Background: Abnormal immune responses, specifically excessive differentiation of Th2 cells, are associated with the development of atopic dermatitis (AD). Sophoricoside, the genistein-4'-β-D-glucoside isolated from Styphnolobium japonicum, has previously demonstrated anti-inflammatory and immunosuppressive effects along with IL-3 and IL-5 inhibitory activities. Therefore, we speculated that sophoricoside could regulate AD by regulating abnormal immune responses.
Purpose: To investigate the role of sophoricoside on AD-like allergic skin inflammation induced by ovalbumin (OVA) or 2,4,6-trinitrochlorobenzene (TNCB) in mouse models.
Methods: Sophoricoside was isolated from the 70% ethanol extract of S. japonicum dried mature seeds. After being submitted to a purification process, its purity was assessed by high-performance liquid chromatography (HPLC). The effects of sophoricoside were determined in vivo by OVA- and TNCB-induced AD-like allergic skin inflammation in mice. Skin tissues were subjected with hematoxylin-eosin (H&E), Giemsa and toluidine blue staining. In vitro CD4+ T cell differentiation was performed and the levels of serum immunoglobulins, cytokines, and genes related to CD4+ T cell differentiation were determined by enzyme-linked immunosorbent assay (ELISA) and quantitative real-time PCR. Cytokine bioassay, mixed lymphocytes reaction and cell viability assay were performed.
Results: Topical application of sophoricoside decreased the symptoms of AD-like allergic skin inflammation, including elevated hypertrophic scars with spongiotic epidermis, epidermal hyperplasia, hyperkeratosis, infiltration of immune, and mast cells, dermal thickness, amounts of immunoglobulins, and pro-inflammatory cytokines, and the mast cell population in the skin. Sophoricoside also decreased T cell antigen receptor (TCR)-mediated immune responses. In particular, sophoricoside suppressed the differentiation of naïve CD4+ T cells into Th cell subsets, including Th1, Th2, and Th17, by inhibiting the expression of their subset-specific master transcription factors, leading to suppression of the expression and production of these cell subset-specific cytokines.
Conclusion: Sophoricoside can improve AD-like allergic skin diseases mainly by inhibiting pathogenic CD4+ T cell differentiation and immune responses.
Keywords: 2,4,6-trinitrochlorobenzene (TNCB); Atopic dermatitis (AD); Helper T (Th) cell; Ovalbumin (OVA); Skin inflammation; Sophoricoside.
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