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

Accumulation of polyunsaturated fatty acid-derived metabolites in the sarcopenic muscle of aging mice

AIM

Although it is known that advanced age alters skeletal muscle lipid metabolism, the role(s) of polyunsaturated fatty acid-derived metabolites (mostly eicosanoids and docosanoids) in sarcopenia are not clear. We therefore examined the changes in the metabolites of arachidonic acid, eicosapentaenoic acid and docosahexaenoic acid in the sarcopenic muscle of aged mice.

METHODS

We used 6- and 24-month-old male C57BL/6J mice as healthy and sarcopenic muscle models, respectively. Skeletal muscles were removed from the lower limb and subjected to a liquid chromatography-tandem mass spectrometry analysis.

RESULTS

The liquid chromatography-tandem mass spectrometry analysis detected distinct changes of metabolites in the muscles of the aged mice. Of the 63 metabolites identified, nine were significantly higher in the sarcopenic muscle of aged mice compared with the healthy muscle of young mice. In particular, prostaglandin E2 , prostaglandin F2a , thromboxane B2 , 5-hydroxyeicosatetraenoic acid, and 15-oxo-eicosatetraenoic acid (arachidonic acid-derived metabolites), 12-hydroxy-eicosapentaenoic acid and 14,15-epoxy-eicosatetraenoic acid (eicosapentaenoic acid-derived metabolites) and 10-hydroxydocosa-hexaenoic acid and 14-hydroxyoctadeca-pentaenoic acid (docosahexaenoic acid-derived metabolites) were significantly higher in aged tissue compared with young tissue (all P < 0.05).

CONCLUSIONS

We observed the accumulation of metabolites in the sarcopenic muscle of aged mice. Our results may provide new insights into the pathogenesis and progression of aging- or disease-related sarcopenia. Geriatr Gerontol Int 2023; 23: 297-303.

Effects of Erchen Decoction on Oxidative Stress-Related Cytochrome P450 Metabolites of Arachidonic Acid in Dyslipidemic Mice with Phlegm-Dampness Retention Syndrome: A Randomized, Controlled Trial on the Correspondence between Prescription and Syndrome

Phlegm-dampness retention (PDR) syndrome is one of the main syndromes of dyslipidemia. This study investigated the effects of Erchen decoction (ECD) on concentrations of two oxidative stress-related cytochrome P450 (CYP450) metabolites of arachidonic acid—14,15-dihydroxyeicosatrienoic acid (14,15-DHET) and 20-hydroxyeicosatetraenoic acid (20-HETE)—in mice with dyslipidemia and phlegm-dampness retention (PDR) syndrome (n = 5 C57BL/6J mice and n = 30 apolipoprotein E knockout mice). Murine models of the disease and syndrome were established using multifactor stimulation. Then, all mice were assigned to normal, model, low- (L-), medium- (M-), or high- (H-) dose ECD groups or to a control or an unmatched prescription-syndrome (unmatched P-S) group; five mice were included in each group. Dose formulations were administered by oral gavage for 30 days to animals in the corresponding groups. We detected and analyzed hematoxylin and eosin (HE) staining characteristics of the mouse aorta and serum total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), peroxynitrite (ONOO⁻), 14,15-DHET, and 20-HETE concentrations in each group. TC and LDL-C concentrations significantly decreased in the M-ECD versus control group (P < 0.05); however, the TC and LDL-C concentrations were not significantly different in the unmatched P-S versus model group (P > 0.05). After treatment in the P-S correspondence groups (L-ECD, M-ECD, and H-ECD groups), the concentration of ONOO⁻ decreased to different degrees in each group. Among these groups, the concentration of ONOO⁻ significantly decreased in the L-ECD, M-ECD, and H-ECD groups versus the model group (P < 0.05). However, the concentration of ONOO⁻ was not significantly different in the unmatched P-S versus the model group (P > 0.05). From the perspective of aortic HE staining, the P-S group experienced an improved endothelium structure after treatment. 14,15-DHET concentrations significantly increased in the normal, M-ECD, and H-ECD groups versus the model group; in the H-ECD versus the L-ECD group; and in the H-ECD versus the control group (all P < 0.05) to various extents after different doses of the prescription. 20-HETE concentrations pronouncedly decreased in the M-ECD versus normal group; in the M- and H-ECD groups versus the model group; in the M-ECD versus the L-ECD group; in the M-ECD versus the control group; and in the M-ECD versus the unmatched P-S (P < 0.05). However, the concentrations of 14,15-DHET and 20-HETE in the model group were not significantly different from those of the unmatched P-S (P > 0.05). In this study, ECD reversed blood lipid indexes and ameliorated oxidative stress-related metabolites, elevating serum 14,15-DHET and lowering serum 20-HETE in mice with dyslipidemia and PDR syndrome via CYP450 pathways of arachidonic acid metabolism. The efficacy of ECD relies on correspondence between the prescription and the syndrome. These findings scientifically validate the treatment according to traditional Chinese medicine syndrome differentiation. ECD can strengthen the protective effect on the vascular endothelium by driving out pathogenic factors and strengthening healthy resistance. Its efficacy may be related to the adjustment of the polarization state of macrophages.

