Chronic therapy with metoprolol attenuates cardiomyocyte apoptosis in dogs with heart failure

Chronic treatment with carvedilol improves ventricular function and reduces myocyte apoptosis in an animal model of heart failure

BACKGROUND

Beta blocker treatment has emerged as an effective treatment modality for heart failure. Interestingly, beta-blockers can activate both pro-apoptotic and anti-apoptotic pathways. Nevertheless, the mechanism for improved cardiac function seen with beta-blocker treatment remains largely unknown. Carvedilol is a non-selective beta-blocker with alpha-receptor blockade and antioxidant properties. We therefore studied the impact of the effects of carvedilol in an animal model of end-stage heart failure.

RESULTS

To test whether chronic treatment with beta-blockade decreases apoptosis, we treated myopathic turkeys with two dosages of carvedilol, 1 mg/kg (DCM1) and 20 mg/kg (DCM20), for four weeks and compared them to non-treated DCM animals (DCM0) and to control turkeys (CON). Echocardiographic measurements showed that non-treated DCM animals had a significantly lower fractional shortening (FS) when compared to CON (68.73 +/- 1.37 vs. 18.76 +/- 0.59%, p < 0.001). Both doses of carvedilol significantly improved FS (33.83 +/- 10.11 and 27.73 +/- 6.18% vs. 18.76 +/- 0.59% for untreated DCM, p < 0.001). DCM left ventricles were characterized by a higher percentage of apoptotic nuclei when compared to CON (5.64 +/- 0.49 vs. 1.72 +/- 0.12%, respectively p < 0.001). Both doses of carvedilol significantly reduced the number of apoptotic nuclei (2.32 +/- 0.23% and 2.36 +/-6% 1 mg and 20 mg/kg respectively).

CONCLUSIONS

Carvedilol improves ventricular function. Furthermore, treatment with carvedilol decreased the incidence of apoptosis in cardiac myocytes from failing hearts at both doses. These data suggest that the inhibition of apoptosis with carvedilol may lead to improvement in ventricular function and may underlie a beneficial effect of beta-blockade independent of heart rate lowering effects.

Prognostic importance of the oxidized product of catecholamines, adrenolutin, in patients with severe heart failure

OBJECTIVES

The purpose of this study was to assess whether adrenolutin, the inert product of the highly reactive molecules aminochromes, is increased in severe chronic heart failure and whether it is associated with a poor prognosis.

BACKGROUND

Experimental evidence suggests that oxidative products of catecholamines, aminochromes, are more cardiotoxic than unoxidized catecholamines and may be increased in heart failure.

METHODS

Adrenolutin was measured at baseline and at 1 and 3 months in 263 patients with chronic New York Heart Association class III or IV heart failure and a left ventricular ejection fraction of 22% +/- 7%. Adrenolutin levels were compared with normal levels, and their relation to prognosis was evaluated.

RESULTS

Baseline adrenolutin was increased (55 +/- 90 pg/mL vs 8.4 +/- 9.1 pg/mL for control, P <.02) and remained increased at 1 month (49 +/- 65 pg/mL). During a mean follow-up of 309 +/- 148 days (22-609 days), 57 patients died. Baseline adrenolutin levels correlated with mortality rates by univariate and multivariate analyses (relative risk 1.06, 95% CI 1.01-1.10 for each 17.9-pg/mL rise, P =.032). Left ventricular ejection fraction (P =.013) and New York Heart Association class (P =.009) were the only other variables associated with survival. Age, sex, plasma creatinine, plasma N-terminal atrial natriuretic peptide, and plasma norepinephrine levels were not retained in our model. Adrenolutin levels 1 month after random assignment were not significantly correlated with total mortality rate (P =.061) but were correlated with mortality rate from low output (relative risk 1.14, 95% CI 1.06-1.22, P =.002).

CONCLUSIONS

Plasma adrenolutin is increased in patients with heart failure and correlates with a poor prognosis independent of other important predictors of survival. This finding has potentially important pathophysiologic, prognostic, and therapeutic implications.

