Contribution of alpha-adrenoceptor activation to the pathogenesis of norepinephrine cardiomyopathy

Cardioprotective effect of thymol against adrenaline-induced myocardial injury in rats

Cardiovascular disease represents a vital global disease burden. This study aims to assess the possible cardioprotective effect of thymol against adrenaline-induced myocardial injury (MI) in rats. Furthermore the effect of thymol on cardiac function biomarkers, electrocardiogram (ECG) alterations, oxidative stress, inflammation, apoptosis and histopathological changes was assessed. MI was induced by adrenaline (2 mg/kg, s.c.) injected as a single dose for 2 consecutive days (24 h apart). Normal and control groups received the vehicle for 21 consecutive days. The other 3 groups were orally administered thymol (15, 30, 60 mg/kg) for 21 consecutive days and on day 22, adrenaline was injected as a single dose for 2 consecutive days. Then ECG examination, biochemical, histopathological, immunohistochemical analyses were carried out. Thymol reversed adrenaline-induced reduction of heart rate, prolongation of RR interval and elevation of ST interval. Thymol pretreatment significantly reduced serum aspartate dehydrogenase (AST), lactate dehydrogenase (LDH), and creatine kinase (CK) levels in MI rats. Oral pretreatment with thymol increased reduced glutathione (GSH), reduced malondialdehyde (MDA), nuclear factor-kappa B (NF-κB), and interleukin-1β (IL-1β) cardiac contents in MI rats. Additionally, thymol administration significantly decreased protein expression of caspase-3, increased Bcl-2 protein expression in cardiac tissue and ameliorated histopathological changes. This study reveals that thymol exerted cardioprotective effect against adrenaline-induced MI in rats evidenced by improving cardiac function, attenuating ECG and histopathological changes which may be partly mediated through its anti-oxidant, anti-inflammatory and anti-apoptotic effect.

Comparative toxicology studies in Sprague-Dawley rats, rhesus monkeys, and New Zealand White rabbits to determine a no observed adverse effect level for 1,1'-methylenebis[4-[(hydroxyimino)methyl]-pyridinium] dimethanesulfonate

Studies were conducted in Sprague-Dawley rats, New Zealand White (NZW) rabbits, and rhesus monkeys to characterize the toxicity of 1,1'-methylenebis[4-[(hydroxyimino)methyl]-pyridinium] dimethanesulfonate (MMB4 DMS) following intramuscular administration. Rats received MMB4 DMS once daily for 7 days at 100, 200, 400, and 800 mg/kg/d; rabbits received a range of dose levels in 3 separate 7-day studies from 3 to 800 mg/kg/d and in a single-dose study from 50 to 200 mg/kg; and monkeys received MMB4 DMS at 150 to 600 mg/kg/d. Mortality was noted in rats and rabbits administered ≥ 200 mg/kg. All monkeys survived until scheduled termination. Adverse clinical observations were noted in the rats at ≥ 400 mg/kg/d and in rabbits administered ≥ 200 mg/kg; no adverse findings were noted in the monkeys. Clinical pathology changes were noted in the rabbit related to cardiac and renal function. In the rabbit and monkey, elevations in myoglobin, alanine aminotransferase/aspartate aminotransferase, platelets, creatine kinase, and coagulation factors were related to local inflammation at the intramuscular administration site. Light microscopic examination at the injection sites revealed acute skeletal muscle necrosis in vehicle control and treated groups. Target tissues in the rabbit studies were identified as kidney, heart, and lungs at ≥ 100 mg/kg/d. All changes noted in all the species demonstrated partial to complete recovery comparable to control values or to a clinically irrelevant level of effect. The NZW rabbit was the most sensitive species, and the no observed adverse effect level (NOAEL) was determined as 50 mg/kg/d; the NOAEL in the rat was 100 mg/kg/d; and the NOAEL in rhesus monkeys was >600 mg/kg/d.

Long-term outcome of Tako-tsubo cardiomyopathy

BACKGROUND

Current data suggest an excellent outcome for patients with Tako-tsubo cardiomyopathy (TC). The objectives of this study were to evaluate the long-term outcome and the prognostic implication of thrombolysis in myocardial infarction myocardial perfusion grade (TMPG) in patients with TC.

METHODS

Retrospective analysis of all patients diagnosed with TC at our hospital between 2003 and 2008.

