Sympathetic Nerve Activity and Baroreflex are Strongly Altered in a Context of Severe Hypertension Using the Spontaneously Hypertensive Rat Model Associated with Chronic Reduction of Nitric Oxide.

The aim of our study is to investigate the sympathetic output and baroreflex via renal sympathetic nerve activity (RSNA) recording in a model of severe hypertension which exhibits arterial, cardiac, and renal damages, the spontaneously hypertensive rat (SHR) under lowered NO bioavailability. SHR are treated from 18 to 20 weeks of age with a low dose of L-NAME, a NO synthase inhibitor, in drinking water (SHRLN) and compared to SHR and normotensive Wistar Kyoto (WKY) rats. After the two-week treatment, rats are anesthetized for RSNA, mean blood pressure (MBP), and heart rate (HR) recording. MBP is higher in SHR than in WKY and higher in SHRLN than in SHR. Compared to WKY, SHR displays an alteration in the baroreflex with a displacement of the sympathoinhibition curve to highest pressures; this displacement is greater in SHRLN rats. The bradycardic response is reduced in SHRLN compared to both SHR and WKY. In hypertensive rats, SHR and SHRLN, basal RSNA is modified, the maximal amplitude of burst is reduced, but minimal values are increased, indicating an increased basal RSNA with reduced bursting activity. The temporal correlation between RSNA and HR is preserved in SHR but altered in 10 SHRLN out of 10. The RSNA inhibition triggered by the Bezold-Jarisch reflex activation is not modified in hypertensive rats, SHR or SHRLN, in contrast to that triggered by the baroreflex. Histological analysis of the carotid bifurcation does not reveal any abnormality in SHRLN at the level of the carotid sinus. In conclusion, data indicate that the sympathetic outflow is altered in SHRLN with a strong reduction of the baroreflex sympathoinhibition and suggest that its central pathway is not involved. These additional results on SHRLN also confirm the usefulness of this model of severe hypertension with multiple target organ damages.

Mineralocorticoid receptor blockade with finerenone improves heart function and exercise capacity in ovariectomized mice.

AIMS: In post-menopausal women, incidence of heart failure with preserved ejection fraction is higher than in men. Hormonal replacement therapies did not demonstrate benefits. We tested whether the non-steroidal mineralocorticoid receptor antagonist finerenone limits the progression of heart failure in ovariectomized (OVX) mice with metabolic disorders. METHODS AND RESULTS: Ovariectomy was performed in 4-month-old mice, treated or not at 7 months old for 1 month with finerenone (Fine) 1 mg/kg/day. Left ventricular (LV) cardiac and coronary endothelial functions were assessed by echocardiography, catheterization, and myography. Blood pressure was measured by plethysmography. Insulin and glucose tolerance tests were performed. Exercise capacity and spontaneous activity were measured on treadmill and in combined indirect calorimetric cages equipped with voluntary running wheel. OVX mice presented LV diastolic dysfunction without modification of ejection fraction compared with controls (CTL), whereas finerenone improved LV filling pressure (LV end-diastolic pressure, mmHg: CTL 3.48 ± 0.41, OVX 6.17 ± 0.30**, OVX + Fine 3.65 ± 0.55† , **P < 0.01 vs. CTL, † P < 0.05 vs. OVX) and compliance (LV end-diastolic pressure-volume relation, mmHg/RVU: CTL 1.65 ± 0.42, OVX 4.77 ± 0.37***, OVX + Fine 2.87 ± 0.26†† , ***P < 0.001 vs. CTL, †† P < 0.01 vs. OVX). Acetylcholine-induced endothelial-dependent relaxation of coronary arteries was impaired in ovariectomized mice and improved by finerenone (relaxation, %: CTL 86 ± 8, OVX 38 ± 3**, OVX + Fine 83 ± 7†† , **P < 0.01 vs. CTL, †† P < 0.01 vs. OVX). Finerenone improved decreased ATP production by subsarcolemmal mitochondria after ovariectomy. Weight gain, increased blood pressure, and decreased insulin and glucose tolerance in OVX mice were improved by finerenone. The exercise capacity at race was diminished in untreated OVX mice only. Spontaneous activity measurements in ovariectomized mice showed decreased horizontal movements, reduced time spent in a running wheel, and reduced VO2 and VCO2 , all parameters improved by finerenone. CONCLUSIONS: Finerenone improved cardiovascular dysfunction and exercise capacity after ovariectomy-induced LV diastolic dysfunction with preserved ejection fraction.

