Role of leukotrienes in asthma pathophysiology

Mast Cells and Basophils in IgE-Independent Anaphylaxis

Anaphylaxis is a life-threatening or even fatal systemic hypersensitivity reaction. The incidence of anaphylaxis has risen at an alarming rate in the past decades in the majority of countries. Generally, the most common causes of severe or fatal anaphylaxis are medication, foods and Hymenoptera venoms. Anaphylactic reactions are characterized by the activation of mast cells and basophils and the release of mediators. These cells express a variety of receptors that enable them to respond to a wide range of stimulants. Most studies of anaphylaxis focus on IgE-dependent reactions. The mast cell has long been regarded as the main effector cell involved in IgE-mediated anaphylaxis. This paper reviews IgE-independent anaphylaxis, with special emphasis on mast cells, basophils, anaphylactic mediators, risk factors, triggers, and management.

Synthesis, Characterization and In Vitro Evaluation of Chitosan Nanoparticles Physically Admixed with Lactose Microspheres for Pulmonary Delivery of Montelukast

This study aimed to synthesise montelukast-loaded polymeric nanoparticles via the ionic gelation method using chitosan as a natural polymer and tripolyphosphate as a crosslinking agent. Tween 80, hyaluronic acid and leucine were added to modify the physicochemical properties of nanoparticles, reduce the nanoparticles’ uptake by alveolar macrophages and improve powder aerosolisation, respectively. The nanoparticles ranged from 220 nm to 383 nm with a polydispersity index of ≤0.50. The zeta potential of nanoparticles ranged from 11 mV to 22 mV, with a drug association efficiency of 46–86%. The simple chitosan nanoparticles (F2) were more spherical in comparison to other formulations (F4–F6), while the roughness of hyaluronic acid (F5) and leucine (F6) added formulations was significantly high er than F2 and Tween 80 added formulation (F4). The DSC and FTIR analysis depict that the physical and chemical properties of the drug were preserved. The release of the drugs from nanoparticles was more sustained in the case of F5 and F6 when compared to F2 and F4 due to the additional coating of hyaluronic acid and leucine. The nanoparticles were amorphous and cohesive and prone to exhalation due to their small size. Therefore, nanoparticles were admixed with lactose microspheres to reduce particle agglomeration and improve powder dispersion from a dry powder inhaler (DPI). The DPI formulations achieved a dispersed fraction of 75 to 90%, a mass median aerodynamic diameter (MMAD) of 1–2 µm and a fine particle fraction (FPF) of 28–83% when evaluated using the Anderson cascade impactor from Handihaler®. Overall, the montelukast-loaded nanoparticles physically admixed with lactose microspheres achieved optimum deposition in the deep lung for potential application in asthmatic patients.

Addition of a nutraceutical to montelukast or inhaled steroid in the treatment of wheezing during COVID-19 pandemic: a multicenter, open-label, randomized controlled trial

Background and aim Recurrent wheezing is often triggered by viral respiratory infections. The aims of our study were: i) to evaluate whether the addition of a nutraceutical (Leucodif®), could improve the efficacy of montelukast or inhaled steroids (ICS) compared to the single treatment; ii) to verify whether a treatment is more effective than another. Our study was biased by the COVID-19 pandemic, which resulted in a lockdown of almost two months in Italy. Methods The multicenter, open-label study enrolled 84 children aged 2-6 years diagnosed with recurrent wheezing and randomized them into four treatment arms for three months: ICS treatment; ii) montelukast; iii) montelukast + Leucodif; iv) ICS + Leucodif. Children were assessed at baseline and after one, two, and three months of treatment using the TRACK score for both the caregiver and the physician. Results Out of the 84 patients, 18 patients received ICS therapy, 22 patients ICS + Leucodif, 24 patients montelukast, and 20 patients montelukast + Leucodif. All four treatments resulted in a significant reduction in symptoms with no differences among the various groups. Conclusions Our study demonstrates that montelukast therapy appears to be equally effective as ICS therapy and that the addition of the nutraceutical Leucodif does not appear to improve the treatment outcome. However, in our opinion our study was strongly influenced and biased by the lockdown due to the COVID-19 pandemic, which inherently resulted in reduced exposure to the viruses that commonly cause respiratory infections in children.

Allergic asthma is a risk factor for human cardiovascular diseases

Asthma is an allergic airway disease in which type 2-mediated inflammation has a pathogenic role. Cardiovascular diseases (CVDs) are type 1-dominant inflammatory diseases in which type 2 cytokines often have a protective role. However, clinical studies demonstrate that allergic asthma and associated allergies are essential risk factors for CVD, including coronary heart diseases, aortic diseases, peripheral arterial diseases, pulmonary embolism, right ventricular dysfunction, atrial fibrillation, cardiac hypertrophy and even hypertension. Mast cells, eosinophils, inflammatory cytokines and immunoglobulin (Ig)E accumulate in asthmatic lungs and in the injured heart and vasculature of patients with CVD. Clinical studies show that many anti-asthmatic therapies affect the risk of CVD. As such, allergic asthma and CVD may share common pathogenic mechanisms. Preclinical investigations indicate that anti-asthmatic drugs have therapeutic potential in certain CVDs. In this Review, we discuss how asthma and allied allergic conditions may contribute to the prevalence, incidence and progression of CVD and vice versa.

Inflammatory modulation of the response of bronchial epithelial cells to lipopolysaccharide with pretreatment by montelukast

Montelukast, a leukotriene receptor antagonist, is the most prescribed nonsteroidal anti-inflammatory drug used as an add-on therapy for asthma. Besides its effect on blocking leukotriene action, montelukast has been proposed to have secondary anti-inflammatory properties. This study aimed to investigate the modulatory effect of montelukast on the expression of major genes involved in airway inflammation (TNF, IL6) and remodeling (MMP9, TGFB1) in response to lipopolysaccharide (LPS) in vitro. The expression of selected genes was measured by quantitative real-time polymerase chain reaction 0h and 24h after LPS stimulation in cells pretreated with montelukast. Montelukast was found to significantly attenuate increased TNF and IL6 gene expression, to have a mild effect on MMP9 and have no effect on TGFB1 expression upon stimulation with LPS. The results of our study indicate that patients on montelukast therapy would have an adequate response to acute microorganism-induced inflammation, so additional anti-inflammatory effects of montelukast should be better exploited.

A novel anti-inflammatory treatment for bradykinin-induced sore throat or pharyngitis

BACKGROUND

Often thought of as a minor health concern, sore throat or pharyngitis is an important public health issue. It is one of the most common symptoms of upper respiratory diseases including COVID-19 and is a leading cause of physician visits and antibiotic prescriptions. However, few over-the-counter medications are proven to heal sore throat inflammation.

