DNA damage by carbonyl stress in human skin cells

Reactive carbonyl species (RCS) are potent mediators of cellular carbonyl stress originating from endogenous chemical processes such as lipid peroxidation and glycation. Skin deterioration as observed in photoaging and diabetes has been linked to accumulative protein damage from glycation, but the effects of carbonyl stress on skin cell genomic integrity are ill defined. In this study, the genotoxic effects of acute carbonyl stress on HaCaT keratinocytes and CF3 fibroblasts were assessed. Administration of the alpha-dicarbonyl compounds glyoxal and methylglyoxal as physiologically relevant RCS inhibited skin cell proliferation, led to intra-cellular protein glycation as evidenced by the accumulation of N(epsilon)-(carboxymethyl)-L-lysine (CML) in histones, and caused extensive DNA strand cleavage as assessed by the comet assay. These effects were prevented by treatment with the carbonyl scavenger D-penicillamine. Both glyoxal and methylglyoxal damaged DNA in intact cells. Glyoxal caused DNA strand breaks while methylglyoxal produced extensive DNA-protein cross-linking as evidenced by pronounced nuclear condensation and total suppression of comet formation. Glycation by glyoxal and methylglyoxal resulted in histone cross-linking in vitro and induced oxygen-dependent cleavage of plasmid DNA, which was partly suppressed by the hydroxyl scavenger mannitol. We suggest that a chemical mechanism of cellular DNA damage by carbonyl stress occurs in which histone glycoxidation is followed by reactive oxygen induced DNA stand breaks. The genotoxic potential of RCS in cultured skin cells and its suppression by a carbonyl scavenger as described in this study have implications for skin damage and carcinogenesis and its prevention by agents selective for carbonyl stress.     

Ex vivo detection of histone H1 modified with advanced glycation end products

A number of oxidative stress agents cause DNA and protein damage, which may compromise genomic integrity. Whereas oxidant-induced DNA damage has been extensively studied, much less is known concerning the occurrence and fate of nuclear protein damage, particularly of proteins involved in the regulation and maintenance of chromatin structure. Protein damage may be caused by the formation of reactive carbonyl species such as glyoxal, which forms after lipid peroxide degradation. It may also result from degradation of early protein glycation adducts and from methylglyoxal, formed in the process of glycolytic intermediate degradation. Major adducts indicative of protein damage include the advanced glycation end product (AGE) carboxymethyllysine (CML) and argpyrimidine protein adducts. Thus, the formation of CML and argpyrimidine protein adducts represents potential biomarkers for nuclear protein damage deriving from a variety of sources. The purpose of this study was to identify and quantify AGE adducts formed in vivo in a nuclear protein, specifically histone H1, using CML and argpyrimidine as biomarkers. Histone H1 was isolated from calf thymus collected immediately after slaughter under conditions designed to minimize AGE formation before isolation. Using antibodies directed against oxidative protein adducts, we identified CML, argpyrimidine, and protein crosslinks present in the freshly isolated histone H1. Detailed mass spectroscopy analysis of histone H1 revealed the presence of two specific lysine residues modified by CML adducts. Our results strongly suggest that glycation of important nuclear protein targets such as histone H1 occurs in vivo and that these oxidative changes may alter chromatin structure, ultimately contributing to chronic changes associated with aging and diseases such as diabetes.     

Etheno DNA-base adducts from endogenous reactive species

Promutagenic etheno (epsilon) adducts in DNA are generated through reactions of DNA bases with LPO products derived from endogenous sources or from exposure to several xenobiotics. The availability of sensitive methods has made it possible to detect three epsilon-adducts in vivo, namely epsilon dA, epsilon dC and N2,3-epsilon dG. One probable endogenous source for the formation of these adducts arises from LPO products such as trans-4-hydroxy-2-nonenal (HNE), resulting in highly variable background epsilon-adduct levels in tissues from unexposed humans and rodents. The range of background levels of epsilon dAx10-8dA detected inhuman tissues was <0.05 to 25 and in rodent tissues 0.02 to 10; the corresponding values for epsilon dCx10-8dC were 0.01 to 11 and 0.03 to 24, respectively. Part of this variability may be associated with different dietary intake of antioxidants and/or omega-6 PUFAs which oxidize readily to form 4-hydroxyalkenals, as epsilon dA and epsilon dC levels in WBC-DNA of female volunteers on a high omega-6 PUFA diet were drastically elevated. Increased levels of etheno adducts were also found in the liver of cancer-prone patients suffering from hereditary metal storage diseases, i.e., Wilson's disease (WD) and primary hemochromatosis (PH) as well as in Long-Evans Cinnamon rats, an animal model for WD. Increased metal-induced oxidative stress and LPO-derive epsilon-adducts, along with other oxidative damage, may trigger this hereditary liver cancer. Epsilon-Adducts could hence be explored as biomarkers (i) to ascertain the role of LPO mediated DNA damage in human cancers associated with oxidative stress imposed by certain lifestyle patterns, chronic infections and inflammations, and (ii) to verify the reduction of these epsilon-adducts by cancer chemopreventive agents. This article summarizes recent results on the formation, occurrence and possible role of epsilon-DNA adducts in carcinogenesis and mutagenesis.     

