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Background: The 3 cysteinyl leukotrienes (cysLTs), leukotriene (LT) C 4 (LTC 4 ), LTD 4 , and LTE 4 , have different biologic half-lives, cellular targets, and receptor specificities. CysLT 2 R binds LTC 4 and LTD 4 in vitro with similar affinities, but it displays a marked selectivity for LTC 4 in vivo. LTC 4 , but not LTD 4 , strongly potentiates allergen-induced pulmonary eosinophilia in mice through a CysLT 2 R-mediated, platelet- and IL-33-dependent pathway., Objective: We sought to determine whether LTD 4 functionally antagonizes LTC 4 signaling at CysLT 2 R., Methods: We used 2 different in vivo models of CysLT 2 R-dependent immunopathology, as well as ex vivo activation of mouse and human platelets., Results: LTC 4 -induced CD62P expression; HMGB1 release; and secretions of thromboxane A 2 , CXCL7, and IL-33 by mouse platelets were all were blocked by a selective CysLT 2 R antagonist and inhibited by LTD 4 . These effects did not depend on CysLT 1 R. Inhaled LTD 4 blocked LTC 4 -mediated potentiation of ovalbumin-induced eosinophilic inflammation; recruitment of platelet-adherent eosinophils; and increases in IL-33, IL-4, IL-5, and IL-13 levels in lung tissue. In contrast, the effect of administration of LTE 4 , the preferred ligand for CysLT 3 R, was additive with LTC 4 . The administration of LTD 4 to Ptges -/- mice, which display enhanced LTC 4 synthesis similar to that in aspirin-exacerbated respiratory disease, completely blocked the physiologic response to subsequent lysine-aspirin inhalation challenges, as well as increases in levels of IL-33, type 2 cytokines, and biochemical markers of mast cell and platelet activation., Conclusion: The conversion of LTC 4 to LTD 4 may limit the duration and extent of potentially deleterious signaling through CysLT 2 R, and it may contribute to the therapeutic properties of desensitization to aspirin in aspirin-exacerbated respiratory disease., (Copyright © 2020 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.)

Mast cells (MCs) play an essential role in host defense, primarily because of their location, their ability to pathogen destruction via several mechanisms, and the pattern recognition receptors they express. Even though most data is available regarding MC activation by various bacteria- or virus-derived molecules, those cells' activity in response to constituents associated with fungi is not recognized enough. Our research aimed to address whether Saccharomyces cerevisiae-derived zymosan, i.e., β-(1,3)-glucan containing mannan particles, impacts MC activity aspects. Overall, the obtained results indicate that zymosan has the potential to elicit a pro-inflammatory response of rat peritoneal MCs. For the first time ever, we provided evidence that zymosan induces fully mature MC migration, even in the absence of extracellular matrix (ECM) proteins. Moreover, the zymosan-induced migratory response of MCs is almost entirely a result of directional migration, i.e., chemotaxis. We found that zymosan stimulates MCs to degranulate and generate lipid mediators (cysLTs), cytokines (IFN-α, IFN-β, IFN-γ, GM-CSF, TNF), and chemokine (CCL2). Zymosan also upregulated mRNA transcripts for several cytokines/chemokines with pro-inflammatory/immunoregulatory activity. Moreover, we documented that zymosan activates MCs to produce reactive oxygen species (ROS). Lastly, we established that the zymosan-induced MC response is mediated through activation of the Dectin-1 receptor. In general, our results strongly support the notion that MCs contribute to innate antifungal immunity and bring us closer to elucidate their role in host-pathogenic fungi interactions. Besides, provided findings on IgE-sensitized MCs appear to indicate that exposure to fungal zymosan could affect the severity of IgE-dependent disorders, including allergic ones.

Context: In nonallergic (naive) mice, type I cysteinyl-leukotriene receptors (CysLT 1 R) mediate the stimulatory effects of cytokines (eotaxin/CCL11, interleukin[IL] - 13), and nonsteroidal anti-inflammatory drugs (NSAID; indomethacin, aspirin) on eosinophil production by IL-5-stimulated bone-marrow. In ovalbumin (OVA)-sensitized mice, airway challenge-induced bone-marrow eosinophilia and eosinopoiesis are prevented by pretreatment with blockers of adrenal glucocorticoid signaling (RU486, metyrapone) or cysteinyl-leukotriene (CysLT) signaling (montelukast). Objective: To define whether allergen challenge modifies subsequent bone-marrow responses to CysLT, NSAID, and cytokines which act through type 1 CysLT receptor (CysLT 1 R). Methods: We examined the effects of sensitization/challenge, and of in vivo blockade of endogenous glucocorticoid or CysLT signaling, on ex vivo responses to CysLT1R-dependent stimuli. Results and discussion: Challenge abolished the stimulatory ex vivo responses to CysLT 1 R-dependent agents in the eosinophil lineage. In cultured bone-marrow of naive, sensitized and sensitized/challenged mice, responses to leukotriene D 4 (LTD 4 ) in eosinophil differentiation ex vivo shifted from stimulatory (without challenge) to suppressive (following challenge). Both stimulatory and suppressive LTD 4 effects were blocked by montelukast. The suppressive LTD 4 effect was accounted for by accelerated maturation followed by apoptosis of eosinophils. RU486/metyrapone or montelukast pretreatments before challenge prevented the challenge-induced change in subsequent responses to all these agents. Hence, allergen challenge has two separate effects on bone-marrow: (a) it enhances eosinopoiesis in vivo and upregulates ex vivo responses to IL-5; (b) it promotes a faster, but self-limiting, response to LTD 4 and CysLT1R-dependent stimuli. Conclusion: Allergen challenge modifies eosinopoiesis through systemic (glucocorticoid- and CysLT1R-dependent) mechanisms, increasing responses to IL-5 but restricting responses to subsequent CysLT1R stimulation.

The cysteinyl leukotrienes (cys-LTs), leukotriene C 4 , (LTC 4 ), LTD 4 , and LTE 4 , are lipid mediators of inflammation. LTC 4 is the only intracellularly synthesized cys-LT through the 5-lipoxygenase and LTC 4 synthase pathway and after transport is metabolized to LTD 4 and LTE 4 by specific extracellular peptidases. Each cys-LT has a preferred functional receptor in vivo; LTD 4 to the type 1 cys-LT receptor (CysLT 1 R), LTC 4 to CysLT 2 R, and LTE 4 to CysLT 3 R (OXGR1 or GPR99). Recent studies in mouse models revealed that there are multiple regulatory mechanisms for these receptor functions and each receptor plays a distinct role as observed in different mouse models of inflammation and immune responses. This review focuses on the integrated host responses to the cys-LT/CysLTR pathway composed of sequential ligands with preferred receptors as seen from mouse models. It also discusses potential therapeutic targets for LTC 4 synthase, CysLT 2 R, and CysLT 3 R., (© 2019 Elsevier Inc. All rights reserved.)

IL-33 and cysteinyl leukotrienes (cysLTs) are key components of asthma pathogenesis, and both contribute to the initiation and maintenance of the type 2 inflammatory environment. However, little is known about the potential interactions between the two mediators. In this work, we aimed at studying the regulation of expression of the cysLT receptors CysLT1 and CysLT2 by IL-33 in human PBLs. Our results show that the IL-33/ST2L axis increases CysLT1 but not CysLT2 expression in a concentration- and time-dependent manner in PBLs. IL-33-induced CysLT1 upregulation was observed at the protein but not at the mRNA level and was accompanied by an increase in LTD 4 -induced calcium mobilization and migration of CD4 + T lymphocytes. We also show that purified naive CD4 + T lymphocytes expressed ST2L and responded to IL-33 in the absence of Ag or TCR stimulation, suggesting a mechanism independent of Ag presentation. These results contribute to expanding our knowledge in the field of IL-33 by proposing a new mode of action of the cytokine on T cells and by extending its role to the regulation of naive T cell trafficking, therefore reinforcing its interest as a potential therapeutic target for the treatment of asthma., (Copyright © 2018 by The American Association of Immunologists, Inc.)

