The steady-state levels of oxidative DNA damage and of lipid peroxidation (F2-isoprostanes) are not correlated in healthy human subjects

Reduced retinol (vitamin A) and α-tocopherol (vitamin E) blood levels and increased myeloperoxidase (MPO) activity in children with high myopia

The study assessed selected parameters of redox status in the plasma of patients suffering from high myopia (HM). Thirty-five children with mean age 13.7 ± 2.7 years with HM and 40 healthy children were included. Plasma redox status parameters were determined using colorimetric kits. The levels of retinol, α-tocopherol and coenzyme Q10 were determined with a high-performance liquid chromatograph. Negative correlations were observed between the concentrations of retinol and the axial length of the eye (r = - 0.514 p < 0.001). Increased myeloperoxidase (MPO) activity (p < 0.018), and decreased concentrations of retinol (p < 0.001) and α-tocopherol (p < 0.023) in patients with HM and the axial length of the eye > 26 mm compared to controls were established. Significantly lower retinol and α-tocopherol concentrations were found in patients with the axial length of the eye > 26 mm compared to those with the axial length of the eye ≤ 26 mm (p < 0.001, p < 0.021, respectively). Increased MPO activity in advanced stages of HM may confirm an inflammatory process in HM patients. Reduced retinol and α-tocopherol concentrations and their link to disease progression indicate a need for monitoring their levels and supplementation in children with HM.

Oxidative stress induction in woodworkers occupationally exposed to wood dust and formaldehyde

BACKGROUND

Many workers are exposed to wood dust (WD) and formaldehyde (FA), whose carcinogenic activity is supposed to be oxidative stress-mediated. This study aims to assess to what extent the occupational exposure to WD and FA, albeit within regulatory limits, could result in OS induction in a woodworkers' population.

METHODS

The sample population consisted of 127 woodworkers from 4 factories and 111 unexposed controls. Individual exposure was assessed by personal air-samplers. Each participant enrolled in the study filled out a questionnaire and provided a urinary sample to quantify OS biomarkers, namely 15-F2t-IsoProstane (15-F2t-IsoP) and 7,8-dihydro-8-oxo-2'-deoxyguanosine (8-oxo-dGuo). The main confounding factor for OS, i.e. tobacco smoking exposure, was assessed by measuring cotinine in urine samples.

RESULTS

Woodworkers were exposed to significantly higher amounts of WD and FA as compared to controls (p < 0.001). Among OS biomarkers, 15-F2t-IsoP showed statistically significant higher values in woodworkers compared to controls (p = 0.004). A significant, positive correlation was observed between 15-F2t-IsoP and 8-oxo-dGuo (p = 0.005), cotinine (p = 0.05), FA (p < 0.001) and WD (p = 0.01); 8-oxo-dGuo was significantly correlated with cotinine (p = 0.001) and WD (p = 0.004). In addition, WD and FA were significantly correlated each other (p < 0.001).

CONCLUSIONS

The study confirms that WD and FA may induce OS in woodworkers, and highlights that even the compliance with occupational exposure limits can result in measurable biological outcomes.

Assessing Free-Radical-Mediated DNA Damage during Cardiac Surgery: 8-Oxo-7,8-dihydro-2'-deoxyguanosine as a Putative Biomarker

Coronary artery bypass grafting (CABG), one of the most common cardiac surgical procedures, is characterized by a burst of oxidative stress. 8-Oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodG), produced following DNA repairing, is used as an indicator of oxidative DNA damage in humans. The effect of CABG on oxidative-induced DNA damage, evaluated through the measurement of urinary 8-oxodG by a developed and validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) method in 52 coronary artery disease (CAD) patients, was assessed before (T0), five days (T1), and six months (T2) after CABG procedure. These results were compared with those obtained in 40 subjects with cardiovascular risk factors and without overt cardiovascular disease (CTR). Baseline (T0) 8-oxodG was higher in CAD than in CTR (p = 0.035). A significant burst was detected at T1 (p = 0.019), while at T2, 8-oxodG levels were significantly lower than those measured at T0 (p < 0.0001) and comparable to those found in CTR (p = 0.73). A similar trend was observed for urinary 8-iso-prostaglandin F_2α (8-isoPGF_2α), a reliable marker of oxidative stress. In the whole population baseline, 8-oxodG significantly correlated with 8-isoPGF_2α levels (r = 0.323, p = 0.002). These data argue for CABG procedure in CAD patients as inducing a short-term increase in oxidative DNA damage, as revealed by 8-oxodG concentrations, and a long-term return of such metabolite toward physiological levels.

