Quantitative profiling of epoxyeicosatrienoic, hydroxyeicosatetraenoic, and dihydroxyeicosatetraenoic acids in human intrauterine tissues using liquid chromatography/electrospray ionization tandem mass spectrometry

Gut Microbial Succession Patterns and Metabolic Profiling during Pregnancy and Lactation in a Goat Model

The maternal gut microbiome affects the duration of pregnancy, delivery, and lactation. It also coordinates the stability of maternal metabolism by regulating and modulating inflammatory cytokines and reproductive hormones. This has been shown in several species; however, the situation in ruminants remains a black box. Here, we aimed to elucidate the relationship between the hindgut microbiota, metabolism, and reproductive hormones in domestic goats (Capra hircus) during nonpregnancy, pregnancy, and lactation stages. The hindgut microbiota was altered during these three stages, with a drastic decrease in the abundance of Family_XIII_AD3011_group in the second and third trimesters of pregnancy. Additionally, a decline in the abundance of Christensenellaceae_R-7_group and Turicibacter was observed from the nonpregnancy stage to late gestation. Family_XIII_AD3011_group and Paeniclostridium were strongly correlated with decreased fecal estradiol and progesterone. Furthermore, we generated a metabolome atlas of the gut and serum from nonpregnancy to lactation to reveal the specific metabolic fingerprints of each physiological stage. Several specific gut metabolites, including carnitine C8:1, γ-aminobutyric acid, and indole-3-carboxylic acid, were negatively correlated with the fecal and serum estradiol concentrations. In contrast, 2'-deoxyinosine, deoxyadenosine, and 5'-deoxyadenosine were positively correlated with the fecal and serum estradiol concentrations. The levels of 2'-deoxyinosine, deoxyadenosine, and 5'-deoxyadenosine in fecal samples were positively correlated with Family_XIII_AD3011_group. Other serum metabolites, such as (±)12-HEPE (hydroxy eicosapentaenoic acid), (±)15-HEPE, (±)18-HEPE, cytidine, uracil, and 5-hydroxyindole-3-acetic acid, were negatively correlated with the serum concentrations of estradiol and progesterone. Finally, Corynebacterium and Clostridium_sensu_stricto_1 in the fecal samples were positively correlated with the abundance of 11,12-EET (epoxy-eicosatrienoic acid), (±)18-HEPE, (±)15-HEPE, and (±)12-HEPE in the serum. IMPORTANCE Our findings revealed that the activity of Family_XIII_AD3011_group and Corynebacterium is strongly correlated with the beneficial regulation of physiological hormones and metabolic changes during pregnancy and lactation. These findings are key for guiding targeted microbial therapeutic approaches to modulate microbiomes in gestating and lactating mammals.

Dissecting the Regulation of Arachidonic Acid Metabolites by Uncaria rhynchophylla (Miq). Miq. in Spontaneously Hypertensive Rats and the Predictive Target sEH in the Anti-Hypertensive Effect Based on Metabolomics and Molecular Docking

Uncariarhynchophylla (Miq). Miq. (UR), as a traditional Chinese medicine, was employed in treating hypertension as a safe and effective therapy. The pharmacological properties of UR have characteristics of multiple biological targets and multiple functional pathways. Hypertension is related to impaired metabolic homeostasis and is especially associated with the abnormal regulation of arachidonic acid metabolites, the classical cardiovascular active compounds. This study aimed to examine the anti-hypertensive effect of UR extract (URE) and its regulating role in differential metabolic pathways. The results showed that daily administration of URE at a dose of 4 g crude drug/kg orally could exert hypotensive effects on spontaneously hypertensive rats (SHRs) for 8 weeks. Non-targeted metabolomics analysis of the plasma samples suggested that the anti-hypertension effect of URE in SHRs was associated with the reorganization of the perturbed metabolic network, such as the pathways of glycerophospholipid metabolism, linoleic acid metabolism, and arachidonic acid metabolism. For the targeted metabolomics, twenty-eight arachidonic acid metabolites in SHRs were quantitatively analyzed for the first time based on ultra-high performance liquid chromatography-tandem mass spectrometry method after URE administration. URE restored the functions of these cardiovascular active compounds and rebalanced the dynamics of arachidonic acid metabolic flux. Among them, the inhibition of soluble epoxide hydrolase (sEH) enzyme activity and up-regulation of vasodilators epoxyeicosatrienoic acids (EETs) were identified as contributors to the anti-hypertension effect of URE on SHRs, and sEH represented an attractive and promising drug-binding target of URE. With the molecular docking approach, 13 potential anti-hypertension ingredients as well as sEH inhibitors were discovered, which were worthy of further investigation and verification in future studies.

Profiling oxylipins released from human platelets activated through the GPVI collagen receptor

In addition to haemostasis, platelets are involved in pathological processes, often driven by material released upon activation. Interaction between collagen and glycoprotein VI (GPVI) is a primary platelet stimulus that liberates arachidonic acid and linoleic acid from membrane phospholipids. These are oxidised by cyclooxygenase-1 (COX-1) and 12-lipoxygenase (12-LOX) to eicosanoids and other oxylipins with various biological properties. Using liquid chromatography-tandem mass spectrometry we found that GPVI-stimulated platelets released significant levels of ten oxylipins; the well documented TxA2 and 12-HETE, PGD₂ and PGE_2, as well as 8-, 9-, 11-, and 15-HETE, 9- and 13-HODE.¹ Levels of oxylipins released from washed platelets mirrored those from platelets stimulated in the presence of plasma, indicating generation from intracellular, rather than exogenous AA/LA. Inhibition of COX-1 with aspirin, as expected, completely abolished production of TxA₂ and PGD/E₂, but also significantly inhibited the release of 11-HETE (89 ± 3%) and 9-HODE (74 ± 6%), and reduced 15-HETE and 13-HODE by ∼33 %. Inhibition of 12-LOX by either esculetin or ML355 inhibited the release of all oxylipins apart from 15-HETE. These findings suggest routes to modify the production of bioactive molecules released by activated platelets.

Targeted analysis of eicosanoids derived from cytochrome P450 pathway by high-resolution multiple-reaction monitoring mass spectrometry

Cytochrome P450 (CYP450) pathway is one of the critical enzymatic via eicosanoid biosynthesis. Nevertheless, their metabolites are far less explored. This pathway plays a crucial role in converting arachidonic acid to hydroxyeicosatetraenoic (HETEs), epoxyeicosatrienoic (EETs), dihydroxyeicosatetraenoic acids (DiHETEs), and dihydroxyeicosatrienoic acids (DiHETrEs), which mediate several physiological and pathological functions. However, CYP450-derived eicosanoids are structurally complex, making those analyses a challenge in lipidomics studies. Herein, a high-resolution multiple-reaction monitoring (MRM^HR ) method has been proposed as a powerful tool for the simultaneous analysis of CYP450-eicosanoids on different biological samples. The developed liquid chromatography (LC)-MRM^HR method was partially validated according to the Food and Drug Administration (FDA) criteria, demonstrating adequate specificity, linearity, precision, and accuracy. Besides, several biological samples were analyzed to guarantee the feasibility of the method. The proposed strategy may improve the understanding of CYP450-derived eicosanoids in biological systems, which could be fundamental to reveal new aspects of those in physiologic and pathologic conditions.

