Murine Model Of Heart Failure Research Articles

Abstract 585: CDK8 Activity-dependent Regulation of Heart Disease

Pathological cardiac hypertrophy represents a major risk factor for heart failure (HF). The hypertrophic response is orchestrated in part through transcriptional alterations that ultimately modify cardiac function. Mediator is a multiprotein complex that coordinates signal dependent transcription factors with basal transcriptional machinery including RNA polymerase II and general transcription factors. Transcriptional regulation by Mediator complex can be modified by the association of the Mediator complex kinase submodule with the core complex. Cyclin-dependent kinase 8 (CDK8) is a kinase present in the submodule that has been demonstrated to have a complex role in transcriptional regulation through a number of mechanisms involving both transcriptional activation and inhibition. Our lab has demonstrated that CDK8 expression is upregulated in murine HF models as well as in failing human hearts. In addition, cardiac CDK8 over-expression promotes transcriptional remodeling that results in dilated cardiomyopathy suggesting that CDK8 inhibition may represent a novel pharmacological target. This study utilizes CDK8 kinase inhibitor, Senexin A, which is being evaluated as an anti-cancer chemotherapeutic agent. Here, we demonstrate that Senexin A inhibits kinase activity in an in vitro neonatal rat cardiomyocyte (NRCM) model resulting in reduced cardiomyocyte hypertrophy as well as a reduction in expression of specific cardiomyocyte hypertrophy markers. These studies demonstrate a role for CDK8 activity in transcriptional regulation of genes associated with pathological cardiac remodeling that drives cardiac hypertrophy and ultimately HF.

P4776Targeting metabolic remodeling in a murine heart failure model by AAV-mediated over-expression of organic cation/carnitine transporter 2 (OCTN2)

P4776Targeting metabolic remodeling in a murine heart failure model by AAV-mediated over-expression of organic cation/carnitine transporter 2 (OCTN2)

P4774Empagliflozin improves exercise endurance via the activation of fatty acid oxidation in the skeletal muscle in murine model of post-infarct heart failure

P4774Empagliflozin improves exercise endurance via the activation of fatty acid oxidation in the skeletal muscle in murine model of post-infarct heart failure

A novel fibroblast activation inhibitor attenuates left ventricular remodeling and preserves cardiac function in heart failure.

Cardiac fibroblasts are critical mediators of fibrotic remodeling in the failing heart and transform into myofibroblasts in the presence of profibrotic factors such as transforming growth factor-β. Myocardial fibrosis worsens cardiac function, accelerating the progression to decompensated heart failure (HF). We investigated the effects of a novel inhibitor (NM922; NovoMedix, San Diego, CA) of the conversion of normal fibroblasts to the myofibroblast phenotype in the setting of pressure overload-induced HF. NM922 inhibited fibroblast-to-myofibroblast transformation in vitro via a reduction of activation of the focal adhesion kinase-Akt-p70S6 kinase and STAT3/4E-binding protein 1 pathways as well as via induction of cyclooxygenase-2. NM922 preserved left ventricular ejection fraction ( P < 0.05 vs. vehicle) and significantly attenuated transverse aortic constriction-induced LV dilation and hypertrophy ( P < 0.05 compared with vehicle). NM922 significantly ( P < 0.05) inhibited fibroblast activation, as evidenced by reduced myofibroblast counts per square millimeter of tissue area. Picrosirius red staining demonstrated that NM922 reduced ( P < 0.05) interstitial fibrosis compared with mice that received vehicle. Similarly, NM922 hearts had lower mRNA levels ( P < 0.05) of collagen types I and III, lysyl oxidase, and TNF-α at 16 wk after transverse aortic constriction. Treatment with NM922 after the onset of cardiac hypertrophy and HF resulted in attenuated myocardial collagen formation and adverse remodeling with preservation of left ventricular ejection fraction. Future studies are aimed at further elucidation of the molecular and cellular mechanisms by which this novel antifibrotic agent protects the failing heart. NEW & NOTEWORTHY Our data demonstrated that a novel antifibrotic agent, NM922, blocks the activation of fibroblasts, reduces the formation of cardiac fibrosis, and preserves cardiac function in a murine model of heart failure with reduced ejection fraction.

