Habitual exercise induced resistance to oxidative stress

We investigated whether habitual exercise (HE) modulates levels of oxidative DNA damage and responsiveness to oxidative stress induced by renal carcinogen Fe-nitrilotriacetic acid (Fe-NTA). During a ten week protocol, two groups of rats either remained sedentary or underwent swimming for 15–60?min per day, 5 days per week, with or without a weight equivalent to 5% of their body weight. Then we injected Fe-NTA and sacrificed the rats 1?h after the injection. We determined the activity of superoxide dismutase (SOD) in diaphragm and kidney, evaluated levels of 8-hydroxydeoxyguanosine (8OHdG), catalase, and glutathione peroxidase, and assayed OGG1 protein levels in kidney. SOD activity in the diaphragm and kidney was increased in HE rats. By itself, HE had no effect on the level of 8OHdG, but it did significantly suppress induction of 8OHdG by Fe-NTA, and the amount of suppression correlated with intensity of exercise. These results suggest that HE induces resistance to oxidative stress and, at least at the initiation stage, inhibits carcinogenesis.     

Habitual long-distance running does not enhance urinary excretion of 8-hydroxydeoxyguanosine

 The energy demand during physical exercise causes an increased oxygen uptake and supply to active tissues, which may increase the rate of free oxygen radical production and thereby affect the capacity of endogenous cellular defense systems. This could result in DNA base modifications, among which 8-hydroxydeoxyguanosine (8OHdG) is one of the most important and has widely been used as a biomarker of in vivo oxidative lesions. Therefore, we examined the effect of regular running exercise on the urinary levels of 8OHdG in 32 long-distance runners and in a group of untrained healthy subjects. The range of 8OHdG in urine was 0.12–6.45 μmol/mol creatinine in both groups, and no significant difference in the mean excretion levels between runners and control probands was observed. This gives no reason to believe that physical exercise in trained individuals may induce a disturbance of the oxidant-to-antioxidant balance. Accepted: 30 January 1997     

Circadian variation in oxidative stress markers in healthy and type II diabetic men

Seven clinically healthy, nondiabetic (ND) and four Type II diabetic (D) men were assessed for circadian rhythms in oxidative “stress markers.” Blood samples were collected at 3h intervals for ～27 h beginning at 19:00h. Urine samples were collected every 3 h beginning with the 16:00h–19:00h sample. The dark (sleep) phase of the light–dark cycle extended from 22:30h to 06:30h, with brief awakening for sampling at 01:00h and 04:00h. Subjects were offered general hospital meals at 16:30h, 07:30h, and 13:30h (2400 cal in total/24 h). Serum samples were analyzed for uric acid (UA) and nitrite (NO) concentrations, and urine samples were assayed for 8-hydroxydeoxyguanosine (8-OHdG), malondialdehyde (MDA), and 8-isoprostane (ISP). Data were analyzed statistically both by the population multiple-components method and by the analysis of variance (ANOVA). The 24h mean level of UA and NO was greater in D than in ND subjects (424 vs. 338 μmol/L and 39.2 vs. 12.7 μM, respectively). A significant circadian rhythm in UA (p=0.001) and NO (p=0.048) was evident in ND but not in D (p=0.214 and 0.065). A circadian rhythm (p=0.004, amplitude=8.6 pmol/kgbw/3h urine vol.) was also evident in urine 8-OHdG of ND but not of D. The 24h mean levels of ND and D were comparable (76.8 vs. 65.7 pmol/kgbw/3h urine vol.). No circadian rhythm by population multiple-components was evident in MDA and ISP levels of ND subjects, or in 8-OHdG, MDA, and ISP in D. However, a significant time-effect was demonstrated by ANOVA in all variables and groups. The 24h mean of MDA and ISP in D was significantly greater than in ND (214 vs. 119 nmol/3h urine vol. and 622 vs. 465 ng/3h urine vol.). The peak concentrations of the three oxidative “stress markers” in urine, like those of serum NO, occurred early in the evening in both groups of men. This observation suggests a correlation between increased oxidative damage and increased rate of anabolic–catabolic events as evidenced by similarities in the timing of peak NO production and in parameters relevant to metabolic functions.     