Inflammation with the participation of arachidonic (AA) and linoleic acid (LA) derivatives (HETEs and HODEs) is necessary in the course of a normal reproductive cycle and pregnancy

Data on arachidonic (AA) and linoleic (LA) acid derivatives and their role in the reproductive cycle are limited. In order to systematize these reports, 54 scientific investigations were analyzed, which revealed the important role of AA and LA in the planning and course of pregnancy. Ovulation, menstruation, pregnancy, and childbirth are strongly related to the occurrence of physiological inflammatory reactions. Ovulation and menstruation are cyclic tissue remodeling processes that cause changes in the synthesis of inflammation mediators, such as prostaglandins and leukotrienes. Thus, the cyclooxygenase (COX) and lipoxygenase-5 (5-LOX) pathway for AA transformation is activated. Only the absence of neutrophils during this process differentiates an embryo implantation from a standard inflammatory response. It has been found that in COX-2 deficiency conditions, incorrect embryo implantation and decidual reaction occur; therefore, the mechanism associated with the activation of the nuclear factor (NF)-κB pathway seems to play an important role in the course of embryo implantation. In addition, 12/15-LOX may be key modulators of uterine activity during the implantation process. According to the current state of knowledge, AA derivatives synthesized throughout the cytochrome P450 (CYP) and LOX pathways play a special role in the late pregnancy period. Decreased 5-HETE levels have been related to slowing down the progression of labor, while 11-HETE and 15-HETrE to its acceleration. It has been also proven that renal 20-HETE contents undergo significant changes in the late pregnancy period, which are caused by an increase in their adrenal medulla and vascular synthesis, leading to decrease of blood pressure and an increase of sodium excretion, finally conditioning a normal course of labor.

Soluble epoxide hydrolase in the human placenta throughout gestation

OBJECTIVE

To investigate the spatial and temporal changes of soluble epoxide hydrolase (sEH) in the human placenta throughout gestation and to study the effects of hypoxia-reoxygenation (HR) on the expression of sEH in villous explants in vitro.

MATERIALS AND METHODS

Placental samples were obtained from women of different gestation and grouped as early (8-12 weeks, n = 10), mid- (16-28 weeks, n = 6), and late gestation (38-39 weeks, n = 10) according to gestational age. Immunohistochemistry, western blot, and real-time quantitative PCR were used to assess the cellular distribution and temporal changes of sEH. Villous explant cultures were used to study the effect of HR (8 h at 2% oxygen, followed by 16 h at 8% oxygen, two cycles) on the expression of sEH.

RESULTS

Using a mouse monoclonal antibody against human sEH, immunoreactivity of sEH was observed mainly localized in the cytotrophoblasts and, to a lesser extent, the syncytiotrophoblast in the villous tissues throughout gestation. Compared to villous tissues of early gestation, the levels of sEH mRNA and protein were significantly increased in villous samples of mid- and late gestation. Furthermore, villous explants subjected to HR had significantly higher levels of sEH mRNA and protein compared to villous tissues kept at 8% oxygen throughout the experiment.

CONCLUSION

Our results indicate that sEH is likely to play an essential role in the development of human placenta and HR is a possible factor regulating the expression of sEH in the placenta.

Evaluation of extraction and normalisation strategies for the analysis of lipids in placental vessels

The analysis of lipids in tough or fibrous biological tissues can be challenging due to difficulties in obtaining a representative sample following homogenisation of the tissue. Furthermore, the choice of normalisation method can have a major effect on the quality of quantitative results. Therefore, a range of mechanical homogenisation techniques and normalisation strategies were evaluated for application to human placental vessels. The findings showed that rotor-stator homogenisation in a suitable solvent and wet weight normalisation were the best combination of procedures for quantitative analysis of lipids in placental blood vessels.

Omega-6 oxylipins generated by soluble epoxide hydrolase are associated with knee osteoarthritis

Omega-6 FAs are inflammatory mediators that are increased in joints with osteoarthritis (OA), but their association with OA progression is not yet well defined. To investigate the relationship between omega-6 FAs and knee OA, we measured with LC-MS the levels of 22 omega-6 lipids (arachidonic acid, linoleic acid, and 20 oxylipins) in synovial fluid (SF) from 112 knees of 102 individuals (58 with knee OA; 44 controls). We hypothesized that oxylipin metabolites would increase in OA knee SF and with radiographically progressive disease. We validated results by comparing samples from affected and unaffected knees in 10 individuals with unilateral OA. In adjusted analysis, SF levels of three omega-6 oxylipins [prostaglandin D2, 11,12-dihydroxyeicosatrienoic acid (DHET), and 14,15-DHET] were associated with OA. Of these, 11,12-DHET and 14,15-DHET were higher in affected versus unaffected knees of people with unilateral disease (P < 0.014 and P < 0.003, respectively). Levels of these and 8,9-DHET were also associated with radiographic progression over 3.3 years in 87 individuals. Circulating levels of all three were associated with gene variants at the soluble epoxide hydrolase enzyme. Lipidomic profiling in SF identified an additional inflammatory pathway associated with knee OA and radiographic progression.

Association of the resolvin precursor 17-HDHA, but not D- or E- series resolvins, with heat pain sensitivity and osteoarthritis pain in humans

Resolvins are omega-3 fatty acid derived potent bioactive lipids that resolve inflammation and modulate transient receptor potential channels. Exogenous administration of the resolvin precursor 17-HDHA shows a strong analgesic effect in animal models of osteoarthritis and acute inflammatory pain, but has not been studied in humans. Our aim was to assess the role of 17-HDHA and resolvins in heat pain sensitivity and in osteoarthritis pain in humans. Resolvins D1, D2, D3, D5, E1 and 17-HDHA, were measured by liquid chromatography-mass spectrometry and tested for association with heat pain thresholds in 250 healthy volunteers who had undergone quantitative sensory testing. Resolvins D1, D2 and 17-HDHA were then tested in 62 individuals affected with knee osteoarthritis and 52 age matched controls and tested for association with knee pain. Circulating levels of docosahexaenoic acid (DHA) were also measured. Levels of 17-HDHA, but not those of the other 5 resolvins tested, were associated with increased heat pain thresholds (beta = 0.075; 95% CI 0.024, 0.126; p < 0.0046). 17-HDHA was associated with lower pain scores in OA patients (beta −0.41; 95% CI-0.69, −0.12; p < 0.005; adjusted for covariates) but not with radiographic osteoarthritis. The associations of 17-HDHA with heat pain sensitivity and osteoarthritis pain were independent of DHA levels.

Increased epoxyeicosatrienoic acids and reduced soluble epoxide hydrolase expression in the preeclamptic placenta

BACKGROUND

Epoxyeicosatrienoic acids (EETs) derived from cytochrome P450 (CYP)-dependent metabolism of arachidonic acid are increased in the plasma of women with preeclampsia as compared with normal pregnancy and are significantly higher in fetal than in maternal plasma and erythrocytes. We hypothesized that differences in EET synthesis or metabolism in the feto-placental unit contributed to the observed differences in circulating EETs.

METHOD

To evaluate EETs, formation as well as the expression of relevant CYP isoforms and the metabolizing enzyme, soluble epoxide hydrolase (sEH), biopsies of placenta were collected from 19 normal pregnancy and 10 preeclampsia at the time of cesarean section delivery. EETs were extracted from tissue homogenates and analyzed by liquid chromatography coupled with tandem mass spectrometry.

RESULTS

Both cis-EETs and trans-EETs were detected in the placenta. Concentration of total EETs was higher in the placenta from preeclampsia compared with normal pregnancy (2.37 ± 1.42 ng/mg vs. 1.20 ± 0.72 ng/mg, mean ± SD, P < 0.01), especially the 5,6-, 8,9- and 11,12-EETs, measured in a subgroup of tissue samples (normal pregnancy = 10, preeclampsia = 5). By immunohistochemistry, sEH, CYP2J2, CYP4A11 were present in placental villi with different pattern distribution, whereas CYP2C8 was not detectable. Neither were CYP2J2, CYP4A11, and CYP2C8 detected in the umbilical cord. Western blot analysis of placenta homogenates showed reduced expression of sEH in preeclampsia as compared with normal pregnancy.

