A functional study on CysLT(1) receptors in human eosinophils

A Dual Role for Cysteinyl Leukotriene Receptors in the Pathogenesis of Corneal Infection

Cysteinyl leukotrienes (CysLTs) have been defined as central mediators of inflammation. Despite our extensive understanding of these bioactive lipid mediators in the pathogenesis of diseases such as asthma, allergic rhinitis, and even neurological disorders, information regarding the eye is markedly lacking. As a result, this study examined the expression profiles of two major CysLT receptors, CysLT₁ and CysLT₂, in the cornea using experimental mouse models of Pseudomonas aeruginosa-induced keratitis with contrasting outcomes: susceptible C57BL/6 (B6) and resistant BALB/c. Postinfection, disparate levels of CysLT receptors were accompanied by distinct expression profiles for select proinflammatory and anti-inflammatory cell surface markers detected on macrophages and polymorphonuclear neutrophils between the two strains. Further, inhibition of either CysLT receptor converted the disease response of both strains, where corneal perforation was prevented in B6 mice, and BALB/c mice fared significantly worse. In addition, receptor antagonist studies revealed changes in inflammatory cell infiltrate phenotypes and an influence on downstream CysLT receptor signaling pathways. Although the B6 mouse model highlights the established proinflammatory activities related to CysLT receptor activation, results generated from BALB/c mice indicate a protective mechanism that may be essential to disease resolution. Further, basal expression levels of CysLT₁ and CysLT₂ were significantly higher in uninfected corneas of both mouse strains as opposed to during infection, suggestive of a novel role in homeostatic maintenance within the eye. In light of these findings, therapeutic targeting of CysLT receptors extends beyond inhibition of proinflammatory activities and may impact inflammation resolution, as well as corneal surface homeostasis.

A review of non-prostanoid, eicosanoid receptors: expression, characterization, regulation, and mechanism of action

Eicosanoid signaling controls a wide range of biological processes from blood pressure homeostasis to inflammation and resolution thereof to the perception of pain and to cell survival itself. Disruption of normal eicosanoid signaling is implicated in numerous disease states. Eicosanoid signaling is facilitated by G-protein-coupled, eicosanoid-specific receptors and the array of associated G-proteins. This review focuses on the expression, characterization, regulation, and mechanism of action of non-prostanoid, eicosanoid receptors.

Current state and future prospect of the therapeutic strategy targeting cysteinyl leukotriene metabolism in asthma

Asthma is an allergic disorder with dominant type 2 airway inflammation, and its prevalence is increasing worldwide. Inhalation of corticosteroids is the primary treatment for asthma along with add-on drugs, including long-acting β2 agonists and/or cysteinyl leukotriene (cys-LT) receptor antagonists, in patients with poorly controlled asthma. Cys-LTs are composed of leukotriene C4 (LTC₄), LTD₄, and LTE₄, which are enzymatically metabolized from arachidonic acid. These molecules act as inflammatory mediators through different types of high-affinity receptors, namely, CysLT₁, CysLT₂, and CysLT₃ (also named as GPR99). CysLT₁ antagonists possessing anti-inflammatory and bronchodilatory effects can be orally administered to patients with asthma. Recently, molecular biology-based studies have revealed the mechanism of inflammatory responses via other receptors, such as CysLT₂ and CysLT₃, as well as the importance of upstream inflammatory regulators, including type 2 cytokines (e.g., interleukins 4 and 5), in controlling cys-LT metabolism. These findings indicate the therapeutic potential of pharmacological agents targeting cys-LT metabolism-related receptors and enzymes, and antibody drugs neutralizing or antagonizing type 2 cytokines. This review focuses on the current state and future prospect of the therapeutic strategy targeting cys-LT metabolism.

