Animal Models Of Heart Failure Research Articles

Role of MAPK-mediated endoplasmic reticulum stress signaling in the heart during aging in senescence-accelerated prone mice.

Heart failure is typically related to aging as there is a definite relationship between age-related changes in the heart and the pathogenesis of heart failure. We have previously reported the involvement of p38 mitogen-activated protein kinase protein in cardiac function using animal models of heart failure. To further understand its relationship with aging-induced heart failure, we have compared its expression in the hearts of senescence accelerated-prone (SAMP8) mice and their control (SAMR1) with normal aging behavior. We have identified its activation along with reduced expression of 14-3-3η protein in SAMP8 mice hearts than in SAMR1 mice. To reveal the downstream signaling, we have measured the endoplasmic reticulum stress marker proteins along with some inflammatory and apoptosis markers and identified a significant increase in SAMP8 mice hearts than that of SAMR1. In addition, we have performed comet assay and revealed a significant DNA damage in the cardiomyocytes of SAMP8 mice when compared with SAMR1 mice. All these results demonstrate the role of 14-3-3η protein and the downstream mitogen-activated protein kinase-mediated endoplasmic reticulum stress, and apoptosis and DNA damage in aging-induced cardiac malfunction in SAMP8 mice. Thus targeting this signaling might be effective in treating age-related cardiac dysfunction. © 2016 BioFactors, 42(4):368-375, 2016.

Statin Therapy Reduces Differentiation of Ventricular Fibroblast to Myofibroblasts in Human Failing Heart

BackgroundCardiac fibrosis (CF) is a major factor underlying the progression of heart failure (HF). Apart from the established lipid lowering effect, HMG‐CoA (3‐hydroxy‐3‐methylglutaryl‐CoenzymeA) reductase inhibition by statins reverses CF in various animal models of HF but its effect in human failing heart ventricular fibroblasts (hVF), responsible for fibrosis, is not known. Hence, we tested the differentiation phenotype of hVF isolated from HF patients under statin therapy (HF+Statin) for at least 1 year or not (HF‐No_Statin) and normal, as fibroblast to myofibroblast trans‐differentiation precedes fibrosis.MethodsPrimary hVF cultures obtained from HF patients undergoing left‐ventricle assist device implantation (n=4 each) and non‐diseased hVF from trauma victims (n=3) were used at passage 3 or 4. Confocal microscopy, immunohistochemistry, western blotting, Edu (5‐ethynyl‐2′‐deoxyuridine)‐incorporation assay data were obtained and analyzed by unpaired t test or one‐Way Analysis of Variance.ResultsImmunoblot (Fig. A) data showed significantly (P<0.05) higher expression of α‐smooth muscle actin (α‐SMA+) and immunohistochemistry (Fig. B) showed significantly high population of myofibroblasts (α‐SMA+) in the HF‐No_Statin group vs the control or HF+Statin groups, suggesting statin‐sensitive increased hVF differentiation in failing heart. In vitro treatment of simvastatin (0.3μM for 72 hrs) on HF‐No_Statin group hVFs significantly (P<0.05) reduced the high expression of α‐SMA, indicating a reversal effect of statins on myofibroblast to fibroblast. Edu‐incorporation data showed that the percentage of proliferating hVFs was not significantly different in failing heart without statins(82±3%) compared to control(82±4%) and HF+ Statin (69±5%), indicating that the DNA synthesis and proliferative capacity of hVFs remain unaltered in failing heart, irrespective of statin therapy, compared to normal.ConclusionThe failing heart ventricle has a large population of differentiated myofibroblasts. Statins prevent/reverse hVF differentiation decreasing the ratio of myofibroblast to fibroblasts, which is anti‐fibrotic. The significance of statins’ anti‐fibrotic effect for HF therapeutics may be in reducing the CF progression by inhibiting/reversing hVF differentiation to myofibroblasts, thereby improving the cardiovascular outcome in HF patientsSupport or Funding InformationAurora Health Care ‐ Cardiovascular Surgery Research Award (CVSRA 2015) to Gracious R Ross and NIH R01‐HL101240 to Arshad Jahangir.

