Leukotriene receptor antagonists in asthma therapy

The pharmacoeconomics of the state-of-the-art drug treatments for asthma: a systematic review

Asthma is a chronic disease characterized by significant morbidities and mortality, with a large impact on socio-economic resources and a considerable burden on health-care systems. In the standard care of asthma, inhaled corticosteroids (ICS) associated with long-acting β-adrenoceptor agonists (LABA) are a reliable and often cost-effective choice, especially if based on the single inhaler therapy (SIT) strategy; however, in a subset of patients it is not possible to reach an adequate asthma control. In these cases, it is possible to resort to other pharmacologic options, including corticosteroids (OCS) or biologics. Unfortunately, OCS are associated with important side effects, whilst monoclonal antibodies (mAbs) allow excellent results, even if far more expensive. Up to now, the economic impact of asthma has not been compared with equivalent indicators in several studies. In fact, a significant heterogeneity of the cost analysis is evident in literature, for which the assessment of the real cost-effectiveness of asthma therapies is remarkably complex. To maximize the cost-effectiveness of asthma strategies, especially of biologics, attention must be paid on phenotyping and identification of predictors of response. Several studies were included, involving comparative analysis of drug treatments for asthma, comparative analysis of the costs and consequences of therapies, measurement and evaluation of direct drug costs, and the reduction of health service use. The initial research identified 389 articles, classified by titles and abstracts. A total of 311 articles were excluded as irrelevant and 78 articles were selected. Pharmacoeconomic studies on asthma therapies often report conflicting data also due to heterogeneous indicators and different populations examined. A careful evaluation of the existing literature is extremely important, because the scenario is remarkably complex, with an attempt to homogenize and interpret available data. Based on these studies, the improvement of prescriptive appropriateness and the reduction of the use of healthcare resources thanks to controller medications and to innovative therapies such as biologics partially reduce the economic burden of these treatments. A multidisciplinary stakeholder approach can also be extremely helpful in deciding between the available options and thus optimizing healthcare resources.

How does race and ethnicity effect the precision treatment of asthma?

Introduction

Asthma is a common condition that affects large numbers of children and adults, yet the burden of disease is not equally distributed amongst groups. In the United States, African Americans and Puerto Ricans have higher rates of asthma and its complications when compared with European Americans. However, clinical trials and genetic studies have largely focused on the latter group.

Areas covered

Here we examine what is known regarding differences in asthma treatment response by race-ethnicity. We also review existing genetic studies related to the use of asthma medications, paying special attention to studies that included substantial numbers of non-white population groups. Publicly accessible search engines of the medical literature were queried using combinations of the terms asthma, race, ethnicity, pharmacogenomics, and pharmacogenetics, as well as the names of individual asthma medication classes. The list of articles reviewed was supplemented by bibliographies and expert knowledge.

Expert opinion

A substantial and coordinated effort is still needed to both identify and validate genetic biomarkers of asthma medication response, as currently there are no clinically actionable genetic markers available for this purpose. The path to identifying such markers in non-white populations is even more formidable, since these groups are underrepresented in existing data.

Cysteinyl leukotriene receptor-1 antagonists as modulators of innate immune cell function

Cysteinyl leukotrienes (cysLTs) are produced predominantly by cells of the innate immune system, especially basophils, eosinophils, mast cells, and monocytes/macrophages. Notwithstanding potent bronchoconstrictor activity, cysLTs are also proinflammatory consequent to their autocrine and paracrine interactions with G-protein-coupled receptors expressed not only on the aforementioned cell types, but also on Th2 lymphocytes, as well as structural cells, and to a lesser extent neutrophils and CD8⁺ cells. Recognition of the involvement of cysLTs in the immunopathogenesis of various types of acute and chronic inflammatory disorders, especially bronchial asthma, prompted the development of selective cysLT receptor-1 (cysLTR1) antagonists, specifically montelukast, pranlukast, and zafirlukast. More recently these agents have also been reported to possess secondary anti-inflammatory activities, distinct from cysLTR1 antagonism, which appear to be particularly effective in targeting neutrophils and monocytes/macrophages. Underlying mechanisms include interference with cyclic nucleotide phosphodiesterases, 5′-lipoxygenase, and the proinflammatory transcription factor, nuclear factor kappa B. These and other secondary anti-inflammatory mechanisms of the commonly used cysLTR1 antagonists are the major focus of the current review, which also includes a comparison of the anti-inflammatory effects of montelukast, pranlukast, and zafirlukast on human neutrophils in vitro, as well as an overview of both the current clinical applications of these agents and potential future applications based on preclinical and early clinical studies.

