Characterization and identification of cytochrome P450 metabolites of arachidonic acid released by human peritoneal macrophages obtained from the pouch of Douglas

Methods of the Analysis of Oxylipins in Biological Samples

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 In turn, the old analysis methods have been replaced by new approaches based on mass spectrometry (MS) coupled with liquid chromatography (LC) and gas chromatography (GC), and the best of these methods allow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

A stable method for routine analysis of oxylipins from dried blood spots using ultra-high performance liquid chromatography-tandem mass spectrometry

Oxylipins are biologically important lipid mediators that are derived enzymatically from polyunsaturated fatty acids (PUFA) and have a major role in regulating inflammatory processes. The currently available methods for measuring oxylipins from human biological samples have limitations, which restricts their use in large studies. We have developed a novel method for measuring 21 oxylipins from dried blood spot (DBS) using ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) and stable isotope dilution analysis. Our new method is reproducible and precise and enables the high throughput analysis and quantitation of bioactive oxylipins in small volumes of blood. In the future, this new method can be readily applied to measure oxylipins in large studies. Abstract Oxylipins are downstream lipid mediators enzymatically-produced from polyunsaturated fatty acids (PUFA) that are implicated as the biological effectors of these fatty acids. Recently reported methods for the quantitation of oxylipins require complex extraction procedures. In this study, we report the development and validation of a novel system for the quantitation of 21 individual oxylipins from a dried blood spot (DBS) using ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) and stable isotope dilution analysis. Linearity and precision of the method were determined and the stabilities of the 12 most abundant oxylipins were tested during 2 months of storage at room temperature, after being spiked into blood and prepared as DBS on PUFAcoat™ paper. Responses were linear across the concentration range analysed for all oxylipins (r² values ranged from 0.953 to 0.998). Intra-day and inter-day variations were ≤16% for all oxylipins. Recovery of oxylipins from the DBS ranged from 80 - 115%. The 12 spiked oxylipins were stable for 2 months when stored as DBS at room temperature. Our method is reproducible and precise, and provides the opportunity to accurately quantitate these oxylipins in a small sample volume.

Cytochrome P450 2J2: distribution, function, regulation, genetic polymorphisms and clinical significance

Cytochrome P450 2J2 (CYP2J2) is an enzyme mainly found in human extrahepatic tissues, with predominant expression in the cardiovascular systems and lower levels in the intestine, kidney, lung, pancreas, brain, liver, etc. During the past 15 years, CYP2J2 has attracted much attention for its epoxygenase activity in arachidonic acid (AA) metabolism. It converts AA to four epoxyeicosatrienoic acids (EETs) that have various biological effects, especially in the cardiovascular systems. In recent publications, CYP2J2 is shown highly expressed in various human tumor cells, and its EET metabolites are demonstrated to implicate in the pathologic development of human cancers. CYP2J2 is also a human CYP that involved in phase I xenobiotics metabolism. Antihistamine drugs and many other compounds were identified as the substrates of CYP2J2, and studies have demonstrated that these substrates have a broad structural diversity. CYP2J2 is found not readily induced by known P450 inducers; however, its expression could be regulated in some pathological conditions, might through the activator protein-1(AP-1), the AP-1-like element and microRNA let-7b. Several genetic mutations in the CYP2J2 gene have been identified in humans, and some of them have been shown to have potential associations with some diseases. With the increasing awareness of its roles in cancer disease and drug metabolism, studies about CYP2J2 are still going on, and various inhibitors of CYP2J2 have been determined. Further studies are needed to delineate the roles of CYP2J2 in disease pathology, drug development and clinical practice.

Inducible CYP2J2 and its product 11,12-EET promotes bacterial phagocytosis: a role for CYP2J2 deficiency in the pathogenesis of Crohn's disease?

