Cardiac resynchronization sensitizes the sarcomere to calcium by reactivating GSK-3β

Cardiac resynchronization therapy (CRT), the application of biventricular stimulation to correct discoordinate contraction, is the only heart failure treatment that enhances acute and chronic systolic function, increases cardiac work, and reduces mortality. Resting myocyte function also increases after CRT despite only modest improvement in calcium transients, suggesting that CRT may enhance myofilament calcium responsiveness. To test this hypothesis, we examined adult dogs subjected to tachypacing-induced heart failure for 6 weeks, concurrent with ventricular dyssynchrony (HF(dys)) or CRT. Myofilament force-calcium relationships were measured in skinned trabeculae and/or myocytes. Compared with control, maximal calcium-activated force and calcium sensitivity declined globally in HF(dys); however, CRT restored both. Phosphatase PP1 induced calcium desensitization in control and CRT-treated cells, while HF(dys) cells were unaffected, implying that CRT enhances myofilament phosphorylation. Proteomics revealed phosphorylation sites on Z-disk and M-band proteins, which were predicted to be targets of glycogen synthase kinase-3β (GSK-3β). We found that GSK-3β was deactivated in HF(dys) and reactivated by CRT. Mass spectrometry of myofilament proteins from HF(dys) animals incubated with GSK-3β confirmed GSK-3β–dependent phosphorylation at many of the same sites observed with CRT. GSK-3β restored calcium sensitivity in HF(dys), but did not affect control or CRT cells. These data indicate that CRT improves calcium responsiveness of myofilaments following HF(dys) through GSK-3β reactivation, identifying a therapeutic approach to enhancing contractile function

Mechanisms of Ghrelin anti-heart failure: inhibition of Ang II-induced cardiomyocyte apoptosis by down-regulating AT1R expression

Background

Ghrelin is a novel growth hormone–releasing peptide administered to treat chronic heart failure (CHF). However, the underlying mechanism of its protective effects against heart failure (HF) remains unclear.

Methods and Results

A total of 68 patients with CHF and 20 healthy individuals were included. The serum levels of Angiotensin II (Ang II) and ghrelin were measured using ELISA. The results showed that Ang II and ghrelin were both significantly increased in CHF patients and that the ghrelin levels were significantly positively correlated with Ang II. The left anterior descending coronary artery was ligated to establish a rat model of CHF, and cultured cardiomyocytes from neonatal rats were stimulated with Ang II to explore the role of ghrelin in CHF. The results showed that ghrelin inhibited cardiomyocyte apoptosis both in vivo and in vitro. Furthermore, caspase-3 expression was examined, and the results revealed that Ang II induces cardiomyocyte apoptosis through the caspase-3 pathway, whereas ghrelin inhibits this action. Lastly, to further elucidate the mechanism by which ghrelin inhibits Ang II action, the expression of the AT1 and AT2 receptors was evaluated; the results showed that Ang II up-regulates the AT1 and AT2 receptors in cardiomyocytes, whereas ghrelin inhibits AT1 receptor up-regulation but does not affect AT2 receptor expression.

Conclusions

These data suggest that the serum levels of ghrelin are significantly positively correlated with Ang II in CHF patients and that ghrelin can inhibit Ang II-induced cardiomyocyte apoptosis by down-regulating AT1R, thereby playing a role in preventing HF.

Vidarabine is neither a potent nor a selective AC5 inhibitor

Vidarabine was the first clinically approved antiviral drug, but due to safety and efficacy issues the drug is currently only used topically for herpes virus keratitis. Scientific interest in vidarabine has been recently renewed due to the fact that the compound exhibits beneficial effects in animal models of heart failure and cancer, replicating effects of the knockout of adenylyl cyclase 5 (AC5). Therefore, vidarabine has been suggested to mediate these effects via selective inhibition of AC5. Based on these results, clinical studies with vidarabine in humans for heart failure and cancer have been proposed. Here, evidence is presented that vidarabine is neither a potent nor a selective AC5 inhibitor. Greatest caution should be exerted when proposing new mechanisms of actions and clinical uses for vidarabine.

