Cardiac Dysfunction In Heart Failure Research Articles

Mkk7 Protects Against Cardiac Dysfunction in Heart Failure with Preserved Ejection Fraction

Article Mkk7 Protects Against Cardiac Dysfunction in Heart Failure with Preserved Ejection Fraction Tayyiba Azam 1, * , Hongyuan Zhang 1, Susanne S. Hille 2, Elizabeth J. Cartwright 1, Oliver J. Müller 2, and Xin Wang 1, * 1 Faculty of Biology, Medicine, and Health, University of Manchester, Oxford Road, M13 9PT, Manchester, UK 2 Department of Internal Medicine III, University of Kiel, Germany; German Centre for Cardiovascular Research (DZHK), 24105 Partner Site Hamburg/Kiel/Lübeck, Germany * Correspondence: xin.wang@manchester.ac.uk (Xin Wang); tayyiba.azam@manchester.ac.uk (Tayyiba Azam) Received: 12 June 2023 Accepted: 25 September 2023 Published: 6 March 2024 Abstract: Shifts in epidemiological patterns foretell a rapid increase in the number of patients with heart failure (HF) globally, representing a significant health and economic burden. Heart failure with preserved ejection (HFpEF) is now considered the prevailing subtype of HF, with no effective treatment available to combat this syndrome. Previous studies have highlighted the cardioprotective role of MKK7 during cardiac pathology, however, no extensive research has been performed to examine MKK7 in the context of HFpEF. This study aimed to address this shortcoming by using adeno-associated virus (AAV) 9 to overexpress MKK7 in the two-hit clinically relevant HFpEF mouse model. We report that cardiomyocyte-specific overexpression of MKK7 improved the HFpEF phenotype in mice, by impeding cardiac diastolic dysfunction and myocardial fibrosis. Mechanistically, it was found that MKK7 ameliorated ER stress by maintaining IRE1-XBP1 signalling and blunted CHOP increase in the myocardium. To summarise, MKK7 overexpression holds the ability to protect the myocardium from HFpEF associated pathologies.

Early Renal Denervation Attenuates Cardiac Dysfunction in Heart Failure With Preserved Ejection Fraction.

The renal sympathetic nervous system modulates systemic blood pressure, cardiac performance, and renal function. Pathological increases in renal sympathetic nerve activity contribute to the pathogenesis of heart failure with preserved ejection fraction (HFpEF). We investigated the effects of renal sympathetic denervation performed at early or late stages of HFpEF progression. Male ZSF1 obese rats were subjected to radiofrequency renal denervation (RF-RDN) or sham procedure at either 8 weeks or 20 weeks of age and assessed for cardiovascular function, exercise capacity, and cardiorenal fibrosis. Renal norepinephrine and renal nerve tyrosine hydroxylase staining were performed to quantify denervation following RF-RDN. In addition, renal injury, oxidative stress, inflammation, and profibrotic biomarkers were evaluated to determine pathways associated with RDN. RF-RDN significantly reduced renal norepinephrine and tyrosine hydroxylase content in both study cohorts. RF-RDN therapy performed at 8 weeks of age attenuated cardiac dysfunction, reduced cardiorenal fibrosis, and improved endothelial-dependent vascular reactivity. These improvements were associated with reductions in renal injury markers, expression of renal NLR family pyrin domain containing 3/interleukin 1β, and expression of profibrotic mediators. RF-RDN failed to exert beneficial effects when administered in the 20-week-old HFpEF cohort. Our data demonstrate that early RF-RDN therapy protects against HFpEF disease progression in part due to the attenuation of renal fibrosis and inflammation. In contrast, the renoprotective and left ventricular functional improvements were lost when RF-RDN was performed in later HFpEF progression. These results suggest that RDN may be a viable treatment option for HFpEF during the early stages of this systemic inflammatory disease.

INO80-Dependent Remodeling of Transcriptional Regulatory Network Underlies the Progression of Heart Failure.

Progressive remodeling of cardiac gene expression underlies decline in cardiac function, eventually leading to heart failure. However, the major determinants of transcriptional network switching from normal to failed hearts remain to be determined. In this study, we integrated human samples, genetic mouse models, and genomic approaches, including bulk RNA sequencing, single-cell RNA sequencing, chromatin immunoprecipitation followed by high-throughput sequencing, and assay for transposase-accessible chromatin with high-throughput sequencing, to identify the role of chromatin remodeling complex INO80 in heart homeostasis and dysfunction. The INO80 chromatin remodeling complex was abundantly expressed in mature cardiomyocytes, and its expression further increased in mouse and human heart failure. Cardiomyocyte-specific overexpression of Ino80, its core catalytic subunit, induced heart failure within 4 days. Combining RNA sequencing, chromatin immunoprecipitation followed by high-throughput sequencing, and assay for transposase-accessible chromatin with high-throughput sequencing, we revealed INO80 overexpression-dependent reshaping of the nucleosomal landscape that remodeled a core set of transcription factors, most notably the MEF2 (Myocyte Enhancer Factor 2) family, whose target genes were closely associated with cardiac function. Conditional cardiomyocyte-specific deletion of Ino80 in an established mouse model of heart failure demonstrated remarkable preservation of cardiac function. In summary, our findings shed light on the INO80-dependent remodeling of the chromatin landscape and transcriptional networks as a major mechanism underlying cardiac dysfunction in heart failure, and suggest INO80 as a potential preventative or interventional target.

