Experimental Models Of Heart Failure Research Articles

Gut Dysbiosis Induced by Cardiac Pressure Overload Promotes T Cell Activation and Adverse Cardiac Remodeling Through Alterations in the Aryl Hydrocarbon Receptor Expression

Heart failure (HF), a leading cause of morbidity and mortality worldwide, has been recently associated with gut microbiota alterations (gut dysbiosis) and T cell mediated inflammation in humans, and in experimental models of HF. The gut is a major reservoir of T cells, which are in close proximity with the gut microbiota. Gut bacterial populations process nutrients and produce metabolites that signal through cellular receptors, to maintain homeostasis or induce inflammation at distal organs. The aryl hydrocarbon receptor (AhR) is one of such receptors that recognize ligands that include gut derived tryptophan metabolites to modulate immune responses in the gut and systemically. We hypothesized that cardiac pressure overload induces gut dysbiosis and contributes to adverse cardiac remodeling through T cell activation and via AhR signaling in the gut and in the heart. We performed 16S rRNA sequencing in feces from mice undergoing Sham or transverse aortic constriction (TAC) surgery to test whether cardiac pressure overload induced gut dysbiosis, and in T cell deficient (Tcra−/−) mice to evaluate the contribution of T cells in gut dysbiosis induced by TAC. In addition, we studied the role of gut microbes in T cell activation, cardiac remodeling, and AhR expression, in mice that were orally treated with an antibiotic cocktail (ABX) to deplete the microbiota, and in ABX‐treated mice that spontaneously reconstituted the microbiota upon ABX removal during the 4 weeks of TAC (TAC‐REC). TAC resulted in increased abundance of phylum Bacteroidetes, and in a decrease in genus Lactobacillus, a tryptophan derivative producer, as compared to Sham. These microbiota alterations were not observed in Tcra−/− TAC mice, which were protected from adverse cardiac remodeling and exhibited a closer gut microbiota profile to WT Sham than to WT TAC mice in principal component analysis. However, TAC did not induce leaky gut, determined by LPS levels in serum, or T cell activation in the lamina propria, but increased T cell activation in the mediastinal lymph nodes (mLNs) that drain the heart, and drastically resulted in decreased AhR expression in the gut and in the heart. Strikingly, depletion of the gut microbiota in the onset of TAC (TAC‐ABX) resulted in a reduction in the number of activated T cells in the mLNs and heart infiltrated T cells, lack of cardiac fibrosis and systolic dysfunction, and an induction of AhR expression in the gut and the heart as compared to TAC mice that had not been depleted of the microbiota. Moreover, gut microbiota reconstitution in TAC‐REC mice resulted in decreased expression of AhR in the gut and in the heart as compared to ABX treated mice, and showed similar expression levels of AhR and systolic dysfunction as TAC mice. Our data demonstrate a role of gut microbes in T cell activation and adverse cardiac remodeling induced by cardiac pressure overload that likely involves decreased AhR signaling in the gut and in the heart.Support or Funding InformationThese studies were supported by NIH HL 123658 and the American Heart Association grant 19POST34430075/2019

Effects of Central Intervention of Tumor Necrosis Factor‐α Converting Enzyme (TACE) on Neuroinflammation and Cardiac Function in Heart Failure