Endogenous mitochondrial oxidative stress in MnSOD-deficient mouse embryonic fibroblasts promotes mitochondrial DNA glycation

The accumulation of somatic mutations in mitochondrial DNA (mtDNA) induced by reactive oxygen species (ROS) is regarded as a major contributor to aging and age-related degenerative diseases. ROS have also been shown to facilitate the formation of certain advanced glycation end-products (AGEs) in proteins and DNA and N(2)-carboxyethyl-2'-deoxyguanosine (CEdG) has been identified as a major DNA-bound AGE. Therefore, the influence of mitochondrial ROS on the glycation of mtDNA was investigated in primary embryonic fibroblasts derived from mutant mice (Sod2(-/+)) deficient in the mitochondrial antioxidant enzyme manganese superoxide dismutase. In Sod2(-/+) fibroblasts vs wild-type fibroblasts, the CEdG content of mtDNA was increased from 1.90 ± 1.39 to 17.14 ± 6.60 pg/μg DNA (p<0.001). On the other hand, the CEdG content of nuclear DNA did not differ between Sod2(+/+) and Sod2(-/+) cells. Similarly, cytosolic proteins did not show any difference in advanced glycation end-products or protein carbonyl contents between Sod2(+/+) and Sod2(-/+). Taken together, the data suggest that mitochondrial oxidative stress specifically promotes glycation of mtDNA and does not affect nuclear DNA or cytosolic proteins. Because DNA glycation can change DNA integrity and gene functions, glycation of mtDNA may play an important role in the decline of mitochondrial functions.     

Aging increases Nepsilon-(carboxymethyl)lysine and caloric restriction decreases Nepsilon-(carboxyethyl)lysine and Nepsilon-(malondialdehyde)lysine in rat heart mitochondrial proteins

The present investigation studies the effect of aging, short-term and long-term caloric restriction on four different markers of oxidative, glycoxidative or lipoxidative damage to heart mitochondrial proteins: protein carbonyls (measured by ELISA); N epsilon -(carboxyethyl)lysine (CEL), N epsilon -(carboxymethyl)lysine (CML), and N epsilon -(malondialdehyde)lysine (MDA-lys) measured by gas chromatography/mass spectrometry. Aging increased the steady state level of CML in rat heart mitochondria without changing the levels of the other three markers of protein damage. Short-term caloric restriction (six weeks) did not change any of the parameters measured. However, long-term (one year) caloric restriction decreased CEL and MDA-lys in heart mitochondria and did not change protein carbonyls and CML levels. The decrease in MDA-lys was not due to changes in the sensitivity of mitochondrial lipids to peroxidation since the measurements of the fatty acid composition showed that the total number of fatty acid double bonds was not changed by caloric restriction. The decrease in CEL and MDA-lys in caloric restriction agrees with the previously and consistently described finding that caloric restriction agrees with the previously and consistently described finding that caloric restriction lowers the rate of generation of reactive oxygen species (ROS) in rodent heart mitochondria, although in the case of CEL a caloric restriction-induced lowering of glycaemia can also be involved. The CEL and MDA-lys results support the notion that caloric restriction decreases oxidative stress-derived damage to heart mitochondrial proteins.     

