Inhibition of scratching behavior associated with allergic dermatitis in mice by tacrolimus, but not by dexamethasone

Exploring the Metabolic Effects of a Herbal Remedy of Asarum sieboldii, Platycodon grandiflorum, and Cinnamomum cassia Extracts: Unraveling Its Therapeutic Potential as a Topical Application for Atopic Dermatitis Treatment

Our previous study demonstrated that our novel herbal remedy, a mixture of Asarum sieboldii, Platycodon grandiflorum, and Cinnamomum Cassia extracts, exhibits a therapeutic effect in 1-chloro-2,4-dinitrobenzene (DNCB)-induced mice by inhibiting the Th-2 inflammatory response upon oral administration. It also ameliorated imbalances in lipid metabolism related to the skin barrier function in keratinocytes, indicating its potential as a topical agent. This study aims to further investigate the therapeutic effects and metabolic mechanisms of its topical application. The anti-atopic effect was evaluated using dermatitis scores, histopathological analysis, and immune cell factors in DNCB-induced mice. Metabolomic profiling of serum and lesional skin was conducted to elucidate the metabolic mechanisms. The topical application significantly reduced dermatitis scores, mast cell infiltration, and serum levels of immunoglobulin E (IgE), IFN-γ, interleukin (IL)-4, IL-17, and thymic stromal lymphopoietin (TSLP), demonstrating its effectiveness in treating atopic dermatitis (AD). Serum metabolomics revealed alterations in fatty acid metabolism related to the pro-inflammatory response. In lesional skin, metabolic markers associated with oxidative stress, immune regulation, and AD symptoms were restored. This study demonstrated its potential as a topical agent in suppressing Th-2 inflammatory responses and improving metabolic abnormalities related to AD symptoms, providing crucial insights for developing natural AD treatments.

Epimedin A ameliorates DNFB-induced allergic contact dermatitis in mice: Role of NF-κB/NLRP3-driven pyroptosis, Nrf2/HO-1 pathway, and inflammation modulation

AIMS

The present study aimed to investigate the potential of epimedin A to ameliorate DNFB-induced allergic contact dermatitis (CD) and reveal its potential underlying mechanisms of action, emphasizing its role in modulating NF-κB/NLRP3, Nrf2/HO-1 pathways, and inflammation.

MAIN METHODS

Seven-week-old BALB/c mice received epimedin A orally for 11 days at doses of 5, 10, or 20 mg/kg/day, starting from the seventh day of DNFB-inducing CD.

KEY FINDINGS

Epimedin A dose-dependently ameliorated DNFB-induced CD, as revealed by the repression of the mice's scratching behavior, dermatitis score, ear thickness and weight, and ear tissue's histopathological changes, and area percent of collagen fibers induced by DNFB. These potentials were due to the NF-κB/NLRP3 pathway suppression and the Nrf2 pathway enhancement, as demonstrated by the reduction of NF-κB, NLRP3, ASC, caspase-1, and 8 mRNA expression, and NF-κBp65, IL-1β, MDA levels, and NF-κBp65 binding activity, along with the enhancement of the Nrf2, HO-1, IκB-α, GSH levels, SOD activity, and Nrf2 binding activity. Besides, it suppressed ear tissues' NLRP3 and caspase-8 induced pyroptosis by suppressing the ear tissues' caspase-1, 8, GSDMD upregulation, and LDH activity. Additionally, it repressed the local inflammatory reaction of ear tissue, as evidenced by the reduction of the elevated inflammatory cytokines (IL-1β, IL-6, Il-4, TNF-α, and IFN-γ), the serum level of t-IgE, DNFB s-IgE, s-IgE/t-IgE ratio, and the abrogation of the ear tissues histopathological changes.

SIGNIFICANCE

Epimedin A is a novel, hopeful, natural therapeutic agent for CD by modulating NF-κB/NLRP3, Nrf2 pathways, and inflammation.

Lycopus lucidus Turcz ameliorates DNCB‑induced atopic dermatitis in BALB/c mice

Atopic dermatitis (AD) is a chronic inflammatory allergic skin disease, characterized by pruritic and eczematous skin lesions. Lycopus lucidus Turcz (LLT) is a perennial herb that has been reported to have various biological properties, including effects on blood circulation, as well as anti-inflammatory, antioxidant, anti-vascular inflammation and wound-healing effects. However, whether LLT improves dermatitis and the underlying mechanisms has yet to be determined. The aim of the present study was to determine whether LLT can improve 2,4-dinitrochlorobenzene (DNCB)-induced dermatitis and to verify the inhibitory effect of LLT on the expression of chemokines and pro-inflammatory cytokines in the HaCaT immortalized keratinocyte cell line. In addition, the anti-inflammatory function of LLT in RAW264.7 mouse macrophages was investigated. In the DNCB-induced AD mouse model, LLT inhibited infiltration by mast cells, eosinophils and CD8⁺ cells in the dorsal skin tissue of AD mice, and suppressed the expression of IgE and IL-6 in serum. In addition, LLT inhibited the phosphorylation of ERK and JNK, as well as NF-κB in skin tissue. In the HaCaT cell model induced by TNF-α/IFN-γ, LLT inhibited the expression of thymus and activation-regulated chemokine, granulocyte-macrophage colony-stimulating factor, monocyte chemoattractant protein-1, TNF-α and IL-1β, whilst inhibiting the phosphorylation of NF-κB. In addition, in the lipopolysaccharide-induced RAW 264.7 cell inflammation model, LLT inhibited the expression of TNF-α and IFN-γ, the nuclear translocation of NF-κB and the phosphorylation of ERK and JNK. These results suggested that LLT may be a promising candidate for the treatment of inflammatory dermatitis.

