Role of inflammation and oxidative stress in atrial fibrillation

BACKGROUND

Atrial fibrillation (AF) is the most common arrhythmia seen in clinical practice. Increasing evidence indicates that inflammation and oxidative stress contribute to the pathogenesis of AF, but their role remains poorly defined. In addition, whether inflammation and oxidative stress are associated with particular types of AF is unclear.

OBJECTIVE

The purpose of this study was to define the role of inflammation and oxidative stress in AF.

METHODS

Using a case-control study design, 305 patients with AF were compared with 150 control patients. AF was categorized into lone and typical AF and further subcategorized as paroxysmal, persistent, or permanent AF. Serum concentrations of interleukin (IL)-6, IL-8, IL-10, tumor necrosis factor (TNF)-alpha, monocyte chemoattractant protein (MCP)-1, vascular endothelial growth factor (VEGF), N-terminal pro-brain (B-type) natriuretic peptide (NTpBNP), and urinary F(2)-isoprostanes, a measure of oxidative stress, were measured.

RESULTS

IL-6, IL-8, IL-10, TNF-alpha, MCP1, VEGF, and NTpBNP concentrations were independently associated with AF (all P <.05). However, F(2)-isoprostane excretion was not elevated (P = .50). Graded increases in TNF-alpha [median (interquartile range) 6.8 (3.4-11.3), 8.0 (5.6-10.9), 10.1 (5.7-12.4) pg/mL, P <.05] and NTpBNP [170.6 (67.3-481.9), 681.39 (310.3-1,439.0), 1,179.9 (653.1-2,096.0) pg/mL, P <.001] were seen among the subgroups of paroxysmal, persistent, and permanent AF, respectively.

CONCLUSION

Inflammatory biomarkers were significantly increased in patients with AF, supporting a strong association between inflammation and AF. Surprisingly, urinary F(2)-isoprostanes, a sensitive index of systemic oxidative stress in vivo, were not increased in AF overall or in different subtypes of AF.

Isoprostanes and related products of lipid peroxidation in neurodegenerative diseases

Lipid peroxidation is a major outcome of free radical-mediated injury to brain, where it directly damages membranes and generates a number of oxidized products. Some of the chemically and metabolically stable oxidation products are useful in vivo biomarkers of lipid peroxidation. These include the isoprostanes (IsoPs) and isofurans (IsoFs), derived from arachidonic acid (AA), and neuroprostanes (NeuroPs), derived from docosahexaenoic acid (DHA). We have shown increased levels of IsoPs, NeuroPs, and IsoFs in diseased regions of brain from patients who died from advanced Alzheimer's disease (AD) or Parkinson's disease (PD). Increased cerebrospinal fluid (CSF) levels of IsoPs are present in patients with AD or Huntington's disease (HD) early in the course of their illness, and CSF IsoPs may improve the laboratory diagnostic accuracy for AD. In contrast, quantification of IsoPs in plasma and urine of AD patients has yielded inconsistent results. These results indicate that brain lipid peroxidation is a potential therapeutic target early in the course of AD and HD, that CSF IsoPs may aid in the assessment of anti-oxidant experimental therapeutics and laboratory diagnosis of AD.

Virgin Olive Oil Study (VOLOS): vasoprotective potential of extra virgin olive oil in mildly dyslipidemic patients

BACKGROUND

In vitro, olive phenols exert potent antioxidant and enzyme-modulating activities.

AIM OF THE STUDY

We comparatively evaluate, in mildly dyslipidemic patients, the vasoprotective potential of extra virgin olive oil.

METHODS

22 patients were administered 40 mL/day of either extra-virgin, i. e. phenol rich, or refined, i. e. phenol poor, olive oils (EVOO or ROO, respectively, with nearly identical fatty acid composition), with a crossover design. Each treatment was carried out for seven weeks, with four weeks of washout in between. Plasma antioxidant capacity, serum thromboxane B2 (TXB2) formation, and urinary isoprostane excretion were evaluated as surrogate markers of cardioprotective potential and vascular function.

RESULTS

No effects on plasma lipid/lipoprotein profile were observed. Conversely, EVOO consumption was associated with favorable effects on circulating markers. Namely, decreased serum TXB2 production and increased plasma antioxidant capacity were observed when EVOO was administered in both treatment arms. Neither treatment had any significant effect on isoprostane excretion.

CONCLUSIONS

EVOO consumption by mildly dyslipidemic patients is associated with favorable changes in circulating markers of cardiovascular condition. Based on current knowledge, these effects may be associated with cardioprotection.

Leptin decreases plasma paraoxonase 1 (PON1) activity and induces oxidative stress: the possible novel mechanism for proatherogenic effect of chronic hyperleptinemia

Obesity is an important risk factor of atherosclerosis; however, the mechanism of proatherogenic effect of obesity is not definitely established. Recent studies suggest an important role of leptin in obesity associated complications. We investigated the effect of chronic hyperleptinemia on two antioxidant enzymes contained in plasma lipoproteins: paraoxonase 1 (PON1) and platelet activating factor-acetylhydrolase (PAF-AH). The study was performed on three groups of male Wistar rats: (1) control, fed ad libitum, (2) leptin treated, receiving leptin (0.25 mg/kg twice daily s.c. for 7 days), (3) pair-fed, in which food intake was identical as in leptin-treated animals. PON1 activity toward paraoxon, phenyl acetate, gamma-decanolactone and homogentisic acid lactone was lower in leptin-treated than in control group by 30.4, 30.8, 34.5 and 62%, respectively. Leptin increased plasma concentration and urinary excretion of isoprostanes by 46.4 and 49.2%, respectively. Leptin treatment had no effect on plasma lipid profile and glucose level. Plasma leptin was 208.8% higher in leptin-treated and 51.5% lower in pair-fed than in control group. These data indicate that hyperleptinemia induced by exogenous leptin administration markedly decreases plasma PON1 activity and induces oxidative stress. These mechanisms may be involved in atherogenesis in hyperleptinemic obese individuals.

