Up-regulation of endothelial nitric-oxide synthase by endothelium-derived hyperpolarizing factor involves mitogen-activated protein kinase and protein kinase C signaling pathways

The involvement of soluble epoxide hydrolase in the development of cardiovascular diseases through epoxyeicosatrienoic acids

Arachidonic acid (AA) has three main metabolic pathways: the cycloxygenases (COXs) pathway, the lipoxygenases (LOXs) pathway, and the cytochrome P450s (CYPs) pathway. AA produces epoxyeicosatrienoic acids (EETs) through the CYPs pathway. EETs are very unstable in vivo and can be degraded in seconds to minutes. EETs have multiple degradation pathways, but are mainly degraded in the presence of soluble epoxide hydrolase (sEH). sEH is an enzyme of bifunctional nature, and current research focuses on the activity of its C-terminal epoxide hydrolase (sEH-H), which hydrolyzes the EETs to the corresponding inactive or low activity diol. Previous studies have reported that EETs have cardiovascular protective effects, and the activity of sEH-H plays a role by degrading EETs and inhibiting their protective effects. The activity of sEH-H plays a different role in different cells, such as inhibiting endothelial cell proliferation and migration, but promoting vascular smooth muscle cell proliferation and migration. Therefore, it is of interest whether the activity of sEH-H is involved in the initiation and progression of cardiovascular diseases by affecting the function of different cells through EETs.

Heat stress induces ferroptosis of porcine Sertoli cells by enhancing CYP2C9-Ras- JNK axis

Heat stress leads to the accumulation of lipid peroxides in Sertoli cells. Unrestricted lipid peroxidation of catalyzed polyunsaturated fatty acids by Cytochrome P450 (CYP) drive the ferroptosis. However, little is known about the role of CYP cyclooxygenase in heat stress-induced ferroptosis in Sertoli cells. In this study, we investigated the relationship between CYP cyclooxygenase and heat stress-induced ferroptosis in porcine Sertoli cells, as well as whether Ras-JNK signaling is involved in the process. The results showed that heat stress significantly increased the expression of cytochrome P450 cyclooxygenase 2C9 (CYP2C9) and the content of epoxyeicosatrienoic acids (EETs), although there are no significant effect on the expression of cytochrome P450 cyclooxygenase 2J2 (CYP2J2) and cytochrome P450 cyclooxygenase 2C8 (CYP2C8). In addition, heat stress reduced the cell viability, the protein expression level of glutathione peroxidase 4 (GPX4) and Ferritin (all P < 0.01) while increased the level of intracellular reactive oxygen species (ROS) and the protein level of Transferrin receptor 1(TFR1) (both P < 0.01), as well as activating the Ras-JNK signaling pathway. Ferrostatin-1, a ferroptosis-specific inhibitor, reduced ROS levels and the protein level of TFR1 (both P < 0.01), but elevated the cell viability, the protein level of GPX4, and Ferritin (all P < 0.01). Sulfaphenazole, a specific inhibitor of CYP2C9 or two small interfering RNAs targaring CYP2C9 enhanced the cell viability (all P < 0.01), while reduced the content of EETs (all P < 0.01) and inhibited the Ras-JNK signaling and ferroptosis under heat stress. Salirasib, a specific inhibitor of Ras, significantly elevated the cell viability, whereas reduced the level of intracellular ROS and inhibited the phosphorylation of JNK, and alleviated heat stress-induced ferroptosis in porcine Sertoli cells. Notably, there is no effect on the expression of CYP2C9 and the content of EETs. These results indicate that heat stress can induce ferroptosis in Sertoli cells by increasing the expression of CYP2C9 and the content of EETs, which in true activates the Ras-JNK signaling pathway, but there is no feedback from Ras-JNK signaling to the expression of CYP2C9. Our study finds a novel heat stress-induced cell death model of Sertoli cells as well as providing the therapeutic potential for anti-ferroptosis.

Effect of inflammation on cytochrome P450-mediated arachidonic acid metabolism and the consequences on cardiac hypertrophy

The incidence of heart failure (HF) is generally preceded by cardiac hypertrophy (CH), which is the enlargement of cardiac myocytes in response to stress. During CH, the metabolism of arachidonic acid (AA), which is present in the cell membrane phospholipids, is modulated. Metabolism of AA gives rise to hydroxyeicosatetraenoic acids (HETEs) and epoxyeicosatrienoic acids (EETs) via cytochrome P450 (CYP) ω-hydroxylases and CYP epoxygenases, respectively. A plethora of studies demonstrated the involvement of CYP-mediated AA metabolites in the pathogenesis of CH. Also, inflammation is known to be a characteristic hallmark of CH. In this review, our aim is to highlight the impact of inflammation on CYP-derived AA metabolites and CH. Inflammation is shown to modulate the expression of various CYP ω-hydroxylases and CYP epoxygenases and their respective metabolites in the heart. In general, HETEs such as 20-HETE and mid-chain HETEs are pro-inflammatory, while EETs are characterized by their anti-inflammatory and cardioprotective properties. Several mechanisms are implicated in inflammation-induced CH, including the modulation of NF-κB and MAPK. This review demonstrated the inflammatory modulation of cardiac CYPs and their metabolites in the context of CH and the anti-inflammatory strategies that can be employed in the treatment of CH and HF.

The multifaceted role of cytochrome P450-Derived arachidonic acid metabolites in diabetes and diabetic cardiomyopathy

Understanding lipid metabolism is a critical key to understanding the pathogenesis of Diabetes Mellitus (DM). It is known that 60-90% of DM patients are obese or used to be obese. The incidence of obesity is rising owing to the modern sedentary lifestyle that leads to insulin resistance and increased levels of free fatty acids, predisposing tissues to utilize more lipids with less glucose uptake. However, the exact mechanism is not yet fully elucidated. Diabetic cardiomyopathy seems to be associated with these alterations in lipid metabolism. Arachidonic acid (AA) is an important fatty acid that is metabolized to several bioactive compounds by cyclooxygenases, lipoxygenases, and the more recently discovered, cytochrome P450 (P450) enzymes. P450 metabolizes AA to either epoxy-AA (EETs) or hydroxy-AA (HETEs). Studies showed that EETs could have cardioprotective effects and beneficial effects in reversing abnormalities in glucose and insulin homeostasis. Conversely, HETEs, most importantly 12-HETE and 20-HETE, were found to interfere with normal glucose and insulin homeostasis and thus, might be involved in diabetic cardiomyopathy. In this review, we highlight the role of P450-derived AA metabolites in the context of DM and diabetic cardiomyopathy and their potential use as a target for developing new treatments for DM and diabetic cardiomyopathy.

ROS-responsive nanoparticle-mediated delivery of CYP2J2 gene for therapeutic angiogenesis in severe hindlimb ischemia

With critical limb ischemia (CLI) being a multi-factorial disease, it is becoming evident that gene therapy with a multiple bio-functional growth factor could achieve better therapeutic outcomes. Cytochrome P450 epoxygenase-2J2 (CYP2J2) and its catalytic products epoxyeicosatrienoic acids (EETs) exhibit pleiotropic biological activities, including pro-angiogenic, anti-inflammatory and cardiovascular protective effects, which are considerably beneficial for reversing ischemia and restoring local blood flow in CLI. Here, we designed a nanoparticle-based pcDNA3.1-CYP2J2 plasmid DNA (pDNA) delivery system (nanoparticle/pDNA complex) composed of a novel three-arm star block copolymer (3S-PLGA-po-PEG), which was achieved by conjugating three-armed PLGA to PEG via the peroxalate ester bond. Considering the multiple bio-functions of CYP2J2-EETs and the sensitivity of the peroxalate ester bond to H₂O₂, this nanoparticle-based gene delivery system is expected to exhibit excellent pro-angiogenic effects while improving the high oxidative stress and inflammatory micro-environment in ischemic hindlimb. Our study reports the first application of CYP2J2 in the field of therapeutic angiogenesis for CLI treatment and our findings demonstrated good biocompatibility, stability and sustained release properties of the CYP2J2 nano-delivery system. In addition, this nanoparticle-based gene delivery system showed high transfection efficiency and efficient VEGF expression in vitro and in vivo. Intramuscular injection of nanoparticle/pDNA complexes into mice with hindlimb ischemia resulted in significant rapid blood flow recovery and improved muscle repair compared to mice treated with naked pDNA. In summary, 3S-PLGA-po-PEG/CYP2J2-pDNA complexes have tremendous potential and provide a practical strategy for the treatment of limb ischemia. Moreover, 3S-PLGA-po-PEG nanoparticles might be useful as a potential non-viral carrier for other gene delivery applications.

