Modulation of oxidant stress in vivo in chronic cigarette smokers

The Role of Oxidative Stress in the Pathogenesis??of COPD

Chronic inflammation and oxidative stress are important features in the pathogenesis of COPD. The increased oxidative stress in patients with COPD is the result of an increased burden of inhaled oxidants, as well as increased amounts of reactive oxygen species (ROS) generated by various inflammatory, immune and epithelial cells of the airways. Oxidative stress has important implications on several events of lung physiology and for the pathogenesis of COPD. These include oxidative inactivation of antiproteases and surfactants, mucus hypersecretion, membrane lipid peroxidation, mitochondrial respiration, alveolar epithelial injury, remodeling of extracellular matrix, and apoptosis. An increased level of ROS produced in the airways is reflected by increased markers of oxidative stress in the airspaces, sputum, breath, lungs, and blood in patients with COPD. The biomarkers of oxidative stress such as H2O2, F2-isoprostanes, malondialdehyde and 4-hydroxy-2-nonenal have been successfully measured in breath condensate. ROS and aldehydes play a key role in enhancing the inflammation through the activation of mitogen-activated protein kinases and redox-sensitive transcription factors such as nuclear factor kappa B and activator protein-1. Oxidative stress also alters nuclear histone acetylation and deacetylation leading to increased gene expression of pro-inflammatory mediators in the lung. Oxidative stress may play a role in the poor clinical efficacy of corticosteroids in the treatment of COPD. Since a variety of oxidants, free radicals, and aldehydes are implicated in the pathogenesis of COPD it is likely that a combination of antioxidants may be effective in the treatment of COPD. Antioxidant compounds may also be of therapeutic value in monitoring oxidative biomarkers indicating disease progression. Various approaches to enhance the lung antioxidant screen and the clinical effectiveness of antioxidant compounds in the treatment of COPD are discussed.

Creatine kinase isoenzyme patterns upon chronic exposure to cigarette smoke: protective effect of Bacoside A

Cigarette smoking is implicated as a major risk factor in the development of cardiovascular and cerebrovascular diseases. Creatine kinase (CK) and its isoforms (CK-MM, MB, BB) have been advocated as sensitive markers in the assessment of cardiac and cerebral damage. Therefore, in the present study, we report the isoenzyme patterns of CK in rats upon exposure to cigarette smoke and the protective effect of Bacoside A against chronic smoking induced toxicity. Adult male albino rats were exposed to cigarette smoke and simultaneously administered with Bacoside A, the active constituent from the plant Bacopa monniera, for a period of 12 weeks. The activity of CK was assayed in serum, heart and brain, and its isoenzymes in serum were separated electrophoretically. Rats exposed to cigarette smoke showed significant increase in serum CK activity with concomitant decrease in heart and brain. Also cigarette smoke exposure resulted in a marked increase in all the three isoforms in serum. Administration of Bacoside A prevented these alterations induced by cigarette smoking. Cigarette smoking is known to cause free radical mediated lipid peroxidation leading to increased membrane permeability and cellular damage in the heart and brain resulting in the release of CK into the circulation. The protective effect of Bacoside A on the structural and functional integrity of the membrane prevented the leakage of CK from the respective tissues, which could be attributed to its free radical scavenging and anti-lipid peroxidative effect.

Effects of vitamin C and aspirin in ischemic stroke-related lipid peroxidation: results of the AVASAS (Aspirin Versus Ascorbic acid plus Aspirin in Stroke) Study

A condition of oxidative stress is known to occur in ischemic stroke, the current therapeutic intervention of which is largely limited to thrombolysis. To assess the effect of vitamin C - in conjunction to aspirin - in ischemic stroke-related lipid peroxidation, we measured plasma levels of ascorbate, of 8,12-isoprostanes F2alpha-VI (8,12-iPF2alpha-VI) and activities and levels of a broad spectrum of antioxidant enzymes and micronutrients in stroke patients randomized to receive, from stroke onset and up to three months, either vitamin C (200 mg/day) plus aspirin (300 mg/day) or only aspirin (300 mg/day). By the end of the first week, patients treated with vitamin C plus aspirin had higher vitamin C levels (p = 0.02) and lower 8,12-iPF2alpha-VI levels (p = 0.01) than patients treated with aspirin alone. The significance was maintained for the increase of vitamin C after three months of therapy (p < 0.01). The clinical functional outcome for both groups of patients similarly ameliorated after three months of treatment. We conclude that vitamin C, at the dose of 200 mg/day and in conjunction with aspirin, significantly decreases ischemic stroke-related lipid peroxidation in humans. Further studies are warranted to clarify whether the use of vitamin C may add clinical long-term beneficial effects in patients with stroke.

{alpha}-Tocopherol disappearance is faster in cigarette smokers and is inversely related to their ascorbic acid status

BACKGROUND

Cigarette smokers have enhanced oxidative stress from cigarette smoke exposure and from their increased inflammatory responses.

OBJECTIVE

The objective of this study was to determine whether cigarette smoking increases plasma alpha-tocopherol disappearance in otherwise healthy humans.

DESIGN

Smokers and nonsmokers (n = 10/group) were supplemented with deuterium-labeled alpha-tocopheryl acetates (75 mg each of d(3)-RRR-alpha-tocopheryl acetate and d(6)-all-rac-alpha-tocopherols acetate) for 6 evenings (days -6 to -1). Plasma alpha-tocopherols, ascorbic acid, uric acid, and F(2alpha)-isoprostanes were measured in blood samples collected on days -6 through 17. The urinary alpha-tocopherol metabolite, alpha-carboxy-ethyl-hydroxy-chroman (alpha-CEHC), was measured on days -6, 0, and 17 in 24-h urine samples.

RESULTS

F(2alpha)-isoprostanes were, on average, approximately 40% higher in smokers than in nonsmokers. On day 0, plasma labeled and unlabeled alpha-tocopherol concentrations were not significantly different between groups. Smoking resulted in faster fractional disappearance of plasma alpha-tocopherol (0.215 +/- 0.011 compared with 0.191 +/- 0.009 pools/d; P < 0.05). Fractional disappearance rates of alpha-tocopherol correlated with plasma ascorbic acid concentrations in smokers (P = 0.021) but not in nonsmokers despite plasma ascorbic acid concentrations that were not significantly different between groups. By day 17, cigarette smoking resulted in lower plasma alpha-tocopherol concentrations and urinary excretion of labeled and unlabeled alpha-CEHC (P < 0.05).

CONCLUSIONS

Cigarette smoking increased alpha-tocopherol disappearance. Greater rates of alpha-tocopherol disappearance in smokers appear to be related to increased oxidative stress accompanied by lower plasma ascorbic acid concentrations. Thus, smokers have an increased requirement for both alpha-tocopherol and ascorbic acid.

Lipid peroxidation and 5-lipoxygenase activity in chronic obstructive pulmonary disease

We studied the urinary excretion of the isoprostane 8-iso-prostaglandin F(2alpha) as an index of in vivo oxidant stress, and the production of leukotriene (LT) B(4) (LTB(4)) by neutrophils in subjects with chronic obstructive pulmonary disease (COPD) and normal subjects. Overnight urinary excretion of the isoprostane was significantly higher in patients with COPD than in control subjects, and LTB(4) production by challenge of neutrophils obtained from patients with COPD was also significantly higher than that observed in control neutrophils. Treatment with a standardized polyphenol extract caused a significant decrease in isoprostane excretion, accompanied by a statistically significant increase of Pa(O(2)). Furthermore, changes in FEV(1) significantly correlated with the changes in isoprostane urinary excretion observed from enrollment to the end of treatment. The results of this study suggest that enhanced oxidative stress in subjects with COPD is paralleled by the increased ability of neutrophils to synthesize the chemotactic factor LTB(4), and may ultimately contribute to the infiltration/activation of neutrophils into the airways of subjects with COPD. Antioxidant treatment in subjects with COPD is effective in reducing oxidant stress as shown by the decrease of urinary isoprostane, a reduction that correlates with the severity of the disease, as indicated by changes in Pa(O(2)) and FEV(1).

