Serum cortisol in asthma: marker of nocturnal worsening of symptoms and lung function?

Basophil degranulation in response to IgE ligation is controlled by a distinctive circadian clock in asthma

BACKGROUND

Several factors may contribute to the circadian variability of clinical manifestations in asthma and allergy. Basophils play a pivotal role in allergic inflammation. However, evidence for a functional clock governing the effector function of these cells is sparse and contradictory. We have systematically sampled the 24-hour response of basophils to IgE- and non-IgE-dependent ligands in asthma to understand their possible contribution to the diurnal variations of allergic symptoms.

METHODS

Leukocytes were collected every 4 hours for 24 hours from 10 patients with moderate, persistent asthma and 10 matched, nonallergic controls, and then incubated with concentrations of anti-IgE, formyl-methionyl-leucylphenylalanine (fMLP), or the Ca²⁺ ionophore, A23187. Histamine release (HR) was tested for time-of-day- or disease-related variability by conventional statistics and for 24-hour rhythmicity by the cosinor method.

RESULTS

HR induced by anti-IgE was significantly increased at 08:00 vs. 20:00 in basophils from asthmatics but not controls. No significant differences were seen at any time in the response to A23187, while the response to fMLP was significantly higher at 08:00 vs. 20:00 in controls but not asthmatics. The basophil response to anti-IgE, but not fMLP or A23187, varied significantly across the 24 hours in asthma, and its amplitude, percent rhythm, and acrophase were comparable to those of peak expiratory flow or serum cortisol.

CONCLUSION

Using an integrated statistical approach, we show that basophil responsiveness undergoes significant circadian variability and that distinct patterns of rhythmicity can be recognized depending on the signal delivered, the activation parameters assessed, and the disease status.

The 24 h duration of bronchodilator action of the budesonide/formoterol combination inhaler

INTRODUCTION

The duration of bronchodilator action of the long-acting beta-agonist formoterol when administered in the evening has not been investigated. In this study we have investigated whether a single evening dose of formoterol, administered from the combination budesonide/formoterol (BUD/F) Turbuhaler significantly attenuates the circadian rhythm in airway tone over 24 h.

METHODS

Twenty subjects with mild to moderate asthma (mean FEV1 84% predicted) participated in a double-blind, placebo-controlled, cross-over study. Subjects inhaled, in random order, placebo or BUD/F (2x100/6 microg) administered in the evening (2000 h) on two separate occasions. Lung function measurements including FEV1, specific airways conductance (sGaw) and maximum expiratory flow at 25-75% of vital capacity (MEF(25-75%)) were assessed at baseline, at 1 h and subsequently every 4 h post-dose for 24 h.

RESULTS

Compared with placebo, BUD/F significantly improved the three measures of airways function throughout the 24 h period, with a difference in FEV1 at 24 h of 0.20L (0.04-0.35L). BUD/F attenuated the biphasic pattern of the circadian rhythm in airway tone.

CONCLUSION

The single evening administration of formoterol from the combination BUD/F inhaler resulted in a duration of bronchodilation of at least 24 h.

The 24 h duration of bronchodilator action of the salmeterol/fluticasone combination inhaler

INTRODUCTION

The duration of bronchodilator action of the long-acting beta agonist salmeterol when administered in the evening has not been investigated. In this study we have investigated whether a single evening dose of salmeterol, administered from the combination salmeterol/fluticasone (SFC) Accuhaler significantly attenuates the circadian rhythm in airway tone over 24 h.

METHODS

Eighteen subjects with mild to moderate asthma (mean FEV1 84% predicted) participated in a double-blind, double dummy, placebo controlled, cross-over study. Subjects inhaled, in random order, placebo, salbutamol (200 microg) or SFC (50/100 microg) administered in the evening (2000 h) on three separate occasions. Lung function measurements including FEV1, specific airways conductance (sGaw) and maximum expiratory flow at 25-75% of vital capacity (MEF(25-75%)) were assessed at baseline, at 1 h and subsequently every 4 h post-dose for 24 h.

RESULTS

Compared with placebo, SFC significantly improved the three measures of airways function throughout the 24 h period, with a difference in FEV1 at 24 h of 0.24 l (0.00-0.47 l). SFC abolished the biphasic pattern of the circadian rhythm in airway tone. In contrast, salbutamol had a significant bronchodilator action of 4-8 h, depending on the lung function parameter measured.

