β-adrenergic blockade attenuates cardiac dysfunction and myofibrillar remodelling in congestive heart failure

Topical Anti-ulcerogenic Effect of the Beta-adrenergic Blockers on Diabetic Foot Ulcers: Recent Advances and Future Prospectives

BACKGROUND

Patients with diabetes suffer from major complications like Diabetic Retinopathy, Diabetic Coronary Artery Disease, and Diabetic Foot ulcers (DFUs). Diabetes complications are a group of ailments whose recovery time is especially delayed, irrespective of the underlying reason. The longer duration of wound healing enhances the probability of problems like sepsis and amputation. The delayed healing makes it more critical for research focus. By understanding the molecular pathogenesis of diabetic wounds, it is quite easy to target the molecules involved in the healing of wounds. Recent research on beta-adrenergic blocking drugs has revealed that these classes of drugs possess therapeutic potential in the healing of DFUs. However, because the order of events in defective healing is adequately defined, it is possible to recognize moieties that are currently in the market that are recognized to aim at one or several identified molecular processes.

OBJECTIVE

The aim of this study was to explore some molecules with different therapeutic categories that have demonstrated favorable effects in improving diabetic wound healing, also called the repurposing of drugs.

METHOD

Various databases like PubMed/Medline, Google Scholar and Web of Science (WoS) of all English language articles were searched, and relevant information was collected regarding the role of beta-adrenergic blockers in diabetic wounds or diabetic foot ulcers (DFUs) using the relevant keywords for the literature review.

RESULT

The potential beta-blocking agents and their mechanism of action in diabetic foot ulcers were studied, and it was found that these drugs have a profound effect on diabetic foot ulcer healing as per reported literatures.

CONCLUSION

There is a need to move forward from preclinical studies to clinical studies to analyze clinical findings to determine the effectiveness and safety of some beta-antagonists in diabetic foot ulcer treatment.

Beta-Blockers and Their Current Role in Maternal and Neonatal Health: A Narrative Review of the Literature

Beta-blockers are a class of medications that act on beta-adrenergic receptors and are categorized as cardio-selective and non-selective. They are principally used to treat cardiovascular conditions such as hypertension and arrhythmias. Beta-blockers have also been used to treat non-cardiogenic indications in non-pregnant individuals and the pediatric population. In pregnancy, labetalol is the mainstay treatment for hypertension and other cardiovascular indications. However, contraindications to certain sub-types of beta-blockers include bradycardia, heart failure, obstructive lung diseases, and hemodynamic instability. There is conflicting evidence of the adverse effects on fetal and neonatal health due to a scarce safety and efficacy profile, and further studies are necessary to understand the pharmacokinetics of the different classes of beta-blockers in pregnancy and fetal health. Understanding the hemodynamic changes during the stages of pregnancy is important to target a more beneficial therapy for both mother and fetus as well as better neonatal outcomes. Beta-blocker use in the pediatric population is less documented in studies but does have the potential to treat various cardiogenic and non-cardiogenic conditions. Future comprehensive studies would further benefit the direction of beta-blocker treatment during pregnancy in neonates and pediatrics.

Medication and ECG Patterns That May Hinder SPECT Myocardial Perfusion Scans

Coronary artery disease (CAD) is the leading cause of death followed by cancer, in men and women. With risk factors being endemic and the increasing costs of healthcare for management and treatment, myocardial perfusion imaging (MPI) finds a central role in risk stratification and prognosis for CAD patients, but it comes with its limitations in that the referring clinician and managing team must be aware of and use at their advantage. This narrative review examines the utility of myocardial perfusion scans in the diagnosis and management of patients with ECG alterations such as atrioventricular block (AVB), and medications including calcium channel blockers (CCB), beta blockers (BB), and nitroglycerin which may impact the interpretation of the exam. The review analyzes the current evidence and provides insights into the limitations, delving into the reasons behind some of the contraindications to MPI.

