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Hypertrophy of myocytes in the heart ventricles is an important adaptation that in vivo occurs in response to a requirement for increased contractile power. It involves changes at the level of gene transcription, stimulation of the rate of protein synthesis (translation), and increased assembly of myofibrils. There is mounting evidence of the involvement of reversible protein phosphorylation and dephosphorylation in most of these processes. Protein kinase C, mitogen-activated protein kinases, and transcription factors have been implicated in the modulation of the transcriptional changes. Activation of translation may also be mediated through protein phosphorylation/dephosphorylation, although this has not been clearly established in the heart. Here we provide a critical overview of the signalling pathways involved in the hypertrophic response and provide a scheme to account for many of its features. [ABSTRACT FROM AUTHOR]

We identified the main changes in serum metabolites associated with severe (n = 46) and mild (n = 19) COVID-19 patients by gas chromatography coupled to mass spectrometry. The modified metabolic profiles were associated to an altered amino acid catabolism in hypoxic conditions. Noteworthy, three α-hydroxyl acids of amino acid origin increased with disease severity and correlated with altered oxygen saturation levels and clinical markers of lung damage. We hypothesize that the enzymatic conversion of α-keto-acids to α- hydroxyl-acids helps to maintain NAD recycling in patients with altered oxygen levels, highlighting the potential relevance of amino acid supplementation during SARS-CoV-2 infection. [ABSTRACT FROM AUTHOR]

Thioacetamide (TAA) administration is widely used for induction of liver cirrhosis in rats, where reactive oxygen radicals (ROS) and nitric oxide (NO) participate in development of liver damage. Cardiac dysfunction is an important complication of liver cirrhosis, but the role of ROS or NO in cardiac abnormalities during liver cirrhosis is not well understood. This was investigated in animals after TAA-induced liver cirrhosis and temporal changes in oxidative stress, NO and mitochondrial function in the heart evaluated. TAA induced elevation in cardiac levels of nitrate before development of frank liver cirrhosis, without gross histological alterations. This was accompanied by an early induction of P38 MAP kinase, which is influenced by ROS and plays an important signaling role for induction of iNOS. Increased nitrotyrosine, protein oxidation and lipid peroxidation in the heart and cardiac mitochondria, suggestive of oxidative stress, also preceded frank liver cirrhosis. However, compromised cardiac mitochondrial function with a decrease in respiratory control ratio and increased mitochondrial swelling was seen later, when cirrhosis was evident. In conclusion, TAA induces elevations in ROS and NO in the heart in parallel to early liver damage. This leads to later development of functional deficits in cardiac mitochondria after development of liver cirrhosis. [ABSTRACT FROM AUTHOR]

In part 1, we considered cytomolecular mechanisms underlying calcific aortic valve disease (CAVD), hemodynamics, and adaptive feedbacks controlling pathological left ventricular hypertrophy provoked by ensuing aortic valvular stenosis (AVS). In part 2, we survey diverse signal transduction pathways that precede cellular/molecular mechanisms controlling hypertrophic gene expression by activation of specific transcription factors that induce sarcomere replication in-parallel. Such signaling pathways represent potential targets for therapeutic intervention and prevention of decompensation/failure. Hypertrophy provoking signals, in the form of dynamic stresses and ligand/effector molecules that bind to specific receptors to initiate the hypertrophy, are transcribed across the sarcolemma by several second messengers. They comprise intricate feedback mechanisms involving gene network cascades, specific signaling molecules encompassing G protein-coupled receptors and mechanotransducers, and myocardial stresses. Future multidisciplinary studies will characterize the adaptive/maladaptive nature of the AVS-induced hypertrophy, its gender- and individual patient-dependent peculiarities, and its response to surgical/medical interventions. They will herald more effective, precision medicine treatments. [ABSTRACT FROM AUTHOR]

The present study was to determine the preventive effect of resveratrol (Res) on diabetes-induced cardiac dysfunction and the possible signaling pathway involved. Diabetes was induced in rats by injection of streptozotocin (STZ) at 45 mg/kg. The animals were randomly divided into three groups (10 rats/group): normal group, diabetes groups with or without Res (80 mg/kg) treatment. Biochemistry, cardiac function and fibrosis were detected. Moreover, pro-inflammatory cytokines were evaluated, and heart tissues were homogenized for western blot analysis to analyze the possible mechanisms. The results indicated that Res might regulate glucose and lipid metabolism, ameliorate cardiac function and fibrosis response in STZ-induced diabetic rats. The protective effects were consistent with the inhibition of inflammatory factors such as TNF-α, IL-6 and IL-1β. In addition, Res favorably shifted STZ-induced AT1R, ERK1/2 and p38 MAPK activation in rat heart. In conclusion, the results suggested that Res attenuated diabetes-induced cardiac dysfunction, and the effects were associated with attenuation inflammatory response and down-regulation of AT1R-ERK/p38 MAPK signaling pathway. [ABSTRACT FROM AUTHOR]

Epigenetic mechanisms are fundamental in cardiac adaptations, remodeling, reverse remodeling, and disease. A primary goal of translational cardiovascular research is recognizing whether disease-related changes in phenotype can be averted by eliminating or reducing the effects of environmental epigenetic risks. There may be significant medical benefits in using gene-by-environment interaction knowledge to prevent or reverse organ abnormalities and disease. This survey proposes that 'environmental' forces associated with diastolic RV/LV rotatory flows exert important, albeit still unappreciated, epigenetic actions influencing functional and morphological cardiac adaptations. Mechanisms analogous to Murray's law of hydrodynamic shear-induced endothelial cell modulation of vascular geometry are likely to link diastolic vortex-associated shear, torque and 'squeeze' forces to RV/LV adaptations. The time has come to explore a new paradigm in which such forces play a fundamental epigenetic role, and to work out how heart cells react to them. Findings from various imaging modalities, computational fluid dynamics, molecular cell biology and cytomechanics are considered. The following are examined, among others: structural dynamics of myocardial cells (endocardium, cardiomyocytes, and fibroblasts), cytoskeleton, nucleoskeleton, and extracellular matrix; mechanotransduction and signaling; and mechanical epigenetic influences on genetic expression. To help integrate and focus relevant pluridisciplinary research, rotatory RV/LV filling flow is placed within a working context that has a cytomechanics perspective. This new frontier in cardiac research should uncover versatile mechanistic insights linking filling vortex patterns and attendant forces to variable expressions of gene regulation in RV/LV myocardium. In due course, it should reveal intrinsic homeostatic arrangements that support ventricular myocardial function and adaptability. [ABSTRACT FROM AUTHOR]

