The roles of cysteinyl leukotrienes in eosinophilic inflammation of asthmatic airways

Prioritizing Molecular Biomarkers in Asthma and Respiratory Allergy Using Systems Biology

Highly prevalent respiratory diseases such as asthma and allergy remain a pressing health challenge. Currently, there is an unmet need for precise diagnostic tools capable of predicting the great heterogeneity of these illnesses. In a previous study of 94 asthma/respiratory allergy biomarker candidates, we defined a group of potential biomarkers to distinguish clinical phenotypes (i.e. nonallergic asthma, allergic asthma, respiratory allergy without asthma) and disease severity. Here, we analyze our experimental results using complex algorithmic approaches that establish holistic disease models (systems biology), combining these insights with information available in specialized databases developed worldwide. With this approach, we aim to prioritize the most relevant biomarkers according to their specificity and mechanistic implication with molecular motifs of the diseases. The Therapeutic Performance Mapping System (Anaxomics’ TPMS technology) was used to generate one mathematical model per disease: allergic asthma (AA), non-allergic asthma (NA), and respiratory allergy (RA), defining specific molecular motifs for each. The relationship of our molecular biomarker candidates and each disease was analyzed by artificial neural networks (ANNs) scores. These analyses prioritized molecular biomarkers specific to the diseases and to particular molecular motifs. As a first step, molecular characterization of the pathophysiological processes of AA defined 16 molecular motifs: 2 specific for AA, 2 shared with RA, and 12 shared with NA. Mechanistic analysis showed 17 proteins that were strongly related to AA. Eleven proteins were associated with RA and 16 proteins with NA. Specificity analysis showed that 12 proteins were specific to AA, 7 were specific to RA, and 2 to NA. Finally, a triggering analysis revealed a relevant role for AKT1, STAT1, and MAPK13 in all three conditions and for TLR4 in asthmatic diseases (AA and NA). In conclusion, this study has enabled us to prioritize biomarkers depending on the functionality associated with each disease and with specific molecular motifs, which could improve the definition and usefulness of new molecular biomarkers.

Leukotriene D4 role in allergic asthma pathogenesis from cellular and therapeutic perspectives

Asthma is a chronic inflammatory and allergic disease that is mainly characterized by reversible airway obstruction and bronchial hyperresponsiveness. The incidence of asthma is increasing with more than 350 million people worldwide are affected. Up to now, there is no therapeutic option for asthma and most of the prescribed drugs aim to ameliorate the symptoms of the disease especially during the acute exacerbations after trigger exposure. Asthma is a heterogonous disease that involves interactions between inflammatory mediators and cellular components within the disease microenvironment including inflammatory and structural cells. Cysteinyl leukotrienes (cys-LTs) are inflammatory lipid mediators that have potent roles in asthma pathogenesis. CysLTs consisting of LTC₄, LTD₄, and LTE₄ are mainly secreted by leukocytes and act through three main G-protein coupled receptors (CysLT₁R, CysLT₂R, and CysLT₃R). LTD₄ is the most potent bronchoconstrictor which gives it the priority to be discussed in detail in this review. LTD₄ binds with high affinity to CysLT₁R and many studies showed that using CysLT₁R antagonists such as montelukast has a beneficial effect for asthmatics especially in corticosteroid refractory cases. Since asthma is a heterogeneous inflammatory disease of many cell types involved in the disease pathogenies and LTD₄ has a special role in inflammation and bronchoconstriction, this review highlights the role of LTD₄ on each cellular component in asthma and the benefits of using CysLT₁R antagonists in ameliorating LTD₄-induced effects.