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Cytochrome P450 epoxygenase-2J2 (CYP2J2) was first applied in the field of therapeutic angiogenesis for critical limb ischemia treatment.

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The ROS-responsive three-arm star block copolymer (3S-PLGA-po-PEG) was synthesized with peroxalate ester as H₂O₂-responsive linkages through the esterification reaction of oxalyl chloride and hydroxyl group.

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The CYP2J2 nano-delivery system achieved high transfection efficiency and significant therapeutic angiogenesis effect.

Soluble Epoxide Hydrolase Inhibitors Regulate Ischemic Arrhythmia by Targeting MicroRNA-1

Background: Soluble epoxide hydrolase inhibitors (sEHis) inhibit the degradation of epoxyeicosatrienoic acids (EETs) in cells, and EETs have antiarrhythmic effects. Our previous experiments confirmed that t-AUCB, a preparation of sEHis, inhibited ischemic arrhythmia by negatively regulating microRNA-1 (miR-1), but its specific mechanism remained unclear. Aim: This study aimed to examine the role of serum response factor (SRF) and the PI3K/Akt/GSK3β pathway in t-AUCB-mediated regulation of miR-1 and the interaction between them. Methods/Results: We used SRF small interfering RNA (siSRF), SRF small hairpin (shSRF) RNA sequence adenovirus, PI3K/Akt/GSK3β pathway inhibitors, t-AUCB, and 14,15-EEZE (a preparation of EETs antagonists) to treat mouse cardiomyocytes overexpressing miR-1 and mice with myocardial infarction (MI). We found that silencing SRF attenuated the effects on miR-1 and its target genes KCNJ2 and GJA1 in the presence of t-AUCB, and inhibition of the PI3K/Akt/GSK3β pathway antagonized the effects of t-AUCB on miR-1, KCNJ2, and GJA1, which were associated with PI3Kα, Akt, and Gsk3β but not PI3Kβ or PI3Kγ. Moreover, the PI3K/Akt/GSK3β pathway was involved in the regulation of SRF by t-AUCB, and silencing SRF inhibited the t-AUCB-induced increases in Akt and Gsk3β phosphorylation. Conclusions: Both the SRF and the PI3K/Akt/GSK3β pathway are involved in the t-AUCB-mediated regulation of miR-1, and these factors interact with each other.

Soluble epoxide hydrolase inhibition improves cognitive function and parenchymal artery dilation in a hypertensive model of chronic cerebral hypoperfusion

OBJECTIVE

Parenchymal arterioles (PAs) regulate perfusion of the cerebral microcirculation, and impaired PA endothelium-dependent dilation occurs in dementia models mimicking chronic cerebral hypoperfusion (CCH). Epoxyeicosatrienoic acids (EETs) are vasodilators; their actions are potentiated by soluble epoxide hydrolase (sEH) inhibition. We hypothesized that chronic sEH inhibition with trifluoromethoxyphenyl-3 (1-propionylpiperidin-4-yl) urea (TPPU) would prevent cognitive dysfunction and improve PA dilation in a hypertensive CCH model.

METHODS

Bilateral carotid artery stenosis (BCAS) was used to induce CCH in twenty-week-old male stroke-prone spontaneously hypertensive rats (SHSRP) that were treated with vehicle or TPPU for 8 weeks. Cognitive function was assessed by novel object recognition. PA dilation and structure were assessed by pressure myography, and mRNA expression in brain tissue was assessed by qRT-PCR.

RESULTS

TPPU did not enhance resting cerebral perfusion, but prevented CCH-induced memory deficits. TPPU improved PA endothelium-dependent dilation but reduced the sensitivity of PAs to a nitric oxide donor. TPPU treatment had no effect on PA structure or biomechanical properties. TPPU treatment increased brain mRNA expression of brain derived neurotrophic factor, doublecortin, tumor necrosis factor-alpha, sEH, and superoxide dismutase 3, CONCLUSIONS: These data suggest that sEH inhibitors may be viable treatments for cognitive impairments associated with hypertension and CCH.

Cyp2j5-Gene Deletion Affects on Acetylcholine and Adenosine-Induced Relaxation in Mice: Role of Angiotensin-II and CYP-Epoxygenase Inhibitor

Previously, we showed vascular endothelial overexpression of human-CYP2J2 enhances coronary reactive hyperemia in Tie2-CYP2J2 Tr mice, and eNOS^−/− mice had overexpression of CYP2J-epoxygenase with adenosine A_2A receptor-induced enhance relaxation, but we did not see the response in CYP2J-epoxygenase knockout mice. Therefore, we hypothesized that Cyp2j5-gene deletion affects acetylcholine- and 5'-N-ethylcarboxamidoadenosine (NECA) (adenosine)-induced relaxation and their response is partially inhibited by angiotensin-II (Ang-II) in mice. Acetylcholine (Ach)-induced response was tested with N-(methylsulfonyl)-2-(2-propynyloxy)-benzenehexanamide (MS-PPOH, CYP-epoxygenase inhibitor; 10⁻⁵M) and Ang-II (10⁻⁶M). In Cyp2j5^−/− mice, ACh-induced relaxation was different from C57Bl/6 mice, at 10⁻⁵ M (76.1 ± 3.3 vs. 58.3 ± 5.2, P < 0.05). However, ACh-induced relaxation was not blocked by MS-PPOH in Cyp2j5^−/−: 58.5 ± 5.0%, P > 0.05, but blocked in C57Bl/6: 52.3 ± 7.5%, P < 0.05, and Ang-II reduces ACh-induced relaxation in both Cyp2j5^−/− and C57Bl/6 mice (38.8 ± 3.9% and 45.9 ± 7.8, P <0.05). In addition, NECA-induced response was tested with Ang-II. In Cyp2j5^−/− mice, NECA-induced response was not different from C57Bl/6 mice at 10⁻⁵M (23.1 ± 2.1 vs. 21.1 ± 3.8, P > 0.05). However, NECA-induced response was reduced by Ang-II in both Cyp2j5^−/− and C57Bl/6 mice (−10.8 ± 2.3% and 3.2 ± 2.7, P < 0.05). Data suggest that ACh-induced relaxation in Cyp2j5^−/− mice depends on nitric oxide (NO) but not CYP-epoxygenases, and the NECA-induced different response in male vs. female Cyp2j5^−/− mice when Ang-II treated.