Transforming growth factor-beta1 in asthmatic airway smooth muscle enlargement: is fibroblast growth factor-2 required?

Enlargement of airway smooth muscle (ASM) tissue around the bronchi/bronchioles is a histopathological signature of asthmatic airway remodelling and has been suggested to play a critical role in the increased lung resistance and airway hyperresponsiveness seen in asthmatic patients. The pleiotropic cytokine, TGF-beta1, is believed to contribute to several aspects of asthmatic airway remodelling and is known to influence the growth of many cell types. Increased TGF-beta1 expression/signalling and ASM growth have been shown to occur concurrently in animal models of asthma. Abundant studies further substantiate this association by showing that therapeutic strategies that reduce or prevent TGF-beta1 overexpression/signalling lead to a parallel decrease or prevention of ASM enlargement. Finally, recent findings have supported a direct link of causality between TGF-beta1 overexpression/signalling and the overgrowth of ASM tissue. To follow-up on these in vivo studies, many investigators have pursued detailed investigation of ASM in cell culture conditions, assessing the direct role of TGF-beta1 on cellular proliferation and/or hypertrophy. Inconsistencies among the in vitro studies suggest that the effect of TGF-beta1 on ASM cell proliferation/hypertrophy is contextual. A hypothesis focusing on fibroblast growth factor-2 is presented at the end of this review, which could potentially reconcile the apparent discrepancy between the conflicting in vitro findings with the consistent in vivo finding that TGF-beta1 is required for ASM enlargement in asthma.

Can montelukast shorten prednisolone therapy in children with mild to moderate acute asthma? A randomized controlled trial

OBJECTIVE

To examine whether outpatient post-stabilization therapy with montelukast produces more treatment failures than prednisolone.

STUDY DESIGN

In this randomized, double-blind, double-dummy non-inferiority trial, 130 children 2 to 17 years of age with mild to moderate acute asthma stabilized with prednisolone in the emergency department received 5 daily treatments with either prednisolone or montelukast after discharge. The primary outcome was treatment failure within 8 days (ie, an asthma-related unscheduled visit, hospitalization, or additional systemic corticosteroids).

RESULTS

The rates of treatment failure were 7.9% in the prednisolone group and 22.4% in the montelukast group (95% CI, 26.5%-2.4%). Treatment was more likely to fail in younger patients (odds ratio, 4.9). In the montelukast group, more patients received additional pharmacotherapy than in patients receiving prednisolone (23.9% versus 9.5%, P = .03). The differences in the daily salbutamol treatments, asymptomatic days, and changes in the Pediatric Respiratory Assessment Measure score were not significant (P = .85, .75, and .26, respectively).

CONCLUSION

Montelukast does not represent an adequate alternative to corticosteroids after outpatient stabilization in mild to moderate acute asthma. This population should receive oral corticosteroids after discharge.