Patients with rheumatic heart disease (RHD) often experience persistent atrial fibrillation (AF) associated with adverse atrial structural remodeling (ASR) manifested by atrial fibrosis and left atrial enlargement. The aim of this study was to explore the potential molecular signaling mechanisms for atrial fibrosis and ASR. Twenty RHD patients with persistent AF and 10 RHD patients with sinus rhythm (Group A) were recruited in our study, which all underwent transthoracic echocardiography. Right atrial appendage (RAA) tissue samples were obtained from these patients during mitral/aortic valve replacement operation. The AF patients were further divided into two groups according to left atrial diameter (LAD): Group B with LAD ranging 50-65 mm and Group C with LAD >65 mm. Histological examinations were performed with hematoxylin-eosin staining and Masson's trichrome staining. Atrial angiotensin II (AngII) content was measured by ELISA. Rac1 and STAT3 protein levels were determined by Western blot analysis. Hematoxylin-eosin staining demonstrated highly organized arrangement of atrial muscles in control Group A and significant derangement in both Group B and C AF patients with reduced cell density and increased cell size. Moreover, Masson's trichrome staining showed that atrial myocytes were surrounded by large trunks of collagen fibers in both Group B and C, but not in Group A. There was a positive correlation between atrial tissue fibrosis and LAD. AngII content was markedly higher in Group C than in Group B than in Group A, which was positively correlated with LAD. Similarly, Rac1 and STAT3 protein levels were found considerably higher in Group C and B than in Group A with excellent correlation to LAD. Our study unraveled for the first time the AngII/Rac1/STAT3 signaling as a mechanism for ASR thereby AF in a particular clinical setting-RHD patients with persistent AF and indicated inhibition of this pathway may help ameliorating adverse ASR. [ABSTRACT FROM AUTHOR]

Using conditional-knockout animals, we studied the expression of the genes involved in the canonical Wnt signaling pathway ( TCF-4, Axin-2) and the genes controlled by this signaling pathway ( c-fos, cyclin D1, c-myc, and Cx43) in the myocardium of mice under the condition of embryonic cardio-specific ablation of one allele of the β-catenin gene. The inhibition of the canonical Wnt signaling was observed in all age groups tested (1, 3, and 6 months). An analysis of the genes controlled by the canonical Wnt pathway allowed us to reveal changes of their expression in the tissue of animals with cardiac-specific β-catenin haploinsufficiency. The importance of a normally functioning canonical Wnt signaling for the growth and development of the adult heart is especially underlined in the article. [ABSTRACT FROM AUTHOR]

The contractile actomyosin cytoskeleton and its connection to the plasma membrane are critical for control of cell shape and migration. We identify three STRIPAK complex components, FAM40A, FAM40B and STRN3, as regulators of the actomyosin cortex. We show that FAM40A negatively regulates the MST3 and MST4 kinases, which promote the co-localization of the contractile actomyosin machinery with the Ezrin/Radixin/Moesin family proteins by phosphorylating the inhibitors of PPP1CB, PPP1R14A-D. Using computational modelling, in vitro cell migration assays and in vivo breast cancer metastasis assays we demonstrate that co-localization of contractile activity and actin-plasma membrane linkage reduces cell speed on planar surfaces, but favours migration in confined environments similar to those observed in vivo. We further show that FAM40B mutations found in human tumours uncouple it from PP2A and enable it to drive a contractile phenotype, which may underlie its role in human cancer. [ABSTRACT FROM AUTHOR]

Right ventricular (RV) failure in response to pulmonary hypertension (PH) is a severe disease that remains poorly understood. PH-induced pressure overload leads to changes in the RV free wall (RVFW) that eventually results in RV failure. While the development of computational models can benefit our understanding of the onset and progression of PH-induced pressure overload, detailed knowledge of the underlying structural and biomechanical events remains limited. The goal of the present study was to elucidate the structural and biomechanical adaptations of RV myocardium subjected to sustained pressure overload in a rat model. Hemodynamically confirmed severe chronic RV pressure overload was induced in Sprague-Dawley rats via pulmonary artery banding. Extensive tissue-level biaxial mechanical and histomorphological analyses were conducted to assess the remodeling response in the RV free wall. Simultaneous myofiber hypertrophy and longitudinal re-orientation of myo- and collagen fibers were observed, with both fiber types becoming more highly aligned. Transmural myo- and collagen fiber orientations were co-aligned in both the normal and diseased state. The overall tissue stiffness increased, with larger increases in longitudinal vs. circumferential stiffness. The latter was attributed to longitudinal fiber re-orientation, which increased the degree of anisotropy. Increased mechanical coupling between the two axes was attributed to the increased fiber alignment. Interestingly, estimated myofiber stiffness increased while the collagen fiber stiffness remained unchanged. The increased myofiber stiffness was consistent with clinical results showing titin-associated increased sarcomeric stiffening observed in PH patients. These results further our understanding of the underlying adaptive and maladaptive remodeling mechanisms and may lead to improved techniques for prognosis, diagnosis, and treatment for PH. [ABSTRACT FROM AUTHOR]

Cordycepin (3′-deoxyadenosine) isolated from Cordyceps militaris, a species of the fungal genus Cordyceps, has been shown to exhibit many pharmacological functions, such as anticancer, anti-inflammatory, and antioxidant activities. In this study, we investigated the preventive role of cordycepin in ischemic/reperfusion (I/R) injury of isolated rat hearts and anesthetized rats. After Sprague-Dawley rats received cordycepin (3, 10, and 30 mg/kg) or control (0.5 % carboxyl methylcellulose) orally once a day for a week, hearts were isolated and mounted on Langendorff heart perfusion system. Isolated hearts were perfused with Krebs-Henseleit buffer for 15-min pre-ischemic stabilization period and subjected to 30-min global ischemia and 30-min reperfusion. Cordycepin administration (10 mg/kg, p.o.) significantly increased left ventricular developed pressure during the reperfusion period compared to that in the control group, but without any effect on coronary flow. Cordycepin (10 mg/kg, p.o.) significantly increased the phosphorylation of Akt/GSK-3β/p70S6K pathways, which are known to modulate multiple survival pathways. In addition, cordycepin decreased Bax and cleaved caspase-3 expression while increasing Bcl-2 expression, Bcl-2/Bax ratio, and heme oxygenase (HO-1) expression in isolated rat hearts. In anesthetized rats subjected to 30 min occlusion of left anterior descending coronary artery/2.5-h reperfusion, cordycepin (1, 3, and 10 mg/kg, i.v.) administered 15 min before the onset of ischemia dose-dependently decreased the infarct size in left ventricle. In conclusion, cordycepin could be an attractive therapeutic candidate with oral activity against I/R-associated heart diseases such as myocardial infarction. [ABSTRACT FROM AUTHOR]

