Interleukin-13 in asthma pathogenesis

Molecular and cellular factors determining the functional pleiotropy of cytokines

Cytokines are soluble factors vital for mammalian physiology. Cytokines elicit highly pleiotropic activities, characterized by their ability to induce a wide spectrum of functional responses in a diverse range of cell subsets, which makes their study very challenging. Cytokines activate signalling via receptor dimerization/oligomerization, triggering activation of the JAK (Janus kinase)/STAT (signal transducer and activator of transcription) signalling pathway. Given the strong crosstalk and shared usage of key components of cytokine signalling pathways, a long-standing question in the field pertains to how functional diversity is achieved by cytokines. Here, we discuss how biophysical - for example, ligand-receptor binding affinity and topology - and cellular - for example, receptor, JAK and STAT protein levels, endosomal compartment - parameters contribute to the modulation and diversification of cytokine responses. We review how these parameters ultimately converge into a common mechanism to fine-tune cytokine signalling that involves the control of the number of Tyr residues phosphorylated in the receptor intracellular domain upon cytokine stimulation. This results in different kinetics of STAT activation, and induction of specific gene expression programs, ensuring the generation of functional diversity by cytokines using a limited set of signalling intermediaries. We describe how these first principles of cytokine signalling have been exploited using protein engineering to design cytokine variants with more specific and less toxic responses for immunotherapy.

Angiotensin converting enzyme 2 activation improves allergic rhinitis and suppresses Th2 cytokine release

OBJECTIVE

Allergic rhinitis (AR) is primarily regulated by type I hypersensitivity, with Th2 and immunoglobulin E (IgE) playing essential roles. This study aimed to determine whether angiotensin converting enzyme (ACE)2 could participate in the regulation of AR.

METHODS

Nasal mucosal tissues of AR patients were collected to determine ACE2 levels. Following AR mouse models were established, ACE2 levels in nasal mucosa were determined. Then the influences of diminazene aceturate (ACE2 agonist) on AR symptoms, pathology, specific antibodies, histamine, and interleukins (ILs) release in vivo were evaluated. Afterward, human nasal mucosa epithelial cells were exposed to IL-13, and the impacts of ACE2 overexpression on the secretion of pro-inflammatory factors in vitro were assessed.

RESULTS

ACE2 levels significantly declined in nasal mucosa both in patients and mouse models (p < .001). Diminazene aceturate treatment elevated the ACE2 level in mice (p < .01), accompanied by reduced frequency of nasal spray and nasal friction, decreased eosinophils and goblet cells (p < .001) according to histopathological staining. Furthermore, lgE, lgG1, histamine, and IL levels in mice were also decreased (p < .05). In vitro experiments revealed that ACE2 overexpression suppressed the secretion of pro-inflammatory factors (p < .001).

CONCLUSION

Together, ACE2 activation can alleviate the symptoms of AR in mice and inhibit the release of Th2 cytokines. Activating ACE2 is a promising therapeutic approach for AR.

Development of Neutralizing Multimeric Nanobody Constructs Directed against IL-13: From Immunization to Lead Optimization

IL-13 is a pleiotropic cytokine mainly secreted by Th2 cells. It reacts with many different types of cells involved in allergy, inflammation, and fibrosis, e.g., mastocytes, B cells, and fibroblasts. The role of IL-13 in conditions involving one or several of these phenotypes has therefore been extensively investigated. The inhibition of this cytokine in animal models for various pathologies yielded highly promising results. However, most human trials relying on anti-IL-13 conventional mAbs have failed to achieve a significant improvement of the envisaged disorders. Where some studies might have suffered from several weaknesses, the strategies themselves, such as targeting only IL-13 using conventional mAbs or employing a systemic administration, could be questioned. Nanobodies are recombinant Ag-binding fragments derived from the variable part of H chain-only Abs occurring in Camelidae. Thanks to their single-domain structure, small size (≈15 kDa), good stability, and solubility, they can be engineered into multispecific constructs for combined therapies or for use in new strategies such as formulations for local administration, e.g., pulmonary administration. In this study, we describe the generation of 38 nanobodies that can be subdivided into five CDR3 families. Nine nanobodies were found to have a good affinity profile (K_D = 1-200 nM), but none were able to strongly inhibit IL-13 biological activity in vitro (IC₅₀ > 50 µM: HEK-Blue IL-13/IL-4 cells). Multimeric constructs were therefore designed from these inhibitors and resulted in an up to 36-fold improvement in affinity and up to 300-fold enhancement of the biological activity while conserving a high specificity toward IL-13.

Disease modelling following organoid-based expansion of airway epithelial cells

Air-liquid interface (ALI) cultures are frequently used in lung research but require substantial cell numbers that cannot readily be obtained from patients. We explored whether organoid expansion (3D) can be used to establish ALI cultures from clinical samples with low epithelial cell numbers. Airway epithelial cells were obtained from tracheal aspirates (TA) from preterm newborns, and from bronchoalveolar lavage (BAL) or bronchial tissue (BT) from adults. TA and BAL cells were 3D-expanded, whereas cells from BT were expanded in 3D and 2D. Following expansion, cells were cultured at ALI to induce differentiation. The impact of cell origin and 2D or 3D expansion was assessed with respect to (i) cellular composition; (ii) response to cigarette smoke exposure; (iii) effect of Notch inhibition or IL-13 stimulation on cellular differentiation. We established well-differentiated ALI cultures from all samples. Cellular compositions (basal, ciliated and goblet cells) were comparable. All 3D-expanded cultures showed a similar stress response following cigarette smoke exposure but differed from the 2D-expanded cultures. Higher peak levels of antioxidant genes HMOX1 and NQO1 and a more rapid return to baseline, and a lower unfolded protein response was observed after cigarette smoke exposure in 3D-derived cultures compared to 2D-derived cultures. Additionally, TA- and BAL-derived cultures were less sensitive to modulation by DAPT or IL-13 than BT-derived cultures. Organoid-based expansion of clinical samples with low cell numbers, such as TA from preterm newborns is a valid method and tool to establish ALI cultures.

Evaluation of Antibody Properties and Clinically Relevant Immunogenicity, Anaphylaxis, and Hypersensitivity Reactions in Two Phase III Trials of Tralokinumab in Severe, Uncontrolled Asthma

Introduction

Tralokinumab is a monoclonal antibody (mAb) that neutralizes interleukin (IL)-13, a cytokine involved in the pathogenesis of asthma.

Objective

The objectives of this study were to characterize the potential immunogenic properties of tralokinumab and report data for anti-drug antibodies (ADAs) and hypersensitivity reactions from two phase III clinical trials.

Methods

The oligosaccharide structure of tralokinumab, Fab-arm exchange, and ADAs were characterized by standard techniques. Hypersensitivity adverse events (AEs) were evaluated in two pivotal clinical trials of tralokinumab in severe, uncontrolled asthma: STRATOS 1 and 2 (NCT02161757 and NCT02194699).

Results

No galactose-α-1,3-galactose (α-Gal) epitopes were found in the Fab region of tralokinumab and only 4.5% of glycoforms contained α-Gal in the Fc region. Under non-reducing conditions, Fab-arm exchange did not take place with another immunoglobulin (Ig) G₄ mAb (mavrilimumab). However, following glutathione reduction, a hybrid antibody with monovalent bioactivity was detected. ADA incidences (titers) were as follows: STRATOS 1—every 2 weeks (Q2 W) 0.8% (26.0), every 4 weeks (Q4 W) 0.5% (26.0), placebo 0.8% (52.0); STRATOS 2—Q2 W 1.2% (39.0), placebo 0.8% (13.0). Participant-reported hypersensitivity AE rates were as follows: STRATOS 1—Q2 W 25.9%, Q4 W 25.0%, placebo 25.5%; STRATOS 2—Q2 W 13.2%, placebo 9.0%. External evaluation for anaphylaxis by Sampson criteria found no tralokinumab-related severe hypersensitivity or anaphylaxis reactions.

