Direct inhibitory action of glucocorticoid on glycoconjugate secretion from airway submucosal glands

Airway Gland Structure and Function

Submucosal glands contribute to airway surface liquid (ASL), a film that protects all airway surfaces. Glandular mucus comprises electrolytes, water, the gel-forming mucin MUC5B, and hundreds of different proteins with diverse protective functions. Gland volume per unit area of mucosal surface correlates positively with impaction rate of inhaled particles. In human main bronchi, the volume of the glands is ∼ 50 times that of surface goblet cells, but the glands diminish in size and frequency distally. ASL and its trapped particles are removed from the airways by mucociliary transport. Airway glands have a tubuloacinar structure, with a single terminal duct, a nonciliated collecting duct, then branching secretory tubules lined with mucous cells and ending in serous acini. They allow for a massive increase in numbers of mucus-producing cells without replacing surface ciliated cells. Active secretion of Cl(-) and HCO3 (-) by serous cells produces most of the fluid of gland secretions. Glands are densely innervated by tonically active, mutually excitatory airway intrinsic neurons. Most gland mucus is secreted constitutively in vivo, with large, transient increases produced by emergency reflex drive from the vagus. Elevations of [cAMP]i and [Ca(2+)]i coordinate electrolyte and macromolecular secretion and probably occur together for baseline activity in vivo, with cholinergic elevation of [Ca(2+)]i being mainly responsive for transient increases in secretion. Altered submucosal gland function contributes to the pathology of all obstructive diseases, but is an early stage of pathogenesis only in cystic fibrosis.

Dexamethasone reduces bronchial wall remodeling during pulmonary migration of Strongyloides venezuelensis larvae in rats

Strongyloidiasis is an intestinal parasitosis with an obligatory pulmonary cycle. A Th2-type immune response is induced and amplifies the cellular response through the secretion of inflammatory mediators. Although this response has been described as being similar to asthma, airway remodeling during pulmonary migration of larvae has not yet been established. The aim of this study was to identify the occurrence of airway remodeling during Strongyloides venezuelensis (S. v.) infection and to determine the ability of dexamethasone treatment to interfere with the mechanisms involved in this process. Rats were inoculated with 9,000 S. v. larvae, treated with dexamethasone (2 mg/kg) and killed at 1, 3, 5, 7, 14 and 21 days. Morphological and morphometric analyzes with routine stains and immunohistochemistry were conducted, and some inflammatory mediators were evaluated using ELISA. Goblet cell hyperplasia and increased bronchiolar thickness, characterized by edema, neovascularization, inflammatory infiltrate, collagen deposition and enlargement of the smooth muscle cell layer were observed. VEGF, IL1-β and IL-4 levels were elevated throughout the course of the infection. The morphological findings and the immunomodulatory response to the infection were drastically reduced in dexamethasone-treated rats. The pulmonary migration of S. venezuelensis larvae produced a transitory, but significant amount of airway remodeling with a slight residual bronchiolar fibrosis. The exact mechanisms involved in this process require further study.

Complementary anti-inflammatory effects of a β-blocker and a corticosteroid in an asthma model

Glucocorticosteroids are the mainstay treatment for chronic asthma; however, adverse effects can limit their usefulness. We previously determined in experimental asthma that chronic administration of β₂-adrenoceptor inverse agonists reduced airway hyperresponsiveness and indexes of inflammation. However, the effect of co-administration of glucocorticosteroids with β₂-adrenoceptor inverse agonists is unknown. Therefore, we evaluated the anti-inflammatory effect of co-administration of dexamethasone, a glucocorticosteroid, and nadolol, a β₂-inverse agonist, in a murine asthma model. We measured eosinophils and cytokines in bronchoalveolar lavage fluid and mucin content in epithelial cells after exposure to different concentrations of dexamethasone and nadolol. Dexamethasone was administered for 3 days and nadolol for 24 days prior to ovalbumin challenge. Both drugs were continued during five daily intranasal challenges with ovalbumin. Independent administration of dexamethasone (0.4 mg/kg/day) or nadolol (25 ppm) reduced bronchoalveolar lavage eosinophils by 58% and 36%, respectively (P < 0.05). Co-administration of both drugs yielded an additive reduction in eosinophils (81%, P < 0.05). Co-administration of both drugs (dexamethasone 0.4 mg/kg/day and nadolol 25 ppm) also yielded a greater reduction in mucin volume density (83%) than either drug alone (18% for dexamethasone and 62% for nadolol) and greater than high-dose dexamethasone (71%) alone (P < 0.05). Similarly, co-administration of both drugs (dexamethasone 0.4 mg/kg/day and nadolol 25 ppm) yielded an additive effect on the reduction of type 2 cytokines in bronchoalveolar lavage fluid equivalent to the administration of a 10-fold higher dose of dexamethasone. In Summary, the simultaneous administration of a glucocorticosteroid and a β₂-adrenoceptor inverse agonist was more effective at reducing indexes of airway inflammation than either drug given alone; suggesting nadolol may possess "glucocorticoid-sparing" properties.

