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Atopic dermatitis is a common skin disease caused by genetic susceptibility, environmental factors, immune response, and skin barrier dysfunction. Kaempferol is a natural flavonoid widely found in tea, vegetables, and fruits and has been reported to have excellent anti-inflammation activity. However, the therapeutic effect of kaempferol on atopic dermatitis is unclear. This study aimed to elucidate the effect of kaempferol on skin inflammation in atopic dermatitis. The suppressive effect of kaempferol administration on skin inflammation was examined using MC903-induced atopic dermatitis-like skin inflammation mouse model. Quantification of skin dermatitis and transepidermal water loss was performed. A histopathological study was performed to examine thymic stromal lymphopoietin expression, cornified envelope proteins such as filaggrin, loricrin, and involucrin, and the numbers of infiltrating inflammatory cells, including lymphocytes, macrophages, and mast cells in the dermatitis area. The expressions of IL-4 and IL-13 were investigated by qPCR and flow cytometry analysis using skin tissues. The expression of HO-1 was investigated by western blot and qPCR. Kaempferol therapy significantly suppressed MC903-induced dermatitis, TEWL, TSLP, and HO-1 expression, and infiltration of inflammatory cells. Kaempferol therapy improved the decreased expressions of filaggrin, loricrin, and involucrin in MC903-induced dermatitis skin site. The expressions of IL-4, and IL-13 were partially decreased in kaempferol-treated mice. Kaempferol might improve MC903-induced dermatitis via suppression of type 2 inflammation and improvement of barrier dysfunction by inhibition of TSLP expression and oxidative stress. Kaempferol might have the potential to be a new treatment for atopic dermatitis. • Kaempferol improved AD-like dermatitis in mouse. • Kaempferol inhibited TSLP expression in AD mouse model. • Kaempferol inhibited oxidative stress in AD mouse model. • Kaempferol suppressed type 2 inflammation in AD mouse model. [ABSTRACT FROM AUTHOR]

The "itch-scratch cycle" is a clinically well-known cause of exacerbation of atopic dermatitis (AD), but the underlying molecular mechanisms remain largely unknown. To test our hypothesis that some molecules released from damaged epidermal keratinocytes by scratching inducetype 2 responses in intact skin dermal cells, leading to exacerbation of AD. Normal human dermal fibroblasts (NHDF) and human dermal blood microvascular endothelial cells (HMVEC-dBl) were treated with an epidermal keratinocyte homogenate (EKH). We used qPCR and ELISA, respectively, to measure the mRNA expressions and protein concentrations of various cytokines, including IL-6, IL-8, thymic stromal lymphopoietin (TSLP), and IL-33. We analyzed IL-33 protein expression in the nuclear fractions of NHDF by Western blotting. We also investigated the effects of IL-1R1 gene-silencing and several AD therapeutic drugs on EKH induction of cytokine production by the dermal cells. EKH significantly induced IL-6 and IL-8 in NHDF and HMVEC-dBl. EKH also induced type 2 cytokines, TSLP and IL-33, in NHDF. IL-1R1 gene-silencing in NHDF partially attenuated the induction. Dexamethasone (a corticosteroid) significantly inhibited, while ABT494 (a JAK1 inhibitor) partially inhibited, EKH's induction of cytokines in fibroblasts. In contrast, ABT494 was more effective than dexamethasone in inhibiting the cytokine induction in HMVEC-dBl. This study showed that a homogenate of epidermal keratinocytes significantly induced AD-related cytokines in cultured dermal cells, and IL-1α, an alarmin, might be involved in that induction. Combined use of corticosteroids and JAK1 inhibitors is likely to block the itch-scratch cycle by targeting different types of dermal cells. • The "itch-scratch cycle" is a clinically well-known cause of exacerbation of atopic dermatitis (AD). • A homogenate of epidermal keratinocytes significantly induced AD-related cytokines in dermal cells. • IL-1α, an alarmin, might be partially involved in that induction. • Corticosteroids are effective in suppressing fibroblasts' inflammation due to disruption of keratinocytes by scratching. • In contrast, JAK1 inhibitors may effectively suppress vascular endothelial cells' role in dermal inflammation. [ABSTRACT FROM AUTHOR]