Artemisia anomala Herba Alleviates 2,4-Dinitrochlorobenzene-Induced Atopic Dermatitis-Like Skin Lesions in Mice and the Production of Pro-Inflammatory Mediators in Tumor Necrosis Factor Alpha-/Interferon Gamma-Induced HaCaT Cells

Artemisia anomala S. Moore is a perennial herbaceous plant classified as Asteraceae of the genus Artemisia. Many species of Artemisia have been used as medicinal materials. Artemisia anomala S. Moore has been widely used in China to treat inflammatory diseases. However, the mechanism of its action on the keratinocyte inflammatory response is poorly understood. Here, we investigated the anti-inflammatory reaction of Artemisia anomala S. Moore ethanol extract (EAA) using human keratinocyte (HaCaT) cells, which involved investigating the nuclear factor kappa B (NF-κB), signal transducer, and activator of transcription-1 (STAT-1), as well as mitogen-activated protein kinase (MAPK) signaling pathways and atopic dermatitis-like skin lesions in mice. We elucidated the anti-inflammatory effects of EAA on tumor necrosis factor-α/interferon-γ (TNF-α/IFN-γ)-treated human keratinocyte cells and 2,4-dinitrochlorobenzene (DNCB)-induced atopic dermatitis (AD)-like mice. The levels of chemokines and cytokines (IL-8, IL-6, TARC, and RANTES) were determined by an enzyme-linked immunosorbent assay. The NF-κB, STAT-1, and MAPK signaling pathways in HaCaT cells were analyzed by western blotting. Thickening of the mice dorsal and ear skin was measured and inflammatory cell infiltration was observed by hematoxylin and eosin staining. Results showed that EAA suppressed IL-8, IL-6, TARC, and RANTES production. EAA inhibited nuclear translocation of NFκB and STAT-1, as well as reduced the levels of phosphorylated ERK MAPKs. EAA improved AD-like skin lesions in DNCB-treated mice. These findings suggest that EAA possesses stronger anti-inflammatory properties and can be useful as a functional food or candidate agent for AD.

Anti-Inflammatory Activity of a Cyclic Tetrapeptide in Mouse and Human Experimental Models

A cyclic tetrapeptide Pro-Pro-Pheβ³ho-Phe (4B8M) was tested for immunosuppressive activity and potential therapeutic utility in several in vitro and in vivo mouse and human models. The tetrapeptide was less toxic for mouse splenocytes in comparison to cyclosporine A (CsA) and a parent cyclolinopeptide (CLA). The tetrapeptide demonstrated potent anti-inflammatory properties in antigen-specific skin inflammatory reactions to oxazolone and toluene diisocyanate as well to nonspecific irritants such as salicylic acid. It also inhibited inflammatory processes in an air pouch induced by carrageenan. In addition, 4B8M proved effective in amelioration of animal models corresponding to human diseases, such as nonspecific colon inflammation induced by dextran sulfate and allergic pleurisy induced by ovalbumin (OVA) in sensitized mice. The tetrapeptide lowered expression of EP1 and EP3 but not EP2 and EP4 prostaglandin E2 (PGE2) receptors on lipopolysaccharide-stimulated Jurkat T cells and ICAM-1 expression on human peripheral blood mononuclear cells (PBMC). Its anti-inflammatory property in the carrageenan reaction was blocked by EP3 and EP4 antagonists. In addition, 4B8M induced an intracellular level of PGE2 in a human KERTr keratinocyte cell line. In conclusion, 4B8M is a low toxic and effective inhibitor of inflammatory disorders with potential therapeutic use, affecting the metabolism of prostanoid family molecules.

Solanum nigrum Linne improves DNCB‑induced atopic dermatitis‑like skin disease in BALB/c mice

The present study aimed to investigate the effects of Solanum nigrum Linne (SNL) in a model of 1-chloro-2,4-dinitrobenzene (DNCB)-induced atopic dermatitis (AD) and in TNF-α/IFN-γ-stimulated HaCaT cells. AD is a chronic inflammatory skin disease and is characterized by erythema, edema, increased pruritus and eczema. Steroids are most commonly used for anti-inflammatory therapy; however, their long-term use is limited due to side-effects, such as osteoporosis, brittle skin, muscle weaknesses and diabetes. Therefore, patients with AD require alternative treatment strategies. In previous studies, SNL has been reported to be effective against oxidants and cancer. However, to the best of our knowledge, the effects of SNL on AD have not yet been investigated. The present study examined the effects of SNL ethanol extract on a model of DNCB induced AD and on TNF-α/IFN-γ-stimulated HaCaT cells. The skin tissue was sectioned to measure the thicknesses of the epidermis and dermis, as well as the numbers of eosinophils, mast cells and CD8 infiltration by H&E, toluidine blue, Masson's trichrome and IHC staining. ELISA was performed using serum to measure IgE levels. The present study also examined the expression of various inflammatory cytokines, MAPK and NF-κB in TNF-α/IFN-γ-stimulated HaCaT cells. SNL significantly reduced the levels of cytokines released from HaCaT cells stimulated with TNF-α/IFN-γ. SNL also significantly reduced the levels of p-p38 at 30 min and significantly reduced the activation of NF-κB in a time course experiment. In addition, SNL significantly reduced the level of serum IgE and dermal thickness and the infiltration of mast cells and CD8 in the BALB/c mouse model of DNCB-induced AD. The results of the current study suggest that SNL exerts a suppressive effect on pro-inflammatory cytokines in vitro and in vivo through the regulation of the immune system.

Piperine Ameliorates Trimellitic Anhydride-Induced Atopic Dermatitis-Like Symptoms by Suppressing Th2-Mediated Immune Responses via Inhibition of STAT6 Phosphorylation

Atopic dermatitis (AD) is a common inflammatory skin disease predominately related to Type 2 helper T (Th2) immune responses. In this study, we investigated whether piperine is able to improve AD symptoms using a trimellitic anhydride (TMA)-induced AD-like mouse model. Topical treatment with piperine reduced ear swelling (ear thickness and epidermal thickness) induced by TMA exposure. Furthermore, piperine inhibited pro-inflammatory cytokines such as TNF-α and IL-1β in mouse ears, compared with the TMA-induced AD group. In measuring allergic immune responses in draining lymph nodes (dLNs), we found that IL-4 secretion, GATA3 mRNA level, and STAT6 phosphorylation were suppressed by piperine treatment. In an ex vivo study, piperine also inhibited the phosphorylation of STAT6 on the CD4⁺ T cells isolated from splenocytes of BALB/c mice, and piperine suppressed IL-4-induced CCL26 mRNA expression and STAT6 phosphorylation in human keratinocytes resulting in the inhibition of infiltration of CCR3⁺ cells into inflammatory lesions. These results demonstrate that piperine could ameliorate AD symptoms through suppression of Th2-mediated immune responses, including the STAT6/GATA3/IL-4 signaling pathway. Therefore, we suggest that piperine is an excellent candidate as an inhibitor of STAT6 and may help to improve AD symptoms.