Regulation of Eosinophil and Group 2 Innate Lymphoid Cell Trafficking in Asthma

Asthma is an inflammatory disease usually characterized by increased Type 2 cytokines and by an infiltration of eosinophils to the airways. While the production of Type 2 cytokines has been associated with T_H2 lymphocytes, increasing evidence indicates that group 2 innate lymphoid cells (ILC2) play an important role in the production of the Type 2 cytokines interleukin (IL)-5 and IL-13, which likely amplifies the recruitment of eosinophils from the blood to the airways. In that regard, recent asthma treatments have been focusing on blocking Type 2 cytokines, notably IL-4, IL-5, and IL-13. These treatments mainly result in decreased blood or sputum eosinophil counts as well as decreased asthma symptoms. This supports that therapies blocking eosinophil recruitment and activation are valuable tools in the management of asthma and its severity. Herein, we review the mechanisms involved in eosinophil and ILC2 recruitment to the airways, with an emphasis on eotaxins, other chemokines as well as their receptors. We also discuss the involvement of other chemoattractants, notably the bioactive lipids 5-oxo-eicosatetraenoic acid, prostaglandin D₂, and 2-arachidonoyl-glycerol. Given that eosinophil biology differs between human and mice, we also highlight and discuss their responsiveness toward the different eosinophil chemoattractants.

A Mathematical Modeling Approach to Understanding the Effect of Anti-Interleukin Therapy on Eosinophils

Emerging T‐helper type 2 (Th₂) cytokine‐based asthma therapies, such as tralokinumab, lebrikizumab (anti‐interleukin (IL)‐13), and mepolizumab (anti‐IL‐5), have shown differences in their blood eosinophil (EOS) response. To better understand these effects, we developed a mathematical model of EOS dynamics. For the anti‐IL‐13 therapies, lebrikizumab and tralokinumab, the model predicted an increase of 30% and 10% in total and activated EOS in the blood, respectively, and a decrease in the total and activated EOS in the airways. The model predicted a rapid decrease in total and activated EOS levels in blood and airways for the anti‐IL‐5 therapy mepolizumab. All model‐based predictions were consistent with published clinical observations. The modeling approach provided insights into EOS response after treatment with Th₂‐targeted therapies, and supports the hypothesis that an increase in blood EOS after anti‐IL‐13 therapy is part of the pharmacological action of these therapies.

The protective role of montelukast against intestinal ischemia-reperfusion injury in rats

Several drugs are effective in attenuating intestinal ischemia-reperfusion injury (IRI); however little is known about the effect of montelukast. Fifty rats were randomly assigned to 3 groups: model group (operation with clamping), sham group (operation without clamping), and study group (operation with clamping and 0.2, 2 and 20 mg/kg montelukast pretreatment). Intestinal ischemia-reperfusion was performed by occlusion (clamping) of the arteria mesenterica anterior for 45 min, followed by 24 h reperfusion. Intestinal IRI in the model group led to severe damage of the intestinal mucosa, liver and kidney. The Chiu scores of the intestines from the study group (2 and 20 mg/kg) were lower than that of the model group. Intestinal IRI induced a marked increase in CysLTR1, Caspase-8 and -9 expression in intestine, liver and kidney, which were markedly reduced by preconditioning with 2 mg/kg montelukast. Preconditioning with 2 g/kg montelukast significantly attenuated hepatic tissue injury and kidney damage, and decreased plasma interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) levels in plasma after intestinal IRI. In conclusion, preconditioning with montelukast could attenuate intestinal IRI and the subsequent systemic inflammatory response in rats.

Role of cysteinyl leukotriene receptor 1 in intestinal ischemia-reperfusion injury

AIM: To explore the role of cysteinyl leukotriene receptor 1 (CysLTsR1) in intestinal ischemia-reperfusion (I/R) injury.

METHODS: Forty rats were divided into 5 groups: a control group, a model group and low-, medium- and high-dose montelukast groups. After treatment, the water content of the small bowel was determined, and the histological changes in the intestinal tissues were assessed by HE staining. Immunohistochemical assessment of the expression of CysLTR1 and 5-lipoxygenase (5-LOX) was also performed.

RESULTS: Intestinal I/R, small bowel water content (model group 78.13 g ± 1.35 g vs normal group 78.13 g ± 1.35 g, P < 0.05), and CysLTR1 protein and mRNA expression significantly increased in the model group compared with the control group. Application of montelukast decreased intestinal water content (low-, medium-, and high-dose groups 76.47 g ± 1.48 g, 72.67 g ± 5.35 g and 75.39 g ± 3.66 g vs model group 78.13 g ± 1.35 g, P < 0.05), relieved the intestinal tissue injury, and reduced CysLTR1 protein and mRNA expression in intestinal tissues (P < 0.05).

