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PubMed1997

Lactoperoxidase-catalyzed oxidation of the anticancer agent mitoxantrone by nitrogen dioxide (NO2.) radicals.

Mitoxantrone [1,4-dihydroxy-5,8-bis[[2-[(2-hydroxyethyl)amino]ethyl] amino]-9,10-anthracenedione, MXH2] is a novel anticancer agent frequently employed in the chemotherapy of leukemia and breast cancer. Earlier studies have shown that metabolic oxidation to reactive 1,4-quinone or/and 5,8-diiminequinone intermediates may be an important mechanism of activation of this agent, pertinent to its cytotoxic action in vivo. Here we report that in the presence of nitrite ions (NO2-), MXH2 undergoes oxidation by the mammalian enzyme lactoperoxidase (LPO) and hydrogen peroxide and that the process proceeds at a rate that is proportional to NO2- concentration. In contrast, when MXH2 was exposed to LPO/H2O2 in the absence of nitrite, oxidation of the drug was either completely absent or markedly inhibited. These experiments were carried out using concentrated solutions of MXH2 (approximately 100 microM) at near neutral pH where dimers of the drug predominate. We propose that oxidation of MXH2 is mediated by an LPO/ H2O2 metabolite of NO2-, most likely the .NO2 radical. Because in mitoxantrone therapy the drug is administered intravenously, it is directly exposed to nitrogen oxides and other free radicals produced by blood components. It is therefore possible that the ability of mitoxantrone to react with the nitrogen dioxide radical may be relevant to the biological action of the drug in vivo.

Animals↗
PubMedDate not supplied

Sensitive spectrophotometric determination of nitrite in human saliva and rain water and of nitrogen dioxide in the atmosphere.

A new simple, sensitive, and selective spectrophotometric method was developed for the determination of nitrite. The method is based on the reaction of nitrite with sulfathiazole in acidic medium to form a diazonium cation, which is subsequently coupled with N-(1-naphthyl)ethylenediamine dihydrochloride to form a highly stable, violet azo dye. The reaction product has an absorption maximum at 546 nm and obeys Beer's law over a nitrite range of 0.054-0.816 microg/mL. The molar absorptivity of the colored compound is 4.61 x 10(4) L/mol x cm). The detection limit is 12.1 microg/L. The relative standard deviation is 0.85% for 5 determinations of nitrite at 0.27 microg/mL. The reproducibility and validity of the proposed method are discussed in the present paper. The simplicity of the method is demonstrated by the high stability of the azo-dye product as well as the short time required for its complete formation in a reaction at room temperature without pH control or extra extraction. The sensitivity of the method is shown by the successful determination of nitrite in human saliva and rain water, and of nitrogen dioxide in the atmosphere. The results compare favorably with those obtained by the reference method. The selectivity of the method is indicated by its freedom from most interferences, even at high concentrations of nitrate (500 microg/mL).

Air Pollutants↗
PubMed1997

Association between ambient air concentrations of nitrogen dioxide and respiratory symptoms in children in Prague, Czech Republic. Preliminary results from the Czech part of the SAVIAH Study. Small Area Variation in Air Pollution and Health.

The primary objective of the SAVIAH, a multi-centre study funded by European Union, was to assess new methodology for study of small area health statistics and to implement it in epidemiological health statistics and geography. In Prague, the study has been conducted in two city districts with large variation in air pollution. Data at individual level (health symptoms and socio-economic circumstances of the family) were collected by questionnaires completed by parents of 3680 children aged 7-10 both resident and attending schools within the area (response rate 88%). Aggregated data for geographical areas were available from census and urban planning sources for 692 enumeration districts in the study area which were aggregated into 75 medium sized areas. Outdoor concentrations of nitrogen dioxide (NO2) were monitored by passive samplers. All these data were integrated into a geographic information system (GIS). Spatial distribution of air pollution was estimated by kriging and multiple regression modelling. These models explained about 80% of the variation in air pollution measured by passive samplers. GIS was then used to assign to individuals an exposure based on place of residence and school in order to conduct individual based analyses. Association between NO2 and life-time prevalence of wheezing and/or whistling, and wheezing/whistling in the last 12 months was studied by logistic regression. For both outcomes, school levels of NO2 were positively related to symptoms but home levels of NO2 showed a negative association. Logistic regression at individual level gives similar results as ecological analysis and multilevel modelling. Hierarchical model yielded somewhat wider confidence limits. Adjustment for parental behavioural and socio-economic factors did not affect these estimates substantially. This study demonstrated the power of the GIS methodology in studying the effects of complex environmental factors on respiratory health of children.