Oxidative Stress and Erythrocyte Membrane Alterations in Children with Autism: Correlation with Clinical Features

It has been suggested that oxidative stress may play a role in the pathogenesis of Autism Spectrum Disorders (ASD), but the literature reports somewhat contradictory results. To further investigate the issue, we evaluated a high number of peripheral oxidative stress parameters, and some related issues such as erythrocyte membrane functional features and lipid composition. Twenty-one autistic children (Au) aged 5 to 12 years, were gender and age-matched with 20 typically developing children (TD). Erythrocyte thiobarbituric acid reactive substances, urinary isoprostane and hexanoyl-lysine adduct levels were elevated in Au, thus confirming the occurrence of an imbalance of the redox status of Au, whilst other oxidative stress markers or associated parameters (urinary 8-oxo-dG, plasma radical absorbance capacity and carbonyl groups, erythrocyte superoxide dismutase and catalase activities) were unchanged. A very significant reduction of Na(+)/K(+)-ATPase activity (-66%, p<0.0001), a reduction of erythrocyte membrane fluidity and alteration in erythrocyte fatty acid membrane profile (increase in monounsaturated fatty acids, decrease in EPA and DHA-ω3 with a consequent increase in ω6/ω3 ratio) were found in Au compared to TD, without change in membrane sialic acid content. Some Au clinical features appear to be correlated with these findings; in particular, hyperactivity score appears to be related with some parameters of the lipidomic profile and membrane fluidity. Oxidative stress and erythrocyte membrane alterations may play a role in the pathogenesis of ASD and prompt the development of palliative therapeutic protocols. Moreover, the marked decrease in NKA could be potentially utilized as a peripheral biomarker of ASD.

Increased renal medullary oxidative stress produces hypertension

The present study examined whether chronic increased oxidative stress within the medulla of the kidney lowers medullary blood flow and leads to hypertension. Optical fibers were implanted into the renal cortex and medulla of uninephrectomized Sprague-Dawley rats (Harlan Sprague-Dawley, Madison, Wis) for the daily measurement of blood flow to these regions using laser-Doppler flowmetry techniques, while arterial pressure was measured from an indwelling aortic catheter. A renal medullary interstitial catheter was implanted for the continuous delivery of the superoxide dismutase (SOD) inhibitor, diethyldithiocarbamic acid (DETC), at a dose of 7.5 mg/kg/d. Renal interstitial superoxide (O(2)(-)) levels were determined by perfusing an O(2)(-) sensitive fluorescent dye, dihydroethidium, through a microdialysis probe implanted into the medulla. Urine samples (24 hours) were collected for measurements of isoprostane excretion. The results indicate that medullary DETC infusions increased tissue O(2)(-) concentrations in the renal medulla (93.4 +/- 22.3,n=8, saline and 867.3 +/- 260.2, n=8, DETC; fluorescence units) and increased urinary 8-isoprostane excretion (4.1 +/- 0.4 ng/d, n=9, saline and 8.8 +/- 1.6 ng/d, n=10, DETC). Mean arterial pressure increased 24 hours after the start of intrarenal DETC infusion and remained nearly 20 mm Hg above control pressure throughout the 5 days of medullary SOD inhibition. During chronic medullary DETC infusion, medullary blood flow was significantly reduced (42.7%), whereas cortical blood flow was unchanged. Intravenous infusion of the same dose of DETC produced no changes in renal medullary or cortical blood flow or arterial blood pressure. The present experiments indicate that an increase in superoxide concentration within the renal medulla selectively reduces medullary blood flow resulting in chronic hypertension.

Increased Oxidative Stress Following Acute and Chronic High Altitude Exposure

The generation of reactive oxygen species is typically associated with hyperoxia and ischemia reperfusion. Recent evidence has suggested that increased oxidative stress may occur with hypoxia. We hypothesized that oxidative stress would be increased in subjects exposed to high altitude hypoxia. We studied 28 control subjects living in Lima, Peru (sea level), at baseline and following 48 h exposure to high altitude (4300 m). To assess the effects of chronic altitude exposure, we studied 25 adult males resident in Cerro de Pasco, Peru (altitude 4300 m). We also studied 27 subjects living in Cerro de Pasco who develop excessive erythrocytosis (hematocrit > 65%) and chronic mountain sickness. Acute high altitude exposure led to increased urinary F(2)-isoprostane, 8-iso PGF(2 alpha) (1.31 +/- 0.8 microg/g creatinine versus 2.15 +/- 1.1, p = 0.001) and plasma total glutathione (1.29 +/- 0.10 micromol versus 1.37 +/- 0.09, p = 0.002), with a trend to increased plasma thiobarbituric acid reactive substance (TBARS) (59.7 +/- 36 pmol/mg protein versus 63.8 +/- 27, p = NS). High altitude residents had significantly elevated levels of urinary 8-iso PGF(2 alpha) (1.3 +/- 0.8 microg/g creatinine versus 4.1 +/- 3.4, p = 0.007), plasma TBARS (59.7 +/- 36 pmol/mg protein versus 85 +/- 28, p = 0.008), and plasma total glutathione (1.29 +/- 0.10 micromol versus 1.55 +/- 0.19, p < 0.0001) compared to sea level. High altitude residents with excessive erythrocytosis had higher levels of oxidative stress compared to high altitude residents with normal hematological adaptation. In conclusion, oxidative stress is increased following both acute exposure to high altitude without exercise and with chronic residence at high altitude.

