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

Aspirin exacerbated respiratory disease: Current topics and trends

Aspirin-exacerbated respiratory disease is a chronic and treatment-resistant disease, characterized by the presence of eosinophilic rhinosinusitis, nasal polyposis, bronchial asthma, and nonsteroidal anti-inflammatory drugs hypersensitivity. Alterations in arachidonic acid metabolism may induce an imbalance between pro-inflammatory and anti-inflammatory substances, expressed as an overproduction of cysteinyl leukotrienes and an underproduction of prostaglandin E2. Although eosinophils play a key role, recent studies have shown the importance of other cells and molecules in the development of the disease like mast cells, basophils, lymphocytes, platelets, neutrophils, macrophages, epithelial respiratory cells, IL-33 and thymic stromal lymphopoietin, making each of them promissory diagnostic and treatment targets. In this review, we summarize the most important clinical aspects of the disease, including the current topics about diagnosis and treatment, like provocation challenges and aspirin desensitization. We also discuss recent findings in the pathogenesis of the disease, as well as future trends in diagnosis and treatment, including monoclonal antibodies and a low salicylate diet as a treatment option.

Traditional Therapies for Severe Asthma

Severe asthma is a complex and heterogeneous disease. The European Respiratory Society and American Thoracic Society guidelines define severe asthma for patients 6 years or older as "asthma which requires treatment with high-dose inhaled corticosteroids…plus a second controller or systemic corticosteroids to prevent it from becoming 'uncontrolled' or which remains 'uncontrolled' despite this therapy." This article reviews available traditional therapies, data behind their uses in severe asthma, and varying recommendations. As various asthma endotypes and phenotypes are better understood and characterized, targeted therapies should help improve disease outcomes, efficacy, and cost-effectiveness.

Dietary Fatty Acid Modification for the Treatment of Aspirin-Exacerbated Respiratory Disease: A Prospective Pilot Trial

BACKGROUND

The high levels of eicosanoid production and the clinical efficacy of leukotriene-modifying pharmacotherapies for patients with aspirin-exacerbated respiratory disease (AERD) suggest that other interventions targeting arachidonic acid dysregulation may also improve disease control.

OBJECTIVE

To assess the utility of a high omega-3/low omega-6 diet for the treatment of AERD.

METHODS

Prospective, nonblinded dietary intervention in 10 adult patients with AERD at Brigham and Women's Hospital in Boston, MA. The primary objective was for subjects to reduce dietary omega-6 fatty acid consumption to less than 4 g/d and increase omega-3 intake to more than 3 g/d. The primary outcome was change in urinary leukotriene E₄, with changes in other eicosanoids, platelet activation, lung function, and patient-reported questionnaires also assessed.

RESULTS

Of the 10 subjects who screened for the study, all 10 completed the dietary intervention. Urinary leukotriene E₄ decreased by 0.17 ng/mg (95% CI, -0.29 to -0.04; P = .02) and tetranor prostaglandin D-M decreased by 0.66 ng/mg creatinine (95% CI, -1.21 to -0.11; P = .02). There was a 15.1-point reduction in the 22-item Sino-Nasal Outcome Test score (95% CI, -24.3 to -6.0; P = .01), a 0.27-point reduction in the 7-item Asthma Control Questionnaire score (95% CI, -0.52 to -0.03; P = .03), and no change in FEV₁ % predicted (P = .92) or forced vital capacity % predicted (P = .74). All patients lost some weight over the 2-week intervention period, and there were no diet-associated adverse events.

CONCLUSIONS

A high omega-3/low omega-6 diet may be an appropriate adjunct treatment option for patients with AERD.

Aspirin or Nonsteroidal Anti-inflammatory Drug-Exacerbated Chronic Rhinosinusitis

Aspirin (ASA)-exacerbated respiratory disease (AERD) is characterized by upper airway congestion due to eosinophilic inflammation of the nasal and sinus membranes and nasal polyposis, associated with increased leukotriene production that is further accentuated by ASA or other nonsteroidal anti-inflammatory drug (NSAID) ingestion. It occurs in 5% to 10% of subjects with chronic rhinosinusitis (CRS) and in 15% to 40% of those with nasal polyposis. Although AERD with CRS is usually associated with asthma, this is not always the case. The eosinophilic airway inflammation and symptoms precede clinical reactions to ASA or other NSAIDs, but ultimately affected subjects experience worsening of symptoms with ingestion of ASA/NSAIDs. The endotypic mechanism for this worsening is related to a chronic increase in leukotriene and a decrease in prostaglandin production, particularly prostaglandin E2, that is further aggravated by the inhibition of cycloxgenase I. IgE does not likely play a role in the pathogenesis of the disease although nasal and sinus staphylococcal infection increases local IgE level and may increase total IgE and specific IgE levels. Genetic studies suggest that multiple genes may be involved, but the genetic abnormalities may differ in affected subjects from different ethnicities and candidate genes have not been confirmed in multiple studies. Genome-wide association studies have not been revealing. The phenotype is recognized by the mucosal inflammation and worsening of symptoms acutely with ASA/NSAID. There is clinical improvement with ASA desensitization followed by regular ingestion of ASA or other NSAIDs. Further understanding of this unique phenotype and endotype of CRS will likely improve the understanding of other eosinophilic airway diseases.

Aspirin and Nonsteroidal Antiinflammatory Drugs Hypersensitivity and Management

Aspirin and nonsteroidal antiinflammatory drugs (NSAIDs) are widely used in the United States and throughout the world for a variety of indications. Several unique hypersensitivity syndromes exist to this class of medications, making them one of the common reasons for consultation to the allergist. The lack of any laboratory-based diagnostic studies to assist in identifying the culprits in these reactions make evaluation of aspirin and NSAID hypersensitivity challenging. Identifying patients appropriate for oral challenge and/or desensitization protocols is the standard pragmatic approach to this issue when it arises.