SERCA2a gene therapy in heart failure: an anti-arrhythmic positive inotrope

Therapeutic options that directly enhance cardiomyocyte contractility in chronic heart failure (HF) therapy are currently limited and do not improve prognosis. In fact, most positive inotropic agents, such as β-adrenoreceptor agonists and PDE inhibitors, which have been assessed in HF patients, cause increased mortality as a result of arrhythmia and sudden cardiac death. Cardiac sarcoplasmic reticulum Ca(2)(+) -ATPase2a (SERCA2a) is a key protein involved in sequestration of Ca(2)(+) into the sarcoplasmic reticulum (SR) during diastole. There is a reduction of SERCA2a protein level and function in HF, which has been successfully targeted via viral transfection of the SERCA2a gene into cardiac tissue in vivo. This has enhanced cardiac contractility and reduced mortality in several preclinical models of HF. Theoretical concerns have been raised regarding the possibility of arrhythmogenic adverse effects of SERCA2a gene therapy due to enhanced SR Ca(2)(+) load and induction of SR Ca(2)(+) leak as a result. Contrary to these concerns, SERCA2a gene therapy in a wide variety of preclinical models, including acute ischaemia/reperfusion, chronic pressure overload and chronic myocardial infarction, has resulted in a reduction in ventricular arrhythmias. The potential mechanisms for this unexpected beneficial effect, as well as mechanisms of enhancement of cardiac contractile function, are reviewed in this article.

Metabolic rates of ATP transfer through creatine kinase (CK Flux) predict clinical heart failure events and death

Morbidity and mortality from heart failure (HF) are high, and current risk stratification approaches for predicting HF progression are imperfect. Adenosine triphosphate (ATP) is required for normal cardiac contraction, and abnormalities in creatine kinase (CK) energy metabolism, the primary myocardial energy reserve reaction, have been observed in experimental and clinical HF. However, the prognostic value of abnormalities in ATP production rates through CK in human HF has not been investigated. Fifty-eight HF patients with nonischemic cardiomyopathy underwent ³¹P magnetic resonance spectroscopy (MRS) to quantify cardiac high-energy phosphates and the rate of ATP synthesis through CK (CK flux) and were prospectively followed for a median of 4.7 years. Multiple-event analysis (MEA) was performed for HF-related events including all-cause and cardiac death, HF hospitalization, cardiac transplantation, and ventricular-assist device placement. Among baseline demographic, clinical, and metabolic parameters, MEA identified four independent predictors of HF events: New York Heart Association (NYHA) class, left ventricular ejection fraction (LVEF), African-American race, and CK flux. Reduced myocardial CK flux was a significant predictor of HF outcomes, even after correction for NYHA class, LVEF, and race. For each increase in CK flux of 1 μmol g⁻¹ s⁻¹, risk of HF-related composite outcomes decreased by 32 to 39%. These findings suggest that reduced CK flux may be a potential HF treatment target. Newer imaging strategies, including noninvasive ³¹P MRS that detect altered ATP kinetics, could thus complement risk stratification in HF and add value in conditions involving other tissues with high energy demands, including skeletal muscle and brain.

Exposure of cardiomyocytes to angiotensin II induces over-activation of monoamine oxidase type A: implications in heart failure

Several evidences indicate that increased cardiac mitochondrial monoamine oxidase type A (MAO-A) activity associates with a failing phenotype. Till now, the mechanism underlying such relation is largely unknown. We explored the hypothesis that exposure of cardiomyocytes to AT-II caused activation of MAO-A and also of catalase and aldehyde dehydrogenase activities, enzymes involved in degrading MAO's end products. Left ventricular cardiomyocytes were isolated from normoglycemic (N) and streptozotocin-injected (50 mg/kg) rats (D) treated or not treated with losartan (20 mg/kg/day in drinking water; DLos and NLos, respectively), a type 1 receptor (AT1) antagonist, for 3 weeks. In each group of cells, MAO, catalase and aldehyde dehydrogenase activities were measured radiochemically and spectrophotometrically. The same enzymes were also measured in HL-1 immortalized cardiomyocytes not exposed and exposed to AT-II (100 nM for 18 h) in the absence and in the presence of irbesartan (1 μM), an AT1 antagonist. MAO-A catalase and aldehyde dehydrogenase activities were found significantly higher in D, than in N cells. MAO-A positively correlated with catalase activity in D cells. MAO-A and aldehyde dehydrogenase but not catalase over-activation, were prevented in DLos cells. Similarly, MAO-A activity, but not catalase and aldehyde dehydrogenase increased significantly in HL-1 cells acutely exposed to AT-II and this increase was prevented when irbesartan, an AT1 antagonist was present. Over-activation of cardiomyocyte MAO-A activity is among acute (18 h) and short-term (2-weeks of diabetes) cardiac effects of AT-II and a novel target of AT1 antagonists, first line treatments of diabetic cardiomyopathy.