Central nervous system inflammation has been implicated in the neurohumoral activation and disease progression in experimental animal models of heart failure (HF). The pro‐inflammatory cytokine tumor necrosis factor‐α (TNF‐α) increases in cardiovascular/autonomic brain regions including the paraventricular nucleus of the hypothalamus (PVN) and subfornical organ (SFO), and contributes significantly to the augmented sympathetic nerve activity in HF. TNF‐α is initially synthesized as a membrane bound protein that is proteolytically cleaved by TNF‐α converting enzyme (TACE), also known as a disintegrin and metalloprotease 17 (ADAM17), to become the fully functional inflammatory mediator. Our previous study demonstrated that TACE has elevated expression in the PVN and SFO and mediates TNF‐α‐induced sympathetic excitation and hemodynamic responses in HF rats. However, whether inhibition of TACE in the brain has a protective effect on central inflammation and cardiac function in HF remains unclear. We hypothesized that inhibition of TACE activity in the brain reduces central inflammation and improves left ventricular (LV) function during HF. Adult male Sprague‐Dawley rats were studied 4–5 weeks after induction of HF by coronary artery ligation. TACE activity was chronically inhibited specifically in the brain by infusion of the TACE inhibitor TAPI‐1 (30μg/day) via an osmotic minipump connected to an intracerebroventricular (ICV) cannula. Treatment with TAPI‐1 or vehicle began immediately following the myocardial infarction. At the end of experiments, LV function was assessed by echocardiography and tissues were collected for molecular analysis. In HF rats‐treated with TAPI‐1, the LV ejection fraction (26.8±0.9% vs 34.8±6.4%) was improved, although this did not reach statistical significance vs. HF treated with vehicle. Wet lung weight to body weight ratio also showed a trend towards being improved in TAPI‐1 treated animals (6.3±0.3mg/g vs. 4.8±0.4mg/g, vehicle vs. TAPI‐1, p=0.32). Additionally, TAPI‐1 treatment significantly decreased mRNA levels of proinflammatory mediators including TNF‐α, IL‐1β, and TACE in the SFO (TNF‐α: 0.28±0.10, p<0.05; IL1‐β: 0.25±0.11, p>0.05; TACE: 0.68±0.14, p<0.05, fold change vs. vehicle) and resulted in a trend toward reduced levels of these measurements in the PVN (TNF‐α: 0.52±0.13, p=0.24; IL1‐β: 0.58±0.11, p=0.21; TACE: 0.87±0.11, p=0.43, fold change vs. vehicle). TNF‐α expression was also reduced in both the superior cervical (0.35±0.07, p<0.05, fold change vs. vehicle) and stellate ganglia (0.44±0.14, p<0.05 fold change vs. vehicle). Taken together, these data suggest that central inhibition of TACE activity diminishes the inflammatory state in the brain and improve cardiac function in HF.

Indexes of Angiogenic Activation in Myocardial Samples of Patients with Advanced Chronic Heart Failure.

Background and objectives: Ischemic and idiopathic heart failure are characterized by reactive cardiac fibrosis and impaired vasculogenesis involving pro-angiogenic factors such as angiogenin, angiopoietin-1 (Ang-1), and angiopoietin-2 (Ang-2), as demonstrated in experimental models of heart failure. However, differences in the molecular pathways between these cardiomyopathies are still unclear. In this short communication, we evaluate and compare the expression of pro-angiogenic molecules in the heart tissue of patients with advanced chronic heart failure (CHF) of ischemic vs. nonischemic etiology. Materials and Methods: We obtained heart tissue at transplantation from left ventricular walls of 16 explanted native hearts affected by either ischemic (ICM) or nonischemic dilated cardiomyopathy (NIDCM). Tissue samples were examined using immunohistochemistry for angiogenic molecules. Results: We found immunopositivity (I-pos) for angiopoietin-1 mainly in the cardiomyocytes, while we observed I-pos for Ang-2 and Tie-2 receptor mainly in endothelial cells. Expression of Procollagen-I (PICP), angiogenin, Ang-1, and Tie-2 receptor was similar in ICM and NIDCM. In contrast, endothelial immunopositivity for Ang-2 was higher in ICM samples than NIDCM (p = 0.03). Conclusions: In our series of CHF heart samples, distribution of Ang-1 and angiogenin was higher in cardiomyocytes while that of Ang-2 was higher in endothelial cells; moreover, Ang-2 expression was higher in ICS than NIDCM. Despite the small series examined, these findings suggest different patterns of angiogenic stimulation in ICM and NIDCM, or at least a more altered endothelial integrity in ICD. Our data may contribute to a better understanding of the angiogenesis signaling pathways in CHF. Further studies should investigate differences in the biochemical processes leading to heart failure.

Degradation of GRK2 and AKT is an early and detrimental event in myocardial ischemia/reperfusion.

BackgroundIdentification of signaling pathways altered at early stages after cardiac ischemia/reperfusion (I/R) is crucial to develop timely therapies aimed at reducing I/R injury. The expression of G protein-coupled receptor kinase 2 (GRK2), a key signaling hub, is up-regulated in the long-term in patients and in experimental models of heart failure. However, whether GRK2 levels change at early time points following myocardial I/R and its functional impact during this period remain to be established.MethodsWe have investigated the temporal changes of GRK2 expression and their potential relationships with the cardioprotective AKT pathway in isolated rat hearts and porcine preclinical models of I/R.FindingsContrary to the maladaptive up-regulation of GRK2 reported at later times after myocardial infarction, successive GRK2 phosphorylation at specific sites during ischemia and early reperfusion elicits GRK2 degradation by the proteasome and calpains, respectively, thus keeping GRK2 levels low during early I/R in rat hearts. Concurrently, I/R promotes decay of the prolyl-isomerase Pin1, a positive regulator of AKT stability, and a marked loss of total AKT protein, resulting in an overall decreased activity of this pro-survival pathway. A similar pattern of concomitant down-modulation of GRK2/AKT/Pin1 protein levels in early I/R was observed in pig hearts. Calpain and proteasome inhibition prevents GRK2/Pin1/AKT degradation, restores bulk AKT pathway activity and attenuates myocardial I/R injury in isolated rat hearts.InterpretationPreventing transient degradation of GRK2 and AKT during early I/R might improve the potential of endogenous cardioprotection mechanisms and of conditioning strategies.

