Inhaled glucocorticoids: new developments relevant to updating of the asthma management guidelines

Corticosteroid resistance in asthma: Cellular and molecular mechanisms

Inhaled glucocorticoids (GCs) are drugs widely used as treatment for asthma patients. They prevent the recruitment and activation of lung immune and inflammatory cells and, moreover, have profound effects on airway structural cells to reverse the effects of disease on airway inflammation. GCs bind to a specific receptor, the glucocorticoid receptor (GR), which is a member of the nuclear receptor superfamily and modulates pro- and anti-inflammatory gene transcription through a number of distinct and complementary mechanisms. Targets genes include many pro-inflammatory mediators such as chemokines, cytokines, growth factors and their receptors. Inhaled GCs are very effective for most asthma patients with little, if any, systemic side effects depending upon the dose. However, some patients show poor asthma control even after the administration of high doses of topical or even systemic GCs. Several mechanisms relating to inflammation have been considered to be responsible for the onset of the relative GC resistance observed in these patients. In these patients, the side-effect profile of GCs prevent continued use of high doses and new drugs are needed. Targeting the defective pathways associated with GC function in these patients may also reactivate GC responsiveness.

Nongenomic effects of fluticasone propionate and budesonide on human airway anion secretion

This study investigated the physiological effects of inhaled corticosteroids, which are used widely to treat asthma. The application of fluticasone propionate (FP, 100 μM) induced sustained increases in the short-circuit current (I(SC)) in human airway Calu-3 epithelial cells. The FP-induced I(SC) was prevented by the presence of H89 (10 μM, a protein kinase A inhibitor) and SQ22536 (100 μM, an adenylate cyclase inhibitor). The FP-induced responses involved bumetanide (a Na(+)-K(+)-2Cl(-) cotransporter inhibitor)-sensitive and 4,4'-dinitrostilbene-2,2'-disulfonic acid (an inhibitor of HCO(3)(-)-dependent anion transporters)-sensitive components, both of which reflect basolateral anion transport. Further, FP augmented apical membrane Cl(-) current (I(Cl)), reflecting cystic fibrosis transmembrane conductance regulator (CFTR)-mediated conductance, in the nystatin-permeabilized monolayer. In I(SC) and I(Cl) responses, FP failed to enhance the responses to forskolin (10 μM, an adenylate cyclase activator). Nevertheless, we found that FP synergistically increased cytosolic cAMP concentrations in combination with forskolin. All these effects of FP were reproduced with the use of budesonide. Collectively, inhaled corticosteroids such as FP and budesonide stimulate CFTR-mediated anion transport through adenylate cyclase-mediated mechanisms in a nongenomic fashion, thus sharing elements of a common pathway with forskolin. However, the corticosteroids cooperate with forskolin for synergistic cAMP production, suggesting that the corticosteroids and forskolin do not compete with each other to exert their effects on adenylate cyclase. Considering that such synergism was also observed in the FP/salmeterol combination, these nongenomic aspects may play therapeutic roles in mucus congestive airway diseases, in addition to genomic aspects that are generally recognized.

Benefits of low-dose inhaled fluticasone on airway response and inflammation in mild asthma

RATIONALE

Current guidelines suggest that asthma should be controlled with the lowest dose of maintenance medication required.

OBJECTIVES

To evaluate the effects of a low dose of inhaled corticosteroid compared to a placebo, on airway inflammation and responsiveness in patients with mild symptomatic asthma.

METHODS

In this randomized double-blind, placebo-controlled, parallel group study, we looked at the influence of inhaled fluticasone propionate 250 microg/day for 3 months followed by 100 microg/day for 9 months on airway inflammation and methacholine responsiveness in non-smoking subjects with mild allergic asthma. Subjects were evaluated at baseline and 3, 6, 9 and 12 months after treatments; a 2-week evaluation of respiratory symptoms and peak expiratory flow measurements was done before each visit.