Volume overload induces differential spatiotemporal regulation of myocardial soluble guanylyl cyclase in eccentric hypertrophy and heart failure

Nitric oxide activation of soluble guanylyl cyclase (sGC) blunts the cardiac stress response, including cardiomyocyte hypertrophy. In the concentric hypertrophied heart, oxidation and re-localization of myocardial sGC diminish cyclase activity, thus aggravating depressed nitric oxide-cyclic guanosine monophosphate (NO-cGMP) signaling in the pressure-overloaded failing heart. Here, we hypothesized that volume-overload differentially disrupts myocardial sGC activity during early compensated and late decompensated stages of eccentric hypertrophy. To this end, we studied the expression, redox state, subcellular localization, and activity of sGC in the left ventricle of dogs subjected to chordal rupture-induced mitral regurgitation (MR). Unoperated dogs were used as Controls. Animals were studied at 4weeks and 12months post chordal rupture, corresponding with early (4wkMR) and late stages (12moMR) of eccentric hypertrophy. We found that the sGC heterodimer subunits relocalized away from caveolae-enriched lipid raft microdomains at different stages; sGCβ1 at 4wkMR, followed by sGCα1 at 12moMR. Moreover, expression of both sGC subunits fell at 12moMR. Using the heme-dependent NO donor DEA/NO and NO-/heme-independent sGC activator BAY 60-2770, we determined the redox state and inducible activity of sGC in the myocardium, within caveolae and non-lipid raft microdomains. sGC was oxidized in non-lipid raft microdomains at 4wkMR and 12moMR. While overall DEA/NO-responsiveness remained intact in MR hearts, DEA/NO responsiveness of sGC in non-lipid raft microdomains was depressed at 12moMR. Caveolae-localization protected sGC against oxidation. Further studies revealed that these modifications of sGC were also reflected in caveolae-localized cGMP-dependent protein kinase (PKG) and MAPK signaling. In MR hearts, PKG-mediated phosphorylation of vasodilator-stimulated phosphoprotein (VASP) disappeared from caveolae whereas caveolae-localization of phosphorylated ERK5 increased. These findings show that differential oxidation, re-localization, and expression of sGC subunits distinguish eccentric from concentric hypertrophy as well as compensated from decompensated heart failure.

Nitric oxide synthases and heart failure - lessons from genetically manipulated mice

Nitric oxide (NO) is synthesized by three distinct NO synthase (NOS) isoforms (neuronal, inducible, and endothelial NOS), all of which are expressed in the human heart. The roles of NOSs in the pathogenesis of heart failure have been described in pharmacological studies with NOS inhibitors. Recently, genetically engineered animals have been used. We have generated mice in which all 3 NOS isoforms are completely disrupted (triple n/i/eNOS(-/-) mice). Morphological, echocardiographic, and hemodynamic analysis were performed in wild-type, singly nNOS(-/-), iNOS(-/-), eNOS(-/-), and triple n/i/eNOS(-/-) mice. Importantly, significant left ventricular (LV) hypertrophy and diastolic dysfunction was noted only in n/i/eNOS(-/-) mice, and those pathology was similar to diastolic heart failure in humans. Finally, treatment with an angiotensin II type 1 (AT1) receptor blocker, significantly prevented those abnormalities. These results provide the evidence that AT1 receptor pathway plays a center role in the pathogenesis of cardiac disorders in the n/i/eNOS(-/-) mice. Our studies with triple n/i/eNOS(-/-) mice provide pivotal insights into an understanding of the pathophysiology of NOSs in human heart failure.

Identification of a novel de novo mutation associated with PRKAG2 cardiac syndrome and early onset of heart failure

Introduction

The major structure elements of the AMP-activated protein kinase (AMPK) are α, β, and γ sunbunits. Mutations in γ2 subunit (PRKAG2) have been associated with a cardiac syndrome including inherited ventricular preexcitation, conduction disorder and hypertrophy mimicking hypertrophic cardiomyopathy. The aim of the present study was to identify PRKAG2 syndrome among patients presenting with left ventricular hypertrophy (LVH).