Ephx2-gene deletion affects acetylcholine-induced relaxation in angiotensin-II infused mice: role of nitric oxide and CYP-epoxygenases

Previously, we showed that adenosine A_2A receptor induces relaxation independent of NO in soluble epoxide hydrolase-null mice (Nayeem et al. in Am J Physiol Regul Integr Comp Physiol 304:R23-R32, 2013). Currently, we hypothesize that Ephx2-gene deletion affects acetylcholine (Ach)-induced relaxation which is independent of A_2AAR but dependent on NO and CYP-epoxygenases. Ephx2^-/- aortas showed a lack of sEH (97.1%, P < 0.05) but an increase in microsomal epoxide hydrolase (mEH, 37%, P < 0.05) proteins compared to C57Bl/6 mice, and no change in CYP2C29 and CYP2J protein (P > 0.05). Ach-induced response was tested with nitro-L-arginine methyl ester (L-NAME) NO-inhibitor; 10^-4 M), N-(methylsulfonyl)-2-(2-propynyloxy)-benzenehexanamide (MS-PPOH) (CYP-epoxygenase inhibitor; 10^-5 M), 14,15-epoxyeicosa-5(Z)-enoic acid (14,15-EEZE, an epoxyeicosatrienoic acid-antagonist; 10^-5 M), SCH-58261 (A_2AAR-antagonist; 10^-6 M), and angiotensin-II (Ang-II, 10^-6 M). In Ephx2^-/- mice, Ach-induced relaxation was not different from C57Bl/6 mice except at 10^-5 M (92.75 ± 2.41 vs. 76.12 ± 3.34, P < 0.05). However, Ach-induced relaxation was inhibited with L-NAME (Ephx2^-/-: 23.74 ± 3.76% and C57Bl/6: 11.61 ± 2.82%), MS-PPOH (Ephx2^-/-: 48.16 ± 6.53% and C57Bl/6: 52.27 ± 7.47%), and 14,15-EEZE (Ephx2^-/-: 44.29 ± 8.33% and C57Bl/6: 39.27 ± 7.47%) vs. non-treated (P < 0.05). But, it did not block with SCH-58261 (Ephx2^-/-: 68.75 ± 11.41% and C57Bl/6: 66.26 ± 9.43%, P > 0.05) vs. non-treated (P > 0.05). Interestingly, Ang-II attenuates less relaxation in Ehx2^-/- vs. C57Bl/6 mice (58.80 ± 7.81% vs. 45.92 ± 7.76, P < 0.05). Our data suggest that Ach-induced relaxation in Ephx2^-/- mice depends on NO and CYP-epoxygenases but not on A_2A AR, and Ephx2-gene deletion attenuates less Ach-induced relaxation in Ang-II-infused mice.

Vascular Endothelial Cell Biology: An Update

The vascular endothelium, a monolayer of endothelial cells (EC), constitutes the inner cellular lining of arteries, veins and capillaries and therefore is in direct contact with the components and cells of blood. The endothelium is not only a mere barrier between blood and tissues but also an endocrine organ. It actively controls the degree of vascular relaxation and constriction, and the extravasation of solutes, fluid, macromolecules and hormones, as well as that of platelets and blood cells. Through control of vascular tone, EC regulate the regional blood flow. They also direct inflammatory cells to foreign materials, areas in need of repair or defense against infections. In addition, EC are important in controlling blood fluidity, platelet adhesion and aggregation, leukocyte activation, adhesion, and transmigration. They also tightly keep the balance between coagulation and fibrinolysis and play a major role in the regulation of immune responses, inflammation and angiogenesis. To fulfill these different tasks, EC are heterogeneous and perform distinctly in the various organs and along the vascular tree. Important morphological, physiological and phenotypic differences between EC in the different parts of the arterial tree as well as between arteries and veins optimally support their specified functions in these vascular areas. This review updates the current knowledge about the morphology and function of endothelial cells, particularly their differences in different localizations around the body paying attention specifically to their different responses to physical, biochemical and environmental stimuli considering the different origins of the EC.

Effects of epoxygenases on the nonadrenergic noncholinergic relaxant responses induced by electrical field stimulation in rabbit corpus cavernosum

We aimed to investigate the effects of epoxygenases on electrical field stimulation (EFS)-mediated nitric oxide (NO)-dependent and NO-independent nonadrenergic noncholinergic (NANC) relaxations in isolated rabbit corpus cavernosum. The tissues of 20 male adult albino rabbits (2.5-3 kg) were suspended in organ baths containing aerated Krebs solution, and isometric contractions were recorded. EFS-mediated NANC relaxations were obtained on phenylephrin (3 × 10^-5  M)-contracted tissues in the presence of guanethidine (10^-6  M) and atropine (10^-6  M). Miconazole (10^-9 -10^-4  M), 17-octadecynoic acid (ODYA) (10^-10 -10^-5  M), 14,15-epoxyeicosatrienoic acid (EET) (10^-11 -10^-8  M), 11,12-EET (10^-12 -3 × 10^-8  M) and 20-hydroxyeicosatetraenoic acid (HETE) (10^-11 -3 × 10^-8  M) were added cumulatively (n = 5-7 for each set of experiments). For NO-independent relaxations, N^ω -nitro-l-arginine methyl ester (l-NAME) (10^-4  M) was added before a group of experiments. Depending on the concentration, miconazole, 17-ODYA, 14,15-EET, 11,12-EET, and 20-HETE significantly enhanced both NO-dependent and NO-independent EFS-mediated relaxations (p < 0.05). Epoxygenases showed similar effect on NO-dependent and NO-independent relaxant responses except 20-HETE which caused significantly more enhanced relaxation on NO-dependent responses (p < 0.05). No drug caused a significant relaxation response on tissues contracted with phenylephrine. Epoxygenases contribute to EFS-mediated NO-dependent and NO-independent NANC relaxations by presynaptic mechanisms, offering a new treatment alternative for erectile dysfunction which needs to be explored in further in vivo, molecular and clinical studies.

Qishen Yiqi Dropping Pills Ameliorates Doxorubicin-induced Cardiotoxicity in Mice via Enhancement of Cardiac Angiogenesis

Background

Qishen Yiqi Dropping Pills (QYDP) is a Chinese traditional medicine that has been applied to treat coronary heart disease and ischemic heart failure in China. However, few studies have explored whether QYDP exerted an effect on doxorubicin (Doxo)-induced cardiotoxicity. Hence, in this study we investigated the effect of QYDP on cardiotoxicity induced by doxorubicin (Doxo) and its potential mechanism.

Material/Methods

Male C57BL/6 mice (20–25 g, 8–10 weeks old) were randomly assigned to 4 groups: Control group, QYDP group, Doxo group, and QYDP+Doxo group. The mice were intraperitoneal injected with Doxo weekly for 4 weeks to mimic the chronic toxicity. Four weeks after Doxo injection, echocardiography was applied to evaluate the left ventricular (LV) function, and the structure of the cardiac muscle fibers was analyzed with anti-actinin-2 antibody staining by immunofluorescence. Moreover, TUNEL staining and western blot analysis of Bax protein, Bcl-2 protein, and cleaved caspase-3 protein expression levels were conducted to explore whether QYDP exerted effect on cardiac apoptosis. In addition, Masson trichrome staining and western blot analysis of α-SMA protein expression levels were used to evaluate whether QYDP exerted an effect on cardiac fibrosis. Western blots and quantitative real-time polymerase chain reaction were applied to detect the vascular endothelial growth factor (VEGF) protein and mRNA levels in the myocardial tissue, and anti-CD31 antibody staining by immunohistochemistry was employed to explore whether QYDP exerted an effect on cardiac angiogenesis.

Results

QYDP effectively attenuated cardiac dysfunction and cardiac muscle fibers disruption in Doxo treated mice. Moreover, QYDP reduced myocardial apoptosis and myocardial fibrosis in Doxo treated mice, accompanied with elevated protein levels of VEGF and enhancement of myocardial microvessel density.

Conclusions

QYDP could protect against Doxo-induced cardiotoxicity, which may be closely associated with enhanced cardiac angiogenesis. Hence, QYDP could be a promising alternative for the treatment of Doxo-induced cardiotoxicity.

