Search

Aims Lymphatics are essential for cardiac health, and insufficient lymphatic expansion (lymphangiogenesis) contributes to development of heart failure (HF) after myocardial infarction. However, the regulation and impact of lymphangiogenesis in non-ischaemic cardiomyopathy following pressure-overload remains to be determined. Here, we investigated cardiac lymphangiogenesis following transversal aortic constriction (TAC) in C57Bl/6 and Balb/c mice, and in end-stage HF patients. Methods and results Cardiac function was evaluated by echocardiography, and cardiac hypertrophy, lymphatics, inflammation, oedema, and fibrosis by immunohistochemistry, flow cytometry, microgravimetry, and gene expression analysis. Treatment with neutralizing anti-VEGFR3 antibodies was applied to inhibit cardiac lymphangiogenesis in mice. We found that VEGFR3-signalling was essential to prevent cardiac lymphatic rarefaction after TAC in C57Bl/6 mice. While anti-VEGFR3-induced lymphatic rarefaction did not significantly aggravate myocardial oedema post-TAC, cardiac immune cell levels were increased, notably myeloid cells at 3 weeks and T lymphocytes at 8 weeks. Moreover, whereas inhibition of lymphangiogenesis did not aggravate interstitial fibrosis, it increased perivascular fibrosis and accelerated development of left ventricular (LV) dilation and dysfunction. In clinical HF samples, cardiac lymphatic density tended to increase, although lymphatic sizes decreased, notably in patients with dilated cardiomyopathy. Similarly, comparing C57Bl/6 and Balb/c mice, lymphatic remodelling post-TAC was linked to LV dilation rather than to hypertrophy. The striking lymphangiogenesis in Balb/c was associated with reduced cardiac levels of macrophages, B cells, and perivascular fibrosis at 8 weeks post-TAC, as compared with C57Bl/6 mice that displayed weak lymphangiogenesis. Surprisingly, however, it did not suffice to resolve myocardial oedema, nor prevent HF development. Conclusions We demonstrate for the first time that endogenous lymphangiogenesis limits TAC-induced cardiac inflammation and perivascular fibrosis, delaying HF development in C57Bl/6 but not in Balb/c mice. While the functional impact of lymphatic remodelling remains to be determined in HF patients, our findings suggest that under settings of pressure-overload poor cardiac lymphangiogenesis may accelerate HF development.

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

RationaleLymphatics are essential for cardiac health, and insufficient lymphatic expansion (lymphangiogenesis) contributes to development of heart failure (HF) after myocardial infarction. However, the regulation and impact of lymphatics in non-ischemic cardiomyopathy induced by pressure-overload remains to be determined.ObjectiveInvestigate cardiac lymphangiogenesis following transverse aortic constriction (TAC) in adult male or female C57Bl/6J or Balb/c mice, and in patients with end-stage HF.Methods & ResultCardiac function was evaluated by echocardiography, and cardiac hypertrophy, lymphatics, inflammation, edema, and fibrosis by immunohistochemistry, flow cytometry, microgravimetry, and gene expression analysis, respectively. Treatment with neutralizing anti-VEGFR3 antibodies was applied to inhibit cardiac lymphangiogenesis in mice.The gender- and strain-dependent mouse cardiac hypertrophic response to TAC, especially increased ventricular wall stress, led to lymphatic expansion in the heart. Our experimental findings that ventricular dilation triggered cardiac lymphangiogenesis was mirrored by observations in clinical HF samples, with increased lymphatic density found in patients with dilated cardiomyopathy. Surprisingly, the striking lymphangiogenesis observed post-TAC in Balb/c mice, linked to increased cardiac Vegfc, did not suffice to resolve myocardial edema, and animals progressed to dilated cardiomyopathy and HF. Conversely, selective inhibition of the essentially Vegfd-driven capillary lymphangiogenesis observed post-TAC in male C57Bl/6J mice did not significantly aggravate cardiac edema. However, cardiac immune cell levels were increased, notably myeloid cells at 3 weeks and T lymphocytes at 8 weeks. Moreover, while the TAC-triggered development of interstitial cardiac fibrosis was unaffected by anti-VEGFR3, inhibition of lymphangiogenesis increased perivascular fibrosis and accelerated the development of left ventricular dilation and cardiac dysfunction.ConclusionsWe demonstrate for the first time that endogenous cardiac lymphangiogenesis limits pressure-overload-induced cardiac inflammation and perivascular fibrosis, thus delaying HF development. While these findings remain to be confirmed in a larger study of HF patients, we propose that under settings of pressure-overload poor cardiac lymphangiogenesis may accelerate HF development.

International audience; 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.