Methods and Results

Nineteen unrelated subjects with unexplained LVH were clinically and genetically evaluated. Among 4 patients with bradycardia, manifestations of preexcitation were only found in a 19 year old male who also developed congestive heart failure 3 years later. Electrophysiological study of this case identified the coexistence of an AV accessory pathway and AV conduction defect. Histological analysis of his ventricular tissue isolated by biopsy confirmed excessive glycogen accumulation, prominent myofibrillar disarray and interstitial fibrosis. Direct sequencing of his DNA revealed a heterozygous mutation in PRKAG2 consisting of an A-to-G transition at nucleotide 1453 (c.1453A>G), predicting a substitution of a glutamic acid for lysine at highly-conserved residue 485 (p.Lys485Glu, K485E), which was absent in his unaffected family members and in 215 healthy controls. To assess the role of K485 in the structure and function of the protein, computational modeling calculations and conservation analyses were performed. Electrostatic calculations indicate that K485 forms a salt bridge with the conserved D248 residue in the AMPK β subunit, which is critical for proper regulation of the enzyme, and the K485E mutant disrupts the connection.

Conclusions

Our study identifies a novel de novo PRKAG2 mutation in a young, in which progression of the disease warrants close medical attention. It also underlines the importance of molecular screening of PRKAG2 gene in patients with unexplained LVH, ventricular preexcitation, conduction defect, and/or early onset of heart failure.

Calpain inhibition reduces amplitude and accelerates decay of the late sodium current in ventricular myocytes from dogs with chronic heart failure

Calpain is an intracellular Ca²⁺ -activated protease that is involved in numerous Ca²⁺ dependent regulation of protein function in many cell types. This paper tests a hypothesis that calpains are involved in Ca²⁺ -dependent increase of the late sodium current (I_NaL) in failing heart. Chronic heart failure (HF) was induced in 2 dogs by multiple coronary artery embolization. Using a conventional patch-clamp technique, the whole-cell I_NaL was recorded in enzymatically isolated ventricular cardiomyocytes (VCMs) in which I_NaL was activated by the presence of a higher (1μM) intracellular [Ca²⁺] in the patch pipette. Cell suspensions were exposed to a cell- permeant calpain inhibitor MDL-28170 for 1–2 h before I_NaL recordings. The numerical excitation-contraction coupling (ECC) model was used to evaluate electrophysiological effects of calpain inhibition in silico. MDL caused acceleration of I_NaL decay evaluated by the two-exponential fit (τ₁ = 42±3.0 ms τ₂ = 435±27 ms, n = 6, in MDL vs. τ₁ = 52±2.1 ms τ₂ = 605±26 control no vehicle, n = 11, and vs. τ₁ = 52±2.8 ms τ₂ = 583±37 ms n = 7, control with vehicle, P<0.05 ANOVA). MDL significantly reduced I_NaL density recorded at –30 mV (0.488±0.03, n = 12, in control no vehicle, 0.4502±0.0210, n = 9 in vehicle vs. 0.166±0.05pA/pF, n = 5, in MDL). Our measurements of current-voltage relationships demonstrated that the I_NaL density was decreased by MDL in a wide range of potentials, including that for the action potential plateau. At the same time the membrane potential dependency of the steady-state activation and inactivation remained unchanged in the MDL-treated VCMs. Our ECC model predicted that calpain inhibition greatly improves myocyte function by reducing the action potential duration and intracellular diastolic Ca²⁺ accumulation in the pulse train.

[Modification of sarco-endoplasmic reticulum Ca(2 +) -ATPase in the failing cardiomyocyte]

The amplitude and velocity of intracellular Ca(2 +) cycling determines contractility in normal and failing hearts. Cardiac sarcoplasmic reticulum (SR) is a specialized membranous organelle which determines the property of such intracellular calcium transport in cardiomyocytes. In the SR membrane, sarco-endoplasmic reticulum ATPase (SERCA2a) sequestrates Ca(2 +) from the cytosol to the SR, thereby regulating cardiac diastolic performance. In the failing hearts, depressed SERCA2a function has been shown to be associated with impaired contractility and aberrant increase in cytosolic Ca(2 +) concentration. Therefore, molecular targeting of SERCA2a complexes becomes an emerging therapeutic target. In this review, mechanisms modifying SERCA2a function and associated topics is reviewed.