Transient heart rate reduction improves acute decompensated heart failure-induced left ventricular and coronary dysfunction.

AIMS: Acute decompensated heart failure (ADHF), a live-threatening complication of heart failure (HF), associates a further decrease of the already by HF-impaired cardiac function with an increase in heart rate. We evaluated, using a new model of ADHF, whether heart rate reduction (HRR) opposes the acute decompensation-related aggravation of cardiovascular dysfunction. METHODS AND RESULTS: Cardiac output (echocardiography), cardiac tissue perfusion (magnetic resonance imaging), pulmonary wet weight, and in vitro coronary artery relaxation (Mulvany) were assessed 1 and 14 days after acute decompensation induced by salt-loading (1.8 g/kg, PO) in rats with well-established HF due to coronary ligation. HRR was induced by administration of the If current inhibitor S38844, 12 mg/kg PO twice daily for 2.5 days initiated 12 h or 6 days after salt-loading (early or delayed treatment, respectively). After 24 h, salt-loading resulted in acute decompensation, characterized by a reduction in cardiac output (HF: 130 ± 5 mL/min, ADHF: 105 ±  8 mL/min; P < 0.01), associated with a decreased myocardial perfusion (HF: 6.41 ± 0.53 mL/min/g, ADHF: 4.20 ± 0.11 mL/min/g; P < 0.01), a slight increase in pulmonary weight (HF: 1.68 ± 0.09 g, ADHF: 1.81 ± 0.15 g), and impaired coronary relaxation (HF: 55 ± 1% of pre-contraction at acetylcholine 4.5 10-5  M, ADHF: 27 ± 7 %; P < 0.01). Fourteen days after salt-loading, cardiac output only partially recovered (117 ± 5 mL/min; P < 0.05), while myocardial tissue perfusion (4.51 ± 0.44 mL/min; P < 0.01) and coronary relaxation (28 ± 4%; P < 0.01) remained impaired, but pulmonary weight further increased (2.06 ± 0.15 g, P < 0.05). Compared with untreated ADHF, HRR induced by S38844 improved cardiac output (125 ± 1 mL/min; P < 0.05), myocardial tissue perfusion (6.46 ± 0.42 mL/min/g; P < 0.01), and coronary relaxation (79 ± 2%; P < 0.01) as soon as 12 h after S38844 administration. These effects persisted beyond S38844 administration, illustrated by the improvements in cardiac output (130 ± 6 mL/min; P < 0.05), myocardial tissue perfusion (6.38 ± 0.48 mL/min/g; P < 0.01), and coronary relaxation (71 ± 4%; P < 0.01) at Day 14. S38844 did not modify pulmonary weight at Day 1 (1.78 ± 0.04 g) but tended to decrease pulmonary weight at Day 14 (1.80 ± 0.18 g). While delayed HRR induced by S38844 never improved cardiac function, early HRR rendered less prone to a second acute decompensation. CONCLUSIONS: In a model mimicking human ADHF, early, but not delayed, transient HRR induced by the If current inhibitor S38844 opposes acute decompensation by preventing the decompensated-related aggravation of cardiovascular dysfunction as well as the development of pulmonary congestion, and these protective effects persist beyond the transient treatment. Whether early transient HRR induced by If current inhibitors or other bradycardic agents, i.e. beta-blockers, exerts beneficial effects in human ADHF warrants further investigation.

