatory mechanism was by decreasing the phosphorylation of p65 and IκB.

CONCLUSION

The study demonstrated that metabolomics provides a better understanding of the actions of TWDS acupoint sticking therapy on OVA-induced allergic asthma.

Redistribution of adrenomedullary nicotinic acetylcholine receptor subunits and the effect on circulating epinephrine levels in a murine model of acute asthma

The lack of circulating epinephrine (EPI) in the pathogenesis of asthma has long been attributed to the lack of adrenergic nerves in human airways. However, in this study we considered that EPI levels are regulated by EPI release in addition to synthesis. Nicotinic acetylcholine receptors (nAChRs) have been shown to control EPI release, and we hypothesized that redistribution of nAChR subunits modulates EPI release and circulating EPI levels. Using a mouse model of asthma, circulating EPI levels were measured by enzyme-linked immunosorbent assays. Changes in the expression of nAChR subunits in the adrenal medulla were observed by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blot analysis. Expression of phenylethanolamine N-methyltransferase, tyrosine hydroxylase and galanin was detected by RT-qPCR. Lung pathology, airway resistance (RL) and EPI levels were also assessed after treatment with an α7 nAChR agonist or antagonist. α7 nAChR mRNA expression in the adrenal medulla was increased by more than 2-fold (P<0.05), and circulating EPI levels increased rapidly after treatment with the α7 nAChR agonist. These results indicated that increased EPI release, which was caused by the overexpression of α7 nAChR, was responsible for elevated circulating EPI levels. After treatment with an agonist of α7 nAChR, RL was significantly decreased. Serum corticosterone levels in individual mice were measured to rule out glucocorticoid as the main mediator of changes in EPI levels. On the whole, redistribution of nAChR subunits, primarily α7 nAChR, occurs in the adrenal medulla in asthmatic mice. Increased α7 nAChR expression can rapidly increase serum EPI levels and decrease airway responsiveness.

Role of serum cortisol levels in children with asthma

Decreased serum cortisol levels have been proposed to contribute to nocturnal airway obstruction. We investigated whether endogenous cortisol levels are lower, and also whether the 24-h cortisol variation is greater, in children with asthma than in control subjects and assessed the relationship between serum cortisol and nocturnal airflow limitation in children with asthma. Cortisol and FEV(1) were measured every 4 h over 24 h; blood eosinophils, airway responsiveness to methacholine and adenosine 5'-monophosphate (AMP) were measured at 0400 and 1600. Children with asthma had lower cortisol levels than did control subjects; at midnight the difference was significant. Subjects with nocturnal asthma (24-h FEV(1) variation > or =15%) had significantly lower cortisol levels than did control subjects at 0000, 0800, and 1200. A higher mean 24-h cortisol level in subjects with asthma was associated with a significantly higher FEV(1) as a percentage of the predicted value (FEV(1) %pred) at 0400, 0800, and 2000, yet not in control subjects. Higher 24-h cortisol variation was associated with lower FEV(1) %pred at all time points in both control subjects and subjects with nonnocturnal asthma. There was no significant association between the level or variation of cortisol and PD(20) methacholine (provocative dose of methacholine causing a 20% fall in FEV(1)), PD(20) AMP, or eosinophils. Our data suggest that lower cortisol levels contribute to both overall lower levels of FEV(1) especially at night. This may be due to a lack of suppression of airway inflammation.

Urinary histamine metabolite elevations during experimental influenza infection

BACKGROUND

Although histamine is hypothesized to mediate symptoms induced by viral upper respiratory infections, elevations of this mediator have not been observed in nasal lavage fluids recovered from patients with viral upper respiratory infections.

OBJECTIVE

The purpose of this study was to use a novel method to determine whether histamine is released during experimental influenza A infection.

METHODS

Healthy adults (n = 15) were cloistered and inoculated intranasally with influenza A virus, and monitored for infection and illness. Daily morning void urines were collected and assayed for histamine and its metabolites by gas chromatography-mass spectrometry. Total histamine was calculated for each urine specimen by summing the assayed values of histamine and its metabolites.

RESULTS

All subjects were infected and developed illness. ANOVA documented a significant effect of study day (viral infection) on urinary levels of total histamine (P < 0.02). Pairwise analysis showed a significant elevation 2 days after inoculation.

CONCLUSIONS

These results provide the first direct evidence that histamine is released in vivo during infection with a virus that causes cold/flu symptoms.

