Total Glucosides of Paeony Ameliorate Myocardial Injury in Chronic Heart Failure Rats by Suppressing PARP-1

Total glucosides of paeony (TGP) have a potential protective effect on chronic heart failure (CHF) rats, but the mechanism remains unclear. PARP inhibition prevents the decrease in myocardial contractility. Therefore, we aim to investigate the effects and mechanisms of TGP on CHF and the role of PARP-1 in CHF. Left anterior descending ligation rats and adriamycin-treated H9C9 cells were used as CHF models, and captopril as a positive control for in vivo experiments. We found that TGP alleviated myocardial remodeling and improved cardiac morphology and function. TGP also reduced myocardial apoptosis and autophagy, decreased inflammatory factor release, and inhibited the PARP-1 and NF-κB proteins. Through cell transfection, we found that PAPR-1 knockdown inhibited NF-κB nuclear translocation. Additionally, TGP inhibited apoptosis, autophagy, and inflammation in CHF cells, while PARP-1 overexpression partially antagonized them. In conclusion, TGP has the potential to improve CHF and PARP-1 may be a potential target.

G protein-coupled receptor kinase 5 (GRK5) contributes to impaired cardiac function and immune cell recruitment in post-ischemic heart failure

AIMS

Myocardial infarction (MI) is the most common cause of heart failure (HF) worldwide. G protein-coupled receptor kinase 5 (GRK5) is upregulated in failing human myocardium and promotes maladaptive cardiac hypertrophy in animal models. However, the role of GRK5 in ischemic heart disease is still unknown. In this study, we evaluated whether myocardial GRK5 plays a critical role post-MI in mice and included the examination of specific cardiac immune and inflammatory responses.

METHODS AND RESULTS

Cardiomyocyte-specific GRK5 overexpressing transgenic mice (TgGRK5) and non-transgenic littermate control (NLC) mice as well as cardiomyocyte-specific GRK5 knockout mice (GRK5cKO) and wild type (WT) were subjected to MI and, functional as well as structural changes together with outcomes were studied. TgGRK5 post-MI mice showed decreased cardiac function, augmented left ventricular dimension and decreased survival rate compared to NLC post-MI mice. Cardiac hypertrophy and fibrosis as well as fetal gene expression were increased post-MI in TgGRK5 compared to NLC mice. In TgGRK5 mice, GRK5 elevation produced immuno-regulators that contributed to the elevated and long-lasting leukocyte recruitment into the injured heart and ultimately to chronic cardiac inflammation. We found an increased presence of pro-inflammatory neutrophils and macrophages as well as neutrophils, macrophages and T-lymphocytes at 4-days and 8-weeks respectively post-MI in TgGRK5 hearts. Conversely, GRK5cKO mice were protected from ischemic injury and showed reduced early immune cell recruitment (predominantly monocytes) to the heart, improved contractility and reduced mortality compared to WT post-MI mice. Interestingly, cardiomyocyte-specific GRK2 transgenic mice did not share the same phenotype of TgGRK5 mice and did not have increased cardiac leukocyte migration and cytokine or chemokine production post-MI.

CONCLUSIONS

Our study shows that myocyte GRK5 has a crucial and GRK-selective role on the regulation of leucocyte infiltration into the heart, cardiac function and survival in a murine model of post-ischemic HF, supporting GRK5 inhibition as a therapeutic target for HF.

Protective role of emodin in rats with post-myocardial infarction heart failure and influence on extracellular signal-regulated kinase pathway

We aimed to explore the effects of emodin on the energy metabolism of myocardial cells in rats with post-myocardial infarction (MI) heart failure (HF) and the extracellular signal-regulated kinase (ERK) pathway. The model of MI was established by ligation of the left anterior descending branch. After 4 weeks, the rats with left ventricular ejection fraction (LVEF) of ≤45% were used aspost-MI HF model animals and randomly divided into model, low-dose, middle-dose, high-dose and control groups (n=10). Low-, middle- and high-dose groups were gavaged with 20 mg/kg, 40 mg/kg and 60 mg/kg emodin daily, respectively. After administration for 14 d, the changes in LVEF, left ventricular end-systolic diameter (LVESD), left ventricular end-diastolic diameter (LVEDD) and interventricular septum thickness (IVS) were analyzed. The apoptosis rate of myocardial cells was detected by TUNEL staining. The levels of serum cardiac troponin I (cTnI) and peroxisome proliferator-activated receptor-γ coactivator-1 (PGC-1) were determined using ELISA, and the expressions of mitochondrial respiratory chain complex I protein and phosphorylated-ERK (p-ERK) in myocardial tissues were determined by Western blotting.  Compared with model group, LVEDD, LVESD, apoptosis rate of myocardial cells, levels of serum cTnI and PGC-1, and expressions of complex I and p-ERK in myocardial tissues significantly decreased, while LVEF and IVS increased in low-dose, middle-dose, high-dose and control groups (P<0.05). The changes in the above indices were significantly dependent on the dose of emodin (P<0.05).Emodin can significantly relieve post-MI HF, reduce the apoptosis rate of myocardial tissues, and ameliorate the cardiac function of rats.

Ubiquitin ligase Wwp1 gene deletion attenuates diastolic dysfunction in pressure-overload hypertrophy

Heart failure with a preserved left ventricular (LV) ejection fraction (HFpEF) often arises from a prolonged LV pressure overload (LVPO) and accompanied by abnormal extracellular matrix (ECM) accumulation. The E3 ubiquitin ligase WWP1 is a fundamental determinant ECM turnover. We tested the hypothesis that genetic ablation of Wwp1 would alter the progression of LVPO-induced HFpEF. LV echocardiography in mice with global Wwp1 deletion (n = 23; Wwp1-/-) was performed at 12 wk of age (baseline) and then at 2 and 4 wk following LVPO (transverse aortic banding) or surgery without LVPO induction. Age-matched wild-type mice (Wwp1+/+; n = 23) underwent identical protocols. LV EF remained constant and unchanged with LVPO and LV mass increased in both groups but was lower in the Wwp1-/- mice. With LVPO, the E/A ratio, an index of LV filling, was 3.97 ± 0.46 in Wwp1+/+ but was 1.73 ± 0.19 in the Wwp1-/- group (P < 0.05). At the transcriptional level, mRNA for fibrillar collagens (types I and III) decreased by approximately 50% in Wwp1-/- compared with the Wwp1+/+ group at 4 wk post-LVPO (P < 0.05) and was paralleled by a similar difference in LV fibrillar collagen content as measured by histochemistry. Moreover, mRNA levels for determinants favoring ECM accumulation, such as transforming growth factor (TGF), increased with LVPO, but were lower in the Wwp1-/- group. The absence of Wwp1 reduced the development of left ventricular hypertrophy and subsequent progression to HFpEF. Modulating the WWP1 pathway could be a therapeutic target to alter the natural history of HFpEF.NEW & NOTEWORTHY Heart failure with a preserved left ventricular (LV) ejection fraction (HFpEF) often arises from a prolonged LV pressure overload (LVPO) and is accompanied by abnormal extracellular matrix (ECM) accumulation. It is now recognized that the ECM is a dynamic entity that is regulated at multiple post-transcriptional levels, including the E3 ubiquitin ligases, such as WWP1. In the present study, WWP1 deletion in the context of an LVPO stimulus reduced functional indices of HFpEF progression and determinants of ECM remodeling.

Relevance of Neutrophil Neprilysin in Heart Failure

Significant expression of neprilysin (NEP) is found on neutrophils, which present the transmembrane integer form of the enzyme. This study aimed to investigate the relationship of neutrophil transmembrane neprilysin (mNEP) with disease severity, adverse remodeling, and outcome in HFrEF. In total, 228 HFrEF, 30 HFpEF patients, and 43 controls were enrolled. Neutrophil mNEP was measured by flow-cytometry. NEP activity in plasma and blood cells was determined for a subset of HFrEF patients using mass-spectrometry. Heart failure (HF) was characterized by reduced neutrophil mNEP compared to controls (p < 0.01). NEP activity on peripheral blood cells was almost 4-fold higher compared to plasma NEP activity (p = 0.031) and correlated with neutrophil mNEP (p = 0.006). Lower neutrophil mNEP was associated with increasing disease severity and markers of adverse remodeling. Higher neutrophil mNEP was associated with reduced risk for mortality, total cardiovascular hospitalizations, and the composite endpoint of both (p < 0.01 for all). This is the first report describing a significant role of neutrophil mNEP in HFrEF. The biological relevance of neutrophil mNEP and exact effects of angiotensin-converting-enzyme inhibitors (ARNi) at the neutrophil site have to be determined. However, the results may suggest early initiation of ARNi already in less severe HF disease, where effects of NEP inhibition may be more pronounced.

Impacts of Yangxin decoction on the expressions of MMP-9, CaN, NFAT3 and GATA4 in myocardial tissue of rats with chronic heart failure

To investigate the impacts of Yangxin decoction on the expressions of matrix metalloproteinase 9 (MMP-9), calcineurin (CaN), T cell activated nuclear factor 3 (NFAT3) and zinc finger transcription factor 4 (GATA4) in myocardial tissue of rats with chronic heart failure (CHF). 50 healthy SD rats were randomly divided into the normal control group (n = 10) and the operation group (n = 40). After successful modeling, the rats were randomly divided into 4 groups. And they were treated with Yangxin decoctions of low concentration (1.5 g/kg), medium concentration (2.5 g/kg), high concentration (3.5 g/kg) and distilled water (for 4 weeks). The LVSP, SAP, DAP and LVEDP in Yangxin decoction treatment groups were significantly superior to the model group. The LVEF, LVIDd and LVIDs in Yangxin decoction treatment groups were significantly superior to the model group. The activity of CaN in each group treated with Yangxin decoction was significantly lower than that in the model group. The expression levels of MMP-9, NFAT3, GATA4 protein in each group treated with Yangxin decoction were significantly lower than that in the model group.. Yangxin decoction can significantly improve the cardiac function, reduce CaN activity, decrease the expression levels of MMP-9, NFAT3 and GATA4, inhibit CaN/NFAT3 signaling pathway, increase myocardial remodeling and protect myocardial tissue in rats with CHF.

