Temperature stability of urinary F2-isoprostane and 8-hydroxy-2'-deoxyguanosine

Background

Clinical and epidemiological studies employ long-term temperature storage but the effect of temperature on the stability of oxidative stress (OS) markers is unknown. We investigated the effects of storage at -20 °C and -80 °C over 4-9 months on F2-isoprostanes (F2-IsoP) and 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels in urine of children, a population group among whom the measurement of these markers is still limited.

Methods

Paired spot urine samples from 87 children aged 8.9-16.9 years (52.9% boys) were analyzed. Samples were preserved with 0.005% (w/v) butylated hydroxytoluene, portioned and stored within 2.5 h (median) of collection. Samples were analyzed in duplicate or triplicate using commercial ELISA kits and their correlations were evaluated.

Results

F2-IsoP and 8-OHdG showed high correlations (Spearman rho of 0.90 and 0.97, respectively; P < 0.0001) with storage at -20 °C and -80 °C. There was a strong agreement among categories of values for F2-IsoP (Kappa = 0.76 ± 0.08, agreement = 83.9%, P < 0.0001) and 8-OHdG: (Kappa = 0.83 ± 0.08, agreement = 88.4%, P < 0.0001). The correlation between the temperatures for F2-IsoP concentrations was also high when stored for <4 (0.93), 4 (0.93), and 5 months (0.88), all P < 0.0001. For 8-OHdG, Spearman correlations at <8, 8, and 9 months of storage at -20 °C and -80 °C were 0.95, 0.98, and 0.96 (all P < 0.0001), respectively.

Conclusions

Urine storage with BHT for up to nine months at a temperature of -20 °C to -80 °C yields highly comparable concentrations of F2-IsoP and 8-OHdG.

Oxidative balance score reflects vascular endothelial function of Chinese community dwellers

Background: The oxidative balance score (OBS) is a composite estimate of the overall pro- and antioxidant risk status in an individual. The aim of this study is to explore the association between the OBS and vascular endothelial function in Chinese community dwellers. Methods: In total, 339 community dwelling adults (aged 20-75 years) were recruited in this study. The overall OBS was calculated on the basis of 16 pro- and antioxidant factors related to diet (measured by fasting blood samples) and lifestyle (evaluated by questionnaires). The dietary OBS and lifestyle OBS were calculated on the basis of the corresponding components. Serum iso-prostaglandin F2α (FIP) was measured to evaluate the oxidative stress degree, and brachial artery blood flow-mediated dilation (FMD) was measured for vascular endothelial function. The FIP and FMD levels were dichotomized as "low" or "high" using the corresponding median values (low FIP, n = 159; high FIP, n = 180; low FMD, n = 192; and high FMD, n = 147). The components of the OBS were compared between the stratified FIP and FMD groups. Logistic regression was used to analyze the OBS associations with FIP and FMD. Results: The higher overall OBS and dietary OBS were associated with lower FIP (p < 0.001), whereas the higher overall OBS (p < 0.01) and dietary OBS (p < 0.05) were associated with higher FMD. The lifestyle OBS was not associated with FIP and FMD (p > 0.05). Except for the body mass index (BMI) and low physical activity, all other OBS components were significantly different between the low FIP and high FIP groups (p < 0.05). Four diet-related antioxidants (α-carotene, zeaxanthin, α-tocopherol, and γ-tocopherol) showed significant differences between the high and low FMD groups (p < 0.05). Conclusion: The decreasing OBS level was associated with low endothelial function and high oxidative stress. The dietary OBS, rather than the lifestyle OBS, was more closely associated with endothelial function.

A Study to Validate the Relevance of Semen F2-Isoprostanes on Human Male Infertility

F₂-isoprostanes (F₂-IsoPs), byproducts of arachidonic acid oxidation, are one of the most reliable indices for assessing lipid peroxidation in vivo. This study aimed at evaluating the seminal F₂-IsoP level in 147 patients with different reproductive conditions (varicocele, urogenital infection, idiopathic infertility) and 45 fertile controls to establish a cut-off value discriminating physiological and pathological ranges. Semen analyses were performed following WHO guidelines; F₂-IsoP levels were measured by gas chromatography/negative-ion chemical ionization tandem mass spectrometry. Considering the whole group of patients, F₂-IsoPs correlated negatively with normal morphology (r = −0.283, p < 0.01), viability (r = −0.245, p < 0.01), total progressive motility (r = −0.309, p < 0.01) and rapid motility (r = −0.535, p < 0.01). The area under the ROC curve for F₂-IsoP levels was 0.839, indicating a good performance of the test; the Youden index showed a cut-off value of 29.96 ng/mL. Fertile men (except one) were distributed in the group of patients with F₂-IsoP level < 29.96 ng/mL. Varicocele and urogenital infection groups showed the highest levels of F₂-IsoPs in semen. For the first time, a cut-off for F₂-IsoPs is identified in human semen. It allows discriminating different male infertility conditions by the semen F₂-IsoP amounts, as an additional parameter for clinical evaluation.

Inspiratory flow-resistive breathing, respiratory muscle-induced systemic oxidative stress, and diaphragm fatigue in healthy humans