Abstract 15205: miR-132 Inhibition Improves Myocardial Strain in a Large Animal Model of Chronic Adverse Remodeling

Background: MicroRNAs (miRNAs) are transcriptional regulators and essential drivers of heart failure (HF). The miR-132 is necessary and sufficient to progress adverse cardiac remodeling. The strong effects are exhibited by, amongst others, cardiomyocyte hypertrophy and calcium signaling impairment. Treatments directly targeting the roots of the disease are scarce, but miR-132 inhibition by CDR132L, a rationally designed synthetic oligonucleotide, significantly improves cardiac dysfunction in HF early after myocardial infarction (MI). Rational: The aim of the current study was to gain further data on myocardial function and efficacy of CDR132L by analyzing left ventricular (LV) and atrial (LA) wall motion by serial cardiac magnetic resonance (cMRI) strain imaging in a clinically relevant large animal (pig) model of chronic HF. Methods and Results: Mangalica pigs (n=15) were randomized 1-month post-MI, initiated by left anterior descending artery occlusion followed by reperfusion as a chronic model of post-MI HF. Animals received CDR132L over 5 months by monthly intravenous treatments with 5 mg/kg. LV and LA strain parameters were deteriorated after MI over time but significantly ameliorated by CDR132L treatment, compared to placebo. Strain parameters showed significant correlations with pharmacodynamic measures such as left-ventricular ejection fraction, NT-proBNP and cardiac interstitial fibrosis in remodeling hearts 6 months post-MI. Conclusions: LV and LA motion and contractility were improved by repeated dosing of CDR132L with monthly frequency in a large animal model of chronic post-MI HF. The results highlight the translational value and usability of MRI-based cardiac strain imaging in HF drug development and support further clinical development of CDR132L.

THE SYNERGISTIC EFFECTS OF PROINFLAMMATORY CYTOKINES ON CARDIOVASCULAR FUNCTION AND SYMPATHETIC OUTFLOW IN RAT

Objective: Inflammation has been implicated in the pathophysiology of cardiovascular dysfunction and neurohumoral activation in cardiovascular diseases. Our previous work has demonstrated that proinflammatory cytokines (PICs) in cardiovascular/autonomic brain regions contribute significantly to the sympathetic excitation and cardiac dysfunction in heart failure and hypertension. Notably, the chronic inflammatory conditions in these disease settings are caused by numerous inflammatory cytokines and chemokines. Given that the elevated levels of a single effector cytokine in the pathophysiological condition are insufficient to cause a significant change in hemodynamic and sympathetic responses, how PIC-driven neuroinflammation promotes sympathetic activation remains unclear. This work sought to determine whether PICs in the brain have a synergistic action to exaggerate their inflammatory effects on hemodynamic and sympathetic responses in rats. Design and method: Blood pressure (BP, mmHg), heart rate (HR, beats/min) and renal sympathetic nerve activity (RSNA, % change) were continuously recorded for 4-5 hours in urethane anesthetized male Sprague Dawley rats. The inflammatory cytokines tumor necrosis factor-↑ (TNF-↑), interleukin (IL)-1↓, IL-6 and vehicle were injected intracerebroventricularly (ICV). Results: We found that while ICV injection of TNF-↑, IL-1↓ or IL-6 alone at a low dose (10 ng, respectively) did not induce significant changes in BP, HR and RSNA, the combined injection of all three cytokines at the same dose (10 ng) elicited a substantial (*p<0.05) increase in BP (18.2 ± 2.1*), HR (62 ± 7*) and RSNA (94.5 ± 5.2 %*), that began within 15-20 mins. These responses peaked at 2-3 hours after ICV injection and remained elevated for the rest of the recording period. Additionally, ICV injection of TNF-↑, IL-1↓ or IL-6 alone at a high dose (50 ng, respectively), produced a dramatic and long-lasting increase in BP, HR and RSNA, that closely resembles the time course and response pattern induced by ICV injection of all three cytokines concurrently at the low dose (10 ng). Conclusions: These data suggest a synergistically excitatory action of PICs in the brain on sympathetic outflow. Interventions that simultaneously target multiple cytokines may have an extended anti-inflammatory effect of reducing sympathetic excitation in hypertension and heart failure.

OR19-2 Treatment of Heart Failure with Preserved Ejection Fraction (HFpEF) with Low and High Dose of Triiodothyronine: an Animal Model of Metabolic Syndrome with HFpEF

