Although it is currently recognized that bronchial asthma is not a single disease but a syndrome, we have not yet made use of our new understanding of this heterogeneity as we treat asthma patients. To increase the efﬁcacy of anti-asthma drugs and to decrease costs, it is important to stratify asthma patients into subgroups and to develop therapeutic strategies for each subgroup. Periostin has recently emerged as a biomarker for bronchial asthma, unique in that it is useful not in diagnosis but in categorizing asthma patients. We ﬁrst found that periostin is a novel component of subepithelial ﬁbrosis in bronchial asthma downstream of IL-13 signals. Thereafter, it was shown that periostin can be a surrogate biomarker of type 2 immune responses, the basis of the notion that a detection system of serum periostin is potentially a companion diagnostic for type 2 antagonists. Furthermore, we have recently shown that serum periostin can predict resistance or hyporesponsiveness to inhaled corticosteroids, based on its contribution to tissue remodeling or ﬁbrosis in bronchial asthma. Thus, serum periostin has two characteristics as a biomarker for bronchial asthma: it is both a surrogate biomarker of type 2 immune responses and a biomarker reﬂecting tissue remodeling or ﬁbrosis. We can take advantage of these characteristics to develop stratiﬁed medicine in bronchial asthma.
Background: The activation of liver X receptor (LXR) α or LXRβ negatively regulates the expression of pro- inﬂammatory genes in mammalian cells. We recently reported that 25-hydroxycholesterol, a represen- tative LXR-activating oxysterol, suppresses IL-6 production in mouse mast cells (MCs) following its engagement of the high-afﬁnity IgE receptor (FcεRI). This ﬁnding suggests that murine MCs express functional LXRs; however, the mechanisms underlying the LXR-dependent repression of the MC- mediated production of pro-inﬂammatory cytokines, including IL-6, are poorly understood. Therefore, we employed the synthetic LXR ligand GW3965 to examine the functions of LXRα and LXRβ in the production of pro-inﬂammatory cytokines by murine bone marrow-derived MCs (BMMCs).
Methods: We prepared BMMCs from wild-type (WT), LXRα−⁄−, and LXRα/β−⁄− mice. Each group of BMMCs was pretreated with GW3965 and then stimulated with IgEþantigen (Ag) or lipopolysaccharide (LPS). Cytokine production was then analyzed using speciﬁc ELISA kits.
Results: The activation of LXRs by GW3965 signiﬁcantly attenuated the production of IL-1a and IL-1b, but not of IL-6, in the WT and LXRα−⁄− BMMCs stimulated with IgE+Ag. However, GW3965 treatment decreased the production of IL-1α, IL-1β, and IL-6 in WT and LXRα−⁄− BMMCs upon stimulation with LPS, while the GW3965-mediated suppression of cytokine production was nearly absent from the LXRα/β−⁄−BMMCs.
Conclusions: These ﬁndings demonstrate, for the ﬁrst time, that the activation of LXRs by GW3965 at- tenuates the antigen- or LPS-induced production of pro-inﬂammatory cytokines, such as IL-1α and IL-1β, in murine MCs and that LXRβ plays an important role in the LXR-mediated repression of cytokine production.
Background: Eosinophilic otitis media (EOM) is an intractable disease characterized by a remarkably viscous effusion and accumulation of numerous eosinophils in both the middle ear effusion and the mucosa. The key factors in EOM pathogenesis remain unclear. The purpose of this study is to identify the important factors involved in EOM pathogenesis.
Methods: Middle ear effusion samples were collected from 12 patients with EOM and 9 patients with secretory otitis media (SOM), as controls. Multiple cytokines in the effusion were measured using a Bio- Plex™ Human Cytokine 27-Plex panel. Eosinophil-derived neurotoxin (EDN) and elastase were measured by ELISA. The concentrations of EDN, elastase, and each cytokine were compared between the EOM and SOM groups. Furthermore, in the EOM group, each cytokine was examined for correlation with EDN and elastase.
Results: EDN and elastase concentrations were signiﬁcantly higher in the EOM group than in the SOM group (p < 0.05). IL-5, IL-1β, MIP-1α, G-CSF, IL-1ra, IL-4, IFN-γ, MIP-1β, IL-10, TNF-α, VEGF, and IL-2
concentration was signiﬁcantly higher in the EOM group than in the SOM group (p < 0.05). Signiﬁcant positive correlations were found between EDN and IL-1ra, IL-2, IL-5, IL-9, IL-13, eotaxin, MIP-1α, PDGF- BB, and RANTES in the EOM group (p < 0.05).
Conclusions: Our study showed that IL-5, IL-2, MIP-1α, and IL-1ra are the important factors involved in EOM pathogenesis. Furthermore, not only eosinophil, but also neutrophil are involved in middle ear inﬂammation of EOM.
Background: The role of interleukin (IL)-23 in asthma pathophysiology is still controversial. We exam- ined its role in allergic airway inﬂammation in response to two distinct antigens using IL-23-deﬁcient mice.