Circadian variation in oxidative stress markers in healthy and type II diabetic men

Seven clinically healthy, nondiabetic (ND) and four Type II diabetic (D) men were assessed for circadian rhythms in oxidative “stress markers.” Blood samples were collected at 3h intervals for ∼27 h beginning at 19:00h. Urine samples were collected every 3 h beginning with the 16:00h-19:00h sample. The dark (sleep) phase of the light-dark cycle extended from 22:30h to 06:30h, with brief awakening for sampling at 01:00h and 04:00h. Subjects were offered general hospital meals at 16:30h, 07:30h, and 13:30h (2400 cal in total/24 h). Serum samples were analyzed for uric acid (UA) and nitrite (NO) concentrations, and urine samples were assayed for 8-hydroxydeoxyguanosine (8-OHdG), malondialdehyde (MDA), and 8-isoprostane (ISP). Data were analyzed statistically both by the population multiple-components method and by the analysis of variance (ANOVA). The 24h mean level of UA and NO was greater in D than in ND subjects (424 vs. 338 μmol/L and 39.2 vs. 12.7 μM, respectively). A significant circadian rhythm in UA (p=0.001) and NO (p=0.048) was evident in ND but not in D (p=0.214 and 0.065). A circadian rhythm (p=0.004, amplitude=8.6 pmol/kgbw/3h urine vol.) was also evident in urine 8-OHdG of ND but not of D. The 24h mean levels of ND and D were comparable (76.8 vs. 65.7 pmol/kgbw/3h urine vol.). No circadian rhythm by population multiple-components was evident in MDA and ISP levels of ND subjects, or in 8-OHdG, MDA, and ISP in D. However, a significant time-effect was demonstrated by ANOVA in all variables and groups. The 24h mean of MDA and ISP in D was significantly greater than in ND (214 vs. 119 nmol/3h urine vol. and 622 vs. 465 ng/3h urine vol.). The peak concentrations of the three oxidative “stress markers” in urine, like those of serum NO, occurred early in the evening in both groups of men. This observation suggests a correlation between increased oxidative damage and increased rate of anabolic-catabolic events as evidenced by similarities in the timing of peak NO production and in parameters relevant to metabolic functions.     

Damage to Cultivated Japanese Pearl Oysters by Oxidative Stress That Was Related to “Mass Mortality”

Increased blood-DNA breakage was observed in diseased pearl oysters. They showed significant formation of 8-hydroxydeoxyguanosine (8-OHdG) and malondialdehyde (MDA), whereas the oysters that had a low mortality rate from the disease had high activity of superoxide dismutase (SOD) and low amounts of 8-OHdG and MDA. These results suggest that radical damage had occurred only in the diseased pearl oysters with the cytolysis of their haemocytes, which was related to the mass mortality of the Japanese pearl oysters.     

Two distinct pathways of cell death triggered by oxidative damage to nuclear and mitochondrial DNAs

Oxidative base lesions, such as 8-oxoguanine (8-oxoG), accumulate in nuclear and mitochondrial DNAs under oxidative stress, resulting in cell death. However, it is not known which form of DNA is involved, whether nuclear or mitochondrial, nor is it known how the death order is executed. We established cells which selectively accumulate 8-oxoG in either type of DNA by expression of a nuclear or mitochondrial form of human 8-oxoG DNA glycosylase in OGG1-null mouse cells. The accumulation of 8-oxoG in nuclear DNA caused poly-ADP-ribose polymerase (PARP)-dependent nuclear translocation of apoptosis-inducing factor, whereas that in mitochondrial DNA caused mitochondrial dysfunction and Ca2+ release, thereby activating calpain. Both cell deaths were triggered by single-strand breaks (SSBs) that had accumulated in the respective DNAs, and were suppressed by knockdown of adenine DNA glycosylase encoded by MutY homolog, thus indicating that excision of adenine opposite 8-oxoG lead to the accumulation of SSBs in each type of DNA. SSBs in nuclear DNA activated PARP, whereas those in mitochondrial DNA caused their depletion, thereby initiating the two distinct pathways of cell death.     

