Lipocalin‐2 exacerbates psoriasiform skin inflammation by augmenting T‐helper 17 response

Lipocalin‐2 (LCN2) is an antimicrobial protein and adipokine associated with insulin resistance, obesity and atherosclerotic disease. Psoriasis is a T‐helper (Th)1/Th17‐mediated, chronic inflammatory dermatosis related to metabolic syndromes and serum LCN2 levels are elevated in psoriatic patients. We examined the in vivo effects of LCN2 on topical imiquimod (IMQ)‐induced psoriasiform skin in BALB/c mice and in vitro on human keratinocytes (KC). Clinically, i.p. injected LCN2 exacerbated erythema and scaling in IMQ‐treated murine skin compared with phosphate‐buffered saline injection alone, and it augmented interleukin (IL)‐17A, IL‐17F, IL‐22, IL‐23p19, IL‐12p40, CCL20, tumor necrosis factor‐α, chemokine (C‐X‐C motif) ligand (CXCL)1, CXCL2, DEFB4, DEFB14, LCN2 and S100A7 mRNA levels of IMQ‐treated murine skin while it did not increase the mRNA levels of interferon‐γ, IL‐12p35 or CXCL10. LCN2 in synergy with IL‐17 increased mRNA levels of CCL20, LCN2 and DEFB4A but not of CXCL10 in human KC in vitro. These results suggest that LCN2 enhances the expression of Th17 cytokines/chemokines and antimicrobial peptides in murine IMQ‐treated psoriatic skin and KC. LCN2 may potentiate the development of psoriasis via the enhancement of Th17‐ and antimicrobial peptide‐mediated inflammation.     

Insufficient generation of Th17 cells in IL‐23p19‐deficient BALB/c mice protects against progressive cutaneous leishmaniasis

Healing of leishmaniasis—a parasitic skin disease—is associated with high levels of secreted interferon (IFN)γ and IL‐12 in resistant C57BL/6 mice and humans. Susceptible BALB/c mice predominantly react with a Th17/Th2/Treg‐related immune response and finally succumb to infection. Previously, we showed that BALB/c IL‐17A^?/? mice are protected against Leishmania (L.) major infections, indicating that IL‐17A—predominantly produced by Th17 cells—plays an important role for disease outcome. We now investigated DC‐derived cytokines and finally identified IL‐23p19 as key cytokine responsible for induction of Leishmania‐specific Th17 cells that play an important role for progressive disease in susceptible BALB/c mice.     

Malassezia‐derived aryl hydrocarbon receptor ligands enhance the CCL20/Th17/soluble CD163 pathogenic axis in extra‐mammary Paget's disease

Malassezia yeast play a role in the pathogenesis of chronic dermatitis, especially in apocrine areas, by polarizing the local immunologic background to a Th2/Th17 state through aryl hydrocarbon receptor (AhR)‐dependent pathways. Extra‐mammary Paget's disease (EMPD) is an adenocarcinoma of apocrine origin, and except for cases associated with Malassezia yeast and their metabolites, the lesions typically develop in areas not exposed to environmental material. The purpose of this study was to investigate (a) the immunomodulatory effects of Malassezia metabolites on normal human keratinocytes (NHKCs), focusing on interleukin (IL)‐17 and related cytokines/chemokines (IL‐23, IL‐36γ, CCL20), (b) the expression of these factors in lesion‐affected skin in EMPD and (c) the activation of tumor‐associated macrophages (TAMs) by these factors. Malassezia metabolites augmented the expression of cytochrome P450, family 1, subfamily A, polypeptide 1 (CYP1A1), CCL20 and IL‐36γ mRNA in NHKCs in vitro. In lesion‐affected skin of patients with EMPD, epidermal keratinocytes expressed CYP1A1 and CCL20. In addition, Paget cells expressed CCL20 and IL‐23. IL‐17–producing cells were distributed adjacent to Paget cells. Compared to healthy donors, patients with EMPD exhibited significantly increased serum levels of soluble (s)CD163, CXCL5, CXCL10 and CCL20. In addition, serum levels of sCD163 decreased significantly following tumor resection. Our study demonstrates a possible mechanism for the development of EMPD involving AhR‐mediated signalling by epidermal keratinocytes and RANKL‐induced recruitment of Th17 cells and TAMs.     

