Epidemiological marker for oxidant status: comparison of the ELISA and the gas chromatography/mass spectrometry assay for urine 2,3-dinor-5,6-dihydro-15-F2t-isoprostane

Lipid peroxidation and colorectal cancer risk: a time-varying relationship

Importance

We recently observed an inverse and time-dependent association between systemic oxidative stress (OxS), measured by urinary biomarkers of nucleic acid oxidation, and colorectal cancer (CRC) risk. Further investigations into other types of OxS markers are warranted.

Objective

To extend the investigation into systemic lipid peroxidation and CRC risk.

Design Setting and Participants

Utilizing a nested case-control design, this study's primary analysis was performed in two large prospective cohorts in Shanghai, China, and replicated in an independent cohort in the US.

Exposures

Systemic lipid peroxidation was assessed by urinary F 2 -isoprostanes (F 2 -IsoPs) using UPLC-MS/MS assays.

Main Outcomes and Measures

During 15.1-year follow-up in the Shanghai cohorts, 1938 incident CRC cases were identified and matched to one control each through incidence-density sampling. In the US cohort, 285 incident CRC cases were included, each matched to two controls. Odds ratios (ORs) for CRC were calculated using multivariable conditional logistic regression models.

Results

Elevated levels of urinary 5-F 2t -IsoP (5-iPF 2α -VI), a major isomer of F 2 -IsoPs induced solely by free radicals, were associated with reduced risk of CRC in the Shanghai cohorts. This finding was replicated in the US cohort. Moreover, this inverse association was time-dependent, manifesting only in the later years of cancer development. Multivariable-adjusted ORs (95% CI) for CRC diagnosed within 5 years of enrollment at the 10th and 90th percentiles of 5-F 2t -IsoP levels, relative to the median, were 1.57 (1.26-1.96) and 0.61 (0.42-0.89), respectively, indicating a 2.2-fold difference in risk between the two groups. A stronger association was observed when using the composite index of DNA, RNA and lipid OxS markers, showing a 3.9-fold difference in risk between the two groups. No significant association was found for CRC diagnosed beyond 5 years of enrollment.

Conclusions

This study provides new evidence that systemic OxS is inversely and time-dependently associated with CRC risk in humans.

Key Points

Question: Is the time-dependent relationship between oxidative stress and tumorigenesis observed at the cellular level in experimental models also present at the systemic level in a population-based setting?Findings: Elevated systemic lipid peroxidation, measured by urinary F 2 -isoprostanes, was associated with a reduced risk of colorectal cancer (CRC) in two large prospective cohort studies in Shanghai, China, which was replicated in an independent cohort in the United States. This association varied over time, showing a stronger effect as cancer advanced. Meaning: This study provides new evidence that systemic oxidative stress is inversely and time-dependently associated with CRC risk in humans.

Saliva as a Diagnostic Tool for Early Detection of Exercise-Induced Oxidative Damage in Female Athletes

Although blood still remains the most commonly utilized medium to detect increased levels of oxidative damage induced by exercise, saliva diagnostics have gained increasing popularity due to their non-invasive nature and athlete-friendly collection process. Given that the contribution of various phases of the menstrual cycle to the levels of oxidative damage may differ, the aim of this study was to evaluate an agreement between salivary and plasmatic levels of lipid peroxidation products in female swimmers in both the follicular (F) and luteal (L) phases of the menstrual cycle at rest and following exercise. Twelve well-trained female swimmers aged 19.6 ± 1.1 years old were examined. We measured diene conjugates (DCs), triene conjugates (TCs), and Schiff bases (SBs) in lipids immediately after their extraction from both saliva and blood plasma. All female swimmers were studied two times each, in the two different phases of one menstrual cycle, before and after high-intensity interval exercise (HIIE). Salivary and plasmatic levels of DCs, TCs, and SBs significantly increased post-exercise compared to pre-exercise, in both the F and L phases. A high positive correlation was observed between the concentrations of DCs, TCs, and SBs in the saliva and blood plasma of participants in the F and L phases, both at rest and following HIIE. Ordinary least products regression analysis indicates that there was no proportional and differential bias in the data. The Bland-Altman method also declares that there was no differential bias, since the line of equality was within the 95% confidence interval of the mean difference between salivary and plasmatic levels of DCs, TCs, and SBs in female swimmers, in both the F and L phases, before and after HIIE. There was also no proportional bias in the Bland-Altman plots. Thus, this is the first study to report a high agreement between the quantifications of DCs, TCs, and SBs in the saliva and blood plasma of female swimmers in both the F and L phases, at rest and following HIIE.

Liver fibrosis is a common pathological change in the liver of dairy cows with fatty liver

Fatty liver (i.e., hepatic lipidosis) is a prevalent metabolic disorder in dairy cows during the transition period, characterized by excess hepatic accumulation of triglyceride (TG), tissue dysfunction, and cell death. Detailed pathological changes, particularly hepatic fibrosis, during fatty liver remain to be determined. Liver fibrosis occurs as a consequence of liver damage, resulting from the excessive accumulation of extracellular matrix, which distorts the architecture of the normal liver, compromising its normal synthetic and metabolic functions. Thus, we aimed to investigate liver fibrosis status and its potential causal factors including oxidative stress, hepatocyte apoptosis, and production of inflammatory cytokines in the liver of cows with fatty liver. Forty-five dairy cows (parity, 3-5) were selected, and liver biopsy and blood were collected on the second week postpartum (days in milk, 10-14 d). On the basis of the degree of lipid accumulation in liver, selected cows were categorized into normal (n = 25; TG <1% wet wt), mild fatty liver (n = 15; 1% ≤ TG <5% wet wt), and moderate fatty liver (n = 5; 5% ≤ TG <10% wet wt). Compared with normal cows, blood concentrations of nonesterified fatty acids and β-hydroxybutyrate, along with alanine aminotransferase and aspartate aminotransferase activities, were greater in the cows with fatty liver (mild and moderate). Hepatic extracellular matrix deposition, as indicated by Picrosirius red staining, was greater in cows with fatty liver than those with normal ones. In addition, we observed an increased proportion of collagen type I fiber in extracellular matrix with increased lipid accumulation in the liver. Compared with normal cows, the area of α-smooth muscle actin (α-SMA)-positive staining along with the mRNA abundance of collagen type I α 1 (COL1A1), ACTA2 (gene encoding α-SMA), and transforming growth factor-β (TGFB) were greater in cows with fatty liver. Compared with normal cows, hepatic contents of malondialdehyde, glutathione disulfide, and 8-isoprostane were greater, whereas total antioxidant capacity, the hepatic content of glutathione, and activities of antioxidant indicators, including superoxide dismutase, glutathione peroxidase, and catalase, were lower in cows with fatty liver. The number of terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling-positive cells and abundance of apoptosis-related molecules BAX, CASP3, CASP8, and CASP9 were greater in cows with fatty liver. However, mRNA abundance of the anti-apoptotic gene BCL2 did not differ. The mRNA abundance of pro-inflammatory cytokines including tumor necrosis factor-α (TNFA), interleukin-1β (IL1B), and interleukin-6 (IL6) was greater in the liver of cows with fatty liver. Overall, the present study indicated that fibrosis is a common pathological response to liver damage and is associated with oxidative stress, hepatocyte death, and inflammation.