RESULTS

Fifty-seven subjects completed the 3-month study period. Airway responsiveness, expressed as the PC20 methacholine, increased by 0.27 and 1.14 doubling concentrations, respectively, in placebo-treated (n=33) and in fluticasone-treated (n=24) asthmatic subjects (p=0.03). An additional improvement in PC20 up to 2.16 doubling concentrations was observed in the fluticasone-treated group during the 9-month lower-dose treatment (p=0.0004, end of low-dose period compared with placebo). Sputum eosinophil counts decreased after 3 months of fluticasone 250 microg/day compared with placebo (p<0.0001) and remained in the normal range during the 9-month lower-dose treatment. Respiratory symptoms and peak expiratory flows did not change significantly throughout the study in both groups.

CONCLUSION

In mild asthma, keeping a regular minimal dose of ICS after asthma control has been achieved, may lead to a further reduction in airway responsiveness and keep sputum eosinophil count within the normal range.

Effects of inhaled fluticasone on angiogenesis and vascular endothelial growth factor in asthma

BACKGROUND

Subepithelial hypervascularity and angiogenesis in the airways are part of structural remodelling of the airway wall in asthma, but the effects of inhaled corticosteroids (ICS) on these have not been explored. Increased vascularity in asthma may contribute to a number of functional abnormalities. A study was undertaken to explore angiogenic modulation by ICS and its likely regulation via vascular endothelial growth factor (VEGF), its receptors and the angiopoietins.

METHODS

A placebo-controlled intervention study with ICS in asthma was performed, examining vascularity, VEGF, its receptors (VEGFR1 and VEGFR2), and angiopoietin-1 (Ang1) to assess which of these factors were changed in the asthmatic airways after ICS treatment. Airway wall biopsy specimens, lavage fluid and cells were obtained from 35 patients with mild asthma randomised to receive ICS or placebo for 3 months, after which bronchoscopic examination and sample collection were repeated. Immunohistochemistry and image analysis were used to obtain quantitative measures of vessels, angiogenic sprouts, VEGF, VEGFR1, VEGFR2 and Ang1 staining in airway biopsy specimens. ELISA was used to assess VEGF concentrations in the lavage fluid.

RESULTS

Vessel, VEGF and sprout staining were decreased after 3 months of ICS treatment. VEGF levels remained unchanged. VEGF receptors and Ang1 staining were not reduced after treatment.

CONCLUSIONS

The findings of this study support an effect of ICS in downregulating angiogenic remodelling in the airways in asthma, associated with decreasing VEGF activity within the airway wall. The environment of the airways after treatment with ICS, with changes in the balance between VEGF, its receptors, Ang1 and sprouts, appears to be less angiogenic than in untreated asthma.

Anti-inflammatory effects of once daily low dose inhaled ciclesonide in mild to moderate asthmatic patients

BACKGROUND

Ciclesonide exhibits clinical efficacy at 160 microg (ex-actuator) once daily but the anti-inflammatory effects at this dose are not known. We wished to know whether 4 weeks therapy with ciclesonide pMDI 160 microg once daily in the morning exhibited significant anti-inflammatory effects.

METHODS

Seventeen patients with mild persistent asthma (FEV(1) 3.35 l) were recruited into a double-blind placebo-controlled randomized crossover study. Measurements were made after ciclesonide and placebo treatment as well as after run-in and washout periods, for adenosine monophosphate (AMP) bronchial challenge (primary variable), exhaled nitric oxide (NO) and induced sputum (in a subgroup).

RESULTS

The mean (SEM) AMP bronchial challenge PC(20) following ciclesonide (140 (63) mg/ml) was significantly (P < 0.001) increased compared with placebo (17 (8) mg/ml), run-in (13 (5) mg/ml) and washout (9 (3) mg/ml) periods. This amounted to an eightfold (CI: 5.3-12.0) for ciclesonide vs placebo. Likewise, there were significant improvements in exhaled NO levels and a significant reduction in induced sputum eosinophil cell counts.

CONCLUSION

We have shown that inhaled ciclesonide given at 160 microg once daily in the morning exhibits significant anti-inflammatory effects that are in keeping with the previously described clinical effects.