The epoxygenase CYP2J2 has an emerging role in inflammation and vascular biology. The role of CYP2J2 in phagocytosis is not known and its regulation in human inflammatory diseases is poorly understood. Here we investigated the role of CYP2J2 in bacterial phagocytosis and its expression in monocytes from healthy controls and Crohns disease patients. CYP2J2 is anti-inflammatory in human peripheral blood monocytes. Bacterial LPS induced CYP2J2 mRNA and protein. The CYP2J2 arachidonic acid products 11,12-EET and 14,15-EET inhibited LPS induced TNFα release. THP-1 monocytes were transformed into macrophages by 48h incubation with phorbol 12-myristate 13-acetate. Epoxygenase inhibition using a non-selective inhibitor SKF525A or a selective CYP2J2 inhibitor Compound 4, inhibited E. coli particle phagocytosis, which could be specifically reversed by 11,12-EET. Moreover, epoxygenase inhibition reduced the expression of phagocytosis receptors CD11b and CD68. CD11b also mediates L. monocytogenes phagocytosis. Similar, to E. coli bioparticle phagocytosis, epoxygenase inhibition also reduced intracellular levels of L. monocytogenes, which could be reversed by co-incubation with 11,12-EET. Disrupted bacterial clearance is a hallmark of Crohn’s disease. Unlike macrophages from control donors, macrophages from Crohn’s disease patients showed no induction of CYP2J2 in response to E. coli. These results demonstrate that CYP2J2 mediates bacterial phagocytosis in macrophages, and implicates a defect in the CYP2J2 pathway may regulate bacterial clearance in Crohn’s disease.

Anti-inflammatory effects of epoxyeicosatrienoic acids

Epoxyeicosatrienoic acids (EETs) are generated by the activity of both selective and also more general cytochrome p450 (CYP) enzymes on arachidonic acid and inactivated largely by soluble epoxide hydrolase (sEH), which converts them to their corresponding dihydroxyeicosatrienoic acids (DHETs). EETs have been shown to have a diverse range of effects on the vasculature including relaxation of vascular tone, cellular proliferation, and angiogenesis as well as the migration of smooth muscle cells. This paper will highlight the growing evidence that EETs also mediate a number of anti-inflammatory effects in the cardiovascular system. In particular, numerous studies have demonstrated that potentiation of EET activity using different methods can inhibit inflammatory gene expression and signalling pathways in endothelial cells and monocytes and in models of cardiovascular diseases. The mechanisms by which EETs mediate their effects are largely unknown but may include direct binding to peroxisome proliferator-activated receptors (PPARs), G-protein coupled receptors (GPCRs), or transient receptor potential (TRP) channels, which initiate anti-inflammatory signalling cascades.

Epoxides and soluble epoxide hydrolase in cardiovascular physiology

Epoxyeicosatrienoic acids (EETs) are arachidonic acid metabolites that importantly contribute to vascular and cardiac physiology. The contribution of EETs to vascular and cardiac function is further influenced by soluble epoxide hydrolase (sEH) that degrades EETs to diols. Vascular actions of EETs include dilation and angiogenesis. EETs also decrease inflammation and platelet aggregation and in general act to maintain vascular homeostasis. Myocyte contraction and increased coronary blood flow are the two primary EET actions in the heart. EET cell signaling mechanisms are tissue and organ specific and provide significant evidence for the existence of EET receptors. Additionally, pharmacological and genetic manipulations of EETs and sEH have demonstrated a contribution for this metabolic pathway to cardiovascular diseases. Given the impact of EETs to cardiovascular physiology, there is emerging evidence that development of EET-based therapeutics will be beneficial for cardiovascular diseases.

Endogenous epoxygenases are modulators of monocyte/macrophage activity

Background

Arachidonic acid is metabolized through three major metabolic pathways, the cyclooxygenase, lipoxygenase and CYP450 enzyme systems. Unlike cyclooxygenase and lipoxygenases, the role of CYP450 epoxygenases in monocyte/macrophage-mediated responses is not known.

Methodology/Principal Findings

When transfected in vitro, CYP2J2 is an efficient activator of anti-inflammatory pathways through the nuclear receptor peroxisome proliferator-activated receptor (PPAR) α. Human monocytes and macrophages contain PPARα and here we show they express the epoxygenases CYP2J2 and CYP2C8. Inhibition of constitutive monocyte epoxygenases using the epoxygenase inhibitor SKF525A induces cyclooxygenase (COX)-2 expression and activity, and the release of TNFα, and can be reversed by either add back of the endogenous epoxygenase products and PPARα ligand 11,12- epoxyeicosatrienoic acid (EET) or the addition of the selective synthetic PPARα ligand GW7647. In alternatively activated (IL-4-treated) monocytes, in contrast to classically activated cells, epoxygenase inhibition decreased TNFα release. Epoxygenases can be pro-inflammatory via superoxide anion production. The suppression of TNFα by SKF525A in the presence of IL-4 was associated with a reduction in superoxide anion generation and reproduced by the superoxide dismutase MnCl₂. Similar to these acute activation studies, in monocyte derived macrophages, epoxygenase inhibition elevates M1 macrophage TNFα mRNA and further decreases M2 macrophage TNFα.

