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Background: Whileβ2-adrenoceptor agonists (β2-agonists) are widely used as bronchodilators in the treatment of asthma, there has been increasing concern that regular use of β2-agonists may adversely affect the control of asthma. However, the molecular mechanisms of such undesirable effects of β2-agonists are not fully understood. In this study, we examined the effects of β2-agonists on cytokine-induced production of thymic stromal lymphopoietin (TSLP), an indispensable cytokine in the development of allergic diseases, by lung tissue cells. Methods: Normal human bronchial epithelial cells (NHBE), smooth muscle cells (BSMC) and fibroblasts (NHLF) were stimulated with the IL-4 and TNF-α cytokines, alone and in combination, and their production of TSLP was examined by ELISA. The effects of β2-agonists (salmeterol, formoterol, salbutamol), intracellular cyclic adenosine monophosphate (cAMP)-elevating agents (8-bromo-cAMP, dibutyryl cAMP, forskolin) and a corticosteroid (fluticasone) on the cytokine-induced TSLP production were examined. Results: The following results were observed in all three types of lung tissue cells tested (that is, NHBE, BSMC and NHLF). Costimulation with IL-4 and TNF-α significantly induced TSLP production, and β2-agonists further enhanced it via upregulation of intracellular cAMP. However, addition of a corticosteroid to the cytokines and β2-agonist resulted in a marked decrease in TSLP production. Conclusions: β2-Agonists significantly enhanced the cytokine-induced TSLP production by primary human lung tissue cells. This may be partly responsible for the undesirable clinical effects of continuous β2-agonist monotherapy, and combination therapy with a corticosteroid might effectively inhibit TSLP-mediated allergic inflammation.

Background Although platelets play a key role in allergic inflammation in addition to their well-established role in hemostasis, the precise mechanisms of how platelets modulate allergic inflammation are not fully understood. IL-33 is an essential regulator of innate immune responses and allergic inflammation. Objective We sought to determine the expression of IL-33 protein by platelets and its functional significance in airway inflammation. Methods IL-33 protein in human platelets, the human megakaryocyte cell line MEG-01, and bone marrow–derived mouse megakaryocytes was detected by using Western blot analysis and fluorescent immunostaining. We examined the functional relevance of IL-33 protein in platelets by comparing platelet-intact and platelet-depleted groups in a murine model of IL-33–dependent airway eosinophilia elicited by intranasal administration of papain. We further compared the additive effect of administration of platelets derived from wild-type versus IL-33–deficient mice on the papain-induced eosinophilia. Results Platelets and their progenitor cells, megakaryocytes, constitutively expressed IL-33 protein (31 kDa). Papain-induced IL-33–dependent airway eosinophilia in mice was significantly attenuated by platelet depletion. Conversely, concomitant administration of platelets derived from wild-type mice but not IL-33–deficient mice enhanced the papain-induced airway eosinophilia. Conclusions Our novel findings suggest that platelets might be important cellular sources of IL-33 protein in vivo and that platelet-derived IL-33 might play a role in airway inflammation. Therefore platelets might become an attractive novel therapeutic target for asthma and probably allergic inflammation.

Overproduction of periostin, an IL-13-inducible matricellular protein, despite corticosteroid treatment is thought to be involved in the chronicity of allergic inflammation seen in corticosteroid-refractory tissue fibrosis. Therefore, we hypothesized that some tissue cells must produce periostin in a corticosteroid-insensitive manner. Here, we show that IL-4 and IL-13 each induced comparable levels of periostin production by primary normal human fibroblasts and microvascular endothelial cells derived from lung and skin. Dexamethasone, a corticosteroid, completely inhibited IL-4/13-induced, but did not affect TGF-β-induced, periostin production by fibroblasts. In contrast, dexamethasone synergistically enhanced IL-4/13-induced periostin production by microvascular endothelial cells. TGF-β did not induce periostin production by microvascular endothelial cells. Our novel findings suggest that IL-4/13-induced microvascular endothelium-derived and/or TGF-β-induced fibroblast-derived periostin might play a pivotal role in corticosteroid-refractory tissue fibrosis, leading to chronic allergic inflammation in the lung and/or skin.

The unfolded protein response (UPR), which is induced by stress to the endoplasmic reticulum (ER), is involved in the functional alteration of certain cells, such as the differentiation of B cells to plasma cells. The aim of this study is to determine whether the UPR is activated during epidermal keratinocyte (KC) differentiation. Here, we show that the expression of the UPR-induced proteins Bip/GRP78 and HRD1 was increased in cells in the supra-basal layers of normal human epidermis that contain KCs undergoing differentiation as well as in skin-equivalent cultured KCs. However, Bip/GRP78 and HRD1 were poorly expressed in proliferating KCs in squamous cell carcinoma and psoriasis vulgaris tissues. The epidermal growth factor receptor tyrosine kinase inhibitor, PD153035, which induces KC differentiation, upregulated UPR-induced marker mRNAs and proteins. Furthermore, microarray analyses and quantitative PCR revealed that ER stress-inducing reagents, tunicamycin (TU), thapsigargin, and brefeldin A, altered the expression of genes essential for human epidermal KC differentiation, including C/EBPbeta, KLF4, and ABCA12 in vitro. However, ABCA12 and KLF4 mRNA did not increase with TU treatment after siRNA-mediated knockdown of XBP-1. Taken together, our findings strongly suggest that the UPR is activated during normal epidermal KC differentiation and induces C/EBPbeta, KLF4, and ABCA12 mRNAs.