• PM2.5 facilitated IgE-mediated degranulation and increased cytokines expression in mast cells. • PM2.5 raised Gadd45b-induced activation of the MEKK4/JNK signaling pathway. • JNK1/2-specific inhibitor SP600125 blocked IgE-mediated mast cell activation and cytokine release. • PM2.5 increased the ROS level and ROS inhibitor blocked the PM2.5-induced ROS production. • ROS inhibitor reversed the PM2.5-mediated gene expression in the mitochondrial respiratory chain. Mast cells play an important role in allergic responses and persistently exposure to environmental fine particulate matter (PM2.5) exacerbates allergic diseases,but the details remained elucidative. To investigate the effect of PM2.5 on IgE-mediated mast cell responses through an IgE-mediated mouse model and mast cell activation. The β-hexosaminidase release and a BALB/c model of passive cutaneous anaphylaxis (PCA) was used to test IgE-mediated mast cells activation in vitro and in vivo. RNA-Seq technique was conducted to study the gene expression profile. Reactive oxygen species (ROS) production was measured by flow-cytometry. RT-PCR,WB and ELISA were performed to examine targeting molecules expression. PM2.5 facilitated IgE-mediated degranulation and increased cytokines expression in mast cells. Meanwhile, the Evan's blue extravasation as well as serum cytokines in mice was increased after treatment with PM2.5. Furthermore, PM2.5 treatment dramatically increased the expression of Gadd45b which is an oxidative stress molecule that directly activates down-stream pathway, such as MEKK4/JNK. PM2.5 treatment activated MEKK4, JNK1/2 but not ERK1/2 and p38. Meanwhile, Knockdown of Gadd45b significantly attenuated PM2.5-mediated JNK1/2 activation and expression of cytokines. In addition, a JNK1/2-specific inhibitor SP600125 blocked IgE-mediated mast cell activation and cytokine release in PCA model mice. Moreover, PM2.5 treatment increased the ROS level and ROS inhibitor dramatically blocked the PM2.5-induced ROS production and reversed the PM2.5-mediated gene expression in the mitochondrial respiratory chain. PM2.5 regulates ROS production through Gadd45b/MEKK4/JNK pathway, facilitating IgE-mediated mast cell activation. [ABSTRACT FROM AUTHOR]

• CIS1, a member of SOCS/CIS family, is expressed by Th2 cytokines in keratinocytes. • Expression of CIS1 was enhanced in the epidermis of atopic dermatitis. • CIS1 selectively attenuated IL-17A-induced CCL20 production via inhibition of ERK. • The Src family kinase Yes was the upstream activator of ERK in IL-17R signaling. • CIS1 changes the response to IL-17A by suppression of Src family kinase. Lesions of atopic dermatitis have fewer Th17 cells than those of psoriasis, resulting in frequent skin infections. Expression of CCL20, a chemokine that is important for recruiting Th17 cells, is suppressed in the lesions of atopic dermatitis. We previously reported that IL-4 induces the expression of cytokine-inducible SH2-containing protein 1 (CIS1), a member of the CIS/SOCS family, in epidermal keratinocytes. To investigate whether CIS1 influences CCL20 production in epidermal keratinocytes. Expression of CIS1 was examined in atopic dermatitis skin and in cultured keratinocytes. The effects of overexpression of CIS1 on CCL20 production by IL-17A, and on signaling pathways inhibited by CIS1, were assessed in vitro. Expression of CIS1 was enhanced in the basal layer of the lesional epidermis of skin with atopic dermatitis. When CIS1 was expressed in keratinocytes using adenoviral vectors, IL-17A-induced CCL20 expression, but not HBD2 or S100A7 expression, was significantly suppressed. TNF-α/IL-1-induced CCL20 production was not altered by CIS1. Overexpression of CIS1 attenuated IL-17A-induced ERK phosphorylation. ERK phosphorylation was mediated by the Act1 and Src family kinase pathways. CIS1 overexpression suppressed Src phosphorylation. Among the Src family kinases, the Yes kinase may have an important role because knockdown of Yes in epidermal keratinocytes resulted in suppression of ERK phosphorylation and CCL20 mRNA expression by IL-17A. CIS1 induced by Th2 cytokines has the ability to change the response of epidermal keratinocytes to IL-17A by suppression of Src family kinases. [ABSTRACT FROM AUTHOR]

