Abstract

COX-2 (Cyclooxygenase-2) and iNOS (inducible nitric oxide synthase) are involved in various pathophysiological processes such as inflammation. In a search for inhibitors of COX-2 and iNOS, we found that extracts of Dictyota dichotoma inhibit Nitric oxide (NO) and PGE₂ generation in LPS-stimulated RAW 264.7 macrophage cells, as well as levels of iNOS and COX-2 mRNA and protein.D. dichotoma were extracted with 80% EtOH. The extract was then partitioned with hexane, CH₂Cl₂, EtOAc, BuOH, and water, successively. The results indicate that the CH₂Cl₂ fraction of D. dichotoma extract is an effective inhibitor of LPS-induced NO and PGE₂ production in RAW 264.7 cells. These inhibitory effects of the CH₂Cl₂ fraction of D. dichotoma were accompanied by decreases in the expression of iNOS and COX-2 proteins and iNOS and COX-2 mRNA in dose-dependent pattern. To test the inhibition effects of D. dichotoma fractions on other cytokines, we also performed RT-PCR on TNF-α, IL-1β, and IL-6 in LPS-stimulated RAW 264.7 macrophage cells. In these assays, the CH₂Cl₂ fraction ofD. dichotoma also showed decreases in the expression of TNF-α, IL-1β, and IL-6 mRNA. Based on these results, we suggest that D. dichotoma extracts may be considered possible anti-inflammatory candidates for human health.

Key words: COX-2, Cytokine, Dictyota dichotoma, inflammation, iNOS (inducible nitric oxide synthase), PGE₂.