The effects of inhaled corticosteroids on intrinsic responsiveness and histology of airways from infant monkeys exposed to house dust mite allergen and ozone

Inhaled corticosteroids (ICS) are recommended to treat infants with asthma, some with intermittent asthma. We previously showed that exposing infant monkeys to allergen/ozone resulted in asthma-like characteristics of their airways. We evaluated the effects of ICS on histology and intrinsic responsiveness of allergen/ozone-exposed and normal infant primate airways. Infant monkeys were exposed by inhalation to (1) filtered air and saline, (2) house dust mite allergen (HDMA)+ozone and saline, (3) filtered air and ICS (budesonide) or (4) HDMA+ozone and ICS. Allergen/ozone exposures started at 1 month and ICS at 3 months of age. At 6 months of age, methacholine-induced changes in luminal area of airways in proximal and distal lung slices were determined using videomicrometry, followed by histology of the same slices. Proximal airway responsiveness was increased by allergen/ozone and by ICS. Eosinophil profiles were increased by allergen/ozone in both proximal and distal airways, an effect that was decreased by ICS in distal airways. In both allergen/ozone- and air-exposed monkeys, ICS increased the number of alveolar attachments in distal airways, decreased mucin in proximal airways and decreased epithelial volume in both airways. ICS increased smooth muscle in air-exposed animals while decreasing it in allergen/ozone-exposed animals in both airways. In proximal airways, there was a small but significant positive correlation between smooth muscle and airway responsiveness, as well as between alveolar attachments and responsiveness. ICS change morphology and function in normal airways as well as allergen/ozone-exposed airways, suggesting that they should be reserved for infants with active symptoms.

Inhaled Corticosteroids Adverse Events In Asthmatic Children: A Review

BACKGROUND: Inhaled corticosteroids (ICS) have an important role in the treatment of chronic asthma in children. The prevalence of asthma symptoms in children varies from 0 to 30 percent in different populations with the highest prevalence occurring in Australia, New Zealand and England. METHODS: A review of the literature and studies about inhaled corticosteroids safety, action and adverse events in children and adults where applicable was done. CONCLUSION: Inhaled corticosteroids are the main stay therapy for persistent asthma in children. Their safety and efficacy is proven from the literature. Proper education of the parents about asthma and inhaled corticosteroids is very important and improve asthma control. Keeping in mind to taper the inhaled corticosteroids to the lowest dose needed to control asthma and using correct inhalation technique by the use of spacers with metered dose inhalers or dry powder inhalers (Turbuhaler and Diskus) will prevent the occurrence of adverse events.

Inhaled dexamethasone differentially attenuates disease relapse and established allergic asthma in mice

Inhaled glucocorticoids are effective in patients with chronic allergic asthma. We examined the effects of inhaled glucocorticoids on relapse (allergen challenge after disease remission) and established/overt allergic asthma (repeated allergen challenge in weekly intervals) in mice to establish a reference standard for novel treatments. BALB/c mice were treated before relapse or during overt disease with 1 h of nebulized PBS or 10 mg% dexamethasone twice daily for 5 days. Dexamethasone eliminated airway hyperresponsiveness before relapse and during overt disease. They more efficiently reduced airway inflammation, mucus production, and OVA-specific IgG1 and IgE during relapse compared to overt disease. However, during overt disease, parenchymal inflammatory infiltrates were more effectively eliminated compared to relapse, suggesting that activated infiltrating leukocytes have increased sensitivity to steroids. These data demonstrate that inhaled corticosteroids attenuate relapse and overt disease differentially and suggest that both airway and parenchymal inflammation need to be evaluated for treatment efficacy.

Pharmacology of airway inflammation in asthma and COPD

The current asthma therapies are not cures and symptoms return soon after treatment is stopped even after long term treatment. Although inhaled glucocorticoids are highly effective in controlling airway inflammation in asthma, they are ineffective in the small group of patients with glucocorticoid-dependent and -resistant asthma. With very few exceptions, COPD is caused by tobacco smoking, and smoking cessation is the only truly effective treatment of COPD available. Current pharmacological treatment of COPD is unsatisfactory, as it does not significantly influence the severity of the disease or its natural course. Glucocorticoids are scarcely effective in COPD patients without concomitant asthma. Bronchodilators improves symptoms and quality of life, in COPD patients, but, with the exception of tiotropium, they do not significantly influence the natural course of the disease. Theophylline is the only drug which has been demonstrated to have a significant effect on airway inflammation in patients with COPD. Here we review the pharmacology of currently used antiinflammatory therapies for asthma and COPD and their proposed mechanisms of action. Recent understanding of disease mechanisms in severe steroid-dependent and -resistant asthma and in COPD, has lead to the development of novel compounds, which are in various stages of clinical development. We review the current status of some of these new potential drugs.