CONCLUSION

The single evening administration of SFC via the Accuhaler resulted in a duration of bronchodilation of at least 24 h, with the abolition of the accentuated biphasic circadian variation in airway tone observed in asthma.

Altered pituitary-adrenal interaction in nocturnal asthma

BACKGROUND

Increased airway inflammation at night contributes to the nocturnal worsening of asthma, but the mechanisms regulating circadian variations in airway inflammation are unknown.

OBJECTIVE

We hypothesized that altered hypothalamic-pituitary-adrenal axis function serves as an endogenous controller of inflammation in nocturnal asthma.

METHODS

Patients with nocturnal asthma (n = 7), patients with nonnocturnal asthma (n = 13), and healthy control subjects (n = 11) adhered to a regular sleep-wake cycle for 1 week. Corticotropin and cortisol levels were assayed every 2 hours for 24 hours. Low-dose corticotropin stimulation was performed. Circadian hormonal flux was analyzed by means of cosinor modeling and calculation of the area under the 24-hour curve.

RESULTS

Corticotropin peak levels and areas under the 24-hour curve were significantly increased in patients with nocturnal asthma versus values in patients with nonnocturnal asthma and control subjects. Patients with nonnocturnal asthma demonstrated significantly increased areas under the 24-hour cortisol curve when compared with control subjects, but peak cortisol levels did not differ between groups. Cortisol levels after low-dose corticotropin stimulation did not differ between groups. Corticotropin and cortisol levels were not correlated with the degree of physiologic impairment.

CONCLUSION

Nocturnal asthma is marked by increased corticotropin levels that are not accompanied by commensurate increases in cortisol levels. This observation might indicate blunted adrenal responsiveness in the nocturnal asthma phenotype. Conversely, adrenal response to corticotropin might be enhanced in nonnocturnal asthma, attenuating nocturnal worsening of airway inflammation.

Circadian variation of sputum inflammatory cells in mild asthma

BACKGROUND

Asthma, like many conditions, demonstrates a circadian rhythm with a worsening of lung function in the early morning hours compared with in the late afternoon.

OBJECTIVE

Because eosinophilic airway inflammation is a proposed mechanism for worsening asthma, we characterized circadian variation in airway eosinophils and determined its relationship to variability in airway function.

METHODS

Pulmonary function testing, sputum induction, and phlebotomy were performed at 7 am and 4 pm in 11 allergic subjects with mild asthma. Sputum was analyzed for cell viability, differential, and eosinophil-derived neurotoxin levels. IL-5 levels in serum were measured by means of ELISA.

RESULTS

Subjects had a significant decrease in FEV(1) (median [interquartile range] = 80% [70%-86%] vs 85% [82%-94%], P =.009) and a greater beta-agonist reversibility (median [interquartile range] = 13% [7%-32%] vs 8% [5%-14%], P =.024) in the early morning compared with in the late afternoon. Sputum analysis showed an increase in early morning total sputum leukocytes (median [interquartile range] = 4.3 x 10(6) [2.3 x 10(6) to 6.1 x 10(6)] vs 2.6 x 10(6) [1.7 x 10(6) to 3.6 x 10(6)], P =.044) and eosinophils (median [interquartile range] = 7.0 x 10(4) [2.7 x 10(4) to 18.7 x 10(4)] vs 3.6 x 10(4) [1.0 x 10(4) to 8.2 x 10(4)], P =.024). Furthermore, sputum eosinophils correlated with beta-agonist reversibility (R (s) = 0.665, P =.019). Finally, levels of IL-5 in serum and eosinophil-derived neurotoxin in sputum were significantly increased at 7 am.

CONCLUSION

These data suggest that circadian variability in pulmonary function in asthma could be related to changes in airway eosinophil recruitment and activation.

Hormones and breathing

A number of hormones, including hypothalamic neuropeptides acting as neurotransmitters and neuromodulators in the CNS, are involved in the physiologic regulation of breathing and participate in adjustment of breathing in disease. In addition to central effects, some hormones also control breathing at peripheral chemoreceptors or have local effects on the lungs and airways. Estrogen and progesterone seem to protect from sleep-disordered breathing, whereas testosterone may predispose to it. Progesterone and thyroxine have long been known to stimulate respiration. More recently, several hormones such as corticotropin-releasing hormone and leptin have been suggested to act as respiratory stimulants. Somatostatin, dopamine, and neuropeptide Y have a depressing effect on breathing. Animal models and experimental human studies suggest that also many other hormones may be involved in respiratory control.