Androgen-mediated sex bias impairs efficiency of leukotriene biosynthesis inhibitors in males

Proinflammatory leukotrienes (LTs) are produced by 5-lipoxygenase (5-LO) aided by 5-LO-activating protein (FLAP). LT biosynthesis inhibitors are currently under clinical investigation as treatments for respiratory and cardiovascular diseases. Here, we have revealed a sex bias in the efficiency of clinically relevant LT biosynthesis inhibitors, showing that their effects are superior in females. We found that androgens cause these sex differences by impeding the LT-biosynthetic 5-LO/FLAP complex assembly. Lower doses of the FLAP inhibitor MK886 were required to reduce LTB4 levels in exudates of female versus male mice and rats. Following platelet-activating factor-induced shock, MK886 increased survival exclusively in female mice, and this effect was abolished by testosterone administration. FLAP inhibitors and the novel-type 5-LO inhibitors licofelone and sulindac sulfide exhibited higher potencies in human blood from females, and bioactive 5-LO/FLAP complexes were formed in female, but not male, human and murine leukocytes. Supplementation of female blood or leukocytes with 5α-dihydrotestosterone abolished the observed sex differences. Our data suggest that females may benefit from anti-LT therapy to a greater extent than males, prompting consideration of sex issues in LT modifier development.

Role of Eosinophil Granulocytes in Allergic Airway Inflammation Endotypes

Eosinophil granulocytes are intriguing members of the innate immunity system that have been considered important defenders during parasitic diseases as well as culprits during allergy-associated inflammatory diseases. Novel studies have, however, found new homoeostasis-maintaining roles for the cell. Recent clinical trials blocking different Th2 cytokines have uncovered that asthma is heterogeneous entity and forms different characteristic endotypes. Although eosinophils are present in allergic asthma with early onset, the cells may not be essential for the pathology. The cells are, however, likely disease causing in asthma with a late onset, which is often associated with chronic rhinosinusitis. Assessment of eosinophilia, fraction exhaled nitric oxide (FeNO) and periostin are markers that have emerged useful in assessing and monitoring asthma severity and endotype. Current scientific knowledge suggests that eosinophils are recruited by the inflammatory environment, activated by the innate interleukin (IL)-33 and prevented from apoptosis by both lymphocytes and innate immune cells such as type two innate immune cells. Eosinophils contain four specific granule proteins that exhibit an array of toxic and immune-modulatory activates. The granule proteins can be released by different mechanisms. Additionally, eosinophils contain a number of inflammatory cytokines and lipid mediators as well as radical oxygen species that might contribute to the disease both by the recruitment of other cells and the direct damage to supporting cells, leading to exacerbations and tissue fibrosis. This review aimed to outline current knowledge how eosinophils are recruited, activated and mediate damage to tissues and therapies used to control the cells.

Eosinophil activation and novel mediators in the aspirin-induced nasal response in AERD

BACKGROUND

Eosinophil activation is the key feature of upper and lower airway inflammation in aspirin-exacerbated respiratory disease (AERD).

OBJECTIVE

To investigate the mechanism of eosinophil activation and identify novel inflammatory mediators using proteomics.

METHODS

Thirty-two asthmatic subjects were enrolled: 18 AERD patients who showed positive responses to the lysine-aspirin nasal provocation test (L-ASA NPT) and 14 aspirin-tolerant asthma (ATA) patients who showed negative responses to the L-ASA NPT (control group). Nasal lavage fluid (NLF) was collected before (baseline), at 10, 30 and 60 min (early response), and at 3 h (late response) after the L-ASA NPT. Eosinophil cationic protein (ECP) and cysteinyl leucotriene (CysLT) levels were measured using an ImmunoCAP system and ELISA respectively. To identify proteins involved in AERD, comparative proteomics was applied using NLFs collected before and after L-ASA NPTs in AERD patients. The clinical relevance of identified novel proteins was evaluated by ELISA using NLFs from the AERD and ATA groups.

RESULTS

Eosinophil cationic protein and CysLT levels both increased significantly during the early response in AERD. ECP levels increased until the late response in AERD, while CysLT levels were not significantly increased during the late response. Proteomic analysis showed up-regulation of apolipoprotein A1 (ApoA1), α2-macroglobulin (α2M) and ceruloplasmin (CP), with significant increases in NLF of AERD patients, which was significantly higher in AERD patients with chronic rhinosinusitis. Significant correlations were noted between ECP and CysLT, ApoA1, α2M and CP levels during the early response in AERD patients.