Investigation of the content differences of arachidonic acid metabolites in a mouse model of breast cancer by using LC-MS/MS

Arachidonic acid (AA) is closely associated with breast cancer. In addition to the two metabolic pathways regulated by cyclooxygenase and lipoxygenase, AA has a third metabolic pathway through which cytochrome P450 (CYP) enzymes produce hydroxyeicosatetraenoic acids (HETEs) and epoxyeicosatrienoic acids (EETs). The targeted CYP-mediated pathway of AA can not only kill cancer cells but also inhibit the interstitial microenvironment around a tumor. Therefore, it makes sense to identify potential biomarkers from the AA metabolome for the diagnosis and treatment of breast cancer. This study established a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the analysis of AA and its main metabolites, EETs and HETEs, in MMTV-PyMT mice, a spontaneous breast cancer mouse model. The results showed that there were significant differences in the concentrations of AA, 12-HETE, 19-HETE and 8,9-EET in plasma and tumor tissues between normal and MMTV-PyMT mice. Therefore, the eicosanoids mentioned above may be used as new biomarkers for breast cancer diagnosis. This study provides a new perspective for the recognition and diagnosis of breast cancer.

Inflammation, Lipid (Per)oxidation, and Redox Regulation

Significance: Inflammation increases during the aging process. It is linked to mitochondrial dysfunction and increased reactive oxygen species (ROS) production. Mitochondrial macromolecules are critical targets of oxidative damage; they contribute to respiratory uncoupling with increased ROS production, redox stress, and a cycle of senescence, cytokine production, and impaired oxidative phosphorylation. Targeting the formation or accumulation of oxidized biomolecules, particularly oxidized lipids, in immune cells and mitochondria could be beneficial for age-related inflammation and comorbidities. Recent Advances: Inflammation is central to age-related decline in health and exhibits a complex relationship with mitochondrial redox state and metabolic function. Improvements in mass spectrometric methods have led to the identification of families of oxidized phospholipids (OxPLs), cholesterols, and fatty acids that increase during inflammation and which modulate nuclear factor erythroid 2-related factor 2 (Nrf2), peroxisome proliferator-activated receptor gamma (PPARγ), activator protein 1 (AP1), and NF-κB redox-sensitive transcription factor activity. Critical Issues: The kinetic and spatial resolution of the modified lipidome has profound and sometimes opposing effects on inflammation, promoting initiation at high concentration and resolution at low concentration of OxPLs. Future Directions: There is an emerging opportunity to prevent or delay age-related inflammation and vascular comorbidity through a resolving (oxy)lipidome that is dependent on improving mitochondrial quality control and restoring redox homeostasis.

HT-29 and Caco2 Cell Lines Are Suitable Models for Studying the Role of Arachidonic Acid-Metabolizing Enzymes in Intestinal Cell Differentiation

INTRODUCTION

Cytochrome (CYP) epoxygenases (CYP2C and CYP2J) and soluble epoxide hydrolase (sEH) participate in the metabolism of arachidonic acid and may also have a potential role in enterocyte differentiation. The first critical step in the study of intestinal cell differentiation is the determination of a suitable in vitro model, which must be as similar as possible to the conditions of a living organism. It is known that HT-29 and Caco2 cell lines derived from human colorectal carcinomas can differentiate into enterocyte-like cells in appropriate culture conditions.