Neuroendocrine regulation of immunity

A reciprocal regulation exists between the central nervous and immune systems through which the CNS signals the immune system via hormonal and neuronal pathways and the immune system signals the CNS through cytokines. The primary hormonal pathway by which the CNS regulates the immune system is the hypothalamic-pituitary-adrenal axis, through the hormones of the neuroendocrine stress response. The sympathetic nervous system regulates the function of the immune system primarily via adrenergic neurotransmitters released through neuronal routes. Neuroendocrine regulation of immune function is essential for survival during stress or infection and to modulate immune responses in inflammatory disease. Glucocorticoids are the main effector end point of this neuroendocrine system and, through the glucocorticoid receptor, have multiple effects on immune cells and molecules. This review focuses on the regulation of the immune response via the neuroendocrine system. Particular details are presented on the effects of interruptions of this regulatory loop at multiple levels in predisposition and expression of immune diseases and on mechanisms of glucocorticoid effects on immune cells and molecules.

Effects of topical glucocorticoids on in vitro lactoferrin glandular secretion: comparison between human upper and lower airways

BACKGROUND

Mucus hypersecretion is a hallmark of upper and lower airway diseases, such as rhinitis, asthma, and chronic obstructive pulmonary disease. Although topical glucocorticoids are widely used to treat mucosal inflammation, their effect on mucus hypersecretion remains uncertain.

OBJECTIVE

The aim of this study was to investigate the effect of budesonide and beclomethasone dipropionate on in vitro lactoferrin glandular secretion from both human nasal and bronchial mucosa and the potential mediating role of lipocortin 1.

METHODS

Nasal and bronchial explants obtained from patients undergoing surgery were cultured in a controlled atmosphere. Lactoferrin (ELISA) was measured in culture supernatants, and lipocortin 1 (Western blot) was analyzed in explant tissues.

RESULTS

Both budesonide and beclomethasone dipropionate (10(-6) mol/L) decreased spontaneous lactoferrin secretion in nasal and bronchial mucosa. The maximum effect of cortico-steroids (10(-6) mol/L) was obtained at day 3 in bronchial mucosa (budesonide: -56% +/- 9%, P <.05; beclomethasone dipropionate: -32% +/- 6%, P <.05) and at day 5 in nasal mucosa (budesonide: -34% +/- 10%, P <.05; beclomethasone dipropionate: -37% +/- 10%, P <.05). Methacholine (10(-4) mol/L) increased lactoferrin secretion in both bronchial (248% +/- 72%, P <.05) and nasal (107% +/- 28%, P <.05) explants, with this effect being completely abrogated by atropine. Budesonide caused a dose-related inhibitory effect on methacholine-induced lactoferrin secretion that was similar in both bronchial (down to -86% at 10(-6) mol/L) and nasal (down to -73% at 10(-6) mol/L) mucosa. Budesonide (10(-6) mol/L) did not show any effect on lipocortin 1 expression.

CONCLUSIONS

These results suggest that glucocorticoid effects on airway inflammation may include a reduction of mucus hypersecretion in both nasal and bronchial mucosa.

Signal transduction of mucous secretion by bronchial gland cells

Bronchial glands, which consist of mucous and serous cells, are abundant in human airways, playing a major role in the airway secretion. Cl(-) secretion is accompanied by water transport to the lumen in the acinar cells of bronchial glands. Agonists that increase [Ca(2+)]i induce the Cl(-) secretion in bronchial glands. Ca(2+) release from a IP(3)-sensitive Ca(2+) pool at the apical portion stimulates and opens Ca(2+)-sensitive Cl(-) channels at the apical membrane, producing Cl(-) secretion in bronchial glands. K(+) channels at the basolateral membranes are Ca(2+)-sensitive and activated by Ca(2+) release from a cADPribose-sensitive Ca(2+) pool, maintaining the Cl(-) secretion in bronchial glands. Further, cADP ribose in concert with IP(3) induce [Ca(2+)]i oscillation, inducing Cl(-) secretion in bronchial glands. Some tyrosine kinases are involved in the Cl(-) secretion in bronchial glands. Mucous and serous cells in bronchial glands take part in mucin secretion and the secretion of defensive substances (glycoconjugates), respectively. [Ca(2+)]i oscillations are shown to play a central role in the exocytosis of secretory granules in serous cells of bronchial glands. Other signal transductions of mucin and glycoconjugates in airway gland cells remain to be studied, although agonists which increase [cAMP]i are also well known to induce mucin and glycoconjugate secretion from airway glands.