CONCLUSION: CysLTR1 participates in the pathogenesis of intestinal ischemia-reperfusion injury, and may be a target for treatment of I/R injury.

Placebo-controlled study with OHIO chamber of prophylactic pranlukast for children with Japanese cedar pollinosis: TOPIC-J III study

Objective

This double-blind, placebo-controlled comparative study was designed to investigate whether pranlukast dry syrup, a leukotriene receptor antagonist, has a protective effect against priming, controlled pollen exposure, and natural pollen exposure in children with Japanese cedar pollinosis.

Research design and methods

Thirty children aged 12–15 years with Japanese cedar pollinosis (positive skin test for Japanese cedar pollen), who had suffered from pollinosis for at least 2 years and developed severe nasal obstruction when exposed to Japanese cedar pollen, were enrolled in this study. They were randomly allocated to treatment with pranlukast or placebo orally after breakfast and dinner for 8 weeks during the Japanese cedar pollen season. Soon after the start of the pollen season, all subjects underwent a challenge by exposure for 3 h to Japanese cedar pollen (8000 grains/m³) in an artificial exposure chamber (OHIO chamber).

Clinical trial registration

The University Hospital Medical Information Network in Japan (UMIN000009840).

Main outcome measures

The effect of pranlukast was evaluated using self-rating of nasal symptoms by the subjects and measurement of eosinophil cationic protein in nasal discharge specimens.

Results

Scores for the symptoms of pollinosis were lower in the pranlukast group than in the placebo group during treatment in the priming state, as well as after controlled pollen exposure and natural pollen exposure. Pranlukast significantly improved the score for nasal obstruction, compared with placebo. A correlation was found between changes of the scores for symptoms of pollinosis and changes of the eosinophil cationic protein level.

Conclusions

These results confirm a protective effect of pranlukast against both priming and challenge (controlled and natural) with Japanese cedar pollen. The present findings suggested that pranlukast dry syrup may be useful for prophylaxis against pollinosis in children.

Trial of pranlukast inhibitory effect for cedar exposure using an OHIO chamber

Objective

In practical guidelines for management of allergic rhinitis in Japan, pranlukast is a leukotriene receptor antagonist recommended for the treatment of pollinosis. However, the effect of pranlukast on nasal symptoms for cedar pollinosis has not been thoroughly investigated. The aim of this study is to examine this effect in a double-blind controlled crossover study using a pollen challenge chamber (the OHIO Chamber) developed in Japan.

Research design and methods

A total of 39 patients with cedar pollinosis were targeted. The subjects were exposed to a specific amount of cedar pollen (8000/m³) in the OHIO Chamber during the non-cedar pollen season. Efficacy of pranlukast for the treatment of artificially induced nasal symptoms was compared with that of a placebo using the crossover method. Pranlukast was administered orally for 3 days, after dinner on the day before cedar pollen exposure, after breakfast and after dinner on the day of cedar pollen exposure, and after breakfast on the following day. Pollen testing was carried out twice, with a 1-week wash-out interval.

Clinical trial registration

The University Hospital Medical Information Network in Japan (UMIN), number UMIN000001282.

Main outcome measures

The effect of pranlukast was evaluated using self-rating of nasal symptoms by the subjects.

Results

All 39 subjects demonstrated a positive skin reaction to cedar pollen by a positive CAP-RAST score (class 2 or higher) within the last 3 years, and experienced aggravated congestion during the cedar pollen season for more than 2 years. Nasal congestion was inhibited significantly in the pranlukast group compared to the placebo group during cedar pollen exposure. Furthermore, pranlukast significantly inhibited nasal congestion compared to the placebo on the day after exposure and on the following day.

Conclusions

The effect of pranlukast on cedar pollinosis indicates immediate action, and such an effect could take place continuously after cedar pollen exposure. These results demonstrate that pranlukast is effective for the relief of congestion due to pollinosis.

Delay of onset of symptoms of Japanese cedar pollinosis by treatment with a leukotriene receptor antagonist

BACKGROUND

Leukotriene receptor antagonists (LTRAs) are effective for prophylactic treatment of pollinosis based on studies showing that administration of LTRAs prior to or at the start of the pollen season reduces symptoms and QOL disturbance at the peak of pollen dispersal. Two goals of prophylactic treatment of pollinosis are use of fewer types of drugs and delay of onset of symptoms and impairement of QOL. Therefore, this study was performed to determine if pranlukast, a LTRA, met these goals in treatment of pollinosis.

