Clinical and genetic features underlying the response of patients with bronchial asthma to treatment with a leukotriene receptor antagonist

Immunogenetics and pharmacogenetics of allergic asthma in Africa

Asthma is a common chronic condition in children and in an African setting is often highly prevalent in urban areas as compared to rural areas. Asthma is a heritable disease and the genetic risk is often exacerbated by unique localised environmental factors. The Global Initiative for Asthma (GINA) recommendation for the control of asthma includes inhaled corticosteroids (ICS) alone or together with short-acting β₂-agonists (SABA) or long-acting β₂-agonists (LABA). While these drugs can relieve asthma symptoms, there is evidence of reduced efficacy in people of African ancestry. Whether this is due to immunogenetics, genomic variability in drug metabolising genes (pharmacogenetics) or genetics of asthma-related traits is not well defined. Pharmacogenetic evidence of first-line asthma drugs in people of African ancestry is lacking and is further compounded by the lack of representative genetic association studies in the continent. In this review, we will discuss the paucity of data related to the pharmacogenetics of asthma drugs in people of African ancestry, mainly drawing from African American data. We will further discuss how this gap can be bridged to improve asthma health outcomes in Africa.

Baseline Conservative and Surgical Management in the Treatment of NSAID-Exacerbated Respiratory Disease

Non-steroidal anti-inflammatory drug (NSAID)-exacerbated respiratory disease (N-ERD) is a chronic medical condition that includes asthma, chronic rhinosinusitis with nasal polyposis, and hypersensitivity to aspirin and other NSAIDs. Eosinophilic inflammation in the upper and lower airways is treated with local corticosteroids, repeated antibiotics, oral corticosteroid courses, endoscopic sinus surgery, and in some cases aspirin treatment after desensitization (ATAD). Nevertheless, the disease may be uncontrolled and it has a great impact on quality of life. A better understanding of the pathomechanisms of the disease and the development of medications that target type 2 inflammation mediators may have a crucial role in achieving better disease control in patients with N-ERD.

Urinary Leukotriene E4 as a Biomarker in NSAID-Exacerbated Respiratory Disease (N-ERD): a Systematic Review and Meta-analysis

PURPOSE OF REVIEW

Non-steroidal exacerbated respiratory disease (N-ERD) currently requires aspirin challenge testing for diagnosis. Urinary leukotriene E4 (uLTE₄) has been extensively investigated as potential biomarker in N-ERD. We aimed to assess the usefulness of uLTE₄ as a biomarker in the diagnosis of N-ERD.

RECENT FINDINGS

N-ERD, formerly known as aspirin-intolerant asthma (AIA), is characterised by increased leukotriene production. uLTE₄ indicates cysteinyl leukotriene production, and a potential biomarker in N-ERD. Although several studies and have examined the relationship between uLTE₄ and N-ERD, the usefulness of uLTE₄ as a biomarker in a clinical setting remains unclear.

FINDINGS

Our literature search identified 38 unique eligible studies, 35 were included in the meta-analysis. Meta-analysis was performed (i.e. pooled standardised mean difference (SMD) with 95% confidence intervals (95% CI)) and risk of bias assessed (implementing Cochrane Handbook for Systematic Reviews of Diagnostic Test Accuracy (Cochrane DTA)). Data from 3376 subjects was analysed (1354 N-ERD, 1420 ATA, and 602 HC). uLTE₄ was higher in N-ERD vs ATA (n = 35, SMD 0.80; 95% CI 0.72-0.89). uLTE4 increased following aspirin challenge in N-ERD (n = 12, SMD 0.56; 95% CI 0.26-0.85) but not ATA (n = 8, SMD 0.12; CI - 0.08-0.33). This systematic review and meta-analysis showed that uLTE₄ is higher in N-ERD than ATA or HC. Likewise, people with N-ERD have greater increases in uLTE₄ following aspirin challenge. However, due to the varied uLTE₄ measurement and result reporting practice, clinical utility of these findings is limited. Future studies should be standardised to increase clinical significance and interpretability of the results.

Current perspective on eicosanoids in asthma and allergic diseases: EAACI Task Force consensus report, part I

Eicosanoids are biologically active lipid mediators, comprising prostaglandins, leukotrienes, thromboxanes, and lipoxins, involved in several pathophysiological processes relevant to asthma, allergies, and allied diseases. Prostaglandins and leukotrienes are the most studied eicosanoids and established inducers of airway pathophysiology including bronchoconstriction and airway inflammation. Drugs inhibiting the synthesis of lipid mediators or their effects, such as leukotriene synthesis inhibitors, leukotriene receptors antagonists, and more recently prostaglandin D₂ receptor antagonists, have been shown to modulate features of asthma and allergic diseases. This review, produced by an European Academy of Allergy and Clinical Immunology (EAACI) task force, highlights our current understanding of eicosanoid biology and its role in mediating human pathology, with a focus on new findings relevant for clinical practice, development of novel therapeutics, and future research opportunities.

Heterogeneity of NSAID-Exacerbated Respiratory Disease: has the time come for subphenotyping?

PURPOSE OF REVIEW

NSAID-Exacerbated Disease (N-ERD) is a chronic eosinophilic inflammatory disorder of the respiratory tract occurring in patients with asthma and/or rhinosinusitis with nasal polyps, whose symptoms are exacerbated by NSAIDs. The purpose of this review is to provide an update on clinical characteristics, pathophysiology, and management of N-ERD, and to emphasize heterogeneity of this syndrome.

