Methanol Extracts of Stewartia koreana Inhibit Cyclooxygenase-2 (COX-2) and Inducible Nitric Oxide Synthase (iNOS) Gene Expression by Blocking NF-κB Transactivation in LPS-activated RAW 264.7 Cells

Cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) are involved in various pathophysiological processes such as inflammation and carcinogenesis. In a search for inhibitors of COX-2 and iNOS production we found that extracts of Stewartia koreana strongly inhibited NO and PGE2 production in LPS-treated macrophage RAW 264.7 cells. We have now shown that the mRNA and protein levels of iNOS and COX-2 are reduced by the Stewartia koreana extract (SKE). SKE inhibited expression of an NF-κB reporter gene in response to LPS, and gel mobility shift assays revealed that SKE reduced NF-κB DNA-binding activity. The extract also inhibited LPS-induced phosphorylation of IκB-α and nuclear translocation of p65. Administration of the extract reduced the symptoms of arthritis in a collagen-induced arthritic mouse model. These results indicate that Stewartia extracts contain potentially useful agents for preventing and treating inflammatory diseases.