Inflammageing and Cardiovascular System: Focus on Cardiokines and Cardiac-Specific Biomarkers

The term "inflammageing" was introduced in 2000, with the aim of describing the chronic inflammatory state typical of elderly individuals, which is characterized by a combination of elevated levels of inflammatory biomarkers, a high burden of comorbidities, an elevated risk of disability, frailty, and premature death. Inflammageing is a hallmark of various cardiovascular diseases, including atherosclerosis, hypertension, and rapid progression to heart failure. The great experimental and clinical evidence accumulated in recent years has clearly demonstrated that early detection and counteraction of inflammageing is a promising strategy not only to prevent cardiovascular disease, but also to slow down the progressive decline of health that occurs with ageing. It is conceivable that beneficial effects of counteracting inflammageing should be most effective if implemented in the early stages, when the compensatory capacity of the organism is not completely exhausted. Early interventions and treatments require early diagnosis using reliable and cost-effective biomarkers. Indeed, recent clinical studies have demonstrated that cardiac-specific biomarkers (i.e., cardiac natriuretic peptides and cardiac troponins) are able to identify, even in the general population, the individuals at highest risk of progression to heart failure. However, further clinical studies are needed to better understand the usefulness and cost/benefit ratio of cardiac-specific biomarkers as potential targets in preventive and therapeutic strategies for early detection and counteraction of inflammageing mechanisms and in this way slowing the progressive decline of health that occurs with ageing.

Inflammation and oxidative stress as mediators of the impacts of environmental exposures on human pregnancy: Evidence from oxylipins

Inflammation and oxidative stress play major roles in healthy and pathological pregnancy. Environmental exposure to chemical pollutants may adversely affect maternal and fetal health in pregnancy by dysregulating these critical underlying processes of inflammation and oxidative stress. Oxylipins are bioactive lipids that play a major role in regulating inflammation and increasing lines of evidence point towards an importance in pregnancy. The biosynthetic production of oxylipins requires oxygenation of polyunsaturated fatty acids, which can occur through several well-characterized enzymatic and nonenzymatic pathways. This review describes the state of the science of epidemiologic evidence on oxylipin production in pregnancy and its association with 1) key pregnancy outcomes and 2) environmental exposures. We searched PubMed for studies of pregnancy that measured one or more oxylipin analytes during pregnancy or delivery. We evaluated oxylipin associations with three categories of adverse pregnancy outcomes, including preeclampsia, preterm birth, and fetal growth restriction, along with several categories of environmental pollutants. The majority of studies evaluated one to two oxylipins, most of which focused on oxylipins produced from nonenzymatic processes of oxidative stress. However, an increasing number of recent studies have leveraged technological advancements to profile a large number of oxylipins produced from distinct biosynthetic pathways. Although the literature indicated robust evidence that oxylipins produced via nonenzymatic pathways are associated with pregnancy outcomes and environmental exposures, evidence for enzymatically produced oxylipins showed that associations may differ between biosynthetic pathways. Along with summarizing this evidence, we review promising therapeutic options to regulate oxylipin production and provide a set of recommendations for future epidemiologic studies in these research areas. Further evidence is needed to improve our understanding of how oxylipins may act as key biological mediators for the adverse effects of environmental pollutants on pregnancy outcomes.

Quantification of Plasma 8-Isoprostane by High-Performance Liquid Chromatography with Tandem Mass Spectrometry in a Case-Control Study of Lung Cancer

AIM

8-iso-prostaglandin F2α is a biomarker of lipid peroxidation, and one of the most commonly used measures of oxidative stress. It is an established biomarker of lung cancer risk. It is commonly measured by enzyme-linked immunosorbent assay. Given its importance, we developed a stable isotope dilution UPLC-tandem mass spectrometric method for the rapid determination of 8-isoprostane in blood.

METHODS

We tested the discriminatory capability of the method in 49 lung cancer patients, 55 benign lung nodule patients detected by chest X-ray, and 41 patients with chronic obstructive pulmonary disease (COPD) or asthma.

RESULTS

Significant differences were found in mean 8-isoprostane levels between the three groups (p = 0.027), and post-hoc tests found higher levels in the lung cancer patients than in patients with benign nodules (p = 0.032) and COPD/asthma (p = 0.014). The receiving operating characteristic area under the curve (AUC) was 0.69 for differentiating the lung cancer group from the benign nodule group, and 0.7 for differentiating from the COPD/asthma group.

CONCLUSIONS

The UPLC-MS/MS-based method is an efficient analytical tool for measuring 8-isoprostane plasma concentrations. The results suggest exploring its utility as a marker for early lung cancer screening.

Prostanoid Metabolites as Biomarkers in Human Disease

Prostaglandins (PGD₂, PGE₂, PGF_2α), prostacyclin (PGI₂), and thromboxane A₂ (TXA₂) together form the prostanoid family of lipid mediators. As autacoids, these five primary prostanoids propagate intercellular signals and are involved in many physiological processes. Furthermore, alterations in their biosynthesis accompany a wide range of pathological conditions, which leads to substantially increased local levels during disease. Primary prostanoids are chemically instable and rapidly metabolized. Their metabolites are more stable, integrate the local production on a systemic level, and their analysis in various biological matrices yields valuable information under different pathological settings. Therefore, prostanoid metabolites may be used as diagnostic, predictive, or prognostic biomarkers in human disease. Although their potential as biomarkers is great and extensive research has identified major prostanoid metabolites that serve as target analytes in different biofluids, the number of studies that correlate prostanoid metabolite levels to disease outcome is still limited. We review the metabolism of primary prostanoids in humans, summarize the levels of prostanoid metabolites in healthy subjects, and highlight existing biomarker studies. Since analysis of prostanoid metabolites is challenging because of ongoing metabolism and limited half-lives, an emphasis of this review lies on the reliable measurement and interpretation of obtained levels.

