Experimental Models Of Heart Failure Research Articles

Setmelanotide Administration Improves Cardiac Systolic Function in Sirtuin-3 Deficient Mice

We previously showed that activation of the brain leptin-melanocortin system, particularly melanocortin-4 receptors (MC4R), markedly improves cardiac function in experimental models of heart failure (HF) via mechanisms that are still poorly understood. Sirtuin 3 (Sirt3) is an important regulator of mitochondrial oxidative phosphorylation and deficiency of Sirt3 has been implicated in cardiovascular diseases. We recently found increased Sirt3 expression as well as increased levels of NAD+, the main Sirt3 activator, in cardiomyocytes of rats treated with chronic intracerebroventricular infusion of leptin at a dose that does not spill over into the systemic circulation. Therefore, we hypothesized that stimulation of Sirt3 activity is required for the improvement of cardiac function during activation of the brain leptin-MC4R axis. To test this hypothesis, we first examined if chronic MC4R activation, using an MC4R agonist, setmelanotide, improves cardiac function in naïve Sirt3-deficient (Sirt3-KO) mice. Baseline cardiac function was assessed by echocardiography (VisualSonics-VEVO3100®) in male and female Sirt3-KO and wild-type (WT) control mice (n=5/group) at 20 weeks of age, and then weekly during setmelanotide treatment (2 mg/kg/day — i.p. via osmotic minipump model 1002) for 3 weeks. Chronic MC4R activation with setmelanotide transiently reduced food intake in both groups and promoted weight loss in Sirt3-KO mice. Setmelanotide treatment improved systolic function in WT mice as evidenced by increases in ejection fraction and fractional shortening (EF: 52.8±4.4 vs. 72.4±4.4%; FS: 26.9±2.7 vs. 42.8±6.4%, for baseline vs. week 3, respectively) and other measures of systolic function including circumferential and longitudinal strains. Despite showing a tendency for reduced systolic function compared to WT controls at baseline, Sirt3-KO mice also exhibited improvement in systolic function with setmelanotide administration (EF: 44.1±1.8 vs. 65.3±2.9% and FS: 21.4±1.0 vs. 35.1±2.1%). No major changes were observed in measures of diastolic function. These results suggest that in a non-HF model, MC4R activation does not require stimulation of Sirt3 to improve indices of systolic function. (1R01HL163076, 1R01DK121411, P20GM104357, P30GM149404, U54GM115428, and AHA-835218). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Rectifying METTL4-Mediated N6-Methyladenine Excess in Mitochondrial DNA Alleviates Heart Failure.

Myocardial mitochondrial dysfunction underpins the pathogenesis of heart failure (HF), yet therapeutic options to restore myocardial mitochondrial function are scarce. Epigenetic modifications of mitochondrial DNA (mtDNA), such as methylation, play a pivotal role in modulating mitochondrial homeostasis. However, their involvement in HF remains unclear. Experimental HF models were established through continuous angiotensin II and phenylephrine (AngII/PE) infusion or prolonged myocardial ischemia/reperfusion injury. The landscape of N6-methyladenine (6mA) methylation within failing cardiomyocyte mtDNA was characterized using high-resolution mass spectrometry and methylated DNA immunoprecipitation sequencing. A tamoxifen-inducible cardiomyocyte-specific Mettl4 knockout mouse model and adeno-associated virus vectors designed for cardiomyocyte-targeted manipulation of METTL4 (methyltransferase-like protein 4) expression were used to ascertain the role of mtDNA 6mA and its methyltransferase METTL4 in HF. METTL4 was predominantly localized within adult cardiomyocyte mitochondria. 6mA modifications were significantly more abundant in mtDNA than in nuclear DNA. Postnatal cardiomyocyte maturation presented with a reduction in 6mA levels within mtDNA, coinciding with a decrease in METTL4 expression. However, an increase in both mtDNA 6mA level and METTL4 expression was observed in failing adult cardiomyocytes, suggesting a shift toward a neonatal-like state. METTL4 preferentially targeted mtDNA promoter regions, which resulted in interference with transcription initiation complex assembly, mtDNA transcriptional stalling, and ultimately mitochondrial dysfunction. Amplifying cardiomyocyte mtDNA 6mA through METTL4 overexpression led to spontaneous mitochondrial dysfunction and HF phenotypes. The transcription factor p53 was identified as a direct regulator of METTL4 transcription in response to HF-provoking stress, thereby revealing a stress-responsive mechanism that controls METTL4 expression and mtDNA 6mA. Cardiomyocyte-specific deletion of the Mettl4 gene eliminated mtDNA 6mA excess, preserved mitochondrial function, and mitigated the development of HF upon continuous infusion of AngII/PE. In addition, specific silencing of METTL4 in cardiomyocytes restored mitochondrial function and offered therapeutic relief in mice with preexisting HF, irrespective of whether the condition was induced by AngII/PE infusion or myocardial ischemia/reperfusion injury. Our findings identify a pivotal role of cardiomyocyte mtDNA 6mA and the corresponding methyltransferase, METTL4, in the pathogenesis of mitochondrial dysfunction and HF. Targeted suppression of METTL4 to rectify mtDNA 6mA excess emerges as a promising strategy for developing mitochondria-focused HF interventions.

