Antileukotriene therapy. Future directions

Comparison of the efficacy of KOB03, ketotifen, and montelukast in an experimental mouse model of allergic rhinitis

KOB03 is a polyherbal medicine derived from an oriental prescription traditionally used to treat allergic diseases. In the present study, we compared the efficacy of KOB03 with modern drugs such as ketotifen and montelukast in an experimental mouse model of allergic rhinitis (AR). Ketotifen is a H1 receptor antagonist and montelukast is a leukotriene receptor antagonist. Mice were treated with KOB03, ketotifen or montelukast in an established AR mouse model using ovalbumin (OVA)-sensitized/challenged BALB/c mice. The treatment of KOB03 had inhibitory effects on symptom scores, serum levels of OVA-specific IgE, histamine, leukotriene C4, IL-4, TNF-α, and IL-1β in AR mice, and the histolopathological changes of nasal mucosa with mucin release and inflammation. AR mice treated with KOB03 had significantly lower serum levels of OVA-specific IgE, LTC4, IL-4, and IL-1β than mice treated with ketotifen, whereas they only had significantly lower serum levels of OVA-specific IgE and IL-4 than those treated with montelukast. In addition, the histolopathological changes of nasal mucosa with eosinophil infiltration were significantly lower in the KOB03-treated mice than those in the ketotifen and montelukast-treated group. These results suggest that KOB03 has therapeutic potential for treating AR like other modern medicines.

Eosinophilic inflammation in allergic asthma

Eosinophils are circulating granulocytes involved in pathogenesis of asthma. A cascade of processes directed by Th2 cytokine producing T-cells influence the recruitment of eosinophils into the lungs. Furthermore, multiple elements including interleukin (IL)-5, IL-13, chemoattractants such as eotaxin, Clara cells, and CC chemokine receptor (CCR)3 are already directly involved in recruiting eosinophils to the lung during allergic inflammation. Once recruited, eosinophils participate in the modulation of immune response, induction of airway hyperresponsiveness and remodeling, characteristic features of asthma. Various types of promising treatments for reducing asthmatic response are related to reduction in eosinophil counts both in human and experimental models of pulmonary allergic inflammation, showing that the recruitment of these cells really plays an important role in the pathophysiology of allergic diseases such asthma.

Application of proteomics in asthma research

Bronchial asthma is caused by allergic airway inflammation, resulting in reversible airway obstruction, characterized by airway hyper-responsiveness, bronchoconstriction, increased mucus secretion and an increase in lung vessel permeability. The pathophysiological changes in asthma have been attributed to the altered expression of biologically plausible proteins associated with transcriptional pathways, inflammatory mediators, chemokines, cytokines, apoptosis and cell proliferation. Such multifactorial diseases characteristically involve an interplay of many genetic variations of molecular and biochemical pathways and their interactions with environmental factors. The complex nature of the asthma phenotype, together with genetic heterogeneity and environmental influences, has made it difficult to uncover the aspects that underlie this common disease. Recently, genomic and proteomic technologies have been developed to identify associations between genes, proteins and disease. This approach, called 'omics biology', aims to recognize early onset of disease, institute preventive treatment and identify new molecular targets for novel drugs in multifactorial diseases. This article reviews examples of how proteomic technology can be used to find asthma marker proteins (from the cell model to clinical samples). Identification of protein changes in different stages of asthma could provide further insights into the complex molecular mechanisms involved in this disease. These studies provide new insights for finding novel pathological mediators and biomarkers of asthma.

Natural anti-inflammatory products and leukotriene inhibitors as complementary therapy for bronchial asthma

OBJECTIVE

To assess the efficacy of a combination of Boswellia serrata, licorice root (Glycyrrhiza glabra) and Tumeric root (Curcuma longa) as natural leukotriene inhibitor, antiinflammatory and antioxidant products respectively in controlling bronchial asthma.

SUBJECTS AND METHODS

The study comprised 63 patients with bronchial asthma that are further subdivided into two groups .Group 1 receiving oral capsule (combined herb) in a soft-gelatin capsule 3 times daily for 4weeks and group 2 receiving placebo. Plasma leukotriene C(4) (LTC(4))(,) nitric oxide (NO) and malondialdehyde (MDA) levels were measured and pulmonary function was also assessed in all patients enrolled in the study.

RESULTS

There was a statistically significant decrease in the plasma levels of LTC(4), (MDA), and NO in target therapy group when compared with placebo group.

CONCLUSION

The used extract contained Boswellia serrata, Curcuma longa and Glycyrrhiza has a pronounced effect in the management of bronchial asthma.