Guidelines for measuring reactive oxygen species and oxidative damage in cells and in vivo

Multiple roles of reactive oxygen species (ROS) and their consequences for health and disease are emerging throughout biological sciences. This development has led researchers unfamiliar with the complexities of ROS and their reactions to employ commercial kits and probes to measure ROS and oxidative damage inappropriately, treating ROS (a generic abbreviation) as if it were a discrete molecular entity. Unfortunately, the application and interpretation of these measurements are fraught with challenges and limitations. This can lead to misleading claims entering the literature and impeding progress, despite a well-established body of knowledge on how best to assess individual ROS, their reactions, role as signalling molecules and the oxidative damage that they can cause. In this consensus statement we illuminate problems that can arise with many commonly used approaches for measurement of ROS and oxidative damage, and propose guidelines for best practice. We hope that these strategies will be useful to those who find their research requiring assessment of ROS, oxidative damage and redox signalling in cells and in vivo.

Challenges in Quantifying 8-OHdG and 8-Isoprostane in Exhaled Breath Condensate

Exhaled breath condensate (EBC) has attracted substantial interest in the last few years, enabling the assessment of airway inflammation with a non-invasive method. Concentrations of 8-Hydroxydesoxyguanosine (8-OHdG) and 8-isoprostane in EBC have been suggested as candidate biomarkers for lung diseases associated with inflammation and oxidative stress. EBC is a diluted biological matrix and consequently, requires highly sensitive chemical analytic methods (picomolar range) for biomarker quantification. We developed a new liquid chromatography coupled to tandem mass spectrometry method to quantify 8-OHdG and 8-isoprostane in EBC simultaneously. We applied this novel biomarker method in EBC obtained from 10 healthy subjects, 7 asthmatic subjects, and 9 subjects with chronic obstructive pulmonary disease. Both biomarkers were below the limit of detection (LOD) despite the good sensitivity of the chemical analytical method (LOD = 0.5 pg/mL for 8-OHdG; 1 pg/mL for 8-isoprostane). This lack of detection might result from factors affecting EBC collections. These findings are in line with methodological concerns already raised regarding the reliability of EBC collection for quantification of 8-OHdG and 8-isoprostane. Precaution is therefore needed when comparing literature results without considering methodological issues relative to EBC collection and analysis. Loss of analyte during EBC collection procedures still needs to be resolved before using these oxidative stress biomarkers in EBC.

Mechanisms of Oxidative Stress and Therapeutic Targets following Intracerebral Hemorrhage

Oxidative stress (OS) is induced by the accumulation of reactive oxygen species (ROS) following intracerebral hemorrhage (ICH) and plays an important role in secondary brain injury caused by the inflammatory response, apoptosis, autophagy, and blood-brain barrier (BBB) disruption. This review summarizes the current state of knowledge regarding the pathogenic mechanisms of brain injury after ICH, markers for detecting OS, and therapeutic strategies that target OS to mitigate brain injury.

Isoprostanes in Veterinary Medicine: Beyond a Biomarker

Oxidative stress has been associated with many pathologies, in both human and animal medicine. Damage to tissue components such as lipids is a defining feature of oxidative stress and can lead to the generation of many oxidized products, including isoprostanes (IsoP). First recognized in the early 1990s, IsoP are formed in numerous biological fluids and tissues, chemically stable, and easily measured by noninvasive means. Additionally, IsoP are highly specific indicators of lipid peroxidation and thereby are regarded as excellent biomarkers of oxidative stress. Although there have been many advancements in the detection and use of IsoP as a biomarker, there is still a paucity of knowledge regarding the biological activity of these molecules and their potential roles in pathology of oxidative stress. Furthermore, the use of IsoP has been limited in veterinary species thus far and represents an avenue of opportunity for clinical applications in veterinary practice. Examples of clinical applications of IsoP in veterinary medicine include use as a novel biomarker to guide treatment recommendations or as a target to mitigate inflammatory processes. This review will discuss the history, biosynthesis, measurement, use as a biomarker, and biological action of IsoP, particularly in the context of veterinary medicine.

Feline urinary F2-isoprostanes measured by enzyme-linked immunoassay and gas chromatography-mass spectroscopy are poorly correlated

15-F_2T-isoprostanes are byproducts of lipid peroxidation and were determined to be the best marker of oxidative injury in a rodent model of oxidative stress. A previous study compared methods for measurement of urinary F₂-isoprostanes (gas chromatography and negative ion chemical ionization-mass spectrometry, GC-NICI-MS; and ELISA) and found poor agreement in dogs, horses, and cows. Surprisingly, fair agreement between these methods was identified in a small population of cats. We evaluated the agreement between GC-NICI-MS and ELISA of urinary F₂-isoprostanes in the urine of 50 mature cats ranging from healthy to systemically ill. All urine samples had detectable levels of F₂-isoprostanes by both methods. Significant proportional bias and poor agreement were identified between the 2 methods (ρ = 0.364, p = 0.009) for all cats, and in subgroup analysis based on health status. The concentration of urinary F₂-isoprostanes was significantly lower in systemically ill cats compared to healthy cats when measured by ELISA (p = 0.002) but not by GC-NICI-MS (p = 0.068). Our results indicate that GC-NICI-MS and ELISA have poor agreement when measuring urinary F₂-isoprostanes in cats.

Methods of the Analysis of Oxylipins in Biological Samples

Oxylipins are derivatives of polyunsaturated fatty acids and due to their important and diverse functions in the body, they have become a popular subject of studies. The main challenge for researchers is their low stability and often very low concentration in samples. Therefore, in recent years there have been developments in the extraction and analysis methods of oxylipins. New approaches in extraction methods were described in our previous review. In turn, the old analysis methods have been replaced by new approaches based on mass spectrometry (MS) coupled with liquid chromatography (LC) and gas chromatography (GC), and the best of these methods allow hundreds of oxylipins to be quantitatively identified. This review presents comparative and comprehensive information on the progress of various methods used by various authors to achieve the best results in the analysis of oxylipins in biological samples.

Associations between socioeconomic status, psychosocial stress, and urinary levels of 8-iso-prostaglandin-F2α during pregnancy in Puerto Rico

BACKGROUND

Lower socioeconomic status (SES) and psychosocial stress during pregnancy have been associated with adverse birth outcomes. While hypothalamic-pituitary-axis activation is thought to be the primary driver, oxidative stress may also be involved mechanistically. We used data from the Puerto Rico Testsite for Exploring Contamination Threats (PROTECT) cohort (N=476) to examine associations between self-reported psychosocial stress measures, SES indicators, and urinary oxidative stress biomarker concentrations, hypothesizing that women with lower SES and increased psychosocial stress would have elevated oxidative stress biomarkers.

METHODS

Maternal age, education, marital status, insurance status, alcohol use and smoking status were obtained via self-reported questionnaires and were used as indicators of SES. Perceived stress, depression, negative life experiences, neighborhood perceptions, and social support were self-reported in questionnaires administered during pregnancy. Responses were grouped into tertiles for analysis, where the highest tertile corresponded to highest level of psychosocial stress. Urinary concentrations of 8-iso-prostaglandin F2α (8-iso-PGF2α) and its primary metabolite were measured at three study visits (median 18, 24, 28 weeks gestation) and averaged to reflect oxidative stress across pregnancy. Linear models were used to examine associations between SES indicators, tertiles of psychosocial stress and oxidative stress biomarkers.

