Inhibitory effect of citrus 5-hydroxy-3,6,7,8,3',4'-hexamethoxyflavone on 12-O-tetradecanoylphorbol 13-acetate-induced skin inflammation and tumor promotion in mice.
5-Hydroxy-3,6,7,8,3',4'-hexamethoxyflavone (5-OH-HxMF), a polymethoxyflavone, is found exclusively in the Citrus genus, particularly in the peels of sweet orange. Herein, we report the first investigation of the inhibitory effects of 5-OH-HxMF on 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) in mouse skin. We found that the topical application of 5-OH-HxMF can effectively inhibit the transcriptional activation of iNOS and COX-2 mRNA and protein in mouse skin stimulated by TPA. Pre-treatment with 5-OH-HxMF resulted in the reduction of TPA-induced nuclear translocation of nuclear factor-kappaB (NF-kappaB) subunit and DNA binding by blocking phosphorylation of inhibitor kappaB (IkappaB) alpha and p65 and subsequent degradation of IkappaBalpha. In addition, 5-OH-HxMF can inhibit TPA-induced phosphorylation and nuclear translocation of the signal transducer and activator of transcription-3. Moreover, 5-OH-HxMF can suppress TPA-induced activation of extracellular signal-regulated kinase 1/2, p38 mitogen-activated protein kinase and phosphatidylinositol 3-kinase/Akt, which are upstream of NF-kappaB. We also found that 5-OH-HxMF significantly inhibited TPA-induced mouse skin inflammation by decreasing inflammatory parameters. Furthermore, 5-OH-HxMF significantly inhibited 7,12-dimethylbenz[a]anthracene/TPA-induced skin tumor formation by reducing the tumor incidence and tumor multiplicity of papillomas at 20 weeks. Therefore, all these results revealed for the first time that 5-OH-HxMF is an effective antitumor agent and its inhibitory effect is through the down-regulation of inflammatory iNOS and COX-2 gene expression in mouse skin, suggesting that 5-OH-HxMF is a novel functional agent capable of preventing inflammation-associated tumorigenesis.
Lai
Ching-Shu
CS
Department of Environmental and Occupational Health, National Cheng Kung University Medical College, 138 Sheng-Li Road, Tainan 70428, Taiwan.
Li
Shiming
S
Chai
Chee-Yin
CY
Lo
Chih-Yu
CY
Ho
Chi-Tang
CT
Wang
Ying-Jan
YJ
Pan
Min-Hsiung
MH
D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology* / Q000627:therapeutic use; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology* / Q000627:therapeutic use; D002957:Citrus / Q000737:chemistry*; D051546:Cyclooxygenase 2 / Q000096:biosynthesis; D003872:Dermatitis / Q000188:drug therapy*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005260:Female; D047309:Flavones / Q000494:pharmacology* / Q000627:therapeutic use; D051550:I-kappa B Kinase / Q000378:metabolism; D051379:Mice; D008813:Mice, Inbred ICR; D016328:NF-kappa B / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000096:biosynthesis; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D050796:STAT3 Transcription Factor / Q000378:metabolism; D012878:Skin Neoplasms / Q000139:chemically induced / Q000517:prevention & control*; D013755:Tetradecanoylphorbol Acetate; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D000894:Anti-Inflammatory Agents, Non-Steroidal; D000972:Antineoplastic Agents, Phytogenic; D047309:Flavones; D016328:NF-kappa B; D050796:STAT3 Transcription Factor; C494087:Stat3 protein, mouse; C521815:5-hydroxy-3,6,7,8,3',4'-hexamethoxyflavone; D052247:Nitric Oxide Synthase Type II; C077623:Ptgs2 protein, mouse; D051546:Cyclooxygenase 2; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D051550:I-kappa B Kinase; D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D013755:Tetradecanoylphorbol Acetate