Animal Models Of Heart Failure Research Articles

Small animal models of heart failure.

Heart disease is a major cause of death worldwide with increasing prevalence, which urges the development of new therapeutic strategies. Over the last few decades, numerous small animal models have been generated to mimic various pathomechanisms contributing to heart failure (HF). Despite some limitations, these animal models have greatly advanced our understanding of the pathogenesis of the different aetiologies of HF and paved the way to understanding the underlying mechanisms and development of successful treatments. These models utilize surgical techniques, genetic modifications, and pharmacological approaches. The present review discusses the strengths and limitations of commonly used small animal HF models, which continue to provide crucial insight and facilitate the development of new treatment strategies for patients with HF.

Is increased plasma TMAO a compensatory response to hydrostatic and osmotic stress in cardiovascular diseases?

Recent clinical studies show a positive correlation between elevated plasma TMAO and increased cardiovascular risk. However, the mechanism of the increase and biological effects of TMAO in the circulatory system are obscure.Plasma TMAO level depends mostly on the following three factors. First, the liver produces TMAO from TMA, a gut bacteria metabolite of dietary choline and carnitine. Second, plasma TMAO increases after ingestion of dietary TMAO from fish and seafood. Finally, plasma TMAO depends on TMAO and TMA excretion by the kidneys.Ample evidence highlights protective functions of TMAO, including the stabilization of proteins and cells exposed to hydrostatic and osmotic stresses, for example in fish exposed to hydrostatic stress (deep water) and osmotic stress (salty water).Osmotic stress and hydrostatic stresses are augmented in cardiovascular diseases such as hypertension. In hypertensive subjects a diastole-systole change in hydrostatic pressure in the heart may exceed 220 mmHg with a frequency of 60–220/min. This produces environment in which hydrostatic pressure changes over 100,000 times per 24 h. Furthermore, cardiovascular diseases are associated with disturbances in water-electrolyte balance which produce changes in plasma osmolarity. Perhaps, the increase in plasma TMAO in cardiovascular diseases is analogous to increased level of plasma natriuretic peptide B, which is both a cardiovascular risk marker and a compensatory response producing beneficial effects for pressure/volume overloaded heart. In this regard, there is some evidence that a moderate increase in plasma TMAO due to TMAO supplementation may be beneficial in animal model of hypertension-related heart failure. Finally, increased plasma TMAO is present in humans consuming seafood-rich diet which is thought to be health-beneficial.We hypothesize that increased plasma TMAO serves as a compensatory response mechanism which protects cells from hydrostatic and osmotic stresses.

Molecular evidence of tissue remodeling in an animal model of heart failure.

Heart failure (HF) is the final common pathway of many cardiovascular diseases. Metalloproteinases and their inhibitors, such as MMP9 and TIMP-1, assist in maintaining the extracellular matrix, leading to tissue remodeling observed after HF. Previous studies have shown that L-Arginine (LA) appears to have beneficial effects for the treatment of HF, contributing to vasodilation, the reestablishment of the endothelial function and an increase in muscle contractile force. This study analyzed heart tissue remodeling in an animal model of HF induced by aortocaval fistula (ACF) and submitted to LA treatment. After 4 weeks of ACF, animals were treated with LA for 4 weeks (SHAM-LA, HF-LA) or for 8-12 weeks with saline (SHAM, HF8, HF12). Rats were euthanized and the hearts removed for histological processing. The samples were stained with Hematoxylin-Eosin (HE), Masson's Thichome (MT), or submitted to immunohistochemistry (IHC) for MMP9 and TIMP-1. Light microscopy analysis showed cardiac striated muscle without fibrosis in all experimental groups. Immunostaining of MMP9 and TIMP-1 were positive for all experimental groups. LA administration significatively reduced MMP9 content after HF. These data indicate molecular changes in metalloproteinases expression prior to tissue remodeling and point out LA as an adjuvant therapy to pharmacological treatment of patients with HF.

Reversion of cardiac dysfunction by a novel orally available calcium/calmodulin-dependent protein kinase II inhibitor, RA306, in a genetic model of dilated cardiomyopathy.