METHODS

Adenocarcinomic human alveolar basal epithelial cells (A549 cells) and three dimensional organotypic human respiratory tissues were used to study inflammation and various treatment effects on respiratory epithelia. The cells and tissues were studied both in the presence and absence of bradykinin, one of the first inflammatory mediators of pharyngitis. Inflammation was measured by analyzing the levels of prostaglandin E2 (PGE2), interleukin 8 (IL-8), and leukotriene B4 (LTB4), transepithelial electrical resistance (TEER), and lactate dehydrogenase (LDH) release. Tissue morphology was analyzed by immunohistochemistry.

RESULTS

In studying pharyngitis using organotypic human respiratory tissue stimulated with bradykinin, we saw an increase in PGE2 and interleukin-8 (IL-8) in response to bradykinin. Acetyl salicylic acid (ASA), a nonspecific COX inhibitor, was able to mitigate a bradykinin-induced increase in PGE2 in our studies. However, ASA was inflammatory above its therapeutic window, increasing the levels of PGE2 and IL-8 above those seen with bradykinin stimulation alone. We describe a novel, scientifically validated treatment for sore throat, that contains a low dose of ASA and other anti-inflammatory ingredients.

CONCLUSION

This study elucidates the complex mechanisms involved in healing pharyngitis, an inflammatory condition of the upper respiratory epithelia. An ASA-based formula (Biovanta) mitigated bradykinin-induced inflammation more strongly than ASA alone in organotypic human respiratory tissues. Surprisingly, we found that many of the most common over the counter sore throat therapies exacerbate inflammation and IL-8 in organotypic human respiratory tissues, suggesting these common treatments may increase the likelihood of further respiratory complications.

Immune recovery following bronchiolitis is linked to a drop in cytokine and LTC4 levels

BACKGROUND

Bronchiolitis is the main cause of hospitalization of children younger than 1 year; however, the immune mechanism of bronchiolitis is not completely understood. The aim of this study was to analyze the recovery of immune response after a bronchiolitis episode.

METHODS

Forty-nine infants hospitalized with bronchiolitis diagnosis were enrolled. Nasopharyngeal aspirates (NPAs) were processed. Twenty-seven pro-inflammatory biomarkers linked to innate immunity, inflammation, and epithelial damage, as well as nitrites and lipid mediators, were evaluated in the NPA supernatant by ELISA (enzyme-linked immunosorbent assay) and Luminex. Also, 11 genes were analyzed in NPA cells by quantitative PCR.

RESULTS

A widespread statistically significant decline of multiple pro-inflammatory parameters and cytokines were detected in the recovery period after respiratory infection: interferon-α2 (IFNα2), IFNγ, interleukin-10 (IL-10), IL-1β, IL-8, IFN-γ-inducible protein-10, vascular endothelial growth factor, monocyte chemoattractant protein-1, macrophage inflammatory protein-1α (MIP-1α), and MIP-1β. Supporting these results, a decreased nuclear factor-κB gene expression was observed (P = 0.0116). A significant diminution of cysteinyl leukotriene C4 (LTC4) soluble levels (P = 0.0319) and cyclooxygenase-2 (COX-2) gene expression were observed in the recovery sample. In children classified by post-bronchiolitis wheezing, LTC4 remains elevated in the NPA supernatant.

CONCLUSIONS

After bronchiolitis, cytokines and biomarkers linked to innate immune response in NPA decrease significantly in the recovery period accompanied by a drop in LTC4 levels; however, this reduction was lower in infants with post-bronchiolitis wheezing.

Relation between asthma and sleep disordered breathing in children: is the association causal?

Over the last few decades, asthma and sleep disordered breathing (SDB) in children have experienced similar increases in prevalence, and have both been shown to have airway inflammation, leading investigators to postulate an association between asthma and SDB. However, whether this relationship is causal or not needs to be proven. In this manuscript, we use the most widely accepted epidemiologic criteria for causality, the Bradford Hill criteria, to test step-by-step whether the relation between asthma and SBD in children is causal or not. We found studies supporting 8 of the 9 criteria (strength, consistency, specificity, biological gradient, coherence and biological plausibility, experiment, and analogy) for association between asthma and SDB. However, we did not find any study showing temporality or directionality between asthma and SDB. Therefore, establishing a causal association between asthma and SDB is not yet possible.

A review on leukotrienes and their receptors with reference to asthma

OBJECTIVE AND METHODS

Leukotrienes (LTs) including cysteinyl leukotrienes (CysLTs) and LTB4 are the most potent inflammatory lipid mediators and play a central role in the pathophysiology of asthma and other inflammatory diseases. These biological molecules mediate a plethora of contractile and inflammatory responses through specific interaction with distinct G protein-coupled receptors (GPCRs). The main objective of this review is to present an overview of the biological effects of CysLTs and their receptors, along with the current knowledge of mechanisms and role of LTs in the pathogenesis of asthma.

RESULTS

CysLTs including LTC4, LTD4 and LTE4 are ligands for CysLT1 and CysLT2 receptors, and LTB4 is the agonist for BLT1 and BLT2 receptors. The role of CysLT1 receptor is well established, and most of the pathophysiological effects of CysLTs in asthma are mediated by CysLT1 receptor. Several CysLT1 antagonists have been developed to date and are currently in clinical practice. Most common among them are classical CysLT1 receptor antagonists such as montelukast, zafirlukast, pranlukast, pobilukast, iralukast, cinalukast and MK571. The pharmacological role of CysLT2 receptor, however, is less defined and there is no specific antagonist available so far. The recent demonstration that mice lacking both known CysLT receptors exhibit full/augmented response to CysLT points to the existence of additional subtypes of CysLT receptors. LTB4, on the other hand, is another potent inflammatory leukotriene, which acts as a strong chemoattractant for neutrophils, but weaker for eosinophils. LTB4 is known to play an important role in the development of airway hyper-responsiveness in severe asthma. However there is no LTB4 antagonist available in clinic to date.

CONCLUSION

This review gives a recent update on the LTs including their biosynthesis, biological effects and the role of anti-LTs in the treatment of asthma. It also discusses about the possible existence of additional subtypes of CysLT receptors.