Going retro: Oxidative stress biomarkers in modern redox biology

The field of redox biology is inherently intertwined with oxidative stress biomarkers. Oxidative stress biomarkers have been utilized for many different objectives. Our analysis indicates that oxidative stress biomarkers have several salient applications: (1) diagnosing oxidative stress, (2) pinpointing likely redox components in a physiological or pathological process and (3) estimating the severity, progression and/or regression of a disease. On the contrary, oxidative stress biomarkers do not report on redox signaling. Alternative approaches to gain more mechanistic insights are: (1) measuring molecules that are integrated in pathways linking redox biochemistry with physiology, (2) using the exomarker approach and (3) exploiting -omics techniques. More sophisticated approaches and large trials are needed to establish oxidative stress biomarkers in the clinical setting.

Sociodemographic and Lifestyle Determinants of Plasma Oxidative Stress Markers 8-OHdG and F2-Isoprostanes and Associations with Metabolic Syndrome

Background. Oxidative stress is increasingly important in health research. Therefore, it is necessary to understand which factors determine basal oxidative stress. This study examines the associations of various determinants with markers of oxidative DNA and lipid damage: 8-hydroxy-2'-deoxyguanosine (8-OHdG) and F2-isoprostanes. Methods. Data are from the Netherlands Study of Depression and Anxiety; 1117 subjects (18-65 years) without a current psychiatric diagnosis. Multivariable regression analyses were conducted with plasma levels of 8-OHdG and F2-isoprostanes (measured by LC/MS-MS) including sociodemographic, lifestyle, and sampling variables. Associations with metabolic syndrome (MetS) and chronic disease were examined. Results. 8-OHdG and F2-isoprostanes were weakly correlated (r = 0.06, p = 0.045). Both were positively associated with age and cotinine (cigarette exposure); 8-OHdG was lower in females and after longer sample storage. F2-isoprostanes were higher in females, alcohol users, and in samples collected in spring and lower in supplement users and those with more education. Both markers were lower in fasting subjects. F2-isoprostanes, not 8-OHdG, were positively associated with MetS. Conclusion. The weak correlation between 8-OHdG and F2-isoprostanes suggests they reflect specific aspects of oxidative stress. Both markers are associated with a range of sociodemographic, lifestyle, and sampling determinants which should be considered in future research. F2-isoprostanes are associated with MetS.

Oxidative stress, insulin resistance, dyslipidemia and type 2 diabetes mellitus

Oxidative stress is increased in metabolic syndrome and type 2 diabetes mellitus (T2DM) and this appears to underlie the development of cardiovascular disease, T2DM and diabetic complications. Increased oxidative stress appears to be a deleterious factor leading to insulin resistance, dyslipidemia, β-cell dysfunction, impaired glucose tolerance and ultimately leading to T2DM. Chronic oxidative stress, hyperglycemia and dyslipidemia are particularly dangerous for β-cells from lowest levels of antioxidant, have high oxidative energy requirements, decrease the gene expression of key β-cell genes and induce cell death. If β-cell functioning is impaired, it results in an under production of insulin, impairs glucose stimulated insulin secretion, fasting hyperglycemia and eventually the development of T2DM.

A dose-response study of arsenic exposure and markers of oxidative damage in Bangladesh

OBJECTIVE

To evaluate the dose-response relationship between arsenic (As) exposure and markers of oxidative damage in Bangladeshi adults.

METHODS

We recruited 378 participants drinking water from wells assigned to five water As exposure categories; the distribution of subjects was as follows: (1) less than 10 μg/L (n=76); (2) 10 to 100 μg/L (n=104); (3) 101 to 200 μg/L (n=86); (4) 201 to 300 μg/L (n=67); and (5) more than 300 μg/L (n=45). Arsenic concentrations were measured in well water, as well as in urine and blood. Urinary 8-oxo-2'-deoxyguanosine and plasma protein carbonyls were measured to assess oxidative damage.

RESULTS

None of our measures of As exposure were significantly associated with protein carbonyl or 8-oxo-2'-deoxyguanosine levels.

CONCLUSIONS

We found no evidence to support a significant relationship between long-term exposure to As-contaminated drinking water and biomarkers of oxidative damage among Bangladeshi adults.