Heart Failure with Improved Ejection Fraction: Insight into the Variable Nature of Left Ventricular Systolic Function

The progress of contemporary cardiovascular therapy has led to improved survival in patients with myocardial disease. However, the development of heart failure (HF) represents a common clinical challenge, regardless of the underlying myocardial pathology, due to the severely impaired quality of life and increased mortality comparable with malignant neoplasms. Left ventricular ejection fraction (LVEF) is the main index of systolic function and a key predictor of mortality among HF patients, hence its improvement represents the main indicator of response to instituted therapy. The introduction of complex pharmacotherapy for HF, increased availability of cardiac-implantable electronic devices and advances in the management of secondary causes of HF, including arrhythmia-induced cardiomyopathy, have led to significant increase in the proportion of patients with prominent improvement or even normalization of LVEF, paving the way for the identification of a new subgroup of HF with an improved ejection fraction (HFimpEF). Accumulating data has indicated that these patients share far better long-term prognoses than patients with stable or worsening LVEF. Due to diverse HF aetiology, the prevalence of HFimpEF ranges from roughly 10 to 40%, while the search for reliable predictors and genetic associations corresponding with this clinical presentation is under way. As contemporary guidelines focus mainly on the management of HF patients with clearly defined LVEF, the present review aimed to characterize the definition, epidemiology, predictors, clinical significance and principles of therapy of patients with HFimpEF.

The mechanism of BAF60c in myocardial metabolism through the PGC1α/PPARα/mTOR signaling pathway in rats with heart failure

BRM-associated factor (BAF) 60c promotes muscle glycolysis and improves glucose homeostasis. This study explored the mechanism of BAF60c in heart failure (HF). Fetal/adult rat models of HF were established, and the levels of cardiac contractile proteins and energy metabolism-, oxidative metabolism- and glycolysis-related factors were detected. Overexpression/siRNA BAF60c plasmids were injected into adult HF rats to estimate myocardial glucose uptake, high-energy phosphate contents, mitochondrial function, and cell proliferation and apoptosis. The overexpression/siRNA BAF60c plasmids were transfected into cardiac hypertrophic H9C2 cells to explore the in vitro effects. The interaction of BAF60c and PGC1α was detected. The results suggested that adult HF rats presented increased levels of fetal proteins (ssTnI and fTnT), BAF60c and glycolysis-related factors, and reduced levels of cardiac contractile proteins, PGC1α, PPARα, and oxidative metabolism-related factors. BAF60c knockdown improved glucose uptake, maintained the oxidative metabolism/glycolysis balance, promoted H9C2 cell proliferation, and inhibited apoptosis. PGC1α interacted with BAF60c. Knocking down BAF60c also activated the PGC1α/PPARα/mTOR pathway. Overexpression of PGC1α decreased the damage to H9C2 cells caused by BAF60c. Altogether, BAF60c downregulation activated the PGC1α/PPARα/mTOR pathway, maintained the oxidative metabolism/glycolysis balance and improved mitochondrial function in rat models of HF. This study may offer novel insights into HF treatment.

Intermittent β-adrenergic blockade downregulates the gene expression of β-myosin heavy chain in the mouse heart

Expression of the β-myosin heavy chain (β-MHC), a major component of the cardiac contractile apparatus, is tightly regulated as even modest increases can be detrimental to heart under stress. In healthy hearts, continuous inhibition of β-adrenergic tone upregulates β-MHC expression. However, it is unknown whether the duration of the β-adrenergic inhibition and β-MHC expression are related. Here, we evaluated the effects of intermittent β-blockade on cardiac β-MHC expression. To this end, the β-blocker propranolol, at the dose of 15mg/kg, was administered once a day in mice for 14 days. This dosing schedule caused daily drug-free periods of at least 6 h as evidenced by propranolol plasma concentrations and cardiac β-adrenergic responsiveness. Under these conditions, β-MHC expression decreased by about 75% compared to controls. This effect was abolished in mice lacking β1- but not β2-adrenergic receptors (β-AR) indicating that β-MHC expression is regulated in a β1-AR-dependent manner. In β1-AR knockout mice, the baseline β-MHC expression was fourfold higher than in wild-type mice. Also, we evaluated the impact of intermittent β-blockade on β-MHC expression in mice with systolic dysfunction, in which an increased β-MHC expression occurs. At 3 weeks after myocardial infarction, mice showed systolic dysfunction and upregulation of β-MHC expression. Intermittent β-blockade decreased β-MHC expression while attenuating cardiac dysfunction. In vitro studies showed that propranolol does not affect β-MHC expression on its own but antagonizes catecholamine effects on β-MHC expression. In conclusion, a direct relationship occurs between the duration of the β-adrenergic inhibition and β-MHC expression through the β1-AR.