MATERIAL AND METHODS

We tested 4 different approaches of enterocyte-like differentiation and determined the most appropriate culture conditions for each model. Subsequently, the changes in the expression of CYP epoxygenases and sEH in undifferentiated and differentiated cells were measured by In-Cell ELISA. These results were compared with immunohistochemical profiles of expression of CYP epoxygenases and sEH in samples of human embryonic and fetal intestines as well as adult duodenum and colon.

RESULTS

Our results show that sodium butyrate (NaBt)-differentiated HT-29 cells and spontaneously differentiated Caco2 cells resemble CYP epoxygenases and sEH profiles, corresponding with different types of intestines.

CONCLUSION

Our study revealed that the most suitable models for the study of the role of CYP epoxygenases and sEH expression in differentiation of intestinal epithelium are NaBt-differentiated HT-29 cells and spontaneously differentiated Caco2 cells.

Development and validation of a rapid, specific and sensitive LC-MS/MS bioanalytical method for eicosanoid quantification - assessment of arachidonic acid metabolic pathway activity in hypertensive rats

Lipid mediators such as eicosanoids maintain various physiological processes, and their alterations are involved in the development of numerous cardiovascular diseases. Therefore, the reliable assessment of their profile could be helpful in diagnosis as well as in eicosanoid biomarker-based treatment. Hence, the presented study aimed to develop and validate a new rapid, specific and sensitive LC-MS/MS method for quantification of arachidonic acid-derived eicosanoids in plasma, including lipid mediators generated via COX-, LOX- and CYP450-dependent pathways. The developed method features high sensitivity because the lower limit of quantification ranged from 0.05 to 0.50 ng mL^-1 as well as the accuracy and precision estimated within 88.88-111.25% and 1.03-11.82%, respectively. An application of a simple and fast liquid-liquid extraction procedure for sample cleaning resulted in a highly satisfactory recovery of the analytes (>88.30%). Additionally, the method was validated using artificial plasma, an approach that enabled the elimination of the matrix effect caused by an endogenous concentration of studied lipid mediators. Importantly, the presented LC-MS/MS method allowed for simultaneous quantitative and qualitative [quan/qual] analysis of the selected eicosanoids, leading to an additional improvement of the method specificity. Moreover, the validated method was successfully applied for eicosanoid profiling in rat, mouse and human plasma samples, clearly demonstrating the heterogeneity of the profile of studied lipid mediators in those species.

Metabolic indices of polyunsaturated fatty acids: current evidence, research controversies, and clinical utility

The n-3 and n-6 polyunsaturated fatty acids (PUFA) are among the most studied nutrients in human metabolism. In the past few decades, prospective studies and controlled trials have supported the view that the effects of these essential fatty acids are clinically relevant. PUFA profiles in different blood compartments are reflections of both diet and metabolism, and their levels may be related to disease risk. Despite widespread interest, there is no consensus regarding which biomarkers best reflect PUFA status in the body. The measurement of PUFA levels is not straight-forward, and a wide variety of indices have been used in clinical studies, producing conflicting results. A major source of heterogeneity among studies is associated with research design, sampling, and laboratory analyses. To date, the n-3 index, n-6/n-3 ratio, and arachidonic acid (AA)/eicosapentaenoic acid (EPA) ratio are the most promising biomarkers associated with PUFA metabolism. Although hotly debated, these indices may be considered at least markers, if not risk factors, for several diseases, especially cardiovascular events and brain disorders. Here, we summarize the most updated evidence of n-3 and n-6 PUFA effects on human health, reviewing current controversies on the aforementioned indices and whether they can be considered valuable predictors of clinical outcomes.

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.

