Hiroyuki Nagase

Expression and Function of Toll-Like Receptors in Eosinophils: Activation by Toll-Like Receptor 7 Ligand

We investigated the expression of a panel of Toll-like receptors (TLRs) and their functions in human eosinophils. Eosinophils constitutively expressed TLR1, TLR4, TLR7, TLR9, and TLR10 mRNAs (TLR4 greater than TLR1, TLR7, TLR9, and TLR10 greater than TLR6). In contrast, neutrophils expressed a larger variety of TLR mRNAs (TLR1, TLR2, TLR4, TLR6, TLR8 greater than TLR5, TLR9, and TLR10 greater than TLR7). Although the expression levels in eosinophils were generally less prominent compared with those in neutrophils, eosinophils expressed a higher level of TLR7. Furthermore, among various TLR ligands (S-(2,3-bis(palmitoyloxy)-(2-RS)-propyl)-N-palmitoyl-Cys-Ser-(Lys)4, poly(I:C), LPS, R-848, and CpG DNA), only R-848, a ligand of TLR7 and TLR8, regulated adhesion molecule (CD11b and L-selectin) expression, prolonged survival, and induced superoxide generation in eosinophils. Stimulation of eosinophils by R-848 led to p38 mitogen-activated protein kinase activation, and SB203580, a p38 mitogen-activated protein kinase inhibitor, almost completely attenuated R-848-induced superoxide generation. Although TLR8 mRNA expression was hardly detectable in freshly isolated eosinophils, mRNA expression of TLR8 as well as TLR7 was exclusively up-regulated by IFN-γ but not by either IL-4 or IL-5. The up-regulation of the TLRs by IFN-γ had potentially functional significance: the extent of R-848-induced modulation of adhesion molecule expression was significantly greater in cells treated with IFN-γ compared with untreated cells. Although the natural ligands for TLR7 and TLR8 have not yet been identified, our results suggest that eosinophil TLR7/8 systems represent a potentially important mechanism of a host-defensive role against viral infection and mechanism linking exacerbation of allergic inflammation and viral infection.

An IL-1 Cytokine Member, IL-33, Induces Human Basophil Activation via Its ST2 Receptor

Basophils are thought to play pivotal roles in allergic inflammation through rapid release of chemical mediators in addition to sustained production of Th2 cytokines, including IL-4. A newly identified cytokine, IL-33, has been recognized as one of the key cytokines enhancing Th2-balanced immune regulation through its receptor, ST2. The present study was conducted to elucidate whether IL-33 acts directly on, and affects the functions of, human basophils. Real-time PCR analysis showed that basophils express transcripts for ST2. The expression levels were significantly higher compared with eosinophils and neutrophils, and treatment with IL-33 significantly up-regulated basophil ST2 mRNA expression. Expressions of IL-4 and IL-13 mRNA were also up-regulated by IL-33, and there was also enhanced secretion of IL-4 protein. IL-33 increased the surface levels of basophil CD11b expression and enhanced basophil adhesiveness. Although IL-33 failed to directly induce degranulation or attract basophils, it exerted priming effects on basophils. It enhanced degranulation in response to IgE-crosslinking stimulus and also enhanced basophil migration toward eotaxin without changing surface CCR3. Also, IL-33 synergistically enhanced IL-4 production and CD11b expression by IL-3-stimulated basophils. Neutralization using Ab specific for ST2 significantly diminished the enhancing effects of IL-33 on both basophil CD11b expression and migration toward eotaxin, indicating that IL-33 signals via ST2 expressed on basophils. This study revealed that IL-33 potently regulates migration and activation of human basophils. IL-33 may be a key cytokine in the pathogenesis of Th2-dominant inflammation by acting not only on lymphocytes but also on effector cells such as basophils.

Expression of CXCR4 in eosinophils: functional analyses and cytokine-mediated regulation.

