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

Future scope and challenges for congestive heart failure: Moving towards development of pharmacotherapy

Heart failure is invariably associated with cardiac hypertrophy and impaired cardiac performance. Although several drugs have been developed to delay the progression of heart failure, none of the existing interventions have shown beneficial effects in reducing morbidity and mortality. In order to determine specific targets for future drug development, we have discussed different mechanisms involving both cardiomyocytes and non-myocyte (extracellular matrix) alterations for the transition of cardiac hypertrophy to heart failure as well as for the progression of heart failure. We have emphasized the role of oxidative stress, inflammatory cytokines, metabolic alterations and Ca2+-handling defects in adverse cardiac remodeling and heart dysfunction in hypertrophied myocardium. Alterations in the regulatory process due to several protein kinases as well as participation of mitochondrial Ca2+-overload, activation of proteases and phospholipases and changes in gene expression for subcellular remodeling have also been described for the occurrence of cardiac dysfunction. Association of cardiac arrhythmia with heart failure has been explained as a consequence of catecholamine oxidation products. Since these multifactorial defects in extracellular matrix and cardiomyocytes are evident in the failing heart, it is a challenge for experimental cardiologists to develop appropriate combination drug therapy for improving cardiac function in heart failure.

Cardiovascular and Hepatic Toxicity of Cocaine: Potential Beneficial Effects of Modulators of Oxidative Stress

Oxidative stress (OS) is thought to play an important role in the pharmacological and toxic effects of various drugs of abuse. Herein we review the literature on the mechanisms responsible for the cardiovascular and hepatic toxicity of cocaine with special focus on OS-related mechanisms. We also review the preclinical and clinical literature concerning the putative therapeutic effects of OS modulators (such as N-acetylcysteine, superoxide dismutase mimetics, nitroxides and nitrones, NADPH oxidase inhibitors, xanthine oxidase inhibitors, and mitochondriotropic antioxidants) for the treatment of cocaine toxicity. We conclude that available OS modulators do not appear to have clinical efficacy.

Novel rat model reveals important roles of β-adrenoreceptors in stress-induced cardiomyopathy

BACKGROUND

Stress-induced cardiomyopathy (SIC), also known as Takotsubo cardiomyopathy, is an acute cardiac syndrome with substantial morbidity and mortality. The unique hallmark of SIC is extensive ventricular akinesia involving apical segments with preserved function in basal segments. Adrenergic overstimulation plays an important role in initiating SIC but the pathophysiological pathways and receptors involved are unknown.

METHODS

Sprague Dawley rats (~300 g) were injected with a single dose of the β-adrenergic agonist isoprenaline (ISO, i.p.) and echocardiography was used to study cardiac function. The akinetic part of the left ventricle was biopsied in six SIC patients. Amount of intracellular lipid and glycogen as well as degree of permanent cardiac damage were assessed by histology.

RESULTS

In rats, ISO at doses ≥ 50 mg/kg induced severe SIC-like regional akinesia that completely resolved within seven days. Intracellular lipid content was higher in akinetic, but not in normokinetic myocardium in both SIC patients and rats. β2-receptor blockade or Gi-pathway inhibition was associated with less widespread akinesia and low lipid accumulation but significantly increased acute mortality.

CONCLUSIONS

We provide a novel rat model of SIC that supports the hypothesis of circulating catecholamines as initiators of SIC. We propose that the β-adrenoreceptor pathway is important in the setting of severe catecholamine overstimulation and that perturbations of cardiac metabolism occur in SIC.

Role of the excessive amounts of circulating catecholamines and glucocorticoids in stress-induced heart disease

