Simultaneous quantification of F2-isoprostanes and prostaglandins in human urine by liquid chromatography tandem-mass spectrometry

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.

University of Alabama at Birmingham Nathan Shock Center: comparative energetics of aging

The UAB Nathan Shock Center focuses on comparative energetics and aging. Energetics, as defined for this purpose, encompasses the causes, mechanisms, and consequences of the acquisition, storage, and use of metabolizable energy. Comparative energetics is the study of metabolic processes at multiple scales and across multiple species as it relates to health and aging. The link between energetics and aging is increasingly understood in terms of dysregulated mitochondrial function, altered metabolic signaling, and aberrant nutrient responsiveness with increasing age. The center offers world-class expertise in comprehensive, integrated energetic assessment and analysis from the level of the organelle to the organism and across species from the size of worms to rats as well as state-of-the-art data analytics. The range of services offered by our three research cores, (1) The Organismal Energetics Core, (2) Mitometabolism Core, and (3) Data Analytics Core, is described herein.

Simultaneous Quantitation of Lipid Biomarkers for Inflammatory Bowel Disease Using LC-MS/MS

Eicosanoids are key mediators and regulators of inflammation and oxidative stress that are often used as biomarkers for severity and therapeutic responses in various diseases. We here report a highly sensitive LC-MS/MS method for the simultaneous quantification of at least 66 key eicosanoids in a widely used murine model of colitis. Chromatographic separation was achieved with Shim-Pack XR-ODSIII, 150 × 2.00 mm, 2.2 µm. The mobile phase was operated in gradient conditions and consisted of acetonitrile and 0.1% acetic acid in water with a total flow of 0.37 mL/min. This method is sensitive, with a limit of quantification ranging from 0.01 to 1 ng/mL for the various analytes, has a large dynamic range (200 ng/mL), and a total run time of 25 min. The inter- and intraday accuracy (85-115%), precision (≥85%), and recovery (40-90%) met the acceptance criteria per the US Food and Drug Administration guidelines. This method was successfully applied to evaluate eicosanoid metabolites in mice subjected to colitis versus untreated, healthy control mice. In summary, we developed a highly sensitive and fast LC-MS/MS method that can be used to identify biomarkers for inflammation and potentially help in prognosis of the disease in inflammatory bowel disease (IBD) patients, including the response to therapy.

Rapid Liquid Chromatography-Tandem Mass Spectrometry Analysis of Two Urinary Oxidative Stress Biomarkers: 8-oxodG and 8-isoprostane

Human biomonitoring of oxidative stress relies on urinary effect biomarkers such as 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), and 8-iso-prostaglandin F2α (8-isoprostane); however, their levels reported for similar populations are inconsistent in the scientific literature. One of the reasons is the multitude of analytical methods with varying degrees of selectivity used to quantify these biomarkers. Single-analyte methods are often used, requiring multiple injections that increase both time and cost. We developed a rapid ultra-high-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method to quantify both urinary biomarkers simultaneously. A reversed-phase column using a gradient consisting of 0.1% acetic acid in water and 0.1% acetic acid in methanol/acetonitrile (70:30) was used for separation. The MS detection was by positive (8-oxodG) and negative (8-isoprostane) ion-mode by multiple reaction monitoring. Very low limit of detection (<20 pg/mL), excellent linearity (R2 > 0.999), accuracy (near 100%), and precision (CV < 10%) both for intra-day and inter-day experiments were achieved, as well as high recovery rates (>91%). Matrix effects were observed but were compensated by using internal standards. Our newly developed method is applicable for biomonitoring studies as well as large epidemiological studies investigating the effect of oxidative damage, as it requires only minimal clean up using solid phase extraction.

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.

