Contribution of itch-associated scratch behavior to the development of skin lesions in Dermatophagoides farinae-induced dermatitis model in NC/Nga mice

Skin repair and immunoregulatory effects of myeloid suppressor cells from human cord blood in atopic dermatitis

Introduction

Previously, we achieved large-scale expansion of bone marrow-derived suppressor cells (MDSCs) derived from cluster of differentiation (CD)34+ cells cultured in human umbilical cord blood (hUCB) and demonstrated their immunomodulatory properties. In the present study, we assessed the therapeutic efficacy of hUCB-MDSCs in atopic dermatitis (AD).

Methods

Dermatophagoides farinae (Df)-induced NC/Nga mice (clinical score of 7) were treated with hUCB-MDSCs or a control drug. The mechanisms underlying the therapeutic effects of hUCB-MDSCs were evaluated.

Results and discussion

hUCB-MDSCs demonstrated immunosuppressive effects in both human and mouse CD4+ T cells. hUCB-MDSCs significantly reduced the clinical severity scores, which were associated with histopathological changes, and reduced inflammatory cell infiltration, epidermal hyperplasia, and fibrosis. Furthermore, hUCB-MDSCs decreased the serum levels of immunoglobulin E, interleukin (IL)-4, IL-5, IL-13, IL-17, thymus- and activation-regulated chemokines, and thymic stromal lymphopoietin. Additionally, they altered the expression of the skin barrier function-related proteins filaggrin, involucrin, loricrin, cytokeratin 10, and cytokeratin 14 and suppressed the activation of Df-restimulated T-cells via cell-cell interactions. hUCB-MDSCs promoted skin recovery and maintained their therapeutic effect even after recurrence. Consequently, hUCB-MDSC administration improved Df-induced AD-like skin lesions and restored skin barrier function. Our findings support the potential of hUCB-MDSCs as a novel treatment strategy for AD.

IL-31-dependent neurogenic inflammation restrains cutaneous type 2 immune response in allergic dermatitis

Despite robust literature associating IL-31 with pruritic inflammatory skin diseases, its influence on cutaneous inflammation and the interplay between inflammatory and neurosensory pathways remain unmapped. Here, we examined the consequences of disrupting Il31 and its receptor Il31ra in a mouse model of house dust mite (HDM)-induced allergic dermatitis. Il31-deficient mice displayed a deficit in HDM dermatitis-associated scratching, consistent with its well-established role as a pruritogen. In contrast, Il31 deficiency increased the number and proportion of cutaneous type 2 cytokine-producing CD4+ T cells and serum IgE in response to HDM. Furthermore, Il4ra+ monocytes and macrophages capable of fueling a feedforward type 2 inflammatory loop were selectively enriched in Il31ra-deficient HDM dermatitis skin. Thus, IL-31 is not strictly a proinflammatory cytokine but rather an immunoregulatory factor that limits the magnitude of type 2 inflammatory responses in skin. Our data support a model wherein IL-31 activation of IL31RA+ pruritoceptors triggers release of calcitonin gene-related protein (CGRP), which can mediate neurogenic inflammation, inhibit CD4+ T cell proliferation, and reduce T cell production of the type 2 cytokine IL-13. Together, these results illustrate a previously unrecognized neuroimmune pathway that constrains type 2 tissue inflammation in the setting of chronic cutaneous allergen exposure and may explain paradoxical dermatitis flares in atopic patients treated with anti-IL31RA therapy.

Calcitriol, an Active Form of Vitamin D3, Mitigates Skin Barrier Dysfunction in Atopic Dermatitis NC/Nga Mice

Atopic dermatitis and psoriasis are prevalent chronic inflammatory skin diseases that are characterized by dysfunctional skin barriers and substantially impact patients' quality of life. Vitamin D3 regulates immune responses and keratinocyte differentiation and improves psoriasis symptoms; however, its effects on atopic dermatitis remain unclear. Here, we investigated the effects of calcitriol, an active form of vitamin D3, on an NC/Nga mouse model of atopic dermatitis. We observed that the topical application of calcitriol decreased the dermatitis scores and epidermal thickness of NC/Nga mice with atopic dermatitis compared to untreated mice. In addition, both stratum corneum barrier function as assessed by the measurement of transepidermal water loss and tight junction barrier function as evaluated by biotin tracer permeability assay were improved following calcitriol treatment. Moreover, calcitriol treatment reversed the decrease in the expression of skin barrier-related proteins and decreased the expression of inflammatory cytokines such as interleukin (IL)-13 and IL-33 in mice with atopic dermatitis. These findings suggest that the topical application of calcitriol might improve the symptoms of atopic dermatitis by repairing the dysfunctional epidermal and tight junction barriers. Our results suggest that calcitriol might be a viable therapeutic agent for the treatment of atopic dermatitis in addition to psoriasis.