Heart disease is associated with increased sympathetic nerve activity and elevated levels of circulating catecholamines, resulting in chronic stimulation of the β-adrenergic receptors (β-AR) and consequent pathological cardiac remodeling. Experimentally, chronic administration of the β-AR agonist isoproterenol (ISO) has been most commonly used to model β-AR-induced cardiac remodeling. However, it remains unclear whether β-AR-mediated cardiac remodeling and dysfunction differs between sustained versus pulsatile (intermittent) exposure to a β-agonist. Here, we compare the effects of intermittent versus sustained administration of ISO on cardiac remodeling and function in mice. Animals were administered 5 mg (kg d) ISO for 2 weeks either by daily subcutaneous injection, or continuous infusion via an implanted osmotic minipump. Cardiac function and remodeling were determined by echocardiography, micromanometry and histology. Moreover, Western blotting and quantitative real-time polymerase chain reaction (qRT-PCR) were utilized to define the proteins and genes involved. Both sustained and intermittent administration of ISO resulted in a similar degree of cardiac hypertrophy (16% and 19%, respectively). However, mice receiving ISO by daily injection developed more severe ventricular systolic and diastolic dysfunction and myocardial fibrosis compared with mice receiving ISO via the osmotic minipump. The disparity in results between the delivery methods is suggested to be due, at least in part, to increased expression of fibrogenic factors, including connective tissue growth factor (CTGF) and NADPH oxidase (NOX4), in mice receiving intermittent application of ISO. In summary, compared with sustained exposure to a β-AR agonist, intermittent β-AR stimulation leads to more severe cardiac dysfunction and fibrosis. These findings not only further our understanding of β-AR function in the setting of cardiac pathophysiology, but also highlight that significant differences can result dependent upon the mode of experimental β-AR stimulation in inducing cardiomyopathy. [ABSTRACT FROM AUTHOR]

The β-selective adrenoreceptor agonist clenbuterol promotes both skeletal and cardiac muscle hypertrophy and is undergoing clinical trials in the treatment of muscle wasting and heart failure. We have previously demonstrated that clenbuterol induces a mild physiological ventricular hypertrophy in vivo with normal contractile function and without induction of α-skeletal muscle actin (αSkA), a marker of pathological hypertrophy. The mechanisms of this response remain poorly defined. In this study, we examine the direct action of clenbuterol on cardiocyte cultures in vitro. Clenbuterol treatment resulted in increased cell size of cardiac myocytes with increased protein accumulation and myofibrillar organisation characteristic of hypertrophic growth. Real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR) revealed elevated mRNA expression of ANP and brain natriuretic peptide (BNP) but without change in αSkA, consistent with physiological hypertrophic growth. Clenbuterol-treated cultures also showed elevated insulin-like growth factor I (IGF-1) mRNA and activation of the protein kinase Akt. Addition of either IGF-1 receptor-blocking antibodies or LY294002 in order to inhibit phosphatidylinositol 3-kinase, a downstream effector of the IGF-1 receptor, inhibited the hypertrophic response indicating that IGF-1 signalling is required. IGF-1 expression localised primarily to the minor population of cardiac fibroblasts present in the cardiocyte cultures. Together these data show that clenbuterol acts to induce mild cardiac hypertrophy in cardiac myocytes via paracrine signalling involving fibroblast-derived IGF-1. [ABSTRACT FROM AUTHOR]

Trichloroethylene is an organic solvent used as an industrial degreasing agent. Due to its widespread use and volatile nature, TCE is a common environmental contaminant. Trichloroethylene exposure has been implicated in the etiology of heart defects in human populations and animal models. Recent data suggest misregulation of Ca2+ homeostasis in H9c2 cardiomyocyte cell line after TCE exposure. We hypothesized that misregulation of Ca2+ homeostasis alters myocyte function and leads to changes in embryonic blood flow. In turn, changes in cardiac flow are known to cause cardiac malformations. To investigate this hypothesis, we dosed developing chick embryos in ovo with environmentally relevant doses of TCE (8 and 800 ppb). RNA was isolated from control and treated embryos at specific times in development for real-time PCR analysis of blood flow markers. Effects were observed on Endothelin-1 (ET-1), Nitric Oxide Synthase-3 (NOS-3) and Krüppel-like Factor 2 (KLF2) expression relative to TCE exposure and consistent with reduced flow. Further, we measured function in the developing heart after TCE exposure by isolating cardiomyocytes and measuring half-width of contraction and sarcomere lengths. These functional data showed a significant increase in half-width of contraction after TCE exposure. These data suggest that perturbation of cardiac function contributes to the etiology of congenital heart defects in TCE-exposed embryos. [ABSTRACT FROM AUTHOR]

MicroRNAs (miRNAs) are endogenous small non-coding ribonucleotides that regulate expression of target genes governing diverse biological functions. Mechanistically, miRNA binding to the target complimentary sequences on the mRNA results in degradation or inhibition of protein translation. The short guiding and binding sequence of miRNA allows them to target a large repertoire of transcripts altering expression of many proteins. These miRNA targets are not restricted to specific signaling pathways but to a diverse group of transcripts, which harbor the target complimentary sequence. miRNA targeting of these diverse transcripts result in regulation of multiple signaling pathways establishing miRNAs as regulators of systems biomolecular networks. Accumulating evidence shows that miRNAs play an important role in cardiac development, hypertrophy, and failure, thereby are integral to regulating adaptive and maladaptive remodeling. Since cardiac remodeling and failure is a complex phenotype, it is apparent that global biomolecular networks and miRNAs profiles would be altered. Indeed, the miRNA profiles are varied with different etiologies of heart failure indicating that miRNAs could be the global regulators. Although the idea of miRNA being global regulators is not new, we believe that the time is ripe to discuss the role of miRNAs in regulating biomolecular networks. We discuss in the review, the use of Ingenuity Pathways Analysis algorithms with predicted targets of altered miRNA in dilated cardiomyopathy to computationally determine the alterations in canonical functional pathways and to generate biomolecular networks. [ABSTRACT FROM AUTHOR]

Clenbuterol is currently being used as part of a clinical trial into a novel therapeutic approach for the treatment of end-stage heart failure. The purpose of this study was to determine the global pattern of myocardial gene expression in response to clenbuterol and to identify novel targets and pathways involved. Rats were treated with clenbuterol ( n = 6) or saline ( n = 6) for periods of 1, 3, 9, or 28 days. Rats treated for 28 days were also subject to continuous electrocardiogram analysis using implantable telemetry. RNA was extracted from rats at days 1 and 28 and used from microarray analysis, and further samples from rats at days 1, 3, 9, and 28 were used for analysis by real-time polymerase chain reaction. Clenbuterol treatment induced rapid development of cardiac hypertrophy with increased muscle mass at day 1 and elevated heart rate and QT interval throughout the 28-day period. Microarray analysis revealed a marked but largely transitory change in gene expression with 1,423 genes up-regulated and 964 genes down-regulated at day 1. Up-regulated genes revealed an unexpected association with angiogenesis and integrin-mediated cell adhesion and signaling. Moreover, direct treatment of endothelial cells cultured in vitro resulted in increased cell proliferation and tube formation. Our data show that clenbuterol treatment is associated with rapid cardiac hypertrophy and identify angiogenesis and integrin signaling as novel pathways of clenbuterol action. The data have implications both for our understanding of the physiologic hypertrophy induced by clenbuterol and for treatment of heart failure. [ABSTRACT FROM AUTHOR]

