Jeremy Bellien

Epoxyeicosatrienoic acid pathway in human health and diseases.

Abstract: In response to endothelial cell activation, arachidonic acid can be converted by cytochrome P450 (CYP) epoxygenases to epoxyeicosatrienoic acids (EETs), which have potent vasodilator and anti-inflammatory properties. EETs are rapidly degraded in vivo to the less active dihydroxyeicosatrienoic acids (DHETs) by soluble epoxide hydrolase (sEH). Since the beginning of the 2000s, the role of EET pathway in human health and its alteration in diseases has been shown by measuring EETs/DHET levels in blood, by evaluating the relationship between CYP/sEH gene polymorphisms, which modify enzyme activity and thus EETs/DHET level, and by assessing the inhibitory effect of the local administration of CYP epoxygenase inhibitor on endothelium-dependent dilatation. By combining these functional and biological approaches, we demonstrated that EETs are the endothelial factors released by CYP epoxygenases involved in the flow-mediated dilatation of conduit arteries in healthy subjects, together with the impairment of EET availability in essential hypertensive patients at this level. The modulation of EET pathway now emerges as a new promising pharmacological target that may improve the clinical management of patients at high cardiovascular risk. In this respect, the restoration of EET availability using a new class of agents, the inhibitors of sEH, gave promising results in various animal models of cardiovascular diseases, reducing blood pressure and target organ damage, and a first product has entered clinical evaluation.

Immunosuppressant Regimen Based on Sirolimus Decreases Aortic Stiffness in Renal Transplant Recipients in Comparison to Cyclosporine

Whether or not a cyclosporine A (CsA)‐free immunosuppressant regimen based on sirolimus (SRL) prevents aortic stiffening and improves central hemodynamics in renal recipients remains unknown. Forty‐four patients (48 ± 2 years) enrolled in the CONCEPT trial were randomized at week 12 (W12) to continue CsA or switch to SRL, both associated with mycophenolate mofetil. Carotid systolic blood pressure (cSBP), pulse pressure (cPP), central pressure wave reflection (augmentation index, AIx) and carotid‐to‐femoral pulse‐wave velocity (PWV: aortic stiffness) were blindly assessed at W12, W26 and W52 together with plasma endothelin‐1 (ET‐1), thiobarbituric acid‐reactive substances (TBARS) and superoxide dismutase (SOD) and catalase erythrocyte activities. At W12, there was no difference between groups. At follow‐up, PWV, cSBP, cPP and AIx were lower in the SRL group. The difference in PWV remained significant after adjustment for blood pressure and eGFR. In parallel, ET‐1 decreased in the SRL group, while TBARS, SOD and catalase erythrocyte activities increased in both groups but to a lesser extent in the SRL group. Our results demonstrate that a CsA‐free regimen based on SRL reduces aortic stiffness, plasma endothelin‐1 and oxidative stress in renal recipients suggesting a protective effect on the arterial wall that may be translated into cardiovascular risk reduction.

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 (NG-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.

Early stage detection of conduit artery endothelial dysfunction in patients with type 1 diabetes

Flow-mediated dilatation evaluation using hand skin heating may possibly be more accurate than post-ischaemic hyperaemia to detect conduit artery endothelial dysfunction in type 1 diabetes. We measured in 24 type 1 diabetic patients (n=16 without microangiopathy) and 24 healthy matched subjects radial artery diameter (echotracking), blood flow and mean wall shear stress during heating and post-ischaemic hyperaemia. Compared with controls, flow-mediated dilatation was lower in diabetic patients during post-ischaemic hyperaemia and heating. However, in the subgroup of uncomplicated patients, a decreased flow-mediated dilatation was only apparent during heating (17.1±1.6% vs. 24.3±0.7%, p<0.05) but not during post-ischaemic hyperaemia (10.1±1.1% vs. 10.5±0.6%, NS). This was confirmed by the lower slope of the diameter—mean wall shear stress relationship in these patients in the absence of modification in endothelium-independent dilatation. We conclude that hand skin heating permits the early detection of conduit artery endothelial dysfunction in type 1 diabetic patients with normal response to post-ischaemic hyperaemia. This procedure could be useful to investigate the prognostic role of vascular dysfunction and the impact of vasculoprotective treatments in this patient population.