Copper-mediated oxidative stress in rat liver

Copper is an essential trace element with various biological functions. Excess copper, however, is extremely toxic, leading to many pathological conditions that are consistent with oxidative damage to membranes and molecules. Exposure to high levels of copper results in various changes in the tissues. In liver, hypertrophy of hepatocytes, hepatitis, hepatocellular necrosis, and hepatocellular death are the results. Lipid peroxidation causes dysfunction in the cell membrane, decreased fluidity, inactivation of receptors and enzymes, and changes ion permeability. In this study, we aimed to determine the effect of copper on oxidative and antioxidative substances in plasma and liver tissue in a rat model. Sixteen male Sprague—Dawley rats were divided into two groups: Group 1 rats included control rats given tap water. Group 2 rats were given water containing copper in a dose of 100 μg/mL. All rats were sacrificed at 4 wk under ether anesthesia. Plasma and liver superoxide dismutase (SOD) activities, plasma and liver MDA (malondialdehyde) levels, and liver glutathione (GSH) levels were studied. Plasma and liver SOD activities were found to be higher in group 2 than those in group 1. Although plasma MDA levels were higher in group 2, MDA levels in liver tissues were comparable. Liver tissue glutathione levels were lower in group 2. It was concluded that although copper is needed in trace amounts, an excess amount is toxic for the organism. It increases lipid peroxidation and depletes GSH reserves, which makes the organism more vulnerable to other oxidative challenges.     

p8 Upregulation sensitizes astrocytes to oxidative stress

Here we studied the mechanism of cell sensitization to oxidative stress by analyzing the gene expression profile of serum-deprived astrocytes. Exposure to serum-free medium (i) sensitized astrocytes to oxidative stress, (ii) reduced the expression of several genes involved in protection against oxidative stress, including heme oxygenase 1, and (iii) changed the expression of several genes involved in the control of cell survival, including the stress-regulated protein p8. Our results support that serum deprivation sensitizes astrocytes to oxidative stress via a p38 mitogen-activated protein kinase-dependent p8 upregulation that leads in turn to decreased heme oxygenase 1 expression.     

Mitochondrial oxidative stress causes chromosomal instability of mouse embryonic fibroblasts

Reactive oxygen species are an inevitable by-product of mitochondrial respiration. It has been estimated that between 0.4 and 4% of molecular oxygen is converted to the radical superoxide (O2*-) and this level is significantly influenced by the functional status of the mitochondria. It is well established that exogenous oxidative stress and high doses of mitochondrial poisons such as paraquat and carbonyl cyanide 4 (trifluoromethoxy) phenylhydrazone (FCCP) can lead to genomic instability. In this report we show for the first time that endogenous mitochondrial oxidative stress in standard cell culture conditions results in nuclear genomic instability in primary mouse embryonic fibroblasts (MEFs). We show that lack of mitochondrial superoxide dismutase in MEFs leads to a severe increase of double strand breaks, end-to-end fusions, chromosomal translocations, and loss of cell viability and proliferative capacity. Our results predict that endogenous mitochondrial oxidative stress can induce genomic instability, and therefore may have a profound effect in cancer and aging.     

Age-dependent changes in 8-oxoguanine-DNA glycosylase activity are modulated by adaptive responses to physical exercise in human skeletal muscle

8-Oxo-7,8-dihydroguanine (8-oxoG) accumulates in the genome over time and is believed to contribute to the development of aging characteristics of skeletal muscle and various aging-related diseases. Here, we show a significantly increased level of intrahelical 8-oxoG and 8-oxoguanine-DNA glycosylase (OGG1) expression in aged human skeletal muscle compared to that of young individuals. In response to exercise, the 8-oxoG level was lastingly elevated in sedentary young and old subjects, but returned rapidly to preexercise levels in the DNA of physically active individuals independent of age. 8-OxoG levels in DNA were inversely correlated with the abundance of acetylated OGG1 (Ac-OGG1), but not with total OGG1, apurinic/apyrimidinic endonuclease 1 (APE1), or Ac-APE1. The actual Ac-OGG1 level was linked to exercise-induced oxidative stress, as shown by changes in lipid peroxide levels and expression of Cu,Zn-SOD, Mn-SOD, and SIRT3, as well as the balance between acetyltransferase p300/CBP and deacetylase SIRT1, but not SIRT6 expression. Together these data suggest that that acetylated form of OGG1, and not OGG1 itself, correlates inversely with the 8-oxoG level in the DNA of human skeletal muscle, and the Ac-OGG1 level is dependent on adaptive cellular responses to physical activity, but is age independent.     