Skin barrier response to occlusion of healthy and irritated skin: Differences in trans‐epidermal water loss,erythema and stratum corneum lipids

Background. Occlusion of the skin is a risk factor for development of irritant contact dermatitis. Occlusion may, however, have a positive effect on skin healing. No consensus on the effect of occlusion has been reached. Objectives. To investigate skin barrier response to occlusion on intact and damaged skin. Methods. In study A, the response to occlusion (nitrile glove material) for either 8 hr daily for 7 days or for 72 consecutive hours, respectively, was determined and compared with that of non‐occluded skin. In study B, the response to occlusion of for 72 consecutive hours of skin that had been damaged by either sodium lauryl sulfate (SLS) or tape stripping, respectively, was determined and compared with that of to non‐occluded pre‐damaged skin. Skin barrier function was assessed by measurements of trans‐epidermal water loss (TEWL) and erythema. In study A, stratum corneum lipids were analysed. Results. Occlusion of healthy skin did not significantly influence skin barrier function, ceramide profile or the ceramide/cholesterol ratio. Occlusion of the skin after SLS irritation resulted in higher TEWL than in the control (P = 0.049). Occlusion of the skin after tape stripping resulted in lower TEWL than in control skin (P = 0.007). Conclusions. A week of occlusion did not significantly affect healthy skin, but was found to decrease healing of SLS‐damaged skin, and to improve healing of tape‐stripped skin.     

Cutaneous gene expression by DNA microarray in murine sclerodermatous graft-versus-host disease, a model for human scleroderma

The molecular mechanisms governing skin fibrosis in murine sclerodermatous graft-versus-host disease (Scl GVHD) are not known. We used Affymetrix DNA microarrays representing >14,000 mouse genes to characterize global gene expression in skin during development of Scl GVHD in lethally irradiated BALB/c (H-2d) mice transplanted with B10.D2 (H-2d) bone marrow and spleen cells. These mice develop skin thickening, whereas control mice transplanted with syngeneic BALB/c (H-2d) bone marrow and spleen cells do not develop disease. We found consistent differences between mice with Scl GVHD and controls in cytokine messenger RNAs (mRNAs) for both Th1-like (IFN-gamma) and Th2-like (IL-6, Il-10, and IL-13) inflammatory patterns. mRNAs for chemokines CCL2, CCL5, CCL17, IFN-gamma inducible chemokines (CXCL9/Mig, CXCL10/IP-10, and CXCL11/I-TAC), and for growth factors such as platelet-derived growth factor-c, connective tissue growth factor, fibroblast growth factor 1, epidermal growth factor, nerve growth factor-beta, vascular endothelial growth factor (VEGF)-alpha, and VEGF-beta were elevated, similar to human scleroderma. mRNAs for cell adhesion molecules, such as L-selectin (selectin lymphocyte), P-selectin (selectin platelet), E-selectin (selectin endothelium), and vascular cell adhesion molecule 1, were also upregulated. In separate experiments, we confirmed the increased synthesis of IFN-gamma and IL-2, unchanged IL-10, and absence of tumor necrosis factor-alpha, and IL-4 proteins by flow cytometry of isolated skin T cells. These constellations of immunologic changes provide a "fingerprint" for fibrosing autoimmune disease. They are useful to understand the pathogenesis of Scl GVHD, to identify markers for early diagnosis of disease, and to devise more effective strategies for intervention in early scleroderma and Scl GVHD.     

Proteomic analysis of stratum corneum in Cutaneous T‐Cell Lymphomas and psoriasis

Stratum corneum collected by tape stripping from 10 and 24 subjects with cutaneous T‐cell lymphomas (CTCL) or psoriasis, respectively, were compared using quantitative label‐free mass spectrometry analysis. A non‐supervised statistical analysis (Posneg NMF) based on 352 differentially expressed proteins in both CTCL and psoriasis samples was able to separate the two disease groups and finally able to identify a set of 112 proteins that contributed most and significantly to the separation when compared to non‐lesional samples. In addition, Luminex assay revealed that the increase in the amount of chemokines related to the inflammatory response, and immune cell infiltration and recruitment in lesional stratum corneum in CTCL, including CXCL8, CXCL9, CXCL10, CCL27, TNF and sICAM‐1 was in agreement with published data on entire skin biopsies. Proteome analysis using quantitative methods including mass spectrometry and Luminex technology offered the possibility to investigate the relevant protein signature in CTCL and may be helpful to diagnose and investigate the efficacy of treatments in clinical investigations using non‐invasive methods in future.     