Update on leukotriene receptor antagonists in preschool children wheezing disorders

Asthma is the most common chronic disease in young children. About 40% of all preschool children regularly wheeze during common cold infections. The heterogeneity of wheezing phenotypes early in life and various anatomical and emotional factors unique to young children present significant challenges in the clinical management of this problem. Anti-inflammatory therapy, mainly consisting of inhaled corticosteroids (ICS), is the cornerstone of asthma management. Since Leukotrienes (LTs) are chemical mediators of airway inflammation in asthma, the leukotriene receptor antagonists (LTRAs) are traditionally used as potent anti-inflammatory drugs in the long-term treatment of asthma in adults, adolescents, and school-age children. In particular, montelukast decreases airway inflammation, and has also a bronchoprotective effect. The main guidelines on asthma management have confirmed the clinical utility of LTRAs in children older than five years. In the present review we describe the most recent advances on the use of LTRAs in the treatment of preschool wheezing disorders. LTRAs are effective in young children with virus-induced wheeze and with multiple-trigger disease. Conflicting data do not allow to reach definitive conclusions on LTRAs efficacy in bronchiolitis or post-bronchiolitis wheeze, and in acute asthma. The excellent safety profile of montelukast and the possibility of oral administration, that entails better compliance from young children, represent the main strengths of its use in preschool children. Montelukast is a valid alternative to ICS especially in poorly compliant preschool children, or in subjects who show adverse effects related to long-term steroid therapy.

Urinary leukotriene excretion profile in children with exercise-induced asthma compared with controls: a preliminary study

BACKGROUND

Leukotrienes are among the most important mediators associated with inflammatory responses in patients with exercise induced asthma (EIA). The aim of this study was to investigate the impact of exercise on the urinary leukotriene profile. Hence, we compared post exercise changes of urinary leukotriene E4 (LTE4) concentration between children with EIA and healthy controls.

METHODS

Ten children with EIA and 15 controls were enrolled. Both groups underwent a standardised exercise challenge test (ECT). LTE4 concentration was measured in urine samples obtained pre and post ECT, using enzyme immunoassay and adjusted by urinary creatinine concentrations.

RESULTS

Median (minimum-maximum) pre ECT concentration of LTE4 was 17.82 (7.58-90.23 pg/ml) in EIA and 17.24 (4.64-64.02 pg/ml) in controls, p=0.86. LTE4 concentration post ECT were 23.37 (4.02-93.00 pg/ml) in EIA and 11.74 (0.13-25.09 pg/ml) in controls, p=0.02. Changes of LTE4 concentration post ECT were 2.54 (-31.98 to 43.31 pg/ml) in cases and -13.53 (-46.00 to 11.02 pg/ml) in controls, p=0.03. There was no significant correlation between basal predicted FEV(1) [%] and changes in LTE4 concentration in cases (i.e., r(s)=0.14) nor controls (i.e., r(s)=0.12). There was a tendency towards more pronounced changes in LTE4 concentration post ECT in children with moderate/mild persistent asthma compared to those with mild but intermittent asthma.

CONCLUSIONS

Children with EIA had significantly higher changes of urinary LTE4 concentrations post ECT compared to healthy controls. Urinary measurement of LTE4 may be an interesting and non-invasive option to assess control of EIA in children.

Treatment options for the management of exercise-induced asthma and bronchoconstriction

Treatment for exercise-induced bronchospasm and exercise-induced asthma includes both pharmacologic and nonpharmacologic options. Pharmacologic agents that have been proven to be effective for treating these conditions include short- and long-acting β2-adrenoceptor agonists, mast cell-stabilizing agents, anticholinergics, leukotriene receptor antagonists, and inhaled corticosteroids (ICS). When selecting the most appropriate medication, factors to consider include the effectiveness of each, the duration of action, frequency of administration, potential side effects, and tolerance level. Long-acting β2-adrenoceptor agonists should not be used without ICS. Nonpharmacologic treatments include physical conditioning, incorporating a warm-up before and a cool-down period after exercise, performing nasal breathing, avoiding cold weather or environmental allergens, using a face mask or other aid to warm and humidify inhaled air, and modifying dietary intake. The data to support nonpharmacologic treatments are limited; however, they are routinely recommended because of the low risk associated with their use. This article highlights the advantages and limitations of each treatment option.

CysLT1-R expression following allergen provocation in asthma and allergic rhinitis

Cysteinyl leukotrienes (CysLTs) contribute to allergic and inflammatory diseases through CysLT(1)-R. We aimed to assess CysLT(1)-R mRNA expression in induced sputum of rhinitics with or without asthma before and following allergen challenges. Both groups underwent nasal and "low dose" lung allergen challenges. Asthmatics also underwent "standard" lung challenge. Sputum was obtained before and at different time-points following the challenges for CysLT(1)-R, 5-lipoxygenase (5-LO), and eotaxin mRNA assessments. At baseline, there was no difference in mediator levels between groups. An increase in CysLT(1)-R mRNA (p=0.04) and a trend towards an increase in 5-LO and eotaxin (p=0.06 for both) at 24 h post-nasal challenge were observed. Following "low dose" lung allergen challenge, there was a trend towards an increase in CysLT(1)-R (p=0.07). In conclusion, CysLT(1)-R gene expression changes can be detected in sputum following allergen challenges. No difference was observed between groups, suggesting that changes in CysLT(1)-R expression occur whether or not the subject has concurrent asthma.

Blocking leukotrienes optimize asthma control: the BLOC survey

Objective:

The aim of this study was to evaluate asthma control after the introduction of a leukotriene modifier (Montelukast), in addition to the current controller asthma therapies, in patients with inadequately controlled mild-to-moderate persistent asthma. Asthma control and patient perception were assessed prior to, and 4 weeks after, the introduction of Montelukast, and the pre-introduction and post-introduction results were compared.

Materials and Methods:

A cross-sectional, observational study collected information on 1,490 eligible adult asthmatic patients in Saudi Arabia. The eligibility criteria included patients aged 15 years or more with symptomatic mild-to-moderate persistent asthma despite treatment with inhaled corticosteroids with or without long-acting beta agonist; also, the patient should attend the initial visit and follow-up visits after at least 4 weeks.

Results:

Of the 1,490 eligible patients, 79.5% received inhaled corticosteroids alone, and the remaining 20.5% received combination of inhaled corticosteroids and long-acting bronchodilator. Despite the treatment with daily controller medications, asthma symptoms persisted in more than two-thirds of the study population. Upon adding Montelukast, more than 80% of patients reported improvement in symptoms, which was consistent in all patients irrespective of corticosteroid type or dose (stratum) or the addition of long-acting β2-agonist. At the follow-up visit, 92.2% of patients reported that they felt better on Montelukast.

Conclusion:

Leukotriene modifier Montelukast has significant additive benefits in the management of patients who suffer from mild-to-moderate asthma and who are inadequately controlled on inhaled corticosteroids therapy with or without long-acting bronchodilator.