Short‐term calorie restriction reverses vascular endothelial dysfunction in old mice by increasing nitric oxide and reducing oxidative stress

To determine if short‐term calorie restriction reverses vascular endothelial dysfunction in old mice, old (O, n = 30) and young (Y, n = 10) male B6D2F1 mice were fed ad libitum (AL) or calorie restricted (CR, approximately 30%) for 8 weeks. Ex vivo carotid artery endothelium‐dependent dilation (EDD) was impaired in old ad libitum (OAL) vs. young ad libitum (YAL) (74 ± 5 vs. 95 ± 2% of maximum dilation, P < 0.05), whereas old calorie‐restricted (OCR) and YCR did not differ (96 ± 1 vs. 94 ± 3%). Impaired EDD in OAL was mediated by reduced nitric oxide (NO) bioavailability associated with decreased endothelial NO synthase expression (aorta) (P < 0.05), both of which were restored in OCR. Nitrotyrosine, a cellular marker of oxidant modification, was markedly elevated in OAL (P < 0.05), whereas OCR was similar to Y. Aortic superoxide production was 150% greater in OAL vs. YAL (P < 0.05), but normalized in OCR, and TEMPOL, a superoxide dismutase (SOD) mimetic that restored EDD in OAL (to 97 ± 2%), had no effect in Y or OCR. OAL had increased expression and activity of the oxidant enzyme, NADPH oxidase, and its inhibition (apocynin) improved EDD, whereas NADPH oxidase in OCR was similar to Y. Manganese SOD activity and sirtuin1 expression were reduced in OAL (P < 0.05), but restored to Y in OCR. Inflammatory cytokines were greater in OAL vs. YAL (P < 0.05), but unaffected by CR. Carotid artery endothelium‐independent dilation did not differ among groups. Short‐term CR initiated in old age reverses age‐associated vascular endothelial dysfunction by restoring NO bioavailability, reducing oxidative stress (via reduced NADPH oxidase–mediated superoxide production and stimulation of anti‐oxidant enzyme activity), and upregulation of sirtuin‐1.     

Defences against oxidative stress in vibrios associated with corals

Bacteria colonizing healthy coral tissue may produce enzymes capable of overcoming the toxic effects of reactive oxygen species, including superoxide dismutase (SOD) and catalase. Significant differences in the activities of these enzymes were observed in cultures of Vibrio campbellii, Vibrio coralliilyticus, Vibrio harveyi, Vibrio mediterranei, Vibrio pelagius, Vibrio rotiferanus, Vibrio tasmaniensis, and Photobacterium eurosenbergii isolated from healthy, bleached or necrotic tropical and cold water corals. Levels of SOD in exponential phase cultures of V. coralliilyticus grown at 28 degrees C were only slightly higher than those grown at 16 degrees C whereas the levels in stationary phase cultures at 28 degrees C were 7.3 x higher than those at 16 degrees C. The increase in catalase activity of V. coralliilyticus and V. harveyi upon entry to stationary phase conferred protection against killing by oxidative stress. Increased temperature affected up-regulation of enzymes in stationary phase cultures, but pretreatment of cultures with hydrogen peroxide had no significant effect on induction of catalase or SOD. The increased activities appear to be due to up-regulation of gene expression rather than induction of different forms of the enzymes. We suggest that SOD and catalase are unlikely to be major factors in the virulence of these bacteria for corals and that their main function may be to protect against endogenous superoxide.     

