Intralesional cytokines in chronic oxazolone-induced contact sensitivity suggest roles for tumor necrosis factor alpha and interleukin-4

Granzyme K contributes to endothelial microvascular damage and leakage during skin inflammation

BACKGROUND

Granzyme K (GzmK) is a serine protease with minimal presence in healthy tissues while abundant in inflamed tissues. Initially thought to play an exclusive role in immune-mediated cell death, extracellular GzmK can also promote inflammation.

OBJECTIVES

To evaluate the role of GzmK in the pathogenesis of atopic dermatitis (AD), the most common inflammatory skin disease.

METHODS

A panel of human AD and control samples was analysed to determine if GzmK is elevated. Next, to determine a pathological role for GzmK in AD-like skin inflammation, oxazolone-induced dermatitis was induced in GzmK-/- and wild-type (WT) mice.

RESULTS

In human lesional AD samples, there was an increase in the number of GzmK+ cells compared with healthy controls. GzmK-/- mice exhibited reduced overall disease severity characterized by reductions in scaling, erosions and erythema. Surprisingly, the presence of GzmK did not notably increase the overall pro-inflammatory response or epidermal barrier permeability in WT mice; rather, GzmK impaired angiogenesis, increased microvascular damage and microhaemorrhage. Mechanistically, GzmK contributed to vessel damage through cleavage of syndecan-1, a key structural component of the glycocalyx, which coats the luminal surface of vascular endothelia.

CONCLUSIONS

GzmK may provide a potential therapeutic target for skin conditions associated with persistent inflammation, vasculitis and pathological angiogenesis.

CD103 Regulates Dermal Regulatory T Cell Motility and Interactions with CD11c-Expressing Leukocytes to Control Skin Inflammation

Dermal regulatory T cells (Tregs) are essential for maintenance of skin homeostasis and control of skin inflammatory responses. In mice, Tregs in the skin are characterized by high expression of CD103, the αE integrin. Evidence indicates that CD103 promotes Treg retention within the skin, although the mechanism underlying this effect is unknown. The main ligand of CD103, E-cadherin, is predominantly expressed by cells in the epidermis. However, because Tregs are predominantly located within the dermis, the nature of the interactions between E-cadherin and CD103-expressing Tregs is unclear. In this study, we used multiphoton intravital microscopy to examine the contribution of CD103 to Treg behavior in resting and inflamed skin of mice undergoing oxazolone-induced contact hypersensitivity. Inhibition of CD103 in uninflamed skin did not alter Treg behavior, whereas 48 h after inducing contact hypersensitivity by oxazolone challenge, CD103 inhibition increased Treg migration. This coincided with E-cadherin upregulation on infiltrating myeloid leukocytes in the dermis. Using CD11c-enhanced yellow fluorescent protein (EYFP) × Foxp3-GFP dual-reporter mice, inhibition of CD103 was found to reduce Treg interactions with dermal dendritic cells. CD103 inhibition also resulted in increased recruitment of effector CD4+ T cells and IFN-γ expression in challenged skin and resulted in reduced glucocorticoid-induced TNFR-related protein expression on Tregs. These results demonstrate that CD103 controls intradermal Treg migration, but only at later stages in the inflammatory response, when E-cadherin expression in the dermis is increased, and provide evidence that CD103-mediated interactions between Tregs and dermal dendritic cells support regulation of skin inflammation.

Treg cells require Izumo1R to regulate γδT cell-driven inflammation in the skin

Izumo1R is a pseudo-folate receptor with an essential role in mediating tight oocyte/spermatozoa contacts during fertilization. Intriguingly, it is also expressed in CD4+ T lymphocytes, in particular Treg cells under the control of Foxp3. To understand Izumo1R function in Treg cells, we analyzed mice with Treg-specific Izumo1r deficiency (Iz1rTrKO). Treg differentiation and homeostasis were largely normal, with no overt autoimmunity and only marginal increases in PD1+ and CD44hi Treg phenotypes. pTreg differentiation was also unaffected. Iz1rTrKO mice proved uniquely susceptible to imiquimod-induced, γδT cell-dependent, skin disease, contrasting with normal responses to several inflammatory or tumor challenges, including other models of skin inflammation. Analysis of Iz1rTrKO skin revealed a subclinical inflammation that presaged IMQ-induced changes, with an imbalance of Rorγ+ γδT cells. Immunostaining of normal mouse skin revealed the expression of Izumo1, the ligand for Izumo1R, electively in dermal γδT cells. We propose that Izumo1R on Tregs enables tight contacts with γδT cells, thereby controlling a particular path of skin inflammation.

The contribution of mouse models to understanding atopic dermatitis

Atopic dermatitis (AD) is a dermatological disease accompanied by dry and cracked skin with severe pruritus. Although various therapeutic strategies have been introduced to alleviate AD, it remains challenging to cure the disorder. To achieve such a goal, understanding the pathophysiological mechanisms of AD is a prerequisite, requiring mouse models that properly reflect the AD phenotypes. Currently, numerous AD mouse models have been established, but each model has its own advantages and weaknesses. In this review, we categorized and summarized mouse models of AD and described their characteristics from a researcher's perspective.

Comprehensive Phytochemical Profiling of Polyherbal Divya-Kayakalp-Vati and Divya-Kayakalp-Oil and Their Combined Efficacy in Mouse Model of Atopic Dermatitis-Like Inflammation Through Regulation of Cytokines

Purpose

Atopic dermatitis (AD) is a chronic inflammatory disease that varies in signs and symptoms in different individuals. General symptoms include dryness of the skin, itching, and development of red to brownish-gray patches. Divya-Kayakalp-Vati (DKV) and -Oil (DKO) are Indian polyherbal compositions prescribed for treating inflammatory skin diseases. In the present study, we evaluated the anti-inflammatory efficacy of DKV and DKO co-treatment (DKV-O) in ameliorating Oxazolone (OXA)-stimulated AD-like inflammation and pro-inflammatory cytokine release in a Swiss albino mouse model.

Methods

Phytochemical profiling of the DKV and DKO were done using Liquid Chromatography-Mass Spectroscopy (LC-MS) QToF. Swiss albino mice were sensitized for 7 days and treated with OXA in their ear region. Stimulated and control animals were orally treated with DKV and topically with DKO. Anti-inflammatory efficacy of DKV-O was determined in OXA-treated animals through physiological, histopathological, and biochemical parameter analysis.

Results

DKV and DKO formulations individually contained 39 and 59 phytochemicals, respectively. Many of the phytochemicals have been reported to have anti-inflammatory activities. In the OXA-sensitized Swiss albino mice, combined treatment with DKV-O, and separately with Dexamethasone (positive control) significantly reduced the OXA-stimulated ear edema, biopsy weight, and epidermal thickness. DKV-O further reduced OXA-stimulated induction of inflammatory lesions, neutrophil influx, and release of Interleukin (IL)-1β, IL-6, tumor necrosis factor-α, and myeloperoxidase.

