N-chloroamino acids cause oxidative protein modifications in the erythrocyte membrane

The influence of piperine on oxidation-induced porcine myofibrillar protein gelation behavior and fluorescent advanced glycation end products formation in model systems

This study investigated the effects of piperine on oxidation-induced porcine myofibrillar protein (MP) gelation behavior and fluorescent advanced glycation end products (fAGEs) formation. Model systems were prepared, lipid oxidation, MP gelling behavior, and fAGEs content were determined daily. The results indicated that lipid oxidation, carbonyl content, S₀, cooking loss, and tryptophan fluorescence intensity of MP significantly decreased, whereas gel strength, WHC, and whiteness markedly increased as the concentration of piperine increased (from 0 to 30 μM/g protein), indicating that piperine could reduce lipid oxidation and oxidative damage to MP. The fluorescence intensity of fAGEs markedly decreased (P < 0.05), from 93.1 ± 4.4 to 61.2 ± 3.0, as the concentration of piperine increased from 0 μM/g protein to 30 μM/g protein after 5 days of incubation. These results in model systems suggest that the presence of piperine has an important role in the inhibition of MP oxidation and fAGEs formation.

Is there a halo-enzymopathy in Parkinson's disease?

Laboratory studies identified changes in the metabolism of halogens in the serum and cerebrospinal fluid (CSF) of patients with Parkinson's disease, which indicates the presence of «accelerated self-halogenation» of CSF and/or an increase in haloperoxidases, specifically serum thyroperoxidase and CSF lactoperoxidase. Furthermore, an excess of some halogenated derivatives, such as advanced oxygenation protein products (AOPP), has been detected in the CSF and serum. «Accelerated self-halogenation» and increased levels of haloperoxidases and AOPP proteins indicate that halogenative stress is present in Parkinson's disease. In addition, 3-iodo-L-tyrosine, a halogenated derivative, shows «parkinsonian» toxicity in experimental models, since it has been observed to induce α-synuclein aggregation and damage to dopaminergic neurons in the mouse brain and intestine. The hypothesis is that patients with Parkinson's disease display halogenative stress related to a haloenzymatic alteration of the synthesis or degradation of oxyacid of halogens and their halogenated derivatives. This halogenative stress would be related to nervous system damage.

Halogen-Induced Chemical Injury to the Mammalian Cardiopulmonary Systems

The halogens chlorine (Cl₂) and bromine (Br₂) are highly reactive oxidizing elements with widespread industrial applications and a history of development and use as chemical weapons. When inhaled, depending on the dose and duration of exposure, they cause acute and chronic injury to both the lungs and systemic organs that may result in the development of chronic changes (such as fibrosis) and death from cardiopulmonary failure. A number of conditions, such as viral infections, coexposure to other toxic gases, and pregnancy increase susceptibility to halogens significantly. Herein we review their danger to public health, their mechanisms of action, and the development of pharmacological agents that when administered post-exposure decrease morbidity and mortality.

Salivary Redox Biomarkers in Different Stages of Dementia Severity

This study is the first to evaluate oxidative stress biomarkers in saliva/blood of patients with varying degrees of dementia progression. The study included 50 healthy controls and 50 dementia patients divided into two groups: those with mild and moderate dementia (MMSE 11–23) and patients suffering from severe dementia (MMSE 0–10). Cognitive functions of the subjects were assessed using the Mini Mental State Examination (MMSE). Enzymatic and non-enzymatic antioxidants, oxidative damage products and protein glycoxidative modifications were determined in non-stimulated (NWS) and stimulated (SWS) saliva as well as erythrocyte/plasma samples. Generally, in dementia patients, we observed the depletion of antioxidant defences leading to oxidative and glycoxidative damage in NWS, SWS and blood samples. Both salivary and blood oxidative stress increased with the severity of the disease, and correlated with a decrease of cognitive functions. Interestingly, in dementia patients, reduced glutathione (GSH) in NWS correlated not only with the severity of dementia, but also with GSH concentration in the plasma. In receiver operating characteristic (ROC) analysis, we have demonstrated that salivary GSH clearly distinguishes patients with severe dementia from those suffering from mild or moderate dementia (area under the curve (AUC) = 1). Therefore, salivary GSH can be used as a non-invasive biomarker of cognitive impairment.

