Mitochondrial superoxide production in kainate-induced hippocampal damage

The objective of this study was to determine the role of mitochondrial superoxide radical-mediated oxidative damage in seizure-induced neuronal death. Using aconitase inactivation as an index of superoxide production, we found that systemic administration of kainate in rats increased mitochondrial superoxide production in the hippocampus at times preceding neuronal death. 8-Hydroxy-2-deoxyguanosine, an oxidative lesion of DNA, was also increased in the rat hippocampus following kainate administration. Manganese(III) tetrakis(4-benzoic acid)porphyrin, a catalytic antioxidant, inhibited kainate-induced mitochondrial superoxide production, 8-hydroxy-2-deoxyguanosine formation and neuronal loss in the rat hippocampus. Kainate-induced increases of mitochondrial superoxide production and hippocampal neuronal loss were attenuated in transgenic mice overexpressing mitochondrial superoxide dismutase-2.We propose that these results demonstrate a role for mitochondrial superoxide production in hippocampal pathology produced by kainate seizures.     

Neuroprotective effects of brain-derived neurotrophic factor in seizures during development.

Although the immature brain is highly susceptible to seizures, it is more resistant to seizure-induced neuronal loss than the adult brain. The developing brain contains high levels of neurotrophins which are involved in growth, differentiation and survival of neurons. To test the hypothesis that neurotrophins may protect the developing brain from seizure-induced neuronal loss, brain-derived neurotrophic factor up-regulation was blocked by intracerebroventricular infusion of an 18mer antisense oligodeoxynucleotide sequence to brain-derived neurotrophic factor in 19-day-old rats using micro-osmotic pumps. Control rats were infused with sense or missense oligodeoxynucleotide. Status epilepticus was induced by intraperitoneal administration of kainic acid 24 h after the start of oligodeoxynucleotide infusion. Seizure duration was significantly increased in the antisense oligodeoxynucleotide plus kainic acid group compared to groups that received kainic acid alone or kainic acid plus sense or missense oligodeoxynucleotide. There was no difference between groups in the latency to forelimb clonus. A twofold increase in brain-derived neurotrophic factor levels was observed in the hippocampus 20 h following kainic acid-induced seizures. This kainic acid-induced increase was absent in animals receiving infusion of antisense oligodeoxynucleotide to brain-derived neurotrophic factor at time of seizure induction. Hippocampi of rats in this group (antisense oligodeoxynucleotide plus kainic acid) showed a loss of CA1 and CA3 pyramidal cells and hilar interneurons. This neuronal loss was not dependent upon seizure duration since animals injected with diazepam to control seizure activity in the antisense plus kainic acid group also showed similar neuronal loss. Administration of kainic acid or infusion of antisense alone did not produce any cell loss in these regions. Induction of seizures at postnatal day 20, in the presence or absence of antisense oligonucleotide, did not produce an impairment in learning and memory when tested 15 days later in the Morris water maze. The hippocampi of these animals did not show any synaptic reorganization as assessed by growth-associated protein-43 immunostaining and Timm staining. Our findings confirm prior studies demonstrating that seizures in the immature brain are associated with little, if any, cell loss. However, when seizure-induced increase in brain-derived neurotrophic factor is blocked, seizures do result in neuronal loss in the developing brain. Thus, brain-derived neurotrophic factor appears to provide protection against kainic acid seizure-induced neuronal damage in the developing brain.     

Non-linear accumulation of 8-hydroxy-2′-deoxyguanosine,a marker of oxidized DNA damage,during aging