RESULTS

During the five-year period, we identified 27 patients with TC out of 1374 cases of emergent left heart catheterisation (2%). Mean follow-up was 27 ± 16 months. The majority were Caucasian (81%) female (96%), postmenopausal (96%), with a mean age of 68 ± 14 years. A precipitating stressor event was found in 74% of the patients, 30% being gastrointestinal triggers. Fourteen patients (52%) reached a combined end point of all cause death, cardiogenic shock, sudden cardiac death and rehospitalisation for cardiac reasons. TMPG was abnormal in 37% cases with no correlation with the outcome.

CONCLUSIONS

The long-term outcome of patients with TC is worse than previously reported. TMPG does not correlate with the outcome in TC.

Pheochromocytoma-induced cardiomyopathy is modulated by the synergistic effects of cell-secreted factors

BACKGROUND

Pheochromocytomas are rare tumors derived from the chromaffin cells of the adrenal medulla. Although these tumors have long been postulated to induce hypertension and cardiomyopathy through the hypersecretion of catecholamines, catecholamines alone may not fully explain the profound myocardial remodeling induced by these tumors. We sought to determine whether changes in myocardial function in pheochromocytoma-induced cardiomyopathy result solely from catecholamines secretion or from multiple pheochromocytoma-derived factors.

METHODS AND RESULTS

Isolated cardiomyocytes incubated with pheochromocytoma-conditioned growth media contracted at a higher frequency than cardiomyocytes incubated with norepinephrine (NE) only. Sprague-Dawley rats and black-6 mice were implanted with agarose-encapsulated pheochromocytoma (PC12) cells, dihydroxyphenylalanine decarboxylase knock-out PC12 cells deficient in NE (PC12-KO), or NE-secreting pumps. PC12 cell implantation increased left ventricular dilation by 35+/-6% and 9.6+/-1.4% and reduced left ventricular fractional shortening by 20+/-3% and 28+/-4% in rats and mice compared with animals dosed only with NE, respectively. Elimination of NE secretion in PC12-KO cells induced neither cardiac dilation (3.9%+/-1.8% increase versus control) nor changes in (1.9%+/-0.4% reduction) fractional shortening compared to controls.

CONCLUSIONS

Pheochromocytomas induce a greater degree of cardiomyopathy than equivalent doses of NE, suggesting pheochromocytoma-induced cardiomyopathy is not solely mediated by NE, rather pheochromocytoma secretory factors in combination with catecholamines act synergistically to induce greater cardiac damage than catecholamines alone.

[Takotsubo cardiomyopathy or transient left ventricular apical ballooning syndrome]

Takotsubo is a reversible cardiomyopathy, often triggered by a stressful event. It combines clinical features mimicking a myocardial infarction, transient apical ballooning of the left ventricle, normal coronary arteries and a small rise in troponin level. There is a striking female predominance with mean age ranging from 65 to 76 years among series. Preceding stressful event is documented in 50 to 100% of patients. The most common clinical presentation is an angor-like chest pain with ST-segment elevation on the electrocardiogram (70%). The prognosis is excellent even if serious complications may occur: pulmonary oedema, cardiogenic shock, transient dynamic intraventricular gradient, life-threatening arrhythmias. In-hospital mortality is in the range of 0 to 10%. The recurrence rate is low. The precise physiopathology of the syndrome remains unknown but catecholamine mediated myocardial stunning is the most favored explanation.

Cardiovascular disorders associated with cocaine use: myths and truths

Cocaine produces a pattern of cardiovascular responses that are associated with apparent myocardial ischemia, arrhythmias, and other life-threatening complications in some individuals. Despite recent efforts to better understand the causes of cocaine-induced cardiovascular dysfunction, there remain a number of unanswered questions regarding the specific mechanisms by which cocaine elicits hemodynamic responses. This review will describe the actions of cocaine on the cardiovascular system and the evidence for the mechanisms by which cocaine elicits hemodynamic and pathologic responses in humans and animals. The emphasis will be on experimental data that provide the basis for our understanding of the mechanisms of cardiovascular toxicity associated with cocaine. More importantly, this review will identify several controversies regarding the causes of cocaine-induced cardiovascular toxicity that as yet are still debated. The evidence supporting these findings will be described. Finally, this review will outline the obvious deficits in our current concepts regarding the cardiovascular actions of cocaine in hope of encouraging additional studies on this grave problem in our society.

