Soluble epoxide hydrolase inhibition prevents coronary endothelial dysfunction in mice with renovascular hypertension

Soluble Epoxide Hydrolase Inhibitor t-AUCB Ameliorates Vascular Endothelial Dysfunction by Influencing the NF-κB/miR-155-5p/eNOS/NO/IκB Cycle in Hypertensive Rats

Epoxyeicosatrienoic acids (EETs), angiogenic mediators degraded by soluble epoxide hydrolase (sEH), have been shown to exert beneficial effects on the cardiovascular system. The current study assessed the impact of increased EETs with an sEH inhibitor, t-AUCB, on two-kidney-one-clip (2K1C)-induced renovascular endothelial dysfunction, associated with hypertension, in rats. The hypertensive rats exhibited increased systolic blood pressure, reduced renal blood flow, impaired endothelium-dependent relaxation and eNOS phosphorylation in the renal arteries, elevated ROS production in the endothelium of the renal arteries, and decreased EET levels in plasma, the renal arteries, and endothelial cells; however, t-AUCB reversed all the deleterious effects. Moreover, we found that the stimulation of AMPK/UCP2 scavenged ROS and restored endothelial function in the renal arteries of hypertensive rats undergoing therapy with t-AUCB. In addition, we were the first to reveal the potential role of miR-155-5p in the occurrence and development of vascular endothelial dysfunction in hypertension. Importantly, t-AUCB recovered NO bioavailability by regulating the NF-κB/miR-155-5p/eNOS/NO/IκB cycle after the activation of AMPK/UCP2 and the subsequent inhibition of ROS in hypertensive rat renal artery endothelial cells. This study will provide evidence for this additional new mechanism, underlying the benefits of EETs and the related agents against hypertensive vasculopathy.

Soluble Epoxide Hydrolase Inhibition Prevents Experimental Type 4 Cardiorenal Syndrome

Objectives: Cardiovascular diseases (CVD) remain the leading cause of morbimortality in patients with chronic kidney disease (CKD). The aim of this study was to assess the cardiovascular impact of the pharmacological inhibition of soluble epoxide hydrolase (sEH), which metabolizes the endothelium-derived vasodilatory and anti-inflammatory epoxyeicosatrienoic acids (EETs) to dihydroxyeicosatrienoic acid (DHETs), in the 5/6 nephrectomy (Nx) mouse model.

Methods and Results: Compared to sham-operated mice, there was decrease in EET-to-DHET ratio 3 months after surgery in vehicle-treated Nx mice but not in mice treated with the sEH inhibitor t-AUCB. Nx induced an increase in plasma creatinine and in urine albumin-to-creatinine ratio as well as the development of kidney histological lesions, all of which were not modified by t-AUCB. In addition, t-AUCB did not oppose Nx-induced blood pressure increase. However, t-AUCB prevented the development of cardiac hypertrophy and fibrosis induced by Nx, as well as normalized the echocardiographic indices of diastolic and systolic function. Moreover, the reduction in endothelium-dependent flow-mediated dilatation of isolated mesenteric arteries induced by Nx was blunted by t-AUCB without change in endothelium-independent dilatation to sodium nitroprusside.

Conclusion: Inhibition of sEH reduces the cardiac remodelling, and the diastolic and systolic dysfunctions associated with CKD. These beneficial effects may be mediated by the prevention of endothelial dysfunction, independent from kidney preservation and antihypertensor effect. Thus, inhibition of sEH holds a therapeutic potential in preventing type 4 cardiorenal syndrome.

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.

Endothelium-dependent adaptation of arterial wall viscosity during blood flow increase is impaired in essential hypertension

BACKGROUND AND AIMS

Arterial wall viscosity (AWV) is regulated by endothelium-derived NO and epoxyeicosatrienoic acids (EETs) under baseline physiological conditions. Whether these factors regulate AWV during blood flow increase and whether this mechanism is affected in essential hypertensive patients (HT) remain unknown.

METHODS

The evolution of radial artery diameter, wall thickness and arterial pressure in response to an increase in flow induced by hand skin heating were measured in 18 untreated HT and 14 normotensive controls (NT) during local infusion of saline and the respective pharmacological inhibitors of NO-synthase and EETs synthesis by cytochrome P450, L-NMMA and/or fluconazole. AWV was estimated by the ratio of the viscous energy dissipated (W_V) to the elastic energy stored (W_E) obtained from the pressure-diameter relationship. Concomitant changes in operating conditions, which influence the AWV, were taken into account by calculating the midwall stress.