Abstract Introduction Low levels of triiodothyronine (T3) are common in patients with heart failure (HF). It has been proposed that the decreased levels of T3 contribute to metabolic and cardiac dysfunction in HF. We aimed to evaluate the effects of treatment with low dose and high dose of T3 in an animal model of HF with preserved ejection fraction (HFpEF). Materials and Methods We evaluated four groups: ZSF1 Lean (Lean-Ctrl, n=8), ZSF1 obese (rat model of metabolic syndrome with HFpEF, HFpEF-Ctrl, n=13), ZSF1 obese supplemented with a replacement dose of T3 (initially 0.04mg/ml, increased to 0.06mg/ml after 4 weeks; HFpEF-T3high, n=8), and ZSF1 Obese supplemented with a low-dose of T3 (0.03mg/mL; HFpEF-T3low, n=8). T3 was supplemented in drinking water from week 13 to 24. The animals were submitted to anthropometric and metabolic evaluation, echocardiography, VO2max evaluation, hemodynamic evaluation, single cardiomyocyte evaluation, and myocardial tissue collection at 24 weeks. Results HFpEF-Ctrl animals had lower serum and myocardial thyroid hormone levels than Lean-Ctrl. Treatment with low dose and high dose of T3 did not correct serum T3 levels, but increased myocardial T3 levels, with normalization of myocardial T3 levels in the HFpEF-T3high group. In comparison to HFpEF-Ctrl, body weight was significantly decreased in HFpEF-T3low and HFpEF-T3high groups (616±39g, 572±24g and 535±18g respectively, p<0.001). An improvement in glucose metabolism was observed only in HFpEF-T3high, with a decreased AUC of glucose during OGTT and insulin tolerance test. Both treated groups presented an improvement in diastolic function (with decreased isovolumetric relaxation time) and systolic function (with increased peak systolic velocity and decreased ejection time) comparing to HFpEF-Ctrl. These results were supported by enhanced Ca2+ transients during diastole and sarcomere relaxation. Comparing with HFpEF-Ctrl, animals treated with T3 had higher myocardial expression of the calcium transporter RYR2, of the transcriptional coactivator PGC-1α, and of the α-myosin heavy chain (MHC), with a lower expression of β-MHC. VO2max was improved with low-dose and high-dose T3 compared with HFpEF-Ctrl. Comparing with HFpEF-Ctrl, heart rate was increased with high-dose (277.9±30.2 vs 313.5±35.8, p=0.049) but not significantly with low-dose (277.9±30.2 vs 299.8±30.9 bpm, p=0.13). Mortality was increased in the HFpEF-T3high comparing with the other groups (no animals died during the protocol in the Lean-Ctrl, HFpEF-Ctrl and HFpEF-T3low groups; three animals had sudden death in the HFpEF-T3high group). Conclusion Treatment with T3 improves metabolic function, myocardial calcium handling, diastolic and systolic function, and exercise capacity in this animal model of HFpEF. While the low dose was well tolerated and safe, the high dose was associated with increased heart rate and a higher risk of sudden death. Modulation of thyroid hormones may be a potential therapeutic target in HFpEF; however such approaches must take into account a narrow therapeutic window of T3 in HFpEF. Presentation: Monday, June 13, 2022 11:15 p.m. - 11:30 a.m.

Brain Interleukin-17A contributes to neuroinflammation and cardiac dysfunction in rats with myocardial infarction.

Proinflammatory cytokines produced outside the central nervous system can act in the brain to promote sympathetic activation that contributes to the progression of heart failure (HF). Interleukin (IL)-17A, a key inflammatory regulator which orchestrates immune responses to promote chronic inflammation, has been implicated in the pathophysiology of HF. We previously reported that IL-17A acts within the brain, particularly in the hypothalamic paraventricular nucleus (PVN), to increase expression of inflammatory mediators and, consequently, sympathetic outflow. The present study sought to determine whether IL-17A levels are elevated in a rat model of HF induced by myocardial infarction and, if so, whether increased expression of IL-17A in the brain itself contributes to neuroinflammation and cardiac dysfunction in this disease setting. Male SD rats underwent coronary artery ligation (CL) to induce HF or sham operation (SHAM). Compared with SHAM rats, HF rats exhibited significantly increased IL-17A levels in plasma, beginning within 1 week with a peak increase at 4 weeks after CL. IL-17A levels in cerebrospinal fluid (CSF) were also increased in HF rats and correlated with IL-17A levels in the plasma. The mRNA expression of IL-17A and its receptor IL-17RA, but not IL-17RC, was markedly upregulated in the PVN of HF when compared with SHAM rats. Genetic knockdown of IL-17RA by bilateral PVN microinjections of an IL-17RA siRNA AAV virus attenuated mRNA expression of proinflammatory cytokines and chemokines, and ameliorated sympathetic activation and cardiac function in HF rats. These data indicate that elevated expression of IL-17A in the brain in HF contributes to the excessive central inflammatory state and cardiac dysfunction in HF. Interventions to suppress IL-17A/IL-17RA axis in the brain have the potential for treating HF.

Abstract 11062: The δC Isoform of Ca 2+ /Calmodulin-Dependent Protein Kinase II (camk2) Regulates Cardiac Metabolic Substrate Switching in Mice

Introduction: Ca 2+ /calmodulin-dependent protein kinase II (CaMK2) is a recognized driver of pathological cardiac remodeling and heart failure, but its role in the metabolic reprogramming of heart failure remains unclear, as do the molecular processes that trigger this pathologic switch. Hypothesis: Myocardial CaMKIIδ drives the pathological remodeling of cardiac metabolic substrate preference. Methods and Results: Adeno-associated viral (ssAAV9) overexpression of constitutively-active cytosolic (CaMK2δC) and nuclear (CaMK2δB) CaMK2δ isoforms, as well as the catalytic PKA subunit (PKAca), were created under the control of the cardiac troponin-T promoter and introduced via tail-vein injection into 12-week old mice (1 x 10 12 v.g., n = 5). In vivo metabolic phenotyping via 18-fluorodeoxyglucose ( 18 FDG)-based positron emission tomography (PET) revealed a 3.4-fold (P = 0.02) higher glucose uptake among mice receiving ssAAV9-TnnT-CaMK2δC commensurate with cardiac CaMK2δC expression. In contrast, no differences were seen in glucose uptake following AAV overexpression of cardiac CaMK2δB or PKAca relative to luciferase control vector. Echocardiography subsequently revealed a 14.6% decrease in left ventricular ejection fraction at 6 weeks following CaMK2δC overexpression (P = 0.047), whereas no changes were seen following CaMK2δB or PKAca overexpression in systolic or diastolic cardiac parameters. Conversely, transcriptomic analysis of hearts from mice lacking cardiac CaMK2δC expression revealed disproportionate up-regulation of fatty acid oxidative genes (P < 0.001). Conclusion: Taken together, these preliminary findings implicate CaMK2δC as a crucial regulator of the cardiac metabolic reprogramming that likely precedes the hemodynamic manifestations of cardiac dysfunction in heart failure.

