Protein Carbonyl Formation Research Articles

Cytoprotection by almond skin extracts or catechins of hepatocyte cytotoxicity induced by hydroperoxide (oxidative stress model) versus glyoxal or methylglyoxal (carbonylation model)

Oxidative and carbonyl stress are detrimental in the pathogenesis of diabetic complications, as well as in other chronic diseases. However, this process may be decreased by dietary bioactive compounds. Almond skin is an abundant source of bioactive compounds and antioxidants, including polyphenolic flavonoids, which may contribute to the decrease in oxidative and carbonyl stress. In this study, four Almond Skin Extracts (ASEI, ASEII, ASEIII, and ASEIV) were prepared by different methods and evaluated for their antioxidant activity. The order of the polyphenol content (total μM gallic acid equivalents) of the four extracts was found to be, in decreasing order of effectiveness: ASEI > ASEIII > ASEIV > ASEII. The order of Ferric-reducing antioxidant power (FRAP, μM FeSO 4/g) value, in decreasing order was ASEI (216) > ASEIII (176) > ASEIV (89) > ASEII (85). The order of ASE effectiveness for decreasing protein carbonyation induced by the copper Fenton reaction was ASEI > ASEIV > ASEII > ASEIII. The order of antioxidant effectiveness for inhibiting tertiary-butyl hydroperoxide (TBH) induced microsomal lipid peroxidation was ASEI > ASEIV > ASEII, ASEIII. Also, the order of ASE effectiveness for inhibiting TBH induced hepatocyte cell death was: ASEIII, ASEIV > ASEI, ASEII. Catechin also protected hepatocytes from TBH induced hepatocyte, lipid peroxidation and cytotoxicity. In a cell free model, equimolar concentrations of catechin or epicatechin rescued serum albumin from protein carbonylation induced by methylglyoxal (MGO). Catechin, epicatechin and ASEI all decreased gloxal induced hepatocyte cell death and reactive oxygen species (ROS) formation in GSH-depleted hepatocytes. Catechin and epicatechin protected against GO or MGO induced hepatocyte cell death, protein carbonylation and ROS formation. Catechin was more effective than epicatechin. Our results suggest that (a) bioactive almond skin constituents in the non-lipophilic polyphenol extract were the most effective at protecting hepatocytes against hydroperoxide induced hepatocyte oxidative stress and in protecting against dicarbonyl induced cytotoxicity; (b) catechins, the major polyphenol in the extract, were also effective at preventing GO or MGO cytotoxicity likely by trapping GO and MGO and/or rescuing hepatocytes from protein carbonylation.

Effect of Phenolic Compounds on the Formation of α-Aminoadipic and γ-Glutamic Semialdehydes from Myofibrillar Proteins Oxidized by Copper, Iron, and Myoglobin

The effect of selected phenolic compounds, namely, gallic acid, chlorogenic acid, genistein, catechin, cyanidin-3-glucoside and rutin, on the formation of specific protein carbonyls, alpha-aminoadipic and gamma-glutamic semialdehydes (AAS and GGS, respectively), from oxidized myofibrillar proteins, was studied in the present article. Suspensions containing myofibrillar proteins (20 mg/mL) and the aforementioned phenolic compounds (1 mM) were oxidized (37 degrees C for 20 days) in the presence of copper acetate, iron (FeCl(3)), or myoglobin (10 microM) in combination with 1 mM H(2)O(2) and analyzed for AAS and GGS using liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS). Suspensions with added alpha-tocopherol (1 mM) and a control group (with no phenolic compound) were also considered. In the presence of copper, the alpha-tocopherol and most phenolic compounds significantly inhibited the formation of AAS and GGS. In iron- and myoglobin-oxidized suspensions, however, some of those phenolic compounds (i.e., chlorogenic acid and genistein) promoted the formation of the semialdehydes. Besides the influence of the oxidation promoters, the overall effect of plant phenolics on protein oxidation is likely affected by the chemical structure of the phenolics and the result of the interactions between these compounds and myofibrillar proteins. Plausible mechanisms for the antioxidant and pro-oxidant effects of plant phenolics on myofibrillar proteins are proposed in the present article. This study highlights the complexity of redox reactions between plant phenolics and oxidizing myofibrillar proteins.