RECENT FINDINGS

Growing evidence indicates that N-ERD, which has been considered a separate asthma phenotype, is heterogenous, and can be divided in several subphenotypes varying in clinical characteristics. Pathophysiology of N-ERD is complex and extends beyond abnormalities in the arachidonic acid metabolism. Heterogeneity of pathophysiological mechanisms underlying development of airway inflammation seems to be associated with variability in response to both anti-inflammatory and disease-specific treatments (e.g., with aspirin after desensitization).

SUMMARY

Progress in understanding of the pathophysiology of N-ERD leads to discovery and validation of new biomarkers facilitating diagnosis and predicting the response to treatment of the chronic inflammation underlying upper (CRSwNP) and lower airway (asthma) symptoms. Better characterization of the immunophysiopathological heterogeneity of N-ERD (identification of endotypes) may allow more personalized, endotype-driven approach to treatment in the future.

Update on the Management of Nonsteroidal Anti-Inflammatory Drug Hypersensitivity

The clinical phenotypes of nonsteroidal anti-inflammatory drug (NSAID) hypersensitivity are heterogeneous with various presentations including time of symptom onset, organ involvements, and underlying pathophysiology. Having a correct diagnosis can be challenging. Understanding their respective mechanisms as well as developing a comprehensive classification and diagnostic algorithm are pivotal for appropriate management strategy. Treatment modalities are based on the subtypes and severity of hypersensitivity reactions. Insights into the phenotypes and endotypes of hypersensitivity reactions enable personalized management in patients with suboptimal control of disease. This review updated the recent evidence of pathophysiology, classification, diagnostic algorithm, and management of NSAID hypersensitivity reactions.

BSACI guideline for the diagnosis and management of allergic and non-allergic rhinitis (Revised Edition 2017; First edition 2007)

This is an updated guideline for the diagnosis and management of allergic and non-allergic rhinitis, first published in 2007. It was produced by the Standards of Care Committee of the British Society of Allergy and Clinical Immunology, using accredited methods. Allergic rhinitis is common and affects 10-15% of children and 26% of adults in the UK, it affects quality of life, school and work attendance, and is a risk factor for development of asthma. Allergic rhinitis is diagnosed by history and examination, supported by specific allergy tests. Topical nasal corticosteroids are the treatment of choice for moderate to severe disease. Combination therapy with intranasal corticosteroid plus intranasal antihistamine is more effective than either alone and provides second line treatment for those with rhinitis poorly controlled on monotherapy. Immunotherapy is highly effective when the specific allergen is the responsible driver for the symptoms. Treatment of rhinitis is associated with benefits for asthma. Non-allergic rhinitis also is a risk factor for the development of asthma and may be eosinophilic and steroid-responsive or neurogenic and non- inflammatory. Non-allergic rhinitis may be a presenting complaint for systemic disorders such as granulomatous or eosinophilic polyangiitis, and sarcoidoisis. Infective rhinitis can be caused by viruses, and less commonly by bacteria, fungi and protozoa.

Diagnosis and management of NSAID-Exacerbated Respiratory Disease (N-ERD)-a EAACI position paper

NSAID-exacerbated respiratory disease (N-ERD) is a chronic eosinophilic, inflammatory disorder of the respiratory tract occurring in patients with asthma and/or chronic rhinosinusitis with nasal polyps (CRSwNP), symptoms of which are exacerbated by NSAIDs, including aspirin. Despite some progress in understanding of the pathophysiology of the syndrome, which affects 1/10 of patients with asthma and rhinosinusitis, it remains a diagnostic and therapeutic challenge. In order to provide evidence-based recommendations for the diagnosis and management of N-ERD, a panel of international experts was called by the EAACI Asthma Section. The document summarizes current knowledge on the pathophysiology and clinical presentation of N-ERD pointing at significant heterogeneity of this syndrome. Critically evaluating the usefulness of diagnostic tools available, the paper offers practical algorithm for the diagnosis of N-ERD. Recommendations for the most effective management of a patient with N-ERD stressing the potential high morbidity and severity of the underlying asthma and rhinosinusitis are discussed and proposed. Newly described sub-phenotypes and emerging sub-endotypes of N-ERD are potentially relevant for new and more specific (eg, biological) treatment modalities. Finally, the document defines major gaps in our knowledge on N-ERD and unmet needs, which should be addressed in the future.

Asthma Phenotypes and Endotypes: Implications for Personalised Therapy

Asthma is increasingly recognised as a heterogeneous group of diseases with similar clinical presentations rather than a singular disease entity. Asthma was historically categorised by clinical symptoms; however, newer methods of subgrouping, describing and categorising the disease have sub-defined asthma. These sub-definitions are intermittently called phenotypes or endotypes, but the real meanings of these words are poorly understood. Novel treatments are currently and increasingly available, partly in the monoclonal antibody environment, and also some physical therapies (bronchial thermoplasty), but additionally small molecules are not far away from clinical practice. Understanding the disease pathogenesis and the mechanism of action more completely may enable identification of treatable traits, biomarkers, mediators and modifiable therapeutic targets. However, there remains a danger that clinicians become preoccupied with the concept of endotypes and biomarkers, ignoring therapies that are hugely effective but have no companion biomarker. This review discusses our understanding of the concept of phenotypes and endotypes in appreciating and managing the heterogeneous condition that is asthma. We consider the role of functional imaging, physiology, blood-, sputum- and breath-based biomarkers and clinical manifestations that could be used to produce a personalised asthma profile, with implications on prognosis, pathophysiology and most importantly specific therapeutic responses. With the advent of increasing numbers of biological therapies and other interventional options such as bronchial thermoplasty, the importance of targeting expensive therapies to patients with the best chance of clinical response has huge health economic importance.