Abstract 851: NCLX Expression Attenuates Pathological Remodeling in Experimental Cardiac Hypertrophy and Non-ischemic Heart Failure

Mitochondrial calcium ( m Ca 2+ ) uptake couples acute changes in cardiomyocyte bioenergetic demand to ATP production, but in excess triggers mitochondrial permeability transition and cardiomyocyte necrosis, as occurs during cardiac injury. Despite established roles for m Ca 2+ flux in response to acute stress, the role of m Ca 2+ signaling in chronic stress is poorly defined. As m Ca 2+ regulates the TCA cycle with the potential to affect mitochondrial signaling and/or metabolite pools required for biosynthesis, we reasoned that altered m Ca 2+ homeostasis may be an essential mechanism underlying hypertrophic growth and remodeling of the myocardium. Here, we used mice with cardiac-specific overexpression (OE) of the mitochondrial Na + /Ca 2+ exchanger (NCLX), the primary mediator of m Ca 2+ efflux in the heart, to test the hypothesis that m Ca 2+ signaling contributes to cardiac remodeling during sustained hemodynamic stress. We subjected NCLX OE (TRE-NCLX x α-MHC-tTA) and control (αMHC-tTA) mice to 12-wk transverse aortic constriction (TAC) or 4-wk infusion with angiotensin II + phenylephrine (AngII/PE) as experimental models of cardiac hypertrophy and non-ischemic heart failure. Cardiac function of NCLX OE and control mice was monitored throughout these studies via echocardiography and remodeling was assessed via tissue gravimetrics, histology, and qPCR gene expression analysis. Cardiac NCLX OE preserved ejection fraction, prevented afterload-induced hypertrophy and fibrosis, and attenuated the induction of both hypertrophic ( Nppa , Nppb , Acta1 ) and fibrotic ( Postn1 , Spp1 ) gene programs in mice subjected to 12-wk TAC. Examination at 2-wk post-TAC revealed attenuated hypertrophy and blunted hypertrophic and fibrotic gene expression in NCLX OE mice. These data indicate that increased capacity for m Ca 2+ efflux mitigates TAC-induced remodeling, prior to the development of contractile dysfunction. NCLX OE similarly attenuated atrial hypertrophy and the induction of hypertrophic and fibrotic gene programs in mice infused with AngII/PE. Together, these findings support a critical role for m Ca 2+ in driving pathological remodeling in non-ischemic heart disease and point to NCLX as a potent therapeutic target for cardiovascular disease.

Renin Activity in Heart Failure with Reduced Systolic Function-New Insights.

Regardless of the cause, symptomatic heart failure (HF) with reduced ejection fraction (rEF) is characterized by pathological activation of the renin–angiotensin–aldosterone system (RAAS) with sodium retention and extracellular fluid expansion (edema). Here, we review the role of active renin, a crucial, upstream enzymatic regulator of the RAAS, as a prognostic and diagnostic plasma biomarker of heart failure with reduced ejection fraction (HFrEF) progression; we also discuss its potential as a pharmacological bio-target in HF therapy. Clinical and experimental studies indicate that plasma renin activity is elevated with symptomatic HFrEF with edema in patients, as well as in companion animals and experimental models of HF. Plasma renin activity levels are also reported to be elevated in patients and animals with rEF before the development of symptomatic HF. Modulation of renin activity in experimental HF significantly reduces edema formation and the progression of systolic dysfunction and improves survival. Thus, specific assessment and targeting of elevated renin activity may enhance diagnostic and therapeutic precision to improve outcomes in appropriate patients with HFrEF.

