Benefits from adding the 5-lipoxygenase inhibitor zileuton to conventional therapy in aspirin-intolerant asthmatics

Asthma phenotypes: the evolution from clinical to molecular approaches

Although asthma has been considered as a single disease for years, recent studies have increasingly focused on its heterogeneity. The characterization of this heterogeneity has promoted the concept that asthma consists of multiple phenotypes or consistent groupings of characteristics. Asthma phenotypes were initially focused on combinations of clinical characteristics, but they are now evolving to link biology to phenotype, often through a statistically based process. Ongoing studies of large-scale, molecularly and genetically focused and extensively clinically characterized cohorts of asthma should enhance our ability to molecularly understand these phenotypes and lead to more targeted and personalized approaches to asthma therapy.

Challenge of isolated sputum cells supports in vivo origin of intolerance reaction to aspirin/non-steroidal anti-inflammatory drugs in asthma

BACKGROUND

There is no in vitro test to diagnose aspirin-intolerant asthma (AIA). The aim of this study was to test if challenge with aspirin of sputum cells from subjects with AIA triggers the release of cysteinyl leukotrienes (CysLTs), known to be mediators of bronchoconstriction in AIA.

METHODS

Sputum induction was performed at baseline and at another visit 2 h after a lysine-aspirin bronchoprovocation in 10 subjects with AIA and 9 subjects with aspirin-tolerant asthma (ATA). The isolated sputum cells were incubated for ex vivo challenge.

RESULTS

Release of CysLTs by sputum cells from patients with AIA was not induced by lysine-aspirin ex vivo, neither when cells were collected at baseline nor in sputum cells recovered after lysine-aspirin-induced bronchoconstriction, whereas release of CysLTs from sputum cells was triggered by an ionophore on both occasions. However, the CysLT levels elicited by the ionophore were higher in the AIA group both at baseline (AIA vs. ATA: 3.3 vs. 1.6 ng/million cells; p < 0.05) and after the lysine-aspirin bronchoprovocation (3.9 vs. 1.7 ng/million cells; p < 0.05). This difference in the amount of CysLTs released between the groups appeared to be related to the number of eosinophils.

CONCLUSIONS

Intolerance to aspirin could not be triggered in sputum cells isolated from subjects with AIA. Together with the previous inability to demonstrate intolerance to non-steroidal anti-inflammatory drugs in isolated blood cells, these results support the requirement of tissue-resident cells in the adverse reaction. However, ex vivo stimulation of sputum cells may be developed into a new test of capacity for LT release in inflammatory cells recovered from airways.

Leukotriene Inhibitors in Sinusitis

It has been recognized for many years that leukotrienes play an important role in mediating various effects of the allergic reaction. Recent evidence has shown that they play a role in other diseases including chronic sinusitis, particularly those sub-types involving eosinophils. Leukotrienes can be separated into the fairly well characterized cysteinyl leukotrienes and less well characterized leukotriene B(4). Effects of the leukotrienes are mediated through receptors that are expressed on a variety of cell types and can be modulated based on the inflammatory environment present. The pharmaceutical industry has long been interested in blocking leukotriene action and as such, two approaches have been developed that led to drugs approved for treatment of allergic disease. The most widely used class is the cysteinyl type 1 receptor antagonists, which block binding of the cysteinyl leukotrienes to the cell. The second class is an inhibitor of the 5-lipoxygenase enzyme that prevents synthesis of both the cysteinyl leukotrienes and leukotriene B(4). This review will focus on the role that leukotrienes play in chronic sinusitis and consider the rationale for choosing either a leukotriene antagonist or synthesis inhibitor as a treatment option. We will also discuss off-label uses for other medications that might be useful in these diseases as they relate to their ability to modulate leukotriene action.

Cysteinyl leukotriene overproduction in aspirin-exacerbated respiratory disease is driven by platelet-adherent leukocytes

Cysteinyl leukotriene (cysLT) overproduction is a hallmark of aspirin-exacerbated respiratory disease (AERD), but its mechanism is poorly understood. Because adherent platelets can convert the leukocyte-derived precursor leukotriene (LT)A(4) to LTC(4), the parent cysLT, through the terminal enzyme LTC(4) synthase, we investigated the contribution of platelet-dependent transcellular cysLT production in AERD. Nasal polyps from subjects with AERD contained many extravascular platelets that colocalized with leukocytes, and the percentages of circulating neutrophils, eosinophils, and monocytes with adherent platelets were markedly higher in the blood of subjects with AERD than in aspirin-tolerant controls. Platelet-adherent subsets of leukocytes had higher expression of several adhesion markers than did platelet nonadherent subsets. Adherent platelets contributed more than half of the total LTC(4) synthase activity of peripheral blood granulocytes, and they accounted for the higher level of LTC(4) generation by activated granulocytes from subjects with AERD compared with aspirin-tolerant controls. Urinary LTE(4) levels, a measure of systemic cysLT production, correlated strongly with percentages of circulating platelet-adherent granulocytes. Because platelet adherence to leukocytes allows for both firm adhesion to endothelial cells and augmented transcellular conversion of leukotrienes, a disturbance in platelet-leukocyte interactions may be partly responsible for the respiratory tissue inflammation and the overproduction of cysLTs that characterize AERD.

Current treatment of severe asthma

Severe asthma is considered a heterogeneous disease in which a variety of clinical, physiological and inflammatory markers determine disease severity. Pivotal studies in the last 5 years have led to substantial progress in many areas, ranging from a more accurate definition of truly severe, refractory asthma, to classification of the disease into distinct clinical phenotypes, and introduction of new therapies. This review focuses on three common clinical phenotypes of severe asthma in adults (early onset severe allergic asthma, late onset non-atopic eosinophilic asthma, late onset non-eosinophilic asthma with obesity), and provides an overview of recent developments regarding treatment options that are best suited for each of these phenotypes.

A geranyl acetophenone targeting cysteinyl leukotriene synthesis prevents allergic airway inflammation in ovalbumin-sensitized mice

Asthma is associated with increased pulmonary inflammation and airway hyperresponsiveness. The current use of corticosteroids in the management of asthma has recently raised issues regarding safety and lack of responsiveness in 5-10% of asthmatic individuals. The aim of the present study was to investigate the therapeutic effect of a non-steroidal small molecule that has cysteinyl leukotriene (cysLT) inhibitory activity, upon attenuation of allergic lung inflammation in an acute murine model. Mice were sensitized with ovalbumin (OVA) and treated with several intraperitoneal doses (100, 20, 2 and 0.2mg/kg) of 2,4,6,-trihydroxy-3-geranylacetophenone (tHGA). Bronchoalveolar lavage was performed, blood and lung samples were obtained and respiratory function was measured. OVA sensitization increased pulmonary inflammation and pulmonary allergic inflammation was significantly reduced at doses of 100, 20 and 2mg/kg with no effect at the lowest dose of 0.2mg/kg. The beneficial effects in the lung were associated with reduced eosinophilic infiltration and reduced secretion of Th2 cytokines and cysLTs. Peripheral blood reduction of total IgE was also a prominent feature. Treatment with tHGA significantly attenuated altered airway hyperresponsiveness as measured by the enhanced pause (Penh) response to incremental doses of methacholine. These data demonstrate that tHGA, a synthetic non-steroidal small molecule, can prevent acute allergic inflammation. This proof of concept opens further avenues of research and development of tHGA as an additional option to the current armamentarium of anti-asthma therapeutics.