Telomere length, oxidative damage, antioxidants and breast cancer risk

Telomeres play a critical role in maintaining the integrity and stability of the genome, and are susceptible to oxidative damage after telomere shortening to a critical length. In the present study, we explored the role of white blood cell DNA telomere length on breast cancer risk, and examined whether urinary 15-F(2)-isoprostanes (15-F(2t)-IsoP) and 8-oxo-7,8-dihydrodeoxyguanosine (8-oxodG) or dietary antioxidant intake modified the relationship between telomere length and breast cancer risk. A population-based case-control study-the Long Island Breast Cancer Study Project-was conducted among 1,067 cases and 1,110 controls. Telomere length was assessed by quantitative PCR. Overall, the mean levels of telomere length (T/S ratio), 15-F(2t)-IsoP and 8-oxodG were not significantly different between cases and controls. Among premenopausal women only, carrying shorter telomeres (Q3 and Q4), as compared with the longest (Q1), was associated with significantly increased breast cancer risk. Age-adjusted OR and 95% CI were 1.71 (1.10-2.67) and 1.61 (1.05-2.45). The 5-F(2t)-IsoP and 8-oxodG biomarkers did not modify the telomere-breast cancer association. A moderate increase in breast cancer risk was observed among women with the shortest telomeres (Q4) and lower dietary and supplemental intake of beta-carotene, vitamin C or E intake [OR (95% CI) = 1.48 (1.08-2.03), 1.39 (1.01-1.92) and 1.57 (1.14-2.18), respectively], although the trend test exhibited statistical significance only within the lower vitamin E intake subgroup (p(trend) = 0.01). These results provided the strongest evidence to date that breast cancer risk may be affected by telomere length among premenopausal women or women with low dietary intake of antioxidants or antioxidant supplements.

IL-17-mediated oxidative stress is an important stimulator of AT1-AA and hypertension during pregnancy

Preeclampsia is associated with autoimmune cells T(H)17, secreting interleukin-17, autoantibodies activating the angiotensin II type I receptor (AT1-AA), and placental oxidative stress (ROS). The objective of our study was to determine whether chronic IL-17 increases blood pressure by stimulating ROS and AT1-AAs during pregnancy. To answer this question four groups of rats were examined: normal pregnant (NP, n = 20), NP+IL-17 (n = 12), NP+tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl) (n = 7) (a superoxide dismutase mimetic that scavenges ROS), and NP+IL-17+tempol (n = 11). IL-17 (150 pg/day) was infused into NP rats while tempol was administered via the drinking water ad libitum. On day 19 blood pressure (MAP) was recorded, and plasma, urine, and tissue were collected for isolation of ROS detected by chemilluminescent technique. Urinary isoprostane was measured by ELISA. AT1-AAs were determined via cardiomyocyte assay and expressed as beats per minute. MAP increased from 98 ± 3 mmHg in NP to 123 ± 3 mmHg in IL-17-infused NP rats. Urinary isoprostane increased from 1,029 ± 1 in NP to 3,526 ± 2 pg·mg(-1)·day(-1) in IL-17-infused rats (P < 0.05). Placental ROS was 436 ± 4 RLU·ml(-1)·min(-1) (n = 4) in NP and 702 ± 5 (n = 5) RLU·ml(-1)·min(-1) in IL-17-treated rats. Importantly, AT1-AA increased from 0.41 ± 0.05 beats/min in NP rats (n = 8) to 18.4 ± 1 beats/min in IL-17 rats (n = 12). Administration of tempol attenuated the hypertension (101 ± 3 mmHg) ROS (459 ± 5 RLU·ml(-1)·min(-1)) and blunted AT1-AAs (7.3 ± 0.6 beats/min) in NP+IL-17+tempol-treated rats. Additionally, AT1 receptor blockade inhibited IL-17-induced hypertension and placental oxidative stress. MAP was 105 ± 5 mmHg and ROS was 418 ± 5 RLU·ml(-1)·min(-1) in NP+IL 17-treated with losartan. These data indicate that IL-17 causes placental oxidative stress, which serves as stimulus modulating AT1-AAs that may play an important role in mediating IL-17-induced hypertension during pregnancy.

Phenotypes of Mice Lacking Extracellular Superoxide Dismutase and Copper- and Zinc-containing Superoxide Dismutase

Mice lacking the secreted extracellular superoxide dismutase (EC-SOD) or the cytosolic copper- and zinc-containing SOD (CuZn-SOD) show relatively mild phenotypes. To explore the possibility that the isoenzymes have partly overlapping functions, single and double knockout mice were examined. The absence of EC-SOD was found to be without effect on the lifespan of mice, and the reduced lifespan of CuZn-SOD knockouts was not further shortened by EC-SOD deficiency. The urinary excretion of isoprostanes was increased in CuZn-SOD knockout mice, and plasma thiobarbituric acid-reactive substances levels were elevated in EC-SOD knockout mice. These oxidant stress markers showed potentiated increases in the absence of both isoenzymes. Other alterations were mainly found in CuZn-SOD knockout mice, such as halved glutathione peroxidase activity in the tissues examined and increased glutathione and iron in the liver. There were no changes in tissue content of the alternative superoxide scavenger ascorbate, but there was a 25% reduction in ascorbate in blood plasma in mice lacking CuZn-SOD. No increase was found in the urinary excretion of the terminal metabolites of NO, nitrite, and nitrate in any of the genotypes. In conclusion, apart from the increases in the global urinary and plasma oxidant stress markers, our phenotype studies revealed no other evidence that the copper- and zinc-containing SOD isoenzymes have overlapping roles.

