title: Nitric oxide induces expression of cyclooxygenase-2 in mouse skin through activation of NF-kappaB.
abstract: Inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) are frequently overexpressed in tumor tissues or transformed cells. In the present work, we assessed the effects of 12-O-tetradecanoylphorbol-13-acetate (TPA) on expression of iNOS and COX-2 in mouse skin. Topical application to the dorsal skin of female ICR mice of 10 nmol TPA led to maximal induction of iNOS and COX-2 protein expression at approximately 2 and 4 h, respectively. When applied topically onto shaven backs of mice 30 min prior to TPA, the NOS inhibitor aminoguanidine (AG) inhibited the expression of COX-2 protein at the pharmacologically effective dose. Pretreatment with a more specific iNOS inhibitor, N(G)-nitro-l-arginine-methyl ester, also suppressed TPA-induced COX-2 expression. Immunohistochemical analysis of TPA-treated mouse skin using an anti-nitrotyrosine antibody reveals enhanced levels of nitrotyrosine protein localized in epidermal and dermal layers. Topical application of NO donors, such as sodium nitroprusside (SNP) and S-nitroso-N-acetyl-d,l-penicillamine, induced expression of COX-2 in mouse skin, which was attenuated by the NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethyl imidazoline-1-oxyl 3-oxide. SNP treatment stimulated NF-kappaB activation in mouse skin, which was associated with the degradation of IkappaBalpha. Topical application of inhibitors of NF-kappaB, such as pyrrolidine dithiocarbamate or N-alpha-p-tosyl-l-lysine chloromethylketone, inhibited the SNP-induced COX-2 expression. SNP induced a weak but concentration-related increase in COX-2 expression in cultured mouse keratinocytes, which was abolished by treatment with SN50, a specific inhibitor of nuclear translocation of NF-kappaB. Mouse keratinocytes treated with SNP exhibited an elevated NF-kappaB-driven COX-2 promoter activity. Topical application of AG (10 micro mol) prior to each TPA treatment after initiation reduced the multiplicity of papillomas by 44% at 22 weeks. In conclusion, up-regulation of COX-2 by NO may be mediated by activation of NF-kappaB in mouse skin, which provides a molecular mechanism by which COX-2 is induced during tumor promotion.
authors: College of Pharmacy, Seoul National University, Shinlim-dong, Kwanak-ku, Seoul 151742, South Korea.
authors: Kyung-Soo
authors: KS
authors: Chun
authors: Hyun-Ho
authors: HH
authors: Cha
authors: Jun-Wan
authors: JW
authors: Shin
authors: Hye-Kyung
authors: HK
authors: Na
authors: Kwang-Kyun
authors: KK
authors: Park
authors: Won-Yoon
authors: WY
authors: Chung
authors: Young-Joon
authors: YJ
authors: Surh
mesh_terms: D000818:Animals; D051546:Cyclooxygenase 2; D016166:Free Radical Scavengers / Q000494:pharmacology*; D007527:Isoenzymes / Q000187:drug effects*; D051379:Mice; D016328:NF-kappa B / Q000187:drug effects*; D009569:Nitric Oxide / Q000494:pharmacology*; D019001:Nitric Oxide Synthase / Q000187:drug effects; D052247:Nitric Oxide Synthase Type II; D011451:Prostaglandin-Endoperoxide Synthases / Q000187:drug effects*; D012867:Skin / Q000187:drug effects*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D016166:Free Radical Scavengers; D007527:Isoenzymes; D016328:NF-kappa B; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; D013755:Tetradecanoylphorbol Acetate