Nocturnal worsening of asthma and sleep-disordered breathing

Asthma has a tendency, to destabilize and get worse at night, probably due to a nocturnal increase in airiway inflammation and bronchial responsiveness. Nocturnal airway narrowing in asthma is often associated with sleep disorders, such as episodes of nocturnal and early morning awakening, difficulty in maintaining sleep, and day time sleepiness. On the other hand, an association has been documented between nocturnal sleep-disordered breathing and asthma. This review highlights the causes of nocturnal worsening of asthma and examines the evidence pointing toward a causal relationship between nocturnal asthma and sleep-disordered breathing.

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.

Decreased steroid responsiveness at night in nocturnal asthma. Is the macrophage responsible?

As peripheral blood mononuclear cells from patients with nocturnal asthma (NA) exhibit reduced steroid responsiveness at 4:00 A.M. as compared with 4:00 P.M., we hypothesized that NA is associated with increased nocturnal airway cell expression of GRbeta, an endogenous inhibitor of steroid action. Ten subjects with NA and seven subjects with nonnocturnal asthma (NNA) underwent bronchoscopy with bronchoalveolar lavage (BAL) at 4:00 P.M. and 4:00 A.M. BAL lymphocytes and macrophages were incubated with dexamethasone (DEX) at 10(-5) to 10(-8) M. DEX suppressed proliferation of BAL lymphocytes similarly at 4:00 P.M. and 4:00 A.M. in both groups. However, BAL macrophages from NA exhibited less suppression of IL-8 and TNF-alpha production by DEX at 4:00 A.M. as compared with 4:00 P.M. (p = 0.0001), whereas in the NNA group DEX suppressed IL-8 and TNF-alpha production equally at both time points. GRbeta expression was increased at night only in NA, primarily due to significantly increased expression by BAL macrophages (p = 0.008). IL-13 mRNA expression was increased at night, but only in the NA group and addition of neutralizing antibodies to IL-13 reduced GRbeta expression by BAL macrophages. We conclude that the airway macrophage may be the airway inflammatory cell driving the reduction in steroid responsiveness at night in NA, and this function is modulated by IL-13.

Sleep in patients with asthma and chronic obstructive pulmonary disease

Sleep abnormalities are common in patients with asthma and chronic obstructive pulmonary disease. Recent studies have provided new insight into the mechanisms involved in circadian changes in airway resistance, analyzed the effect of disease treatment on sleep quality, and re-examined issues relating to oxygen supplementation at night in patients with chronic obstructive pulmonary disease. Although providing new and useful information, some of these studies also raise new questions that will need answering in the future. This article reviews our current understanding of the complex interactions between sleep and lung disease in patients with asthma and chronic obstructive pulmonary disease.

Corticosteroids and leukotrienes: chronobiology and chronotherapy

Corticosteroids and leukotrienes play opposite roles in asthma. Corticosteroids, both endogenously secreted and exogenously administered, are antiinflammatory and are very effective in the treatment of asthma. They have also been evaluated chronotherapeutically and have been found to be very effective in reducing the enhanced airway inflammation and decrement in lung function associated with nocturnal worsening of asthma. Leukotrienes are potent proinflammatory and spasmogenic mediators that have been shown to be increased at night in patients with nocturnal asthma (NA). Leukotriene modifiers, a new class of medications to treat asthma, improve, but do not abolish, the symptoms and decrement in lung function associated with nocturnal asthma. However, they have not been evaluated chronotherapeutically. This article addresses the roles of corticosteroids and leukotrienes in nocturnal asthma and their position as therapeutic agents or targets for therapy.