Fatal adverse reaction to ketorolac tromethamine in asthmatic patient

A case of an asthmatic woman who collapsed within a few minutes after intramuscular ketorolac tromethamine (KT) injection is reported. Autopsy findings revealed anatomic evidence of a recent asthma attack. KT was found to be present in the blood at a concentration within the therapeutic range and consistent with the administered dose. Based on the timing of the collapse in relation to the KT administration, death was attributed to an adverse reaction to KT, resulting in acute bronchospasm and cardiac arrest, with asthma as an underlying contributing factor. In this case, asthma alone was not responsible for the death of the patient but only a contributing factor. Physicians have to be aware that in asthmatic patients bronchospasm can be induced by drugs among which aspirin or nonsteroidal anti-inflammatory drugs such as KT are the most common; therefore, death may have an iatrogenic cause. The paper also describes the pathogenic mechanism of an adverse reaction to such drugs and analytical methods for the isolation and detection of KT in postmortem blood.

Exercise-induced bronchoconstriction: The effects of montelukast, a leukotriene receptor antagonist

Exercise-induced bronchoconstriction (EIB) is very common in both patients with asthma and those who are otherwise thought to be normal. The intensity of exercise as well as the type of exercise is important in producing symptoms. This may make some types of exercise such as swimming more suitable and extended running more difficult for patients with this condition. A better understanding of EIB will allow the physician to direct the patient towards a type of exercise and medications that can result in a more active lifestyle without the same concern for resulting symptoms. This is especially important for schoolchildren who are usually enrolled in physical education classes and elite athletes who may desire to participate in competitive sports. Fortunately several medications (short- and long-acting beta(2)-agonists, cromolyn, nedocromil, inhaled corticosteroids, and more recently leukotriene modifiers) have been shown to be effective in preventing or attenuating the effects of exercise in many patients. In addition, inhaled beta(2)-agonists have been shown to quickly reverse the airway obstruction that develops in patients and continue to be the reliever medications of choice. Inhaled corticosteroids are increasingly being recommended as regular therapy now that the role of inflammation and airway injury has been identified in EIB. With the discovery that there is a release of mediators such as histamine and leukotrienes from cells in the airway following exercise with resulting airway obstruction in susceptible individuals, interest has turned to attenuating their effects with mediator antagonists especially those that block the effects of leukotrienes. Studies with an oral leukotriene antagonist, montelukast, have shown beneficial effects in adults and children aged as young as 6 years with EIB. These effects can be demonstrated as soon as two hours and as long as 24 hours after administration without a demonstrated loss of a protective effect after months of treatment. The studies leading up to and resulting in an approval of montelukast for EIB for patients aged 15 years and older are reviewed in this paper.

Montelukast inhibits tumour necrosis factor-alpha-mediated interleukin-8 expression through inhibition of nuclear factor-kappaB p65-associated histone acetyltransferase activity

BACKGROUND

Montelukast is a potent cysteinyl leukotriene-1 receptor antagonist possessing some anti-inflammatory effects although the molecular mechanism of these anti-inflammatory effects is unknown. In this study, we aimed to investigate the effect of montelukast on nuclear factor (NF)-kappaB-associated histone acetylation activity in phorbol myristate acetate (PMA)-differentiated U937 cells.

METHODS

We examined the inhibitory effects of montelukast on TNF-alpha-induced IL-8 production in PMA-differentiated U-937 cells. U-937 cells were exposed to PMA (50 ng/mL) for 48 h to allow differentiation to macrophages. Macrophages were then exposed to TNF-alpha (10 ng/mL) in the presence or absence of montelukast (0.01-10 microm) for 24 h. After this time, the concentration of IL-8 in the culture supernatant was measured by sandwich-type ELISA kit. The effect of signalling pathways on TNF-alpha-induced IL-8 release was examined pharmacologically using selective NF-kappaB/IKK2 (AS602868, 3 microm), (PD98059, 10 microm) and p38 mitogen activated protein kinase (MAPK) (SB203580, 1 microm) inhibitors. NF-kappaB DNA binding activity was measured by a DNA-binding ELISA-based assay. NF-kappaB-p65-associated histone acetyltransferase (HAT) activity was measured by immunoprecipitation linked to commercial fluorescent HAT.

RESULTS

TNF-alpha-induced IL-8 release was suppressed by an NF-kappaB inhibitor but not by MEK or p38 MAPK inhibitors. Montelukast induced a concentration-dependent inhibition of TNF-alpha-induced IL-8 release and mRNA expression that reached a plateau at 0.1 microm without affecting cell viability. Montelukast did not affect NF-kappaB p65 activation as measured by DNA binding but suppressed NF-kappaB p65-associated HAT activity.

CONCLUSION

Montelukast inhibits TNF-alpha-stimulated IL-8 expression through changes in NF-kappaB p65-associated HAT activity. Drugs targeting these enzymes may enhance the anti-inflammatory actions of montelukast.

Cysteinyl leukotriene-1 receptor activation in a human bronchial epithelial cell line leads to signal transducer and activator of transcription 1-mediated eosinophil adhesion

We studied the effect of leukotriene D(4) (LTD(4)) on a human bronchial epithelial cell line (16HBE) overexpressing the cysteinyl leukotriene (CysLT) (1) receptor (HBECysLT(1)R), looking at the associated signal transduction mechanisms as well as at effects on inflammatory cell adhesion. The results obtained showed that LTD(4) increases the phosphorylation of extracellular signal-regulated protein kinase (ERK) 1/2 and of the signal transducer and activator of transcription 1 (STAT-1) in serine 727 (STAT-1Ser727), resulting in increased eosinophil adhesion to HBECysLT(1)R, associated with enhanced surface expression of intercellular adhesion molecule (ICAM) 1. Pretreatment with a CysLT(1)R-selective antagonist or with a selective inhibitor of protein kinase C (PKC) or with a selective inhibitor of the mitogen-activated protein kinase kinase (MEK) successfully suppressed both LTD(4)-induced STAT-1Ser727 phosphorylation and the associated increase in eosinophil adhesion. The use of the MEK inhibitor and of the selective CysLT(1)R antagonist in electrophoretic mobility shift assay experiments showed that LTD(4) promotes the nuclear translocation of STAT-1 through the activation of ERK1/2 pathway. The key role of STAT-1 in leukotriene D(4) transduction signaling was confirmed by RNA interference experiments, where silencing of STAT-1 expression abolished the effect of leukotriene D(4) on eosinophil adhesion. In conclusion, for the first time, we provide evidence of the involvement of STAT-1 in the signal transduction mechanism of the CysLT(1) receptor; phosphorylation of STAT-1, through PKC and ERK1/2 activation, causes enhanced ICAM-1 surface expression and eosinophil adhesion. Effective CysLT(1)R antagonism may therefore contribute to the control of the chronic inflammatory condition that characterizes human airways in asthma.

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.

Single-Dose Montelukast or Salmeterol as Protection Against Exercise-Induced Bronchoconstriction

BACKGROUND AND OBJECTIVE

It has been previously established that montelukast provides protection against exercise-induced bronchoconstriction (EIB) after a single dose. The present objective was to assess the onset and duration of this protective action in a trial that included both positive and negative controls.

