It has been previously determined that pro-inflammatory mediators including nitric oxide (NO), prostaglandin E₂ (PGE₂), tumor necrosis factor (TNF)-α, and interleukin (IL)-1β and IL-6 contribute to the courses of a variety of inflammatory diseases. In this study, we evaluated the anti-inflammatory effects of fucoxanthin (FX), a natural biologically active substance isolated from Ishige okamurae, by determining its inhibitory effects on pro-inflammatory mediators in lipopolysaccharide (LPS)-stimulated murine macrophage RAW 264.7 cells. FX induced dose-dependent reductions in the levels of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) proteins and concomitant reductions in the production of NO and PGE₂. Additionally, FX was shown to suppress the production of inflammatory cytokines including IL-1β, TNF-α, and IL-6. Furthermore, FX inhibited the cytoplasmic degradation of inhibitors of B (IκB)-α and the nuclear translocation of p50 and p65 proteins, resulting in lower levels of nuclear factor (NF)-κB transactivation. Additionally, FX was shown to induce a dose-dependent inhibition of the phosphorylation of mitogen-activated protein kinases (MAPKs; JNK, ERK and p38). Collectively, the results of this study demonstrate that FX reduces the levels of pro-inflammatory mediators including NO, PGE₂, IL-1β, TNF-α, and IL-6 via the inhibition of NF-κB activation and the suppression of MAPK phosphorylation in RAW 264.7 cells. These findings reveal, in part, the molecular basis underlying the anti-inflammatory properties of FX.
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