Nitric oxide synthases in heart failure

SIGNIFICANCE

The regulation of myocardial function by constitutive nitric oxide synthases (NOS) is important for the maintenance of myocardial Ca(2+) homeostasis, relaxation and distensibility, and protection from arrhythmia and abnormal stress stimuli. However, sustained insults such as diabetes, hypertension, hemodynamic overload, and atrial fibrillation lead to dysfunctional NOS activity with superoxide produced instead of NO and worse pathophysiology.

RECENT ADVANCES

Major strides in understanding the role of normal and abnormal constitutive NOS in the heart have revealed molecular targets by which NO modulates myocyte function and morphology, the role and nature of post-translational modifications of NOS, and factors controlling nitroso-redox balance. Localized and differential signaling from NOS1 (neuronal) versus NOS3 (endothelial) isoforms are being identified, as are methods to restore NOS function in heart disease.

CRITICAL ISSUES

Abnormal NOS signaling plays a key role in many cardiac disorders, while targeted modulation may potentially reverse this pathogenic source of oxidative stress.

FUTURE DIRECTIONS

Improvements in the clinical translation of potent modulators of NOS function/dysfunction may ultimately provide a powerful new treatment for many hearts diseases that are fueled by nitroso-redox imbalance.

Quantification of carbonic anhydrase gene expression in ventricle of hypertrophic and failing human heart

BACKGROUND

Carbonic anhydrase enzymes (CA) catalyze the reversible hydration of carbon dioxide to bicarbonate in mammalian cells. Trans-membrane transport of CA-produced bicarbonate contributes significantly to cellular pH regulation. A body of evidence implicates pH-regulatory processes in the hypertrophic growth pathway characteristic of hearts as they fail. In particular, Na+/H+ exchange (NHE) activation is pro-hypertrophic and CA activity activates NHE. Recently Cardrase (6-ethoxyzolamide), a CA inhibitor, was found to prevent and revert agonist-stimulated cardiac hypertrophy (CH) in cultured cardiomyocytes. Our goal thus was to determine whether hypertrophied human hearts have altered expression of CA isoforms.

METHODS

We measured CA expression in hypertrophied human hearts to begin to examine the role of carbonic anhydrase in progression of human heart failure. Ventricular biopsies were obtained from patients undergoing cardiac surgery (CS, n = 14), or heart transplantation (HT, n = 13). CS patients presented mild/moderate concentric left ventricular hypertrophy and normal right ventricles, with preserved ventricular function; ejection fractions were ~60%. Conversely, HT patients with failing hearts presented CH or ventricular dilation accompanied by ventricular dysfunction and EF values of 20%. Non-hypertrophic, non-dilated ventricular samples served as controls.

RESULTS

Expression of atrial and brain natriuretic peptide (ANP and BNP) were markers of CH. Hypertrophic ventricles presented increased expression of CAII, CAIV, ANP, and BNP, mRNA levels, which increased in failing hearts, measured by quantitative real-time PCR. CAII, CAIV, and ANP protein expression also increased approximately two-fold in hypertrophic/dilated ventricles.

CONCLUSIONS

These results, combined with in vitro data that CA inhibition prevents and reverts CH, suggest that increased carbonic anhydrase expression is a prognostic molecular marker of cardiac hypertrophy.

Simvastatin activates the PPARγ-dependent pathway to prevent left ventricular hypertrophy associated with inhibition of RhoA signaling

Left ventricular hypertrophy is an independent risk factor for major adverse cardiovascular events. Statins have positive effects on this condition; however, the mechanisms are incompletely understood. In this study, we examined whether the effect of simvastatin on left ventricular hypertrophy can be mediated with the peroxisome proliferator-activated receptor (PPAR)γ-dependent pathway in rabbits with nonischemic heart failure (HF). We induced aortic insufficiency and constriction in 48 rabbits and divided them equally into control, HF, and HF with simvastatin therapy (HF-SIM) groups. The HF-SIM group was given 10 mg/kg/d of simvastatin. We echocardiographically measured baseline and 8-week cardiac structure and function, and we used Western blot, polymerase chain reaction, and electrophoretic analytic techniques to evaluate messenger RNA expression and protein expression and activity. In comparison with the HF group, the HF-SIM rabbits had an increased ejection fraction and decreased left ventricular mass index, interventricular septal thickness, ventricular posterior-wall thickness, and collagen volume fraction. Moreover, the messenger RNA and protein expression of PPARγ in the HF-SIM rabbits were significantly higher than those in the HF rabbits; and the activity and expression of nuclear factor-κB subunit p65, RhoA, and Rho GTPase were significantly lower. Our results indicate that simvastatin therapy attenuates the PPARγ-dependent pathway in association with the inhibition of RhoA and Rho GTPase signaling to inhibit nuclear factor-κB activation, thus preventing the development of left ventricular hypertrophy and fibrosis in rabbits with nonischemic heart failure.

