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Hepoxilins are lipid signaling molecules derived from arachidonic acid through the 12-lipoxygenase pathway. These trans-epoxy hydroxy eicosanoids play a role in a variety of physiological processes, including inflammation, neurotransmission, and formation of skin barrier function. Mammalian hepoxilin hydrolase, partly purified from rat liver, has earlier been reported to degrade hepoxilins to trioxilins. Here, we report that hepoxilin hydrolysis in liver is mainly catalyzed by soluble epoxide hydrolase (sEH): i) purified mammalian sEH hydrolyses hepoxilin A₃ and B₃ with a V(max) of 0.4-2.5 μmol/mg/min; ii) the highly selective sEH inhibitors N-adamantyl-N'-cyclohexyl urea and 12-(3-adamantan-1-yl-ureido) dodecanoic acid greatly reduced hepoxilin hydrolysis in mouse liver preparations; iii) hepoxilin hydrolase activity was abolished in liver preparations from sEH(-/-) mice; and iv) liver homogenates of sEH(-/-) mice show elevated basal levels of hepoxilins but lowered levels of trioxilins compared with wild-type animals. We conclude that sEH is identical to previously reported hepoxilin hydrolase. This is of particular physiological relevance because sEH is emerging as a novel drug target due to its major role in the hydrolysis of important lipid signaling molecules such as epoxyeicosatrienoic acids. sEH inhibitors might have undesired side effects on hepoxilin signaling.

Chemical mutagenesis of the phototrophic green microalga Parietochloris incisa, producing high amounts of arachidonic acid (ARA), resulted in selection of a mutant deficient in ARA and rich in dihomo-γ-linolenic acid (DGLA) and thus ∆5 desaturase defective. The mutagenesis produced a nonsense mutation in the ∆5 desaturase gene, resulting in alteration of the 62nd codon TGG into a stop codon. Thus, the polypeptide encoded by the mutant ∆5 desaturase gene is severely truncated and biochemically inactive, as was confirmed by heterologous expression in Saccharomyces cerevisiae. The mutation did not affect the oleogenic nature of the strain, and the total fatty acid content in the mutant biomass reached 39%, in comparison to 34% in the wild type, after 14 days of nitrogen starvation; biomass yields amounted to 5.1 and 3.6 g/l, respectively. While in the wild type, DGLA and ARA comprised about 1% and 58% of total fatty acids, respectively; the mutation annulled ARA almost totally but increased the DGLA proportion to 32% only with a corresponding increase in the proportion of oleic acid. Consequently, DGLA comprised 12.3% of dry weight, in comparison to 19.4% ARA in the wild type. The expression profiles of the genes coding enzymes involved in VLC-PUFA biosynthesis, ∆12, ∆6, ∆5 desaturases and ∆6 PUFA elongase, during nitrogen starvation, were compared. The transcript levels of all four genes, which were coordinately up-regulated in the wild type, appeared to be drastically reduced in the mutant, indicating their co-regulated transcription.

Cardiorenal syndromes were defined and classified recently, but the mechanism of chronic renocardiac syndrome remains disputed. Theories about chronic renocardiac syndrome cannot offer a convincing explanation for it. As a result, the current therapies of chronic renocardiac syndrome do not contribute to a satisfied prognosis. Epoxyeicosatrienoic acids, the products of arachidonic acid metabolized by cytochrome P450 enzymes, play an important role in the maintenance of renal hemodynamics, and regulation of renal, cardiac, and vascular function with antihypertensive and anti-inflammatory properties. It is well documented that down-regulation of epoxyeicosatrienoic acids might be involved in alterations in various pathophysiological states, including hypertension, uremia and hepatorenal syndrome. Likewise, epoxyeicosatrienoic acids were reduced in heart failure and renal dysfunction. This leads to the proposed hypothesis that epoxyeicosatrienoic acids down-regulation may be the novel mechanism of chronic renocardiac syndrome. These findings suggest that manipulation of epoxyeicosatrienoic acid levels could be a novel pharmacological therapy strategy for chronic renocardiac syndrome., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

The eicosanoids 20-hydroxyeicosatetraenoic acid (20-HETE) and epoxyeicosatrienoic acids (EETs), which are generated from the metabolism of arachidonic acid by cytochrome P450 (CYP) enzymes, possess a wide array of biological actions, including the regulation of blood flow to organs. 20-HETE and EETs are generated in various cell types in the brain and cerebral blood vessels, and contribute significantly to cerebral blood flow autoregulation and the coupling of regional brain blood flow to neuronal activity (neurovascular coupling). Investigations are beginning to unravel the molecular and cellular mechanisms by which these CYP eicosanoids regulate cerebral vascular function and the changes that occur in pathological states. Intriguingly, 20-HETE and the soluble epoxide hydrolase (sEH) enzyme that regulates EET levels have been explored as molecular therapeutic targets for cerebral vascular diseases. Inhibition of 20-HETE, or increasing EET levels by inhibiting the sEH enzyme, decreases cerebral damage following stroke. The improved outcome following cerebral ischaemia is a consequence of improving cerebral vascular structure or function and protecting neurons from cell death. Thus, the CYP eicosanoids are key regulators of cerebral vascular function and novel therapeutic targets for cardiovascular diseases and neurological disorders.

Elevated concentrations of aldosterone are associated with several cardiovascular diseases. Angiotensin II (Ang II) increases aldosterone secretion and adrenal blood flow. This concurrent increase in steroidogenesis and adrenal blood flow is not understood. We investigated the role of zona glomerulosa (ZG) cells in the regulation of vascular tone of bovine adrenal cortical arteries by Ang II. ZG cells enhanced endothelium-dependent relaxations to Ang II. The ZG cell-dependent relaxations to Ang II were unchanged by removing the endothelium-dependent response to Ang II. These ZG cell-mediated relaxations were ablated by cytochrome P450 inhibition, epoxyeicosatrienoic acid (EET) antagonism, and potassium channel blockade. Analysis of ZG cell EET production by liquid chromatography/mass spectrometry demonstrated an increase in EETs and dihydroxyeicosatrienoic acids with Ang II stimulation. These EETs and dihydroxyeicosatrienoic acids produced similar concentration-dependent relaxations of adrenal arteries, which were attenuated by EET antagonism. Whole-cell potassium currents of adrenal artery smooth muscle cells were increased by Ang II stimulation in the presence of ZG cells but decreased in the absence of ZG cells. This increase in potassium current was abolished by iberiotoxin. Similarly, 14,15-EET induced concentration-dependent increases in potassium current, which was abolished by iberiotoxin. ZG cell aldosterone release was not directly altered by EETs. These data suggest that Ang II stimulates ZG cells to release EETs and dihydroxyeicosatrienoic acids, resulting in potassium channel activation and relaxation of adrenal arteries. This provides a mechanism by which Ang II concurrently increases adrenal blood flow and steroidogenesis.

Airway neutrophil infiltration is a pathological hallmark observed in multiple lung diseases including pneumonia and cystic fibrosis. Bacterial pathogens such as Pseudomonas aeruginosa instigate neutrophil recruitment to the air space. Excessive accumulation of neutrophils in the lung often contributes to tissue destruction. Previous studies have unveiled hepoxilin A(3) as the key molecular signal driving neutrophils across epithelial barriers. The eicosanoid hepoxilin A(3) is a potent neutrophil chemoattractant produced by epithelial cells in response to infection with P. aeruginosa. The enzyme phospholipase A(2) liberates arachidonic acid from membrane phospholipids, the rate-limiting step in the synthesis of all eicosanoids, including hepoxilin A(3). Once generated, aracidonic acid is acted upon by multiple cyclooxygenases and lipoxygenases producing an array of functionally diverse eicosanoids. Although there are numerous phospholipase A(2) isoforms capable of generating arachidonic acid, the isoform most often associated with eicosanoid generation is cytoplasmic phospholipase A(2)α. In the current study, we observed that the cytoplasmic phospholipase A(2)α isoform is required for mediating P. aeruginosa-induced production of certain eicosanoids such as prostaglandin E(2). However, we found that neutrophil transepithelial migration induced by P. aeruginosa does not require cytoplasmic phospholipase A(2)α. Furthermore, P. aeruginosa-induced hepoxilin A(3) production persists despite cytoplasmic phospholipase A(2)α suppression and generation of the 12-lipoxygenase metabolite 12-HETE is actually enhanced in this context. These results suggest that alterative phospholipase A(2) isoforms are utilized to synthesize 12-lipoxygenase metabolites. The therapeutic implications of these findings are significant when considering anti-inflammatory therapies based on targeting eicosanoid synthesis pathways.