Conclusion

Finally, DKV-O co-treatment showed good pharmacological effects in ameliorating AD-like inflammation through the modulation of inflammatory cell influx and release of soluble mediators. Therefore, DKV-O treatment can be used as a suitable polyherbal therapeutic against AD-like inflammatory diseases.

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Characterization of a Murine Model of Oxazolone-Induced Orbital Inflammation

Purpose

Acute orbital inflammation can lead to irreversible vision loss in serious cases. Treatment thus far has been limited to systemic steroids or surgical decompression of the orbit. An animal model that mimics the characteristic features of acute orbital inflammation as found in thyroid eye disease can be used to explore novel treatment modalities.

Methods

We developed a murine model of orbital inflammation by injecting oxazolone into the mouse orbit. The mice underwent magnetic resonance imaging (MRI) and were euthanized at various time points for histologic examination. Immunofluorescence studies of specific inflammatory cells and cytokine arrays were performed.

Results

We found clinical and radiographic congruity between the murine model and human disease. After 72 hours, sensitized mice exhibited periorbital dermatitis and inflammation in the eyelids of the injected side. By one week, increased proptosis in the injected eye with significant eyelid edema was appreciated. By four weeks, inflammation and proptosis were decreased. At all three time points, the mice demonstrated exophthalmos and periorbital edema. Histopathologically, populations of inflammatory cells including T cells, macrophages, and neutrophils shared similarities with patient samples in thyroid eye disease. Proteomic changes in the levels of inflammatory and angiogenic markers correlated to the expected angiogenic, inflammatory, and fibrotic responses observed in patients with thyroid eye disease.

Conclusions

A murine model of orbital inflammation created using oxazolone recapitulates some of the clinical features of thyroid eye disease and potentially other nonspecific orbital inflammation, typified by inflammatory cell infiltration, orbital tissue expansion and remodeling, and subsequent fibrosis.

Translational Relevance

This animal model could serve as a viable platform with which to understand the underlying mechanisms of acute orbital inflammation and to investigate potential new, targeted treatments.

Granzyme B Contributes to Barrier Dysfunction in Oxazolone-Induced Skin Inflammation through E-Cadherin and FLG Cleavage

Atopic dermatitis (AD) is the most common inflammatory skin condition. Skin barrier dysfunction is of major importance in AD because it facilitates allergen sensitization and systemic allergic responses. Long regarded as a pro-apoptotic protease, emerging studies indicate granzyme B (GzmB) to have extracellular roles involving the proteolytic cleavage of extracellular matrix, cell adhesion proteins, and basement membrane proteins. Minimally expressed in normal skin, GzmB is elevated in AD and is positively correlated with disease severity and pruritus. We hypothesized that GzmB contributes to AD through extracellular protein cleavage. A causative role for GzmB was assessed in an oxazolone-induced murine model of dermatitis, comparing GzmB^-/- mice with wild-type mice, showing significant reductions in inflammation, epidermal thickness, and lesion formation in GzmB^-/- mice. Topical administration of a small-molecule GzmB inhibitor reduced disease severity compared with vehicle-treated controls. Mechanistically, GzmB impaired epithelial barrier function through E-cadherin and FLG cleavage. GzmB proteolytic activity contributes to impaired epidermal barrier function and represents a valid therapeutic target for AD.

Metabolome Analysis Reveals Dermal Histamine Accumulation in Murine Dermatitis Provoked by Genetic Deletion of P-Glycoprotein and Breast Cancer Resistance Protein

PURPOSE

P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) are xenobiotic transporters which pump out variety types of compounds, but information on their interaction with endogenous substrates in the skin is limited. The purpose of the present study was to clarify possible association of these transporters in dermal accumulation of inflammatory mediators.

METHODS

Dermatitis model was constructed by repeated topical application of oxazolone in wild-type, and P-gp and BCRP gene triple knockout (Mdr1a/1b/Bcrp^-/-) mice to observe difference in phenotype. Target metabolome analysis of 583 metabolites was performed using skin and plasma.

RESULTS

Dermatitis and scratching behavior in dermatitis model of Mdr1a/1b/Bcrp^-/- mice were more severe than wild-type mice, suggesting protective roles of these transporters. This hypothesis was supported by the metabolome analysis which revealed that concentration of histamine and other dermatitis-associated metabolites like urate and serotonin in the dermatitis skin, but not normal skin, of Mdr1a/1b/Bcrp^-/- mice was higher than that of wild-type mice. Gene expression of P-gp and BCRP was reduced in oxazolone-treated skin and the skin of patients with atopic dermatitis or psoriasis.

CONCLUSIONS

These results suggest possible association of these efflux transporters with dermal inflammatory mediators, and such association could be observed in the dermatitis skin.

Effects of Supplementary Seleno-L-methionine on Atopic Dermatitis-Like Skin Lesions in Mice

Effects of selenium supplementation on atopic dermatitis (AD) were investigated by administering seleno-L-methionine (SeMet) using a mouse model of AD caused by repeated application of 2,4,6-trinitrochlorobenzene (TNCB). BALB/c mice were sensitized with TNCB to the abdomen on day -7; then, TNCB was applied repeatedly to each ear three times a week from days 0 to 23. SeMet was orally administered to the mice from days 0 to 23. The efficacy of SeMet on AD was assessed by measuring ear thickness, histologic evaluation, serum total immunoglobulin (Ig) E levels, and expression of interleukin (IL)-4 in the ear and superficial parotid lymph node. Ear thickness was remarkably increased by repeated application of TNCB, and SeMet significantly suppressed ear thickness in BALB/c mice. SeMet inhibited epidermal hyperplasia and dense infiltration of inflammatory cells. The number of TNCB-induced mast cells was significantly decreased by SeMet. Serum total IgE levels that increased by the repeated application of TNCB were significantly suppressed by SeMet. Repeated application of TNCB induced expression of IL-4, a T-helper (Th) 2 cytokine, in the ear and superficial parotid lymph node of BALB/c mice and its expression was significantly inhibited by SeMet. These results demonstrated that SeMet supplementation suppresses AD-like skin lesions in BALB/c mice and inhibits the expression of total IgE and IL-4.

Design and Synthesis of Enantiomerically Pure Decahydroquinoxalines as Potent and Selective κ-Opioid Receptor Agonists with Anti-Inflammatory Activity in Vivo

In order to develop novel κ agonists restricted to the periphery, a diastereo- and enantioselective synthesis of (4aR,5S,8aS)-configured decahydroquinoxalines 5-8 was developed. Physicochemical and pharmacological properties were fine-tuned by structural modifications in the arylacetamide and amine part of the pharmacophore as well as in the amine part outside the pharmacophore. The decahydroquinoxalines 5-8 show single-digit nanomolar to subnanomolar κ-opioid receptor affinity, full κ agonistic activity in the [³⁵S]GTPγS assay, and high selectivity over μ, δ, σ₁, and σ₂ receptors as well as the PCP binding site of the NMDA receptor. Several analogues were selective for the periphery. The anti-inflammatory activity of 5-8 after topical application was investigated in two mouse models of dermatitis. The methanesulfonamide 8a containing the (S)-configured hydroxypyrrolidine ring was identified as a potent (K_i = 0.63 nM) and highly selective κ agonist (EC₅₀ = 1.8 nM) selective for the periphery with dose-dependent anti-inflammatory activity in acute and chronic skin inflammation.

