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Abstract: Background: 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. Methods: We systematically identified periostin‐dependent expression profile using DNA microarrays. We then investigated whether IL‐24 downregulates filaggrin expression downstream of the IL‐13 signals and whether IL‐13‐induced IL‐24 expression and IL‐24‐induced downregulation of filaggrin expression are dependent on the JAK/STAT pathway. To build on the significance of in vitro findings, we investigated expression of IL‐24 and activation of STAT3 in mite‐treated mice and in AD patients. Results: We identified IL‐24 as an IL‐13‐induced molecule in a periostin‐dependent manner. Keratinocytes are the main IL‐24‐producing tissue‐resident cells stimulated by IL‐13 in a periostin‐dependent manner via STAT6. IL‐24 significantly downregulated filaggrin expression via STAT3, contributing to barrier dysfunction downstream of the IL‐13/periostin pathway. Wild‐type mite‐treated mice showed significantly enhanced expression of IL‐24 and activation of STAT3 in the epidermis, which disappeared in both STAT6‐deficient and periostin‐deficient mice, suggesting that these events are downstream of both STAT6 and periostin. Moreover, IL‐24 expression was enhanced in the epidermis of skin tissues taken from AD patients. Conclusions: The IL‐13/periostin pathway induces IL‐24 production in keratinocytes, playing an important role in barrier dysfunction in AD. [ABSTRACT FROM AUTHOR]

Background We recently reported that the interaction between Lyn and Fcε RIβ is indispensable for Fcε RI-mediated human mast cell ( MC) activation and that Fcε RIβ functions as an amplifier of Fcε RI-mediated activation signal. Some of Fcε RIβ in cytoplasm appeared not to be co-localized with Fcε RIα. The function of Fcε RIβ in the cytoplasm remains unknown. Methods The localization of Fcε RIβ and Fcε RIα in giant papillae specimens from patients with allergic keratoconjunctivitis and of Fcε RIβ, Fcε RIα, and Lyn in cultured human MCs was examined using confocal microscopy. Fcε RIβ was overexpressed using an adenovirus vector system. Mediators were measured by enzyme immunoassays or enzyme-linked immunosorbent assays. Results In the subepithelial region, Fcε RIβ was mainly localized in the cell membrane of MCs. In the perivascular region, Fcε RIβ expression was scattered throughout the cytoplasm and in the cell membrane of MCs. Overexpression of Fcε RIβ in MCs mainly increased its cytoplasmic expression and slightly up-regulated cell surface Fcε RI expression. However, overexpression of Fcε RIβ in MCs resulted in down-regulation of the tyrosine phosphorylation levels of Fcε RIβ and Syk and down-regulation of the Ca2+ influx soon after Fcε RI aggregation and then resulted in down-regulation of degranulation, PGD2 synthesis, and production of a set of cytokines. This negative regulatory effect may be due to inhibition of the redistribution of Lyn to small patches within the plasma membrane. Conclusion Cytoplasmic Fcε RIβ, which is not co-localized with Fcε RIα, may function as a negative regulator, as it can capture important signalling molecules such as Lyn. [ABSTRACT FROM AUTHOR]

Background Fcε RIβ reportedly functions as an amplifier of the Fcε RIγ-mediated activation signal using a reconstitution system. However, the amplification mechanisms in human mast cells ( MCs) are poorly understood. We previously reported the hyperexpression of Fcε RIβ of MCs in giant papillae from vernal keratoconjunctivitis patients, compared with that in conjunctivae from nonallergic conjunctivitis patients. Elucidation of the molecular mechanisms of the amplification induced by Fcε RIβ should provide new targets for novel therapeutic interventions. The aim is to understand in greater details the function of Fcε RIβ in human MC Fcε RI expression and signaling. Methods Fcε RIβ and Lyn expression was reduced using a lentiviral sh RNA silencing technique. Localization of Lyn and Fcε RIβ in cultured MCs was examined by confocal microscopic analysis. Mediators were measured by ELISAs. Results The diminution of Fcε RIβ significantly downregulated cell surface Fcε RI expression and Fcε RI-mediated mediator release/production. The downregulation of Fcε RI-mediated degranulation was not only due to the decrease in Fcε RI expression. The diminution of Fcε RIβ inhibited the redistribution of Lyn within the cell membrane following Ig E sensitization. The diminution of Lyn in MCs significantly downregulated Fcε RI-mediated degranulation. The recombinant cell-penetrating forms of phosphorylated Fcε RIβ immunoreceptor tyrosine-based activation motif ( ITAM) for intracellular delivery disturbed the interaction between Lyn and phosphorylated endogenous Fcε RIβ ITAM, resulted in inhibiting Ig E-dependent histamine release from MCs in vitro and from giant papillae specimens ex vivo. Conclusion The interaction between Lyn and Fcε RIβ is indispensable for Fcε RI-mediated human MC activation, and specific inhibition of the interaction may represent a new therapeutic strategy for the treatment of human allergic diseases. [ABSTRACT FROM AUTHOR]