Atlas of cardiac endothelial cell enhancer elements linking the mineralocorticoid receptor to pathological gene expression.

Endothelial cells play crucial roles in physiology and are increasingly recognized as therapeutic targets in cardiovascular disease. Here, we analyzed the regulatory landscape of cardiac endothelial cells by assessing chromatin accessibility, histone modifications, and 3D chromatin organization and confirmed the functional relevance of enhancer-promoter interactions by CRISPRi-mediated enhancer silencing. We used this dataset to explore mechanisms of transcriptional regulation in cardiovascular disease and compared six different experimental models of heart failure, hypertension, or diabetes. Enhancers that regulate gene expression in diseased endothelial cells were enriched with binding sites for a distinct set of transcription factors, including the mineralocorticoid receptor (MR), a known drug target in heart failure and hypertension. For proof of concept, we applied endothelial cell-specific MR deletion in mice to confirm MR-dependent gene expression and predicted direct MR target genes. Overall, we have compiled here a comprehensive atlas of cardiac endothelial cell enhancer elements that provides insight into the role of transcription factors in cardiovascular disease.

Renal denervation improves cardiac function independently of afterload and restores myocardial norepinephrine levels in a rodent heart failure model.

Renal nerves play a critical role in cardiorenal interactions. Renal denervation (RDN) improved survival in some experimental heart failure (HF) models. It is not known whether these favorable effects are indirect, explainable by a decrease in vascular afterload, or diminished neurohumoral response in the kidneys, or whether RDN procedure per se has direct myocardial effects in the failing heart. To elucidate mechanisms how RDN affects failing heart, we studied load-independent indexes of ventricular function, gene markers of myocardial remodeling, and cardiac sympathetic signaling in HF, induced by chronic volume overload (aorto-caval fistula, ACF) of Ren2 transgenic rats. Volume overload by ACF led to left ventricular (LV) hypertrophy and dysfunction, myocardial remodeling (upregulated Nppa, MYH 7/6 genes), increased renal and circulating norepinephrine (NE), reduced myocardial NE content, increased monoaminoxidase A (MAO-A), ROS production and decreased tyrosine hydroxylase (+) nerve staining. RDN in HF animals decreased congestion in the lungs and the liver, improved load-independent cardiac function (Ees, PRSW, Ees/Ea ratio), without affecting arterial elastance or LV pressure, reduced adverse myocardial remodeling (Myh 7/6, collagen I/III ratio), decreased myocardial MAO-A and inhibited renal neprilysin activity. RDN increased myocardial expression of acetylcholinesterase (Ache) and muscarinic receptors (Chrm2), decreased circulating and renal NE, but increased myocardial NE content, restoring so autonomic control of the heart. These changes likely explain improvements in survival after RDN in this model. The results suggest that RDN has remote, load-independent and favorable intrinsic myocardial effects in the failing heart. RDN therefore could be a useful therapeutic strategy in HF.

Ultrasonographic assessment of pulmonary and Central venous congestion in experimental heart failure.