Relaxin Family Member Insulin-Like Peptide 6 Ameliorates Cardiac Fibrosis and Prevents Cardiac Remodeling in Murine Heart Failure Models.

BackgroundThe insulin/insulin‐like growth factor/relaxin family represents a group of structurally related but functionally diverse proteins. The family member relaxin‐2 has been evaluated in clinical trials for its efficacy in the treatment of acute heart failure. In this study, we assessed the role of insulin‐like peptide 6 (INSL6), another member of this protein family, in murine heart failure models using genetic loss‐of‐function and protein delivery methods.Methods and ResultsInsl6‐deficient and wild‐type (C57BL/6N) mice were administered angiotensin II or isoproterenol via continuous infusion with an osmotic pump or via intraperitoneal injection once a day, respectively, for 2 weeks. In both models, Insl6‐knockout mice exhibited greater cardiac systolic dysfunction and left ventricular dilatation. Cardiac dysfunction in the Insl6‐knockout mice was associated with more extensive cardiac fibrosis and greater expression of fibrosis‐associated genes. The continuous infusion of chemically synthesized INSL6 significantly attenuated left ventricular systolic dysfunction and cardiac fibrosis induced by isoproterenol infusion. Gene expression profiling suggests liver X receptor/retinoid X receptor signaling is activated in the isoproterenol‐challenged hearts treated with INSL6 protein.ConclusionsEndogenous Insl6 protein inhibits cardiac systolic dysfunction and cardiac fibrosis in angiotensin II– and isoproterenol‐induced cardiac stress models. The administration of recombinant INSL6 protein could have utility for the treatment of heart failure and cardiac fibrosis.

An emerging role for the Cdk-inhibitors p21Cip1/Waf1 and p27Kip1 as potential therapies for the treatment of cardiac hypertrophy

Heart failure is the leading cause of morbidity and mortality worldwide. Adult cardiomyocytes are post-mitotic cells that are substantially refractory to re-enter the cell cycle. This is exemplified by the absence of significant proliferative potential in differentiated cardiomyocytes. When exposed to aberrant growth stimuli, cardiomyocytes undergo maladaptive changes characterized by hypertrophic growth. The existing armamentarium of conventional pharmacological therapy can only slow the progression of the disease by alleviating the workload of the heart. Various agonist- and stress-induced extracellular signal transduction pathways could be target by novel agents for the treatment of pathological cardiac growth. Among these, the cyclin-dependent kinase inhibitors p21 and p27 have been recognized as potent inhibitors of apoptosis, growth and proliferation in cardiovascular disease. The role of the cell cycle factors p21 and p27 in the regulation of growth-associated processes in the heart, and their potential therapeutic implications are not immediately obvious, as it is the case in cardiovascular biology. In this review, we focus on the multiple functions of p21 and p27 in the regulation of hypertrophy, and briefly discuss pathways that play critical play therein. All these selected studies attest an important role of p21 and p27 in the regulation of hypertrophy in isolated rat cardiomyocytes, and in various genetic murine models of heart failure. The available evidence suggests that therapeutic clinical approaches involving p21 and p27 have the potential to to treat heart failure in patients.

A Hydrogen Sulfide Donor, JK1, Preserves Endothelial Function and Improves Exercise Capacity in Pressure Overload ‐ Induced Heart Failure