Respiratory epithelial cells (EpCs) orchestrate airway mucosal inflammation in response to diverse environmental stimuli, but how distinct EpC programs are regulated remains poorly understood. Here, we report that inhalation of aeroallergens leads to expansion of airway brush cells (BrCs), specialized chemosensory EpCs and the dominant epithelial source of interleukin-25 (IL-25). BrC expansion was attenuated in mice lacking either LTC 4 synthase, the biosynthetic enzyme required for cysteinyl leukotriene (CysLT) generation, or the EpC receptor for leukotriene E 4 (LTE 4 ), CysLT 3 R. LTE 4 inhalation was sufficient to elicit CysLT 3 R-dependent BrC expansion in the murine airway through an IL-25-dependent but STAT6-independent signaling pathway. Last, blockade of IL-25 attenuated both aeroallergen and LTE 4 -elicited CysLT 3 R-dependent type 2 lung inflammation. These results demonstrate that CysLT 3 R senses the endogenously generated lipid ligand LTE 4 and regulates airway BrC number and function., (Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

Background: Viral respiratory tract infections increase the risk of development and exacerbation of atopic disease. Previously, we demonstrated the requirement for a neutrophil (PMN) subset expressing CD49d to drive development of postviral atopic airway disease in mice., Objective: We sought to determine whether human CD49d + PMNs are present in the nasal mucosa during acute viral respiratory tract infections and further characterize this PMN subset in human subjects and mice., Methods: Sixty subjects (5-50 years old) were enrolled within 4 days of acute onset of upper respiratory symptoms. Nasal lavage for flow cytometry and nasal swabs for viral PCR were performed at enrollment and during convalescence. The Sendai virus mouse model was used to investigate the phenotype and functional relevance of CD49d + PMNs., Results: CD49d + PMN frequency was significantly higher in nasal lavage fluid during acute respiratory symptoms in all subjects (2.9% vs 1.0%, n = 42, P < .001). In mice CD49d + PMNs represented a "proatopic" neutrophil subset that expressed cysteinyl leukotriene receptor 1 (CysLTR1) and produced TNF, CCL2, and CCL5. Inhibition of CysLTR1 signaling in the first days of a viral respiratory tract infection was sufficient to reduce accumulation of CD49d + PMNs in the lungs and development of postviral atopic airway disease. Similar to the mouse, human CD49d + PMNs isolated from nasal lavage fluid during a viral respiratory tract infection expressed CysLTR1., Conclusion: CD49d and CysLTR1-coexpressing PMNs are present during symptoms of an acute viral respiratory tract infection in human subjects. Further study is needed to examine selective targeting of proatopic neutrophils as a potential therapeutic strategy to prevent development of postviral atopic airway disease., (Copyright © 2017 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.)

Cysteinyl leukotrienes (cysLTs) facilitate mucosal type 2 immunopathology by incompletely understood mechanisms. Aspirin-exacerbated respiratory disease, a severe asthma subtype, is characterized by exaggerated eosinophilic respiratory inflammation and reactions to aspirin, each involving the marked overproduction of cysLTs. Here we demonstrate that the type 2 cysLT receptor (CysLT 2 R), which is not targeted by available drugs, is required in two different models to amplify eosinophilic airway inflammation via induced expression of IL-33 by lung epithelial cells. Endogenously generated cysLTs induced eosinophilia and expanded group 2 innate lymphoid cells (ILC2s) in aspirin-exacerbated respiratory disease-like Ptges -/- mice. These responses were mitigated by deletions of either Cysltr2 or leukotriene C 4 synthase ( Ltc4s ). Administrations of either LTC 4 (the parent cysLT) or the selective CysLT 2 R agonist N-methyl LTC 4 to allergen sensitized wild-type mice markedly boosted ILC2 expansion and IL-5/IL-13 generation in a CysLT 2 R-dependent manner. Expansion of ILC2s and IL-5/IL-13 generation reflected CysLT 2 R-dependent production of IL-33 by alveolar type 2 cells, which engaged in a bilateral feed-forward loop with ILC2s. Deletion of Cysltr1 blunted LTC 4 -induced ILC2 expansion and eosinophilia but did not alter IL-33 induction. Pharmacological blockade of CysLT 2 R prior to inhalation challenge of Ptges -/- mice with aspirin blocked IL-33-dependent mast cell activation, mediator release, and changes in lung function. Thus, CysLT 2 R signaling, IL-33-dependent ILC2 expansion, and IL-33-driven mast cell activation are necessary for induction of type 2 immunopathology and aspirin sensitivity. CysLT 2 R-targeted drugs may interrupt these processes., (Copyright © 2018 by The American Association of Immunologists, Inc.)

Tyrosine kinase inhibitors targeting the BCR-ABL oncoprotein in chronic myeloid leukemia (CML) are remarkably effective inducing deep molecular remission in most patients. However, they are less effective to eradicate the leukemic stem cells (LSC), resulting in disease persistence. Therefore, there is great need to develop novel therapeutic strategies to specifically target the LSC. In an experimental mouse CML model system, the leukotriene pathway, and specifically, the expression ALOX5, encoding 5-lipoxygenase (5-LO), has been reported as a critical regulator of the LSC. Based on these results, the 5-LO inhibitor zileuton has been introduced in clinical trials as a therapeutic option to target the LSC although its effect on primary human CML LSC has not been studied. We have here by using multiplex single cell PCR analyzed the expression of the mediators of the leukotriene pathway in bone marrow (BM) BCR-ABL + CD34 + CD38 - cells at diagnosis, and found low or undetectable expression of ALOX5. In line with this, zileuton did not exert significant overall growth inhibition in the long-term culture-initiating cell (LTC-IC) and colony (CFU-C) assays of BM CD34 + CD38 - cells from 7 CML patients. The majority of the single leukemic BCR-ABL + CD34 + CD38 - cells expressed cysteinyl leukotriene receptors CYSLT1 and CYSLT2. However, montelukast, an inhibitor of CYSLT1, also failed to significantly suppress CFU-C and LTC-IC growth. These findings indicate that targeting ALOX5 or CYSLT1 signaling with leukotriene antagonists, introduced into the clinical practice primarily as prophylaxis and treatment for asthma, may not be a promising pharmacological strategy to eradicate persisting LSC in CML patients., (Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.)

Asthma is a complex disease that is promoted by dysregulated immunity and the presence of many cytokine and lipid mediators. Despite this, there is a paucity of data demonstrating the combined effects of multiple mediators in asthma pathogenesis. Group 2 innate lymphoid cells (ILC2s) have recently been shown to play important roles in the initiation of allergic inflammation; however, it is unclear whether lipid mediators, such as cysteinyl leukotrienes (CysLTs), which are present in asthma, could further amplify the effects of IL-33 on ILC2 activation and lung inflammation. In this article, we show that airway challenges with the parent CysLT, leukotriene C4 (LTC4), given in combination with low-dose IL-33 to naive wild-type mice, led to synergistic increases in airway Th2 cytokines, eosinophilia, and peribronchial inflammation compared with IL-33 alone. Further, the numbers of proliferating and cytokine-producing lung ILC2s were increased after challenge with both LTC4 and IL-33. Levels of CysLT1R, CysLT2R, and candidate leukotriene E4 receptor P2Y12 mRNAs were increased in ILC2s. The synergistic effect of LTC4 with IL-33 was completely dependent upon CysLT1R, because CysLT1R -/- mice, but not CysLT2R -/- mice, had abrogated responses. Further, CysLTs directly potentiated IL-5 and IL-13 production from purified ILC2s stimulated with IL-33 and resulted in NFAT1 nuclear translocation. Finally, CysLT1R -/- mice had reduced lung eosinophils and ILC2 responses after exposure to the fungal allergen Alternaria alternata Thus, CysLT1R promotes LTC4- and Alternaria -induced ILC2 activation and lung inflammation. These findings suggest that multiple pathways likely exist in asthma to activate ILC2s and propagate inflammatory responses., (Copyright © 2017 by The American Association of Immunologists, Inc.)