Sodium channel Nax is a regulator in epithelial sodium homeostasis

The mechanisms by which the epidermis responds to disturbances in barrier function and restores homeostasis are unknown. With a perturbation of the epidermal barrier, water is lost, resulting in an increase in extracellular sodium concentration. We demonstrate that the sodium channel Nax functions as a sodium sensor. With increased extracellular sodium, Nax up-regulates prostasin, which results in activation of the sodium channel ENaC, resulting in increased sodium flux and increased downstream mRNA synthesis of inflammatory mediators. Nax is present in multiple epithelial tissues, and up-regulation of its downstream genes is found in hypertrophic scars. In animal models, blocking Nax expression results in improvement in scarring and atopic dermatitis-like symptoms, both of which are pathological conditions characterized by perturbations in barrier function. These findings support an important role for Nax in maintaining epithelial homeostasis.

Regulatory roles of mast cells in immune responses

Mast cells are important immune cells for host defense through activation of innate immunity (via toll-like receptors or complement receptors) and acquired immunity (via FcεRI). Conversely, mast cells also act as effector cells that exacerbate development of allergic or autoimmune disorders. Yet, several lines of evidence show that mast cells act as regulatory cells to suppress certain inflammatory diseases. Here, we review the mechanisms by which mast cells suppress diseases.

An in vitro human skin test for assessing sensitization potential

Sensitization to chemicals resulting in an allergy is an important health issue. The current gold-standard method for identification and characterization of skin-sensitizing chemicals was the mouse local lymph node assay (LLNA). However, for a number of reasons there has been an increasing imperative to develop alternative approaches to hazard identification that do not require the use of animals. Here we describe a human in-vitro skin explant test for identification of sensitization hazards and the assessment of relative skin sensitizing potency. This method measures histological damage in human skin as a readout of the immune response induced by the test material. Using this approach we have measured responses to 44 chemicals including skin sensitizers, pre/pro-haptens, respiratory sensitizers, non-sensitizing chemicals (including skin-irritants) and previously misclassified compounds. Based on comparisons with the LLNA, the skin explant test gave 95% specificity, 95% sensitivity, 95% concordance with a correlation coefficient of 0.9. The same specificity and sensitivity were achieved for comparison of results with published human sensitization data with a correlation coefficient of 0.91. The test also successfully identified nickel sulphate as a human skin sensitizer, which was misclassified as negative in the LLNA. In addition, sensitizers and non-sensitizers identified as positive or negative by the skin explant test have induced high/low T cell proliferation and IFNγ production, respectively. Collectively, the data suggests the human in-vitro skin explant test could provide the basis for a novel approach for characterization of the sensitizing activity as a first step in the risk assessment process.

Protective effect of small molecule analogues of the Acanthocheilonema viteae secreted product ES-62 on oxazolone-induced ear inflammation

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Small molecule analogues (SMAs) of the immunomodulator, ES-62, have been produced.

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Two SMAs protect against oxazolone-induced skin inflammation in mouse ears.

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Protection is associated with reduced cellular infiltration and collagen deposition.

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Protection is associated with decreased IFNγ mRNA in the ears.

ES-62 is the major secreted protein of the rodent filarial nematode Acanthocheilonema viteae. The molecule contains covalently attached phosphorylcholine (PC) residues, which confer anti-inflammatory properties on ES-62, underpinning the idea that drugs based on this active moiety may have therapeutic potential in human diseases associated with aberrant inflammation. Here we demonstrate that two synthetic small molecule analogues (SMAs) of ES-62 termed SMA 11a and SMA 12b are protective in the oxazolone-induced acute allergic contact dermatitis mouse model of skin inflammation, as measured by a significant reduction in ear inflammation following their administration before oxazolone sensitisation and before oxazolone challenge. Furthermore, it was found that when tested, 12b was effective at reducing ear swelling even when first administered before challenge. Histological analysis of the ears showed elevated cellular infiltration and collagen deposition in oxazolone-treated mice both of which were reduced by treatment with the two SMAs. Likewise, the oxazolone-induced increase in IFNγ mRNA in the ears was reduced but no effect on other cytokines investigated was observed. Finally, no influence on the mast cell populations in the ear was observed.

Contact hypersensitivity to oxazolone provokes vulvar mechanical hyperalgesia in mice

The interplay among pain, allergy and dysregulated inflammation promises to yield significant conceptual advances in immunology and chronic pain. Hapten-mediated contact hypersensitivity reactions are used to model skin allergies in rodents but have not been utilized to study associated changes in pain perception in the affected skin. Here we characterized changes in mechanical hyperalgesia in oxazolone-sensitized female mice challenged with single and repeated labiar skin exposure to oxazolone. Female mice were sensitized with topical oxazolone on their flanks and challenged 1-3 times on the labia. We then measured mechanical sensitivity of the vulvar region with an electronic pressure meter and evaluated expression of inflammatory genes, leukocyte influx and levels of innervation in the labiar tissue. Oxazolone-sensitized mice developed vulvar mechanical hyperalgesia after a single labiar oxazolone challenge. Hyperalgesia lasted up to 24 hours along with local influx of neutrophils, upregulation of inflammatory cytokine gene expression, and increased density of cutaneous labiar nerve fibers. Three daily oxazolone challenges produced vulvar mechanical hyperalgesic responses and increases in nerve density that were detectable up to 5 days post-challenge even after overt inflammation resolved. This persistent vulvar hyperalgesia is resonant with vulvodynia, an understudied chronic pain condition that is remarkably prevalent in 18-60 year-old women. An elevated risk for vulvodynia has been associated with a history of environmental allergies. Our pre-clinical model can be readily adapted to regimens of chronic exposures and long-term assessment of vulvar pain with and without concurrent inflammation to improve our understanding of mechanisms underlying subsets of vulvodynia and to develop new therapeutics for this condition.

Tumor necrosis factor-α, monocyte chemoattractant protein-1 and intercellular adhesion molecule-1 increase during the development of a 2,4-dinitrofluorobenzene-induced immediate-type dermatitis in rats

BACKGROUND

Due to the steadily increasing incidence of atopic dermatitis, there is a great medical need for new therapies and improved animal models.

OBJECTIVE

To provide more detailed analysis of a Sprague-Dawley rat dermatitis model.

METHODS

Sprague-Dawley rats were actively sensitized by intraperitoneal injections of dinitrophenylated ovalbumin (DNP-OVA) plus alum. Skin reactions were elicited by repeated epicutaneous challenge with 2,4-dinitrofluorobenzene (DNFB).

RESULTS

The ear thickness exhibited a significant increase from the first challenge. A relatively steep increase in ear thickness was observed at the fifth DNFB application. After the fifth DNFB application, total serum immunoglobulin (Ig) E and IgG1 levels reached a plateau at 1 h compared with the normal group. The peak production of tumor necrosis factor (TNF)-α and monocyte chemoattractant protein (MCP)-1 was found at 1 h, while that of intercellular adhesion molecule (ICAM)-1 was found at 24 h. Infiltration of CD4+ T cells, CD8+ T cells, eosinophils and mast cells increased in the skin lesion.