Concentrations of urinary 8-hydroxy-2'-deoxyguanosine and 8-isoprostane in women exposed to woodsmoke in a cookstove intervention study in San Marcos, Peru

Nearly half of the world's population is exposed to household air pollution (HAP) due to long hours spent in close proximity to unvented cooking fires. The effect of woodsmoke exposure on oxidative stress was examined by investigating the association between woodsmoke exposure and biomarkers of DNA oxidation (8-hydroxy-2'-deoxyguanosine [8-OHdG]) and lipid peroxidation (8-isoprostane) among control and intervention stove users. HAP exposure assessment was conducted within the framework of a community-randomized controlled trial of 51 communities in San Marcos Province, Cajamarca Region, Peru. The first morning urine voids after 48h HAP exposure assessment from a subset of 45 control and 39 intervention stove users were analyzed for 8-OHdG and 8-isoprostane. General linear models and correlation analyses were performed. Urinary oxidative stress biomarkers ranged from 11.2 to 2270.0μg/g creatinine (median: 132.6μg/g creatinine) for 8-OHdG and from 0.1 to 4.5μg/g creatinine (median: 0.8μg/g creatinine) for 8-isoprostane among all study subjects (n=84). After controlling for the effects of traffic in the community and eating food exposed to fire among all subjects, cooking time was weakly, but positively associated with urinary 8-OHdG (r=0.29, p=0.01, n=80). Subjects' real-time personal CO exposures were negatively associated with 8-OHdG, particularly the maximum 30-second CO exposure during the sampling period (r=-0.32, p=0.001, n=73). 48h time integrated personal PM2.5 was negatively, but marginally associated with urinary 8-isoprostane (r=-0.21, p=0.09, n=69) after controlling for the effect of distance of homes to the road. Urinary 8-isoprostane levels reported in the available literature are comparable to results found in the current study. However there were relatively high levels of urinary 8-OHdG compared to data in the available literature for 8-OHdG excretion. Results suggest a sustained systemic oxidative stress among these Peruvian women chronically exposed to wood smoke.

A top-down LC-FTICR MS-based strategy for characterizing oxidized calmodulin in activated macrophages

A liquid chromatography-mass spectrometry (LC-MS)-based approach for characterizing the degree of nitration and oxidation of intact calmodulin (CaM) has been used to resolve approximately 250 CaM oxiforms using only 500 ng of protein. The analysis was based on high-resolution data of the intact CaM isoforms obtained by Fourier-transform ion cyclotron resonance mass spectrometry (FTICR MS) coupled with an on-line reversed-phase LC separation. Tentative identifications of post-translational modifications (PTMs), such as oxidation or nitration, have been assigned by matching observed protein mass to a database containing all theoretically predicted oxidation products of CaM and verified through a combination of tryptic peptide information (generated from bottom-up analyses) and on-line collisionally induced dissociation (CID) tandem mass spectrometry (MS/MS) at the intact protein level. The reduction in abundance and diversity of oxidatively modified CaM (i.e., nitrated tyrosines and oxidized methionines) induced by macrophage activation has been explored and semiquantified for different oxidation degrees (i.e., no oxidation, moderate, and high oxidation). This work demonstrates the power of the top-down approach to identify and quantify hundreds of combinations of PTMs for single protein target such as CaM and implicate competing repair and peptidase activities to modulate cellular metabolism in response to oxidative stress.

Chronic oxidative stress as a mechanism for radiation nephropathy

Suppression of the renin-angiotensin system has proven efficacy for mitigation and treatment of radiation nephropathy, and it has been hypothesized that this efficacy is due to suppression of radiation-induced chronic oxidative stress. It is known that radiation exposure leads to acute oxidative stress, but direct evidence for radiation-induced chronic renal oxidative stress is sparse. We looked for evidence of oxidative stress after total-body irradiation in a rat model, focusing on the period before there is physiologically significant renal damage. No statistically significant increase in urinary 8-isoprostane (a marker of lipid peroxidation) or carbonylated proteins (a marker of protein oxidation) was found over the first 42 days after irradiation, while a small but statistically significant increase in urinary 8-hydroxydeoxy-guanosine (a marker of DNA oxidation) was detected at 35-55 days. When we examined renal tissue from these animals, we found no significant increase in either DNA or protein oxidation products over the first 89 days after irradiation. Using five different standard methods for detecting oxidative stress in vivo, we found no definitive evidence for radiation-induced renal chronic oxidative stress. If chronic oxidative stress is part of the pathogenesis of radiation nephropathy, it does not leave widespread or easily detectable evidence behind.

