Carvedilol effectively blocks oxidative stress-mediated downregulation of sarcoplasmic reticulum Ca2+-ATPase 2 gene transcription through modification of Sp1 binding

Remodelling of T-Tubules and Associated Calcium Handling Dysfunction in Heart Failure: Mechanisms and Therapeutic Insights

In cardiomyocytes, transverse tubules (T-tubules) are sarcolemmal invaginations that facilitate excitation-contraction coupling and diastolic function. The clinical significance of T-tubules has become evident in that their remodelling is recognised as a hallmark feature of heart failure (HF) and a key contributor to disrupted Ca2+ homeostasis, compromised cardiac function, and arrhythmogenesis. Further investigations have revealed that T-tubule remodelling is particularly pronounced in HF with reduced ejection fraction (HFrEF), but not in HF with preserved ejection fraction, implying that T-tubule remodelling may play a crucial pathophysiologic role in HFrEF. While research on the functional importance of T-tubules is ongoing, T-tubule remodelling has been found to be reversible. That finding has triggered a surge in studies aimed at identifying specific therapeutic approaches for HFrEF. This review discusses the functional importance of T-tubules and their microdomains, the pathophysiology of T-tubule remodelling, and the potential mechanisms of current HFrEF therapeutic approaches in reversing T-tubule alterations. We also highlight discrepancies regarding the roles of T-tubule proteins in the recovery process across studies to offer valuable insights for future research.

Carvedilol Selectively Stimulates βArrestin2-Dependent SERCA2a Activity in Cardiomyocytes to Augment Contractility

Heart failure (HF) carries the highest mortality in the western world and β-blockers [β-adrenergic receptor (AR) antagonists] are part of the cornerstone pharmacotherapy for post-myocardial infarction (MI) chronic HF. Cardiac β1AR-activated βarrestin2, a G protein-coupled receptor (GPCR) adapter protein, promotes Sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA)2a SUMO (small ubiquitin-like modifier)-ylation and activity, thereby directly increasing cardiac contractility. Given that certain β-blockers, such as carvedilol and metoprolol, can activate βarrestins and/or SERCA2a in the heart, we investigated the effects of these two agents on cardiac βarrestin2-dependent SERCA2a SUMOylation and activity. We found that carvedilol, but not metoprolol, acutely induces βarrestin2 interaction with SERCA2a in H9c2 cardiomyocytes and in neonatal rat ventricular myocytes (NRVMs), resulting in enhanced SERCA2a SUMOylation. However, this translates into enhanced SERCA2a activity only in the presence of the β2AR-selective inverse agonist ICI 118,551 (ICI), indicating an opposing effect of carvedilol-occupied β2AR subtype on carvedilol-occupied β1AR-stimulated, βarrestin2-dependent SERCA2a activation. In addition, the amplitude of fractional shortening of NRVMs, transfected to overexpress βarrestin2, is acutely enhanced by carvedilol, again in the presence of ICI only. In contrast, metoprolol was without effect on NRVMs' shortening amplitude irrespective of ICI co-treatment. Importantly, the pro-contractile effect of carvedilol was also observed in human induced pluripotent stem cell (hIPSC)-derived cardiac myocytes (CMs) overexpressing βarrestin2, and, in fact, it was present even without concomitant ICI treatment of human CMs. Metoprolol with or without concomitant ICI did not affect contractility of human CMs, either. In conclusion, carvedilol, but not metoprolol, stimulates βarrestin2-mediated SERCA2a SUMOylation and activity through the β1AR in cardiac myocytes, translating into direct positive inotropy. However, this unique βarrestin2-dependent pro-contractile effect of carvedilol may be opposed or masked by carvedilol-bound β2AR subtype signaling.

Silica nanoparticles induce cardiac injury and dysfunction via ROS/Ca2+/CaMKII signaling

Interest is growing to better comprehend the interaction of silica nanoparticles (SiNPs) with the cardiovascular system. In particular, the extremely small size, relatively large surface area and associated unique properties may greatly enhance its toxic potentials compared to larger-sized counterparts. Nevertheless, the underlying mechanisms still need to be evaluated. In this context, the cardiotoxicity of nano-scale (Si-60; particle diameter about 60 nm) and submicro-scale silica particles (Si-300; 300 nm) were examined in ApoE^-/- mice via intratracheal instillation, 6.0 mg/kg·bw, once per week for 12 times. The echocardiography showed that the sub-chronic exposure of Si-60 declined cardiac output (CO) and stroke volume (SV), shorten LVIDd and LVIDs, and thickened LVAWs of ApoE^-/- mice in compared to the control and Si-300 groups. Histological investigations manifested Si-60 enhanced inflammatory infiltration, myocardial fiber arrangement disorder, hypertrophy and fibrosis in the cardiac tissue, as well as mitochondrial ultrastructural injury. Accordingly, the serum cTnT, cTnI and ANP were significantly elevated by Si-60, as well as cardiac ANP content. In particular, Si-60 greatly increased cardiac ROS, Ca²⁺ levels and CaMKII activation in comparison with Si-300. Further, in vitro investigations revealed silica particles induced a dose- and size-dependent activation of oxidative stress, mitochondrial membrane permeabilization, intracellular Ca²⁺ overload, CaMKII signaling activation and ensuing myocardial apoptosis in human cardiomyocytes (AC16). Mechanistic analyses revealed SiNPs induced myocardial apoptosis via ROS/Ca²⁺/CaMKII signaling, which may contribute to the abnormalities in cardiac structure and function in vivo. In summary, our research revealed SiNPs caused myocardial impairments, dysfunction and even structural remodeling via ROS/Ca²⁺/CaMKII signaling. Of note, a size-dependent myocardial toxicity was noticed, that is, Si-60 greater than Si-300.

Involvement of Oxidative Stress in the Development of Subcellular Defects and Heart Disease

It is now well known that oxidative stress promotes lipid peroxidation, protein oxidation, activation of proteases, fragmentation of DNA and alteration in gene expression for producing myocardial cell damage, whereas its actions for the induction of fibrosis, necrosis and apoptosis are considered to result in the loss of cardiomyocytes in different types of heart disease. The present article is focused on the discussion concerning the generation and implications of oxidative stress from various sources such as defective mitochondrial electron transport and enzymatic reactions mainly due to the activation of NADPH oxidase, nitric oxide synthase and monoamine oxidase in diseased myocardium. Oxidative stress has been reported to promote excessive entry of Ca²⁺ due to increased permeability of the sarcolemmal membrane as well as depressions of Na⁺-K⁺ ATPase and Na⁺-Ca²⁺ exchange systems, which are considered to increase the intracellular of Ca²⁺. In addition, marked changes in the ryanodine receptors and Ca²⁺-pump ATPase have been shown to cause Ca²⁺-release and depress Ca²⁺ accumulation in the sarcoplasmic reticulum as a consequence of oxidative stress. Such alterations in sarcolemma and sarcoplasmic reticulum are considered to cause Ca²⁺-handling abnormalities, which are associated with mitochondrial Ca²⁺-overload and loss of myofibrillar Ca²⁺-sensitivity due to oxidative stress. Information regarding the direct effects of different oxyradicals and oxidants on subcellular organelles has also been outlined to show the mechanisms by which oxidative stress may induce Ca²⁺-handling abnormalities. These observations support the view that oxidative stress plays an important role in the genesis of subcellular defects and cardiac dysfunction in heart disease.

Cardiovascular Drugs and Osteoarthritis: Effects of Targeting Ion Channels

Osteoarthritis (OA) and cardiovascular diseases (CVD) share many similar features, including similar risk factors and molecular mechanisms. A great number of cardiovascular drugs act via different ion channels and change ion balance, thus modulating cell metabolism, osmotic responses, turnover of cartilage extracellular matrix and inflammation. These drugs are consumed by patients with CVD for many years; however, information about their effects on the joint tissues has not been fully clarified. Nevertheless, it is becoming increasingly likely that different cardiovascular drugs may have an impact on articular tissues in OA. Here, we discuss the potential effects of direct and indirect ion channel modulating drugs, including inhibitors of voltage gated calcium and sodium channels, hyperpolarization-activated cyclic nucleotide-gated channels, β-adrenoreceptor inhibitors and angiotensin-aldosterone system affecting drugs. The aim of this review was to summarize the information about activities of cardiovascular drugs on cartilage and subchondral bone and to discuss their possible consequences on the progression of OA, focusing on the modulation of ion channels in chondrocytes and other joint cells, pain control and regulation of inflammation. The implication of cardiovascular drug consumption in aetiopathogenesis of OA should be considered when prescribing ion channel modulators, particularly in long-term therapy protocols.

