Abstract:
:Both cooked red meat intake and chronic inflammation/infection are thought to play a role in the etiology of colon cancer. The heterocyclic amine 2-amino-3-methylimidazo[4,5-f ]quinoline (IQ) is formed during cooking of red meat and may be involved in initiation of colon cancer. Reactive nitrogen oxygen species (RNOS), components of the inflammatory response, contribute to the deleterious effects attributed to inflammation on normal tissues. This study assessed the possible chemical transformation of IQ by RNOS. RNOS were generated by various conditions to react with (14)C-IQ, and samples were evaluated by HPLC. Myeloperoxidase (MPO)-catalyzed reaction was dependent upon both H(2)O(2) and NO(2)(-). This reaction produced an azo-IQ dimer and IQ dimer along with two nitrated IQ products identified by ESI/MS. 2-Nitro-IQ was not detected. Product formation was inhibited by 2 mM cyanide. Reduction in nitrated products observed with 100 mM chloride was not altered with 0.5 mM taurine. Nitrated products were also produced by other conditions, ONOO(-) and NO(2)(-) + HOCl, which generate nitrogen dioxide radical. In contrast, conditions which generate N(2)O(3), such as diethylamine NONOate, produced only small amounts of nitrated products with the major product identified by MS and NMR as N-nitroso-IQ. MPO activation of IQ to bind DNA was dependent upon both H(2)O(2) and NO(2)(-). RNOS generated by ONOO(-) and DEA NONOate also activated IQ DNA binding. The nitrated IQ products were not activated by MPO to bind DNA. In contrast, N-nitroso-IQ was activated to bind DNA by MPO +/- NO(2)(-). HOCl activated N-nitroso-IQ, but not IQ. RAW cells produced N-nitroso-IQ and increased amounts of NO(2)(-)/NO(3)(-), when incubated with 0.1 mM IQ and stimulated with lipopolysaccharide and interferon gamma. Results demonstrate chemical transformation and activation of IQ by RNOS and activation of its N-nitroso product by biological oxidants, events which may contribute to initiation of colon cancer.
journal_name
Chem Res Toxicoljournal_title
Chemical research in toxicologyauthors
Lakshmi VM,Hsu FF,Zenser TVdoi
10.1021/tx020008hsubject
Has Abstractpub_date
2002-08-01 00:00:00pages
1059-68issue
8eissn
0893-228Xissn
1520-5010pii
tx020008hjournal_volume
15pub_type
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