Pulmonary and systemic congestion as a consequence of heart failure are clinically recognized as alarm signals for clinical outcome and mortality. Although signs and symptoms of congestion are well detectable in patients, monitoring of congestion in small animals with heart failure lacks adequate noninvasive methodology yet. Here, we developed a novel ultrasonography-based scoring system to assess pulmonary and systemic congestion in experimental heart failure, by using lung ultrasound (LUS) and imaging of the inferior vena cava (Cava), termed CavaLUS. CavaLUS was established and tested in a rat model of supracoronary aortic banding and a mouse model of myocardial infarction, providing high sensitivity and specificity while correlating to numerous parameters of cardiac performance and disease severity. CavaLUS, therefore, provides a novel comprehensive tool for experimental heart failure in small animals to noninvasively assess congestion.NEW & NOTEWORTHY As thorough, noninvasive assessment of congestion is not available in small animals, we developed and validated an ultrasonography-based research tool to evaluate pulmonary and central venous congestion in experimental heart failure models.

Blockade of Inflammatory Markers Attenuates Cardiac Remodeling and Fibrosis in Rats with Supravalvular Aortic Stenosis.

Since cardiac inflammation has been considered an important mechanism involved in heart failure, an anti-inflammatory treatment could control cardiac inflammation and mitigate the worsening of cardiac remodeling. This study evaluated the effects of dexamethasone (DEX) and ramipril treatment on inflammation and cardiac fibrosis in an experimental model of heart failure induced by supravalvular aortic stenosis. Wistar rats (21d) were submitted to an aortic stenosis (AS) protocol. After 21 weeks, an echocardiogram and a maximal exercise test were performed, and after 24 weeks, rats were treated with DEX, ramipril or saline for 14d. The left ventricle (LV) was removed for histological and inflammatory marker analyses. The AS group showed exercise intolerance (-32% vs. Sham), higher relative wall thickness (+63%), collagen deposition and capillary rarefaction, followed by cardiac disfunction. Both treatments were effective in reducing cardiac inflammation, but only DEX attenuated the increased relative wall thickness (-17%) and only ramipril reduced LV fibrosis. In conclusion, both DEX and ramipril decreased cardiac inflammatory markers, which probably contributed to the reduced cardiac fibrosis and relative wall thickness; however, treated AS rats did not show any improvement in cardiac function. Despite the complex pharmacological treatment of heart failure, treatment with an anti-inflammatory could delay the patient's poor prognosis.

Abstract 15818: Association of Clonal Hematopoiesis of Indeterminate Potential With Incident Heart Failure With Preserved Ejection Fraction

Introduction: Clonal hematopoiesis of indeterminate potential (CHIP) is the age-related expansion of blood cells with somatic mutations, most commonly in DMNT3A , TET2 , and ASXL1 . CHIP is a risk factor for coronary heart disease as well as heart failure (HF). Experimental HF models suggest a role of CHIP pro-inflammatory myeloid cells on cardiac dysfunction via fibrotic remodeling and hypertrophy. However, whether CHIP associates with incident HF with preserved ejection fraction (HFpEF), HF with reduced ejection fraction (HFrEF), or both is currently unknown. Hypothesis: We hypothesized that CHIP is more strongly related to HFpEF than HFrEF. Methods: We studied a multiethnic sample of postmenopausal women without prevalent HF from the Women’s Health Initiative (WHI). Whole genome sequencing was performed through the NHLBI TOPMed Program, and CHIP was detected based on 74 pre-specified myeloid driver mutations. Participants were followed through March 2020 with physician adjudication of HFrEF and HFpEF. Cox models tested the association of CHIP with incident HFpEF and HFrEF with adjustment for demographic/clinical risk factors and inverse probability weighting to account for the TOPMed sampling scheme. Results: Among 5,214 women, the mean age was 62 years, and 7.8% had CHIP. Over a median follow-up of 15 years, age-adjusted HFpEF incidence rates were 5.86 (95%CI 5.63-6.10) vs. 3.72 (95%CI 3.68-3.77) per 1,000 person-years among CHIP carriers vs. non-carriers. After multivariable adjustment, CHIP was associated with a 42% increased risk of incident HFpEF (HR 1.42, 95%CI 6-91%; P =0.02). In contrast, there was no evidence of association between CHIP and HFrEF ( Table 1 ). HFpEF was more strongly associated with TET2 CHIP (HR 2.50, 95%CI 1.54-4.06; P <0.001) than with DNMT3A or ASXL1 ( Table 1 ). Conclusions: CHIP, especially TET2 CHIP, is associated with incident HFpEF. This finding has potential precision medicine implications for HFpEF prevention and treatment.

