Sargassum horneri extract containing polyphenol alleviates DNCB-induced atopic dermatitis in NC/Nga mice through restoring skin barrier function.

Atopic dermatitis (AD) is a chronic inflammatory skin disease characterized by skin barrier dysfunction. Sargassum horneri (S. horneri) is a brown alga that has been widely used in traditional medicine of eastern Asian countries. Recent studies proved that a brown alga S. horneri has anti-inflammatory activity. In this study, we investigated the effect of S. horneri ethanol extract (SHE) against AD in 2,4-dinitrobenzene (DNCB) induced AD in NC/Nga mice. We observed that SHE treatment decreased the epidermal thickness and epidermal hyperplasia that had been worsened through DNCB application. Moreover, SHE significantly inhibited the proliferation of mast cells and decreased the expression of IL-13 on CD4⁺ cells prompted by elevated thymic stromal lymphopoietin (TSLP) expression in DNCB-induced AD in mice. We also demonstrated that SHE directly inhibited the expression of keratinocyte-produced TSLP known to exacerbate skin barrier impairment. Especially, the decrease of filaggrin, an integral component of proper skin barrier function through a function in aggregating keratin filaments, observed in DNCB-induced AD mice was significantly improved when treated with SHE. More importantly, we proved that SHE was able to decrease the serum levels of IgG₁ and IgG₂ₐ, two crucial factors of AD, indicating the protective effect of SHE. Taken together, our findings suggest that SHE may protect NC/Nga mice against DNCB-induced AD via promoting skin barrier function.