METHODS

A randomized, active-controlled and placebo-controlled, double-blind, double-dummy, three-way crossover study was conducted in 47 patients (age range, 15 to 44 years) in whom there was a 20 to 40% fall in FEV(1) following exercise (DeltaFEV(1)). In randomized sequence, patients received oral montelukast (10 mg), placebo, or inhaled salmeterol (50 microg) as a positive control. Dosing was followed by exercise challenges at 2, 8.5, and 24 h. The primary end point was maximum DeltaFEV(1) at 2 h postdose. Secondary end points included maximum DeltaFEV(1) at the two later time points, and other measures (including recovery time and need for beta-agonist rescue) at all time points.

RESULTS

The maximum DeltaFEV(1) magnitudes at 2, 8.5, and 24 h were significantly smaller after montelukast administration than after placebo administration (least squares mean [+/- SE], 13.2 +/- 1.2%, 11.7 +/- 1.2%, and 10.0 +/- 1.1% vs 21.8 +/- 1.2%, 16.8 +/- 1.3%, and 14.0 +/- 1.1%, respectively; p <or= 0.001, < 0.01, and < 0.05). All secondary end point results supported the primary end point. Montelukast and salmeterol had similar efficacy at 2 and 8.5 h, but only montelukast was effective at 24 h.

CONCLUSION

Montelukast provided significant protection against EIB having an onset within 2 h following a single oral dose and lasting for at least 24 h.

Nasal lavage leukotrienes in infants with RSV bronchiolitis

Respiratory syncytial virus (RSV) bronchiolitis is a very common infection in infants and, after the acute phase, a number of patients develop a reactive airway disease that lasts for years. Although the pathogenesis of the lung damage after RSV bronchiolitis is still largely unknown, previous studies suggest that leukotrienes may play an active part in it. The aim of this study was to measure leukotriene levels in the nasal lavage fluid (NLF) collected in infants during RSV bronchiolitis and 1 month later. Cysteinyl leukotrienes (Cys-LTs) and leukotriene B(4) (LTB(4)) were measured in the NLF of 22 infants with their first episode of RSV bronchiolitis and 16 healthy infants. A second NLF sample was collected to measure leukotriene levels 1 month after the acute disease. NLF Cys-LT levels were significantly higher in infants with RSV bronchiolitis than in healthy controls [950 pg/ml (285.5-2155.9) vs. 110.5 pg/ml (66.5-451.3), p = 0.01], and they remained so a month after the acute infection (p = 0.02). A subanalysis showed no difference in Cys-LTs concentrations, either between bronchiolitis infants with and without a family history of atopy, or between those with and without passive exposure to cigarette smoke. No significant difference was found between the LTB(4) levels measured in the bronchiolitis cases and the control children. Cys-LTs are significantly increased in the NLF of infants with acute RSV bronchiolitis, and remain so at 1-month follow-up, suggesting a possible role of these eicosanoids in the pathogenesis of the disease.

G-protein-coupled receptors and asthma endophenotypes: the cysteinyl leukotriene system in perspective

Genetic variation in specific G-protein coupled receptors (GPCRs) is associated with a spectrum of respiratory disease predispositions and drug response phenotypes. Although certain GPCR gene variants can be disease-causing through the expression of inactive, overactive, or constitutively active receptor proteins, many more GPCR gene variants confer risk for potentially deleterious endophenotypes. Endophenotypes are traits, such as bronchiole hyperactivity, atopy, and aspirin intolerant asthma, which have a strong genetic component and are risk factors for a variety of more complex outcomes that may include disease states. GPCR genes implicated in asthma endophenotypes include variants of the cysteinyl leukotriene receptors (CYSLTR1 and CYSLTR2), and prostaglandin D2 receptors (PTGDR and CRTH2), thromboxane A2 receptor (TBXA2R), beta2-adrenergic receptor (ADRB2), chemokine receptor 5 (CCR5), and the G protein-coupled receptor associated with asthma (GPRA). This review of the contribution of variability in these genes places the contribution of the cysteinyl leukotriene system to respiratory endophenotypes in perspective. The genetic variant(s) of receptors that are associated with endophenotypes are discussed in the context of the extent to which they contribute to a disease phenotype or altered drug efficacy.

Leukotriene receptor antagonists in children with cystic fibrosis lung disease : anti-inflammatory and clinical effects

Cystic fibrosis (CF) lung disease is characterized by chronic endobronchial infection resulting in progressive pulmonary destruction; this is a major cause of mortality and morbidity. Neutrophils are the primary effector cells responsible for the progressive deterioration of lung function. Peptido-leukotriene B4 antagonists, new anti-inflammatory agents that block the neutrophil-dominated inflammation, could have had the potential for long-term use. A trial on the pharmacokinetics of amelubant administered orally as a single dose of up to 75 mg in pediatric patients with CF and 300 mg in adults, and as a repeated dose of 75 mg and 150 mg, respectively, once daily for 15 days provided evidence that amelubant metabolism in adult and pediatric patients with CF is similar to that in healthy adults. In another study using the same dosage regimen, amelubant appeared to be safe and well tolerated. Safety measures included physical examination, vital signs, spirometry, oximetry, ECG, and clinical laboratory testing. However, a randomized, double-blind, placebo-controlled, multinational, phase II trial (Boehringer Ingelheim 543.45) was conducted to investigate the clinical efficacy of 24 weeks of treatment with amelubant in patients with CF with mild-to-moderate lung disease. Two doses of amelubant (75 and 150 mg) were tested in adult patients (> or = 18 years) and one dose of amelubant (75mg) was tested in pediatric (6-17 years) patients. The trial was terminated early due to a statistically significant increase in the risk of pulmonary-related, serious adverse events in adults receiving amelubant. Cysteinyl leukotrienes, eosinophilic inflammation, and viral infections also contribute to progressive pulmonary destruction in CF. Cysteinyl leukotrienes are potential targets for cysteinyl leukotriene receptor antagonist use. A study on the pharmacokinetics of montelukast in children with CF provided evidence that the dose of montelukast and the administration interval does not need to be modified if the goal is to mimic the serum concentrations used to treat asthma. In a randomized, double-blind, crossover, placebo-controlled study, 16 children with mild CF (median age 9.5 years; vital capacity [VC] >70%) were treated with montelukast (5 to < or =14 years; 5 mg; >14 years; 10 mg) or placebo as a once-daily tablet for 21 days. There was a significant (p < or = 0.02) reduction in serum eosinophil cationic protein levels and eosinophils (p < or = 0.027) with montelukast. However, neither lung function tests (VC, forced expiratory volume in 1 second [FEV1], maximum expiratory flow at 25% of forced VC), nor clinical symptom scores changed significantly. In another study, 26 patients aged 6-18 years with moderate CF (VC between 40% and 69% predicted) received montelukast or placebo for 8 weeks in a 20-week, randomized, double-blind, crossover, placebo-controlled trial. After treatment with montelukast there was a significant improvement in FEV1, peak expiratory flow, and forced expiratory flow between 25% and 75%, and a significant decrease in cough and wheezing scale scores (p < 0.001 for all). Montelukast treatment decreased serum and sputum levels of eosinophil cationic protein and interleukin-8 (IL-8), decreased sputum levels of myeloperoxidase, and increased serum and sputum levels of IL-10 (p < 0.001 for all) compared with placebo. To date, clinical experience and research data on the anti-inflammatory effects of leukotriene receptor antagonists in CF are limited. Multicenter trials with longer observation periods and greater patient numbers are needed to prove the hypothesis that leukotriene receptor antagonists have the potential to ameliorate CF lung disease with long term use.

