Therapeutic modulation of allergic airways disease with leukotriene receptor antagonists

Dose-response effect of Montelukast on post-extraction dental socket repair and skeletal phenotype of mice

Bone metabolism and repair are directly regulated by arachidonic acid metabolites. At present, we analyzed the dose-response effects of a selective cysteinyl leukotriene receptor type-1 antagonist during bone repair after tooth extraction and on non-injured skeleton. Sixty-three 129 Sv/Ev male mice composed the groups: C-Control (saline solution); MTK2-2 mg/Kg of Montelukast (MTK) and MTK4-4 mg/Kg of MTK, daily administered by mouth throughout all experimental periods set at 7, 14, and 21 days post-operative. Dental sockets were analyzed by computed microtomography (microCT), histopathology, and immunohistochemistry. Femurs, L5 vertebra and organs were also removed for observation. Blood was collected for plasma bone and liver markers. Histopathology and microCT analysis revealed early socket repair of MTK2 and MTK4 animals, with significant increased BV/TV at days 14 and 21 compared to C. Higher plasma calcium was detected at days 7 and 21 in MTK4 in comparison to C, while phosphate was significantly increased in MTK2 in the same periods in comparison to C and MTK4. No significant differences were found regarding plasma ALP and TRAP, neither for local TRAP and Runx2 immunolabeling at the healing sockets. Organs did not present histological abnormalities. Increased AST levels have been detected in distinct groups and periods. In general, femur phenotype was improved in MTK treated animals. Collectively, MTK promoted early bone formation after tooth extraction and increased bone quality of femurs and vertebra in a time-dose-dependent manner, and should be considered as an alternative therapy when improved post-extraction socket repair or skeleton preservation is required.

Small Airway Disease in Pediatric Asthma: the Who, What, When, Where, Why, and How to Remediate. A Review and Commentary

Asthma affects all portions of the airways. Small airways, however, comprise a substantial component of the conducting lung air flow. In asthma, inflammatory processes can affect the whole respiratory tract, from central to peripheral/small airways. The emphasis in adult and pediatric respiratory disease clinics is to focus on large airway obstruction and reversibility. This information, although valuable, underemphasizes a large portion of the conduction airway of asthmatics. Standard descriptions of asthma management focus on a multiple medication approaches. We particularly focused on the management of asthma in the international guidelines for the Global Initiative for Asthma (GINA). Overall, however, minimal attention is placed on the small airway pool in asthma medical management. We took the opportunity to thoroughly review and present specific data from the adult asthma literature which supported the concept that small airway abnormalities may play a role in the pathogenesis and clinical expression of asthma. Based on the conclusions of the adult asthma literature, we here present a thorough review of the literature as it relates to small airway disease in children with asthma. We used, collectively, individual data sources of data to expand the information available from standard diagnostic techniques, especially spirometry, in the evaluation of small airway disease. As the pharmacological approaches to moderate to severe asthma are advancing rapidly into the realm of biologics, we sought to present potential pharmacological options for small airway dysfunction in pediatrics prior to biological modifier intervention.

Investigating the Role of Altered Systemic Albumin Concentration on the Disposition of Theophylline in Adult and Pediatric Patients with Asthma by Using the Physiologically Based Pharmacokinetic Approach