Differential effects of exercise on aortic mitochondria

Routine exercise is widely recognized as cardioprotective. Exercise induces a variety of effects within the cardiovasculature, including decreased mitochondrial damage and improved aerobic capacity. It has been generally thought that the transient increase in oxidative stress associated with exercise initiates cardioprotective processes. Somewhat paradoxically, increased oxidative stress associated with cardiovascular disease (CVD) risk factors is thought to play an important role in the promotion and development of CVD. Hence, it is possible that CVD risk factors that increase oxidative stress (e.g., hypercholesterolemia) may modulate the cardioprotective effects of exercise. In this regard, the interaction between CVD risk factors and exercise on atherosclerotic lesion development and basal oxidant load is less defined. To determine the influence of preexistent hypercholesterolemia on cardioprotective effects of exercise, atherosclerotic lesion formation, oxidant load, mitochondrial damage, protein nitration (3-nitrotyrosine levels), and mitochondrial enzyme activities were determined in aortic tissues from normocholesterolemic (C57 control) and hypercholesterolemic [apoliprotein E-deficient (apoE(-/-))] mice after 16 wk of regular exercise. In normocholesterolemic mice, regular exercise was associated with decreased mitochondrial damage and oxidant load and increased SOD2 and adenine nucleotide translocator activities. Exercise did not decrease endogenous oxidant load and mitochondrial damage in hypercholesterolemic mice and did not reduce atherosclerotic lesion development. These data are consistent with the notion that CVD risk factors associated with increased oxidative stress can alter the benefits of exercise and that mitochondrial damage appears to be correlated with the cardiovascular effects of exercise.

Ex vivo measures of LDL oxidative susceptibility predict carotid artery disease

AIM

The purpose of the study was to assess whether ex vivo measures of low-density lipoprotein (LDL) oxidation improved prediction of carotid artery disease (CAAD) case-control status compared to standard lipid and smoking measures.

METHODS

One hundred and forty cases with a high degree of carotid artery stenosis aged 40-83 years and an equal number of controls without stenosis or other vascular disease were matched by censored age within 2 years. Matched logistic regression evaluated the significance of copper-induced oxidative measures with and without covariates. The relationship of LDL oxidation measures with statin use and current smoking was also evaluated.

RESULTS

Logistic regression demonstrated a significant effect of the three correlated measures of oxidative susceptibility (lag time, oxidation rate and maximal rate of oxidation) separately on disease prediction (all p<0.05). These oxidative measures remained significant predictors of case-control status when other cardiovascular disease predictors (age; LDL-C, HDL-C and ApoAI levels; current smoking, ever smoking and pack-years smoked) were jointly considered. This relationship was not attributable to the effects of statin use on LDL oxidation.

CONCLUSIONS

Ex vivo measures of oxidation improved the prediction of carotid artery disease status, suggesting that this is an important determinant of atherosclerotic risk in this older population.

Moderate alcohol consumption and levels of antioxidant vitamins and isoprostanes in postmenopausal women

BACKGROUND

Although alcohol intake has been positively associated with breast cancer risk in epidemiologic studies, the mechanisms mediating this association are speculative.

OBJECTIVE

The Postmenopausal Women's Alcohol Study was designed to explore the effects of moderate alcohol consumption on potential risk factors for breast cancer. In the present analysis, we evaluated the relationship of alcohol consumption with antioxidant nutrients and a biomarker of oxidative stress.

DESIGN

Participants (n=53) consumed a controlled diet plus each of three treatments (15 or 30 g alcohol/day or a no-alcohol placebo beverage), during three 8-week periods in random order. We measured the antioxidants, vitamin E (alpha (alpha)- and gamma (gamma)-tocopherols), selenium, and vitamin C in fasting blood samples which were collected at the end of diet periods, treated and frozen for assay at the end of the study. We also measured 15-F(2t)-IsoP isoprostane, produced by lipid peroxidation, which serves as an indicator of oxidative stress and may serve as a biomarker for conditions favorable to carcinogenesis.

RESULTS

After adjusting for BMI (all models) and total serum cholesterol (tocopherol and isoprostane models) we observed a significant 4.6% decrease (P=0.02) in alpha-tocopherol and a marginally significant 4.9% increase (P=0.07) in isoprostane levels when women consumed 30 g alcohol/day (P=0.06 and 0.05 for overall effect of alcohol on alpha-tocopherol and isoprostanes, respectively). The other antioxidants were not significantly modified by the alcohol treatment.

CONCLUSIONS

These results suggest that moderate alcohol consumption increases some biomarkers of oxidative stress in postmenopausal women.

Isoprostanes: novel bioactive products of lipid peroxidation

Isoprostanes, are a novel group of prostaglandin-like compounds that are biosynthesised from esterified polyunsaturated fatty acid (PUFA) through a non-enzymatic free radical-catalysed reaction. Several of these compounds possess potent biological activity, as evidenced mainly through their pulmonary and renal vasoconstrictive effects, and have short half-lives. It has been shown that isoprostanes act as full or partial agonists through thromboxane receptors. Both human and experimental studies have indicated associations of isoprostanes and severe inflammatory conditions, ischemia-reperfusion, diabetes and atherosclerosis. Reports have shown that F2-isoprostanes are authentic biomarkers of lipid peroxidation and can be used as potential in vivo indicators of oxidant stress in various clinical conditions, as well as in evaluations of antioxidants or drugs for their free radical-scavenging properties. Higher levels of F2-isoprostanes have been found in the normal human pregnancy compared to non-pregnancy, but their physiological role has not been well studied so far. Since bioactive F2-isoprostanes are continuously formed in various tissues and large amounts of these potent compounds are found unmetabolised in their free acid form in the urine in normal basal conditions with a wide inter-individual variation, their role in the regulation of normal physiological functions could be of further biological interest, but has yet to be disclosed. Their potent biological activity has attracted great attention among scientists, since these compounds are found in humans and animals in both physiological and pathological conditions and can be used as reliable biomarkers of lipid peroxidation.

Elevated urinary 8-isoprostaglandin F(2alpha) in females with Graves' hyperthyroidism

In this study, we investigate how oxidative stress alters the urinary F2-isoprostanes' level and we examine the correlation between 8-isoPGF(2alpha) and thyroid hormones in female patients with Graves' hyperthyroidism. We quantitatively determined the concentrations of urinary F2-isoprostanes using gas chromatography-mass spectrometry in the selected ion-monitoring mode. We recruited individuals in the following three groups of subjects for this study: (1) female hyperthyroidism patients (n = 14, 21-71 years), (2) female hypothyroidism patients (n = 16, 16-66 years), and (3) female age-matched normal controls (n = 10, 20-61 years). The average concentration of 8-iso prostaglandin F(2alpha) (8-isoPGF(2alpha)) in hyperthyroidism patients was significantly higher than that in the healthy controls (P < 0.05). The concentration of 8-isoPGF(2alpha) in hypothyroidism patients was similar to that in normal controls. Although the level of 8-isoPGF(2alpha) in two of the patients was slightly elevated, the P value was not significant (NS). Our data suggest that the increased level of urinary 8-isoPGF(2alpha) may reflect possible oxidation injuries in hyperthyroidism patients due to the high level of thyroid hormones. Therefore, the elevated 8-isoPGF(2alpha) in patients could be used as an important biomarker for hyperthyroidism disease.

Application of gas chromatography-mass spectrometry for analysis of isoprostanes: their role in cardiovascular disease

Cardiovascular disease (CVD) is the major cause of death in the Western hemisphere. Oxidative stress is involved in the pathophysiology of cancer, neurodegenerative conditions and CVD. Lipid peroxidation is one of the oxidative modifications possible in biological systems. The isoprostanes are derivatives of one specific lipid, i.e., arachidonic acid, after lipid peroxidation. Several isoprostanes have been identified in biological tissues and fluids, among them 8-iso prostaglandin F2alpha (8-iso-PGF2alpha, 8-epi-PGF2alpha, iPF2alpha-III, 15-F2t-IsoP) and its metabolite, 2,3-dinor-4,5-dihydro-8-iso-PGF2alpha. The isoprostanes are reliable in vivo markers of lipid peroxidation in humans: they are endogenously formed, characteristic in structure, ubiquitous in nature, stable in- and ex vivo and reliably quantitatable. In this Review, different analytical approaches will be discussed including immunologic, chromatographic and spectrometric techniques with the main emphasis on mass spectrometry. Analysis of isoprostanes applying radio immunoassay (RIA), enzyme immunoassay (EIA), high performance-liquid chromatography (HPLC), liquid chromatography-tandem mass spectrometry (LC-tandem MS), gas chromatography-mass spectrometry (GC-MS) and GC-tandem MS will be exemplified in the field of cardiovascular research. Results from several clinical studies are included indicating the validity of isoprostanes as surrogate parameters of oxidative stress in cardiovascular disease.

