8-11-14-eicosatrienoic-acid and 14-15-epoxy-5-8-11-eicosatrienoic-acid

Neuroinflammation is a crucial process associated with the pathogenesis of neurodegenerative diseases, including Parkinson's disease (PD). Several pieces of evidence suggest an active role of lipid mediators, especially epoxy-fatty acids (EpFAs), in the genesis and control of neuroinflammation; 14,15-epoxyeicosatrienoic acid (14,15-EET) is one of the most commonly studied EpFAs, with anti-inflammatory properties. Soluble epoxide hydrolase (sEH) is implicated in the hydrolysis of 14,15-EET to its corresponding diol, which lacks anti-inflammatory properties. Preventing EET degradation thus increases its concentration in the brain through sEH inhibition, which represents a novel pharmacological approach to foster the reduction of neuroinflammation and by end neurodegeneration. Recently, it has been shown that sEH levels increase in brains of PD patients. Moreover, the pharmacological inhibition of the hydrolase domain of the enzyme or the use of sEH knockout mice reduced the deleterious effect of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) administration. This paper overviews the knowledge of sEH and EETs in PD and the importance of blocking its hydrolytic activity, degrading EETs in PD physiopathology. We focus on imperative neuroinflammation participation in the neurodegenerative process in PD and the putative therapeutic role for sEH inhibitors. In this review, we also describe highlights in the general knowledge of the role of sEH in the central nervous system (CNS) and its participation in neurodegeneration. We conclude that sEH is one of the most promising therapeutic strategies for PD and other neurodegenerative diseases with chronic inflammation process, providing new insights into the crucial role of sEH in PD pathophysiology as well as a singular opportunity for drug development.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Anti-Inflammatory Agents; Brain; Enzyme Inhibitors; Epoxide Hydrolases; Humans; Neuroprotective Agents; Parkinson Disease

Biologically active epoxyeicosatrienoic acid (EET) regioisomers are synthesized from arachidonic acid by cytochrome P450 epoxygenases of endothelial, myocardial, and renal tubular cells. EETs relax vascular smooth muscle and decrease inflammatory cell adhesion and cytokine release. Renal EETs promote sodium excretion and vasodilation to decrease hypertension. Cardiac EETs reduce infarct size after ischemia-reperfusion injury and decrease fibrosis and inflammation in heart failure. In diabetes, EETs improve insulin sensitivity, increase glucose tolerance, and reduce the renal injury. These actions of EETs emphasize their therapeutic potential. To minimize metabolic inactivation, 14,15-EET agonist analogs with stable epoxide bioisosteres and carboxyl surrogates were developed. In preclinical rat models, a subset of agonist analogs, termed EET-A, EET-B, and EET-C22, are orally active with good pharmacokinetic properties. These orally active EET agonists lower blood pressure and reduce cardiac and renal injury in spontaneous and angiotensin hypertension. Other beneficial cardiovascular actions include improved endothelial function and cardiac antiremodeling actions. In rats, EET analogs effectively combat acute and chronic kidney disease including drug- and radiation-induced kidney damage, hypertension and cardiorenal syndrome kidney damage, and metabolic syndrome and diabetes nephropathy. The compelling preclinical efficacy supports the prospect of advancing EET analogs to human clinical trials for kidney and cardiovascular diseases.

Topics: 8,11,14-Eicosatrienoic Acid; Administration, Oral; Animals; Blood Pressure; Cardiovascular Diseases; Fatty Acids, Monounsaturated; Humans; Hypertension; Kidney Diseases; Muscle, Smooth, Vascular; Structure-Activity Relationship; Vasodilation

Cytochrome P450 (CYP) epoxygenases metabolize arachidonic acid to generate epoxyeicosatrienoic acids (EETs). The latter are biologically active and reported to act as an endothelium-derived hyperpolarizing factor (EDHF) as well as to affect angiogenic and inflammatory signaling pathways. In addition to arachidonic acid, the CYP epoxygenases also metabolize the Ω-3 polyunsaturated fatty acids (PUFAs), eicosapentaenoic acid and docosahexaenoic acid, to generate bioactive lipid epoxide mediators. The latter can be more potent than the EETs but their actions are under investigated. The Ω3-epoxides, like the EETs, are metabolized by the soluble epoxide hydrolase to corresponding diols and epoxide hydrolase inhibition increases epoxide levels and demonstrates anti-hypertensive as well as anti-inflammatory effects. It seems that the overall consequences of CYP epoxygenase activation largely depend on enzyme substrate preference and the endogenous Ω-3/Ω-6 PUFA ratio. This review outlines the evidence for a physiological role for EETs in the regulation of vascular homeostasis.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acid; Biological Factors; Cytochrome P-450 CYP2J2; Cytochrome P-450 Enzyme System; Docosahexaenoic Acids; Eicosapentaenoic Acid; Endothelium, Vascular; Epoxide Hydrolases; Fatty Acids, Omega-3; Fatty Acids, Omega-6; Humans; Signal Transduction

Cardiovascular disease remains the leading cause of death worldwide. Among many potential targets for pharmacological intervention, a promising strategy involves epoxyeicosatrienoic acid (EET) and soluble epoxide hydroxylase (sEH) inhibition. sEH is the enzyme that converts EET to its less potent metabolite; therefore, EET is upregulated by its inhibitor. EET has pleotropic effects that collectively reduce inflammation, while increasing vasodilation and insulin sensitivity. Recent reports indicate that EET agonists and sEH inhibitors are capable of not only reversing endothelial dysfunction and hypertension, but also of reversing cardiac remodeling, which is a hallmark of cardiomyopathy and the metabolic syndrome. EET agonists and sEH inhibitors are in development as potential therapies, and at least one drug is already in clinical trials. This review examines the activity of EET in biological systems, proposes a series of pathways to explain its mechanism of action, and discusses how these might be exploited for potential therapeutic use.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Cardiovascular Diseases; Diabetic Cardiomyopathies; Drug Design; Endothelium, Vascular; Enzyme Inhibitors; Epoxide Hydrolases; Humans; Myocardial Ischemia; Vasodilator Agents

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Antihypertensive Agents; Disease Models, Animal; Disease Progression; Endothelium, Vascular; Fatty Acids; Humans; Hypertension; Kidney Diseases; Mice; Rats

The reactivity and Ca2+ sensitivity of fresh as well as organ-cultured guinea pig bronchi challenged with 5-oxo-ETE and 14,15-EET were compared. Tension measurements, performed on fresh and 3-day cultured bronchi, revealed that the contractile responses to 5-oxo-ETE were largely increased in cultured explants, while 14,15-EET induced larger relaxations on Carbamylcholine (CCh) pre-contracted explants. In fresh bronchi, the contractile responses to 5-oxo-ETE were inhibited by 10 microM indomethacin whereas the relaxing responses induced by 14,15-EET were amplified in the presence of COX inhibitors. COX down expression resulted in a lack of indomethacin effect in cultured explants. One micromolar 5-oxo-ETE increased Ca2+ sensitivity in beta-escin-permeabilized cultured explants, while 1 microM Y-27632 abolished this hypersensitivity. In contrast, 1 microM 14,15-EET significantly reduced the Ca2+ hypersensitivity developed by cultured bronchi. In conclusion, pre-treatment of cultured guinea pig bronchi for 48 h with these eicosanoids modifies the pharmacological responsiveness and Ca2+ sensitivity of these cultured explants.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acids; Bronchi; Calcium; Cyclooxygenase Inhibitors; Female; Guinea Pigs; Male; Organ Culture Techniques

Cytochrome P450 epoxygenases metabolize arachidonic acid to biologically active eicosanoids. Primary epoxidation products are four regioisomers of cis-epoxyeicosatrienoic acid (EET), 5,6-, 8,9-, 11,12-, and 14,15-EET. One of the predominant epoxygenase isoforms involved in EET formation belongs to the CYP2 gene family. In humans, the P450 epoxygenase, CYP2J2, is expressed in the cardiovascular system, namely the endothelium, vascular smooth muscle, and cardiomyocyte. CYP2J2 possesses vascular protective effects, which include but are not limited to, protection against ischemia-reperfusion injury, suppression of reactive oxygen species following hypoxia-reoxygenation, inhibition of the pro-inflammatory transcription factor, nuclear factor-kappaB (NF-kappaB), attenuation of vascular smooth muscle migration, and enhancement of a fibrinolytic pathway. Although regioisomers of EET elicit these effects to varying degrees, 11,12-EET appears to be the most potent with respect to anti-inflammatory, anti-migratory, and pro-fibrinolytic effects. Thus, CYP2J2 and its derived arachidonic acid metabolites may play important roles in regulating vascular function under normal and pathophysiological conditions.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acid; Cell Movement; Cytochrome P-450 CYP2J2; Cytochrome P-450 Enzyme System; Eicosanoids; Fibrinolysis; Humans; Inflammation; Isoenzymes; Models, Biological; Muscle, Smooth, Vascular; Myocytes, Cardiac; NF-kappa B; Oxygenases; Protective Agents; Stereoisomerism; Vasodilation

Epoxyeicosatrienoic acids (EETs) are lipid metabolites that are synthesized in vascular endothelial cells. They are released by stimulation of their muscarinic receptors, and induce vaso-relaxation of cerebral blood vessels. In addition, cytochrome P450 epoxygenase enzymes, which catalyze the formation of epoxyeicosatrienoic acids, especially after stimulation by the excitatory neurotransmitter glutamate, are present in astrocytes, an abundant cell type in the brain that extends foot processes onto the cerebral microvessels. Using a modification of an efficient, recently developed, fluorescent assay, we have detected the presence of EETs in endothelial cells cultured from the cortex of rat brains as well as in neonatal astrocytes. We propose that both these cell types provide a dual supply of EETs to increase cerebral blood flow in order to meet systemic as well as localized nutrient demands of cells in the brain.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Astrocytes; Brain Chemistry; Cerebrovascular Circulation; Endothelium, Vascular; Humans; Microcirculation; Muscle, Smooth, Vascular; Vasodilation

The list of functions attributed to astrocytes in the brain is ever increasing. These cells contain cytochrome P450 enzymes that have recently demonstrated a number of exciting roles besides detoxification. The P450 monooxygenases can covert the substrate arachidonic acid to epoxyeicosatrienoic acids (EETs), metabolites that mediate vasodilation, mitogenesis, platelet aggregation, Ca2+ signaling and steroidogenesis. Integration of other physiological pathways present in astrocytes with P450 mediated EET formation has generated a number of interesting hypotheses to yield deeper insight into the role of astrocytes in the brain. In order to test these hypotheses as well as to enhance the benefits of EETs in astrocytes, we have used viral-mediated gene transfer and overexpression of one cytochrome P450 monooxygenase, 2C11, to engineer astrocytes for gene manipulation and possible gene therapy. This review outlines evidence for the presence of EETs in astrocytes, the function of EETs and the progress made with viral vectors expressing epoxygenase for gene manipulation in astrocytes.

Topics: 8,11,14-Eicosatrienoic Acid; Adenoviridae; Animals; Astrocytes; Cytochrome P-450 CYP2J2; Cytochrome P-450 Enzyme System; Gene Transfer Techniques; Genetic Therapy; Genetic Vectors; Humans; Oxygenases; Platelet Aggregation; Signal Transduction; Steroids; Vasodilation

Several mediators contribute to postocclusive reactive hyperemia (PORH) of the skin, including sensory nerves and endothelium-derived hyperpolarizing factors. The main objective of our study was to investigate the specific contribution of epoxyeicosatrienoic acids in human skin PORH. Eight healthy volunteers were enrolled in two placebo-controlled experiments. In the first experiment we studied the separate and combined effects of 6.5 mM fluconazole, infused through microdialysis fibers, and lidocaine/prilocaine cream on skin PORH following 5 min arterial occlusion. In the second experiment we studied the separate and combined effects of 6.5 mM fluconazole and 10 mM N(G)-monomethyl-l-arginine (l-NMMA). Skin blood flux was recorded using two-dimensional laser speckle contrast imaging. Maximal cutaneous vascular conductance (CVC(max)) was obtained following 29 mM sodium nitroprusside perfusion. The PORH peak at the placebo site averaged 66 ± 11%CVC(max). Compared with the placebo site, the peak was significantly lower at the fluconazole (47 ± 10%CVC(max); P < 0.001), lidocaine (29 ± 10%CVC(max); P < 0.001), and fluconazole + lidocaine (30 ± 10%CVC(max); P < 0.001) sites. The effect of fluconazole on the area under the curve was more pronounced. In the second experiment, the PORH peak was significantly lower at the fluconazole site, but not at the l-NMMA or combination site, compared with the placebo site. In addition to sensory nerves cytochrome epoxygenase metabolites, putatively epoxyeicosatrienoic acids, play a major role in healthy skin PORH, their role being more important in the time course rather than the peak.

Topics: 8,11,14-Eicosatrienoic Acid; Adult; Cytochrome P-450 CYP2J2; Cytochrome P-450 Enzyme System; Female; Fluconazole; Humans; Hyperemia; Lidocaine; Male; NG-Nitroarginine Methyl Ester; Nitroprusside; Regional Blood Flow; Sensory Receptor Cells; Skin; Skin Diseases

Central post stroke pain (CPSP) is an intractable neuropathic pain syndrome that occurs after the acute focal lesion of the central nervous system (CNS) due to a cerebrovascular cause. Epoxyeicosatrienoic acids (EETs) exert many pharmacological effects in vivo and in vitro, such as anti-apoptosis, anti-inflammatory, and anti-oxidative stress. Neuroinflammation and apoptosis are the potential pathophysiological mechanisms of neuropathic pain. This study aimed to investigate whether 14,15-EET has an antinociception effect on CPSP rats through its anti-inflammation and anti-apoptosis mechanisms. Rats were treated with type IV collagenase (CPSP group) or saline (Sham group) via injection with a Hamilton syringe into the ventral posterior lateral nucleus (VPL) according to the stereotaxic coordinates. We first tested the mechanical withdrawal threshold, as well as neuroinflammation- and apoptosis-related protein expressions in the per-lesion site of CPSP and Sham rats. Sprague-Dawley rats were randomly divided into five groups, as follows: vehicle; EET at 0.025, 0.05, and 0.1 μg; and EET (0.1 μg) + EEZE (3.25 ng). EET or and vehicle were administered into VPL nuclei three consecutive days after hemorrhagic stroke. Immunostaining, ELISA, and Western blot were performed to evaluate neuroinflammation and apoptosis. Hemorrhagic stroke induced mechanical allodynia, glial activation, neuroinflammation, and apoptosis-related protein upregulation. However, early treatment with 14,15-EET inhibited glial cell activation, decreased proinflammatory cytokines and apoptosis-related protein, and alleviated the pain behavior of CPSP rats. Our results provided strong evidence that antinociception produced by 14,15-EET is partly mediated by the inhibition of neuroinflammation and apoptosis.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Anti-Inflammatory Agents; Neuralgia; Rats; Rats, Sprague-Dawley

Cardiac hypertrophy is a key structural change in diabetic cardiomyopathy, which mechanism is unknown. 14,15-Epoxyeicosatrienoic acid (14,15-EET) generated from arachidonic acid by CYP2J2 has beneficial effects in metabolic syndrome, which also plays vital roles in inflammatory response. Peroxisome proliferator activated receptors (PPARs) are members of the nuclear receptor superfamily and have three subtypes of α, β (or δ) and γ. Studies have found that 14,15-EET can perform various biological functions by activating PPARs, but its role in diabetic cardiac hypertrophy is unknown. This study aimed to investigate the role of 14,15-EET-PPARs signaling pathway in the development of diabetic cardiac hypertrophy. Diabetic cardiac hypertrophy was developed by high-fat diet feeding combined with streptozotocin (40 mg/kg/d for 5 days, i.p.) in mice and was induced by glucose at 25.5 mmol/L (high glucose, HG) in H9c2 cells. The decreased level of 14,15-EET and the down-regulated expression of PPARα, PPARβ and PPARγ were found following diabetic cardiac hypertrophy in mice. Similarly, both the level of 14,15-EET and the PPARs expression were also reduced in HG-induced hypertrophic cardiomyocytes. Supplementation with 14,15-EET improved the cardiomyocyte hypertrophy and up-regulated PPARs expression, which were nullified by 14,15-EEZE, a 14,15-EET antagonist. Taken together, we conclude that the decreased 14,15-EET is involved in the development of diabetic cardiac hypertrophy through the down-regulation of PPARs.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Cardiomegaly; Diabetes Mellitus; Diabetic Cardiomyopathies; Glucose; Mice; Myocytes, Cardiac; PPAR gamma

Central post-stroke pain (CPSP) is a chronic and intolerable neuropathic pain syndrome following a cerebral vascular insult, which negatively impacts the quality of life of stroke survivors but currently lacks efficacious treatments. Though its underlying mechanism remains unclear, clinical features of hyperalgesia and allodynia indicate central sensitization due to excessive neuroinflammation. Recently, the crosslink between neuroinflammation and endoplasmic reticulum (ER) stress has been identified in diverse types of diseases. Nevertheless, whether this interaction contributes to pain development remains unanswered. Epoxyeicosatrienoic acids (EETs)/soluble epoxy hydrolase inhibitors (sEHi) are emerging targets that play a significant role in pain and neuroinflammatory regulation. Moreover, recent studies have revealed that EETs are effective in attenuating ER stress. In this study, we hypothesized that ER stress around the stroke site may activate glial cells and lead to further inflammatory cascades, which constitute a positive feedback loop resulting in central sensitization and CPSP. Additionally, we tested whether EETs/sEHi could attenuate CPSP by suppressing ER stress and neuroinflammation, as well as their vicious cycle, in a rat model of CPSP.. Young male SD rats were used to induce CPSP using a model of thalamic hemorrhage and were then treated with TPPU (sEHi) alone or in combination with 14,15-EET or 14,15-epoxyeicosa-5(Z)-enoic acid (14,15-EEZE, the EET antagonist), tunicamycin (Tm, ER stress inducer), or 4-PBA (ER stress inhibitor). Nociceptive behaviors, ER stress markers, JNK and p38 (two well-recognized inflammatory kinases of mitogen-activated protein kinase (MAPK) signaling) expression, and glial cell activation were assessed. In addition, some healthy rats were intrathalamically microinjected with Tm or lipopolysaccharide (LPS) to test the interaction between ER stress and neuroinflammation in central pain.. Analysis of the perithalamic lesion tissue from the brain of CPSP rats demonstrated decreased soluble epoxy hydrolase (sEH) expression, which was accompanied by increased expression of ER stress markers, including BIP, p-IRE, p-PERK, and ATF6. In addition, inflammatory kinases (p-p38 and p-JNK) were upregulated and glial cells were activated. Intrathalamic injection of sEHi (TPPU) increased the paw withdrawal mechanical threshold (PWMT), reduced hallmarks of ER stress and MAPK signaling, and restrained the activation of microglia and astrocytes around the lesion site. However, the analgesic effect of TPPU was completely abolished by 14,15-EEZE. Moreover, microinjection of Tm into the thalamic ventral posterior lateral (VPL) nucleus of healthy rats induced mechanical allodynia and activated MAPK-mediated neuroinflammatory signaling; lipopolysaccharide (LPS) administration led to activation of ER stress along the injected site in healthy rats.. The present study provides evidence that the interaction between ER stress and neuroinflammation is involved in the mechanism of CPSP. Combined with the previously reported EET/sEHi effects on antinociception and neuroprotection, therapy with agents that target EET signaling may serve as a multi-functional approach in central neuropathic pain by attenuating ER stress, excessive neuroinflammation, and subsequent central sensitization. The use of these agents within a proper time window could not only curtail further nerve injury but also produce an analgesic effect.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Endoplasmic Reticulum Stress; Epoxide Hydrolases; Male; Neuralgia; Neuroinflammatory Diseases; Nociception; Phenylurea Compounds; Piperidines; Rats; Rats, Sprague-Dawley; Stroke; Vasodilator Agents

To investigate the effect of 14,15-EET on the parthanatos in neurons induced by cerebral ischemia and reperfusion, middle cerebral artery occlusion and reperfusion (MCAO/R) and oxygen glucose deprivation/reoxygenation (OGD/R) were used to simulate cerebral ischemia reperfusion in vivo and in vitro, respectively. TTC staining and the Tunel method were used to detect cerebral infarct volume and neuronal apoptosis. Western blot and immunofluorescence were used to detect poly (ADP-ribose) polymerase-1 (PARP-1) activation and AIF nuclear translocation. The production of reactive oxygen species (ROS) and the expression of antioxidant genes were detected by Mito SOX, DCFH-DA and qPCR methods. MCAO/R increased cerebral infarct volume and neuronal apoptosis in mice, while 14,15-EET pretreatment increased cerebral infarct volume and neuronal apoptosis. OGD/R induced reactive oxygen species generation, PARP-1 cleavage, and AIF nuclear translocation in cortical neurons. 14,15-EET pretreatment could enhance the antioxidant gene expression of glutathione peroxidase (GSH-Px), heme oxygenase-1 (HO-1) and superoxide dismutase (SOD) in cortical neurons after ischemia and reperfusion. 14,15-EET inhibits the neuronal parthanatos induced by MCAO/R through upregulation of the expression of antioxidant genes and by reducing the generation of reactive oxygen species. This study advances the EET neuroprotection theory and provides a scientific basis for targeted clinical drugs that reduce neuronal parthanatos following cerebral ischemia and reperfusion.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Brain Injuries; Brain Ischemia; Disease Models, Animal; Glucose; Male; Mice; Models, Biological; Neurons; Neuroprotective Agents; Oxidative Stress; Parthanatos; Reactive Oxygen Species; Reperfusion Injury

Studies have shown that epoxyeicosatrienoic acids (EETs) can regulate glucose homeostasis, but the specific mechanisms need further exploration. The sodium-glucose co-transporter 2 (SGLT2) is highly expressed in diabetic kidneys, which further promotes renal reabsorption of glucose to respond to the hyperglycemic state of diabetes. Herein, whether EETs can be a latent inhibitor of SGLT2 to regulate glucose homeostasis in diabetic state needs to be elucidated. Our study demonstrated that EETs attenuated the glucose reabsorption via renal tubular epithelial cells in diabetic mice, which partly accounted for the beneficial effects of EETs on glucose homeostasis. Moreover, 14,15-EET suppressed SGLT2 expression in both diabetic kidney and renal tubular epithelial cells. Further, inhibition of NF-κB with BAY 11-7082 decreased insulin-induced SGLT2 expression while NF-κB overexpression reversed the above effects. In addition, 14,15-EET attenuated SGLT2 expression via inactivating NF-κB. Mechanistically, 14,15-EET attenuated NF-κB mediated SGLT2 transcription at the -1821/-1812 P65-binding site. These results showed that EETs ameliorated glucose homeostasis via preventing NF-κB-mediated transcription of SGLT2 in renal tubular epithelial cells, providing a unique therapeutic strategy for insulin resistance and diabetes.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Cell Line; Diabetes Mellitus, Experimental; Epithelial Cells; Glucose; Homeostasis; Humans; Insulin; Kidney Tubules, Proximal; Mice, Inbred C57BL; NF-kappa B; Phenylurea Compounds; Piperidines; Sodium-Glucose Transporter 2; Transcription, Genetic

Diabetic cardiomyopathy (DCM) is a well-established complication of type 1 and type 2 diabetes associated with a high rate of morbidity and mortality. DCM is diagnosed at advanced and irreversible stages. Therefore, it is of utmost need to identify novel mechanistic pathways involved at early stages to prevent or reverse the development of DCM. In vivo experiments were performed on type 1 diabetic rats (T1DM). Functional and structural studies of the heart were executed and correlated with mechanistic assessments exploring the role of cytochromes P450 metabolites, the 20-hydroxyeicosatetraenoic acids (20-HETEs) and epoxyeicosatrienoic acids (EETs), and their crosstalk with other homeostatic signaling molecules. Our data displays that hyperglycemia results in CYP4A upregulation and CYP2C11 downregulation in the left ventricles (LV) of T1DM rats, paralleled by a differential alteration in their metabolites 20-HETEs (increased) and EETs (decreased). These changes are concomitant with reductions in cardiac outputs, LV hypertrophy, fibrosis, and increased activation of cardiac fetal and hypertrophic genes. Besides, pro-fibrotic cytokine TGF-ß overexpression and NADPH (Nox4) dependent-ROS overproduction are also correlated with the observed cardiac functional and structural modifications. Of interest, these observations are attenuated when T1DM rats are treated with 12-(3-adamantan-1-yl-ureido) dodecanoic acid (AUDA), which blocks EETs metabolism, or N-hydroxy-N'-(4-butyl-2-methylphenol)Formamidine (HET0016), which inhibits 20-HETEs formation. Taken together, our findings confer pioneering evidence about a potential interplay between CYP450-derived metabolites and Nox4/TGF-β axis leading to DCM. Pharmacologic interventions targeting the inhibition of 20-HETEs synthesis or the activation of EETs synthesis may offer novel therapeutic approaches to treat DCM.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acid; Cardiomyopathies; Cytochrome P-450 Enzyme System; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 1; Hydroxyeicosatetraenoic Acids; Male; NADPH Oxidase 4; Rats; Rats, Sprague-Dawley; Reactive Oxygen Species; Streptozocin

G-protein coupled receptors (GPCRs) sense a wide variety of stimuli, including lipids, and transduce signals to the intracellular environment to exert various physiological responses. However, the structural features of GPCRs responsible for detecting and triggering responses to distinct lipid ligands have only recently begun to be revealed. 14,15-epoxyeicosatrienoic acid (14,15-EET) is one such lipid mediator that plays an essential role in the vascular system, displaying both vasodilatory and anti-inflammatory properties. We recently reported multiple low-affinity 14,15-EET-binding GPCRs, but the mechanism by which these receptors sense 14,15-EET remains unclear. Here, we have taken a combined computational and experimental approach to identify and confirm critical residues and properties within the lipid-binding pocket. Furthermore, we generated mutants to engineer selected GPCR-predicted binding sites to either confer or abolish 14,15-EET-induced signaling. Our structure-function analyses indicate that hydrophobic and positively charged residues of the receptor-binding pocket are prerequisites for recognizing lipid ligands such as 14,15-EET and possibly other eicosanoids.

Topics: 8,11,14-Eicosatrienoic Acid; Binding Sites; Humans; Ligands; Lipids; Protein Binding; Receptors, G-Protein-Coupled

Airway remodeling in asthma is difficult to treat because of its complex pathophysiology that involves proinflammatory cytokines, as well as the arachidonic acid cytochrome P-450 (CYP) pathway; however, it has received little attention. In this study, we assessed the efficacy of a soluble epoxide hydrolase (sEH) on airway remodeling in a mouse model of chronic asthma. The expression of sEH and CYP2J2 and the level of 14,15-epoxyeicosatrienoic acid (14,15-EET), airway remodeling and hyperresponsiveness (AHR) were analyzed to determine the level of sEH inhibition. AUDA, a sEH inhibitor, was given daily for 9 weeks orally, which significantly increased the level of 14,15-EET by inhibiting the expression of sEH and increasing the expression of CYP2J2 in lung tissues. The inhibition of sEH reduced the expression of remodeling-related molecular markers, such as interleukin (IL)-13, IL-17, matrix metalloproteinase 9, N-cadherin, α-smooth muscle actin (α-SMA), S100A4, Twist, epithelial goblet cell metaplasia, and collagen deposition in bronchoalveolar lavage fluid (BAL fluid) and lung tissues. Moreover, remodeling-related eosinophil accumulation in the BAL fluid and infiltration into the lung tissue were improved by AUDA. Finally, AUDA alleviated AHR, which is a functional indicator of airway remodeling. The effect of AUDA on airway remodeling was related to the downregulation of extracellular-regulated protein kinases (Erk1/2), c-Jun N-terminal kinases (JNK) and signal transducer and activator of transcription 3 (STAT3). To our knowledge, this is the first report to demonstrate that inhibition of sEH exerts significant protective effects on airway remodeling in asthma.

Topics: 8,11,14-Eicosatrienoic Acid; Adamantane; Airway Remodeling; Animals; Asthma; Bronchoalveolar Lavage Fluid; Cytochrome P-450 CYP2J2; Cytochrome P-450 Enzyme System; Disease Models, Animal; Epoxide Hydrolases; Female; Humans; Lauric Acids; Lung; MAP Kinase Signaling System; Mice; Ovalbumin; Signal Transduction; STAT3 Transcription Factor

Diabetes mellitus is a metabolic disorder that can lead to blood-brain barrier (BBB) disruption and cognitive decline. However, the mechanisms of BBB breakdown in diabetes are still unclear. Soluble epoxide hydrolase (sEH) is an enzyme that degrades epoxyeicosatrienoic acids (EETs), which have multiple protective effects on vascular structure and functions. In the current study, we showed increased vascular permeability of the BBB, which was accompanied by upregulation of sEH and downregulation of 14,15-EET. Moreover, the sEH inhibitor t-AUCB restored diabetic BBB integrity in vivo, and 14,15-EET prevented ROS accumulation and MEC injury in vitro. t-AUCB or 14,15-EET treatment provoked AMPK/HO-1 activation under diabetic conditions in vivo and in vitro. Thus, we suggest that decreased EET degradation by sEH inhibition might be a potential therapeutic approach to attenuate the progression of BBB injury in diabetic mice via AMPK/HO-1 pathway activation.

Topics: 8,11,14-Eicosatrienoic Acid; AMP-Activated Protein Kinases; Animals; Blood-Brain Barrier; Diabetes Mellitus, Type 2; Disease Models, Animal; Enzyme Inhibitors; Epoxide Hydrolases; Heme Oxygenase-1; Male; Membrane Proteins; Mice; Oxidative Stress; Protective Agents; Reactive Oxygen Species; Signal Transduction

Epoxyeicosatrienoic acids (EETs) are epoxy fatty acids that have biological actions that are essential for maintaining water and electrolyte homeostasis. An inability to increase EETs in response to a high-salt diet results in salt-sensitive hypertension. Vasodilation, inhibition of epithelial sodium channel, and inhibition of inflammation are the major EET actions that are beneficial to the heart, resistance arteries, and kidneys. Genetic and pharmacological means to elevate EETs demonstrated antihypertensive, anti-inflammatory, and organ protective actions. Therapeutic approaches to increase EETs were then developed for cardiovascular diseases. sEH (soluble epoxide hydrolase) inhibitors were developed and progressed to clinical trials for hypertension, diabetes mellitus, and other diseases. EET analogs were another therapeutic approach taken and these drugs are entering the early phases of clinical development. Even with the promise for these therapeutic approaches, there are still several challenges, unexplored areas, and opportunities for epoxy fatty acids.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acid; Cardiovascular Diseases; Cytochrome P-450 Enzyme System; Disease Models, Animal; Epoxide Hydrolases; Forecasting; Humans; Hypertension; Kidney; Kidney Diseases; Mice; Natriuresis; Potassium; Rats; Rats, Inbred Dahl; Sodium Chloride; Sodium Chloride, Dietary; Vasodilation; Water-Electrolyte Balance; Water-Electrolyte Imbalance

Central poststroke pain (CPSP) is a neuropathic pain syndrome arising after a lesion of the central nervous system owing to cerebrovascular insult. Impaired daily activities and reduced quality of life in people suffering from CPSP justify the need for improved treatment. The detailed mechanism of CPSP is not well understood, but central disinhibition has been suggested. Recent reports indicated that epoxyeicosatrienoic acids (EETs), the cytochrome P450 metabolites of arachidonic acid, promoted neuronal survival after stroke, displayed antinociception in peripheral inflammatory pain, and reduced neuronal excitability in seizure model. Here, we tested the hypothesis that 14,15-EET may attenuate CPSP by suppressing thalamic disinhibition through neurosteroids-δ-subunit-containing gamma-aminobutyric acid A receptors (δGABA

Topics: 8,11,14-Eicosatrienoic Acid; Analgesics; Animals; Cerebral Hemorrhage; Disease Models, Animal; Gabapentin; Hyperalgesia; Male; Pregnanolone; Proof of Concept Study; Random Allocation; Rats, Sprague-Dawley; Receptors, GABA-A; Stroke; Thalamus

Imbalances in cytochrome P450 (CYP)-dependent eicosanoid formation may play a central role in ischemic acute kidney injury (AKI). We reported previously that inhibition of 20-hydroxyeicosatetraenoic acid (20-HETE) action ameliorated ischemia/reperfusion (I/R)-induced AKI in rats. Now we tested the hypothesis that enhancement of epoxyeicosatrienoic acid (EET) actions may counteract the detrimental effects of 20-HETE and prevent the initiation of AKI.. Male Lewis rats underwent right nephrectomy and ischemia was induced by 45 min clamping of the left renal pedicle followed by up to 48 h of reperfusion. Circulating CYP-eicosanoid profiles were compared in patients who underwent cardiac surgery with (n = 21) and without (n = 38) developing postoperative AKI.. Ischemia induced an about eightfold increase of renal 20-HETE levels, whereas free EETs were not accumulated. To compensate for this imbalance, a synthetic 14,15-EET analogue was administered by intrarenal infusion before ischemia. The EET analogue improved renal reoxygenation as monitored by in vivo parametric MRI during the initial 2 h reperfusion phase. The EET analogue improved PI3K- as well as mTORC2-dependent rephosphorylation of Akt, induced inactivation of GSK-3β, reduced the development of tubular apoptosis and attenuated inflammatory cell infiltration. The EET analogue also significantly alleviated the I/R-induced drop in creatinine clearance. Patients developing postoperative AKI featured increased preoperative 20-HETE and 8,9-EET levels.. Pharmacological interventions targeting the CYP-eicosanoid pathway could offer promising new options for AKI prevention. Individual differences in CYP-eicosanoid formation may contribute to the risk of developing AKI in clinical settings.

Topics: 8,11,14-Eicosatrienoic Acid; Acute Kidney Injury; Animals; Cardiac Surgical Procedures; Fatty Acids; Humans; Hydroxyeicosatetraenoic Acids; Ischemia; Kidney; Male; Postoperative Complications; Rats; Rats, Inbred Lew; Reperfusion Injury; Signal Transduction

Astrocytes play pivotal roles in regulating glutamate homeostasis at tripartite synapses. Inhibition of soluble epoxide hydrolase (sEHi) provides neuroprotection by blocking the degradation of 14,15-epoxyeicosatrienoic acid (14,15-EET), a lipid mediator whose synthesis can be activated downstream from group 1 metabotropic glutamate receptor (mGluR) signaling in astrocytes. However, it is unclear how sEHi regulates glutamate excitotoxicity. Here, we used three primary rat cortical culture systems, neuron-enriched (NE), astrocyte-enriched glia-neuron mix (GN), and purified astrocytes, to delineate the underlying mechanism by which sEHi and 14,15-EET attenuate excitotoxicity. We found that sEH inhibitor 12-(3-adamantan-1-yl-ureido)-dodecanoic acid (AUDA) and 14,15-EET both attenuated N-methyl-D-aspartate (NMDA)-induced neurite damage and cell death in GN, not NE, cortical cultures. The anti-excitotoxic effects of 14,15-EET and AUDA were both blocked by the group 1 mGluR5 antagonist 2-methyl-6-(phenylethynyl)pyridine (MPEP), as were their protective effects against NMDA-disrupted perineuronal astrocyte processes expressing glutamate transporter-1 (GLT-1) and subsequent glutamate uptake. Knockdown of sEH expression also attenuated NMDA neurotoxicity in mGluR5- and GLT-1-dependent manners. The 14,15-EET/AUDA-preserved astroglial integrity was confirmed in glutamate-stimulated primary astrocytes along with the reduction of the c-Jun N-terminal kinase 1 phosphorylation, in which the 14,15-EET effect is mGluR5-dependent. In vivo studies validated that sEHi and genetic deletion of sEH (Ephx2-KO) ameliorated excitotoxic kainic acid-induced seizure, memory impairment, and neuronal loss while preserving GLT-1-expressing perineuronal astrocytes in hippocampal CA3 subregions. These results suggest that 14,15-EET mediates mGluR5-dependent anti-excitotoxicity by protecting astrocytes to maintain glutamate homeostasis, which may account for the beneficial effect of sEH inhibition in excitotoxic brain injury and diseases.

Topics: 8,11,14-Eicosatrienoic Acid; Adamantane; Animals; Astrocytes; Cell Survival; Cells, Cultured; Enzyme Inhibitors; Epoxide Hydrolases; Excitatory Amino Acid Transporter 2; Glutamic Acid; Hippocampus; Homeostasis; Kainic Acid; Lauric Acids; Mice, Inbred C57BL; Mitogen-Activated Protein Kinase 8; Models, Biological; N-Methylaspartate; Neuroglia; Neuronal Plasticity; Neurons; Neurotoxins; Rats, Sprague-Dawley; Receptor, Metabotropic Glutamate 5; Solubility

Dronedarone and amiodarone are structurally similar antiarrhythmic drugs. Dronedarone worsens cardiac adverse effects with unknown causes while amiodarone has no cardiac adversity. Dronedarone induces preclinical mitochondrial toxicity in rat liver and exhibits clinical hepatotoxicity. Here, we further investigated the relative potential of the antiarrhythmic drugs in causing mitochondrial injury in cardiomyocytes. Differentiated rat H9c2 cardiomyocytes were treated with dronedarone, amiodarone, and their respective metabolites namely N-desbutyldronedarone (NDBD) and N-desethylamiodarone (NDEA). Intracellular ATP content, mitochondrial membrane potential (Δψm), and inhibition of carnitine palmitoyltransferase I (CPT1) activity and arachidonic acid (AA) metabolism were measured in H9c2 cells. Inhibition of electron transport chain (ETC) activities and uncoupling of ETC were further studied in isolated rat heart mitochondria. Dronedarone, amiodarone, NDBD and NDEA decreased intracellular ATP content significantly (IC50 = 0.49, 1.84, 1.07, and 0.63 µM, respectively) and dissipated Δψm potently (IC50 = 0.5, 2.94, 12.8, and 7.38 µM, respectively). Dronedarone, NDBD, and NDEA weakly inhibited CPT1 activity while amiodarone (IC50 > 100 µM) yielded negligible inhibition. Only dronedarone inhibited AA metabolism to its regioisomeric epoxyeicosatrienoic acids (EETs) consistently and potently. NADH-supplemented ETC activity was inhibited by dronedarone, amiodarone, NDBD and NDEA (IC50 = 3.07, 5.24, 11.94, and 16.16 µM, respectively). Cytotoxicity, ATP decrease and Δψm disruption were ameliorated via exogenous pre-treatment of H9c2 cells with 11, 12-EET and 14, 15-EET. Our study confirmed that dronedarone causes mitochondrial injury in cardiomyocytes by perturbing Δψm, inhibiting mitochondrial complex I, uncoupling ETC and dysregulating AA-EET metabolism. We postulate that cardiac mitochondrial injury is one potential contributing factor to dronedarone-induced cardiac failure exacerbation.

Topics: 8,11,14-Eicosatrienoic Acid; Adenosine Triphosphate; Anti-Arrhythmia Agents; Cardiotonic Agents; Cell Line; Cell Survival; Dronedarone; Humans; Membrane Potential, Mitochondrial; Mitochondria, Heart; Myocytes, Cardiac

14,15-epoxyeicosatrienoic acid (14,15-EET) is an important lipid signaling molecule involved in the regulation of tumor metastasis, however, the role and molecular mechanisms of 14,15-EET activity in breast cancer cell epithelial-mesenchymal transition (EMT) and drug resistance remain enigmatic.. The 14, 15-EET level in serum and in tumor or non-cancerous tissue from breast cancer patients was measured by ELISA. qRT-PCR and western blot analyses were used to examine expression of integrin αvβ3. The role of 14, 15-EET in breast cancer cell adhesion, invasion was explored by adhesion and Transwell assays. The role of 14, 15-EET in breast cancer cell cisplatin resistance in vitro was determined by MTT assay. Western blot was conducted to detect the protein expressions of EMT-related markers and FAK/PI3K/AKT signaling. Xenograft models in nude mice were established to explore the roles of 14, 15-EET in breast cancer cells EMT and cisplatin resistance in vivo.. In the present study, we show that serum level of 14, 15-EET increases in breast cancer patients and 14, 15-EET level of tumor tissue is higher than that of non-cancerous tissue. Moreover, 14, 15-EET increases integrin αvβ3 expression, leading to FAK activation. 14, 15-EET induces breast cancer cell EMT via integrin αvβ3 and FAK/PI3K/AKT cascade activation in vitro. Furthermore, we find that 14, 15-EET induces breast cancer cells EMT and cisplatin resistance in vivo, αvβ3 integrin and the resulting FAK/PI3K/AKT signaling pathway are responsible for 14, 15-EET induced-breast cancer cells cisplatin resistance.. Our findings suggest that inhibition of 14, 15-EET or inactivation of integrin αvβ3/FAK/PI3K/AKT pathway could serve as a novel approach to reverse EMT and cisplatin resistance in breast cancer cells.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Breast Neoplasms; Cell Adhesion; Cell Line, Tumor; Cell Movement; Cell Proliferation; Cisplatin; Disease Models, Animal; Drug Resistance, Neoplasm; Epithelial-Mesenchymal Transition; Female; Humans; Immunohistochemistry; Integrin alphaVbeta3; Mice; Phosphatidylinositol 3-Kinases; Phosphorylation; Proto-Oncogene Proteins c-akt; Signal Transduction; Xenograft Model Antitumor Assays

This study aimed to explore the metabololipidome in mice upon cupping treatment.. A nude mouse model mimicking the cupping treatment in humans was established by administrating four cupping sets on the back skin for 15 minutes. UPLC-MS/ MS was performed to determine the PUFA metabolome in mice skin and blood before and after cupping treatment. The significantly changed lipids were administered in macrophages to assess the production of pro-inflammatory cytokines IL-6 and TNF-α by ELISA.. The anti-inflammatory lipids, e.g. PGE1, 5,6-EET, 14,15-EET, 10S,17S-DiHDoHE, 17R-RvD1, RvD5 and 14S-HDoHE were significantly increased while pro-inflammatory lipids, e.g. 12-HETE and TXB2 were deceased in the skin or plasma post cupping treatment. Cupping treatment reversed the LPS-stimulated IL-6 and TNF-α expression in mouse peritoneal exudates. Moreover, 5,6-EET, PGE1 decreased the level of TNF-α, while 5,6-EET, 5,6-DHET downregulated IL-6 production in macrophages. Importantly, 14,15-EET and 14S-HDoHE inhibited both IL-6 and TNF-α induced by lipopolysaccharide (LPS). 17-RvD1, RvD5 and PGE1 significantly reduced the LPS-initiated TNF-α, while TXB2 and 12-HETE further upregulated the LPS-enhanced IL-6 and TNF-α expression in macrophages.. Our results reveal the identities of anti-inflammatory versus pro-inflammatory metabolipidome and suggest the potential therapeutic mechanism of cupping treatment.

Topics: 12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; 8,11,14-Eicosatrienoic Acid; Animals; Bone Marrow Cells; Cells, Cultured; Fatty Acids, Unsaturated; Hematoma; Interleukin-6; Lipids; Lipopolysaccharides; Macrophages; Male; Metabolome; Mice; Mice, Inbred C57BL; Mice, Nude; RAW 264.7 Cells; Skin; Thromboxane B2; Tumor Necrosis Factor-alpha; Up-Regulation

We have shown that epoxyeicosatrienoic acids (EETs), specifically 11,12- and 14,15-EETs, reduce adipogenesis in human mesenchymal stem cells and mouse preadipocytes (3T-3L1). In this study, we explore the effects of soluble epoxide hydrolase (sEH) deletion on various aspects of adipocyte-function, including programing for white vs. beige-like fat, and mitochondrial and thermogenic gene-expressions. We further hypothesize that EETs and heme-oxygenase 1 (HO-1) form a synergistic, functional module whose effects on adipocyte and vascular function is greater than the effects of sEH deletion alone. In in vitro studies, we examined the effect of sEH inhibitors on MSC-derived adipocytes. MSC-derived adipocytes exposed to AUDA, an inhibitor of sEH, exhibit an increased number of small and healthy adipocytes, an effect reproduced by siRNA for sEH. in vivo studies indicate that sEH deletion results in a significant decrease in adipocyte size, inflammatory adipokines NOV, TNFα, while increasing adiponectin (p < 0.05). These findings are associated with a decrease in body weight (p < 0.05), and visceral fat (p < 0.05). Importantly, sEH deletion was associated with a significant increase in Mfn1, COX 1, UCP1 and adiponectin (p < 0.03). sEH deletion was manifested by a significant increase in EETs isomers 5,6-EET, 8,9-EET, 11,12-EET, and 14,15-EET and an increased EETs/DHETEs ratio. Notably, activation of HO-1 gene expression further increased the levels of EETs, suggesting that the antioxidant HO-1 system protects EETs from degradation by ROS. These results are novel in that sEH deletion, while increasing EET levels, resulted in reprograming of white fat to express mitochondrial and thermogenic genes, a phenotype characteristic of beige-fat. Thus, EETs agonist(s) and sEH inhibitors may have therapeutic potential in the treatment of metabolic syndrome and obesity.

Topics: 3T3-L1 Cells; 8,11,14-Eicosatrienoic Acid; Adipocytes; Adiponectin; Adipose Tissue, Beige; Adipose Tissue, White; Animals; Cells, Cultured; Epoxide Hydrolases; Gene Expression; Heme Oxygenase-1; Humans; Mesenchymal Stem Cells; Mice; Mice, Knockout; Mitochondria; RNA Interference; Solubility; Vasodilator Agents

A method for the detection and quantification of hydroxyl and epoxy arachidonic acid (AA) metabolites in human plasma was developed using liquid-liquid extraction, phospholipid saponification followed by derivatization of the acid moiety and liquid chromatographic tandem mass spectrometric detection. Derivatization with a pyridinium analog allowed for detection in the positive ion mode, greatly improving sensitivity and the stability of the more labile AA metabolites. The entire method utilizes a 96-well plate format, increasing sample throughput, and was optimized to measure 5-, 8-, 9-, 11-, 12-, 15-, 19-, and 20- hydroxyeicosatetraenoic acid (HETE), 5,6-, 8,9-, 11,12-, and 14,15- dihydroxyeicosatrienoic acid (DHET), and the regio- and cis-/ trans- isomers of 5,6-, 8,9-, 11,12-, and 14,15-epoxyeicosatrienoic acid (EET). The method was validated for its applicability over the FA concentration range found in human plasma. Using 100 μL aliquots of pooled human plasma, EET levels, particularly 5,6-EET, were observed to be higher than previously reported, with measured concentrations of 23.6 ng/ml for 5,6-EET, 5.6 ng/mL for 5,6-trans-EET, 8.0 ng/mL for 8,9-EET, 1.9 ng/mL for 8,9-trans-EET, 8.8 ng/mL for 11,12-EET, 3.4 ng/mL for 11,12-trans-EET, 10.7 ng/mL for 14,15-EET, and 1.7 ng/mL 14,15-trans- EET. This method is suitable for large population studies to elucidate the complex interactions between the eicosanoids and various disease states and may be used for quantitation of a wide variety of fattyacids beyond eicosanoids from small volumes of human plasma.

Topics: 8,11,14-Eicosatrienoic Acid; Arachidonic Acid; Chromatography, High Pressure Liquid; Cytochrome P-450 Enzyme System; Humans; Molecular Structure; Solid Phase Extraction; Stereoisomerism; Tandem Mass Spectrometry

Polyunsaturated fatty acids, such as arachidonic acid, are accumulated in brain and induce neuronal differentiation. Arachidonic acid is metabolized to epoxyeicosatrienoic acids (EETs) and hydroxyeicosatetraenoic acids (HETEs) by cytochrome P450s. In this study, we found that 14,15-EET and 20-HETE-enhanced NGF-induced rat pheochromocytoma PC12 cell neurite outgrowth even at the concentration of 100 nmol L

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acid; Calcium; Capsaicin; Cytochrome P-450 Enzyme Inhibitors; Cytochrome P-450 Enzyme System; Embryo, Mammalian; Hippocampus; Neurites; Neuronal Outgrowth; PC12 Cells; Primary Cell Culture; Rats; Rats, Wistar; TRPV Cation Channels

We previously demonstrated that the direct transplantation of human umbilical cord blood-derived mesenchymal stem cells (hUCB-MSCs) into the dentate gyrus ameliorated the neurological symptoms of Niemann-Pick type C1 (NPC1)-mutant mice. However, the clinical presentation of NPC1-mutant mice was not fully understood with a molecular mechanism. Here, we found 14,15-epoxyeicosatrienoic acid (14,15-EET), a cytochrome P450 (CYP) metabolite, from hUCB-MSCs and the cerebella of NPC1-mutant mice and investigated the functional consequence of this metabolite. Our screening of the CYP2J family indicated a dysregulation in the CYP system in a cerebellar-specific manner. Moreover, in Purkinje cells, CYP2J6 showed an elevated expression level compared to that of astrocytes, granule cells, and microglia. In this regard, we found that one CYP metabolite, 14,15-EET, acts as a key mediator in ameliorating cholesterol accumulation. In confirming this hypothesis, 14,15-EET treatment reduced the accumulation of cholesterol in human NPC1 patient-derived fibroblasts in vitro by suppressing cholesterol synthesis and ameliorating the impaired autophagic flux. We show that the reduced activity within the CYP system in the cerebellum could cause the neurological symptoms of NPC1 patients, as 14,15-EET treatment significantly rescued cholesterol accumulation and impaired autophagy. We also provide evidence that the intranasal administration of hUCB-MSCs is a highly promising alternative to traumatic surgical transplantation for NPC1 patients.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Autophagy; Cells, Cultured; Cholesterol; Cytochrome P-450 CYP2J2; Cytochrome P-450 Enzyme System; Homeostasis; Humans; Mesenchymal Stem Cell Transplantation; Mesenchymal Stem Cells; Mice; Mice, Inbred BALB C; Niemann-Pick Disease, Type C; Purkinje Cells

Cytochrome P450 (CYP) 2C9, CYP2C8 and CYP2J2 enzymes, which metabolize arachidonic acid (AA) to epoxyeicosatrienoic acids, have cardioprotective effects including anti-inflammation and vasodilation. We have recently shown that some angiotensin II receptor blockers (ARBs) may inhibit AA metabolism via CYP2C8. Using recombinant CYP2C9, CYP2J2 and human liver microsomes (HLMs), the aim was now to compare the ability of six different clinically used ARBs to inhibit AA metabolism in vitro. The rank order of the ARBs for the 50% inhibitory concentration (IC

Topics: 8,11,14-Eicosatrienoic Acid; Angiotensin II Type 1 Receptor Blockers; Arachidonic Acid; Cytochrome P-450 CYP2C9; Cytochrome P-450 CYP2C9 Inhibitors; Cytochrome P-450 CYP2J2; Cytochrome P-450 Enzyme System; Dose-Response Relationship, Drug; Drug Interactions; Humans; Kinetics; Liver; Microsomes, Liver; Recombinant Proteins

Arachidonic acid (ARA) is metabolized by cyclooxygenase (COX) and cytochrome P450 to produce proangiogenic metabolites. Specifically, epoxyeicosatrienoic acids (EETs) produced from the P450 pathway are angiogenic, inducing cancer tumor growth. A previous study showed that inhibiting soluble epoxide hydrolase (sEH) increased EET concentration and mildly promoted tumor growth. However, inhibiting both sEH and COX led to a dramatic decrease in tumor growth, suggesting that the contribution of EETs to angiogenesis and subsequent tumor growth may be attributed to downstream metabolites formed by COX. This study explores the fate of EETs with COX, the angiogenic activity of the primary metabolites formed, and their subsequent hydrolysis by sEH and microsomal EH. Three EET regioisomers were found to be substrates for COX, based on oxygen consumption and product formation. EET substrate preference for both COX-1 and COX-2 were estimated as 8,9-EET > 5,6-EET > 11,12-EET, whereas 14,15-EET was inactive. The structure of two major products formed from 8,9-EET in this COX pathway were confirmed by chemical synthesis:

Topics: 8,11,14-Eicosatrienoic Acid; Angiogenesis Inducing Agents; Arachidonic Acid; Cyclooxygenase 1; Cyclooxygenase 2; Humans

Neuronal apoptosis mediated by the mitochondrial apoptosis pathway is an important pathological process in cerebral ischemia-reperfusion injury. 14,15-EET, an intermediate metabolite of arachidonic acid, can promote cell survival during ischemia/reperfusion. However, whether the mitochondrial apoptotic pathway is involved this survival mechanism is not fully understood. In this study, we observed that infarct size in ischemia-reperfusion injury was reduced in sEH gene knockout mice. In addition, Caspase 3 activation, cytochrome C release and AIF nuclear translocation were also inhibited. In this study, 14,15-EET pretreatment reduced neuronal apoptosis in the oxygen-glucose deprivation and re-oxygenation group in vitro. The mitochondrial apoptosis pathway was also inhibited, as evidenced by AIF translocation from the mitochondria to nucleus and the reduction in the expressions of cleaved-caspase 3 and cytochrome C in the cytoplasm. 14,15-EET could reduce neuronal apoptosis through upregulation of the ratio of Bcl-2 (anti-apoptotic protein) to Bax (apoptosis protein) and inhibition of Bax aggregation onto mitochondria. PI3K/AKT pathway is also probably involved in the reduction of neuronal apoptosis by EET. Our study suggests that 14,15-EET could suppress neuronal apoptosis and reduce infarct volume through the mitochondrial apoptotic pathway. Furthermore, the PI3K/AKT pathway also appears to be involved in the neuroprotection against ischemia-reperfusion by 14,15-EET.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Apoptosis; Cytochromes c; Male; Mice, Inbred C57BL; Mitochondria; Phosphatidylinositol 3-Kinases; Reperfusion Injury; Signal Transduction

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Anticonvulsants; G Protein-Coupled Inwardly-Rectifying Potassium Channels; Glutamic Acid; Hippocampus; Immunohistochemistry; Male; Mice, Inbred C57BL; Neurotransmitter Agents; Patch-Clamp Techniques; Presynaptic Terminals; Pyramidal Cells; Synaptic Transmission; Tissue Culture Techniques

Epoxyeicosatrienoic acids (EETs) are metabolites of arachidonic acid (AA) oxidation that have important cardioprotective and signaling properties. AA is an ω-6 polyunsaturated fatty acid (PUFA) that is prone to autoxidation. Although hydroperoxides and isoprostanes are major autoxidation products of AA, EETs are also formed from the largely overlooked peroxyl radical addition mechanism. While autoxidation yields both cis- and trans-EETs, cytochrome P450 (CYP) epoxygenases have been shown to exclusively catalyze the formation of all regioisomer cis-EETs, on each of the double bonds. In plasma and red blood cell (RBC) membranes, cis- and trans-EETs have been observed, and both have multiple physiological functions. We developed a sensitive ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) assay that separates cis- and trans- isomers of EETs and applied it to determine the relative distribution of cis- vs. trans-EETs in reaction mixtures of AA subjected to free radical oxidation in benzene and liposomes in vitro. We also determined the in vivo distribution of EETs in several tissues, including human and mouse heart, and RBC membranes. We then measured EET levels in heart and RBC of young mice compared to old. Formation of EETs in free radical reactions of AA in benzene and in liposomes exhibited time- and AA concentration-dependent increase and trans-EET levels were higher than cis-EETs under both conditions. In contrast, cis-EET levels were overall higher in biological samples. In general, trans-EETs increased with mouse age more than cis-EETs. We propose a mechanism for the non-enzymatic formation of cis- and trans-EETs involving addition of the peroxyl radical to one of AA's double bonds followed by bond rotation and intramolecular homolytic substitution (S

Topics: 8,11,14-Eicosatrienoic Acid; Aging; Animals; Arachidonic Acid; Benzene; Chromatography, High Pressure Liquid; Cytochrome P-450 Enzyme System; Erythrocyte Membrane; Female; Humans; Liposomes; Male; Mice; Mice, Inbred C57BL; Myocardium; Oxidation-Reduction; Peroxides; Stereoisomerism; Tandem Mass Spectrometry

Preeclampsia is a serious complication of pregnancy characterized by the development of vasospasm, hypertension and often associated with proteinuria after the 20th week of gestation. Because termination of pregnancy results in the most efficacious resolution of preeclampsia, it is a leading cause of premature delivery worldwide. In pregnancy, 14,15-epoxyeicosatrienoic acids (EETs) have been shown to facilitate uterine blood flow during preeclampsia, in which the classic vasodilator agents such as nitric oxide and prostacyclin are reduced. EETs are converted to dihydroxyeicosatrienoic acids (DHETs) by the activity of soluble epoxide hydrolase (sEH). We tested the hypothesis that sEH activity is increased in preeclampsia by measuring urinary 14,15-DHET in healthy and preeclamptic pregnant women. Urine samples were collected and incubated with or without β-glucuronidase to enable the measurement of both the glucuronidated and free forms of 14,15-DHET, which were quantified using a 14,15-DHET ELISA. Levels of total (free+glucuronidated) 14,15-DHET, which is a measurement of EET-dependent sEH activity, were higher in urine samples obtained from preeclamptic women compared to healthy pregnant women. Considering the fact that free+glucuronidated 14,15-DHET levels are increased in urine of preeclamptic women, we hypothesize that sEH expression or activity is augmented in these patients, reducing EET and increasing blood pressure. Moreover we suggest that novel anti-hypertensive agents that target sEH might be developed as therapeutics to control high blood pressure in women with preeclampsia.