Conclusion

Preclinical assessments suggested a low likelihood of immunogenicity for tralokinumab. In STRATOS 1 and 2, ADA incidence was low, no differences were found between tralokinumab-treated and placebo groups in reporting of hypersensitivity reactions, and there were no Sampson criteria-evaluated anaphylaxis events with tralokinumab treatment. Together, the results suggest that tralokinumab treatment would not increase the risk for severe hypersensitivity or anaphylactic reactions.

Electronic supplementary material

The online version of this article (10.1007/s40264-018-00788-w) contains supplementary material, which is available to authorized users.

Differential effects of inhaled R- and S-terbutaline in ovalbumin-induced asthmatic mice

Inhaled terbutaline is commercially available β₂-agonist which consists of equivalent amount of R- and S-enantiomer. In this study, we aimed to investigate the effects of single enantiomers of terbutaline and its racemate in an ovalbumin (OVA)-induced mouse model of asthma via. seven days inhalation and the potential mechanisms involved. In a standard experimental asthma model, BALB/c mice were sensitized and challenged with OVA. R-terbutaline (R-ter), S-terbutaline (S-ter) or racemic terbutaline (rac-ter) was given via. nose-only inhalation for one week. Airway responsiveness to methacholine was measured by the plethysmography in conscious mice. Eosinophils counts in blood and bronchoalveolar (BAL) fluid were determined. The OVA-sIgE in plasma and inflammatory cytokines and mediators in BAL fluid or lung tissue were analyzed by ELISA, qRT-PCR or western blotting. Airway inflammation and remodeling were evaluated with hematoxylin and eosin (HE), periodic acid-Schiff (PAS), and Masson staining. Drug distribution and deposition after inhalation were determined by LC-MS/MS. Our data showed that R-ter efficiently ameliorated asthma responses, including airway hyperresponsiveness, eosinophils influx and IL-5 in BALF, plasma OVA-sIgE and significantly reduced pulmonary inflammation, peribronchial smooth muscle layer thickness, goblet cell hyperplasia, and deposition of collagen fibers, as well as downregulation of p38 MAPK phosphorylation and NF-κB expression. Racemic mixture exhibited diminished effects while S-ter enhanced airway responsiveness to methacholine and exerted pro-asthmatic effects.

The effects of neutralizing anti-murine interleukin-17A monoclonal antibody on ozone-induced inflammation and glucocorticoids insensitivity in a murine model of asthma

BACKGROUND AND OBJECTIVE

Exposure to ozone contributed to the worsening of inflammation and glucocorticoids insensitivity in OVA-challenged asthma. Interleukin-17A participates centrally in stages of the inflammatory response and glucocorticoids insensitivity. In this study, the effect of neutralizing anti-murine interleukin-17A monoclonal antibody (IL-17A mAb) on inflammation and glucocorticoids insensitivity in ozone-exposed and ovalbumin (OVA)-challenged mice was investigated.

METHODS

Mice were sensitized and challenged with OVA and then exposed to ozone. Dexamethasone (Dex) and IL-17A mAb were administrated in corresponding periods.

RESULTS

Compared with OVA-challenged mice, combination administration of ozone exposure and OVA challenge increased the recruitment of inflammatory cells in bronchoalveolar lavage fluid, enhanced the inflammation scores and levels of inflammatory cytokines and IL-17A mRNA, and caused the activation of p38 MAPK together with down regulation of glucocorticoids recepters (GR) in lung tissue. Monotherapy of IL-17A mAb partially attenuated lung inflammation in OVA-challenged and ozone-exposed mice, while the combination treatment of Dex and IL-17A mAb effectively reduced lung inflammation, inactivated p38 MAPK and up regulated GR in lung tissue.

CONCLUSIONS

Ozone exposure worsened OVA-challenged airway inflammation, activation of p38 MAPK and down regulation of GR in OVA-sensitized and -challenged mice, which was effectively counteracted by IL-17A mAb, and combination treatment of IL-17A mAb and Dex shows profound efficacy in inhibiting airway inflammation and improving glucocorticoids insensitivity synergistically.

Chronic Obstructive Pulmonary Disease Molecular Subtyping and Pathway Deviation-Based Candidate Gene Identification

OBJECTIVE

The aim of this study was to identify the molecular subtypes of chronic obstructive pulmonary disease (COPD) and to prioritize COPD candidate genes using bioinformatics methods.

MATERIALS AND METHODS

In this bioinformatics study, the gene expression dataset GSE76705 (including 229 COPD samples) and known COPD-related genes (candidate genes) were downloaded from the Gene Expression Omnibus (GEO) and the Online Mendelian Inheritance in Man (OMIM) databases respectively. Based on the expression values of the candidate genes, COPD samples were divided into molecular subtypes through hierarchical clustering analysis. Candidate genes were accordingly allocated into the defined molecular subtypes and functional enrichment analysis was undertaken. Pathway deviation scores were then analyzed, followed by the analysis of clinical indicators (FEV1, FEV1/FVC, age and gender) of COPD patients in each subtype, and prediction models were constructed. Furthermore, the gene expression dataset GSE71220 was used to bioinformatically validate our results.

RESULTS

A total of 213 COPD-related genes were identified, which divided samples into three subtypes based on the gene expression values. After intersection analysis, 160 common genes including transforming growth factor β1 (TGFB1), epidermal growth factor receptor (EGFR) and interleukin 13 (IL13) were obtained. Functional enrichment analysis identified 22 pathways such as 'hsa04060: cytokine-cytokine receptor interaction pathways, 'hsa04110: cell cycle' and 'hsa05222: small cell lung cancer'. Pathways in subtype 2 had higher deviation scores. Furthermore, three receiver operating characteristic (ROC) curves (accuracies >80%) were constructed. The three subtypes in COPD samples were also identified in the validation dataset GSE71220.

CONCLUSION

COPD may be further subdivided into several molecular subtypes, which may be useful in improving COPD therapy based on the molecular subtype of a patient.

Mapping Determinants of Cytokine Signaling via Protein Engineering

Cytokines comprise a large family of secreted ligands that are critical for the regulation of immune homeostasis. Cytokines initiate signaling via dimerization or oligomerization of the cognate receptor subunits, triggering the activation of the Janus Kinases (JAKs)/ signal transducer and activator of transcription (STATs) pathway and the induction of specific gene expression programs and bioactivities. Deregulation of cytokines or their downstream signaling pathways are at the root of many human disorders including autoimmunity and cancer. Identifying and understanding the mechanistic principles that govern cytokine signaling will, therefore, be highly important in order to harness the therapeutic potential of cytokines. In this review, we will analyze how biophysical (ligand-receptor binding geometry and affinity) and cellular (receptor trafficking and intracellular abundance of signaling molecules) parameters shape the cytokine signalosome and cytokine functional pleiotropy; from the initial cytokine binding to its receptor to the degradation of the cytokine receptor complex in the proteasome and/or lysosome. We will also discuss how combining advanced protein engineering with detailed signaling and functional studies has opened promising avenues to tackle complex questions in the cytokine signaling field.

Airway Eosinophilopoietic and Autoimmune Mechanisms of Eosinophilia in Severe Asthma

Eosinophils are critical in asthma biology, contributing to symptoms, airflow obstruction, airway hyperresponsiveness, and remodeling. In severe asthma, in addition to local maturation in bone marrow, in situ eosinophilopoiesis plays a key role in the persistence of airway eosinophilia. Local milieu of structural, epithelial and inflammatory cells contribute by generating eosinophilopoietic cytokines in response to epithelial-derived alarmins. Another mechanism of persistent airway eosinophilia is glucocorticosteroid insensitivity, which is linked to recurrent airway infections and presence of local autoantibodies. Novel molecules are being developed to target specific immune pathways as potential steroid-sparing strategies.