METHODS

Pranlukast or placebo was administered to patients who visited our hospital immediately before the start of Japanese cedar pollen dispersal. The study was performed for 4 weeks as a double blind randomized trial. Subsequently, all patients were given pranlukast for a further 4 weeks from the peak until the end of pollen dispersal. The incidence of symptoms and use of concomitant drugs were investigated from daily nasal allergy records kept by patients. QOL was evaluated using the JRQLQ questionnaire.

RESULTS

In the double blind period of the study, the percentage of patients who used concomitant drugs for nasal symptoms was significantly lower in the pranlukast group compared to the placebo group. Development of nasal symptoms (sneezing, runny nose and nasal congestion) and disturbance of daily activities were significantly delayed in the pranlukast group. No serious adverse reactions occurred in the pranlukast group and no patient withdrew from treatment with pranlukast.

CONCLUSIONS

Pranlukast is effective for prophylactic treatment of pollinosis.

Effects of leukotriene receptor antagonists on peripheral eosinophil counts and serum IgE levels in children with food allergy

BACKGROUND

Although the efficacy of leukotriene receptor antagonists (LTRAs) for bronchial asthma is already established, their effect on food allergy remains unclear.

OBJECTIVE

To investigate the efficacy of LTRAs in children with food allergy.

METHODS

This retrospective study examined 65 children with food allergy who were aged between 3 and 36 months (mean 14 ± 9.6 months) from 2005 to 2008. Thirty-two children were treated as a dietary control group by avoiding any antigenic foods to which they had previously experienced adverse reactions. The remaining 33 children, designated the LTRA group, were treated with pranlukast (7 mg/kg bodyweight/day) in addition to maintaining dietary control. Clinical symptoms and laboratory data before and after 1 year of treatment were compared between the groups.

RESULTS

Allergic symptoms improved in both the dietary controlled and LTRA groups, and there was no significant difference observed in the clinical parameters examined between the groups after the 1-year trial. Peripheral eosinophil count, serum IgE, interleukin (IL)-4, IL-5, IL-6, and eosinophil cationic protein (ECP) levels in children with food allergy were above standardized values in both groups. Although both the dietary controlled and LTRA groups showed a decreased eosinophil count (-273 ± 232 vs -595 ± 295/μL; p < 0.05 and p < 0.001, respectively), only children treated with LTRA showed a significant decrease in serum IgE (-73.5 ± 115 IU/mL; p < 0.01); conversely, the control group exhibited a significant increase in serum IgE (+159 ± 138 IU/mL; p < 0.01). Furthermore, the LTRA group also showed a significant decrease in serum IL-4 (54.5 ± 31.0 to 27.3 ± 10.1 pg/mL), IL-5 (6.7 ± 5.2 to 5.0 ± 0.4 pg/mL), and ECP (45.4 ± 15.0 to 15.0 ± 9.8 μg/L) levels (p < 0.05 for each).

CONCLUSION

Early intervention with LTRAs may be effective in regulating eosinophil count and serum IgE, IL-4, IL-5, and ECP levels. These data support the potential effectiveness of LTRAs in young children with food allergy to prevent further allergic development.

Effects of KP-496, a novel dual antagonist for cysteinyl leukotriene receptor 1 and thromboxane A2 receptor, on Sephadex-induced airway inflammation in rats

Bronchial asthma is characterized by chronic airway inflammation. Eosinophils are involved in airway inflammation and play crucial roles in asthma. There is accumulating evidence to suggest contributions of cysteinyl leukotrienes (cysLTs) and thromboxane (TX) A(2) to the recruitment of eosinophils into lung in asthmatics. KP-496 is a novel dual antagonist for CysLT receptor type 1 and TXA(2) receptors. The aim of this study was to evaluate the anti-inflammatory effects of KP-496 on Sephadex-induced airway inflammation. Sephadex suspension was intratracheally injected into rats. Amounts of regulated on activation, normal T cell expressed and secreted (RANTES) and eotaxin, and numbers of infiltrating cells in bronchoalveolar lavage fluid were measured 24 and 48 h after Sephadex injection, respectively. KP-496 (30, 100 microg/head) was intratracheally administered to rats 1 h before and 7 h after Sephadex injection. KP-496 and prednisolone (10 mg/kg, per os) exhibited significant inhibitory effects on infiltration of total cells and eosinophils into lung. Production of RANTES was significantly inhibited by KP-496 and prednisolone. Production of eotaxin was significantly inhibited by prednisolone. KP-496 also inhibited the production of eotaxin, though this effect was not significant. These results demonstrate that KP-496 exhibited the anti-inflammatory effects by inhibiting infiltration of inflammatory cells and productions of RANTES and eotaxin.