Lymphocyte and eosinophil influx into alveolar tissue in nocturnal asthma

We have shown in nocturnal asthma that alveolar tissue eosinophils are increased at night as compared with the proximal airway, and that they correlate with the overnight decrement in lung function. As the CD4+ cell is thought to be the principal orchestrating cell in eosinophil recruitment, we evaluated its presence in the proximal and distal airways in nocturnal asthma. Eleven patients with nocturnal asthma (NA) and 10 patients with non-nocturnal asthma (NNA) underwent two bronchoscopies with proximal airway endobronchial and distal alveolar tissue transbronchial biopsy in a random order at 4:00 P.M. and at 4:00 A.M. separated by 1 wk. Immunohistochemical staining and morphometric analysis were used to determine the number of CD3+, CD4+, and CD8+ cells and EG2+ eosinophils per mm2 in the epithelium, lamina propria, and alveolar tissue. At 4:00 A.M., the NA group had a significantly greater number of CD4+ cells in the alveolar tissue than the NNA group (9.8 cells/ mm2 [5.6-30.8, interquartile (IQ)] versus 1.5 cells/mm2 [0-6. 3, IQ], p = 0.04). Within the NA group, there were significantly greater numbers of CD3+, CD4+, CD8+, and EG2+ cells in the proximal airway lamina propria than in the distal airway at both 4:00 P.M. and 4:00 A.M. There were no differences within the epithelium between the groups at either time point. Only alveolar tissue, not airway tissue, CD4+ cells correlated inversely with the percentage predicted FEV1 at 4:00 A.M. (r = -0.68, p = 0.0018) and positively with the number of alveolar tissue EG2+ cells (r = 0.66, p = 0.01). These findings suggest that the CD4+ lymphocyte is increased in the alveolar tissue at night in nocturnal asthma as compared with non-nocturnal asthma.

Nocturnal asthma is associated with reduced glucocorticoid receptor binding affinity and decreased steroid responsiveness at night

BACKGROUND

The mechanisms for heightened nocturnal inflammation in patients with nocturnal asthma (NA) are not well understood.

OBJECTIVE

We sought to determine the glucocorticoid receptor (GR) characteristics and steroid responsiveness in subjects with NA.

METHODS

Eleven subjects with NA, 12 subjects with nonnocturnal asthma (NNA), and 16 nonasthmatic control subjects underwent blood sampling at 4 pm and 4 am in a random order separated by 1 week. GR binding affinity was measured in PBMCs by using a [3H]-dexamethasone (DX) radioligand binding assay and Scatchard analysis. The capacity of hydrocortisone (HC) and DX to suppress proliferation of PBMCs stimulated with PHA was also determined.

RESULTS

The subjects with NA exhibited a significantly lower GR binding affinity at 4 am, detected by an elevated dissociation constant (Kd) of 22.2 +/- 1.6 nmol/L compared with Kd at 4 pm (10.9 +/- 0.7 nmol/L; P =.0001). The GR Kd of the NNA and control groups did not change significantly from 4 pm to 4 am. Within the NA group, there was also a significant inverse correlation between the absolute FEV1 at 4 am and the Kd at 4 am (r = -0.65, P =.04). PBMCs from subjects with NA exhibited less suppression of PBMC proliferation with HC and DX at 4 am compared with that at 4 pm (P =.0004 and.03 for HC and DX, respectively). There were no circadian changes in suppression of PBMC proliferation in either the NNA or control groups.

CONCLUSION

GR binding affinity and steroid responsiveness exhibit a circadian variation in subjects with NA, with a reduced GR binding affinity and suppression of PBMC proliferation at 4 am that is not observed in normal subjects or asthmatic subjects without nocturnal exacerbation. These observations may contribute to nocturnal airway inflammation by inhibiting the antiinflammatory effects of glucocorticoids.

Pathophysiology of nocturnal asthma

LEARNING OBJECTIVES

This article will focus on the pathophysiologic changes underlying the nocturnal worsening of asthma and the therapeutic approach to this disorder.

DATA SOURCES

Selected articles appearing since 1985 dealing specifically with the underlying pathologic features and therapy of nocturnal asthma.

STUDY SELECTION

Studies that aimed to elucidate the pathologic features, mechanisms, and therapeutic strategies for the treatment of nocturnal asthma are summarized.

RESULTS

Nocturnal asthma is associated with significant decline in pulmonary function and increase of airway inflammation at night. The administration of medications must be designed to achieve the maximal effect during the night in nocturnal asthma.

CONCLUSIONS

The further elucidation of the reasons underlying nocturnal asthma should lead to more specific therapeutic interventions with maximal effect at night.