Divergent effects of losartan and metoprolol on cardiac remodeling, c-kit+ cells, proliferation and apoptosis in the left ventricle after myocardial infarction.
ABSTRACT: There is strong evidence for the use of angiotensin converting enzyme inhibitors and beta-blockers to reduce morbidity and mortality in patients with myocardial infarction (MI), whereas the effect of angiotensin receptor blockers is less clear. We evaluated the effects of an angiotensin receptor blocker losartan and a beta-blocker metoprolol on left ventricular (LV) remodeling, c-kit+ cells, proliferation, fibrosis, apoptosis, and angiogenesis using a model of coronary ligation in rats. Metoprolol treatment for 2 weeks improved LV systolic function. In contrast, losartan triggered deleterious structural remodeling and functional deterioration of LV systolic function, ejection fraction being 41% and fractional shortening 47% lower in losartan group than in controls 2 weeks after MI. The number of c-kit+ cells as well as expression of Ki-67 was increased by metoprolol. Losartan-induced thinning of the anterior wall and ventricular dilation were associated with increased apoptosis and fibrosis, while losartan had no effect on the expression of c-kit or Ki-67. Metoprolol or losartan had no effect on microvessel density. These results demonstrate that beta-blocker treatment attenuated adverse remodeling via c-kit+ cells and proliferation, whereas angiotensin receptor blocker-induced worsening of LV systolic function was associated with increased apoptosis and fibrosis in the peri-infarct region.
Project description:The aim of this study was to evaluate the effects of losartan on left ventricular (LV) hypertrophy and fibrosis in patients with nonobstructive hypertrophic cardiomyopathy (HCM).Despite evidence that myocardial hypertrophy and fibrosis are mediated by angiotensin II and are important determinants of morbidity and mortality in patients with HCM, no prior studies have evaluated the effects of angiotensin receptor blockers on LV hypertrophy and fibrosis with cardiac magnetic resonance imaging.In double-blind fashion, 20 patients (3 women, 17 men; age: 51 ± 13 years) with HCM were randomly assigned to receive placebo (n = 9) or losartan 50 mg twice a day (n = 11) for 1 year. Cardiac magnetic resonance imaging was performed at baseline and 1 year to measure LV mass and extent of fibrosis as assessed by late gadolinium enhancement.There was a trend toward a significant difference in the percent change in LV mass (median [interquartile range]: +5% [-4% to +21%] with placebo vs. -5% [-11% to -0.9%] with losartan; p = 0.06). There was a significant difference in the percent change in extent of late gadolinium enhancement, with the placebo group experiencing a larger increase (+31% ± 26% with placebo vs. -23% ± 45% with losartan; p = 0.03).This pilot study suggests attenuation of progression of myocardial hypertrophy and fibrosis with losartan in patients with nonobstructive HCM. Confirmation of these results in a larger trial is required to confirm a place for angiotensin receptor blockers in the management of patients with HCM. (Effect of Losartan in Patients With Nonobstructive Hypertrophic Cardiomyopathy; NCT01150461).
Project description:The myocardial longitudinal relaxation time (T1) on cardiac magnetic resonance imaging (CMR) can quantify myocardial fibrosis in the presence or absence of visually detectable late gadolinium (Gd) enhancement (LGE). Mineralocorticoid receptor antagonist (MRA) treatment produces beneficial remodeling in nonischemic dilated cardiomyopathy (NIDCM). We assessed the hypothesis that interstitial myocardial fibrosis measured with the use of CMR predicts left ventricular (LV) beneficial remodeling in NIDCM after heart failure (HF) treatment including MRAs.Twelve patients with NIDCM, on stable beta-blocker and angiotensin-converting enzyme inhibitor/angiotensin receptor-blocking therapy, were studied before and after 6-29 months of treatment with MRAs, by means of CMR assessment of LV structure, function, and T1 from standard Look-Locker sequences (T1LL). All patients had depressed cardiac function, dilated left ventricles, and no visual LGE. After adding MRA to HF treatment, the LV ejection fraction increased and the LV end-systolic volume index (LV end-systolic volume/m2) decreased in all patients (P?<?.0001). This this was inversely proportional to the baseline myocardial T1LL (r?=?-0.65; P?=?.02).Myocardial T1LL, in the absence of visually detectable LGE, was quantitatively related to the degree of beneficial LV remodeling achieved in response to adding MRA to a HF regimen.