Oxidative modifications of blood serum proteins in myasthenia gravis

Myasthenia gravis (MG) is an autoimmune disease caused by production of antibodies against acetylcholine receptors of the neuromuscular junction (Ab). The aim of this study was to ascertain if oxidative stress accompanies MG by estimation of the several independent parameters of oxidative damage, mainly the levels of oxidative modifications of blood serum proteins. The group studied consisted of 50 MG patients (28 females and 22 males), 24 with ocular MG (OMG) and 26 with generalized MG (GMG), of mean age of 66.7 (30-81)years (y), mean disease duration of 9.5 (0.5-34)y, mean level of Ab of 8.9 (0.1-85)nmol/ml, and 25 age-matched healthy controls. MG patients were stratified into groups according to disease duration (<5y or >5y), Ab level (low, <3 or high, >3nmol/l) as well as symptoms (GMG or OMG). Glycophore fluorescence was increased in OMG^a. Dityrosine was increased in both types of MG^c, in patients ill <5^b and >5^cy, with low^c and high^c levels of Ab. N-formylkynurenine was increased in OMG^a and GMG^b, in both disease duration groups^a, in the group of low Ab^a. Kynurenine was increased in the group with high Ab^a. Tryptophan fluorescence was decreased in OMG^b and GMG^c, in patients ill for <5^b and >5^ay, with low^a and high^c Ab. Serum thiol group concentration were decreased in GMG^c, in patients ill for >5y^b. AOPP level was elevated in OMG^a, in patients ill for >5y^a with high Ab^a. Protein carbonyls were increased in both OMG^c and GMG^c, in patients ill for >5^ay, with low^b and high^b Ab. FRAP and ABTS^• scavenging by fast antioxidants were unchanged, but ABTS^• scavenging by slow antioxidants was lower in OMG^b and GMG^c, in patients ill for >5^cy, in patients with low^c and high^b Ab (^ap<0.05, ^bp<0.01, ^cp<0.001). These results demonstrate systemic oxidative stress in MG, suggesting therapeutic use of antioxidants.

Glycation of bovine serum albumin by ascorbate in vitro: Possible contribution of the ascorbyl radical?

Ascorbic acid (AA) has been reported to be both pro-and antiglycating agent. In vitro, mainly proglycating effects of AA have been observed. We studied the glycation of bovine serum albumin (BSA) induced by AA in vitro. BSA glycation was accompanied by oxidative modifications, in agreement with the idea of glycoxidation. Glycation was inhibited by antioxidants including polyphenols and accelerated by 2,​2′-​azobis-​2-​methyl-​propanimidamide and superoxide dismutase. Nitroxides, known to oxidize AA, did not inhibit BSA glycation. A good correlation was observed between the steady-state level of the ascorbyl radical in BSA samples incubated with AA and additives and the extent of glycation. On this basis we propose that ascorbyl radical, in addition to further products of AA oxidation, may initiate protein glycation.

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Ascorbic acid (AA) induced glycation of bovine serum albumin (BSA) in vitro.

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Antioxidants, including polyphenols, inhibited glycation.

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Nitroxides, known to oxidize AA, did not protect from glycation.

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BSA glycation was accelerated by AAPH and superoxide dismutase.

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Good correlation was found between the level of ascorbyl radical and extent of glycation.

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We postulate that ascorbyl radical is able to induce protein glycation.