Vibrational spectroscopy identifies myocardial chemical modifications in heart failure with preserved ejection fraction

BackgroundVibrational spectroscopy can be a valuable tool to monitor the markers of cardiovascular diseases. In the present work, we explored the vibrational spectroscopy characteristics of the cardiac tissue in an experimental model of heart failure with preserved ejection fraction (HFpEF). The goal was to detect early cardiac chemical modifications associated with the development of HFpEF.MethodsWe used the Fourier-transform infrared (FTIR) and Raman micro-spectroscopic techniques to provide complementary and objective tools for the histological assessment of heart tissues from an animal model of HFpEF. A new sampling technique was adopted (tissue print on a CaF2 disk) to characterize the extracellular matrix.ResultsSeveral spectroscopic markers (lipids, carbohydrates, and glutamate bands) were recognized in the cardiac ventricles due to the comorbidities associated with the pathology, such as obesity and diabetes. Besides, abnormal collagen cross-linking and a decrease in tryptophan content were observed and related to the stiffening of ventricles and to the inflammatory state which is a favourable condition for HFpEF.ConclusionsBy the analyses of tissues and tissue prints, FTIR and Raman techniques were shown to be highly sensitive and selective in detecting changes in the chemistry of the heart in experimental HFpEF and its related comorbidities. Vibrational spectroscopy is a new approach that can identify novel biomarkers for early detection of HFpEF.

Comparative Efficacy of Levosimendan, Ramipril, and Sacubitril/ Valsartan in Isoproterenol-induced Experimental Heart Failure: A Hemodynamic and Molecular Approach.

Cardiac ischemia-related myocardial damage has been considered a major reason for heart failure. We aimed to investigate the role of levosimendan (LEVO) in comparison to ramipril and sacubitril/valsartan (Sac/Val) in preventing damage associated with isoproterenol (ISO) induced myocardial infarction. Myocardial infarction was induced by injecting subcutaneous isoproterenol (5 mg/kg once for 7 consecutive days) to establish an experimental heart failure model. Simultaneously, LEVO (1 mg/kg/day), ramipril (3mg/kg/day) and Sac/Val (68 mg/kg/day) suspension were administered orally for four weeks. We observed a significant correlation between ISO-induced ischemia with cardiac remodeling and alterations in myocardial architecture. LEVO, ramipril, and Sac/Val significantly prevented lipid peroxidation and damaged antioxidant enzymes like superoxide dismutase, catalase, glutathione and thioredoxin reductase. We also observed their ameliorative effects in myocardium's cardiac hypertrophy, evidenced by reduced heart weight to body weight ratio and transforming growth factor β related collagen deposition. LEVO, ramipril, and Sac/Val also maintained cardiac biomarkers like lactate dehydrogenase, creatine kinase-MB, brain natriuretic peptide and cardiac Troponin-I, indicating reduced myocardial damage that was further demonstrated by histopathological examination. Decreased sarcoplasmic endoplasmic reticulum Ca2+ATPase2a and sodium-calcium exchanger-1 protein depletion after LEVO, ramipril, and Sac/Val administration indicated improved Ca2+ homeostasis during myocardial contractility. Our findings suggest that LEVO has comparable effects to ramipril, and Sac/Val in preventing myocardial damage via balancing oxidant-antioxidant system, decreased collagen deposition, reduced myocardial stress as well as improved Ca2+ homeostasis during myocardial contractility.

Renin-angiotensin system in the central nervous system: focus on Huntington's disease.

Renin-angiotensin system in the central nervous system: focus on Huntington's disease.

Experimental heart failure models in small animals.

Heart failure (HF) is one of the most critical health and economic burdens worldwide, and its prevalence is continuously increasing. HF is a disease that occurs due to a pathological change arising from the function or structure of the heart tissue and usually progresses. Numerous experimental HF models have been created to elucidate the pathophysiological mechanisms that cause HF. An understanding of the pathophysiology of HF is essential for the development of novel efficient therapies. During the past few decades, animal models have provided new insights into the complex pathogenesis of HF. Success in the pathophysiology and treatment of HF has been achieved by using animal models of HF. The development of new in vivo models is critical for evaluating treatments such as gene therapy, mechanical devices, and new surgical approaches. However, each animal model has advantages and limitations, and none of these models is suitable for studying all aspects of HF. Therefore, the researchers have to choose an appropriate experimental model that will fully reflect HF. Despite some limitations, these animal models provided a significant advance in the etiology and pathogenesis of HF. Also, experimental HF models have led to the development of new treatments. In this review, we discussed widely used experimental HF models that continue to provide critical information for HF patients and facilitate the development of new treatment strategies.