Suppressive effect of verproside isolated from Pseudolysimachion longifolium on airway inflammation in a mouse model of allergic asthma

Allergic inflammation of the airways has a critical role in asthma development. We investigated a suppressive effect of verproside (3,4-dihydroxy catalpol) isolated from the extract of Pseudolysimachion longifolium on asthmatic parameters--such as immunoglobulin E (IgE) level, cytokine release, eosinophilia, airway hyperresponsiveness and mucus hypersecretion--in an OVA-sensitized/challenged mouse model. Verproside significantly inhibited the increase of total IgE and the cytokines IL-4 and IL-13 in plasma and bronchoalveolar lavage fluid, and also effectively suppressed airway hyperresponsiveness, eosinophilia and mucus hypersecretion in OVA-induced asthmatic mice. The efficacy of verproside was comparable to montelukast, an anti-asthmatic drug that is currently available. These results suggest that verproside could be a major marker in herbal medicines that are used for asthma treatment, and could also act as a lead for anti-asthmatic drugs.

Pranlukast, a Leukotriene Receptor Antagonist, Inhibits Interleukin-5 Production via a Mechanism Distinct from Leukotriene Receptor Antagonism

BACKGROUND

Pranlukast, a cysteinyl leukotriene receptor 1 (CysLTR1) antagonist, inhibits not only airway smooth muscle contraction, but also allergic inflammation. The aim of this study was to determine the mechanism of pranlukast-induced interleukin-5 (IL-5) inhibition in allergic inflammation.

METHODS

Surgically resected human lung tissue was passively sensitized in vitro with mite-allergen-sensitized sera, followed by stimulation with mite allergen after pretreatment of the tissue with pranlukast, dexamethasone, or both. The IL-5 protein level in the culture medium was measured, and in situ hybridization of IL-5 and CysLTR1 mRNA was performed using lung tissues.

RESULTS

Pretreatment of lung tissues with pranlukast alone significantly decreased the amount of IL-5 protein in the culture medium by 40%. The combination of pranlukast and dexamethasone synergistically enhanced this effect. Quantitative in situ hybridization with image analysis revealed abundant expression of IL-5 mRNA in eosinophils, lymphocytes, and mast cells in sensitized and allergen-stimulated lung tissues. CysLTR1 mRNA was detected in macrophages, smooth muscle cells, eosinophils, and mast cells, but was less expressed in lymphocytes. Pranlukast-induced inhibition of IL-5 mRNA expression was noted in various cells, irrespective of their CysLTR1 mRNA expression status. In addition, cysteinyl leukotrienes per se failed to upregulate the IL-5 production.

CONCLUSION

Our results indicate that pranlukast inhibits IL-5 synthesis via a mechanism distinct from CysLTR1 antagonism.

Development of ultra short-acting muscle relaxant agents: History, research strategies, and challenges

Author has reviewed the literature and his own work related to the chemistry, pharmacology, and clinical aspects of new muscle relaxants. Emphasis has been placed on the basic science concepts and technologies (e.g. structure-activity relationships, nicotinic receptor pharmacology, and investigation of side effects) behind the development of rapidly and short acting nondepolarizing muscle relaxants.

Adenosine 5'-monophosphate increases levels of leukotrienes in breath condensate in asthma

Hyperresponsiveness (AHR) is a key physiological abnormality in asthma. In clinical and research studies AHR is measured bronchial challenge, with methacholine (MCh), but more recently with adenosine-5'-monophosphate (AMP). In the search for markers of airway inflammation in asthmatic patients, we measured the concentrations of histamine and cysteinyl-leukotrienes (cys-LTs) before and after MCh and AMP challenges in the exhaled breath condensate of 13 patients with mild asthma (FEV1 78.5%pred) and nine healthy non-smokers, using specific enzyme immunoassays. With methacholine challenge we did not find any differences between asthmatics and normal subjects in the pre- and post-challenge concentrations of cys-LTs: 27.2+/-1.4 vs. 29.2+/-1.2 pg/ml and 26.3+/-2.2 vs. 27.5+/-4.2 pg/ml, respectively or histamine: 5.1+/-0.4 vs. 5.1+/-0.6 nM and 4.5+/-0.4 vs. 4.4+/-0.3 nM; P>0.05). In asthmatic patients cys-LT levels were significantly higher after AMP challenge (56.2+/-9.7 vs. 31.7+/-6.9 pg/ml; P<0.05); but there was no difference in healthy subjects (27.2+/-4.6 vs. 30.3+/-4.7 pg/ml). There was no difference in histamine concentrations in asthmatic (5.9+/-1.8 vs. 4.5+/-0.5 nM), or healthy subjects (5.5+/-0.4 vs.5.7+/-0.9 nM) after AMP challenge. In conclusion, our results show that the cys-LTs are increased in exhaled breath condensate after AMP challenge, which may indicate that the AMP acts indirectly by releasing cys-LTs from primed mast cells. The detection of LTs and histamine in exhaled breath condensate may be useful in monitoring asthma.

Management of exercise-induced bronchospasm in children: the role of leukotriene antagonists

This review assesses the evidence on the efficacy of leukotriene antagonists in the management of exercise-induced bronchospasm (EIB) in children. Only two randomized, double-blind, placebo-controlled, crossover studies have examined the effect of leukotriene antagonists in EIB in a pediatric setting. All other studies, including those comparing leukotriene antagonists with other agents such as beta(2)-adrenoceptor agonists (beta(2)-agonists) and inhaled corticosteroids, primarily involve adult patients. In children, not receiving other asthma medication, leukotriene antagonists can offer statistically significant protection from EIB compared with placebo. However, protection is not complete, as a significant proportion of children will continue to experience a >15% reduction in FEV(1). None of the studies involved children treated concurrently with other asthma medications; therefore, comments on additive therapy cannot be made. Despite evidence from only a few studies, leukotriene antagonists are seen to be well tolerated, efficacious, and of benefit to some children. In addition, current management for EIB with short-acting beta(2)-agonists is less than ideal. It is therefore concluded that in children with EIB, leukotriene antagonists are indicated on a trial basis with individualized therapy and follow-up to evaluate treatment response.