MCU overexpression evokes disparate dose-dependent effects on mito-ROS and spontaneous Ca2+ release in hypertrophic rat cardiomyocytes.

Cardiac dysfunction in heart failure (HF) and diabetic cardiomyopathy (DCM) is associated with aberrant intracellular Ca2+ handling and impaired mitochondrial function accompanied with reduced mitochondrial calcium concentration (mito-[Ca2+]). Pharmacological or genetic facilitation of mito-Ca2+ uptake was shown to restore Ca2+ transient amplitude in DCM and HF, improving contractility. However, recent reports suggest that pharmacological enhancement of mito-Ca2+ uptake can exacerbate ryanodine receptor-mediated spontaneous sarcoplasmic reticulum (SR) Ca2+ release in ventricular myocytes (VMs) from diseased animals, increasing propensity to stress-induced ventricular tachyarrhythmia. To test whether chronic recovery of mito-[Ca2+] restores systolic Ca2+ release without adverse effects in diastole, we overexpressed mitochondrial Ca2+ uniporter (MCU) in VMs from male rat hearts with hypertrophy induced by thoracic aortic banding (TAB). Measurement of mito-[Ca2+] using genetic probe mtRCamp1h revealed that mito-[Ca2+] in TAB VMs paced at 2 Hz under β-adrenergic stimulation is lower compared with shams. Adenoviral 2.5-fold MCU overexpression in TAB VMs fully restored mito-[Ca2+]. However, it failed to improve cytosolic Ca2+ handling and reduce proarrhythmic spontaneous Ca2+ waves. Furthermore, mitochondrial-targeted genetic probes MLS-HyPer7 and OMM-HyPer revealed a significant increase in emission of reactive oxygen species (ROS) in TAB VMs with 2.5-fold MCU overexpression. Conversely, 1.5-fold MCU overexpression in TABs, that led to partial restoration of mito-[Ca2+], reduced mitochondria-derived reactive oxygen species (mito-ROS) and spontaneous Ca2+ waves. Our findings emphasize the key role of elevated mito-ROS in disease-related proarrhythmic Ca2+ mishandling. These data establish nonlinear mito-[Ca2+]/mito-ROS relationship, whereby partial restoration of mito-[Ca2+] in diseased VMs is protective, whereas further enhancement of MCU-mediated Ca2+ uptake exacerbates damaging mito-ROS emission.NEW & NOTEWORTHY Defective intracellular Ca2+ homeostasis and aberrant mitochondrial function are common features in cardiac disease. Here, we directly compared potential benefits of mito-ROS scavenging and restoration of mito-Ca2+ uptake by overexpressing MCU in ventricular myocytes from hypertrophic rat hearts. Experiments using novel mito-ROS and Ca2+ biosensors demonstrated that mito-ROS scavenging rescued both cytosolic and mito-Ca2+ homeostasis, whereas moderate and high MCU overexpression demonstrated disparate effects on mito-ROS emission, with only a moderate increase in MCU being beneficial.

Stress activated signalling impaired protein quality control pathways in human hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a complex myocardial disorder with no well-established disease-modifying therapy so far. Our study aimed to investigate how autophagy, oxidative stress, inflammation, stress signalling pathways, and apoptosis are hallmark of HCM and their contribution to the cardiac dysfunction. Demembranated cardiomyocytes from patients with HCM display increased titin-based stiffness (Fpassive), which was corrected upon antioxidant treatment. Titin as a main determinant of Fpassive was S-glutathionylated and highly ubiquitinated in HCM patients. This was associated with a shift in the balance of reduced and oxidized forms of glutathione (GSH and GSSG, respectively). Both heat shock proteins (HSP27 and α-ß crystalline) were upregulated and S-glutathionylated in HCM. Administration of HSPs in vitro significantly reduced HCM cardiomyocyte stiffness. High levels of the phosphorylated monomeric superoxide anion-generating endothelial nitric oxide synthase (eNOS), decreased nitric oxide (NO) bioavailability, decreased soluble guanylyl cyclase (sGC) activity, and high levels of 3-nitrotyrosine were observed in HCM. Many regulators of signal transduction pathways that are involved in autophagy, apoptosis, cardiac contractility, and growth including the mitogen-activated protein kinase (MAPK), protein kinase B (AKT), glycogen synthase kinase 3ß (GSK-3ß), mammalian target of rapamycin (mTOR), forkhead box O transcription factor (FOXO), c-Jun N-terminal protein kinase (JNK), and extracellular-signal-regulated kinase (ERK1/2) were modified in HCM. The apoptotic factors cathepsin, procaspase 3, procaspase 9 and caspase 12, but not caspase 9, were elevated in HCM hearts and associated with increased proinflammatory cytokines (Interleukin 6 (IL-6), interleukin 18 (IL-18), intercellular cell adhesion molecule-1 (ICAM1), vascular cell adhesion molecule-1 (VCAM1), the Toll-like receptors 2 (TLR2) and the Toll-like receptors 4 (TLR4)) and oxidative stress (3-nitrotyrosine and hydrogen peroxide (H2O2)). Here we reveal stress signalling and impaired PQS as potential mechanisms underlying the HCM phenotype. Our data suggest that reducing oxidative stress can be a viable therapeutic approach to attenuating the severity of cardiac dysfunction in heart failure and potentially in HCM and prevent its progression.