CONCLUSION

Eosinophil activation occurred in early and late responses after L-ASA NPT in upper airway mucosa of AERD patients, where ApoA1, α2M and CP as well as CysLT may be involved in eosinophilic inflammation.

Expression of the cysteinyl leukotriene 1 receptor and glucocorticoid receptor-β in nasal polyps

The objective of this study was to analyze the expression of cysteinyl leukotriene 1 (CysLT1) receptor and glucocorticoid receptors (GRs) in nasal polyps, and to evaluate the relationship between the expression of CysLT1 receptors and that of GRs. Nasal polyps were taken from 32 patients of chronic rhinosinusitis with nasal polyposis. Samples of middle turbinate from seven healthy subjects were used as controls. Specimens were immunohistochemically stained for CysLT1 receptor, GR-α and GR-β receptor, and were quantified in the unit area of the tissues. Numbers of CysLT1 receptor-positive cells were much increased in nasal polyps than in middle turbinate (281 ± 67 vs. 157 ± 85 cells/mm(2), P = .01). There was no significant difference in the numbers of GR-α positive cells between nasal polyps and normal turbinate mucosa. GR-β positive cells were increased in nasal polyps as compared to normal turbinate mucosa (36 ± 8 vs. 19 ± 7 cells/mm(2), P = .03). A significant relationship was found between the expression of CysLT1 receptor and GR-β in nasal polyps (R = .525, P = .04), whereas there was no significant relationship between the expression of CysLT1 receptor and GR-α in nasal polyps. Our study shows that CysLT1 receptor expression predominates on GR-β over-expressed polyps. This may suggest the additional effect of CysLT1 receptor antagonist for the treatment of nasal polyposis resistant to steroid alone.

Radiation protection following nuclear power accidents: a survey of putative mechanisms involved in the radioprotective actions of taurine during and after radiation exposure

There are several animal experiments showing that high doses of ionizing radiation lead to strongly enhanced leakage of taurine from damaged cells into the extracellular fluid, followed by enhanced urinary excretion. This radiation-induced taurine depletion can itself have various harmful effects (as will also be the case when taurine depletion is due to other causes, such as alcohol abuse or cancer therapy with cytotoxic drugs), but taurine supplementation has been shown to have radioprotective effects apparently going beyond what might be expected just as a consequence of correcting the harmful consequences of taurine deficiency per se. The mechanisms accounting for the radioprotective effects of taurine are, however, very incompletely understood. In this article an attempt is made to survey various mechanisms that potentially might be involved as parts of the explanation for the overall beneficial effect of high levels of taurine that has been found in experiments with animals or isolated cells exposed to high doses of ionizing radiation. It is proposed that taurine may have radioprotective effects by a combination of several mechanisms: (1) during the exposure to ionizing radiation by functioning as an antioxidant, but perhaps more because it counteracts the prooxidant catalytic effect of iron rather than functioning as an important scavenger of harmful molecules itself, (2) after the ionizing radiation exposure by helping to reduce the intensity of the post-traumatic inflammatory response, and thus reducing the extent of tissue damage that develops because of severe inflammation rather than as a direct effect of the ionizing radiation per se, (3) by functioning as a growth factor helping to enhance the growth rate of leukocytes and leukocyte progenitor cells and perhaps also of other rapidly proliferating cell types, such as enterocyte progenitor cells, which may be important for immunological recovery and perhaps also for rapid repair of various damaged tissues, especially in the intestines, and (4) by functioning as an antifibrogenic agent. A detailed discussion is given of possible mechanisms involved both in the antioxidant effects of taurine, in its anti-inflammatory effects and in its role as a growth factor for leukocytes and nerve cells, which might be closely related to its role as an osmolyte important for cellular volume regulation because of the close connection between cell volume regulation and the regulation of protein synthesis as well as cellular protein degradation. While taurine supplementation alone would be expected to exert a therapeutic effect far better than negligible in patients that have been exposed to high doses of ionizing radiation, it may on theoretical grounds be expected that much better results may be obtained by using taurine as part of a multifactorial treatment strategy, where it may interact synergistically with several other nutrients, hormones or other drugs for optimizing antioxidant protection and minimizing harmful posttraumatic inflammatory reactions, while using other nutrients to optimize DNA and tissue repair processes, and using a combination of good diet, immunostimulatory hormones and perhaps other nontoxic immunostimulants (such as beta-glucans) for optimizing the recovery of antiviral and antibacterial immune functions. Similar multifactorial treatment strategies may presumably be helpful in several other disease situations (including severe infectious diseases and severe asthma) as well as for treatment of acute intoxications or acute injuries (both mechanical ones and severe burns) where severely enhanced oxidative and/or nitrative stress and/or too much secretion of vasodilatory neuropeptides from C-fibres are important parts of the pathogenetic mechanisms that may lead to the death of the patient. Some case histories (with discussion of some of those mechanisms that may have been responsible for the observed therapeutic outcome) are given for illustration of the likely validity of these concepts and their relevance both for treatment of severe infections and non-infectious inflammatory diseases such as asthma and rheumatoid arthritis.