A cysteinyl leukotriene 2 receptor variant is associated with atopy in the population of Tristan da Cunha

The clinical heterogeneity of asthma suggests that the contribution of genetic variability in candidate gene loci to well-defined phenotypes, such as atopy, may be examined to identify appropriate genetic risk factors for asthma. The gene encoding the cysteinyl leukotriene 2 (CysLT2) receptor has been implicated in atopy since it is localized to a region of chromosome 13q14 that has been linked to atopy in several populations and the cysteinyl leukotrienes are known to activate eosinophils and mast cells in atopy. Accordingly, we analysed the contribution of CysLT2 receptor gene variation to atopy in the inhabitants of Tristan da Cunha, a population characterized by both a founder effect and a 47% prevalence of atopy. Single-stranded conformational polymorphism analysis revealed four variants. Among these, the M201V [corrected] variant was activated with four-fold less potency by leukotriene D4 (LTD4) in a calcium flux assay. The CysLT2 receptor partial agonist, BAY u9773, also showed four-fold lower potency on the M201V [corrected] variant. The M201V [corrected] mutation is located within the extracellular region of the fifth transmembrane spanning domain of CysLT2 receptor, a position that may alter ligand binding and effector signalling. The novel M201V [corrected] CysLT2 receptor variant was associated with atopy (21%) on Tristan da Cunha compared with those who were non-atopic (7%) (Fisher's exact test, P=0.0016) in a manner that was independent of asthma (two-way ANOVA, P=0.0015). This represents the first association of a coding mutation in the CysLT2 receptor gene, located on chromosome 13q14, with the atopic phenotype found in the Tristan da Cunha population.

General principles of asthma management: pharmacotherapy

Asthma, a disease of urbanized societies, has been increasing at an alarming rate on a worldwide basis. In recognition of this problem, the NHLBI developed the NAEPP in 1991. An expert panel was appointed that developed guidelines for the diagnosis and management of asthma. The original report has been updated several times, most recently in 2002. In this article the author focuses on the general principles of asthma pharmacotherapy in accordance with the conceptual framework that characterizes drugs as relievers or controllers. The preeminent use of ICS in the management of asthma sufferers who are characterized as having more than mild intermittent disease is emphasized, as is the principle of matching therapy with severity of disease.

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.

Measuring subepithelial thickness using endobronchial ultrasonography in a patient with asthma: a case report

The chronic inflammation of bronchial asthma is characterized by swelling of the subepithelial mucosa. However, it is difficult to assess subepithelial edema clinically. We report the case of a patient with asthma whose subepithelial edema was evaluated by endobronchial ultrasonography. Receiving montelukast 10 mg/day for 2 weeks, a 42-year-old man with mild, persistent asthma had his symptoms controlled by beta2-inhalation alone. Pretreatment endobronchial ultrasonography revealed subepithelial thickening in the right main stem bronchus, with a low absorption area suggestive of edema. Two weeks of montelukast therapy diminished the amount of subepithelial edema. Endobronchial ultrasonography is a promising technique for determining subepithelial edema in the asthmatic airway.

An evaluation of the activity related to inflammation of four plants used in Thailand to treat arthritis

The leaves of Acanthus ebracteatus, stembark of Oroxylum indicum and the stems of Cryptolepis buchanani and Derris scandens are used as traditional remedies in Thailand for arthritis. Aqueous and alcoholic extracts were tested using three different in vitro systems for effects relevant to anti-inflammatory activity. The aqueous extracts of O. indicum and D. scandens significantly reduced myeloperoxide release. Eicosanoid production was reduced only by the aqueous extracts of A. ebracteatus and D. scandens. D. scandens extract showed potent inhibitory activity against generation of leukotriene B(4) and also displayed antioxidant activity. In the rat hind paw edema test, D. scandens extract showed significant activity when given intraperitoneally but did not produce a significant reduction when given orally. The results therefore supported to some extent the traditional use of D. scandens for arthritic conditions and provided slight indication of activity which could explain the use of O. indicum and A. ebracteatus. No relevant activity was demonstrated in any of the tests for C. buchanani extracts.

The activity against leukocyte eicosanoid generation of essential oil and polar fractions of Adesmia boronioides Hook.f

The polar fractions (methanol and aqueous extract) and essential oil of Adesmia boronioides aerial parts were tested in vitro at concentrations of 15 and 50 microg/mL, for their effects on the COX and 5-LOX pathways of eicosanoid generation (TXB2, PGE2 and LTB4) in stimulated rat peritoneal leukocytes. Potent inhibition of LTB4 generation was displayed by the methanol extract and the essential oil, whereas the aqueous extract was essentially inactive. The methanol extract also caused potent inhibition of TXB2 generation but the essential oil and the aqueous extract were much less active. The effects on PGE2 production were much less striking, implying that the main effect is on thromboxane synthetase rather than on COX. Although the essential oil caused LDH release in leukocytes treated concurrently with ionophore, suggesting substantial toxicity to the cells, this extract did not affect cell viability according to the MTT test when incubated with the cells in the absence of ionophore. The two other extracts did not affect cell viability at the concentrations tested. It is concluded that Adesmia boronioides contains substance(s) that preferentially inhibit the 5-lipoxygenase activity of arachidonic acid metabolism and suggest that this may contribute to the antiinflammatory actions of extracts of this plant.

Using a matrix as an educational approach to asthma

Health care providers agree that asthma care must be individualized to fit the need of the child and family. A written plan in the form of a matrix enables the health care provider to give families a step-by-step individualized plan of care for asthma. This article discusses the use of a long-term treatment plan in matrix form as an educational tool for health care providers and for families. The written long-term plan can be used to guide treatment for any level of asthma severity. Following a review of asthma pathogenesis and diagnosis, categories of medications are presented, along with their role in a long-term treatment plan. The National Heart, Lung, and Blood Institute guidelines are used as a basis for the recommendations in the long-term treatment plan.