CONCLUSIONS

The indices such as thickness and inflammatory cell infiltration in the lesional skin were increased by repeated hapten application; TNF-α, MCP-1 and ICAM-1 increased with the development of the dermatitis.

Topical azithromycin and clarithromycin inhibit acute and chronic skin inflammation in sensitized mice, with apparent selectivity for Th2-mediated processes in delayed-type hypersensitivity

Macrolide antibiotics inhibit the secretion of Th1 cytokines while their effects on the release of Th2 cytokines are variable. We investigated molecular and cellular markers of Th1- and Th2-mediated inflammatory mechanisms and the anti-inflammatory activity of azithromycin and clarithromycin in phorbol 12-myristate 13-acetate (PMA) and oxazolone (OXA)-induced skin inflammation. Dexamethasone (50 μg/ear), azithromycin, and clarithromycin (500 μg/ear) reduced TNF-α and interleukin (IL)-1β concentration in ear tissue by inhibiting inflammatory cell accumulation in PMA-induced inflammation. In OXA-induced early delayed-type hypersensitivity (DTH), the macrolides (2 mg/ear) and dexamethasone (25 μg/ear) reduced ear tissue inflammatory cell infiltration and secretion of IL-4 while clarithromycin also decreased IFN-γ concentration. Macrolides showed better activity when administered after the challenge. In OXA-induced chronic DTH, azithromycin (1 mg/ear) reduced the number of ear tissue mast cells and decreased the concentration of IL-4 in ear tissue and of immunoglobulin (Ig)E in serum. Clarithromycin (1 mg/ear) reduced serum IgE concentration, possibly by a mechanism independent of IL-4, while both macrolides attenuated mast cell degranulation. In conclusion, azithromycin and clarithromycin attenuate pro-inflammatory cytokine production and leukocyte infiltration during innate immune reactions, while selectively affecting Th2 rather than Th1 immunity in DTH reactions.

Tissue inflammation modulates gene expression of lymphatic endothelial cells and dendritic cell migration in a stimulus-dependent manner

Chemokines and adhesion molecules up-regulated in lymphatic endothelial cells (LECs) during tissue inflammation are thought to enhance dendritic cell (DC) migration to draining lymph nodes, but the in vivo control of this process is not well understood. We performed a transcriptional profiling analysis of LECs isolated from murine skin and found that inflammation induced by a contact hypersensitivity (CHS) response up-regulated the adhesion molecules ICAM-1 and VCAM-1 and inflammatory chemokines. Importantly, the lymphatic markers Prox-1, VEGFR3, and LYVE-1 were significantly down-regulated during CHS. By contrast, skin inflammation induced by complete Freund adjuvant induced a different pattern of chemokine and lymphatic marker gene expression and almost no ICAM-1 up-regulation in LECs. Fluorescein isothiocyanate painting experiments revealed that DC migration to draining lymph nodes was more strongly increased in complete Freund adjuvant-induced than in CHS-induced inflammation. Surprisingly, DC migration did not correlate with the induction of CCL21 and ICAM-1 protein in LECs. Although the requirement for CCR7 signaling became further pronounced during inflammation, CCR7-independent signals had an additional, albeit moderate, impact on enhancing DC migration. Collectively, these findings indicate that DC migration in response to inflammation is stimulus-specific, mainly CCR7-dependent, and overall only moderately enhanced by LEC-induced genes other than CCL21.

The role of mitogen- and stress-activated protein kinase 1 and 2 in chronic skin inflammation in mice

Mitogen- and stress-activated protein kinase 1 and 2 (MSK1/2) are two kinases phosphorylated by both ERK1/2 and p38 MAPK. Recently, MSK1 and 2 have been reported to act as negative regulators of acute inflammation. In this study, we investigated the role of MSK1/2 in chronic skin inflammation using an oxazolone-induced allergic contact dermatitis model in MSK1/2 knockout mice and wild-type mice. MSK1/2 knockout mice were demonstrated to have significantly increased inflammation compared with wild-type mice. This was measured by an increased ear thickness, elevated infiltration of neutrophils in the skin and increased inflammatory histological changes. Furthermore, we found significantly elevated levels of the proinflammatory cytokines Tumor necrosis factor-α (TNF-α), IL-1β and IL-6 at both mRNA and protein levels in MSK1/2 knockout mice compared with wild-type mice after oxazolone treatment. In addition, the mRNA expression of the chemokine Thymus and activation regulated chemokine (TARC) was demonstrated to be significantly elevated in oxazolone-treated MSK1/2 knockout mice compared with wild-type mice. The increased expression of TARC was paralleled by increased infiltration of cells positive for the TARC receptor, CCR4, in the dermis of MSK1/2 knockout mice. Our results indicate that MSK1/2 are involved in the activation of feedback mechanisms that dampen oxazolone-induced skin inflammation.

Transmural flow modulates cell and fluid transport functions of lymphatic endothelium

RATIONALE

Lymphatic transport of peripheral interstitial fluid and dendritic cells (DCs) is important for both adaptive immunity and maintenance of tolerance to self-antigens. Lymphatic drainage can change rapidly and dramatically on tissue injury or inflammation, and therefore increased fluid flow may serve as an important early cue for inflammation; however, the effects of transmural flow on lymphatic function are unknown.

OBJECTIVE

Here we tested the hypothesis that lymph drainage regulates the fluid and cell transport functions of lymphatic endothelium.

METHODS AND RESULTS

Using in vitro and in vivo models, we demonstrated that lymphatic endothelium is sensitive to low levels of transmural flow. Basal-to-luminal flow (0.1 and 1 mum/sec) increased lymphatic permeability, dextran transport, and aquaporin-2 expression, as well as DC transmigration into lymphatics. The latter was associated with increased lymphatic expression of the DC homing chemokine CCL21 and the adhesion molecules intercellular adhesion molecule-1 and E-selectin. In addition, transmural flow induced delocalization and downregulation of vascular endothelial cadherin and PECAM-1 (platelet/endothelial cell adhesion molecule-1). Flow-enhanced DC transmigration could be reversed by blocking CCR7, intercellular adhesion molecule-1, or E-selectin. In an experimental model of lymphedema, where lymphatic drainage is greatly reduced or absent, lymphatic endothelial expression of CCL21 was nearly absent.

CONCLUSIONS

These findings introduce transmural flow as an important regulator of lymphatic endothelial function and suggest that flow might serve as an early inflammatory signal for lymphatics, causing them to regulate transport functions to facilitate the delivery of soluble antigens and DCs to lymph nodes.

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.

