Anti-Inflammatory Effects Exerted by 14-Methoxyalternate C from Antarctic Fungal Strain Pleosporales sp. SF-7343 via the Regulation of NF-κB and JAK2/STAT3 in HaCaT Human Keratinocytes

Abstract

Atopic dermatitis (AD) is a chronic inflammatory skin disease with a profound negative impact on patients' quality of life. Four known secondary fungal metabolites were found in the chemical study of the Antarctic fungus Pleosporales sp. SF-7343, including 14-methoxyalternate C (1), 5'-methoxy-6-methyl-biphenyl-3,4,3'-triol (2), 3,8,10-trihydroxy-4-methoxy-6-methylbenzocoumarin (3), and alternariol monomethyl ether (4). Additionally, we identified the skin anti-inflammatory composition from the SF-7343 strain. Interleukin-8 and -6 Screening results showed that compound 1 inhibited IL-8 and IL-6 in tumor necrosis factor-α/interferon-γ stimulated HaCaT cells. Compound 1 showed inhibitory effects on MDC and RANTES. It also downregulated the expression of intercellular adhesion molecule-1 (ICAM-1) and upregulated the expression of involucrin. The results of the mechanistic study showed that compound 1 inhibited the nuclear translocation of nuclear factor-kappa B p65 and STAT3. In conclusion, this study demonstrates the potential of the Antarctic fungal strain SF-7343 as a bioactive resource to inhibit skin inflammation, such as AD.

Keywords: Antarctic fungi; HaCaT; JAK2/STAT3; NF-κB; skin inflammation.

Figure 1

Structure of isolated compounds 1–4 (A–D).

Figure 2

Cytotoxicities of the compounds 1, 2, 3, and 4 used in this study(A–D). Cells were treated for 24 h with the indicated concentration of each of the four compounds and the cytotoxicity was evaluated. Data are presented as the mean ± SD (n = 3). * p < 0.05 vs. control.

Figure 3

Effects of compound 1 on MDC and RANTES secretion in TNF-α/IFN-γ-stimulated HaCaT cells. (A,B) The MDC and RANTES levels were measured using the cell cuture supernatant. Data are represented as the mean ± SD (n = 3). * p < 0.05 vs. TNF-α/IFN-γ-treated group.

Figure 4

Effects of compound 1 on TNF-α/IFN-γ-induced ICAM-1 and barrier-related molecules, Filaggrin (FLG)/Involucrin (IVL) in HaCaT cells (A–D). Data are represented as the mean ± SD (n = 3). * p < 0.05 vs. TNF-α/IFN-γ-treated group.

Figure 5

Effects of compound 1 on the JAK2/STAT3 signaling pathways in HaCaT cells. (A–C) The expression of p-STAT3 and p-JAK2 were measured using Western blotting. Data are represented as the mean ± SD (n = 3). * p < 0.05, ** p < 0.01 vs. TNF-α/IFN-γ-treated group.

Figure 6

Effects of compound 1 on NF-κB signaling pathways in HaCaT cells (A–C). The expression of p65, p-IκBα, and IκBα in the fractions were determined by using Western blotting. Immunofluorescence assay was performed as described in the methods section. Data are represented as the mean ± SD (n = 3). * p < 0.05, ** p < 0.01, vs. TNF-α/IFN-γ-treated group.