The prognosis for patients with human immunodeficiency virus (HIV) infection has improved remarkably as a result of effective antiretroviral therapy. This has resulted in an increased awareness of cardiac complications from HIV infection, including cardiomyopathy and overt heart failure. Mechanisms responsible for HIV cardiomyopathy and heart failure are unknown, but may include direct effects of HIV proteins on the heart. We have previously reported that the HIV envelope glycoprotein, gp120, has a p38 MAP kinase-dependent negative inotropic effect on adult rat ventricular myocytes (ARVM). This signaling pathway presumably results from the binding of gp 120 to a specific receptor on the surface of cardiac myocytes. HIV gp120 has been shown to bind to CD4, CXCR4, and CCR5 receptors on lymphocytes and macrophages. Accordingly, we sought to determine if HIV gp120 regulated its negative inotropic effect through activation of one of these binding sites on cardiac myocytes. AMD3100, a highly selective CXCR4 receptor antagonist, reversed HIV gp120-induced negative inotropic effect on ARVM. AMD3100 also blocked HIV gp120 phosphorylation of both p38 MAP kinase and Troponin I. The binding of gp120 to the CXCR4 receptor on ARVM was confirmed by co-immunoprecipitation. We conclude that the negative inotropic effect of HIV gp120 is mediated by a novel signaling pathway that begins with binding to a cardiac myocyte CXCR4 receptor, followed by phosphorylation of both p38 MAP kinase and Troponin I. [ABSTRACT FROM AUTHOR]

The mitogen-activated protein kinase (MAPK) pathways are known to be involved in various processes of growth, differentiation and cell death. In spite of their ubiquitous presence and seemingly enormous cross-talk with each other, their action is very specific. This review deals with various aspects of the three different MAPK pathways (ERK, p38 and JNK) and how their specificity is brought about. [ABSTRACT FROM AUTHOR]

Cardiac dysfunction following acute myocardial infarction is a major cause of death in the world and there is a compelling need for new therapeutic strategies. In this report we demonstrate that a direct cardiac injection of drug-loaded microparticles, formulated from the polymer poly(cyclohexane-1,4-diylacetone dimethylene ketal) (PCADK), improves cardiac function following myocardial infarction. Drug-delivery vehicles have great potential to improve the treatment of cardiac dysfunction by sustaining high concentrations of therapeutics within the damaged myocardium. PCADK is unique among currently used polymers in drug delivery in that its hydrolysis generates neutral degradation products. We show here that PCADK causes minimal tissue inflammatory response, thus enabling PCADK for the treatment of inflammatory diseases, such as cardiac dysfunction. PCADK holds great promise for treating myocardial infarction and other inflammatory diseases given its neutral, biocompatible degradation products and its ability to deliver a wide range of therapeutics. [ABSTRACT FROM AUTHOR]

The effects of angiotensin II (Ang II) on whole-cell large conductance Ca2+-activated K+ (BKCa) currents was investigated in control and Apurinic/apyrimidinic endonuclease1/redox factor 1 (APE1/Ref-1)-overexpressing human umbilical vein endothelial cells (HUVECs). Ang II blocked the BKCa current in a dose-dependent fashion, and this inhibition was greater in APE1/Ref-1-overexpressing HUVECs than in control HUVECs (half-inhibition values of 102.81 ± 9.54 nM and 11.34 ± 0.39 nM in control and APE1/Ref-1-overexpressing HUVECs, respectively). Pretreatment with the NADPH oxidase inhibitor diphenyleneiodonium (DPI) or knock down of NADPH oxidase (p22 phox) using siRNA increased the inhibitory effect of Ang II on the BKCa currents, similar to the effect of APE1/Ref-1 overexpression. In addition, application of Ang II increased the superoxide and hydrogen peroxide levels in the control HUVECs but not in APE1/Ref-1-overexpressing HUVECs. Furthermore, direct application of hydrogen peroxide increased BKCa channel activity. Finally, the inhibitory effect of Ang II on the BKCa current was blocked by an antagonist of the Ang II type 1 (AT1) receptor in both control and APE1/Ref-1-overexpressing HUVECs. From these results, we conclude that the inhibitory effect of Ang II on BKCa channel function is NADPH oxidase-dependent and may be promoted by APE1/Ref-1. [ABSTRACT FROM AUTHOR]

Abstract  Tumor necrosis factor-alpha (TNF-α), a proinflammatory cytokine involved in mitogen-activated protein kinase (MAPK) signaling pathways, contributes to the pathogenesis of cardiovascular diseases. Recently, suppressor of cytokine signaling-1 (SOCS-1) has been shown to modulate responses to TNF-α. However, whether SOCS-1 suppresses TNF-α-dependent apoptotic processes in cardiomyocytes and whether MAPK pathways mediate this effect have not been clearly elucidated. This study was carried out to define the role of SOCS-1 on TNF-α-induced apoptosis in neonatal rat cardiomyocytes and to investigate the signal pathways involved. Exposure to TNF-α (10 ng/ml for 24 h) significantly increased the number of apoptotic cells, the activity of caspase-8 and caspase-3, and the Bax/Bcl-xl ratio. In contrast, adenovirus-mediated gene transfer of SOCS-1 reversed the pro-apoptotic effect of TNF-α. Additionally, preincubation of cardiomyocytes with the extracellular signal-regulated kinase-1 and -2 (ERK1/2) inhibitor PD98059 attenuated the protective effect of SOCS-1, but the p38-MAPK inhibitor SB203580 and the c-Jun amino-terminal kinase (JNK) inhibitor SP600125 had no effect. Furthermore, the TNF-α-induced decrease in the phosphorylation of ERK1/2 was abolished by overexpression of SOCS-1. These findings suggest that SOCS-1 prevents TNF-α-induced apoptosis in cardiac myocytes via ERK1/2 pathway activation. [ABSTRACT FROM AUTHOR]