New drugs targeting Th2 lymphocytes in asthma

Asthma represents a profound worldwide public health problem. The most effective anti-asthmatic drugs currently available include inhaled beta2-agonists and glucocorticoids and control asthma in about 90-95% of patients. The current asthma therapies are not cures and symptoms return soon after treatment is stopped even after long term therapy. Although glucocorticoids are highly effective in controlling the inflammatory process in asthma, they appear to have little effect on the lower airway remodelling processes that appear to play a role in the pathophysiology of asthma at currently prescribed doses. The development of novel drugs may allow resolution of these changes. In addition, severe glucocorticoid-dependent and resistant asthma presents a great clinical burden and reducing the side-effects of glucocorticoids using novel steroid-sparing agents is needed. Furthermore, the mechanisms involved in the persistence of inflammation are poorly understood and the reasons why some patients have severe life threatening asthma and others have very mild disease are still unknown. Drug development for asthma has been directed at improving currently available drugs and findings new compounds that usually target the Th2-driven airway inflammatory response. Considering the apparently central role of T lymphocytes in the pathogenesis of asthma, drugs targeting disease-inducing Th2 cells are promising therapeutic strategies. However, although animal models of asthma suggest that this is feasible, the translation of these types of studies for the treatment of human asthma remains poor due to the limitations of the models currently used. The myriad of new compounds that are in development directed to modulate Th2 cells recruitment and/or activation will clarify in the near future the relative importance of these cells and their mediators in the complex interactions with the other pro-inflammatory/anti-inflammatory cells and mediators responsible of the different asthmatic phenotypes. Some of these new Th2-oriented strategies may in the future not only control symptoms and modify the natural course of asthma, but also potentially prevent or cure the disease.

Anti-inflammatory effects of Lafoensia pacari and ellagic acid in a murine model of asthma

We have shown that the ethanolic extract of Lafoensia pacari inhibits eosinophilic inflammation induced by Toxocara canis infection, and that ellagic acid is the secondary metabolite responsible for the anti-eosinophilic activity seen in a model of beta-glucan peritonitis. In the present study, we investigated the preventive and curative effects of L. pacari extract and ellagic acid on allergic lung inflammation using a murine model of ovalbumin-induced asthma. In bronchoalveolar lavage fluid, preventive (22-day) treatment with L. pacari (200 mg/kg) and ellagic acid (10 mg/kg) inhibited neutrophil counts (by 75% and 57%) and eosinophil counts (by 78% and 68%). L. pacari reduced IL-4 and IL-13 levels (by 67% and 73%), whereas ellagic acid reduced IL-4, IL-5 and IL-13 (by 67%, 88% and 85%). To investigate curative anti-inflammatory effects, we treated mice daily with ellagic acid (0.1, 1, or 10 mg/kg), also treating selected mice with L. pacari (200 mg/kg) from day 18 to day 22. The highest ellagic acid dose reduced neutrophil and eosinophil numbers (by 59% and 82%), inhibited IL-4, IL-5, and IL-13 (by 62%, 61%, and 49%). Neither L. pacari nor ellagic acid suppressed ovalbumin-induced airway hyperresponsiveness or cysteinyl leukotriene synthesis in lung homogenates. In mice treated with ellagic acid (10 mg/kg) or L. pacari (200 mg/kg) at 10 min after the second ovalbumin challenge, eosinophil numbers were 53% and 69% lower, respectively. Cytokine levels were unaffected by this treatment. L. pacari and ellagic acid are effective eosinophilic inflammation suppressors, suggesting a potential for treating allergies.

Anti-asthmatic potential of a D-galactose-binding lectin from Synadenium carinatum latex

Extracts from the plant Synadenium carinatum latex are widely and indiscriminately used in popular medicine to treat a great number of inflammatory disorders and although the mechanisms underlying these effects remain undefined, the lectin isolated from S. carinatum latex (ScLL) is thought to be in part responsible for these anti-inflammatory effects. In order to elucidate possible immunoregulatory activities of ScLL, we investigated the effects of ScLL administration in models of acute and chronic inflammation. Oral administration of ScLL significantly inhibited neutrophil and eosinophil extravasation in models of acute and chronic inflammation and reduced eosinophil and mononuclear blood counts during chronic inflammation. ScLL administration reduced IL(interleukin)-4 and IL-5 levels but increased interferon-gamma and IL-10 in an asthma inflammatory model, which suggested that it might induce a TH2 to TH1 shift in the adaptive immune response. ScLL also inhibited IkappaBalpha degradation, a negative regulator of proinflammatory NF-kappaB. Taken together, these results provide the first description of a single factor isolated from S. carinatum latex extract with immunoregulatory functions and suggest that ScLL may be useful in the treatment of allergic inflammatory disorders.

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.

Functional characterization of human cysteinyl leukotriene 1 receptor gene structure

The 5-lipoxygenase pathway has been strongly implicated in the pathogenesis of chronic inflammatory disorders, such as bronchial asthma and atherosclerosis. Cysteinyl leukotrienes (cysLTs), 5-lipoxygenase pathway products, are recognized now not only as important factors in asthmatic inflammation, but also as mediators of cell trafficking and innate immune responses. To study a role of cysLTs in inflammatory reactions we have characterized the gene structure of human cysteinyl leukotriene receptor type I (cysLT(1)R). The cysLT(1)R gene consists of 5 exons that are variably spliced and a single promoter region with multiple transcription start sites. Four different cysLT(1)R transcripts were identified. RT-PCR showed dominant and wide expression of the transcript I, containing exons 1, 4, and 5, with the strongest presence in blood leukocytes, spleen, thymus, lung, and heart. The expression of cysLT(1)R is functionally regulated at the transcriptional level by IL-4 through a STAT6 response element localized to the proximal cysLT(1)R promoter region. IL-4 stimulation increased cysLT(1)R mRNA (real-time PCR) and surface protein expression (flow cytometry) in a time-dependent fashion. CysLTs (LTD(4) and LTC(4)) induced an increased production of a potent monocyte chemoattractant CCL2 (MCP-1) in IL-4-primed THP-1 cells in a dose-dependent manner. This effect was effectively inhibited by the cysLT(1)R-selective antagonist MK571 in a dose-dependent manner and only partially by a nonselective cysLT(1)R/cysLT(2)R inhibitor BAY-u9773, implying a cysLT(1)R-mediated mechanism. Thus, cysLTs signaling through cysLT(1)R might contribute to inflammatory reactions by cooperating with IL-4 in enhanced CCL2 production in human monocytic cells.