Heart Rate Reduction Improves Right Ventricular Function and Fibrosis in Pulmonary Hypertension

The potential benefit of heart rate reduction (HRR), independent of β-blockade, on right ventricular (RV) function in pulmonary hypertension (PH) remains undecided. We studied HRR effects on RV fibrosis and function in PH and RV pressure-loading models. Adult rats were randomized to 1) sham controls, 2) monocrotaline (MCT)-induced PH, 3) SU5416 + hypoxia (SUHX)-induced PH, or 4) pulmonary artery banding (PAB). Ivabradine (IVA) (10 mg/kg/d) was administered from 2 weeks after PH induction or PAB. Exercise tolerance, echocardiography, and pressure-volume hemodynamics were obtained at a terminal experiment 3 weeks later. RV myocardial samples were analyzed for putative mechanisms of HRR effects through fibrosis, profibrotic molecular signaling, and Ca⁺⁺ handling. The effects of IVA versus carvedilol on human induced pluripotent stem cell-derived cardiomyocytes beat rate and relaxation properties were evaluated in vitro. Despite unabated severely elevated RV systolic pressures, IVA improved RV systolic and diastolic function, profibrotic signaling, and RV fibrosis in PH/PAB rats. RV systolic-elastance (control, 121 ± 116; MCT, 49 ± 36 vs. MCT+IVA, 120 ± 54; PAB, 70 ± 20 vs. PAB+IVA, 168 ± 76; SUHX, 86 ± 56 vs. SUHX +IVA, 218 ± 111; all P < 0.05), the time constant of RV relaxation, echo indices of RV function, and fibrosis (fibrosis: control, 4.6 ± 1%; MCT, 13.4 ± 6.5 vs. MCT+IVA, 6.7 ± 2.6%; PAB, 11.4 ± 4.5 vs. PAB+IVA, 6.4 ± 5.1%; SUHX, 10 ± 4.6 vs. SUHX+IVA, 3.9 ± 2.2%; all P < 0.001) were improved by IVA versus controls. IVA had a dose-response effect on induced pluripotent stem cell-derived cardiomyocytes beat rate by delaying Ca⁺⁺ loss from the cytoplasm. In experimental PH or RV pressure loading, HRR improves RV fibrosis, function, and exercise endurance independent of β-blockade. The balance between adverse tachycardia and bradycardia requires further study, but judicious HRR may provide a promising strategy to improve RV function in clinical PH.

Luteolin modulates SERCA2a via Sp1 upregulation to attenuate myocardial ischemia/reperfusion injury in mice

The sarco/endoplasmic reticulum Ca2+ ATPase 2a (SERCA2a) is responsible for calcium transport during excitation-contraction coupling and is essential for maintaining myocardial systolic/diastolic function and intracellular Ca2+ levels. Therefore, it is important to investigate mechanisms whereby luteolin modulates SERCA2a expression to attenuate myocardial ischemia/reperfusion injury. C57BL/6j mice were randomly divided into eight groups. The expression and activity of SERCA2a was measured to assess interactions between the SERCA2a promoter and the Sp1 transcription factor, and the regulatory effects of luteolin. We used serum LDH release, serum cardiac troponin I level, hemodynamic data, myocardial infarction size and apoptosis-related indices to measure SERCA2a cardio-protective effects of luteolin pretreatment. Sp1 binding to SERCA2a promoter under ischemia/reperfusion conditions in the presence or absence of luteolin was analyzed by chromatin immunoprecipitation. Our experimental results indicated that during myocardial ischemia/reperfusion injury, luteolin pretreatment upregulated the expression levels of SERCA2a and Sp1. Sp1 overexpression enhanced the expression of SERCA2a at the transcriptional level. Luteolin pretreatment reversed the expression of SERCA2a through the increased expression of Sp1. Moreover, we demonstrated that luteolin pretreatment appeared to exert myocardial protective effects by upregulating the transcriptional activity of SERCA2a, via Sp1. In conclusion, during myocardial ischemia/reperfusion, Sp1 appeared to downregulate the expression of SERCA2a. Luteolin pretreatment was shown to improve SERCA2a expression via the upregulation of Sp1 to attenuate myocardial ischemia/reperfusion injury.

Liposomal Resveratrol and/or Carvedilol Attenuate Doxorubicin-Induced Cardiotoxicity by Modulating Inflammation, Oxidative Stress and S100A1 in Rats

Doxorubicin (DOX) is a cytotoxic anthracycline antibiotic and one of the important chemotherapeutic agents for different types of cancers. DOX treatment is associated with adverse effects, particularly cardiac dysfunction. This study examined the cardioprotective effects of carvedilol (CAR) and/or resveratrol (RES) and liposomal RES (LIPO-RES) against DOX-induced cardiomyopathy, pointing to their modulatory effect on oxidative stress, inflammation, S100A1 and sarco/endoplasmic reticulum calcium ATPase2a (SERCA2a). Rats received CAR (30 mg/kg) and/or RES (20 mg/kg) or LIPO-RES (20 mg/kg) for 6 weeks and were challenged with DOX (2 mg/kg) twice per week from week 2 to week 6. DOX-administered rats exhibited a significant increase in serum creatine kinase-MB (CK-MB), troponin-I and lactate dehydrogenase (LDH) along with histological alterations, reflecting cardiac cell injury. Cardiac toll-like receptor 4 (TLR-4), inducible nitric oxide synthase (iNOS), tumor necrosis factor (TNF)-α and interleukin (IL)-6 protein expression were up-regulated, and lipid peroxidation was increased in DOX-administered rats. Treatment with CAR, RES or LIPO-RES as well as their alternative combinations ameliorated all observed biochemical and histological alterations with the most potent effect exerted by CAR/LIPO-RES. All treatments increased cardiac antioxidants, and the expression of S100A1 and SERCA2a. In conclusion, the present study conferred new evidence on the protective effects of CAR and its combination with either RES or LIPO-RES on DOX-induced inflammation, oxidative stress and calcium dysregulation.

miR-181c Activates Mitochondrial Calcium Uptake by Regulating MICU1 in the Heart

Background

Translocation of miR‐181c into cardiac mitochondria downregulates the mitochondrial gene, mt‐COX1. miR‐181c/d^−/− hearts experience less oxidative stress during ischemia/reperfusion (I/R) and are protected against I/R injury. Additionally, miR‐181c overexpression can increase mitochondrial matrix Ca²⁺ ([Ca²⁺]_m), but the mechanism by which miR‐181c regulates [Ca²⁺]_m is unknown.

Methods and Results

By RNA sequencing and analysis, here we show that hearts from miR‐181c/d^−/− mice overexpress nuclear‐encoded Ca²⁺ regulatory and metabolic pathway genes, suggesting that alterations in miR‐181c and mt‐COX1 perturb mitochondria‐to‐nucleus retrograde signaling and [Ca²⁺]_m regulation. Quantitative polymerase chain reaction validation of transcription factors that are known to initiate retrograde signaling revealed significantly higher Sp1 (specificity protein) expression in the miR‐181c/d^−/− hearts. Furthermore, an association of Sp1 with the promoter region of MICU1 was confirmed by chromatin immunoprecipitation‐quantitative polymerase chain reaction and higher expression of MICU1 was found in the miR‐181c/d^−/− hearts. Conversely, downregulation of Sp1 by small interfering RNA decreased MICU1 expression in neonatal mouse ventricular myocytes. Changes in PDH activity provided evidence for a change in [Ca²⁺]_m via the miR‐181c/MICU1 axis. Moreover, this mechanism was implicated in the pathology of I/R injury. When MICU1 was knocked down in the miR‐181c/d^−/− heart by lentiviral expression of a short‐hairpin RNA against MICU1, cardioprotective effects against I/R injury were abrogated. Furthermore, using an in vitro I/R model in miR‐181c/d^−/− neonatal mouse ventricular myocytes, we confirmed the contribution of both Sp1 and MICU1 in ischemic injury.

