Atopic Dermatitis Model Research Articles

042 Epidermal loss of RORα accelerates skin inflammation in a mouse model of atopic dermatitis

One of the most common skin diseases is atopic dermatitis (AD), a chronic inflammation featuring skin barrier dysfunction and immune dysregulation. Previously, we reported that the nuclear orphan nuclear receptor RORα was highly expressed in the epidermis of human skin and positively regulated the expression of skin barrier-related genes, including filaggrin, in human keratinocytes. In contrast, RORα was downregulated in AD lesions. We then aimed to evaluate the in vivo function of RORα in regulating AD pathogenesis, using the newly generated mice with epidermis-specific Rora knockout (RoraΔepi) and an AD mouse model induced by MC903.

Angelica Yinzi alleviates 1-chloro-2,4-dinitrobenzene-induced atopic dermatitis by inhibiting activation of NLRP3 inflammasome and down-regulating the MAPKs/NF-kB signaling pathway

BackgroundAtopic dermatitis (AD), characterized by eczema as a chronic pruritic inflammatory skin disease, has become a serious health problem with recurrent clinical episodes. However, current clinical treatments have limited relief and are accompanied by adverse effects. Therefore, there is a necessity to develop new effective drugs for AD treatment. Angelica Yinzi (AYZ) is a classic ancient prescription for nourishing blood, moistening dryness, dispelling wind, and relieving itching. However, its mechanism for alleviating atopic dermatitis remains unknown. Therefore, this study aimed at determining the effects of AYZ and its potential mechanism in alleviating AD-like symptoms. MethodsIn the present study, we used 1-chloro-2,4-dinitrobenzene (DNCB) to establish a mouse model of atopic dermatitis, where DNCB readily penetrates the epidermis to cause inflammation. Histopathological analysis was performed to examine the thickening of dorsal skin and infiltration in the inflammatory and mast cells in C57BL/6 mice. Additionally, the immunoglobulin E (IgE) levels in serum were determined by enzyme-linked immunosorbent assay (ELISA) kits. The IL-1β and TNF-α expression were detected using qRT-PCR. Next, the Western blotting and immunohistochemistry assays were performed to assess the contribution of MAPKs/NF-κB signaling pathways and the NLRP3 inflammasome in AD responses. ResultsHistopathological examination revealed that AYZ reduced the epidermal thickness of AD-like lesioned skin and repressed the infiltration of mast cells into AD-like lesioned skin. AYZ significantly decreased the phosphorylation of p38 MAPK, JNK, ERK and NF-κB and downregulated serum IgE levels and IL-1β and TNF-α mRNA levels. Additionally, the NLRP3, ASC, Caspase-1, and IL-1β expression in dorsal skin were effectively down-regulated following AYZ treatment (p < 0.05 and p < 0.01). ConclusionThese findings revealed that AYZ effectively suppressed AD-induced skin inflammation by inhibiting the activation of the NLRP3 inflammasome and the MAPKs/NF-kB signaling. Therefore, AYZ is a potential therapeutic agent against AD in the clinical setting.

ICOS-Deficient Regulatory T Cells Can Prevent Spontaneous Autoimmunity but Are Impaired in Controlling Acute Inflammation.

ICOS is induced in activated T cells and its main role is to boost differentiation and function of effector T cells. ICOS is also constitutively expressed in a subpopulation of Foxp3+ regulatory T cells under steady-state condition. Studies using ICOS germline knockout mice or ICOS-blocking reagents suggested that ICOS has supportive roles in regulatory T (Treg) cell homeostasis, migration, and function. To avoid any compounding effects that may arise from ICOS-deficient non-Treg cells, we generated a conditional knockout system in which ICOS expression is selectively abrogated in Foxp3-expressing cells (ICOS FC mice). Compared to Foxp3-Cre control mice, ICOS FC mice showed a minor numerical deficit of steady-state Treg cells but did not show any signs of spontaneous autoimmunity, indicating that tissue-protective Treg populations do not heavily rely on ICOS costimulation. However, ICOS FC mice showed more severe inflammation in oxazolone-induced contact hypersensitivity, a model of atopic dermatitis. This correlated with elevated numbers of inflammatory T cells expressing IFN-γ and/or TNF-α in ICOS FC mice compared with the control group. In contrast, elimination of ICOS in all T cell compartments negated the differences, confirming that ICOS has a dual positive role in effector and Treg cells. Single-cell transcriptome analysis suggested that ICOS-deficient Treg cells fail to mature into T-bet+CXCR3+ "Th1-Treg" cells in the draining lymph node. Our results suggest that regimens that preferentially stimulate ICOS pathways in Treg cells might be beneficial for the treatment of Th1-driven inflammation.

