Periostin activates distinct modules of inflammation and itching downstream of the type 2 inflammation pathway.

Atopic dermatitis (AD) is a chronic relapsing skin disease accompanied by recurrent itching. Although type 2 inflammation is dominant in allergic skin inflammation, it is not fully understood how non-type 2 inflammation co-exists with type 2 inflammation or how type 2 inflammation causes itching. We have recently established the FADS mouse, a mouse model of AD. In FADS mice, either genetic disruption or pharmacological inhibition of periostin, a downstream molecule of type 2 inflammation, inhibits NF-κB activation in keratinocytes, leading to downregulating eczema, epidermal hyperplasia, and infiltration of neutrophils, without regulating the enhanced type 2 inflammation. Moreover, inhibition of periostin blocks spontaneous firing of superficial dorsal horn neurons followed by a decrease in scratching behaviors due to itching. Taken together, periostin links NF-κB-mediated inflammation with type 2 inflammation and promotes itching in allergic skin inflammation, suggesting that periostin is a promising therapeutic target for AD.

A Positive Loop Formed by SOX11 and Periostin Upregulates TGF-ß Signals Leading to Skin Fibrosis.

Systemic sclerosis (SSc) is a chronic, heterogeneous disease of connective tissue characterized by organ fibrosis together with vascular injury and autoimmunity. TGF-ß plays a central role in generating fibrosis, including SSc. Periostin is a matricellular protein playing a key role in the generation of fibrosis by amplifying the TGF-ß signals. SOX11 is a transcription factor playing several important roles in organ development in embryos. We have previously shown that SOX11 induces periostin expression. However, the roles of the interactions among the TGF-ß signals, periostin, and SOX11 remain unknown in the pathogenesis of SSc. In this study, we found that most clones of dermal fibroblasts derived from patients with SSc showed constitutive, high expression of SOX11, which is significantly induced by TGF-ß1. SOX11 forms a positive loop with periostin to activate the TGF-ß signals in SSc dermal fibroblasts. Genetic deletion of Sox11 in Postn-expressing fibroblasts impairs dermal fibrosis by bleomycin. Moreover, using the DNA microarray method, we identified several fibrotic factors dependent on the TGF-ß/SOX11/periostin pathway in SSc dermal fibroblasts. Our findings, taken together, show that a positive loop formed by SOX11 and periostin in fibroblasts upregulates the TGF-ß signals, leading to skin fibrosis.

Establishment of a novel ELISA system for measuring periostin independently of formation of the IgA complex.

BACKGROUND: Periostin, a matricellular protein that modulates cell functions having various pathophysiological roles, has the potential to be a useful biomarker for various diseases. We recently found that periostin forms a complex with IgA in human serum, which may affect the periostin measurement. METHODS: We investigated (1) whether the formation of the periostin-IgA complex affects the original periostin ELISA system, decreasing the values of serum periostin? (2) bow each domain of periostin affects periostin measurement by the original periostin ELISA system? (3) whether we can establish a novel ELISA system that is not affected by formation of the IgA complex? RESULTS: The periostin value at the reducing condition was significantly higher than that of the non-reducing condition, demonstrating that formation of the IgA complex affects periostin measurement. The monoclonal antibodies (mAbs) for periostin recognizing the EMI and R1 domains immunoprecipitated serum periostin in the reducing condition more than in the non-reducing condition, whereas the mAbs recognizing the R2 or R3 domain immunoprecipitated comparable amounts of serum periostin in the reducing and non-reducing conditions, suggesting the EMI and R1 domains contribute to formation of the complex with IgA. Using SS16A recognizing the R3 domain combined with SS17B recognizing the R4 domain, we established an ELISA system that was able to measure periostin independently of the IgA complex. CONCLUSIONS: We have established a novel ELISA system that measures periostin independently of the IgA complex. This system is promising in identifying periostin as a biomarker for various diseases.

The FADS mouse: A novel mouse model of atopic keratoconjunctivitis.