Effect of fish oil-derived omega-3 polyunsaturated Fatty Acid supplementation on exercise-induced bronchoconstriction and immune function in athletes

Exercise-induced bronchoconstriction (EIB) is a condition in which vigorous physical activity triggers acute airway obstruction in asthmatic and nonasthmatic individuals with hyperresponsive airways. Studies have shown that inflammatory mediators and contraction of airway smooth muscle are central components in the pathogenesis of EIB, and it has long been recognized that leukotrienes and prostaglandins play an important role in the EIB response. Clinical responses to current therapy, such as leukotriene modifiers and corticosteroids are heterogeneous, and even with optimal treatment there is a substantial burden of unaddressed disease. While daily medications such as leukotriene modifiers provide only modest protection against symptoms, prolonged use of several medications can result in reduced effectiveness or tachyphylaxis. Although the treatment of EIB almost exclusively involves pharmacotherapy, there is now convincing evidence that dietary modification has the potential to reduce the severity of this condition. Omega-3 polyunsaturated fatty acids, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in fish oils, compete with arachidonic acid as substrates for the formation of proinflammatory mediators, such as leukotrienes, prostaglandins, and cytokines. Studies have shown that 3 weeks of fish oil supplementation, rich in EPA and DHA, reduces exercise-induced airway narrowing, airway inflammation, and bronchodilator use in elite athletes and asthmatic individuals with EIB. Based on the evidence to date, fish oil supplementation may represent a potentially beneficial treatment intervention for athletes and asthmatic individuals with EIB. From this, it follows that physicians should pay more attention to what their asthma/EIB patients eat, and incorporate dietary assessment and nutritional counseling in their everyday practice.

KEYWORDS

omega-3; polyunsaturated fatty acid; fish oil; exercise-induced bronchoconstriction.

Leukotriene D4 activates distinct G-proteins in intestinal epithelial cells to regulate stress fibre formation and to generate intracellular Ca2+ mobilisation and ERK1/2 activation

We have shown that the pro-inflammatory mediator LTD4, via its G-protein-coupled receptor CysLT1, signals through both pertussis-toxin-sensitive and -insensitive G-proteins to induce various cellular responses. To further characterise the initial step of the different signalling pathways emanating from the CysLT1 receptor, we transfected intestinal epithelial cells, Int 407, with different mini vectors that each express a specific inhibitory peptide directed against a unique alpha subunit of a specific heterotrimeric G-protein. Our results revealed that LTD4-induced stress fibre formation is inhibited approximately 80% by a vector expressing an inhibitory peptide against the pertussis-toxin-insensitive Galpha12-protein in intestinal epithelial Int 407 cells. Control experiments revealed that the LPA-induced stress fibre formation, mediated via the Galpha12-protein in other cell types, was blocked by the same peptide in intestinal Int 407 cells. Furthermore, the CysLT1-receptor-mediated calcium signal and activation of the proliferative ERK1/2 kinase are blocked in cells transfected with a vector expressing an inhibitory peptide against the Galphai3-protein, whereas in cells transfected with an empty ECFP-vector or vectors expressing inhibitory peptides against the Galphai1-2-, Galpha12-, GalphaR-proteins these signals are not significantly affected. Consequently, the CysLT1 receptor has the capacity to activate at least two distinctly different heterotrimeric G-proteins that transduce activation of unique downstream cellular events.

Regulation of cysteinyl leukotriene type 1 receptor internalization and signaling

Cysteinyl leukotrienes activate the cysteinyl leukotriene type 1 receptor (CysLT1R) to regulate numerous cell functions important in inflammatory processes and diseases such as asthma. Despite its physiologic importance, no studies to date have examined the regulation of CysLT1R signaling or trafficking. We have established model systems for analyzing recombinant human CysLT1R and found regulation of internalization and signaling of the CysLT1R to be unique among G protein-coupled receptors. Rapid and profound LTD4-stimulated internalization was observed for the wild type (WT) CysLT1R, whereas a C-terminal truncation mutant exhibited impaired internalization yet signaled robustly, suggesting a region within amino acids 310-321 as critical to internalization. Although overexpression of WT arrestins significantly increased WT CysLT1R internalization, expression of dominant-negative arrestins had minimal effects, and WT CysLT1R internalized in murine embryonic fibroblasts lacking both arrestin-2 and arrestin-3, suggesting that arrestins are not the primary physiologic regulators of CysLT1Rs. Instead, pharmacologic inhibition of protein kinase C (PKC) was shown to profoundly inhibit CysLT1R internalization while greatly increasing both phosphoinositide (PI) production and calcium mobilization stimulated by LTD4 yet had almost no effect on H1 histamine receptor internalization or signaling. Moreover, mutation of putative PKC phosphorylation sites within the CysLT1R C-tail (CysLT1RS(313-316)A) reduced receptor internalization, increased PI production and calcium mobilization by LTD4, and significantly attenuated the effects of PKC inhibition. These findings characterized the CysLT1R as the first G protein-coupled receptor identified to date in which PKC is the principal regulator of both rapid agonist-dependent internalization and rapid agonist-dependent desensitization.