MicroRNA‑16 inhibits interleukin‑13‑induced inflammatory cytokine secretion and mucus production in nasal epithelial cells by suppressing the IκB kinase β/nuclear factor‑κB pathway

Chronic inflammation of the nasal mucosal tissue plays important roles in the pathogenesis of allergic rhinitis (AR). Aberrantly expressed microRNAs (miRNAs) have been found to have strong associations with inflammatory reactions in allergic diseases; however, its functional significance and molecular mechanism underlying in AR remains unclear. The aim of the present study was to investigate the biological functions of miRNA and reveal its underlying molecular mechanisms in AR. miRNA microarray was performed to analyze miRNAs expression levels in 3 paired nasal mucosal samples from patients with AR and a control group. Subsequently, human nasal epithelial cells (JME/CF15) were used as an in vitro model to further explore the functions of miRNAs. Microarray data revealed that miR‑16 was one of the miRNAs being most significantly downregulated. Interleukin (IL)‑13 stimulation gradually decreased the levels of miR‑16 in JME/CF15 cells. Moreover, upregulation of miR‑16 inhibited inflammatory cytokines, including granulocyte‑macrophage colony‑stimulating factor (GM‑CSF), eotaxin, IL‑1β, IL‑6 and IL‑10 in IL‑13‑treated JME/CF15 cells. Furthermore, overexpression of miR‑16 significantly decreased the mRNA and protein expression levels of mucin 5AC (MUC5AC). IκB kinase β (IKKβ) was identified as a direct target of miR‑16 and its expression was negatively regulated by miR‑16 at mRNA and protein levels. Notably, forced expression of miR‑16 blocked NF‑κB signaling by decreasing the expression of nuclear p‑p65 and p‑IκB‑α, as well as increasing the expression of IκB‑α in IL‑13‑treated nasal epithelial cells. Moreover, enhanced IKKβ reactivated the NF‑κB pathway that was blocked by miR‑16 mimics and then effectively suppressed the miR‑16‑mediated inhibitory effects on inflammatory response. These findings suggested that miR‑16 suppressed the inflammatory response by inhibiting the activation of IKKβ/NF‑κB signaling pathways.

Selective release of miRNAs via extracellular vesicles is associated with house-dust mite allergen-induced airway inflammation

BACKGROUND

MicroRNAs (miRNAs) may facilitate cell-to-cell communication via extracellular vesicles (EVs). The biological roles of miRNAs in EVs on allergic airway inflammation are unclear.

METHODS

Airway-secreted EVs (AEVs) were isolated from bronchoalveolar lavage fluid (BALF) of control and house-dust mite (HDM) allergen-exposed HDM-sensitized mice. The expression of miRNAs in AEVs or miRNAs and mRNAs in lung tissue was analysed using miRNA microarray.

RESULTS

The amount of AEV increased 8.9-fold in BALF from HDM-exposed mice compared with that from sham-control mice. HDM exposure resulted in significant changes in the expression of 139 miRNAs in EVs and 175 miRNAs in lung tissues, with 54 miRNAs being common in both samples. Expression changes of these 54 miRNAs between miRNAs in AEVs and lung tissues after HDM exposure were inversely correlated. Computational analysis revealed that 31 genes, including IL-13 and IL-5Ra, are putative targets of the miRNAs up-regulated in AEVs but down-regulated in lung tissues after HDM exposure. The amount of AEV in BALF after HDM exposure was diminished by treatment with the sphingomyelinase inhibitor GW4869. The treatment with GW4869 also decreased Th2 cytokines and eosinophil counts in BALFs and reduced eosinophil accumulation in airway walls and mucosa.

CONCLUSION

These results indicate that selective sorting of miRNA including Th2 inhibitory miRNAs into AEVs and increase release to the airway after HDM exposure would be involved in the pathogenesis of allergic airway inflammation.

IL-17-producing ST2+ group 2 innate lymphoid cells play a pathogenic role in lung inflammation

BACKGROUND

IL-17 plays a pathogenic role in asthma. ST2^- inflammatory group 2 innate lymphoid cells (ILC2s) driven by IL-25 can produce IL-17, whereas ST2⁺ natural ILC2s produce little IL-17.

OBJECTIVE

We characterized ST2⁺IL-17⁺ ILC2s during lung inflammation and determined the pathogenesis and molecular regulation of ST2⁺IL-17⁺ ILC2s.

METHODS

Lung inflammation was induced by papain or IL-33. IL-17 production by lung ILC2s from wild-type, Rag1^-/-, Rorc^gfp/gfp, and aryl hydrocarbon receptor (Ahr)^-/- mice was examined by using flow cytometry. Bone marrow transfer experiments were performed to evaluate hematopoietic myeloid differentiation primary response gene-88 (MyD88) signaling in regulating IL-17 production by ILC2s. mRNA expression of IL-17 was analyzed in purified naive ILC2s treated with IL-33, leukotrienes, and inhibitors for nuclear factor of activated T cells, p38, c-Jun N-terminal kinase, or nuclear factor κ light-chain enhancer of activated B cells. The pathogenesis of IL-17⁺ ILC2s was determined by transferring wild-type or Il17^-/- ILC2s to Rag2^-/-Il2rg^-/- mice, which further induced lung inflammation. Finally, expression of 106 ILC2 signature genes was compared between ST2⁺IL-17⁺ ILC2s and ST2⁺IL-17^- ILC2s.

RESULTS

Papain or IL-33 treatment boosted IL-17 production from ST2⁺ ILC2s (referred to by us as ILC2₁₇s) but not ST2^- ILC2s. Ahr, but not retinoic acid receptor-related orphan receptor γt, facilitated the production of IL-17 by ILC2₁₇s. The hematopoietic compartment of MyD88 signaling is essential for ILC2₁₇ induction. IL-33 works in synergy with leukotrienes, which signal through nuclear factor of activated T-cell activation to promote IL-17 in ILC2₁₇s. Il17^-/- ILC2s were less pathogenic in lung inflammation. ILC2₁₇s concomitantly expressed IL-5 and IL-13 but expressed little GM-CSF.

CONCLUSION

During lung inflammation, IL-33 and leukotrienes synergistically induce ILC2₁₇s. ILC2₁₇s are a highly pathogenic and unexpected source for IL-17 in lung inflammation.

Role of Polyamines in Asthma Pathophysiology

Asthma is a complex disease of airways, where the interactions of immune and structural cells result in disease outcomes with airway remodeling and airway hyper-responsiveness. Polyamines, which are small-sized, natural super-cations, interact with negatively charged intracellular macromolecules, and altered levels of polyamines and their interactions have been associated with different pathological conditions including asthma. Elevated levels of polyamines have been reported in the circulation of asthmatic patients as well as in the lungs of a murine model of asthma. In various studies, polyamines were found to potentiate the pathogenic potential of inflammatory cells, such as mast cells and granulocytes (eosinophils and neutrophils), by either inducing the release of their pro-inflammatory mediators or prolonging their life span. Additionally, polyamines were crucial in the differentiation and alternative activation of macrophages, which play an important role in asthma pathology. Importantly, polyamines cause airway smooth muscle contraction and thus airway hyper-responsiveness, which is the key feature in asthma pathophysiology. High levels of polyamines in asthma and their active cellular and macromolecular interactions indicate the importance of the polyamine pathway in asthma pathogenesis; therefore, modulation of polyamine levels could be a suitable approach in acute and severe asthma management. This review summarizes the possible roles of polyamines in different pathophysiological features of asthma.

Ouabain attenuates ovalbumin-induced airway inflammation

PURPOSE

Ouabain, an Na⁺/K⁺-ATPase inhibitor hormone, presents immunomodulatory actions, including anti-inflammatory effect on acute inflammation models.

METHODS

In the present study, the effect of ouabain in a model of allergic airway inflammation induced by ovalbumin (OVA) was assessed.