CONCLUSION

Increased EETs in the placenta and umbilical cord are associated with the presence of CYP2J2, whereas reduced expression of sEH in preeclampsia may be the key factor of increased EETs in the placenta.

Simultaneous profiling of eicosanoid metabolome in plasma by UPLC-MS/MS method: Application to identify potential makers for rheumatoid arthritis

To evaluate the potential relationship between rheumatoid arthritis and arachidonic acid (AA) metabonomics via cyclooxygenase (COX) and lipoxygenase (LOX) pathways, a UPLC-MS/MS method has been developed and validated for simultaneous and quantitative profiling of eicosanoid metabolome in rat plasma. The analytes were extracted from plasma samples by protein precipitation procedure, and then separated on a Shim-pack XR-ODS column with mobile phase A (0.05% formic acid in water, pH=3.3 adjusted with dilute ammonium hydroxide) and mobile phase B [methanol: acetonitrile (20:80, v/v)]. The detection was performed on UPLC-MS/MS system with an electro spray ion source in the negative ion and multiple reaction-monitoring modes. The developed method was optimized to completely separate all twenty-three analytes and three internal standards in 12min. All standard calibration curves were linear and the calibration regression coefficients were ranged from 0.9903 to 0.9992 for all analytes. The recoveries of analytes were all more than 60%. By means of the method developed, the plasma samples from model rats and normal rats had been successfully determined. Results showed that AA and fifteen kinds of metabolites by LOX and COX pathways in model rat plasma were significant higher than those in normal ones(P<0.05), while 5-HpETE and LTD₄ in model rat plasma were significantly lower than those in normal ones(P<0.05). The methods demonstrated the changes of eicosanoid metabolome occurring in plasma from rat subjects with rheumatoid arthritis. It could be a powerful manner to diagnostic and/or prognostic values for rheumatoid arthritis.

Cardiotonic Pill Reduces Myocardial Ischemia-Reperfusion Injury via Increasing EET Concentrations in Rats

Accumulating data suggest that epoxyeicosatrienoic acids (EETs) and 20-hydroxyeicosatetraenoic acid, both cytochrome P450 (P450) enzyme metabolites of arachidonic acid (AA), play important roles in cardiovascular diseases. For many years, the cardiotonic pill (CP), an herbal preparation derived from Salviae Miltiorrhizae Radix et Rhizoma, Notoginseng Radix et Rhizoma, and Borneolum Syntheticum, has been widely used in China for the treatment of coronary artery disease. However, its pharmacological mechanism has not been well elucidated. The purpose of this study was to investigate the chronic effects of the CP on myocardial ischemia-reperfusion injury (MIRI) and AA P450 enzyme metabolism in rats (in vivo) and H9c2 cells (in vitro). The results showed that CP dose dependently (10, 20, and 40 mg/kg/d; 7 days) mitigated MIRI in rats. The plasma concentrations of EETs in CP-treated ischemia-reperfusion (I/R) rats (40 mg/kg/d; 7 days) were significantly higher (P < 0.05) than those in controls. Cardiac Cyp1b1, Cyp2b1, Cyp2e1, Cyp2j3, and Cyp4f6 were significantly induced (P < 0.05); CYP2J and CYP2C11 proteins were upregulated (P < 0.05); and AA-epoxygenases activity was significantly increased (P < 0.05) after CP (40 mg/kg/d; 7 days) administration in rats. In H9c2 cells, the CP also increased (P < 0.05) the EET concentrations and showed protection in hypoxia-reoxygenation (H/R) cells. However, an antagonist of EETs, 14,15-epoxyeicosa-5(Z)-enoic acid, displayed a dose-dependent depression of the CP's protective effects in H/R cells. In conclusion, upregulation of cardiac epoxygenases after multiple doses of the CP-leading to elevated concentrations of cardioprotective EETs after myocardial I/R-may be the underlying mechanism, at least in part, for the CP's cardioprotective effect in rats.

Association between the maternal serum levels of 19 eicosanoids and pre-eclampsia

OBJECTIVE

To investigate whether serum levels of 19 eicosanoids are associated with pre-eclampsia.

METHODS

A case-control study was performed using data for pregnant women with pre-eclampsia, normotensive pregnant women, and nonpregnant women, for all of whom serum samples had been collected at a hospital in Shanghai, China, between December 2012 and December 2013. Ultra-performance liquid chromatography-tandem mass spectrometry was used to measure the serum levels of 19 eicosanoids.

RESULTS

Overall, 49 pregnant women with pre-eclampsia, 26 normotensive pregnant women, and 14 nonpregnant women were included. Women with pre-eclampsia had significantly higher serum levels of 11,12-epoxyeicosatrienoic acid (11,12-EET), the hydroxyeicosatetraenoic acids 5-HETE, 8-HETE, 12-HETE, and 15-HETE, and leukotriene B4 than did women with a normal pregnancy and nonpregnant women, both before and after the onset of pre-eclampsia (P<0.01 for all comparisons). Women with severe pre-eclampsia had significantly higher serum levels of 5-HETE, 15-HETE, and leukotriene B4 than did women with mild pre-eclampsia, women with a normal pregnancy, and nonpregnant women (P<0.01 for all comparisons).

CONCLUSION

The eicosanoids 11,12-EET, 5-HETE, 8-HETE, 12-HETE, 15-HETE, and leukotriene B4 might play important parts in the occurrence and development of pre-eclampsia.

Development and Validation of a High-Throughput Ultrahigh-Performance Liquid Chromatography-Mass Spectrometry Approach for Screening of Oxylipins and Their Precursors

Lipid mediators, highly bioactive compounds synthesized from polyunsaturated fatty acids (PUFAs), have a fundamental role in the initiation and signaling of the inflammatory response. Although extensively studied in isolation, only a limited number of analytical methods offer a comprehensive coverage of the oxylipin synthetic cascade applicable to a wide range of human biofluids. We report the development of an ultrahigh-performance liquid chromatography-electrospray ionization triple quadrupole mass spectrometry (UHPLC-MS) assay to quantify oxylipins and their PUFA precursors in 100 μL of human serum, plasma, urine, and cell culture supernatant. A single 15 min UHPLC run enables the quantification of 43 oxylipins and 5 PUFAs, covering pro and anti-inflammatory lipid mediators synthesized across the cyclooxygenase (COX), lipoxygenase (LOX), and cytochrome P450 (CYP450) pathways. The method was validated in multiple biofluid matrixes (serum, plasma, urine, and cell supernatant) and suppliers, ensuring its suitability for large scale metabonomic studies. The approach is accurate, precise, and reproducible (RSD < 15%) over multiple days and concentrations. Very high sensitivity is achieved with limits of quantification inferior to picograms for the majority of analytes (0.05-125 pg) and linear range spanning up to 5 orders of magnitude. This enabled the quantification of the great majority of these analytes at their low endogenous level in human biofluids. We successfully applied the procedure to individuals undergoing a fasting intervention; oxylipin profiles highlighted significantly altered PUFA and inflammatory profiles in accordance with previously published studies as well as offered new insight on the modulation of the biosynthetic cascade responsible for the regulation of oxylipins.

The contribution of the endogenous TRPV1 ligands 9-HODE and 13-HODE to nociceptive processing and their role in peripheral inflammatory pain mechanisms

BACKGROUND AND PURPOSE

The transient receptor potential vanilloid type 1 (TRPV1) plays a fundamental role in the detection of heat and inflammatory pain responses. Here we investigated the contribution of two potential endogenous ligands [9- and 13- hydroxyoctadecadienoic acid (HODE)] to TRPV1-mediated noxious responses and inflammatory pain responses.