Effects of neprilysin-renin inhibition in comparison with neprilysin-angiotensin inhibition on the neurohumoral changes in rats with heart failure

BackgroundThe activation of neurohumoral compensatory mechanisms is a common physiological phenomenon in heart failure in order to make up for a failing heart, which will usually have a deteriorating effect on overall health condition. Many medications, such as neprilysin and angiotensin inhibitors, have recently been introduced to remediate neurohumoral changes. This study was conducted to evaluate the efficacy of the sacubitril-aliskiren combination versus the sacubitril-ramipril combination in the treatment of neurohumoral changes in rats with experimentally induced heart failure.MethodThirty Wister rats were randomly assigned into five groups each of six rats, the first group was the control group. Intraperitoneal isoprenaline injections of 5 mg/kg/day for 1 week were used to induce experimental models of heart failure in rats of the rest of experimental groups. The second group served as a positive control. Rats in the third, fourth, and fifth groups received oral daily dose of sacubitril 30 mg/kg/day, sacubitril-aliskiren 30,10 mg/kg/day, and sacubitril-ramipril 30/10 mg/kg/day respectively, for 2 weeks.ResultsInduction of heart failure in rats has significantly increased circulating NT-proBNP (980 ± 116.71 pg/ml), MMP9 (15.85 ± 0.57 ng/ml), troponin-I (3.09 ± 0.147 ng/ml), CK-MB (31.55 ± 1.69 ng/ml), renin (736 ± 45.8 pg/ml), urea (52.1 ± 1.57 mg/dl), and creatinine (0.92 ± 0.04 mg/dl). Significant decreases in glomerular filtration rate (7.031 ± 1.6 ml/hr./kg), urine flow (0.2761 ± 0.06 ml/h/kg), total solute excretion (0.11 ± 0.03 meq/m), and mean blood pressure (83.5 ± 2.6 mm hg) were seen in rats with heart failure.Rats treated with sacubitril combined with aliskiren or ramipril showed a statistically significant reduction of NT-proBNP, MMP9, troponin serum urea, and serum creatinine.Sacubitril-aliskiren or sacubitril-ramipril administration produced a significant increase in renin plasma level, total solute excretion, urine flow, and glomerular filtration rate.ConclusionSacubitril in combination with aliskiren or with ramipril effectively reduced plasma cardiac biomarkers, such as CK-MB, MMP9, and NT-proBNP, in rats with heart failure. Both combinations showed significant remediation of renal function through increasing GFR, urine flow, and total solute excretion, as well as reducing plasma level of renin. Net results revealed that the sacubitril-aliskiren combination has similar remediating effects on neurohumoral changes compared to the sacubitril-ramipril combination.

C-type natriuretic peptide co-ordinates cardiac structure and function.

AimsC-type natriuretic peptide (CNP) is an essential endothelium-derived signalling species that governs vascular homoeostasis; CNP is also expressed in the heart but an intrinsic role for the peptide in cardiac function is not established. Herein, we employ unique transgenic strains with cell-specific deletion of CNP to define a central (patho)physiological capacity of CNP in maintaining heart morphology and contractility.Methods and resultsCardiac structure and function were explored in wild type (WT), cardiomyocyte (cmCNP−/−), endothelium (ecCNP−/−), and fibroblast (fbCNP−/−)—specific CNP knockout mice, and global natriuretic peptide receptor (NPR)-B−/−, and NPR-C−/− animals at baseline and in experimental models of myocardial infarction and heart failure (HF). Endothelium-specific deletion of CNP resulted in impaired coronary responsiveness to endothelium-dependent- and flow-mediated-dilatation; changes mirrored in NPR-C−/− mice. Ex vivo, global ischaemia resulted in larger infarcts and diminished functional recovery in cmCNP−/− and NPR-C−/−, but not ecCNP−/−, vs. WT. The cardiac phenotype of cmCNP−/−, fbCNP−/−, and NPR-C−/− (but not ecCNP−/− or NPR-B−/−) mice was more severe in pressure overload- and sympathetic hyperactivation-induced HF compared with WT; these adverse effects were rescued by pharmacological CNP administration in WT, but not NPR-C−/−, mice. At a molecular level, CNP/NPR-C signalling is impaired in human HF but attenuates activation of well-validated pro-hypertrophic and pro-fibrotic pathways.ConclusionC-type natriuretic peptide of cardiomyocyte, endothelial and fibroblast origins co-ordinates and preserves cardiac structure, function, and coronary vasoreactivity via activation of NPR-C. Targeting NPR-C may prove an innovative approach to treating HF and ischaemic cardiovascular disorders.