PKD Translocation to the Outer Mitochondrial Membrane Induces Mitochondrial Fragmentation and Cell Death via DLP1 Phosphorylation in Cardiomyocytes

Heart failure (HF) occurs in response to various types of stimulus including Gq‐protein coupled receptor (GqPCR) stimulation. GqPCR‐mediated mitochondrial dysfunction is frequently observed in HF animal models, but the molecular mechanism remains unclear. Recently, Protein kinase D (PKD) located at GqPCR downstream has been recognized as a key signaling nodal point affecting various cardiac functions. Therefore, we hypothesize that PKD acts as a mitochondrial signaling component and induces mitochondrial dysfunctions under GqPCR‐mediated HF. Using the outer mitochondrial membrane (OMM)‐targeted CFP (mt‐CFP), we found that the value of the Förster resonance energy transfer (FRET) between mt‐CFP and YFP‐tagged PKD significantly increases upon GqPCR stimulation, indicating PKD translocation from cytosol to the OMM. Next, using the FRET‐based OMM‐targeted PKD‐activity sensor, we observed that PKD is activated at the OMM after GqPCR stimulation. Furthermore, we found that GqPCR‐mediated PKD activation at the OMM induced mitochondrial fragmentation, increased reactive oxygen species generation and mitochondrial permeability transition pore opening, followed by caspase‐3 activation in cardiomyocytes. These morphological and functional alterations in cardiac mitochondria were mediated via PKD‐dependent phosphorylation of Dynamin‐Like Protein 1 (DLP1) at S637. Importantly, PKD‐dependent DLP1 phosphorylation concurrent with abnormal mitochondrial morphology and apoptotic signaling were also observed in ventricular tissue from transgenic mice with cardiac‐specific overexpression of constitutively active Gaq. In summary, we conclude that GqPCR stimulation induces PKD translocation to the OMM and induces mitochondrial fragmentation and dysfunction, which likely contributes to cardiomyocyte dysfunction during HF.Support or Funding InformationThis work was partly supported by American Heart Association (AHA) grant (14BGIA18830032 to J.O.‐U.), Medical Research Grant from W.W. Smith Charitable Trust (H1403 to J.O.‐U.) and NIH grants (2R01HL093671 and 1R01HL122124 to SSS).

FIRST-IN-HUMAN SINGLE-ASCENDING-DOSE STUDY OF IW-1973, A NEW SOLUBLE GUANYLATE CYCLASE STIMULATOR

IW-1973 is an orally active soluble guanylate cyclase (sGC) stimulator that reduces blood pressure (BP) and exhibits anti-fibrotic, anti-inflammatory and organ-protective effects in animal models of systemic hypertension, pulmonary hypertension and heart failure. A Phase 1a first-in-human clinical

The dual effect of ephaptic coupling on cardiac conduction with heterogeneous expression of connexin 43

Decreased and heterogeneous expression of connexin 43 (Cx43) are common features in animal heart failure models. Ephpatic coupling, which relies on the presence of junctional cleft space between the ends of adjacent cells, has been suggested to play a more active role in mediating intercellular electrical communication when gap junctions are reduced. To better understand the interplay of Cx43 expression and ephaptic coupling on cardiac conduction during heart failure, we performed numerical simulations on our model when Cx43 expression is reduced and heterogeneous. Under severely reduced Cx43 expression, we identified three new phenomena in the presence of ephaptic coupling: alternating conduction, in which ephaptic and gap junction-mediated mechanisms alternate; instability of planar fronts; and small amplitude action potential (SAP), which has a smaller potential amplitude than the normal action potential. In the presence of heterogeneous Cx43 expression, ephaptic coupling can either prevent or promote conduction block (CB) depending on the Cx43 knockout (Cx43KO) content. When Cx43KO content is relatively high, ephaptic coupling reduces the probabilities of CB. However, ephaptic coupling promotes CB when Cx43KO and wild type cells are mixed in roughly equal proportion, which can be attributed to an increase in current-to-load mismatch.

Animal models of heart failure with preserved ejection fraction

Heart failure with preserved ejection fraction (HFpEF) constitutes a clinical syndrome in which the diagnostic criteria of heart failure are not accompanied by gross disturbances of systolic function, as assessed by ejection fraction. In turn, under most circumstances, diastolic function is impaired. Although it now represents over 50 % of all patients with heart failure, the mechanisms of HFpEF remain understood, precluding effective therapy. Understanding the pathophysiology of HFpEF has been restricted by both limited access to human myocardial biopsies and by the lack of animal models that fully mimic human pathology. Animal models are valuable research tools to clarify subcellular and molecular mechanisms under conditions where the comorbidities and other confounding factors can be precisely controlled. Although most of the heart failure animal models currently available represent heart failure with reduced ejection fraction, several HFpEF animal models have been proposed. However, few of these fulfil all the features present in human disease. In this review we will provide an overview of the currently available models to study HFpEF from rodents to large animals as well as present advantages and disadvantages of these models.