Oxidative modification of proteins in pediatric cystic fibrosis with bacterial infections

Pseudomonas aeruginosa and Staphylococcus aureus cause chronic lung infection in cystic fibrosis (CF) patients, inducing chronic oxidative stress. Several markers of plasma protein oxidative damage and glycoxidation and activities of erythrocyte antioxidant enzymes have been compared in stable CF patients chronically infected with Pseudomonas aeruginosa (n = 12) and Staphylococcus aureus (n = 10) in relation to healthy subjects (n = 11). Concentration of nitric oxide was also measured in the exhaled air from the lower respiratory tract of patients with CF. Elevated glycophore (4.22 ± 0.91 and 4.19 ± 1.04 versus control 3.18 ± 0.53 fluorescence units (FU)/mg protein; P < 0.05) and carbonyl group levels (1.9 ± 0.64, 1.87 ± 0.45 versus control 0.94 ± 0.19 nmol/mg protein; P < 0.05) as well as increased glutathione S-transferase activity (2.51 ± 0.88 and 2.57 ± 0.79 U/g Hb versus 0.77 ± 0.16 U/g Hb; P < 0.05) were noted in Pseudomonas aeruginosa and Staphylococcus aureus infected CF. Kynurenine level (4.91 ± 1.22 versus 3.89 ± 0.54 FU/mg protein; P < 0.05) was elevated only in Staphylococcus aureus infected CF. These results confirm oxidative stress in CF and demonstrate the usefulness of the glycophore level and protein carbonyl groups as markers of oxidative modifications of plasma proteins in this disease.

Oxidative modification of blood serum proteins in multiple sclerosis after interferon or mitoxantrone treatment

This study was aimed at (i) comparison of the usefulness of serum protein oxidation parameters for assessment of oxidative stress (OS) in multiple sclerosis (MS), and (ii) comparison of OS in MS patients subject to various therapies. Elevated glycophore level was noted in relapsing-remitting (RRMS) patients without treatment and patients treated with interferons β1a and β1b (10.33±3.27, 8.02±2.22 and 8.56±2.45 vs control 5.27±0.73 fluorescence units (FU)/mg protein). Advanced oxidation protein products (295±135 vs 83±65nmol/mg protein), carbonyl groups (3.68±1.44nmol/mg protein vs 2.03±0.23nmol/mg protein), kynurenine (7.71±0.1.67 vs 5.5±0.63 FU/mg protein) and N'-formylkynurenine (7.69±0.7 vs 4.97±0.59 FU/mg protein) levels were increased, while thioredoxin level was decreased in RRMS patients without treatment (5.03±2.18 vs 10.83±2.75ng/ml) with respect to control. The level of OS was higher in untreated RRMS patients and in SPMS patients treated with mitoxantrone than in patients treated with interferon.

Dimethyl sulfoxide induces oxidative stress in the yeast Saccharomyces cerevisiae

Dimethyl sulfoxide (DMSO) is used as a cryoprotectant for the preservation of cells, including yeast, and as a solvent for chemical compounds. We report that DMSO induces oxidative stress in the yeast. Saccharomyces cerevisiae wt strain EG-103 and its mutants Δsod1, Δsod2, and Δsod1 Δsod2 were used. Yeast were subjected to the action of 1-14% DMSO for 1 h at 28 °C. DMSO induced a concentration-dependent inhibition of yeast growth, the effect being more pronounced for mutants devoid of SOD (especially Δsod1 Δsod2). Cell viability was compromised. DMSO-concentration-dependent activity loss of succinate dehydrogenase, a FeS enzyme sensitive to oxidative stress, was observed. DMSO enhanced formation of reactive oxygen species, estimated with dihydroethidine in a concentration-dependent manner, the effect being again more pronounced in mutants devoid of superoxide dismutases. The content of cellular glutathione was increased with increasing DMSO concentrations, which may represent a compensatory response. Membrane fluidity, estimated by fluorescence polarization of DPH, was decreased by DMSO. These results demonstrate that DMSO, although generally considered to be antioxidant, induces oxidative stress in yeast cells.