Increased Intra-abdominal Pressure Induces Acute Kidney Injury in an Experimental Model of Congestive Heart Failure

Congestive heart failure (CHF) entails a complex interaction between the heart and the kidney that represents a clinical entity called cardiorenal syndrome (CRS). One of the mechanisms underlying CRS includes increased intra-abdominal pressure (IAP). We examined the effect of elevated IAP on kidney function in rats with low- and high-output CHF. Rats with compensated and decompensated CHF induced by means of aortocaval fistula, rats with myocardial infraction (MI) induced by means of left anterior descending artery ligation, and sham control rats were subjected to either 10 or 14 mm Hg IAP. Urine flow (V), Na+ excretion (UNaV), glomerular filtration rate (GFR), and renal plasma flow (RPF) were determined. The effects of pretreatment with tadalafil (10 mg/kg orally for 4 days) on the adverse renal effects of IAP were examined in decompensated CHF and MI. Basal V and GFR were significantly lower in rats with decompensated CHF compared with sham control rats. Decompensated CHF rats and MI rats subjected to 10 and 14 mm Hg IAP exhibited more significant declines in V, UNaV, GFR and RPF than compensated and sham controls. Elevated IAP also induced tubular injury, as evidenced by significantly increased absolute urinary excretion of neutrophil gelatinase-associated lipocalin. In addition, in a nonquantitative histologic analysis, elevated IAP was associated with increase in necrosis and cell shedding to the tubule lumens, especially in the decompensated CHF subgroup. Pretreatment of decompensated CHF rats and MI rats with tadalafil ameliorated the adverse renal effects of high IAP. Elevated IAP contributes to kidney dysfunction in high- and low-cardiac output CHF. IAP induces both hemodynamic alterations and renal tubular dysfunction. These deleterious effects are potentially reversible and can be ameliorated with the use of phosphodiesterase-5 inhibition.

Increased Cardiac Uptake of Ketone Bodies and Free Fatty Acids in Human Heart Failure and Hypertrophic Left Ventricular Remodeling.

Deranged energy metabolism contributes to the pathophysiology of heart failure (HF). Recent studies showed diminished free fatty acid (FFA) oxidation in experimental HF models with a shift towards oxidation of ketone bodies. However, conflicting clinical data on FFA metabolism and limited knowledge on ketone body metabolism in human HF mandate additional metabolic profiling studies. We, therefore, investigated cardiac uptake of FFAs and ketone bodies (β-hydroxybutyrate and acetoacetate) in patients with HF with reduced ejection fraction (HFrEF) or with aortic stenosis (AS)-induced left ventricular hypertrophy. We hypothesized that FFA oxidation is impaired in HFrEF and in AS and results in decreased concentrations of free carnitine, the necessary carrier for mitochondrial entry of activated FFAs, and in accumulation of metabolic intermediates. We collected arterial and coronary sinus blood samples in patients with HFrEF (n=15), in AS patients with preserved systolic function (n=15), and in control patients (n=15). Plasma concentration gradients across the heart show significantly greater uptake of ketone bodies in patients with HFrEF than in controls. Patients with AS show significantly increased uptake of β-hydroxybutyrate and FFAs. Free carnitine concentration and concentration gradients of intermediates of FFA oxidation were comparable between groups. In conclusion, our results show significantly increased cardiac uptake of ketone bodies in patients with stable HFrEF and AS and increased uptake of FFAs in AS compared with control patients. The lack of myocardial release of acyl-carnitine species or change in free carnitine uptake suggests no impairment of FFA oxidation.

Pulmonary Production of Soluble ST2 in Heart Failure.

Serum concentrations of ST2 (interleukin-1 receptor-like 1) represent a meaningful prognostic marker in cardiac diseases. Production of soluble ST2 (sST2) may be partially extracardiac. Identification of sST2 sources is relevant to design strategies for modulating its signaling. An experimental model of ischemic heart failure was used. sST2, membrane-bound ST2 (ST2L), and IL-33 were measured in lungs, heart, kidney, and liver by quantifying mRNA and protein expression in tissue samples obtained at different times (1, 2, 4, and 24 weeks). Primary human type II pneumocyte cell cultures were subjected to strain. sST2 was measured in samples of bronchial aspirate and serum obtained from patients treated with invasive respiratory support. In the experimental model, sST2 increased significantly from the first week in both lungs and myocardium, whereas ST2L/IL-33 response was unfavorable in lungs (decrease) and favorable in myocardium (increase). No changes were observed in liver and kidneys. ST2 immunostaining was intensely observed in alveolar epithelium, and sST2 was secreted by primary human type II pneumocytes in response to strain. sST2 levels in lung aspirates were substantially higher in the presence of cardiogenic pulmonary edema (median, 228 [interquartile range, 28.4-324.0] ng/mL; P<0.001) than bronchopneumonia (median, 5.5 [interquartile range, 1.6-6.5]) or neurological disorders (median, 2.9 [interquartile range, 1.7-10.1]), whereas sST2 concentrations in serum did not differ. The lungs are a relevant source of sST2 in heart failure. These results may have implications for the progression of disease and the development of therapies targeting the ST2 system in patients with heart failure.