Analysis of oxidative stress biomarkers using a simultaneous competitive/non-competitive micromosaic immunoassay

Immunoassays represent a core workhorse methodology for many applications ranging from clinical diagnostics to environmental monitoring. In traditional formats such as the enzyme linked immunosorbent assay (ELISA), analytes are measured singly or in small sets. As more biomarkers are identified for disease states, there is a need to develop methods that can measure multiple markers simultaneously. Immunoaffinity arrays are one such chemistry that can achieve multi-marker screening. Most arrays are performed in either competitive or non-competitive formats, where the former are used predominantly for small molecules and the later for macromolecules. To date, ELISA and immunoaffinity array methods have relied exclusively on one of these formats and not the other. Here an immunoaffinity array method capable of performing simultaneous competitive and non-competitive analysis generated using micromosaic immunoassay techniques is introduced for the analysis of metabolites and proteins. In this report, three markers of oxidative stress were used as a model system. The method described here demonstrates the simultaneous analysis of 3-nitrotyrosine, by indirect competitive immunoassay while the enzymes catalase and superoxide dismutase are analyzed by non-competitive sandwich immunoassay. The method requires less than 1 microL sample and 45 min for completion. Logistic curve fits and LOD (limits of detection) statistical analysis of the binding results are presented and show good agreement with published data for these antibody-antigen systems.

Oxidative stress biomarkers and lifestyles in Japanese healthy people

The urinary concentrations of 8-isoprostane and 8-hydroxy-2’-deoxyguanosine (8-OHdG), which are biomarkers of oxidative stress, were measured in 677 Japanese people without any diseases, and their correlations with lifestyle facotrs, lifestyle-related blood biochemical parameters, and dietary intake of antioxidative vitamins were investigated. The mean urinary concentration of 8-isoprostane and 8-OHdG was 0.58 ng/mg creatinine and 8.43 ng/mg creatinine, respectively. Mean urinary 8-isoprostane was significantly different in terms of age, gender, smoking and alcohol consumption but not different in terms of body mass index (BMI) and exercise. By multiple regression analysis, urinary 8-isoprostane was significantly influenced by smoking and age. On the other hand, mean urinary 8-OHdG showed differences only by age group. Multiple regression analysis revealed that urinary 8-OHdG was significantly influenced by age, smoking, body weight, levels of high-sensitivity C-reactive protein (Hs-CRP) and low density lipoprotein-cholesterol in females, although it was significantly influenced by body weight in males. The present study shows that urinary 8-isoprostane is associated with lipid peroxidation related-lifestyles such as smoking, and urinary 8-OHdG is associated with arteriosclerosis related-factors such as Hs-CRP. Our findings suggest that 8-isoprostane and 8-OHdG appear to be prospective biomarkers for early prediction of lifestyle related-disease risk at the population level.

Increased oxidative damage in peripheral blood correlates with severity of Parkinson's disease

Increased oxidative stress contributes to neuronal dysfunction in Parkinson's disease (PD). We investigated whether the pathological changes in PD brains may also be present in peripheral tissues. Leukocyte 8-hydroxydeoxyguanosine (8-OHdG), plasma malondialdehyde (MDA), erythrocyte glutathione peroxidase (GPx) and plasma vitamin E (Vit E) were measured for 211 PD patients and 135 healthy controls. Leukocyte 8-OHdG and plasma MDA were elevated, whereas erythrocyte GPx and plasma Vit E were reduced in PD patients when compared to the controls. After adjusting for environmental factors, logistic regression analysis showed that PD severity was independently correlated with 8-OHdG and MDA level, and inversely correlated with GPx activity and Vit E level. Leucocyte 8-OHdG level was continuously increased with advanced PD Hoehn-Yahr stages, while plasma MDA level peaked at early disease stages, among PD patients. These results suggest increased oxidative damage and decreased anti-oxidant capacity in peripheral blood, and a significant correlation between leucocyte 8-OHdG level and disease severity in PD.

Prevention of DNA damage in renal transplantation by losartan and enalapril: the role of renin-angiotensin system polymorphisms

BACKGROUND

In this study the effect of losartan and enalapril on the reduction of DNA damage was evaluated in regard to renin-angiotensin system (RAS) polymorphisms.