Increased neutrophil numbers and IL-8 levels in airway secretions in acute severe asthma: Clinical and biologic significance

The inflammatory events in the airways at the time of acute respiratory failure from acute severe asthma are poorly understood. To determine the patterns of cellular inflammation in the airways in acute severe asthma, we analyzed tracheal aspirates collected within 12 h of intubation from patients intubated emergently for acute severe asthma (n = 10) and from patients intubated electively for nonpulmonary surgery (n = 14). The number of neutrophils in tracheal aspirates from asthma patients was 10 times higher than normal (4.2 [0.6 to 335.0] [median, range] versus 0.4 [0.009 to 9.4] x 10(6)/ml, p = 0.001), and there was a strong trend for a positive relationship between neutrophil number and duration of intubation (r(s) = 0.64, p = 0.06). Although eosinophil numbers were also significantly higher than normal (0.5 [0.0 to 23.3] versus 0.0 [0.0 to 0.1] x 10(6)/ml, p = 0.003), the numbers of eosinophils were 8-fold less than neutrophils, and there was no significant correlation between eosinophil number and duration of intubation (r(s) = 0.4, p = 0.26). Interleukin-8 (IL-8), a chemoattraction for neutrophils, was 19 times higher than normal in tracheal aspirates from asthmatic patients (75.0 [9.0 to 168.0] versus 4.0 [0.08 to 24.0] ng/ml, p < 0. 05) and correlated significantly with the neutrophil number (r(s) = 0.77, p = 0.03). Furthermore, the IL-8 levels correlated positively with the duration of mechanical ventilation (r(s) = 0.74, p = 0.03). Surprisingly, the number of neutrophils increased significantly during the period of intubation in the asthmatic subjects, possibly because of intravenous corticosteroid treatment. We conclude that neutrophils are the dominant inflammatory leukocyte characterizing airway inflammation in acute severe asthma that requires mechanical ventilation, and that IL-8 is an important mediator of this neutrophilia.

Downregulation of gastric mucin gene expression and its biosynthesis by dexamethasone in the human

The effect of corticosteroids on the release and biosynthesis of gastric mucin remains unclear. We studied the effects of dexamethasone on biosynthesis of mucin and MUC1 gene expression in the human stomach in vitro. Gastric mucosal specimens, obtained from six subjects at gastrectomy, were cultured with various concentrations of dexamethasone. Biosynthesis of mucin was studied by labeling gastric mucosa for 2 h with [3H]-glucosamine. After purification of mucin by CsCl gradient centrifugation, radioactivity of intra- and extracellular samples was counted. MUC1 gene expression was studied by Northern and dot-blot analysis using a cDNA encoding human gastric mucin gene MUC1. The dexamethasone treatment decreased mucin secretion from the isolated mucosa in a time- and concentration-dependent manner, with maximal inhibition of secretion (32+/-6%) observed after 8 h and 10(-5) M. Dexamethasone treatment also decreased MUC1 levels (28+/-9%). The inhibitory effect was also observed in carbachol-evoked secretion. These findings suggest that a decrease in mucin biosynthesis by corticosteroids may be involved in steroid-induced gastric mucosal damage.

Early nebulized budesonide in the treatment of bronchiolitis and the prevention of postbronchiolitic wheezing

OBJECTIVE

To determine the effectiveness of nebulized budesonide in the treatment of acute bronchiolitis and in the prevention of postbronchiolitic wheezing.

STUDY DESIGN

A randomized, double-blind, placebo-controlled trial was performed.

PATIENTS

Forty infants with bronchiolitis (83% RSV), mean age 13.5 weeks (range 4 to 41 weeks), were admitted to the Royal Alexandra Children's Hospital, Brighton, UK.

METHODS

Twenty-one infants received nebulized budesonide 1 mg every 12 hours for 5 days, then 500 micrograms every 12 hours continuing to a total of 6 weeks. Nineteen received nebulized placebo (0.9% saline) for 6 weeks. A clinical scoring system was used to rate acute symptoms, and diary cards were used to assess persistent respiratory symptoms over a 6-month follow-up period.