Conclusions

miR‐181c regulates mt‐COX1, which in turn regulates MICU1 expression through the Sp1‐mediated mitochondria‐to‐nucleus retrograde pathway. Loss of miR‐181c can protect the heart from I/R injury by modulating [Ca²⁺]_m through the upregulation of MICU1.

Cardiac safety of systemic therapy in breast cancer patients with high risk of atherosclerosis complications

Aim: This study was designed to verify the efficacy of breast cancer treatment and its cardiac toxicity in population with significant cardiac comorbidities. Materials & methods: Prospective observational study was conducted in 48 patients. Results: The increase and dependence of echocardiographic parameter early/late were observed on hemoglobin level in all patients, and white blood cells and cholesterol in patients with diabetic were reported. Patients undergo left ventricle diameter change on treatment. Conclusion: Use of potentially cardiotoxic chemo regimens in breast cancer patients with cardiac comorbidities, with optimized cardiac therapy accordingly can save patients from development of early myocardial dysfunction induced by chemotherapy – limiting factor to minimize the risk is optimization of lipid level, red blood cell count and platelets count.

Phospholamban degradation is induced by phosphorylation-mediated ubiquitination and inhibited by interaction with cardiac type Sarco(endo)plasmic reticulum Ca(2+)-ATPase

Phospholamban (PLN) regulates cardiac type sarco (endo)plasmic reticulum Ca(2+)-ATPase (SERCA2a) via Ser(16)-phosphorylation. During heart failure, PLN expression is downregulated with SERCA2a; however, the mechanism of its regulation is not fully understood. Phosphorylation triggers protein degradation and because PLN phosphorylation is upregulated in failing hearts, we examined whether PLN is degraded by Ser(16)-phosphorylation. Cells overexpressing PLN exhibited its degradation post isoproterenol (Iso), forskolin, or 3-isobutyl-1-methylxanthine (IBMX) addition. Moreover, this degradation was inhibited by a cAMP-dependent protein kinase (PKA) inhibitor--H89. Co-immunoprecipitation revealed that Lys(3) of PLN was oligo-ubiquitinated when ubiquitin was overexpressed, and was degraded by Iso treatment. However, when co-expressed with SERCA2a, oligo-ubiquitinated PLN at Lys(3) was not degraded by Iso treatment. In failing hearts from 16 week-old TgPLN(R9C) mice, oligo-ubiquitinated PLN levels increased and PLN expression was downregulated. Furthermore, SERCA2a mRNA levels in TgPLN(R9C) mice hearts were lower than that in wild type mice; however, PLN mRNA levels showed no changes. In another heart failure model, MG132 treatment reversed PLN degradation. These data suggest that PLN is, at least partially, oligo-ubiquitinated at Lys(3) and degraded through Ser(16)-phosphorylation-mediated poly-ubiquitination during heart failure.

Identification of gene signatures regulated by carvedilol in mouse heart

Chronic treatment with the β-blocker carvedilol has been shown to reduce established maladaptive left ventricle (LV) hypertrophy and to improve LV function in experimental heart failure. However, the detailed mechanisms by which carvedilol improves LV failure are incompletely understood. We previously showed that carvedilol is a β-arrestin-biased β1-adrenergic receptor ligand, which activates cellular pathways in the heart independent of G protein-mediated second messenger signaling. More recently, we have demonstrated by microRNA (miR) microarray analysis that carvedilol upregulates a subset of mature and pre-mature miRs, but not their primary miR transcripts in mouse hearts. Here, we next sought to identify the effects of carvedilol on LV gene expression on a genome-wide basis. Adult mice were treated with carvedilol or vehicle for 1 wk. RNA was isolated from LV tissue and hybridized for microarray analysis. Gene expression profiling analysis revealed a small group of genes differentially expressed after carvedilol treatment. Further analysis categorized these genes into pathways involved in tight junction, malaria, viral myocarditis, glycosaminoglycan biosynthesis, and arrhythmogenic right ventricular cardiomyopathy. Genes encoding proteins in the tight junction, malaria, and viral myocarditis pathways were upregulated in the LV by carvedilol, while genes encoding proteins in the glycosaminoglycan biosynthesis and arrhythmogenic right ventricular cardiomyopathy pathways were downregulated by carvedilol. These gene expression changes may reflect the molecular mechanisms that underlie the functional benefits of carvedilol therapy.

Chronic β1-adrenergic blockade enhances myocardial β3-adrenergic coupling with nitric oxide-cGMP signaling in a canine model of chronic volume overload: new insight into mechanisms of cardiac benefit with selective β1-blocker therapy

The β1-adrenergic antagonist metoprolol improves cardiac function in animals and patients with chronic heart failure, isolated mitral regurgitation (MR), and ischemic heart disease, though the molecular mechanisms remain incompletely understood. Metoprolol has been reported to upregulate cardiac expression of β3-adrenergic receptors (β3AR) in animal models. Myocardial β3AR signaling via neuronal nitric oxide synthase (nNOS) activation has recently emerged as a cardioprotective pathway. We tested whether chronic β1-adrenergic blockade with metoprolol enhances myocardial β3AR coupling with nitric oxide-stimulated cyclic guanosine monophosphate (β3AR/NO-cGMP) signaling in the MR-induced, volume-overloaded heart. We compared the expression, distribution, and inducible activation of β3AR/NO-cGMP signaling proteins within myocardial membrane microdomains in dogs (canines) with surgically induced MR, those also treated with metoprolol succinate (MR+βB), and unoperated controls. β3AR mRNA transcripts, normalized to housekeeping gene RPLP1, increased 4.4 × 10(3)- and 3.2 × 10(2)-fold in MR and MR+βB hearts, respectively, compared to Control. Cardiac β3AR expression was increased 1.4- and nearly twofold in MR and MR+βB, respectively, compared to Control. β3AR was detected within caveolae-enriched lipid rafts (Cav3(+)LR) and heavy density, non-lipid raft membrane (NLR) across all groups. However, in vitro selective β3AR stimulation with BRL37344 (BRL) triggered cGMP production within only NLR of MR+βB. BRL induced Ser (1412) phosphorylation of nNOS within NLR of MR+βB, but not Control or MR, consistent with detection of NLR-specific β3AR/NO-cGMP coupling. Treatment with metoprolol prevented MR-associated oxidation of NO biosensor soluble guanylyl cyclase (sGC) within NLR. Metoprolol therapy also prevented MR-induced relocalization of sGCβ1 subunit away from caveolae, suggesting preserved NO-sGC-cGMP signaling, albeit without coupling to β3AR, within MR+βB caveolae. Chronic β1-blockade is associated with myocardial β3AR/NO-cGMP coupling in a microdomain-specific fashion. Our canine study suggests that microdomain-targeted enhancement of myocardial β3AR/NO-cGMP signaling may explain, in part, β1-adrenergic antagonist-mediated preservation of cardiac function in the volume-overloaded heart.

Redox signaling in cardiac renewal

SIGNIFICANCE

Utilizing oxygen (O2) through mitochondrial oxidative phosphorylation enables organisms to generate adenosine triphosphate (ATP) with a higher efficiency than glycolysis, but it results in increased reactive oxygen species production from mitochondria, which can result in stem cell dysfunction and senescence.

RECENT ADVANCES

In the postnatal organism, the hematopoietic system represents a classic example of the role of stem cells in cellular turnover and regeneration. However, in other organs such as the heart, both the degree and source of cellular turnover have been heavily contested.

CRITICAL ISSUES

Although recent evidence suggests that the major source of the limited cardiomyocyte turnover in the adult heart is cardiomyocyte proliferation, the identity and potential role of undifferentiated cardiac progenitor cells remain controversial. Several types of cardiac progenitor cells have been identified, and several studies have identified an important role of redox and metabolic regulation in survival and differentiation of cardiac progenitor cells. Perhaps a simple way to approach these controversies is to focus on the multipotentiality characteristics of a certain progenitor population, and not necessarily its ability to give rise to all cell types within the heart. In addition, it is important to note that cycling cells in the heart may express markers of differentiation or may be truly undifferentiated, and for the purpose of this review, we will refer to these cycling cells as progenitors.

FUTURE DIRECTIONS

We propose that hypoxia, redox signaling, and metabolic phenotypes are major regulators of cardiac renewal, and may prove to be important therapeutic targets for heart regeneration.

