Hiroki Murai

IL-17A/F Modulates Fibrocyte Functions in Cooperation with CD40-Mediated Signaling

T helper 17 (Th17) cells that produce interleukin (IL)-17A and IL-17F have been found to participate in the development of bronchial asthma and bleomycin-induced pulmonary fibrosis. However, whether they play a causative role in the airway remodeling observed in these respiratory diseases remains unclear. Because fibrocytes are involved in tissue repair and fibrosis and are presumably precursors of lung fibroblasts and myofibroblasts, we examined the effects of IL-17A/F on fibrocyte functions. Both IL-17A and IL-17F enhanced fibrocytes’ α-smooth muscle actin expression. Priming fibrocytes with IL-17A enhanced their CD40-mediated IL-6 production, whereas IL-17F-priming increased the CD40-mediated mRNA expression of collagen I, vascular endothelial growth factor, and angiogenin. CD4+ T cells co-cultured with fibrocytes produced IL-17A, which was inhibited by blocking CD40 and CD40 ligand interactions. These findings suggest that cooperative interactions between fibrocytes and Th17 cells play an important role via CD40- and IL-17A/F-mediated signaling for collagen and proangiogenic factor production, which may lead to the extracellular matrix deposition and neovascularization seen in airway remodeling.

FcγRIIb Inhibits Allergic Lung Inflammation in a Murine Model of Allergic Asthma

Allergic asthma is characterized by airway eosinophilia, increased mucin production and allergen-specific IgE. Fc gamma receptor IIb (FcγRIIb), an inhibitory IgG receptor, has recently emerged as a negative regulator of allergic diseases like anaphylaxis and allergic rhinitis. However, no studies to date have evaluated its role in allergic asthma. Our main objective was to study the role of FcγRIIb in allergic lung inflammation. We used a murine model of allergic airway inflammation. Inflammation was quantified by BAL inflammatory cells and airway mucin production. FcγRIIb expression was measured by qPCR and flow cytometry and the cytokines were quantified by ELISA. Compared to wild type animals, FcγRIIb deficient mice mount a vigorous allergic lung inflammation characterized by increased bronchoalveolar lavage fluid cellularity, eosinophilia and mucin content upon ragweed extract (RWE) challenge. RWE challenge in sensitized mice upregulated FcγRIIb in the lungs. Disruption of IFN-γ gene abrogated this upregulation. Treatment of naïve mice with the Th1-inducing agent CpG DNA increased FcγRIIb expression in the lungs. Furthermore, treatment of sensitized mice with CpG DNA prior to RWE challenge induced greater upregulation of FcγRIIb than RWE challenge alone. These observations indicated that RWE challenge upregulated FcγRIIb in the lungs by IFN-γ- and Th1-dependent mechanisms. RWE challenge upregulated FcγRIIb on pulmonary CD14+/MHC II+ mononuclear cells and CD11c+ cells. FcγRIIb deficient mice also exhibited an exaggerated RWE-specific IgE response upon sensitization when compared to wild type mice. We propose that FcγRIIb physiologically regulates allergic airway inflammation by two mechanisms: 1) allergen challenge mediates upregulation of FcγRIIb on pulmonary CD14+/MHC II+ mononuclear cells and CD11c+ cells by an IFN-γ dependent mechanism; and 2) by attenuating the allergen specific IgE response during sensitization. Thus, stimulating FcγRIIb may be a therapeutic strategy in allergic airway disorders.

Alternaria-induced release of IL-18 from damaged airway epithelial cells: An NF-κB dependent mechanism of Th2 differentiation?

Background A series of epidemiologic studies have identified the fungus Alternaria as a major risk factor for asthma. The airway epithelium plays a critical role in the pathogenesis of allergic asthma. These reports suggest that activated airway epithelial cells can produce cytokines such as IL-25, TSLP and IL-33 that induce Th2 phenotype. However the epithelium-derived products that mediate the pro-asthma effects of Alternaria are not well characterized. We hypothesized that exposure of the airway epithelium to Alternaria releasing cytokines that can induce Th2 differentiation. Methodology/Principal Finding We used ELISA to measure human and mouse cytokines. Alternaria extract (ALT-E) induced rapid release of IL-18, but not IL-4, IL-9, IL-13, IL-25, IL-33, or TSLP from cultured normal human bronchial epithelial cells; and in the BAL fluids of naïve mice after challenge with ALT-E. Both microscopic and FACS indicated that this release was associated with necrosis of epithelial cells. ALT-E induced much greater IL-18 release compared to 19 major outdoor allergens. Culture of naïve CD4 cells with rmIL-18 induced Th2 differentiation in the absence of IL-4 and STAT6, and this effect was abrogated by disrupting NF- κB p50 or with a NEMO binding peptide inhibitor. Conclusion/Significance Rapid and specific release of IL-18 from Alternaria-exposed damaged airway epithelial cells can directly initiate Th2 differentiation of naïve CD4+ T-cells via a unique NF-κB dependent pathway.

IL-33 enhanced the proliferation and constitutive production of IL-13 and IL-5 by fibrocytes.