Chronic rhinosinusitis phenotypes

OBJECTIVE

To review the current knowledge surrounding different chronic rhinosinusitis (CRS) presentations and the relative roles of nasal polyps, eosinophilia, and allergies in discerning phenotypes.

DATA SOURCES

PubMed literature review.

STUDY SELECTIONS

Articles discussing the various phenotypes of CRS with emphasis on pathologic and immune mechanistic studies that distinguish disease.

RESULTS

Current guidelines primarily separate CRS based on the presence or absence of nasal polyps. This is largely driven by the tendency of eosinophilic disease to present with nasal polyps (NPs) in contrast to noneosinophilic presentations, which less often lead to the development NPs. Further separations have been proposed based on expression of aeroallergen sensitization.

CONCLUSION

The presence of NPs may only poorly predict the presence of an underlying eosinophilic process and as such may have poor utility in forming the basis for recommending eosinophil-target therapies. Similarly, there is little evidence to support a significant role for aeroallergen exposure in contributing to the presence, severity, or natural history of CRS. Appropriate separation of CRS into specific phenotypes will allow therapeutic approaches to be individualized to each distinct presentation.

Troglitazone, a PPAR-γ agonist, decreases LTC4 concentration in mononuclear cells in patients with asthma

BACKGROUND

Asthma is an inflammatory disorder with multiple mediators involved in the inflammatory response. Despite several attempts, no new anti-inflammatory drugs have been registered for asthma treatment for several years. However, thiazolidinediones, peroxisome proliferator-activated receptor agonists, have demonstrated some anti-inflammatory properties in various experimental settings. The aim of this study was to assess the influence of troglitazone on LTC₄ and 15-HETE concentrations. It also evaluates TNF-induced eotaxin synthesis in peripheral blood mononuclear cells from 14 patients with mild asthma and 13 healthy controls.

METHODS

PBMCs were isolated from the whole blood of the asthmatics and healthy subjects and pretreated with 0.1, 1 or 10μM of Troglitazone. The cells were then exposed to 10^-6M calcium jonophore or 10ng/ml TNF. The production and release of LTC₄, 15-HETE and eotaxin were then assessed.

RESULTS

Troglitazone caused a dose-dependent inhibition in LTC₄ synthesis in both asthmatics and healthy subjects. Troglitazone did not influence 15-HETE or eotaxin production in either asthmatic patients or in healthy individuals.

CONCLUSION

Due to its inhibition of LTC₄ synthesis, troglitazone therapy is an interesting potential therapeutic approach in asthma and other LTC₄ related inflammatory disorders.

Aspirin-Exacerbated Respiratory Disease

Aspirin-exacerbated respiratory disease (AERD) is characterized by the triad of asthma, sinonasal polyposis, and aspirin intolerance. The hallmark of the disease is baseline overproduction of cysteinyl leukotrienes via the 5-lipoxygenase pathway, exacerbated by ingestion of aspirin. Patients with AERD have high rates of recidivistic polyposis following sinus surgery, although the improvement in quality of life following surgery is similar to aspirin-tolerant patients. The diagnosis is secured by a positive aspirin provocation test, usually administered by a medical allergist. Aspirin therapy is a unique treatment consideration for patients with AERD.

Position statement of the Brazilian Academy of Rhinology on the use of antihistamines, antileukotrienes, and oral corticosteroids in the treatment of inflammatory sinonasal diseases

Introduction

Inflammatory conditions of the nose and paranasal sinuses are very prevalent in the general population, resulting in marked loss of quality of life in affected patients, as well as significant work, leisure, and social activity losses. These patients require specific and specialized treatment. A wide range of oral medications are available.

Objective

The present document is aimed to clarify, for professionals treating patients with inflammatory sinonasal diseases, both specialists and general practitioners, specific oral therapies in noninfectious nasal inflammatory conditions.

Methods

The methodology used to create this article included the search for the key words: oral corticosteroids, antihistamines, antileukotrienes, rhinitis, rhinosinusitis in the MEDLINE and EMBASE databases in the last 5 years. Since no relevant article was found for the text on the subject of interest in the last 5 years, the search was extended for another 5 years, and so on, according to the authors’ needs.

Results

Relevant literature was found regarding the use of antihistamines, antileukotrienes and oral corticosteroids in these conditions. The Brazilian Academy of Rhinology emphasizes, after extensive discussion by the collegiate, key points in the treatment with these drugs.

Conclusion

There is support in the literature for the use of these drugs; however, final considerations about the role of each of them have been made.

Leukotrienes provide an NFAT-dependent signal that synergizes with IL-33 to activate ILC2s

von Moltke et al. demonstrate that optimal cytokine induction in group 2 innate lymphocytes results from synergy between NFAT-dependent leukotriene signaling and IL-33 signaling. This integration of signaling pathways may represent an innate substitute for the T cell receptor.

Group 2 innate lymphoid cells (ILC2s) and type 2 helper T cells (Th2 cells) are the primary source of interleukin 5 (IL-5) and IL-13 during type 2 (allergic) inflammation in the lung. In Th2 cells, T cell receptor (TCR) signaling activates the transcription factors nuclear factor of activated T cells (NFAT), nuclear factor κB (NF-κB), and activator protein 1 (AP-1) to induce type 2 cytokines. ILC2s lack a TCR and respond instead to locally produced cytokines such as IL-33. Although IL-33 induces AP-1 and NF-κB, NFAT signaling has not been described in ILC2s. In this study, we report a nonredundant NFAT-dependent role for lipid-derived leukotrienes (LTs) in the activation of lung ILC2s. Using cytokine reporter and LT-deficient mice, we find that complete disruption of LT signaling markedly diminishes ILC2 activation and downstream responses during type 2 inflammation. Type 2 responses are equivalently attenuated in IL-33– and LT-deficient mice, and optimal ILC2 activation reflects potent synergy between these pathways. These findings expand our understanding of ILC2 regulation and may have important implications for the treatment of airways disease.