Synapsin 2 regulates NCX1 trafficking and is down-regulated in the failing myocardium, which increases the risk of ventricular arrhythmia and heart failure mortality

Abstract Background Synapsin 2 (Syn2) modulates vesicle transport in the post-synaptic terminal in the brain, and has been linked to sudden unexplained death in epilepsy, but has never previously been studied in the myocardium. Purpose Given the association of vesicle transport in the brain and the heart, and the similarity of sudden death in epilepsy and cardiac arrhythmias, we have studied the role of Syn2 in the heart. Methods We explored left ventricular (LV) Syn2 levels in various experimental heart failure (HF) models and assessed mortality in Syn2 knock out (KO) mice vs. wild type (WT) littermates after pressure-overload induced by aortic banding. We used confocal imaging and virus transduction to characterize Syn2 localization and co-localization with NCX and Rab proteins. We verified Syn2-NCX interaction by immunoprecipitation, mass spectrometry, and surface resonance experiments. We investigated calcium handling in isolated cardiomyocytes. Susceptibility for ventricular arrhythmias was also tested in Langendorff-perfused hearts. Results We found Syn2, but not synapsin 1, to be expressed in the myocardium. LV Syn2 levels were markedly downregulated in the failing myocardium after experimental myocardial infarction or aortic banding. Syn2 KO mice had increased mortality compared to WT littermates following aortic banding, but demonstrated no clear clinical or echocardiographic phenotype, except reduced fractional shortening. Given no clear etiology for increased mortality, we next explored the association between Syn2 and ion-channel vesicle transport, calcium handling and ventricular arrhythmias. By confocal imaging and viral transduction, we found Syn2 to localize in vesicles in HL-1 cells, where Syn2 co-localized with Rab2, Rab3, Rab7 and NCX1. Syn2 was also found to interact with NCX1 as tested by immunoprecipitation, mass spectrometry, and surface resonance experiments. NCX1 levels were downregulated in the membrane fraction in the left ventricle of Syn2 KO mice compared to WT littermates following aortic banding. We observed increased frequency of calcium sparks and waves in isolated Syn2 KO cardiomyocytes compared to controls. We found enhanced susceptibility of Syn2 KO mice for ventricular arrhythmias compared to WT littermates mice during ISO stress testing in explanted hearts. Hearts from Syn2 KO mice also demonstrated more severe ventricular arrhythmias compared to hearts from WT littermates controls. Conclusions We report for the first time that Syn2 is expressed in the myocardium and that Syn2 seems to regulate NCX1 transport and localization. We also found markedly reduced LV Syn2 levels in HF individuals and mice that lacked Syn2 more frequent displayed severe ventricular arrhythmias and had increased mortality. Hence, our data suggest that reduced Syn2 in the failing myocardium may lead to increased mortality, possibly linked to altered NCX trafficking and subsequent ventricular arrhythmias. Funding Acknowledgement Type of funding sources: None.

Searching for an experimental rodent model of heart failure with preserved ejection fraction: Re-visited.

Heart failure with preserved ejection fraction (HFpEF) currently accounts for over 50% of all heart failure cases. It displays a large number of comorbidities, and the pathophysiological mechanisms underlying the disease remain uncertain and treatment options are limited. The heterogeneity and complexity of the disease, and its specific comorbidities, can limit the number of animal models that could ideally mimic it. The current study describes and compares the efficacy of the most popular approaches from a quantitative point of view. A review and meta-analysis of more than 500 experimental protocols was performed with special attention to these models created to induce heart failure by the most common comorbidities associated with human HFpEF, e.g., hypertension, diabetes, obesity and aging. The analysis included a wide spectrum of outcomes (alterations in body weight, lung and left ventricle weights, laboratory, hemodynamic, echocardiographic, and histopathological data as well as animal mortality) and possible covariates that could determine the utility of the particular model, such as animal age, species, experimental period and genetic modification. A wide range of systemic hypertension as well as diabetes (obesity) - related animal models are used for pre-clinical studies on heart failure, but some of them fail to replicate HFpEF. Future studies should include an evaluation of other features besides diastolic dysfunction that confirm that this is an HFpEF model, or the potential to progress to heart failure with reduced ejection fraction (HFrEF).

