| First Author | Chun KS | Year | 2004 |
| Journal | Carcinogenesis | Volume | 25 |
| Issue | 3 | Pages | 445-54 |
| PubMed ID | 14633657 | Mgi Jnum | J:87033 |
| Mgi Id | MGI:2682997 | Doi | 10.1093/carcin/bgh021 |
| Citation | Chun KS, et al. (2004) Nitric oxide induces expression of cyclooxygenase-2 in mouse skin through activation of NF-kappaB. Carcinogenesis 25(3):445-54 |
| abstractText | 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. |