We examined the expression of transcripts of a panel of chemokine receptors in human eosinophils and found intense constitutive expression of CXCR4 mRNA. Although surface CXCR4 protein was hardly detectable in the peripheral blood or freshly isolated eosinophils, surface expression of CXCR4 became gradually apparent during incubation at 37°C. In contrast, the level of CCR3 expression was virtually unchanged during the incubation. Stromal cell-derived factor-1α (SDF-1α), the natural ligand of CXCR4, elicited an apparent Ca2+ influx in these cells and induced a strong migratory response comparable to that by eotaxin. The surface expression of CXCR4 in eosinophils was up-regulated by IFN-γ, TNF-α, and TGF-β while it was down-regulated by IL-4 and eosinophil-directed hemopoietins such as IL-5. The CXCR4 expression did not always parallel the apoptotic changes in cytokine-treated eosinophils. In contrast to IL-4 and IFN-γ, IL-5 potently reduced the level of CXCR4 mRNA. It seems unlikely that CXCR4 is fundamentally involved in the pathogenesis of allergic disorders by inducing the migration of eosinophils toward inflammatory sites, because a Th2-dominant state down-regulates eosinophil CXCR4 expression. However, CXCR4 may affect the size of the mobilizable pool by holding eosinophils at noninflamed tissues. Th2-dominant state may favor the liberation of eosinophils by down-regulating CXCR4 expression. The interplay between CXCR4 and SDF-1α in eosinophils potentially plays an important role in the accumulation of these cells at the allergic inflammatory sites.

Effect of tiotropium bromide on airway inflammation and remodelling in a mouse model of asthma

Background Tiotropium bromide, a long acting muscarinic receptor inhibitor, is a potent agent for patients with bronchial asthma as well as chronic obstructive pulmonary disease.

Differential modulation of human basophil functions through prostaglandin D2 receptors DP and chemoattractant receptor‐homologous molecule expressed on Th2 cells/DP2

Background Both prostaglandin (PG) D receptor (DP) and CRTH2 (chemoattractant receptor‐homologous molecule expressed on Th2 cells)/DP2 are high‐affinity receptors for PGD2. Previous studies have demonstrated that PGD2 enhances releasability and induces CRTH2/DP2‐mediated migration in human basophils, but the precise effects of PGD2 on basophils as well as receptor usage have not been fully clarified.

Leptin Enhances Survival and Induces Migration, Degranulation, and Cytokine Synthesis of Human Basophils

Basophils are the rarest leukocytes in human blood, but they are now recognized as one of the most important immunomodulatory as well as effector cells in allergic inflammation. Leptin, a member of the IL-6 cytokine family, has metabolic effects as an adipokine, and it is also known to participate in the pathogenesis of inflammatory reactions. Because there is an epidemiologic relationship between obesity and allergy, we examined whether basophil functions are modified by leptin. We found that human basophils express leptin receptor (LepR) at both the mRNA and surface protein levels, which were upregulated by IL-33. Leptin exerted strong effects on multiple basophil functions. It induced a strong migratory response in human basophils, similar in potency to that of basophil-active chemokines. Also, leptin enhanced survival of human basophils, although its potency was less than that of IL-3. Additionally, CD63, a basophil activation marker expressed on the cell surface, was upregulated by leptin, an effect that was neutralized by blocking of LepR. Assessments of basophil degranulation and cytokine synthesis found that leptin showed a strong priming effect on human basophil degranulation in response to FcεRI aggregation and induced Th2, but not Th1, cytokine production by the cells. In summary, the present findings indicate that leptin may be a key molecule mediating the effects of adipocytes on inflammatory cells such as basophils by binding to LepR and activating the cellular functions, presumably exacerbating allergic inflammation.

Expression and Function of Toll-Like Receptors in Human Basophils

We investigated the expression and function of a panel of Toll-like receptors (TLRs) in human basophils. Basophil preparations constitutively expressed TLR2, TLR4, TLR9 and TLR10 mRNAs (TLR4 > TLR2 >> TLR9, TLR10). Although TLR mRNA expression in basophils was generally less prominent compared with those in neutrophils and monocytes, basophils expressed significantly higher levels of TLR2 and TLR4 mRNA than eosinophils. Various TLR ligands (Pam3Cys-Ser-Lys4, poly I:C, lipopolysaccharide, R-848, CpG DNA) were tested, but none affected the expression level of adhesion molecule CD11b or the viability of freshly purified basophils. On the other hand, when basophils were pretreated with interferon-γ before stimulation with TLR ligands, only the TLR4 ligand, lipopolysaccharide, upregulated CD11b expression. However, the surface levels of TLR2 and TLR4 on the interferon-γ-treated basophils showed no obvious changes. These results suggest that TLR4 on basophils may be involved in the pathogenesis of infection-induced exacerbation of allergic inflammation by modulating basophil functions.