BACKGROUND: Atopic keratoconjunctivitis (AKC) is a chronic allergic conjunctival disease. However, a mouse model of AKC to investigate the underlying mechanism of the therapeutic agents and estimate their efficacy has not been established. We recently generated mice in which Ikk2 is specifically deleted in facial skin fibroblasts and found that these mice spontaneously develop atopic dermatitis (AD)-like facial skin inflammation and scratching behaviors; thus, we named them facial AD with scratching (FADS) mice. OBJECTIVE: We sought to evaluate whether the ocular lesions that FADS mice spontaneously develop are similar to those of patients with AKC and to estimate the efficacy of topical treatments with tacrolimus and betamethasone for FADS mice by using tear periostin, a novel biomarker for allergic conjunctival disease. METHODS: FADS mice, in which Ikk2 is deleted in dermal fibroblasts, were generated by crossing female Ikk2Flox/Flox mice to male Nestincre; Ikk2Flox/+ mice. We conducted histologic analysis of the ocular lesions in FADS mice. Furthermore, we measured periostin in the tears collected from FADS mice untreated or treated with tacrolimus or betamethasone. RESULTS: The FADS mice exhibited severe blepharitis and scratch behaviors for their faces. In these mice, corneal epithelium and stroma showed hyperplasia and infiltration of eosinophils, mast cells, and TH2/TC2 cells. Periostin was significantly expressed in the lesions and tear periostin was upregulated. Betamethasone showed more suppressive effects than did tacrolimus on severe corneal lesions and increased tear periostin level. CONCLUSIONS: The FADS mouse is a novel mouse model of AKC and is useful to examine the therapeutic effects of anti-AKC agents.

Epithelial SOX11 regulates eyelid closure during embryonic eye development.

Fibroblast growth factor (FGF10)-mediated signals are essential for embryonic eyelid closure in mammals. Systemic SOX11-deficient mice are born with unclosed eyelids, suggesting a possible role of SOX11 in eyelid closure. However, the underlying mechanisms of this process remain unclear. In this study, we show that epithelial deficiency of SOX11 causes a defect in the extension of the leading edge of the eyelid, leading to failure of embryonic eyelid closure. c-Jun in the eyelid is a transcription factor downstream of FGF10 required for the extension of the leading edge of the eyelid, and c-Jun level was decreased in epithelial SOX11-deficient embryos. These results suggest that epithelial SOX11 plays an important role in embryonic eyelid closure.

Periostin plays a critical role in the cell cycle in lung fibroblasts.

BACKGROUND: Idiopathic pulmonary fibrosis (IPF) is a devastating disease with a median survival of only three to 5 years. Fibroblast proliferation is a hallmark of IPF as is secretion of extracellular matrix proteins from fibroblasts. However, it is still uncertain how IPF fibroblasts acquire the ability to progressively proliferate. Periostin is a matricellular protein highly expressed in the lung tissues of IPF patients, playing a critical role in the pathogenesis of pulmonary fibrosis. However, it remains undetermined whether periostin affects lung fibroblast proliferation. METHODS: In this study, we first aimed at identifying periostin-dependently expressed genes in lung fibroblasts using DNA microarrays. We then examined whether expression of cyclins and CDKs controlling cell cycle progression occur in a periostin-dependent manner. We next examined whether downregulation of cell proliferation-promoting genes by knockdown of periostin or integrin, a periostin receptor, using siRNA, is reflected in the cell proliferation of lung fibroblasts. We then looked at whether lung fibroblasts derived from IPF patients also require periostin for maximum proliferation. We finally investigated whether CP4715, a potent inhibitor against integrin αVß3 (a periostin receptor), which we have recently found blocks TGF-ß signaling, followed by reduced BLM-induced pulmonary fibrosis in mice, can block proliferation of lung fibroblasts derived from IPF patients. RESULTS: Many cell-cycle-related genes are involved in the upregulated or downregulated genes by periostin knockdown. We confirmed that in lung fibroblasts, periostin silencing downregulates expression of several cell-cycle-related molecules, including the cyclin, CDK, and, E2F families, as well as transcription factors such as B-MYB and FOXM1. Periostin or integrin silencing slowed proliferation of lung fibroblasts and periostin silencing increased the distribution of the G0/G1 phase, whereas the distribution of the G2/M phase was decreased. Lung fibroblasts derived from IPF patients also required periostin for maximum proliferation. Moreover, CP4715 downregulated proliferation along with expression of cell-cycle-related genes in IPF lung fibroblasts as well as in normal lung fibroblasts. CONCLUSIONS: Periostin plays a critical role in the proliferation of lung fibroblasts and the present results provide us a solid basis for considering inhibitors of the periostin/integrin αVß3 interaction for the treatment of IPF patients.