Interleukin-4 in the Generation of the AERD Phenotype: Implications for Molecular Mechanisms Driving Therapeutic Benefit of Aspirin Desensitization

Aspirin-exacerbated respiratory disease (AERD) is explained in part by over-expression of 5-lipoxygenase, leukotriene C4 synthase (LTC₄S) and the cysteinyl leukotriene (CysLT) receptors (CysLT1 and 2), resulting in constitutive over-production of CysLTs and the hyperresponsiveness to CysLTs that occurs with aspirin ingestion. Increased levels of IL-4 have been found in the sinus mucosa and nasal polyps of AERD subjects. Previous studies demonstrated that IL-4 is primarily responsible for the upregulation of LTC4S by mast cells and the upregulation of CysLT1 and 2 receptors on many immune cell types. Prostaglandin E₂ (PGE₂) acts to prevent CysLT secretion by inhibiting mast cell and eosinophil activation. PGE₂ concentrations are reduced in AERD reflecting diminished expression of cyclooxygenase (COX)-2. IL-4 can inhibit basal and stimulated expression of COX-2 and microsomal PGE synthase 1 leading to decreased capacity for PGE₂ secretion. Thus, IL-4 plays an important pathogenic role in generating the phenotype of AERD. This review will examine the evidence supporting this hypothesis and describe a model of how aspirin desensitization provides therapeutic benefit for AERD patients.

Expression of arachidonate metabolism enzymes and receptors in nasal polyps of aspirin-hypersensitive asthmatics

BACKGROUND

The pathogenesis of rhinosinusitis in aspirin-exacerbated airway disease is closely linked to the disequilibrium in arachidonic acid metabolism. Although considerable amounts of data concerning impaired eicosanoid production are available, the precise mechanism and pathogenesis of the disease are still unknown. The aim of the present study was to assess the expression of enzymes belonging to the arachidonic acid cascade and receptors for arachidonate derivative metabolites in nasal polyps from aspirin- hypersensitive (AH) and aspirin-tolerant (AT) patients with rhinosinusitis.

METHODS

Cells expressing cysteinyl leukotriene (CysLT) receptors (CysLT(1) and CysLT(2)), arachidonate 5-lipoxygenase, leukotriene B(4) receptor type 1, E-prostanoid receptors (EP(2) and EP(4)), cyclooxygenase (COX)-1 and COX-2 were detected by immunocytochemistry in nasal polyps obtained from 10 AH patients and 18 AT patients.

RESULTS

There was a significantly higher density of cells expressing CysLT(1) and CysLT(2) receptors in nasal polyps from AH patients than from AT patients (p < 0.001). In contrast, the density of cells expressing EP(2) receptor and COX-2 was significantly lower in AH patients than in AT patients (p < 0.02). The number of COX-2-positive epithelial cells was significantly reduced in AH polyps (p < 0.04).

CONCLUSIONS

The elevated number of nasal polyp cells expressing CysLT receptors and lack of cells expressing EP(2) receptor and COX-2 may be related to a more severe course of hyperplastic rhinosinusitis in aspirin hypersensitivity.

Leukotrienes and airway inflammation

BACKGROUND

Asthma is a common chronic inflammatory disease of the airways characterized by airway obstruction and hyperresponsiveness. Leukotrienes (LTs) are lipid mediators that contribute to many aspects of asthma pathogenesis. As the LT pathway is relatively steroid-resistant, its blockade by alternative strategies is a desirable component of asthma management. Cysteinyl LT (cysLT) receptor 1 antagonists (LTRAs) have been utilized worldwide for more than 10years, and while their efficacy in asthma is well accepted, their limitations are also evident.

SCOPE OF REVIEW

In this review, we summarize the biological effects of LTs in asthma, review recent advances in LT receptors, and consider possible new therapeutic targets in the LT pathway that offer the potential to achieve better control of asthma in the future.

MAJOR CONCLUSIONS

CysLTs play pathogenetic roles in many aspects of asthma, and blockade of cysLT receptor 1 by currently available LTRAs is certainly beneficial in disease management. On the other hand, the limitations of LTRAs are also apparent. Recent studies have revealed new receptors for cysLTs other than classical cysLT receptors 1 and 2, as well as the potential importance of LTB(4) in asthma.

GENERAL SIGNIFICANCE

Recent findings provide clues to new approaches for targeting the LT pathway that may overcome the current limitations of LTRAs and achieve superior control of asthma. This article is part of a Special Issue entitled: Biochemistry of Asthma.

Comparison of montelukast and mometasone furoate in the prevention of recurrent nasal polyps

BACKGROUND

The aim of our study was to compare the effects of montelukast and mometasone furoate nasal spray on the postoperative course of patients with nasal polyposis.

PATIENTS AND METHODS

Fifty patients diagnosed with nasal polyposis between March 2006 and August 2007 were included in the study. All patients underwent bilateral endoscopic sphenoethmoidectomy and were randomized postoperatively into two groups. Group A (n = 25) received 10 mg montelukast per day and group B (n = 25) received 400 µg mometasone furoate nasal spray twice daily. All patients were followed up for 6 months. Sino-Nasal Outcome Test (SNOT)-22 scores, polyp grades, computerized tomography (CT) scores (Lund-Mackay), eosinophils in peripheral blood and polyp tissue were evaluated before and after surgery.

RESULTS

There was a significant reduction in SNOT-22 scores in both groups throughout the study period. There was a significant difference in the recurrence rate between both groups with a marginal advantage of mometasone furoate nasal spray. Eosinophils in peripheral blood were found to be effective on the recurrence rate (p < 0.05).

CONCLUSIONS

In conclusion, both drugs seem to have a complementary action and further studies are needed to determine which patients should receive which treatment.

[Exacerbations of asthma--precipitating factors: drugs]

Asthmatic exacerbations are sometimes triggered by medications, primarily the non-steroidal anti-inflammatory agents (NSAIDS) and beta-blockers. Asthma attacks induced by NSAIDS occur rapidly and can be severe. Widal syndrome is a specific disease entity whose physiopathology remains incompletely explained. Asthma is characteristically severe and steroid dependent; desensitisation with aspirin has been proposed, but this remains controversial. Beta-blockers are contra-indicated in asthma; the β1 "cardioselectivity" of some agents is not absolute, disappearing at high doses and the "partial agonists" are not better tolerated. However, certain authors have called into question the harmful effect of beta-blockade in moderate and stable asthma. More studies are needed, but the current data suggest that in some cases beta-blockers may be safe but their use requires close supervision. Other molecules can pose problems in asthmatics (dipyridamole, synthetic sex hormones and certain excipients). On the whole, there has been little innovation concerning the hazard that drugs can pose for some asthmatics. The task for the future will be to specify the physiopathology of Widal syndrome, and to clarify the categories of patients in whom beta-blockers can be safely employed as the public health consequences of cardiovascular pathologies make this an important issue for lung specialists.