Combined TRPC3 and TRPC6 blockade by selective small-molecule or genetic deletion inhibits pathological cardiac hypertrophy

Chronic neurohormonal and mechanical stresses are central features of heart disease. Increasing evidence supports a role for the transient receptor potential canonical channels TRPC3 and TRPC6 in this pathophysiology. Channel expression for both is normally very low but is increased by cardiac disease, and genetic gain- or loss-of-function studies support contributions to hypertrophy and dysfunction. Selective small-molecule inhibitors remain scarce, and none target both channels, which may be useful given the high homology among them and evidence of redundant signaling. Here we tested selective TRPC3/6 antagonists (GSK2332255B and GSK2833503A; IC50, 3-21 nM against TRPC3 and TRPC6) and found dose-dependent blockade of cell hypertrophy signaling triggered by angiotensin II or endothelin-1 in HEK293T cells as well as in neonatal and adult cardiac myocytes. In vivo efficacy in mice and rats was greatly limited by rapid metabolism and high protein binding, although antifibrotic effects with pressure overload were observed. Intriguingly, although gene deletion of TRPC3 or TRPC6 alone did not protect against hypertrophy or dysfunction from pressure overload, combined deletion was protective, supporting the value of dual inhibition. Further development of this pharmaceutical class may yield a useful therapeutic agent for heart disease management.

Calcium pumps: why so many?

Ca(2+)-ATPases (pumps) are key to the regulation of Ca(2+) in eukaryotic cells: nine are known today, belonging to three multigene families. The three endo(sarco)plasmic reticulum (SERCA) and the four plasma membrane (PMCA) pumps have been known for decades, the two Secretory Pathway Ca(2+) ATPase (SPCA) pumps have only become known recently. The number of pump isoforms is further increased by alternative splicing processes. The three pump types share the basic features of the catalytic mechanism, but differ in a number of properties related to tissue distribution, regulation, and role in the cellular homeostasis of Ca(2+). The molecular understanding of the function of all pumps has received great impetus from the solution of the three-dimensional (3D) structure of one of them, the SERCA pump. This landmark structural advance has been accompanied by the emergence and rapid expansion of the area of pump malfunction. Most of the pump defects described so far are genetic and produce subtler, often tissue and isoform specific, disturbances that affect individual components of the Ca(2+)-controlling and/or processing machinery, compellingly indicating a specialized role for each Ca(2+) pump type and/or isoform.

Managing cardiotoxicity of chemotherapy

OPINION STATEMENT

The increase in survivorship of cancer patients makes the understanding of the available options for prevention and treatment of cardiotoxicity induced by antineoplastic agents a crucial topic both for cardiologists and oncologists. The most frequent and typical clinical manifestation of cardiotoxicity is asymptomatic or symptomatic left ventricular dysfunction, which may progress to overt heart failure. It may be induced not only by conventional cancer therapy, like anthracyclines, but also by new antitumoral targeted therapy such as trastuzumab. The current standard for monitoring cardiac damage during antineoplastic treatment, mainly based on the quantification of left ventricular ejection fraction, detects cardiac toxicity only when a functional impairment has already occurred. Evaluation of cardiac biomarkers such as troponin, however, has shown excellent sensitivity in the early detection of cardiotoxicity by the identification of patients with subclinical cardiac injury that precedes the development of cardiac dysfunction. The use of angiotensin-converting enzyme inhibitors in patients with troponin elevation during chemotherapy may be an effective tool to prevent left ventricular ejection fraction reduction and late cardiac events. There are no well established recommendations for treatment of cancer patients who develop cardiac dysfunction. Angiotensin-converting enzyme inhibitors and beta-blockers have proven to be effective in this setting. However, there are concerns in using these medications in cancer patients, and therefore the tendency is to treat patients only if symptomatic. However, the clinical benefit of these medications may be more evident in asymptomatic patients, and the recovery of cardiac function strongly depends on the amount of time elapsed from the end of chemotherapy to the start of heart failure therapy. This observation suggests that the early detection of cardiac damage is crucial and early use of angiotensin-converting enzyme inhibitors and beta-blockers should be considered in patients with left ventricular dysfunction induced by antineoplastic agents.

Integrative effect of carvedilol and aerobic exercise training therapies on improving cardiac contractility and remodeling in heart failure mice

The use of β-blockers is mandatory for counteracting heart failure (HF)-induced chronic sympathetic hyperactivity, cardiac dysfunction and remodeling. Importantly, aerobic exercise training, an efficient nonpharmacological therapy to HF, also counteracts sympathetic hyperactivity in HF and improves exercise tolerance and cardiac contractility; the latter associated with changes in cardiac Ca²⁺ handling. This study was undertaken to test whether combined β–blocker and aerobic exercise training would integrate the beneficial effects of isolated therapies on cardiac structure, contractility and cardiomyocyte Ca²⁺ handling in a genetic model of sympathetic hyperactivity-induced HF (α_2A/α_2C- adrenergic receptor knockout mice, KO). We used a cohort of 5–7 mo male wild-type (WT) and congenic mice (KO) with C57Bl6/J genetic background randomly assigned into 5 groups: control (WT), saline-treated KO (KOS), exercise trained KO (KOT), carvedilol-treated KO (KOC) and, combined carvedilol-treated and exercise-trained KO (KOCT). Isolated and combined therapies reduced mortality compared with KOS mice. Both KOT and KOCT groups had increased exercise tolerance, while groups receiving carvedilol had increased left ventricular fractional shortening and reduced cardiac collagen volume fraction compared with KOS group. Cellular data confirmed that cardiomyocytes from KOS mice displayed abnormal Ca²⁺ handling. KOT group had increased intracellular peak of Ca²⁺ transient and reduced diastolic Ca²⁺ decay compared with KOS group, while KOC had increased Ca²⁺ decay compared with KOS group. Notably, combined therapies re-established cardiomyocyte Ca²⁺ transient paralleled by increased SERCA2 expression and SERCA2:PLN ratio toward WT levels. Aerobic exercise trained increased the phosphorylation of PLN at Ser¹⁶ and Thr¹⁷ residues in both KOT and KOCT groups, but carvedilol treatment reduced lipid peroxidation in KOC and KOCT groups compared with KOS group. The present findings provide evidence that the combination of carvedilol and aerobic exercise training therapies lead to a better integrative outcome than carvedilol or exercise training used in isolation.

Carvedilol prevents ovariectomy-induced myocardial contractile dysfunction in female rat

Carvedilol has beneficial effects on cardiac function in patients with heart failure but its effect on ovariectomy-induced myocardial contractile dysfunction remains unclear. Estrogen deficiency induces myocardial contractile dysfunction and increases cardiovascular disease risk in postmenopausal women. Our aim was to investigate whether carvedilol, a beta receptor blocker, would prevent ovariectomy-induced myocardial contractile dysfunction. Female rats (8 weeks old) that underwent bilateral ovariectomy were randomly assigned to receive daily treatment with carvedilol (OVX+CAR, 20 mg/kg), placebo (OVX) and SHAM for 58 days. Left ventricle papillary muscle was mounted for isometric tension recordings. The inotropic response to Ca²⁺ (0.62 to 3.75 mM) and isoproterenol (Iso 10⁻⁸ to 10⁻² M) were assessed. Expression of calcium handling proteins was measured by western blot analysis. Carvedilol treatment in the OVX animals: prevented weight gain and slight hypertrophy, restored the reduced positive inotropic responses to Ca²⁺ and isoproterenol, prevented the reduction in SERCA2a expression, abolished the increase in superoxide anion production, normalized the increase in p22^phox expression, and decreased serum angiotensin converting enzyme (ACE) activity. This study demonstrated that myocardial contractile dysfunction and SERCA2a down regulation were prevented by carvedilol treatment. Superoxide anion production and NADPH oxidase seem to be involved in this response.