Damage to DNA seems to be involved in aging and the etiology of age-associated degenerative disease. The purpose of this study is to examine changes in DNA damage during aging. Am oxidized nucleoside, 8-hydroxy-2′-deoxyguanosine (8-OHdG), is a proposed biomarker for DNA damaged by oxidative stress. The content of 8-OHdG in nuclear DNA isolated from brain, heart, liver, and kidneys of male Fischer 344 rats of different ages was measured. 8-OHdG can be detected selectivity and sensitivity at the fmol level by high performance liquid chromatography-electrochemical detection at an applied ptential of +350 mV. The amount of 8-OHdG, expressed as the ratio oto deoxyguanosine in nuclear DNA, in heart, liver, and kidney remained steady from 2 to 24 months and then increased progressively. The content of 8-OHdG in teh DNA in brain showed no changes from 2 to 27 months, but was significantly higher in 30 month-old rats. There was a significant 2-fold increase in the amount of 8-OHdG in the nuclear DNA of all organs tested in 30 month-old rats as compared to 2–24 month-old rats. These results indicate that the accumulation of 8-OHdG in the DNA of rat organs begins at ages above 24 months.     

Cytoplasmic fine granular expression of 8-hydroxydeoxyguanosine reflects early mitochondrial oxidative DNA damage in nonalcoholic fatty liver disease.

To clarify the possible role of oxidative stress in hepatocytes in nonalcoholic fatty liver disease, the hepatic expression of 8-hydroxydeoxyguanosine (8-OHdG), a good marker of oxidative DNA damage, was immunohistochemically investigated in nonalcoholic steatohepatitis (NASH) and steatosis. In double immunostaining, the cytoplasmic fine granular 8-OHdG expression was considered to reflect 8-OHdG-positive mitochondrial DNA affecting oxidation stress. In steatosis, 4 of 8 cases showed cytoplasmic 8-OHdG, 1 case showed nuclear 8-OHdG and 1 case showed both cytoplasmic and nuclear 8-OHdG. In contrast, 8-OHdG expression was more frequently detected in NASH (12 of 13 cases, 92%). Immunoreactivity for 8-OHdG was observed only in the cytoplasm with a fine granular pattern (1 of 13 cases, 8%), only in the nucleus (6 of 13 cases, 46%), and in both the cytoplasm and the nucleus (5 of 13 cases, 38%). Megamitochondria also exhibited 8-OHdG intensely. We indicate that 8-OHdG expression in the cytoplasm with a fine granular pattern reflects oxidative damage to the mitochondrial DNA of hepatocytes in both NASH and steatosis. We propose herein that the evaluation of cytoplasmic 8-OHdG may be a sensitive diagnostic marker of early nonalcoholic fatty liver disease events.     

Increased mitochondrial DNA oxidative damage after transient middle cerebral artery occlusion in mice

Oxidative stress and DNA oxidation play important roles in the induction of ischemic neuronal cell death. However, the subcellular source of oxidized DNA detected by 8-hydroxy-2'-deoxyguanosine (8-OHdG) after ischemia has not been clarified although it is known to increase in the brain after ischemia. One-hour transient ischemia of the middle cerebral artery was induced in mice utilizing an intraluminal filament. The occurrence of superoxide anion as an ethidium (Et) signal, 8-OHdG, cytochrome c release and neuronal cell death were examined using immunohistological and biochemical techniques in sham-operated control (0h) and 1, 3, 6, 24, or 96h after reperfusion. Et signals were prominent in the cortical neurons of ipsilateral hemisphere 3h after reperfusion. Strong 8-OHdG immunoreactivity was observed 3-6h after reperfusion. Immunoassays after cell fractionation revealed a significant increase of 8-OHdG in mitochondria 6h after reperfusion. Immunohistochemistry revealed that the 8-OHdG immunoreactivity colocalized with a neuronal marker, microfilament 200 and a mitochondrial marker, cytochrome oxidase subunit I. Cytochrome c rose in cytoplasm at 6h and TUNEL-positive neurons noted 6-24h after ischemia. The present results suggest the possibility that the mitochondrial damage including mitochondrial DNA oxidation might be responsible for the induction of ischemic neuronal cell death.     

Cu/Zn superoxide dismutase expression in the postnatal rat brain following an excitotoxic injury

Background  

In the nervous system, as in other organs, Cu/Zn superoxide dismutase (Cu/Zn SOD) is a key antioxidant enzyme involved in superoxide detoxification in normal cellular metabolism and after cell injury. Although it has been suggested that immature brain has a different susceptibility to oxidative damage than adult brain, the distribution and cell-specific expression of this enzyme in immature brain and after postnatal brain damage has not been documented.     