High-efficiency on-line haemodiafiltration improves conduit artery endothelial function compared with high-flux haemodialysis in end-stage renal disease patients

BACKGROUND Middle molecular weight uraemic toxins are considered to play an important role in vascular dysfunction and cardiovascular outcomes in end-stage renal disease (ESRD) patients. Recent dialysis techniques based on convection, specifically high-efficiency on-line haemodiafiltration (HDF), enhance the removal of middle molecular weight toxins and reduce all-cause mortality in haemodialysis (HD) patients. However, the mechanisms of these improved outcomes remain to be established. METHODS This prospective study randomly assigned 42 ESRD patients to switch from high-flux HD to high-efficiency on-line HDF (n=22) or to continue HD (n=20). Brachial artery endothelium-dependent flow-mediated dilatation, central pulse pressure, carotid artery intima-media thickness (IMT), internal diastolic diameter and distensibility and circulating markers of uraemia, inflammation and oxidative stress were blindly assessed before and after a 4-month follow-up. RESULTS Brachial flow-mediated dilatation and carotid artery distensibility increased significantly in the HDF group compared with HD, while carotid IMT and diameter remained similar. HDF decreased predialysis levels of the uraemic toxins β2-microglobulin, phosphate and blood TNFα mRNA expression. Oxidative stress markers were not different between the HD and HDF groups. Blood mRNA expression of protein kinase C β2, an endothelial NO-synthase (eNOS) inhibitor, decreased significantly with HDF. CONCLUSIONS High-efficiency on-line HDF prevents the endothelial dysfunction and stiffening of the conduit arteries in ESRD patients compared with high-flux HD. HDF decreases uraemic toxins, vascular inflammation, and is associated with subsequent improvement in eNOS functionality. These results suggest that reduced endothelial dysfunction may be an intermediate mechanism explaining the beneficial outcomes associated with HDF.

Role of Toll‐like Receptors 2 and 4 in Mediating Endothelial Dysfunction and Arterial Remodeling in Primary Arterial Antiphospholipid Syndrome

To assess the role of Toll‐like receptors (TLRs) in antiphospholipid antibody (aPL)–mediated vascular abnormalities in patients with primary arterial antiphospholipid syndrome (APS).

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

Objectives The study addresses the hypothesis that endothelial dysfunction in experimental arterial hypertension can be related to an alteration in epoxyeicosatrienoic acids (EETs) pathway and can be prevented by the inhibition of EETs degradation by soluble epoxide hydrolase (sEH). Methods and results Arterial hypertension was induced in FVB/N mice by renal artery stenosis (‘two-kidney–one-clip’, 2K1C). Seven weeks after surgery, increased aortic pressures (Millar tonometer; Millar Instruments, Houston, Texas, USA) and cardiac hypertrophy (echocardiography) were present in 2K1C mice as compared with control mice. Left coronary artery endothelium-dependent relaxations to acetylcholine were decreased in 2K1C mice without modification in the relaxing responses to NS309 and NS1619, the openers of calcium-activated potassium channels mediating the hyperpolarizing effect of EETs. The inhibitors of the EET-synthesizing enzymes cytochrome P450 epoxygenases, fluconazole and N-methylsulfonyl-6-(2-propargyloxyphenyl)-hexanamide (MSPPOH), reduced the coronary relaxations to acetylcholine in control but not in 2K1C mice. The sEH expression was increased in 2K1C mice. The sEH inhibitor 12-(3-adamantan-1-yl-ureido)dodecanoic acid administered for 2 weeks starting 5 weeks after surgery in 2K1C mice (25 mg/l in drinking water) reduced aortic pressures and cardiac hypertrophy, improved the coronary relaxations to acetylcholine and restored the inhibitory effect of fluconazole and MSPPOH on acetylcholine-induced relaxations, without modifying the relaxations to NS309 and NS1619. Conclusion These results demonstrate that a reduced EET-mediated relaxations related to an increased degradation by sEH contributes to coronary endothelial dysfunction in 2K1C hypertensive mice. Inhibiting sEH prevents endothelial dysfunction by restoring EET-mediated relaxations and thus, could represent a promising pharmacological intervention to limit cardiovascular morbidity and mortality in arterial hypertension.

ROLE OF ENDOTHELIUM-DERIVED HYPERPOLARIZING FACTOR IN THE REGULATION OF RADIAL ARTERY BASAL DIAMETER AND ENDOTHELIUM-DEPENDENT DILATATION IN VIVO