International Union of Basic and Clinical Pharmacology. LXXXIV: leukotriene receptor nomenclature, distribution, and pathophysiological functions

The seven-transmembrane G protein-coupled receptors activated by leukotrienes are divided into two subclasses based on their ligand specificity for either leukotriene B(4) or the cysteinyl leukotrienes (LTC(4), LTD(4), and LTE(4)). These receptors have been designated BLT and CysLT receptors, respectively, and a subdivision into BLT(1) and BLT(2) receptors and CysLT(1) and CysLT(2) receptors has been established. However, recent findings have also indicated the existence of putative additional leukotriene receptor subtypes. Furthermore, other ligands interact with the leukotriene receptors. Finally, leukotrienes may also activate other receptor classes, such as purinergic receptors. The aim of this review is to provide an update on the pharmacology, expression patterns, and pathophysiological roles of the leukotriene receptors as well as the therapeutic developments in this area of research.

Chronic rhinosinusitis: therapeutic efficacy of anti-inflammatory and antibiotic approaches

Despite the high prevalence of chronic rhinosinusitis (CRS) worldwide, the exact pathogenesis of the disease remains unknown. Even with therapeutic intervention, treatment response is often only partial and frequently ineffective. The inability to define exact disease phenotypes in relation to specific disease mechanisms has led to a broad based approach with both anti-inflammatory and anti-microbial intervention. The clinical efficacy of such current therapeutic strategies is highlighted and the urgent need for further robust therapeutic intervention studies in CRS is discussed in this article.

Asthma phenotypes in adults and clinical implications

It is becoming increasingly recognized that asthma is a heterogeneous disease, whether based on clinical factors, including the patient's age at diagnosis, symptom spectrum and treatment response, triggering factors, or the level and type of inflammation. Attempts to analyze the importance of these characteristics to the clinical presentation of asthma have led to the appreciation of numerous separate and overlapping asthma phenotypes. However, these approaches are 'biased' and based on the clinician/scientist's own experience. Recently, unbiased approaches have also been attempted using both molecular and statistical tools. Early results from these approaches have supported and expanded on the clinician's concepts. However, until specific biologic markers are identified for any of these proposed phenotypes, the definitive nature of any phenotype will remain speculative.

Application of proteomics in asthma research

Bronchial asthma is caused by allergic airway inflammation, resulting in reversible airway obstruction, characterized by airway hyper-responsiveness, bronchoconstriction, increased mucus secretion and an increase in lung vessel permeability. The pathophysiological changes in asthma have been attributed to the altered expression of biologically plausible proteins associated with transcriptional pathways, inflammatory mediators, chemokines, cytokines, apoptosis and cell proliferation. Such multifactorial diseases characteristically involve an interplay of many genetic variations of molecular and biochemical pathways and their interactions with environmental factors. The complex nature of the asthma phenotype, together with genetic heterogeneity and environmental influences, has made it difficult to uncover the aspects that underlie this common disease. Recently, genomic and proteomic technologies have been developed to identify associations between genes, proteins and disease. This approach, called 'omics biology', aims to recognize early onset of disease, institute preventive treatment and identify new molecular targets for novel drugs in multifactorial diseases. This article reviews examples of how proteomic technology can be used to find asthma marker proteins (from the cell model to clinical samples). Identification of protein changes in different stages of asthma could provide further insights into the complex molecular mechanisms involved in this disease. These studies provide new insights for finding novel pathological mediators and biomarkers of asthma.

Pharmacotherapy of patients with mild persistent asthma: strategies and unresolved issues

In studies comparing regular versus on-demand treatment for patients with mild persistent asthma, on-demand treatment seems to have a similar efficacy on clinical and functional outcomes, but it does not suppress chronic airway inflammation or airway hyper-responsiveness (AHR) associated with asthma. Data on the efficacy of a continuous treatment with inhaled corticosteroids (ICS) in preventing the progression of asthma are conflicting. There is the possibility that patients without a regular treatment with ICS may develop a more severe asthma associated with airway structural changes (remodeling) and a progressive loss of lung function. However, the possible clinical and functional consequences of persistent, not controlled, airway inflammation in patients with asthma have to be established. Assessment of asthma control should include inflammatory outcomes, such as fraction of exhaled nitric oxide and sputum eosinophil counts. Until the relationships between symptoms, lung function tests, AHR, airway inflammation, exacerbations, and airway remodeling are clarified, regular treatment seems to be generally more appropriate than on-demand treatment to warrant a greater control of asthma. Select subgroups of patients with mild asthma who are well controlled by regular treatment might adopt the on-demand treatment plan as an intermediate step toward the suspension of controller medication. The increasing evidence for heterogeneity of asthma, the growing emphasis on asthma subphenotypes, including molecular phenotypes identified by omics technologies, and their possible implications for different asthma severity and progression and therapeutic response, are changing the paradigm of treating patients with asthma only based on classification of their disease severity to a pharmacological strategy more focused on the individual asthmatic patient. Pharmacological treatment of asthma is going toward a personalized approach.

New approaches to managing asthma: a US perspective

Despite remarkable advances in diagnosis and long-term management, asthma remains a serious public health concern. Newly updated expert guidelines emphasize the intra- and inter-individual variability of asthma and highlight the importance of periodic assessment of asthma control. These guidelines update recommendations for step-wise asthma treatment, address the burgeoning field of asthma diagnostics, and stress the importance of a patient and health care professional partnership, including written action plans and self monitoring. The field of asthma therapeutics is expanding rapidly, with promising new treatment options available or in development that may address some of the existing barriers to successful asthma management. These approaches simplify treatment, use combinations of agents in one delivery device that have complementary actions, or target specific pathways involved in asthma patho-physiology. Considerable activity is taking place in asthma pharmacogenetics. This review provides an overview of these new approaches to managing asthma, including their present status and future potential.

Genetics and phenotyping in chronic sinusitis

Chronic sinusitis with nasal polyposis historically has been treated as a single monolithic clinical disorder. Just as asthma is now accepted as numerous heterogeneous diseases, chronic sinusitis should also be viewed as comprising several diseases with varying causes, with each one characterized by distinct histologic and gene and protein expression patterns. This includes recognition of the need to define these diseases based on the presence or absence of an eosinophilic infiltrate but also on additional distinctions based on unique agents that drive their development and perpetuation. As a collection of heterogeneous diseases, proper differential diagnosis is required to delineate appropriate therapeutic intervention. This review will focus on recognized distinct presentations of chronic sinus disease, including distinguishing the clinical presentations, cellular and molecular characteristics, genetic differences, and current treatment options for each.

Over-expression of the LTC4 synthase gene in mice reproduces human aspirin-induced asthma

BACKGROUND

The pathogenesis of aspirin-induced asthma (AIA) is presumed to involve the aspirin/non-steroidal anti-inflammatory drug (NSAID)-induced abnormal metabolism of arachidonic acid, resulting in an increase in 5-lipoxygenase (5-LO) metabolites, particularly leukotriene C(4) (LTC(4) ). However, the role of LTC(4) in the development of AIA has yet to be conclusively demonstrated.