Quantitative metabolic profiling of urinary eicosanoids for clinical phenotyping

The eicosanoids are a family of lipid mediators of pain and inflammation involved in multiple pathologies, including asthma, hypertension, cancer, atherosclerosis, and neurodegenerative diseases. These signaling mediators act locally, but are rapidly metabolized and transported to the systemic circulation as a mixture of primary and secondary metabolites. Accordingly, urine has become a useful readily accessible biofluid for monitoring the endogenous synthesis of these molecules. Herein, we present the validation of a rapid, repeatable, and precise method for the extraction and quantification of 32 eicosanoid urinary metabolites by LC-MS/MS. For 12 out of 17 deconjugated glucuronide eicosanoids, there was no improvement in recovered signal. These metabolites cover the major synthetic pathways, including prostaglandins, leukotrienes, and isoprostanes. The method linearity was >0.99 for all metabolites analyzed, the limit of detection ranged from 0.05-5 ng/ml, and the average extraction recoveries were >90%. All analytes were stable for at least three freeze/thaw cycles. The method was formatted for large-scale analysis of clinical cohorts, and the long-term repeatability was demonstrated over 15 months of acquisition, evidencing high precision (CV <15%, except for tetranorPGEM and 2,3-dinor-11β-PGF_2α, which were <30%). The presented method is suitable for focused mechanistic studies as well as large-scale clinical and epidemiological studies that require repeatable methods capable of producing data that can be concatenated across multiple cohorts.

Urinary Biomarkers of Oxidative Stress in Atrial Fibrillation

There is increasing evidence from molecular studies to support the role of inflammation and increased oxidative stress that produce structural and electrical atrial remodeling to produce Atrial Fbrillation (AF). Oxidative damage to cardiomyocytes yields chemical substances that are secreted in urine. These substances can serve as biomarkers that can be measured, potentially allowing clinicians to quantify oxidative damage to the heart.

Simultaneous Quantitation of Isoprenoid Pyrophosphates in Plasma and Cancer Cells Using LC-MS/MS

Isoprenoids (IsoP) are an important class of molecules involved in many different cellular processes including cholesterol synthesis. We have developed a sensitive and specific LC-MS/MS method for the quantitation of three key IsoPs in bio-matrices, geranyl pyrophosphate (GPP), farnesyl pyrophosphate (FPP), and geranylgeranyl pyrophosphate (GGPP). LC-MS/MS analysis was performed using a Nexera UPLC System connected to a LCMS-8060 (Shimadzu Scientific Instruments, Columbia, MD) with a dual ion source. The electrospray ionization source was operated in the negative MRM mode. The chromatographic separation and detection of analytes was achieved on a reversed phase ACCQ-TAG Ultra C18 (1.7 µm, 100 mm × 2.1 mm I.D.) column. The mobile phase consisted of (1) a 10 mM ammonium carbonate with 0.1% ammonium hydroxide in water, and (2) a 0.1% ammonium hydroxide in acetonitrile/methanol (75/25). The flow rate was set to 0.25 mL/min in a gradient condition. The limit of quantification was 0.04 ng/mL for all analytes with a correlation coefficient (r2) of 0.998 or better and a total run time of 12 min. The inter- and intra-day accuracy (85–115%) precision (<15%), and recovery (40–90%) values met the acceptance criteria. The validated method was successfully applied to quantitate basal concentrations of GPP, FPP and GGPP in human plasma and in cultured cancer cell lines. Our LC-MS/MS method may be used for IsoP quantification in different bio-fluids and to further investigate the role of these compounds in various physiological processes.

Determination of potential childhood asthma biomarkers using a powerful methodology based on microextraction by packed sorbent combined with ultra-high pressure liquid chromatography. Eicosanoids as case study

Leukotrienes and prostaglandins are arachidonic acid bioactive derived eicosanoids and key mediators of bronchial inflammation and response modulation in the airways contributing to the pathophysiology of asthma. An easy-to-use ultra-high pressure liquid chromatography (UHPLC)-based strategy was developed to characterize biomarkers of lipid peroxidation: leukotrienes E (LTE₄) and B₄ (LTB₄) and 11β-prostaglandin F_2α (11βPGF_2α), present in urine of asthmatic patients (N = 27) and healthy individuals (N = 17). A semi-automatic eVol®-microextraction by packed sorbent (MEPS) was used to isolate the target analytes. Several experimental parameters with influence on the extraction efficiency and on the chromatographic resolution, were evaluated and optimized. The method was fully validated under optimal extraction (R-AX sorbent, 3 conditioning-equilibration cycles with 250 μL of ACN-water at 0.1% FA, 10 extract-discard cycles of 250 μL of sample at a pH of 5.1, elution with 2 times 50 μL of MeOH and concentration of the eluate until half of its volume) and chromatographic conditions (14-min analysis at a flow rate of 300 μL min-1 in an UHPLC-PDA equipped with a BEH C18 column), according to IUPAC guidelines. The findings indicated good recoveries (>95%) in addition to excellent extraction efficiency (>95%) at three concentration levels (low mid and high) with precision (RSDs) less than 11%. The lack-of-fit test, goodness-of-fit test and Mandel's fitting test, revealed good linearity within the concentration range. Good selectivity and sensitivity were achieved with a limits of detection ranging from 0.04 μg L^-1 for LTB4 to 1.12 μg L^-1 for 11βPGF2α, and limits of quantification from 0.10 μg L^-1 for the LTB4 to 2.11 μg L^-1 for 11βPGF2α. The successful application of the fully validated method shows that, on average, the asthmatic patients had significantly higher concentrations of 11βPGF_2α (112.96 μg L^-1vs 62.56 μg L^-1 in normal controls), LTE₄ (1.27 μg L^-1vs 0.89 μg L^-1 in normal controls), and LTB₄ (1.39 μg L^-1vs 0.76 μg L^-1 in normal controls). The results suggest the potential of the target eicosanoids on asthma diagnosis, however, a larger and more extensive study will be necessary to confirm the data obtained and to guarantee a greater robustness to the approach.