Aging Increases N epsilon -(Carboxymethyl)lysine and Caloric Restriction Decreases N epsilon -(Carboxyethyl)lysine and N epsilon -(Malondialdehyde)lysine in Rat Heart Mitochondrial Proteins

The present investigation studies the effect of aging, short-term and long-term caloric restriction on four different markers of oxidative, glycoxidative or lipoxidative damage to heart mitochondrial proteins: protein carbonyls (measured by ELISA); N epsilon -(carboxyethyl)lysine (CEL), N epsilon -(carboxymethyl)lysine (CML), and N epsilon -(malondialdehyde)lysine (MDA-lys) measured by gas chromatography/mass spectrometry. Aging increased the steady state level of CML in rat heart mitochondria without changing the levels of the other three markers of protein damage. Short-term caloric restriction (six weeks) did not change any of the parameters measured. However, long-term (one year) caloric restriction decreased CEL and MDA-lys in heart mitochondria and did not change protein carbonyls and CML levels. The decrease in MDA-lys was not due to changes in the sensitivity of mitochondrial lipids to peroxidation since the measurements of the fatty acid composition showed that the total number of fatty acid double bonds was not changed by caloric restriction. The decrease in CEL and MDA-lys in caloric restriction agrees with the previously and consistently described finding that caloric restriction agrees with the previously and consistently described finding that caloric restriction lowers the rate of generation of reactive oxygen species (ROS) in rodent heart mitochondria, although in the case of CEL a caloric restriction-induced lowering of glycaemia can also be involved. The CEL and MDA-lys results support the notion that caloric restriction decreases oxidative stress-derived damage to heart mitochondrial proteins.     

Chronically and acutely exercised rats: biomarkers of oxidative stress and endogenous antioxidants.

The responses to oxidative stress induced by chronic exercise (8-wk treadmill running) or acute exercise (treadmill running to exhaustion) were investigated in the brain, liver, heart, kidney, and muscles of rats. Various biomarkers of oxidative stress were measured, namely, lipid peroxidation [malondialdehyde (MDA)], protein oxidation (protein carbonyl levels and glutamine synthetase activity), oxidative DNA damage (8-hydroxy-2'-deoxyguanosine), and endogenous antioxidants (ascorbic acid, alpha-tocopherol, glutathione, ubiquinone, ubiquinol, and cysteine). The predominant changes are in MDA, ascorbic acid, glutathione, cysteine, and cystine. The mitochondrial fraction of brain and liver showed oxidative changes as assayed by MDA similar to those of the tissue homogenate. Our results show that the responses of the brain to oxidative stress by acute or chronic exercise are quite different from those in the liver, heart, fast muscle, and slow muscle; oxidative stress by acute or chronic exercise elicits different responses depending on the organ tissue type and its endogenous antioxidant levels.     

Mitochondrial DNA Damage and Dysfunction,and Oxidative Stress Are Associated with Endoplasmic Reticulum Stress,Protein Degradation and Apoptosis in High Fat Diet-Induced Insulin Resistance Mice

Background

Recent studies showed a link between a high fat diet (HFD)-induced obesity and lipid accumulation in non-adipose tissues, such as skeletal muscle and liver, and insulin resistance (IR). Although the mechanisms responsible for IR in those tissues are different, oxidative stress and mitochondrial dysfunction have been implicated in the disease process. We tested the hypothesis that HFD induced mitochondrial DNA (mtDNA) damage and that this damage is associated with mitochondrial dysfunction, oxidative stress, and induction of markers of endoplasmic reticulum (ER) stress, protein degradation and apoptosis in skeletal muscle and liver in a mouse model of obesity-induced IR.

Methodology/Principal Findings

C57BL/6J male mice were fed either a HFD (60% fat) or normal chow (NC) (10% fat) for 16 weeks. We found that HFD-induced IR correlated with increased mtDNA damage, mitochondrial dysfunction and markers of oxidative stress in skeletal muscle and liver. Also, a HFD causes a change in the expression level of DNA repair enzymes in both nuclei and mitochondria in skeletal muscle and liver. Furthermore, a HFD leads to activation of ER stress, protein degradation and apoptosis in skeletal muscle and liver, and significantly reduced the content of two major proteins involved in insulin signaling, Akt and IRS-1 in skeletal muscle, and Akt in liver. Basal p-Akt level was not significantly influenced by HFD feeding in skeletal muscle and liver.

Conclusions/Significance

This study provides new evidence that HFD-induced mtDNA damage correlates with mitochondrial dysfunction and increased oxidative stress in skeletal muscle and liver, which is associated with the induction of markers of ER stress, protein degradation and apoptosis.     

