Ethanol Extract of Sargassum siliquastrum Inhibits Lipopolysaccharide-Induced Nitric Oxide Generation by Downregulating the Nuclear Factor-Kappa B Signaling Pathway

Sargassum siliquastrum (SS) is an edible brown seaweed widely consumed in Korea and considered a functional food source. Previous studies have reported various biological activities of SS extracts, including antioxidant and hepatoprotective properties. In the present study, we examined the anti-inflammatory effects of the SS extract and assessed the underlying mechanism of action. The SS extract significantly inhibited lipopolysaccharide (LPS)-induced nitric oxide (NO) production in a dose-dependent manner (% of NO production at 500 mu g/mL: 60.1 +/- 0.9%), with no obvious toxicity. Furthermore, the SS extract inhibited mRNA and protein expression levels of inducible NO synthase, as well as LPS-induced expression and production of proinflammatory cytokines such as IL-1 beta, IL-6, or TNF-alpha (IL-6 production (ng/mL) : LPS-: 0.7 +/- 0.3; LPS+: 68.1 +/- 2.8; LPS + SS extract: 51.9 +/- 1.2; TNF-alpha production (ng/mL) : LPS-: 0.3 +/- 0.1; LPS+: 23.0 +/- 0.1; LPS + SS extract: 18.2 +/- 10.8). Mechanistically, the SS extract attenuated LPS-induced activation of the nuclear factor kappa-light-chain-enhancer of activated B cells (nuclear factor-kappa B, NF-kappa B) signaling pathway such as phosphorylation of NF-kappa B p65 and degradation of I kappa B-alpha, thereby blocking LPS-induced activation of NF-kappa B transcriptional activity. The SS extract also enhanced LPS-induced heme oxygenase-1 expression and attenuated LPS-induced cellular reactive oxygen species production (% of ROS production at 500 mu g/mL: 52.2 +/- 1.3%). Collectively, these findings suggest that the SS extract elicits anti-inflammatory effects in mouse macrophage cells.