Inhibitory effect of citrus nobiletin on phorbol ester-induced skin inflammation, oxidative stress, and tumor promotion in mice.

Abstract

The intake of citrus fruits has been suggested as a way to prevent the development of some types of human cancer. Nitric oxide (NO) is closely associated with the processes of epithelial carcinogenesis. We attempted a search for NO generation inhibitors in Citrus unshiu. The active constituent was traced by an activity-guiding separation. NO and superoxide (O2-) generation was induced by a combination of lipopolysaccharide and IFN-gamma in mouse macrophage RAW 264.7 cells, and by 12-O-tetradecanoylphorbol-13-acetate (TPA) in differentiated human promyelocyte HL-60, respectively. Expression of inducible NO synthase and cyclooxygenase 2 proteins were detected by Western blotting. The in vivo anti-inflammatory and antitumor promoting activities were evaluated by topical TPA application to ICR mouse skin with measurement of edema formation, epidermal thickness, leukocyte infiltration, hydrogen peroxide production, and the rate of proliferating cell nuclear antigen-stained cells. As a result, nobiletin, a polymethoxyflavonoid, was identified as an inhibitor of both NO and O2- generation. Nobiletin significantly inhibited two distinct stages of skin inflammation induced by double TPA application [first stage priming (leukocyte infiltration) and second stage activation (oxidative insult by leukocytes)] by decreasing the inflammatory parameters. It also suppressed the expression of cyclooxygenase-2 and inducible NO synthase proteins and prostaglandin E2 release. Nobiletin inhibited dimethylbenz[a]anthracene (0.19 micromol)/TPA (1.6 nmol)-induced skin tumor formation at doses of 160 and 320 nmol by reducing the number of tumors per mouse by 61.2% (P < 0.001) and 75.7% (P < 0.001), respectively. The present study suggests that nobiletin is a functionally novel and possible chemopreventive agent in inflammation-associated tumorigenesis.

• Authors: A Murakami, Y Nakamura, K Torikai, T Tanaka, T Koshiba, K Koshimizu, S Kuwahara, Y Takahashi, K Ogawa, M Yano, H Tokuda, H Nishino, Y Mimaki, Y Sashida, S Kitanaka, H Ohigashi
• Journal: Cancer research (Cancer Res) Vol. 60 Issue 18 Pg. 5059-66 (Sep 15 2000) ISSN: 0008-5472 [Print] United States
• PMID: 11016629 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Anti-Inflammatory Agents, Non-Steroidal
• Anticarcinogenic Agents
• Antioxidants
• Carcinogens
• Flavones
• Flavonoids
• Isoenzymes
• Lipopolysaccharides
• Membrane Proteins
• Superoxides
• Nitric Oxide
• Interferon-gamma
• nobiletin
• Cyclooxygenase 2
• PTGS2 protein, human
• Prostaglandin-Endoperoxide Synthases
• Dinoprostone
• Tetradecanoylphorbol Acetate

Topics

• Animals
• Anti-Inflammatory Agents, Non-Steroidal (pharmacology)
• Anticarcinogenic Agents (therapeutic use)
• Antioxidants (pharmacology)
• Carcinogens
• Cell Line
• Citrus (chemistry)
• Cyclooxygenase 2
• Dinoprostone (biosynthesis)
• Drug Eruptions (metabolism, prevention & control)
• Female
• Flavones
• Flavonoids (isolation & purification, therapeutic use)
• HL-60 Cells (drug effects, metabolism)
• Humans
• Interferon-gamma (pharmacology)
• Isoenzymes (biosynthesis)
• Lipopolysaccharides (pharmacology)
• Macrophage Activation (drug effects)
• Macrophages (drug effects, metabolism)
• Membrane Proteins
• Mice
• Mice, Inbred ICR
• Nitric Oxide (antagonists & inhibitors, biosynthesis)
• Oxidative Stress (drug effects)
• Prostaglandin-Endoperoxide Synthases (biosynthesis)
• Skin (drug effects, metabolism)
• Skin Neoplasms (chemically induced, metabolism, prevention & control)
• Superoxides (antagonists & inhibitors, metabolism)
• Tetradecanoylphorbol Acetate