P38 MAPK Inhibitor NJK14047 Suppresses CDNB-Induced Atopic Dermatitis-Like Symptoms in BALB/c Mice.

Atopic dermatitis (AD) is a chronic inflammatory skin disorder. Suppression of MAPKs and NF-κB is implicated as a vital mechanism of action of several traditional Chinese medicines for AD therapy. Although overexpression of MAPK mRNA in the skin tissue has been shown in the AD model, the roles of each MAPK in AD pathogenesis have rarely been studied. This study examined the effect of NJK14047, an inhibitor of p38 MAPKs, on AD-like skin lesions induced in BALB/c mice by sensitization and challenges with 1-chloro-2,4-dinitrobenzene (CDNB) on dorsal skin and ears, respectively. After induction of AD, NJK14047 (2.5 mg/kg) or dexamethasone (10 mg/kg) was administrated for 3 weeks via intraperitoneal injection. Following its administration, NJK14047 suppressed CDNB-induced AD-like symptoms such as skin hypertrophy and suppressed mast cell infiltration into the skin lesions. It also reduced CDNB-induced increase in TH2 cytokine (IL-13) and TH1 cytokines (interferon-γ and IL-12A) levels but did not decrease serum IgE level. Furthermore, NJK14047 blocked CDNB-induced lymph node enlargement. These results suggest that NJK14047, a p38 MAPK inhibitor, might be an optimal therapeutic option with unique modes of action for AD treatment.

Terminalia chebula Retz. extract ameliorates the symptoms of atopic dermatitis by regulating anti-inflammatory factors in vivo and suppressing STAT1/3 and NF-ĸB signaling in vitro

BackgroundTerminalia chebula (TC) is a traditional medicinal plant used for treating various diseases in humans. However, pharmacological mechanisms underlying the effects of TC in atopic treatment remain unelucidated. Hypothesis/purposeWe investigated the therapeutic effects of TC extract in a mouse model of atopic dermatitis (AD) in vivo and the anti-inflammatory mechanism in vitro. Study design/methodsFor the in vivo study, AD was induced by Dermatophagoides farinae extract (Dfe) in NC/Nga mice. After 14 days of oral administration, the effects of TC concentrations of 30, 100, and 300 mg/kg were analyzed by assessing morphological changes visually; measuring serum levels of inflammatory chemokines/cytokines, IgE, histamine, MDC, TARC, RANTES, and TSLP using ELISA kits; and counting infiltrated mast cells. For in vitro analyses, we used IFNγ/TNF-α-stimulated human keratinocyte cell lines to study the mechanism of action. The production of chemokines/cytokines in the IFNγ/TNF-α-stimulated HaCaT cells was measured using ELISA and a bead array kit. The signaling pathways were analyzed by western blotting and the expression of the transcriptional factors using RT-PCR and luciferase assay. ResultsAdministration of TC significantly alleviated AD-like symptoms in vivo and decreased the ear thickness, dermatitis score, keratinization, and mast cell infiltration. It also resulted in decreased serum levels of IgE, histamine, and inflammation-related mediators MDC, TARC, RANTES, and TSLP compared with those in the Dfe treatment group. Moreover, TC downregulated the expression of the inflammatory chemokines RANTES and MDC in IFNγ/TNF-α-stimulated HaCaT cells. TC inhibited phosphorylated STAT1/3 and NK-κB subunits and nuclear translocation of NF-κB. It also suppressed the transcription of IFNγ, IL-6, IL-8 and MCP-1 in the IFNγ/TNF-α-stimulated HaCaT cells. TC and its constituents, chebulic acid, gallic acid, corlagin, chebulanin, chbulagic acid, ellagic acid, and chebulinic acid, strongly inhibited the nuclear translocation of NF-κB, STAT1, and STAT3 and decreased the expression of inflammatory cytokines at the mRNA level. ConclusionsOverall, TC extract alleviated AD-like symptoms by regulating anti-inflammatory factors in vivo and suppressing STAT1/3 and NF-κB signaling in vitro. In addition, our results show the in vivo effect of partial improvements in AD, as well as the in vitro effect on inflammatory factors by the constituents of TC. This finding provides that TC extract and its components could be potential therapeutic drugs for AD.

