Asthma: new developments concerning immune mechanisms, diagnosis and treatment

The bioflavonoid hispidulin effectively attenuates T helper type 2-driven allergic lung inflammation in the ovalbumin-induced allergic asthma mouse model

BACKGROUND

Allergic asthma affects nearly 300 million people worldwide and causes ahigh burden of disability and death. Effective treatments rely heavily on corticosteroids, which are associated with various complications. So, the alternative treatment is of significance. Hispidulin is a bioflavonoid found in herbs that were used in traditional medicine to treat inflammatory diseases, including asthma. This study aims to investigate the efficacy of hispidulin compound in the treatment of allergic lung inflammation using the mouse model of allergic asthma.

METHODS

BALB/c mice were sensitized and challenged with chicken egg ovalbumin. Cells and cytokines from bronchoalveolar lavage (BAL) fluid were examined. Lung tissues were collected for histologic study. Mouse splenic CD4+ cells were cultured to observe the effect of hispidulin on T-helper 2 (Th2) cell differentiation in vitro.

RESULTS

Hispidulin treatment could alleviate allergic airway inflammation as evidenced by a significant reduction in the inflammatory cell count and Th2 cytokines interleukin (IL)-4, IL-5, IL-13 in BAL fluid. Histologic examination of lung tissues revealed lower inflammatory cell infiltration to the bronchi and less airway goblet cell hyperplasia in the treatment group compared to the control group. At the cellular level, hispidulin (25, 50, and 100 μM) was found to directly suppress the differentiation and proliferation of Th2 cells and to suppress the production of Th2 cytokines, such as IL-4, IL-5, and IL-13, in vitro.

CONCLUSIONS

Hispidulin treatment was shown to effectively decrease type 2 lung inflammation in an ovalbumin-induced allergic asthma mouse model by directly suppressing Th2 cell differentiation and functions.

Airway epithelial barrier dysfunction in the pathogenesis and prognosis of respiratory tract diseases in childhood and adulthood

The lungs are in direct contact with the environment through the tubular structure that constitutes the airway. Starting from the nasal orifice, the airway is exposed to foreign particles including infectious agents, allergens, and other substances that can damage the airways. Therefore, the airway must have a functional epithelial barrier both in the upper and lower airways to protect against these threats. As with the skin, it is likely that the pathogenesis of respiratory diseases is a consequence of epithelial barrier defects in these airways. The characteristics of this system, starting from the beginning of life and extending into maturing and aging, determine the prognosis of respiratory diseases. In this article, we discuss the pathogenesis, clinical phenotype, and prognosis of respiratory diseases from newborns to adulthood in the context of epithelial barrier function and dysfunction.

Blockade of Notch Signalling by γ-Secretase Inhibitor in Lung T Cells of Asthmatic Mice Affects T Cell Differentiation and Pulmonary Inflammation

Notch is a single-pass transmembrane receptor protein expressed by T cells, which contributes to the pathogenesis of asthma through regulation of the development and differentiation of T cells. γ-Secretase inhibitor (GSI) acts as an effective blocker of Notch signalling. The present study aimed to investigate the role of GSI MW167 in T cell differentiation and antigen-induced airway inflammation. An OVA-induced airway inflammation mouse model was established. Blockade of Notch signalling was achieved using MW167. The expression of IL-4, IL-5, IFN-γ, Notch1 signalling and pro-inflammatory transcription factors in activated lung T cells was evaluated. Finally, the therapeutic effect of MW167 was investigated by haematoxylin and eosin staining, real-time PCR and ELISA. The expression of IL-4 and IL-5 decreased and that of IFN-γ increased significantly, and the protein expression levels of pro-inflammatory transcription factors reduced in active lung T cells after administration of MW167, compared to the control group. MW167 treatment prevented OVA-induced airway inflammation and histological changes. The serum and bronchoalveolar lavage fluid (BALF) levels of IL-4 and IL-5 in MW167-treated mice decreased significantly, whereas those of IFN-γ increased, relative to the levels in OVA-challenged animals treated with PBS. Our findings indicate that Notch signalling plays an important role in the pathogenesis of asthma and that MW167 may be a potential therapeutic target for allergen-induced airway inflammation.