• Th2, Th17 cell numbers increased, and Treg cell numbers decreased in acute AD. • Treg cell number increased in chronic AD. • YAP was downregulated in Treg and upregulated in Th17 cells. • YAP downregulation in AD epidermis inhibited proliferation and migration. • YAP downregulation induced apoptosis of keratinocytes. Atopic dermatitis (AD) is characterized by impaired skin barrier function and immune system dysfunction. The expression and role of Yes-associated protein (YAP) in AD are unclear. To characterize the role of the YAP in T cell imbalance and epidermal keratinocyte dysfunction in the pathogenesis of AD. We included 35 patients with AD (21 acute and 14 chronic). An AD mouse model was constructed using 2,4-dinitrofluorobenzene, and AD-like inflammatory cell model was constructed using TNF-α/IFN-γ-activated HaCaT cells. The proportion of Th1/Th2/Th17/Treg cells was detected using flow cytometry. After mononuclear cells were obtained from human peripheral blood or mouse spleen and induced to differentiate into different T cell subsets, YAP mRNA and protein expression were analyzed. Up-regulation of YAP was induced by lentivirus and down-regulation of YAP was induced by its specific inhibitor verteporfin (VP). The expression of YAP in skin lesions and infiltrating T cell subsets was detected using immunohistochemistry and double immunofluorescence staining, respectively. We found differing degrees of Th1/Th2/Th17/Treg imbalance in acute and chronic AD. YAP expression was downregulated in Treg cells and upregulated in Th17 cells; YAP expression was downregulated in the AD epidermis. After YAP overexpression, the proportion of both Th17 and the Treg cells differentiated from mouse spleen mononuclear cells increased. There was an opposite trend after YAP inhibition. The proliferation and migration decreased and apoptosis increased after YAP inhibition in HaCaT cells. Change of YAP expression may cause T cell imbalance and hamper the healing of the epidermis in AD. [ABSTRACT FROM AUTHOR]

• Carvacrol (TRPV3 agonist) increased ECM production. • TRPV3 regulates TSLP/Smad2/3pathways. • TRPV3 inhibits dermal fibrosis by reducing ECM production. Excessive wound healing can lead to hypertrophic scars, which are not only a cosmetic issue but could also be itchy or painful. Previously, we reported that, in comparison with normal tissue, thymic stromal lymphopoietin (TSLP) expression was increased in skin burn scars when the activation of transient receptor potential vanilloid-3 (TRPV3) of keratinocytes was increased. However, the functional role of TRPV3 in dermal fibrosis remains unclear. We aimed to determine whether TRPV3 affects the collagen production of human primary dermal fibroblasts (HPDFs) and to investigate the mechanism involved. Human primary dermal fibroblasts were cultured and transformed into myofibroblasts using TSLP and carvacrol. Expression levels of α-SMA, fibronectin, and COL1A1 were determined using qPCR, western blotting, and immunofluorescence staining. Ca2+ influx was measured using a calcium-sensitive fluorescent dye, Fura3-AM. Nuclear factor of activated T-cells (NFAT) and phosphorylated-Smad2/3 were determined by western blotting. Silencing of TRPV3 with TRPV3-specific small interference RNA was evaluated using qPCR and western blotting. The expression levels of α-SMA, fibronectin, COL1A1, and TSLP were significantly increased in carvacrol-treated HPDFs. The expression levels of α-SMA, fibronectin, and COL1A1 were significantly increased by TSLP. The expression levels of TSLP and COL1A1 were significantly blocked by TRPV3 silencing in HPDFs. Regulation of Ca2+ influx and the expression levels of NFAT and p-Smad2/3 were significantly increased in carvacrol-treated HPDFs. ECM productions induced via the TRPV3/TSLP/Smad2/3 pathways. The activation of the TRPV3 channels regulates dermal fibrosis by reducing extracellular matrix production via the TRPV3/TSLP/Smad2/3 pathways in dermal fibroblasts. [ABSTRACT FROM AUTHOR]