Abstract P210: Central Blockade Of Tumor Necrosis Factor-Á-Converting Enzyme (tace) Ameliorates Neuroinflammation, Sympathetic Excitation And Cardiac Dysfunction In Heart Failure Rat

TACE is a key metalloprotease involved in ectodomain shedding of tumor necrosis factor (TNF)-α and transforming growth factor (TGF)-α. We previously reported that TACE-mediated production of TNF-α in the hypothalamic paraventricular nucleus (PVN) contributes to the sympathetic excitation in heart failure (HF). Additionally, the upregulated TGF-α in the PVN transactivates the epidermal growth factor receptor (EGFR) to activate extracellular signal-regulated kinase (ERK) 1/2 in HF. Here we sought to determine whether central inhibition of TACE attenuates neuroinflammation and prevents the progress of HF. Male rats underwent coronary artery ligation to induce HF or sham surgery (Sham). These rats were treated with bilateral PVN microinjection of a TACE siRNA or control siRNA while some rats received a 4-week intracerebroventricular (ICV) infusion of TACE inhibitor TAPI-0 or vehicle. Compared with Sham rats, HF rats treated with control siRNA, had higher (*P<0.05) levels of TNF-α (7.88±1.32* vs 2.77±0.98 pg/mL) and TGF-α (28.27±2.76* vs 11.62±2.48 pg/mL) in cerebrospinal fluid, and increased mRNA expression of TACE (2.53±0.30* vs 1.04±0.12), TNF-α (3.43±0.55* vs 1.03±0.11), TNF-α receptor 1 (2.32±0.27* vs 1.07±0.19), cyclooxygenase-2 (2.96±0.31* vs 1.10±0.19) and TGF-α (2.68±0.41* vs 1.06±0.14) in the PVN, but these levels were markedly reduced (39-54%*) in TACE siRNA-treated HF rats. Compared with control HF rats, HF rats treated with TACE siRNA had reduced expression of phosphorylated (p-) NF-κB p65 (1.27±0.14 vs 0.84±0.07*), p-EGFR (0.52±0.05 vs 0.37±0.04*) and p-ERK1/2 (1.06±0.10 vs 0.62±0.09*) in the PVN. Moreover, the elevated plasma norepinephrine levels, lung/body weight, heart/body weight and left ventricular (LV) end-diastolic pressure along with decreased LV dP/dt max in HF rats-treated with control siRNA were significantly attenuated in HF rats treated with TACE siRNA. Treatments with TACE siRNA in the PVN also improved the indicators of cardiac hypertrophy and fibrosis of HF. ICV infusion of TAPI-0 had the similar effects with PVN TACE siRNA on these variables in HF. These data indicate that central interventions suppressing TACE activity ameliorate neuroinflammation, sympathetic activation and cardiac dysfunction in HF.

Rg3 promotes the SUMOylation of SERCA2a and corrects cardiac dysfunction in heart failure

SUMOylation of sarcoplasmic/endoplasmic reticulum Ca2+ ATPase 2a (SERCA2a) has been shown to play a critical role in the abnormal Ca2+ cycle of heart failure. Ginsenoside Rg3 (Rg3), the main active constituent of Panax ginseng, exerts a wide range of pharmacological effects in cardiovascular diseases. However, the effect of Rg3 on abnormal Ca2+ homeostasis in heart failure has not been reported. In this study, we showed a novel role of Rg3 in the abnormal Ca2+ cycle in cardiomyocytes of mice with heart failure. Among mice undergoing transverse aortic constriction, animals that received Rg3 showed improvements in cardiac function and Ca2+ homeostasis, accompanied by increases in the SUMOylation level and SERCA2a activity. In an isoproterenol (ISO)-induced cell hypertrophy model, Rg3 reduced the ISO-induced Ca2+ overload in HL-1 cells. Gene knockout of SUMO1 in mice inhibited the cardioprotective effect of Rg3, and SUMO1 knockout mice that received Rg3 did not exhibit improved Ca2+ homeostasis in cardiomyocytes. Additionally, mutation of the SUMOylation sites of SERCA2a blocked the positive effect of Rg3 on the ISO-induced abnormal Ca2+ cycle in HL-1 cells, and was accompanied by an abnormal endoplasmic reticulum stress response and generation of ROS. Our data demonstrated that Rg3 has a positive effect on the abnormal Ca2+ cycle in the cardiomyocytes of mice with heart failure. SUMO1 is an important factor that mediates the protective effect of Rg3. Our findings suggest that drug intervention by regulating the SUMOylation of SERCA2a can provide a novel therapeutic strategy for the treatment of heart failure.

Effects of different exercise modalities on cardiac dysfunction in heart failure with preserved ejection fraction.