Hypoxia induces the constriction of pulmonary resistance arteries, which results in the redistribution of blood from poor to better ventilated areas, thus optimizing its oxygenation. Many different oxygen-sensing mechanisms have been proposed to regulate this process, including cytochrome P450 enzymes. These enzymes, which convert substrates such as arachidonic acid into bioactive epoxides (the epoxyeicosatrienoic acids [EETs]), are highly expressed in the lung as is the soluble epoxide hydrolase which metabolizes the epoxides to their less active diols. The EETs play a well-documented role as endothelium-derived vasodilators in the systemic vasculature, but in the pulmonary circulation, they are generated in vascular smooth muscle cells and potentiate vasoconstriction. Preventing the breakdown of 11,12-EET by the inhibition or genetic deletion of the soluble epoxide hydrolase strongly augments the response to hypoxia. Mechanistically, 11,12-EET potentiates the contractile response by recruiting transient receptor potential C6 channels to caveolae. Indeed, neither 11,12-EET nor hypoxia is able to elicit pulmonary vasoconstriction in TRPC6 knockout mice. The cytochrome and soluble epoxide hydrolase enzymes are also implicated in the vascular remodeling associated with chronic hypoxia and pulmonary hypertension. Thus, targeting this pathway may be in an attractive new therapeutic approach to treat this incapacitating disease.

Hepoxilins are epoxy alcohols synthesized through the 12-lipoxygenase (12-LO) pathway in animal cells. The epidermis is the principal source of hepoxilins in humans. Here we report on the formation of novel hepoxilin regioisomers formed by the 15-LO pathway in human cells. The Hodgkin lymphoma cell line L1236 possesses high 15-lipoxygenase-1 (15-LO-1) activity and incubation of L1236 cells with arachidonic acid led to the formation of 11(S)-hydroxy-14(S),15(S)-epoxy 5(Z),8(Z),12(E) eicosatrienoic acid (14,15-HxA(3) 11(S)) and 13(R)-hydroxy-14(S),15(S)-epoxy 5(Z),8(Z),11(Z) eicosatrienoic acid (14,15-HxB(3) 13(R)). In addition, two hitherto unidentified products were detected and these products were collected and analyzed by positive ion electrospray tandem mass spectrometry. These metabolites were identified as 11(S),15(S)-dihydroxy-14(R)-glutathionyl-5(Z),8(Z),12(E)-eicosatrienoic acid (14,15-HxA(3)-C) and 11(S),15(S)-dihydroxy-14(R)-cysteinyl-glycyl-5(Z),8(Z),12(E)-eicosatrienoic acid (14,15-HxA(3)-D). Incubation of L1236 cells with synthetic 14,15-HxA(3) 11(S) also led to the formation of 14,15-HxA(3)-C and 14,15-HxA(3)-D. Several soluble glutathione transferases, in particular GST M1-1 and GST P1-1, were found to catalyze the conversion of 14,15-HxA(3) to 14,15-HxA(3)-C. L1236 cells produced approximately twice as much eoxins as cysteinyl-containing hepoxilins upon stimulation with arachidonic acid. Human eosinophils, nasal polyps and dendritic cells selectively formed 14,15-HxA(3) 11(S) and 14,15-HxB(3) 13(R) stereoisomers, but not cysteinyl-containing hepoxilins, after stimulation with arachidonic acid. Furthermore, purified recombinant 15-LO-1 alone catalyzed the conversion of arachidonic acid to 14,15-HxA(3) 11(S) and 14,15-HxB(3) 13(R), showing that human 15-LO-1 possesses intrinsic 14,15-hepoxilin synthase activity.

Pulmonary arterial hypertension (PAH) is a life-threatening disease that leads to progressive pulmonary hypertension, right heart failure, and death. Endothelial dysfunction and inflammation were implicated in the pathogenesis of PAH. Epoxyeicosatrienoic acids (EETs), products of the cytochrome P450 epoxygenase metabolism of arachidonic acid, are potent vasodilators that possess anti-inflammatory and other protective properties in endothelial cells. We investigated whether gene delivery with the human cytochrome P450 epoxygenase 2J2 (CYP2J2) ameliorates monocrotaline (MCT)-induced pulmonary hypertension in rats. Significant pulmonary hypertension developed 3 weeks after the administration of MCT, but gene therapy with CYP2J2 significantly attenuated the development of pulmonary hypertension and pulmonary vascular remodeling, without causing changes in systemic arterial pressure or heart rate. These effects were associated with increased pulmonary endothelial NO synthase (eNOS) expression and its activity, inhibition of inflammation in the lungs, and transforming growth factor (TGF)-β/type II bone morphogenetic protein receptor (BMPRII)-drosophila mothers against decapentaplegic proteins (Smads) signaling. Collectively, these data suggest that gene therapy with CYP2J2 may have potential as a novel therapeutic approach to this progressive and oftentimes lethal disorder.

Human mesenchymal stem cells (MSCs) expressed substantial levels of CYP2J2, a major CYP450 involved in epoxyeicosatrienoic acid (EET) formation. MSCs synthesized significant levels of EETs (65.8 ± 5.8 pg/mg protein) and dihydroxyeicosatrienoic acids (DHETs) (15.83 ± 1.62 pg/mg protein), suggesting the presence of soluble epoxide hydrolase (sEH). The addition of an sEH inhibitor to MSC culture decreased adipogenesis. EETs decreased MSC-derived adipocytes in a concentration-dependent manner, 8,9- and 14,15-EET having the maximum reductive effect on adipogenesis. We examined the effect of 12-(3-hexylureido)dodec-8(Z)-enoic acid, an EET agonist, on MSC-derived adipocytes and demonstrated an increased number of healthy small adipocytes, attenuated fatty acid synthase (FAS) levels (P < 0.01), and reduced PPARγ, C/EBPα, FAS, and lipid accumulation (P < 0.05). These effects were accompanied by increased levels of heme oxygenase (HO)-1 and adiponectin (P < 0.05), and increased glucose uptake (P < 0.05). Inhibition of HO activity or AKT by tin mesoporphyrin (SnMP) and LY2940002, respectively, reversed EET-induced inhibition of adipogenesis, suggesting that activation of the HO-1-adiponectin axis underlies EET effect in MSCs. These findings indicate that EETs decrease MSC-derived adipocyte stem cell differentiation by upregulation of HO-1-adiponectin-AKT signaling and play essential roles in the regulation of adipocyte differentiation by inhibiting PPARγ, C/EBPα, and FAS and in stem cell development. These novel observations highlight the seminal role of arachidonic acid metabolism in MSCs and suggest that an EET agonist may have potential therapeutic use in the treatment of dyslipidemia, diabetes, and the metabolic syndrome.

The metabolism of arachidonic acid (AA) to epoxyeicosatrienoic acids (EETs) is thought to be mediated primarily by the cytochromes P450 (P450s) from the 2 family (2C9, 2C19, 2D6, and 2J2). In contrast, P450s of the 4 family are primarily involved in omega oxidation of AA (4A11 and 4A22). The ability to determine enantioselective formation of the regioisomeric EETs is important in order to establish their potential biological activities and to asses which P450 isoforms are involved in their formation. It has been extremely difficult to analyze individual EET enantiomers in biological fluids because they are present in only trace amounts and they are extremely difficult to separate from each other. In addition, the deuterium-labeled internal standards that are commonly used for stable isotope dilution liquid chromatography/mass spectrometry (LC/MS) analyses have different LC retention times when compared with the corresponding protium forms. Therefore, quantification by LC/MS-based methodology can be compromised by differential suppression of ionization of the closely eluting isomers. We report the preparation of [(13)C(20)]-EET analog internal standards and the use of a validated high-sensitivity chiral LC/electron capture atmospheric pressure chemical ionization (ECAPCI)-MS method for the trace analysis of endogenous EETs as their pentafluorobenzyl (PFB) ester derivatives. The assay was then used to show the exquisite enantioselectivity of P4502C19-, P4502D6-, P4501A1-, and P4501B1-mediated conversion of AA into EETs and to quantify the enantioselective formation of EETs produced by AA metabolism in a mouse epithelial hepatoma (Hepa) cell line., (2010 John Wiley & Sons, Ltd.)

Lipoxygenase, cyclo-oxygenase and cytochrome P450 (CYP) products of arachidonic acid (AA) are implicated in pulmonary vasoregulation. The CYP-mediated epoxyeicosatrienoates (EETs) have been described previously as the predominant eicosanoids in human lungs upon stimulation with the Ca(2+) ionophore A23187. In this study, we challenged perfused human lungs with two microbial agents: Escherichia coli haemolysin (ECH) and formyl-methionyl-leucyl-phenylalanine (fMLP). Both stimuli elicited pronounced generation of leukotrienes (LTs), hydroxyeicosatetraenoic acids (HETEs), prostanoids (PTs) and EETs/dihydroxyeicosatrienoic acids (DHETs), as assessed by liquid chromatography-mass spectrometry, paralleled by pulmonary artery pressor response and lung oedema formation. The maximum buffer concentrations of EETs/DHETs surpassed those of LTs plus HETEs and PTs by a factor of four (ECH) or three (AA/fMLP). Dual 5-lipoxygenase/cyclo-oxygenase inhibition caused pronounced reduction of AA/fMLP-induced LT/PT synthesis and oedema formation but only limited attenuation of pulmonary vasoconstriction, while inhibition of CYP epoxygenase clearly attenuated AA/fMLP-induced EET/DHET synthesis and vasoconstriction but not oedema formation, suggesting a major contribution of LTs/PTs to vascular leakage and of EETs/DHETs to pressor response. Consequently, generation of EETs/DHETs is greater than that of LTs plus HETEs and PTs in ex vivo perfused human lungs upon microbial challenge suggesting a substantial contribution of these mediators to inflammatory-infectious pulmonary injury.

