Oxidative stress regulates left ventricular PDE5 expression in the failing heart

Phosphodiesterase in heart and vessels: from physiology to diseases

Phosphodiesterases (PDEs) are a superfamily of enzymes that hydrolyze cyclic nucleotides, including cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). Both cyclic nucleotides are critical secondary messengers in the neurohormonal regulation in the cardiovascular system. PDEs precisely control spatiotemporal subcellular distribution of cyclic nucleotides in a cell- and tissue-specific manner, playing critical roles in physiological responses to hormone stimulation in the heart and vessels. Dysregulation of PDEs has been linked to the development of several cardiovascular diseases, such as hypertension, aneurysm, atherosclerosis, arrhythmia, and heart failure. Targeting these enzymes has been proven effective in treating cardiovascular diseases and is an attractive and promising strategy for the development of new drugs. In this review, we discuss the current understanding of the complex regulation of PDE isoforms in cardiovascular function, highlighting the divergent and even opposing roles of PDE isoforms in different pathogenesis.

The impact of phosphodiesterase-5 inhibition or angiotensin-converting enzyme inhibition on right and left ventricular remodeling in heart failure due to chronic volume overload

While phosphodiesterase-5 inhibition (PED5i) may prevent hypertrophy and failure in pressure-overloaded heart in an experimental model, the impact of PDE5i on volume-overload (VO)-induced hypertrophy is unknown. It is also unclear whether the hypertrophied right ventricle (RV) and left ventricle (LV) differ in their responsiveness to long-term PDE5i and if this therapy affects renal function. The goal of this study was to elucidate the effect of PDE5i treatment in VO due to aorto-caval fistula (ACF) and to compare PDE5i treatment with standard heart failure (HF) therapy with angiotensin-converting enzyme inhibitor (ACEi). ACF/sham procedure was performed on male HanSD rats aged 8 weeks. ACF animals were randomized for PDE5i sildenafil, ACEi trandolapril, or placebo treatments. After 20 weeks, RV and LV function (echocardiography, pressure-volume analysis), myocardial gene expression, and renal function were studied. Separate rat cohorts served for survival analysis. ACF led to biventricular eccentric hypertrophy (LV: +68%, RV: +145%), increased stroke work (LV: 3.6-fold, RV: 6.7-fold), and reduced load-independent systolic function (PRSW, LV: -54%, RV: -51%). Both ACF ventricles exhibited upregulation of the genes of myocardial stress and glucose metabolism. ACEi but not PDE5i attenuated pulmonary congestion, LV remodeling, albuminuria, and improved survival (median survival in ACF/ACEi was 41 weeks vs. 35 weeks in ACF/placebo, p = .02). PDE5i increased cyclic guanosine monophosphate levels in the lungs, but not in the RV, LV, or kidney. PDE5i did not improve survival rate and cardiac and renal function in ACF rats, in contrast to ACEi. VO-induced HF is not responsive to PDE5i therapy.

Modulation of the nitric oxide/cGMP pathway in cardiac contraction and relaxation: Potential role in heart failure treatment

Evidence exists that heart failure (HF) has an overall impact of 1-2 % in the global population being often associated with comorbidities that contribute to increased disease prevalence, hospitalization, and mortality. Recent advances in pharmacological approaches have significantly improved clinical outcomes for patients with vascular injury and HF. Nevertheless, there remains an unmet need to clarify the crucial role of nitric oxide/cyclic guanosine 3',5'-monophosphate (NO/cGMP) signalling in cardiac contraction and relaxation, to better identify the key mechanisms involved in the pathophysiology of myocardial dysfunction both with reduced (HFrEF) as well as preserved ejection fraction (HFpEF). Indeed, NO signalling plays a crucial role in cardiovascular homeostasis and its dysregulation induces a significant increase in oxidative and nitrosative stress, producing anatomical and physiological cardiac alterations that can lead to heart failure. The present review aims to examine the molecular mechanisms involved in the bioavailability of NO and its modulation of downstream pathways. In particular, we focus on the main therapeutic targets and emphasize the recent evidence of preclinical and clinical studies, describing the different emerging therapeutic strategies developed to counteract NO impaired signalling and cardiovascular disease (CVD) development.