Contributions of Diet and Age to Ulcerative Dermatitis in Female C57BL/6J Mice

C57BL/6J (B6) mice are commonly affected by ulcerative dermatitis (UD), a disease of unknown etiology with poor response to treatment. To study the possible role of diet in UD, we compared skin changes in B6 female mice fed a high-fat diet with those of mice fed a control diet. In addition, skin samples from mice with no, mild, moderate, and severe clinical signs of UD were examined by light and transmission electron microscopy (TEM). Mice fed a high-fat diet for 2 mo had more skin mast cell degranulation than did mice fed the control diet for the same period. Regardless of diet, older mice had more skin mast cells and more of these cells were degranulating as compared with younger mice. Microscopic changes in very early lesions were characterized by an increase in dermal mast cells and degranulation with focal areas of epidermal hyperplasia with or without hyperkeratosis. As the condition progressed, a mixed but predominantly neutrophilic inflammatory cell infiltrate appeared in the dermis, with or without epidermal erosion and scab formation. TEM showed that dermal mast cell membranes had disrupted and released of large number of electron-dense granules, whereas degranulated mast cells were filled with isolated and coalescing empty spaces due to fusion of granule membranes. Ulceration appeared to occur very quickly, probably as result of intense scratching due to the pruritogenic properties of the histamine released from mast cell granules. This study showed a direct correlation between dietary fat and skin mast cell degranulation in female B6 mice. In addition, the number of skin mast cells and degranulation rates was higher in older mice. Treatments directed at preventing mast cell degranulation may result in better outcomes when applied early in UD cases. As noted previously in studies using caloric restriction, lower fat content in rodent diets may help prevent UD.

Perampanel attenuates scratching behavior induced by acute or chronic pruritus in mice

An itch is defined as an unpleasant sensation that evokes a desire to scratch. Glutamate is a major excitatory neurotransmitter in the mammalian central nervous system and has a crucial role in pruriceptive processing in the spinal dorsal horn. It is well known that glutamate exerts its effects by binding to various glutamate receptors including α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, and that AMPA/kainate receptors play a crucial role in pruriceptive processing; however, the precise role of AMPA receptors remains uncertain. Perampanel, an antiepileptic drug, is an antagonist of AMPA receptors. Pretreatment with perampanel dose-dependently attenuated the induction of scratching, a behavior typically associated with pruritus, by intradermal administration of the pruritogen chloroquine. In addition, the induction of scratching in mice painted with diphenylcyclopropenone and NC/Nga mice treated with Biostir AD, animal models of contact dermatitis and atopic dermatitis, respectively, was dose-dependently alleviated by administration of perampanel. These findings indicate that AMPA receptors play a crucial role in pruriceptive processing in mice with acute or chronic pruritus.

Comparison of the presentation of atopic dermatitis induced by trinitrochlorobenzene and house dust mite in NC/Nga mice

Background

Atopic dermatitis (AD) is a common chronic inflammatory skin disease. To understand AD, there have been many trials establishing AD animal models. Although various trials to establish AD animal models have been existed, even the mechanisms of AD in animal models are not enough clarified.

Objectives

This study assessed AD characteristics induced in Nishiki-nezumi Cinnamon/Nagoya (Nc/Nga) mice following trinitrochlorobenzene (TNCB) treatment for different periods and house dust mite (HDM) treatment to compare each model's immunological patterns, especially with cytokine antibody array tool.

Methods

In this study, we exposed Nc/Nga mice to TNCB or HDM extract to induce AD. Nc/Nga mice were divided into 4 groups: control, TNCB 2 weeks-treated, TNCB 8 weeks-treated, and HDM-treated groups. After AD induction, all mice were evaluated by serum immunoglobulin E (IgE) concentration and serum cytokine antibody assays, scoring of skin lesions, scoring of scratching frequency, and histological analysis.