The role of demethylases in cardiac development and disease

Heart failure is a worldwide health condition that currently has limited noninvasive treatments. Heart disease includes both structural and molecular remodeling of the heart which is driven by alterations in gene expression in the cardiomyocyte. Therefore, understanding the regulatory mechanisms which instigate these changes in gene expression and constitute the foundation for pathological remodeling may be beneficial for developing new treatments for heart disease. These gene expression changes are largely preceded by epigenetic alterations to chromatin, including the post-translational modification of histones such as methylation, which alters chromatin to be more or less accessible for transcription factors or regulatory proteins to bind and modify gene expression. Methylation was once thought to be a permanent mark placed on histone or non-histone targets by methyltransferases, but is now understood to be a reversible process after the discovery of the first demethylase, KDM1A/LSD1. Since this time, it has been shown that demethylases play key roles in embryonic development, in maintaining cellular homeostasis and disease progression. However, the role of demethylases in the fetal and adult heart remains largely unknown. In this review, we have compiled data on the 33 mammalian demethylases that have been identified to date and evaluate their expression in the embryonic and adult heart as well as changes in expression in the failing myocardium using publicly available RNA-sequencing and proteomic datasets. Our analysis detected expression of 14 demethylases in the normal fetal heart, and 5 demethylases in the normal adult heart. Moreover, 8 demethylases displayed differential expression in the diseased human heart compared to healthy hearts. We then examined the literature regarding these demethylases and provide phenotypic information of 13 demethylases that have been functionally interrogated in some way in the heart. Lastly, we describe the 6 arginine and lysine residues on histones which have been shown to be methylated but have no corresponding demethylase identified which removes these methyl marks. Overall, this review highlights our current knowledge on the role of demethylases, their importance in cardiac development and pathophysiology and provides evidence for the use of pharmacological inhibitors to combat disease.

Effects of Hsp90 inhibitor on the RIP1-RIP3-MLKL pathway during the development of heart failure in mice

Necroptosis is a programmed form of necrotic cell death. Necroptosis is regulated by the necroptosis-regulating proteins including receptor-interacting protein (RIP) 1, RIP3, and mixed lineage kinase domain-like (MLKL), the activities of which are modulated by the molecular chaperone heat-shock protein (Hsp) 90. Presently, to clarify the relationship between Hsp90 and necroptotic pathway proteins, RIP1, RIP3, and MLKL in the development of heart failure, we examined the effects of Hsp90 inhibitor treatment on the RIP1-RIP3-MLKL pathway in mice following transverse aortic constriction (TAC). In this study, TAC mice showed typical signs of heart failure at the 8th week after the operation. In the failing heart, the levels of these regulatory proteins and those of their phosphorylated forms were increased, suggesting that necroptosis contributed to the development of heart failure in the TAC mice. The increases in RIP1, RIP3, and MLKL after TAC were reversed by the administration of an Hsp90 inhibitor. Furthermore, the rise in the phosphorylation levels of these 3 proteins were attenuated by the Hsp90 inhibitor. Concomitantly, cardiac functions were preserved. We also found that exposure of cultured adult mouse cardiomyocytes to the Hsp90 inhibitor attenuated necrotic cell death induced by tumor necrosis factor-α via suppression of RIP1, RIP3, and MLKL activation in in vitro experiments. Taken together, our findings suggest that inhibition of Hsp90 should have therapeutic effects by reducing the activation of RIP1-RIP3-MLKL pathway in the hypertrophied heart and thus could be a new therapeutic strategy for chronic heart failure.

Nuanxin capsule enhances cardiac function by inhibiting oxidative stress-induced mitochondrial dependent apoptosis through AMPK/JNK signaling pathway

OBJECTIVE

Oxidative stress and apoptosis play critical roles in the pathogenesis of heart failure (HF).Nuanxin capsule (NX) is a Chinese medicine that has outstanding protective effects on HF. The present study aimed to elucidate whether NX could protect HF against oxidative stress-induced apoptosis through intrinsic mitochondrial pathway.

METHODS

In vivo, HF was induced by transverse aortic constriction. NX and Compound C (Comp C) were administered to C57BL/6 J mice for over a 4-week period. Cardiac function was assessed with echocardiography. In vitro, H9c2 cells were exposed to H2O2 in the presence or absence of NX and Compound C. Cell viability, cytotoxicity, reactive oxygen species (ROS) production, apoptosis, mitochondrial membrane potential (ΔΨm) and mitochondrial function by oxygen consumption rate (OCR) were detected. The expressions of cytochrome c, BAX, Bcl-2, cleaved caspase-3, AMPK and JNK were evaluated by western blotting.

RESULTS

The results indicated that NX significantly improved cardiac function and enhanced the cell viability, ΔΨm and mitochondrial respiration. Also NX treatment reduced cell cytotoxicity and ROS production. Moreover, NX inhibited mitochondrial-mediated apoptosis by upregulating AMPK and downregulating JNK both in vivo and in vitro. The protective effects of NX on cardiac function by reducing oxidative stress-induced mitochondrial dependent apoptosis were reversed by Compound C treatment.

CONCLUSIONS

These findings demonstrated that NX effectively improved cardiac function in TAC mice by reducing oxidative stress-induced mitochondrial dependent apoptosis by activating AMPK/JNK signaling pathway.

Amylin deposition activates HIF1α and 6-phosphofructo-2-kinase/fructose-2, 6-biphosphatase 3 (PFKFB3) signaling in failing hearts of non-human primates

Hyperamylinemia induces amylin aggregation and toxicity in the pancreas and contributes to the development of type-2 diabetes (T2D). Cardiac amylin deposition in patients with obesity and T2D was found to accelerate heart dysfunction. Non-human primates (NHPs) have similar genetic, metabolic, and cardiovascular processes as humans. However, the underlying mechanisms of cardiac amylin in NHPs, particularly related to the hypoxia inducible factor (HIF)1α and 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3) signaling pathways, are unknown. Here, we demonstrate that in NHPs, amylin deposition in heart failure (HF) contributes to cardiac dysfunction via activation of HIF1α and PFKFB3 signaling. This was confirmed in two in vitro cardiomyocyte models. Furthermore, alterations of intracellular Ca2+, reactive oxygen species, mitochondrial function, and lactate levels were observed in amylin-treated cells. Our study demonstrates a pathological role for amylin in the activation of HIF1α and PFKFB3 signaling in NHPs with HF, establishing amylin as a promising target for heart disease patients.

Empagliflozin improves endothelial and cardiomyocyte function in human heart failure with preserved ejection fraction via reduced pro-inflammatory-oxidative pathways and protein kinase Gα oxidation

AIMS

Sodium-glucose-cotransporter-2 inhibitors showed favourable cardiovascular outcomes, but the underlying mechanisms are still elusive. This study investigated the mechanisms of empagliflozin in human and murine heart failure with preserved ejection fraction (HFpEF).

METHODS AND RESULTS

The acute mechanisms of empagliflozin were investigated in human myocardium from patients with HFpEF and murine ZDF obese rats, which were treated in vivo. As shown with immunoblots and ELISA, empagliflozin significantly suppressed increased levels of ICAM-1, VCAM-1, TNF-α, and IL-6 in human and murine HFpEF myocardium and attenuated pathological oxidative parameters (H2O2, 3-nitrotyrosine, GSH, lipid peroxide) in both cardiomyocyte cytosol and mitochondria in addition to improved endothelial vasorelaxation. In HFpEF, we found higher oxidative stress-dependent activation of eNOS leading to PKGIα oxidation. Interestingly, immunofluorescence imaging and electron microscopy revealed that oxidized PKG1α in HFpEF appeared as dimers/polymers localized to the outer-membrane of the cardiomyocyte. Empagliflozin reduced oxidative stress/eNOS-dependent PKGIα oxidation and polymerization resulting in a higher fraction of PKGIα monomers, which translocated back to the cytosol. Consequently, diminished NO levels, sGC activity, cGMP concentration, and PKGIα activity in HFpEF increased upon empagliflozin leading to improved phosphorylation of myofilament proteins. In skinned HFpEF cardiomyocytes, empagliflozin improved cardiomyocyte stiffness in an anti-oxidative/PKGIα-dependent manner. Monovariate linear regression analysis confirmed the correlation of oxidative stress and PKGIα polymerization with increased cardiomyocyte stiffness and diastolic dysfunction of the HFpEF patients.

CONCLUSION

Empagliflozin reduces inflammatory and oxidative stress in HFpEF and thereby improves the NO-sGC-cGMP-cascade and PKGIα activity via reduced PKGIα oxidation and polymerization leading to less pathological cardiomyocyte stiffness.

Relation of Aspartate Aminotransferase to Alanine Aminotransferase Ratio to Nutritional Status and Prognosis in Patients With Acute Heart Failure

Elevated liver fibrosis markers are associated with worse prognosis in acute heart failure (AHF). The aspartate aminotransferase to alanine aminotransferase ratio (AAR) is one such fibrosis marker, and low ALT is a surrogate marker of malnutrition. Here, we evaluated the association between AAR and nutritional status and prognosis in patients with AHF. Consecutive 774 patients who were admitted due to AHF were divided into 3 groups according to AAR at discharge: first tertile, AAR<1.16 (n = 262); second tertile, 1.16≤AAR<1.70 (n = 257); and third tertile, AAR≥1.70 (n = 255). Nutritional indices and a composite of all-cause death or HF rehospitalization were compared in the 3 tertiles. Patients in the third AAR tertile were older and had lower body mass index than patients in other AAR tertiles. A higher AAR was associated with worse nutritional indices (i.e., controlling nutritional status score, geriatric nutritional risk index, and prognostic nutritional index). Clinical outcome rates significantly increased along AAR tertiles (first tertile, 28%; second tertile, 43%; third tertile, 58%, p < 0.001). Cox proportional hazards models including potential prognostic factors revealed high AAR was an independent prognostic factor of AHF. In conclusion, AAR at discharge may be associated with nutritional status and worse clinical outcomes in patients with AHF.

Nox2+ myeloid cells drive vascular inflammation and endothelial dysfunction in heart failure after myocardial infarction via angiotensin II receptor type 1

AIMS

Heart failure (HF) ensuing myocardial infarction (MI) is characterized by the initiation of a systemic inflammatory response. We aimed to elucidate the impact of myelomonocytic cells and their activation by angiotensin II on vascular endothelial function in a mouse model of HF after MI.