Topics: 8,11,14-Eicosatrienoic Acid; Adult; Antihypertensive Agents; Blood Pressure; Epoprostenol; Epoxide Hydrolases; Female; Glucuronidase; Humans; Hypertension; Maternal Age; Nitric Oxide; Pre-Eclampsia; Pregnancy; Pregnancy Complications; Vasoconstriction; Vasodilator Agents; Young Adult

Acute kidney injury (AKI) causes severe morbidity and mortality for which new therapeutic strategies are needed. Docosahexaenoic acid (DHA), arachidonic acid (ARA), and their metabolites have various effects in kidney injury, but their molecular mechanisms are largely unknown. Here, we report that 14 (15)-epoxyeicosatrienoic acid [14 (15)-EET] and 19 (20)-epoxydocosapentaenoic acid [19 (20)-EDP], the major epoxide metabolites of ARA and DHA, respectively, have contradictory effects on kidney injury in a murine model of ischemia/reperfusion (I/R)-caused AKI. Specifically, 14 (15)-EET mitigated while 19 (20)-EDP exacerbated I/R kidney injury. Manipulation of the endogenous 19 (20)-EDP or 14 (15)-EET by alteration of their degradation or biosynthesis with selective inhibitors resulted in anticipated effects. These observations are supported by renal histological analysis, plasma levels of creatinine and urea nitrogen, and renal NGAL. The 14 (15)-EET significantly reversed the I/R-caused reduction in glycogen synthase kinase 3β (GSK3β) phosphorylation in murine kidney, dose-dependently inhibited the hypoxia/reoxygenation (H/R)-caused apoptosis of murine renal tubular epithelial cells (mRTECs), and reversed the H/R-caused reduction in GSK3β phosphorylation in mRTECs. In contrast, 19 (20)-EDP dose-dependently promoted H/R-caused apoptosis and worsened the reduction in GSK3β phosphorylation in mRTECs. In addition, 19 (20)-EDP was more metabolically stable than 14 (15)-EET in vivo and in vitro. Overall, these epoxide metabolites of ARA and DHA function conversely in I/R-AKI, possibly through their largely different metabolic stability and their opposite effects in modulation of H/R-caused RTEC apoptosis and GSK3β phosphorylation. This study provides AKI patients with promising therapeutic strategies and clinical cautions.

Topics: 8,11,14-Eicosatrienoic Acid; Acute Kidney Injury; Animals; Blood Urea Nitrogen; Creatinine; Docosahexaenoic Acids; Gene Expression Regulation; Glycogen Synthase Kinase 3 beta; Humans; Kidney Tubules; Lipocalin-2; Male; Mice; Mice, Inbred C57BL; Phosphorylation; Reperfusion Injury; Signal Transduction; Survival Analysis

Epoxyeicosatrienoic acids (EETs) are derived from arachidonic acid and metabolized by soluble epoxide hydrolase (sEH). The role of EETs in synaptic function in the central nervous system is still largely unknown. We found that pharmacological inhibition of sEH to stabilize endogenous EETs and exogenous 14,15-EET significantly increased the field excitatory postsynaptic potential (fEPSP) response in the CA1 area of the hippocampus, while additionally enhancing high-frequency stimulation- (HFS-) induced long-term potentiation (LTP) and forskolin- (FSK-) induced LTP. sEH inhibitor (sEHI) N-[1-(oxopropyl)-4-piperidinyl]-N'-[4-(trifluoromethoxy) phenyl)-urea (TPPU) and exogenous 14,15-EET increased HFS-LTP, which could be blocked by an N-methyl-D-aspartate (NMDA) receptor subunit NR2B antagonist. TPPU- or 14,15-EET-facilitated FSK-mediated LTP can be potentiated by an A1 adenosine receptor antagonist and a phosphodiesterase inhibitor, but is prevented by a cAMP-dependent protein kinase (PKA) inhibitor. sEHI and 14,15-EET upregulated the activation of extracellular signal-regulated kinases (ERKs) and Ca2+/calmodulin- (CaM-) dependent protein kinase II (CaMKII). Phosphorylation of synaptic receptors NR2B and

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Calcium-Calmodulin-Dependent Protein Kinase Type 2; Cyclic AMP; Epoxide Hydrolases; Hippocampus; Long-Term Potentiation; Mice, Inbred C57BL; Neurons; Receptors, AMPA; Receptors, N-Methyl-D-Aspartate; Signal Transduction

Epoxyeicosatrienoic acids (EETs) are potent vasodilators that play important roles in cardiovascular physiology and disease, yet the molecular mechanisms underlying the biological actions of EETs are not fully understood. Multiple lines of evidence suggest that the actions of EETs are in part mediated via G protein-coupled receptor (GPCR) signaling, but the identity of such a receptor has remained elusive. We sought to identify 14,15-EET-responsive GPCRs. A set of 105 clones were expressed in Xenopus oocyte and screened for their ability to activate cAMP-dependent chloride current. Several receptors responded to micromolar concentrations of 14,15-EET, with the top five being prostaglandin receptor subtypes (PTGER

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; 8,11,14-Eicosatrienoic Acid; Animals; beta-Arrestins; Cyclic AMP; Cystic Fibrosis Transmembrane Conductance Regulator; Drug Evaluation, Preclinical; Extracellular Signal-Regulated MAP Kinases; HEK293 Cells; Humans; Intracellular Space; Mesenteric Arteries; Mice; Oocytes; Phosphorylation; Protein Transport; Receptors, G-Protein-Coupled; Receptors, Prostaglandin; Receptors, Prostaglandin E, EP2 Subtype; Receptors, Prostaglandin E, EP4 Subtype; Vasoconstriction; Xenopus

Acute lung injury (ALI) is characterized by rapid alveolar injury, vascular leakage, lung inflammation, neutrophil accumulation, and induced cytokines production leading to lung edema. The mortality rate of patients suffering from ALI remains high. Epoxyeicosatrienoic acids (EETs) are cytochrome P450-dependent derivatives of polyunsaturated fatty acid with antihypertensive, profibrinolytic, and anti-inflammatory functions. EETs are rapidly hydrated by soluble epoxide hydrolase (sEH) to their less potent diols. The aim of this study was to investigate the role of sEH inhibitor trifluoromethoxyphenyl propionylpiperidin urea (TPPU) and EETs in lipopolysaccharide (LPS)-induced ALI of mice. Our studies revealed that inhibition of sEH with TPPU attenuated the morphological changes in mice, decreased the neutrophil infiltration to the lung, pro-inflammatory cytokine levels (IL-1β and TNF-α) in serum and bronchoalveolar lavage fluid (BALF), and alveolar capillary leakage (lung wet/dry ratio and total protein concentration in BALF). TPPU improved the survival rate of LPS-induced ALI. In addition, in vitro experiments revealed that both TPPU and EETs (11,12-EET and 14,15-EET) suppressed the expression of IL-1β and TNF-α, and LDH release in RAW264.7 cells. These results indicate that EETs play a role in dampening LPS-induced acute lung inflammation, and suggest that sEH could be a valuable candidate for the treatment of ALI.

Topics: 8,11,14-Eicosatrienoic Acid; Acute Lung Injury; Animals; Anti-Inflammatory Agents; Epoxide Hydrolases; Interleukin-1beta; Lipopolysaccharides; Mice; NF-kappa B; Pneumonia; RAW 264.7 Cells; Tumor Necrosis Factor-alpha

Pathophysiological mechanisms underlying the development of renal dysfunction and progression of congestive heart failure (CHF) remain poorly understood. Recent studies have revealed striking differences in the role of epoxyeicosatrienoic acids (EETs), active products of cytochrome P-450-dependent epoxygenase pathway of arachidonic acid, in the progression of aorto-caval fistula (ACF)-induced CHF between hypertensive Ren-2 renin transgenic rats (TGR) and transgene-negative normotensive Hannover Sprague-Dawley (HanSD) controls. Both ACF TGR and ACF HanSD strains exhibited marked intrarenal EETs deficiency and impairment of renal function, and in both strains chronic pharmacologic inhibition of soluble epoxide hydrolase (sEH) (which normally degrades EETs) normalized EETs levels. However, the treatment improved the survival rate and attenuated renal function impairment in ACF TGR only. Here we aimed to establish if the reported improved renal function and attenuation of progression of CHF in ACF TGR observed after she blockade depends on increased vasodilatory responsiveness of renal resistance arteries to EETs. Therefore, we examined the responses of interlobar arteries from kidneys of ACF TGR and ACF HanSD rats to EET-A, a new stable 14,15-EET analog. We found that the arteries from ACF HanSD kidneys rats exhibited greater vasodilator responses when compared to the ACF TGR arteries. Hence, reduced renal vasodilatory responsiveness cannot be responsible for the lack of beneficial effects of chronic sEH inhibition on the development of renal dysfunction and progression of CHF in ACF HanSD rats.

Topics: 8,11,14-Eicosatrienoic Acid; Acetylcholine; Animals; Disease Progression; Dose-Response Relationship, Drug; Heart Failure; Hypertension; Kidney; Male; Norepinephrine; Rats; Rats, Sprague-Dawley; Rats, Transgenic; Renal Circulation; Renin; Vasodilation

Recurrent Pseudomonas aeruginosa infections coupled with robust, damaging neutrophilic inflammation characterize the chronic lung disease cystic fibrosis (CF). The proresolving lipid mediator, 15-epi lipoxin A

Topics: 8,11,14-Eicosatrienoic Acid; Bacterial Proteins; Bronchoalveolar Lavage Fluid; Cell Line; Crystallography, X-Ray; Cystic Fibrosis; Humans; Inflammation; Lipoxins; Lung Diseases; Neutrophil Activation; Neutrophils; Pseudomonas aeruginosa; Pseudomonas Infections; Retrospective Studies; Virulence Factors

Intervertebral disc (IVD) degeneration is considered a common cause of low back pain. In the degenerating IVD, the production of pro-inflammatory cytokines, including IL-1 and TNF-α, progressively increases, contributing to the degenerative process. Epoxyeicosatrienoic acids (EETs), synthesized from arachidonic acid by cytochrome P450 enzymes, act as autocrine and paracrine effectors in regulating inflammation, cardiovascular functions, and angiogenesis. EETs were shown to be especially potent promoters of tissue regeneration. Considering their anti-inflammatory and anti-catabolic potential, we investigated whether EETs can influence IVD degeneration. We found that 14,15-EET protected rat nucleus pulposus (NP) cells against death induced by treatment with H2O2and TNF-α in vitro. At the molecular level, 14,15-EET significantly inhibited the NF-κB pathway, which plays essential roles in the degeneration and survival of NP cells. As a result, 14,15-EET efficiently prevented the matrix remodeling response of NP cells to TNF-α. Using a needle-punctured rat tail model, the influence of 14,15-EET on IVD degeneration in vivo was evaluated using radiographs, magnetic resonance images (MRI), and histological analysis. We observed that 14,15-EET prevented IVD degeneration. Our findings demonstrated that 14,15-EET can enhance the survival of NP cells and inhibit IVD degeneration. The EET pathway may be a novel therapeutic target against IVD degeneration.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Apoptosis; Cells, Cultured; Disease Models, Animal; Hydrogen Peroxide; Intervertebral Disc Degeneration; Male; NF-kappa B; Nucleus Pulposus; Rats; Signal Transduction; Tumor Necrosis Factor-alpha

The biological role of epoxyeicosatrienoic acids (EETs) in the regulation of pulmonary circulation is currently under debate. We hypothesized that EETs initiate increases in right ventricular systolic pressure (RVSP) via perhaps, pulmonary vasoconstriction.. Mice were anesthetized with isoflurane. Three catheters, inserted into the left jugular vein, the left carotid artery, and the right jugular vein, were used for infusing EETs, monitoring blood pressure (BP), and RVSP respectively. BP and RVSP were continuously recorded at basal conditions, in response to administration of 4 regioisomeric EETs (5,6-EET; 8,9-EET; 11,12-EET, and 14,15-EET; 1, 2, 5 and 10 ng/g body weight (BW) for each EET), and during exposure of mice to hypoxia.. All 4 EETs initiated dose-dependent increases in RVSP, though reduced BP. 11,12-EET elicited the greatest increment in RVSP among all EET isoforms. To clarify the direct elevation of RVSP in a systemic BP-independent manner, equivalent amounts of 14,15-EET were injected over 1 and 2 minutes respectively. One-minute injection of 14,15-EET elicited significantly faster and greater increases in RVSP than the 2-minute injection, whereas their BP changes were comparable. Additionally, direct injection of low doses of 14,15-EET (0.1, 0.2, 0.5, and 1 ng/g BW) into the right ventricle caused significant increases in RVSP without effects on BP, confirming that systemic vasodilation-induced increases in venous return are not the main cause for the increased RVSP. Acute exposure of mice to hypoxia significantly elevated RVSP, as well as 14,15-EET-induced increases in RVSP.. EETs directly elevate RVSP, a response that may play an important role in the development of hypoxia-induced pulmonary hypertension (PH).

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arterial Pressure; Disease Models, Animal; Dose-Response Relationship, Drug; Hypertension, Pulmonary; Hypoxia; Infusions, Intravenous; Male; Mice, Inbred C57BL; Pulmonary Artery; Time Factors; Ventricular Function, Right; Ventricular Pressure

14,15-Epoxyeicosatrienoic acid (14,15-EET) is abundantly expressed in brain and exerts protective effects against ischaemia. 14,15-EET is hydrolysed by soluble epoxide hydrolase (sEH). sEH. A mouse model of focal cerebral ischaemia was induced by middle cerebral artery occlusion. Oxygen-glucose deprivation/reoxygenation (OGD/R) was performed on cultured murine astrocytes, neurons and a human cell line. Cell viabilities were measured by 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2H-tetrazolium bromide (MTT) assay. The mRNA expressions were quantified by real-time PCR. Brain derived neurotrophic factor (BDNF) concentration was measured by ELISA. Protein expressions were quantified by Western blotting. BDNF and peroxisome proliferators-activated receptor gamma (PPAR-γ) expressions were analysed by confocal microscopy.. Our study demonstrates the importance of 14,15-EET-mediated production of astrocyte-derived BDNF for enhancing viability of astrocytes and protecting neurons from the ischaemic injury and provides insights into the mechanism by which 14,15-EET is involved in neuroprotection.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Astrocytes; Brain Ischemia; Brain-Derived Neurotrophic Factor; Cell Line, Tumor; Cell Survival; Epoxide Hydrolases; Humans; Male; MAP Kinase Signaling System; Mice, Inbred C57BL; Mice, Knockout; Neuroprotective Agents; Signal Transduction

Multiple players are involved in the highly complex pathophysiologic responses after stroke. Therefore, therapeutic approaches that target multiple cellular elements of the neurovascular unit in the damage cascade hold considerable promise for the treatment of stroke. Cytochrome P450 (CYP) epoxygenases metabolize arachidonic acid to biologically active eicosanoids called epoxyeicosatrienoic acids (EETs), which are further converted by soluble epoxide hydrolase (sEH) to less bioactive diols. EETs have been shown to exert direct cytoprotective effects upon several individual components of the neurovascular unit under simulated ischemic conditions in vitro. However, the cellular mechanism underlying EET-mediated neuroprotective effects after ischemia remains to be clarified. In this study, we investigated the effects of 14,15-EET and 12-(3-adamantan-1-yl-ureido)dodecanoic acid (AUDA), a selective inhibitor of sEH, on multiple elements of neurovascular unit of the rat brain after middle cerebral artery occlusion-induced focal ischemia. The results showed that exogenous administration of 14,15-EET or AUDA could suppress astrogliosis and glial scar formation, inhibit microglia activation and inflammatory response, promote angiogenesis, attenuate neuronal apoptosis and infarct volume, and further promote the behavioral function recovery after focal ischemia. The results suggest that epoxyeicosanoid signaling is a promising multi-mechanism therapeutic target for the treatment of stroke.

Topics: 8,11,14-Eicosatrienoic Acid; Adamantane; Animals; Apoptosis; Epoxide Hydrolases; Infarction, Middle Cerebral Artery; Lauric Acids; Male; Neovascularization, Physiologic; Neuroglia; Neurons; Neuroprotective Agents; Rats; Rats, Sprague-Dawley; Signal Transduction

Small renal arteries have a significant role in the regulation of renal hemodynamics and blood pressure (BP). To study potential changes in the regulation of vascular function in hypertension, we examined renal vasodilatory responses of small arteries from nonclipped kidneys of the 2-kidney, 1-clip Goldblatt hypertensive rats to native epoxyeicosatrienoic acids (EETs) that are believed to be involved in the regulation of renal vascular function and BP. A total of 2 newly synthesized EET analogues were also examined.. Renal interlobular arteries isolated from the nonclipped kidneys on day 28 after clipping were preconstricted with phenylephrine, pressurized and the effects of a 14,15-EET analogue, native 14,15-EET and 11,12-ether-EET-8ZE, an analogue of 11,12-EET, on the vascular diameter were determined and compared to the responses of arteries from the kidneys of sham-operated rats.. In the arteries from nonclipped kidneys isolated in the maintenance phase of Goldblatt hypertension, the maximal vasodilatory response to 14,15-EET analogue was 30.1 ± 2.8% versus 49.8 ± 7.2% in sham-operated rats; the respective values for 11,12-ther-EET-8ZE were 31.4 ± 6.4% versus 80.4 ± 6%, and for native EETs they were 41.7 ± 6.6% versus 62.8 ± 4.4% (P ≤ 0.05 for each difference).. We propose that reduced vasodilatory action and decreased intrarenal bioavailability of EETs combined with intrarenal angiotensin II levels that are inappropriately high for hypertensive rats underlie functional derangements of the nonclipped kidneys of 2-kidney, 1-clip Goldblatt hypertensive rats. These derangements could play an important role in pathophysiology of sustained BP elevation observed in this animal model of human renovascular hypertension.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Hypertension, Renovascular; Kidney; Male; Rats; Rats, Sprague-Dawley; Renal Artery; Vasodilation; Vasodilator Agents

Epoxyeicosatrienoic acids (EETs) are potent lipid mediators formed by cytochrome P450 epoxygenases from arachidonic acid. They consist of four regioisomers of cis-epoxyeicosatrienoic acids: 5,6-, 8,9-, 11,12- and 14,15-EET. Here we investigated whether these triene epoxides are electrophilic enough to form covalent adducts with DNA in vitro. Using the thin-layer chromatography (TLC) (32)P-postlabelling method for adduct detection we studied the reaction of individual deoxynucleoside 3'-monophosphates and calf thymus DNA with the four racemic EETs. Under physiological conditions (pH 7.4) only ±11,12-EET11,12-EET formed adducts with DNA in a dose dependent manner detectable by the (32)P-postlabelling method. However, when pre-incubated at pH 4 all four racemic EETs were capable to bind to DNA forming several adducts. Under these conditions highest DNA adduct levels were found with ±11,12-EET followed by ±5,6-EET, ±8,9-EET, and ±14,15-EET, all of them two orders of magnitude higher (between 3 and 1 adducts per 10(5) normal nucleotides) than those obtained with ±11,12-EET at pH 7.4. Similar DNA adduct patterns consisting of up to seven spots were observed with all four racemic EETs the most abundant adducts being derived from the reaction with deoxyguanosine and deoxyadenosine. In summary, when analysed by the (32)P-postlabelling method all four racemic EETs formed multiple DNA adducts after activation by acidic pH, only ±11,12-EET produced DNA adducts in aqueous solution at neutral pH. Therefore, we conclude from our in vitro studies that EETs might be endogenous genotoxic compounds.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Cattle; Deoxyadenine Nucleotides; Deoxyguanine Nucleotides; DNA; DNA Adducts; Hydrogen-Ion Concentration; Kinetics; Phosphorus Radioisotopes; Solutions; Stereoisomerism

Infiltrating neutrophils are known to promote in the development of tumor. However, it is unclear whether and how neutrophils are involved in triggering the growth of dormant metastases. Here we show that 14,15-epoxyeicosatrienoic acid (14,15-EET) can trigger the growth of dormant micrometastases by inducing neutrophilic infiltration and converting neutrophil function. 14,15-EET triggered neutrophil infiltration in metastatic lesions by activating STAT3 and JNK pathways to induce the expression of human IL-8 and murine CXCL15 in corresponding tumor cells. The continuous expression of hIL-8/mCXCL15 was maintained by the sustained and enhanced activation of JNK pathway. 14,15-EET up-regulated miR-155 expression by activating STAT3 and JNK pathways. miR-155 in turn down-regulated the expression of SHIP1 and DET1, thus augmenting the activation of JNK and c-Jun. Moreover, the function of neutrophils was converted from tumor-suppressing to tumor-promoting by 14,15-EET in vivo. By inducing the production of G-CSF/IL-6 in vivo, 14,15-EET induced the enhancement of STAT3 activation in neutrophils to increase MMP-9 expression and decrease TRAIL expression. Neutrophil-derived MMP-9 was required for 14,15-EET to induce angiogenesis during the growth of dormant micrometastases. Depleting neutrophils or inhibiting hIL-8/mCXCL15 up-regulation resulted in the failure of 14,15-EET to promote the development of micrometastases. These findings reveal a mechanism through which the infiltration and tumor-promoting function of neutrophils could be induced to trigger the growth of dormant metastases, which might be a driving force for the tumor recurrence based on dormant metastases.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Chemokines, CXC; Down-Regulation; Granulocyte Colony-Stimulating Factor; Hep G2 Cells; Humans; Interleukin-6; Interleukin-8; Matrix Metalloproteinase 9; MCF-7 Cells; Mice; Mice, Inbred C57BL; Mice, Nude; MicroRNAs; Neoplasm Invasiveness; Neoplasm Micrometastasis; Neoplasm Recurrence, Local; Neovascularization, Pathologic; Neutrophil Infiltration; Neutrophils; RNA Interference; RNA, Small Interfering; Signal Transduction; STAT3 Transcription Factor; Up-Regulation; Xenograft Model Antitumor Assays

Maintenance of a healthy pool of mitochondria is important for the function and survival of terminally differentiated cells such as cardiomyocytes. Epoxyeicosatrienoic acids (EETs) are epoxy lipids derived from metabolism of arachidonic acid by cytochrome P450 epoxygenases. We have previously shown that EETs trigger a protective response limiting mitochondrial dysfunction and reducing cellular death. The aim of this study was to investigate whether EET-mediated effects influence mitochondrial quality in HL-1 cardiac cells during starvation. HL-1 cells were subjected to serum- and amino acid free conditions for 24h. We employed a dual-acting synthetic analog UA-8 (13-(3-propylureido)tridec-8-enoic acid), possessing both EET-mimetic and soluble epoxide hydrolase (sEH) inhibitory properties, or 14,15-EET as model EET molecules. We demonstrated that EET-mediated events significantly improved mitochondrial function as assessed by preservation of the ADP/ATP ratio and oxidative respiratory capacity. Starvation induced mitochondrial hyperfusion observed in control cells was attenuated by UA-8. However, EET-mediated events did not affect the expression of mitochondrial dynamic proteins Fis1, DRP-1 or Mfn2. Rather we observed increased levels of OPA-1 oligomers and increased mitochondrial cristae density, which correlated with the preserved mitochondrial function. Increased DNA binding activity of pCREB and Nrf1/2 and increased SIRT1 activity together with elevated mitochondrial proteins suggest EET-mediated events led to preserved mitobiogenesis. Thus, we provide new evidence for EET-mediated events that preserve a healthier pool of mitochondria in cardiac cells following starvation-induced stress.

Topics: 8,11,14-Eicosatrienoic Acid; Aconitate Hydratase; Cell Line; Cyclic AMP Response Element-Binding Protein; GTP Phosphohydrolases; Humans; Mitochondria, Heart; NF-E2-Related Factor 2; Nuclear Respiratory Factor 1; Oleic Acids; Sirtuin 1

Epoxyeicosatrienoic acids (EETs) are metabolic products of free arachidonic acid, which are produced through cytochrome P-450 (CYP) epoxygenases. EETs have anti-inflammatory, antiapoptotic, and antioxidative activities. However, the effect of EETs on cigarette smoke-induced lung inflammation is not clear. Autophagy is believed to be involved in the pathogenesis of chronic obstructive pulmonary disease. In addition, nuclear erythroid-related factor 2 (Nrf2), a transcription factor that regulates many antioxidant genes, is thought to regulate antioxidant defenses in several lung diseases. In addition, interaction between EETs, autophagy, and Nrf2 has been reported. The aim of this study was to explore the effect of 14,15-EET on cigarette smoke condensate (CSC)-induced inflammation in a human bronchial epithelial cell line (Beas-2B), and to determine whether the underlying mechanisms involved in the regulation of Nrf2 through inhibition of autophagy. Autophagy and expression of autophagy signaling pathway proteins (LC3B, p62, PI3K, Akt, p-Akt, and p-mTOR) and anti-inflammatory proteins (Nrf2 and HO-1) were assessed via Western blot analysis. Autophagosomes and autolysosomes were detected by adenoviral mRFP-GFP-LC3 transfection. Inflammatory factors (IL-6, IL-8, and MCP-1) were detected by ELISA. Lentiviral vectors carrying p62 short hairpin RNA were used to interfere with p62 expression to evaluate the effect of p62 on Nrf2 expression. Nrf2 expression was determined through immunocytochemistry. 14,15-EET treatment resulted in a significant reduction in IL-6, IL-8, and MCP-1 secretion, and increased accumulation of Nrf2 and expression of HO-1. In addition, 14,15-EET inhibited CSC-induced autophagy in Beas-2B cells. The mechanism of the anti-inflammatory effect of 14,15-EET involved inhibition of autophagy and an increase in p62 levels, followed by translocation of Nrf2 into the nucleus, which then upregulated expression of the antioxidant enzyme HO-1. 14,15-EET protects against CSC-induced lung inflammation by promoting accumulation of Nrf2 via inhibition of autophagy.

Topics: 8,11,14-Eicosatrienoic Acid; Anti-Inflammatory Agents; Autophagy; Cell Line; Cell Nucleus; Epithelial Cells; Gene Knockdown Techniques; Heme Oxygenase-1; Humans; Inflammation; Inflammation Mediators; Lung; NF-E2-Related Factor 2; Phosphatidylinositol 3-Kinases; Protein Transport; RNA-Binding Proteins; Signal Transduction; Smoking; TOR Serine-Threonine Kinases; Up-Regulation

Soluble epoxide hydrolase (sEH) inhibition has been demonstrated to have beneficial effects on various diseases, such as hypertension, diabetes, and brain ischemia. However, whether sEH inhibition has therapeutic potential in Parkinson's disease is still unknown. In this paper, we found that sEH expression is increased in 1-methyl-4-phenyl-1,2,3,6-tetrahydro pyridine (MPTP)-treated mice, and sEH deficiency and inhibition significantly attenuated tyrosine hydroxylase (TH)-positive cell loss and improved rotarod performance. The substrate of sEH, 14,15-epoxyeicosatrienoic acid (14,15-EET), protected TH-positive cells and alleviated the rotarod performance deficits of wild-type mice but not sEH-knockout mice. Moreover, the 14,15-EET antagonist 14,15-epoxyeicosa-5(Z)-enoic acid (14,15-EEZE) abolished the neuronal protective effects of sEH deficiency. In primary cultured cortical neurons, MPP(+) induced significant Akt inactivation in neurons from sEH wild-type mice, and this effect was not observed in neurons from knockout mice. Our data indicate that sEH deficiency and inhibition increased 14,15-EET in MPTP-treated mice, which activated the Akt-mediated protection of TH-positive neurons and behavioral functioning. We also found that sEH deficiency attenuated TH-positive cell loss in a paraquat-induced mouse model of Parkinson's. Our data suggest that sEH inhibition might be a powerful tool to protect dopaminergic neurons in Parkinson's disease.

Topics: 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine; 8,11,14-Eicosatrienoic Acid; Adamantane; Animals; Behavior, Animal; Cell Survival; Cells, Cultured; Dopaminergic Neurons; Epoxide Hydrolases; Lauric Acids; Male; Mice, Inbred C57BL; Mice, Knockout; Neuroprotective Agents; Paraquat; Parkinsonian Disorders; Rotarod Performance Test; Solubility; Substantia Nigra; Tyrosine 3-Monooxygenase; Up-Regulation

Patients recovering from aneurysmal subarachnoid hemorrhage (SAH) are at risk for developing delayed cerebral ischemia (DCI). Experimental and human studies implicate the vasoconstrictor P450 eicosanoid 20-hydroxyeicosatetraenoic acid (20-HETE) in the pathogenesis of DCI. To date, no studies have evaluated the role of vasodilator epoxyeicosatrienoic acids (EETs) in DCI.. Using mass spectrometry, we measured P450 eicosanoids in cerebrospinal fluid (CSF) from 34 SAH patients from 1 to 14 days after admission. CSF eicosanoid levels were compared in patients who experienced DCI versus those who did not. We then studied the effect of EETs in a model of SAH using mice lacking the enzyme soluble epoxide hydrolase (sEH), which catabolizes EETs into their inactive diol. To assess changes in vessel morphology and cortical perfusion in the mouse brain, we used optical microangiography, a non-invasive coherence-based imaging technique.. Along with increases in 20-HETE, we found that CSF levels of 14,15-EET were elevated in SAH patients compared to control CSF, and levels were significantly higher in patients who experienced DCI compared to those who did not. Mice lacking sEH had elevated 14,15-EET and were protected from the delayed decrease in microvascular cortical perfusion after SAH, compared to wild type mice.. Our findings suggest that P450 eicosanoids play an important role in the pathogenesis of DCI. While 20-HETE may contribute to the development of DCI, 14,15-EET may afford protection against DCI. Strategies to enhance 14,15-EET, including sEH inhibition, should be considered as part of a comprehensive approach to prevent DCI.

Topics: 8,11,14-Eicosatrienoic Acid; Aged; Animals; Brain Ischemia; Disease Models, Animal; Female; Humans; Hydroxyeicosatetraenoic Acids; Male; Mice; Middle Aged; Neuroprotective Agents; Subarachnoid Hemorrhage

Epoxyeicosatrienoic acids (EETs), the cytochrome P450 epoxygenase metabolite of arachidonic acid, have been demonstrated to have neuroprotective effect. Phosphatidylinositol 3-kinase (PI3K)/Akt and ATP-sensitive potassium (KATP) channels are thought to be important factors that mediate neuroprotection. However, little is known about the role of PI3K/Akt and KATP channels in brain after EETs administration. In vitro experiment, oxygen-glucose deprivation (OGD) was performed in cultured rat cerebral microvascular smooth muscle cells (SMCs) for 4 h. The effect of 14,15-EET on OGD induced cell apoptosis was examined after reoxygenation. Western blot and real-time PCR were used to analyze the expression of Kir6.1, SUR2B (two subunits of KATP channels) and p-Akt on cerebral microvascular SMCs. In vivo experiments, we use 12-(3-adamantan-1-yl-ureido)-dodecanoic acid [AUDA, a specific soluble epoxide hydrolase (sEH) inhibitor] to confirm the effect of EETs indirectly. Rats were injected intraperitoneally with AUDA before being subjected to middle cerebral artery occlusion (MCAO). We detected the apoptosis and the expression of p-Akt, Kir6.1 and SUR2B in ischemic penumbra. The results showed that EETs protect against cerebral ischemia/reperfusion (I/R) injury and upregulated the expression of p-Akt and Kir6.1 in both of ischemic penumbra and OGD induced cerebral microvascular SMCs. The protective effect was inhibited by Wortmannin (a specific PI3K inhibitor) and Glib (a specific KATP inhibitor) respectively in vitro experiment. In conclusion, these results suggested that the protective effect of EETs on cerebral I/R injury is associated with PI3K/Akt pathway and KATP channels. Furthermore, the PI3K pathway may contribute to mediating KATP channels on cerebral microvascular SMCs.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Brain Injuries; Cell Survival; Cells, Cultured; Hypoxia, Brain; KATP Channels; Male; Neuroprotective Agents; Oncogene Protein v-akt; Phosphatidylinositol 3-Kinases; Rats; Rats, Sprague-Dawley; Reperfusion Injury; Signal Transduction; Vasodilator Agents

Adipocyte fatty acid-binding protein (FABP4) is a member of a highly conserved family of cytosolic proteins that bind with high affinity to hydrophobic ligands, such as saturated and unsaturated long-chain fatty acids and eicosanoids. Recent evidence has supported a novel role for FABP4 in linking obesity with metabolic and cardiovascular disorders. In this context, we identified FABP4 as a main bioactive factor released from human adipose tissue that directly suppresses heart contraction in vitro. As FABP4 is known to be a transport protein, it cannot be excluded that lipid ligands are involved in the cardiodepressant effect as well, acting in an additional and/or synergistic way.. We investigated a possible involvement of lipid ligands in the negative inotropic effect of adipocyte factors in vitro.. We verified that blocking the CYP epoxygenase pathway in adipocytes attenuates the inhibitory effect of adipocyte-conditioned medium (AM) on isolated adult rat cardiomyocytes, thus suggesting the participation of epoxyeicosatrienoic acids (EETs) in the cardiodepressant activity. Analysis of AM for EETs revealed the presence of 5,6-, 8,9-, 11,12- and 14,15-EET, whereas 5,6-EET represented about 45% of the total EET concentration in AM. Incubation of isolated cardiomyocytes with EETs in similar concentrations as found in AM showed that 5,6-EET directly suppresses cardiomyocyte contractility. Furthermore, after addition of 5,6-EET to FABP4, the negative inotropic effect of FABP4 was strongly potentiated in a concentration-dependent manner.. These data suggest that adipocytes release 5,6-EET and FABP4 into the extracellular medium and that the interaction of these factors modulates cardiac function. Therefore elevated levels of FABP4 and 5,6-EET in obese patients may contribute to the development of heart dysfunction in these subjects.

Topics: 8,11,14-Eicosatrienoic Acid; Adipose Tissue; Animals; Cardiovascular Diseases; Fatty Acid-Binding Proteins; Female; Humans; Male; Myocardial Contraction; Myocytes, Cardiac; Obesity; Rats

Cytochrome P-450 epoxygenase-derived epoxyeicosatrienoic acids (EETs) exert diverse biological activities, which include potent vasodilatory, anti-inflammatory, antiapoptotic, and antioxidatant effects, and cardiovascular protection. Liver has abundant epoxygenase expression and high levels of EET production; however, the roles of epoxygenases in liver diseases remain to be elucidated. In this study, we investigated the protection against high-fat diet-induced nonalcoholic fatty liver disease (NAFLD) in mice with endothelial-specific CYP2J2 overexpression (Tie2-CYP2J2-Tr). After 24 wk of high-fat diet, Tie2-CYP2J2-Tr mice displayed attenuated NAFLD compared with controls. Tie2-CYP2J2-Tr mice showed significantly decreased plasma triglyceride levels and liver lipid accumulation, improved liver function, reduced inflammatory responses, and less increase in hepatic oxidative stress than wild-type control mice. These effects were associated with inhibition of NF-κB/JNK signaling pathway activation and enhancement of the antioxidant defense system in Tie2-CYP2J2-Tr mice in vivo. We also demonstrated that 14,15-EET treatment protected HepG2 cells against palmitic acid-induced inflammation and oxidative stress. 14,15-EET attenuated palmitic acid-induced changes in NF-κB/JNK signaling pathways, malondialdehyde generation, glutathione levels, reactive oxygen species production, and NADPH oxidase and antioxidant enzyme expression in HepG2 cells in vitro. Together, these results highlight a new role for CYP epoxygenase-derived EETs in lipotoxicity-related inflammation and oxidative stress and reveal a new molecular mechanism underlying EETs-mediated anti-inflammatory and antioxidant effects that could aid in the design of new therapies for the prevention and treatment of NAFLD.

Topics: 8,11,14-Eicosatrienoic Acid; Alanine Transaminase; Animals; Aspartate Aminotransferases; Catalase; Cytochrome P-450 CYP2J2; Cytochrome P-450 Enzyme System; Cytokines; Diet, High-Fat; Disease Models, Animal; Glutathione Peroxidase; Hep G2 Cells; Humans; Male; Mice; Mice, Inbred C57BL; Mice, Transgenic; NF-kappa B; Non-alcoholic Fatty Liver Disease; Oxidative Stress; Palmitic Acid; Reverse Transcriptase Polymerase Chain Reaction; RNA; Signal Transduction; Superoxide Dismutase; Triglycerides

In response to endothelial cell activation, arachidonic acid can be converted by cytochrome P450 (CYP) epoxygenases to epoxyeicosatrienoic acids (EETs), which have potent vasodilator and anti-inflammatory properties. In this study, we investigated the effects of exogenous EETs on cigarette smoke extract (CSE)-induced inflammation in human bronchial epithelial cells (NCI-H292). We found that CSE inhibited the expression of CYP2C8 and mildly stimulated the expression of epoxide hydrolase 2 (EPHX2) but did not change the expression of CYP2J2. Treatment with 11,12-EET or 14,15-EET attenuated the CSE-induced release of interleukin (IL)-8 by inhibiting the phosphorylation of p38 mitogen-activated protein kinases (MAPKs). Our results demonstrated that CSE may reduce the anti-inflammatory ability of epithelial cells themselves by lowering the EET level. EETs from pulmonary epithelial cells may play a critical protective role on epithelial cell injury.

Topics: 8,11,14-Eicosatrienoic Acid; Anti-Inflammatory Agents; Bronchi; Cell Line; Cytochrome P-450 CYP2J2; Cytochrome P-450 Enzyme System; Epithelial Cells; Gene Expression Regulation; Humans; Interleukin-8; MAP Kinase Signaling System; Smoking; Vasodilator Agents

Culex mosquitoes have emerged as important model organisms for mosquito biology, and are disease vectors for multiple mosquito-borne pathogens, including West Nile virus. We characterized epoxide hydrolase activities in the mosquito Culex quinquefasciatus, which suggested multiple forms of epoxide hydrolases were present. We found EH activities on epoxy eicosatrienoic acids (EETs). EETs and other eicosanoids are well-established lipid signaling molecules in vertebrates. We showed EETs can be synthesized in vitro from arachidonic acids by mosquito lysate, and EETs were also detected in vivo both in larvae and adult mosquitoes by LC-MS/MS. The EH activities on EETs can be induced by blood feeding, and the highest activity was observed in the midgut of female mosquitoes. The enzyme activities on EETs can be inhibited by urea-based inhibitors designed for mammalian soluble epoxide hydrolases (sEH). The sEH inhibitors have been shown to play diverse biological roles in mammalian systems, and they can be useful tools to study the function of EETs in mosquitoes. Besides juvenile hormone metabolism and detoxification, insect epoxide hydrolases may also play a role in regulating lipid signaling molecules, such as EETs and other epoxy fatty acids, synthesized in vivo or obtained from blood feeding by female mosquitoes.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Blood; Culex; Eicosanoic Acids; Eicosanoids; Epoxide Hydrolases; Epoxy Compounds; Fatty Acids; Feeding Behavior; Female; Insect Proteins; Larva; Lipid Metabolism; Male

Epoxyeicosatrienoic acids (EETs), a type of lipid mediators produced by cytochrome P450 epoxygenases, exert anti-inflammatory, angiogenic, anti-oxidative and anti-apoptotic effects. However, the role of EETs in cigarette smoke-induced lung injury and the underlying mechanisms are not fully known. The aim of this study was to explore the effects of CYP2J2-EETs on cigarette smoke extracts (CSE)-induced apoptosis in human bronchial epithelial cell line (Beas-2B) and the possible mechanisms involved.. Cytochrome P450 epoxygenase 2J2 (CYP2J2) and its metabolites EETs were assessed by western blotting or LC-MS-MS. Cell viability and apoptosis were determined by MTT assay and AnnexinV-PI staining. Reactive oxygen species (ROS) were assessed by measuring H2DCFDA. Caspase-3, HO-1, MAPK and endoplasmic reticulum (ER) stress-related markers GRP78, p-elF2a, and CHOP were evaluated by western blotting.. CSE suppressed expression of both CYP2J2 and EET by Beas-2B cells. CSE also induced apoptosis, the generation of ROS and the ER stress in Beas-2B cells. These changes were abolished by pretreatment with exogenous 14,15-EET while pretreatment with 14,15-EEZE, a selective EET antagonist, abolished the protective effects of 14,15-EET. In addition, EETs increased the expression of antioxidant enzyme HO-1. Furthermore, 14,15-EET reduced CSE-induced activation of p38 and JNK.. The data suggest that CYP2J2-derived EETs protect against CSE-induced lung injury possibly through attenuating ER stress.

Topics: 8,11,14-Eicosatrienoic Acid; Antioxidants; Apoptosis; Cell Line; Cytochrome P-450 CYP2J2; Cytochrome P-450 Enzyme System; Endoplasmic Reticulum Chaperone BiP; Endoplasmic Reticulum Stress; Epithelial Cells; Humans; Lung; Nicotiana; Reactive Oxygen Species; Smoke; Smoking

Cytochrome P-450 epoxygenase (EPOX)-derived epoxyeicosatrienoic acids (EETs), 5-lipoxygenase (5-LO), and leukotriene B4 (LTB4), the product of 5-LO, all play a pivotal role in the vascular inflammatory process. We have previously shown that EETs can alleviate oxidized low-density lipoprotein (ox-LDL)-induced endothelial inflammation in primary rat pulmonary artery endothelial cells (RPAECs). Here, we investigated whether ox-LDL can promote LTB4 production through the 5-LO pathway. We further explored how exogenous EETs influence ox-LDL-induced LTB4 production and activity. We found that treatment with ox-LDL increased the production of LTB4 and further led to the expression and release of both monocyte chemoattractant protein-1 (MCP-1/CCL2) and intercellular adhesion molecule-1 (ICAM-1). All of the above ox-LDL-induced changes were attenuated by the presence of 11,12-EET and 14,15-EET, as these molecules inhibited the 5-LO pathway. Furthermore, the LTB4 receptor 1 (BLT1 receptor) antagonist U75302 attenuated ox-LDL-induced ICAM-1 and MCP-1/CCL2 expression and production, whereas LY255283, a LTB4 receptor 2 (BLT2 receptor) antagonist, produced no such effects. Moreover, in RPAECs, we demonstrated that the increased expression of 5-LO and BLT1 following ox-LDL treatment resulted from the activation of nuclear factor-κB (NF-κB) via the p38 mitogen-activated protein kinase (MAPK) pathway. Our results indicated that EETs suppress ox-LDL-induced LTB4 production and subsequent inflammatory responses by downregulating the 5-LO/BLT1 receptor pathway, in which p38 MAPK phosphorylation activates NF-κB. These results suggest that the metabolism of arachidonic acid via the 5-LO and EPOX pathways may present a mutual constraint on the physiological regulation of vascular endothelial cells.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonate 5-Lipoxygenase; Blotting, Western; Cells, Cultured; Inflammation; Leukotriene B4; Lipoproteins, LDL; Male; p38 Mitogen-Activated Protein Kinases; Phosphorylation; Pulmonary Artery; Rats; Rats, Sprague-Dawley; Real-Time Polymerase Chain Reaction; Receptors, Leukotriene B4; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Vasodilator Agents

Haematopoietic stem and progenitor cell (HSPC) transplant is a widely used treatment for life-threatening conditions such as leukaemia; however, the molecular mechanisms regulating HSPC engraftment of the recipient niche remain incompletely understood. Here we develop a competitive HSPC transplant method in adult zebrafish, using in vivo imaging as a non-invasive readout. We use this system to conduct a chemical screen, and identify epoxyeicosatrienoic acids (EETs) as a family of lipids that enhance HSPC engraftment. The pro-haematopoietic effects of EETs were conserved in the developing zebrafish embryo, where 11,12-EET promoted HSPC specification by activating a unique activator protein 1 (AP-1) and runx1 transcription program autonomous to the haemogenic endothelium. This effect required the activation of the phosphatidylinositol-3-OH kinase (PI(3)K) pathway, specifically PI(3)Kγ. In adult HSPCs, 11,12-EET induced transcriptional programs, including AP-1 activation, which modulate several cellular processes, such as migration, to promote engraftment. Furthermore, we demonstrate that the EET effects on enhancing HSPC homing and engraftment are conserved in mammals. Our study establishes a new method to explore the molecular mechanisms of HSPC engraftment, and discovers a previously unrecognized, evolutionarily conserved pathway regulating multiple haematopoietic generation and regeneration processes. EETs may have clinical application in marrow or cord blood transplantation.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Cell Line; Cell Movement; Core Binding Factor Alpha 2 Subunit; Female; Gene Expression Regulation; Hematopoiesis; Hematopoietic Stem Cell Transplantation; Hematopoietic Stem Cells; Human Umbilical Vein Endothelial Cells; Humans; Kidney; Male; Mice; Phosphatidylinositol 3-Kinases; Transcription Factor AP-1; Transcription, Genetic; Zebrafish

Cytochrome P450 metabolites of arachidonic acid (AA) belong to eicosanoids and are potent lipid mediators of inflammation. It is well-known that eicosanoids play an important role in numerous pathophysiological processes. Therefore, quantitative analysis of cytochrome P450 metabolites of AA, including hydroxyeicosatetraenoic acids (HETEs), epoxyeicosatreinoic acids (EETs), and dihydroxyeicosatrienoic acids (DHETs) can provide crucial information to uncover underlying mechanisms of cytochrome P450 metabolites of AA related diseases. Herein, we developed a highly sensitive method to identify and quantify HETEs, EETs, and DHETs in lipid extracts of biological samples based on stable isotope probe labeling coupled with ultra high-performance liquid chromatography/mass spectrometry. To this end, a pair of stable isotope probes, 2-dimethylaminoethylamine (DMED) and d4-2-dimethylaminoethylamine (d4-DMED), were utilized to facilely label eicosanoids. The heavy labeled eicosanoid standards were prepared and used as internal standards for quantification to minimize the matrix and ion suppression effects in mass spectrometry analysis. In addition, the detection sensitivities of DMED labeled eicosanoids improved by 3-104 folds in standard solution and 5-138 folds in serum matrix compared with unlabeled analytes. Moreover, a good separation of eicosanoids isomers was achieved upon DMED labeling. The established method provided substantial sensitivity (limit of quantification at sub-picogram), high specificity, and broad linear dynamics range (3 orders of magnitude). We further quantified cytochrome P450 metabolites of AA in rat liver, heart, brain tissues and human serum using the developed method. The results showed that 19 eicosanoids could be distinctly detected and the contents of 11-, 15-, 16-, 20-HETE, 5,6-EET, and 14,15-EET in type 2 diabetes mellitus patients and 5-, 11-, 12-, 15-, 16-, 20-HETE, 8,9-EET, and 5,6-DHET in myeloid leukemia patients had significant changes, demonstrating that these eicosanoids may have important roles on the pathogenesis of type 2 diabetes mellitus and myeloid leukemia.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acid; Brain; Case-Control Studies; Chromatography, High Pressure Liquid; Cytochrome P-450 Enzyme System; Deuterium; Diabetes Mellitus, Type 2; Eicosanoids; Humans; Hydroxyeicosatetraenoic Acids; Isotope Labeling; Leukemia, Myeloid; Liver; Male; Myocardium; Organ Specificity; Rats, Sprague-Dawley; Spectrometry, Mass, Electrospray Ionization; Tandem Mass Spectrometry

This study examined the effects of a novel orally active 14,15-epoxyeicosatrienoic acid analog (EET-A) on blood pressure (BP) and myocardial infarct size (IS) in two-kidney, one-clip (2K1C) Goldblatt hypertensive rats during sustained phase of hypertension. Between days 31 and 35 after clip placement the rats were treated with EET-A and BP was monitored by radiotelemetry; sham-operated normotensive rats were used as controls. Tissue concentrations of epoxyeicosatrienoic acids served as a marker of production of epoxygenase metabolites. The rats were subjected to acute myocardial ischemia/reperfusion (I/R) injury and IS was determined. We found that EET-A treatment did not lower BP in 2K1C rats and did not alter availability of biologically active epoxygenase metabolites in 2K1C or in sham-operated rats. The myocardial IS was significantly smaller in untreated 2K1C rats as compared with normotensive controls and EET-A reduced it in controls but not in 2K1C rats. Our findings suggest that during the phase of sustained hypertension 2K1C Goldblatt hypertensive rats exhibit increased cardiac tolerance to I/R injury as compared with normotensive controls, and that in this animal model of human renovascular hypertension short-term treatment with EET-A does not induce any antihypertensive and cardioprotective actions.

Topics: 8,11,14-Eicosatrienoic Acid; Administration, Oral; Animals; Blood Pressure; Blood Pressure Monitoring, Ambulatory; Disease Models, Animal; Glycogen Synthase Kinase 3; Glycogen Synthase Kinase 3 beta; Hydroxyeicosatetraenoic Acids; Hypertension, Renovascular; Kidney; Male; Myocardial Infarction; Myocardial Reperfusion Injury; Myocardium; Proto-Oncogene Proteins c-akt; Rats, Sprague-Dawley; Renin-Angiotensin System; Signal Transduction; Telemetry; Time Factors

We tested the hypothesis that suppression of epoxyeicosatrienoic acid (EET) metabolism via genetic knockout of the gene for soluble epoxide hydrolase (sEH-KO), or female-specific downregulation of sEH expression, plays a role in the potentiation of pulmonary hypertension. We used male (M) and female (F) wild-type (WT) and sEH-KO mice; the latter have high pulmonary EETs. Right ventricular systolic pressure (RVSP) and mean arterial blood pressure (MABP) in control and in response to in vivo administration of U46619 (thromboxane analog), 14,15-EET, and 14,15-EEZE [14,15-epoxyeicosa-5(z)-enoic acid; antagonist of EETs] were recorded. Basal RVSP was comparable among all groups of mice, whereas MABP was significantly lower in F-WT than M-WT mice and further reduced predominantly in F-KO compared with M-KO mice. U46619 dose dependently increased RVSP and MABP in all groups of mice. The increase in RVSP was significantly greater and coincided with smaller increases in MABP in M-KO and F-WT mice compared with M-WT mice. In F-KO mice, the elevation of RVSP by U46619 was even higher than in M-KO and F-WT mice, associated with the least increase in MABP. 14,15-EEZE prevented the augmentation of U46619-induced elevation of RVSP in sEH-KO mice, whereas 14,15-EET-induced pulmonary vasoconstriction was comparable in all groups of mice. sEH expression in the lungs was reduced, paralleled with higher levels of EETs in F-WT compared with M-WT mice. In summary, EETs initiate pulmonary vasoconstriction but act as vasodilators systemically. High pulmonary EETs, as a function of downregulation or deletion of sEH, potentiate U46619-induced increases in RVSP in a female-susceptible manner.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; 8,11,14-Eicosatrienoic Acid; Animals; Arterial Pressure; Epoxide Hydrolases; Female; Hypertension, Pulmonary; Male; Mice; Mice, Knockout; Pulmonary Artery; Sex Characteristics; Vasoconstriction

Prolonged endoplasmic reticulum (ER) stress causes apoptosis and is associated with heart failure. Whether CYP2J2 and its arachidonic acid metabolites [epoxyeicosatrienoic acids (EETs)] have a protective influence on ER stress and heart failure has not been studied. Assays of myocardial samples from patients with end-stage heart failure showed evidence of ER stress. Chronic infusion of isoproterenol (ISO) or angiotensin II (AngII) by osmotic mini-pump induced cardiac hypertrophy and heart failure in mice as evaluated by hemodynamic measurements and echocardiography. Interestingly, transgenic (Tr) mice with cardiomyocyte-specific CYP2J2 expression were protected against heart failure compared with wild-type mice. ISO or AngII administration induced ER stress and apoptosis, and increased levels of intracellular Ca(2+). These phenotypes were abolished by CYP2J2 overexpression in vivo or exogenous EETs treatment of cardiomyocytes in vitro. ISO or AngII reduced sarcoplasmic/endoplasmic reticulum calcium ATPase (SERCA2a) expression in hearts or isolated cardiomyocytes; however, loss of SERCA2a expression was prevented in CYP2J2 Tr hearts in vivo or in cardiomyocytes treated with EETs in vitro. The reduction of SERCA2a activity was concomitant with increased oxidation of SERCA2a. EETs reversed SERCA2a oxidation through increased expression of antioxidant enzymes and reduced reactive oxygen species levels. Tempol, a membrane-permeable radical scavenger, similarly decreased oxidized SERCA2a levels, restored SERCA2a activity, and markedly reduced ER stress response in the mice treated with ISO. In conclusion, CYP2J2-derived EETs suppress ER stress response in the heart and protect against cardiac failure by maintaining intracellular Ca(2+) homeostasis and SERCA2a expression and activity.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Apoptosis; Calcium; Cardiomegaly; Cell Line; Cytochrome P-450 CYP2J2; Cytochrome P-450 Enzyme System; Endoplasmic Reticulum Stress; Heart Failure; Humans; In Vitro Techniques; Major Histocompatibility Complex; Mice; Mice, Transgenic; Myocardium; Myocytes, Cardiac; Rats; Reactive Oxygen Species; Sarcoplasmic Reticulum Calcium-Transporting ATPases

It has been previously shown that the cytochrome P450 (P450) modulator, fenofibrate, protects against cardiovascular diseases. P450 and their metabolites, epoxyeicosatrienoic acids (EETs) and 20-hydroxyeicosatetraenoic acid (20-HETE) were found to play an important role in cardiovascular diseases. Therefore, it is important to examine whether fenofibrate would modulate the cardiac P450 and its associated arachidonic acid metabolites and whether this modulation protects against isoproterenol-induced cardiac hypertrophy. For this purpose, male Sprague-Dawley rats were treated with fenofibrate (30 mg·kg·d), isoproterenol (4.2 mg·kg·d), or the combination of both. The expression of hypertrophic markers and different P450s along with their metabolites was determined. Our results showed that fenofibrate significantly induced the cardiac P450 epoxygenases, such as CYP2B1, CYP2B2, CYP2C11, and CYP2C23, whereas it decreased the cardiac ω-hydroxylase, CYP4A3. Moreover, fenofibrate significantly increased the formation of 14,15-EET, 11,12-EET, and 8,9-EET, whereas it decreased the formation of 20-HETE in the heart. Furthermore, fenofibrate significantly decreased the hypertrophic markers and the increase in heart-to-body weight ratio induced by isoproterenol. This study demonstrates that fenofibrate alters the expression of cardiac P450s and their metabolites and partially protects against isoproterenol-induced cardiac hypertrophy, which further confirms the role of P450s, EETs, and 20-HETE in the development of cardiac hypertrophy.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acid; Cardiomegaly; Cytochrome P-450 CYP2J2; Cytochrome P-450 Enzyme System; Fenofibrate; Gene Expression Regulation, Enzymologic; Hydroxyeicosatetraenoic Acids; Hypolipidemic Agents; Isoproterenol; Male; Rats; Rats, Sprague-Dawley

The environmental toxin and carcinogen 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, dioxin) binds and activates the transcription factor aryl hydrocarbon receptor (AHR), inducing CYP1 family cytochrome P450 enzymes. CYP1A2 and its avian ortholog CYP1A5 are highly active arachidonic acid epoxygenases. Epoxygenases metabolize arachidonic acid to four regioisomeric epoxyeicosatrienoic acids (EETs) and selected monohydroxyeicosatetraenoic acids (HETEs). EETs can be further metabolized by epoxide hydrolases to dihydroxyeicosatrienoic acids (DHETs). As P450-arachidonic acid metabolites affect vasoregulation, responses to ischemia, inflammation, and metabolic disorders, identification of their production in vivo is needed to understand their contribution to biologic effects of TCDD and other AHR activators. Here we report use of an acetonitrile-based extraction procedure that markedly increased the yield of arachidonic acid products by lipidomic analysis over a standard solid-phase extraction protocol. We show that TCDD increased all four EETs (5,6-, 8,9-, 11,12-, and 14,15-), their corresponding DHETs, and 18- and 20-HETE in liver in vivo and increased 5,6-EET, the four DHETs, and 18-HETE in heart, in a chick embryo model. As the chick embryo heart lacks arachidonic acid-metabolizing activity, the latter findings suggest that arachidonic acid metabolites may travel from their site of production to a distal organ, i.e., heart. To determine if the TCDD-arachidonic acid-metabolite profile could be altered pharmacologically, chick embryos were treated with TCDD and the soluble epoxide hydrolase inhibitor 12-(3-adamantan-1-yl-ureido)-dodecanoic acid (AUDA). Cotreatment with AUDA increased hepatic EET-to-DHET ratios, indicating that the in vivo profile of P450-arachidonic acid metabolites can be modified for potential therapeutic intervention.