Identification of phenotypic clusters of nonsteroidal anti-inflammatory drugs exacerbated respiratory disease

BACKGROUND

Clinical presentation of nonsteroidal anti-inflammatory drugs exacerbated respiratory disease (NERD) is found to be heterogeneous. This study classified phenotypic clusters to determine NERD subtypes.

METHODS

We performed two-step cluster analysis using urticaria, chronic rhinosinusitis (CRS), and atopy, in a NERD cohort comprising 302 patients. Asthma exacerbation was defined as receiving at least one burst of intravenous steroid treatment and/or at least two bursts of oral steroid use (≥ 45 mg/3 days) per year. The possession rate of anti-asthmatic medications was estimated during the follow-up period.

RESULTS

There were four subtypes: subtype 1 (NERD with CRS/atopy and no urticaria), subtype 2 (NERD with CRS and no urticaria/atopy), subtype 3 (NERD without CRS/urticaria), and subtype 4 (NERD with urticaria). Significant differences were found between the four subtypes in the female proportion, baseline FEV1%, serum total IgE level, and sputum/peripheral eosinophil count. A higher frequency of asthma exacerbations was noted in subtype 1 compared to subtype 3. The possession rates of medium- to high-dose inhaled corticosteroids/long-acting beta₂ -agonists showed significant differences among the four subtypes. Metabolomic analysis showed that the four subtypes of NERD had a higher serum leukotriene E4 (LTE4) level than those with aspirin-tolerant asthma. The patients with subtypes 1 and 3 had a higher urine LTE4 level than those with subtype 2.

CONCLUSION

We found four distinct subtypes with different clinical/biochemical findings and asthma exacerbations in a NERD cohort. These findings suggest that stratified strategies by applying subtype classification may help achieve better outcomes in the management of NERD.

Pharmacogenomics of inhaled corticosteroids and leukotriene modifiers: a systematic review

BACKGROUND

Pharmacogenetics studies of anti-inflammatory medication of asthma have expanded rapidly in recent decades, but the clinical value of their findings remains limited.

OBJECTIVE

To perform a systematic review of pharmacogenomics and pharmacogenetics of inhaled corticosteroids (ICS) and leukotriene modifiers (LTMs) in patients with asthma.

METHODS

Articles published between 1999 and June 2015 were searched using PubMed and EMBASE. Pharmacogenomics/genetics studies of patients with asthma using ICS or LTMs were included if ≥1 of the following outcomes were studied: lung function, exacerbation rates or asthma symptoms. The studies of Single Nucleotide Polymorphisms (SNPs) that had been replicated at least once were assessed in more detail.

RESULTS

In total, 59 publications were included in the systematic review: 26 addressed LTMs (including two genomewide Genome-Wide association studies [GWAS]) and 33 addressed ICS (including four GWAS). None of the GWAS reported similar results. Furthermore, none of the SNPs assessed in candidate gene studies were identified in a GWAS. No consistent reports were found for candidate gene studies of LTMs. In candidate gene studies of ICS, the most consistent results were found for rs28364072 in FCER2. This SNP was associated with all three outcomes of poor response, and the largest effect was reported with the risk of exacerbations (hazard ratio, 3.95; 95% CI, 1.64-9.51).

CONCLUSION AND CLINICAL RELEVANCE

There is a lack of replication of genetic variants associated with poor ICS or LTM response. The most consistent results were found for the FCER2 gene [encoding for a low-affinity IgE receptor (CD23)] and poor ICS response. Larger studies with well-phenotyped patients are needed to assess the clinical applicability of ICS and LTM pharmacogenomics/genetics.

Asthma phenotypes: the intriguing selective intervention with Montelukast

Asthma is a heterogeneous disease, usually characterized by chronic airway inflammation and a variable course associated with various underlying mechanisms that can differ between individuals. Patients with asthma can therefore exhibit different phenotypes, a term used to define the observable characteristics of an organism resulting from the interaction between its genetic makeup and the environment. The heterogeneity of asthma has received a large amount of attention in the last few years in order to better tailor treatment according to the different clinical and biological phenotypes of the disease. Specific asthma phenotypes may require an approach to treatment sometimes different from that recommended by current guidelines, so a personalized approach to asthma pharmacotherapy is recommended. Growing evidence suggests that leukotrienes play an important role in the pathogenesis of bronchial asthma. The mechanisms of action of leukotriene-receptor antagonists theoretically predict a good response in some asthma “phenotypes”.In this article we have performed an analysis of the recent literature (controlled clinical trials and real-life studies) about a possible selective intervention with Montelukast in specific asthma phenotypes.

Personalized medicine in children with asthma

Personalized medicine for children with asthma aims to provide a tailored management of asthma, which leads to faster and better asthma control, has less adverse events and may be cost saving. Several patient characteristics, lung function parameters and biomarkers have been shown useful in predicting treatment response or predicting successful reduction of asthma medication. As treatment response to the main asthma therapies is partly genetically determined, pharmacogenetics may open the way for personalized medicine in children with asthma. However, the number of genes identified for the various asthma drug response phenotypes remains small and randomized controlled trials are lacking. Biomarkers in exhaled breath or breath condensate remain promising but did not find their way from bench to bedside yet, except for the fraction of exhaled nitric oxide. E-health will most likely find its way to clinical practice and most interventions are at least non-inferior to usual care. More studies are needed on which interventions will benefit most individual children.