Vitamin C Has No Effect on Endothelium-Dependent Vasomotion and Acute Endogenous Fibrinolysis in Healthy Smokers

Blood flow and plasma fibrinolytic factors were measured on five occasions in both forearms of eight otherwise healthy male smokers during unilateral brachial artery infusion of the endothelium-dependent vasodilator, substance P (2 to 8 pmol/min), and the endothelium-independent vasodilator, sodium nitroprusside (2 to 8 microg/min). On the first occasion, intra-arterial vitamin C was co-infused at 25 mg/min. On subsequent occasions, subjects attended after 28 and 35 days treatment with oral vitamin C (1 g daily) or placebo in a double-blind randomized crossover design still smoking but with and without acute smoke inhalation (3 cigarettes over 30 minutes). Basal plasma ascorbate concentrations increased from 37 +/- 6 micromol/L to 105 +/- 11 micromol/L following oral vitamin C supplementation (P = 0.002). Substance P caused dose-dependent increases in forearm blood flow (P < 0.001, ANOVA) and t-PA release (P < 0.05, ANOVA) that was unaffected by acute recent smoke inhalation, intra-arterial vitamin C, or oral vitamin C administration (p = ns). Likewise there were no effects on sodium nitroprusside-induced vasodilatation (p = ns). Neither acute local intra-arterial nor prolonged oral vitamin C supplementation reverses smoking-related endothelial dysfunction and impaired endogenous t-PA release. We conclude that the adverse vascular actions of smoking are not principally mediated through oxidative stress.

F2-isoprostanes as indices of lipid peroxidation in inflammatory diseases

Isoprostanes are a new class of lipids, isomers of conventional enzymatically derived prostaglandins, which are produced in vivo primarily by a free radical-catalyzed peroxidation of polyunsaturated fatty acids. F2-isoprostanes, isomers of the enzyme-derived prostaglandin F2alpha, are the most studied species. Because of their mechanisms of formation, specific structural features that distinguish them from other free radical-generated products and chemical stability, they provide a reliable index of the oxidative component of several diseases in vivo. Consistent data suggest that formation of F2-isoprostanes is indeed altered in a variety of clinical settings associated with inflammation and oxidant stress. Moreover, measurement of F2-isoprostanes might provide a sensitive biochemical basis of dose-selection in studies of natural and synthetic antioxidants.

Reports: Supplemental β-Carotene, Smoking, and Urinary F2-Isoprostane Excretion in Patients With Prior Early Stage Head and Neck Cancer

Supplemental beta-carotene has been shown to increase lung cancer risk in recent chemoprevention trials, especially in current smokers. Several possible mechanisms for this effect have been suggested based upon in vitro and animal studies, but mechanistic data from human studies to explain the excess risk are lacking. beta-Carotene has both antioxidant and prooxidant effects in vitro; therefore, we evaluated whether or not high-dose supplemental beta-carotene might have prooxidant effects in vivo, especially in current smokers taking high-dose supplemental beta-carotene for several years (median 4.0 yr). Urine samples (n = 55 total) were collected from both smokers and nonsmokers participating in a multiyear randomized chemoprevention trial of supplemental beta-carotene (50 mg/day) versus placebo. Samples were analyzed by GC/MS for total isoprostanes and for 8-iso-prostaglandin F2 (8-iso-PGF2), stable end products of lipid peroxidation in vivo. Smokers had higher levels of both total isoprostanes and 8-iso-PGF2. Smokers and nonsmokers randomized to beta-carotene had nonsignificantly lower concentrations of total isoprostanes and of 8-iso-PGF2 [mean +- SD 8-iso-PGF2/ml = 2.00 +- 1.72 (placebo smoker); 1.72 +- 1.66 (beta-carotene smoker); 1.22 +- 0.68 (placebo nonsmoker); 0.97 +- 0.62 (beta-carotene nonsmoker)]. These results indicate that supplemental beta-carotene, even when given at high doses for many years, does not have prooxidant effects in either smokers or nonsmokers, as measured by urinary excretion of F2-isoprostanes.

Antioxidant Effect of a New Calcium Antagonist, Azelnidipine, in Cultured Human Arterial Endothelial Cells

Azelnidipine is a novel dihydropyridine-type calcium antagonist with long-acting anti-hypertensive action and a low reported incidence of tachycardia. We aimed to evaluate its antioxidant activity in cultured human arterial endothelial cells under oxidative stress. Endothelial cells were exposed to 1 mM H2O2 and treated with 100 μM α-tocopherol, 1 nM, 10 nM or 100 nM azelnidipine, 100 nM nifedipine or 100 nM amlodipine. After 3 h, the cell number and level of lipid peroxidation were evaluated by measuring the total protein and 8-iso-PGF2α concentrations, respectively. The total protein concentration was similar with each treatment. Inhibition of 8-iso-PGF2α was greatest with 10 nM azelnidipine (compared with the other drugs); the difference between 10 nM and 100 nM azelnidipine was not significant. We conclude that azelnidipine has a potent antioxidative effect that could be of significant clinical benefit when combined with its long-lasting anti-hypertensive action and low incidence of tachycardia.

Biomarkers in breath condensate: a promising new non-invasive technique in free radical research

Oxidative stress is associated with a range of inflammatory lung diseases including asthma, adult respiratory distress syndrome, idiopathic pulmonary fibrosis, pneumonia, lung transplantation, chronic obstructive pulmonary disease, cystic fibrosis, bronchiectasis and lung cancer. Increased concentrations of reactive oxygen species (ROS) in the airways of such patients are reflected by elevated concentrations of oxidative stress markers in the breath, airways, lung tissue and blood. Traditionally, the measurement of these biomarkers has involved invasive procedures to procure the samples, or examine the compartments. As a consequence, there is a need for less invasive approaches to measure oxidative stress. Analysis of breath hydrocarbons has partly fulfilled this need, however only gas phase volatile constituents can be assessed by this approach. The collection of exhaled breath condensate (EBC) is a simple, non-invasive approach, which comprehensively samples the lower respiratory tract. It is currently used as a research and diagnostic tool in the free radical field, yielding information on redox disturbance and the degree and type of inflammation in the lung. With further technical developments, such an approach may ultimately have a role in the clinic, in helping to diagnose specific lung diseases. EBC can be exploited to assess a spectrum of potential biomarkers, thus generating a "finger print" characteristic of the disease. By assessing the nature of oxidative stress in this manner, the most appropriate therapy can be selected and the response to treatment monitored.

Isoketals: highly reactive γ-ketoaldehydes formed from the H2-isoprostane pathway

Oxidation of arachidonic acid leads to the formation of highly reactive gamma-ketoaldehydes now termed isoketals. Isoketals react with proteins at a rate that far exceeds other well studied products of lipid peroxidation such as 4-hydroxynonenal and demonstrate a remarkable proclivity to crosslink these proteins. For these reasons, isoketals have the potential to significantly alter protein function and contribute to disease processes. This article reviews the chemistry of isoketal formation, of their adduction to proteins, and of their proclivity to crosslink proteins, as well as their effects on protein function, and their potential role in diseases associated with oxidative injury.