Cardiac norepinephrine release: modulation by ovariectomy and estrogen

Previously, we have demonstrated that in contrast to male rats, female rats do not show an age-related reduction of depolarization-elicited norepinephrine (NE) release from cardiac synaptosomes (resealed nerve terminals). These results suggest that sex hormones such as estrogen may modulate NE release from cardiac synaptosomes prepared from female rats. The present study was designed to test the hypotheses that long-term estrogen depletion, resulting from ovariectomy, and estrogen replacement alters depolarization-elicited NE release from cardiac synaptosomes. Female F344 rats were divided into two groups, one of which underwent bilateral ovariectomy, whereas the other underwent a sham operation. Three ovariectomized subgroups received daily injections of conjugated equine estrogens, delta8,9-dehydroestrone or 17 alpha-dihydroequilenin. Another ovariectomized control subgroup and the sham-operated animals received daily injections of vehicle. After 90 or 270 days of treatment, the animals were sacrificed. Cardiac synaptosomes were prepared from each heart, incubated with [(3)H]-NE, and used to evaluate NE release capacity by exposure to 50 mM K(+). The effectiveness of the ovariectomy and the estrogenic actions of the test compounds was confirmed by evaluating vaginal smears, determining uterine weights, and measuring serum luteinizing hormone (LH) concentrations. Ovariectomy (after both 90 and 270 days) significantly increased depolarization-induced NE release compared with sham-operated rats. Treatment with all three estrogenic preparations reduced NE release in ovariectomized rats to values similar to those observed in sham-operated animals. Interestingly, NE release rates from rats treated with conjugated estrogens for 270 but not 90 days were significantly below that observed in age-matched sham animals. These results demonstrate that estrogen modulates depolarization-elicited NE release from cardiac nerve terminals. Such modulation may represent a protective action by estrogen at the cardiac synapse.

Delisting of infants and children from the heart transplantation waiting list after carvedilol treatment

OBJECTIVES

We performed a prospective, randomized, double-blind, placebo-controlled study of carvedilol effects in children with severe, chronic heart failure (HF), despite the use of conventional therapy.

BACKGROUND

Little is known about the effects of carvedilol in youngsters with chronic HF and severe left ventricular (LV) dysfunction.

METHODS

We conducted a double-blind, placebo-controlled study of 22 consecutive children with severe LV dysfunction. The children had chronic HF and left ventricular ejection fraction (LVEF) <30%. Patients were randomly assigned to receive either placebo (8 patients) or the beta-blocker carvedilol (14 patients) at 0.01 mg/kg/day titrated up to 0.2 mg/kg/day, followed-up for six months.

RESULTS

During the follow-up and the up-titration period in the carvedilol group, four patients died and one underwent heart transplantation. In patients receiving carvedilol evaluated after six months, a significant increase occurred in LVEF, from 17.8% (95% confidence interval [CI], 14.1 to 21.4%) to 34.6% (95% CI, 25.2 to 44.0%); p = 0.001. Modified New York Heart Association (NYHA) functional class improved in nine patients taken off the transplant waiting list. All nine patients were alive at follow-up. In the placebo group, during the six-month follow-up, two patients died, and two underwent heart transplantation. Four patients persisted with HF symptoms (NYHA functional class IV). No significant change occurred in LVEF or fractional shortening.

CONCLUSIONS

Carvedilol added to standard therapy may reduce HF progression and improve cardiac function, allowing some youngsters to be removed from the heart transplantation waiting list.

Phentolamine reduces myocardial injury and mortality in a rat model of phenylpropanolamine poisoning

BACKGROUND

Phenylpropanolamine produces dose-related, life-threatening cardiovascular, and central nervous toxicity from alpha-adrenergic overstimulation. Although some recommend the alpha-adrenergic antagonist, phentolamine, as treatment for such toxicity, its therapeutic efficacy has not been previously studied. We sought to determine if pretreatment with phentolamine could reduce acute myocardial injury and mortality in rats administered an overdose of phenylpropanolamine.

METHODS

In the mortality arm of the study, 28 unanesthetized, male Wistar rats (14 animals per group) were randomized to receive an intraperitoneal injection of phentolamine (3 mg/kg) or an equal volume of normal saline diluent (control group). Twenty-five minutes later, all rats received an intraperitoneal injection of phenylpropanolamine (150 mg/kg). Mortality was compared at 24 hours. In the myocardial injury arm of the study, 20 unanesthetized rats (10 per group) were randomized to receive an intraperitoneal injection of phentolamine (3 mg/kg) or normal saline (control group). Twenty-five minutes later, all rats received an intraperitoneal injection of phenylpropanolamine (75 mg/kg). Seventy-two hours after phenylpropanolamine administration, all surviving animals were sacrificed and transverse sections of their hearts were graded histologically for injury by a blinded cardiac pathologist.