RF26 HYDROGEL MYOCARDIAL INJECTION AS USEFUL STRATEGY TO PREVENT CARDIAC REMODELING: A SYSTEMATIC REVIEW AND META-ANALYSIS, IN MODELS OF HEART FAILURE

Background: The main objective of this systematic review (PROSPERO ID 96223) is to determine the advantage in hydrogel-based treatment to achieve sustained improvement of cardiac function in heart failure (HF), compared to drug therapy or placebo in clinical and experimental models of HF. The association between different types of hydrogel and myocardial function impairment, performance status and injection-induced complications, is analysed. Methods: Literature search has been performed using computer-assisted databases (MEDLINE, EMBASE, CENTRAL and JBI database of systematic reviews and implementation reports). The search strategy and the search string (“hydrogel” AND “heart”) has been formulated following the PICO method. Outcomes aim to assess myocardial improved function as: myocardial thickness by post-mortem analysis measurement, end-diastolic volumes (left and right ventricles), 30 days mortality, post-mortem analysis of myocardial composition, dimensions and histological and immunohistochemical changes. A standardised, pre-piloted form has been used to extract data from the included studies for assessment of study quality and evidence synthesis. Risk of bias and study quality (ie. CAMARDES-checklist) have been assessed by two review authors and resolving incongruencies through discussion with a third author. Results: We provide a narrative synthesis of the findings from the included studies, structured around the type of intervention, target population characteristics, type of outcome and intervention content. Conclusions: Hydrogels injection for cardiac tissue repair seems to be a promising therapeutic approach in miocardial infarction (MI) treatment, nowadays under clinical evaluation. Hydrogels effectiveness in limiting extension and expansion of ischemic injury, resulting in improved MI survival rates, in now under investigation.

Human Myocardium Has a Robust α1A-Subtype Adrenergic Receptor Inotropic Response.

Recent studies report that a single subtype of α1-adrenergic receptor (α1-AR), the α1A-subtype, mediates robust cardioprotective effects in multiple experimental models of heart failure, suggesting that the α1A-subtype is a potential therapeutic target for an agonist to treat heart failure. Moreover, we recently found that the α1A-subtype is present in human heart. The goal of this study was to assess the inotropic response mediated by the α1A-subtype in human myocardium, and to determine whether the response is downregulated in myocardium from failing human heart. We measured in vitro contractile responses of cardiac muscle preparations (trabeculae) isolated from the right ventricle from nonfailing and failing human hearts. Addition of the α1A-subtype agonist A61603 (100 nM) resulted in a large positive inotropic response (force increased ≈ 2-fold). This response represented ≈70% of the response mediated by the β-adrenergic receptor agonist isoproterenol (1 μM). Moreover, in myocardium from failing hearts, α1A-subtype responses remained robust, and only slightly reduced relative to nonfailing hearts. We conclude that α1A-subtype-mediated inotropy could represent a significant source of inotropic support in the human heart. Furthermore, the α1A-subtype remains functional in myocardium from failing human hearts and thus, might be a therapeutic target to support cardioprotective effects in patients with heart failure.

Angiotensin-(1-9) reduces cardiovascular and renal inflammation in experimental renin-independent hypertension