Short-term and long-term vitamin C supplementation in humans dose-dependently increases the resistance of plasma to ex vivo lipid peroxidation

To assess the effects of short-term and long-term vitamin C supplementation in humans on plasma antioxidant status and resistance to oxidative stress, plasma was obtained from 20 individuals before and 2h after oral administration of 2g of vitamin C, or from eight subjects enrolled in a vitamin C depletion-repletion study using increasing daily doses of vitamin C from 30 to 2500 mg. Plasma concentrations of ascorbate, but not other physiological antioxidants, increased significantly after short-term supplementation, and increased progressively in the long-term study with increasing vitamin C doses of up to 1000 mg/day. Upon incubation of plasma with a free radical initiator, ascorbate concentrations were positively correlated with the lag phase preceding detectable lipid peroxidation. We conclude that vitamin C supplementation in humans dose-dependently increases plasma ascorbate concentrations and, thus, the resistance of plasma to lipid peroxidation ex vivo. Plasma and body saturation with vitamin C in humans appears desirable to maximize antioxidant protection and lower risk of oxidative damage.

Determinants of F2-isoprostane biosynthesis and inhibition in man

Several cardiovascular risk factors are characterized by the coexistence of low-grade inflammation, enhanced oxidative stress and lipid peroxidation. It has been hypothesized that F2-isoprostanes, a product of in vivo lipid peroxidation, may transduce the effects of metabolic and hemodynamic abnormalities into increased cardiovascular risk. Thus, the formation of these compounds, including urinary 8-iso-Prostaglandin (PG) F2alpha, has been investigated in clinical settings putatively associated with oxidant stress. Enhanced lipid peroxidation together with increased in vivo platelet activation have been found in association with the major cardiovascular risk factors. Thus, F2-isoprostanes may transduce the effects of oxidant stress associated with complex metabolic disorders into specialized forms of cellular activation. In particular, the low-grade inflammatory state characterizing metabolic disorders such as obesity, hypercholesterolemia, type 2 diabetes mellitus, and homozygous homocystinuria may be the primary trigger of thromboxane-dependent platelet activation mediated, at least in part, through enhanced lipid peroxidation. Moreover, oxidative stress may promote endothelial dysfunction through increased production of reactive oxygen species that inactivate nitric oxide. Accumulation and activation of leukocytes plays a key role in atherosclerosis and its complications. Interestingly, neutrophil adhesion induced by minimally modified low-density lipoproteins is mainly mediated by F2-isoprostanes. Although epidemiological studies suggest an inverse relationship between antioxidant vitamin intake and cardiovascular disease, several clinical trials have obtained conflicting results on the effects of vitamin E supplementation on the risk of cardiovascular events. On the other hand, the use of F2-isoprostane formation as a biochemical end-point for dose-finding studies of vitamin E supplementation has helped clarifying the unique features of its pharmacodynamic effects on lipid peroxidation. This information could be extremely valuable in the selection of the appropriate patient subgroups that may benefit from antioxidant interventions.

The effects of smoking and its cessation on 8-epi-PGF2alpha and transforming growth factor-beta 1 in Type 1 diabetes mellitus

BACKGROUND

Oxidative stress and transforming growth factor-beta 1 (TGF-beta1) are associated with diabetic complications, and smoking is a risk factor.

AIMS

This study aimed (i) to compare urinary 8-epi-PGF2alpha and plasma and urinary TGF-beta1 levels obtained in heavy smokers with Type 1 diabetes with those observed in age-matched non-smoker patients with Type 1 diabetes and controls, and (ii) to investigate the effects of smoking cessation (SC) on the above-mentioned parameters in patients with Type 1 diabetes.

METHODS AND RESULTS

Compared with control subjects (n = 12), non-smoker diabetic patients (n = 12) presented higher values of urinary 8-epi-PGF2alpha (74.2 +/- 29.6 vs. 29.6 +/- 11.1 pg/mg urinary creatinine, P = 0.01), plasma TGF-beta1 (7.7 +/- 4.7 vs. 3.6 +/- 1.7 ng/ml, P = 0.001) and urinary TGF-beta1 (15.3 +/- 6.3 vs. 8.1 +/- 4.4 ng/mg urinary creatinine, P = 0.02). Compared with non-smoker diabetic patients, smoker diabetic patients (n = 16) showed higher levels of urinary 8-epi-PGF2alpha (107.8 +/- 40.2 vs. 74.2 +/- 29.6 pg/mg urinary creatinine, P = 0.0001), plasma TGF-beta1 (12.6 +/- 4.9 vs. 7.7 +/- 4.7 ng/ml, P = 0.001) and urinary TGF-beta1 (27.5 +/- 16.0 vs. 15.3 +/- 6.3 ng/mg urinary creatinine, P = 0.01). Smoker patients were included in a smoking cessation programme. In the 10 patients that gave up smoking there was a reduction of urinary 8-epi-PGF2alpha (basal: 110.47 +/- 47.0 vs. week 12: 73.2 +/- 25.6; P < 0.001), plasma TGF-beta1 (basal: 11.2 +/- 5.9 vs. week 12: 4.89 +/- 2.25; P < 0.01) and urinary TGF-beta1 (basal: 18.12 +/- 9.27 vs. week 12: 10.32 +/- 2.0; P < 0.01) levels.

CONCLUSIONS

In patients with Type 1 diabetes, smoking increased oxidative stress, evaluated by lipid peroxidation, and TGF-beta1 production. Smoking cessation decreased these parameters, providing additional support to encourage diabetic patients to give up smoking.

Isoprostanes: an emerging role in vascular physiology and disease?

Among the isoprostanes, the 15-series F2-isoprostanes and 15-E2t-IsoP mediate vasoconstriction in different vascular beds and species. In addition, 15-F2t-IsoP induces smooth muscle cells mitogenesis and monocyte adhesion to endothelial cells. In clinical studies, 15-F2t-IsoP levels are increased in some vascular disorders involving atherosclerosis, ischemia-reperfusion and inflammation. Whether the same effects observed in vitro are observed consistently in vivo at physiological concentrations and whether these effects contribute to pathological states in vivo is still debated.

Vitamin C supplementation decreases oxidative stress biomarker f2-isoprostanes in plasma of nonsmokers exposed to environmental tobacco smoke

Exposure to environmental tobacco smoke (ETS) has been linked to increased risk of lung cancer and cardiovascular diseases in nonsmokers. Current research suggests that some of these diseases are associated with elevated oxidative stress. We investigated the effect of antioxidant (AO) intervention on the lipid peroxidation biomarker F2-isoprostanes (F2-IsoPs), an index of oxidative stress, in plasma of nonsmokers exposed to ETS (passive smokers). We measured free F2-IsoP concentrations in plasma of 67 passive smokers at baseline and after 2 mo of daily intervention with AOs or placebo. The study subjects (47 females, 20 males; mean age 46 +/-15) were randomized into one of three treatment groups: vitamin C, "mixture" (vitamin C, vitamin E, and a-lipoic-acid), and placebo. Investigated confounders included plasma baseline AO levels, lipid and total cholesterol profiles, transferrin saturation, and C-reactive protein. Plasma F2IsoP concentrations of subjects in the vitamin C and mixture groups decreased significantly by 17.2 pmol/l (P = 0.0105) and 19.2 pmol/l (P = 0.0083) when compared with the placebo group (11.4% and 12.7%, respectively). Daily AO supplementation (especially with vitamin C) decreases this oxidative stress biomarker in passive smokers. This finding might be of importance for the prevention of ETS-associated adverse health effects in nonsmokers.

Effect of Young Barley Leaf Extract and Adlay on Plasma Lipids and LDL Oxidation in Hyperlipidemic Smokers

Forty hyperlipidemic patients, smokers and non-smokers, were studied. Subjects received 15 g young barley leaf extract (BL) or 60 g adlay daily for four weeks. Overnight fasting blood samples were drawn immediately prior to and after four weeks of supplementation. Blood samples were analyzed for plasma lipid profiles and their susceptibility to low-density lipoprotein (LDL) oxidation. The plasma total and LDL-cholesterol (LDL-C) levels were reduced following treatment with either BL or adlay; furthermore, the lag phase of LDL oxidation increased after either supplementation. However, it seemed that BL had stronger antioxidative effect on the prevention of LDL oxidation than adlay. Our results also indicated that the antioxidative effect was less pronounced in smokers than in non-smokers. Therefore, supplementation with BL or adlay can decrease plasma lipids and inhibit LDL oxidation in hyperlipidemic smokers and/or non-smokers.