Various stressful stimuli are known to activate the sympathetic nervous system to release catecholamines and the hypothalamic-pituitary-adrenal axis to release glucocorticoids in the circulation. Although initial actions of both catecholamines and glucocorticoids are beneficial for the function of the cardiovascular system, their delayed effects on the heart are deleterious. Glucocorticoids not only increase plasma levels of catecholamines by inhibiting their extraneuronal uptake, but they have also been shown to induce supersensitivity to catecholamines in the heart by upregulating different components of the betta-adrenoceptor signal transduction system. Low concentrations of catecholamines stimulate the heart by promoting Ca2+ movements, whereas excessive amounts of catecholamines produce cardiac dysfunction by inducing intracellular Ca2+ overload in cardiomyocytes. Several studies have shown, however, that under stressful conditions high concentrations of catecholamines become oxidized to form aminolutins and generate oxyradicals. These oxidation products of catecholamines have been demonstrated to produce coronary spasm, arrhythmias, and cardiac dysfunction by inducing Ca2+-handling abnormalities in both sarcolemmal and sarcoplasmic reticulum, defects in energy production by mitochondria, and myocardial cell damage. In this article we have focused the discussion to highlight the interrelationship between catecholamines and glucocorticoids and to emphasize the role of oxidation products of catecholamines in the development of stress-induced heart disease.

Mice over-expressing the myocardial creatine transporter develop progressive heart failure and show decreased glycolytic capacity

The metabolic phenotype of the failing heart includes a decrease in phosphocreatine and total creatine concentration [Cr], potentially contributing to contractile dysfunction. Surprisingly, in 32- week-old mice over-expressing the myocardial creatine transporter (CrT-OE), we previously demonstrated that elevated [Cr] correlates with left ventricular (LV) hypertrophy and failure. The aim of this study was to determine the temporal relationship between elevated [Cr] and the onset of cardiac dysfunction and to screen for potential molecular mechanisms. CrT-OE mice were compared with wild-type (WT) littermate controls longitudinally using cine-MRI to measure cardiac function and single-voxel (1)H-MRS to measure [Cr] in vivo at 6, 16, 32, and 52 weeks of age. CrT-OE mice had elevated [Cr] at 6 weeks (mean 1.9-fold), which remained constant throughout life. Despite this increased [Cr], LV dysfunction was not apparent until 16 weeks and became more pronounced with age. Additionally, LV tissue from 12 to 14 week old CrT-OE mice was compared to WT using 2D difference in-gel electrophoresis (DIGE). These analyses detected a majority of the heart's metabolic enzymes and identified seven proteins that were differentially expressed between groups. The most pronounced protein changes were related to energy metabolism: alpha- and beta-enolase were selectively decreased (p<0.05), while the remaining enzymes of glycolysis were unchanged. Consistent with a decrease in enolase content, its activity was significantly lower in CrT-OE hearts (in WT, 0.59+/-0.02 micromol ATP produced/microg protein/min; CrT-OE, 0.31+/-0.06; p<0.01). Additionally, anaerobic lactate production was decreased in CrT-OE mice (in WT, 102+/-3 micromol/g wet myocardium; CrT-OE, 78+/-13; p=0.02), consistent with decreased glycolytic capacity. Finally, we found that enolase may be regulated by increased expression of the beta-enolase repressor transcription factor, which was significantly increased in CrT-OE hearts. This study demonstrates that chronically increased myocardial [Cr] in the CrT-OE model leads to the development of progressive hypertrophy and heart failure, which may be mediated by a compromise in glycolytic capacity at the level of enolase.

Prognostic value and echocardiographic determinants of plasma myeloperoxidase levels in chronic heart failure

OBJECTIVES

The purpose of this study was to explore the relationship between myeloperoxidase (MPO) and cardiac structure, performance, and prognosis.

BACKGROUND

Myeloperoxidase is an inflammatory marker that is elevated in patients with heart failure (HF) and cardiac dysfunction, with mechanistic links to plaque vulnerability and left ventricular (LV) remodeling.

METHODS

We evaluated plasma MPO levels (CardioMPO, PrognostiX, Inc., Cleveland, Ohio) in 140 patients with chronic systolic HF (LV ejection fraction <35%) and examined the plasma MPO levels' relationships with echocardiographic indexes of systolic and diastolic performance, as well as long-term clinical outcomes (death, cardiac transplantation, or HF hospitalization).