Cannabinoid 1 receptors in keratinocytes attenuate fluorescein isothiocyanate‐induced mouse atopic‐like dermatitis

Atopic dermatitis is a chronic inflammatory disease characterized by an impaired epidermal barrier function combined with a chronic Th2‐type inflammatory response and an intense pruritus. Here, we used an experimental mouse model for Th2‐type contact hypersensitivity (CHS) to fluorescein isothiocyanate (FITC) to investigate the potential role of cannabinoid 1 receptors (CB1) in the pathophysiology of mouse atopic‐like dermatitis. Mice lacking CB1 receptors globally (Cnr1^?/?) or specifically in keratinocytes (KC‐Cnr1^?/?) as well as wild‐type (WT) control mice were sensitized and challenged with FITC. We examined ear swelling responses, transepidermal water loss, Th2‐type skin inflammatory responses and serum IgE levels. Both Cnr1^?/? and KC‐Cnr1^?/? showed enhanced CHS responses to FITC and a delayed epidermal barrier repair when compared with WT mice. mRNA levels for IL‐4, thymic stromal lymphopoietin (TSLP) and CCL8, as well as eosinophil activity, were significantly increased in inflamed ear tissue of FITC‐challenged Cnr1^?/? and KC‐Cnr1^?/? mice. Importantly, CB1 receptor‐deficient keratinocytes secreted increased levels of TSLP, a proinflammatory mediator that drives Th2‐type skin inflammation in atopic dermatitis, under basal and Th2‐type inflammatory conditions. Taken together, our results demonstrate that CB1 receptors in keratinocytes help to maintain epidermal barrier homoeostasis and attenuate Th2‐type allergic inflammatory responses. Based on our work, we propose that enhanced epidermal allergen penetrance cooperates with increased production of TSLP and CCL8 by epidermal keratinocytes for the induction of type 2 CD4+ T helper cells. Our results place keratinocytes at the cross‐roads of outside‐in and inside‐out pathophysiologic mechanisms of atopic dermatitis.     

Differential production of Th1- and Th2-type chemokines by mouse Langerhans cells and splenic dendritic cells

Some chemokines specifically attract T helper 1 (Th1) cells, whereas others attract T helper 2 (Th2) cells. In this study, we investigated the capacity of Langerhans cells (LC) to produce Th1- and Th2-type chemokines in comparison with that of splenic CD11c(+) dendritic cells (DC). We prepared highly purified (>95%) LC from BALB/c mouse skin using the panning method. With regard to Th1-type chemokines, exogenous stimulus, such as interferon-gamma (IFN-gamma), lipopolysaccharide, or polyinosinic-polycytidylic acid, was mandatory for the production of substantial amounts of CXCL10, CXCL9, and CXCL11 both in LC and splenic DC. LC, as a whole, exhibited low ability to produce Th1-type chemokines in comparison with splenic DC. As for Th2-type chemokines, LC, but not splenic DC, produced high levels of CCL22 and CCL17 constitutively during culture even without exogenous stimuli. The production of Th2-type chemokines was regulated in a complicated manner. In particular, interleukin-4 upregulated, and IFN-gamma downregulated both CCL22 and CCL17 production by LC. Of note, LC produced much more amounts of Th2-type chemokines than splenic DC under any conditions tested. Finally, Th1- and Th2-type chemokines produced by LC were shown to be functional using chemokine receptor-transfected-2B4 T cells. The high production of CC chemokine receptor 4 ligands by LC in the absence of IFN-gamma may be an important character discriminating LC from other DC.     

IL‐17A/F in Leishmania major‐resistant C57BL/6 mice

Proinflammatory IL‐17 plays an important role in various diseases and defence against extracellular microorganisms. Healing of leishmaniasis is promoted by Th1/Tc1 cells, whereas Th2/Treg are associated with worsened disease outcome. In addition, high expression of IL‐17A in Leishmania‐susceptible BALB/c and artificial overexpression of IL‐17A in T cells in resistant C57BL/6 mice worsened disease outcome. Since C57BL/6 mice lacking only IL‐17A exhibited no phenotype, and IL‐17A and IL‐17F share similar receptors, but differentially regulate chemokine secretion, we studied mice lacking both IL‐17A and IL‐17F (IL‐17A/F^?/?) in infections with Leishmania major. Interestingly, lesion volumes and parasite burdens were comparable to controls, IL‐17A/F^?/? mice developed a Th1/Tc1 phenotype, and exhibited normal lesion resolution. Thus, in C57BL/6 mice, secretion of IL‐17A and IL‐17F does not influence disease progression. It appears that—depending on the genetic background—cytokines of the IL‐17 family might be responsible for disease progression primarily in susceptible mice.     

