Dendrobium officinale Kimura et Migo polysaccharide ameliorated DNFB-induced atopic dermatitis in mice associated with suppressing MAPK/NF-κB/STAT3 signaling pathways

Ethnopharmacological relevance: Dendrobium officinale Kimura et Migo as a valuable Chinese medicine has been used in China for more than 2000 years. Its main active components, polysaccharide (DOP), has been reported to have various pharmacological effects, including anti-inflammatory, antioxidant and alleviating AD effects. However, the precise mechanism underlying its therapeutic effect in AD remains largely unclear. Aim of the study: The present study sought to assess the efficacy of DOP and elucidate its intricate mechanisms in ameliorating DNFB-induced AD. Materials and methods: Mice were sensitized with DNFB and treated with DOP application for 14 days. Treatment effects were assessed using dermatitis scores, ear thickness and scratching frequency. Epidermal thickness, mast cells and CD4+ T cells infiltration were detected by using H&E, toluidine blue staining and immunofluorescence staining respectively. Serum histamine (HIS), immunoglobulin E (IgE), thymic stromal lymphopoietin (TSLP), skin SOD, MDA, GHS, CAT, inflammatory cytokines (TNF-alpha, IFN-gamma, IL-1 beta, IL-4, IL-5, IL-13) and chemokine (MIP alpha, MDC, MCP-1) levels were quantify by ELISA and immunohistochemistry. Additionally, qPCR and Western blot analyses were performed to assess genes and proteins expression associated with MAPK/NF-kappa B/STAT3 signaling pathway. Results: The results indicated that DOP effectively mitigated AD-like skin lesions in mice through multiple pathways. It reduced epidermal thickness, ear thickness and scratching frequency in AD mice. Additionally, DOP mitigated inflammatory responses by decreasing the levels of inflammatory factors, as well as reducing serum levels of IgE, HIS, and TSLP. Moreover, DOP inhibited infiltration of mast cells and CD4+ T cells, suppressed the expression of skin chemokines such as MDC, MCP-1, and MIP-alpha, and enhanced filaggrin content in AD mice. Furthermore, DOP significantly boosted antioxidant capacity, as well as significantly reduced the expression of JAK1, STAT3, NF-kappa B p65, I kappa B alpha, ERK1/2, and p38 proteins and phosphorylated proteins such as p-JAK1, pSTAT3, p-NF-kappa B p65, p-I kappa B alpha, p-ERK1/2, and p-p38. Conclusions: These findings suggested that DOP has significant anti-AD activity, primarily through reducing inflammatory responses, improving antioxidant capacity, repairing the skin barrier, and down-regulating key genes and proteins in MAPK/NF-kappa B/STAT3 signaling pathway, and that this study may provide valuable insights into the development of innovative therapies for the treatment of AD.