Eosinophils: biological properties and role in health and disease

Eosinophils are pleiotropic multifunctional leukocytes involved in initiation and propagation of diverse inflammatory responses, as well as modulators of innate and adaptive immunity. In this review, the biology of eosinophils is summarized, focusing on transcriptional regulation of eosinophil differentiation, characterization of the growing properties of eosinophil granule proteins, surface proteins and pleiotropic mediators, and molecular mechanisms of eosinophil degranulation. New views on the role of eosinophils in homeostatic function are examined, including developmental biology and innate and adaptive immunity (as well as their interaction with mast cells and T cells) and their proposed role in disease processes including infections, asthma, and gastrointestinal disorders. Finally, strategies for targeted therapeutic intervention in eosinophil-mediated mucosal diseases are conceptualized.

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.

Cysteinyl leukotrienes: multi-functional mediators in allergic rhinitis

Cysteinyl leukotrienes (CysLTs) are a family of inflammatory lipid mediators synthesized from arachidonic acid by a variety of cells, including mast cells, eosinophils, basophils, and macrophages. This article reviews the data for the role of CysLTs as multi-functional mediators in allergic rhinitis (AR). We review the evidence that: (1) CysLTs are released from inflammatory cells that participate in AR, (2) receptors for CysLTs are located in nasal tissue, (3) CysLTs are increased in patients with AR and are released following allergen exposure, (4) administration of CysLTs reproduces the symptoms of AR, (5) CysLTs play roles in the maturation, as well as tissue recruitment, of inflammatory cells, and (6) a complex inter-regulation between CysLTs and a variety of other inflammatory mediators exists.

Cysteinyl leukotriene receptor 1 promoter polymorphism is associated with aspirin-intolerant asthma in males

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.

Interferon-gamma up-regulates expression of cysteinyl leukotriene type 2 receptors on eosinophils in asthmatic patients

STUDY OBJECTIVES

Cysteinyl leukotrienes (cysLTs) are strong bronchoconstrictive mediators that play a key role in asthma inflammation. They act through specific receptors including cysLT type 1 receptor (CysLT1R) and cysLT type 2 receptor (CysLT2R). Although these two receptors are co-expressed on inflammatory cells, little is known about CysLT2R in patients with asthma. The aims of this study were to investigate the changes in cysLT receptors (CysLTRs) during asthma exacerbations and to determine which cytokine modulates CysLTR expression on eosinophils.

METHODS

We assessed protein expression and messenger RNA of CysLT1R and CysLT2R in peripheral blood eosinophils and measured urinary leukotriene E(4) levels in 36 patients with stable asthma, 23 subjects with asthma exacerbation, and 15 healthy subjects. We also evaluated the modulation of these receptors by interleukin (IL)-1beta, IL-4, IL-5, IL-13, interferon (IFN)-gamma and tumor necrosis factor-alpha in cultured eosinophils.

RESULTS

Expression of both CysLT1R and CysLT2R on eosinophils during asthma exacerbations was significantly higher (p < 0.05) than in stable asthma and healthy subjects. A greater expression of CysLT2R in exacerbation was found in nonatopic asthmatics. Only IFN-gamma up-regulated cell-surface expression of CysLT2R in a dose-dependent manner and enhanced messenger RNA levels. No cytokine affected CysLT1R expression or messenger RNA level.

CONCLUSIONS

CysLT2R expression on eosinophils was increased in patients, especially in nonatopic subjects, during asthma exacerbation, and was up-regulated by IFN-gamma; therefore we speculate that a pathway through CysLT2R might modulate exacerbations of asthma.