Epidermal calcium release (ECR) in vivo sampled with a simple washout chamber technique

Background/aims: Epidermis forms the protective barrier of the skin by its outermost layer, stratum corneum. The purpose of this study was to investigate the epidermal barrier in view of epidermal calcium release (ECR), phosphate release, transepidermal water loss (TEWL) and skin surface pH. Calcium is mainly an intracellular ion. Calcium was sampled introducing a new and simple washout chamber technique for the study of epidermal release in vivo. Methods: Test sites on forearms of 13 healthy subjects were pre-treated with 24 h water occlusion, 24 h 2% sodium lauryl sulphate (SLS) or tape stripped. Both untreated and pre-treated test sites were exposed to a water washout chamber with 200µ deionized water as a solvent. Water washout chambers were removed after two hours and calcium and phosphate in the water was analyzed. Transepidermal water loss and pH were measured before and after the trial. Results: pH increased after tape stripping and after exposure to SLS. Transepidermal water loss increased significantly at all test sites. Calcium was significantly released from SLS-treated sites but not from tape stripped sites. There was generally a correlation between ECR, phosphate release, TEWL and pH. In this study ECR is showed to be a barrier marker of high reproducibility. Conclusions: Epidermal calcium release or ECR is found useful as an indicator of skin barrier function. Calcium release and increase of pH appear mainly to illustrate direct and corrosive damage to epidermal cells and functions contrasting TEWL, in this experiment probably reflecting intercellular damage of fracturing as exemplified by mechanical damage resulting from surface stripping. This new distinction of skin barrier damage into cellular damage resulting from a corrosive chemical trauma and intercellular damage and fracturing resulting from a mechanical trauma is exemplified in SLS provocative testing and tape stripping, the former characterized by increased ECR. The washout chamber technique was deemed technically reliable and reproducible, and has a major potential in experimental dermatology and skin pharmacology for the study of in vivo epidermal release of a range of endogenous and exogenous substances.     

Dermal dendritic cells,but not Langerhans cells,are critical in murine single epicutaneous sensitization

A murine repeated protein‐patch model has been established to study epicutaneous sensitization in atopic dermatitis. This model has shown a predominant Th2 and a weak Th1 response in both BALB/c and C57BL/6 mice. However, Th responses induced in the repeated model are not consistent with the generally accepted theory that BALB/c and C57BL/6 mice are Th2 and Th1 prone and are representatives of human atopy and non‐atopy, respectively. In this study, a single protein‐patch model was established, which showed in addition to the Th2 response, a remarkable Th1 response in C57BL/6 mice, but not in BALB/c mice. Moreover, using muLangerin‐DTR mice, we demonstrated that dermal dendritic cells, but not Langerhans cells, are critical in single epicutaneous sensitization in both strains of mice.     

Differential expression of inflammatory cytokines and chemokines in lipopolysaccharide‐stimulated melanocytes from lightly and darkly pigmented skin

Increasing evidence suggests that human epidermal melanocytes play an important role in the skin immune system; however, a role of their pigmentation in immune and inflammatory responses is poorly examined. In the study, the expression of Toll‐like receptor 4 (TLR4) and inflammatory cytokines and chemokines by cultured normal melanocytes derived from lightly and darkly pigmented skin was investigated after cell stimulation with lipopolysaccharide (LPS). The basal TLR4 mRNA level in heavily pigmented cells was higher as compared to their lightly pigmented counterparts. Melanocyte exposure to LPS upregulated the expression of TLR4 mRNA and enhanced the DNA‐binding activity of NF‐κB p50 and p65. We found substantial differences in the LPS‐stimulated expression of numerous genes encoding inflammatory cytokines and chemokines between the cells with various melanin contents. In lightly pigmented melanocytes, the most significantly upregulated genes were nicotinamide phosphoribosyltransferase (NAMPT/visfatin), the chemokines CCL2 and CCL20, and IL6, while the genes for CXCL12, IL‐16 and the chemokine receptor CCR4 were the most significantly upregulated in heavily pigmented cells. Moreover, the lightly pigmented melanocytes secreted much more NAMPT, CCL2 and IL‐6. The results of our study suggest modulatory effect of melanogenesis on the immune properties of normal epidermal melanocytes.     