METHODS

After determination of genotypes of RAS polymorphism by PCR, 64 renal transplant recipients were randomly allocated to one of four groups: the first and second groups were treated with E (E+: 10 mg/day) and L (L+: 50 mg/day) alone, respectively. The third group received E+L (E+L+: 10 + 50 mg/day), and the forth group received no medication (E-L-). The subjects were followed for 8 weeks. After a 2-week washout period, the E group changed to L and vice versa as a cross-over design. They were followed for another 8 weeks. Before and after treatment, we checked 8-OHdG and malondialdehyde (MDA) as biomarkers of DNA damage and lipid peroxidation, respectively.

RESULTS

8-OHdG levels were significantly decreased after treatment in the E+L+ and L+ groups (P < 0.001, P = 0.001, respectively). Only the TT genotype of AGT had the most antioxidative role regarding the treatment (P = 0.01). We found a remarkable correlation between MDA and DNA damage levels before and after intervention (r = 0.48, P < 0.001; r = 0.35, P = 0.006).

CONCLUSION

The protective effects of L+ and E+L+ on DNA breaks are surprising regarding the RAS polymorphisms.

Health promotion by flavonoids, tocopherols, tocotrienols, and other phenols: direct or indirect effects? Antioxidant or not?

Foods and beverages rich in phenolic compounds, especially flavonoids, have often been associated with decreased risk of developing several diseases. However, it remains unclear whether this protective effect is attributable to the phenols or to other agents in the diet. Alleged health-promoting effects of flavonoids are usually attributed to their powerful antioxidant activities, but evidence for in vivo antioxidant effects of flavonoids is confusing and equivocal. This may be because maximal plasma concentrations, even after extensive flavonoid intake, may be low (insufficient to exert significant systemic antioxidant effects) and because flavonoid metabolites tend to have decreased antioxidant activity. Reports of substantial increases in plasma total antioxidant activity after flavonoid intake must be interpreted with caution; findings may be attributable to changes in urate concentrations. However, phenols might exert direct effects within the gastrointestinal tract, because of the high concentrations present. These effects could include binding of prooxidant iron, scavenging of reactive nitrogen, chlorine, and oxygen species, and perhaps inhibition of cyclooxygenases and lipoxygenases. Our measurements of flavonoids and other phenols in human fecal water are consistent with this concept. We argue that tocopherols and tocotrienols may also exert direct beneficial effects in the gastrointestinal tract and that their return to the gastrointestinal tract by the liver through the bile may be physiologically advantageous.

Effect of I-deprenyl and gliclazide on oxidant stress/antioxidant status and dna damage in a diabetic rat model

BACKGROUND

This study investigates the possible effect of monoamine oxidase inhibitor (MAOI), selegyline (l-deprenyl), in combination with oral antidiabetic-gliclazide (OAD), in preventing oxidative stress in streptozotocin-induced diabetes model in male Swiss Albino rats by measuring oxidant stress/ DNA damage and antioxidant levels.

METHODS

Diabetic rats were divided into four groups (n = 10) as (1) diabetic untreated (DM), (2) deprenyl treated (DM + D), (3) gliclazide treated (DM + O), and (4) gliclazide and deprenyl treated (DM + O + D). Controls were divided into two groups (n = 8) (1) untreated (C), and (2) deprenyl treated (C + D). Gliclazide 5 mg/kg and/or MAOI 0.25 mg/kg daily were given orally by gavage for 4 weeks. At the end of the 12th week, catalase and superoxide dismutase (SOD) levels in erythrocyte lysates (EL); total antioxidant status (TAS), 8-hydroxy-deoxyguanosine (8-OHdG), malondialdehyde (MDA), and vitamin A and E levels in plasma, MDA, and MAO in liver homogenates were determined.

RESULTS

Diabetic rats showed a decrease in EL-SOD, plasma TAS, and vitamin E, and an increase in plasma 8-OHdG, plasma, and liver MDA levels (p < 0.05). Gliclazide and/or deprenyl decreased 8OHdG levels and increased antioxidant levels and survival when compared with untreated diabetic rats (p < 0.05). The lowest 8-OHdG levels were determined in the DM +O + D group.

CONCLUSIONS

The combined treatment of deprenyl and gliclazide may contribute to the control of the physiopathological mechanisms underlying both the process of aging and type 2 diabetes by reducing oxidant stress and DNA damage, improving antioxidant status, and increasing survival, and may have implications for further clinical studies.

