Nitration of tyrosyl-residues from extra- and intracellular proteins in human whole blood

Protein oxidation markers in women with and without gestational diabetes mellitus: a possible relation with paraoxonase activity

AIMS

To clarify the levels of protein oxidation markers such as protein carbonyl (PCO), protein hydroperoxides (P-OOH), advanced oxidation protein products (AOPP) and nitrotyrosine (NT), as well as antioxidative enzymes such as paraoxonase (PON-1) in women with and without gestational diabetes mellitus (GDM).

METHODS

The study was conducted on 23 women with GDM and 22 women without GDM. The levels of the P-OOH, AOPP, and PON-1 were determined by colorimetric methods; whereas NT and PCO levels were measured by ELISA.

RESULTS

The concentrations of protein oxidation markers were significantly increased and PON1 activity was significantly decreased in GDM group compared to those of normal pregnant women. The control group showed a significant negative correlation between PON-1 and PCO (r=-0.451, p=0.027); whereas in GDM group, there was a significant positive correlation between P-OOH and HbA1c (r=0.89, p=0.001). There was no significant correlation between AOPP, PON-1, P-OOH, PCO, and HbA1c in either group.

CONCLUSIONS

There is evidence of a possible association between protein oxidation and decreased PON1 activity in GDM. The increase in protein oxidation parameters in the GDM group leading to decreased PON1 activity might, we think, create a predisposition for clinical complications in GDM group.

Determining the effects of antioxidants on oxidative stress induced carbonylation of proteins

There is potential that the pathological effects of oxidative stress (OS) associated diseases such as diabetes could be ameliorated with antioxidants, but this will require a clearer understanding of the pathway(s) by which proteins are damaged by OS. This study reports the development and use of methods that assess the efficacy of dietary antioxidant supplementation at a mechanistic level. Data reported here evaluate the impact of green tea supplementation on oxidative stress induced post-translational modifications (OSi-PTMs) in plasma proteins of Zucker diabetic fatty (ZDF) rats. The mechanism of antioxidant protection was examined through both the type and amount of OSi-PTMs using mass spectrometry based identification and quantification. Carbonylated proteins in freshly drawn blood samples were derivatized with biotin hydrazide. Proteins thus biotinylated were selected from plasma samples of green tea fed diabetic rats and control animals by avidin affinity chromatography, further fractionated by reversed phase chromatography (RPC); fractions from the RPC column were tryptic digested, and the tryptic digest was fractionated by RPC before being identified by tandem mass spectrometry (MS/MS). Relative quantification of peptides bearing carbonylation sites was achieved for the first time by RPC-MS/MS using selective reaction monitoring (SRM). Seventeen carbonylated peptides were detected and quantified in both control and treated plasma. The relative concentration of eight was dramatically different between control and green tea treated animals. Seven of the OSi-PTM bearing peptides had dropped dramatically in concentration with treatment while one increased, indicating differential regulation of carbonylation by antioxidants. Green tea antioxidants were found to reduce carbonylation of proteins by lipid peroxidation end products most, followed by advanced glycation end products to a slightly lower extent. Direct oxidation of proteins by reactive oxygen species (ROS) was protected the least by green tea.

Pathophysiological roles of peroxynitrite in circulatory shock

Peroxynitrite is a reactive oxidant produced from nitric oxide and superoxide, which reacts with proteins, lipids, and DNA, and promotes cytotoxic and proinflammatory responses. Here, we overview the role of peroxynitrite in various forms of circulatory shock. Immunohistochemical and biochemical evidences demonstrate the production of peroxynitrite in various experimental models of endotoxic and hemorrhagic shock both in rodents and in large animals. In addition, biological markers of peroxynitrite have been identified in human tissues after circulatory shock. Peroxynitrite can initiate toxic oxidative reactions in vitro and in vivo. Initiation of lipid peroxidation, direct inhibition of mitochondrial respiratory chain enzymes, inactivation of glyceraldehyde-3-phosphate dehydrogenase, inhibition of membrane Na+/K+ ATPase activity, inactivation of membrane sodium channels, and other oxidative protein modifications contribute to the cytotoxic effect of peroxynitrite. In addition, peroxynitrite is a potent trigger of DNA strand breakage, with subsequent activation of the nuclear enzyme poly(ADP-ribose) polymerase, which promotes cellular energetic collapse and cellular necrosis. Additional actions of peroxynitrite that contribute to the pathogenesis of shock include inactivation of catecholamines and catecholamine receptors (leading to vascular failure) and endothelial and epithelial injury (leading to endothelial and epithelial hyperpermeability and barrier dysfunction), as well as myocyte injury (contributing to loss of cardiac contractile function). Neutralization of peroxynitrite with potent peroxynitrite decomposition catalysts provides cytoprotective and beneficial effects in rodent and large-animal models of circulatory shock.

The role of signalling molecules on actin glutathionylation and protein carbonylation induced by cadmium in haemocytes of mussel Mytilus galloprovincialis (Lmk)

This study investigated the role of Na(+)/H(+) exchanger (NHE) and signalling molecules, such as cAMP, PKC, PI 3-kinase, and immune defence enzymes, NADPH oxidase and nitric oxide synthase, in the induction of protein glutathionylation and carbonylation in cadmium-treated haemocytes of mussel Mytilus galloprovincialis. Glutathionylation was detected by western blot analysis and showed actin as its main target. A significant increase of both actin glutathionylation and protein carbonylation, were observed in haemocytes exposed to micromolar concentration of cadmium chloride (5 micromol l(-1)). Cadmium seems to cause actin polymerization that may lead to its increased glutathionylation, probably to protect it from cadmium-induced oxidative stress. It is therefore possible that polymerization of actin plays a signalling role in the induction of both glutathionylation and carbonylation processes. NHE seems to play a regulatory role in the induction of oxidative damage and actin glutathionylation, since its inhibition by 2 micromol l(-1) cariporide, significantly diminished cadmium effects in each case. Similarly, attenuation of cadmium effects were observed in cells pre-treated with either 11 micromol l(-1) GF-109203X, a potent inhibitor of PKC, 50 nmol l(-1) wortmannin, an inhibitor of PI 3-kinase, 0.01 mmol l(-1) forskolin, an adenylyl cyclase activator, 10 micromol l(-1) DPI, a NADPH oxidase inhibitor, or 10 micromol l(-1) L-NAME, a nitric oxide synthase inhibitor, suggesting a possible role of PKC, PI 3-kinase and cAMP, as well as NADPH oxidase and nitric oxide synthase in the enhancement of cadmium effects on both actin glutathionylation and protein carbonylation.