Electrical, contractile and structural remodeling have been characterized in atrial fibrillation (AF), and the latter is considered to be the major contributor to AF persistence. Recent data show that interstitial fibrosis can predispose to atrial conduction impairment and AF induction. The interplay between cardiac matrix metalloproteinases (MMPs) and their endogenous inhibitors, tissue inhibitors of MMPs (TIMPs), is thought to be critical in atrial extracellular matrix (ECM) metabolism. At the molecular level, angiotensin II, transforming growth factor-β1, inflammation and oxidative stress are particularly important for ECM dysregulation and atrial fibrotic remodeling in AF. Therefore, we review recent advances in the understanding of the atrial fibrotic process, the major downstream components in this remodeling process, and the expression and regulation of MMPs and TIMPs. We also describe the activation of bioactive molecules in both clinical studies and animal models to modulate MMPs and TIMPs and their effects on atrial fibrosis in AF. [ABSTRACT FROM AUTHOR]

Reactive oxygen species (ROS) have been shown to play a critical role in propagating the signals of several growth factors, peptide hormones, and cytokines, such as epidermal growth factor, insulin, and interleukin-1. We investigated a possible role for ROS generation in mediating the action of ET-1 on activation of ERK1/2 in cultured feline esophageal smooth muscle cells (ESMC). Confluent layers of ESMC were stimulated by 10nM ET-1; activation of ERK was examined by western blot analysis with phospho-specific antibodies of ERKs. ET-1 induced ERK1/2 phosphorylation in a dose- and time- dependent manner. ERK1/2 activation by ET-1 reached the maximal levels at 5min showing slight activation up to 20min, and then slowly declined. It was confirmed that the activation of ERK1/2 was reduced by MEK inhibitor PD98059. We observed the dose-dependent inhibitory effect of diphenyleneiodonium (DPI), an inhibitor of reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase on the ET-1-enhanced ERK1/2 phosphorylation in ESMC. Pretreatment of ESMC with N-acetylcysteine, a ROS scavenger, also attenuated the ET-1-induced ERK1/2 activation. In addition, DPI significantly inhibited the ET-1 - induced ROS production when ROS was measured as a function of DCF fluorescence. The results suggest that ROS might be critical mediators of the ET-1-induced ERK1/2 signaling events in ESMC. [ABSTRACT FROM AUTHOR]

Numerous neurohumoral factors such as endothelin (ET)-1 and angiotensin (Ang) II as well as the stretchstimulus act concertedly in the in vivo overloaded heart in inducing hypertrophy and failure. The primary cultureof rat neonatal cardiomyocytes is the only in vitro model that allows the comparative analysis of growthresponses and signaling events in response to different stimuli. In the present study, we examined stretched ratcardiomyocytes grown on flexible bottomed culture plates for hypertrophic growth responses (protein synthesis,protein/DNA ratio, and cell volume), F-actin filaments rearrangement (by confocal laser scanningmicroscopy), and for signaling events (activation of phospholipase C [PLC]-β, protein kinase C [PKC], mitogenactivatedprotein [MAP] kinases) and compared these responses with ET-1 (10-8 M)-stimulated cells. Cyclicstretch for 48 h induced hypertrophic growth in cardiomyocytes indicated by increases in the rate of protein synthesis,cell volume, and diameter, which were less pronounced in comparison to stimulation by ET-1. Duringcyclic stretch, we observed disoriented F-actin, particularly stress-fibers whereas during ET-1 stimulation, Factinsrearranged clearly in alignment with sarcomeres and fibers. The upstream part of signaling by cyclicstretch did not follow the PLCβ-PKC cascade, which, in contrast, was strongly activated during ET-1 stimulation.Cyclic stretch and, to greater extent, ET-1 stimulated downstream signaling through ERK, p38 MAP kinase,and JNK pathways, but the involvement of tyrosine kinase and PI3 kinase-Akt signaling during cyclic stretchcould not be proven. Taken together, our results demonstrate that both cyclic stretch and ET-1 induce hypertrophicresponses in cardiomyocytes with different effects on organization of F-actin stress fibers in case ofstretch. Furthermore, on the short-term basis, cyclical stretch, unlike ET-1, mediates its hypertrophic responsenot through activation of PLC-β and PKC but more likely through integrin-linked pathways, which both lead todownstream activation of the MAP kinase family. [ABSTRACT FROM AUTHOR]

Mitogen-activated protein kinase (MAPK) signal pathways are important components in signal transduction connecting cell-surface receptors to critical regulatory targets within cells, mediating multiple intracellular signal cascades and phosphorylating their target proteins, such as transcriptional factors ELK-1, SRE and AP-1, and finally activating the expression of intracellular functional genes. Zinc finger genes are some of the largest gene families in humans, and Zinc finger proteins play an essential role in altering gene expression by acting as transcription factors. Zinc finger proteins are also involved in multiple cell processes, including proliferation, differentiation and development, by interacting with DNA. Here, we reported the transcriptional activities of the domains of zinc finger gene ZNF569 taking advantage of MAPK pathway. Overexpression of ZNF569 in COS-7 cells dramatically inhibited the transcriptional repressor activities of SRE and AP-1, which was also confirmed by subcellular localization analysis. Report assays indicated that the potent repression domains of ZNF569 were the KRAB and ZNF motifs. The results suggested that ZNF569 protein might act as a transcriptional repressor in MARK signaling pathway to regulate cellular processes. [ABSTRACT FROM AUTHOR]

Transforming growth factor (TGF-β) is a multifunctional peptide growth factor that has an important role in the regulation of cell growth, differentiation, and repair in a variety of tissues. In mammals, the cytokine has three isoforms, TGF-β1, TGF-β2, and TGF-β3. TGF- β1 is up-regulated by Ang II and induction of TGF-β1 causes cardiac fibrosis. The stimulus that triggers the expression of TGF-β1 may be repeated causing continual injury, which is associated with an increase in the activity of Ang II in heart tissue. The interplay between Ang II and TGF-β1 causes continued activation that may result in chronic hypertension and progressive myocardial fibrosis, leading to heart failure. The regulation of TGF-β1 secretion and action involves complex transcriptional events. Overproduction of TGF-β1 underlies tissue fibrosis. Understanding the actions and signaling transduction of TGF-β could lead to the development of therapeutic options that may be effective in inhibiting myocardial fibrosis triggered by TGF-β1 in heart failure. [ABSTRACT FROM AUTHOR]

The mammalian heart is a dynamic organ that can grow and change to accommodate alterations in its workload. During development and in response to physiological stimuli or pathological insults, the heart undergoes hypertrophic enlargement, which is characterized by an increase in the size of individual cardiac myocytes. Recent findings in genetically modified animal models implicate important intermediate signal-transduction pathways in the coordination of heart growth following physiological and pathological stimulation. [ABSTRACT FROM AUTHOR]

On the basis of evidence collected from the literature, we propose a general model by which protein kinase (PK) A and the different PKC isoforms can inversely affect cell growth. Molecular switches, which are able to direct the signal towards antiproliferative or mitogenic pathways, are the different isoforms of Raf and PKC. Conflicting data are also reported and discussed in an attempt to reconcile them. [ABSTRACT FROM AUTHOR]