Acupoint Autohemotherapy Attenuates Atopic Dermatitis Lesions by Regulating Th1/Th2 Balance in DNCB-Induced BALB/c Mice.

To evaluate the therapeutic effects of acupoint autohemotherapy (A-AHT) on 1-chloro-2,4-dinitrobenzene (DNCB)-induced atopic dermatitis (AD) in mice focusing on regulating T helper 1/T helper 2 (Th1/Th2) immune responses. Thirty BALB/c mice were divided into 5 groups by a random number table, including normal control (NC), AD model (AD), A-AHT, sham A-AHT (sA-AHT), and acupoint injection of normal saline (A-NS) groups, 6 mice per group. Mice were challenged by DNCB for the establishment of experimental AD model. On the 8th day, except for the NC and AD groups, the mice in the other groups received management once every other day for a total of 28 days. For the A-AHT and sA-AHT groups, 0.05 mL of autologous whole blood (AWB) was injected into bilateral Zusanli (ST 36) and Quchi (LI 11) and sham-acupoints (5 mm lateral to ST 36 and LI 11), respectively. The A-NS group was administrated with 0.05 mL of normal saline by acupoint injection into ST 36 and LI 11. Dermatitis severity for dorsal skin of mice was determined using the Severity Scoring of Atopic Dermatitis (SCORAD) every week. The total immunoglobulin E (IgE), interleukin-4 (IL-4), and interferon-gamma (IFN-γ) cytokine levels in serum were examined by enzyme-linked immunosorbent assay (ELISA). Spleen Th1/Th2 expression were analyzed via flow cytometry and immunohistochemical assay was used to detect T-box expressed in T cell (T-bet) and GATA-binding protein 3 (GATA3) expressions in skin lesions of mice. Compared with the AD group, both A-AHT and sA-AHT reduced the SCORAD index and serum IgE level (P<0.05 or P<0.01); A-AHT, sA-AHT and A-NS down-regulated serum IL-4 level and upregulated IFN-γ/IL-4 ratio (P<0.05 or P<0.01); A-AHT regulated the Th1/Th2 shift specifically and increased the related transcription factors such as T-bet expression and T-bet/GATA3 ratio (P<0.05). A-AHT showed significant effectiveness on the AD model mice, through regulating Th1/Th2 immune responses.

Regulation of Th2 responses by Lactococcus lactis subsp. cremoris YRC3780 alleviates DNCB-induced atopic dermatitis in the mouse model

• L. cremoris YRC3780 acted on various types of immune cells to inhibit IL-4. • L. cremoris YRC3780 regulated Th1/Th2 balance in intestinal DC-T cell coculture. • Oral administration of L. cremoris YRC3780 alleviated symptoms in AD mice. • L. cremoris YRC3780 inhibited IL-4 in Peyer’s patch CD4 + T cells of AD mice. Lactococcus lactis subsp . cremoris YRC3780 ( L. cremoris YRC3780) was isolated from kefir, and anti-allergic effects have been confirmed in humans. The mechanisms by which L. cremoris YRC3780 affects the Th1/Th2 balance in mice were investigated in vitro , focusing on the intestinal immune response. Simultaneously, a 2,4-dinitrochlorobenzene-induced atopic dermatitis mouse model was used to evaluate the symptom improvement effect of oral administration of L. cremoris YRC3780. The results showed that L. cremoris YRC3780 enhanced IFN-γ and IL-12 production and inhibited IL-4 production from CD4 + T cells in the presence of various types of immune cells. Oral administration of L. cremoris YRC3780 attenuated serum total IgE ( p < 0.05) and decreased ear thickness ( p < 0.05) in the atopic dermatitis model. The examination of cytokine expression suggested that L. cremoris YRC3780 improved AD-like symptoms by inhibiting IL-4 gene expression from Peyer's patches CD4 + T cells ( p < 0.01) and IL-33 gene expression ( p < 0.05) in the draining lymph nodes.

Claudin-1 Mediated Tight Junction Dysfunction as a Contributor to Atopic March.