Leukotriene-related gene polymorphisms in patients with aspirin-intolerant urticaria and aspirin-intolerant asthma: differing contributions of ALOX5 polymorphism in Korean population

The pathogenesis of aspirin (acetylsalicylic acid, ASA)-intolerant urticaria (AIU) is still poorly understood but it has recently been suggested that it is associated with the overproduction of leukotriene (LT). This is supported by evidence that cyclooxygenase 2 inhibitor is given safely to patients with AIU. The present study was designed to investigate the role of genetic polymorphism of LT related genes in the pathogenesis of AIU via a case-control study. We screened single nucleotide polymorphisms (SNPs) in genes encoding enzymes involved in leukotriene synthesis in the Korean population with AIU (n = 101), ASA-intolerant asthma (AIA, n = 95) and normal healthy controls (n = 123). Genotype was determined by primer extension reactions using the SNapShot ddNTP primer extension kit. Among 8 SNPs of four LT related genes, the polymorphism of ALOX5 at positions of -1708 G > A showed significant difference in genotype frequency between AIU and AIA (p = 0.01). Furthermore, there were significant differences observed in the frequencies of two ALOX5 haplotypes between the AIU group and AIA group (p < 0.05). However, there were no differences in allele, genotype, or haplotype frequencies of ALOX5 between the AIU group and the normal control group. These results suggested that ALOX5 has a differing contribution in two major clinical pathogenesis related to ASA-sensitivity.

Polymorphism of tandem repeat in promoter of 5-lipoxygenase in ASA-intolerant asthma: a positive association with airway hyperresponsiveness

BACKGROUND

5-Lipooxygenase (ALOX5) and 5-lipoxygenase-activating protein (ALOX5AP) are known as key enzymes in cysteinyl-leukotriene (cys-LT) production, critical mediators in aspirin acetylsalicyclic acid (ASA)-intolerant asthma (AIA). To date, studies of the promoter region of ALOX5 gene has revealed the potential influence of a variable number of tandem repeats of a Sp1- and Egr1-binding motif, on the transcription rate.

METHODS

To understand the pathological process that arises from cys-LT overproduction in AIA, we genotyped ALOX5 Sp1 and ALOX5AP poly(A) repeat promoter polymorphism by fluorescent-based capillary electrophoresis in the Korean population.

RESULTS

No significant differences in allele and genotype frequencies of the ALOX5 and ALOX5AP promoter polymorphisms were observed between the three groups. However, there was a strong association of the ALOX5 Sp1 repeat polymorphism with airway hyperresponsiveness (AHR; PC20 methacholine); AIA patients carrying a mutant allele (n > 5 or n < 5 repeats) showed increased AHR compared to AIA patients with wild-type genotype (P=0.003).

CONCLUSION

Although the alleles of the ALOX5 and ALOX5AP promoter cannot be considered as a prominent risk factor in the development of AIA, the genetic variant of tandem repeat (GGGCGG; Sp1-binding motif) in ALOX5 promoter is associated with the severity of airway hyperresponsiveness in AIA patients.

Leukotriene E(4)-induced persistent eosinophilia and airway obstruction are reversed by zafirlukast in patients with asthma

BACKGROUND

We have shown that inhalation of leukotriene (LT) E 4 contributes to specific recruitment of eosinophils to the airway mucosa in patients with asthma at the time of maximal decrease in airway-specific conductance.

OBJECTIVE

We examined the ability of the cysteinyl LT 1 receptor antagonist, zafirlukast, to improve or prevent LT-mediated eosinophilia and airway obstruction in asthma.

METHODS

Bronchial biopsies were taken and pulmonary function was measured before and 4 to 6 hours after the dose of inhaled LTE 4 causing a > or =15% fall in FEV 1 at baseline both at week 0 and after 6-week randomly assigned treatment with a high dose of zafirlukast, 80 mg twice daily.

RESULTS

Leukotriene E 4 inhalation at week 0 doubled the number of eosinophils in the airway mucosa in 21 of 25 patients with mild asthma, increased the numbers of neutrophils and lymphocytes, and decreased FEV 1 (-17%). Zafirlukast reduced both airway eosinophilia and obstruction in FEV 1 , whereas with a double-blind placebo treatment, the effect of LTE 4 on both parameters persisted for 6 weeks. On repeat LTE 4 inhalation challenge after 6 weeks, zafirlukast treatment prevented further airway eosinophilia and decrease in FEV 1 seen in the placebo group.

CONCLUSION

Persistent LTE 4 -induced airway eosinophilia may form the basis of an amplification mechanism for further eosinophil recruitment. Zafirlukast prevents LTE 4 -induced eosinophilic airway inflammation in mild asthma.