METHODS AND RESULTS

HF was induced in male C57BL/6J mice by permanent ligation of the left anterior descending coronary artery. Compared to sham, HF mice had significantly impaired endothelial function accompanied by enhanced mobilization of Sca-1+c-Kit+ haematopoietic stem cells and Sca-1-c-Kit+ common myeloid and granulocyte-macrophage progenitors in the bone marrow as well as increased vascular infiltration of CD11b+Ly6G-Ly6Chigh monocytes and accumulation of CD11b+ F4/80+ macrophages, assessed by flow cytometry. Using mice with Cre-inducible expression of diphtheria toxin receptor in myeloid cells, we selectively depleted lysozyme M+ myelomonocytic cells for 10 days starting 28 days after MI. While the cardiac phenotype remained unaltered until 38 days post-MI, myeloid cell depletion attenuated vascular accumulation of Nox2+CD45+ cells, endothelial dysfunction, oxidative stress, and vascular expression of adhesion molecules and angiotensin II receptor type 1 (AT1R). Pharmacological blockade of this receptor for 4 weeks did not significantly alter cardiac function, but mimicked the effects of myeloid cell depletion: telmisartan (20 mg/kg/day, fed to C57BL/6J mice) diminished bone marrow myelopoesis and myeloid reactive oxygen species production, attenuated endothelial leucocyte rolling and vascular accumulation of CD11b+Ly6G-Ly6Chigh monocytes and macrophages, resulting in improved vascular function with less abundance of Nox2+CD45+ cells.

CONCLUSION

Endothelial dysfunction in HF ensuing MI is mediated by inflammatory Nox2+ myeloid cells infiltrating the vessel wall that can be targeted by AT1R blockade.

Clinical and Proteomic Correlates of Plasma ACE2 (Angiotensin-Converting Enzyme 2) in Human Heart Failure

ACE2 (angiotensin-converting enzyme 2) is a key component of the renin-angiotensin-aldosterone system. Yet, little is known about the clinical and biologic correlates of circulating ACE2 levels in humans. We assessed the clinical and proteomic correlates of plasma (soluble) ACE2 protein levels in human heart failure. We measured plasma ACE2 using a modified aptamer assay among PHFS (Penn Heart Failure Study) participants (n=2248). We performed an association study of ACE2 against ≈5000 other plasma proteins measured with the SomaScan platform. Plasma ACE2 was not associated with ACE inhibitor and angiotensin-receptor blocker use. Plasma ACE2 was associated with older age, male sex, diabetes mellitus, a lower estimated glomerular filtration rate, worse New York Heart Association class, a history of coronary artery bypass surgery, and higher pro-BNP (pro-B-type natriuretic peptide) levels. Plasma ACE2 exhibited associations with 1011 other plasma proteins. In pathway overrepresentation analyses, top canonical pathways associated with plasma ACE2 included clathrin-mediated endocytosis signaling, actin cytoskeleton signaling, mechanisms of viral exit from host cells, EIF2 (eukaryotic initiation factor 2) signaling, and the protein ubiquitination pathway. In conclusion, in humans with heart failure, plasma ACE2 is associated with various clinical factors known to be associated with severe coronavirus disease 2019 (COVID-19), including older age, male sex, and diabetes mellitus, but is not associated with ACE inhibitor and angiotensin-receptor blocker use. Plasma ACE2 protein levels are prominently associated with multiple cellular pathways involved in cellular endocytosis, exocytosis, and intracellular protein trafficking. Whether these have a causal relationship with ACE2 or are relevant to novel coronavirus-2 infection remains to be assessed in future studies.

Chrysophanol Protects Against Acute Heart Failure by Inhibiting JNK1/2 Pathway in Rats

BACKGROUND Acute heart failure (AHF) usually requires urgent therapy. Myocardial damage, oxidative stress, and inflammation are major components in the pathology of AHF. This study was designed to investigate the effects of chrysophanol on AHF. MATERIAL AND METHODS Sprague-Dawley rats were injected with isoprenaline hydrochloride to construct AHF rat models. AHF rats were treated with normal saline (negative control), chrysophanol, the combination of chrysophanol and SP600125, or benazepril (positive control) using sham rats as blank controls. Echocardiography, histological staining, and enzyme activity analysis were performed to assess the heart functions and myocardial damage. Effects on apoptosis, oxidative stress (OS), and inflammation were evaluated by biochemical analysis, TUNEL staining, and ELISA. RESULTS Chrysophanol improved the parameters of cardiac functions and alleviated the myocardial damage accompanied by the reduction of creatine kinase and lactate dehydrogenase activity. Meanwhile, chrysophanol inhibited the myocardial apoptosis along with the upregulation of Bcl-2 and downregulation of Bax and cleaved caspase-3. AHF-induced abnormal changes of OS parameters (MDA, GPx, CAT, SOD) and inflammatory markers (IL-6, IL-1ß, TNF-alpha, IFN-γ) were alleviated by chrysophanol. Benazepril treatment showed similar results with chrysophanol, while the addition of SP600125 enhanced the chrysophanol-mediated protection effects in AHF rats. Western blot analysis demonstrated that chrysophanol inhibited the phosphorylation of JNK1/2 and its upstream/downstream factors. CONCLUSIONS Chrysophanol improved cardiac functions and protected against myocardial damage, apoptosis, OS, and inflammation by inhibiting activation of the JNK1/2 pathway in AHF rat models. These finding indicate that chrysophanol may be a promising approach for treatment of AHF.

A Common Missense Variant in OMA1 Associated with the Prognosis of Heart Failure

PURPOSE

Mitochondrial dysfunction plays a vital role in the pathophysiologic process of heart failure (HF). As a quality control system, mitochondrial fusion and fission are under control of mitochondrial fusion and fission-related proteins. The objective of this study was to investigate the effects of common variants in mitochondrial fusion and fission-related genes on the prognosis of HF.

METHODS

We performed whole exome sequencing (WES) with 1000 HF patients; the statistically significant variant was further genotyped in the replicated population with 2324 HF patients. A series of function analysis including western blot, cell proliferation assay, and in vitro OMA1 activity assay were conducted to illuminate the underlying mechanism.

RESULTS

We identified a missense variant rs17117699 associated with the prognosis of HF in group without β-blocker use rather than with β-blocker use in two-stage population: adjusted P = 0.79, HR = 0.88 (0.36-2.13) in group with β-blocker use and adjusted P = 0.016, HR = 1.43 (1.07-1.91) in group without β-blocker in first-stage population; adjusted P = 0.42, HR = 0.85 (0.56-1.28) in group with β-blocker use and adjusted P = 0.015, HR = 1.39 (1.06-1.82) in group without β-blocker in replicated stage. Functional analysis indicated that rs17117699-G allele increased the activity of OMA1 assessed by the ratio of S-OPA1 to L-OPA1 and suppressed cells proliferation under ISO treatment when compared with rs17117699-T allele. Furthermore, OMA1 functioned downstream of β-adrenergic receptor signaling and ISO-induced OPA1 cleavage is dependent on OMA1.

CONCLUSIONS

Our findings demonstrate that rs17117699T>G in OMA1 increases the risk of HF mortality via enhancing its OPA1 cleavage activity. It is a promising potential treatment target for HF.

CLINICAL TRIAL REGISTRATION

NCT03461107. https://www.clinicaltrials.gov/ct2/show/NCT03461107?term=03461107&cond=Heart+Failure&cntry=CN&rank=1.

Glutamyl-Prolyl-tRNA Synthetase Regulates Proline-Rich Pro-Fibrotic Protein Synthesis During Cardiac Fibrosis

RATIONALE

Increased protein synthesis of profibrotic genes is a common feature in cardiac fibrosis and heart failure. Despite this observation, critical factors and molecular mechanisms for translational control of profibrotic genes during cardiac fibrosis remain unclear.

OBJECTIVE

To investigate the role of a bifunctional ARS (aminoacyl-tRNA synthetase), EPRS (glutamyl-prolyl-tRNA synthetase) in translational control of cardiac fibrosis.

METHODS AND RESULTS

Results from reanalyses of multiple publicly available data sets of human and mouse heart failure, demonstrated that EPRS acted as an integrated node among the ARSs in various cardiac pathogenic processes. We confirmed that EPRS was induced at mRNA and protein levels (≈1.5-2.5-fold increase) in failing hearts compared with nonfailing hearts using our cohort of human and mouse heart samples. Genetic knockout of one allele of Eprs globally (Eprs+/-) using CRISPR-Cas9 technology or in a Postn-Cre-dependent manner (Eprsflox/+; PostnMCM/+) strongly reduces cardiac fibrosis (≈50% reduction) in isoproterenol-, transverse aortic constriction-, and myocardial infarction (MI)-induced heart failure mouse models. Inhibition of EPRS using a PRS (prolyl-tRNA synthetase)-specific inhibitor, halofuginone, significantly decreases translation efficiency (TE) of proline-rich collagens in cardiac fibroblasts as well as TGF-β (transforming growth factor-β)-activated myofibroblasts. Overexpression of EPRS increases collagen protein expression in primary cardiac fibroblasts under TGF-β stimulation. Using transcriptome-wide RNA-Seq and polysome profiling-Seq in halofuginone-treated fibroblasts, we identified multiple novel Pro-rich genes in addition to collagens, such as Ltbp2 (latent TGF-β-binding protein 2) and Sulf1 (sulfatase 1), which are translationally regulated by EPRS. SULF1 is highly enriched in human and mouse myofibroblasts. In the primary cardiac fibroblast culture system, siRNA-mediated knockdown of SULF1 attenuates cardiac myofibroblast activation and collagen deposition. Overexpression of SULF1 promotes TGF-β-induced myofibroblast activation and partially antagonizes anti-fibrotic effects of halofuginone treatment.

CONCLUSIONS

Our results indicate that EPRS preferentially controls translational activation of proline codon rich profibrotic genes in cardiac fibroblasts and augments pathological cardiac remodeling. Graphical Abstract: A graphical abstract is available for this article.