Cardioprotective Effects of QiShenYiQi Dripping Pills on Transverse Aortic Constriction-Induced Heart Failure in Mice

QiShenYiQi dripping pills (QSYQ), a traditional Chinese medicine, are commonly used to treat coronary heart disease, and QSYQ was recently approved as a complementary treatment for ischemic heart failure in China. However, only few studies reported on whether QSYQ exerts a protective effect on heart failure induced by pressure overload. In this study, we explored the role of QSYQ in a mouse model of heart failure induced by transverse aortic constriction (TAC). Twenty-eight C57BL/6J mice were divided into four groups: Sham + NS group, Sham + QSYQ group, TAC + NS group, and TAC + QSYQ group. QSYQ dissolved in normal saline (NS) was administered intragastrically (3.5 mg/100 g/day) in the Sham + QSYQ and TAC + QSYQ groups. In the Sham + NS and TAC + NS groups, NS was provided every day intragastrically. Eight weeks after TAC, echocardiography, and cardiac catheterization were performed to evaluate the cardiac function, and immunofluorescent staining with anti-actinin2 antibody was performed to determine the structure of the myocardial fibers. Moreover, TUNEL staining and Masson trichrome staining were employed to assess the effects of QSYQ on cardiac apoptosis and cardiac fibrosis. Western blots and real-time polymerase chain reaction (PCR) were used to measure the expression levels of vascular endothelial growth factor (VEGF) in the heart, and immunohistochemical staining with anti-CD31 antibody was performed to explore the role of QSYQ in cardiac angiogenesis. Results showed that TAC-induced cardiac dysfunction and disrupted structure of myocardial fibers significantly improved after QSYQ treatment. Moreover, QSYQ treatment also significantly improved cardiac apoptosis and cardiac fibrosis in TAC-induced heart failure, which was accompanied by an increase in VEGF expression levels and maintenance of microvessel density in the heart. In conclusion, QSYQ exerts a protective effect on TAC-induced heart failure, which could be attributed to enhanced cardiac angiogenesis, which is closely related to QSYQ. Thus, QSYQ may be a promising traditional Chinese medicine for the treatment of heart failure induced by pressure overload such as hypertension.

Epoxyeicosatrienoic Acid Inhibits the Apoptosis of Cerebral Microvascular Smooth Muscle Cells by Oxygen Glucose Deprivation via Targeting the JNK/c-Jun and mTOR Signaling Pathways

As a component of the neurovascular unit, cerebral smooth muscle cells (CSMCs) are an important mediator in the development of cerebral vascular diseases such as stroke. Epoxyeicosatrienoic acids (EETs) are the products of arachidonic acid catalyzed by cytochrome P450 epoxygenase. EETs are shown to exert neuroprotective effects. In this article, the role of EET in the growth and apoptosis of CSMCs and the underlying mechanisms under oxygen glucose deprivation (OGD) conditions were addressed. The viability of CMSCs was decreased significantly in the OGD group, while different subtypes of EETs, especially 14,15-EET, could increase the viability of CSMCs under OGD conditions. RAPA (serine/threonine kinase Mammalian Target of Rapamycin), a specific mTOR inhibitor, could elevate the level of oxygen free radicals in CSMCs as well as the anti-apoptotic effects of 14,15-EET under OGD conditions. However, SP600125, a specific JNK (c-Jun N-terminal protein kinase) pathway inhibitor, could attenuate oxygen free radicals levels in CSMCs as well as the anti-apoptotic effects of 14,15-EET under OGD conditions. These results strongly suggest that EETs exert protective functions during the growth and apoptosis of CSMCs, via the JNK/c-Jun and mTOR signaling pathways in vitro. We are the first to disclose the beneficial roles and underlying mechanism of 14,15-EET in CSMC under OGD conditions.

CYP2J2 metabolites, epoxyeicosatrienoic acids, attenuate Ang II-induced cardiac fibrotic response by targeting Gα12/13

The arachidonic acid-cytochrome P450 2J2-epoxyeicosatrienoic acid (AA-CYP2J2-EET) metabolic pathway has been identified to be protective in the cardiovascular system. This study explored the effects of the AA-CYP2J2-EET metabolic pathway on cardiac fibrosis from the perspective of cardiac fibroblasts and underlying mechanisms. In in vivo studies, 8-week-old male CYP2J2 transgenic mice (aMHC-CYP2J2-Tr) and littermates were infused with angiotensin II (Ang II) or saline for 2 weeks. Results showed that CYP2J2 overexpression increased EET production. Meanwhile, impairment of cardiac function and fibrotic response were attenuated by CYP2J2 overexpression. The effects of CYP2J2 were associated with reduced activation of the α subunits of G12 family G proteins (Gα_12/13)/RhoA/Rho kinase (ROCK) cascade and elevation of the NO/cyclic guanosine monophosphate (cGMP) level in cardiac tissue. In in vitro studies, cardiac fibroblast activation, proliferation, migration, and collagen production induced by Ang II were associated with activation of the Gα_12/13/RhoA/ROCK pathway, which was inhibited by exogenous 11,12-EET. Moreover, silencing of Gα_12/13 or RhoA exerted similar effects as 11,12-EET. Furthermore, inhibitory effects of 11,12-EET on Gα_12/13 were blocked by NO/cGMP pathway inhibitors. Our findings indicate that enhancement of the AA-CYP2J2-EET metabolic pathway by CYP2J2 overexpression attenuates Ang II-induced cardiac dysfunction and fibrosis by reducing the fibrotic response of cardiac fibroblasts by targeting the Gα_12/13/RhoA/ROCK pathway via NO/cGMP signaling.

miR-320a mediates doxorubicin-induced cardiotoxicity by targeting VEGF signal pathway

Background

Vascular homeostasis abnormalities may involve in doxorubicin induced cardiotoxicity.

Methods

Enhanced cardiac miR-320a expression, reduced cardiac microvessel density and impaired cardiac function were observed in mice treated by anthracycline doxorubicin. To further explore the role of miR-320a in doxorubicin induced cardiotoxicity, microRNA mimics/inhibitor in vitro and rAAV administration in vivo were employed in mice.

Results

Knockdown of miR-320a not only resulted in enhanced proliferation and inhibited apoptosis in cultured endothelial cells, but also attenuated cardiac abnormalities induced by doxorubicin. On the contrary, overexpression of miR-320a enhanced apoptosis in vitro, and aggravated vessel abnormalities in heart and subsequent cardiac dysfunction in mice. Furthermore, Western blot assays showed that VEGF-A was a potential target of miR-320a, which was verified by anti-Ago2 co-immunoprecipitation. Moreover, as same as miR-320a, siRNA against VEGF-A reinforced doxorubicin induced endothelial cells injury. Finally, the negative effects of miR-320a on vascular homeostasis and cardiac function were alleviated by VEGF-A re-expression in doxorubicin treated mice.

Conclusion

Our observations demonstrate that miR-320a play important roles in doxorubicin induced cardiotoxicity via vessel homeostasis in heart and thus, inhibition of miR-320a may be applied to the treatment of cardiac dysfunction induced by anthracycline.

The Role of Cytochrome P450 Epoxygenases, Soluble Epoxide Hydrolase, and Epoxyeicosatrienoic Acids in Metabolic Diseases

Metabolic diseases are associated with an increased risk of developing cardiovascular disease. The features comprising metabolic diseases include obesity, insulin resistance, hyperglycemia, hyperlipidemia, and hypertension. Recent evidence has emerged showcasing a role for cytochrome P450 epoxygenases, soluble epoxide hydrolase, and epoxyeicosatrienoic acids (EETs) in the development and progression of metabolic diseases. This review discusses the current knowledge related to the modulation of cytochrome P450 epoxygenases and soluble epoxide hydrolase to alter concentrations of biologically active EETs, resulting in effects on insulin resistance, lipid metabolism, obesity, and diabetes. Future areas of research to address current deficiencies in the understanding of these enzymes and their eicosanoid metabolites in various aspects of metabolic diseases are also discussed.

Cardiotonic Pill Reduces Myocardial Ischemia-Reperfusion Injury via Increasing EET Concentrations in Rats

Accumulating data suggest that epoxyeicosatrienoic acids (EETs) and 20-hydroxyeicosatetraenoic acid, both cytochrome P450 (P450) enzyme metabolites of arachidonic acid (AA), play important roles in cardiovascular diseases. For many years, the cardiotonic pill (CP), an herbal preparation derived from Salviae Miltiorrhizae Radix et Rhizoma, Notoginseng Radix et Rhizoma, and Borneolum Syntheticum, has been widely used in China for the treatment of coronary artery disease. However, its pharmacological mechanism has not been well elucidated. The purpose of this study was to investigate the chronic effects of the CP on myocardial ischemia-reperfusion injury (MIRI) and AA P450 enzyme metabolism in rats (in vivo) and H9c2 cells (in vitro). The results showed that CP dose dependently (10, 20, and 40 mg/kg/d; 7 days) mitigated MIRI in rats. The plasma concentrations of EETs in CP-treated ischemia-reperfusion (I/R) rats (40 mg/kg/d; 7 days) were significantly higher (P < 0.05) than those in controls. Cardiac Cyp1b1, Cyp2b1, Cyp2e1, Cyp2j3, and Cyp4f6 were significantly induced (P < 0.05); CYP2J and CYP2C11 proteins were upregulated (P < 0.05); and AA-epoxygenases activity was significantly increased (P < 0.05) after CP (40 mg/kg/d; 7 days) administration in rats. In H9c2 cells, the CP also increased (P < 0.05) the EET concentrations and showed protection in hypoxia-reoxygenation (H/R) cells. However, an antagonist of EETs, 14,15-epoxyeicosa-5(Z)-enoic acid, displayed a dose-dependent depression of the CP's protective effects in H/R cells. In conclusion, upregulation of cardiac epoxygenases after multiple doses of the CP-leading to elevated concentrations of cardioprotective EETs after myocardial I/R-may be the underlying mechanism, at least in part, for the CP's cardioprotective effect in rats.