Conclusions/Significance

In conclusion, epoxygenase activity represents an important endogenous pathway which limits monocyte activation. Moreover endogenous epoxygenases are immuno-modulators regulating monocyte/macrophage activation depending on the underlying activation state.

Profiling the regulatory lipids: another systemic way to unveil the biological mystery

PURPOSE OF REVIEW

The regulatory lipids are a class of bioactive lipids which regulate various important biological processes. Profiling these regulatory lipids is an attractive method to understand the role of these metabolites. This is especially true because most of these regulatory lipids are derived from several important pharmacological targets: cyclooxygenase, lipoxygenase, and cytochrome P450 enzymes. This review highlights the development of methods to profile these regulatory lipids and the recent publications employing these profiling methods.

RECENT FINDINGS

The recent development of methods for the profiling of regulatory lipids target two different directions: to expand coverage for discovery studies (fingerprinting) and to make the quantitative method more accurate, sensitive, and faster for diagnostic or more detailed studies. Recent applications of these profiling methods including assessment of in-vivo drug engagement, pathways crosstalk, and possible mechanisms for side-effects of a withdrawn anti-inflammatory drug rofecoxib are also reviewed here.

SUMMARY

The profiling of regulatory lipids is a useful tool for many investigations. The breadth of coverage, throughput limits with detection, and reproducibility of quantitation are being improved. The resulting data will assist with fundamental investigation, disease biomarker discovery, drug discovery, and drug development.

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.

Expression of the cytochrome P450 epoxygenase CYP2J2 in human monocytic leukocytes

CYP2J2 is one of the cytochrome P450 epoxygenases involved in the metabolism of arachidonic acid. CYP2J2 has been identified in several tissues, especially cardiovascular tissues. CYP2J2 has cardiovascular effects, as epoxyeicosatrienoic acid, one of its metabolites, has anti-inflammatory and vasodilative activities. We investigated the expression of CYP2J2 in human leukocytes using reverse transcription-polymerase chain reaction, immunoblotting and immunostaining. Human monocytic cells, but not human neutrophils, exhibited constitutive expression of CYP2J2. Furthermore, the expression of CYP2J2 mRNA increased when the human monocytic cell line THP-1 cells and human monocytes were stimulated with phorbol 12-myristate 13-acetate and macrophage-colony stimulating factor in combination with granulocyte/macrophage-colony stimulating factor, respectively. These results suggest that expression of CYP2J2 was up-regulated when human monocytes differentiated into macrophages and that human monocytic cells and macrophages have a pathway to metabolize arachidonic acid using CYP epoxygenases.

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

A reversed-phase liquid chromatography negative ion electrospray tandem mass spectrometry (LC/ESI-MS/MS) method was developed and validated to quantify a range of physiologically relevant eicosanoids, including 5,6-, 8,9-, 11,12-, and 14,15-epoxyeicosatrienoic acids (EETs); 5-, 8-, 9-, 12-, and 15-hydroxyeicosatetraenoic acids (HETEs), and 5,6-, 8,15-, and 12,20-dihydroxyeicosatetraenoic acids (DiHETEs) in human intrauterine tissues. A solid-phase extraction method was employed to extract the eicosanoids, and gradient LC separation was performed on a Kromasil C(18) column. Mass spectrometric detection was performed by multiple reaction monitoring over a 31-min run time. The calibration curves were linear over the range of 4-400pmol/g tissue, and the intra- and interday precision and accuracy were within a coefficient of variation of 2.0 to 27.4% and 4.6 to 17.9%, respectively. The lower limit of quantitation was 1.0pmol/g tissue. The method was applied successfully to the characterization and quantitation of eicosanoids in the different compartments of human intrauterine tissues. Our results demonstrate significantly greater amounts of HETEs than of either the EETs or DiHETEs (P<0.001), irrespective of tissue type. Specifically, the metabolite 12-HETE was significantly more abundant (P<0.001) than all other HETEs. Of the EET metabolites, 5,6-EET predominated (P<0.001). A significant negative correlation between EETs and HETEs for all tissues (rho=-0.390, P<0.001) was identified, implying a biological feedback mechanism between these two arachidonate metabolite classes.