Modulation of NR1 receptor by CaMKIIα plays an important role in chronic itch development in mice

Intractable scratching is the characteristic of chronic itch, which represents a great challenge in clinical practice. However, the mechanism underlying chronic itch development is largely unknown. In the present study, we investigated the role of NMDA receptor in acute itch and in development of chronic itch. A mouse model was developed by painting DNFB to induce allergic contact dermatitis (ACD). We found that the expression of pNR1, which is a subunit of NMDA receptor, was significantly increased in the dorsal root ganglion in the DNFB model. The DNFB-evoked spontaneous scratching was blocked by the NMDA antagonist D-AP-5, the calcium-calmodulin-dependent protein kinase (CaMK) inhibitor KN-93, a CaMKIIα siRNA and the PKC inhibitor LY317615. Moreover, activation of PKC did not reverse the CaMKIIα knockdown-induced decrease in scratching, suggesting that PKC functions upstream of CaMKIIα. Thus, our study indicates that modulation of NR1 receptor by CaMKIIα plays an important role in the development of chronic itch.

Effects of 2'-3'-dihydroxy-4',6'-dimethoxychalcone derived from green perilla on auricle thickness in chronic contact dermatitis model mice

Oxidative stress has been implicated in the pathogenesis of allergic contact dermatitis. The nuclear factor erythroid 2-related factor 2 (Nrf2)-antioxidant response element (ARE) pathway, an in vivo antioxidant system, induces antioxidant enzymes. In our previous studies, we isolated 2',3'-dihydroxy-4',6'-dimethoxychalcone (DDC) from green perilla and identified it as a novel activator of the Nrf2-ARE pathway. We also discovered that it exerted cytoprotective effects against oxidative stress in PC12 cells. However, its effects on skin disease model animals in vivo remain unclear. In the present study, auricular thickness time-dependently increased with the repeated application of picryl chloride, and significant increases were observed from Day 2 in chronic contact hypersensitivity (cCHS) model mice. Histological changes, such as higher numbers of cells in the epidermis, were observed with increases in auricular thickness. The administration of DDC every two days from Day 6 suppressed the increases in auricular thickness and the number of scratching events in a dose-dependent manner. The expression levels of antioxidant enzymes increased in the mouse auricle 24 h after the administration of DDC. These results presume that DDC inhibits increases in auricular thickness in cCHS mice by up-regulating the expression of antioxidative enzymes through the activation of the Nrf2-ARE pathway.

Topical Application of JAK1/JAK2 Inhibitor Momelotinib Exhibits Significant Anti-Inflammatory Responses in DNCB-Induced Atopic Dermatitis Model Mice

Atopic dermatitis (AD) is a chronic recurrent skin disease dominated by T-helper 2 inflammation. Momelotinib (MMB) is a novel JAK1/JAK2 inhibitor suppressing the signal transduction of multiple pro-inflammatory cytokines. Recent studies indicated that JAK inhibitor could play a therapeutic role in AD disease. In this study, we evaluated the efficacy of MMB as a novel JAK1/JAK2 inhibitor in DNCB-induced AD mice and TSLP-activated dendritic cells. Our data showed that topical application of MMB reduced the skin severity scores and total serum IgE levels, and alleviated the histological indexes including epidermal thickness measurement and mast cell number. Also, it was demonstrated that MMB down-regulated the mRNA expression of IL-4, IL-5, IFN-γ and TSLP, and inhibited the phosphorylation of STAT1, STAT3 and STAT5 in skin lesions. Moreover, MMB reduced the expression of CD80, CD86, MHCII and mRNA of OX40L in TSLP-activated dendritic cells. In general, our study suggests that MMB can improve the symptoms of AD and topical application of MMB can become a promising new therapy strategy for AD.

Glucocorticoid insensitivity by staphylococcal enterotoxin B in keratinocytes of allergic dermatitis is associated with impaired nuclear translocation of the Glucocorticoid Receptor α

BACKGROUND

staphylococcal enterotoxin plays an important role in patients with glucocorticoid (GC)-resistant atopic dermatitis (AD), but the exact mechanism is not fully understood.

OBJECTIVE

The aim of this study was to investigate the mechanisms underlying the ability of staphylococcal enterotoxin B (SEB) to induce steroid insensitivity through impaired nuclear translocation of GRα in keratinocytes.

METHODS

The steroid-resistant AD induced by SEB was assessed by analyzing dermatitis score, dermal thickness, scratching behavior, infiltrating cells/HPF, levels of SEB-specific IgE and IgG2a antibody. In addition, dexamethasone (DEX)-induced GRα nuclear translocation and keratinocyte-derived cytokines and chemokines were analyzed in the lesional keratinocytes of AD and in HaCaT cells. Furthermore, the expressions of immunophilins FKBP51, FKBP52 and HSP90 responsive to GC in HaCaT cells were determined in the presence of SEB.

RESULTS

SEB dose-dependently diminished the inhibitory effect of DEX on dermatitis score, dermal thickness, scratching behavior, infiltrating cells/HPF, keratinocyte-derived cytokines and chemokines such as RANTES, MCP-1, TSLP and GM-CSF. In vivo and in vitro data showed that in the presence of DEX, SEB dose-dependently caused a marked decrease of GRα nuclear translocation in lesional keratinocytes of AD and in HaCaT cells. Importantly, in the presence of DEX, SEB increased the expression of FKBP51 and the product of keratinocyte-derived cytokines and chemokines in HaCaT cells.

CONCLUSION

These results demonstrate that GC insensitivity by SEB in keratinocytes of AD is associated with impaired nuclear translocation of the GRα. Increased DEX-induced FKBP51 by SEB may contribute to accumulation of the GRα in cytoplasm of keratinocytes.

A murine model of atopic dermatitis can be generated by painting the dorsal skin with hapten twice 14 days apart

Drug development involves pharmacometric experiments in animals. Such experiments should limit animal pain and stress. Conventional murine models of atopic dermatitis (AD) used in drug development are generated by weekly painting of hapten on dorsal skin for 5 weeks. The present study aimed to develop a protocol that involves less animal distress. The experiments focused on serum total IgE levels, which are a marker of AD. The conventional protocol induced ever rising IgE levels. Experiments with extended intervals between sensitizations showed that IgE peaked ~5 days after the second sensitization, after which it returned to the control level within 12-19 days. An additional third sensitization on day 28 further increased the serum IgE level. In the 4-5 days after the second sensitization, the dorsal skin exhibited typical AD-like lesions with edema, scabs, epithelial-cell hypertrophy, marked mast-cell and lymphocyte infiltration of dermis, and increased IL-4, IL-6, IL-10, IL-1β, IL-17A, IFN-γ and TNF-α expression. Thus, two 2,4-dinitrofluorobenzene sensitizations yield a murine AD model in less than 20 days. This study shows that animal model protocols used in drug development can be fine-tuned so that they remain effective yet cause animals less stress and pain.