Dietary management of heart failure: room for improvement?

There is growing awareness of the role of diet in both health and disease management. Much data are available on the cardioprotective diet in the primary and secondary prevention of CVD. However, there is limited information on the role of diet in the management of heart failure (HF). Animal models of HF have provided interesting insight and potential mechanisms by which dietary manipulation may improve cardiac performance and delay the progression of the disease, and small-scale human studies have highlighted beneficial diet patterns. The aim of this review is to summarise the current data available on the role of diet in the management of human HF and to demonstrate that dietary manipulation needs to progress further than the simple recommendation of salt and fluid restriction.

Effects of Beta-Adrenergic Stimulation on Rat Failing Cardiomyocytes

Beta-adrenoceptors start the most powerful signaling pathway for the sympathetic control of the cardiac function. Human and animal models of heart failure (HF), one of the most important causes of mortality worldwide, show alterations of the sympathetic system. Number and function of beta-adrenoceptors, namely the beta-1 subtype, are impaired in HF, representing a major (mal)adaptive feature of myocardial remodeling. Moreover, HF is characterized by structural and functional remodeling of T-tubules (TT). We previously observed failure of action potential conduction in about 6% of HF TTs accompanied by profound alterations of local Ca2+ transient (Crocini et al. PNAS 2014). Here, we employ an ultrafast random access multi-photon (RAMP) microscope to assess the effect of beta-adrenoceptor activation on Ca2+ release in electrically coupled and uncoupled tubular elements. We find that HF cells exhibit a significantly higher Ca2+ sparks frequency compared to controls that are not affected by beta-receptor activation (10-7 M isoproterenol). Control cardiomyocytes treated with isoproterenol show instead a more than 3-fold increase of Ca2+ sparks frequency. To better examine this difference, we assess beta-adrenergic signaling role on Ca2+ release. We observe an accelerated Ca2+ rise exclusively in the vicinity of electrically coupled TT, while Ca2+ rise close to failing elements is unchanged in beta-adrenergic stimulated cells. This finding indicates a patchy response of HF cells to beta-adrenergic stimulation. On the contrary, isoproterenol reduces the beat-to-beat variability of Ca2+ release time to peak at every membrane site of HF cardiomyocytes. Simultaneous recording of action potential and Ca2+ transient allows us to probe the effect of beta-adrenergic stimulation at subcellular level, disclosing specific local effects that may help understanding the changes of beta-adrenergic signaling in HF.

Evidence for Intramyocardial Disruption of Lipid Metabolism and Increased Myocardial Ketone Utilization in Advanced Human Heart Failure.

The failing human heart is characterized by metabolic abnormalities, but these defects remains incompletely understood. In animal models of heart failure there is a switch from a predominance of fatty acid utilization to the more oxygen-sparing carbohydrate metabolism. Recent studies have reported decreases in myocardial lipid content, but the inclusion of diabetic and nondiabetic patients obscures the distinction of adaptations to metabolic derangements from adaptations to heart failure per se. We performed both unbiased and targeted myocardial lipid surveys using liquid chromatography-mass spectroscopy in nondiabetic, lean, predominantly nonischemic, advanced heart failure patients at the time of heart transplantation or left ventricular assist device implantation. We identified significantly decreased concentrations of the majority of myocardial lipid intermediates, including long-chain acylcarnitines, the primary subset of energetic lipid substrate for mitochondrial fatty acid oxidation. We report for the first time significantly reduced levels of intermediate and anaplerotic acyl-coenzyme A (CoA) species incorporated into the Krebs cycle, whereas the myocardial concentration of acetyl-CoA was significantly increased in end-stage heart failure. In contrast, we observed an increased abundance of ketogenic β-hydroxybutyryl-CoA, in association with increased myocardial utilization of β-hydroxybutyrate. We observed a significant increase in the expression of the gene encoding succinyl-CoA:3-oxoacid-CoA transferase, the rate-limiting enzyme for myocardial oxidation of β-hydroxybutyrate and acetoacetate. These findings indicate increased ketone utilization in the severely failing human heart independent of diabetes mellitus, and they support the role of ketone bodies as an alternative fuel and myocardial ketone oxidation as a key metabolic adaptation in the failing human heart.