Theophylline is commonly used for the treatment of asthma and has a low hepatic clearance. The changes in plasma albumin concentration occurring in asthma may affect the exposure of theophylline. The aim of the presented work was to predict theophylline pharmacokinetics (PK) after incorporating the changes in plasma albumin concentration occurring in patients with asthma into a physiologically based pharmacokinetic (PBPK) model to see whether these changes can affect the systemic theophylline concentrations in asthma. The PBPK model was developed following a systematic model building approach using Simcyp. The predictions were performed initially in healthy adults after intravenous and oral drug administration. Only when the developed adult PBPK model had adequately predicted theophylline PK in healthy adults, the changes in plasma albumin concentrations were incorporated into the model for predicting drug exposure in patients with asthma. After evaluation of the developed model in the adult population, it was scaled to children on physiologic basis. The model evaluation was performed by using visual predictive checks and comparison of ratio of observed and predicted (R_obs/Pre) PK parameters along with their 2-fold error range. The developed PBPK model has effectively described theophylline PK in both healthy and diseased populations, as R_obs/Pre for all the PK parameters were within the 2-fold error limit. The predictions in patients with asthma showed that there were no significant changes in PK parameters after incorporating the changes in serum albumin concentration. The mechanistic nature of the developed asthma-PBPK model can facilitate its extension to other drugs. SIGNIFICANCE STATEMENT: Exposure of a low hepatic clearance drug like theophylline may be susceptible to plasma albumin concentration changes that occur in asthma. These changes in systemic albumin concentrations can be incorporated into a physiologically based pharmacokinetic model to predict theophylline pharmacokinetics in adult and pediatric asthma populations. The presented work is focused on predicting theophylline absorption, distribution, metabolism, and elimination in adult and pediatric asthma populations after incorporating reported changes in serum albumin concentrations to see their impact on the systemic theophylline concentrations.

Cysteinyl leukotriene receptor 1 (cysLT1R) regulates osteoclast differentiation and bone resorption

Excessive bone resorption induced by abnormal osteoclast differentiation has been associated with bone microstructure damage and bone-associated disorders, including osteoporosis. Here, we investigated the physiological roles of the type 1 cysteinyl leukotriene receptor (cysLTR-1) and the pharmacological functions of the specific cysLTR-1 antagonist montelukast on M-CSF- and RANKL-induced osteoclast differentiation. We showed that cysLTR-1 but not cysLTR-2 is expressed in osteoclast precursor cells: mouse bone marrow-derived macrophages (BMMs). We also found that treatment with M-CSF and RANKL significantly increased expression of cysLTR-1. Overexpression of cysLTR-1 promoted osteoclast differentiation of BMMs by increasing NFATc1 and TRAP. In contrast, treatment with montelukast prevented M-CSF- and RANKL-induced osteoclast differentiation of BMMs. Mechanically, our findings demonstrate that montelukast treatment attenuated activation of the ERK1/2, p38, JNK and NF-κB signalling pathways. Additionally, we reported that montelukast treatment ameliorated the generation of ROS and calcium signalling. Importantly, the co-immunoprecipitation assay displayed that montelukast treatment prevented the interaction of RANK and TRAF6. Finally, in vivo experiments indicated that montelukast rescued the reduction of bone volume as well as trabecular number in an ovariectomy mouse model.

Efficacy and Safety of Modified Pranlukast (Prakanon(®)) Compared with Pranlukast (Onon(®)): A Randomized, Open-Label, Crossover Study

INTRODUCTION

Pranlukast is a leukotriene receptor antagonist (LTRA) that is used as an additional controller of mild to moderate asthma. This study compared the efficacy and side effects of two bioequivalent preparations of pranlukast: original pranlukast (Onon(®); Ono Pharmaceutical, Japan) and a modified formulation of pranlukast (Prakanon(®); Yuhan Co, Korea) in patients with mild to moderate asthma.

METHODS

Of the 34 subjects screened, 30 patients who were using standard medication to control asthma and scored less than 20 points on the Asthma Control Test(™) (ACT) were assigned randomly to one of the two groups in a prospective, open label, crossover study: group 1 received Prakanon(®) (150 mg/day) and group 2 received Onon(®) (450 mg/day) for 8 weeks each; after a 1-week rest period, the groups were switched to the alternative medication for further 8 weeks and monitored for 2 more weeks without study medication. Evaluation parameters included the ACT, quality of life questionnaire adult Korean asthmatics (QLQAKA), pulmonary function tests, peripheral blood tests, vital signs, and adverse events.

RESULTS

Thirty patients were enrolled and 21 completed the trial: 10 in group 1 and 11 in group 2. The baseline data of the two groups did not differ. No statistical significant differences were observed in efficacy and lung function at each time and in changes from baseline value between the two kinds of pranlukast. The final asthma control rate was 81% with Prakanon(®) and 76% with Onon(®). There were no differences in vital signs and laboratory data at each time and in changes from baseline value between the two drugs. There were no differences in adverse events between the two drugs. The most common side effect was abdominal pain. Drug compliance was high, without differences between the two drugs.