Despite improvements in patient identification and management, heart failure (HF) remains a major public health burden and an important clinical challenge. A variety of animal and human studies have provided evidence suggesting a central role of calcium/calmodulin-dependent protein kinase II (CaMKII) in the development of pathological cardiac remodelling and HF. Here, we describe a new potent, selective, and orally available CaMKII inhibitor. Chemical optimization led to the identification of RA306 as a selective CaMKII inhibitor. This compound was found potent on the cardiac CaMKII isoforms delta and gamma (IC50 in the 10 nM range), with pharmacokinetic properties allowing oral administration in animal models of HF. RA306 was administered to diseased mice carrying a mutation in alpha-actin that is responsible for dilated cardiomyopathy (DCM) in humans. In two separate studies, RA306 was orally administered at 30 mg/kg either for 2 weeks (twice a day) or for 2 months (once a day). Echocardiography monitoring showed that RA306 significantly improved cardiac function (ejection fraction and cardiac output) as compared to vehicle. These disease modifying effects of RA306 were associated with inhibition of cardiac phosphorylation of phospholamban (PLN) at threonine-17, indicating reduced cardiac CaMKII activity. This work supports the feasibility of identifying potent orally available CaMKII inhibitors suitable for clinical use to treat heart disease.

Sleeve Gastrectomy in Obese Zucker Rats Restores Cardiac Function and Geometry Toward a Lean Phenotype Independent of Weight Loss

Bariatric surgery, including sleeve gastrectomy (SG), significantly improves cardiac geometry and function in patients with heart failure. In this study, we used the obese Zucker rat as an animal model of heart failure with preserved ejection fraction (HFpEF) to test the hypothesis that a SG will improve cardiac function independent of weight loss. Obese, male Zucker rats underwent SG, pair-fed sham, or ad-lib sham surgery. Lean Zucker rats also underwent ad-lib sham surgery. Echocardiograms were performed preoperatively and at 6 weeks postoperatively. Obese SG and obese pair-fed sham rats had similar body weights postoperatively. Obese SG and lean, ad-lib, sham rats had a significant increase in postoperative stroke volume, and left ventricular internal diameter in diastole and systole. SG preserved systolic function and significantly improved isovolumetric relaxation time (13.9 ± 2.4 to 11.1 ± 2.1 ms, P = .02) independent of weight loss. SG has a beneficial impact on both systolic and diastolic cardiac function in obese Zucker rats toward a lean phenotype independent of weight loss and caloric restriction. These findings may represent a weight-loss independent mechanism generated from the gastrointestinal tract that has the potential to improve diastolic dysfunction independent of obesity status and translate to patients with HFpEF.

Antioxidant Effect of Resveratrol on Autonomic Cardiocirculatory Control in Heart Failure Rats

In animal models of heart failure (HF), resveratrol (RESV) reduced the disease progression and increased the survival rate. Nevertheless, there are no reports in the literature about the effect of RESV on autonomic cardiocirculatory control during the establishment of HF. This study aimed to evaluate the antioxidant effect of RESV on the cardiac autonomic balance and baroreflex sensitivity of HF rats induced by myocardial infarction (MI). Wistar rats were divided into the following groups: Control; Control + RESV; HF; HF + RESV (10mg/kg/day, p.o.). The MI‐induced HF model was produced by ligation of the coronary artery. After four weeks, the animals were anaesthetized for femoral artery and vein catheterization and, 24 hours later, recordings were carried out in conscious animals. Baseline arterial pressure and heart rate (HR, bpm) were recorded during 30 minutes to assess spontaneous baroreflex sensitivity and HR variability. Phenylephrine and sodium nitroprusside (NPS), and methylatropine and propranolol were used for baroreflex evaluation and estimation of cardiac parasympathetic and sympathetic tone, respectively. At the end of the experiments, the animals were anaesthetized to evaluate the cardiac function, using the intraventricular pressure curve, and to withdraw the heart for calculation of heart weight/body weight ratio (HW/BW, mg/g) and the infarct size. The oxidative stress was assessed by measurement of thiobarbituric acid reactive substances (TBARS) in plasma samples. HF and HF+RESV showed 41±3% and 35±3% of infarct size, respectively, and HW/BW ratio increase (3.9±0.1 vs 3.7±0.2 vs 3.0±0.07). HF rats exhibited higher HR compared to control animals (374±12 vs 333±6). RESV did not alter basal parameters in the control group but prevented HR alterations in HF+RESV group (337±6). HF blunted baroreflex sensitivity to phenylephrine (1.3±0.2 vs 2.3±0.3) and NPS (−3.9±0.5 vs −6.0±0.6), increased cardiac sympathetic tone (−44±9 vs −20±4) and decreased parasympathetic tone (54±12 vs 120±7), intrinsic HR (381±8 vs. 401±5), baroreflex effectiveness index (0.06±0.01 vs 0.15±0.01) and LF/HF ratio (0.17±0.05 vs 0.43±0.06). RESV hampered alterations in baroreflex function and cardiac vagal tone (103±13), improve HR variability indexes (LF/HF: 0.3±0.07) and reduced sympathetic control of HR (−29±3) and intrinsic HR in HF+RESV group (360±9). In cardiac function, RESV improved the maximal slope of the systolic increment of left ventricular pressure in HF animals (9004±1120 vs 5956±605 vs 6914±581 mmHg/s). HF increased TBARS compared to control, whereas RESV produced an antioxidant effect in HF+RESV group (11.2±0.9 vs 21.7±3 vs 8.2±1.4 μmol/L). In conclusion, the antioxidant effect of RESV counteracts the cardiovascular autonomic dysfunction and improves systolic left ventricle function during the onset of HF.Support or Funding InformationCNPq e UnaerpThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Prevention of Cardiac Dysfunction Development by a Methanocarba Adenosine Monophosphonate Derivative

