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Protein Thiols (protein + thiol)
Selected AbstractsOestradiol Protects Against the Harmful Effects of Fluoride More by Increasing Thiol Group Levels than Scavenging Hydroxyl RadicalsBASIC AND CLINICAL PHARMACOLOGY & TOXICOLOGY, Issue 6 2009Anna Dlugosz Interactions between xenobiotics and oestrogens need to be investigated, especially as many chemicals interact with the oestrogen receptor. It is still unknown whether free radical-generating xenobiotics can influence the antioxidative ability of oestradiol (E2). In an in vitro examination of human placental mitochondria, thiobarbituric active reagent species (TBARS), hydroxyl radical (,OH) generation and protein thiol (,SH) groups were detected. 17,-E2 was examined in physiological (0.15,0.73 nM) and experimental (1,10 µM) concentrations and sodium fluoride (NaF) in concentrations of 6,24 µM. E2 in all the concentrations significantly decreased lipid peroxidation measured as the TBARS level, in contrast to NaF, which increased lipid peroxidation. Lipid peroxidation induced by NaF was decreased by E2. The influence of E2 on ,OH generation was not very significant and depended on the E2 concentration. The main mechanism of E2 protection in NaF exposure appeared to be connected with the influence of E2 on thiol group levels, not ,OH scavenging ability. The E2 in concentrations 0.44,0.73 nM and 1,10 µM significantly increased the levels of ,SH groups, in contrast to NaF, which significantly decreased them. E2 at every concentration reversed the harmful effects of NaF on ,SH group levels. No unfavourable interactions in the influence of E2 and NaF on TBARS production, ,OH generation, or ,SH group levels were observed. The results suggest that postmenopausal women could be more sensitive to NaF-initiated oxidative stress. [source] Effects of antioxidant stobadine on protein carbonylation, advanced oxidation protein products and reductive capacity of liver in streptozotocin-diabetic rats: Role of oxidative/nitrosative stressBIOFACTORS, Issue 3 2007Ahmet Cumao Background: Increased oxidative/nitrosative stress is important in the pathogenesis of diabetic complications, and the protective effects of antioxidants are a topic of intense research. The purpose of this study was to investigate whether a pyridoindole antioxidant stobadine (STB) have a protective effect on tissue oxidative protein damage represented by the parameters such as protein carbonylation (PC), protein thiol (P-SH), total thiol (T-SH) and non-protein thiol (Np-SH), nitrotyrosine (3-NT), and advanced oxidation protein products (AOPP) in streptozotocin-diabetic rats. Methods: Diabetes was induced in male Wistar rats by intraperitonal injection of streptozotocin (55 mg/kg). Some of the non-diabetic (control) and diabetic rats treated with STB (24.7 mg/kg/day) during 16 weeks, and the effects on blood glucose, PC, AOPP, 3-NT, P-SH, T-SH and Np-SH were studied. Biomarkers were assayed by enzyme-linked immunosorbent assay (ELISA) or by colorimetric methods. Results: Administration of stobadine to diabetic animals lowered elevated blood glucose levels by ,16% relative to untreated diabetic rats. Although stobadine decreased blood glucose, poor glycemic control was maintained in stobadine treated diabetic rats during the treatment period. Biochemical analyses of liver proteins showed significant diminution of sulfhydryl groups, P-SH, T-SH, Np-SH, and elevation of carbonyl groups in diabetic animals in comparison to healthy controls. As a biomarker of nitrosative stress, 3-NT levels did not significantly change by diabetes induction or by stobadine treatment when compared to control animals. However, the treatment with stobadine resulted in a significant decrease in PC, AOPP levels and normalized P-SH, T-SH, Np-SH groups in liver of diabetic animals. [source] Alterations of plasma antioxidants and mitochondrial DNA mutation in hair follicles of smokersENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 3 2002Chin-San Liu Abstract The effects of long-term smoking on mitochondrial DNA (mtDNA) deletions in hair follicles were investigated in subjects with different antioxidant capacity. Twenty-two male smokers with a smoking index of greater than 5 pack-years and without any known systemic diseases were recruited for this study. Forty healthy nonsmoking males were included as controls. We found that the concentrations of ascorbate and ,-tocopherol and the activities of glutathione S -transferase (GST) and glutathione peroxidase in blood plasma were significantly decreased in smokers. The levels of glutathione and protein thiols in whole blood and the incidence of a 4,977 bp deletion of mtDNA (dmtDNA) in hair follicles were significantly increased in smokers. A significantly higher incidence of the 4,977 bp dmtDNA was found in smokers with plasma GST activity less than 5.66 U/l (OR = 7.2, P = 0.020). Using multiple covariate ANOVA and logistic regression, we found that age and low plasma GST activity were the only two risk factors for the 4,977 bp dmtDNA. These results suggest that smoking depletes antioxidants and causes mtDNA deletions and that plasma GST may play an important role in the preservation of the mitochondrial genome in tissue cells of smokers. Environ. Mol. Mutagen. 