5-Lipoxygenase products regulate basophil functions: 5-Oxo-ETE elicits migration, and leukotriene B4 induces degranulation

BACKGROUND

5-Lipoxygenase (5-LO) products have been strongly implicated in the pathogenesis of allergic diseases. In addition to their physiologic effects on residential cells, 5-LO products are capable of stimulating various eosinophil functions. However, little is known regarding the effects of 5-LO products on basophil functions.

OBJECTIVE

This study was designed to elucidate the effects of the main 5-LO products (ie, leukotriene [LT] B(4), LTD(4), and 5-oxo-6,8,11,14-eicosatetraenoic acid [5-oxo-ETE]), as well as their receptor expression on human basophils.

METHODS

We studied the effects of 5-LO products on Ca(2+) mobilization, migration, CD 11b expression, and degranulation of human basophils. Expression of the receptors for LTC(4)/D(4)/E(4) (cysteinyl leukotriene 1 [CysLT(1)] and CysLT(2)), LTB4 (BLT(1) and BLT(2)), and 5-oxo-ETE (oxoeicosanoid [OXE]) was assessed by means of real-time PCR and flow cytometry.

RESULTS

At the mRNA level, basophils strongly expressed OXE and predominantly expressed CysLT(1) and BLT(2). The expression level of OXE mRNA in basophils was approximately 20-fold higher than in neutrophils and similar to that in eosinophils. At the protein level, basophils expressed CysLT(1), CysLT(2), BLT(1), and OXE, but not BLT(2). All products elicited a transient increase of cytosolic calcium, with the order of magnitude being LTB(4)>5-oxo-ETE>LTD(4). 5-Oxo-ETE induced a strong basophil migratory response that was almost equivalent to that of prostaglandin D(2). LTB(4) elicited significant degranulation of IL-3-primed basophils. In contrast, no functional significance was observed for LTD(4).

CONCLUSION

Among 5-LO products, 5-oxo-ETE induces a potent basophil migratory response, and LTB(4) elicits degranulation under certain conditions. Our results strongly suggest that 5-oxo-ETE might afford opportunities for therapeutic targeting in allergic inflammation.

Leukotriene D4 induces production of transforming growth factor-beta1 by eosinophils

Eosinophils may play an important role in the pathogenesis of airway remodeling in asthma through the production of various fibrogenic cytokines such as transforming growth factor-beta1 (TGF-beta1). Cysteinyl leukotrienes are also suggested to be involved in remodeling with their potential to induce proliferation of airway smooth muscle cells. Since massive eosinophil infiltration and the release of cysteinyl leukotrienes in airway secretions are often seen in asthma, we hypothesized that cysteinyl leukotrienes may be involved in airway remodeling through induction of TGF-beta1 from eosinophils. Peripheral blood eosinophils were cultured with leukotriene D(4) (LTD(4)) and/or interleukin-5 (IL-5) or granulocyte colony-stimulating factor (GM-CSF) for 16 h and gene expression of TGF-beta1 was quantified with real-time PCR. A combination of LTD(4) and IL-5 or LTD(4) and GM-CSF synergistically induced TGF-beta1 expression in eosinophils although stimulation with single factor, LTD(4), IL-5 or GM-CSF did not induce the gene expression. LTD(4) also induced significant gene expression in eosinophils cultured in an intercellular adhesion molecule-1-coated plate. The results suggested that CysLTs stimulate eosinophils to induce TGF-beta1 production in allergic inflammation where IL-5 and GM-CSF are abundant and may be involved in the pathogenesis of airway remodeling.

Leukotriene D4 and eosinophil transendothelial migration, superoxide generation, and degranulation via beta2 integrin

BACKGROUND

Evidence indicates that cysteinyl leukotriene (cysLT) 1 receptor antagonists possess anti-inflammatory properties in asthmatic patients in vivo. Although the exact mechanisms of these actions remain unknown, cysLTs regulate the locomotion and functions of eosinophils. We previously reported that leukotriene D4 augments the expression of eosinophil beta2 integrin and the adhesion of eosinophils to rh intercellular adhesion molecule 1 via beta2 integrin.

OBJECTIVE

To examine whether leukotriene D4 modifies the transendothelial migration (TEM) and effector functions of eosinophils.

