title: Suppression of inducible cyclooxygenase and inducible nitric oxide synthase by apigenin and related flavonoids in mouse macrophages.
abstract: Prostaglandins biosynthesis and nitric oxide production have been implicated in the process of carcinogenesis and inflammation. In this study, we investigated the effect of various flavonoids and (-)-epigallocatechin-3-gallate on the activities of inducible cyclooxygenase (COX-2) and inducible nitric oxide synthase (iNOS) in lipopolysaccharide (LPS)-activated RAW 264.7 macrophages. Apigenin, genistein and kaempferol were markedly active inhibitors of transcriptional activation of COX-2, with IC(50) < 15 microM. In addition, apigenin and kaempferol were also markedly active inhibitors of transcriptional activation of iNOS, with IC(50) < 15 microM. Of those compounds tested, apigenin was the most potent inhibitor of transcriptional activation of both COX-2 and iNOS. Western and northern blot analyses demonstrated that apigenin significantly blocked protein and mRNA expression of COX-2 and iNOS in LPS-activated macrophages. Transient transfection experiments showed that LPS caused an approximately 4-fold increase in both COX-2 and iNOS promoter activities, these increments were suppressed by apigenin. Moreover, electrophoretic mobility shift assay (EMSA) experiments indicated that apigenin blocked the LPS-induced activation of nuclear factor-kB (NF-kB). The inhibition of NF-kB activation occurs through the prevention of inhibitor kB (IkB) degradation. Transient transfection experiments also showed that apigenin inhibited NF-kB-dependent transcriptional activity. Finally, we showed that apigenin could inhibit the IkB kinase activity induced by LPS or interferon-gamma. The results of further studies suggest that suppression of transcriptional activation of COX-2 and iNOS by apigenin might mainly be mediated through inhibition of IkB kinase activity. This study suggests that modulation of COX-2 and iNOS by apigenin and related flavonoids may be important in the prevention of carcinogenesis and inflammation.
authors.affiliation: Institute of Biochemistry, College of Medicine, National Taiwan University, No. 1, Section 1, Taipei, Taiwan.
authors.forename: Y C
authors.initials: YC
authors.lastname: Liang
authors.forename: Y T
authors.initials: YT
authors.lastname: Huang
authors.forename: S H
authors.initials: SH
authors.lastname: Tsai
authors.forename: S Y
authors.initials: SY
authors.lastname: Lin-Shiau
authors.forename: C F
authors.initials: CF
authors.lastname: Chen
authors.forename: J K
authors.initials: JK
authors.lastname: Lin
mesh_terms: D000818:Animals; D001483:Base Sequence; D020843:Chamomile / Q000737:chemistry*; D017931:DNA Primers; D004790:Enzyme Induction; D005419:Flavonoids / Q000494:pharmacology*; D008070:Lipopolysaccharides / Q000494:pharmacology; D008262:Macrophage Activation; D008264:Macrophages / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D051379:Mice; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors*; D052247:Nitric Oxide Synthase Type II; D009573:Nitrites / Q000378:metabolism; D010946:Plants, Medicinal; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis*
chemical_list: D017931:DNA Primers; D005419:Flavonoids; D008070:Lipopolysaccharides; D009573:Nitrites; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D011451:Prostaglandin-Endoperoxide Synthases