Pharmacological characterization of a chronic pruritus model induced by multiple application of 2,4,6-trinitrochlorobenzene in NC mice

Anti-IL-33 Antibody Has a Therapeutic Effect in an Atopic Dermatitis Murine Model Induced by 2, 4-Dinitrochlorobenzene

IL-33 is a new member of the IL-1 family that plays a role in allergic disease. In this study, we evaluated the potential on the inhibition of atopic dermatitis (AD) of anti-mouse IL-33 antibody (αIL-33Ab) using 2, 4-dinitrochlorobenzene (DNCB)-induced AD mice model. We treated mice with αIL-33Ab via subcutaneous injection of each DNCB treatment 1 h later from day 1 to day 33 for 14 times. A control group received tacrolimus. Skin lesion and scratching behavior were compared. Ear thickness, dermatitis score, eosinophils and mast cells infiltration, and serum IgE levels were also analyzed. Correlations between serum IL-33 as well as soluble(s) ST2 and AD disease activity index in human AD were also investigated. DNCB-induced AD-like mice treated with αIL-33Ab showed improved AD-like symptoms. Eosinophils and mast cells infiltration and serum IgE levels were also significantly reduced by αIL-33Ab. Our study suggests that blockade of IL-33 has a curative effect on AD.

Stigmasterol Alleviates Cutaneous Allergic Responses in Rodents

The therapeutic potential of stigmasterol, a natural steroid alcohol with established immune-modulatory properties, was assessed on allergic cutaneous responses. We examined its suppressive effect on immunoglobulin E (IgE)-mediated active cutaneous anaphylaxis (ACA), compound 48/80 (C48/80)-induced pruritus, and irritant dermatitis induced by 12-O-tetradecanoylphorbol-13-acetate (TPA). Stigmasterol at 10–100 mg/kg significantly inhibited ACA with reduction in reaction area and concentration of the extravasated Evans blue dye. Given at 50 and 100 mg/kg, stigmasterol significantly inhibited C48/80-induced scratching behaviour when compared to saline-treated C48/80-injected control. Skin histopathology of injected sites confirmed that stigmasterol reduced mast cell trafficking and degranulation associated with C48/80-induced pruritus. Stigmasterol controlled inflammatory features such as ear skin oedema and neutrophilia and also reduced serum levels of TNFα induced by topical application of TPA. Epidermal layer thickening and inflammatory cell infiltration of ear skin tissue were significantly reduced by stigmasterol. Taken together, stigmasterol demonstrates significant potential as a molecule of interest in allergic skin disease therapy.

Anti-IL-31 receptor antibody is shown to be a potential therapeutic option for treating itch and dermatitis in mice

BACKGROUND AND PURPOSE

IL-31, which is described as a pruritogenic cytokine, is linked to the itching that is associated with allergic and non-allergic eczema, but the precise pruritogenic mechanism of IL-31 and its potential as a therapeutic target for atopic dermatitis (AD) have not been determined.

EXPERIMENTAL APPROACH

We investigated the effects of existing drugs on the scratching behaviour induced by an i.v. injection of IL-31 to clarify whether IL-31 induced pruritus indirectly. In addition, we studied the effects of an anti-IL-31 receptor α subunit (anti-IL-31 receptor α) neutralizing antibody on chronic pruritus-inducing dermatitis in an AD-like model to determine whether IL-31 not only induces scratching behaviour, but is also the causative factor in an AD phenotype.

KEY RESULTS

The scratching behaviour induced by an i.v. injection of IL-31 was inhibited by pretreatment with an anti-IL-31 receptor α-neutralizing antibody. In contrast, it was not inhibited significantly by a non-sedative antihistamine (terfenadine), immunosuppressants (dexamethasone and tacrolimus), or a μ-opioid receptor antagonist (naloxone). The anti-IL-31 receptor α-neutralizing antibody reduced the ear swelling and dermatitis score in a chronic pruritus-inducing AD-like model. Moreover, treatment with the anti-IL-31 receptor α-neutralizing antibody showed therapeutic effects on the dermatitis even if it was injected after the disease had developed.

CONCLUSIONS AND IMPLICATIONS

Anti-IL-31 receptor α is a potential novel therapeutic approach for escaping from the itch-scratch cycle and also a treatment for dermatitis in AD.

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.