Managing the cardiovascular complications of renal failure is a major therapeutic challenge in clinical practice. Mineralocorticoid Receptor (MR) blockade is a highly effective strategy for the management of heart failure, but the use of MR antagonists (MRA) is limited by their side effects rendering them contraindicated in patients with renal failure. Finerenone is a new non-steroidal MRA that shows fewer hyperkaliaemic events than the traditional steroidal MRAs and could therefore represent an alternative to these molecules in patients with damaged kidney function. The aim of this study is to characterize the effects of Finerenone on the cardiac complications of renal failure in a mouse model of chronic kidney disease (CKD). CKD was induced by subtotal nephrectomy (Nx), and finerenone was administered at a low dose (2.5 mg/kg/d) from week 4 to week 10 post-Nx. Cardiac function was assessed by echocardiography and invasive hemodynamics while cardiac fibrosis was measured by Sirius Red staining. Renal failure induced cardiac systolic and diastolic dysfunctions in the untreated CKD mice, as well as minor changes on cardiac structure. We also observed alterations in the phosphorylation of proteins playing key roles in the calcium handling (Phospholamban, Calmodulin kinase II) in these mice. Finerenone prevented most of these lesions with no effects on neither the renal dysfunction nor kaliemia. The benefits of finerenone suggest that activation of MR is involved in the cardiac complication of renal failure and strengthen previous studies showing beneficial effects of MRA in patients with CKD.

Myocardial infarction (MI) is accompanied by cardiac fibrosis, which contributes to cardiac dysfunction. Mineralocorticoid receptor (MR) antagonists have beneficial effects in patients with left ventricular (LV) dysfunction after MI. We herein investigated the role of the MR target NGAL (neutrophil gelatinase–associated lipocalin) in post-MI cardiac damages. Both higher baseline NGAL and a greater increase in serum NGAL levels during follow-up were significantly associated with lower 6-month LV ejection fraction recovery in a cohort of 119 post-MI patients, as assessed by cardiac magnetic resonance imaging. NGAL protein levels increased in the LV at 7 days post-MI in wild-type mice with MI. This effect was prevented by treatment with the nonsteroidal MR antagonist finerenone (1 mg/kg per day). NGAL knockout mice with MI had lower LV interstitial fibrosis and inflammation, better LV contractility and compliance, and greater stroke volume and cardiac output than wild-type mice with MI at 3 months post-MI. Aldosterone (10 −8 mol/L) increased NGAL expression in cultured human cardiac fibroblasts. Cells treated with aldosterone or NGAL (500 ng/mL) showed increased production of collagen type I. The effects of aldosterone were abolished by finerenone (10 −6 mol/L) or NGAL knockdown. This NGAL-mediated activity relied on NFκB (nuclear factor-κB) activation, confirmed by the use of the NFκB-specific inhibitor BAY11-7082, which prevented the effect of both aldosterone and NGAL on collagen type I production. In conclusion, NGAL, a downstream MR activation target, is a key mediator of post-MI cardiac damage. NGAL may be a potential therapeutic target in cardiovascular pathological situations in which MR is involved.

Although optimal therapy for myocardial infarction includes reperfusion to restore blood flow to the ischemic region, ischemia/reperfusion (IR) also initiates an inflammatory response likely contributing to adverse left ventricular (LV) extracellular matrix (ECM) remodeling. Galectin-3 (Gal-3), a β-galactoside-binding-lectin, promotes cardiac remodeling and dysfunction. Our aim is to investigate whether Gal-3 pharmacological inhibition using modified citrus pectin (MCP) improves cardiac remodeling and functional changes associated with IR. Wistar rats were treated with MCP from 1 day before until 8 days after IR (coronary artery ligation) injury. Invasive hemodynamics revealed that both LV contractility and LV compliance were impaired in IR rats. LV compliance was improved by MCP treatment 8 days after IR. Cardiac magnetic resonance imaging showed decreased LV perfusion in IR rats, which was improved with MCP. There was no difference in LV hypertrophy in MCP-treated compared to untreated IR rats. However, MCP treatment decreased the ischemic area as well as Gal-3 expression. Gal-3 blockade paralleled lower myocardial inflammation and reduced fibrosis. These novel data showing the benefits of MCP in compliance and ECM remodeling in IR reinforces previously published data showing the therapeutic potential of Gal-3 inhibition.

International audience; Aim: To determine whether non-steroidal mineralocorticoid receptor (MR) antagonists oppose metabolic syndrome-related end-organ, i.e. cardiac, damage. Materials and methods: In Zucker fa/fa rats, a rat model of metabolic syndrome, we assessed the effects of the non-steroidal MR antagonist finerenone (oral 2 mg/kg/day) on left ventricular (LV) function, haemodynamics and remodelling (using echocardiography, magnetic resonance imaging and biochemical methods). Results: Long-term (90 days) finerenone modified neither systolic blood pressure nor heart rate, but reduced LV end-diastolic pressure and LV end-diastolic pressure-volume relationship, without modifying LV end-systolic pressure and LV end-systolic pressure-volume relationship. Simultaneously , long-term finerenone reduced both LV systolic and diastolic diameters, associated with reductions in LV weight and LV collagen density, while proteinuria and renal nGAL expression were reduced. Short-term (7 days) finerenone improved LV haemodynamics and reduced LV systolic diameter, without modifying LV diastolic diameter. Moreover, short-term finerenone increased myocardial tissue perfusion and reduced myocardial reactive oxygen species, while plasma nitrite levels, an indicator of nitric oxide (NO) bio-availability, were increased. Conclusions: In rats with metabolic syndrome, the non-steroidal MR antagonist finerenone opposed metabolic syndrome-related diastolic cardiac dysfunction and nephropathy. This involved acute effects, such as improved myocardial perfusion, reduced oxidative stress/ increased NO bioavailability, as well as long-term effects, such as modifications in the myocar-dial structure. K E Y W O R D S animal pharmacology, cardiovascular disease, diabetes complications, drug development, experimental pharmacology, type 2 diabetes