Background and HypothesisHydrogen sulfide (H2S) protects against heart failure by ameliorating oxidative stress, improving mitochondrial function, and attenuating apoptosis. At present there is a lack of data demonstrating the protective actions of H2S in the late stages of heart failure. And the effects of H2S on exercise intolerance, the clinical hallmark of heart failure, has not been evaluated in preclinical models. In current study, we tested the efficacy of delayed therapy with a novel H2S donor, JK1, on cardiac function, endothelial function, and exercise capacity in a murine model of pressure overload‐induced heart failure.MethodsMale C57/BL6J mice at 10 weeks (wks) of age were subjected to transverse aortic constriction (TAC) for 18 weeks. JK1 (200 μg/kg/d, n=20) or the H2S deficient control compound (200 μg/kg/d, n=18) was administered via i.p. injection twice per day starting at 10 wks post TAC, in which time all mice had EF lower than 45%. Echocardiography was performed at baseline and tri‐weekly to assess LV structure and function. LV hemodynamics, cardiac fibrosis, vascular reactivity (isolated thoracic aorta), and exercise capacity were measured at the endpoint, 18 wks post TAC.ResultsDelayed treatment with JK1 initiated at 10 wks post TAC reduced LV dilation (p &lt; 0.01) and attenuated eccentric hypertrophy (p &lt; 0.01). However, no significant difference was noted in LV ejection fraction and cardiac fibrosis. JK1 treated mice displayed lower LV end‐diastolic pressure (LVEDP 17.8 ± 1.8 mmHg vs. 22.9 ± 1.23 mmHg, p &lt; 0.05) and improved relaxation time constant (Tau 8 ± 0.27 ms vs. 10.05 ± 0.58 ms, p &lt; 0.01). In addition, aortic vasorelaxation in response to acetylcholine treatment was markedly improved in mice received JK1 treatment (Max. Relaxation 51.8 ± 4.2% vs. 31.5 ± 3.6%, p &lt; 0.01). More importantly, mice received JK1 treatment exhibited improved exercise capacity (Distance 312 ± 13.4 m vs. 89 ± 6.3 m, p &lt; 0.05) as compared to those received control.ConclusionThese results demonstrate that delayed administration of a novel H2S donor, JK1, improves exercise capacity in severe heart failure following TAC. JK1 treatment initiated at 10 weeks post TAC did not improve systolic function or reduce cardiac fibrosis, suggesting that the beneficial effects of 10‐wks‐delayed H2S therapy in pressure overload heart failure are a result of the improved vascular function and LV hemodynamics.Support or Funding Information

Ablation of the stress protease OMA1 protects against heart failure in mice.

Heart failure (HF) is a major health and economic burden in developed countries. It has been proposed that the pathogenesis of HF may involve the action of mitochondria. We evaluate three different mouse models of HF: tachycardiomyopathy, HF with preserved left ventricular (LV) ejection fraction (LVEF), and LV myocardial ischemia and hypertrophy. Regardless of whether LVEF is preserved, our results indicate that the three models share common features: an increase in mitochondrial reactive oxygen species followed by ultrastructural alterations in the mitochondrial cristae and loss of mitochondrial integrity that lead to cardiomyocyte death. We show that the ablation of the mitochondrial protease OMA1 averts cardiomyocyte death in all three murine HF models, and thus loss of OMA1 plays a direct role in cardiomyocyte protection. This finding identifies OMA1 as a potential target for preventing the progression of myocardial damage in HF associated with a variety of etiologies.

Development of a murine model of heart failure with preserved ejection fraction

Pathophysiology of heart failure with preserved ejection fraction (HFpEF) is poorly understood today. One of the hypothesis is the role played by the endothelial dysfunction. To develop a murine model of HFpEF to study the role of EC dysfunction. We chose to develop a model that reproduce cardiovascular risk factors and co-morbidity seen in humans HFpEF by using aging, obese diabetic mice (db/db) perfused with Angiotensin II pump for one month (low grade inflammation). Males and females mice were studied at 1, 6 and 12 months by echocardiography, histology (parameters of EC dysfunction, fibrosis) and hemodynamic. At 1 and 6 months, we recorded no difference in cardiac functional, histologic and hemodynamic parameters in males db/db as compared to male db+. At 6 months females db/db displayed discrete echocardiographic and hemodynamic parameters of HFpEF as compared to female db+. Results at 12 months will be available for the meeting. Obese diabetic with low-grade inflammation mice do not develop clear markers of HFpEF within 6 months of life.