RESULTS

No significant differences were found between the budesonide and placebo groups in change in clinical score 48 hours after trial entry, mean oxygen requirements, or length of hospital stay during the acute illness. At 6-month follow-up, the two groups did not differ significantly in prevalence of wheeze, respiratory symptom scores, or proportion requiring bronchodilators or steroids.

CONCLUSION

This study did not demonstrate that a 6-week course of nebulized budesonide reduced the symptoms of acute bronchiolitis or prevented postbronchiolitic wheezing.

Glucocorticoids: mechanisms of action and anti-inflammatory potential in asthma

GLUCOCORTICOIDS are potent inhibitors of inflammatory processes and are widely used in the treatment of asthma. The anti-inflammatory effects are mediated either by direct binding of the glucocorticoid/glucocorticoid receptor complex to glucocorticoid responsive elements in the promoter region of genes, or by an interaction of this complex with other transcription factors, in particular activating protein-1 or nuclear factor-kappaB. Glucocorticoids inhibit many inflammation-associated molecules such as cytokines, chemokines, arachidonic acid metabolites, and adhesion molecules. In contrast, anti-inflammatory mediators often are up-regulated by glucocorticoids. In vivo studies have shown that treatment of asthmatic patients with inhaled glucocorticoids inhibits the bronchial inflammation and simultaneously improves their lung function. In this review, our current knowledge of the mechanism of action of glucocorticoids and their anti-inflammatory potential in asthma is described. Since bronchial epithelial cells may be important targets for glucocorticoid therapy in asthma, the effects of glucocorticoids on epithelial expressed inflammatory genes will be emphasized.

Effects of indomethacin, dexamethasone, and erythromycin on endotoxin-induced intraepithelial mucus production of rat nasal epithelium

We produced hypertrophic and metaplastic changes of goblet cells in rat nasal respiratory epithelium by the intranasal instillation of endotoxin (ETN). In the present study, we examined in vivo effects of indomethacin (IND), dexamethasone (DEX), and erythromycin (EM) on intraepithelial mucus production using this animal model. Intraperitoneal injection of IND (2 to 4 mg/kg body weight x 4 days) or DEX (4 to 8 mg/kg body weight x 4 days) significantly inhibited intraepithelial mucus production induced after 3 days of ETN instillations. Intraperitoneal injection of EM (100 mg/kg body weight x 8 days), aminobenzylpenicillin (ABPC, 200 mg/kg body weight x 8 days), and cephalothin (CET, 200 mg/kg body weight x 8 days) also inhibited intraepithelial mucus production induced after 7 days of ETN instillations. When compared with ABPC and CET, EM had a greater inhibitory effect. These results indicate that ETN-induced intraepithelial mucus production can be inhibited by treatment with the anti-inflammatory drugs IND and DEX. Antibiotics such as EM, ABPC, and CET will also be effective, probably by preventing secondary bacterial infection, and EM has an additional inhibitory effect on intraepithelial mucus production.

HMT regulates histamine-induced glycoconjugate secretion from human airways in vitro

To determine whether histamine N-methyltransferase (HMT) regulates mucus glycoprotein (MGP) secretion from airways, we examined the effect of an HMT inhibitor, SKF 91488, on MGP secretion from human airways in vitro. MGP secretion from human airway explants (with epithelium) and isolated submucosal glands was estimated by measuring trichloroacetic acid (TCA) precipitable glycoconjugates using secretory indices. Histamine induced significant MGP secretion from both explants and isolated glands. Pretreatment with SKF 91488 significantly inhibited histamine-induced secretion from explants, while it did not alter significantly the secretion from isolated glands. H1-blocker significantly reversed the inhibition by SKF 91488 of the secretion from explants, while H2-blocker abolished histamine-induced secretion from both explants and isolated glands. Prostaglandin E2 (PGE2) significantly inhibited histamine-induced secretion from isolated glands. The inhibitory action of SKF 91488 in airway explants was blocked by indomethacin and was significantly reduced by a prostanoid EP4 receptor antagonist (AH23848B). These findings suggest that HMT regulates MGP secretion from human airway submucosal glands through an interaction with epithelial cells which involves the release of PGE2.

Dexamethasone inhibits mucous glycoprotein secretion via a phospholipase A2-dependent mechanism in cultured chinchilla middle ear epithelial cells

Inhibition or attenuation of mucous hypersecretion in middle ear epithelium is a key step toward resolution of mucoid otitis media. Mucous hypersecretion induced by platelet-activating factor (PAF) in cultured Chinchilla middle ear epithelial cells is dependent on arachidonic acid metabolites via PAF receptors, suggestive of the role of phospholipase A2 (PLA2) in mucous glycoprotein (MGP) secretion. In this study, dexamethasone added to cultured Chinchilla middle ear epithelial cells inhibited baseline and PAF-induced MGP secretion in a concentration-dependent manner. A definite time lag (16 h) was observed between administration of dexamethasone and MGP inhibition. This inhibition was reversed by the addition of exogenous PLA2 (the rate-limiting enzyme of arachidonic acid metabolism) and actinomycin D (an inhibitor of mRNA synthesis). This suggests that dexamethasone inhibits baseline and PAF-induced MGP secretion via a PLA2-dependent mechanism.