Engineering erythrocytes as a novel carrier for the targeted delivery of the anticancer drug paclitaxel

Paclitaxel (PTX) is formulated in a mixture of Cremophor EL and dehydrated alcohol. The intravenous administration of this formula is associated with a risk of infection and hypersensitivity reactions. The presence of Cremophor EL as a pharmaceutical vehicle contributes to these effects. Therefore, in this study, we used human erythrocytes, instead of Cremophor, as a pharmaceutical vehicle. PTX was loaded into erythrocytes using the preswelling method. Analysis of the obtained data indicates that 148.8 μg of PTX was loaded/mL erythrocytes, with an entrapment efficiency of 46.36% and a cell recovery of 75.94%. Furthermore, we observed a significant increase in the mean cell volume values of the erythrocytes, whereas both the mean cell hemoglobin and the mean cell hemoglobin concentration decreased following the loading of PTX. The turbulence fragility index values for unloaded, sham-loaded and PTX-loaded erythrocytes were 3, 2, and 1 h, respectively. Additionally, the erythrocyte glutathione level decreased after PTX loading, whereas lipid peroxidation and protein oxidation increased. The release of PTX from loaded erythrocytes followed first-order kinetics, and about 81% of the loaded drug was released into the plasma after 48 h. The results of the present study revealed that PTX was loaded successfully into human erythrocytes with acceptable loading parameters and with some oxidative modification to the erythrocytes.

Protective effect of pravastatin against mercury induced vascular cells damage: erythrocytes as surrogate markers

In the present study we investigated the protective effect of pravastatin (PRV) against mercury-induced cellular damage. Human erythrocytes were incubated with PRV, HgCl(2) and HgCl(2) pretreated with PRV. Our results revealed that incubation of erythrocytes with HgCl(2) induces a significant increase the ratios of superoxide dismutase/glutathione peroxidase (SOD/GPx), superoxide dismutase/catalase (SOD/CAT), oxidized/reduced glutathione (GSSG/GSH), malondialdehyde(MDA) and protein carbonyl(PCO) by 60%, 50%, 333%, 400% and 208% respectively. Whereas, prior incubation of erythrocytes with PRV maintains these parameters at values similar to control cells. Furthermore, the level of nitrite in erythrocytes decreases significantly on treatment with HgCl(2), whereas it remains similar to the control when pretreated with PRV. Also, there was an increase in erythrocytes hemolysis when treated with HgCl(2), whereas it remained the like to the control when pretreated with PRV. In conclusion, PRV pretreatment maintained the erythrocytes oxidant/antioxidant balance and nitrite level during mercury exposure. Consequently, PRV pretreatment is worthy of further investigation in the reduction of the cardiovascular risk of mercury.

Detection of 3-chlorinated tyrosine residues in human cells by flow cytometry

Hypochlorite is a strong oxidant, generated under pathological conditions, with the potency to introduce chlorine atom into a number of molecules. 3-Chloro- and 3,5-dichlorotyrosine are documented to be generated by this oxidant and their elevated levels were found in many diseases. Thus, we decided to check the possibility of use of FITC-conjugated antibodies for flow cytometric detection of 3-chlorotyrosine residues in human cells (A549, MCF-7, HUVEC-ST) exposed to the action of hypochlorite. Additionally, we compared the effects of chlorohydrins and N-chloroamino acids as chlorine donors. Cell fixation and permeabilization was followed by incubation with rabbit polyclonal anti-3-chlorotyrosine primary antibody and subsequent staining with goat anti-rabbit FITC-labeled secondary antibody. For antibody isotypic control, normal rabbit IgG was employed. Hypochlorite appeared to be the most efficient from the chlorocompounds analyzed in chlorotyrozine generation in all cell lines. Statistically significant increase of fluorescence corresponding to the level of 3-chlorotyrosine residues was found in cells treated with hypochlorite even at non-toxic concentrations (<5μM). This effect was not observed in cells exposed to the action of chlorinated amino acids or chlorohydrins. The use of anti-3-chlorotyrosine antibodies in conjunction with fluorophore-conjugated secondary antibodies analysis allows for detection of 3-chlorotyrosine residues by flow cytometry in cells treated with low doses of hypochlorite.