Protein oxidation in emulsified cooked burger patties with added fruit extracts: Influence on colour and texture deterioration during chill storage

The influence of protein oxidation, as measured by the dinitrophenylhydrazine (DNPH) method, on colour and texture changes during chill storage (2 degrees C, 12days) of cooked burger patties was studied. Extracts from arbutus-berries (Arbutus unedoL., AU), common hawthorns (Crataegus monogynaL., CM), dog roses (Rosa caninaL., RC) and elm-leaf blackberries (Rubus ulmifoliusSchott., RU) were prepared, added to burger patties (3% of total weight) and evaluated as inhibitors of protein oxidation and colour and texture changes. Negative (no added extract, C) and positive control (added quercetin; 230mg/kg, Q) groups were also considered. The significant increase of protein carbonyls during chill storage of control burger patties reflect the intense oxidative degradation of the muscle proteins. Concomitantly, an intense loss of redness and increase of hardness was found to take place in burger patties throughout refrigerated storage. Most fruit extracts as well as Q significantly reduced the formation of protein carbonyls and inhibited colour and texture deterioration during chill storage. Likely mechanisms through which protein oxidation could play a major role on colour and texture changes during chill storage of burger patties are discussed. Amongst the extracts, RC was most suitable for use as a functional ingredient in processed meats since it enhanced oxidative stability, colour and texture properties of burger patties with no apparent drawbacks.

Effects of a gastrin-releasing peptide receptor antagonist on d-amphetamine-induced oxidative stress in the rat brain

Previous studies have suggested that bipolar disorder may be associated with oxidative stress. Administration of D: -amphetamine (AMPH) has been put forward as an animal model of mania, and has shown to increase oxidative stress parameters in the rat brain. Thus, we have used the gastrin-releasing peptide receptor antagonist [D-Tpi(6)Leu(13)psi (CH(2)NH)-Leu(14)] bombesin (RC-3095) as a pharmacological tool to investigate the role of bombesin-like peptides in the redox balance in the hippocampus and cortex of rats treated with AMPH. Rats were given a single 10 ml/kg intraperitoneal (i.p.) injection of saline (SAL) or RC-3095 (0.1, 1.0 or 10.0 mg/kg) followed by an i.p. injection of SAL or amphetamine (AMPH 2.0 mg/kg) 30 min later. Locomotor activity was evaluated 2 h after the last drug injection. The thiobarbituric acid reactive substances (TBARS), protein carbonyl formation, superoxide dismutase and catalase (CAT) activity were measured in hippocampus, striatum and cortex as markers of oxidative stress. The results show that RC-3095 blocks AMPH-induced hyperlocomotion. Moreover, specific doses of RC-3095 alone increased the levels of oxidative stress in the dorsal hippocampus and cortex. However, when AMPH was subsequently administrated, RC-3095 decreased TBARS and protein carbonyls formation and increased the superoxide dismutase and CAT activity in the hippocampus, striatum and cortex. The effects of GRPR antagonist seemed to be region and dose specific. In conclusion, the results suggest that GRPR antagonists might display antioxidant properties in the brain.

Protein Carbonyl and the Methionine Sulfoxide Reductase System

The formation and accumulation of protein-carbonyl by reactive oxygen species may serve as a marker of oxidative stress, aging, and age-related diseases. Enzymatic reversal of the protein-carbonyl modification has not yet been detected. However, an enzymatic reversal of protein-methionine sulfoxide modification exists and is mediated by the methionine sulfoxide reductase (Msr) system. Methionine sulfoxide modifications to proteins may precede the formation of protein-carbonyl adducts because of consequent structural changes that increase the vulnerability of amino acid residues to carbonylation. Supportive evidence for this possibility arises from the elevated protein-carbonyl accumulations observed in organisms, such as yeast and mice, lacking the methionine sulfoxide reductase A (MsrA) enzyme. In addition, advanced age or enhanced oxidative-stress conditions foster the accumulations of protein-carbonyls. This review discusses the possible involvement of methionine sulfoxide formation in the occurrence of protein-carbonyl adducts and their relevance to the aging process and neurodegenerative diseases.