Sacubitril/valsartan in an experimental model of heart failure with preserved ejection fraction

Abstract Funding Acknowledgements Type of funding sources: Public Institution(s). Main funding source(s): Ministry for Education, University and Research Introduction The majority of elderly patients with heart failure has a preserved ejection fraction (HFpEF) that constitutes a syndrome characterized by frequent hospitalizations and high mortality. Despite the growing social burden of HFpEF, the comprehension of its pathophysiology is incomplete, and treatment remains largely undefined. Aging itself may contribute independently to deterioration of diastolic function. Methods 18-month old female Fischer 344 rats were treated with oral administration of either sacubitril/valsartan (60 mg/kg/die, 1:1 ratio) or valsartan alone (30 mg/kg/die) for 12 weeks. Tail-cuff method was used to monitor blood pressure weekly. Echocardiography and left ventricle catheterization were employed to assess systolic and diastolic function, at baseline, and before sacrifice. Cardiac tissue was used for molecular biology and histochemistry assays. Results Tail-cuff analysis indicated a comparable decrease in blood pressure between treatments. Hypertrophy also showed a significant reduction with both treatments. On the contrary, myocardial function analysis demonstrated that no treatment was efficacy on diastolic dysfunction. The lack of improvement of cardiac function could be attributed to the inability of the treatments to counteract the accumulation of fibrotic tissue in the left ventricle, which, in turn, is attributable to the failure to reduce the inflammatory process and oxidative stress, and to the inability to modulate angiotensin II pathway. Conclusion Our results evidenced that both sacubitril/valsartan or valsartan treatment was able to improve diastolic function and pro-fibrotic remodeling, partly due to a lack of effect on classical and non-classical pathways of angiotensin II.

Cardiorenal Syndrome: The Role of Neural Connections Between the Heart and the Kidneys.

The maintenance of cardiovascular homeostasis is highly dependent on tightly controlled interactions between the heart and the kidneys. Therefore, it is not surprising that a dysfunction in one organ affects the other. This interlinking relationship is aptly demonstrated in the cardiorenal syndrome. The characteristics of the cardiorenal syndrome state include alterations in neurohumoral drive, autonomic reflexes, and fluid balance. The evidence suggests that several factors contribute to these alterations. These may include peripheral and central nervous system abnormalities. However, accumulating evidence from animals with experimental models of congestive heart failure and renal dysfunction as well as humans with the cardiorenal syndrome suggests that alterations in neural pathways, from and to the kidneys and the heart, including the central nervous system are involved in regulating sympathetic outflow and may be critically important in the alterations in neurohumoral drive, autonomic reflexes, and fluid balance commonly observed in the cardiorenal syndrome. This review focuses on studies implicating neural pathways, particularly the afferent and efferent signals from the heart and the kidneys integrating at the level of the paraventricular nucleus in the hypothalamus to alter neurohumoral drive, autonomic pathways, and fluid balance. Further, it explores the potential mechanisms of action for the known beneficial use of various medications or potential novel therapeutic manipulations for the treatment of the cardiorenal syndrome. A comprehensive understanding of these mechanisms will enhance our ability to treat cardiorenal conditions and their cardiovascular complications more efficaciously and thoroughly.

Characterization of the spontaneous right ventricular hypertrophy and evolution to heart failure in Wistar Kyoto rat strain

