TANK Promotes Pressure Overload Induced Cardiac Hypertrophy via Activating AKT Signaling Pathway

Background: TANK (TRAF family member associated NF-κB activator) acts as a member of scaffold proteins participated in the development of multiple diseases. However, its function in process of cardiac hypertrophy is still unknown.Methods and Results: In this study, we observed an increased expression of TANK in murine hypertrophic hearts after aortic banding, suggesting that TANK may be involved in the pathogenesis of cardiac hypertrophy. We generated cardiac-specific TANK knockout mice, and subsequently subjected to aortic banding for 4–8 weeks. TANK knockout mice showed attenuated cardiac hypertrophy and dysfunction compared to the control group. In contrast, cardiac-specific TANK transgenic mice showed opposite signs. Consistently, in vitro experiments revealed that TANK knockdown decreased the cell size and expression of hypertrophic markers. Mechanistically, AKT signaling was inhibited in TANK knockout mice, but activated in TANK transgenic mice after aortic banding. Blocking AKT signaling with a pharmacological AKT inhibitor alleviated the cardiac hypertrophy and dysfunction in TANK transgenic mice.Conclusions: Collectively, we identified TANK accelerates the progression of pathological cardiac hypertrophy and is a potential therapeutic target.

Homoarginine Treatment of Rats Improves Cardiac Function and Remodeling in Response to Pressure Overload

Purpose Low serum concentrations of the amino acid homoarginine (HA) are associated with increased cardiovascular mortality by incompletely understood mechanisms. This study sought to assess the influence of HA on myocardial function and remodeling in rats undergoing aortic banding or given the nitric oxide synthesis inhibitor Nω-Nitro-L-arginine methyl ester hydrochloride (L-NAME). Methods Male Wistar rats (n = 136) underwent sham operation (SH) or aortic banding (AB) and were equally divided into fourteen subgroups, receiving different doses of HA alone or in combination with either lisinopril, spironolactone or L-NAME over a 4-week period. Results HA treatment in AB animals resulted in a dose-dependent improvement of cardiac function up to a concentration of 800 mg·kg− 1·day− 1. Combining 800 mg·kg− 1·day− 1 HA with spironolactone or lisinopril yielded synergistic effects, showing a positive correlation with LV ejection fraction (+ 27%, p < 0.05), fractional shortening (+ 37%, p < 0.05) and an inverse association with collagen area fraction (-56%, p < 0.05), myocyte cross-sectional area (-22%, p < 0.05) and the molecular markers atrial natriuretic factor (-78%, p = 0.04), brain natriuretic peptide (-28%, p = 0.22), beta-myosin heavy chain (-42%, p = 0.19) and collagen type V alpha 1 chain (-73%, p = 0.06) compared to placebo treated AB animals. Even co-administration of HA and L-NAME was found to attenuate cardiac remodeling and to prevent NO-deficient hypertension following AB. Conclusion HA treatment has led to a dose-dependent improvement of myocardial function and marked histological and molecular changes of cardiac remodeling following AB. Combining HA with standard heart failure medication resulted in synergistic beneficial effects boosting the direct impact of HA on heart failure pathophysiology.

Abstract 16434: Temporal Metabolomic and Transcriptomic Changes in a Large-Animal Model of Hfpef

Heart failure with preserved ejection fraction (HFpEF) accounts for ~50% of HF cases, with no effective treatments. We previously reported that a feline aortic banding model recapitulates many of the multi-factorial features of HFpEF, including: LV hypertrophy, left atrial enlargement, elevated LV filling pressures, impaired pulmonary mechanics and fibrosis. Importantly, this model lacks obesity and hypertension enabling the discovery of cardiac centric targets independent of comorbidities. We examined early changes in metabolism and transcription to gain mechanistic insight into HFpEF development. Male short-hair kittens (2mo old) underwent aortic banding or sham operation. Cardiac function was assessed at baseline and 1mo post-banding prior to tissue collection and downstream analyses. Following banding, we observed significant cardiac hypertrophy and initiation of LV fibrosis in the absence of changes in cardiac function. We observed LV mitochondrial dysfunction, indicated by impaired complex-I and -II respiration prompting the examination of cardiac metabolism by unbiased metabolomics. 82 metabolites were significantly different (≥ 1.25 fold, p ≤ 0.1) between 1mo banded and sham hearts, with an overrepresentation of amino acid (aa) and lipid species. Pathway enrichment analysis highlighted an increase in aa metabolism (e.g. serine, proline) that is associated with ECM remodeling and tissue fibrosis. Additionally, an increase in lipid species (i.e. acyl-carnitines) suggests reduced fatty acid utilization and a shift towards glycolysis. Correlations of metabolomics data with mitochondrial function and cardiac phenotyping revealed strong associations between mitochondrial function and the cardiac energy state, as well as aa and LV fibrosis. RNA-seq and enrichment analyses revealed a significant inflammatory response early in disease progression and a decrease in protein/histone acetylation. Collectively, this systems-based approach provides new insights into the cellular biology underlying HFpEF-like disease progression. The metabolic and transcriptional signature that precede the clinical features of HFpEF, will provide new pre-clinical research directions and may yield novel therapeutic targets.