Reduction of lipid and protein damage in patients with disorders of propionate metabolism under treatment: a possible protective role of l-carnitine supplementation

Disorders of propionate metabolism are autosomal recessive diseases clinically characterized by acute metabolic crises in the neonatal period and long-term neurological deficits whose pathophysiology is not completely established. There are increasing evidences demonstrating antioxidant properties for l-carnitine, which is used in the treatment of propionic and methylmalonic acidemias to increase the excretion of organic acids accumulated in tissues and biological fluids of the affected patients. In this work we aimed to evaluate lipid (malondialdehyde content) and protein (carbonyl formation and sulfhydryl oxidation) oxidative damage in plasma from patients with propionic and methylmalonic acidemias at the moment of diagnosis and during treatment with l-carnitine. We also correlated the parameters of oxidative damage with plasma total, free and esterified l-carnitine levels. We found a significant increase of malondialdehyde and carbonyl groups, as well as a reduction of sulfhydryl groups in plasma of these patients at diagnosis compared to controls. Furthermore, patients under treatment presented a marked reduction of the content of protein carbonyl groups, similar to controls, and malondialdehyde content in relation to patients at diagnosis. In addition, plasma total and free l-carnitine concentrations were negatively correlated with malondialdehyde levels. Taken together, the present data indicate that treatment significantly reduces oxidative damage in patients affected by disorders of propionate metabolism and that l-carnitine supplementation may be involved in this protection.

Eicosapentaenoic acid preserves diaphragm force generation following endotoxin administration.

IntroductionInfections produce severe respiratory muscle weakness, which contributes to the development of respiratory failure. An effective, safe therapy to prevent respiratory muscle dysfunction in infected patients has not been defined. This study examined the effect of eicosapentaenoic acid (EPA), an immunomodulator that can be safely administered to patients, on diaphragm force generation following endotoxin administration.MethodsRats were administered the following (n = 5/group): (a) saline, (b) endotoxin, 12 mg/kg IP, (c) endotoxin + EPA (1.0 g/kg/d), and (d) EPA alone. Diaphragms were removed and measurements made of the diaphragm force-frequency curve, calpain activation, caspase activation, and protein carbonyl levels.ResultsEndotoxin elicited large reductions in diaphragm specific force generation (P < 0.001), and increased diaphragm caspase activation (P < 0.01), calpain activation (P < 0.001) and protein carbonyl levels (P < 0.01). EPA administration attenuated endotoxin-induced reductions in diaphragm specific force, with maximum specific force levels of 27 ± 1, 14 ± 1, 23 ± 1, and 24 ± 1 N/cm2, respectively, for control, endotoxin, endotoxin + EPA, and EPA treated groups (P < 0.001). EPA did not prevent endotoxin induced caspase activation or protein carbonyl formation but significantly reduced calpain activation (P < 0.02).ConclusionsThese data indicate that endotoxin-induced reductions in diaphragm specific force generation can be partially prevented by administration of EPA, a nontoxic biopharmaceutical that can be safely given to patients. We speculate that it may be possible to reduce infection-induced skeletal muscle weakness in critically ill patients by administration of EPA.

Effects of different acute high ambient temperatures on function of hepatic mitochondrial respiration, antioxidative enzymes, and oxidative injury in broiler chickens