The pathological roles of environmental and redox stresses in cardiovascular diseases

Oxidative stress and inflammation are implicated in cardiovascular diseases such as atherosclerosis, reperfusion injury, hypertension, and heart failure. High levels of oxidative stress resulting from increased cardiac generation of reactive oxygen species (ROS) is thought to contribute to contractile and endothelial dysfunction, apoptosis and necrosis of myocytes, and extracellular matrix remodeling in the heart. ROS activate several transcription factors known as redox-regulated transcription factors, and these transcription factors play important roles in the pathophysiology of cardiovascular diseases. This review focuses on the pathological roles of environmental and redox stresses in cardiovascular diseases, especially severe cardiac dysfunction and the transition from compensated hypertrophy to heart failure. The aryl hydrocarbon receptor (AHR) and NF-E2 p45-related factor (Nrf2) are transcription factors involved in the regulation of drug-metabolizing enzymes. AHR has been studied as a receptor for environmental contaminants and as a mediator of chemical toxicity. However, other roles for AHR in cardiac and vascular development have recently been described. Moreover, Nrf2 protects against oxidative stress by increasing the transcription of genes, including those for several antioxidant enzymes. The roles of these transcription factors, AHR and Nrf2 in angiogenesis are also discussed in this review.

Nicorandil prevents Gαq-induced progressive heart failure and ventricular arrhythmias in transgenic mice

BACKGROUND

Beneficial effects of nicorandil on the treatment of hypertensive heart failure (HF) and ischemic heart disease have been suggested. However, whether nicorandil has inhibitory effects on HF and ventricular arrhythmias caused by the activation of G protein alpha q (Gα(q)) -coupled receptor (GPCR) signaling still remains unknown. We investigated these inhibitory effects of nicorandil in transgenic mice with transient cardiac expression of activated Gα(q) (Gα(q)-TG).

METHODOLOGY/PRINCIPAL FINDINGS

Nicorandil (6 mg/kg/day) or vehicle was chronically administered to Gα(q)-TG from 8 to 32 weeks of age, and all experiments were performed in mice at the age of 32 weeks. Chronic nicorandil administration prevented the severe reduction of left ventricular fractional shortening and inhibited ventricular interstitial fibrosis in Gα(q)-TG. SUR-2B and SERCA2 gene expression was decreased in vehicle-treated Gα(q)-TG but not in nicorandil-treated Gα(q)-TG. eNOS gene expression was also increased in nicorandil-treated Gα(q)-TG compared with vehicle-treated Gα(q)-TG. Electrocardiogram demonstrated that premature ventricular contraction (PVC) was frequently (more than 20 beats/min) observed in 7 of 10 vehicle-treated Gα(q)-TG but in none of 10 nicorandil-treated Gα(q)-TG. The QT interval was significantly shorter in nicorandil-treated Gα(q)-TG than vehicle-treated Gα(q)-TG. Acute nicorandil administration shortened ventricular monophasic action potential duration and reduced the number of PVCs in Langendorff-perfused Gα(q)-TG mouse hearts. Moreover, HMR1098, a blocker of cardiac sarcolemmal K(ATP) channels, significantly attenuated the shortening of MAP duration induced by nicorandil in the Gα(q)-TG heart.

CONCLUSIONS/SIGNIFICANCE

These findings suggest that nicorandil can prevent the development of HF and ventricular arrhythmia caused by the activation of GPCR signaling through the shortening of the QT interval, action potential duration, the normalization of SERCA2 gene expression. Nicorandil may also improve the impaired coronary circulation during HF.

Protective effect of carvedilol on adriamycin-induced left ventricular dysfunction in children with acute lymphoblastic leukemia

BACKGROUND

Adriamycin (ADR) is a potent chemotherapeutic agent widely used in the treatment of childhood acute lymphoblastic leukemia (ALL); its clinical use is limited owing to its marked cardiotoxicity. The present study investigated the possible protective role of carvedilol on ADR-induced left ventricular dysfunction in children with ALL.

METHODS AND RESULTS

Fifty children with newly diagnosed ALL were included in this study. They were divided into 2 equal groups: 1) ADR; and 2) ADR + carvedilol. Patients were evaluated with conventional 2-dimensional echocardiographic examination (2D), pulsed tissue Doppler (PTD), and 2-dimensional longitudinal strain echocardiography (2DS) before and after therapy. Plasma lactic dehydrogenase (LDH), creatine phosphokinase (CPK), and troponin I levels were also determined before and after therapy. ADR treatment reduced left ventricular systolic dysfunction as assessed by a significant decrease in fractional shortening (FS) (2D) and global peak-systolic strain (GPSS; 2DS). In addition, ADR treatment significantly increased plasma troponin I and LDH. Pretreatment of ADR-treated patients with carvedilol resulted in a significant increase in FS (2D) and GPSS (2DS). Furthermore, carvedilol pretreatment inhibited ADR-induced increase in plasma troponin I and LDH.

CONCLUSIONS

These results suggested a protective role of carvedilol against ADR-induced cardiotoxicity.

β-Adrenergic regulation of cardiac progenitor cell death versus survival and proliferation

RATIONALE

Short-term β-adrenergic stimulation promotes contractility in response to stress but is ultimately detrimental in the failing heart because of accrual of cardiomyocyte death. Endogenous cardiac progenitor cell (CPC) activation may partially offset cardiomyocyte losses, but consequences of long-term β-adrenergic drive on CPC survival and proliferation are unknown.

OBJECTIVE

We sought to determine the relationship between β-adrenergic activity and regulation of CPC function.

METHODS AND RESULTS

Mouse and human CPCs express only β2 adrenergic receptor (β2-AR) in conjunction with stem cell marker c-kit. Activation of β2-AR signaling promotes proliferation associated with increased AKT, extracellular signal-regulated kinase 1/2, and endothelial NO synthase phosphorylation, upregulation of cyclin D1, and decreased levels of G protein-coupled receptor kinase 2. Conversely, silencing of β2-AR expression or treatment with β2-antagonist ICI 118, 551 impairs CPC proliferation and survival. β1-AR expression in CPC is induced by differentiation stimuli, sensitizing CPC to isoproterenol-induced cell death that is abrogated by metoprolol. Efficacy of β1-AR blockade by metoprolol to increase CPC survival and proliferation was confirmed in vivo by adoptive transfer of CPC into failing mouse myocardium.

CONCLUSIONS

β-adrenergic stimulation promotes expansion and survival of CPCs through β2-AR, but acquisition of β1-AR on commitment to the myocyte lineage results in loss of CPCs and early myocyte precursors.

Regulation of sarco(endo)plasmic reticulum Ca2+-ATPase and calsequestrin gene expression in the heart

The precise control of Ca2+levels during the contraction–relaxation cycle in cardiac myocytes is extremely important for normal beat-to-beat contractile activity. The sarcoplasmic reticulum (SR) plays a key role controlling calcium concentration in the cytosol. The SR Ca2+-ATPase (SERCA2) transports Ca2+inside the SR lumen during relaxation of the cardiac myocyte. Calsequestrin (Casq2) is the main protein in the SR lumen, functioning as a Ca2+buffer and participating in Ca2+release by interacting with the ryanodine receptor 2 (RyR2) Ca2+-release channel. Alterations in normal Ca2+handling significantly contribute to the contractile dysfunction observed in cardiac hypertrophy and in heart failure. Transcriptional regulation of the SERCA2 gene has been extensively studied and some of the mechanisms regulating its expression have been elucidated. Overexpression of Sp1 factor in cardiac hypertrophy downregulates SERCA2 gene expression and increased levels of thyroid hormone up-regulates its transcription. Other hormones such norepinephrine, angiotensin II, endothelin-1, parathyroid hormone, prostaglandin-F2α, as well the cytokines tumor necrosis factor-α and interleukin-6 also downregulate SERCA2 expression. Calcium acting through the calcineurin–NFAT (nuclear factor of activated T cells) pathway has been suggested to regulate SERCA2 and CASQ2 gene expression. This review focuses on the current knowledge regarding transcriptional regulation of SERCA2 and CASQ2 genes in the normal and pathologic heart.

Regulation of myocardial SERCA2a expression in ventricular hypertrophy and heart failure

Diminished contractility of the hypertrophic cardiomyocyte is a principal determinant of ventricular dysfunction in chronic heart failure. Reduction of activity of the sarcoplasmic/endoplasmic reticulum calcium ion (Ca2+)-ATPase (SERCA2a), underlies many of the effects of overload-induced hypertrophy on cardiomyocyte performance, and it may be critical in the progression of compensatory hypertrophy to heart failure. This review shall focus on the transcriptional regulation of SERCA2a expression as the primary cause of decreased SERCA2a activity in heart failure. Furthermore, the relevance for SERCA2a expression of signal transduction routes involved in pathologic hypertrophy and the possible therapeutic implications, shall be addressed.

