Immunomodulation in asthma: a distant dream or a close reality?

Prediction of chemical respiratory sensitizers using GARD, a novel in vitro assay based on a genomic biomarker signature

Background

Repeated exposure to certain low molecular weight (LMW) chemical compounds may result in development of allergic reactions in the skin or in the respiratory tract. In most cases, a certain LMW compound selectively sensitize the skin, giving rise to allergic contact dermatitis (ACD), or the respiratory tract, giving rise to occupational asthma (OA). To limit occurrence of allergic diseases, efforts are currently being made to develop predictive assays that accurately identify chemicals capable of inducing such reactions. However, while a few promising methods for prediction of skin sensitization have been described, to date no validated method, in vitro or in vivo, exists that is able to accurately classify chemicals as respiratory sensitizers.

Results

Recently, we presented the in vitro based Genomic Allergen Rapid Detection (GARD) assay as a novel testing strategy for classification of skin sensitizing chemicals based on measurement of a genomic biomarker signature. We have expanded the applicability domain of the GARD assay to classify also respiratory sensitizers by identifying a separate biomarker signature containing 389 differentially regulated genes for respiratory sensitizers in comparison to non-respiratory sensitizers. By using an independent data set in combination with supervised machine learning, we validated the assay, showing that the identified genomic biomarker is able to accurately classify respiratory sensitizers.

Conclusions

We have identified a genomic biomarker signature for classification of respiratory sensitizers. Combining this newly identified biomarker signature with our previously identified biomarker signature for classification of skin sensitizers, we have developed a novel in vitro testing strategy with a potent ability to predict both skin and respiratory sensitization in the same sample.

Exhaled nitric oxide and nasal tryptase are associated with wheeze, rhinitis and nasal allergy in primary school children

Rhinitis and asthma are the most common respiratory diseases in children. We assessed whether airway inflammation markers were associated with nasal allergies and self-reported symptoms of wheeze and rhinitis in 130 children 6-12 year old in an epidemiological context. Independent of sex and age, the fraction of exhaled nitric oxide (FeNO) and nasal mast cell (MC) activation (tryptase ≥ 5 ng/mL) were positively associated with wheeze, rhinitis and with nasal allergy. Nasal eosinophil cationic protein (ECP) and exhaled breath condensate (EBC) markers (pH, 8-isoprostane, interleukin-1β) were not associated with symptoms or with nasal allergy. In conclusion, FeNO and nasal tryptase reflect allergic inflammation in the respiratory system.

Oleanolic acid suppresses ovalbumin-induced airway inflammation and Th2-mediated allergic asthma by modulating the transcription factors T-bet, GATA-3, RORγt and Foxp3 in asthmatic mice

The natural product oleanolic acid is commonly found in a variety of medicinal plants. It is a triterpenoid compound known for its anti-inflammatory effects as well as various other pharmacological properties. The aim of the current study was to use a mouse model of allergic asthma to investigate whether oleanolic acid has anti-asthmatic effects, and if so, to determine the mechanism of these effects. Oleanolic acid suppressed eosinophil infiltration, allergic airway inflammation, and Penh, which occurred by suppressing the production of IL-5, IL-13, IL-17, and ovalbumin-specific IgE through the upregulation of T-bet and Foxp3, and the downregulation of GATA-3 and RORγt. The therapeutic effect of oleanolic acid was due to suppression of Th2 cytokines (IL-5 and IL-13), B cell-dependent production of OVA-specific IgE, and Gr-1 expression through the T-bet, GATA-3, retinoic acid-related orphan receptor γ t (RORγ t) and forkhead box p3 (Foxp3) transcription pathways. It is therefore reasonable to suggest that the anti-inflammatory and anti-asthmatic effects of oleanolic acid may be exerted through inhibition of the GATA-3 and RORγt pathways.

Effect of oral administration with pravastatin and atorvastatin on airway hyperresponsiveness and allergic reactions in asthmatic mice

BACKGROUND

Asthma is characterized by airway hyperresponsiveness and remodeling. Pravastatin and atorvastatin are used clinically as cholesterol-lowering agents but also exhibit anti-inflammatory and immunomodulating properties.

OBJECTIVE

To investigate the therapeutic effect of oral statins on airway hyperresponsiveness and allergic reaction.