Deubiquitinase Ubiquitin‐Specific Protease 10 Deficiency Regulates Sirt6 signaling and Exacerbates Cardiac Hypertrophy

Background Cardiac hypertrophy (CH) is a physiological response that compensates for blood pressure overload. Under pathological conditions, hypertrophy can progress to heart failure as a consequence of the disorganized growth of cardiomyocytes and cardiac tissue. USP10 (ubiquitin‐specific protease 10) is a member of the ubiquitin‐specific protease family of cysteine proteases, which are involved in viral infection, oxidative stress, lipid drop formation, and heat shock. However, the role of USP10 in CH remains largely unclear. Here, we investigated the roles of USP10 in CH. Methods and Results Cardiac‐specific USP10 knockout (USP10‐CKO) mice and USP10‐transgenic (USP10‐TG) mice were used to examined the role of USP10 in CH following aortic banding. The specific functions of USP10 were further examined in isolated cardiomyocytes. USP10 expression was increased in murine hypertrophic hearts following aortic banding and in isolated cardiomyocytes in response to hypertrophic agonist. Mice deficient in USP10 in the heart exhibited exaggerated cardiac hypertrophy and fibrosis following pressure overload stress, which resulted in worsening of cardiac contractile function. In contrast, cardiac overexpression of USP10 protected against pressure overload‐induced maladaptive CH. Mechanistically, we demonstrated that USP10 activation and interaction with Sirt6 in response to angiotensin II led to a marked increase in the ubiquitination of Sirt6 and resulted in Akt signaling downregulation and attenuation of cardiomyocyte hypertrophy. Accordingly, inactivation of USP10 reduced Sirt6 abundance and stability and diminished Sirt6‐induced downstream signaling in cardiomyocytes. Conclusions USP10 functions as a Sirt6 deubiquitinase that induces cardiac myocyte hypertrophy and triggers maladaptive CH.

Deletion of Microfibrillar‐Associated Protein 4 Attenuates Left Ventricular Remodeling and Dysfunction in Heart Failure

Background Cardiac remodeling predisposes individuals to heart failure if the burden is not solved, and heart failure is a growing cause of morbidity and mortality worldwide. The cardiac extracellular matrix not only provides structural support, but also is a core aspect of the myocardial response to various biomechanical stresses and heart failure. MFAP4 (microfibrillar‐associated protein 4) is an integrin ligand located in the extracellular matrix, whose biological functions in the heart remain poorly understood. In the current study we aimed to test the role of MFAP4 in cardiac remodeling. Methods and Results MFAP4‐deficient (MFAP4 −/− ) and wild‐type mice were subjected to aortic banding surgery and isoproterenol to establish models of cardiac remodeling. We also evaluated the functional effects of MFAP4 on cardiac hypertrophy, fibrosis, and cardiac electrical remodeling. The expression of MFAP4 was increased in the animal cardiac remodeling models induced by pressure overload and isoproterenol. After challenge of 8 weeks of aortic banding or 2 weeks of intraperitoneal isoproterenol, MFAP4 −/− mice exhibited lower levels of cardiac fibrosis and fewer ventricular arrhythmias than wild‐type mice. However, there was no significant effect on cardiomyocyte hypertrophy. In addition, there was no significant difference in cardiac fibrosis severity, hypertrophy, or ventricular arrhythmia incidence between wild‐type‐sham and knockout‐sham mice. Conclusions These findings are the first to demonstrate that MFAP4 deficiency inhibits cardiac fibrosis and ventricular arrhythmias after challenge with 8 weeks of aortic banding or 2 weeks of intraperitoneal isoproterenol but does not significantly affect the hypertrophy response. In addition, MFAP4 deficiency had no significant effect on cardiac fibrosis, hypertrophy, or ventricular arrhythmia in the sham group in this study.