Lipoxins in asthma: potential therapeutic mediators on bronchial inflammation?

Arachidonic acid metabolism represents an important source of mediators with ambivalent actions. Among these, lipoxins (LXs) are the first agents identified and recognized as anti-inflammatory endogenous lipid mediators, which are involved in the resolution of inflammation and are present in the airways of asthmatic patients. Lipoxins result mainly from the interaction between 5 and 15-lipoxygenases (LO) and their levels are modulated by the degree of bronchial inflammation as well as by the long-term glucocorticoid treatments. In the airways, LX synthesis is higher in mild asthmatics than in severe asthmatics, whereas in vitro chemokine release inhibition by LXs is more effective in cells from severe asthmatics than from mild asthmatics. LipoxinA(4) effects on interleukin (IL)-8 released by blood mononuclear cells and on calcium influx in epithelial cells are mediated by the specific receptor ALX. Lipoxin generation by lung epithelial cells depends mainly on 15-LO activity. Mild asthmatics present higher 15-LOb expression at the epithelium level than severe patients, whereas the LX deficit in severe asthma is associated with an up-regulation of the 15-LOa expressions. Therefore, bronchial epithelial cells become a target for therapeutic intervention and LXs represent a potential therapeutic solution for bronchial inflammation resolution in asthma.

Perioperative implications of common respiratory problems

Pediatric surgical patients can present with a number of challenging common respiratory problems. This article reviews potential perioperative implications and anesthetic management of asthma, upper respiratory tract infections, bronchopulmonary dysplasia, and the effects of passive environmental smoke on children presenting for surgery.

The eicosanoid cascade: possible role in gliomas and meningiomas

Eicosanoids constitute a large family of biologically active lipid mediators that are produced by two enzyme classes, cyclooxygenases (COX-1 and COX-2) and lipoxygenases (5-LO, 12-LO, and 15-LO). Increasing evidence suggests that in addition to a variety of epithelial malignancies, the two most common types of human brain tumour, gliomas and meningiomas, aberrantly overexpress eicosanoid producing enzymes and release a spectrum of eicosanoids that may promote tumorigenesis and the development of peritumorous brain oedema. Glioma and meningioma cells are killed in vitro and in animal models when exposed to COX-2 and 5-LO inhibitors, and their effectiveness is under investigation in clinical trials for treatment of patients with malignant brain tumours. However, despite research into the role of the eicosanoid cascade in the tumorigenesis of human brain tumours, many important questions remain unanswered. Current and newer agents that specifically target key players of the eicosanoid cascade could change the approach to treating brain tumours, because their benefits may lie in their synergism with conventional cytotoxic treatments and/or with other novel agents targeted against other procarcinogenic pathways.

Applications of hyperpolarized helium-3 gas magnetic resonance imaging in pediatric lung disease

Hyperpolarized gas magnetic resonance imaging (MRI) of the lung provides high temporal and spatial resolution images of the air spaces of the lung and can be used to elucidate both lung ventilation and morphology. Because no ionizing radiation is involved, hyperpolarized gas MRI is ideal for the evaluation of pediatric lung diseases. In the article, we describe briefly the basic principles of hyperpolarized gas MRI, review the literature of hyperpolarized gas MRI in two pediatric lung diseases (asthma and cystic fibrosis), and discuss possible future clinical applications of hyperpolarized gas imaging in pediatric lung disease.