Oxidative regulation of the Na(+)-K(+) pump in the cardiovascular system

The Na(+)-K(+) pump is an essential heterodimeric membrane protein, which maintains electrochemical gradients for Na(+) and K(+) across cell membranes in all tissues. We have identified glutathionylation, a reversible posttranslational redox modification, of the Na(+)-K(+) pump's β1 subunit as a regulatory mechanism of pump activity. Oxidative inhibition of the Na(+)-K(+) pump by angiotensin II- and β1-adrenergic receptor-coupled signaling via NADPH oxidase activation demonstrates the relevance of this regulatory mechanism in cardiovascular physiology and pathophysiology. This has implications for dysregulation of intracellular Na(+) and Ca(2+) as well as increased oxidative stress in heart failure, myocardial ischemia-reperfusion, and regulation of vascular tone under conditions of elevated oxidative stress. Treatment strategies that are able to reverse this oxidative inhibition of the Na(+)-K(+) pump have the potential for cardiovascular-protective effects.

SOCS1 gene transfer accelerates the transition to heart failure through the inhibition of the gp130/JAK/STAT pathway

AIMS

The suppressors of cytokine signalling (SOCS) are identified inhibitors of cytokine and growth factor signalling that act via the Janus kinase (JAK) signal transducers and activators of transcription (STAT) pathways. Aberrant JAK/STAT signalling promotes progression from hypertrophy to heart failure. Little information is available concerning the role of SOCS in the transition from hypertrophy to heart failure. To this aim, we investigated the effects of SOCS1 overexpression obtained by in vivo adeno-associated gene transfer using an aortopulmonary cross-clamping technique in a chronic pressure-overload cardiac rat model.

METHODS AND RESULTS

Rats were randomized into four groups: sham-operated (n = 18), aortic banding (AB) (n = 18), AB + viral vector encoding for haemoagglutinin (AB + HA, n = 16), and AB + viral vector encoding for SOCS1 (AB + SOCS1, n = 18). Echocardiographic and haemodynamic measurements were performed 15 weeks after banding. While SOCS3 was upregulated during the hypertrophic phase, SOCS1 transcript levels increased significantly between 15 and 20 weeks. Remodelling was markedly worse in AB + SOCS1, showed larger left ventricular internal dimensions (+16%), higher end-diastolic pressures (+57%) and wall stress (+45%), and reduced fractional shortening (-32%) compared with AB + HA; apoptotic rate was increased three-fold and the gp130 pathway was inhibited. Ex vivo experiments showed that mechanical stretch upregulated SOCS1 expression, which was in turn attenuated by tumour necrosis factor-α (TNF-α) inhibition.

CONCLUSION

Enhanced SOCS1 myocardial signalling is associated with accelerated transition from hypertrophy to failure in an established model of pressure overload. SOCS1 may represent an attractive target for the prevention of heart failure progression.

Plasma metalloproteinase-9 and restrictive filling pattern as major predictors of outcome in patients with ischemic cardiomyopathy

OBJECTIVE

Assessment of plasma matrix metalloproteinase-9 (MMP-9) and Doppler markers of increased left ventricular (LV) filling pressure may be added to risk stratify patients with ischemic cardiomyopathy (IC). Therefore, we aimed at investigating the value of plasma MMP-9 and restrictive filling pattern (RFP) in IC patients.

METHODS

Eighty-eight consecutive patients hospitalized for heart failure (LV ejection fraction ≤ 40%) due to IC were enrolled. A complete M-mode and two-dimensional echo-Doppler examination were performed. Patients were defined as having RFP if they had a mitral E wave deceleration time<150 ms. Plasma MMP-9 and N-terminal protype-B natriuretic peptide levels were assessed at the time of the index echocardiogram. The end point was all-cause mortality or hospitalization for worsening HF. Follow-up period was 25 ± 17 months.