This study investigated the effects of different acute high ambient temperatures on dysfunction of hepatic mitochondrial respiration, the antioxidative enzyme system, and oxidative injury in broiler chickens. One hundred twenty-eight 6-wk-old broiler chickens were assigned randomly to 4 groups and subsequently exposed to 25 (control), 32, 35, and 38 degrees C (RH, 70 +/- 5%) for 3 h, respectively. The rectal temperatures, activity of antioxidative enzymes (superoxide dismutase, catalase, and glutathione peroxidase), content of malondialdehyde and protein carbonyl, and the activity of mitochondrial respiratory enzymes were determined. The results showed that exposure to high ambient temperature induced a significant elevation of rectal temperature, antioxidative enzyme activity, and formation of malondialdehyde and protein carbonyl, as well as dysfunction of the mitochondrial respiratory chain in comparison with control (P < 0.05). Almost all of the indicators changed in a temperature-dependent manner with the gradual increase of ambient temperature from 32 to 38 degrees C; differences in each parameter (except catalase) among the groups exposed to different high ambient temperatures were also statistically significant (P < 0.05). The results of the present study suggest that, in the broiler chicken model used here, acute exposure to high temperatures may depress the activity of the mitochondrial respiratory chain. This inactivation results subsequently in overproduction of reactive oxygen species, which ultimately results in oxidative injury. However, this hypothesis needs to be evaluated more rigorously in future studies. It has also been shown that, with the gradual increase in temperature, the oxidative injury induced by heat stress in broiler chickens becomes increasingly severe, and this stress response presents in a temperature-dependent manner in the temperature range of 32 to 38 degrees C.

Pycnogenol and Ginkgo biloba extract: effect on peroxynitrite-oxidized sarcoplasmic reticulum Ca-ATPase.

The effect of two natural standardized plant extracts, Pycnogenol® and EGb 761, on sarcoplasmic reticulum Ca2+-ATPase (SERCA) activity and posttranslational modifications induced by peroxynitrite was investigated to assess their possible protective role. EGb 761 was found to have a protective effect on SERCA activity in the concentration range of 5–40 µg/ml. On the other hand, Pycnogenol® caused a decrease of SERCA activity at concentrations of 25 µg/ml. EGb 761 did not prevent protein carbonyl formation upon oxidation with peroxynitrite. On the contrary, Pycnogenol® at the concentrations of 5 and 10 µg/ml significantly decreased the level of protein carbonyls by 44% and 54%, respectively. Neither Pycnogenol® nor EGb 761 exerted a protective effect against thiol group oxidation.The plant extracts studied modulated peroxynitrite-injured SERCA activity by different ways and failed to correlate with posttranslational modifications. Their effect seems to be associated with their ability to change SERCA conformation rather than by their antioxidant capacity.

Traditional reactive carbonyl scavengers do not prevent the carbonylation of brain proteins induced by acute glutathione depletion

This study investigated the effect of reactive carbonyl species (RCS)-trapping agents on the formation of protein carbonyls during depletion of brain glutathione (GSH). To this end, rat brain slices were incubated with the GSH-depletor diethyl maleate in the absence or presence of chemically different RCS scavengers (hydralazine, methoxylamine, aminoguanidine, pyridoxamine, carnosine, taurine and z-histidine hydrazide). Despite their strong reactivity towards the most common RCS, none of the scavengers tested, with the exception of hydralazine, prevented protein carbonylation. These findings suggest that the majority of protein-associated carbonyl groups in this oxidative stress paradigm do not derive from stable lipid peroxidation products like malondialdehyde (MDA), acrolein and 4-hydroxynonenal (4-HNE). This conclusion was confirmed by the observation that the amount of MDA-, acrolein- and 4-HNE-protein adducts does not increase upon GSH depletion. Additional studies revealed that the efficacy of hydralazine at preventing carbonylation was due to its ability to reduce oxidative stress, most likely by inhibiting mitochondrial production of superoxide and/or by scavenging lipid free radicals.

Protective effect of resveratrol on formation of membrane protein carbonyls and lipid peroxidation in erythrocytes subjected to oxidative stress

Many of the biological actions of resveratrol have been attributed to its antioxidant properties. In this work, we subjected human erythrocytes to in vitro oxidative stress by incubating them with tert-butylhydroperoxide (t-BHP). This caused a significant increase in the malondialdehyde (MDA) level and the protein carbonyl group content above the basal values. The presence of trans-resveratrol at micromolar concentrations in the incubation medium protected the erythrocytes from t-BHP-induced oxidative stress, as evidenced by the decrease in the MDA level and the protein carbonyl group content. The effect of resveratrol was concentration and time-dependent. Our findings help to explain some of the beneficial effects of resveratrol.