Quantification of eicosanoids and their metabolites in biological matrices: a review

The quantification of eicosanoids and their metabolites in biological samples remain an analytical challenge, even though a number of methodologies/techniques have been developed. The major difficulties encountered are related to the oxidation of eicosanoids and their low quantities in biological matrices. Among the known methodologies, liquid chromatography-mass spectrometry (LC-MS/MS) is the standard method for eicosanoid quantification in biological samples. Recently advances have improved the ability to identify and simultaneous quantitate eicosanoids in biological matrices. The present article reviews the quantitative analysis of eicosanoids in different biological matrices by LC and ultra performance liquid chromatography (UPLC)-MS/MS and discusses important aspects to be considered during the collection, sample preparation and the generation of calibration curves required for eicosanoid analysis.

Detection of Lipid Mediators of Inflammation in the Human Tear Film

PURPOSE

Lipid mediators of inflammation are a group of signaling molecules produced by various cells under physiological conditions and modulate the inflammatory process during various pathologic conditions. Although eicosanoids and F2-isoprostanes are recognized lipid mediators of inflammation, there is no consensus yet on the extraction and mass spectrometry (MS) method for their analysis in individual human tear samples. Thus, the aim of this study was to develop an optimal method for extraction of lipid mediators of inflammation in the tear film and evaluate MS techniques for their analysis.

METHODS

Basal tears were collected from each eye of 19 subjects using glass microcapillaries. Lipid extraction was performed using either varying concentrations of acidified methanol, a modified Folch method, or solid-phase extraction. Initially, an untargeted analysis of the extracts was performed using SCIEX TripleTOF 5600 mass spectrometer to identify any lipid mediators of inflammation (eicosanoids) and later a targeted analysis was performed using the SCIEX 6500 Qtrap to identify and quantify prostaglandins and isoprostanes. Mass spectra and chromatograms were analyzed using Peakview, XCMS, and Multiquant software.

RESULTS

Prostaglandins and isoprostanes were observed and quantified using the Qtrap mass spectrometer under multiple reaction monitoring (MRM) mode after solid-phase extraction. Extraction with acidified methanol along with the Folch method produced cleaner spectra during MS with the Triple time of flight (TOF) mass spectrometer. Lipid mediators of inflammation were not observed in any of the tear samples using the Triple TOF mass spectrometer.

CONCLUSIONS

Solid-phase extraction may be the method of choice for extraction of prostaglandins and isoprostanes in low volumes of tears. The SCIEX Qtrap 6500 in MRM mode may be suitable to identify and quantify similar lipid mediators of inflammation.

Influence of Diosmin Treatment on the Level of Oxidative Stress Markers in Patients with Chronic Venous Insufficiency

Oxidative stress plays an important role in the pathophysiology of many human disorders, while antioxidants prevent the development of various adverse symptoms. Diosmin is a natural flavonoid applied in vascular system disorders, especially in chronic venous insufficiency (CVI), and it plays a significant part in the alleviation of CVI symptoms. Due to antioxidant activity, it also has the ability to scavenge the oxygen free radicals and hence decreases the level of oxidative stress biomarkers, such as prostaglandins and their precursors—isoprostanes. In the study, the influence of diosmin treatment on the level of isoprostanes in plasma samples of patients suffering from CVI was examined. The qualitative analysis was performed using high-performance liquid chromatography with spectrometry detection (LC-MS). The statistically significant decrease of isoprostane content after 3 months of treatment was observed within the studied group; however, the most significant changes were observed in patients who smoke.