We have previously shown that protein tyrosine phosphatase 1B (PTP1B) inactivation in mice [PTP1B-deficient (PTP1B−/−) mice] improves left ventricular (LV) angiogenesis, perfusion, remodeling, and function and limits endothelial dysfunction after myocardial infarction. However, whether PTP1B inactivation slows aging-associated cardiovascular dysfunction remains unknown. Wild-type (WT) and PTP1B−/− mice were allowed to age until 18 mo. Compared with old WT mice, in which aging increased the LV mRNA expression of PTP1B, old PTP1B−/− mice had 1) reduced cardiac hypertrophy with decreased LV mRNA levels of hypertrophic markers and atrial and brain natriuretic peptides, 2) lower LV fibrosis (collagen: 16 ± 3% in WT mice and 5 ± 3% in PTP1B−/− mice, P < 0.001) with decreased mRNA levels of transforming growth-factor-β1 and matrix metalloproteinase-2, and 3) higher LV capillary density and lower LV mRNA level of hypoxic inducible factor-1α, which was associated over time with a higher rate of proangiogenic M2 type macrophages and a stable LV mRNA level of VEGF receptor-2. Echocardiography revealed an age-dependent LV increase in end-diastolic volume in WT mice together with alterations of fractional shortening and diastole (transmitral Doppler E-to-A wave ratio). Invasive hemodynamics showed better LV systolic contractility and better diastolic compliance in old PTP1B−/− mice (LV end-systolic pressure-volume relation: 13.9 ± 0.9 in WT mice and 18.4 ± 1.6 in PTP1B−/− mice; LV end-diastolic pressure-volume relation: 5.1 ± 0.8 mmHg/relative volume unit in WT mice and 1.2 ± 0.3 mmHg/relative volume unit in PTP1B−/− mice, P < 0.05). In addition, old PTP1B−/− mice displayed a reduced amount of LV reactive oxygen species. Finally, in isolated resistance mesenteric arteries, PTP1B inactivation reduced aging-associated endothelial dysfunction (flow-mediated dilatation: −0.4 ± 2.1% in WT mice and 8.2 ± 2.8% in PTP1B−/− mice, P < 0.05). We conclude that PTP1B inactivation slows aging-associated LV remodeling and dysfunction and reduces endothelial dysfunction in mesenteric arteries. NEW & NOTEWORTHY The present study shows that protein tyrosine phosphatase 1B inactivation in aged mice improves left ventricular systolic and diastolic function associated with reduced adverse cardiac remodeling (hypertrophy, fibrosis, and capillary rarefaction) and limits vascular endothelial dysfunction. This suggests that protein tyrosine phosphatase 1B inhibition could be an interesting treatment approach in age-related cardiovascular dysfunction.

Background Exacerbation of chronic heart failure (HF), better known as acute decompensated HF, is characterized by a rapid further decrease of an already HF-related impaired cardiac function, which despite medical treatment only partially recovers. However, no representative experimental model of acute decompensated HF exists, limiting pre-clinical evaluation of emerging therapies and mechanistic understanding. Objective We evaluated the time course of cardiac dysfunction of acute decompensation in rats with chronic HF. Methods Three months after coronary artery ligation resulting in established chronic HF, rats received 2.5 ml tap water (control) or 1.8 g/kg NaCl (dissolved in 2.5 ml tap water) provoking acute decompensation. Cardiac output (echocardiography), LV tissue perfusion (MRI) and coronary endothelial function (Mulvany) were assessed 1 and 13 days after NaCl loading. Results One day after NaCl loading, the HF-related impairment of cardiac output was already aggravated (sham: 145±2 ml/min; HF: 125±3 ml/min; p Conclusion Our data show that in rats with HF, NaCl loading provokes immediately a further aggravation of cardiac and coronary dysfunctions. Moreover, the aggravation is sustained and only partially recovery over-time. This rat model allows the evaluation cardiac systolic and diastolic function of emerging therapies for humans with acute decompensation of chronic HF. The author hereby declares no conflict of interest