Asian dust (AD) can aggravate airway inflammation in asthma, but the association between AD and the development of asthma remains unclear. This study aimed to investigate the effects of AD on the early stage of antigen sensitization using a mouse model of asthma, as well as the role of leukotrienes (LTs) in antigen-induced airway inflammation potentiated by AD particles. NC/Nga mice were co-sensitized by intranasal instillation of AD particles and/or Dermatophagoides farinae (Df) for five consecutive days. Df-sensitized mice were stimulated with an intranasal Df challenge at seven days. Mice were treated with the type 1 cysteinyl LT (CysLT₁) receptor antagonist orally 4 h before and 1 h after the allergen challenge. At 24 h post-challenge, the differential leukocyte count, inflammatory cytokines, and LTs in bronchoalveolar lavage fluid were assessed, and airway inflammation was evaluated histopathologically. AD augmented neutrophilic and eosinophilic airway inflammation with increased CysLTs and dihydroxy-LT in a mouse model of asthma. The CysLT₁ receptor antagonist was shown to attenuate both neutrophilic and eosinophilic airway inflammation augmented by AD. Therefore, exposure to AD may be associated with the development of asthma and LTs may play important roles in airway inflammation augmented by AD., Competing Interests: The authors declare no conflict of interest.

Unlabelled: Backgroud: It has already been reported that the prophylactic treatment by leukotoriene receptor antagonists is more effective on reducing symptoms of Japanese cedar pollinosis than the authentic treatment after the pollen dispersal. However, the treatment above has never evaluated in children cases around school age in ENT out-patient clinic. This study about the prophylactic treatment was planned to focus on the effect in the generation of pre- and post-elementary school entrance., Methods: Children of pre- and post-elementary school entrance were enrolled for this study. This study was achieved in seasons of Japanese cedar pollinosis both in 2013 and 2014, and was designed as the comparison of clinical symptoms and quality of life in between two such groups as one group with the prophylactic treatment and another with the authentic treatment., Results: Efficacy of prophylactic treatment by leukotoriene receptor antagonists was elucidated as follows; quality of sleep was significantly better both in 2013 and 2014, and more kinds of clinical symptoms or quality of life impairments were significantly more suppressed than in the group with the authentic treatment in 2014 when less pollen was dispersed., Conclusion: Even in the children of pre- and post-elementary school entrance, the prophylactic treatment by leukotoriene receptor antagonists is more effective on reducing symptoms of Japanese cedar pollinosis than the authentic treatment.

Background: Although arachidonic acid metabolites, cysteinyl leukotrienes (cys-LTs; leukotriene [LT] C4, LTD4, and LTE4), and prostaglandin (PG) E2 are generated at the site of inflammation, it is not known whether crosstalk exists between these 2 classes of inflammatory mediators., Objective: We sought to determine the role of LTD4-PGE2 crosstalk in inducing vascular inflammation in vivo, identify effector cells, and ascertain specific receptors and pathways involved in vitro., Methods: Vascular (ear) inflammation was assessed by injecting agonists into mouse ears, followed by measuring ear thickness and histology, calcium influx with Fura-2, phosphorylation and expression of signaling molecules by means of immunoblotting, PGD2 and macrophage inflammatory protein 1β generation by using ELISA, and expression of transcripts by using RT-PCR. Candidate receptors and signaling molecules were identified by using antagonists and inhibitors and confirmed by using small interfering RNA., Results: LTD4 plus PGE2 potentiated vascular permeability and edema, gearing the system toward proinflammation in wild-type mice but not in Kit(W-sh) mice. Furthermore, LTD4 plus PGE2, through cysteinyl leukotriene receptor 1 (CysLT1R) and E-prostanoid receptor (EP) 3, enhanced extracellular signal-regulated kinase (Erk) and c-fos phosphorylation, inflammatory gene expression, macrophage inflammatory protein 1β secretion, COX-2 upregulation, and PGD2 generation in mast cells. Additionally, we uncovered that this synergism is mediated through Gi, protein kinase G, and Erk signaling. LTD4 plus PGE2-potentiated effects are partially sensitive to CysLT1R or EP3 antagonists but completely abolished by simultaneous treatment both in vitro and in vivo., Conclusions: Our results unravel a unique LTD4-PGE2 interaction affecting mast cells through CysLT1R and EP3 involving Gi, protein kinase G, and Erk and contributing to vascular inflammation in vivo. Furthermore, current results also suggest an advantage of targeting both CysLT1R and EP3 in attenuating inflammation., (Copyright © 2015 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.)

Aspirin-exacerbated respiratory disease (AERD) is a chronic inflammatory disease characterized clinically by the triad of asthma, nasal polyposis, and pathognomonic respiratory reactions after ingestion of aspirin. It is a distinct syndrome associated with eosinophilic infiltration of respiratory tissues and excessive production of cysteinyl leukotrienes. Despite the consistent clinical phenotype of the respiratory disease, the underlying pathogenesis of the disease remains unclear. In addition to their role in hemostasis, platelets have the capacity to influence the activation state and function of other immune cells during inflammation and to facilitate granulocyte recruitment into the tissues. Platelets also possess a repertoire of potent preformed mediators of inflammation that are released on activation and are a rich source of newly synthesized lipid mediators that alter vascular permeability and smooth muscle tone. Accordingly, platelet activity has been linked to diverse inflammatory diseases, including asthma. Both human and animal studies strongly suggest that platelet activity is uniquely associated with the pathophysiology of AERD. This article summarizes the evidence supporting an effector role for platelets in asthmatic patients in general and in patients with AERD in particular and considers the potential therapeutic implications., (Copyright © 2015 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.)

Cysteinyl leukotrienes (cysLTs) are cell membrane-impermeant lipid mediators that play major roles in the pathogenesis of eosinophilic inflammation and are recognized to act via at least 2 receptors, namely, cysLT1 receptor (cysLT1R) and cysLT2 receptor (cysLT2R). Eosinophils, which are granulocytes classically associated with host defense against parasitic helminthes and allergic conditions, are distinguished from leukocytes by their dominant population of cytoplasmic crystalloid (also termed secretory, specific, or secondary) granules that contain robust stores of diverse preformed proteins. Human eosinophils are the main source of cysLTs and are recognized to express both cysLTs receptors (cysLTRs) on their surface, at the plasma membrane. More recently, we identified the expression of cysLTRs in eosinophil granule membranes and demonstrated that cysLTs, acting via their granule membrane-expressed receptors, elicit secretion from cell-free human eosinophil granules. Herein, we review the multifaceted roles of cysLTs in eliciting eosinophil granule protein secretion. We discuss the intracrine and autocrine/paracrine secretory responses evoked by cysLTs in eosinophils and in cell-free extracellular eosinophil crystalloid granules. We also discuss the importance of this finding in eosinophil immunobiology and speculate on its potential role(s) in eosinophilic diseases.

This study aimed at establishing the immunological signature and an algorithm for clinical management of the different clinical stages of the HTLV-1-infection based on serum biomarkers. A panel of serum biomarkers was evaluated by four sets of innovative/non-conventional data analysis approaches in samples from 87 HTLV-1 patients: asymptomatic carriers (AC), putative HTLV-1 associated myelopathy/tropical spastic paraparesis (pHAM/TSP) and HAM/TSP. The analysis of cumulative curves and molecular signatures pointed out that HAM/TSP presented a pro-inflammatory profile mediated by CXCL10/LTB-4/IL-6/TNF-α/IFN-γ, counterbalanced by IL-4/IL-10. The analysis of biomarker networks showed that AC presented a strongly intertwined pro-inflammatory/regulatory net with IL-4/IL-10 playing a central role, while HAM/TSP exhibited overall immune response toward a predominant pro-inflammatory profile. At last, the classification and regression trees proposed for clinical practice allowed for the construction of an algorithm to discriminate AC, pHAM and HAM/TSP patients with the elected biomarkers: IFN-γ, TNF-α, IL-10, IL-6, IL-4 and CysLT. These findings reveal a complex interaction among chemokine/leukotriene/cytokine in HTLV-1 infection and suggest the use of the selected but combined biomarkers for the follow-up/diagnosis of disease morbidity of HTLV-1-infected individuals.