Hyperleukotrieneuria in patients with allergic and inflammatory disease

Cysteinyl leukotrienes (CysLTs: leukotrienes C(4), D(4), and E(4)) have long been implicated in the pathogenesis of asthma and several allergic diseases. LTE(4) has been identified as a major metabolite of LTC(4), and urinary LTE(4) (U-LTE(4)) is considered as the most reliable analytic parameter for monitoring the endogenous synthesis of CysLTs. From recent studies on the U-LTE(4) associated with adult stable asthma we identified four factors for hyperleukotrieneuria, namely, aspirin intolerance, eosinophilic nasal polyposis (ENP), vasculitis, and severe asthma. In ENP, there is prominent infiltration of eosinophils in the sinus and polyp tissues, which is linked to adult asthma and aspirin sensitivity, and ENP is the most important factor for the overproduction of CysLTs in asthmatics. We also demonstrated that anaphylaxis and eosinophilic pneumonia (EP) are associated with a marked increase in the U-LTE(4) concentration. Under these disease conditions, U-LTE(4) may be one of the candidate biomarkers. Moreover, the changes in U-LTE(4) concentrations may provide valuable information concerning therapeutic targets.

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

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

The effects of montelukast on tissue inflammatory and bone marrow responses in murine experimental allergic rhinitis: interaction with interleukin-5 deficiency

The cysteinyl leukotrienes (cysLTs) are potent lipid mediators in allergic disease, acting through the receptors, cysLT1R and cysLTR2, and are produced by eosinophils derived from eosinophil/basophil (Eo/B) bone marrow (BM) progenitors. We have demonstrated the suppressive effects of either interleukin-5 (IL-5) deficiency or montelukast on eosinophil recruitment in murine allergic rhinitis, but neither of them fully abrogated the symptoms caused by residual inflammation and cytokine redundancy in eliciting BM Eo/B responses. We hypothesized that IL-5 deficiency and montelukast act synergistically to suppress tissue inflammatory and BM responses. Our objective was to investigate the effects of the cysLT1R antagonist, montelukast, on in vivo tissue inflammatory and BM responses in murine experimental allergic rhinitis with or without IL-5 deficiency. Three groups of age-matched BALB/c mice with or without IL-5 deficiency were tested: controls (ovalbumin sensitization and challenge, placebo treatment) and two montelukast-treated groups (2.5 mg/kg or 5 mg/kg). Nasal symptoms, BM and nasal mucosal eosinophils, basophils, and BM Eo/B colony-forming units (CFU) were evaluated. Montelukast decreased nasal symptoms in a dose-dependent manner, and significantly decreased the number of eosinophils in both BM and nasal tissue in IL-5-replete mice compared to controls. In IL-5-deficient mice, in which eosinophilia was absent, montelukast significantly decreased both nasal symptoms and basophils in BM and nasal mucosal tissue, and lowered IL-5-responsive Eo/B-CFU ex vivo, compared to controls. The addition of cysLT1R blockade to IL-5 deficiency more fully attenuates symptoms and upper airway inflammation than either factor alone, providing evidence of systemic, BM mechanisms in allergic rhinitis.