RESULTS

Baseline W_V and W_E were higher in HT than in NT but W_V/W_E was similar. In saline condition, W_V/W_E increased in HT during heating but not in NT. In the presence of L-NMMA and/or fluconazole, W_V/W_E increased during heating in NT. In contrast, these inhibitors did not modify the increase in W_V/W_E during heating in HT compared to saline. In all conditions, a larger increase in W_V than W_E was responsible for the increase in W_V/W_E.

CONCLUSIONS

The release of NO and EETs maintains a stable AWV during flow increase and this endothelial adaptive regulation is lost during essential hypertension, which may promote excessive viscous energy dissipation and cardiovascular uncoupling. Restoration of EETs availability with inhibitors of soluble epoxide hydrolase could thus constitute a promising pharmacological approach to restore the endothelial adaptive regulation of AWV.

[Cardiovascular consequences of chronic kidney disease, impact of modulation of epoxyeicosatrienoic acids]

Cardiovascular events are more prevalent in chronic kidney disease than in the general population, being the main cause of morbi-mortality. The physiopathology explaining this association remains complex. Thus, research for new therapies to prevent cardiovascular events in chronic kidney disease is a major issue. Epoxyeicosatrienoic acids, products of the arachidonic acid metabolism, are endothelium-derived hyperpolarizing factors with vasodilatory, anti-inflammatory, thrombolytic, pro-angiogenic and anti-apoptotic properties. A decrease in the bioavailability of epoxyeicosatrienoic acids has been observed in many cardiovascular diseases such as hypertension, myocardial infarction or diabetes. Moreover, human studies of genetic polymorphisms of soluble epoxide hydrolase, the enzyme degrading epoxyeicoatrienoic acids, have shown that allelic variants related to an increase in its activity is associated with higher risk of cardiovascular events. Modulation of epoxyeicosatrienoic acids by soluble epoxide hydrolase inhibitors in some cardiovascular diseases induces structural improvements in the heart, vessels and kidneys, including decrease in cardiomyocyte hypertrophy, reduction in cardiac and renal interstitial fibrosis, improvement in renal hemodynamics, and prevention of endothelial dysfunction. In this context, increasing the bioavailability of epoxyeicosatrienoic acids appears to be an interesting therapeutic option in the prevention of cardiovascular events related to chronic kidney disease.

The role of epoxyeicosatrienoic acids in the cardiovascular system

There is increasing evidence suggesting that epoxyeicosatrienoic acids (EETs) play an important role in cardioprotective mechanisms. These include regulating vascular tone, modulating inflammatory responses, improving cardiomyocyte function and reducing ischaemic damage, resulting in attenuation of animal models of cardiovascular risk factors. This review discusses the current knowledge on the role of EETs in endothelium-dependent control of vascular tone in the healthy and in subjects with cardiovascular risk factors, and considers the pharmacological potential of targeting this pathway.

Impact of soluble epoxide hydrolase inhibition on early kidney damage in hyperglycemic overweight mice

This study addressed the hypothesis that inhibition of the EETs degrading enzyme soluble epoxide hydrolase affords renal protection in the early stage of diabetic nephropathy. The renal effects of the sEH inhibitor t-AUCB (10mg/l in drinking water) were compared to those of the sulfonylurea glibenclamide (80mg/l), both administered for 8 weeks in FVB mice subjected to a high-fat diet (HFD, 60% fat) for 16 weeks. Mice on control chow diet (10% fat) and non-treated HFD mice served as controls. Compared with non-treated HFD mice, HFD mice treated with t-AUCB had a decreased EET degradation, as shown by their higher plasma EETs-to-DHETs ratio, and an increased EET production, as shown by the increase in EETs+DHETs levels, which was associated with induction of CYP450 epoxygenase expression. Both agents similarly reduced fasting glycemia but only t-AUCB prevented the increase in the urinary albumine-to-creatinine ratio in HFD mice. Histopathological analysis showed that t-AUCB reduced renal inflammation, which was associated with an increased mRNA expression of the NFκB inhibitor Iκ≡ and related decrease in MCP-1, COX2 and VCAM-1 expressions. Finally, there was a marginally significant increase in reactive oxygen species production in HFD mice, together with an enhanced NOX2 expression. Both agents did not modify these parameters but t-AUCB increased the expression of the antioxidant enzyme superoxide dismutase 1. These results demonstrate that, independently from its glucose-lowering effect, sEH inhibition prevents microalbuminuria and renal inflammation in overweight hyperglycemic mice, suggesting that this pharmacological strategy could be useful in the management of diabetic nephropathy.