Interleukin-33 appears to play important roles in the induction of allergic airway inflammation. However, whether IL-33 is involved in airway remodeling remains unclear. Because fibrocytes contribute to tissue remodeling in the setting of chronic inflammation, we examined the effects of IL-33 on fibrocyte functions. Fibrocytes were generated in vitro from peripheral blood mononuclear cells by culturing in the presence of platelet derived growth factors and the cells were stimulated with IL-33. IL-33 enhanced cell proliferation, α-SMA expression, and pro-MMP-9 activity by the fibrocytes without increasing endogenous transforming growth factor-β1 production. Fibrocytes constitutively expressed IL-13 and IL-5, and their production was augmented by stimulation with IL-33. Dexamethasone inhibited the functions of fibrocytes, but IL-33 made fibrocytes slightly refractory to the inhibitory effect of dexamethasone in terms of IL-13 production. Montelukast suppressed IL-13 production by nonstimulated fibrocytes but not those stimulated by IL-33. These findings suggest that IL-33 is involved in the airway remodeling process through its modulation of fibrocyte function independent of antigen stimulation. IL-33 might partially reduce the therapeutic effects of glucocorticoid and cysteinyl leukotriene receptor antagonist on fibrocyte-mediated Th2 responses.

Alternaria extract activates autophagy that induces IL-18 release from airway epithelial cells

Alternaria alternata is a major outdoor allergen that causes allergic airway diseases. Alternaria extract (ALT-E) has been shown to induce airway epithelial cells to release IL-18 and thereby initiate Th2-type responses. We investigated the underlying mechanisms involved in IL-18 release from ALT-E-stimulated airway epithelial cells. Normal human bronchial epithelial cells and A549 human lung adenocarcinoma cells were stimulated with ALT-E in the presence of different inhibitors of autophagy or caspases. IL-18 levels in culture supernatants were measured by ELISA. The numbers of autophagosomes, an LC3-I to LC3-II conversion, and p62 degradation were determined by immunofluorescence staining and immunoblotting. 3-methyladenine and bafilomycin, which inhibit the formation of preautophagosomal structures and autolysosomes, respectively, suppressed ALT-E-induced IL-18 release by cells, whereas caspase 1 and 8 inhibitors did not. ALT-E-stimulation increased autophagosome formation, LC-3 conversion, and p62 degradation in airway epithelial cells. LPS-stimulation induced the LC3 conversion in A549 cells, but did not induce IL-18 release or p62 degradation. Unlike LPS, ALT-E induced airway epithelial cells to release IL-18 via an autophagy dependent, caspase 1 and 8 independent pathway. Although autophagy has been shown to negatively regulate canonical inflammasome activity in TLR-stimulated macrophages, our data indicates that this process is an unconventional mechanism of IL-18 secretion by airway epithelial cells.

The Biomarker Salivary SP-D May Indicate Small Airway Inflammation and Asthma Exacerbation

BACKGROUND Noninvasive and child-friendly biomarkers are important tools for understanding the various phenotypes of childhood asthma. Objective: The aim of this study was to examine the usefulness of salivary surfactant protein (SP) D in assessing the pathophysiology of childhood asthma. METHODS We measured salivary concentrations of SP-D and forced oscillation technique (FOT) indexes in 19 healthy controls and 21 asthmatic children. Regression equations for the predictive values of FOT indexes were generated from healthy controls. We analyzed the correlations between salivary SP-D concentration and percentages of the predictive values of FOT indexes, as well as the severity of exacerbation. RESULTS We found that salivary SP-D levels were higher in asthmatic children than in healthy controls. In the asthmatic children, salivary SP-D levels correlated with the percentages of predicted differences in resistance between 5 Hz and 20 Hz (%R5-R20), which represented the resistance of peripheral airways, and with the severity of asthma exacerbation. CONCLUSIONS Salivary SP-D may reflect asthmatic inflammation in peripheral small airways and may be a useful marker for monitoring the degree of exacerbation in childhood asthma.

Rice protein-induced enterocolitis syndrome with transient specific IgE to boiled rice but not to retort-processed rice.

Described herein is the case of an 8‐month‐old girl with atypical food protein‐induced enterocolitis syndrome due to rice. She presented with vomiting and poor general activity 2 h after ingestion of boiled rice. Oral food challenge test using high‐pressure retort‐processed rice was negative, but re‐exposure to boiled rice elicited gastrointestinal symptoms. On western blot analysis the patients serum was found to contain IgE bound to crude protein extracts from rice seed or boiled rice, but not from retort‐processed rice. The major protein bands were not detected in the electrophoresed gel of retort‐processed rice extracts, suggesting decomposition by high‐temperature and high‐pressure processing. Oral food challenge for diagnosing rice allergy should be performed with boiled rice to avoid a false negative. Additionally, some patients with rice allergy might be able to ingest retort‐processed rice as a substitute for boiled rice.

Skin inflammation exacerbates food allergy symptoms in epicutaneously sensitized mice

Cutaneous exposure to food antigen through impaired skin barrier has been shown to induce epicutaneous sensitization, thereby causing IgE‐mediated food allergies.