Production of superoxides and nitric oxide generation in haemocytes of mussel Mytilus galloprovincialis (Lmk.) after exposure to cadmium: a possible involvement of Na(+)/H(+) exchanger in the induction of cadmium toxic effects

The present study investigates cadmium (Cd) ability to enhance superoxides (O(2-)) and nitric oxide (NO) production (as nitrites) in haemocytes of mussel Mytilus galloprovincialis as well as the possible involvement of Na(+)/H(+) exchanger (NHE) in the induction of NADPH oxidase and NO synthase activity. PMA, a well-known PKC-mediated NADPH oxidase as well as NO synthase stimulator was also used, in order to verify Cd effects on both O(2-) and NO generation. According to the results of the present study, micromolar concentrations of Cd (0.05, 5, 10 and 50 microM) seemed to enhance O(2-) and NO generation in haemocytes of mussels. Moreover, O(2-) and NO generation in haemocytes exposed to Cd could be enhanced by its ability to induce reactive oxygen species (ROS) but respiratory burst activation as well. Inhibition of NO synthase with 10 microM l-NAME, significantly attenuated Cd ability to enhance O(2-) production and diminished NO generation, thus leading to the suggestion that Cd toxic effects, started at concentration of 50 muM, could enhance NADPH oxidase and NO synthase stimulation in haemocytes of mussels. NHE seems to play a regulatory role in the induction of either O(2-) or NO generation in haemocytes exposed to the metal, since its inhibition with the use of 10 microM EIPA significantly decrease both O(2-) and NO production. The involvement of NHE in the induction of O(2-) and NO generation, probably via PKC-mediated NADPH oxidase and NO synthase activation, is likely to be crucial to haemocytes exposed to heavy metals, such as Cd.

Potential Benefits of Peroxynitrite

Peroxynitrite (PN) is generated by the reaction of nitric oxide (NO) and superoxide in one of the most rapid reactions in biology. Studies have reported that PN is a cytotoxic molecule that contributes to vascular injury in a number of disease states. However, it has become apparent that PN has beneficial effects including vasodilation, inhibition of platelet aggregation, inhibition of inflammatory cell adhesion, and protection against ischemia/reperfusion injury in the heart. It is our hypothesis that PN may serve to inactivate superoxide and prolong the actions of NO in the circulation. This manuscript reviews the beneficial effects of PN in the cardiovascular system.

Simultaneous determination of 3-nitro tyrosine, o-, m-, and p-tyrosine in urine samples by liquid chromatography–ultraviolet absorbance detection with pre-column cloud point extraction

Stable 3-nitro tyrosine (3-NO(2)-Tyr), o-, m-, and p-tyrosine isomers induced by oxidation of tyrosine residues in protein were considered important biomarkers for the existence of toxic oxidizing agents peroxynitrite (ONOO(-)) and OH*, which could lead to such diseases as acute lung injury, neurodegenerative disorders, atherosclerosis, cancers and many other diseases. Therefore, development of an accurate, simple and sensitive method to simultaneously detect o-, m-, and p-tyrosine and 3-NO(2)-Tyr is necessary. Fluorescence detection is highly sensitive to o-, m-, and p-tyrosine, but it cannot be used to detect 3-NO(2)-Tyr, due to the strong fluorescence-quenching characteristic of the NO(2) group. In this study, we developed a highly sensitive reversed HPLC-UV method, combined with pre-column cloud point extraction (CPE), to simultaneously determine o-, m-, and p-tyrosine and 3-NO(2)-Tyr. The procedure included derivatization of a sample with 6-aminoquinolyl-N-hydroxy-succinimidyl carbomate (AccQ) at 0.20 mol/l borate buffer (pH 8.80) for 30 min at 70 degrees C, and pre-concentration with surfactant cloud point extraction. The surfactant-rich phase was then diluted with deionized water and injected directly into the to HPLC column for analysis. A C(18) column (3.9 mm i.d. x 300 mm) was used for gradient elution separation at 25 degrees C and the detection wavelength was at 254 nm. Nineteen general amino acids showed no interference. The detection limits of p-, o-, m-Tyr and 3-NO(2)-Tyr were between 5 and 15 nmol/l. The linear range was from 0.05 to approximately 100 micromol/l.

Determination of oxidative protein and lipid damage in adult hypopituitary patients with GH deficiency

The aim of this study is to determine oxidative protein and lipid damage in adult hypopituitary GH-deficient patients. Eighteen hypopituitary GH-deficient--otherwise healthy-adults on conventional replacement therapy other than GH (9 male, 9 female, age 41.8 +/- 16.4 yr) and 18 healthy subjects (6 male, 12 female, age 40.3 +/- 16.2 yr) participated in the study. Plasma products of oxidative protein damage [protein carbonyl (PCO) and nitrotyrozine (NT)], plasma oxidized LDL (oxLDL), plasma product of oxidative lipid damage [lipid hydroperoxide (LHP)] and antioxidant status of the plasma [total thiol (T-SH)] were measured. Body fat percentage, total and LDL-cholesterol concentrations were significantly higher in the hypopituitary group. Plasma PCO, NT, LHP and T-SH concentrations did not differ significantly between patients and controls. OxLDL concentration was significantly higher in the hypopituitary patients (62.4 +/- 17.8 vs 43.1 +/- 11.3 U/l, p = 0.001). In the patients, oxLDL correlated significantly with the duration of hypopituitarism (r = 0.6323, p = 0.01). In the controls, oxLDL correlated significantly with blood pressure, total and VLDL-cholesterol concentrations. Increased oxLDL concentration may indicate increased oxidative stress within the vascular compartment and may contribute to the proatherogenic state in GH-deficient hypopituitary patients independent from conventional risk factors.

