Mio Kawaguchi

Synthetic double-stranded RNA induces multiple genes related to inflammation through Toll-like receptor 3 depending on NF-κB and/or IRF-3 in airway epithelial cells

Background We hypothesized that synthetic double‐stranded (ds)RNA may mimic viral infection and induce expression of genes related to inflammation in airway epithelial cells.

Role of interleukin‐17F in chronic inflammatory and allergic lung disease

IL‐17 family members belong to a distinct category of cytokines that coordinate local tissue inflammation by inducing the release of pro‐inflammatory and neutrophil‐mobilizing cytokines. The importance of the IL‐17 family in inflammatory and autoimmune disease is becoming increasingly apparent. IL‐17F is a recently discovered member of the IL‐17 family that has a number of biological activities through induction of various cytokines, chemokines, and mediators. IL‐17A, the founding member of the IL‐17 family, and IL‐17F are produced by several inflammatory cells, including activated T cells, in response to infectious and antigenic stimuli. Overexpression of IL‐17A or IL‐17F in the lungs results in induction of CXC chemokines and neutrophil recruitment. In a case–control study of 1125 unrelated Japanese subjects, a His161 to Arg161 (H161R) substitution in the third exon of the IL17F gene was shown to be associated with asthma and chronic obstructive pulmonary disease (COPD). Functionally, this variant failed to induce cytokines and chemokines, and interestingly, was able to antagonize the activity of wild‐type IL‐17F. These results provide an experimental basis for the observed genetic association with chronic inflammatory lung diseases, and also suggest the potential therapeutic utility of this antagonistic variant of IL‐17F. Given that asthma and COPD are complex diseases involving a number of genetic and environmental factors, the genetic impact of IL‐17F H161R with regard to the development of chronic airway inflammation likely varies among individuals with different genetic backgrounds and environmental exposures.

Role of RIG-I, MDA-5, and PKR on the Expression of Inflammatory Chemokines Induced by Synthetic dsRNA in Airway Epithelial Cells

Background: We hypothesized that synthetic double-stranded (ds)RNA may mimic viral infection and reported that dsRNA stimulates expression of inflammatory chemokines through a receptor of dsRNA Toll-like receptor (TLR) 3 in airway epithelial cells. In this study, we focused our study on the role of other receptors for dsRNA, such as retinoic acid-inducible gene I (RIG-I), melanoma differentiation-associated gene 5 (MDA-5), and double-stranded RNA-dependent protein kinase (PKR). Methods: Airway epithelial cell BEAS-2B was cultured in vitro. Expression of target RNA and protein were analyzed by PCR and ELISA. To analyze the role of receptors for dsRNA, knockdown of theses genes was performed with short interfering RNA (siRNA). Results: We first investigated the effects of chloroquine, an inhibitor of lysosomal acidification, on the expression of chemokines. Preincubation with 100 µM chloroquine significantly inhibited the expression of mRNA for RANTES, IP-10, and IL-8, stimulated by poly I:C, indicating that poly I:C may react with a receptor expressed inside the cells. RIG-I, MDA-5, and PKR are supposed to be expressed inside the airway epithelial cells. However, the expression of chemokines stimulated with poly I:C was not significantly inhibited for these putative receptors in the cells which were transfected with siRNA. Conclusions: Synthetic dsRNA poly I:C stimulates the expression of inflammatory chemokines in airway epithelial cells, but the putative receptors for dsRNA such as RIG-I, MDA-5, or PKR may not play pivotal roles in this process. TLR3 may play a major role as reported previously.

Double‐stranded RNA activates RANTES gene transcription through co‐operation of nuclear factor‐κB and interferon regulatory factors in human airway epithelial cells

Background Regulated on activation, normal T cells expressed and secreted (RANTES) is a member of the CC chemokine family and contributes to viral‐induced airway inflammation including exacerbations of asthma. Double‐stranded RNA (dsRNA) is known to be synthesized during replication of many viruses and a ligand of Toll‐like receptor 3. We hypothesized that dsRNA may mimic viral infection and induce RANTES expression in airway epithelial cells.

Expression of Interleukin-17F in a Mouse Model of Allergic Asthma

Background: Interleukin (IL)-17F is a recently discovered cytokine and is derived from a panel of limited cell types, such as activated CD4+ T cells, basophils, and mast cells. IL-17F is known to induce several cytokines and chemokines. However, its involvement in airway inflammation has not been well understood. To this end, the expression of IL-17F and the inhibitory effects of glucocorticoids on its expression in a mouse model of asthma were examined. Methods: Five-week-old BALB/c male mice were sensitized by intraperitoneal injection (i.p.) of ovalbumin (OVA) with alum, and challenged by daily inhalation of aerosolized 1% OVA. 24 h after last challenge (OVA/OVA), the expression of IL-17F was examined in lung tissues by immunohistochemistry and reverse-transcription polymerase chain reaction. Control mice were sensitized and challenged with saline (Sham/Sham). In addition, a group of OVA-sensitized mice received i.p. injection of water-soluble dexamethasone (DEX) in saline 1 h before OVA challenge (OVA/DEX). Results: In sham-challenged mice, IL-17F was not expressed in the lungs, while, in contrast, IL-17F was predominantly expressed in bronchial epithelial cells in addition to the infiltrating inflammatory cells in OVA/OVA mice. Further, the expression of IL-17 F was significantly attenuated by the treatment of mice with DEX. Conclusion: These results suggest that bronchial epithelium-derived IL-17F may represent a new pharmacological target for glucocorticoids and may play a role in allergic asthma.