Aspirin-exacerbated respiratory disease: Prevalence, diagnosis, treatment, and considerations for the future

Aspirin-exacerbated respiratory disease (AERD) is a late onset condition characterized by the Samter triad (aspirin sensitivity [as well as sensitivity to any nonselective cyclooxygenase inhibitor], nasal polyps, asthma) and additional features, including eosinophilic chronic rhinosinusitis, hypereosinophilia, anosmia, frequent absence of atopy, and, intolerance to ingestion of red wine and other alcoholic beverages. The diagnosis is rare, and, because of this, it is also often missed by physicians. However, it is highly overexpressed in patients with severe asthma (and severe chronic rhinosinusitis with nasal polyps), which makes its recognition essential. For this review, we considered mechanisms involved in the pathogenesis of this disease and discussed the clinical symptoms of AERD. We also discussed the role of aspirin desensitization in the treatment of AERD. Also, we considered medications (e.g, leukotriene modifiers) and surgical interventions that have a role in the treatment of AERD.

Inundation of asthma target research: Untangling asthma riddles

Asthma is an inveterate inflammatory disorder, delineated by the airway inflammation, bronchial hyperresponsiveness (BHR) and airway wall remodeling. Although, asthma is a vague term, and is recognized as heterogenous entity encompassing different phenotypes. Targeting single mediator or receptor did not prove much clinical significant, as asthma is complex disease involving myriad inflammatory mediators. Asthma may probably involve a large number of different types of molecular and cellular components interacting through complex pathophysiological pathways. This review covers the past, present, and future therapeutic approaches and pathophysiological mechanisms of asthma. Furthermore, review describe importance of targeting several mediators/modulators and receptor antagonists involved in the physiopathology of asthma. Novel targets for asthma research include Galectins, Immunological targets, K ⁺ Channels, Kinases and Transcription Factors, Toll-like receptors, Selectins and Transient receptor potential channels. But recent developments in asthma research are very promising, these include Bitter taste receptors (TAS2R) abated airway obstruction in mouse model of asthma and Calcium-sensing receptor obliterate inflammation and in bronchial hyperresponsiveness allergic asthma. All these progresses in asthma targets, and asthma phenotypes exploration are auspicious in untangling of asthma riddles.

Eosinophils and Mast Cells in Aspirin-Exacerbated Respiratory Disease

Aspirin-exacerbated respiratory disease (AERD) involves overexpression of proinflammatory mediators, including 5-lipoxygenase and leukotriene C₄ synthase (LTC₄S), resulting in constitutive overproduction of cysteinyl leukotrienes. Mast cells and eosinophils have roles in mediating many of the observed effects. Increased levels of both interleukin-4 (IL-4) and interferon (IFN)-γ are present in the tissue of patients with AERD. Previous studies showed that IL-4 is primarily responsible for the upregulation of LTC₄S by mast cells. Our studies show that IFN-γ, but not IL-4, drives this process in eosinophils. This article examines the overall role that eosinophils and mast cells contribute to the pathophysiology of AERD.

Aspirin-exacerbated respiratory disease and current treatment modalities

Aspirin-exacerbated respiratory disease (AERD) refers to the combination of asthma, chronic rhinosinusitis with nasal polyposis, and acute upper and lower respiratory tract reactions to the ingestion of aspirin (acetylsalicylic acid, ASA) and other cyclooxygenase-1 inhibiting non-steroidal anti-inflammatory drugs. AERD affects 0.3-0.9 % of the general population. AERD generally occurs due to abnormalities in mediators and expression of arachidonic acid biosynthesis. Local IgE responses to staphylococcal enterotoxins may also be responsible for eosinophilic activation in the nasal polyp tissues of AERD patients. Clinical features of AERD include the onset of nasal congestion with anosmia, progressing to chronic pansinusitis and nasal polyps that regrow rapidly after surgery. Aspirin desensitization, Leukotriene-modifying agents, biologic agents, management of asthma, chronic rhinosinusitis, and nasal polyposis are recommended as treatment modalities. Immunotherapy is prescribed only to those AERD patients who experience clear seasonal or perennial allergy symptoms in addition to the symptoms attributable to chronic nasal polyposis. There are also investigational and dietary therapies. In this review, the important aspects of AERD will be presented, along with a literature survey.

Inhibition of 5-lipoxygenase suppresses vascular endothelial growth factor-induced angiogenesis in endothelial cells

5-Lipoxygenase (5-LOX) is an enzyme that converts arachidonic acid from the cell membrane into leukotriene, a signal lipid mediator. 5-LOX deficiency markedly attenuates the formation of aneurysms in knockout mice. In addition, Zileuton, a clinical drug targeting 5-LOX, is used for treatment of asthma. However, it is unclear whether 5-LOX inhibition results in anti-angiogenic effects for applications in cancer therapy. To explore the roles of 5-LOX in angiogenesis and its potential as a therapeutic target in cancer, the effects of a newly synthesized 5-LOX inhibitor, F3, on in vitro and in vivo angiogenesis were investigated. The results showed that 5-LOX inhibition by F3 suppressed in vitro vascular endothelial growth factor (VEGF)-induced tube formation and chemo-invasion of endothelial cells (ECs). 5-LOX inhibition also decreased VEGF-induced extracellular signal-regulated kinase (ERK) phosphorylation in ECs. Notably, 5-LOX knockdown phenocopied the anti-angiogenic activity of the 5-LOX inhibitor F3 in a concentration-dependent manner. F3 did not affect the activities of VEGF receptor 2 or AKT. In vivo, the compound significantly inhibited the formation of the chorioallantoic membrane at nontoxic doses. These results demonstrated that 5-LOX played an important role in angiogenesis and that its inhibitor F3 could be a new anti-angiogenic agent targeting VEGF signaling.

Contemporary management of chronic rhinosinusitis with nasal polyposis in aspirin-exacerbated respiratory disease: an evidence-based review with recommendations

BACKGROUND

Chronic rhinosinusitis (CRS) in aspirin-exacerbated respiratory disease (AERD) represents a recalcitrant form of sinonasal inflammation for which a multidisciplinary consensus on patient management has not been reached. Several medical interventions have been investigated, but a formal comprehensive evaluation of the evidence has never been performed. The purpose of this article is to provide an evidence-based approach for the multidisciplinary management of CRS in AERD.

