Modification of the Picryl Chloride-Induced Allergic Dermatitis Model in Mouse Ear Lobes by 12-<i>O</i>-Tetradecanoylphorbol 13-Acetate, and Analysis of the Role of Histamine in the Modified Model

Abstract

Background: In atopic dermatitis, inflammation induced by antigen-nonspecific stimuli further enhances the allergic inflammation. However, there is no experimental model in which allergic dermatitis is evoked where the inflammation has been induced by antigen-nonspecific stimuli. Here, we established a novel dermatitis model in mice and analyzed the role of histamine. Methods: After sensitization with picryl chloride (PiCl) by painting on ear lobes of cyclophosphamide-treated mice, 12-O-tetradecanoylphorbol 13-acetate (TPA) was painted twice at the same site, and then allergic inflammation was induced by painting PiCl. Histamine antagonists and cyclosporine A (CsA) were administered intravenously. Results: The application of TPA shifted the PiCl-induced allergic inflammation from a delayed-type response to a biphasic response, increased the infiltration of eosinophils and mast cells at the inflammatory site, shifted the cytokine milieu from Th1 to Th2 and induced the expression of thymic stromal lymphopoietin in the ear lobes. The PiCl-induced increase in the thickness of the ear lobe in the immediate phase was suppressed by the H1 antagonist pyrilamine. In contrast, the increase in the swelling in the late phase and the infiltration of eosinophils were suppressed by the H3/H4 antagonist thioperamide. The inhibitory effect of the combined treatment with pyrilamine and thioperamide on the TPA-modified contact dermatitis was as potent as that of CsA. Conclusion: Induction of the antigen-nonspecific inflammation by TPA enhanced the PiCl-induced allergic inflammation. Histamine plays significant roles in the early-phase swelling via H1 receptors, and the late-phase swelling via H3/H4 receptors in this TPA-modified allergic dermatitis model.

Analysis of the Mechanism for the Development of Allergic Skin Inflammation and the Application for Its Treatment: Establishment of a Modified Allergic Dermatitis Model in Mouse Ear Lobes by Application of 12-O-Tetradecanoyl Phorbol 13-Acetate: Putative Involvement of Thymic Stromal Lymphopoietin and Roles of Histamine

“…We found that this model showed features similar to those observed in atopic dermatitis: crust formation, epidermal hyperplasia, and a vigorous infiltration of leukocytes including eosinophils (12). Analysis of the time course changes in the PiCl-induced swelling showed that the allergic inflammation was shifted from a delayed-type response to a biphasic response consisting of a weak immediate-phase response and a late-phase response by painting with TPA (Fig.…”

“…The application of TPA on days 5 and 10 decreased the level of IFN-γ mRNA, but increased that of IL-4 mRNA (Fig. 3, hatched columns), indicating that the application of TPA induced a shift in the cytokine milieu from a Th1-to a Th2-type profile (12). Thus, this model will be a suitable model for studying the mechanisms by which the antigennonspecific inflammation worsens allergic dermatitis.…”

“…Grabbe et al (11) reported that antigennonspecific irritant applied with a small amount of the antigen enhanced the antigen-induced response. To clarify whether antigen-nonspecific inflammation induced before antigen challenge affects the antigeninduced immune response, we established a novel contact dermatitis model in mouse ear lobes in which antigen-nonspecific inflammation was induced by painting 12-O-tetradecanoylphorbol 13-acetate (TPA) between sensitization and challenge with PiCl (12). Using this modified contact dermatitis model, we analyzed the shift to Th2-dominant inflammation and roles of thymic stromal lymphopoietin (TSLP) and histamine.…”

“…Thereafter, 20 μl of a 0.04 μg/μl TPA (Sigma-Aldrich, St. Louis, MO, USA) solution (3:1 in acetone : ethanol) was applied to the same site twice (days 5 and 10) to induce antigen-nonspecific inflammation. On day 12, mice were challenged with 20 μl of a 1% (w /v) PiCl solution or the vehicle by painting it on the right ear lobe (12) (Fig. 1).…”

“…Sections, 4-μm thickness, were cut and stained with a Luxol-fast blue (EM Science, Cherry Hill, NJ, USA) solution for the detection of eosinophils or with a 0.05% (w /v) toluidine blue (EM Science) solution for the detection of mast cells. The numbers of eosinophils and mast cells were counted and expressed as the number of cells in the range of 0.25 mm (12). The number of eosinophils in blood was determined by Giemsa staining.…”