Project description:Angiotensin II promotes liver fibrogenesis by stimulating nonphagocytic NADPH oxidase (NOX)-induced oxidative stress. Angiotensin II type 1 (AT1) receptor blockers attenuate experimental liver fibrosis, yet their effects in human liver fibrosis are unknown. We investigated the effects of losartan on hepatic expression of fibrogenic, inflammatory, and NOX genes in patients with chronic hepatitis C (CHC). Fourteen patients with CHC and liver fibrosis received oral losartan (50 mg/day) for 18 mo. Liver biopsies were performed at baseline and after treatment. The degree of inflammation and fibrosis was evaluated by histological analysis (METAVIR). Collagen content was measured by morphometric quantification of Sirius red staining. Overall collagen content and fibrosis stage remained stable in the whole series, yet the fibrosis stage decreased in seven patients. Inflammatory activity improved in seven patients. The effect of losartan on hepatic expression of 31 profibrogenic and inflammatory genes and components of the NOX complex was assessed by quantitative PCR. Losartan treatment was associated with a significant decrease in the expression of several profibrogenic and NOX genes including procollagen alpha1(I) and alpha1(IV), urokinase-type plasminogen activator, metalloproteinase type 2, NOX activator 1 (NOXA-1) and organizer 1 (NOXO-1), and Rac-1. Losartan was well tolerated in all patients and was effective in attenuating the activity of the systemic renin-angiotensin system. No effects on serum liver tests or viral load were observed. We conclude that prolonged administration of losartan, an oral AT1 receptor blocker, is associated with downregulation of NOX components and fibrogenic genes in patients with CHC. Controlled studies are warranted to assess the effect of AT1 receptor blockers in chronic liver injury.
Project description:G-protein coupled receptors (GPCRs) have long been known as receptors that activate G protein-dependent cellular signaling pathways. In addition to the G protein-dependent pathways, recent reports have revealed that several ligands called "biased ligands" elicit G protein-independent and ?-arrestin-dependent signaling through GPCRs (biased agonism). Several ?-blockers are known as biased ligands. All ?-blockers inhibit the binding of agonists to the ?-adrenergic receptors. In addition to ?-blocking action, some ?-blockers are reported to induce cellular responses through G protein-independent and ?-arrestin-dependent signaling pathways. However, the physiological significance induced by the ?-arrestin-dependent pathway remains much to be clarified in vivo. Here, we demonstrate that metoprolol, a ?(1)-adrenergic receptor-selective blocker, could induce cardiac fibrosis through a G protein-independent and ?-arrestin2-dependent pathway. Metoprolol, a ?-blocker, increased the expression of fibrotic genes responsible for cardiac fibrosis in cardiomyocytes. Furthermore, metoprolol induced the interaction between ?(1)-adrenergic receptor and ?-arrestin2, but not ?-arrestin1. The interaction between ?(1)-adrenergic receptor and ?-arrestin2 by metoprolol was impaired in the G protein-coupled receptor kinase 5 (GRK5)-knockdown cells. Metoprolol-induced cardiac fibrosis led to cardiac dysfunction. However, the metoprolol-induced fibrosis and cardiac dysfunction were not evoked in ?-arrestin2- or GRK5-knock-out mice. Thus, metoprolol is a biased ligand that selectively activates a G protein-independent and GRK5/?-arrestin2-dependent pathway, and induces cardiac fibrosis. This study demonstrates the physiological importance of biased agonism, and suggests that G protein-independent and ?-arrestin-dependent signaling is a reason for the diversity of the effectiveness of ?-blockers.
Project description:We had proposed previously a novel combination of beta2-adrenoreceptor (AR) agonist and beta1-AR blocker that in the rat model of postmyocardial infarction (MI) dilated cardiomyopathy exceeds the therapeutic effectiveness of either monotherapy. In the present study, we compared that treatment with a combination of beta1-AR blocker and angiotensin-converting enzyme inhibitor (ACEi), a current standard chronic heart failure (CHF) therapy. Two weeks after coronary artery ligation, rats were divided into groups of similar average MI size, measured by echocardiography, and the following 12-month treatments were initiated: fenoterol (250 microg/kg/day), a beta2-AR agonist, plus metoprolol (100 mg/kg/day), a beta1-AR blocker (beta1-beta2+); metoprolol plus enalapril (20 mg/kg/day), an ACEi (beta1-ACEi); and a combination of all three drugs (beta1-beta2+ACEi). These treatment groups were compared with each other and with nontreated (nT) and sham groups. The 12-month mortality was significantly reduced in all treatment groups (44% in beta1-beta2+, 56% in beta1-beta2+ACEi, 59% in beta1-ACEi versus 81% in nT). Bimonthly echocardiography revealed significant attenuation of the left ventricular (LV) chamber remodeling, LV functional deterioration, and MI expansion in all three treatment groups, but effects were significantly more pronounced when treatment included a beta2-AR agonist. The results indicated that a combination of beta1-AR blocker and beta2-AR agonist is equipotent to a combination of beta1-AR blocker and ACEi in the treatment of CHF in rats, with the respect to mortality, and exceeds the latter with respect to cardiac remodeling and MI expansion. Thus, this novel therapeutic regimen for CHF warrants detailed clinical investigation.