METHODS

BALB/c mice received intraperitoneal sensitization and aerosol inhalation with ovalbumin consequently. One week after ovalbumin aerosol challenge, pravastatin, atorvastatin, or phosphate-buffered saline were given by intragastric gavage daily for 2 weeks. Airway hyperresponsiveness, serum allergen specific antibody levels, cytokine production by splenocytes, and bronchoalveolar lavage fluid were examined.

RESULTS

Both pravastatin and atorvastatin effectively reduced airway hyperresponsiveness. Pravastatin effectively suppressed both T(H)1- and T(H)2-mediated antibody responses, reducing serum specific IgE, IgG, IgG1, and IgG2a levels. Pravastatin also effectively reduced interleukin (IL) 4, IL-5, and interferon γ production but significantly enhanced IL-10 levels in splenocytes and BALF. Similarly, atorvastatin effectively attenuated production of specific IgE, IgG1, and IgG2a antibodies. It also significantly attenuated IL-4, interferon γ, and increased IL-10 concentration in bronchoalveolar lavage fluid and splenocytes.

CONCLUSION

Oral administration of pravastatin or atorvastatin not only was able to inhibit T(H)1 inflammatory responses but also had therapeutic effects on airway hyperresponsiveness and T(H)2 allergic responses. These results seem to suggest that these drugs have potential as a nonimmunosuppressive therapy for asthma and allergic diseases.

The Tec family kinase, IL-2-inducible T cell kinase, differentially controls mast cell responses

The Tec family tyrosine kinase, IL-2-inducible T cell kinase (Itk), is expressed in T cells and mast cells. Mice lacking Itk exhibit impaired Th2 cytokine secretion; however, they have increased circulating serum IgE, but exhibit few immunological symptoms of allergic airway responses. We have examined the role of Itk in mast cell function and FcepsilonRI signaling. We report in this study that Itk null mice have reduced allergen/IgE-induced histamine release, as well as early airway hyperresponsiveness in vivo. This is due to the increased levels of IgE in the serum of these mice, because the transfer of Itk null bone marrow-derived cultured mast cells into mast cell-deficient W/W(v) animals is able to fully rescue histamine release in the W/W(v) mice. Further analysis of Itk null bone marrow-derived cultured mast cells in vitro revealed that whereas they have normal degranulation responses, they secrete elevated levels of cytokines, including IL-13 and TNF-alpha, particularly in response to unliganded IgE. Analysis of biochemical events downstream of the FcepsilonRI revealed little difference in overall tyrosine phosphorylation of specific substrates or calcium responses; however, these cells express elevated levels of NFAT, which was largely nuclear. Our results suggest that the reduced mast cell response in vivo in Itk null mice is due to elevated levels of IgE in these mice. Our results also suggest that Itk differentially modulates mast cell degranulation and cytokine production in part by regulating expression and activation of NFAT proteins in these cells.

Cell types involved in allergic asthma and their use in in vitro models to assess respiratory sensitization

This review first describes the mechanism and cell types involved in allergic asthma, which is a complex clinical disease characterized by airway obstruction, airway inflammation and airway hyperresponsiveness to a variety of stimuli. The development of allergic asthma exists of three phases, namely the induction phase, the early-phase asthmatic reaction (EAR) and the late-phase asthmatic reaction (LAR). In the induction phase, antigen-presenting cells play a major role. Most important cells in the EAR are mast cells, and during the LAR, various cell types, such as eosinophils, neutrophils, T cells, macrophages, dendritic cells (DCs), and cells that endow structure are involved. In occupational asthma, this immunological mechanism is involved in 90% of the cases. The second part of this review gives an overview of in vitro models to assess the hazardous potential of high- and low-molecular weight chemicals on the respiratory system. In order to develop a good in vitro model for respiratory allergy, the choice of appropriate cell types is important. Epithelial cells, macrophages and DCs are currently the most used models in this field of research.

Dendritic cells in allergic airway inflammation

Dendritic cells (DCs) are primary antigen-presenting cells involved in interactions with T cells leading to the proliferation of TH1 or TH2 cell types. In asthma, predominance of TH2 cells appears to be responsible for disease pathogenesis. Differentiation of TH2 cells is driven by a variety of factors such as the expression of high levels of costimulatory molecules, the cytokine profile, and the subset of DCs. Many inflammatory cells involved in the pathogenesis of asthma either directly or indirectly modulate DC function. Traditional treatments for asthma decrease the number of airway DCs in animals as well as in patients with asthma. Immunomodulators including interleukin (IL)-10, transforming growth factor (TGF)-beta, cytosine-phosphate-guanosine-containing oligodeoxynucleotides (CpG-ODN), 1alpha,25-dihydroxyvitamin D3, and fetal liver tyrosine kinase 3 ligand (Flt3L) are involved in the modulation of the function of DCs. Based on the critical review of the interaction between DCs and other inflammatory cells, we propose that activation of T cells by DCs and sensitization to inhaled allergen and resulting airway inflammation are dependent on plasmacytoid and myeloid subset of lung DCs to induce an immune response or tolerance and are tightly regulated by T-regulatory cells. Effects of various therapeutic agents to modulate the function of lung myeloid DCs have been discussed.