We questioned whether the respiratory muscles of humans contribute to systemic oxidative stress following inspiratory flow-resistive breathing, whether the amount of oxidative stress is influenced by the level of resistive load, and whether the amount of oxidative stress is related to the degree of diaphragm fatigue incurred. Eight young and healthy participants attended the laboratory for four visits on separate days. During the first visit, height, body mass, lung function, and maximal inspiratory mouth and transdiaphragmatic pressure (P_dimax) were assessed. During visits 2-4, participants undertook inspiratory flow-resistive breathing with either no resistance (control) or resistive loads equivalent to 50 and 70% of their P_dimax (P_dimax50% and P_dimax70%) for 30 min. Participants undertook one resistive load per visit, and the order in which they undertook the loads was randomized. Inspiratory muscle pressures were higher (P < 0.05) during the 5th and Final min of P_dimax50% and P_dimax70% compared with control. Plasma F₂-isoprostanes increased (P < 0.05) following inspiratory flow-resistive breathing at P_dimax70%. There were no increases in plasma protein carbonyls or total antioxidant capacity. Furthermore, although we evidenced small reductions in transdiapragmaic twitch pressures (P_diTW) after inspiratory flow-resistive breathing at P_dimax50% and P_dimax70%, this was not related to the increase in plasma F₂-isoprostanes. Our novel data suggest that it is only when sufficiently strenuous that inspiratory flow-resistive breathing in humans elicits systemic oxidative stress evidenced by elevated plasma F₂-isoprostanes, and based on our data, this is not related to a reduction in P_diTW.NEW & NOTEWORTHY We examined whether the respiratory muscles of humans contribute to systemic oxidative stress following inspiratory flow-resistive breathing, whether the amount of oxidative stress is influenced by the level of resistive load, and whether the amount of oxidative stress is related to the degree of diaphragm fatigue incurred. It is only when sufficiently strenuous that inspiratory flow-resistive breathing elevates plasma F₂-isoprostanes, and our novel data show that this is not related to a reduction in transdiaphragmatic twitch pressure.

Oxidant stress and renal function among children with chronic kidney disease: a repeated measures study

It is hypothesized that chronic kidney disease (CKD) induces oxidant stress which contributes to the decline in kidney function. However, few studies have incorporated longitudinal designs and no studies have investigated this association among children. Using data from the Chronic Kidney Disease in Children (CKiD) study, we examined longitudinal associations between urinary biomarkers of oxidant stress, 8-OH deoxyguanosine (8-OHdG) and F2-isoprostane, and measures of renal function and blood pressure among children with CKD. Baseline levels of 8-OHdG were positively associated with estimated glomerular filtration rate (eGFR) over time and a log-unit increase in baseline 8-OHdG predicted a 5.68 ml/min/1.73 m2 increase in eGFR (95% Confidence Interval (CI): 3.75, 7.61). This association was attenuated when longitudinal measures of 8-OHdG were analyzed in relation to longitudinal eGFR (per log-unit increase in 8-OHdG, β = 0.81, 95% CI: 0.22, 1.39). Baseline 8-OHdG concentrations were also associated with decreased proteinuria over time, as measured by urinary protein:creatinine ratio. In addition, F2-isoprostane concentrations were associated with increases in eGFR, but only when baseline levels (vs. longitudinal levels) were considered in relation to longitudinal eGFR. There were no significant associations between either 8-OHdG or F2-isoprostane and blood pressure over time. Urinary measures of oxidant stress are not associated with worsening GFR over time. Our findings suggest that excretion of these biomarkers may be influenced by changes in glomerular and tubular function in varying patterns, which would limit their value in evaluating the impact of oxidant stress on CKD progression in children.

Lipidomic methodologies for biomarkers of chronic inflammation in nutritional research: ω-3 and ω-6 lipid mediators

The evolutionary history of hominins has been characterized by significant dietary changes, which include the introduction of meat eating, cooking, and the changes associated with plant and animal domestication. The Western pattern diet has been linked with the onset of chronic inflammation, and serious health problems including obesity, metabolic syndrome, and cardiovascular diseases. Diets enriched with ω-3 marine PUFAs have revealed additional improvements in health status associated to a reduction of proinflammatory ω-3 and ω-6 lipid mediators. Lipid mediators are produced from enzymatic and non-enzymatic oxidation of PUFAs. Interest in better understanding the occurrence of these metabolites has increased exponentially as a result of the growing evidence of their role on inflammatory processes, control of the immune system, cell signaling, onset of metabolic diseases, or even cancer. The scope of this review has been to highlight the recent findings on: a) the formation of lipid mediators and their role in different inflammatory and metabolic conditions, b) the direct use of lipid mediators as antiinflammatory drugs or the potential of new drugs as a new therapeutic option for the synthesis of antiinflammatory or resolving lipid mediators and c) the impact of nutritional interventions to modulate lipid mediators synthesis towards antiinflammatory conditions. In a second part, we have summarized methodological approaches (Lipidomics) for the accurate analysis of lipid mediators. Although several techniques have been used, most authors preferred the combination of SPE with LC-MS. Advantages and disadvantages of each method are herein addressed, as well as the main LC-MS difficulties and challenges for the establishment of new biomarkers and standardization of experimental designs, and finally to deepen the study of mechanisms involved on the inflammatory response.

Oxidative/nitrative stress in the pathogenesis of systemic sclerosis: are antioxidants beneficial?

Systemic sclerosis (SSc) is a multisystem autoimmune disease: characterised from the clinical side by progressive vasculopathy and fibrosis of the skin and different organs and from the biochemical side by fibroblast deregulation with excessive production of collagen and increased expression of nicotinamide adenine dinucleotide phosphate oxidase 4 (NOX4). The latter contributes to an overproduction of reactive oxygen species that through an autocrine loop maintains NOX4 in a state of activation. Reactive oxygen and nitrogen species are implicated in the origin and perpetuation of several clinical manifestations of SSc having vascular damage in common; attempts to dampen oxidative and nitrative stress through different agents with antioxidant properties have not translated into a sustained clinical benefit. Objective of this narrative review is to describe the origin and clinical implications of oxidative and nitrative stress in SSc, with particular focus on the central role of NOX4 and its interactions, to re-evaluate the antioxidant approaches so far used to limit disease progression, to appraise the complexity of antioxidant treatment and to touch on novel pathways elements of which may represent specific treatment targets in the not so distant future.

