We investigated the generation of nitric oxide (.NO) by H2O2-dependent peroxidation of hydroxyurea in the presence of copper-containing proteins such as Cu,Zn-superoxide dismutase (Cu,Zn-SOD) or ceruloplasmin as a catalyst. In the reaction mixture of hydroxyurea, Cu,Zn-SOD, and H2O2, .NO generation was identified by measuring the specific electron spin resonance (ESR) signal of 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (PTIO). The ESR signal of the NO-hemoglobin adduct was also detected in human red blood cells during copper-catalyzed peroxidation of hydroxyurea. The .NO production during peroxidation of hydroxyurea was quantified as NO2- formation, measured by using the Griess assay, and the amount of NO2- was dependent on the concentration of hydroxyurea of the reaction mixture. ESR spin trapping with 5,5-dimethyl-1-pyrroline N-oxide (DMPO) showed hydroxy radical (.OH) generation in the reaction of H2O2 with either Cu,Zn-SOD or ceruloplasmin. Several .OH scavengers, such as ethanol, thiourea, DMPO, and dimethylsulfoxide, and the metal-chelating agent diethylenetriaminepentaacetic acid significantly inhibited .NO generation from hydroxyurea. This indicates that .NO release from hydroxyurea may be mediated by .OH derived from the copper-catalyzed Fenton-like reaction. Incubation of hydroxyurea and Cu,Zn-SOD with xanthine oxidase and hypoxanthine in a system forming O2-→H2O2 also resulted in appreciable .NO production. These results suggest that .NO production from hydroxyurea catalyzed by copper-containing proteins may be the molecular basis of the pharmacological and antitumor action of hydroxyurea.
|ジャーナル||Japanese Journal of Cancer Research|
|出版ステータス||Published - 1997 12|
ASJC Scopus subject areas
- Cancer Research