Chemokine Receptor CXCR3 in the Spinal Cord Contributes to Chronic Itch in Mice

Recent studies have shown that the chemokine receptor CXCR3 and its ligand CXCL10 in the dorsal root ganglion mediate itch in experimental allergic contact dermatitis (ACD). CXCR3 in the spinal cord also contributes to the maintenance of neuropathic pain. However, whether spinal CXCR3 is involved in acute or chronic itch remains unclear. Here, we report that Cxcr3 ^-/- mice showed normal scratching in acute itch models but reduced scratching in chronic itch models of dry skin and ACD. In contrast, both formalin-induced acute pain and complete Freund's adjuvant-induced chronic inflammatory pain were reduced in Cxcr3 ^-/- mice. In addition, the expression of CXCR3 and CXCL10 was increased in the spinal cord in the dry skin model induced by acetone and diethyl ether followed by water (AEW). Intrathecal injection of a CXCR3 antagonist alleviated AEW-induced itch. Furthermore, touch-elicited itch (alloknesis) after compound 48/80 or AEW treatment was suppressed in Cxcr3 ^-/- mice. Finally, AEW-induced astrocyte activation was inhibited in Cxcr3 ^-/- mice. Taken together, these data suggest that spinal CXCR3 mediates chronic itch and alloknesis, and targeting CXCR3 may provide effective treatment for chronic pruritus.

Therapeutic Effects of Korean Red Ginseng Extract in a Murine Model of Atopic Dermatitis: Anti-pruritic and Anti-inflammatory Mechanism

Korean red ginseng (KRG) and ginsenosides exhibit diverse biological effects, including anti-inflammatory and anti-allergic. We aimed to investigate the therapeutic effect of KRG in a murine model of atopic dermatitis (AD) is mediated whether by diminishing the pruritus or by suppressing the inflammation. Thirty NC/Nga mice were randomly divided to 5 groups. AD-like skin lesions were induced by percutaneous challenge with 2,4,6-trinitro-1-chrolobenzene (TNCB) on the ears and backs of NC/Nga mice. KRG extract, evening primrose oil, cyclosporine, and phosphate-buffered saline were administered orally by a gastric tube. Each study group was also divided into scratching-permitted and scratching-restricted subgroups to evaluate the impact of scratching behavior on AD. The effects of KRG and the other agents were assessed by measuring the clinical severity score, ear thickness, extent of transepidermal water loss (TEWL), number of scratching movements, total systemic immunoglobulin E (IgE) and interleukin (IL)-31 levels, histologic changes of cutaneous lesions, and mRNA expression levels of tumor necrosis factor (TNF)-α, interferon (IFN)-γ, thymic stromal lymphopoietin (TSLP), and IL-31. KRG exerts therapeutic effects against AD by inhibiting the T helper 2 (Th2) mediated inflammation as well as by diminishing the itching sensation. Moreover, restricting scratching behavior suppresses the vicious cycle of itching and scratching, thus reducing clinical and systemic inflammation in our murine model of AD.

Glycomacropeptide Attenuates Inflammation, Pruritus, and Th2 Response Associated with Atopic Dermatitis Induced by 2,4-Dinitrochlorobenzene in Rat

Atopic dermatitis (AD) is one of the most common skin diseases, whose incidence is increasing in industrialized countries. The epicutaneous application of a hapten, such as 2,4-dinitrochlorobenzene (DNCB), evokes an experimental murine AD-like reaction. Glycomacropeptide (GMP) is a dairy bioactive peptide derived from hydrolysis of κ-casein by chymosin action. It has anti-inflammatory, prebiotic, and immunomodulatory effects. The present study was aimed to investigate the effect of GMP administration on DNCB-induced AD in rats. The severity of inflammatory process, pruritus, production of cytokines, and total immunoglobulin E (IgE) content were measured, and the histopathological features were analyzed. GMP reduced the intensity of inflammatory process and edema of DNCB-induced dermatitis, with a significant decrease in eosinophils recruitment and mast cells hyperplasia. In addition GMP suppressed the serum levels of total IgE and IL-4, IL-5, and IL-13 expression in AD-lesions. Besides, the levels of IL-10 were significantly increased. Remarkably, GMP administration before AD-induction abolished pruritus in dermatitis-like reactions in the rats. Taken together, these results indicate that GMP has an inhibitory effect on AD by downregulating Th2 dominant immune response, suggesting GMP as a potential effective alternative therapy for the prevention and management of AD.

Forsythia suspensa Suppresses House Dust Mite Extract-Induced Atopic Dermatitis in NC/Nga Mice

Forsythia suspensa (F. suspensa) is a traditional medicine for treatment of inflammation. In this study, we evaluated the therapeutic effects of an ethanol extract from F. suspensa fruits on atopic dermatitis both in vivo and in vitro. We investigated the inhibitory effects of F. suspensa extract on the development of atopic dermatitis-like skin lesions in an NC/Nga mouse model exposed to Dermatophagoides farinae crude extract. Topical application of F. suspensa extract to the mice attenuated the atopic dermatitis symptoms, including increased dermatitis severity score, ear thickness, infiltration of inflammatory cells in the skin lesions, serum levels of IgE, TNF-α, and histamine, and expression of chemokines, cytokines, and adhesion molecules in ear tissue. In addition, F. suspensa extract inhibited the production of chemokines in TNF-α/IFN-γ-activated human keratinocytes. High-performance liquid chromatography analysis of FSE revealed the presence of four chemical constituents (forsythiaside, phillyrin, pinoresinol, and phylligenin). These compounds inhibited the production of chemokines in TNF-α/IFN-γ-activated human keratinocytes. These results suggest that the F. suspensa might be a useful candidate for treating allergic skin inflammatory disorders.