Isoprostanoids in Clinical and Experimental Neurological Disease Models

Isoprostanoids are a large family of compounds derived from non-enzymatic oxidation of polyunsaturated fatty acids (PUFAs). Unlike other oxidative stress biomarkers, they provide unique information on the precursor of the targeted PUFA. Although they were discovered about a quarter of century ago, the knowledge on the role of key isoprostanoids in the pathogenesis of experimental and human disease models remains limited. This is mainly due to the limited availability of highly purified molecules to be used as a reference standard in the identification of biological samples. The accurate knowledge on their biological relevance is the critical step that could be translated from some mere technical/industrial advances into a reliable biological disease marker which is helpful in deciphering the oxidative stress puzzle related to neurological disorders. Recent research indicates the value of isoprostanoids in predicting the clinical presentation and evolution of the neurological diseases. This review focuses on the relevance of isoprostanoids as mediators and potential biomarkers in neurological diseases, a heterogeneous family ranging from rare brain diseases to major health conditions that could have worldwide socioeconomic impact in the health sector. The current challenge is to identify the preferential biochemical pathways that actually follow the oxidative reactions in the neurological diseases and the consequence of the specific isoprostanes in the underlying pathogenic mechanisms.

Isoprostane in systemic sclerosis: A systematic review and meta-analysis

OBJECTIVES

To further the knowledge of oxidative stress in systemic sclerosis (SSc), we performed a systematic review and meta-analysis on studies measuring isoprostane, a vasoactive agent deriving from arachidonic acid and implicated in the vasculopathy of SSc.

METHODS

Systematic search following the PRISMA guidelines in PubMed and EMBASE between January-1990/December-2017 using the terms: oxidative stress, isoprostane, systemic sclerosis and scleroderma.

RESULTS

After the screening process, 8 studies including 240 SSc patients and 192 controls were included in the systematic review and meta-analysis, 6 investigating urinary and 2 serum isoprostane: random effect meta-analysis revealed isoprostane overgeneration in SSc (p < .001) with wide heterogeneity (I² = 75%). Subgroup analysis on urinary isoprostane favoured excess excretion in SSc (p = .009) with slightly lower heterogeneity (I² = 67%); further subgroup analysis according to unit of measurement revealed no increased isoprostane excretion when expressed as pg/mg creatinine but increased when expressed as pmol/mmol creatinine (p = .05) with medium heterogeneity (I² = 32%). Subgroup analysis on serum isoprostane favoured overproduction in SSc (p < .0001) with no heterogeneity.

CONCLUSION

There is some evidence for isoprostane overgeneration in SSc that confirms the occurrence of oxidative stress in this setting: further prospective studies with specified outcomes are needed to evaluate the prognostic value of this functional biomarker.

Determinants of thromboxane biosynthesis in patients with moderate to severe chronic kidney disease

BACKGROUND

Mechanisms of accelerated atherothrombosis in patients with chronic kidney disease (CKD) are only partly characterized. The aims of this study were to evaluate the extent of thromboxane (TX)-dependent platelet activation in patients with CKD, and to characterize the determinants of altered TX biosynthesis in this setting, with particular reference to enhanced lipid peroxidation, low grade inflammation and CKD-related anemia.

PATIENTS AND METHODS

A cross sectional comparison between urinary 8-iso-PGF2α and 11-dehydro-TXB2, in vivo markers of oxidative stress and platelet activation, respectively, was performed in 115 patients with stage 1-4 CKD.

RESULTS

Levels of both urinary 11-dehydro-TXB2 and 8-iso-PGF2α increased sequentially across the four CKD stages (P<0.0001, Kruskal-Wallis test). Both urinary prostanoids were inversely associated with either estimated glomerular filtration rate (eGFR, P<0.0001) or hemoglobin levels (P<0.0001). A significant direct correlation was also observed between urinary 11-dehydro-TXB2 and 8-iso-PGF2α (Rho=0.620, P<0.0001). On multivariate analysis, urinary 8-iso-PGF2α (β=0.459, P<0.0001), hemoglobin levels (β=- 0.261, P=0.002) and eGFR (β=-0.172, P=0.032) were independent predictors of urinary 11-dehydro-TXB2 (adjusted R(2)=0.488).

CONCLUSIONS

This study provides biochemical evidence of persistent platelet activation in patients with CKD. This condition occurs early in the natural history of the disease and is related to kidney function and oxidative stress. Moreover, we found an independent inverse relationship between hemoglobin levels and TX-dependent platelet activation. This finding may provide a mechanistic link between CKD-related anemia and increased cardiovascular risk.

Effect of long-term vitamin E and selenium supplementation on urine F2-isoprostanes, a biomarker of oxidative stress

BACKGROUND

Cigarette smoking generates reactive oxidant species and contributes to systemic oxidative stress, which plays a role in the pathophysiology of chronic diseases. Nutrients with antioxidant properties, including vitamin E and selenium, are proposed to reduce systemic oxidative burden and thus to mitigate the negative health effects of reactive oxidant species.

OBJECTIVE

Our objective was to determine whether long-term supplementation with vitamin E and/or selenium reduces oxidative stress in smokers, as measured by urine 8-iso-prostaglandin F2-alpha (8-iso-PGF2α).

DESIGN

We measured urine 8-iso-PGF2α with competitive enzyme linked immunoassay (ELISA) in 312 male current smokers after 36 months of intervention in a randomized placebo-controlled trial of vitamin E (400IU/d all rac-α-tocopheryl acetate) and/or selenium (200µg/d L-selenomethionine). We used linear regression to estimate the effect of intervention on urine 8-iso-PGF2α, with adjustments for age and race.

RESULTS

Compared to placebo, vitamin E alone lowered urine 8-iso-PGF2α by 21% (p=0.02); there was no effect of combined vitamin E and selenium (intervention arm lower by 9%; p=0.37) or selenium alone (intervention arm higher by 8%; p=0.52).

CONCLUSIONS

Long-term vitamin E supplementation decreases urine 8-iso-PGF2α among male cigarette smokers, but we observed little to no evidence for an effect of selenium supplementation, alone or combined with vitamin E.