The partnership between renalase and ejection fraction as a risk factor for increased cardiac remodeling biomarkers in chronic heart failure patients

Objective: Heart failure (HF) represents a huge socio-economic burden. It has been demonstrated, experimentally, that renalase, a newly discovered protein, prevents cardiac hypertrophy and adverse remodeling, which is seen in HF. We postulated the following aims: to investigate associations of renalase with biomarkers of cardiac remodeling: galectin-3, soluble suppression of tumorigenicity, (sST2), growth differentiation factor 15 (GDF-15) and syndecan-1, myocardial stretch (BNP) and cardio-renal axis (cystatin C) in HF patients with reduced ejection fraction (HFrEF) and preserved ejection fraction (HFpEF) to determine whether renalase, in combination with left ventricular ejection fraction (LVEF), represents a risk factor for plasma elevation in biomarkers.Methods: We classified HF patients (n = 76) according to LVEF (preserved/reduced), applied a median plasma renalase (113 ng/mL) as a cut-off value (low/high) and created four subgroups of HF patients: HFpEF/low renalase (n = 19), HFrEF/low renalase (n = 19), HFrEF/high renalase (n = 32) and HFpEF/high renalase (n = 6). A control group (n = 35) consisted of healthy volunteers.Results: Plasma concentrations of evaluated biomarkers were determined using an ELISA technique and were highest in HF patients with reduced EF (p < .001, respectively), and renalase's positive correlations were obtained relating to all biomarkers: galectin-3 (r = 0.913; p < .001), sST2 (r = 0.965; p < .001), GDF-15 (r = 0.887; p < .001), syndecan-1 (r = 0.922; p < .001), BNP (r = 0.527; p < .001) and cystatin C (r = 0.844; p < .001) and strong and negative correlation with LVEF (r = -0.456, p < .001). Increased renalase, regardless of the EF (preserved/reduced), was shown to be an independent risk factor for an increase in all evaluated cardiac remodeling biomarkers, p < .001, respectively. However, increased renalase and reduced EF was the only independent risk factor for BNP and cystatin C elevation, p < .001, respectively. Results after multivariable adjustments (age/gender) were identical.Conclusion: When elevated plasma renalase and HF are present, regardless of EF being reduced or preserved, that represents a significant risk factor for increase in cardiac remodeling biomarker plasma concentrations. However, only elevated renalase and reduced EF demonstrated significance as a risk factor for BNP and cystatin C plasma elevation. Renalase may be considered a promising molecule for the improved predictive abilities of conventional biomarkers and is worthy of further investigation.

Antioxidative enzyme activity and total antioxidant capacity in serum of dogs with degenerative mitral valve disease

This study was designed to evaluate the antioxidative status of serum by measuring its total antioxidant capacity, as well as the antioxidant enzyme activity (superoxide dismutase, catalase, and glutathione reductase), in dogs with various stages of degenerative mitral valve disease (DMVD) compared to healthy controls. In total, 71 client-owned dogs in different stages of DMVD, which included healthy controls, took part in the study. Following an anamnesis, clinical examination, standard transthoracic echocardiograpic examination, chest X-ray, complete blood (cell) count, and serum biochemistry, dogs were divided into 2 study groups. Blood was drawn from each dog once at the time of presentation and selected antioxidant parameters were measured using commercially available assay kits. The activity of superoxide dismutase gradually decreased in the more advanced stages of DMVD, while the activity of catalase was significantly higher in the group of dogs with asymptomatic DMVD compared to healthy controls and dogs with symptomatic DMVD. No significant changes were noted in total antioxidant capacity and the activity of glutathione reductase. Results suggested that DMVD has a significant impact on the activity of superoxide dismutase and catalase in the serum of the tested dogs. Knowledge of changes in the activity of antioxidative enzymes may warrant further studies, possibly to evaluate the potential role of compounds with antioxidative properties in the clinical outcome of dogs with DMVD.

Role of CyPA in cardiac hypertrophy and remodeling

Pathological cardiac hypertrophy is a complex process and eventually develops into heart failure, in which the heart responds to various intrinsic or external stress, involving increased interstitial fibrosis, cell death and cardiac dysfunction. Studies have shown that oxidative stress is an important mechanism for this maladaptation. Cyclophilin A (CyPA) is a member of the cyclophilin (CyPs) family. Many cells secrete CyPA to the outside of the cells in response to oxidative stress. CyPA from blood vessels and the heart itself participate in a variety of signaling pathways to regulate the production of reactive oxygen species (ROS) and mediate inflammation, promote cardiomyocyte hypertrophy and proliferation of cardiac fibroblasts, stimulate endothelial injury and vascular smooth muscle hyperplasia, and promote the dissolution of extracellular matrix (ECM) by activating matrix metalloproteinases (MMPs). The events triggered by CyPA cause a decline of diastolic and systolic function and finally lead to the occurrence of heart failure. This article aims to introduce the role and mechanism of CyPA in cardiac hypertrophy and remodeling, and highlights its potential role as a disease biomarker and therapeutic target.

Both gain and loss of Nampt function promote pressure overload-induced heart failure

The heart requires high-energy production, but metabolic ability declines in the failing heart. Nicotinamide phosphoribosyl-transferase (Nampt) is a rate-limiting enzyme in the salvage pathway of nicotinamide adenine dinucleotide (NAD) synthesis. NAD is directly involved in various metabolic processes and may indirectly regulate metabolic gene expression through sirtuin 1 (Sirt1), an NAD-dependent protein deacetylase. However, how Nampt regulates cardiac function and metabolism in the failing heart is poorly understood. Here we show that pressure-overload (PO)-induced heart failure is exacerbated in both systemic Nampt heterozygous knockout (Nampt+/-) mice and mice with cardiac-specific Nampt overexpression (Tg-Nampt). The NAD level declined in Nampt+/- mice under PO (wild: 377 pmol/mg tissue; Nampt+/-: 119 pmol/mg tissue; P = 0.028). In cultured cardiomyocytes, Nampt knockdown diminished mitochondrial NAD content and ATP production (relative ATP production: wild: 1; Nampt knockdown: 0.56; P = 0.0068), suggesting that downregulation of Nampt induces mitochondrial dysfunction. On the other hand, the NAD level was increased in Tg-Nampt mice at baseline but not during PO, possibly due to increased consumption of NAD by Sirt1. The expression of Sirt1 was increased in Tg-Nampt mice, in association with reduced overall protein acetylation. PO-induced downregulation of metabolic genes was exacerbated in Tg-Nampt mice. In cultured cardiomyocytes, Nampt and Sirt1 cooperatively suppressed mitochondrial proteins and ATP production, thereby promoting mitochondrial dysfunction. In addition, Nampt overexpression upregulated inflammatory cytokines, including TNF-α and monocyte chemoattractant protein-1. Thus endogenous Nampt maintains cardiac function and metabolism in the failing heart, whereas Nampt overexpression is detrimental during PO, possibly due to excessive activation of Sirt1, suppression of mitochondrial function, and upregulation of proinflammatory mechanisms.NEW & NOTEWORTHY Nicotinamide phosphoribosyl-transferase (Nampt) is a rate-limiting enzyme in the salvage pathway of nicotinamide adenine dinucleotide synthesis. We demonstrate that pressure overload-induced heart failure is exacerbated in both systemic Nampt heterozygous knockout mice and mice with cardiac-specific Nampt overexpression. Both loss- and gain-of-function models exhibited reduced protein acetylation, suppression of metabolic genes, and mitochondrial energetic dysfunction. Thus endogenous Nampt maintains cardiac function and metabolism in the failing heart, but cardiac-specific Nampt overexpression is detrimental rather than therapeutic.

Lipoxygenase drives lipidomic and metabolic reprogramming in ischemic heart failure

BACKGROUND

After myocardial infarction (MI), delayed progression or reversal of cardiac remodeling is a prime target to limit advanced chronic heart failure (HF). However, the temporal kinetics of lipidomic and systemic metabolic signaling is unclear in HF. There is no consensus on metabolic and lipidomic signatures that influence structure, function, and survival in HF. Here we use genetic knock out model to delineate lipidomic, and metabolic changes to describe the role of lipoxygenase in advancing ischemic HF driven by leukocyte activation with signs of non-resolving inflammation. Bioactive lipids and metabolites are implicated in acute and chronic HF, and the goal of this study was to define the role of lipoxygenase in temporal kinetics of lipidomic and metabolic reprogramming in HF.

MATERIALS AND METHODS

To address this question, we used a permanent coronary ligation mouse model which showed profound metabolic and lipidomic reprogramming in acute HF. Additionally, we defined the lipoxygenase-mediated changes in cardiac pathophysiology in acute and chronic HF. For this, we quantitated systemic metabolic changes and lipidomic profiling in infarcted heart tissue with obvious structural remodeling and cardiac dysfunction progressing from acute to chronic HF in the survival cohort.

RESULTS

After MI, lipoxygenase-derived specialized pro-resolving mediators were quantitated and showed lipoxygenase-deficient mice (12/15LOX^-/-) biosynthesize epoxyeicosatrienoic acid (EETs; cypoxins) to facilitate cardiac healing. Lipoxygenase-deficient mice reduced diabetes risk biomarker 2-aminoadipic acid with profound alterations of plasma metabolic signaling of hexoses, amino acids, biogenic amines, acylcarnitines, glycerophospholipids, and sphingolipids in acute HF, thereby improved survival.

CONCLUSION

Specific lipoxygenase deletion alters lipidomic and metabolic signatures, with modified leukocyte profiling that delayed HF progression and improved survival. Future studies are warranted to define the molecular network of lipidome and metabolome in acute and chronic HF patients.

Calcium/calmodulin-dependent protein kinase II causes atrial structural remodeling associated with atrial fibrillation and heart failure

BACKGROUND

Atrial fibrillation (AF) is sustained by reentrant mechanisms that depend, in part, on atrial structural remodeling. Increased Ca2+/calmodulin-dependent protein kinase II (CaMKII) activity occurs in persistent AF. A general consensus has been that electrophysiological actions of CaMKII must be the contributing factor, but electrical remodeling in AF differs considerably with electrophysiological effects of CaMKII. CaMKII has been associated with structural remodeling in several tissues, but not the cardiac atria. The role of CaMKII in sustaining AF remains undefined.