OBJECTIVE

The aim of this study was to evaluate the contribution of the lipid product LTC(4) secreted by the 5-LO pathway to the pathogenesis of AIA.

METHODS

To evaluate antigen-induced airway inflammation, the concentrations of T-helper type 2 cytokine in bronchoalveolar lavage fluid (BALF) obtained from LTC(4) synthase-transgenic (Tg) and wild-type (WT) mice after challenge with ovalbumin were measured. Subsequently, the ex vivo and in vivo effects of the NSAID sulpyrine were investigated in these Tg and WT mice by measuring the secretion of LTC(4) from sulpyrine-treated BAL cells and the levels of LTC(4) in BALF following challenge with sulpyrine. Finally, the sulpyrine-induced airway response by the administration of pranlukast, an antagonist of the cysteinyl (cs)-LT1 receptor, was analysed.

RESULTS

The concentrations of IL-4, -5, and -13 in BALF from Tg mice were significantly higher than those in WT mice. In addition, sulpyrine augmented the secretion of LTC(4) in BALF and by BAL cells in Tg mice, but not in WT mice. Additionally, the increased airway resistance induced by sulpyrine could be reduced by treatment with pranlukast. Furthermore, the secretion of LTC(4) from mast cells, eosinophils, and macrophages was increased in the allergen-stimulated LTC(4) synthase gene Tg mice, even in the absence of sulpyrine, as well as in BAL cells after sulpyrine.

CONCLUSION AND CLINICAL RELEVANCE

The over-expression of the LTC(4) synthase in a mouse asthma model also replicates the key features of AIA. And our study supports that cys-LTs play a major role in the pathogenesis of AIA in patients with chronic asthma.

Leukotriene modifiers for asthma treatment

Leukotrienes (LTs), including cysteinyl LTs (CysLTs) and LTB(4) , are potent lipid mediators that have a role in the pathophysiology of asthma. At least two receptor subtypes for CysLTs, CysLT(1) and CysLT(2) , have been identified. The activation of the CysLT(1) receptor is responsible for most of the pathophysiological effects of CysLTs in asthma, including increased airway smooth muscle activity, microvascular permeability, and airway mucus secretion. LTB(4) might have a role in severe asthma, asthma exacerbations, and the development of airway hyperresponsiveness. CysLT(1) receptor antagonists can be given orally as monotherapy in patients with mild persistent asthma, but these drugs are generally less effective than inhaled glucocorticoids. Combination of CysLT(1) receptor antagonists and inhaled glucocorticoids in patients with more severe asthma may improve asthma control and enable the dose of inhaled glucocorticoids to be reduced while maintaining similar efficacy. The identification of subgroups of asthmatic patients who respond to CysLT(1) receptor antagonists is relevant for asthma management as the response to these drugs is variable. CysLT(1) receptor antagonists have a potential anti-remodelling effect that might be important for preventing or reversing airway structural changes in patients with asthma. This review discusses the role of LTs in asthma and the role of LT modifiers in asthma treatment.

Canadian clinical practice guidelines for acute and chronic rhinosinusitis

This document provides healthcare practitioners with information regarding the management of acute rhinosinusitis (ARS) and chronic rhinosinusitis (CRS) to enable them to better meet the needs of this patient population. These guidelines describe controversies in the management of acute bacterial rhinosinusitis (ABRS) and include recommendations that take into account changes in the bacteriologic landscape. Recent guidelines in ABRS have been released by American and European groups as recently as 2007, but these are either limited in their coverage of the subject of CRS, do not follow an evidence-based strategy, or omit relevant stakeholders in guidelines development, and do not address the particulars of the Canadian healthcare environment.

Advances in understanding the pathophysiology of CRS, along with the development of appropriate therapeutic strategies, have improved outcomes for patients with CRS. CRS now affects large numbers of patients globally and primary care practitioners are confronted by this disease on a daily basis. Although initially considered a chronic bacterial infection, CRS is now recognized as having multiple distinct components (eg, infection, inflammation), which have led to changes in therapeutic approaches (eg, increased use of corticosteroids). The role of bacteria in the persistence of chronic infections, and the roles of surgical and medical management are evolving. Although evidence is limited, guidance for managing patients with CRS would help practitioners less experienced in this area offer rational care. It is no longer reasonable to manage CRS as a prolonged version of ARS, but rather, specific therapeutic strategies adapted to pathogenesis must be developed and diffused.

Guidelines must take into account all available evidence and incorporate these in an unbiased fashion into management recommendations based on the quality of evidence, therapeutic benefit, and risks incurred. This document is focused on readability rather than completeness, yet covers relevant information, offers summaries of areas where considerable evidence exists, and provides recommendations with an assessment of strength of the evidence base and degree of endorsement by the multidisciplinary expert group preparing the document.

These guidelines have been copublished in both Allergy, Asthma & Clinical Immunology and the Journal of Otolaryngology-Head and Neck Surgery.

Antileukotrienes in rhinosinusitis and nasal polyposis

Nasal polyposis is a chronic inflammatory disease of the nasal and paranasal sinus mucosa that, despite different hypotheses of its cause, remains poorly understood. The management of nasal polyposis has been the topic of countless frequent controversial debates for many decades. International guidelines generally suggest that first-line treatment should be based on a medical approach with mainly nasal and oral corticosteroids. Surgical procedures are often viewed as adjunctive to medical therapy. Given that antileukotrienes are currently indicated in the treatment of asthma and allergic rhinitis and there exists an increased leukotriene production in nasal polyps, antileukotrienes, especially montelukast, may represent a potential effective therapy for chronic rhinosinusitis, including nasal polyps.

Role of Leukotrienes and Leukotriene Modifiers in Asthma

Leukotrienes (LTs), including cysteinyl LTs (CysLTs) and LTB₄, are potent lipid mediators that are pivotal in the pathophysiology of asthma phenotypes. At least two receptor subtypes for CysLTs - CysLT1 and CysLT₂ - have been identified. Most of the pathophysiological effects of CysLTs in asthma, including increased airway smooth muscle activity, microvascular permeability and airway mucus secretion, are mediated by the activation of the CysLT1 receptor. LTB₄ may have a role in the development of airway hyperresponsiveness, severe asthma and asthma exacerbations. Although generally less effective than inhaled glucocorticoids, CysLT₁ receptor antagonists can be given orally as monotherapy in patients with persistent mild asthma. In patients with more severe asthma, CysLT₁ receptor antagonists can be combined with inhaled glucocorticoids. This therapeutic strategy improves asthma control and enables the dose of inhaled glucocorticoids to be reduced, while maintaining similar efficacy. The identification of subgroups of patients with asthma who respond to CysLT₁ receptor antagonists is relevant for asthma management, as the response to these drugs is variable. The potential anti-remodeling effect of CysLT₁ receptor antagonists might be important for preventing or reversing airway structural changes in patients with asthma. This review discusses the role of LTs in asthma and the therapeutic implications of the pharmacological modulation of the LT pathway for asthma.