Prospective study in a porcine model of sarcoptes scabiei indicates the association of Th2 and Th17 pathways with the clinical severity of scabies

Background

Understanding of scabies immunopathology has been hampered by the inability to undertake longitudinal studies in humans. Pigs are a useful animal model for scabies, and show clinical and immunologic changes similar to those in humans. Crusted scabies can be readily established in pigs by treatment with the glucocorticoid dexamethasone (Dex).

Methodology/ Principal Findings

Prospective study of 24 pigs in four groups: a) Scabies+/Dex+, b) Scabies+/Dex-, c) Scabies-/Dex+ and d) Scabies-/Dex-. Clinical symptoms were monitored. Histological profiling and transcriptional analysis of skin biopsies was undertaken to compare changes in cell infiltrates and representative cytokines. A range of clinical responses to Sarcoptes scabiei were observed in Dex treated and non-immunosuppressed pigs. An association was confirmed between disease severity and transcription of the Th2 cytokines IL-4 and IL-13, and up-regulation of the Th17 cytokines IL-17 and IL-23 in pigs with crusted scabies. Immunohistochemistry revealed marked infiltration of lymphocytes and mast cells, and strong staining for IL-17.

Conclusions/ Significance

While an allergic Th2 type response to scabies has been previously described, these results suggest that IL-17 related pathways may also contribute to immunopathology of crusted scabies. This may lead to new strategies to protect vulnerable subjects from contracting recurrent crusted scabies.

Scabies is a neglected tropical skin disease caused by the tiny parasitic mite Sarcoptes scabiei. Scabies is common in developing countries, and scabies outbreaks also occur in institutional settings worldwide. Scabies often underlies secondary bacterial skin infection and resulting complications, and is thus associated with considerable morbidity. Crusted scabies is a an extremely severe and debilitating clinical form of the disease, but host immune responses leading to the development of crusted or ordinary scabies are poorly understood. This is largely due to limited access to clinical samples, and the difficulty in monitoring the progression of infestation in human patients. We have overcome this challenge by using a pig model of scabies infestation, since pigs and humans with scabies display clinical and immunological similarities. In this study, we undertook longitudinal analysis of clinical, histological and molecular immunological changes in pigs experimentally infected with scabies. We confirmed that disease severity was associated with a pronounced allergic, Th2 immune response, as previously reported. In a novel finding, we showed that the Th17 associated cytokines interleukin-17 and interleukin-23 were also associated with the development of crusted scabies. This may lead to new immunotherapeutic strategies to protect vulnerable subjects from contracting recurrent crusted scabies.

Low-dose ethanol aggravates allergic dermatitis in mice

Alcohol injures dendritic cells and suppresses cellular immunity, while some evidence indicates that drinking alcohol aggravates allergic asthma. This study investigated the effect of low doses of ethanol in enhancing allergic reactions in the skin of mice. Liquid food containing alcohol was administered to conventional NC/Nga mice to induce alcoholic hepatic steatosis, and spontaneous dermatitis was evaluated. BALB/c mice were administered approximately 1 g/kg body weight of ethanol by gavage, and contact hypersensitivity (CHS) or active cutaneous anaphylaxis (ACA) was induced. Spleens were collected 24 h after the elicitation of CHS and mRNA expressions of interferon (IFN)-γ, interleukin (IL)-4, IL-6, IL-10, and IL-18 were measured by quantitative RT-PCR. Alcohol-containing diet exaggerated spontaneous dermatitis in conventional NC/Nga mice and contact hypersensitivity in BALB/c mice. Ethanol administered by gavage for 5 days enhanced contact hypersensitivity in BALB/c mice. Ethanol administration with gavage also enhanced ACA of BALB/c mice. Ethanol did not affect mRNA expression of IFN-γ and IL-4, but did enhance IL-6, IL-10, and IL-18 mRNA expression. Histological evaluation revealed an absence of hepatic steatosis in mice administered ethanol by gavage for 5 days. In ethanol-administered mice, inflamed areas presented as lesions or a local extreme accumulation of mononuclear cells in the epidermis. These findings suggest that ethanol enhances the expression of inflammatory cytokines independently from T helper (Th)1/Th2 cytokine phenotypes, causing abnormalities in the epidermis resulting in exacerbated allergic reactivity.

Extracellular signal-regulated kinase (ERK) activation is required for itch sensation in the spinal cord

Background

Itch, chronic itch in particular, can have a significant negative impact on an individual’s quality of life. However, the molecular mechanisms underlying itch processing in the central nervous system remain largely unknown.

Results

We report here that activation of ERK signaling in the spinal cord is required for itch sensation. ERK activation, as revealed by anti-phosphorylated ERK1/2 immunostaining, is observed in the spinal dorsal horn of mice treated with intradermal injections of histamine and compound 48/80 but not chloroquine or SLIGRL-NH2, indicating that ERK activation only occurs in histamine-dependent acute itch. In addition, ERK activation is also observed in 2, 4-dinitrofluorobenzene (DNFB)-induced itch. Consistently, intrathecal administration of the ERK phosphorylation inhibitor U0126 dramatically reduces the scratching behaviors induced by histamine and DNFB, but not by chloroquine. Furthermore, administration of the histamine receptor H1 antagonist chlorpheniramine decreases the scratching behaviors and ERK activation induced by histamine, but has no effect on DNFB-induced itch responses. Finally, the patch-clamp recording shows that in histamine-, chloroquine- and DNFB-treated mice the spontaneous excitatory postsynaptic current (sEPSC) of dorsal horn neurons is increased, and the decrease of action potential threshold is largely prevented by bathing of U0126 in histamine- and DNFB-treated mice but not those treated with chloroquine.

Conclusion

Our results demonstrate a critical role for ERK activation in itch sensation at the spinal level.