Heart failure is a pathological condition that remains as a major cause of morbi‐mortality in the world, and several cellular mechanisms involved in the development of heart failure remain unknown. In this study it was characterized a spontaneous experimental model of right ventricular hypertrophy from Wistar Kyoto rat strain and monocrotaline injection as a factor to induce the development of heart failure. Morphological and functional cardiovascular parameters, and atrial natriuretic factor (ANF) in serum were measured to determine criteria to be considered as a model of heart failure. Male WK rats 2 months old were assigned to 3 experimental groups (n=8 each group): control, right ventricular hypertrophy + saline (RVH+S) and right ventricular hypertrophy + monocrotaline (RVH+MCT). RVH was diagnosed through no invasive electrocardiographic record in awake animals, and one dose of monocrotaline (60 mg/Kg, ip) was injected. After 3 weeks, cardiovascular parameters were recorded (systemic and pulmonary systolic arterial blood pressure, heart rate), and arterial blood from aorta was taken and the heart was removed and analyzed. Total heart, right ventricle, left ventricle weights (g), and right ventricle free wall (in mm) were significantly different in the RVH+S (1.3±0.02, 0.40±14.11, 0.58±13, 2.86±0.19) and the RVH+MCT (1.6±0.09, 0.53±17.5, 0.67±18.94, 4±0.32) groups in comparison with the control group (0.99±0.04, 0.22±4.0, 0.55±14.38, 2.13±0.05), P>0.001 for all parameters, except for LV weight in the RVH+S group. The systemic arterial blood pressure analysis demonstrates absence of significant difference between groups, however, right ventricular pressure (RVP in mm Hg) in the RVH+S (42±2.53), and RVH+MCT (78±4.22), was significantly increased in comparison with the control group (22±1.16), P<0.001. ANF levels in serum were higher in the RVH+S and RVH+MCT experimental groups in comparison with the control group (537±11.04, 557±7.7 and 473±10.65 in pg/ml, respectively; P<0.01). The results suggest that a sub‐strain from WK rats develop right ventricular hypertrophy spontaneously and with the administration of monocrotaline, severe right and left ventricular hypertrophy was developed, changes associated to an increase in levels of atrial natriuretic peptide suggesting heart failure, then could be a useful experimental model of heart failure where right ventricular hypertrophy is a central pathologic mechanism.

Sexual Dimorphism in Response to Vitamins B3, B9 and B12, Used in Combination, in a Mice Model of Heart Failure Induced by Pressure Overload

IntroductionHeart failure (HF) is still a major cause of mortality worldwide. HF pathogenesis involves disturbances in cardiac energy metabolism. Studies have shown that preventive treatment with a diet supplemented with vitamins B3 or B9/B12 in experimental models of HF, exhibits beneficial effects on cardiac and mitochondrial functions and improves survival. Therefore, the overall objective of our pilot study is to evaluate the curative benefit of a synthetic diet enriched with vitamins B3 (nicotinamide riboside), B9 and B12 (BVit) in a mouse model of HF based on the hypothesis that this enriched diet is beneficial for cardiac function via an improvement of cardiac metabolism.MethodPressure overload was induced by transverse aortic constriction (TAC) in 8‐week‐old male and female C57Bl6/N mice. Four weeks post‐TAC and according to their cardiac function evaluated by echocardiography, mice were randomised to a BVit‐enriched diet or not and compared to SHAM animals. The criteria of selection for randomisation were as follows: 10% decrease in ejection fraction (EF), 30% increase in left ventricular (LV) mass and an average pressure gradient of 60mmHg. Mice survival was evaluated and cardiac function was assessed by echocardiography every 4 weeks. Blood samples were taken at 8 weeks of treatment in fasted mice (5 hours) for non‐targeted lipidomics mass spectrometry‐based analysis.ResultsOur pilot study show that survival is not improved in males while mortality is reduced in females from 12 weeks of treatment. In males, the reduced EF in the TAC group is not improved by BVit treatment and myocardial hypertrophy, as illustrated by the left ventricular mass (+20% in TAC), is exacerbated with BVit treatment. In contrast, in females, both EF and cardiac hypertrophy were improved (+20% and ‐13% respectively) after 12 weeks of BVit treatment. To better understand the sexual dimorphism in the response of BVit, non‐targeted lipidomics was used on plasma from mice following 8 weeks of treatment. In TAC‐females, compared to their SHAM controls, a decrease in triglycerides (TG) and an increase in choline phospholipids were observed while the lipid profile was normalized with BVit treatment. In TAC‐males vs SHAM, however, TGs were significantly increased and the treatment with BVit exacerbated the lipidomic profile both in terms of TGs and additional lipid species (identification in progress).ConclusionOur pilot study suggests a sexual dimorphism in the response to BVit treatment in experimental HF. Indeed, the benefit of BVit treatment is only shown in females with a delay in the mortality rate associated with improved cardiac function and normalisation of lipid disturbances. To explore and understand the mechanisms underlying this sexual dimorphism, the lipid profile hypothesis appears as a relevant avenue to explore in the future.