Results

The results showed significant differences between groups in serum IgE concentration, skin lesion scores, and scratching frequency. The analysis results for serum cytokine antibody arrays showed that in the TNCB 8 weeks- and HDM-treated groups, but not in the TNCB 2 weeks-treated group, expressions of genes related to the immune response were enriched. Among the histological results, the skin lesions in the HDM-treated group were most similar to those of AD.

Conclusions

We confirmed that immunological pattern of AD mice was markedly different between HDM and TNCB treated groups. In addition, the immunological pattern was quietly different dependent on TNCB treated duration.

Clec10a regulates mite-induced dermatitis

House dust mite (HDM) is a major allergen that causes allergic diseases such as atopic dermatitis. However, the regulatory mechanisms of HDM-induced immune responses are incompletely understood. NC/Nga mice are an inbred strain that is more susceptible to HDM and develops more severe dermatitis than other strains. Using whole-exome sequencing, we found that NC/Nga mice carry a stop-gain mutation inClec10a, which encodes a C-type lectin receptor, Clec10a (MGL1/CD301a). The repair of this gene mutation using the CRISPR-Cas9 system ameliorated HDM-induced dermatitis, indicating that the Clec10a mutation is responsible for hypersensitivity to HDM in NC/Nga mice. Similarly,Clec10a−/−mice on the C57BL/6J background showed exacerbated HDM-induced dermatitis. Clec10a expressed on skin macrophages inhibits HDM-induced Toll-like receptor 4 (TLR4)–mediated inflammatory cytokine production through the inhibitory immunoreceptor tyrosine activating motif in its cytoplasmic portion. We identified asialoglycoprotein receptor 1 (Asgr1) as a functional homolog of mouse Clec10a in humans. Moreover, we found that a mucin-like molecule in HDM is a ligand for mouse Clec10a and human Asgr1. Skin application of the ligand ameliorated a TLR4 ligand-induced dermatitis in mice. Our findings suggest that Clec10a in mice and Asgr1 in humans play an important role in skin homeostasis against inflammation associated with HDM-induced dermatitis.

Therapeutic application of human leukocyte antigen-G1 improves atopic dermatitis-like skin lesions in mice

Human leukocyte antigen (HLA)-G is an immune checkpoint molecule that plays critical roles in immune response and in triggering inhibitory signaling to immune cells such as T cells, natural killer cells, and antigen-presenting cells. Thus, the application of HLA-G can be considered for treating immune response-related inflammatory disorders. We have previously reported that treatment with HLA-G1 and HLA-G2 ameliorates the joint swelling associated with collagen-induced arthritis of DBA/1 mice, an animal model for rheumatoid arthritis. In this study, we further investigated the effects of HLA-G1 on atopic dermatitis (AD), the most common inflammatory skin disorder. AD-like lesions were induced with the extract of the house dust mite Dermatophagoides farinae in NC/Nga mice. Continuous administration of HLA-G1 ameliorated the AD-like skin lesions in the mice. Furthermore, production of immunoglobulin E, interleukin (IL)-13, and IL-17A was significantly reduced in HLA-G1-treated mice, suggesting a Th2/Th17-mediated immune-inhibitory function of HLA-G1 in vivo. Our studies shed light on novel therapeutic strategies with recombinant HLA-G proteins for immune reaction-mediated chronic inflammatory disorders.

Biphasic increase in scratching behaviour induced by topical application of Dermatophagoides farinae extract in NC/Nga mice

Atopic dermatitis (AD) is a chronic inflammatory skin disease accompanied by severe itching and eczematous lesion. In this study, we applied an ointment containing Dermatophagoides farinae body (Dfb) extract repeatedly on the dorsal skin of NC/Nga mice with barrier disruption to investigate the characteristics of this murine model of human AD. Following repeated topical application of Dfb ointment twice weekly for 2 weeks, the dermatitis score increased gradually, accompanied by an elevation of total immunoglobulin E level in plasma. Topical application of Dfb ointment also caused epidermal hyperplasia and accumulation of inflammatory cells in the lesional skin and increased expression of T-helper (Th) 1/Th2/Th17 cytokines in axillary lymph node cells. Furthermore, increased sprouting of intraepidermal nerve fibres was observed with an increase in the content of nerve growth factor and decrease in that of semaphorin 3A in the lesional skin. These findings suggest that the characteristics in this model were similar to those observed in patients with AD. Interestingly, it was observed for the first time that scratching behaviour increased in a biphasic fashion by topical application of Dfb ointment in addition to an increase in spontaneous scratching behaviour in this model. It is also suggested that further clarifying the underlying mechanisms of scratching behaviour in this model leads not only to elucidating the pathogenesis of AD but also to discovering novel therapeutic drugs for AD.