Biochemically altered human erythrocytes as a carrier for targeted delivery of primaquine: an in vitro study

The aim of this study was to investigate human erythrocytes as a carrier for targeted drug delivery of primaquine (PQ). The process of PQ loading in human erythrocytes, as well as the effect of PQ loading on the oxidative status of erythrocytes, was also studied. At PQ concentrations of 2, 4, 6, and 8 mg/mL and an incubation time of 2 h, the ratios of the concentrations of PQ entrapped in erythrocytes to that in the incubation medium were 0.515, 0.688, 0.697 and 0.788, respectively. The maximal decline of erythrocyte reduced glutathione content was observed at 8 mg/mL of PQ compared with native erythrocytes p < 0.001. In contrast, malondialdehyde and protein carbonyl were significantly increased in cells loaded with PQ (p < 0.001). Furthermore, osmotic fragility of PQ carrier erythrocytes was increased in comparison with unloaded cells. Electron microscopy revealed spherocyte formation with PQ carrier erythrocytes. PQ-loaded cells showed sustained drug release over a 48 h period. Erythrocytes were loaded with PQ successfully, but there were some biochemical as well as physiological changes that resulted from the effect of PQ on the oxidative status of drug-loaded erythrocytes. These changes may result in favorable targeting of PQ-loaded cells to reticulo-endothelial organs. The relative impact of these changes remains to be explored in ongoing animal studies.

Ascorbate and deferoxamine administration after chlorine exposure decrease mortality and lung injury in mice

Chlorine (Cl(2)) gas exposure poses an environmental and occupational hazard that frequently results in acute lung injury. There is no effective treatment. We assessed the efficacy of antioxidants, administered after exposure, in decreasing mortality and lung injury in C57BL/6 mice exposed to 600 ppm of Cl(2) for 45 minutes and returned to room air. Ascorbate and deferoxamine were administered intramuscularly every 12 hours and by nose-only inhalation every 24 hours for 3 days starting after 1 hour after exposure. Control mice were exposed to Cl(2) and treated with vehicle (saline or water). Mortality was reduced fourfold in the treatment group compared with the control group (22 versus 78%; P = 0.007). Surviving animals in the treatment group had significantly lower protein concentrations, cell counts, and epithelial cells in their bronchoalveolar lavage (BAL). Lung tissue ascorbate correlated inversely with BAL protein as well as with the number of neutrophils and epithelial cells. In addition, lipid peroxidation was reduced threefold in the BAL of mice treated with ascorbate and deferoxamine when compared with the control group. Administration of ascorbate and deferoxamine reduces mortality and decreases lung injury through reduction of alveolar-capillary permeability, inflammation, and epithelial sloughing and lipid peroxidation.

Pravastatin provides antioxidant activity and protection of erythrocytes loaded Primaquine

Loading erythrocytes with Primaquine (PQ) is advantageous. However, PQ produces damage to erythrocytes through free radicals production. Statins have antioxidant action and are involved in protective effect against situation of oxidative stress. Thus the protective effect of pravastatin (PS) against PQ induced oxidative damage to human erythrocytes was investigated in the current studies upon loading to erythrocytes.The erythrocytes were classified into; control erythrocytes, erythrocytes incubated with either 2 mM of PS or 2 mM of PQ, and erythrocytes incubated with combination of PS plus PQ. After incubation for 30 min, the effect of the drugs on erythrocytes hemolysis as well as some biomarkers of oxidative stress (none protein thiols, protein carbonyl, thiobarbituric acid reactive substance) were investigated.Our results revealed that PS maintains these biomarkers at values similar to that of control ones. On the other hand, PQ cause significant increases of protein carbonyl by 115% and thiobarbituric acid reactive substance by 225% while non-protein thiols were significantly decreased by 112 % compared with control erythrocytes. PS pre-incubation before PQ exerts marked reduction of these markers in comparison with PQ alone. Moreover, at NaCl concentrations between 0.4% and 0.8%, PQ causes significant increase of Red Blood Cells (RBCs) hemolysis in comparison with the other groups (P<0. 001). Scanning electron micrograph indicates spherocytes formation by PQ incubation, but in the other groups the discocyte shape of erythrocytes was preserved.The reduction of protein oxidation and lipids peroxidation by PS is related to antioxidants effect of this statin. Preservation of erythrocytes fragility and morphology by PS are related to its free radicals scavenging effect. It is concluded that pravastatin has protective effect against erythrocytes dysfunction related any situations associated with increased oxidative stress, especially when loaded with PQ.