Extra Virgin Olive Oil Minor Compounds Modulate Mitogenic Action of Oleic Acid on Colon Cancer Cell Line

Experimental and clinical findings suggest that olive oil has a protective effect, whereas oleic acid consumption induces colorectal cancer (CRC). Considering this apparent contradiction and that olive oil is a complex mix of fatty acids, mainly oleic acid and minor compounds such as phenolic compounds, lignans, hydrocarbons, and triterpenes, we study its effects on intestinal epithelial cell growth. Our results show that oleic acid (1-100 μM) but not elaidic acid induced DNA synthesis and Caco-2 cell growth (2-fold higher than cells without growth factors, p < 0.05). These effects were inhibited by 5-lipoxygenase inhibitors as well as the leukotriene antagonist (p < 0.05), suggesting the implication of this pathway in this mitogenic action. Hydroxytyrosol, oleuropein, pinoresinol, squalene, and maslinic acid (0.1-10 μM) reverted DNA synthesis and Caco-2 cell growth induced by oleic acid. These effects were not the consequence of the cell cycle arrest or the impairment of cell viability with the exception of hydroxytyrosol and maslinic acid that induced cell detachment and apoptosis (35.6 ± 2.3 and 43.2 ± 2.4%, respectively) at the higher concentration assayed. Oleuropein effects can be related with hydroxytyrosol release as a consequence of oleuropein hydrolysis by Caco-2 cells (up to 25%). Furthermore, hydroxytyrosol modulates the arachidonic acid cascade, and this event can be associated with its antimitogenic action. In conclusion, oleic acid and oleic acid in the presence of olive oil representative minor components have opposite effects, suggesting that the consumption of seed oils, high oleic acid seed oils, or olive oil will probably have different effects on CRC.

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.

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.

Leukotriene D4-induced Caco-2 cell proliferation is mediated by prostaglandin E2 synthesis

Leukotriene D₄ (LTD₄) is a pro-inflammatory mediator formed from arachidonic acid through the action of 5-lipoxygenase (5-LOX). Its biological effects are mediated by at least two G-coupled plasmatic cysteinyl LT receptors (CysLT_1-2R). It has been reported an upregulation of the 5-LOX pathway in tumor tissue unlike in normal colon mucosa. Colon tumors generally have an increased expression of CysLT₁R and colon cancer patients with high expression levels of CysLT₁R have poor prognosis. We previously observed that the cyclooxygenase pathway is involved in the control of intestinal epithelial cancer cell growth through PGE₂ production. The aim of this study was therefore to assess the effect of LTD₄ binding with CysLT₁R on Caco-2 cell growth. We note a number of key findings from this research. We observed that at a concentration similar to that found under inflammatory conditions, LTD₄ was able to induce Caco-2 cell proliferation and DNA synthesis. Moreover, with the use of a specific receptor antagonist this study has demonstrated that the effect of LTD₄ is a result of its interaction with CystLT₁R. We also note the possible participation of the PLC-IP₃-Ca²⁺/DAG-PKC signaling pathways in cytosolic PLA₂ and [³H]AA release induced by LTD₄-CystLT₁R interaction. Finally, we found that the resulting activation of the AA cascade and the production of PGE₂ eicosanoid could be related to the activation of cell signaling pathways such as ERK and CREB. These findings will help facilitate our understanding of how inflammatory mediators can affect the survival and dissemination of intestinal carcinoma cells.

Targeted lipidomic strategies for oxygenated metabolites of polyunsaturated fatty acids

Oxidation of polyunsaturated fatty acids (PUFA) through enzymatic or non-enzymatic free radical-mediated reactions can yield an array of lipid metabolites including eicosanoids, octadecanoids, docosanoids and related species. In mammals, these oxygenated PUFA mediators play prominent roles in the physiological and pathological regulation of many key biological processes in the cardiovascular, renal, reproductive and other systems including their pivotal contribution to inflammation. Mass spectrometry-based technology platforms have revolutionized our ability to analyze the complex mixture of lipid mediators found in biological samples, with increased numbers of metabolites that can be simultaneously quantified from a single sample in few analytical steps. The recent development of high-sensitivity and high-throughput analytical tools for lipid mediators affords a broader view of these oxygenated PUFA species, and facilitates research into their role in health and disease. In this review, we illustrate current analytical approaches for a high-throughput lipidomic analysis of eicosanoids and related mediators in biological samples. This article is part of a Special Issue entitled "Oxygenated metabolism of PUFA: analysis and biological relevance."

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.