Pharmacokinetics, pharmacodynamics and adverse event profile of GSK2256294, a novel soluble epoxide hydrolase inhibitor

AIMS

Endothelial-derived epoxyeicosatrienoic acids may regulate vascular tone and are metabolized by soluble epoxide hydrolase enzymes (sEH). GSK2256294 is a potent and selective sEH inhibitor that was tested in two phase I studies.

METHODS

Single escalating doses of GSK2256294 2-20 mg or placebo were administered in a randomized crossover design to healthy male subjects or obese smokers. Once daily doses of 6 or 18 mg or placebo were administered for 14 days to obese smokers. Data were collected on safety, pharmacokinetics, sEH enzyme inhibition and blood biomarkers. Single doses of GSK2256294 10 mg were also administered to healthy younger males or healthy elderly males and females with and without food. Data on safety, pharmacokinetics and biliary metabolites were collected.

RESULTS

GSK2256294 was well-tolerated with no serious adverse events (AEs) attributable to the drug. The most frequent AEs were headache and contact dermatitis. Plasma concentrations of GSK2256294 increased with single doses, with a half-life averaging 25-43 h. There was no significant effect of age, food or gender on pharmacokinetic parameters. Inhibition of sEH enzyme activity was dose-dependent, from an average of 41.9% on 2 mg (95% confidence interval [CI] -51.8, 77.7) to 99.8% on 20 mg (95% CI 99.3, 100.0) and sustained for up to 24 h. There were no significant changes in serum VEGF or plasma fibrinogen.

CONCLUSIONS

GSK2256294 was well-tolerated and demonstrated sustained inhibition of sEH enzyme activity. These data support further investigation in patients with endothelial dysfunction or abnormal tissue repair, such as diabetes, wound healing or COPD.

miR-21-3p regulates cardiac hypertrophic response by targeting histone deacetylase-8

AIMS

Growing evidences indicate that microRNAs (miRNAs) are involved in cardiac hypertrophy development. Multiple miRNAs have been identified as diagnostic and prognostic biomarkers of cardiac hypertrophy, as well as potential therapeutic tools. The present study aimed to investigate the functions and regulatory mechanisms of miR-21-3p in cardiac hypertrophy.

METHODS AND RESULTS

Decreased expression of miR-21-3p was observed in cardiac hypertrophy induced by transverse aortic constriction (TAC) and angiotensin (Ang) II infusion in mice. To further explore the role of miR-21-3p in cardiac hypertrophy, rAAV-miR-21-3p was administered intravenously in mice. Overexpression of miR-21-3p markedly suppressed TAC-induced cardiac hypertrophy and also blocked Ang II-induced cardiac hypertrophy as determined by cardiac function measurement and biomarker detection. Furthermore, western blot assays showed that histone deacetylase-8 (HDAC8) was silenced by miR-21-3p, and luciferase reporter assays showed that miR-21-3p binds to the 3' UTR of HDAC8. Moreover, re-expression of HDAC8 attenuated miR-21-3p-mediated suppression of cardiac hypertrophy by enhancing phospho-Akt and phospho-Gsk3β expression.

CONCLUSION

Our data reveal a role of miR-21-3p in regulating HDAC8 expression and Akt/Gsk3β pathway, and suggest that modulation of miR-21-3p levels may provide a therapeutic approach for cardiac hypertrophy.

Chronic inhibition of cyclic guanosine monophosphate-specific phosphodiesterase 5 prevented cardiac fibrosis through inhibition of transforming growth factor β-induced Smad signaling

Recent evidences suggested that cyclic guanosine monophosphate-specific phosphodiesterase 5 (PDE5) inhibitor represents an important therapeutic target for cardiovascular diseases. Whether and how it ameliorates cardiac fibrosis, a major cause of diastolic dysfunction and heart failure, is unknown. The purpose of this study was to investigate the effects of PDE5 inhibitor on cardiac fibrosis. We assessed cardiac fibrosis and pathology in mice subjected to transverse aortic constriction (TAC). Oral sildenafil, a PDE5 inhibitor, was administered in the therapy group. In control mice, 4 weeks of TAC induced significant cardiac dysfunction, cardiac fibrosis, and cardiac fibroblast activation (proliferation and transformation to myofibroblasts). Sildenafil treatment markedly prevented TAC-induced cardiac dysfunction, cardiac fibrosis and cardiac fibroblast activation but did not block TAC-induced transforming growth factor-β1 (TGF-β1) production and phosphorylation of Smad2/3. In isolated cardiac fibroblasts, sildenafil blocked TGF-β1-induced cardiac fibroblast transformation, proliferation and collagen synthesis. Furthermore, we found that sildenafil induced phosphorylated cAMP response element binding protein (CREB) and reduced CREB-binding protein 1 (CBP1) recruitment to Smad transcriptional complexes. PDE5 inhibition prevents cardiac fibrosis by reducing CBP1 recruitment to Smad transcriptional complexes through CREB activation in cardiac fibroblasts.

Chronic inhibition of cGMP-specific phosphodiesterase 5 suppresses endoplasmic reticulum stress in heart failure

BACKGROUND AND PURPOSE

Inhibition of the cGMP-specific phosphodiesterase 5 (PDE5) exerts profound beneficial effects on failing hearts. However, the mechanisms underlying the therapeutic effects of PDE5 inhibition on heart failure are unclear. The purpose of this study was to investigate whether PDE5 inhibition decreases endoplasmic reticulum (ER) stress, a key event in heart failure.

EXPERIMENTAL APPROACH

Heart failure was induced by isoprenaline s.c. injection in Sprague-Dawley rats and transverse aortic constriction (TAC) in mice. PDE5 was inhibited with sildenafil. Heart function was detected by invasive pressure-volume analysis and echocardiography. ER stress markers were analysed by Western blotting. Apoptosis was measured by flow cytometric analysis.

KEY RESULTS

PDE5 inhibition markedly attenuated isoprenaline-induced and TAC-induced cardiac hypertrophy and dysfunction, and reduced ER stress and apoptosis. Further, PDE5 inhibition with sildenafil largely prevented ER stress and reduced apoptosis in isoprenaline- or thapsigargin-treated cardiomyocytes. PKG inhibition markedly prevented the protective effects of sildenafil in vivo and in vitro. To further understand the mechanism of the effect of PDE5 inhibition on ER stress, we demonstrated that PDE5 inhibitor increased sarco-(endo)-plasmic reticulum Ca(2+) -ATPase activity via phosphorylation of phospholamban at Ser(16) . This may contribute to the attenuation of ER stress induced by PDE5 inhibition.

CONCLUSION AND IMPLICATIONS

These results suggest that PDE5 inhibition can attenuate ER stress and improve cardiac function in vivo and in vitro. Suppression of ER stress by inhibiting PDE5 may contribute to the therapeutic effects on heart failure.