Relation of aging with oxidative protein damage parameters in the rat skeletal muscle

OBJECTIVES

An increase in oxidative stress may contribute to the development of oxidative protein damage in the aging rat skeletal muscle. Our aim was to reveal protein carbonyl (PCO), advanced oxidation protein products (AOPP), a novel marker of oxidative stress, and protein thiol (P-SH) levels as markers of protein oxidation, as well as lipid hydroperoxide (LHP) levels as a marker of lipid peroxidation, and relation of nitrotyrosine (NT) levels with these markers in skeletal muscle tissue of young, adult, and old male Wistar rats.

DESIGN AND METHODS

In the present study, we investigated the relation between aging and oxidative protein damage parameters such as PCO, NT, AOPP, and P-SH, as well as oxidative stress parameters such as total thiol, nonprotein thiol, and LHP in the skeletal muscle tissue of young, adult, and old Wistar rats.

RESULTS

PCO and NT levels of old rats were significantly increased compared with those of young and adult rats. Skeletal muscle AOPP levels were significantly increased in old rats compared with those of adult rats. P-SH levels were significantly decreased in old rats compared with those of young rats.

CONCLUSIONS

The finding that the increase in PCO levels of young vs. old group was more significant than that of adult vs. old group may suggest that PCO formation is an early specific marker of aging process in skeletal muscle. In addition, increased levels of nitrotyrosine in the skeletal muscle of the old rat group may be a novel specific marker of oxidative protein damage in the aging muscle. The absence of correlation between oxidative protein damage markers mentioned above and LHP levels may indicate that protein oxidation and lipid peroxidation in the aging rat skeletal tissue are two distinct mechanisms.

The evaluation of oxidative stress in patients with chronic renal failure

BACKGROUND

Free radical-mediated changes are thought to be involved with atherosclerosis in patients with chronic renal failure.

METHODS

The protein carbonyl and malondialdehyde (MDA) levels in serum as the markers of radical-induced protein and lipid oxidations were measured in chronic renal failure patients.

RESULTS

Serum carbonyl and MDA levels in both hemodialysis and peritoneal dialysis patients were not found to be different as compared with healthy subjects. In both patient groups, the approximately twofold increment in total antioxidant activity (ferric reducing/antioxidant power; FRAP) and uric acid values in serum were found. The high uric acid levels in both patient groups might be partly responsible for the increment in FRAP values. In addition, all patients received multivitamin preparations including ascorbate, which was also a major antioxidant in serum.

CONCLUSIONS

Our data suggest that oxidative stress does not become the major threat for patients with chronic renal failure. The increment in endogenous and exogenous antioxidant capacities in serum might be thought to prevent any possible radical-induced damage in patients with chronic renal failure. In addition, the increased nitric oxide (NO) levels especially in hemodialysis patients might likely favor an antioxidant effect.

Catalase catalyzes nitrotyrosine formation from sodium azide and hydrogen peroxide

Sodium azide (NaN3) is known as an inhibitor of catalase, and a nitric oxide (NO) donor in the presence of catalase and H2O2. We showed here that catalase-catalyzed oxidation of NaN3 can generate reactive nitrogen species which contribute to tyrosine nitration in the presence of H2O2. The formation of free-tyrosine nitration and protein-bound tyrosine nitration by the NaN3/catalase/H2O2 system showed a maximum level at pH 6.0. Free-tyrosine nitration induced by peroxynitrite was inhibited by ethanol and dimethylsulfoxide (DMSO), and augmented by superoxide dismutase (SOD). However, free-tyrosine nitration induced by the NaN3/catalase/H2O2 system was not affected by ethanol, DMSO and SOD. NO2- and NO donating agents did not affect free-tyrosine nitration by the NaN3/catalase/H2O2 system. The reaction of NaN3 with hydroxyl radical generating system showed free-tyrosine nitration, but no formation of nitrite and nitrate. The generation of nitrite (NO2-) and nitrate (NO3-) by the NaN3/catalase/H2O2 system was maximal at pH 5.0. These results suggested that the oxidation of NaN3 by the catalase/H2O2 system generates unknown peroxynitrite-like reactive nitrogen intermediates, which contribute to tyrosine nitration.

The mechanisms for nitration and nitrotyrosine formation in vitro and in vivo: impact of diet

The detection of 3-nitro-L-tyrosine residues associated with many disease states, including gastric cancer, has implicated a role for peroxynitrite in vivo, and thus endogenously produced nitric oxide and superoxide. Additionally, dietary nitrate has been suggested to be involved in the pathogenesis of gastric cancer through a mechanism involving reduction to nitrite and subsequent formation of potentially mutagenic nitroso-compounds. Studies have now demonstrated that a multitude of reactive nitrogen species other than peroxynitrite are capable of producing nitrotyrosine. Thus, we have reviewed the evidence that dietary nitrate, amongst other reactive nitrogen species, may contribute to the body burden of nitrotyrosine.

Tyrosine nitration: localisation, quantification, consequences for protein function and signal transduction

The nitration of free tyrosine or protein tyrosine residues generates 3-nitrotyrosine the detection of which has been utilised as a footprint for the in vivo formation of peroxynitrite and other reactive nitrogen species. The detection of 3-nitrotyrosine by analytical and immunological techniques has established that tyrosine nitration occurs under physiological conditions and levels increase in most disease states. This review provides an updated, comprehensive and detailed summary of the tissue, cellular and specific protein localisation of 3-nitrotyrosine and its quantification. The potential consequences of nitration to protein function and the pathogenesis of disease are also examined together with the possible effects of protein nitration on signal transduction pathways and on the metabolism of proteins.