AimsHeart failure with preserved ejection fraction (HFpEF) is an increasingly prevalent disease. Physical exercise has been shown to alter disease progression in HFpEF. We examined cardiomyocyte Ca2+ homeostasis and left ventricular function in a metabolic HFpEF model in sedentary and trained rats following 8 weeks of moderate‐intensity continuous training (MICT) or high‐intensity interval training (HIIT).Methods and resultsLeft ventricular in vivo function (echocardiography) and cardiomyocyte Ca2+ transients (CaTs) (Fluo‐4, confocal) were compared in ZSF‐1 obese (metabolic syndrome, HFpEF) and ZSF‐1 lean (control) 21‐ and 28‐week‐old rats. At 21 weeks, cardiomyocytes from HFpEF rats showed prolonged Ca2+ reuptake in cytosolic and nuclear CaTs and impaired Ca2+ release kinetics in nuclear CaTs. At 28 weeks, HFpEF cardiomyocytes had depressed CaT amplitudes, decreased sarcoplasmic reticulum (SR) Ca2+ content, increased SR Ca2+ leak, and elevated diastolic [Ca2+] following increased pacing rate (5 Hz). In trained HFpEF rats (HIIT or MICT), cardiomyocyte SR Ca2+ leak was significantly reduced. While HIIT had no effects on the CaTs (1–5 Hz), MICT accelerated early Ca2+ release, reduced the amplitude, and prolonged the CaT without increasing diastolic [Ca2+] or cytosolic Ca2+ load at basal or increased pacing rate (1–5 Hz). MICT lowered pro‐arrhythmogenic Ca2+ sparks and attenuated Ca2+‐wave propagation in cardiomyocytes. MICT was associated with increased stroke volume in HFpEF.ConclusionsIn this metabolic rat model of HFpEF at an advanced stage, Ca2+ release was impaired under baseline conditions. HIIT and MICT differentially affected Ca2+ homeostasis with positive effects of MICT on stroke volume, end‐diastolic volume, and cellular arrhythmogenicity.

Short-term but not long-term high fat diet feeding protects against pressure overload-induced heart failure through activation of mitophagy

AimsRecent studies have shown that enhancement of fatty acid utilization through feeding animals a high fat diet (HFD) attenuated cardiac dysfunction in heart failure (HF). Here, we aimed to examine the temporal effects of HFD feeding on cardiac function in mice with heart failure and its underlying mechanism. Main methodsPressure overload-induced HF was established via transverse aortic constriction (TAC) surgery. After surgery, the mice were fed on either normal diet or HFD for 8 or 16 weeks. Key findingsHFD feeding exerted opposite effects on cardiac function at different time points post-surgery. Short-term HFD feeding (8 wk) protected the heart against pressure overload, inhibiting cardiac hypertrophy and improving cardiac function, while long-term HFD feeding (16 wk) aggravated cardiac dysfunction in TAC mice. Short-term HFD feeding elevated cardiac fatty acid utilization, while long-term HFD feeding showed no significant effects on cardiac fatty acid utilization in TAC mice. Specifically, an increase in cardiac fatty acid utilization was accompanied with activated mitophagy and improved mitochondrial function. Palmitic acid treatment (400 μM, 2 h) stimulated fatty acid oxidation and mitophagy in neonatal myocytes. Mechanistically, fatty acid utilization stimulated mitophagy through upregulation of Parkin. Cardiac-specific knockdown of Parkin abolished the protective effects of short-term HFD feeding on cardiac function in TAC mice. SignificancesThese results suggested that short-term but not long-term HFD feeding protects against pressure overload-induced heart failure through activation of mitophagy, and dietary fat intake should be used with caution in treatment of heart failure.

Abstract 14803: Activin A Directly Impaired Human IPSC-cardiomyocyte Contractility and Electrophysiology

Activin A is a homo-dimeric TGF-β family member involved in embryonic development, tissue morphogenesis, and cellular differentiation. Levels of activin A correlate with NYHA functional classification and age dependent cardiac dysfunction; however, no data are available to demonstrate a direct role for activin A in regulating human cardiomyocyte dysfunction. The purpose of this study was to characterize the functional impact of chronic activin A on human cardiomyocyte electrophysiology, contractility, calcium handling, and gene expression. Methods: Human iPSC-cardiomyocytes (iPSC-CM) were supplied by Fujifilm Cellular Dynamics. Calcium transients were captured using the FLIPR Tetra imager and impedance/electrophysiology by the Nanion CardioExcyte96. Cells were plated (50k/well), allowed to reach a stable synchronous monolayer, and dosed with 1nM of activin A (A) at each media change alongside a media control (C) or in the presence of inhibitory anti-activin A antibodies. Gene expression was determined using Taqman. Results: Activin A reduced contractile impedance amplitude (C=9.82±0.30, A=6.82±0.21 Ohms, p<0.01) and slowed relaxation velocity kinetics (C=48.78±2.65, A=35.07±1.07 Ohms/sec, p<0.01). Elongated extracellular field potential durations were observed with activin A treatment compared to control (C=0.49±0.02, A=0.56±0.01 sec, p<0.01). Impaired calcium handling peak amplitude (C=609±99, A= C=447±33 RFU, p<0.05) was also observed alongside slower calcium flux falling times (C=0.52±0.05, A=0.70±0.04 sec, p<0.01). An inhibitory activin-A antibody restored all parameters to control values. Chronic exposure of iPSC-CM to activin A reduced expression of calcium handling genes RYR2 (C=1.01±0.07, A=0.75±0.03, p<0.01) and ATP2A2 (C=1.00±0.05, A=0.89±0.05, p<0.05). Conclusions: Chronic activin A treatment reduced cardiomyocyte contractile amplitude, slowed contractile kinetics, impaired cardiomyocyte calcium handling, elongated the action potential, and reduced expression of genes regulating key calcium handling proteins. These data demonstrate that elevated levels of activin A can directly act on cardiomyocytes and therefore may contribute to cardiac dysfunction in heart failure and aged populations.