Accumulating evidence supports a therapeutic role of purinergic signaling in cardiac diseases. Previous studies showed that MRS2339, a charged methanocarba derivative of 2‐Cl‐adenosine monophosphate, is efficacious in animal models of heart failure when infused systemically. However, MRS2339 lacks oral bioavailability as a nucleoside 5’‐phosphate derivative and is subject to hydrolysis in vivo leading to the inactive nucleoside MRS1873. We now test the hypothesis that uncharged adenine nucleoside phosphonates, suitable as oral agents with a hydrolysis‐resistant phospho moiety, can prevent the development of cardiac dysfunction in a post‐infarction ischemic or pressure overloaded heart failure model. Of the diester‐masked uncharged phosphonates evaluated, MRS2978 but not MRS4074, was efficacious in preventing cardiac dysfunction with improved left ventricular (LV) fractional shortening (FS increased from 21±0.79% with vehicle (N=13) to 25.1±0.63% with MRS2978 (N=11), P<0.05) and with preservation of LV wall thickness when administered orally at onset of ischemic heart failure (within 24h after left anterior descending artery (LAD) ligation). MRS2925, the charged, unmasked analog of MRS2978, was able to prevent heart dysfunction only when it was infused subcutaneously; its oral gavage was not efficacious. In the established heart failure models caused either by LAD ligation or transverse aortic constriction (TAC), orally administrated MRS2978 (4 weeks after LAD ligation or 3 weeks after TAC), but not MRS2925, could partially restore cardiac dysfunction by increasing the FS in both ischemic (from 19.7±0.95% with vehicle (N=18) to 26.1±1.37% with MRS2978 (N=11), P<0.05) and pressure overload (FS from 17.5±0.76% with vehicle(N=9) to 23.7±1.25% with MRS2978 (N=10), P<0.05) heart failure models. MRS2978 was orally bioavailable (57–75%F) and highly stable in human, mouse and rat plasma, with 96–100% remaining after 2 h. MRS2925 could be formed from hydrolysis of MRS2978 in vivo, but as a minor metabolite (only 10%), suggesting that the effects of MRS2978 are not dependent on the MRS2925. Either MRS2978 or MRS2925, combining with 2me‐SATP, was capable of activating cardiac myocyte eNOS, consistent with myocyte eNOS activation as a mechanism for the salutary effect of these two phosphonates nucleotides. These data demonstrated the ability of oral therapy with MRS2978 to treat heart failure, both at the inception of heart failure for prevention and after the development of heart failure as a rescue.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Effect of oxidative stress in rostral ventrolateral medulla on sympathetic hyperactivity after traumatic brain injury.

Sympathetic hyperactivity occurs in a subgroup of patients after traumatic brain injury (TBI). The rostral ventrolateral medulla (RVLM) is a key region for the activity of sympathetic nervous system. Oxidative stress in the RVLM is proved to be responsible for the increased level of sympathetic activity in animal models of hypertension and heart failure. In this study, we investigated whether oxidative stress in the RVLM contributed to the development of sympathetic hyperactivity after TBI in rats. Model of diffuse axonal injury was induced using Sprague-Dawley rats, and level of mean arterial pressure (MAP) and plasma Norepinephrine (NE) was measured to evaluate the sympathetic activity. For the assessment of oxidative stress, expression of reactive oxygen species (ROS), malondialdehyde (MDA), and superoxide dismutase (SOD) in the RVLM was determined. Microinjection of Tempol into the RVLM was performed to determine the effect of oxidative stress on sympathetic hyperactivity. According to the results, TBI led to elevated MAP and plasma NE in rats. It also induced a significantly increased level of ROS, MDA production and decreased level of SOD in the RVLM. The sympathetic activity, ROS, and MDA in the RVLM decreased significantly after microinjection of Tempol. Therefore, the present results suggested that oxidative stress in the RVLM was involved in the development of sympathetic hyperactivity following TBI.