Nitrogen Dioxide Inhalation Exposures Induce Cardiac Mitochondrial Reactive Oxygen Species Production, Impair Mitochondrial Function and Promote Coronary Endothelial Dysfunction.

Traffic air pollution is a major health problem and is recognized as an important risk factor for cardiovascular (CV) diseases. In a previous experimental study, we showed that diesel exhaust (DE) exposures induced cardiac mitochondrial and CV dysfunctions associated with the gaseous phase. Here, we hypothesized that NO2 exposures to levels close to those found in DE induce a mitochondrial reactive oxygen species (ROS) production, which contribute to an endothelial dysfunction, an early indicator for numerous CV diseases. For this, we studied the effects of NO2 on ROS production and its impacts on the mitochondrial, coronary endothelial and cardiac functions, after acute (one single exposure) and repeated (three h/day, five days/week for three weeks) exposures in Wistar rats. Acute NO2 exposure induced an early but reversible mitochondrial ROS production. This event was isolated since neither mitochondrial function nor endothelial function were impaired, whereas cardiac function assessment showed a reversible left ventricular dysfunction. Conversely, after three weeks of exposure this alteration was accompanied by a cardiac mitochondrial dysfunction highlighted by an alteration of adenosine triphosphate (ATP) synthesis and oxidative phosphorylation and an increase in mitochondrial ROS production. Moreover, repeated NO2 exposures promoted endothelial dysfunction of the coronary arteries, as shown by reduced acetylcholine-induced vasodilatation, which was due, at least partially, to a superoxide-dependent decrease of nitric oxide (NO) bioavailability. This study shows that NO2 exposures impair cardiac mitochondrial function, which, in conjunction with coronary endothelial dysfunction, contributes to cardiac dysfunction. Together, these results clearly identify NO2 as a probable risk factor in ischemic heart diseases.

The IL-1ß Antibody Gevokizumab Limits Cardiac Remodeling and Coronary Dysfunction in Rats With Heart Failure.

This study reports preclinical data showing that the interleukin (IL)-1ß modulation is a new promising target in the pathophysiological context of heart failure. Indeed, in nondiabetic Wistar and diabetic Goto-Kakizaki rats with chronic heart failure induced by myocardial infarction, administration of the IL-1ß antibody gevokizumab improves 'surrogate' markers of survival (i.e., left ventricular remodeling, hemodynamics, and function as well as coronary function). However, whether IL-1ß modulation per se or in combination with standard treatments of heart failure improves long-term outcome in human heart failure remains to be determined.

Vascular Smooth Muscle Mineralocorticoid Receptor Contributes to Coronary and Left Ventricular Dysfunction After Myocardial Infarction.

Mineralocorticoid receptor (MR) antagonists slow down the progression of heart failure after myocardial infarction (MI), but the cell-specific role of MR in these benefits is unclear. In this study, the role of MR expressed in vascular smooth muscle cells (VSMCs) was investigated. Two months after coronary artery ligation causing MI, mice with VSMC-specific MR deletion (MI-MR(SMKO)) and mice treated with the MR antagonist finerenone (MI-fine) had improved left ventricular compliance and elastance when compared with infarcted control mice (MI-CTL), as well as reduced interstitial fibrosis. Importantly, the coronary reserve assessed by magnetic resonance imaging was preserved (difference in myocardial perfusion before and after induction of vasodilatation, mL mg(-1) min(-1): MI-CTL: 1.1 ± 0.5, nonsignificant; MI-MR(SMKO): 4.6 ± 1.6 [P<0.05]; MI-fine: 3.6 ± 0.7 [P<0.01]). The endothelial function, tested on isolated septal coronary arteries by analyzing the acetylcholine-induced nitric oxide-dependent relaxation, was also improved by MR deletion in VSMCs or by finerenone treatment (relaxation %: MI-CTL: 36 ± 5, MI-MR(SMKO): 54 ± 3, and MI-fine: 76 ± 4; P<0.05). Such impairment of the coronary endothelial function on MI involved an oxidative stress that was reduced when MR was deleted in VSMCs or by finerenone treatment. Moreover, short-term incubation of coronary arteries isolated from noninfarcted animals with low-dose angiotensin-II (10(-9) mol/L) induced oxidative stress and impaired acetylcholine-induced relaxation in CTL but neither in MR(SMKO) nor in mice pretreated with finerenone. In conclusion, deletion of MR in VSMCs improved left ventricular dysfunction after MI, likely through maintenance of the coronary reserve and improvement of coronary endothelial function. MR blockage by finerenone had similar effects.