Chronic itch development in sensory neurons requires BRAF signaling pathways

Chronic itch, or pruritus, is associated with a wide range of skin abnormalities. The mechanisms responsible for chronic itch induction and persistence remain unclear. We developed a mouse model in which a constitutively active form of the serine/threonine kinase BRAF was expressed in neurons gated by the sodium channel Nav1.8 (BRAF(Nav1.8) mice). We found that constitutive BRAF pathway activation in BRAF(Nav1.8) mice results in ectopic and enhanced expression of a cohort of itch-sensing genes, including gastrin-releasing peptide (GRP) and MAS-related GPCR member A3 (MRGPRA3), in nociceptors expressing transient receptor potential vanilloid 1 (TRPV1). BRAF(Nav1.8) mice showed de novo neuronal responsiveness to pruritogens, enhanced pruriceptor excitability, and heightened evoked and spontaneous scratching behavior. GRP receptor expression was increased in the spinal cord, indicating augmented coding capacity for itch subsequent to amplified pruriceptive inputs. Enhanced GRP expression and sustained ERK phosphorylation were observed in sensory neurons of mice with allergic contact dermatitis– or dry skin–elicited itch; however, spinal ERK activation was not required for maintaining central sensitization of itch. Inhibition of either BRAF or GRP signaling attenuated itch sensation in chronic itch mouse models. These data uncover RAF/MEK/ERK signaling as a key regulator that confers a subset of nociceptors with pruriceptive properties to initiate and maintain long-lasting itch sensation.

Highly deformable and highly fluid vesicles as potential drug delivery systems: theoretical and practical considerations

Vesicles that are specifically designed to overcome the stratum corneum barrier in intact skin provide an efficient transdermal (systemic or local) drug delivery system. They can be classified into two main groups according to the mechanisms underlying their skin interaction. The first group comprises those possessing highly deformable bilayers, achieved by incorporating edge activators to the bilayers or by mixing with certain hydrophilic solutes. The vesicles of this group act as drug carriers that penetrate across hydrophilic pathways of the intact skin. The second group comprises those possessing highly fluid bilayers, owing to the presence of permeation enhancers. The vesicles of this group can act as carriers of drugs that permeate the skin after the barrier of the stratum corneum is altered because of synergistic action with the permeation enhancers contained in the vesicle structure. We have included a detailed overview of the different mechanisms of skin interaction and discussed the most promising preclinical applications of the last five years of Transfersomes® (IDEA AG, Munich, Germany), ethosomes, and invasomes as carriers of antitumoral and anti-inflammatory drugs applied by the topical route.

Investigational drugs for pruritus

INTRODUCTION

Chronic pruritus (CP), defined as itch lasting for > 6 weeks, is a burdensome symptom of several different diseases, dermatological and systemic, with a high negative impact on the quality of life of patients. Given the manifold aetiologies of CP, therapy is often difficult. In recent years, however, novel substances have been developed for treatment of certain CP entities and identified targets.

AREAS COVERED

In this review, the authors present a survey of targets currently believed to be promising (H4R, IL-31, MOR, KOR, GRPR, NGF, NK-1R, TRP channels) and related investigational drugs that are in the preclinical or clinical stage of development. Some substances have already undergone clinical testing, but only one of them (nalfurafine) has been licensed so far. Many of them are most likely to exert their effects on the skin and interfere there with the cutaneous neurobiology of CP.

EXPERT OPINION

Currently, the most promising candidates for new therapeutic agents in CP are neurokinin-1 receptor antagonists and substances targeting the kappa- or mu-opioid receptor, or both. They have the potential to target the neuronal pathway of CP and are thus of interest for several CP entities. The goal for the coming years is to validate these concepts and move forward in developing new drugs for the therapy of CP.

Antibody responses to Sarcoptes scabiei apolipoprotein in a porcine model: relevance to immunodiagnosis of recent infection

No commercial immunodiagnostic tests for human scabies are currently available, and existing animal tests are not sufficiently sensitive. The recombinant Sarcoptes scabiei apolipoprotein antigen Sar s 14.3 is a promising immunodiagnostic, eliciting high levels of IgE and IgG in infected people. Limited data are available regarding the temporal development of antibodies to Sar s 14.3, an issue of relevance in terms of immunodiagnosis. We utilised a porcine model to prospectively compare specific antibody responses to a primary infestation by ELISA, to Sar s 14.3 and to S. scabiei whole mite antigen extract (WMA). Differences in the antibody profile between antigens were apparent, with Sar s 14.3 responses detected earlier, and declining significantly after peak infestation compared to WMA. Both antigens resulted in >90% diagnostic sensitivity from weeks 8-16 post infestation. These data provide important information on the temporal development of humoral immune responses in scabies and further supports the development of recombinant antigen based immunodiagnostic tests for recent scabies infestations.

A randomized, open-label, multicenter trial of topical tacrolimus for the treatment of pruritis in patients with atopic dermatitis

Background

Pruritis caused by atopic dermatitis (AD) is not always well controlled by topical corticosteroid therapy, but use of tacrolimus often helps to soothe such intractable pruritis in clinical settings.

Objective

To determine the anti-pruritic efficacy of topical tacrolimus in treating AD in induction and maintenance therapy.

Methods

Prior to the study, patients were randomly allocated into two groups, induction therapy followed by tacrolimus monotherapy maintenance, and induction therapy followed by emollient-only maintenance. In the induction therapy, the patients were allowed to use topical tacrolimus and emollients in addition to a low dose (<10 g/week) of topical steroids. Patients showing relief from pruritis were allowed to proceed to maintenance therapy. Recurrence of pruritis in maintenance therapy was examined as a major endpoint.

Results

Two-thirds of patients (44/68; 64.7%) showed relief from pruritis after induction therapy. Pruritis recurred in 23.8% (5/21) of the tacrolimus monotherapy group and in 100% (21/21) of the emollient group during maintenance period, a difference that was statistically significant.

Conclusion

Use of topical tacrolimus is effective in controlling pruritis of AD compared to emollient.

Red ginseng inhibits scratching behavior associated with atopic dermatitis in experimental animal models

Pruritus is a severe symptom that is difficult to treat in atopic dermatitis patients. Red ginseng (RG), a natural medicine, has various biological activities such as anti-inflammatory effects. In this study, we examined the efficacy of RG extract (RGE) and its mechanism on experimental atopic dermatitis in mice. The effects of RGE on vascular permeability and itching were first evaluated. Histamine-induced permeability and itching were significantly inhibited by embrocation with RGE as well as diphenhydramine, an antihistamine drug. Next, we assessed the therapeutic effect of topical RGE in a mouse model of atopic dermatitis. Dermatitis was induced by repeated application of 2,4-dinitrofluorobenzene (DNFB) acetone solution to the mouse ear. The effects of tacrolimus (a calcineurin blocker), dexamethasone (a corticosteroid), and RGE on dermatitis and associated scratching behavior were compared. Repeated DNFB application caused frequent scratching behaviors and ear swelling. Topical treatment with tacrolimus, dexamethasone, and RGE for 8 days before the final challenge with DNFB significantly inhibited ear swelling. Tacrolimus and RGE significantly inhibited scratching behavior, whereas dexamethasone failed to do so. DNFB-induced nerve growth factor expression and nerve fiber extension were significantly attenuated by tacrolimus and RGE, but not by dexamethasone. RGE may have the potential for treatment of atopic dermatitis.