Cytochrome P450 1A2 (CYP1A2) activity, mammographic density, and oxidative stress: a cross-sectional study

Introduction

Mammographically dense breast tissue is a strong predictor of breast cancer risk, and is influenced by both mitogens and mutagens. One enzyme that is able to affect both the mitogenic and mutagenic characteristics of estrogens is cytochrome P450 1A2 (CYP1A2), which is principally responsible for the metabolism of 17β-estradiol.

Methods

In a cross-sectional study of 146 premenopausal and 149 postmenopausal women, we examined the relationships between CYP1A2 activity, malondialdehyde (MDA) levels, and mammographic density. In vivo CYP1A2 activity was assessed by measuring caffeine metabolites in urine. Levels of serum and urinary MDA, and MDA–deoxyguanosine adducts in DNA were measured. Mammograms were digitized and measured using a computer-assisted method.

Results

CYP1A2 activity in postmenopausal women, but not in premenopausal women, was positively associated with mammographic density, suggesting that increased CYP1A2 activity after the menopause is a risk factor for breast cancer. In premenopausal women, but not in postmenopausal women, CYP1A2 activity was positively associated with serum and urinary MDA levels; there was also some evidence that CYP1A2 activity was more positively associated with percentage breast density when MDA levels were high, and more negatively associated with percentage breast density when MDA levels were low.

Conclusion

These findings provide further evidence that variation in the activity level of enzymes involved in estrogen metabolism is related to levels of mammographic density and potentially to breast cancer risk.

Measuring reactive species and oxidative damage in vivo and in cell culture: how should you do it and what do the results mean?

Free radicals and other reactive species (RS) are thought to play an important role in many human diseases. Establishing their precise role requires the ability to measure them and the oxidative damage that they cause. This article first reviews what is meant by the terms free radical, RS, antioxidant, oxidative damage and oxidative stress. It then critically examines methods used to trap RS, including spin trapping and aromatic hydroxylation, with a particular emphasis on those methods applicable to human studies. Methods used to measure oxidative damage to DNA, lipids and proteins and methods used to detect RS in cell culture, especially the various fluorescent "probes" of RS, are also critically reviewed. The emphasis throughout is on the caution that is needed in applying these methods in view of possible errors and artifacts in interpreting the results.

Urinary excretion of three nucleic acid oxidation adducts and isoprostane F(2)alpha measured by liquid chromatography-mass spectrometry in smokers, ex-smokers, and nonsmokers

To assess novel liquid chromatography/mass spectrometric methods for measuring oxidative damage to nucleic acids and lipids, we compared urinary excretion of 8-hydroxy-2'-deoxyguanosine (8-OHdG), 5-hydroxymethyl-2'-deoxyuridine (5-OHmU), and 8-hydroxyguanosine (8-OxoG), and an isoprostane, 8-iso-prostaglandin F(2)alpha (IsopF(2)alpha) in 234 healthy men (n = 113) and women (n = 121), 80 current smokers, 96 never-smokers), and 58 ex-smokers (no tobacco use for 3 years). The 8-OHdG and 8-OxoG did not differ significantly by group; 5-OHmU was higher in smokers, compared with ex- (p <.003) and never- (p <.0001) smokers and in ex- vs. never-smokers (p =.014) at, respectively, 13.5 +/- 0.7, 11.3 +/- 1.0, and 8.7 +/- 0.3 microg/g creatinine. IsopF(2)alpha was higher in smokers, compared with ex- (p =.007) and never-smokers (p <.0001) and in ex- vs. never- smokers (p =.002) at, respectively, 1.1 +/- 0.10; 0.74 +/- 0.07, and 0.51 +/- 0.04 microg/g creatinine. There were significant correlations among all three nucleic acid adducts and between IsopF(2)alpha and both 5-OHmU and 8-OHdG. Many smokers and ex-smokers had high levels of either 5-OHmU excretion or IsopF(2)alpha excretion, but not both. We conclude that 5-OHmU and IsopF(2)alpha are more discriminating of oxidative stress from tobacco smoke than the other two compounds measured. Whether characteristic patterns of excretion of these indicators forecast differential disease risk should be explored in future research.