Surgical and physiological challenges in the development of left and right heart failure in rat models.

Rodent surgical animal models of heart failure (HF) are critically important for understanding the proof of principle of the cellular alterations underlying the development of the disease as well as evaluating therapeutics. Robust, reproducible rodent models are a prerequisite to the development of pharmacological and molecular strategies for the treatment of HF in patients. Due to the absence of standardized guidelines regarding surgical technique and clear criteria for HF progression in rats, objectivity is compromised. Scientific publications in rats rarely fully disclose the actual surgical details, and technical and physiological challenges. This lack of reporting is one of the main reasons that the outcomes specified in similar studies are highly variable and associated with unnecessary loss of animals, compromising scientific assessment. This review details rat circulatory and coronary arteries anatomy, the surgical details of rat models that recreate the HF phenotype of myocardial infarction, ischemia/reperfusion, left and right ventricular pressure, and volume overload states, and summarizes the technical and physiological challenges of creating HF. The purpose of this article is to help investigators understand the underlying issues of current HF models in order to reduce variable results and ensure successful, reproducible models of HF.

The Potential Beneficial Effects of Resveratrol on Cardiovascular Complications in Marfan Syndrome Patients⁻Insights from Rodent-Based Animal Studies.

Marfan syndrome (MFS) patients are at risk for cardiovascular disease. In particular, for aortic aneurysm formation, which ultimately can result in a life-threatening aortic dissection or rupture. Over the years, research into a sufficient pharmacological treatment option against aortopathy has expanded, mostly due to the development of rodent disease models for aneurysm formation and dissections. Unfortunately, no optimal treatment strategy has yet been identified for MFS. The biologically-potent polyphenol resveratrol (RES), that occurs in nuts, plants, and the skin of grapes, was shown to have a positive effect on aortic repair in various rodent aneurysm models. RES demonstrated to affect aortic integrity and aortic dilatation. The beneficial processes relevant for MFS included the improvement of endothelial dysfunction, extracellular matrix degradation, and smooth muscle cell death. For the wide range of beneficial effects on these mechanisms, evidence was found for the following involved pathways; alleviating oxidative stress (change in eNOS/iNOS balance and decrease in NOX4), reducing protease activity to preserve the extracellular matrix (decrease in MMP2), and improving smooth muscle cell survival affecting aortic aging (changing the miR21/miR29 balance). Besides aortic features, MFS patients may also suffer from manifestations concerning the heart, such as mitral valve prolapse and left ventricular impairment, where evidence from rodent models shows that RES may aid in promoting cardiomyocyte survival directly (SIRT1 activation) or by reducing oxidative stress (increasing superoxide dismutase) and increasing autophagy (AMPK activation). This overview discusses recent RES studies in animal models of aortic aneurysm formation and heart failure, where different advantageous effects have been reported that may collectively improve the aortic and cardiac pathology in patients with MFS. Therefore, a clinical study with RES in MFS patients seems justified, to validate RES effectiveness, and to judge its suitability as potential new treatment strategy.

Posttranslational modifications of mitochondrial fission and fusion proteins in cardiac physiology and pathophysiology.