Safety, tolerability and acceptability of two dry powder inhalers in the administration of budesonide in steroid-treated asthmatic patients

The purpose of this randomized, double-blind parallel group study was to compare the safety, tolerability and acceptability of Easyhaler and Turbuhaler dry powder inhalers for the delivery of budesonide 800 microg day(-1) in adult asthmatic patients who had already been treated with inhaled corticosteroids for at least 6 months prior to the study Additionally the efficacy of the products was evaluated. The main objective was to evaluate the systemic safety of budesonide inhaled from Easyhaler (Giona Easyhaler, Orion Pharma, Finland) as determined by serum and urine cortisol measurements. The secondary objective was to compare the tolerability acceptability and efficacy of the two devices in the administration of budesonide. After a 2-week run-in period (baseline), patients were randomized on a 2:1 basis to receive budesonide from Easyhaler (n = 103) or from Turbuhaler (Pulmicort Turbuhaler, AstraZeneca, Sweden) (n = 58) 200 g dose(-1), two inhalations twice daily for 12 weeks. There was no statistically significant change in morning serum cortisol values from baseline to the end of treatment in either group. Urine free cortisol and urine cortisol/ creatinine ratio increased from baseline in both groups. There were no significant differences between the groups in terms of morning serum cortisol, urine cortisol, adverse events or efficacy variables, but Easyhaler was generally considered more acceptable to the patients. In conclusion, at 800 microg day(-1), Giona Easyhaler is as safe and efficacious as Pulmicort Turbuhaler in adult asthmatic patients previously treated with corticosteroids, but more acceptable to patients.

Benefits of high altitude allergen avoidance in atopic adolescents with moderate to severe asthma, over and above treatment with high dose inhaled steroids

Some patients with severe asthma cannot be controlled with high doses of inhaled steroids (ICS), which may be related to ongoing environmental allergen exposure. We investigated whether 10 weeks of high altitude allergen avoidance leads to sustained benefits regarding clinical and inflammatory markers of disease control in adolescents with persistent asthma despite treatment with high dose ICS. Eighteen atopic asthmatic adolescents (12-18 yr, 500-2000 microg ICS daily) with established house dust mite allergy, participated in a parallel-group study. Quality of life (PAQL), lung function, bronchial hyperresponsiveness (BHR) to adenosine and histamine, induced sputum and urine samples were collected repeatedly from 10 patients during a 10-week admission period to the Swiss Alps (alt. 1560 m) and at 6 weeks after return to sea level. Results were compared with those in eight patients, studied in their home environment at sea level for a similar time period. Throughout the study, asthma medication remained unchanged in both groups. During admission to high altitude, PAQL, lung function, BHR to adenosine and histamine, and urinary levels of eosinophil protein X (U-EPX), leukotriene E4 (U-LTE4) and 9alpha11beta prostaglandin F2 (U-9alpha11beta PGF2) improved significantly (P < 0.05), with a similar tendency for sputum eosinophils (P < 0.07). Furthermore, the changes in PAQL and BHR to adenosine and histamine were greater in the altitude than in the control group (P < 0.05). At 6 weeks after renewed allergen exposure at sea level, the improvements in PAQL (P < 0.05), BHR to adenosine (P < 0.07) and histamine (P < 0.05), as well as U-EPX (P < 0.05) and U-LTE4 (P < 0.05) were maintained. A short period of high altitude allergen avoidance, on top of regular treatment with ICS and long-acting beta2-agonists, results in improvement of asthma, as assessed by clinical and inflammatory markers of disease severity. These findings indicate that short-term, rigorous allergen avoidance can improve the long-term control of severe asthma over and above what can be achieved even by high doses of inhaled steroids.