Redox modulation of global phosphatase activity and protein phosphorylation in intact skeletal muscle

Skeletal muscles produce transient reactive oxygen species (ROS) in response to intense stimulation, disuse atrophy, heat stress, hypoxia, osmotic stress, stretch and cell receptor activation. The physiological significance is not well understood. Protein phosphatases (PPases) are known to be highly sensitive to oxidants and could contribute to many different signalling responses in muscle. We tested whether broad categories of PPases are inhibited by levels of acute oxidant exposure that do not result in loss of contractile function or gross oxidative stress. We also tested if this exposure results in elevated levels of global protein phosphorylation. Rat diaphragm muscles were treated with either 2,3-dimethoxy-1-naphthoquinone (DMNQ; 1, 10, 100 microm; a mitochondrial O(2)(.-)/H2O2 generator) or exogenous H2O2 (5, 50, 500 microm) for 30 min. Supernatants were assayed for serine/threonine PPase (Ser/Thr-PPase) or protein tyrosine PPase (PTP) activities. With the exception of 500 microm H2O2, no other oxidant exposures significantly elevated protein carbonyl formation, nor did they alter the magnitude of twitch force. DMNQ significantly decreased all categories of PPase activity at 10 and 100 microm and reduced PTP at 1 microm. Similar reductions in Ser/Thr-PPase activity were seen in response to 50 and 500 microm H2O2 and PTP at 500 microm H2O2. ROS treatments resulted a dose-dependent increase in the phosphorylation states of many proteins. The data are consistent with the concept that PPases, within intact skeletal muscles, are highly sensitive to acute changes in ROS activity and that localized ROS play a critical role in lowering the barriers for effective phosphorylation events to occur in muscle cells, thus increasing the probability for cell signalling responses to proceed.

Apoptosis in HepG2 cells exposed to high glucose

Hyperglycemia which characterizes diabetes, leads to several abnormalities in the cellular pathways. We examined the toxicity of glucose in human hepatoma HepG2 cells. HepG2 cells when incubated with 50 mM glucose for 72 h showed altered morphology i.e. presence of detached and shrunken rounded cells. Glucose treated HepG2 cells also exhibited a significant decrease in viability. Caspase-3 activity and Annexin V staining were significantly increased in glucose treated HepG2 cells, suggesting an apoptotic mode of cell death. Glucose induced apoptosis in HepG2 cells was a consequence of increased oxidative stress as evidenced by the increased reactive oxygen species (ROS) level, lipid peroxidation, protein carbonyl and 3-nitrotyrosine adduct formation. The intracellular antioxidant glutathione was found to be increased in HepG2 cells treated with glucose, possibly to aid the cells to overcome the persistent oxidative stress elicited by glucose in HepG2 cells. N-Acetyl cysteine, a precursor of glutathione and an antioxidant was effective in reversing the morphological changes, increasing the viability, decreasing the ROS level and 4-hydroxynonenal and 3-nitrotyrosine adduct formation, thus validating the role of oxidative stress as a major mechanism for glucose induced apoptosis in HepG2 cells. These results suggest that glucose induces apoptosis in liver cells through increased oxidative stress.

Risk Reduction of Ethyl Acetate Fraction of Empetrum nigrum var. japonicum via Antioxidant Properties Against Hydrogen Peroxide-Induced Cell Damage

Reactive oxygen species (ROS) produce damage to all major cellular constituents. The antioxidant properties of the ethyl acetate fraction of Empetrum nigrum was assessed against hydrogen peroxide (H2O2)-induced cell damage. Empetrum extract was found to scavenge (1) intracellular ROS in cell system, (2) hydroxyl radicals generated by the Fenton reaction (FeSO4 + H2O2), and (3) superoxide radicals generated by xanthine/xanthine oxidase in a cell-free system as detected by electron spin resonance (ESR) spectrometry. Cell damage was produced by H2O2 treatment as evidenced by DNA damage, lipid peroxidation, and increased protein carbonyl formation; however, Empetrum extract prevented H2O2-induced damage to these parameters. Empetrum extract increased viability of Chinese hamster lung fibroblast (V79-4) cells exposed to H2O2, as evidenced by decreased apoptotic nuclear fragmentation, and lower sub G1 cell population. Further, Empetrum extract restored the cellular antioxidant enzyme activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and heme oxygenase-1 (HO-1), which were reduced by H2O2 treatment. In conclusion, Empetrum extract protected cells against H2O2-induced cell damage via antioxidant properties by scavenging ROS and enhancing antioxidant enzyme activities.