Classification and practical approach to the diagnosis and management of hypersensitivity to nonsteroidal anti-inflammatory drugs

Hypersensitivity reactions to aspirin (acetylsalicylic acid) and other nonsteroidal anti-inflammatory drugs (NSAIDs) constitute only a subset of all adverse reactions to these drugs, but due to their severity pose a significant burden to patients and are a challenge to the allergist. In susceptible individuals, NSAIDs induce a wide spectrum of hypersensitivity reactions with various timing, organ manifestations, and severity, involving either immunological (allergic) or nonimmunological mechanisms. Proper classification of reactions based on clinical manifestations and suspected mechanism is a prerequisite for the implementation of rational diagnostic procedures and adequate patient management. This document, prepared by a panel of experts from the European Academy of Allergy and Clinical Immunology Task Force on NSAIDs Hypersensitivity, aims at reviewing the current knowledge in the field and proposes uniform definitions and clinically useful classification of hypersensitivity reactions to NSAIDs. The document proposes also practical algorithms for the diagnosis of specific types of NSAIDs hypersensitivity (which include drug provocations, skin testing and in vitro testing) and provides, when data are available, evidence-based recommendations for the management of hypersensitive patients, including drug avoidance and drug desensitization.

Impact of montelukast on asthma associated with rhinitis, and other triggers and co-morbidities

INTRODUCTION

Rhinitis and other specific triggers or co-morbidities (tobacco exposure, excess weight, aspirin sensitivity or heredity factors) are frequently associated with uncontrolled asthma. Asthma associated with these exacerbating factors appears to be related to an increase in leukotriene-mediated inflammation.

METHODS

We reviewed the role of montelukast, a leukotriene receptor antagonist, in the treatment of asthma associated with these factors by using the PubMed database to search the English and French biomedical literature for articles describing randomized-controlled trials, large observational studies and reviews (published up to May 2012, inclusive).

RESULTS

Montelukast, either alone or in combination with other drugs, is an effective treatment against rhinitis-associated asthma. Montelukast also offers therapeutic benefits against exercise-induced asthma or in cases of asthma linked to tobacco exposure, excess weight or aspirin hypersensitivity. Thus, for some patients, montelukast may constitute an alternative to the gold-standard treatment of inhaled corticosteroids. Polymorphisms in several genes encoding proteins of the leukotriene signaling pathway may contribute to the variability in response to montelukast.

CONCLUSIONS

In conclusion, we have shown that montelukast treatment could be of particular benefit to subgroups of patients with asthma associated with rhinitis, exercise, tobacco exposure, being overweight or aspirin hypersensitivity.

Genetic variants of the arachidonic acid pathway in non-steroidal anti-inflammatory drug-induced acute urticaria

BACKGROUND

To date, genetic studies of hypersensitivity reactions to non-steroidal anti-inflammatory drugs (NSAIDs) have been carried out mainly in aspirin-induced asthma and to a lesser extent in chronic urticaria, with no studies in patients with acute urticaria (AU), the most common entity induced by these drugs.

OBJECTIVE

In this work, we analysed the association of common variants of 15 relevant genes encoding both enzymes and receptors from the arachidonic acid (AA) pathway with NSAID-induced AU.

METHODS

Patients were recruited in several Allergy Services that are integrated into the Spanish network RIRAAF, and diagnosed of AU induced by cross-intolerance (CRI) to NSAIDs. Genotyping was carried out by TaqMan allelic discrimination assays.

RESULTS

A total of 486 patients with AU induced by CRI to NSAIDs and 536 unrelated controls were included in this large Spanish case-control study. Seven variants from 31 tested in six genes were associated in a discovery study population from Malaga (0.0003 ≤ p-value ≤ 0.041). A follow-up analysis in an independent sample from Madrid replicated three of the SNPs from the ALOX15 (rs7220870), PTGDR (rs8004654) and CYSLTR1 (rs320095) genes (1.055x10(-6) ≤meta-analysis p-value ≤ 0.003).

CONCLUSIONS AND CLINICAL RELEVANCE

Genetic variants of the AA pathway may play an important role in NSAID-induced AU. These data may help understand the mechanism underlying this disease.

Integrative systems biology approaches in asthma pharmacogenomics

In order to improve therapeutic outcomes, there is a tremendous need to identify patients who are likely to respond to a given asthma treatment. Pharmacogenomic studies have explained a portion of the variability in drug response and provided an increasing list of candidate genes and SNPs. However, as phenotypic variation arises from a network of complex interactions among genetic and environmental factors, rather than individual genes or SNPs, a multidisciplinary, systems-level approach is required in order to understand the inter-relationships among these factors. Systems biology, which seeks to capture interactions between genetic factors and other variables, offers a promising approach to improved therapeutic outcomes in asthma. This aritcle will review and update progress in the pharmacogenomics of asthma and then discuss the application of systems biology approaches to asthma pharmacogenomics.

Genetic basis for personalized medicine in asthma

There is heterogeneity in patient responses to current asthma medications. Significant progress has been made identifying genetic polymorphisms that influence the efficacy and potential for adverse effects to asthma drugs, including; β(2)-adrenergic receptor agonists, corticosteroids and leukotriene modifiers. Pharmacogenetics holds great promise to maximise clinical outcomes and minimize adverse effects. Asthma is heterogeneous with respect to clinical presentation and inflammatory mechanisms underlying the disease, which is likely to contribute to variable results in clinical trials targeting specific inflammatory mediators. Genome-wide association studies have begun to identify genes underlying asthma (e.g., IL1RL1), which represent future therapeutic targets. In this article, we review and update the pharmacogenetics of current asthma therapies and discuss the genetics underlying selected Phase II and future targets.

New approaches to personalized medicine for asthma: where are we?