In salt-sensitive hypertension, increased superoxide production is linked to functional upregulation of angiotensin II

The balance between endothelial nitric oxide (NO) and angiotensin II (Ang II) maintains the homeostasis of the cardiovascular and renal systems. We tested the hypothesis that increased oxidant stress linked to a functional imbalance between NO and Ang II might play a central pathogenetic role in salt-sensitive (SS) hypertension. We studied Dahl SS (DS) rats during the prehypertensive (5 days) and hypertensive (12 weeks) phases of a high-salt (4% NaCl) diet. Control rats received a normal-salt (0.5% NaCl, [NS]) diet. Prehypertensive DS rats (systolic blood pressure [SBP] 138+/-2 mm Hg) manifested a 35% increase (P<0.05) in aortic superoxide (O2-) production without evidence of end-organ damage. Hypertensive DS rats (SBP 214+/-11 mm Hg) had impaired endothelium-dependent relaxation (EDR) and increased aortic O2- production (320%), urinary isoprostane excretion (83%), aortic (20%) and left ventricular (LVH, 21%) hypertrophy, and proteinuria (124%). In prehypertensive DS rats, candesartan (10 mg x kg(-1) x d(-1)) an Ang II type 1 receptor blocker (ARB), normalized O2- production. In hypertensive DS rats, the ARB decreased aortic O2- production by 71% and normalized EDR without affecting SBP (212+/-8 mm Hg), aortic hypertrophy, LVH, or proteinuria. Switching hypertensive DS rats to an NS diet did not affect SBP (208+/-8 mm Hg), LVH, aortic hypertrophy, or proteinuria and had minimal effects on O2- and EDR. Concomitant ARB administration plus a switch to an NS diet normalized SBP (138+/-8 mm Hg) as well as end-organ damage. Dahl salt-resistant rats fed an HS diet for 12 weeks did not show hypertension or increased O2- production. Thus, SS hypertension might represent a specific vascular diathesis linked to functional upregulation of Ang II action (increased O2- synthesis) accompanied by insufficient NO bioavailability, which promotes severe endothelial dysfunction.

Quantitation of isoprostane isomers in human urine from smokers and nonsmokers by LC-MS/MS

A simple, rapid liquid chromatography-tandem mass spectrometry method was developed to identify and quantitate in human urine the isoprostanes iPF(2 alpha)-III, 15-epi-iPF(2 alpha)-III, iPF(2 alpha)-VI, and 8,12-iso-iPF(2 alpha)-VI along with the prostaglandin PGF(2 alpha) and 2,3-dinor-iPF(2 alpha)-III, a metabolite of iPF(2 alpha)-III. Assay specificity, linearity, precision, and accuracy met the required criteria for most analytes. The urine sample storage stability and standard solution stability were also tested. The methodology was applied to analyze 24 h urine samples collected from smokers and nonsmokers on controlled diets. The results for iPF(2 alpha)-III obtained by our method were significantly correlated with results by an ELISA, although an approximately 2-fold high bias was observed for the ELISA data. For iPF(2 alpha)-III and its metabolite 2,3-dinor-iPF(2 alpha)-III, smokers had significantly higher concentrations than nonsmokers (513 +/- 275 vs. 294 +/- 104 pg/mg creatinine; 3,030 +/- 1,546 vs. 2,046 +/- 836 pg/mg creatinine, respectively). The concentration of iPF(2 alpha)-VI tended to be higher in smokers than in nonsmokers; however, the increase was not statistically significant in this sample set. Concentrations of the other three isoprostane isomers showed no trends toward differences between smokers and nonsmokers. Among smokers, the daily output of two type VI isoprostanes showed a weak correlation with the amount of tobacco smoke exposure, as determined by urinary excretion of total nicotine equivalents.

Profiling of oxidative stress in patients with inborn errors of metabolism

Free radical formation resulting in oxidative stress is a hallmark of mitochondrial dysfunction. Indeed, oxidative stress has been demonstrated to be an underlying pathophysiologic process in various inborn errors of metabolism. Metabolic profiling of oxidative stress may provide a non-specific measure of disease activity that may further enable physicians to monitor disease. In the present study, we investigated two markers of oxidative damage in urinary samples from IEM subjects and controls: F-2 isoprostanes, a measure of lipid peroxidation and di-tyrosine, a measure of protein oxidation. We also determined urinary antioxidant activity in these samples. Subsets of IEM patients showed significantly higher levels of the damage markers isoprostanes and di-tyrosine. Of note, patients with cobalamin disorders (i.e., CblB and CblC) consistently had the highest levels of oxidative damage markers. Lower urine antioxidant capacity was seen in all subject categories, particularly cobalamin disorders and propionic acidemia. Longitudinal studies in subjects with MSUD showed good concordance between markers of oxidative damage and acute decompensation. Overall, quantifying oxidative stress offers a unique perspective to IEM. These measures may provide a means of addressing mitochondrial function in IEM and aid in the development of therapeutic targets and clinical monitoring in this diverse set of disorders.