RESULTS

Within the overall cohort, increasing plasma MPO levels were associated with increasing likelihood of more advanced HF (restrictive diastolic stage, right ventricular systolic dysfunction > or =3+, and tricuspid regurgitation area > or =1.8 cm2). Plasma MPO levels were predictive of long-term clinical outcomes (risk ratio [95% confidence interval] = 3.35 [1.52 to 8.86]), even after adjustment for age, LV ejection fraction, plasma B-type natriuretic peptide (BNP), creatinine clearance, or diastolic stage. In receiver-operator characteristic curve analyses, addition of MPO to BNP testing augmented the predictive accuracy of future adverse clinical events (area under the curve 0.66 for BNP only [chi-square test = 12.9, p = 0.0003], and 0.70 for BNP plus MPO [chi-square test = 15.87, p = 0.0004]).

CONCLUSIONS

In chronic systolic HF, elevated plasma MPO levels are associated with an increased likelihood of more advanced HF. Moreover, elevated plasma MPO levels within a HF subject seem to be predictive of increased adverse clinical outcomes.

Effect of adrenalin, adrenochrome, and adrenolutin on connexin proteins in the cardiovasculature

Reported myocardial pathology resulting from increased levels of catecholamines in vivo has led us to investigate the effect of adrenalin on the gap junction proteins connexin 40 (Cx40) and Cx43 and the possible relationship to vascular toxicity. Adrenalin and its known metabolites, adrenochrome and adrenolutin, were used in this study. Utilizing the A7r5 rat aortic cell line, we evaluated the effects of adrenalin, adrenochrome, and adrenolutin on the expression and function of connexin 40 and 43 that are present in both cardiac and vascular tissues.

Improvement of sympathetic response to exercise by oral administration of ascorbic acid in patients after myocardial infarction

BACKGROUND

Recent studies indicated that excessive oxidative stress in an animal heart failure model injures both the sympathetic nerve endings and receptors, resulting in disturbance of norepinephrine release and sensitivity to norepinephrine. However, it has not been clarified whether this phenomenon is expressed clinically in patients with heart disease. Therefore, we examined the efficacy of ascorbic acid administration as an antioxidant vitamin in relation to the heart rate and norepinephrine response to exercise in patients after myocardial infarction.

METHODS

In this randomized crossover trial, 21 male patients who had had myocardial infarction underwent symptom-limited ergometer cardiopulmonary exercise testing twice, that is, without and with ascorbic acid (2 g) administration. Plasma norepinephrine concentrations were assessed at rest and at peak exercise, and heart rate responsiveness to the norepinephrine increment from rest to peak exercise (DeltaHR/logDeltaNE) was calculated.

RESULTS

In the exercise test after ascorbic acid administration, peak oxygen consumption (VO(2)) improved over baseline. Ascorbic acid administration significantly increased the change in heart rate and norepinephrine from rest to peak exercise and DeltaHR/logDeltaNE. The increment in heart rate was significantly correlated with peak VO(2) in each test.

CONCLUSION

Ascorbic acid intake before exercise improved exercise capacity through enhancement of the heart rate and norepinephrine response to exercise in patients after myocardial infarction. These findings suggest that ascorbic acid intake improves sympathetic dysfunction resulting from injury by excessive oxidative stress after myocardial infarction.

A direct comparison of the natriuretic peptides and their relationship to survival in chronic heart failure of a presumed non-ischaemic origin

The natriuretic peptides have been validated as sensitive and specific markers of left ventricular dysfunction; brain natriuretic peptide (BNP), N-terminal atrial natriuretic peptide (NT-proANP) and N-terminal brain natriuretic peptide (NT-proBNP) elevations have been associated with New York Heart Association (NYHA) Class I-IV heart failure. We directly compared the association of each of these markers with 1-year survival in 173 patients with chronic heart failure of a presumed nonischaemic origin entering the PRAISE-2 Trial, a clinical study which assessed the therapeutic effect of Amlodipine in patients with NYHA Class III and IV heart failure and a left ventricular ejection fraction (LVEF) <30%. BNP, NT-proBNP, and NT-proANP levels were all correlated with 1-year mortality by univariate Cox proportional hazards analyses. With respect to multivariate Cox proportional hazards regression models containing variables deemed significant in univariate analyses, NT-proANP alone was identified as an independent predictor of 1-year mortality when log-transformed continuous covariates were utilized in the analysis. When the analysis was repeated using dichotomous covariates, NT-proANP remained the most significant predictor of 1-year mortality, followed by NT-proBNP, NYHA classification and BNP. We conclude that all three natriuretic peptides are significant predictors of short-term mortality in subjects with chronic congestive heart failure (CHF) of a presumed nonischaemic origin. Larger prospective studies are required to validate the clinical utility of NT-proANP as a discriminating marker of short-term survival, and to validate proposed cutoffs of approximately 2300 pmol/l for NT-proANP, 1500 pg/ml for NT-proBNP, and 50 pmol/l for BNP as prognostic indicators of adverse short-term outcome.