Access to an electronic medical record is essential for personalized medicine. Currently, only 40% of US physicians have such access, but this is rapidly changing. It is expected that 100,000 Americans will have their whole genome sequenced in 2012. The cost of such sequencing is rapidly dropping, and is estimated to be $1000 by 2013. These technological advances will make interpretation of whole genome sequence data a major clinical challenge for the foreseeable future. At present, a relatively small number of genes have been identified to determine drug treatment response phenotypes for asthma. It is anticipated that this will dramatically increase over the next 10 years as personalized medicine becomes more of a reality for asthma patients.

The pharmacogenetics and pharmacogenomics of asthma therapy

Despite the availability of several classes of asthma medications and their overall effectiveness, a significant portion of patients fail to respond to these therapeutic agents. Evidence suggests that genetic factors may partly mediate the heterogeneity in asthma treatment response. This review discusses important findings in asthma pharmacogenetic and pharmacogenomic studies conducted to date, examines limitations of these studies and, finally, proposes future research directions in this field. The focus will be on the three major classes of asthma medications: β-adrenergic receptor agonists, inhaled corticosteroids and leukotriene modifiers. Although many studies are limited by small sample sizes and replication of the findings is needed, several candidate genes have been identified. High-throughput technologies are also allowing for large-scale genetic investigations. Thus, the future is promising for a personalized treatment of asthma, which will improve therapeutic outcomes, minimize side effects and lead to a more cost-effective care.

[Montelukast in the treatment of mild to moderate persistent asthma]

INTRODUCTION

Anti-inflammatory preventive treatment is recommended in cases of persistent asthma. Besides inhaled corticosteroids (ICS), which represent the mainstay of treatment, other therapeutic options are available, of which only antileukotrienes are approved for all age groups.

BACKGROUND

Given as a substitute of low-dose ICS, montelukast prevents exacerbations as efficiently and for a longer period than long-acting β2-agonists. Montelukast is as efficient as doubling the dose of ICS on asthma symptoms in cases of inadequate control with low-dose ICS. Combined with ICS, it can lead to better control of asthma and potentially to ICS sparing.

CONCLUSIONS

Given the efficacy, tolerance and long-term treatment compliance of montelukast in mild persistent asthma in adults and children, montelukast, given as a substitute or combined with ICS, could contribute to enhanced control of asthma, especially in children.

Leukotriene pathway genetics and pharmacogenetics in allergy

Leukotrienes (LT) are biologically active lipid mediators known to be involved in allergic inflammation. Leukotrienes have been shown to mediate diverse features of allergic conditions including inflammatory cell chemotaxis/activation and smooth muscle contraction. Cysteinyl leukotrienes (LTC(4), LTD(4) and, LTE(4)) and the dihydroxy leukotriene LTB(4) are generated by a series of enzymes/proteins constituting the LT synthetic pathway or 5-lipoxygenase (5-LO) pathway. Their function is mediated by interacting with multiple receptors. Leukotriene receptor antagonists (LTRA) and LT synthesis inhibitors (LTSI) have shown clinical efficacy in asthma and more recently in allergic rhinitis. Despite growing knowledge of leukotriene biology, the molecular regulation of these inflammatory mediators remains to be fully understood. Genes encoding enzymes of the 5-LO pathway (i.e. ALOX5, LTC4S and LTA4H) and encoding for LT receptors (CYSLTR1/2 and LTB4R1/2) provide excellent candidates for disease susceptibility and severity; however, their role remains unclear. Preliminary data also suggest that 5-LO pathway/receptor gene polymorphism can predict patient responses to LTSI and LTRA; however, the exact mechanisms require elucidation. The aim of this review was to summarize the recent advances in the knowledge of these important mediators, focusing on genetic and pharmacogenetic aspects in the context of allergic phenotypes.

Aspirin-exacerbated asthma

: This review focuses on aspirin-exacerbated asthma (AEA). The review includes historical perspective of aspirin, prevalence, pathogenesis, clinical features and treatment of AEA. The pathogenesis of AEA involves the cyclooxygenase and lipooxygenase pathway. Aspirin affects both of these pathways by inhibiting the enzyme cycooxygenase-1 (COX-1). Inhibition of COX-1 leads to a decrease in prostaglandin E2 (PGE2). The decrease in PGE2 results in an increase in cysteinyl leukotrienes by the lipooxygenase pathway involving the enzyme 5-lipooxygenase (5-LO). Leukotriene C4 (LTC4) synthase is the enzyme responsible for the production of leukotriene C4, the chief cysteinyl leukotriene responsible for AEA. There have been familial occurences of AEA. An allele of the LTC4 synthase gene in AEA is known as allele C. Allele C has a higher frequency in AEA. Clinical presentation includes a history of asthma after ingestion of aspirin, nasal congestion, watery rhinorrhea and nasal polyposis. Treatment includes leukotriene receptor antagonists, leukotriene inhibitors, aspirin desinsitaztion and surgery. AEA is the most well-defined phenotype of asthma. Although AEA affects adults and children with physician-diagnosed asthma, in some cases there is no history of asthma and AEA often goes unrecognized and underdiagnosed.

CysLTR1 promoter polymorphism and requirement for leukotriene receptor antagonist in aspirin-intolerant asthma patients

OBJECTIVES

Leukotriene receptor antagonists (LTRA), such as montelukast, have been used as a first-line treatment for patients with aspirin-intolerant asthma (AIA). This study evaluated associations between the clinical requirement for LTRA and genetic polymorphisms of the ALOX5, LTC4S, COX-2, CysLTR1 and TBXA2R genes in the arachidonic acid cascade in the long-term management of 89 AIA patients from a Korean population.