Tet2-Mediated Clonal Hematopoiesis Accelerates Heart Failure Through a Mechanism Involving the IL-1β/NLRP3 Inflammasome

BackgroundRecent studies have shown that hematopoietic stem cells can undergo clonal expansion secondary to somatic mutations in leukemia-related genes, thus leading to an age-dependent accumulation of mutant leukocytes in the blood. This somatic mutation-related clonal hematopoiesis is common in healthy older individuals, but it has been associated with an increased incidence of future cardiovascular disease. The epigenetic regulator TET2 is frequently mutated in blood cells of individuals exhibiting clonal hematopoiesis. ObjectivesThis study investigated whether Tet2 mutations within hematopoietic cells can contribute to heart failure in 2 models of cardiac injury. MethodsHeart failure was induced in mice by pressure overload, achieved by transverse aortic constriction or chronic ischemia induced by the permanent ligation of the left anterior descending artery. Competitive bone marrow transplantation strategies with Tet2-deficient cells were used to mimic TET2 mutation-driven clonal hematopoiesis. Alternatively, Tet2 was specifically ablated in myeloid cells using Cre recombinase expressed from the LysM promoter. ResultsIn both experimental heart failure models, hematopoietic or myeloid Tet2 deficiency worsened cardiac remodeling and function, in parallel with increased interleukin-1beta (IL-1β) expression. Treatment with a selective NLRP3 inflammasome inhibitor protected against the development of heart failure and eliminated the differences in cardiac parameters between Tet2-deficient and wild-type mice. ConclusionsTet2 deficiency in hematopoietic cells is associated with greater cardiac dysfunction in murine models of heart failure as a result of elevated IL-1β signaling. These data suggest that individuals with TET2-mediated clonal hematopoiesis may be at greater risk of developing heart failure and respond better to IL-1β–NLRP3 inflammasome inhibition.

MiR-25 Tough Decoy Enhances Cardiac Function in Heart Failure.

MicroRNAs are promising therapeutic targets, because their inhibition has the potential to normalize gene expression in diseased states. Recently, our group found that miR-25 is a key SERCA2a regulating microRNA, and we showed that multiple injections of antagomirs against miR-25 enhance cardiac contractility and function through SERCA2a restoration in a murine heart failure model. However, for clinical application, a more stable suppressor of miR-25 would be desirable. Tough Decoy (TuD) inhibitors are emerging as a highly effective method for microRNA inhibition due to their resistance to endonucleolytic degradation, high miRNA binding affinity, and efficient delivery. We generated a miR-25 TuD inhibitor and subcloned it into a cardiotropic AAV9 vector to evaluate its efficacy. The AAV9 TuD showed selective inhibition of miR-25 invitro cardiomyoblast culture. Invivo, AAV9-miR-25 TuD delivered to the murine pressure-overload heart failure model selectively decreased expression of miR-25, increased levels of SERCA2a protein, and ameliorated cardiac dysfunction and fibrosis. Our data indicate that miR-25 TuD is an effective long-term suppressor of miR-25 and a promising therapeutic candidate to treat heart failure.

GW28-e0385 Multimodal imaging for in vivo evaluation of induced pluripotent stem cells in a murine model of heart failure

GW28-e0385 Multimodal imaging for in vivo evaluation of induced pluripotent stem cells in a murine model of heart failure

A Novel α-Calcitonin Gene-Related Peptide Analogue Protects Against End-Organ Damage in Experimental Hypertension, Cardiac Hypertrophy, and Heart Failure.