Cysteinyl leukotrienes (cysLTs) are produced predominantly by cells of the innate immune system, especially basophils, eosinophils, mast cells, and monocytes/macrophages. Notwithstanding potent bronchoconstrictor activity, cysLTs are also proinflammatory consequent to their autocrine and paracrine interactions with G-protein-coupled receptors expressed not only on the aforementioned cell types, but also on Th2 lymphocytes, as well as structural cells, and to a lesser extent neutrophils and CD8(+) cells. Recognition of the involvement of cysLTs in the immunopathogenesis of various types of acute and chronic inflammatory disorders, especially bronchial asthma, prompted the development of selective cysLT receptor-1 (cysLTR1) antagonists, specifically montelukast, pranlukast, and zafirlukast. More recently these agents have also been reported to possess secondary anti-inflammatory activities, distinct from cysLTR1 antagonism, which appear to be particularly effective in targeting neutrophils and monocytes/macrophages. Underlying mechanisms include interference with cyclic nucleotide phosphodiesterases, 5'-lipoxygenase, and the proinflammatory transcription factor, nuclear factor kappa B. These and other secondary anti-inflammatory mechanisms of the commonly used cysLTR1 antagonists are the major focus of the current review, which also includes a comparison of the anti-inflammatory effects of montelukast, pranlukast, and zafirlukast on human neutrophils in vitro, as well as an overview of both the current clinical applications of these agents and potential future applications based on preclinical and early clinical studies.

Leukotrienes constitute a group of lipid mediators, which may be subdivided into two groups, with leukotriene B4 on the one hand and cysteinyl leukotrienes on the other. Although leukotrienes are abundantly expressed in skin affected by diverse chronic inflammatory diseases, including atopic dermatitis, psoriasis, pemphigus vulgaris and bullous pemphigoid, their pathological roles in these diseases have remained elusive. Recent data now reveal that both leukotriene B4 and cysteinyl leukotrienes are indispensable in the pathogenesis of atopic dermatitis, with leukotriene B4 initiating the recruitment of inflammatory cells, particularly neutrophils and TH 2 cells into the skin, and cysteinyl leukotrienes later inducing characteristic structural alterations of chronically affected skin, specifically skin fibrosis and keratinocyte proliferation. Thus, these results reveal a sequential cooperation of LTB4 and cysteinyl leukotrienes to initiate and perpetuate allergic skin inflammation. These new insights highlight leukotrienes as promising therapeutic targets in allergic skin inflammation and should encourage more research into the role of leukotrienes in other inflammatory skin diseases., (© 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Objective and Methods: Leukotrienes (LTs) including cysteinyl leukotrienes (CysLTs) and LTB4 are the most potent inflammatory lipid mediators and play a central role in the pathophysiology of asthma and other inflammatory diseases. These biological molecules mediate a plethora of contractile and inflammatory responses through specific interaction with distinct G protein-coupled receptors (GPCRs). The main objective of this review is to present an overview of the biological effects of CysLTs and their receptors, along with the current knowledge of mechanisms and role of LTs in the pathogenesis of asthma., Results: CysLTs including LTC4, LTD4 and LTE4 are ligands for CysLT1 and CysLT2 receptors, and LTB4 is the agonist for BLT1 and BLT2 receptors. The role of CysLT1 receptor is well established, and most of the pathophysiological effects of CysLTs in asthma are mediated by CysLT1 receptor. Several CysLT1 antagonists have been developed to date and are currently in clinical practice. Most common among them are classical CysLT1 receptor antagonists such as montelukast, zafirlukast, pranlukast, pobilukast, iralukast, cinalukast and MK571. The pharmacological role of CysLT2 receptor, however, is less defined and there is no specific antagonist available so far. The recent demonstration that mice lacking both known CysLT receptors exhibit full/augmented response to CysLT points to the existence of additional subtypes of CysLT receptors. LTB4, on the other hand, is another potent inflammatory leukotriene, which acts as a strong chemoattractant for neutrophils, but weaker for eosinophils. LTB4 is known to play an important role in the development of airway hyper-responsiveness in severe asthma. However there is no LTB4 antagonist available in clinic to date., Conclusion: This review gives a recent update on the LTs including their biosynthesis, biological effects and the role of anti-LTs in the treatment of asthma. It also discusses about the possible existence of additional subtypes of CysLT receptors.

Background: Phospholipases A2 (PLA2) hydrolyzes phospholipids, initiating the production of inflammatory lipid mediators. We have previously shown that in rats, sPLA2 and cPLA2 play opposing roles in the pathophysiology of ovalbumin (OVA)-induced experimental allergic bronchitis (OVA-EAB), an asthma model: Upon disease induction sPLA2 expression and production of the broncho-constricting CysLTs are elevated, whereas cPLA2 expression and the broncho-dilating PGE2 production are suppressed. These were reversed upon disease amelioration by treatment with an sPLA2 inhibitor. However, studies in mice reported the involvement of both sPLA2 and cPLA2 in EAB induction., Objectives: To examine the relevance of mouse and rat models to understanding asthma pathophysiology., Methods: OVA-EAB was induced in mice using the same methodology applied in rats. Disease and biochemical markers in mice were compared with those in rats., Results: As in rats, EAB in mice was associated with increased mRNA of sPLA2, specifically sPLA2gX, in the lungs, and production of the broncho-constricting eicosanoids CysLTs, PGD2 and TBX2 in bronchoalveolar lavage (BAL). In contrast, EAB in mice was associated also with elevated cPLA2 mRNA and PGE2 production. Yet, treatment with an sPLA2 inhibitor ameliorated the EAB concomitantly with reverting the expression of both cPLA2 and sPLA2, and eicosanoid production., Conclusions: In both mice and rats sPLA2 is pivotal in OVA-induced EAB. Yet, amelioration of asthma markers in mouse models, and human tissues, was observed also upon cPLA2 inhibition. It is plausible that airway conditions, involving multiple cell types and organs, require the combined action of more than one, essential, PLA2s.

Aim of the Study: Sceptridium ternatum Lyon (ST), a common Chinese herb, has been used in treatment of allergic asthma and whooping cough. In the present study, we investigated the Th1/Th2 ratio of peripheral blood and mRNA levels of leukotriene receptors after the treatment of ST in allergic asthma mouse model., Materials and Methods: Mouse asthma model was developed by ovalbumin (OVA) sensitization followed by the inhalation of aerosol allergen. Montelukast (10mg/kg), as a positive control drug, and ST were administrated six days before the OVA sensitization for ten days. Airway responsiveness was evaluated by the Medlab 12.0 biological signal processing system. The ratio of Th1/Th2 cells was determined by flow cytometry. The expression level of Cyslt1 was measured by PCR. Pathological changes of lung tissues were examined by H&E staining., Results: ST significantly reduced the airway responsiveness, elevated the ratio of Th1/Th2, and decreased Cyslt1 mRNA level in a dose-dependent manner. High-dose ST distinctly prevented the pathological changes of lung tissues., Conclusion: High-dose ST had the same efficacy as Montelukast in a mouse asthma model, and ST could be a potential anti-asthmatic agent., (© 2013 Elsevier Ireland Ltd. All rights reserved.)