Repeated application of glucocorticoids exacerbate pruritus via inhibition of prostaglandin D2 production of mast cells in a murine model of allergic contact dermatitis

Rebound is known to occur most typically when topical glucocorticoids are abruptly discontinued; however, its frequency and severity are poorly characterized. We previously created a novel murine model of topical glucocorticoid-induced pruritus; however, the mechanism underlying pruritus in this model has not been elucidated. Using this murine model, we aimed to determine the cause of augmentation of pruritus with a focus on the production of prostaglandin (PG) D(2). BALB/c mice with chronic allergic contact dermatitis induced by 5 weeks of repeated application of 2,4,6-trinitro-1-chlorobenzene (TNCB) were treated topically with dexamethasone for 5 weeks immediately after the elicitation of dermatitis and after ear-swelling and scratching behavior were measured. RBL-2H3 mast cells were used to investigate the effect of dexamethasone on degranulation or PGD(2) production in IgE/antigen-stimulated mast cells. The scratching behavior induced by TNCB was augmented by topical application of dexamethasone, but dexamethasone did not have any effect on scratching bouts in mice that had not been treated with TNCB. Topical dexamethasone reduced the PGD(2) level, which increase in TNCB-treated mice, to the baseline level. Moreover, dexamethasone significantly decreased the PGD(2) production in IgE/antigen-stimulated RBL-2H3 mast cells; however, the same concentration of dexamethasone did not have any effect on the degranulation of stimulated mast cells. Topical glucocorticoids may exacerbate pruritus in a mouse model of allergic contact dermatitis via inhibition of PGD(2) production in antigen-mediated activated mast cells in the skin.

The role of IgE and repeated challenge in the induction of persistent increases in scratching behavior in a mouse model of allergic dermatitis

Previously, we indicated that athymic BALB/c-nu/nu (nude) mice that had been repeatedly treated with 2,4,6-trinitrochlorobenzene (TNCB) failed to exhibit chronic scratching behavior in spite of the accumulation of dermal mast cells in the lesion. The mice also failed to produce specific IgE or potent dermatitis. In the present study, therefore, we aimed to examine the role of IgE and repeated hapten treatment in the induction of scratching behavior and dermatitis using nude mice and trinitrophenol (TNP)-specific IgE-transgenic mice. The ears of nude mice were treated with TNCB 6 times at intervals of 48 h, and TNP-specific IgE was administered to the mice intravenously before the sixth TNCB treatment. The nude mice that had been supplemented with IgE exhibited a persistent increase in scratching behavior and continuous degranulation of mast cells. Furthermore, a potent immediate ear swelling was induced, although no biphasic dermatitis pattern was observed. On the other hand, the IgE-transgenic mice failed to exhibit persistent increases in scratching behavior after a single TNCB treatment, although biphasic ear swelling was observed. These results indicate that specific IgE plays an essential role in the induction of persistent increases in scratching behavior and continuous degranulation of mast cells. Furthermore, repeated challenge with the hapten also plays an important role in persistent increases in scratching behavior through accumulation and continuous activation of mast cells.

Effects of maternal exposure to di-(2-ethylhexyl) phthalate during fetal and/or neonatal periods on atopic dermatitis in male offspring

BACKGROUND

Di-(2-ethylhexyl) phthalate (DEHP) has been widely used in polyvinyl chloride products and is ubiquitous in developed countries. Although maternal exposure to DEHP during fetal and/or neonatal periods reportedly affects reproductive and developmental systems, its effects on allergic diseases in offspring remain to be determined.

OBJECTIVES

In the present study, we examined whether maternal exposure to DEHP during fetal and/or neonatal periods in NC/Nga mice affects atopic dermatitis-like skin lesions related to mite allergen in offspring.

METHODS

We administered DEHP at a dose of 0, 0.8, 4, 20, or 100 microg/animal/week by intraperitoneal injection into dams during pregnancy (gestation days 0, 7, and 14) and/or lactation (postnatal days 1, 8, and 15). Eight-week-old male offspring of these treated females were injected intradermally with mite allergen into their right ears. We then evaluated clinical scores, ear thickening, histologic findings, and protein expression of eotaxin in the ear.

RESULTS

Maternal exposure to a 100-microg dose of DEHP during neonatal periods, but not during fetal periods, enhanced atopic dermatitis-like skin lesions related to mite allergen in males. The results were concomitant with the enhancement of eosinophilic inflammation, mast cell degranulation, and protein expression of eotaxin in overall trend.

CONCLUSION

Maternal exposure to DEHP during neonatal periods can accelerate atopic dermatitis-like skin lesions related to mite allergen in male offspring, possibly via T helper 2 (T(H)2)-dominant responses, which can be responsible, at least in part, for the recent increase in atopic dermatitis.