Project description:In patients with conduction abnormalities or left ventricle (LV) dysfunction the use of ?-blockers for post cardiac surgery rhythm control is difficult and controversial, with a paucity of information about other drugs such ivabradine used postoperatively. The objective of this study was to compare the efficacy and safety of ivabradine versus metoprolol used perioperatively in cardiac surgery patients with conduction abnormalities or LV systolic dysfunction.This was an open-label, randomized clinical trial enrolling 527 patients with conduction abnormalities or LV systolic dysfunction undergoing coronary artery bypass grafting or valvular replacement, randomized to take ivabradine or metoprolol, or metoprolol plus ivabradine. The primary endpoints were the composites of 30-day mortality, in-hospital atrial fibrillation (AF), in-hospital three-degree atrioventricular block and need for pacing, in-hospital worsening heart failure (HF; safety endpoints), duration of hospital stay and immobilization and the above endpoint plus in-hospital bradycardia, gastrointestinal symptoms, sleep disturbances, cold extremities (efficacy plus safety endpoint).Heart rate reduction and prevention of postoperative AF or tachyarrhythmia with combined therapy was more effective than with metoprolol or ivabradine alone during the immediate postoperative management of cardiac surgery patients. In the Ivabradine group, the frequency of early postoperative pacing and HF worsening was smaller than in the Metoprolol group and in combined therapy group. The frequency of primary combined endpoint was lower in the combined Ivabradine + Metoprolol group compared with the monotherapy groups.Considering efficacy and safety, the cardiac rhythm reduction after open heart surgery in patients with conduction abnormalities or LV dysfunction with ivabradine plus metoprolol emerged as the best treatment in this trial.
Project description:BACKGROUND:Mineralocorticoid receptor antagonist (MRA) treatment produces beneficial left ventricular (LV) remodeling in nonischemic dilated cardiomyopathy (NIDCM). This study addressed the timing of maximal beneficial LV remodeling in NIDCM when adding MRA. MATERIALS AND METHODS:We studied 12 patients with NIDCM on stable ?-blocker and angiotensin-converting enzyme inhibitor/angiotensin receptor-blocking therapy who underwent cardiac magnetic resonance imaging before and after 6-31 months of continuous MRA therapy. RESULTS:At baseline, the LV ejection fraction (LVEF) was 24% (19-27); median [interquartile range]. The LV end-systolic volume index (LVESVI) was 63 ml (57-76) and the LV stroke volume index (LVSVI) was 19 ml (14-21), all depressed. After adding MRA to the HF regimen, the LVEF increased to 47% (42-52), with a decrease in LVESVI to 36 ml (33-45) and increase in LVSVI to 36 ml (28-39) (for each, P ?< 0?.0001). Using generalized least squares analysis, the maximal beneficial remodeling (defined by maximal increase in LVEF, the maximal decrease in LVESVI and maximal increase in LVSVI) was achieved after approximately 12-16 months of MRA treatment. CONCLUSIONS:Adding MRA to a standard medical regimen for NIDCM resulted in beneficial LV remodeling. The maximal beneficial remodeling was achieved with 12-16 months of MRA therapy. These results have implications for the timing of other advanced therapies, such as placing internal cardioverter-defibrillators.
Project description:Angiotensin receptor blocker-neprilysin inhibitor (ARNi) therapy improves the prognosis of heart failure patients. However, the mechanisms remain unclear. This study investigated the biological effects of ARNi with neprilysin inhibitor sacubitril and angiotensin receptor blocker valsartan on myocardial remodeling and cardiac perfusion in experimental heart failure (HF) after myocardial infarction (MI). Male Lewis rats (10-weeks old) with confirmed HF were randomized one-week post-MI to treatment with vehicle (water), sacubitril/valsartan or valsartan, as comparator group, for either 1 or 5 weeks. Sacubitril/valsartan for 1-week limited LV contractile dysfunction vs. vehicle and both sacubitril/valsartan and valsartan attenuated progressive LV dilation after 1 and 5 weeks treatment. After 5 weeks, both sacubitril/valsartan and valsartan reduced CTGF expression in the remote myocardium, although only sacubitril/valsartan prevented interstitial fibrosis. In the border zone, sacubitril/valsartan and valsartan reduced hypertrophic markers, but only sacubitril/valsartan reduced cardiomyocyte size and increased VEGFA expression. In the infarct, sacubitril/valsartan induced an early uptake of 99mTc-NC100692 (a radiotracer of angiogenesis) and improved perfusion, as determined by 201Tl microSPECT/CT imaging. In conclusion, ARNi improved global LV function, limited remodeling in the remote and border zones, and increased perfusion to the infarct. Sacubitril/valsartan had more consistent effects than valsartan on LV remodeling in experimental HF.