Atopic march refers to the phenomenon wherein the occurrence of asthma and food allergy tends to increase after atopic dermatitis. The mechanism underlying the progression of allergic inflammation from the skin to gastrointestinal (GI) tract and airways has still remained elusive. Impaired skin barrier was proposed as a risk factor for allergic sensitization. Claudin-1 protein forms tight junctions and is highly expressed in the epithelium of the skin, airways, and GI tract, thus, the downregulation of claudin-1 expression level caused by CLDN-1 gene polymorphism can mediate common dysregulation of epithelial barrier function in these organs, potentially leading to allergic sensitization at various sites. Importantly, in patients with atopic dermatitis, asthma, and food allergy, claudin-1 expression level was significantly downregulated in the skin, bronchial and intestinal epithelium, respectively. Knockdown of claudin-1 expression level in mouse models of atopic dermatitis and allergic asthma exacerbated allergic inflammation, proving that downregulation of claudin-1 expression level contributes to the pathogenesis of allergic diseases. Therefore, we hypothesized that the tight junction dysfunction mediated by downregulation of claudin-1 expression level contributes to atopic march. Further validation with clinical data from patients with atopic march or mouse models of atopic march is needed. If this hypothesis can be fully confirmed, impaired claudin-1 expression level may be a risk factor and likely a diagnostic marker for atopic march. Claudin-1 may serve as a valuable target to slowdown or block the progression of atopic march.

An Atopic Dermatitis-Like Mouse Model by Alternate Epicutaneous Application of Dinitrofluorobenzene and an Extract of Dermatophagoides Farinae.

Several studies have tried to establish mice models of atopic dermatitis (AD) through the allergen of Dermatophagoides farinae (Df). However, there are no typical skin lesions after epicutaneous application of an extract of Df (DfE) on BALB/c mice. Dinitrofluorobenzene (DNFB) is a common hapten that brings about contact dermatitis. Skin dysfunction induced by DNFB may be a way to enhance the effects of DfE on mice skin. Thus, we hypothesized that alternate epicutaneous application of DNFB and DfE could induce AD-like skin lesions on BALB/c mice. To test this hypothesis, we alternately applied the DNFB and DfE to the back skin of BALB/c mice for 8 weeks. Changes in mice skin lesions and the frequency of scratching behavior were recorded. The variation of Th1-related cytokines (interferon-γ [IFN-γ] and interleukin two [IL-2]) and Th2-related cytokines (IL-4 and IL-13) was detected in serum and lesional skin. Eventually, the BALB/c mice developed severe erythema, erosion, scarring, and excoriation on the entire back, showing a high frequency of scratching behavior. In addition, Th2 cells' dominant cytokines appeared in both serum and lesional skin. Those results indicate that alternating epicutaneous exposure to DNFB and DfE can produce AD-like models with typical clinical features and Th2-type immune responses in BALB/c mice. This model could be valuable for studying the pathogenesis of AD and developing novel therapeutic agents for it.

Jiu-Wei-Yong-An Formula suppresses JAK1/STAT3 and MAPK signaling alleviates atopic dermatitis-like skin lesions

Ethnopharmacological relevanceJiu-Wei-Yong-An (JWYA) formula is a traditional Chinese medicine (TCM) prescription used to treat atopic dermatitis (AD) in the clinic. JWYA is considered to have anti-inflammatory and antipruritic properties. However, the mechanism of JWYA remains unclear.Aim of the study: This study aimed to investigate the effect of JWYA on an experimental mouse AD model. Materials and methodsMice were sensitized with 2,4-dinitrochlorobenzene (DNCB) and intragastrically administered with JWYA for 14 days. The therapeutic effect was assessed using a grade four dermatitis score, skin moisture, thickness measurements, and a mouse behavior tests. H&E and toluidine blue staining were used to observe epidermal inflammatory thickening and mast cells in mouse skin lesions. Serum IgE levels and skin TNF-α and IL-4 levels were determined using ELISAs. The TNF-α, IL-1β, IL-4, IL-13, IL-31, IL-33, and IFN-γ mRNA expression levels in skin lesions were detected using qPCR. Network pharmacology analysis based on serum active components was performed to elucidate the mechanism, and the results were verified by Western blotting. Finally, we tested the binding affinity between the active ingredients of JWYA and JAK1 via molecular docking. ResultsJWYA improved the skin lesions of AD mice, relieved itching and reduced skin thickening. Additionally, JWYA decreased the serum IgE level and the levels of TNF-α, IL-1β, IL-4, IL-13, IL-31, IL-33, and IFN-γ in skin. Moreover, JWYA inhibited the activation of JAK1/STAT3 and MAPK (p38, ERK, and JNK) signaling. Molecular docking showed that kaempferol, luteolin, and forsythin have high affinity for JAK1. ConclusionsJWYA alleviates AD-like skin lesions and inhibited inflammation and skin itch. The effect of JWYA is attributed to blocking the JAK1/STAT3 and MAPK signaling pathways. We suggest that JWYA may be an alternative therapy for the treatment of AD.