Inhibition of Galectin-3 Pathway Prevents Isoproterenol-Induced Left Ventricular Dysfunction and Fibrosis in Mice

Galectin-3 (Gal-3) is involved in inflammation, fibrogenesis, and cardiac remodeling. Previous evidence shows that Gal-3 interacts with aldosterone in promoting macrophage infiltration and vascular fibrosis and that Gal-3 genetic and pharmacological inhibition prevents remodeling in a pressure-overload animal model of heart failure. We aimed to explore the contribution of Gal-3 and aldosterone in mechanisms leading to heart failure in a murine model. Male mice with cardiac-specific hyperaldosteronism underwent isoproterenol subcutaneous injections, to be then randomized to receive placebo, a Gal-3 inhibitor (modified citrus pectin [MCP]), an aldosterone antagonist (potassium canrenoate), or MCP+canrenoate for 14 days. Isoproterenol induced a rapid and persistent decrease in left ventricular fractional shortening (-20% at day 14); this was markedly improved by treatment with either MCP or canrenoate (both P<0.001 versus placebo). MCP and canrenoate also reduced cardiac hypertrophy and fibrosis and the expression of genes involved in fibrogenesis (Coll-1 and Coll-3) and macrophage infiltration (CD-68 and MCP-1). After isoproterenol, Gal-3 gene expression (P<0.05 versus placebo) and protein levels (-61% and -69% versus placebo) were decreased by both canrenoate and MCP. The combined use of antagonists of Gal-3 and aldosterone resulted in more pronounced effects on cardiac hypertrophy, inflammation, and fibrosis, when compared with either MCP or canrenoate alone. Inhibition of Gal-3 and aldosterone can reverse isoproterenol-induced left ventricular dysfunction, by reducing myocardial inflammation and fibrogenesis. Gal-3 likely participates in mechanisms of aldosterone-mediated myocardial damage in a heart failure murine model with cardiac hyperaldosteronism. Gal-3 inhibition may represent a new promising therapeutic option in heart failure.

Digitoxin improves cardiovascular autonomic control in rats with heart failure.

The effects of chronic treatment with digitoxin on arterial baroreceptor sensitivity for heart rate (HR) and renal sympathetic nerve activity (rSNA) control, cardiopulmonary reflex, and autonomic HR control in an animal model of heart failure (HF) were evaluated. Wistar rats were treated with digitoxin, which was administered in their daily feed (1 mg/kg per day) for 60 days. The following 3 experimental groups were evaluated: sham, HF, and HF treated with digitoxin (HF + DIG). We observed an increase in rSNA in the HF group (190 ± 29 pps, n = 5) compared with the sham group (98 ± 14 pps, n = 5). Digitoxin treatment prevented an increase in rSNA (98 ± 14 pps, n = 7). Therefore, arterial baroreceptor sensitivity was decreased in the HF group (-1.24 ± 0.07 bpm/mm Hg, n = 8) compared with the sham group (-2.27 ± 0.23 bpm/mm Hg, n = 6). Digitoxin did not alter arterial baroreceptor sensitivity in the HF + DIG group. Finally, the HF group showed an increased low frequency band (LFb: 23 ± 5 ms(2), n = 8) and a decreased high frequency band (HFb: 77 ± 5 ms(2), n = 8) compared with the sham group (LFb: 14 ± 3 ms(2); HFb: 86 ± 3 ms(2), n = 9); the HF+DIG group exhibited normalized parameters (LFb: 15 ± 3 ms(2); HFb: 85 ± 3 ms(2), n = 9). In conclusion, the benefits of decreasing rSNA are not directly related to improvements in peripheral cardiovascular reflexes; such occurrences are due in part to changes in the central nuclei of the brain responsible for autonomic cardiovascular control.

Cardiac Myosin Activation with Gene Therapy Produces Sustained Inotropic Effects and May Treat Heart Failure with Reduced Ejection Fraction.