Research into the therapeutic potential of α-calcitonin gene-related peptide (α-CGRP) has been limited because of its peptide nature and short half-life. Here, we evaluate whether a novel potent and long-lasting (t½ ≥7 hours) acylated α-CGRP analogue (αAnalogue) could alleviate and reverse cardiovascular disease in 2 distinct murine models of hypertension and heart failure in vivo. The ability of the αAnalogue to act selectively via the CGRP pathway was shown in skin by using a CGRP receptor antagonist. The effect of the αAnalogue on angiotensin II-induced hypertension was investigated over 14 days. Blood pressure was measured by radiotelemetry. The ability of the αAnalogue to modulate heart failure was studied in an abdominal aortic constriction model of murine cardiac hypertrophy and heart failure over 5 weeks. Extensive ex vivo analysis was performed via RNA analysis, Western blot, and histology. The angiotensin II-induced hypertension was attenuated by cotreatment with the αAnalogue (50 nmol·kg-1·d-1, SC, at a dose selected for lack of long-term hypotensive effects at baseline). The αAnalogue protected against vascular, renal, and cardiac dysfunction, characterized by reduced hypertrophy and biomarkers of fibrosis, remodeling, inflammation, and oxidative stress. In a separate study, the αAnalogue reversed angiotensin II-induced hypertension and associated vascular and cardiac damage. The αAnalogue was effective over 5 weeks in a murine model of cardiac hypertrophy and heart failure. It preserved heart function, assessed by echocardiography, while protecting against adverse cardiac remodeling and apoptosis. Moreover, treatment with the αAnalogue was well tolerated with neither signs of desensitization nor behavioral changes. These findings, in 2 distinct models, provide the first evidence for the therapeutic potential of a stabilized αAnalogue, by mediating (1) antihypertensive effects, (2) attenuating cardiac remodeling, and (3) increasing angiogenesis and cell survival to protect against and limit damage associated with the progression of cardiovascular diseases. This indicates the therapeutic potential of the CGRP pathway and the possibility that this injectable CGRP analogue may be effective in cardiac disease.

Abstract 100: A MicroRNA Signature for Left Ventricular Reverse Remodeling in Chronic Systolic Heart Failure

Introduction: Left ventricular reverse remodeling (LVRR) in heart failure (HF) is linked to improved patient outcomes. Current strategies to identify individuals who respond favorably to therapy in HF are limited. Though circulating microRNAs (miRs) show epigenetic regulation of LVRR in vivo , there is little clinical data linking plasma-circulating miRs to LVRR. Here we employ a point-of-care microRNA assay, Firefly, in silico analyses, and murine models of HF to characterize profiles of circulating miRs that prognosticate LVRR in patients with HF undergoing guideline directed therapy. Hypothesis: Profiles of miRs in circulating plasma will prognosticate LVRR in patients with HF better than the current clinical model alone and may play a functional role in LVRR. Methods: Plasma from 64 patients from the PROTECT study who had serial echocardiography and available plasma at pre-randomization study visit were run on Abcam’s Firefly platform to assay levels of 51 miRs, selected on prior sequencing efforts (for discovery) and published roles in CVD. miR levels were subject to PC analysis to predict LVRR. Candidate miRs were then validated in a murine model of transverse aortic constriction-induced heart failure (TAC-HF) and their function assessed in cardiomyocyte culture systems. Results: Principle component analysis revealed 4 PCs accounting for 62.4% of the observed variation without significant association with extant markers of HF. When PC2 miR levels were added to the clinical model prognostic ability for LVRR improved substantially (AIC 79.5, (OR=6.84, 95% CI 1.81-25.80, P= 0.005). In silico analysis was then applied to generate networks of mRNAs regulated by PC2 miRs. In the murine TAC-HF model, miRs 423, 212, 221, 193b were differentially regulated, as were the predicted targets of these miRs. These miRs, particularly in combination, appeared to be regulators of cardiac hypertrophy in vitro . Conclusions: Circulating miR profiles in HF improve prognosticative ability for patients who will undergo LVRR over the clinical model alone. Additionally these miRs and their targets are dynamically regulated in murine models of HF, suggesting they may have functional and potential therapeutic utility in addition to their prognostic power.

Reduced activin receptor-like kinase 1 activity promotes cardiac fibrosis in heart failure.