Quantitative profiling of prostaglandins as oxidative stress biomarkers in vitro and in vivo by negative ion online solid phase extraction - Liquid chromatography-tandem mass spectrometry

Free radical-mediated oxidation of arachidonic acid to prostanoids has been implicated in a variety of pathophysiological conditions such as oxidative stress. Here, we report on the development of a liquid chromatography-mass spectrometry method to measure several classes of prostaglandin derivatives based on regioisomer-specific mass transitions down to levels of 20 pg/ml applied to the measurement of prostaglandin biomarkers in primary hepatocytes. The quantitative profiling of prostaglandin derivatives in rat and human hepatocytes revealed the increase of several isomers on stress response. In addition to the well-established markers for oxidative stress such as 8-iso-prostaglandin F2α and the prostaglandin isomers PE2 and PD2, this method revealed a significant increase of 15R-prostaglandin D2 from 236.1 ± 138.0 pg/1E6 cells in untreated rat hepatocytes to 2001 ± 577.1 pg/1E6 cells on treatment with ferric NTA (an Fe(3+) chelate with nitrilotriacetic acid causing oxidative stress in vitro as well as in vivo). Like 15R-prostaglandin D2, an unassigned isomer that revealed a more significant increase than commonly analyzed prostaglandin derivatives was identified. Mass spectrometric detection on a high-resolution instrument enabled high-quality quantitative analysis of analytes in plasma levels from rat experiments, where increased concentrations up to 23-fold change treatment with Fe(III)NTA were observed.

Oxidative Stress and DNA Damage: Implications in Inflammatory Bowel Disease

This review will focus on published human studies on oxidative stress and DNA damage in inflammatory bowel disease (IBD), both ulcerative colitis and Crohn's disease, assessing their role in the pathophysiology of these diseases. Search was performed over PubMed and ScienceDirect databases to identify relevant bibliography, using keywords including "oxidative stress," "DNA damage," "IBD," and "oxidative DNA damage." Whether as cause or effect, mechanisms underlying oxidative stress have the potential to condition the course of various pathologies, particularly those driven by inflammatory scenarios. IBDs are chronic inflammatory relapsing conditions. Oxidative stress has been associated with some of the characteristic clinical features exhibited in IBD, namely tissue injury and fibrosis, and also to the ulcerative colitis-associated colorectal cancer. The possible influence of oxidative stress over therapeutic behavior and response, as well as their contribution to the oxidative burden and consequences, is also addressed. Due to the high prevalence and incidence of IBD worldwide, and also to its associated morbidity, complications, and disease and treatment costs, it is of paramount importance to better understand the pathophysiology of these diseases.

The isoprostanes--25 years later

Isoprostanes (IsoPs) are prostaglandin-like molecules generated independent of the cyclooxygenase (COX) by the free radical-induced peroxidation of arachidonic acid. The first isoprostane species discovered were isomeric to prostaglandin F2α and were thus termed F2-IsoPs. Since the initial discovery of the F2-IsoPs, IsoPs with differing ring structures have been identified as well as IsoPs from different polyunsaturated fatty acids, including eicosapentaenoic acid and docosahexanenoic acid. The discovery of these molecules in vivo in humans has been a major contribution to the field of lipid oxidation and free radical research over the course of the past 25 years. These molecules have been determined to be both biomarkers and mediators of oxidative stress in numerous disease settings. This review focuses on recent developments in the field with an emphasis on clinical research. Special focus is given to the use of IsoPs as biomarkers in obesity, ischemia-reperfusion injury, the central nervous system, cancer, and genetic disorders. Additionally, attention is paid to diet and lifestyle factors that can affect endogenous levels of IsoPs. This article is part of a Special Issue entitled "Oxygenated metabolism of PUFA: analysis and biological relevance."

Effects of 8 weeks of CPAP on lipid-based oxidative markers in obstructive sleep apnea: a randomized trial

Dyslipidaemia and increased oxidative stress have been reported in severe obstructive sleep apnea, and both may be related to the development of cardiovascular disease. We have previously shown in a randomized crossover study in patients with moderate to severe obstructive sleep apnea that therapeutic continuous positive airway pressure treatment for 8 weeks improved postprandial triglycerides and total cholesterol when compared with sham continuous positive airway pressure. From this study we have now compared the effect of 8 weeks of therapeutic continuous positive airway pressure and sham continuous positive airway pressure on oxidative lipid damage and plasma lipophilic antioxidant levels. Unesterified cholesterol, esterified unsaturated fatty acids (cholesteryl linoleate: C18:2; and cholesteryl arachidonate: C20:4; the major unsaturated and oxidizable lipids in low-density lipoproteins), their corresponding oxidized products [cholesteryl ester-derived lipid hydroperoxides and hydroxides (CE-O(O)H)] and antioxidant vitamin E were assessed at 20:30 hours before sleep, and at 06:00 and 08:30 hours after sleep. Amongst the 29 patients completing the study, three had incomplete or missing [CE-O(O)H] data. The mean apnea -hypopnoea index, age and body mass index were 38 per hour, 49 years and 32 kg m(-2) , respectively. No differences in lipid-based oxidative markers or lipophilic antioxidant levels were observed between the continuous positive airway pressure and sham continuous positive airway pressure arms at any of the three time-points [unesterified cholesterol 0.01 mm, P > 0.05; cholesteryl linoleate: C18:2 0.05 mm, P > 0.05; cholesteryl arachidonate: C20:4 0.02 mm, P = 0.05; CE-O(O)H 2.5 nm, P > 0.05; and lipid-soluble antioxidant vitamin E 0.03 μm, P > 0.05]. In this study, accumulating CE-O(O)H, a marker of lipid oxidation, does not appear to play a role in oxidative stress in obstructive sleep apnea.