RESULTS

Average levels of 8-iso-PGF2α and the 8-iso-PGF2α metabolite were higher among pregnant women who were younger, who had public compared to private insurance, and who were unemployed compared to employed. However, no associations were observed between psychosocial stress measures and biomarker concentrations in adjusted analyses.

CONCLUSIONS

Psychosocial stress during pregnancy, as indicated by self-reported questionnaire measures, was not associated with biomarkers of oxidative stress in the PROTECT study. However, results suggest that these biomarkers are elevated among women of lower SES, which is typically associated with stress. Notably, compared to other populations, self-reported psychosocial stress measures were lower in PROTECT compared to other populations.

Mass Spectrometry in Advancement of Redox Precision Medicine

Redox (portmanteau of reduction-oxidation) reactions involve the transfer of electrons between chemical species in biological processes fundamental to life. It is of outmost importance that cells maintain a healthy redox state by balancing the action of oxidants and antioxidants; failure to do so leads to a multitude of diseases including cancer, diabetes, fibrosis, autoimmune diseases, and cardiovascular and neurodegenerative diseases. From the perspective of precision medicine, it is therefore beneficial to interrogate the redox phenotype of the individual-similar to the use of genomic sequencing-in order to design tailored strategies for disease prevention and treatment. This chapter provides an overview of redox metabolism and focuses on how mass spectrometry (MS) can be applied to advance our knowledge in redox biology and precision medicine.

Urinary oxidative stress biomarkers and accelerated time to spontaneous delivery

BACKGROUND

Oxidative stress has been implicated in numerous birth outcomes, including spontaneous preterm birth. However, the relationship with presentation at delivery has been less well studied. We assessed the relationship between oxidative stress biomarkers and gestational duration with a focus on spontaneous presentation for delivery.

METHODS

Our sample included 740 women from a multi-center prospective cohort study, recruited from 2010 to 2012. Resultant measures of oxidative stress in pregnancy prostaglandin F_2α (PGF_2α), 8-iso-prostaglandin F_2α (8-iso-PGF_2α), and the primary 8-iso-PGF_2α metabolite were measured in third trimester urine samples. Information on presentation for delivery was abstracted from medical records. We examined associations with preterm birth using adjusted logistic models. Time to event (overall delivery and spontaneous delivery) was examined using adjusted accelerated failure time models.

RESULTS

The 8-iso-PGF_2α metabolite was associated with increased odds of overall preterm birth (OR: 1.44 [95% CI: 1.00, 2.06]), and the association with spontaneous preterm birth was similar in magnitude but not statistically significant (OR: 1.45 [95% CI: 0.96, 2.20]). We did not detect associations between other biomarkers and preterm birth, or between biomarkers and timing of overall or spontaneous delivery in accelerated failure time models.

CONCLUSIONS

Our data suggest that increased oxidative stress, as indicated by the 8-iso-PGF_2α metabolite, may be associated with preterm birth. In contrast to previous studies, associations were similar among individuals with spontaneous versus non-spontaneous presentation for delivery.

Development of an LC-ESI(-)-MS/MS method for the simultaneous quantification of 35 isoprostanes and isofurans derived from the major n3- and n6-PUFAs

Misregulation of oxidative and antioxidative processes in the organism - oxidative stress - contributes to the pathogenesis of different diseases, e.g. inflammatory or neurodegenerative diseases. Oxidative stress leads to autoxidation of polyunsaturated fatty acids giving rise to prostaglandin-like isoprostanes (IsoP) and isofurans (IsoF). On the one hand they could serve as biomarker of oxidative stress and on the other hand may act as lipid mediators, similarly as the enzymatically formed oxylipins. In the present paper we describe the development of an LC-ESI(-)-MS/MS method allowing the parallel quantification of 27 IsoP and 8 IsoF derived from 6 different PUFA (ALA, ARA, EPA, AdA, n6-DPA, DHA) within 12 min. The chromatographic separation was carried out on an RP-C18 column (2.1 × 150 mm, 1.8 μm) yielding narrow peaks with an average width at half maximum of 3.3-4.2 s. Detection was carried out on a triple quadrupole mass spectrometer operating in selected reaction monitoring mode allowing the selective detection of regioisomers. The limit of detection ranged between 0.1 and 1 nM allowing in combination with solid phase extraction the detection of IsoP and IsoF at subnanomolar concentrations in biological samples. The method was validated for human plasma showing high accuracy and precision. Application of the approach on the investigation of oxidative stress in cultured cells indicated a distinct pattern of IsoP and IsoF in response to reactive oxygen species which warrants further investigation. The described method is not only the most comprehensive approach for the simultaneous quantification of IsoP and IsoF, but it was also integrated in a targeted metabolomics method (Ostermann et al. (2015) Anal Bioanal Chem) allowing the quantification of in total 164 oxylipins formed enzymatically and non-enzymatically within 30.5 min.

Measurement and Clinical Significance of Biomarkers of Oxidative Stress in Humans

Oxidative stress is the result of the imbalance between reactive oxygen species (ROS) formation and enzymatic and nonenzymatic antioxidants. Biomarkers of oxidative stress are relevant in the evaluation of the disease status and of the health-enhancing effects of antioxidants. We aim to discuss the major methodological bias of methods used for the evaluation of oxidative stress in humans. There is a lack of consensus concerning the validation, standardization, and reproducibility of methods for the measurement of the following: (1) ROS in leukocytes and platelets by flow cytometry, (2) markers based on ROS-induced modifications of lipids, DNA, and proteins, (3) enzymatic players of redox status, and (4) total antioxidant capacity of human body fluids. It has been suggested that the bias of each method could be overcome by using indexes of oxidative stress that include more than one marker. However, the choice of the markers considered in the global index should be dictated by the aim of the study and its design, as well as by the clinical relevance in the selected subjects. In conclusion, the clinical significance of biomarkers of oxidative stress in humans must come from a critical analysis of the markers that should give an overall index of redox status in particular conditions.

The role played by oxidative stress in evoking the exercise pressor reflex in health and simulated peripheral artery disease

KEY POINTS

Ligating the femoral artery of a rat for 72 h, a model for peripheral artery disease, causes an exaggerated exercise pressor reflex in response to muscle contraction. Likewise, the hindlimb muscles of rats with ligated femoral arteries show increased levels of reactive oxygen species. Infusion of tiron, a superoxide scavenger, attenuated the exaggerated pressor reflex and reduced reactive oxygen species production in rats with ligated femoral arteries. Conversely, we found no effect of tiron infusion on the pressor reflex in rats with patent femoral arteries. These results suggest a role of reactive oxygen species with respect to causing the exaggerated pressor response to contraction seen in rats with ligated arteries and peripheral artery disease.