Mechanisms and modification of chlorine-induced lung injury in animals

Chlorine (Cl(2)) is a reactive oxidant gas used extensively in industrial processes. Exposure of both humans and animals to high concentrations of Cl(2) results in acute lung injury, which may resolve spontaneously or progress to acute respiratory failure. Injury to airway and alveolar epithelium may result from chemical reactions of Cl(2), from HOCl (the hydrolysis product of Cl(2)), and/or from the various reaction products, such as chloramines, that are formed from the reactions of these chlorinating species with biological molecules. Subsequent reactions may initiate self-propagating reactions and induce the production of inflammatory mediators compounding injury to pulmonary surfactant, ion channels, and components of lung epithelial and airway cells. Low-molecular-weight antioxidants, such as ascorbate, glutathione, and urate, present in the lung epithelial lining fluid and tissue, remove Cl(2) and HOCl and thus decrease injury to critical target biological targets. However, levels of lung antioxidants of animals exposed to Cl(2) in concentrations likely to be encountered in the vicinity of industrial accidents decrease rapidly and irreversibly. Our measurements show that prophylactic administration of a mixture containing ascorbate and desferal N-acetyl-cysteine, a precursor of reduced glutathione, prevents Cl(2)-induced injury to the alveolar epithelium of rats exposed to Cl(2). The clinical challenge is to deliver sufficient quantities of antioxidants noninvasively, after Cl(2) exposure, to decrease morbidity and mortality.

Lipid peroxyl radicals mediate tyrosine dimerization and nitration in membranes

Protein tyrosine dimerization and nitration by biologically relevant oxidants usually depend on the intermediate formation of tyrosyl radical ((*)Tyr). In the case of tyrosine oxidation in proteins associated with hydrophobic biocompartments, the participation of unsaturated fatty acids in the process must be considered since they typically constitute preferential targets for the initial oxidative attack. Thus, we postulate that lipid-derived radicals mediate the one-electron oxidation of tyrosine to (*)Tyr, which can afterward react with another (*)Tyr or with nitrogen dioxide ((*)NO(2)) to yield 3,3'-dityrosine or 3-nitrotyrosine within the hydrophobic structure, respectively. To test this hypothesis, we have studied tyrosine oxidation in saturated and unsaturated fatty acid-containing phosphatidylcholine (PC) liposomes with an incorporated hydrophobic tyrosine analogue BTBE (N-t-BOC l-tyrosine tert-butyl ester) and its relationship with lipid peroxidation promoted by three oxidation systems, namely, peroxynitrite, hemin, and 2,2'-azobis (2-amidinopropane) hydrochloride. In all cases, significant tyrosine (BTBE) oxidation was seen in unsaturated PC liposomes, in a way that was largely decreased at low oxygen concentrations. Tyrosine oxidation levels paralleled those of lipid peroxidation (i.e., malondialdehyde and lipid hydroperoxides), lipid-derived radicals and BTBE phenoxyl radicals were simultaneously detected by electron spin resonance spin trapping, supporting an association between the two processes. Indeed, alpha-tocopherol, a known reactant with lipid peroxyl radicals (LOO(*)), inhibited both tyrosine oxidation and lipid peroxidation induced by all three oxidation systems. Moreover, oxidant-stimulated liposomal oxygen consumption was dose dependently inhibited by BTBE but not by its phenylalanine analogue, BPBE (N-t-BOC l-phenylalanine tert-butyl ester), providing direct evidence for the reaction between LOO(*) and the phenol moiety in BTBE, with an estimated second-order rate constant of 4.8 x 10(3) M(-1) s(-1). In summary, the data presented herein demonstrate that LOO(*) mediates tyrosine oxidation processes in hydrophobic biocompartments and provide a new mechanistic insight to understand protein oxidation and nitration in lipoproteins and biomembranes.