Corticosteroid unresponsiveness in asthma: primary or acquired?

Nasal airway epithelial cell IL-6 and FKBP51 gene expression and steroid sensitivity in asthmatic children

Background

Many asthmatic patients exhibit uncontrolled asthma despite high-dose inhaled corticosteroids (ICS). Airway epithelial cells (AEC) have distinct activation profiles that can influence ICS response.

Objectives

A pilot study to identify gene expression markers of AEC dysfunction and markers of corticosteroid sensitivity in asthmatic and non-asthmatic control children, for comparison with published reports in adults.

Methods

AEC were obtained by nasal brushings and primary submerged cultures, and incubated in control conditions or in the presence of 10 ng/ml TNFalpha, 10^-8M dexamethasone, or both. RT-PCR-based expression of FKBP51 (a steroid hormone receptor signalling regulator), NF-kB, IL-6, LIF (an IL-6 family neurotrophic cytokine), serpinB2 (which inhibits plasminogen activation and promotes fibrin deposition) and porin (a marker of mitochondrial mass) were determined.

Results

6 patients without asthma (median age 11yr; min-max: 7–13), 8 with controlled asthma (11yr, 7–13; median daily fluticasone dose = 100 μg), and 4 with uncontrolled asthma (12yr, 7–14; 1000 μg fluticasone daily) were included. Baseline expression of LIF mRNA was significantly increased in uncontrolled vs controlled asthmatic children. TNFalpha significantly increased LIF expression in uncontrolled asthma. A similar trend was observed regarding IL-6. Dexamethasone significantly upregulated FKBP51 expression in all groups but the response was blunted in asthmatic children. No significant upregulation was identified regarding NF-kB, serpinB2 and porin.

Conclusion

LIF and FKBP51 expression in epithelial cells were the most interesting markers of AEC dysfunction/response to corticosteroid treatment.

Caerulomycin A inhibits Th2 cell activity: a possible role in the management of asthma

We have recently demonstrated that Caerulomycin A induces regulatory T cells differentiation by suppressing Th1 cells activity. The role of regulatory T cells is well established in suppressing the function of Th2 cells. Th2 cells are known to inflict the induction of the activation of asthma. Consequently, in the present study, we monitored the influence of Caerulomycin A in inhibiting the activity of Th2 cells and its impact in recuperating asthma symptoms. Interestingly, we observed that Caerulomycin A significantly suppressed the differentiation of Th2 cells, as evidenced by downregulation in the GATA-3 expression. Further, decline in the levels of IL-4, IL-5 and IL-13 cytokines and IgE was noted in the animals suffering from asthma. Furthermore, we noticed substantial suppression in the inflammatory response and number of eosinophils in the lungs. In essence, this study signifies an important therapeutic role of Caerulomycin A in asthma.

Vitamin D and asthma in children

Vitamin D deficiency and insufficiency are increasingly being recognized in the general population, and have been largely attributed to lifestyle changes (reduced exposure to sunshine due to working indoors or the use of protective clothing and sunscreen; changes in diet) over the last few decades. The musculoskeletal consequences of severe vitamin D deficiency are well established, however, a number of other disorders have now been linked to vitamin D insufficiency, including asthma. There is growing appreciation of the likely importance of vitamin D as a pleiotrophic mediator that contributes to pulmonary health. Children with asthma appear to be at increased risk of vitamin D insufficiency. Epidemiologic data suggest that low serum vitamin D in children with asthma is associated with more symptoms, exacerbations, reduced lung function, increased medication usage and severe disease. In vitro studies have demonstrated that vitamin D enhances steroid responsiveness in adult asthmatics. Vitamin D may play an important role in pulmonary health by inhibiting inflammation, in part through maintaining regulatory T cells, and direct induction of innate antimicrobial mechanisms. More research is required to fully understand the role of vitamin D in the maintenance of airway homeostasis and address the diagnostic and therapeutic implications vitamin D may have in the future of asthma management. This review summarises the current understanding and uncertainties regarding the effect of vitamin D deficiency and insufficiency in children with asthma.

Management of severe asthma in children

Children who are referred to specialist care with asthma that does not respond to treatment (problematic severe asthma) are a heterogeneous group, with substantial morbidity. The evidence base for management is sparse, and is mostly based on data from studies in children with mild and moderate asthma and on extrapolation of data from studies in adults with severe asthma. In many children with severe asthma, the diagnosis is wrong or adherence to treatment is poor. The first step is a detailed diagnostic assessment to exclude an alternative diagnosis ("not asthma at all"), followed by a multidisciplinary approach to exclude comorbidities ("asthma plus") and to assess whether the child has difficult asthma (improves when the basic management needs, such as adherence and inhaler technique, are corrected) or true, therapy-resistant asthma (still symptomatic even when the basic management needs are resolved). In particular, environmental causes of secondary steroid resistance should be identified. An individualised treatment plan should be devised depending on the clinical and pathophysiological characterisation. Licensed therapeutic approaches include high-dose inhaled steroids, the Symbicort maintenance and reliever (SMART) regimen (with budesonide and formoterol fumarate), and anti-IgE therapy. Unlicensed treatments include methotrexate, azathioprine, ciclosporin, and subcutaneous terbutaline infusions. Paediatric data are needed on cytokine-specific monoclonal antibody therapies and bronchial thermoplasty. However, despite the interest in innovative approaches, getting the basics right in children with apparently severe asthma will remain the foundation of management for the foreseeable future.