A potential therapeutic effect of CYP2C8 overexpression on anti-TNF-α activity

Epoxyeicosatrienoic acids (EETs) are generated from arachidonic acid catalysed by cytochrome P450 (CYP) epoxygenases. In addition to regulating vascular tone EETs may alleviate inflammation and ROS. The present study was conducted to determine whether CYP2C8 gene overexpression was able to increase the level of EETs, and subsequently prevent TNF-α induced inflammation and reactive oxygen species (ROS) in human umbilical vein endothelial cells (HUVECs) and macrophages. Peroxisome proliferator-activated receptor γ (PPARγ) activation, nuclear factor-κB (NF-κB) activation, endothelial nitric oxide synthase (eNOS) activation, gp-91 activation, and inflammatory cytokine expression were detected by western blot analysis or enzyme-linked immunosorbent assay. Intracellular reactive oxygen species (ROS) was measured by flow cytometry, while the migration of vascular smooth muscle cells (VSMCs) was detected by Transwell assay. pCMV-mediated CYP2C8 overexpression and its metabolites, EETs, markedly suppressed TNF-α induced inflammatory cytokines IL-6 and MCP-1 expression via the activation of NF-κB and degradation of IκBα. Moreover, pretreatment with 11,12-EET significantly blocked TNF-α-induced ROS production. CYP2C8-derived EETs also effectively alleviated the migration of VSMCs and improved the function of endothelial cells through the upregulation of eNOS, which was significantly decreased under the stimulation of TNF-α. Furthermore, these protective effects observed were mediated by PPARγ activation. To the best of our knowledge, the results of the present study demonstrated for the first time that CYP2C8-derived EETs exerted antivascular inflammatory and anti-oxidative effects, at least in part, through the activation of PPARγ. Thus, the CYP2C8 gene may be useful in the prevention and treatment of vascular inflammatory diseases.

Cardiac-specific overexpression of CYP2J2 attenuates diabetic cardiomyopathy in male streptozotocin-induced diabetic mice

Cytochrome P450 (CYP) epoxygenases metabolize arachidonic acid to biologically active cis-epoxyeicosatrienoic acids, which have potent vasodilatory, antiinflammatory, antiapoptotic, and antidiabetes properties. Here, we showed the effects of cardiac-specific overexpression of CYP epoxygenase 2J2 (CYP2J2) on diabetic cardiomyopathy and insulin resistance in high-fat (HF) diet fed, low-dose streptozotocin-treated mice. Diabetic cardiomyopathy was induced by HF and streptozotocin in cardiac-specific CYP2J2 transgenic mice. Physiological parameters and systemic metabolic parameters were monitored using ELISA kits. Intraperitoneal injection glucose tolerance test and hyperinsulinemic-euglycemic clamp study were implied to indicate insulin resistance. Cardiac function was assessed by echocardiography and Millar catheter system. Real-time PCR and Western blotting were used in signal pathway detection. αMHC-CYP2J2 transgenic mice showed significantly lower plasma glucose and insulin levels, improved glucose tolerance, and increased cardiac glucose uptake. Furthermore, αMHC-CYP2J2 transgenic mice were significantly protected from HF-streptozotocin-induced diabetic cardiomyopathy. Strikingly, CYP2J2 overexpression attenuated myocardial hypertrophy induced by diabetes. We conclude that cardiac-specific overexpression of CYP2J2 significantly protects against diabetic cardiomyopathy, which may be due to improved cardiac insulin resistance, glucose uptake, and reversal of cardiac hypertrophy. Relevant mechanisms may include up-regulation of peroxisome proliferator-activated receptor γ, activation of insulin receptor and AMP-activated protein kinase signaling pathways, and inhibition of nuclear factor of activated T cells c3 signal by enhanced atrial natriuretic peptide production. These results suggest that CYP2J2 epoxygenase metabolites likely play an important role in plasma glucose homeostasis, and enhancement of epoxyeicosatrienoic acids activation may serve as an effective therapeutic strategy to prevent diabetic cardiomyopathy.

Indapamide lowers blood pressure by increasing production of epoxyeicosatrienoic acids in the kidney

Diuretics are widely used in the treatment of hypertension, although the precise mechanisms remain unknown. Epoxyeicosatrienoic acids (EETs), cytochrome P450 (P450) epoxygenase metabolites of arachidonic acid, play critical roles in regulation of blood pressure. The present study was carried out to investigate whether EETs participate in the antihypertensive effect of thiazide diuretics [hydrochlorothiazide (HCTZ)] and thiazide-like diuretics (indapamide). Male spontaneously hypertensive rats (SHRs) were treated with indapamide or HCTZ for 8 weeks. Systolic blood pressure, measured via tail-cuff plethysmography and confirmed via intra-arterial measurements, was significantly decreased in indapamide- and HCTZ-treated SHRs compared with saline-treated SHRs. Indapamide increased kidney CYP2C23 expression, decreased soluble epoxide hydrolase expression, increased urinary and renovascular 11,12- and 14,15-EETs, and decreased production of 11,12- and 14,15-dihydroxyeicosatrienoic acids in SHRs. No effect on expression of CYP4A1 or CYP2J3, or on 20-hydroxyeicosatetraenoic acid production, was observed, suggesting indapamide specifically targets CYP2C23-derived EETs. Treatment of SHRs with HCTZ did not affect the levels of P450s or their metabolites. Increased cAMP activity and protein kinase A expression were observed in the renal microvessels of indapamide-treated SHRs. Indapamide ameliorated oxidative stress and inflammation in renal cortices by down-regulating the expression of p47phox, nuclear factor-κB, transforming growth factor-β1, and phosphorylated mitogen-activated protein kinase. Furthermore, the p47phox-lowering effect of indapamide in angiotensin II-treated rat mesangial cells was partially blocked by the presence of N-(methylsulfonyl)-2-(2-propynyloxy)-benzenehexanamide (MS-PPOH) or CYP2C23 small interfering RNA. Together, these results indicate that the hypotensive effects of indapamide are mediated, at least in part, by the P450 epoxygenase system in SHRs, and provide novel insights into the blood pressure-lowering mechanisms of diuretics.

Roles of endothelial nitric oxide synthase (eNOS) and mitochondrial permeability transition pore (MPTP) in epoxyeicosatrienoic acid (EET)-induced cardioprotection against infarction in intact rat hearts

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 suggest that the cardioprotective effects of the EETs in an acute ischemia-reperfusion model are mediated by distinct mediators depending on the time of EET administration. The cardioprotective effects of EETs administered prior to ischemia were regulated by the activation of eNOS and increased NO production, while sarcKATP channels and MPTP were involved in the beneficial effects of the EETs when administered just prior to reperfusion.

Cytochrome P450 2J2 is protective against global cerebral ischemia in transgenic mice

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.

Genetic disruption of soluble epoxide hydrolase is protective against streptozotocin-induced diabetic nephropathy

Cytochrome P-450 (CYP) epoxygenases metabolize arachidonic acid into epoxyeicosatrienoic acids (EETs), which play important roles in regulating cardiovascular functions. The anti-inflammatory, antiapoptotic, proangiogenic, and antihypertensive properties of EETs suggest a beneficial role for EETs in diabetic nephropathy. Endogenous EET levels are maintained by a balance between synthesis by CYP epoxygenases and hydrolysis by epoxide hydrolases into physiologically less active dihydroxyeicosatrienoic acids. Genetic disruption of soluble epoxide hydrolase (sEH/EPHX2) results in increased EET levels through decreased hydrolysis. This study investigated the effects of sEH gene disruption on diabetic nephropathy in streptozotocin-induced diabetic mice. Streptozotocin-induced diabetic manifestations were attenuated in sEH-deficient mice relative to wild-type controls, with significantly decreased levels of Hb A(1c), creatinine, and blood urea nitrogen and urinary microalbumin excretion. The sEH-deficient diabetic mice also had decreased renal tubular apoptosis that coincided with increased levels of antiapoptotic Bcl-2 and Bcl-xl, and decreased levels of the proapoptotic Bax. These effects were associated with activation of the PI3K-Akt-NOS3 and AMPK signaling cascades. sEH gene inhibition and exogenous EETs significantly protected HK-2 cells from TNFα-induced apoptosis in vitro. These findings highlight the beneficial role of the CYP epoxygenase-EETs-sEH system in the pathogenesis of diabetic nephropathy and suggest that the sEH inhibitors available may be potential therapeutic agents for this condition.