Topics: 8,11,14-Eicosatrienoic Acid; Adamantane; Animals; Chick Embryo; Enzyme Inhibitors; Epoxide Hydrolases; Gene Expression Regulation, Enzymologic; Heart; Hydroxyeicosatetraenoic Acids; Lauric Acids; Liver; Polychlorinated Dibenzodioxins; RNA, Messenger

Mercury exposure is associated with increased risk of cardiovascular disease and profound cardiotoxicity. However, the correlation between Hg(2+)-mediated toxicity and alteration in cardiac cytochrome P450s (Cyp) and their dependent arachidonic acid metabolites has never been investigated. Therefore, we investigated the effect of acute mercury toxicity on the expression of Cyp-epoxygenases and Cyp-ω-hydroxylases and their associated arachidonic acid metabolites in mice hearts. In addition, we examined the expression and activity of soluble epoxide hydrolase (sEH) as a key player in arachidonic acid metabolism pathway. Mercury toxicity was induced by a single intraperitoneal injection (IP) of 2.5 mg/kg of mercuric chloride (HgCl₂). Our results showed that mercury treatment caused a significant induction of the cardiac hypertrophy markers, atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP); in addition to Cyp1a1, Cyp1b1, Cyp2b9, Cyp2b10, Cyp2b19, Cyp2c29, Cyp2c38, Cyp4a10, Cyp4a12, Cyp4a14, Cyp4f13, Cyp4f15, Cyp4f16 and Cyp4f18 gene expression. Moreover, Hg(2+) significantly increased sEH protein expression and activity levels in hearts of mercury-treated mice, with a consequent decrease in 14,15-, and 11,12-epoxyeicosatrienoic acids (EETs) levels. Whereas the formation of 14,15-, 11,12-, 8,9-dihydroxyeicosatrienoic acids (DHETs) was significantly increased. In conclusion, acute Hg(2+) toxicity modulates the expression of several Cyp and sEH enzymes with a consequent decrease in the cardioprotective EETs which could represent a novel mechanism by which mercury causes progressive cardiotoxicity. Furthermore, inhibiting sEH might represent a novel therapeutic approach to prevent Hg(2+)-induced hypertrophy.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acid; Atrial Natriuretic Factor; Biomarkers; Cardiomegaly; Cytochrome P-450 Enzyme System; Epoxide Hydrolases; Gene Expression Regulation, Enzymologic; Heart; Injections, Intraperitoneal; Isoenzymes; Male; Mercuric Chloride; Mice; Mice, Inbred C57BL; Myocardium; Natriuretic Peptide, Brain; RNA, Messenger

Oxidized low-density lipoprotein (Ox-LDL) is associated with atherosclerotic events through the modulation of arachidonic acid (AA) metabolism and activation of inflammatory signaling. Cytochrome P450 (CYP) epoxygenase-derived epoxyeicosatrienoic acids (EETs) mitigate inflammation through nuclear factor-κB (NF-κB). In this study, we explored the effects and mechanisms of exogenous EETs on the ox-LDL-induced inflammation of pulmonary artery endothelial cells (PAECs), which were cultured from rat pulmonary arteries. We determined that pre-treatment with 11,12-EET or 14,15-EET attenuated the ox-LDL-induced expression and release of intercellular adhesion molecule-1 (ICAM-1), E-selectin, and monocyte chemoattractant protein-1 (MCP-1) in a concentration-dependent manner. In addition, the ox-LDL-induced expression of CYP2J4 was upregulated by 11,12-EET and 14,15-EET (1μM). Furthermore, the endothelial receptor of lectin-like oxidized low-density lipoprotein (LOX-1) was downregulated in PAECs treated with EETs. The inflammatory responses evoked by ox-LDL (100μg/mL) were blocked by pharmacological inhibitors of Erk1/2 mitogen-activated protein kinase (MAPK) (U0126), p38 MAPK (SB203580), and NF-κB (PDTC). In addition, we confirmed that 11,12-EET suppresses phosphorylation of p38, degradation of IκBα, and activation of NF-κB (p65), whereas 14,15-EET can significantly suppress the phosphorylation of p38 and Erk1/2. Our results indicate that EETs exert beneficial effects on ox-LDL-induced inflammation primarily through the inhibition of LOX-1 receptor upregulation, MAPK phosphorylation, and NF-κB activation and through the upregulation of CYP2J4 expression. This study helps focus the current understanding of the contribution of EETs to the regulation of the inflammation of pulmonary vascular endothelial cells. Furthermore, the therapeutic potential of targeting the EET pathway in pulmonary vascular disease will be highlighted.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Anti-Inflammatory Agents; Cells, Cultured; Cytochrome P-450 Enzyme System; Cytochrome P450 Family 2; Dose-Response Relationship, Drug; Endothelial Cells; Enzyme Activation; Inflammation; Inflammation Mediators; Lipoproteins, LDL; Male; Mitogen-Activated Protein Kinases; NF-kappa B; Phosphorylation; Pulmonary Artery; Rats, Sprague-Dawley; RNA, Messenger; Scavenger Receptors, Class E; Signal Transduction

Therapies to reverse the vascular endothelial aging process may play as a novel strategy for the treatment of cardiovascular diseases. 14,15-epoxyeicosatrienoic acid (14,15-EET) is a predominant cytochrome P450 epoxygenases-derived arachidonic acid metabolite and possesses multiple biological effects on the vascular system. The present study sought to investigate the roles of mammalian target of rapamycin complex 2 (mTORC2)/Akt signaling pathways in mediating the effect of 14,15-EET on endothelial senescence. By measuring the isometric tension in rat mesenteric arteries, we demonstrated that 14,15-EET improved the impaired endothelium-dependent vasodilatation in aged rats through activating mTORC2/Akt signaling pathway. Meanwhile, by promoting the formation of mTORC2 and the phosphorylation of Akt (Ser473), 14,15-EET inhibited the senescence of rat mesenteric arterial endothelial cells, which was not influenced by rapamycin but was significantly attenuated by Akt1/2 kinase inhibitor. The knockdown of Rictor gene by RNA interference abolished the inhibitory effect of 14,15-EET on endothelial senescence. Furthermore, 14,15-EET down-regulated the expression of p53 protein in aged endothelial cells. Meanwhile, the nuclear translocation of telomerase reverse transcriptase and the nuclear telomerase activity were also enhanced by treatment with 14,15-EET. Therefore, our present study suggests the crucial role of mTORC2/Akt signaling pathways in the inhibitory effects of 14,15-EET on the endothelial senescence. Our findings reveal important mechanistic clues to understanding of the effects of 14,15-EET on the endothelial functions.

Topics: 8,11,14-Eicosatrienoic Acid; Age Factors; Animals; Cellular Senescence; Endothelial Cells; Endothelium, Vascular; Male; Mechanistic Target of Rapamycin Complex 2; Mesenteric Arteries; Multiprotein Complexes; Phosphorylation; Proto-Oncogene Proteins c-akt; Rats; Rats, Sprague-Dawley; Risk Factors; Signal Transduction; TOR Serine-Threonine Kinases

The objective of this study was to investigate the 14,15-epoxyeicosatrienoic acid (14,15-EET)-induced vasodilatations as well as the underlying signaling pathways in rat mesenteric arteries from young, adult and old normotensive (WKY) and hypertensive rats. Protein expressions for prostaglandin EP(1-4) receptors, large conductance Ca(2+)-activated K(+) (BK(Ca)) channels, and adenylate cyclase (AC) were determined together with 14,15-EET-induced vasodilatations in primary- versus secondary-branches of the mesenteric artery. Responses to 14,15-EET were greater in the smaller secondary- versus primary-branches (and also more sensitive with lower EC50) and were reduced in vessels from old (80 weeks) rats as well as from vessels from the spontaneous hypertensive rats (SHR). Regardless of age or hypertension responses to 14,15-EET were inhibited by the EP2 antagonist AH6809, BK(Ca) channel inhibitor iberiotoxin, or 3',5'-cyclic monophosphate (cAMP)-protein kinase A (PKA) pathway antagonists. These data indicate 14,15-EET-induced vasodilatation is mediated via the activation of EP2 receptors and opening of BK(Ca) channels. The expressions of the EP2 receptor and AC were markedly reduced in vessels from SHR as well as old rats, whereas BK(Ca) expression was reduced in old WKY and SHR, but not adult SHR. Furthermore, expression of the p53 protein, an indicator of cell senescence and apoptosis, was elevated in adult and old SHR as well as in old WKY. In summary, attenuated 14,15-EET-induced vasodilatation in mesenteric arteries from old normotensive WKY as well as adult and old SHR is associated with reduced expression of EP2 receptors and AC.

Topics: 8,11,14-Eicosatrienoic Acid; Aging; Animals; Cyclic AMP-Dependent Protein Kinases; Endothelium, Vascular; Enzyme Activation; Hypertension; Male; Mesenteric Arteries; Potassium Channels, Calcium-Activated; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Receptors, Prostaglandin E, EP2 Subtype; Vasodilator Agents

14,15-Epoxyeicosatrienoic acid (14,15-EET), a metabolite of arachidonic acid, is enriched in the brain cortex and exerts protective effect against neuronal apoptosis induced by ischemia/reperfusion. Although apoptosis has been well recognized to be closely associated with mitochondrial biogenesis and function, it is still unclear whether the neuroprotective effect of 14,15-EET is mediated by promotion of mitochondrial biogenesis and function in cortical neurons under the condition of oxygen-glucose deprivation (OGD). In this study, we found that 14,15-EET improved cell viability and inhibited apoptosis of cortical neurons. 14,15-EET significantly increased the mitochondrial mass and the ratio of mitochondrial DNA to nuclear DNA. Key makers of mitochondrial biogenesis, peroxisome proliferator activator receptor gamma-coactivator 1 alpha (PGC-1α), nuclear respiratory factor 1 (NRF-1) and mitochondrial transcription factor A (TFAM), were elevated at both mRNA and protein levels in the cortical neurons treated with 14,15-EET. Moreover, 14,15-EET markedly attenuated the decline of mitochondrial membrane potential, reduced ROS, while increased ATP synthesis. Knockdown of cAMP-response element binding protein (CREB) by siRNA blunted the up-regulation of PGC-1α and NRF-1 stimulated by 14,15-EET, and consequently abolished the neuroprotective effect of 14,15-EET. Our results indicate that 14,15-EET protects neurons from OGD-induced apoptosis by promoting mitochondrial biogenesis and function through CREB mediated activation of PGC-1α and NRF-1.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Apoptosis; Cell Hypoxia; Cells, Cultured; Cerebral Cortex; Glucose; Mice; Mice, Inbred C57BL; Mitochondria; Neurons; Neuroprotective Agents; Oxygen

The cytochrome P450 eicosanoid 14,15-epoxyeicosa-5,8,11-trienoic acid (14,15-EET) is a powerful endogenous autacoid that has been ascribed an impressive array of physiologic functions including regulation of blood pressure. Because 14,15-EET is chemically and metabolically labile, structurally related surrogates containing epoxide bioisosteres were introduced and have become useful in vitro pharmacologic tools but are not suitable for in vivo applications. A new generation of EET mimics incorporating modifications to the carboxylate were prepared and evaluated for vasorelaxation and inhibition of soluble epoxide hydrolase (sEH). Tetrazole 19 (ED50 0.18 μM) and oxadiazole-5-thione 25 (ED50 0.36 μM) were 12- and 6-fold more potent, respectively, than 14,15-EET as vasorelaxants; on the other hand, their ability to block sEH differed substantially, i.e., 11 vs >500 nM. These data will expedite the development of potent and specific in vivo drug candidates.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Cattle; Chemistry Techniques, Synthetic; Coronary Vessels; Enzyme Inhibitors; Epoxide Hydrolases; Humans; In Vitro Techniques; Molecular Mimicry; Oxadiazoles; Oxamic Acid; Tetrazoles; Vasodilation; Vasodilator Agents

14,15-epoxyeicosatrienoic acid (14,15-EET) is implicated in regulating physiological functions of endothelial cells (ECs), yet the potential molecular mechanisms underlying the beneficial effects in ECs are not fully understood. In this study, we investigated whether transient receptor potential vanilloid receptor type 1 (TRPV1) is involved in 14,15-EET-mediated Ca(2+) influx, nitric oxide (NO) production and angiogenesis. In human microvascular endothelial cells (HMECs), 14,15-EET time-dependently increased the intracellular level of Ca(2+). Removal of extracellular Ca(2+), pharmacological inhibition or genetic disruption of TRPV1 abrogated 14,15-EET-mediated increase of intracellular Ca(2+) level in HMECs or TRPV1-transfected HEK293 cells. Furthermore, removal of extracellular Ca(2+) or pharmacological inhibition of TRPV1 decreased 14,15-EET-induced NO production. 14,15-EET-mediated tube formation was abolished by TRPV1 pharmacological inhibition. In an animal experiment, 14,15-EET-induced angiogenesis was diminished by inhibition of TRPV1 and in TRPV1-deficient mice. TRPV1 may play a crucial role in 14,15-EET-induced Ca(2+) influx, NO production and angiogenesis.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Calcium; Endothelial Cells; Gene Expression Regulation; HEK293 Cells; Humans; Mice; Mice, Inbred C57BL; Mice, Knockout; Neovascularization, Physiologic; Nitric Oxide; Signal Transduction; TRPV Cation Channels; Vasodilator Agents

Herein, we characterize a generally applicable transformation of fatty acid epoxides by lipoxygenase (LOX) enzymes that results in the formation of a five-membered endoperoxide ring in the end product. We demonstrated this transformation using soybean LOX-1 in the metabolism of 15,16-epoxy-α-linolenic acid, and murine platelet-type 12-LOX and human 15-LOX-1 in the metabolism of 14,15-epoxyeicosatrienoic acid (14,15-EET). A detailed examination of the transformation of the two enantiomers of 15,16-epoxy-α-linolenic acid by soybean LOX-1 revealed that the expected primary product, a 13S-hydroperoxy-15,16-epoxide, underwent a nonenzymatic transformation in buffer into a new derivative that was purified by HPLC and identified by UV, LC-MS, and ¹H-NMR as a 13,15-endoperoxy-16-hydroxy-octadeca-9,11-dienoic acid. The configuration of the endoperoxide (cis or trans side chains) depended on the steric relationship of the new hydroperoxy moiety to the enantiomeric configuration of the fatty acid epoxide. The reaction mechanism involves intramolecular nucleophilic substitution (SNi) between the hydroperoxy (nucleophile) and epoxy group (electrophile). Equivalent transformations were documented in metabolism of the enantiomers of 14,15-EET by the two mammalian LOX enzymes, 15-LOX-1 and platelet-type 12-LOX. We conclude that this type of transformation could occur naturally with the co-occurrence of LOX and cytochrome P450 or peroxygenase enzymes, and it could also contribute to the complexity of products formed in the autoxidation reactions of polyunsaturated fatty acids.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonate 12-Lipoxygenase; Arachidonate 15-Lipoxygenase; Biocatalysis; Blood Platelets; Chromatography, High Pressure Liquid; Eicosanoids; Epoxy Compounds; Gas Chromatography-Mass Spectrometry; Humans; Hydroxylation; Linolenic Acids; Lipid Peroxides; Lipoxygenase; Mice; Molecular Structure; Nuclear Magnetic Resonance, Biomolecular; Oxidation-Reduction; Recombinant Proteins; Soybean Proteins; Spectrometry, Mass, Electrospray Ionization; Stereoisomerism

Epoxyeicosatrienoic acids (EETs) are derived from arachidonic acid by cytochrome P450 (CYP) and metabolized by soluble epoxide hydrolase (sEH). EETs have been associated with cardiovascular disease, diabetes and several cancer diseases. However, the distribution in tissue and role of CYP2C8, 2C9, 2J2 and sEH in human breast carcinogenesis remains uncertain.. Breast cancer (BC) and adjacent noncancerous tissue was obtained from 40 breast cancer patients in the Chaoshan region in China from 2010 to 2012. The level of 14,15-EET/14,15-DHET in BC patients was detected by ELISA; the expression and distribution of CYP2C8, 2C9, 2J2 and sEH was determined by quantitative RT-PCR and immunohistochemical staining; and cell proliferation and migration was analyzed by MTT and transwell assays, respectively.. The median 14,15-EET and 14,15-EET/DHET level was 2.5-fold higher in BC than noncancerous tissue. The mRNA and protein levels of CYP2C8, 2C9 and 2J2 were higher, and sEH was lower in BC than noncancerous tissue. Furthermore, CYP2C8 and 2C9 protein levels positively correlated with Ki67 status, and CYP2J2 levels positively correlated with histological grade and tumor size. The sEH protein level negatively correlated with tumor size, estrogen receptors and Ki67. In MDA-MB-231 cells, siRNA knockdown of CYP2C8, 2C9 or 2J2 reduced cell proliferation, by 24.5%, 29.13%, or 22.7% and decreased cell migration by 49.1%, 44.9%, and 50.9%, respectively. Similarly, with adenovirus overexpression of sEH, both cell proliferation and migration rates were reduced by 31.4% and 45.8%, respectively.. The present study shows that elevated EET levels in BC tissues are associated with upregulation of CYP2C8, 2C9, and 2J2, and downregulation of sEH, and are also associated with aggressive cell behavior in BC patients.

Topics: 8,11,14-Eicosatrienoic Acid; Adult; Aged; Breast Neoplasms; Cell Line, Tumor; Cell Movement; Cell Proliferation; Cytochrome P-450 CYP2C8; Cytochrome P-450 CYP2C9; Cytochrome P-450 CYP2J2; Cytochrome P-450 Enzyme System; Disease Progression; Epoxide Hydrolases; Female; Humans; Immunohistochemistry; Intracellular Space; Lymphatic Metastasis; Middle Aged; Neoplasm Grading; Tumor Burden

Epoxyeicosanoids (EETs) are produced by cytochrome P-450 epoxygenase; however, it is not yet known what triggers their endogenous production in epithelial cells. The relaxing effects of bradykinin are known to be related to endogenous production of epithelial-derived hyperpolarizing factors (EpDHF). Because of their effects on membrane potential, EETs have been reported to be EpDHF candidates (Benoit C, Renaudon B, Salvail D, Rousseau E. Am J Physiol Lung Cell Mol Physiol 280: L965-L973, 2001.). Thus, we hypothesized that bradykinin (BK) may stimulate endogenous EET production in human bronchi. To test this hypothesis, the relaxing and hyperpolarizing effects of BK and 14,15-EET were quantified on human bronchi, as well as the effects of various enzymatic inhibitors on these actions. One micromolar BK or 1 μM 14,15-EET induced a 45% relaxation on the tension induced by 30 nM U-46619 [a thromboxane-prostanoid (TP)-receptor agonist]. These BK-relaxing effects were reduced by 42% upon addition of 10 nM iberiotoxin [a large-conductance Ca(2+)-sensitive K(+) (BK(Ca)) channel blocker], by 27% following addition of 3 μM 14,15-epoxyeicosa-5(Z)-enoic acid (an EET antagonist), and by 32% with 3 μM N-methanesulfonyl-6-(2-propargyloxyphenyl)hexanamide (MS-PPOH, an epoxygenase inhibitor). Hence, BK and 14,15-EET display net hyperpolarizing effects on airway smooth muscle cells that are related to the activation of BK(Ca) channels and ultimately yielding to relaxation. Data also indicate that 3 μM MS-PPOH reduced the hyperpolarizing effects of BK by 43%. Together, the present data support the current hypothesis suggesting a direct relationship between BK and the production of EET regioisomers. Because of its potent anti-inflammatory and relaxing properties, epoxyeicosanoid signaling may represent a promising target in asthma and chronic obstructive pulmonary disease.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; 8,11,14-Eicosatrienoic Acid; Amides; Bradykinin; Bronchi; Dose-Response Relationship, Drug; Eicosanoids; Humans; In Vitro Techniques; Membrane Potentials; Muscle Relaxation; Respiratory Muscles

We previously demonstrated that 11,12 and 14,15-epoxeicosatrienoic acids (EETs) produce cardioprotection against ischemia-reperfusion injury in dogs and rats. Several signaling mechanisms have been implicated in the cardioprotective actions of the EETs; however, their mechanisms remain largely elusive. Since nitric oxide (NO) plays a significant role in cardioprotection and EETs have been demonstrated to induce NO production in various tissues, we hypothesized that NO is involved in mediating the EET actions in cardioprotection. To test this hypothesis, we used an in vivo rat model of infarction in which intact rat hearts were subjected to 30-min occlusion of the left coronary artery and 2-hr reperfusion. 11,12-EET or 14,15-EET (2.5mg/kg) administered 10min prior to the occlusion reduced infarct size, expressed as a percentage of the AAR (IS/AAR), from 63.9±0.8% (control) to 45.3±1.2% and 45.5±1.7%, respectively. A nonselective nitric oxide synthase (NOS) inhibitor, L-NAME (1.0mg/kg) or a selective endothelial NOS inhibitor, L-NIO (0.30mg/kg) alone did not affect IS/AAR but they completely abolished the cardioprotective effects of the EETs. On the other hand, a selective neuronal NOS inhibitor, nNOS I (0.03mg/kg) and a selective inducible NOS inhibitor, 1400W (0.10mg/kg) did not affect IS/AAR or block the cardioprotective effects of the EETs. Administration of 11,12-EET (2.5mg/kg) to the rats also transiently increased the plasma NO concentration. 14,15-EET (10μM) induced the phosphorylation of eNOS (Ser(1177)) as well as a transient increase of NO production in rat cardiomyoblast cell line (H9c2 cells). When 11,12-EET or 14,15-EET was administered at 5min prior to reperfusion, infarct size was also reduced to 42.8±2.2% and 42.6±1.9%, respectively. Interestingly, L-NAME (1.0mg/kg) and a mitochondrial KATP channel blocker, 5-HD (10mg/kg) did not abolish while a sarcolemmal KATP channel blocker, HMR 1098 (6.0mg/kg) and a mitochondrial permeability transition pore (MPTP) opener, atractyloside (5.0mg/kg) completely abolished the cardioprotection produced by the EETs. 14,15-EET (1.5mg/kg) with an inhibitor of MPTP opening, cyclosporin A (CsA, 1.0mg/kg) produced a greater reduction of infarct size than their individual administration. Conversely, an EET antagonist 14,15-epoxyeicosa-5(Z)-enoic acid (14,15-EEZE, 2.5mg/kg) completely abolished the cardioprotective effects of CsA, suggesting a role of MPTP in mediating the EET actions. Taken together, these results

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Cell Line; Heart; Hemodynamics; Imines; Male; Mitochondrial Membrane Transport Proteins; Mitochondrial Permeability Transition Pore; Myocardial Infarction; Nitric Oxide; Nitric Oxide Synthase Type III; Rats; Rats, Sprague-Dawley; Reperfusion Injury

Diabetic nephropathy (DN), a major complication of diabetes, is characterized by hypertrophy, extracellular matrix accumulation, fibrosis and proteinuria leading to loss of renal function. Hypertrophy is a major factor inducing proximal tubular epithelial cells injury. However, the mechanisms leading to tubular injury is not well defined. In our study, we show that exposure of rats proximal tubular epithelial cells to high glucose (HG) resulted in increased extracellular matrix accumulation and hypertrophy. HG treatment increased ROS production and was associated with alteration in CYPs 4A and 2C11 expression concomitant with alteration in 20-HETE and EETs formation. HG-induced tubular injury were blocked by HET0016, an inhibitor of CYPs 4A. In contrast, inhibition of EETs promoted the effects of HG on cultured proximal tubular cells. Our results also show that alteration in CYPs 4A and 2C expression and 20HETE and EETs formation regulates the activation of the mTOR/p70S6Kinase pathway, known to play a major role in the development of DN. In conclusion, we show that hyperglycemia in diabetes has a significant effect on the expression of Arachidonic Acid (AA)-metabolizing CYPs, manifested by increased AA metabolism, and might thus alter kidney function through alteration of type and amount of AA metabolites.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Blotting, Western; Cells, Cultured; Cytochrome P-450 CYP4A; Cytochrome P-450 Enzyme System; Diabetic Nephropathies; Glucose; Hydroxyeicosatetraenoic Acids; Hypertrophy; Kidney Tubules, Proximal; Oxidative Stress; Rats; Reactive Oxygen Species; Ribosomal Protein S6 Kinases, 70-kDa; TOR Serine-Threonine Kinases

14,15-Epoxyeicosatrienoic acids (14,15-EETs) generated from arachidonic acid by cytochrome P450 epoxygenases have beneficial effects in certain cardiovascular diseases, and increased 14,15-EET levels protect the cardiovascular system. 14,15-EETs are rapidly hydrolyzed by soluble epoxide hydrolase (sEH) to the corresponding 14,15-dihydroxyeicosatrienoic acids (14,15-DHETs), which are generally less biologically active but more stable metabolite. A functionally relevant polymorphism of the CYP2J2 gene is independently associated with an increased risk of coronary heart disease (CHD), and the major CYP2J2 product is 14,15-EETs. 14,15-DHETs can be considered a relevant marker of CYP2J2 activity. Therefore, the aim of the present study was to evaluate the plasma 14,15-DHET levels to reflect the 14,15-EET levels in an indirectly way in patients with CHD, and to highlight the growing body of evidence that 14,15-EETs also play a role in anti-inflammatory and lipid-regulating effects in patients with CHD. This was achieved by investigating the relationship between 14,15-DHETs and high-sensitivity C-reactive protein (hs-CRP) and blood lipoproteins.. Samples of peripheral venous blood were drawn from 60 patients with CHD and 60 healthy controls. A 14,15-DHET enzyme-linked immunosorbent assay kit (14,15-DHET ELISA kit) was used to measure the plasma 14,15-DHET levels. Hs-CRP, total cholesterol, triglyceride, high-density lipoprotein cholesterol, and low-density lipoprotein-cholesterol levels were measured.. 14,15-DHET levels (2.53 ± 1.60 ng/mL) were significantly higher in patients with CHD as compared with those of the healthy controls (1.65 ± 1.54 ng/mL, P < 0.05). There was a significant positive correlation between 14,15-DHETs and hs-CRP levels (R = 0.286, P = 0.027). However, there was no significant correlation between 14,15-DHETs and blood lipoproteins (all, P > 0.05).. Increased plasma 14,15-DHET levels reflect the decreased of 14,15-EET levels in an indirectly way. Indicated that decreased plasma 14,15-EET levels might be involved in the inflammatory reaction process in atherosclerosis.

Topics: 8,11,14-Eicosatrienoic Acid; Aged; C-Reactive Protein; Case-Control Studies; Cholesterol, HDL; Cholesterol, LDL; Coronary Disease; Cytochrome P-450 CYP2J2; Cytochrome P-450 Enzyme System; Female; Humans; Inflammation; Male; Middle Aged; Statistics, Nonparametric; Triglycerides

Epoxyeicosatrienoic acids (EETs) are cytochrome P450 epoxygenase metabolites of arachidonic acid involved in regulating pathways promoting cellular protection. We have previously shown that EETs trigger a protective response limiting mitochondrial dysfunction and reducing cellular death. Considering it is unknown how EETs regulate cell death processes, the major focus of the current study was to investigate their role in the autophagic response of HL-1 cells and neonatal cardiomyocytes (NCMs) during starvation. We employed a dual-acting synthetic analog UA-8 (13-(3-propylureido)tridec-8-enoic acid), possessing both EET-mimetic and soluble epoxide hydrolase (sEH) inhibitory properties, or 14,15-EET as model EET molecules. We demonstrated that EETs significantly improved viability and recovery of starved cardiac cells, whereas they lowered cellular stress responses such as caspase-3 and proteasome activities. Furthermore, treatment with EETs resulted in preservation of mitochondrial functional activity in starved cells. The protective effects of EETs were abolished by autophagy-related gene 7 (Atg7) short hairpin RNA (shRNA) or pharmacological inhibition of autophagy. Mechanistic evidence demonstrated that sarcolemmal ATP-sensitive potassium channels (pmKATP) and enhanced activation of AMP-activated protein kinase (AMPK) played a crucial role in the EET-mediated effect. Our data suggest that the protective effects of EETs involve regulating the autophagic response, which results in a healthier pool of mitochondria in the starved cardiac cells, thereby representing a novel mechanism of promoting survival of cardiac cells. Thus, we provide new evidence highlighting a central role of the autophagic response in linking EETs with promoting cell survival during deep metabolic stress such as starvation.

Topics: 8,11,14-Eicosatrienoic Acid; Adenosine Triphosphate; Amino Acids; AMP-Activated Protein Kinases; Animals; Animals, Newborn; Autophagy; Benzamides; Cardiotonic Agents; Cell Line; Cell Survival; Cytoprotection; Enzyme Activation; Mitochondria, Heart; Myocytes, Cardiac; Oleic Acids; Phosphorylation; Potassium Channels; Rats; Stress, Physiological

The present study further identified factors involved in the cardioprotective phenomenon of remote preconditioning of trauma (RPCT) with special emphasis on the role of the epoxyeicosatrienoic acids (EETs) in mediating this phenomenon. Remote preconditioning of trauma was produced by an abdominal incision only through the skin. Subsequently, all rats were subjected to 30 minutes of left coronary artery occlusion followed by 2 hours of reperfusion and the infarct size was determined. Remote preconditioning of trauma produced a reduction in infarct size expressed as a percentage of the area at risk from 63.0% ± 1.1% to 44.7% ± 1.4%; P < .01 versus control. To test the 3 major triggers of classical preconditioning in mediating RPCT, blockers of the bradykinin B2 receptor (B2BK), (S)-4-[2-[Bis(cyclohexylamino)methyleneamino]-3-(2-naphthalenyl)-1-oxopropylamino]benzyl tributyl phosphonium (WIN 64338, 1 mg/kg, iv), or HOE 140 (50 μg/kg, iv), the nonselective opioid receptor blocker, naloxone (3 mg/kg, iv), or the adenosine A1 receptor blocker, 8-Cyclopentyl-1,3-dipropylxanthine (DPCPX, 1 mg/kg, iv) were administered 10 minutes prior to RPCT. Only the 2 B2BK selective antagonists blocked RPCT (60.2% ± 1.1%, WIN 64338; 62.3% ± 2.0%, HOE 140). To test EETs in RPCT, we administered the EET receptor antagonist 14,15-Epoxyeicosa-5(Z)-enoic acid (14,15-EEZE, 2.5 mg/kg, iv) or the EET synthesis inhibitor, N-(Methylsulfonyl)-2-(2-propynyloxy)-benzenehexanamide (MSPPOH, 3.0 mg/kg, iv) 10 minutes prior to RPCT. In both groups, the EET antagonists completely blocked RPCT (62.0% ± 0.8%, 14,15-EEZE; 61.8% ± 1.0%, MSPPOH). The EET antagonists also blocked the effect of B2BK activation. We also determined whether the sarcolemmal K(ATP) or the mitochondrial K(ATP) channel mediate RPCT by pretreating rats with 1-[5-[2-(5-Chloro-o-anisamido)ethyl]-2-methoxyphenyl]sulfonyl-3 methylthiourea, sodium salt (HMR 1098) or 5-hydroxydecanoic acid (5-HD), respectively. Interestingly, 5-HD blocked RPCT (64.7% ± 1.3%), whereas, HMR 1098 did not (50.3% ± 1.3%). The 2 EET antagonists completely blocked capsaicin-induced cardioprotection. These results clearly suggest that EETs mediate RPCT-, bradykinin- and capsaicin-induced cardioprotection in rat hearts.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Capsaicin; Cytochrome P-450 Enzyme System; Hemodynamics; Ischemic Preconditioning, Myocardial; KATP Channels; Male; Myocardial Infarction; Rats; Rats, Sprague-Dawley; Sarcolemma; Xanthines

Cytochrome P450 (CYP)-derived epoxyeicosatrienoic acids (EETs) possess angiogenic effects. However, the effect of CYP-derived EETs and soluble epoxide hydrolase (sEH) deletion on wound healing in vivo has not been rigorously investigated. In this study, we measured the effect of exogenous CYP-derived EETs and targeted disruption of sEH in an in vivo wound model.. Standardized full-thickness dermal wounds were created on the dorsum of mouse ears. Wound epithelialization was directly viewed and measured using intravital microscopy and computerized planimetry every second day until healing was complete. Wound sections were analyzed by immunostaining for metalloproteinase (MMP) 2, MMP7, MMP9, tissue inhibitor of metalloproteinases (TIMP) 1, and tumor necrosis factor (TNF) α on days 2, 4, and 12.. Treatment with 11,12-EETs, 14,15-EETs, and sEH deletion significantly accelerated wound closure. This effect was attenuated by the EET antagonist 14,15-epoxyeicosa-5(Z)-enoic acid (14,15-EEZE) in sEH(-/-) mice. Neither 11,12- nor 14,15-EETs caused significant alterations in MMP9 expression in wounds. In contrast, MMP2 and MMP7 were significantly upregulated in the EET-treated groups, whereas TIMP1 and TNF-α were downregulated.. Collectively, these data demonstrated that potentiation of the CYP epoxy-genase pathway by either exogenous CYP-derived EETs or sEH deletion significantly accelerated wound epithelialization in vivo. This beneficial effect might be due to downregulation of TNF-α production and, to a lesser degree, to the release of MMPs and could be used as a viable angiogenic therapeutic strategy.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Epoxide Hydrolases; Matrix Metalloproteinase 2; Matrix Metalloproteinase 9; Mice; Mice, Inbred C57BL; Re-Epithelialization; Tumor Necrosis Factor-alpha; Wound Healing

The epithelial sodium channel (ENaC) participates in the regulation of plasma sodium and volume, and gain of function mutations in the human channel cause salt-sensitive hypertension. Roles for the arachidonic acid epoxygenase metabolites, the epoxyeicosatrienoic acids (EETs), in ENaC activity have been identified; however, their mechanisms of action remain unknown. In polarized M1 cells, 14,15-EET inhibited amiloride-sensitive apical to basolateral sodium transport as effectively as epidermal growth factor (EGF). The EET effects were associated with increased threonine phosphorylation of the ENaC β and γ subunits and abolished by inhibitors of (a) mitogen-activated protein kinase/extracellular signal-regulated kinase kinase/extracellular signal regulated kinases 1 and 2 (MEK/ERK1/2) and (b) EGF receptor signaling. CYP2C44 epoxygenase knockdown blunted the sodium transport effects of EGF, and its 14,15-EET metabolite rescued the knockdown phenotype. The relevance of these findings is indicated by (a) the hypertension that results in mice administered cetuximab, an inhibitor of EGF receptor binding, and (b) immunological data showing an association between the pressure effects of cetuximab and reductions in ENaCγ phosphorylation. These studies (a) identify an ERK1/2-dependent mechanism for ENaC inhibition by 14,15-EET, (b) point to ENaC as a proximal target for EET-activated ERK1/2 mitogenic kinases, (c) characterize a mechanistic commonality between EGF and epoxygenase metabolites as ENaC inhibitors, and (d) suggest a CYP2C epoxygenase-mediated pathway for the regulation of distal sodium transport.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Antibodies, Monoclonal; Antibodies, Monoclonal, Humanized; Antihypertensive Agents; Cetuximab; Cytochrome P-450 Enzyme System; Cytochrome P450 Family 2; Epidermal Growth Factor; Epithelial Sodium Channels; Extracellular Signal-Regulated MAP Kinases; Gene Expression Regulation; Humans; Hypertension; Kidney; Male; Mice; Models, Biological; Phosphorylation

Soluble epoxide hydrolase (sEH) plays a key role in the metabolic conversion of the protective eicosanoid 14,15-epoxyeicosatrienoic acid to 14,15-dihydroxyeicosatrienoic acid. Accordingly, inhibition of sEH hydrolase activity has been shown to be beneficial in multiple models of cardiovascular diseases, thus identifying sEH as a valuable therapeutic target. Recently, a common human polymorphism (R287Q) was identified that reduces sEH hydrolase activity and is localized to the dimerization interface of the protein, suggesting a relationship between sEH dimerization and activity. To directly test the hypothesis that dimerization is essential for the proper function of sEH, we generated mutations within the sEH protein that would either disrupt or stabilize dimerization. We quantified the dimerization state of each mutant using a split firefly luciferase protein fragment-assisted complementation system. The hydrolase activity of each mutant was determined using a fluorescence-based substrate conversion assay. We found that mutations that disrupted dimerization also eliminated hydrolase enzymatic activity. In contrast, a mutation that stabilized dimerization restored hydrolase activity. Finally, we investigated the kinetics of sEH dimerization and found that the human R287Q polymorphism was metastable and capable of swapping dimer partners faster than the WT enzyme. These results indicate that dimerization is required for sEH hydrolase activity. Disrupting sEH dimerization may therefore serve as a novel therapeutic strategy for reducing sEH hydrolase activity.

Topics: 8,11,14-Eicosatrienoic Acid; Dimerization; DNA Mutational Analysis; Epoxide Hydrolases; Genetic Complementation Test; HEK293 Cells; Humans; Hydrolases; Kinetics; Models, Molecular; Mutation; Polymorphism, Genetic; Solubility; Transfection

Hyperhomocysteinemia is a risk factor of atherogenesis. Soluble epoxide hydrolase (sEH) is a major enzyme that hydrolyzes epoxyeicosatrienoic acids and attenuates their cardiovascular protective effects. Whether homocysteine (Hcy) regulates sEH and the underlying mechanism remains elusive.. To elucidate the mechanism by which Hcy regulates sEH expression and endothelial activation in vitro and in vivo.. Hcy treatment in cultured human endothelial cells dose-dependently and time-dependently upregulated sEH mRNA and protein. Hcy increased the expression of adhesion molecules, which was markedly reversed by inhibiting sEH activity. Hcy-induced sEH upregulation is associated with activation of activating transcription factor-6 (ATF6). Bioinformatics analysis revealed a putative ATF6-binding motif in the promoter region of the sEH gene, which was found at a methylation site. Site-directed mutagenesis and chromatin immunoprecipitation assays demonstrated that Hcy treatment or ATF6 overexpression promoted ATF6 binding to the promoter of sEH and increased its activity. Results of methylation-specific polymerase chain reaction revealed that the ATF6 binding site on the sEH promoter was partially methylated and was demethylated with Hcy. SiRNA knockdown of ATF6α or SP1 blocked and ATF6 overexpression and DNA methyltransferase inhibitor mimicked the effect of homocysteine on sEH upregulation. In vivo, immunofluorescence assay revealed elevated expression of sEH and adhesion molecules in the aortic intima of mice with mild hyperhomocysteinemia, which was attenuated by sEH deletion or inhibition.. ATF6 activation and DNA demethylation may coordinately contribute to Hcy-induced sEH expression and endothelial activation. Inhibition of sEH may be a therapeutic approach for treating Hcy-induced cardiovascular diseases.

Topics: 8,11,14-Eicosatrienoic Acid; Activating Transcription Factor 6; Animals; Aorta; Base Sequence; DNA Methylation; Endothelial Cells; Epoxide Hydrolases; Gene Expression Regulation, Enzymologic; Homocysteine; Human Umbilical Vein Endothelial Cells; Humans; Hyperhomocysteinemia; Mice; Mice, Inbred C57BL; Mice, Mutant Strains; Promoter Regions, Genetic; Pyrenes; RNA, Small Interfering; Solubility; Up-Regulation

Preclinical and genetic epidemiologic studies suggest that modulating cytochrome P450 (CYP)-mediated arachidonic acid metabolism may have therapeutic utility in the management of coronary artery disease (CAD). However, predictors of inter-individual variation in CYP-derived eicosanoid metabolites in CAD patients have not been evaluated to date. Therefore, the primary objective was to identify clinical factors that influence CYP epoxygenase, soluble epoxide hydrolase (sEH), and CYP ω-hydroxylase metabolism in patients with established CAD.. Plasma levels of epoxyeicosatrienoic acids (EETs), dihydroxyeicosatrienoic acids (DHETs), and 20-hydroxyeicosatetraenoic acid (20-HETE) were quantified by HPLC-MS/MS in a population of patients with stable, angiographically confirmed CAD (N=82) and healthy volunteers from the local community (N=36). Predictors of CYP epoxygenase, sEH, and CYP ω-hydroxylase metabolic function were evaluated by regression.. Obesity was significantly associated with low plasma EET levels and 14,15-EET:14,15-DHET ratios. Age, diabetes, and cigarette smoking also were significantly associated with CYP epoxygenase and sEH metabolic activity, while only renin-angiotensin system inhibitor use was associated with CYP ω-hydroxylase metabolic activity. Compared to healthy volunteers, both obese and non-obese CAD patients had significantly higher plasma EETs (P<0.01) and epoxide:diol ratios (P<0.01), whereas no difference in 20-HETE levels was observed (P=NS).. Collectively, these findings suggest that CYP-mediated eicosanoid metabolism is dysregulated in certain subsets of CAD patients, and demonstrate that biomarkers of CYP epoxygenase and sEH, but not CYP ω-hydroxylase, metabolism are altered in stable CAD patients relative to healthy individuals. Future studies are necessary to determine the therapeutic utility of modulating these pathways in patients with CAD.

Topics: 8,11,14-Eicosatrienoic Acid; Age Factors; Biomarkers; Case-Control Studies; Chromatography, High Pressure Liquid; Coronary Angiography; Coronary Artery Disease; Cross-Sectional Studies; Cytochrome P-450 CYP2J2; Cytochrome P-450 CYP4A; Cytochrome P-450 Enzyme System; Diabetes Mellitus; Eicosanoids; Epoxide Hydrolases; Female; Humans; Hydroxyeicosatetraenoic Acids; Hydroxylation; Male; Middle Aged; North Carolina; Obesity; Regression Analysis; Risk Assessment; Risk Factors; Severity of Illness Index; Smoking; Tandem Mass Spectrometry

Sex differences in cerebral ischemic injury are, in part, attributable to the differences in cerebrovascular perfusion. We determined whether the brain microvascular endothelial cells (ECs) isolated from the female brain are more resistant to ischemic injury compared with male ECs, and whether the difference is attributable to lower expression of soluble epoxide hydrolase and higher levels of vasoprotective epoxyeicosatrienoic acids (EETs). We also determined whether protection by EETs is linked to the inhibition of rho-kinase (ROCK).. EC ischemic damage was measured after oxygen-glucose deprivation (OGD) using propidium iodide (PI) and cleaved caspase-3 labeling. Expression of soluble epoxide hydrolase was determined by quantitative polymerase chain reaction and immunocytochemistry, EETs levels by liquid chromatography-tandem mass spectrometry, and ROCK activity by ELISA. EC damage was higher in males compared with females, which correlated with higher soluble epoxide hydrolase mRNA, stronger immunoreactivity, and lower EETs compared with female ECs. Inhibition of soluble epoxide hydrolase abolished the sex difference in EC damage. ROCK activity was higher in male versus female ECs after OGD, and sex differences in EC damage and ROCK activity were abolished by 14,15-EET and ROCK inhibition.. Sex differences in ischemic brain injury are, in part, attributable to differences in EET-mediated inhibition of EC ROCK activation after ischemia.

Topics: 8,11,14-Eicosatrienoic Acid; Amides; Animals; Brain Ischemia; Cell Survival; Cells, Cultured; Endothelial Cells; Epoxide Hydrolases; Female; Male; Mice; Mice, Inbred C57BL; Pyridines; rho-Associated Kinases; Sex Characteristics; Solubility

Insulin produces capillary recruitment in skeletal muscle through a nitric oxide (NO)-dependent mechanism. Capillary recruitment is blunted in obese and diabetic subjects and contributes to impaired glucose uptake. This study's objective was to define whether inactivity, in the absence of obesity, leads to impaired capillary recruitment and contributes to insulin resistance (IR). A comprehensive metabolic and vascular assessment was performed on 19 adult male rhesus macaques (Macaca mulatta) after sedation with ketamine and during maintenance anesthesia with isoflurane. Thirteen normal-activity (NA) and six activity-restricted (AR) primates underwent contrast-enhanced ultrasound to determine skeletal muscle capillary blood volume (CBV) during an intravenous glucose tolerance test (IVGTT) and during contractile exercise. NO bioactivity was assessed by flow-mediated vasodilation. Although there were no differences in weight, basal glucose, basal insulin, or truncal fat, AR primates were insulin resistant compared with NA primates during an IVGTT (2,225 ± 734 vs. 5,171 ± 3,431 μg·ml⁻¹·min⁻¹, P < 0.05). Peak CBV was lower in AR compared with NA primates during IVGTT (0.06 ± 0.01 vs. 0.12 ± 0.02 ml/g, P < 0.01) and exercise (0.10 ± 0.02 vs. 0.20 ± 0.02 ml/g, P < 0.01), resulting in a lower peak skeletal muscle blood flow in both circumstances. The insulin-mediated changes in CBV correlated inversely with the degree of IR and directly with activity. Flow-mediated dilation was lower in the AR primates (4.6 ± 1.0 vs. 9.8 ± 2.3%, P = 0.01). Thus, activity restriction produces impaired skeletal muscle capillary recruitment during a carbohydrate challenge and contributes to IR in the absence of obesity. Reduced NO bioactivity may be a pathological link between inactivity and impaired capillary function.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Brachial Artery; Capillaries; Contrast Media; Glucose Tolerance Test; Hypertriglyceridemia; Inflammation Mediators; Insulin Resistance; Lipids; Macaca mulatta; Male; Motor Activity; Muscle Contraction; Muscle, Skeletal; Peripheral Vascular Diseases; Regional Blood Flow; Restraint, Physical; Sedentary Behavior; Ultrasonography; Vasodilation

Epoxide hydrolases are a small superfamily of enzymes important for the detoxification of chemically reactive xenobiotic epoxides and for the processing of endogenous epoxides that act as signaling molecules. Here, we report the identification of two human epoxide hydrolases: EH3 and EH4. They share 45% sequence identity, thus representing a new family of mammalian epoxide hydrolases. Quantitative RT-PCR from mouse tissue indicates strongest EH3 expression in lung, skin, and upper gastrointestinal tract. The recombinant enzyme shows a high turnover number with 8,9-, 11,12-, and 14,15-epoxyeicosatrienoic acid (EET), as well as 9,10-epoxyoctadec-11-enoic acid (leukotoxin). It is inhibited by a subclass of N,N'-disubstituted urea derivatives, including 12-(3-adamantan-1-yl-ureido)-dodecanoic acid, 1-cyclohexyl-3-dodecylurea, and 1-(1-acetylpiperidin-4-yl)-3-(4-(trifluoromethoxy)phenyl)urea, compounds so far believed to be selective inhibitors of mammalian soluble epoxide hydrolase (sEH). Its sensitivity to this subset of sEH inhibitors may have implications on the pharmacologic profile of these compounds. This is particularly relevant because sEH is a potential drug target, and clinical trials are under way exploring the value of sEH inhibitors in the treatment of hypertension and diabetes type II.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Epoxide Hydrolases; Epoxy Compounds; Humans; Inactivation, Metabolic; Mice; Mice, Inbred C57BL; Phylogeny; Stearic Acids; Xenobiotics

Astrocytes perform several functions that are essential for normal neuronal activity. They play a critical role in neuronal survival during ischemia and other degenerative injuries and also modulate neuronal recovery by influencing neurite outgrowth. In this study, we investigated the neuroprotective effects of astrocyte-derived 14,15-epoxyeicosatrienoic acid (14,15-EET), metabolite of arachidonic acid by cytochrome P450 epoxygenases (CYP), against oxidative stress induced by hydrogen peroxide (H(2)O(2)). We found that dopaminergic neuronal cells (N27 cell line) stimulated with two different doses of H(2)O(2) (0.1 and 1mM) for 1h showed decreased cell viability compared to the control group, while astrocytes showed less cell death after stimulation with the same doses of H(2)O(2) for 1h. Dopaminergic neuronal cells (N27 cell line) pretreated with different doses of 14,15-EET (0.1-30 μM, 30 min) before H(2)O(2) stimulation also showed increased cell viability. Furthermore, pre-treatment of the co-cultured cells with 12-(3-adamantan-1-yl-ureido)-dodecanoic acid, an inhibitor of the EET metabolizing enzyme, soluble epoxide hydrolase (sEH), before H(2)O(2) stimulation (1mM, for 1h) increased cell viability. It also increased the endogenous level of 14,15-EET in the media compared to control group. However, pretreatment with the CYP epoxygenase inhibitor miconazole (1-20 μM, 1h) before H(2)O(2) (1mM, 1h) stimulation showed decreased cell viability. Our data suggest that 14,15-EET which is released from astrocytes, enhances cell viability against oxidant-induced injury. Further understanding of the mechanism of 14,15-EET-mediated protection in dopaminergic neurons is imperative, as it could lead to novel therapeutic approaches for treating CNS neuropathologies, such as Parkinson's disease.

Topics: 8,11,14-Eicosatrienoic Acid; Analysis of Variance; Animals; Animals, Newborn; Astrocytes; Cell Survival; Cells, Cultured; Chromatography, Liquid; Coculture Techniques; Dopaminergic Neurons; Dose-Response Relationship, Drug; Drug Administration Schedule; Eicosanoids; Hippocampus; Hydrogen Peroxide; Mass Spectrometry; Membrane Potential, Mitochondrial; Neuroprostanes; Oxidants; Rats; Rats, Sprague-Dawley; Time Factors

Cytochrome P450 epoxygenase metabolites of arachidonic acid, EETs, have multiple cardiovascular effects, including reduction of blood pressure, protection against myocardial ischemia-reperfusion injury, and attenuation of endothelial apoptosis. This study investigated the hypothesis that transgenic mice with endothelial overexpression of CYP2J2 (Tie2-CYP2J2-Tr) would be protected against global cerebral ischemia induced by bilateral common carotid artery occlusion (BCCAO) and action mechanisms of EETs on cerebral ischemia in cultures of astrocytes exposed to oxygen-glucose deprivation (OGD). Tie2-CYP2J2-Tr mice had significantly increased CYP2J2 expression, increased 14,15-EET production, increases regional cerebral blood flow (rCBF) and microvascular density, decreased ROS production, decreased brain infarct size and apoptosis after ischemia compared to wild type mice, these were associated with increased activation of the PI3K/AKT and apoptosis-related protein in ischemic brain. Addition of exogenous EETs or CYP2J2 transfection attenuated OGD-induced apoptosis in astrocytes via activation of PI3K/AKT and anti-apoptosis pathways. However, these effects were reduced by pretreatments with inhibitor of the PI3K (LY294002) and 14,15-EET (14,15-EEZE), respectively. These results indicate that CYP2J2 overexpression exerts marked neuroprotective effects against ischemic injury by a mechanism linked to increased level of circulating EETs and increases CBF and reduction of apoptosis.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Apoptosis; Apoptosis Regulatory Proteins; Astrocytes; Brain Ischemia; Cell Hypoxia; Cells, Cultured; Cerebral Infarction; Cerebrovascular Circulation; Coronary Occlusion; Cytochrome P-450 CYP2J2; Cytochrome P-450 Enzyme System; Gene Expression; Glucose; Male; Mice; Mice, Transgenic; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-akt; Signal Transduction

Epoxyeicosatrienoic acids (EETs) and their regulating enzyme soluble epoxide hydrolase (sEH) have been associated with ischemic stroke. Salvianolic acid A (SAA) is proved to display potent cerebroprotection. However, little information is available about the link between them. This study aimed to investigate whether SAA exhibits its protective effects in rats subjected to middle cerebral artery occlusion (MCAO) through sEH and EETs. The results showed that SAA treatment ameliorated neurological deficits and reduced infarct volume. Notably, the beneficial effects of SAA were attenuated by co-administration of (14,15-epoxyeicosa-5(Z)-enoic acid (14,15-EEZE)), a putative selective EETs antagonist. Furthermore, SAA increased the 14,15-EET levels in the blood and brain of sham and MCAO rats. Assay for hydrolase activity showed that 1 and 3 mg/kg of SAA significantly diminished brain sEH activity of MCAO rats. A fluorescent assay in vitro indicated that SAA could inhibit recombinant human sEH activity in a concentration-dependent manner (IC(50) = 1.62 μmol/l). Immunohistochemical analysis showed that SAA at the doses of 1 and 3 mg/kg significantly decreased sEH protein expression in hippocampus CA1 region of MCAO rats. In conclusion, cerebral protection of SAA is mediated, at least in part, via inhibiting sEH to increase EETs levels.

Topics: 8,11,14-Eicosatrienoic Acid; Algorithms; Animals; Caffeic Acids; Epoxide Hydrolases; Hippocampus; Humans; Ischemia; Lactates; Male; Molecular Structure; Rats; Rats, Sprague-Dawley

Preeclampsia is a multisystem disorder of pregnancy, originating in the placenta. Cytochrome P450 (CYP)-dependent eicosanoids regulate vascular function, inflammation, and angiogenesis, which are mechanistically important in preeclampsia.. We performed microarray screening of placenta and decidua (maternal placenta) from 25 preeclamptic women and 23 control subjects. The CYP subfamily 2J polypeptide 2 (CYP2J2) was upregulated in preeclamptic placenta and decidua. Reverse-transcription polymerase chain reaction confirmed the upregulation, and immunohistochemistry localized CYP2J2 in trophoblastic villi and deciduas at 12 weeks and term. The CYP2J2 metabolites, 5,6-epoxyeicosatrienoic acid (EET), 14,15-EET, and the corresponding dihydroxyeicosatrienoic acids, were elevated in preeclamptic women compared with controls in the latter two thirds of pregnancy and after delivery. Stimulating a trophoblast-derived cell line with the preeclampsia-associated cytokine tumor necrosis factor-α enhanced CYP2J2 gene and protein expression. In 2 independent rat models of preeclampsia, reduced uterine-perfusion rat and the transgenic angiotensin II rat, we observed elevated EET, dihydroxyeicosatrienoic acid, and preeclamptic features that were ameliorated by the CYP epoxygenase inhibitor N-(methylsulfonyl)-2-(2-propynyloxy)-benzenehexanamide (MsPPOH). Uterine arterial rings of these rats also dilated in response to MsPPOH. Furthermore, 5,6-EET could be metabolized to a thromboxane analog. In a bioassay, 5,6-EET increased the beating rate of neonatal cardiomyocytes. Blocking thromboxane synthesis reversed that finding and also normalized large-conductance calcium-activated potassium channel activity.. Our data implicate CYP2J2 in the pathogenesis of preeclampsia and as a potential candidate for the disturbed uteroplacental remodeling, leading to hypertension and endothelial dysfunction.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Bridged Bicyclo Compounds, Heterocyclic; Cells, Cultured; Cytochrome P-450 CYP2J2; Cytochrome P-450 Enzyme System; Fatty Acids, Unsaturated; Female; Humans; Hydrazines; Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; Oligonucleotide Array Sequence Analysis; Placenta; Polymorphism, Single Nucleotide; Pre-Eclampsia; Pregnancy; Rats; Rats, Sprague-Dawley

Cytochrome P-450 epoxygenases metabolize arachidonic acid (AA) to epoxyeicosatrienoic acids (EETs). EETs relax vascular smooth muscle by membrane hyperpolarization. 14,15-Epoxyeicosa-5(Z)-enoic acid (14,15-EE5ZE) antagonizes many vascular actions of EETs. EETs are converted to the corresponding dihydroxyeicosatrienoic acids by soluble epoxide hydrolase (sEH). sEH activity in the bovine arterial endothelium and smooth muscle regulates endogenous EETs. This study examined sEH metabolism of 14,15-EE5ZE to 14,15-dihydroxy-eicosa-5(Z)-enoic acid (14,15-DHE5ZE) and the resultant consequences on EET relaxations of bovine coronary arteries (BCAs). BCAs converted 14,15-EE5ZE to 14,15-DHE5ZE. This conversion was blocked by the sEH inhibitor 12-(3-adamantan-1-yl-ureido)-dodecanoic acid (AUDA). 14,15-EET relaxations (maximal relaxation, 83.4 ± 4.5%) were inhibited by 14,15-DHE5ZE (10 μM; maximal relaxation, 36.1 ± 9.0%; p < 0.001). In sharp contrast with 14,15-EE5ZE, 14,15-DHE5ZE is a 14,15-EET-selective inhibitor and did not inhibit 5,6-, 8,9-, or 11,12-EET relaxations. 14,15-EET and 11,12-EET relaxations were similar in the presence and absence of AUDA (1 μM). 14,15-EE5ZE inhibited 14,15-EET relaxations to a similar extent with and without AUDA pretreatment. However, 14,15-EE5ZE inhibited 11,12-EET relaxations to a greater extent with than without AUDA pretreatment. These observations indicate that sEH converts 14,15-EE5ZE to 14,15-DHE5ZE, and this alteration influences antagonist selectivity against EET-regioisomers. 14,15-DHE5ZE inhibited endothelium-dependent relaxations to AA but not endothelium-independent relaxations to sodium nitroprusside. A series of sEH-resistant ether analogs of 14,15-EE5ZE was developed, and analogs with agonist and antagonist properties were identified. The present study indicates that conversion of 14,15-EE5ZE to 14,15-DHE5ZE produces a 14,15-EET-selective antagonist that will be a useful pharmacological tool to identify EET receptor(s) and EET function in the cardiovascular system.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Cattle; Coronary Vessels; Dose-Response Relationship, Drug; Vasodilation

Epoxyeicosatrienoic acids (EETs) are arachidonic acid metabolites produced by cytochrome P450 epoxygenases which are highly expressed in hepatocytes. The functions of EETs in hepatocytes are not well understood. In this study, we investigated the effects of 14,15-EETs treatment on the insulin signal transduction pathway in hepatocytes. We report that chronic treatment, not acute treatment, with 30 μM 14,15-EETs prevents palmitate induced insulin resistance and potentiates insulin action in cultured HepG2 hepatocytes. 14,15-EETs increase Akt phosphorylation at S473, activating Akt, in an insulin dependent manner in HepG2 cells. Under insulin resistant conditions induced by palmitate, 14,15-EETs restore the insulin response by increasing S473-phosphorylated Akt. 8,9-EETs and 11,12-EETs demonstrated similar effects to 14,15-EETs. Furthermore, 14,15-EETs potentiate insulin-suppression of gluconeogenesis in cultured H4IIE hepatocytes. To elucidate the mechanism of EETs function, we analyzed the insulin signaling factors upstream of Akt. Inhibition of phosphatidylinositol 3-kinase (PI3K) with LY294002 attenuated the 14,15-EETs-induced activating phosphorylation of Akt. 14,15-EETs reduced palmitate-stimulated phosphorylation of IRS-1 on S312 and phosphorylation of c-Jun N-terminal kinase (JNK) at threonine 183 and tyrosine 185 residues. The regulation of insulin sensitivity in cultured hepatocytes by chronic 14,15-EETs treatment appears to involve the JNK-IRS-PI3K pathway. The requirement of chronic treatment with EETs suggests that the effects of EETs on insulin response may be indirect.

Topics: 8,11,14-Eicosatrienoic Acid; Hep G2 Cells; Hepatocytes; Humans; Insulin; Insulin Receptor Substrate Proteins; Insulin Resistance; JNK Mitogen-Activated Protein Kinases; Phosphatidylinositol 3-Kinase; Phosphorylation; Signal Transduction

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.