Air Pollution↗
PubMed1994

Lactate-dependent killing of Escherichia coli by nitrite plus hydrogen peroxide: a possible role of nitrogen dioxide.

The killing of Escherichia coli by nitrite plus hydrogen peroxide was observed in lactate, but not in phosphate or acetate. Although nitrite or hydrogen peroxide alone caused a slight decrease in bacterial survival, nitrite plus hydrogen peroxide killed bacteria synergistically in time-, dose-, and pH-dependent manners. The killing was increased with decreasing pH. The plot of viable cells versus [nitrous acid] was linear. Among the hydroxyl radical scavengers used, only benzoate and formate at concentrations higher than that of lactate inhibited the killing by nitrite plus hydrogen peroxide, whereas dimethyl sulfoxide enhanced it. The generation of peroxynitrous acid during the reaction of nitrite and hydrogen peroxide was confirmed by the formation of malondialdehyde using deoxyribose as a hydroxyl radical-like oxidant detector. The nitration of glycyl-tryosine was observed only in lactate buffer, but not in phosphate and acetate buffers. Benzoate and formate inhibited the nitration, whereas dimethyl sulfoxide and ethanol enhanced it. No evidence for the formation of nitric oxide and superoxide during the reaction of nitrite and hydrogen peroxide was found. These data suggest that nitrogen dioxide from the decomposition of peroxynitrous acid or secondary oxidants formed from the reaction of peroxynitrous acid with lactate is responsible for the lactate-dependent killing of E. coli induced by the reaction of protonated nitrite and hydrogen peroxide.

Animals↗
PubMed1998

Nitration of gamma-tocopherol and oxidation of alpha-tocopherol by copper-zinc superoxide dismutase/H2O2/NO2-: role of nitrogen dioxide free radical.

Copper-zinc superoxide dismutase (Cu,ZnSOD) is the antioxidant enzyme that catalyzes the dismutation of superoxide (O2*-) to O2 and H2O2. In addition, Cu,ZnSOD also exhibits peroxidase activity in the presence of H2O2, leading to self-inactivation and formation of a potent enzyme-bound oxidant. We report in this study that lipid peroxidation of L-alpha-lecithin liposomes was enhanced greatly during the SOD/H2O2 reaction in the presence of nitrite anion (NO2-) with or without the metal ion chelator, diethylenetriaminepentacetic acid. The presence of NO2- also greatly enhanced alpha-tocopherol (alpha-TH) oxidation by SOD/H2O2 in saturated 1, 2-dilauroyl-sn-glycero-3-phosphatidylcholine liposomes. The major product identified by HPLC and UV-studies was alpha-tocopheryl quinone. When 1,2-diauroyl-sn-glycero-3-phosphatidylcholine liposomes containing gamma-tocopherol (gamma-TH) were incubated with SOD/H2O2/NO2-, the major product identified was 5-NO2-gamma-TH. Nitrone spin traps significantly inhibited the formation of alpha-tocopheryl quinone and 5-NO2-gamma-TH. NO2- inhibited H2O2-dependent inactivation of SOD. A proposed mechanism of this protection involves the oxidation of NO2- by an SOD-bound oxidant to the nitrogen dioxide radical (*NO2). In this study, we have shown a new mechanism of nitration catalyzed by the peroxidase activity of SOD. We conclude that NO2- is a suitable probe for investigating the peroxidase activity of familial Amyotrophic Lateral Sclerosis-linked SOD mutants.