Activin receptor-like kinase 1 (ALK1) mediates signaling via the transforming growth factor beta-1 (TGFβ1), a pro-fibrogenic cytokine. No studies have defined a role for ALK1 in heart failure. We tested the hypothesis that reduced ALK1 expression promotes maladaptive cardiac remodeling in heart failure. In patients with advanced heart failure referred for left ventricular (LV) assist device implantation, LV Alk1 mRNA and protein levels were lower than control LV obtained from patients without heart failure. To investigate the role of ALK1 in heart failure, Alk1 haploinsufficient (Alk1+/-) and wild-type (WT) mice were studied 2 weeks after severe transverse aortic constriction (TAC). LV and lung weights were higher in Alk1+/- mice after TAC. Cardiomyocyte area and LV mRNA levels of brain natriuretic peptide and β-myosin heavy chain were increased similarly in Alk1+/- and WT mice after TAC. Alk-1 mice exhibited reduced Smad 1 phosphorylation and signaling compared to WT mice after TAC. Compared to WT, LV fibrosis and Type 1 collagen mRNA and protein levels were higher in Alk1+/- mice. LV fractional shortening was lower in Alk1+/- mice after TAC. Reduced expression of ALK1 promotes cardiac fibrosis and impaired LV function in a murine model of heart failure. Further studies examining the role of ALK1 and ALK1 inhibitors on cardiac remodeling are required.

Exercise training in Tgαq*44 mice during the progression of chronic heart failure: cardiac vs. peripheral (soleus muscle) impairments to oxidative metabolism.

Cardiac function, skeletal (soleus) muscle oxidative metabolism, and the effects of exercise training were evaluated in a transgenic murine model (Tgαq*44) of chronic heart failure during the critical period between the occurrence of an impairment of cardiac function and the stage at which overt cardiac failure ensues (i.e., from 10 to 12 mo of age). Forty-eight Tgαq*44 mice and 43 wild-type FVB controls were randomly assigned to control groups and to groups undergoing 2 mo of intense exercise training (spontaneous running on an instrumented wheel). In mice evaluated at the beginning and at the end of training we determined: exercise performance (mean distance covered daily on the wheel); cardiac function in vivo (by magnetic resonance imaging); soleus mitochondrial respiration ex vivo (by high-resolution respirometry); muscle phenotype [myosin heavy chain (MHC) isoform content; citrate synthase (CS) activity]; and variables related to the energy status of muscle fibers [ratio of phosphorylated 5'-AMP-activated protein kinase (AMPK) to unphosphorylated AMPK] and mitochondrial biogenesis and function [peroxisome proliferative-activated receptor-γ coactivator-α (PGC-1α)]. In the untrained Tgαq*44 mice functional impairments of exercise performance, cardiac function, and soleus muscle mitochondrial respiration were observed. The impairment of mitochondrial respiration was related to the function of complex I of the respiratory chain, and it was not associated with differences in CS activity, MHC isoforms, p-AMPK/AMPK, and PGC-1α levels. Exercise training improved exercise performance and cardiac function, but it did not affect mitochondrial respiration, even in the presence of an increased percentage of type 1 MHC isoforms. Factors "upstream" of mitochondria were likely mainly responsible for the improved exercise performance.NEW & NOTEWORTHY Functional impairments in exercise performance, cardiac function, and soleus muscle mitochondrial respiration were observed in transgenic chronic heart failure mice, evaluated in the critical period between the occurrence of an impairment of cardiac function and the terminal stage of the disease. Exercise training improved exercise performance and cardiac function, but it did not affect the impaired mitochondrial respiration. Factors "upstream" of mitochondria, including an enhanced cardiovascular O2 delivery, were mainly responsible for the functional improvement.