Narghile (water pipe) smoking influences platelet function and (iso-)eicosanoids

The biological effects of smoking water pipe on haemostasis and the eicosanoid system is unknown. Water pipe smoking is familiar to approximately 1 billion people around the world. Considering this quite impressive number, we investigated the potential effect of smoking the Narghile on oxidation injury by monitoring parameters of the (iso)eicosanoid system. Patients were allowed to smoke a water pipe once daily for 14 days. Blood was drawn from 7 healthy adult non-cigarette smoking male volunteers before and immediately after the first smoking of the water pipe and additionally after 6 hours. One and 2 weeks thereafter, blood was drawn again before and after smoking. A total of 7 blood samples was drawn during the study, and parameters of in vivo oxidation injury (8-epi-PGF2alpha, malondialdehyde [MDA]) and haemostasis (11-dehydro-thromboxane B2 [11-DH-TXB2]) were investigated. A single smoking session increased oxidation injury (8-epi-PGF2alpha: p=0.03; MDA: p=0.001) and 11-DH-TXB2 (p=0.00003) significantly, and repeated daily smoking induced a persistent long-lasting oxidation injury reflected by elevated prevalues but a smaller response to the actual water pipe smoke. These findings indicate a significant increase of in vivo oxidative stress by regular water pipe smoking.

Oxidant stress is increased during treatment of human immunodeficiency virus infection

Some diseases and environmental exposures, including those that are risk factors for atherosclerosis, are associated with increased oxidant stress. The objective of this cross-sectional, observational study was to determine whether oxidant stress is increased during human immunodeficiency virus type 1 (HIV-1) infection or its therapy. To quantify oxidant stress, plasma F2 isoprostane (F2-IsoP) concentrations were determined by gas chromatography/mass spectroscopy. A total of 120 subjects were enrolled during routine primary care visits. The median CD4+ T cell count was 341 cells/mm3, the median HIV-1 RNA level was 3.4 log10 copies/mL, and 74% of patients were receiving antiretroviral therapy. Plasma F2-IsoP concentrations were 12-149 pg/mL (median, 31 pg/mL). In univariate analysis, higher F2-IsoP concentrations were associated with lower log10 plasma HIV-1 RNA levels (P=.009) and with efavirenz use (P=.02). Both factors remained associated with plasma F2-IsoP concentrations in multivariate analysis. Oxidant stress associated with therapeutic control of viral replication may have important implications for long-term complications of antiretroviral therapy.

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.

Spread supplemented with moderate doses of vitamin E and carotenoids reduces lipid peroxidation in healthy, nonsmoking adults

BACKGROUND

High doses of vitamin E have been shown to decrease lipid peroxidation in persons under oxidative stress. At present, the data are insufficient to predict whether lower doses offer the same benefit in healthy persons.

OBJECTIVE

We studied the effect of moderate doses of a combination of vitamin E and carotenoids, incorporated into a food product, on markers of antioxidant status and lipid peroxidation in healthy persons.

DESIGN

One hundred five healthy adults were randomly, evenly assigned in this double-blind, placebo-controlled, parallel, 11-wk intervention study. After a 2-wk stabilization period during which the subjects consumed a commercial unfortified spread, the subjects consumed 25 g/d of spread containing 43 mg alpha-tocopherol equivalents (alpha-TE; 2-3 fold the US dietary reference intake) and 0.45 mg carotenoids (spread A), 111 mg alpha-TE and 1.24 mg carotenoids (spread B), or 1.3 mg RRR-alpha-tocopherol without carotenoids (spread C).

RESULTS

In subjects consuming spread A, plasma alpha-tocopherol concentrations increased 31% to 32 micromol/L, with small but significant increases in concentrations of alpha-carotene and lutein. This resulted in LDL with significantly higher total antioxidant capacity (17%) and an increased resistance to oxidation, as determined by lag time (18%). These improvements were dose dependent: larger increases in these variables were observed in subjects consuming spread B. Furthermore, consumption of spread B significantly reduced concentrations of the plasma lipid peroxidation biomarker F(2 alpha)-isoprostane (15%).

CONCLUSION

The consumption of food products containing moderate amounts of vitamin E and carotenoids can lead to measurable and significant improvements in antioxidant status and biomarkers of oxidative stress in healthy persons.

Ion trap tandem mass spectrometric determination of F2-isoprostanes

A new tandem mass spectrometry (MS/MS) method based on the use of an ion trap mass spectrometer for the identification and quantitation of F(2)-isoprostanes has been developed. It consists of two solid-phase extractions and two derivation steps followed by gas chromatography/negative ion chemical ionization tandem mass spectrometry (GC/NICI-MS/MS) analysis. This method is highly selective and sensitive and it has been successfully applied to biological samples.

Acute angiotensin II increases plasma F2-isoprostanes in salt-replete human hypertensives

Angiotensin (Ang) II induces oxidative stress in vitro and in animal models of hypertension. We tested the hypothesis that Ang II increases oxidative stress in human hypertension, as assessed by plasma F2-isoprostane concentrations. Plasma F2-isoprostanes, hemodynamic and endocrine parameters were measured at baseline and following a 55 min infusion of 3 ng/kg/min Ang II in 13 normotensive and 13 hypertensive volunteers ingesting a high- (200 mmol/d) or low- (10 mmol/d) sodium diet. Mean arterial pressure (MAP) and body mass index were higher in hypertensive subjects. Ang II infusion increased MAP (p<.001) and plasma aldosterone concentrations (p<.001) and decreased plasma renin activity (p<.001) and renal plasma flow (p<.001) to a similar extent in both groups. Plasma F2-isoprostane concentrations were similar at baseline. There was no effect of Ang II on F2-isoprostane concentrations during low-salt intake in either group (normotensive 51.7 +/- 7.1 to 53.7 +/- 6.5 pg/ml and hypertensive 52.2 +/- 8.2 to 56.2 +/- 10.0 pg/ml; mean +/- SE). During high-salt intake, Ang II increased F2-isoprostane concentrations in the hypertensive group (52.3 +/- 7.2 to 63.2 +/- 10.4 pg/ml, p=0.010) but not in the normotensive group (54.2 +/- 4.4 to 58.9 +/- 6.6 pg/ml, p=0.83). Acute Ang II infusion increases oxidative stress in vivo in hypertensive humans. The renin-angiotensin system may contribute to oxidative stress in human cardiovascular disease.

Variability of antioxidant-related gene expression in the airway epithelium of cigarette smokers

Cigarette smoking is the major risk factor for developing chronic bronchitis, yet only 15-20% of smokers develop this disorder. Because oxidants are the major mechanism of smoking-induced airway damage, we hypothesized that smoking is associated with upregulation of various antioxidant-related genes in the airway epithelium, but the magnitude of the response shows high inter-individual variability. Microarray analysis was used to assess levels of expression of 44 antioxidant-related genes in four categories (catalase/superoxide dismutase family; glutathione metabolism; redox balance; and pentose phosphate cycle) in bronchoscopy-obtained airway epithelium of matched cohorts (13 current smokers, 9 nonsmokers), none of whom had lung disease. There was minimal variation in gene expression levels within the same individual (right versus left lung or over time), but significant upregulation of 16/44 antioxidant-related genes in smoker epithelium compared with nonsmokers. Subgroups of smokers were identified with clusters of expression levels of antioxidant-related genes. We propose that the antioxidant-related genes demonstrating the most variability in the level of expression in smokers may be useful genetic markers in epidemiologic studies assessing susceptibility to smoking-induced chronic bronchitis.

Effect of orange juice intake on vitamin C concentrations and biomarkers of antioxidant status in humans

BACKGROUND

Consumption of fruit and vegetables is associated with improved health and a decreased prevalence of chronic degenerative processes.

OBJECTIVES

The objectives were to assess the bioavailability of vitamin C from orange juice and its influence on plasma vitamin C and 8-epi-prostaglandin F(2 alpha) (8-epi-PGF(2 alpha)) concentrations in a healthy human population.

DESIGN

Six men and 6 women consumed 500 mL commercial fresh-squeezed orange juice/d for 14 d, corresponding to an intake of 250 mg ascorbic acid/d. On the first day of the study, the subjects drank the juice in one dose (dose-response study), and on days 2-14 they consumed 250 mL in the morning and 250 mL in the afternoon. Blood was collected every hour for 6 h on the first day and again on days 7 and 14.