STAT3-dependent reactive astrogliosis in the spinal dorsal horn underlies chronic itch

Chronic itch is an intractable symptom of inflammatory skin diseases, such as atopic and contact dermatitis. Recent studies have revealed neuronal pathways selective for itch, but the mechanisms by which itch turns into a pathological chronic state are poorly understood. Using mouse models of atopic and contact dermatitis, we demonstrate a long-term reactive state of astrocytes in the dorsal horn of the spinal segments that corresponds to lesioned, itchy skin. We found that reactive astrogliosis depended on the activation of signal transducer and activator of transcription 3 (STAT3). Conditional disruption of astrocytic STAT3 suppressed chronic itch, and pharmacological inhibition of spinal STAT3 ameliorated the fully developed chronic itch. Mice with atopic dermatitis exhibited an increase in scratching elicited by intrathecal administration of the itch-inducer gastrin-releasing peptide (GRP), and this enhancement was normalized by suppressing STAT3-mediated reactive astrogliosis. Moreover, we identified lipocalin-2 (LCN2) as an astrocytic STAT3-dependent upregulated factor that was crucial for chronic itch, and we demonstrated that intrathecal administration of LCN2 to normal mice increased spinal GRP-evoked scratching. Our findings indicate that STAT3-dependent reactive astrocytes act as critical amplifiers of itching through a mechanism involving the enhancement of spinal itch signals by LCN2, thereby providing a previously unrecognized target for treating chronic itch.

The ion channel TRPA1 is required for chronic itch

Chronic itch is a debilitating condition that affects one in 10 people. Little is known about the molecules that mediate chronic itch in primary sensory neurons and skin. We demonstrate that the ion channel TRPA1 is required for chronic itch. Using a mouse model of chronic itch, we show that scratching evoked by impaired skin barrier is abolished in TRPA1-deficient animals. This model recapitulates many of the pathophysiological hallmarks of chronic itch that are observed in prevalent human diseases such as atopic dermatitis and psoriasis, including robust scratching, extensive epidermal hyperplasia, and dramatic changes in gene expression in sensory neurons and skin. Remarkably, TRPA1 is required for both transduction of chronic itch signals to the CNS and for the dramatic skin changes triggered by dry-skin-evoked itch and scratching. These data suggest that TRPA1 regulates both itch transduction and pathophysiological changes in the skin that promote chronic itch.

Effects of anti-inflammatory and Rehmanniae radix pharmacopuncture on atopic dermatitis in NC/Nga mice

Atopic dermatitis (AD) is a chronic inflammatory skin disease characterized by pruritic and erythematous skin lesions. The purpose of this study was to investigate the suppressive effects of anti-inflammatory and Rehmanniae radix pharmacopuncture on the development of AD-like skin lesions in NC/Nga mice. The AD was induced on the mice's back skin by using biostir AD. The experimental groups were divided into three groups, PPI (anti-inflammatory pharmacopuncture), PPII (Rehmanniae radix pharmacopuncture, hydrodistillation extraction) and PPIII (Rehmanniae radix pharmacopuncture, MeOH extraction). All mice were treated using a 1-mL syringe to inject 0.1 mL of pharmacopuncture at right and left acupoints (BL13) on alternate days. In the control group, normal saline was used instead of pharmacopuncture. The following factors were investigated: (1) optical observations made with a handscope and clinical skin scores were evaluated; (2) tissue (general/immune) mast cells and CCR3(+) eosinophils, as well as vascular endothelial growth factor, fibroblast growth factor, and epidermal growth factor immunoreactive changes were evaluated; (3) CD4(+) and CD8(+) cells in the spleen were immunohistochemically examined; and, (4) the serum immunoglobulin (Ig)E level and lymphokines [interleukin (IL)-2, IL-4] were measured. In the PPI and the PPIII groups, the clinical skin score, total number of mast cells, CCR3(+) eosinophils immunoreaction, and total serum IgE, IL-2, and IL-4 levels were lower than the control group. The PPI and the PPIII groups also showed strong immunohistochemical reactions for vascular endothelial growth factor and fibroblast growth factor. The PPI group particularly showed a very strong immunohistochemical reaction for epidermal growth factor. All groups showed strong immune activity for CD8(+). The PPIII group showed strong immunity for both CD4(+) and CD8(+). From the above results, Rehmanniae radix pharmacopuncture (MeOH extraction) and anti-inflammatory pharmacopuncture exerted anti-allergic and anti-inflammatory effects, suggesting that they are promising agents for improving AD-related symptoms.