Phthalate ester-induced thymic stromal lymphopoietin mediates allergic dermatitis in mice

Recently air pollutants and irritants have been labelled as possible exogenous risk factors for allergic disorders. Although the underlying causes of allergic disorders such as atopic dermatitis and asthma remain unclear, the T helper type 2 (Th2) cell-mediated allergic inflammatory cascade may contribute to their pathogenesis. In the last decade, it has been documented that one of the candidates for triggering Th2 commitment is thymic stromal lymphopoietin (TSLP), the expression of which is up-regulated in the lesions of allergic patients. Here, we describe TSLP function in a fluorescein isothiocyanate (FITC) -induced contact hypersensitivity (CHS) model. A cytokine profile indicated that the model was dominantly mediated by the Th2 milieu. Interestingly, TSLP was increased in the skin during the sensitization phase when stimulated by a solvent, dibutyl phthalate (DBP), but not by FITC hapten or another solvent, acetone. Ear swelling in FITC-induced CHS was totally abrogated by removing DBP from the sensitization or elicitation phase, and was restored by complementary injection of TSLP. Inversely, the ear swelling was suppressed by injection of small interfering RNA against TSLP during the sensitization phase, which was concomitant with decreasing expression of interleukin-4 at the swollen skin site. Taken together, DBP-induced TSLP during the sensitization phase plays a role in establishing FITC-induced CHS and may be one of the causes of Th2 commitment in the model, suggesting that certain environmental toxins, such as DBP, may endow pro-allergic and atopic predisposition in humans or animals.

Reduced oxazolone-induced skin inflammation in MAPKAP kinase 2 knockout mice

Mitogen-activated protein kinase (MAPK) AP kinase 2 (MK2) is a serine/threonine kinase that is phosphorylated and activated by p38 MAPK. MK2 regulates the expression of various proinflammatory cytokines including TNF-alpha, IL-1beta, IL-6, and IL-8. Recently, MK2 was demonstrated to be activated in lesional psoriatic epidermis. This study investigates for the first time the role of MK2 in skin inflammation using the model of oxazolone-induced acute allergic contact dermatitis in mice. We show that oxazolone treatment leads to increased expression and sustained activation of both p38 MAPK and MK2. The inflammatory response was determined by ear thickness, myeloperoxidase activity, and histology after oxazolone challenge. Pretreatment with the p38 MAPK inhibitor SB202190 and genetic ablation of MK2 inhibit this inflammatory response. In particular, IL-1beta and, to a smaller but significant extent, also TNF-alpha and IFN-gamma expression were decreased in MK2 knockout mice compared with wild-type mice. These results indicate that MK2 is a potential target for the treatment of inflammatory skin diseases.

Interferon-gamma limits Th1 lymphocyte adhesion to inflamed endothelium: a nitric oxide regulatory feedback mechanism

CD4(+) T helper (Th1 and Th2) cell localization to a site of inflammation is important for the development, maintenance and regulation of an immune response. The factors that regulate Th1 and Th2 cell recruitment into tissue are not fully understood. The aim of the present study was to examine the effect of different cytokine microenvironments on the recruitment of Th1 and Th2 lymphocytes into tissue. Fluorescently labelled Th1 or Th2 lymphocyte-endothelial interactions were observed via intravital microscopy of the cytokine-treated cremaster muscle. Our results show that TNF-alpha alone is sufficient to maximally recruit Th1 cells. Surprisingly, treatment with TNF-alpha + IFN-gamma significantly decreased Th1 adhesion and emigration in comparison to TNF-alpha treatment alone. The decreased adhesion of Th1 cells in response to TNF-alpha + IFN-gamma reflected a decreased ability to bind to ICAM-1 and was iNOS-dependent. This phenomenon was not observed with Th2 cells. These results suggest that IFN-gamma may play a key immunomodulatory role in the recruitment of different T lymphocyte subsets. Indeed, blockade of IFN-gamma or iNOS function during the Th1-mediated contact hypersensitivity response resulted in an acceleration and exacerbation of the late-phase inflammatory response.

Topical application of a novel ceramide derivative, K6PC-9, inhibits dust mite extract-induced atopic dermatitis-like skin lesions in NC/Nga mice

Atopic dermatitis (AD) is a chronic inflammatory skin disease. K6PC-9 (N-Ethanol-2-hexyl-3-oxo-decanamide) is a novel synthetic ceramide derivative of PC-9S (N-Ethanol-2-mirystyl-3-oxo-stearamide), which was known to be effective in atopic and psoriatic patients. To investigate the immunomodulatory activity of K6PC-9, we examined the effect of K6PC-9 on T lymphocyte and macrophage function and the effect of topical application of K6PC-9 on skin inflammation and AD-like skin lesions in mouse models. K6PC-9 had no effect on concanavalin A-induced proliferation, interleukin (IL)-2 secretion and IL-4 secretion in mouse splenocytes. In contrast, lipopolysaccharide-induced nitrite generation was potently suppressed by K6PC-9 in mouse peritoneal macrophages. In mouse model of skin inflammation, K6PC-9 inhibited phorbol ester-induced increase in ear thickness and expression of tumor necrosis factor-alpha in the ear of BALB/c mice. Topical application of K6PC-9 also suppressed mite extract-induced AD-like skin lesions in NC/Nga mice. Increase in ear thickness was significantly inhibited by K6PC-9 in this model. K6PC-9 also blocked the infiltration of mast cells and neutrophils into the ear. Further study demonstrated that the mRNA expression of tumor necrosis factor-alpha and adhesion molecules, such as vascular cell adhesion molecule-1, intercellular adhesion molecule-1, E-selectin, was also suppressed by K6PC-9 in the ear of mite extract-treated NC/Nga mice. Taken together, the results presented in this report show that K6PC-9 has an anti-inflammatory potential and exerts beneficial effects in an animal model of AD, indicating that K6PC-9 might be used as a topical agent for the treatment of AD.

Phase-dependent roles of E-selectin during chronic contact hypersensitivity responses

Chronic contact hypersensitivity (CH) models induced by repeated hapten exposure exhibit chronic dermatitis and immunological abnormalities resembling atopic dermatitis. To assess the contribution of endothelial selectins (P- and E-selectins) to cutaneous chronic inflammation, chronic CH responses were assessed in mice lacking P- or E-selectin. Elicitation with oxazolone on the ears of P-selectin(-/-) mice 7 days after the sensitization induced a typical delayed-type hypersensitivity response similar to that found in wild-type mice. By contrast, a significant increase in ear swelling was observed in E-selectin(-/-) mice 36 to 48 hours after first elicitation. E-selectin(-/-) mice showed augmented P-selectin up-regulation, and administration of anti-P-selectin monoclonal antibody significantly inhibited the enhanced ear response, suggesting that the enhanced ear-swelling response in E-selectin(-/-) mice resulted from compensatory increase in P-selectin expression. In the late phase of chronic CH, acceleration of ear swelling was significantly reduced in both E- and P-selectin(-/-) mice relative to wild-type littermates. Thus, the loss of P- or E-selectin suppressed inflammatory responses during the chronic phase of the chronic models, whereas early-phase inflammatory responses were exacerbated by E-selectin blockade. Collectively, P- and E-selectins cooperatively regulate CH response, although their roles may be different depending on the phase of the reaction.