Introduction: The lymphadenoid tissues in the upper airway are sparse and organized lympho-epithelial structures playing an important role against foreign pathogens, with the palatine tonsils being the major components of the lymphoid tissues contained in the Waldeyer's ring. Obstructive sleep apnea (OSA) has emerged as a very frequent condition in the pediatric age range that is associated with substantial neurobehavioral, cardiovascular and metabolic morbidities. Adenotonsillar hypertrophy is the major pathophysiological contributor to OSA occurrence in children., Areas Covered: Here, the authors provide a systematic review and summary of some of the known histological and pathological features of human lymphadenoid tissues and their fundamental immunological functions, provide insights into the pathophysiology of pediatric OSA, particularly focusing on inflammatory pathways and the available outcomes associated with targeting such pathways with compounds such as corticosteroids and leukotriene modifiers. Furthermore, they present findings from an unbiased approach to discovery of therapeutic targets and formulate constructs toward putative future interventional approaches for this highly prevalent condition., Expert Opinion: Surgical approaches for pediatric OSA may not be as effective as previously anticipated. Accordingly, expanded use of existing systemic or topical anti-inflammatory agents or development of novel compounds targeting selected immune cell populations underlying pathophysiological determinants of OSA is needed.

Background: Atopic asthma, the most common chronic disease affecting children and young adults, is a complex disorder with variable phenotypes. Cysteine leukotrienes (Cys-LTs) are powerful bronchoconstrictors and play a critical role in airway inflammation and remodeling that are characteristic of asthma., Objective: To investigate the association of ALOX5, LTC4S and CysLTR2 gene polymorphisms with atopic asthma in an Indian population., Methods: A total of 19 single nucleotide polymorphisms (SNPs) within these genes were genotyped in a family-based cohort (n = 239) and a case-control cohort (139 cases and 194 controls) followed by association analyses., Results: We found a significant association of the -1072G/A (rs3776944) SNP with atopic asthma in the family-based association analysis (p = 0.0004). These results were also replicated in the case-control cohort (p = 0.009). The allele A was negatively associated with atopic asthma. We also noted a significant association in the two-locus (rs3776944G/A and rs730012A/C) haplotypic analysis of this gene both in the family-based (p = 0.03) and the case-control (p = 0.02) analyses., Conclusion: This study supports the role of the LTC4S gene polymorphism in genetic susceptibility to atopic asthma in an Indian population., (Copyright © 2012 S. Karger AG, Basel.)

Background: Leukotrienes are potent inflammatory mediators which modulate immune responses and induce bronchoconstriction in susceptible individuals. Montelukast (MK) is a leukotriene receptor (CysLT1) antagonist that has been shown to prevent exacerbation of asthma. Considering the plethora of potential cellular targets for MK, specific mechanisms for its therapeutic action are still not fully understood. In vitro, we determined whether human dendritic cell function could be affected by leukotriene C(4) (LTC(4)) treatment and whether MK had potential in modulating this response. We also studied the effect of LTC(4) in the context of response to an airway virus (respiratory syncytial virus, RSV)., Methods: Human monocyte-derived dendritic cells (moDCs) exposed to LTC(4), MK, or both, were cocultured with autologous T cells, with or without RSV. The effects of LTC(4) and MK on cell function were determined by ELISA and proliferation assays., Results: Both moDCs and their precursors--monocytes--express LTC(4) receptor CysLT1, making them potential targets for MK. moDCs cultured with LTC(4) release the eosinophil chemoattractant RANTES (CCL5) and induce greater T cell proliferation. Both were blocked by the presence of MK. MK treatment, albeit anti-inflammatory, did not interfere with the moDC-dependent T cell-proliferative responses induced by RSV., Conclusions: LTC(4), chronically present in the airways of asthma patients, could induce an exaggerated inflammatory response to airway infection via dendritic cell activation, which would be prevented by MK. Our study provides additional insight into the mechanisms of action of this leukotriene receptor antagonist., (Copyright © 2012 S. Karger AG, Basel.)

Background: HLA Class II antibody-initiated activation of monocytes possessing the corresponding antigen is thought to participate in the pathogenesis of transfusion-related acute lung injury (TRALI). Pulmonary edema, a hallmark of TRALI, is caused by increasing vascular permeability., Study Design and Methods: To investigate the contribution of HLA Class II antibody and monocytes to the development of pulmonary edema in TRALI, we studied whether the permeability of human lung microvascular endothelial cells (HMVECs) could be enhanced by coculturing HMVECs with peripheral blood mononuclear cells (PBMNCs) in the presence of HLA Class II antibody-containing plasma, which was implicated in TRALI (anti-HLA-DR plasma). In addition, similar experiments were performed with human umbilical vein endothelial cells (HUVECs). The endothelial permeability to fluoresceinated dextran, which was added from the start of coculture, was measured., Results: The coculture of HMVECs or HUVECs with PBMNCs in the presence of anti-HLA-DR plasma resulted in the increase of endothelial permeability in the corresponding antigen-antibody-dependent manner. CV-3988, a platelet-activating factor (PAF) receptor antagonist, almost completely suppressed the increase in endothelial permeability. Neutralizing antibodies to tumor necrosis factor (TNF)-α alone and simultaneous addition of the antibodies to TNF-α and interleukin (IL)-1β to the coculture partially suppressed the permeability increase of HMVECs and HUVECs, respectively., Conclusions: HLA Class II antibody and monocytes in the corresponding antigen-antibody combination caused the enhancement of endothelial permeability. PAF, TNF-α, and/or IL-1β might be involved in the endothelial permeability increase. HLA Class II antibody-initiated monocyte activation could lead to the development of pulmonary edema in TRALI., (© 2010 American Association of Blood Banks.)

Objective: To prepare and identify a polyclonal antibody (pAb) against (mouse) cysteinyl leukotriene receptor 1 (CysLT(1)) and to investigate the changes of CysLT(1) receptor expression in BV2 microglial cells after rotenone treatment., Methods: Rabbits were immunized with KLH-coupled CysLT(1) peptide to prepare the pAb. The titer of the pAb in rabbit plasma was detected by ELISA method, and the specificity of the pAb was tested by antigen blockade. After BV2 cells were treated with rotenone (0.01-1 μmol/L) for 24 h, the expression of CysLT(1) was determined by immunostaining, Western blotting and RT-PCR., Result: The pAb showed a titer of 1/32728, and was not cross-reacted with antigens of CysLT(2) receptor and GPR17. Immunostaining, Western blotting and RT-PCR analysis showed the expression of CysLT(1) receptor in BV2 microglia. Rotenone at 1μmol/L significantly induced an increased expression of CysLT(1) receptor., Conclusion: The prepared CysLT(1) receptor polyclonal antibody has a high titer and high specificity to meet testing requirements of Western blotting and immunostaining; CysLT(1) is associated with rotenone-induced injury of BV2 microglial cells.

One possible mechanism of the nasal obstruction observed in allergic rhinitis is thought to be a dilatation of veins in nasal mucosa, although the exact mechanism(s) is not fully understood. An involvement of cysteinyl leukotrienes (CysLTs) in the nasal obstruction has also been suggested. In addition to the specific antigen-induced nasal symptoms, nasal hyperresponsiveness to non-specific stimuli is one of the characteristic features of patients with allergic rhinitis. Augmentation of LTD(4)-induced venodilatation (a part of nasal hyperresponsiveness) of nasal mucosae in antigen-challenged rats was investigated. The LTD(4)-induced venodilatation was significantly increased in antigen-challenged rats, although venodilatation by application of LTD(4) was not induced in nasal mucosae of control rats. The LTD(4)-induced venodilatation was significantly inhibited by pretreatment with L-NMMA [an inhibitor of nitrix oxide synthase (NOS)]. Although mRNA of CysLT1 receptor of nasal mucosa was within control level, the LTD(4)-induced production of NOx in nasal cavity was augmented in repeatedly antigen challenge rats. In addition, the level of iNOS mRNA was also significantly augmented in nasal mucosae of repeatedly antigen-challenged rats. Interestingly, sodium nitroprusside (SNP; an NO donor)-induced venodilatation itself was significantly augmented in nasal mucosae of repeatedly antigen challenge rats. In conclusion, we here suggest that the sensitivity of venodilatation to LTD(4) was augmented in nasal mucosae of challenged rats. Therein, not only increased NO production but also enhanced NO responsiveness might be involved in the development of nasal hyperresponsiveness in allergic rhinitis., (Copyright 2010 Elsevier B.V. All rights reserved.)