High dietary potassium stimulates the renal expression of cytochrome P450 (CYP) epoxygenase 2C23, which metabolizes arachidonic acid (AA). Because the AA metabolite 11,12-epoxyeicosatrienoic acid (11,12-EET) can inhibit the epithelial sodium channel (ENaC) in the cortical collecting duct, we tested whether dietary potassium modulates ENaC function. High dietary potassium increased 11,12-EET in the isolated cortical collecting duct, an effect mimicked by inhibiting the angiotensin II type I receptor with valsartan. In patch-clamp experiments, a high potassium intake or treatment with valsartan enhanced AA-induced inhibition of ENaC, an effect mediated by a CYP-epoxygenase-dependent pathway. Moreover, high dietary potassium and valsartan each augmented the inhibitory effect of 11,12-EET on ENaC. Liquid chromatography/mass spectrometry showed that the rate of EET conversion to dihydroxyeicosatrienoic acids (DHET) was lower in renal tissue obtained from rats on a high-potassium diet than from those on a control diet, but this was not a result of altered expression of soluble epoxide hydrolase (sEH). Instead, suppression of sEH activity seemed to be responsible for the 11,12-EET-mediated enhanced inhibition of ENaC in animals on a high-potassium diet. Patch-clamp experiments demonstrated that 11,12-DHET was a weak inhibitor of ENaC compared with 11,12-EET, whereas 8,9- and 14,15-DHET were not. Furthermore, inhibition of sEH enhanced the 11,12-EET-induced inhibition of ENaC similar to high dietary potassium. In conclusion, high dietary potassium enhances the inhibitory effect of AA and 11,12-EET on ENaC by increasing CYP epoxygenase activity and decreasing sEH activity, respectively.

Cytochrome P450 (P450)-derived epoxyeicosatrienoic acids (EETs) exert well recognized vasodilatory, diuretic, and tubular fluid-electrolyte transport actions that are predictive of a hypotensive effect. The study sought to determine the improvement of hypertension and cardiac function by overexpressing P450 epoxygenases in vivo. Long-term expression of CYP102 F87V or CYP2J2 in spontaneously hypertensive rats (SHR) was mediated by using a type 8 recombinant adeno-associated virus (rAAV8) vector. Hemodynamics was measured by a Millar Instruments, Inc. (Houston, TX) microtransducer catheter, and atrial natriuretic peptide (ANP) mRNA levels were tested by real-time polymerase chain reaction. Results showed that urinary excretion of 14,15-EET was increased at 2 and 6 months after injection with rAAV-CYP102 F87V and rAAV-CYP2J2 compared with controls (p < 0.05). During the course of the 6-month study, systolic blood pressure significantly decreased in P450 epoxygenase-treated rats, but the CYP2J2-specific inhibitor C26 blocked rAAV-CYP2J2-induced hypotension and the increase in EET production. Cardiac output was improved by P450 epoxygenase expression at 6 months (p < 0.05). Furthermore, cardiac collagen content was reduced in P450 epoxygenase-treated rats. ANP mRNA levels were up-regulated 6- to 14-fold in the myocardium, and ANP expression was significantly increased in both myocardium and plasma in P450 epoxygenase-treated rats. However, epidermal growth factor (EGF) receptor antagonist 4-(3'-chloroanilino)-6,7-dimethoxy-quinazoline (AG-1478) significantly attenuated the increase in the EET-induced expression of ANP in vitro. These data indicate that overexpression of P450 epoxygenases attenuates the development of hypertension and improves cardiac function in SHR, and that these effects may be mediated, at least in part, by ANP via activating EGF receptor.

Epoxyeicosatrienoic acids (EETs) play important protective functions in cardiovascular and renal systems. Under physiological conditions, EETs are quickly converted by the soluble epoxide hydrolase (sEH) to diols which do not have the beneficiary roles. Inhibition of sEH with small molecules to increase the concentration of EETs therefore provides an attractive therapeutic strategy for cardiovascular diseases. We describe here the development of a high throughput cell-based assay to measure sEH activity and screen small molecular compounds as sEH inhibitors. This assay is based on the technology of fluorescence polarization (FP), utilizing a Cy3B labeled 14,15-DHET ligand and a rabbit anti-14,15-DHET antibody. With the optimized assay, we measured the cellular sEH activity of several cell lines expressing endogenous sEH as well as sEH BacMam transduced HEK-293 cells. The inhibitory effect of several known sEH inhibitors was evaluated in sEH BacMam transduced HEK-293 cells. Our data show that there is good agreement of pIC(50) values obtained between the FP format and a commercially available ELISA kit. To our knowledge, this is the first report of a high throughput cell-based assay for screening sEH inhibitors.

We investigated the alterations of major fatty acid components in epidermis by natural aging and photoaging processes, and by acute ultraviolet (UV) irradiation in human skin. Interestingly, we found that 11,14,17-eicosatrienoic acid (ETA), which is one of the omega-3 polyunsaturated acids, was significantly increased in photoaged human epidermis in vivo and also in the acutely UV-irradiated human skin in vivo, while it was significantly decreased in intrinsically aged human epidermis. The increased ETA content in the epidermis of photoaged human skin and acute UV-irradiated human skin is associated with enhanced expression of human elongase 1 and calcium-independent phosphodiesterase A(2). We demonstrated that ETA inhibited matrix metalloproteinase (MMP)-1 expression after UV-irradiation, and that inhibition of ETA synthesis using EPTC and NA-TCA, which are elongase inhibitors, increased MMP-1 expression. Therefore, our results suggest that the UV increases the ETA levels, which may have a photoprotective effect in the human skin.

Lowered sperm quality associated with reduced superoxide dismutase activity in testis and spermatozoa has been observed in red deer from a mined area in South-central Spain. Here we present fatty acid profiles for testis and spermatozoa of deer from this mined area (n=29) and a control area (n=33). Despite elevated Pb in liver and bone of red deer from this area, concentrations in testis and sperm were not significantly higher than in control areas; however, Cu in testis was lower in mined areas. Testis from mined areas also contained higher percentages of linoleic acid (18:2n-6) and dihomo-gamma-linolenic acid (20:3n-6), but lower arachidonic acid (20:4n-6). The percentage of 20:4n-6 was also lower in spermatozoa of deer from the mined area. Copper levels in testis correlated positively with the percentage of 20:4n-6. The imbalance in Cu homeostasis caused by metal pollution may have caused the observed effects on deer sperm., (Copyright 2010 Elsevier Inc. All rights reserved.)

The widespread use of statins for hypercholesterolemia has uncovered pleiotropic anti-inflammatory properties that were unexpected based on the drugs' original design; yet, mechanisms for these protective actions remain uncertain. In this study lovastatin triggered biosynthesis of the anti-inflammatory and pro-resolving mediator 15-epi-lipoxin A(4) (15-epi-LXA(4)). During interactions between human neutrophils and airway epithelial cells, the statin-induced increase in 15-epi-LXA(4) was associated with increased 14,15-epoxyeicosatrienoic acid (14,15-EET) generation. When added to activated neutrophils, 14,15-EET enhanced 15-epi-LXA(4) biosynthesis. In a murine model of airway mucosal injury and inflammation, lovastatin increased 15-epi-LXA(4) formation in vivo and markedly decreased acute lung inflammation. Administration of 15-epi-LXA(4) also inhibited lung inflammation in an additive manner with lovastatin. Together, these results indicate that statin-triggered 15-epi-LXA(4) generation during human leukocyte-airway epithelial cell interactions is an endogenous mechanism for statin-mediated tissue protection at mucosal surfaces that may also be relevant in the statins' ability to stimulate the resolution of inflammation.