Differential regulation of chemokine expression by Th1 and Th2 cytokines and mechanisms of eotaxin/CCL-11 expression in human airway smooth muscle cells.

Background: Airway smooth muscle (ASM) cells may contribute to the pathogenesis of asthma including airway inflammation and remodeling. We focused our study on the regulation of chemokine expression by cytokines and analyzed the mechanisms of eotaxin/CCL-11 expression in ASM cells. Methods: Human ASM cells were cultured in vitroand treated with IL-4, interferon-γ (IFNγ), and tumor necrosis factor-α (TNFα). Secretion of chemokines into the culture medium was analyzed by ELISA. Expression of eotaxin mRNA was analyzed by reverse transcription-polymerase chain reaction (RT-PCR). Binding of transcription factor signal transducer activator of transcription (STAT) 6 to the eotaxin promoter-derived DNA was analyzed by pull-down Western blot. To assess transcriptional regulation of eotaxin, cells were transfected with eotaxin promoter-luciferase reporter plasmids, and activity was determined by dual luciferase assay. Results: The Th2 cytokine IL-4 preferentially stimulated the expression of the CC chemokine receptor (CCR) 3-ligand chemokines eotaxin, eotaxin-3, and MCP-4. The Th1 cytokine IFNγ stimulated the expression of chemokines IP-10 and RANTES. IL-4 stimulated nuclear translocation of signal transducer activator of transcription 6 (STAT6) and its binding to the eotaxin promoter region. IL-4 activated the eotaxin promoter and its activity was inhibited by mutation of the binding site for STAT6 in the promoter. Conclusions: The Th2 cytokine IL-4 preferentially stimulated the expression of CCR3 ligand chemokines including eotaxin in ASM cells. The transcription factor STAT6 may play a pivotal role in the activation of eotaxin transcription in response to IL-4.

Effects of Corticosteroids on Osteopontin Expression in a Murine Model of Allergic Asthma

Background: Osteopontin (OPN) contributes to the development of T helper 1 (Th1)-mediated immunity and Th1-associated diseases. However, the role of OPN in bronchial asthma is unclear. Corticosteroids reduce airway inflammation, as reflected by the low eosinophil and T-cell counts, and the low level of cytokine expression. We investigated OPN production and the inhibitory effects of corticosteroids on OPN production in a murine model of allergic asthma. Methods: BALB/c mice were sensitized by intraperitoneal injections of ovalbumin (OVA) with alum. Some mice received daily injections of dexamethasone (DEX) or phosphate-buffered saline for 1 week. All OVA-challenged mice were exposed to aerosolized 1% OVA for 30 min an hour after these injections. After the OVA challenge, the mice were killed, and bronchoalveolar lavage (BAL) fluid and lung tissue were examined. Results: The levels of OPN protein in BAL fluid and OPN mRNA in lung tissue increased after OVA challenge. Most OPN-expressing cells were CD11c+ cells and some were T cells. DEX decreased the levels of OPN protein in the BAL fluid, and those of OPN mRNA and OPN protein in lung tissue. Conclusions: OPN may play an important role in allergic bronchial asthma. Corticosteroids inhibit OPN production in mice with allergic asthma. The beneficial effect of corticosteroids in bronchial asthma is partly due to their inhibitory effects on OPN production.

Molecular Mechanisms of Repression of Eotaxin Expression with Fluticasone Propionate in Airway Epithelial Cells

Background: Glucocorticoids are known to repress the expression of CC chemokine eotaxin in airway epithelial cells. We focused our study on the molecular mechanisms of the glucocorticoid, fluticasone, in the inhibition of the expression of the eotaxin gene in the cells. Methods: The airway epithelial cell line, BEAS-2B, was stably transfected with signal transducers and activators of transcription 6 (STAT6)-expressing vector and used in the following experiments to clarify the function of STAT6. Levels of eotaxin mRNA and protein expression were determined with RT-PCR and ELISA. Mechanisms of transcriptional regulation were assessed by the electrophoretic mobility shift assay and dual luciferase assay using eotaxin promoter-luciferase reporter plasmids. Results: Fluticasone significantly inhibited the induction of eotaxin protein stimulated with TNF-α and IL-4 in the cells. Fluticasone also repressed the induction of eotaxin mRNA with these stimuli. It partially inhibited the activity of eotaxin promoter; however, it did not inhibit the nuclear translocation and binding of transcription factors, nuclear factor-kappa B (NF-ĸB) or STAT6, to the DNA derived from the proximal promoter region of the eotaxin gene. Moreover, the inhibitory effect was also conserved in the experiments using the reporter plasmid of which the putative glucocorticoid-responsive element was mutated. Conclusions: Fluticasone inhibits the expression of eotaxin gene in airway epithelial cells in part through repression of the transcription. However, the mechanisms depend neither on the inhibition of transcription factors’ translocation into nuclei nor the function of the putative glucocorticoid-responsive element in the promoter, indicating that other mechanisms would be related to the transcriptional repression of the eotaxin gene in airway epithelial cells.