METHODS

A systematic review of the literature was performed and the guidelines for development of an evidence-based review with recommendations were followed. Study inclusion criteria included: adult population >18 years old; CRS based on published diagnostic criteria, and a presumptive diagnosis of AERD. We focused on reporting higher-quality studies (level 2 or higher) when available, but reported lower-quality studies if the topic contained insufficient evidence. Treatment recommendations were based on American Academy of Otolaryngology (AAO) guidelines, with defined grades of evidence and evaluation of research quality and risk/benefits associated with each treatment.

RESULTS

This review identified and evaluated the literature on 3 treatment strategies for CRS in AERD: dietary salicylate avoidance, leukotriene modification, and desensitization with daily aspirin therapy.

CONCLUSION

Based on the available evidence, dietary salicylate avoidance and leukotriene-modifying drugs are options following appropriate treatment with nasal corticosteroids and saline irrigation. Desensitization with daily aspirin therapy is recommended following revision endoscopic sinus surgery (ESS).

Automated identification of an aspirin-exacerbated respiratory disease cohort

BACKGROUND

Aspirin-exacerbated respiratory disease (AERD) is characterized by 3 clinical features: asthma, nasal polyposis, and respiratory reactions to cyclooxygenase-1 inhibitors (nonsteroidal anti-inflammatory drugs). Electronic health records (EHRs) contain information on each feature of this triad.

OBJECTIVE

We sought to determine whether an informatics algorithm applied to the EHR could electronically identify patients with AERD.

METHODS

We developed an informatics algorithm to search the EHRs of patients aged 18 years and older from the Partners Healthcare system over a 10-year period (2004-2014). Charts with search terms for asthma, nasal polyps, and record of respiratory (cohort A) or unspecified (cohort B) reactions to nonsteroidal anti-inflammatory drugs were identified as "possible AERD." Two clinical experts reviewed all charts to confirm a diagnosis of "clinical AERD" and classify cases as "diagnosed AERD" or "undiagnosed AERD" on the basis of physician-documented AERD-specific terms in patient notes.

RESULTS

Our algorithm identified 731 "possible AERD" cases, of which 638 were not in our AERD patient registry. Chart review of cohorts A (n = 511) and B (n = 127) demonstrated a positive predictive value of 78.4% for "clinical AERD," which rose to 88.7% when unspecified reactions were excluded. Of those with clinical AERD, 12.4% had no mention of AERD by any treating caregiver and were classified as "undiagnosed AERD." "Undiagnosed AERD" cases were less likely than "diagnosed AERD" cases to have been seen by an allergist/immunologist (38.7% vs 93.2%; P < .0001).

CONCLUSIONS

An informatics algorithm can successfully identify both known and previously undiagnosed cases of AERD with a high positive predictive value. Involvement of an allergist/immunologist significantly increases the likelihood of an AERD diagnosis.

Eosinophil production of prostaglandin D2 in patients with aspirin-exacerbated respiratory disease

BACKGROUND

Aspirin-exacerbated respiratory disease (AERD) differs from aspirin-tolerant disease in part because of eosinophilic tissue infiltration and overexpression of arachidonic acid metabolic pathway components that lead to enhanced secretion of cysteinyl leukotrienes and prostaglandin (PG) D₂ observed constitutively and paradoxically in response to aspirin and other COX inhibitors. We have previously demonstrated the capacity of IFN-γ to drive cysteinyl leukotriene expression and response.

OBJECTIVE

We investigated eosinophils as a source of PGD₂ production in patients with AERD.

METHODS

Eosinophils were enriched from tissue and peripheral blood obtained from control subjects, patients with aspirin-tolerant disease, and patients with AERD. mRNA was extracted and evaluated for expression of hematopoietic prostaglandin D synthase (hPGDS). Expression of hPGDS protein was confirmed with Western hybridization and immunofluorescence staining. Cells were stimulated with aspirin, and secretion of PGD₂ was quantified. CD34⁺ progenitor cells were isolated and matured into eosinophils in the presence or absence of IFN-γ and hPGDS mRNA, and PGD₂ release was measured.

RESULTS

Gene expression analysis revealed that eosinophils from tissue and blood of patients with AERD display increased levels of hPGDS compared with asthmatic and control samples. Western hybridization confirmed the increase in hPGDS mRNA translated to increased protein expression. Immunofluorescence confirmed mast cells and eosinophils from tissue of patients with AERD and asthma demonstrated hPGDS expression, with higher levels in eosinophils from patients with AERD. Incubation of eosinophils from blood and tissue with aspirin stimulated PGD₂ release. IFN-γ-matured eosinophil progenitors showed enhanced hPGDS expression and increased levels of PGD₂ release at baseline and after aspirin stimulation.

CONCLUSIONS

In addition to mast cells, eosinophils represent an important source of PGD₂ in patients with AERD and identify a new target for therapeutic intervention.

Pathogenesis of eosinophilic chronic rhinosinusitis

Eosinophilic chronic rhinosinusitis (ECRS) is considered a refractory and intractable disease. Patients with ECRS present with thick mucus production, long-term nasal congestion, loss of sense of smell, and intermittent acute exacerbations secondary to bacterial infections. Despite medical and surgical interventions, there is a high rate of recurrence with significant impairment to quality of life. The recent increasing prevalence of ECRS in south Asian countries and the strong tendency of ECRS to reoccur after surgery should be considered. The majority of cases need repeat surgery, and histological examinations of these cases show eosinophilic-dominant inflammation. The degradation and accumulation of eosinophils, release of cytokines, and mucus secretion have important roles in the pathogenesis of ECRS. ECRS differs from non-ECRS, in which eosinophils are not involved in the pathogenesis of the disease, and also in terms of many clinical characteristics, blood examination and nasal polyp histological findings, clinical features of the disease after surgery, efficacy of medications, and computed tomography findings. This review describes the clinical course, diagnosis, and treatment of ECRS as well as its pathophysiology and the role of eosinophils, mucus, cytokines, and other mediators in the pathogenesis of ECRS.