Project description:Peroxisome proliferator activated receptor ? (PPAR?) has been reported to play a protective role in the vasculature; however, the underlying mechanisms involved are not entirely known. We previously showed that vascular smooth muscle-specific overexpression of a dominant negative human PPAR? mutation in mice (S-P467L) leads to enhanced myogenic tone and increased angiotensin-II-dependent vasoconstriction. S-P467L mice also exhibit increased arterial blood pressure. Here we tested the hypotheses that a) mesenteric smooth muscle cells isolated from S-P467L mice exhibit enhanced angiotensin-II AT1 receptor signaling, and b) the increased arterial pressure of S-P467L mice is angiotensin-II AT1 receptor dependent. Phosphorylation of mitogen-activated protein/extracellular signal-regulated kinase (ERK1/2) was robustly increased in mesenteric artery smooth muscle cell cultures from S-P467L in response to angiotensin-II. The increase in ERK1/2 activation by angiotensin-II was blocked by losartan, a blocker of AT1 receptors. Angiotensin-II-induced ERK1/2 activation was also blocked by Tempol, a scavenger of reactive oxygen species, and correlated with increased Nox4 protein expression. To investigate whether endogenous renin-angiotensin system activity contributes to the elevated arterial pressure in S-P467L, non-transgenic and S-P467L mice were treated with the AT1 receptor blocker, losartan (30 mg/kg per day), for 14-days and arterial pressure was assessed by radiotelemetry. At baseline S-P467L mice showed a significant increase of systolic arterial pressure (142.0 ± 10.2 vs 129.1 ± 3.0 mmHg, p<0.05). Treatment with losartan lowered systolic arterial pressure in S-P467L (132.2 ± 6.9 mmHg) to a level similar to untreated non-transgenic mice. Losartan also lowered arterial pressure in non-transgenic (113.0 ± 3.9 mmHg) mice, such that there was no difference in the losartan-induced depressor response between groups (-13.53 ± 1.39 in S-P467L vs -16.16 ± 3.14 mmHg in non-transgenic). Our results suggest that interference with PPAR? in smooth muscle: a) causes enhanced angiotensin-II AT1 receptor-mediated ERK1/2 activation in resistance vessels, b) and may elevate arterial pressure through both angiotensin-II AT1 receptor-dependent and -independent mechanisms.
Project description:We investigated the effect of ginsenoside Rb1 on cardiac function and remodeling in heart failure (HF). Four weeks after HF induction, the rats were administrated with ginsenoside Rb1 (35 and 70 mg/kg) and losartan (4.5 mg/kg) for 8 weeks. Losartan was used as a positive control. Cardiac function was assessed by measuring hemodynamic parameters. Histological changes were analyzed by HE and Masson's trichrome staining. Cardiac hypertrophy, fibrosis, mitochondrial membrane potential and glucose transporter type 4 (GLUT4) levels were evaluated. In the present study, high dose of (H-) ginsenoside Rb1 decreased heart rate, improved cardiac function and alleviated histological changes induced by HF. H-ginsenoside Rb1 attenuated cardiac hypertrophy and myocardial fibrosis by decreasing left ventricular (LV) weight/heart weight ratio and cardiomyocyte cross-sectional area and reducing the levels of atrial natriuretic factor (ANF), ?-myosin heavy chain (?-MHC), periostin, collagen I, Angiotensin II (Ang II), Angiotensin converting enzyme (ACE) and Ang II type 1 (AT1) receptor. Moreover, H-ginsenoside Rb1 decreased mitochondrial membrane potential and enhanced the translocation of GLUT4 to plasma membrane. The TGF-?1/Smad and ERK signaling pathways were inhibited and the Akt pathway was activated. These findings suggest that ginsenoside Rb1 might restore cardiac/mitochondrial function, increase glucose uptake and protect against cardiac remodeling via the TGF-?1/Smad, ERK and Akt signaling pathways.