Topics: 8,11,14-Eicosatrienoic Acid; Adrenal Glands; Aldosterone; Angiotensin II; Animals; Arachidonic Acid; Arteries; Cattle; Cells, Cultured; Dose-Response Relationship, Drug; Epoxide Hydrolases; In Vitro Techniques; Membrane Potentials; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Patch-Clamp Techniques; Potassium Channels; Vasoconstrictor Agents; Vasodilation; Vasodilator Agents; Zona Glomerulosa

Anandamide is an arachidonic acid-derived endogenous cannabinoid that regulates normal physiological functions and pathophysiological responses within the central nervous system and in the periphery. Several cytochrome P450 (P450) isoforms metabolize anandamide to form hydroxylated and epoxygenated products. Human CYP2B6 and CYP2D6, which are expressed heterogeneously throughout the brain, exhibit clinically significant polymorphisms and are regulated by external factors, such as alcohol and smoking. Oxidative metabolism of anandamide by these two P450s may have important functional consequences for endocannabinoid system signaling. In this study, we investigated the metabolism of anandamide by wild-type CYP2B6 (2B6.1) and CYP2D6 (2D6.1) and by their common polymorphic mutants 2B6.4, 2B6.6, 2B6.9, and 2D6.34. Major differences in anandamide metabolism by the two isoforms and their mutants were found in vitro with respect to the formation of 20-hydroxyeicosatetraenoic acid ethanolamide (20-HETE-EA) and 14,15-epoxyeicosatetraenoic acid ethanolamide (14,15-EET-EA). Pharmacological studies showed that both 20-HETE-EA and 14,15-EET-EA bind to the rat brain cannabinoid CB1 receptor with lower affinities relative to that of anandamide. In addition, both products are degraded more rapidly than anandamide in rat brain homogenates. Their degradation occurs via different mechanisms involving either fatty acid amide hydrolase (FAAH), the major anandamide-degrading enzyme, or epoxide hydrolase (EH). Thus, the current findings provide potential new insights into the actions of inhibitors FAAH and EH, which are being developed as novel therapeutic agents, as well as a better understanding of the interactions between the cytochrome P450 monooxygenases and the endocannabinoid system.

Topics: 8,11,14-Eicosatrienoic Acid; Amidohydrolases; Animals; Arachidonic Acids; Aryl Hydrocarbon Hydroxylases; Brain; Cannabinoid Receptor Modulators; Cytochrome P-450 CYP2B6; Cytochrome P-450 CYP2D6; Endocannabinoids; Epoxide Hydrolases; Humans; Hydroxyeicosatetraenoic Acids; Hydroxylation; Male; Oxidation-Reduction; Oxidoreductases, N-Demethylating; Polymorphism, Genetic; Polyunsaturated Alkamides; Rats; Rats, Sprague-Dawley; Receptor, Cannabinoid, CB1

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

Topics: 8,11,14-Eicosatrienoic Acid; Active Transport, Cell Nucleus; Breast Neoplasms; Cell Division; Cell Line, Tumor; Cytochrome P-450 CYP3A; Female; G2 Phase; Gene Silencing; Humans; Neoplasm Proteins; Phosphorylation; Signal Transduction; STAT3 Transcription Factor

Endothelium-derived epoxyeicosatrienoic acids (EETs) relax vascular smooth muscle by activating potassium channels and causing membrane hyperpolarization. Recent evidence suggests that EETs act via a membrane binding site or receptor. To further characterize this binding site or receptor, we synthesized 20-iodo-14,15-epoxyeicosa-8(Z)-enoyl-3-azidophenylsulfonamide (20-I-14,15-EE8ZE-APSA), an EET analogue with a photoactive azido group. 20-I-14,15-EE8ZE-APSA and 14,15-EET displaced 20-(125)I-14,15-epoxyeicosa-5(Z)-enoic acid binding to U937 cell membranes with K(i) values of 3.60 and 2.73 nM, respectively. The EET analogue relaxed preconstricted bovine coronary arteries with an ED(50) comparable to that of 14,15-EET. Using electrophoresis, 20-(125)I-14,15-EE8ZE-APSA labeled a single 47 kDa band in U937 cell membranes, smooth muscle and endothelial cells, and bovine coronary arteries. In U937 cell membranes, the 47 kDa radiolabeling was inhibited in a concentration-dependent manner by 8,9-EET, 11,12-EET, and 14,15-EET (IC(50) values of 444, 11.7, and 8.28 nM, respectively). The structurally unrelated EET ligands miconazole, MS-PPOH, and ketoconazole also inhibited the 47 kDa labeling. In contrast, radiolabeling was not inhibited by 8,9-dihydroxyeicosatrienoic acid, 5-oxoeicosatetraenoic acid, a biologically inactive thiirane analogue of 14,15-EET, the opioid antagonist naloxone, the thromboxane mimetic U46619, or the cannabinoid antagonist AM251. Radiolabeling was not detected in membranes from HEK293T cells expressing 79 orphan receptors. These studies indicate that vascular smooth muscle, endothelial cells, and U937 cell membranes contain a high-affinity EET binding protein that may represent an EET receptor. This EET photoaffinity labeling method with a high signal-to-noise ratio may lead to new insights into the expression and regulation of the EET receptor.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Azides; Binding Sites; Cattle; Cell Line; Coronary Vessels; Endothelial Cells; Fatty Acids, Unsaturated; Humans; Inhibitory Concentration 50; Kinetics; Ligands; Photoaffinity Labels; Protein Binding; Sulfonamides; U937 Cells

Soluble epoxide hydrolase (sEH) is a promising therapeutic target for the treatment of hypertension, pain, and inflammation-related diseases. In order to enable the development of sEH inhibitors (sEHIs), assays are needed for determination of their potency. Therefore, we developed a new method utilizing an epoxide of arachidonic acid (14(15)-EpETrE) as substrate. Incubation samples were directly injected without purification into an online solid phase extraction (SPE) liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI-MS-MS) setup allowing a total run time of only 108 s for a full gradient separation. Analytes were extracted from the matrix within 30 s by turbulent flow chromatography. Subsequently, a full gradient separation was carried out on a 50X2.1 mm RP-18 column filled with 1.7 μm core-shell particles. The analytes were detected with high sensitivity by ESI-MS-MS in SRM mode. The substrate 14(15)-EpETrE eluted at a stable retention time of 96 ± 1 s and its sEH hydrolysis product 14,15-DiHETrE at 63 ± 1 s with narrow peak width (full width at half maximum height: 1.5 ± 0.1 s). The analytical performance of the method was excellent, with a limit of detection of 2 fmol on column, a linear range of over three orders of magnitude, and a negligible carry-over of 0.1% for 14,15-DiHETrE. The enzyme assay was carried out in a 96-well plate format, and near perfect sigmoidal dose-response curves were obtained for 12 concentrations of each inhibitor in only 22 min, enabling precise determination of IC(50) values. In contrast with other approaches, this method enables quantitative evaluation of potent sEHIs with picomolar potencies because only 33 pmol L(-1) sEH were used in the reaction vessel. This was demonstrated by ranking ten compounds by their activity; in the fluorescence method all yielded IC(50) ≤ 1 nmol L(-1). Comparison of 13 inhibitors with IC(50) values >1 nmol L(-1) showed a good correlation with the fluorescence method (linear correlation coefficient 0.9, slope 0.95, Spearman's rho 0.9). For individual compounds, however, up to eightfold differences in potencies between this and the fluorescence method were obtained. Therefore, enzyme assays using natural substrate, as described here, are indispensable for reliable determination of structure-activity relationships for sEH inhibition.

Topics: 8,11,14-Eicosatrienoic Acid; Enzyme Inhibitors; Epoxide Hydrolases; Humans; Solid Phase Extraction; Tandem Mass Spectrometry

CYP450AAM [arachidonic acid metabolites of the CYP450 (cytochrome P450) enzyme system] have a range of biological functions. CYP450AAM are involved in the pathogenesis of hypertension, renal function and vascular function, yet their role in stroke has not been clarified. We aimed at determining the levels of circulating CYP450 metabolites in patients with acute ischaemic stroke (<96 h) compared with healthy age- and gender-matched controls. This was a retrospective case-controlled study of 44 acute ischaemic stroke patients and 44 matched controls. A subset of acute ischaemic stroke patients was available for follow-up. Acute ischaemic stroke patients had elevated plasma CYP450AAM, including 20-HETE (20-hydroxyeicosatetraenoic acid) (1921±170 compared with 1108±170 pmol/l, P<0.001), EETs (epoxyeicosatrienoic acids) (77.88±3.34 compared with 35.35±3.34 nmol/l, P<0.0001) and DiHETEs (dihydroxyeicosatetraenoic acids) (92.87±4.61 compared with 68.17±4.61 nmol/l, P<0.0001), as well as increased plasma F2-isoprostane levels (3754±538 compared with 1947±538 pmol/l, P<0.02), the latter a marker of oxidative stress, compared with controls. In a subset analysis of the stroke patients, plasma 20-HETE, EETs and F2-isoprostanes were attenuated 30 days after the stroke. Baseline 20-HETE levels were also associated with lesion size and functional indices within the stroke patients. The present study highlights the elevation in CYP450AAM and oxidative stress in acute ischaemic stroke patients. Further investigation of the effect this has on long-term clinical outcome or whether this can be modified by treatment is warranted.

Topics: 8,11,14-Eicosatrienoic Acid; Arachidonic Acid; Case-Control Studies; Cytochrome P-450 Enzyme System; F2-Isoprostanes; Female; Humans; Hydroxyeicosatetraenoic Acids; Male; Middle Aged; Oxidative Stress; Stroke

Sodium reabsorption via the epithelial Na(+) channel (ENaC) in the aldosterone-sensitive distal nephron plays a central role in the regulation of body fluid volume. Previous studies have indicated that arachidonic acid (AA) and its metabolite 11,12-EET but not other regioisomers of EETs inhibit ENaC activity in the collecting duct. The goal of this study was to investigate the endogenous metabolism of AA in cultured mpkCCD(c14) principal cells and the effects of these metabolites on ENaC activity. Liquid chromatography/mass spectrometry analysis of the mpkCCD(c14) cells indicated that these cells produce prostaglandins, 8,9-EET, 11,12-EET, 14,15-EET, 5-HETE, 12/8-HETE, and 15-HETE, but not 20-HETE. Single-channel patch-clamp experiments revealed that 8,9-EET, 14,15-EET, and 11,12-EET all decrease ENaC activity. Neither 5-, 12-, nor 15-HETE had any effect on ENaC activity. Diclofenac and ibuprofen, inhibitors of cyclooxygenase, decreased transepithelial Na(+) transport in the mpkCCD(c14) cells. Inhibition of cytochrome P-450 (CYP450) with MS-PPOH activated ENaC-mediated sodium transport when cells were pretreated with AA and diclofenac. Coexpression of CYP2C8, but not CYP4A10, with ENaC in Chinese hamster ovary cells significantly decreased ENaC activity in whole-cell experiments, whereas 11,12-EET mimicked this effect. Thus both endogenously formed EETs and their exogenous application decrease ENaC activity. Downregulation of ENaC activity by overexpression of CYP2C8 was PKA dependent and was prevented by myristoylated PKI treatment. Biotinylation experiments and single-channel analysis revealed that long-term treatment with 11,12-EET and overexpression of CYP2C8 decreased the number of channels in the membrane. In contrast, the acute inhibitory effects are mediated by a decrease in the open probability of the ENaC. We conclude that 11,12-EET, 8,9-EET, and 14,15-EET are endogenously formed eicosanoids that modulate ENaC activity in the collecting duct.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acid; Cell Line; CHO Cells; Cricetinae; Cricetulus; Cytochrome P-450 Enzyme System; Diclofenac; Epithelial Sodium Channels; Female; Ibuprofen; Kidney Tubules, Collecting; Mice; Models, Animal; Ovary; Patch-Clamp Techniques; Transfection

Cytochrome P-450 metabolites of arachidonic acid, the epoxyeicosatrienoic acids (EETs) and hydrogen peroxide (H(2)O(2)), are important signaling molecules in the kidney. In renal arteries, EETs cause vasodilation whereas H(2)O(2) causes vasoconstriction. To determine the physiological contribution of H(2)O(2), catalase is used to inactivate H(2)O(2). However, the consequence of catalase action on EET vascular activity has not been determined. In rat renal afferent arterioles, 14,15-EET caused concentration-related dilations that were inhibited by Sigma bovine liver (SBL) catalase (1,000 U/ml) but not Calbiochem bovine liver (CBL) catalase (1,000 U/ml). SBL catalase inhibition was reversed by the soluble epoxide hydrolase (sEH) inhibitor tAUCB (1 μM). In 14,15-EET incubations, SBL catalase caused a concentration-related increase in a polar metabolite. Using mass spectrometry, the metabolite was identified as 14,15-dihydroxyeicosatrienoic acid (14,15-DHET), the inactive sEH metabolite. 14,15-EET hydrolysis was not altered by the catalase inhibitor 3-amino-1,2,4-triazole (3-ATZ; 10-50 mM), but was abolished by the sEH inhibitor BIRD-0826 (1-10 μM). SBL catalase EET hydrolysis showed a regioisomer preference with greatest hydrolysis of 14,15-EET followed by 11,12-, 8,9- and 5,6-EET (V(max) = 0.54 ± 0.07, 0.23 ± 0.06, 0.18 ± 0.01 and 0.08 ± 0.02 ng DHET·U catalase(-1)·min(-1), respectively). Of five different catalase preparations assayed, EET hydrolysis was observed with two Sigma liver catalases. These preparations had low specific catalase activity and positive sEH expression. Mass spectrometric analysis of the SBL catalase identified peptide fragments matching bovine sEH. Collectively, these data indicate that catalase does not affect EET-mediated dilation of renal arterioles. However, some commercial catalase preparations are contaminated with sEH, and these contaminated preparations diminish the biological activity of H(2)O(2) and EETs.

Topics: 8,11,14-Eicosatrienoic Acid; Amitrole; Animals; Arterioles; Benzoates; Catalase; Cattle; Drug Contamination; Enzyme Inhibitors; Epoxide Hydrolases; Kidney; Rats; Urea; Vasodilation; Vasodilator Agents

Functional hyperemia is an important metabolic autoregulation mechanism by which increased neuronal activity is matched by a rapid and regional increase in blood supply. This mechanism is facilitated by a process known as "neurovascular coupling"--the orchestrated communication system involving neurons, astrocytes and arterioles. Important steps in this process are the production of EETs in the astrocyte and the release of potassium, via two potassium channels (BK and KIR), into the perivascular space. We provide a model which successfully accounts for several observations seen in experiment. The model is capable of simulating the approximate 15% arteriolar dilation caused by a 60-s neuronal activation (modelled as a release of potassium and glutamate into the synaptic cleft). This model also successfully emulates the paradoxical experimental finding that vasoconstriction follows vasodilation when the astrocytic calcium concentration (or perivascular potassium concentration) is increased further. We suggest that the interaction of the changing smooth muscle cell membrane potential and the changing potassium-dependent resting potential of the KIR channel are responsible for this effect. Finally, we demonstrate that a well-controlled mechanism of potassium buffering is potentially important for successful neurovascular coupling.

Topics: 8,11,14-Eicosatrienoic Acid; Arterioles; Astrocytes; Calcium; Humans; Models, Neurological; Muscle, Smooth, Vascular; Neurons; Potassium; Potassium Channels; Signal Transduction; Synapses; Vasodilation

Substrates and products of soluble epoxide hydrolase (sEH) such as 14,15-epoxyeicosatrienoic acid (14,15-EET), 14,15-dihydroxyeicosatrienoic acid (14,15-DHET), leukotoxin, and leukotoxin diol are potential biomarkers for assessing sEH activity in clinical trial subjects. To quantify them, we have developed and validated a semi-automated and relatively high-throughput assay in a 96-well plate format using liquid chromatography-mass spectrometry. 14,15-EET, 14,15-DHET, leukotoxin and leukotoxin diol, as well as their deuterium labeled internal standards were extracted from human plasma by liquid-liquid extraction using ethyl acetate. The four analytes were separated from other endogenous lipid isomers using liquid chromatography coupled with tandem mass spectrometry. The method was validated over a concentration range of 0.05-50 ng/mL. The validation results show that the method is precise, accurate and well-suited for analysis of clinical samples. The turn-around rate of the assay is approximately 200 samples per day.

Topics: 8,11,14-Eicosatrienoic Acid; Biomarkers; Chromatography, Liquid; Epoxide Hydrolases; Female; Humans; Linoleic Acids; Male; Reproducibility of Results; Sensitivity and Specificity; Stearic Acids; Tandem Mass Spectrometry

Epoxyeicosatrienoic acid (EET) and thromboxane A(2) are arachidonic acid derivatives. The former has initially been defined as an epithelium-derived hyperpolarizing factor displaying broncho-relaxing and anti-inflammatory properties, as recently demonstrated, whereas thromboxane A(2) induces vaso- and bronchoconstriction upon binding to thromboxane-prostanoid (TP)-receptor. EETs, however, are quickly degraded by the soluble epoxide hydrolase (sEH) into inactive diol compounds. The aim of this study was to investigate the effects of 14,15-EET on TP-receptor activation in human bronchi. Tension measurements performed on native bronchi from various species, acutely treated with increasing 14,15-EET concentrations, revealed specific and concentration-dependent relationships as well as a decrease in the tension induced by 30 nM U-46619, used as a synthetic TP-receptor agonist. Interestingly, acute treatments with 3 μM N-(methylsulfonyl)-2-(2-propynyloxy)-benzenehexanamide, an epoxygenase inhibitor, which minimizes endogenous production of EET, resulted in an increased reactivity to U-46619. Furthermore, we demonstrated that chronic treatments with trans-4-[4-(3-adamantan-1-yl-ureido)-cyclohexyloxy]-benzoic acid (t-AUCB), a sEH inhibitor, reduced human bronchi reactivity to U-46619. During our tension measurements, we also observed that human bronchi generated small-amplitude contractions; these spontaneous activities were reduced upon acute 14,15-EET treatments in the presence of t-AUCB. Altogether, these data demonstrate that endogenous and exogenous 14,15-EET could interfere with the activation of TP-receptors as well as with spontaneous oscillations in human airway smooth muscle tissues.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acid; Benzoates; Blotting, Western; Bronchi; Cells, Cultured; Eicosapentaenoic Acid; Electrophoresis, Polyacrylamide Gel; Epoxide Hydrolases; Epoxy Compounds; Fluorescent Antibody Technique; Guinea Pigs; Humans; Mice; Muscle Tonus; Muscle, Smooth; Myocytes, Smooth Muscle; Rats; Receptors, Prostaglandin E; Receptors, Thromboxane; Signal Transduction; Thromboxane A2; Urea

One of the prominent features of Alzheimer's disease is the excessive accumulation of the protein amyloid beta (Aβ) in certain areas of the brain leading to neurodegeneration. Aβ is cytotoxic and disrupts several cytoprotective pathways. Recent literature has demonstrated that certain cytochrome P450 (CYP) products are neuroprotective, including epoxide metabolites of arachidonic acid (AA), epoxyeicosatrienoic acids (EETs). The action of Aβ with respect to regionally produced EETs in the brain has yet to be defined. Epoxygenases metabolize AA into four regioisomers of EETs (14,15-, 11,12-, 8,9- and 5,6-EET). EETs are rapidly degraded into dihydroxyeicosatrienoic acids (DiHETEs) by soluble epoxide hydrolase (sEH). To determine the effect of Aβ on the epoxygenase activity in different regions of the brain, microsomes were prepared from the cerebrum and cerebellum of adult Sprague-Dawley rats and incubated with 1 and 10 μM Aβ for 30 min after which epoxygenase activity assay was performed. Mass spectrometry indicated that incubation with Aβ reduced 14,15-EET production by 30% as compared to vehicle in the cerebrum, but not in the cerebellum. When we separated the cerebrum into cortex and hippocampus, significant decrease in the production of total EETs and DiHETEs were seen in presence of Aβ (81% and 74%) in the cortex. Moreover, 11,12-EET production was decreased to ∼70% of vehicle in both cortex and hippocampus. Epoxygenase activity in the cultured astrocytes and neurons also showed reduction in total EET and DiHETE production (to 80% and ∼70% of vehicle respectively) in presence of Aβ. Altogether, our data suggest that Aβ reduces epoxygenase activity differentially in a region-specific and cell-specific manner. The reduction of cytoprotective EETs by Aβ in the cerebrum may make it more prone to degeneration than the cerebellum. Further understanding of these interactions will improve our ability to protect against the pathology of Alzheimer's disease.

Topics: 8,11,14-Eicosatrienoic Acid; Alzheimer Disease; Amyloid beta-Peptides; Animals; Animals, Newborn; Brain; Cytochrome P-450 CYP2J2; Cytochrome P-450 Enzyme Inhibitors; Cytochrome P-450 Enzyme System; Disease Models, Animal; Male; Neuroprotective Agents; Primary Cell Culture; Rats; Rats, Sprague-Dawley

P-450-dependent epoxygenase pathway of arachidonic acid and the products of epoxyeicosatrienoic acids (EETs) have been demonstrated to be involved in angiogenesis and tumor progression. This study examined the expression of EETs and the role of the pathway in the angiogenesis of multiple myeloma (MM). MM cell lines of U266 and RPMI8226 were cultured, and the EETs levels (11, 12-EET and 14, 15-EET) in the supernatant were determined by ELISA. Human umbilical vein endothelial cells (HUVECs) were cultured and used for analysis of the angiogenesis activity of the two MM cell lines, which was examined both in vitro and in vivo by employing MTT, chemotaxis, tube formation and matrigel plug assays. 11, 12-EET and 14, 15-EET were found in the supernatant of the cultured MM cells. The levels of the two EETs in the supernatant of U266 cells were significantly higher than those in the RPMI8226 cell supernatant (P<0.05), and the levels paralleled the respective angiogenesis activity of the two different MM cell lines. 17-octadecynoic acid (17-ODYA), as a specific inhibitor of P450 enzyme, suppressed HUVECs proliferation and tube formation induced by MM cells. Furthermore, 17-ODYA decreased the EET levels in the supernatant of MM cells. These results suggest that EETs may play an important role in the angiogenesis of MM, and the inhibitor 17-ODYA suppresses this effect.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acids; Bone Marrow Neoplasms; Cell Line; Cell Line, Tumor; Cytochrome P-450 CYP2J2; Cytochrome P-450 Enzyme System; Endothelial Cells; Fatty Acids, Unsaturated; Humans; Mice; Mice, Inbred C57BL; Multiple Myeloma; Neovascularization, Pathologic

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.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Cell Survival; Cells, Cultured; Disease Models, Animal; Epoxide Hydrolases; Janus Kinases; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Mutation; Myocardial Reperfusion Injury; Myocytes, Cardiac; Polymorphism, Single Nucleotide; Signal Transduction; STAT3 Transcription Factor

This study sought to assess putative pathways involved in the anti-inflammatory effects of 17,18-epoxyeicosatetraenoic acid (17,18-EpETE), as measured by a decrease in the contractile reactivity and Ca(2+) sensitivity of TNF-α-pretreated human bronchi. Tension measurements performed in the presence of 12-(3-adamantan-1-yl-ureido)-dodecanoic acid (AUDA), a soluble epoxide hydrolase (sEH)-specific inhibitor, demonstrated that 17,18-EpETE reduced the reactivity of TNF-α-pretreated tissues. The overexpression of sEH detected in patients with asthma and TNF-α-treated bronchi contributed to the maintenance of hyperresponsiveness in our models, which involved intracellular proinflammatory cascades. The inhibition of peroxisome proliferator-activated receptor (PPAR)γ by GW9662 abolished 17,18-EpETE + AUDA-mediated anti-inflammatory effects by inducing IκBα degradation and cytokine synthesis, indicating that PPARγ is a molecular target of epoxy-eicosanoids. Western blot analysis revealed that 17,18-EpETE pretreatment reversed the phosphorylation of p38 mitogen-activated protein kinase (p38-MAPK) induced by TNF-α in human bronchi. The Ca(2+) sensitivity of human bronchial explants was also quantified on β-escin permeabilized preparations. The presence of SB203580, a p38-MAPK inhibitor, reversed the effect induced by epoxy-eicosanoid in the presence of AUDA on TNF-α-triggered Ca(2+) hypersensitivity by increasing the phosphorylation level of PKC Potentiated Inhibitor Protein-17 (CPI-17) regulatory protein. Moreover, PPARγ ligands, such as rosiglitazone and 17,18-EpETE, decreased the expression of CPI-17, both at the mRNA and protein levels, whereas this effect was countered by GW9662 treatment in TNF-α-treated bronchi. These results demonstrate that 17,18-EpETE is a potent regulator of human lung inflammation and concomitant hyperresponsiveness, and may represent a valuable asset against critical inflammatory bronchial disorder.

Topics: 8,11,14-Eicosatrienoic Acid; Anti-Inflammatory Agents; Arachidonic Acids; Bronchi; Calcium; Cyclooxygenase 2; Epoxide Hydrolases; Humans; Intracellular Signaling Peptides and Proteins; Lung; Models, Biological; Muscle Proteins; Myosin-Light-Chain Phosphatase; p38 Mitogen-Activated Protein Kinases; Phosphoprotein Phosphatases; Phosphorylation; Pneumonia; PPAR gamma; Protein Kinase Inhibitors; Solubility; Tumor Necrosis Factor-alpha

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.

Topics: 8,11,14-Eicosatrienoic Acid; Arachidonic Acid; Cloning, Molecular; Cytochrome P-450 Enzyme System; DNA Transposable Elements; Escherichia coli; Ferredoxin-NADP Reductase; Ferredoxins; Gene Expression; Mixed Function Oxygenases; Mutagenesis, Insertional; NADP; Streptomyces coelicolor; Substrate Specificity

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.

Topics: 8,11,14-Eicosatrienoic Acid; Acute Disease; Animals; Anticholesteremic Agents; Cell Line; Disease Models, Animal; Female; Humans; Hypercholesterolemia; Inflammation; Inflammation Mediators; Lipoxins; Lovastatin; Male; Mice; Neutrophils; Pneumonia; Respiratory Mucosa

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.. 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.. 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.. 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.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Capillary Permeability; Cell Adhesion Molecules; Endothelium, Vascular; In Vitro Techniques; Lung; Lung Injury; Rats; Reperfusion Injury; TRPV Cation Channels; Vascular Cell Adhesion Molecule-1

We previously demonstrated that several epoxyeicosatrienoic acids (EETs) produce reductions in myocardial infarct size in rats and dogs. Since a recent study demonstrated the release of opioids in mediating the antinociceptive effect of 14,15-EET, we hypothesized that endogenous opioids may also be involved in mediating the cardioprotective effect of the EETs. To test this hypothesis, we used an in vivo rat model of infarction and a rat Langendorff model. In the infarct model, hearts were subjected to 30 min occlusion of the left coronary artery and 2 h reperfusion. Animals were treated with 11,12-EET or 14,15-EET (2.5 mg/kg) alone 15 min before occlusion or with opioid antagonists [naloxone, naltrindole, nor-binaltorphimine (nor-BNI), and d-Phe-Cys-Tyr-d-Trp-Om-Thr-Pen-Thr-NH(2) (CTOP), a nonselective, a selective delta, a selective kappa, and a selective mu receptor antagonist, respectively] 10 min before EET administration. In four separate groups, antiserum to Met- and Leu-enkephalin and dynorphin-A-(1-17) was administered 50 min before the 11,12-EET administration. Infarct size expressed as a percent of the area at risk (IS/AAR) was 63.5 + or - 1.2, 45.3 + or - 1.0, and 40.9 + or - 1.2% for control, 11,12-EET, and 14,15-EET, respectively. The protective effects of 11,12-EET were abolished by pretreatment with either naloxone (60.5 + or - 1.8%), naltrindole (60.8 + or - 1.0%), nor-BNI (62.3 + or - 2.8%), or Met-enkephalin antiserum (63.2 + or - 1.7%) but not CTOP (42.0 + or - 3.0%). In isolated heart experiments, 11,12-EET was administered to the perfusate 15 min before 20 min global ischemia followed by 45 min reperfusion in control hearts or in those pretreated with pertussis toxin (48 h). 11,12-EET increased the recovery of left ventricular developed pressure from 33 + or - 1 to 45 + or - 6% (P < 0.05) and reduced IS/AAR from 37 + or - 4 to 20 + or - 3% (P < 0.05). Both pertussis toxin and naloxone abolished these beneficial effects of 11,12-EET. Taken together, these results suggest that the major cardioprotective effects of the EETs depend on activation of a G(i/o) protein-coupled delta- and/or kappa-opioid receptor.

Topics: 8,11,14-Eicosatrienoic Acid; Analgesics, Opioid; Animals; Disease Models, Animal; GTP-Binding Protein alpha Subunits, Gi-Go; Male; Myocardial Infarction; Myocardial Reperfusion Injury; Naloxone; Naltrexone; Narcotic Antagonists; Rats; Rats, Sprague-Dawley; Receptors, Opioid; Somatostatin

Epoxyeicosatrienoic acids (EETs) induce vasorelaxation, probably through G protein-coupled receptors. The identity of these receptors is unclear, but it has been reported that EETs may bind to peroxisome proliferator activated receptors (PPARs) and E-prostanoid (EP) receptors. Therefore, we studied whether PPARs or EP receptors were involved in 14,15-EET-induced vasorelaxation. Isometric tensions of rat mesenteric arteries were measured. The vasorelaxant effect of 14,15-EET was inhibited by NF449 (G(s)-protein inhibitor), Rp-cAMP (cAMP antagonist) and KT5720 (PKA inhibitor), suggesting that the effect of 14,15-EET was mediated through G(s) protein-coupled receptors which were linked to the cAMP/PKA-dependent pathway. Pretreatments with MK886 (PPAR(alpha) antagonist) and GW9662 (PPAR(gamma) antagonist) did not influence 14,15-EET-induced vasorelaxation. The vasorelaxant effect of 14,15-EET was inhibited by AH6809 (EP(2) receptor antagonist), whereas SC19220 (EP(1) receptor antagonist), L798106 (EP(3) receptor antagonist) and GW627368X (EP(4) receptor antagonist) had no effect. The effect of 14,15-EET and the mechanism involved was mimicked by prostaglandin E(2) (an EP(2) receptor agonist). The 14,15-EET-induced relaxation was slightly potentiated in the presence of indomethacin (cyclooxygenase inhibitor which block PGE(2) synthesis). Binding study showed that the amount of 14,15-EET bound to the cell membrane of rat mesenteric arterial smooth muscle cells was much higher than that bound to the nuclear membrane. The binding of 14,15-EET to the cell membrane was attenuated by AH6809 and siRNA against EP(2) receptors. In conclusion, our study has demonstrated that 14,15-EET exerts relaxant effects on rat mesenteric arteries, at least partly via the stimulation of EP(2) receptors. This subsequently leads to activation of cAMP/PKA-dependent pathway in vascular smooth muscle cells.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Mesenteric Arteries; Muscle, Smooth, Vascular; Rats; Rats, Sprague-Dawley; Receptors, Prostaglandin E, EP2 Subtype; Vasodilation; Vasodilator Agents

To determine in vivo if L-4F differentially alters plasma levels of oxidized fatty acids resulting in more anti-inflammatory HDL. Injecting L-4F into apoE null mice resulted in a significant reduction in plasma levels of 15-HETE, 5-HETE, 13-HODE and 9-HODE. In contrast, plasma levels of 20-HETE were not reduced and plasma levels of 14,15-EET, which are derived from the cytochrome P450 pathway, were elevated after injection of L-4F. Injection of 13(S)-HPODE into wild-type C57BL/6J mice caused an increase in plasma levels of 13-HODE and 9-HODE and was accompanied by a significant loss in the anti-inflammatory properties of HDL. The response of atherosclerosis resistant C3H/HeJ mice to injection of 13(S)-HPODE was similar but much more blunted. Injection of L-4F at a site different from that at which the 13(S)-HPODE was injected resulted in significantly lower plasma levels of 13-HODE and 9-HODE and significantly less loss of HDL anti-inflammatory properties in both strains. i) L-4F differentially alters plasma levels of oxidized fatty acids in vivo. ii) The resistance of the C3H/HeJ strain to atherosclerosis may in part be mediated by a reduced reaction of this strain to these potent lipid oxidants.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Anti-Inflammatory Agents; Apolipoproteins E; Atherosclerosis; Chromatography, Liquid; Enzyme-Linked Immunosorbent Assay; Fatty Acids; Female; Hydroxyeicosatetraenoic Acids; Injections, Subcutaneous; Linoleic Acids; Linoleic Acids, Conjugated; Lipid Peroxides; Lipoproteins, HDL; Mice; Mice, Inbred C3H; Mice, Inbred C57BL; Mice, Knockout; Oxidation-Reduction; Peptides; Species Specificity; Tandem Mass Spectrometry; Time Factors; Up-Regulation

Epoxy- and dihydroxy-eicosatrienoic acids (EETs and DHETs) are vasoactive cytochrome P450 metabolites of arachidonic acid. Interestingly, however, the mechanism(s) by which EETs/DHETs mediate smooth muscle relaxation remains unclear. In contrast to previous reports, where dilation was purportedly large-conductance Ca(2+)-activated K(+) (BK(Ca)) and/or transient receptor potential cation channel, subfamily V, member 4 (TRPV4) channel-mediated, 14,15-EET-induced vasodilation [reversal of contractile tone established with the thromboxane receptor (TP) agonist 15-hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic acid (U-46619)] was unaltered in BK(Ca) and TRPV4 knockout mouse isolated aortae compared with wild-type controls, indicating a significant BK(Ca)/TRPV4-resistant mechanism. Whereas all EET and DHET regioisomers reversed U-46619 contraction in rat aortae and mouse mesenteric resistance arteries, these eicosanoids failed to alter phenylephrine-induced contraction, suggesting that they mediated dilation via a "TP-selective" mechanism. Competitive TP antagonism was also observed in nonvascular tissue, including rat fundus and tertiary bronchus, indicating that the effect is not specific to blood vessels. Such effects were TP-selective because 14,15-EET failed to inhibit "non-TP" prostanoid receptor-mediated function in multiple cell/tissue-based assays (K(b) > 10 microM). In accordance, 14,15-EET inhibited specific [(3)H]7-(3-((2-((phenylamino)carbonyl)hydrazino)-methyl)-7-oxabicyclo(2.2.1)hept-2-yl)-5-heptenoic acid (SQ-29548) binding to human recombinant TP receptor, with a K(i) value of 3.2 microM, and it showed weaker affinity for non-TP prostanoid receptors, including DP, FP, EP(1-4), and IP receptors (K(i) values of 6.1, 5.3, 42.6, 19.7, 13.2, 20.2, and >25 microM, respectively) and no appreciable affinity (K(i) values >10 microM) for a diverse array of pharmacologically distinct receptors, including the leukotriene receptors Cys-LT(1/2) and BLT(1). As such, EETs/DHETs represent a unique class of "endogenous" G protein-coupled receptor competitive antagonists, inducing vasodilation via direct TP inhibition. Thus, EETs/DHETs represent novel autoregulatory agents, directly modulating the actions of cyclooxygenase-derived eicosanoids following arachidonic acid mobilization.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; 8,11,14-Eicosatrienoic Acid; Animals; Aorta, Thoracic; Arachidonic Acids; Guinea Pigs; Hydroxyeicosatetraenoic Acids; Male; Mice; Mice, Knockout; Rats; Rats, Sprague-Dawley; Receptors, Thromboxane; Splanchnic Circulation; Trachea; TRPV Cation Channels; Vascular Resistance; Vasoconstriction; Vasodilation

All-cis-14,15-epoxyeicosa-5,8,11-trienoic acid (14,15-EET) is a labile, vasodilatory eicosanoid generated from arachidonic acid by cytochrome P450 epoxygenases. A series of robust, partially saturated analogues containing epoxide bioisosteres were synthesized and evaluated for relaxation of precontracted bovine coronary artery rings and for in vitro inhibition of soluble epoxide hydrolase (sEH). Depending upon the bioisostere and its position along the carbon chain, varying levels of vascular relaxation and/or sEH inhibition were observed. For example, oxamide 16 and N-iPr-amide 20 were comparable (ED(50) 1.7 microM) to 14,15-EET as vasorelaxants but were approximately 10-35 times less potent as sEH inhibitors (IC(50) 59 and 19 microM, respectively); unsubstituted urea 12 showed useful activity in both assays (ED(50) 3.5 microM, IC(50) 16 nM). These data reveal differential structural parameters for the two pharmacophores that could assist the development of potent and specific in vivo drug candidates.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Cattle; Coronary Vessels; Epoxide Hydrolases; Epoxy Compounds; Humans; In Vitro Techniques; Isometric Contraction; Recombinant Proteins; Solubility; Stereoisomerism; Structure-Activity Relationship; Vasodilation; Vasodilator Agents

Epoxyeicosatrienoic acids (EETs) are endothelium-derived metabolites of arachidonic acid. They relax vascular smooth muscle by membrane hyperpolarization. These actions are inhibited by the EET antagonist, 14,15-epoxyeicosa-5(Z)-enoic acid (14,15-EE5ZE). We synthesized 20-(125)iodo-14,15-EE5ZE (20-(125)I-14,15-EE5ZE), a radiolabeled EET antagonist, and characterized its binding to cell membranes. 14,15-EET (10(-9)-10(-5)M) caused a concentration-related relaxation of the preconstricted bovine coronary artery and phosphorylation of p38 in U937 cells that were inhibited by 20-(125)I-14,15-EE5ZE. Specific 20-(125)I-14,15-EE5ZE binding to U937 cell membranes reached equilibrium within 5 min and remained unchanged for 30 min. The binding was saturable and reversible, and it exhibited K(D) and B(max) values of 1.11 +/- 0.13 nM and 1.13 +/- 0.04 pmol/mg protein, respectively. Guanosine 5'-O-(3-thio)triphosphate (10 muM) did not change the binding, indicating antagonist binding of the ligand. Various EETs and EET analogs (10(-10)-10(-5)M) competed for 20-(125)I-14,15-EE5ZE binding with an order of potency of 11,12-EET = 14,15-EET > 8,9-EET = 14,15-EE5ZE > 15-hydroxyeicosatetraenoic acid = 14,15-dihydroxyeicosatrienoic acid. 8,9-Dihydroxyeicosatrienoic acid and 11-hydroxyeicosatetraenoic acid did not compete for binding. The soluble and microsomal epoxide hydrolase inhibitors (1-cyclohexyl-3-dodecyl-urea, elaidamide, and 12-hydroxyl-elaidamide) and cytochrome P450 inhibitors (sulfaphenazole and proadifen) did not compete for the binding. However, two cytochrome P450 inhibitors, N-methylsulfonyl-6-(2-propargyloxyphenyl)hexanamide (MS-PPOH) and miconazole competed for binding with K(i) of 1558 and 315 nM, respectively. Miconazole and MS-PPOH, but not proadifen, inhibited 14,15-EET-induced relaxations. These findings define an EET antagonist's binding site and support the presence of an EET receptor. The inhibition of binding by some cytochrome P450 inhibitors suggests an alternative mechanism of action for these drugs and could lead to new drug candidates that target the EET binding sites.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Binding Sites; Blotting, Western; Cattle; Cell Membrane; Coronary Vessels; Cytochrome P-450 Enzyme Inhibitors; Dose-Response Relationship, Drug; Epoxide Hydrolases; Epoxy Compounds; Humans; Iodine Radioisotopes; Ligands; p38 Mitogen-Activated Protein Kinases; Phosphorylation; U937 Cells; Vasodilation

Members of the cytochrome P450 (P450) family of drug-metabolizing enzymes are present in the human brain, and they may have important roles in the oxidation of endogenous substrates. The polymorphic CYP2D6 is one of the major brain P450 isoforms and has been implicated in neurodegeneration, psychosis, schizophrenia, and personality traits. The objective of this study was to determine whether the endocannabinoid arachidonoylethanolamide (anandamide) is a substrate for CYP2D6. Anandamide is the endogenous ligand to the cannabinoid receptor CB1, which is also activated by the main psychoactive component in marijuana. Signaling via the CB1 receptor alters sensory and motor function, cognition, and emotion. Recombinant CYP2D6 converted anandamide to 20-hydroxyeicosatetraenoic acid ethanolamide and 5,6-, 8,9-, 11,12-, and 14,15-epoxyeicosatrienoic acid ethanolamides (EET-EAs) with low micromolar K(m) values. CYP2D6 further metabolized the epoxides of anandamide to form novel dioxygenated derivatives. Human brain microsomal and mitochondrial preparations metabolized anandamide to form hydroxylated and epoxygenated products, respectively. An inhibitory antibody against CYP2D6 significantly decreased the mitochondrial formation of the EET-EAs. To our knowledge, anandamide and its epoxides are the first eicosanoid-like molecules to be identified as CYP2D6 substrates. Our study suggests that anandamide may be a physiological substrate for brain mitochondrial CYP2D6, implicating this polymorphic enzyme as a potential component of the endocannabinoid system in the brain. This study also offers support to the hypothesis that neuropsychiatric phenotype differences among individuals with genetic variations in CYP2D6 could be ascribable to interactions of this enzyme with endogenous substrates.

Topics: 8,11,14-Eicosatrienoic Acid; Arachidonic Acid; Arachidonic Acids; Brain; Cytochrome P-450 CYP2D6; Endocannabinoids; Epoxy Compounds; Humans; Hydroxylation; Microsomes; Mitochondria; Polyunsaturated Alkamides; Time Factors

Under pathophysiologic conditions, the modulation of Ca2+ sensitivity and reactivity of bronchial smooth muscle is controlled by protein kinase C-dependent phosphorylation of the newly described protein, CPI-17. The goal of the present study was to assess the key role of this regulatory protein in airway hyperresponsiveness (AHR) using control and TNF-alpha-treated human bronchi as well as a specific siRNA duplex against human CPI-17 transcripts. Validity of a mixed transfection strategy was assessed using the reversible permeabilization method to introduce X-TremeGene (X-TG)-siRNA complexes in an overreactive model of human bronchi treated with TNF. Data demonstrate that X-TG-siRNA complexes targeted against CPI-17 transcripts resulted in a reduction in mRNA and specific protein expression in human bronchial tissues. This approach revealed that overall reactivity of bronchial smooth muscle to methacholine was reduced, while their relaxing responses to beta2-agonist were increased, when compared with responses triggered in control TNF-alpha-treated bronchi. Quantification analysis showed that Ca2+ -sensitivity in both untreated and TNF-alpha-treated bronchi were largely reduced upon transfection with human CPI-17 siRNA-X-TremeGene complexes, while Western blot analysis corroborated the decrease in CPI-17 and MLC phosphorylation levels in pretreated human bronchi. Identical results were obtained upon treatment with an antiinflammatory eicosanoid, 14,15-EET, known to inhibit CPI-17 phosphorylation. Together these results are consistent with a key molecular role for CPI-17 in AHR, in the absence of bronchial wall remodeling.

Topics: 8,11,14-Eicosatrienoic Acid; Bronchi; Calcium; Gene Silencing; Humans; Intracellular Signaling Peptides and Proteins; Muscle Proteins; Myosin-Light-Chain Phosphatase; Permeability; Phosphoprotein Phosphatases; Phosphorylation; Respiratory Hypersensitivity; RNA, Small Interfering; Tumor Necrosis Factor-alpha

The calcineurin inhibitors (CNIs) cyclosporine A (CsA) and tacrolimus (Tac) help prevent allograft rejection but are associated with nephrotoxicity. Cytochrome P450 2C8 (CYP2C8) and CYP2J2 are polymorphic enzymes expressed in the kidney that metabolize arachidonic acid (AA) to epoxyeicosatrienoic acids, promoting kidney homeostasis. This study examined the association between CNI-induced nephrotoxicity in liver transplant patients and CYP2C8 and CYP2J2 polymorphisms.. Liver transplantation patients receiving CNIs for at least 3 years were genotyped for CYP2C8*3, CYP2C8*4, CYP2C8 Haplotypes B and C, and CYP2J2*7 and evaluated for nephrotoxicity (serum creatinine > or = 1.6 mg/dl) 3-year post-transplantation. CYP2C8 proteins were also engineered in E. coli and their activity towards AA and inhibition by CNIs was investigated in vitro.. The risk of kidney disease post-transplantation was positively associated with CYP2C8*3 genotype. Odds ratios for all participants carrying at least one CYP2C8*3 allele were significant [odds ratio=2.38 (1.19-4.78)]. Stratification by CNI indicated a significant association between CYP2C8*3 and nephrotoxicity among patients receiving Tac but not CsA. The risk of renal dysfunction was not significantly influenced by CYP2C8*4, CYP2J2*7, or CYP2C8 haplotype B genotypes although inheritance of haplotype C seems to be protective. In vitro, the gene products of CYP2C8*3 and CYP2C8*4 were deficient in AA epoxidation, retaining 26 and 18% of wild-type activity, respectively. Circulating plasma concentrations of CsA and Tac inhibited CYP2C8 wild-type in vitro epoxidation of AA by 17 and 35%, respectively.. Inheritance of CYP2C8*3 is associated with a higher risk of developing renal toxicity in patients treated chronically with CNIs, and especially Tac, possibly by reducing formation of kidney protecting vasodilatory epoxyeicosatrienoic acids.

Topics: 8,11,14-Eicosatrienoic Acid; Arachidonic Acid; Aryl Hydrocarbon Hydroxylases; Calcineurin Inhibitors; Cyclosporine; Cytochrome P-450 CYP2C8; Cytochrome P-450 CYP2J2; Cytochrome P-450 Enzyme System; Demography; Female; Genetic Predisposition to Disease; Genotype; Humans; Incidence; Kidney Failure, Chronic; Kidney Function Tests; Kidney Transplantation; Kinetics; Male; Middle Aged; Tacrolimus; United States

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.

Topics: 8,11,14-Eicosatrienoic Acid; Adamantane; Animals; Disease Models, Animal; Enzyme Inhibitors; Epoxide Hydrolases; Female; Gene Deletion; Heart Ventricles; Injections, Intraperitoneal; Injections, Intravenous; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Myocardial Infarction; Myocardial Reperfusion Injury; Myocytes, Cardiac; Time Factors; Urea

Epoxyeicosatrienoic acids (EETs) are generated from arachidomic acid by cytochrome P450(CYP). Previous studies revealed very strong and selective expression of CYP expoxygenase in human cancer tissues, but almost none in adjacent normal tissues. This study was to investigate the promotive effect of EETs on proliferation of tumor cells and the possible mechanisms.. Four tumor cell lines, Tca-8113, A549, Ncl-H446 and HepG2, were treated with different concentrations of EETs (8,9-EET, 11,12-EET and 14,15-EET) for 12, 24, 48 and 72 h, respectively. Cell proliferation was measured using the MTT assay. The effect of exogenous EETs on cell cycle of Tca-8113 cells was assessed by flow cytometry. Signal transduction inhibitors of PI3K (LY294002), MAPKK (PD98059), MAPK (apigenin) and PKC (H7) were used to block EETs-induced cell proliferation. Expressions of the total protein and phosphorylated ERK1/2 and Akt were determined by Western blot.. EETs promoted proliferation of tumor cells compared with the control and vehicle group in a dose-and time-dependent manner (P<0.01). Incubation of tumor cells with EETs markedly increased the cell number at S/G2-M phase. The percentages of Tca-8113 cells at S and G2-M phases were (49.7+/-7.5%) vs. (17.2+/-9.7%) (P<0.01) and (21.0+/-5.3%) vs. (4.9+/-7.3%), respectively(P<0.01) with and without the treatment of 11,12-EET. EETs incubation significantly enhanced phosphorylation of MARK as well as PI3K/Akt in tumor cells. LY294002, PD98059, apigenine and H7 reduced the stimulative effect of EETs on cell proliferation.. EETs possess the promotive effect on proliferation of tumor cells via activation of MAPK and PI3K/Akt signal pathways.

Topics: 8,11,14-Eicosatrienoic Acid; Apigenin; Cell Cycle; Cell Line, Tumor; Cell Proliferation; Chromones; Dose-Response Relationship, Drug; Flavonoids; Humans; Mitogen-Activated Protein Kinase Kinases; Morpholines; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Phosphorylation; Proto-Oncogene Proteins c-akt; Signal Transduction

The aim of the present study was to investigate the anti-inflammatory effects of 14,15-epoxyeicosatrienoic acid (EET) on reactivity and Ca(2+) sensitivity in TNF-alpha-stimulated human bronchi. Tension measurements performed on either control, TNF-alpha-, or TNF-alpha + EET-pretreated bronchi revealed that 100 nM 14,15-EET pretreatments significantly reduced the reactivity of TNF-alpha-pretreated tissues to contractile agonists. EET also normalized the relaxing response to isoproterenol in TNF-alpha-treated bronchi. Pretreatment with 100 nM 14,15-EET prevented TNF-alpha-induced IkappaBalpha degradation, as demonstrated by an increase in IkappaBalpha protein levels on Western blot analysis. The anti-inflammatory properties of EET were mediated by the inhibition of IkappaBalpha degradation, suggesting a lower activation of NF-kappaB. The Ca(2+) sensitivity of TNF-alpha-stimulated bronchi was also evaluated on beta-escin-permeabilized preparations. Observed mean responses demonstrated that EET pretreatments abolished Ca(2+) hypersensitivity developed by TNF-alpha-stimulated bronchial explants. Moreover, 14,15-EET significantly reduced PDBu-induced Ca(2+) sensitivity in TNF-alpha-stimulated bronchi. Western blot and RT-PCR analyses revealed that CPI-17 protein and transcript levels were increased in TNF-alpha-treated bronchi, as opposed to being decreased in the presence of 14,15-EET. This eicosanoid also reduced U-46619-induced Ca(2+) sensitivity, which is related to the activation of Rho-kinase pathway. These results were also correlated with an increase in protein staining and transcription level of p116(Rip), a RhoA inhibitory-binding protein. Altogether, these data demonstrate that 14,15-EET is a potent modulator of the hyperreactivity triggered by TNF-alpha in human airway smooth muscle cells.

Topics: 8,11,14-Eicosatrienoic Acid; Anti-Inflammatory Agents; Base Sequence; Blotting, Western; Bronchi; Calcium; DNA Primers; Electrophoresis, Polyacrylamide Gel; Humans; Hydrolysis; In Vitro Techniques; NF-kappa B; Phorbol 12,13-Dibutyrate; Reverse Transcriptase Polymerase Chain Reaction; Tumor Necrosis Factor-alpha

Cytochrome P450-derived epoxyeicosatrienoic acids (EET) are biologically active metabolites of arachidonic acid that have potent effects on renal vascular reactivity and tubular ion transport and have been implicated in the control of blood pressure. EETs are hydrolyzed to their less active diols, dihydroxyeicosatrienoic acids (DHET), by the enzyme soluble epoxide hydrolase (sEH). 1,3-dicyclohexylurea (DCU), a potent sEH inhibitor, lowers systemic blood pressure in spontaneously hypertensive rats when dosed intraperitoneally. However, DCU has poor aqueous solubility, posing a challenge for in vivo oral delivery. To overcome this limitation, we formulated DCU in a nanosuspension using wet milling. Milling reduced particle size, increasing the total surface area by approximately 40-fold. In rats chronically infused with angiotensin II, the DCU nanosuspension administered orally twice daily for 4 days produced plasma exposures an order of magnitude greater than unmilled DCU and lowered blood pressure by nearly 30 mmHg. Consistent with the mechanism of sEH inhibition, DCU increased plasma 14,15-EET and decreased plasma 14,15-DHET levels. These data confirm the antihypertensive effect of sEH inhibition and demonstrate that greatly enhanced exposure of a low-solubility compound is achievable by oral delivery using a nanoparticle drug delivery system.

Topics: 8,11,14-Eicosatrienoic Acid; Administration, Oral; Animals; Blood Pressure; Chromatography, Liquid; Disease Models, Animal; Epoxide Hydrolases; Hypertension; Male; Nanoparticles; Particle Size; Rats; Rats, Sprague-Dawley; Solubility; Suspensions; Tandem Mass Spectrometry; Urea

Cytochrome P450 (CYP) epoxygenase-derived epoxyeicosatrienoic acids (EETs) elicit cell proliferation and promote angiogenesis. The aim of this study was to determine the expression of CYP epoxygenases in the bovine retina and the potential role of EETs in hypoxia-induced angiogenesis in bovine retinal endothelial cells.. Bovine retinal endothelial cells were cultured under normoxic (21% O(2)) or hypoxic (1% O(2)) conditions, and CYP2C expression was determined by Western blot analysis. The effect of hypoxia on EET levels was determined by LC-MS/MS. Cell migration (Transwell filter assays) and endothelial cell tube formation (on basement membrane matrix) were assessed in vitro in the absence and presence of pharmacologic inhibitors and CYP2C antisense oligonucleotides.. Bovine retinal endothelial cells expressed CYP2C protein in culture and generated detectable levels of EETs under basal conditions. Hypoxia (6-48 hours) enhanced CYP2C protein expression (2-fold) and EET formation (1.5-fold). Moreover, endothelial cells preexposed to hypoxia demonstrated an increase in serum-induced cell migration that was sensitive to the CYP2C inhibitors sulfaphenazole and MS-PPOH and the EET antagonist 14,15-epoxyeicosa-5(Z)-enoic acid. Furthermore, preventing the hypoxia-induced expression of CYP2C (antisense oligonucleotides) suppressed hypoxia-induced cell migration. In an in vitro angiogenesis model, the preexposure of endothelial cells to hypoxia increased CYP2C expression and enhanced endothelial tube formation, which was blocked by the EET antagonist and by the CYP2C antisense oligonucleotides.. Taken together, these data indicate that CYP2C-derived EETs are implicated in angiogenesis by retinal endothelial cells, especially under hypoxic conditions.

Topics: 8,11,14-Eicosatrienoic Acid; Amides; Animals; Blotting, Western; Cattle; Cell Culture Techniques; Cell Hypoxia; Cell Movement; Chromatography, High Pressure Liquid; Cytochrome P-450 Enzyme Inhibitors; Cytochrome P-450 Enzyme System; Eicosanoids; Endothelium, Vascular; Enzyme Inhibitors; Fluorescent Antibody Technique, Indirect; Mass Spectrometry; Neovascularization, Physiologic; Oligonucleotides, Antisense; Retinal Vessels; Sulfaphenazole

To understand the molecular mechanisms underlying 14,15-epoxyeicosatrienoic acid (14,15-EET)-induced angiogenesis, here we have studied the role of signal transducer and activator of transcription-3 (STAT-3). 14,15-EET stimulated the tyrosine phosphorylation of STAT-3 and its translocation from the cytoplasm to the nucleus in human dermal microvascular endothelial cells (HDMVECs). Adenovirus-mediated delivery of dominant negative STAT-3 substantially inhibited 14,15-EET-induced HDMVEC migration, and tube formation and Matrigel plug angiogenesis. 14,15-EET activated Src, as measured by its tyrosine phosphorylation and blockade of its activation by adenovirus-mediated expression of its dominant negative mutant, significantly attenuated 14,15-EET-induced STAT-3 phosphorylation in HDMVECs and the migration and tube formation of these cells and Matrigel plug angiogenesis. 14,15-EET induced the expression of vascular endothelial cell growth factor (VEGF) in a time- and Src-STAT-3-dependent manner in HDMVECs. Transfac analysis of VEGF promoter revealed the presence of STAT-binding elements and 14,15-EET induced STAT-3 binding to this promoter in vivo, and this interaction was inhibited by suppression of Src-STAT-3 signaling. Neutralizing anti-VEGF antibodies completely blocked 14,15-EET-induced HDMVEC migration and tube formation and Matrigel plug angiogenesis. These results reveal that Src-dependent STAT-3-mediated VEGF expression is a major mechanism of 14,15-EET-induced angiogenesis.

Topics: 8,11,14-Eicosatrienoic Acid; Aorta; Cell Movement; Cells, Cultured; Collagen; Drug Combinations; Endothelial Cells; Gene Expression; Humans; Laminin; Myocytes, Smooth Muscle; Neovascularization, Physiologic; Phosphorylation; Proteoglycans; Signal Transduction; src-Family Kinases; STAT3 Transcription Factor; Vascular Endothelial Growth Factor A

Previously, we demonstrated (17) that 11,12- and 14,15-epoxyeicosatrienoic acids (EETs) produce marked reductions in myocardial infarct size. Although it is assumed that this cardioprotective effect of the EETs is due to a specific interaction with a membrane-bound receptor, no evidence has indicated that novel EET antagonists selectively block the EET actions in dogs. Our goals were to investigate the effects of 11,12- and 14,15-EET, the soluble epoxide hydrolase inhibitor, 12-(3-adamantan-1-yl-ureido)-dodecanoic acid (AUDA), and the putative selective EET antagonist, 14,15-epoxyeicosa-5(Z)-enoic acid (14,15-EEZE), on infarct size of barbital anesthetized dogs subjected to 60 min of coronary artery occlusion and 3 h of reperfusion. Furthermore, the effect of 14,15-EEZE on the cardioprotective actions of the selective mitochondrial ATP-sensitive potassium channel opener diazoxide was investigated. Both 11,12- and 14,15-EET markedly reduced infarct size [expressed as a percentage of the area at risk (IS/AAR)] from 21.8 +/- 1.6% (vehicle) to 8.7 +/- 2.2 and 9.4 +/- 1.3%, respectively. Similarly, AUDA significantly reduced IS/AAR from 21.8 +/- 1.6 to 14.4 +/- 1.2% (low dose) and 9.4 +/- 1.8% (high dose), respectively. Interestingly, the combination of the low dose of AUDA with 14,15-EET reduced IS/AAR to 5.8 +/- 1.6% (P < 0.05), further than either drug alone. Diazoxide also reduced IS/AAR significantly (10.2 +/- 1.9%). In contrast, 14,15-EEZE had no effect on IS/AAR by itself (21.0 +/- 3.6%), but completely abolished the effect of 11,12-EET (17.8 +/- 1.4%) and 14,15-EET (19.2 +/- 2.4%) and AUDA (19.3 +/- 1.6%), but not that of diazoxide (10.4 +/- 1.4%). These results suggest that activation of the EET pathway, acting on a putative receptor, by exogenous EETs or indirectly by blocking EET metabolism, produced marked cardioprotection, and the combination of these two approaches resulted in a synergistic effect. These data also suggest that 14,15-EEZE is not blocking the mitochondrial ATP-sensitive potassium channel as a mechanism for antagonizing the cardioprotective effects of the EETs.