Differential cell growth/apoptosis behavior of 13-hydroxyoctadecadienoic acid enantiomers in a colorectal cancer cell line

Cyclooxygenases (COXs) and lipoxygenases (LOXs) are important enzymes that metabolize arachidonic and linoleic acids. Various metabolites generated by the arachidonic acid cascade regulate cell proliferation, apoptosis, differentiation, and senescence. Hydroxyoctadecadienoic acids (HODEs) are synthesized from linoleic acid, giving two enantiomeric forms for each metabolite. The aim was to investigate the effect of 13-HODE enantiomers on nondifferentiated Caco-2 cell growth/apoptosis. Our results indicate that 13(S)-HODE decreases cell growth and DNA synthesis of nondifferentiated Caco-2 cells cultured with 10% fetal bovine serum (FBS). Moreover, 13(S)-HODE showed an apoptotic effect that was reduced in the presence of a specific peroxisome proliferator-activated receptor-γ (PPARγ) antagonist. In addition, we observed that 13(S)-HODE but not 13(R)-HODE is a ligand to PPARγ, confirming the implication of this nuclear receptor in 13(S)-HODE actions. In contrast, 13(R)-HODE increases cell growth and DNA synthesis in the absence of FBS. 13(R)-HODE interaction with BLT receptors activates ERK and CREB signaling pathways, as well as PGE2 synthesis. These results suggest that the proliferative effect of 13(R)-HODE could be due, at least in part, to COX pathway activation. Thus both enantiomers use different receptors and have contrary effects. We also found these differential effects of 9-HODE enantiomers on cell growth/apoptosis. Therefore, the balance between (R)-HODEs and (S)-HODEs in the intestinal epithelium could be important to its cell growth/apoptosis homeostasis.

Mice deficient in intestinal epithelium cytochrome P450 reductase are prone to acute toxin-induced mucosal damage

Cytochrome P450 (P450) enzymes are a superfamily of heme-containing enzymes involved in the metabolism of various endogenous compounds, including retinoids, glucocorticoids, and eicosanoids, that are postulated to participate in the maintenance and/or development of inflammatory and immune reactions in the intestinal mucosa. To investigate the role of P450 enzymes in intestinal inflammation and immunity, we took advantage of IE-Cpr-null mice, which are deficient in intestinal epithelium of NADPH-cytochrome P450 reductase (CPR), the obligate redox partner of all microsomal P450 enzymes. We report that IE-Cpr-null mice, following an acute toxin challenge, had higher levels of pro-inflammatory chemokines and increased tissue damage compared to wild-type mice. IE-Cpr-null mice had normal Peyer's patch numbers and elicited normal secretory IgA (SIgA) responses. However, SIgA baseline levels in IE-Cpr-null mice were consistently elevated over WT littermates. While neither retinoic acid nor glucocorticoid levels in serum and intestinal homogenates were altered in IE-Cpr-null mice, basal levels of arachidonic acid metabolites (11,12-DiHETE and 14,15-DiHETE) with known anti-inflammatory property were significantly lower compared to WT controls. Overall, these findings reveal immunological and metabolic changes resulting from a genetic deficiency in CPR expression in the intestine, and support a role for microsomal P450 enzymes in mucosal homeostasis and immunity.

Liquid chromatography-tandem mass spectrometry analysis of eicosanoids and related compounds in cell models

Enzyme- and free radical-catalyzed oxidation of polyunsaturated fatty acids (PUFAs) produces the eicosanoids, docosanoids and octadecanoids. This large family of potent bioactive lipids is involved in many biochemical and signaling pathways which are implicated in physiological and pathophysiological processes and can be viable therapeutic targets. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) offers selectivity, sensitivity, robustness and high resolution and is able to analyze a large number of eicosanoids in biological samples in a short time. The present article reviews and discusses reported LC-MS/MS methods and the results obtained from their application in cell models. Reliable analytical outcomes are critically important for understanding physiological and pathophysiological cellular processes, such as inflammation, diseases with inflammatory components (e.g., cardiovascular disease, diabetes, metabolic syndrome), as well as cancer. Reported findings obtained by using the LC-MS/MS methodology in cell systems may have important predictive as well as nutritional and pharmacological implications. We conclude that the LC-MS/MS methodology is a versatile and reliable analytical tool for the simultaneous analysis of multiple PUFA-derived metabolites including the eicosanoids in cell culture samples at concentrations on the pM/nM threshold, i.e. at baseline and after stimulation.