Coronary microembolization

Atherosclerotic plaque rupture is a key event in the pathogenesis of acute coronary syndromes and during coronary interventions. However, it does not always result in complete thrombotic occlusion of the entire epicardial coronary artery with subsequent acute myocardial infarction; in milder forms the result can be embolization of atherosclerotic and thrombotic debris into the coronary microcirculation. This review summarizes the available morphological evidence for coronary microembolization in patients who died from coronary artery disease, most notably from sudden death, and then goes on to address the experimental pathophysiology of coronary microembolization in animal models of acute coronary syndromes and heart failure. Finally, the review presents the available clinical evidence for coronary microembolization in patients, highlights its key features (ie, arrhythmias, contractile dysfunction, infarctlets and reduced coronary reserve) and addresses its prevention by mechanical protection devices and glycoprotein IIb/IIIa antagonism.

Increased myocardial apoptosis in patients with unfavorable left ventricular remodeling and early symptomatic post-infarction heart failure

OBJECTIVES

The purpose of this study was to evaluate a potential correlation between apoptotic rate (AR), post-infarction left ventricular (LV) remodeling, and clinical characteristics in subjects who died late (>or=10 days) after an acute myocardial infarction (AMI) with evidence of persistent occlusion of the infarct-related artery at autopsy.

BACKGROUND

Apoptosis contributes to myocardiocyte loss in cardiac disease and may have a pathophysiologic role in post-infarction LV remodeling.

METHODS

The AR was calculated at the site of infarction and in remote unaffected LV regions, using co-localization of in situ end labeling for deoxyribonucleic acid fragmentation and immunohistochemistry for caspase-3, in 14 subjects who died within two months after AMI. Correlation between AR and clinical characteristics such as age, site of AMI, transmural extension, multivessel coronary disease, and signs and/or symptoms of heart failure (HF), at the time of initial hospitalization for AMI or subsequently before death, was assessed using non-parametric statistical tests. Parameters of LV remodeling including diameters, free wall thickness, diameter-to-wall-thickness ratio, and mass were measured at gross examination at autopsy. Values are expressed as median (interquartile range).

RESULTS

Among clinical variables, early symptomatic post-infarction HF (9 cases, 64%) was associated with nearly fourfold increased AR at the site of infarction (26.2% [24.5% to 28.8%] vs. 6.4% [1.9% to 13.3%], p = 0.001). Moreover, AR both at the site of infarction and in unaffected regions was significantly correlated with parameters of progressive LV remodeling (p < 0.05).

CONCLUSIONS

Our data show that in patients dying >or=10 days after AMI, myocardial apoptosis is strongly associated with and may be a major determinant of unfavorable LV remodeling and early symptomatic post-infarction HF.

Reduced Ca2+-calmodulin-dependent protein kinase activity and expression in LV myocardium of dogs with heart failure

Studies on the status of multifunctional Ca(2+)-calmodulin (CaM)-dependent protein kinase-II (CaMKII) in failing hearts are limited and controversial. The study was performed in the left ventricular (LV) myocardium of six dogs with heart failure (HF) (LV ejection fraction, 23 +/- 2%) and six normal (NL) dogs. In the LV homogenate, CaMKII activity and its protein level were determined by using the CaMKII peptide and antibody, respectively. Furthermore, the protein level of CaM and phosphorylated phospholamban (PLB) at threonine-17 (PLB-Thr(17)) and serine-16 (PLB-Ser(16)) were also determined in the LV homogenate using a specific antibody. In addition, the level of zinc, which inhibits protein kinase A activity, was determined in the LV tissue by inductively coupled plasma mass spectrometry. CaMKII activity and phosphorylated PLB-Thr(17) and PLB-Ser(16) levels, but not CaM and Zn levels, were significantly reduced in the LV homogenate of dogs with HF compared with NL dogs. These results suggest that CaMKII activity is reduced in the failing LV myocardium, and this abnormality is associated with reduced protein expression level of the enzyme but not due to changes in CaM and zinc levels. In conclusion, reduced CaMKII activity and phosphorylated PLB level may be partly responsible for impaired sarcoplasmic reticulum function in HF.