RESULTS

Baseline plasma vitamin C concentrations were significantly higher (P = 0.03) among the women than among the men (56.4 +/- 4.4 compared with 44.3 +/- 3.5 micromol/L). In the dose-response study, the maximum increase in plasma vitamin C occurred 3 h postdose in both the men and the women. Vitamin C concentrations remained significantly higher on days 7 and 14 than at baseline. Baseline concentrations of 8-epi-PGF(2 alpha) were significantly higher (P = 0.03) among the men than among the women (249.6 +/- 25.4 compared with 177.7 +/- 6.2 pg/mL) but decreased significantly (P = 0.04) by day 14 of the intervention. A significant inverse correlation was observed between vitamin C and 8-epi-PGF(2 alpha) (r = -0.791, P = 0.0022). Among smokers, baseline vitamin C was lower and 8-epi-PGF(2 alpha) higher than among nonsmokers.

CONCLUSIONS

Drinking orange juice (500 mL/d) increases plasma concentrations of vitamin C and reduces concentrations of 8-epi-PGF(2 alpha) in humans. These effects were significantly more pronounced in smokers.

Effect of perchloroethylene, smoking, and race on oxidative DNA damage in female dry cleaners

Perchloroethylene (PERC) is used widely as an industrial dry cleaning solvent and metal degreaser. PERC is an animal carcinogen that produces increased incidence of renal adenomas, adenocarcinomas, mononuclear cell leukemia, and hepatocellular tumors. Oxidative DNA damage and lipid peroxidation were assessed in 38 women with (dry cleaners) or without (launderers) occupational exposure to PERC. PERC exposure was assessed by collecting breathing zone samples on two consecutive days of a typical work week. PERC levels were measured in blood drawn on the morning of the second day of breathing zone sample collection in dry cleaners and before a typical workday in launderers. Blood PERC levels were two orders of magnitude higher in dry cleaners compared to launderers. A significant correlation was noted between time weighted average (TWA) PERC and blood PERC in dry cleaners (r=0.7355, P<0.002). 8-Hydroxydeoxyguanosine (8-OHdG), ng/mg deoxyguanosine (dG) in leukocyte nuclear DNA was used as an index of steady-state oxidative DNA damage. Urinary 8-OHdG, microg/g creatinine was used as an index of oxidative DNA damage repair. Urinary 8-epi-prostaglandin F(2alpha) (8-epi-PGF), ng/g creatinine was used as an index of lipid peroxidation. The mean+/-S.D. leukocyte 8-OHdG in launderers was 16.0+/-7.3 and was significantly greater than the 8.1+/-3.6 value for dry cleaners. Urinary 8-OHdG and 8-epi-PGF were not significantly different between dry cleaners and launderers. Unadjusted Pearson correlation analysis of log transformed PERC exposure indices and biomarkers of oxidative stress indicated a significant association in launderers between blood PERC and day 1 urinary 8-OHdG (r=0.4661, P<0.044). No significant associations between exposure indices and biomarkers were evident in linear models adjusted for age, body mass index, race, smoking (urinary cotinine, mg/g creatinine) and blood levels of the antioxidants Vitamin E and beta-carotene. The mean+/-S.D. leukocyte 8-OHdG value in control white women was 17.8+/-7.4 and was significantly greater than the 11.8+/-5.9 in control black women. No significant differences by race were evident for the other biomarkers. Smoking status was not significantly associated with any of the oxidative damage indices. Results indicate a reduction in oxidative DNA damage in PERC exposed dry cleaners relative to launderers, but PERC could not clearly be defined as the source of the effect.

Oxidative stress and smoking-induced vascular injury

The relative importance of mechanisms relevant to smoking-induced vascular injury is poorly understood. Cigarette smoke is a source of free radicals but also results in cellular activation and consequent generation of free radicals in vivo. Here we consider several approaches to estimating the consequences of free radical generation in vivo, using measurements of modified lipids, proteins, and DNA. Smoking appears to result in elevation of several biomarkers of oxidant stress, some in a dose-related fashion. There is also some evidence that disordered endothelial function in smokers may be partly attributable to oxidant stress. Other effects of smoking on hemostatic activation, sympathoadrenal function, and lipoprotein structure and function may also be modulated by smoking-induced oxidant stress. The emergence and application of rational quantitatively reliable indexes of oxidant stress in vivo is likely to elucidate the relative contribution of oxidant stress to smoking-induced vascular injury.

High-pressurized orange juice consumption affects plasma vitamin C, antioxidative status and inflammatory markers in healthy humans

We examined the bioavailability of vitamin C in orange juice processed using high pressure (HP) and its effects on plasma levels of vitamin C, uric acid (UA), F2-isoprostanes (8-epiPGF(2alpha)), C-reactive protein (CRP) and prostaglandin E(2) (PGE(2)) in a healthy human population. Subjects (6 men, 6 women) enrolled in the study consumed 500 mL/d of HP orange juice for 14 d, corresponding to an intake of 250 mg of vitamin C. On d 1 of the study, subjects drank the juice in one dose; on d 2 until the end of the study, d 14, they drank 250 mL in the morning and 250 mL in the afternoon. Blood was collected every h for 6 h, on d 1, and then on d 7 and 14 of the study. Baseline plasma vitamin C concentration was higher (P = 0.014) in women (55.8 +/- 3.8 micro mol/L) than in men (42.8 +/- 2.1 micro mol/L). The maximum plasma vitamin C increase occurred 3 h after drinking the juice, and it remained elevated on d 7 and 14. Plasma 8-epiPGF(2alpha) concentration did not differ between men and women at baseline. However, it was lower at the end of the study in both men (P = 0.044) and women (P = 0.034). Plasma levels of vitamin C and 8-epiPGF(2alpha) were inversely correlated (r = -0.615, P = 0.001). Plasma CRP concentrations tended to be lower on d 14 than at baseline in men (P = 0.317) and women (P = 0.235). Plasma PGE(2) was lower at the end of the study in both men and women (P <or= 0.037). Drinking orange juice increases plasma vitamin C, and decreases 8-epiPGF(2alpha) and PGE(2) levels in humans, which may help reduce the risk of chronic diseases.

Effects of ANG II type 1 and 2 receptors on oxidative stress, renal NADPH oxidase, and SOD expression

Oxidative stress accompanies angiotensin (ANG) II infusion, but the role of ANG type 1 vs. type 2 receptors (AT1-R and AT2-R, respectively) is unknown. We infused ANG II subcutaneously in rats for 1 wk. Excretion of 8-isoprostaglandin F2alpha (8-Iso) and malonyldialdehyde (MDA) were related to renal cortical mRNA abundance for subunits of NADPH oxidase and superoxide dismutases (SODs) using real-time PCR. Subsets of ANG II-infused rats were given the AT1-R antagonist candesartan cilexetil (Cand) or the AT2-R antagonist PD-123,319 (PD). Compared to vehicle (Veh), ANG II increased 8-Iso excretion by 41% (Veh, 5.4 +/- 0.8 vs. ANG II, 7.6 +/- 0.5 pg/24 h; P < 0.05). This was prevented by Cand (5.6 +/- 0.5 pg/24 h; P < 0.05) and increased by PD (15.8 +/- 2.0 pg/24 h; P < 0.005). There were similar changes in MDA excretion. Compared to Veh, ANG II significantly (P < 0.005) increased the renal cortical mRNA expression of p22phox (twofold), Nox-1 (2.6-fold), and Mn-SOD (1.5-fold) and decreased expression of Nox-4 (2.1-fold) and extracellular (EC)-SOD (2.1-fold). Cand prevented all of these changes except for the increase in Mn-SOD. PD accentuated changes in p22phox and Nox-1 and increased p67phox. We conclude that ANG II infusion stimulates oxidative stress via AT1-R, which increases the renal cortical mRNA expression of p22phox and Nox-1 and reduces abundance of Nox-4 and EC-SOD. This is offset by strong protective effects of AT2-R, which are accompanied by decreased expression of p22phox, Nox-1, and p67phox.