Protective effect of curcumin on acute airway inflammation of allergic asthma in mice through Notch1-GATA3 signaling pathway

Curcumin, a natural product derived from the plant Curcuma longa, has been found to have anti-inflammatory, antineoplastic and antifibrosis effects. It has been reported that curcumin attenuates allergic airway inflammation in mice through inhibiting NF-κB and its downstream transcription factor GATA3. It also has been proved the antineoplastic effect of curcumin through down-regulating Notch1 receptor and its downstream nuclear transcription factor NF-κB levels. In this study, we aimed to investigate the anti-inflammatory effect of curcumin on acute allergic asthma and its underlying mechanisms. 36 male BALB/c mice were randomly divided into four groups (normal, asthma, asthma+budesonide and asthma+curcumin groups). BALF (bronchoalveolar lavage fluid) and lung tissues were analyzed for airway inflammation and the expression of Notch1, Notch2, Notch3, Notch4 and the downstream transcription factor GATA3. Our findings showed that the levels of Notch1 and Notch2 receptors were up-regulated in asthma group, accompanied by the increased expression of GATA3. But the expression of Notch2 receptor was lower than Notch1 receptor. Curcumin pretreatment improved the airway inflammatory cells infiltration and reversed the increasing levels of Notch1/2 receptors and GATA3. Notch3 receptor was not expressed in all of the four groups. Notch4 receptor protein and mRNA expression level in the four groups had no significant differences. The results of the present study suggested that Notch1 and Notch2 receptor, major Notch1 receptor, played an important role in the development of allergic airway inflammation and the inhibition of Notch1–GATA3 signaling pathway by curcumin can prevent the development and deterioration of the allergic airway inflammation. This may be a possible therapeutic option of allergic asthma.

Immunomodulatory impact of a synbiotic in T(h)1 and T(h)2 models of infection

BACKGROUND AND METHODS

The immunomodulatory activity of a synbiotic combination containing three bacterial strains (Lactobacillus helveticus R0052, Bifidobacterium longum subsp. infantis R0033 and Bifidobacterium bifidum R0071) and short-chain fructooligosaccharide was examined in two distinct infectious rat models. In the T(h)1 model, Wistar rats were administered the synbiotic combination for 2 weeks prior to challenge with a single oral dose of enterotoxigenic Escherichia coli or vehicle. In the T(h)2 model, pretreated rats were challenged with a single subcutaneous dose of hook worm, Nippostrongylus brasiliensis. Blood samples were collected 3 hours or 4 days postchallenge and serum levels of pro- and anti-inflammatory cytokines were measured.

RESULTS

Significant reductions in pro-inflammatory cytokines interleukin (IL)-1α, IL-1β, IL-6, and tumour necrosis factor (TNF)-α were observed in both models suggesting a single, unifying mode of action on an upstream regulator. The N. brasiliensis study also compared the effect of the individual strains to synbiotic. For most of cytokines the combination appeared to average the effect of the individual strains with the exception of IL-4 and IL-10 where there was apparent synergy for the combination. Furthermore, the cytokine response varied by strain.

CONCLUSIONS

It was concluded that this synbiotic combination of these three microbes could be beneficial in both T(h)1 and T(h)2 diseases.

Effects of combination therapy with montelukast and carbocysteine in allergen-induced airway hyperresponsiveness and airway inflammation

BACKGROUND AND PURPOSE

Montelukast and S-carbocysteine have been used in asthmatic patients as an anti-inflammatory or mucolytic agent respectively. S-carbocysteine also exhibits anti-inflammatory properties.

EXPERIMENTAL APPROACH

Ovalbumin (OVA) sensitized BALB/c mice were challenged with OVA for 3 days followed by single OVA re-challenge (secondary challenge) 2 weeks later. Forty-eight hours after secondary challenge, mice were assessed for airway hyperresponsiveness (AHR) and cell composition in bronchoalveolar lavage (BAL) fluid. Suboptimal doses of 10 mg.kg(-1) of S-carbocysteine by intraperitoneal injection (ip), 20 mg.kg(-1) of montelukast by gavage, the combination of S-carbocysteine and montelukast or 3 mg.kg(-1) of dexamethasone as a control were administered from 1 day before the secondary challenge to the last experimental day. Isolated lung cells were cultured with OVA and montelukast to determine the effects on cytokine production.

KEY RESULTS

Treatment with S-carbocysteine or montelukast reduced both AHR and the numbers of eosinophils in BAL fluid. Neutralizing IFN-gamma abolished the effects of S-carbocysteine on these airway responses. Combination of the two drugs showed further decreases in both AHR and eosinophils in the BAL fluid. Goblet cell metaplasia and Th2-type cytokines, interleukin (IL)-4, IL-5 and IL-13, in BAL fluid were decreased with montelukast treatment. Conversely, S-carbocysteine increased Th1-type cytokines, IFN-gamma and IL-12 in BAL fluid.