The key components to the molecular understanding of the pathophysiology of various forms of heart failure involve global and/or large-scale identifications of proteins, their patterns of expression, posttranslational modifications, and functional characterization. Particularly, proteins involved in the induction of cardiac (mal)adaptive hypertrophic growth, interstitial fibrosis, and contractile dysfunction are of interest. In general, with the accumulation of vast amounts of DNA sequences in databases, researchers have become aware that merely having complete sequences of genomes and transcriptional changes for thousands of genes simultaneously will not be sufficient to elucidate, in molecular terms, the etiology and pathophysiology of cardiovascular disease. In the last decade, a new technology called proteomics has become available that allows biological and (patho)physiological questions to be approached exclusively from the protein perspective. Proteomics may enable us to map the entire complement of proteins expressed by the heart at any time and condition. This approach creates the unique possibility to identify, by differential analysis, protein alterations associated with the etiology of heart disease and its progression, outcome, and response to therapy. To illustrate the true power of proteomics, most of the currently available methodologies are first reviewed, including their limitations. This review also deals with the current status and the perspectives of proteomics applications in research on heart failure in general. Furthermore, examples of our recent data on global protein profiling of the pressure-overloaded rat right ventricle and of endothelin-1-stimulated cultures of neonatal rat cardiac myocytes are provided. The last section is devoted to the continuous advances in proteomic technologies, including protein separation methods, mass spectrometric instrumentation, computational analysis, and bioinformatic tools, together with integrative databases. [ABSTRACT FROM AUTHOR]

Total protein kinase C (PKC) activity, its isoform expression, and concentration and fatty acid (FA) composition of diacylglycerol (DAG) were determined in the left ventricular myocardium of the rat during early postnatal development (d 2, 3, 5, 7, and 10). PKC activity measured by the incorporation of 32P into histone IIIS decreased between d 2 and 10 in the homogenate as well as in cytosolic, membrane (100,000g), and nuclear-cytoskeletal-myofilament fractions (1000g). Likewise, the expression of PKC isoforms (a, d, and e) determined by immunoblotting generally declined during the period analyzed, although with a variable pattern. In the membrane and nuclear cytoskeletal myofilament fractions, PKCd and PKCe expression decreased markedly by d 3, returning to or close to the d 2 level immediately on d 5. PKCa expression in the membrane fraction remained almost unchanged by d 7, declining thereafter. PKCd and PKCe were associated predominantly with particulate fractions, whereas PKCa was more abundant in the cytosolic fraction. DAG concentration exhibited a significant decline by d 5, consistent with the decrease in maximal PKC activity. The unsaturation index of FA in DAG tended to decrease on d 3 owing to the lowered proportion of all polyunsaturated FA of n-6 and n-3 series. These results demonstrate that the developmental decrease in PKC activity and expression in the rat myocardium is not linear and that subcellular localization of the enzyme exhibits isoform-specific day-by-day changes during the early postnatal period. These changes are compatible with the view that PKC signaling may be involved in the control of a rapid switch of myocardial growth pattern during the first week of life. [ABSTRACT FROM AUTHOR]

Chronic pressure overload (PO) and volume overload (VO) result in morphologically and functionally distinct forms of myocardial hypertrophy. However, the molecular mechanism initiating these two types of hypertrophy is not yet understood. Data obtained from different cell types have indicated that the mitogen-activated protein kinases (MAPKs) comprising c-Jun NH2-terminal kinase (JNK), extracellular signal-regulated kinase (ERK), and p38 play an important role in transmitting signals of stress stimuli to elicit the cellular response. We tested the hypothesis that early induction of MAPKs differs in two types of overload on the heart and associates with distinct expression of hypertrophic marker genes, namely ANF, a-myosin heavy chain (a-MHC), and -MHC. In rats, VO was induced by aortocaval shunt and PO by constriction of the abdominal aorta. The PO animals were further divided into two groups depending on the severity of the constriction, mild (MPO) and severe pressure overload (SPO), having 35 and 85% aortic constriction, respectively. Early changes in MAPK activity (2120 min and 1 to 2 d) were analyzed by the in vitro kinase assay using kinase-specific antibodies for p38, JNK, and ERK2. The change in expression of hypertrophy marker genes was examined by Northern blot analysis. In VO hypertrophy, the activity of p38 was markedly increased (10-fold), without changing the activity of ERK and JNK. However, during PO hypertrophy, the activity of JNK was significantly increased (two- to sixfold) and depended on the severity of the load. The activity of p38 was not changed in MPO hypertrophy, whereas it was slightly elevated (50%) in hearts with SPO. Similarly, ERK activity was not changed in hearts with MPO, but a transient rise in activity was observed in hearts with SPO. The expression of ANF and -MHC genes was elevated in both PO and VO hypertrophy; however, this change was much greater in hearts subjected to PO than VO hypertrophy. a-MHC expression was downregulated in PO but remained unchanged in VO hypertrophy hearts. Thus, these results demonstrate differential activation of MAPKs in two types of cardiac hypertrophy and this, in part, may contribute to differential expression of cardiac muscle gene expression, giving rise to unique cardiac phenotype associated with different hemodynamic overloads. [ABSTRACT FROM AUTHOR]

Hypertension leads to impaired contractile function. This study examined the impact of inhibition of sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) by thapsigargin or cyclopiazonic acid (CPA) on cardiac contractile function in ventricular myocytes from Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR). Mechanical properties were examined including peak shortening (PS), time-to-PS (TPS), time-to-90% relengthening (TR90), and maximal velocity of shortening/relengthening (±dL/dt). Intracellular Ca2+ transients were evaluated as fura-2 fluorescent intensity (FFI), excitation-induced change in FFI (ΔFFI=peak-basal), and fluorescence decay rate (τ). Expression of Ca2+ regulatory proteins SERCA2a, Na+−Ca2+ exchanger (NCX), and phospholamban (PLB) were assessed by reverse transcriptase polymerase chain reaction and Western blot. SHR rats exhibited elevated blood pressure. SHR myocytes displayed decreased PS±dL/dt, peak FFI, and ΔFFI; shortened TPS; prolonged τ with normal TR90; and basal FFI compared with WKY myocytes. Inhibition of SERCA with thapsigargin (5μ M) or CPA (10 μ M) significantly depressed PS±dL/dt, baseline FFI, and ΔFFI, and prolonged TPS, TR90, and τ in WKY myocytes. However, SHR myocytes were relatively insensitive to thapsigargin or CPA with only TPS and TR90 prolonged. Both mRNA and protein expressions of NCX and PLB were significantly enhanced, whereas SERCA2a protein abundance was reduced in SHR rats compared with the WKY group. Our data suggest that inhibition of SERCA function differentially affected cardiac contractile function in ventricular myocytes from normotensive and hypertensive rats possibly through reduced SERCA2a, elevated PLB, and NCX expression under hypertension. [ABSTRACT FROM AUTHOR]