International audience; C hronic heart failure (HF) after myocardial infarction (MI) is steadily increasing worldwide and remains a major cause of death. Mineralocorticoid receptor (MR) antagonists (MRAs) improve survival in patients with HF as illustrated by spironolactone in the RALES (Randomized Aldactone Evaluation Study) 1 trial and by eplerenone in the EPHESUS (Eplerenone Post-Acute Myocardial Infarction Heart Failure Efficacy and Survival Study) trial, 2 which only included patients with post-MI. Recently, the EMPHASIS (Eplerenone in Mild Patients Hospitalization and Survival Study in Heart Failure) study even showed that eplerenone is effective in slowing down the progression of mild-to-moderate HF. 3 However, MRAs are associated with side effects, such as hyperkalemia or gynecomastia; the latter is caused by the antiandrogenic properties of their steroidal structure. These adverse effects are responsible for the underuse of MRAs. 4 Understanding of the cell-specific contribution of MR to HF and of the effects of MRA on various cell subtypes will be useful for the future development of tissue-selective MR targeting approaches that would improve the benefit/risk ratio. 5 A crucial role of cardiomyocyte MR has been demonstrated in mice with cardiomyocyte-specific MR deletion, which allows improving left ventricular (LV) function after either MI 6 or pressure overload induced by transverse aortic constriction. 7 The deletion of MR specifically in fibroblasts does not affect cardiac failure after aortic constriction. 7 The role of vascular MR has been underlined recently: the MR expressed in vas-cular smooth muscle cells (VSMCs) is involved in age-related Abstract-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

Selenoproteins are mediators of the essential micronutrient selenium, but their biological effects are not yet fully understood. Selenoprotein T (SelT), a recently discovered thioredoxin-like selenoprotein, is abundant during embryonic development but declines during adulthood. Bioinformatical studies suggested that SelT had antioxidant properties but its role has not already been established in vivo . Preliminary data obtained in our laboratory showed that myocardial infarction increases SelT protein expression in mouse heart as revealed by Western blotting analysis, suggesting that SelT may play a yet unrevealed role in the cardiovascular system. Thus, we sought to investigate SelT’s role in myocardial infarction. Male Wistar rats were subjected to either cardiac ischaemia (45 min) followed by reperfusion (I/R) or sham surgery. Five days before I/R, SelT (15 μg/kg/day, IP) or saline infusion was started by osmotic minipump. Eight days after myocardial infarction, left ventricular (LV) function was assessed by echocardiography, MRI and LV hemodynamics (pressurevolume loops). I/R resulted in a significant increase of LV systolic and diastolic diameters, in a decrease of cardiac output and fractional shortening. This was associated with a decrease of LV end-systolic pressure and an increase of LV end-diastolic pressure. SelT restored cardiac output and LV fractional shortening (+26% and +52%, respectively in comparison with I/R) associated with an improvement of LV end-diastolic/end-systolic pressures and LV tissue perfusion (–61%, +54% and +30%, respectively in comparison with I/R). Furthermore, SelT did not modify LV infarct size. SelT, administered before I/R, preserves LV function and perfusion in a rat model of myocardial infarction and might be a new therapeutic target in the treatment of this disease.

Background Experimentally, aldosterone in association with NaCl induces cardiac fibrosis, oxidative stress, and inflammation through mineralocorticoid receptor activation; however, the biological processes regulated by aldosterone alone in the heart remain to be identified. Methods and Results Mice were treated for 7 days with aldosterone, and then cardiac transcriptome was analyzed. Aldosterone regulated 60 transcripts (51 upregulated and 9 downregulated) in the heart (fold change ≥1.5, false discovery rate CD 68, α‐smooth muscle actin, CD 31, or caveolin 1 revealed that the cycling cells were essentially endothelial cells. Aldosterone‐induced mineralocorticoid receptor–dependent proliferation was confirmed ex vivo in human endothelial cells. Moreover, pharmacological‐specific blockade of mineralocorticoid receptor by eplerenone inhibited endothelial cell proliferation in a preclinical model of heart failure (transverse aortic constriction). Conclusions Aldosterone modulates cardiac gene expression and induces the proliferation of cardiac endothelial cells in vivo.

International audience; 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.

Background— Life-threatening cardiac arrhythmia is a major source of mortality worldwide. Besides rare inherited monogenic diseases such as long-QT or Brugada syndromes, which reflect abnormalities in ion fluxes across cardiac ion channels as a final common pathway, arrhythmias are most frequently acquired and associated with heart disease. The mineralocorticoid hormone aldosterone is an important contributor to morbidity and mortality in heart failure, but its mechanisms of action are incompletely understood. Methods and Results— To specifically assess the role of the mineralocorticoid receptor (MR) in the heart, in the absence of changes in aldosteronemia, we generated a transgenic mouse model with conditional cardiac-specific overexpression of the human MR. Mice exhibit a high rate of death prevented by spironolactone, an MR antagonist used in human therapy. Cardiac MR overexpression led to ion channel remodeling, resulting in prolonged ventricular repolarization at both the cellular and integrated levels and in severe ventricular arrhythmias. Conclusions— Our results indicate that cardiac MR triggers cardiac arrhythmias, suggesting novel opportunities for prevention of arrhythmia-related sudden death.