Eosinophils and asthma

Recruitment and activation of eosinophils into the airways of asthma patients is suggested to be a contributing causative agent in the histopathologies and lung dysfunction that are characteristic of asthma. Recent studies in mouse models of asthma and in human patients implicate eosinophils in immune regulation and remodeling in the lung in addition to their hypothesized role as destructive agents. Specifically, eosinophils not only participate in release of granule proteins, lipid mediators, reactive oxygen species, cytokines, and growth factors but also function through complex cell-cell interactions to elicit chronic T helper 2 inflammation in the lung. This review highlights the roles of eosinophils in asthma.

Recent advances in eosinophil biology

Eosinophils are pleiotropic multi-functional leukocytes involved in initiation and propagation of diverse inflammatory responses. Recent studies examining eosinophil biology have focused on delineating the molecular basis of FIP1L1/PDGRFalpha-fusion gene induced HES, the molecular steps involved in eosinophil recruitment in tumor-associated eosinophilia and EGID, and the role of eosinophils in asthma. In this review, these studies are summarized, focusing on the implications of these findings in the understanding the role of eosinophils in diseases.

Montelukast prevents the decrease of interleukin-10 and inhibits NF-kappaB activation in inflammatory airway of asthmatic guinea pigs

Interleukin (IL)-10 is an important immunoregulatory and anti-inflammatory cytokine, whereas nuclear factor-kappaB (NF-kappaB) plays an important role in the pathogenesis of asthma. In the present study, the effects of montelukast on the level of IL-10 and on the activation of NF-kappaB in the inflammatory airway of asthmatic guinea pigs were investigated. Guinea pigs were sensitized by ovalbumin. Pulmonary inflammation was observed by hematoxylin and eosin staining. The eosinophils in broncho-alveolar lavage fluid and blood were separated by density gradient centrifugation and counted under microscope. The level of IL-10 in broncho-alveolar lavage fluid was measured by enzyme-linked immunoadsorbent assay. Activation of NF-kappaB in lung tissues was inspected by immunohistochemistry. Montelukast at medium and high doses prevented the decrease of IL-10 in broncho-alveolar lavage fluid (n = 8, p < 0.01 vs. asthma model group), inhibited the activation of NF-kappaB in lung tissues (n = 8; medium dose, p < 0.05; high dose, p < 0.01; vs. asthma model group). There was a significantly negative correlation between the level of IL-10 and the activation of NF-kappaB in lung tissues (r = -0.488, p < 0.01). Montelukast reduced the severity of airway inflammation and the number of eosinophils in asthmatic guinea pigs. From all these findings we conclude that montelukast can prevent the decrease of IL-10 and inhibit the activation of NF-kappaB in inflammatory airway of asthmatic guinea pigs, which may be the new important mechanisms of montelukast's anti-airway-inflammation effects in asthmatic guinea pigs.

Differential effects of salbutamol and montelukast on eosinophil adhesion and superoxide anion generation

BACKGROUND

Beta2-agonists, a representative class of bronchodilators used for asthma, have been shown to modulate some functions of eosinophils, including cell adhesion. Similarly, a leukotriene receptor antagonist (LTRA) may be beneficial in controlling inflammation in asthma, as cysteinyl leukotrienes (cysLTs) can cause accumulation or activation of eosinophils. Recent evidence suggests that the addition of an LTRA, but not a long-acting beta2-agonist, to inhaled corticosteroid additionally reduces the number of eosinophils in sputum and blood from patients with asthma. The present study examined whether a beta2-agonist and an LTRA differentially modify eosinophil adhesion and activation induced by cysLTs and other activators.