Disparate patterns of age-related changes in lipid peroxidation in long-lived naked mole-rats and shorter-lived mice

A key tenet of the oxidative stress theory of aging is that levels of accrued oxidative damage increase with age. Differences in damage generation and accumulation therefore may underlie the natural variation in species longevity. We compared age-related profiles of whole-organism lipid peroxidation (urinary isoprostanes) and liver lipid damage (malondialdehyde) in long living naked mole-rats [maximum lifespan (MLS) > 28.3 years] and shorter-living CB6F1 hybrid mice (MLS approximately 3.5 years). In addition, we compared age-associated changes in liver non-heme iron to assess how intracellular conditions, which may modulate oxidative processes, are affected by aging. Surprisingly, even at a young age, concentrations of both markers of lipid peroxidation, as well as of iron, were at least twofold (P < 0.005) greater in naked mole tats than in mice. This refutes the hypothesis that prolonged naked mole-rat longevity is due to superior protection against oxidative stress. The age-related profiles of all three parameters were distinctly species specific. Rates of lipid damage generation in mice were maintained throughout adulthood, while accrued damage in old animals was twice that of young mice. In naked mole-rats, urinary isoprostane excretion declined by half with age (P < 0.001), despite increases in tissue iron (P < 0.05). Contrary to the predictions of the oxidative stress theory, lipid damage levels did not change with age in mole-rats. These data suggest that the patterns of age-related changes in levels of markers of oxidative stress are species specific, and that the pronounced longevity of naked mole-rats is independent of oxidative stress parameters.

A protective effect of adiponectin against oxidative stress in Japanese Americans: the association between adiponectin or leptin and urinary isoprostane

Adiponectin, which is produced by adipose tissue, is thought to play an important role in inflammation. On the other hand, adiposity, or the hypertrophy of adipose tissue, has been reported to increase oxidative stress. Accordingly, the possibility exists that adiponectin, as well as leptin, influences oxidative stress, resulting in a proinflammatory state. However, the relationship between adiponectin and oxidative stress is unclear. We examined 259 Japanese Americans living in Hawaii who were diagnosed as having normal glucose tolerance (NGT), impaired glucose tolerance, or diabetes by a 75-g oral glucose tolerance test. First, we measured their serum adiponectin, leptin, and high-sensitivity C-reactive protein levels as markers of inflammation, and urinary 8-iso-protaglandin F(2 alpha) (isoprostane) as a relevant marker of oxidative stress. We investigated the relationship between adiponectin or leptin and isoprostane among these subjects. In the diabetic subjects, the adiponectin and leptin levels were significantly lower and higher, respectively, than among the NGT subjects. Urinary isoprostane levels tended to decrease significantly after a rise in adiponectin levels (P = .014) among the NGT subjects. Next, we investigated the association between the 2 adipocytokines and isoprostane by regression models. Adiponectin was negatively but significantly associated with urinary isoprostane levels adjusted for age, gender, and smoking status, whereas leptin was positively and significantly correlated with urinary isoprostane levels (P = .014 and .004, respectively). With respect to adiponectin, this association was attenuated but still significant when further adjustments were made for waist-to-hip ratio, body mass index, percent body fat, C-reactive protein levels, glucose tolerance status, or homeostasis model assessment. In conclusion, this study suggests that adiponectin and leptin might be associated with oxidative stress levels. These results also suggest the possibility that adiponectin might modulate oxidative stress, leading to antidiabetic and anti-arteriosclerotic effects.

Quantification of 15-F2t-isoprostane in human plasma and urine: results from enzyme-linked immunoassay and liquid chromatography/tandem mass spectrometry cannot be compared

Quantification of F(2)-isoprostanes is considered a reliable index of the oxidative stress status in vivo. Several immunoassays and chromatography/mass spectrometry-based assays are available for 15-F(2t)-isoprostane quantification. However, it remains unclear if results of immunoassays using different assays can be compared with those of liquid chromatography/mass spectrometry (LC/MS) assays. Previous studies comparing enzyme-linked immunosorbent assay (ELISA) and more specific gas chromatography/mass spectrometry assays have already indicated that ELISAs may overestimate 15-F(2t)-isoprostane concentrations in human plasma. Concentrations of 15-F(2t)-isoprostane in 25 human plasma and urine samples were measured by three commercially available ELISA assays (Assay Designs, Cayman Chemical and Oxford Biomedical Research) and compared with the concentrations measured with a validated, semi-automated high-throughput HPLC tandem mass spectrometry assay (LC/LC-MS/MS). All three ELISAs measured substantially higher 15-F(2t)-isoprostane concentrations (2.1-182.2-fold higher in plasma; 0.4-61.9-fold higher in urine) than LC/LC-MS/MS. Utilization of solid-phase extraction (SPE) columns, especially isoprostane affinity purification columns, brought ELISA isoprostane urine concentrations closer to the LC/LC-MS/MS results. However, SPE did not have much of an effect on ELISA plasma concentrations which remained significantly higher than corresponding LC/LC-MS/MS results. A poor correlation not only between LC/LC-MS/MS and immunoassay results, but also among the immunoassays was found. Especially in plasma, ELISAs grossly overestimate 15-F(2t)-isoprostane concentrations and are not comparable with each other or with LC/LC-MS/MS. It is most disturbing that a sample with relatively high concentrations measured with one ELISA may show low concentrations with another ELISA, and vice versa, potentially affecting the conclusions drawn from such data. The use of specific mass spectrometry-based assays seems advisable.