Effects of statins on oxidative stress

Free oxygen radicals and insufficient antioxidant enzymes have been implicated in the pathogenesis of hypercholesterolemia (HC). Trace elements function as cofactors in antioxidant enzymes. Antioxidant system and trace elements were investigated in many different studies including HC, but these subjects have not been investigated as a whole in these patients. The aim of the present study was to investigate the antioxidative system and trace elements in hypercholesterolemic patients given fluvastatin therapy. We examined malondialdehyde (MDA), copper zinc-superoxide dismutase (CuZn-SOD), and glutathione peroxidase (GSH-Px) activities together with copper (Cu), iron (Fe), and zinc (Zn) levels in erythrocytes of 35 patients with HC and 27 healthy control subjects. It was found that in patients with HC, erythrocyte MDA was significantly higher than those of controls and erythrocyte CuZn-SOD and GSH-Px activities were significantly lower in patients with HC. Erythrocyte iron levels were significantly higher than those of controls, and erythrocyte copper and zinc levels were significantly lower in patients with HC. Plasma lipid levels and the oxidative state were analyzed in statin-treatment groups given fluvastatin therapy before and after a 3-mo treatment period. In conclusion, we found that fluvastatin has significant antioxidant properties and these effects might be very important in managing dyslipidemia by improving endothelial function.     

Spermine and putrescine enhance oxidative stress tolerance in maize leaves

The protective effects of spermine (SPM) and putrescine (PUT) against paraquat (PQ), a herbicide in agriculture and oxidative stress inducer, were investigated in the leaves of maize. Maize leaves were pretreated to SPM and PUT at concentrations of 0.2 and 1 mM and treated with PQ afterwards. Pretreatment with 1 mM of SPM and PUT significantly prevented the losses in chlorophyll and carotenoid levels induced by PQ. Ascorbic acid content in the leaves pretreated with both polyamines was found to be higher than those of the leaves pretreated with water. Also, pretreatment with SPM and PUT was determined to have some effects on the activities of superoxide dismutase (SOD) and peroxidase (POD). 1 mM of SPM increased SOD activity, but PUT has no significant effect on SOD activity. On the other hand, POD activity was recorded to increase slightly in response to both concentrations of SPM and 1 mM of PUT. The results showed that such polyamine pretreated plants may become more tolerant to oxidative stress due to increases in the antioxidative enzymes and antioxidants.     

Autophagy in osteoporosis: Relation to oxidative stress

Impaired autophagy and oxidative stress are implicated in the development of many diseases. This study aimed to investigate the involvement of autophagy represented by autophagy-related gene 7 (Atg7) and oxidative stress represented by superoxide dismutase 2 (SOD2) gene expression and enzyme activity in the pathogenesis of osteoporosis. Atg7 and SOD2 gene relative expression were evaluated by SYBR green quantitative real-time-polymerase chain reaction in the osteoporotic group (n = 26) versus the osteoporosis free group (n = 14). SOD2 enzyme activity was evaluated by colorimetric method in both study groups. Both Atg7 and SOD2 relative expression showed highly significant decrease (P < 0.01) between both groups. However, SOD2 enzyme activity showed no significant difference between the two groups. There was a significant direct correlation between Atg7 and SOD2 gene expression in both study groups. Atg7 relative expression showed significant ( P < 0.01) direct correlation with vitamin D serum levels and body mass index in osteoporotic group. In conclusion, both genes are involved in the pathogenesis of osteoporosis and this could be amenable to future therapeutic intervention.     

Increased levels of oxidative stress biomarkers in metal oxides nanomaterial-handling workers

This study assessed oxidatively damaged DNA and antioxidant enzyme activity in workers occupational exposure to metal oxides nanomaterials. Exposure to TiO₂, SiO₂, and ITO resulted in significant lower antioxidant enzymes (glutathione peroxidase and superoxide dismutase) and higher oxidative biomarkers 8-hydroxydeoxyguanosine (8-oxodG) than comparison workers. Statistically significant correlations were noted between plasma and urine 8-oxodG, between white blood cells (WBC) and urine 8-oxodG, and between WBC and plasma 8-oxodG. In addition, there were significant negative correlations between WBC 8-oxodG and SOD and between urinary 8-oxodG and GPx levels. The results showed that urinary 8-oxodG may be considered to be better biomarker.     