Cardiac Effects of Phosphodiesterase-5 Inhibitors: Efficacy and Safety

The coexistence of cardiovascular disease and erectile dysfunction is widespread, possibly owing to underlying endothelial dysfunction in both diseases. Millions of patients with cardiovascular disease are prescribed phosphodiesterase-5 (PDE5) inhibitors for the management of erectile dysfunction. Although the role of PDE5 inhibitors in erectile dysfunction therapy is well established, their effects on the cardiovascular system are unclear. Preclinical studies investigating the effect of PDE5 inhibitors on ischemia-reperfusion injury, pressure overload-induced hypertrophy, and chemotoxicity suggested a possible clinical role for each of these medications; however, attempts to translate these findings to the bedside have resulted in mixed outcomes. In this review, we explore the biologic preclinical effects of PDE5 inhibitors in mediating cardioprotection. We then examine clinical trials investigating PDE5 inhibition in patients with heart failure, coronary artery disease, and ventricular arrhythmias and discuss why the studies likely have yet to show positive results and efficacy with PDE5 inhibition despite no safety concerns.

Beyond Erectile Dysfunction: cGMP-Specific Phosphodiesterase 5 Inhibitors for Other Clinical Disorders

Cyclic guanosine monophosphate (cGMP), an important intracellular second messenger, mediates cellular functional responses in all vital organs. Phosphodiesterase 5 (PDE5) is one of the 11 members of the cyclic nucleotide phosphodiesterase (PDE) family that specifically targets cGMP generated by nitric oxide-driven activation of the soluble guanylyl cyclase. PDE5 inhibitors, including sildenafil and tadalafil, are widely used for the treatment of erectile dysfunction, pulmonary arterial hypertension, and certain urological disorders. Preclinical studies have shown promising effects of PDE5 inhibitors in the treatment of myocardial infarction, cardiac hypertrophy, heart failure, cancer and anticancer-drug-associated cardiotoxicity, diabetes, Duchenne muscular dystrophy, Alzheimer's disease, and other aging-related conditions. Many clinical trials with PDE5 inhibitors have focused on the potential cardiovascular, anticancer, and neurological benefits. In this review, we provide an overview of the current state of knowledge on PDE5 inhibitors and their potential therapeutic indications for various clinical disorders beyond erectile dysfunction.

Investigation into the protective effects of hypaconitine and glycyrrhetinic acid against chronic heart failure of the rats

Background

The present study aimed to determine the protective effects of hypaconitine (HA) and glycyrrhetinic acid (GA) against chronic heart failure (CHF) in the rats and to explore the underlying molecular mechanisms.

Methods

The CHF rat model was established by transverse-aortic constriction (TAC) operation. Transthoracic echocardiography and hematoxylin eosin (HE) staining were used to evaluate the pathophysiological and histopathological changes of CHF model. The total cholesterol (TCHO) and triglyceride (TG) levels were determined by ELISA assay. The protein expression of fibroblast growth factor 2 (FGF2), vascular endothelial growth factor A (VEGFA) and endothelial nitric oxide synthase (eNOS) in the rat ventricular tissues was determined by immunohistochemistry. The serum metabolites were determined by LC-MS/MS assay.

Results

After applied the HA + GA, the cardiac tissue and structure were obviously improved, and the HA + GA treatment also significantly reduced the plasma levels of TCHO and TG in the CHF rats. The expression of FGF2 and VEGFA protein was up-regulated and the expression of eNOS protein was down-regulated in the ventricular tissues of CHF rats, which was significantly restored after HA + GA treatment. HA + GA treatment down-regulated serum isonicotinic acid, phosphatidylcholine, cardiolipin, estrogen glucuronide, and glycocholic acid, up-regulated serum sphingosine and deoxycholic acid in the CHF rats.

Conclusions

In conclusion, HA + GA showed protective effects on CHF in the rats, and the HA + GA may exert protective effects by reducing lipid levels, up-regulating the expression of FGF2 and VEGFA proteins, attenuating eNOS protein expression, and modulating metabolic pathways. However, the molecular mechanisms underlying HA + GA-mediated effects still require further examination.

A Review on the Pharmacological Importance of PDE5 and Its Inhibition to Manage Biomedical Conditions

Phosphodiesterase type 5 (PDE5) is a cyclic GMP (cGMP) specific protein. It hydrolyzes the phosphodiesterase linkage and catalyzes the conversion of cGMP to 5’ GMP, which controls different physiological activities of the body. PDE5 is associated with biomedical conditions like neurological disorders, pulmonary arterial hypertension, cardiomyopathy, cancer, erectile dysfunction, and lower urinary tract syndrome. Inhibition of PDE5 has now been proven pharmaceutically effective in a variety of therapeutic conditions. Avanafil, tadalafil, sildenafil, and vardenafil are the most commonly used PDE5 inhibitors (PDE5i) today which are often used for the management of erectile dysfunction, lower urinary tract syndromes, malignancy, and pulmonary arterial hypertension. However, these synthetic PDE5i come with a slew of negative effects. Some of the most common side effects include mild headaches, flushing, dyspepsia, altered color vision, back discomfort, priapism, melanoma, hypotension and dizziness, non-arteritic anterior ischemic optic neuropathy (NAION), and hearing loss. In light of the potential negative effects of this class of medications, there is a lot of room for new, selective PDE5 inhibitors to be discovered. We have found 25 plant botanical compounds effectively inhibiting PDE5 which might be useful in treating a variety of disorders with minimal or no adverse effects.