A Novel Experimental Heme Oxygenase-1–Targeted Therapy for Hormone-Refractory Prostate Cancer

Heme oxygenase-1 (HO-1), a member of the heat shock protein family, plays a key role as a sensor and regulator of oxidative stress. Herein, we identify HO-1 as a biomarker and potential therapeutic target for advanced prostate cancer (PCA). Immunohistochemical analysis of prostate tissue using a progression tissue microarray from patients with localized PCA and across several stages of disease progression revealed a significant elevation of HO-1 expression in cancer epithelial cells, but not in surrounding stromal cells, from hormone-refractory PCA (HRPCA) compared with hormone-responsive PCA and benign tissue. Silencing the ho-1 gene in HRPCA cells decreased the HO-1 activity, oxidative stress, and activation of the mitogen-activated protein kinase-extracellular signal-regulated kinase/p38 kinase. This coincided with reduced cell proliferation, cell survival, and cell invasion in vitro, as well as inhibition of prostate tumor growth and lymph node and lung metastases in vivo. The effect of ho-1 silencing on these oncogenic features was mimicked by exposure of cells to a novel selective small-molecule HO-1 inhibitor referred to as OB-24. OB-24 selectively inhibited HO-1 activity in PCA cells, which correlated with a reduction of protein carbonylation and reactive oxygen species formation. Moreover, OB-24 significantly inhibited cell proliferation in vitro and tumor growth and lymph node/lung metastases in vivo. A potent synergistic activity was observed when OB-24 was combined with Taxol. Together, these results establish HO-1 as a potential therapeutic target for advanced PCA.

The Proteasome Is an Integral Part of Solar Ultraviolet A Radiation-induced Gene Expression

Solar ultraviolet (UV) A radiation is a well known trigger of signaling responses in human skin fibroblasts. One important consequence of this stress response is the increased expression of matrix metalloproteinase-1 (MMP-1), which causes extracellular protein degradation and thereby contributes to photoaging of human skin. In the present study we identify the proteasome as an integral part of the UVA-induced, intracellular signaling cascade in human dermal fibroblasts. UVA-induced singlet oxygen formation was accompanied by protein oxidation, the cross-linking of oxidized proteins, and an inhibition of the proteasomal system. This proteasomal inhibition subsequently led to an accumulation of c-Jun and phosphorylated c-Jun and activation of activator protein-1, i.e. transcription factors known to control MMP-1 expression. Increased transcription factor activation was also observed if the proteasome was inhibited by cross-linked proteins or lactacystin, indicating a general mechanism. Most importantly, inhibition of the proteasome was of functional relevance for UVA-induced MMP-1 expression, because overexpression of the proteasome or the protein repair enzyme methionine sulfoxide reductase prevented the UVA-induced induction of MMP-1. These studies show that an environmentally relevant stimulus can trigger a signaling pathway, which links intracellular and extracellular protein degradation. They also identify the proteasome as an integral part of the UVA stress response.

Inverse correlation of protein oxidation and proteasome activity in liver and lung

Several studies have demonstrated that proteasome activity decreases whereas protein oxidation increases with aging in various tissues. However, no studies are available correlating both parameters directly comparing different tissues of one organism. Therefore, we determined whether there is an age-related change in proteasome activity and protein oxidation in heart, lung, liver, kidney and skeletal muscle samples of 6-, 10-, 18- and 26-month-old rats. There was a significant age-related increase in protein carbonyls at 18 and 26 months compared to young rats. Thereby, protein carbonyl formation was rather due to a general than a specific protein carbonylation as shown by immunblot studies. The highest increase in protein carbonyl formation was found in liver, lung and kidney samples. Proteasome activity decreased significantly with age in lung and liver samples. Proteasome activity in liver and lung decreased by factor five compared to young rats. Strong correlations between proteasome activity and protein oxidation were found in liver and lung, whereas in other tissues only a trend was found. These results demonstrate that the increase in protein oxidation and the decline in proteasome activity are correlating. Further studies are needed to determine the mechanisms which cause organ-specific aging-rates and their consequences.