A large and diverse array of chemoattractants control leukocyte trafficking, but how these apparently redundant signals collaborate in vivo is still largely unknown. We previously demonstrated an absolute requirement for the lipid chemoattractant leukotriene B(4) (LTB(4)) and its receptor BLT1 for neutrophil recruitment into the joint in autoantibody-induced arthritis. We now demonstrate that BLT1 is required for neutrophils to deliver IL-1 into the joint to initiate arthritis. IL-1-expressing neutrophils amplify arthritis through the production of neutrophil-active chemokines from synovial tissue cells. CCR1 and CXCR2, two neutrophil chemokine receptors, operate nonredundantly to sequentially control the later phase of neutrophil recruitment into the joint and mediate all neutrophil chemokine activity in the model. Thus, we have uncovered a complex sequential relationship involving unique contributions from the lipid mediator LTB(4), the cytokine IL-1, and CCR1 and CXCR2 chemokine ligands that are all absolutely required for effective neutrophil recruitment into the joint., (Copyright 2010 Elsevier Inc. All rights reserved.)

Background and Aim: Multiple sclerosis (MS) is a chronic inflammatory disease that involves central nervous system, and is generally associated with demyelination and axonal lesion. The effective factors for initiation of the inflammatory responses have not been known precisely so far. Leukotrienes (LTs) are inflammatory mediators with increased levels in the cerebrospinal fluid of MS patients and in experimental models of multiple sclerosis. Inhibition of LT receptors with specific antagonists can decrease inflammatory responses. In this review article we try to clarify the role of LT receptor antagonists and also inhibitors of enzymes which are involved in LTs generating pathway for treating multiple sclerosis as new targets for MS therapy. Moreover, we suggest that blockage of LT receptors by potent specific antagonists and/or agonists can be as a novel useful method in treatment of MS.

Cysteinyl-leukotrienes (cysteinyl-LT) are rapidly generated at sites of inflammation and, in addition to their role in asthma, rhinitis, and other immune disorders, are increasingly regarded as significant inflammatory factors in cancer, gastrointestinal, cardiovascular diseases. We recently demonstrated that in monocyte/macrophage-like U937 cells, extracellular nucleotides heterologously desensitize CysLT(1) receptor (CysLT(1)R)-induced Ca(2+) transients. Given that monocytes express a number of other inflammatory and chemoattractant receptors, this study was aimed at characterizing transregulation between these different stimuli. We demonstrate that in U937 cells and in primary human monocytes, a series of inflammatory mediators activating G(i)-coupled receptor (FPR1, BLT(1)) desensitize CysLT(1)R-induced Ca(2+) response unidirectionally through activation of PKC. Conversely, PAF-R, exclusively coupled to G(q), cross-desensitizes CysLT(1)R without the apparent involvement of any kinase. Interestingly, G(s)-coupled receptors (beta(2)AR, H(1/2)R, EP(2/4)R) are also able to desensitize CysLT(1)R response through activation of PKA. Heterologous desensitization seems to affect mostly the G(i)-mediated signaling of the CysLT(1)R. The hierarchy of desensitization among agonists may be important for leukocyte signal processing at the site of inflammation. Considering that monocytes/macrophages are likely to be the major source of cysteinyl-LT in many immunological and inflammatory processes, shedding light on how their receptors are regulated will certainly help to better understand the role of these cells in orchestrating this complex network of integrated signals.

TLRs sense microbial products and initiate adaptive immune responses by activating dendritic cells (DCs). DCs have been shown to produce leukotrienes and, conversely, leukotrienes are known to modulate several DC functions. In this study, we examined the modulation of expression and function of cysteinyl-leukotriene receptor type 1 (CysLT1) on human monocyte-derived DCs during their differentiation and subsequent maturation with zymosan, a TLR2 agonist. Maturation of DCs with zymosan reduced CysLT1 mRNA levels and protein expression in a time-dependent fashion and was associated with a diminution of functional responsiveness to leukotriene D(4) as assessed by intracellular calcium mobilization, CCL2 and CCL3 production, and chemotaxis. The effect of zymosan was mediated by both TLR2 and dectin-1 activation. Zymosan also induced a rapid expression of cyclooxygenase-2 and the production of PGE(2) and IL-10. Addition of an anti-IL-10 neutralizing Ab or inhibitors of cyclooxygenase greatly reduced the ability of zymosan to down-regulate CysLT1 expression. Down-regulation of CysLT1 expression by zymosan could be reproduced by a combination of IL-10 and PGE(2), and was dependent on MAPK activation. Taken together, our findings indicate that zymosan down-regulates CysLT1 expression in DCs with consequently reduced functional responsiveness of the cells to leukotriene D(4) stimulation. This effect is partially dependent on an endogenous production of PGs and IL-10 by DCs.

Objective: To prepare and identify a polyclonal antibody against cysteinyl leukotriene receptor (CysLT(2)receptor)., Methods: Rabbits were immunized with KLH-coupled CysLT(2) receptor peptide to prepare the polyclonal antibody (pAb). The titer of the pAb in rabbit plasma was detected by indirect ELISA, and the specificity of the pAb was tested by antigen blockade. The tissue distribution of CysLT(2) receptor was detected by Western blot and immunohistochemistry with the prepared pAb., Result: The pAb showed a titer higher than 1/1047296, and was specific to CysLT(2) receptor, without cross-reaction with the antigens of CysLT(1) receptor and GPR17. A higher expression of CysLT(2) receptor in kidney, brain and lung of rats and mice was detected by Western blot analysis using the prepared pAb. The molecular weight of CysLT(2) receptor protein was about 40 kD. Immunohistochemical examination showed that CysLT(2) receptor was expressed mainly in the neuron, and partly in astrocytes in rat brain., Conclusion: The prepared CysLT(2) receptor pAb has high sensitivity and specificity, and can be used in Western blot and immunohistochemistry.

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.

Leukotrienes are now established contributors to the inflammatory process in asthma, and leukotriene modifiers are mainstays in the therapy of asthma. This review focuses on published association studies implicating the role of leukotriene pathway genes in asthma pathogenesis and treatment response, specifically focusing on those genetic variants associated with asthma affection status, the development of aspirin-exacerbated respiratory disease, and pharmacogenetic response. Although published studies have been limited by small sample sizes and a lack of independent replication, multiple loci within multiple leukotriene pathway genes have now been associated in more than 1 study related to asthma or asthma treatment response. Those specific variants include 2 variants in the 5-lipoxygenase gene (ALOX5) that are both associated with response to 5-lipoxygenase inhibition and to leukotriene receptor antagonists, variants in genes encoding the 2 established cysteinyl leukotriene receptor antagonists (CYSLTR1 and CYSLTR2) that are both associated with asthma susceptibility in at least 2 independent populations, and a leukotriene C(4) synthase promoter polymorphism (LTC4s) that has been associated with asthma affection status and asthma-exacerbated respiratory disease. Despite these successes, genetic investigations into this pathway remain in their formative stages. Future studies aimed at providing a broader scope of investigation through increased sample sizes and through genome-wide approaches are needed.