When surgery, antibiotics, and steroids fail to resolve chronic rhinosinusitis

This article examines the modalities in the treatment of chronic rhinosinusitis (CRS). A correct diagnosis is the first requirement in the successful management of CRS. CRS-directed therapy might fail if the actual cause of symptoms is nonsinogenic. Nasal endoscopy and sinus computed tomography are the primary modalities used in the diagnosis of sinusitis. Allergy and gastroesophageal reflux, may not directly cause sinusitis, but they frequently mimic the symptoms of sinusitis. Therapy can include avoidance of allergens and desensitization in the former and antireflux therapy in the latter. Underlying systemic causes of refractory sinusitis include immunodeficiency and systemic granulomatous and eosinophilic syndromes. Correct diagnosis is essential to directed therapy. Patients with aspirin exacerbated respiratory disease may benefit from aspirin desensitization. Optimization of mucociliary clearance can be augmented with nasal lavage and mucolytics. Additional nonsteroidal antiinflammatory modalities include use of the leukotriene modulators, montelukast and zileuton. Patients with elevated IgE may benefit from omalizumab (anti-IgE); however, cost constraints restrict use to those patients who have severe asthma. This article also includes management strategies beyond the usual antibiotics, steroids, and sinus surgery. Once immunodeficiency and confounding local mimics of sinusitis are addressed, additional interventions should be tried separately initially to assess the individual patient's response to therapy.

Protection of leukotriene receptor antagonist against aspirin-induced bronchospasm in asthmatics

PURPOSE

Leukotriene receptor antagonists (LTRAs) are used to treat aspirin-intolerant asthma (AIA); however, the protective effects of long-term LTRA administration against aspirin-induced bronchospasm have not been evaluated.

OBJECTIVES

We investigated the efficacy of a 12-week treatment with a LTRA in protecting against aspirin-induced asthma in AIA patients.

METHODS

Fifty-two adult patients with AIA underwent an aspirin challenge test just before administration of montelukast (10 mg/day) and just after 12 weeks of treatment. The protective effect was assessed as the disappearance of aspirin-induced bronchospasm after 12 weeks of treatment. The results were compared according to the patients' clinical and physiological parameters.

RESULTS

The decline in FEV1 following aspirin challenge was significantly reduced from 28.6+/-1.9% to 10.2+/-1.7% (P=0.0001) after 12 weeks of montelukast treatment. However, 14 subjects (30%) still showed a positive response (>15% decline in FEV1) to aspirin challenge. Grouping the subjects into good and poor responders according to post-treatment responses revealed that the pretreatment aspirin-induced FEV1 decline was significantly greater in the poor responders and that the triggering dose of aspirin and the induction time for a positive response were lower and shorter, respectively, in the poor responders. Histories of aspirin hypersensitivity and sinusitis were more prevalent among the poor responders than among the good responders.

CONCLUSIONS

Twelve weeks of treatment with montelukast protected against aspirin-induced bronchospasm in 70% of the AIA cases. A poor response was associated with more severe aspirin-induced bronchospasms before treatment and a history of aspirin hypersensitivity or sinusitis.

CLINICAL IMPLICATIONS

A severe response to aspirin challenge may be a predictor of poor responsiveness to leukotriene antagonist treatment.

Severe asthma: what makes it so hard to manage?

Severe asthma presents significant management challenges. Patients can be difficult to control despite use of current standard-of-care therapy, including inhaled corticosteroids and long-acting beta-agonists. Alternative diagnoses, noncompliance, and comorbidities all can influence asthma control, future risk, and response to currently available therapy. Definitions of severe asthma evaluate and address these confounding variables, and yet patients are still symptomatic despite aggressive, appropriate therapy. Severe asthma has a distinct pathophysiology including airway remodeling that contributes to the decreased effectiveness of standard therapy. Multiple phenotypes exist within severe asthma that likely require distinct therapeutic approaches to achieve control and improve long-term health outcomes. New therapeutic approaches to these distinct phenotypes will improve our understanding and treatment of this difficult-to-manage disease.

Leukotriene E4-induced pulmonary inflammation is mediated by the P2Y12 receptor

Of the potent lipid inflammatory mediators comprising the cysteinyl leukotrienes (LTs; LTC₄, LTD₄, and LTE₄), only LTE₄ is stable and abundant in vivo. Although LTE₄ shows negligible activity at the type 1 and 2 receptors for cys-LTs (CysLT₁R and CysLT₂R), it is a powerful inducer of mucosal eosinophilia and airway hyperresponsiveness in humans with asthma. We show that the adenosine diphosphate (ADP)–reactive purinergic (P2Y₁₂) receptor is required for LTE₄-mediated pulmonary inflammation. P2Y₁₂ receptor expression permits LTE₄ -induced activation of extracellular signal-regulated kinase in Chinese hamster ovary cells and permits chemokine and prostaglandin D₂ production by LAD2 cells, a human mast cell line. P2Y₁₂ receptor expression by LAD2 cells is required for competition between radiolabeled ADP and unlabeled LTE₄ but not for direct binding of LTE₄, suggesting that P2Y₁₂ complexes with another receptor to recognize LTE₄. Administration of LTE₄ to the airways of sensitized mice potentiates eosinophilia, goblet cell metaplasia, and expression of interleukin-13 in response to low-dose aerosolized allergen. These responses persist in mice lacking both CysLT₁R and CysLT₂R but not in mice lacking P2Y₁₂ receptors. The effects of LTE₄ on P2Y₁₂ in the airway were abrogated by platelet depletion. Thus, the P2Y₁₂ receptor is required for proinflammatory actions of the stable abundant mediator LTE₄ and is a novel potential therapeutic target for asthma.

Modulation by aspirin of nuclear phospho-signal transducer and activator of transcription 6 expression: Possible role in therapeutic benefit associated with aspirin desensitization

BACKGROUND

Aspirin-exacerbated respiratory disease is characterized by asthma, nasal polyps, and intolerance to aspirin with overexpression of leukotriene (LT) C(4) synthase and cysteinyl leukotriene receptors. Through an unknown mechanism, aspirin desensitization is an effective treatment.

OBJECTIVE

We hypothesized that aspirin desensitization blocks IL-4-induced expression of these LT activities through inhibition of signal transducer and activator of transcription 6 (STAT6)-mediated transcription.

METHODS

Nuclear extracts were derived from THP-1 and normal human monocytes resting and cocultured with aspirin before IL-4 stimulation. Quantitative PCRs were conducted. Electrophoretic mobility shift assays were performed by using oligomers for STAT6 sites within the LT receptor and synthase promoters. Western blots of nuclear extracts were probed by using anti-phospho-STAT6 antibodies.

RESULTS

Upregulation of LT receptor mRNA by IL-4 was negated by aspirin and ketorolac but not by sodium salicylate. The STAT6 site in the LT receptor and synthase promoters was confirmed by using mobility shift assays by competing with unlabeled STAT6 consensus probes and supershifts with anti-STAT6 antibodies. Aspirin and ketorolac decreased the IL-4-inducible expression of nuclear STAT6 observed in mobility shift assays and Western hybridization.