Simultaneous LC-MS/MS analysis of eicosanoids and related metabolites in human serum, sputum and BALF

The differences among individual eicosanoids in eliciting different physiological and pathological responses are largely unknown because of the lack of valid and simple analytical methods for the quantification of individual eicosanoids and their metabolites in serum, sputum and bronchial alveolar lavage fluid (BALF). Therefore, a simple and sensitive LC-MS/MS method for the simultaneous quantification of 34 eicosanoids in human serum, sputum and BALF was developed and validated. This method is valid and sensitive with a limit of quantification ranging from 0.2 to 3 ng/mL for the various analytes, and has a large dynamic range (500 ng/mL) and a short run time (25 min). The intra- and inter-day accuracy and precision values met the acceptance criteria according to US Food and Drug Administration guidelines. Using this method, detailed eicosanoid profiles were quantified in serum, sputum and BALF from a pilot human study. In summary, a reliable and simple LC-MS/MS method to quantify major eicosanoids and their metabolites was developed and applied to quantify eicosanoids in human various fluids, demonstrating its suitability to assess eicosanoid biomarkers in human clinical trials.

Separation and simultaneous quantitation of PGF2α and its epimer 8-iso-PGF2α using modifier-assisted differential mobility spectrometry tandem mass spectrometry

Because many therapeutic agents are contaminated by epimeric impurities or form epimers as a result of metabolism, analytical tools capable of determining epimers are increasingly in demand. This article is a proof-of-principle report of a novel DMS-MS/MS method to separate and simultaneously quantify epimers, taking PGF2α and its 8-epimer, 8-iso-PGF2α, as an example. Good accuracy and precision were achieved in the range of 10-500 ng/mL with a run time of only 1.5 min. Isopropanol as organic modifier facilitated a good combination of sensitivity and separation. The method is the first example of the quantitation of epimers without chromatographic separation.

Urine Arsenic and Arsenic Metabolites in U.S. Adults and Biomarkers of Inflammation, Oxidative Stress, and Endothelial Dysfunction: A Cross-Sectional Study

BACKGROUND

Arsenic (As) exposure has been associated with increased risk for cardiovascular disease (CVD) and with biomarkers of potential CVD risk and inflammatory processes. However, few studies have evaluated the effects of As on such biomarkers in U.S. populations, which are typically exposed to low to moderate As concentrations.

OBJECTIVES

We investigated associations between As exposures and biomarkers relevant to inflammation, oxidative stress, and CVD risk in a subset of participants from the New Hampshire Health Study, a population with low to moderate As exposure (n=418).

METHODS

Associations between toenail As, total urine As (uAs), and %uAs metabolites [monomethyl (%uMMA^V), dimethyl (%uDMA^V), and inorganic (%iAs) species] and plasma biomarkers, including soluble plasma vascular and cellular adhesion molecules (VCAM-1 and ICAM-1, respectively), matrix metalloproteinase-9 (MMP-9), tumor necrosis factor-α, plasminogen activator inhibitor-1 (PAI-1), and urinary oxidative stress marker 15-F_2t-isoprostane (15-F_2t-IsoP), were evaluated using linear regression models.

RESULTS

Covariate-adjusted estimates of associations with a doubling of urinary As suggested an 8.8% increase in 15-F_2t-IsoP (95% CI: 3.2, 14.7), and a doubling of toenail As was associated with a 1.7% increase in VCAM-1 (95% CI: 0.2, 3.2). Additionally, a 5% increase in %uMMA was associated with a 7.9% increase in 15-F_2t-IsoP (95% CI: 2.1, 14.1), and a 5% increase in %uDMA was associated with a 2.98% decrease in 15-F_2t-IsoP [(95% CI: -6.1, 0.21); p=0.07]. However, in contrast with expectations, a doubling of toenail As was associated with a 2.3% decrease (95% CI: -4.3, -0.3) in MMP-9, and a 5% increase in %uMMA was associated with a 7.7% decrease (95% CI: -12.6, -2.5) in PAI-1.

