Laminaria japonica Suppresses the Atopic Dermatitis-Like Responses in NC/Nga Mice and Inflamed HaCaT Keratinocytes via the Downregulation of STAT1.

Atopic dermatitis (AD) is a skin allergy accompanied by acute and chronic dermal inflammation. In traditional oriental medicine, Laminaria japonica has been used to treat various diseases, including inflammatory diseases. Therefore, to determine the therapeutic potential of L. japonica against AD, we investigated the inhibitory effects of L. japonica water extract (LJWE) on the inflammatory mediators and AD-like skin lesions. We determined the cell viability of LJWE-treated HaCaT cells using the cell counting kit-8 assay and the levels of inflammatory cytokines using cytometric bead array kits. Additionally, we analyzed the modulatory effects of LJWE on the signaling pathways in tumor necrosis factor-α/interferon-γ-stimulated HaCaT cells via Western blotting. Furthermore, we determined the in vivo effect of LJWE on NC/Nga mice and found that LJWE remarkably improved the skin moisture, reduced dermatitis severity, and inhibited the overproduction of inflammatory mediators in 2,4-dinitrochlorobenzene-sensitized NC/Nga mice. We also observed that LJWE inhibits the expression of inflammatory chemokines in human keratinocytes by downregulating the p38 mitogen-activated protein kinase signaling pathway and activating the signal transducer and activator of transcription 1. In conclusion, LJWE has the therapeutic potential against AD by healing AD-like skin lesions, and suppressing inflammatory mediators and major signaling molecules.