Pathophysiologic role of myocardial apoptosis in post-infarction left ventricular remodeling

Left ventricular (LV) remodeling and heart failure (HF) complicate acute myocardial infarction (AMI) even weeks to months after the initial insult. Apoptosis may represent an important pathophysiologic mechanism causing progressive myocardiocyte loss and LV dilatation even late after AMI. This review will discuss the role of apoptosis according to findings in animal experimental data and observational studies in humans in order to assess clinical relevance, determinants, and mechanisms of myocardial apoptosis and potential therapeutic implications. More complete definition of the impact of myocardiocyte loss on prognosis and of the mechanisms involved may lead to improved understanding of cardiac remodeling and possibly improved patients' care. Mitochondrial damage and bcl-2 to bax balance play a central role in ischemia-dependent apoptosis while angiotensin II and beta(1)-adrenergic-stimulation may be major causes of receptor-mediated apoptosis. Benefits due to treatment with ACE-inhibitors and beta-blockers appear to be in part due to reduced myocardial apoptosis. Moreover, infarct-related artery patency late after AMI may be a major determinant of myocardial apoptosis and clinical benefits deriving from an open artery late post AMI (the "open artery hypothesis") may be, at least in part, due to reduced myocardiocyte loss.

Combined effects of metoprolol and spironolactone in dilated cardiomyopathic hamsters

The use of beta-blockers reduces angiotensin II levels, but could not adequately suppress aldosterone production. Thus, the combination of a beta-blocker with an aldosterone receptor antagonist could exert additive effects. The effects of metoprolol and spironolactone and their combination on hemodynamics and cardiac remodeling in cardiomyopathic hamsters (CMH) were investigated. The Bio TO-2 dilated strain of CMH was treated orally with metoprolol (10 mg/kg/day), spironolactone (20 mg/kg/day), or both according to a 2 x 2 factorial design (24 animals per group) from 120 days of age and during 120 days. As compared to corresponding untreated groups, metoprolol significantly decreased mean blood pressure (-7%), and metoprolol and spironolactone significantly increased cardiac output (18% and 19%, respectively), mesenteric blood flow (11% and 14%), and femoral blood flow (13% and 17%), and significantly decreased systemic (-24% and -15%), mesenteric (-14% and -13%) and femoral (-19% and -10%) vascular resistances. Metoprolol significantly increased renal blood flow (22%) and significantly decreased renal vascular resistance (-23%). Metoprolol and spironolactone significantly decreased the cavity area of the left ventricle (-21% and -32%, respectively) and the collagen density of the left (-36% and -39%) and right (-38% and -43%) ventricles. Although the combination did not induce stronger effects than each drug alone on the systemic and most regional hemodynamic variables, it did have a stronger effect on the cardiac remodeling (compared to control group: -24%, -34%, and -46% for the left ventricle cavity area, -33%, -35%, and -62% for collagen density in the left ventricle, and -52%, -57%, and -59% for collagen density in the right ventricle, respectively, in the metoprolol, spironolactone, and metoprolol + spironolactone groups). In CMH, metoprolol and spironolactone combined did not improve hemodynamics more than each drug alone, but did exert additive effects on cardiac remodeling.

Glucocorticoids reduce ischemia-reperfusion-induced myocardial apoptosis in immature hearts

BACKGROUND

Transient myocardial dysfunction often occurs after ischemia-reperfusion with immature myocardium appearing particularly susceptible. Neutrophil adhesion and activation contribute to ischemia-reperfusion injury after cardiopulmonary bypass (CPB), possibly resulting in cell death. The hypothesis was that glucocorticoids could prevent reperfusion-induced myocardial dysfunction by blunting leukocyte-mediated injury.

METHODS

Neonatal piglets were cooled with CPB followed by 2 hours of circulatory arrest. Animals were rewarmed, removed from CPB, and allowed to recover for 2 hours. Methylprednisolone (60 mg/kg) was administered in the CPB priming solution to one group (intraoperative glucocorticoids). In another group (preoperative glucocorticoids), 30 mg/kg methylprednisolone was administered 6 hours before CPB in addition to the intraoperative dose (30 mg/kg). Control animals received no glucocorticoids.