Increased salivary level of 8-hydroxydeoxyguanosine is a marker of premature oxidative mitochondrial DNA damage in gingival tissue of patients with periodontitis

Introduction:  

Oxidative stress may contribute to the pathogenesis of periodontitis. However, the detailed molecular mechanism remains unclear. Both 8-hydroxydeoxyguanosine (8-OHdG) and mitochondrial DNA (mtDNA) deletion have been reported as early oxidative DNA damage markers. In this study, 8-OHdG levels in saliva and mtDNA deletions in gingival tissue of patients with chronic periodontitis (CP) were evaluated.     

Possible involvement of oxidative stress in salivary gland of patients with Sjogren's syndrome.

OBJECTIVE: To determine the involvement of oxidative stress in the salivary gland of patients with Sjogren's syndrome (SS). METHODS: Oxidative damage to the gland was measured by 8-hydroxy-2'-deoxyguanosine (8-OHdG) and hexanoyl-lysine (HEL) using the SS saliva. In addition, lactate dehydrogenase (LDH) and mitochondrial glutamic-oxaloacetic transaminase (m-GOT), both general markers for cell damage, were also analyzed. RESULTS: Increased levels of 8-OHdG and HEL were found in the saliva of SS patients, but not in that of patients with other salivary gland dysfunction or of healthy individuals. Levels of LDH and m-GOT were significantly correlated with 8-OHdG and HEL levels, respectively. Furthermore, the increased levels of 8-OHdG and HEL were also correlated in the SS saliva. CONCLUSION: These findings suggested the involvement of oxidative stress in glandular tissue destruction in SS. It was indicated that the detection of 8-OHdG and HEL in the saliva may become a useful tool for the diagnosis of SS.     

Kainate-induced seizures, oxidative stress and neuronal loss in aging rats

Aging is a significant risk factor for developing epilepsy. The mechanisms underlying age-related increase in seizure susceptibility and resultant injury remain unknown. Oxidative stress is an important mechanism that contributes to diverse age-related disorders. Whether age-related increased seizure susceptibility is accompanied by increased oxidative stress remains unknown. The goal of this study was to determine if aging per se increases the susceptibility of rats to kainate-induced behavioral seizures and oxidative stress. Adult (3-4 month-old) and aging (18-19 month-old) Sprague-Dawley rats were administered a single low dose of kainate (5 mg/kg, s.c.) or saline. Behavioral seizures were monitored in all four groups for a period for a period of approximately 6 h. Oxidative stress (8-hydroxy-2'deoxyguanosine/2-deoxyguanosine; 8OHdG/2dG) was assessed 24 h following kainate injection. Stereological assessment of cell counts was performed in hippocampal tissue 7 days following kainate injection. In adult rats, administration of the low dose of kainate did not produce significant behavioral seizures, oxidative stress or cell loss. However, aging rats exhibited intense behavioral seizures consistent with status epilepticus following the low dose of kainate. In aging rats, kainate produced a significant increase in oxidative DNA damage (8OHdG/2dG) and neuronal loss in cornu ammonis regions 3 and 1 (CA3 and CA1), but not dentate gyrus compared with both age-matched controls and adult kainate-treated rats. These data suggest that the process of aging per se increases kainate-induced seizure susceptibility, oxidative stress and hippocampal pyramidal cell loss.     