OBJECTIVE

The purpose of this study was to assess the effects of CaMKII on AF-related structural remodeling.

METHODS

We evaluated the objective in a porcine AF-heart failure model using atrial gene transfer of the CaMKII inhibitory peptide CaMKIIn. We used conventional methods including in vivo electrophysiological study, telemetry, western blot, echocardiography, and histology to quantify rhythm, function, microstructure, and signaling pathways relevant to CaMKII and structural remodeling.

RESULTS

CaMKII levels and activity increased progressively in the early stages of AF-heart failure. Inhibiting CaMKII preserved atrial contractile function and attenuated atrial hypertrophy, fibrosis, and apoptosis but did not affect inflammation or myolysis. These effects were accompanied by significantly decreased phosphorylation of HDAC4, decreased expression of p38MAP-kinase, and alterations in the phosphorylation pattern and relative ratios of JNK isoforms.

CONCLUSION

Our findings suggest that CaMKII mediates signaling pathways related to atrial contractile function and structural remodeling in AF. CaMKII inhibition is potentially a novel therapy for AF. These findings are of importance because no clinically relevant mediators of either atrial contractile function or structural remodeling have yet been identified.

Therapeutic Effect of Targeting Branched-Chain Amino Acid Catabolic Flux in Pressure-Overload Induced Heart Failure

Background Branched-chain amino acid (BCAA) catabolic defect is an emerging metabolic hallmark in failing hearts in human and animal models. The therapeutic impact of targeting BCAA catabolic flux under pathological conditions remains understudied. Methods and Results BT2 (3,6-dichlorobenzo[b]thiophene-2-carboxylic acid), a small-molecule inhibitor of branched-chain ketoacid dehydrogenase kinase, was used to enhance BCAA catabolism. After 2 weeks of transaortic constriction, mice with significant cardiac dysfunctions were treated with vehicle or BT2. Serial echocardiograms showed continuing pathological deterioration in left ventricle of the vehicle-treated mice, whereas the BT2-treated mice showed significantly preserved cardiac function and structure. Moreover, BT2 treatment improved systolic contractility and diastolic mechanics. These therapeutic benefits appeared to be independent of impacts on left ventricle hypertrophy but associated with increased gene expression involved in fatty acid utilization. The BT2 administration showed no signs of apparent toxicity. Conclusions Our data provide the first proof-of-concept evidence for the therapeutic efficacy of restoring BCAA catabolic flux in hearts with preexisting dysfunctions. The BCAA catabolic pathway represents a novel and potentially efficacious target for treatment of heart failure.

Pressure-dependent NOS activation contributes to endothelial hyperpermeability in a model of acute heart failure

Aims: Acute increases in left ventricular end diastolic pressure (LVEDP) can induce pulmonary edema (PE). The mechanism(s) for this rapid onset edema may involve more than just increased fluid filtration. Lung endothelial cell permeability is regulated by pressure-dependent activation of nitric oxide synthase (NOS). Herein, we demonstrate that pressure-dependent NOS activation contributes to vascular failure and PE in a model of acute heart failure (AHF) caused by hypertension.Methods and results: Male Sprague-Dawley rats were anesthetized and mechanically ventilated. Acute hypertension was induced by norepinephrine (NE) infusion and resulted in an increase in LVEDP and pulmonary artery pressure (Ppa) that were associated with a rapid fall in PaO2, and increases in lung wet/dry ratio and injury scores. Heart failure (HF) lungs showed increased nitrotyrosine content and ROS levels. L-NAME pretreatment mitigated the development of PE and reduced lung ROS concentrations to sham levels. Apocynin (Apo) pretreatment inhibited PE. Addition of tetrahydrobiopterin (BH4) to AHF rats lung lysates and pretreatment of AHF rats with folic acid (FA) prevented ROS production indicating endothelial NOS (eNOS) uncoupling.Conclusion: Pressure-dependent NOS activation leads to acute endothelial hyperpermeability and rapid PE by an increase in NO and ROS in a model of AHF. Acute increases in pulmonary vascular pressure, without NOS activation, was insufficient to cause significant PE. These results suggest a clinically relevant role of endothelial mechanotransduction in the pathogenesis of AHF and further highlights the concept of active barrier failure in AHF. Therapies targetting the prevention or reversal of endothelial hyperpermeability may be a novel therapeutic strategy in AHF.

Cardiac work is related to creatine kinase energy supply in human heart failure: a cardiovascular magnetic resonance spectroscopy study

BACKGROUND

It has been hypothesized that the supply of chemical energy may be insufficient to fuel normal mechanical pump function in heart failure (HF). The creatine kinase (CK) reaction serves as the heart's primary energy reserve, and the supply of adenosine triphosphate (ATP flux) it provides is reduced in human HF. However, the relationship between the CK energy supply and the mechanical energy expended has never been quantified in the human heart. This study tests whether reduced CK energy supply is associated with reduced mechanical work in HF patients.

METHODS

Cardiac mechanical work and CK flux in W/kg, and mechanical efficiency were measured noninvasively at rest using cardiac pressure-volume loops, magnetic resonance imaging and phosphorus spectroscopy in 14 healthy subjects and 27 patients with mild-to-moderate HF.

RESULTS

In HF, the resting CK flux (126 ± 46 vs. 179 ± 50 W/kg, p < 0.002), the average (6.8 ± 3.1 vs. 10.1 ± 1.5 W/kg, p  <0.001) and the peak (32 ± 14 vs. 48 ± 8 W/kg, p < 0.001) cardiac mechanical work-rates, as well as the cardiac mechanical efficiency (53% ± 16 vs. 79% ± 3, p < 0.001), were all reduced by a third compared to healthy subjects. In addition, cardiac CK flux correlated with the resting peak and average mechanical power (p < 0.01), and with mechanical efficiency (p = 0.002).

CONCLUSION

These first noninvasive findings showing that cardiac mechanical work and efficiency in mild-to-moderate human HF decrease proportionately with CK ATP energy supply, are consistent with the energy deprivation hypothesis of HF. CK energy supply exceeds mechanical work at rest but lies within a range that may be limiting with moderate activity, and thus presents a promising target for HF treatment.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT00181259 .

Protein kinase C and cardiac dysfunction: a review

Heart failure (HF) is a physiological state in which cardiac output is insufficient to meet the needs of the body. It is a clinical syndrome characterized by impaired ability of the left ventricle to either fill or eject blood efficiently. HF is a disease of multiple aetiologies leading to progressive cardiac dysfunction and it is the leading cause of deaths in both developed and developing countries. HF is responsible for about 73,000 deaths in the UK each year. In the USA, HF affects 5.8 million people and 550,000 new cases are diagnosed annually. Cardiac remodelling (CD), which plays an important role in pathogenesis of HF, is viewed as stress response to an index event such as myocardial ischaemia or imposition of mechanical load leading to a series of structural and functional changes in the viable myocardium. Protein kinase C (PKC) isozymes are a family of serine/threonine kinases. PKC is a central enzyme in the regulation of growth, hypertrophy, and mediators of signal transduction pathways. In response to circulating hormones, activation of PKC triggers a multitude of intracellular events influencing multiple physiological processes in the heart, including heart rate, contraction, and relaxation. Recent research implicates PKC activation in the pathophysiology of a number of cardiovascular disease states. Few reports are available that examine PKC in normal and diseased human hearts. This review describes the structure, functions, and distribution of PKCs in the healthy and diseased heart with emphasis on the human heart and, also importantly, their regulation in heart failure.

Altered sarco(endo)plasmic reticulum calcium adenosine triphosphatase 2a content: Targets for heart failure therapy

Sarco(endo)plasmic reticulum calcium adenosine triphosphatase is responsible for transporting cytosolic calcium into the sarcoplasmic reticulum and endoplasmic reticulum to maintain calcium homeostasis. Sarco(endo)plasmic reticulum calcium adenosine triphosphatase is the dominant isoform expressed in cardiac tissue, which is regulated by endogenous protein inhibitors, post-translational modifications, hormones as well as microRNAs. Dysfunction of sarco(endo)plasmic reticulum calcium adenosine triphosphatase is associated with heart failure, which makes sarco(endo)plasmic reticulum calcium adenosine triphosphatase a promising target for heart failure therapy. This review summarizes current approaches to ameliorate sarco(endo)plasmic reticulum calcium adenosine triphosphatase function and focuses on phospholamban, an endogenous inhibitor of sarco(endo)plasmic reticulum calcium adenosine triphosphatase, pharmacological tools and gene therapies.

Novel H2S-NO hybrid molecule (ZYZ-803) promoted synergistic effects against heart failure

Therapeutic strategies that increase hydrogen sulfide (H₂S) or nitric oxide (NO) are cytoprotective in various models of cardiovascular injury. However, the nature of interaction between H₂S and NO in heart failure and the underlying mechanisms for the protective effects remain undefined. The present study tested the cardioprotective effect of ZYZ-803, a novel synthetic H₂S-NO hybrid molecule that decomposed to release H₂S and NO. ZYZ-803 dose dependently improved left ventricular remodeling and preserved left ventricular function in the setting of isoprenaline-induced heart failure. The cardioprotective effect of ZYZ-803 is significantly more potent than that of H₂S and/or NO donor alone. ZYZ-803 stimulated the expression of cystathionine γ-lyase (CSE) for H₂S generation and the activity of endothelial NO synthase (eNOS) for NO production. Blocking CSE and/or eNOS suppressed ZYZ-803-induced H₂S and NO production and cardioprotection. ZYZ-803 increased vascular endothelial growth factor (VEGF) concentration and cyclic guanosine 5′-monophosphate (cGMP) level. Moreover, ZYZ-803 upregulated the endogenous antioxidants, glutathione peroxidase (GPx) and heme oxygenase 1 (HO-1). These findings indicate that H₂S and NO cooperatively attenuates left ventricular remodeling and dysfunction during the development of heart failure through VEGF/cGMP pathway and ZYZ-803 provide expanding insight into strategies for treatment of heart failure.