Angiotensin II type 2 (AT(2)) receptors can be regarded as an endogenous repair system, because the AT(2) receptor is upregulated in tissue damage and mediates tissue protection. A potential therapeutic use of this system has only recently come within reach through synthesis of the first selective, orally active, nonpeptide AT(2) receptor agonist, compound 21 (C21; dissociation constant for AT(2) receptor: 0.4 nM; dissociation constant for angiotensin II type 1 receptor: >10,000 nM). This study tested AT(2) receptor stimulation with C21 as a potential future therapeutic approach for the inhibition of proinflammatory cytokines and of nuclear factor kappaB. C21 dose-dependently (1 nM to 1 micromol/L) reduced tumor necrosis factor-alpha-induced interleukin 6 levels in primary human and murine dermal fibroblasts. AT(2) receptor specificity was controlled for by inhibition with the AT(2) receptor antagonist PD123319 and by the absence of effects in AT(2) receptor-deficient cells. AT(2) receptor-coupled signaling leading to reduced interleukin 6 levels involved inhibition of nuclear factor kappaB, activation of protein phosphatases, and synthesis of epoxyeicosatrienoic acid. Inhibition of interleukin 6 promoter activity by C21 was comparable in strength to inhibition by hydrocortisone. C21 also reduced monocyte chemoattractant protein 1 and tumor necrosis factor-alpha in vitro and in bleomycin-induced toxic cutaneous inflammation in vivo. This study is the first to show the anti-inflammatory effects of direct AT(2) receptor stimulation in vitro and in vivo by the orally active, nonpeptide AT(2) receptor agonist C21. These data suggest that pharmacological AT(2) receptor stimulation may be an orally applicable future therapeutic approach in pathological settings requiring the reduction of interleukin 6 or inhibition of nuclear factor kappaB.

Epoxyeicosatrienoic acids (EETs) build a family consisting of four arachidonic acid derived regioisomers that are generated by P450 epoxygenases. In the past years, growing interest in influencing EET level arose since EETs possess numerous beneficial effects in the cardiovascular system, for example, vasodilation, anti-inflammation and elicit renal and myocardial protection. Because EETs are primarily metabolized by the soluble epoxide hydrolase (sEH) and potent inhibitors of this enzyme are currently available, pharmacological sEH inhibition seems to be a feasible approach to elevate EET level in vivo. Hence, first clinical trials on sEH inhibition in man have begun. This review focuses on sEH inhibition as a novel pharmacological cardiovascular protective strategy with special regard to in vivo investigations., (Copyright 2010 Elsevier Ltd. All rights reserved.)

The gene from Streptomyces coelicolor A3(2) encoding CYP102B1, a recently discovered CYP102 subfamily which exists solely as a single P450 heme domain, has been cloned, expressed in Escherichia coli, purified, characterized, and compared to its fusion protein family members. Purified reconstitution metabolism experiments with spinach ferredoxin, ferredoxin reductase, and NADPH revealed differences in the regio- and stereoselective metabolism of arachidonic acid compared to that of CYP102A1, exclusively producing 11,12-epoxyeicosa-5,8,14-trienoic acid in addition to the shared metabolites 18-hydroxy arachidonic acid and 14,15-epoxyeicosa-5,8,11-trienoic acid. Consequently, in order to elucidate the physiological function of CYP102B1, transposon mutagenesis was used to generate an S. coelicolor A3(2) strain lacking CYP102B1 activity and the phenotype was assessed.

Recent studies have shown that the renal CYP450 (cytochrome P450) metabolites of AA (arachidonic acid), the vasoconstrictor 20-HETE (20-hydroxyeicosatetraenoic acid) and the vasodilator EETs (epoxyeicosatrienoic acids), play an important role in the pathophysiology of AngII (angiotensin II)-dependent forms of hypertension and the associated target organ damage. The present studies were performed in Ren-2 renin transgenic rats (TGR) to evaluate the effects of chronic selective inhibition of 20-HETE formation or elevation of the level of EETs, alone or in combination, on the course of hypertension and hypertension-associated end-organ damage. Both young (30 days of age) prehypertensive TGR and adult (190 days of age) TGR with established hypertension were examined. Normotensive HanSD (Hannover Sprague-Dawley) rats served as controls. The rats were treated with N-methylsulfonyl-12,12-dibromododec-11-enamide to inhibit 20-HETE formation and/or with N-cyclohexyl-N-dodecyl urea to inhibit soluble epoxide hydrolase and prevent degradation of EETs. Inhibition in TGR of 20-HETE formation combined with enhanced bioavailability of EETs attenuated the development of hypertension, cardiac hypertrophy, proteinuria, glomerular hypertrophy and sclerosis as well as renal tubulointerstitial injury. This was also associated with attenuation of the responsiveness of the systemic and renal vascular beds to AngII without modifying their responses to noradrenaline (norepinephrine). Our findings suggest that altered production and/or action of 20-HETE and EETs plays a permissive role in the development of hypertension and hypertension-associated end-organ damage in this model of AngII-dependent hypertension. This information provides a basis for a search for new therapeutic approaches for the treatment of hypertension.

Soluble epoxide hydrolase (sEH) metabolizes epoxyeicosatrienoic acids (EETs), primarily 14,15-EET. EETs are derived from arachidonic acid via P-450 epoxygenases and are cardioprotective. We tested the hypothesis that sEH deficiency and pharmacological inhibition elicit tolerance to ischemia via EET-mediated STAT3 signaling in vitro and in vivo. In addition, the relevance of single nucleotide polymorphisms (SNPs) of EPHX2 (the gene encoding sEH) on tolerance to oxygen and glucose deprivation and reoxygenation and glucose repletion (OGD/RGR) was assessed in male C57BL\6J (WT) or sEH knockout (sEHKO) cardiomyocytes by using transactivator of transcription (TAT)-mediated transduction with sEH mutant proteins. Cell death and hydrolase activity was lower in Arg287Gln EPHX2 mutants vs. nontransduced controls. Excess 14,15-EET and SEH inhibition did not improve cell survival in Arg287Gln mutants. In WT cells, the putative EET receptor antagonist, 14,15-EEZE, abolished the effect of 14,15-EET and sEH inhibition. Cotreatment with 14,15-EET and SEH inhibition did not provide increased protection. In vitro, STAT3 inhibition blocked 14,15-EET cytoprotection, but not the effect of SEH inhibition. However, STAT3 small interfering RNA (siRNA) abolished cytoprotection by 14,15-EET and sEH inhibition, but cells pretreated with JAK2 siRNA remained protected. In vivo, STAT3 inhibition abolished 14,15-EET-mediated infarct size reduction. In summary, the Arg287Gln mutation is associated with improved tolerance against ischemia in vitro, and inhibition of sEH preserves cardiomyocyte viability following OGD/RGR via an EET-dependent mechanism. In vivo and in vitro, 14,15-EET-mediated protection is mediated in part by STAT3.

Objective: Epoxyeicosatrienoic acids (EETs) are protective in both myocardial and brain ischemia, variously attributed to activation of K(ATP) channels or blockade of adhesion molecule upregulation. In this study, we tested whether EETs would be protective in lung ischemia-reperfusion injury., Methods: The filtration coefficient (K(f)), a measure of endothelial permeability, and expression of the adhesion molecules vascular cell adhesion molecule (VCAM) and intercellular adhesion molecule (ICAM) were measured after 45 minutes ischemia and 30 minutes reperfusion in isolated rat lungs., Results: K(f) increased significantly after ischemia-reperfusion alone vs time controls, an effect dependent upon extracellular Ca(2+) although not on the EET-regulated channel TRPV4. Inhibition of endogenous EET degradation or administration of exogenous 11,12- or 14,-15-EET at reperfusion significantly limited the permeability response to ischemia-reperfusion. The beneficial effect of 11,12-EET was not prevented by blockade of K(ATP) channels nor by blockade of TRPV4. Finally, 11,12-EET-dependent alteration in adhesion molecules expression is unlikely to explain its beneficial effect, since the expression of the adhesion molecules VCAM and ICAM in lung after ischemia-reperfusion was similar to that in controls., Conclusion: EETs are beneficial in the setting of lung ischemia-reperfusion, when administered at reperfusion. However, further study will be needed to elucidate the mechanism of action.

Epoxyeicosatrienoic acids (EETs) are cytochrome P450 metabolites of arachidonic acid that are produced by the vascular endothelium in responses to various stimuli such as the agonists acetylcholine (ACH) or bradykinin or by shear stress which activates phospholipase A(2) to release arachidonic acid. EETs are important regulators of vascular tone and homeostasis. In the modulation of vascular tone, EETs function as endothelium-derived hyperpolarizing factors (EDHFs). In models of vascular inflammation, EETs attenuate inflammatory signaling pathways in both the endothelium and vascular smooth muscle. Likewise, EETs regulate blood vessel formation or angiogenesis by mechanisms that are still not completely understood. Soluble epoxide hydrolase (sEH) converts EETs to dihydroxyeicosatrienoic acids (DHETs) and this metabolism limits many of the biological actions of EETs. The recent development of inhibitors of sEH provides an emerging target for pharmacological manipulation of EETs. Additionally, EETs may initiate their biological effects by interacting with a cell surface protein that is a G protein-coupled receptor (GPCR). Since GPCRs represent a common target of most drugs, further characterization of the EET receptor and synthesis of specific EET agonists and antagonist can be used to exploit many of the beneficial effects of EETs in vascular diseases, such as hypertension and atherosclerosis. This review will focus on the current understanding of the contribution of EETs to the regulation of vascular tone, inflammation, and angiogenesis. Furthermore, the therapeutic potential of targeting the EET pathway in vascular disease will be highlighted., (Copyright © 2010 Elsevier Inc. All rights reserved.)