RESULTS

Twelve rats died within 6 hours of phenylpropanolamine administration. Mortality was significantly lower in the phentolamine-pretreated rats (2/14; 14%) as compared to the control group (10/14; 71%; p = 0.006). The degree of myocardial injury was significantly lower in the phentolamine-pretreated rats (0) as compared to the control group (1.4 +/- 1.6; p = 0.012).

CONCLUSION

In this rat model, phentolamine pretreatment prevented acute myocardial injury and significantly reduced lethality from an intraperitoneal phenylpropanolamine overdose.

Effect of carvedilol on survival in severe chronic heart failure

BACKGROUND

Beta-blocking agents reduce the risk of hospitalization and death in patients with mild-to-moderate heart failure, but little is known about their effects in severe heart failure.

METHODS

We evaluated 2289 patients who had symptoms of heart failure at rest or on minimal exertion, who were clinically euvolemic, and who had an ejection fraction of less than 25 percent. In a double-blind fashion, we randomly assigned 1133 patients to placebo and 1156 patients to treatment with carvedilol for a mean period of 10.4 months, during which standard therapy for heart failure was continued. Patients who required intensive care, had marked fluid retention, or were receiving intravenous vasodilators or positive inotropic drugs were excluded.

RESULTS

There were 190 deaths in the placebo group and 130 deaths in the carvedilol group. This difference reflected a 35 percent decrease in the risk of death with carvedilol (95 percent confidence interval, 19 to 48 percent; P=0.00013, unadjusted; P=0.0014, adjusted for interim analyses). A total of 507 patients died or were hospitalized in the placebo group, as compared with 425 in the carvedilol group. This difference reflected a 24 percent decrease in the combined risk of death or hospitalization with carvedilol (95 percent confidence interval, 13 to 33 percent; P<0.001). The favorable effects on both end points were seen consistently in all the subgroups we examined, including patients with a history of recent or recurrent cardiac decompensation. Fewer patients in the carvedilol group than in the placebo group withdrew because of adverse effects or for other reasons (P=0.02).

CONCLUSIONS

The previously reported benefits of carvedilol with regard to morbidity and mortality in patients with mild-to-moderate heart failure were also apparent in the patients with severe heart failure who were evaluated in this trial.

Current role of beta-adrenergic blockers in the management of chronic heart failure

Long-term activation of the sympathetic nervous system exerts adverse biologic effects that are mediated through alpha(1), beta(1) and beta(2) receptors and that contribute importantly to the progression of heart failure. As a result, beta blockers are no longer considered to be contraindicated for use in these patients but instead now play a critical role in the successful management of chronic heart failure. Beta blockers have been evaluated in >15,000 patients with heart failure who have participated in placebo-controlled trials. The results of these studies indicate that, like angiotensin-converting enzyme (ACE) inhibitors, long-term treatment with beta blockers can lessen symptoms and improve clinical status and can reduce the risk of death as well as the combined risk of death or hospitalization. The database supporting the use of beta blockers is now as persuasive (and arguably more persuasive) than the database supporting the use of ACE inhibitors in heart failure (which comprises about 7,000 patients). Yet, the benefits of beta blockers are seen in patients already receiving ACE inhibitors, suggesting that combined blockade of two neurohormonal systems (renin-angiotensin system and sympathetic nervous system) can produce additive effects.

Beta-adrenergic blockade in chronic heart failure: principles, progress, and practice

Prolonged activation of the sympathetic nervous system in patients with impaired ventricular function exerts adverse effects on the heart and circulation by a variety of mechanisms that are triggered by the interaction of norepinephrine and epinephrine with alpha1-, beta1-, and beta2-adrenergic receptors. Drugs that interfere with the actions of the sympathetic nervous system on alpha- and beta-receptors might be expected to antagonize these deleterious effects. beta1-receptor blockers have been shown to prevent and reverse many of the structural and functional changes that occur during the progression of heart failure, and beta2- and alpha1-receptor blockade seems to enhance the ability of beta1-blockers to prevent the toxic effects of catecholamines. In a large number of randomized, double-blind, placebo-controlled trials, long-term treatment of patients with chronic heart failure with beta-adrenergic blockers improves cardiac function, ameliorates symptoms, and reduces the risk of death and hospitalization. The nature and consistency of these benefits have led an increasing number of physicians to conclude that most patients with heart failure should be considered candidates for long-term treatment with these drugs. Analysis of these clinical trials has also raised the possibility that beta-blockers might differ from each other. Specifically, might agents that block alpha1-, betal-, and beta2-receptors be more effective and better tolerated that agents that act selectively on the beta1-receptor? This hypothesis is now being evaluated in a large-scale, long-term, international trial.