METHODS

Asthma control status was monitored for 1 year with maintenance medications of inhaled corticosteroid and oral LTRA, and AIA patients were classified into three groups according to the mean montelukast dose required per month to maintain asthma control for 1 year: group I (> or = 200 mg montelukast/month; n = 37), group II (5-150 mg/month; n = 25) and group III (< 5 mg/month; n = 27). Genetic polymorphisms in the arachidonic acid cascade were determined using a single-base extension method.

RESULTS

We found that there was a significant difference in the genotype frequency of the CysLTR1 promoter polymorphism -634C > T among the three groups (p = 0.007 for group I vs group II, p = 0.017 for group I vs group III), while there were no significant associations between LTRA requirements and polymorphisms of the other genes. The patients with the variant genotype (CT or TT) of the -634C = T CysLTR1 promoter polymorphism showed a higher expression level than those with the common genotype (CC).

CONCLUSION

These findings indicate that the CysLTR1 promoter polymorphism is a useful genetic marker for predicting LTRA requirements in the long-term management of AIA patients.

Pharmacogenetics of aspirin-intolerant asthma

Leukotriene overproduction is the major characteristic of aspirin-intolerant asthma (AIA). Most studies examining the molecular genetic mechanisms of AIA have focused on leukotriene-related genes, including ALOX5, LTC4S, TXA2R and prostanoid-receptor genes. One study suggested that the human leukocyte antigen (HLA) allele DPB1*0301 may be a genetic marker for the AIA phenotype in European and Asian populations, and HLA-DPB1*0301 has been suggested as a useful genetic marker for predicting more favorable responders to leukotriene-receptor antagonists for long-term management of AIA. Although several reports have indicated possible associations between genetic polymorphisms and variable responses to leukotriene modifiers in nonaspirin sensitive asthmatic patients, few have suggested relationships between such genetic polymorphisms and variable responses to asthma drugs in AIA patients.

BSACI guidelines for the management of allergic and non-allergic rhinitis

This guidance for the management of patients with allergic and non-allergic rhinitis has been prepared by the Standards of Care Committee (SOCC) of the British Society for Allergy and Clinical Immunology (BSACI). The guideline is based on evidence as well as on expert opinion and is for use by both adult physicians and paediatricians practicing in allergy. The recommendations are evidence graded. During the development of these guidelines, all BSACI members were included in the consultation process using a web-based system. Their comments and suggestions were carefully considered by the SOCC. Where evidence was lacking, consensus was reached by the experts on the committee. Included in this guideline are clinical classification of rhinitis, aetiology, diagnosis, investigations and management including subcutaneous and sublingual immunotherapy. There are also special sections for children, co-morbid associations and pregnancy. Finally, we have made recommendations for potential areas of future research.

Cysteinyl-leukotrienes and their receptors in asthma and other inflammatory diseases: critical update and emerging trends

Cysteinyl-leukotrienes (cysteinyl-LTs), that is, LTC4, LTD4, and LTE4, trigger contractile and inflammatory responses through the specific interaction with G protein-coupled receptors (GPCRs) belonging to the purine receptor cluster of the rhodopsin family, and identified as CysLT receptors (CysLTRs). Cysteinyl-LTs have a clear role in pathophysiological conditions such as asthma and allergic rhinitis (AR), and have been implicated in other inflammatory conditions including cardiovascular diseases, cancer, atopic dermatitis, and urticaria. Molecular cloning of human CysLT1R and CysLT2R subtypes has confirmed most of the previous pharmacological characterization and identified distinct expression patterns only partially overlapping. Interestingly, recent data provide evidence for the immunomodulation of CysLTR expression, the existence of additional receptor subtypes, and of an intracellular pool of CysLTRs that may have roles different from those of plasma membrane receptors. Furthermore, genetic variants have been identified for the CysLTRs that may interact to confer risk for atopy. Finally, a crosstalk between the cysteinyl-LT and the purine systems is being delineated. This review will summarize and attempt to integrate recent data derived from studies on the molecular pharmacology and pharmacogenetics of CysLTRs, and will consider the therapeutic opportunities arising from the new roles suggested for cysteinyl-LTs and their receptors.

The expanding role of leukotriene receptor antagonists in chronic asthma

OBJECTIVE

To provide a comprehensive review of studies that evaluate the effects of leukotriene receptor antagonists in adult chronic asthma.

DATA SOURCES

A literature search using MEDLINE, Clinical Evidence, and the Cochrane Library was performed using the following keywords: randomized controlled trial, asthma, cysteinyl leukotriene, leukotriene receptor antagonist, antileukotriene, montelukast, zafirlukast, pranlukast, inflammation, lung function, exacerbations, and symptoms.

STUDY SELECTION

Relevant peer-reviewed articles (mostly randomized controlled trials, meta-analyses, and reviews) published up to July 2006 were selected and extracted.

RESULTS

Leukotriene receptor antagonists are beneficial across a range of asthma severities and may have a particular role in exercise-induced asthma, aspirin-sensitive asthma, and individuals with concomitant allergic rhinitis.

CONCLUSION

In the management of chronic asthma, leukotriene receptor antagonists have emerged as a useful oral nonsteroidal anti-inflammatory adjunct both as monotherapy and in combination with other classes of drugs. Monitoring their effects in terms of lung function alone may result in clinicians missing beneficial effects on inflammatory biomarkers, airway hyperresponsiveness, and exacerbations.