We used liquid chromatography for analysis of fatty acids (FA) in lipids of erythrocytes of patients with hypertensive disease (HD) with normo- (group 1) and hyperlipidemia (group 2). Abnormalities of FA composition of erythrocyte lipids were revealed in both groups. In group 1 we found deficit of polyenic acids of omega-6 family, accumulation of Mead acid - prostanoid precursor with pronounced vasoconstrictor and pro inflammatory properties. In group 2 we noted more profound rearrangement of lipid matrix of erythrocyte membrane manifested as deficiency of omega-3 polyenic acids, accumulation of palmitinic and arachidonic acids. Preponderance of saturated FA in erythrocytes and deficiency of polyenic acids might evidence for pathology of their ligand-receptor transport into the cell. Blockade of active FA transport initiates formation of HD, promotes accumulation of atherogenic fractions of lipoproteins in blood. These results evidence for important pathogenetic role of FA in development of hypertension.

The transmigration of polymorphonuclear leukocytes (PMNs; neutrophils) into the intestinal lumen is a classical phenomenon associated with a wide variety of disease states, including those of both pathogenic and autoimmune/idiopathic origin. While PMNs are highly effective at killing invading pathogens by releasing microbiocidal products, excessive or unnecessary release of these substances can cause substantial damage to the intestinal epithelium. Therefore, it is necessary to understand the underlying mechanisms that lure neutrophils into the lumen allowing them to perform their desired functions, so that researchers may begin to identify which processes may be potential targets for inhibiting the transmigration of PMNs during noninfectious states.

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.

Heme oxygenase (HO) and cytochrome P450 (P450)-derived epoxyeicosatrienoic acids (EETs) participate in vascular protection, and recent studies suggest these two systems are functionally linked. We examined the consequences of HO deficiency on P450-derived EETs with regard to body weight, adiposity, insulin resistance, blood pressure, and vascular function in HO-2-null mice. The HO-2-null mice were obese, displayed insulin resistance, and had high blood pressure. HO-2 deficiency was associated with decreases in cyp2c expression, EET levels, HO-1 expression, and HO activity and with an increase in superoxide production and an impairment in the relaxing response to acetylcholine. In addition, HO-2-null mice exhibited increases in serum levels of tumor necrosis factor (TNF)-alpha and macrophage chemoattractant protein (MCP)-1 and a decrease in serum adiponectin levels. Treatment of HO-2-null mice with a dual-activity EET agonist/soluble epoxide hydrolase inhibitor increased renal and vascular EET levels and HO-1 expression, lowered blood pressure, prevented body weight gain, increased insulin sensitivity, reduced subcutaneous and visceral fat, and decreased serum TNF-alpha and MCP-1, while increasing adiponectin and restoring the relaxing responses to acetylcholine. The decrease in cyp2c expression and EETs levels in HO-2-null mice underscores the importance of the HO system in the regulation of epoxygenase levels and suggests that protection against obesity-induced cardiovascular complications requires interplay between these two systems. A deficiency in one of these protective systems may contribute to the adverse manifestations associated with the clinical progression of the metabolic syndrome.

ω-3 fatty acids, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), have beneficial effects on cardiovascular diseases. Cytochrome P-450 (CYP) 2J2 that is expressed in endothelial cells metabolizes arachidonic acids to biologically active epoxyeicosatrienoic acids (EETs) that possess anti-inflammatory and anti-thrombotic effects. We studied the effects of EPA and DHA on the expression of CYP 2J2 mRNA by reverse transcription-polymerase chain reaction in cultured human umbilical vein endothelial cells and found that EPA, but not DHA, increased the expression of CYP 2J2 mRNA in a dose-dependent and a time-dependent manner. EPA-induced CYP 2J2 expression was significantly inhibited by pretreatment with a peroxisome proliferator-activated receptor (PPAR) γ antagonist, GW9662. EPA, but not DHA, caused a significant increase in cellular levels of 11,12-dihydroxyeicosatrienoic acid that is a stable metabolite of 11,12-EET, which was blocked by pretreatment with GW9662. These data demonstrate that EPA increases CYP 2J2 mRNA expression and 11,12-EET production via PPARγ in endothelial cells and indicate a novel protective role of EPA and PPARγ against vascular inflammation.

Arachidonic acid (AA) is metabolized by endothelial 15-lipoxygenase (15-LO) to several vasodilatory eicosanoids such as 11,12,15-trihydroxyeicosatrienoic acid (11,12,15-THETA) and its proposed unstable precursor 15-hydroxy-11,12-epoxyeicosatrienoic acid (15-H-11,12-EETA). In the present study, the acid-stable 13-hydroxy-trans-14,15-epoxy-eicosatrienoic acid (13-H-14,15-EETA) was identified and its vascular activities characterized. Rabbit aorta, mesenteric arteries, and the combination of 15-LO and cytochrome P450 2J2 converted AA to two distinct HEETA metabolites. The HEETA metabolites were resistant to acidic hydrolysis but were hydrolyzed by recombinant sEH to a more polar metabolite identified by mass spectrometry as 13,14,15-THETA. Mass spectrometric analyses and HPLC comigration identified the HEETAs as threo- and erythro-diastereomers of 13-H-trans-14,15-EETA. Erythro- and threo-diastereomers of 13-H-trans-14,15-EETA relaxed endothelium-denuded rabbit small mesenteric arteries with maximum relaxations of 22.6 +/- 6.0% and 8.6 +/- 4.3%, respectively. Apamin (10(-7) m) inhibited the relaxations to the erythro-isomer (maximum relaxation = 1.2 +/- 5.6%) and increasing [K(+)](o) from 4.6 to 30 mm blocked relaxations to both isomers. In cell-attached patches of mesenteric arterial smooth muscle cells (SMCs), erythro-13-H-trans-14,15-EETA (1-3 x 10(-6) m) increased mean open time of small conductance K(+) channels (13-14 pS) from 0.0007 +/- 0.0007 to 0.0053 +/- 0.0042. This activation was inhibited by apamin. The erythro, but not the threo, isomer blocked angiotensin II-stimulated aortic SMC migration. These studies demonstrate that 13-H-14,15-EETAs induces vascular relaxation via K(+) channel activation to cause SMC hyperpolarization. Thus, 13-H-14,15-EETA represents a new endothelial factor.

The hepoxilin pathway was discovered over two decades ago. Products in this pathway are derived through the 12S-lipoxygenase/hepoxilin synthase enzyme system and contain intrinsic biological activity. This activity relates to the reorganization of calcium and potassium ions within the cell, and in inflammation and insulin secretion. Although the natural hepoxilins are chemically unstable, chemical analogues (PBTs) have been synthesized with chemical and biological stability. The PBTs antagonize the natural hepoxilins. The PBTs showed bioavailability, excellent tolerance and stability in vivo. In proof of principle studies in vivo in animal models, the PBTs have shown actions as anti-inflammatory agents, anti-thrombotic agents, anti-cancer agents and anti-diabetic agents. These studies demonstrate the effectiveness of the base structure of the hepoxilin (and PBT) molecule and serve as an excellent framework for the design and preparation of second-generation compounds with improved pharmaceutical properties as therapeutics for the above-mentioned diseases.

3,3-Disubstituted piperidine-derived trisubstituted urea entA-2b was discovered as a highly potent and selective soluble epoxide hydrolase (sEH) inhibitor. Despite the good compound oral exposure, excellent sEH inhibition in whole blood, and remarkable selectivity, compound entA-2b failed to lower blood pressure acutely in spontaneously hypertensive rats (SHRs). This observation further challenges the premise that sEH inhibition can provide a viable approach to the treatment of hypertensive patients.

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.