EXPERIMENTAL APPROACH

9- and 13-HODE, and their precursor, linoleic acid, were measured in dorsal root ganglion (DRG) neurons and in the hindpaws of control and carrageenan-inflamed rats by liquid chromatography/tandem electrospray mass spectrometry. Calcium imaging studies of DRG neurons were employed to determine the role of TRPV1 in mediating linoleic acid, 9-HODE- and 13-HODE-evoked responses, and the contribution of 15-lipoxygenase to the generation of the HODEs. Behavioural studies investigated the contribution of 9- and 13-HODE and 15-lipoxygenase to inflammatory pain behaviour.

KEY RESULTS

9-HODE (35 ± 7 pmol g(-1)) and 13-HODE (32 ± 6 pmol g(-1)) were detected in hindpaw tissue, but were below the limits of detection in DRGs. Following exposure to linoleic acid, 9- and 13-HODE were detected in DRGs and TRPV1 antagonist-sensitive calcium responses evoked, which were blocked by the 15-lipoxygenase inhibitor PD146176 and an anti-13-HODE antibody. Levels of linoleic acid were significantly increased in the carrageenan-inflamed hindpaw (P < 0.05), whereas levels of 9- and 13-HODE were, however, decreased. Intraplantar co-administration of anti-9- and 13-HODE antibodies and treatment with PD146176 significantly (P < 0.01) attenuated carrageenan-induced hyperalgesia.

CONCLUSIONS AND IMPLICATIONS

This study demonstrates that, although 9- and 13-HODE can activate TRPV1 in DRG cell bodies, the evidence for a role of these lipids as endogenous peripheral TRPV1 ligands in a model of inflammatory pain is at best equivocal.

Simultaneous quantification of leukotrienes and hydroxyeicosatetraenoic acids in cell culture medium using liquid chromatography/tandem mass spectrometry

Leukotrienes (LTs) and hydroxyeicosatetraenoic acids (HETEs) are important bioactive lipid mediators that participate in various pathophysiological processes. To advance understanding of the mechanisms that regulate these mediators in physiological and pathological processes, an analytical method using liquid chromatography/tandem mass spectrometry for the simultaneous quantification of LTB4, LTC4, LTD4, LTE4, 5-HETE, 8-HETE, 12-HETE and 15-HETE in cell culture media was developed. A Supel™-Select HLB solid-phase extraction cartridge was used for sample preparation. The compounds were separated on a C18 column using gradient elution with acetonitrile-water-formic acid (20:80:0.1, v/v/v) and acetonitrile-formic acid (100:0.1, v/v). The calibration curves of LTB4, LTD4, LTE4 and HETEs were linear in the range of 0.025-10 ng/mL, and the calibration curve of LTC4 was linear in the range of 0.25-10 ng/mL. Validation assessment showed that the method was highly reliable with good accuracy and precision. The stability of LTs and HETEs was also investigated. Using the developed method, we measured LTs and HETEs in the culture supernatant of the human mast cell line HMC-1. The present method could facilitate investigations of the mechanisms that regulate the production, release and signaling of LTs and HETEs.

Functional insights into modulation of BKCa channel activity to alter myometrial contractility

The large-conductance voltage- and Ca(2+)-activated K(+) channel (BKCa) is an important regulator of membrane excitability in a wide variety of cells and tissues. In myometrial smooth muscle, activation of BKCa plays essential roles in buffering contractility to maintain uterine quiescence during pregnancy and in the transition to a more contractile state at the onset of labor. Multiple mechanisms of modulation have been described to alter BKCa channel activity, expression, and cellular localization. In the myometrium, BKCa is regulated by alternative splicing, protein targeting to the plasma membrane, compartmentation in membrane microdomains, and posttranslational modifications. In addition, interaction with auxiliary proteins (i.e., β1- and β2-subunits), association with G-protein coupled receptor signaling pathways, such as those activated by adrenergic and oxytocin receptors, and hormonal regulation provide further mechanisms of variable modulation of BKCa channel function in myometrial smooth muscle. Here, we provide an overview of these mechanisms of BKCa channel modulation and provide a context for them in relation to myometrial function.

Simultaneous tissue profiling of eicosanoid and endocannabinoid lipid families in a rat model of osteoarthritis

We describe a novel LC method for the simultaneous and quantitative profiling of 43 oxylipins including eicosanoids, endocannabinoids, and structurally related bioactive lipids with modified acyl groups. The LC-MS/MS method uses switching at a defined time between negative and positive electrospray ionization modes to achieve optimal detection sensitivity for all the lipids. The validated method is linear over a range of 0.01–5 nmol/g (0.1–50 nmol/g for 2-arachidonoyl glycerol) with intra- and interday precision and accuracy between 1.38 and 26.76% and 85.22 and 114.3%, respectively. The method successfully quantified bioactive lipids in different tissue types in the rat, including spinal cord, dorsal root ganglia (DRGs), knee joint, brain, and plasma. Distinct regional differences in the pattern of lipid measured between tissue types were observed using principle component analysis. The method was applied to analyze tissue samples from an established preclinical rat model of osteoarthritis (OA) pain and showed that levels of 12-hydroxyeicosatetraenoic acid were significantly increased in the OA rat knee joint compared with controls, and that 15-hydroxyeicosatetraenoic acid was significantly increased in the DRGs in the model of OA compared with controls. The developed LC-MS/MS method has the potential to provide detailed pathway profiling in tissues and biofluids where the disruption of bioactive oxylipins may be involved in disease states.

Eicosanomic profiling reveals dominance of the epoxygenase pathway in human amniotic fluid at term in spontaneous labor

Lipid mediators play an important role in reproductive biology, especially, in parturition. Enhanced biosynthesis of eicosanoids, such as prostaglandin E2 (PGE2) and PGF2α, precedes the onset of labor as a result of increased expression of inducible cyclooxygenase 2 (COX-2) in placental tissues. Metabolism of arachidonic acid results in bioactive lipid mediators beyond prostaglandins that could significantly influence myometrial activity. Therefore, an unbiased lipidomic approach was used to profile the arachidonic acid metabolome of amniotic fluid. In this study, liquid chromatography-mass spectrometry was used for the first time to quantitate these metabolites in human amniotic fluid by comparing patients at midtrimester, at term but not in labor, and at term and in spontaneous labor. In addition to exposing novel aspects of COX pathway metabolism, this lipidomic study revealed a dramatic increase in epoxygenase- and lipoxygenase-pathway-derived lipid mediators in spontaneous labor with remarkable product selectivity. Despite their recognition as anti-inflammatory lipid mediators and regulators of ion channels, little is known about the epoxygenase pathway in labor. Epoxygenase pathway metabolites are established regulators of vascular homeostasis in cardiovascular and renal physiology. Their presence as the dominant lipid mediators in spontaneous labor at term portends a yet undiscovered physiological function in parturition.

Leukotriene receptor antagonist as a novel tocolytic in an in vitro model of human uterine contractility

OBJECTIVE

This study analyzed the ability of montelukast, a cysteinyl-leukotrienes receptor antagonist and anti-inflammatory agent, to produce a consistent tocolytic effect alone or in combination with nifedipine, a calcium (Ca(2+)) channel blocker currently used in clinical practice.

STUDY DESIGN

Uterine biopsies were obtained from consenting women undergoing elective cesarean sections at term (n=20). Myometrial microsomal fractions were analyzed by immunoblotting to quantify relative cysteinyl leukotrienes receptor 1 (CysLTR1) levels. Isometric tension measurements were performed in vitro on human myometrial strips (n=120) in isolated organ baths in order to establish concentration-response curves to montelukast and to quantify changes in Ca(2+) sensitivity on β-escin permeabilized tissues.