Body iron is a contributor to oxidative damage of DNA

The transition metal iron is catalytically highly active in vitro, and not surprisingly, body iron has been suggested to promote oxidative stress in vivo. In the current analysis we studied the association of serum ferritin concentration and serum soluble transferrin receptor concentration with daily urinary 8-hydroxydeoxyguanosine excretion, a marker of oxidative stress, in 48 mildly dyslipidemic men in East Finland. In multivariate linear regression analyses allowing for age, smoking, body mass index and physical exercise, serum ferritin concentration predicted the excretion rate at B = 0.17 (95% CI 0.08–0.26, P = 0.001), and serum soluble transferrin receptor to ferritin concentration ratio (TfR/ferritin) predicted the excretion rate at B = ? 0.13 (95% CI ? 0.21 to ? 0.05, P = 0.002). Our data suggest that body iron contributes to excess oxidative stress already at non-iron overload concentrations in these subjects.     

Body iron is a contributor to oxidative damage of DNA

The transition metal iron is catalytically highly active in vitro, and not surprisingly, body iron has been suggested to promote oxidative stress in vivo. In the current analysis we studied the association of serum ferritin concentration and serum soluble transferrin receptor concentration with daily urinary 8-hydroxydeoxyguanosine excretion, a marker of oxidative stress, in 48 mildly dyslipidemic men in East Finland. In multivariate linear regression analyses allowing for age, smoking, body mass index and physical exercise, serum ferritin concentration predicted the excretion rate at B = 0.17 (95% CI 0.08-0.26, P = 0.001), and serum soluble transferrin receptor to ferritin concentration ratio (TfR/ferritin) predicted the excretion rate at B = - 0.13 (95% CI - 0.21 to - 0.05, P = 0.002). Our data suggest that body iron contributes to excess oxidative stress already at non-iron overload concentrations in these subjects.     

Hepatic response to the oxidative stress induced by E. coli endotoxin: Glutathione as an index of the acute phase during the endotoxic shock

Reactive oxygen species are important mediators of cellular damage during endotoxic shock. In order to investigate the hepatic response to the oxidative stress induced by endotoxin, hepatic and plasma glutathione (total, GSH and GSSG), GSSG/GSH ratio as well as Mn-superoxide dismutase and catalase activities were determined during the acute and recovery phases of reversible endotoxic shock in the rat. A significant increase in liver and plasma total glutathione content was observed 5 h after endotoxin treatment (acute phase), followed by a diminution of these parameters below control values at 48 h (recovery phase). The significant increases of GSSG levels and GSSG/GSH ratio are indicative of oxidative stress occurring during the acute phase. Liver Mn-SOD activity showed a similar time dependency as the GSSG/GSH ratio; however, a marked decrease in the liver catalase activity was observed during the process. These results indicate the participation of liver glutathione in the response to endotoxin and the possible use of plasma glutathione levels and GSSG/GSH ratio as indicators of the acute phase during the endotoxic process. (Mol Cell Biochem 159: 115-121, 1996)     

Cellular accumulation of Cys326-OGG1 protein complexes under conditions of oxidative stress

The common Ser326Cys polymorphism in the base excision repair protein 8-oxoguanine glycosylase 1 is associated with a reduced capacity to repair oxidative DNA damage particularly under conditions of intracellular oxidative stress and there is evidence that Cys326-OGG1 homozygous individuals have increased susceptibility to specific cancer types. Indirect biochemical studies have shown that reduced repair capacity is related to OGG1 redox modification and also possibly OGG1 dimer formation. In the current study we have used bimolecular fluorescence complementation to study for the first time a component of the base excision repair pathway and applied it to visualise accumulation of Cys326-OGG1 protein complexes in the native cellular environment. Fluorescence was observed both within and around the cell nucleus, was shown to be specific to cells expressing Cys326-OGG1 and only occurred in cells under conditions of cellular oxidative stress following depletion of intracellular glutathione levels by treatment with buthionine sulphoximine. Furthermore, OGG1 complex formation was inhibited by incubation of cells with the thiol reducing agents β-mercaptoethanol and dithiothreitol and the antioxidant dimethylsulfoxide indicating a causative role for oxidative stress in the formation of OGG1 cellular complexes.