CONCLUSION

The LT receptor and synthase promoters have STAT6-binding sites that are engaged by IL-4-induced nuclear extracts and inhibited by aspirin. Assuming that normal monocytes behave like monocytes from patients with aspirin-exacerbated respiratory disease, inhibition of IL-4-STAT6 might explain a mechanism in aspirin desensitization daily treatment, resulting in downregulation of production and responsiveness to cysteinyl leukotrienes. This biologic activity of aspirin likely reflects COX inhibition because it was shared with ketorolac but not sodium salicylate.

Pharmacotherapy of asthma: regular treatment or on demand?

Some studies have raised the question of the need for chronic controller therapy in mild persistent asthma as suggested by international guidelines. Although the Improving Asthma Control (IMPACT) and Beclomethasone plus Salbutamol (BEST) studies suggest that on-demand therapy in some patients with mild persistent asthma achieves a similar degree of asthma control based on symptoms and functional outcomes, the IMPACT study indicates that regular and on-demand therapy is not equivalent for controlling airway inflammation. Persistent airway inflammation might lead to airway remodelling with onset or worsening of symptoms, deterioration in lung function, and reduced response to pharmacological therapy. However, the relationships between chronic airway inflammation and airway remodelling need to be clarified. Choosing the 'right' pharmacological strategy (regular versus on-demand treatment) for asthma control is currently difficult due to the fact that (1) inflammatory outcome measures were not generally incorporated into asthma clinical trials; (2) the relationships between chronic airway inflammation and airway remodelling are largely unknown; (3) current clinical asthma trials that are generally based on symptomatic and functional outcome measures are too short to assess the impact of regular anti-inflammatory therapy on natural history of asthma; (4) asthma is an heterogeneous disease and different phenotypes of asthma patients likely requiring a different therapeutic approach can be identified, even in the same class of asthma severity. Guidelines for asthma management are valuable tools, although they are necessarily based on a strategy directed to the best outcome in a group of patients. Asthma phenotyping is becoming central for asthma management. The issue of regular versus on-demand treatment of intermittent and mild persistent asthma would be better addressed if considered within an individualized approach to asthma management and assessment. Identification of clinical, functional, morphological and biochemical phenotypes of patients with asthma and its clinical implications is likely to lead to a tailored, individualized, pharmacological therapy and asthma management.

Aspirin sensitivity and desensitization for asthma and sinusitis

NSAIDs-including aspirin (ASA)-that inhibit cyclooxygenase (COX)-1 induce nonallergic hypersensitivity reactions consisting of attacks of rhinitis and asthma. Such reactions occur exclusively in a subset of asthmatic patients who also have underlying nasal polyps and chronic hyperplastic eosinophilic sinusitis. We now refer to their underlying inflammatory disease of the entire respiratory tract as aspirin-exacerbated respiratory disease. This review focuses on descriptions of these patients; methods available to diagnose ASA-exacerbated respiratory disease; the unique ability of all NSAIDs that inhibit COX-1 to cross-react with ASA; lack of cross-reactivity with selective COX-2 inhibitors; an update on pathogenesis; and current thoughts about treatment, including ASA desensitization and daily ingestion of ASA itself.

Nasal mucosal expression of the leukotriene and prostanoid pathways in seasonal and perennial allergic rhinitis

BACKGROUND

Leukotrienes (LTs) and prostanoids are potent pro-inflammatory and vasoactive lipid mediators implicated in airway disease, but their cellular sources in the nasal airway in naturally occurring allergic rhinitis (AR) are unclear.

OBJECTIVE

To quantify cellular expression of enzymes of the 5-lipoxygenase (5-LO) and cyclooxygenase (COX) pathways by immunohistochemistry in nasal biopsies from patients with symptomatic perennial AR (PAR, n = 13) and seasonal AR (SAR, n = 14) and from normal subjects (n = 12).

METHODS

Enzymes of the 5-LO pathway (5-LO, FLAP, LT A4 hydrolase, LTC4 synthase) and the COX pathway (COX-1, COX-2, prostaglandin D2 synthase) were immunostained in glycol methacrylate resin-embedded inferior turbinate biopsy specimens, quantified in the lamina propria and epithelium, and co-localized to leucocyte markers by camera lucida.

RESULTS

In the lamina propria of PAR biopsies, median counts of cells expressing FLAP were fourfold higher than in normal biopsies (Mann-Whitney, P = 0.014), and also tended to be higher than in SAR biopsies (P = 0.06), which were not different from normal. PAR biopsies showed threefold more cells immunostaining for LTC4 synthase compared with SAR biopsies (P = 0.011) but this was not significant compared with normal biopsies (P = 0.2). These changes were associated with ninefold more eosinophils (P = 0.0005) with no differences in other leucocytes. There were no significant differences in the lamina propria in immunostaining for 5-LO, LTA4 hydrolase, COX-1, COX-2 or PGD2 synthase. Within the epithelium, increased expression of COX-1 was evident in PAR biopsies (P = 0.014) and SAR biopsies (P = 0.037), associated with more intra-epithelial mast cells in both rhinitic groups (P < 0.02).

CONCLUSIONS

In the nasal biopsies of PAR subjects, increased expression of regulatory enzymes of the cysteinyl-LT biosynthetic pathway was associated with lamina propria infiltration by eosinophils. Seasonal rhinitis biopsies shared only some of these changes, consistent with transient disease. Increased intra-epithelial mast cells and epithelial COX-1 expression in both rhinitic groups may generate modulatory prostanoids.

PPARalpha/gamma-Independent Effects of PPARalpha/gamma Ligands on Cysteinyl Leukotriene Production in Mast Cells

Peroxisome proliferator-activated receptor (PPAR) α ligands (Wy-14,643, and fenofibrate) and PPARγ ligands (troglitazone and ciglitazone) inhibit antigen-induced cysteinyl leukotriene production in immunoglobulin E-treated mast cells. The inhibitory effect of these ligands on cysteinyl leukotriene production is quite strong and is almost equivalent to that of the anti-asthma compound zileuton. To develop new aspects for anti-asthma drugs the pharmacological target of these compounds should be clarified. Experiments with bone-marrow-derived mast cells from PPARα knockout mice and pharmacological inhibitors of PPARγ suggest that the inhibitory effects of these ligands are independent of PPARs α and γ. The mechanisms of the PPAR-independent inhibition by these agents on cysteinyl leukotriene production are discussed in this review.

Asthma: a syndrome composed of heterogeneous diseases

OBJECTIVE

To review the concept that asthma comprises distinct heterogeneous inflammatory disorders characterized by patients showing different phenotypes with distinct genetic components, environmental causes, and immunopathologic signa-

DATA SOURCES

Ovid MEDLINE and PubMed databases from 1950 to the present time were searched for relevant articles and references regarding the heterogeneity of asthma.

STUDY SELECTION

Articles that described the various phenotypes of asthma were used for this review.

RESULTS

Asthma is unlikely to be a single disease but rather a series of complex, overlapping individual diseases or phenotypes, each defined by its unique interaction between genetic and environmental factors. These conditions include syndromes characterized by allergen-exacerbated, nonallergic, and aspirin-exacerbated factors along with syndromes best distinguished by their pathologic findings (eosinophilic, neutrophilic, pauci-granulocytic), response to therapy (corticosteroid resistant), and natural history (remodeling prone). Additional phenotypes will almost certainly be identified as advances in genetics and other profiling methods are made and will be accompanied by the availability of clear biomarkers for distinguishing among them.