The postprandial effects of dietary antioxidants in humans

Traditional risk factors as measured in the fasted individual are reported to be responsible for the prediction of only half of the incident cases of cardiovascular disease. However, many complex and deleterious reactions occur in the postprandial state. The consequences of oxidative reactions occurring during this time represent major risk for fatal and nonfatal heart disease, ischemia, and stroke, and include oxidative modifications to low-density lipoproteins (LDL), decreased production and bioactivity of nitric oxide (NO) in endothelial cells, and reduced endothelial function. Supplementation with antioxidants may prevent or reduce many of these risks. Antioxidants have been shown to reduce oxidative modification to LDL cholesterol, prevent glucose auto-oxidation, improve the bioactivity of NO, and attenuate or prevent the decrease in endothelial function associated with the postprandial state. Because many nonfasting reactions represent major risk for disease, postprandial risk analysis must form a larger part of the diagnostic strategy for disease prevention in the future.

Protective effect of supplementation of fish oil with high n-3 polyunsaturated fatty acids against oxidative stress-induced DNA damage of rat liver in vivo

The present study was undertaken to know the effect of supplementation of fish oil with high n-3 polyunsaturated fatty acids (PUFA) on oxidative stress-induced DNA damage of rat liver in vivo. Male Wistar rats were fed a diet containing fish oil or safflower oil with high n-6 PUFA at 50 g/kg of diet and an equal amount of vitamin E at 59 mg/kg of diet for 6 weeks. Livers of rats fed fish oil were rich in n-3 PUFA, whereas those of rats fed safflower oil were rich in n-6 PUFA. Ferric nitrilotriacetate was intraperitoneally injected to induce oxidative stress. The degree of lipid peroxidation of the liver was assessed by the levels of phospholipid hydroperoxides and thiobarbituric acid-reactive substances (TBARS), and the degree of oxidative DNA damage was assessed by comet type characterization in alkaline single-cell gel electrophoresis and 8-hydroxy-2'-deoxyguanosine levels. The levels of TBARS of the livers of the fish oil diet group increased to a greater extent than those of the safflower oil diet group, whereas the levels of the hydroperoxides of the livers of both diet groups increased to a similar extent. The vitamin E level of livers of the fish oil diet group was remarkably decreased. The degree of DNA damage of both diet groups was increased, but the increased level of the fish oil diet group was remarkably lower than that of the safflower oil diet group. The above results indicate that fish oil supplementation does not enhance but appears to protect against oxidative stress-induced DNA damage and suggest that lipid peroxidation does not enhance but lowers the DNA damage.

Suppression of free radical-induced DNA strand breaks by linoleic acid and low density lipoprotein in vitro

The results of the present study have shown that unoxidized linoleic acid (LA) and low density lipoprotein (LDL) suppressed free radical-induced supercoiled plasmid DNA strand breaks. Unoxidized LA suppressed DNA strand breaks induced by free radicals generated from hydrogen peroxide/Fe(II) ion, 2'-azobis(2-amidinopropane)hydrochloride (AAPH), and 4-(hydroxymethyl)benzene diazonium salt. Thiobarbituric acid reactive substances (TBARS) of LA were increased on treatment with the radical generators. The intensities of the electron spin resonance (ESR) signals of the spin adducts of the radicals were reduced by unoxidized LA. Although LA hydroperoxide caused DNA strand breaks as has already been shown, its strand breaking activity was observed only at the higher concentrations. Unoxidized LDL inhibited ascorbic acid/Cu(II) ion-, ascorbic acid/Fe(II) ion-, peroxynitrite- and AAPH-induced DNA strand breaks. The TBARS of LDL were increased by treatment with the agents. LDL oxidized with Cu(II) ion did not cause DNA strand breaks. The results indicate that the potency of the free radicals to cause DNA strand breaks was attenuated by the fatty acid and the lipoprotein through lipid peroxidation.

Effect of vitamin E and eccentric exercise on selected biomarkers of oxidative stress in young and elderly men

