Tomohito Yoshihara

Periostin in inflammation and allergy

We found for the first time that IL-4 and IL-13, signature type 2 cytokines, are able to induce periostin expression. We and others have subsequently shown that periostin is highly expressed in chronic inflammatory diseases―asthma, atopic dermatitis, eosinophilc chronic sinusitis/chronic rhinosinusitis with nasal polyp, and allergic conjunctivitis—and that periostin plays important roles in the pathogenesis of these diseases. The epithelial/mesenchymal interaction via periostin is important for the onset of allergic inflammation, in which periostin derived from fibroblasts acts on epithelial cells or fibroblasts, activating their NF-κB. Moreover, the immune cell/non-immune cell interaction via periostin may be also involved. Now the significance of periostin has been expanded into other inflammatory or fibrotic diseases such as scleroderma and pulmonary fibrosis. The cross-talk of periostin with TGF-β or pro-inflammatory cytokines is important for the underlying mechanism of these diseases. Because of its pathogenic importance and broad expression, diagnostics or therapeutic drugs can be potentially developed to target periostin as a means of treating these diseases.

Clarithromycin attenuates IL-13–induced periostin production in human lung fibroblasts

BackgroundPeriostin is a biomarker indicating the presence of type 2 inflammation and submucosal fibrosis; serum periostin levels have been associated with asthma severity. Macrolides have immunomodulatory effects and are considered a potential therapy for patients with severe asthma. Therefore, we investigated whether macrolides can also modulate pulmonary periostin production.MethodsUsing quantitative PCR and ELISA, we measured periostin production in human lung fibroblasts stimulated by interleukin-13 (IL-13) in the presence of two 14-member–ring macrolides—clarithromycin or erythromycin—or a 16-member–ring macrolide, josamycin. Phosphorylation of signal transducers and activators of transcription 6 (STAT6), downstream of IL-13 signaling, was evaluated by Western blotting. Changes in global gene expression profile induced by IL-13 and/or clarithromycin were assessed by DNA microarray analysis.ResultsClarithromycin and erythromycin, but not josamycin, inhibited IL-13–stimulated periostin production. The inhibitory effects of clarithromycin were stronger than those of erythromycin. Clarithromycin significantly attenuated STAT6 phosphorylation induced by IL-13. Global gene expression analyses demonstrated that IL-13 increased mRNA expression of 454 genes more than 4-fold, while decreasing its expression in 390 of these genes (85.9%), mainly “extracellular,” “plasma membrane,” or “defense response” genes. On the other hand, clarithromycin suppressed 9.8% of the genes in the absence of IL-13. Clarithromycin primarily attenuated the gene expression of extracellular matrix protein, including periostin, especially after IL-13.ConclusionsClarithromycin suppressed IL-13–induced periostin production in human lung fibroblasts, in part by inhibiting STAT6 phosphorylation. This suggests a novel mechanism of the immunomodulatory effect of clarithromycin in asthmatic airway inflammation and fibrosis.

Induction of airway allergic inflammation by hypothiocyanite via epithelial cells.

Hypothiocyanite (OSCN−) serves as a potent innate defense system against microbes in the lungs. OSCN− is generated by the catalysis of peroxidases using thiocyanate transported via several anion transporters, including pendrin/SLC26A4 and hydrogen peroxide (H2O2) generated by Duox1 and Duox2. We previously demonstrated that expression of pendrin, peroxidases, and Duox1/Duox2 is up-regulated in bronchial asthma patients and/or asthma model mice and that these molecules are important in accelerating airway inflammation. However, it remained unclear how activating these molecules would lead to airway inflammation. In this study, we examined whether OSCN− produced via the pendrin/peroxidase/Duox pathway causes inflammation via airway epithelial cells. In an in vitro OSCN− production system, OSCN−, but not H2O2, activated NF-κB, a transcription factor critical for inflammatory responses, in the airway epithelial cells. OSCN− was sensed by protein kinase A (PKA) followed by formation of the dimerization of PKA. The dimerized PKA, the active form, was critical in activating NF-κB. Detoxifying H2O2, mainly by catalase, enabled the dominant abilities of OSCN− to dimerize PKA and activate NF-κB, compared with untreated H2O2. Furthermore, OSCN− in high doses caused necrosis of the cells, inducing release of IL-33, a trigger to initiate type 2 inflammation. These results demonstrate that OSCN− in low doses activates NF-κB via PKA in airway epithelial cells, whereas OSCN− in high doses causes necrosis, suggesting an important role in airway allergic inflammation for the production of OSCN− via the pendrin/peroxidase/Duox pathway.