1 The role of the balance between nitric oxide (NO) and endothelium‐derived hyperpolarizing factor (EDHF), synthesized by cytochrome epoxygenase and acting through calcium‐activated potassium channels, in the regulation of basal diameter and endothelium‐dependent flow‐mediated dilatation of conduit arteries has been poorly assessed in humans. 2 Radial artery diameter and flow (echotracking coupled to Doppler) were measured in healthy volunteers under basal conditions and during flow‐mediated dilatation induced by hand skin heating, in the presence of saline and inhibitors of NO‐synthase, NG‐monomethyl‐L‐arginine (L‐NMMA), calcium‐activated potassium channels, tetraethylammonium (TEA) and cytochrome epoxygenases, fluconazole, infused alone and in combination. Mean wall shear stress, the flow‐mediated dilatation stimulus, was calculated and taken as cofactor into statistical analysis. 3 Under basal conditions, the radial artery diameter was not affected by L‐NMMA and fluconazole infused alone but was decreased by TEA, the combinations of L‐NMMA + fluconazole and, to a greater extent, L‐NMMA + TEA. During heating, radial artery diameter increased with temperature in all cases. This increase in diameter, compared with saline, was reduced by L‐NMMA, TEA, fluconazole and to a greater extent, by L‐NMMA + TEA and L‐NMMA + fluconazole. 4 These data show that EDHF is involved in balance with NO in the regulation of basal diameter and endothelium‐dependent dilatation of human peripheral conduit arteries. The alteration of this balance could play a major role in the physiopathology of the endothelial dysfunction, in particular during essential hypertension.

Fixed combination of perindopril and indapamide at low dose improves endothelial function in essential hypertensive patients after acute administration.

BACKGROUND Fixed combination of angiotensin-converting enzyme inhibitors (ACEIs) with thiazide-type diuretics at low dose has been used as first-line therapy for the treatment of essential hypertension but their effect on conduit artery endothelial dysfunction remains unknown. METHODS Thirteen hypertensive patients were assessed after acute administration of a placebo, fixed combination of perindopril-indapamide at low dose: D1 (2 mg/0.625 mg) and twice this dose: D2 (4 mg/1.25 mg), during a double-blind, randomized, crossover study, and were compared with 13 matched controls. Mean arterial pressure (MAP), radial artery diameter (echotracking) and flow (Doppler) were measured during flow-mediated dilatation (FMD) induced by post-ischemic hyperemia (PIH). PIH was characterized by peak flow and duration of hyperemia (t(1/2)). Endothelium-independent dilatation was assessed by trinitrine. RESULTS In hypertensive patients compared with controls, basal radial artery diameter and flow, peak flow, and trinitrine responses were similar while MAP was increased (115 +/- 3 vs. 87 +/- 2 mm Hg), t(1/2) was decreased (11.1 +/- 1.9 vs. 17.2 +/- 2.2 s), and FMD was altered (radial diameter increase: 203 +/- 14 vs. 304 +/- 15 microm). Compared with placebo, only D2 decreased MAP (placebo: 115 +/- 3; D1: 112 +/- 4; D2: 103 +/- 4 mm Hg) and increased t(1/2) (placebo: 11.1 +/- 1.9; D1: 8.7 +/- 1.5; D2:13.0 +/- 1.9 s). Conversely, D1 and D2 increased FMD (placebo: 203 +/- 14; D1: 218 +/- 22; D2: 227 +/- 23 microm) with no change in basal diameter and flow, peak flow, and trinitrine responses. CONCLUSION These results demonstrate that a fixed combination of ACEI/diuretic at low dose significantly improves radial artery FMD in hypertensive patients and suggest a direct effect on conduit artery endothelium that may contribute to vascular protection.

Polycystin deficiency induces dopamine-reversible alterations in flow-mediated dilatation and vascular nitric oxide release in humans

Autosomal dominant polycystic kidney disease (ADPKD) is a renal hereditary disorder associated with increased cardiovascular mortality, due to mutations in polycystin-1 and polycystin-2 genes. Endothelial polycystin-deficient cells have an altered mechanosensitivity to fluid shear stress and subsequent deficit in calcium-induced nitric oxide release, prevented by dopamine receptor stimulation. However, the impact of polycystin deficiency on endothelial function in ADPKD patients is still largely unknown. Here we assessed endothelium-dependent flow-mediated dilatation in 21 normotensive ADPKD patients and 21 healthy control subjects, during sustained (hand skin heating) and transient (postischemic hyperemia) flow stimulation. Flow-mediated dilatation was less marked in ADPKD patients than in controls during heating, but it was similar during postischemic hyperemia. There was no difference in endothelium-independent dilatation in response to glyceryl trinitrate. Local plasma nitrite, an indicator of nitric oxide availability, increased during heating in controls but not in patients. Brachial infusion of dopamine in a subset of ADPKD patients stimulated plasma nitrite increase during heating and improved flow-mediated dilatation. Thus, ADPKD patients display a loss of nitric oxide release and an associated reduction in endothelium-dependent dilatation of conduit arteries during sustained blood flow increase. The correction of these anomalies by dopamine suggests future therapeutic strategies that could reduce the occurrence of cardiovascular events in ADPKD.