RESULTS

Initially, it was observed that ouabain treatment inhibited cellular migration induced by OVA on bronchoalveolar lavage fluid (BALF), mostly granulocytes, without modulating macrophage migration. In addition, it was observed, by flow cytometry, that ouabain reduces CD3^high lymphocytes cells on BALF. Furthermore, treatment with ouabain decreased IL-4 and IL-13 levels on BALF. Ouabain also promoted pulmonary histological alterations, including decreased cell migration into peribronchiolar and perivascular areas, and reduced mucus production in bronchioles regions observed through hematoxylin-eosin (HE) and by periodic acid-Schiff stain, respectively. Allergic airway inflammation is characterized by high OVA-specific IgE serum titer. This parameter was also reduced by the treatment with ouabain.

CONCLUSIONS

Therefore, our data demonstrate that ouabain negatively modulates allergic airway inflammation induced by OVA.

MiR-146a overexpression effectively improves experimental allergic conjunctivitis through regulating CD4+CD25-T cells

OBJECTIVE

To study the mechanism of miR-146a in the regulation of allergic conjunctivitis (AC) through CD4⁺CD25^-T cells.

METHODS

BALB/c mice were sensitized with ragweed pollen (RW) and alum, and then challenged with RW. Eosinophil infiltration was determined using Giemsa assay. ELISA assay was performed to examine the level of antigen-specific IgE in the serum and cytokine levels in splenocytes. The expression of miR-146a was measured by qRT-PCR. Flow cytometric analysis was used to analyze the percentage of CD4⁺CD25^-T cells and Tregs.

RESULTS

In this study, we found that miR-146a overexpression could effectively improve the symptoms of AC in mouse models. Moreover, in vitro experiments, the proliferation of splenocytes was controlled and the expression of IL-5 and IL-13 was also decreased after transfected with miR-146a mimic. In addition, the inhibitory effect of Tregs on Tcons was affected by the change of miR-146a content in Tcons and had a positive correlation effect. When the content of miR-146a in Tregs changed, the inhibition was not affected. In addition, when inhibited miR-146a, NF-κB signaling pathway was activated, and the expression of IL-5 and IL-13 in Tcons increased. While after added Bay (NF-κB blocker), the NF-κB activity was decreased, and the expression of IL-5 and IL-13 in Tcons also reduced.

CONCLUSION

MiR-146a decreased in Tcons was contributed to the development of AC through regulating the inhibitory effect of Tregs on Tcons and NF-κB signaling pathway.

Prenatal environmental tobacco smoke exposure increases allergic asthma risk with methylation changes in mice

Allergic asthma remains an inadequately understood disease. In utero exposure to environmental tobacco smoke (ETS) has been identified as an environmental exposure that can increase an individual's asthma risk. To improve our understanding of asthma onset and development, we examined the effect of in utero ETS exposure on allergic disease susceptibility in an asthmatic phenotype using a house dust mite (HDM) allergen-induced murine model. Pregnant C57BL/6 mice were exposed to either filtered air or ETS during gestation, and their offspring were further exposed to HDM at 6-7 weeks old to induce allergic inflammation. Methylation in the promoter regions of allergic inflammation-related genes and genomic DNA was quantified. Exposure to HDM resulted in the onset of allergic lung inflammation, with an increased presence of inflammatory cells, Th2 cytokines (IL-4, IL-5, and IL-13), and airway remodeling. These asthmatic phenotypes were significantly enhanced when the mice had been exposed to in utero ETS. Furthermore, prenatal ETS exposure and subsequent HDM (ETS/HDM)-induced asthmatic phenotypes agree with methylation changes in the selected asthma-related genes, including IL-4, IL-5, IL-13, INF-γ, and FOXP3. Global DNA methylation was significantly lower in ETS/HDM-exposed mice than that of controls, which coincides with the results observed in lung, spleen, and blood DNAs. Prenatal ETS exposure resulted in a severe increase in allergic inflammatory responses after an HDM challenge, with corresponding methylation changes. Prenatal ETS exposure may influence developmental plasticity and result in altered epigenetic programming, leading to an increased susceptibility to asthma. Environ. Mol. Mutagen. 58:423-433, 2017. © 2017 Wiley Periodicals, Inc.

Cordycepin inhibits airway remodeling in a rat model of chronic asthma

The potential suppression role of cordycepin (Cor) on airway remodeling in a rat model of chronic asthma was investigated in this paper. We evaluated the anti-remodeling of Cor (50mg/kg) combined with or without budesonide (BUD) and investigated the possible underlying molecular mechanisms. We found that Cor attenuated immunoglobulin (Ig) E, alleviated the airway wall thickness, and decreased eosinophils and neutrophils in the bronchoalveolar lavage fluid (BALF). Notably, Cor reduced the up-regulation of IL-5, IL-13 and TNF-α in the BALF. Cor also regulated the increase of A_2AARmRNA and the decrease of TGF-β₁ expression. Furthermore, Cor markedly blocked p38MAPK signaling pathway activation in the OVA-driven asthmatic mice. The combination treatment of Cor and BUD showed profound efficacy in regulating the levels of inflammatory cells and the expression of IL-13, TGF-β₁ and A_2AARmRNA. Collectively, this study demonstrated that Cor combined with glucocorticoids treatment shows synergistically profound efficacy in inhibiting airway remodeling, and some benefits of Cor may result from the increased A_2AARmRNA expression, the reduced TGF-β₁ levels and the inhibition of Th2-cytokines through the suppression of the p38MAPK signaling pathways.

Macrophages redirect phagocytosis by non-professional phagocytes and influence inflammation

Professional phagocytes (such as macrophages) and non-professional phagocytes (such as epithelial cells) clear billions of apoptotic cells and particles on a daily basis. Although professional and non-professional macrophages reside in proximity in most tissues, whether they communicate with each other during cell clearance, and how this might affect inflammation, is not known. Here we show that macrophages, through the release of a soluble growth factor and microvesicles, alter the type of particles engulfed by non-professional phagocytes and influence their inflammatory response. During phagocytosis of apoptotic cells or in response to inflammation-associated cytokines, macrophages released insulin-like growth factor 1 (IGF-1). The binding of IGF-1 to its receptor on non-professional phagocytes redirected their phagocytosis, such that uptake of larger apoptotic cells was reduced whereas engulfment of microvesicles was increased. IGF-1 did not alter engulfment by macrophages. Macrophages also released microvesicles, whose uptake by epithelial cells was enhanced by IGF-1 and led to decreased inflammatory responses by epithelial cells. Consistent with these observations, deletion of IGF-1 receptor in airway epithelial cells led to exacerbated lung inflammation after allergen exposure. These genetic and functional studies reveal that IGF-1- and microvesicle-dependent communication between macrophages and epithelial cells can critically influence the magnitude of tissue inflammation in vivo.

Pharmacokinetics of tralokinumab in adolescents with asthma: implications for future dosing

AIMS

Tralokinumab, an investigational human immunoglobulin G4 monoclonal antibody, potently and specifically neutralizes interleukin-13, a central mediator of asthma. Tralokinumab has shown improvements in clinical endpoints in adults with uncontrolled asthma. The present study explored the pharmacokinetics (PK) and safety of a single tralokinumab dose, and utilized a population PK modelling and simulation approach to evaluate the optimal dosing strategy for adolescents.

METHODS

Adolescent subjects with asthma, using daily controller medication, received a single subcutaneous dose of tralokinumab 300 mg. Safety, immunogenicity and PK data were collected during a 57-day follow-up. A population PK model was developed using data from the present study and prior studies in adults. Simulations were performed to evaluate dose adjustment requirements for adolescents.

RESULTS

Twenty adolescents (12-17 years) were enrolled; all completed the study. No clinically relevant safety findings or antidrug antibodies were detected. PK parameters were similar to those observed in adults. PK modelling showed that body weight was a minor predictor of tralokinumab PK; after incorporating body weight into the PK model, a 15% (nonparametric 95% confidence interval 5%, 26%) lower clearance was found in adolescents compared with adults [173 (151, 209) vs. 204 (191, 229) ml day(-1)]. Simulations showed no therapeutically relevant differences in exposures between adolescent and adult populations, and similar PK profiles for weight-based (4 mg kg(-1)) and fixed (300 mg) fortnightly subcutaneous doses of tralokinumab.