METHODS

Eosinophils were isolated from blood of healthy donors and then incubated in the presence or absence of salbutamol (albuterol) or montelukast. Eosinophils were then exposed to leukotriene D4 (LTD4) or another activator, and the generation of superoxide anion (O2-) was evaluated by cytochrome C reduction assay. Eosinophil adhesion was examined by an eosinophil peroxidase assay.

RESULTS

Montelukast, but not salbutamol (both at 1 microM), inhibited LTD4-induced (100 nM) eosinophil adhesion to recombinant human intercellular adhesion molecule 1. Both drugs similarly and partially inhibited the 100 pM interleukin-5-induced adhesive response of eosinophils to recombinant human intercellular adhesion molecule 1. Montelukast, but not salbutamol, blocked LTD4-induced eosinophil O2- generation of eosinophils. Finally, neither salbutamol nor montelukast modified phorbol myristate acetate (1 ng/ml)-induced O2- generation from eosinophils.

CONCLUSION

These results confirm that LTD4 directly induces activation of eosinophils via the cysLT1 receptor. Furthermore, the results suggest that a beta2-agonist has no effect on eosinophil adhesion and activation induced by cysLTs. These results explain the differential effects of an LTRA and a beta2-agonist in the treatment of eosinophilic inflammation in asthma.

Pranlukast reduces neutrophil but not macrophage/microglial accumulation in brain after focal cerebral ischemia in mice

AIM

To determine whether pranlukast, a cysteinyl leukotriene receptor-1 antagonist, exerts an anti-inflammatory effect on focal cerebral ischemia in mice.

METHODS

Focal cerebral ischemia in mice was induced by permanent middle cerebral artery occlusion (MCAO). In addition to neurological deficits, infarct volume, degenerated neurons and endogenous IgG exudation, we detected accumulation of neutrophils and macrophage/microglia in the ischemic brain tissue 72 h after MCAO. Pranlukast was ip injected 30 min before and after MCAO.

RESULTS

Pranlukast significantly attenuated neurological deficits, infarct volume, neuron degeneration and IgG exudation. Importantly, pranlukast (0.01 and 0.1 mg/kg) inhibited myeloperoxidase-positive neutrophil, but not CD11b-positive macrophage/microglial accumulation in the ischemic cortical tissue.

CONCLUSION

Pranlukast exerts an anti-inflammatory effect on focal cerebral ischemia in the subacute phase that is limited to neutrophil recruitment through the disrupted blood-brain barrier.

Up-regulation of prostaglandin biosynthesis by leukotriene C4in elicited mice peritoneal macrophages activated with lipopolysaccharide/interferon-γ

Leukotrienes (LT) and prostaglandins (PG) are proinflammatory mediators generated by the conversion of arachidonic acid via 5-lipoxygenase (5-LO) and cyclooxygenase (COX) pathways. It has long been proposed that the inhibition of the 5-LO could enhance the COX pathway leading to an increased PG generation. We have found that in in vitro models of inflammation, such as mice-elicited peritoneal macrophages activated with lipopolysaccharide (LPS)/interferon-gamma (IFN-gamma), the deletion of the gene encoding for 5-LO or the enzyme activity inhibition corresponded to a negative modulation of the COX pathway. Moreover, exogenously added LTC(4), but not LTD(4), LTE(4), and LTB(4), was able to increase PG production in stimulated cells from 5-LO wild-type and knockout mice. LTC(4) was not able to induce COX-2 expression by itself but rather potentiated the action of LPS/IFN-gamma through the extracellular signal-regulated kinase-1/2 activation, as demonstrated by the use of a specific mitogen-activated protein kinase (MAPK) kinase inhibitor. The LT-induced increase in PG generation, as well as MAPK activation, was dependent by a specific ligand-receptor interaction, as demonstrated by the use of a cys-LT1 receptor antagonist, although also a direct action of the antagonist used, on PG generation, cannot be excluded. Thus, the balance between COX and 5-LO metabolites could be of great importance in controlling macrophage functions and consequently, inflammation and tumor promotion.