ABSTRACT

Contraction of muscle evokes the exercise pressor reflex (EPR), which is expressed partly by increases in heart rate and arterial pressure. Patients with peripheral artery disease (PAD) show an exaggerated EPR, sometimes report pain when walking and are at risk for cardiac arrthymias. Previous research suggested that reactive oxygen species (ROS) mediate the exaggerated EPR associated with PAD. To examine the effects of ROS on the EPR, we infused a superoxide scavenger, tiron, into the superficial epigastric artery of decerebrated rats. In some, we simulated PAD by ligating a femoral artery for 72 h before the experiment. The peak EPR in 'ligated' rats during saline infusion averaged 31 ± 4 mmHg, whereas the peak EPR in these rats during tiron infusion averaged 13 ± 2 mmHg (n = 12; P < 0.001); the attenuating effect of tiron on the EPR was partly reversed when saline was reinfused into the superficial epigastric artery (21 ± 2 mmHg; P < 0.01 vs. tiron). The peak EPR in 'ligated' rats was also attenuated (n = 7; P < 0.01) by infusion of gp91ds-tat, a peptide that blocks the activity of NAD(P)H oxidase. Tiron infusion had no effect on the EPR in rats with patent femoral arteries (n = 9). Western blots showed that the triceps surae muscles of 'ligated' rats expressed more Nox2 and p67phox, which are components of NADPH oxidase, compared to triceps surae muscles of 'freely perfused' rats. Tiron added to muscle homogenates reduced ROS production in vitro. The results of the present study provide further evidence indicating that ROS mediates the exaggeration of EPR in rats with simulated PAD.

Biomarkers in adult asthma: a systematic review of 8-isoprostane in exhaled breath condensate

OBJECTIVES

We aimed to assess the evidence for the use of 8-isoprostane in exhaled breath condensate (EBC) as a biomarker in adult asthma.

DESIGN

A systematic review and meta-analysis of EBC 8-isoprostane.

METHODS

We searched a number of online databases (including PubMed, Embase and Scopus) in January 2016. We included studies of adult non-smokers with EBC collection and asthma diagnosis conducted according to recognised guidelines. We aimed to pool data using random effects meta-analysis and assess heterogeneity using I ².

RESULTS

We included twenty studies, the findings from which were inconsistent. Seven studies (n = 329) reported 8-isoprostane levels in asthma to be significantly higher than that of control groups, whilst six studies (n = 403) did not. Only four studies were appropriate for inclusion in a random effects meta-analysis of mean difference. This found a statistically significant between-groups difference of 22 pg ml^-1. Confidence in the result is limited by the small number of studies and by substantial statistical heterogeneity (I ² = 94).

CONCLUSION

The clinical value of EBC 8-isoprostane as a quantitative assessment of oxidative stress in asthma remains unclear due to variability in results and methodological heterogeneity. It is essential to develop a robust and standardised methodology if the use of EBC 8-isoprostane in asthma is to be properly evaluated.

Oxidative stress in relation to diet and physical activity among premenopausal women

Higher levels of oxidative stress, as measured by F2-isoprostanes, have been associated with chronic diseases such as CVD and some cancers. Improvements in diet and physical activity may help reduce oxidative stress; however, previous studies regarding associations between lifestyle factors and F2-isoprostane concentrations have been inconsistent. The aim of this cross-sectional study was to investigate whether physical activity and intakes of fruits/vegetables, antioxidant nutrients, dietary fat subgroups and alcohol are associated with concentrations of F2-isoprostane and the major F2-isoprostane metabolite. Urinary F2-isoprostane and its metabolite were measured in urine samples collected at enrolment from 912 premenopausal women (aged 35-54 years) participating in the Sister Study. Physical activity, alcohol consumption and dietary intakes were self-reported via questionnaires. With adjustment for potential confounders, the geometric means of F2-isoprostane and its metabolite were calculated according to quartiles of dietary intakes, alcohol consumption and physical activity, and linear regression models were used to evaluate trends. Significant inverse associations were found between F2-isoprostane and/or its metabolite and physical activity, vegetables, fruits, vitamin C, α-carotene, vitamin E, β-carotene, vitamin A, Se, lutein+zeaxanthin and long-chain n-3 fatty acids. Although trans fats were positively associated with both F2-isoprostane and its metabolite, other dietary fat subgroups including SFA, n-6 fatty acids, n-3 fatty acids, MUFA, PUFA, short-chain n-3 fatty acids, long-chain n-3 fatty acids and total fat were not associated with either F2-isoprostane or its metabolite. Our findings suggest that lower intake of antioxidant nutrients and higher intake of trans fats may be associated with greater oxidative stress among premenopausal women.

Measurement of Reactive Oxygen Species, Reactive Nitrogen Species, and Redox-Dependent Signaling in the Cardiovascular System: A Scientific Statement From the American Heart Association

Reactive oxygen species and reactive nitrogen species are biological molecules that play important roles in cardiovascular physiology and contribute to disease initiation, progression, and severity. Because of their ephemeral nature and rapid reactivity, these species are difficult to measure directly with high accuracy and precision. In this statement, we review current methods for measuring these species and the secondary products they generate and suggest approaches for measuring redox status, oxidative stress, and the production of individual reactive oxygen and nitrogen species. We discuss the strengths and limitations of different methods and the relative specificity and suitability of these methods for measuring the concentrations of reactive oxygen and reactive nitrogen species in cells, tissues, and biological fluids. We provide specific guidelines, through expert opinion, for choosing reliable and reproducible assays for different experimental and clinical situations. These guidelines are intended to help investigators and clinical researchers avoid experimental error and ensure high-quality measurements of these important biological species.

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.

Clinical Relevance of Biomarkers of Oxidative Stress

SIGNIFICANCE

Oxidative stress is considered to be an important component of various diseases. A vast number of methods have been developed and used in virtually all diseases to measure the extent and nature of oxidative stress, ranging from oxidation of DNA to proteins, lipids, and free amino acids.

RECENT ADVANCES

An increased understanding of the biology behind diseases and redox biology has led to more specific and sensitive tools to measure oxidative stress markers, which are very diverse and sometimes very low in abundance.

CRITICAL ISSUES

The literature is very heterogeneous. It is often difficult to draw general conclusions on the significance of oxidative stress biomarkers, as only in a limited proportion of diseases have a range of different biomarkers been used, and different biomarkers have been used to study different diseases. In addition, biomarkers are often measured using nonspecific methods, while specific methodologies are often too sophisticated or laborious for routine clinical use.