Effect of nut consumption on oxidative stress and the endothelial function in metabolic syndrome

BACKGROUND & AIMS

Oxidative stress has a key role in atherosclerosis, cancer and other chronic diseases. Some bioactive compounds in nuts have been implicated in antioxidant activities.

OBJECTIVE

We assessed how nut consumption affected several markers of oxidation and endothelial function (EF) in metabolic syndrome (MetS) patients.

PATIENTS AND METHODS

A randomized, controlled, parallel feeding trial was conducted on 50 MetS adults who were recommended a healthy diet supplemented or not with 30 g of mixed nuts (Nut and Control groups, respectively) every day for 12 weeks. The plasma antioxidant capacity (AC), oxidized LDL (oxLDL), conjugated diene (CD) formation, urine 8-isoprostanes, DNA damage assessed by yield of urine 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dG), and EF assessed by peripheral artery tonometry (PAT) and biochemical markers, were measured at baseline and the end of the intervention.

RESULTS

No significant differences in changes between groups were observed in AC, oxLDL, CD, 8-isoprostanes or EF during the intervention, whereas the reduction in DNA damage was significant in the Nut group compared to Control group (P < 0.001).

CONCLUSION

Nut consumption has no deleterious effect on lipid oxidation. The decrease in DNA damage observed in this study could contribute to explain the beneficial effects of regular nut consumption on some MetS features and several chronic diseases.

Deficiency of adrenomedullin induces insulin resistance by increasing oxidative stress

Hypertension, insulin resistance, and obesity are common age-related metabolic disorders that are often associated with increased oxidative stress and the resultant vascular damage. Underlying mechanisms have been suggested, and age-related overproduction of oxidative stress is one possible candidate. Since we recently found a vasoactive peptide, adrenomedullin, to be an endogenous antioxidant that potently inhibits oxidative stress-induced vascular damage, in the current study we evaluated oxidative stress-induced changes in aged mice. Insulin sensitivities in young and aged adrenomedullin-deficient mice were measured by means of the hyperinsulinemic-euglycemic clamp method; insulin resistance was apparent in aged adrenomedullin-deficient mice with increased urinary excretion of 8-iso-prostaglandin F2alpha, a marker of oxidative stress, but not in young adrenomedullin-deficient mice. Concomitantly, only aged adrenomedullin-deficient mice not only showed increased production of muscular reactive oxygen species, as demonstrated by the electron spin resonance method, but also had significantly decreased insulin-stimulated glucose uptake into the soleus muscle associated with impairment of insulin signals such as insulin receptor substrate-1,2 and phosphatidylinositol-3 kinase activities. In turn, these abnormalities could be nearly reversed by either treatment with 4-hydroxy-2,2,6,6-tetramethyl-piperidine-N-oxyl, a membrane-permeable superoxide dismutase mimetic, or adrenomedullin supplementation. Evidence presented in this report suggests that age-related accumulation of oxidative stress is involved in blood pressure regulation and insulin resistance in aged adrenomedullin-deficient mice, and adrenomedullin is thus an endogenous substance counteracting oxidative stress-induced insulin resistance associated with aging.

Melatonin supplementation ameliorates oxidative stress and inflammatory signaling induced by strenuous exercise in adult human males

Strenuous exercise induces inflammatory reactions together with high production of free radicals and subsequent muscle damage. This study was designed to investigate for the first time and simultaneously whether over-expression of inflammatory mediators, oxidative stress, and alterations in biochemical parameters induced by acute exercise could be prevented by melatonin. This indoleamine is a potent, endogenously produced free radical scavenger and a broad-spectrum antioxidant; consequently, it might have positive effects on the recovery following an exercise session. The participants were classified into two groups: melatonin-treated men (MG) and placebo-treated individuals (controls group, CG). The physical test consisted in a constant run that combined several degrees of high effort (mountain run and ultra-endurance). The total distance of the run was 50 km with almost 2800 m of ramp in permanent climbing and very changeable climatic conditions. Exercise was associated with a significant increase in TNF-α, IL-6, IL-1ra (in blood), and also an increase in 8-hydroxy-2'-deoxyguanosine (8-OHdG) and isoprostane levels (in urine), and indicated the degree of oxidative stress and inflammation induced. Oral supplementation of melatonin during high-intensity exercise proved efficient in reducing the degree of oxidative stress (lower levels of lipid peroxidation, with a significant increase in antioxidative enzyme activities); this would lead to the maintenance of the cellular integrity and reduce secondary tissue damage. Data obtained also indicate that melatonin has potent protective effects, by preventing over-expression of pro-inflammatory mediators and inhibiting the effects of several pro-inflammatory cytokines. In summary, melatonin supplementation before strenuous exercise reduced muscle damage through modulation of oxidative stress and inflammation signaling associated with this physical challenge.

A ultra-pressure liquid chromatography/triple quadrupole tandem mass spectrometry method for the analysis of 13 eicosanoids in human urine and quantitative 24 hour values in healthy volunteers in a controlled constant diet

RATIONALE

Isoprostanes (IsoPs) are a series of prostaglandin (PG)-like compounds formed non-enzymatically through free-radical-induced peroxidation of arachidonic acid. They are considered as 'gold-standard' biomarkers for oxidative stress, in general, and lipid peroxidation, in particular.