The RAS-mitogen activated protein kinase (MAPK) signalling pathway has long been viewed as an attractive pathway for anticancer therapies, based on its central role in regulating the growth and survival of cells from a broad spectrum of human tumours. Small-molecule inhibitors designed to target various steps of this pathway have entered clinical trials. What have we recently learned about their safety and effectiveness? Will the MAPK pathway prove amenable to therapeutic intervention? [ABSTRACT FROM AUTHOR]

Congestive heart failure is the leading cause of death in the Western world. Abnormal intracellular calcium (Ca2+) handling is central to the pathogenesis of heart failure because it contributes to a decrease in ventricular contractile function. Chronic hyperactivity of the sympathetic nervous system causes increased phosphorylation of the ryanodine receptor intracellular Ca2+-release channel, a key Ca2+-handling protein in the heart, by protein kinase A. Alteration of the structure and function of ryanodine receptors contributes to defective intracellular Ca2+ handling and an increased propensity for cardiac arrhythmias in failing hearts. Novel therapeutic strategies are now being evaluated to specifically correct defective Ca2+-handling in heart failure. [ABSTRACT FROM AUTHOR]

Cardiac cells respond to external stimuli by activating signal-transduction cascades involving protein and lipid kinases. These enzymes are attractive therapeutic targets as they are responsible for the direct or indirect control of most signalling pathways in cells. Existing therapies for heart failure are directed against the renin-angiotensin system and the β-adrenoceptor, and prevent the initiation of signalling cascades. However, as molecular signalling events in the progression of heart failure are elucidated, new downstream signalling targets have emerged as candidates for therapeutic intervention. [ABSTRACT FROM AUTHOR]

Demonstrates that exposure of a rat brain synaptosome fraction to the amyloid beta peptide fragment BetaA(25-35), but not the inverted peptide BetaA(35-25), stimulated production of reactive oxygen species (ROS) in concentration- and time-dependent manner. ROS formation by the tyrosine kinase inhibitor genistein, mitogen-activated protein kinase inhibitor U0126, and phospholipase A[sub 2] inhibitor 7,7-dimethyl-(5Z,8Z)-eicosadienoic acid.

Parathyroid hormone-related peptide (PTHrP) receptors, coupled to trimeric G proteins, operate in most target cells through at least three different transduction routes: Gαs-mediated stimulation of adenylylcyclase (AC), Gαq-mediated activation of phospholipase Cβ (PLC) and mitogen-activated protein kinase (MAPK) activation. In this study we investigated the relative role of different pathways in human skin fibroblast prolifera-tion. Using chemical inhibitors and activators of signal transduction, we demonstrated that: (i) AC/cAMP and PLC/1,4,5 inositol triphosphate/diacylglycerol second-messenger systems are simultaneously activated following PTHrP binding to its receptors; (ii) the mitogenic response to PTHrP derives from a balance between two counteracting pathways – an activating route mediated by protein kinase C (PKC) and an inhibitory route mediated by protein kinase A (PKA); (iii) PTHrP mitogenic effects are largely dependent on MAPKs, whose activity can be modulate d by both PKA and PKC. Our results indicate that MAPKs are common targets of both transduction routes and, at the same time, their point of divergence in mediating PTHrP dual and opposite mitogenic effects. [ABSTRACT FROM AUTHOR]

Smooth muscles are important constituents of vertebrate organisms that provide for contractile activity of internal organs and blood vessels. Basic molecular mechanism of both smooth and striated muscle contractility is the force-producing ATP-dependent interaction of the major contractile proteins, actin and myosin II molecular motor, activated upon elevation of the free intracellular Ca2+ concentration ([Ca2+]i). However, whereas striated muscles display a proportionality of generated force to the [Ca2+]i level, smooth muscles feature molecular mechanisms that modulate sensitivity of contractile machinery to [Ca2+]i. Phosphorylation of proteins that regulate functional activity of actomyosin plays an essential role in these modulatory mechanisms. This provides an ability for smooth muscle to contract and maintain tension within a broad range of [Ca2+]i and with a low energy cost, unavailable to a striated muscle. Detailed exploration of these mechanisms is required to understand the molecular organization and functioning of vertebrate contractile systems and for development of novel advances for treating cardiovascular and many other disorders. This review summarizes the currently known and hypothetical mechanisms involved in regulation of smooth muscle Ca2+-sensitivity with a special reference to phosphorylation of regulatory proteins of the contractile machinery as a means to modulate their activity. [ABSTRACT FROM AUTHOR]

The modern classification of small heat shock proteins (sHsp) is presented and peculiarities of their primary structure and the mechanism of formation of oligomeric complexes are described. Data on phosphorylation of sHsp by different protein kinases are presented and the effect of phosphorylation on oligomeric state and chaperone activity of sHsp is discussed. Intracellular location of sHsp under normal and stress conditions is described and it is emphasized that under certain condition sHsp interact with different elements of cytoskeleton. The literature concerning the effect of sHsp on polymerization of actin in vitro is analyzed. An attempt is made to compare effects of sHsp on polymerization of actin in vitro with the results obtained on living cells under normal conditions and after heat shock or hormone action. The literature concerning possible effects of sHsp on cell motility is also analyzed. [ABSTRACT FROM AUTHOR]

Investigates the complex interactions that occur between the receptors and the signalling pathways of the heart. Concepts of receptor regulation; Analysis of the G-protein-coupled receptor; Effect of beta-blockade on cardiac function.

Mild cerebral anoxic/ischemic/stress insults promote ‘tolerance’ and thereby protect the brain from subsequent ‘lethal’ anoxic/ischemic insults. We examined whether specific activation of PKC α, δ, ∈, or ζ isoforms is associated with ischemic preconditioning (IPC) in rat brain. IPC was produced by a 2-minute global cerebral ischemia. Membrane and cytosolic fractions of the hippocampi were immunoblotted using specific antibodies for PKCα, δ, ∈, and ζ. PKCα showed a significant translocation to the membrane fraction from 30 min to 4 h and PKCδ at 4 h following IPC. In contrast, the membrane/cytosol ratio of PKC∈ showed a tendency to decrease at 30 min and 8 h, and the membrane/cytosol ratio of PKCζ was significantly decreased from 30 min to 24 h following IPC. These findings indicate PKC isoform-specific membrane translocations in the hippocampus after brief global brain ischemia and suggest that activation of PKCα and PKCδ may be associated with IPC-induced tolerance in the rat hippocampus. [ABSTRACT FROM AUTHOR]