Glucocorticoid modulation of muscarinic and beta-adrenergic receptors in guinea pig lung

We investigated the effect of the in vivo treatment of guinea pigs with methylprednisolone, 10 mg/kg daily, on lung muscarinic and beta-adrenergic receptors. Receptor densities were assessed by saturation experiments of tritiated N-methylscopolamine and dihydroalprenolol binding to lung membranes. After 3 h of treatment, methylprednisolone induced a decrease of 19.2% (P < 0.05) of muscarinic receptors but was without effect on beta-adrenergic receptor density. After 24 h, an increase of 39.7% (P < 0.01) and 16.9% (P < 0.05) was observed for muscarinic and beta-adrenergic receptors, respectively. For muscarinic receptors, this increase reached 53.4% (P < 0.01) within 48 h and stayed at this level until 96 h. The increase of beta-adrenergic receptors was maximal (24.9%) after 72 h and returned to the control value after 96 h. The dissociation constant (Kd) values of both ligands were not affected by the glucocorticoid treatment. Functional studies showed that the 96 h treatment did not affect the contractile response of guinea pig lung parenchymal strips to carbachol since the 50% concentration value (EC50) and the maximal contraction value (Emax) were not significatively different from control values. These data show that glucocorticoids control the expression of both muscarinic and beta-adrenergic receptors in guinea pig lung but with different time courses and to a larger extent for muscarinic receptors. The glucocorticoid treatment did not modify the contractile response of lung strips to carbachol, confirming the absence of effect on the affinity of muscarinic receptors and suggesting that the receptor reserve exceed the increase of their density by the steroid.

The role of corticosteroids in respiratory diseases of children

Glucocorticosteroids are potent anti-inflammatory agents and have an important role in a variety of respiratory diseases. Although their exact mode of action is unknown, it is thought that they exert their effects by binding to cytoplasmic glucocorticoid receptors. In certain conditions, such as asthma, the value of steroids cannot be questioned, and inhaled steroids have revolutionized management. In other situations, such as interstitial lung disease, the true role of steroids is still to be defined. In the management of diseases such as tuberculosis, the use of steroids is solely based on anecdotal experience.

Topical corticosteroids potentiate mucin secretion in the normal nose

The exact mode of action of topical nasal corticosteroids is still uncertain. The aim of this study was to determine their effects on microvascular permeability and cellular and glandular secretion by measuring the levels of total protein, albumin, lysozyme and mucin recovered in nasal lavage fluid before and after 3 weeks of treatment with a topical nasal corticosteroid in 12 normal non-atopic subjects. Six subjects applied 200 micrograms fluticasone propionate and six applied 200 micrograms beclomethasone dipropionate to one nostril in each 24 h: matched placebo was applied to the other nostril. There was a significant rise in the level of mucin recovered compared with baseline values following fluticasone administration (baseline 76.2 micrograms/ml (mean) +/- 5.5 (SEM), fluticasone 118.3 micrograms/ml +/- 11.6 P = 0.015) and beclomethasone administration (baseline 64.3 micrograms/ml +/- 6.6, beclomethasone 87.2 micrograms/ml +/- 4.8, P = 0.041). There was no significant change in the levels of total protein, albumin or lysozyme following either active medication or placebo treatment. Topical corticosteroids appear to potentiate mucin secretion and do not alter serous secretion or microvascular permeability in the unchallenged non-atopic nose.

Nitric oxide regulation of glycoconjugate secretion from feline and human airways in vitro

To determine whether nitric oxide (NO) regulates mucus secretion from airway submucosal glands which are the main source of human airway secretion, we examined the effects of NO synthase inhibitors (L-NAME and L-NMMA) on mucus glycoprotein (MGP) secretion from feline and human airway explants (with epithelium) and isolated submucosal glands. MGP secretion was estimated by measuring trichloroacetic-acid (TCA) precipitable [H3]-glycoconjugates using secretory indices. NO synthase inhibitors alone did not alter significantly MGP secretion from explants or isolated glands. Pretreatment with NO synthase inhibitors significantly inhibited both methacholine (MCh) and bradykinin (BK)-induced secretion from isolated glands, but not significantly inhibit the secretion from explants. The inhibition by L-NAME was reversed by the addition of L-arginine in both MCh- and BK-induced secretions from isolated glands. Further, a NO generator isosorbide dinitrate induced a significant increase in the secretion. These findings suggest that endogenous NO has a stimulatory action in airway submucosal gland secretion and directly regulates the secretion from submucosal glands independently of superficial epithelial cells.