Asthma, asthma medication and autonomic nervous system dysfunction

Asthma is associated with autonomic nervous imbalance: an increased bronchial sensitivity to cholinergic constrictors and possibly a decreased sensitivity to beta2-adrenergic dilators have been reported in this disease. Also, non-adrenergic and non-cholinergic (NANC) mediators have a small regulatory effect on airway function. These mediators contribute to the pathogenesis of asthma not only by regulating smooth muscle tone in the airways but also by affecting pulmonary blood flow, endothelial permeability and airway secretions. In many studies increased parasympathetic responsiveness has been associated with clinical asthma or the worsening of asthma in adults. However, most of the studies in children have not found association between autonomic dysfunction and asthma. Therefore, the autonomic dysfunction in asthma may be related to more advanced disease or long-term asthma medication in adults. This article briefly reviews the relationships between airway inflammation, beta2-agonist, anticholinergic and glucocorticoid medication as well as autonomic nervous function in asthma.

Is childhood asthma an inflammatory disease?

There is now extensive evidence that asthma results from inflammation in large and small airways, and that the degree of inflammation reflects the clinical severity of the disease. Most of this evidence, however, has come from studies in adult patients. Evidence in children comes largely from indirect studies such as measurements of peripheral blood cells and inflammatory markers, rather than from direct bronchoscopic examination. Studies in adults show that inflammation in asthma is characterized by eosinophilia, epithelial damage, and bronchial hyperresponsiveness, and that activation of allergen-specific T cells plays an important role in orchestrating the inflammatory process. In children, indirect evidence of inflammation comes from the observation that anti-inflammatory agents such as inhaled corticosteroids improve symptoms and bronchial hyperresponsiveness, reduce the number of asthma exacerbations, and limit the progressive decline in lung function. Further evidence comes from measurements of nitric oxide and hydrogen peroxide (potential inflammatory markers) in exhaled air, and of inflammatory mediators in plasma and urine. As in adults, there is evidence that lymphocytes play an important role in orchestrating the inflammatory process. The immunologic profile appears to shift from a Th1-type cytokine profile to an allergen-related Th2-type profile prior to birth. Such a Th2 predominance constitutes a risk factor for the subsequent development of bronchial hyperresponsiveness and asthma in response to allergen.

Urinary N-methylhistamine in asthmatic children receiving azelastine hydrochloride

BACKGROUND

Histamine has a particular role in the pathogenesis of bronchial asthma, and many antiallergic drugs have been developed with antihistaminic action in mind. Recently, a sensitive and specific assay for measuring histamine and its metabolites has been developed. There are, however, no reports of the effect of antiallergic drugs on histamine levels in asthmatic patients.

OBJECTIVES

To determine the relationship between clinical symptoms and histamine levels in asthmatic patients receiving an antiallergic agent.

METHODS

A prospective study was designed in asthmatic children treated with azelastine hydrochloride. The evaluation of clinical symptoms was based on scores of the severity of exacerbations, activities of daily living, quality of sleep, and required therapy. Urinary excretion of N-methylhistamine, a major metabolite of histamine, was measured by double antibody radioimmunoassay.

RESULTS

In the patients treated with azelastine, the improvement in clinical symptoms of bronchial asthma correlated significantly with a decrease in urinary N-methylhistamine excretion (r2 = 0.434, P < .001), while no such relationship was noted in patients receiving no antiallergic agent. Urinary N-methylhistamine excretion showed no diurnal change or influence of meals.

CONCLUSIONS

Decreased urinary N-methylhistamine excretion may be a direct reflection of the antihistaminic action of azelastine in vivo. Measurement of urinary N-methylhistamine excretion can be used to evaluate the efficacy of agents with antihistaminic action in the treatment of bronchial asthma.

Cardiovascular autonomic regulation in asthmatic children evidenced by spectral analysis of heart rate and blood pressure variability

The objective of the study was to investigate the features of cardiovascular and respiratory autonomic nervous regulation in asthmatic and control children. Cardiorespiratory reactivity was studied by continuous and non-invasive recording of the electrocardiogram, finger systolic arterial pressure (SAP) and flow-volume spirometry in supine and upright positions and during a deep breathing test in 19 children with bronchial asthma and 10 healthy control children (age 8-11 years). The periodic variability components of R-R intervals (the time between successive heart beats) and SAP in relation to respiration were assessed using spectral analysis techniques. Nine asthmatic children without beta2-agonist medication had a lower respiratory rate and larger high frequency (HF) variability of SAP than the controls, and 10 asthmatic children with beta2-agonist medication had greater low-frequency (LF) variability of SAP and LF/HF ratio of R-R intervals, but their respiratory rate did not differ from the controls. No intergroup differences were found in the postural change of variables. Stable bronchial asthma appears to increase respiratory-induced alterations in systolic blood pressure in children. Beta2-agonist medication, on the other hand, increases sympathetic cardiovascular activity in children with asthma.