Topics: 8,11,14-Eicosatrienoic Acid; Adamantane; Animals; Blood Pressure; Cardiovascular Agents; Coronary Circulation; Diazoxide; Disease Models, Animal; Dogs; Dose-Response Relationship, Drug; Enzyme Inhibitors; Epoxide Hydrolases; Female; Heart Rate; Lauric Acids; Male; Mitochondria, Heart; Myocardial Infarction; Myocardium; Potassium Channels

Cytochrome P450 genes catalyze formation of epoxyeicosatrienoic acids (EETs) from arachidonic acid. The effects of 5,6-EET, 8,9-EET, 11,12-EET, and 14,15-EET microinjected into the ventrolateral periaqueductal gray (vlPAG) on the thermally produced tail-flick response were studied in male Sprague-Dawley rats. 14,15-EET microinjected into vlPAG (3-156 pmol) dose-dependently inhibited the tail-flick response (ED50 = 32.5 pmol). In contrast, 5,6-EET, 8,9-EET, and 11,12-EET at a dose of 156 pmol were not active when injected into the vlPAG. 14,15-EET failed to displace the radiobinding of [3H][D-Ala2,NHPe4, Gly-ol5]enkephalin (mu-opioid receptor ligand) or [3H]naltrindole (delta-opioid receptor ligand) in crude membrane fractions of rat brain. Tail-flick inhibition produced by 14,15-EET from vlPAG was blocked by intra-vlPAG pretreatment with antiserum against beta-endorphin or Met-enkephalin or the mu-opioid receptor antagonist D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH2 (CTOP) or the delta-opioid receptor antagonist naltrindole but not with dynorphin A[1-17] antiserum or the kappa-opioid receptor antagonist nor-binaltorphimine. In addition, tail-flick inhibition produced by 14,15-EET treatment was blocked by intrathecal pretreatment with Met-enkephalin antiserum, naltrindole, or CTOP but not with beta-endorphin antiserum. It is concluded that 1) 14,15-EET itself does not have any affinity for mu- or delta-opioid receptors and 2) 14,15-EET activates beta-endorphin and Met-enkephalin, which subsequently act on mu- and delta-opioid receptors to produce antinociception.

Topics: 8,11,14-Eicosatrienoic Acid; Analgesics; Animals; beta-Endorphin; Dose-Response Relationship, Drug; Enkephalin, Methionine; Male; Microinjections; Pain Measurement; Periaqueductal Gray; Rats; Rats, Sprague-Dawley; Reaction Time

Endothelial nitric oxide synthase (eNOS) is a key enzyme in NO-mediated cardiovascular homeostasis and its activity is modulated by a variety of hormonal and mechanical stimuli via phosphorylation modification. Our previous study has demonstrated that epoxyeicosatrienoic acids (EETs), the cytochrome P450 (CYP)-dependent metabolites of arachidonic acid, could robustly up-regulate eNOS expression. However, the molecular mechanism underlying the effects of EETs on eNOS remains elusive. Particularly, whether and how EETs affect eNOS phosphorylation is unknown. In the present study, we investigated the effects of EETs on eNOS phosphorylation with cultured bovine aortic endothelial cells (BAECs). BAECs were either treated with exogenous EETs or infected with recombinant adeno-associated virus (rAAV) carrying CYP2C11-CYPOR, CYP102 F87V mutant and CYP2J2, respectively, to increase endogenous EETs. Both addition of EETs and CYP epoxygenase transfection markedly increased eNOS phosphorylation at its Ser1179 and Thr497 residues. Inhibition of phosphatidylinositol 3-kinase (PI3K) with LY294002 prevented EETs-induced increases of eNOS-Ser(P)1179 but had no effect on the phosphorylation status of Thr497. However, inhibitors of protein kinase B (Akt), mitogen-activated protein kinase (MAPK) and MAPK kinase could block phosphorylation of eNOS at both sites. Inhibition of these kinases also attenuated the up-regulation of eNOS expression by EETs. Finally, administration of viral CYP epoxygenases expression vectors into rats enhanced eNOS phosphorylation and function in vivo. Thus, in addition to up-regulating eNOS expression, EETs also augment eNOS function by enhancing eNOS phosphorylation. EETs-induced up-regulation of eNOS phosphorylation and expression appears to involve in both PI3K/Akt and MAPK pathways.

Topics: 8,11,14-Eicosatrienoic Acid; Amino Acid Sequence; Animals; Aorta, Thoracic; Apigenin; Cattle; Cells, Cultured; Chromones; Cytochrome P-450 CYP2J2; Cytochrome P-450 Enzyme System; Epoxy Compounds; Flavonoids; Inositol; Male; MAP Kinase Signaling System; Morpholines; Nitric Oxide Synthase Type III; Oxygenases; Phosphoinositide-3 Kinase Inhibitors; Phosphorylation; Phosphothreonine; Proto-Oncogene Proteins c-akt; Rats; Serine

Cytochrome P450 (CYP) epoxygenases and their arachidonic acid (AA) metabolites, the epoxyeicosatrienoic acids (EETs), have been shown to produce reductions in infarct size in canine myocardium following ischemia-reperfusion injury via opening of either the sarcolemmal K(ATP) (sarcK(ATP)) or mitochondrial K(ATP) (mitoK(ATP)) channel. In the present study, we subjected intact rat hearts to 30 min of left coronary artery occlusion and 2 h of reperfusion followed by tetrazolium staining to determine infarct size as a percent of the area at risk (IS/AAR, %). The results demonstrate that the two major regioisomers of the CYP epoxygenase pathway, 11,12-EET (2.5 mg/kg, iv) and 14,15-EET (2.5 mg/kg, iv) significantly reduced myocardial infarct size (IS/AAR, %) in rats as compared with control (41.9+/-2.3%, 40.9+/-1.2% versus 61.5+/-1.6%, respectively), whereas, a third regioisomer, 8,9-EET (2.5 mg/kg, iv) had no effect (55.2+/-1.4). The protective effect of pretreatment with 11,12- and 14,15-EETs was completely abolished (61.9+/-0.7%, 58.6+/-3.1%, HMR; 63.3+/-1.2%, 63.2+/-2.5%, 5-HD) in the presence of the selective sarcK(ATP) channel antagonist, HMR 1098 (6 mg/kg, iv) or the selective mitoK(ATP) channel antagonist, 5-HD (10 mg/kg, iv) given 10 min after 11,12- or 14,15-EET administration but 5 min prior to index ischemia. Furthermore, concomitant pretreatment with 11,12- or 14,15-EET in combination with the free radical scavenger, 2-mercaptopropionyl glycine (2-MPG), at a dose (20 mg/kg, iv) that had no effect on IS/AAR (57.7+/-1.3%), completely abolished the cardioprotective effect of 11,12- and 14,15-EETs (58.2+/-1.6%, 61.4+/-1.0%), respectively. These data suggest that part of the cardioprotective effects of EETs in rat hearts against infarction is the result of an initial burst of reactive oxygen species (ROS) and subsequent activation of both the sarcK(ATP) and mitoK(ATP) channel.

Topics: 8,11,14-Eicosatrienoic Acid; Adenosine Triphosphate; Animals; Male; Myocardial Infarction; Potassium Channels; Rats; Rats, Sprague-Dawley; Regional Blood Flow; Tiopronin

The aim of the present study was to provide a mechanistic insight into how 14,15-epoxyeicosatrienoic acid (EET) relaxes organ-cultured human bronchi. Tension measurements, performed on either fresh or 3-d-cultured bronchi, revealed that the contractile responses to 1 microM methacholine and 10 microM arachidonic acid were largely relaxed by the eicosanoid regioisomer in a concentration-dependent manner (0.01-10 microM). Pretreatments with 14,15-epoxyeicosa-5(Z)-enoic acid, a specific 14,15-EET antagonist, prevented the relaxing effect, whereas iberitoxin pretreatments (10 nM) partially abolished EET-induced relaxations. In contrast, pretreatments with 1 microM indomethacin amplified relaxations in explants and membrane hyperpolarizations triggered by 14,15-EET on airway smooth muscle cells. The relaxing responses induced by 14,15-EET were likely related to reduced Ca2+ sensitivity of the myofilaments, because free Ca2+ concentration-response curves performed on beta-escin-permeabilized cultured explants were shifted toward higher [Ca2+] (lower pCa2+ values). 14,15-EET also abolished the tonic responses induced by phorbol-ester-dybutyrate (PDBu) (a protein kinase C [PKC]-sensitizing agent), on both fresh (intact) and beta-escin-permeabilized explants. Western blot analyses, using two specific primary antibodies against CPI-17 and its PKC-dependent phosphorylated isoform (p-CPI-17), confirmed that the eicosanoid interferes with this intracellular process. These data indicate that 14,15-EET hyperpolarizes airway smooth muscle cells and relaxes precontracted human bronchi while reducing Ca2+ sensitivity of fresh and cultured explants. The intracellular effects are related to a PKC-dependent process involving a lower phosphorylation level of CPI-17.

Topics: 8,11,14-Eicosatrienoic Acid; Amides; Bronchi; Calcium; Humans; In Vitro Techniques; Intracellular Signaling Peptides and Proteins; Ion Channel Gating; Membrane Potentials; Muscle Proteins; Muscle Relaxation; Muscle Tonus; Myocytes, Smooth Muscle; Phorbol Esters; Phosphoprotein Phosphatases; Phosphorylation; Potassium; Potassium Channels, Calcium-Activated

Arachidonic acid is an essential constituent of cell membranes that is esterified to the sn-2 position of glycerophospholipids and is released from selected phospholipid pools by tightly regulated phospholipase cleavage. Metabolism of the released arachidonic acid by the cytochrome P450 enzyme system (cP450) generates biologically active compounds, including epoxyeicosatrienoic acids (EETs) and hydroxyeicosatetraenoic acids. Here we report that 2-(14,15-epoxyeicosatrienoyl)glycerol (2-14,15-EG), a novel cP450 arachidonate metabolite produced in the kidney, is a potent mitogen for renal proximal tubule cells. This effect is mediated by activation of tumor necrosis factor alpha-converting enzyme (ADAM17), which cleaves membrane-bound transforming growth factor alpha (proTGF-alpha) and releases soluble TGF-alpha as a ligand that binds and activates epidermal growth factor receptor (EGFR). The present studies additionally demonstrate that the structurally related 14,15-EET stimulates release of soluble heparin-binding EGF-like growth factor as an EGFR ligand by activation of ADAM9, another member of the ADAM family. Thus, in addition to the characterization of 2-14,15-EG's mitogenic activity and signaling mechanism, our study provides the first example that two structurally related biologically active lipid mediators can activate different metalloproteinases and release different EGFR ligands in the same cell type to activate EGFR and stimulate cell proliferation.

Topics: 8,11,14-Eicosatrienoic Acid; ADAM Proteins; ADAM17 Protein; Animals; Arachidonic Acid; Cell Line; Cytochrome P-450 Enzyme System; Down-Regulation; Enzyme Activation; Epidermal Growth Factor; Epithelial Cells; ErbB Receptors; Extracellular Signal-Regulated MAP Kinases; Gene Expression Regulation, Enzymologic; Glycerol; Heparin-binding EGF-like Growth Factor; Intercellular Signaling Peptides and Proteins; Kidney Tubules, Proximal; Membrane Proteins; Mitogens; Models, Biological; Monoglycerides; Receptors, Cannabinoid; RNA, Small Interfering; Signal Transduction; Swine; Transforming Growth Factor alpha

Epoxyeicosatrienoic acids (EETs) are cytochrome P450 epoxygenase metabolites of arachidonic acid. EETs mediate numerous biological functions. In coronary arteries, they regulate vascular tone by the activation of smooth muscle large-conductance, calcium-activated potassium (BK(Ca)) channels to cause hyperpolarization and relaxation. We developed a series of 14,15-EET agonists, 14,15-EET-phenyliodosulfonamide (14,15-EET-PISA), 14,15-EET-biotinsulfonamide (14,15-EET-BSA), and 14,15-EET-benzoyldihydrocinnamide-sulfonamide (14,15-EET-BZDC-SA) as tools to characterize 14,15-EET metabolism and binding. Agonist activities of these analogs were characterized in precontraced bovine coronary arterial rings. All three analogs induced concentration-dependent relaxation and were equipotent with 14,15-EET. Relaxations to these analogs were inhibited by the BK(Ca) channel blocker iberiotoxin (100 nM), the 14,15-EET antagonist 14,15-epoxyeicosa-5(Z)-enoylmethylsulfonamide (10 muM), and abolished by 20 mM extracellular K(+). 14,15-EET-PISA is metabolized to 14,15-dihydroxyeicosatrienoyl-PISA by soluble epoxide hydrolase in bovine coronary arteries and U937 cells but not U937 cell membrane fractions. 14,15-EET-P(125)ISA binding to human U937 cell membranes was time-dependent, concentration-dependent, and saturable. The specific binding reached equilibrium by 15 min at 4 degrees C and remained unchanged up to 30 min. The estimated K(d) and B(max) were 148.3 +/- 36.4 nM and 3.3 +/- 0.5 pmol/mg protein, respectively. These data suggest that 14,15-EET-PISA, 14,15-EET-BSA, and 14,15-EET-BZDC-SA are full 14,15-EET agonists. 14,15-EET-P(125)ISA is a new radiolabeled tool to study EET metabolism and binding. Our results also provide preliminary evidence that EETs exert their biological effect through a membrane binding site/receptor.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; 8,11,14-Eicosatrienoic Acid; Animals; Binding, Competitive; Cattle; Cell Membrane; Coronary Vessels; Humans; In Vitro Techniques; Large-Conductance Calcium-Activated Potassium Channels; Ligands; Molecular Structure; Peptides; Subcellular Fractions; Sulfonamides; U937 Cells; Vasodilation; Vasodilator Agents

Single nucleotide polymorphisms (SNPs) in the human EPHX2 gene have recently been implicated in susceptibility to cardiovascular disease, including stroke. EPHX2 encodes for soluble epoxide hydrolase (sEH), an important enzyme in the metabolic breakdown of arachidonic acid-derived eicosanoids referred to as epoxyeicosatrienoic acids (EETs). We previously demonstrated that EETs are protective against ischemic cell death in culture. Therefore, we tested the hypothesis that polymorphisms in the human EPHX2 gene alter sEH enzyme activity and affect neuronal survival after ischemic injury in vitro. Human EPHX2 mutants were recreated by site-directed mutagenesis and fused downstream of TAT protein transduction domain. Western blot analysis and immunocytochemistry staining revealed high-transduction efficiency of human TAT-sEH variants in rat primary cultured cortical neurons, associated with increased metabolism of 14,15-EET to corresponding 14,15-dihydroxyeicosatrienoic acid. A human variant of sEH with Arg103Cys amino acid substitution, previously demonstrated to increase sEH enzymatic activity, was associated with increased cell death induced in cortical neurons by oxygen-glucose deprivation (OGD) and reoxygenation. In contrast, the Arg287Gln mutation was associated with reduced sEH activity and protection from OGD-induced neuronal cell death. We conclude that sequence variations in the human EPHX2 gene alter susceptibility to ischemic injury and neuronal survival in a manner linked to changes in the hydrolase activity of the enzyme. The findings suggest that human EPHX2 mutations may in part explain the genetic variability in sensitivity to ischemic brain injury and stroke outcome.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Brain Ischemia; Cell Death; Cell Survival; Cells, Cultured; Cerebral Cortex; Epoxide Hydrolases; Female; Gene Expression Regulation, Enzymologic; Humans; Neurons; Polymorphism, Genetic; Pregnancy; Rats; Rats, Sprague-Dawley; Solubility; Stroke; Transduction, Genetic; Vasodilator Agents

Epoxyeicosatrienoic acids (EETs), lipid mediators synthesized from arachidonic acid by cytochrome P-450 epoxygenases, are converted by soluble epoxide hydrolase (SEH) to the corresponding dihydroxyeicosatrienoic acids (DHETs). Originally considered as inactive degradation products of EETs, DHETs have biological activity in some systems. Here we examined the capacity of EETs and DHETs to activate peroxisome proliferator-activated receptor-alpha (PPARalpha). We find that among the EET and DHET regioisomers, 14,15-DHET is the most potent PPARalpha activator in a COS-7 cell expression system. Incubation with 10 microM 14,15-DHET produced a 12-fold increase in PPARalpha-mediated luciferase activity, an increase similar to that produced by the PPARalpha agonist Wy-14643 (20 microM). Although 10 microM 14,15-EET produced a threefold increase in luciferase activity, this was abrogated by the SEH inhibitor dicyclohexylurea. 14-Hexyloxytetradec-5(Z)-enoic acid, a 14,15-EET analog that cannot be converted to a DHET, did not activate PPARalpha. However, PPARalpha was activated by 2-(14,15-epoxyeicosatrienoyl)glycerol, which was hydrolyzed and the released 14,15-EET converted to 14,15-DHET. COS-7 cells incorporated 14,15-[3H]DHET from the medium, and the cells also retained a small amount of the DHET formed during incubation with 14,15-[3H]EET. Binding studies indicated that 14,15-[3H]DHET binds to the ligand binding domain of PPARalpha with a Kd of 1.4 microM. Furthermore, 14,15-DHET increased the expression of carnitine palmitoyltransferase 1A, a PPARalpha-responsive gene, in transfected HepG2 cells. These findings suggest that 14,15-DHET, produced from 14,15-EET by the action of SEH, may function as an endogenous activator of PPARalpha.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acids; Carnitine O-Palmitoyltransferase; Cell Line, Tumor; Chlorocebus aethiops; COS Cells; Epoxide Hydrolases; Epoxy Compounds; Humans; PPAR alpha; Urea

Epoxyeicosatrienoic acids (EETs) are endothelium-derived cytochrome P-450 (CYP) metabolites of arachidonic acid that relax vascular smooth muscle by large-conductance calcium-activated potassium (BK(Ca)) channel activation and membrane hyperpolarization. We hypothesized that if smooth muscle cells (SMCs) had the capacity to synthesize EETs, endogenous EET production would increase BK(Ca) channel activity. Bovine coronary SMCs were transduced with adenovirus coding the CYP Bacillus megaterium -3 (F87V) (CYP BM-3) epoxygenase that metabolizes arachidonic acid exclusively to 14(S),15(R)-EET. Adenovirus containing the cytomegalovirus promoter-Escherichia coli beta-galactosidase was used as a control. With the use of an anti-CYP BM-3 (F87V) antibody, a 124-kDa immunoreactive protein was detected only in CYP BM-3-transduced cells. Protein expression increased with increasing amounts of virus. When CYP BM-3-transduced cells were incubated with [14C]arachidonic acid, HPLC analysis detected 14,15-dihydroxyeicosatrienoic acid (14,15-DHET) and 14,15-EET. The identity of 14,15-EET and 14,15-DHET was confirmed by mass spectrometry. In CYP BM-3-transduced cells, methacholine (10(-5) M) increased 14,15-EET release twofold and BK(Ca) channel activity fourfold in cell-attached patches. Methacholine-induced increases in BK(Ca) channel activity were blocked by the CYP inhibitor 17-octadecynoic acid (10(-5) M). 14(S),15(R)-EET was more potent than 14(R),15(S)-EET in relaxing bovine coronary arteries and activating BK(Ca) channels. Thus CYP BM-3 adenoviral transduction confers SMCs with epoxygenase activity. These cells acquire the capacity to respond to the vasodilator agonist by synthesizing 14(S),15(R)-EET from endogenous arachidonic acid to activate BK(Ca) channels. These studies indicate that 14(S),15(R)-EET is a sufficient endogenous activator of BK(Ca) channels in coronary SMCs.

Topics: 8,11,14-Eicosatrienoic Acid; Adenoviridae; Animals; Bacillus megaterium; beta-Galactosidase; Cattle; Coronary Vessels; Cytochrome P-450 CYP2J2; Cytochrome P-450 Enzyme System; Cytomegalovirus; Methacholine Chloride; Muscle Tonus; Muscle, Smooth, Vascular; Oxygenases; Potassium Channels; Stereoisomerism; Transduction, Genetic

To determine the efficacy of cytochrome P450 2C9 metabolites of arachidonic acid, viz. 5,6-, 8,9-, 11,12-, and 14,15-epoxyeicosatrienoic acids (EETs), in inducing angiogenesis, we have studied their effects on human dermal microvascular endothelial cell (HDMVEC) tube formation and migration. All four EETs stimulated HDMVEC tube formation and migration in a dose-dependent manner. Because 14,15-EET was found to be slightly more efficacious than 5,6-, 8,9-, and 11,12-EETs in stimulating HDMVEC tube formation and migration, we next focused on elucidation of the signaling mechanisms underlying its angiogenic activity. 14,15-EET stimulated Akt and S6K1 phosphorylation in Src- and phosphatidylinositol 3-kinase (PI3K)-dependent manner in HDMVECs. Inhibition of Src and PI3K-Akt-mTOR signaling by both pharmacological and dominant-negative mutant approaches suppressed 14,15-EET-induced HDMVEC tube formation and migration in vitro and Matrigel plug angiogenesis in vivo. In addition, 14,15-EET induced the expression of fibroblast growth factor-2 (FGF-2) in Src- and PI3K-Akt-dependent and mTOR-independent manner in HDMVECs. Neutralizing anti-FGF-2 antibodies completely suppressed 14,15-EET-induced HDMVEC tube formation and migration in vitro and Matrigel plug angiogenesis in vivo. Together, these results show for the first time that Src and PI3K-Akt signaling via targeting in parallel with FGF-2 expression and mTOR-S6K1 activation plays an indispensable role in 14,15-EET-induced angiogenesis.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Cell Movement; Cells, Cultured; Collagen; Dose-Response Relationship, Drug; Drug Combinations; Endothelium, Vascular; Fibroblast Growth Factor 2; Genetic Vectors; Green Fluorescent Proteins; Humans; Laminin; Mice; Mice, Inbred C57BL; Microcirculation; Neovascularization, Pathologic; Oxygen; Phosphatidylinositol 3-Kinases; Phosphorylation; Protein Kinases; Proteoglycans; Proto-Oncogene Proteins c-akt; Ribosomal Protein S6 Kinases, 70-kDa; RNA, Messenger; Signal Transduction; TOR Serine-Threonine Kinases

An HPLC method for the chiral analysis of the four regioisomeric epoxyeicosatrienoic acids (EETs) is described. The cytochrome P450 arachidonic acid epoxygenase metabolites are resolved, without the need for derivatization, by chiral-phase HPLC on a Chiralcel OJ column. Application of this methodology to the analysis of the liver endogenous EETs demonstrates stereospecific biosynthesis and corroborates the role of cytochrome P450 as the endogenous arachidonic acid epoxygenase.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Chromatography, High Pressure Liquid; Cytochrome P-450 CYP2J2; Cytochrome P-450 Enzyme System; Liver; Male; Microsomes, Liver; Oxygenases; Rats; Rats, Sprague-Dawley; Stereoisomerism; Vasodilator Agents

Recently, we reported that 11,12-epoxyeicosatrienoic acid (11,12-EET) potently activates rat mesenteric arterial ATP-sensitive K(+) (K(ATP)) channels and produces significant vasodilation through protein kinase A-dependent mechanisms. In this study, we tried to further delineate the signaling steps involved in the activation of vascular K(ATP) channels by EETs. Whole cell patch-clamp recordings [0.1 mM ATP in the pipette, holding potential (HP) = 0 mV and testing potential (TP) = -100 mV] in freshly isolated rat mesenteric smooth muscle cells showed small glibenclamide-sensitive K(ATP) currents (19.0 +/- 7.9 pA, n = 5) that increased 6.9-fold on exposure to 5 microM 14,15-EET (132.0 +/- 29.0 pA, n = 7, P < 0.05 vs. control). With 1 mM ATP in the pipette solution, K(ATP) currents (HP = 0 mV and TP = -100 mV) were increased 3.5-fold on exposure to 1 microM 14,15-EET (57.5 +/- 14.3 pA, n = 9, P < 0.05 vs. baseline). In the presence of 100 nM iberiotoxin, 1 microM 14,15-EET hyperpolarized the membrane potential from -20.5 +/- 0.9 mV at baseline to -27.1 +/- 3.0 mV (n = 6 for both, P < 0.05 vs. baseline), and the EET effects were significantly reversed by 10 microM glibenclamide (-21.8 +/- 1.4 mV, n = 6, P < 0.05 vs. EET). Incubation with 5 microM 14,15-epoxyeicosa-5(Z)-enoic acid (14,15-EEZE), a 14,15-EET antagonist, abolished the 14,15-EET effects (31.0 +/- 11.8 pA, n = 5, P < 0.05 vs. 14,15-EET, P = not significant vs. control). The 14,15-EET effects were inhibited by inclusion of anti-G(s)alpha antibody (1:500 dilution) but not by control IgG in the pipette solution. The effects of 14,15-EET were mimicked by cholera toxin (100 ng/ml), an exogenous ADP-ribosyltransferase. Treatment with the ADP-ribosyltransferase inhibitors 3-aminobenzamide (1 mM) or m-iodobenzylguanidine (100 microM) abrogated the effects of 14,15-EET on K(ATP) currents. These results were corroborated by vasodilation studies. 14,15-EET dose-dependently dilated isolated small mesenteric arteries, and this was significantly attenuated by treatment with 14,15-EEZE or 3-aminobenzamide. These results suggest that 14,15-EET activates vascular K(ATP) channels through ADP-ribosylation of G(s)alpha.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Cells, Cultured; Ion Channel Gating; Male; Mesenteric Arteries; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Potassium Channels; Rats; Rats, Sprague-Dawley; Vasodilation; Vasodilator Agents

11,12-Epoxyeicosatrienoic acid (11,12-EET), a potent vasodilator produced by the endothelium, acts on calcium-activated potassium channels and shares biological activities with the heme oxygenase/carbon monoxide (HO/CO) system. We examined whether activation of HO mediates the dilator action of 11,12-EET, and that of the other EETs, on rat mesenteric arteries. Dose-response curves (10(-9) to 10(-6) M) to 5,6-EET, 8,9-EET, 11,12-EET, 14,15-EET, and ACh (10(-9) to 10(-4) M) were evaluated in preconstricted (10(-6) mol/l phenylephrine) mesenteric arteries (<350 microm diameter) in the presence or absence of 1) the cyclooxygenase inhibitor indomethacin (2.8 microM), 2) the HO inhibitor chromium mesoporphyrin (CrMP) (15 microM), 3) the soluble guanylyl cyclase (GC) inhibitor ODQ (10 microM), and 4) the calcium-activated potassium channel inhibitor iberiotoxin (25 nM). The vasodilator response to 11,12-EET was abolished by CrMP and iberiotoxin, whereas indomethacin and ODQ had no effect. In contrast, the effect of ACh was attenuated by ODQ but not by CrMP. The vasodilator effect of 8,9-EET, like that of 11,12-EET, was greatly attenuated by HO inhibition. In contrast, the mesenteric vasodilator response to 5,6-EET was independent of both HO and GC, whereas that to 14,15-EET demonstrated two components, an HO and a GC, of equal magnitude. Incubation of mesenteric microvessels with 11,12-EET caused a 30% increase in CO release, an effect abolished by inhibition of HO. We conclude that the rat mesenteric vasodilator action of 11,12-EET is mediated via an increase in HO activity and an activation of calcium-activated potassium channels.

Topics: 8,11,14-Eicosatrienoic Acid; Acetylcholine; Animals; Carbon Monoxide; Dose-Response Relationship, Drug; Heme Oxygenase (Decyclizing); Male; Mesenteric Arteries; Mesoporphyrins; Organometallic Compounds; Oxadiazoles; Peptides; Potassium Channels, Calcium-Activated; Quinoxalines; Rats; Rats, Wistar; Vasodilation; Vasodilator Agents

Epoxyeicosatrienoic acids (EETs), the cytochrome P450 metabolites of arachidonic acid (AA), are potent and stereospecific activators of cardiac ATP-sensitive K(+)(K(ATP)) channels. EETs activate K(ATP) channels by reducing channel sensitivity to ATP. In this study, we determined the direct effects of EETs on the binding of ATP to K(ATP) channel protein. A fluorescent ATP analog, 2,4,6-trinitrophenyl (TNP)-ATP, which increases its fluorescence emission significantly upon binding with proteins, was used for binding studies with glutathione-S-transferase (GST) Kir6.2 fusion proteins. TNP-ATP bound to GST fusion protein containing the C-terminus of Kir6.2 (GST-Kir6.2C), but not to the N-terminus of Kir6.2, or to GST alone. 11,12-EET (5 muM) did not change TNP-ATP binding K(D) to GST-Kir6.2C, but B(max) was reduced by half. The effect of 11,12-EET was dose-dependent, and 8,9- and 14,15-EETs were as effective as 11,12-EET in inhibiting TNP-ATP binding to GST-Kir6.2C. AA and 11,12-dihydroxyeicosatrienoic acid (11,12-DHET), the parent compound and metabolite of 11,12-EET, respectively, were not effective inhibitors of TNP-ATP binding to GST-Kir6.2C, whereas the methyl ester of 11,12-EET was. These findings suggest that the epoxide group in EETs is important for modulation of ATP binding to Kir6.2. We conclude that EETs bind to the C-terminus of K(ATP) channels, inhibiting binding of ATP to the channel.

Topics: 8,11,14-Eicosatrienoic Acid; Adenosine Triphosphate; Animals; ATP-Binding Cassette Transporters; Cell Line; Glutathione Transferase; Humans; Ion Channel Gating; Mice; Potassium Channels, Inwardly Rectifying; Protein Binding; Receptors, Drug; Recombinant Fusion Proteins; Sulfonylurea Receptors

Epoxyeicosatrienoic acids (EETs), the cytochrome P-450 epoxygenase metabolites of arachidonic acid, are candidates of endothelium-derived hyperpolarizing factors. We have previously reported that EETs are potent activators of cardiac ATP-sensitive K(+) (K(ATP)) channels, but their effects on the vascular K(ATP) channels are unknown. With the use of whole cell patch-clamp techniques with 0.1 mM ATP in the pipette and holding at -60 mV, freshly isolated smooth muscle cells from rat mesenteric arteries had small glibenclamide-sensitive currents at baseline (13.1 +/- 3.9 pA, n = 5) that showed a 7.2-fold activation by 10 microM pinacidil (94.1 +/- 21.9 pA, n = 7, P < 0.05). 11,12-EET dose dependently activated the K(ATP) current with an apparent EC(50) of 87 nM. Activation of the K(ATP) channels by 500 nM 11,12-EET was inhibited by inclusion of the PKA inhibitor peptide (5 microM) but not by the inclusion of the PKC inhibitor peptide (100 microM) in the pipette solution. These results were corroborated by vasoreactivity studies. 11,12-EET produced dose-dependent vasorelaxation in isolated small mesenteric arteries, and this effect was reduced by 50% with glibenclamide (1 microM) preincubation. The 11,12-EET effects on vasorelaxation were also significantly attenuated by preincubation with cell-permeant PKA inhibitor myristoylated PKI(14-22), and, in the presence of PKA inhibitor, glibenclamide had no additional effects. These results suggest that 11,12-EET is a potent activator of the vascular K(ATP) channels, and its effects are dependent on PKA activities.

Topics: 8,11,14-Eicosatrienoic Acid; Adenosine Triphosphate; Animals; Cyclic AMP-Dependent Protein Kinases; In Vitro Techniques; Mesenteric Arteries; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Potassium Channels; Rats; Vasodilation; Vasodilator Agents

Acetylcholine stimulates the release of endothelium-derived arachidonic acid (AA) metabolites including prostacyclin and epoxyeicosatrienoic acids (EETs), which relax coronary arteries. However, mechanisms of endothelial cell (EC) AA activation remain undefined. We propose that 2-arachidonylglycerol (2-AG) plays an important role in this pathway. An AA metabolite isolated from bovine coronary ECs was identified as 2-AG by mass spectrometry. In ECs pretreated with the fatty acid amidohydrolase inhibitor diazomethylarachidonyl ketone (DAK; 20 micromol/l), methacholine (10 micromol/l)-stimulated 2-AG release was blocked by the phospholipase C inhibitor U-73122 (10 micromol/l) or the diacylglycerol lipase inhibitor RHC-80267 (40 micromol/l). In U-46619-preconstricted bovine coronary arterial rings, 2-AG relaxations averaging 100% at 10 micromol/l were inhibited by endothelium removal, by DAK, by the hydrolase inhibitor methyl arachidonylfluorophosphate (10 micromol/l), by the cyclooxygenase inhibitor indomethacin (10 micromol/l), but not by the CB1 cannabinoid receptor antagonist SR-141716 (1 micromol/l). The cytochrome P-450 inhibitor SKF-525a (10 micromol/l) and the 14,15-epoxyeicosa-5Z-enoic acid EET antagonist (14,15-EEZE; 10 micromol/l) further attenuated the indomethacin-resistant relaxations. The nonhydrolyzable 2-AG analogs noladin ether, 2-AG amide, and 14,15-EET glycerol amide did not induce relaxation. N-nitro-L-arginine-resistant relaxations to methacholine were also inhibited by U-73122, RHC-80267, and DAK. 14,15-EET glycerol ester increased opening of large-conductance K(+) channels 12-fold in cell-attached patches of isolated smooth muscle cells and induced relaxations averaging 95%. These results suggest that methacholine stimulates EC 2-AG production through phospholipase C and diacylglycerol lipase activation. 2-AG is further hydrolyzed to AA, which is metabolized to vasoactive eicosanoids. These studies reveal a role for 2-AG in EC AA release and the regulation of coronary tone.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acid; Arachidonic Acids; Carbon Radioisotopes; Cattle; Cells, Cultured; Coronary Vessels; Endocannabinoids; Endothelium, Vascular; Glycerides; Hydroxyeicosatetraenoic Acids; Vasodilation

Bradykinin causes arterial relaxation and hyperpolarization, which is mediated by a transferable endothelium-derived hyperpolarizing factor (EDHF). In coronary arteries, epoxyeicosatrienoic acids (EETs) are involved in the EDHF response. However, the role of EETs as transferable mediators of EDHF-dependent relaxation remains poorly defined. Two small bovine coronary arteries were cannulated and perfused in tandem in the presence of the nitric oxide synthase inhibitor, nitro-L-arginine (30 micromol/L), and the cyclooxygenase inhibitor, indomethacin (10 micromol/L). Luminal perfusate from donor arteries with intact endothelium perfused endothelium-denuded detector arteries. Detector arteries were constricted with U46619 and diameters were monitored. Bradykinin (10 nmol/L) added to detector arteries did not induce dilation (5+/-2%), whereas bradykinin addition to donor arteries dilated detector arteries by 26.5+/-7% (P<0.05). These dilations were blocked by donor artery endothelium removal and detector artery treatment with the EET-selective antagonist, 14,15-epoxyeicosa-5(Z)-monoenoic acid (14,15-EEZE; 10 micromol/L, -5+/-6%) but not 14,15-EEZE treatment of donor arteries (20+/-5%). 14,15-EET (0.1 to 10 micromol/L) added to detector arteries induced maximal dilations of 82+/-5% that were inhibited 50% by detector artery treatment with 14,15-EEZE (32+/-12%) but not donor artery treatment with 14,15-EEZE. Liquid chromatography-electrospray ionization mass spectrometry analysis verified the presence of 14,15-EET in the perfusate from an endothelium-intact but not denuded artery. These results show that bradykinin stimulates donor artery 14,15-EET release that dilates detector arteries. 14,15-EEZE blocked the donor artery, endothelium-dependent, bradykinin-induced relaxations, and attenuated relaxations to 14,15-EET. These results suggest that EETs are transferable EDHFs in coronary arteries.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Biological Assay; Bradykinin; Cattle; Coronary Vessels; Endothelium-Dependent Relaxing Factors; Endothelium, Vascular; In Vitro Techniques; Muscle, Smooth, Vascular; Vasodilation

Soluble epoxide hydrolase (sEH) plays a major role in regulating vascular epoxyeicosatrienoic acid metabolism and function, and substituted urea derivatives that inhibit sEH activity reduce blood pressure in hypertensive rats. We found that substituted urea derivatives containing a dodecanoic acid group, besides effectively inhibiting sEH, increased peroxisome proliferator-activated receptor (PPAR) alpha activity. In PPARalpha transfected COS-7 cells, treatment with 10 microM N-cyclohexyl-N'-dodecanoic acid urea (CUDA) or N-adamantanyl-N'-dodecanoic acid urea (AUDA) produced 6- and 3-fold increases, respectively, in PPARalpha activation. Neither CUDA nor AUDA activated PPARdelta or PPARgamma directly, indicating selectivity for PPARalpha. CUDA did not alter PPARalpha protein expression, and it competitively inhibited the binding of Wy-14643 (pirinixic acid) to the ligand binding domain of PPARalpha, suggesting that it functions as a PPARalpha ligand. CUDA and AUDA were metabolized to chain-shortened beta-oxidation products, a process that reduced their potency as sEH inhibitors and their ability to bind and activate PPARalpha. N,N'-Dicylclohexylurea and N-cyclohexyl-N'-dodecylurea, sEH inhibitors that do not contain a carboxylic acid group, did not activate PPARalpha. In HepG2 cells, CUDA increased the expression of the PPARalpha-responsive gene carnitine palmitoyltransferase 1A. We conclude that CUDA and AUDA, by virtue of their carboxylic acid substitution, activate PPARalpha in addition to potently inhibiting sEH. Further development of these compounds could lead to a class of agents with hypotensive and lipid-lowering properties that may be valuable for the prevention and treatment of cardiovascular disease.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Binding, Competitive; Biotransformation; Blotting, Western; Carnitine O-Palmitoyltransferase; Cell Movement; Chlorocebus aethiops; COS Cells; Cyclohexanes; Enzyme Inhibitors; Epoxide Hydrolases; Lauric Acids; Ligands; Mice; PPAR alpha; Pyrimidines; Reverse Transcriptase Polymerase Chain Reaction; RNA; Transfection; Urea

Cytochrome P450 (CYP) arachidonic acid epoxygenase 2J2 converts arachidonic acid to four regioisomeric epoxyeicosatrienoic acids, which exert diverse biological activities in cardiovascular system and endothelial cells. However, it is unknown whether this enzyme highly expresses and plays any role in cancer. In this study, we found that very strong and selective CYP2J2 expression was detected in human carcinoma tissues in 101 of 130 patients (77%) as well as eight human carcinoma cell lines but undetectable in adjacent normal tissues and nontumoric human cell lines by Western, reverse transcription-PCR, and immunohistochemical staining. In addition, forced overexpression of CYP2J2, and CYP BM3F87V or addition of epoxyeicosatrienoic acids (EET) in cultured carcinoma cell lines in vitro markedly accelerated proliferation by analyses of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, cell accounts, and cell cycle analysis, and protected carcinoma cells from apoptosis induced by tumor necrosis factor alpha (TNF-alpha) in cultures. In contrast, antisense 2J2 transfection or addition of epoxygenase inhibitors 17-ODYA inhibited proliferation and accelerated cell apoptosis induced by TNF-alpha. Examination of signaling pathways on the effects of CYP2J2 and EETs revealed activation of mitogen-activated protein kinases and PI3 kinase-AKT systems and elevation of epithelial growth factor receptor phosphorylation level. These results strongly suggest that CYP epoxygenase 2J2 plays a previously unknown role in promotion of the neoplastic cellular phenotype and in the pathogenesis of a variety of human cancers.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Biomarkers, Tumor; Carcinoma; Cell Growth Processes; Cell Line, Tumor; Cytochrome P-450 CYP2J2; Cytochrome P-450 Enzyme System; ErbB Receptors; Humans; MAP Kinase Signaling System; Mice; Mice, Inbred BALB C; Mice, Nude; Neoplasm Transplantation; Neoplasms; Oxygenases; Phosphatidylinositol 3-Kinases; Phosphorylation; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Transplantation, Heterologous

Shell-less culture of chick chorioallantoic membrane (CAM) of developing chicken embryos is a useful model to evaluate the effects of vascular agents. We assessed the response of CAM vessels to epoxyeicosatrienoic acids (EETs), derivatives of the essential fatty acid arachidonic acid, that have a number of important biological functions, including dilation of microvessels in the coronary, cerebral, renal, and mesenteric circulations. Three of four regioisomers of EETs, 14,15-, 11,12-, and 8,9-EET, induced a characteristic dose-dependent acute hyperemia within 4 min after application on 10-day-old CAMs. This response was marked in early stages of development (between days 8 and 10), but the frequency and intensity of the response were reduced after 11 days of development. Histological examination demonstrated that the hyperemia was not due to extravasation of erythrocytes. However, many capillaries were distended and contained densely packed erythrocytes as compared to uniformly arranged vessels and erythrocytes in untreated CAMs. Transmission electron microscopy showed the basal laminae surrounding capillaries remained intact, similar to those in vehicle-treated or untreated CAM tissue. The hyperemia was specific to EETs since we did not observe it to be induced by other vasodilators such as nitric oxide or prostacyclin. In conclusion, we report a novel vascular response to EETs using the CAM as an in vivo model. These lipids specifically distend a subset of capillaries in a dose- and development-dependent manner.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Capillaries; Chick Embryo; Chorioallantoic Membrane; Culture Techniques; Disease Models, Animal; Dose-Response Relationship, Drug; Hyperemia; Neovascularization, Physiologic; Nitric Oxide Donors; Time Factors; Vasodilator Agents; Vitelline Membrane

In chronic heart failure, the lung endothelial permeability response to angiotensin II or thapsigargin-induced store depletion is ablated, although the mechanisms are not understood.. To determine whether the ablated permeability response to store depletion during heart failure was due to impaired expression of store operated Ca2+ channels in lung endothelium.. Heart failure was induced by aortocaval fistula in rats. Permeability was measured in isolated lungs using the filtration coefficient and a low Ca2+/Ca2+ add-back strategy to identify the component of the permeability response dependent on Ca2+ entry.. In fistulas, right ventricular mass and left ventricular end diastolic pressure were increased and left ventricular shortening fraction decreased compared with shams. Thapsigargin-induced store depletion increased lung endothelial permeability in shams, but not in fistulas. Permeability increased in both groups after the Ca2+ ionophore A23187 or 14,15-epoxyeicosatrienoic acid, independent of store depletion. A diacylglycerol analog had no impact on permeability. Increased distance between the endoplasmic reticulum and the plasmalemmal membrane was ruled out as a mechanism for the loss of the permeability response to store depletion. Endothelial expression of the endoplasmic reticulum Ca2+ ATPase was not altered in fistulas compared with shams, whereas the store-operated canonical transient receptor potential channels 1, 3, and 4 were downregulated in extraalveolar vessel endothelium.. We conclude that the adaptive mechanism limiting store depletion-induced endothelial lung injury in the aortocaval model of heart failure involves downregulation of store-operated Ca2+ channels.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Calcimycin; Calcium Channels; Calcium-Transporting ATPases; Disease Models, Animal; Endothelium; Enzyme Inhibitors; Heart Failure; Ionophores; Lung; Permeability; Rats; Sarcoplasmic Reticulum Calcium-Transporting ATPases; Thapsigargin; Tissue Culture Techniques; Vasodilator Agents

Endothelial nitric oxide synthase (eNOS) is a key enzyme responsible for the regulation of vascular homeostasis. Many humor factors and mechanical forces can affect eNOS activity via phosphorylation modification but the mechanisms involved vary with stimuli applied. We have demonstrated that cytochrome P450 (CYP) epoxygenase-dependent metabolites of arachidonic acid, epoxyeicosatrienoic acids (EETs), can robustly up-regulate eNOS expression and its activity, however the relevant signaling pathways responsible for activity regulation are not well known. In this study, we explored the role of PI3 kinase (PI3K)/protein kinase B (Akt) signaling pathway in eNOS expression and its phosphorylation in response to EETs via direct addition of EETs into cultured bovine aorta endothelial cells (BAECs) and recombinant adeno-associated virus-mediated transfection of CYP epoxygenase genes CYPF87V and CYP2C11 to produce endogenous EETs followed by co-treatment with PI3K or Akt inhibitor. Results show that both exogenous and endogenous EETs could remarkably enhance eNOS expression and its phosphorylation at Ser1179 and Thr497 residues; PI3K inhibitor LY294002 could inhibit EETs-induced increase in eNOS-Ser(P)1179 but had no effect on the change of eNOS-Thr(P)497, while Akt inhibitor could attenuate the increase in phosphor-eNOS at both residues; both of the two inhibitors could block EETs-enhanced eNOS expression. These results lead to conclusions: (i) EETs-mediated regulation of eNOS activity may be related with the changes of phosphorylation level at eNOS-Ser1179 via P13K/Akt and eNOS-Thr497 via Akt; (ii) PI3K/Akt signaling pathway is involved in the up-regulation of eNOS expression by EETs.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Aryl Hydrocarbon Hydroxylases; Cattle; Cells, Cultured; Cytochrome P450 Family 2; Endothelial Cells; Endothelium, Vascular; Fatty Acids, Unsaturated; Nitric Oxide Synthase Type III; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Phosphorylation; Proto-Oncogene Proteins c-akt; Rats; Signal Transduction; Steroid 16-alpha-Hydroxylase; Up-Regulation

This study tested the hypothesis that epoxyeicosatrienoic acids (EETs) derived from arachidonic acid via P-450 epoxygenases are soluble factors linking depletion of endoplasmic reticulum Ca(2+) stores and store-dependent regulation of endothelial cell (EC) permeability in rat lung. EC permeability was measured via the capillary filtration coefficient (K(f,c)) in isolated, perfused rat lungs. 14,15-EET and 5,6-EET increased EC permeability, a response that was significantly different from that of 8,9-EET, 11,12-EET, and vehicle control. The permeability response to 14,15-EET was not significantly attenuated by the nonspecific Ca(2+) channel blocker Gd(3+) (P = 0.068). In lungs perfused with low [Ca(2+)], 14,15-EET tended to increase EC permeability, although a significant increase in K(f,c) was observed only following Ca(2+) add-back. As positive control, we showed that the 3.7-fold increase in K(f,c) evoked by thapsigargin (TG), a known activator of store depletion-induced Ca(2+) entry, was blocked by both Gd(3+) and low [Ca(2+)] buffer. Nonetheless, the permeability response to TG could not be blocked by the phospholipase A(2) inhibitors mepacrine or methyl arachidonyl fluorophosphonate or the P-450 epoxygenase inhibitors 17-octadecynoic acid or propargyloxyphenyl hexanoic acid. Similarly, combined pretreatment with ibuprofen and dicyclohexylurea to block EET metabolism had no effect on the permeability response to TG. We conclude that EETs have a heterogeneous impact on EC permeability. Despite a requirement for Ca(2+) entry with both TG and 14,15-EET, our data suggest that distinct signaling pathways or heterogeneity in EC responsiveness is responsible for the observed EC injury evoked by EETs and store depletion in the isolated rat lung.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Calcium; Capillary Permeability; Endothelium, Vascular; Lung; Male; Pulmonary Circulation; Rats; Rats, Inbred Strains; Vasodilator Agents

Epoxyeicosatrienoic acids (EETs) are potent vasodilators produced by endothelial cells. In many vessels, they are an endothelium-derived hyperpolarizing factor (EDHF). However, it is unknown whether they act as an EDHF on platelets and whether this has functional consequences.. Flow cytometric measurement of platelet membrane potential using the fluorescent dye DiBac4 showed a resting potential of -58+/-9 mV. Different EET regioisomers hyperpolarized platelets down to -69+/-2 mV, which was prevented by the non-specific potassium channel inhibitor charybdotoxin and by use of a blocker of calcium-activated potassium channels of large conductance (BK(Ca) channels), iberiotoxin. EETs inhibited platelet adhesion to endothelial cells under static and flow conditions. Exposure to EETs inhibited platelet P-selectin expression in response to ADP. Stable overexpression of cytochrome P450 2C9 in EA.hy926 cells (EA.hy2C9 cells) resulted in release of EETs and a factor that hyperpolarized platelets and inhibited their adhesion to endothelial cells. These effects were again inhibited by charybdotoxin and iberiotoxin.. EETs hyperpolarize platelets and inactivate them by inhibiting adhesion molecule expression and platelet adhesion to cultured endothelial cells in a membrane potential-dependent manner. They act as an EDHF on platelets and might be important mediators of the anti-adhesive properties of vascular endothelium.

Topics: 8,11,14-Eicosatrienoic Acid; Apamin; Aryl Hydrocarbon Hydroxylases; Biological Factors; Blood Platelets; Cells, Cultured; Charybdotoxin; Cytochrome P-450 CYP2C9; Endothelial Cells; Endothelium, Vascular; Humans; Hydroxyeicosatetraenoic Acids; Ion Channels; Membrane Potentials; Peptides; Platelet Adhesiveness; Platelet Aggregation; Potassium Channels; Recombinant Fusion Proteins; Transfection; Umbilical Veins

Arachidonic acid metabolites contribute to the regulation of vascular tone and therefore tissue blood flow. The vascular endothelium metabolizes arachidonic acid by cytochrome P450 epoxygenases to epoxyeicosatrienoic acids or EETs. The placement of the epoxide group can occur on any of the double bonds of arachidonic acid resulting in four EET regioisomers; 5,6-, 8,9-, 11,12- and 14,15-EET. In the vasculature, EETs are key components of cellular signaling cascades that culminate in the activation of smooth muscle potassium channels to induce membrane hyperpolarization and vascular relaxation. In some vasculatures such as bovine coronary arteries, EET regioisomers are equipotent in inducing relaxations, while in other arteries, a specific EET regioisomer induces relaxation while others do not. Therefore, the position of the double bonds and/or the epoxide group may alter vascular agonist activity. This observation suggests that small alterations in the chemical structure of EETs can significantly impact vascular activity. To explore this hypothesis, we synthesized a series of EET analogs and characterized their vasodilator agonist and antagonist activity in bovine coronary arteries. In this chapter, we first review the mechanisms of EET-dependent relaxations in bovine coronary arteries to familiarize the reader with the role of EETs in these arteries. The second component is a synopsis of the functional characterization of the 14,15-EET analogs and the resulting description of structural components required for vascular dilator activity. Lastly, we discussed the characterization of three 14,15-EET analogs with specific EET-antagonist activity and compared this to the activity of similar 11,12-EET analogs. These studies have revealed that specific structural components of the 14,15-EET molecule are critical for dilator activity and that alteration of these components influences agonist activity and may confer antagonist properties.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Cattle; Coronary Vessels; Dose-Response Relationship, Drug; In Vitro Techniques; Muscle, Smooth, Vascular; Structure-Activity Relationship; Vasodilation

We investigated the effects of soluble epoxide hydrolase (sEH) inhibition on epoxyeicosatrienoic acid (EET) metabolism in intact human blood vessels, including the human saphenous vein (HSV), coronary artery (HCA), and aorta (HA). When HSV segments were perfused with 2 micromol/l 14,15-[3H]EET for 4 h, >60% of radioactivity in the perfusion medium was converted to 14,15-dihydroxyeicosatrienoic acid (DHET). Similar results were obtained with endothelium-denuded vessels. 14,15-DHET was released from both the luminal and adventitial surfaces of the HSV. When HSVs were incubated with 14,15-[3H]EET under static (no flow) conditions, formation of 14,15-DHET was detected within 15 min and was inhibited by the selective sEH inhibitors N,N'-dicyclohexyl urea and N-cyclohexyl-N'-dodecanoic acid urea (CUDA). Similarly, CUDA inhibited the conversion of 11,12-[3H]EET to 11,12-DHET by the HSV. sEH inhibition enhanced the uptake of 14,15-[3H]EET and facilitated the formation of 10,11-epoxy-16:2, a beta-oxidation product. The HCA and HA converted 14,15-[3H]EET to DHET, and this also was inhibited by CUDA. These findings in intact human blood vessels indicate that conversion to DHET is the predominant pathway for 11,12- and 14,15-EET metabolism and that sEH inhibition can modulate EET metabolism in vascular tissue.

Topics: 8,11,14-Eicosatrienoic Acid; Cells, Cultured; Cyclohexanes; Endothelium, Vascular; Epoxide Hydrolases; Epoxy Compounds; Humans; Hydroxyeicosatetraenoic Acids; Lauric Acids; Lipid Metabolism; Muscle, Smooth, Vascular; Oxidation-Reduction; Saphenous Vein; Solubility; Tritium; Vasodilator Agents

Epoxyeicosatrienoic acids (EETs) are endothelium-derived eicosanoids that activate potassium channels, hyperpolarize the membrane, and cause relaxation. We tested 19 analogs of 14,15-EET on vascular tone to determine the structural features required for activity. 14,15-EET relaxed bovine coronary arterial rings in a concentration-related manner (ED(50) = 10(-6) M). Changing the carboxyl to an alcohol eliminated dilator activity, whereas 14,15-EET-methyl ester and 14,15-EET-methylsulfonimide retained full activity. Shortening the distance between the carboxyl and epoxy groups reduced the agonist potency and activity. Removal of all three double bonds decreased potency. An analog with a Delta8 double bond had full activity and potency. However, the analogs with only a Delta5 or Delta11 double bond had reduced potency. Conversion of the epoxy oxygen to a sulfur or nitrogen resulted in loss of activity. 14(S),15(R)-EET was more potent than 14(R),15(S)-EET, and 14,15-(cis)-EET was more potent than 14,15-(trans)-EET. These studies indicate that the structural features of 14,15-EET required for relaxation of the bovine coronary artery include a carbon-1 acidic group, a Delta8 double bond, and a 14(S),15(R)-(cis)-epoxy group.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arteries; Cattle; Coronary Vessels; In Vitro Techniques; Structure-Activity Relationship; Vasodilation; Vasodilator Agents

Angiogenesis is one of the most recent physiological functions attributed to products of cytochrome P-450 (CYP450) enymes. To test this at a molecular level in human cells, we used a cloned cDNA for the human endothelial enzyme CYP450 2C9 (CYP2C9) to study growth as well as differentiation of human microvascular endothelial cells from the lung (HMVEC-L). Using adenoviral vectors overexpressing mRNA for CYP2C9, we show that the presence of CYP2C9 doubles thymidine incorporation and stimulates proliferation of primary cultures of endothelial cells compared with Ad5-GFP (control) in 24 h. In addition, there is a significant increase of tube formation in Matrigel after infection of HMVEC-L with Ad5-2C9 than with Ad5-GFP. More interestingly, Ad5-2C9 expressing the antisense product of CYP2C9 (2C9AS) inhibited tube formation compared with both Ad5-GFP as well as the Ad5-2C9 constructs. Finally, we tested the most abundant arachidonic acid metabolite of CYP2C9, 14,15-epoxyeicosatrienoic acid, which induced angiogenesis in vivo when embedded in Matrigel plugs and implanted in adult rats. These data support an important role for CYP2C9 in promoting angiogenesis.

Topics: 8,11,14-Eicosatrienoic Acid; Adenoviridae; Animals; Aryl Hydrocarbon Hydroxylases; Cells, Cultured; Cytochrome P-450 CYP2C9; DNA; Endothelium, Vascular; Gene Transfer Techniques; Genetic Vectors; Humans; Microcirculation; Neovascularization, Physiologic; Pulmonary Circulation; Rats; Rats, Sprague-Dawley; Vasodilator Agents

Linoleoylamide is physiological constituent of neurons. The effects of this agent, also a sleep-inducing agent, on ion currents in pituitary GH(3) cells were investigated. Hyperpolarization-elicited K(+) currents in GH(3) cells bathed in a high-K(+), Ca(2+)-free solution were studied to determine the effects of linoleoylamide and other related compounds on the I(K(IR)) that was sensitive to inhibition by E-4031 and identified as an erg (ether-à-go-go-related-gene) current. Linoleoylamide suppressed the amplitude of I(K(IR)) in a concentration-dependent manner with an IC(50) value of 5 microM. Oleamide (20 microM) inhibited the amplitude of I(K(IR)), while neither arachidonic acid (20 microM) nor 14,15-epoxyeicosatrienoic acid (20 microM) had an effect on it. In GH(3) cells incubated with anandamide (20 microM) or arachidonic acid (20 microM), the linoleoylamide-induced inhibition of I(K(IR)) remained unaltered. In inside-out patches, arachidonic acid (20 microM) and 14,15-epoxyeicosatrienoic acid (20 microM) stimulated large-conductance Ca(2+)-activated K(+) channels; however, linoleoylamide (20 microM) had little or no effect on them. Under current-clamp mode, linoleoylamide (20 microM) increased the firing rate. In IMR-32 neuroblastoma cells, linoleoylamide also suppressed I(K(IR)). This study provides the evidence that linoleoylamide has a depressant effect on the erg current, and suggests that this effect may affect hormonal secretion.