Raspberry ketone protects against isoproterenol-induced myocardial infarction in rats

AIM

The cardioprotective role of raspberry ketone (RK) against isoproterenol (ISO)-induced myocardial infarction (MI) in rats was assessed.

MATERIALS AND METHODS

Rats were randomly divided into Group I - Vehicle control; Group II - Toxic control ISO (85mg/kg, s.c.); Group III, IV and V - RK (50, 100 and 200mg/kg, respectively) with ISO; Group VI- RK (200mg/kg) alone; Group VII - Propranolol (10mg/kg) with ISO; and Group VIII - Propranolol (10mg/kg) alone. After twenty-four hours of the last dose, animals were sacrificed and creatine kinase-MB, lactate dehydrogenase, total cholesterol, triglycerides, high-density-lipoprotein, low-density-lipoprotein, very-low-density-lipoprotein, malondialdehyde, reduced glutathione, superoxide dismutase, catalase, Na⁺, K⁺-ATPase, nitric oxide, histopathological and immunohistochemical analysis (tumor necrosis factor-α and inducible nitric oxide synthase) were performed.

KEY FINDINGS

Treatment with ISO significantly deviated the biochemical parameters from the normal levels, which were considerably restored by RK at 100 and 200mg/kg doses. 50mg/kg dose, however, did not demonstrate any significant cardioprotective action. The histopathological and immunohistochemical analysis further substantiated these findings.

SIGNIFICANCE

Our study showed a dose-dependent reduction in oxidative stress, inflammation and dyslipidemia by RK in ISO-intoxicated rats, which signifies that RK from the European red raspberry plant might be a valuable entity for the management of MI.

Proteomics of acute heart failure in a rat post-myocardial infarction model

The aim of the present study was to identify the mechanisms underlying the development of post-myocardial infarction (post-MI) heart failure. The left anterior descending coronary artery of rats was occluded to mimic human ischemic heart disease. Linear Trap Quadropole OrbiTrap mass spectrometry was used to profile the expressions of energy metabolism‑associated and calcium‑binding proteins in the post‑MI and control groups. Using the online Protein Analysis Through Evolutionary Relationships classification system, 78 differentially expressed proteins were identified, including 50 downregulated proteins and 28 upregulated proteins in post‑MI group when compared with the control group. The differentially expressed proteins were closely associated with energy metabolism, contractile function, calcium handling, pathological hypertrophy and cardiac remodeling. These results were further validated using western blotting. At different postoperative time points (1st and 14th day following surgery) during the progression of advanced heart failure post‑MI, dynamic alterations in differential protein expression were identified. The expression of the vitamin D protein was significantly upregulated on the 1st day post‑MI however, was then downregulated with progression of the disease on the 14th day post‑MI. These results identified various target proteins associated with the disease, which may be used as diagnostic markers.