Chronic inotropic therapy is effective for the treatment of heart failure with reduced ejection fraction, but has been limited by adverse long-term safety profiles, development of tolerance, and the need for chronic parenteral administration. A safe and convenient therapeutic agent that produces sustained inotropic effects could improve symptoms, functional capacity, and quality of life. Small amounts of 2-deoxy-adenosine triphosphate (dATP) activate cardiac myosin leading to enhanced contractility in normal and failing heart muscle. Cardiac myosin activation triggers faster myosin crossbridge cycling with greater force generation during each contraction. This paper describes the rationale and results of a translational medicine effort to increase dATP levels using a gene therapy strategy to deliver and upregulate ribonucleotide reductase (R1R2), the enzyme responsible for dATP synthesis, selectively in cardiomyocytes. In small and large animal models of heart failure, a single dose of this gene therapy has led to sustained inotropic effects with a benign safety profile. Further animal studies are appropriate with the goal of testing this agent in patients with heart failure.

Clinical impact of myocardial mTORC1 activation in nonischemic dilated cardiomyopathy

BackgroundActivity of mTOR complex 1 (mTORC1) has been shown to be up-regulated in animal models of heart failure. Here, we investigated the change and role of mTORC1 in human nonischemic dilated cardiomyopathy (NICM). MethodsEndomyocardial biopsy specimens were obtained from patients with NICM (n=52) and from Brugada syndrome patients with normal LVEF as controls (n=10). The specimens were stained for phospho-ribosomal protein S6 (p-Rps6) and phospho-p70S6K (p-p70S6K), and the area with p-Rps6 signal was used as an index of mTORC1 activity. Using median mTORC1 activity, patients were divided into a high mTORC1 activity (H-mTOR) group and a low mTORC1 activity (L-mTOR) group. ResultsThe ratio of p-Rps6-positive area in biopsy samples was 10-fold larger in patients with NICM than in controls (2.0±2.2% vs. 0.2±0.2%, p<0.01). p-p70S6K signal level was higher in the H-mTOR group than in the L-mTOR group. The proportion of patients with a family history of cardiomyopathy was higher and the proportion of patients on ACE inhibitors or angiotensin receptor blockers was lower in the H-mTOR group than in the L-mTOR group. The p-Rps6-positive area was correlated with extent of myocardial fibrosis (r=0.46, p<0.01). The cardiac event-free survival rate during a 5-year follow-up period tended to be lower in the H-mTOR group than in the L-mTOR group (52.9% vs. 81.6%, P=0.10). ConclusionAberrant activation of mTORC1 in cardiomyocytes was associated with myocardial fibrosis and a trend for worse prognosis in patients with NICM, indicating that persistently activated mTORC1 contributes to progression of human heart failure.

Elevated Soluble Fms-Like Tyrosine Kinase-1 and Placental-Like Growth Factor Levels Are Associated With Development and Mortality Risk in Heart Failure.

Vascular endothelial dysfunction may play an important role in the progression of heart failure (HF). We hypothesize that elevated levels of vascular markers, placental-like growth factor, and soluble Fms-like tyrosine kinase-1 (sFlt-1) are associated with adverse outcomes in patients with HF. We also assessed possible triggers of sFlt-1 elevation in animal HF models. We measured plasma placental-like growth factor and sFlt-1 in 791 HF patients undergoing elective coronary angiogram. Median (interquartile range) placental-like growth factor and sFlt-1 levels were 24 (20-29) and 382 (277-953) pg/mL, respectively. After 5 years of follow-up, and after using receiver operator characteristic curves to determine optimal cutoffs, high levels of sFlt-1 (≥ 280 pg/mL; adjusted hazard ratio, 1.47; 95% confidence interval, 1.03-2.09; P=0.035) but not placental-like growth factor (≥ 25 pg/mL; adjusted hazard ratio, 1.26; 95% confidence interval, 0.94-1.71, P=0.12) were associated with adverse cardiovascular outcomes. In addition, significant elevation of sFlt-1 levels was observed in left anterior descending artery ligation and transverse aortic constriction HF mouse models after 4 and 8 weeks of follow-up, suggesting vascular stress and ischemia as triggers for sFlt-1 elevation in HF. Circulating sFlt-1 is generated as a result of myocardial injury and subsequent HF development. Elevated levels of sFlt-1 are associated with adverse outcomes in stable patients with HF.