CONCLUSION

In a cross-sectional study of U.S. adults, we observed some positive associations of uAs and toenail As concentrations with biomarkers potentially relevant to CVD pathogenesis and inflammation, and evidence of a higher capacity to metabolize inorganic As was negatively associated with a marker of oxidative stress. https://doi.org/10.1289/EHP2062.

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.

Isoprostanes, neuroprostanes and phytoprostanes: An overview of 25years of research in chemistry and biology

Since the beginning of the 1990's diverse types of metabolites originating from polyunsaturated fatty acids, formed under autooxidative conditions were discovered. Known as prostaglandin isomers (or isoprostanoids) originating from arachidonic acid, neuroprostanes from docosahexaenoic acid, and phytoprostanes from α-linolenic acid proved to be prevalent in biology. The syntheses of these compounds by organic chemists and the development of sophisticated mass spectrometry methods has boosted our understanding of the isoprostanoid biology. In recent years, it has become accepted that these molecules not only serve as markers of oxidative damage but also exhibit a wide range of bioactivities. In addition, isoprostanoids have emerged as indicators of oxidative stress in humans and their environment. This review explores in detail the isoprostanoid chemistry and biology that has been achieved in the past three decades.

Mitogen-Activated Protein Kinase 14 Promotes AKI

An improved understanding of pathogenic pathways in AKI may identify novel therapeutic approaches. Previously, we conducted unbiased liquid chromatography-tandem mass spectrometry-based protein expression profiling of the renal proteome in mice with acute folate nephropathy. Here, analysis of the dataset identified enrichment of pathways involving NFκB in the kidney cortex, and a targeted data mining approach identified components of the noncanonical NFκB pathway, including the upstream kinase mitogen-activated protein kinase kinase kinase 14 (MAP3K14), the NFκB DNA binding heterodimer RelB/NFκB2, and proteins involved in NFκB2 p100 ubiquitination and proteasomal processing to p52, as upregulated. Immunohistochemistry localized MAP3K14 expression to tubular cells in acute folate nephropathy and human AKI. In vivo, kidney expression levels of NFκB2 p100 and p52 increased rapidly after folic acid injection, as did DNA binding of RelB and NFκB2, detected in nuclei isolated from the kidneys. Compared with wild-type mice, MAP3K14 activity-deficient aly/aly (MAP3K14^aly/aly) mice had less kidney dysfunction, inflammation, and apoptosis in acute folate nephropathy and less kidney dysfunction and a lower mortality rate in cisplatin-induced AKI. The exchange of bone marrow between wild-type and MAP3K14^aly/aly mice did not affect the survival rate of either group after folic acid injection. In cultured tubular cells, MAP3K14 small interfering RNA targeting decreased inflammation and cell death. Additionally, cell culture and in vivo studies identified the chemokines MCP-1, RANTES, and CXCL10 as MAP3K14 targets in tubular cells. In conclusion, MAP3K14 promotes kidney injury through promotion of inflammation and cell death and is a promising novel therapeutic target.

Simultaneous quantitative profiling of 20 isoprostanoids from omega-3 and omega-6 polyunsaturated fatty acids by LC-MS/MS in various biological samples

Isoprostanoids are a group of non-enzymatic oxygenated metabolites of polyunsaturated fatty acids. It belongs to oxylipins group, which are important lipid mediators in biological processes, such as tissue repair, blood clotting, blood vessel permeability, inflammation and immunity regulation. Recently, isoprostanoids from eicosapentaenoic, docosahexaenoic, adrenic and α-linolenic namely F3-isoprostanes, F4-neuroprostanes, F2-dihomo-isoprostanes and F1-phytoprostanes, respectively have attracted attention because of their putative contribution to health. Since isoprostanoids are derived from different substrate of PUFAs and can have similar or opposing biological consequences, a total isoprostanoids profile is essential to understand the overall effect in the testing model. However, the concentration of most isoprostanoids range from picogram to nanogram, therefore a sensitive method to quantify 20 isoprostanoids simultaneously was formulated and measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The lipid portion from various biological samples was extracted prior to LC-MS/MS evaluation. For all the isoprostanoids LOD and LOQ, and the method was validated on plasma samples for matrix effect, yield of extraction and reproducibility were determined. The methodology was further tested for the isoprostanoids profiles in brain and liver of LDLR(-/-) mice with and without docosahexaenoic acid (DHA) supplementation. Our analysis showed similar levels of total F2-isoprostanes and F4-neuroprostanes in the liver and brain of non-supplemented LDLR(-/-) mice. The distribution of different F2-isoprostane isomers varied between tissues but not for F4-neuroprostanes which were predominated by the 4(RS)-4-F4t-neuroprostane isomer. DHA supplementation to LDLR(-/-) mice concomitantly increased total F4-neuroprostanes levels compared to F2-isoprostanes but this effect was more pronounced in the liver than brain.