Calcium and potassium inhibit barrier recovery after disruption, independent of the type of insult in hairless mice

Abstract Disruption of the cutaneous permeability barrier induces metabolic responses in the epidermis which result in barrier recovery. Barrier disruption by either solvent treatment or tape stripping results in the loss of the epidermal calcium gradient. Previous studies in acetone treated hairless mice have shown that maintaining this calcium gradient inhibits barrier repair, suggesting that alterations in the epidermal calcium concentration may be an important signal for barrier homeostasis. In the present study, we show that in hairless mice disruption of the barrier by treatment with the detergent. SDS, also results in the loss of the calcium gradient, as demonstrated both semi-quantitatively with ultrastructural cytochemical localization and quantitatively using proton induced X-ray emission (PIXE). Additionally, immersion in calcium containing solutions delays barrier repair after either detergent (SDS treatment) or mechanical (tape stripping) disruption of the barrier, as reported previously for acetone treated skin. These results indicate that barrier disruption, regardless of the insult, induces changes in the epidermal calcium gradient which may play an important role in signaling the metabolic changes required for barrier homeostasis.     

Effect of endothelial nitric oxide synthase on epidermal permeability barrier recovery after disruption

Background We previously demonstrated that neuronal nitric oxide synthase (nNOS) in epidermal keratinocytes is associated with epidermal permeability barrier homeostasis. Objectives In the present study, we examined the contributions of inducible nitric oxide synthase (iNOS) and endothelial nitric oxide synthase (eNOS) to epidermal permeability barrier homeostasis. Methods We measured the barrier recovery rate after tape stripping of the epidermis of iNOS and eNOS knockout mice, and carried out electron‐microscopic observation of the epidermis after acetone treatment. Results The barrier recovery rate of eNOS knockout mice was significantly faster than that of the wild‐type control, while no significant difference was observed between iNOS knockout mice and wild‐type mice. Electron‐microscopic observation at 1 h after acetone treatment indicated that barrier recovery of both nNOS and eNOS mice was faster than that of wild‐type mice, and lamellar body secretion was accelerated in both types of knockout mice. Conclusions These results suggested that both nNOS and eNOS play roles in epidermal barrier homeostasis and lamellar body secretion.     

CCL7 contributes to the TNF‐alpha‐dependent inflammation of lesional psoriatic skin

Chemokines are small chemotactic proteins that have a crucial role in leukocyte recruitment into tissue. Targeting these mediators has been suggested as a potential therapeutic option in inflammatory skin diseases such as psoriasis. Using quantitative RT‐PCR, we found CCL7, a chemokine ligand known to interact with multiple C‐C chemokine receptors, to be markedly increased in lesional psoriasis as opposed to atopic dermatitis, lichen planus, non‐lesional psoriatic and normal control skin. Surprisingly, this increase in CCL7 mRNA expression exceeded that of all other chemokines investigated, and keratinocytes and dermal blood endothelial cells were identified as its likely cellular sources. In an imiquimod‐induced psoriasis‐like mouse model, CCL7 had a profound impact on myeloid cell inflammation as well as on the upregulation of key pro‐psoriatic cytokines such as CCL20, IL‐12p40 and IL‐17C, while its blockade led to an increase in the antipsoriatic cytokine IL‐4. In humans receiving the TNF‐α‐blocker infliximab, CCL7 was downregulated in lesional psoriatic skin already within 16 hours after a single intravenous infusion. These data suggest that CCL7 acts as a driver of TNF‐α‐dependent Th1/Th17‐mediated inflammation in lesional psoriatic skin.     

Anti‐inflammatory effects of the GABAB receptor agonist baclofen in allergic contact dermatitis

