Epoxyeicosatrienoic acids limit damage to mitochondrial function following stress in cardiac cells

Epoxyeicosatrienoic acids (EETs) are polyunsaturated fatty acids synthesized from arachidonic acid by CYP2J2 epoxygenase and inactivated by soluble epoxide hydrolase (sEH or Ephx2) to dihydroxyeicosatrienoic acids. Mitochondrial function following ischemic insult is a critical determinant of reperfusion-induced cell death in the myocardium. The objectives of the current study were to investigate the protective role of EETs in mitochondrial function. Mice with the targeted disruption of the Ephx2 gene, cardiomyocyte-specific overexpression of CYP2J2 or perfused with EETs all have improved postischemic LVDP recovery compared to wild-type (WT). Perfusion with the mPTP opener, atractyloside, abolished the improved postischemic functional recovery observed in CYP2J2 Tr, sEH null and EET perfused hearts. Electron micrographs demonstrated WT hearts to have increased mitochondrial fragmentation and T-tubule swelling compared to CYP2J2 Tr hearts following 20 min global ischemia and 20 min reperfusion. Direct effects of EETs on mitochondria were assessed in isolated rat cardiomyocytes and H9c2 cells. Laser-induced loss of mitochondrial membrane potential (ΔΨ_m) and mPTP opening was significantly reduced in cells treated with 14, 15-EET (1 μM). The EET protective effect was blocked by the putative EET antagonist 14,15-epoxyeicosa-5(Z)-enoic acid (1 μM, 14, 15-EEZE), paxilline (10 μM, BK_Ca inhibitor) and 5HD (100 μM, K_ATP inhibitor). Our studies show that EETs can limit mitochondrial dysfunction following cellular stress via a K⁺ channel-dependent mechanism.     

花生四烯酸细胞色素P450表氧化酶代谢产物EET促进血管生成的研究

目的研究花生四烯酸细胞色素P450（cytochrome P450,CYP）表氧化酶代谢产物表氧二十碳三烯酸（epoxyeicosatrienoic acid,EET）对牛主动脉内皮细胞（bovine endothelial cells,BAEC）、对血管生成的影响及其机制.方法分离BAEC培养,给予外源性EET刺激、重组腺相关病毒介导的各种CYP表氧化酶（CYP2J2,CYP2C11,CYPF87V）转染后,采用细胞计数、噻唑蓝比色法检测细胞增殖改变,用流式细胞仪检测对细胞增殖周期的影响,同时检测细胞趋化移行的改变,比较对Matrigel中毛细血管样结构形成的影响,观察表氧化酶过度表达对鸡胚尿囊绒毛膜血管生成和大鼠缺血后肢毛细血管生成的影响.结果各种EET刺激或表氧化酶病毒转染均显著促进BAEC的增殖、趋化和移行,并使Matrigel中毛细血管样结构的形成明显增加,且EET呈剂量依赖性效应,而合用一氧化氮合酶抑制剂、丝裂原激活的蛋白激酶（mitogen-activated protein kinase,MAPK）抑制剂或磷脂酰肌醇-3激酶（phosphatidylinositol 3-kinase,PI3K）抑制剂均可显著抑制上述效应,另外表氧化酶病毒转染尚能明显促进CAM小血管和大鼠缺血后肢毛细血管的生成.结论花生四烯酸细胞色素P450（CYP）表氧化酶及其代谢产物EET可显著促进血管的生成,可改善局部组织的缺血,其作用由MAKP和PI3K介导,部分效应由其对一氧化氮的上调作用介导.     

花生四烯酸细胞色素P450表氧化酶在自发性高血压大鼠血压的调节中的作用

背景与目的花生四烯酸细胞色素P450（CYP）表氧化酶代谢花生四烯酸产生表氧化廿烷酸（EETs），又称为内皮源性超极化因子（EDHFs），在局部微循环的调节中起着重要作用。然而EETs在血压的调节中是否起作用还不清楚。本研究通过对成年自发性高血压大鼠导入花生四烯酸细胞色素表氧化酶基因来观察其血压变化，从而进一步明确EETs在血压调节中的作用。方法：将含人类细胞色素P450表氧化酶CYP2J2 cDNA的真核细胞表达质粒pcDNA．2J2经静脉注射（3mg／kg）人雄性成年自发性高血压大鼠，并以pcDNA3．1对照。然后用尾部血压计测量血压。并在注射后3周和4周时处死动物，检测CYP2J2在不同组织中的表达情况。结果：注射质粒后对照组血压一直无显著性变化，而pcDNA．2J2治疗组大鼠血压显著降低（P〈0．05），这一降压效应持续两周以上。Western blotting显示在实验组动物肺、肝和肾的总蛋白中通过特异性抗-CYP2J2抗体可检测出显著量的人类CYP2J2蛋白的表达。结论：本实验显示对成年自发性高血压大鼠导人人类CYP2J2基因，使CYP2J2可以在动物组织中高表达，从而引起相对持久的降压作用，这些结果提示花生四烯酸细胞色素P450表氧化酶通过产生EDHFs参与了动物血压的调节作用。     