Arterial stiffness is recognized as a risk factor for many cardiovascular diseases. Aldosterone via its binding to and activation of the mineralocorticoid receptors (MRs) is a main regulator of blood pressure by controlling renal sodium reabsorption. Although both clinical and experimental data indicate that MR activation by aldosterone is involved in arterial stiffening, the molecular mechanism is not known. In addition to the kidney, MR is expressed in both endothelial and vascular smooth muscle cells (VSMCs), but the specific contribution of the VSMC MR to aldosterone-induced vascular stiffness remains to be explored. To address this question, we generated a mouse model with conditional inactivation of the MR in VSMC (MR SMKO ). MR SMKO mice show no alteration in renal sodium handling or vascular structure, but they have decreased blood pressure when compared with control littermate mice. In vivo at baseline, large vessels of mutant mice presented with normal elastic properties, whereas carotids displayed a smaller diameter when compared with those of the control group. As expected after aldosterone/salt challenge, the arterial stiffness increased in control mice; however, it remained unchanged in MR SMKO mice, without significant modification in vascular collagen/elastin ratio. Instead, we found that the fibronectin/α5-subunit integrin ratio is profoundly altered in MR SMKO mice because the induction of α5 expression by aldosterone/salt challenge is prevented in mice lacking VSMC MR. Altogether, our data reveal in the aldosterone/salt hypertension model that MR activation specifically in VSMC leads to the arterial stiffening by modulation of cell-matrix attachment proteins independent of major vascular structural changes.

International audience; The protein tyrosine phosphatase 1B (PTP1B) modulates tyrosine kinase receptors, among which is the vascular endothelial growth factor receptor type 2 (VEGFR2), a key component of angiogenesis. Because PTP1B deficiency in mice improves left ven-tricular (LV) function 2 mo after myocardial infarction (MI), we hypothesized that enhanced angiogenesis early after MI via activated VEGFR2 contributes to this improvement. At 3 d after MI, capillary density was increased at the infarct border of PTP1B ؊/؊ mice [؉7؎2% vs. wild-type (WT), P ‫؍‬ 0.05]. This was associated with increased extracellular signal-regulated kinase 2 phosphorylation and VEGFR2 activation (i.e., phosphorylated-Src/Src/VEGFR2 and dissocia-tion of endothelial VEGFR2/VE-cadherin), together with higher infiltration of proangiogenic M2 macro-phages within unchanged overall infiltration. In vitro, we showed that PTP1B inhibition or silencing using RNA interference increased VEGF-induced migration and proliferation of mouse heart microvascular endo-thelial cells as well as fibroblast growth factor (FGF)-induced proliferation of rat aortic smooth muscle cells. At 8 d after MI in PTP1B ؊/؊ mice, increased LV capillary density (؉21؎3% vs. WT; P

Inappropriate mineralocorticoid receptor (MR) activation is involved in cardiac diseases. Whether and how aldosterone is involved in the deleterious effects of cardiac mineralocorticoid activation is still unclear. Mice overexpressing MR in cardiomyocytes and their controls were treated for 7 days with aldosterone, and cardiac transcriptome was analyzed. Aldosterone regulated 265 genes in cardiomyocyte-targeted MR overexpression mice. Forty three of these genes were also differentially expressed between untreated cardiomyocyte-targeted MR overexpression and controls mice, thus representing putative aldosterone-regulated genes in cardiomyocytes. Among these genes, we focused on connective tissue growth factor (CTGF). In vivo, in cardiomyocyte-targeted MR overexpression mice, aldosterone (but not corticosterone) induced CTGF expression (mRNA and protein) in cardiomyocytes. Ex vivo, aldosterone induced the binding of mineralocorticoid receptor to CTGF promoter and increased the expression of its transcript. Aldosterone induction of CTGF synthesis in cardiomyocytes seems pathologically relevant as the increase in CTGF observed in a model of heart failure (transverse aortic constriction) in rats was prevented by eplerenone, a mineralocorticoid receptor blocker. This study demonstrates that aldosterone specifically regulates gene expression in cardiomyocytes despite large prevalence of glucocorticoids in plasma.