Omecamtiv mecarbil: a new cardiac myosin activator for the treatment of heart failure

Introduction: Current available inotropic agents increase cardiac contractility, but are associated with myocardial ischemia, arrhythmias, and mortality. A novel selective cardiac myosin activator, omecamtiv mecarbil (CK-1827452/ AMG-423) is a small molecule that activates the sarcomere proteins directly, resulting in prolonged systolic ejection time and increased cardiac contractility.Areas covered: This paper discusses the chemistry, pharmacokinetics, clinical efficacy and safety of omecamtiv mecarbil. Omecamtiv mecarbil represents a novel therapeutic approach to directly improve cardiac function and is therefore proposed as a potential new treatment of patients with systolic heart failure. The authors review results of previous studies investigating the effect of omecamtiv mecarbil in heart failure animal models, healthy volunteers, and patients with acute and chronic systolic heart failure.Expert opinion: Results of phase I and phase II studies demonstrate that omecamtiv mecarbil is safe and well tolerated both as an intravenous and oral formulation. In healthy volunteers and chronic systolic heart failure patients, administration of omecamtiv mecarbil resulted in a concentration-dependent increase of left ventricular ejection time, ejection fraction, fractional shortening, and stroke volume. The first results of a double-blind, randomized, placebo-controlled phase IIb dose-finding study with the oral formulation of omecamtiv mecarbil demonstrated beneficial effects on cardiac function and N-terminal pro-brain natriuretic peptide levels. This study will provide essential dosing information for the requisite phase III trials which will investigate whether the beneficial effects of omecamtiv mecarbil translate into improved clinical outcomes.

Abstract 17429: A Porcine Model of Heart Failure With Preserved Ejection Fraction Induced by Sustained Severe Hypertension

Background: Currently, the lack of well-established large animal models of heart failure with preserved ejection fraction (HFpEF) is one of the major hurdles for developing effective therapies for HFpEF. Here, we describe a large animal model of HFpEF induced by sustained hypertension (HT) that mimics human diseases. Methods: We induced sustained severe hypertension in 9 adult pigs using a combination of intravenous Angiotensin-II (Ang-II, 0.015mg/hr) delivery with an osmotic infusion pump and subcutaneous implantation of deoxycorticosterone acetate (DOCA) pellets (100mg/kg) for 10 weeks. All animals underwent invasive blood pressure (BP) telemetry monitoring and serial invasive pressure-volume (PV) loop assessment as well as echocardiographic examination at baseline, 10 weeks and 18 weeks. Results: Mean systolic and diastolic BP at baseline was 88/61 mmHg which increased immediately after Ang-II infusion plus DOCA (Week 0,158/105 mmHg) and progressively elevated up to Week 10 (171/126mmHg) that persisted out to Week 18 (183/137mmHg) despite termination of Ang-II infusion. Serial echocardiograms showed the development of left ventricular hypertrophy with significant increase in left ventricular mass with preserved left ventricular ejection fraction (Figure, upper panel). PV loop showed progressive elevation of pulmonary artery capillary wedge pressure (PCWP), left ventricular end-diastolic pressure (LVEDP) and end-diastolic pressure volume relationship (EDPVR) without change in end-systolic pressure volume relationship, suggestive of left ventricular diastolic dysfunction (Figure, lower panel). Conclusions: We successfully established a clinically relevant large animal model of HFpEF induced by sustained HT, which can be used for future investigation of new treatments for HFpEF.

Irisin - a myokine potentially bridging muscle and fat tissue in cachexia.

We read with great interest the recent article reporting muscle atrophy in heart failure animal models by Matsuo et al.1 Cachexia is characterized by loss of muscle mass with or without fat mass.2 Also, in patients with heart failure, muscle, fat and even bone loss were shown and reported to be associated with worse outcome.3,4 Although studies in muscle wasting attract much attention in heart failure,5 cross-talk among these three different tissues has been increasingly investigated and discussed6 as Matsuo et al. stated them in Introduction of this article.1 Large number of muscle biomarkers are in development7–10 and mentioned in several issues of Journal of Cachexia, Sarcopenia and Muscle. Under these circumstances, myokines including irisin, myostatin, interleukin-6, follistatin, and so on, which are produced by muscle tissue and affect other organs, are highlighted as both biomarkers and hormonal substances, which may have therapeutic implication.11 Irisin has been investigated as a key myokine, which has a bridging potential between muscle and fat.12,13 There are a number of articles reporting the plasma levels of irisin in patients with diabetes,14 chronic kidney disease,15 and myocardial infarction.16 However, there is almost no data about irisin levels in heart failure patients. In addition, recent reports have just been casting some doubt on the detection methods for human plasma irisin.17,18 In this context, further clinical studies in heart failure patients performed with improved assays are needed.