Cross-Talk between Transforming Growth Factor-ß and Periostin Can Be Targeted for Pulmonary Fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a devastating disease characterized as progressive and irreversible fibrosis in the interstitium of lung tissues. There is still an unmet need to develop a novel therapeutic drug for IPF. We have previously demonstrated that periostin, a matricellular protein, plays an important role in the pathogenesis of pulmonary fibrosis. However, the underlying mechanism of how periostin causes pulmonary fibrosis remains unclear. In this study, we sought to learn whether the cross-talk between TGF-ß (transforming growth factor-ß), a central mediator in pulmonary fibrosis, and periostin in lung fibroblasts leads to generation of pulmonary fibrosis and whether inhibitors for integrin αVß3, a periostin receptor, can block pulmonary fibrosis in model mice and the TGF-ß signals in fibroblasts from patients with IPF. We found that cross-talk exists between TGF-ß and periostin signals via αVß3/ß5 converging into Smad3. This cross-talk is necessary for the expression of TGF-ß downstream effector molecules important for pulmonary fibrosis. Moreover, we identified several potent integrin low-molecular-weight inhibitors capable of blocking cross-talk with TGF-ß signaling. One of the compounds, CP4715, attenuated bleomycin-induced pulmonary fibrosis in vivo in mice and the TGF-ß signals in vitro in fibroblasts from patients with IPF. These results suggest that the cross-talk between TGF-ß and periostin can be targeted for pulmonary fibrosis and that CP4715 can be a potential therapeutic agent to block this cross-talk.

Periostin forms a functional complex with IgA in human serum.

BACKGROUND: Periostin is a matricellular protein belonging to the fasciclin family, playing a role for the pathogenesis of allergic diseases by binding to integrins on cell surfaces. Serum periostin is elevated in various allergic diseases reflecting type 2 inflammation and tissue remodeling so that for allergic diseases, periostin is expected to be a novel biomarker for diagnosis, assessing severity or prognosis, and predicting responsiveness to treatments. We have previously shown that most serum periostin exists in the oligomeric form by intermolecular disulfide bonds. METHODS: In this study, we examined how periostin forms a complex in serum, whether the periostin complex in serum is functional, and whether the complex formation interferes with reactivity to anti-periostin Abs. RESULTS: We found that periostin formed a complex with IgA1 at a 1:1 ratio. The periostin in the serum complex contained at least five different isoforms. However, IgA was not essential for the oligomeric formation of periostin in mouse serum or in IgA-lacking serum. The periostin-IgA complex in human serum was functional, sustaining the ability to bind to αVß3 integrin on cell surfaces. Moreover, periostin formed the complex with IgA broadly, which interferes the binding of the Abs recognizing all of the domains except the R4 domain to periostin. CONCLUSIONS: Periostin is a novel member of the IgA-associated molecules. These results are of great potential use to understand the pathological roles of periostin in allergic diseases and, from a practical standpoint, to develop diagnostics or therapeutic agents against periostin.

Periostin: An emerging biomarker for allergic diseases.

Periostin is a matricellular protein as well as an extracellular matrix (ECM) protein belonging to the fasciclin family. Periostin plays important roles as a matricellular protein in the setting of allergic diseases by binding to several integrins on various cells. Since periostin is induced mainly by IL-4 and IL-13, signature type 2 cytokines, and it is highly expressed in the subepithelial regions of many chronic allergic diseases, periostin has emerged as a novel biomarker reflecting type 2 inflammation in allergic diseases. It has, moreover, been revealed that periostin has characteristics different from other type 2 biomarkers such as eosinophil count and fractional exhaled nitric oxide (FeNO), reflecting fibrosis or tissue remodeling. From this, we may say that serum periostin is a "chronic" type 2 biomarker, whereas FeNO and possibly the eosinophil count are "acute" type 2 biomarkers. In contrast, it is still uncertain how we can apply periostin measurement to the use of biologics for allergic diseases. By examining the roles of periostin in allergy and the utility and potential of periostin in developing diagnostics against allergic diseases, it is hoped that in the near future, we can develop a new strategy to treat allergic patients.

Establishment of a Mouse Model of Atopic Dermatitis by Deleting Ikk2 in Dermal Fibroblasts.

Atopic dermatitis is a chronic inflammatory skin disease with persistent pruritus. To clarify its molecular mechanism, it is important to establish a mouse model similar to the phenotypes of atopic dermatitis patients, particularly in exhibiting scratching behavior. Ikk2, a component of the IκB kinase complex, exerts pro-inflammatory responses, whereas its deficiency in keratinocytes paradoxically causes skin inflammation. In this study, we sought to generate a mouse model exhibiting skin inflammation by which dermal fibroblasts lack Ikk2 expression and evaluate whether cutaneous inflammatory phenotypes are similar to those of atopic dermatitis patients. To generate Ikk2-deficient mice (Nestincre;Ikk2FL/FL) in which Ikk2 is deleted in dermal fibroblasts, we crossed female Ikk2FL/FL mice to male Nestincre;Ikk2FL/+mice. These mice spontaneously developed skin inflammation limited to the face, with the appearance of Ikk2-deficient fibroblasts in the facial skin. These mice showed phenotypes similar to those of atopic dermatitis patients, including scratching behaviors, which are resistant to immunosuppressive or molecularly targeted drugs. These findings suggest that the Nestincre;Ikk2FL/FL mouse is an atopic dermatitis model that will be useful in clarifying atopic dermatitis pathogenesis and in developing a novel therapeutic agent for atopic dermatitis symptoms.