40:168,174, 2002. © 2002 Wiley-Liss, Inc. [source] Erythrocytes as targets for gamma-glutamyltranspeptidase initiated pro-oxidant reactionEUROPEAN JOURNAL OF HAEMATOLOGY, Issue 5 2002Hayet Aberkane Abstract: Gamma-glutamyltranspeptidase (GGT) is a well known cell plasma membrane and serum circulating enzyme. In clinical chemistry, GGT is used as a marker of alcohol consumption and drug uptake. Serum GGT activity varies in hepatobiliary diseases and cancer. This enzyme is involved in glutathione (GSH) metabolism, which is generally associated with antioxidant properties. However, in recent years, findings from our group and from others showed that GGT-catalysed extracellular metabolism of GSH leads, in the presence of iron, to the generation of reactive oxygen species (ROS). It was demonstrated that those highly reactive species oxidise lipids, cell surface protein thiols or activate transcriptional factors such as Nuclear Factor ,B (NF,B). The objective of the present work is to determine whether the red blood cells are targets for plasma GGT-initiated pro-oxidant reaction. The results obtained demonstrate that the GGT/GSH/iron system oxidises isolated erythrocyte membranes. A significant release of haemoglobin and a decrease of erythrocyte deformability are also observed. In addition, in vivo studies showed a relationship between plasma GGT activity and erythrocyte deformability in 20 studied subjects. In conclusion, GGT-mediated ROS production is able to oxidise erythrocytes and thus disturbs their functions. [source] Induction of hepatotoxicity by sanguinarine is associated with oxidation of protein thiols and disturbance of mitochondrial respirationJOURNAL OF APPLIED TOXICOLOGY, Issue 8 2008Cheuk-Sing Choy Abstract Sanguinarine (SANG) has been suggested to be one of the principle constituents responsible for the toxicity of Argemone mexicana seed oil. In this study, we focused on the possible mechanism of SANG-induced hepatotoxicity. The serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), and lactate dehydrogenase (LDH) activities, hepatic vacuolization, lipid accumulation and lipid peroxidation of the liver were increased, and triglyceride (TG) was decreased in SANG-treated mice (10 mg kg,1 i.p.), indicating damage to the liver. SANG induced cell death and DNA fragmentation, in a concentration- (0,30 µm) and time-dependent (0,24 h) manner, and the cytotoxicity of SANG (15 µm) was accompanied by an increase in reactive oxygen species and a lessening in protein thiol content; these outcomes were reversed by glutathione, N -acetyl- l -cysteine and 1,4-dithiothretol, and slightly improved by other antioxidants in hepatocytes. SANG can affect the function of mitochondria, leading to the depletion of the mitochondrial membrane potential and adenosine 5,-triphosphate content of hepatocytes. SANG caused an uncoupling effect of the respiratory chain at lower concentrations, but inhibited the respiratory chain at higher concentrations in mitochondria isolated from rat liver. In conclusion, the data suggest that SANG is a liver toxin that induces cytotoxicity in liver cells, possibly through oxidation of protein thiols, resulting in oxidative stress on the cells and disturbance of mitochondrial function. Copyright © 2008 John Wiley & Sons, Ltd. [source] Lipid,protein modifications during ascorbate-Fe2+ peroxidation of photoreceptor membranes: protective effect of melatoninJOURNAL OF PINEAL RESEARCH, Issue 3 2006Margarita H. Guajardo Abstract:, The rod outer segment (ROSg) membranes are essentially lipoprotein complexes. Rhodopsin, the major integral protein of ROSg, is surrounded by phospholipids highly enriched in docosahexaenoic acid (22:6 n3). This fluid environment plays an important role for conformational changes after photo-activation. Thus, ROSg membranes are highly susceptible to oxidative damage. Melatonin synthesized in the pineal gland, retina and other tissues is a free radical scavenger. The principal aim of this work was to study the changes in the ROSg membranes isolated from bovine retina submitted to nonenzymatic lipid peroxidation (ascorbate-Fe2+ induced), during different time intervals (0,180 min). Oxidative stress was monitored by increase in the chemiluminescence and fatty acid alterations. In addition we studied the in vitro protective effect of 5 mm melatonin. The total cpm originated from light emission (chemiluminescence) was