RESULTS

Median value of MMP-9 was 714 ng/ml. On univariate analysis, a number of measurements predicted the composite end point: NYHA class>2, RFP, MMP-9>60.5 ng/ml, LV ejection fraction<27%, anemia, pulmonary pressure ≥ 35 mm Hg, N-terminal protype-B natriuretic peptide>1742 pg/ml, and glomerular filtration rate<60 ml/min/1.73 m(2). Independent variables of outcome were anemia (HR=1.9, p=0.031), and the combination of plasma MMP-9 and RFP (HR=3.2, p=0.004). On Kaplan-Meier survival curves, patients with elevated MMP-9 levels and RFP had the lowest event-free survival rate (log-rank: 29.0, p<0.0001). The net reclassification improvement showed a significant increase in the prediction model when elevated MMP-9 and RFP were added to the base model that included clinical, biochemical and echocardiographic parameters (p<0.0001).

CONCLUSION

MMP-9 levels and RFP have an incremental predictive value to risk classify IC patients.

Short-term akt activation in cardiac muscle cells improves contractile function in failing hearts

Akt is a serine/threonine protein kinase that is activated by a variety of growth factors or cytokines in a phosphatidylinositol 3-kinase-dependent manner. By using a conditional transgenic system in which Akt signaling can be turned on or off in the adult heart, we previously showed that short-term Akt activation induces a physiological form of cardiac hypertrophy with enhanced coronary angiogenesis and maintained contractility. Here we tested the hypothesis that induction of physiological hypertrophy by short-term Akt activation might improve contractile function in failing hearts. When Akt signaling transiently was activated in murine hearts with impaired contractility, induced by pressure overload or doxorubicin treatment, contractile dysfunction was attenuated in both cases. Importantly, improvement of contractility was observed before the development of cardiac hypertrophy, indicating that Akt activation improves contractile function independently of its growth-promoting effects. To gain mechanistic insights into Akt-mediated positive inotropic effects, transcriptional profiles in the heart were determined in a pressure overload-induced heart failure model. Biological network analysis of differentially expressed transcripts revealed significant alterations in the expression of genes associated with cell death, and these alterations were reversed by short-term Akt activation. Thus, short-term Akt activation improves contractile function in failing hearts. This beneficial effect of Akt on contractility is hypertrophy-independent and may be mediated in part by inhibition of cell death associated with heart failure.

Cardiomyocyte aldose reductase causes heart failure and impairs recovery from ischemia

Aldose reductase (AR), an enzyme mediating the first step in the polyol pathway of glucose metabolism, is associated with complications of diabetes mellitus and increased cardiac ischemic injury. We investigated whether deleterious effects of AR are due to its actions specifically in cardiomyocytes. We created mice with cardiac specific expression of human AR (hAR) using the α–myosin heavy chain (MHC) promoter and studied these animals during aging and with reduced fatty acid (FA) oxidation. hAR transgenic expression did not alter cardiac function or glucose and FA oxidation gene expression in young mice. However, cardiac overexpression of hAR caused cardiac dysfunction in older mice. We then assessed whether hAR altered heart function during ischemia reperfusion. hAR transgenic mice had greater infarct area and reduced functional recovery than non-transgenic littermates. When the hAR transgene was crossed onto the PPAR alpha knockout background, another example of greater heart glucose oxidation, hAR expressing mice had increased heart fructose content, cardiac fibrosis, ROS, and apoptosis. In conclusion, overexpression of hAR in cardiomyocytes leads to cardiac dysfunction with aging and in the setting of reduced FA and increased glucose metabolism. These results suggest that pharmacological inhibition of AR will be beneficial during ischemia and in some forms of heart failure.