Stimulation of vascular endothelial cells with agonists such as acetylcholine (ACh) or bradykinin or with shear stress activates phospholipases and releases arachidonic acid (AA). AA is metabolized by cyclooxygenases, cytochrome P-450s, and lipoxygenases (LOs) to vasoactive products. In some arteries, a substantial component of the vasodilator response is dependent on LO metabolites of AA. Nitric oxide (NO)- and prostaglandin (PG)-independent vasodilatory responses to ACh and AA are reduced by inhibitors of LO and by antisense oligonucleotides specifically against 15-LO-1. Vasoactive 15-LO metabolites derived from the vascular endothelium include 15-hydroxy-11,12-epoxyeicosatrienoic acid (15-H-11,12-HEETA) that is hydrolyzed by soluble epoxide hydrolase to 11,12,15-trihydroxyeicosatrienoic acid (11,12,15-THETA). HEETA and THETA are endothelium-derived hyperpolarizing factors that induce vascular relaxations by activation of smooth muscle apamin-sensitive, calcium-activated, small-conductance K(+) channels causing hyperpolarization. In other arteries, the 12-LO metabolite 12-hydroxyeicosatetraenoic acid is synthesized by the vascular endothelium and relaxes smooth muscle by large-conductance, calcium-activated K(+) channel activation. Thus formation of vasodilator eicosanoids derived from LO pathways contributes to the regulation of vascular tone, local blood flow, and blood pressure.

Aims: This study examined the functional role of B-type natriuretic peptide (BNP) in epoxyeicosatrienoic acid (EET)-mediated cardioprotection in mice with targeted disruption of the sEH or Ephx2 gene (sEH null)., Methods and Results: Isolated mouse hearts were perfused in the Langendorff mode and subjected to global no-flow ischaemia followed by reperfusion. Hearts were analysed for recovery of left ventricular developed pressure (LVDP), mRNA levels, and protein expression. Naïve hearts from sEH null mice had similar expression of preproBNP (Nppb) mRNA compared with wild-type (WT) hearts. However, significant increases in Nppb mRNA and BNP protein expression occurred during post-ischaemic reperfusion and correlated with improved post-ischaemic recovery of LVDP. Perfusion with the putative EET receptor antagonist 14,15-epoxyeicosa-5(Z)-enoic acid prior to ischaemia reduced the preproBNP mRNA in sEH null hearts. Inhibitor studies demonstrated that perfusion with the natriuretic peptide receptor type-A (NPR-A) antagonist, A71915, limited the improved recovery in recombinant full-length mouse BNP (rBNP)- and 11,12-EET-perfused hearts as well as in sEH null mice. Increased expression of phosphorylated protein kinase C epsilon and Akt were found in WT hearts perfused with either 11,12-EET or rBNP, while mitochondrial glycogen synthase kinase-3beta was significantly lower in the same samples. Furthermore, treatment with the phosphoinositide 3-kinase (PI3K) inhibitor wortmannin abolished improved LVDP recovery in 11,12-EET-treated hearts but not did significantly inhibit recovery of rBNP-treated hearts., Conclusion: Taken together, these data indicate that EET-mediated cardioprotection involves BNP and PI3K signalling events.

The mammalian Delta6-desaturase coded by fatty acid desaturase 2 (FADS2; HSA11q12-q13.1) catalyzes the first and rate-limiting step for the biosynthesis of long-chain polyunsaturated fatty acids. FADS2 is known to act on at least five substrates, and we hypothesized that the FADS2 gene product would have Delta8-desaturase activity. Saccharomyces cerevisiae transformed with a FADS2 construct from baboon neonate liver cDNA gained the function to desaturate 11,14-eicosadienoic acid (20:2n-6) and 11,14,17-eicosatrienoic acid (20:3n-3) to yield 20:3n-6 and 20:4n-3, respectively. Competition experiments indicate that Delta8-desaturation favors activity toward 20:3n-3 over 20:2n-6 by 3-fold. Similar experiments show that Delta6-desaturase activity is favored over Delta8-desaturase activity by 7-fold and 23-fold for n-6 (18:2n-6 vs 20:2n-6) and n-3 (18:3n-3 vs 20:3n-3), respectively. In mammals, 20:3n-6 is the immediate precursor of prostaglandin E1 and thromboxane B1. 20:3n-6 and 20:4n-3 are also immediate precursors of long-chain polyunsaturated fatty acids arachidonic acid and eicosapentaenoic acid, respectively. These findings provide unequivocal molecular evidence for a novel alternative biosynthetic route to long-chain polyunsaturated fatty acids in mammals from substrates previously considered to be dead-end products.

Oxidation of the endocannabinoid anandamide by cytochrome P450 (P450) enzymes has the potential to affect signaling pathways within the endocannabinoid system and pharmacological responses to novel drug candidates targeting this system. We previously reported that the human cytochromes P450 2D6, 3A4, and 4F2 are high-affinity, high-turnover anandamide oxygenases in vitro, forming the novel metabolites hydroxyeicosatetraenoic acid ethanolamides and epoxyeicosatrienoic acid ethanolamides. The objective of this study was to investigate the possible biological significance of these metabolic pathways. We report that the 5,6-epoxide of anandamide, 5,6-epoxyeicosatrienoic acid ethanolamide (5,6-EET-EA), is a potent and selective cannabinoid receptor 2 (CB2) agonist. The K(i) values for the binding of 5,6-EET-EA to membranes from Chinese hamster ovary (CHO) cells expressing either recombinant human CB1 or CB2 receptor were 11.4 microM and 8.9 nM, respectively. In addition, 5,6-EET-EA inhibited the forskolin-stimulated accumulation of cAMP in CHO cells stably expressing the CB2 receptor (IC(50) = 9.8 +/- 1.3 nM). Within the central nervous system, the CB2 receptor is expressed on activated microglia and is a potential therapeutic target for neuroinflammation. BV-2 microglial cells stimulated with low doses of interferon-gamma exhibited an increased capacity for converting anandamide to 5,6-EET-EA, which correlated with increased protein expression of microglial P450 4F and 3A isoforms. Finally, we demonstrate that 5,6-EET-EA is more stable than anandamide in mouse brain homogenates and is primarily metabolized by epoxide hydrolase. Combined, our results suggest that epoxidation of anandamide by P450s to form 5,6-EET-EA represents an endocannabinoid bioactivation pathway in the context of immune cell function.

20-Hydroxyeicosatetraenoic acid (20-HETE) has been implicated as a potential mediator in epithelial cell proliferation and cyst formation in polycystic kidney disease (PKD). In the present study, we studied the effects of chronic blockade of 20-HETE synthesis in an orthologous rodent model of autosomal recessive polycystic kidney disease (ARPKD), the PCK rat. RT-PCR analysis indicated that the expression of CYP4A1, CYP4A2, CYP4A3, and CYP4A8 mRNA was increased two- to fourfold in cystic PCK compared with noncystic Sprague-Dawley rat kidneys. Daily administration of a 20-HETE synthesis inhibitor, HET-0016 (10 mg x kg(-1) x day(-1) ip) for 4-7 wk significantly reduced kidney size by 24% from 4.95 +/- 0.19 g in vehicle-treated PCK rats to 3.76 +/- 0.15 g (n = 4). Collecting tubule morphometric cystic indices were reduced in HET-0016-treated PCK rats (2.1 +/- 0.2; n = 4) compared with vehicle-treated PCK rats (4.4 +/- 0.1; n = 4). The cellular mechanism by which 20-HETE may play a role in cyst formation has not been well characterized, but there was a significantly lower (P < 0.05) level of intracellular cAMP and decreased phosphorylation (activation) of ERK1/2 protein in PCK rat kidneys (n = 3) treated with HET-0016 . These studies indicate a potential role of 20-HETE in cyst formation in the orthologous rodent PCK model of ARPKD.

The cortical collecting duct (CCD), which is involved in renal potassium (K) excretion, expresses cytochrome P450 (CYP)-epoxygenase. Here, we examined the effect of high dietary K on renal expression of CYP2C23 and CYP2J2 in the rat, as well as the role of CYP-epoxygenase-dependent metabolism of arachidonic acid in the regulation of Ca(2+)-activated big-conductance K (BK) channels. By Western blot analysis, high dietary K stimulated the expression of CYP2C23 but not CYP2J2 and increased 11,12-epoxyeicosatrienoic acid (11,12-EET) levels in isolated rat CCD tubules. Application of arachidonic acid increased BK channel activity, and this occurred to a greater extent in rats on a high-K diet compared with a normal-K diet. This effect was unlikely due to arachidonic acid-induced changes in membrane fluidity, because 11,14,17-eicosatrienoic acid did not alter BK channel activity. Inhibiting CYP-epoxygenase but not cyclooxygenase- or CYP-omega-hydroxylase-dependent pathways completely abolished the stimulatory effect of arachidonic acid on BK channel activity. In addition, application of 11,12-EET mimicked the effect of arachidonic acid on BK channel activity, even in the presence of CYP-epoxygenase inhibition. This effect seemed specific to 11,12-EET, because both 8,9- and 14,15-EET failed to stimulate BK channels. Finally, inhibition of CYP-epoxygenase abolished iberiotoxin-sensitive and flow-stimulated but not basal net K secretion in isolated microperfused CCD. In conclusion, high dietary K stimulates the renal CYP-epoxygenase pathway, which plays an important role in activating BK channels and flow-stimulated K secretion in the CCD.