Effect of paroxetine on left ventricular remodeling in an in vivo rat model of myocardial infarction

Left ventricular (LV) remodeling following a myocardial infarction (MI) involves formation of reactive oxygen species (ROS). Paroxetine, a selective serotonin reuptake inhibitor, has an antioxidant effect in the vascular wall. We investigated whether paroxetine reduces myocardial ROS formation and LV remodeling following a MI. In a total of 32 Wistar rats, MI was induced by a 30-min ligation of the left anterior descending artery followed by 7- or 28-day reperfusion. During the 28 days of reperfusion, LV remodeling was evaluated by magnetic resonance imaging (MRI) and echocardiography (n = 20). After 28 days of reperfusion, the susceptibility to ventricular tachycardia was evaluated prior to sacrifice and histological assessment of myocyte cross-sectional area, fibrosis, and presence of myofibroblasts. Myocardial ROS formation was measured with dihydroethidium after 7 days of reperfusion in separate groups (n = 12). Diastolic LV volume, evaluated by MRI (417 ± 60 vs. 511 ± 64 µL, p < 0.05), and echocardiography (515 ± 80 vs. 596 ± 83 µL, p < 0.05) as well as diastolic LV internal diameter evaluated with echocardiography (7.2 ± 0.6 vs. 8.1 ± 0.7 mm, p < 0.05) were lower in the paroxetine group than in controls. Furthermore, myocyte cross-sectional area was reduced in the paroxetine group compared with controls (277 ± 26 vs. 354 ± 23 mm³, p < 0.05) and ROS formation was reduced in the remote myocardium (0.415 ± 0.19 normalized to controls, p < 0.05). However, no differences in the presence of fibrosis or myofibroblasts were observed. Finally, paroxetine reduced the susceptibility to ventricular tachycardia (induced in 2/11 vs. 6/8 rats, p < 0.05). Paroxetine treatment following MI decreases LV remodeling and susceptibility to arrhythmias, probably by reducing ROS formation.

Low-Level Vagus Nerve Stimulation Reverses Cardiac Dysfunction and Subcellular Calcium Handling in Rats With Post-Myocardial Infarction Heart Failure

Vagus nerve stimulation (VNS), targeting the imbalanced autonomic nervous system, is a promising therapeutic approach for chronic heart failure (HF). Moreover, calcium cycling is an important part of cardiac excitation-contraction coupling (ECC), which also participates in the antiarrhythmic effects of VNS. We hypothesized that low-level VNS (LL-VNS) could improve cardiac function by regulation of intracellular calcium handling properties. The experimental HF model was established by ligation of the left anterior descending coronary artery (LAD). Thirty-two male Sprague-Dawley rats were divided into 3 groups as follows; control group (sham operated without coronary ligation, n = 10), HF-VNS group (HF rats with VNS, n = 12), and HF-SS group (HF rats with sham nerve stimulation, n = 10). After 8 weeks of treatment, LL-VNS significantly improved left ventricular ejection fraction (LVEF) and attenuated myocardial interstitial fibrosis in the HF-VNS group compared with the HF-SS group. Elevated plasma norepinephrine and dopamine, but not epinephrine, were partially reduced by LL-VNS. Additionally, LL-VNS restored the protein and mRNA levels of sarcoplasmic reticulum Ca(2+) ATPase (SERCA2a), Na(+)-Ca(2+) exchanger 1 (NCX1), and phospholamban (PLB) whereas the expression of ryanodine receptor 2 (RyR2) as well as mRNA level was unaffected. Thus, our study results suggest that the improvement of cardiac performance by LL-VNS is accompanied by the reversal of dysfunctional calcium handling properties including SERCA2a, NCX1, and PLB which may be a potential molecular mechanism of VNS for HF.

A Potential Link between the C5a Receptor 1 and the β1-Adrenoreceptor in the Mouse Heart

Purpose

Inflammation may contribute to the pathogenesis of specific cardiovascular diseases, but it is uncertain if mediators released during the inflammatory process will affect the continued efficacy of drugs used to treat clinical signs of the cardiac disease. We investigated the role of the complement 5a receptor 1 (C5aR1/CD88) in the cardiac response to inflammation or atenolol, and the effect of C5aR1 deletion in control of baseline heart rate in an anesthetized mouse model.