Histoenzymological characteristics of the contractile myocardium in experimental stenosis of the aorta

Contractile cardiomyocyte metabolism was studied by histochemical methods in experimental stenosis of the aorta complicated and not by heart failure. Acceleration of the citric acid cycle, more intense oxidation of free fatty acids and their metabolites, glycolysis intensification, and higher activity of shuttle mechanisms were found in the contractile cardiomyocytes in stenosis of the aorta not complicated by heart failure. The presence of these metabolic shifts in the myocardium of all studied compartments suggests their association with not only more intense heart work, but also with the effects of total systems neurohumoral factors. Comparative study of myocardial metabolism in two variants of experimental stenosis of the aorta has revealed changes prognostically unfavorable for the development of heart failure. These changes include exhaustion of glycogen reserve, glycolysis inhibition, and metabolism shift towards biosynthetic processes. These data indicate an important role of glycolysis in support of myocardial contractile function during the acute phase of pressure overloading of the heart.

Gi-biased β2AR signaling links GRK2 upregulation to heart failure

RATIONALE

Phosphorylation of β(2)-adrenergic receptor (β(2)AR) by a family of serine/threonine kinases known as G protein-coupled receptor kinase (GRK) and protein kinase A (PKA) is a critical determinant of cardiac function. Upregulation of G protein-coupled receptor kinase 2 (GRK2) is a well-established causal factor of heart failure, but the underlying mechanism is poorly understood.

OBJECTIVE

We sought to determine the relative contribution of PKA- and GRK-mediated phosphorylation of β(2)AR to the receptor coupling to G(i) signaling that attenuates cardiac reserve and contributes to the pathogenesis of heart failure in response to pressure overload.

METHODS AND RESULTS

Overexpression of GRK2 led to a G(i)-dependent decrease of contractile response to βAR stimulation in cultured mouse cardiomyocytes and in vivo. Importantly, cardiac-specific transgenic overexpression of a mutant β(2)AR lacking PKA phosphorylation sites (PKA-TG) but not the wild-type β(2)AR (WT-TG) or a mutant β(2)AR lacking GRK sites (GRK-TG) led to exaggerated cardiac response to pressure overload, as manifested by markedly exacerbated cardiac maladaptive remodeling and failure and early mortality. Furthermore, inhibition of G(i) signaling with pertussis toxin restores cardiac function in heart failure associated with increased β(2)AR to G(i) coupling induced by removing PKA phosphorylation of the receptor and in GRK2 transgenic mice, indicating that enhanced phosphorylation of β(2)AR by GRK and resultant increase in G(i)-biased β(2)AR signaling play an important role in the development of heart failure.

CONCLUSIONS

Our data show that enhanced β(2)AR phosphorylation by GRK, in addition to PKA, leads the receptor to G(i)-biased signaling, which, in turn, contributes to the pathogenesis of heart failure, marking G(i)-biased β(2)AR signaling as a primary event linking upregulation of GRK to cardiac maladaptive remodeling, failure and cardiodepression.

NADPH oxidase-dependent oxidative stress in the failing heart: From pathogenic roles to therapeutic approach

Heart failure (HF) occurs when the adaptation mechanisms of the heart fail to compensate for stress factors, such as pressure overload, myocardial infarction, inflammation, diabetes, and cardiotoxic drugs, with subsequent ventricular hypertrophy, fibrosis, myocardial dysfunction, and chamber dilatation. Oxidative stress, defined as an imbalance between reactive oxygen species (ROS) generation and the capacity of antioxidant defense systems, has been authenticated as a pivotal player in the cardiopathogenesis of the various HF subtypes. The family of NADPH oxidases has been investigated as a key enzymatic source of ROS in the pathogenesis of HF. In this review, we discuss the importance of NADPH oxidase-dependent ROS generation in the various subtypes of HF and its implications. A better understanding of the pathogenic roles of NADPH oxidases in the failing heart is likely to provide novel therapeutic strategies for the prevention and treatment of HF.

[Microbiocenosis and activity of the inflammatory process in the colon of the patients with chronic cardiac failure]

The aim of this work was to study colonic microbiocenosis, endotoxin level, intensity of systemic inflammation and the state of matrix metalloproteinase (MMP) system and MMP tissue inhibitors (TIMP) in 75 patients with post-infarction cardiosclerosis at different stages of chronic cardiac failure (CCF). The patients were examined by clinical, echocardiographic and laboratory methods including bacteriological analysis of feces and measurement of amino-terminal brain natriuruetic peptide, endotoxin, TNF-alpha, MMP-9, and TIMP-4. The progress of CCF was shown to be associated with increasing colonic dysbiosis, endotoxin and TNF-alpha levels, disbalance in the MMO and TIMP systems.