RESULTS

Immunodetection analysis revealed the presence of CysLTR1 receptor in uterine tissues, fetal membranes and placenta. A significant increase in area under the curve (AUC) was quantified following the addition of leukotriene D4 (LTD4) (0.01-0.3 μM), an end-product of the lipoxygenase pathway. Conversely, addition of montelukast produced a significant tocolytic effect by decreasing the frequency and AUC (IC₅₀=1 μM). Moreover, addition of montelukast also resulted in a reduced Ca(2+) sensitivity as compared to control tissues (EC₅₀ values of 654 and 403 nM; p=0.02 at pCa 6), while an additive effect was observed in combination with 0.1 nM nifedipine (p=0.004).

CONCLUSION

This original study demonstrates the potency of montelukast as a tocolytic agent in an in vitro human uterine model. Montelukast, in combination with nifedipine, could represent a therapeutic approach to reduce inflammation associated with prematurity while facilitating the inhibition of preterm labor.

Isolation and characterization of Xenopus soluble epoxide hydrolase

Soluble epoxide hydrolase (sEH) contributes to cell growth, but the contribution of sEH to embryonic development is not well understood. In this study, Xenopus sEH cDNA was isolated from embryos of Xenopus laevis. The Xenopus sEH was expressed in Escherichia coli and was purified. The epoxide hydrolase and phosphatase activities of purified sEH were investigated. The Xenopus sEH did not show phosphatase activity toward 4-methylumbelliferyl phosphate or several lysophosphatidic acids although it had EH activity. The amino acid sequence of Xenopus sEH was compared with that reported previously. We found amino acid substitutions of the 29th Thr to Asn and the 146th Arg to His and prepared a sEH mutant (N29T/H146R), designed as mutant 1. Neither wild-type sEH nor mutant 1 had phosphatase activity. Additional substitution of the 11th Gly with Asp was found by comparison with human sEH which has phosphatase activity, but the Xenopus sEH mutant G11D prepared as mutant 2 did not have phosphatase activity. The epoxide hydrolase activity of sEH seemed to be similar to that of human sEH, while Xenopus sEH did not have phosphatase activity toward several substrates that human sEH metabolizes.

Analysis, physiological and clinical significance of 12-HETE: a neglected platelet-derived 12-lipoxygenase product

While the importance of cyclooxygenase (COX) in platelet function has been amply elucidated, the identification of the role of 12-lipoxygenase (12-LOX) and of its stable metabolite, 12-hydroxyeicosatretraenoic acid (12-HETE), has not been clarified as yet. Many studies have analysed the implications of 12-LOX products in different pathological disorders but the information obtained from these works is controversial. Several analytical methods have been developed over the years to simultaneously detect eicosanoids, and specifically 12-HETE, in different biological matrices, essentially enzyme-linked immunosorbent assays (ELISA), radioimmunoassays (RIA), high performance liquid chromatography (HPLC) and mass spectrometry coupled with both gas and liquid chromatography methods (GC- and LC-MS). This review is aimed at summarizing the up to now known physiological and clinical features of 12-HETE together with the analytical methods used for its determination, focusing on the critical issues regarding its measurement.

Oxidized fatty acid analysis by charge-switch derivatization, selected reaction monitoring, and accurate mass quantitation

A highly sensitive, specific, and robust method for the analysis of oxidized metabolites of linoleic acid (LA), arachidonic acid (AA), and docosahexaenoic acid (DHA) was developed using charge-switch derivatization, liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI MS/MS) with selected reaction monitoring (SRM) and quantitation by high mass accuracy analysis of product ions, thereby minimizing interferences from contaminating ions. Charge-switch derivatization of LA, AA, and DHA metabolites with N-(4-aminomethylphenyl)-pyridinium resulted in a 10- to 30-fold increase in ionization efficiency. Improved quantitation was accompanied by decreased false positive interferences through accurate mass measurements of diagnostic product ions during SRM transitions by ratiometric comparisons with stable isotope internal standards. The limits of quantitation were between 0.05 and 6.0pg, with a dynamic range of 3 to 4 orders of magnitude (correlation coefficient r(2)>0.99). This approach was used to quantitate the levels of representative fatty acid metabolites from wild-type (WT) and iPLA2γ(-/-) mouse liver identifying the role of iPLA2γ in hepatic lipid second messenger production. Collectively, these results demonstrate the utility of high mass accuracy product ion analysis in conjunction with charge-switch derivatization for the highly specific quantitation of diminutive amounts of LA, AA, and DHA metabolites in biologic systems.

Cytochrome P450 subfamily 2J polypeptide 2 expression and circulating epoxyeicosatrienoic metabolites in preeclampsia

BACKGROUND

Preeclampsia is a multisystem disorder of pregnancy, originating in the placenta. Cytochrome P450 (CYP)-dependent eicosanoids regulate vascular function, inflammation, and angiogenesis, which are mechanistically important in preeclampsia.

METHODS AND RESULTS

We performed microarray screening of placenta and decidua (maternal placenta) from 25 preeclamptic women and 23 control subjects. The CYP subfamily 2J polypeptide 2 (CYP2J2) was upregulated in preeclamptic placenta and decidua. Reverse-transcription polymerase chain reaction confirmed the upregulation, and immunohistochemistry localized CYP2J2 in trophoblastic villi and deciduas at 12 weeks and term. The CYP2J2 metabolites, 5,6-epoxyeicosatrienoic acid (EET), 14,15-EET, and the corresponding dihydroxyeicosatrienoic acids, were elevated in preeclamptic women compared with controls in the latter two thirds of pregnancy and after delivery. Stimulating a trophoblast-derived cell line with the preeclampsia-associated cytokine tumor necrosis factor-α enhanced CYP2J2 gene and protein expression. In 2 independent rat models of preeclampsia, reduced uterine-perfusion rat and the transgenic angiotensin II rat, we observed elevated EET, dihydroxyeicosatrienoic acid, and preeclamptic features that were ameliorated by the CYP epoxygenase inhibitor N-(methylsulfonyl)-2-(2-propynyloxy)-benzenehexanamide (MsPPOH). Uterine arterial rings of these rats also dilated in response to MsPPOH. Furthermore, 5,6-EET could be metabolized to a thromboxane analog. In a bioassay, 5,6-EET increased the beating rate of neonatal cardiomyocytes. Blocking thromboxane synthesis reversed that finding and also normalized large-conductance calcium-activated potassium channel activity.

CONCLUSIONS

Our data implicate CYP2J2 in the pathogenesis of preeclampsia and as a potential candidate for the disturbed uteroplacental remodeling, leading to hypertension and endothelial dysfunction.

Quantitative profiling of oxylipins through comprehensive LC-MS/MS analysis: application in cardiac surgery

Oxylipins, including eicosanoids, affect a broad range of biological processes, such as the initiation and resolution of inflammation. These compounds, also referred to as lipid mediators, are (non-) enzymatically generated by oxidation of polyunsaturated fatty acids such as arachidonic acid (AA). A plethora of lipid mediators exist which makes the development of generic analytical methods challenging. Here we developed a robust and sensitive targeted analysis platform for oxylipins and applied it in a biological setting, using high performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS) operated in dynamic multiple reaction monitoring (dMRM). Besides the well-described AA metabolites, oxylipins derived from linoleic acid, dihomo-γ-linolenic acid, α-linolenic acid, eicosapentaenoic acid and docosahexaenoic acid were included. Our comprehensive platform allows the quantitative evaluation of approximately 100 oxylipins down to low nanomolar levels. Applicability of the analytical platform was demonstrated by analyzing plasma samples of patients undergoing cardiac surgery. Altered levels of some of the oxylipins, especially in certain monohydroxy fatty acids such as 12-HETE and 12-HEPE, were observed in samples collected before and 24 h after cardiac surgery. These findings indicate that this generic oxylipin profiling platform can be applied broadly to study these highly bioactive compounds in relation to human disease.