Muscle damage resulting from eccentric exercise provides a useful model of oxyradical-induced injury and can be used to examine age-related responses to oxidative stress. Sixteen young (26.4 +/- 3.3 years) and 16 older (71.1 +/- 4.0 years) healthy men were randomly assigned to 1000 IU/d vitamin E or placebo for 12 weeks and ran downhill for 45 min at 75% VO(2)max, once before and following supplementation. Blood samples were obtained before (baseline) and immediately postexercise (0 h), and at 6, 24, and 72 h postexercise to determine antioxidant status, muscle damage, lipid peroxidation, and DNA damage. Following exercise, young and older men experienced similar increases in serum creatine kinase (CK), F(2alpha)-isoprostanes (iPF(2alpha); p <.001) and malondialdehyde (MDA; p <.01), although iPF(2alpha) peaked at 72 h postexercise and MDA peaked at 0 h. Oxygen Radical Absorbance Capacity (ORAC) decreased at 72 h (p <.01) and correlated with the rise in iPF(2alpha), MDA, and CK in the young men (p <.05). Leukocyte 8-hydroxy-2'-deoxyguanosine (8-OHdG) was unaffected by exercise. Vitamin E decreased peak CK in young men, while in older men it decreased resting levels of iPF(2alpha) and suppressed the 24 h postexercise increases in iPF(2alpha) (p <.05). Thus, vitamin E supplementation induced modest changes eccentric exercise-induced oxidative stress, although differentially between the young and older subjects, while age had no direct influence on these responses among this group of physically fit subjects.

Role of free radicals in the neurodegenerative diseases: therapeutic implications for antioxidant treatment

Free radicals and other so-called 'reactive species' are constantly produced in the brain in vivo. Some arise by 'accidents of chemistry', an example of which may be the leakage of electrons from the mitochondrial electron transport chain to generate superoxide radical (O2*-). Others are generated for useful purposes, such as the role of nitric oxide in neurotransmission and the production of O2*- by activated microglia. Because of its high ATP demand, the brain consumes O2 rapidly, and is thus susceptible to interference with mitochondrial function, which can in turn lead to increased O2*- formation. The brain contains multiple antioxidant defences, of which the mitochondrial manganese-containing superoxide dismutase and reduced glutathione seem especially important. Iron is a powerful promoter of free radical damage, able to catalyse generation of highly reactive hydroxyl, alkoxyl and peroxyl radicals from hydrogen peroxide and lipid peroxides, respectively. Although most iron in the brain is stored in ferritin, 'catalytic' iron is readily mobilised from injured brain tissue. Increased levels of oxidative damage to DNA, lipids and proteins have been detected by a range of assays in post-mortem tissues from patients with Parkinson's disease, Alzheimer's disease and amyotrophic lateral sclerosis, and at least some of these changes may occur early in disease progression. The accumulation and precipitation of proteins that occur in these diseases may be aggravated by oxidative damage, and may in turn cause more oxidative damage by interfering with the function of the proteasome. Indeed, it has been shown that proteasomal inhibition increases levels of oxidative damage not only to proteins but also to other biomolecules. Hence, there are many attempts to develop antioxidants that can cross the blood-brain barrier and decrease oxidative damage. Natural antioxidants such as vitamin E (tocopherol), carotenoids and flavonoids do not readily enter the brain in the adult, and the lazaroid antioxidant tirilazad (U-74006F) appears to localise in the blood-brain barrier. Other antioxidants under development include modified spin traps and low molecular mass scavengers of O2*-. One possible source of lead compounds is the use of traditional remedies claimed to improve brain function. Little is known about the impact of dietary antioxidants upon the development and progression of neurodegenerative diseases, especially Alzheimer's disease. Several agents already in therapeutic use might exert some of their effects by antioxidant action, including selegiline (deprenyl), apomorphine and nitecapone.

The gastrointestinal tract: a major site of antioxidant action?

Diets rich in fruits and vegetables delay the onset of many age-related diseases, and contain a complex mixture of antioxidants (including ascorbate, carotenoids, vitamin E and other phenolics such as the flavonoids). However, diet also contains pro-oxidants, including iron, copper, H2O2, haem, lipid peroxides and aldehydes. Nitrite is frequently present in diet, leading to generation of reactive nitrogen species in the stomach. In considering the biological importance of dietary antioxidants, attention has usually focussed on those that are absorbed through the gastrointestinal tract into the rest of the body. In the present paper we develop the argument that the high levels of antioxidants present in certain foods (fruits, vegetables, grains) and beverages (e.g. green tea) play an important role in protecting the gastrointestinal tract itself from oxidative damage, and in delaying the development of stomach, colon and rectal cancer. Indeed, carotenoids and flavonoids do not seem to be as well absorbed as vitamins C and E. Hence their concentrations can be much higher in the lumen of the GI tract than are ever achieved in plasma or other body tissues, making an antioxidant action in the GI tract more likely. Additional protective mechanisms of these dietary constituents (e.g. effects on intercellular communication, apoptosis, cyclooxygenases and telomerase) may also be important.