Therapeutic effects of myricetin on atopic dermatitis in vivo and in vitro

BackgroundMyricetin (Myr) is a flavonoid compound that exist widely in many natural plants. Myr has been proven to have multiple biological functions, including immunomodulatory and anti-inflammatory effects. PurposeIn this study, we investigated the therapeutic effect of Myr on calcipotriol (MC903) induced atopic dermatitis (AD) mouse model and tumor necrosis factor (TNF)-α/interferon (IFN)-γ stimulated human immortal keratinocyte line (HaCaT) in vivo and in vitro. MethodsMC903 was applied topically to the left ears of mice to establish AD mouse model. After the AD model established successfully, the cream base, dexamethasone (DEX) cream or Myr cream were applied on the lesions of mice for 8 days. Through measuring ear thickness and scoring dermatitis severity, we evaluated the therapeutic effect of Myr, the draining lymph nodes (DLNs) and ears of the mice were collected for mechanistic study. In addition, TNF-α and IFN-γ-activated HaCaT cells were used to investigate the underlying mechanism. ResultsOur data demonstrated that Myr alleviated the symptoms of AD by exerting anti-inflammatory and anti-allergic functions in vivo. We found that Myr treatment suppressed ear swelling and IgE level in the serum, reduced the infiltration of mast cells in skin lesions, decreased expressions of thymus and activation regulated chemokine (TARC), IL-4, IFN-γ and thymic stromal lymphopoietin (TSLP) in ear lesions, increased the expressions of filaggrin (FLG). Furthermore, our experimental results demonstrated that Myr down-regulated the mRNA expressions of T-bet and GATA-3 in DLNs. In vitro, Myr treatment decreased MDC and TARC expressions in IFN-γ and TNF-α-induced HaCaT cells by blocking the NF-κB and STAT1 signal pathway. ConclusionThe present study is the first to investigate the anti-atopic effects of Myr. Our findings suggested the therapeutic effects of Myr against MC903-induced AD-like skin lesions in mice. Therefore, Myr may be a potential therapeutic agent for AD.

Ta-Xi-San Suppresses Atopic Dermatitis Involved in Multitarget Mechanism Using Experimental and Network Pharmacology Analysis.

Atopic dermatitis (AD) is a relapsing and chronic skin inflammation with a common incidence worldwide. Ta-Xi-San (TXS) is a Chinese herbal formula usually used for atopic dermatitis in clinic; however, its active compounds and mechanisms of action are still unclear. Our study was designed to reveal the pharmacological activities, the active compounds, and the pharmacological mechanisms of TXS for atopic dermatitis. Mice were induced by 2,4-dinitrocluorobenzene (DNCB) to build atopic dermatitis model. The pathological evaluation, enzyme-linked immunosorbent assay (ELISA), and hematoxylin and eosin (H&E) assay were performed. The UPLC-Q-Exactive-MSE and network pharmacology analysis were performed to explore active ingredients and therapeutic mechanisms of TXS. TXS treatment decreased levels of immunoglobulin E (IgE), interleukin-4 (IL-4), and tumor necrosis factor-α (TNF-α) in serum induced by DNCB. TXS reduced scratching behavior and alleviated inflammatory pathology of skin and ear. Meanwhile, TXS decreased the spleen index and increased spleen index. The UPLC-Q-Exactive-MSE results showed that 65 compounds of TXS were detected and 337 targets were fished. We collected 1371 AD disease targets, and the compound-target gene network reveled that the top 3 active ingredients were (−)-epigallocatechin gallate, apigenin, and esculetin, and the core target genes were PTGS2, PTGS1, and HSP90AA1. The KEGG pathway and GO analysis showed that TXS remedied atopic dermatitis via PI3K-Akt signaling pathway, mitogen-activated protein kinase (MAPK) signaling pathway, and Toll-like receptor (TLR) signaling pathway with the regulation of inflammatory response and transcription. Further, we found that the targets of PTGS2 and HSP90AA1 were both elevated in ears and skin of AD model mouse; however, TXS decreased the elevated expressions of PTGS2 and HSP90AA1. Our study revealed that TXS ameliorated AD based on (−)-epigallocatechin gallate, apigenin, and esculetin via targeting PTGS2 and HSP90AA1.