Opposite effects of catalase and MnSOD ectopic expression on stress induced defects and mortality in the desmin deficient cardiomyopathy model

Oxidative stress has been linked strongly to cell death and cardiac remodeling processes, all hallmarks of heart failure. Mice deficient for desmin (des-/-), the major muscle specific intermediate filament protein, develop dilated cardiomyopathy and heart failure characterized by mitochondrial defects and cardiomyocyte death. The cellular and biochemical alterations in the hearts of these mice strongly suggest that oxidative stress is one of the mechanisms contributing to the pathogenesis of the phenotype. Recently, we showed that indeed the desmin deficient cardiomyocytes are under increased oxidative stress. In order to verify these findings in vivo, we generated transgenic animals overexpressing SOD2 (MnSOD) and/or catalase in the heart and crossed them with des-/- mice, thus allowing us to evaluate the contribution of oxidative injury in inherited cardiomyopathies, as well as the therapeutic potential of antioxidant strategies. Moderate MnSOD and/or catalase overexpression in des-/- hearts leads to a marked decrease in intracellular reactive oxygen species (ROS), ameliorates mitochondrial and other ultrastructural defects, minimizes myocardial degeneration and leads to a significant improvement of cardiac function. Importantly, catalase overexpression increased the 50% survival rate of des-/- mice in an obligatory exercise to 100%. In contrast, MnSOD overexpression enhanced the lethality of des-/- mice, underscoring the importance of a fine balanced cellular redox status. Overall, the present study supports the contribution of oxidative stress in the development of des-/- cardiomyopathy and points to a well-considered antioxidant treatment as therapeutic for cardiomyopathies.

Mitogen-activated protein kinase phosphatase 1 (MKP-1) in macrophage biology and cardiovascular disease. A redox-regulated master controller of monocyte function and macrophage phenotype

MAPK pathways play a critical role in the activation of monocytes and macrophages by pathogens, signaling molecules and environmental cues and in the regulation of macrophage function and plasticity. MAPK phosphatase 1 (MKP-1) has emerged as the main counter-regulator of MAPK signaling in monocytes and macrophages. Loss of MKP-1 in monocytes and macrophages in response to metabolic stress leads to dysregulation of monocyte adhesion and migration, and gives rise to dysfunctional, proatherogenic monocyte-derived macrophages. Here we review the properties of this redox-regulated dual-specificity MAPK phosphatase and the role of MKP-1 in monocyte and macrophage biology and cardiovascular diseases.

Protective effects of low-dose rosuvastatin on isoproterenol-induced chronic heart failure in rats by regulation of DDAH-ADMA-NO pathway

AIMS

Cardiovascular disease is the leading cause of death with high morbidity and mortality, and chronic heart failure is the terminal phase of it. This study aimed to investigate the protective effects of the low-dose rosuvastatin on isoproterenol-induced chronic heart failure and to explore the possible related mechanisms.

METHODS

Male Sprague Dawley rats were given isoproterenol 5 mg/kg once a day for 7 days to establish heart failure model by subcutaneous injection. Simultaneously, low-dose rosuvastatin (5 mg/kg) was orally administrated from day 1 to day 14. Protective effects were evaluated by hemodynamic parameter, histopathological variables, serum asymmetric dimethylarginine (ADMA), cardiac troponin I (cTnI), brain natriuretic peptide (BNP) and myocardial nitric oxide (NO), and the levels of dimethylarginine dimethylaminohydrolase 2 (DDAH2), arginine methyltransferases 1 (PRMT1) and endothelial nitric oxide synthase (eNOS) expression were analyzed.

RESULTS

Therapeutic rosuvastatin (5 mg/kg) significantly attenuated isoproterenol-induced hypertrophy, remodeling and dysfunction of ventricle, reduced the increased serum content of ADMA, cTnI, and BNP, and elevated myocardial NO in rats (P<.05). Besides, rosuvastatin also significantly inhibited fibrosis of myocardium, normalized the increased PRMT1 and decreased DDAH2 expression.

CONCLUSIONS

Low-dose rosuvastatin exerted cardioprotective effects on isoproterenol-induced heart failure in rats by modulating DDAH-ADMA-NO pathway, and it may present the new therapeutic value in ameliorating chronic heart failure.

The influence of oral copper-methionine on matrix metalloproteinase-2 gene expression and activation in right-sided heart failure induced by cold temperature: A broiler chicken perspective

This study was designed to investigate the expression, activation and activity of matrix metalloproteinase-2 (MMP-2) in the heart of broiler chickens reared in cold conditions and fed with copper-methionine supplement at different levels. The chickens (n=480) were randomly allotted to six treatments and four replicates. Treatments included two rearing temperatures (i.e. normal and cold temperatures) each combined with three levels of supplemental copper-methionine (i.e. 0, 100 and 200mg/kg). On d 38 and 45 of age, four broilers from each treatment were sacrificed and their hearts were stored at -80°C. Right-sided heart failure, as evident from abdominal and pericardial fluid accumulation, was observed in broilers under cold stress and not receiving supplemental copper. This clinical observation was confirmed at molecular level through increased MMP-2 expression, activation and activity in this group. Birds reared under normal temperature, however, were not involved in right-sided heart failure nor benefitted from copper-methionine supplementation. In contrast, gelatin zymography and real-time PCR demonstrated that dietary supplementation with copper-methionine decreased pro-MMP-2 and MMP-2 in the heart of chickens reared in cold conditions. However, gelatin reverse zymography did not show any difference between treatments in tissue inhibitor of metalloproteinase-2. Level of supplementation showed similar effects on parameters determined. It is concluded that dietary supplementation with copper-methionine reduced right-sided heart failure at clinical and molecular levels in cold-stressed chickens.

Gender Modulates the Expression of Calcium-Regulating Proteins in Pediatric Atrial Myocardium

A differential expression of sarcoplasmic reticulum calcium-ATPase (SERCA2a) and phospholamban (PLB) characterizes the remodeling process in heart failure and atrial arrhythmias in adult patients. Gender is known to modulate the course and Prognosis of different forms of heart disease. We hypothesized that gender plays a role in molecular changes of myocardial calcium regulating components already in childhood. Moreover, we studied the influence of volume overloaded (VO) on SERCA2a and PLB in pediatric patients. Quantitative reverse transcription-polymerase chain reaction was used to measure mRNA expression of SERCA2a and PLB in atrial myocardium from 30 pediatric patients (12 girls, 18 boys). Eighteen patients had VO right atria, and 12 patients had not-overloaded atria (NO). Protein expression was studied by Western blot. In the entire population, SERCA2a and PLB expression was not different between girls and boys. If hemodynamic overload was taken into account, SERCA2a mRNA expression was significantly reduced in the VO group compared with the NO group (P = 0.021). The VO versus NO difference was restricted to toys, which corresponds to a highly significant interaction of gender versus VO status (P = 0.002). The PLB to SERCA2a Protein ratio was significantly lower in girls (P = 0.028). The decrease in SERCA2a mRNA expression in VO atrial myocardium and the PLB to SERCA2a ratio of protein expression was modulated by gender in this pediatric population. To our knowledge, this study is the first to show the impact of gender on the differential expression of calcium-regulating components in Pediatric cardiac patients.

Posttranslational modifications and dysfunction of mitochondrial enzymes in human heart failure

Deficiency of energy supply is a major complication contributing to the syndrome of heart failure (HF). Because the concurrent activity profile of mitochondrial bioenergetic enzymes has not been studied collectively in human HF, our aim was to examine the mitochondrial enzyme defects in left ventricular myocardium obtained from explanted end-stage failing hearts. Compared with nonfailing donor hearts, activity rates of complexes I and IV and the Krebs cycle enzymes isocitrate dehydrogenase, malate dehydrogenase, and aconitase were lower in HF, as determined spectrophotometrically. However, activity rates of complexes II and III and citrate synthase did not differ significantly between the two groups. Protein expression, determined by Western blotting, did not differ between the groups, implying posttranslational perturbation. In the face of diminished total glutathione and coenzyme Q10 levels, oxidative modification was explored as an underlying cause of enzyme dysfunction. Of the three oxidative modifications measured, protein carbonylation was increased significantly by 31% in HF (P < 0.01; n = 18), whereas levels of 4-hydroxynonenal and protein nitration, although elevated, did not differ. Isolation of complexes I and IV and F1FoATP synthase by immunocapture revealed that proteins containing iron-sulphur or heme redox centers were targets of oxidative modification. Energy deficiency in end-stage failing human left ventricle involves impaired activity of key electron transport chain and Krebs cycle enzymes without altered expression of protein levels. Augmented oxidative modification of crucial enzyme subunit structures implicates dysfunction due to diminished capacity for management of mitochondrial reactive oxygen species, thus contributing further to reduced bioenergetics in human HF.

Dyrk1a regulates the cardiomyocyte cell cycle via D-cyclin-dependent Rb/E2f-signalling

AIMS

Down syndrome-associated dual-specificity tyrosine-(Y)-phosphorylation-regulated kinase 1A (DYRK1A) is a ubiquitously expressed protein kinase. Up to date a variety of targets have been identified, establishing a key role for Dyrk1a in selected signalling pathways. In cardiomyocytes, Dyrk1a acts as a negative regulator of hypertrophy by phosphorylating transcription factors of the NFAT family, but its mechanistic function in the heart remains poorly understood. This study was designed to investigate a potential protective role of Dyrk1a in cardiac hypertrophy in vivo.

METHODS AND RESULTS

We generated transgenic mice with cardiac-specific overexpression of Dyrk1a. Counterintuitively, these mice developed severe dilated cardiomyopathy associated with congestive heart failure and premature death. In search for the cause of this unexpected phenotype, we found that Dyrk1a interacts with all members of the D-cyclin family and represses their protein levels in vitro and in vivo. Particularly, forced expression of Dyrk1a leads to increased phosphorylation of Ccnd2 on Thr280 and promotes its subsequent proteasomal degradation. Accordingly, cardiomyocytes overexpressing Dyrk1a display hypo-phosphorylated Rb1, suppression of Rb/E2f-signalling, and reduced expression of E2f-target genes, which ultimately results in impaired cell cycle progression.

CONCLUSIONS

We identified Dyrk1a as a novel negative regulator of D-cyclin-mediated Rb/E2f-signalling. As dysregulation of this pathway with impaired cardiomyocyte proliferation leads to cardiomyopathy, dose-specific Dyrk1a expression and activity appears to be critical for the hyperplastic and hypertrophic growth of the developing heart.