Lipidomic analysis of polyunsaturated fatty acids and their oxygenated metabolites in plasma by solid-phase extraction followed by LC-MS

The present work describes the development of a robust and sensitive targeted analysis platform for the simultaneous quantification in blood plasma of lipid oxygenated mediators and fatty acids using solid-phase extraction (SPE) and high-performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS). The concurrent analysis of these lipid mediators is challenging because of their instability, differences in solubility, and the frequent occurrence of isobaric forms with similar fragmentation patterns. Results demonstrated that the reduction of SPE temperature to 4 °C is a critical parameter for preserving the hydroperoxy derivatives. Polymeric HLB cartridges increased 40-50 % ARA, EPA, and DHA sensitivity compared to C18 sorbent and also provided higher global performance for most hydroxides and other oxidation products. The proposed method for the two tested mass analyzers yields high sensitivity, good linearity, and reproducibility, with detection limits ranging 0.002-7 ng/mL and global recoveries as high as 85-112 %. However, the additional advantage of the linear ion trap (LIT) mass analyzer working in full scan product ion mode, compared to the triple quadrupole (QqQ) operating in multiple reaction monitoring (MRM), should be noted: the full scan product ion mode provides the full fragmentation spectra of compounds that allowed the discrimination of coeluting isomers and false positive identifications without additional chromatography development. The proposed lipidomic procedure demonstrates a confident, simple, and sensitive method to profile in plasma a wide range of lipid eicosanoid and docosanoid mediators, including innovatively the analysis of hydroperoxy congeners and nonoxidized PUFA precursors.

Urinary concentration of 8-isoprostane as marker of severity of pediatric OSAS

BACKGROUND

F2-isoprostanes are considered to be a reliable standard biomarker of oxidative stress in vivo because they are not influenced by the intake of lipids in the diet, and they are chemically stable molecules and easily detected. This study aimed to test the hypothesis that 8-isoprostane level is a useful marker to valuate the severity of pediatric obstructive sleep apnea (OSA).

METHODS

Sixty-five children with sleep-disordered breathing (SDB) (mean age 5.9±2.0 years; 63.1% males) were recruited. The urine sample for the measurement of 8-isoprostane was collected the morning after the polysomnographic recording. Children were divided into two groups according to their apnea-hypopnea index (AHI).

RESULTS

Urinary 8-isoprostane levels positively correlated with the sleep clinical record score (r=0.38, p=0.002) and AHI (r=0.24, p=0.05) and negatively correlated with age (r=-0.36, p=0.003) and body surface area (r=-0.38, p=0.002). Urinary 8-isoprostane levels were significantly higher in the group with AHI of ≥5 events (ev)/h than in the group with AHI of <5 ev/h (p<0.01).

CONCLUSIONS

Urinary 8-isoprostane may be used as a specific inflammatory marker to predict the severity of OSA; this method has the advantage of being noninvasive and easy to use in both compliant and noncompliant children.

Increased oxidative stress in patients with depression and its relationship to treatment

Oxidative stress may play a role in the pathogenesis of depression. We tested the hypothesis that urinary F2 isoprostanes, a robust marker of oxidative stress, was increased in patients with depression and associated with symptoms and response to treatment. Urinary F2 isoprostanes was compared in 18 patients with depression and 36 age and sex matched control subjects. In patients, we tested the association between oxidative stress, depression questionnaires and antidepressant treatment. Urinary F2 isoprostane excretion was significantly higher in patients with depression than in control subjects. This association remained significant after adjustment for age, sex and BMI. Depression symptom severity scores were not correlated with F2 isoprostane excretion. Nine patients were treated with sertraline or bupropion for 8 weeks. Depression severity rating scale scores decreased significantly and F2 isoprostane excretion increased. The increase in F2 isoprostane excretion was inversely correlated with the improvement in Hamilton Depression Rating 17 items. In conclusion, oxidative stress is increased in patients with depression. However, although treatment with either bupropion or sertraline reduces the symptoms of depression, it may increase F2 isoprostane excretion. These results suggest that alternative mechanisms, beyond oxidative stress, may be involved in the development of depression and subsequent responses to treatment.

Resistin - the link between adipose tissue dysfunction and insulin resistance in patients with obstructive sleep apnea

Background

Resistin is an adipocytokine, associated with obesity and inflammation. Its exact role in insulin resistance and diabetes in the general population is still controversial. The relation between resistin plasma levels, insulin resistance and risk of impaired glucose metabolism in OSA patients has not been investigated.

Materials and methods

Plasma levels of resistin were measured in 67 patients with OSA and impaired glucose metabolism. 34,7% (23/67) had diabetes; 40% (27/67) patients had impаired glucose tolerance(IGT); 25,3%(17/67) had normal glucose metabolism (NGM). The association between resistin, BMI, obesity, markers of insulin resistance, oxidative stress and sleep study characteristics was analysed. The different groups of patients were compared in regards to glucometabolic parameters and biomarkers of oxidative stress – isoprostanes and insulin resistance – free fatty acids (FFA).

Results

Plasma levels of resistin were higher in patients with diabetes (6,12 ±5,93ng/ml), compared to those with IGT (3,85±2,81ng/ml, p-0,021) and NGM (3,77±3,23, p-0,043). Resistin did not differ between patients with IGT and NGM (p-0,954). In OSA patients with BMI>40 resistin plasma levels correlated neither to the clinical parameters (BMI, IRI, HOMA-I, HbA1C, AHI, desaturation index), nor to the biomarkers of oxidative stress and insulin resistance. Free fatty acids (0,232>0,177mmol/l, p-0,037) were higher in diabetics in comparison to NGM.

Conclusions

Plasma resistin levels in OSA patients with BMI>40 are independent of insulin resistance and are not associated with the parameters, characterising the oxidative stress or severity of OSA. Resistin could be used in a multiple panel of clinical and biomarkers to discern patients with diabetes from those with IGT; in OSA patients with BMI >40 resistin together with HbA1C could discern patients with diabetes from those with NGM. In OSA patients with BMI >40 FFA and HbA1C are useful clinical markers in assessing the risk of dysglycaemia among patients with normal and IGT.