Rapid simultaneous analysis of cyclooxygenase, lipoxygenase and cytochrome P-450 metabolites of arachidonic and linoleic acids using high performance liquid chromatography/mass spectrometry in tandem mode

Eicosanoids are oxidized arachidonate-derived lipid products generated by cyclooxygenase, lipoxygenase and cytochrome P-450 pathways. They are involved in diverse processes in health and disease and they are highly bioactive. Gas chromatography and enzyme immunoassays were used to quantify these mediators in the past. However, the recent availability of high-sensitivity liquid chromatography-mass spectrometry has provided a new approach for quantification that minimizes the sample size and the required preparation. This paper describes a rapid and simple technique for the simultaneous quantitative analysis of prostaglandin (PG) E(2) and PGJ(2); leukotrienes (LT) B(4) and D(4); 5-, 12-, 15- and 20-hydroxyeicosatetraenoic acids (HETEs); 13-hydroxyoctadecadienoic acid (13-HODE); 5,6-, 8,9-, 11,12- and 14,15-epoxyeicosatrienoic acids (EETs); and 11,12- and 14,15-dihydroxieicosatrienoic acids (DHETs) in cell culture supernatants and urine. We simultaneously analyzed 14 arachidonic acid metabolites representative from the three pathways, together with 13-HODE, a linoleic-derived product. Solid phase extraction was used for the sample preparation. The recoveries obtained ranged from 25% to 100%, depending on the metabolites. The LC/MS/MS method used the gradient on a C(18) column and electrospray ionization in negative ion detection mode. The method was optimized for sensitivity and for separation within 20 min. The linear ranges of the calibration curves were 0.1-200 ng/ml for PGE(2), PGJ(2), LTB(4), 5-HETE, 12-HETE, 15-HETE, 13-HODE, 11,12-EET, 11,12-DHET and 14,15-DHET, and 1-200ng/ml for LTD(4), 20-HETE, 5,6-EET, 8,9-EET and 14,15-EET. The advantages of this method include minimal sample preparation, high sensitivity and elimination of the problem associated with thermal instability in gas chromatography analysis.

Measurement of vasoactive metabolites (hydroxyeicosatetraenoic and epoxyeicosatrienoic acids) in uterine tissues of normal and compromised human pregnancy

BACKGROUND

Preeclampsia and intrauterine growth restriction define two disorders of a multifactorial etiology that compromise maternal and fetal well being as well as cardiovascular health in later life. Many of the overt symptoms of preeclampsia are attributable to the systemic endothelial dysfunction observed in the uteroplacental and systemic circulation, leading to a generalized vasoconstriction, hypertension and inadequate placental perfusion. Mounting evidence implicates nonprostanoid eicosanoids, epoxyeicosatrienoic acids (EETs) and hydroxyeicosatetraenoic acids (HETEs) in the control of vascular function and dysfunction.

OBJECTIVE

To determine whether levels of EETs and HETEs are altered in preeclampsia and intrauterine growth restriction compared with normal term pregnancy.

METHODS

An analytical liquid chromatography-tandem mass spectrometry profiling method was utilized in order to analyze differential levels of EETs and HETEs in intrauterine tissues of term nonlaboring, laboring and preeclamptic women as well as women with a growth-restricted pregnancy.

RESULTS

Placentae of preeclamptic women contained significantly (P < 0.05) larger amounts of 5-HETE, 12-HETE and 15-HETE known to possess either vasoconstrictive or proinflammatory actions. Laboring tissues were characterized by significantly higher (P < 0.05) EET levels in the amnion compared with the other clinical groups. EET and HETE levels in preeclampsia and intrauterine growth restriction were positively correlated (P < 0.05), whereas in normal and laboring pregnancies, EETs and HETEs were negatively correlated.

CONCLUSION

Increased production of 5-HETE, 12-HETE and 15-HETE metabolites in preeclamptic placentae indicates an important role for this family of eicosanoids in the cause of this disease.

CYP3A4 mediates growth of estrogen receptor-positive breast cancer cells in part by inducing nuclear translocation of phospho-Stat3 through biosynthesis of (±)-14,15-epoxyeicosatrienoic acid (EET)

CYP3A4 expression in breast cancer correlates with decreased overall survival, but the mechanisms are unknown. Cytochrome P450 gene profiling by RNAi silencing demonstrates that CYP3A or 2C8 gene expression is specifically required for growth of the breast cancer lines MCF7, T47D, and MDA-MB-231. CYP3A4 silencing blocks the cell cycle at the G(2)/M checkpoint and induces apoptosis in the MCF7 line, thereby inhibiting anchorage-dependent growth and survival. CYP3A4 was profiled for NADPH-dependent arachidonic acid (AA) metabolism and synthesized AA epoxygenase products (±)-8,9-, (±)-11,12-, and (±)-14,15-epoxyeicosatrienoic acid (EET) (total turnover of ∼2 pmol/pmol CYP3A4/min) but not hydroxylase products (±)-15-, (±)-19-, or 20-hydroxyeicosatetraenoic acid. Furthermore, eicosanoid profiling revealed that MCF7 cells synthesize EETs in a CYP3A4-dependent manner. The (±)-14,15-EET regioisomer selectively rescues breast cancer cells from CYP3A4 silencing in a concentration-dependent fashion and promotes mitogenesis and anchorage-dependent cloning. Stat3 (Tyr-705) phosphorylation was inhibited by CYP3A4 silencing, providing a potential mechanism for CYP3A4 involvement in breast cancer cell growth. Silencing Stat3 blocks breast cancer cell growth and abrogates (±)-14,15-EET-induced proliferation, indicating a Stat3 requirement for (±)-14,15-EET-mediated cell growth. Although silencing of CYP3A4 reduces nuclear Tyr(P)-705-Stat3, (±)-14,15-EET restores this signaling process and promotes Tyr(P)-705-Stat3 translocation to the nucleus, suggesting that (±)-14,15-EET may be involved in an autocrine/paracrine pathway driving cell growth. These studies indicate that CYP3A4 is a highly active AA epoxygenase that promotes Stat3-mediated breast cancer cell growth in part through (±)-14,15-EET biosynthesis. Furthermore, these studies indicate an essential role for Stat3 as a mediator of epoxygenase activity in breast cancer.

Comprehensive lipidomics analysis of bioactive lipids in complex regulatory networks

In the present work we describe the development of an analytical technique for simultaneous profiling of over 100 biochemically related lipid mediators in biological samples. A multistep procedure was implemented to extract eicosanoids and other bioactive lipids from the biological matrix, chromatographically separate them using fast reversed-phase liquid chromatography, tentatively identify new candidate eicosanoids through a matching process of retention times, isotope distribution patterns, and high-resolution orbitrap MS/MS fragmentation patterns, and subsequently quantify tentative candidates by means of analytical reference standards. Key new aspects of this profiling technique included the classification of bioactive lipids into 12 groups according to their calculated exact masses and the development of optimized liquid chromatographic conditions for these groups to achieve sufficient separation of the numerous isobaric and isomeric species, many of which exhibited virtually identical collision-induced dissociation behavior. Importantly, no analytical standards were required at this screening stage of the assay, and tentative identifications were achieved by matching results to selected reference species from each of the groups. The analytical figures of merit for the orbitrap assay such as linear dynamic range, limit of detection, limit of quantitation, and precision demonstrated that the performance of the assay was very similar to that of a quadrupole linear ion trap assay, which was used for validation purposes. The method allowed us to examine eicosanoid profiles within the signaling cascade in chronic lymphocytic leukemia (CLL) cells under basal conditions and following arachidonic acid stimulation. The preliminary screening based on high-resolution tandem mass spectrometry data along with isotope pattern and retention time matching revealed the presence of 15 bioactive lipids, belonging to a range of prostaglandin, leukotriene, and hydroxy and epoxy fatty acid lipid mediators produced by CLL cells.