CONCLUSION

These findings suggest that Prakanon(®) which is an improved formulation of pranlukast at a lower dose than the original formulation, Onon(®), has a similar efficacy and side effect profile in the control of persistent asthma.

Effects of Montelukast on free radical production in whole blood and isolated human polymorphonuclear neutrophils (PMNs) in asthmatic children

Montelukast is a highly selective leukotriene-receptor antagonist (LTRA). It is widely used in the treatment of bronchial asthma, primarily as an adjunct to corticosteroids. Reactive oxygen species (ROSs) play an important role in the pathogenesis of asthma and oxidative stress contributing to the initiation and worsening of inflammatory respiratory disorders, such as asthma. Antioxidant drugs may have a role in minimizing or preventing damage in asthmatic children. The aim of this study was to assess the antioxidant effect of montelukast on the production of free radicals in the whole blood and polymorphonuclear neutrophils (PMNs) in asthmatic children. A group of 48 (38 males and 10 females), apparently healthy asthmatic children were recruited with ages ranging between 6 and 14 years. In asthmatic children, base line (premedication) and post medication free radicals activity in the whole blood and polymorphonuclear neutrophils (PMNs) was determined by measuring chemiluminescence (CL) response through chemiluminescence luminometer. Free radical productions were significantly decreased in the whole blood, when stimulated with Phorbol Myristate Acetate (p < 0.04) and Opsonised Zymosan (p < 0.05). The free radicals were also significantly decreased in isolated polymorphonuclear neutrophils (PMNs) when stimulated with Opsonised Zymosan (p < 0.05) after the post medication treatment of montelukast in asthmatic children. Montelukast decreased the reactive oxygen species production, both in the whole blood as well as isolated PMNs in asthmatic children.

Effects of asthma treatment: the present and future

The increasing burden of asthma in both primary and secondary care has led to extensive research into its genetics, pathophysiology and treatment over the past few decades. Inhaled corticosteroids remain an integral component in all but the mildest disease, although despite a low-to-moderate dose, many individuals remain symptomatic. In patients with persistent symptoms despite inhaled corticosteroids, a variety of different nonsteroidal second-line therapies are available as add-on therapy. In this review, existing and potential future pharmacological strategies involved in the management of asthma will be highlighted.