Stretching of cardiac muscle modulates contraction through the enhancement of the Ca[sup 2+] transient, but how this occurs is still not known. We found that stretching of myocytes modulates the elementary Ca[sup 2+] release process from ryanodine-receptor Ca[sup 2+]-release channels (RyRCs), Ca[sup 2+] sparks and the electrically stimulated Ca[sup 2+] transient. Stretching induces Ptdlns-3-OH kinase (PI(3)K)-dependent phosphorylation of both Akt and the endothelial isoform of nitric oxide synthase (NOS), nitric oxide (NO) production, and a proportionate increase in Ca[sup 2+]-spark frequency that is abolished by inhibiting NOS and PI(3)K. Exogenously generated NO reversibly increases Ca[sup 2+]-spark frequency without cell stretching. We propose that myocyte NO produced by activation of the PI(3)K-Akt-endothelial NOS axis acts as a second messenger of stretch by enhancing RyRC activity, contributing to myocardial contractile activation. [ABSTRACT FROM AUTHOR]

In heart tissue from mice lacking the intermediate filament (IF) desmin, mitochondria show an abnormal shape and distribution (Thornell et al., 1997). In the present study we have isolated heart mitochondria from desmin null (D−/−) and control (D+/+) mice, and analyzed their composition by SDS–PAGE, immunoblotting, and enzyme measurements. We found both in vitro and in situ that the conventional kinesin, the microtubule-associated plus-end directed motor, was frequently associated with D+/+ heart mitochondria, but not with D−/− heart mitochondria, suggesting that the positioning of mitochondria in heart is a dynamic event involving the IF desmin, the molecular motor kinesin, and, most likely, the microtubules (MT) network. Furthermore, an increased capacity in energy production was found, as indicated by a threefold higher creatine kinase activity in heart mitochondria from D−/− compared to D+/+ mice. We also observed a significantly lower amount of cytochrome c in heart mitochondria from D−/− mice, and a relocalization of Bcl-2, which may indicate an apoptotic condition in the cell leading to the earlier reported pathological events, such as cardiomyocytes degeneration and calcinosis of the heart (Thornell et al., 1997). [ABSTRACT FROM AUTHOR]

Although nitric oxide (NO) plays key signaling roles in the nervous systems, excess NO leads to cell death. In this study, the involvement of p38 mitogen-activated protein kinase (p38 MAPK) and apoptosis signal-regulating kinase-1 (ASK1) in NO-induced cell death was investigated in PC12 cells. NO donor transiently activated p38 MAPK in the wild type parental PC12 cells, whereas the p38 MAPK activation was abolished in NO-resistant PC12 cells (PC12-NO-R). p38 MAPK inhibitors protected the cells against NO-induced death, whereas the inhibitors were not significantly protective against the cytotoxicity of reactive oxygen species. Stable transfection with dominant negative p38 MAPK mutant reduced NO-induced cell death. Stable transfection with dominant negative mutant of ASK1 attenuated NO-stimulated activation of p38 MAPK and decreased NO-induced cell death. These results suggest that p38 MAPK and its upstream regulator ASK1 are involved in NO-induced PC12 cell death. [ABSTRACT FROM AUTHOR]

Presents a report on the 4.25-kilobase region surrounding the PH05 gene and how it is acetylated extensively by ESA1 and GCN5 and deacetylated by HDA1 and RPD3. How the widespread histone modification affects three separate chromosomal regions examined; Indication that targeted modification occurs in a background of global acetylation and deacetylation that not only reduces basal transcription, but allows a rapid return to the initial state of acetylation when targeting is removed.

Presents a report on the inhibition of the Betagamma-subunit of G protein (GBetagamma) and how it attenuates hydrogen peroxide H[sub2]O[sub2]-induced ERK activation in rat neonatal cardiomyocytes. Identification of reactive oxygen species as central mediators in certain signalling events; Analysis using heterotrimeric G[sub0} and its individual subunits; Conclusion that Galpha[sub1] and Galpha[sub0] are targets of oxidative stress for activation of ERK.

The syndrome of congestive heart failure (CHF) is an entity of ever increasing clinical significance. CHF is characterized by a steady decrease in cardiac pump function, which is eventually lethal. The mechanisms that underlie the decline in cardiac function are incompletely understood. A central theme in solving the mystery of heart failure is the identification of mechanisms by which the myofilament contractile machine of the myocardium is altered in CHF and how these alterations act in concert with pathways that signal cell growth and death. The cardiac myofilaments are a point of confluence of signals that promote the hypertrophic/failure process. Our hypothesis is that a prevailing hemodynamic stress leads to an increased strain on the myocardium. The increased strain in turn leads to miscues of the normal physiological pathway by which heart cells are signaled to match and adapt the intensity and dynamics of their mechanical activity to prevailing hemodynamic demands. These miscues result in a maladaptation to the stressor and failure of the heart to respond to hemodynamic loads at optimal end diastolic volumes. The result is a vicious cycle exacerbating the failure. Cardiac myofilament activity, the ultimate determinant of cellular dynamics and force, is a central player in the integration and regulation of pathways that signal hypertrophy and failure. © 2000 Biomedical Engineering Society. PAC00: 8719Hh, 8719Ff, 8719Xx, 8719Rr, 8717-d [ABSTRACT FROM AUTHOR]

Recent evidence suggests that energy substrate metabolism forms the link between gene expression and contractile function of the heart. This hypothesis draws on three seemingly unconnected observations, made in 1941 by three different investigators. The first gave rise to the concept of the dynamic nature of body constituents, the second to the concept of one gene for one enzyme, and the third to the concept of energy conservation in the phosphate bond of adenosine triphosphate (ATP), the “∼ P.” The heart employs different mechanisms to adapt to acute and to sustained changes in energy demand. While acute changes in energy demand are met by the coordinated activation or inactivation of enzymes, chronic changes in energy demand are met by adjustments in the rate of “metabolic” gene expression which are often isoform specific. Transcriptional analysis by quantitative polymerase chain reaction (PCR) defines changes in energy substrate metabolism in response to an altered physiologic environment at the transcriptional level. The paradigm of cardiac hypertrophy and atrophy has revealed a surprisingly uniform and rapid response in cardiac gene expression including the reactivation of fetal metabolic genes. The physiologic consequences are revealed in a shift in substrate utilization from fatty acids to glucose. Clinical consequences include a change in metabolic gene expression of the failing human heart, including the downregulation of glucose transporters and the enzymes of fatty acid metabolism. Although it is possible to study regulation of metabolism at the level of gene expression, the complexities of the interactions between metabolic intermediates and transcription factors may be difficult to elucidate by simple reductionist approaches. A model of feedback/feedforward between genes and proteins is needed to explain the principle of reestablishing homeostatic control of metabolism as cellular and external environments change. © 2000 Biomedical Engineering Society. PAC00: 8719Hh, 8716Sr [ABSTRACT FROM AUTHOR]