Polynucleotides Enhance Skin Barrier Function and Reduce Inflammation in a 2,4-Dinitrochlorobenzene-Induced Mouse Model of Atopic Dermatitis.

Background: Atopic dermatitis (AD) is a chronic inflammatory dermatological disorder characterized by skin barrier dysfunction, dry skin, pruritus, and aberrant immune responses to external stimuli. Although polynucleotides (PNs) have anti-inflammatory properties, their effect on AD remains unexplored.

Materials and methods: This study investigated the effects of PNs on a 2,4-dinitrochlorobenzene (DNCB)-induced AD mouse model. The effects were evaluated by the dermatitis severity score (DSS), the spleen index, the serum immunoglobulin E (IgE) concentration, trans-epidermal water loss (TEWL), histological findings, and the expression levels of cytokine mRNA and filaggrin protein in skin tissue.

Results: Topical application of PNs significantly reduced the DSS, the spleen index, the serum IgE concentration, and TEWL compared with the control. Additionally, histopathological analysis showed that PNs reduced epidermal and dermal thickness, the mast cell count, collagen deposition, and eosinophil infiltration in the dermis. Moreover, PNs significantly downregulated the expression of key inflammatory cytokines, including interleukin (IL)-4, IL-5, IL-13, IL-25, IL-33, and thymic stromal lymphopoietin (TSLP), in affected skin tissue. Immunohistochemical (IHC) staining and Western blot revealed that PNs inhibited DNCB-induced suppression of filaggrin. A combination of hyaluronic acid (HA) and PNs showed enhanced efficacy compared with PNs alone, particularly for reducing the serum IgE concentration and TEWL and increasing filaggrin expression.

Conclusion: These results suggest that PNs are potential candidates to treat AD because they possess anti-inflammatory properties and improve skin barrier function.