Reference Ranges for Exhaled Nitric Oxide Fraction in Healthy Japanese Adult Population

BACKGROUND The measurement of the exhaled nitric oxide fraction (FE(NO)) is proposed as a useful marker of airway inflammation. In healthy adults, there have been a few studies of the reference ranges for FE(NO) in Caucasians. A community study in other regions may reveal any possible ethnic differences in the FE(NO) levels. METHODS A total of 240 healthy adults aged between 18 to 74 years were recruited from four medical centers in Japan. Current smokers and subjects having a history of atopic disease were not included. FE(NO) was measured using an online electrochemical nitric oxide analyzer according to the current guidelines. The reference ranges for FE(NO) were estimated using two different statistical methods recommended by International Federation of Clinical Chemistry and Laboratory Medicine. RESULTS The mean FE(NO) was 16.9 ppb (parts per billion) with a 95% prediction interval (2.5 to 97.5 percentiles) of 6.5 to 35.0 ppb in healthy Japanese adults. Normality assumptions were met for the logarithm-transformed FE(NO). The geometric mean FE(NO) was 15.4 ppb with a mean ± two standard deviations of 6.5 to 36.8 ppb. Age, gender, height, and past smoking history were not associated with the FE(NO) levels. CONCLUSIONS The reference ranges for FE(NO) in healthy Japanese adults were similar to those of Caucasians. It seems reasonable that the upper limit of FE(NO) for healthy adults should be set at approximately 36.0 ppb irrespective of ethnic differences.

A Functional Study on CysLT1 Receptors in Human Eosinophils

Background: The cysteinyl leukotrienes (CysLTs) mediate their biological actions through two receptors: CysLT₁ receptor and CysLT₂ receptor. Objective: This study was undertaken to examine the direct effects of CysLTs on eosinophils, such as chemotaxis and degranulation, focusing on CysLT₁. Methods: Eosinophils were isolated from venous blood from normal volunteers who had no history of allergy (purity >99%). They were subjected to reverse transcription-PCR analysis and flow-cytometric analysis for CysLT₁. Binding assays were performed with [³H]LTD₄. Purified eosinophils loaded with Fura-2 acetoxymethyl ester were stimulated with CysLTs, and Ca²⁺ influx was measured. Eosinophil migration in response to CysLTs was measured using a 96-well multiwell Boyden chamber. Eosinophils were treated with LTD₄ at 10^–6M for 60 min followed by incubation for 4 h at 37°C in the presence or absence of IL-5 and eosinophil-derived neurotoxin (EDN) release was evaluated. Results: The expression of the mRNA and protein of CysLT₁ on eosinophils and [³H]LTD₄-specific binding to eosinophils were observed. Neither Th1 cytokine (IFN-γ) nor Th2 cytokines (IL-4 or IL-5) affected CysLT₁ expression in eosinophils. CysLTs induced an increase in intracellular free Ca²⁺ in eosinophils via CysLT₁, as suggested by the efficient inhibition by a CysLT₁ antagonist, pranlukast, in addition to the rank order of potency being LTD₄, LTC₄ and LTE₄. LTD₄ stimulated eosinophils to migrate at 10^–6M via CysLT₁. LTE₄ also induced significant eosinophil migration at 10^–6M. LTD₄ enhanced EDN release induced by IL-5 via CysLT₁. Conclusion: CysLTs induce migration and enhance degranulation in eosinophils via CysLT₁. Accordingly, interaction of CysLTs and CysLT₁ on eosinophils has the potential to play a prominent role in the pathophysiology of asthma.

Japanese Guideline for Adult Asthma 2014.

Adult bronchial asthma (hereinafter, asthma) is characterized by chronic airway inflammation, reversible airway narrowing, and airway hyperresponsiveness. Long-standing asthma induces airway remodeling to cause intractable asthma. The number of patients with asthma has increased, and that of patients who die from asthma has decreased (1.5 per 100,000 patients in 2012). The aim of asthma treatment is to enable patients with asthma to lead a normal life without any symptoms. A good relationship between physicians and patients is indispensable for appropriate treatment. Long-term management with antiasthmatic agents and elimination of the causes and risk factors of asthma are fundamental to its treatment. Four steps in pharmacotherapy differentiate between mild and intensive treatments; each step includes an appropriate daily dose of an inhaled corticosteroid, varying from low to high. Long-acting 02-agonists, leukotriene receptor antagonists, and sustained-release theophylline are recommended as concomitant drugs, while anti-immunoglobulin E antibody therapy has been recently developed for the most severe and persistent asthma involving allergic reactions. Inhaled 02-agonists, aminophylline, corticosteroids, adrenaline, oxygen therapy, and others are used as needed in acute exacerbations by choosing treatment steps for asthma exacerbations depending on the severity of attacks. Allergic rhinitis, chronic obstructive pulmonary disease, aspirin-induced asthma, pregnancy, asthma in athletes, and coughvariant asthma are also important issues that need to be considered.