The neprilysin pathway in heart failure: a review and guide on the use of sacubitril/valsartan

Inhibition of neurohumoural pathways such as the renin angiotensin aldosterone and sympathetic nervous systems is central to the understanding and treatment of heart failure (HF). Conversely, until recently, potentially beneficial augmentation of neurohumoural systems such as the natriuretic peptides has had limited therapeutic success. Administration of synthetic natriuretic peptides has not improved outcomes in acute HF but modulation of the natriuretic system through inhibition of the enzyme that degrades natriuretic (and other vasoactive) peptides, neprilysin, has proven to be successful. After initial failures with neprilysin inhibition alone or dual neprilysin-angiotensin converting enzyme (ACE) inhibition, the Prospective comparison of angiotensin receptor neprilysin inhibitor (ARNI) with ACEI to Determine Impact on Global Mortality and morbidity in Heart Failure trial (PARADIGM-HF) trial demonstrated that morbidity and mortality can be improved with the angiotensin receptor blocker neprilysin inhibitor sacubitril/valsartan (formerly LCZ696). In comparison to the ACE inhibitor enalapril, sacubitril/valsartan reduced the occurrence of the primary end point (cardiovascular death or hospitalisation for HF) by 20% with a 16% reduction in all-cause mortality. These findings suggest that sacubitril/valsartan should replace an ACE inhibitor or angiotensin receptor blocker as the foundation of treatment of symptomatic patients (NYHA II–IV) with HF and a reduced ejection fraction. This review will explore the background to neprilysin inhibition in HF, the results of the PARADIGM-HF trial and offer guidance on how to use sacubitril/valsartan in clinical practice.

Reduced Arrhythmia Inducibility With Calcium/Calmodulin-dependent Protein Kinase II Inhibition in Heart Failure Rabbits

RATIONALE

Calcium/calmodulin-dependent protein kinase II (CaMKII) is activated in heart failure (HF) and can contribute to arrhythmias induced by β-adrenergic receptor-mediated sarcoplasmic reticulum calcium leak.

OBJECTIVE

To evaluate the effect of CaMKII inhibition on ventricular tachycardia (VT) induction in conscious HF and naive rabbits.

METHODS AND RESULTS

Nonischemic HF was induced by aortic insufficiency and constriction. Electrocardiograms were recorded in rabbits pretreated with vehicle (saline) or the CaMKII inhibitor KN-93 (300 μg/kg); VT was induced by infusion of increasing doses of norepinephrine (1.56-25 μg·kg⁻¹·min⁻¹) in naive (n = 8) and HF (n = 7) rabbits. With saline, median VT dose threshold in HF was 6.25 versus 12.5 μg·kg⁻¹·min⁻¹ norepinephrine in naive rabbits (P = 0.06). Pretreatment with KN-93 significantly increased VT threshold in HF and naive rabbits (median = 25 μg·kg⁻¹·min⁻¹, P < 0.05 vs. saline for both groups). Mean cycle length of VT initiation was shorter in HF (221 ± 20 milliseconds) than naive (296 ± 23 milliseconds, P < 0.05) rabbits with saline; this difference was not significant after treatment with KN-93.

CONCLUSIONS

KN-93 significantly reduced arrhythmia inducibility and slowed initiation of VT, suggesting that CaMKII inhibition may have antiarrhythmic effects in the failing human heart.

Two repetition time saturation transfer (TwiST) with spill-over correction to measure creatine kinase reaction rates in human hearts

BACKGROUND

Phosphorus saturation transfer (ST) magnetic resonance spectroscopy can measure the rate of ATP generated from phosphocreatine (PCr) via creatine kinase (CK) in the human heart. Recently, the triple-repetition time ST (TRiST) method was introduced to measure the CK pseudo-first-order rate constant kf in three acquisitions. In TRiST, the longitudinal relaxation time of PCr while γ-ATP is saturated, T1`, is measured for each subject, but suffers from low SNR because the PCr signal is reduced due to exchange with saturated γ-ATP, and the short repetition time of one of the acquisitions. Here, a two-repetition time ST (TwiST) method is presented. In TwiST, the acquisition with γ-ATP saturation and short repetition time is dropped. Instead of measuring T1`, an intrinsic relaxation time T1 for PCr, T1 (intrinsic), is assumed. The objective was to validate TwiST measurements of CK kinetics in healthy subjects and patients with heart failure (HF).

METHODS

Bloch equation simulations that included the effect of spillover irradiation on PCr were used to derive formulae for T1 (intrinsic) and kf measured by both TRiST and TwiST methods. Spillover was quantified from an unsaturated PCr measurement used in the current protocol for determining PCr and ATP concentrations. Cardiac TRiST and TwiST data were acquired at 3 T from 12 healthy and 17 HF patients.

RESULTS

Simulations showed that both kf measured by TwiST and T1 (intrinsic) require spill-over corrections. In human heart at 3 T, the spill-over corrected T1 (intrinsic) = 8.4 ± 1.4 s (mean ± SD) independent of study group. TwiST and TRiST kf measurements were the same, but TwiST was 9 min faster. Spill-over corrected TwiST kf was 0.33 ± 0.08 s(-1) vs. 0.20 ± 0.06 s(-1) in healthy vs HF hearts, respectively (p < 0.0001).

CONCLUSION

TwiST was validated against TRiST in the human heart at 3 T, generating the same results 9 min faster. TwiST detected significant reductions in CK kf in HF compared to healthy subjects, consistent with prior 1.5 T studies using different methodology.

Proprotein convertases in atherogenesis

PURPOSE OF REVIEW

The proprotein convertases subtilisin/kexin (PCSKs) are endoproteases identified as activators of precursors from hormones and peptides. On the basis of the variety of substrates and regulation in disease, they have been recognized as mediators in atherogenesis. The discovery of PCSK9, which regulates low-density lipoprotein receptor cell membrane availability, has led to a resurgence of interest in these enzymes and their function in cardiovascular diseases.

RECENT FINDINGS

Recent data demonstrate that PCSKs are expressed in human atheroma and are regulated in animal models of atherosclerosis. In animal models, inhibition of PCSKs, such as PCSK3, affects cell proliferation and migration as well as inflammation, reducing atherosclerosis. In addition, targeting PCSK9 lowers cholesterol levels and has now been demonstrated to lessen vascular lesion formation in mice. Experimentally investigated novel anti-PCSK9 strategies include genome editing and vaccination. Furthermore, studies show that PCSKs contribute to the initiation and progression of cardiometabolic risk factors, such as insulin resistance and obesity.

SUMMARY

PCSKs affect cardiovascular diseases on multiple levels, including atherosclerotic lesion formation as well as their contribution to cardiometabolic risk factors. PCSK9 is a key regulator of plasma cholesterol levels, thereby potentially affecting atherosclerosis and has rapidly emerged as a pharmacological target.

Heart-Specific Knockout of the Mitochondrial Thioredoxin Reductase (Txnrd2) Induces Metabolic and Contractile Dysfunction in the Aging Myocardium

BACKGROUND

Ubiquitous deletion of thioredoxin reductase 2 (Txnrd2) in mice is embryonically lethal and associated with abnormal heart development, while constitutive, heart-specific Txnrd2 inactivation leads to dilated cardiomyopathy and perinatal death. The significance of Txnrd2 in aging cardiomyocytes, however, has not yet been examined.

METHODS AND RESULTS

The tamoxifen-inducible heart-specific αMHC-MerCreMer transgene was used to inactivate loxP-flanked Txnrd2 alleles in adult mice. Hearts and isolated mitochondria from aged knockout mice were morphologically and functionally analyzed. Echocardiography revealed a significant increase in left ventricular end-systolic diameters in knockouts. Fractional shortening and ejection fraction were decreased compared with controls. Ultrastructural analysis of cardiomyocytes of aged mice showed mitochondrial degeneration and accumulation of autophagic bodies. A dysregulated autophagic activity was supported by higher levels of lysosome-associated membrane protein 1 (LAMP1), microtubule-associated protein 1A/1B-light chain 3-I (LC3-I), and p62 in knockout hearts. Isolated Txnrd2-deficient mitochondria used less oxygen and tended to produce more reactive oxygen species. Chronic hypoxia inducible factor 1, α subunit stabilization and altered transcriptional and metabolic signatures indicated that energy metabolism is deregulated.

CONCLUSIONS

These results imply a novel role of Txnrd2 in sustaining heart function during aging and suggest that Txnrd2 may be a modifier of heart failure.

Decreased creatine kinase is linked to diastolic dysfunction in rats with right heart failure induced by pulmonary artery hypertension

Our objective was to investigate the role of creatine kinase in the contractile dysfunction of right ventricular failure caused by pulmonary artery hypertension. Pulmonary artery hypertension and right ventricular failure were induced in rats by monocrotaline and compared to saline-injected control animals. In vivo right ventricular diastolic pressure-volume relationships were measured in anesthetized animals; diastolic force-length relationships in single enzymatically dissociated myocytes and myocardial creatine kinase levels by Western blot. We observed diastolic dysfunction in right ventricular failure indicated by significantly steeper diastolic pressure-volume relationships in vivo and diastolic force-length relationships in single myocytes. There was a significant reduction in creatine kinase protein expression in failing right ventricle. Dysfunction also manifested as a shorter diastolic sarcomere length in failing myocytes. This was associated with a Ca(2+)-independent mechanism that was sensitive to cross-bridge cycling inhibition. In saponin-skinned failing myocytes, addition of exogenous creatine kinase significantly lengthened sarcomeres, while in intact healthy myocytes, inhibition of creatine kinase significantly shortened sarcomeres. Creatine kinase inhibition also changed the relatively flat contraction amplitude-stimulation frequency relationship of healthy myocytes into a steeply negative, failing phenotype. Decreased creatine kinase expression leads to diastolic dysfunction. We propose that this is via local reduction in ATP:ADP ratio and thus to Ca(2+)-independent force production and diastolic sarcomere shortening. Creatine kinase inhibition also mimics a definitive characteristic of heart failure, the inability to respond to increased demand. Novel therapies for pulmonary artery hypertension are needed. Our data suggest that cardiac energetics would be a potential ventricular therapeutic target.