In vivo pharmacological disease models for psoriasis and atopic dermatitis in drug discovery

In order to perform relevant in vivo pharmacological investigations in drug discovery within dermatology it is fundamental to master or have access to relevant skin disease models that makes it possible to identify and validate targets and to screen and discover drugs in vivo. There is a strong need for highly predictive in vivo models in order to introduce the right drug candidates into the clinical phases of development. Recent advances in dermatological in vivo pharmacological disease models for psoriasis and atopic dermatitis are reviewed together with a discussion of the rationale for their application in drug discovery.

CCL17 transgenic mice show an enhanced Th2-type response to both allergic and non-allergic stimuli

CC chemokine ligand (CCL)17 is implicated in the pathogenesis of atopic dermatitis (AD). To study the effect of CCL17 produced by keratinocytes (KC) during inflammation, we created transgenic (Tg) mice in which CCL17 is overexpressed in KC. Th2-type contact hypersensitivity (CHS) was enhanced and Th1-type CHS was suppressed in these mice. Increased numbers of CC chemokine receptor (CCR)4(+) cells and mast cells infiltrated in Tg mice. Levels of IL-4 mRNA were higher and those of IFN-gamma mRNA were lower in both acute and chronic CHS. Higher levels of serum IgE were observed after CHS. Numbers of CCR4(+) cells among PBMC were increased in Tg mice challenged acutely on the trunk. Chronic irritation with croton oil induced dermatitis and an elevation of serum IgE levels. Tg mice showed enhanced ear swelling after tape stripping. CCL17 was thought to modify the inflammation caused by sensitizing reagents as well as irritant reagents by attracting CCR4(+) cells into the lesional skin and creating a Th2-dominant condition. AD-like conditions such as increased number of mast cells and elevated levels of serum IgE were observed. Thus, CCL17 may participate in the pathogenesis of skin diseases such as AD by regulating both allergic and irritant inflammation.

The effects of olopatadine hydrochloride on the number of scratching induced by repeated application of oxazolone in mice

It is suggested that atopic dermatitis is a skin disease associated with itching as subjective symptoms, and histamine H(1) receptor antagonists are used in order to prevent the itching, and the deterioration for scratch by itching. Histamine H(1) receptor selective anti-histamine olopatadine hydrochloride (olopatadine; Allelock shows consistent efficacy and safety in the treatment of allergic disorders. We investigated the possible efficacy of olopatadine on the number of scratching induced by repeated application of oxazolone in BALB/c mice. The repeated treatment of olopatadine significantly inhibited the ear swelling and the increased number of scratching. It significantly inhibited the increased production of interleukin (IL)-4, IL-1beta and granulocyte-macrophage colony-stimulating factor (GM-CSF) in the lesioned ear. Moreover, it significantly inhibited the increased production of nerve growth factor (NGF) and substance P. On the other hand, loratadine, bepotastine and chlorpheniramine did not inhibit the ear swelling and the increased number of scratching. These results indicate that olopatadine inhibited not only the increased production of cytokines but also NGF and substance P unlike other histamine H(1) receptor antagonists. It was suggested that olopatadine suppressed the increased number of scratching by the anti-inflammatory effects. Therefore, olopatadine appears to exert additional biological effects besides its blockade of a histamine H(1) receptor.

Effect of Olopatadine and Other Histamine H1 Receptor Antagonists on the Skin Inflammation Induced by Repeated Topical Application of Oxazolone in Mice

Histamine H1 receptor antagonists have long been prescribed for atopic dermatitis as an adjuvant therapy with topical therapy by local applied steroids. Olopatadine is one of the second-generation histamine H1 receptor antagonists that are treated for allergic disorders. We investigated that the effect of olopatadine on oxazolone-induced chronic contact hypersensitivity response in BALB/c mice compared with other histamine H1 receptor antagonists loratadine, cetirizine and fexofenadine. The chronic contact hypersensitivity induced by repeated application of oxazolone was treated with olopatadine and other histamine H1 receptor antagonists at the effective doses on histamine-induced paw edema in mice. The effects of these drugs in the oxazolone-induced model were quantified by measurements of ear swelling, and levels of cytokines in the lesioned ear. Olopatadine significantly inhibited the ear swelling and the increased production of IL-4, IL-1beta, IL-6, GM-CSF and NGF in the lesioned ear. On the other hand, the other histamine H1 receptor antagonists did not significantly suppress the increase in ear thickness. Moreover, they did not affect the production of cytokines in the lesioned ear. These results indicate that olopatadine appears to exert additional biological effects besides its blockade of the histamine H1 receptor.

Evidence for a novel protective role of the vanilloid TRPV1 receptor in a cutaneous contact allergic dermatitis model

The purpose of this study was to examine the involvement of the transient receptor potential vanilloid receptor 1 (TRPV1) in inflammatory processes observed in murine allergic contact dermatitis (ACD). Oxazolone-induced ACD evoked a significant ear swelling after 24-72 h. It was augmented in TRPV1 knockout mice at all time points and supported by histological analysis and measure of TNF-alpha. However, tissue swelling and cytokine generation was significantly reduced in both neurokinin 1 receptor and calcitonin gene-related peptide (CGRP) knockout mice. A protective involvement of the TRPV1 receptor was identified of contact dermatitis distinct from mechanisms involving the major pro-inflammatory neuropeptides.

Effects of olopatadine hydrochloride, an antihistamine drug, on skin inflammation induced by repeated topical application of oxazolone in mice

BACKGROUND

Olopatadine hydrochloride (olopatadine) is one of the second-generation antihistamines, which is prescribed for allergic disorders such as rhinitis, urticaria and eczema dermatitis.

OBJECTIVES

To investigate the possible anti-inflammatory effect of olopatadine on the chronic contact hypersensitivity response to repeated topical application of oxazolone in mice.

METHODS

The preventive and therapeutic effects of oral olopatadine were quantified by measurements of ear swelling, cytokine protein and mRNA expression in the ear lesion, and were compared with those of topical betamethasone 17-valerate (betamethasone).

RESULTS

The ear receiving repeated applications of oxazolone exhibited erythema, oedema and abrasion. Both preventive and therapeutic administration of olopatadine (10 mg kg(-1) day(-1)) significantly inhibited the ear swelling and the increased production of interleukin (IL)-4, IL-1beta, granulocyte-macrophage colony-stimulating factor (GM-CSF) and nerve growth factor. In the histopathological analysis, olopatadine ameliorated epidermal hyperplasia and infiltration of inflammatory cells. Consistent with these results, olopatadine significantly reduced the increased expression of interferon-gamma and IL-4 mRNA. Although betamethasone (0.012 mg ear(-1) day(-1)) showed similar activities to olopatadine against these responses, it caused atrophy of the ear skin.

CONCLUSIONS

These results indicate that olopatadine is an antihistamine agent having inhibitory activities against chronic inflammatory dermatitis, possibly resulting from its diminishing effect on elevated cytokines.