FUTURE DIRECTIONS

Several markers of oxidative stress still represent a viable biomarker opportunity for clinical use. However, positive findings with currently used biomarkers still need to be validated in larger sample sizes and compared with current clinical standards to establish them as clinical diagnostics. It is important to realize that oxidative stress is a nuanced phenomenon that is difficult to characterize, and one biomarker is not necessarily better than others. The vast diversity in oxidative stress between diseases and conditions has to be taken into account when selecting the most appropriate biomarker.

Reduction in oxidative stress biomarkers after adenotonsillectomy

OBJECTIVES

A number of otolaryngic conditions such as chronic tonsillitis, adenoid hypertrophy, and obstructive sleep apnea are associated with oxidative stress and elevated levels of serum oxidants. The objective of this study is to measure changes in urine biomarkers of oxidative stress in children after adenotonsillectomy.

METHODS

Twenty-two children with sleep disordered breathing (SDB) with tonsil and adenoid hypertrophy were enrolled prior to adenotonsillectomy. Controls consisted of 20 healthy children. Urine samples were collected from all patients. Levels of three urinary biomarkers for oxidative status, 8-hydroxy-2-deoxyguanosine (8-OxodG), F(2)-isoprostane, and malondialdehyde (MDA) were measured using high performance liquid chromatography. For the study group, urine samples were repeated 3 weeks after surgery.

RESULTS

In the study group, preoperative urinary levels of 8-OxodG were higher than in controls (p=0.015). Levels decreased after surgery compared to preoperative levels (p=0.002), and reached control levels (p=0.167) at 3 weeks. Levels of urinary F(2)-isoprostane were similar in both groups (p=0.252), but decreased significantly after surgery (p=0.020).

CONCLUSIONS

Children with SDB have elevated levels of urinary 8-OxodG, a marker of oxidative stress. Adenotonsillectomy results in decreased 8-OxodG and F(2)-isoprostane. These findings suggest that urine analysis may represent a valuable tool for the measurement of oxidative stress.

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."

Biomarker modelling of early molecular changes in Alzheimer's disease

The preclinical phase of Alzheimer's disease (AD) occurs years, possibly decades, before the onset of clinical symptoms. Being able to detect the very earliest stages of AD is critical to improving understanding of AD biology, and identifying individuals at greatest risk of developing clinical symptoms with a view to treating AD pathophysiology before irreversible neurodegeneration occurs. Studies of dominantly inherited AD families and longitudinal studies of sporadic AD have contributed to knowledge of the earliest AD biomarkers. Here we appraise this evidence before reviewing novel, particularly fluid, biomarkers that may provide insights into AD pathogenesis and relate these to existing hypothetical disease models.

A review of the application of inflammatory biomarkers in epidemiologic cancer research

Inflammation is a facilitating process for multiple cancer types. It is believed to affect cancer development and progression through several etiologic pathways, including increased levels of DNA adduct formation, increased angiogenesis, and altered antiapoptotic signaling. This review highlights the application of inflammatory biomarkers in epidemiologic studies and discusses the various cellular mediators of inflammation characterizing the innate immune system response to infection and chronic insult from environmental factors. Included is a review of six classes of inflammation-related biomarkers: cytokines/chemokines, immune-related effectors, acute-phase proteins, reactive oxygen and nitrogen species, prostaglandins and cyclooxygenase-related factors, and mediators such as transcription factors and growth factors. For each of these biomarkers, we provide a brief overview of the etiologic role in the inflammation response and how they have been related to cancer etiology and progression within the literature. We provide a discussion of the common techniques available for quantification of each marker, including strengths, weaknesses, and potential pitfalls. Subsequently, we highlight a few under-studied measures to characterize the inflammatory response and their potential utility in epidemiologic studies of cancer. Finally, we suggest integrative methods for future studies to apply multifaceted approaches to examine the relationship between inflammatory markers and their roles in cancer development.

Microextraction by Packed Sorbent (MEPS) and Solid-Phase Microextraction (SPME) as Sample Preparation Procedures for the Metabolomic Profiling of Urine

For a long time, sample preparation was unrecognized as a critical issue in the analytical methodology, thus limiting the performance that could be achieved. However, the improvement of microextraction techniques, particularly microextraction by packed sorbent (MEPS) and solid-phase microextraction (SPME), completely modified this scenario by introducing unprecedented control over this process. Urine is a biological fluid that is very interesting for metabolomics studies, allowing human health and disease characterization in a minimally invasive form. In this manuscript, we will critically review the most relevant and promising works in this field, highlighting how the metabolomic profiling of urine can be an extremely valuable tool for the early diagnosis of highly prevalent diseases, such as cardiovascular, oncologic and neurodegenerative ones.

Optimized method for quantification of total F(2)-isoprostanes using gas chromatography-tandem mass spectrometry

F2-isoprostanes are produced from the oxidative degradation of arachidonic acid and are considered the gold standard marker of lipid peroxidation in biological samples. We developed a liquid-liquid extraction method for the determination of total isoprostanes using negative chemical ionization gas chromatography-tandem mass spectrometry in plasma and tissue homogenates. Incorporating liquid-liquid extraction allows for greater sample through-put than current approaches. Here we describe the protocol and include numerous trouble-shooting suggestions. The method found healthy individuals with 150-250 pg of isoprostanes per ml of plasma and end stage kidney disease patients to have the highest measured values of up to 1100 pg/ml. This assay has an accurate working linear range of 40-1000 pg of isoprostanes (100-2500 pg/ml) and an average coefficient of variance of 7%. Tissue values for healthy mice liver were 50-70 pg/μg protein. This method provides increased ion selectivity and detection capabilities with economical sample through-put.

Measurement of F2- isoprostanes and isofurans using gas chromatography-mass spectrometry

F2-Isoprostanes (IsoPs) are isomers of prostaglandin F2α formed from the nonenzymatic free radical-catalyzed peroxidation of arachidonic acid. Since discovery of these molecules by Morrow and Roberts in 1990, F2-IsoPs have been shown to be excellent biomarkers as well as potent mediators of oxidative stress in vivo in humans. Isofurans (IsoFs) are also oxidation products generated from the nonenzymatic oxidation of arachidonic acid. IsoFs are preferentially formed instead of F2-IsoPs in settings of increased oxygen tension. The protocol presented herein is the current methodology that our laboratory uses to quantify F2-IsoPs and IsoFs in biological tissues and fluids using gas chromatography/mass spectrometry (GC/MS). A variety of analytical procedures to measure F2-IsoPs, including other GC/MS methods and liquid chromatography/MS and immunological approaches, are reported in the literature. This method provides a very low limit of quantitation and is suitable for analysis of both F2-IsoPs and IsoFs from a variety of biological sources including urine, plasma, tissues, cerebral spinal fluid, exhaled breath condensate, and amniotic fluid, among others.