Mitochondrial fragmentation frequently occurs in chronic pathological conditions as seen in various human diseases. In fact, abnormal mitochondrial morphology and mitochondrial dysfunction are hallmarks of heart failure (HF) in both human patients and HF animal models. A link between mitochondrial fragmentation and cardiac pathologies has been widely proposed, but the physiological relevance of mitochondrial fission and fusion in the heart is still unclear. Recent studies have increasingly shown that posttranslational modifications (PTMs) of fission and fusion proteins are capable of directly modulating the stability, localization, and/or activity of these proteins. These PTMs include phosphorylation, acetylation, ubiquitination, conjugation of small ubiquitin-like modifier proteins, O-linked-N-acetyl-glucosamine glycosylation, and proteolysis. Thus, understanding the PTMs of fission and fusion proteins may allow us to understand the complexities that determine the balance of mitochondrial fission and fusion as well as mitochondrial function in various cell types and organs including cardiomyocytes and the heart. In this review, we summarize present knowledge regarding the function and regulation of mitochondrial fission and fusion in cardiomyocytes, specifically focusing on the PTMs of each mitochondrial fission/fusion protein. We also discuss the molecular mechanisms underlying abnormal mitochondrial morphology in HF and their contributions to the development of cardiac diseases, highlighting the crucial roles of PTMs of mitochondrial fission and fusion proteins. Finally, we discuss the future potential of manipulating PTMs of fission and fusion proteins as a therapeutic strategy for preventing and/or treating HF.

The Crosstalk between Acetylation and Phosphorylation: Emerging New Roles for HDAC Inhibitors in the Heart.

Approximately five million United States (U.S.) adults are diagnosed with heart failure (HF), with eight million U.S. adults projected to suffer from HF by 2030. With five-year mortality rates following HF diagnosis approximating 50%, novel therapeutic treatments are needed for HF patients. Pre-clinical animal models of HF have highlighted histone deacetylase (HDAC) inhibitors as efficacious therapeutics that can stop and potentially reverse cardiac remodeling and dysfunction linked with HF development. HDACs remove acetyl groups from nucleosomal histones, altering DNA-histone protein electrostatic interactions in the regulation of gene expression. However, HDACs also remove acetyl groups from non-histone proteins in various tissues. Changes in histone and non-histone protein acetylation plays a key role in protein structure and function that can alter other post translational modifications (PTMs), including protein phosphorylation. Protein phosphorylation is a well described PTM that is important for cardiac signal transduction, protein activity and gene expression, yet the functional role for acetylation-phosphorylation cross-talk in the myocardium remains less clear. This review will focus on the regulation and function for acetylation-phosphorylation cross-talk in the heart, with a focus on the role for HDACs and HDAC inhibitors as regulators of acetyl-phosphorylation cross-talk in the control of cardiac function.

A phenotype of increased sleepiness in a mouse model of pulmonary hypertension and right ventricular hypertrophy.

The relationship between cardiovascular disease and abnormalities in sleep architecture is complex and bi-directional. Sleep disordered breathing (SDB) often confounds human studies examining sleep in the setting of heart failure, and the independent impact of isolated right or left heart failure on sleep is difficult to assess. We utilized an animal model of right heart failure using pulmonary artery banding (PAB) in mice to examine the causal effect of right heart failure on sleep architecture. Four weeks after PAB or sham (control) surgery, sleep was measured by polysomnography for 48 hours and right ventricular (RV) hypertrophy confirmed prior to sacrifice. PAB resulted in right ventricular hypertrophy based on a 30% increase in the Fulton Index (p < 0.01). After PAB, mice spent significantly more time in NREM sleep compared to the control group over a 24 hour period (53.5 ± 1.5% vs. 46.6 ± 1.4%; p < 0.01) and exhibited an inability to both cycle into REM sleep and decrease delta density across the light/sleep period. Our results support a phenotype of impaired sleep cycling and increased ‘sleepiness’ in a mouse model of RV dysfunction.

Abstract 17367: Infusion of the Ketone Body β-Hydroxybutyrate Improves Left Ventricular Systolic Function in an Animal Model of Heart Failure With Reduced Ejection Fraction