Effects of pranlukast administration on vascular endothelial growth factor levels in asthmatic patients

STUDY OBJECTIVES

We have previously found that vascular endothelial growth factor (VEGF) levels in induced sputum were increased in asthmatic patients, and that its levels were closely associated with the degree of airway obstruction and microvascular permeability. Therefore, this study was designed to examine the effects of pranlukast, a selective leukotriene receptor antagonist, on VEGF levels in induced sputum from steroid-untreated or steroid-treated asthmatic patients.

DESIGN

Double-blind, randomized, placebo-controlled, crossover study.

SETTING

University hospital.

PARTICIPANTS

Twenty-three asthmatic patients (steroid-untreated, 13 patients; steroid-treated, 10 patients) and 10 healthy control subjects.

INTERVENTIONS

All asthmatic patients received 4-weeks of therapy with pranlukast (225 mg bid), and sputum induction was performed before and after the 4-week treatment course.

MEASUREMENTS AND RESULTS

In steroid-untreated asthmatic patients, the mean percentage of eosinophils (%EOS) and mean eosinophil cationic protein (ECP) levels in induced sputum were significantly decreased after 4 weeks of pranlukast administration (%EOS: before, 16.7% [SD, 7.1%]; after, 12.3% [SD, 4.0%]; p = 0.03; ECP levels: before, 774 ng/mL [SD, 258 ng/mL]; after, 564 ng/mL [SD, 204 ng/mL]; p = 0.034). Moreover, VEGF levels in the induced sputum and the airway vascular permeability index also were decreased after pranlukast administration (VEGF levels: before, 5,670 pg/mL [SD, 1,780 pg/mL]; after, 4,380 pg/mL [SD, 1,540 pg/mL]; p = 0.026; airway vascular permeability index: before, 0.032 [SD, 0.012]; after, 0.017 [SD, 0.006]; p = 0.01). In addition, the change in airway vascular permeability index from before to after pranlukast administration was significantly correlated with the change in VEGF levels (r = 0.782; p = 0.007). However, in steroid-treated asthmatic patients there was no significant difference in mean VEGF levels in induced sputum between placebo administration (before, 3,640 pg/mL [SD, 1,020 pg/mL]; after, 3,640 pg/mL [SD, 960 pg/mL] and pranlukast administration (before, 3,660 pg/mL [SD, 940 pg/mL]; after, 2,950 pg/mL [SD, 890 pg/mL]).

CONCLUSIONS

Pranlukast administration decreased airway microvascular permeability through, at least in part, a decrease in airway VEGF levels in steroid-untreated asthmatic patients. However, it is likely that pranlukast administration added little efficacy to inhaled corticosteroid therapy for reduction in airway VEGF levels.

Comparison of glucocorticoid and cysteinyl leukotriene receptor antagonist treatments in an experimental model of chronic airway inflammation in guinea-pigs

BACKGROUND

Leukotriene receptor antagonists have been demonstrated in several studies to possess bronchodilating and anti-inflammatory properties in asthma. However, there are few experimental studies performed to compare the effects of anti-leukotrienes and glucocorticoids, most used anti-inflammatory agents in asthma. In the present study, we evaluated the effects of treatment with dexamethasone or montelukast on eosinophil and mononuclear cell recruitment in an experimental model of allergen-induced chronic airway inflammation in guinea-pigs (GP).

METHODS

GP were submitted to increasing concentrations of aerosols of ovalbumin (OVA) twice a week for 4 weeks. After 2 weeks, animals were treated daily with dexamethasone, montelukast or saline solution. After this period, GP were anaesthetized, tracheostomized, mechanically ventilated and challenged with OVA aerosol.

RESULTS

Maximal changes of respiratory system resistance and elastance induced by OVA challenge were attenuated by dexamethasone (P<0.001), but not by montelukast treatment. Neither dexamethasone nor montelukast significantly influenced bronchial oedema formation. Dexamethasone but not montelukast induced a decrease in mononuclear cells in airways (P<0.001). Eosinophil infiltration in the bronchial wall was reduced by both dexamethasone and montelukast (P<0.005). Only dexamethasone treatment reduced the levels of exhaled nitric oxide (P<0.025).

CONCLUSION

Although leukotriene receptor antagonist treatment reduces eosinophil accumulation induced by multiple antigen challenges, glucocorticoid treatment attenuates both eosinophil and mononuclear cell infiltration.

Clinical efficacy and pharmacokinetics of montelukast in dyspeptic children with duodenal eosinophilia

BACKGROUND

Montelukast, a competitive cysteinyl leucotriene-1 receptor antagonist, reduces airway eosinophilia in asthmatics. We evaluated the effect of this drug in children with eosinophilic duodenitis, defined histologically as duodenal mucosa with peak eosinophil count of more than 10 eosinophils/hpf.

METHODS

Forty children and adolescents (6-18 yr) with dyspepsia and duodenal eosinophilia were enrolled in a double blind, randomized, placebo-controlled, cross-over study of monteleukast therapy. Subjects were randomized to receive either 10 mg montelukast or an identical placebo once daily and were evaluated on day 14 for symptomatic and biochemical responses. Subjects were also randomized to one of two blood sampling schemes to evaluate montelukast pharmacokinetics.