Please cite this paper as: Anti‐inflammatory effects of the GABA_B receptor agonist baclofen in allergic contact dermatitis. Experimental Dermatology 2010; 19: 661–666. Abstract: The gamma amino butyric acid B (GABA_B) receptor is a G protein‐coupled receptor (GPCR) involved in synaptic transmission. Recent data indicate it to be also expressed on immune cells, along with chemokine receptors, which are also GPCRs. As GPCRs can undergo heterologous desensitization, we have examined the ability of baclofen, a GABA_B receptor selective agonist, to interfere with the function of pro‐inflammatory chemokine receptors known to be upregulated in cutaneous inflammation. In vitro, baclofen reduces chemotaxis of human peripheral blood mononuclear cells towards CCL2, CCL5, CXCL10, CXCL2 and CX3CL1 in a dose‐dependant manner. Protein kinase C inhibitors calphostin C and G0 6976 could reverse this effect, pointing towards the involvement of both calcium‐dependent and ‐independent protein kinase C in baclofen‐induced inhibition of chemokine receptors. In an in vivo model of contact hypersensitivity in C57BL/6 mice, intraperitoneal injection of baclofen markedly alleviated signs of inflammation as well as recruitment of neutrophils, monocytes and lymphocytes into the skin. This study demonstrates a new role for the GABA_B receptor in inflammation, making it a potential new therapeutic target to treat inflammatory skin diseases.     

Visualizing CD4 T‐cell migration into inflamed skin and its inhibition by CCR4/CCR10 blockades using in vivo imaging model

Background Chemokines are critical mediators of T‐cell homing into inflamed skin. The complex nature of this multicellular response makes it difficult to analyse mechanisms mediating the early responses in vivo. Objectives To visualize directly T‐cell homing into inflamed skin and its inhibition by blockades using a unique noninvasive confocal microscopy. Materials and methods A mouse model of allergic contact dermatitis was used. T cells from oxazolone‐sensitized and ‐challenged Balb/c mice were first analysed phenotypically in vitro. CD4 T cells were then labelled with a tracker dye and transferred into Balb/c‐SCID mice. The recipient mice were challenged with oxazolone and CD4 T‐cell homing into inflamed skin was visualized. Results T cells with the skin homing receptors CCR4 and CCR10 were increased in the affected skin and draining lymph nodes, and effectively attracted by their specific chemokines CCL17, CCL22 and CCL27 in vitro. Using in vivo imaging, T‐cell migration into the inflamed skin was observed at 2 h after application, peaking at 12 h and continuing for 48 h. Simultaneous systemic administration of neutralizing antibodies against CCR4 ligands (CCL17 and CCL22) and CCR10 ligand (CCL27) led to a significant suppression of T‐cell migration and skin inflammation. Conclusions Our data indicate that these tissue‐selective adhesion molecules and chemokine/receptor pathways act in concert to attract specialized T‐cell populations to mediate cutaneous inflammation. The in vivo imaging technique can be applicable to other models of cutaneous diseases to help with better understanding of the pathogenesis and monitoring the therapeutic effects.     

Olopatadine hydrochloride accelerates the recovery of skin barrier function in mice

BACKGROUND: The skin barrier function in patients with atopic dermatitis is disrupted and prolonged topical steroid therapy produces epidermal barrier disturbance. Olopatadine hydrochloride (olopatadine; Allelock; Kyowa Hakko Kogyo Co., Ltd, Shizuoka, Japan) is an antiallergic drug with histamine H(1) receptor antagonistic action. This drug alleviates skin inflammation and decreases the number of scratching episodes in a murine model of chronic contact dermatitis. OBJECTIVES: To investigate the effects of olopatadine and a steroid on the recovery of skin barrier function after barrier disruption in mice. METHODS: The skin barrier of the ears of mice was disrupted by tape stripping. The recovery of skin barrier function was monitored by measurement of transepidermal water loss (TEWL) after barrier disruption. Epidermal hyperplasia was induced by repeated tape stripping for 7 days. Olopatadine was administered orally once daily from 3 days before the first barrier disruption. Betamethasone 17-valerate (betamethasone) was applied topically once daily from 3 days before barrier disruption. RESULTS: Tape stripping led to a significant increase in TEWL. TEWL decreased with time after tape stripping and the skin barrier function recovered by over 60% within 9 h after tape stripping. The recovery of skin barrier in olopatadine-treated mice was significantly accelerated, compared with that in vehicle-treated mice. In contrast, the skin barrier recovery in mice treated with topical betamethasone was significantly delayed, compared with that in vehicle-treated mice. Combined treatment with olopatadine and betamethasone ameliorated the delay in barrier recovery induced by topical treatment with betamethasone. In addition, olopatadine significantly prevented the increase in epidermal thickness induced by prolonged barrier disruption. CONCLUSIONS: These results suggest that systemic administration of olopatadine accelerates the recovery of skin barrier function and ameliorates the adverse effects of topical steroids on skin barrier recovery.