Soluble epoxide hydrolase inhibition improves coronary endothelial function and prevents the development of cardiac alterations in obese insulin-resistant mice

This study addressed the hypothesis that inhibiting the soluble epoxide hydrolase (sEH)-mediated degradation of epoxy-fatty acids, notably epoxyeicosatrienoic acids, has an additional impact against cardiovascular damage in insulin resistance, beyond its previously demonstrated beneficial effect on glucose homeostasis. The cardiovascular and metabolic effects of the sEH inhibitor trans-4-[4-(3-adamantan-1-yl-ureido)-cyclohexyloxy]-benzoic acid (t-AUCB; 10 mg/l in drinking water) were compared with those of the sulfonylurea glibenclamide (80 mg/l), both administered for 8 wk in FVB mice subjected to a high-fat diet (HFD; 60% fat) for 16 wk. Mice on control chow diet (10% fat) and nontreated HFD mice served as controls. Glibenclamide and t-AUCB similarly prevented the increased fasting glycemia in HFD mice, but only t-AUCB improved glucose tolerance and decreased gluconeogenesis, without modifying weight gain. Moreover, t-AUCB reduced adipose tissue inflammation, plasma free fatty acids, and LDL cholesterol and prevented hepatic steatosis. Furthermore, only the sEH inhibitor improved endothelium-dependent relaxations to acetylcholine, assessed by myography in isolated coronary arteries. This improvement was related to a restoration of epoxyeicosatrienoic acid and nitric oxide pathways, as shown by the increased inhibitory effects of the nitric oxide synthase and cytochrome P-450 epoxygenase inhibitors l-NA and MSPPOH on these relaxations. Moreover, t-AUCB decreased cardiac hypertrophy, fibrosis, and inflammation and improved diastolic function, as demonstrated by the increased E/A ratio (echocardiography) and decreased slope of the end-diastolic pressure-volume relation (invasive hemodynamics). These results demonstrate that sEH inhibition improves coronary endothelial function and prevents cardiac remodeling and diastolic dysfunction in obese insulin-resistant mice.

Epoxyeicosatrienoic acid analogue lowers blood pressure through vasodilation and sodium channel inhibition

Epoxyeicosatrienoic acids (EETs) contribute to haemodynamics, electrolyte homoeostasis and blood pressure regulation, leading to the concept that EETs can be therapeutically targeted for hypertension. In the present study, multiple structural EET analogues were synthesized based on the EET pharmacophore and vasodilator structure-activity studies. Four EET analogues with 91-119% vasodilatory activity in the isolated bovine coronary artery (EC50: 0.18-1.6 μM) were identified and studied for blood-pressure-lowering in hypertension. Two EET analogues in which the COOH group at carbon 1 of the EET pharmacophore was replaced with either an aspartic acid (EET-A) or a heterocyclic surrogate (EET-X) were administered for 14 days [10 mg/kg per day intraperitoneally (i.p.)]. Both EET-A and EET-X lowered blood pressure in spontaneously hypertensive rats (SHRs) and in angiotensin II (AngII) hypertension. On day 14, the mean arterial pressures in EET analogue-treated AngII-hypertensive and SHRs were 30-50 mmHg (EET-A) and 15-20 mmHg (EET-X) lower than those in vehicle-treated controls. These EET analogues (10 mg/kg per day) were further tested in AngII hypertension by administering orally in drinking water for 14 days and EET-A lowered blood pressure. Additional experiments demonstrated that EET-A inhibits epithelial sodium channel (ENaC) activity in cultured cortical collecting duct cells and reduced renal expression of ENaC subunits in AngII hypertension. In conclusion, we have characterized EET-A as an orally active antihypertensive EET analogue that protects vascular endothelial function and has ENaC inhibitory activity in AngII hypertension.