Abstract 435: P53 Temporally Regulates the Myofibroblast Activation Response in Pressure Overload

Heart disease is invariably accompanied by the accumulation of resident cardiac fibroblasts (CF) that secrete extracellular matrix and drive the progression of fibrosis and cardiac dysfunction in heart failure. We recently reported that CF exhibit a unique transcriptional response in physiological and pathological remodeling that may underlie the cardioprotective benefits of exercise, and that p53 targets represent the most dysregulated family between the two. To further investigate the role of p53 in pathological cardiac remodeling, we deleted floxed p53 alleles in adult CF using the tamoxifen-inducible Tcf21 MerCreMer mouse (p53-CFKO). p53-CFKO mice initially retain normal cardiac function through 14 days of pressure overload, but eventually progress to heart failure more rapidly than do p53-CFWT, which show gradual functional decline throughout. CF accumulation and fibrosis at these time points match the functional results closely, with p53-CFKO mice protected from both at 14 days relative to p53-CFWT. Conversely, deletion of p53 in myofibroblasts (MF) using the tamoxifen-inducible Postn MerCreMer mouse (p53-MFKO) resulted in no delay in functional loss nor in CF accumulation and fibrosis, suggesting a distinct temporal window of p53 activity in CF exists in pressure overload. In vitro experimentation confirmed that adenovirally-mediated deletion of p53 could delay, but not reverse, myofibroblast activation - and that this irreversible activation is due to induction of Cdkn2a -mediated cell cycle arrest. Furthermore, unbiased single-cell transcriptomic analysis of CF from pressure-overloaded Tcf21 MerCreMer mice at the 14-day functional inflection point revealed p53-CFKO mice have a unique CF cluster defined primarily by a mitotic signature, and this cluster comes at the direct expense of the myofibroblast population. Clusters representing migrating and quiescent CF were unchanged in response to p53. This work describes an inverse correlation of proliferative capacity and myofibroblast activation that indicates p53 exerts master control of the timing of CF accumulation and pathological fibrosis in heart disease.

Cardiomyocyte Krüppel‐like Factor 5 Regulates Ceramide Biosynthesis and miR‐30 Suppression in Ischemic Cardiomyopathy and Promotes Systolic Dysfunction

Our lab previously identified Krϋppel‐like factor (KLF) 5 as a regulator of fatty acid oxidation in the heart during diabetes‐associated cardiac dysfunction. The regulation of cardiomyocyte KLF5 and its significance during ischemic heart failure has not been studied. Therefore, we assessed KLF5 expression in human ischemic heart failure samples and in rodent models 2‐ and 4‐weeks post‐permanent LAD ligation. In human and mouse heart failure samples KLF5 levels were increased. We therefore hypothesized that aberrant regulation of cardiac KLF5 contributes to disease progression in ischemic heart failure. To address our hypothesis, we generated a novel mouse model of inducible (Dox‐ON), cardiomyocyte specific expression of KLF5 and assessed cardiac function using echocardiography. We further characterized the response of our previously described αMHC‐Klf5−/− mice and mice treated with pharmacological KLF5 inhibitor ML264 (10 mg/kg 2xper day) to MI. KLF5 overexpression resulted in systolic dysfunction beginning 2‐weeks after induction. Conversely, αMHC‐Klf5−/− mice and mice treated with ML264 subjected to LAD ligation had increased ejection fraction, lower end‐diastolic volume, and reduced heart weights compared to control mice after MI. To identify lipid metabolism‐related processes affected by KLF5 in the heart, we performed lipidomic analysis by LC‐MS/MS, which showed that KLF5 transgenic heart tissue had increased levels of ceramides and ceramide‐derived lipids. Among the three pathways that contribute in ceramide biosynthesis, KLF5 altered expression of the de novo biosynthesis pathway by increasing SPTLC1 and SPTLC2. After MI, αMHC‐Klf5−/− had lower cardiac SPTLC1 and SPTLC2 expression compared with control mice. To pursue potential post‐transcriptional mechanisms that are triggered by KLF5, we performed cardiac miR array analysis and gene expression analysis in primary cardiomyocytes of αMHC‐Klf5−/− hearts. We found increased levels of all 5 miR‐30 family members, which have been associated with better prognosis in heart failure patients. Conversely, cardiac miR‐30s were decreased in KLF5 transgenic mice and in human heart failure samples. After MI, miR‐30 levels were partially restored in αMHC‐Klf5−/− hearts compared to controls. We suggest that MI upregulates KLF5, which stimulates ceramide biosynthesis and suppresses miR‐30, both of which have been attributed causality for cardiac dysfunction in heart failure.Support or Funding InformationNational Heart Lung and Blood Institute of the National Institutes of Health HL130218 (KD); American Heart Association predoctoral fellowship 18PRE34060115 (MH); Ruth L. Kirschstein National Research Service Award (NRSA) F30 predoctoral fellowship F30HL146007 (MH); American Heart Association and the Kahn Family Post‐Doctoral Fellowship in Cardiovascular Research 18POST34060150 (IDK)