Cardiovascular Protective Effects of AT2R Activation by Peptide Drug NP‐6A4

Introduction and ObjectiveLiterature shows that elevated Angiotensin II Type 2 receptor (AT2R) expression is cardiovascular reparative and mediates protection from hypertension, as well as vascular and renal injury. AT2R is a member of the anti‐inflammatory branch of the renin‐angiotensin system (RAS). Clinically, loss of AT2R expression in men due to the intronic G1675A or A1818T polymorphism is associated with impaired kidney function, pulse pressure and increased arterial stiffness. Given the pathological consequences of the loss of AT2R expression there is need for a drug that can increase AT2R gene (Agtr2) expression to mitigate cardiovascular damage. Currently there are no FDA‐approved drugs that meet these parameters. NP‐6A4 is a peptide agonist for AT2R, recently developed by Novopyxis Inc. We have shown that NP‐6A4 increases the viability of nutrient‐stressed mouse and human cardiovascular cells. Chemotherapeutic agents such as anthracyclins are inducers of cardiotoxicity. Therefore we investigated whether NP‐6A4 can protect cardiac cells from Doxorubicin (Dox; an anthracyclin) induced toxicity. To test the translational potential of a treatment paradigm that utilizes NP‐6A4 to improve cardiac functions and mitigate cardiac structural damage, we investigated the effects of NP‐6A4 treatment in Male Zucker Obese (ZO‐M) rats, a model for heart failure with preserved ejection fraction and cardiomyopathy.MethodsMTS assay (BioVision) was used to determine the effect of Dox treatment (0.5–2 μM) with and without co‐treatment with NP‐6A4 (1μM) on the survival of H9c2 cardiomyoblasts. To evaluate the effect of NP‐6A4 on cardiac structure and function, we treated 11‐week‐old ZO‐M rats that had fully developed cardiovascular disease with NP‐6A4 (1.8mg/kg/day by subcutaneous delivery). Echocardiography was used to assess cardiac function parameters. Cardiac architecture, hypertrophy, capillary density and fibrosis were assessed by staining using hematoxylin and eosin, Helix pomatia agglutinin (HPA), isolectin B4 (IB4) and Picrosirius Red (PSR) respectively. Expression levels of AT2R in the heart were assessed by quantitative RT‐PCR.Results24‐hour Dox treatment of H9c2 cardiomyoblasts suppressed cell viability (78% for 2μM vs untreated) and co‐treatment with NP‐6A4 restored cell survival. NP‐6A4 improved several cardiac parameters including endocardial circumferential strain (p≤0.05), myocardial performance index (MPI) (p≤0.005), and E/E' ratio (p≤0.002). NP‐6A4 reduced cardiomyocyte hypertrophy and fibrosis, and increased capillary density (p≤0.05). Importantly, cardiac Agtr2 (AT2R) mRNA levels were increased by about 9‐fold in NP‐6A4 treated rats vs. saline treated rats. Histopathology staining revealed regions of micro‐infarcts present in the saline group which were largely absent in the NP‐6A4 treated animals.ConclusionNP‐6A4 could mitigate Dox‐induced cardiac cell toxicity in vitro. NP‐6A4 also improved cardiac functions in a murine model of heart failure with preserved ejection fraction and cardiomyopathy, decreased risk of cardiac event (as measured by E/E'), mitigated myocardial structural damage, and improved cardiac vascularization. To our knowledge, NP‐6A4 is the first AT2R agonist that can increase cardiac AT2R expression. Based on these observations, we propose that this therapeutic candidate has the potential to treat chemotherapy‐induced cardiotoxicity as well as heart failure.Support or Funding InformationThis work was supported by NIH grant 1R01HL118376‐01 (LP), a small grant from Novopyxis Inc (LP), and Research Services facilities of HSTMVH.

Dietary Supplementation with Homoarginine Preserves Cardiac Function in a Murine Model of Post-Myocardial Infarction Heart Failure.

Low plasma homoarginine (HA) is an emerging biomarker for cardiovascular disease and an independent predictor of mortality in patients with heart failure.1 Plasma levels appear to reflect cardiac dysfunction, positively correlating with ejection fraction and inversely with circulating brain natriuretic peptide.2 However, whether this outcome is a bystander or cause-and-effect has yet to be established. Within the context of stroke, a direct causal relationship has been inferred because normal mice pretreated with 14 mg/L HA had a smaller stroke size.3 In the present study, we show for the first time that dietary supplementation with HA improves cardiac function in the setting of chronic heart failure, suggesting a novel preventive strategy and inferring that low HA levels may be inherently detrimental because of a loss of this effect. We first confirmed that oral supplementation of C57BL/6J mice (Harwell, UK) with 14 mg/L L-HA hydrochloride (Sigma-Aldrich) in the drinking water for 4 weeks increased HA concentrations in both plasma (0.29±0.03 vs 0.89±0.07 µmol/L) and myocardial tissue (17.6±2.7 vs 48.8±6.8 nmol/g protein; n=5–10; P <0.01 for both), demonstrating a strong correlation between levels in plasma and myocardium ( r =0.74, P <0.01). This dose did …

Interleukin-19 is cardioprotective in dominant negative cyclic adenosine monophosphate response-element binding protein-mediated heart failure in a sex-specific manner.