Topics: 8,11,14-Eicosatrienoic Acid; alpha-Linolenic Acid; Amides; Animals; Arachidonic Acid; Arachidonic Acids; Calcium; Calcium Channels, L-Type; Dose-Response Relationship, Drug; Endocannabinoids; Humans; Hydantoins; Imidazoles; Imidazolidines; Infant, Newborn; Linoleic Acids; Membrane Potentials; Neuroblastoma; Patch-Clamp Techniques; Piperazines; Piperidines; Pituitary Neoplasms; Polyunsaturated Alkamides; Potassium Channels; Pyridines; Tumor Cells, Cultured

Three genes cloned from Fundulus heteroclitus (killifish) define a new P450 subfamily, CYP2P. Structurally, the CYP2Ps are related to fish CYP2Ns and mammalian CYP2Js. CYP2P transcripts are expressed predominantly in liver and intestine. CYP2P3 coexpressed with P450 oxidoreductase in a baculovirus system catalyzed benzphetamine-N-demethylation and arachidonic acid oxidation, forming 14,15-, 11,12-, and 8,9-epoxyeicosatrienoic acids and 19-hydroxyeicosatetraenoic acid. CYP2P3 regio- and enantioselectivities with arachidonic acid were remarkably similar to human CYP2J2 and rat CYP2J3. Epoxyeicosatrienoic acids and their corresponding hydration products, the dihydroxyeicosatrienoic acids, were detected in killifish liver and intestine, indicating metabolism of arachidonic acid by killifish P450s in vivo. Levels of these products in killifish intestine were higher than those in mammalian intestine. 12-O-Tetradecanoyl phorbol 13-acetate suppressed expression of CYP2P2 and CYP2P3 in killifish intestine; fasting itself suppressed expression of CYP2P2/3 but not CYP2P1. In rat intestine fasting similarly depressed the levels of CYP2J proteins. The CYP2Ps and the CYP2Js appear to be derived from a common ancestral gene, likely a fatty acid monooxygenase.

Topics: 8,11,14-Eicosatrienoic Acid; Amino Acid Sequence; Animals; Arachidonic Acid; Benzphetamine; Cloning, Molecular; Conserved Sequence; Cytochrome P-450 Enzyme System; Fasting; Fundulidae; Gene Expression Regulation, Enzymologic; Hydroxyeicosatetraenoic Acids; Male; Molecular Sequence Data; Multigene Family; Organ Specificity; Phylogeny; Rats; Rats, Inbred F344; RNA, Messenger; Sequence Alignment; Tetradecanoylphorbol Acetate; Vertebrates

Epoxyeicosatrienoic acids (EETs) are readily incorporated into phospholipids of smooth muscle cells (SMC) and endothelial cells (EC). Incorporation of EETs into intact porcine coronary arteries potentiates EC-dependent relaxation, but not vasorelaxation induced by agents that act solely on SMC. To explore the potential mechanisms responsible for this difference, porcine coronary artery SMC and EC preloaded with [3H]14,15-EET were treated with calcium ionophore A23187. Although the amount of EET incorporated into EC and SMC was similar, A23187 stimulated a five-fold increase in release of radioactivity from EC, but only a 21% increase in release from SMC. Thin layer chromatography (TLC) examination of cell lipids demonstrated that > 70% of the incorporated radioactivity was present in phosphatidylcholine (PC) in both SMC and BC. After treatment of EC PC with PLA2, TLC analysis indicated that approximately equal to 75% of radioactivity was present as free EET, and 25% of radioactivity was present as lyso-PC. Therefore, most of the 14,15-EET was esterified into the sn-2 position of PC in EC. However, in SMC, approximately equal to 70% of radioactivity was present as lyso-PC after PLA2 treatment, indicating that the EET was predominately esterified into the sn-1 position. In contrast, all of the 14,15-EET was esterified into the sn-2 position of PI in both EC and SMC. These results suggest that the preferential incorporation of 14,15-EET into the sn-1 position of PC in SMC may help to explain the greater retention of the compound in SMC, while incorporation into the sn-2 position of PC in EC may facilitate agonist-induced 14,15-EET release and potentiation of EC-dependent porcine coronary artery relaxation.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Calcimycin; Cells, Cultured; Coronary Vessels; Endothelium, Vascular; Esterification; Muscle, Smooth, Vascular; Phosphatidylcholines; Swine; Tritium; Vasodilator Agents

Acetylcholine-induced endothelium-dependent relaxation in the renal afferent arteriole has been ascribed to nitric oxide, but the role of endothelium-derived hyperpolarizing factors (EDHFs) and 14,15-epoxyeicosatrienoic acid (14,15-EET) are unclear.. Single afferent arterioles were dissected from kidney of normal rabbits and microperfused in vitro at 60 mm Hg. Vessels were preconstricted submaximally with norepinephrine (10(-8) mol/L). Relaxation was assessed following cumulative addition of ACh (10(-9) to 10(-4) mol/L) alone, or in the presence of indomethacin (to inhibit cyclooxygenase), Nw-nitro-L-arginine (L-NNA) (to inhibit nitric oxide synthase), methylene blue (to inhibit soluble guanylate cyclase), or a combination of L-NNA + methylene blue. To assess contributions by EDHF, studies were repeated with either apamin + charybdotoxin [to block Ca2+-activated K+ channels (KCa)] or with 40 mmol/L KCl. To asses the role of 14,15-EET, relaxations were evaluated in the presence of its competitive inhibitor 14,15-epoxyeicosa-5(Z)-enoic acid (14,15-EEZE).. Relaxation by acetylcholine was abolished following endothelial denudation. It was unaffected by indomethacin but was inhibited 54%+/- 5% (P < 0.001) by L-NNA, 57%+/- 5% by methylene blue, and 60%+/- 4% by the combination of L-NNA plus methylene blue. Relaxation was inhibited further by KCl (80%+/- 6%) or by apamin + charybdotoxin (96%+/- 2%). 14,15-EEZE, alone, inhibited acetylcholine-induced relaxation by 29%+/- 3%, and by 80%+/- 5% in the presence of L-NNA.. Acetylcholine-induced afferent arteriolar relaxation depends strongly on both nitric oxide, acting via soluble guanylate cyclase, and on an EDHF, likely 14,15-EET, acting via KCa.

Topics: 8,11,14-Eicosatrienoic Acid; Acetylcholine; Animals; Apamin; Arterioles; Biological Factors; Charybdotoxin; Endothelium, Vascular; Enzyme Inhibitors; Male; Nitric Oxide; Nitroarginine; Nitroprusside; Potassium Channels, Calcium-Activated; Rabbits; Renal Circulation; Vasodilation; Vasodilator Agents

Vascular complications during liver cirrhosis are often severe, particularly in the kidney. These complications are the result of complex and poorly understood interactions between the injured liver and other organs such as the lungs, heart, and kidney. The purpose of this study was to investigate the alterations to renal hemodynamics during cirrhosis, focusing on the actions of epoxyeicosatrienoic acids (EET), known to be potent regulators of renal hemodynamics. Cirrhosis was induced in rats by common bile duct ligation (CBDL), and they were compared with sham rats. Experiments were conducted 4 wk after either the sham or CBDL surgery. Vasoreactivity was assessed in isolated perfused kidneys. cPLA(2) expression and cytochrome P450 (CYP450) expression were measured using Western blot. cPLA(2) enzymatic activity was measured by radioenzymatic assay. EET production was measured using rpHPLC analysis. The major findings were that kidneys from CBDL rats had significantly greater acetylcholine-induced vasodilation that was partially blocked by nitric oxide (NO) and prostaglandin inhibition and fully blocked by the combined inhibition of NO, prostaglandins, and CYP450 metabolites. Expression and activity of cPLA(2) in CBDL kidneys was increased, providing arachidonic acid substrate to the CYP450 enzymes. Finally, expression and activity of CYP450 enzymes was elevated in CBDL kidneys, resulting in significantly greater production of the vasodilating 11,12-EET and 14,15-EET. While it is well documented that renal vasoconstriction leading to impaired renal function occurs during cirrhosis, our data clearly demonstrate that endogenous production of EET is increased in cirrhotic kidneys. This may be a homeostatic response to preserve renal perfusion.

Topics: 8,11,14-Eicosatrienoic Acid; Acetylcholine; Animals; Arachidonic Acid; Bile Ducts; Blotting, Western; Body Weight; Cell Division; Chromatography, High Pressure Liquid; Cytochrome P-450 Enzyme System; Dose-Response Relationship, Drug; Hemodynamics; Kidney; Liver Cirrhosis; Nitric Oxide; Perfusion; Phospholipases A; Protein Isoforms; Rats; Time Factors

The cytochrome P450 CYP2B19 is a keratinocyte-specific arachidonic acid epoxygenase expressed in the granular cell layer of mouse epidermis. In cultured keratinocytes, CYP2B19 mRNAs are up-regulated coordinately with those of profilaggrin, another granular cell-specific marker. We investigated effects of the CYP2B19 metabolites 11,12- and 14,15-epoxyeicosatrienoic acids (EETs) on keratinocyte transglutaminase activities and cornified cell envelope formation. Keratinocytes were differentiated in vitro in the presence of biotinylated cadaverine. Transglutaminases cross-linked this substrate into endogenous proteins in situ; an enzyme-linked immunosorbent assay was used to quantify the biotinylated proteins. Exogenously added or endogenously formed 14,15-EET increased transglutaminase cross-linking activities in cultured human and mouse epidermal keratinocytes in a modified in situ assay. Transglutaminase activities increased approximately 8-fold (p < or = 0.02 versus mock control) in human keratinocytes transduced with adenovirus particles expressing a 14S,15R-EET epoxygenase (P450 BM3v). The physiological transglutaminase substrate involucrin was preferentially biotinylated in situ, determined by immunoblotting and mass spectrometry. P450 BM3v-induced transglutaminase activation was associated with increased 14,15-EET formation (p = 0.002) and spontaneous cell cornification (p < or = 0.001). Preferential involucrin biotinylation and the increased cornified cell envelope formation provided evidence that transglutaminases mediated the P450 BM3v-induced cross-linking activities. These results support a physiological role for 14,15-EET epoxygenases in regulating epidermal cornification, and they have important implications for epidermal barrier functions in vivo.

Topics: 8,11,14-Eicosatrienoic Acid; Adenoviridae; Amino Acid Sequence; Animals; Aryl Hydrocarbon Hydroxylases; Biotinylation; Cadaverine; Cell Differentiation; Cells, Cultured; Cytochrome P450 Family 2; Enzyme Activation; Genetic Vectors; Humans; Keratinocytes; Mice; Mixed Function Oxygenases; Molecular Sequence Data; Peptide Fragments; Protein Precursors; Skin; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Substrate Specificity; Transglutaminases

Endothelium-dependent hyperpolarizations and relaxation of vascular smooth muscle induced by acetylcholine and bradykinin are mediated by endothelium-derived hyperpolarizing factors (EDHFs). In bovine coronary arteries, arachidonic acid metabolites, epoxyeicosatrienoic acids (EETs), function as EDHFs. The 14,15-EET analog 14,15-epoxyeicosa-5(Z)-enoic-methylsulfonylimide (14,15-EEZE-mSI) was synthesized and tested for agonist and antagonist activity. In U46619-preconstricted bovine coronary arterial rings, 14,15-, 11,12-, 8,9-, and 5,6-EET induced maximal concentration-related relaxation averaging 75% to 87% at 10 micromol/L, whereas, 14,15-EEZE-mSI induced maximal relaxation averaging only 7%. 14,15-EEZE-mSI (10 micromol/L) preincubation inhibited relaxation to 14,15- and 5,6- EET but not 11,12- or 8,9- EET. 14,15-EEZE-mSI also inhibited indomethacin-resistant relaxation to arachidonic acid and indomethacin-resistant and l-nitroarginine-resistant relaxation to bradykinin and methacholine. It did not alter the relaxation to sodium nitroprusside, iloprost, or the K+ channel openers bimakalim or NS1619. In cell-attached patches of isolated bovine coronary arterial smooth muscle cells, 14,15-EEZE-mSI (100 nmol/L) blocked the 14,15-EET-induced (100 nmol/L) activation of large-conductance, calcium-activated K+ channels. Mass spectrometric analysis of rat renal cortical microsomes incubated with arachidonic acid showed that 14,15-EEZE-mSI (10 micromol/L) increased EET concentrations while decreasing the concentrations of the corresponding dihydroxyeicosatrienoic acids. Therefore, 14,15-EEZE-mSI inhibits relaxation to 5,6- and 14,15- EET and the K+ channel activation by 14,15-EET. It also inhibits the EDHF component of bradykinin-induced, methacholine-induced, and arachidonic acid-induced relaxation. These results suggest that 14,15- or 5,6 -EET act as an EDHF in bovine coronary arteries.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acid; Cattle; Coronary Vessels; Culture Techniques; Patch-Clamp Techniques; Potassium Channels, Calcium-Activated; Rats; Sulfonamides; Vasodilator Agents

Epoxyeicosatrienoic acids (EETs) are synthesized in the endothelial cells of vascular tissues. They are released from the endothelial cells and produce relaxation of the smooth muscle cells by hyperpolarization. The present findings demonstrate that EETs also regulate aromatase activity in vascular smooth muscle cells. Exposure of cultured rat aortic smooth muscle cells to either 1 microM 14,15-EET or 1 microM 11,12-EET inhibits dibutyryl cAMP-induced aromatase activity by 80-100%. 11,12-Dihydroxyeicosatrienoic acid, the hydration product of 11,12-EET, has no effect on dibutyryl cAMP-induced vascular smooth muscle aromatase activity. In contrast to 14,15-EET, the N-methylsulfanilamide derivative of 14,15-EET (14,15-EET-SA) was neither metabolized nor incorporated into cell lipids, but it retained the ability to inhibit cAMP-induced aromatase activity. Furthermore, the 14,15-EET-SA inhibition of cAMP-induced aromatase activity persisted when the sulfanilamide derivative of 14,15-EET was covalently tethered to silica beads (average diameter, 0.5 microm), which restricted 14,15-EET-SA from entering the cell. These data are consistent with the presence of a receptor for EETs in the plasma membrane and support the hypothesis that the inhibition of aromatase by EETs is initiated by the interaction of EET with the putative plasma membrane receptor.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Aorta, Thoracic; Aromatase; Carbon Radioisotopes; Cell Membrane; Cells, Cultured; Enzyme Activation; Microspheres; Muscle, Smooth, Vascular; Rats; Rats, Sprague-Dawley; Vasodilator Agents

Cytochrome P-450 epoxygenase-derived epoxyeicosatrienoic acids (EETs) play an important role in the regulation of vascular reactivity and function. Conversion to the corresponding dihydroxyeicosatrienoic acids (DHETs) by soluble epoxide hydrolases is thought to be the major pathway of EET metabolism in mammalian vascular cells. However, when human coronary artery endothelial cells (HCEC) were incubated with (3)H-labeled 14,15-EET, chain-shortened epoxy fatty acids, rather than DHET, were the most abundant metabolites. After 4 h of incubation, 23% of the total radioactivity remaining in the medium was converted to 10,11-epoxy-hexadecadienoic acid (16:2), a product formed from 14,15-EET by two cycles of beta-oxidation, whereas only 15% was present as 14,15-DHET. Although abundantly present in the medium, 10,11-epoxy-16:2 was not detected in the cell lipids. Exogenously applied (3)H-labeled 10,11-epoxy-16:2 was neither metabolized nor retained in the cells, suggesting that 10,11-epoxy-16:2 is a major product of 14,15-EET metabolism in HCEC. 10,11-Epoxy-16:2 produced potent dilation in coronary microvessels. 10,11-Epoxy-16:2 also potently inhibited tumor necrosis factor-alpha-induced production of IL-8, a proinflammatory cytokine, by HCEC. These findings implicate beta-oxidation as a major pathway of 14,15-EET metabolism in HCEC and provide the first evidence that EET-derived chain-shortened epoxy fatty acids are biologically active.

Topics: 8,11,14-Eicosatrienoic Acid; Cell Line; Chromatography, Liquid; Coronary Vessels; Culture Media, Conditioned; Endothelium, Vascular; Epoxy Compounds; Fatty Acids, Unsaturated; Humans; Interleukin-8; Mass Spectrometry; Oxidation-Reduction; Tumor Necrosis Factor-alpha; Vasodilator Agents

Each of the four regioisomers of epoxyeicosatrienoic acids (EETs) is a candidate for being an endothelial-dependent hyperpolarizing factor (EDHF). One regioisomer, 14,15-EET, stereospecifically blocks cyclooxygenases from converting arachidonic acid to prostaglandins and stereospecifically binds to cellular receptors. Both stereospecific actions emphasize the need to establish the tissue availability of the 14,15-EET enantiomers. The present work describes a method to quantitate picogram amounts of 14,15-EET enantiomers by capillary electrophoresis. The 14,15-EET enantiomers were baseline resolved (R = 1.3) using unsubstituted beta-cyclodextrin and 32% acetonitrile (v/v). When absorption at 194 nm was monitored using a photodiode array detector, 8 and 1 pg of underivatized 14,15-EET were readily quantitated and detected, respectively. Capillary electrophoresis accurately assessed chiral excesses up to 97:3 for either 14,15-EET enantiomer. Moreover, capillary electrophoresis with a photodiode array detector was sufficiently sensitive to detect and measure 14,15-EET enantiomers from murine liver. Thus, unlike chiral-phase high-performance liquid chromatography, capillary electrophoresis can be used to directly assess the chirality of trace amounts of underivatized eicosanoids.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acid; Calibration; Cyclodextrins; Cytochrome P-450 CYP2J2; Cytochrome P-450 Enzyme System; Electrophoresis, Capillary; Liver; Mice; Oxygenases; Spectrophotometry, Ultraviolet; Stereoisomerism

Background and Purpose- Epoxyeicosatrienoic acids (EETs) are products of cytochrome P450 epoxygenation of arachidonic acid. We have previously demonstrated that astrocyte-conditioned medium induced mitogenesis in brain capillary endothelial cells. The goals of the present studies are to further define the mechanism through which this can occur and to confirm that EETs are derived from astrocytes, through which astrocytic activity can regulate cerebral angiogenesis in response to neuronal activation.. Astrocytes and cerebral capillary endothelial cells in primary cultures were cocultured to examine the interaction of the 2 cell types. We used multiple immunohistochemical techniques to characterize the multicellular nature of the capillaries, which is not simply an artifact related to the culture conditions. The mitogenic effect of EETs was determined by (3)H-thymidine incorporation and cell proliferation assay. Endothelial tube formation was examined in vitro and in vivo with the use of a reconstituted basement membrane (Matrigel) assay.. In cocultures of astrocytes and capillary endothelium, we observed morphological changes in both cell types such that each assumed certain physiological characteristics, ie, endothelial networks and astrocytes with "footlike" projections as well as intermittent gap junctions forming within the endothelial cells. EETs from astrocytes as well as synthetic EETs promoted mitogenesis of endothelial cells, a process sensitive to inhibition of tyrosine kinase with genistein. Treatments with exogenous EETs were sufficient for endothelial cells to differentiate into capillary-like structures in culture as well as in vivo in a Matrigel matrix.. The 2 major conclusions from these data are that astrocytes may play an important role in regulating angiogenesis in the brain and that cytochrome P450-derived EETs from astrocytes are mitogenic and angiogenic.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Astrocytes; Brain; Capillaries; Cell Differentiation; Cells, Cultured; Coculture Techniques; Culture Media, Conditioned; Cytochrome P-450 Enzyme Inhibitors; Cytochrome P-450 Enzyme System; Dose-Response Relationship, Drug; Endothelial Growth Factors; Endothelium, Vascular; Enzyme Inhibitors; Intercellular Signaling Peptides and Proteins; Lymphokines; Mitosis; Neovascularization, Physiologic; Rats; Thymidine; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factors

Topics: 8,11,14-Eicosatrienoic Acid; Antibodies; Arachidonic Acids; Cross Reactions; Enzyme-Linked Immunosorbent Assay; Hydroxylation; Isomerism; Sensitivity and Specificity

We describe the biochemical properties of an eicosanoid-modulated Cl- channel and assess the mechanisms by which the epoxyeicosatrienoic acids (EETs) alter both its unitary conductance and its open probability (P(o)). After a purification protocol involving wheat-germ agglutinin affinity and anion-exchange chromatography, the proteins were sequentially inserted into liposomes, which were then fused into PLBs. Functional and biochemical characterization tests confirm that the Cl- channel is a 55-kDa glycosylated monomer with voltage- and Ca(2+) concentration-independent activity. 5,6- and 8,9-EET decreased the conductance of the native channel (control conductance: 70 +/- 5 pS in asymmetrical 50 mM trans/250 mM cis CsCl) in a concentration-dependent manner, with respective 50% inhibitory concentration values of 0.31 and 0.42 microM. These regioisomers similarly decreased the conductance of the purified channel (control conductance value: 75 +/- 5 pS in asymmetrical 50 mM trans/250 mM cis CsCl), which had been stripped of its native proteic and lipidic environment. On the other hand, 5,6- and 8,9-EETs decreased the P(o) of the native channel with respective 50% inhibitory concentration values of 0.27 and 0.30 microM but failed to alter the P(o) of the purified protein. Thus we suggest that the effects of these EETs on channel conductance likely result from direct interactions of EET- anions with the channel pore, whereas the alteration of P(o) requires a lipid environment of specific composition that is lost on solubilization and purification of the protein.

Topics: 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; 8,11,14-Eicosatrienoic Acid; Animals; Calcium; Cattle; Cell Fractionation; Chloride Channels; Electric Conductivity; Electrophysiology; Immunoblotting; Lipid Bilayers; Liposomes; Muscle, Smooth; Sarcolemma; Trachea; Vasodilator Agents

Epoxyeicosatrienoic acids (EETs) cause vascular relaxation by activating smooth muscle large conductance Ca(2+)-activated K(+) (K(Ca)) channels. EETs are metabolized to dihydroxyeicosatrienoic acids (DHETs) by epoxide hydrolase. We examined the contribution of 14,15-DHET to 14,15-EET-induced relaxations and characterized its mechanism of action. 14,15-DHET relaxed U-46619-precontracted bovine coronary artery rings but was approximately fivefold less potent than 14,15-EET. The relaxations were inhibited by charybdotoxin, iberiotoxin, and increasing extracellular K(+) to 20 mM. In isolated smooth muscle cells, 14,15-DHET increased an iberiotoxin-sensitive, outward K(+) current and increased K(Ca) channel activity in cell-attached patches and inside-out patches only when GTP was present. 14,15-[(14)C]EET methyl ester (Me) was converted to 14,15-[(14)C]DHET-Me, 14,15-[(14)C]DHET, and 14,15-[(14)C]EET by coronary arterial rings and endothelial cells but not by smooth muscle cells. The metabolism to 14,15-DHET was inhibited by the epoxide hydrolase inhibitors 4-phenylchalcone oxide (4-PCO) and BIRD-0826. Neither inhibitor altered relaxations to acetylcholine, whereas relaxations to 14,15-EET-Me were increased slightly by BIRD-0826 but not by 4-PCO. 14,15-DHET relaxes coronary arteries through activation of K(Ca) channels. Endothelial cells, but not smooth muscle cells, convert EETs to DHETs, and this conversion results in a loss of vasodilator activity.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; 8,11,14-Eicosatrienoic Acid; Acetylcholine; Animals; Calcium; Cattle; Charybdotoxin; Coronary Vessels; Electric Conductivity; Endothelium, Vascular; Enzyme Inhibitors; Epoxide Hydrolases; GTP-Binding Proteins; Guanosine Triphosphate; Hydroxyeicosatetraenoic Acids; Muscle Relaxation; Muscle, Smooth, Vascular; Peptides; Potassium Channels

Endothelium-dependent hyperpolarization and relaxation of vascular smooth muscle are mediated by endothelium-derived hyperpolarizing factors (EDHFs). EDHF candidates include cytochrome P-450 metabolites of arachidonic acid, K(+), hydrogen peroxide, or electrical coupling through gap junctions. In bovine coronary arteries, epoxyeicosatrienoic acids (EETs) appear to function as EDHFs. A 14,15-EET analogue, 14,15-epoxyeicosa-5(Z)-enoic acid (14,15-EEZE) was synthesized and identified as an EET-specific antagonist. In bovine coronary arterial rings preconstricted with U46619, 14,15-EET, 11,12-EET, 8,9-EET, and 5,6-EET induced concentration-related relaxations. Preincubation of the arterial rings with 14,15-EEZE (10 micromol/L) inhibited the relaxations to 14,15-EET, 11,12-EET, 8,9-EET, and 5,6-EET but was most effective in inhibiting 14,15-EET-induced relaxations. 14,15-EEZE also inhibited indomethacin-resistant relaxations to methacholine and arachidonic acid and indomethacin-resistant and L-nitroarginine-resistant relaxations to bradykinin. It did not alter relaxation responses to sodium nitroprusside, iloprost, or the K(+) channel activators (NS1619 and bimakalim). Additionally, in small bovine coronary arteries pretreated with indomethacin and L-nitroarginine and preconstricted with U46619, 14,15-EEZE (3 micromol/L) inhibited bradykinin (10 nmol/L)-induced smooth muscle hyperpolarizations and relaxations. In rat renal microsomes, 14,15-EEZE (10 micromol/L) did not decrease EET synthesis and did not alter 20-hydroxyeicosatetraenoic acid synthesis. This analogue acts as an EET antagonist by inhibiting the following: (1) EET-induced relaxations, (2) the EDHF component of methacholine-induced, bradykinin-induced, and arachidonic acid-induced relaxations, and (3) the smooth muscle hyperpolarization response to bradykinin. Thus, a distinct molecular structure is required for EET activity, and alteration of this structure modifies agonist and antagonist activity. These findings support a role of EETs as EDHFs.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acid; Benzimidazoles; Benzopyrans; Bradykinin; Cattle; Coronary Vessels; Dihydropyridines; Dose-Response Relationship, Drug; Endothelium, Vascular; Iloprost; In Vitro Techniques; Kidney Cortex; Male; Microsomes; Muscle, Smooth, Vascular; Nitroprusside; Rats; Rats, Sprague-Dawley; Structure-Activity Relationship; Vasoconstriction; Vasoconstrictor Agents; Vasodilation

Endothelium-derived hyperpolarizing factor (EDHF) is released in response to agonists such as ACh and bradykinin and regulates vascular smooth muscle tone. Several studies have indicated that ouabain blocks agonist-induced, endothelium-dependent hyperpolarization of smooth muscle. We have demonstrated that epoxyeicosatrienoic acids (EETs), cytochrome P-450 metabolites of arachidonic acid, function as EDHFs. To further test the hypothesis that EETs represent EDHFs, we have examined the effects of ouabain on the electrical and mechanical effects of 14,15- and 11,12-EET in bovine coronary arteries. These arteries are relaxed in a concentration-dependent manner to 14,15- and 11,12-EET (EC(50) = 6 x 10(-7) M), bradykinin (EC(50) = 1 x 10(-9) M), sodium nitroprusside (SNP; EC(50) = 2 x 10(-7) M), and bimakalim (BMK; EC(50) = 1 x 10(-7) M). 11,12-EET-induced relaxations were identical in vessels with and without an endothelium. Potassium chloride (1-15 x 10(-3) M) inhibited [(3)H]ouabain binding to smooth muscle cells but failed to relax the arteries. Ouabain (10(-5) to 10(-4) M) increased basal tone and inhibited the relaxations to bradykinin, 11,12-EET, and 14,15-EET, but not to SNP or BMK. Barium (3 x 10(-5) M) did not alter EET-induced relaxations and ouabain plus barium was similar to ouabain alone. Resting membrane potential (E(m)) of isolated smooth muscle cells was -50.2 +/- 0.5 mV. Ouabain (3 x 10(-5) and 1 x 10(-4) M) decreased E(m) (-48.4 +/- 0.2 mV), whereas 11,12-EET (10(-7) M) increased E(m) (-59.2 +/- 2.2 mV). Ouabain inhibited the 11,12-EET-induced increase in E(m). In cell-attached patch clamp studies, 11,12-EET significantly increased the open-state probability (NP(o)) of a calcium-activated potassium channel compared with control cells (0.26 +/- 0.06 vs. 0.02 +/- 0.01). Ouabain did not change NP(o) but blocked the 14,15-EET-induced increase in NP(o). These results indicate that: 1) EETs relax coronary arteries in an endothelium-independent manner, 2) unlike EETs, potassium chloride does not relax the coronary artery, and 3) ouabain inhibits bradykinin- and EET-induced relaxations as has been reported for EDHF. These findings provide further evidence that EETs are EDHFs.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; 8,11,14-Eicosatrienoic Acid; Animals; Benzopyrans; Biological Factors; Bradykinin; Cardiotonic Agents; Cattle; Coronary Vessels; Dihydropyridines; Electrophysiology; Endothelium, Vascular; Membrane Potentials; Muscle, Smooth, Vascular; Nitroprusside; Ouabain; Peptides; Potassium; Potassium Channels; Tritium; Vasoconstrictor Agents; Vasodilation; Vasodilator Agents

Epoxyeicosatrienoic acids (EETs) are products of cytochrome P-450 epoxygenase that possess important vasodilating and anti-inflammatory properties. EETs are converted to the corresponding dihydroxyeicosatrienoic acid (DHET) by soluble epoxide hydrolase (sEH) in mammalian tissues, and inhibition of sEH has been proposed as a novel approach for the treatment of hypertension. We observed that sEH is present in porcine coronary endothelial cells (PCEC), and we found that low concentrations of N,N'-dicyclohexylurea (DCU), a selective sEH inhibitor, have profound effects on EET metabolism in PCEC cultures. Treatment with 3 microM DCU reduced cellular conversion of 14,15-EET to 14,15-DHET by 3-fold after 4 h of incubation, with a concomitant increase in the formation of the novel beta-oxidation products 10,11-epoxy-16:2 and 8,9-epoxy-14:1. DCU also markedly enhanced the incorporation of 14,15-EET and its metabolites into PCEC lipids. The most abundant product in DCU-treated cells was 16,17-epoxy-22:3, the elongation product of 14,15-EET. Another novel metabolite, 14,15-epoxy-20:2, was present in DCU-treated cells. DCU also caused a 4-fold increase in release of 14,15-EET when the cells were stimulated with a calcium ionophore. Furthermore, DCU decreased the conversion of [3H]11,12-EET to 11,12-DHET, increased 11,12-EET retention in PCEC lipids, and produced an accumulation of the partial beta-oxidation product 7,8-epoxy-16:2 in the medium. These findings suggest that in addition to being metabolized by sEH, EETs are substrates for beta-oxidation and chain elongation in endothelial cells and that there is considerable interaction among the three pathways. The modulation of EET metabolism by DCU provides novel insight into the mechanisms by which pharmacological or molecular inhibition of sEH effectively treats hypertension.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Cell Line; Endothelium, Vascular; Epoxide Hydrolases; Lipid Metabolism; Solubility; Swine

The epoxyeicosatrienoic acids (EETs) are products of cytochrome P450 (CYP) epoxygenases that have vasodilatory and anti-inflammatory properties. Here we report that EETs have additional fibrinolytic properties. In vascular endothelial cells, physiological concentrations of EETs, particularly 11,12-EET, or overexpression of the endothelial epoxygenase, CYP2J2, increased tissue plasminogen activator (t-PA) expression by 2.5-fold without affecting plasminogen activator inhibitor-1 expression. This increase in t-PA expression correlated with a 4-fold induction in t-PA gene transcription and a 3-fold increase in t-PA fibrinolytic activity and was blocked by the CYP inhibitor, SKF525A, but not by the calcium-activated potassium channel blocker, charybdotoxin, indicating a mechanism that does not involve endothelial cell hyperpolarization. The t-PA promoter is cAMP-responsive, and induction of t-PA gene transcription by EETs correlated with increases in intracellular cAMP levels and, functionally, with cAMP-driven promoter activity. To determine whether increases in intracellular cAMP levels were due to modulation of guanine nucleotide-binding proteins, we assessed the effects of EETs on Galpha(s) and Galpha(i2). Treatment with EETs increased Galpha(s), but not Galpha(i2), GTP-binding activity by 3.5-fold. These findings indicate that EETs possess fibrinolytic properties through the induction of t-PA and suggest that endothelial CYP2J2 may play an important role in regulating vascular hemostasis.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Aorta; Atropine Derivatives; Cattle; Cells, Cultured; Cyclic AMP; Cytochrome P-450 CYP2J2; Cytochrome P-450 Enzyme System; Endothelium, Vascular; Gene Expression Regulation, Enzymologic; GTP-Binding Protein alpha Subunits, Gi-Go; GTP-Binding Protein alpha Subunits, Gs; Humans; Oxygenases; Polymerase Chain Reaction; Proadifen; Promoter Regions, Genetic; Saphenous Vein; Tissue Plasminogen Activator; Transcription, Genetic; Transfection

Epoxyeicosatrienoic acids (EETs) are produced from arachidonic acid via the cytochrome P-450 epoxygenase pathway. EETs are able to modulate smooth muscle tone by increasing K(+) conductance, hence generating hyperpolarization of the tissues. However, the molecular mechanisms by which EETs induce smooth muscle relaxation are not fully understood. In the present study, the effects of EETs on airway smooth muscle (ASM) were investigated using three electrophysiological techniques. 8,9-EET and 14,15-EET induced concentration-dependent relaxations of the ASM precontracted with a muscarinc agonist (carbamylcholine chloride), and these relaxations were partly inhibited by 10 nM iberiotoxin (IbTX), a specific large-conductance Ca(2+)-activated K(+) (BK(Ca)) channel blocker. Moreover, 3 microM 8,9- or 14,15-EET induced hyperpolarizations of -12 +/- 3.5 and -16 +/- 3 mV, with EC(50) values of 0.13 and 0.14 microM, respectively, which were either reversed or blocked on addition of 10 nM IbTX. These results indicate that BK(Ca) channels are involved in hyperpolarization and participate in the relaxation of ASM. In addition, complementary experiments demonstrated that 8,9- and 14,15-EET activate reconstituted BK(Ca) channels at low free Ca(2+) concentrations without affecting their unitary conductance. These increases in channel activity were IbTX sensitive and correlated well with the IbTX-sensitive hyperpolarization and relaxation of ASM. Together these results support the view that, in ASM, the EETs act through an epithelium-derived hyperpolarizing factorlike effect.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Biological Factors; Bronchoconstriction; Cattle; Cyclooxygenase Inhibitors; Dose-Response Relationship, Drug; Enzyme Inhibitors; Guinea Pigs; In Vitro Techniques; Large-Conductance Calcium-Activated Potassium Channels; Male; Membrane Potentials; Muscarinic Agonists; Muscle, Smooth; Nitric Oxide Synthase; Peptides; Potassium Channels; Potassium Channels, Calcium-Activated; Rabbits; Trachea

Arachidonic acid (AA) can be metabolized by cytochrome P450 enzymes to many biologically active compounds including 5,6-, 8,9-, 11,12-, and 14,15-epoxyeicosatrienoic acids (EETs), their corresponding dihydroxyeicosatrienoic acids (DHETs), as well as 19- and 20-hydroxyeicosatetraenoic acids (HETEs). These eicosanoids are potent regulators of vascular tone. However, their role in the ischemic myocardium has not been well investigated. In this study, we used a gas chromatographic-mass spectrometric technique to analyze total EETs, DHETs, and 20-HETE released into coronary venous plasma during coronary artery occlusion and reperfusion in anesthetized dogs. Pentafluorobenzyl esters (PFB-esters) of EETs and PFB-esters/trimethylsilyl ethers (TMS-ethers) of DHETs and 20-HETE were detected in the negative ion chemical ionization (NICI) using methane as a reagent gas. Under the conditions used, all four regioisomers of EET eluted from the capillary gas chromatographic column at similar retention times while four regioisomers of DHETs and 20-HETE eluted separately. The detection limits in plasma samples are 5 pg for total EETs, 40 pg for DHET, and 15 pg for 20-HETE. 14,15-DHET is the major regioisomer detected in the plasma samples while other regioisomers of DHETs are probably present at too low a concentration for detection. During the first 5 to 15 min of coronary occlusion, a slight decrease in the concentration of EETs, 14,15-DHET, and 20-HETE from the control values was observed in coronary venous plasma. At 60 min of occlusion, their concentrations significantly increased and remained elevated during 5 to 60 min of reperfusion. The concentrations decreased at 120 min of reperfusion. The NICI GC-MS was successfully used as a sensitive technique to determine cP450 metabolites of AA in plasma during prolonged occlusion-reperfusion periods. Furthermore, the results indicate that these metabolites may play a role in mediating ischemic-reperfusion injury.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acid; Biological Factors; Coronary Vessels; Cytochrome P-450 Enzyme System; Dogs; Eicosanoids; Gas Chromatography-Mass Spectrometry; Hydroxyeicosatetraenoic Acids; Ischemia; Reference Standards; Reperfusion

Epoxyeicosatrienoic acids (EETs) are released from endothelial cells and potently dilate small arteries by hyperpolarizing vascular myocytes. In the present study, we investigated the structural specificity of EETs in dilating canine and porcine coronary microvessels (50-140 microm ID) and activating large-conductance Ca2+-activated K+ (BK(Ca)) channels. The potencies and efficacies of EET regioisomers and enantiomers were compared with those of two EET homologs: epoxyeicosaquatraenoic acids (EEQs), which are made from eicosapentaenoic acid by the same cytochrome P-450 epoxygenase that generates EETs from arachidonic acid, and epoxydocosatetraenoic acids (EDTs), which are EETs that are two carbons longer. With EC50 values of 3-120 pM but without regio- or stereoselectivity, EETs potently dilated canine and porcine microvessels. Surprisingly, the EEQs and EDTs had comparable potencies and efficacies in dilating microvessels. Moreover, 50 nM 13,14-EDT activated the BK(Ca) channels with the same efficacy as either 11,12-EET enantiomer at 50 nM. We conclude that coronary microvessels and BK(Ca) channels possess low structural specificity for EETs and suggest that EEQs and EDTs may thereby also be endothelium-derived hyperpolarizing factors.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arterioles; Calcium Channel Agonists; Coronary Vessels; Dogs; Dose-Response Relationship, Drug; Endothelium, Vascular; Fatty Acids, Unsaturated; Female; In Vitro Techniques; Large-Conductance Calcium-Activated Potassium Channels; Male; Microcirculation; Muscle, Smooth, Vascular; Potassium Channel Blockers; Potassium Channels; Potassium Channels, Calcium-Activated; Stereoisomerism; Swine; Vasodilation; Vasodilator Agents

This study focused on the mechanisms of the negative inotropic response to bradykinin (BK) in isolated rat hearts perfused at constant flow. BK (100 nM) significantly reduced developed left ventricular pressure (LVP) and the maximal derivative of systolic LVP by 20-22%. The cytochrome P-450 (CYP) inhibitors 1-aminobenzotriazole (1 mM and 100 microM) or proadifen (5 microM) abolished the cardiodepression by BK, which was not affected by nitric oxide and cyclooxygenase inhibitors (35 microM NG-nitro-L-arginine methyl ester and 10 microM indomethacin, respectively). The CYP metabolite 14,15-epoxyeicosatrienoic acid (14,15-EET; 50 ng/ml) produced effects similar to those of BK in terms of the reduction in contractility. After the coronary endothelium was made dysfunctional by Triton X-100 (0.5 microl), the BK-induced negative inotropic effect was completely abolished, whereas the 14,15-EET-induced cardiodepression was not affected. In hearts with normal endothelium, after recovery from 14,15-EET effects, BK reduced developed LVP to a 35% greater extent than BK in the control. In conclusion, CYP inhibition or endothelial dysfunction prevents BK from causing cardiodepression, suggesting that, in the rat heart, endothelial CYP products mediate the negative inotropic effect of BK. One of these mediators appears to be 14,15-EET.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acid; Blood Pressure; Bradykinin; Coronary Vessels; Cytochrome P-450 Enzyme Inhibitors; Cytochrome P-450 Enzyme System; Endothelium, Vascular; Enzyme Inhibitors; Heart; Heart Rate; In Vitro Techniques; Indomethacin; Male; Myocardium; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase; Octoxynol; Proadifen; Rats; Rats, Wistar; Tachyphylaxis; Triazoles; Ventricular Function, Left

Epoxygenase metabolites produced by the kidney affect renal blood flow and tubular transport function and 11,12-epoxyeicosatrienoic acid (11,12-EET) has been putatively identified as an endothelium-derived hyperpolarizing factor. The current studies were performed to determine the influence of 11,12-EET on the regulation of afferent arteriolar diameter in angiotensin II-infused hypertensive rats.. Male Sprague-Dawley rats received angiotensin II (60 ng/min) or vehicle via an osmotic minipump. Angiotensin II-infused hypertensive and vehicle-infused normotensive rats were studied for 2 weeks following implantation of the minipump. Renal microvascular responses to the sulfonimide analog of 11,12-EET (11,12-EET-SI) and angiotensin II were observed utilizing the in-vitro juxtamedullary nephron preparation. Renal cortical epoxygenase enzyme protein levels were quantified by Western blot analysis. Renal microvessels were also isolated and epoxygenase metabolite levels measured by negative ion chemical ionization (NICI)/gas chromatography-mass spectroscopy.. Systolic blood pressure averaged 118 +/- 2 mmHg prior to pump implantation and increased to 185 +/- 7 mmHg in rats infused with angiotensin II for 2 weeks. Afferent arteriolar diameters of 2-week normotensive animals averaged 22 +/- 1 microm. Diameters of the afferent arterioles were 17% smaller in hypertensive rats (P< 0.05); however, arterioles from both groups responded to 11,12-EET-SI (100 nmol) with similar 15-17% increases in diameter. As we previously demonstrated, the afferent arteriolar reactivity to angiotensin II was enhanced in angiotensin II-infused animals. Interestingly, elevation of 11,12-EET-SI levels to 100 nmol reversed the enhanced vascular reactivity to angiotensin II associated with angiotensin II hypertension. Renal microvascular EET levels were not different between groups and averaged 81 +/- 9 and 87 +/- 13 pg/mg per 30 min in normotensive and hypertensive animals, respectively. Renal cortical microsomal levels of the epoxygenase CYP2C23 and CYP2C11 proteins were also similar in normotensive and angiotensin II hypertensive rats.. Taken together, these data support the concept that renal microvascular 11,12-EET activity and levels may not properly offset the enhanced angiotensin II renal vasoconstriction during angiotensin II hypertension.

Topics: 8,11,14-Eicosatrienoic Acid; Angiotensin II; Animals; Arterioles; Cytochrome P-450 CYP2J2; Cytochrome P-450 Enzyme System; Drug Synergism; Hypertension; Kidney Cortex; Male; Microcirculation; Microsomes; Rats; Rats, Sprague-Dawley; Renal Circulation; Sulfonamides; Vasoconstriction

An effective synthesis is described for the preparation of all four mono trans isomers of arachidonic acid via deoxidation of epoxide precursors with lithium diphenylphosphide and quaternization with methyl iodide.

Topics: 8,11,14-Eicosatrienoic Acid; Arachidonic Acid; Biochemistry; Chromatography, High Pressure Liquid; Magnetic Resonance Spectroscopy; Stereoisomerism

We assessed the effect of epoxyeicosatrienoic acids (EETs) in intact mesenteric arteries and Ca(2+)-activated K(+) (BK(Ca)) channels of isolated vascular smooth muscle cells from control and insulin-resistant (IR) rats. The response to 11,12-EET and 14,15-EET was assessed in small mesenteric arteries from control and IR rats in vitro. Mechanistic studies were performed in endothelium intact or denuded arteries and in the presence of pharmacological inhibitors. Moreover, EET-induced activation of the BK(Ca) channel was assessed in myocytes in both the cell-attached and the inside-out (I/O) patch-clamp configurations. In control arteries, both EET isomers induced relaxation. Relaxation was impaired by endothelium denudation, N(omega)-nitro-L-arginine, or iberiotoxin (IBTX), whereas it was abolished by IBTX + apamin or charybdotoxin + apamin. In contrast, the EETs did not relax IR arteries. In control myocytes, the EETs increased BK(Ca) activity in both configurations. Conversely, in the cell-attached mode, EETs had no effect on BK(Ca) channel activity in IR myocytes, whereas in the I/O configuration, BK(Ca) channel activity was enhanced. EETs induce relaxation in small mesenteric arteries from control rats through K(Ca) channels. In contrast, arteries from IR rats do not relax to the EETs. Patch-clamp studies suggest impaired relaxation is due to altered regulatory mechanisms of the BK(Ca) channel.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; In Vitro Techniques; Insulin Resistance; Male; Mesenteric Arteries; Patch-Clamp Techniques; Rats; Rats, Sprague-Dawley; Reference Values; Vasodilation; Vasodilator Agents

Endothelium-derived hyperpolarizing factor (EDHF) mediates NO/prostacyclin-independent relaxation in the coronary circulation. Because hemodynamic stimuli modulate endothelial gene expression and because coronary arteries are subjected to pronounced variations in vessel distension, we determined the effects of cyclic stretch on the expression and activity of the coronary EDHF synthase/cytochrome P450 (CYP) 2C8/9. In cultured porcine coronary and human umbilical vein endothelial cells, acute application of cyclic stretch (6%, 1 Hz, 10 minutes) elicited the generation of 8,9-epoxyeicosatrienoic acid (EET), 11,12-EET, and 14,15-EET. Prolonged stretch (4 to 36 hours) increased the expression of CYP 2C mRNA and protein 5- to 10-fold and was accompanied by a 4- to 8-fold increase in EET generation. A corresponding increase in CYP 2C mRNA and protein was also observed in pressurized segments of porcine coronary artery perfused under pulsatile conditions (8%, 1 Hz) for 6 hours. Although in cultured endothelial cells, cyclic stretch elicited the rapid activation of tyrosine kinases as well as Akt and the p38 mitogen-activated protein kinase, the mechanism by which cyclic stretch induces the expression of CYP 2C could not be elucidated, because inhibitors of these pathways induced CYP 2C expression in cells maintained under static conditions. These results have identified coronary EDHF synthase/CYP 2C as a novel mechanosensitive gene product in native and cultured endothelial cells. Because this enzyme generates both EETs and superoxide anions, this finding has wide-reaching implications for vascular homeostasis in conditions of manifest endothelial dysfunction.

Topics: 8,11,14-Eicosatrienoic Acid; Androstadienes; Animals; Benzoquinones; Cells, Cultured; Coronary Vessels; Cytochrome P-450 Enzyme System; Cytochrome P450 Family 2; Endothelium, Vascular; Enzyme Inhibitors; Humans; Ionomycin; Lactams, Macrocyclic; Oxygenases; Patch-Clamp Techniques; Periodicity; Pulsatile Flow; Quinones; Rifabutin; Sirolimus; Stress, Mechanical; Swine; Umbilical Veins; Vasodilation; Wortmannin

Little information is available regarding the vasoactive effects of epoxyeicosatrienoic acids (EETs) in the lung. We demonstrate that 5, 6-, 8,9-, 11,12-, and 14,15-EETs contract pressurized rabbit pulmonary arteries in a concentration-dependent manner. Constriction to 5,6-EET methyl ester or 14,15-EET is blocked by indomethacin or ibuprofen (10(-5) M), SQ-29548, endothelial denuding, or submaximal preconstriction with the thromboxane mimetic U-46619. Constriction of pulmonary artery rings to phenylephrine is blunted by treatment with the epoxygenase inhibitor N-methylsulfonyl-6-(2-propargyloxyphenyl)hexanamide. Pulmonary arteries and peripheral lung microsomes metabolize arachidonate to products that comigrate on reverse-phrase HPLC with authentic regioisomers of 5,6-, 8,9-, 11,12-, and 14,15-EETs, but no cyclooxygenase products of EETs could be demonstrated. Proteins of the CYP2B, CYP2E, CYP2J, CYP1A, and CYP2C subfamilies are present in pulmonary artery and peripheral lung microsomes. Constriction of isolated rabbit pulmonary arteries to EETs is nonregioselective and depends on intact endothelium and cyclooxygenase, consistent with the formation of a pressor prostanoid compound. These data raise the possibility that EETs may contribute to regulation of pulmonary vascular tone.

Topics: 8,11,14-Eicosatrienoic Acid; Amides; Animals; Arachidonic Acid; Cytochrome P-450 Enzyme System; Dogs; In Vitro Techniques; Male; Pressure; Pulmonary Artery; Rabbits; Vasoconstriction; Vasoconstrictor Agents; Vasomotor System

Epoxyeicosatrienoic acids (EETs) are major products of cytochrome P450 (CYP)-catalyzed metabolism of arachidonic acid in the kidney. The potent effect of EETs on renal vascular tone and tubular ion and water transport implicates their role in the regulation of renal function and blood pressure. The present study was designed to test the hypothesis that CYP-catalyzed EET formation was altered in the spontaneously hypertensive rat (SHR) kidney. The formation of 14,15- and 11,12-EET was approximately 2-fold higher in incubations of arachidonic acid with SHR renal cortical microsomes relative to microsomes from normotensive Wistar-Kyoto (WKY) rats. This was consistent with increased expression of a CYP2J2 immunoreactive protein in the SHR cortex and outer medulla. In contrast, there was no significant difference in the levels of the CYP2E and CYP2C epoxygenases in SHR and WKY kidneys. Protein and RNA analysis suggests that the CYP2J2 immunoreactive protein that is overexpressed in the SHR kidney is distinct from the known rat CYP2J isoforms. EET formation also was documented in vivo from measurements of urinary EET excretion. Importantly, the excretion rates of 14,15-, and 11,12-EETs were 2.5- and 1.8-fold higher, respectively, in SHR than WKY kidney. These studies provide both in vitro and in vivo evidence for increased EET formation in the SHR kidney and identify a novel CYP2J2 immunoreactive protein that is differentially expressed in the hypertensive kidney. In light of the known biological properties of the EETs, these findings may be important in elucidating the mechanisms that control renal vascular tone and tubular ion transport in the SHR.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Cytochrome P-450 CYP2J2; Cytochrome P-450 Enzyme System; Hypertension; Kidney; Liver; Male; Oxygenases; Rats; Rats, Inbred SHR; Rats, Inbred WKY; RNA, Messenger

We have previously reported that 14,15-epoxyeicosatrienoic acid (14, 15-EET) is a potent mitogen for the renal epithelial cell line, LLCPKcl4. This mitogenic effect is dependent upon activation of a protein-tyrosine kinase cascade that results in activation of mitogen-activated protein kinase and phosphatidylinositol 3-kinase. Because of suggestive evidence that 14,15-EET also activated Src in these cells, we stably transfected LLCPKcl4 with an expression construct of the C-terminal Src kinase (CSK), which inhibits Src family kinase activity. In vitro Src kinase activity assays confirmed that in empty vector-transfected cells (Vector cells), 14, 15-EET increased Src kinase activity, while in clones overexpressing CSK mRNA and immunoreactive protein (CSK cells), 14,15-EET-induced activation of Src was almost completely blocked (94% inhibition). Of interest, epidermal growth factor (EGF) and fetal bovine serum (FBS) also increased Src activity in Vector cells, but not in CSK cells, further confirming the ability of CSK overexpression to prevent Src activation. CSK cells failed to increase [(3)H]thymidine incorporation in response to exogenous 14,15-EET. In contrast, both EGF and FBS significantly increased [(3)H]thymidine incorporation in CSK cells. Immunoprecipitation with anti-phosphotyrosine antibodies and immunoblotting with an antibody against extracellular signal-regulated kinase (ERK) indicated that in CSK cells, 14,15-EET failed to activate ERK1 and ERK2; however, EGF- and FBS-induced activation of ERKs was not different from that seen in Vector cells. In Vector cells, the 14,15-EET-stimulated tyrosine phosphorylation of ERKs was blocked by pretreatment with 1 microm PP2, a selective inhibitor of Src kinases. The present study demonstrates that 14, 15-EET exerts its mitogenic effects predominantly through a Src kinase-mediated pathway, which is the most upstream signaling step determined to date in the 14,15-EET-activated tyrosine kinase cascade in renal epithelial cells.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Cattle; Cell Line; Mitosis; Phosphorylation; Signal Transduction; src-Family Kinases; Tyrosine

A modification of the human monooxygenase system have been previously associated with the sudden infant death syndrome (SIDS): the hepatic CYP2C content was markedly enhanced and resulted from an activation of CYP2C gene transcription. To determine the possible consequence of the up-regulation of CYP2C in SIDS, we examined the metabolism of arachidonic acid (AA) an endogenous substrate of CYP2C involved in the physiologic regulation of vascular tone. The overall AA metabolism was extremely low during the fetal period and rose after birth to generate 14,15 epoxyeicosatrienoic acid (EET), 11,12 EET and the sum of 5,6 dihydroxyeicosatrienoic acid (diHETE)+omega/omega-1 hydroxy AA. In SIDS, the accumulation of CYP2C proteins was associated with a significant increase in the formation of 14,15 and 11,12 diHETE, which were shown to be supported by individually expressed CYP2C8 and 2C9 and HETE1 (presumably 15 HETE). This increase was markedly inhibited by addition of sulfaphenazole, a selective inhibitor of CYP2C9. So, we propose that the higher CYP2C content in SIDS stimulates the production of EETs and diHETEs and might have severe pathologic consequences in children.