Introduction: In vitro, ketone bodies (KB) are the most energetically efficient fuel for myocardium. Ex vivo, KB infusion in the perfusion medium of working rat hearts increases the heat of combustion (produced energy) by 31%. However, there is no report about the in vivo effects of KB on LV function. We hypothesized that KB infusion in HFREF would improve energy production and thus LV systolic function. Methods: HFREF was induced in 15 pigs by 2-hour balloon occlusion of LAD: proximal LAD (n=8, severe HREF) and mid LAD (n=7, moderate HFREF). At 2 months, LV systolic function was evaluated during saline infusion and during infusion of the KB β-hydroxybutyrate. Severe HFREF animals underwent cardiac MRI for baseline LVEF, feature tracking strains, and contractile reserve (ΔLVEF under dobutamine 5μg/kg/min). Moderate HFREF pigs underwent invasive hemodynamic assessment (dP/dt) and 3D-echocadiography (3D-LVEF and 3D-strains). Simultaneous sampling from coronary artery and coronary sinus was performed to measure myocardial fuel consumption. Results: Proximal and mid LAD occlusion resulted in severe and moderate LV systolic dysfunction, respectively. In the severe HFREF, ketone infusion improved baseline LVEF, feature-tracking strains (both longitudinal and circumferencial strain), and contractile reserve. In the moderate HFREF, ketone infusion improved 3D-LVEF, 3D-strains and dP/dt (Table). Ketone infusion switched myocardial metabolism from glucose to ketone consumption. Conclusions: Continuous infusion of the KB hydroxybutyrate improves LV systolic function independent of LV systolic dysfunction severity via a shift in myocardial fuel metabolism away from glucose oxidation (energy inefficient) toward a more energy-efficient fuel like KB. This effect can explain the mechanism of action of the benefits of SGLT2 inhibitors in heart failure, as empagliflozin-induced mild kyperketonemia may increase LV systolic function and thus improve patient outcomes.

24 - 4-HNE-mediated post-translational modulation of DICER in heart failure

4-hydroxy-2-nonenal (4-HNE) is a major by-product of lipid peroxidation, a process that is exacerbated under oxidative stress conditions. This aldehyde is a very reactive molecule associated with the establishment and progression of many diseases, including cardiovascular diseases. Using mass spectrometry analysis, our group has recently found that 4-HNE directly targets DICER— a critical enzyme for microRNA (miRNA) biology— in failing hearts. Considering that targeted deletion of DICER in the heart leads to dilated cardiomyopathy and heart failure (HF), we hypothesized that 4-HNE adducted DICER could compromise its function and drive cardiac dysfunction. In a post-myocardial infarction-induced HF animal model, we found that DICER activity dropped 46.5% (53,5% ±3,9; n=6) in failing hearts when compared to sham group, followed by a reduction in miRNA levels. Pharmacological activation of aldehyde dehydrogenase 2 (ALDH2), a key mitochondrial enzyme responsible for 4-HNE removal, prevented cardiac 4-HNE protein adduct accumulation and minimized DICER loss of activity (72,15% ±14,6; n=6) in heart failure. Consistent with our in vivo data, H9C2 myoblasts acutely exposed to 50µM 4-HNE showed an increase in 4-HNE-protein adducts followed by a 16,7% reduction (83,3% ±1,2; n=4) in DICER activity. Notably, in vitro experiments using recombinant protein revealed that 4-HNE directly interacts with DICER, and the formation of 4-HNE-DICER adduct causes loss of DICER enzymatic activity in a time- and concentration-dependent manner. Taken together, our findings using animal and cellular models suggest that DICER is impaired under acute and chronic (cardiac dysfunction) aldehyde load. Moreover, a better clearance of cardiac 4-HNE improves both DICER activity and heart failure outcome in rodents. Overall, a better understanding of post-translational DICER regulation and its impact on microRNA profiles will certainly contribute to the discovery/development of improved and novel therapeutic strategies to tackle heart failure.

Assessment of Intra-Aortic Counterpulsation in an Animal Model of Heart Failure and Myocardial Ischemia.

The effectiveness of intra-aortic balloon pumping (IABP) is currently evaluated using indirect indexes. The diastolic pressure augmentation is quantified using the subendocardial viability ratio (SEVR) and the DABAC/SABAC index (areas beneath the aortic pressure-time signals during the diastolic and systolic periods, respectively). The SEVR requires invasive recordings of left ventricular pressure; the DABAC/SABAC index may represent an alternative, since it only requires an aortic pressure signal. Nonetheless, it has never been used in an animal model of counterpulsated heart failure and ischemia-reperfusion episode. The aims of this work were: (i) to develop an animal model of heart failure, with a myocardial ischemia-reperfusion episode, treated with IABP during the reperfusion period; (ii) to evaluate the effects of the IABP using the SEVR and DABAC/SABAC indices; and (iii) to assess the relationship between both ratios. Cardiovascular parameters were obtained in anesthetized sheep, in which induced heart failure and ischemia-reperfusion episodes were monitored with and without IABP 1:2. Systolic and diastolic blood pressure signals were assessed in the aorta and in the left ventricle. Values of cardiac output and left ventricular wall thickness signals were obtained. Induction of ischemia and heart failure determined decreases in SEVR and DABAC/SABAC indices with respect to their basal stage (0.807±0.118 vs. 0.601±0.107, P<0.05 and 1.062±0.136 vs. 0.902±0.161, P<0.05, respectively). Counterpulsated animals whose myocardial reperfusion was accompanied by heart failure showed a significant improvement of wall thickening fraction along time (R2 =0.7627, P<0.001). During counterpulsated heart failure accompanied by myocardial reperfusion, the SEVR was positively correlated with DABAC/SABAC index.