15-Lipoxygenase (15-LO-1) metabolizes arachidonic acid (AA) to 11,12,15-trihydroxyeicosatrienoic acids (THETAs) and 15-hydroxy-11,12-epoxyeicosatrienoic acids (HEETA) that dilate rabbit arteries. Increased endothelial 15-LO-1 expression enhances arterial relaxations to agonists. We tested the effect of hypoxia on 15-LO-1 expression, THETA and HEETA synthesis, and relaxations in rabbit arteries. The incubation of rabbit aortic endothelial cells and isolated aortas in 0.7% O(2) increased 15-LO-1 expression. Rabbits were housed in a hypoxic atmosphere of 12% O(2) for 5 days. 15-LO-1 expression increased in the endothelium of the arteries of rabbits in 12% O(2) compared with room air. THETA and HEETA synthesis was also enhanced in aortas and mesenteric arteries. AA hyperpolarized the smooth muscle cells in indomethacin- and phenylephrine-treated mesenteric arteries of hypoxic rabbits from -29.4 +/- 1 to -50.1 +/- 3 mV. The hyperpolarization to AA was less in arteries of normoxic rabbits (from -26.0 +/- 2 to -37 +/- 2 mV). This AA-induced hyperpolarization was inhibited by the 15-LO inhibitor BW-755C. Nitric oxide and prostaglandin-independent maximum relaxations to acetylcholine (79.7 +/- 2%) and AA (38.3 +/- 4%) were enhanced in mesenteric arteries from hypoxic rabbits compared with the normoxic rabbits (49.7 +/- 6% and 19.9 +/- 2%, respectively). These relaxations were inhibited by BW-755C and nordihydroguaiaretic acid. Therefore, hypoxia increased the relaxations to agonists in the rabbit mesenteric arteries by enhancing endothelial 15-LO-1 expression and synthesis of the hyperpolarizing factors THETA and HEETA.

The early stage of diabetic nephropathy (DN) is linked to proteinuria. Transforming growth factor (TGF)-beta1 increases glomerular permeability to albumin (P(alb)), whereas 20-HETE and EETs reduce P(alb). To investigate the impact of hyperglycemia and hyperlipidemia on 20-HETE, EETs, and TGF-beta1 in the glomeruli, rats were divided into four groups: ND rats were fed a normal diet, HF rats were fed a high-fat diet, STZ rats were treated with 35 mg/kg of streptozotocin, and HF/STZ rats were fed a HF diet and treated with STZ. After 10 wk on these regimens, blood glucose, urinary albumin, serum cholesterol, serum triglyceride levels, and the kidney-to-body weight ratio were significantly elevated in STZ and HF/STZ rats compared with HF and ND rats. STZ and HF/STZ rats had histopathologic changes and abnormal renal hemodynamics. Expression of glomerular CYP4A, enzymes for 20-HETE production, was significantly decreased in STZ rats, whereas expression of glomerular CYP2C and CYP2J, enzymes for EETs production, was significantly decreased in both STZ and HF/STZ rats. Moreover, glomerular TGF-beta1 levels were significantly greater in STZ and HF/STZ rats than in HF and ND rats. Five-week treatment of STZ rats with clofibrate induced glomerular CYP4A expression and 20-HETE production, but reduced glomerular TGF-beta1 and urinary protein excretion. These results demonstrate that hyperglycemia increases TGF-beta1 but decreases 20-HETE and EETs production in the glomeruli, changes that may be important in causing glomerular damage in the early stage of DN.

Objectives: The soluble epoxide hydrolase (sEH) metabolizes epoxyeicosatrienoic acids (EETs) to their less active dihydroxy derivatives. Because EETs have antiinflammatory properties, we determined whether or not inhibition of sEH attenuates disease development in the monocrotaline model of pulmonary hypertension in rats., Methods: sEH inhibition was achieved using 12-(3-adamantan-1-yl-ureido)-dodecanoic acid (25 mg/l) and cis- 4-[4-(3-adamantan-1-yl-ureido)-cyclohexyloxy]-benzoic acid (5 mg/l) administered via drinking water starting 3 days prior to monocrotaline injection (60 mg/kg)., Results: Monocrotaline induced the development of progressive pulmonary hypertension. sEH inhibition increased the plasma ratio of EETs to DHETs and attenuated the monocrotaline-induced increase in pulmonary artery medial wall thickness as well as the degree of vascular muscularization. Moreover, right ventricular pressure was significantly lower in the group treated with sEH inhibitors. Pulmonary sEH protein expression and sEH activity, as well as pulmonary cytochrome P450 epoxygenase activity were all impaired in monocrotaline-treated rats as compared with control animals. sEH inhibitors, however, increased the plasma ratio of EETs to dihydroxy epoxyeicosatrienoic acids. Monocrotaline induced the proliferation of pulmonary endothelial and vascular smooth muscle cells in vivo as determined by 5-Bromo-2'-deoxy-Uridine incorporation, and this effect was significantly blunted in animals treated with sEH inhibitors. Proliferation of cultured pulmonary smooth muscle cell, however, was not affected by EETs or sEH inhibitors suggesting that the in-vivo effects are a consequence of a direct EET-mediated protection against the inflammation induced by monocrotaline., Conclusion: sEH inhibition reduces pulmonary vascular remodeling and the development of pulmonary hypertension in the monocrotaline model of primary pulmonary hypertension in rats.

1 This study examined the contribution of cytochrome P450 metabolites of arachidonic acid in mediating ischaemia/reperfusion (I/R)-induced cardiac dysfunction in normal and diabetic rats. 2 We first compared the metabolism of arachidonic acid in microsomes prepared from the hearts of control rats and rats treated with streptozotocin (55 mg kg(-1)) to induce diabetes. The production of dihydroxyeicosatrienoic acids and epoxyeicosatrienoic acids (EETs) were similar in microsomes prepared from the hearts of control and diabetic rats, but the production of 20-hydroxyeicosatetraenoic acid (20-HETE) was two-fold higher in diabetic hearts than in control animals. 3 We then compared the change in left ventricular pressure (P(max)), left ventricular end-diastolic pressure, coronary flow and coronary vascular resistance in isolated perfused hearts obtained from control and diabetic animals after 40 min of global ischaemia (I) followed by 30 min of reperfusion (R). The decline in cardiac function was three- to five-fold greater in the hearts obtained from diabetic vs. control animals. 4 Pretreatment of the hearts with N-hydroxy-N'-(4-butyl-2-methyl-phenyl)-formamidine (HET0016, 1 microm), a selective inhibitor of the synthesis of 20-HETE, for 30 min before I/R resulted in significant improvement in the recovery of cardiac function in the hearts obtained from diabetic but not in control rats. Perfusion with an inhibitor of soluble epoxide hydrolase, 1-cyclohexyl-3-dodecyl urea (CDU), before I/R improved the recovery of cardiac function in hearts obtained from both control and diabetic animals. Perfusion with both HET0016 and CDU resulted in significantly better recovery of cardiac function of diabetic hearts following I/R than that seen using either drug alone. Pretreatment of the hearts with glibenclamide (1 microm), an inhibitor of ATP-sensitive potassium channels, attenuated the cardioprotective effects of both CDU and HET0016. 5 This is the first study to suggest that acute blockade of the formation of 20-HETE and/or reduced inactivation of EETs could be an important strategy to reduce cardiac dysfunction following I/R events in diabetes.

Aims: Fluid shear stress elicits endothelium-dependent vasodilatation via nitric oxide and prostacyclin-dependent and -independent mechanisms. The latter includes the opening of Ca(2+)-operated potassium channels by cytochrome P450 (CYP) epoxygenase-derived epoxyeicosatrienoic acids (EETs) leading to endothelial hyperpolarization. We previously reported that EETs activate the transient receptor potential (TRP) V4 channel in vascular endothelial cells and that Ca(2+) influx in these cells in response to mechanical stimuli is dependent on the activation of CYP epoxygenases. We therefore hypothesized that the TRPV4 channel is involved in the flow-induced vasodilatation attributed to the endothelium-derived hyperpolarizing factor (EDHF)., Methods and Results: In the presence of N(omega)-nitro-l-arginine methyl ester and diclofenac, precontracted mouse carotid arteries displayed a considerable vasodilatation in response to step-wise increases in luminal flow. The EDHF-mediated, flow-induced vasodilatation could be inhibited by the epoxygenase inhibitor MS-PPOH, was abolished after down-regulation of CYP epoxygenases in tissue culture, and could be restored by viral expression of CYP2C9 in the endothelium. The TRPV4-channel inhibitor ruthenium red (RuR) inhibited the EDHF-mediated flow response, but the combination of MS-PPOH and RuR had no further effect. RuR also inhibited the response in CYP2C9-overexpressing vessels. Moreover, TRPV4-deficient mice demonstrated a blunted EDHF-mediated response to increases in luminal flow in comparison to their wild-type littermates, and the addition of MS-PPOH was without effect in these mice (up to 38 +/- 3% in TRPV4(-/-) vs. 57 +/- 6% in TRPV4(+/+), P < 0.01). In cultured human endothelial cells, exposure to fluid shear stress induced the translocation of the TRPV4 channel from a perinuclear localization to the cell membrane., Conclusion: We conclude that the TRPV4 channel is involved in flow-induced, endothelium-dependent vasodilatation of murine carotid arteries. Moreover, the activation of the TRPV4 channel by flow requires an active CYP epoxygenase and the translocation of the channel to the cell membrane.