RESULTS

Apoptotic myocardial cells measured by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling assay and caspase-3 activity were reduced in animals administered glucocorticoids compared with controls (p < 0.05). Animals receiving either intraoperative or preoperative glucocorticoids had 0.10 +/- 0.07 and 0.13 +/- 0.05 apoptotic cells per high-power field, respectively, whereas 0.33 +/- 0.15 apoptotic cells were detected with terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling in control animals. Glucocorticoid administration reduced myocardial intercellular adhesion molecule-1 and monocyte chemoattractant protein-1 mRNA expression compared with control piglets. Maximum rate of increase of left ventricular pressure was 62% +/- 9% of baseline in control animals at 120 minutes of recovery compared with 96% +/- 6% and 95% +/- 10% of baseline in animals receiving intraoperative and preoperative glucocorticoids, respectively (p < 0.05).

CONCLUSIONS

The reduction of neutrophil adhesion and activation proteins in neonatal myocardium was associated with less apoptotic cell death after glucocorticoid administration. The blunting of apoptosis in glucocorticoid-treated animals was also associated with improved recovery of left ventricular systolic function in neonatal animals after CPB and circulatory arrest. Glucocorticoid attenuation of myocardial apoptosis might have important implications for maintaining long-term ventricular function after ischemia and reperfusion.

Myocardial dysfunction with coronary microembolization: signal transduction through a sequence of nitric oxide, tumor necrosis factor-alpha, and sphingosine

Coronary microembolization results in progressive myocardial dysfunction, with causal involvement of tumor necrosis factor-alpha (TNF-alpha). TNF-alpha uses a signal transduction involving nitric oxide (NO) and/or sphingosine. Therefore, we induced coronary microembolization in anesthetized dogs and studied the role and sequence of NO, TNF-alpha, and sphingosine for the evolving contractile dysfunction. Four sham-operated dogs served as controls (group 1). Eleven dogs received placebo (group 2), 6 dogs received the NO synthase inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME, group 3), and 6 dogs received the ceramidase inhibitor N-oleoylethanolamine (NOE, group 4) before microembolization was induced by infusion of 3000 microspheres (42-microm diameter) per milliliter inflow into the left circumflex coronary artery. Posterior systolic wall thickening (PWT) remained unchanged in group 1 but decreased progressively in group 2 from 20.6+/-4.9% (mean+/-SD) at baseline to 4.1+/-3.7% at 8 hours after microembolization. Leukocyte count, TNF-alpha, and sphingosine contents were increased in the microembolized posterior myocardium. In group 3, PWT remained unchanged (20.3+/-2.6% at baseline) with intracoronary administration of L-NAME (20.8+/-3.4%) and 17.7+/-2.3% at 8 hours after microembolization; TNF-alpha and sphingosine contents were not increased. In group 4, PWT also remained unchanged (20.7+/-4.6% at baseline) with intravenous administration of NOE (19.5+/-5.7%) and 16.4+/-6.3% at 8 hours after microembolization; TNF-alpha, but not sphingosine content, was increased. In all groups, systemic hemodynamics, anterior systolic wall thickening, and regional myocardial blood flow remained unchanged throughout the protocols. A signal transduction cascade of NO, TNF-alpha, and sphingosine is causally involved in the coronary microembolization-induced progressive contractile dysfunction.

Long-term effects of carvedilol on left ventricular function, remodeling, and expression of cardiac cytokines after large myocardial infarction in the rat

Carvedilol (20 mg/kg, bid) or vehicle was given to rats surviving a myocardial infarction (MI) 24 h (n = 409). In rats with large MI, carvedilol partially preserved left ventricular (LV) function and intrinsic myocardial contractility and reactivity to beta-adrenergic stimulation. Carvedilol led to scar thickening, increased LV hypertrophy, and decreased cardiac fibrosis but did not prevent LV dilatation. Carvedilol reduced cardiac expression of interleukin-1beta but did not prevent cardiac fetal gene re-expression or modify cardiac oxidative stress. Despite these beneficial effects, carvedilol decreased survival (38.8%, versus vehicle, 50.6%) due to excessive early mortality. Thus, post-MI carvedilol has many beneficial effects, however, in this study it increased post-MI mortality, perhaps due to excessive hypotension.