RESULTS

Using a post treatment global pain assessment, a positive clinical response was observed in 62.1% of patients receiving montelukast compared with 32.4% on placebo (p < 0.02). Pain assessment score deteriorated in 45% of montelukast responders (5/11) after cross-over to placebo and improved in 62% (8/13) of placebo non-responders on cross-over to montelukast. In patients with peak duodenal eosinophil counts between 20-29/hpf (n=19), a positive pain assessment response was observed in 84% of patients receiving montelukast compared to 42% receiving placebo (p < 0.01). Response rate did not differ by age, gender or histologic findings at baseline. Pharmacokinetic analysis yielded parameter estimates for absorption rate constant (Ka), apparent volume of distribution (Vd/F) and elimination rate constant (Kel) of 0.42 h, 0.19 L/kg and 0.26 h, respectively. The relative extent of systemic drug exposure was comparable to that observed in previous pediatric investigations with similar weight-adjusted montelukast doses. Neither dose nor calculated drug exposure were associated with the level of post treatment pain assessment or the change in biochemical markers.

CONCLUSIONS

These data suggest a beneficial role for montelukast in the treatment of pediatric patients with dyspepsia associated with duodenal eosinophilia.

Spotlight on montelukast in asthma in children 2 to 14 years of age

Montelukast is a cysteinyl leukotriene receptor antagonist which is used as a preventive treatment for persistent asthma in patients > or =2 years of age. In children aged 6 to 14 years montelukast (5 mg/day) treatment resulted in a significant increase in FEV1 (forced expiratory volume in 1 second, primary clinical outcome) during an 8-week randomized, double-blind trial. Moreover, significant improvements were observed for a range of secondary endpoints assessing symptoms, exacerbation rates, beta-agonist usage and quality of life. Concomitant administration of montelukast (5 mg/day) and inhaled budesonide (200 microg twice daily) resulted in a trend towards an increase in FEV1 (p=0.06, primary endpoint) and a statistically significant reduction in both as-needed beta2-agonist usage and the percentage of days with asthma exacerbations compared with budesonide plus placebo. No significant differences were observed in asthma-related quality of life between the two groups. During clinical trials both improvements in lung function and reductions in as-needed beta2-agonist usage were generally observed within 1 day after initiation of therapy in children 2 to 14 years of age with persistent asthma. Data from a randomized, nonblind trial in 6- to 11-year-old children and a 6-month extension to this trial suggest that both compliance to therapy and patient satisfaction are greater for montelukast than for either inhaled cromolyn sodium (sodium cromoglycate) or inhaled beclomethasone. In addition, patients and parents preferred oral montelukast over cromolyn sodium. In 2- to 5-year-old children with persistent asthma, montelukast (4 mg/day) treatment resulted in significant improvements in a range of outcomes, such as as-needed beta2-agonist usage, symptom scores and percentage of days with asthma symptoms, as assessed during a randomized, double-blind trial primarily designed to assess tolerability. Data from small randomized, double-blind trials suggest that montelukast reduces exercise-induced bronchoconstriction in 6- to 14-year-old children. Montelukast is generally well tolerated. The frequency of adverse events in montelukast-treated children of all ages was comparable to that in patients receiving placebo.

CONCLUSION

Oral montelukast has shown efficacy as a preventive treatment for asthma during clinical trials in children aged 2 to 14 years. The drug offers benefits over more standard therapies such as inhaled cromolyn sodium and nedocromil in terms of compliance and convenience. In addition, the drug offers significant benefits when added to inhaled corticosteroids (according to secondary endpoints). Montelukast offers an effective, well tolerated and convenient treatment option for children with asthma.

Promoter polymorphism in the 5-lipoxygenase (ALOX5) and 5-lipoxygenase-activating protein (ALOX5AP) genes and asthma susceptibility in a Caucasian population

BACKGROUND

5-Lipoxygenase (5-LO) and 5-lipoxygenase-activating protein (FLAP) are essential for cysteinyl-leukotriene (cys-LT) production, critical mediators in asthma.

OBJECTIVE

We sought to identify novel promoter polymorphisms within the FLAP (ALOX5AP) gene promoter and test the role of these and the previously identified 5-LO (ALOX5) Sp1 promoter polymorphism in asthma susceptibility.

METHODS

To assess genetic association with asthma phenotypes, we genotyped 341 Caucasian families (containing two asthmatic siblings) and non-asthmatic control subjects (n=184). Genetic association was determined by case-control and transmission disequilibrium test (TDT) analyses. To determine the functional role of polymorphisms on basal transcription, we generated ALOX5AP-promoter-luciferase constructs and transiently transfected human HeLa cells.

RESULTS

A novel G/A substitution at -336 bp and a poly(A) repeat (n=19 or 23) at position -169 to -146 bp were identified in the ALOX5AP promoter. Genotyping found the -336 A and poly(A19) alleles at frequencies of q=0.06 and 0.12, respectively. No ALOX5AP allele was associated with asthma or asthma-related phenotypes in case-control or TDT analyses. ALOX5AP-promoter-luciferase analyses did not support a functional role of the -336 or poly(A) polymorphism in determining basal transcription. The ALOX5 Sp1 polymorphism was predominantly homozygous wild-type 5/5 (frequency q=0.70) and heterozygous 4/5 (q=0.23) genotypes and no allele was associated with asthma or asthma-related phenotypes.

CONCLUSION

Taken together, these data do not support a significant role for these polymorphisms in genetic susceptibility to asthma in the Caucasian population.