Human G109E-inhibitor-1 impairs cardiac function and promotes arrhythmias

A hallmark of human and experimental heart failure is deficient sarcoplasmic reticulum (SR) Ca-uptake reflecting impaired contractile function. This is at least partially attributed to dephosphorylation of phospholamban by increased protein phosphatase 1 (PP1) activity. Indeed inhibition of PP1 by transgenic overexpression or gene-transfer of constitutively active inhibitor-1 improved Ca-cycling, preserved function and decreased fibrosis in small and large animal models of heart failure, suggesting that inhibitor-1 may represent a potential therapeutic target. We recently identified a novel human polymorphism (G109E) in the inhibitor-1 gene with a frequency of 7% in either normal or heart failure patients. Transgenic mice, harboring cardiac-specific expression of G109E inhibitor-1, exhibited decreases in contractility, Ca-kinetics and SR Ca-load. These depressive effects were relieved by isoproterenol stimulation. Furthermore, stress conditions (2Hz +/− Iso) induced increases in Ca-sparks, Ca-waves (60% of G109E versus 20% in wild types) and after-contractions (76% of G109E versus 23% of wild types) in mutant cardiomyocytes. Similar findings were obtained by acute expression of the G109E variant in adult cardiomyocytes in the absence or presence of endogenous inhibitor-1. The underlying mechanisms included reduced binding of mutant inhibitor-1 to PP1, increased PP1 activity, and dephosphorylation of phospholamban at Ser16 and Thr17. However, phosphorylation of the ryanodine receptor at Ser2808 was not altered while phosphorylation at Ser2814 was increased, consistent with increased activation of Ca/calmodulin-dependent protein kinase II (CaMKII), promoting aberrant SR Ca-release. Parallel in vivo studies revealed that mutant mice developed ventricular ectopy and complex ventricular arrhythmias (including bigeminy, trigeminy and ventricular tachycardia), when challenged with isoproterenol. Inhibition of CaMKII activity by KN-93 prevented the increased propensity to arrhythmias. These findings suggest that the human G109E inhibitor-1 variant impairs SR Ca-cycling and promotes arrhythmogenesis under stress conditions, which may present an additional insult in the compromised function of heart failure carriers.

Translational Research of iPS Cell Sheet-Based Myocardial Regeneration Therapy

LVAD implantation and Heart transplantation have been well accepted as the ultimate lifesaving means of supporting end-staged heart failure patients. However, due to the limited durability of the LVAD and the shortage of donors, there are some limitations in these procedures. In this clinical situation, we developed cell sheet technology experimentally and introduced this to the treatment of severely damaged myocardium in clinical setting as translational research. In a series of pre-clinical experiments using animal heart failure model, we proved that myoblast sheets could heal the impaired heart mainly by cytokine paracrine effect. Evidenced by pre-clinical experiments, we applied myoblast sheets to 4 DCM patient receiving LVAD and 2 patients showed the recovery from LVAD. Although we implanted myoblast sheet to 20 heart failure patients without LVAD and some patients showed LV reverse remodeling. Recently we have developed human iPS cell derived cardiomyocyte sheet and obtained Proof of Concept by using porcine myocardial infarction model as preclinical study. And we have proved synchronous movement with recipient myocardium in vivo study. And also we have established large culture system and checked safety of iPS cell derived cardiomyocyte sheets for the purpose of clinical trial. iPS cell derived cardiomyocyte sheet may open new era in the treatment of severely damaged myocardium.

Tadalafil protects from doxorubicin-induced heart failure by attenuating PKG Iα disulfide dimerisation

Background Phosphodiesterase (PDE) 5 inhibitors, which prevent cGMP degradation and therefore elevate its level in the heart, have been shown to protect the myocardium in several animal models of heart failure and in human trials. cGMP binding to protein kinase G (PKG) results in its classical activation and also prevents disulfide dimerisation-dependent activation of this kinase. Doxorubicin (DOX) is an anti-cancer drug which commonly causes cardiomyopathy, the pathogenesis of which is associated with increased oxidant production and apoptosis. We hypothesised that oxidative activation of PKG Ia may mediate DOX-induced cardiotoxicity, and PDE5 inhibitors may be protective because they elevate cGMP which then limits the oxidative activation.