Peroxynitrite and reactive nitrogen species: The contribution of ABB in two decades of research

Neuronal-glial Interactions Define the Role of Nitric Oxide in Neural Functional Processes

Nitric oxide (NO) is a versatile cellular messenger performing a variety of physiologic and pathologic actions in most tissues. It is particularly important in the nervous system, where it is involved in multiple functions, as well as in neuropathology, when produced in excess. Several of these functions are based on interactions between NO produced by neurons and NO produced by glial cells, mainly astrocytes and microglia. The present paper briefly reviews some of these interactions, in particular those involved in metabolic regulation, control of cerebral blood flow, axonogenesis, synaptic function and neurogenesis. Aim of the paper is mainly to underline the physiologic aspects of these interactions rather than the pathologic ones.

Biologically relevant oxidants and terminology, classification and nomenclature of oxidatively generated damage to nucleobases and 2-deoxyribose in nucleic acids

A broad scientific community is involved in investigations aimed at delineating the mechanisms of formation and cellular processing of oxidatively generated damage to nucleic acids. Perhaps as a consequence of this breadth of research expertise, there are nomenclature problems for several of the oxidized bases including 8-oxo-7,8-dihydroguanine (8-oxoGua), a ubiquitous marker of almost every type of oxidative stress in cells. Efforts to standardize the nomenclature and abbreviations of the main DNA degradation products that arise from oxidative pathways are reported. Information is also provided on the main oxidative radicals, non-radical oxygen species, one-electron agents and enzymes involved in DNA degradation pathways as well in their targets and reactivity. A brief classification of oxidatively generated damage to DNA that may involve single modifications, tandem base modifications, intrastrand and interstrand cross-links together with DNA-protein cross-links and base adducts arising from the addition of lipid peroxides breakdown products is also included.

Phosphorylation and nitration levels of photosynthetic proteins are conversely regulated by light stress

Using a label-free mass spectrometric approach, we investigated light-induced changes in the distribution of phosphorylated and nitrated proteins within subpopulations of native photosynthetic complexes in the thylakoid membrane of Arabidopsis thaliana leaves adapted to growth light (GL) and subsequently exposed to high light (HL). Eight protein phosphorylation sites were identified in photosystem II (PSII) and the phosphorylation level of seven was regulated by HL as determined based on peak areas from ion chromatograms of phosphorylated and non-phosphorylated peptides. Although the phosphorylation of PSII proteins was reported in the past, we demonstrated for the first time that two minor antenna LHCB4 isoforms are alternately phosphorylated under GL and HL conditions in PSII monomers, dimers and supercomplexes. A role of LHCB4 phosphorylation in state transition and monomerization of PSII under HL conditions is proposed. We determined changes in the nitration level of 23 tyrosine residues in five photosystem I (PSI) and nine PSII proteins and demonstrated for the majority of them a lower nitration level in PSI and PSII complexes and supercomplexes under HL conditions, as compared to GL. In contrast, the nitration level significantly increased in assembled/disassembled PSI and PSII subcomplexes under HL conditions. A possible role of nitration in (1) monomerization of LHCB1-3 trimers under HL conditions (2) binding properties of ferredoxin-NADP+ oxidoreductase to photosystem I, and (3) PSII photodamage and repair cycle, is discussed. Based on these data, we propose that the conversely regulated phosphorylation and nitration levels regulate the stability and turnover of photosynthetic complexes under HL conditions.

Protective effects of Kurozu and Kurozu Moromimatsu on dextran sulfate sodium-induced experimental colitis

BACKGROUND

Kurozu, a traditional Japanese black vinegar made from unpolished rice, and Kurozu Moromimatsu (Kurozu-M), its sediment, are both consumed in Japan as health foods or supplements. However, it is not known whether they have anti-colitis activity.

AIMS

We examined the protective effects of Kurozu and Kurozu-M in an animal model of dextran sulfate sodium (DSS)-induced colitis.

METHODS

DSS-induced colitis was induced in C57 black 6 mice by orally administering 3.5% DSS solution for 12 days. The control group received basal CE-2 diet (n = 10), the Kurozu group received CE-2 containing Kurozu (n = 10), the Kurozu-M group received CE-2 containing Kurozu-M (n = 10), and the acetic acid group received CE-2 containing acetic acid (n = 10), starting a week before DSS administration. Changes of body weight and bloody stool frequency were monitored. At 12 days after DSS administration, mice were killed for pathological examination and measurement of nitrotyrosine levels in rectal tissues.

RESULTS

Kurozu significantly inhibited body weight loss during 6-12 days after DSS administration and reduced bloody stool frequency during 2-12 days, and also significantly decreased nitrotyrosine levels at 12 days, compared to the control group. Kurozu-M significantly inhibited body weight loss during 6-8 days after DSS administration and reduced bloody stool frequency during 2-12 days, but tissue nitrotyrosine level was not significantly different from the control. Acetic acid had no ameliorating effect on DSS-induced colitis compared to the control group.