Effect of KN93 on delayed afterdepolarization and calcium ion in ventricular myocytes of rabbits with heart failure

Objective To observe the effect of KN93, a CaMKⅡ inhibitor, on delayed afterdepolarization (DAD) and calcium ion in ventricular myocytes of rabbits with heart failure, and to investigate the effect of CaMKⅡ signaling pathway on trigged arrhythmia after heart failure. Methods Thirty male New Zealand White rabbits were randomized(random number) into the sham operated group (sham group), heart failure group (HF group) and heart failure with KN93 group (HF+KN93 group) (n=10 each group). The rabbit heart failure model was established by abdominal aortic constriction combined with aortic valve regurgitation. The ventricular myocytes were isolated by double enzyme digestion. The action potential and the transient inward current (Iti) were recorded by the whole-cell patch-clamp. The intracellular calcium transient was measured by the ion concentration measurement system. The main calcium transporter protein was detected by Western blotting. Data were analyzed by pCLAMP10.2. Statistical analysis was performed using SPSS 17.0. Comparisons among groups were conducted using ANOVA, and SNK-q multiple comparison procedure was utilized for post-hoc analysis. Results (1) After induction of heart failure, DAD and increment of trigger activity (TA) were observed in rabbit ventricular myocytes. Treatment of KN93 with 1.0 μmol/L reduced the events of DAD and TA. (2) After induction of heart failure, Iti densities were increased from -0.12±0.02 pA/pF to -0.95±0.06 pA/pF at the polarization potential of -50 mV (n=10, P<0.01). The current densities were reduced to -0.44±0.04 pA/pF after application of 1.0 μmol/L of KN93 (n=10, P<0.01). (3) KN93 led to decrement of intracellular calcium ion concentration and calcium transient amplitude, and acceleration of the decay process of calcium transient. (4) KN93 upregulated the expression of pPLN and SERCA2a, increased the uptake of intracellular calcium ion, downregulated the expression of NCX, decreased the Iti, and reduced the occurrence of DAD and TA. Conclusions KN93 can reduce the intracellular calcium ion concentration of the heart failure animal model, and the occurrence of the DAD and TA. CaMKⅡ may be a new therapeutic target for arrhythmias in the heart failure. Key words: KN93; Heart failure; Delayed afterdepolarization; Transient inward current; Calcium ion

Primary Effect of SERCA 2a Gene Transfer on Conduction Reserve in Chronic Myocardial Infarction.

Background SERCA2a gene transfer (GT) improves mechano‐electrical function in animal models of nonischemic heart failure Whether SERCA2a GT reverses pre‐established remodeling at an advanced stage of ischemic heart failure is unclear. We sought to uncover the electrophysiological effects of adeno‐associated virus serotype 1.SERCA2a GT following myocardial infarction (MI).Methods and ResultsPigs developed mechanical dysfunction 1 month after anterior MI, at which point they received intracoronary adeno‐associated virus serotype 1.SERCA2a (MI+SERCA2a) or saline (MI) and were maintained for 2 months. Age‐matched naive pigs served as controls (Control). In vivo ECG‐and‐hemodynamic properties were assessed before and after dobutamine stress. The electrophysiological substrate was measured using optical action potential (AP) mapping in controls, MI, and MI+SERCA2a preparations. In vivo ECG measurements revealed comparable QT durations between groups. In contrast, prolonged QRS duration and increased frequency of R′ waves were present in MI but not MI+SERCA2a pigs relative to controls. SERCA2a GT reduced in in vivo arrhythmias in response to dobutamine. Ex vivo preparations from MI but not MI+SERCA2a or control pigs were prone to pacing‐induced ventricular tachycardia and fibrillation. Underlying these arrhythmias was pronounced conduction velocity slowing in MI versus MI+SERCA2a at elevated rates leading to ventricular tachycardia and fibrillation. Reduced susceptibility to ventricular tachycardia and fibrillation in MI+SERCA2a pigs was not related to hemodynamic function, contractile reserve, fibrosis, or the expression of Cx43 and Nav1.5. Rather, SERCA2a GT decreased phosphoactive CAMKII‐delta levels by >50%, leading to improved excitability at fast rates.Conclusions SERCA2a GT increases conduction velocity reserve, likely by preventing CAMKII overactivation. Our findings suggest a primary effect of SERCA2a GT on myocardial excitability, independent of altered mechanical function.