Epoxyeicosatrienoic acid analog attenuates angiotensin II hypertension and kidney injury

Epoxyeicosatrienoic acids (EETs) contribute to blood pressure regulation leading to the concept that EETs can be therapeutically targeted for hypertension and the associated end organ damage. In the present study, we investigated anti-hypertensive and kidney protective actions of an EET analog, EET-B in angiotensin II (ANG II)-induced hypertension. EET-B was administered in drinking water for 14 days (10 mg/kg/d) and resulted in a decreased blood pressure elevation in ANG II hypertension. At the end of the two-week period, blood pressure was 30 mmHg lower in EET analog-treated ANG II hypertensive rats. The vasodilation of mesenteric resistance arteries to acetylcholine was impaired in ANG II hypertension; however, it was improved with EET-B treatment. Further, EET-B protected the kidney in ANG II hypertension as evidenced by a marked 90% decrease in albuminuria and 54% decrease in nephrinuria. Kidney histology demonstrated a decrease in renal tubular cast formation in EET analog-treated hypertensive rats. In ANG II hypertension, EET-B treatment markedly lowered renal inflammation. Urinary monocyte chemoattractant protein-1 excretion was decreased by 55% and kidney macrophage infiltration was reduced by 52% with EET-B treatment. Overall, our results demonstrate that EET-B has anti-hypertensive properties, improves vascular function, and decreases renal inflammation and injury in ANG II hypertension.

Design and discovery of soluble epoxide hydrolase inhibitors for the treatment of cardiovascular diseases

INTRODUCTION

Cardiovascular diseases are a leading cause of death in developed countries. Increasing evidence shows that the alteration in the normal functions of the vascular endothelium plays a major role in the development of cardiovascular diseases. However, specific agents designed to prevent endothelial dysfunction and related cardiovascular complications are still lacking. One emerging strategy is to increase the bioavailability of epoxyeicosatrienoic acids (EETs), synthesized by cytochrome P450 epoxygenases from arachidonic acid. EETs are endothelium-derived hyperpolarising and relaxing factors and display attractive anti-inflammatory and metabolic properties. Genetic polymorphism studies in humans, and experiments in animal models of diseases, have identified soluble epoxide hydrolase (sEH), the major enzyme involved in EET degradation, as a potential pharmacological target.

AREAS COVERED

This review presents EET pathway and its functions and summarises the data supporting the development of sEH inhibitors for the treatment of cardiovascular and metabolic diseases. Furthermore, the authors present the different chemical families of sEH inhibitors developed and their effects in animal models of cardiovascular and metabolic diseases.

EXPERT OPINION

Several generations of sEH inhibitors have now been designed to treat endothelial dysfunction and cardiovascular complications for a variety of diseases. The safety of these drugs remains to be carefully investigated, particularly in relation to carcinogenesis. The increasing knowledge of the biological role of each of the EET isomers and of their metabolites may improve their pharmacological profile. This, in turn, could potentially lead to the identification of new pharmacological agents that achieve the cellular effects needed without the deleterious side effects.

Soluble epoxide hydrolase: gene structure, expression and deletion

Mammalian soluble epoxide hydrolase (sEH) converts epoxides to their corresponding diols through the addition of a water molecule. sEH readily hydrolyzes lipid signaling molecules, including the epoxyeicosatrienoic acids (EETs), epoxidized lipids produced from arachidonic acid by the action of cytochrome p450s. Through its metabolism of the EETs and other lipid mediators, sEH contributes to the regulation of vascular tone, nociception, angiogenesis and the inflammatory response. Because of its central physiological role in disease states such as cardiac hypertrophy, diabetes, hypertension, and pain sEH is being investigated as a therapeutic target. This review begins with a brief introduction to sEH protein structure and function. sEH evolution and gene structure are then discussed before human small nucleotide polymorphisms and mammalian gene expression are described in the context of several disease models. The review ends with an overview of studies that have employed the sEH knockout mouse model.

Non-invasive assessment of cardiac function in a mouse model of renovascular hypertension

