Polynucleotides Attenuate Atopic Dermatitis-like Inflammatory Signaling in Keratinocytes and Macrophages

Background: Atopic dermatitis (AD) is a persistent and recurring skin disease characterized by epidermal barrier dysfunction, immune dysregulation, and elevated expression of proinflammatory mediators. We investigated the anti-inflammatory potential of polynucleotides (PN), highly purified DNA biopolymers isolated from salmonid gonads, in keratinocyte and macrophage activation models. Methods: RAW 264.7 macrophages were stimulated with lipopolysaccharide (LPS), whereas HaCaT keratinocytes were stimulated with tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ). The effects of PN treatment on the production or expression of inflammatory mediators, cytokines, and chemokines were evaluated. Changes in the phosphorylation of mitogen-activated protein kinases (MAPKs) and Janus kinase 1/signal transducer and activator of transcription 3 (JAK1/STAT3) and in the nuclear localization of nuclear factor-κB (NF-κB) were also assessed. Results: In LPS-activated RAW 264.7 macrophages, PN treatment significantly suppressed nitric oxide production and downregulated the expression of inducible nitric oxide synthase (iNOS), TNF-α, IL-1β, and IL-8, accompanied by reduced NF-κB nuclear translocation. In TNF-α/IFN-γ-stimulated HaCaT keratinocytes, PN treatment markedly decreased the secretion levels of IL-6, IL-1β, and thymic stromal lymphopoietin. Moreover, PN treatment markedly reduced T-cell-recruiting chemokines, including MDC/CCL22, TARC/CCL17, RANTES/CCL5, and IL-8. Signaling analyses demonstrated that PN treatment attenuated the phosphorylation of key MAPKs (ERK, JNK, and p38) and the JAK1/STAT3 axis. Furthermore, PN treatment markedly reduced NF-κB nuclear translocation. Conclusions: These in vitro findings indicate that the anti-inflammatory effects of PN are associated with reduced activation of multiple core signaling pathways governing cytokine and chemokine responses, supporting further investigation of PN in AD and other chronic inflammatory skin diseases.