Acute severe asthma: new approaches to assessment and treatment

The precise definition of a severe asthmatic exacerbation is an issue that presents difficulties. The term 'status asthmaticus' relates severity to outcome and has been used to define a severe asthmatic exacerbation that does not respond to and/or perilously delays the repetitive or continuous administration of short-acting inhaled beta(2)-adrenergic receptor agonists (SABA) in the emergency setting. However, a number of limitations exist concerning the quantification of unresponsiveness. Therefore, the term 'acute severe asthma' is widely used, relating severity mostly to a combination of the presenting signs and symptoms and the severity of the cardiorespiratory abnormalities observed, although it is well known that presentation does not foretell outcome. In an acute severe asthma episode, close observation plus aggressive administration of bronchodilators (SABAs plus ipratropium bromide via a nebulizer driven by oxygen) and oral or intravenous corticosteroids are necessary to arrest the progression to severe hypercapnic respiratory failure leading to a decrease in consciousness that requires intensive care unit (ICU) admission and, eventually, ventilatory support. Adjunctive therapies (intravenous magnesium sulfate and/or others) should be considered in order to avoid intubation. Management after admission to the hospital ward because of an incomplete response is similar. The decision to intubate is essentially based on clinical judgement. Although cardiac or respiratory arrest represents an absolute indication for intubation, the usual picture is that of a conscious patient struggling to breathe. Factors associated with the increased likelihood of intubation include exhaustion and fatigue despite maximal therapy, deteriorating mental status, refractory hypoxaemia, increasing hypercapnia, haemodynamic instability and impending coma or apnoea. To intubate, sedation is indicated in order to improve comfort, safety and patient-ventilator synchrony, while at the same time decrease oxygen consumption and carbon dioxide production. Benzodiazepines can be safely used for sedation of the asthmatic patient, but time to awakening after discontinuation is prolonged and difficult to predict. The most common alternative is propofol, which is attractive in patients with sudden-onset (near-fatal) asthma who may be eligible for extubation within a few hours, because it can be titrated rapidly to a deep sedation level and has rapid reversal after discontinuation; in addition, it possesses bronchodilatory properties. The addition of an opioid (fentanyl or remifentanil) administered by continuous infusion to benzodiazepines or propofol is often desirable in order to provide amnesia, sedation, analgesia and respiratory drive suppression. Acute severe asthma is characterized by severe pulmonary hyperinflation due to marked limitation of the expiratory flow. Therefore, the main objective of the initial ventilator management is 2-fold: to ensure adequate gas exchange and to prevent further hyperinflation and ventilator-associated lung injury. This may require hypoventilation of the patient and higher arterial carbon dioxide (PaCO(2)) levels and a more acidic pH. This does not apply to asthmatic patients intubated for cardiac or respiratory arrest. In this setting the post-anoxic brain oedema might demand more careful management of PaCO(2) levels to prevent further elevation of intracranial pressure and subsequent complications. Monitoring lung mechanics is of paramount importance for the safe ventilation of patients with status asthmaticus. The first line of specific pharmacological therapy in ventilated asthmatic patients remains bronchodilation with a SABA, typically salbutamol (albuterol). Administration techniques include nebulizers or metered-dose inhalers with spacers. Systemic corticosteroids are critical components of therapy and should be administered to all ventilated patients, although the dose of systemic corticosteroids in mechanically ventilated asthmatic patients remains controversial. Anticholinergics, inhaled corticosteroids, leukotriene receptor antagonists and methylxanthines offer little benefit, and clinical data favouring their use are lacking. In conclusion, expertise, perseverance, judicious decisions and practice of evidence-based medicine are of paramount importance for successful outcomes for patients with acute severe asthma.

Leukotriene modifiers in the treatment of asthma in children

Asthma is one of the most common respiratory disorders in clinical practice, affecting up to 13% of people worldwide. Inflammation is the most important component of asthma and inhaled corticosteroids (ICS) are recommended as the first line controller treatment for patients of all ages. Treatment with corticosteroids is often unable to fully control asthma symptoms and progression. Recently, leukotrienes have come to the forefront of research as they have been found play a pivotal role in the airway inflammatory process, and specific drugs have been developed to target them. Cysteiny leukotriene antagonists (LTRAs) have recently emerged as important therapeutic options that show a large potential clinical utility. Three specific LTRAs are licensed for clinical use: montelukast, zafirlukast and pranlukast, although montelukast is the only drug approved in the paediatric age range. It is well tolerated (although adverse effects such as headaches, abdominal pain, rashes, angioedema, pulmonary eosinophilia and arthralgia have been reported) and shows many positive effects in asthmatic patients. Current Global Initiative for Asthma guidelines recommend LTRAs as: (1) a second choice treatment to ICS for patients with mild persistent asthma, (2) an add-on therapy to reduce the dose of ICS in patients with moderate or severe asthma, due to the different and complementary mechanisms of action of these agents. LTRAs may be particularly appropriate choices in a number of clinical situations, including the following: patients with concomitant rhinitis; patients with viral-induced wheeze; patients with exercise-induced bronchoconstriction (EIB) and, in children aged 2-5 years, to reduce the frequency of asthma exacerbations.

Montelukast inhibits neutrophil pro-inflammatory activity by a cyclic AMP-dependent mechanism

BACKGROUND AND PURPOSE

The objective of this study was to characterize the effects of the cysteinyl leukotriene receptor antagonist, montelukast (0.1-2 micromol x L(-1)), on Ca(2+)-dependent pro-inflammatory activities, cytosolic Ca(2+) fluxes and intracellular cAMP in isolated human neutrophils activated with the chemoattractants, N-formyl-L-methionyl-L-leucyl-L-phenylalanine (1 micromol x L(-1)) and platelet-activating factor (200 nmol x L(-1)).