Leucoisoprenochrome-o-semiquinone Formation in Freshly Isolated Adult Rat Cardiomyocytes

Sustained high levels of circulating catecholamines can lead to cardiotoxicity. There is increasing evidence that this process may result from metal-catalyzed catecholamine oxidation into semiquinones, quinones, and aminochromes. We have previously shown that Cu2+-induced oxidation of isoproterenol into isoprenochrome induces toxic effects in isolated cardiomyocytes. The aim of this study was to characterize the isoproterenol oxidation process and to locate the formation of semiquinone radicals in cardiomyocyte suspensions. Freshly isolated rat cardiomyocytes were incubated with 1 or 10 mM isoproterenol and 20 microM Cu2+ for 4 h. The formation of an isoproterenol oxidation radical was detected in the extracellular medium, cells, membranes, and heavy organelles by electron spin resonance spectroscopy. An electron spin resonance signal assigned to leucoisoprenochrome-o-semiquinone increased in a time-dependent manner in the extracellular medium. A second electron spin resonance signal, characteristic of an immobilized radical, was also found in the cardiomyocytes. The latter was attributed to leucoisoprenochrome-o-semiquinone immobilized on cellular components such as membranes, cytoskeleton, nucleus, and heavy organelles. In addition, the levels of leucoisoprenochrome-o-semiquinone decreased in the presence of glutathione. Computer simulations of the experimental spectra indicate the formation of two distinct isomeric leucoisoprenochrome-o-semiquinone radicals during isoproterenol oxidation. The present study shows that the isoproterenol oxidation in isolated rat cardiomyocytes correlates with the formation of leucoisoprenochrome-o-semiquinone in the cells and in the extracellular medium, suggesting that it might be involved in cardiotoxicity induced by the oxidation of catecholamines.

Neurohormones and oxidative stress in nonischemic cardiomyopathy: relationship to survival and the effect of treatment with amlodipine

OBJECTIVES

The purpose of this study was to assess the effects of amlodipine on neurohormones and oxidative stress in nonischemic cardiomyopathy, and determine the relationship between baseline and posttreatment levels of these markers with survival.

BACKGROUND

Neurohormones and oxidative stress are important in the pathophysiology of heart failure. Calcium-channel blockers are associated with poor outcomes in patients with heart failure, in part due to neurohormonal activation. In contrast, amlodipine, a second-generation dihydropyridine, has a more favorable clinical profile.

METHODS

In the Prospective Randomized Amlodipine Survival Evaluation 2 (PRAISE-2) trial, a subset of 181 patients with nonischemic cardiomyopathy were randomized to amlodipine (10 mg/day) or placebo. Blood samples were evaluated at baseline, 2 weeks and 26 weeks for norepinephrine, epinephrine, angiotensin II, dopamine, N-terminal pro-atrial natriuretic peptide (Nt-pro-ANP), brain natriuretic peptide (BNP), adrenolutin and malondialdehyde.

RESULTS

There was no difference in levels of neurohormones or oxidative stress markers between the amlodipine and placebo groups at the different times. Both Nt-pro-ANP and BNP decreased at 2 weeks and at 26 weeks. Baseline Nt-pro-ANP correlated with survival in multivariate analysis (P =.001). A strong relationship was found between a reduction in BNP at 26 weeks and survival, with a hazard ratio of 0.153 (95% CI 0.051-0.461, P =.017). No relationship was found between markers of oxidative stress and survival.

CONCLUSIONS

We conclude that amlodipine does not affect circulating neurohormones and oxidative stress markers in patients with nonischemic cardiomyopathy treated with angiotensin-converting enzyme inhibitors, digoxin and diuretics. In addition, low circulating Nt-pro-ANP and a reduction in BNP over time confers a good prognosis.