Methods

An initial study showed that PMX53, an antagonist of C5aR1 in normal C57BL6/J (wild type, WT) mice reduced heart rate (HR) and appeared to have a protective effect on the heart following induced sepsis. C5aR1 knockout (CD88-/-) mice had a lower HR than wild type mice, even during sham surgery. A model to assess heart rate variability (HRV) in anesthetized mice was developed to assess the effects of inhibiting the β₁-adrenoreceptor (β₁-AR) in a randomized crossover study design.

Results

HR and LF Norm were constitutively lower and SDNN and HF Norm constitutively higher in the CD88-/- compared with WT mice (P< 0.001 for all outcomes). Administration of atenolol (2.5 mg/kg) reduced the HR and increased HRV (P< 0.05, respectively) in the wild type but not in the CD88-/- mice. There was no shift of the sympathovagal balance post-atenolol in either strains of mice (P> 0.05), except for the reduced LF/HF (Lower frequency/High frequency) ratio (P< 0.05) at 60 min post-atenolol, suggesting increased parasympathetic tone of the heart due to the effect of atenolol administration. The HR of the WT mice were lower post atenolol compared to the CD88-/- mice (P = 0.001) but the HRV of CD88-/- mice were significantly increased (P< 0.05), compared with WT mice.

Conclusion

Knockout of the C5aR1 attenuated the effect of β₁-AR in the heart, suggesting an association between the β₁-AR and C5aR1, although further investigation is required to determine if this is a direct or causal association.

Small and large animal models in cardiac contraction research: advantages and disadvantages

The mammalian heart is responsible for not only pumping blood throughout the body but also adjusting this pumping activity quickly depending upon sudden changes in the metabolic demands of the body. For the most part, the human heart is capable of performing its duties without complications; however, throughout many decades of use, at some point this system encounters problems. Research into the heart's activities during healthy states and during adverse impacts that occur in disease states is necessary in order to strategize novel treatment options to ultimately prolong and improve patients' lives. Animal models are an important aspect of cardiac research where a variety of cardiac processes and therapeutic targets can be studied. However, there are differences between the heart of a human being and an animal and depending on the specific animal, these differences can become more pronounced and in certain cases limiting. There is no ideal animal model available for cardiac research, the use of each animal model is accompanied with its own set of advantages and disadvantages. In this review, we will discuss these advantages and disadvantages of commonly used laboratory animals including mouse, rat, rabbit, canine, swine, and sheep. Since the goal of cardiac research is to enhance our understanding of human health and disease and help improve clinical outcomes, we will also discuss the role of human cardiac tissue in cardiac research. This review will focus on the cardiac ventricular contractile and relaxation kinetics of humans and animal models in order to illustrate these differences.

Reversal of subcellular remodelling by losartan in heart failure due to myocardial infarction

This study tested the reversal of subcellular remodelling in heart failure due to myocardial infarction (MI) upon treatment with losartan, an angiotensin II receptor antagonist. Twelve weeks after inducing MI, rats were treated with or without losartan (20 mg/kg; daily) for 8 weeks and assessed for cardiac function, cardiac remodelling, subcellular alterations and plasma catecholamines. Cardiac hypertrophy and lung congestion in 20 weeks MI-induced heart failure were associated with increases in plasma catecholamine levels. Haemodynamic examination revealed depressed cardiac function, whereas echocardiographic analysis showed impaired cardiac performance and marked increases in left ventricle wall thickness and chamber dilatation at 20 weeks of inducing MI. These changes in cardiac function, cardiac remodelling and plasma dopamine levels in heart failure were partially or fully reversed by losartan. Sarcoplasmic reticular (SR) Ca²⁺-pump activity and protein expression, protein and gene expression for phospholamban, as well as myofibrillar (MF) Ca²⁺-stimulated ATPase activity and α-myosin heavy chain mRNA levels were depressed, whereas β-myosin heavy chain expression was increased in failing hearts; these alterations were partially reversed by losartan. Although SR Ca²⁺-release activity and mRNA levels for SR Ca²⁺-pump were decreased in failing heart, these changes were not reversed upon losartan treatment; no changes in mRNA levels for SR Ca²⁺-release channels were observed in untreated or treated heart failure. These results suggest that the partial improvement of cardiac performance in heart failure due to MI by losartan treatment is associated with partial reversal of cardiac remodelling as well as partial recovery of SR and MF functions.

