Search

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.