Hypertension continues to be a significant cause of morbidity and mortality, underscoring the need to better understand its early effects on the myocardium. The aim of this study is to determine the feasibility of in vivo longitudinal assessment of cardiac function, particularly diastolic function, in a mouse model of renovascular hypertension. Renovascular hypertension (RVH) was induced in 129S1/SvImJ male mice (n=9). To assess left ventricular (LV) systolic and diastolic function, M-mode echocardiography, pulsed-wave Doppler echocardiography and tissue Doppler imaging were performed at baseline, 2 and 4 weeks after the induction of renal artery stenosis. Myocardial tissue was collected to assess cellular morphology, fibrosis, extracellular matrix remodeling and inflammation ex vivo. RVH led to a significant increase in systolic blood pressure after 2 and 4 weeks (baseline: 99.26±1.09 mm Hg; 2 weeks: 140.90±7.64 mm Hg; 4 weeks: 147.52±5.91 mm Hg, P<0.05), resulting in a significant decrease in LV end-diastolic volume, associated with a significant elevation in ejection fraction and preserved cardiac output. Furthermore, the animals developed an abnormal diastolic function profile, with a shortening in the E velocity deceleration time as well as increases in the E/e' and the E/A ratio. The ex vivo analysis revealed a significant increase in myocyte size and deposition of extracellular matrix. Non-invasive high-resolution ultrasonography allowed assessment of the diastolic function profile in a small animal model of renovascular hypertension.

Impaired role of epoxyeicosatrienoic acids in the regulation of basal conduit artery diameter during essential hypertension

In young healthy subjects, epoxyeicosatrienoic acids synthesized by endothelial cytochrome P450 epoxygenases maintain basal conduit artery diameter during altered NO availability. Whether this compensatory mechanism is effective during essential hypertension is unknown. Radial artery diameter, blood flow, and mean wall shear stress were determined in 14 nontreated essential hypertensive patients and 14 normotensive control subjects during 8 minutes of brachial infusion for inhibitors of cytochrome P450 epoxygenases (fluconazole, 0.4 µmol/min) and NO synthase (N(G)-monomethyl-L-arginine, 8 µmol/min) alone and in combination. In controls, the radial artery diameter was reduced by fluconazole (-0.034 ± 0.012 mm) and N(G)-monomethyl-L-arginine (-0.037 ± 0.010 mm) and to a larger extent by their combination (-0.137 ± 0.011 mm), demonstrating a synergic effect. In contrast, the radial diameter in hypertensive patients was not affected by fluconazole (0.010 ± 0.014 mm) but was reduced by N(G)-monomethyl-L-arginine (-0.091 ± 0.008 mm) to a larger extent than in controls. In parallel, N(G)-monomethyl-L-arginine decreased local plasma nitrite to a lesser extent in hypertensive patients (-14 ± 5 nmol/L) than in controls (-50 ± 10 nmol/L). Moreover, the addition of fluconazole to N(G)-monomethyl-L-arginine did not further decrease radial diameter in patients (-0.086 ± 0.011 mm). Accordingly, fluconazole significantly decreased local epoxyeicosatrienoic acid plasma level in controls (-2.0 ± 0.6 ng/mL) but not in patients (-0.9 ± 0.4 ng/mL). Inhibitors effects on blood flow and endothelium-independent dilatation to sodium nitroprusside were similar between groups. These results show that, in contrast to normotensive subjects, epoxyeicosatrienoic acids did not contribute to the regulation of basal conduit artery diameter and did not compensate for altered NO availability to maintain this diameter in essential hypertensive patients.

Soluble epoxide hydrolase inhibition exhibits antihypertensive actions independently of nitric oxide in mice with renovascular hypertension

OBJECTIVE

The present study was performed to examine whether the blood pressure (BP)-lowering effects of soluble epoxide hydrolase (sEH) inhibition in two-kidney, one-clip (2K1C) Goldblatt hypertension are nitric oxide (NO) dependent.

METHODS

Mice lacking the endothelial NO synthase (eNOS) gene (eNOS-/-) and their wild-type controls (eNOS+/+) underwent clipping of one renal artery. BP was monitored by radiotelemetry and the treatment with the sEH inhibitor cis-4-[4-(3-adamantan-1-yl-ureido)cyclohex-yloxy]-benzoic acid (c-AUCB) was initiated on day 25 after clipping and lasted for 14 days. Renal concentrations of epoxyeicosatrienoic acids (EETs) and their inactive metabolite dihydroxyeicosatrienoic acids (DHETs) were measured in the nonclipped kidney. Renal NO synthase (NOS) activity was determined by measuring the rate of formation of L-[(14)C]citruline from L-[(14)C]arginine.

RESULTS

Treatment with the sEH inhibitor elicited similar BP decreases that were associated with increases in daily sodium excretion in 2K1C eNOS+/+ as well as 2K1C eNOS-/- mice. In addition, treatment with the sEH inhibitor increased the ratio of EETs/DHETs in the nonclipped kidney of 2K1C eNOS+/+ as well as 2K1C eNOS-/- mice. Treatment with the sEH inhibitor did not alter renal NOS activity in any of the experimental groups.

