Diagnosis and management of steroid-resistant asthma

Allergic diseases: From bench to clinic - Contribution of the discovery of interleukin-5

T helper 2 cells produce a number of cytokines including inteleukin (IL)-5, IL-4 and IL-13. Group 2 innate lymphoid cells (ILC2s) also produce IL-5 under sterile conditions. IL-5 is interdigitating homodimeric glycoprotein and a member of the four α helical bundle motifs conserved among hematopoietic cytokines. IL-5 exerts its effects on target cells via IL-5 receptor (IL-5R), composed of an IL-5R α and βc subunit. The membrane proximal proline-rich motif of the cytoplasmic domain of both IL-5R α and βc subunits is essential for IL-5 signal transduction. Although IL-5 was initially identified by its ability to support the growth and terminal differentiation of mouse B cells into antibody-secreting cells, recombinant IL-5 exerts pleiotropic activities on various target cells. For example, IL-5 is now recognized as the major maturation and differentiation factor for eosinophils in mice and humans. Overexpression of IL-5 in mouse significantly increases eosinophil numbers and antibody levels in vivo, while mice lacking a functional gene for IL-5 or IL-5R display developmental and functional impairments in B cell and eosinophil lineages. In mice, the role of the IL-5/IL-5R system in the production and secretion of Immunoglobulin (Ig) M and IgA in mucosal tissues has been reported. Although eosinophils protect against invading pathogens including virus, bacteria and helminthes, they are also involved in the pathogenesis of various diseases, such as food allergy, asthma, and inflammatory bowel diseases. The recent expansion in our understanding in the context of IL-5 and IL-5-producing ILC2s in eosinophil activation and the pathogenesis of eosinophil-dependent inflammatory diseases has led to advances in therapeutic options. A new therapy currently under invetigarion in clinical trials uses humanized monoclonal antibodies against IL-5 or the IL-5R. In this review, we summarize our current understanding of the functions of IL-5 and its receptor, the innate regulation of IL-5-producing cells, and therapeutic potential of anti-IL-5 and anti-eosinophil (IL-5R) antibodies.

Traditional Therapies for Severe Asthma

Severe asthma is a complex and heterogeneous disease. The European Respiratory Society and American Thoracic Society guidelines define severe asthma for patients 6 years or older as "asthma which requires treatment with high-dose inhaled corticosteroids…plus a second controller or systemic corticosteroids to prevent it from becoming 'uncontrolled' or which remains 'uncontrolled' despite this therapy." This article reviews available traditional therapies, data behind their uses in severe asthma, and varying recommendations. As various asthma endotypes and phenotypes are better understood and characterized, targeted therapies should help improve disease outcomes, efficacy, and cost-effectiveness.

Inhibiting AKT phosphorylation employing non-cytotoxic anthraquinones ameliorates TH2 mediated allergic airways disease and rhinovirus exacerbation

BACKGROUND

Severe asthma is associated with T helper (TH) 2 and 17 cell activation, airway neutrophilia and phosphoinositide-3-kinase (PI3K) activation. Asthma exacerbations are commonly caused by rhinovirus (RV) and also associated with PI3K-driven inflammation. Anthraquinone derivatives have been shown to reduce PI3K-mediated AKT phosphorylation in-vitro.

OBJECTIVE

To determine the anti-inflammatory potential of anthraquinones in-vivo.

METHODS

BALB/c mice were sensitized and challenged with crude house dust mite extract to induce allergic airways disease and treated with mitoxantrone and a novel non-cytotoxic anthraquinone derivative. Allergic mice were also infected with RV1B to induce an exacerbation.

RESULTS

Anthraquinone treatment reduced AKT phosphorylation, hypoxia-inducible factor-1α and vascular endothelial growth factor expression, and ameliorated allergen- and RV-induced airways hyprereactivity, neutrophilic and eosinophilic inflammation, cytokine/chemokine expression, mucus hypersecretion, and expression of TH2 proteins in the airways. Anthraquinones also boosted type 1 interferon responses and limited RV replication in the lung.

CONCLUSION

Non-cytotoxic anthraquinone derivatives may be of therapeutic benefit for the treatment of severe and RV-induced asthma by blocking pro-inflammatory pathways regulated by PI3K/AKT.

Steroid-resistant asthma

Steroid-resistant asthma (SRA) refers to patients with symptoms consistent with asthma who show very poor or no response at all to high doses of inhaled or even of systemic corticosteroids. The current article reviews the SRA related literature focusing on the problems associated with the definition of SRA (especially its association with difficult to control, or severe asthma), its various phenotypes, its molecular basis, and the potential treatment options. The article also discusses the limitations of some of the key criteria used for the determination of SRA and proposes a modified set of criteria that are more applicable to children.