Phenotype-specific treatment of difficult asthma in children

Most children with asthma can be treated successfully with low-to-moderate doses of inhaled corticosteroid and long-acting beta-2 agonist. Those that fail to respond are a heterogeneous group. We propose that the nature and type of any steroid-resistant inflammation, the extent of any persistent airflow limitation and the extent of bronchial hyper-reactivity should be determined separately to allow a rational treatment approach to these children, rather than the haphazard advice of many current guidelines. Reasons for persistent difficult asthma include persistent eosinophilic inflammation, non-eosinophilic inflammation, airway reactivity without residual inflammation and persistent airflow limitation. We propose a protocol that uses non-invasive and invasive (bronchoscopic) methods to document the response to systemic steroids (depot triamcinolone). The aim of the protocol is to determine an individualised treatment plan; for example, cyclosporin for persistent eosinophilic inflammation, azithromycin for persistent neutrophilic inflammation and continuous subcutaneous terbutaline if there is airway reactivity without residual inflammation. Multi-centre studies are required to test the utility of this approach.

Corticosteroids for hospitalised children with acute asthma

BACKGROUND

Systemic corticosteroids are used routinely in the management of children with severe acute asthma. There is a lack of consensus regarding the agent, dose and route of corticosteroid administration.

OBJECTIVES

To determine the benefit of systemic corticosteroids (oral, intravenous, or intramuscular) compared to placebo and inhaled steroids in acute paediatric asthma.

SEARCH STRATEGY

All controlled trials were identified from the Cochrane Airways Review Group Register, hand searching of respiratory journals, reference lists and contacts with experts and pharmaceutical companies.

SELECTION CRITERIA

Studies were included if they described a randomised controlled trial (RCT) involving children aged 1-18 years with severe acute asthma who received oral, inhaled, intravenous or intramuscular corticosteroids. Only studies in which patients required hospital admission were included.

DATA COLLECTION AND ANALYSIS

Two reviewers using a standard form extracted all data. All data, numeric calculations and graphic extrapolations were independently confirmed.

MAIN RESULTS

Seven trials were included with a total of 426 children studied (274 with oral prednisone vs. placebo, 106 with intravenous steroids vs placebo and 46 with nebulised budesonide vs prednisolone). A significant number of steroid treated children were discharged early after admission (>4 hours) with an OR of 7.00 (95% CI: 2.98 to 16.45) and NNT of 3 (95%CI: 2 to 8). The length of stay was shorter in the steroid groups with a WMD of -8.75 hours (95% CI: -19.23 to 1.74). There were no significant differences between groups in pulmonary function or oxygen saturation measurements. Children treated with steroids in hospital were less likely to relapse within one to three months with OR 0.19 (95%CI: 0.07 to 0.55) and NNT of 3 (95%CI: 2 to 7). The single small study that compared nebulised budesonide to oral prednisone failed to demonstrate equivalence or a difference between each therapy.

REVIEWER'S CONCLUSIONS

Systemic corticosteroids produce some improvements for children admitted to hospital with acute asthma. The benefits may include earlier discharge and fewer relapses. Inhaled or nebulised corticosteroids cannot be recommended as equivalent to systemic steroids at this time. Further studies examining differing doses and routes of administration for corticosteroids will clarify the optimal therapy.

Invasive monitoring of airway inflammation

What we know: Ethical concerns have limited research involving invasive bronchoscopy techniques in young children. No longitudinal studies have been conducted to compare the findings of bronchial biopsy or bronchoalveolar lavage in young children with transient episodic wheeze versus asthma. Children with atopic asthma have more airway eosinophils and mast cells than children with viral-associated wheeze. Both neutrophilic and eosinophilic patterns of inflammation are present in asthma. What we need to know: Can we establish robust normal values for tissue and fluid samples obtained at bronchoscopy or bronchoalveolar lavage? Do biopsy specimens taken at the carina tell us about the pathological processes occurring in asthma? Can we use invasive procedures to predict which children with wheeze will continue to wheeze and develop a classical asthma phenotype? Can we use invasive procedures to guide asthma therapy? Can we expect airway inflammation to resolve with anti-inflammatory medication? Can we correlate invasive with non-invasive measures of inflammation? Can we use our understanding of pro- and anti-inflammatory pathways to develop new therapeutic interventions? Is there a presymptomatic phase of inflammation?