Objective: Arachidonic acid (AA) metabolites from 15-lipoxygenase-1 (15-LO-1), trihydroxyeicosatrienoic acid (THETA), and hydroxyepoxyeicosatrienoic acid (HEETA) relax arteries. We studied 15-LO-1 expression, THETA and HEETA synthesis, and their effect on arterial relaxations and blood pressure in hypercholesterolemic nonatherosclerotic rabbits., Methods and Results: Immunoblots, RTPCR analysis, and (14)C-AA metabolism revealed that hypercholesterolemia increased 15-LO-1 expression in the endothelium and THETA and HEETA synthesis in the arteries. Isometric tension recording, in presence of nitric oxide synthase (NOS) and cyclooxygenase (COX) inhibitors, showed greater relaxations to acetylcholine (ACH) and AA (max 76.0+/-4.6% and 79.5+/-2.4%, respectively) in aortas from hypercholesterolemic rabbits compared with normal rabbits (max 39.1+/-2.8% and 39.9+/-2.2%, respectively). AA induced greater hyperpolarization in the smooth muscle cells of hypercholesterolemic aortas (-45.85+/-3.0 mV) compared with normal aortas (-31.45+/-1.9 mV). The ACH- and AA-relaxations were inhibited by 15-LO-1 inhibitors. ACH induced hypotensive responses were greater in hypercholesterolemic rabbits in absence (-54.9+/-3.3%) or presence (-48.5+/-3.2%) of NOS and COX-inhibitors compared with control rabbits (-31.6+/-3.3% and -24.3+/-1.6%, respectively). BW755C reduced these responses in hypercholesterolemic rabbits to -29.3+/-2.3%., Conclusions: Hypercholesterolemia increases endothelial 15-LO-1 expression, THETA and HEETA synthesis and enhances vasorelaxation.

Neutrophil transmigration across mucosal surfaces contributes to dysfunction of epithelial barrier properties, a characteristic underlying many mucosal inflammatory diseases. Thus, insight into the directional movement of neutrophils across epithelial barriers will provide important information relating to the mechanisms of such inflammatory disorders. The eicosanoid hepoxilin A(3), an endogenous product of 12-lipoxygenase activity, is secreted from the apical surface of the epithelial barrier and establishes a chemotactic gradient to guide neutrophils from the submucosa across epithelia to the luminal site of an inflammatory stimulus, the final step in neutrophil recruitment. Currently, little is known regarding how hepoxilin A(3) is secreted from the intestinal epithelium during an inflammatory insult. In this study, we reveal that hepoxilin A(3) is a substrate for the apical efflux ATP-binding protein transporter multidrug resistance-associated protein 2 (MRP2). Moreover, using multiple in vitro and in vivo models, we show that induction of intestinal inflammation profoundly up-regulates apical expression of MRP2, and that interfering with hepoxilin A(3) synthesis and/or inhibition of MRP2 function results in a marked reduction in inflammation and severity of disease. Lastly, examination of inflamed intestinal epithelia in human biopsies revealed up-regulation of MRP2. Thus, blocking hepoxilin A(3) synthesis and/or inhibiting MRP2 may lead to the development of new therapeutic strategies for the treatment of epithelial-associated inflammatory conditions.

The role of CYP-450 dependent arachidonic acid (AA) metabolites (vasoconstrictor 20-HETE and vasodilator EETs) and NO in control of blood pressure (MABP) and kidney function remains unclear. NO affects the activity of heme-containing enzymes, like CYP-450 related monooxygenases, moreover, their activity depends on Na(+) intake. The focus of this review and underlying studies is on the role of high sodium intake (pro-hypertensive factor) in interrelation between CYP-450 and NOS. The acute vs. chronic non-selective inhibition of CYP-450 AA metabolites (ABT), and selective inhibition of 20-HETE (HET 0016) has also been tested. The renal artery flow (RBF, Transonic probe), medullary blood flow (MBF, laser-Doppler flux), renal excretion, and medullary tissue NO (selective electrode) were measured in male anaesthetized Wistar rats. We conclude that on standard Na(+) intake, opposed effects of 20-HETE and EETs are almost in equilibrium; however, in the renal circulation the vasodilator EETs influence slightly prevails. High sodium intake stimulates NOS, which limits CYP-450 impact on MABP and kidney function. However, this protection disappears after prolonged sodium intake. Long-lasting high sodium intake lowers NO bioavailability and promotes systemic and intrarenal vasoconstrictor activity of 20-HETE. Opposed effects of NO and AA metabolites of CYP-450 on water and solute excretion are also described.

Adenosine-activated renovascular dilatation in Sprague-Dawley (SD) rats is mediated by stimulating adenosine(2A) receptors (A(2A)R), which is linked to epoxyeicosatrienoic acid (EET) synthesis. The A(2A)R-EET pathway is upregulated by high salt (HS) intake in normotensive SD rats. Because this pathway is antipressor, we examined the role of the A(2A)R-EET pathway in Dahl salt-sensitive (SS) rats. Male Dahl salt-resistant (SR) and SS rats were fed either HS (8.0% NaCl) or normal salt (NS; 0.4% NaCl) diet for 7 days. On day 8, isolated kidneys were perfused with Krebs-Henseleit buffer containing indomethacin and N(G)-nitro-l-arginine methyl ester and preconstricted with phenylephrine. Bolus injections of the stable adenosine analog 2-chloroadenosine (2-CA; 0.1-20 microg) elicited dose-dependent dilation in both Dahl SR and SS rats. Dahl SR rats fed a HS diet demonstrated a greater renal vasodilator response to 10 microg of 2-CA, as measured by the reduction in renal perfusion pressure, than that of Dahl SR rats fed a NS diet (-104 +/- 6 vs. -77 +/- 7 mmHg, respectively; P < 0.05). In contrast, Dahl SS rats did not exhibit a difference in the vasodilator response to 2-CA whether fed NS or HS diet (96 +/- 6 vs. 104 +/- 13 mmHg in NS- and HS-fed rats, respectively). In Dahl SR but not Dahl SS rats, HS intake significantly increased purine flux, augmented the protein expression of A(2A)R and the cytochrome P-450 2C23 and 2C11 epoxygenases, and elevated the renal efflux of EETs. Thus the Dahl SR rat is able to respond to HS intake by recruiting EET formation, whereas the Dahl SS rat appears to have exhausted its ability to increase EET synthesis above the levels observed on NS intake, and this inability of Dahl SS rats to upregulate the A(2A)R-EET pathway in response to salt loading may contribute to the development of salt-sensitive hypertension.

Soluble epoxide hydrolase (sEH) metabolizes epoxyeicosatrienoic acids (EETs) to dihydroxyeicosatrienoic acids. EETs are formed from arachidonic acid during myocardial ischemia and play a protective role against ischemic cell death. Deletion of sEH has been shown to be protective against myocardial ischemia in the isolated heart preparation. We tested the hypothesis that sEH inactivation by targeted gene deletion or pharmacological inhibition reduces infarct size (I) after regional myocardial ischemia-reperfusion injury in vivo. Male C57BL\6J wild-type or sEH knockout mice were subjected to 40 min of left coronary artery (LCA) occlusion and 2 h of reperfusion. Wild-type mice were injected intraperitoneally with 12-(3-adamantan-1-yl-ureido)-dodecanoic acid butyl ester (AUDA-BE), a sEH inhibitor, 30 min before LCA occlusion or during ischemia 10 min before reperfusion. 14,15-EET, the main substrate for sEH, was administered intravenously 15 min before LCA occlusion or during ischemia 5 min before reperfusion. The EET antagonist 14,15-epoxyeicosa-5(Z)-enoic acid (EEZE) was given intravenously 15 min before reperfusion. Area at risk (AAR) and I were assessed using fluorescent microspheres and triphenyltetrazolium chloride, and I was expressed as I/AAR. I was significantly reduced in animals treated with AUDA-BE or 14,15-EET, independent of the time of administration. The cardioprotective effect of AUDA-BE was abolished by the EET antagonist 14,15-EEZE. Immunohistochemistry revealed abundant sEH protein expression in left ventricular tissue. Strategies to increase 14,15-EET, including sEH inactivation, may represent a novel therapeutic approach for cardioprotection against myocardial ischemia-reperfusion injury.