Liquid chromatography-tandem mass spectrometry for simultaneous measurement of thromboxane B2 and 12(S)-hydroxyeicosatetraenoic acid in serum

Arachidonic acid (AA) is metabolized in human platelets by two main pathways: via cyclooxygenase (COX-1) to prostaglandins and thromboxane (TX)A2 and via 12-lipoxygenase (12-LOX) to 12(S)-hydroxyeicosatetraenoic acid (12(S)-HETE). While COX products are known to regulate platelet reactivity, the role of 12-LOX metabolites is still controversial. To better understand the platelet enzymatic pathways, we developed a simple and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay for the simultaneous measurement of both platelet metabolites in human serum. After the addition of deuterated d4-TXB2 and d8-12(S)-HETE as internal standards and the solid-phase extraction of serum samples, analytes were resolved using reversed-phase C18 column and quantified using negative ion electrospray ionization-tandem mass spectrometry. Intra and interassay imprecisions were less than 10% for both analytes. The lower limits of quantification were 0.244ng/ml and 0.976ng/ml for TXB2 and 12(S)-HETE, respectively. This method was applied to measure platelet metabolites in healthy subjects (n=35). LC-MS/MS allows rapid, simultaneous, sensitive and accurate quantification of both platelet AA products in human serum with a small sample volume required and a minimal sample preparation.

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.

Rapid and simultaneous quantitation of prostanoids by UPLC-MS/MS in rat brain

The metabolites of arachidonic acid (AA) produced from the cyclooxygenase (COX) pathway, collectively termed as prostanoids, and from the CYP 450 pathway, eicosanoids, have been implicated in various neuro-degenerative and neuroinflammatory diseases. This study developed a quantitative UPLC-MS/MS method to simultaneously measure 11 prostanoids including prostaglandins and cyclopentenone metabolites in the rat brain cortical tissue. Linear calibration curves ranging from 0.104 to 33.3ng/ml were validated. The inter-day and intra-day variance for all metabolites was less than 15%. The extraction recovery efficiency and matrix (deionized water) effects measured at 12.5ng/ml (750pg on column) ranged from 88 to 100% and 3 to 14%, respectively, with CV% values below 20%. Additionally, applying the processing and extraction conditions of this method to our previous CYP450 eicosanoids method resulted in overall improvement in extraction recovery and reduction in matrix effects at low (0.417ng/ml) and high (8.33ng/ml) concentrations. In rat brain cortical tissue samples, concentrations of prostanoids ranged from 10.2 to 937pmol/g wet tissue and concentration of eicosanoids ranged from 2.23 to 793pmol/g wet tissue. These data demonstrate that the successive measurement of prostanoids and eicosanoids from a single extracted sample of rat brain tissue can be achieved with a UPLC-MS/MS system and that this method is necessary for evaluation of these metabolites to delineate their role in various neuroinflammatory and cerebrovascular disorders.

Endogenous synthesis of n-3 PUFA modifies fatty acid composition of kidney phospholipids and eicosanoid levels in the fat-1 mouse

The goal of the present study was to determine whether endogenous synthesis of n-3 polyunsaturated fatty acids (PUFA) in the fat-1 mouse is comparable to fish oil feeding with respect to kidney n-3 PUFA composition and eicosanoid levels. Wild-type and heterozygous fat-1 mice, capable of synthesizing n-3 PUFA endogenously, were given diets enriched in either n-3 or n-6 PUFA in a 2×2 factorial design and terminated after 12 weeks. Kidney phospholipid fatty acids were analysed by gas chromatography. Kidney eicosanoids were analysed by liquid chromatography tandem mass spectrometry. Relative to control mice fed n-6 PUFA, n-3 PUFA fed and fat-1 mice had higher levels of kidney phospholipid n-3 PUFA, and lower levels of n-6 PUFA and eicosanoids. However, mice fed n-3 PUFA mice had higher levels of n-3 PUFA and lower levels of eicosanoids as compared to fat-1 mice. In conclusion, diet feeding had a greater impact on kidney fatty acid composition and eicosanoid levels than the genetic effect of the fat-1 gene. However, the fat-1 mouse remains a close approximation that can be used as a complementary model to study the role of n-3 PUFA in the kidney.