Activation of mast cells by lipopolysaccharide (LPS) results in the production of TNF-α and IL-13. TNF-α and IL-13 are key mediators in the development of neutrophilic and allergic inflammation, respectively. LPS-induced TNF-α and IL-13 production in mast cells has been reported to be mediated by Toll-like receptor 4 (TLR4) signalling, but differences in signal transduction mechanisms leading to the production of these cytokines are not clearly defined.We investigated the molecular mechanisms responsible for LPS-induced TNF-α and IL-13 production in mast cells.TNF-α and IL-13 production by LPS was assessed by transfecting RBL-2H3 cells with dominant-negative (DN) expression vectors.Transfection of RBL-2H3 cells with plasmids encoding DN mutants of myeloid differentiation protein (MyD88) and TNFR-associated factor (TRAF6) inhibited both LPS-induced TNF-α and IL-13 production. IκBα-DN inhibited LPS-induced production of TNF-α, but not IL-13. We also found that inhibition of p38 kinase suppressed both TNF-α and IL-13 induction by LPS, and inhibition of JNK reduced IL-13 production, but not TNF-α. Furthermore, we found that protein kinase R (PKR) was activated by LPS in these cells. Treatment with 2-aminopurine, a PKR inhibitor, attenuated LPS-induced nuclear factor-κB activation and TNF-α production, whereas inhibition of PKR had little effect on IL-13 production.These findings indicate that the production of TNF-α and IL-13 by LPS required TLR4/MyD88/TRAF6 signalling as a common pathway of mast cell-mediated inflammation. We furthermore found that TNF-α and IL-13 production were differentially regulated by signalling cascades through PKR and mitogen-activated protein kinases downstream of TRAF6 in mast cells. [ABSTRACT FROM AUTHOR]

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., (© 2019 EAACI and John Wiley and Sons A/S. Published by John Wiley and Sons Ltd.)

Background: FcεRIβ reportedly functions as an amplifier of the FcεRIγ-mediated activation signal using a reconstitution system. However, the amplification mechanisms in human mast cells (MCs) are poorly understood. We previously reported the hyperexpression of FcεRIβ of MCs in giant papillae from vernal keratoconjunctivitis patients, compared with that in conjunctivae from nonallergic conjunctivitis patients. Elucidation of the molecular mechanisms of the amplification induced by FcεRIβ should provide new targets for novel therapeutic interventions. The aim is to understand in greater details the function of FcεRIβ in human MC FcεRI expression and signaling., Methods: FcεRIβ and Lyn expression was reduced using a lentiviral shRNA silencing technique. Localization of Lyn and FcεRIβ in cultured MCs was examined by confocal microscopic analysis. Mediators were measured by ELISAs., Results: The diminution of FcεRIβ significantly downregulated cell surface FcεRI expression and FcεRI-mediated mediator release/production. The downregulation of FcεRI-mediated degranulation was not only due to the decrease in FcεRI expression. The diminution of FcεRIβ inhibited the redistribution of Lyn within the cell membrane following IgE sensitization. The diminution of Lyn in MCs significantly downregulated FcεRI-mediated degranulation. The recombinant cell-penetrating forms of phosphorylated FcεRIβ immunoreceptor tyrosine-based activation motif (ITAM) for intracellular delivery disturbed the interaction between Lyn and phosphorylated endogenous FcεRIβ ITAM, resulted in inhibiting IgE-dependent histamine release from MCs in vitro and from giant papillae specimens ex vivo., Conclusion: The interaction between Lyn and FcεRIβ is indispensable for FcεRI-mediated human MC activation, and specific inhibition of the interaction may represent a new therapeutic strategy for the treatment of human allergic diseases., (© 2012 John Wiley & Sons A/S.)