Solutions of N-nitrosamines, N-nitrosodimethylamine, N-nitrosodiethylamine, N-nitrosomorpholine and N-nitrosopyrrolidine in phosphate buffer (pH 7.4) were irradiated by ultraviolet (UV) light at room temperature. The N-nitrosamines were extensively degraded due to irradiation for 120 min in a time-dependent fashion as monitored by UV-absorption or high performance liquid chromatographic analysis. Carbon-centered radicals were generated from four N-nitrosamines during the short time irradiation of 10-60 s as monitored by electron spin resonance (ESR) technique using 5,5-dimethyl-1-pyrroline N-oxide and N-tert-butyl-alpha-phenylnitrone as spin traps. Nitric oxide (NO) was generated during the short time irradiation as monitored by ESR technique using cysteine-Fe(II) complex, N-methyl-D-glucamine dithiocarbamate and 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide. Significant amounts of nitrite (4-16%) from four N-nitrosamines and also a significant amount of nitrate (4%) was produced from N-nitrosodimethylamine during the irradiation time of 120 min. Released NO from the N-nitrosamines must be converted into nitrite through intermediary reactive nitrogen oxide species including nitrogen dioxide and dinitrogen trioxide in contact with dissolved oxygen.
Nitric oxide (NO) has many important biological functions, 1,2) but related nitrogen oxide species including dinitrogen trioxide (N 2 O 3 ), nitrogen dioxide (NO 2 ), and peroxynitrite/peroxynitrous acid (ONOO Ϫ /ONOOH) are known to cause damage to biomolecules such as lipids, proteins, and DNA. There are many reports showing the reactivitiy and decomposition of these nitrogen oxide species in relation to the biologically toxic functions of NO. The reactivity of NO is enhanced by oxygen (O 2 ) through its conversion into the reactive intermediates NO 2 and N 2 O 3 as in Eqs. 1 and 2, and finally into nitrite (NO 2 Ϫ ) as in Eqs. 3 and 4. 3,4) 12) The reactivity and decomposition of ONOO Ϫ are regulated by rapid formation of the CO 2 adduct shown by Eq. 9, [13][14][15][16][17] and the reactivity of this adduct is considered to be important because biological fluids contain a high concentration of CO 2 .Biologically important nitrated and nitrosated compounds are produced by reaction with the nitrogen oxide species. 3-Nitrotyrosine (3-NO 2 Tyr) is produced by reaction of tyrosine (Tyr) 23,24) and N-nitrosomorpholine (NMOR) 23,25) are formed by reaction of glutathione (GSH) and morpholine (MOR), respectively, with NO/O 2 . The reaction of GSH with ONOO Ϫ /ONOOH gives small amounts of GSNO,26,27) whereas the reaction of MOR gives NMOR and N-nitroMOR. 28) GSNO is considered to be a stable NO pool in biological systems, 27,29) and thiol- 30) and metal ion 31)-induced release of NO from nitrosothiols and transnitrosation are known. N-Nitrosamines can be metabolized to form strongly alkylating electrophiles that react with DNA.32) It is conceivable that the presence or absence of O 2 at the locus of generation of nitrogen oxide species can greatly affect the reactivity of the species for the production of nitrated and nitrosated products.The aim of the present study was to compare the reactivity of these nitrogen oxide species for the formation of 3-NO 2 Tyr, GSNO, and NMOR in the presence and absence of O 2 and to determine the effects of O 2 on their reactivity. MATERIALS AND METHODS MaterialsPurified air, NO gas (purity 99.9%), and NO 2 gas (5% in nitrogen gas) were obtained from Nihonsanso Ltd. (Tochigi, Japan), and highly purified nitrogen gas (purity more than 99.9%) was obtained from Taiyo-Toyosanso Ltd. January 2004Biol. Pharm. Bull. 27(1) 17-23 (2004) 17 * To whom correspondence should be addressed. e-mail: kikugawa@ps.toyaku.ac.jp © 2004 Pharmaceutical Society of Japan Effects of Oxygen on the Reactivity of Nitrogen Oxide Species Including PeroxynitriteKiyomi KIKUGAWA,* Kazuyuki HIRAMOTO, and Takumi
Antioxidant and prooxidant effects of nitric oxide (NO) on lipid peroxidation in aqueous and non-aqueous media were examined. In an aqueous solution, NO did not induce peroxidation of unoxidized methyl linoleate (ML) and suppressed the radical initiator-induced oxidation of ML. NO suppressed the Fe(II) ion-induced oxidation of mouse liver microsomes. NO reduced the O2 consumption during the radical initiator-induced oxidation of linoleic acid in an aqueous medium. NO conversion into NO2- in an aqueous medium was not affected by unoxidized ML and was slightly reduced by peroxidizing ML. On the other hand, as well as pure NO2, NO induced peroxidation of unoxidized ML in n-hexane in a dose-dependent fashion. NO did not suppress the radical initiator-induced oxidation of ML in n-hexane. Nitrogen oxide species (NO2 or N2O3) formed by autoxidation was dramatically lost in n-hexane in the presence of unoxidized ML. The results indicated that NO terminated lipid peroxidation in an aqueous medium, whereas NO induced lipid peroxidatiton in a non-aqueous medium. Hence, NO showed both antioxidant and prooxidant effects on lipid peroxidation depending on the solvents.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.