METHODS

A new qualitative and quantitative analytical method for the determination of 13 eicosanoids in human urine using solid-phase extraction (SPE) and ultra-pressure liquid chromatography coupled to tandem mass spectrometry (UPLC/MS/MS) has been developed. The SPE was optimized by comparison of the extraction efficiency and recoveries of three distinct cartridges: Strata X-AW, C18 Sep-Pak, and Oasis HLB. The UPLC/MS/MS approach in the multiple reaction monitoring (MRM) mode was developed using negative electrospray ionization (ESI).

RESULTS

The validated method provides a high-throughput assay with an adequate linearity from 0.16 to 330 ng mL(-1). The limit of detection (LOD) and limit of quantification (LOQ) for each analyte showed low intervals (0.021-0.64 ng mL(-1) and 0.042-1.28 ng mL(-1), respectively). Urinary IsoPs were determined in 24 healthy volunteers and ranged from 685 to 3480 ng 24 h(-1) and from 864 to 7511 ng 24 h(-1) in urine from women and men, respectively.

CONCLUSIONS

This analytical method could constitute a useful tool for the determination of oxidative stress biomarkers in clinical studies in which IsoPs may evidence early pathological conditions, as suggested by the determination of the baseline IsoPs content in human urine, since it improves upon the detection capacity of previously described methods. The quantity of IsoPs excreted in urine was higher than that found in previous reports due to the total hydrolysis of the conjugated forms.

Lower bone mineral density in children with type 1 diabetes is associated with poor glycemic control and higher serum ICAM-1 and urinary isoprostane levels

The purpose of the study was to investigate bone mineral density (BMD) in children with type 1 diabetes (DM1) and to establish the relationships between BMD, physical activity, glycemic control, and markers of systemic oxidative stress and inflammation. We studied 30 children with DM1, aged 4.7-18.6 years, and 30 healthy subjects, matched by sex, age, and body mass index (BMI). Mean duration of DM1 was 5.4 +/- 3.4 years and mean glycosylated hemoglobin (HbA(1c)) level over 12 months was 9.8 +/- 1.5%. Lumbar and total bone mineral density (BMD, g/cm(2)) were measured by dual-energy X-ray absorptiometry (DXA). We calculated the apparent volumetric lumbar BMD (BMDvol, g/cm(3)) and total mineral content adjusted for age and height (BMCadj), and measured plasma intercellular adhesion molecule-1 (ICAM-1), high sensitivity C-reactive protein (hs-CRP), and urinary 8-iso-prostaglandin F(2a) (F(2)-IsoPs). Calcium (Ca) intake was assessed by questionnaire and physical activity by questionnaire and accelerometer (ActiGraph, count/h). Total BMCadj and lumbar BMDvol were significantly lower in children with DM1 than in controls (101.8 +/- 7.7 vs. 107 +/- 5.7%, P = 0.005; 0.32 +/- 0.08 vs. 0.36 +/- 0.09 g/cm(3), P = 0.05, respectively). These differences were mostly caused by the differences in boys. Plasma ICAM-1 and hs-CRP levels were significantly higher in the DM1 group compared to the controls. Ca intake and urine F(2)-IsoPs levels were similar between the groups. Diabetic boys were less active than controls (18231 +/- 6613 vs. 24145 +/- 7449 count/h, P = 0.04). In the DM1 group, lumbar BMDvol correlated inversely with urinary F(2)-IsoPs (r = -0.5; P = 0.005) and plasma ICAM-1 levels (r = -0.4; P = 0.02), and also with HbA(1c) levels after adjustment for age (r = -0.45; P < 0.05). Total BMCadj correlated inversely with HbA(1c) levels (r = -0.4; P = 0.02). We conclude that children with DM1, particularly boys, have lower BMD. Poor glycemic control, elevated markers of oxidative stress, and inflammation are associated with lower BMD.

Enhanced superoxide generation modulates renal function in ANG II-induced hypertensive rats

This study was performed to examine the role of superoxide formation in the regulation of renal hemodynamic and excretory function and to assess its contribution in the pathogenesis of ANG II-dependent hypertension. Renal responses to acute intra-arterial infusion of the O2− scavenger tempol (50 μg·min−1·100 g body wt−1) with or without catalase (1,500 U·min−1·100 g−1; both native and polyethylene glycol-catalase), which reduces H2O2, were evaluated in anesthetized male Sprague-Dawley rats treated chronically with ANG II (65 ng/min) for 2 wk and compared with nontreated control rats. In ANG II-treated hypertensive rats, tempol caused increases in medullary (13 ± 2%), cortical (5 ± 2%), and total renal blood flow (9 ± 2%) without altering systemic arterial pressure. There were also increases in glomerular filtration rate (9 ± 2%), urine flow (17 ± 4%), and sodium excretion (26 ± 5%). However, tempol infusion in nontreated normotensive rats did not cause significant changes in any of these renal parameters. Coinfusion of catalase with tempol did not alter the responses observed with tempol alone, indicating that the observed renal responses to tempol in ANG II-treated rats were attributed to its O2− scavenging effects without the involvement of H2O2. Tempol infusion also significantly decreased 8-isoprostane excretion in ANG II-treated rats (39 ± 6%) without changes in H2O2 excretion. However, coinfusion of catalase reduced H2O2 excretion in both ANG II-treated (41 ± 6%) and nontreated rats (28 ± 5%). These data demonstrate that enhanced generation of O2− modulates renal hemodynamic and tubular reabsoptive function, possibly leading to sodium retention and thus contributing to the pathogenesis of ANG II-induced hypertension.