Genetic aspects of the etiology and treatment of asthma

This article provides a clinical review of the genetic aspects of the etiology and treatment of asthma for pediatric practitioners who are experienced in asthma diagnosis and management but lack expertise in genetics and immunology. Asthma is caused by the interaction of genetic susceptibility with environmental factors. The asthmatic response is characterized by elevated production of IgE, cytokines, and chemokines; mucus hypersecretion; airway obstruction; eosinophilia; and enhanced airway hyperreactivity to spasmogens. The genes most clearly associated with asthma include disintegrin and metalloprotease ADAM-33, dipeptidyl peptidase 10, PHD finger protein 11, and the prostanoid DP1 receptor. Within a few years, practitioners may apply sophisticated knowledge of cell and molecular biology to expand pharmacotherapeutic approaches and to personalize diagnosis and management.

The broken balance in aspirin hypersensitivity

Aspirin was introduced into medicine over a century ago and has become the most popular drug in the world. Although the first hypersensitivity reaction was described soon after aspirin had been marketed, only recently a phenomenon of cysteinyl leukotriene overproduction brought new insights on a balance between pro- and anti-inflammatory mediators derived from arachidonic acid. We describe the most common clinical presentations of aspirin hypersensitivity, i.e. aspirin-induced asthma, rhinosinusitis and aspirin-induced urticaria. We also present their biochemical background. Despite relatively high incidence of these reactions, aspirin hypersensitivity remains underdiagnosed worldwide. Acute reactions of aspirin hypersensitivity are elicited via cyclooxygenase inhibition by non-steroid anti-inflammatory drugs. Coxibs, selective inhibitors of cyclooxygenase-2 isoenzyme, do not precipitate symptoms in susceptible patients. Though hypersensitivity correlates with cyclooxygenase-1 inhibition, diminished tissue expression was described only for cyclooxygenase-2. Aspirin-induced asthma and aspirin-induced urticaria, in a substantial part of the patients, are driven by a release of mediators from activated mast cells. These cells in physiological conditions are under inhibitory control of prostaglandin E2. The origin of aspirin hypersensitivity remains unknown, but accumulating data from genetic studies strongly suggest that environmental factor, possibly a common viral infection, can trigger the disease in susceptible subjects.

Pathogenesis and management of aspirin-intolerant asthma

In 2-23% of adults with asthma, and rarely in children with asthma, aspirin (acetylsalicylic acid) and non-steroidal anti-inflammatory drugs (NSAIDs) cause asthma exacerbations. Within 3 hours of ingestion of aspirin/NSAIDs, individuals with aspirin-intolerant asthma (AIA) develop bronchoconstriction, often accompanied by rhinorrhea, conjunctival irritation, and scarlet flush. In severe cases, a single therapeutic dose of aspirin/NSAIDs can provoke violent bronchospasm, loss of consciousness, and respiratory arrest. In order to diagnose AIA, oral, inhaled, nasal or intravenous aspirin challenge tests are performed in facilities where experienced physicians are present and emergency treatment is available. The exact differences in the pathogenesis of AIA and other types of asthma are not fully understood. The interference of aspirin/NSAIDs with arachidonic acid metabolism in the lungs plays an important role in the mechanism of AIA; inhibition of cyclo-oxygenase is accompanied by overproduction of cysteinyl leukotrienes (cys-LTs). It has been proposed that overproduction of cys-LTs, together with removal by aspirin/NSAIDs of the 'brake' imposed by the bronchodilator prostaglandin E2, may cause an asthma attack in patients with AIA. Development of a suitable animal model to investigate the pathogenesis of AIA would help to clarify this question. Although it is still controversial whether leukotriene modifiers are more effective in patients with AIA compared with other types of asthma, because LT plays an important role in the pathogenesis of AIA, leukotriene modifiers are the preferred medication for the long-term control of AIA. Add-on efficacy of leukotriene modifiers has been confirmed in patients with AIA already treated with inhaled corticosteroids. However, this does not mean that aspirin/NSAIDs can be safely taken by aspirin-sensitive patients treated with leukotriene modifiers. To prevent attacks of AIA, sensitive patients should avoid the use of aspirin/NSAIDs or use selective cyclo-oxygenase 2 inhibitors when required. When patients with AIA need aspirin for specific situations they should receive aspirin desensitization therapy or treatment with selective cyclo-oxygenase 2 inhibitors.

Mechanism of chronic urticaria exacerbation by aspirin

In some patients with chronic idiopathic urticaria (CIU), aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) that inhibit cyclooxygenase 1 (COX-1) precipitate wheals and swelling. There is no in vitro diagnostic, and diagnosis can be established only by provocation challenges with aspirin or other NSAIDs. Skin reactions triggered by aspirin are associated with the inhibition of cyclooxygenase, specifically COX-1, but not COX-2, and are characterized by overproduction of cysteinyl leukotrienes (cys-LTs). Aspirin and other NSAIDs should be avoided, but highly specific COX-2 inhibitors, known as coxibs, are well tolerated and can probably be safely used. Evidence has been accumulated that these reactions are due to the interference of aspirin-like drugs with arachidonic-acid metabolism. In this article, we discuss the mechanism of these reactions, and the characteristic course of aspirin-induced urticaria and its management.

Pharmacogenetic approaches in the treatment of asthma

A patient's response to asthma therapy is determined by both genetic and environmental factors. In the past 10 years, we have witnessed significant progress in the field of asthma pharmacogenetics--the study of how a patient's genetic background determines the efficacy and potential for adverse effects to current asthma medication. There are now clear examples of gene polymorphisms that can influence responses to beta(2)-agonists, glucocorticosteroids, and leukotriene modifier drugs, the three main classes of medication used clinically to treat asthma. Identification of genetic polymorphism that predicts drug responses has the potential to lead to the development of new therapeutics, improve asthma management, and reduce serious episodes and hospitalizations. In this review, we discuss the current understanding of asthma pharmacogenetics, focusing on the main three classes of drugs currently used clinically.