• IL-33 is up-regulated in the lesional skin of patients with atopic dermatitis (AD). • The skin-specific expression of IL-33 causes AD-like eczema in mice. • Group 2 innate lymphoid cells (ILC2s) produce type2 cytokines in response to IL-33. • IL-33 promotes itch and disrupts the skin barrier. • Clinical applications of anti-IL-33 (or ST2) antibodies are expected. Atopic dermatitis (AD) is characterized by pruritus, barrier disruption, and inflammationincluding type 2 cytokine production. Interleukin-33 (IL-33) is an inflammatory cytokine that is over-expressed in the keratinocytes of patients with AD. IL-33 transgenic mice, which express IL-33 specifically in keratinocytes, spontaneously develop AD-like eczema, suggesting that IL-33 is sufficient for the development of AD. IL-33 stimulates various cells, including group 2 innate lymphoid cells (ILC2s), to produce type 2 cytokines, such as IL-5 and IL-13, and IL-33-stimulated basophils activate ILC2s via IL-4. ILC2s are enriched in human AD skin lesions, and ILC2 isolated from AD lesions, are activated by IL-33, not by thymic stromal lymphopoietin (TSLP). IL-33 induces IL-31, thereby promoting pruritus and scratching behavior. Conversely, scratching the skin promotes IL-33 release from keratinocytes. IL-33 reduces the expression of filaggrin and claudin-1; it also reduces the skin barrier function. However, barrier destruction causes percutaneous exposure to allergens or IL-33 release. Thus, IL-33 is a common point of entry into the itch–scratch cycle of AD. These new findings can facilitate the development of novel therapeutic drugs targeting IL-33. [ABSTRACT FROM AUTHOR]

Highlights from the article: However, TLR3 expression in the lesions of AD patients and its involvement in the pathogenesis of AD have not been examined in previous studies. We examined TLR3 expressions in the skin of AD patients and healthy controls and investigated whether the degree of TLR3 expressions in the skin is related to the severity of AD; eruption type; or epidermal barrier function in AD patients. The scTLR3 expression level of the trunk was significantly higher in the affected skin of AD patients than that in the unaffected skin of AD patients or the skin of healthy controls.

Background Thymic stromal lymphopoietin (TSLP) is an epithelial cell-derived cytokine involved in the pathology of inflammatory skin diseases, such as atopic dermatitis and psoriasis. Tumor necrosis factor (TNF)-α, a key cytokine in inflammatory skin diseases, is a known TSLP inducer. TNF-α activates NF-κB and induces transactivation of epidermal growth factor receptor (EGFR) in epithelial cells. However, the detailed mechanism of TSLP induction by TNF-α has remained unclear. Objective We investigated the involvement of TNF-α-induced EGFR transactivation in TSLP expression. Methods HaCaT cells were stimulated with TNF-α or EGF in the presence or absence of an EGFR kinase inhibitor or other signaling inhibitors. The expression of TSLP mRNA was analyzed by RT-PCR and the phosphorylation level of signal proteins was analyzed by western blot. TSLP promoter and NF-κB transcription activities were analyzed by luciferase assay. Results TNF-α-induced TSLP expression was inhibited by the EGFR kinase inhibitor AG1478. While TSLP expression was induced by EGF, it was inhibited by the MEK inhibitor, U0126. Inhibitors of p38 and ADAM proteases suppressed the TNF-α-induced TSLP expression and EGFR phosphorylation, but not the EGF-induced expression. Conclusion TNF-α-induced EGFR transactivation results in TSLP induction through ERK activation. The activation of p38 and ADAM proteases mediates TNF-α-induced EGFR phosphorylation. These findings suggested that the TNF-α-induced EGFR transactivation pathway could be a target for the treatment of inflammatory skin diseases. [ABSTRACT FROM AUTHOR]

Background Atopic dermatitis (AD) is a chronic, pruritic inflammatory skin disease in which type 2 allergic inflammation plays an important role. Collagen tripeptide (CTP) is a functional collagen fraction with a high content of Gly-X-Y tripeptides. Objective To examine the effect of CTP on inflammation in AD. Methods Levels of inflammatory cytokines and chemokines, such as thymus- and activation-regulated chemokine (TARC), macrophage-derived chemokine, and thymic stromal lymphopoietin (TSLP), were examined in human keratinocytes supplemented with or without CTP under AD-like inflammation. To evaluate the functional effect of CTP, a migration assay was performed using the supernatants of cultured keratinocytes treated with CTP. The signaling pathway for CTP inhibitory activity was also determined. Additionally, we conducted a clinical trial with seventeen AD patients who were assigned randomly to receive daily for 12 weeks either 3.9 g of a CTP product or normal collagen peptides (CP). The eruption area, severity scoring of atopic dermatitis (SCORAD), skin hydration, transepidermal water loss (TEWL), and itching score were evaluated. The levels of TARC, serum IgE, lactate dehydrogenase, and eosinophil counts at week 12 were also compared with those at the start of administration. Results In human keratinocytes, TARC and TSLP mRNA and protein levels were inhibited significantly by CTP treatment under AD-like inflammation. Supernatants obtained from CTP-treated keratinocytes inhibited cell migration. STAT1 phosphorylation was significantly decreased by CTP in a dose-dependent manner. In the clinical trial, 13 patients (7 for CTP, 6 for CP) completed the study. The eruption area, SCORAD, and TEWL at week 12 were reduced significantly compared with the initial values in the CTP but not CP group. A significant reduction in the serum TARC level was observed only in the CTP group at week 12. Other blood parameters were not improved in either group. Conclusion CTP may have therapeutic benefit for AD by inhibiting type 2-skewed allergic inflammation. [ABSTRACT FROM AUTHOR]