CONCLUSION

Single-dose administration of tralokinumab 300 mg in adolescents was well tolerated, with a PK profile similar to that in adults. Exposure predictions suggest that dose adjustment is not required for adolescents.

Differential activation of airway eosinophils induces IL-13-mediated allergic Th2 pulmonary responses in mice

BACKGROUND

Eosinophils are hallmark cells of allergic Th2 respiratory inflammation. However, the relative importance of eosinophil activation and the induction of effector functions such as the expression of IL-13 to allergic Th2 pulmonary disease remain to be defined.

METHODS

Wild-type or cytokine-deficient (IL-13(-/-) or IL-4(-/-) ) eosinophils treated with cytokines (GM-CSF, IL-4, IL-33) were adoptively transferred into eosinophil-deficient recipient mice subjected to allergen provocation using established models of respiratory inflammation. Allergen-induced pulmonary changes were assessed.

RESULTS

In contrast to the transfer of untreated blood eosinophils to the lungs of recipient eosinophil deficient mice, which induced no immune/inflammatory changes either in the lung or in the lung draining lymph nodes (LDLN), pretreatment of blood eosinophils with GM-CSF prior to transfer elicited trafficking of these eosinophils to LDLN. In turn, these LDLN eosinophils elicited the accumulation of dendritic cells and CD4(+) T cells to these same LDLNs without inducing pulmonary inflammation. However, exposure of eosinophils to GM-CSF, IL-4, and IL-33 prior to transfer induced not only immune events in the LDLN, but also allergen-mediated increases in airway Th2 cytokine/chemokine levels, the subsequent accumulation of CD4(+) T cells as well as alternatively activated (M2) macrophages, and the induction of pulmonary histopathologies. Significantly, this allergic respiratory inflammation was dependent on eosinophil-derived IL-13, whereas IL-4 expression by eosinophils had no significant role.

CONCLUSION

The data demonstrate the differential activation of eosinophils as a function of cytokine exposure and suggest that eosinophil-specific IL-13 expression by activated cells is a necessary component of the subsequent allergic Th2 pulmonary pathologies.

Insights into cytokine-receptor interactions from cytokine engineering

Cytokines exert a vast array of immunoregulatory actions critical to human biology and disease. However, the desired immunotherapeutic effects of native cytokines are often mitigated by toxicity or lack of efficacy, either of which results from cytokine receptor pleiotropy and/or undesired activation of off-target cells. As our understanding of the structural principles of cytokine-receptor interactions has advanced, mechanism-based manipulation of cytokine signaling through protein engineering has become an increasingly feasible and powerful approach. Modified cytokines, both agonists and antagonists, have been engineered with narrowed target cell specificities, and they have also yielded important mechanistic insights into cytokine biology and signaling. Here we review the theory and practice of cytokine engineering and rationalize the mechanisms of several engineered cytokines in the context of structure. We discuss specific examples of how structure-based cytokine engineering has opened new opportunities for cytokines as drugs, with a focus on the immunotherapeutic cytokines interferon, interleukin-2, and interleukin-4.

Beyond TGFβ--novel ways to target airway and parenchymal fibrosis

Within the lungs, fibrosis can affect both the parenchyma and the airways. Fibrosis is a hallmark pathological change in the parenchyma in patients with idiopathic pulmonary fibrosis (IPF), whilst in asthma or chronic obstructive pulmonary disease (COPD) fibrosis is a component of the remodelling of the airways. In the past decade, significant advances have been made in understanding the disease behaviour and pathogenesis of parenchymal and airway fibrosis and as a result a variety of novel therapeutic targets for slowing or preventing progression of these fibrotic changes have been identified. This review highlights a number of these targets and discusses the potential for treating parenchymal or airway fibrosis through these mediators/pathways in the future.

A novel method for pulmonary research: assessment of bioenergetic function at the air-liquid interface

Air–liquid interface cell culture is an organotypic model for study of differentiated functional airway epithelium in vitro. Dysregulation of cellular energy metabolism and mitochondrial function have been suggested to contribute to airway diseases. However, there is currently no established method to determine oxygen consumption and glycolysis in airway epithelium in air–liquid interface. In order to study metabolism in differentiated airway epithelial cells, we engineered an insert for the Seahorse XF24 Analyzer that enabled the measure of respiration by oxygen consumption rate (OCR) and glycolysis by extracellular acidification rate (ECAR). Oxidative metabolism and glycolysis in airway epithelial cells cultured on the inserts were successfully measured. The inserts did not affect the measures of OCR or ECAR. Cells under media with apical and basolateral feeding had less oxidative metabolism as compared to cells on the inserts at air-interface with basolateral feeding. The design of inserts that can be used in the measure of bioenergetics in small numbers of cells in an organotypic state may be useful for evaluation of new drugs and metabolic mechanisms that underlie airway diseases.

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Endothelial cells generate hydrogen peroxide through several enzymatic systems and the mitochondrial electron transport chain

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Redox-sensitive thiols within specific families of proteins such as kinases are key targets for hydrogen peroxide in endothelial cells

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Hydrogen peroxide regulates fundamental processes in endothelial cells including cell growth, proliferation, angiogenesis and vascular tone

Salmeterol attenuates chemotactic responses in rhinovirus-induced exacerbation of allergic airways disease by modulating protein phosphatase 2A

BACKGROUND

β-Agonists are used for relief and control of asthma symptoms by reversing bronchoconstriction. They might also have anti-inflammatory properties, but the underpinning mechanisms remain poorly understood. Recently, a direct interaction between formoterol and protein phosphatase 2A (PP2A) has been described in vitro.

OBJECTIVE

We sought to elucidate the molecular mechanisms by which β-agonists exert anti-inflammatory effects in allergen-driven and rhinovirus 1B-exacerbated allergic airways disease (AAD).

METHODS

Mice were sensitized and then challenged with house dust mite to induce AAD while receiving treatment with salmeterol, formoterol, or salbutamol. Mice were also infected with rhinovirus 1B to exacerbate lung inflammation and therapeutically administered salmeterol, dexamethasone, or the PP2A-activating drug (S)-2-amino-4-(4-[heptyloxy]phenyl)-2-methylbutan-1-ol (AAL[S]).

RESULTS

Systemic or intranasal administration of salmeterol protected against the development of allergen- and rhinovirus-induced airway hyperreactivity and decreased eosinophil recruitment to the lungs as effectively as dexamethasone. Formoterol and salbutamol also showed anti-inflammatory properties. Salmeterol, but not dexamethasone, increased PP2A activity, which reduced CCL11, CCL20, and CXCL2 expression and reduced levels of phosphorylated extracellular signal-regulated kinase 1 and active nuclear factor κB subunits in the lungs. The anti-inflammatory effect of salmeterol was blocked by targeting the catalytic subunit of PP2A with small RNA interference. Conversely, increasing PP2A activity with AAL(S) abolished rhinovirus-induced airway hyperreactivity, eosinophil influx, and CCL11, CCL20, and CXCL2 expression. Salmeterol also directly activated immunoprecipitated PP2A in vitro isolated from human airway epithelial cells.

CONCLUSIONS

Salmeterol exerts anti-inflammatory effects by increasing PP2A activity in AAD and rhinovirus-induced lung inflammation, which might potentially account for some of its clinical benefits.

Role of periostin, FENO, IL-13, lebrikzumab, other IL-13 antagonist and dual IL-4/IL-13 antagonist in asthma

INTRODUCTION

Asthma markedly diminishes quality of life due to limited activity, absences from work or school and hospitalizations. Patients with severe asthma which are not controlled despite taking effective therapy are most in need of new treatment approaches. IL-13 was demonstrated as 'central mediator of allergic asthma'.