EXPERIMENTAL APPROACH

Generation of reactive oxygen species was measured by lucigenin- and luminol-enhanced chemiluminescence, elastase release by a colourimetric assay, leukotriene B(4) and cAMP by competitive binding ELISA procedures, and Ca(2+) fluxes by fura-2/AM-based spectrofluorimetric and radiometric ((45)Ca(2+)) procedures.

KEY RESULTS

Pre-incubation of neutrophils with montelukast resulted in dose-related inhibition of the generation of reactive oxygen species and leukotriene B(4) by chemoattractant-activated neutrophils, as well as release of elastase, all of which were maximal at 2 micromol x L(-1) (mean percentages of the control values of 30 +/- 1, 12 +/- 3 and 21 +/- 3 respectively; P < 0.05). From a mechanistic perspective, treatment of chemoattractant-activated neutrophils with montelukast resulted in significant reductions in both post-peak cytosolic Ca(2+) concentrations and store-operated Ca(2+) influx. These montelukast-mediated alterations in Ca(2+) handling by the cells were associated with a significant elevation in basal cAMP levels, which resulted from inhibition of cyclic nucleotide phosphodiesterases.

CONCLUSIONS AND IMPLICATIONS

Montelukast, primarily a cysteinyl leukotriene (CysLT(1)) receptor antagonist, exhibited previously undocumented, secondary, neutrophil-directed anti-inflammatory properties, which appeared to be cAMP-dependent.

Histamine and leukotriene receptor antagonism in the treatment of allergic rhinitis: an update

Allergic rhinitis represents a global health burden. The disease can seriously affect quality of life and is associated with multiple co-morbidities. Histamine and leukotrienes are important pro-inflammatory mediators in nasal allergic inflammation. Their actions on target cells are mediated through specific receptors and, consequently, molecules that block the binding of histamine and leukotrienes to their receptors have been important areas of pharmacological research. The published literature of the pathophysiology of histamine and leukotrienes, and the effects of histamine H(1)-receptor antagonists (H(1) antihistamines) and leukotriene antagonists in monotherapy or in combination therapy in the treatment of allergic rhinitis was reviewed. The presented results are based on the best available evidence. The efficacy of H(1) antihistamines and leukotriene antagonists (montelukast in particular) in allergic rhinitis has been established in numerous randomised placebo-controlled trials. Results from meta-analyses indicate that H(1) antihistamines and leukotriene antagonists are equally effective in improving symptoms of allergic rhinitis and quality of life, but that both drugs are less effective than intranasal corticosteroids. Data on the combination of H(1) antihistamines and leukotriene antagonists in allergic rhinitis are limited. The available evidence shows that a combined mediator inhibition has additional benefits over the use of each agent alone, but is still inferior to intranasal corticosteroids. More well designed studies are needed to fully understand the benefits of a concomitant use of these agents.

Immunoglobulin E blockade in the treatment of asthma

Patients with moderate-to-severe asthma often have persistent symptoms despite aggressive pharmacotherapy, enthusiastic patient compliance, and proper technique in using delivery devices. Persistent symptoms have detrimental effects on patients' quality of life and result in a tremendous financial burden because of an increased utilization of health care resources. Guidelines from the National Asthma Education and Prevention Program list symptom prevention, near-normal lung function, and participation in activities (e.g., school, work) as goals of successful asthma therapy. The development of pharmacologic and biologic therapies that target different aspects of airway inflammation will help patients with persistent asthma symptoms achieve these goals. Immunoglobulin E (IgE) is increasingly recognized as a key component of asthma pathophysiology and contributes to both the early- and late-phase inflammatory cascade of the airways by inhibiting allergen-induced activation of mast cells. Both epidemiologic and clinical evidence support the use of IgE blockade for asthma treatment. Omalizumab is currently the only IgE-targeted therapy approved by the United States Food and Drug Administration for asthma treatment. The drug improves symptoms, reduces exacerbations, and improves quality of life in certain patient populations.

Many asthma patients experience persistent symptoms despite appropriate clinical and guideline-based treatment with inhaled corticosteroids

PURPOSE

To review possible reasons for persistence of asthma symptoms despite appropriate use of clinical and guideline-based treatments, including the use of inhaled corticosteroids.