Leukotriene (LT) E(4) mediates many of the principal features of bronchial asthma, such as bronchial constriction, hyperresponsiveness, eosinophilia, and increased vascular permeability. Furthermore, it is the most stable of the cysteinyl leukotrienes (CysLTs) and can be active at the site of release for a prolonged time after its synthesis. There might be several reasons why LTE(4) has been forgotten. LTE(4) demonstrated low affinity for CysLT(1) and CysLT(2) receptors in equilibrium competition assays. It was less potent than other CysLTs in functional assays, such as calcium flux, in cells transfected with CysLT(1) and CysLT(2). The introduction of CysLT(1) antagonists into clinical practice diverted interest into CysLT(1)-related mechanisms, which were mediated mainly by LTD(4). However, experiments with animal models and human studies have revealed that LTE(4) has unique characteristics that cannot be explained by the current knowledge of CysLT(1) and CysLT(2). These activities include its potency relative to other CysLTs to increase airway responsiveness to histamine, to enhance eosinophilic recruitment, and to increase vascular permeability. Asthmatic airways also demonstrate marked in vivo relative hyperresponsiveness to LTE(4), especially in patients with aspirin-sensitive respiratory disease. This has stimulated a search for additional LT receptors that would respond preferentially to LTE(4) stimulation.

Background: Cysteinyl leukotrienes (CysLTs) play an important role in the pathophysiology of many allergic inflammatory disorders. However, data on the contribution of genetic variability of the cysteinyl leukotriene receptor 1 gene (CYSLTR1) in asthma and atopy remain conflicting., Objective: We investigated the association of polymorphisms of interest located at this locus and allergic disease prevalence in a national population with an established DNA archive, the British 1958 birth cohort., Methods: The British 1958 birth cohort comprises all persons born in Britain during 1 week in 1958. Asthma, wheezy bronchitis, and wheezing were ascertained by interview at ages 7, 11, 16, 23, 33, and 42 years. At age 44 to 45 years, serum total circulating IgE levels were measured and atopy was defined as a serum total IgE level of greater than 30 kU/L and specific IgE levels to 1 or more of dust mite, cat fur, and mixed grass of greater than 0.3 kU/L. DNA samples from 8018 participants were genotyped for 2 variants of the CYSLTR1 promoter (Xq13-Xq21)., Results: The rare polymorphism C > T (rs7066737) was not associated with any of the phenotypes studied. The common promoter polymorphism A > G (rs2806489) was not associated with total IgE levels or the prevalence or age of onset of asthma, wheezy bronchitis, or wheeze. However, the wild-type allele A was significantly associated with atopy in female subjects (chi(2) = 8.30, P = .004), although not in male subjects (P = .841)., Conclusions: These data suggest that a CYSLTR1 polymorphism previously shown to affect the gene transcription in vitro might influence the risk of atopy in the female white population with suggestive evidence of heterozygote vigor.

Objective: To prepare and identify a polyclonal antibody (pAb) against GPR17, a novel cysteinyl leukotriene receptor., Methods: Rabbits were immunized with KLH-coupled GPR17 peptide to prepare the pAb. The titer of the pAb in rabbit plasma was detected by indirect ELISA, and the specificity of the pAb was tested by antigen blockade. GPR17 tissue distribution was detected by Western blot with the pAb., Results: The pAb showed a titer as high as 1:16 364,and was not cross-reacted with the antigens of CysLT(1) and CysLT(2) receptors. A higher expression of GPR17 in the rat brain and heart was detected using the newly prepared pAb. The molecular weigh of GPR17 protein was about 43 kD., Conclusion: The prepared GPR17 pAb has high sensitivity and specificity,and can be used in Western blot for detecting GPR17.

Background: We recently demonstrated that the T-helper type 1 (Th1) immune response plays an important role in the development of non-eosinophilic inflammation induced by airway exposure of an allergen plus double-stranded RNA (dsRNA). However, the role of lipoxygenase (LO) metabolites in the development of Th1 inflammation is poorly understood., Objective: To evaluate the role of LO metabolites in the development of Th1 inflammation induced by sensitization with an allergen plus dsRNA., Methods: A Th2-allergic inflammation mouse model was created by an intraperitoneal injection of lipopolysaccharide-depleted ovalbumin (OVA, 75 microg) and alum (2 mg) twice, and the Th1 model was created by intranasal application of OVA (75 microg) and synthetic dsRNA [10 microg of poly(I : C)] four times, followed by an intranasal challenge with 50 microg of OVA four times. The role of LO metabolites was evaluated using two approaches: a transgenic approach using 5-LO(-/-) and 15-LO(-/-) mice, and a pharmacological approach using inhibitors of cysteinyl leucotriene receptor-1 (cysLTR1), LTB4 receptor (BLT1), and 15-LO., Results: We found that the Th1-allergic inflammation induced by OVA+dsRNA sensitization was similar between 5-LO(-/-) and wild-type (WT) control mice, although Th2 inflammation induced by sensitization with OVA+alum was reduced in the former group. In addition, dsRNA-induced Th1 allergic inflammation, which is associated with down-regulation of 15-hydroxyeicosateraenoic acids production, was not affected by treatment with cysLTR1 or BLT1 inhibitors, whereas it was significantly lower in 12/15-LO(-/-) mice compared with WT control mice. Moreover, dsRNA-induced allergic inflammation and the recruitment of T cells following an allergen challenge were significantly inhibited by treatment with a specific 15-LO inhibitor (PD146176)., Conclusion: 15-LO metabolites appear to be important mediators in the development of Th1-allergic inflammation induced by sensitization with an allergen plus dsRNA. Our findings suggest that the 15-LO pathway is a novel therapeutic target for the treatment of virus-associated asthma characterized by Th1 inflammation.

Objective: To present a historic perspective and an up-to-date understanding of the involvement of cysteinyl-leukotrienes (cys-LTs) in asthmatic airway smooth muscle (ASM) cell hyperplasia., Data Sources: Data collected from human tissues, from animal models of airway inflammation, and from ASM cells cultured in vitro are included., Study Selection: All studies regarding the potential contribution of cys-LTs on ASM cell hyperplasia are reviewed., Results: Whereas in vivo observations are consistent and seem to attribute an important role for cys-LTs in ASM cell hyperplasia, the observations made in cultured ASM cells are inconsistent, with studies documenting a mitogenic potential only reporting marginal effects., Conclusion: This dichotomy between in vitro and in vivo results led to the elaboration of a hypothesis suggesting that the mitogenic effect of cys-LTs on ASM cells may be indirect and mediated by a paracrine loop involving transforming growth factor beta1 production by airway resident and inflammatory cells.

Background: We have previously demonstrated that cysteinyl leukotriene (CysLT) induced monocyte chemoattractant protein-1 (MCP-1) production in monocytes/macrophages. The intracellular signal transduction pathway of MCP-1 production induced by CysLT in human monocytes/macrophages is unclear., Methods: The activation of mitogen-activated protein kinase (MAPK), including extracellular signal-regulated kinases 1/2 (ERK1/2), c-Jun N-terminal kinase (JNK) and p38 MAPK by phosphorylation, and nuclear factor-kappaB (NF-kappaB) by leukotriene (LT) D(4) and LTC(4) was determined in THP-1 cells, a human monocytic leukemia cell line, and peripheral blood CD14+ monocytes/macrophages. We examined the inhibitory effects of inhibitors of ERK1/2, JNK, p38 MAPK and NF-kappaB and pranlukast as a CysLT1 receptor antagonist on induction of MCP-1 production by LTD(4) and LTC(4)., Results: LTD(4) and LTC(4) induced significant phosphorylations of ERK1/2 and JNK, but not p38 MAPK, in THP-1 cells and peripheral blood CD14+ monocytes/macrophages. Pretreatment with the ERK1/2 inhibitor PD98059 and JNK inhibitor SP600125 attenuated MCP-1 production by CysLTs. NF-kappaB activation was induced by addition of LTD(4) and LTC(4). Pretreatment with the NF-kappaB inhibitors caffeic acid phenylethyl ester and MG-132 inhibited MCP-1 production by CysLTs. Pranlukast inhibited phosphorylation of ERK1/2 and JNK, NF-kappaB activation, and the MCP-1 production induced by CysLTs., Conclusion: CysLTs induce MCP-1 and this induction is mediated by ERK1/2 and JNK in MAPK, and NF-kappaB pathways via the CysLT1 receptor, for the most part, in human monocytes/macrophages.