Lipidomics of oxidized polyunsaturated fatty acids

Lipid mediators are produced from the oxidation of polyunsaturated fatty acids through enzymatic and free radical-mediated reactions. When subject to oxygenation via cyclooxygenases, lipoxygenases, and cytochrome P450 monooxygenases, polyunsaturated fatty acids give rise to an array of metabolites including eicosanoids, docosanoids, and octadecanoids. These potent bioactive lipids are involved in many biochemical and signaling pathways, with inflammation being of particular importance. Moreover, because they are produced by more than one pathway and substrate, and are present in a variety of biological milieus, their analysis is not always possible with conventional assays. Liquid chromatography coupled to electrospray mass spectrometry offers a versatile and sensitive approach for the analysis of bioactive lipids, allowing specific and accurate quantitation of multiple species present in the same sample. Here we explain the principles of this approach to mediator lipidomics and present detailed protocols for the assay of enzymatically produced oxygenated metabolites of polyunsaturated fatty acids that can be tailored to answer biological questions or facilitate assessment of nutritional and pharmacological interventions.

Role of arachidonic acid metabolites on the control of non-differentiated intestinal epithelial cell growth

Increasingly evidence indicates that enzymes, receptors and metabolites of the arachidonic acid (AA) cascade play a role in intestinal epithelial cell proliferation and colorectal tumorigenesis. However, the information available does not provide a complete picture and contains a number of discrepancies. For this reason it might be appropriate a thorough study into the impacts of the AA cascade on intestinal epithelial cell growth. Our data show that non-differentiated Caco-2 cells cultured with 10% fetal bovine serum (FBS) synthesize appreciable amounts of prostaglandin E2 (PGE2), leukotriene B4 (LTB4) and 5-, 12 and 15-hydroxyeicosatetraenoic acid (HETE) but not LTD4, 20-HETE and epoxyeicosatrienoic acids. We also found that inhibitors of PGE2, LTB4 and 5-, 12-, 15-HETE synthesis as well as receptor antagonists of PGE2 and LTB4 blocked Caco-2 cell growth and DNA synthesis induced by 10% FBS without cytotoxic or apoptotic activity. Interestingly, PGE2, LTB4 and 5-, 12- and 15-HETE at concentrations reached in 10% FBS Caco-2 cultures (1-10nM) were able to induce Caco-2 cell growth and DNA synthesis. This was due to the interaction of PGE2 with EP1 and EP4 receptors and LTB4 and HETEs with BLT1 and BLT2 receptors. Moreover, we provide evidence that PGE2 stimulates several cell signaling pathways such as ERK, P38α, CREB and GSKβ/β-catenin involved in the regulation of Caco-2 growth. Finally, we provide evidence that the mitogenic effects of LTB4 and HETEs can be dependent, at least in part, on PGE2 synthesis.

A simple and robust UPLC-SRM/MS method to quantify urinary eicosanoids

Eicosanoids are key mediators and regulators of inflammation and oxidative stress often used as biomarkers for diseases and pathological conditions such as cardiovascular and pulmonary diseases and cancer. Analytically, comprehensive and robust quantification of different eicosanoid species in a multi-method approach is problematic because most of these compounds are relatively unstable and may differ in their chemical properties. Here we describe a novel ultra-performance liquid chromatography-selected reaction monitoring mass spectroscopy (UPLC-SRM/MS) method for simultaneous quantification of key urinary eicosanoids, including the prostaglandins (PG) tetranor PGE-M, 8-iso-, and 2,3-dinor-8-iso-PGF(2α); the thromboxanes (TXs) 11-dehydro- and 2,3-dinor-TXB₂; leukotriene E₄; and 12-hydroxyeicosatetraenoic acid. In contrast to previous methods, which used time-consuming and complex solid phase extraction, we prepared samples with a simple liquid/liquid extraction procedure. Because collision-induced dissociation produced characteristic product ions for all analytes, no derivatization step for SRM/MS analysis was necessary. Analytes were separated with a short UPLC reversed-phase column (1.7 µm particles), allowing shorter run times than conventional HPLC columns. The method was validated and applied to human urine samples showing excellent precision, accuracy, detection limits, and robustness. In summary, the developed method allows robust and sensitive profiling of urinary eicosanoid species, making it a useful and valuable tool for biomarker profiling in clinical/toxicological studies.