Expression and distribution of glucocorticoid receptor isoforms in eosinophilic chronic rhinosinusitis

OBJECTIVE

Patients with eosinophilic chronic rhinosinusitis (ECRS) show a high percentage of eosinophilic infiltration in the paranasal sinus mucosa. It is well documented that topical steroids have a beneficial effect in ECRS with nasal polyposis. We investigated mucosal distribution and cellular localization of glucocorticoid receptor (GR) isoform expression in human paranasal sinuses in relation to the clinical characteristics of eosinophilic chronic rhinosinusitis (ECRS) patients.

METHODS

Mucosal specimens were obtained from 20 sinusitis patients by endoscopic sinus surgery (ESS). Quantitative fluorescence immunohistochemical analysis was employed to examine the degree of glucocorticoid receptor (GR) isoform expression in sinus mucosa specimens. An RT-PCR procedure was performed to determine the relative quantities of mRNA for the human GRalpha and GRbeta genes.

RESULTS

Patients in the ECRS group showed significant increases in peripheral blood eosinophils as compared to the non-ECRS group (16.98% vs. 2.31%). Positive immunoreactivity of GRbeta expression was predominantly found to be positive in inflammatory cells. The absolute number of GRbeta-positive cells in the ECRS group was increased in comparison with that in the non-ECRS group. The difference was statistically significant both in the maxillary (179.7 cells/mm(2) vs. 82.5 cells/mm(2)) and ethmoid sinus (302.0 cells/mm(2) vs. 61.5 cells/mm(2)) mucosa. The GRbeta/GRalpha cell ratio in the ECRS group was elevated when compared with that in the non-ECRS group both in the maxillary and the ethmoid sinus mucosa, with the latter difference being significant.

CONCLUSIONS

The presence of high peripheral eosinophilia indicates a high likelihood of ECRS disease. Our results support the association of GRbeta expression with ECRS. The expression of GRbeta immunoreactivity, an endogenous inhibitor of steroid action previously associated with steroid insensitivity, may be one of major contributing factors in ECRS.

Neural regulation of innate immunity: a coordinated nonspecific host response to pathogens

The central nervous system (CNS) regulates innate immune responses through hormonal and neuronal routes. The neuroendocrine stress response and the sympathetic and parasympathetic nervous systems generally inhibit innate immune responses at systemic and regional levels, whereas the peripheral nervous system tends to amplify local innate immune responses. These systems work together to first activate and amplify local inflammatory responses that contain or eliminate invading pathogens, and subsequently to terminate inflammation and restore host homeostasis. Here, I review these regulatory mechanisms and discuss the evidence indicating that the CNS can be considered as integral to acute-phase inflammatory responses to pathogens as the innate immune system.

Brain-immune interactions and disease susceptibility

Many studies have established the routes by which the immune and central nervous (CNS) systems communicate. This network of connections permits the CNS to regulate the immune system through both neuroendocrine and neuronal pathways. In turn, the immune system signals the CNS through neuronal and humoral routes, via immune mediators and cytokines. This regulatory system between the immune system and CNS plays an important role in susceptibility and resistance to autoimmune, inflammatory, infectious and allergic diseases. This review focuses on the regulation of the immune system via the neuroendocrine system, and underlines the link between neuroendocrine dysregulation and development of major depressive disorders, autoimmune diseases and osteoporosis.

Risk-benefit value of inhaled glucocorticoids: a pharmacokinetic/pharmacodynamic perspective

Inhaled glucocorticoids induce therapeutic and adverse systemic effects via the same types of receptors. Analysis of the pharmacokinetic/pharmacodynamic parameters of inhaled glucocorticoids generates a risk-benefit value (RBV). Targeted efficacy with minimal adverse effects helps to quantify an appropriate RBV. High lung deposition/targeting, high receptor binding, longer pulmonary retention, and high lipid conjugation are among the pharmacokinetic parameters to be considered for improved efficacy of the compound. Low or negligible oral bioavailability, small particle size and inactive drug at the oropharynx, high plasma protein binding, rapid metabolism, high clearance, and lower systemic concentrations are associated with low risks for adverse effects. Inhaled glucocorticoid potency is enhanced by solution inhalers, which result in higher pulmonary deposition and minimize local adverse effects. These properties, among others, determine the efficacy and safety of inhaled glucocorticoids. Currently available inhaled glucocorticoids do not provide the complete pharmacokinetic/pharmacodynamic parameters to optimize RBV, leaving room for improvement in the development of future agents.