Oxidative lipidomics coming of age: advances in analysis of oxidized phospholipids in physiology and pathology

SIGNIFICANCE

Oxidized phospholipids are now well recognized as markers of biological oxidative stress and bioactive molecules with both pro-inflammatory and anti-inflammatory effects. While analytical methods continue to be developed for studies of generic lipid oxidation, mass spectrometry (MS) has underpinned the advances in knowledge of specific oxidized phospholipids by allowing their identification and characterization, and it is responsible for the expansion of oxidative lipidomics.

RECENT ADVANCES

Studies of oxidized phospholipids in biological samples, from both animal models and clinical samples, have been facilitated by the recent improvements in MS, especially targeted routines that depend on the fragmentation pattern of the parent molecular ion and improved resolution and mass accuracy. MS can be used to identify selectively individual compounds or groups of compounds with common features, which greatly improves the sensitivity and specificity of detection. Application of these methods has enabled important advances in understanding the mechanisms of inflammatory diseases such as atherosclerosis, steatohepatitis, leprosy, and cystic fibrosis, and it offers potential for developing biomarkers of molecular aspects of the diseases.

CRITICAL ISSUES AND FUTURE DIRECTIONS

The future in this field will depend on development of improved MS technologies, such as ion mobility, novel enrichment methods and databases, and software for data analysis, owing to the very large amount of data generated in these experiments. Imaging of oxidized phospholipids in tissue MS is an additional exciting direction emerging that can be expected to advance understanding of physiology and disease.

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."

Hemoglobin-associated oxidative stress in the pericardial compartment of postoperative cardiac surgery patients

Atherosclerosis and valvular heart disease often require treatment with corrective surgery to prevent future myocardial infarction, ischemic heart disease, and heart failure. Mechanisms underlying the development of the associated complications of surgery are multifactorial and have been linked to inflammation and oxidative stress, classically as measured in the blood or plasma of patients. Postoperative pericardial fluid (PO-PCF) has not been investigated in depth with respect to the potential to induce oxidative stress. This is important because cardiac surgery disrupts the integrity of the pericardial membrane surrounding the heart and causes significant alterations in the composition of the pericardial fluid (PCF). This includes contamination with hemolyzed blood and high concentrations of oxidized hemoglobin, which suggests that cardiac surgery results in oxidative stress within the pericardial space. Accordingly, we tested the hypothesis that PO-PCF is highly pro-oxidant and that the potential interaction between inflammatory cell-derived hydrogen peroxide with hemoglobin is associated with oxidative stress. Blood and PCF were collected from 31 patients at the time of surgery and postoperatively from 4 to 48 h after coronary artery bypass grafting, valve replacement, or valve repair (mitral or aortic). PO-PCF contained high concentrations of neutrophils and monocytes, which are capable of generating elevated amounts of superoxide and hydrogen peroxide through the oxidative burst. In addition, PO-PCF primed naive neutrophils resulting in an enhanced oxidative burst upon stimulation. The PO-PCF also contained increased concentrations of cell-free oxidized hemoglobin that was associated with elevated levels of F2α isoprostanes and prostaglandins, consistent with both oxidative stress and activation of cyclooxygenase. Lastly, protein analysis of the PO-PCF revealed evidence of protein thiol oxidation and protein carbonylation. We conclude that PO-PCF is highly pro-oxidant and speculate that it may contribute to the risk of postoperative complications.