CysLT1 receptor upregulation by TGF-beta and IL-13 is associated with bronchial smooth muscle cell proliferation in response to LTD4

BACKGROUND

Airway remodeling is a feature of chronic asthma. It involves a number of structural changes, including bronchial smooth muscle cell (BSMC) hyperplasia and hypertrophy. Cysteinyl leukotrienes (cysLTs) have been suggested to play a role in airway remodeling in addition to their numerous other physiopathologic effects.

OBJECTIVES

This work was aimed at characterizing the potential modulation of CysLT1 receptor expression by cytokines and the eventual functional relevance of this modulation.

METHODS

Expression of CysLT1 receptor was measured by flow cytometry and immunofluorescence microscopy. Transcripts were measured by RT-PCR and BSMC proliferation by crystal violet staining.

RESULTS

When human BSMC were exposed to transforming growth factor (TGF)-beta, IL-13, or IFN-gamma, their expression of CysLT1 receptor was significantly augmented in a time- and concentration-dependent manner. Interestingly, IL-4 had no significant effect on CysLT1 receptor expression in BSMC. Moreover, IL-13 and IFN-gamma but not TGF-beta were able to increase CysLT1 mRNA levels. Finally, when BSMC were pretreated with TGF-beta or IL-13 but not IFN-gamma, their responsiveness to LTD(4) was markedly enhanced in terms of BSMC proliferation. Whereas TGF-beta, IL-13, or LTD(4) alone had little effect on BSMC proliferation, preexposure of the cells to TGF-beta or IL-13 for 24 hours resulted in a significant increase in proliferation in response to LTD(4). The enhanced proliferation was totally prevented by pretreating the cytokine-primed BSMC with the selective CysLT1 receptor antagonist Montelukast.

CONCLUSIONS

Taken together, our findings indicate a synergy between certain cytokines and cysLTs, mediated by the augmented expression of the CysLT1 receptor and subsequent LTD(4)-triggered BSMC proliferation. These findings support a role for cysLTs in the airway remodeling observed in asthmatic patients and may provide a rationale for preventive and therapeutic intervention.

Effects of cysteinyl leukotrienes and leukotriene receptor antagonists on markers of inflammation

The understanding that asthma pathophysiology includes an inflammatory component has spurred the more aggressive use of anti-inflammatory therapies and created a need for effective tools to measure inflammation. Biomarkers of airway inflammation proposed are obtained by methods that are direct but highly invasive (bronchial biopsy, bronchoalveolar lavage), moderately direct, and less invasive (indirect sputum, exhaled air, breath condensate) or indirect and least invasive (blood, urine). Several studies described in this review have implicated the cysteinyl leukotrienes (CysLTs) as inflammatory mediators in a wide range of diseases, implying that their biological activities reach far beyond acute bronchoconstriction, the activity traditionally ascribed to them. The validity of examining sputum for "biomarkers" has improved the understanding of asthma pathophysiology, optimization of asthma treatment and management, and investigation of the relation between CysLTs and airway inflammation in asthma. Nitric oxide is also a surrogate marker of asthma and reflects airway inflammation. The anti-inflammatory effects of the leukotriene receptor antagonists and the markers of their activity continue to grow.

Cysteinyl leukotriene receptors

Cysteinyl leukotrienes (CysLTs) are important inflammatory mediators in asthma and allergic disorders. Two types of CysLT receptors, CysLT(1) and CysLT(2), which were originally defined pharmacologically based on their sensitivity to CysLT(1) specific antagonists, are responsible for most of the known CysLT biological actions. The regulation of CysLT receptor expression and signaling in disease processes is largely unclear. Recent molecular cloning of both receptor subtypes from several different species will greatly facilitate future research in understanding CysLT signal transduction mechanisms. Expression of the relatively better-studied CysLT(1) is verified in lung tissues and peripheral blood cells. Elucidating how this receptor mediates airway inflammation will deepen our understanding of asthma etiology. On the other hand, detection of CysLT(2) in the heart, brain, and adrenal glands will inject new excitement into the search for novel CysLT functions. This review summarizes receptor cloning, ligand binding, expression, signaling, and functions in an effort to bridge early pharmacological studies to future studies at the molecular level.

Clinical and genetic features underlying the response of patients with bronchial asthma to treatment with a leukotriene receptor antagonist

BACKGROUND

Treatment with antileukotriene drugs results in clinical improvement in many, though not all, patients with asthma. It can be hypothesized that the subpopulation of asthmatic patients, characterized by aspirin intolerance and cysteinyl-leukotriene overproduction, might profit most from antileukotriene treatment.

MATERIALS AND METHODS

We compared the clinical response to montelukast in two well-matched groups of patients with mild asthma: 26 aspirin-intolerant asthmatics (AIAs) and 33 aspirin-tolerant asthmatics (ATAs). We also searched for possible predictors of the clinical response among the parameters reflecting the expression and production of cysteinyl-leukotrienes (cys-LTs). This was an 8-week, single-blind, placebo-controlled trial.