Subcutaneous terbutaline in children with chronic severe asthma

A continuous subcutaneous infusion of terbutaline (CSIT) was used to treat 8 children with chronic severe asthma who continued to experience frequent symptoms, despite treatment with regular oral prednisolone. Five patients experienced a symptomatic improvement from CSIT, leading to a reduction in regular medication. Three patients did not experience any lasting benefit from CSIT. The most common side effects were related to the infusion site (bruising and local infection). CSIT may lead to an improvement in symptoms and a reduction in oral steroid dose in selected children with chronic severe asthma. These initial findings support the need for further controlled studies to evaluate the use of CSIT in severe childhood asthma.

Relationship between exhaled nitric oxide and mucosal eosinophilic inflammation in children with difficult asthma, after treatment with oral prednisolone

Exhaled nitric oxide (FE(NO)) has been proposed as a noninvasive marker of airway inflammation in asthma, and may reflect airway eosinophilia. We examined the relationship between FE(NO) and eosinophilic inflammation in endobronchial biopsies from 31 children with difficult asthma (mean age [range] 11.9 [6-17] yr), following 2 wk of prednisolone (40 mg/d). Endobronchial biopsy was also performed in seven children without asthma. Biopsy eosinophils were detected using antibody to major basic protein, and point-counting used to derive an "eosinophil score." FE(NO) readings and suitable biopsies for analysis were both obtained in 21 of 31 children with asthma. Adherence to prednisolone was demonstrated in 17 of these 21. Within this group, there was a correlation between FE(NO) and eosinophil score (r = 0.54, p = 0.03). The relationship was strongest in patients with persistent symptoms after prednisolone, in whom FE(NO) > 7 ppb was associated with a raised eosinophil score. For all patients, FE(NO) < 7 ppb was associated with an eosinophil score within the nonasthmatic range, regardless of symptoms. We propose that FE(NO) is associated with eosinophilic inflammation in children with difficult asthma, following prednisolone, and may help in identifying patients in whom persistent symptoms are associated with airway eosinophilia.

Safety and ethics of bronchoscopy and endobronchial biopsy in difficult asthma

AIM

To investigate the safety of bronchoscopy and endobronchial biopsy in children with difficult asthma, and discuss the ethical issues associated with the procedure.

METHODS

A three year prospective observational study was performed in two tertiary paediatric respiratory centres specialising in the management of children with difficult asthma. A total of 48 children with difficult asthma and 35 non-asthmatic children were studied.

RESULTS

Flexible bronchoscopy was performed under general anaesthesia in 38 children with difficult asthma, and rigid bronchoscopy was performed in 10, following a two week course of prednisolone. Endobronchial biopsy was performed in 47 patients. Perioperative complications occurred in one asthmatic undergoing flexible bronchoscopy (desaturation) and in two undergoing rigid bronchoscopy (desaturation in one, and bronchospasm and desaturation in one). There were no cases of significant bleeding or pneumothorax among the asthmatics. Flexible bronchoscopy was performed in 35 non-asthmatic patients with a variety of clinical indications. The total number of perioperative complications was greater in the non-asthmatics undergoing flexible bronchoscopy than in the asthmatics (17 complications in 35 children versus one in 38). Fever requiring hospital admission was documented in two asthmatics following bronchoscopy. Four asthmatics reported an increase in symptoms in the week following bronchoscopy.

CONCLUSIONS

Bronchoscopy and endobronchial biopsy under general anaesthesia can be performed safely in children with difficult asthma, when the bronchoscopist and anaesthetist are suitably trained. The procedure is acceptable to the families involved.

Children with difficult asthma: a practical approach

Many open studies investigating the effects of innovative treatments for steroid-dependent asthma demonstrate some benefit. This is also true of the majority of placebo arms in placebo-controlled trials. This suggests that children with difficult asthma benefit from the high level of input that is typically provided in clinical trials, with or without additional medication. Such intensive management of patients, with the emphasis on establishing the diagnosis, improving adherence, and identifying provoking factors, is the key to optimizing asthma control for these children. For patients with genuinely severe asthma, despite high doses of conventional treatment, a greater understanding of the pathological basis of persistent symptoms is needed. Identification of different pathological subtypes of severe asthma should allow for more rational prescribing of asthma therapy, as well as the design of further trials of potential steroid-sparing treatments.

Difficult asthma: defining the problems

A retrospective survey was undertaken of children with difficult asthma, attending a respiratory clinic. The clinical and laboratory profiles of asthmatic children who were poorly controlled on > or = 800 microg of inhaled corticosteroids (ICS) were studied and compared to children well-controlled on > or = 800 microg ICS. Assessments were made of atopy, growth, lung function, treatment adherence, home environment, and responsiveness to corticosteroids (CS). Fiftyseven "difficult" and 23 well-controlled children were studied. Significant differences in the home environment were identified. Smoking was significantly more common in the difficult-to-control group. Nine children had alternative diagnoses. Poor CS responsiveness was present in 10 children. Adverse home environments, poor treatment supervision, alternative diagnoses, and unresponsiveness to CS were the most important factors in difficult asthma. A full assessment, including bronchoscopy, is indicated to avoid unnecessary increases in CS to doses that could cause side-effects.