Exploration of the Potential Mechanism of the Common Differentially Expressed Genes in Psoriasis and Atopic Dermatitis.

Backgrounds Psoriasis and atopic dermatitis are two common chronic inflammatory skin diseases that enormously deteriorate the psycho-physical and socio-economic condition of the patients. Although differential immune responses have been found to operate in the pathomechanisms of atopic dermatitis and psoriasis, the epidermal keratinocytes are the major targets in both diseases, and sometimes, they show similar clinical presentations. The skin barrier, itching, and inflammation are current and future treatment targets for both of them, but the relevant shared mechanisms of the two diseases are far from understood. Methods The differential analyses of GSE14905 (psoriasis) and GSE32924 (atopic dermatitis) deposited in GEO database were conducted and obtained their differential expressed genes. Moreover, PPI, functional modules, GO, and KEGG enrichment analyses were used for the further analysis. The mouse models of psoriasis and atopic dermatitis were established, and then, RT-qPCR and Western blotting assay were performed to check the abundant changes of hub genes. Results There are 732 differentially expressed genes in psoriasis versus nonlesional skin samples. Besides, 611 differentially expressed genes were identified in atopic dermatitis versus nonlesional skin data sets. Based on these differentially expressed genes, we predicted their joint and individual protein-protein interaction networks and functional modules in both psoriasis and atopic dermatitis. Through the PPI network of genes, we calculated the hub nodes and do the GO and KEGG enrichment analysis of overlapped genes of psoriasis and atopic dermatitis, which suggested there were some terms like “positive regulation of interleukin-12 production,” “centromeric region,” and “TNF signaling pathway.” Conclusion We constructed the predicted PPI networks and functional modules related to psoriasis and atopic dermatitis and distinguished the key candidate target genes CXCL8, STAT1, and MMP9 in the diagnosis and therapy of similar pathogenesis.

Immunomodulatory effects of human myeloid-derived suppressor cells expanded from cord blood on dermatophagoides farinae-induced atopic dermatitis in NC/Nga mice

Abstract Myeloid-derived suppressor cells (MDSCs) plays an important role in controlling the immune response against cancer and in suppressing autoimmunity and allergic inflammation. However, the therapeutic effect of MDSCs on experimental mouse model of atopic dermatitis (AD) has not been reported. We investigated the therapeutic efficacy of human myeloid-derived suppressor cells expanded from cord blood (hUCB-MDSCs) in dermatophagoides farinae (Df)-induced AD-like skin lesions in NC/Nga mice and explored the mechanisms involved. The administration of hUCB-MDSCs (1×105 and 1×106 cells per mouse) significantly reduced in clinical severity scores and was associated with the reduction of histopathological changes including inflammatory cellular infiltration, epidermal hyperplasis, and hyperkeratosis. hUCB-MDSCs decreased the serum levels of IgE, Th2-mediated cytokines and chemokines. Particularly, the expression of filaggrin and involucrin in the skin lesions was recovered, whereas the expression of keratin-10 and keratin-14 decreased. These immunomodulatory effects of hUCB-MDSCs in a murine model of AD may provide helpful evidence for the clinical development of cell therapies to treat AD.