Inducible expression of a Th2-type CC chemokine thymus- and activation-regulated chemokine by human bronchial epithelial cells

CCR4 is now known to be selectively expressed in Th2 cells. Since the bronchial epithelium is recognized as an important source of mediators fundamental to the manifestation of respiratory allergic inflammation, we studied the expression of two functional ligands for CCR4, i.e., macrophage-derived chemokine (MDC) and thymus- and activation-regulated chemokine (TARC), in bronchial epithelial cells. The bronchial epithelium of asthmatics and normal subjects expressed TARC protein, and the asthmatics showed more intense expression than the normal subjects. On the other hand, MDC expression was only weakly detected in the asthmatics, but the intensity was not significantly different from that of normal subjects. Combination of TNF-alpha and IL-4 induced expression of TARC protein and mRNA in bronchial epithelial A549 cells, which was slightly up-regulated by IFN-gamma. The enhancement by IFN-gamma was more pronounced in bronchial epithelial BEAS-2B cells, and a maximum production occurred with combination of TNF-alpha, IL-4, and IFN-gamma. On the other hand, MDC was essentially not expressed in any of the cultures. Furthermore, expressions of TARC protein and mRNA were almost completely inhibited by glucocorticoids. These results indicate that the airway epithelium represents an important source of TARC, which potentially plays a role via a paracrine mechanism in the development of allergic respiratory diseases. Furthermore, the beneficial effect of inhaled glucocorticoids on asthma may be at least in part due to their direct inhibitory effect on TARC generation by the bronchial epithelium.

Salmeterol/fluticasone propionate (50/100 microg) in combination in a Diskus inhaler (Seretide) is effective and safe in children with asthma

The aim of this study was to compare the efficacy and safety in children of salmeterol (50 microg twice daily) plus fluticasone propionate (100 microg twice daily) when delivered together via a single Diskus inhaler (Seretide; combination therapy) or concurrently using two separate Diskus inhalers (concurrent therapy). In a multicenter, randomized, double-blind, double-dummy, parallel-group study, 257 children with reversible airways obstruction who remained symptomatic on inhaled corticosteroids (200-500 microg daily) alone were randomized to combination or concurrent therapy for 12 weeks. Efficacy was assessed by measuring daily peak expiratory flow (PEF), symptom scores, and rescue salbutamol use. In addition, lung function tests were performed at each clinic visit. Safety assessments included monitoring of adverse events and morning serum cortisol concentrations. The primary efficacy parameter (mean morning PEF) increased during treatment in both groups; adjusted mean changes were 33 and 28 L/min for the combination and concurrent therapies, respectively. The 90% confidence interval for the difference in mean morning PEF between treatment groups was within the +15 L/min criterion for clinical equivalence. Similarly, there were improvements in pulmonary function, symptom score, and rescue salbutamol use during treatment in both groups, with no significant differences between the combination and concurrent therapy groups for any of these secondary efficacy parameters. Both treatment regimens were well-tolerated and had comparable adverse event profiles. Mean morning serum cortisol levels increased similarly in both groups during the study. In conclusion, salmeterol and fluticasone propionate therapy given as a new combination product is as safe and effective in children with asthma as the same drugs given concurrently via separate inhalers.

Underuse of inhaled corticosteroids in adults with asthma

Despite strong evidence that inhaled corticosteroids are beneficial in treating asthma, a number of small studies suggest a use rate of only 34-56%. The primary objective of this study was to determine patterns of prescribing inhaled corticosteroids for high-risk patients with asthma. Secondary objectives were to assess patterns of practice with respect to other agents prescribed before and at hospital discharge, and to determine if an emergency room asthma care map at one of the study hospitals was being followed. We retrospectively reviewed charts of 1022 patients with an acute attack of asthma treated in the emergency rooms of the Royal Alexandra Hospital and University of Alberta Hospital from January 1, 1996, to March 31, 1997. A forward stepwise logistic regression analysis was performed with the dependent variable defined as whether or not the patient was using an inhaled or oral corticosteroid during the index visit, and the independent variable being all major demographic variables. Inhaled corticosteroids were prescribed for 460 patients (52.0%) at the index visit. Overall, antiinflammatory drugs were prescribed for 548 patients (62.1%). An asthma care map was followed for 107 (16.8%) patients treated at the Royal Alexandra Hospital at the index visit. Logistic regression analysis showed that women and patients with more than one emergency room visit most likely were to be using inhaled or inhaled plus oral corticosteroids at the index visit. Documentation of drug therapy at discharge was poor for 42% of patients; therefore, analysis of practice patterns in this group was not attempted. This study shows that inhaled corticosteroids were prescribed for only about one-half of patients with an acute asthma attack. Given this low use by high-risk patients, the need for programs designed to improve asthma therapy is evident.