A GPR40 agonist GW9508 suppresses CCL5, CCL17, and CXCL10 induction in keratinocytes and attenuates cutaneous immune inflammation

G-protein coupled receptors (GPCR) exert diverse physiological functions, many of which are exploited therapeutically. The roles of GPCR in keratinocytes in immune response in the skin, however, remain poorly defined. In this study, we focused on Gi-coupled GPCR in keratinocytes and defined their actions in immunoactivation of cultured keratinocytes in vitro and immune reaction in the skin in vivo. We first activated HaCaT cells by tumor necrosis factor (TNF)-α and IFN-γ and examined effects of various ligands for GPCR on production of CCL17 and CCL5. Agonists for Gi-coupled receptors, particularly GW9508 for GPR40, inhibited CCL17 and CCL5 expression in a pertussis toxin-sensitive manner. The inhibitory effect by GW9508 was abrogated by depletion of GPR40 with RNA interference. GW9508 further suppressed expression of IL-11, IL-24, and IL-33 induced in HaCaT cells by TNF-α and IFN-γ. GW9508 also inhibited CCL5 and CXCL10 production by normal human epidermal keratinocytes. Administration of GW9508 topically to the skin in the challenging phase suppressed ear swelling in a repeated hapten application model and contact hypersensitivity with downregulation of CCL5 and CXCL10, respectively. Thus, in the skin, stimulation of Gi-coupled receptors attenuates induction of critical cytokines and chemokines by proinflammatory cytokines in keratinocytes and suppresses allergic inflammation in the skin.

Topical application of Rehmannia glutinosa extract inhibits mite allergen-induced atopic dermatitis in NC/Nga mice

AIM OF THE STUDY

Rehmannia glutinosa is known in Asia as a traditional herbal medicine with anti-inflammatory properties. Atopic dermatitis (AD) is an inflammatory skin disease associated with enhanced T-helper 2 (Th2) lymphocyte responses to allergens that results in elevated serum IgE levels and leukocyte infiltration. Although some studies have shown that Rehmannia glutinosa extract (RGE) has anti-inflammatory and anti-allergic activities, these properties have not been demonstrated in AD. This study investigated the effectiveness of RGE as a therapeutic candidate in an AD model as well as its underlying mechanism of action.

MATERIALS AND METHODS

The effects of RGE on mite allergen (Dermatophagoides farinae)-treated NC/Nga mice were evaluated by skin symptom severity, ear thickness, production of serum IgE and histamine, and expression of cytokines, chemokines, and adhesion molecules in the ear lesions. In addition, the levels of thymus and activation-regulated chemokine (TARC), macrophage-derived chemokine (MDC), and regulated on activation, normal T cell expressed and secreted (RANTES) produced in both TNF-α- and IFN-γ-stimulated human keratinocytes were investigated by enzyme-linked immunosorbent assay (ELISA).

RESULTS

RGE treatment of NC/Nga mice significantly reduced dermatitis scores, ear thicknesses, and serum histamine levels. Histological analyses demonstrated decreased thickening of the epidermis/dermis as well as dermal infiltration by inflammatory cells. In the ear lesions, mRNA expression levels of IL-4, TNF-α, VCAM-1, and ICAM-1 were inhibited by RGE treatment. RGE also suppressed the production of TARC, MDC, and RANTES in both the ear lesions and keratinocytes.

CONCLUSIONS

RGE inhibits the development of AD in NC/Nga mice by suppressing the expression of cytokines, chemokines, and adhesion molecules.

Comparison of the efficacy of tacrolimus and cyclosporine A in a murine model of dinitrofluorobenzene-induced atopic dermatitis

Tacrolimus (FK506) and cyclosporine A (Cys A) are immunosuppressive drugs used in the treatment of inflammatory diseases and for preventing rejection of allogeneic transplants. Tacrolimus forms a complex with FK506 binding protein (FKBP), and Cys A forms a complex with cyclophilin. These tacrolimus-FKBP and Cys A-cyclophilin complexes interact with calcineurin (CaN), thereby suppressing activation of T cells. In contrast, steroidal anti-inflammatory drugs suppress the immune system mainly via inhibition of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kappaB) and the activating protein-1 (AP-1) pathway. Previously, we reported that tacrolimus, but not dexamethasone, reduced scratching behavior in a murine model of atopic dermatitis. To elucidate the mechanism involved in the inhibition of scratching behavior, we used a mouse model of allergic dermatitis to compare the characteristics of tacrolimus and Cys A treatment. We found that Cys A suppressed scratching behavior induced by application of 2,4-dinitrofluorobenzene, as did tacrolimus. In addition, both drugs attenuated increases in vascular permeability and scratching behavior induced by passive cutaneous anaphylaxis. These results indicate that inhibition of the CaN pathway plays an important role in tacrolimus- and Cys A-induced inhibition of scratching behavior in mice. Furthermore, we observed that CaN inhibitors suppressed mast cell-dependent allergic reaction.

Scratching behavior does not necessarily correlate with epidermal nerve fiber sprouting or inflammatory cell infiltration

BACKGROUND

Increased sprouting of epidermal nerve fibers of lesional skin are thought to be associated with persistent pruritus in chronic inflammatory dermatitis such as atopic dermatitis as supported by a murine study using tacrolimus (or FK506: FK) which was shown to inhibit both epidermal sprouting of nerves and scratching behavior or by immunohistochemical observations of lesional skin in the patients with atopic dermatitis or prurigo, etc.

OBJECTIVES

To examine a mitogen-activated protein kinase/extracellular signal-regulated kinase kinase 1/2 (MEK1/2) inhibitor (CX-659S: CX) for a possible anti-pruritic property in vivo since some MEK1/2 inhibitors have been reported to inhibit neurite growth in vitro.

METHODS

CX, FK and corticosteroids (betamethasone valerate: BV) were topically applied on inflamed skin in a mouse model of chronic dermatitis using repetitive hapten painting to examine anti-pruritic property and anti-inflammatory effects. Scratching behaviors were assessed using MicroAct automatic measuring system, and epidermal sprouting of nerves and skin inflammation was assessed histologically.