Cyclic GMP/PKG-dependent inhibition of TRPC6 channel activity and expression negatively regulates cardiomyocyte NFAT activation Novel mechanism of cardiac stress modulation by PDE5 inhibition

Increased cyclic GMP from enhanced synthesis or suppressed catabolism (e.g. PDE5 inhibition by sildenafil, SIL) activates protein kinase G (PKG) and blunts cardiac pathological hypertrophy. Suppressed calcineurin (Cn)-NFAT (nuclear factor of activated T-cells) signaling appears to be involved, though it remains unclear how this is achieved. One potential mechanism involves activation of Cn/NFAT by calcium entering via transient receptor potential canonical (TRPC) channels (notably TRPC6). Here, we tested the hypothesis that PKG blocks Cn/NFAT activation by modifying and thus inhibiting TRPC6 current to break the positive feedback loop involving NFAT and NFAT-dependent TRPC6 upregulation. TRPC6 expression rose with pressure-overload in vivo, and angiotensin (ATII) or endothelin (ET1) stimulation in neonatal and adult cardiomyocytes in vitro. 8Br-cGMP and SIL reduced ET1-stimulated TRPC6 expression and NFAT dephosphorylation (activity). TRPC6 upregulation was absent if its promoter was mutated with non-functional NFAT binding sites, whereas constitutively active NFAT triggered TRPC6 expression that was not inhibited by SIL. PKG phosphorylated TRPC6, and both T70 and S322 were targeted. Both sites were functionally relevant, as 8Br-cGMP strongly suppressed current in wild-type TRPC6 channels, but not in those with phospho-silencing mutations (T70A, S322A or S322Q). NFAT activation and increased protein synthesis stimulated by ATII or ET1 was blocked by 8Br-cGMP or SIL. However, transfection with T70A or S322Q TRPC6 mutants blocked this inhibitory effect, whereas phospho-mimetic mutants (T70E, S322E, and both combined) suppressed NFAT activation. Thus PDE5-inhibition blocks TRPC6 channel activation and associated Cn/NFAT activation signaling by PKG-dependent channel phosphorylation.

Calcium Pumps in Health and Disease

Ca2+-ATPases (pumps) are key actors in the regulation of Ca2+ in eukaryotic cells and are thus essential to the correct functioning of the cell machinery. They have high affinity for Ca2+ and can efficiently regulate it down to very low concentration levels. Two of the pumps have been known for decades (the SERCA and PMCA pumps); one (the SPCA pump) has only become known recently. Each pump is the product of a multigene family, the number of isoforms being further increased by alternative splicing of the primary transcripts. The three pumps share the basic features of the catalytic mechanism but differ in a number of properties related to tissue distribution, regulation, and role in the cellular homeostasis of Ca2+. The molecular understanding of the function of the pumps has received great impetus from the solution of the three-dimensional structure of one of them, the SERCA pump. These spectacular advances in the structure and molecular mechanism of the pumps have been accompanied by the emergence and rapid expansion of the topic of pump malfunction, which has paralleled the rapid expansion of knowledge in the topic of Ca2+-signaling dysfunction. Most of the pump defects described so far are genetic: when they are very severe, they produce gross and global disturbances of Ca2+ homeostasis that are incompatible with cell life. However, pump defects may also be of a type that produce subtler, often tissue-specific disturbances that affect individual components of the Ca2+-controlling and/or processing machinery. They do not bring cells to immediate death but seriously compromise their normal functioning.

Ryanodine receptor-mediated arrhythmias and sudden cardiac death

The cardiac ryanodine receptor-Ca²⁺ release channel (RyR2) is an essential sarcoplasmic reticulum (SR) transmembrane protein that plays a central role in excitation–contraction coupling (ECC) in cardiomyocytes. Aberrant spontaneous, diastolic Ca²⁺ leak from the SR due to dysfunctional RyR2 contributes to the formation of delayed after-depolarisations, which are thought to underlie the fatal arrhythmia that occurs in both heart failure (HF) and in catecholaminergic polymorphic ventricular tachycardia (CPVT). CPVT is an inherited disorder associated with mutations in either the RyR2 or a SR luminal protein, calsequestrin. RyR2 shows normal function at rest in CPVT but the RyR2 dysfunction is unmasked by physical exercise or emotional stress, suggesting abnormal RyR2 activation as an underlying mechanism. Several potential mechanisms have been advanced to explain the dysfunctional RyR2 observed in HF and CPVT, including enhanced RyR2 phosphorylation status, altered RyR2 regulation at luminal/cytoplasmic sites and perturbed RyR2 intra/inter-molecular interactions. This review considers RyR2 dysfunction in the context of the structural and functional modulation of the channel, and potential therapeutic strategies to stabilise RyR2 function in cardiac pathology.

Alterations in mitochondrial function and cytosolic calcium induced by hyperglycemia are restored by mitochondrial transcription factor A in cardiomyocytes

Mitochondrial transcription factor A (TFAM) is essential for mitochondrial DNA transcription and replication. TFAM transcriptional activity is decreased in diabetic cardiomyopathy; however, the functional implications are unknown. We hypothesized that a reduced TFAM activity may be responsible for some of the alterations caused by hyperglycemia. Therefore, we investigated the effect of TFAM overexpression on hyperglycemia-induced cytosolic calcium handling and mitochondrial abnormalities. Neonatal rat cardiomyocytes were exposed to high glucose (30 mM) for 48 h, and we examined whether TFAM overexpression, by protecting mitochondrial DNA, could reestablish calcium fluxes and mitochondrial alterations toward normal. Our results shown that TFAM overexpression increased to more than twofold mitochondria copy number in cells treated either with normal (5.5 mM) or high glucose. ATP content was reduced by 30% and mitochondrial calcium decreased by 40% after high glucose. TFAM overexpression returned these parameters to even higher than control values. Calcium transients were prolonged by 70% after high glucose, which was associated with diminished sarco(endo)plasmic reticulum Ca(2+)-ATPase 2a and cytochrome-c oxidase subunit 1 expression. These parameters were returned to control values after TFAM overexpression. High glucose-induced protein oxidation was reduced by TFAM overexpression, indicating a reduction of the high glucose-induced oxidative stress. In addition, we found that TFAM activity can be modulated by O-linked beta-N-acetylglucosamine glycosylation. In conclusion, TFAM overexpression protected cell function against the damage induced by high glucose in cardiomyocytes.

Modulating sarco(endo)plasmic reticulum Ca2+ ATPase 2 (SERCA2) activity: cell biological implications

Of the three mammalian members belonging to the sarco(endo)plasmic reticulum Ca2+ ATPase (SERCA) family, SERCA2 is evolutionary the oldest and shows the most wide tissue-expression pattern. Two major SERCA2 splice variants are well-characterized: the muscle-specific isoform SERCA2a and the housekeeping isoform SERCA2b. Recently, several interacting proteins and post-translational modifications of SERCA2 were identified which may modulate the activity of the Ca2+ pump. This review aims to give an overview of the vast literature concerning the cell biological implications of the SERCA2 isoform diversity and the factors regulating SERCA2. Proteins reported to interact with SERCA2 from the cytosolic domain involve the anti-apoptotic Bcl-2, the insulin receptor substrates IRS1/2, the EF-hand Ca2+-binding protein S100A1 and acylphosphatase. We will focus on the very particular position of SERCA2 as an enzyme functioning in a thin, highly fluid, leaky and cholesterol-poor membrane. Possible differential interactions of SERCA2b and SERCA2a with calreticulin, calnexin and ERp57, which could occur within the lumen of the endoplasmic reticulum will be discussed. Reported post-translational modifications possibly affecting pump activity involve N-glycosylation, glutathionylation and Ca2+/calmodulin kinase II-dependent phosphorylation. Finally, the pronounced vulnerability to oxidative damage of SERCA2 appears to be pivotal in the etiology of various pathologies.