Heart Failure with Preserved Ejection Fraction and Pulmonary Hypertension: Focus on Phosphodiesterase Inhibitors

Pulmonary hypertension (PH) is common in patients with heart failure with preserved ejection fraction (HFpEF). A chronic increase in mean left atrial pressure leads to passive remodeling in pulmonary veins and capillaries and modest PH (isolated postcapillary PH, Ipc-PH) and is not associated with significant right ventricular dysfunction. In approximately 20% of patients with HFpEF, "precapillary" alterations of pulmonary vasculature occur with the development of the combined pre- and post-capillary PH (Cpc-PH), pertaining to a poor prognosis. Current data indicate that pulmonary vasculopathy may be at least partially reversible and thus serves as a therapeutic target in HFpEF. Pulmonary vascular targeted therapies, including phosphodiesterase (PDE) inhibitors, may have a valuable role in the management of patients with PH-HFpEF. In studies of Cpc-PH and HFpEF, PDE type 5 inhibitors were effective in long-term follow-up, decreasing pulmonary artery pressure and improving RV contractility, whereas studies of Ipc-PH did not show any benefit. Randomized trials are essential to elucidate the actual value of PDE inhibition in selected patients with PH-HFpEF, especially in those with invasively confirmed Cpc-PH who are most likely to benefit from such treatment.

Inhibition of GCN2 Alleviates Cardiomyopathy in Type 2 Diabetic Mice via Attenuating Lipotoxicity and Oxidative Stress

Diabetic cardiomyopathy (DCM) is a kind of heart disease that affects diabetic patients and is one of the primary causes of death. We previously demonstrated that deletion of the general control nonderepressible 2 (GCN2) kinase ameliorates cardiac dysfunction in diabetic mice. The aim of this study was to investigate the protective effect of GCN2iB, a GCN2 inhibitor, in type 2 diabetic (T2D) mice induced by a high-fat diet (HFD) plus low-dose streptozotocin (STZ) treatments or deletion of the leptin receptor (db/db). GCN2iB (3 mg/kg/every other day) treatment for 6 weeks resulted in significant decreases in fasting blood glucose levels and body weight and increases in the left ventricular ejection fraction. GCN2iB treatment also attenuated myocardial fibrosis, lipid accumulation and oxidative stress in the hearts of T2D mice, which was associated with decreases in lipid metabolism-related genes and increases in antioxidative genes. Untargeted metabolomics and RNA sequencing analysis revealed that GCN2iB profoundly affected myocardial metabolomic profiles and gene expression profiles. In particular, GCN2iB increased myocardial phosphocreatine and taurine levels and upregulated genes involved in oxidative phosphorylation. In conclusion, the data provide evidence that GCN2iB effectively protects against cardiac dysfunction in T2D mice. Our findings suggest that GCN2iB might be a novel drug candidate for DCM therapy.

Phosphodiesterases and Compartmentation of cAMP and cGMP Signaling in Regulation of Cardiac Contractility in Normal and Failing Hearts

Cardiac contractility is regulated by several neural, hormonal, paracrine, and autocrine factors. Amongst these, signaling through β-adrenergic and serotonin receptors generates the second messenger cyclic AMP (cAMP), whereas activation of natriuretic peptide receptors and soluble guanylyl cyclases generates cyclic GMP (cGMP). Both cyclic nucleotides regulate cardiac contractility through several mechanisms. Phosphodiesterases (PDEs) are enzymes that degrade cAMP and cGMP and therefore determine the dynamics of their downstream effects. In addition, the intracellular localization of the different PDEs may contribute to regulation of compartmented signaling of cAMP and cGMP. In this review, we will focus on the role of PDEs in regulating contractility and evaluate changes in heart failure.