The allergic cascade: review of the most important molecules in the asthmatic lung

Asthma is the most common chronic inflammatory disorder of the airways among children. It is a complex clinical disease characterized by airway obstruction, airway inflammation and airway hyperresponsiveness to a variety of stimuli. The development of allergic asthma exists of three phases, namely the induction phase, the early-phase asthmatic reaction (EAR) and the late-phase asthmatic reaction (LAR). Each phase is characterized by the production and interplay of various cell-derived mediators. In the induction phase, T helper cytokines are important in the development of asthma. Most important mediators in the EAR are preformed mediators, newly synthesized lipid mediators and cytokines that are produced by mast cells. During the LAR, inflammatory molecules are produced by various cell types, such as eosinophils, neutrophils, T cells, macrophages, dendritic cells, and structural cells. Chronical inflammation leads to structural changes of the airway architecture. In this review, the most important mediators involved in the induction phase, the early-phase and late-phase asthmatic reaction are discussed.

Mechanisms underlying the relaxation induced by isokaempferide from Amburana cearensis in the guinea-pig isolated trachea

The present study examines possible mechanisms by which the flavonoid isokaempferide (IKPF; 5,7,4'-trihydroxy-3-methoxyflavone) from Amburana cearensis, a Brazilian medicinal plant popularly used as bronchodilator, induces relaxation of guinea-pig isolated trachea. In the trachea (with intact epithelium) contracted by carbachol, IKPF (1-1000 microM) caused a graded relaxation, and the epithelium removal increased the sensitivity of the airway smooth muscle to IKPF (EC50, in intact tissue: 77.4 [54.8-109.2] microM; in denuded epithelium: 15.0 [11.3-20.1] microM). The IKPF-induced relaxation was inhibited in 41% by the nitric oxide (NO) synthase inhibitor L-NAME (100 microM); in 31% and 50% by the soluble guanylate cyclase (sGC) inhibitor ODQ (3 and 33 microM); by propranolol (31%) and also by capsaicin (37%). In the trachea pre-contracted by 40 mM KCl the pre-incubation with glibenclamide (33 microM) or iberiotoxin (IbTX, 0.1 microM), selective K(+) channel inhibitors, inhibited the IKPF-induced relaxation by 39% and 38%, respectively. On the other hand, 4-aminopyridine (100 microM), a nonselective K(+) channel antagonist, did not significantly influence the effect of IKPF, while IbTX induced a rightward displacement of the IKPF concentration-response curve. However, in muscle pre-contracted with 120 mM KCl the relaxant effect of IKPF was significantly reduced and not affected by glibenclamide. In conclusion, these results indicate a direct and epithelium-independent relaxant effect of IKPF on smooth muscle fibers. Although this IKPF relaxant action seems to be multi-mediated, it occurs via both Ca(2+) and ATP-sensitive K(+) channels, but some other possible mechanisms unrelated to K(+) channels cannot be excluded.

Allergic airway inflammation

Several genes, including ADAM33, DPP10, PHF11, GPRA, and TIM-1, have been implicated in the pathogenesis and susceptibility to atopy and asthma. Advances have been made in defining the mechanism for the control of allergic airway inflammation in response to inhaled antigens. There is growing evidence that associates asthma with a systemic propensity for allergic type 2 T-cell cytokines. Disordered coagulation and fibrinolysis could also exacerbate asthma symptoms. Major emphasis on immunotherapy for asthma during the past decade has been to direct the immune response to a type 1 response. Recent literature supports the pivotal role of plasmacytoid dendritic cells and allergen-specific T-regulatory cells in the development of tolerance to allergens. In this review article, we discuss the current information on the pathogenesis of allergic airway inflammation and potential allergen immunotherapies, which could be beneficial in the treatment of airway inflammation, allergy, and asthma.