AREAS COVERED

IL-13 has been implicated in the pathogenesis of asthma, idiopathic pulmonary fibrosis and COPD. IL-13 levels in the sputum and bronchial biopsy samples remain elevated in severe asthma despite the use of inhaled and systemic corticosteroids. Thus, IL-13 is a mediator involved in corticosteroid resistance. Periostin enhances profibrotic TGF-β signaling in subepithelial fibrosis associated with asthma. IL-13 induces bronchial epithelial cells to secrete periostin. Periostin may be a biomarker for Th2 induced airway inflammation. Lebrikizumab is a monoclonal antibody against IL-13. Lebrikizumab improved lung function in asthmatics who were symptomatic despite treatment with long acting beta agonist and inhaled corticosteroids and provided benefit in the treatment of severe uncontrolled asthma.

EXPERT OPINION

Lebrikizumab block IL-13 signaling through the IL-13Rα1/IL-4Rα receptor. There was a larger reduction in FENO in the high periostin subgroup than in the low periostin subgroup (34.4 vs 4.3%). Serum CCL17, CCL13 and total IgE levels decreased in the lebrikizumab group.

Tralokinumab for uncontrolled asthma

INTRODUCTION

Asthma is a chronic inflammatory disease of the airways mainly related to allergen exposure, in which various cytokine-specific pathways interact among themselves to promote IgE hyperproduction, bronchial hyperresponsiveness, eosinophil local recruitment and airways remodeling. IL-13 is known for its prominent pathogenic role in this disease and therapeutic blocking approaches are underway.

AREAS COVERED

Anti-IL-13 antibodies are currently investigated in clinical studies in uncontrolled asthma. Tralokinumab is a human IgG4 anti IL-13 antibody which was recently evaluated in a Phase II study demonstrating the maximal efficacy in a subset of asthma patients characterized by the highest sputum IL-13 levels. The results of this study are discussed in this paper.

EXPERT OPINION

The IL-13 blockade with various therapeutic approaches such as tralokinumab has the potential to improve the asthma control in patients subsets in whom the blocked cytokine is demonstrated to be overexpressed.

Vitamin D, invariant natural killer T-cells and experimental autoimmune disease

Vitamin D is an important regulator of the immune system in general and multiple sclerosis in particular. Experimentally (i), invariant natural killer T (iNKT) cells have been shown to be important suppressors of autoimmune diseases such as experimental autoimmune encephalomyelitis (EAE; an animal model of multiple sclerosis). Conversely, in experimental allergic asthma iNKT cells are required for disease induction and are therefore pathogenic. The active form of vitamin D (calcitriol) suppresses EAE. The development of EAE symptoms is accelerated in vitamin D deficiency. Interestingly experimental asthma is less severe in vitamin D deficiency although there is no effect of calcitriol on disease severity. The data suggest that an important target of vitamin D in EAE and asthma are the iNKT cells. Vitamin D and/or vitamin D receptor deficiency results in the impaired development of iNKT cells. Vitamin D is critical very early during development of the immune system. Low levels of vitamin D in utero resulted in significantly reduced numbers of iNKT cells that failed to recover when calcitriol was used to supplement neonatal or adult mice. The data suggest that one of the consequences of early vitamin D deficiency is a reduction in the numbers of iNKT cells that develop. The iNKT cells are required for the beneficial effects of calcitriol in EAE. The important role of vitamin D on iNKT cells could impact the development of human immune-mediated diseases including multiple sclerosis and asthma.

Vitamin D, invariant natural killer T-cells and experimental autoimmune disease

Vitamin D is an important regulator of the immune system in general and multiple sclerosis in particular. Experimentally (i), invariant natural killer T (iNKT) cells have been shown to be important suppressors of autoimmune diseases such as experimental autoimmune encephalomyelitis (EAE; an animal model of multiple sclerosis). Conversely, in experimental allergic asthma iNKT cells are required for disease induction and are therefore pathogenic. The active form of vitamin D (calcitriol) suppresses EAE. The development of EAE symptoms is accelerated in vitamin D deficiency. Interestingly experimental asthma is less severe in vitamin D deficiency although there is no effect of calcitriol on disease severity. The data suggest that an important target of vitamin D in EAE and asthma are the iNKT cells. Vitamin D and/or vitamin D receptor deficiency results in the impaired development of iNKT cells. Vitamin D is critical very early during development of the immune system. Low levels of vitamin D in utero resulted in significantly reduced numbers of iNKT cells that failed to recover when calcitriol was used to supplement neonatal or adult mice. The data suggest that one of the consequences of early vitamin D deficiency is a reduction in the numbers of iNKT cells that develop. The iNKT cells are required for the beneficial effects of calcitriol in EAE. The important role of vitamin D on iNKT cells could impact the development of human immune-mediated diseases including multiple sclerosis and asthma.

A mechanistic role for type III IFN-λ1 in asthma exacerbations mediated by human rhinoviruses

RATIONALE

Human rhinoviruses (HRV) are the leading cause of upper respiratory infections and have been postulated to trigger asthma exacerbations. However, whether HRV are detected during crises because upper respiratory infections often accompany asthma attacks, or because they specifically elicit exacerbations, is unclear. Moreover, although several hypotheses have been advanced to explain virus-induced exacerbations, their mechanism remains unclear.

OBJECTIVES

To determine the role of HRV in pediatric asthma exacerbations and the mechanisms mediating wheezing.

METHODS

We prospectively studied 409 children with asthma presenting with upper respiratory infection in the presence or absence of wheezing. Candidate viral and immune mediators of illness were compared among children with asthma with different degrees of severity of acute asthma.

MEASUREMENTS AND MAIN RESULTS

HRV infections specifically associated with asthma exacerbations, even after adjusting for relevant demographic and clinical variables defined a priori (odds ratio, 1.90; 95% confidence interval, 1.21-2.99; P = 0.005). No difference in virus titers, HRV species, and inflammatory or allergic molecules was observed between wheezing and nonwheezing children infected with HRV. Type III IFN-λ(1) levels were higher in wheezing children infected with HRV compared with nonwheezing (P < 0.001) and increased with worsening symptoms (P < 0.001). Moreover, after adjusting for IFN-λ(1), children with asthma infected with HRV were no longer more likely to wheeze than those who were HRV-negative (odds ratio, 1.18; 95% confidence interval, 0.57-2.46; P = 0.66).

CONCLUSIONS

Our findings suggest that HRV infections in children with asthma are specifically associated with acute wheezing, and that type III IFN-λ(1) responses mediate exacerbations caused by HRV. Modulation of IFN- λ(1) should be studied as a therapeutic target for exacerbations caused by HRV.

Potential role of antioxidant food supplements, preservatives and colorants in the pathogenesis of allergy and asthma

A significant increase in the incidence of allergy and asthma has been observed during the past decades. The background of this phenomenon has not been well explained, but changes in lifestyle and habits are heavily discussed as contributing factors. Among these is a too clean environment, which may predispose individuals to increased sensitivity to allergic responses. Also the increase in dietary supplements including preservatives and colorants may contribute to this. In vitro, we and others have shown in freshly isolated human peripheral blood mononuclear cells that antioxidant compounds like vitamins C and E as well as food preservatives and colorants exert significant suppressive effects on the Th1 immune activation cascade. The effects observed may be based on the interaction of antioxidant compounds with proinflammatory cascades involving important signal transduction elements such as nuclear factor-κB. Although only obtained in vitro, these results show an anti-inflammatory property of compounds which could shift the Th1-Th2-type immune balance towards Th2-type immunity. This review article discusses the potential role of increased use of antioxidant food supplements as well as preservatives and colorants in the increase in allergy and asthma in the Western world.