Olopatadine hydrochloride suppresses the rebound phenomenon after discontinuation of treatment with a topical steroid in mice with chronic contact hypersensitivity

BACKGROUND

Olopatadine hydrochloride (olopatadine; Allelock) is one of the second-generation antihistamines that are treated for allergic disorders such as rhinitis, urticaria and eczema dermatitis. Olopatadine has recently been shown to have inhibitory effects on the chronic contact hypersensitivity induced by repeated application of oxazolone in mice. Although topical steroids have widely been prescribed for atopic dermatitis, a relapse often occurs within several days after discontinuation of their prolonged use.

OBJECTIVES

We investigated the possible efficacy of olopatadine against the relapse after discontinuation of prolonged use of topical prednisolone in the Balb/c mice with oxazolone-induced chronic contact hypersensitivity.

METHODS

Mice with the chronic contact hypersensitivity induced by repeated application of oxazolone were treated with olopatadine as a sequential therapeutic agent. The effects of olopatadine were quantified by measurements of ear-swelling, and levels of cytokines and histamine in the lesioned ear. Results Topical prednisolone (0.05 mg/ear/day) significantly inhibited the increases in ear swelling and production of IL-1beta, IL-4, IL-18, granulocyte-macrophage colony-stimulating factor (GM-CSF) and histamine. However, after discontinuation of the treatment with topical prednisolone, the inflammation relapsed and the IL-4 level exceeded the control one. The sequential treatment with olopatadine (10 mg/kg/day) after discontinuation of the treatment with topical prednisolone alone, or topical prednisolone with olopatadine, significantly inhibited the increases in ear swelling and levels of IL-1beta, IL-4, IL-18, GM-CSF, nerve growth factor and histamine.

CONCLUSIONS

These results indicate that olopatadine is an antihistamine agent having inhibitory activities against the rebound phenomenon following the discontinuation of topical steroid therapy. Olopatadine is thus expected to be a sequential therapeutic agent after discontinuation of the chronic treatment with a topical steroid.

Immune Sensitization in the Skin Is Enhanced by Antigen-Independent Effects of IgE

Contact sensitivity responses require both effective immune sensitization following cutaneous exposure to chemical haptens and antigen-specific elicitation of inflammation upon subsequent hapten challenge. We report that antigen-independent effects of IgE antibodies can promote immune sensitization to haptens in the skin. Contact sensitivity was markedly impaired in IgE(-/-) mice but was restored by either transfer of sensitized cells from wild-type mice or administration of hapten-irrelevant IgE before sensitization. Moreover, IgE(-/-) mice exhibited impairment in the reduction of dendritic cell numbers in the epidermis after hapten exposure. Monomeric IgE has been reported to influence mast cell function. We observed diminished contact sensitivity in mice lacking FcepsilonRI or mast cells, and mRNA for several mast cell-associated genes was reduced in IgE(-/-) versus wild-type skin after hapten exposure. We speculate that levels of IgE normally present in mice favor immune sensitization via antigen-independent but FcepsilonRI-dependent effects on mast cells.

Modulation of Skin Norepinephrine Turnover by Allergen Sensitization: Impact on Contact Hypersensitivity and T Helper Priming

The information gathered by dendritic cells during the innate immune response is determinant for the type and strength of the adaptive response. We showed that the sympathetic neurotransmitter norepinephrine influences dendritic cell migration and T helper priming via alpha- and beta-adrenoceptors. Others have shown that Langerhans cells also express mRNA for beta 1-, beta 2-, and alpha 1A-adrenoceptors and that catecholamines may inhibit the antigen-presenting capability via beta 2-adrenoceptors. Here we report that oxazolone, which induces a predominant T-helper-1-type contact hypersensitivity response, but not fluorescein isothiocyanate, which induces a prevailing T-helper-2-type response, inhibits the local norepinephrine turnover in the skin of mice during the first 8 h of sensitization. Oxazolone also induced higher expression of the inflammatory cytokines interleukin-1 and interleukin-6 mRNA in the skin. Lack or blockade of these cytokines as well as inhibition of prostaglandin synthesis, however, did not influence the oxazolone effect. Only the nonspecific anti-inflammatory steroid dexamethasone could neutralize the effect of oxazolone. Furthermore, fluorescein isothiocyanate but not oxazolone sensitization in the presence of the specific beta 2-adrenoceptor antagonist ICI 118,551 enhanced the consequent contact hypersensitivity response as well as the production of T helper 1 cytokines in draining lymph nodes; conversely T helper 2 cytokines were not affected. Thus, the extent of T helper 1 priming in the adaptive response to a sensitizing agent seems to depend also on its ability to modulate the local sympathetic nervous activity during the innate immune response.

Inhibitory activity of CX-659S, a novel diaminouracil derivative, against the rebound phenomenon following withdrawal of corticosteroid therapy for chronic contact hypersensitivity responses

BACKGROUND

CX-659S, a newly discovered anti-inflammatory compound, exerts inhibitory effects on chronic contact hypersensitivity responses (CHRs) induced by repeated application with picryl chloride (PC), which is known to mimic many, if not all, events occurring within lesional skin of patients with atopic dermatitis (AD). CX-659S suppresses the expression of mRNA for interleukin (IL)-4 and IL-10 but not that for IFN-gamma, and inhibits serum IgE production in a chronic CHR model. Although topical corticosteroids have been widely utilized in steroid-responsive dermatoses such as AD, their chronic use may be associated with significant side effects. In addition, a rebound phenomenon often occurs after discontinuation of prolonged use of topical corticosteroids, with enhanced production of IgE and Th2 cell cytokines. The purpose of this study was to assess whether CX- 659S inhibits the rebound phenomenon after discontinuation of chronic treatment with prednisolone in a chronic CHR model in mice.

METHODS

The efficacy of CX-659S as a sequential therapeutic agent after discontinuation of chronic treatment with prednisolone was tested on PC-treated ears of BALB/c mice with chronic CHR. Effects were quantified by measurements of ear thickness, serum IgE and cytokine mRNA expression.

RESULTS

The rebound phenomenon was confirmed after discontinuation of chronic treatment with prednisolone in chronic CHR in mice, i.e. by evidence of flare thickening of the ear, enhanced expression of mRNA for IL-4 and IL-10 and increased serum IgE. Sequentially applied CX-659S suppressed these rebound phenomena with a good cosmetic result.

CONCLUSIONS

CX-659S is the first promising compound with inhibitory activity on the rebound phenomenon following withdrawal of corticosteroid therapy without immunosuppression.