Aspirin-exacerbated respiratory disease: pathophysiological insights and clinical advances

Asthma and chronic rhinosinusitis are heterogeneous airway diseases of the lower and upper airways, respectively. Molecular and cellular studies indicate that these diseases can be categorized into unique endotypes, which have therapeutic implications. One such endotype is aspirin-exacerbated respiratory disease (AERD), which encompasses the triad of asthma, aspirin (or nonsteroidal anti-inflammatory drug) hypersensitivity, and nasal polyposis. AERD has unique pathophysiological features that distinguish it from aspirin-tolerant asthma and other forms of chronic rhinosinusitis. This review details molecular and cellular features of AERD and highlights current and future therapies that are based on these insights.

Dynamic model of eicosanoid production with special reference to non-steroidal anti-inflammatory drug-triggered hypersensitivity

The authors developed a mathematical model of arachidonic acid (AA) degradation to prostaglandins (PGs) and leukotrienes (LTs), which are implicated in the processes of inflammation and hypersensitivity to non-steroidal anti-inflammatory drugs (NSAIDs). The model focuses on two PGs (PGE2 and PGD2) and one LT (LTC4), their % increases and their ratios. Results are compared with experimental studies obtained from non-asthmatics (NAs), and asthmatics tolerant (ATA) or intolerant (AIA) to aspirin. Simulations are carried out for predefined model populations NA, ATA and three AIA, based on the differences of two enzymes, PG E synthase and/or LTC4-synthase in two states, that is, no-inflammation and inflammation. Their model reveals that the model population with concomitant malfunctions in both enzymes is the most sensitive to NSAIDs, since the duration and the capacity for bronchoconstriction risk are highest after simulated oral dosing of indomethacin. Furthermore, inflammation prolongs the duration of the bronchoconstriction risk in all AIA model populations, and the sensitivity analysis reveals multiple possible scenarios leading to hypersensitivity, especially if inflammatory processes affect the expression of multiple enzymes of the AA metabolic pathway. Their model estimates the expected fold-changes in enzyme activities and gives valuable information for further targeted transcriptomic/proteomic and metabolomic studies.

Hypersensitivity to Aspirin and other NSAIDs: Diagnostic Approach in Patients with Chronic Rhinosinusitis

Hypersensitivity to nonsteroidal anti-inflammatory drugs (NSAIDs) associated with chronic rhinosinusitis (CRS) and/or asthma comprises a distinct clinical syndrome referred to as NSAIDs exacerbated respiratory disease (NERD). Patients with NERD tend to have more severe course of both upper (CRS and nasal polyps) and lower airway (asthma) diseases and are usually recalcitrant to conventional treatment modalities. Diagnosing and phenotyping of patients with NERD are critical for prevention of drug-induced adverse reactions and open novel options for management of underlying chronic airway inflammatory diseases. Diagnosis of NERD is based on detailed clinical history confirmed by challenge with aspirin, but new diagnostic approaches are currently being developed. This review article focuses on the diagnostic approach to a patient with CRS and hypersensitivity to NSAIDs, emphasizing the importance of diagnosis for proper patient's management.

Managing severe asthma in adults: lessons from the ERS/ATS guidelines

PURPOSE OF REVIEW

To review the latest guidelines on severe asthma.

RECENT FINDINGS

An updated definition of severe asthma is provided together with the evaluation steps necessary to reach a diagnosis of severe asthma. The importance of phenotyping is emphasized, and recommendations are provided for therapies specifically directed for severe asthma.

SUMMARY

Severe asthma is widely recognized as a major unmet need. It is defined as asthma that requires treatment with high-dose inhaled corticosteroids and a second controller and/or systemic corticosteroid to prevent it from becoming 'uncontrolled' or that remains 'uncontrolled' despite this therapy. Severe asthma is a heterogeneous condition that consists of phenotypes such as eosinophilic asthma. More phenotypes need to be defined. Evaluation of the patient referred to as having severe or difficult-to-control asthma must take into account adherence to treatment, comorbidities and associated factors including side effects from therapies. These need to be addressed. Recommendations on the use of sputum eosinophil count and exhaled nitric oxide to guide therapy are presented. Treatment with anti-IgE antibody, methotrexate, macrolide antibiotics, antifungal agents and bronchial thermoplasty is reviewed and recommendations made. Research efforts into phenotyping of severe asthma will provide both biomarker-driven approaches and newer effective therapies to severe asthma management.

Dipeptidyl-peptidase 10 as a genetic biomarker for the aspirin-exacerbated respiratory disease phenotype

BACKGROUND

Aspirin-exacerbated respiratory disease (AERD) is an endotype of severe and eosinophilic adult asthma characterized by chronic rhinosinusitis with nasal polyps and hypersensitivity to aspirin and/or nonsteroidal anti-inflammatory drugs. A genetic contribution of dipeptidyl-peptidase 10 (DPP10) to asthma susceptibility and lung function decline has been reported. However, little is known about the role of DPP10 in the pathogenesis of AERD.

OBJECTIVE

To identify genetic variants of DPP10 that confer susceptibility to AERD or severe asthma.

METHODS

A case-control association study of DPP10 gene polymorphisms was performed in 3 groups of patients: 274 with AERD, 272 with aspirin-tolerant asthma, and 99 normal healthy controls. The rs17048175 single-nucleotide polymorphism was targeted based on a preliminary genomewide association study using an Affymetrix genomewide human single-nucleotide polymorphism array in a Korean population. DPP10, 15-hydroxyeicosatetraenoic acid, and YKL-40/chitinase-3-like protein were measured by enzyme-linked immunosorbent assay in sera taken from the study subjects.