AIMTo investigate the role of interleukin-19 (IL-19) in a murine model of female-dominant heart failure (HF).METHODSExpression of one copy of a phosphorylation-deficient cyclic adenosine monophosphate response-element binding protein (dnCREB) causes HF, with accelerated morbidity and mortality in female mice compared to males. We assessed expression of IL-19, its receptor isoforms IL-20R α/β, and downstream IL-19 signaling in this model of female-dominant HF. To test the hypothesis that IL-19 is cardioprotective in dnCREB-mediated HF, we generated a novel double transgenic (DTG) mouse of dnCREB and IL-19 knockout and assessed cardiac morbidity by echocardiography and survival of male and female mice.RESULTSIL-19 is expressed in the murine heart with decreased expression in dnCREB female compared to male mice. Further, the relative expression of the two IL-19 receptor isoforms manifests differently in the heart by sex and by disease. Male DTG mice had accelerated mortality and cardiac morbidity compared to dnCREB males, while female DTG mice showed no additional detriment, supporting the hypothesis that IL-19 is cardioprotective in this model.CONCLUSIONTogether, these data suggest IL-19 is an important cytokine mediating sex-specific cardiac (dys) function. Ongoing investigations will elucidate the mechanism(s) of sex-specific IL-19 mediated cardiac remodeling.

Abstract 80: PI3Kα Regulates Biomechanical Stress-induced Cytoskeletal Remodeling: A Critical Role of Gelsolin

Background: Biomechanical stress and cytoskeletal remodeling are key determinants in pressure overload-induced heart failure. Class Ia phosphoinositide 3-kinases (PI3Ks) mediate a variety of cellular activities, in response to agonist binding to cell-surface receptors, by generating the phosphatidylinositol (3,4,5)-trisphosphate (PIP 3 ) phosphoinositide lipid. Gelsolin is a Ca 2+ - and phosphoinositide-regulated actin filament severing and capping protein that is upregulated in failing human hearts and animal models of heart failure. Hypothesis: We hypothesize that PI3Kα regulates cytoskeletal remodeling through PIP 3 -mediated regulation of gelsolin. In addition, loss of gelsolin could attenuate the adverse cytoskeletal remodeling and result in increased resistance to the development of heart failure in response to pressure-overload. Methods and Results: Loss of p110α kinase activity, in two different transgenic models (PI3Kα dominant-negative (PI3KαDN) and cardiomyocyte-specific PI3Kα-null), resulted in dilated cardiomyopathy and markedly worsened cardiac dysfunction in response to transverse aortic constriction-induced pressure overload. Increased levels of mechanosensor proteins along with decreased F/G-actin ratio exhibited an uncoupling between cardiac mechanotransduction and cytoskeletal remodeling in p110α-null mice. Gelsolin activity was markedly increased in the p110α-null hearts in response to pressure-overload, whereas loss of gelsolin in PI3KαDN/gelsolin-null double mutant mice prevented the adverse cytoskeletal remodeling and preserved the cardiac function. In a murine model of chronic heart failure, loss of gelsolin prevented the pressure overload-induced cardiac dysfunction, fibrosis, and impaired cardiomyocyte contractility resulting in increased survival. Loss of gelsolin also mitigated the biomechanical stress-induced adverse cytoskeletal remodeling, via the attenuation of actin severing activity. Conclusions: We have identified a novel role of gelsolin as a mediator of adverse cytoskeletal remodeling leading to heart failure, where PI3Kα is a key regulator of gelsolin activity.