The Role of Pendrin in the Airways: Links with Asthma and COPD

Interleukin (IL)-4 and IL-13 are related cytokines correlated with type 2 immunity involved in the pathogenesis of bronchial asthma. Pendrin is induced by IL-4 or IL-13 in airway epithelial cells and is highly expressed in the lung tissues of asthma model mice or asthma patients. The signal transducer and activator of transcription (STAT) 6, the critical transcriptional factor for IL-4 or IL-13 signals, is required for IL-4– or IL-13–induced pendrin expression. Although the pathological roles of pendrin have been confirmed by the analyses of model mice, the underlying mechanisms are still unclear. Furthermore, pendrin has a potential to be correlated with other pulmonary diseases—chronic obstructive pulmonary disease, environmental chemical compound–exposed diseases or infectious diseases. In addition to these detrimental effects in pathological settings, the physiological role of pendrin in the lung, such as promoting antimicrobial activity, may be protective. Thus, whereas pendrin inhibition appears as a promising therapeutic strategy to treat asthma and other chronic respiratory diseases, it will be important to evaluate the effect of this inhibition in the lungs and other organs.

Hierarchical control of IL-13 signals in lung fibroblasts by STAT6 and SOX11

Interleukin (IL)-13 is a signature cytokine of type 2 inflammation important for the pathogenesis of various diseases, including allergic diseases. Signal transducer and activator of transcription (STAT) 6 is a critical transcriptional factor for the IL-13 signals; however, it remains unknown how expression of the IL-13–induced genes is differentiated by the transcriptional machineries. In this study, we identified IL-13–induced transcriptional factors in lung fibroblasts using DNA microarrays in which SOX11 was included. Knockdown of SOX11 down-regulated expression of periostin and CCL26, both of which are known to be downstream molecules of IL-13, whereas enforced expression of SOX11 together with IL-13 stimulation enhanced expression of periostin. Moreover, we found that in DNA microarrays combining IL-13 induction and SOX11 knockdown there exist both SOX11-dependent and -independent molecules in IL-13–inducible molecules. In the former, many inflammation-related and fibrosis-related molecules, including periostin and CCL26, are involved. These results suggest that SOX11 acts as a trans-acting transcriptional factor downstream of STAT6 and that in lung fibroblasts the IL-13 signals are hierarchically controlled by STAT6 and SOX11.

The IL-13/periostin/IL-24 pathway causes epidermal barrier dysfunction in allergic skin inflammation

Barrier dysfunction is an important feature of atopic dermatitis (AD) in which IL‐4 and IL‐13, signature type 2 cytokines, are involved. Periostin, a matricellular protein induced by IL‐4 or IL‐13, plays a crucial role in the onset of allergic skin inflammation, including barrier dysfunction. However, it remains elusive how periostin causes barrier dysfunction downstream of the IL‐13 signal.

The Significance of Hypothiocyanite Production via the Pendrin/DUOX/Peroxidase Pathway in the Pathogenesis of Asthma.

Inhaled corticosteroids (ICSs) are used as first-line drugs for asthma, and various novel antiasthma drugs targeting type 2 immune mediators are now under development. However, molecularly targeted drugs are expensive, creating an economic burden on patients. We and others previously found pendrin/SLC26A4 as a downstream molecule of IL-13, a signature type 2 cytokine critical for asthma, and showed its significance in the pathogenesis of asthma using model mice. However, the molecular mechanism of how pendrin causes airway inflammation remained elusive. We have recently demonstrated that hypothiocyanite (OSCN−) produced by the pendrin/DUOX/peroxidase pathway has the potential to cause airway inflammation. Pendrin transports thiocyanate (SCN−) into pulmonary lumens at the apical side. Peroxidases catalyze SCN− and H2O2 generated by DUOX into OSCN−. Low doses of OSCN− activate NF-κB in airway epithelial cells, whereas OSCN− in high doses causes necrosis of the cells, inducing the release of IL-33 and accelerating inflammation. OSCN− production is augmented in asthma model mice and possibly in some asthma patients. Heme peroxidase inhibitors, widely used as antithyroid agents, diminish asthma-like phenotypes in mice, indicating the significance of this pathway. These findings suggest the possibility of repositioning antithyroid agents as antiasthma drugs.