Lentiviral vector-mediated SERCA2 gene transfer protects against heart failure and left ventricular remodeling after myocardial infarction in rats

Reduced expression of the SERCA2 gene impairs the calcium-handling and contractile functions of the heart. We developed an SERCA2 gene transfer system using lentiviral vectors, and examined the long-term effect of SERCA2 gene transfer in the rat ischemic heart failure model. A lentiviral vector containing the SERCA2 gene was infused into a rat heart by hypothermic intracoronary delivery 2 weeks after myocardial infarction (MI). The transduction efficiency was approximately 40%. Six months after transduction, echocardiogram and pressure-volume measurements revealed that the SERCA2 gene transfer had significantly protected against left ventricular (LV) dilation, and had improved systolic and diastolic function, resulting in reduction in mortality rates. The brain natriuretic peptide mRNA level showed a significantly decrease and the phosphorylation level of serine residue of phospholamban (PLN) showed an increase in the Lenti-SERCA2-transduced heart. Further, DNA microarray analysis disclosed that SERCA2 gene transfer had increased cardioprotective gene expression and lowered the expression of genes that are known to exacerbate heart failure. The SERCA2 gene was successfully integrated into the host heart, induced favorable molecular remodeling, prevented LV geometrical remodeling, and improved the survival rate. These results suggest that a strategy to compensate for reduced SERCA2 gene expression by lentiviral vectors serves as a positive inotropic, lucitropic, and cardioprotective therapy for post-MI heart failure.

Time-course of changes in cardiac function during recovery after acute exercise

Exercise-induced cardiac dysfunction (EICD) has been observed immediately following exhaustive exercise in trained individuals, but limited and conflicting data are available regarding EICD in a previously untrained population days after an exhaustive exercise bout. The purpose of this study was to examine the effects of a single bout of acute exercise on cardiac function during the 72 h after exercise and identify potential contributing mechanisms. After completing an acute exercise bout on a motorized treadmill (25 m/min, 5% grade, 60 min), rats were sacrificed immediately, 24 h, 48 h, or 72 h after the exercise bout. At the scheduled time of sacrifice, hearts were isolated and perfused for determination of ex vivo cardiac function, and examined for malondialdehyde (MDA), a lipid peroxidation index, and antioxidant potential (AOP). During the 48 h post exercise, left ventricular developed pressure decreased by 30%, dP/dtmax declined by 37%, and dP/dtmin showed a 34% decrease (p < 0.05). By 72 h, cardiac function had returned to control levels. MDA was increased immediately after the exercise bout and at the 24 and 48 h intervals (p < 0.05). Conversely, AOP progressively decreased at the 24 and 48 h intervals. As with cardiac function, MDA and AOP had returned to control levels by 72 h post-exercise. These data indicate that a single bout of prolonged, moderately intense exercise performed by previously sedentary rats impaired cardiac function for up to 48 h. This decrement in cardiac function was associated with increased lipid peroxidation and decreased antioxidant potential.

Antioxidant activity of carvedilol in cardiovascular disease

Oxidative and inflammatory stresses are cardinal in the pathogenesis of hypertension and atherosclerosis. Oxidative stress also leads to the induction of inflammation through the activation of proinflammatory transcription factors. Understanding the mechanisms leading to oxidative stress and the means of suppressing it are important in controlling complications related to atherogenesis, since oxidative and inflammatory stress are important in the pathogenesis of atherosclerosis. The failure of chemical antioxidants [which scavenge reactive oxygen species (ROS)], such as vitamins E and C, has led to further exploration of the ROS-suppressive effects of drugs used in the treatment of cardiovascular disease. Carvedilol has been shown to possess both ROS-scavenging and ROS-suppressive effects, and its use is associated with a reduction in oxidative stress. Furthermore, anti-inflammatory effects of carvedilol have now been described. Although further clinical investigations are required, these properties may contribute to the improvement in clinical outcomes observed with carvedilol.

Emerging drugs for acute and chronic heart failure: current and future developments

Heart failure continues to be a major public health issue. Although angiotensin-converting enzyme inhibitors and beta-adrenergic blockers have been broadly used as evidence-based therapies in heart failure, morbidity and mortality remains high. Furthermore, treatment for acute decompensated heart failure and diastolic heart failure (or 'heart failure with preserved ejection fraction') is far from perfect. This review provides a broad overview of some of the novel compounds under investigation for the treatment of heart failure. Novel strategies include drugs that aim to alleviate congestion and improve hemodynamics, drugs that preserve renal function, drugs that reduce arterial and myocardial stiffness, drugs that module myocardial contractility, drugs that affect metabolic and hormonal balance, and drugs that act on existing and novel physiologic targets.

Carvedilol Reduces Elevated B-type Natriuretic Peptide in Dialyzed Patients Without Heart Failure: Cardioprotective Effect of the β-blocker

Elevated plasma B-type natriuretic peptide (BNP) predicts future cardiovascular events in dialyzed patients without heart failure. We investigated whether carvedilol reduces the elevated BNP in these patients. Asymptomatic patients on chronic hemodialysis with elevated BNP but without clinical signs of heart failure were randomly assigned to receive either carvedilol (n = 10) or nothing (control group, n = 10). BNP and malondialdehyde-low density lipoprotein (MDA-LDL) were measured, and ultrasound cardiography was performed at baseline and at 3 months. Carvedilol reduced the concentrations of BNP (551 +/- 90 to 237 +/- 174 ng/L, P < 0.01) and MDA-LDL (174 +/- 63 to 85 +/- 23 U/L, P < 0.01) and increased the velocity ratio of E to A waves of the transmitral flow (E/A: 0.59 +/- 0.04 to 0.71 +/- 0.05, P < 0.05), while no such alterations were observed in the control group. The reduction in BNP concentration was correlated with that in MAD-LDL and the increase in the E/A. There was a significant correlation between the increase in the E/A and the reduction in MDA-LDL concentration. Thus, carvedilol reduces the elevated BNP by improving left ventricular diastolic function in dialyzed patients without heart failure, which may be attributable to the antioxidant property of the beta-blocker. Administering carvedilol may improve the prognosis in this population.

Carvedilol inhibits mitochondrial complex I and induces resistance to H2O2 -mediated oxidative insult in H9C2 myocardial cells

Carvedilol, a beta-adrenoreceptor antagonist with strong antioxidant activity, produces a high degree of cardioprotection in a variety of experimental models of ischemic cardiac injury. Although growing evidences suggest specific effects on mitochondrial metabolism, how carvedilol would exert its overall activity has not been completely disclosed. In the present work we have investigated the impact of carvedilol-treatment on mitochondrial bioenergetic functions and ROS metabolism in H9C2 cells. This analysis has revealed a dose-dependent decrease in respiratory fluxes by NAD-dependent substrates associated with a consistent decline of mitochondrial complex I activity. These changes were associated with an increase in mitochondrial H(2)O(2) production, total glutathione and protein thiols content. To evaluate the antioxidant activity of carvedilol, the effect of the exposure of control and carvedilol-pretreated H9C2 cells to H(2)O(2) were investigated. The H(2)O(2)-mediated oxidative insult resulted in a significant decrease of mitochondrial respiration, glutathione and protein thiol content and in an increased level of GSSG. These changes were prevented by carvedilol-pretreatment. A similar protective effect on mitochondrial respiration could be obtained by pre-treatment of the cells with a sub-saturating amount of rotenone, a complex I inhibitor. We therefore suggest that carvedilol exerts its protective antioxidant action both by a direct antioxidant effect and by a preconditioning-like mechanism, via inhibition of mitochondrial complex I.

Protective effects of carvedilol against anthracycline-induced cardiomyopathy

OBJECTIVES

The aim of this study was to determine the protective effect of carvedilol in anthracycline (ANT)-induced cardiomyopathy (CMP).

BACKGROUND

Despite its broad effectiveness, ANT therapy is associated with ANT-induced CMP. Recent animal studies and experimental observations showed that carvedilol prevented development of CMP due to chemotherapeutics. However, there is no placebo-controlled clinical trial concerning prophylactic carvedilol use in preventing ANT-induced CMP.

METHODS

Patients in whom ANT therapy was planned were randomized to administration of carvedilol or placebo. We enrolled 25 patients in carvedilol and control groups. In the carvedilol group, 12.5 mg once-daily oral carvedilol was given during 6 months. The patients were evaluated with echocardiography before and after chemotherapy. Left ventricular ejection fraction (EF) and systolic and diastolic diameters were calculated.

RESULTS

At the end of 6 months of follow-up, 1 patient in the carvedilol group and 4 in the control group had died. Control EF was below 50% in 1 patient in the carvedilol group and in 5 in the control group. The mean EF of the carvedilol group was similar at baseline and control echocardiography (70.5 vs. 69.7, respectively; p = 0.3), but in the control group the mean EF at control echocardiography was significantly lower (68.9 vs. 52.3; p < 0.001). Both systolic and diastolic diameters were significantly increased compared with basal measures in the control group. In Doppler study, whereas E velocities in the carvedilol group decreased, E velocities and E/A ratios were significantly reduced in the control group.

