Anti-Atopic Dermatitis Effect of Seaweed Fulvescens Extract via Inhibiting the STAT1 Pathway

Abstract

Seaweed fulvescens (SF) is a green alga rich in chlorophyll with unique flavor and taste. It is also called Maesaengi which has antioxidant and other physiological activities. In the present study, we evaluated the therapeutic effects of SF in a mouse model of Dermatophagoides farinae body-induced atopic dermatitis (AD) and in tumor necrosis factor-α and interferon-γ-stimulated HaCaT keratinocytes. SF treatment (200 mg/mouse) inhibited the development of AD symptoms, compared to that in the control group, as evidenced from the improved dorsal skin lesion, reduced thickness and infiltration of inflammatory cells and smaller lymph nodes, and reduced levels of proinflammatory cytokines. In HaCaT keratinocytes, SF (10, 25, and 50 μg/mL) suppressed the production of proinflammatory cytokines in a dose-dependent manner. In addition, SF reduced the phosphorylation of signal transducer and activator of transcription 1, which is one of the major signaling molecules involved in cellular inflammation. These results suggested that SF could be a potential therapeutic alternative for the treatment of AD.

Figure 1

Effects of SF on Df-induced AD-like skin lesions in NC/Nga mice. (a) Schematic depiction of the development of SDS/Df-induced AD and treatment with SF. (b) Representative photographs of the dorsal regions of mice from each group at 29 days after AD induction and treatment with SF. CON: control mouse group, Df: Df-induced atopic dermatitis (AD) NC/Nga mice, and SF: seaweed fulvescens (SF) extract-treated AD mice. (c) Dermatitis scores for 4 weeks. Dermatitis score were determined as the sum of scores graded as 0 (none), 1 (mild), 2 (moderate), or 3 (severe) for each of the four symptoms (erythema/hemorrhage, scarring/dryness, edema, and excoriation/erosion). Data are expressed as the mean ± standard deviation (SD; n = 6). Data were analyzed using one-way analysis of variance followed by Dunnett's post hoc test. ^∗ P < 0.05 and ^∗∗∗ P < 0.001 versus the Df group; ^# P < 0.05 versus the control group.

Figure 2

Effects of SF on skin integrity and mast cell infiltration in Df-treated NC/Nga mice. (a) Histological examination of NC/Nga mice. The tissues were excised and fixed in 10% formaldehyde. Then, they were embedded in paraffin and sectioned. The sections were stained with H&E (40x and 200x magnifications). (b) Epidermal thickness was examined after sacrifice. (c) Staining with toluidine blue was used to identify mast cells, and (d) mast cell counts were determined using a microscope at 200x magnification. Data were expressed as the mean ± SD (n = 6). Data were analyzed using one-way analysis of variance followed by Dunnett's post hoc test. ^∗∗∗ P < 0.001 versus the Df group; ^### P < 0.001 versus the control group.

Figure 3

Effects of SF on Df-induced systemic immunological abnormalities in NC/Nga mice. (a–d) The mRNA expression and production of inflammatory cytokines were determined in skin lesions. Total RNA was isolated from the skin lesions of NC/Nga mice treated with SF, and quantitative reverse transcription polymerase chain reaction was performed. The production of inflammatory cytokines was measured by ELISA. Data were presented as the mean ± SD (n = 6). Data were analyzed using one-way analysis of variance followed by Dunnett's post hoc test. ^∗ P < 0.05 and ^∗∗∗ P < 0.001 versus the Df group; ^# P < 0.05, ^## P < 0.01, and ^### P < 0.001 versus the control group.

Figure 4

Effects of SF on inflammatory signaling pathways in Df-induced skin lesions. Protein was isolated from normal or Df-induced dermatitis dorsal skin. Phosphorylation of STAT1 was measured by western blot analysis. The graph shows the ratio of phosphorylated STAT1 to total STAT1. Values represent the mean ± SD of triplicate independent experiments. ^∗∗∗ P < 0.001 versus the Df group; ^### P < 0.001 versus the control group.

Figure 5

Effects of SF on the mRNA expression and production of inflammatory cytokines in HaCaT keratinocytes. (a) Cell viability was determined using the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. Cells were seeded in 96-well microplates at 1 × 10⁵ cells/well, and various concentrations of SF were added to each well for 24 h. The mRNA expression levels (b, d) and production of inflammatory cytokines (c, e) were determined in HaCaT keratinocytes. Total RNA was isolated from the cells treated with SF for 6 h, and quantitative reverse transcription-polymerase chain reaction was performed. The production of inflammatory cytokines was measured by ELISA. Proinflammatory cytokine levels were measured in the culture supernatants from cells treated with SF (10, 25, and 50 μg/mL) and TNF-α and IFN-γ (each 10 ng/mL) for 24 h. Values represent the mean ± SD of three independent experiments. ^∗∗ P < 0.01 and ^∗∗∗ P < 0.001 versus the Df group; ^# P < 0.05, ^## P < 0.01, and ^### P < 0.001 versus the control group.

Figure 6

Effect of SF on the activation of STAT1 in HaCaT keratinocytes. Phosphorylation of STAT1 was measured in HaCaT cells pretreated with SF (10, 25, and 50 μg/mL) for 1 h and stimulated with TNF-α and IFN-γ (10 ng/mL each) for 2 h. The graph shows the ratio of phosphorylated STAT1 to total STAT1. Values represent the mean ± SD of three independent experiments. ^∗∗∗ P < 0.001 versus the Df group; ^### P < 0.001 versus the control group.