Effects of Neuropeptides In The Development Of The Atopic Dermatitis Of Mouse Models

A Role of Staphyococcus aureus, Interleukin-18, Nerve Growth Factor and Semaphorin 3A, an Axon Guidance Molecule, in Pathogenesis and Treatment of Atopic Dermatitis

Staphylococcus aureus (SA) is usually present not only in the skin lesions of atopic dermatitis (AD) but also in the atopic dry skin. SA discharges various toxins and enzymes that injure the skin, results in activation of epidermal keratinocytes, which produce and release IL-18. IL-18 that induces the super Th1 cells secreting IFN-γ and IL-13 is supposed to be involved in development of AD and its pathogenesis. Indeed, the number of SA colonies on the skin surface and the serum IL-18 levels in patients with AD significantly correlated with the skin scores of AD lesions. Also, there is strong positive correlation between the skin scores and serum IL-18 levels in DS-Nh mice (P<0.0001, r=0.64), which develop considerable AD-like legions when they are housed under conventional conditions, but develop skin legions with less severity and less frequency under specific pathogens free (SPF) conditions. Therefore, they are well-known as model mice of AD, in which SA is presumed to be critical factor for the development of AD lesions. Also, theses DS-Nh mice pretreated with Cy developed more remarkable AD-like lesions in comparison with non-treated ones. The levels of INF-r and IL-13 in the supernatants of the lymph node cell cultures stimulated with staphylococcal enterotoxin B (SEB) or ConA were increased in the Cy-treated mice, although the serum levels of total IgE were not. In this experiment, we revealed that Cy-treated mice, to which CD25 +CD4 + reguratory T cells taken from non-treated ones had been transferred, developed the AD-like legions with less severity and less number of SA colonies on the skin surface. Therefore, it is presumed that CD25 +CD4 + reguratory T cells might be involved in the suppression of super Th1 cells which are induced by IL-18 and are involved in the development of AD-like lesions rather than IgE production. The efficient induction of CD25 +CD4 + reguratory T cells is expected for the new type of treatment of AD. We also found that farnesol (F) and xylitol (X) synergistically inhibited biofilm formation by SA, and indeed the ratio of SA in total bacteria at sites to which the FX cream containing F and X had been applied was significantly decreased 1 week later, accompanied with improvement of AD, when compared with that before application and at placebo sites. Therefore, the FX cream is a useful skin-care agent for atopic dry skin colonized by SA. The nerve growth factor (NGF) in the horny layer (the horn NGF) of skin lesions on the cubital fossa was collected by tape stripping and measured using ELISA in AD patients before and after 2 and 4 weeks treatments. Simultaneously, the itch and eruptions on the whole body and on the lesions, in which the horn NGF was measured, were recorded, and also the peripheral blood eosinophil count, serum LDH level and serum total IgE level were examined. The level of NGF was significantly higher in AD patients than in healthy controls, correlated with the severity of itch, erythema, scale/xerosis, the eosinophil count and LDH level, and also significantly decreased after treatments with olopatadine and/or steroid ointment for 2 and 4 weeks. Therefore, the measurement of the NGF by this harmless method seems to be useful to assess the severity of AD and the therapeutic effects on AD. In AD patients, C-fiber in the epidermis increase and sprout, inducing hypersensitivity, which is considered to aggravate the disease. Semaphorin 3A (Sema3A), an axon guidance molecule, is a potent inhibitor of neurite outgrowth of sensory neurons. We administered recombinant Sema3A intracutaneously into the skin lesions of NC/Nga mice, an animal model of AD, and investigated the effect of Sema3A on the skin lesions and their itch. Sema3A dose-dependently improved skin lesions and attenuated the scratching behavior in NC/Nga mice. Histological examinations revealed a decrease in the epidermal thickness, the density of invasive nerve fibers in the epidermis, inflammatory infiltrate including mast cells and CD4 +T cells, and the production of IL-4 in the Sema3A-treated lesions. Because the interruption of the itch-scratch cycle likely contributes to the improvement of the AD-like lesions, Sema3A is expected to become a promising treatment of patients with refractory AD.

Effect of epinastine hydrochloride on murine self-scratching behavior after skin-scratching stimulation

The itch-scratch cycle aggravates chronic inflammatory skin diseases. We have previously reported that mice begin to scratch themselves within several minutes after skin-scratching stimulation. This is associated with an increase in release of substance P (SP) from sensory nerve fibers in the skin, and the self-scratching behavior is suppressed by neurokinin-1 receptor (NK-1R) antagonist. Thus, SP may play a pivotal role in self-scratching behavior. The purpose of this study was to investigate the effect of second-generation histamine H(1)-receptor antagonists on self-scratching behavior in mice. After oral administration of epinastine hydrochloride (epinastine) (total dose 50 +/- 5 mg/kg for 7 days) or the vehicle only to ICR mice for 7 days, skin-scratching stimulation was administered to the dorsal skin for 10 min. Self-scratching behavior was recorded by video camera for 10 min. Twenty-four hours later, skin tissue was harvested and stained with toluidine blue. Immunohistochemical staining for SP was performed, and SP and nerve growth factor (NGF) concentrations were measured by enzyme-linked immunosorbent assay. Self-scratching behavior, mast cell degranulation, and NGF concentration decreased, and the length of SP-positive nerve fibers and SP concentrations increased significantly in the epinastine-treated group, when compared with the vehicle control group. We conclude that epinastine inhibits mast cell degranulation by attenuating SP release from sensory nerve fibers, which results in inhibition of self-scratching behavior. These results suggest that second-generation histamine H(1)-receptor antagonists might efficaciously control itch-scratch cycle-related skin diseases.

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.