CONCLUSIONS

Prophylactic use of carvedilol in patients receiving ANT may protect both systolic and diastolic functions of the left ventricle.

Attenuation of oxidative stress and cardiac dysfunction by bisoprolol in an animal model of dilated cardiomyopathy

Oxidative stress is an important susceptibility factor for dilated cardiomyopathy. We have investigated the effects of bisoprolol, a beta1-selective adrenoceptor blocker, on oxidative stress and the development of cardiac dysfunction in a model of dilated cardiomyopathy. Male TO-2 and control hamsters at 8 weeks of age were treated with bisoprolol (5 mg/kg per day) or vehicle for 4 weeks. Treatment with bisoprolol prevented the progression of cardiac dysfunction in TO-2 hamsters. This drug did not affect the increase in NADPH oxidase activity but prevented the reduction in activity and expression of mitochondrial manganese-dependent superoxide dismutase as well as the increases in the concentrations of interleukin-1beta and tumor necrosis factor-alpha in the left ventricle of TO-2 hamsters. Attenuation of the development of cardiac dysfunction by bisoprolol may thus result in part from normalization of the associated increases in the levels of oxidative stress and pro-inflammatory cytokines in the left ventricle.

AT1 receptor antagonist restores cardiac ryanodine receptor function, rendering isoproterenol-induced failing heart less susceptible to Ca2+ -leak induced by oxidative stress

BACKGROUND

The Ca(2+) regulatory proteins in the sarcoplasmic reticulum (SR) play a key role in the pathogenesis of heart failure. In the present study the effect of chronic beta-receptor-stimulation on cardiac and SR functions was assessed, with or without angiotensin-II receptor antagonist treatment recently reported to have anti-beta-adrenergic activity.

METHODS AND RESULTS

Rats were treated with isoproterenol with (+) or without (-) candesartan (CAN) and then SR vesicles were isolated from the left ventricular muscle. Both Ca(2+)-uptake and the amount of SR Ca(2+)-ATPase were significantly lower in the CAN (-) group than in the shams, but those were almost normally restored in the CAN (+). Although the level of the protein kinase A (PKA)-phosphorylation of the SR Ca(2+) release channel, known as the ryanodine receptor (RyR2), was elevated in the CAN (-), no Ca(2+)-leak was detected. However, SIN-1 (O(2) (-) donor) induced Ca(2+)-leak in the CAN (-) at a 10-fold lower dose than in the sham and CAN (+). In cardiomyocytes, SIN-1 decreased cell shortening and the peak Ca(2+) transient and prolonged time from peak to 70% decline in CAN (-), again at 10-fold lower dose than in the sham and CAN (+).

CONCLUSION

Chronic beta-receptor-stimulation did not induce any Ca(2+)-leak from the SR, whereas Ca(2+)-leak was easily induced when oxidative stress was applied to the PKA-phosphorylated RyR2. Candesartan not only improved Ca(2+)-uptake, but also prevented PKA-phosphorylation, rendering the SR less susceptible to Ca(2+)-leak.

Pleiotropic effects of the beta-adrenoceptor blocker carvedilol on calcium regulation during oxidative stress-induced apoptosis in cardiomyocytes

Carvedilol is a nonselective beta-adrenoceptor blocker with multiple pleiotropic actions. A recent clinical study suggested that carvedilol may be superior to other beta-adrenoceptor blockers in the treatment of heart failure. Despite numerous investigations, the underlying mechanisms of carvedilol on improving heart failure are yet to be fully established. The purpose of this study is to clarify the pleiotropic effect of carvedilol on cytosolic and mitochondrial calcium regulation during oxidative stress-induced apoptosis in cardiomyocytes. Carvedilol (10 microM), but not metoprolol (10 microM), reduced H2O2 (100 microM)-induced apoptosis in neonatal rat cardiomyocytes. During the process, changes in cytosolic calcium concentration ([Ca2+]i) and mitochondrial calcium concentration ([Ca2+]m) and mitochondrial membrane potential (DeltaPsim) were measured by fluorescent probes [Fluo-3/acetoxymethyl ester (AM), Rhod-2/AM, and tetramethylrhodamine ethyl ester, respectively] and imaged by laser confocal microscopy. The results showed that H2O2 caused [Ca2]m overload first, followed by [Ca2+]i overload, leading to DeltaPsim dissipation and the induction of apoptosis. Carvedilol (10 microM) significantly delayed these processes and reduced apoptosis. These effects were not observed with other beta-adrenoceptor blockers (metoprolol, atenolol, and propranolol) or with a combination of the alpha (phentolamine)- and the beta-adrenoceptor blocker. The antioxidant N-acetyl-L-cysteine (NAC, 5 mM) and the combination of NAC and propranolol (10 microM) showed an effect similar to that of carvedilol. Therefore, the effect of carvedilol on H2O2-induced changes in [Ca2+]m, [Ca2+]i, and DeltaPsi(m) is independent of alpha- and beta-adrenoceptors but is probably dependent on the antioxidant effect.

Vitamins C and E attenuate apoptosis, beta-adrenergic receptor desensitization, and sarcoplasmic reticular Ca2+ ATPase downregulation after myocardial infarction

Oxidative stress plays an important role in mediating ventricular remodeling and dysfunction in heart failure (HF), but its mechanism of action has not been fully elucidated. In this study we determined whether a combination of antioxidant vitamins reduced myocyte apoptosis, beta-adrenergic receptor desensitization, and sarcoplasmic reticular (SR) Ca2+ ATPase downregulation in HF after myocardial infarction (MI) and whether these effects were associated with amelioration of left ventricular (LV) remodeling and dysfunction. Vitamins (vitamin C 300 mg and vitamin E 300 mg) were administered to rabbits 1 week after MI or sham operation for 11 weeks. The results showed that MI rabbits exhibited cardiac dilation and LV dysfunction measured by fractional shortening and the maximal rate of pressure rise (dP/dt), an index of contractility. These changes were associated with elevation of oxidative stress, decreases of mitochondrial Bcl-2 and cytochrome c proteins, increases of cytosolic Bax and cytochrome c proteins, caspase 9 and caspase 3 activities and myocyte apoptosis, and downregulation of beta-adrenergic receptor sensitivity and SR Ca2+ ATPase. Combined treatment with vitamins C and E diminished oxidative stress, increased mitochondrial Bcl-2 protein, decreased cytosolic Bax, prevented cytochrome c release from mitochondria to cytosol, reduced caspase 9 and caspase 3 activities and myocyte apoptosis, blocked beta-adrenergic receptor desensitization and SR Ca2+ ATPase downregulation, and attenuated LV dilation and dysfunction in HF after MI. The results suggest that antioxidant therapy may be beneficial in HF.

Regulation of the sarcoplasmic reticulum Ca2+-ATPase expression in the hypertrophic and failing heartThis paper is part of a series in the Journal's “Made in Canada” section. The paper has undergone peer review

The sarcoplasmic reticulum (SR) plays a central role in the contraction and relaxation coupling in the myocardium. The SR Ca2+-ATPase (SERCA2) transports Ca2+ inside the SR lumen during relaxation of the cardiac myocyte. It is well known that diminished contractility of the hypertrophic cardiac myocyte is the main factor of ventricular dysfunction in the failing heart. A key feature of the failing heart is a decreased content and activity of SERCA2, which is the cause of some of the physiological defects observed in the hypertrophic cardiomyocyte performance that are important during transition of compensated hypertrophy to heart failure. In this review different possible mechanisms responsible for decreased transcriptional regulation of the SERCA2 gene are examined, which appear to be the primary cause for decreased SERCA2 expression in heart failure. The experimental evidence suggests that several signalling pathways are involved in the downregulation of SERCA2 expression in the hypertrophic and failing cardiomyocyte. Therapeutic upregulation of SERCA2 expression using replication deficient adenoviral expression vectors, pharmacological interventions using thyroid hormone analogues, β-adrenergic receptor antagonists, and novel metabolically active compounds are currently under investigation for the treatment of uncompensated cardiac hypertrophy and heart failure.