Effects of CP-900691, a novel peroxisome proliferator-activated receptor α, agonist on diabetic nephropathy in the BTBR ob/ob mouse

Piperidine-based peroxisome proliferator-activated receptor-α agonists are agents that are efficacious in improving lipid, glycemic, and inflammatory indicators in diabetes and obesity. This study sought to determine whether CP-900691 ((S)-3-[3-(1-carboxy-1-methyl-ethoxy)-phenyl]-piperidine-1-carboxylic acid 4-trifluoromethyl-benzyl ester; CP), a member of this novel class of agents, by decreasing plasma triglycerides, could prevent diabetic nephropathy in the Black and Tan, BRachyuric (BTBR) ob/ob mouse model of type 2 diabetes mellitus. Four-week old female BTBR WT and BTBR ob/ob mice received either regular chow or one containing CP (3 mg/kg per day) for 14 weeks. CP elevated plasma high-density lipoprotein, albuminuria, and urinary excretion of 8-epi PGF(2α), a product of the nonenzymatic metabolism of arachidonic acid and whose production is elevated in oxidative stress, in BTBR WT mice. In BTBR ob/ob mice, CP reduced plasma triglycerides and non-esterified fatty acids, fasting blood glucose, body weight, and plasma interleukin-6, while concomitantly improving insulin resistance. Despite these beneficial metabolic effects, CP had no effect on elevated plasma insulin, 8-epi PGF(2α) excretion, and albuminuria, and surprisingly, did not ameliorate the development of diabetic nephropathy, having no effect on the accumulation of renal macrophages, glomerular hypertrophy, and increased mesangial matrix expansion. In addition, CP did not increase plasma high-density lipoprotein in BTBR ob/ob mice, while paradoxically increasing total cholesterol levels. These findings indicate that 8-epi PGF(2α), possibly along with hyperinsulinemia and inflammatory and dysfunctional lipoproteins, is integral to the development of diabetic nephropathy and should be considered as a potential target of therapy in the treatment of diabetic nephropathy.

Improved high sensitivity analysis of polyphenols and their metabolites by nano-liquid chromatography-mass spectrometry

This study was conducted to assess the value of a high resolution, high mass accuracy time-of-flight analyzer in combination with nanoliquid chromatography for the analysis of polyphenols and their metabolites. The goal was to create a method that utilizes small volumes of biological fluids and provides a significant improvement in sensitivity compared with existing methods. Accordingly, nanoLC-MS and nanoLC-pseudo-multiple reaction monitoring (MRM) methods were developed that had a lower limit of quantification of 0.5 nM for several polyphenols and were linear over 2-3 orders of magnitude (R(2)>0.999). Using urine samples, the ability to observe and quantify polyphenols in such a complex biological fluid depended on much narrower mass windows (0.050 amu or less) on a TOF analyzer than those used on a quadrupole analyzer (0.7 amu). Although a greater selectivity was possible with the low mass resolution of a triple quadrupole instrument using the MRM approach, for the daidzein metabolite O-DMA, a chromatographically resolvable second peak could only be substantially reduced by using a 0.01 amu mass window. The advantage of a TOF analyzer for product ion data is that the whole MSMS spectrum is collected at high mass accuracy and MRM experiments are conducted in silico after the analysis.

Analysis of lipid peroxidation biomarkers in extremely low gestational age neonate urines by UPLC-MS/MS

Extremely low gestational age neonates (ELGAN) frequently require the use of oxygen supply in the delivery room leading to systemic inflammation and oxidative stress that are responsible for increased morbidity and mortality. The objective of this study was to establish reference ranges of a set of representative isoprostanes and prostaglandins, which are stable biomarkers of lipid peroxidation often correlated with oxidative stress-related disorders. First, a quantitative ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed and validated. The proposed analytical method was tailored for its application in the field of neonatology, enabling multi-analyte detection in non-invasive, small-volume urine samples. Then, the lipid peroxidation product concentrations in a total of 536 urine samples collected within the framework of two clinical trials including extremely low gestational age neonates (ELGAN) were analyzed. The access to a substantially large number of samples from this very vulnerable population provided the chance to establish reference ranges of the studied biomarkers. Up to the present, and for this population, this is the biggest reference data set reported in literature. Results obtained should assist researchers and pediatricians in interpreting test results in future studies involving isoprostanes and prostaglandins, and could help assessing morbidities and evaluate effectiveness of treatment strategies (e.g., different resuscitation conditions) in the neonatal field.