Topics: 8,11,14-Eicosatrienoic Acid; Adult; Age Factors; Arachidonic Acid; Arachidonic Acids; Aryl Hydrocarbon Hydroxylases; Cytochrome P-450 CYP2C8; Cytochrome P-450 CYP2C9; Cytochrome P-450 Enzyme System; Humans; Hydroxyeicosatetraenoic Acids; Infant; Isoenzymes; Liver; Microsomes, Liver; NADP; Recombinant Proteins; Steroid 16-alpha-Hydroxylase; Steroid Hydroxylases; Sudden Infant Death; Up-Regulation

Epoxyeicosatrienoic acids (EETs), a family of cytochrome P450 epoxygenase metabolites of arachidonic acid, are believed to have an autocrine or paracrine role in the regulation of neurons or neuroendocrine cells. The effects of 14,15-EET on ionic currents were investigated in rat pituitary GH(3) cells. In the whole-cell configuration, 14,15-EET (3 microM) reversibly increased the amplitude of the Ca(2+)-activated K(+) current (I(K(Ca))). The 14, 15-EET-induced increase in I(K(Ca)) was unaffected in the presence of 10 microM thyrotropin-releasing hormone externally or 10 microM inositol trisphosphate in the recording pipette. In cells preincubated with pertussis toxin or herbimycin A, the 14, 15-EET-induced increase in I(K(Ca)) was also not changed. In the inside-out configuration, 14,15-EET applied intracellularly did not change single-channel conductance, but did increase the opening probability of large-conductance Ca(2+)-activated K(+) (BK(Ca)) channels. 14,15-EET (3 microM) shifted the activation curve of BK(Ca) channels to less positive membrane potential by approximately 15 mV. The change in the kinetic behavior of BK(Ca) channels caused by 14,15-EET is explained by a lengthening of open and a shortening of closed times. 14,15-EET increased the activity of BK(Ca) channels in a concentration-dependent manner with an EC(50) value of 1 microM. However, 14,15-EET did not affect the Ca(2+) sensitivity of BK(Ca) channels. The present study indicates that 14,15-EET is an opener of BK(Ca) channels in GH(3) cells and that the stimulatory effect of 14, 15-EET on these channels may, at least in part, contribute to the underlying cellular mechanisms by which EETs affect neuronal or neuroendocrine function.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Calcium; Cells, Cultured; Dose-Response Relationship, Drug; Kinetics; Large-Conductance Calcium-Activated Potassium Channels; Pertussis Toxin; Pituitary Gland; Potassium Channels; Potassium Channels, Calcium-Activated; Protein-Tyrosine Kinases; Rats; Virulence Factors, Bordetella

Epoxyeicosatrienoic acids (EETs) are cytochrome P-450 metabolites of arachidonic acid involved in the regulation of vascular tone. The method of microbore column high-performance liquid chromatography with fluorescence detection was developed to determine 14,15-EET, 11, 12-EET, and the mixture of 8,9-EET and 5,6-EET. Tridecanoic acid (TA) was used as an internal standard. EETs were reacted with 2-(2, 3-naphthalimino)ethyl trifluoromethanesulfonate (NT) to form highly fluorescent derivatives. A C(18) microbore column and a water-acetonitrile mobile phase were used for separation. Samples were excited at 259 nm, and the fluorescence was detected at 395 nm. The overall recoveries were 88% for EETs and 40% for TA. EETs were detected in concentrations as low as 2 pg (signal-to-noise ratio = 3). The method was used to determine the EET production from endothelial cells (ECs). Bradykinin and methacholine (10(-6) M) stimulated an increase in the production of EETs by ECs two- and fivefold, respectively. This sensitive method may be used for determination of EETs at low concentrations normally detected in complex biological samples.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Bradykinin; Cattle; Cells, Cultured; Chromatography, High Pressure Liquid; Coronary Vessels; Endothelium, Vascular; Methacholine Chloride; Microchemistry; Spectrometry, Fluorescence

14(R), 15(S)-epoxyeicosatrienoic acid (14,15-EET) is a cytochrome P-450 monooxygenase (epoxygenase) metabolite of arachidonic acid (AA). In this study, we have identified a population of specific high affinity binding sites for 14,15-EET in the guinea pig mononuclear (GPM) cells. The results of competition studies showed that 14(R), 15(S)-EET was an effective competing ligand with a Ki of 226.3 nM followed by 11(R), 12(S)-EET, 14(S), 15(R)-EET, 14,15 thia(S)-ET, and 14,15-aza(N)-ET. The binding was sensitive to various protease treatments suggesting that the binding site is protein in nature. Cholera toxin (CT) and dibutyryl cAMP attenuated 14,15-EET binding in GPM cells. Mean binding site density (Bmax), decreased 32.0% and 19.1% by the pretreatment with cholera toxin (200 micrograms/ml) and dibutyryl cAMP (100 nM), respectively, without changing the dissociation constant. A specific protein kinase A (PKA) inhibitor, H-89, but not the PKC inhibitor K252a reversed the down regulation of 14,15-EET receptor binding caused by dibutyryl cAMP in GPM cells. Thus, the results sug-gest that the specific binding site of 14,15-EET in GPM cells be associated with a receptor that could be down regulated through an increase in intracellular cAMP and activation of a PKA signal trans-duction. We propose that the signal transduction mechanism begins with the binding of 14,15-EET to its receptor that leads to increase intracellular cAMP levels and the activation of PKA, and finally, with the down regulation of 14,15-EET receptor binding.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acid; Binding Sites; Binding, Competitive; Bucladesine; Cholera Toxin; Cyclic AMP; Cyclic AMP-Dependent Protein Kinases; Cytochrome P-450 CYP2J2; Cytochrome P-450 Enzyme System; Endopeptidases; Enzyme Activation; Enzyme Inhibitors; Female; Guinea Pigs; Leukocytes, Mononuclear; Oxygenases; Signal Transduction; Tritium

The cytochrome P450-derived epoxyeicosatrienoic acids (EETs) have potent effects on renal vascular reactivity and tubular sodium and water transport; however, the role of these eicosanoids in the pathogenesis of hypertension is controversial. The current study examined the hydrolysis of the EETs to the corresponding dihydroxyeicosatrienoic acids (DHETs) as a mechanism for regulation of EET activity and blood pressure. EET hydrolysis was increased 5- to 54-fold in renal cortical S9 fractions from the spontaneously hypertensive rat (SHR) relative to the normotensive Wistar-Kyoto (WKY) rat. This increase was most significant for the 14,15-EET regioisomer, and there was a clear preference for hydrolysis of 14, 15-EET over the 8,9- and 11,12-EETs. Increased EET hydrolysis was consistent with increased expression of soluble epoxide hydrolase (sEH) in the SHR renal microsomes and cytosol relative to the WKY samples. The urinary excretion of 14,15-DHET was 2.6-fold higher in the SHR than in the WKY rat, confirming increased EET hydrolysis in the SHR in vivo. Blood pressure was decreased 22+/-4 mm Hg (P:<0.01) 6 hours after treatment of SHRs with the selective sEH inhibitor N:, N:'-dicyclohexylurea; this treatment had no effect on blood pressure in the WKY rat. These studies identify sEH as a novel therapeutic target for control of blood pressure. The identification of a potent and selective inhibitor of EET hydrolysis will be invaluable in separating the vascular effects of the EET and DHET eicosanoids.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acids; Blood Pressure; Cytosol; Eicosanoids; Enzyme Inhibitors; Epoxide Hydrolases; Epoxy Compounds; Hydrolysis; Hypertension; Kidney Cortex; Male; Microsomes; Microsomes, Liver; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Rats, Sprague-Dawley; Species Specificity; Urea

We present evidence in astrocytes that 5,6-epoxyeicosatrienoic acid, a cytochrome P450 epoxygenase metabolite of arachidonic acid, may be a component of calcium influx factor, the elusive link between release of Ca2+ from intracellular stores and capacitative Ca2+ influx. Capacitative influx of extracellular Ca2+ was inhibited by blockade of the two critical steps in epoxyeicosatrienoic acid synthesis: release of arachidonic acid from phospholipid stores by cytosolic phospholipase A2 and cytochrome P450 metabolism of arachidonic acid. AAOCF3, which inhibits cytosolic phospholipase A2, blocked thapsigargin-stimulated release of arachidonic acid as well as thapsigargin-stimulated elevation of intracellular free calcium. Inhibition of P450 arachidonic acid metabolism with SKF525A, econazole, or N-methylsulfonyl-6-(2-propargyloxyphenyl)hexanamide, a substrate inhibitor of P450 arachidonic acid metabolism, also blocked thapsigargin-stimulated Ca2+ influx. Nano- to picomolar 5, 6-epoxyeicosatrienoic acid induced [Ca2+]i elevation consistent with capacitative Ca2+ influx. We have previously shown that 5, 6-epoxyeicosatrienoic acid is synthesized and released by astrocytes. When 5,6-epoxyeicosatrienoic acid was applied to the rat brain surface, it induced vasodilation, suggesting that calcium influx factor may also serve a paracrine function. In summary, our results suggest that 5,6-epoxyeicosatrienoic acid may be a component of calcium influx factor and may participate in regulation of cerebral vascular tone.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acid; Astrocytes; Calcium; Cytochrome P-450 Enzyme Inhibitors; Enzyme Inhibitors; Ion Transport; Phospholipases A; Phospholipases A2; Rats; Signal Transduction; Thapsigargin

A common feature of most isolated cell systems is low or undetectable levels of bioactive cytochrome P450. We therefore developed stable transfectants of the renal epithelial cell line, LLCPKcl4, that expressed an active regio- and enantioselective arachidonic acid (AA) epoxygenase. Site-specific mutagenesis was used to convert bacterial P450 BM-3 into an active regio- and stereoselective 14S,15R-epoxygenase (F87V BM-3). In clones expressing F87V BM-3 (F87V BM-3 cells), exogenous AA induced significant 14S,15R-epoxyeicosatrienoic acid (EET) production (241. 82 ng/10(8) cells, >97% of total EETs), whereas no detectable EETs were seen in cells transfected with vector alone. In F87V BM-3 cells, AA stimulated [3H]thymidine incorporation and increased cell proliferation, which was blocked by the tyrosine kinase inhibitor, genistein, by the phosphatidylinositol 3 (PI-3) kinase inhibitors, wortmannin and LY294002, and by the mitogen-activated protein kinase kinase inhibitor, PD98059. AA also induced tyrosine phosphorylation of extracellular signal-regulated kinase (ERK) and PI-3 kinase that was inhibited by the cytochrome P450 BM-3 inhibitor, 17-ODYA. Epidermal growth factor (EGF) increased EET production in F87V BM-3 cells, which was completely abolished by pretreatment with either 17-ODYA or the phospholipase A2 (PLA2) inhibitor, quinacrine. Compared with vector-transfected cells, F87 BM-3 transfected cells demonstrated marked increases in both the extent and sensitivity of DNA synthesis in response to EGF. These changes occurred in the absence of significant differences in EGF receptor expression. As seen with exogenous AA, EGF increased ERK tyrosine phosphorylation to a significantly greater extent in F87V BM-3 cells than in vector-transfected cells. Furthermore, in these control cells, neither 17-ODYA nor quinacrine inhibited EGF-induced ERK tyrosine phosphorylation. On the other hand, in F87V BM-3 cells, both inhibitors reduced ERK tyrosine phosphorylation to levels indistinguishable from that seen in cells transfected with vector alone. These studies provide the first unequivocal evidence for a role for the AA epoxygenase pathway and endogenous EET synthesis in EGF-mediated signaling and mitogenesis and provide compelling evidence for the PLA2-AA-EET pathway as an important intracellular-signaling pathway in cells expressing high levels of cytochrome P450 epoxygenase.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Cytochrome P-450 CYP2J2; Cytochrome P-450 Enzyme System; Epidermal Growth Factor; LLC-PK1 Cells; Mitogens; Oxygenases; Phosphorylation; Second Messenger Systems; Swine; Transfection

We have studied interleukin-1 (IL-1)-stimulated signals and gene expression in mesangial cells (MCs) to identify molecular mechanisms of MC activation, a process characteristic of glomerular inflammation. The JNK1 pathway has been implicated in cell fate decisions, and IL-1 stimulates the Jun N-terminal/stress-activated protein kinases (JNK1/SAPK). However, early postreceptor mechanisms by which IL-1 activates these enzymes remain unclear. Free arachidonic acid (AA) activates several protein kinases, and because IL-1 rapidly stimulates phospholipase A2 (PLA2) activity release AA, IL-1-induced activation of JNK1/SAPK may be mediated by AA release.. MCs were grown from collagenase-treated glomeruli, and JNK/SAPK activity in MC lysates was determined using an immunocomplex kinase assay.. Treatment of MCs with IL-1 alpha induced a time-dependent increase in JNK1/SAPK kinase activity, assessed by phosphorylation of the activating transcription factor-2 (ATF-2). Using similar incubation conditions, IL-1 also increased [3H]AA release from MCs. Pretreatment of MCs with aristolochic acid, a PLA2 inhibitor, concordantly reduced IL-1-regulated [3H]AA release and JNK1/SAPK activity, suggesting that cytosolic AA in part mediates IL-1-induced JNK1/SAPK activation. Addition of AA stimulated JNK1/SAPK activity in a time- and concentration-dependent manner. This effect was AA specific, as only AA and its precursor linoleic acid stimulated JNK1/SAPK activity. Other fatty acids failed to activate JNK1/SAPK. Pretreatment of MCs with specific inhibitors of AA oxidation by cyclooxygenase, lipoxygenase, and cytochrome P-450 epoxygenase had no effect on either IL-1- or AA-induced JNK1/SAPK activation. Furthermore, stimulation of MCs with the exogenous cyclooxygenase-, lipoxygenase-, phosphodiesterase-, and epoxygenase-derived arachidonate metabolites, in contrast to AA itself, did not activate JNK1/SAPK.. We conclude that IL-1-stimulated AA release, in part, mediates stimulation of JNK1/SAPK activity and that AA activates JNK1/SAPK by a mechanism that does not require enzymatic oxygenation. JNK1 signaling pathway components may provide molecular switches that mediate structural rearrangements and biochemical processes characteristic of MC activation and could provide a novel target(s) for therapeutic intervention.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acid; Aristolochic Acids; Calcium-Calmodulin-Dependent Protein Kinases; Cells, Cultured; Dinoprostone; Enzyme Activation; Enzyme Inhibitors; Fatty Acids, Unsaturated; Glomerular Mesangium; Interleukin-1; JNK Mitogen-Activated Protein Kinases; Leukotrienes; Lipid Peroxides; Mitogen-Activated Protein Kinases; Nephritis; Phenanthrenes; Phosphodiesterase Inhibitors; Phospholipases A; Phospholipases A2; Rats; Signal Transduction; Stearic Acids; Tritium; Vasoconstrictor Agents

1. Whole-cell Na+ currents (holding potential, -80 mV; test potential, -30 mV) in rat myocytes were inhibited by 8, 9-epoxyeicosatrienoic acid (8,9-EET) in a dose-dependent manner with 22+/-4% inhibition at 0.5 microM, 48+/-5% at 1 microM, and 73+/-5% at 5 microM (mean +/- S.E.M., n = 10, P<0.05 for each dose vs. control). Similar results were obtained with 5,6-, 11,12-, and 14,15-EETs, while 8,9-dihydroxyeicosatrienoic acid (DHET) was 3-fold less potent and arachidonic acid was 10- to 20-fold less potent. 2. 8,9-EET produced a dose-dependent, hyperpolarized shift in the steady-state membrane potential at half-maximum inactivation (V ), without changing the slope factor. 8,9-EET had no effect on the steady-state activation of Na+ currents. 3. Inhibition of Na+ currents by 8,9-EET was use dependent, and channel recovery was slowed. The effects of 8,9-EET were greater at depolarized potentials. 4. Single channel recordings showed 8,9-EET did not change the conductance or the number of active Na+ channels, but markedly decreased the probability of Na+ channel opening. These results were associated with a decrease in the channel open time and an increase in the channel closed times. 5. Incubation of cultured cardiac myocytes with 1 microM [3H]8,9-EET showed that 25% of the radioactivity was taken up by the cells over a 2 h period, and most of the uptake was incorporated into phospholipids, principally phosphatidylcholine. Analysis of the medium after a 2 h incubation indicated that 86% of the radioactivity remained as [3H]8,9-EET while 13% was converted into [3H]8,9-DHET. After a 30 min incubation, 1-2% of the [3H]8,9-EET uptake by cells remained as unesterified EET. 6. These results demonstrate that cardiac cells have a high capacity to take up and metabolize 8,9-EET. 8,9-EET is a potent use- and voltage-dependent inhibitor of the cardiac Na+ channels through modulation of the channel gating behaviour.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Animals, Newborn; Arachidonic Acid; Cells, Cultured; Heart; Heart Ventricles; Membrane Potentials; Myocardium; Rats; Rats, Sprague-Dawley; Sodium Channels; Structure-Activity Relationship

The epoxyeicosatrienoic acids (EETs) are products of cytochrome P450 epoxygenases that have vasodilatory properties similar to that of endothelium-derived hyperpolarizing factor. The cytochrome P450 isoform CYP2J2 was cloned and identified as a potential source of EETs in human endothelial cells. Physiological concentrations of EETs or overexpression of CYP2J2 decreased cytokine-induced endothelial cell adhesion molecule expression, and EETs prevented leukocyte adhesion to the vascular wall by a mechanism involving inhibition of transcription factor NF-kappaB and IkappaB kinase. The inhibitory effects of EETs were independent of their membrane-hyperpolarizing effects, suggesting that these molecules play an important nonvasodilatory role in vascular inflammation.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Anti-Inflammatory Agents, Non-Steroidal; Carotid Arteries; Cattle; Cell Adhesion; Cell Adhesion Molecules; Cells, Cultured; Coronary Vessels; Cytochrome P-450 CYP2J2; Cytochrome P-450 Enzyme System; DNA-Binding Proteins; Endothelium, Vascular; Humans; Hydroxyeicosatetraenoic Acids; I-kappa B Kinase; I-kappa B Proteins; Mice; Mice, Inbred C57BL; NF-kappa B; NF-KappaB Inhibitor alpha; Oxygenases; Protein Serine-Threonine Kinases; Tumor Necrosis Factor-alpha; Vascular Cell Adhesion Molecule-1

Cytochrome P-450-derived epoxyeicosatrienoic acids (EETs) are avidly incorporated into and released from endothelial phospholipids, a process that results in potentiation of endothelium-dependent relaxation. EETs are also rapidly converted by epoxide hydrolases to dihydroxyeicosatrienoic acid (DHETs), which are incorporated into phospholipids to a lesser extent than EETs. We hypothesized that epoxide hydrolases functionally regulate EET incorporation into endothelial phospholipids. Porcine coronary artery endothelial cells were treated with an epoxide hydrolase inhibitor, 4-phenylchalcone oxide (4-PCO, 20 micromol/l), before being incubated with (3)H-labeled 14,15-EET (14,15-[(3)H]EET). 4-PCO blocked conversion of 14,15-[(3)H]EET to 14,15-[(3)H]DHET and doubled the amount of radiolabeled products incorporated into cell lipids, with >80% contained in phospholipids. Moreover, pretreatment with 4-PCO before incubation with 14,15-[(3)H]EET enhanced A-23187-induced release of radiolabeled products into the medium. In contrast, 4-PCO did not alter uptake, distribution, or release of [(3)H]arachidonic acid. In porcine coronary arteries, 4-PCO augmented 14,15-EET-induced potentiation of endothelium-dependent relaxation to bradykinin. These data suggest that epoxide hydrolases may play a role in regulating EET incorporation into phospholipids, thereby modulating endothelial function in the coronary vasculature.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acid; Arteries; Bradykinin; Cells, Cultured; Chalcone; Chalcones; Coenzyme A Ligases; Coronary Vessels; Drug Synergism; Endothelium, Vascular; Enzyme Inhibitors; Epoxide Hydrolases; Hydroxyeicosatetraenoic Acids; Lipid Metabolism; Phospholipids; Swine; Vasodilation

The cytochrome P450-dependent monoxygenase pathway represents a major route for the metabolism of arachidonic acid (AA) in the kidney. In turn, AA metabolites have been shown to affect renal electrolyte metabolism, including sodium transport. Specifically AA, 20-HETE and 12-HETE inhibit sodium-dependent (Na+-Pi) uptake into renal culture cells, and both 12-HETE and 14,15 EET have been shown to reduce renin release from renal cortical slices. Since the bulk of Pi transport occurs in the proximal tubule (PT), and the PT is a major site of AA metabolism, we studied the effect of AA and several of its metabolites on Na+-Pi uptake into PT-like opossum kidney (OK) cells. Incubation of OK cells in AA (10(-8) M) resulted in 17% inhibition of Pi uptake. Three metabolites of omega-hydroxylation of AA induced significant decreases in Pi uptake: 19R-HETE (10(-8) M) by 36% (P=0.008), 19S-HETE (10(-8) M) by 24% (P=0.002) and 20-COOH-AA (10(-8) M), a metabolite of 20-HETE, by 25% (P<0.0001). 14,15 EET (10(-8) M), a breakdown product of AA by the epoxygenase pathway, had the greatest effect on Pi uptake in OK cells. It decreased Pi uptake by 47% (P < 0.0001). Addition of the P450 inhibitor, 7-ER (10(-8) M), to OK cells resulted in a significant stimulation (28%) of Pi uptake (P=0.016). These results indicate that these AA metabolites have a significant inhibitory effect on Na+-Pi uptake in OK cells.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acid; Biological Transport; Cell Line; Electrolytes; Hydroxyeicosatetraenoic Acids; Ion Transport; Kidney Cortex; Kidney Tubules, Proximal; Opossums; Oxazines; Phosphates; Renin; Sodium

Epoxyeicosatrienoic acids (EETs) are cytochrome P450-derived metabolites of arachidonic acid. They are potent endogenous vasodilator compounds produced by vascular cells, and EET-induced vasodilation has been attributed to activation of vascular smooth muscle cell (SMC) K(+) channels. However, in some cells, EETs activate Ca(2+) channels, resulting in Ca(2+) influx and increased intracellular Ca(2+) concentration ([Ca(2+)](i)). We investigated whether EETs also can activate Ca(2+) channels in vascular SMC and whether the resultant Ca(2+) influx can influence vascular tone. The 4 EET regioisomers (1 micromol/L) increased porcine aortic SMC [Ca(2+)](i) by 52% to 81%, whereas arachidonic acid, dihydroxyeicosatrienoic acids, and 15-hydroxyeicosatetraenoic acid (1 micromol/L) produced little effect. The increases in [Ca(2+)](i) produced by 14,15-EET were abolished by removal of extracellular Ca(2+) and by pretreatment with verapamil (10 micromol/L), an inhibitor of voltage-dependent (L-type) Ca(2+) channels. 14,15-EET did not alter Ca(2+) signaling induced by norepinephrine and thapsigargin. When administered to porcine coronary artery rings precontracted with a thromboxane mimetic, 14,15-EET produced relaxation. However, when administered to rings precontracted with acetylcholine or KCl, 14,15-EET produced additional contractions. In rings exposed to 10 mmol/L KCl, a concentration that did not affect resting ring tension, 14,15-EET produced small contractions that were abolished by EGTA (3 mmol/L) or verapamil (10 micromol/L). These observations indicate that 14,15-EET enhances [Ca(2+)](i) influx in vascular SMC through voltage-dependent Ca(2+) channels. This 14,15-EET-induced increase in [Ca(i)(2+)] can produce vasoconstriction and therefore may act to modulate EET-induced vasorelaxation.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Aorta, Thoracic; Calcium; Calcium Channel Blockers; Cell Membrane Permeability; Cells, Cultured; Chelating Agents; Coronary Vessels; Dose-Response Relationship, Drug; In Vitro Techniques; Intracellular Fluid; Muscle Contraction; Muscle, Smooth, Vascular; Structure-Activity Relationship; Swine; Vasoconstrictor Agents; Vasodilator Agents

Arachidonic acid, but not eicosapentaenoic acid, increased prostaglandin G/H endoperoxide synthase-2 transcription in cultured intestinal epithelial cells. This stimulatory effect on PGHS-2 synthesis was prevented by an AA utilization inhibitor, eicosatetraynoic acid. Specific inhibitors of the cyclooxygenase or the lipoxygenase pathways of AA metabolism did not prevent AA-mediated induction of PGHS-2 synthesis; however, the involvement of cytochrome P450 monoxygenases (CYP450) was indicated as several CYP450 blockers, ketoconazole, miconazole, and metyrapone, inhibited the induction of PGHS-2 mRNA synthesis by AA. This blockade by CYP450 inhibitors could be overcome by the addition of the AA epoxygenase metabolite 14,15-epoxyeicosatrienoic acid (14,15-EET); other EET regio-isomers were unable to elevate PGHS-2 mRNA level. Blockade of protein kinase C with a specific inhibitor, bisindolyl maleimide-1, or translational inhibition of protein kinase C alpha by antisense oligonucleotides reduced PGHS-2 transcription, suggesting the involvement of protein kinase C alpha in the signal transduction pathway.

Topics: 16,16-Dimethylprostaglandin E2; 8,11,14-Eicosatrienoic Acid; Animals; Cell Line; Colforsin; Cyclooxygenase 2; Diclofenac; Epithelial Cells; Intestinal Mucosa; Isoenzymes; Ketoconazole; Metyrapone; Miconazole; Peroxidases; Prostaglandin-Endoperoxide Synthases; Prostaglandins F, Synthetic; Protein Kinase C; Protein Kinase C-alpha; Rats; RNA, Messenger; Signal Transduction; Tetradecanoylphorbol Acetate; Transcription, Genetic

14,15-Epoxyeicosatrienoic acid (EET), a cytochrome P-450 epoxygenase product of arachidonic acid (AA), reduced PGE2 formation by 40-75% in porcine aortic and murine brain microvascular smooth muscle cells. The inhibition was reversed 6-10 h after removal of 14,15-EET from the medium and was regioisomeric specific; 8,9-EET produced a smaller effect, whereas 11,12- and 5,6-EET were ineffective. Although the cells converted 14,15-EET to 14, 15-dihydroxyeicosatrienoic acid (14,15-DHET), 14,15-DHET did not inhibit PGE2 formation, and the 14,15-EET-induced inhibition was potentiated by 4-phenylchalcone oxide, an epoxide hydrolase inhibitor. The inhibition occurred when substrate amounts of AA were used and was not accompanied by enhanced production of other PGs, suggesting an effect on PGH synthase; however, in murine cells, 14, 15-EET did not reduce PGH synthase mRNA or protein. Moreover, the 14, 15-EET-induced decrease in PGE2 production was overcome by increasing the concentration of AA, but not oleic acid (which is not a substrate for PGH synthase). These findings suggest that 14,15-EET competitively inhibits PGH synthase activity in vascular smooth muscle cells. The 14,15-EET-induced inhibition of PGE2 production resulted in potentiation of platelet-derived growth factor-induced smooth muscle cell proliferation, suggesting that the competitive inhibition of PGH synthase by 14,15-EET can affect growth responses in smooth muscle cells.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Aorta; Cell Division; Cells, Cultured; Cerebrovascular Circulation; Dinoprostone; Hydroxyeicosatetraenoic Acids; Microcirculation; Muscle, Smooth, Vascular; Platelet-Derived Growth Factor; Swine

In spite of the large quantities of epoxyeicosatrienoic acids (EEts) released by reproductive tissues, their function has not yet been determined. In order to analyze the influence of epoxygenase products on isolated uterine function, Clotrimazole, a cytochrome P450 inhibitor was used. The drug decreased isolated rat uterine isometric developed tension (IDT) and frequency (FC). 14,15 EEt induced a contractile response when added at 10(11) M, 8,9 EEt and 11,12 EEt produced an increment of IDT when added to 10(-7) M and 5,6 EEt did not modify IDT values. A contractile stimulatory effect was observed when 14,15 EEt (10(-7) M) was added to a tissue bath preparation containing Clotrimazole (20 microM). On the other hand, uterine contractile response to 14,15 EEt addition was partially abolished by indomethacin (10(-6) M), a well known cyclooxygenase inhibitor. Uterine response to 5,6; 8,9 and 11,12 EEts was not modified by indomethacin. This is the first evidence of 14-15 EEt uterotonic properties, possibly exerted in part through the cyclooxygenase pathway.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Clotrimazole; Cyclooxygenase Inhibitors; Cytochrome P-450 Enzyme Inhibitors; Dose-Response Relationship, Drug; Estradiol; Female; In Vitro Techniques; Indomethacin; Isometric Contraction; Ovariectomy; Prostaglandin-Endoperoxide Synthases; Rats; Rats, Wistar; Uterine Contraction

A fluoroimmunoassay (FIA) for 14,15-epoxyeicosatrienoic acid (14,15-EET) and 14,15-dihydroxyeicosatrienoic acid (14,15-DHET), cytochrome P450 epoxygenase products of arachidonic acid, was developed using fluorescence polarization. 14-15-EET was hydrolyzed and analyzed as 14,15-DHET. 14,15-DHET was conjugated to thyroglobulin and a specific antibody was raised in rabbits. Both [3H8]14,15-DHET in radioimmunoassay or fluorescein-labeled 14,15-DHET (14, 15-DHET*) in FIA bound to this antibody and were competitively displaced by 14,15-DHET. The binding activity and cross-reactivity of 14,15-DHET antibody were also studied by RIA compared to FIA. The antibody cross-reacted < or = 1% with 11,12-DHET and 14,15-EET and < 0.1% with other regioisomeric DHETs and arachidonic acid metabolites. The detection limit of 14,15-DHET was 2 pg/0.6 ml by FIA. Using this method, we found that A23187 stimulated the production of 14,15-EET by endothelial cells by angiotensin II stimulated 14,15-EET release from zona glomerulosa cells. The production of 14,15-EET in these samples was confirmed by gas chromatography/mass spectrometry. These studies demonstrate a sensitive and specific FIA for 14,15-EET and 14,15-DHET and that agonists stimulate the release of these eicosanoids in two cell types, bovine coronary artery endothelial cells and bovine zona glomerulosa cells.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Antibodies; Cattle; Cells, Cultured; Cross Reactions; Endothelium, Vascular; Fluoroimmunoassay; Gas Chromatography-Mass Spectrometry; Hydroxyeicosatetraenoic Acids; Rabbits; Radioimmunoassay; Zona Glomerulosa

Epoxyeicosatrienoic acids (EETs) are potent endothelium-derived vasodilators formed from cytochrome P-450 metabolism of arachidonic acid. EETs and their diol products (DHETs) are also avidly taken up by endothelial cells and incorporated into phospholipids that participate in signal transduction. To investigate the possible functional significance of EET and DHET incorporation into cell lipids, we examined the capacity of EETs and DHETs to relax porcine coronary arterial rings and determined responses to bradykinin (which potently activates endothelial phospholipases) before and after incubating the rings with these eicosanoids. 14,15-EET and 11,12-EET (5 mumol/L) produced 75 +/- 9% and 52 +/- 4% relaxation, respectively, of U46619-contracted rings, whereas 8,9-EET and 5,6-EET did not produce significant relaxation. The corresponding DHET regioisomers produced comparable relaxation responses. Preincubation with 14,15-EET, 11,12-EET, 14,15-DHET, and 11,12-DHET augmented the magnitude and duration of bradykinin-induced relaxation, whereas endothelium-independent relaxations to aprikalim and sodium nitroprusside were not potentiated. Pretreatment with 2 mumol/L triacsin C (an inhibitor of acyl coenzyme A synthases) inhibited [3H]14,15-EET incorporation into endothelial phospholipids and blocked 11,12-EET- and 14,15-DHET-induced potentiation of relaxation to bradykinin. Exposure of [3H]14,15-EET-labeled endothelial cells to the Ca2+ ionophore A23187 (2 mumol/L) resulted in a 4-fold increased release of EET and DHET into the medium. We conclude that incorporation of EETs and DHETs into cell lipids results in potentiation of bradykinin-induced relaxation in porcine coronary arteries, providing the first evidence that incorporated EETs and DHETs are capable of modulating vascular function.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; 8,11,14-Eicosatrienoic Acid; Animals; Bradykinin; Cells, Cultured; Coronary Vessels; Endothelium, Vascular; Prostaglandin Endoperoxides, Synthetic; Swine; Thromboxane A2; Vasoconstrictor Agents; Vasodilation

14(R),15(S)-epoxyeicosatrienoic acid (14,15-EET), a cytochrome P-450 monooxygenase (epoxygenase) metabolite of arachidonic acid has been reported to induce adhesion of a monocyte cell line (U-937) to cultured endothelial cells. In this study, we identified a population of specific, high affinity binding sites for 14(R),15(S)-EET in U-937 cell surface with Kd of 13.84 +/- 2.58 nM and Bmax of 3.54 +/- 0.28 pmol/10(6) cells. The specific binding of [3H]-14,15-EET on U-937 cells is more effectively displaced by 14(R),15(S)-EET than the 14(S),15(R)-isomer thus indicating stereospecificity. The binding was sensitive to various protease treatments suggesting the binding site is protein in nature. 14,15-EET binding in U937 cells is attenuated by cholera toxin (CT) and dibutyryl cAMP. Mean binding site density (Bmax) decreased 31.61% and 34.8% by the pretreatment with cholera toxin (200 micrograms/ml) and dibutyryl cAMP (300 nM), respectively, without affecting the dissociation constant. Under similar conditions, pertussis toxin (20-200 ng/ml) was less effective as compared to CT and dibutyryl cAMP. The down regulation of 14,15-EET binding caused by dibutyryl cAMP in U-937 cell was reversed by a specific protein kinase A (PKA) inhibitor, H-89, but not by the PKC inhibitor K252a. Thus, the results suggest that the specific binding site of 14,15-EET in U-937 cells is associated with a receptor that could be down regulated through an increase in intracellular cAMP and activation of a PKA signal transduction mechanism. We propose that the signal transduction mechanism of 14,15-EET begins with the binding of the receptor, which leads to the increase of intracellular cAMP levels and the activation of PKA, and finally with the down regulation of 14,15-EET receptor binding.

Topics: 8,11,14-Eicosatrienoic Acid; Binding Sites; Bucladesine; Cell Adhesion; Cell Line; Cholera Toxin; Cyclic AMP; Cyclic AMP-Dependent Protein Kinases; Down-Regulation; Enzyme Activation; Enzyme Inhibitors; Humans; Isoquinolines; Monocytes; Pertussis Toxin; Protein Binding; Receptors, Cell Surface; Signal Transduction; Stereoisomerism; Sulfonamides; Virulence Factors, Bordetella

The present study on the newborn pig cerebral microcirculation determined the vasoactive properties of epoxyeicosatrienoic acids (EETs) and the contributions of prostaglandin cyclooxygenase to these properties. Pial arterioles of anesthetized piglets were observed through closed cranial windows, EETs were applied topically, and artificial cerebrospinal fluid from beneath the cranial windows was collected for the determination of adenosine 3',5'-cyclic monophosphate and 6-ketoprostaglandin F1 alpha. EETs caused dilation of pial arterioles and increased adenosine 3',5'-cyclic monophosphate. 5,6-EET produced a dose-dependent dilation at 10(-8) M and above, whereas 10(-6) M was required for 8,9-EET, 11,12-EET, and 14,15-EET. Indomethacin abolished pial arteriolar dilation to the EETs. However, EETs did not increase cortical 6-ketoprostaglandin F1 alpha concentration. Treatment of indomethacin-treated piglets with iloprost (10(-12) M topically) restored dilation to 5,6-EET. Neither isoproterenol nor sodium nitroprusside allowed vasodilation to 5,6-EET in indomethacin-treated piglets. Therefore, in the newborn pig cerebral microvasculature. EETs are potent vasodilators and prostacyclin-receptor agonists are necessary to allow this dilation to occur.

Topics: 6-Ketoprostaglandin F1 alpha; 8,11,14-Eicosatrienoic Acid; Animals; Animals, Newborn; Arterioles; Carbon Dioxide; Cyclic AMP; Dose-Response Relationship, Drug; Iloprost; Indomethacin; Muscle, Smooth, Vascular; Nitroprusside; Pia Mater; Structure-Activity Relationship; Swine; Vasodilation; Vasodilator Agents

The relationship between arachidonic acid (AA) mobilization and transcription of immediate-early genes, particularly of prostaglandin G/H synthase-2 (PGHS-2), in intestinal crypt epithelial cells was analyzed. PGHS-2 mRNA and protein synthesis were stimulated by its own substrate, AA; actinomycin D, a transcription inhibitor, prevented the AA-induced increase in PGHS-2 mRNA. Eicosatetraynoic acid, an inhibitor of AA utilization, significantly reduced PGHS-2 mRNA synthesis elicited by AA. Inhibitors of cytochrome P450 monoxygenases, ketoconazole and miconazole, also prevented PGHS-2 mRNA synthesis in a dose-dependent manner. Phenyl chalcone oxide, an epoxide hydrolase inhibitor, potentiated AA-induced PGHS-2 mRNA synthesis. Of the four regioisomers of arachidonic acid epoxides, only 14,15-epoxyeicosatrienoic acid elicited the expression of PGHS-2 in intestinal crypt epithelial cells. This is the first direct evidence of stimulation of an immediate-early gene product, specifically PGHS-2, by an AA epoxygenase metabolite, 14,15-epoxyeicosatrienoic acid, as well as of a heterologous regulation of PGHS-2 synthesis by these monoxygenase products.

Topics: 5,8,11,14-Eicosatetraynoic Acid; 8,11,14-Eicosatrienoic Acid; Animals; Aryl Hydrocarbon Hydroxylases; Cell Line; Cyclooxygenase 2; Cytochrome P450 Family 2; Dactinomycin; Gene Expression Regulation, Enzymologic; Intestinal Mucosa; Isoenzymes; Isomerism; Kinetics; Mixed Function Oxygenases; Oxygenases; Prostaglandin-Endoperoxide Synthases; Rats; RNA, Messenger; Transcription, Genetic

1. Epoxyeicosatrienoic acids (EETs) have been described as endothelium-derived hyperpolarizing factors (EDHFs), based on their stimulatory effects on smooth muscle K+ channels. In order to reveal a putative autocrine effect of EETs on endothelial channels, we have studied the effects of the four EET regioisomers (5,6-EET, 8,9-EET, 11,12-EET and 14,15-EET) on the high-conductance, Ca(2+)-dependent K+ (BKCa) channel recorded in inside-out patches of primary cultured pig coronary artery endothelial cells. Currents were recorded in the presence of either 500 nm or 1 microM free Ca2+ on the cytosolic side of the membrane. 2. In 81% of experiments, EETs at < 156 nM, applied on the cytosolic side of the membrane, transiently increased BKCa channel open state probability (PO) without affecting its unitary conductance, thus providing evidence for direct action of EETs, without involvement of a cytosolic transduction pathway. 3. The four EET regioisomers appeared to be equally active, multiplying the BKCa channel PO by a mean factor of 4.3 +/- 0.6 (n = 15), and involving an increase in the number and duration of openings. 4. The EET-induced increase in BKCa channel activity was more pronounced with low initial PO. When the BKCa channel was activated by 500 nM Ca2+, application of EETs increased the initial PO value of below 0.1 by a factor of 5. When the channel was activated by 1 microM Ca2+, application of EETs increased the initial PO value by a factor of 3. 5. Our results show that EETs potentiate endothelial BKCa channel activation by Ca2+. The autocrine action of EETs on endothelial cells, which occurs in the same concentration range as their action on muscle cells, should therefore fully participate in the vasoactive effects of EETs, and thus be taken into account when considering their putative EDHF function.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Calcium; Cells, Cultured; Coronary Vessels; Endothelium, Vascular; Membrane Potentials; Potassium Channels; Swine

Arachidonic acid is converted to epoxyeicosatrienoic acids (EETs) by cytochrome P450 monooxygenases. EETs produce arterial vasodilatation, and recent evidence suggests that they are endothelium-derived hyperpolarizing factors. In porcine coronary arteries contracted with a thromboxane mimetic agent, we find that relaxation is rapidly initiated by exposure to 14,15-EET. The relaxation slowly increases in magnitude, resulting in a response which is sustained for more than 10 min. Cultured porcine aortic smooth muscle cells rapidly take up [3H]14,15-EET. After 3 min, radioactivity is present in neutral lipids, phosphatidylcholine, and phosphatidylinositol. The cells also convert 14,15-EET to 14,15-dihydroxyeicosatrienoic acid (14,15-DHET), and some DHET is detected in the medium after only 1 min of incubation. Like 14,15-EET, 14,15-DHET produces relaxation of the contracted coronary artery rings. These findings suggest that the incorporation into phospholipids and conversion to 14,15-DHET can occur at a rate that is fast enough to modulate the vasorelaxation produced by 14,15-EET.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acid; Arteries; Cytochrome P-450 Enzyme System; Hydroxyeicosatetraenoic Acids; Muscle Relaxation; Muscle, Smooth, Vascular; Phospholipids; Swine

Topics: 8,11,14-Eicosatrienoic Acid; Arachidonic Acids; Calcimycin; Cytochrome P-450 Enzyme System; Female; Humans; Hydroxyeicosatetraenoic Acids; Organ Culture Techniques; Placenta; Pregnancy; Reference Values

Brain parenchymal tissue metabolizes arachidonic acid (AA) via the cytochrome P450 (P450) epoxygenase to epoxyeicosatrienoic acids (EETs). EETs dilate cerebral arterioles and enhance K+ current in vascular smooth muscle cells from large cerebral arteries. Because of the close association between astrocytes and the cerebral microcirculation, we hypothesized that brain epoxygenase activity originates from astrocytes. This study was designed to identify and localize an AA epoxygenase in rat brain astrocytes. We also tested the effect of EETs on whole-cell K+ current in rat cerebral microvascular smooth muscle cells.. A functional assay was used to demonstrate endogenous epoxygenase activity of intact astrocytes in culture. Oligonucleotide primers derived from the sequence of a known hepatic epoxygenase, P450 2C11, were used in reverse transcription/polymerase chain reaction of RNA isolated from cultured rat astrocytes. The appropriate size reverse transcription/polymerase chain reaction product was cloned into a plasmid vector and sequenced. A polyclonal peptide antibody was raised against P450 2C11 and used in Western blotting and immunocytochemical staining of cultured astrocytes. A voltage-clamp technique was used to test the effect of EETs on whole-cell K+ current recorded from rat cerebral microvascular muscle cells.. Based on elution time of known standards and inhibition by miconazole, an inhibitor of P450 AA epoxygenase, cultured astrocytes produce 11,12- and 14,15-EETs when incubated with AA. The sequence of a cDNA derived from RNA isolated from cultured rat astrocytes was 100% identical to P450 2C11. Immunoreactivity to glial fibrillary acidic protein, a marker for astrocytes, colocalized with 2C11 immunoreactivity in double immunochemical staining of cultured astrocytes. EETs enhanced outward K+ current in muscle cells from rat brain microvessels.. Our results demonstrate that a P450 2C11 mRNA is expressed in astrocytes and may be responsible for astrocyte epoxygenase activity. Given the vasodilatory effect of EETs, our findings suggest a role for astrocytes in the control of cerebral microcirculation mediated by P450 2C11-catalyzed conversion of AA to EETs. The mechanism of EET-induced dilation of rat cerebral microvessels may involve activation of K+ channels.

Topics: 8,11,14-Eicosatrienoic Acid; Amino Acid Sequence; Animals; Animals, Newborn; Antibodies; Aryl Hydrocarbon Hydroxylases; Astrocytes; Base Sequence; Blotting, Southern; Blotting, Western; Cells, Cultured; Cerebral Cortex; Cerebrovascular Circulation; Cloning, Molecular; Cytochrome P-450 CYP2J2; Cytochrome P-450 Enzyme System; DNA Primers; DNA, Complementary; Immunohistochemistry; Liver; Membrane Potentials; Microcirculation; Molecular Sequence Data; Muscle, Smooth, Vascular; Oxygenases; Patch-Clamp Techniques; Peptide Fragments; Polymerase Chain Reaction; Potassium Channels; Rats; Rats, Sprague-Dawley; Steroid 16-alpha-Hydroxylase; Steroid Hydroxylases

Cytochrome P450BM-3 catalyzes NADPH-dependent metabolism of arachidonic acid to nearly enantiomerically pure 18(R)-hydroxyeicosatetraenoic acid and 14(S), 15(R)-epoxyeicosatrienoic acid (80 and 20% of total products, respectively). P450BM-3 oxidizes arachidonic acid with a rate of 3.2 +/- 0.4 micromol/min/nmol at 30 degrees C, the fastest ever reported for an NADPH-dependent, P450-catalyzed reaction. Fatty acid, oxygen, and NADPH are utilized in an approximately 1:1:1 molar ratio, demonstrating efficient coupling of electron transport to monooxygenation. Eicosapentaenoic and eicosatrienoic acids, two arachidonic acid analogs that differ in the properties of the C-15-C-18 carbons, are also actively metabolized by P450BM-3 (1.4 +/- 0.2 and 2.9 +/- 0.1 micromol/min/nmol at 30 degrees C, respectively). While the 17,18-olefinic bond of eicosapentaenoic acid is epoxidized with nearly absolute regio- and stereochemical selectivity to 17(S),18(R)-epoxyeicosatetraenoic acid (>/=99% of total products, 97% optical purity), P450BM-3 is only moderately regioselective during hydroxylation of the eicosatrienoic acid omega-1, omega-2, and omega-3 sp3 carbons, with 17-, 18-, and 19-hydroxyeicosatrienoic acid formed in a ratio of 2.4:2.2:1, respectively. Based on the above and on a model of arachidonic acid-bound P450BM-3, we propose: 1) the formation by P450BM-3 of a single oxidant species capable of olefinic bond epoxidation and sp3 carbon hydroxylation and 2) that product chemistry and, thus, catalytic outcome are critically dependent on active site spatial coordinates responsible for substrate binding and productive orientation between heme-bound active oxygen and acceptor carbon bond(s).

Topics: 8,11,14-Eicosatrienoic Acid; Arachidonic Acid; Bacterial Proteins; Chromatography, High Pressure Liquid; Cytochrome P-450 Enzyme System; Fatty Acids, Unsaturated; Hydroxyeicosatetraenoic Acids; Mass Spectrometry; Mixed Function Oxygenases; Models, Molecular; NADP; NADPH-Ferrihemoprotein Reductase; Oxidation-Reduction; Plasmids; Spectrophotometry, Atomic; Stereoisomerism

Cytochrome P450 (P450) monooxygenases catalyze the epoxidation of arachidonic acid to form epoxyeicosatrienoic acids, which modulate bronchial smooth muscle tone and airway transepithelial ion transport. We recently described a new human P450 arachidonic acid epoxygenase (CYP2J2) and the corresponding rat homologue (CYP2J3). Northern analysis of lung RNA using CYP2J cDNA probes demonstrated that CYP2J2 and CYP2J3 mRNAs were expressed in the lung. Immunoblotting of microsomal fractions prepared from human and rat lungs using a polyclonal antibody raised against recombinant human CYP2J2 revealed a single 56-kDa band confirming abundant pulmonary CYP2J2 and CYP2J3 protein expression. Immunohistochemical analysis of formalin-fixed paraffin-embedded human and rat lung sections using the anti-human CYP2J2 IgG and avidin/biotin/peroxidase detection showed that CYP2J proteins were primarily expressed in ciliated epithelial cells lining the airway. Prominent staining was also noted in nonciliated airway epithelial cells, bronchial and pulmonary vascular smooth muscle cells, pulmonary vascular endothelium, and alveolar macrophages, whereas less intense staining was noted in alveolar epithelial cells. Endogenous epoxyeicosatrienoic acids were detected in both human and rat lung using gas chromatography/mass spectrometry, thus providing direct evidence for the in vivo human and rat pulmonary P450 metabolism of arachidonic acid. Based on these data, we conclude that CYP2J2 and CYP2J3 are abundant pulmonary arachidonic acid epoxygenases and that CYP2J products, the epoxyeicosatrienoic acids, are endogenous constituents of human and rat lung. In addition to known effects on airway smooth muscle tone and transepithelial electrolyte transport, the localization of CYP2J proteins to vascular smooth muscle and endothelium suggests that epoxyeicosatrienoic acids may also be involved in the modulation of pulmonary vascular tone.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acid; Blotting, Northern; Cytochrome P-450 Enzyme System; Endothelium, Vascular; Gas Chromatography-Mass Spectrometry; Humans; Immunoblotting; Immunohistochemistry; Isoenzymes; Lung; Macrophages, Alveolar; Muscle, Smooth, Vascular; Rats

The present study examined the effects of 11,12- and 14,15-epoxyeicosatrienoic acids (EETs) on the diameter of small renal arteries of the rat and assessed their action on K(+)-channel activity in vascular smooth muscle (VSM) cells isolated from these vessels. The R,S-isomer of 11,12-EET (1, 10, and 100 nM) increased the diameter of small renal arteries preconstricted with phenylephrine; however, the S,R-isomer was inactive. Both the R,S- and S,R-isomers of 14,15-EET had little effect on the diameter of these vessels even at a high concentration (100 nM). The vasodilator effect of 11(R),12(S)-EET was attenuated by tetraethylammonium (TEA, 1 mM) and iberiotoxin (100 nM), selective inhibitors of the large-conductance Ca(2+)-activated K+ (KCa) channel. In contrast, apamin (100 nM) and 4-aminopyridine (2 mM), which are inhibitors of other types of K+ channels, had no effect on the vasodilatory effect of 11,12-EET. In patch-clamp experiments, 100 nM racemic 11,12-EET increased outward K+ currents in VSM cells. Addition of the R,S-isomer or racemic 11,12-EET (1-100 nM), but not the S,R-isomer, increased the activity of KCa channel recorded from renal VSM cells with cell-attached patches. However, racemic EET had no effect on this channel when added to the internal (inside-out) or external (outside-out) face of excised membrane patches. These results suggest that 11,12-EET is a potent dilator of small renal arteries and that the R,S-isomer is the active enantiomer. The vasodilator effect of 11,12-EET appears to involve activation of KCa channel.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Calcium; Electric Conductivity; Muscle Tonus; Muscle, Smooth, Vascular; Patch-Clamp Techniques; Potassium Channels; Rats; Rats, Sprague-Dawley; Renal Artery; Stereoisomerism; Vasoconstriction

Human granulosa-luteal cells cultured in the presence of arachidonic acid produced low levels of the epoxygenase metabolite 14,15-epoxy-5,8,11-(Z,Z,Z)-eicosatrienoic acid (14,15-EpETrE) as determined by HPLC analysis and gas chromatography mass spectrometry. When authentic 14,15-[3H]EpETrE was incubated with these cells in the absence of serum it was metabolised initially to the dihydroxy derivative (14,15-dihydroxy-5,8,11-eicosatrienoic acid, 14,15-DiHETrE) and subsequently to a number of more polar metabolites as determined by HPLC. Fetal calf serum protected 14,15-EpETrE from metabolism for at least 2 h. A similar pattern of metabolism was obtained when 14,15-[3H]EpETrE was incubated with a human choriocarcinoma cell line (BeWo). Microsomes from this cell line converted arachidonic acid to a large number of radioactive metabolites including 14,15-DiHETrE and 11,12-DiHETrE although there was no evidence for the parent epoxides. These results extend earlier findings that human reproductive tissues produce epoxygenase metabolites, and demonstrate the rapid metabolism of these compounds by intact cells in the absence of serum.

Topics: 8,11,14-Eicosatrienoic Acid; Arachidonic Acid; Blood; Cells, Cultured; Chromatography, High Pressure Liquid; Culture Media; Female; Gas Chromatography-Mass Spectrometry; Granulosa Cells; Humans; Molecular Structure; Tumor Cells, Cultured

Epoxyeicosatrienoic acids (EETs) are eicosanoids synthesized from arachidonic acid by the cytochrome P450 eposygenase pathway. The present studies demonstrate that 8,9-, 11,12-, and 14,15-EET are rapidly taken up by porcine aortic smooth muscle cells. About half of the uptake is incorporated into phospholipids, and saponification indicates that most of this remains in the form of EET. The EETs also are converted to the corresponding dihydroxyeicosatrienoic acids (DHETs) and during prolonged incubations, additional metabolites that do not retain the EET carboxyl group are formed. Most of these products are released into the medium. However, some DHET and metabolites less polar than EET are incorporated into the phospholipids, and a small amount of unesterified EET is also present in the cells. The incorporation of 14,15-EET and its conversion to DHET did not approach saturation until the concentration exceeded 10-20 microM, indicating that vascular smooth muscle has a large capacity to utilize this EET. These findings suggest that certain vasoactive effects of EETs may be due to their incorporation by smooth muscle cells. Furthermore, through conversion to DHET and other oxidized metabolites, smooth muscle apparently has the capacity to inactivate EETs that are either formed in or penetrate into the vascular wall.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Aorta; Cell Division; Cells, Cultured; Chromatography, High Pressure Liquid; Endothelium, Vascular; Gas Chromatography-Mass Spectrometry; Hydroxyeicosatetraenoic Acids; Kinetics; Muscle, Smooth, Vascular; Phospholipids; Swine; Tritium

Phospholipase A2 (Naja mocambique) catalyzed release of epoxyeicosatrienoic acids (EETs) and 20-hydroxyeicosatetraenoic acid (20-HETE) from phospholipids of isolated human platelets. The amount of EETs released by phospholipase A2 measured by gas chromatography/mass spectrometry (GC/MS) was 4.3 +/- 0.9 pmol/10(6) platelets. No EETs were detected when phospholipase A2 was omitted from the incubations. The relative abundance of EET isomers (14,15-EET, 11,12-EET, 8,9-EET, and 5,6-EET) from human platelets was 5.4:4.5:3.7:1, respectively, as established by a new method based on particle-beam liquid chromatography/mass spectrometry (LC/MS). Fractionation of platelet phospholipids by normal-phase high-performance liquid chromatography followed by hydrolysis and GC/MS analyses indicated that the amount of EETs was highest in fractions containing phosphatidylinositol and phosphatidylserine (142 and 61 pmol/nmol of phosphorus, respectively) while low in phosphatidylcholine and phosphatidylethanolamine (19 and 11 pmol/nmol of phosphorus, respectively). The majority of EETs associated with phosphatidylcholine was found in fractions containing 1-O-alkylphosphatidylcholine. Human platelet phospholipids also released 20-HETE on phospholipase treatment (9.7 +/- 1.6 fmol/10(5) cells) and at least three other HETEs, one of which was tentatively identified as 16-HETE. Activation of human platelets by thrombin or platelet-activating factor released 5 to 7 fmol EET/10(6) cells. Receptor-mediated hydrolysis of phospholipids containing EETs and 20-HETE may play a role in stimulus-response coupling in platelets.

Topics: 8,11,14-Eicosatrienoic Acid; Arachidonic Acid; Blood Platelets; Chromatography, High Pressure Liquid; Cytochrome P-450 Enzyme System; Gas Chromatography-Mass Spectrometry; Humans; Hydroxyeicosatetraenoic Acids; Phospholipids

Topics: 8,11,14-Eicosatrienoic Acid; Blood Platelets; Gas Chromatography-Mass Spectrometry; Humans; Mass Spectrometry; Phospholipids

Topics: 8,11,14-Eicosatrienoic Acid; Amiloride; Animals; Biological Transport; Cell Line; Epithelium; Kidney; Rubidium; Rubidium Radioisotopes; Structure-Activity Relationship

Epoxyeicosatrienoic acids (EETs), normally present in brain and blood, appear to be released from atherosclerotic vessels in large amounts. Once intravascular, EETs can constrict renal arteries in vivo and dilate cerebral and coronary arteries in vitro. Whether EETs in blood will alter cerebral blood flow (CBF) in vivo is unknown. In the present study, the chemical synthesis of four EET regioisomers was optimized, and their identity and structural integrity established by chromatographic and mass spectral methods. The chemically labile EETs were converted to a sodium salt, complexed with albumin, and infused into anesthetized rats via the common carotid. The objective was to test whether sustained, high levels of intravascular EETs alter CBF. The CBF (cortical H2 clearance) was measured before and 30 min after the continuous infusion of 14,15- (n = 5), 11,12- (n = 5), 8,9- (n = 7) and 5,6-EET (unesterified or as the methyl ester, n = 5 for each). Neither the CBF nor the systemic blood pressure was affected by EETs. Because the infusions elevated the plasma concentrations of EETs about 700-fold above normal levels (1.0 nM), it is unlikely that EETs released from atherosclerotic vessels will alter CBF.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Cerebrovascular Circulation; Chromatography, High Pressure Liquid; Gas Chromatography-Mass Spectrometry; Infusions, Intravenous; Male; Rats; Rats, Wistar

Our previous studies have shown that 14,15-epoxyeicosatrienoic acid (14,15-EET) is a major product of arachidonic acid metabolism in astrocytes. The purpose of this study was to investigate cellular regulation of 14,15-EET incorporation, distribution, and metabolism in primary cultures of rat brain cortical astrocytes. Incorporation of 14,15-EET into astrocytes was lower (93,390 +/- 11,121 dpm/5 x 10(6) cells) than incorporation of 8,9-EET (226,500 +/- 5,567 dpm/5 x 10(6) cells) and arachidonic acid (321,600 +/- 1,200 dpm/5 x 10(6) cells). 14,15-EET was distributed in the order neutral lipids and free fatty acids (solvent front) >> phosphatidylcholine (PC) > phosphatidylinositol (PI) > phosphatidylethanolamine. In contrast, 8,9-EET and arachidonic acid were exclusively incorporated into PC. During incubation, astroglial epoxide hydrolase selectively metabolized 14,15-EET, but not 8,9-EET, to its vic-diol. Although 4-phenylchalcone oxide, a potent inhibitor of epoxide hydrolase, completely inhibited 14,15-EET metabolism, a large amount of cell-incorporated radioactivity remained as free 14,15-EET. Long-term exposure of astrocytes to 4 beta-phorbol 12-myristate 13-acetate (4 beta-PMA) resulted in a time-dependent incorporation of 14,15-EET into PI but not in control cells exposed to 4 alpha-phorbol 12,13-didecanoate. PKC down-regulation completely inhibited epoxide hydrolase metabolism of 14,15-EET. Following recovery of down-regulated PKC, 1 week after treatment with 4 beta-PMA, astrocytes regained their normal pattern of low incorporation of 14,15-EET. Protein kinase C (PKC) inhibition by staurosporine enhanced 14,15-EET incorporation without affecting its metabolism to 14,15-dihydroxyeicosatrienoic acid.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acid; Astrocytes; Cells, Cultured; Chromatography, High Pressure Liquid; Phosphatidylinositols; Phospholipases; Phospholipases A; Phospholipids; Protein Kinase C; Rats; Rats, Sprague-Dawley

In the present study, the regio- and stereoselective epoxidation of arachidonic acid by cytochromes P450 2C8 and 2C9, two members of the CYP2C gene subfamily expressed in human liver, was determined. Purified P450 isozymes, reconstituted with NADPH:P450 oxidoreductase, cytochrome b5 and lipid, or microsomes isolated from human liver, were incubated with [1-14C]-arachidonic acid. For regioselective analysis, the epoxide metabolites formed, 14,15-, 11,12- and 8,9-epoxyeicosatrienoic acids (EETs), were resolved by reverse-phase high-performance liquid chromatography. P450 2C8 produces only the 14,15- and 11,12-EETs in a 1.25:1.00 ratio. The two epoxides represent 68% of the total metabolites. P450 2C9 produces 14,15-, 11,12- and 8,9-EETs in a 2.3:1.0:0.5 ratio. The three epoxides represent 69% of the total metabolites. Neither P450 isoform catalyzes the formation of 5,6-EET. For chiral analysis, the two major epoxide metabolites, 14,15- and 11,12-EETs, were derivatized to methyl and pentafluorbenzyl esters, respectively. Enantiomers of 14,15- and 11,12-EET esters were subsequently resolved on Chiralcel OB and OD columns (J.T. Baker, Phillipsburg, PA), respectively. Both P450 2C8 and 2C9 are stereoselective at the 14,15- position, preferentially producing 14(R), 15(S)-EET with 86.2% and 62.5% selectivity, respectively. Both enzymes are also stereoselective at the 11,12-position but have the opposite selectivity. P450 2C8 is 81.1% selective for 11(R), 12(S)-EET; P450 2C9 is 69.4% selective for the 11(S), 12(R)-EET. Immunoinhibition studies performed with anti-2C9 immunoglobulin G (which also reacts with P450 2C8) and hepatic microsomes indicate that these two P450s are important arachidonic acid epoxygenases in human liver.

Topics: 8,11,14-Eicosatrienoic Acid; Amino Acid Sequence; Animals; Arachidonic Acid; Aryl Hydrocarbon Hydroxylases; Cytochrome P-450 Enzyme System; Humans; In Vitro Techniques; Male; Microsomes, Liver; Molecular Sequence Data; Rabbits; Stereoisomerism; Steroid 16-alpha-Hydroxylase; Steroid Hydroxylases

Epoxyeicosatrienoic acids (EETs) are arachidonic acid metabolites formed endogenously via the cytochrome P450 pathway in rat, rabbit, and human kidney. We characterized the effects of the four regioisomeric EETs on ion transport in the renal epithelial cell line, LLC-PK1. Among the EETs, 14,15-EET was the most potent inhibitor of 86Rb uptake. Its effect was concentration-dependent (IC50 = 75 nM) and stereoselective to the 14S, 15R-EET. Experiments measuring 14,15-EET-induced 86Rb uptake inhibition in the presence of inhibitors of Na(+)-K(+)-ATPase activity (ouabain), Na(+)-K(+)-Cl- cotransporter (furosemide), and Na(+)-H+ exchanger (amiloride) suggested that 14,15-EET inhibits ion transport via an amiloride-sensitive mechanism. These results, together with previous reports demonstrating their endogenous production in the kidney, suggest an important role for EETs, specifically 14,15-EET, in the regulation of ion and water reabsorption in the kidney and implicate their function in renal pathophysiology.