Modulation of the Ca2 permeable cation channel TRPV4 by cytochrome P450 epoxygenases in vascular endothelium

TRPV4 is a broadly expressed Ca2+-permeable cation channel in the vanilloid subfamily of transient receptor potential channels. TRPV4 gates in response to a large variety of stimuli, including cell swelling, warm temperatures, the synthetic phorbol ester 4alpha-phorbol 12,13-didecanoate (4alpha-PDD), and the endogenous lipid arachidonic acid (AA). Activation by cell swelling and AA requires cytochrome P450 (CYP) epoxygenase activity to convert AA to epoxyeicosatrienoic acids (EETs) such as 5,6-EET, 8,9-EET, which both act as direct TRPV4 agonists. To evaluate the role of TRPV4 and its modulation by the CYP pathway in vascular endothelial cells, we performed Ca2+ imaging and patch-clamp measurements on mouse aortic endothelial cells (MAECs) isolated from wild-type and TRPV4(-/-) mice. All TRPV4-activating stimuli induced robust Ca2+ responses in wild-type MAECs but not in MAECs isolated from TRPV4(-/-) mice. Upregulation of CYP2C expression by preincubation with nifedipine enhanced the responses to AA and cell swelling in wild-type MAECs, whereas responses to other stimuli remained unaffected. Conversely, inhibition of CYP2C9 activity with sulfaphenazole abolished the responses to AA and hypotonic solution (HTS). Moreover, suppression of EET hydrolysis using 1-adamantyl-3-cyclo-hexylurea or indomethacin, inhibitors of soluble epoxide hydrolases (sEHs), and cyclooxygenases, respectively, enhanced the TRPV4-dependent responses to AA, HTS, and EETs but not those to 4alpha-PDD or heat. Together, our data establish that CYP-derived EETs modulate the activity of TRPV4 channels in endothelial cells and shows the unraveling of novel modulatory pathways via CYP2C modulation and sEH inhibition.     

Downregulation of renal CYP-derived eicosanoid synthesis in rats with diet-induced hypertension

The incidence of essential hypertension increases with obesity; however, the mechanisms that link obesity with hypertension are unclear. Renal cytochrome P450 (CYP)-derived eicosanoids--hydroxyeicosatetraenoic acids (HETEs), epoxyeicosatrienoic acids (EETs), and dihydroxyeicosatrienoic acids (DHETs)--have been shown to play an important role in the regulation of renal function, vascular tone, and blood pressure. The objective of this study was to examine CYP-derived eicosanoid synthesis in the different renal zones (cortex, medulla, and papilla) of rats fed a high fat diet (HF). Male Sprague-Dawley rats were fed a HF diet or regular rat chow for 10 weeks. After 10 weeks, HF rats showed significantly higher systolic blood pressure, body weight, and fat:body weight ratio. The renal omega-hydroxylase activity was decreased by 46% in cortex, 43% in medulla, and 46% in papilla of HF rats. The renal epoxygenase activity was decreased by 46% in cortex, 31% in medulla, and 56% in papilla of HF rats. Interestingly, the changes in the rate of 20-HETE and EET formation in different renal zones were consistent with the levels of expression of CYP4A and CYP2C23 proteins, respectively. Furthermore, there were no significant changes in the synthesis of these metabolites in the renal microvessels. These results demonstrate that HF diet causes the downregulation of CYP4A and CYP2C23 in renal tubules, and these proteins are responsible for renal 20-HETE and EET formation. The reduction in the synthesis of these eicosanoids may play an important role in the regulation of renal function and blood pressure in obesity-induced hypertension.     