Mechanisms of Cardiac Dysfunction in Heart Failure due to Myocardial Infarction

Acute myocardial infarction (MI) is associated with marked elevation of plasma vasoactive hormones, ventricular arrhythmias, scar formation in the ischemic portion of left ventricle (LV) and hypertrophy of the viable LV as well as the right ventricle (RV). Particularly, elevated levels of plasma catecholamines and angiotensin II activate their membrane receptors and stimulate different signal transduction systems for producing cardiac hypertrophy, augmenting the activities of subcellular organelles and increasing cardiac function. While marked arrhythmias due to acute MI produce 30 to 40% mortality, hypertrophic alterations in the viable LV as well as RV are compensatory for maintaining hemodynamic homeostasis due to loss of cardiomyocytes. On the other hand, prolonged elevation of plasma vasoactive hormones in chronic MI produce deleterious effects on the hypertrophied heart by promoting the formation of oxyradicals, inducing Ca2+ - handling abnormalities in subcellular organelles, depressing cardiac gene expression, activating different proteases and resulting in the development of cardiac dysfunction. Thus, in view of the complexities of mechanisms for both acute and chronic effects of MI, there is a real challenge of developing new interventions for preventing the transition of cardiac hypertrophy to heart failure as well as progression of the MI-induced cardiovascular abnormalities.

Abstract 220: Gut Microbiota Alterations Associate With T Cell Activation and Adverse Cardiac Remodeling in Response to Cardiac Pressure Overload

Background: The complex syndrome of heart failure (HF), a leading cause of morbidity and mortality affecting more than 24 million people worldwide, is recently becoming associated with alterations in gut microbiota, also known as gut dysbiosis, as well as with T cell mediated systemic inflammation and T cell infiltration in the heart. Specifically, certain bacteria promote T cell activation, and T cell activation contributes to adverse cardiac remodeling and cardiac dysfunction in HF. We hypothesize that gut dysbiosis modulates cardiac remodeling and function in a T cell-dependent manner. Results: C57/BL6 mice were orally treated with a well-stablished wide spectrum antibiotic cocktail (ABX) and subjected to transverse aortic constriction (TAC), a model of non-ischemic HF. ABX was present during the duration of TAC (4 weeks), thus sterilizing the gut completely, or during 3 weeks before TAC followed by removal during the 4 weeks of TAC duration for spontaneous recovery of the gut microbiota (TAC-REC). The lack of gut microbiota showed a reduced T cell activation in the mediastinal lymph nodes and heart T cell infiltration, as well as cardiac fibrosis and cardiac hypertrophy were prevented in response to TAC. Nevertheless, gut dysbiosis induced by bacterial recolonization only partially recovered this phenotype. In addition, we sequenced 16S RNA to study the changes in bacterial populations in Sham, TAC, and TAC-REC. TAC induced changes in the gut microbiota compared to Sham surgery, which resulted in a higher relative abundance of several genera, such as Bacteroides, and lower relative abundance of Coprococcus, Lactobacillus and Bifidobacterium, these last two normally associated to an anti-inflammatory response. At the end of the experiment, bacterial recolonization in TAC-REC mice showed different relative bacterial abundance between TAC and TAC-REC, although there were no significant changes in diversity at 4 weeks post-TAC. Conclusion: Collectively, our findings suggest that changes in gut microbiota constitution modify T cell activation and migration to the heart in the TAC model. Exploring the role of gut microbiota in modulating adverse cardiac remodeling and cardiac function can become an optimal therapeutic target to treat HF patients.

GUT BACTERIA MODULATE T CELL RESPONSES AND ADVERSE CARDIAC REMODELING IN PRESSURE OVERLOAD INDUCED HEART FAILURE

Changes in the bacterial composition of the gut, defined as gut dysbiosis, are recently becoming associated with the pathogenesis of heart failure (HF), a leading cause of mortality worldwide. Certain bacteria promote T cell activation, and T cell activation contributes to adverse cardiac remodeling and cardiac dysfunction in HF. We tested the hypothesis that gut dysbiosis modulates cardiac remodeling and function in a T cell‐dependent manner. C57/BL6 mice were orally treated with a wide spectrum antibiotic cocktail (ABX) and subjected to transverse aortic constriction (TAC), a stablished model of HF. ABX was present during the 4 week duration of TAC, thus sterilizing the gut completely, or during 3 weeks before TAC followed by removal during the 4 weeks of TAC duration to allow spontaneous reconstitution of the gut microbiota. We report that gut microbiota depletion results in reduced T cell activation in the mediastinal lymph nodes, heart T cell infiltration, and prevents cardiac fibrosis and cardiac hypertrophy in response to TAC. However, gut dysbiosis induced by bacterial reconstitution after ABX removal, only partially recovered this phenotype. We used 16S RNA sequencing to characterize the bacterial populations in Sham, TAC, and in ABX treated TAC mice after ABX removal and spontaneous bacterial colonization in the gut (TAC‐REC). TAC induced changes in the gut microbiota compared to Sham surgery, which at the genus level resulted in a higher relative abundance of Bacteroides (p=0.048) and lower relative abundance of Coprococcus (p=0.024), Lactobacillus (p=0.021) and Bifidobacterium (p=0.042), these last two normally associated to an anti‐inflammatory response. Bacterial reconstitution in TAC‐REC mice started after 2 weeks of ABX removal, but was incomplete even by 4 weeks post ABX removal, as reflected by the different relative bacterial abundance between TAC and TAC‐REC 4 weeks post TAC. Several genera were identified as colonizing the gut in TAC‐REC mice that could potentially be associated with cardiac dysfunction. Ongoing studies are focused on the characterization of bacterial populations responsible for this effect and on determining the type of T cell response involved.Support or Funding InformationThis work was supported by the NIH‐R01‐HL123658.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.