8-Hydroxy-2′-deoxyguanosine expression predicts outcome of esophageal cancer

Esophageal cancer is characterized by increased oxidative stress and the production of 8-hydroxy-2'-deoxyguanosine (8-OHdG), which is one of the main mutagenic modifications of DNA. We analyzed the predictive value of 8-OHdG expression on postoperative survival of patients with esophageal cancer with univariate and multivariate analysis. The high levels of 8-OHdG are associated with significantly shorter survival time by log-rank test using Kaplan-Meier methods. Moreover, the level of 8-OHdG expression was identified as an independent predictor for esophageal cancer outcome using Cox proportional hazards model analysis (relative risk, 0.294; 95% confidence interval, 0.178-0.487; P = .000). These results suggest that oxidative damage marker of 8-OHdG is a useful prognostic marker in esophageal cancer. The analysis of 8-OHdG levels can help in the identification of patient subgroups that are at high risk for poor disease outcomes     

Mitochondrial DNA damage as a mechanism of cell loss in Alzheimer's disease

Aging is associated with impaired mitochondrial function caused by accumulation of oxygen free radical-induced mitochondrial (Mt) DNA mutations. One prevailing theory is that age-associated diseases, including Alzheimer's disease (AD), may be precipitated, propagated, or caused by impaired mitochondrial function. To investigate the role of MtDNA relative to genomic (Gn) DNA damage in AD, temporal lobe samples from postmortem AD (n = 37) and control (n = 25) brains were analyzed for MtDNA and GnDNA fragmentation, mitochondrial protein and cytochrome oxidase expression, MitoTracker Green fluorescence (to assess mitochondrial mass/abundance), and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-OHdG) immunoreactivity. Brains with AD had more extensive nicking and fragmentation of both MtDNA and GnDNA as demonstrated by agarose gel electrophoresis, end-labeling, and the in situ terminal deoxynucleotide transferase end-labeling (TUNEL) assay, and only the brains with AD had detectable 8-OHdG immunoreactivity in cortical neurons. Increased MtDNA damage in AD was associated with reduced MtDNA content, as demonstrated by semiquantitative PCR analysis and reduced levels of Mt protein and cytochrome oxidase expression by Western blot analysis or immunohistochemical staining with image analysis. The finding of reduced MitoTracker Green fluorescence in AD brains provided additional evidence that reduced Mt mass/abundance occurs with AD neurodegeneration. The presence of increased MtDNA and GnDNA damage in AD suggest dual cell death cascades in AD. Impaired mitochondrial function caused by MtDNA damage may render brain cells in AD more susceptible to oxidative injury and thereby provide a mechanism by which systemic or environmental factors could influence the course of disease.     

The scavenging of reactive oxygen species and the potential for cell protection by functionalized fullerene materials

We demonstrated that three different types of water-soluble fullerenes materials can intercept all of the major physiologically relevant ROS. C(60)(C(COOH)(2))(2), C(60)(OH)(22), and Gd@C(82)(OH)(22) can protect cells against H(2)O(2)-induced oxidative damage, stabilize the mitochondrial membrane potential and reduce intracellular ROS production with the following relative potencies: Gd@C(82)(OH)(22)> or =C(60)(OH)(22)>C(60)(C(COOH)(2))(2). Consistent with their cytoprotective abilities, these derivatives can scavenge the stable 2,2-diphenyl-1-picryhydrazyl radical (DPPH), and the reactive oxygen species (ROS) superoxide radical anion (O(2)(*-)), singlet oxygen, and hydroxyl radical (HO(*)), and can also efficiently inhibit lipid peroxidation in vitro. The observed differences in free radical-scavenging capabilities support the hypothesis that both chemical properties, such as surface chemistry induced differences in electron affinity, and physical properties, such as degree of aggregation, influence the biological and biomedical activities of functionalized fullerenes. This represents the first report that different types of fullerene derivatives can scavenge all physiologically relevant ROS. The role of oxidative stress and damage in the etiology and progression of many diseases suggests that these fullerene derivatives may be valuable in vivo cytoprotective and therapeutic agents.     