Regulation of immunological balance by sustained interferon-γ gene transfer for acute phase of atopic dermatitis in mice

Interferon (IFN)-γ, a potent T helper 1 (Th1) cell cytokine, is suggested to suppress Th2 cell responses. Here, we aimed to investigate whether pCpG-Muγ, a plasmid continuously expressing murine IFN-γ, is an effective treatment of atopic dermatitis, a Th2-dominant skin disease. Nishiki-nezumi Cinnamon/Nagoya (NC/Nga) atopic mice with early dermatitis were transfected with pCpG-Muγ by a hydrodynamic tail vein injection at a dose of 0.05 or 0.2 pmol per mouse. The skin lesions improved only in mice receiving the high dose of pCpG-Muγ. IFN-γ gene transfer resulted in a high mRNA expression of IFN-γ and interleukin (IL)-12 and regulatory T cell (Treg) related cytokines, such as IL-10 and transforming growth factor-β, in the spleen, whereas it reduced the IL-4 mRNA expression, and serum levels of immunoglobulin (Ig) G1 and IgE. In addition, the gene transfer markedly inhibited the epidermal thickening, infiltration of inflammatory cells into the skin, the occurrence of dry skin and pruritus. No exacerbating effect on the Th1-mediated contact dermatitis was observed after IFN-γ gene transfer. Taken together, these results indicate that sustained IFN-γ gene transfer induced polarized Th1 immunity under Th2-dominant conditions in NC/Nga mice, leading to an improvement in the symptoms of acute atopic dermatitis without adverse side effects.

Evaluation of eosinophilic inflammation in a novel murine atopic keratoconjunctivitis model induced by crude Dermatophagoides farinae antigen

BACKGROUND

The purpose of this study is to conduct a histopathological research of the conjunctival findings and eosinophilic inflammation of novel atopic keratoconjunctivitis in a NC/Nga mouse model using crude Dermatophagoides farina.

METHODS

NC/Nga mice were sensitized by repeated topical applications of an ointment containing Dermatophagoides farinae body (Dfb). They were then divided into 4 groups depending on the following topical ophthalmic treatment: DFb group undergoing topical ophthalmic ointment containing Dfb; DFco group undergoing topical instillation of allergen extracts of Dermatophagoides farinae; Ba group undergoing topical ointment with substrate alone and NT group without after-topical ophthalmic treatment. At 24 hours after the last ophthalmic treatment, histopathological examination was performed. The density of the subepithelial infiltration of the eosinophils was determined. Serum total IgE and house-dust-mite (HDM)-specific IgE antibody concentrations were determined by enzyme-linked immunosorbent assay (ELISA).

RESULTS

In the DFb group, the conjunctiva showed similar findings to those of atopic keratoconjunctivitis, i.e. intraepithelial pseudotubular formation, Torus-form infiltration due to massive lymphocytes in the palpebral conjunctiva and gelatinous hyperplasia in the limbus with subepithelial granuloma composed of lymphocytes and eosinophils. Subepithelial infiltration of eosinophil density in the DFb group [878.4 ± 399.7cells/mm2 (mean ± SD)] was significantly higher than in the other 2 groups (DFco 85.6 ± 40.1 Ba 49.2 ± 32.3) (P < 0.001). Total serum IgE concentration and HDM-specific serum IgE antibody concentration in the DFb group and the DFco group were significantly higher compared with those in the NT group.