Inhibition of vascular smooth muscle cell migration by cytochrome p450 epoxygenase-derived eicosanoids

Vascular smooth muscle cell (SMC) migration and proliferation contribute to neointimal hyperplasia and restenosis after vascular injury. The epoxyeicosatrienoic acids (EETs), which are products of cytochrome P450 (CYP) epoxygenases, possess vasodilatory, antiinflammatory, and fibrinolytic properties. To determine whether these compounds also possess antimigratory and antiproliferative properties, we stimulated rat aortic SMCs with either 20% serum or platelet-derived growth factor (PDGF-BB, 20 ng/mL). In a concentration-dependent manner, treatment with EETs, particularly 11,12-EET, inhibited SMC migration through a modified transwell filter by 53% to 60%. EETs, however, have no inhibitory effects on PDGF-stimulated SMC proliferation. Adenoviral-mediated overexpression of the CYP isoform, CYP2J2, in SMCs also inhibited serum- and PDGF-induced SMC migration by 32% and 26%, respectively; both effects of which were reversed by the CYP inhibitors SKF525A or clotrimazole, but not by the K(Ca) channel blocker, charybdotoxin, or the cyclooxygenase inhibitor, diclofenac. The effect of EETs correlated with increases in intracellular cAMP levels. Indeed, forskolin and 8-bromo-cAMP exert similar inhibitory effects on SMC migration as 11,12-EET and the effects of 11,12-EET were blocked by cAMP and protein kinase A (PKA) inhibitors. These findings indicate that EETs possess antimigratory effects on SMCs through the cAMP-PKA pathway and suggest that CYP epoxygenase-derived eicosanoids may play important roles in vascular disease and remodeling.     

Insulin resistance and endothelial dysfunction: Are epoxyeicosatrienoic acids the link?

Epoxyeicosatrienoic acids (EETs), the cytochrome P450 epoxygenase metabolites of arachidonic acid, are potent vasodilators and are believed to be the endothelium-derived hyperpolarizing factor in a number of vascular beds. In addition, EETs may play a role in the secretion and action of insulin and the metabolism of carbohydrates and lipids. Pharmacological manipulation of EETs may be a useful therapeutic approach for disease states such as hypertension, diabetes mellitus and the metabolic syndrome. EET mimetics and antagonists and drugs that increase EET synthesis or decrease their degradation are currently under investigation. The cellular mechanism of action of EETs appears to be complex and is being intensively studied by a number of investigators. In the present article, EET production, metabolism, isomerism and vasodilatory effects will be reviewed and potential mechanisms of action discussed. The role of EETs in insulin secretion and sensitivity and their implication in diabetes mellitus and the metabolic syndrome will also be reviewed. Drugs affecting EET bioavailability and action may be promising agents to use to treat hypertension/insulin resistance. The effects of these agents in experimental vascular disorders will also be discussed.     

Hydrogen peroxide inhibits cytochrome p450 epoxygenases: interaction between two endothelium-derived hyperpolarizing factors

The cytochrome P450 epoxygenase (CYP)-derived metabolites of arachidonic acid the epoxyeicosatrienoic acids (EETs) and hydrogen peroxide (H2O2) both function as endothelium-derived hyperpolarizing factors (EDHFs) in the human coronary microcirculation. However, the relative importance of and potential interactions between these 2 vasodilators remain unexplored. We identified a novel inhibitory interaction between CYPs and H2O2 in human coronary arterioles, where EDHF-mediated vasodilatory mechanisms are prominent. Bradykinin induced vascular superoxide and H2O2 production in an endothelium-dependent manner and elicited a concentration-dependent dilation that was reduced by catalase but not by 14,15-epoxyeicosa-5(Z)-enoic acid (EEZE), 6-(2-propargyloxyphenyl)hexanoic acid, sulfaphenazole, or iberiotoxin. However, in the presence of catalase, an inhibitory effect of these compounds was unmasked. In a tandem-bioassay preparation, application of bradykinin to endothelium-intact donor vessels elicited dilation of downstream endothelium-denuded detectors that was partially inhibited by donor-applied catalase but not by detector-applied EEZE; however, EEZE significantly inhibited dilation in the presence of catalase. EET production by human recombinant CYP 2C9 and 2J2, 2 major epoxygenase isozymes expressed in human coronary arterioles, was directly inhibited in a concentration-dependent fashion by H2O2 in vitro, as observed by high-performance liquid chromatography (HPLC); however, EETs were not directly sensitive to oxidative modification. H2O2 inhibited dilation to arachidonic acid but not to 11,12-EET. These findings suggest that an inhibitory interaction exists between 2 EDHFs in the human coronary microcirculation. CYP epoxygenases are directly inhibited by H2O2, and this interaction may modulate vascular EET bioavailability.     