RESULTS

There was a significant association between rs17048175 and the AERD phenotype, but not with aspirin-tolerant asthma. The DPP10 level was significantly higher in sera from patients with AERD compared with patients with aspirin-tolerant asthma and control subjects (P = .021 and P < .001, respectively). In addition, there was a significant difference of serum DPP10 level according to the single-nucleotide polymorphism (P = .001). Serum DPP10 level showed a strong correlation with 15-hydroxyeicosatetraenoic acid (r = 0.226, P = .017) and YKL-40 (r = 0.364, P = .004).

CONCLUSION

This study suggests a genetic contribution of rs17048175 to DPP10 in eosinophilic inflammation induction in the airways and to AERD susceptibility.

The role of leukotrienes in allergic diseases

Leukotrienes (LTs), both LTB4 and the cysteinyl LTs (CysLTs) LTC4, LTD4 and LTE4, are implicated in a wide variety of inflammatory disorders. These lipid mediators are generated from arachidonic acid via multistep enzymatic reactions through which arachidonic acid is liberated from membrane phospholipids through the action of phospholipase A2. LTB4 and CysLTs exert their biological effects by binding to cognate receptors, which belong to the G protein-coupled receptor superfamily. LTB4 is widely considered to be a potent chemoattractant for most subsets of leukocytes, whereas CysLTs are potent bronchoconstrictors that have effects on airway remodeling. LTs play a central role in the pathogenesis of asthma and many other inflammatory diseases. This review will provide an update on the synthesis, biological function, and relevance of LTs to the pathobiology of allergic diseases, and examine the current and future therapeutic prospects of LT modifiers.

Prostanoids in allergy

Prostanoids, which include prostaglandin and thromboxane, are metabolites of arachidonic acid released in various pathophysiological conditions. They induce a range of actions mediated through their respective receptors expressed on target cells. It has been demonstrated that each prostanoid receptor has multiple functions and that the effect of receptor stimulation can vary depending on context; this sometimes results in opposing effects, such as simultaneous excitatory and inhibitory outcomes. The balance between the production of each prostanoid and the expression of its receptors has been shown to be important for maintaining homeostasis but also involved in the development of various pathological conditions such as allergy. Here, we review the recent findings on the roles of prostanoids in allergy, especially focusing on atopic dermatitis and asthma.

HLA and asthma phenotypes/endotypes: a review

Asthma is a complex chronic inflammatory disease of the airways caused by the interaction of genetic susceptibility with environmental influences. Genome-wide association studies (GWAS) represent the most powerful approach for asthma, that have identified several genes (e.g., IL18R1, IL33, SMAD3, ORMDL3, HLA-DQ and IL2RB loci). HLA super-locus is a genomic region in the chromosomal position 6p21. Since no gene can be considered as an asthma gene, able to reflect the complex etiology and the heterogeneity of the disease the terms 'phenotype' and more recently 'endotype' have been used. This review, according to literature availability, focuses on the relationship between human leukocyte antigens (HLA) region specifically the HLA class II genes and different asthma phenotypes/endotypes, such as allergic asthma/Th2 associated, occupational and aspirin-sensitive asthma. The most common HLA haplotypes in the different asthma phenotypes are HLA-DRB1in allergic asthma, HLA-DQB1in occupational asthma and HLA-DPB1 in aspirin-sensitive asthma. However, it is difficult to study the role of class II genes in vivo because of the heterogeneity of human population, the complexity of MHC, and the strong linkage disequilibrium among different class II genes. Despite the variation and the inconsistency of the HLA haplotypes and alleles in different types of asthma, the association between HLA class II genes and asthma has been demonstrated in the majority of studies.

Aspirin activation of eosinophils and mast cells: implications in the pathogenesis of aspirin-exacerbated respiratory disease

Reactions to aspirin and nonsteroidal anti-inflammatory drugs in patients with aspirin-exacerbated respiratory disease (AERD) are triggered when constraints upon activated eosinophils, normally supplied by PGE2, are removed secondary to cyclooxygenase-1 inhibition. However, the mechanism driving the concomitant cellular activation is unknown. We investigated the capacity of aspirin itself to provide this activation signal. Eosinophils were enriched from peripheral blood samples and activated with lysine ASA (LysASA). Parallel samples were stimulated with related nonsteroidal anti-inflammatory drugs. Activation was evaluated as Ca2+ flux, secretion of cysteinyl leukotrienes (CysLT), and eosinophil-derived neurotoxin (EDN) release. CD34+ progenitor-derived mast cells were also used to test the influence of aspirin on human mast cells with measurements of Ca2+ flux and PGD2 release. LysASA induced Ca2+ fluxes and EDN release, but not CysLT secretion from circulating eosinophils. There was no difference in the sensitivity or extent of activation between AERD and control subjects, and sodium salicylate was without effect. Like eosinophils, aspirin was able to activate human mast cells directly through Ca2+ flux and PGD2 release. AERD is associated with eosinophils maturing locally in a high IFN-γ milieu. As such, in additional studies, eosinophil progenitors were differentiated in the presence of IFN-γ prior to activation with aspirin. Eosinophils matured in the presence of IFN-γ displayed robust secretion of both EDN and CysLTs. These studies identify aspirin as the trigger of eosinophil and mast cell activation in AERD, acting in synergy with its ability to release cells from the anti-inflammatory constraints of PGE2.

Prostaglandin E2 resistance in granulocytes from patients with aspirin-exacerbated respiratory disease

BACKGROUND

Aspirin-exacerbated respiratory disease (AERD) is an inflammatory condition of the respiratory tract and is characterized by overproduction of leukotrienes (LT) and large numbers of circulating granulocyte-platelet complexes. LT production can be suppressed by prostaglandin E(2) (PGE(2)) and the cyclic AMP-dependent protein kinase A (PKA).

OBJECTIVE

To determine if PGE(2)-dependent control of LT production by granulocytes is dysregulated in AERD.

METHODS

Granulocytes from well-characterized patients with and without AERD were activated ex vivo and subjected to a range of functional and biochemical analyses.