Induction of urinary excretion of 3-nitrotyrosine, a marker of oxidative stress, following administration of pyridostigmine bromide, DEET (N,N-diethyl-m-toluamide) and permethrin, alone and in combination in rats

In this study, we determined levels of 3-nitrotyrosine in rat urine following administration of a single oral dose of 13 mg/kg pyridostigmine bromide (PB) (3-dimethylaminocarbonyloxy-N-methylpyridinum bromide), a single dermal dose of 400 mg/kg N,N-diethyl-m-toluamide (DEET) and a single dermal dose of 1.3 mg/kg permethrin, alone and in combination. Urine samples were collected from five treated and five control rats at 4, 8, 16, 24, 48, and 72 h following dosing. Solid-phase extraction coupled with high-performance liquid chromatography with ultraviolet detection at 274 nm was used for the determination of tyrosine and 3-nitrotyrosine. A single oral dose of PB and a single dermal dose of DEET or their combination significantly (P<0.05) increased levels of 3-nitrotyrosine starting 24 h after dosing compared with control urine samples. The maximum increase of 3-nitroytyrosine was detected 48 h after combined administration of PB and DEET. The ratio of 3-nitrotyrosine to tyrosine in urine excreted 48 h after dosing was 0.19+/-0.04, 0.20+/-0.05, 0.28+/-0.03, 0.32+/-0.04, 0.19+/-0.05, 0.42+/-0.04, 0.27+/-0.03, 0.36+/-0.04, and 0.48+/-0.04 following administration of water, ethanol, PB, DEET, permethrin, PB+DEET, PB+permethrin, DEET+permethrin, and PB+DEET+permethrin, respectively. The results indicate that an oral dose of PB and a dermal administration of DEET, alone and in combination, could generate free radical species, and thus increase levels of 3-nitrotyrosine in rat urine. Induction of 3-nitrotyrosine, a marker of oxidative stress, following exposure to these compounds could be significant in understanding the proposed enhanced toxicity following combined exposure to these compounds.

Relation of oxidative protein damage and nitrotyrosine levels in the aging rat brain

An increase in oxidative stress may contribute to the development of oxidative protein damage in the aging rat brain. In the present study, we investigated the relation between nitrotyrosine levels and other oxidative protein damage parameters such as protein carbonyl and protein thiol, as well as oxidative stress parameters such as total thiol, nonprotein thiol, and lipid hydroperoxides in the brain tissue of young, adult, and old Wistar rats. Brain nitrotyrosine levels of old rats were significantly decreased compared with those of young rats. Young and adult rats were not significantly different as far as these parameters were concerned, however, brain protein carbonyl and lipid hydroperoxide levels of old rats were significantly increased compared with those of young and adult rats. On the other hand, brain tissue total thiol, nonprotein thiol, and protein thiol levels of old rats were significantly decreased compared with those of young and adult rats. The strong correlation we found between protein carbonyl and lipid hydroperoxide levels indicates a striking relation between protein oxidation and lipid peroxidation in the aging brain tissue. The results of this study suggest that protein carbonyl formation is both a sensitive and a specific marker of brain aging. However, decreased nitrotyrosine levels in old rats, in contradiction to the expected, may be due to mechanisms other than oxidative protein damage in the aging rat brain.

Nitric oxide generation by hemocytes of the mussel Mytilus galloprovincialis

The phagocytic activity of Mytilus galloprovincialis hemocytes is thought to be associated with NADPH-oxidase activity of the plasma membrane, thus producing superoxide anions. Few studies, however, have been devoted to nitric oxide release by these haemocytes. We investigated NO generation in M. galloprovincialis in order to understand its role in the defensive mechanisms of these organisms. The presence of NO-synthase-like enzymatic activity in protein homogenates from M. galloprovincialis hemocytes was revealed by the conversion of radiolabelled L-arginine to L-citrulline. We observed partial inhibition of the luminol-dependent chemiluminescence of stimulated M. galloprovincialis hemocytes by both NO-synthase inhibitors and superoxide dismutase, indicating that peroxynitrite (which results from the reaction between nitric oxide and superoxide anions) partially mediated this chemiluminescence. Furthermore, we confirmed the production of nitric oxide by M. galloprovincialis by highlighting the nitric oxide-synthase-dependence of the nitrate and nitrite production of stimulated hemocytes.

In vitro production of peroxynitrite by haemocytes from marine bivalves: C-ELISA determination of 3-nitrotyrosine level in plasma proteins from Mytilus galloprovincialis and Crassostrea gigas

BACKGROUND

Peroxynitrite is increasingly proposed as a contributor to defence system in marine bivalve. It can be formed by combination of superoxide and nitric oxide, and can react with tyrosine residues of proteins giving rise to 3-nitrotyrosine.

RESULTS

The present article describes a competitive ELISA for the measurement of 3-nitrotyrosine contents of plasma proteins from marine bivalves by means of a monoclonal anti 3-nitrotyrosine antibody mouse IgG.

CONCLUSIONS

This assay is sensitive enough to determine the amounts of 3-nitrotyrosine in plasma proteins from one animal only. Using the C-ELISA, we have shown that the phagocytosis of zymosan particles increased the 3-nitrotyrosine levels of plasma proteins from mussel M. galloprovincialis and oyster C. gigas 5.8 and 7.5 times respectively.

Role of the recombinant protein of the platelet receptor for type I collagen in the release of nitric oxide during platelet aggregation

Nitric oxide plays an important role in platelet function and platelets possess the endothelial isoform of nitric oxide synthase. Several reports have indicated that nitric oxide is released upon exposure of platelets to collagen. We have reported that a non-integrin platelet protein of 65 kDa is a receptor for type I collagen. By direct measurement of NO release from washed human platelets suspended in Tyrode buffer with a ISO-NO Mark II, World Precision Instruments, Sarasota, FL, USA, p30 sensor, type I collagen, but not ADP and epinephrine, induces the release of NO in a time-dependent manner. The production of NO is inhibited either by preincubation of type I collagen with the platelet type I collagen receptor recombinant protein or by preincubation of platelets with the antibody to the receptor protein, the anti-65 antibody. However, preincubation of platelets with anti-P-selectin and anti-glycoprotein IIb/IIIa did not affect the release of NO by platelets. These results suggest that the 65 kDa platelet receptor for type I collagen is specifically linked to the generation of NO, and that the 65 kDa platelet receptor for type I collagen plays an important new role in platelet function.