Tachykinins induce a [Ca2+]i rise in the acinar cells of feline tracheal submucosal gland

The intracellular Ca2+ concentration ([Ca2+]i) of acinar cells of isolated submucosal glands from trachea was measured using a fluorescent dye, Fura-2. Neurokinin A (NK-A) produced a sustained rise in [Ca2+]i in a dose-dependent manner, reaching a response of 500 to 600% of the prior baseline value at 10(-6) or 10(-5) M, and the NK-A evoked [Ca2+]i was significantly higher than that by substance P (SP) at similar concentrations. NK-B did not induce significant increases in [Ca2+]i. In a Ca(2+)-free solution, NK-A produced a transient rise in [Ca2+]i, which returned to the baseline within 3 min. Mucus glycoprotein (MGP) secretion, estimated by measuring trichloroacetic-acid (TCA) precipitable glycoconjugates, was stimulated by NK-A or SP. These findings indicate that tachykinins produce a rise in [Ca2+]i by both entry from the extracellular solution and release from intracellular storage, probably by NK-2 receptor stimulation, and stimulate MGP secretion from airway submucosal glands.

CGRP induces [Ca2+]i rise and glycoconjugate secretion in feline tracheal submucosal gland

Submucosal glands were isolated from feline trachea. The intracellular Ca2+ concentration ([Ca2+]i) of the acinar cells of isolated glands was measured using the fluorescent dye Fura-2. Calcitonin gene-related peptide (CGRP) at 10(-8) to 10(-5) M produced a significant and sustained rise in the [Ca2+]i of isolated glands, reaching a maximal response of 127% of the prior baseline level but did not alter the intracellular adenosine 3', 5'-cyclic monophosphate ([cAMP]i). In a Ca(2+)-free solution, CGRP produced no significant alteration in [Ca++]i. Glycoconjugate secretion from isolated glands was stimulated by CGRP in a dose dependent fashion, reaching a maximal response of 167% of control at 10(-6) M but was without effect in tracheal explants. Further, CGRP did not produce any significant increase in glycoconjugate secretion in the Ca(2+)-free medium. These findings indicate that CGRP stimulates glycoconjugate secretion from airway submucosal glands by inducing Ca2+ influx from the extracellular solution.

New perspectives in understanding and management of the respiratory disease in cystic fibrosis

In the past 40 years, the mean survival of patients with cystic fibrosis (CF) has increased from less than 1 year to 30 years. The identification of the gene mutated in CF in 1989 has already been followed by the first phase of somatic gene therapy in 1993. The target organ of somatic gene therapy is the respiratory epithelium, which is progressively damaged by the chronic infection and inflammation characteristic of the disease. Since in the future, more patients may benefit from somatic gene therapy, the understanding of the mechanisms leading to chronic infection and inflammation becomes increasingly important. In the future, current therapeutic measures to protect the respiratory epithelium from damage, such as intravenous antimicrobial treatment, will be improved by the additional delivery of new drugs to the bronchial tree by aerosol. Amiloride and recombinant human DNAse administered by this route have the potential to improve mucociliary clearance. Antibiotics as well as protease inhibitors delivered by aerosol should contribute to prevent damage by infection and inflammation in order to increase the probability of successful somatic gene therapy in this disease.

Efficacy and safety of inhaled corticosteroids in asthma. Report of a workshop held in Eze, France, October 1992