Icariin Protects H9c2 Rat Cardiomyoblasts from Doxorubicin-Induced Cardiotoxicity: Role of Caveolin-1 Upregulation and Enhanced Autophagic Response

Doxorubicin (Doxo) is a widely used antineoplastic drug which often induces cardiomyopathy, leading to congestive heart failure through the intramyocardial production of reactive oxygen species (ROS). Icariin (Ica) is a flavonoid isolated from Epimedii Herba (Berberidaceae). Some reports on the pharmacological activity of Ica explained its antioxidant and cardioprotective effects. The aim of our study was to assess the protective activities of Ica against Doxo-detrimental effects on rat heart-tissue derived embryonic cardiac myoblasts (H9c2 cells) and to identify, at least in part, the molecular mechanisms involved. Our results showed that pretreatment of H9c2 cells with 1 μM and 5 μM of Ica, prior to Doxo exposure, resulted in an improvement in cell viability, a reduction in ROS generation, the prevention of mitochondrial dysfunction and mPTP opening. Furthermore, for the first time, we identified one feasible molecular mechanism through which Ica could exerts its cardioprotective effects. Indeed, our data showed a significant reduction in Caveolin-1(Cav-1) expression levels and a specific inhibitory effect on phosphodiesterase 5 (PDE5a) activity, improving mitochondrial function compared to Doxo-treated cells. Besides, Ica significantly prevented apoptotic cell death and downregulated the main pro-autophagic marker Beclin-1 and LC3 lipidation rate, restoring physiological levels of activation of the protective autophagic process. These results suggest that Ica might have beneficial cardioprotective effects in attenuating cardiotoxicity in patients requiring anthracycline chemotherapy through the inhibition of oxidative stress and, in particular, through the modulation of Cav-1 expression levels and the involvement of PDE5a activity, thereby leading to cardiac cell survival.

Cardioprotector effect of Phosphodiesterase 5 inhibitors in experimental model for Diabetes Mellitus

Diabetes mellitus (DM) is considered a 21st century pandemic and is often associated with cardiovascular disease (CVD). The aim of this integrative review was to analyze the cardioprotective effects of phosdodiesterase-5 (PDE5i) inhibitors in experimental diabetes models. The articles were selected from the PubMed, SciElo and LILACS databases from 2014 to 2019. The following descriptors were used in combination with the Boolean operators: Diabetes mellitus experimental AND Phosphodiesterase 5 inhibitors; Diabetic cardiomyopathies AND Phosphodiesterase 5 inhibitors. An initial sample of 155 articles was obtained, of which six met the criteria for the synthesis of the review. The studies analyzed showed that treatment with PDE5i in experimental models, resulted in positive effects on cardiac function and metabolic parameters. Similar results have also been seen in humans. The reduction in cardiac hypertrophy, apoptosis of cardiomyocytes, pro-inflammatory factors and oxidative stress and the modulation of transcription factors involved in diabetes homeostasis, were prevalent among studies. The mechanisms of action involved in cardioprotection have not yet been fully elucidated, however the restoration of the activated cyclic guanosine monofate (cGMP) pathway by soluble guanylate cyclase (sGC) via nitric oxide (NO) was a common mechanism among the studies.

Long-Term PDE-5A Inhibition Improves Myofilament Function in Left and Right Ventricular Cardiomyocytes through Partially Different Mechanisms in Diabetic Rat Hearts

Heart failure with preserved ejection fraction (HFpEF) and right ventricular (RV) dysfunction are frequent complications of diabetic cardiomyopathy. Here we aimed to characterize RV and left ventricular (LV) remodeling and its prevention by vardenafil (a long-acting phosphodiesterase-5A (PDE-5A) inhibitor) administration in a diabetic HFpEF model. Zucker Diabetic Fatty (ZDF) and control, ZDF Lean (Lean) male rats received 10 mg/kg vardenafil (ZDF + Vard; Lean + Vard) per os, on a daily basis for a period of 25 weeks. In vitro force measurements, biochemical and histochemical assays were employed to assess cardiomyocyte function and signaling. Vardenafil treatment increased cyclic guanosine monophosphate (cGMP) levels and decreased 3-nitrotyrosine (3-NT) levels in the left and right ventricles of ZDF animals, but not in Lean animals. Cardiomyocyte passive tension (F_passive) was higher in LV and RV cardiomyocytes of ZDF rats than in those receiving preventive vardenafil treatment. Levels of overall titin phosphorylation did not differ in the four experimental groups. Maximal Ca²⁺-activated force (F_max) of LV and RV cardiomyocytes were preserved in ZDF animals. Ca²⁺-sensitivity of isometric force production (pCa₅₀) was significantly higher in LV (but not in RV) cardiomyocytes of ZDF rats than in their counterparts in the Lean or Lean + Vard groups. In accordance, the phosphorylation levels of cardiac troponin I (cTnI) and myosin binding protein-C (cMyBP-C) were lower in LV (but not in RV) cardiomyocytes of ZDF animals than in their counterparts of the Lean or Lean + Vard groups. Vardenafil treatment normalized pCa₅₀ values in LV cardiomyocytes, and it decreased pCa₅₀ below control levels in RV cardiomyocytes in the ZDF + Vard group. Our data illustrate partially overlapping myofilament protein alterations for LV and RV cardiomyocytes in diabetic rat hearts upon long-term PDE-5A inhibition. While uniform patterns in cGMP, 3-NT and F_passive levels predict identical effects of vardenafil therapy for the diastolic function in both ventricles, the uneven cTnI, cMyBP-C phosphorylation levels and pCa₅₀ values implicate different responses for the systolic function.