DATA SOURCES

Review of the worldwide scientific literature on factors related to persistent symptoms in patients with asthma.

CONCLUSIONS

Patients with asthma may not respond as expected to therapy because of factors that include poor adherence, improper inhaler technique, persistent exposure to symptom triggers, and limitations of current standard therapy, including steroid insensitivity or the steroid plateau effect. Persistent symptoms may also be associated with IgE-mediated airway inflammation, as current standard asthma therapies do not directly address the IgE-mediated component of the inflammatory cascade. Asthma is a complex disease and its treatment requires the full cooperation and participation of the patient.

IMPLICATIONS FOR PRACTICE

Healthcare professionals can play a key role by educating patients and their family members about the nature of asthma and rationale for treatment, supporting the importance of strict adherence to prevention measures and the prescribed treatment regimen.

Critical appraisal of antileukotriene use in asthma management

PURPOSE OF REVIEW

Recognition of the importance of leukotrienes in the pathogenesis of asthma has led to the development of leukotriene modifiers, the first new class of drugs for asthma treatment to become available since the introduction of inhaled corticosteroids. Nevertheless, despite their widespread use in clinical practice, the role of leukotriene modifiers in the management of asthma remains controversial. In the present article the clinical applications of this class of drugs have been critically reviewed based on recent evidence.

RECENT FINDINGS

In an effort to try and establish the proper place of antileukotrienes in the management of asthma, important systematic reviews have been carried out over these recent years in three critical areas: antileukotrienes as second choice first line agents after inhaled corticosteroids; antileukotrienes as add-on therapy to inhaled corticosteroids; add-on antileukotrienes versus long acting beta-agonists to patients not controlled by inhaled corticosteroids. In addition, novel and useful clinical targets for this class of drugs have been recently explored and include: patients with severe asthma; aspirin-intolerant asthma; asthmatic patients with allergic rhinitis.

SUMMARY

Use of antileukotrienes is not recommended as first-line monotherapy in patients with asthma, except those who have aspirin intolerant asthma. Patients with concomitant allergic rhinitis may be a good target population for therapy with antileukotrienes. Addition of leukotriene modifiers to inhaled corticosteroids produces only a modest improvement in the clinical response, and is not greater to that of add-on long acting beta-agonists. The exact role of antileukotrienes in asthma management guidelines still continues to evolve.

Localization and upregulation of cysteinyl leukotriene-1 receptor in asthmatic bronchial mucosa

We have tested the hypothesis that the CysLT(1) receptor is expressed by a variety of bronchial mucosal immune cells and that the numbers of these cells increase in asthma, when stable and in exacerbations. We have applied in situ hybridization and immunohistochemistry to endobronchial biopsy tissue to identify and count inflammatory cells expressing CysLT(1) receptor mRNA and protein, respectively, and used double immunohistochemistry to identify the specific cell immunophenotypes expressing the receptor. Double-labeling demonstrated that bronchial mucosal eosinophils, neutrophils, mast cells, macrophages, B-lymphocytes, and plasma cells, but not T-lymphocytes, expressed the CysLT(1) receptor. The numbers of CysLT(1) receptor mRNA and protein positive inflammatory cells in nonsmoking, nonatopic control subjects without asthma were 13 and 16 mm(-2), respectively (median values; n = 15), and were significantly greater in stable asthma (50 and 43 mm(-2), respectively; n = 17; P < 0.001). Compared with stable asthma, there were further significant increases in subjects hospitalized for a severe exacerbation of their asthma (mRNA: median = 113 and protein: 156 mm(-2); n = 15; P < 0.002). For the combined data of both asthma subgroups, there were strong positive correlations between the increased numbers of CD45+ leukocytes and the greater numbers of cells expressing CysLT(1) receptor (mRNA: r = 0.60, P < 0.001; protein: r = 0.73, P < 0.0001). In conclusion, a variety of immunohistologically distinct inflammatory cells express the CysLT(1) receptor in the bronchial mucosa and both these and the total number of leukocytes increase in mild stable disease and increase further when there is a severe exacerbation of asthma.