MicroRNA-24 regulates vascularity after myocardial infarction.

BACKGROUND: Myocardial infarction leads to cardiac remodeling and development of heart failure. Insufficient myocardial capillary density after myocardial infarction has been identified as a critical event in this process, although the underlying mechanisms of cardiac angiogenesis are mechanistically not well understood. METHODS AND RESULTS: Here, we show that the small noncoding RNA microRNA-24 (miR-24) is enriched in cardiac endothelial cells and considerably upregulated after cardiac ischemia. MiR-24 induces endothelial cell apoptosis, abolishes endothelial capillary network formation on Matrigel, and inhibits cell sprouting from endothelial spheroids. These effects are mediated through targeting of the endothelium-enriched transcription factor GATA2 and the p21-activated kinase PAK4, which were identified by bioinformatic predictions and validated by luciferase gene reporter assays. Respective downstream signaling cascades involving phosphorylated BAD (Bcl-XL/Bcl-2-associated death promoter) and Sirtuin1 were identified by transcriptome, protein arrays, and chromatin immunoprecipitation analyses. Overexpression of miR-24 or silencing of its targets significantly impaired angiogenesis in zebrafish embryos. Blocking of endothelial miR-24 limited myocardial infarct size of mice via prevention of endothelial apoptosis and enhancement of vascularity, which led to preserved cardiac function and survival. CONCLUSIONS: Our findings indicate that miR-24 acts as a critical regulator of endothelial cell apoptosis and angiogenesis and is suitable for therapeutic intervention in the setting of ischemic heart disease.

Improvement in left ventricular remodeling by the endothelial nitric oxide synthase enhancer AVE9488 after experimental myocardial infarction.

BACKGROUND: Reduced endothelial nitric oxide (NO) bioavailability contributes to the progression of heart failure. In this study, we investigated whether the transcription enhancer of endothelial NO synthase (eNOS) AVE9488 improves cardiac remodeling and heart failure after experimental myocardial infarction (MI). METHODS AND RESULTS: Starting 7 days after coronary artery ligation, rats with MI were treated with placebo or AVE9488 (25 ppm) as a dietary supplement for 9 weeks. AVE9488 therapy versus placebo substantially improved left ventricular (LV) function, reduced LV filling pressure, and prevented the rightward shift of the pressure-volume curve. AVE9488 also attenuated the extent of pulmonary edema, reduced LV fibrosis and myocyte cross-sectional area, and prevented the increases in LV gene expression of atrial natriuretic factor, brain natriuretic peptide, and endothelin-1. eNOS protein levels and calcium-dependent NOS activity were decreased in the surviving LV myocardium from placebo MI rats and normalized by AVE9488. The beneficial effects of AVE9488 on LV dysfunction and remodeling after MI were abrogated in eNOS-deficient mice. Aortic eNOS protein expression and endothelium-dependent NO-mediated vasorelaxation were significantly enhanced by AVE9488 treatment after infarction, whereas increased vascular superoxide anion formation was reduced. Moreover, AVE9488 prevented the marked depression of circulating endothelial progenitor cell levels in rats with heart failure after MI. CONCLUSIONS: Long-term treatment with the eNOS enhancer AVE9488 improved LV remodeling and contractile dysfunction after MI. Molecular alterations, circulating endothelial progenitor cell levels, and endothelial vasomotor dysfunction were improved by AVE9488. Pharmacological interventions designed to increase eNOS-derived NO constitute a promising therapeutic approach for the amelioration of postinfarction ventricular remodeling and heart failure.

Peroxisome proliferator activated-receptor agonism and left ventricular remodeling in mice with chronic myocardial infarction.

1. Peroxisome proliferator activated receptor gamma (PPARgamma) has been implicated in several cellular pathways assumed to beneficially affect heart failure progression. In contrast, population-based studies demonstrate an increased incidence of heart failure in patients treated with PPARgamma agonists. Therefore, we examined the effect of pioglitazone, a PPARgamma agonist, on chronic left ventricular remodeling after experimental myocardial infarction (MI) in mice. 2. Mice were treated with placebo or pioglitazone (20 mg x kg(-1) by gavage) from week 1 to week 6 after ligation of the left anterior descending artery. Serial transthoracic echocardiography was performed at weeks 1, 3, and 6. 3. Over 6 weeks, there was no difference in mortality (placebo 12%, pioglitazone 10%). Echocardiography showed significant left ventricular dilatation in animals with MI (week 6, end-systolic area, placebo sham 9.6+/-1.3 vs placebo MI 14.4+/-2.5 mm(2)). However, there was no difference between the placebo and pioglitazone groups (week 6, end-systolic area, pioglitazone MI 14.8+/-2.9 mm(2), P=NS vs placebo). 4. Moreover, there were no changes in metabolic parameters, inflammation, and collagen deposition. Endothelial function in the aorta was not changed by PPARgamma activation. 5. In conclusion, PPARgamma activation did not adversely affect left ventricular remodeling and survival in mice with chronic MI. However, we were also not able to identify a protective effect of pioglitazone.