RESULTS

FK significantly decrease scratching behavior, but CX and BV failed to do so despite of their ability to significantly inhibit epidermal nerve fiber sprouting and skin inflammation, respectively. In addition, CX+BV mixture synergistically inhibited epidermal nerve fiber sprouting and skin inflammation even more potently than FK without decreasing scratching behavior.

CONCLUSIONS

These findings suggest that the scratching behavior does not necessarily correlate with epidermal nerve fiber sprouting or inflammatory cell infiltration.

Effects and mechanisms of aloperine on 2, 4-dinitrofluorobenzene-induced allergic contact dermatitis in BALB/c mice

Allergic contact dermatitis is a prototypic T-cell-mediated cutaneous inflammatory response. Multiple cell types, inflammatory mediators and cytokines are involved in the regulation of immunologic and inflammatory processes in allergic contact dermatitis. Aloperine is an isolated alkaloid found in the plant of Sophora alopecuroides L. It has been clinically proved effective in China for a long time for skin inflammatory diseases such as allergic contact dermatitis. However, the mechanism of aloperine on allergic contact dermatitis is largely unknown. Therefore, the aim of this study was to investigate the effect of aloperine on 2, 4-dinitrofluorobenzene (DNFB)-induced allergic contact dermatitis in BALB/c mice and the possible underlying mechanisms. The results showed that topical application of DNFB on the ear provoked typical allergic contact dermatitis with ear swelling and ear erythema in BALB/c mice. Treatments with 1% aloperine suppressed DNFB-induced increase in ear thickness and ear erythema. Moreover, 1% aloperine treatment significantly decreased the up-regulated mRNA and protein levels of tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta) and interleukin-6 (IL-6) induced by DNFB in ear biopsy homogenates. Our findings suggest that aloperine greatly improves the DNFB-induced allergic contact dermatitis in mice. The therapeutic mechanism might be related to the reduction of TNF-alpha, IL-1beta and IL-6 production induced by DNFB.

Participation of proteinase-activated receptor-2 in passive cutaneous anaphylaxis-induced scratching behavior and the inhibitory effect of tacrolimus

Proteinase-activated receptor-2 (PAR2) may be an important regulator of skin mast cell function during cutaneous inflammation and hypersensitivity. However, little is known of the role of PAR2 in allergic pruritus, because mast cells, which are thought to be responsible for this symptom, can release a number of different pruritogens. In the present study, we investigated the effects of several agents on passive cutaneous anaphylaxis-induced scratching behavior in ICR mice. As a result, cetirizine and ketanserin produced dose-dependent inhibition of scratching behavior induced by passive cutaneous anaphylaxis. Combined cetirizine with ketanserin exhibited significant inhibitory effects for the number of passive cutaneous anaphylaxis-induced scratching behavior. Pretreatment of the experimental animals with PAR2-neutralizing antibody and protease inhibitor leupeptin significantly inhibited passive cutaneous anaphylaxis-induced scratching behavior. Furthermore, we found that topical application of tacrolimus significantly reduced the number of scratching behavior induced by passive cutaneous anaphylaxis in a dose-dependent manner. Combined cetirizine with tacrolimus also exhibited significant inhibitory effects for the number of passive cutaneous anaphylaxis-induced scratching behavior. Tacrolimus in doses of 3% and 10% significantly inhibited tryptase-induced scratching behavior. These results suggest that PAR2 may be involved in passive cutaneous anaphylaxis-induced scratching behavior and tacrolimus produces an anti-allergic pruritus effect in ICR mice.

Depletion of substance P, a mechanism for inhibition of mouse scratching behavior by tacrolimus

Itching is the most important problem in atopic dermatitis and tacrolimus has been suggested to attenuate the itching by topical application. However, the anti-itch mechanism of tacrolimus has not been well elucidated. In the present study, an allergic dermatitis accompanied by frequent scratching behaviors was induced by repeated paintings with 2,4-dinitrofluorobenzene (DNFB) acetone solution onto the mouse ear and the effects of tacrolimus and dexamethasone on the dermatitis and associated scratching behavior were comparatively examined. Repeated DNFB paintings caused a typical dermatitis accompanied by elevated serum immunoglobulin E (IgE) and frequent scratching behaviors. Both tacrolimus and dexamethasone given topically for 10 days before the final challenge significantly inhibited the ear swelling and reduced the expression of interferon-gamma mRNA. Dexamethasone inhibited the accumulation of eosinophils completely, although tacrolimus did not. Both drugs did not affect the elevation of serum IgE levels. Tacrolimus significantly inhibited the scratching behavior, whereas dexamethasone failed to affect it. Repeated DNFB challenge depleted substance P in the dermis. Treatment with tacrolimus before the final challenge completely inhibited the recovery of substance P content, whereas dexamethasone facilitated the recovery. DNFB-induced ear swelling and scratching behavior were significantly inhibited by FK888, a tachykinin NK(1) receptor antagonist. Therefore, substance P seems to participate in the induction of ear swelling and scratching behavior upon final challenge with DNFB, and depletion of substance P by tacrolimus in the dermis contributes to its inhibition of ear swelling and scratching behavior at least in part.

Analysis of the mechanism for the development of allergic skin inflammation and the application for its treatment:mouse models for the development of remedies for human allergic dermatitis

Animal models for human diseases are important for the elucidation of mechanisms involved in as well as for the establishment of effective treatment strategies for the diseases. Many mouse allergic dermatitis models have been established and applied for the development of remedies for human allergic dermatitis. One of the simplest allergic cutaneous reaction models is passive cutaneous anaphylaxis. Skin mast cells passively sensitized with antigen-specific IgE are activated upon antigen challenge to cause vascular permeability increase. The triphasic cutaneous reaction is another interesting model in which triphasic cutaneous swelling appears in mice passively sensitized with IgE upon challenge with specific antigen. Recently, many allergic dermatitis models have been established by repeated antigen exposure. Although the induced dermatitis seems to be complex, these models may possess the characteristic features observed in patients. Naturally occurring dermatitis model mice such as NC/Nga, NOA, and DS-Nh mice, and gene-knockout and transgenic mice exhibiting spontaneous dermatitis are also known. Establishment and characterization of the mouse dermatitis models seem to be important for understanding dermatitis and development of new strategies for the treatment of these diseases.