Background Atopic dermatitis (AD) is a chronic inflammatory skin disease that often cannot be completely controlled by modern medicine. Since multiple factors are intricately involved in the pathogenesis of AD, wide-ranging research is required for further advancement of AD treatment. Epidermal keratinocytes are the forefront to the external environment and play a pivotal role in the initiation of immune reaction against exogenous invasion. Objective Thymic stromal lymphopoietin (TSLP) is a keratinocyte-derived cytokine that induces differentiation and activation of type 2 helper T cells and innate lymphoid cells, cardinal effectors in pathophysiology of AD. We previously reported that ΔNp63, a p53-related molecule, regulates the expression of TSLP receptors and suggested the entity of a potential TSLP autocrine loop in the AD epidermis. In this study, we further explored the significance of p53 family transcription factors in TSLP production from human keratinocytes. Method Expression profile of p73, a p53-related molecule, was evaluated in human AD tissue by immunohistochemistry. In addition, the function of p73 in producing TSLP was investigated with in vitro cultured keratinocytes via molecular biological analysis. Results ΔNp73 was abundantly expressed in the AD epidermis and increased the release of TSLP via NF-κB activation. Furthermore, the Toll-like receptor 3 signal enhanced ΔNp73 expression and thereby induced TSLP expression. Conclusion Our results indicate that ΔNp73 is an additional participant in the mechanism of TSLP production. Amending the aberrant state of keratinocytes, represented by overexpression of ΔNp73, can be a novel therapeutic target of AD. [ABSTRACT FROM AUTHOR]

Background Thymic stromal lymphopoietin (TSLP) initiates the Th2-type allergic inflammation, and is thought to play an important role in the pathogenesis of atopic dermatitis (AD). TNF-α is a key cytokine which is involved in the pathophysiology of various inflammatory diseases, and the expression level is elevated in the sera and skin of patients with AD. In addition, TNF-α has been reported to induce TSLP expression in epidermal keratinocytes. Topical glucocorticoids and calcineurin inhibitors are safe and effective agents for AD, but the effects of these agents on TNF-α-induced TSLP expression are not fully understood. Objective To investigate whether the glucocorticosteroid dexamethasone and the calcineurin inhibitor tacrolimus could affect TSLP expression induced by TNF-α in lesional keratinocytes of AD. Methods The effects of topical dexamethasone and tacrolimus on TSLP expression were evaluated in an AD mouse model induced by repeated 2,4,6-trinitro-1-chlorobenzene application. Co-immunostaining for TSLP and TNF-α was performed using skin samples from AD patients and the mouse model. Normal human epidermal keratinocytes (NHEKs) were cultured with dexamethasone or tacrolimus in the presence of TNF-α to analyze TSLP expression. Results Topical application of dexamethasone but not tacrolimus repressed TSLP expression in the mouse model. TSLP and TNF-α showed similar distribution pattern in epidermal keratinocytes of AD lesions and the mouse model. TSLP expression was induced by TNF-α via NF-κB in a dose-dependent and an autocrine and/or paracrine manner in NHEKs, which was significantly suppressed by dexamethasone but not by tacrolimus. Similarly to TSLP expression, IL-6, TNF-α, IL-8, and IL-36γ expression induced by TNF-α were significantly suppressed by dexamethasone but not by tacrolimus in NHEKs. Conclusion Dexamethasone but not tacrolimus suppresses the TSLP expression induced by TNF-α in lesional keratinocytes of AD model. Our observations uncover the unreported functional difference between topical glucocorticosteroids and calcineurin inhibitors in cutaneous inflammatory diseases. [ABSTRACT FROM AUTHOR]