Epoxides and soluble epoxide hydrolase in cardiovascular physiology

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

Factors mediating remote preconditioning of trauma in the rat heart: central role of the cytochrome p450 epoxygenase pathway in mediating infarct size reduction

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.

Epoxyeicosatrienoic acids protect rat hearts against tumor necrosis factor-α-induced injury

Epoxyeicosatrienoic acids (EET), the primary arachidonic acid metabolites of cytochrome P450 2J (CYP2J) epoxygenases, possess potent vasodilatory, anti-inflammatory, antiapoptotic, and mitogenic effects. To date, little is known about the role of CYP2J2 and EETs in tumor necrosis factor (TNF)-α-induced cardiac injury. We utilized cell culture and in vivo models to examine the effects of exogenously applied EETs or CYP2J2 overexpression on TNF-α-induced cardiac apoptosis and cardiac dysfunction. In neonatal rat cardiomyocytes, TNF-α-induced apoptosis was markedly attenuated by EETs or CYP2J2 overexpression, leading to significantly improved cell survival. Further studies showed that TNF-α decreased expression of the antiapoptotic proteins Bcl-2 and Bcl-xL, decreased IκBα and PPARγ, and also inhibited PI3K-dependent Akt and EGFR signaling. Both EETs and CYP2J2 overexpression reversed the effects of TNF-α on these pathways. Furthermore, overexpression of CYP2J2 in rats prevented the decline in cardiac function that is normally observed in TNF-α-challenged animals. These results demonstrate that EETs or CYP2J2 overexpression can prevent TNF-α-induced cardiac cell injury and cardiac dysfunction by inhibiting apoptosis, reducing inflammation, and enhancing PPARγ expression. Targeting the CYP2J2 epoxygenase pathway may represent a novel approach to mitigate cardiac injury in diseases such as heart failure, where increased TNF-α levels are known to occur.

CYP2J3 gene delivery reduces insulin resistance via upregulation of eNOS in fructose-treated rats

Accumulating evidence suggests that cytochrome P450 (CYP) epoxygenases metabolize arachidonic acid into epoxyeicosatrienoic acids (EETs) which play important roles in various pathophysiological processes. Interestingly, CYP-derived eicosanoids are vasodilatory, at least in part through their ability to activate eNOS and subsequent NO release. This study investigated the roles of eNOS in CYP2J3 gene delivery reducing blood pressure and improving insulin resistance in fructose-treated rats. CYP2J3 overexpression in vivo increased EET generation, reduced blood pressure and reversed insulin resistance as determined by insulin resistance index (HOMA-IR). Furthermore, administration of eNOS inhibitor L-NMMA significantly and partially abolished the beneficial effects of CYP2J3 gene delivery on hypertension and insulin resistance induced by fructose intake, and possible mechanism is associated with increased ET-1, ET_A-receptor mRNA expression and reduced sensitivity of insulin to peripheral tissues and organs characterized by reduced activity of IRS-1/PI3K/AKT and AMPK signalling pathways. These data provide direct evidence that CYP2J3-derived EETs may alleviate insulin resistance at least in part through upregulated eNOS expression.

Epoxyeicosatrienoic acids attenuate reactive oxygen species level, mitochondrial dysfunction, caspase activation, and apoptosis in carcinoma cells treated with arsenic trioxide

Epoxyeicosatrienoic acids (EETs) and the cytochrome P450 epoxygenase CYP2J2 promote tumorogenesis in vivo and in vitro via direct stimulation of tumor cell growth and inhibition of tumor cell apoptosis. Herein, we describe a novel mechanism of inhibition of tumor cell apoptosis by EETs. In Tca-8113 cancer cells, the antileukemia drug arsenic trioxide (ATO) led to the generation of reactive oxygen species (ROS), impaired mitochondrial function, and induced apoptosis. 11,12-EET pretreatment increased expression of the antioxidant enzymes superoxide dismutase and catalase and inhibited ATO-induced apoptosis. 11,12-EET also prevented the ATO-induced activation of p38 mitogen-activated protein kinase, c-Jun NH(2)-terminal kinase, caspase-3, and caspase-9. Therefore, 11,12-EET-pretreatment attenuated the ROS generation, loss of mitochondrial function, and caspase activation observed after ATO treatment. Moreover, the CYP2J2-specific inhibitor compound 26 enhanced arsenic cytotoxicity to a clinically relevant concentration of ATO (1-2 μM). Both the thiol-containing antioxidant, N-acetyl-cysteine, and 11,12-EET reversed the synergistic effect of the two agents. Taken together, these data indicate that 11,12-EET inhibits apoptosis induced by ATO through a mechanism that involves induction of antioxidant proteins and attenuation of ROS-mediated mitochondrial dysfunction.

The roles of CYP450 epoxygenases and metabolites, epoxyeicosatrienoic acids, in cardiovascular and malignant diseases

Cytochrome P450 (CYP) epoxygenases metabolize arachidonic acid to biologically active eicosanoids. The primary epoxidation products are four regioisomers of cis-epoxyeicosatrienoic acid (EET): 5,6-, 8,9-, 11,12-, and 14,15-EET. CYP2J2, CYP2C8, and CYP2C9 are the predominant epoxygenase isoforms involved in EET formation. CYP2J and CYP2C gene families in humans are abundantly expressed in the endothelium, myocardium, and kidney. The cardiovascular effects of CYP epoxygenases and EETs range from vasodilation, anti-hypertension, pro-angiogenesis, anti-atherosclerosis, and anti-inflammation to anti-injury caused by ischemia-reperfusion. Using transgenic animals for in vivo analyses of CYP epoxygenases revealed comprehensive and marked cardiovascular protective effects. In contrast, CYP epoxygenases and their metabolites, EETs, are upregulated in human tumors and promote tumor progression and metastasis. These biological effects result from the anti-apoptosis, pro-mitogenesis, and anti-migration roles of CYP epoxygenases and EETs at the cellular level. Importantly, soluble epoxide hydrolase (sEH) inhibitors are anti-hypertensive and anti-inflammatory and, therefore, protect the heart from damage, whereas the terfenadine-related, specific inhibitors of CYP2J2 exhibit strong anti-tumor activity in vitro and in vivo. Thus, CYP2J2 and arachidonic acid-derived metabolites likely play important roles in regulating cardiovascular functions and malignancy under physiological and/or pathological conditions. Moreover, although challenges remain to improving the drug-like properties of sEH inhibitors and identifying efficient ways to deliver sEH inhibitors, sEH will likely become an important therapeutic target for cardiovascular diseases. In addition, CYP2J2 may be a therapeutic target for treating human cancers and leukemia.

Cytochrome P450 epoxygenase CYP2J2 attenuates nephropathy in streptozotocin-induced diabetic mice

Cytochrome P450 (CYP) epoxygenases metabolize arachidonic acid into epoxyeicosatrienoic acids (EETs), which play important and diverse roles in the cardiovascular system. The anti-inflammatory, anti-apoptotic, pro-angiogenic, and anti-hypertensive properties of EETs in the cardiovascular system suggest a beneficial role for EETs in diabetic nephropathy. This study investigated the effects of endothelial specific overexpression of CYP2J2 epoxygenase on diabetic nephropathy in streptozotocin-induced diabetic mice. Endothelial CYP2J2 overexpression attenuated renal damage as measured by urinary microalbumin and glomerulosclerosis. These effects were associated with inhibition of TGF-β/Smad signaling in the kidney. Indeed, overexpression of CYP2J2 prevented TGF-β1-induced renal tubular epithelial-mesenchymal transition in vitro. These findings highlight the beneficial roles of the CYP epoxygenase-EET system in the pathogenesis of diabetic nephropathy.