Angiotensin II regulates adrenal vascular tone through zona glomerulosa cell-derived EETs and DHETs

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.     

Involvement of eicosanoids in release of oxytocin and vasopressin from the neural lobe of the rat pituitary

Arachidonic acid (AA) is oxidized via three pathways which result in several series of distinct metabolites. Cyclooxygenase produces prostaglandins (PGs), prostacyclins, and thromboxanes. Lipoxygenase produces hydroperoxy/hydroxyeicosatetraenoic acids (HPETE/HETEs) and leukotrienes. Epoxygenase, a recently uncovered pathway, results in epoxyeicosatrienoic acids (EETs). Based on reverse phase HPLC product analysis, this study establishes that all three pathways of AA metabolism are present in microsomal incubates of the neural lobe of the pituitary gland. Addition of PGE2 to incubated fragments of neural lobes of the rat pituitary stimulates secretion of both arginine vasopressin (AVP) and oxytocin in vitro. Inclusion of 5-HETE and 12-HETE in the incubation medium stimulates marginal release of AVP and oxytocin by 12-HETE only. The magnitude of AVP and oxytocin secretion stimulated by the epoxygenase metabolites 8,9-, 11,12-, and 14,15-EET is equal to that caused by PGE2. Maximal stimulation of secretion (3- to 4-fold) requires an EET concentration 10-15 times greater than that of PGE2. In contrast, 5,6-EET is inactive. These data suggest that oxygenated products of AA play a role in AVP and oxytocin secretion. Although PGs appear to be the dominant arachidonate metabolites involved in the release of AVP and oxytocin, the EETs probably have a contributing role.     

Endothelium-derived epoxyeicosatrienoic acids and vascular function

Epoxyeicosatrienoic acids (EETs) are epoxides of arachidonic acid generated by cytochrome P450 (CYP) epoxygenases. The activation of CYP epoxygenases in endothelial cells is an important step in the NO and prostacyclin-independent vasodilatation of several vascular beds, and EETs have been identified as an endothelium-derived hyperpolarizing factor. However, EETs also exert membrane potential-independent effects and modulate several signaling cascades that affect endothelial cell proliferation and angiogenesis. This review summarizes the role of CYP-derived EETs in endothelium-derived hyperpolarizing factor-mediated responses and highlights the evidence indicating that EETs are important second messengers involved in endothelial cell signaling pathways related to angiogenesis.     

Cytochrome P450 2C is an EDHF synthase in coronary arteries

Studies designed to elucidate the identity of the potent vasodilator autacoid endothelium-derived hyperpolarizing factor (EDHF) in the coronary vascular bed have highlighted a role for vascular cytochrome P450 (CYP) enzymes in cardiovascular homeostasis. Not only is there strong evidence suggesting that the putative coronary EDHF synthase is an endothelially expressed CYP epoxygenase, but CYP products such as epoxyeicosatrienoic acids and reactive oxygen species have been implicated in the regulation of intracellular signalling cascades and vascular cell proliferation.     

Epoxygenase products of arachidonic acid are endogenous constituents of the hypothalamus involved in D2 receptor-mediated, dopamine-induced release of somatostatin