Oxidative protein damage in early stage Type 1 diabetic patients

To examine the influence of oxidative stress on oxidative protein damage, we studied 51 young Type 1 diabetic patients clinically free of complications and 48 healthy normolipidaemic age-matched controls. We determined: (1) plasma carbonyl (PCO), plasma total thiol (T-SH), and nitrotyrosine (NT) levels as markers of oxidative protein damage; (2) plasma lipid hydroperoxide (LHP), and nitric oxide (NO) levels as markers of oxidative stress; (3) plasma total antioxidant capacity (TAO), ceruloplasmin (Cp), transferrin (TRF), unsaturated iron binding capacity (UIBC), erythrocyte glutathione (GSH), and erythrocyte superoxide dismutase (SOD) as markers of free radical scavengers. There were no significant differences in the levels of these markers between prepubertal diabetic patients and the controls. The levels of both of PCO and LHP were increased in adolescent and young adult Type 1 diabetic patients with respect to their controls. In the adolescent group, patient versus control values for PCO were 1.04+/-0.067 versus 0.67+/-0.0274 nmol/mg and for LHP they were 2. 10+/-1.09 versus 1.00+/-0.4 nmol/mg. In the young adult group, patient versus control values for PCO were 0.99+/-0.054 versus 0. 66+/-0.02 nmol/mg and for LHP they were 1.96+/-0.78 versus 1.15+/-0. 4 nmol/mg. TAO levels were significantly decreased in adolescent diabetic patients compared to their controls (0.92+/-0.27 vs. 1. 86+/-0.37) and in young adult diabetic patients compared to their controls (0.80+/-0.27 vs. 2.11+/-0.54 nmol/mg). T-SH was not different between diabetic patients and the controls. Serum NT, NO, and erythrocyte SOD levels were not different either between three groups of diabetic patients or between the patients and their controls. We attribute this lack of difference to limited disease duration. Changes in markers of oxidative stress other than NT, NO, and SOD observed in adolescent and young adult early stage Type 1 diabetic patients contribute to the imbalance in the redox status of the plasma. We attribute this imbalance to metal-catalyzed protein oxidation in both groups of Type 1 diabetic patients clinically free from complications.

Oxidative protein damage in type I diabetic patients with and without complications

To examine the influence of oxidative stress on oxidative protein damage, we studied 47 Type I diabetic patients with and without complications. We determined plasma protein carbonyl, plasma protein thiol and nitrotyrosine levels as markers of oxidative protein damage, plasma lipid hydroperoxide levels as markers of oxidative stress, and plasma total thiol, plasma nonprotein thiol, erythrocyte glutathione, plasma ceruloplasmin, transferrin and total iron binding capacity as markers of free radical scavenging. There were no significant differences in nitrotyrosine, total plasma thiol, protein thiol, and erythrocyte glutathione levels between diabetic patients with complications and without complications. However, plasma protein carbonyl, lipid hydroperoxide, and nonprotein thiol levels were significantly increased in diabetic patients with complications compared with diabetic patients without complications. Although redox status of plasma is impaired in diabetic patients, we suppose these significantly different markers reflect enhanced oxidative protein damage in diabetic patients with complications.

Nitration and hydroxylation of aromatic amino acid and guanine by the air pollutant peroxyacetyl nitrate

Peroxyacetyl nitrate (PAN) is a common gaseous photochemical compound in polluted air and cigarette smog. The toxicity of PAN has been found to depend on three pathways: (1) its oxidizing property that mimics peroxide or peroxynitrite; (2) its nitrating and hydroxylating properties similar to peroxynitrite; and (3) its acetylating property like acetic anhydride. The present investigations were intended to focus on the reactions of PAN with aromatic amino acids and guanine. When PAN interacted with tyrosine and guanine the major products were 3-nitrotyrosine, 3, 5-dinitrotyrosine, 8-hydroxyguanine and 8-nitroguanine. These compounds have been used as indicators for the presence of peroxynitrite in previous studies. When PAN interacted with phenylalanine, the products were 3-nitrotyrosine, 4-nitrophenylalanine, p-tyrosine, o-tyrosine and m-tyrosine. 5-Hydroxytryptophan is produced from the reaction of PAN with tryptophan. Furthermore, the formation of nitrated tyrosines was also found in the PAN-treated HL-60 cells. A high yield of dityrosine was formed when PAN and peroxynitrite were reacted with tyrosine, probably through free radical oxidation. We also found that peroxynitrite and PAN are similar in their oxidizing activity. From these findings, we suggest that peroxynitrite may be considered as the reactive intermediate of PAN.

Measurement of 3-nitrotyrosine and 5-nitro-gamma-tocopherol by high-performance liquid chromatography with electrochemical detection

Nitric oxide (NO) is a lipophilic gaseous molecule synthesized by the enzymatic oxidation of L-arginine. During periods of inflammation, phagocytic cells generate copious quantities of NO and other reactive oxygen species. The combination of NO with other reactive oxygen species promotes nitration of ambient biomolecules, including protein tyrosine residues and membrane-localized gamma-tocopherol. The oxidative chemistry of NO and derived redox congeners is reviewed. Techniques are described for the determination of 3-nitro-tyrosine and 5-nitro-gamma-tocopherol in biological samples using high-performance liquid chromatography with electrochemical detection.