Oryzadine, a new alkaloid of Oryza sativa cv. Heugjinjubyeo, attenuates oxidative stress-induced cell damage via a radical scavenging effect

The antioxidant properties of oryzadine, a new alkaloid, obtained from Oryza sativa cv. Heugjinjubyeo was investigated by applying various methods based on cell-free and cell experiments. Oryzadine showed scavenging effects on the hydroxyl radical, superoxide radical, and intracellular reactive oxygen species (ROS). Oryzadine inhibited H2O2-induced DNA damage, which was demonstrated by DNA tail formation, lipid peroxidation which was demonstrated by the formation of thiobarbituric acid reactive substance (TBARS), and protein oxidation which was demonstrated by protein carbonyl formation. Therefore, oryzadine protected H2O2-induced cell damage. Our results show that the cytoprotective effects of oryzadine stem from its ability to inhibit H2O2-induced apoptosis, as demonstrated by a decrease in apoptotic body formation and the inhibition of mitochondrial membrane potential (ΔΨ) loss. Taken together, these findings suggest that oryzadine protected cells against H2O2-induced cell damage via ROS scavenging effect. Therefore, oryzadine could be considered a significant natural source of antioxidant.

Oxidative Modification of Albumin in Predialysis, Hemodialysis, and Peritoneal Dialysis Patients

Background/Aims: Oxidative damage has been reported to be involved in the pathophysiology of chronic kidney disease (CKD) as well as in the pathogenesis of cardiovascular complications of CKD patients. The aim of the present investigation was to evaluate the levels of plasma carbonyl formation, a sensitive marker of enhanced oxidative stress in predialysis, hemodialysis (HD) and peritoneal dialysis (PD) patients. Methods: Plasma samples from 20 apparently healthy control individuals and 127 CKD (stages 2, 3, 4, HD and PD) patients were evaluated by Western blot analysis for the estimation of the levels of protein carbonyl formation. Results: Albumin represented the main plasma carbonylated protein. Increasing carbonylation of albumin was detected along with the severity of CKD, reaching significance at stages 3 and 4 (p < 0.01, compared to healthy controls). The carbonylation of albumin was even higher in the plasma of HD patients (p < 0.001), while in PD patients it was not statistically significant compared to controls (p = 0.224). Conclusions: The data presented in this work indicate that oxidative stress in CKD patients gradually increased during the development of the disease. This stress is probably intensified during HD, but not in PD subjects.

Peroxynitrite and heme protein – Mediated nitrative/oxidative modification of human plasma protein: The role of free radical scavenging vs. complex forming

The major pathways of protein tyrosine nitration in vivo include peroxynitrite (ONOO −) and heme peroxidase– NO 2 - –H 2O 2 dependent reaction in which free radicals and iron catalysis are involved. In this paper, we chose three classic antioxidants (GSH, a major intracellular antioxidant; Trolox, a phenolic antioxidant without chelating effect; and DFO, a good iron chelator), to study their efficiencies against ONOO − or heme/NaNO 2/H 2O 2 – mediated nitrative/oxidative damage to human plasma proteins in vitro. Protein nitration was efficiently inhibited by the three antioxidants regardless of nitration pathways, whereas the efficiencies of antioxidants on protein oxidation depended on the concentration of antioxidants and categories of oxidant. In both models, GSH exhibited protective activity in protein oxidation and Trolox promoted the formation of plasma protein carbonyl groups at lower concentration (0.01 and 0.1 mM). DFO dose-dependently inhibited ONOO −-induced protein oxidation, while it enhanced heme/NaNO 2/H 2O 2-triggered protein oxidation at lower concentration. However, both DFO and Trolox exhibited protective effect on protein carbonyl formation when the higher concentration was used. The pro-oxidant or antioxidant effect for these antioxidants at different concentration, may provide useful information about the selection of the suitable antioxidant and dosage in experimental and clinical application.