RESULTS

Granulocytes from subjects with AERD generated more LTB4 and cysteinyl LTs than did granulocytes from controls with aspirin-tolerant asthma and controls without asthma. When compared with controls, granulocytes from subjects with AERD had comparable levels of EP(2) protein expression and PGE(2)-mediated cAMP accumulation, yet were resistant to PGE(2)-mediated suppression of LT generation. Percentages of platelet-adherent neutrophils correlated positively with LTB4 generation and inversely with responsiveness to PGE(2)-mediated suppression of LTB(4). The PKA inhibitor H89 potentiated LTB4 generation by control granulocytes but was inactive in granulocytes from individuals with AERD and had no effect on platelet P-selectin induction. Both tonic PKA activity and levels of PKA catalytic gamma subunit protein were significantly lower in granulocytes from individuals with AERD relative to those from controls.

CONCLUSIONS

Impaired granulocyte PKA function in AERD may lead to dysregulated control of 5-lipoxygenase activity by PGE(2), whereas adherent platelets lead to increased production of LTs, which contributes to the features of persistent respiratory tract inflammation and LT overproduction.

Cysteinyl leukotrienes and their receptors; emerging concepts

Cysteinyl leukotrienes (cys-LTs) are potent mediators of inflammation derived from arachidonic acid through the 5-lipoxygenase/leukotriene C4 synthase pathway. The derivation of their chemical structures and identification of their pharmacologic properties predated the cloning of their classical receptors and the development of drugs that modify their synthesis and actions. Recent studies have revealed unanticipated insights into the regulation of cys-LT synthesis, the function of the cys-LTs in innate and adaptive immunity and human disease, and the identification of a new receptor for the cys-LTs. This review highlights these studies and summarizes their potential pathobiologic and therapeutic implications.

Identifying asthma triggers

Asthma has many triggers including rhinosinusitis; allergy; irritants; medications (aspirin in aspirin-exacerbated respiratory disease); and obesity. Paradoxic vocal fold dysfunction mimics asthma and may be present along with asthma. This article reviews each of these triggers, outlining methods of recognizing the trigger and then its management. In many patients more than one trigger may be present. Full appreciation of the complexity of these relationships and targeted therapy to the trigger is needed to best care for the patient with asthma.

Management of asthma: the current US and European guidelines

Asthma management guidelines aim to improve the implementation of current knowledge into daily clinical practice by establishing a consensus of scientific practices for the management of asthma. Initial guidelines were based on consensus of expert opinion in order to employ a severity-based classification system as a guide to treatment. However, advances in asthma research led to the development of evidence-based guidelines and a major paradigm shift to control-based asthma management. Control-based management is central to the published guidelines developed by The National Heart, Lung, and Blood Institute (NHLBI), The Global Initiative for Asthma (GINA), and The British Thoracic Society (BTS), each one using the same volume of evidence but emphasizing aspects particular to their specific patient populations and socioeconomic needs. This chapter summarizes the evolution of these guidelines and summarizes the key points and evidence used in the recommendations for the assessment, monitoring, and management of asthma in all ages, with particular emphasis on the NHLBI guidelines.

Severe Asthma: The Evolution of Patient-directed Management

Severe asthma has been increasingly recognized as a heterogenous disease with varied clinical characteristics and pathophysiological processes. Patients with severe asthma suffer significant impairment in their daily life and impose a substantial burden on health care resources. The recent work of consortia groups has led to an improved definition of severe asthma as well as better characterization of the patients with severe disease. Different approaches, including unbiased cluster analyses, have been utilized to identify severe asthma phenotypes (subgroups) defined by their clinical characteristics and immune processes. Recognition of severe asthma phenotypes has assisted the development of targeted therapies by identifying patients more likely to respond to the specific agent. In this article, we discuss the evolution of our understanding of severe asthma and review the currently available therapies and promising drugs in development. In addition, we examine the role of bronchoscopy in severe asthma and the emerging evidence regarding bronchial thermoplasty.

Antileukotriene agents for the treatment of lung disease

Leukotrienes (LTs) C4, D4, and E4, collectively termed cysteinyl LTs (cysLTs), are lipid mediators formed by the 5-lipoxygenase (5-LO) pathway of arachidonic acid metabolism. Originally recognized for their potent bronchoconstrictor actions, they were subsequently determined also to promote inflammation, microvascular permeability, and mucus secretion. These actions that are so central to asthma pathophysiology are mediated to a significant extent by ligation of the cysLT receptor 1 (CysLT1). Antagonism of CysLT1 and inhibition of 5-LO have both been shown to have clinical use in the management of asthma, but substantial interindividual heterogeneity is observed in the response to these agents. In this article, we review the biologic actions of LTs, their biosynthetic pathways and cognate receptors, the pharmacology of available anti-LT agents, and the clinical evidence for the use of anti-LT agents as monotherapy and combination therapy in asthma. We also consider heterogeneity of response, the possible roles of cysLT receptors other than CysLT1, the role of another class of LT, LTB4, and the potential role of LTs in lung diseases other than asthma.

Stratified approaches to the treatment of asthma

While asthma is a chronic inflammatory disorder that is managed with inhaled controller and reliever drugs, there remains a large unmet need at the severe end of the disease spectrum. Here, a novel stratified approach to its treatment is reviewed, based upon identification of causal pathways, with a focus on biologics. A systematic search of the literature was made using Medline, and publications were selected on the basis of their relevance to the topic. Despite strong preclinical data for many of the more recently identified asthma targets, especially those relating to the T-helper 2 allergic pathway, clinical trials with specific biologics in moderate to severe asthma as a group have been disappointing. However, subgroup analyses based upon pathway-specific biomarkers suggest specific endotypes that are responsive. Application of hypothesis-free analytical approaches (the 'omics') to well-defined phenotypes is leading to the stratification of asthma along causal pathways. Refinement of this approach is likely to be the future for diagnosing and treating this group of diseases, as well as helping to define new causal pathways. The identification of responders and nonresponders to targeted asthma treatments provides a new way of looking at asthma diagnosis and management, especially with biologics that are costly. The identification of novel biomarkers linked to well-phenotyped patients provides a stratified approach to disease management beyond simple disease severity and involving causal pathways. In order to achieve this effectively, a closer interaction will be required between industry (therapeutic and diagnostic), academia and health workers.