L-selectin or ICAM-1 deficiency reduces an immediate-type hypersensitivity response by preventing mast cell recruitment in repeated elicitation of contact hypersensitivity

Repeated Ag exposure results in a shift in the time course of contact hypersensitivity (CH) from a typical delayed-type to an immediate-type response followed by a late phase reaction. Chronic CH responses are clinically relevant to human skin allergic diseases, such as atopic dermatitis, that are usually caused by repeated stimulation with environmental Ags. Chronic inflammatory responses result in part from infiltrating leukocytes. To determine the role of leukocyte adhesion molecules in chronic inflammation, chronic CH responses were assessed in mice lacking L-selectin, ICAM-1, or both adhesion molecules. Following repeated hapten sensitization for 24 days at 2-day intervals, wild-type littermates developed an immediate-type response at 30 min after elicitation, followed by a late phase reaction. By contrast, loss of ICAM-1, L-selectin, or both, eliminated the immediate-type response and inhibited the late phase reaction. Similar results were obtained when wild-type littermates repeatedly exposed to hapten for 22 days were treated with mAbs to L-selectin and/or ICAM-1 before the elicitation on day 24. The lack of an immediate-type response on day 24 paralleled a lack of mast cell accumulation after 30 min of elicitation and decreased serum IgE production. Repeated Ag exposure in wild-type littermates resulted in increased levels of serum L-selectin, a finding also observed in atopic dermatitis patients. The current study demonstrates that L-selectin and ICAM-1 cooperatively regulate the induction of the immediate-type response by mediating mast cell accumulation into inflammatory sites and suggests that L-selectin and ICAM-1 are potential therapeutic targets for regulating human allergic reactions.

Sensitization potential of gold sodium thiosulfate in mice and guinea pigs

Since gold sodium thiosulfate (GST) has been included in a standard patch test series for diagnosis of allergic contact dermatitis from gold, the incidence of patients showing positive reactions to gold is increasing. However, there were little reports on induction of gold sensitization in animals. In this study, we have examined the sensitization potential of GST using mice and guinea pigs. In the guinea pig maximization test, 2 or 6 out of 10 animals showed positive skin responses, mainly edema, by challenge with 2% or 5% GST in 50% ethanol solution, respectively. In the mouse ear swelling test, positive ear swelling (20% greater increase in ear thickness) after challenge with GST was shown in 2 out of 6 mice those previously treated with GST. Topical exposure of mice to GST in 70% dimethylsulfoxide solution induced small increases in the lymph node weight and the lymph node cell (LNC) number in the murine local lymph node assay (LLNA). A greater degree of LNC responses were observed in the sensitive mouse lymph node assay (SLNA) compared with the LLNA, but the stimulation index of total lymph node response by GST was not so high. From these results, GST was identified as a contact allergen, but the sensitization potential was not so strong. In the mouse IgE test, treatment of mice with GST resulted in a statistically significant increase in the serum IgE antibody concentration that associated with immediate-type hypersensitivity reaction. It may suggest that the sensitization responses from gold would appear not only at the contact site but also systematically.

Protective and curative effects of topically applied CX-659S, a novel diaminouracil derivative, on chronic picryl chloride-induced contact hypersensitivity responses

BACKGROUND

CX-659S, a newly discovered anti-inflammatory compound, exerts inhibitory effects against acute contact hypersensitivity responses (CHRs) induced by picryl chloride (PC), oxazolone and dinitrochlorobenzene. The murine model of chronic CHR induced by repeated application of PC is known to mimic many, if not all, events occurring within the lesional skin of patients with atopic dermatitis (AD).

OBJECTIVES

To investigate the ability of CX-659S to inhibit PC-induced chronic CHR in mice.

METHODS

The protective and curative effects of CX-659S were tested on PC-treated ears of BALB/c mice, and were compared with those of prednisolone. Effects were quantified by measurements of ear thickness, serum IgE and cytokine mRNA expression.

RESULTS

Both protectively applied and curatively applied CX-659S significantly inhibited increases in ear thickness and total serum IgE. Inhibition was dose-dependent. Although protectively applied prednisolone showed similar activities to CX-659S against chronic CHR, curatively applied prednisolone did not affect the serum IgE level despite inhibiting increases in ear thickness and inflammatory cell infiltration. Consistent with these results, CX-659S reduced mRNA expression of interleukin (IL)-4 and IL-10 but not of interferon (IFN)-gamma, whereas prednisolone inhibited not only mRNA expression of IL-4 and IL-10 but also that of IFN-gamma in the ear lesion. In contrast to prednisolone, CX-659S did not show any side-effect such as atrophy, alopecia or telangiectasia.

CONCLUSIONS

CX-659S is the first promising compound having inhibitory activities against chronic CHR accompanied by a diminishing effect on elevated serum IgE, without any other side-effect. Therefore, CX-659S may be a promising candidate for management of patients with recurring AD who require long-term therapy.

Subcutaneous or oral administration of rhIL-11 modulated the contact hypersensitivity response

Recombinant human interleukin 11 (rhIL-11) is a multifunctional cytokine with immunomodulatory activity on both T cells and macrophages. The effects of rhIL-11 in a murine model of contact hypersensitivity (CHS) response have been studied. The CHS response is a T cell-mediated response directed against chemically modified self-proteins following epidermal exposure to haptens. CHS is generated in two phases. The sensitization phase involves dermal dendritic cell recognition of haptenized proteins and antigen presentation. The effector phase involves T cell recognition and activation. In mice sensitized with oxazolone, CHS was induced by secondary challenge to the right ear and measured by ear swelling 24 h later. rhIL-11 significantly suppressed CHS as measured by ear swelling and tissue myeloperoxidase activity when injected subcutaneously for 5 days from the day of sensitization or when administered only on the day before and the day of challenge, but was not effective when administered prior to or on the day of sensitization. These results indicate that subcutaneously administered rhIL-11 may modulate the effector phase of CHS. Administration of rhIL-11 as an oral gavage prior to sensitization also reduced CHS. However oral administration of rhIL-11 after sensitization had no effect. These results suggest that orally and subcutaneously administered rhIL-11 may act through different mechanisms to affect CHS.

Mast cells control neutrophil recruitment during T cell-mediated delayed-type hypersensitivity reactions through tumor necrosis factor and macrophage inflammatory protein 2

Polymorphonuclear leukocytes (PMNs) characterize the pathology of T cell-mediated autoimmune diseases and delayed-type hypersensitivity reactions (DTHRs) in the skin, joints, and gut, but are absent in T cell-mediated autoimmune diseases of the brain or pancreas. All of these reactions are mediated by interferon gamma-producing type 1 T cells and produce a similar pattern of cytokines. Thus, the cells and mediators responsible for the PMN recruitment into skin, joints, or gut during DTHRs remain unknown. Analyzing hapten-induced DTHRs of the skin, we found that mast cells determine the T cell-dependent PMN recruitment through two mediators, tumor necrosis factor (TNF) and the CXC chemokine macrophage inflammatory protein 2 (MIP-2), the functional analogue of human interleukin 8. Extractable MIP-2 protein was abundant during DTHRs in and around mast cells of wild-type (WT) mice but absent in mast cell-deficient WBB6F(1)-Kit(W)/Kit(W-)(v) (Kit(W)/Kit(W)(-v)) mice. T cell-dependent PMN recruitment was reduced >60% by anti-MIP-2 antibodies and >80% in mast cell-deficient Kit(W)/Kit(W)(-v) mice. Mast cells from WT mice efficiently restored DTHRs and MIP-2-dependent PMN recruitment in Kit(W)/Kit(W)-(v) mice, whereas mast cells from TNF(-/)- mice did not. Thus, mast cell-derived TNF and MIP-2 ultimately determine the pattern of infiltrating cells during T cell-mediated DTHRs.