Urinary 8-hydroxy-2'-deoxyguanosin (8-OHdG) in patients with chronic liver diseases

Urinary 8-hydroxy-2'-deoxyguanosin(8-OHdG) has been reported as sensitive biomarker of oxidative DNA damage and also of oxidative stress. We measured the urinary 8-OHdG in patients with chronic liver diseases by competitive ELISA, and analyzed the relationship with clinical characteristics. Fifty patients (male/female: 22/28) with chronic liver disease were enrolled this study. The mean concentration of urinary 8-OHdG in healthy control and patients with liver cirrhosis, chronic hepatitis C, chronic hepatitis B, and autoimmune hepatitis were 10.40+/-3.14, 10.14+/-4.19, 11.79+/-5.58, 14.99+/-4.46, and 13.64+/-3.84 microg/gCr, respectively. There were no significant differences among the five group. The mean concentration of urinary 8-OHdG in inveterate drinker was significantly higher than that in non-drinker (16.67+/-4.29 vs. 11.19+/-4.80 microg/gCr, p<0.05). The smoking enhanced the elevation of urinary 8-OHdG in drinkers. In clinical characteristics, serum y-GTP, a marker of alcoholic liver disease, had significant positive correlation with urinary 8-OHdG on the drinker with chronic hepatitis. In addition, there was a positive correlation between serum ferritin levels and urinary 8-OHdG levels. Iron in the liver suggested oxidative damage of hepatocytes through the fenton reaction in patients with chronic liver disease. In conclusion, drinking and smoking induced liver damage by oxidative stress, and urinary 8-OHdG may be reliable marker of oxidative stress in patients with chronic liver disease.     

New aspects in genotoxic risk assessment of styrene exposure--a working hypothesis

Styrene is one of the most important plastic monomers worldwide. Styrene-7,8-oxide (SO), the major in-vivo metabolite of styrene, is classified as probably carcinogenic to humans and carcinogenic in rodents. Biological monitoring of exposure to styrene is usually carried out by determination of mandelic acid and phenylglyoxylic acid, the two main styrene metabolites in urine. SO binds covalently to human plasma protein and haemoglobin. The ability of SO to induce DNA adducts and DNA strand-breaks has been well documented. Recently in-vitro results showed that SO may disrupt the pre-existing oxidative status in white blood cells. This disruption would alter the balance between oxidants and antioxidants in cells. Styrene exposure can also result in oxidative DNA damage. A significant increase of 8-hydroxy-2;-deoxyguanosine (8-OHdG) has been found in white blood cells of styrene-exposed workers. According to these findings we propose a new hypothesis for the genotoxic risk assessment of styrene. Depletion of glutathione and increase in lipid peroxidation, similarity in the decrease of high molecular weight (HMW) DNA fragments after SO exposure compared to hydrogen peroxide (H(2)O(2)) exposure, oxidative DNA damage (increased amounts of 8-OHdG and an increased level of DNA strand-breaks) following styrene or SO exposure are due to oxidative stress which can be a result of the imbalance between oxidants and antioxidants. Formation of protein-, RNA- and DNA-adducts, changes in DNA repair capacity and styrene metabolism following styrene exposure could cause this imbalance between oxidants and antioxidants. Oxidative stress seems to be the basis for genotoxic risk assessment of styrene.     

Oxidative Alterations in Alzheimer's Disease

There is increasing evidence that free radical damage to brain lipids, carbohydrates, proteins, and DNA is involved in neuron death in neurodegenerative disorders. The largest number of studies have been performed in Alzheimer's disease (AD) where there is considerable support for the oxidative stress hypothesis in the pathogenesis of neuron degeneration. In autopsied brain there is an increase in lipid peroxidation, a decline in polyunsaturated fatty acids (PUFA) and an increase in 4-hydroxynonenal (HNE), a neurotoxic aldehyde product of PUFA oxidation. Increased protein oxidation and a marked decline in oxidative-sensitive enzymes, glutamine synthetase and creatinine kinase, are found in the brain in AD. Increased DNA oxidation, especially 8-hydroxy-2'-deoxyguanosine (8-OHdG) is present in the brain in AD. Immunohistochemical studies show the presence of oxidative stress products in neurofibrillary tangles and senile plaques in AD. Markers of lipid peroxidation (HNE, isoprostanes) and DNA (8-OHdG) are increased in CSF in AD. In addition, inflammatory response markers (the complement cascade, cytokines, acute phase reactants and proteases) are present in the brain in AD. These findings, coupled with epidemiologic studies showing that anti-inflammatory agents slow the progression or delay the onset of AD, suggest that inflammation plays a role in AD. Overall these studies indicate that oxidative stress and the inflammatory cascade, working in concert, are important in the pathogenetic cascade of neurodegeneration in AD, suggesting that therapeutic efforts aimed at both of these mechanisms may be beneficial.     

