Hisashi Tanida

Staphylococcus aureus directly activates eosinophils via platelet‐activating factor receptor

Colonization by SA is associated with exacerbation of AD. Eosinophilic inflammation is a cardinal pathological feature of AD, but little is known about possible direct interaction between SA and eosinophils. PAFR appears to be involved in phagocytosis of Gram‐positive bacteria by leukocytes. The objective of this study was to investigate whether SA directly induces eosinophil effector functions via PAFR in the context of AD pathogenesis. Peripheral blood eosinophils were cultured with heat‐killed SA, and EDN release, superoxide generation, and adhesion to fibronectin‐coated plates were measured. Cytokines, released in the supernatants, were quantified by multiplex bead immunoassays. FISH‐labeled SA was incubated with eosinophils and visualized by confocal laser‐scanning microscopy. PAFR‐blocking peptide and PAFR antagonists were tested for inhibitory effects on SA‐induced reactions. SA induced EDN release and superoxide generation by eosinophils in a dose‐dependent manner. IL‐5 significantly enhanced SA‐induced EDN release. IL‐5 and IL‐17A significantly enhanced SA‐induced superoxide generation. SA enhanced eosinophil adhesion to fibronectin, which was blocked by anti‐CD49d, and induced eosinophil secretion of various cytokines/chemokines (IL‐2R, IL‐9, TNFR, IL‐1β, IL‐17A, IP‐10, TNF‐α, PDGF‐bb, VEGF, and FGF‐basic). After incubation of eosinophils with SA, FISH‐labeled SA was visualized in the eosinophilsˈ cytoplasm, indicating phagocytosis. A PAFR‐blocking peptide and two PAFR antagonists completely inhibited those reactions. In conclusion, SA directly induced eosinophil activation via PAFR. Blockade of PAFR may be a novel, therapeutic approach for AD colonized by SA.

1,25-Dihydroxyvitamin D3 upregulates functional C-x-C chemokine receptor type 4 expression in human eosinophils.

Background: Epidemiological studies suggest that vitamin D may be protective against the inception and exacerbation of allergic diseases. However, the direct effect of vitamin D on eosinophils, the major effector cells in allergic inflammation, is not known. It has been reported that C-X-C chemokine receptor type 4 (CXCR4) in eosinophils is induced in non-Th2 cytokine milieu or in response to glucocorticoids, recruiting the cell to noninflammatory sites. Objectives: To test whether 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3 or calcitriol], the active metabolite of vitamin D, acts directly on eosinophils to induce upregulation of CXCR4. Methods: Peripheral blood eosinophils from normal volunteers were isolated by CD16 immunomagnetic beads. Vitamin D receptor (VDR) expression was detected by RT-PCR. Eosinophils were cultured with 1,25-(OH)2D3 and the survival and expression of CXCR4 on eosinophils were measured by flowcytometry. Eosinophil migration by CXCL-12/SDF-1 in the presence of 1,25-(OH)2D3 was also analyzed. Results: Eosinophils expressed VDR. 1,25-(OH)2D3 prolonged eosinophil survival and upregulated eosinophil surface expression of CXCR4 in a concentration-dependent manner. Interleukin (IL)-5 significantly reduced CXCR4 expression and migration induced by the ligand CXCL-12/SDF-1. 1,25-(OH)2D3 reversed the negative effects of IL-5 on the CXCR4-CXCL12 pathway. Conclusion: 1,25-(OH)2D3 regulates CXCR4 expression in eosinophils. The mechanism may be involved in eosinophil recruitment to noninflammatory sites where the ligand of CXCR4 is constitutively expressed.

Inhibition of Eosinophil Activation Mediated by a Toll-Like Receptor 7 Ligand with a Combination of Procaterol and Budesonide

Background: Viral respiratory tract infections play an important role in the inception and exacerbation of asthma. Eosinophils, major effector cells in asthma, often accumulate in the airways during viral infections and are possibly activated by respiratory RNA viruses through Toll-like receptor (TLR) 7. We investigated the effect of a β2-agonist, i.e. procaterol, and a corticosteroid, i.e. budesonide, that are commonly used for viral-induced asthma, on TLR7 ligand-induced activation of eosinophils in vitro. Methods: Purified peripheral blood eosinophils were incubated with procaterol and/or budesonide and stimulated with a TLR7 ligand, i.e. R-837. Expression of CD11b was analyzed by flow cytometry. Superoxide generation was measured via the cytochrome C reduction method. IL-8 in the supernatants was assayed by ELISA. Results: Although procaterol or budesonide alone did not inhibit R-837-induced CD11b expression, combinations of the 2 drugs significantly inhibited CD11b. Likewise, the combinations significantly inhibited O2– generation at low concentrations. Budesonide significantly inhibited R-837-induced IL-8 production in a concentration-dependent manner, and procaterol potentiated inhibition by budesonide although single-agent procaterol had no effect. Conclusion: A combination of procaterol and budesonide inhibits the TLR7-mediated effector function of eosinophils, indicating their possible anti-inflammatory effect for virus-induced asthma.