Stability and analysis of eicosanoids and docosanoids in tissue culture media

Bioactive lipids derived from polyunsaturated fatty acids constitute an important set of lipid mediators with diverse homeostatic and pathophysiological activities. The role of bioactive lipids in inflammation, active resolution of inflammation, reproduction, cardiovascular biology, chronic diseases such as cancer and metabolic disorders is an active area of research. Other than the few clinically used eicosanoids such as prostaglandin F(2)α, prostacyclin, and prostaglandin E(2), little is known about the stability of a majority of the bioactive lipids in aqueous solutions despite their extensive use under in vitro experimental conditions. The present study evaluated the stability of eicosanoids and docosanoids as well as their parent polyunsaturated fatty acids in tissue culture media with respect to incubation time, temperature, and composition of the media using multiple reaction monitoring (MRM) LC-MS. The results provide a comprehensive and valuable data set on the stability of these bioactive lipid mediators to guide in vitro experimentation.

Lipoxygenase and cyclooxygenase inhibitors reveal a complementary role of arachidonic acid derivatives in pregnant human myometrium

OBJECTIVE

The aim of this study was to assess the involvement of lipoxygenase (LOX) metabolic pathways in uterine tissues from pregnant women as well as the combined inhibition of LOX and cyclooxygenase (COX) on contractile activity.

STUDY DESIGN

Uterine biopsies were performed from consenting women undergoing elective caesarean sections at term (n = 24). Western blot analysis and isometric tension measurements were performed in vitro on fresh human myometrial strips. Concentration-response curves to arachidonic acid (AA) 861 and baicalein (5- and 12-LOX inhibitors, respectively) were performed. The combined effects of baicalein and indomethacin were also assessed. Contractile activities were quantified by calculating both amplitude and the area under the curve over 20 minute periods.

RESULTS

5- and 12-LOX were present in all tested tissues. Addition of AA861 or baicalein resulted in tocolytic effects (P < .05). Finally, the combined inhibition of both COX and 12-LOX pathways resulted in additive tocolytic effects.

CONCLUSION

5- and 12-LOX pathways modulate human myometrium contractility.

Stable-isotope dilution LC–MS for quantitative biomarker analysis

The ability to conduct validated analyses of biomarkers is critically important in order to establish the sensitivity and selectivity of the biomarker in identifying a particular disease. The use of stable-isotope dilution (SID) methodology in combination with LC–MS/MS provides the highest possible analytical specificity for quantitative determinations. This methodology is now widely used in the discovery and validation of putative exposure and disease biomarkers. This review will describe the application of SID LC–MS methodology for the analysis of small-molecule and protein biomarkers. It will also discuss potential future directions for the use of this methodology for rigorous biomarker analysis.

HPLC/MS/MS-based approaches for detection and quantification of eicosanoids

Eicosanoids are oxygenated, endogenous, unsaturated fatty acids derived from arachidonic acid. Detection and quantification of these compounds are of great interest because they play important roles in a number of significant diseases, including asthma, chronic obstructive pulmonary disease (COPD), cardiovascular disease, and cancer. Because the endogenous levels of eicosanoids are quite low, sensitive and specific analytical methods are required to reliably quantify these compounds. High-performance liquid chromatography mass spectrometry (HPLC/MS) has emerged as one of the main techniques used in eicosanoid profiling. Herein, we describe the main LC/MS techniques and principles as well as their application in eicosanoid analysis. In addition, a protocol is given for extracting eicosanoids from biological samples, using bronchoalveolar lavage fluid (BALF) as an example. The method and instrument optimization procedures are presented, followed by the analysis of eicosanoid standards using reverse phase HPLC interfaced with an ion trap mass spectrometer (LC/MS/MS). This protocol is intended to provide a broad description of the field for readers looking for an introduction to the methodologies involved in eicosanoid quantification.

Rapid, simultaneous quantitation of mono and dioxygenated metabolites of arachidonic acid in human CSF and rat brain

Currently, there are few biomarkers to predict the risk of symptomatic cerebral vasospasm (SV) in subarachnoid hemorrhage (SAH) patients. Mono and dioxygenated arachidonic acid metabolites, involved in the pathogenesis of ischemic injury, may serve as indicators of SV. This study developed a quantitative UPLC-MS/MS method to simultaneously measure hydroxyeicosatetraenoic acid (HETE), dihydroxyeicosatrienoic acid (DiHETrE), and epoxyeicosatrienoic acid (EET) metabolites of arachidonic acid in cerebrospinal fluid (CSF) samples of SAH patients. Additionally, we determined the recovery of these metabolites from polyvinylchloride (PVC) bags used for CSF collection. Linear calibration curves ranging from 0.208 to 33.3 ng/ml were validated. The inter-day and intra-day variance was less than 15% at most concentrations with extraction efficiency greater than 73%. The matrix did not affect the reproducibility and reliability of the assay. In CSF samples, peak concentrations of 8,9-DiHETrE, 20-HETE, 15-HETE, and 12-HETE ranged from 0.293 to 24.9 ng/ml. In rat brain cortical tissue samples, concentrations of 20-, 15-, 12-HETE, 8,9-EET, and 14,15-, 11,12-DiHETrE ranged from 0.57 to 23.99 pmol/g wet tissue. In rat cortical microsomal incubates, all 10 metabolites were measured with formation rates ranging from 0.03 to 7.77 pmol/mg/min. Furthermore, 12-HETE and EET metabolites were significantly altered by contact with PVC bags at all time points evaluated. These data demonstrate that the simultaneous measurement of these compounds in human CSF and rat brain can be achieved with a UPLC-MS/MS system and that this method is necessary for evaluation of these metabolites as potential quantitative biomarkers in future clinical trials.

Why eicosanoids could represent a new class of tocolytics on uterine activity in pregnant women

OBJECTIVE

The purpose of this study was to assess the effects of exogenous eicosanoids on spontaneous uterine contractile activity.

STUDY DESIGN

Eight uterine biopsies were performed from women who were undergoing elective cesarean delivery. Tension measurements were performed in vitro on myometrial strips. Contractile activities were quantified by the calculation of the area under the curve. The effects of eicosanoids and specific enzyme inhibitors were assessed. Fractions from various uterine tissues were analyzed by Western blot.

RESULTS

Data demonstrate the presence, in some tested tissues, of cytochrome P-450 epoxygenase and soluble epoxide hydrolase, which respectively produce and degrade epoxyeicosatrienoic acid regioisomers. Inhibition of soluble epoxide hydrolase with 12-(3-adamantan-1-yl-ureido)-dodecanoic acid or omega-hydroxylase with N-methylsulfonyl-12,12-dibromododec-11-enamide resulted in a tocolytic effect; N-methylsulfonyl-6-[2-propargyloxyphenyl] hexanamide, which is an epoxygenase inhibitor, had no effect. Exogenous epoxyeicosatrienoic acids displayed significant tocolytic effects on spontaneous contractile activities.