Fasting stress exacerbates classical conditioned histamine release in guinea pigs

To clarify the contribution of stress to classical conditioning-associated asthmatic responses, the effect of fasting stress on conditioned histamine release was investigated in a guinea pig model of asthma. The animals were randomly divided into 2 groups for Experiment 1 and 2, and received a conditioning procedure in which ovalbumin (OA) as an unconditioned stimulus (US) and dimethylsulfide (DMS, sulfur smelling) as a conditioned stimulus (CS) were simultaneously inhaled after fasting for 16 h. Then, one group was given food as a reward for respiratory distress, and the other group was denied it for more than 3 h, while being placed in front of the feeding group. After this procedure was repeated 5 times, the plasma histamine levels in response to the CS were measured in half of each group in Experiment 1, and the respiratory resistance (Rrs) was assessed similarly in the other half of each group in Experiment 2. The same experiments were again performed after exchanging assignments of feeding group or fasting group in both experiments. The control groups in both experiments received the CS and the US 10 times separately in a random order under 16 h fasting conditions and were provided food after the exposures. After these pseudo-conditioning presentations, the plasma histamine levels or the Rrs in response to the CS were measured. In Experiment 1, the plasma histamine levels in the fasting stress group after the first conditioning sessions were significantly higher than those of the other groups. This difference was not observed when the groups were exchanged. In Experiment 2, the fasting stress group showed higher values in the Rrs compared to the other groups, irrespective of the first or second conditionings; however, they were not significant. The present study indicates that fasting stress after the conditioning procedures exacerbates the following conditioned histamine release, although the stress effect on bronchoconstriction was not confirmed.

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.

Exercise-induced bronchoconstriction

Exercise-induced asthma, or more appropriately, exercise-induced bronchoconstriction (EIB), occurs in 80 to 90% of individuals with asthma and in approximately 11% of the general population without asthma. EIB is characterised by post-exercise airways obstruction resulting in reductions in forced expiratory volume in 1 second (FEV(1)) of greater than 10% compared with pre-exercise values. The mechanism of EIB remains elusive, although both cooling and drying of airways play prominent roles. Cold, dry inhaled air during exercise or voluntary hyperventilation is the most potent stimulus for EIB. Inflammatory mediators play central roles in causing the post-exercise airways obstruction. Diagnosis of EIB requires the use of an exercise test. The exercise can be a field or laboratory based test, but should be of relatively high intensity (80 to 90% of maximal heart rate) and duration (at least 5 to 8 minutes). Pre- and post-exercise pulmonary function should be compared, and post exercise pulmonary function determined over 20 to 30 minutes for characterisation of EIB. A pre- to post-exercise drop in FEV(1) of greater than 10% is abnormal. Approaches to treatment of EIB include both nonpharmacological and pharmacological strategies. A light exercise warm up prior to moderate to heavy exercise reduces the severity of EIB. More recently, studies have supported a role for dietary salt as a modifier of the severity of EIB, suggesting that salt restrictive diets should reduce symptoms of EIB. Short acting, inhaled beta(2)-agonists constitute the most used prophylactic treatment for EIB. However, antileukotriene agents are emerging as effective, well tolerated, long-term treatments for EIB.

Gene expression profile of HIV-1 Tat expressing cells: a close interplay between proliferative and differentiation signals

BACKGROUND

Expression profiling holds great promise for rapid host genome functional analysis. It is plausible that host expression profiling in an infection could serve as a universal phenotype in virally infected cells. Here, we describe the effect of one of the most critical viral activators, Tat, in HIV-1 infected and Tat expressing cells. We utilized microarray analysis from uninfected, latently HIV-1 infected cells, as well as cells that express Tat, to decipher some of the cellular changes associated with this viral activator.

RESULTS

Utilizing uninfected, HIV-1 latently infected cells, and Tat expressing cells, we observed that most of the cellular host genes in Tat expressing cells were down-regulated. The down-regulation in Tat expressing cells is most apparent on cellular receptors that have intrinsic receptor tyrosine kinase (RTK) activity and signal transduction members that mediate RTK function, including Ras-Raf-MEK pathway. Co-activators of transcription, such as p300/CBP and SRC-1, which mediate gene expression related to hormone receptor genes, were also found to be down-regulated. Down-regulation of receptors may allow latent HIV-1 infected cells to either hide from the immune system or avoid extracellular differentiation signals. Some of the genes that were up-regulated included co-receptors for HIV-1 entry, translation machinery, and cell cycle regulatory proteins.

CONCLUSIONS

We have demonstrated, through a microarray approach, that HIV-1 Tat is able to regulate many cellular genes that are involved in cell signaling, translation and ultimately control the host proliferative and differentiation signals.

Thromboxane A2 inhibition: therapeutic potential in bronchial asthma

Bronchial asthma is a disease defined by reversible airway obstruction, bronchial hyperresponsiveness and inflammation. In addition to histamine and acetylcholine, recent studies have emphasized the role of arachidonic acid metabolites (leukotrienes, prostaglandins and thromboxane A(2)) in the pathogenesis of asthma. Among these mediators, thromboxane A(2) (TXA(2)) has attracted attention as an important mediator in the pathophysiology of asthma because of its potent bronchoconstrictive activity. Thromboxane A(2) is believed to be involved not only in late asthmatic responses but also in bronchial hyperresponsiveness, a typical feature of asthma. Strategies for inhibition of TXA(2) include TXA(2) receptor antagonism and thromboxane synthase inhibition. Results of double-blind, placebo-controlled clinical trials have proven the efficacies of the thromboxane receptor antagonist seratrodast and the thromboxane synthase inhibitor ozagrel in the treatment of patients with asthma. Seratrodast and ozagrel are available in Japan for the treatment of asthma. Ramatroban, another thromboxane receptor antagonist, is currently under phase III clinical evaluation in Europe and Japan for the treatment of asthma. The pharmacological profiles of the thromboxane modulators may be improved by combination with leukotriene D(4) receptor antagonists. A multi-pathway inhibitory agent such as YM 158, which is a novel orally active dual antagonist for leukotriene D(4) and thromboxane A(2 )receptors, may have potent therapeutic effects in the treatment of bronchial asthma. Large scale clinical trials are necessary to further define the role of thromboxane modulators in the treatment of patients with asthma.

History and future perspectives of treating asthma as a systemic and small airways disease

Asthma is an inflammatory disorder in which the small airways of the lung play an important role. There is also evidence for the systemic nature of asthma. No current method adequately measures small airways function alone. Therefore, a combination of functional and clinical parameters should be used to ensure that patients with asthma are adequately treated with due consideration of the small airways. Previously therapeutic strategies have focused on bronchodilation and attenuation of airway inflammation. While early oral therapies had the advantage of reaching the small airways and treating the systemic aspect of asthma, they were associated with serious side-effects. Inhaled therapies were therefore developed to limit these effects. However, inhaled therapies have the disadvantage of limited penetration into the peripheral airways and an inability to treat the systemic component of asthma. They are also associated with local and systemic side-effects. The future for asthma treatment is likely to be a systemically administered medication with few side-effects targeting disease-specific mediators. The leukotriene receptor antagonists and anti-IgE monoclonal antibodies are examples of such therapies and the emergence of other new strategies is awaited.