Diurnal variation of urinary leukotriene E4 and histamine excretion rates in normal subjects and patients with mild-to-moderate asthma

BACKGROUND

Leukotriene E4 (LTE4) and histamine excreted into the urine reflect the in vivo synthesis and release of cysteinyl leukotrienes and histamine, respectively. We examined the diurnal variation of the excretion rate of these mediators over 4 consecutive days in normal subjects (n = 5) and patients with stable mild-to-moderate asthma (n = 8).

METHODS

Sixteen consecutive 6-hour urine samples were collected over 4 days. Urinary LTE4 concentrations were determined by reverse-phase high-pressure liquid chromatography, followed by ELISA. Urinary histamine concentrations were measured by ELISA. The excretion rates of these compounds were normalized relative to urinary creatinine content.

RESULTS

The mean urinary LTE4 excretion rate was 83.8 +/- 38.2 pg/mg creatinine (mean +/- SD) in normal subjects; in patients with asthma, the urinary LTE4 excretion rate (110.0 +/- 59.2 pg/mg creatinine) was significantly higher than that in normal subjects (p < 0.05). The urinary histamine excretion rate was not different between normal subjects (24.0 +/- 12.5 ng/mg creatinine) and patients with asthma (31.5 +/- 25.8 ng/mg creatinine). A robust and systematic within-day variation (p < 0.01), but no day-to-day variation, was observed in histamine excretion rate. Although the magnitude of variation in LTE4 excretion within a day was significantly greater in patients with asthma than in normal subjects (p < 0.05), we could not identify any specific diurnal variation pattern in either the normal or the asthma group. No significant correlation was observed between urinary LTE4 and histamine excretion rate within any subject.

CONCLUSIONS

Patients with asthma excrete LTE4 in the urine at a greater rate than normal subjects. Although no systematic variation in urinary LTE4 excretion rates over the course of a day was observed in either normal subjects or patients with stable asthma, the presence of a systematic diurnal variation of urinary histamine excretion exists in both groups.

Effects of propranolol inhalation on the diurnal increase in FEV1 and on propranolol airways responsiveness in atopic subjects with asthma

BACKGROUND

Propranolol inhalation provocation tests are used to measure indirect airways responsiveness in the investigation of asthma. In this study the effects of repeated propranolol inhalation provocation tests within the same day on normal diurnal variation in the forced expiratory volume in one second (FEV1) and subsequent propranolol airways responsiveness were investigated.

METHODS

Fifteen atopic asthmatic subjects were challenged with doubling concentrations of propranolol at 08.00 and 16.00 hours on the same study day and at 16.00 hours on a control day to exclude changes related to normal diurnal variation.

RESULTS

Mean (SD) baseline FEV1 at 16.00 hours on the study day was 3.38 (0.23) 1, significantly lower than the value at 16.00 hours on the control day of 3.70 (0.24) 1 (p = 0.001). No differences were found between the geometric mean provocative concentration of propranolol causing a 20% fall in FEV1 (PC20) measured on the study day (08.00 hours, 9.3 mg/ml; 16.00 hours, 11.3 mg/ml) and on the control day (16.00 hours 9.3 mg/ml).

CONCLUSIONS

The results suggest that propranolol provocation at 08.00 hours has a long lasting effect on FEV1, thereby counteracting the normal diurnal increase in diameter of the airways. This makes propranolol challenge tests less suitable for studying indirect airways responsiveness in the course of one day. Because the FEV1 does not return to control values, it is not possible to determine whether tachyphylaxis to repeated propranolol challenge with a time interval of up to eight hours occurs.

Inflammation in nocturnal asthma?

At present there is some indirect evidence for increased nocturnal inflammation in patients suffering from nocturnal asthma: 1. Circulating eosinophil numbers and activation, as reflected by increased levels of ECP and EDN and low-density eosinophils, are increased at night. 2. Circulating histamine levels are increased at night. 3. Hyperresponsiveness to AMP at night is increased compared with hyperresponsiveness to methacholine. However, most results of various studies point to nocturnal asthma's being an expression of more severe asthma: 1. Both AMP and propranolol responsiveness, indirect measures of airway hyperresponsiveness, are lower both at 4:00 A.M. and 4:00 P.M. in asthmatics with nocturnal asthma than those without nocturnal asthma. 2. Patients with nocturnal asthma have higher circulating numbers of eosinophils at both 4:00 A.M. and 4:00 P.M. than those without nocturnal asthma, and eosinophil survival is not different at these times. 3. Patients with nocturnal asthma have higher PGD2 levels in BAL both at 4:00 A.M. and 4:00 P.M. than those without nocturnal asthma, but show no significant difference between levels at these two times. 4. Two studies have shown no difference in BAL eosinophil numbers and activation parameters at night in nocturnal asthma. 5. Histamine levels in BAL fluid are comparable day and night in patients with and without nocturnal asthma. 6. Inflammatory mediators in BAL are higher in asthmatic patients than in normal subjects, but are not different between patients with and without nocturnal asthma. Thus, patients with nocturnal asthmatic symptoms show an overall increased burden of mediators released from mast cells and other inflammatory cells. In conclusion, we feel that the term "nocturnal asthma" is misleading, in that it does not describe a unique entity in certain patients with asthma. We prefer, in view of the previous arguments, to consider nocturnal asthma a mere expression of more severe asthma. Thus we suggest the term "nocturnal asthma" be changed to "asthma with nocturnal symptoms."