Systematic review on the association between F2-isoprostanes and cardiovascular disease

Background

Oxidative stress may play an aetiological role in the development and progression of cardiovascular disease (CVD). However, evidence on its biochemical markers has been controversial. This article aimed to assess the role of F2-isoprostanes, a marker for measuring in vivo lipid oxidation, as a biomarker for CVD, including coronary artery disease, stroke and peripheral artery disease.

Methods

A literature search was performed using PubMed and EMBASE (from 1966 to February 2012). Studies that investigated the association between F2-isoprostanes and CVD were eligible.

Results

Of the 22 eligible studies retrieved, 20 studies showed a significant association between F2-isoprostanes and CVD. However, to date, there have been only four population-based studies, with one study reporting null association. Although data from prospective studies are ideal to examine a role of such biomarkers in predicting future CVD events, only two studies were prospective. In addition, differences in population characteristics, sample handling/storage and assays, coupled with a lack of confounding adjustment, may all contribute to the enormous variation in previous studies.

Conclusions

High levels of F2-isoprostanes in urine or blood may be a non-specific indicator of CVD. However, further population-based studies are needed. In addition, multivariable analyses are required for future studies to control confounding and improve classification accuracy.

Exposure to cooking oil fumes and oxidative damages: a longitudinal study in Chinese military cooks

Cooking oil fumes (COF) contain polycyclic aromatic hydrocarbons (PAHs), heterocyclic aromatic amines, benzene, and formaldehyde, which may cause oxidative damages to DNA and lipids. We assessed the relations between exposure to COF and subsequent oxidative DNA damage and lipid peroxidation among military cooks and office-based soldiers. The study population, including 61 Taiwanese male military cooks and a reference group of 37 office soldiers, collected urine samples pre-shift of the first weekday and post-shift of the fifth workday. We measured airborne particulate PAHs in military kitchens and offices and concentrations of urinary 1-OHP, a biomarker of PAH exposure, urinary 8-hydroxydeoxyguanosine (8-OHdG), a biomarkers of oxidative DNA damage, and urinary isoprostane (Isop). Airborne particulate PAHs levels in kitchens significantly exceeded those in office areas. The concentrations of urinary 1-OHP among military cooks increased significantly after 5 days of exposure to COF. Using generalized estimating equation analysis adjusting for confounding, a change in log(8-OHdG) and log(Isop) were statistically significantly related to a unit change in log(1-OHP) (regression coefficient (β), β=0.06, 95% CI 0.001-0.12) and (β=0.07, 95% CI 0.001-0.13), respectively. Exposure to PAHs, or other compounds in cooking oil fumes, may cause both oxidative DNA damage and lipid peroxidation.

Long-lasting oxidative pulmonary insult in rat after intratracheal instillation of silica nanoparticles doped with cadmium

Silica/cadmium containing nanomaterials are now produced on industrial scale due to their potential for a variety of technological applications. Nevertheless, information on toxicity, exposure and health impact of these nanomaterials is still limited. In this study, in vivo effects of silica nanoparticles (SiNPs) doped with Cd (SiNPs-Cd, 1mg/rat), soluble CdCl(2) (400 μg/rat), or SiNPs (600 μg/rat) have been investigated by evaluating F(2)-isoprostanes (F(2)-IsoPs), superoxide dismutase (SOD1), inducible nitric oxide synthase (iNOS) and cyclooxygenase type 2 (COX-2) enzymes, as markers of oxidative stress, 24h, 7 and 30 days after intra-tracheal (i.t.) instillation to rats. Free and esterified F(2)-IsoPs were evaluated in lung and plasma samples by GC/NICI-MS/MS analysis, and SOD1, iNOS and COX-2 expression in pulmonary tissue by immunocytochemistry. Thirty days after exposure, pulmonary total F(2)-IsoPs were increased by 56% and 43% in CdCl(2) and SiNPs-Cd groups, respectively, compared to controls (32.8 ± 7.8 ng/g). Parallel elevation of free F(2)-IsoPs was observed in plasma samples (by 113% and 95% in CdCl(2) and SiNPs-Cd groups, respectively), compared to controls (28 ± 8 pg/ml). These effects were already detectable at day 7 and lasted until day 30 post-exposure. Pulmonary SOD1-, iNOS-, and COX-2-immunoreactivity was significantly enhanced in a time-dependent manner (7 days <30 days) after both CdCl(2) and SiNPs-Cd treatments. SiNPs did not influence any of the evaluated endpoints. The results indicate the capacity of engineered SiNPs-Cd to cause long-lasting oxidative tissue injury following pulmonary exposure in rat.

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.

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.

A targeted lipidomics approach to the study of eicosanoid release in synovial joints

Introduction

Articular tissues are capable of producing a range of eicosanoid mediators, each of which has individual biological effects and may be affected by anti-inflammatory treatment. We set out to develop and evaluate a high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) approach for the simultaneous analysis of multiple eicosanoid lipid mediators in equine synovial fluid (SF), and to illustrate its use for investigation of the in vivo effects of non-steroidal anti-inflammatory drug (NSAID) treatment.

Methods

Synovial fluid samples were obtained from normal joints of 6 adult horses at baseline (0 hr) and at 8, 24 and 168 hours after experimental induction of transient acute synovitis, with horses treated once daily with oral NSAID (meloxicam, 0.6 mg/kg) or placebo. Following solid-phase extraction, SF lipid mediator quantitation was based on liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) analysis, and results were compared between disease states using linear discriminant analysis (LDA) and analysis of variance (ANOVA) with multiple comparisons corrections.

Results

Of a total of 23 mediators targeted, 14 could be reliably identified and quantified in SF samples based on detection of characteristic fragment ions at retention times similar to those of commercial standards. LDA analysis of baseline, 8, 24 and 168 hour synovial fluid samples revealed a separation of these groups into discrete clusters, reflecting dynamic changes in eicosanoid release over the course of synovitis. Prostaglandin (PG) E₂ was significantly lower in NSAID vs. placebo treated samples at all time points; PGE₁, 11-hydroxyeicosatetraenoic acid (11-HETE) and 13,14-dihydro-15keto PGF₂α were reduced at 8 and 24 hours by NSAID treatment; while 15-HETE, 6-keto PGF₁α, PGF₂α, 13,14-dihydro-15keto PGE₂ and thromboxane B₂ (TXB₂) were reduced at the 8 hour time point only. An interesting pattern was seen for Leukotriene B₄ (LTB₄), NSAID treatment causing an initial increase at 8 hours, but a significant reduction by 168 hours.

Conclusions

The described method allows a comprehensive analysis of synovial fluid eicosanoid profiles. Eicosanoid release in inflamed joints as well as differences between NSAID treated and placebo treated individuals are not limited to PGE₂ or to the early inflammatory phase.