Temporal sequence of major biochemical events during blood bank storage of packed red blood cells

BACKGROUND

We used sensitive spectroscopic techniques to measure changes in Band 3 oligomeric state during storage of packed red blood cells (RBC); these changes were compared to metabolic changes, RBC morphology, cholesterol and membrane protein loss, phospholipid reorganisation of the RBC membrane, and peroxidation of membrane lipid. The aim of the study was to temporally sequence major biochemical events occurring during cold storage, in order to determine which changes may underlie the structural defects in stored RBC.

MATERIALS AND METHODS

Fifteen RBC units were collected from normal volunteers and stored under standard blood bank conditions; both metabolic changes and lipid parameters were measured by multiple novel assays including a new mass spectrometric measurement of isoprostane (lipid peroxidation) and flow cytometric assessment of CD47 expression. Band 3 oligomeric state was assessed by time-resolved phosphorescence anisotropy, and RBC morphology by microscopy of glutaraldehyde-fixed RBC.

RESULTS

Extracellular pH decreased and extracellular potassium increased rapidly during cold storage. Band 3 on the RBC membrane aggregated into large oligomers early in the storage period and coincident with changes in RBC morphology. Membrane lipid changes, including loss of unesterified cholesterol, lipid peroxidation and expression of CD47, also changed early during the storage period. In contrast loss of acetylcholinesterase activity and haemolysis of RBC occurred late during storage.

DISCUSSION

Our results demonstrate that changes in the macromolecular organisation of membrane proteins on the RBC occur early in storage and suggest that lipid peroxidation and/or oxidative damage to the membrane are responsible for irreversible morphological changes and loss of function during red cell storage.

Oxidative stress, anti-oxidant therapies and chronic kidney disease

Chronic kidney disease (CKD) is a common and serious problem that adversely affects human health, limits longevity and increases costs to health-care systems worldwide. Its increasing incidence cannot be fully explained by traditional risk factors. Oxidative stress is prevalent in CKD patients and is considered to be an important pathogenic mechanism. Oxidative stress develops from an imbalance between free radical production often increased through dysfunctional mitochondria formed with increasing age, type 2 diabetes mellitus, inflammation, and reduced anti-oxidant defences. Perturbations in cellular oxidant handling influence downstream cellular signalling and, in the kidney, promote renal cell apoptosis and senescence, decreased regenerative ability of cells, and fibrosis. These factors have a stochastic deleterious effect on kidney function. The majority of studies investigating anti-oxidant treatments in CKD patients show a reduction in oxidative stress and many show improved renal function. Despite heterogeneity in the oxidative stress levels in the CKD population, there has been little effort to measure patient oxidative stress levels before the use of any anti-oxidants therapies to optimize outcome. This review describes the development of oxidative stress, how it can be measured, the involvement of mitochondrial dysfunction and the molecular pathways that are altered, the role of oxidative stress in CKD pathogenesis and an update on the amelioration of CKD using anti-oxidant therapies.

Urinary biomarkers of oxidative status

Oxidative damage produced by reactive oxygen species (ROS) has been implicated in the etiology and pathology of many health conditions, including a large number of chronic diseases. Urinary biomarkers of oxidative status present a great opportunity to study redox balance in human populations. With urinary biomarkers, specimen collection is non-invasive and the organic/metal content is low, which minimizes the artifactual formation of oxidative damage to molecules in specimens. Also, urinary levels of the biomarkers present intergraded indices of redox balance over a longer period of time compared to blood levels. This review summarizes the criteria for evaluation of biomarkers applicable to epidemiological studies and evaluation of several classes of biomarkers that are formed non-enzymatically: oxidative damage to lipids, proteins, DNA, and allantoin, an oxidative product of uric acid. The review considers formation, metabolism, and exertion of each biomarker, available data on validation in animal and clinical models of oxidative stress, analytical approaches, and their intra- and inter-individual variation. The recommended biomarkers for monitoring oxidative status over time are F₂-isoprostanes and 8-oxodG. For inter-individual comparisons, F₂-isoprostanes are recommended, whereas urinary 8-oxodG levels may be confounded by differences in the DNA repair capacity. Promising urinary biomarkers include allantoin, acrolein-lysine, and dityrosine.

Novel cardiac-specific biomarkers and the cardiovascular continuum

The concept of the cardiovascular continuum, introduced during the early 1990s, created a holistic view of the chain of events connecting cardiovascular-related risk factors with the progressive development of pathological-related tissue remodelling and ultimately, heart failure and death. Understanding of the tissue-specific changes, and new technologies developed over the last 25-30 years, enabled tissue remodelling events to be monitored in vivo and cardiovascular disease to be diagnosed more reliably than before. The tangible product of this evolution was the introduction of a number of biochemical markers such as troponin I and T, which are now commonly used in clinics to measure myocardial damage. However, biomarkers that can detect specific earlier stages of the cardiovascular continuum have yet to be generated and utilised. The majority of the existing markers are useful only in the end stages of the disease where few successful intervention options exist. Since a large number of patients experience a transient underlying developing pathology long before the signs or symptoms of cardiovascular disease become apparent, the requirement for new markers that can describe the early tissue-specific, matrix remodelling process which ultimately leads to disease is evident. This review highlights the importance of relating cardiac biochemical markers with specific time points along the cardiovascular continuum, especially during the early transient phase of pathology progression where none of the existing markers aid diagnosis.