Singlet oxygen is the major species participating in the induction of DNA strand breakage and 8-hydroxydeoxyguanosine adduct by lead acetate.

To investigate DNA damage induced by Pb2+ and its prevention by scavengers, we determined DNA strand breakage and the formation of 8-hydroxydeoxyguanosine (8-OHdG) in DNA using plasmid relaxation assay and HPLC with electrochemical detection, respectively. Lead acetate induced DNA strand breakage in 10 mM of Hepes buffer, pH 6.8, in a time- and dose-dependent manner. Compared with lead, zinc acetate did not significantly induce DNA breakage. The singlet oxygen scavengers NaN3 and 2,2,6,6-tetramethyl-4-piperidone (TEMP) inhibited lead-induced DNA breakage more efficiently than the hydroxyl radical scavengers mannitol and DMPO. Deuterium oxide (D2O), a singlet oxygen enhancer, potentiated lead-induced DNA breakage. At low ratios to Pb2+, NADPH, glutathione, and 2-mercaptoethanol enhanced lead-induced DNA breakage, whereas high ratios of these agents protected it. Catalase and superoxide dismutase (SOD) did not protect DNA breaks induced by Pb2+. Lead-induced DNA breakage was markedly enhanced by H2O2, and this induction was inhibited by NaN3, TEMP, EDTA, catalase, BSA, and glutathione. In contrast, mannitol and SOD potentiated Pb2+/H2O2-induced DNA breaks. The results indicate that singlet oxygen, lead, and H2O2 are all involved in the reaction system, whereas hydroxyl radical and superoxide did not. Lead could cause a small amount of 8-OHdG formation in calf thymus DNA and dose-dependently induced the formation of this adduct in the presence of H2O2. Singlet oxygen scavengers were more effective than hydroxyl radical scavengers in protection from lead/H2O2-induced 8-OHdG adducts. Taken together, these results suggest that lead may induce DNA damage through a Fenton-like reaction and that singlet oxygen is the principal species involved.     

Immunolocalization of 8-OHdG and OGG1 in pancreatic islets of streptozotocin-induced diabetic rats

This study examined whether oxidative DNA damage and its repair system contribute to the occurrence of diabetes in an experimental rat model. The changed morphological findings of the 8-hydroxydeoxyguanosine (8-OHdG) and 8-oxoG-DNA glycosylase (OGG1) were examined in the pancreatic islets in streptozotocin-induced diabetic rats (60 mg/kg, i.p.). The patterns of immunolocalization were mainly observed in the periphery of the normal pancreatic islet: 8-OHdG in the nucleus and OGG1 in the cytoplasm. The altered immunolocalization of 8-OHdG and OGG1 were greatest in the first hours after streptozotocin injection, and then declined in parallel with the morphological observations of pancreatic beta cell destruction. These results suggested that increased oxidative DNA damage might play a role as the inducer of diabetes and that OGG1 may not successfully mediate DNA repair in streptozotocin-induced diabetic rat pancreas.     