Inhibition of soluble epoxide hydrolase attenuates endothelial dysfunction in animal models of diabetes, obesity and hypertension

Endothelial dysfunction is a hallmark of, and plays a pivotal role in the pathogenesis of cardiometabolic diseases, including type II diabetes, obesity, and hypertension. It has been well established that epoxyeicosatrienoic acids (EETs) act as an endothelial derived hyperpolarization factor (EDHF). Soluble epoxide hydrolase (s-EH) rapidly hydrolyses certain epoxylipids (e.g. EETs) to less bioactive diols (DHETs), thereby attenuating the evoked vasodilator effects. The aim of the present study was to examine if inhibition of s-EH can restore impaired endothelial function in three animal models of cardiometabolic diseases. Isolated vessel rings of the aorta and/or mesenteric artery from mice or rats were pre-contracted using phenylephrine or U46619. Endothelium-dependent and independent vasorelaxation to acetylcholine and sodium nitroprusside (SNP) were measured using wire myography in vessels isolated from db/db or diet-induced obesity (DIO) mice, and angiotensin II-induced hypertensive rats treated chronically with s-EH inhibitors AR9281 or AR9276 or with vehicle. Vasorelaxation to acetylcholine, but not to SNP was severely impaired in all three animal models. Oral administration of AR9281 or AR9276 abolished whole blood s-EH activity, elevated epoxy/diol lipid ratio, and abrogated endothelial dysfunction in all three models. Incubating the mesenteric artery of db/db mice with L-NAME and indomethacin to block nitric oxide (NO) and prostacyclin formation did not affect AR9821-induced improvement of endothelial function. These data indicate that inhibition of s-EH ameliorates endothelial dysfunction and that effects in the db/db model are independent of the presence of NO and cyclooxygenase derived prostanoids. Thus, preserving vasodilator EETs by inhibition of s-EH may be of therapeutic benefit by improving endothelial function in cardiometabolic diseases.

Role of cytochrome P450 enzymes in the bioactivation of polyunsaturated fatty acids

Cytochrome P450 (CYP)-dependent metabolites of arachidonic acid (AA), such as epoxyeicosatrienoic acids and 20-hydroxyeicosatetraenoic acid, serve as second messengers of various hormones and growth factors and play pivotal roles in the regulation of vascular, renal and cardiac function. As discussed in the present review, virtually all of the major AA metabolizing CYP isoforms accept a variety of other polyunsaturated fatty acids (PUFA), including linoleic, eicosapentaenoic (EPA) and docosahexaenoic acids (DHA), as efficient alternative substrates. The metabolites of these alternative PUFAs also elicit profound biological effects. The CYP enzymes respond to alterations in the chain-length and double bond structure of their substrates with remarkable changes in the regio- and stereoselectivity of product formation. The omega-3 double bond that distinguishes EPA and DHA from their omega-6 counterparts provides a preferred epoxidation site for CYP1A, CYP2C, CYP2J and CYP2E subfamily members. CYP4A enzymes that predominantly function as AA ω-hydroxylases show largely increased (ω-1)-hydroxylase activities towards EPA and DHA. Taken together, these findings indicate that CYP-dependent signaling pathways are highly susceptible to changes in the relative bioavailability of the different PUFAs and may provide novel insight into the complex mechanisms that link essential dietary fatty acids to the development of cardiovascular disease.

Activation of the ERK signaling pathway is involved in CD151-induced angiogenic effects on the formation of CD151-integrin complexes

AIM

To assess the roles of extracellular signal-regulated kinase (ERK), p38, and CD151-integrin complexes on proliferation, migration, and tube formation activities of CD151-induced human umbilical vein endothelial cells (HUVECs).

METHODS

CD151, anti-CD151 and CD151-AAA mutant were inserted into recombinant adeno-associated virus (rAAV) vectors and used to transfect HUVECs. After transfection, the expression of CD151 was measured. Proliferation was assessed using the 3-[4,5-dimethylthiazol- 2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assay. Cell migration was evaluated in Boyden transwell chambers using FBS as the chemotactic stimulus. The tube formation assay was performed on matrigel. The potential involvement of various signaling pathways was explored using selective inhibitors.

RESULTS

CD151 gene delivery increased the expression of CD151 at both the mRNA and protein levels. Overexpression of CD151 promoted cell proliferation, migration and tube formation in vitro, and phosphorylation of ERK was also increased. Further, CD151-induced cell proliferation, migration, and tube formation were attenuated by the ERK inhibitor PD98059 (20 micromol/L) but not by a p38 inhibitor (SB203580, 20 micromol/L). Moreover, there was no significant difference in CD151 protein expression between the CD151 group and the CD151-AAA group, but the CD151-AAA mutant abrogated cellular proliferation, migration, and tube formation and decreased the phosphorylation of ERK.

CONCLUSION

This study suggests that activation of the ERK signaling pathway may be involved in the angiogenic effects of CD151. Activation of ERK was dependent on the formation of CD151-integrin complexes. Therefore modulation of CD151 may be as a novel therapeutic strategy for regulating angiogenesis.

Overexpression of cytochrome P450 epoxygenases prevents development of hypertension in spontaneously hypertensive rats by enhancing atrial natriuretic peptide

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

A novel loss-of-function DDAH1 promoter polymorphism is associated with increased susceptibility to thrombosis stroke and coronary heart disease

RATIONALE

Asymmetrical dimethylarginine (ADMA), an endogenous arginine analogue, inhibits nitric oxide synthases and plays an important role in endothelial dysfunction.

OBJECTIVE

In the present study, we tested whether a novel genetic variant in dimethylarginine dimethylaminohydrolase 1 (DDAH1), an important ADMA hydrolyzing gene, was associated with stroke and coronary heart disease (CHD) susceptibility in the Chinese Han population.

METHODS AND RESULTS

By resequencing, we identified a novel 4-nucleotide deletion/insertion variant in the DDAH1 promoter. The insertion allele disrupted binding of metal-regulatory transcription factor 1, which resulted in significant reduction of in vitro DDAH1 transcriptional activity and in vivo DDAH1 mRNA level, and in turn, increased plasma ADMA level and the ratio of ADMA to L-arginine. We initially genotyped the polymorphism in 1388 stroke patients and 1027 controls as well as 576 CHD patients and 557 controls and then replicated our study in additional independent case-control cohorts comprising 961 stroke patients and 822 controls and 482 CHD patients and 1072 controls. We identified that the -396 4N ins allele was significantly associated with increased risk of thrombosis stroke and CHD after adjusting for environmental factors in both samples for both diseases (thrombosis stroke discovery set: odds ratio [OR]=1.35, P=0.032; replication set: OR=1.51, P=0.006; CHD discovery set: OR=1.45, P=0.035; replication set: OR=1.47, P=0.003).

CONCLUSIONS

Our results suggest that the DDAH1 loss-of-function polymorphism is associated with both increased risk of thrombosis stroke and CHD.

Increased CYP2J3 expression reduces insulin resistance in fructose-treated rats and db/db mice

OBJECTIVE

Accumulating evidence suggests that cytochrome P450 (CYP) epoxygenases metabolize arachidonic acid into epoxyeicosatrienoic acids (EETs), which play crucial and diverse roles in cardiovascular homeostasis. The anti-inflammatory, antihypertensive, and pro-proliferative effects of EETs suggest a possible beneficial role for EETs on insulin resistance and diabetes.

RESEARCH DESIGN AND METHODS

This study investigated the effects of CYP2J3 epoxygenase gene therapy on insulin resistance and blood pressure in diabetic db/db mice and in a model of fructose-induced hypertension and insulin resistance in rats.

RESULTS

CYP2J3 gene delivery in vivo increased EET generation, reduced blood pressure, and reversed insulin resistance as determined by plasma glucose levels, homeostasis model assessment insulin resistance index, and glucose tolerance test. Furthermore, CYP2J3 treatment prevented fructose-induced decreases in insulin receptor signaling and phosphorylation of AMP-activated protein kinases (AMPKs) in liver, muscle, heart, kidney, and aorta. Thus, overexpression of CYP2J3 protected against diabetes and insulin resistance in peripheral tissues through activation of insulin receptor and AMPK pathways.

CONCLUSIONS

These results highlight the beneficial roles of the CYP epoxygenase-EET system in diabetes and insulin resistance.