The epoxyeicosatrienoic acids (EETs) were discovered as products of a cyclooxygenase/lipoxygenase-independent, cytochrome P-450 catalyzed metabolism of arachidonic acid (AA) termed the "epoxygenase" pathway. The rat hypothalamus is able to synthesize EETs from exogenous AA, and 5,6-EET has been found to release the neuropeptide somatostatin (SRIF) from hypothalamic nerve terminals of the median eminence (ME). In the present study, hypothalami from male rats were examined for the presence of endogenous EETs, using chemical, chromatographic, and mass spectral analysis procedures. The samples were initially separated in a C18 Sepralyte column, fractionated on TLC plates, and purified by reverse phase HPLC. Thereafter, they were esterified (pentafluorobenzyl esters) and subjected to negative ion chemical ionization/gas chromatography (GC)/mass spectral (MS) analysis. The GC retention time and the MS fragmentation patterns revealed the presence of a mixture of 8,9-, 11,12- and 14,15-EETs; instability of 5,6-EET during the isolation protocol precluded its identification. Total hypothalamic EET concentration was estimated to be 120 ng/g wet tissue. The 8,9-regiosomer released SRIF from ME nerve terminals with an ED50 of 5 x 10(-12) M; Dopamine (DA) and the D2 receptor agonist PPHT, but not the D1 receptor agonist SKF-38393, induced SRIF release from the ME. This effect was blocked by clotrimazole and ketoconazole, two inhibitors of microsomal cytochrome P-450 function and AA epoxygenase in particular. In contrast, the inhibitors failed to affect the increase in SRIF release induced by 8,9-EET. These results indicate that: 1) in addition to cyclooxygenase and lipoxygenase products, epoxygenase metabolites of AA are endogenous compounds of the hypothalamus, and 2) EETs may mediate the increase in SRIF release from hypothalamic neurons induced by the interaction of DA with D2 receptors.     

花生四烯酸细胞色素P450代谢途径在高血压中作用的研究进展

花生四烯酸是人体必须脂肪酸之一，其代谢产物具有较强生物学活性并在众多生理病理过程中发挥着重要调节作用。其在人体内主要通过环氧化酶、脂氧化酶、细胞色素P450（CYP）三大途径进行代谢。其中，越来越多的研究表明，CYP代谢途径中其关键基因CYP通过调控经ω-羟化酶、表氧化酶作用的下游产物20羟-二十烷四烯酸及表氧一二十碳三烯酸的质／量，从而影响高血压的发生发展，并且对其分子生物学机制及遗传学的研究亦成为当前的研究焦点。本文主要对CYP途径在高血压中的作用简要做一综述。     

Cytochrome P450 and arachidonic acid metabolites: role in myocardial ischemia/reperfusion injury revisited

Ischemia-reperfusion of the heart and other organs results in the accumulation of unesterified arachidonic acid (AA) via the action of membrane-bound phospholipases, primarily phospholipase A2. AA can be metabolized by the classical cyclooxygenase (COX) and lipoxygenase (LOX) pathways to well-characterized metabolites and their respective cardioprotective end products such as prostacyclin (PGI2) and 12-hydroxyeicosatetraenoic acid (12-HETE). However, it has only been recently recognized that another less well-characterized pathway of AA metabolism, the cytochrome P450 (CYP) pathway, may have important cardiovascular effects. Several lines of data support the possibility that certain CYP metabolites resulting from the hydroxylation of AA such as 20-hydroxyeicosatetraenoic acid (20-HETE) are potent vasoconstrictors and may produce detrimental effects in the heart during ischemia and pro-inflammatory effects during reperfusion. On the other hand, a group of regioisomers resulting from the epoxidation of AA, including 5,6-, 8,9-, 11,12- and 14,15-epoxyeicosatrienoic acid (EETs), have been shown to reduce ischemic and/or reperfusion injury in the heart and vasculature. This review will discuss the detrimental and beneficial actions, including the potential cellular mechanisms responsible as a result of stimulating or inhibiting the two arms of this novel CYP pathway. The therapeutic potential of increasing EET concentrations and/or reducing 20-HETE concentrations will also be addressed.     

Epoxyeicosanoids promote organ and tissue regeneration

Epoxyeicosatrienoic acids (EETs), lipid mediators produced by cytochrome P450 epoxygenases, regulate inflammation, angiogenesis, and vascular tone. Despite pleiotropic effects on cells, the role of these epoxyeicosanoids in normal organ and tissue regeneration remains unknown. EETs are produced predominantly in the endothelium. Normal organ and tissue regeneration require an active paracrine role of the microvascular endothelium, which in turn depends on angiogenic growth factors. Thus, we hypothesize that endothelial cells stimulate organ and tissue regeneration via production of bioactive EETs. To determine whether endothelial-derived EETs affect physiologic tissue growth in vivo, we used genetic and pharmacological tools to manipulate endogenous EET levels. We show that endothelial-derived EETs play a critical role in accelerating tissue growth in vivo, including liver regeneration, kidney compensatory growth, lung compensatory growth, wound healing, corneal neovascularization, and retinal vascularization. Administration of synthetic EETs recapitulated these results, whereas lowering EET levels, either genetically or pharmacologically, delayed tissue regeneration, demonstrating that pharmacological modulation of EETs can affect normal organ and tissue growth. We also show that soluble epoxide hydrolase inhibitors, which elevate endogenous EET levels, promote liver and lung regeneration. Thus, our observations indicate a central role for EETs in organ and tissue regeneration and their contribution to tissue homeostasis.     