Nitrotyrosine in plasma of celiac disease patients as detected by a new sandwich ELISA

Inflammation is characterized by increased nitric oxide production. Nitrotyrosine has recently been suggested to be useful as a marker for NO-mediated tissue damage. In context of the development of an ELISA for detection of nitrotyrosine in plasma, monoclonal anti-nitrotyrosine antibodies were developed by injecting mice with nitrated keyhole limpet hemocyanin. The specificity of the antibodies was determined by binding to nitrated BSA, lack of binding to unmodified BSA, tyrosine, 3-chlorotyrosine or phenylalanine and inhibition of binding by nitrotyrosine. The antibodies developed are useful for Western blot analysis and immunohistochemical staining. Using these antibodies a nitrotyrosine sandwich ELISA was developed with a lower detection limit of approximately 0.2 nM. The intra- and interassay variance were 2.4% and 11.9%, respectively. Using this newly developed ELISA, 1.27 +/- 1.03 microM nitrotyrosine was detected in plasma samples of celiac disease patients whereas nitrotyrosine was undetectable in control samples. Elevated nitrotyrosine levels were paralleled by an increase in plasma concentrations of NO-oxidation products (NOx), nitrite and nitrate from 15.1 +/- 6.1 microM in controls to 61.0 +/- 28.2 microM in celiac disease patients. Both nitrotyrosine and NOx levels declined when the patients were on a gluten-free diet, suggesting a relation between intestinal inflammation and plasma nitrotyrosine and NOx levels.

Peroxynitrite formation and apoptosis in transgenic sickle cell mouse kidneys

BACKGROUND

In a previous study, nitric oxide synthases (NOS) were found to be strongly expressed in the tubular epithelium of kidneys of a transgenic mouse model of sickle cell disease (alphaHbetaS[betaMDD]). Because NOS activity is often associated with peroxynitrite formation when superoxide radical (.O-2) is present in abundance, we examined the kidneys of sickle cell mice for nitrotyrosine, considered to be a footprint of ONOO-.

METHODS

Western blot and immunohistochemistry for nitrotyrosine was carried out. Since peroxynitrite and other reactive oxygen radicals are capable of causing apoptosis, we also performed agarose gel electrophoresis of kidney DNA and TUNEL staining of nuclei, indicators of apoptosis.

RESULTS

Nitration of tyrosine residues of three proteins (kD 66, 57 and 22) was found on Western blot of kidney protein extracts of the sickle cell mice. The degree of tyrosine nitration of the 66 kD protein was not significantly different in the control versus transgenic mice, whereas tyrosine nitration of the 57 and 22 kD proteins was clearly increased in transgenic mice. Strong immunostaining for nitrotyrosine was seen in tubular epithelial cells of the sickle cell mice, in close proximity to positive immunostaining of iNOS. Neither iNOS nor nitrotyrosine was expressed in the control mice. DNA "laddering" was found localized to the same zones of the kidney as nitrotyrosine and iNOS immunostaining. TUNEL assay on mouse kidney tissue sections showed minimal tubular cell apoptosis in normal mouse with hypoxia, mild tubular cell apoptosis in sickle cell mouse in room air, and moderate tubular cell apoptosis in sickle cell mouse with hypoxia.

CONCLUSIONS

The observations suggest that ONOO- and perhaps other reactive oxygen species are being produced in the sickle cell kidney. The mechanism may be ischemia/reperfusion due to intermittent vascular occlusion by sickle cells. The resulting hypoxia could result in iNOS activation, superoxide radical and peroxynitrite formation. Two consequences of these reactions appear to be nitration of tyrosine residues of some renal proteins and enhanced apoptosis.

Oxidative chemistry of nitric oxide: the roles of superoxide, peroxynitrite, and carbon dioxide

The roles of superoxide (O2.-), peroxynitrite, and carbon dioxide in the oxidative chemistry of nitric oxide (.NO) are reviewed. The formation of peroxynitrite from .NO and O2.- is controlled by superoxide dismutase (SOD), which can lower the concentration of superoxide ions. The concentration of CO2 in vivo is high (ca. 1 mM), and the rate constant for reaction of CO2 with -OONO is large (pH-independent k = 5.8 x 10(4) M(-l)s(-1)). Consequently, the rate of reaction of peroxynitrite with CO2 is so fast that most commonly used scavengers would need to be present at very high, near toxic levels in order to compete with peroxynitrite for CO2. Therefore, in the presence of physiological levels of bicarbonate, only a limited number of biotargets react directly with peroxynitrite. These include heme-containing proteins such as hemoglobin, peroxidases such as myeloperoxidase, seleno-proteins such as glutathione peroxidase, proteins containing zinc-thiolate centers such as the DNA-binding transcription factors, and the synthetic antioxidant ebselen. The mechanism of the reaction of CO2 with OONO produces metastable nitrating, nitrosating, and oxidizing species as intermediates. An analysis of the lifetimes of the possible intermediates and of the catalysis of peroxynitrite decompositions suggests that the reactive intermediates responsible for reactions with a variety of substrates may be the free radicals .NO2 and CO3.-. Biologically important reactions of these free radicals are, for example, the nitration of tyrosine residues. These nitrations can be pathological, but they also may play a signal transduction role, because nitration of tyrosine can modulate phosphorylation and thus control enzymatic activity. In principle, it might be possible to block the biological effects of peroxynitrite by scavenging the free radicals .NO2 and CO3.-. Because it is difficult to directly scavenge peroxynitrite because of its fast reaction with CO2, scavenging of intermediates from the peroxynitrite/CO2 reaction would provide an additional way of preventing peroxynitrite-mediated cellular effects. The biological effects of peroxynitrite also can be prevented by limiting the formation of peroxynitrite from .NO by lowering the concentration of O2.- using SOD or SOD mimics. Increased formation of peroxynitrite has been linked to Alzheimer's disease, rheumatoid arthritis, atherosclerosis, lung injury, amyotrophic lateral sclerosis, and other diseases.