Contribution of IL-13 to early exocrinopathy in Id3-/- mice

Id3-/- mice represent a model for T cell mediated primary Sjogren's syndrome (PSS). An intriguing feature of this disease model is the early appearance of impaired salivary function or exocrinopathy prior to lymphocytic infiltration of the salivary glands. This phenomenon prompted us to examine the role of cytokines produced by T cells in the systemic regulation of gland function. A comprehensive examination of serum cytokine profiles revealed elevated levels of IL-13 in Id3-/- mice. We found that the increase in serum IL-13 levels in Id3-/- mice was largely dependent on αβ T cells. Removal of αβ T cells in Id3-/- mice also eliminates disease symptoms, including lymphocytic infiltration in the gland tissues, and impaired saliva production. We further show that the number of mast cells in the salivary glands of Id3-/- mice is significantly increased, in a trend inversely related to the saliva production. This increase in the number of mast cells is also dependent on the presence of αβ T cells. Treatment of young Id3-/- mice with anti-IL-13 antibodies over a two-month period resulted in a reduction of both serum IL-13 levels and the number of mast cells in the salivary gland tissues, as well as correspondingly improved saliva production. These findings indicate a potentially important role for IL-13 in gland regulation and disease pathology.

Modern concepts on the role of inflammation in pulmonary fibrosis

CONTEXT

Idiopathic pulmonary fibrosis is a uniformly lethal disease with limited biomarkers and no proven therapeutic intervention short of lung transplantation. Pulmonary fibrosis at one time was thought to be a result of inflammation in the lung. Although some forms of pulmonary fibrosis may result from inflammation, idiopathic pulmonary fibrosis is currently thought to result from cell death primarily and inflammation secondarily.

OBJECTIVE

To determine the role of inflammation in pulmonary fibrosis in light of our laboratory's published and unpublished research and published literature.

DATA SOURCES

Review based on our laboratory's published and unpublished experimental data with relevant background and clinical context provided.

CONCLUSIONS

Although cell death is central to pulmonary fibrosis, the proper cytokine environment leading to macrophage polarization is also critical. Evaluation of this environment is promising both for the development of disease biomarkers and for targets for therapeutic intervention.

Pathways activated during human asthma exacerbation as revealed by gene expression patterns in blood

BACKGROUND

Asthma exacerbations remain a major unmet clinical need. The difficulty in obtaining airway tissue and bronchoalveolar lavage samples during exacerbations has greatly hampered study of naturally occurring exacerbations. This study was conducted to determine if mRNA profiling of peripheral blood mononuclear cells (PBMCs) could provide information on the systemic molecular pathways involved during asthma exacerbations.

METHODOLOGY/PRINCIPAL FINDINGS

Over the course of one year, gene expression levels during stable asthma, exacerbation, and two weeks after an exacerbation were compared using oligonucleotide arrays. For each of 118 subjects who experienced at least one asthma exacerbation, the gene expression patterns in a sample of peripheral blood mononuclear cells collected during an exacerbation episode were compared to patterns observed in multiple samples from the same subject collected during quiescent asthma. Analysis of covariance identified genes whose levels of expression changed during exacerbations and returned to quiescent levels by two weeks. Heterogeneity among visits in expression profiles was examined using K-means clustering. Three distinct exacerbation-associated gene expression signatures were identified. One signature indicated that, even among patients without symptoms of respiratory infection, genes of innate immunity were activated. Antigen-independent T cell activation mediated by IL15 was also indicated by this signature. A second signature revealed strong evidence of lymphocyte activation through antigen receptors and subsequent downstream events of adaptive immunity. The number of genes identified in the third signature was too few to draw conclusions on the mechanisms driving those exacerbations.

CONCLUSIONS/SIGNIFICANCE

This study has shown that analysis of PBMCs reveals systemic changes accompanying asthma exacerbation and has laid the foundation for future comparative studies using PBMCs.

Role of chitin and chitinase/chitinase-like proteins in inflammation, tissue remodeling, and injury

The 18 glycosyl hydrolase family of chitinases is an ancient gene family that is widely expressed from prokaryotes to eukaryotes. In mammals, despite the absence of endogenous chitin, a number of chitinases and chitinase-like proteins (C/CLPs) have been identified. However, their roles have only recently begun to be elucidated. Acidic mammalian chitinase (AMCase) inhibits chitin-induced innate inflammation; augments chitin-free, allergen-induced Th2 inflammation; and mediates effector functions of IL-13. The CLPs BRP-39/YKL-40 (also termed chitinase 3-like 1) inhibit oxidant-induced lung injury, augments adaptive Th2 immunity, regulates apoptosis, stimulates alternative macrophage activation, and contributes to fibrosis and wound healing. In accord with these findings, levels of YKL-40 in the lung and serum are increased in asthma and other inflammatory and remodeling disorders and often correlate with disease severity. Our understanding of the roles of C/CLPs in inflammation, tissue remodeling, and tissue injury in health and disease is reviewed below.

Boosting airway T-regulatory cells by gastrointestinal stimulation as a strategy for asthma control

The hallmark of atopic asthma is transient airways hyperresponsiveness (AHR) preceded by aeroallergen-induced Th-cell activation. This is preceded by upregulation of CD86 on resident airway dendritic cells (DCs) that normally lack competence in T-cell triggering. Moreover, AHR duration is controlled via T-regulatory (Treg) cells, which can attenuate CD86 upregulation on DC. We show that airway mucosal Treg/DC interaction represents an accessible therapeutic target for asthma control. Notably, baseline airway Treg activity in sensitized rats can be boosted by microbe-derived stimulation of the gut, resulting in enhanced capacity to control CD86 expression on airway DC triggered by aeroallergen and accelerated resolution of AHR.

Pitrakinra for asthma

IMPORTANCE OF THE FIELD

In asthma IL-4 and IL-13 have been demonstrated to play major pathogenic roles and therefore their blockade would potentially represent a plausible therapeutic approach.

AREAS COVERED IN THIS REVIEW

Pitrakinra is a dual IL-4/IL-13 inhibitor currently under development for asthma and the existing preclinical and clinical data are discussed.

WHAT THE READER WILL GAIN

Inhaled pitrakinra demonstrated a good anti-inflammatory potential and a good safety profile on a short-term basis but its place in asthma therapy is still to be found.

TAKE HOME MESSAGE

Specific anticytokine therapies might in the near future reshape asthma therapy.

The proximal STAT6 and NF-kappaB sites are responsible for IL-13- and TNF-alpha-induced RhoA transcriptions in human bronchial smooth muscle cells

RhoA protein is involved in the Ca(2+) sensitization of bronchial smooth muscle (BSM) contraction, and an upregulation of RhoA in BSMs has been suggested in allergic bronchial asthma. However, the mechanism of upregulation of RhoA remains poorly understood. In the present study, the transcriptional regulation of human RhoA gene was investigated in cultured human BSM cells stimulated with IL-13 and TNF-alpha, both of which have an ability to upregulate RhoA protein. Luciferase-based assay showed that the RhoA promoter activity was augmented by both IL-13 and TNF-alpha. The deletion studies revealed a significant level of promoter activity between the 112 bp upstream and the transcription start site, which contains the STAT6 (78-70 bp upstream) and NF-kappaB (84-74 bp upstream) binding regions. The promoter activity was also decreased significantly by the mutations of these regions. Thus, the current study for the first time characterized the transcriptional regulation of the human RhoA gene. The findings also suggest that STAT6 and NF-kappaB are important for the upregulation of RhoA in human BSM induced by IL-13 and TNF-alpha, both of which are major cytokines in the pathogenesis of allergic bronchial asthma.

Cytokine antagonists for the treatment of asthma: progress to date

Asthma is a disease of the airways in which several cytokines such as interleukin (IL)-4, IL-5, IL-13 and tumor necrosis factor-alpha (TNFalpha) play a major role in the development and progression of inflammation, airway hyperresponsiveness, mucus production, and airway remodeling. The conventional anti-inflammatory therapies, represented by inhaled corticosteroids and antileukotrienes, are not always able to provide optimal disease control and it is therefore hoped that cytokine antagonists could achieve this goal in such situations. Anticytokine therapies have been tested in preclinical studies and some have entered clinical trials. Anti-IL-4 therapies have been tested in animal models of allergy-related asthma, but because of unclear efficacy their development was discontinued. However, IL-4/IL-13 dual antagonists and IL-13-specific blocking agents are more promising, as they exhibit more sustained anti-inflammatory effects. IL-5 antagonists have been found to be of limited efficacy in clinical studies but might be useful in conditions characterized by severe hypereosinophilia, and in which asthma is one of the disease manifestations. Unlike other chronic inflammatory conditions, such as rheumatoid arthritis, the use of anti-TNFalpha therapies in asthma might be limited by the unfavorable risk/benefit ratio associated with long-term use. The identification of so-called asthma TNFalpha phenotypes and perhaps the use of a less aggressive treatment regimen might address this important aspect. Other cytokine antagonists (for example for IL-9 or IL-25) are currently being evaluated in the asthma setting, and could open new therapeutic perspectives based on their efficacy and safety.