Effect of cysteinyl leukotriene receptor antagonist on CD11b and CD23 expression in asthmatic children

BACKGROUND

Cysteinyl leukotrienes are potent pro-inflammatory mediators that contribute to the pathophysiologic features observed in allergic asthma. Inhibitors of leukotriene receptors represent novel therapy in asthma treatment. In addition to the protection from early asthmatic responses, these drugs have recently been shown to protect from late airway responses too.

METHODS

We studied the effect of treatment with an oral antagonist of cysteinyl leukotriene receptors on the increased expression of the low-affinity IgE receptor, CD23, on B cells, and of its ligands, CD11b and CD11c, on CD4(+) T cells and monocytes in peripheral blood of patients with allergic asthma. In this uncontrolled open-label study, 14 children with allergic asthma received montelukast, a cysteinyl leukotrine receptor antagonist, for a period of 6 weeks after demonstrating forced expiratory volume in 1 s (FEV(1)) of less than 80% of the predicted value. Samples of peripheral heparinized blood and sera were obtained before and after therapy completion. Three-colour immunofluorescence analysis was performed, and expression of CD11b and CD11c on CD4(+) T lymphocytes and monocytes as well as the expression of CD21 and CD23 on B cells were determined (n=12). Peripheral blood eosinophil count, changes in FEV(1) and peak expiratory flow rate (PEFR), asthma exacerbations, and as-needed use of beta-agonist were also monitored.

RESULTS

Montelukast improved FEV(1) and PEFR, and decreased peripheral eosinophil counts in all study patients. There was no significant change in the expression of CD21 and CD23 on B cells. The expression of CD11c on CD4(+) T cells and of both CD11b and CD11c on monocytes remained similar to the pretreatment expression. However, the percentage of CD11b(+)CD4(+) T lymphocytes significantly decreased after treatment with montelukast. This was accompanied by a significant decrease in the levels of total IgE.

CONCLUSION

The capacity of 6-week montelukast therapy to reduce the percentage of CD11b CD4(+) T cells might be a mechanism leading to the immune response modulation on this T cell subset interaction with CD23-expressing B cells and subsequent down-regulation of IgE synthesis.

Cysteinyl leukotrienes regulate dendritic cell functions in a murine model of asthma

Dendritic cells (DCs) act as APCs in the airway and play a critical role in allergy. Cysteinyl leukotrienes (cysLTs) synthesized from arachidonic acid are primary mediators of immediate asthmatic reaction. The aim of this study was to investigate the effects of cysLTs on Dermatophagoides farinae (Der f)-pulsed mouse myeloid DCs in inducing allergic airway inflammation in vitro and in vivo. Control DC (medium-pulsed), Der f-pulsed DC, cysLT-pulsed DC, Der f- and cysLT-pulsed DC, and Der f-pulsed and cysLT receptor antagonist (LTRA)-treated DC were prepared from murine bone marrow, and the production of cytokines ws compared. Subsequently, these DCs were intranasally instilled into another group of naive mice, followed by intranasal Der f challenge to induce allergic airway inflammation in vivo. Der f-pulsed DC produced significantly higher amounts of IL-10 and IL-12 compared with control DC. Der f- and cysLT-pulsed DC further increased IL-10 production compared with Der f-pulsed DC. In contrast, treatment of Der f-pulsed DC with LTRA increased IL-12 and decreased IL-10. Intranasal instillation of Der f-pulsed DC resulted in airway eosinophilia associated with a significant rise in IL-5 levels in the airway compared with control DC. Pulmonary eosinophilia and excess IL-5 were further enhanced in Der f- and cysLT-pulsed DC-harboring mice. In contrast, Der f-pulsed and LTRA-treated DC significantly inhibited airway eosinophilia, reduced IL-5, and increased IFN-gamma in the airway. Our results suggest that cysLTs play an important role in the development of allergic airway inflammation by regulating the immunomodulatory functions of DCs.