CONCLUSIONS

Topical application of an ointment containing DFb to both the skin and eyes of NC/Nga mice can induce an atopic keratoconjunctivitis (AKC) model in these mice.

Anti-inflammatory effects of sacran, a novel polysaccharide from Aphanothece sacrum, on 2,4,6-trinitrochlorobenzene-induced allergic dermatitis in vivo

BACKGROUND

Sacran is a newly discovered sulfated polysaccharide extracted from an algae, Aphanothece sacrum, grown in a river of the Kyushu region in Japan.

OBJECTIVE

To evaluate sacran's inhibitory effect in 2,4,6-trinitrochlorobenzene (TNCB)-induced allergic dermatitis in NC/Nga mice.

METHODS

Sacran was extracted by acid and alkaline treatment of A sacrum cyanobacterial biomaterials. To sensitize mice, 150 μL of 5% TNCB was applied epicutaneously on the abdomen of each mouse on day 1 and challenged with 15 μL of 1% TNCB applied on the ear skin of mice on day 8 and then every other day to induce skin lesions. Serum levels of inflammatory markers were measured and histopathologic examination of ear skin specimens performed. On the other hand, sacran's transepidermal water loss was evaluated in 11 volunteer women with dry skin.

RESULTS

Epicutaneous application of sacran in mice has significantly inhibited the development of allergic dermatitis skin lesions and reduced the number of scratching behavior episodes (P < .01). In addition, sacran efficiently inhibited IgE (P < .001), tumor necrosis factor α (P = .02), interleukin 4, interleukin 5, and interferon γ (P < .01; vs buffer in the TNCB group) production and eosinophilic infiltration in the chemical allergen-exposed ear skin. In addition, sacran-treated body regions of human volunteers with dry skin significantly reduced transepidermal water loss levels compared with exogenous hyaluronic acid (P < .01), which is known to improve skin moisture and exert skin barrier repair activity.

CONCLUSIONS

This study suggests that sacran exerts anti-inflammatory effects by improving skin barrier function and reducing T(H)2 cytokine production.

Pyridone 6, a pan-JAK inhibitor, ameliorates allergic skin inflammation of NC/Nga mice via suppression of Th2 and enhancement of Th17

Atopic dermatitis (AD) is a common pruritic inflammatory disease triggered by a defective skin barrier and immunodysregulation. AD has been considered a typical example of a Th2 response associated with allergic disease. In the early phases of the disease, symptoms include IgE hyperproduction, eosinophil accumulation, and mast cell activation; in the chronic phase, a Th1-dominant immune response is also observed at the sites of AD skin lesions. The role of IL-17-producing Th (Th17) cells in AD has not been established. In the current study, we found that pyridone 6 (P6), a pan-JAK inhibitor, delayed the onset and reduced the magnitude of skin disease in an AD-like skin-disease model of NC/Nga mice. P6 reduced IFN-γ and IL-13, whereas it enhanced IL-17 and IL-22 expression. In vitro, P6 also inhibited both Th1 and Th2 development, whereas it promoted Th17 differentiation from naive T cells when present within a certain range of concentrations. This was probably because P6 strongly inhibited STAT1, STAT5, and STAT6 phosphorylation, whereas STAT3 phosphorylation was less efficiently suppressed by P6 at the same concentration. Furthermore, IL-22 protects keratinocytes from apoptosis induced by IFN-γ, and administration of IL-17 and IL-22 partially ameliorated skin diseases in NC/Nga mice. These results suggested that the JAK inhibitor P6 is therapeutic for AD by modulating the balance of Th2 and Th17.

Mast cells in atopic dermatitis

Mast cells play as the major effector cells in immediate hypersensitivity through activation via the high-affinity IgE receptor, Fc epsilon RI, although many other functions have recently been discovered for this cell type. Given the broad array of proinflammatory mediators secreted from Fc epsilon RI-activated mast cells, as well as sensitization to allergens, IgE elevation, and increased mast cells in a majority of atopic dermatitis patients, mast cells are believed to be involved in the pathogenesis of atopic dermatitis. Numerous animal models have been used to study this epidemic disease. Here we review the recent progress to synthesize our current understanding of this disease and potential mechanisms for a mast cell's role in the disease.