The effect of montelukast on exhaled nitric oxide and lung function in asthmatic children 2 to 5 years old

OBJECTIVE

The study was undertaken to investigate the influence of once-daily treatment with montelukast (Singulair; MSD; Glattbrugg, Switzerland) on levels of exhaled nitric oxide (eNO) and lung function in preschool children with asthma.

METHODS

A total of 30 children (19 girls), 2 to 5 years of age, in whom asthma had been newly diagnosed, who had a positive first-degree family history of asthma and a positive allergy test result, were allocated to undergo a 1-week run-in period of montelukast treatment. eNO and airway resistance were measured in all patients before (visit 1) and after the run-in period (visit 2), and after treatment with montelukast (4 mg once daily) for 4 weeks (visit 3).

RESULTS

There were no significant differences in all parameters before and after the run-in period. However, the mean (SD) levels of eNO and the mean (SD) levels of airway resistance after treatment at visit 3 were 11.6 parts per billion (ppb) [9.5 ppb] and 1.15 kPa/L/s (0.26 kPa/L/s), respectively, and were significantly lower compared to values of 33.1 ppb (12.0 ppb) and 1.28 kPa/L/s (0.23 kPa/L/s), respectively, before treatment (p < 0.001) and at visit 2 (p = 0.01). There was no significant change in mean bronchodilator responsiveness between visit 3 (13.2%; SD, 6.8%) and visit 1/visit 2 (13.3%; SD, 7.0%; p = 0.47).

CONCLUSION

We have shown that montelukast has a positive effect on lung function and airway inflammation as measured by nitric oxide level in preschool children with allergic asthma.

Inhibition of nasal polyp mast cell and eosinophil activation by desloratadine

Nasal polyp tissue which contains mast cells and eosinophils is similar to the inflamed airway mucosa in cellular composition and mediator content. This investigation assessed the effect of desloratadine (DL), on activation of cells in nasal polyp tissue. Polyps were obtained from 22 patients with chronic rhinosinusitis [nine aspirin acetylosalitic acid (ASA)-sensitive and 13 ASA-tolerant]. Polyp tissue was dispersed by digestion, and preincubated with DL and incubated with anti-immunoglobulin E (IgE) or calcium ionophore. LTC4, eosinophil cationic protein (ECP) and tryptase concentrations in supernatants were measured by immunoassays. Desloratadine (1, 10 and 50 microM) inhibited calcium ionophore-induced LTC4 release by a mean of 29%, 50% and 63% respectively, and anti-IgE-induced LTC4 release by a mean of 27%, 35% and 39% respectively. Calcium ionophore-induced tryptase release was inhibited 60% and 69% by 10 and 50 microM of DL, respectively, and anti-IgE-induced tryptase release was inhibited 33%, 47% and 66% for 1, 10 and 50 microM of DL. Desloratadine 10 microM and 50 microM inhibited ECP release by and 45% and 48% respectively. Polyp tissue from ASA-sensitive patients when compared with ASA-tolerant patients released at baseline significantly more ECP (medians 120.0 microg/ml, range: 69.0-182.0 vs 63.4 microg/ml, range: 3.7-172.0; P <0.05), but similar amounts of tryptase and LTC4. This study demonstrated that DL inhibits activation of both eosinophils and mast cells derived from a site of airway mucosal inflammation.

Aspirin intolerance and the cyclooxygenase-leukotriene pathways

PURPOSE OF REVIEW

In up to 10% of patients with bronchial asthma, aspirin and other nonsteroidal antiinflammatory drugs precipitate asthmatic attacks. This is a hallmark of a distinct clinical syndrome that develops according to a characteristic sequence of symptoms. Here we discuss its clinical picture and management as related to the abnormalities in arachidonic acid transformations.

RECENT FINDINGS

At the biochemical level, the characteristic feature is profound alteration in eicosanoid biosynthesis and metabolism. Major advances in the molecular biology of eicosanoids, exemplified by the cloning of cysteinyl-leukotriene receptors and discovery of a whole family of cyclooxygenase enzymes, offer new insights into mechanisms operating in aspirin-induced asthma. Clinical interest has been enhanced by the introduction into therapy of highly specific cyclooxygenase-2 inhibitors and antileukotriene drugs.

SUMMARY

Recent studies have improved our understanding of mechanisms operating in asthma and unvieled the role of eicosanoid mediators in pulmonary disease.

Aspirin-induced asthma: advances in pathogenesis, diagnosis, and management

In some asthmatic individuals, aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) that inhibit cyclooxygen-ase 1 (COX-1) exacerbate the condition. This distinct clinical syndrome, called aspirin-induced asthma (AIA), is characterized by an eosinophilic rhinosinusitis, nasal polyposis, aspirin sensitivity, and asthma. There is no in vitro test for the disorder, and diagnosis can be established only by provocation challenges with aspirin or NSAIDs. Recent major advances in the molecular biology of eicosanoids, exemplified by the cloning of 2 cysteinyl leukotriene receptors and the discovery of a whole family of cyclooxygenase enzymes, offer new insights into mechanisms operating in AIA. The disease runs a protracted course even if COX-1 inhibitors are avoided, and the course is often severe, many patients requiring systemic corticosteroids to control their sinusitis and asthma. Aspirin and NSAIDs should be avoided, but highly specific COX-2 inhibitors, known as coxibs, are well tolerated and can be safely used. Aspirin desensitization, followed by daily aspirin treatment, is a valuable therapeutic option in most patients with AIA, particularly those with recurrent nasal polyposis or overdependence on systemic corticosteroids.