Inhaled glucocorticosteroids have now become first-line therapy for the treatment of chronic asthma in many countries. They are the most effective asthma therapy currently available, and numerous studies have documented their long-term efficacy in asthma control in adults and in children. Inhaled steroids suppress inflammation in asthmatic airways, although their precise molecular mechanism of action is not yet certain. It is likely that steroids affect the transcription of several steroid-responsive genes, and, of particular importance, they may inhibit cytokine gene transcription and cytokine effects, thereby reducing the chronic inflammation in asthmatic airways. Inhaled steroids are now used at a much earlier stage in asthma therapy, and there is a strong argument for their early introduction in both adults and children to prevent asthma morbidity and mortality and possibly the structural changes resulting from uncontrolled chronic inflammation, which may lead to irreversible airflow obstruction in some patients. Of paramount importance is the question of safety as inhaled steroids are likely to be required for a long time. Local side effects caused by oropharyngeal deposition of the inhaled steroid may be reduced by the use of spacer devices and mouthwashing. Systemic side effects caused by gastrointestinal absorption of the fraction deposited in the oropharynx may also be reduced by these devices. There are differences in the systemic bioavailability of the different inhaled steroids currently in use, and inhaled steroids with the lowest bioavailability should be chosen when high doses of inhaled steroids are required for asthma control. Systemic side effects are usually observed only when daily doses of > 800 micrograms are inhaled, and whether effects on very sensitive biochemical indices are relevant to long-term deleterious effects is not yet certain. There is now overwhelming evidence that the doses of inhaled steroids required to control asthma in the majority of adults and children are safe and without systemic side effects. It is important to control asthma with the minimum dose of inhaled steroids possible, however. In the future it may be possible to develop inhaled steroids with even fewer systemic effects if the fraction absorbed from the respiratory tract can be rapidly metabolized in the bloodstream.

A stimulatory role of protein kinase C in feline tracheal submucosal gland secretion

To determine the role of protein kinase C (PKC) in airway submucosal gland secretion, we examined the effect of a selective PKC stimulant, phorbol 12-myristate 13-acetate (PMA), on mucus glycoprotein (MGP) secretion, fluid secretion and intracellular Ca2+ concentration ([Ca2+]i) in isolated feline submucosal glands. MGP and fluid secretions were estimated by measuring trichloroacetic acid (TCA)-precipitable glycoconjugates and 22Na-efflux, respectively, from isolated glands. [Ca2+]i was measured using a Ca(2+)-sensitive fluorescent dye, Fura 2. PMA itself produced a significant increase in MGP secretion in a dose-dependent fashion (173% of control at 10(-5) M). PMA also produced a significant increase in 22Na-efflux (151% of baseline rate constant at 10(-5) M). Indomethacin failed to alter the increase in MGP secretion or in 22Na-efflux in response to PMA. Two PKC inhibitors, 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H-7) and sphingosine, inhibited both MGP secretion and 22Na-efflux stimulated by PMA; there was only a partial inhibition after stimulation by methacholine (MCh). PMA did not significantly alter [Ca2+]i and H-7 did not alter the MCh-induced [Ca2+]i rise. These findings indicate that PKC has a direct stimulatory role in stimulus-secretion coupling of airway submucosal gland secretion.

Eosinophils, secretory responsiveness and glucocorticoid-induced effects on the nasal mucosa during a weak pollen season

This study examined the seasonal effects on eosinophils and secretory responsiveness of the nasal mucosa in 22 patients with allergic rhinitis due to birch pollen (11 patients received placebo and 11 budesonide, 200 micrograms once daily in each nostril). The pollen counts during the study season were too low to produce a significant symptomatology. Hence, our findings demonstrate threshold alterations of the airway mucosa in allergic rhinitis and their inhibition by anti-inflammatory drug intervention. The patients were monitored for 8 weeks with daily recordings of pollen counts and symptom scores. Once every week a series of laboratory tests was carried out: the local eosinophil influx was determined using a Rhinobrush technique; the levels of eosinophil cationic protein (ECP) were analysed in nasal lavage fluids; and the secretory response to intranasal methacholine was measured. Treatments started after a 2-week run-in period. The proportion of eosinophils increased markedly in the placebo group and was elevated also during the last two study weeks when the pollen counts were practically nil. The secretory responsiveness to methacholine increased during the pollen season and returned to baseline towards the end of the study period. The topical glucocorticoid treatment reduced the proportion of eosinophils, the ECP levels, and the secretory response to methacholine compared to placebo. We conclude that the increased traffic and activity of eosinophils and less conspicuously the increased secretory responsiveness are expressions of the mucosal inflammation that precede the development of symptoms in seasonal allergic rhinitis.

Production of lipocortin-like proteins by cultured human tracheal submucosal gland cells

Evidence is obtained for the presence of lipocortin-like proteins in human tracheal gland cells in culture. Using polyclonal antibodies to lipocortin I, indirect immunofluorescence studies demonstrate that lipocortin I is mainly confined to the tracheal gland cell surface. From cell membranes, four Ca2(+)-dependent proteins (35, 40, 45 and 67 kDa) were identified as lipocortin related proteins by using immunoblotting and fluorography following [35S]methionine metabolic labeling experiments. A strong immunoreactivity for the 35 kDa protein was observed. In addition, lipocortin-like proteins with apparent Mr33, 35, 37 and 67 kDa, respectively, were released in the apical culture medium by tracheal gland cells cultured on microporous membrane of a double chamber culture system.