A Critical Role for the Paraventricular Nucleus of the Hypothalamus in the Regulation of the Volume Reflex in Normal and Various Cardiovascular Disease States.

This review focuses on studies implicating forebrain neural pathways and neuromodulator systems, particularly, the nitric oxide system within the paraventricular nucleus of the hypothalamus in regulating neurohumoral drive, autonomic pathways, and fluid balance. Accumulating evidence from animals with experimental models of hypertension and heart failure as well as humans with hypertension suggests that alterations in central neural pathways, particularly, within the PVN neuromodulated by neuronal nitric oxide, are involved in regulating sympathetic outflow particularly to the kidney resulting in alterations in fluid balance commonly observed in hypertension and heart failure states. The characteristics of the hypertensive and heart failure states include alterations in neuronal nitric oxide within the PVN to cause an increase in renal sympathetic nerve activity to result in sodium and fluid retention in these diseases. A comprehensive understanding of these mechanisms will enhance our ability to treat hypertensive and heart failure conditions and their cardiovascular complications more efficiently.

The benefit of antiinflammation treatment via IL-10 in diverse experimental models of heart failure

Aim. The in vitro estimation of IL-10 effects in diverse experimental models of heart failure (HF). Material and methods. HF was induced in rats either by Dx administration in cumulative dose of 16 mg/kg or by isoproterenol administration twice in dose of 150 mg/kg. IL-10 was i/p administration daily during 7 days after HF modeling in single dose of 50 mkg/kg. Functional effects were assayed using perfused isolated heart exposed to hemodynamic and neuroendocrine efforts. Results. IL-10 improved in a similar manner in both HF models capacity of the heart regarding its adaptation to effort by volume and resistance, the most important tool being increasing of isovolumic relaxation and contraction velocity by up to 19%. Noteworthy, IL-10 led to appearance of positive inotropic effect on ET-1 action associated with cardiac output enhancement. Likewise, IL-10 augmented myocardium tolerance to ischemia and reperfusion action according to significant lesser levels of the left ventricle end diastolic pressure. Finally, IL-10 increased coronary functional reserve inherent to acetylcholine action, and coronary flow raised by 25-33% during parasympathetic stimulation. Conclusion. IL-10 notably improves analogically the functional performances of the heart in various models of experimental heart failure during hemodynamic and neuroendocrine efforts, underlying that inflammation is an important pathogenic factor of HF regardless of myocardial injury kind.

Modulation of myosin by cardiac myosin binding protein-C peptides improves cardiac contractility in ex-vivo experimental heart failure models

Cardiac myosin binding protein-C (cMyBP-C) is an important regulator of sarcomeric function. Reduced phosphorylation of cMyBP-C has been linked to compromised contractility in heart failure patients. Here, we used previously published cMyBP-C peptides 302A and 302S, surrogates of the regulatory phosphorylation site serine 302, as a tool to determine the effects of modulating the dephosphorylation state of cMyBP-C on cardiac contraction and relaxation in experimental heart failure (HF) models in vitro. Both peptides increased the contractility of papillary muscle fibers isolated from a mouse model expressing cMyBP-C phospho-ablation (cMyBP-CAAA) constitutively. Peptide 302A, in particular, could also improve the force redevelopment rate (ktr) in papillary muscle fibers from cMyBP-CAAA (nonphosphorylated alanines) mice. Consistent with the above findings, both peptides increased ATPase rates in myofibrils isolated from rats with myocardial infarction (MI), but not from sham rats. Furthermore, in the cMyBP-CAAA mouse model, both peptides improved ATPase hydrolysis rates. These changes were not observed in non-transgenic (NTG) mice or sham rats, indicating the specific effects of these peptides in regulating the dephosphorylation state of cMyBP-C under the pathological conditions of HF. Taken together, these studies demonstrate that modulation of cMyBP-C dephosphorylation state can be a therapeutic approach to improve myosin function, sarcomere contractility and relaxation after an adverse cardiac event. Therefore, targeting cMyBP-C could potentially improve overall cardiac performance as a complement to standard-care drugs in HF patients.