Dynamic modulation of interendothelial gap junctional communication by 11,12-epoxyeicosatrienoic acid

Functional gap junctional communication between vascular cells has been implicated in ascending dilatation and the cytochrome P-450 (CYP) inhibitor-sensitive and NO- and prostacyclin-independent dilatation of many vascular beds. Here, we assessed the mechanisms by which the epoxyeicosatrienoic acids (EETs) generated by a CYP 2C enzyme control interendothelial gap junctional communication. In CYP 2C-expressing porcine coronary endothelial cells, bradykinin, which enhances EET formation, elicited a biphasic effect on the electrical coupling and transfer of Lucifer yellow between endothelial cells, consisting of a transient increase in coupling followed by a sustained uncoupling. The initial phase was sensitive to the CYP 2C9 inhibitor sulfaphenazole and the protein kinase A (PKA) inhibitors Rp-cAMPS and KT5720 and could be mimicked by forskolin and caged cAMP as well as by the PKA activators 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole 3',5'-cyclic monophosphorothioate sodium salt and Sp-cAMPS. Gap junction uncoupling in bradykinin-stimulated porcine coronary endothelial cells was prevented by inhibiting the activation of extracellular signal-regulated kinase (ERK)1/2. In human endothelial cells, which express little CYP 2C, bradykinin elicited only an ERK1/2-mediated inhibition of intercellular communication. The CYP 2C9 product, 11,12-EET, also exerted a dual effect on the electrical and dye coupling of human endothelial cells, which was sensitive to PKA inhibition. These results demonstrate that an agonist-activated CYP-dependent pathway as well as 11,12-EET can positively regulate interendothelial gap junctional communication, most probably via the activation of PKA, an effect that is curtailed by the subsequent activation of ERK1/2.     

Evaluation of cytochrome P450-derived eicosanoids in humans with stable atherosclerotic cardiovascular disease

ObjectivePreclinical 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.MethodsPlasma 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.ResultsObesity 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).ConclusionsCollectively, 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.     

Enhanced postischemic functional recovery in CYP2J2 transgenic hearts involves mitochondrial ATP-sensitive K+ channels and p42/p44 MAPK pathway

Human CYP2J2 is abundant in heart and active in the biosynthesis of epoxyeicosatrienoic acids (EETs); however, the functional role of this P450 and its eicosanoid products in the heart remains unknown. Transgenic mice with cardiomyocyte-specific overexpression of CYP2J2 were generated. CYP2J2 transgenic (Tr) mice have normal heart anatomy and basal contractile function. CYP2J2 Tr hearts have improved recovery of left ventricular developed pressure (LVDP) compared with wild-type (WT) hearts after 20 minutes ischemia and 40 minutes reperfusion. Perfusion with the selective P450 epoxygenase inhibitor N-methylsulphonyl-6-(2-proparglyloxyphenyl)hexanamide (MS-PPOH) for 20 minutes before ischemia results in reduced postischemic LVDP recovery in WT hearts and abolishes the improved postischemic LVDP recovery in CYP2J2 Tr hearts. Perfusion with the ATP-sensitive K(+) channel (K(ATP)) inhibitor glibenclamide (GLIB) or the mitochondrial K(ATP) (mitoK(ATP)) inhibitor 5-hydroxydecanoate (5-HD) for 20 minutes before ischemia abolishes the cardioprotective effects of CYP2J2 overexpression. Flavoprotein fluorescence, a marker of mitoK(ATP) activity, is higher in cardiomyocytes from CYP2J2 Tr versus WT mice. Moreover, CYP2J2-derived EETs (1 to 5 micromol/L) increase flavoprotein fluorescence in WT cardiomyocytes. CYP2J2 Tr mice exhibit increased expression of phospho-p42/p44 mitogen-activated protein kinase (MAPK) after ischemia, and addition of the p42/p44 MAPK kinase (MEK) inhibitor PD98059 during reperfusion abolishes the cardioprotective effects of CYP2J2 overexpression. Together, these data suggest that CYP2J2-derived metabolites are cardioprotective after ischemia, and the mechanism for this cardioprotection involves activation of mitoK(ATP) and p42/p44 MAPK.