The action of p-synephrine on hepatic carbohydrate metabolism and respiration occurs via both Ca(2+)-mobilization and cAMP production

Citrus aurantium extracts, which contain large amounts of p-synephrine, are widely used for weight loss purposes and as appetite suppressants. In the liver, C. aurantium (bitter orange) extracts affect hemodynamics, carbohydrate metabolism, and oxygen uptake. The purpose of the present work was to quantify the action of p-synephrine and also to obtain indications about its mechanism of action, a task that would be difficult to accomplish with C. aurantium extracts due to their rather complex composition. The experimental system was the isolated perfused rat liver. p-Synephrine significantly stimulated glycogenolysis, glycolysis, gluconeogenesis, and oxygen uptake. The compound also increased the portal perfusion pressure and the redox state of the cytosolic NAD(+)/NADH couple. A Ca(2+)-dependency for both the hemodynamic and the metabolic effects of p-synephrine was found. p-Synephrine stimulated both cAMP overflow and the initial Ca(2+) release from the cellular stores previously labeled with (45)Ca(2+). The metabolic and hemodynamic actions of p-synephrine were strongly inhibited by α-adrenergic antagonists and moderately affected by β-adrenergic antagonists. The results allow to conclude that p-synephrine presents important metabolic and hemodynamic effects in the liver. These effects can be considered as both catabolic (glycogenolysis) and anabolic (gluconeogenesis), they are mediated by both α- and β-adrenergic signaling, require the simultaneous participation of both Ca(2+) and cAMP, and could be contributing to the overall stimulation of metabolism that usually occurs during weight loss periods.

Adrenergic metabolic and hemodynamic effects of octopamine in the liver

The fruit extracts of Citrus aurantium (bitter orange) are traditionally used as weight-loss products and as appetite suppressants. A component of these extracts is octopamine, which is an adrenergic agent. Weight-loss and adrenergic actions are always related to metabolic changes and this work was designed to investigate a possible action of octopamine on liver metabolism. The isolated perfused rat liver was used to measure catabolic and anabolic pathways and hemodynamics. Octopamine increased glycogenolysis, glycolysis, oxygen uptake, gluconeogenesis and the portal perfusion pressure. Octopamine also accelerated the oxidation of exogenous fatty acids (octanoate and oleate), as revealed by the increase in ¹⁴CO₂ production derived from ¹⁴C labeled precursors. The changes in glycogenolysis, oxygen uptake and perfusion pressure were almost completely abolished by α₁-adrenergic antagonists. The same changes were partly sensitive to the β-adrenergic antagonist propranolol. It can be concluded that octopamine accelerates both catabolic and anabolic processes in the liver via adrenergic stimulation. Acceleration of oxygen uptake under substrate-free perfusion conditions also means acceleration of the oxidation of endogenous fatty acids, which are derived from lipolysis. All these effects are compatible with an overall stimulating effect of octopamine on metabolism, which is compatible with its reported weight-loss effects in experimental animals.

Cardiac remodeling and subcellular defects in heart failure due to myocardial infarction and aging

