Tumour necrosis factor-α as a therapeutic target in asthma

Modulation by Withania somnifera of stress-induced anxiogenesis and airway inflammation in rats

OBJECTIVES

Stress is an aversive stimulus which disrupts the biological milieu of the organism and a variety of emotional and environmental stressors are known to influence allergic and immunological disorders like bronchial asthma but the pharmacological basis of such interactions is not clearly defined. Withania somnifera (ashwagandha) is a potent anti-stress agent used widely in Indian traditional medicine and the present experimental study evaluated the effects of W. somnifera extract (WSE) on chronic stress-induced neurobehavioral and immunological responses in an experimental model of allergic asthma in rats.

METHODS

Wistar rats (200-250 g) were immunized and challenged with ovalbumin (OVA) and exposed to restraint stress (RS) and WSE treatments for 15 days. Following this, anxiety behavior was assessed by the elevated plus maze (EPM) test, and blood and BAL fluid samples were collected for measuring of inflammatory/immune markers by ELISA and biochemical assay. The data of the various treatment groups were analyzed by ANOVA and Tukey's test.

RESULTS

Restraint stress (RS) induced anxiogenic behavior in the (EPM) test in OVA immunized rats, and this was attenuated by WSE (200 and 400 mg/kg), in a dose related manner. Examination of blood and BAL fluid in these RS exposed rats also resulted in elevations in IgE, TNF-α and IL-4 levels, which were also attenuated by WSE pretreatments. Further, WSE pretreatment neutralized the such RS induced changes in oxidative stress markers viz. elevated MDA and reduced GSH levels.

CONCLUSIONS

The data pharmacologically validates role of stress in asthma and suggests that adaptogens like WSE could be a potential complementary agent for reducing anxiety as well as airway inflammation by a multi-targeted and holistic approach. The study also highlights the significance of integration of traditional and modern medical concepts in such chronic disorders.

Unusual asthma syndromes and their management

Asthma usually presents with symptoms of wheeze, dyspnoea and cough. However, clinicians should be aware of atypical presentation of this disorder when cough is the main or only symptom in conditions such as cough-variant asthma, nonasthmatic eosinophilic bronchitis and atopic cough. Early diagnosis and treatment of these conditions with inhaled corticosteroids improves symptoms in the majority of patients. Up to 10% of patients with asthma remain poorly controlled in spite of optimal standard therapy. These patients have been encompassed under the term 'treatment-refractory asthma' (TRA), have the greatest morbidity and are responsible for more than 50% of healthcare costs. In this review we discuss investigations, management and pathophysiology of the various phenotypes of atypical presentations of asthma as well as novel biological agents licensed and those that have been reported in clinical trials in terms of their efficacy and safety in TRA.

Stratified medicine in selecting biologics for the treatment of severe asthma

PURPOSE OF REVIEW

Despite optimal treatment, asthma symptoms in about 5-10% of patients remain poorly controlled. Apart from having an impact on their asthma-related quality of life and adverse effects of the medications used (especially corticosteroids), their severe symptoms also impact healthcare resources due to frequent admission and requirement for intensive medications use. The last decade has seen an improved understanding in the pathophysiology of the complex cellular and molecular networks involved in the inflammatory and immunological phenotype of severe asthma. This knowledge may help providing strategies by which these phenotypes operate and pave the way for drug development and individualized treatment.

RECENT FINDINGS

Here we review the current evidence of biological agents in patients with severe asthma recently assessed for safety and efficacy. Some of these agents have shown to be useful in specifically targeted subpopulations of patients with severe asthma, whereas others have proven to be unsafe and/or unsuccessful. In addition, we discuss recent data on clinical and pharmacokinetic-pharmacodynamic aspects of omalizumab, the only licensed anti-IgE therapy for severe atopic asthma.

SUMMARY

More basic science work is required to improve the current understanding of severe asthma pathophysiology and proof-of-concept clinical studies are required to explore relevant biomolecular targets in this small subset of patients. At present, only one drug is licensed for allergic asthmatic patients with severe disease, omalizumab. Novel therapies in the form of oligonucleotide therapies and other biological agents are also being investigated in the difficult-to-treat asthmatic patient group.

Managing patients with chronic severe asthma: rise to the challenge

Most asthmatic patients with moderate to severe disease can be satisfactorily managed with a combination of inhaled corticosteroids and beta(2)-agonists. However, there are perhaps 10% of the asthmatic population with persistent symptoms, impaired quality of life and excessive health-care utilization, despite this management regime. These patients often require frequent and even occasionally regular oral corticosteroid use. Chronic, severe asthma is a heterogeneous disease with distinct sub-phenotypes. A systematic diagnostic work-up may help to identify these distinct sub-phenotypes and this may help guide treatment and may even provide information about prognosis. Optimal treatment of chronic severe asthma should achieve the best possible asthma control and quality of life with the least dose of systemic corticosteroids. The choice and formulation of therapeutic agent is dictated by the severity of disease and includes conventional, immunosuppressive/immunomodulating and biologic therapies. Unfortunately, current asthma management guidelines offer little contribution to the care of the challenging patient with chronic severe asthma. This review article aims at summarizing the evidence regarding various therapeutic modalities for chronic severe asthma and also aims to provide a practical approach to diagnosis and management for the benefit of those who have a specific interest in this problematic condition.

Immunomodulatory and biologic therapies for severe refractory asthma

Despite undoubted efficacy of the combination of inhaled corticosteroids and beta(2)-agonists for most asthmatic patients with moderate-to-severe disease, there remains approximately 10% of the asthmatic population with serious unremitting symptoms, resulting in considerable impact on quality of life, disproportionate use of health care resources, and adverse effects from regular systemic steroid use. In an ideal world, optimal treatment of severe refractory asthma should achieve the best possible asthma control and quality of life with the least dose of systemic corticosteroids. The choice and formulation of therapeutic agent are dictated by the severity of disease and may include immunological modifiers and biologic therapies. Unfortunately, current asthma guidelines offer little contribution to the management of the challenging patient with severe refractory asthma and none of them have addressed therapeutic alternatives to oral corticosteroids. This article reviews the current evidence for immunomodulating and biologic approaches in severe refractory asthma.