Methods: Allergic airway inﬂammation was evaluated in wild-type and IL-23p19 −⁄−mice. Mice were
sensitized to ovalbumin (OVA) or house dust mite (HDM) by intraperitoneal injection of antigen and their airways were then exposed to the same antigen. Levels of antigen-speciﬁc immunoglobulins in serum as well as cytokines in bronchoalveolar or peritoneal lavage ﬂuid and lung tissue were determined by enzyme-linked immunosorbent assay and/or quantitative polymerase chain reaction.
Results: Deﬁciency of IL-23p19 decreased eosinophils and Th2 cytokines in bronchoalveolar lavage ﬂuid (BALF) of OVA-treated mice, while it increased BALF eosinophils of HDM-treated mice. Peritoneal in- jection of OVA with alum, but not of HDM, induced local synthesis of IL-6, IL-10, and IL-23. Systemic production of antigen-speciﬁc IgG1 was partially dependent on IL-23. In contrast, airway exposure to HDM, but not to OVA, induced IL-23p19 mRNA expression in the lungs. In IL-23p19-deﬁcient mice, HDM- exposed lungs did not exhibit the induction of IL-17A, which negatively regulates eosinophilic inﬂammation.
Conclusions: Different antigens induced IL-23 at different part of the body in our similar asthma models. Endogenous IL-23 production at the site of antigen sensitization facilitates type-2 immune responses, whereas IL-23 production and subsequent IL-17A synthesis in the airways suppresses allergic inﬂammation.
Background: Eosinophils recognize various stimuli, such as cytokines, chemokines, immunoglobulins, complement, and external pathogens, resulting in their accumulation in mucosal tissues and the progression of inﬂammation. Eosinophils are also involved in innate Th2-type immune responses mediated through endogenous danger signals, including IL-33, uric acid (UA), or ATP, in non-sensitized mice exposed to environmental allergens. However, the mechanism involved in eosinophil responses to these danger signals remains insufﬁciently understood.
Methods: We examined migration, adhesion, superoxide production and degranulation of human eosinophils. Isolated eosinophils were incubated with monosodium urate (MSU) crystals and ATPγS, a non- hydrolysable ATP analogue. To determine the involvement of P2 or P2Y2 receptors in eosinophil responses to UA and ATP, eosinophils were preincubated with a pan-P2 receptor inhibitor, oxidized ATP (oATP), or anti-P2Y2 antibody before incubation with MSU crystals or ATPγS.
Results: MSU crystals induced adhesion of eosinophils to recombinant human (rh)-ICAM-1 and induced production of superoxide. oATP abolished eosinophil responses to MSU crystals, suggesting involvement of endogenous ATP and its receptors. Furthermore, exogenous ATP, as ATPγS, induced migration of eosinophils through a model basement membrane, adhesion to rh-ICAM-1, superoxide generation, and degranulation of eosinophil-derived neurotoxin (EDN). oATP and anti-P2Y2 signiﬁcantly reduced these eosinophil responses.
Conclusions: ATP serves as an essential mediator of functional responses in human eosinophils. Eosinophil responses to ATP may be implicated in airway inﬂammation in patients with asthma.
Background: Allergic sensitization is a key step in the pathogenesis of asthma. However, little is known about the molecules that are critical regulators for establishing allergic sensitization of the airway. Thus, we conducted global gene expression proﬁling to identify candidate genes and signaling pathways involved in house dust mite (HDM)-induced allergic sensitization in the murine airway.
Methods: We sensitized and challenged mice with HDM or saline as a control through the airway on days 1 and 8. We evaluated eosinophilia in bronchoalveolar lavage ﬂuid (BALF), airway inﬂammation, and mucus production on days 7 and 14. We extracted total RNA from lung tissues of HDM- and saline- sensitized mice on days 7 and 14. Microarray analyses were performed to identify up-regulated genes in the lungs of HDM-sensitized mice compared to the control mice. Data analyses were performed using GeneSpring software and gene networks were generated using Ingenuity Pathways Analysis (IPA).
Results: We identiﬁed 50 HDM-mediated, stepwise up-regulated genes in response to allergic sensiti- zation and ampliﬁcation of allergic airway inﬂammation. The highest expressed gene was myeloid differentiation-2 (MD-2), a lipopolysaccharide (LPS)-binding component of Toll-like receptor (TLR) 4 signaling complex. MD-2 protein was expressed in lung vascular endothelial cells and was increased in the serum of HDM-sensitized mice, but not in the control mice.
Conclusions: Our data suggest MD-2 is a critical regulator of the establishment of allergic airway sensitization to HDM in mice. Serum MD-2 may represent a potential biomarker for the ampliﬁcation of allergic sensitization and allergic inﬂammation.