Abstract: Background: Thymic stromal lymphopoietin (TSLP) is produced by epidermal keratinocytes, and it induces Th2-mediated inflammation. TSLP expression is enhanced in lesions with atopic dermatitis, and is a therapeutic target. Antimycotic agents improve the symptoms of atopic dermatitis. Objective: The objective of this study was to examine whether antimycotics suppress TSLP expression in human keratinocytes. Methods: Normal human keratinocytes were incubated with polyinosinic–polycytidylic acid (poly I:C) plus IL-4 in the presence of antimycotics. TSLP expression was analyzed by ELISA and real time PCR. Luciferase assays were performed to analyze NF-κB activity. IκBα degradation was analyzed by Western blot analysis. Results: Poly I:C plus IL-4 increased the secretion and mRNA levels of TSLP, which was suppressed by an NF-κB inhibitor, and also enhanced NF-κB transcriptional activities and induced the degradation of IκBα in keratinocytes. The antimycotics itraconazole, ketoconazole, luliconazole, terbinafine, butenafine, and amorolfine suppressed the secretion and mRNA expression of TSLP, NF-κB activity, and IκBα degradation induced by poly I:C plus IL-4. These suppressive effects were similarly manifested by 15-deoxy-Δ-12,14-PGJ2 (15d-PGJ2), a prostaglandin D2 metabolite. Antimycotics increased the release of 15d-PGJ2 from keratinocytes and decreased the release of thromboxane B2, a thromboxane A2 metabolite. Antimycotic-induced suppression of TSLP production and NF-κB activity was counteracted by an inhibitor of lipocalin type-prostaglandin D synthase. Conclusions: Antimycotics itraconazole, ketoconazole, luliconazole, terbinafine, butenafine, and amorolfine may suppress poly I:C plus IL-4-induced production of TSLP by inhibiting NF-κB via increasing 15d-PGJ2 production in keratinocytes. These antimycotics may block the overexpression of TSLP in lesions with atopic dermatitis. [Copyright &y& Elsevier]

Abstract: Background: Thymic stromal lymphopoietin (TSLP), highly expressed in keratinocytes in atopic dermatitis patients and bronchial epithelial cells in asthma patients, plays a key role in allergic diseases. Two forms of TSLP mRNA (long and short) have been reported. Objective: We compared the expression of the long-form and total TSLP transcripts in primary human keratinocytes. Methods: Primary human keratinocytes were stimulated with Toll-like receptor (TLR) ligands, cytokines, and vitamin D receptor agonists. Gene expression was analyzed by quantitative real-time PCR. The amount of TSLP released was measured by ELISA. Results: PolyI:C (TLR3 ligand), FSL-1 (TLR2–TLR6 ligand) and flagellin (TLR5 ligand) upregulated long-form TSLP expression, which predominantly contributed to upregulation of total TSLP expression. A glucocorticoid or an endosomal acidification inhibitor inhibited the polyI:C-dependent upregulation of total TSLP and the decrease of the total TSLP was due to the decrease of the long-form. An atopic cytokine milieu (TNF-α+IL-4+IL-13) or TNF-α alone also upregulated the long-form. These stimuli also induced the release of TSLP. In contrast, a high concentration of calcitriol (1,25-dihydroxyvitamin D3, the active form of vitamin D3) or its analog MC903 upregulated total TSLP significantly but not the long-form, and did not induce the release of TSLP. Conclusion: TLR ligands or cytokines predominantly upregulate the gene expression of the long TSLP form, which contributes to the TSLP protein production, in primary human keratinocytes. Specific measurement of the long-form rather than total TSLP should be useful for accurate detection of functional human TSLP gene expression. [Copyright &y& Elsevier]