Coronary microembolization

Atherosclerotic plaque rupture is a key event in the pathogenesis of acute coronary syndromes and during coronary interventions. Atherosclerotic plaque rupture does not always result in complete thrombotic occlusion of the entire epicardial coronary artery with subsequent acute myocardial infarction; however, in milder forms it may result in the embolization of atherosclerotic and thrombotic debris into the coronary microcirculation. The present report summarizes the available morphologic evidence for coronary microembolization in patients who died of coronary artery disease, especially sudden death. The report then goes on to address the experimental pathophysiology of coronary microembolization in animal models of acute coronary syndromes and heart failure. Finally, the report presents the available clinical evidence for coronary microembolization, highlights its key features--arrhythmias, contractile dysfunction, infarctlets and reduced coronary reserve--and addresses prevention by mechanical protection devices and glycoprotein IIb/IIIa antagonism.

Heart-targeted overexpression of caspase3 in mice increases infarct size and depresses cardiac function

Up-regulation of proapoptotic genes has been reported in heart failure and myocardial infarction. To determine whether caspase genes can affect cardiac function, a transgenic mouse was generated. Cardiac tissue-specific overexpression of the proapoptotic gene Caspase3 was induced by using the rat promoter of alpha-myosin heavy chain, a model that may represent a unique tool for investigating new molecules and antiapoptotic therapeutic strategies. Cardiac-specific Caspase3 expression induced transient depression of cardiac function and abnormal nuclear and myofibrillar ultrastructural damage. When subjected to myocardial ischemia-reperfusion injury, Caspase3 transgenic mice showed increased infarct size and a pronounced susceptibility to die. In this report, we document an unexpected property of the proapoptotic gene caspase3 on cardiac contractility. Despite inducing ultrastructural damage, Caspase3 does not trigger a full apoptotic response in the cardiomyocyte. We also implicate Caspase3 in determining myocardial infarct size after ischemia-reperfusion injury, because its cardiomyocyte-specific overexpression increases infarct size.

Apoptosis and the systolic dysfunction in congestive heart failure. Story of apoptosis interruptus and zombie myocytes

Although previously it was believed that apoptosis could not occur in the terminally differentiated tissue, such as adult heart muscle cells, recent studies in endomyocardial biopsies from patients with dilated cardiomyopathy and in explanted hearts from patients with end-stage heart failure undergoing cardiac transplantation have demonstrated histologic evidence of apoptosis. Whereas neurohormonal activation during heart failure leads to compensatory hemodynamic alterations, coupled with ventricular dilatation, it induces transcription factors and myocyte hypertrophy. Persistent growth stimulation in terminally differentiated cells may lead paradoxically to apoptotic cell death. The apoptosis in cardiomyopathic hearts is associated with cytochrome c release from mitochondria to cytoplasm and activation of proteolytic caspase-8 and -3. Although the caspases are duly processed, the fragmentation of the nuclear proteins (including DNA) is completed less frequently, and only a variable degree of fragmentation of cytoplasmic proteins (including contractile proteins) is observed. It is hypothesized that release of cytochrome c from mitochondria should interfere with energy production and lead to functional impairment and variable loss of contractile proteins in a living heart muscle cell should contribute to systolic dysfunction. Because a nuclear blueprint is retained, however, the dysfunctional cell may continue to exist and in favorable conditions, such as with LVAD support, the apoptotic process may subside. Potential feasibility of reversal of heart failure should renew efforts to develop more targeted pharmaceutical intervention within the apoptotic cascade and allow newer paradigm for the management of heart failure.

Heart failure therapy at the turn of the century

Major changes in the treatment of heart failure have occurred in the last fifty years that have had a dramatic effect on its morbidity and mortality. Over two hundred years have passed since the demonstration of the benefit of digitalis in heart failure to the development of potent loop diuretics. The observation that vasodilators could improve both cardiac function and mortality led to the investigation of the Angiotensin Converting Enzyme Inhibitors (ACEI). Although these agents had significant vasodilator properties, their major benefit appears to be related to their ability to effect remodeling of the failing left ventricle. The most recent randomized clinical trials demonstrate that Beta Adrenergic Blocking agents can provide an incremental effect on both mortality and morbidity when added to therapy with ACEI. Although these agents have improved the outlook for the heart failure patient, they have had very little effect on the improvement of left ventricular function. Future research must be directed at methods to deal with this issue by either changing the contractile properties of the cardiomyocyte by pharmacologic or electrical therapy or by transplanting functional cells that can increase the number of functioning contractile units.