Electron Spin Resonance Spectroscopy↗
PubMed2000

New High-Resolution Analysis of the nu(3) Band of the (15)N(16)O(2) Isotopomer of Nitrogen Dioxide by Fourier Transform Spectroscopy.

New high-resolution Fourier transform absorption spectra of an (15)N(16)O(2) isotopic sample of nitrogen dioxide were recorded at the University of Bremen in the 6.3-µm region. Starting from the results of a previous study [Y. Hamada, J. Mol. Struct. 242, 367-377 (1991)], a new and more extended analysis of the nu(3) band located at 1582.1039 cm(-1) has been performed. The spin-rotation energy levels were satisfactorily reproduced using a theoretical model which takes into account both the Coriolis interactions between the spin-rotation energy levels of the (001) vibrational state with those of the (020) and (100) states and the spin-rotation resonances within each of the NO(2) vibrational states. Precise vibrational energies and rotational, spin-rotation, and coupling constants were obtained in this way for the first triad of (15)N(16)O(2) interacting states {(020), (100), (001)}. Finally, a comprehensive list of line positions and line intensities of the {nu(1), 2nu(2), nu(3)} interacting bands of (15)N(16)O(2) was generated, using for the line intensities the transition moment operators which were obtained previously for the main isotopic species. Copyright 2000 Academic Press.

Journal Article↗
PubMed2005

Nitrogen dioxide (NO2) created by gamma-rays in Antarctic ice and rime ice.

Antarctic ice and rime ice after gamma-irradiation at 77 K were studied by electron spin resonance (ESR). The signal of nitrogen dioxide (NO2) was detected in both ices. The NO2 in the Antarctic ice, in particular, may be created from NO3- by reactions associated with intrinsic OH radicals. The detection limit of NO2 in solid samples was estimated to be approximately 0.02 ppm with ESR. The analysis using ESR in natural ice has a potential to trace environmental NO2.

Journal Article↗
PubMed2000

New High-Resolution Analysis of the 3nu(3) and 2nu(1) + nu(3) Bands of Nitrogen Dioxide (NO(2)) by Fourier Transform Spectroscopy.

Using new high-resolution Fourier transform spectra recorded at the University of Denver in the 2-µm region, a new and more extended analysis of the 2nu(1) + nu(3) and 3nu(3) bands of nitrogen dioxide, located at 4179.9374 and 4754.2039 cm(-1), respectively, has been performed. The spin-rotation energy levels were satisfactorily reproduced using a theoretical model that takes into account both the Coriolis interactions between the spin-rotation energy levels of the (201) vibrational "bright" state with those of the (220) "dark" state. The interactions between the (003) bright state with the (022) dark state were similarly treated. The spin-rotation resonances within each of the NO(2) vibrational states were also taken into account. The precise vibrational energies and the rotational, spin-rotational, and coupling constants were obtained for the two dyads {(220), (201)} and {(022), (003)} of the (14)N(16)O(2) interacting states. From the experimental line intensities of the 2nu(1) + nu(3) and 3nu(3) bands, a determination of their vibrational transition moment constants was performed. A comprehensive list of line positions and line intensities of the {2nu(1) + 2nu(2), 2nu(1) + nu(3)} and the {2nu(2) + 2nu(3), 3nu(3)} interacting bands of (14)N(16)O(2) was generated. In addition, assuming the harmonic approximation and using the Hamiltonian constants derived in this work and in previous studies (A. Perrin, J.-M. Flaud, A. Goldman, C. Camy-Peyret, W. J. Lafferty, Ph. Arcas, and C. P. Rinsland, J. Quant. Spectrosc. Radiat. Transfer 60, 839-850 (1998)), we have generated synthetic spectra for the {(022), (003)}-{(040), (021), (002)} hot bands at 6.3 µm and for the {(220), (201)}-{(100), (020), (001)} hot bands at 3.5 µm, which are in good agreement with the observed spectra. Copyright 2000 Academic Press.