Prostaglandin E2 deficiency causes a phenotype of aspirin sensitivity that depends on platelets and cysteinyl leukotrienes

Aspirin-exacerbated respiratory disease (AERD) is characterized by asthma, tissue eosinophilia, overproduction of cysteinyl leukotrienes (cysLTs), and respiratory reactions to nonselective cyclooxygenase (COX) inhibitors. Ex vivo studies suggest that functional abnormalities of the COX-2/microsomal prostaglandin (PG)E2 synthase-1 system may underlie AERD. We demonstrate that microsomal PGE2 synthase-1 null mice develop a remarkably AERD-like phenotype in a model of eosinophilic pulmonary inflammation. Lysine aspirin (Lys-ASA)-challenged PGE2 synthase-1 null mice exhibit sustained increases in airway resistance, along with lung mast cell (MC) activation and cysLT overproduction. A stable PGE2 analog and a selective E prostanoid (EP)2 receptor agonist blocked the responses to Lys-ASA by ∼90%; EP3 and EP4 agonists were also active. The increases in airway resistance and MC products were blocked by antagonists of the type 1 cysLT receptor or 5-lipoxygenase, implying that bronchoconstriction and MC activation were both cysLT dependent. Lys-ASA-induced cysLT generation and MC activation depended on platelet-adherent granulocytes and T-prostanoid (TP) receptors. Thus, lesions that impair the inducible generation of PGE2 remove control of platelet/granulocyte interactions and TP-receptor-dependent cysLT production, permitting MC activation in response to COX-1 inhibition. The findings suggest applications of antiplatelet drugs or TP receptor antagonists for the treatment of AERD.

Prominent role of IFN-γ in patients with aspirin-exacerbated respiratory disease

BACKGROUND

Aspirin-exacerbated respiratory disease (AERD) is distinguished from aspirin-tolerant asthma/chronic sinusitis in large part by an exuberant infiltration of eosinophils that are characterized by their overexpression of metabolic pathways that drive the constitutive and aspirin-induced secretion of cysteinyl leukotrienes (CysLTs).

OBJECTIVE

We defined the inflammatory milieu that in part drives CysLT overproduction and, in particular, the role of IFN-γ in the differentiation of eosinophils.

METHODS

Quantitative real-time PCR was performed for TH1 and TH2 signature cytokines on tissue from control subjects, patients with chronic hyperplastic eosinophilic sinusitis, and patients with AERD, and their cellular source was determined. The influence of IFN-γ on maturation, differentiation, and functionality of eosinophils derived from hematopoietic stem cells was determined.

RESULTS

Gene expression analysis revealed that tissue from both aspirin-tolerant subjects and patients with AERD display a TH2 cytokine signature; however, AERD was distinguished from chronic hyperplastic eosinophilic sinusitis by the prominent expression of IFN-γ. Intracellular and immunohistochemical cytokine staining revealed that the major sources of these cytokines were the eosinophils themselves. IFN-γ promoted the maturation of eosinophil progenitors, as measured by increased mRNA and surface expression of CCR3 and sialic acid-binding immunoglobulin-like lectin 8 (Siglec-8). Additionally, IFN-γ increased the expression of genes involved in leukotriene synthesis that led to increased secretion of CysLTs. IFN-γ-matured eosinophil progenitors were also primed, as demonstrated by their enhanced degranulation.

CONCLUSIONS

High IFN-γ levels distinguish AERD from aspirin-tolerant asthma and underlie the robust constitutive and aspirin-induced secretion of CysLTs that characterize this disorder.

Allergic rhinitis and chronic rhinosinusitis: their impact on lower airways

Anatomy, pathophysiology, epidemiology, and disease characteristics link the upper and lower airways. Nonspecific symptoms such as cough, congestion, shortness of breath, and recurrent infection may be related to the upper airway, lower airway, or both. Patients with the most severe disease often exhibit symptoms and findings of inflammation at both sites. Recent literature suggests that medical treatment and, when appropriate, surgical therapy directed at the upper airway can yield improvements in the lower airway. An understanding of the diagnosis and management of diseases at both sites will afford patients the best possible outcomes.

Immunomodulatory treatments for aspirin exacerbated respiratory disease

BACKGROUND

Aspirin triad is a subclass of chronic sinusitis characterized by nasal polyposis, nonallergic induced asthma, and aspirin sensitivity. Also known as Samter's triad or aspirin-exacerbated respiratory disease, aspirin triad commonly affects the adult population and is seldom found in pediatric patients.

METHODS

This rhinosinusitis has multiple layers of pathological process, but the ultimate predicament is caused by cysteinyl leukotrienes (cysLTs).

RESULTS

Pharmacotherapies include oral steroid, lipoxygenase inhibitor, and cysLT receptor inhibitor drugs, which can provide some relief for these patients.

CONCLUSION

Immunomodulation via aspirin desensitization is considered when pharmacotherapy has failed. When aspirin triad is unmanageable with medical treatment alone, endoscopic sinus surgery with polypectomy can alleviate the patient's symptoms, allowing for a better response to postoperative medical management such as topical medication as well as delivery of topical medications.

State of the art treatment of nasal polyposis

BACKGROUND

Nasal polyposis represents the end point of multiple inflammatory pathways and controversy continues as to the exact roles of medical and surgical approaches in the management of nasal polyposis.

METHODS

A combination of both is often required to manage polyps adequately with surgery and intranasal steroids remaining the mainstay of therapy.

RESULTS

Fortunately, new technological advances are making surgery safer and more efficient. In the postoperative period, debridement is effective in reducing the formation of adhesions, and topical medications may play a beneficial role in preventing polyp reformation.

CONCLUSION

Additional investigations into the optimal perioperative medical management is needed to ensure optimal surgical outcomes.