Plasma biomarkers of oxidant stress and development of organ failure in severe sepsis

We hypothesized that circulating levels of lipid peroxidation products in patients with severe sepsis are associated with the development of pulmonary, renal, hepatic, circulatory, and coagulation failure. Plasma levels of F2-isoprostanes and isofurans were measured by mass spectroscopy on intensive care unit day 2 in 50 critically ill patients with severe sepsis. Plasma F2-isoprostane levels were higher in patients who developed renal failure compared with those who did not (65 pg/mL [interquartile range {IQR} 44-112] vs. 44 pg/mL [IQR 29-54], P = 0.009) as were isofuran levels (1,223 pg/mL [IQR 348-2,531] vs. 329 pg/mL [IQR 156-1,127], P = 0.009). Plasma F2-isoprostane levels were higher in patients who developed hepatic failure compared with those who did not (72 pg/mL [IQR 44-112] vs. 44 pg/mL [IQR 30-65], P = 0.023), and there was also a trend for higher isofuran levels (1,411 pg/mL [IQR 298-1,965] vs. 525 pg/mL [IQR 160-1,223], P = 0.14). Coagulation failure (thrombocytopenia) was associated with higher isofuran levels. Circulatory failure and acute lung injury were not associated with elevated levels of isoprostanes or isofurans. Patients with isoprostane levels above the 25th percentile had higher mortality (42%) compared with patients with levels below the 25th percentile (8%, P = 0.03). Plasma levels of F2-isoprostanes and isofurans are associated with renal, hepatic, and coagulation failure, but not with circulatory or pulmonary failure in severe sepsis, suggesting that lipid peroxidation is a prominent feature of septic multisystem organ failure. Plasma isoprostanes and isofurans may be useful for monitoring oxidative stress in treatment trials of antioxidant therapies in severe sepsis.

Amniotic fluid eicosanoids in preterm and term births: effects of risk factors for spontaneous preterm labor

OBJECTIVE

To evaluate amniotic fluid arachidonic acid metabolites using enzymatic and nonenzymatic (lipid peroxidation) pathways in spontaneous preterm birth and term births, and to estimate whether prostanoid concentrations correlate with risk factors (race, cigarette smoking, and microbial invasion of amniotic cavity) associated with preterm birth.

METHODS

In a case-control study, amniotic fluid was collected at the time of labor or during cesarean delivery. Amniotic fluid samples were subjected to gas chromatography, negative ion chemical ionization, and mass spectrometry for prostaglandin (PG) E2, PGF2α, and PGD2 and for 6-keto-PGF1α (thromboxane 2 and F2-isoprostane). Primary analysis examined differences between prostanoid concentrations in preterm birth (n=133) compared with term births (n=189). Secondary stratified analyses (by race, cigarette smoking, and microbial invasion of amniotic cavity) compared eicosanoid concentrations in three epidemiological risk factors.

RESULTS

Amniotic fluid F2-isoprostane, PGE2, and PGD2 were significantly higher at term than in preterm birth, whereas PGF2α was higher in preterm birth 6-keto-PGF1α and thromboxane 2 concentrations were not different. Data stratified by race (African American or white) showed no significant disparity among prostanoid concentrations. Regardless of gestational age status, F2-isoprostane was threefold higher in smokers, and other eicosanoids were also higher in smokers compared with nonsmokers. Preterm birth with microbial invasion of amniotic cavity had significantly higher F2-isoprostane compared with preterm birth without microbial invasion of amniotic cavity.

CONCLUSION

Most amniotic fluid eicosanoid concentrations (F2-isoprostane, PGE2, and PGD2), are higher at term than in preterm births. The only amniotic fluid eicosanoid that is not higher at term is PGF2α.

Oxidative stress measured by urine F2-isoprostane level is associated with prostate cancer

PURPOSE

Oxidative stress is implicated in prostate cancer by several lines of evidence. We studied the relationship between the level of F2-isoprostanes, a validated biomarker of oxidative stress, and prostate cancer and high grade prostatic intraepithelial neoplasia.

MATERIALS AND METHODS

This case-control analysis within the Nashville Men's Health Study included men recruited at prostate biopsy. Body morphometrics, health history and urine were collected from more than 2,000 men before biopsy. F2-isoprostanes were measured by gas chromatography/mass spectrometry within an age matched sample of Nashville Men's Health Study participants that included 140 patients with high grade prostatic intraepithelial neoplasia, 160 biopsy negative controls and 200 prostate cancer cases. Multivariable linear and logistic regression was used to determine the associations between F2-isoprostane level, and high grade prostatic intraepithelial neoplasia and prostate cancer.

RESULTS

Mean patient age was 66.9 years (SD 7.2) and 10.1% were nonwhite. Adjusted geometric mean F2-isoprostane levels were higher in patients with prostate cancer (1.82, 95% CI 1.66-2.00) or high grade prostatic intraepithelial neoplasia (1.82, 95% CI 1.68-1.96) than in controls (1.63, 95% CI 1.49-1.78, p <0.001), but were similar across Gleason scores (p = 0.511). The adjusted odds of high grade prostatic intraepithelial neoplasia and prostate cancer increased with increasing F2-isoprostane quartile (p-trend = 0.015 and 0.047, respectively) and the highest F2-isoprostane quartile was associated with significantly increased odds of prostate cancer (OR 2.44, 95% CI 1.17-5.09, p = 0.017).

CONCLUSIONS

Pre-diagnosis urine F2-isoprostane level is increased in men with high grade prostatic intraepithelial neoplasia or prostate cancer, suggesting urinary F2-isoprostane provides a biomarker for the role for oxidative stress in prostate carcinogenesis. F2-isoprostanes may also serve to estimate the efficacy of interventions targeting oxidative stress mechanisms in prostate cancer prevention or treatment.

F2-isoprostanes as an indicator and risk factor for coronary heart disease

Coronary heart disease (CHD) is the leading single cause of death in the United States and most Western countries, killing more than 400,000 Americans per year. Although CHD often manifests suddenly as a fatal myocardial infarction, the atherosclerosis that gives rise to the infarction develops gradually and can be markedly slowed or even reversed through pharmacological and lifestyle interventions. These same atherosclerotic processes also drive related vascular diseases such as stroke and peripheral artery disease, and individuals surviving occlusive events often develop additional complications including ischemic cardiomyopathy and heart failure. Therefore, better detection of subclinical atherosclerosis, along with more effective treatments, could significantly reduce the rate of death from CHD and related vascular diseases in the United States. In recent years, oxidation of polyunsaturated fatty acids (PUFAs) in plasma lipoproteins has been postulated to be a critical step in the development of atherosclerosis. If so, then monitoring lipid peroxidation should be a useful indicator of disease risk and progression. This review focuses on the evidence that specific PUFA peroxidation products, the F(2)-isoprostanes, are useful biomarkers that could potentially be utilized as indicators of CHD.