Non-enzymatic lipid oxidation products in biological systems: assessment of the metabolites from polyunsaturated fatty acids

Metabolites of non-enzymatic lipid peroxidation of polyunsaturated fatty acids notably omega-3 and omega-6 fatty acids have become important biomarkers of lipid products. Especially the arachidonic acid-derived F2-isoprostanes are the classic in vivo biomarker for oxidative stress in biological systems. In recent years other isoprostanes from eicosapentaenoic, docosahexaenoic, adrenic and α-linolenic acids have been evaluated, namely F3-isoprostanes, F4-neuroprostanes, F2-dihomo-isoprostanes and F1-phytoprostanes, respectively. These have been gaining interest as complementary specific biomarkers in human diseases. Refined extraction methods, robust analysis and elucidation of chemical structures have improved the sensitivity of detection in biological tissues and fluids. Previously the main reliable instrumentation for measurement was gas chromatography-mass spectrometry (GC-MS), but now the use of liquid chromatography-tandem mass spectrometry (LC-MS/MS) and immunological techniques is gaining much attention. In this review, the types of prostanoids generated from non-enzymatic lipid peroxidation of some important omega-3 and omega-6 fatty acids and biological samples that have been determined by GC-MS and LC-MS/MS are discussed.

A nano ultra-performance liquid chromatography-high resolution mass spectrometry approach for global metabolomic profiling and case study on drug-resistant multiple myeloma

Global metabolomics relies on highly reproducible and sensitive detection of a wide range of metabolites in biological samples. Here we report the optimization of metabolome analysis by nanoflow ultraperformance liquid chromatography coupled to high-resolution orbitrap mass spectrometry. Reliable peak features were extracted from the LC-MS runs based on mandatory detection in duplicates and additional noise filtering according to blank injections. The run-to-run variation in peak area showed a median of 14%, and the false discovery rate during a mock comparison was evaluated. To maximize the number of peak features identified, we systematically characterized the effect of sample loading amount, gradient length, and MS resolution. The number of features initially rose and later reached a plateau as a function of sample amount, fitting a hyperbolic curve. Longer gradients improved unique feature detection in part by time-resolving isobaric species. Increasing the MS resolution up to 120000 also aided in the differentiation of near isobaric metabolites, but higher MS resolution reduced the data acquisition rate and conferred no benefits, as predicted from a theoretical simulation of possible metabolites. Moreover, a biphasic LC gradient allowed even distribution of peak features across the elution, yielding markedly more peak features than the linear gradient. Using this robust nUPLC-HRMS platform, we were able to consistently analyze ~6500 metabolite features in a single 60 min gradient from 2 mg of yeast, equivalent to ~50 million cells. We applied this optimized method in a case study of drug (bortezomib) resistant and drug-sensitive multiple myeloma cells. Overall, 18% of metabolite features were matched to KEGG identifiers, enabling pathway enrichment analysis. Principal component analysis and heat map data correctly clustered isogenic phenotypes, highlighting the potential for hundreds of small molecule biomarkers of cancer drug resistance.

Liquid chromatography-tandem mass spectrometry for the analysis of eicosanoids and related lipids in human biological matrices: a review

Today, there is an increasing number of liquid chromatography tandem-mass spectrometric (LC-MS/MS) methods for the analysis of eicosanoids and related lipids in biological matrices. An overview of currently applied LC-MS/MS methods is given with attention to sample preparation strategies, chromatographic separation including ultra high performance liquid chromatography (UHPLC) and chiral separation, as well as to mass spectrometric detection using multiple reacting monitoring (MRM). Further, the application in recent clinical research is reviewed with focus on preanalytical aspects prior to LC-MS/MS analysis as well as applications in major diseases of Western civilization including respiratory diseases, diabetes, cancer, liver diseases, atherosclerosis, and neurovascular diseases.

Metabolomics and systems pharmacology: why and how to model the human metabolic network for drug discovery

Metabolism represents the 'sharp end' of systems biology, because changes in metabolite concentrations are necessarily amplified relative to changes in the transcriptome, proteome and enzyme activities, which can be modulated by drugs. To understand such behaviour, we therefore need (and increasingly have) reliable consensus (community) models of the human metabolic network that include the important transporters. Small molecule 'drug' transporters are in fact metabolite transporters, because drugs bear structural similarities to metabolites known from the network reconstructions and from measurements of the metabolome. Recon2 represents the present state-of-the-art human metabolic network reconstruction; it can predict inter alia: (i) the effects of inborn errors of metabolism; (ii) which metabolites are exometabolites, and (iii) how metabolism varies between tissues and cellular compartments. However, even these qualitative network models are not yet complete. As our understanding improves so do we recognise more clearly the need for a systems (poly)pharmacology.

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.