A newly isolated Pex7-binding, atypical PTS2 protein P7BP2 is a novel dynein-type AAA+ protein.

A newly isolated binding protein of peroxisomal targeting signal type 2 (PTS2) receptor Pex7, termed P7BP2, is transported into peroxisomes by binding to the longer isoform of Pex5p, Pex5pL, via Pex7p. The binding to Pex7p and peroxisomal localization of P7BP2 depends on the cleavable PTS2 in the N-terminal region, suggesting that P7BP2 is a new PTS2 protein. By search on human database, three AAA+ domains are found in the N-terminal half of P7BP2. Protein sequence alignment and motif search reveal that in the C-terminal region P7BP2 contains additional structural domains featuring weak but sufficient homology to AAA+ domain. P7BP2 behaves as a monomer in gel-filtration chromatography and the single molecule observed under atomic force microscope shapes a disc-like ring. Collectively, these results suggest that P7BP2 is a novel dynein-type AAA+ family protein, of which domains are arranged into a pseudo-hexameric ring structure.

Hierarchical control of interleukin 13 (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.

Squamous Cell Carcinoma Antigen 2 (SCCA2, SERPINB4): An Emerging Biomarker for Skin Inflammatory Diseases.

Squamous cell carcinoma antigens 1 and 2 (SCCA1 and 2, SERPIN B3 and B4), members of the ovalbumin serpin (ov-serpin)/clade B serpin family, were originally discovered as tumor-specific antigens and are used as tumor markers for various kinds of squamous cell carcinomas. Recently, our understanding of the underlying mechanisms of how SCCA1/2 enhance tumor growth has greatly increased. Moreover, it has been shown that SCCA1/2 are involved in the pathogenesis of several inflammatory diseases: asthma, psoriasis, and atopic dermatitis (AD). IL-22 and IL-17, signature cytokines of type 17 inflammation, as well as IL-4 and IL-13, signature cytokines of type 2 inflammation, both of which are positively correlated with the pathogenesis of psoriasis and allergic diseases, respectively, can induce expression of SCCA1/2 in airway epithelial cells and/or keratinocytes, leading to high expression of SCCA1/2 in these diseases. Based on these findings, several trials have been performed to examine the potential of applying SCCA1/2 to biomarkers for these diseases. The findings show that SCCA2 is useful to aid diagnosis, estimate clinical severity and disease type, and assess responses to treatment in psoriasis and AD. These results suggest that SCCA2 has emerged as a novel biomarker for skin inflammatory diseases.

Constitutive overexpression of periostin delays wound healing in mouse skin.

Periostin is a matricellular protein involved in development, maintenance, and regulation of tissues and organs via by binding to cell surface integrin receptors. Pathologically, periostin plays an important role in the process of wound healing: as a deficiency of the Postn gene delays wound closure and periostin is consistently up-regulated in response to injury and skin diseases. However, the functional role of elevated periostin in the process of wound healing has not been tested. In this study, we generated Postn-transgenic mice under the control of the CAG promoter/enhancer to investigate the effects of constitutive overexpression of full length periostin during its pathophysiological roles. Transgenic mice showed significant overexpression of periostin in skin, lung, and heart, but no morphological changes were observed. However, when these transgenic mice were injured, periostin overexpression delayed the closure of excisional wounds. Expression of IL-1ß and TNFα, pro-inflammatory cytokines important for wound healing, was significantly decreased in the transgenic mice, prior to delayed healing. Infiltration of neutrophils and macrophages, the main sources of IL-1ß and TNFα, was also down-regulated in the transgenic wound sites. From these data, we conclude that enforced expression of periostin delays wound closure due to reduced infiltration of neutrophils and macrophages followed by down-regulation of IL-1ß and TNFα expression. This suggests that regulated spatiotemporal expression of periostin is important for efficient wound healing and that constitutive periostin overexpression interrupts the normal process of wound closure.

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-ß 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.

BACKGROUND: Periostin 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. METHODS: Using 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. RESULTS: Clarithromycin 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. CONCLUSIONS: Clarithromycin 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.

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.

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.