Journal Article↗
PubMed2003

Nitration of moderately deactivated arenes with nitrogen dioxide and molecular oxygen under neutral conditions. Zeolite-induced enhancement of regioselectivity and reversal of isomer ratios.

In the presence of zeolites, moderately deactivated arenes such as 1-nitronaphthalene, naphthonitriles, and methylated benzonitriles can be smoothly nitrated at room temperature by the combined action of nitrogen dioxide and molecular oxygen. The regioselectivity is considerably improved as compared with the conventional nitration methodology based on nitric and sulfuric acids. In some cases, the minor isomer became favoured to a significant extent, resulting in the reversal of ordinary isomer ratios of nitration products.

Journal Article↗
PubMed1992

The exchange of nitric oxide, nitrogen dioxide and ozone between pasture and the atmosphere.

Fluxes of NO, NO2 and O3 were determined over a drained marshland pasture in south-east England by using flux-gradient techniques. Nitric oxide was found to be emitted at rates of up to 40 ng m(-2) s(-1), the rate of emission being related to the magnitude of the eddy diffusivity. Nitrogen dioxide deposited at rates of up to 90 ng m(-2) s(-1) under the control of stomatal resistance, a clear diurnal cycle being observed. Minimum canopy resistance was of the order of 80 s m(-1). Ozone deposition was also controlled by stomatal resistance, the minimum canopy resistance being around 100 s m(-1) and fluxes reaching a maximum of 220 ng m(-2) s(-1). Corrections made to NO and NO2 fluxes to compensate for chemical reactions showed flux divergences of the order of 30% for NO and NO2, but these were not statistically significantly different from the measured fluxes. The pasture was found to be a net sink for nitrogen in the form of NOx.

Journal Article↗
PubMed1987

Effects of ozone and nitrogen dioxide on human lung proteinase inhibitors.

Based on available knowledge, this study shows that alpha-1-proteinase inhibitor (alpha 1-PI) plays an important role in protecting lung elastin from elastolytic proteinases, particularly human neutrophil elastase (HNE). Studies previous to this one showed that alpha 1-PI was very susceptible to inactivation by oxidants. We sought to use this oxidant sensitivity as an in vivo marker for ozone (O3) and nitrogen dioxide (NO2) exposure. The mechanism of alpha 1-PI inactivation by O3 and NO2 was examined to provide insight concerning the pathogenesis of oxidant-mediated lung damage. Attention also was focused on the bronchial leukocyte proteinase inhibitor (BLPI), which inhibits HNE in the bronchial secretions. Careful examination of blood plasma samples from individuals exposed to 0.5 ppm O3 for four hours on two consecutive days failed to detect any inactivation of alpha 1-PI. This result showed that blood alpha 1-PI was not a satisfactory marker for O3 exposure, but, more importantly, demonstrated that inhaling O3 for short periods does not grossly inactivate this important protein. Studies on BLPI showed that it is a significant inhibitor of HNE and probably plays a more important role in protecting the lung than previously thought. BLPI, like alpha 1-PI, was found to be inactivated by oxidants, including O3 and NO2. The mechanism of O3 inactivation of leukocyte proteinase inhibitors was studied using alpha 1-PI, alpha-1-antichymotrypsin (alpha 1-Achy), BLPI, and Eglin C. While all these inhibitors differed in structure, the concentrations of O3 required for inactivation were essentially the same, except for alpha 1-Achy, which only lost half of its inhibitory activity. It would seem from these results that O3 can damage proteins via the oxidation of any of the following: tryptophan (Trp), methionine (Met), tyrosine (Tyr), or histidine (His) residues. Interestingly, Eglin C, which does not have oxidizable amino acids in its inhibitory active site, was inactivated by the same amount of O3 as BLPI, BLPI was easily inactivated by a methionine-specific oxidant, suggesting an important role for methionine in this inhibitor. In vitro exposure of alpha 1-PI and BLPI to 800 moles of NO2 per mole of inhibitor resulted in 35% and 50% losses of HNE inhibitory activity, respectively. Tryptophan was destroyed by NO2 and studies are in progress to examine effects on other amino acids.

Animals↗