CONCLUSION

Epoxy- and hydroxyeicosanoids represent new bioactive, arachidonic acid by-products with in vitro tocolytic activities. These findings suggest that cytochrome P-450 isozymes may represent relevant pharmacologic targets under physiopathologic conditions.

Quantitative profiling method for oxylipin metabolome by liquid chromatography electrospray ionization tandem mass spectrometry

Cyclooxygenase, lipoxygenase, and epoxygenase derived oxylipins, especially eicosanoids, play important roles in many physiological processes. Assessment of oxidized fatty acid levels is important for understanding their homeostatic and pathophysiological roles. Most reported methods examine these pathways in isolation. The work described here employed a solid phase extraction-liquid chromatography-electrospray ionization MS/MS (SPE-LC-ESI MS/MS) method to monitor these metabolites. In 21 min, 39 oxylipins were quantified along with eight corresponding internal standards. The limits of quantification were between 0.07 and 32 pg (20 pM-10 nM). Finally, the validated method was used to evaluate oxylipin profiles in lipopolysaccharide-exposed mice, an established septic inflammatory model. The method described here offers a useful tool for the evaluation of complex regulatory oxylipin responses in in vitro or in vivo studies.

Targeted quantitative analysis of eicosanoid lipids in biological samples using liquid chromatography-tandem mass spectrometry

The eicosanoids are a large family of arachidonic acid oxidation products that contain 20 carbon atoms. Cyclooxygenase (COX)-derived eicosanoids have important roles as autacoids involved in the regulation of cardiovascular function and tumor progression. Lipoxygenase (LO)-derived eicosanoids have been implicated as important mediators of inflammation, asthma, cardiovascular disease and cancer. Cytochrome P-450 (P450)-derived eicosanoids are both vasodilators and vasoconstrictors. There is intense interest in the analysis of reactive oxygen species (ROS)-derived isoprostanes (isoPs) because of their utility as biomarkers of oxidative stress. Enzymatic pathways of eicosanoid formation are regioselective and enantioselective, whereas ROS-mediated eicosanoid formation proceeds with no stereoselectivity. Many of the eicosanoids are also present in only pM concentrations in biological fluids. This presents a formidable analytical challenge because methodology is required that can separate enantiomers and diastereomers with high sensitivity and specificity. However, the discovery of atmospheric pressure ionization (API)/MS methodology of electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), and electron capture (EC) APCI has revolutionized our ability to analyze endogenous eicosanoids. LC separations of eicosanoids can now be readily coupled with API ionization, collision induced dissociation (CID) and tandem MS (MS/MS). This makes it possible to efficiently conduct targeted eicosanoid analyses using LC-multiple reaction motoring (MRM)/MS. Several examples of targeted eicosanoid lipid analysis using conventional LC-ESI/MS have been discussed and some new data on the analysis of eicosanoids using chiral LC-ECAPCI/MS has been presented.

Detection of EETs and HETE-generating cytochrome P-450 enzymes and the effects of their metabolites on myometrial and vascular function

Cytochrome P-450 (CYP450) enzymes of the CYP2 and -4 family in humans metabolize arachidonic acid to generate bioactive epoxyeicosatrienenoic acids (EETs) and hydroxyeicosatetrenoic acids (HETEs). We report significantly higher levels of CYP 2J2 protein expression following the onset of labor (n = 6, P < 0.05), implying increased EET-generating capacity within the uterus. Myometrial relaxation to 8,9-EET and 5,6-EET was observed, with the latter being inhibited by preincubation with 1 muM paxilline and is supported by whole cell recordings showing a modest effect of 5,6-EET on myometrial outward-current density (n = 4, P < 0.05). Only 5,6-EET of the EETs tested affected vascular reactivity (n = 6). Both 12- and 20-HETE (n = 5-6) caused vasoconstriction of partially depolarized blood vessels, with glibenclamide (n = 5) enhancing the effect of 12-HETE alone. Our findings signify a role for CYP2C9/19, -2J2, and -4A11/22 in late pregnancy, possibly related to the synthesis of lipid metabolites and downstream effects on vascular remodeling in the term pregnant uterus. The presence of CYP4A11/22 and their resultant procontractile metabolites could argue either a role in the control and initiation of labor and/or modification of the vascular delivery system to influence blood flow to the laboring uterus. The differential effects of the EETs and HETEs in the pregnant human uterus identify the CYP pathway as a novel modulator of myometrial and vascular physiology during late pregnancy.

Determination of epoxyeicosatrienoic acids in human red blood cells and plasma by GC/MS in the NICI mode

Epoxyeicosatrienoic acids (EETs) are cytochrome P450 metabolites of arachidonic acid involved in the regulation of vascular tone. Despite the importance of EETs in a variety of physiological effects, few methods have been developed to quantify them in human blood. This led us to develop a method by GC/MS with negative ion chemical ionization. As EETs are primarily located in phospholipids, red blood cells (RBCs) and plasma phospholipids were hydrolyzed with phospholipase A(2) after a solid phase extraction. Then, EETs were derivatized as pentafluorobenzyl esters, and [(2)H(8)]-arachidonic acid was used as internal standard for quantification. EETs were found to be at concentrations of 106+/-37ng mL(-1) in plasma and 33.4+/-8.5 ng/10(9) RBCs (mean+/-S.D.) in 10 healthy volunteers. Their amount in RBCs was 3-fold that in plasma; both parameters proved to be well correlated.

Structural characterization of monohydroxyeicosatetraenoic acids and dihydroxy- and trihydroxyeicosatrienoic acids by ESI-FTICR

The fragmentation characteristics of monohydroxyeicosatetraenoic acids and dihydroxy- and trihydroxyeicosatrienoic acids were investigated by electrospray ionization Fourier transform ion cyclotron resonance (FTICR) mass spectrometry using sustained off-resonance irradiation collision-induced dissociation (SORI-CID) and infrared multiphoton dissociation (IRMPD). The fragmentation patterns of these compounds were associated with the number and positions of the hydroxyl substituents. The fragmentation is more complicated with increasing number of the hydroxyl groups of the compounds. In general, the major carbon-carbon cleavage of [M - H](-) ions occurred at the alpha-position to the hydroxyl group, and the carbon-carbon cleavage occurred when there was a double-bond at the beta-position to the hydroxyl group. SORI-CID and IRMPD produced some common fragmentation patterns; however, each technique provided some unique patterns that are useful for structural identification of these compounds. This study demonstrated the application of FTICR via the identification of regioisomers of trihydroxyeicosatrienoic acids in rabbit aorta samples.

Simultaneous lipidomic analysis of three families of bioactive lipid mediators leukotrienes, resolvins, protectins and related hydroxy-fatty acids by liquid chromatography/electrospray ionisation tandem mass spectrometry

Bioactive lipid mediators derived from polyunsaturated fatty acids (PUFA) exhibit a range of tissue- and cell-specific activities in many physiological and pathological processes. Electrospray ionisation tandem mass spectrometry coupled to liquid chromatography (LC/ESI-MS/MS) is a sensitive, versatile analytical methodology for the qualitative and quantitative analysis of lipid mediators. Here we present an LC/ESI-MS/MS assay for the simultaneous analysis of twenty mono- and poly-hydroxy-fatty acid derivatives of linoleic, arachidonic, eicosapentaenoic and docosahexaenoic acids. The assay was linear over the concentration range 1-100 pg/microL, whilst the limits of detection and quantitation were 10-20 and 20-50 pg, respectively. The recovery of the extraction methodology varied from 76-122% depending on the metabolite. This system is useful for profiling a range of biochemically related potent mediators including the newly discovered resolvins and protectins, and their precursor hydroxyeicosapentaenoic and hydroxydocosahexaenoic acids, and, consequently, advance our understanding of the role of PUFA in health and disease.