found to be lower in those membranes incubated in the presence of melatonin. The docosahexaenoic acid content decreased considerably when the membranes were exposed to oxidative damage. This reduction was from 35.5 ± 2.9% in the native membranes to 12.65 ± 1.86% in those peroxidized during 180 min. In the presence of 5 mm melatonin we observed a content preservation of 22:6 n3 (23.85 ± 2.77%) at the same time of peroxidation. Simultaneously the alterations of membrane proteins under oxidative stress were studied using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Loss of protein sulfhydryl groups and increased incorporation of carbonyl groups were utilized as biomarkers of protein oxidation. In membranes exposed to Fe2+ -ascorbate, we observed a decrease of protein thiols from 50.9 ± 3.38 in native membranes to 1.72 ± 2.81 nmol/mg of protein after 180 min of lipid peroxidation associated with increased incorporation of carbonyl groups into proteins from 7.20 ± 2.50 to 12.50 ± 1.12 nmol/mg of protein. In the SDS-PAGE we observed a decrease in the content of all the proteins, mainly rhodopsin, as a consequence of peroxidation. Melatonin, prevent both lipid peroxidation and protein oxidation. [source] Prediction of reversibly oxidized protein cysteine thiols using protein structure propertiesPROTEIN SCIENCE, Issue 3 2008Ricardo Sanchez Abstract Protein cysteine thiols can be divided into four groups based on their reactivities: those that form permanent structural disulfide bonds, those that coordinate with metals, those that remain in the reduced state, and those that are susceptible to reversible oxidation. Physicochemical parameters of oxidation-susceptible protein thiols were organized into a database named the Balanced Oxidation Susceptible Cysteine Thiol Database (BALOSCTdb). BALOSCTdb contains 161 cysteine thiols that undergo reversible oxidation and 161 cysteine thiols that are not susceptible to oxidation. Each cysteine was represented by a set of 12 parameters, one of which was a label (1/0) to indicate whether its thiol moiety is susceptible to oxidation. A computer program (the C4.5 decision tree classifier re-implemented as the J48 classifier) segregated cysteines into oxidation-susceptible and oxidation-non-susceptible classes. The classifier selected three parameters critical for prediction of thiol oxidation susceptibility: (1) distance to the nearest cysteine sulfur atom, (2) solvent accessibility, and (3) pKa. The classifier was optimized to correctly predict 136 of the 161 cysteine thiols susceptible to oxidation. Leave-one-out cross-validation analysis showed that the percent of correctly classified cysteines was 80.1% and that 16.1% of the oxidation-susceptible cysteine thiols were incorrectly classified. The algorithm developed from these parameters, named the Cysteine Oxidation Prediction Algorithm (COPA), is presented here. COPA prediction of oxidation-susceptible sites can be utilized to locate protein cysteines susceptible to redox-mediated regulation and identify possible enzyme catalytic sites with reactive cysteine thiols. [source] EFFICACY OF SARGASSUM POLYCYSTUM (PHAEOPHYCEAE) SULPHATED POLYSACCHARIDE AGAINST PARACETAMOL-INDUCED DNA FRAGMENTATION AND MODULATION OF MEMBRANE-BOUND PHOSPHATASES DURING TOXIC HEPATITISCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 3 2007HB Raghavendran SUMMARY 1The aim of the present study was to assess the protective effect of Sargassum polycystum (sulphated polysaccharide) extract against paracetamol-induced DNA strand breaks and modulation of membrane-bound phosphatases, protein thiols and inorganic cations during toxic hepatitis. 2Seaweed extract (200 mg/kg per day for 21 days) was administered to male Wistar rats against paracetamol challenge. Serum and liver tissues were used to assess levels of ATPase, protein thiols and inorganic cations using atomic absorption spectroscopy. The fragmentation of DNA was assessed by agarose gel electrophoresis. 3Paracetamol induced intracellular stress, accompanied by changes in the structural and functional characteristics of liver cell membranes, which affected DNA integrity, membrane-bound ATPase and inorganic cations homeostasis. Rats intoxicated with paracetamol (800 mg/kg, i.p.) showed significant impairment in activities of total ATPase, Mg2+ -ATPase, Ca+ -ATPase and Na+/K+ -ATPase, with concomitant changes in the levels of tissue protein thiols and inorganic cations, such as Na+, K+ and Ca2+. These changes were prevented in animals pretreated with S. polycystum extract, which indicates that S. polycystum supplementation could exert some protective effect against paracetamol-induced toxic hepatitis in rats. 4The protective effect of the seaweed extract may be due to the presence of sulphated compounds that have free radical-scavenging activity. [source] | ||||||||||||||||