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 the present study, the role of MR expressed in vascular smooth muscle cells (VSMC) was investigated. Two months after coronary artery ligation causing MI, mice with VSMC-specific MR deletion (MI-MRSMKO) and mice treated with the MR antagonist finerenone (MIfine) had improved left ventricular (LV) compliance and elastance when compared to 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/min: MI-CTL: 1.1±0.5, NS; MIMRSMKO: 4.6±1.6, P In conclusion, deletion of MR in VSMC improved LV dysfunction after MI, likely through maintenance of the coronary reserve and improvement of coronary endothelial function. MR blockage by finerenone had similar effects. The author hereby declares no conflict of interest

International audience; Protein tyrosine phosphatase 1B (PTP1B) regulates tyrosine kinase receptor-mediated responses, and especially negatively influences insulin sensitivity, thus PTP1B inhibitors (PTP1Bi) are currently evaluated in the context of diabetes. We recently revealed another important target for PTP1Bi, consisting in endothelial protection. The present study was designed to test whether reduction of PTP1B activity may be beneficial in chronic heart failure (CHF). We evaluated the impact of either a 2 month pharmacological inhibition, or a gene deletion of PTP1B (PTP1B(-/-)) in CHF mice (2 months post-myocardial infarction). PTP1Bi and PTP1B deficiency reduced adverse LV remodeling, and improved LV function, as shown by the increased LV fractional shortening and cardiac output (measured by echocardiography), the increased LV end systolic pressure, and the decreased LV end diastolic pressure, at identical infarct sizes. This was accompanied by reduced cardiac fibrosis, myocyte hypertrophy and cardiac expression of ANP. In vitro vascular studies performed in small mesenteric artery segments showed a restored endothelial function (i.e. improved NO-dependent, flow-mediated dilatation, increased eNOS phosphorylation) after either pharmacological inhibition or gene deletion. PTP1B(-/-) CHF also displayed an improved insulin sensitivity (assessed by euglycemic-hyperinsulinemic clamp studies), when compared to wild-type CHF associated with an increased insulin mediated mesenteric artery dilation. Thus, chronic pharmacological inhibition or gene deletion of PTP1B improves cardiac dysfunction and cardiac remodeling in the absence of changes in infarct size. Thus this enzyme may be a new therapeutic target in CHF. Diabetic patients with cardiac complications may potentially benefit from PTP1B inhibition via two different mechanisms, reduced diabetic complications, and reduced heart failure.

The deleterious effects of aldosterone excess demonstrated in cardiovascular diseases might be linked in part to coronary vascular dysfunction. However, whether such vascular dysfunction is a cause or a consequence of the changes occurring in the cardiomyocytes is unclear. Moreover, the possible link between mineralocorticoid receptor (MR)-mediated effects on the cardiomyocyte and the coronary arteries is unknown. Thus we used a mouse model with conditional, cardiomyocyte-specific overexpression of human MR (hMR) and observed the effects on endothelial function in isolated coronary segments. hMR overexpression decreased the nitric oxide (NO)-mediated relaxing responses to acetylcholine in coronary arteries (but not in peripheral arteries), and this was prevented by a 1-mo treatment either with an MR antagonist, vitamin E/vitamin C, or a NADPH oxidase inhibitor. hMR overexpression did not affect coronary endothelial NO synthase content nor its level of phosphorylation on serine 1177, but increased cardiac levels of reactive oxygen species, cardiac NADPH oxidase (NOX) activity, and expression of the NOX subunit gp91phox, which was limited to endothelial cells. Thus an increase in hMR activation, restricted to cardiomyocytes, is sufficient to induce a severe coronary endothelial dysfunction. We suggest a new paracrine mechanism by which cardiomyocytes trigger a NOX-dependent, reactive oxygen species-mediated coronary endothelial dysfunction.

The mineralocorticoid receptor (MR) is a major regulator of renal sodium reabsorption and body fluid homeostasis. However, little is known about glucocorticoid receptor (GR)-dependent renal effects. Glucocorticoids may activate both receptors, so it is difficult to distinguish between MR- and GR-mediated effects in vivo. To overcome this complexity, we used a transgenic mouse model allowing conditional GR overexpression (doxycycline inducible TetON system, Hoxb7 promoter) in the renal collecting duct (CD) to identify GR-regulated genes involved in sodium transport in the CD. In microdissected cortical CD, induction of GR expression led (after 2 d of doxycycline) to increased α-epithelial sodium channel and glucocorticoid-induced leucine zipper and decreased abundance of with-no-lysine kinase 4 transcripts, without modification of Na,K-ATPase, serum- and glucocorticoid-kinase-1, or MR expression. No changes occurred in the upstream distal and connecting tubules [distal convoluted tubule (DCT), connecting tubule (CNT)]. Sodium excretion was unaltered, but the urinary aldosterone concentration was reduced, suggesting compensation of transitory extracellular volume expansion that subsequently disappeared. At steady state, i.e. after 15 d of doxycycline administration, transcript abundance remained altered in the CD, whereas mirror changes appeared in the DCT and CNT. Plasma aldosterone or glucocorticoids and blood pressure were all unaffected. These experiments show that: 1) GR, in addition to MR, controls epithelial sodium channel- and glucocorticoid-induced leucine zipper expression in vivo in the CD; 2) with-no-lysine kinase 4 is negatively controlled by GR; and 3) the DCT and CNT compensate for these alterations to maintain normal sodium reabsorption and blood pressure. These results suggest that enhanced GR expression may contribute to enhanced sodium retention in some pathological situations.