Using biomarkers in sewage to monitor community-wide human health: isoprostanes as conceptual prototype

Timely assessment of the aggregate health of small-area human populations is essential for guiding the optimal investment of resources needed for preventing, avoiding, controlling, or mitigating exposure risks. Seeking those interventions yielding the greatest benefit with respect to allocation of resources is essential for making progress toward community sustainability, promoting social justice, and maintaining or improving health and well-being. More efficient approaches are needed for revealing cause-effect linkages between environmental stressors and human health and for measuring overall aggregate health of small-area populations. A new concept is presented--community health assessment via Sewage Chemical Information Mining (SCIM)--for quickly gauging overall, aggregate health status or trends for entire small-area populations. The approach--BioSCIM--would monitor raw sewage for specific biomarkers broadly associated with human disease, stress, or health. A wealth of untapped chemical information resides in raw sewage, a portion comprising human biomarkers of exposure and effects. BioSCIM holds potential for capitalizing on the presence of biomarkers in sewage for accomplishing any number of objectives. One of the many potential applications of BioSCIM could use various biomarkers of stress resulting from the collective excretion from all individuals in a local population. A prototype example is presented using a class of biomarkers that measures collective, systemic oxidative stress--the isoprostanes (prostaglandin-like free-radical catalyzed oxidation products from certain polyunsaturated fatty acids). Sampling and analysis of raw sewage hold great potential for quickly determining aggregate biomarker levels for entire communities. Presented are the basic principles of BioSCIM, together with its anticipated limitations, challenges, and potential applications in assessing community-wide health. Community health assessment via BioSCIM could allow rapid assessments and intercomparisons of health status among distinct populations, revealing hidden or emerging trends or disparities and aiding in evaluating correlations (or hypotheses) between stressor exposures and disease.

Partial rescue of Rett syndrome by ω-3 polyunsaturated fatty acids (PUFAs) oil

Evidence of enhanced oxidative stress (O.S.) and lipid peroxidation has been reported in patients with Rett syndrome (RTT), a relatively rare neurodevelopmental disorder progressing in 4-stages, and mainly caused by loss-of-function mutations in the methyl-CpG-binding protein 2. No effective therapy for preventing or arresting the neurologic regression in the disease in its various clinical presentations is available. Based on our prior evidence of enhanced O.S. and lipid peroxidation in RTT patients, herein we tested the possible therapeutic effects of ω-3 polyunsaturated fatty acids (ω-3 PUFAs), known antioxidants with multiple effects, on the clinical symptoms and O.S. biomarkers in the earliest stage of RTT. A total of 20 patients in stage I were randomized (n = 10 subjects per arm) to either oral supplementation with ω-3 PUFAs-containing fish oil (DHA: 72.9 ± 8.1 mg/kg b.w./day; EPA: 117.1 ± 13.1 mg/kg b.w./day; total ω-3 PUFAs: 246.0 ± 27.5 mg/kg b.w./day) for 6 months or no treatment. Primary outcomes were potential changes in clinical symptoms, with secondary outcomes including variations for five O.S. markers in plasma and/or erythrocytes (nonprotein bound iron, F(2)-dihomo-isoprostanes, F(3)-isoprostanes, F(4)-neuroprostanes, and F(2)-isoprostanes). A significant reduction in the clinical severity (in particular, motor-related signs, nonverbal communication deficits, and breathing abnormalities) together with a significant decrease in all the examined O.S. markers was observed in the ω-3 PUFAs supplemented patients, whereas no significant changes were evidenced in the untreated group. For the first time, these findings strongly suggest that a dietary intervention in this genetic disease at an early stage of its natural history can lead to a partial clinical and biochemical rescue.

The relation between carotid plaque echogenicity and oxidative stress marker 8-iso-prostaglandin F2α

Echolucent plaques are associated with high risk of ischemic cerebrovascular events. Oxidative stress has been implicated in the process of atherosclerotic plaque development from initiation to progression. We assessed the relation between carotid plaque echogenicity and urinary 8-iso-prostaglandin F2α, as an index of oxidative stress. This cross-sectional study was conducted prospectively on 290 consecutive outpatients. Each patient was evaluated for carotid plaque echogenicity using the gray-scale median at the maximal thickness plaque and urinary 8-iso-prostaglandin F2α using enzyme linked immunosorbent assay. By Pearson correlation analysis, we found significant negative linear relation between gray-scale median values and the urinary 8-iso-prostaglandin F2α levels (r = -0.133, p = 0.023). This correlation remained significant after adjustment for atherosclerotic risk factors, thickness of the maximal plaque and medication use (β = -0.137, p = 0.031). We herein show that higher levels of urinary 8-iso-prostaglandin F2α is associated with lower plaque echogenicity.

An inter-laboratory validation of methods of lipid peroxidation measurement in UVA-treated human plasma samples

Lipid peroxidation products like malondialdehyde, 4-hydroxynonenal and F(2)-isoprostanes are widely used as markers of oxidative stress in vitro and in vivo. This study reports the results of a multi-laboratory validation study by COST Action B35 to assess inter-laboratory and intra-laboratory variation in the measurement of lipid peroxidation. Human plasma samples were exposed to UVA irradiation at different doses (0, 15 J, 20 J), encoded and shipped to 15 laboratories, where analyses of malondialdehyde, 4-hydroxynonenal and isoprostanes were conducted. The results demonstrate a low within-day-variation and a good correlation of results observed on two different days. However, high coefficients of variation were observed between the laboratories. Malondialdehyde determined by HPLC was found to be the most sensitive and reproducible lipid peroxidation product in plasma upon UVA treatment. It is concluded that measurement of malondialdehyde by HPLC has good analytical validity for inter-laboratory studies on lipid peroxidation in human EDTA-plasma samples, although it is acknowledged that this may not translate to biological validity.

Advances in methods for the determination of biologically relevant lipid peroxidation products

Lipid peroxidation is recognized to be an important contributor to many chronic diseases, especially those of an inflammatory pathology. In addition to their value as markers of oxidative damage, lipid peroxidation products have also been shown to have a wide variety of biological and cell signalling effects. In view of this, accurate and sensitive methods for the measurement of lipid peroxidation products are essential. Although some assays have been described for many years, improvements in protocols are continually being reported and, with recent advances in instrumentation and technology, highly specialized and informative techniques are increasingly used. This article gives an overview of the most currently used methods and then addresses the recent advances in some specific approaches. The focus is on analysis of oxysterols, F(2)-isoprostanes and oxidized phospholipids by gas chromatography or liquid chromatography mass spectrometry techniques and immunoassays for the detection of 4-hydroxynonenal.