Hypertension-induced cardiovascular and renal damage can be mediated by activation of the renin-angiotensin-aldosterone system. There are different factors beyond renin-angiotensin-aldosterone system involved in hypertension and renal damage. Inflammation has emerged as an important mediator of hypertension and cardiovascular and kidney damage. Angiotensin-(1-9), a peptide of the renin-angiotensin system, counter-regulates both the physiological and pathological actions of angiotensin II. Recent data has shown that angiotensin-(1-9) protects the heart and blood vessels from adverse cardiovascular remodeling in experimental models of hypertension and/or heart failure and reduces cardiac fibrosis in stroke-prone, spontaneously hypertensive rats. These effects are mediated by the angiotensin II type 2 receptor (AT2R). However, it remains unknown whether angiotensin-(1-9) also has an anti-inflammatory effect. In the present study, we investigate whether angiotensin-(1-9) reduces inflammation and fibrosis in the heart, arteries, and kidney in a DOCA-salt hypertensive model and explore the mechanisms underlying the amelioration of end-organ damage. DOCA-salt hypertensive rats received: a) vehicle, b) angiotensin-(1-9), c) PD123319 (AT2R blocker), d) angiotensin-(1-9) plus A779 (a Mas receptor blocker) or e) angiotensin-(1-9) plus PD123319, and sham rats were used as a control. Our results showed that angiotensin-(1-9) decreased hypertension and increased vasodilation in DOCA-salt hypertensive rats. These actions were partially inhibited by PD123319. Moreover, angiotensin-(1-9) decreased diuresis, fibrosis, and inflammation. These beneficial effects were not mediated by Mas or AT2R blockers. We concluded that angiotensin-(1-9) protects against volume overload-induced hypertensive cardiovascular and kidney damage by decreasing inflammation in the heart, aortic wall, and kidney, through mechanisms independent of the Mas or AT2R.

Abstract 445: Essential Role of the S100A1-C-terminus Domain in Maintaining Cardiac-inotrope S100A1 Protein Stability

Introduction: S100A1 is a type of S100 protein with two EF-hand motif. It has a unique characteristic of interacting with multiple proteins of contractile machinery &amp; mitochondria. S100A1 protein able to govern proper systolic &amp; diastolic performance of cardiomyocyte interacting, respectively, with SERCA2A &amp; RYR2. S100A1 level decreases dramatically as a consequence of cellular cues such as oxidative-stress or activation of cellular proteasomes. Selective reconstitution of reduced S100A1 level by AAV9-gene transfer rescued failing heart. Because of the unique ability of S100A1 to interact with myriads of proteins with multiple function, we aimed to dissect the structure-function relationship of the domains of S100A1. Methods &amp; results: The C-terminus domain of S100A1 (S100A1ct) equally recapitulated the inotropic &amp; other benefits of the S100A1-FL in experimental model of heart failure &amp; identified as the bioactive lead domain of S100A1. To elucidate the function of the S100A1 without the C-terminus, here after, referred as S100A1ΔCT, we adenoviraly expressed S100A1ΔCT, &amp; as a control, either expressing GFP or S100A1-FL. We, inadvertently, discovered that S100A1ΔCT could not be detected at protein level. PCR analysis &amp; sequencing proved the presence S100A1ΔCT mRNA transcript. Bioinformatics revealed the presence of SUMO interaction motif (SIM) with in the C-terminus &amp; multiple ubiquitination residues on S100A1ΔCT, suggesting the SIM domain of the S100A1 is crucial for stability. Inhibition of cellular proteasome lead to the detection of the S100A1ΔCT protein in cells over expressing S100A1ΔCT. We overexpressed S100a1ΔCT, deletion mutants having part of the SIM motif (S100a1-SIM - ), the entire motif (S100a1-SIM + ) &amp; the S100a1-FL. Whereas the overexpression of S100A1-SIM + &amp; S100A1-FL were detected, S100A1ΔCT &amp; S100A1-SIM - could not be detected at protein level. Conclusion: The C-terminus of S100A1 is essential for stability of S100A1, besides, its potent inotropic function. Taken together, we deciphered the previously unrecognized posttranslational modification governed S100A1 regulation, thus providing new insight into the development of novel therapeutic strategies for heart failure via posttranslational manipulation of S100A1.

Role of Toll-like receptors and interferon regulatory factors in different experimental heart failure models of diverse etiology: IRF7 as novel cardiovascular stress-inducible factor