Propagation of protein glycation damage involves modification of tryptophan residues via reactive oxygen species: inhibition by pyridoxamine

Nonenzymatic modification of proteins is one of the key pathogenic factors in diabetic complications. Uncovering the mechanisms of protein damage caused by glucose is fundamental to understanding this pathogenesis and in the development of new therapies. We investigated whether the mechanism involving reactive oxygen species can propagate protein damage in glycation reactions beyond the classical modifications of lysine and arginine residues. We have demonstrated that glucose can cause specific oxidative modification of tryptophan residues in lysozyme and inhibit lysozyme activity. Furthermore, modification of tryptophan residues was also induced by purified albumin-Amadori, a ribose-derived model glycation intermediate. The AGE inhibitor pyridoxamine (PM) prevented the tryptophan modification, whereas another AGE inhibitor and strong carbonyl scavenger, aminoguanidine, was ineffective. PM specifically inhibited generation of hydroxyl radical from albumin-Amadori and protected tryptophan from oxidation by hydroxyl radical species. We conclude that oxidative degradation of either glucose or the protein-Amadori intermediate causes oxidative modification of protein tryptophan residues via hydroxyl radical and can affect protein function under physiologically relevant conditions. This oxidative stress-induced structural and functional protein damage can be ameliorated by PM via sequestration of catalytic metal ions and scavenging of hydroxyl radical, a mechanism that may contribute to the reported therapeutic effects of PM in the complications of diabetes.     

Quantitative measurement of specific biomarkers for protein oxidation, nitration and glycation in Arabidopsis leaves

Higher plants are continually exposed to reactive oxygen and nitrogen species during their lives. Together with glucose and reactive dicarbonyls, these can modify proteins spontaneously, leading to protein oxidation, nitration and glycation. These reactions have the potential to damage proteins and have an impact on physiological processes. The levels of protein oxidation, nitration and glycation adducts were assayed, using liquid chromatography coupled with tandem mass spectrometry, in total leaf extracts over a diurnal cycle and when exposed to conditions that promote oxidative stress. Changes in the levels of oxidation, glycation and nitration adducts were found between the light and dark phases under non-stress conditions. A comparison between wild-type plants and a mutant lacking peptide methionine sulfoxide reductase ( pmsr2-1 ) showed increased protein oxidation, nitration and glycation of specific amino acid residues during darkness in pmsr2-1 . Short-term excess light exposure, which promoted oxidative stress, led to increased protein glycation, specifically by glyoxal. This suggested that any increased oxidative damage to proteins was within the repair capacity of the plant. The methods developed here provide the means to simultaneously detect a range of protein oxidation, nitration and glycation adducts within a single sample. Thus, these methods identify a range of biomarkers to monitor a number of distinct biochemical processes that have an impact on the proteome and therefore the physiological state of the plant.     

Differential effects of α-tocopherol and N-acetyl-cysteine on advanced glycation end product-induced oxidative damage and neurite degeneration in SH-SY5Y cells

Advanced glycation end products (AGEs) result from non-enzymatic glycation of proteins and cause cellular oxidative stress in a nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-dependent manner. Due to these effects, AGEs are implicated as a causal factor in diabetic complications. Several antioxidants, including vitamin E, improve cell viability and diminish markers of oxidative damage in cells exposed to AGEs. However, vitamin E has been studied in cell culture systems with primary focus on apoptosis and lipid peroxidation, while its influences on AGE-induced protein and DNA oxidation, intracellular antioxidant status and cell morphology remain largely unknown. Here, we verify the suppression of AGE-induced cell death and lipid peroxidation by 200μM α-tocopherol in SH-SY5Y cells. We report the partial inhibition of DNA oxidation and a decrease in protein carbonyl formation by α-tocopherol with no effects on intracellular GSH concentrations. We observed that 2mM N-acetyl cysteine (NAC) also had a suppressive effect on DNA and protein oxidation, but unlike α-tocopherol, it caused a marked increase in intracellular GSH. Finally, we compared the ability of both antioxidants to maintain neurites in SH-SY5Y cells and found that α-tocopherol had no effect on neurite loss due to AGEs, while NAC fully maintained cell morphology. Thus, while α-tocopherol suppressed AGE-induced macromolecule damage, it was ineffective against neurite degeneration. These results may implicate thiol oxidation and maintenance as a major regulator of neurite degeneration in this model.     