Cysteinyl leukotriene receptor type 1 (leukotriene CysLT(1) receptor) antagonist is one of the most effective anti-inflammatory agents for asthma. The spectrum of protein targets that can be regulated by leukotriene CysLT(1) receptor antagonist in asthma is not fully understood. The present study tried to identify novel protein targets of a selective leukotriene CysLT(1) receptor antagonist MK-571 in allergic airway inflammation by analyzing the proteome of mouse bronchoalveolar lavage fluid. BALB/c mice sensitized and challenged with ovalbumin showed increased pulmonary inflammatory cell infiltration, airway mucus production and serum ovalbumin-specific IgE level. MK-571 inhibited all these allergic airway inflammation endpoints. Lavage fluid proteins were resolved by two-dimensional gel electrophoresis and identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The level of fourteen bronchoalveolar lavage fluid protein spots was markedly altered by MK-571. A family of chitinases (Ym1, Ym2 and acidic mammalian chitinase), lungkine, surfactant protein-D and gamma-actin have been found for the first time to be down-regulated by leukotriene CysLT(1) receptor antagonist in mouse allergic airways. Some of the down-regulatory effects were confirmed with reverse transcription-polymerase chain reaction analyses. Taken together, we have identified novel protein targets that can be regulated by leukotriene CysLT(1) receptor antagonist in mouse allergic airway inflammation, and our findings reveal additional pharmacological actions of leukotriene CysLT(1) receptor antagonist in the treatment of asthma.

Atopy is a well-defined immune phenotype that is reported to be a risk factor for asthma. Among the many loci that contribute to a genetic predisposition to asthma, the cysteinyl leukotriene receptor genes and their variants have been important subjects of study because they are functionally and pharmacologically implicated in the atopy phenotype affecting many asthma subjects. Moreover, the product of cysteinyl-leukotriene 1 receptor gene (CysLT1), located at Xq13.2, is targeted by LT receptor antagonists. In our earlier association study, the M201V variant of the cysteinyl-leukotriene 2 receptor gene (CysLT2), located at 13q14, was implicated in atopic asthma. Here we report the screening of the coding region of the CysLT1, gene in the highly asthmatic Tristan da Cunha population. In this population, we discovered a CysLT1 G300S variant that is carried with a significantly higher frequency in atopics and asthmatics from the Tristan da Cunha population. Furthermore, we report the asthma independent association of the CysLT1 G300S variant with atopy. Subsequently, we compared the changes conferred by each SNP on CysLT function. The CysLT1 300S receptor interacts with LTD4 with significantly greater potency. For the 300S variant, a statistically significant decrease in the effector concentration for half-maximum response (EC50) for intracellular Ca flux and total InsP generation is observed. Other aspects of the receptor function and activity, such as desensitization, pharmacologic profile in response to montelukast, and cellular localization, are unchanged. These in vitro analyses provide evidence that the 300S CysLT1 variant, found more commonly in atopics in the Tristan da Cunha population, encodes a functionally more sensitive variant.

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.

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.

Background: The aim of this study was to detect cysteinyl leukotriene (Cys-LT) receptors in aspirin-sensitive nasal polyposis patients, and compare them with nasal polyposis and chronic rhinosinusitis patients without aspirin sensitivity., Methods: The formalin-fixed, paraffin-embedded tissue blocks of a total of 52 patients undergoing endoscopic sinus surgery were reviewed by an experienced head and neck pathologist. Of these 52 cases, there were 22 nasal polyposis cases with aspirin sensitivity, 15 nasal polyposis cases without aspirin sensitivity and 15 chronic rhinosinusitis cases without aspirin sensitivity. Immunohistochemical analyses for Cys-LT(1) receptors were performed with polyclonal rabbit antibody., Results: Eosinophil receptor intensity levels were 27.68, 21.67, and 14.40, respectively. This was statistically insignificant (p <0.089). Mast cell receptor intensity levels were 8.41, 5.27, and 4.27, respectively. In the aspirin-sensitive group, mast cell receptor intensity was significantly higher when compared to the nasal polyposis and chronic rhinosinusitis group (p < 0.0001 and p < 0.0001, respectively). The difference in Cys-LT(1) receptor immunoreactivity in both eosinophils and mast cells among the 3 groups was also found to be statistically significant (p < 0.001)., Conclusions: Our study revealed that nasal polyps of aspirin-sensitive patients were infiltrated with eosinophils and mast cells, Cys-LT(1) receptor proportions in these inflammatory cells were found to be higher and Cys-LT(1) receptor immunoreactivity in eosinophils and mast cells was increased., (Copyright (c) 2007 S. Karger AG, Basel.)

Asthma and atopic dermatitis share several common features and Cysteinyl-leukotrienes are mediators that participate in the pathogenesis of both diseases. Recently, a new polymorphism (927T>C) has been identified in cysteinyl-leukotriene type-1 receptor (CYSLTR1) gene. This gene is found on the X chromosome. The aim of this study was to analyze this SNP in a population of children with asthma and atopic dermatitis. In this study, 166 individuals, 79 adult controls (CTR) and 87 children with asthma (AA) were included. Forty-one patients with asthma presented atopic dermatitis (AA-AD). Adults were chosen as controls to confirm lack of development of asthma and allergy during childhood. Standardized history, physical examination, skin prick tests, and lung function measurements were performed in all patients. The 927T>C CYSLTR1 SNP was analyzed by direct sequencing after PCR amplification. In males (53 individuals), the C allele was significantly more common among AA-AD patients (47%) than in CTR (8%) (Fisher's p < 0.005; Monte Carlo p < 0.008; OR:9.78; 95%CI: 1.73-55.30). When comparing AA-AD vs. AA-NAD (patients with asthma but not atopic dermatitis), significant differences were observed, (47% vs. 15%, Fisher's p = 0.014; Monte Carlo p = 0.022; OR: 4.97; 95%CI: 1.29-19.13). No differences in allele distribution were observed between these disease sub-groups in females. The 927T>C is a silent SNP; however, it could affect transcription or translation or may be linked to an unidentified, functional polymorphism and thus may pre-dispose male children to asthma and atopic dermatitis in our population. Further studies are needed to confirm these findings.

Background: Cysteinyl leukotrienes (CysLTs) play important roles in the pathogenesis of eosinophilic airway inflammation characterized by bronchoconstriction, mucus secretion and airway hyper-responsiveness via cysteinyl leukotriene receptor 1 (CysLTR1)-mediated mechanism. CysLTR1-selective antagonists have anti-bronchoconstrictive and anti-inflammatory effects in asthma, particularly aspirin-intolerant asthma (AIA)., Methods: To investigate the association of CysLTR1 with AIA development, we identified three single nucleotide polymorphisms (SNPs), -634C>T, -475A>C, -336A>G, in the 5' upstream region of CysLTR1 gene using a direct sequencing method in 105 AIA patients, 110 ASA-tolerant asthma (ATA) patients and 125 normal healthy controls (NC)., Results: Significant differences were observed in allele frequencies of the three SNPs within male subjects; Male AIA patients had higher frequencies of the minor alleles of these three SNPs than male control groups (P=0.03 for AIA vs. NC; P=0.02 for AIA vs. ATA). Moreover, three-SNP haplotype, ht2 [T-C-G], was associated with increased disease risk (odds ratio (OR)=2.71, P=0.03 for AIA vs. NC; OR=2.89, P=0.02 for AIA vs. ATA) in males. CysLTR1 haplotypes were also associated with altered gene expression; luciferase activity was significantly enhanced with the ht2 [T-C-G] construct in comparison with the ht1 [C-A-A] construct in human Jurkat cells (P=0.04)., Conclusion: These results suggest that genetic variants of CysLTR1 are associated with AIA in a Korean population, and may modulate CysLTR1 expression.