Background: Netherton syndrome (NS) is a rare but severe type of ichthyosis characterized by atopy, allergies, and potentially lethal skin overdesquamation associated with highly elevated proteolytic activities in LEKTI-deficient epidermis. NS symptoms are recapitulated in Spink5 -/- mouse where the gene encoding Lekti has been invalidated. Spink5 -/- mice die within 5h from birth due to their severe skin barrier defect leading to dehydration. Spink5 -/- mice also serve as a model for atopic dermatitis. The KLK6 protease is expressed by epidermal keratinocytes and shown in vitro to cleave desmosomal components., Objective: To investigate in vivo whether KLK6 is implicated in epidermal overdesquamation and/or inflammation associated with NS., Methods: The role of KLK6 was evaluated by generating Spink5 -/- Klk6 -/- double knockout mice. The phenotype was assessed by macroscopic observation, immunohistochemistry for differentiation markers, in situ zymography for proteolysis, and quantification of proinflammatory cytokines., Results: Elimination of Klk6 in Spink5 -/- remarkably suppresses the expression of Tslp, a major itching-inducing factor and driver of allergic reactions. Tnfα and the Th17 promoting cytokine Il-23 were also suppressed. Spink5 -/- Klk6 -/- mice display normalized keratinocyte differentiation, nevertheless, epidermal proteolytic activities and the associated overdesquamation were not ameliorated, and Spink5 -/- Klk6 -/- still died from a severe epidermal barrier defect as the Spink5 -/- ., Conclusions: Ablation of Klk6 largely suppresses epidermal inflammation but cannot rescue overdesquamation leading to the lethal NS phenotype. Nonetheless, our findings demonstrate for the first time that KLK6 is implicated in skin inflammation and may represent a novel druggable target for NS and other inflammatory conditions e.g. atopic dermatitis., (Copyright © 2019 Japanese Society for Investigative Dermatology. Published by Elsevier B.V. All rights reserved.)

Background: Measles virus (MV) infection is marked with a skin rash in the acute phase of the disease, which pathogenesis remains poorly understood. Moreover, the association between measles and progression of skin diseases, such as atopic dermatitis (AD), is still elusive., Objective: We have thus analysed the susceptibility of human keratinocytes to MV infection and explore the potential relationship between MV vaccination and the pathogenesis the AD., Methods: We performed immunovirological characterisation of MV infection in human keratinocytes and then tested the effect of live attenuated measles vaccine on the progression of AD in adult patients, in a prospective, double-blind study., Results: We showed that both human primary keratinocytes and the keratinocyte cell line HaCaT express MV receptors and could be infected by MV. The infection significantly modulated the expression of several keratinocyte-produced cytokines, known to be implicated in the pathogenesis of inflammatory allergic diseases, including AD. We then analysed the relationship between exposure to MV by vaccination and the progression of AD in 20 adults during six weeks. We found a significant decrease in CCL26 and thymic stromal lymphopoietin (TSLP) mRNA in biopsies from acute lesions of vaccinated patients, suggesting MV-induced modulation of skin cytokine expression. Clinical analysis revealed a transient improvement of SCORAD index in vaccinated compared to placebo-treated patients, two weeks after vaccination., Conclusions: Altogether, these results clearly demonstrate that keratinocytes are susceptible to MV infection, which could consequently modulate their cytokine production, resulting with a beneficial effect in the progression of AD. This study provides thus a proof of concept for the vaccination therapy in AD and may open new avenues for the development of novel strategies in the treatment of this allergic disease., (Copyright © 2017 Japanese Society for Investigative Dermatology. Published by Elsevier B.V. All rights reserved.)

Background: Topical corticosteroid and calcineurin inhibitor have similar therapeutic benefits in atopic dermatitis (AD), but the differences in therapeutic mechanisms of action of these agents against AD symptoms are not fully understood., Objective: This study was performed to examine the different effects of topical betamethasone valerate (BMV), clobetasol propionate (CBP), and tacrolimus (TAC) on itch-related behavior and dermatitis in NC/Nga mice with AD-like symptoms., Methods: AD-like dermatitis was induced in the dorsal skin of NC/Nga mice by repeated topical application of Dermatophagoides farinae body (Dfb) ointment twice weekly for three weeks. Mice with dermatitis scores over 5 were divided into five groups with equal dermatitis scores and treated with BMV, CBP, TAC, or Vaseline (Vas) once daily for two consecutive days, or were not treated (NT). Scratching behavior was analyzed using a SCLABA ® -Real system. Transepidermal water loss (TEWL) before and after treatment was measured using a Tewameter ® TM210. Skin collected from each group was analyzed histologically., Results: After the second treatment, dermatitis showed significantly greater improvement in the CBP and TAC-treated groups than in the Vas-treated and NT groups. The numbers of scratching bouts were significantly lower in CBP and TAC-treated mice than in Vas-treated mice. TEWL was significantly lower in TAC-, but not in CBP-, treated mice than in Vas-treated mice. Immunohistochemical examination showed that BMV, CBP and TAC did not reduce the increased densities of epidermal protein gene product 9.5- and substance P-immunoreactive fibers. The numbers of dermal CD4-immunoreactive T cells were significantly lower in BMV and CBP-treated mice than in Vas-treated and NT mice. The numbers of dermal eosinophils were significantly lower in BMV, CBP and TAC-treated mice than in Vas-treated and NT mice, with CBP showing the strongest effect. CBP significantly reduced epidermal thickness compared with Vas and NT. There were no significant differences in the numbers of interleukin-31-immunoreactive cells and mast cells, or in expression of epidermal thymic stromal lymphopoietin among all five groups., Conclusion: The therapeutic potency of TAC against AD-like symptoms, including pruritus, is equal to that of the corticosteroid CBP. Epidermal innervation of sensory nerves itself might not be related to the therapeutic effects of topical tacrolimus and corticosteroids in its early phase., (Copyright © 2016 Japanese Society for Investigative Dermatology. Published by Elsevier B.V. All rights reserved.)