CONCLUSIONS

Kurozu and Kurozu-M have protective effects against DSS-induced colitis. Kurozu has anti-oxidative and anti-nitration activity.

Reaction between peroxynitrite and boronates: EPR spin-trapping, HPLC Analyses, and quantum mechanical study of the free radical pathway

Recently, we showed that peroxynitrite (ONOO(-)) reacts directly and rapidly with aromatic and aliphatic boronic acids (k ≈ 10(6) M(-1)s(-1)). Product analyses and substrate consumption data indicated that ONOO(-) reacts stoichiometrically with boronates, yielding the corresponding phenols as the major product (∼85-90%), and the remaining products (10-15%) were proposed to originate from free radical intermediates (phenyl and phenoxyl radicals). Here, we investigated in detail the minor, free radical pathway of boronate reaction with ONOO(-). The electron paramagnetic resonance (EPR) spin-trapping technique was used to characterize the free radical intermediates formed from the reaction between boronates and ONOO(-). Using 2-methyl-2-nitrosopropane (MNP) and 5-diethoxyphosphoryl-5-methyl-1-pyrroline-N-oxide (DEPMPO) spin traps, phenyl radicals were trapped and detected. Although phenoxyl radicals were not detected, the positive effects of molecular oxygen, and inhibitory effects of hydrogen atom donors (acetonitrile, and 2-propanol) and general radical scavengers (GSH, NADH, ascorbic acid, and tyrosine) on the formation of phenoxyl radical-derived nitrated product, suggest that the phenoxyl radical was formed as the secondary species. We propose that the initial step of the reaction involves the addition of ONOO(-) to the boron atom in boronates. The anionic intermediate undergoes both heterolytic (major pathway) and homolytic (minor pathway) cleavage of the peroxy (O-O) bond to form phenol and nitrite as a major product (via a nonradical mechanism), or a radical pair PhB(OH)(2)O(•-)···(•)NO(2) as a minor product. It is conceivable that phenyl radicals are formed by the fragmentation of the PhB(OH)(2)O(•-) radical anion. According to the DFT quantum mechanical calculations, the energy barrier for the dissociation of PhB(OH)(2)O(•-) radical anion to form phenyl radical is only a few kcal/mol, suggesting rapid and spontaneous fragmentation of the PhB(OH)(2)O(•-) radical anion in aqueous media. Biological implications of the minor free radical pathway are discussed in the context of ONOO(-) detection, using the boronate probes.

Mass spectrometric characterization of photooxidative protein modifications in Arabidopsis thaliana thylakoid membranes

Oxidative and nitrosative stress leaves footprints in the plant chloroplast in the form of oxidatively modified proteins. Using a mass spectrometric approach, we identified 126 tyrosine and 12 tryptophan nitration sites in 164 nitrated proteolytic peptides, mainly from photosystem I (PSI), photosystem II (PSII), cytochrome b(6) /f and ATP-synthase complexes and 140 oxidation products of tyrosine, tryptophan, proline, phenylalanine and histidine residues. While a high number of nitration sites were found in proteins from four photosynthetic complexes indicating that the nitration belongs to one of the prominent posttranslational protein modifications in photosynthetic apparatus, amino acid oxidation products were determined mostly in PSII and to a lower extent in PSI. Exposure of plants to light stress resulted in an increased level of tyrosine and tryptophan nitration and tryptophan oxidation in proteins of PSII reaction center and the oxygen-evolving complex, as compared to low light conditions. In contrast, the level of nitration and oxidation of these amino acid residues strongly decreased for all light-harvesting proteins of PSII under the same conditions. Based on these data, we propose that oxidative modifications of proteins by reactive oxygen and nitrogen species might represent an important regulatory mechanism of protein turnover under light stress conditions, especially for PSII and its antenna proteins.

Direct oxidation of boronates by peroxynitrite: mechanism and implications in fluorescence imaging of peroxynitrite

In this study, we show that boronates, a class of synthetic organic compounds, react rapidly and stoichiometrically with peroxynitrite (ONOO(-)) to form stable hydroxy derivatives as major products. Using a stopped-flow kinetic technique, we measured the second-order rate constants for the reaction with ONOO(-), hypochlorous acid (HOCl), and hydrogen peroxide (H(2)O(2)) and found that ONOO(-) reacts with 4-acetylphenylboronic acid nearly a million times (k=1.6x10(6) M(-1) s(-1)) faster than does H(2)O(2) (k=2.2 M(-1) s(-1)) and over 200 times faster than does HOCl (k=6.2x10(3) M(-1) s(-1)). Nitric oxide and superoxide together, but not alone, oxidized boronates to the same phenolic products. Similar reaction profiles were obtained with other boronates. Results from this study may be helpful in developing a novel class of fluorescent probes for the detection and imaging of ONOO(-) formed in cellular and cell-free systems.