Although several risk factors including hypertension, cardiac hypertrophy, coronary artery disease, and diabetes are known to result in heart failure, elderly subjects are more susceptible to myocardial infarction and more likely to develop heart failure. This article is intended to discuss that cardiac dysfunction in hearts failing due to myocardial infarction and aging is associated with cardiac remodeling and defects in the subcellular organelles such as sarcolemma (SL), sarcoplasmic reticulum (SR), and myofibrils. Despite some differences in the pattern of heart failure due to myocardial infarction and aging with respect to their etiology and sequence of events, evidence has been presented to show that subcellular remodeling plays a critical role in the occurrence of intracellular Ca(2+)-overload and development of cardiac dysfunction in both types of failing heart. In particular, alterations in gene expression for SL and SR proteins induce Ca(2+)-handling abnormalities in cardiomyocytes, whereas those for myofibrillar proteins impair the interaction of Ca(2+) with myofibrils in hearts failing due to myocardial infarction and aging. In addition, different phosphorylation mechanisms, which regulate the activities of Ca(2+)-cycling proteins in SL and SR membranes as well as Ca(2+)-binding proteins in myofibrils, become defective in the failing heart. Accordingly, it is suggested that subcellular remodeling involving defects in Ca(2+)-handling and Ca(2+)-binding proteins as well as their regulatory mechanisms is intimately associated with cardiac remodeling and heart failure due to myocardial infarction and aging.

Role of various proteases in cardiac remodeling and progression of heart failure

It is believed that cardiac remodeling due to geometric and structural changes is a major mechanism for the progression of heart failure in different pathologies including hypertension, hypertrophic cardiomyopathy, dilated cardiomyopathy, diabetic cardiomyopathy, and myocardial infarction. Increases in the activities of proteolytic enzymes such as matrix metalloproteinases, calpains, cathepsins, and caspases contribute to the process of cardiac remodeling. In addition to modifying the extracellular matrix, both matrix metalloproteinases and cathepsins have been shown to affect the activities of subcellular organelles in cardiomyocytes. The activation of calpains and caspases has been identified to induce subcellular remodeling in failing hearts. Proteolytic activities associated with different proteins including caspases, calpain, and the ubiquitin-proteasome system have been shown to be involved in cardiomyocyte apoptosis, which is an integral part of cardiac remodeling. This article discusses and compares how the activities of various proteases are involved in different cardiac abnormalities with respect to alterations in apoptotic pathways, cardiac remodeling, and cardiac dysfunction. An imbalance appears to occur between the activities of some proteases and their endogenous inhibitors in various types of hypertrophied and failing hearts, and this is likely to further accentuate subcellular remodeling and cardiac dysfunction. The importance of inhibiting the activities of both extracellular and intracellular proteases specific to distinct etiologies, in attenuating cardiac remodeling and apoptosis as well as biochemical changes of subcellular organelles, in heart failure has been emphasized. It is suggested that combination therapy to inhibit different proteases may prove useful for the treatment of heart failure.

Mechanisms of the beneficial effects of beta-adrenoceptor antagonists in congestive heart failure

Many clinical studies have documented favourable effects (reduced morbidity and mortality) of beta-adrenoceptor (β-AR) antagonists, such as carvedilol, metoprolol, propranolol, atenolol and bisoprolol, in congestive heart failure. These agents attenuate the effects of sympathetic activation during the development of heart failure, prevent ventricular remodelling and improve cardiac function. Because β-AR blockers are known to exert negative inotropic action, the mechanisms responsible for their beneficial effects in heart failure have been a subject of debate. While attenuation of changes in β-AR cyclic AMP-mediated signal transduction in heart failure is considered to be responsible for the beneficial effects of β-AR antagonists, other mechanisms such as the effects of these agents on subcellular remodelling, oxidative stress, apoptosis and defect in calcium handling, are equally important in preventing cardiac alterations in the failing heart. Moreover, β-AR antagonists are not a homogeneous group of drugs because they differ in their pharmacokinetics and pharmacodynamics, in addition to the selective and nonselective nature of their actions on β-AR. Various β-AR blocking agents have been shown to possess different ancillary properties and produce effects that are independent of β-AR. In fact, different β-AR antagonists have been observed to lower the elevated levels of plasma catecholamines in heart failure. Thus, the beneficial effects of β-AR antagonists are not only elicited through their interaction with mediated β-AR signal transduction sites in the myocardium, but other mechanisms may also contribute to their favourable actions in heart failure.