Determination of isoprostanes in urine samples from Alzheimer patients using porous graphitic carbon liquid chromatography–tandem mass spectrometry

F2-isoprostanes (F2-iPs) comprise four classes of isomers produced non-enzymatically by free radical attack on arachidonic acid, a component of the cell membrane. This paper describes a new method for the quantification of F2-isoprostanes in urine samples from thoroughly diagnosed Alzheimer's disease (AD) patients. The sample pretreatment consisted of liquid extraction of 900 microl urine with diethyl ether, its subsequent evaporation, and finally, reconstitution in 50 microl water. Of this, 20 microl was injected into a HPLC system with a 15 mm x 1 mm porous graphitic carbon column coupled to a triple quadrupole mass spectrometer running in negative electrospray ionization mode. The F2-isoprostanes were separated in 15 min using a linear solvent gradient comprising water, methanol, acetonitrile and ammonium hydroxide at a pH of 9.5. The average recovery obtained was approximately 75%. The limit of detection (3S/N) was calculated for iPF2alpha-III to be 0.7 pg injected on column, corresponding to 0.1 nM. The average level of iPF2alpha was 241 +/- 163 pg/mg creatinine in the urine samples from AD patients (average +/- standard deviation). The corresponding control values were 216 +/- 101 pg/mg creatinine, i.e. no statistically significant difference was noticed. No correlation pattern specific to Alzheimer's disease was revealed by principal component analysis of the isoprostane peaks obtained either. The results from this study support earlier findings that levels of peripheral isoprostanes are not increased in patients with Alzheimer's disease.

A dietary pattern that lowers oxidative stress increases antibodies to oxidized LDL: Results from a randomized controlled feeding study

BACKGROUND

Oxidation of LDL (oxLDL) is thought to have an important role in early stages of atherogenesis. Antibody to oxLDL (Ab-oxLDL) has been proposed as a biomarker which might be directly associated with oxidative stress. Yet studies designed to test this hypothesis are lacking. We tested the hypothesis that consumption of a healthy diet rich in fruits and vegetables and reduced in saturated fat, total fat, and cholesterol will concomitantly reduce oxidative stress and Ab-oxLDL.

METHODS

One hundred and three healthy individuals were randomly assigned to consume a typical American (control) diet or the DASH diet rich in fruits, vegetables and low-fat dairy products and reduced in fat (27%), saturated fat (7%), and cholesterol (150 mg/day) for 3 months. Outcomes were urinary isoprostanes (in vivo marker of oxidative stress), oxygen radical absorbing capacity (ORAC, an in vitro assay measuring antioxidant activity in serum), and Ab-oxLDL measured at baseline, 1-3 months of feeding.

RESULTS

Compared to the control diet, consumption of the DASH diet significantly lowered urinary isoprostane (-226 pg/ml, 95% CI: -420 to -32, P=0.023). Compared with the control group, change in ORAC was higher in the DASH group, 143 trolox units/ml (95% CI: -23 to 308, P=0.091). In comparison with the control diet, increased titers of Ab-oxLDL (37 mU/ml [95% CI: 16-57, P=0.006]) were seen after consumption of the DASH diet. Higher titers of Ab-oxLDL occurred at month 2 (56 mU/ml, 95% CI: 20-90, P=0.004) and month 3 (41 mU/ml, 95% CI: -6 to 88, P=0.082), after initially small increases at month 1 (20 mU/ml, 95% CI: -10 to 51, P=0.176). End-of-study increases in AB-oxLDL were highly correlated with increased ORAC (Spearman's rho=0.46, P<0.0001), but not with changes in specific carotenoids, tocopherols or with change in LDL cholesterol (each: P>0.10).

CONCLUSION

Consumption of a healthy diet replete in antioxidants reduced oxidative stress (urinary isoprostanes) yet increased Ab-oxLDL. This indirect association of Ab-oxLDL with urinary isoprostanes hinders use of Ab-oxLDL as a marker of oxidative damage.

In vivo rates of erythrocyte glutathione synthesis in adults with sickle cell disease

Despite reports of lower GSH concentration in sickle cell disease (SCD), the in vivo kinetic mechanism(s) responsible for GSH deficiency is unknown. To determine whether suppressed synthesis was responsible for the lower erythrocyte GSH concentration, we used a primed intermittent infusion of [(2)H(2)]glycine to measure erythrocyte GSH synthesis in vivo in 23 individuals with homozygous beta(s) SCD and 8 healthy controls. Erythrocyte cysteine concentration, the rate-limiting precursor for GSH synthesis, plasma markers of oxidant damage, and dietary intakes of energy and protein were also measured. Compared with values of controls, SCD subjects had significantly lower erythrocyte GSH (P < 0.04) and cysteine concentrations (P < 0.004) but significantly faster fractional rates of GSH synthesis (P < 0.02). The absolute rates of GSH synthesis in SCD subjects compared with control subjects was greater by approximately 57% (P = 0.062). However, the concentrations of markers of oxidative damage, plasma derivatives of reactive oxygen metabolites, plasma nitrotyrosine, urinary isoprostane-to-creatinine ratio, and GSH-to-GSSG ratio, as well as dietary intakes of energy, protein, and GSH precursor amino acids, were not different between SCD subjects and controls. The findings of this study suggest that the lower erythrocyte GSH of SCD patients is not due to suppressed synthesis or impaired regeneration but rather to increased consumption. In addition, the lower erythrocyte cysteine concentration plus the faster rate of GSH synthesis strongly suggest that the endogenous cysteine supply is not sufficient to meet all anabolic demands; hence, cysteine may be a conditionally essential amino acid in individuals with SCD.