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.

Infliximab improves endothelial dysfunction in a mouse model of antiphospholipid syndrome: Role of reduced oxidative stress.

Antiphospholipid syndrome (APS), induces endothelial dysfunction, oxidative stress and systemic inflammation that may be mediated by TNFα. Thus, we investigated the possible protective effect of the anti-TNFα antibody infliximab (5µg/g) on endothelial function in a mouse APS model (induced by injection of purified human anti-ß2GP1-IgG). Seven days after anti-ß2GPI-IgG injection, we observed an increase in plasma sVCAM-1 and sE-selectin levels and in aortic mRNA expression of VCAM-1 and E-selectin. This was associated with a decreased endothelium-dependent relaxation of isolated mesenteric arteries to acetylcholine, together with decreased mesenteric eNOS mRNA expression and increased eNOS uncoupling, accompanied by increased iNOS and gp91phox mRNA and increased left ventricular GSH/GSSH ratio. Infliximab significantly improved the NO-mediated relaxing responses to acetylcholine, and induced a decrease in iNOS and gp91phox mRNA expression. The õpro-adhesive and pro-coagulant phenotypes induced by the anti-ß2GP1-IgG were also reversed. This study provides the first evidence that TNFα antagonism improves endothelial dysfunction in APS and suggests that endothelial dysfunction is mediated by TNFα and oxidative stress. Therefore, infliximab may be of special relevance in clinical practice.

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.

Improvement of left ventricular diastolic function induced by ß-blockade: a comparison between nebivolol and metoprolol.

OBJECTIVES: Enhanced adrenergic drive is involved in the development of left ventricular (LV) diastolic dysfunction observed in metabolic syndrome (MS). Thus, ß-blockers might improve LV dysfunction observed in MS, but whether this occurs is unknown. METHODS: We assessed in Zucker fa/fa rats the effects of short- (5 days) and long-term (90 days) metoprolol ('pure' ß-blockade; 80 mg/kg/day) or nebivolol (ß-blocker with vasodilating properties; 5mg/kg/day) treatment on LV hemodynamics and remodeling, as well as the long-term effects on coronary and peripheral endothelial dysfunction. RESULTS: At identical degree of ß(1)-receptor blockade, metoprolol and nebivolol decreased heart rate to the same extent and preserved cardiac output via increased stroke volume. None of the ß-blockers, either after long- or short-term administration, modified LV end-systolic pressure-volume relation. Both ß-blockers reduced, after long-term administration, LV end-diastolic pressure, Tau and end-diastolic pressure-volume relation, and this was associated with reduced LV collagen density, but not heart weight. Similar hemodynamic effects were also observed after short-term nebivolol, but not short-term metoprolol. These short-term effects of nebivolol were abolished by NO synthase inhibition. At the vascular level, nebivolol, and to a lesser extend metoprolol, improved NO dependent coronary vasorelaxation, which was abolished by NO synthase inhibition. CONCLUSIONS: In a model of MS, the ß-blockers metoprolol and nebivolol improve to the same extent LV hemodynamics, remodeling and diastolic function, but nebivolol prevent more markedly endothelium dependent vasorelaxation involving a more marked enhancement of NO bio-availability.