Recent developments in respiratory care pharmacology

Bronchoactive inhaled aerosol drugs target the respiratory tract directly and seek to minimize systemic exposure and reduce side effects. Common delivery devices such as the metered dose inhaler, the small volume nebulizer, or the dry powder inhaler each deliver approximately the same fraction of dose (10%) to the lungs, although their dose amounts are not equivalent. Major respiratory drug groups are reviewed, and include the beta-adrenergic and anticholinergic bronchodilators, mucolytic agents, corticosteroids, mediator antagonists, anti-infective agents, and exogenous surfactants. New agents in each group are identified and briefly described, along with the clinical use and most commonly observed side effects for each class of drugs.

Starting with a higher dose of inhaled corticosteroids in primary care asthma treatment

New British guidelines on the treatment of asthma (9) advocate starting with a higher dose of inhaled corticosteroids in newly detected asthma patients. We investigated whether initiating inhaled steroid treatment with a higher dose is clinically more effective than a lower dose in steroid naive patients with asthma. The study had a 13-wk randomized, double-blind, parallel design: 1-mo treatment with 400 microg budesonide twice a day, or 100 microg budesonide twice a day by dry powder inhaler, and follow-up treatment period of 2 mo with 200 microg budesonide once daily for all patients. Forty patients started with 400 microg budesonide twice daily, 44 with 100 microg budesonide twice daily. Mean age was 32 yr, baseline FEV1 value 84% predicted, reversibility 9% from baseline, and mean bronchodilator use 1.6 inhalations/d in the run-in period. After 4 wk of treatment with 400 microg and 100 microg budesonide twice daily mean morning peak expiratory flow (PEF) increased 27 L/min (SD 50), and 38 L/ min (SD 53), respectively (p = 0.30); mean symptom score improved from 1.1 to 0.6 and from 1.1 to 0.5. These effects were maintained in the 2 mo follow-up. This study suggests that starting inhaled corticosteroids at a higher dose is not superior to a lower dose in the treatment of newly detected asthma.

Current issues for establishing inhaled corticosteroids as the antiinflammatory agents of choice in asthma

Airway inflammation appears to be present even in the mildest of asthma, and inhaled corticosteroids now form the mainstay of asthma therapy. Inhaled corticosteroids largely avoid the adverse effects associated with oral steroids and are now recommended in newly detected disease. Inhaled corticosteroids reduce airway inflammation, airway hyperresponsiveness, and the symptoms of asthma and improve lung function, irrespective of the patient's age or asthma severity. Several different inhaled corticosteroids are available as therapeutic options for the treatment of asthma, and these include fluticasone propionate, beclomethasone dipropionate, and budesonide. The efficacy and safety of inhaled corticosteroids are compared in this article, and inhaled corticosteroid therapy is also compared with other therapies. Recently, there has been a consensus that the optimal use of inhaled corticosteroids for asthma management is using a "start high--go low" approach, and the reasons for this are discussed.

Pharmacotherapy of Asthma

The approach to asthma therapy has changed from an emphasis on bronchodilation to an emphasis on anti-inflammatory medications. New guidelines from the National Asthma Education and Prevention Program Expert Panel II were released in February 1997 and emphasize that inhaled corticosteroids are the cornerstone of pharmacotherapy. New inhaled corticosteroids and new delivery methods have been introduced which have significant advantages over older products. Pharmacological innovations such as the leukotriene modifiers represent continued research to influence the inflammatory response. Agents or therapies which can decrease the daily dose of systemic corticosteroids continue to be investigated in continued efforts to reduce the side effects and adverse reactions associated with systemic corticosteroid therapy.