CONCLUSIONS

Responses to asthma medications vary considerably among patients, likely reflecting, at least in part, the differing sensitivities of the various asthma phenotypes. Selecting the best possible treatment course in individual patients will be aided by clearly identifying the different phenotypes. Physicians need to recognize this when making decisions to adjust treatment to improve asthma control.

The clinical effectiveness of aspirin desensitization in chronic rhinosinusitis

Aspirin-exacerbated respiratory disease (AERD) is a chronic inflammatory disease characterized by chronic rhinosinusitis, nasal polyposis, asthma, and airway reactivity to aspirin and other nonsteroidal antiinflammatory drugs (NSAIDs). For patients who have inadequately controlled rhinosinusitis and/or asthma despite treatment with topical corticosteroids and leukotriene-modifying drugs, aspirin desensitization is an important therapeutic option. This review examines the evidence supporting the effectiveness of aspirin desensitization for the treatment of chronic rhinosinusitis in patients with AERD. Practical aspects of conducting safe aspirin desensitization procedures and optimizing therapeutic benefits are also reviewed. When conducted in accordance with current guidelines, aspirin desensitization is a safe procedure that allows patients with AERD who have an indication for aspirin or other NSAIDs to safely ingest these medications. There is now strong evidence that aspirin desensitization and daily aspirin therapy is effective for treatment of the chronic inflammatory disease of the upper airway and lower airways in AERD.

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.

BSACI guidelines for the management of rhinosinusitis and nasal polyposis

This guidance for the management of patients with rhinosinusitis and nasal polyposis has been prepared by the Standards of Care Committee (SOCC) of the British Society for Allergy and Clinical Immunology (BSACI). The recommendations are based on evidence and expert opinion and are evidence graded. These guidelines are for the benefit of both adult physicians and paediatricians treating allergic conditions. Rhinosinusitis implies inflammation of the nose and sinuses which may or may not have an infective component and includes nasal polyposis. Acute rhinosinusitis lasts up to 12 weeks and resolves completely. Chronic rhinosinusitis persists over 12 weeks and may involve acute exacerbations. Rhinosinusitis is common, affecting around 15% of the population and causes significant reduction in quality of life. The diagnosis is based largely on symptoms with confirmation by nasendoscopy. Computerized tomography scans and magnetic resonance imaging are abnormal in approximately one third of the population so are not recommended for routine diagnosis but should be reserved for those with acute complications, diagnostic uncertainty or failed medical therapy. Underlying conditions such as immune deficiency, Wegener's granulomatosis, Churg-Strauss syndrome, aspirin hypersensitivity and allergic fungal sinusitis may present as rhinosinusitis. There are few good quality trials in this area but the available evidence suggests that treatment is primarily medical, involving douching, corticosteroids, antibiotics, anti-leukotrienes, and anti-histamines. Endoscopic sinus surgery should be considered for complications, anatomical variations causing local obstruction, allergic fungal disease or patients who remain very symptomatic despite medical treatment. Further well conducted trials in clearly defined patient groups are needed to improve management.

Nasal blockage induced by oral administration of non-steroidal anti-inflammatory drugs in a guinea-pig model of allergic rhinitis

To elucidate the mechanisms underlying nasal symptoms in patients with aspirin hypersensitivity, we evaluated the effects of orally administered non-steroidal anti-inflammatory drugs (NSAIDs) on the nasal patency of guinea pigs with cedar pollen-induced chronic allergic rhinitis. Indomethacin (10 mg/kg) administered 1 h before a pollen challenge amplified the antigen-induced nasal blockage. More interestingly, even in the absence of the pollen challenge, indomethacin induced nasal blockage at 30 min at 4 h after administration. However, indomethacin-induced nasal blockage was not provoked in non-sensitized animals. Another NSAID, diclofenac (30 mg/kg), also evoked nasal blockage, but unexpectedly, aspirin (500 mg/kg) did not affect nasal patency. Indomethacin-induced nasal blockage was unaffected by a cysteinyl leukotriene receptor (CysLT(1) receptor) antagonist, pranlukast (30 mg/kg, p.o.), or by prostaglandin E2 (10(-3) M, intranasal), suggesting that the nasal blockage may not be due to hyperproduction of cysteinyl leukotrienes or inhibition of prostaglandin E2 production. These results indicate that the indomethacin-induced nasal blockage may not be an identical phenomena to airway symptoms in aspirin hypersensitivity patients. However, because chronic nasal inflammation is indispensable for the development of nasal blockage, indomethacin-induced nasal blockage may become a clue to elucidate new mechanisms underlying hypersensitivity to NSAIDs.

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.

Leukotriene synthesis inhibitors versus antagonists: the pros and cons

It has been recognized for many years that leukotrienes play an important role in mediating various effects of the allergic reaction. Recent evidence has shown that they play a role in other diseases. Leukotrienes can be separated into the fairly well-characterized cysteinyl leukotrienes and the less well-characterized leukotriene B(4). Effects of the leukotrienes are mediated through receptors that are expressed on a variety of cell types and can be modulated based on the inflammatory environment present. The pharmaceutical industry has long been interested in blocking leukotriene action. As such, two approaches have been developed that led to drugs approved for treating allergic disease. The most widely used class is the cysteinyl type 1 receptor antagonists, which block binding of the cysteinyl leukotrienes to the cell. The second class is an inhibitor of the 5-lipoxygenase enzyme that prevents synthesis of both the cysteinyl leukotrienes and leukotriene B(4). This review focuses on the role that leukotrienes play in various diseases, with the emphasis on allergic diseases, and considers the rationale for choosing either a leukotriene antagonist or synthesis inhibitor as a treatment option.

Treatment heterogeneity in asthma: genetics of response to leukotriene modifiers

Despite advances in treatment, asthma continues to be a significant health and economic burden. Although asthma cannot be cured, several drugs, including beta2 agonists, corticosteroids, and leukotriene (LT) modifiers, are well tolerated and effective in minimizing symptoms, improving lung function, and preventing exacerbations. However, inter-patient variability in response to asthma drugs limits their effectiveness. It has been estimated that 60-80% of this inter-patient variability may be attributable to genetic variation. LT modifiers, in particular, have been associated with heterogeneity in response. These drugs exert their action by inhibiting the activity of cysteinyl leukotrienes (CysLTs), which are potent bronchoconstrictors and pro-inflammatory agents. Two classes of LT modifiers are 5-lipoxygenase (ALOX5) inhibitors (zileuton) and leukotriene receptor antagonists (LTRAs) [montelukast, pranlukast, and zarfirlukast]. LT modifiers can be used as alternatives to low-dose inhaled corticosteroids (ICS) in mild persistent asthma, as add-on therapy to low- to medium-dose ICS in moderate persistent asthma, and as add-on to high-dose ICS and a long-acting ss2 agonist in severe persistent asthma. At least six genes encode key proteins in the LT pathway: arachidonate 5-lipoxygenase (ALOX5), ALOX5 activating protein (ALOX5AP [FLAP]), leukotriene A4 hydrolase (LTA4H), LTC4 synthase (LTC4S), the ATP-binding cassette family member ABCC1 (multidrug resistance protein 1 [MRP1]), and cysteinyl leukotriene receptor 1 (CYSLTR1). Studies have reported that genetic variation in ALOX5, LTA4H, LTC4S, and ABCC1 influences response to LT modifiers. Plasma concentrations of LTRAs vary considerably among patients. Physio-chemical characteristics make it likely that membrane efflux and uptake transporters mediate the absorption of LTRAs into the systemic circulation following oral administration. Genes that encode efflux and uptake transport proteins harbor many variants that could influence the pharmacokinetics, and particularly the bioavailability, of LTRAs, and could contribute to heterogeneity in response. In the future, large, well designed clinical trials studying the pharmacogenetics of LT modifiers in diverse populations are warranted to determine whether a genetic signature can be developed that will accurately predict which patients will respond.