Heart failure (HF) is a leading cause of morbidity and mortality in the western world. Although optimal medical care and treatment is widely available, the prognosis of patients with HF is still poor.Toll-like receptors (TLRs) are important compartments of the innate immunity. Current studies have identified TLRs as critical mediators in cardiovascular diseases. In the present study, we investigated the involvement of TLRs and interferon (IFN) regulatory factors (IRFs) in different experimental HF models including viral myocarditis, myocardial ischemia, diabetes mellitus, and cardiac hypertrophy. In addition, we investigated for the first time comprehensive TLR and IRF gene and protein expression under basal conditions in murine and human cardiac tissue. We found that Tlr4, Tlr9 and Irf7 displayed highest gene expression under basal conditions, indicating their significant role in first-line defense in the murine and human heart. Moreover, induction of TLRs and IRFs clearly differs between the various experimental HF models of diverse etiology and the concomitant inflammatory status. In the HF model of acute viral-induced myocarditis, TLR and IRF activation displayed the uppermost gene expression in comparison to the remaining experimental HF models, indicating the highest amount of myocardial inflammation in myocarditis. In detail, Irf7 displayed by far the highest gene expression during acute viral infection. Interestingly, post myocardial infarction TLR and IRF gene expression was almost exclusively increased in the infarct zone after myocardial ischemia (Tlr2, Tlr3, Tlr6, Tlr7, Tlr9, Irf3, Irf7). With one exception, Irf3 showed a decreased gene expression in the remote zone post infarction. Finally, we identified Irf7 as novel cardiovascular stress-inducible factor in the pathologically stressed heart. These findings on TLR and IRF function in the inflamed heart highlight the complexity of inflammatory immune response and raise more interesting questions for future investigation.

P311In-vivo and cellular left atrial function in an experimental model of heart failure with preserved ejection fraction

P311In-vivo and cellular left atrial function in an experimental model of heart failure with preserved ejection fraction

Oscillatory behavior of P wave duration and PR interval in experimental congestive heart failure: a preliminary study

Objective: The relationship between the autonomic nervous system (ANS) modulation of the sinus node and heart rate variability has been extensively investigated. The current study sought to evaluate, in an animal experimental model of pacing-induced tachycardia congestive heart failure (CHF), a possible ANS influence on the P wave duration and PR interval oscillations. Approach: Short-term (5 min) time and frequency domain analysis has been obtained in six dogs for the following electrocardiographic intervals: P wave duration (P), from the onset to peak of P wave (Pp), from the onset of P wave to the q onset (PR) and from the end of P wave to the onset of q wave (PeR). Direct vagal nerve activity (VNA), stellate ganglion nerve activity (SGNA) and electrocardiogram (ECG) intervals have been evaluated contextually by implantation of three bipolar recording leads. Main results: At the baseline, multiple regression analysis pointed out that VNA was strongly positively associated with the standard deviation of PP and PeR intervals (r2:0.997, p < 0.05). The same variable was also positively associated with high-frequency (HF) of P expressed in normalized units, of Pp, and of PeR (b: 0.001) (r2: 0.993; p < 0.05). During CHF, most of the time and frequency domain variability significantly decreased from 20% to 50% in comparison to the baseline values (p < 0.05) and SGNA correlated inversely with the low frequency (LF) obtained from PeR (p < 0.05) and PR (p < 0.05) (r2:0.899, p < 0.05). LF components, expressed in absolute and normalized power, obtained from all studied intervals, were reduced significantly during CHF. Any difference between the RR and PP spectral components was observed. Significance: The data showed a significant relationship between ANS and atrial ECG variables, independent of the cycle duration. In particular, the oscillations were vagal mediated at the baseline, while sympathetic mediated during CHF. Whereas P wave variability might have a clinical utility in CHF management, it needs to be addressed in specific studies.

Ectopic expression of S28A-mutated Histone H3 modulates longevity, stress resistance and cardiac function in Drosophila

Histone H3 serine 28 (H3S28) phosphorylation and de-repression of polycomb repressive complex (PRC)-mediated gene regulation is linked to stress conditions in mitotic and post-mitotic cells. To better understand the role of H3S28 phosphorylation in vivo, we studied a Drosophila strain with ectopic expression of constitutively-activated H3S28A, which prevents PRC2 binding at H3S28, thus mimicking H3S28 phosphorylation. H3S28A mutants showed prolonged life span and improved resistance against starvation and paraquat-induced oxidative stress. Morphological and functional analysis of heart tubes revealed smaller luminal areas and thicker walls accompanied by moderately improved cardiac function after acute stress induction. Whole-exome deep gene-sequencing from isolated heart tubes revealed phenotype-corresponding changes in longevity-promoting and myotropic genes. We also found changes in genes controlling mitochondrial biogenesis and respiration. Analysis of mitochondrial respiration from whole flies revealed improved efficacy of ATP production with reduced electron transport-chain activity. Finally, we analyzed posttranslational modification of H3S28 in an experimental heart failure model and observed increased H3S28 phosphorylation levels in HF hearts. Our data establish a critical role of H3S28 phosphorylation in vivo for life span, stress resistance, cardiac and mitochondrial function in Drosophila. These findings may pave the way for H3S28 phosphorylation as a putative target to treat stress-related disorders such as heart failure.

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.