Cigarette smoking cessation increases plasma levels of several antioxidant micronutrients and improves resistance towards oxidative challenge

Cigarette smoking is associated epidemiologically with increased risk of cardiovascular diseases, but the pathophysiological mechanisms are still not fully understood. There is evidence that smoking is related to increased free radical production and antioxidant depletion, but the effects of smoking cessation on plasma concentrations of antioxidants and susceptibility to oxidative stress are largely unknown. Plasma levels of vitamins A, C, E, uric acid, total thiols, carotenoids (including lutein, zeaxanthin, beta-cryptoxanthin, lycopene, alpha- and beta-carotene) and malondialdehyde (MDA, a biomarker of lipid peroxidation) were measured in fifteen healthy, normolipidaemic subjects (seven males, eight females, 35.2 (sd 2.3) years) before and 4 weeks after smoking cessation. To determine plasma resistance towards oxidative challenge, plasma was incubated for up to 5 h with the peroxyl radical-generator 2,2'-azobis(2-amidinopropane) (AAPH); MDA and ascorbate levels were measured at various time points. The concentrations of all plasma antioxidants were lower before smoking cessation than afterwards; MDA levels were higher before than after termination of smoking. Upon AAPH exposure, the consumption of plasma ascorbate and the production of MDA occurred at a significantly faster rate before smoking cessation as compared with afterwards. Cigarette smoking cessation is followed by a marked increase in plasma antioxidant concentrations and substantially improves plasma resistance towards oxidative challenge. Given the importance of cigarette smoking as a risk factor for cardiovascular diseases and the pathophysiological role played by oxidative stress in these illnesses, quitting smoking represents an irreplaceable preventive strategy against tobacco-induced oxidative stress and vascular damage.

8-Epi-PGF2alpha and 6-oxo-PGF1alpha in human (varicose) veins: influence of age, sex, and risk factors

The isoprostane 8-epi PGF2alpha is a vasoconstrictive, mitogenic, proliferative, and mild proaggregatory agent. We examined 8-epi-PGF2alpha and 6-oxo-PGF1alpha from venous tissue derived from varicose (venous) surgery by means of a specific radioimmunoassay. A total of 336 samples from 82 patients (50 females, 32 males; aged 22-68 years) were examined. Tissue samples were classified according to normal, dilated, and varicose. Of these, 94 samples from 31 patients (20 females, 11 males; aged 29-64 years) with additional risk factors (cigarette smoking, hyperlipidemia, diabetes mellitus) were determined in the same way. Mean absolute values for 6-oxo-PGF1alpha are not significantly higher for dilated segments followed by varicose and intact samples. No significant age and sex differences can be monitored. Presence of risk factors, however, results in a significantly diminished 6-oxo-PGF1alpha, irrespective of morphology. 8-Epi-PGF2alpha again showed no age and sex dependence, its presence in varicose segments, however, was significantly (p<0.01) decreased. Risk factors resulted in a significantly increased 8-epi-PGF2alpha. These data indicate that the influence of risk factors on vasomodulatory (iso-)eicosanoids of human veins is more pronounced than the actual morphologic stage. Lower 8-epi-PGF2alpha in varicose veins may shift the venous tone toward vasodilatation and contribute to development and progression of varicosis.

Endothelium-dependent vasodilation and oxidative stress in chronic renal failure: impact on cardiovascular disease

Despite significant progress in renal replacement therapy, the mortality from cardiovascular disease (CVD) in patients with chronic renal failure (CRF) is many times higher than in the general population. The traditional risk factors are frequently present in CRF patients. However, based upon conventional risk factor analysis, these factors do not fully explain the extraordinary increase in morbidity and mortality in CVD among patients with CRF. Accumulating evidence suggests that CRF is associated with impaired endothelial cell function. In recent years, the role of endothelial dysfunction (ED) and excessive oxidative stress (OS) in the development of CVD has been highlighted. ED is an early feature of vascular disease in different diseases such diabetes, hypertension, hypercholesterolemia, and coronary heart disease. The precise mechanism which induces ED is not clear. Several factors however, including OS-related accumulation of uremic toxins, hypertension and shear stress, dyslipidemia with cytotoxic lipoprotein species such as small, dense low-density lipoprotein (LDL) particles, competitive inhibition of endothelial nitric oxide (NO) by increased production by asymmetrical dimethylarginine (ADMA) are pathogenic. In addition, it is known that excessive OS causes ED. An overproduction of reactive oxygen species (ROS) may injure the endothelial cell membrane, inactivate NO, and cause oxidation of an essential cofactor of nitric oxide synthase (NOS). Recent studies have demonstrated that an impaired endothelium-dependent vasodilation and OS are closely related to each other in patients with CRF.

The isoprostane 8-iso-PGE2 stimulates endothelial cells to bind monocytes via cyclic AMP- and p38 MAP kinase-dependent signaling pathways

Increased levels of isoprostanes have been detected in human atherosclerotic lesions. To examine a possible role for 8-iso-prostaglandin E(2) (8-iso-PGE(2)) in atherogenesis, we tested the effect of 8-iso-PGE(2) on adhesion of leukocytes to human umbilical vein endothelial cells (EC). We demonstrate that 8-iso-PGE(2) stimulates EC to bind monocytes, but not neutrophils. This effect was inhibited by the thromboxane A(2) receptor antagonist SQ29548. Moreover, 8-iso-PGE(2) increased levels of cyclic AMP in EC, and monocyte adhesion induced by 8-iso-PGE(2) was blocked by a protein kinase A inhibitor, H89. In addition, 8-iso-PGE(2 )induced phosphorylation of p38 and extracellular signal-regulated kinase (ERK) 1/2 mitogen-activated protein (MAP) kinase and stimulated expression of EGR-1. A specific inhibitor of p38 MAP kinase (SB203580) abrogated monocyte binding, whereas an inhibitor of the ERK pathway (PD98059) did not block monocyte adhesion induced by 8-iso-PGE(2). Activation of nuclear factor-kappaB (NF-kappaB) and expression of NFkappaB-dependent genes intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and E-selectin were not induced by 8-iso-PGE(2). Taken together, these results demonstrate that 8-iso-PGE(2) stimulates EC to specifically bind monocytes, but not neutrophils. This effect is mediated by cyclic AMP/protein kinase A- and p38 MAP kinase-dependent pathways and is independent of the classical inflammatory NFkappaB pathway. Thus, formation of 8-iso-PGE(2) may play an important role in chronic inflammatory diseases such as atherosclerosis by increasing adhesion and extravasation of monocytes.

Cardiopulmonary bypass as a cause of free radical-induced oxidative stress and enhanced blood-borne isoprostanes in humans

Free radicals are believed to be involved in postsurgery-related complications. We studied whether cardiopulmonary bypass (CPB) operation has any immediate impact on the initiation of oxidative stress and inflammatory response by measuring isoprostanes and prostaglandin F2alpha during and 24 h following CPB. The levels of 8-iso-PGF2alpha (a major F2-isoprostane and biomarker of oxidative stress) and 15-keto-dihydro-PGF2alpha (a major metabolite of PGF2alpha and biomarker of inflammatory response) were measured in frequently collected plasma samples before, during, and up to 24 h postsurgery in 21 patients. 8-Iso-PGF2alpha levels significantly increased within 3 min (p <.0001) and continued until 50 min (p <.0001) during CPB. On the contrary, no significant increase of inflammatory response indicator, 15-keto-dihydro-PGF2alpha was found during and up to 24 h postoperatively. These findings establish an increased free radical-induced oxidative stress activity rather than inflammatory response after CPB.