Overexpression of Smad2 drives house dust mite-mediated airway remodeling and airway hyperresponsiveness via activin and IL-25

RATIONALE

Airway hyperreactivity and remodeling are characteristic features of asthma. Interactions between the airway epithelium and environmental allergens are believed to be important in driving development of pathology, particularly because altered epithelial gene expression is common in individuals with asthma.

OBJECTIVES

To investigate the interactions between a modified airway epithelium and a common aeroallergen in vivo.

METHODS

We used an adenoviral vector to generate mice overexpressing the transforming growth factor-beta signaling molecule, Smad2, in the airway epithelium and exposed them to house dust mite (HDM) extract intranasally.

MEASUREMENTS AND MAIN RESULTS

Smad2 overexpression resulted in enhanced airway hyperreactivity after allergen challenge concomitant with changes in airway remodeling. Subepithelial collagen deposition was increased and smooth muscle hyperplasia was evident resulting in thickening of the airway smooth muscle layer. However, there was no increase in airway inflammation in mice given the Smad2 vector compared with the control vector. Enhanced airway hyperreactivity and remodeling did not correlate with elevated levels of Th2 cytokines, such as IL-13 or IL-4. However, mice overexpressing Smad2 in the airway epithelium showed significantly enhanced levels of IL-25 and activin A after HDM exposure. Blocking activin A with a neutralizing antibody prevented the increase in lung IL-25 and inhibited subsequent collagen deposition and also the enhanced airway hyperreactivity observed in the Smad2 overexpressing HDM-exposed mice.

CONCLUSIONS

Epithelial overexpression of Smad2 can specifically alter airway hyperreactivity and remodeling in response to an aeroallergen. Moreover, we have identified novel roles for IL-25 and activin A in driving airway hyperreactivity and remodeling.

Role of IL-13 in a model of Strongyloides venezuelensis infection in rats

IL-13 is a cytokine known to play a role in several pulmonary diseases, including asthma and fibrosis. The role of IL-13 in the context of pulmonary changes induced by helminth infection is unclear. Rats experimentally infected with Strongyloides venezuelensis and treated with anti-IL-13 neutralizing antibody were used to evaluate the role of IL-13 on functional and inflammatory changes of host lungs, and on parasite control. S. venezuelensis-induced airway hyperreactivity was IL-13-independent, but IL-13 played an essential role in driving airway mucus production and eosinophil infiltration. IL-13 was important for the control of egg production but not establishment in the intestine.

Novel biomarkers in asthma: chemokines and chitinase-like proteins

PURPOSE OF REVIEW

Allergic asthma is a frequent lung disease in Western civilizations and is characterized by airway inflammation and tissue remodeling. Without early diagnosis and specific treatment, asthma results in a loss of lung function, impaired quality of life and the risk to die from uncontrolled asthma attacks. Thus, there is a need for specific biomarkers to detect asthma as soon as possible and to initiate the correct clinical treatment.

RECENT FINDINGS

Recent studies have highlighted the potential role of the chemokine (C-C motif) ligand 17 and the chitinase-like protein YKL-40 as novel biomarkers in asthma. Patient studies suggest that these proteins could be useful to identify asthmatics, to characterize disease severity or both in patients with asthma. Functional studies indicate that these molecules are more than correlated epiphenomena and instead contribute in significant ways to asthma pathogenesis.

SUMMARY

Assessments of chemokine (C-C motif) ligand 17 and YKL-40 may allow physicians to more accurately diagnose and predict the course of asthma and thereby allow therapy to be appropriately tailored for a given patient.

Dominant, non-MHC genetic control of food allergy in an adjuvant-free mouse model

Food allergy is a potentially fatal immune-mediated disorder with incompletely understood mechanisms. We studied the genetic control of food allergy using major histocompatibility complex-identical mice (H2(s)) and an adjuvant-free method of sensitization. Whereas, transdermal exposure to hazelnut - a model allergenic food, elicited robust IgG1 response in both strains, an IgE response was evident only in A.SW mice. Following oral challenge, only A.SW but not SJL mice exhibited signs of systemic anaphylaxis and hypothermia. In addition, (A.SW x SJL) F1 hybrids exhibited IgE responsiveness, systemic anaphylaxis and hypothermia similar to A.SW, indicating dominant inheritance of these traits. Furthermore, whereas A.SW and F1 mice but not SJL elicited robust interleukin (IL)-4 response, all three strains elicited IL-5 and IL-13 responses by spleen cells. These data demonstrate for the first time, dominant non-MHC genetic control of food allergy and a critical role of IL-4 but not IL-5 or IL-13 in this model.

Acidic mammalian chitinase regulates epithelial cell apoptosis via a chitinolytic-independent mechanism

Acidic mammalian chitinase (AMCase) is produced during and plays an important role in the pathogenesis of Th2-mediated diseases and antiparasite responses. However, the effector responses of AMCase in these settings have not been adequately defined and the relationship(s) between its chitinolytic and other biologic properties have not been investigated. In these studies, we demonstrate that AMCase protects airway epithelial cells from Fas ligand- and growth factor withdrawal-induced apoptosis. This cytoprotection was associated with Akt phosphorylation and abrogated when the PI3K/Akt pathway was inhibited. Comparable cytoprotection was also seen in experiments comparing wild-type AMCase and mutant AMCase that lacked chitinolytic activity. Importantly, the apoptosis-inhibiting effect of enzymatically active and inactive AMCase was abrogated by treatment with allosamidin. These studies demonstrate that secreted AMCase feeds back in an autocrine and/or paracrine manner to protect pulmonary epithelial cells from growth factor withdrawal- and Fas ligand-induced apoptosis. They also demonstrate that the cytoprotection is mediated via a PI3K/Akt-dependent and allosamidin-sensitive pathway that is independent of the chitinolytic activity of this chitinase.

The development of airway hyperreactivity in T-bet-deficient mice requires CD1d-restricted NKT cells

T-bet(-/-) mice have been shown to have a profound deficiency in the ability to generate invariant NKT (iNKT) cells in the periphery due to a halt in terminal maturation, but despite this deficiency, T-bet(-/-) mice develop spontaneous airway hyperreactivity (AHR) and airway inflammation. Because in some situations the development of AHR requires the presence of iNKT cells, we sought to more clearly understand how AHR develops in T-bet(-/-) mice by examining T-bet(-/-) mice in several distinct mouse models of asthma, including spontaneous, OVA-induced and alpha-galactosylceramide (alpha-GalCer)-induced AHR. Surprisingly, we found that administration of alpha-GalCer, which very specifically activates iNKT cells, greatly increased the AHR response in the T-bet(-/-) mice. Moreover, in T-bet(-/-) mice, spontaneous AHR as well as AHR induced with OVA or alpha-GalCer were all eliminated by blocking CD1d, the restricting element of iNKT cells, using an anti-CD1d-blocking mAb. Although the number of the iNKT cells in T-bet(-/-) mice was reduced compared with that in wild-type mice, the remaining iNKT cells produced primarily IL-4 and IL-13, and only minimal amounts of IFN-gamma. We conclude therefore that the AHR that develops in T-bet(-/-) mice is dependent on the presence of iNKT cells, and that whereas T-bet(-/-) have reduced numbers of iNKT cells, these are sufficient for the development of AHR.