Lymphotoxin β receptor signaling mediates the formation of high endothelial venule-like vessels in atopic dermatitis-like skin lesions in mice

Abstract High endothelial venules (HEVs) are specialized blood vessels contribute to the trafficking of lymphocytes into secondary lymphoid organs by expressing a group of L-selectin ligands called peripheral node addressins (PNAd). In lymph nodes (LNs), lymphotoxin β receptor (LTβR) signaling from dendritic cells (DCs) is essential for the formation of HEVs. On the other hand, PNAd+ HEV-like vessels are observed in the skin under certain inflammatory conditions, such as atopic dermatitis (AD). However, the characteristics and the formation mechanism of HEV-like vessels in the inflammatory skin remains unclear. To address these issues, we first identified PNAd+ HEV-like vessels in the skin using a calcipotriol-induced mouse AD model. HEV-like vessels were located in the postcapillary venules abundant in cellular organelles, which were similar to HEVs in LNs. Blockade of LTβR-signaling by administration of LTβR-Fc fusion protein markedly decreased the formation of HEV-like vessels in the AD-like skin. Analysis using published single-cell RNA-seq data of human AD skin revealed that T cells and DCs highly expressed LTB, a gene encoding LTβ. The expression of LTB was highlighted in T cells by RNAscope in both human AD lesions and mouse AD-like skin. The formation of HEV-like vessels in AD-like skin was normal in Ltbfl/flCD11cCre mice, but was partially impaired in Ltbfl/flCD4Cre mice. Collectively, HEV-like vessels in the inflammatory skin show similar characteristics to HEVs in LNs, and LTβR signaling, partly by LTβ from T cells, is responsible for their formation.

IL-20 promotes cutaneous inflammation and peripheral itch sensation in atopic dermatitis.

Atopic dermatitis (AD) is a chronic skin disease, which is associated with intense itch, skin barrier dysfunction and eczematous lesions. Aberrant IL‐20 expression has been implicated in numerous inflammatory diseases, including psoriasis. However, the role of IL‐20 in AD remains unknown. Here, RNA‐seq, Q‐PCR, and immunocytochemistry were utilized to examine disease‐driven changes of IL‐20 and its cognate receptor subunits in skin from healthy human subjects, AD patients and murine AD‐models. Calcium imaging, knockdown and cytokine array were used to investigate IL‐20‐evoked responses in keratinocytes and sensory neurons. The murine cheek model and behavioral scoring were employed to evaluate IL‐20‐elicited sensations in vivo. We found that transcripts and protein of IL‐20 were upregulated in skin from human AD and murine AD‐like models. Topical MC903 treatment in mice ear enhanced IL‐20R1 expression in the trigeminal sensory ganglia, suggesting a lesion‐associated and epidermal‐driven mechanism for sensitization of sensory IL‐20 signaling. IL‐20 triggered calcium influx in both keratinocytes and sensory neurons, and promoted their AD‐related molecule release and transcription of itch‐related genes. In sensory neurons, IL‐20 application increased TLR2 transcripts, implicating a link between innate immune response and IL‐20. In a murine cheek model of acute itch, intradermal injection IL‐20 and IL‐13 elicited significant itch‐like behavior, though only when co‐injected. Our findings provide novel insights into IL‐20 function in peripheral (skin‐derived) itch and clinically relevant intercellular neuron‐epidermal communication, highlighting a role of IL‐20 signaling in the pathophysiology of AD, thus forming a new basis for the development of a novel antipruritic strategy via interrupting IL‐20 epidermal pathways.

CD4+ T cells play an essential role in chronic MC903-induced skin inflammation

MC903 skin inflammation model is one of well-characterized murine models of atopic dermatitis and driven by TSLP-mediated type 2 inflammation. Since it can be prepared simply by repetitive applications of MC903 and shows consistent clinical results, this model has been widely used. However, in contrast to human atopic dermatitis which is chronic and closely related to TH2 cells, MC903 induces inflammations temporarily and even in the absence of T cells. Here, we modified the MC903 treatment schedule and developed a chronic MC903-induced skin inflammation model. Mice were sensitized with a high dose of MC903 and challenged with a low dose of MC903. Prior to challenge, mice were allowed to recover completely from the inflammation which occurred during the sensitization. The challenge of MC903 induced skin swelling and type 2 inflammations more rapidly, which was dependent on CD4+ T cells and IL-33. We expect that our mouse model will be beneficial for studying the late course of atopic dermatitis.

Anti-allergic effect of ascorbic acid derivative DDH-1 in a mouse model of atopic dermatitis.

