Dieckol, a Component of Ecklonia cava, Suppresses the Production of MDC/CCL22 via Down-Regulating STAT1 Pathway in Interferon-? Stimulated HaCaT Human Keratinocytes

Kang, Na-Jin; Koo, Dong-Hwan; Kang, Gyeoung-Jin; Han, Sang-Chul; Lee, Bang-Won; Koh, Young-Sang; Hyun, Jin-Won; Lee, Nam-Ho; Ko, Mi-Hee; Kang, Hee-Kyoung; Yoo, Eun-Sook

The promoter region of the MDC gene contains binding units for signal transducers and activators of transcription (STAT), activating protein (AP)-1, and NF-κB, and these factors may mediate the transcription of the MDC (Pearson et al., 2001; Ivashkiv and Hu. 2004; Best et al., 2005; Madonna et al., 2008; Qi et al., 2009) . IFN-γ acts via two IFN receptors subunits (IFNGR1 and IFNGR2), which form a heterotetramer on the cell surface, and activates various signaling cascades. Phosphorylated STAT1 functions as a transcription factor that activates the primary genes related to inflammatory responses. Therefore, the STAT1 protein is a crucial and specific regulator of IFN-γ signaling that controls the transcription of target genes, including MDC (Ivashkiv and Hu. 2004; Best et al., 2005) . It has been found that STAT1 phosphorylation plays a critical role in IFN-mediated innate immunity to microbial infection (van den Broek et al., 1995; Han et al., 2002; Semper et al., 2014) . After phosphorylation, STAT1 homodimerizes and translocates to the nucleus, and promotes gene transcription via binding to IFN-γ-activated genes. STAT1 homodimerization is preferentially mediated by the binding of the phosphory- HaCaT cells (5.0 × 10 5 cells/mL) were pre-treated with PD98059 (a specific ERK inhibitor, 10 mM) or dieckol (2.5, 5, 10 mM) for 2 h and stimulated by IFN-γ (10 ng/mL) for 5 mins. The phosphorylation of ERK was determined by Western blotting of whole cell lysates. (C) HaCaT cells (2.0×10 5 cells/mL) were stimulated with IFN-γ (10 ng/mL) in the presence or absence of the specific MAPK inhibitors (SP600125; JNK inhibitor, PD98059; ERK inhibitor, SB203580; p38 inhibitor) for 24 h. The amounts of MDC were measured from the culture supernatants by ELISA. Data are mean ± S.D. of three independent experiments. www.biomolther.org lated STAT1 (at tyrosine 701) to the Src homology 2 domain of another. However, the binding of the phosphorylated serine 727 of STAT1 is required for maximal transcriptional activity (Decker and Kovarik. 2000; Ivashkiv and Hu. 2004; Best et al., 2005) . In our study, dieckol suppressed STAT1 (at serine 727) phosphorylation induced by IFN-γ in a dose dependent manner. The effect of dieckol on the STAT1 phosphorylation is stronger than that of EGCG, a specific STAT inhibitor, at the same concentration (10 mM). In addition, microscopy results showed that dieckol (5, 10 mM) suppressed the nuclear translocation of phosphorylated STAT1 (at serine 727).