Aims Because mineralocorticoid receptor (MR) antagonists have shown efficacy in slowing down the progression of heart failure after myocardial infarction (MI), there is interest to elucidate the cell-specific involvement of MR. Indeed, the role of MR in vascular smooth muscle cells (VSMC) in heart failure, especially its impact on coronary circulation, has never been investigated. Methods and Results Two months after MI, mice lacking the MR specifically in VSMC (MI-MRSMKO) and mice treated with the MR antagonist finerenone (MI-fine) had better coronary function than control (MI-CTL), as assessed by acetylcholine-induced relaxation of isolated arteries (relaxation %: MI-CTL: 36±5, MI-MRSMKO: 54±3, MI-fine: 76±4; P Conclusion After MI, VSMC-specific MR invalidation benefits LV dysfunction, likely through improvement of coronary reserve and of coronary endothelial function, demonstrating for the first time the deleterious role of smooth muscle MR activation in heart failure. Furthermore, systemic MR blockade by finerenone confers additional functional improvements.

International audience; Functional genomic analysis is a challenging step in the so-called post-genomic field. Identification of potential targets using large-scale gene expression analysis requires functional validation to identify those that are physiologically relevant. Genetically modified cell models are often used for this purpose allowing up- or down-expression of selected targets in a well-defined and if possible highly differentiated cell type. However, the generation of such models remains time-consuming and expensive. In order to alleviate this step, we developed a strategy aimed at the rapid and efficient generation of genetically modified cell lines with conditional, inducible expression of various target genes. Efficient knock-in of various constructs, called targeted transgenesis, in a locus selected for its permissibility to the tet inducible system, was obtained through the stimulation of site-specific homologous recombination by the meganuclease I-SceI. Our results demonstrate that targeted transgenesis in a reference inducible locus greatly facilitated the functional analysis of the selected recombinant cells. The efficient screening strategy we have designed makes possible automation of the transfection and selection steps. Furthermore, this strategy could be applied to a variety of highly differentiated cells.

Effects of aldosterone on its target cells have long been considered to be mediated exclusively through the genomic pathway; however, evidence has been provided for rapid effects of the hormone that may involve nongenomic mechanisms. Whether an interaction exists between these two signaling pathways is not yet established. In this study, the authors show that aldosterone triggers both early nongenomic and late genomic increase in sodium transport in the RCCD(2) rat cortical collecting duct cell line. In these cells, the early (up to 2.5 h) aldosterone-induced increase in short-circuit current (Isc) is not blocked by the mineralocorticoid receptor (MR) antagonist RU26752, it does not require mRNA or protein synthesis, and it involves the PKCalpha signaling pathway. In addition, this early response is reproduced by aldosterone-BSA, which acts at the cell surface and presumably does not enter the cells (aldo-BSA is unable to trigger the late response). The authors also show that MR is rapidly phosphorylated on serine and threonine residues by aldosterone or aldosterone-BSA. In contrast, the late (4 to 24 h) aldosterone-induced increase in ion transport occurs through activation of the MR and requires mRNA and protein synthesis. Interestingly, nongenomic and genomic aldosterone actions appear to be interdependent. Blocking the PKCalpha pathway results in the inhibition of the late genomic response to aldosterone, as demonstrated by the suppression of aldosterone-induced increase in MR transactivation activity, alpha1 Na(+)/K(+)/ATPase mRNA, and Isc. These data suggest cross-talk between the nongenomic and genomic responses to aldosterone in renal cells and suggest that the aldosterone-MR mediated increase in mRNA/protein synthesis and ion transport depends, at least in part, upon PKCalpha activation. E-mail: marcel.blot-chabaud@pharmacie.univ-mrs.fr

The renal collecting duct plays a key role in control of ion and fluid homeostasis. Genes encoding for ion transporters, hormone receptors, or regulatory proteins specifically expressed in the collecting duct are mutated in several genetic diseases with altered blood pressure. Suitable cellular models expressing genes in a conditional way should represent attractive systems for structure-function analyses and generation of appropriate physiopathological models of related diseases. However, generation of such systems remains laborious and quite inefficient. We adapted and improved a conditional Cre-lox-inducible system in the highly differentiated aldosterone-sensitive rat cortical collecting duct (RCCD2) cell line. The inducible MerCreMer recombinase allowed tight control and high levels of transgene expression, whereas flanking a selection marker with two loxP sites strongly improved the selection procedure. We have used this system to conditionally express an enhanced green fluorescent protein-tagged human mineralocorticoid receptor. In the future, this will allow structure-function analyses as well as mineralocorticoid receptor trafficking studies in these epithelial cells, which retain the features of the native collecting duct. Improvements in the conditional Cre-lox expression system have potentially wide applications in other epithelial or nonepithelial cell lines.