Topics: 8,11,14-Eicosatrienoic Acid; Amiloride; Animals; Cell Line; Dose-Response Relationship, Drug; Epithelial Cells; Epithelium; Furosemide; Ion Transport; Kidney Tubules, Proximal; Ouabain; Rats; Rubidium Radioisotopes

The renal metabolism of arachidonic acid (AA) was compared in male and female prehypertensive Dahl salt-sensitive (SS/Jr) and salt-resistant (SR/Jr) rats maintained on a low- (0.3%) sodium chloride diet. Renal cortical microsomes incubated with AA produced 20-hydroxyeicosatetraenoic acid (20-HETE), 14,15- and 11,12-epoxyeicosatrienoic acids, and a new metabolite of AA, 11,12-epoxy-20-hydroxyeicosatrienoic acid. The production of 20-HETE was similar in cortical microsomes of female SS/Jr and SR/Jr rats maintained on a low-salt diet (72 +/- 5 vs. 66 +/- 3 pmol.min-1.mg protein-1); however, the formation of epoxygenase metabolites was significantly less in SS/Jr than in SR/Jr rats (45 +/- 2 vs. 70 +/- 3 pmol.min-1.mg protein-1). Outer medullary microsomes produced primarily 20-HETE, and the formation of this compound was significantly lower in SS/Jr than in SR/Jr female rats fed a low-salt diet (8 +/- 2 vs. 18 +/- 3 pmol.min-1.mg protein-1). Renal papillary microsomes produced prostaglandin E2 and F2 alpha, and the formation of these compounds was similar in female SS/Jr and SR/Jr rats fed a low-salt diet. Similar differences in the metabolism of AA by P-450 were observed in microsomes prepared from the renal cortex and outer medulla of male SS/Jr and SR/Jr rats. These results indicate that the renal metabolism of AA by P-450 is altered in prehypertensive Dahl SS/Jr rats; however, the functional significance of this system in resetting renal function and in the development of hypertension in this model remains to be established.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acid; Chromatography, High Pressure Liquid; Cytochrome P-450 Enzyme System; Drug Resistance; Female; Gas Chromatography-Mass Spectrometry; Hydroxyeicosatetraenoic Acids; Hypertension; Kidney; Male; Prostaglandins; Rats; Rats, Inbred Strains; Sodium Chloride

The present study evaluated the effects of cytochrome P-450 inhibitors on the response of the renal microvasculature to changes in renal perfusion pressure and on autoregulation of glomerular capillary pressure using the rat juxtamedullary nephron microvascular preparation perfused in vitro with a cell-free perfusate containing 5% albumin. The basal diameters of the proximal and distal afferent arterioles averaged 28 +/- 1 (n = 32) and 18 +/- 1 micron (n = 23), respectively, at a control perfusion pressure of 80 mmHg. The diameters of these vessels decreased by 8% when perfusion pressure was elevated from 80 to 160 mmHg. After addition of cytochrome P-450 inhibitors (either 17-octadecynoic acid, 20 microM; 7-ethoxyresorufin, 10 microM; or miconazole, 20 microM) to the perfusate, the diameters of the proximal and distal afferent arterioles increased by 6% in response to the same elevation in perfusion pressure. Control glomerular capillary pressure averaged 43 +/- 1 mmHg (n = 32) at a renal perfusion pressure of 80 mmHg and increased by only 9 +/- 1 mmHg when perfusion pressure was elevated to 160 mmHg. Autoregulation of glomerular capillary pressure was impaired after addition of the cytochrome P-450 inhibitors, and it increased by 18 +/- 2 mmHg when perfusion pressure was varied over the same range. These results indicate that cytochrome P-450 inhibitors attenuate the vasoconstrictor response of afferent arterioles to elevations in renal perfusion pressure and impair autoregulation of glomerular capillary pressure, suggesting a possible role for cytochrome P-450 metabolites of arachidonic acid in these responses.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acid; Arterioles; Cytochrome P-450 Enzyme Inhibitors; Fatty Acids, Unsaturated; Hydroxyeicosatetraenoic Acids; In Vitro Techniques; Kidney; Kidney Cortex; Miconazole; Microsomes; Muscle, Smooth, Vascular; Oxazines; Perfusion; Rats; Rats, Sprague-Dawley; Renal Circulation

Metabolites of arachidonic acid regulate several physiological processes, including vascular tone. The purpose of this study was to determine which metabolites of arachidonic acid are produced by bovine coronary arteries and which may regulate coronary vascular tone. Arachidonic acid induced a concentration-related, endothelium-dependent relaxation [one-half maximum effective concentration (EC50) of 2 x 10(-7) M and a maximal relaxation of 91 +/- 2% at 10(-5) M] of bovine coronary arteries that were contracted with U-46619, a thromboxane mimetic. The concentration of 6-ketoprostaglandin F1 alpha (6-keto-PGF1 alpha), a metabolite of prostaglandin I2 (PGI2), increased from 82 +/- 6 to 328 +/- 24 pg/ml with arachidonic acid (10(-5) M). Treatment with the cyclooxygenase inhibitor indomethacin attenuated arachidonic acid-induced relaxations by approximately 50% and blocked the synthesis of 6-keto-PGF1 alpha. PGI2 caused a concentration-related relaxation (EC50 of 10(-8) M and a maximal relaxation of 125 +/- 11% at 10(-7) M). BW755C, a cyclooxygenase and lipoxygenase inhibitor, inhibited arachidonic acid-induced relaxation to the same extent as indomethacin. When vessels were treated with both indomethacin and BW755C, the inhibition of relaxation was the same as either inhibitor alone. SKF 525a, a cytochrome P-450 inhibitor, reduced arachidonic acid-induced relaxation by approximately 50%. When SKF 525a was given in combination with indomethacin, the relaxation by arachidonic acid was almost completely inhibited. SKF 525a inhibited the synthesis of epoxyeicosatrienoic acids (EETs).(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acid; Arteries; Cattle; Coronary Vessels; Epoprostenol; Vasodilation

Effects of cytochrome P-450 metabolites of arachidonic acid, epoxyeicosatrienoic acids (EETS; 5,6-EET, 8,9-EET, 11,12-EET, and 14,15-EET), were examined in isolated guinea pig hearts and ventricular myocytes. Addition of 1-16 ng/ml EETs to normal isolated hearts produced no effects on contractility or coronary pressure. In hearts subjected to 60 min of low-flow ischemia, impairment of contractility and declines in heart rate and coronary perfusion pressure were similar in the presence or absence of 1 ng/ml EETs. However, in the presence of either 5,6- or 11,12-EET, recovery was delayed for the first 10 min only. No significant differences were found in any group regarding heart rate, coronary perfusion pressure, or energy metabolite content after 30 min of reperfusion. In myocytes, both 5,6- and 11,12-EET (100 pg/ml, 1.0 ng/ml, and 20 ng/ml) significantly increased cell shortening as well as intracellular calcium concentrations, whereas 8,9- or 14,15-EET was without effect on these parameters. These results describe for the first time the direct effects of various EETs on cardiac cell function as well as their ability to modulate some of the myocardial responses to postischemic reperfusion. The results suggest a potential role for these substances in the response of the heart to pathological insult.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Calcium; Cytochrome P-450 Enzyme System; Dose-Response Relationship, Drug; Guinea Pigs; Heart; Heart Rate; Heart Ventricles; Male; Myocardium; Reperfusion Injury; Time Factors

The epoxyeicosatrienoic acids derived from the cytochrome P-450 pathway of arachidonic acid metabolism have a unique platelet antiaggregatory profile. This prompted us to examine their influence on cellular Ca2+ mobilization. 14,15-cis-Epoxyeicosatrienoic acid and related compounds inhibited the rise in cytosolic Ca2+ following agonist stimulation of platelets by thapsigargin, a receptor-independent agonist, and thrombin, a receptor-dependent agonist. The epoxyeicosatrienoic acids selectively inhibited the entry of Ca2+ from the exterior of the platelets but did not alter Ca2+ discharge from intracellular pools. The magnitude of inhibition by 14,15-cis-epoxyeicosatrienoic acid was proportional to the rate of Ca2+ entry. 14,15-cis-Epoxyeicosatrienoic acid also inhibited the rate of influx of Mn2+, a cation which enters platelets via pathways similar to Ca2+. The magnitude of inhibition was proportional to the rate of Mn2+ entry, suggesting that epoxyeicosatrienoic acids act on divalent cation channels in a fashion which depends on the state of opening of the channel. Selective inhibition of Ca2+ entry into platelets may account for the antiaggregatory effects of the epoxyeicosatrienoic acids. We are unaware of other endogenous compounds exhibiting this property, suggesting that epoxyeicosatrienoic acids may be useful to probe agonist-stimulated Ca2+ mobilization in nonexcitable cells.

Topics: 8,11,14-Eicosatrienoic Acid; Blood Platelets; Calcium; Cations, Divalent; Cells, Cultured; Humans; Manganese; Platelet Activation; Terpenes; Thapsigargin; Thrombin; Tumor Cells, Cultured

Gas chromatographic/mass spectroscopic and chiral analysis showed the presence of enzymatically derived 8,9-, 11,12- and 14,15-EET in rat plasma (2.8:1:3.4 molar ratio, respectively; 10.2 +/- 0.4 ng total EET/ml plasma). Greater than 90% of the plasma EETs was esterified to the phospholipids of circulating lipoproteins. The lipoprotein fraction with the highest EET concentration was LDL (8.1 +/- 0.9 ng/mg of protein) followed by HDL and VLDL (3.5 +/- 0.1 and 1.9 +/- 0.3 ng/mg of protein, respectively). In light of the biological activities of the EETs, these results suggest a potential systemic function for the cytochrome P-450 epoxygenase.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Cytochrome P-450 CYP2J2; Cytochrome P-450 Enzyme System; Gas Chromatography-Mass Spectrometry; Isomerism; Lipoproteins; Lipoproteins, HDL; Lipoproteins, LDL; Lipoproteins, VLDL; Male; Oxygenases; Rats; Rats, Inbred Strains

The purpose of this study was to determine if whole brain makes epoxygenase metabolites of arachidonic acid and, if so, whether they are vasoactive on the cerebral microcirculation. Blood-free mouse brain slices were incubated with exogenous radiolabeled arachidonic acid, and the extracted metabolites were resolved by HPLC. Metabolite structures were confirmed by gas chromatography/mass spectrometry. In addition to prostaglandins, leukotriene B4, and hydroxyeicosatetraenoic acids, mouse brain metabolized arachidonic acid into several other compounds. Among them, we identified 5,6- and 14,15-epoxyeicosatrienoic acid. Next, we tested the effect of topical application of brain-synthesized 5,6-epoxyeicosatrienoic acid and synthetic epoxyeicosatrienoic acids on in vivo rabbit cerebral arteriolar diameter using the cranial window technique and in vivo microscopy. Brain-synthesized 5,6-epoxyeicosatrienoic acid caused a transient 28% arteriolar dilation, similar to that produced by 5 micrograms/ml of synthetic 5,6-epoxyeicosatrienoic acid. A concentration of synthetic 14,15- and 11,12-epoxyeicosatrienoic acid of 5 micrograms/ml CSF had little or no effect on diameter, whereas 8,9-epoxyeicosatrienoic acid caused a maximum dilation of 8%. These studies suggest that brain-synthesized 5,6-epoxyeicosatrienoic acid may play a role in the normal or pathophysiological regulation of the cerebral microcirculation.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Brain; Cerebrovascular Circulation; Chromatography, High Pressure Liquid; Cytochrome P-450 CYP2J2; Cytochrome P-450 Enzyme System; Gas Chromatography-Mass Spectrometry; Male; Mice; Mice, Inbred ICR; Oxygenases

The renovascular effects of cytochrome P450-dependent arachidonic acid (P450-AA) metabolites synthesized by rat and rabbit kidneys were studied in the rabbit isolated kidney under conditions of constant flow and examined for their dependency on cyclooxygenase relative to their expression of vasoactivity. Kidneys were perfused with Krebs-Henseleit solution, and perfusion pressure was raised to levels of 90 to 110 mm Hg with the addition of 2 to 3 microM phenylephrine to the perfusate. Close arterial injection of 1 to 20 micrograms of 5,6-, 8,9- and 11,12-epoxyeicosatrienoic acid (EET) dose-dependently decreased perfusion pressure. The 5,6-EET was the most potent and the only epoxide dependent on cyclooxygenase for expression of vasoactivity, being inhibited by indomethacin (2.8 microM). In contrast, 14,15-EET resulted in dose-dependent increases in perfusion pressure. The vasodilator effects of the omega- and omega-1 oxidation products, 20-hydroxyeicosatetraenoic acid (HETE) and the stereoisomers of 19-HETE, were also inhibited by indomethacin. Furthermore, the renal vasodilator responses to 5,6-EET were not inhibited by either superoxide dismutase (10 U) or catalase (40 U) and, therefore, were unrelated to the formation of oxygen radicals generated during transformation of the epoxide by cyclooxygenase. As 5,6-EET and 19- and 20-HETE are synthesized by the renal tubules and can affect movement of salt and water, expression of vasoactivity by P450-dependent arachidonic acid metabolites, and after release from a nephron segment, may represent a mechanism that couples altered renal tubular function to appropriate changes in local blood flow.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acid; Arachidonic Acids; Blood Pressure; Cyclooxygenase Inhibitors; Cytochrome P-450 Enzyme System; Eicosanoids; Free Radicals; Hydroxyeicosatetraenoic Acids; In Vitro Techniques; Kidney; Male; Prostaglandin-Endoperoxide Synthases; Rabbits; Renal Circulation; Vascular Resistance

In rat liver cytosol, rapid ADP-ribosylation of a 52 kDa protein by endogenous ADP-ribosyltransferase(s) was observed. This ADP-ribosylation was stimulated dose-dependently by 14,15-epoxyeicosatrienoic acid (14,15-EET), one of the metabolites of arachidonic acid by NADPH-dependent cytochrome P-450 mono-oxygenase. This stimulatory effect required the presence of GTP or its non-hydrolysable analogues, guanosine 5'-[beta gamma-imido]triphosphate or guanosine 5'-[gamma-thio]triphosphate. Of four regioisomeric EETs, 14,15-EET was the most potent. No stimulatory effect was observed with addition of 14,15-dihydroxyeicosatrienoic acid, a stable metabolite of 14,15-EET. The 52 kDa protein was not ADP-ribosylated by cholera toxin A subunit and pertussis toxin, and was not recognized by anti-Gs alpha and anti-Gi alpha antibodies. However, the 52 kDa protein could be photoaffinity-labelled with 8-azidoguanosine 5'-[alpha-32P]triphosphate. These results suggest that the 52 kDa protein is neither Gs nor Gi, though it may have a GTP-binding site. These results contribute to the understanding of the role of mono-oxygenase metabolites of arachidonic acid in intracellular signal transduction.

Topics: 8,11,14-Eicosatrienoic Acid; Adenosine Diphosphate Ribose; Affinity Labels; Animals; Azides; Cholera Toxin; Cytosol; Guanosine 5'-O-(3-Thiotriphosphate); Guanosine Triphosphate; Kinetics; Liver; Male; Molecular Weight; Pertussis Toxin; Proteins; Rats; Rats, Inbred Strains; Virulence Factors, Bordetella

The different regioisomers of epoxyeicosatrienoic acids derived from cytochrome P-450 monooxygenase are readily esterified into phospholipids of mastocytoma cells. Incorporation of 14,15-epoxyeicosatrienoic acid was concentration-dependent, with Km = 1.1 microM and Vmax = 36 pmol/min/10(7) cells. Half-maximal incorporation occurred in 30 min, reaching a steady-state concentration of 470 pmol/10(6) cells. This was slightly lower than the values for arachidonic acid (665 pmol/10(6) cells) or 5-hydroxyeicosatetraenoic acid (554 pmol/10(6) cells). The distribution of 14,15-epoxyeicosatrienoic acid was preferential in the order phosphatidylethanolamine greater than phosphatidylcholine greater than phosphatidylinositol greater than phosphatidyl serine much greater than neutral lipids plus fatty acids. This contrasted with 5(S)-hydroxyeicosatetraenoic acid, which was distributed primarily into phosphatidylcholine. Fast atom bombardment/tandem mass spectrometry facilitated identification of molecular species containing epoxyeicosatrienoic acids without relying on radioisotopes. Phosphatidylethanolamine plasmalogens with 16:1 or 18:2 at the sn-1 position, or an 18:0 acyl group, and phosphatidylcholine with 16:0 alkyl ether or an acyl group at the sn-1 position incorporated all possible epoxyeicosatrienoic acid regioisomers. Under basal conditions, cells eliminated 14,15-cis-epoxyeicosatrienoic acid slowly with a half-life of 34.9 +/- 7 h. Cells stimulated with calcium ionophore A23187 eliminated 14,15-epoxyeicosatrienoic acid rapidly. It was notable that its rate of release from phosphatidylcholine and phosphatidylinositol exceeded that for arachidonic acid. A coenzyme A-independent transacylase also catalyzed the transfer of epoxyeicosatrienoic acids from mastocytoma cell membranes into 1-palmitoyl-2-lysophosphatidylcholine. The cellular incorporation, release, and distribution of epoxyeicosatrienoic acids is distinctive and contrasts with most other eicosanoids, suggesting that these compounds may have both autocoid and nonautocoid functions.

Topics: 8,11,14-Eicosatrienoic Acid; Acylation; Animals; Arachidonic Acid; Calcimycin; Cell Line, Transformed; Chromatography, High Pressure Liquid; Kinetics; Mast Cells; Mice; Phospholipids; Spectrometry, Mass, Fast Atom Bombardment

The vasodilatory effect of epoxyeicosatrienoic acids (EpETrE), especially 5(6)-EpETrE, has been reported recently and a role of P-450-dependent arachidonic acid monooxygenase metabolites was suggested in vasoregulation. Accordingly, the presence of P-450-dependent arachidonic acid monooxygenase was investigated in rat aortic smooth muscle cells. Incubation of the microsomes of rat cultured aortic smooth muscle cells with 14C-arachidonic acid in the presence of 1 mM NADPH resulted in the formation of oxygenated metabolites. The metabolites were separated and purified by reverse phase and straight phase high performance liquid chromatography and identified by gas chromatography-mass spectrometry. Identified metabolites were 5(6)-EpETrE, 5,6-dihydroxyeicosatrienoic acid (DiHETrE), and 14,15-DiHETrE. The formation of these metabolites was totally dependent on the presence of NADPH, and inhibitors of cytochrome P-450-dependent enzymes, SKF-525A and metyrapone, reduced the formation of these metabolites. This is the first report that cytochrome P-450-dependent arachidonic acid metabolites, especially 5(6)-EpETrE and 14(15)-EpETrE, can be produced in the microsomes of vascular smooth muscle cells of rats.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Aorta, Thoracic; Arachidonic Acid; Arachidonic Acids; Bacterial Proteins; Cells, Cultured; Chromatography, High Pressure Liquid; Cytochrome P-450 Enzyme System; Gas Chromatography-Mass Spectrometry; Hydroxyeicosatetraenoic Acids; Leukotriene B4; Male; Metyrapone; Microsomes; Mixed Function Oxygenases; Muscle, Smooth, Vascular; NADP; NADPH-Ferrihemoprotein Reductase; Pyridines; Rats; Rats, Inbred WKY

Topics: 1-Methyl-3-isobutylxanthine; 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; 8,11,14-Eicosatrienoic Acid; Angina, Unstable; Angioplasty, Balloon, Coronary; Arachidonic Acid; Arachidonic Acids; Colforsin; Cyclic AMP; Cytochrome P-450 CYP2J2; Cytochrome P-450 Enzyme System; Female; Humans; Oxygenases; Platelet Activation; Pre-Eclampsia; Pregnancy; Prostaglandin Endoperoxides, Synthetic; Thrombin

Epoxygenase metabolites of arachidonic acid are produced by several tissues and have been shown to inhibit in vitro platelet aggregation. The purpose of the present investigation was to determine whether 14,15- or 8,9-epoxyeicosatrienoic acid, epoxygenase derivatives of arachidonic acid, affect the speed of platelet aggregation in in vivo mouse cerebral arterioles.. We performed a craniectomy in 116 anesthetized male mice and observed the pial arterioles by microscopy. We induced in situ platelet aggregation using a mercury light and intravascularly injected fluorescein dye.. Indomethacin (0.5 mg/kg i.p.), a known cyclooxygenase inhibitor, and 14,15-epoxyeicosatrienoic acid (0.3 mg/kg i.v.) increased the time necessary for the light plus dye to induce the first arterial platelet aggregate by 35% and 26%, respectively, whereas 8,9-epoxyeicosatrienoic acid (0.3 mg/kg i.v.) had no effect. Analysis of mouse serum by radioimmunoassay showed that the degree of inhibition of platelet aggregation by indomethacin and epoxyeicosatrienoic acids correlated with the degree of inhibition of thromboxane production.. We conclude that 14,15-epoxyeicosatrienoic acid is a potent inhibitor of in vivo platelet aggregation but cannot conclusively confirm that its effect on aggregation occurs via its reduction of platelet thromboxane A2. Because epoxyeicosatrienoic acids are produced by several tissues, including brain and vascular tissue, they may be important in vivo modulators of platelet aggregation and hemostasis.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arterioles; Blood Platelets; Cerebrovascular Circulation; Indomethacin; Mice; Platelet Aggregation; Platelet Aggregation Inhibitors; Thromboxane B2

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acid; Arachidonic Acids; Brain Chemistry; Cerebrovascular Circulation; Cytochrome P-450 CYP2J2; Cytochrome P-450 Enzyme System; Free Radicals; Indomethacin; Mice; Oxygen; Oxygenases; Prostaglandins; Vasodilation

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; 8,11,14-Eicosatrienoic Acid; Animals; Cattle; Cells, Cultured; Coronary Vessels; Dogs; Endothelium, Vascular; Epoprostenol; Hydroxyeicosatetraenoic Acids; Muscle, Smooth, Vascular; Platelet Aggregation; Prostaglandin Endoperoxides, Synthetic; Vasodilation

Arachidonic acid metabolism via cyclooxygenase, lipoxygenase, and cytochrome P-450 epoxygenase was investigated in thoracic aortic tissue obtained from rabbits fed either standard rabbit chow or chow containing 2% cholesterol. Aortic strips were incubated with [14C]arachidonic acid and A23187. Metabolites from extracted media were resolved by high-pressure liquid chromatography (HPLC). Normal and cholesterol-fed rabbit aortas synthesized prostaglandins (PGs) and hydroxyeicosatetraenoic acids (HETEs). The major cyclooxygenase products were 6-keto-PGF1 alpha and PGE2. Basal aortic 6-keto-PGF1 alpha production was slightly reduced in cholesterol-fed compared with normal rabbits. 12(S)- and 15(S)-HETE were the major aortic lipoxygenase products from both normal and cholesterol-fed rabbits. The structures were confirmed by gas chromatography-mass spectrometry (GC-MS). Only cholesterol-fed rabbit aortas metabolized arachidonic acid via cytochrome P-450 epoxygenase to the epoxyeicosatrienoic acids (EETs). 14,15-, 11,12-, 8,9-, and 5,6-EET were identified based on comigration on HPLC with known 14C-labeled standards and typical mass spectra. Incubation of normal aorta with 14,15-EET decreased the basal synthesis of 6-keto-PGF1 alpha. The other EETs were without effect. The four EET regioisomers relaxed the norepinephrine-precontracted normal and cholesterol-fed rabbit aorta. The relaxation response to 14,15-EET was greater in aortas from cholesterol-fed rabbits. These studies demonstrate that hypercholesterolemia, before the development of atherosclerosis, alters arachidonic acid metabolism via both the cyclooxygenase and epoxygenase pathways.

Topics: 12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; 4,5-Dihydro-1-(3-(trifluoromethyl)phenyl)-1H-pyrazol-3-amine; 6-Ketoprostaglandin F1 alpha; 8,11,14-Eicosatrienoic Acid; Animals; Aorta, Thoracic; Arachidonic Acids; Carbon Radioisotopes; Cholesterol, Dietary; Clotrimazole; Diet, Atherogenic; Hydroxyeicosatetraenoic Acids; In Vitro Techniques; Indomethacin; Kinetics; Masoprocol; Metyrapone; Muscle, Smooth, Vascular; Rabbits; Reference Values; Stereoisomerism

Noncyclooxygenase metabolites of arachidonic acid may be potent modulators of the mitogenic response of renal mesangial cells to the mitogenic vasoactive peptide arginine vasopressin (AVP). Since Ca2+ is a critical second messenger in the response of mesangial cells to AVP, and Ca2+ has been implicated in the regulation of growth, we determined whether noncyclooxygenase metabolites altered the phospholipase C-Ca2+ signalling cascade which is activated by AVP. Pretreatment of mesangial cells for 10 min with lipoxygenase and cytochrome P450 monooxygenase inhibitors, nordihydroguaiaretic acid (NDGA, 10(-5) M) or SKF-525A (2.5 x 10(-5) M), but not the cyclooxygenase inhibitor indomethacin (2 x 10(-5) M), reduced the magnitude of the AVP (10(-8) and 10(-7) M)-induced increase in cytosolic free Ca2+ concentration ([Ca2+]i) without affecting inositol trisphosphate production. With 10(-8) M AVP, [Ca2+]i increased to 250 +/- 47 nM in NDGA-treated cells versus 401 +/- 59 nM in control cells (p less than 0.01). [Ca2+]i, measured 2 min after exposure to AVP, was also lower with NDGA (152 +/- 21 nM) when compared with AVP alone (220 +/- 22 nM, p less than 0.01). 14,15-epoxyeicosatrienoic acid (EET) (10(-8) M), which had no effect on inositol trisphosphate production, completely reversed the NDGA-induced inhibition of the [Ca2+]i transient, whereas 5-hydroperoxyeicosatetraenoic acid (HPETE) (5 x 10(-7) M) did not. Pretreatment with higher concentrations of 14,15-EET (10(-7)-10(-6) M) markedly potentiated the AVP-induced increase in [Ca2+]i. NDGA-induced inhibition of the AVP-generated [Ca2+]i transient was also observed when cells were incubated in low Ca2+ media ([Ca2+] less than 5 x 10(-8) M), suggesting that NDGA pretreatment impaired intracellular release of Ca2+. Since NDGA had no direct effect on inositol 1,4,5-trisphosphate-induced Ca2+ release, we postulated that NDGA blocked production of a metabolite that releases Ca2+ from intracellular stores. 14,15-EET and 15-HPETE, but not 15-hydroxyeicosatetraenoic acid (each at 3 x 10(-7) M), raised [Ca2+]i when added directly to cells in low Ca2+ media. In permeabilized cells 14,15-EET and 15-HPETE (10(-7) M) potently released Ca2+ from intracellular stores. In summary, noncyclooxygenase metabolites of arachidonic acid, and in particular P450 metabolites, are potent endogenous amplifiers of the AVP-induced [Ca2+]i signal by mechanisms not directly involving phospholipase C activation. This effect is mediated, at least

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acid; Arachidonic Acids; Arginine Vasopressin; Calcium; Cells, Cultured; Dinoprostone; Eicosanoids; Eicosapentaenoic Acid; Glomerular Mesangium; Hydroxyeicosatetraenoic Acids; In Vitro Techniques; Indomethacin; Inositol Phosphates; Leukotrienes; Lipid Peroxides; Masoprocol; Pyridines; Rats; Rats, Inbred Strains; Signal Transduction; Type C Phospholipases

We have recently shown that brain tissue can synthesize cytochrome P-450 monooxygenase metabolites of arachidonic acid (AA), including 5,6-epoxyeicosatrienoic acid (5,6-EET), and 14,15-EET. The purpose of this investigation was to determine the vasoactivity of EETs and AA on the cerebral microcirculation. Pial arteriolar diameter was measured in rabbits and cats using in vivo microscopy and the closed cranial window technique. Prostaglandin (PG) E2 and 6-keto-PGF1 alpha formed by the brain cortex during application of these fatty acids was measured in cerebrospinal fluid by use of radioimmunoassay. A transient dose-dependent dilation was produced by 5,6-EET (1-15 micrograms/ml), with the maximum being 23% of control in both species. Other EETs had little or no activity, and AA-induced dilation was greater in rabbits than in cats. Indomethacin or superoxide dismutase plus catalase prevented dilation by 5,6-EET and AA, indicating that both produce dilation via cyclooxygenase-dependent oxygen radicals. PGE2 and 6-keto-PGF1 alpha levels were increased by AA but not by EETs, implying that EETs do not directly activate AA metabolism. Since 5,6-EET, but not other EETs, is known to be a substrate for cyclooxygenase, our data are consistent with brain cyclooxygenase metabolism of 5,6-EET with concomitant generation of dilator oxygen radicals. An implication of these results is that many previous studies of the cerebral circulation which based conclusions on results with cyclooxygenase inhibitors may need to be additionally interpreted.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acid; Arachidonic Acids; Arterioles; Brain; Cats; Cerebrovascular Circulation; Cytochrome P-450 Enzyme System; Rabbits; Vasodilation

Topics: 8,11,14-Eicosatrienoic Acid; Arachidonic Acid; Arachidonic Acids; Aza Compounds; Blood Platelets; Calcimycin; Collagen; Cytochrome P-450 Enzyme System; Eicosanoids; Humans; Phosphoproteins; Platelet Aggregation; Platelet Aggregation Inhibitors; Prostaglandin Endoperoxides, Synthetic; Sulfides; Thromboxane B2

The effects of products of the cytochrome P-450 epoxygenase pathway of arachidonate metabolism on renin have not been previously examined. Initial high-performance liquid chromatography and gas chromatography-mass spectrometry studies documented the synthesis of four epoxyeicosatrienoic acid (EET) regioisomers of epoxygenase in superficial cortical slices from male Sprague-Dawley rats. Each regioisomer was tested for effects on both isoproterenol (ISO)-stimulated and basal renin secretion from cortical slices. ISO increased renin release significantly (169%, P less than 0.01) in all incubations; 14,15-EET (10(-6) M) significantly reduced this increase in stimulated renin release to 47%. The 5,6-, 8,9-, and 11,12-EETs did not significantly affect renin release. Basal renin release was not affected by any of the four EETs. To examine the mechanism of this inhibitory action, the effects of 14,15-EET on tissue adenosine 3',5'-cyclic monophosphate (cAMP) and guanosine 5'-cyclic monophosphate (cGMP) concentrations were measured. Tissue cAMP concentrations were sharply increased (4.75-fold, P less than 0.001) by ISO; 14,15-EET did not blunt this increase significantly. ISO and 14,15-EET did not affect tissue cGMP concentrations. Incubation of [14C]EET with cortical slices resulted in only 10% conversion of the 14,15-EET to 14,15-dihydroxyeicosatrienoic acid (DHET) (diol) after 90 min; no other metabolites were observed. The 14,15 DHET did not alter either basal or stimulated renin release. These studies document the synthesis of EETs in rat kidney and demonstrate a direct effect of the 14,15-EET to inhibit stimulated renin release. This inhibitory action occurs without an effect on tissue cAMP or cGMP concentrations.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Cyclic AMP; Fatty Acids, Unsaturated; In Vitro Techniques; Isoproterenol; Kidney Cortex; Kinetics; Mass Spectrometry; Rats; Renin; Structure-Activity Relationship

The present study examined responses of cultured rat glomerular mesangial cells to exogenous exposure of epoxyeicosatrienoic acids (EET's), products of cytochrome P450 epoxygenase. One day after administration of 8,9- or 14,15-EET, cultured rat mesangial cells demonstrated significant increases in [3H]thymidine incorporation (10(-7) M 14,15-EET: 120 +/- 7% of control; n = 6; P less than 0.025; 10(-6) M 14,15-EET: 145 +/- 10%; n = 20; P less than 0.0005; 10(-6) M 8,9-EET: 167 +/- 31%; n = 9; P less than 0.05), which was not affected by addition of the cyclooxygenase inhibitor indomethacin. In addition to stimulation of [3H]thymidine incorporation, the epoxides stimulated mesangial cell proliferation. 14,15-EET administration induced intracellular alkalinization of 0.2-0.3 pH units, which was prevented by extracellular Na+ removal and blunted by amiloride (0.5 mM). Following intracellular acidification with NH4Cl addition and removal, greater than 85% of 3 mM 22Na uptake into mesangial cells was inhibited by 1 mM amiloride, indicating Na+/H+ exchange. Under these conditions, 14,15-EET stimulated Na+/H+ exchange by 42% and 8,9-EET stimulated Na+/H+ exchange by 59%. Neither protein kinase C depletion nor addition of the protein kinase C inhibitor, staurosporine, affected this stimulation. In [3H]myo-inositol loaded mesangial cells, no significant stimulation of phosphoinositide hydrolysis was detected in response to administration of 14,15-EET. Twenty-four hours after addition of [14C]14,15-EET, greater than 90% was preferentially esterified to cellular lipids, with predominant incorporation into phosphatidylinositol, phosphatidylethanolamine, and diacylglycerol. Thus, these results demonstrate epoxyeicosatrienoic acids stimulate Na+/H+ exchange and mitogenesis in mesangial cells. These effects do not appear to be mediated via phospholipase C activation. In addition, 14,15-EET was selectively incorporated into cellular lipids known to mediate signal transduction. These observations extend the potential biologic roles of c-P450 arachidonate metabolites to include stimulation of cell proliferation and suggest a role for these compounds in vascular and renal injury.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acids; Carrier Proteins; Cell Division; Cells, Cultured; Fatty Acids, Unsaturated; Glomerular Mesangium; Mitogens; Rats; Sodium-Hydrogen Exchangers; Thymidine

Arachidonic acid is metabolized by means of P450 isoenzyme(s) to form epoxyeicosatrienoic acids (EETs) and their corresponding dihydroxy derivatives (DHETs). In the present study, we established the presence in human urine of 8,9-, 11,12-, and 14,15-EETs and their corresponding DHETs by developing quantitative assays and using negative ion, chemical ionization GC/MS and octadeuterated internal standards. Urinary excretion of 8,9- and 11,12-DHET increased in healthy pregnant women compared with nonpregnant female volunteers. By contrast, excretion of 11,12-DHET and 14,15-DHET, but not the 8,9-DHET regioisomer, increased even further in patients with pregnancy-induced hypertension. Intravenous administration of [3H]14,15-EET to three dogs markedly increased its DHET in plasma. The terminal half-life ranged from 7.9-12.3 min and the volume of distribution (3.5-5.3 liters) suggested limited distribution outside the plasma compartment. Negligible radioactivity was detected in urine; this fact infers that under physiological circumstances, urinary DHETs largely derive from the kidney. That P450 metabolites of arachidonic acid are formed in humans supports the hypothesis that these metabolites contribute to the physiological response to normal pregnancy and the pathophysiology of pregnancy-induced hypertension.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Dogs; Fatty Acids, Unsaturated; Female; Gas Chromatography-Mass Spectrometry; Humans; Hypertension; Pre-Eclampsia; Pregnancy; Pregnancy Complications, Cardiovascular; Radioisotope Dilution Technique; Reference Values; Tritium

Arachidonic acid (AA) can be metabolized in endothelial cells (EC) to a series of epoxides via cytochrome P-450 epoxygenase with 14,15 epoxyeicosatrienoic acid (14,15-EET) as the major product. In this communication we report that 14,15-EET significantly enhances U937 cell attachment to EC with maximal cell attachment at 2.5 to 5 x 10(-7) M 14,15-EET. Thus, 14,15-EET may play a substantial role in inflammation and/or atherogenesis by inducing monocyte attachment to EC.

Topics: 8,11,14-Eicosatrienoic Acid; Cell Adhesion; Cells, Cultured; Chromatography, High Pressure Liquid; Endothelium; Fatty Acids, Unsaturated; Fluorescent Dyes; Humans; L-Lactate Dehydrogenase; Prostaglandins; Thrombin; Tumor Cells, Cultured

Intravenous (IV) and intraarterial (IA) infusion of 14,15-epoxyeicosatrienoic acid (14,15-EET) produced a dose-dependent decrease in mean arterial blood pressure (MAP) in normal and spontaneously hypertensive rats (SHR). The hypotensive effect of 14,15-EET was observed from 1 microgram/kg to 10 micrograms/kg with a maximum reduction in MAP as much as 45 +/- 6 mmHg in both normal and SHR. In normal rats the hypotensive effect was found to be more pronounced when 14,15-EET was infused IA than IV. This suggests that 14,15-EET may be metabolized as it passes through the lungs. However, in SHR there was no difference in MAP when 14,15-EET was infused either IA or IV. This indicates that there is a differential removal of the epoxide across the pulmonary circulation. Administration of indomethacin failed to inhibit the hypotensive action of 14,15-EET, suggesting that it may not be a cyclo-oxygenase dependent mechanism. However, the PAF antagonist of BN-52021 inhibited the hypotensive action of 14,15-EET. This therefore, suggests that the release of PAF may be involved in the hypotensive action of this epoxide of arachidonic acid.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Antihypertensive Agents; Blood Pressure; Diterpenes; Dose-Response Relationship, Drug; Fatty Acids, Unsaturated; Ginkgolides; Hypertension; Indomethacin; Isomerism; Lactones; Male; Plant Extracts; Rats; Rats, Inbred SHR; Rats, Inbred Strains; Reference Values

Four triene monoepoxides of arachidonic acid have been identified as endogenous components of human plasma, the epoxy groups being in the 5,6-, 8,9-, 11,12- and 14,15-positions. Prior to trimethylsilylation and gas chromatographic-mass spectrometric analysis, both the expoxy and ester functions were reduced to hydroxy groups and the double bonds were hydrogenated catalytically. Saturation of the double bonds gave diagnostic spectra that were suitable for elucidating the position of the epoxy group. The shift in the fragmentation of a deuteriated sample verified the presence of the intact epoxides prior to chemical reduction. The presence of the double bonds in the epoxy molecules was demonstrated by reduction using homogeneous catalysis with tris(triphenylphosphine)rhodium(I) chloride and deuterium.

Topics: 8,11,14-Eicosatrienoic Acid; Aluminum; Aluminum Compounds; Deuterium; Fatty Acids, Unsaturated; Gas Chromatography-Mass Spectrometry; Humans; Lithium; Lithium Compounds; Molecular Structure; Oxidation-Reduction

Chiral analysis of the rat liver microsomal arachidonic acid epoxygenase metabolites shows enantioselective formation of 8,9-, 11,12-, and 14,15-cis-epoxyeicosatrienoic acids in an approximately 2:1, 4:1, and 2:1 ratio of antipodes, respectively. Animal treatment with the cytochrome P-450 inducer phenobarbital increased the overall enantiofacial selectivity of the microsomal epoxygenase and caused a concomitant inversion in the absolute configurations of its metabolites. These effects of phenobarbital were time-dependent and temporally linked to increases in the concentration of microsomal cytochrome P-450 enzymes. Reconstitution of the epoxygenase reaction utilizing several purified cytochrome P-450 demonstrated that the asymmetry of epoxidation is under cytochrome P-450 enzyme control. These results established that the chirality of the hepatic arachidonic acid epoxygenase is under regulatory control and confirm cytochromes P-450 IIB1 and IIB2 as two of the endogenous epoxygenases induced in vivo by phenobarbital.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Benzoflavones; beta-Naphthoflavone; Cytochrome P-450 CYP2J2; Cytochrome P-450 Enzyme System; Male; Microsomes, Liver; Oxygenases; Phenobarbital; Rats; Rats, Inbred Strains; Stereoisomerism; Substrate Specificity

Mass spectral and chromatographic analysis demonstrates the presence of 14,15-, 11,12- and 8,9-epoxyeicosatrienoic acids (44%, 33% and 23% of the total, respectively) in human kidney cortex. Chiral analysis of the human renal epoxyeicosatrienoic acids shows the formation of 8,9-, 11,12- and 14,15-epoxyeicosatrienoic acids in a 1:1, 4:1 and 2:1 ratio of antipodes, respectively. These results demonstrate the biosynthetic origin of the human kidney 11,12- and 14,15-epoxyeicosatrienoic acids and suggest a role for renal cytochrome P-450 in the bioactivation of endogenous pools of arachidonic acid.

Topics: 8,11,14-Eicosatrienoic Acid; Cytochrome P-450 CYP2J2; Cytochrome P-450 Enzyme System; Fatty Acids, Unsaturated; Humans; Kidney Cortex; Male; Mass Spectrometry; Oxygenases; Stereoisomerism

Human amnion, trophoblast and umbilical vein endothelial cells synthesise an arachidonic acid metabolite which is neither a lipoxygenase nor a cyclo-oxygenase product. It is sensitive to stimulants and inhibitors of the cytochrome-P450-dependent epoxygenase system and co-migrates on HPLC with 14,15-epoxyeicosatrienoic acid (14,15-EET), which is an epoxygenase product. The function of 14,15-EET in these reproductive tissues is unknown, but it may be involved in the maintenance of vascular function.

Topics: 6-Ketoprostaglandin F1 alpha; 8,11,14-Eicosatrienoic Acid; Arachidonic Acids; Benzoflavones; Dinoprost; Endothelium; Fatty Acids, Unsaturated; Female; Humans; Hydroxyeicosatetraenoic Acids; Lipoxygenase; Placenta; Pregnancy; Prostaglandin-Endoperoxide Synthases; Trophoblasts; Umbilical Veins

Growth hormone secretion was stimulated in vitro by products of arachidonic acid epoxygenase, the epoxyeicosatrienoic acids. 5,6-Epoxyeicosatrienoic and 14,15-epoxyeicosatrienoic acid stimulated growth hormone release from an enriched population of somatotrophs (approximately 85%) by twofold. Inhibition of arachidonic acid metabolism by indomethacin did not affect growth hormone-releasing hormone stimulation of growth hormone release. In contrast, pretreatment of somatotrophs with an 11,12-isonitrile analogue of arachidonic acid that inhibits arachidonic acid epoxygenase, resulted in a 20-25% inhibition of growth hormone-releasing hormone-stimulated growth hormone release. 14,15-Epoxyeicosatrienoic acid stimulated a concentration-dependent increase (twofold) in the cytoplasmic concentration of adenosine 3',5'-cyclic monophosphate (cAMP) in the somatotrophs. 14,15-Epoxyeicosatrienoic acid also rapidly increased the intracellular free calcium concentration in somatotrophs from resting levels (approximately 80 nM) to greater than 250 nM. Growth hormone-releasing hormone increased the free intracellular calcium to 160-180 nM. Preincubation of somatotrophs with somatostatin inhibited growth hormone-releasing hormone-stimulated growth hormone secretion, cAMP accumulation, and 14,15-epoxyeicosatrienoic acid stimulated cAMP accumulation. These data are suggestive that the epoxyeicosatrienoic acids may have a role in the secretion of growth hormone.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Cells, Cultured; Fatty Acids, Unsaturated; Growth Hormone; Growth Hormone-Releasing Hormone; Indomethacin; Kinetics; Male; Pituitary Gland, Anterior; Rats; Rats, Inbred Strains; Somatostatin

Chiral analysis of the endogenous rat liver epoxyeicosatrienoic acids shows the biosynthesis of 8,9-, 11,12-, and 14,15-epoxyeicosatrienoic acids in a 4:1, 2:1, and 3:1 ratio of antipodes, respectively. Animal treatment with phenobarbital results in a 3.7-fold increase in microsomal cytochrome P-450 concentration and a concomitant, regioselective 6.8- and 3.4-fold increase in the liver concentration of 8,9- and 14,15-epoxyeicosatrienoic acids, respectively. Phenobarbital induces the in vivo synthesis of both regioisomers as nearly optically pure enantiomers. These results demonstrate the enzymatic origin of the epoxyeicosatrienoic acids present in rat liver and document a novel metabolic function for cytochrome P-450 in the regio- and enatioselective epoxygenation of endogenous pools of arachidonic acid.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonate Lipoxygenases; Chromatography, High Pressure Liquid; Cytochrome P-450 Enzyme System; Fatty Acids, Unsaturated; Liver; Male; Mass Spectrometry; Microsomes, Liver; Phenobarbital; Rats; Rats, Inbred Strains; Stereoisomerism

A chromatographic method is described for the direct enantiomeric characterization of all four regioisomeric epoxyeicosatrienoic acid (EET) metabolites generated by the cytochrome P450 arachidonate epoxygenase pathway. Following esterification, the individual methyl or pentafluorobenzyl esters are resolved by chiral phase HPLC utilizing a Chiralcel OB or OD column. This methodology will find analytical and preparative applications for chiral epoxides since it is convenient and efficient and does not destroy the epoxide functionality.

Topics: 8,11,14-Eicosatrienoic Acid; Chromatography, High Pressure Liquid; Fatty Acids, Unsaturated; Stereoisomerism

The arachidonic acid epoxygenase metabolite 14,15-epoxyeicosatrienoic acid is further metabolized by rat liver microsomal fractions to regioisomeric diepoxides and epoxyalcohols. Diepoxides result from epoxidation at the 5,6-, 8,9-, or 11,12-olefins. Hydroxylation leading to epoxyalcohols with a cis, trans-conjugated dienol occurs at carbons 5, 8, 9, or 12. Structural assignments were established by chromatographic and mass spectral comparisons with synthetic standards. The reaction requires NADPH and is inhibited by typical cytochrome P-450 inhibitors. Analysis of the time course of product formation during arachidonic acid oxidation by rat liver microsomal fractions indicated that all four regioisomeric epoxyeicosatrienoic acids can be further metabolized by the enzyme system.

Topics: 8,11,14-Eicosatrienoic Acid; Alcohols; Animals; Chromatography, High Pressure Liquid; Cytochrome P-450 Enzyme System; Epoxy Compounds; Fatty Acids, Unsaturated; Male; Mass Spectrometry; Microsomes, Liver; NADP; Oxidation-Reduction; Rats; Rats, Inbred Strains; Spectrophotometry, Ultraviolet

Bovine lung extract contained an enzyme or enzyme system that catalyzed the formation of 14,15-oxido-5,8,11-eicosatrienoic acid from phosphatidylinositol. The enzyme activity increased markedly during the course of purification, apparently due to the removal of two endogenous inhibitors from the enzyme. Using membranes with known molecular weight cut-offs, we estimated the Mr of Inhibitor 1 to be between 10,000 and 100,000 and Inhibitor 2 less than 1,000. Inhibitor 1 appeared to be partially inactivated by trypsin and was heat labile, whereas Inhibitor 2 was resistant to trypsin and was heat resistant. Both inhibitors were hydrophilic.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Cattle; Epoxide Hydrolases; Fatty Acids, Unsaturated; Hot Temperature; Lung; Molecular Weight; Phosphatidylinositols; Phospholipases A

In addition to cyclooxygenase and lipoxygenase pathways, the kidney can also metabolize arachidonic acid by a NADPH-dependent cytochrome P-450 enzyme to epoxyeicosatrienoic acids (EETs); furthermore, 5,6-EET has been shown to alter electrolyte transport across isolated renal tubules. We examined the effects of three EETs (5,6-, 11, 12-, and 14,15-EET) on osmotic water flow across toad urinary bladder. All three EETs reversibly inhibited vasopressin-stimulated osmotic water flow with 5,6- and 11,12-EET being the most potent. The effects appeared to be independent of prostaglandins. EETs inhibited the water flow response to forskolin but not (with the exception of 11,12-EET) the response to adenosine 3',5'-cyclic monophosphate (cAMP) or 8-BrcAMP, consistent with an effect on cAMP generation. For 11,12-EET the question of an additional inhibition at a site beyond or independent of cAMP has to be considered. To determine whether these effects were due to the EETs or to products of their metabolism, we examined the effects of their vicinal diol hydrolysis products, the dihydroxyeicosatrienoic acids. Nonenzymatic conversion of labeled 5,6-EET to its vicinal diol occurred rapidly in the buffer, whereas 11,12-EET was hydrolyzed in a saturable manner only when incubated in the presence of bladder tissue. The dihydroxyeicosatrienoic acids formed inhibited water flow in a manner paralleling that of the EETs. Both 5,6-EET and 11,12-EET (10(-5) M) prevented the increase in intracellular cAMP content observed in control tissues after vasopressin stimulation. Finally, 11,12- and 14,15-dihydroxyeicosatrienoic acid inhibited vasopressin- and forskolin-stimulated adenylate cyclase in the same rank order as their inhibition of water flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 8,11,14-Eicosatrienoic Acid; Adenylyl Cyclases; Animals; Arachidonic Acid; Arachidonic Acids; Bufo marinus; Colforsin; Cyclic AMP; Epithelium; Fatty Acids, Unsaturated; Female; In Vitro Techniques; Urinary Bladder; Vasopressins; Water-Electrolyte Balance

Purified synthetic products from the cytochrome P450 pathway of arachidonate metabolism were applied to the intestinal serosa. Arteriolar blood flow was calculated using video microscopy. After a steady-state baseline, a bolus containing 10-60 micrograms 14,15-epoxyeicosatrienoic acid/ml (14,15-EET) had no detectable effect on blood flow. However, 25 +/- 3 micrograms 11,12-EET/ml and 36 +/- 2 micrograms 8,9-EET/ml caused increases (134 +/- 8% and 127 +/- 6%) that were similar to those elicited by 8 +/- 2 micrograms adenosine/ml (138 +/- 12%). Furthermore, the increases (275 +/- 38%) produced by 32 +/- 6 micrograms 5,6-EET/ml exceeded those elicited (160 +/- 10%) by a similar concentration (27 +/- 3 micrograms/ml) of adenosine. Thus, a structure-activity relationship is suggested. Nevertheless, these values probably underestimate the potency of the EETs because the vasoactivity was reduced by contact with water. The activity of the cyclooxygenase pathway seemed to limit the formation of vasoactive quantities of EETs, or other nonprostanoids, from exogenous arachidonate in the serosa but not the mucosa. A bolus (1.3 +/- 0.2 mg/ml) or continuous application (122 +/- 45 micrograms/ml) of arachidonate caused blood flow increases (236 +/- 14% or 229 +/- 27%) that were almost eliminated (129 +/- 5% or 121 +/- 9%) by a cyclooxygenase inhibitor; the residual response was abolished by a cytochrome P450 inhibitor. However, cytochrome P450 inhibitors alone did not attenuate the arachidonate response. In contrast, a continuous application of 194 micrograms arachidonate/ml to the mucosa caused a markedly smaller blood flow increase (119 +/- 8%) and cyclooxygenase inhibitors potentiated (132 +/- 8%), rather than reduced, this response. We conclude that EETs are a labile class of vasodilators with a potency comparable to adenosine in the intestinal microcirculation. Indirect evidence suggests regional differences in the formation of vasoactive quantities of arachidonate metabolites within the intestinal wall.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acid; Arachidonic Acids; Cyclooxygenase Inhibitors; Cytochrome P-450 Enzyme Inhibitors; Cytochrome P-450 Enzyme System; Fatty Acids, Unsaturated; Intestinal Mucosa; Intestines; Male; Rats; Regional Blood Flow; Structure-Activity Relationship; Vasodilation

Human platelets contain a soluble enzyme or enzyme system that catalyzes the formation of lysophosphatidylinositol and a compound more polar than arachidonic acid (compound A) from 2-arachidonoyl sn-phosphatidylinositol. Arachidonic acid, 2-arachidonoyl sn-phosphatidylcholine, or 2-arachidonoyl sn-phosphatidylethanolamine did not serve as substrate for the production of compound A. The reaction required Ca2+ and was not affected by aspirin, indomethacin, or mepacrin. Enzyme activity was not enhanced in the presence of NADPH, but it was inhibited greater than 90% by CO or N2; inhibition was readily reversible by exposure to atmospheric air. Neither metapyrone (SKF 525A) nor cyanide, inhibitors of cytochrome P-450, inhibited compound A formation, suggesting that a cytochrome P-450 system was not involved. Thrombin stimulated the formation of compound A in whole platelets; ionophore A23187 did so much less effectively; and other agonists such as collagen, ADP, and epinephrine were ineffective. Compound A exhibited a fragmentation pattern by GC/MS identical to that of authentic cis-14,15-oxido-5,8,11-icosatrienoic acid. Collectively, these data indicate that human platelets may contain an enzyme system that catalyzes the epoxidation of the arachidonic acid moiety of phosphatidylinositol and its hydrolysis to liberate cis-14,15-oxido-5,8,11-icosatrienoic acid.

Topics: 8,11,14-Eicosatrienoic Acid; Arachidonic Acid; Arachidonic Acids; Blood Platelets; Calcium; Cytochrome P-450 Enzyme Inhibitors; Fatty Acids, Unsaturated; Humans; NADP; Oxygenases; Phosphatidylinositols; Phospholipases A; Substrate Specificity; Thrombin

A pool of phosphatidylinositol and phosphatidylethanolamine containing epoxyeicosatrienoic acids esterified to the sn-2 position of the glycerol moiety has been identified in rat liver. The mole fraction of epoxide containing phosphatidylinositol is 7-8 times that of phosphatidylethanolamine.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Fatty Acids, Unsaturated; Liver; Mass Spectrometry; Phosphatidylethanolamines; Phosphatidylinositols; Rats

Arachidonic acid (AA) can be metabolized to epoxides and their corresponding diols via the cytochrome P450 epoxygenase pathway. We have compared the vascular activity of four synthetically prepared epoxyeicosatrienoic acids, i.e. 5,6-, 8,9-, 11,12- and 14,15-EET (2-20 microM) on the isolated perfused rat tail artery. The 5,6-EET was equipotent with acetylcholine in dose dependently reducing vascular resistance (ED50 = 3.4 +/- 0.5 microM). The 8,9-, 11,12- and 14,15-EETs of AA did not affect vascular resistance; neither did the 5,6-DHET and delta-lactone, hydrolysis products of 5,6-epoxide. We suggest that the 5,6-epoxide, in contrast to other cytochrome P450-derived products, contributes to the regulation of regional vascular tone.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acids; Chromatography, High Pressure Liquid; Cytochrome P-450 Enzyme System; Hemodynamics; In Vitro Techniques; Male; Muscle, Smooth, Vascular; Rats; Vasodilator Agents

Certain epoxyeicosatrienoic acids (EETs) that were not cyclooxygenase substrates were effective cyclooxygenase inhibitors. Both (+/-)-14,15-cis-EET and (+/-)-8,9-cis-EET inhibited purified enzyme at concentrations from 1 to 50 microM; (+/-)-11,12-cis-EET was ineffective at concentrations below 100 microM. For the case of 14,15-cis-EET, only the (14R,15S)-stereoisomer was active. Other isomers including (14S,15R)-cis-EET, (14R,15R)-trans-EET, (14S,15S)-trans-EET, and the erythro and threo vicinal 14,15-diols were inactive. In addition to their effects on isolated enzyme preparations, cyclooxygenase activity in platelet suspensions, reflected by thromboxane B2 formation, was also inhibited by (14R,15S)-cis-EET and (+/-)-8,9-cis-EET but not by the other isomers. Thus potency and stereospecificity requirements were maintained for cyclooxygenase within intact platelets. Unlike the stereospecific inhibition of the cyclooxygenase enzyme, platelet aggregation induced by arachidonic acid was inhibited by all EET isomers at concentrations from 1 to 10 microM with no evident stereospecificity. Inhibition of aggregation was not uniformly associated with inhibition of thromboxane B2 formation; ordinarily, these two parameters correlate closely. This dissociation was not maintained for another biochemical process involved in platelet activation. For instance, there was a uniform correlation between inhibition of phosphorylation of a 40-kDa platelet protein and inhibition of aggregation. Our results suggest that effects of EET may originate from either stereospecific or nonspecific mechanisms. Definition of such mechanisms may be important to appreciate any physiological relevance of these substances.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Cyclooxygenase Inhibitors; Fatty Acids, Unsaturated; Humans; Kinetics; Male; Platelet Aggregation; Seminal Vesicles; Sheep; Structure-Activity Relationship

Human erythrocytes contained a soluble cytosolic epoxide hydrolase for stereospecific enzymatic hydration of leukotriene A4 into leukotriene B4. The enzyme was purified 1100-fold, to apparent electrophoretic homogeneity, by conventional DEAE-Sephacel fractionation followed by high performance anion exchange and chromatofocusing procedures. Its characteristics include a molecular weight of 54,000 +/- 1,000, an isoelectric point 4.9 +/- 0.2, a Km apparent from 7 to 36 microM for enzymatic hydration of leukotriene A4, and a pH optimum ranging from 7 to 8. The enzyme was partially inactivated by its initial exposure to leukotriene A4. There was slow but detectable enzymatic hydration (pmol/min/mg) of certain arachidonic acid epoxides including (+/-)-14,15-oxido-5,8-11-eicosatrienoic acid and (+/-)-11,12-oxido-5,8,14-eicosatrienoic acid, but not others, including 5,6-oxido-8,11,14-eicosatrienoic acid. Human erythrocyte epoxide hydrolase did not hydrate either styrene oxide or trans-stilbene oxide. In terms of its physical properties and substrate preference for leukotriene A4, the erythrocyte enzyme differs from previously described versions of epoxide hydrolase. Human erythrocytes represent a novel source for an extrahepatic, cytosolic epoxide hydrolase with a potential physiological role.

Topics: 8,11,14-Eicosatrienoic Acid; Arachidonic Acids; Chromatography; Cytosol; Electrophoresis, Polyacrylamide Gel; Epoxide Hydrolases; Erythrocytes; Humans; Isoelectric Point; Leukotriene A4; Leukotriene B4; Molecular Weight; Stilbenes; Substrate Specificity

The regiospecificity of arachidonic acid oxygenation, catalyzed by rat liver microsomal fractions in the presence of NADPH, can be altered by animal pretreatment with a fibric acid type of hypolipidemic drug, ciprofibrate. While microsomal fractions isolated from either control or phenobarbital-treated animals oxygenate arachidonic acid to mainly epoxyeicosatrienoic acids (EETs), animal pretreatment with ciprofibrate results in an eightfold stimulation of omega and omega-1 oxidation, concomitant with a net decrease in the formation of both HETEs and EETs. The isomeric composition of the EETs and of the omega and omega-1 oxidation products formed is also dependent on the type of animal pretreatment. Associated decreases in the amounts of HETEs and the rate of hydrogen peroxide formation suggests a modification of the "uncoupler action" of arachidonic acid during the function of different cytochromes P-450.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acid; Arachidonic Acids; Benzphetamine; Chromatography, High Pressure Liquid; Clofibrate; Clofibric Acid; Cytochrome P-450 Enzyme System; Fatty Acids, Unsaturated; Fibric Acids; Gas Chromatography-Mass Spectrometry; Hydroxyeicosatetraenoic Acids; Hypolipidemic Agents; Lauric Acids; Male; Microsomes, Liver; NADP; Oxidation-Reduction; Rats; Rats, Inbred Strains