Antioxidant nutrients and chronic disease: use of biomarkers of exposure and oxidative stress status in epidemiologic research

Oxidation of lipid, nucleic acids or protein has been suggested to be involved in the etiology of several chronic diseases including cancer, cardiovascular disease, cataract, age-related macular degeneration and aging in general. A large body of research has investigated the potential role of antioxidant nutrients in the prevention of these and other chronic diseases. This review concentrates on the following antioxidant nutrients: beta-carotene and other carotenoids, vitamin E, vitamin C and selenium. The first part of the review emphasizes the utility of biological markers of exposure for these nutrients and the relationship to dietary intake data. The second part considers functional assays of oxidative stress status in humans including the strengths and limitations of various assays available for use in epidemiologic research. A wide variety of functional assays both in vivo and ex vivo, are covered, including various measures of lipid oxidation (thiobarbituric acid reactive substances, exhaled pentane/ethane, low-density lipoprotein resistance to oxidation, isoprostanes), DNA oxidation (oxidized DNA bases such as 8-OHdG, autoantibodies to oxidized DNA, modified Comet assay) and protein oxidation (protein carbonyls). Studies that have examined the effects of antioxidant nutrients on these functional markers are included for illustrative purposes. The review concludes with a discussion of methodologic issues and challenges for studies involving biomarkers of exposure to antioxidant nutrients and of oxidative stress status.

Moderate antioxidant supplementation has no effect on biomarkers of oxidant damage in healthy men with low fruit and vegetable intakes

The link between high fruit/vegetable intake and reduced chronic disease may be partly explained by antioxidant protection. To determine the effect of moderate antioxidant intake on biomarkers of oxidant damage, we assessed in vivo lipid and protein oxidation in 77 healthy men whose typical diet contained few fruits and vegetables (mean of 2.6 servings/d). The 39 nonsmokers and 38 smokers, age 20- 51 y, were given a daily supplement (272 mg vitamin C, 31 mg all-rac-alpha-tocopherol, and 400 micro g folic acid), or placebo, for 90 d with their usual diet. Blood and urine were taken at baseline and the end of the study for determination of lipid peroxidation products, including F(2)-total and 8-isoprostanes, and protein carbonyls. Urine thiobarbituric acid reactive substances (TBARS) was the only oxidant damage marker that was significantly higher in smokers compared to nonsmokers (P < 0.05). Supplementation increased plasma ascorbate and tocopherol, but had no effect on the oxidant biomarkers. In healthy young men, the endogenous antioxidant defense system and a modest intake of dietary antioxidants are adequate to minimize levels of in vivo oxidant damage such that they cannot be differentiated by current methods.

Vitamin C as an antioxidant: evaluation of its role in disease prevention

Vitamin C in humans must be ingested for survival. Vitamin C is an electron donor, and this property accounts for all its known functions. As an electron donor, vitamin C is a potent water-soluble antioxidant in humans. Antioxidant effects of vitamin C have been demonstrated in many experiments in vitro. Human diseases such as atherosclerosis and cancer might occur in part from oxidant damage to tissues. Oxidation of lipids, proteins and DNA results in specific oxidation products that can be measured in the laboratory. While these biomarkers of oxidation have been measured in humans, such assays have not yet been validated or standardized, and the relationship of oxidant markers to human disease conditions is not clear. Epidemiological studies show that diets high in fruits and vegetables are associated with lower risk of cardiovascular disease, stroke and cancer, and with increased longevity. Whether these protective effects are directly attributable to vitamin C is not known. Intervention studies with vitamin C have shown no change in markers of oxidation or clinical benefit. Dose concentration studies of vitamin C in healthy people showed a sigmoidal relationship between oral dose and plasma and tissue vitamin C concentrations. Hence, optimal dosing is critical to intervention studies using vitamin C. Ideally, future studies of antioxidant actions of vitamin C should target selected patient groups. These groups should be known to have increased oxidative damage as assessed by a reliable biomarker or should have high morbidity and mortality due to diseases thought to be caused or exacerbated by oxidant damage.

Improved antioxidant and fatty acid status of patients with cystic fibrosis after antioxidant supplementation is linked to improved lung function

BACKGROUND

Oxidative stress, as measured by 8-iso-prostaglandin F(2)(alpha) (8-iso-PGF(2)(alpha)), and depleted antioxidant defenses were shown in stable cystic fibrosis (CF) patients. The plasma fatty acid status of CF patients was linked to oxidative stress after respiratory exacerbations.

OBJECTIVE

We examined changes in plasma 8-iso-PGF(2)(alpha), antioxidant defenses, plasma fatty acid status, and clinical markers resulting from short-term antioxidant supplementation.

DESIGN

Forty-six CF patients were randomly assigned to either group A [low dose of supplement (10 mg vitamin E and 500 micro g vitamin A)] or group B [high dose of supplement (200 mg vitamin E, 300 mg vitamin C, 25 mg beta-carotene, 90 micro g Se, and 500 micro g vitamin A)]. Plasma concentrations of 8-iso-PGF(2)(alpha), vitamins E and C, beta-carotene, zinc, selenium, and copper; plasma fatty acid composition; erythrocyte glutathione peroxidase (EC 1.11.1.9) and superoxide dismutase (EC 1.15.1.1) activities; lung function; and dietary intake were measured before and after 8 wk of supplementation.

RESULTS

Antioxidant defenses in group B improved, whereas those in group A did not: in groups B and A, the mean (+/- SEM) changes (Delta) in vitamin E were 10.6 +/- 1.5 and -1.9 +/- 0.9 micro mol/L, respectively (P < 0.001), (Delta)beta-carotene were 0.1 +/- 0.04 and -0.01 +/- 0.02 micro mol/L, respectively (P = 0.007), (Delta)selenium were 0.51 +/- 0.10 and -0.09 +/- 0.04 micro mol/L, respectively (P < 0.001), and (Delta)glutathione peroxidase activity were 1.3 +/- 0.3 and -0.3 +/- 0.6 U/g hemoglobin, respectively (P = 0.016). There were no significant differences between the groups in Delta8-iso-PGF(2)(alpha), (Delta)vitamin C, (Delta)fatty acid composition, (Delta)superoxide dismutase activity, (Delta)lung function, or (Delta)white cell count. Within group B, (Delta)beta-carotene correlated with (Delta)percentage of forced vital capacity (r = 0.586, P = 0.005), (Delta)selenium correlated with (Delta)percentage of forced expiratory volume in 1 s (r = 0.440, P = 0.046), and (Delta)plasma fatty acid concentrations correlated with (Delta)percentage of forced expiratory volume in 1 s (r = 0.583, P = 0.006) and Delta8-iso-PGF(2)(alpha) (r = 0.538, P = 0.010).

CONCLUSIONS

Whereas increased beta-carotene, selenium, and fatty acid concentrations are linked to improved lung function, increased plasma fatty acid concentrations are linked to oxidative stress. If oxidative stress is deemed to be important to the clinical outcome of CF patients, means of reducing oxidative stress while maintaining a high-fat, high-energy diet must be investigated.

Fluvastatin Increases LDL Particle Size and Reduces Oxidative Stress in Patients with Hyperlipidemia

The effects of fluvastatin on levels of urinary 8-iso-prostaglandin F2alpha (iPF2alphaIII), a marker of oxidative stress, and low-density lipoprotein (LDL) particle size in serum were investigated in patients with hypercholesterolemia. After 6 months of fluvastatin therapy, levels of urinary iPF2alphaIII decreased from 1720.1 +/- 392.0 to 539.6 +/- 75.5 pg/mg (p < 0.01), and LDL particle size increased from 24.3 +/- 0.3 to 26.5 +/- 0.2 nm (p < 0.001). These changes from the treatment of fluvastatin were not correlated with those of the serum LDL cholesterol (LDL-C) levels. The results imply that fluvastatin, with its unique antioxidant property among statins, reduces oxidative stress and increases LDL particle size simultaneously in hyperlipidemic patients.

The isoprostanes: their role as an index of oxidant stress status in human pulmonary disease

The isoprostanes are a unique series of prostaglandin-like compounds formed in vivo from the free radical-initiated peroxidation of arachidonic acid independent of the cyclooxygenase enzyme. This article summarizes selected aspects regarding our current knowledge of these compounds and what are considered avenues for future research. Novel aspects related to the biochemistry of isoprostane formation are discussed first, followed by a summary of methods by which these compounds are analyzed. A considerable portion of this article deals with the utility of measuring isoprostanes as markers of oxidant injury in vitro and in vivo, particularly in pulmonary diseases. Studies performed over the past decade have shown that these compounds are extremely accurate measures of lipid peroxidation in animals and humans and have illuminated the role of oxidant injury in a number of human diseases, including those related to the lung.