RESULTS

Following a 3-week montelukast 10 mg day-1 treatment compared with placebo, there was a statistically significant reduction in the mean daytime and nocturnal asthma symptoms and beta 2-agonist use, as well as a significant improvement in the morning and evening peak expiratory flows and quality of life. Both groups showed a similar significant improvement in the parameters studied. Clinical response did not correlate with the baseline urinary LTE4 excretion level. Improvement of asthma was observed mostly in patients with a low baseline and non-IL-5 inducible expression of LTC4 synthase (LTC4S) mRNA in eosinophils. There was a trend toward a better response in carriers of LTC4S allele C, but no relationship to the CC10 genetic polymorphism.

CONCLUSIONS

No difference in the clinical response to the montelukast treatment was observed between the AIAs and the ATAs.

Montelukast: a review of its therapeutic potential in asthma in children 2 to 14 years of age

Montelukast is a cysteinyl leukotriene receptor antagonist which is used as a preventive treatment for persistent asthma in patients > or =2 years of age. In children aged 6 to 14 years montelukast (5 mg/day) treatment resulted in a significant increase in FEV(1) (forced expiratory volume in 1 second, primary clinical outcome) during an 8-week randomized, double-blind trial. Moreover, significant improvements were observed for a range of secondary endpoints assessing symptoms, exacerbation rates, beta-agonist usage and quality of life. Concomitant administration of montelukast (5 mg/day) and inhaled budesonide (200 microg twice daily) resulted in a trend towards an increase in FEV(1) (p = 0.06, primary endpoint) and a statistically significant reduction in both as-needed beta(2)-agonist usage and the percentage of days with asthma exacerbations compared with budesonide plus placebo. No significant differences were observed in asthma-related quality of life between the two groups. During clinical trials both improvements in lung function and reductions in as-needed beta(2)-agonist usage were generally observed within 1 day after initiation of therapy in children 2 to 14 years of age with persistent asthma. Data from a randomized, nonblind trial in 6- to 11-year-old children and a 6-month extension to this trial suggest that both compliance to therapy and patient satisfaction are greater for montelukast than for either inhaled sodium cromoglycate or inhaled beclomethasone. In addition, patients and parents preferred oral montelukast over sodium cromoglycate. In 2- to 5-year-old children with persistent asthma, montelukast (4 mg/day) treatment resulted in significant improvements in a range of outcomes, such as as-needed beta(2)-agonist usage, symptom scores and percentage of days with asthma symptoms, as assessed during a randomized, double-blind trial primarily designed to assess tolerability. Data from small randomized, double-blind trials suggest that montelukast reduces exercise-induced bronchoconstriction in 6- to 14-year-old children. Montelukast is generally well tolerated. The frequency of adverse events in montelukast-treated children of all ages was comparable to that in patients receiving placebo.

CONCLUSION

Oral montelukast has shown efficacy as a preventive treatment for asthma during clinical trials in children aged 2 to 14 years. The drug offers benefits over more standard therapies such as inhaled sodium cromoglycate and nedocromil in terms of compliance and convenience. In addition, the drug offers significant benefits when added to inhaled corticosteroids (according to secondary endpoints). Montelukast offers an effective, well tolerated and convenient treatment option for children with asthma.

Novel phthalimide derivatives, designed as leukotriene D(4) receptor antagonists

A series of phthalimide acid derivatives was synthesized and evaluated as leukotriene D(4) receptor antagonists. The tetrazolephthalimide LASSBio 552 (7) was shown to be able to inhibit the contractile activity induced by 100 nM of LTD(4) in guinea-pig tracheal strips with an IC(50) = 31.2 microM. In addition, LASSBio 552 (7) has been showed to present a better efficacy than zafirlukast (1) used as standard.

Cysteinyl leukotrienes induce human eosinophil locomotion and adhesion molecule expression via a CysLT1 receptor-mediated mechanism

BACKGROUND

The mechanisms involved in eosinophil recruitment by cysteinyl-leukotrienes (CysLTs) remain to be defined.

OBJECTIVE

We investigated whether CysLTs LTC4, LTD4 and LTE4 could directly stimulate in vitro adhesion molecule expression and cell locomotion of blood eosinophils from atopic asthmatic donors.

METHODS

Mab staining and FACS analysis were used to evaluate Mac-1 and LFA-1 expression on eosinophils before and after CysLTs stimulation. Eosinophil locomotion was tested using a 48-well Boyden microchamber.

RESULTS

CysLTs, at the concentrations of 1 and 10 nM, were able to significantly up-regulate Mac-1 expression (P < 0.05, each comparison) but not LFA-1 expression (P > 0.05, each comparison). A dose-dependent, eosinophil chemotaxis was also induced by LTC4, LTD4 and LTE4 (0.1-10 nM) (P < 0.01, each comparison). Montelukast (0.01 nM to 10 nM), a specific CysLT1 receptor antagonist, significantly down-regulated LTC4, LTD4 and LTE4-induced Mac-1 expression (P < 0.01, each comparison) and the CysLT-induced eosinophil migration (P < 0.01, each comparison). In contrast, montelukast did not affect Mac-1 expression or cell migration when eosinophils were stimulated by the 'non-specific activators', such as fMLP or C5a (P > 0.05, each comparison).

CONCLUSION

These data demonstrate that CysLTs are active in vitro in directly up-regulating human eosinophil functions involved in eosinophil recruitment. The down-regulation of Mac-1 expression and eosinophil chemotaxis by the potent and selective CysLT1 receptor antagonist montelukast indicated the specificity of the LTC4-, LTD4- and LTE4-induced response.