Myeloperoxidase and horseradish peroxidase catalyze tyrosine nitration in proteins from nitrite and hydrogen peroxide

Nitration of tyrosine residues in proteins occurs in a wide range of inflammatory diseases involving neutrophil and macrophage activation. We report that both myeloperoxidase (MPO) and horseradish peroxidase (HRP) utilize nitrite (NO2-) and hydrogen peroxide (H2O2) as substrates to catalyze tyrosine nitration in proteins. MPO was approximately 10 times more effective than HRP as a nitration catalyst of bovine serum albumin (BSA). Nitration of BSA by MPO did not require chloride as a cofactor. Physiologic levels of chloride did not significantly inhibit nitration by MPO. Oxidation of chloride to hypochlorous acid (HOCl) is catalyzed by MPO but not by HRP, yet HRP also catalyzed nitration from hydrogen peroxide plus nitrite. Therefore, HOCl formation was not obligatory for tyrosine nitration. Although HOCl plus nitrite can nitrate the amino acid tyrosine in simple solutions, protein nitration by HOCl plus nitrite was not observed in heart homogenates, probably due to the presence of multiple alternative targets of both HOCl and HOCl plus nitrite. In contrast, MPO catalyzed nitration of many proteins in rat heart homogenates using NO2- plus H2O2, suggesting that peroxidase-catalyzed nitration of tyrosine could occur in the presence of competing substrates in vivo. HOCl could substitute for H2O2 as the oxidizing substrate for nitration of either BSA or tissue homogenates catalyzed by either peroxidase. Activated neutrophils may generate nitrotyrosine by several mechanisms, including peroxynitrite, HOCl plus nitrite, and a chloride-independent mechanism involving MPO, nitrite, and hydrogen peroxide.

3-Nitrotyrosine in the proteins of human plasma determined by an ELISA method

The modification of tyrosine residues in proteins to 3-nitrotyrosine by peroxynitrite or other potential nitrating agents has been detected in biological systems that are subject to oxidative stress. A convenient semi-quantitative method has been developed to assay nitrated proteins in biological fluids and homogenates using a competitive ELISA developed in our laboratory. This assay selectivity detected 3-nitro-l-tyrosine residues in a variety of peroxynitrite-treated proteins (BSA, human serum albumin (HSA), alpha1-antiprotease inhibitor, pepsinogen and fibrinogen) and also in a nitrated peptide, but had a low affinity for free 3-nitro-L-tyrosine and 3-chloro-L-tyrosine. The IC50 values for the inhibition of antibody binding by different nitrated proteins were in the range 5-100 nM, suggesting that the antibody discriminated between nitrotyrosine residues in different environments. The presence of nitrotyrosine in plasma proteins was detected by Western blot analysis and quantified by the ELISA. A concentration of 0. 12+/-0.01 microM nitro-BSA equivalents was measured in the proteins of normal plasma which was increased in peroxynitrite-treated plasma and was elevated in inflammatory conditions. HSA and low-density lipoprotein (LDL) isolated from plasma contained 0.085+/-0.04 and 0. 03+/-0.006 nmol nitro-BSA equivalents/mg protein, respectively. Comparison of the level of nitration in peroxynitrite-treated HSA and LDL in the presence and absence of plasma indicates that nitration and presumably oxidation is inhibited by plasma antioxidants. The presence of nitrotyrosine in LDL is consistent with previous reports implicating peroxynitrite in the oxidative modification of lipoproteins and the presence of a low concentration of oxidized LDL in the blood.

Transient changes in the presence of nitric oxide synthases and nitrotyrosine immunoreactivity after focal cortical lesions

Since ischemic insults lead to a deregulation of nitric oxide production which contributes to delayed neuronal death, we investigated changes in the distribution and amount of nitric oxide synthases I and II and in the appearance of nitrotyrosine caused by small, well-defined photothrombic lesions (2 mm in diameter) in the somatosensory cortex of rats. Four hours after lesioning, cell loss was evident in the core of the lesion and no nitric oxide synthase was present within this area, indicating that neurons expressing nitric oxide synthase I were lost or that nitric oxide synthase I was degraded. No increase in the number of neurons expressing nitric oxide synthase I was visible in the area surrounding the lesion, nor in other parts of the brain. One day after lesioning, NADPH-diaphorase- and nitric oxide synthase II-positive leucocytes had invaded the perilesional cortex and were accumulated in injured blood vessels. By two to three days post-lesion, layer V and VI pyramidal neurons, microglia, astrocytes and invading leucocytes had become strongly immunoreactive for nitric oxide synthase II within a perilesional rim. The number of cells expressing nitric oxide synthase I remained stable. Nitric oxide synthase II immunoreactivity and related NADPH-diaphorase had decreased by seven days post-lesion in most animals. However, the number of activated microglia or macrophages and astrocytes, as revealed by other markers, remained elevated. In addition, nitrotyrosine immunoreactivity was evident in the blood vessels close to the lesion, as well as in the ipsilateral hippocampus and thalamus. These findings indicate that no perilesional changes in the number of neurons expressing nitric oxide synthase I occur, but that a transient increase in nitric oxide synthase II does take place in the aftermath of small cortical lesions. The results suggest that increased nitric oxide production is limited to certain post-lesional intervals in this experimental model. It is also obvious that the vast majority of nitric oxide synthase-positive cells are nitric oxide synthase II-containing astrocytes three days after lesioning, suggesting that astrocyte-derived nitric oxide plays a significant role in delayed neuronal death. Such a condition points to an important aspect of post-lesional astrocytosis.