METHODS

We evaluated the effects of leukotriene D4 on (1) eosinophil TEM across human umbilical vein endothelial cells, (2) superoxide anion (O2-) generation, and (3) eosinophil-derived neurotoxin release in eosinophils isolated from the blood of healthy individuals.

RESULTS

Leukotriene D4 (0.1-1 microM) significantly induced eosinophil TEM, O2- generation, and eosinophil-derived neurotoxin release. Pranlukast, a cysLT1 receptor antagonist, significantly inhibited all of these parameters, although the inhibitory effect on O2- generation was partial. All of these responses were significantly inhibited by anti-beta2 integrin but not by anti-alpha4 integrin antibodies.

CONCLUSIONS

Leukotriene D4 directly up-regulates the TEM and effector functions of eosinophils mainly via the cysLT1 receptor and beta2 integrin. These effects of leukotriene D4 probably contribute to the manifestation of eosinophil inflammation in asthmatic airways.

Characterization of interleukin-4-stimulated nasal polyp fibroblasts

Chronic hyperplastic eosinophilic sinusitis is an inflammatory disease that results in the accumulation of eosinophils, fibroblasts, mast cells, and goblet cells at the site of injury. A common feature of this disease is the presence of nasal polyposis (NP). The current studies were designed to assess the contribution of interleukin (IL)-4 to fibroblast-mediated inflammation in chronic hyperplastic eosinophilic sinusitis/NP. In addition, we hypothesized that cysteinyl leukotrienes (CysLT) may directly influence fibroblast-mediated fibrotic and remodeling pathways in this disorder. Fibroblasts were isolated from NP tissue. All fibroblast lines expressed the IL-4 receptor. IL-4 induced changes in mRNA and protein expression of fibrotic (transforming growth factor-beta1 and -beta2) and inflammatory cytokines and chemokines (IL-6 and CCL11) by fibroblasts as measured by semiquantitative and quantitative polymerase chain reaction, RNase protection assay, and enzyme-linked immunosorbent assay. The expression of CysLT and other proinflammatory lipid receptors on fibroblasts was evaluated. CysLT1 and CysLT2 receptors were not expressed on fibroblasts; however, LPA(1) receptor was constitutively expressed and LPA(2) receptor expression was upregulated by IL-4. The metabolic cascade involved in CysLT synthesis was not expressed in fibroblasts and could not be induced by IL-4 treatment.

Expression of cysteinyl leukotriene synthetic and signalling proteins in inflammatory cells in active seasonal allergic rhinitis

BACKGROUND

Cysteinyl leukotrienes (CysLTs) are bioactive lipids that have been shown to contribute to allergic and inflammatory diseases. Eosinophils and mast cells have the capacity to produce large amounts of CysLTs after allergic or non-allergic stimulation. Molecular identification of both the synthetic and signalling proteins in the CysLT pathway allows the investigation of expression of the CysLT enzymes and receptors in active allergic rhinitis.

OBJECTIVE

We examined the expression of the proteins involved in the synthesis of CysLTs and the cysteinyl leukotriene-1 (CysLT1) and cysteinyl leukotriene-2 (CysLT2) receptors in inflammatory cells from patients with active seasonal allergic rhinitis.

METHODS

Nasal lavage samples were obtained from patients during active seasonal allergic rhinitis. Specific cellular immunocytochemical techniques were used to detect the cysteinyl leukotriene synthetic proteins, namely 5-lipoxygenase (5-LO), 5-lipoxygenase-activating protein (FLAP) and leukotriene C4 synthase (LTC4S). In situ hybridization and immunocytochemical techniques were used to identify the mRNA and proteins for the CysLT1 and CysLT2 receptors.

RESULTS

5-LO, FLAP and LTC4S, and the CysLT1 and CysLT2 receptors were expressed in the majority of eosinophils and in subsets of mast cells and mononuclear cells. 5-LO, FLAP and the CysLT1 receptor, but not LTC4S or the CysLT2 receptor, were expressed in a subset of nasal neutrophils.

CONCLUSIONS

Our study demonstrates the presence of CysLT pathway proteins in key allergic and inflammatory cells from the upper airway of patients with active seasonal allergic rhinitis. Our expression data highlight the potential of CysLT-modifying agents to treat both upper and lower airway symptoms in patients suffering from allergic rhinitis and asthma.