Cardiac failure is a common feature in the evolution of cardiac disease. Among the determinants of cardiac failure, the renin–angiotensin–aldosterone system has a central role, and antagonism of the mineralocorticoid receptor (MR) has been proposed as a therapeutic strategy. In this study, we questioned the role of the MR, not of aldosterone, on heart function, using an inducible and cardiac-specific transgenic mouse model. We have generated a conditional knock-down model by expressing solely in the heart an antisense mRNA directed against the murine MR, a transcription factor with unknown targets in cardiomyocytes. Within 2–3 mo, mice developed severe heart failure and cardiac fibrosis in the absence of hypertension or chronic hyperaldosteronism. Moreover, cardiac failure and fibrosis were fully reversible when MR antisense mRNA expression was subsequently suppressed.

ObjectiveEpoxyeicosatrienoic acids (EETs) are synthesized from arachidonic acid, notably in endothelial cells, and display attractive metabolic, vasodilatory and anti-inflammatory properties. We demonstrated previously that inhibiting EET degradation mediated by soluble epoxide hydrolase (sEH) reduces hypertension and heart failure, and others reported that it improves glucose homeostasis in type 2 diabetes. However, the impact of such strategy on target organ damage in diabetes remains to be clarified.Materials and methodsThe pharmacological sEH inhibitor t-AUCB (10 mg/l in drinking water) was administered for 8 weeks in mice subjected to a high-fat diet (HFD, 60% fat) for 16 weeks. Mice on control chow diet (10% fat), non-treated HFD mice and HFD mice treated with glibenclamide (80 mg/l) served as controls.ResultsGlibenclamide and t-AUCB similarly prevented the increased fasting glycemia in HFD mice (Control: 5.4±0.2; HFD: 8.0±0.8; HFD+GLI: 5.1±0.3; HFD+t-AUCB: 5.6±0.2mmol/L; p

First published August 30, 2001; 10.1152/ajprenal.00360.2000.—The renal collecting duct (CD) plays a key role in the control of ion and fluid homeostasis. Several genetic diseases that involve mutations in genes encoding for ion transporters or hormone receptors specifically expressed in CD have been described. Suitable cellular or transgenic animal models expressing such mutated genes in an inducible manner should represent attractive systems for structure-function relationship analyses and the generation of appropriate physiopathological models of related diseases. Our first goal was to develop a CD cell line that allows inducible gene expression using the tetracycline-inducible system (Tet-On). We designed several strategies aimed at the development of a tight and highly inducible system in RCCD1 cells, a rat cortical collecting duct (CCD) cell line exhibiting several properties of the native CCD. Analysis of reporter gene expression demonstrated that the Tet-On system is suitable for inducible gene expression in these cells. In a second step, we have tested whether transgenic Tet-On mice expressing the tetracycline transactivator under the control of the human cytomegalovirus promoter were suitable for inducible gene expression in tubule epithelial cells. The results indicate that, in vivo , the inducible expression of the lacZ reporter gene appeared to be restricted to the CD. This particular strain of transgenic mice may therefore be useful for the expression of genes of interest in an inducible manner in the collecting duct.

Background The mineralocorticoid receptor (MR) and its ligand, aldosterone (aldo), are involved in cardiac diseases. However, the cardiomyocyte-MR regulated processes leading to these injuries are still unclear. Objective To identify new aldosterone-regulated functions involved in cardiac diseases. Methods and Results Double transgenic mice overexpressing MR in cardiomyocytes (DT) and their controls (CT) were treated for 7 days with aldosterone (60 μg/kg/day; n = 6-9 / group) and a genome microarray analysis was performed. In CT mice, aldo regulated 70 genes. In DT mice, aldo induced much more genes (343). To identify the biological processes modulated by aldo, a gene ontology analysis was performed. The majority of aldosteroneregulated genes were involved in cell division, as shown by the relative expression of Cycline B1 and Cdk1 (Cycline; CT untreated 1 ± 0.02, CT aldotreated 2.1 ± 0.5; Cdk1; CT untreated 1 ± 0.05, CT aldo-treated 2.2 ± 0.4). Moreover, the Ki-67 index of aldo-treated mice (CT and DT) was higher than in non-treated ones (% of positive Ki-67 nuclei vs total nuclei; CT untreated 15±4, CT aldo-treated 51±12%; DT untreated 29 ± 5, DT aldo-treated 61 ± 19%). Co-staining of Ki-67 with caveolin 1 revealed that the cycling cells were endothelial cells. Ki-67 index was increased in an experimental model of heart failure (transverse aortic constriction: TAC) in rats. Eplerenone (eple), a MR blocker, prevented this increase (% of positive Ki-67 nuclei vs total nuclei; sham 26 ± 3, TAC 42 ± 5, TAC+eple 23 ± 6%). Conclusion Aldosterone induces cardiac endothelial cells proliferation in vivo and underlines the role of cardiomyocyte-MR activation in this process. Perspectives Favre and collaborators (AJP 2011) reported that cardiomyocyte- MR activation is involved in coronary endothelial dysfunction, via pathways of oxidative stress. It appears interesting to study if the cardiac endothelial cells proliferation induced by aldo is oxidative stress dependent.