CONCLUSIONS AND IMPLICATIONS

The combination of two agents, montelukast and S-carbocysteine, demonstrated additive effects on AHR and airway inflammation in a secondary allergen model most likely through independent mechanisms of action.

Point-counterpoint. The triumph of the null hypothesis: epidemiology in an age of change

The recent confusion concerning the relation between hormone replacement therapy and cardiovascular disease has stirred a new wave of debate about the value and future of epidemiology. Opponents of epidemiology suggest an ever-diminishing role in an age of small risks and complex diseases, yet proponents are not in consensus about how to adapt their discipline to the challenges associated with ageing societies and changing disease patterns. While epidemiology is likely to be increasingly called upon to make sense of the risks involved with these changes, wading into this era with a mindset and tools that were derived from epidemiology's 'golden era' of tackling major risk factors, has created more confusion than understanding. Increasingly, we need to downsize epidemiology to what is testable, measurable, and relevant, based on robust methodology and public health rationale. Applying an evolutionary perspective, that views health problems of modernity as a manifestation of the mismatch between our ancient genes and hi-tech lifestyles, can provide guidance for a 21st century research agenda.

A genetic variation in inositol polyphosphate 4 phosphatase a enhances susceptibility to asthma

RATIONALE

Microarray data from mouse studies have identified a number of genes to be differentially expressed in allergen-sensitized mice lungs.

OBJECTIVES

Taking leads from these datasets, we attempted to identify novel genes associated with atopic asthma in humans.

METHODS

We performed family-based genetic association analysis on selected markers within or in proximity of 21 human homologs of genes short-listed from ovalbumin-sensitized mouse studies in the Gene Expression Omnibus database of the National Center for Biotechnology Information. Family-based and case-control studies were undertaken for fine mapping and functional variation analysis of INPP4A (inositol polyphosphate 4 phosphatase type I). Western blot analysis was performed to analyze INPP4A protein stability from human platelets.

MEASUREMENTS AND MAIN RESULTS

Our genetic association studies of 21 human genes in 171 trios led to the identification of a biallelic repeat (rs3217304) in INPP4A, associated with atopic asthma (P = 0.009). Further studies using additional three single nucleotide polymorphisms (SNPs), +92031A/T, +92344C/T, and +131237C/T, and two microsatellite markers, D2S2311 and D2S2187, revealed significant genetic associations with loci +92031A/T (P = 0.0012) and +92344C/T (P = 0.004). A nonsynonymous SNP, +110832A/G (Thr/Ala), present within a sequence enriched with proline, glutamic acid, serine, and threonine (PEST), in proximity of these two loci, showed a significant association with atopic asthma (P = 0.0006). The association results were also replicated in an independent cohort of 288 patients and 293 control subjects (P = 0.004). PEST score and Western blot analyses indicated a functional role of this SNP in regulating INPP4A protein stability.

CONCLUSIONS

In our study, INPP4A was identified as a novel asthma candidate gene, whereby the +110832A/G (Thr/Ala) variant affected its stability and was significantly associated with asthma.

Respiratory virus-induced regulation of asthma-like responses in mice depends upon CD8 T cells and interferon-gamma production

Respiratory virus infections can significantly influence the development of airway disease by both predisposing and exacerbating the developing lung immune environment. In contrast, the initiation of a more desirable anti-viral response may better prepare the local environment and protect it from developing an adverse long-term disease phenotype. BALB/c or C57BL/6 mice exposed to respiratory syncytial virus (RSV) infection at the same time as allergen sensitization were assessed for airway function, cytokine responses, and inflammatory parameters. Depending on the genetic strain of mouse used, BALB/c versus C57BL/6, RSV could differentially protect against the development of airway allergen responses. Although RSV was able to block allergen sensitization and induction of airway hyperresponsiveness and eosinophilic inflammation in C57BL/6 mice, the infection did not reduce the allergic responses in BALB/c mice. The alteration of airway responsiveness did not depend on the timing of RSV infection in C57BL/6 mice in conjunction to the allergen sensitization protocol. Neutralization experiments demonstrated that interferon-gamma contributed significantly to the RSV-induced airway attenuation of the allergic responses, whereas transfer of CD8 T cells from RSV-infected animals suggested that they were partially responsible for the altered environment. These data suggest that a respiratory viral infection impacts on the local lung environment and may reflect specific aspects of the hygiene hypothesis. However, the outcome of this interaction depends on the immunological response of the host.