The role of antileukotriene drugs in management of rhinitis and rhinosinusitis

Antileukotriene drugs have been studied for more than 15 years. In this review we examine the role of leukotrienes in rhinitis and rhinosinusitis, and explore the clinical literature supporting the use of anti-leukotriene agents in these diseases. Although these medications clearly are efficacious in rhinitis, it is unclear where in the armamentarium they should be used. The evidence for use in sinusitis has not been well studied except in sinusitis-associated aspirin-exacerbated respiratory disease. In this circumstance there is information that allows use of antileukotriene agents to be considered efficacious. We provide our rationale for use and await future clinical studies to answer this important question.

Zileuton: clinical implications of 5-Lipoxygenase inhibition in severe airway disease

The 5-Lipoxygenase pathway results in the formation of leukotrienes, including leukotriene B(4) (LTB(4)), 5-oxo-6E,8Z,11Z,14Z-eicosatetranoic acid and the cysteinyl leukotrienes (LTC(4), LTD(4) and LTE(4)) and activates all four leukotriene receptors, BLT1, BLT2, cysLT(1) and cysLT(2). Zileuton is the only commercially available inhibitor of the 5-Lipoxygenase pathway. In a number of clinical trials, zileuton has been shown to improve airway function and inflammation, asthma symptom control and quality of life in asthmatics. Given the important role that leukotrienes play in airway inflammation, zileuton provides an additional therapeutic option in the management of chronic, persistent asthma, particularly those asthmatics with more severe disease. In addition, zileuton has shown promise in a number of other conditions, including upper airway inflammatory conditions, dermatological disease and chronic obstructive pulmonary disease. The development of new formulations, including a controlled release tablet formulation for b.i.d. dosing and an intravenous preparation for acute asthma exacerbations may enhance clinical utility and expand therapeutic indications.

Zileuton added to low-dose inhaled beclomethasone for the treatment of moderate to severe persistent asthma

OBJECTIVE

To assess the therapeutic effects of oral zileuton tablets combined with low-dose beclomethasone compared to doubling the dose of beclomethasone, in improving lung function and reducing asthma symptoms.

METHODS

Randomized, active-control, double-blind, parallel, multi-center study of zileuton (400 or 600 mg QID)+200 microg beclomethasone dipropionate (BDP) BID versus placebo+BDP 400 microg BID in asthmatics with baseline FEV(1) percent predicted values between 40% and 80% following a single-blind ICS (BDP 200 microg BID) 2-week run-in. During the 3-month double-blind treatment period, assessments included safety, daytime and nighttime symptoms, acute asthma exacerbations, beta(2)-agonist use, AM and PM peak expiratory flow (PEF) and FEV(1).

RESULTS

The addition of a 5-lipoxygenase (5-LO) inhibitor added to a low-dose of BDP showed no significant difference in FEV(1) compared to doubling the dose of BDP. FEV(1) improved in all 3 treatment groups, with mean increases of 10% with zileuton 600 mg QID+BDP 200 microg BID, 12% with zileuton 400mg QID+BDP 200 microg BID, and 11% with BDP 400 microg BID by study end. Within each treatment group, there were significant improvements in asthma symptoms and AM and PM PEF compared to baseline. No significant differences were observed between groups with regards to salbutamol use, acute asthma exacerbations, the requirement for oral/parenteral corticosteroids and adverse clinical events.

CONCLUSIONS

The addition of a 5-LO inhibitor added to low-dose beclomethasone may be an alternative to higher-doses of ICS in patients unable to achieve sufficient asthma control on low-dose ICS therapy.

Concordant modulation of cysteinyl leukotriene receptor expression by IL-4 and IFN-gamma on peripheral immune cells

Arachidonic acid can be metabolized to form a group of compounds known as the cysteinyl leukotrienes (CysLT) that bind to one of two receptors to mediate their actions. On circulating cells, expression of the leukotriene receptors is low, but in inflamed tissue the receptor number is dramatically increased. We hypothesized that the cytokine milieu present during inflammation can increase receptor expression on infiltrating immune cells. Various cell populations were purified from peripheral blood and stimulated in vitro with cytokines characteristic of allergic inflammatory disorders, and CysLT receptor expression was measured using quantitative PCR analysis, Western blot, and flow cytometry. IL-4, but not IL-13, was able to significantly induce mRNA and protein levels for both CysLT receptor 1 and 2 from T cells and B cells. CysLT2 receptor expression was also significantly increased in monocytes and eosinophils after IL-4 stimulation. Surprisingly, CysLT2 receptor expression was increased in monocytes, T cells, and B cells when IFN-gamma was used as the stimulus. Factors involved in eosinophil growth and survival were tested for their ability to alter CysLT receptor expression. These results support the concept that cytokines increase expression of both receptors on lymphocytes and granulocytes, allowing these cells to be more responsive to secreted leukotrienes at sites of inflammation.

Pharmacotherapy of diseases mediated by 5-lipoxygenase pathway eicosanoids

Inflammatory eicosanoids generated by the 5-lipoxygenase (5-LO) pathway of arachidonic acid metabolism are now known to have at least 6 receptors: OXE, which recognizes 5-HETE and 5-oxo-ETE; a putative receptor recognizing a potent 5-oxo-ETE metabolite, FOG(7); the LTB(4) receptors, BLT1 and BLT2; the cysteinyl leukotriene receptors, CysLT(1) and CysLT(2), which recognize leukotrienes LTC(4), LTD(4), LTE(4) and LTF(4). The 5-LO pathway is activated in many diseases and invokes inflammatory responses not affected by glucocorticoids, but therapy with selective BLT1 or CysLT(1) antagonists in asthma has met with variable success. Studies show that 5-LO pathway eicosanoids are not primary mediators in all cases of asthma, but may be especially important in severe persistent asthma, aspirin- and exercise-induced asthma, allergic rhinitis, COPD, idiopathic pulmonary fibrosis, atherosclerosis, atopic dermatitis, acne and ischemia-related organ injury. These disorders appear to involve multiple 5-LO pathway eicosanoids and receptor subtypes, suggesting that inhibition of the pathway at the level of 5-LO may be necessary for maximal efficacy.