Atopic dermatitis (AD) is the most common inflammatory skin disease, which is characterized by excessive Th2 immune responses. In AD patients, the expression of the chemokines CCL17 and CCL22 is increased in skin lesions, leading to the infiltration of Th2 cells. In addition, typical pro-inflammatory cytokines, including TNF-α, IL-1β and IL-6, have also been shown to be associated with the pathogenesis of AD. Recently, DDH-1, an ascorbic acid derivative, has been synthesized and demonstrated to have a more stabilized structure and better skin penetrability. Furthermore, DDH-1 has been shown to suppress pro-inflammatory cytokine expression in vitro and in vivo. Therefore, using an AD mouse model, we evaluated the effect of DDH-1 to reduce allergic skin inflammation. We found that cutaneous administration of DDH-1 significantly reduced the expression levels of TNF-α, IL-1β and IL-6 in the skin lesions of AD-like mice. Additionally, DDH-1 administration also significantly reduced the expression levels of CCL17 and CCL22, resulting in decreased skin infiltration of Th2 cells. Consequently, DDH-1 reduced ear and epidermal thickness, the serum IgE levels and the number of infiltrating inflammatory cells and mast cells into the AD-like skin lesions. Combination treatment with DDH-1 and corticosteroid more efficiently improved the skin lesions compared with corticosteroid alone. Collectively, our results suggest that DDH-1 has an anti-allergic effect in an AD mouse model by reducing not only the pro-inflammatory cytokine expression but also the Th2-associated chemokine expression. Thus, DDH-1 may be beneficial for AD treatment and prevention as a monotherapy or in combination with corticosteroids.

Tacrolimus suppresses itch-related response in diet-induced atopic dermatitis model mice by reducing chloroquine-sensitive sensory neurons

Introduction: Itch (or pruritus) is a common symptom of atopic dermatitis (AD), which significantly decreases the patient’s quality of life. Tacrolimus ointment reduces pruritus in AD; however, the underlying mechanism is not fully understood. Methods: In the present study, we used a diet-induced AD mouse model to examine the antipruritic mechanism of tacrolimus. After induction of AD symptoms, the tacrolimus-containing ointment was applied once daily for 7 days. Responsiveness of isolated dorsal root ganglion (DRG) cells to various stimuli was examined by monitoring intracellular Ca2+ levels. Results: Repeated application of tacrolimus ointment attenuated spontaneous itch-related responses, even when skin barrier dysfunction, skin inflammation, and epidermal nerve sprouting were not ameliorated. Tacrolimus-treated mice also exhibited reduced scratching behavior induced by several pruritogens, such as histamine, SLIGRL-NH2, and chloroquine (CQ), although capsaicin-induced pain behavior was not affected. DRG cells from tacrolimus-treated mice showed significantly lower Ca2+ responses to CQ. Furthermore, a reduction in CQ-sensitive DRG neurons was observed after in vitro treatment with either tacrolimus or rapamycin. Discussion: CQ-sensitive (MrgprA3-expressing) DRG neurons are implicated as itch-specific sensory neurons. Therefore, topically applied tacrolimus may act directly on itch-signaling neurons, consequently suppressing various itch responses in AD mice.

Obesity alters pathology and treatment response in inflammatory disease.

Decades of work have elucidated cytokine signalling and transcriptional pathways that control T cell differentiation and haveled the way to targeted biologic therapies that are effective in a range of autoimmune, allergic and inflammatory diseases. Recent evidence indicates that obesity and metabolic disease can also influence the immune system1-7, although the mechanisms and effects on immunotherapy outcomes remain largely unknown. Here, using two models of atopic dermatitis, we show that lean and obese mice mount markedly different immune responses. Obesity converted the classical type 2 T helper (TH2)-predominant disease associated with atopic dermatitis to a more severe disease with prominent TH17 inflammation.We also observed divergent responses to biologic therapies targeting TH2 cytokines, which robustly protected lean mice but exacerbated disease in obese mice. Single-cell RNA sequencing coupled with genome-wide binding analyses revealed decreased activity of nuclear receptor peroxisome proliferator-activated receptor-γ (PPARγ) in TH2 cells from obese mice relative to lean mice. Conditional ablation of PPARγ in T cells revealed that PPARγ is required to focus the in vivo TH response towards a TH2-predominant state and prevent aberrant non-TH2 inflammation. Treatment of obese mice with a small-molecule PPARγ agonist limited development of TH17 pathology and unlocked therapeutic responsiveness to targeted anti-TH2 biologic therapies. These studies reveal the effects of obesity on immunological disease and suggest a precision medicine approach to target the immune dysregulation caused by obesity.