Role of inflammation in nocturnal asthma

BACKGROUND

Nocturnal airway narrowing is a common problem for patients with asthma but the role of inflammation in its pathogenesis is unclear. Overnight changes in airway inflammatory cell populations were studied in patients with nocturnal asthma and in control normal subjects.

METHODS

Bronchoscopies were performed at 0400 hours and 1600 hours in eight healthy subjects and in 10 patients with nocturnal asthma (> 15% overnight fall in peak flow plus at least one awakening/week with asthma). The two bronchoscopies were separated by at least five days, and both the order of bronchoscopies and site of bronchoalveolar lavage (middle lobe or lingula with contralateral lower lobe bronchial biopsy) were randomised.

RESULTS

In the normal subjects there was no difference in cell numbers and differential cell counts in bronchoalveolar lavage fluid between 0400 and 1600 hours, but in the nocturnal asthmatic subjects both eosinophil counts (median 0.11 x 10(5) cells/ml at 0400 hours, 0.05 x 10(5) cells/ml at 1600 hours) and lymphocyte numbers (0.06 x 10(5) cells/ml at 0400 hours, 0.03 x 10(5) cells/ml at 1600 hours) increased at 0400 hours, along with an increase in eosinophil cationic protein levels in bronchoalveolar lavage fluid (3.0 micrograms/ml at 0400 hours, 2.0 micrograms/l at 1600 hours). There were no changes in cell populations in the bronchial biopsies or in alveolar macrophage production of hydrogen peroxide, GM-CSF, or TNF alpha in either normal or asthmatic subjects at 0400 and 1600 hours. There was no correlation between changes in overnight airway function and changes in cell populations in the bronchoalveolar lavage fluid.

CONCLUSIONS

This study confirms that there are increases in inflammatory cell populations in the airway fluid at night in asthmatic but not in normal subjects. The results have also shown a nocturnal increase in eosinophil cationic protein levels in bronchoalveolar lavage fluid, but these findings do not prove that these inflammatory changes cause nocturnal airway narrowing.

Circadian variation in airway responsiveness to methacholine, propranolol, and AMP in atopic asthmatic subjects

Increased airway hyperresponsiveness is thought to be one of the phenomena underlying nocturnal airway obstruction in asthma. To investigate the mechanisms that influence and modulate this phenomenon, we compared circadian variations in airway responsiveness with AMP and propranolol with the circadian variation in airway responsiveness to methacholine. Inhalation provocation tests were performed at 16.00 and 04.00 h in 16 nonsmoking atopic asthmatic subjects (18 to 42 yr of age), prospectively assigned to Group 1 (mean circadian peak expiratory flow rate [PEFR] variation > or = 15%) and Group 2 (< 15%). The circadian change in airway responsiveness to AMP, in contrast to methacholine, was significantly related to the circadian PEFR-variation of the 16 subjects (r = 0.81, p < 0.001). In Group 1 (n = 7) geometric mean PC20 AMP decreased more than PC20 methacholine during the night (2.3 and 0.9 doubling concentrations respectively, p < 0.05), whereas no difference in baseline FEV1 was found at the same time points during the different study days. Geometric mean PC20 propranolol did not change during the night. Daytime PC20 propranolol and PC20 AMP, in contrast to PC20 methacholine, were significantly lower in Group 1 as compared with Group 2. Together, the results show a higher susceptibility to stimulation of "indirect" airway responsiveness in the subjects with increased circadian PEFR amplitude. This suggests that mast cell activation rather than primary changes in smooth muscle cell contraction may play a role in the development of nocturnal airway obstruction.

Asthma and emotion: a review

This review of the empirical literature on the relationship between asthma and emotion presents an explanatory model of the connection between them. Asthmatics tend to report and display a high level of negative emotion, and asthma exacerbations have been linked temporally to periods of heightened emotionality. Causality may be bidirectional. Hypothesized mediators for the relationship between asthma and emotionality include vagal and alpha-sympathetic hyperreactivity, predominant obstruction in the larger airways, individual response stereotypy, direct effects of emotion-related facial muscle tension on the airways, the emotional effects of asthma medications, heightened respiratory drive, and hyperventilation. Predictions are presented for research on this model of asthma and emotion, and for the psychological treatment of asthma.