Basic mechanisms of disease progression in the failing heart: the role of excessive adrenergic drive

This review examines experimental evidence that suggests that excessive adrenergic stimulation of the heart may actually contribute to the untoward natural history of congestive heart failure. The basic mechanisms for catecholamine-mediated cardiac toxicity are discussed, as well as relatively new evidence that catecholamine-mediated toxicity is the result of beta-adrenoceptor-mediated cyclic adenosine monophosphate-dependent calcium overload of the cardiac myocyte. The studies reviewed herein provide a plausible biological rationale for the use of beta-adrenergic blocking agents in patients with heart failure.

Plasma brain natriuretic peptide as a biochemical marker of high left ventricular end-diastolic pressure in patients with symptomatic left ventricular dysfunction

BACKGROUND

Plasma atrial natriuretic peptide (ANP), mainly from the atrium, brain natriuretic peptide (BNP), mainly from the ventricle, norepinephrine (NE), and endothelin-1 (ET-1) levels are increased with the severity of congestive heart failure (CHF). Although a close correlation between the left ventricular end-diastolic pressure (LVEDP) and plasma ANP in patients with left ventricular dysfunction has been reported, it is not yet known which cardiac natriuretic peptide is a better predictor of high LVEDP in patients with CHF.

METHODS

To investigate the biochemical predictors of the high LVEDP in patients with left ventricular dysfunction, we measured plasma ANP, BNP, NE, and ET-1 levels and the hemodynamic parameters in 72 patients with symptomatic left ventricular dysfunction. Stepwise multivariate regression analyses were also used to determine whether the plasma levels of ANP, BNP, NE, and ET-1 could predict high LVEDP.

RESULTS

Although significant positive correlations were found among the plasma levels of ANP, BNP, ET-1, and NE and the LVEDP, only BNP (p = 0.0001) was an independent and significant predictor of high LVEDP in patients with CHF. In all eight patients with severe CHF measured for hemodynamics before and after the treatments, the plasma BNP levels decreased in association with the decrease of LVEDP, whereas other factors increased in some patients despite the decrease of LVEDP.

CONCLUSIONS

These findings suggest that plasma BNP is superior to ANP as a predictor of high LVEDP in patients with symptomatic left ventricular dysfunction.

Modulation of catecholamine cardiomyopathy by allopurinol

It has been suggested that cardiac injury by catecholamines may be the result of coronary constriction leading to ischemic damage. Allopurinol (ALLO) has been shown to reduce the extent of myocardial necrosis in various systems. Hence the possibility that ALLO might limit norepinephrine (NE) injury was tested. Rabbit hearts were infused with NE (3 micrograms/min/kg) for 90 minutes, with or without ALLO (50 micrograms/min/kg). Control specimens infused with saline solution plus ALLO were also prepared. Hearts were excised 48 hours later and studied as isovolumic isolated heart preparations. Peak systolic pressure, coronary flow, and myocardial oxygen consumption were significantly reduced in the hearts infused with NE but not in the NE + ALLO hearts. Myocardial adenosine triphosphate and glycogen concentrations were 29% and 26% lower in the NE hearts compared with control hearts. These reductions were absent in the NE + ALLO group. Moreover, rates of creatine phosphokinase and lactic dehydrogenase release were sharply elevated in the NE hearts but not in those also given ALLO. These findings are consistent with the changes observed histologically. The amount of myocardial damage was less in the ALLO + NE group compared with the NE group (p less than 0.02). This appears to be the first report to demonstrate that ALLO reduces myocyte damage by NE. Possible mechanisms include decreased free radical production, scavenging of free radicals, and preservation of the adenine nucleotide pool. Because xanthine oxidase activity is absent in the rabbit, the latter two mechanisms are more likely explanations for the findings.

Rationale for beta-adrenergic blocking drugs in cardiomyopathy

Activation of the sympathetic nervous system has traditionally been regarded as an important compensatory mechanism that helps to maintain myocardial contractility in severe heart failure. Recent findings suggest that increased catecholamine levels are linked to decreased beta-adrenergic receptor density and myocardial damage. Thus, rather than aiding the failing heart, increased myocardial exposure to catecholamines may actually contribute to further deterioration in myocardial function. Beta-adrenergic blocking drugs may ameliorate these harmful effects and paradoxically result in improved ventricular performance.