Suppression of inducible cyclooxygenase and inducible nitric oxide synthase by apigenin and related flavonoids in mouse macrophages

• Published in: Carcinogenesis (New York) 1999-10, Vol.20 (10), p.1945-1952
• Main Authors: Liang, Yu-Chih, Huang, Ying-Tang, Tsai, Shu-Huei, Lin-Shiau, Shoei-Yn, Chen, Chieh-Fu, Lin, Jen-Kun
• Format: Article
• Language: English
• Subjects: (–)-epigallocatechin-3-gallate; Animals; Base Sequence; Biological and medical sciences; Carcinogenesis, carcinogens and anticarcinogens; Chamomile - chemistry; Chemical agents; COX; cyclooxygenase; DNA Primers; EGCG; EGF; EIA; electrophoretic mobility shift assay; EMSA; enzyme immunoassay; Enzyme Induction; epidermal growth factor; Flavonoids - pharmacology; GAPDH; glyceraldehyde 3-phosphate dehydrogenase; IFN-γ; IkB; IkB kinase; IKK; inducible nitric oxide synthase; inhibitor kB; iNOS; interferon-γ; lipopolysaccharide; Lipopolysaccharides - pharmacology; LPS; Macrophage Activation; Macrophages - drug effects; Macrophages - enzymology; Macrophages - metabolism; Medical sciences; Mice; NF-kB; nitric oxide; nitric oxide synthase; Nitric Oxide Synthase - antagonists & inhibitors; Nitric Oxide Synthase Type II; Nitrites - metabolism; NOS; nuclear factor-kB; PGE2; Plants, Medicinal; prostaglandin E2; Prostaglandin-Endoperoxide Synthases - biosynthesis; Tumors
• ISSN: 0143-3334; 1460-2180
• DOI: 10.1093/carcin/20.10.1945

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 IC50 < 15 μM. In addition, apigenin and kaempferol were also markedly active inhibitors of transcriptional activation of iNOS, with IC50 < 15 μM. 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 ~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-γ. 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.