Background: Eosinophils play important roles in the development of asthma exacerbation. Viral infection is a major cause of asthma exacerbation, and the expression of IFN-γ-inducible protein of 10 kDa (IP-10) and cysteinyl leukotrienes (cysLTs) is up-regulated in virus-induced asthma. As β2-adrenergic agonists, such as formoterol or salbutamol, are used to treat asthma exacerbation, we examined whether for- moterol or salbutamol could modify eosinophil functions such as adhesiveness, particularly those acti- vated by cysLTs or IP-10.
Methods: Eosinophils were isolated from the blood of healthy subjects and were pre-incubated with either formoterol or salbutamol, and subsequently stimulated with IL-5, LTD4, or IP-10. Adhesion of eosinophils to intercellular cell adhesion molecule (ICAM)-1 was measured using eosinophil peroxidase assays. The generation of eosinophil superoxide anion (O2 ) was examined based on the superoxide dismutase-inhibitable reduction of cytochrome C. Eosinophil-derived neurotoxin (EDN) release was evaluated by ELISA as a marker of degranulation.
Results: Neither formoterol nor salbutamol suppressed the spontaneous adhesion of eosinophils to ICAM-1. However, when eosinophils were activated by IL-5, LTD4, or IP-10, formoterol, but not salbu- tamol, suppressed the adhesion to ICAM-1. Formoterol also suppressed IL-5, LTD4, or IP-10 induced eosinophil O2 generation or EDN release.
Conclusions: These ﬁndings suggest that formoterol, but not salbutamol, suppresses eosinophil functions enhanced by IL-5, LTD4, or IP-10. As these factors are involved in the development of asthma exacer- bation, our results strongly support the hypothesis that administration of formoterol is a novel strategy for treating asthma exacerbation.
Background: Inhaled corticosteroids enhance airway epithelial barrier integrity. However, the mecha-nism by which they accomplish this is unclear. Therefore, we investigated steroid-inducible genes and signaling pathways that were involved in enhancing airway epithelial barrier integrity.
Methods: A human bronchial epithelial cell line (16HBE cells) was cultured with 10¯6M dexamethasone
(DEX) for 3 days to enhance epithelial barrier integrity. After measuring transepithelial electrical resis- tance (TER) and paracellular permeability, we extracted total RNA from 16HBE cells and performed microarray and pathway analysis. After we identiﬁed candidate genes and a canonical pathway, we measured TER and immunostained for tight junction (TJ) and adherent junction (AJ) proteins in cells that had been transfected with speciﬁc small interfering RNAs (siRNAs) for these genes.
Results: We identiﬁed a nuclear factor erythroid 2-related factor 2 (Nrf2)-mediated oxidative stress response pathway which was primarily involved in the steroid-induced enhancement of airway epithelial barrier integrity. Transfecting cells with Nrf2 speciﬁc siRNA reduced the steroid-induced enhancement of airway epithelial barrier integrity and the accumulation of TJ and AJ proteins at sites of cellecell contact. Moreover, based on pathway analysis, aldehyde oxidase 1 (AOX1) was identiﬁed as a downstream enzyme of Nrf2. Transfecting cells with AOX1-speciﬁc siRNA also reduced the steroid- induced enhancement of airway epithelial barrier integrity.
Conclusions: Our results indicated that the Nrf2/AOX1 pathway was important for enhancing airway epithelial barrier integrity. Because the airway epithelium of asthmatics is susceptible to reduced barrier integrity, this pathway might be a new therapeutic target for asthma.
Background: Little information is available regarding eosinophil activation and cytokine proﬁles in relation to age in virus-induced bronchial asthma. We therefore explored the association between age, respiratory viruses, serum eosinophil cationic protein (ECP), and cytokines/chemokines in acute exac- erbations of childhood asthma.
Methods: We investigated viruses in nasal secretions from 88 patients with acute exacerbation of childhood asthma by using antigen detection kits and/or RT-PCR, followed by direct DNA sequencing analysis. We also measured peripheral eosinophil counts, and the serum levels of ECP and 27 types of cytokines/chemokines in 71 virus-induced acute asthma cases and 13 controls.
Results: Viruses were detected in 71(80.7%) of the 88 samples. The three major viruses detected were rhinoviruses, RS viruses, and enteroviruses; enteroviruses were found to be dominant in patients aged ≥3 years. There was no change in the levels of rhinoviruses and RS viruses between the two age groups, deﬁned as children aged <3 years and children aged ≥3 years. Serum concentrations of ECP, IL-5, and IP- 10 were signiﬁcantly elevated in virus-induced acute asthma cases compared with controls. Serum ECP values were signiﬁcantly higher in patients with virus-induced asthma at age ≥3 years compared with those aged <3 years. Among the 27 cytokines/chemokines, serum IP-10 was signiﬁcantly higher in virus- induced asthma in patients <3 years than in those ≥3 years. Serum ECP and IL-5 production correlated signiﬁcantly with age, whereas serum IP-10 showed an inverse correlation with age.
Conclusions: Age-related differences in cytokine proﬁles and eosinophil activation may be related to virus-induced acute exacerbations of childhood asthma.