Increased stiffness is the major early abnormality in a pig model of severe aortic stenosis and predisposes to congestive heart failure in the absence of systolic dysfunction

Background

It remains unclear whether abnormal systolic function and relaxation are essential for developing heart failure in pathophysiology of severe aortic stenosis.

Methods and Results

Yorkshire pigs underwent surgical banding of the ascending aorta. The animals were followed for up to 5 months after surgery, and cardiac function was assessed comprehensively by invasive pressure–volume measurements, 3-dimensional echocardiography, echocardiographic speckle-tracking strain, and postmortem molecular and histological analyses. Pigs with aortic banding (n=6) exhibited significant left ventricular hypertrophy with increased stiffness compared with the control pigs (n=7) (end-diastolic pressure–volume relationship β: 0.053±0.017 versus 0.028±0.009 mm Hg/mL, P=0.007); however, all other parameters corresponding to systolic function, including ejection fraction, end-systolic pressure–volume relationship, preload recruitable stroke work, echocardiographic circumferential strain, and longitudinal strain, were not impaired in pigs with aortic banding. Relaxation parameters were also similar between groups. Sarcoplasmic reticulum calcium (Ca²⁺) ATPase protein levels in the left ventricle were similar. There were significant increases in 3-dimensional echocardiographic left atrial volumes, suggesting the usefulness of these indexes to detect increased stiffness. Right atrial pacing with a heart rate of 120 beats per minute induced increased end-diastolic pressure in pigs with aortic banding in contrast to decreased end-diastolic pressure in the control pigs. Histological evaluation revealed that increased stiffness was accompanied by cardiomyocyte hypertrophy and increased perimysial and perivascular fibrosis.

Conclusion

Increased stiffness is the major early pathological process that predisposes to congestive heart failure without abnormalities in systolic function and relaxation in a clinically relevant animal model of aortic stenosis.

LKB1 knockout mouse develops spontaneous atrial fibrillation and provides mechanistic insights into human disease process

BACKGROUND

Atrial fibrillation (AF) is a complex disease process, and the molecular mechanisms underlying initiation and progression of the disease are unclear. Consequently, AF has been difficult to model. In this study, we have presented a novel transgenic mouse model of AF that mimics human disease and characterized the mechanisms of atrial electroanatomical remodeling in the genesis of AF.

METHODS AND RESULTS

Cardiac-specific liver kinase B1 (LKB1) knockout (KO) mice were generated, and 47% aged 4 weeks and 95% aged 12 weeks developed spontaneous AF from sinus rhythm by demonstrating paroxysmal and persistent stages of the disease. Electrocardiographic characteristics of sinus rhythm were similar in KO and wild-type mice. Atrioventricular block and atrial flutter were common in KO mice. Heart rate was slower with persistent AF. In parallel with AF, KO mice developed progressive biatrial enlargement with inflammation, heterogeneous fibrosis, and loss of cardiomyocyte population with apoptosis and necrosis. Atrial tissue was infiltrated with inflammatory cells. C-reactive protein, interleukin 6, and tumor necrosis factor α were significantly elevated in serum. KO atria demonstrated elevated reactive oxygen species and decreased AMP-activated protein kinase activity. Cardiomyocyte and myofibrillar ultrastructure were disrupted. Intercellular matrix and gap junction were interrupted. Connexins 40 and 43 were reduced. Persistent AF caused left ventricular dysfunction and heart failure. Survival and exercise capacity were worse in KO mice.

CONCLUSIONS

LKB1 KO mice develop spontaneous AF from sinus rhythm and progress into persistent AF by replicating the human AF disease process. Progressive inflammatory atrial cardiomyopathy is the genesis of AF, through mechanistic electrical and structural remodeling.

IDH2 deficiency promotes mitochondrial dysfunction and cardiac hypertrophy in mice

Cardiac hypertrophy, a risk factor for heart failure, is associated with enhanced oxidative stress in the mitochondria, resulting from high levels of reactive oxygen species (ROS). The balance between ROS generation and ROS detoxification dictates ROS levels. As such, disruption of these processes results in either increased or decreased levels of ROS. In previous publications, we have demonstrated that one of the primary functions of mitochondrial NADP(+)-dependent isocitrate dehydrogenase (IDH2) is to control the mitochondrial redox balance, and thereby mediate the cellular defense against oxidative damage, via the production of NADPH. To explore the association between IDH2 expression and cardiac function, we measured myocardial hypertrophy, apoptosis, and contractile dysfunction in IDH2 knockout (idh2(-/-)) and wild-type (idh2(+/+)) mice. As expected, mitochondria from the hearts of knockout mice lacked IDH2 activity and the hearts of IDH2-deficient mice developed accelerated heart failure, increased levels of apoptosis and hypertrophy, and exhibited mitochondrial dysfunction, which was associated with a loss of redox homeostasis. Our results suggest that IDH2 plays an important role in maintaining both baseline mitochondrial function and cardiac contractile function following pressure-overload hypertrophy, by preventing oxidative stress.

Endothelial dysfunction in adipose triglyceride lipase deficiency

Systemic knockout of adipose triglyceride lipase (ATGL), the pivotal enzyme of triglyceride lipolysis, results in a murine phenotype that is characterized by progredient cardiac steatosis and severe heart failure. Since cardiac and vascular dysfunction have been closely related in numerous studies we investigated endothelium-dependent and -independent vessel function of ATGL knockout mice. Aortic relaxation studies and Langendorff perfusion experiments of isolated hearts showed that ATGL knockout mice suffer from pronounced micro- and macrovascular endothelial dysfunction. Experiments with agonists directly targeting vascular smooth muscle cells revealed the functional integrity of the smooth muscle cell layer. Loss of vascular reactivity was restored ~50% upon treatment of ATGL knockout mice with the PPARα agonist Wy14,643, indicating that this phenomenon is partly a consequence of impaired cardiac contractility. Biochemical analysis revealed that aortic endothelial NO synthase expression and activity were significantly reduced in ATGL deficiency. Enzyme activity was fully restored in ATGL mice treated with the PPARα agonist. Biochemical analysis of perivascular adipose tissue demonstrated that ATGL knockout mice suffer from perivascular inflammatory oxidative stress which occurs independent of cardiac dysfunction and might contribute to vascular defects. Our results reveal a hitherto unrecognized link between disturbed lipid metabolism, obesity and cardiovascular disease.

Cardiac resynchronization sensitizes the sarcomere to calcium by reactivating GSK-3β

Cardiac resynchronization therapy (CRT), the application of biventricular stimulation to correct discoordinate contraction, is the only heart failure treatment that enhances acute and chronic systolic function, increases cardiac work, and reduces mortality. Resting myocyte function also increases after CRT despite only modest improvement in calcium transients, suggesting that CRT may enhance myofilament calcium responsiveness. To test this hypothesis, we examined adult dogs subjected to tachypacing-induced heart failure for 6 weeks, concurrent with ventricular dyssynchrony (HF(dys)) or CRT. Myofilament force-calcium relationships were measured in skinned trabeculae and/or myocytes. Compared with control, maximal calcium-activated force and calcium sensitivity declined globally in HF(dys); however, CRT restored both. Phosphatase PP1 induced calcium desensitization in control and CRT-treated cells, while HF(dys) cells were unaffected, implying that CRT enhances myofilament phosphorylation. Proteomics revealed phosphorylation sites on Z-disk and M-band proteins, which were predicted to be targets of glycogen synthase kinase-3β (GSK-3β). We found that GSK-3β was deactivated in HF(dys) and reactivated by CRT. Mass spectrometry of myofilament proteins from HF(dys) animals incubated with GSK-3β confirmed GSK-3β–dependent phosphorylation at many of the same sites observed with CRT. GSK-3β restored calcium sensitivity in HF(dys), but did not affect control or CRT cells. These data indicate that CRT improves calcium responsiveness of myofilaments following HF(dys) through GSK-3β reactivation, identifying a therapeutic approach to enhancing contractile function

Mechanisms of Ghrelin anti-heart failure: inhibition of Ang II-induced cardiomyocyte apoptosis by down-regulating AT1R expression

Background

Ghrelin is a novel growth hormone–releasing peptide administered to treat chronic heart failure (CHF). However, the underlying mechanism of its protective effects against heart failure (HF) remains unclear.

Methods and Results

A total of 68 patients with CHF and 20 healthy individuals were included. The serum levels of Angiotensin II (Ang II) and ghrelin were measured using ELISA. The results showed that Ang II and ghrelin were both significantly increased in CHF patients and that the ghrelin levels were significantly positively correlated with Ang II. The left anterior descending coronary artery was ligated to establish a rat model of CHF, and cultured cardiomyocytes from neonatal rats were stimulated with Ang II to explore the role of ghrelin in CHF. The results showed that ghrelin inhibited cardiomyocyte apoptosis both in vivo and in vitro. Furthermore, caspase-3 expression was examined, and the results revealed that Ang II induces cardiomyocyte apoptosis through the caspase-3 pathway, whereas ghrelin inhibits this action. Lastly, to further elucidate the mechanism by which ghrelin inhibits Ang II action, the expression of the AT1 and AT2 receptors was evaluated; the results showed that Ang II up-regulates the AT1 and AT2 receptors in cardiomyocytes, whereas ghrelin inhibits AT1 receptor up-regulation but does not affect AT2 receptor expression.

Conclusions

These data suggest that the serum levels of ghrelin are significantly positively correlated with Ang II in CHF patients and that ghrelin can inhibit Ang II-induced cardiomyocyte apoptosis by down-regulating AT1R, thereby playing a role in preventing HF.

Vidarabine is neither a potent nor a selective AC5 inhibitor

Vidarabine was the first clinically approved antiviral drug, but due to safety and efficacy issues the drug is currently only used topically for herpes virus keratitis. Scientific interest in vidarabine has been recently renewed due to the fact that the compound exhibits beneficial effects in animal models of heart failure and cancer, replicating effects of the knockout of adenylyl cyclase 5 (AC5). Therefore, vidarabine has been suggested to mediate these effects via selective inhibition of AC5. Based on these results, clinical studies with vidarabine in humans for heart failure and cancer have been proposed. Here, evidence is presented that vidarabine is neither a potent nor a selective AC5 inhibitor. Greatest caution should be exerted when proposing new mechanisms of actions and clinical uses for vidarabine.