IL-5 up-regulates cysteinyl leukotriene 1 receptor expression in HL-60 cells differentiated into eosinophils

The cysteinyl leukotrienes, leukotriene (LT) C(4), LTD(4), and LTE(4), are lipid mediators that have been implicated in the pathogenesis of several inflammatory processes, including asthma. The human LTD(4) receptor, CysLT(1)R, was recently cloned and characterized. We had previously shown that HL-60 cells differentiated toward the eosinophilic lineage (HL-60/eos) developed specific functional LTD(4) receptors. The present work was undertaken to study the potential modulation of CysLT(1)R expression in HL-60/eos by IL-5, an important regulator of eosinophil function. Here, we report that IL-5 rapidly up-regulates CysLT(1)R mRNA expression, with consequently enhanced CysLT(1)R protein expression and function in HL-60/eos. CysLT(1)R mRNA expression was augmented 2- to 15-fold following treatment with IL-5 (1-20 ng/ml). The effect was seen after 2 h, was maximal by 4 h, and maintained at 8 h. Although CysLT(1)R mRNA was constitutively expressed in undifferentiated HL-60 cells, its expression was not modulated by IL-5 in the absence of differentiation. Differentiated HL-60/eos cells pretreated with IL-5 (10 ng/ml) for 24 h showed enhanced CysLT(1)R expression on the cell surface, as assessed by flow cytometry using a polyclonal anti-CysLT(1)R Ab. They also showed enhanced responsiveness to LTD(4), but not to LTB(4) or platelet-activating factor, in terms of Ca(2+) mobilization, and augmented the chemotactic response to LTD(4). Our findings suggest a possible mechanism by which IL-5 can modulate eosinophil functions and particularly their responsiveness to LTD(4), and thus contribute to the pathogenesis of asthma and allergic diseases.

Asthma: where beyond steroids?

The prevalence of asthma is increasing dramatically despite major changes in monitoring and treatment of this disease. Currently available bronchodilators and anti-inflammatory drugs are effective in most patients, although these can have side effects and are mainly symptomatic. Many drugs are now in development for the treatment of asthma. Most of these new therapies are aimed at inhibition of the inflammatory components, with better safety profiles than steroids.

Montelukast: a review of its therapeutic potential in persistent asthma

Montelukast is a cysteinyl leukotriene receptor antagonist used to treat persistent asthma in patients aged > or = 6 years. The drug has a rapid onset of action. Improvements in lung function and reductions in as-needed beta2-agonist usage are apparent within 1 day of initiating montelukast treatment in adults and adolescents (aged > or = 15 years treated with 10 mg/day) or children (aged 6 to 14 years treated with 5 mg/day) with persistent asthma as shown in clinical trials. In two 12-week, multicentre, randomised, double-blind studies in adults and adolescents aged > or = 15 years with persistent asthma [forced expiratory volume in 1 second (FEV1) = 50 to 85% predicted] there was significantly (p < 0.05) greater improvement in FEV1, symptom scores, peak expiratory flow (PEF), as-needed beta2-agonist use, peripheral eosinophil counts and health-related quality of life (QOL) in patients treated with montelukast 10 mg/day than in recipients of placebo. Improvements were significantly greater in patients treated with inhaled beclomethasone 400 microg/day than in recipients of montelukast 10 mg/day in 1 of these studies. Nonetheless, 42% of montelukast recipients experienced > or = 11% improvement in FEV1, the median improvement in this parameter in beclomethasone-treated patients. In an 8-week multicentre, randomised, double-blind, study in children aged 6 to 14 years with persistent asthma (FEV1 50 to 85% predicted), montelukast 5 mg/day produced significantly greater improvements in FEV1, clinic PEF, as-needed beta2-agonist use, peripheral eosinophil counts, asthma exacerbations and QOL scores than placebo. The combination of montelukast 10 mg/day plus inhaled beclomethasone 200 microg twice daily provided significantly better asthma control than inhaled beclomethasone 200 microg twice daily in adults with poorly controlled asthma (mean FEV1 = 72% predicted) despite 4 weeks treatment with inhaled beclomethasone. Patients receiving the combination experienced significant improvements in FEV1 and morning PEF, significant reductions in daytime symptom scores, as-needed beta2 agonist usage and night-time awakenings with asthma, and had significantly lower peripheral blood eosinophil counts after 16 weeks in this multicentre, randomised, double-blind, placebo-controlled study. Among adults (FEV1 > or = 70%) treated with montelukast 10 mg/day for 12 weeks, inhaled corticosteroid dosages were titrated downward by 47% (vs 30% in placebo recipients), 40% of patients were tapered off of inhaled corticosteroids (vs 29%), and significantly fewer patients (16 vs 30%) experienced failed corticosteroid rescues in a multicentre, randomised, double-blind study. During clinical studies, the frequency of adverse events in montelukast-treated adults, adolescents and children was similar to that in placebo recipients. In conclusion, montelukast is well tolerated and effective in adults and children aged > or = 6 years with persistent asthma including those with exercise-induced bronchoconstriction and/or aspirin sensitivity. Furthermore, montelukast has glucocorticoid sparing properties. Hence, montelukast, as monotherapy in patients with mild persistent asthma, or as an adjunct to inhaled corticosteroids is useful across a broad spectrum of patients with persistent asthma.