Background: Atopic dermatitis (AD) is a chronic and relapsing skin disorder with pruritic skin symptoms. We previously reported that dihomo-γ-linolenic acid (DGLA) prevented the development of AD in NC/Tnd mice, though the mechanism remained unclear., Objective: We attempted to investigate the mechanism of preventive effect of DGLA on AD development in NC/Tnd mice., Methods: The clinical outcomes of NC/Tnd mice that were given diets containing DGLA, arachidonic acid, or eicosapentaenoic acid were compared. Lipid mediator contents in the skin in each group were also quantified. In addition, release of lipid mediators from RBL-2H3 mast cells treated with either DGLA or prostaglandin D1 (PGD1) was measured. Furthermore, effect of PGD1 on gene expression of thymic stromal lymphopoietin (TSLP) in PAM212 keratinocyte cells was determined., Results: Only DGLA containing diet suppressed the development of dermatitis in vivo. By quantifying the 20-carbon fatty acid-derived eicosanoids in the skin, the application of DGLA was found to upregulate PGD1, which correlated with a better outcome in NC/Tnd mice. Moreover, we confirmed that mast cells produced PGD1 after DGLA exposure, thereby exerting a suppressive effect on immunoglobulin E-mediated degranulation. PGD1 also suppressed gene expression of TSLP in keratinocytes., Conclusion: These results suggest that oral administration of DGLA causes preventive effects on AD development in NC/Tnd mice by regulating the PGD1 supply., (Copyright © 2015 Japanese Society for Investigative Dermatology. Published by Elsevier Ireland Ltd. All rights reserved.)

Background: Neutralization of stratum corneum (SC) pH, which is induced by a variety of stimuli, such as scratching, use of soap and inflammation, can stimulate activity of serine protease (SPase). Activation of SPase induces production of thymic stromal lymphopoietin (TSLP) through protease-activated receptor-2. Both reduced expression of natural moisturizing factors, which are required for maintenance of SC pH, and the preferential development of atopic dermatitis (AD)-like dermatitis are found in flaky-tail mice (FTM) with a loss-of-function mutation in filaggrin., Objective: We examined possible correlations between disturbance of responses to an exogenous stimulus of SC neutralization and the preferential emergence of AD-like dermatitis in FTM., Methods: FTM and wild-type mice (C57BL/6) were subjected to an SC-neutralization stimulus via application of 1,1,3,3-tetramethylguanidine (TMG). TMG was applied to young mice at a time when FTM had not yet developed significant dermatitis, and we examined their ability to maintain SC acidity and several parameters associated with AD-like dermatitis., Results: The recovery of SC pH after the application of TMG was delayed in FTM, presumably because of unchanged expression of Na(+)/H(+) antiporter 1, which is involved in maintenance of SC acidity. Cutaneous inflammation with elevated SPase activity and serum levels of TSLP, thymus and activation-regulated chemokine and IgE were induced only in TMG-treated FTM., Conclusion: Our results suggest that defective maintenance of pH of SC is correlated with emergence and exacerbation of AD-like dermatitis in FTM., (Copyright © 2014 Japanese Society for Investigative Dermatology. Published by Elsevier Ireland Ltd. All rights reserved.)