CONCLUSIONS

Collectively, our present data suggest that the BP-lowering effects of chronic sEH inhibition in 2K1C mice are mainly associated with normalization of the reduced availability of biologically active EETs in the nonclipped kidney and their direct natriuretic actions.

Epoxyeicosatrienoic Acids Contribute With Altered Nitric Oxide and Endothelin-1 Pathways to Conduit Artery Endothelial Dysfunction in Essential Hypertension

Background—

We sought to clarify, using functional and biological approaches, the role of epoxyeicosatrienoic acids, nitric oxide (NO)/reactive oxygen species balance, and endothelin-1 in conduit artery endothelial dysfunction during essential hypertension.

Methods and Results—

Radial artery diameter and mean wall shear stress were determined in 28 untreated patients with essential hypertension and 30 normotensive control subjects during endothelium-dependent flow-mediated dilatation induced by hand skin heating. The role of epoxyeicosatrienoic acids and NO was assessed with the brachial infusion of inhibitors of cytochrome P450 epoxygenases (fluconazole) and NO synthase ( N G -monomethyl- l -arginine [L-NMMA]). Compared with controls, hypertensive patients exhibited a decreased flow-mediated dilatation in response to postischemic hyperemia as well as to heating, as shown by the lesser slope of their diameter–shear stress relationship. In controls, heating-induced flow-mediated dilatation was reduced by fluconazole, L-NMMA, and, to a larger extent, by L-NMMA+fluconazole. In patients, flow-mediated dilatation was not affected by fluconazole and was reduced by L-NMMA and L-NMMA+fluconazole to a lesser extent than in controls. Furthermore, local plasma epoxyeicosatrienoic acids increased during heating in controls (an effect diminished by fluconazole) but not in patients. Plasma nitrite, an indicator of NO availability, increased during heating in controls (an effect abolished by L-NMMA) and, to a lesser extent, in patients, whereas, inversely, reactive oxygen species increased more in patients (an effect diminished by L-NMMA). Plasma endothelin-1 decreased during heating in controls but not in patients.

Conclusions—

These results show that an impaired role of epoxyeicosatrienoic acids contributes, together with an alteration in NO/reactive oxygen species balance and endothelin-1 pathway, to conduit artery endothelial dysfunction in essential hypertension.

Clinical Trial Registration—

https://www.eudract.ema.europa.eu . Unique identifier: RCB2007-A001–10-53.

Soluble epoxide hydrolase inhibition improves myocardial perfusion and function in experimental heart failure

The study addressed the hypothesis that soluble epoxide hydrolase (sEH) inhibition, which increases cardiovascular protective epoxyeicosatrienoic acids (EETs), exerts beneficial effects in an established chronic heart failure (CHF) model. In CHF rats, left ventricular (LV) function, perfusion and remodeling were assessed using MRI and invasive hemodynamics after 42-day (starting 8 days after coronary ligation) and delayed 3-day (starting 47 days after coronary ligation) treatments with the sEH inhibitor AUDA (twice 0.25 mg/day). Delayed 3-day and 42-day AUDA increased plasma EETs demonstrating the effective inhibition of sEH. Delayed 3-day and 42-day AUDA enhanced cardiac output without change in arterial pressure, thus reducing total peripheral resistance. Both treatment periods increased the slope of the LV end-systolic pressure-volume relation, but only 42-day AUDA decreased LV end-diastolic pressure, relaxation constant Tau and the slope of the LV end-diastolic pressure-volume relation, associated with a reduced LV diastolic volume and collagen density. Delayed 3-day and, to a larger extent, 42-day AUDA increased LV perfusion associated with a decreased LV hypoxia-inducible factor-1alpha. Both treatment periods decreased reactive oxygen species level and increased reduced-oxidized glutathione ratio. Finally, MSPPOH, an inhibitor of the EET-synthesizing enzyme cytochrome epoxygenases, abolished the beneficial effects of 3-day AUDA on LV function and perfusion. Augmentation of EET availability by pharmacological inhibition of sEH increases LV diastolic and systolic functions in established CHF. This notably results from short-term processes, i.e. increased LV perfusion, reduced LV oxidative stress and peripheral vasodilatation, but also from long-term effects, i.e. reduced LV remodeling.