Oxidative damage to proteins and DNA in rats exposed to cadmium and/or ethanol

The study was aimed to estimate whether rat's exposure to cadmium (Cd; 50 mg/l in drinking water for 12 weeks) and/or ethanol (EtOH; 5 g/kg b.wt./24 h p.o. for 12 weeks), noted by us to induce oxidative stress and stimulate lipid peroxidation, can cause oxidative damage to proteins and DNA, and whether and to what extent the effects of co-exposure differ from those observed under the treatment with each substance alone. Protein carbonyl groups (PC) and protein thiol groups (PSH) in the serum, liver and kidney, as markers of oxidative protein damage, and 8-hydroxy-2′-deoxyguanosine (8-OHdG) in the serum, as a marker of DNA oxidation, were determined. The exposure to Cd or/and EtOH led to oxidative protein damage (increased PC and decreased PSH concentrations in the serum and/or liver), and to DNA oxidation (increased 8-OHdG concentration in the serum). The effects were more advanced at the co-exposure than at the treatment with each substance alone. The more serious damage to proteins and DNA at the co-exposure to Cd and EtOH seems to be the effect of independent action of both xenobiotics. The results of the present paper together with our recent findings in the same rats seem to indicate that at co-exposure to Cd and EtOH proteins and DNA may be more vulnerable to oxidation than lipids. The paper is the first report suggesting that excessive EtOH consumption during exposure to Cd may increase the risk of health damage via enhancing protein and DNA oxidation.     

Inhibition of neutral sphingomyelinase decreases elevated levels of nitrative and oxidative stress markers in liver ischemia–reperfusion injury

Oxidative stress and excessive nitric oxide production via induction of inducible nitric oxide synthase (NOS)-2 have been shown in the pathogenesis of liver ischemia–reperfusion (IR) injury. Neutral sphingomyelinase (N-SMase)/ceramide pathway can regulate NOS2 expression therefore this study determined the role of selective N-SMase inhibition on nitrative and oxidative stress markers following liver IR injury. Selective N-SMase inhibitor was administered via intraperitoneal injections. Liver IR injury was created by clamping blood vessels supplying the median and left lateral hepatic lobes for 60 min, followed by 60 min reperfusion. Nitrative and oxidative stress markers were determined by evaluating NOS2 expression, protein nitration, nitrite/nitrate levels, 4-hydroxynonenal (HNE) formation, protein carbonyl levels and xanthine oxidase/xanthine dehydrogenase (XO/XDH) activity. Levels of sphingmyelin and ceramide in liver tissue were determined by an optimized multiple reaction monitoring method using ultra-fast liquid chromatography coupled with tandem mass spectrometry (MS/MS). Spingomyelin levels were significantly increased in all IR groups compared to controls. Treatment with a specific N-SMase inhibitor significantly decreased all measured ceramides in IR injury. NOS2 expression, nitrite/nitrate levels and protein nitration were significantly greater in IR injury and decreased with N-SMase inhibition. Treatment with a selective N-SMase inhibitor significantly decreased HNE formation, protein carbonyl levels and the hepatic conversion of XO. Data confirm the role of nitrative and oxidative injury in IR and highlight the protective effect of selective N-SMase inhibition. Future studies evaluating agents blocking N-SMase activity can facilitate the development of treatment strategies to alleviate oxidative injury in liver I/R injury.     

Protein and DNA oxidation in spinal injury: neurofilaments--an oxidation target

This study measured the time courses of protein and DNA oxidation following spinal cord injury (SCI) in rats and characterized oxidative degradation of proteins. Protein carbonyl content-a marker of protein oxidation-significantly increased at 3-9 h postinjury and the ratio 8-hydroxy-2-deoxyguanosine/deoxyguanosine-an indicator of DNA oxidation-was significantly higher at 3-6 h postinjury in the injured cords than in the sham controls. This suggests that oxidative modification of proteins and DNA contributes to secondary damage in SCI. Densities of selected bands on coomassie-stained gels indicated that most proteins were degraded. Neurofilament protein (NFP) was particularly evaluated immunohistochemically; its light chain (NFP-68) was gradually degraded in nerve fibers, neuron bodies, and large dendrites following SCI. A mixture of Mn (III) tetrakis (4-benzoic acid) porphyrin (10 mg/kg)-a novel SOD mimetic-and nitro-L-arginine (1 mg/kg)-an inhibitor of nitric oxide synthase-injected intraperitoneally, increased NFP-68 immunoreactivity and the numbers of NFP-positive nerve fibers post-SCI, correlating NFP degradation in SCI to free radical-triggered oxidative damage for the first time. Therefore, blockage of protein and DNA oxidation in the secondary injury stage may improve long-term recovery-important information for development of the SCI therapies.     