Prediction of diabetic retinopathy: role of oxidative stress and relevance of apoptotic biomarkers

Diabetic retinopathy (DR) is the foremost cause of blindness in working-aged worldwide; it is characterized by vascular and neuronal degeneration. Features of DR include leukocyte adhesion, increased vascular permeability, neovascularization and neuronal cell death. Early diagnosis and intervention are important to prevent or at least ameliorate the development of DR. Recent reports indicate that pathophysiological mechanisms leading to diabetic retinopathy include oxidative stress and retinal cell death cascades. Circulating biomarkers of oxidative stress such as malondialdehyde (MDA), thiobarbituric acid reacting substances (TBARS), conjugated diene (CD), advanced oxidation protein products (AOPP), protein carbonyl, 8-hydroxydeoxyguanosin (8-OHdG), nitrotyrosine, and F(2) isoprostanes and pro-apoptosis molecules (caspase-3, Fas, and Bax) are associated with increased susceptibility to develop DR in diabetic subjects. Thus, identification of oxidative stress and cell death biomarkers in diabetic patients could be in favor of predicting, diagnosis, and prevention of DR, and to target for novel therapeutic interventions.

Health effects with consumption of the flax lignan secoisolariciresinol diglucoside

Flaxseed is the richest source of the lignan secoisolariciresinol diglucoside (SDG). After ingestion, SDG is converted to secoisolariciresinol, which is further metabolised to the mammalian lignans enterodiol and enterolactone. A growing body of evidence suggests that SDG metabolites may provide health benefits due to their weak oestrogenic or anti-oestrogenic effects, antioxidant activity, ability to induce phase 2 proteins and/or inhibit the activity of certain enzymes, or by mechanisms yet unidentified. Human and animal studies identify the benefits of SDG consumption. SDG metabolites may protect against CVD and the metabolic syndrome by reducing lipid and glucose concentrations, lowering blood pressure, and decreasing oxidative stress and inflammation. Flax lignans may also reduce cancer risk by preventing pre-cancerous cellular changes and by reducing angiogenesis and metastasis. Thus, dietary SDG has the potential to decrease the incidence of several chronic diseases that result in significant morbidity and mortality in industrialised countries. The available literature, though, makes it difficult to clearly identify SDG health effects because of the wide variability in study methods. However, the current evidence suggests that a dose of at least 500 mg SDG/d for approximately 8 weeks is needed to observe positive effects on cardiovascular risk factors in human patients. Flaxseed and its lignan extracts appear to be safe for most adult populations, though animal studies suggest that pregnant women should limit their exposure. The present review discusses the potential health benefits of SDG in humans, with supporting evidence from animal studies, and offers suggestions for future research.

Cerebrospinal fluid secretory Ca2+-dependent phospholipase A2 activity is increased in Alzheimer disease

BACKGROUND

The phospholipase A(2) (PLA2) family comprises multiple isoenzymes that vary in their physicochemical properties, cellular localizations, calcium sensitivities, and substrate specificities. Despite these differences, PLA2s share the ability to catalyze the synthesis of the precursors of the proinflammatory mediators. To investigate the potential of PLA2 as a biomarker in screening neuroinflammatory disorders in both clinical and research settings, we developed a PLA2 assay and determined the predominant types of PLA2 activity in cerebrospinal fluid (CSF).

METHODS

We used liposomes composed of a fluorescent probe (bis-Bodipy FL C11-PC [1,2-bis-(4,4- difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s-indacene-3-undecanoyl)-sn-glycero-3-phosphocholine]) and 1,2-dioleoyl-l-alpha-phosphatidylcholine as a substrate to measure CSF PLA2 activity in a 96-well microtiter plate format. We established the type of CSF PLA2 activity using type-specific inhibitors of PLA2.

RESULTS

Using 5 microL CSF per assay, our PLA2 activity assay was reproducible with CVs <15% in 2 CSF samples and for recombinant secretory Ca(2+)-dependent PLA2 (sPLA2) in concentrations ranging from 0.25 to 1 micromol/L. This PLA2 assay allowed identification of sPLA2 activity in lumbar CSF from healthy individuals 20-77 years old that did not depend on either sex or age. Additionally, CSF sPLA2 activity was found to be increased (P = 0.0008) in patients with Alzheimer disease.

CONCLUSIONS

Adult human CSF has sPLA2 activity that can be measured reliably with the assay described. This enzyme activity in the CSF is independent of both sex and age and might serve as a valuable biomarker of neuroinflammation, as we demonstrated in Alzheimer disease.

Quantification of F2-isoprostanes as a reliable index of oxidative stress in vivo using gas chromatography-mass spectrometry (GC-MS) method

Free radical-induced lipid peroxidation has been implicated in a number of human diseases including atherosclerosis, cancer, and neurodegenerative diseases. F(2)-Isoprostanes (IsoPs) are isomers of prostaglandin PGF(2alpha) that are generated in vivo from the free radical-initiated peroxidation of arachidonic acid independent of cyclooxygenase enzymes. Since the discovery of the IsoPs in the early 1990s, a large body of evidence has been accumulated to indicate that quantification of these F(2)-IsoPs represents the most reliable biomarker to assess oxidative stress in vivo. A variety of analytical approaches have been developed for the quantification of these novel compounds; these methods include mass spectrometry (MS) detection coupled to gas chromatography (GC) or liquid chromatography (LC) separation, and detection using immunological approaches. This article summarizes our current methodology to quantify F(2)-IsoPs in biological fluids and tissues using GC-MS. This method includes solid-phase extraction (SPE), thin-layer chromatography (TLC) purification, chemical derivatization, and MS detection using negative ion chemical ionization (NICI) coupled with GC. The protocol described herein has been optimized and validated to provide the best sensitivity and selectivity for quantification of F(2)-IsoPs from a variety of biological sources.

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.