TCT-30 Renal Denervation Improves Cardiac Function in a Swine Model of Heart Failure

Introduction: Sympathetic nerve overactivity plays a critical role in the pathogenesis of heart failure (HF). Renal denervation (RDN) is currently under evaluation for the treatment of resistant hypertension and reduces blood pressure by disruption of sympathetic pathways that modulate cardiovascular function. We have demonstrated cardioprotective actions of RDN in rodent models of acute myocardial infarction and HF. We sought to determine if RDN treatment could improve cardiac function in a clinically relevant large animal model of HF. Methods: Yucatan miniswine (n=14) underwent 75 min of proximal left anterior descending coronary artery balloon-occlusion followed by 18 wks of reperfusion to generate large transmural infarcts and heart failure. Cardiac function was measured every 3 wks by 2-D echocardiography. HF was defined as left ventricular ejection fraction (LVEF) TM Multi-Electrode System (St. Jude Medical, St. Paul, MN). RDN was performed from distal to proximal in each renal artery, with at total of 24 ablation points separated both longitudinally and rotationally under fluoroscopic guidance. Results: At 3 wks of reperfusion following myocardial ischemia, LVEF was reduced in all pigs (SHAM RDN, 29.92.7%; RDN, 31.41.9%) with no further decline at the 6 wk treatment timepoint. At 6 wks of reperfusion, SHAM RDN and RDN treatments were performed without complication. Three wks after RDN treatment, LVEF was increased compared to SHAM (33.52.5 and 48.04.6%, respectively). LVEF was further increased 6 wks after RDN treatment compared to SHAM (31.51.5 vs. 62.00.6%, respectively). Interestingly, LVEF was higher 6 wks post-RDN compared to 3 wks post-RDN ( p =0.047). Conclusions: Preliminary results demonstrate that RDN significantly improves cardiac function in a clinically relevant swine model of HF.

MiR-146a Suppresses SUMO1 Expression and Induces Cardiac Dysfunction in Maladaptive Hypertrophy.

Abnormal SUMOylation has emerged as a characteristic of heart failure (HF) pathology. Previously, we found reduced SUMO1 (small ubiquitin-like modifier 1) expression and SERCA2a (sarcoplasmic reticulum Ca2+-ATPase) SUMOylation in human and animal HF models. SUMO1 gene delivery or small molecule activation of SUMOylation restored SERCA2a SUMOylation and cardiac function in HF models. Despite the critical role of SUMO1 in HF, the regulatory mechanisms underlying SUMO1 expression are largely unknown. To examine miR-146a-mediated SUMO1 regulation and its consequent effects on cardiac morphology and function. In this study, miR-146a was identified as a SUMO1-targeting microRNA in the heart. A strong correlation was observed between miR-146a and SUMO1 expression in failing mouse and human hearts. miR-146a was manipulated in cardiomyocytes through AAV9 (adeno-associated virus serotype 9)-mediated gene delivery, and cardiac morphology and function were analyzed by echocardiography and hemodynamics. Overexpression of miR-146a reduced SUMO1 expression, SERCA2a SUMOylation, and cardiac contractility in vitro and in vivo. The effects of miR-146a inhibition on HF pathophysiology were examined by transducing a tough decoy of miR-146a into mice subjected to transverse aortic constriction. miR-146a inhibition improved cardiac contractile function and normalized SUMO1 expression. The regulatory mechanisms of miR-146a upregulation were elucidated by examining the major miR-146a-producing cell types and transfer mechanisms. Notably, transdifferentiation of fibroblasts triggered miR-146a overexpression and secretion through extracellular vesicles, and the extracellular vesicle-associated miR-146a transfer was identified as the causative mechanism of miR-146a upregulation in failing cardiomyocytes. Finally, extracellular vesicles isolated from failing hearts were shown to contain high levels of miR-146a and exerted negative effects on the SUMO1/SERCA2a signaling axis and hence cardiomyocyte contractility. Taken together, our results show that miR-146a is a novel regulator of the SUMOylation machinery in the heart, which can be targeted for therapeutic intervention.