Additive improvement of left ventricular remodeling and neurohormonal activation by aldosterone receptor blockade with eplerenone and ACE inhibition in rats with myocardial infarction.

OBJECTIVES: We investigated the effects of the aldosterone blocker eplerenone alone and in combination with angiotensin-converting enzyme (ACE) inhibition on ventricular remodeling in rats with left ventricular (LV) dysfunction after extensive myocardial infarction (MI). BACKGROUND: Adding an aldosterone antagonist to ACE inhibition reduces mortality and morbidity in heart failure. METHODS: Starting 10 days after MI, rats were treated with placebo, eplerenone (100 mg/kg/day), the ACE inhibitor trandolapril (0.3 mg/kg/day), or a combination of both for nine weeks. RESULTS: Both monotherapies attenuated the rise in LV end-diastolic pressure (LVEDP) and LV end-diastolic volume (LVEDV) compared with placebo, whereas combined treatment further attenuated LVEDP and LVEDV, significantly improved LV function and reduced plasma norepinephrine levels. The time constant of LV pressure isovolumic decay (tau) was prolonged in placebo MI rats, significantly shortened by eplerenone, and normalized by eplerenone/trandolapril. Increased collagen type I gene expression and collagen content in the noninfarcted LV myocardium from MI placebo rats was attenuated by trandolapril, but almost completely prevented by eplerenone and eplerenone/trandolapril. The addition of eplerenone to ACE inhibition prevented sarcoplasmic-reticulum calcium ATPase downregulation and the increases in LV gene expression of beta-MHC and atrial natriuretic factor more effectively than either monotherapy. Furthermore, combination treatment attenuated the increase in myocardial angiotensin II type 1 receptor expression and increased phosphorylated endothelial nitric oxide synthase protein levels. CONCLUSIONS: The aldosterone blocker eplerenone improved LV remodeling in rats with LV dysfunction after extensive MI. Combination therapy with an ACE inhibitor substantially potentiates this effect by a complementary prevention of LV fibrosis, cardiac hypertrophy, and molecular alterations.

Impact of hydroxymethylglutaryl coenzyme a reductase inhibition on left ventricular remodeling after myocardial infarction: an experimental serial cardiac magnetic resonance imaging study.

OBJECTIVES: We sought to assess the influence of long-term hydroxymethylglutaryl coenzyme A reductase inhibition (statin) therapy on left ventricular (LV) remodeling after myocardial infarction (MI) by use of serial cardiac magnetic resonance imaging (CMRI) studies. BACKGROUND: Statin therapy has been shown to reduce cardiac hypertrophy in vitro and in vivo, but the influence on LV post-MI remodeling is largely unknown. METHODS: The CMRI measurements were taken four and 12 weeks after left coronary artery ligation in a 7.05-tesla Biospec. The MI size, LV mass and volumes, cardiac output (CO), and ejection fraction were determined. Rats were treated for 12 weeks with either placebo (P), cerivastatin (C; 0.6 mg/kg body weight per day) as a dietary supplement, or cerivastatin plus the nitric oxide synthase (NOS) inhibitor N-methyl-L-arginine methyl ester (L-NAME, 76 mg/100 ml) and hydralazine (8 mg/100 ml) in drinking water (CLH) to assess the contribution of endogenous nitric oxide formation. RESULTS: Administration of cerivastatin attenuated hypertrophy after MI, and this effect was completely abolished by NOS inhibition (increase of LV mass from 4 to 12 weeks after MI: 235.3 +/- 33.7 mg with P vs. 59.8 +/- 20.5 mg with C vs. 239.5 +/- 16.0 mg with CLH; p < 0.05 vs. P and CLH). Left ventricular dilation was not changed (increase of end-diastolic volume from 4 to 12 weeks after MI: 108.7 +/- 28.8 with P vs. 126.6 +/- 20.5 with C vs. 173.7 +/- 25.1 with CLH; p = NS). The CO was higher in the cerivastatin group (12 weeks: 76.1 +/- 2.9 ml/min with P vs. 95.8 +/- 4.8 ml/min with C; p < 0.05). The effects of cerivastatin were abolished by NOS inhibition in the CLH group (CO at 12 weeks: 69.3 +/- 2.8 ml/min, p < 0.05 vs. C). CONCLUSIONS: Left ventricular remodeling was profoundly changed by statin treatment. Hypertrophy was attenuated, and global function was improved. These positive effects were abolished by NOS inhibition.