Oxidative stress in childhood type 1 diabetes: Results from a study covering the first 20 years of evolution

This study aimed to further analyse the potential role of oxidative stress in children and adolescents with type 1 diabetes at clinical onset, during disease progression and when early microvascular complications ( + DC) appeared. Compared with age-matched controls, diabetic patients had greater oxidative damage to lipids, proteins and DNA demonstrated by analysis of plasma and erythrocyte malondialdehyde, carbonyl proteins and leukocyte 8-hydroxy-deoxyguanosine, all of which were significantly raised at onset, decreased during the first 1.5 years of evolution and rose progressively thereafter. Plasma lipid levels were significantly associated with lipid and protein oxidation products. Erythrocyte glutathione and glutathione-peroxidase activity were significantly decreased with the lowest values at onset and in + DC sub-groups. Insulin therapy in the first year improved metabolic and oxidant-antioxidant status and, consequently, hyperglycaemia-derived biomolecular oxidative damage. Diabetes-associated hyperlipidaemia is related to lipid and protein oxidation, thereby supporting the concept of glucotoxicity and lipotoxicity being inter-related. The overall increase in lipid, protein and DNA oxidative damage in diabetic patients with microangiopathy could be pathogenetically relevant in the early development of diabetes-related complications.     

Comparison between modifications of lens proteins resulted from glycation with methylglyoxal,glyoxal, ascorbic acid,and fructose

Cataract is generally associated with the breakdown of the lens microarchitecture. Age-dependent chemical modifications and cross-linking of proteins are the major pathways for development of lens opacity. The specific alterations in lens proteins caused by glycation with four carbonyl metabolites, fructose, methylglyoxal, glyoxal, and ascorbic acid, were investigated. Decrease in intensity of tryptophan related fluorescence and level of reduced protein sulfhydryl groups, parameters that are indicative for changes in protein conformation, were observed after reaction with all studied carbonyl compounds. Protein carbonyl content, an index for oxidative damage to proteins, was strongly enhanced in methylglyoxal-treated proteins. Cross-linking of glycated proteins was confirmed by polyacrylamide electrophoresis. alpha-Oxoaldehydes were the most reactive in protein aggregation. They also formed specific chromophores absorbing UV light above 300 nm. Significant loss in lactate dehydrogenase activity resulted from incubation with methylglyoxal, followed by glyoxal and ascorbic acid. The results obtained showed that alterations in lens proteins do not follow the specific reactivity of studied carbonyl compounds. Despite the similarity in chemical structures of alpha-oxoaldehydes and ascorbic acid degradation products, they cause specific alterations in lens protein structure with different biological consequences.     

Differential effects of α-tocopherol and N-acetyl-cysteine on advanced glycation end product-induced oxidative damage and neurite degeneration in SH-SY5Y cells

Advanced glycation end products (AGEs) result from non-enzymatic glycation of proteins and cause cellular oxidative stress in a nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-dependent manner. Due to these effects, AGEs are implicated as a causal factor in diabetic complications. Several antioxidants, including vitamin E, improve cell viability and diminish markers of oxidative damage in cells exposed to AGEs. However, vitamin E has been studied in cell culture systems with primary focus on apoptosis and lipid peroxidation, while its influences on AGE-induced protein and DNA oxidation, intracellular antioxidant status and cell morphology remain largely unknown. Here, we verify the suppression of AGE-induced cell death and lipid peroxidation by 200 μM α-tocopherol in SH-SY5Y cells. We report the partial inhibition of DNA oxidation and a decrease in protein carbonyl formation by α-tocopherol with no effects on intracellular GSH concentrations. We observed that 2 mM N-acetyl cysteine (NAC) also had a suppressive effect on DNA and protein oxidation, but unlike α-tocopherol, it caused a marked increase in intracellular GSH. Finally, we compared the ability of both antioxidants to maintain neurites in SH-SY5Y cells and found that α-tocopherol had no effect on neurite loss due to AGEs, while NAC fully maintained cell morphology. Thus, while α-tocopherol suppressed AGE-induced macromolecule damage, it was ineffective against neurite degeneration. These results may implicate thiol oxidation and maintenance as a major regulator of neurite degeneration in this model.     