Changes in dihydrolipoamide dehydrogenase expression and activity during postnatal development and aging in the rat brain

Brain energy metabolism is increased during postnatal development and diminished in neurodegenerative diseases linked to senescence. The objective of this study was to determine if these conditions could involve postnatal or senescence-related shifts in activity or expression of dihydrolipoamide dehydrogenase (DLDH), a key mitochondrial oxidoreductase. Rats ranging from 10 to 60 days of age were used in studies of postnatal development, whereas rats aged 5 or 30 months were used in the aging studies. The expression of DLDH was determined by Western blot analysis using anti-DLDH antibodies and DLDH diaphorase activity was measured by an in-gel activity staining method using nitroblue tetrazolium (NBT)/NADH. Activity of DLDH dehydrogenase was measured as NAD⁺ oxidation of dihydrolipoamide. When these measures were considered in separate groups of 10-, 20-, 30-, or 60-day-old rats, all three showed an increase between 10 and 20 days of age. However, dehydrogenase activity of DLDH showed a further, progressive increase from 20 days to adulthood, in the absence of any further change in DLDH expression or diaphorase activity. No age-related decline in DLDH activity or expression was evident over the period from 5 to 30 months of age. Moreover, aging did not render DLDH more susceptible to oxidative inactivation by mitochondria-generated reactive oxygen species (ROS). Taken together, results of the present study indicate that (1) brain DLDH expression and activity undergo independent postnatal maturational increases; (2) senescence does not confer any detectable change in the activity of DLDH or its susceptibility to inactivation by mitochondrial oxidative stress.     

Exercise training decreases DNA damage and increases DNA repair and resistance against oxidative stress of proteins in aged rat skeletal muscle

Regular physical exercise retards a number of age-associated disorders, in spite of the paradox that free radical generation is significantly enhanced with exercise. Eight weeks of treadmill running resulted in nearly a 40% increase in maximal oxygen uptake in both middle-aged (20-month-old) and aged (30-month-old) rats. The age-associated increase in 8-hydroxy-2'-deoxyguanosine (8-OHdG) content was significantly attenuated in gastrocnemius muscle by exercise. The 8-OHdG repair, as measured by the excision of 32P-labeled damaged oligonucleotide, increased in muscle of exercising animals. The reactive carbonyl derivatives (RCD) of proteins did not increase with aging. However, when the muscle homogenate was exposed to a mixture of 1 mM iron sulfate and 50 mM ascorbic acid, the muscle of old control animals accumulated more RCD than that of the trained or adult groups. The chymotrypsin-like activity of proteasome complex increased in muscle of old trained rats. We suggest that regular exercise-induced adaptation attenuates the age-associated increase in 8-OHdG levels, and increases the activity of DNA repair and resistance against oxidative stress in proteins.     

Sleep deprivation and cellular responses to oxidative stress

STUDY OBJECTIVES: It has been hypothesized that sleep deprivation represents an oxidative challenge for the brain and that sleep may have a protective role against oxidative damage. This study was designed to test this hypothesis by measuring in rats the effects of sleep loss on markers of oxidative stress (oxidant production and antioxidant enzyme activities) as well as on markers of cellular oxidative damage (lipid peroxidation and protein oxidation). DESIGN: The analyses were performed in the brain and in peripheral tissues (liver and skeletal muscle), after short-term sleep deprivation (8 hours), after long-term sleep deprivation (3-14 days), and during recovery sleep after 1 week of sleep loss. Short-term sleep deprivation was performed by gentle handling; long-term sleep deprivation was performed using the disk-over-water method. SETTING: Sleep research laboratory at University of Wisconsin-Madison. PARTICIPANTS AND INTERVENTIONS: Adult male Wistar Kyoto rats (n = 69) implanted for polygraphic (electroencephalogram, electromyogram) recording. MEASUREMENTS AND RESULTS: Aliquots of brain, liver, or skeletal muscle homogenate were used to assess oxidant production, superoxide dismutase activity, lipid peroxidation, and protein oxidation. No evidence of oxidative damage was observed at the lipid and/or at the protein level in long-term sleep-deprived animals relative to their yoked controls, nor in the cerebral cortex or in peripheral tissues. Also, no consistent change in antioxidant enzymatic activities was found after prolonged sleep deprivation, nor was any evidence of increased oxidant production in the brain or in peripheral tissues. CONCLUSION: The available data do not support the assumption that prolonged wakefulness may cause oxidative damage, nor that it can represent an oxidative stress for the brain or for peripheral tissue such as liver and skeletal muscle.