Plasma 3-nitrotyrosine in cigarette smokers

Peroxynitrite has been associated with increased oxidative reactions and DNA damage in inflamed tissues as it may cause a reduction of plasma antioxidants as well. Nitration of tyrosine residues of proteins leads to the production of 3-nitrotyrosine (NTYR), which may be considered as a marker of NO.-dependent oxidative damage. We developed a highly sensitive method to detect NTYR in human plasma and tested it in cigarette smokers and in healthy control subjects. Peripheral venous blood (10 ml) was obtained in 20 healthy, asymptomatic cigarette smokers (13 males, 7 females; age: 49 +/- 11 yr) and in 18 healthy nonsmokers (10 males and 8 females; age: 36 +/- 6 yr). In smokers, plasma nicotine, cotinine, and expired CO levels were measured. NTYR was determined with a sequential HPLC/gas chromatography-thermal energy analysis (GC-TEA) technique. The total plasma Trolox-equivalent antioxidant capacity (TEAC) was also measured using metmyoglobin as peroxidase and a phenothiazine as a radical donor. NTYR was detectable (detection limit: 0.02 ng/injection) in 11 smokers (mean +/- SD: 1.60 +/- 1.24 ng/mg protein) and in two nonsmokers (1.10 and 1.20 ng/mg protein, respectively). NTYR was not associated with nicotine and cotinine levels or expired CO in smokers. Plasma TEAC in smokers was significantly lower (0.43 +/- 0.38 mM) than in nonsmokers (1.42 +/- 0.3 mM; p < 0.001) and showed a biphasic, negative relationship with NTYR (r = 0.96, p < 0.001). This highly sensitive HPLC/GC-TEA method for detection and quantitation of plasma NTYR may be used for monitoring oxidative reactions associated with tobacco smoking. This assay might be incorporated into molecular epidemiologic studies for lung chronic inflammatory and neoplastic disorders in which exposure to oxidants may be an important risk factor.

Quantitation of protein-bound 3-nitrotyrosine and 3,4-dihydroxyphenylalanine by high-performance liquid chromatography with electrochemical array detection

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) have been implicated in myriad disease etiologies and may represent an obligate pathologic sequelus of inflammation. Unfortunately, few sensitive and specific analytical techniques exist for the routine assay of biomarkers indicative of ROS and RNS elaboration. In this study, high-performance liquid chromatography is used in conjunction with coulometric electrochemical array (HPLC-EC) detection to allow ultrasensitive determination of protein-bound 3-nitrotyrosine and 3, 4-dihydroxyphenylalanine (3-hydroxytyrosine) as specific in situ biomarkers of protein exposure to reactive nitrating and oxidizing species. Tyrosine and derivatives can be analyzed simultaneously with practical detection limits for tyrosine, 3-NT, and 3,4-Dopa being 10, 50, and 2 pmol, respectively, in as little as 20 microL of sample. HPLC-EC array detection allows two-dimensional resolution of chromatograms, greatly facilitating peak detection and confidence assignment. A method of sample preparation wherein tyrosine analogs are enzymatically hydrolyzed from protein without the need for sample extraction, concentration, or derivatization is reported.

Inflammation and NO(X)-induced nitration: assay for 3-nitrotyrosine by HPLC with electrochemical detection

The identification of 15N-labeled 3-nitrotyrosine (NTyr) by gas chromatography/mass spectroscopy in protein hydrolyzates from activated RAW 264.7 macrophages incubated with 15N-L-arginine confirms that nitric oxide synthase (NOS) is involved in the nitration of protein-bound tyrosine (Tyr). An assay is presented for NTyr that employs HPLC with tandem electrochemical and UV detection. The assay involves enzymatic hydrolysis of protein, acetylation, solvent extraction, O-deacetylation, and dithionite reduction to produce an analyte containing N-acetyl-3-aminotyrosine, an electrochemically active derivative of NTyr. We estimate the level of protein-bound NTyr in normal rat plasma to be approximately 0-1 residues per 10(6) Tyr with a detection limit of 0.5 per 10(7) Tyr when > 100 nmol of Tyr is analyzed and when precautions are taken to limit nitration artifacts. Zymosan-treated RAW 264.7 cells were shown to have an approximately 6-fold higher level of protein-bound NTyr compared with control cells and cells treated with N(G)-monomethyl-L-arginine, an inhibitor of NOS. Intraperitoneal injection of F344 rats with zymosan led to a marked elevation in protein-bound NTyr to approximately 13 residues per 10(6) Tyr, an approximately 40-fold elevation compared with plasma protein of untreated rats; cotreatment with N(G)-monomethyl-L-arginine inhibited the formation of NTyr in plasma protein from blood and peritoneal exudate by 69% and 53%, respectively. This assay offers a highly sensitive and quantitative approach for investigating the role of reactive byproducts of nitric oxide in the many pathological conditions and disease states associated with NO(X) exposure such as inflammation and smoking.

Peroxynitrite: a two-faced metabolite of nitric oxide

The discovery that nitric oxide (NO) reacts with superoxide (O2.-) forming peroxynitrite (ONOO-) (1) and the proof that this reaction occurs in vivo (2,3) holds enormous implications for the understanding of free radicals in biological systems. Not only in mammalian defense mechanisms against microorganisms, but also in pathophysiology during overexposure of tissues to radicals or other highly reactive species. Peroxynitrite is a highly reactive compound with harmful effects on cells and could therefore be an important microbicidal compound. Furthermore, the reaction of superoxide with NO interferes with NO signalling mechanisms. NO is not only released in response to inflammatory agents by inflammatory cells, but is also an important messenger molecule in paracrine mechanisms and neurotransmission. Whether peroxynitrite formation is a negative side effect of NO and superoxide release, or a functional characteristic is yet to be determined, and will be discussed in this review.

Effects of peroxynitrite-induced protein modifications on tyrosine phosphorylation and degradation

The ability of protein tyrosine kinases to phosphorylate a synthetic peptide was inhibited 51% by peroxynitrite-mediated nitration of tyrosine. Exposure of endothelial cells to peroxynitrite decreased the intensity of tyrosine phosphorylated proteins and increased the intensity of nitrotyrosine-containing proteins. Peroxynitrite-modified BSA was degraded by human red blood cell lysates. However, human plasma in a concentration-, time-, and temperature-dependent manner, removed the protein nitrotyrosine epitope. These results suggest that tyrosine nitration interferes with phosphorylation and targets proteins for degradation. Specific enzymatic process(es) for removing nitrotyrosine may be present in vivo.