羰基毒害在糖尿病晚期并发症中的作用

动物机体组织的氧化紧张损伤和老化交联是糖尿病晚期并发症中神经病变、动脉粥样硬化、风湿性关节炎、肾病变、白内障等老化慢性疾病的共同特征.对氧化紧张到底是糖尿病晚期并发症的初始原因还是糖尿病组织衰变的次级诱因提出了探讨.结果表明糖尿病患者机体和血浆中的糖氧化产物及脂类过氧化物的增多表明病患者体内氧化紧张的加强;然而,它们中的某些产物与氧化紧张并不相关;此外,其它一些氧化紧张的直接指标,如氨基酸的氧化,在糖尿病患者的皮肤胶原中也并没有增多.因此,对于糖尿病患者中蛋白质化学修饰的现象,用活性羰基的毒化超过其系统解毒能力的观点来解释更合适.这种在氧化或非氧化反应中形成的不饱和羰基化合物在体内总是以相对恒定的浓度存在,因而在糖尿病中,由羰基毒害引起组织中糖类和脂类衍生物的增长可以被认为是生物化学动力学的一种必然结果.     

Effects of fasting on oxidative stress in rat liver mitochondria

While moderate caloric restriction has beneficial effects on animal health state, fasting may be harmful. The present investigation was designed to test how fasting affects oxidative stress, and to find out whether the effects are opposite to those previously found in caloric restriction studies. We have focused on one of the main determinants of aging rate: the rate of mitochondrial free radical generation. Different parameters related to lipid and protein oxidative damage were also analyzed. Liver mitochondria from rats subjected to 72 h of fasting leaked more electrons per unit of O₂ consumed at complex III, than mitochondria from ad libitum fed rats. This increased leak led to a higher free radical generation under state 3 respiration using succinate as substrate. Regarding lipids, fasting altered fatty acid composition of hepatic membranes, increasing the double bond and the peroxidizability indexes. In accordance with this, we observed that hepatic membranes from the fasted animals were more sensitive to lipid peroxidation. Hepatic protein oxidative damage was also increased in fasted rats. Thus, the levels of oxidative modifications, produced either indirectly by reactive carbonyl compounds (N^epsilon- malondialdehyde-lysine), or directly through amino acid oxidation (glutamic and aminoadipic semialdehydes) were elevated due to the fasting treatment in both liver tissue and liver mitochondria. The current study shows that severe food deprivation increases oxidative stress in rat liver, at least in part, by increasing mitochondrial free radical generation during state 3 respiration and by increasing the sensitivity of hepatic membranes to oxidative damage, suggesting that fasting and caloric restriction have different effects on liver mitochondrial oxidative stress.     

Role of curcuminoids in ameliorating oxidative modification in β-thalassemia/Hb E plasma proteome

Thalassemic patients often exhibit high levels of oxidative stress and iron overload, which can lead to hazardous complications. Curcuminoids, extracted from the spice turmeric, are known to have antioxidant and iron-chelating properties and have been proposed as a potential upstream therapy of thalassemia. Here we have applied proteomic techniques to study the protein profile and oxidative damage in the plasma of β-thalassemia/Hb E patients before and after treatment with curcuminoids. In this study, 10 β-thalassemia/Hb E patients were treated with 500 mg curcuminoids daily for 12 months. The plasma protein profile and protein carbonyl content were determined at baseline, 6 and 12 months using two-dimensional fluorescence difference gel electrophoresis and carbonyl immunoblotting, respectively. Other hematological, clinical, and biochemical parameters were also analyzed. Twenty-six spots, identified as coagulation factors and proteins involved in iron homeostasis, showed significantly decreased intensity in thalassemic plasma, compared to those of normal subjects. Treatment with curcuminoids up-regulated the plasma levels of these proteins and reduced their oxidative damage. Serum non-transferrin bound iron, platelet factor-3 like activity, oxidative stress parameters and antioxidant enzymes were also improved after curcuminoids treatment. This study is the first proteomic study of plasma in the thalassemic state and also shows the ameliorating role of curcuminoids towards oxidative stress and iron overload in the plasma proteome.