An Optimized Model of Hypertrophic Preconditioning Confers Cardioprotection in the Mouse

BACKGROUND

Conventional models of hypertrophic preconditioning (C-HP) can be established surgically through transverse aortic constriction (TAC) → deconstriction (De-TAC) → reconstriction (Re-TAC) characterized by dynamic afterload while it exerts technical difficulty on operators and poses high mortality during perioperative period in mice. We aimed to introduce an optimized method for obtaining a hypertrophic preconditioning (O-HP) model for further study on cardiac hypertrophy.

METHODS

Ninety mice were divided into four groups: sham, TAC, C-HP, and O-HP. The sham group was exerted on three-time thoracotomies. The TAC group experienced twice thoracotomies and one TAC operation. C-HP and O-HP groups were given TAC, De-TAC, and Re-TAC operation at day 0, day 3, and day 7 in conventional and optimized method, respectively. We optimized the operating procedure in O-HP mice compared with the C-HP group by (1) leaving a ∼3-cm suture fixed in the subcutaneous layer after aortic constriction in TAC surgery (2) using two small forceps to untie the constriction knot instead of cutting it in the De-TAC operation. Ultrasound biomicroscopy was used for hemodynamics and cardiac function detection. Four weeks after the third surgery, all mice were sacrificed and pathology was analyzed among four groups.

RESULTS

Four weeks after Re-TAC, the survival of O-HP mice was 63.3% while that of C-HP was 26.7%. Ultrasound biomicroscopy showed a successful establishment of HP models. C-HP and O-HP mice had improved cardiac structure and function indicated by left ventricular end-systolic diameter, left ventricular end-systolic posterior wall thickness, left ventricular ejection fraction, and left ventricular fractional shortening than the TAC group. Pathological analysis showed O-HP as well as C-HP had less hypertrophy than the TAC mice.

CONCLUSIONS

Our results provide a rapid, safe, efficient, and reproducible method for optimized establishment of the HP model, which will facilitate studies for early intervention and prevention of left ventricular hypertrophy and heart failure.

CHDGKB: a knowledgebase for systematic understanding of genetic variations associated with non-syndromic congenital heart disease

Congenital heart disease (CHD) is one of the most common birth defects, with complex genetic and environmental etiologies. The reports of genetic variation associated with CHD have increased dramatically in recent years due to the revolutionary development of molecular technology. However, CHD is a heterogeneous disease, and its genetic origins remain inconclusive in most patients. Here we present a database of genetic variations for non-syndromic CHD (NS-CHD). By manually literature extraction and analyses, 5345 NS-CHD-associated genetic variations were collected, curated and stored in the public online database. The objective of our database is to provide the most comprehensive updates on NS-CHD genetic research and to aid systematic analyses of pathogenesis of NS-CHD in molecular level and the correlation between NS-CHD genotypes and phenotypes. Database URL: http://www.sysbio.org.cn/CHDGKB/.

Dioscin and diosgenin: Insights into their potential protective effects in cardiac diseases

BACKGROUND AND ETHNOPHARMACOLOGICAL RELEVANCE

Dioscin and diosgenin derived from plants of the genus Dioscoreaceae such as D. nipponica and D. panthaica Prain et Burk. Were utilized as the main active ingredients of traditional herbal medicinal products for coronary heart disease in the former Soviet Union and China since 1960s. A growing number of research showed that dioscin and diosgenin have a wide range of pharmacological activities in heart diseases.

AIM OF THE STUDY

To summarize the evidence of the effectiveness of dioscin and diosgenin in cardiac diseases, and to provide a basis and reference for future research into their clinical applications and drug development in the field of cardiac disease.

METHODS

Literatures in this review were searched in PubMed, ScienceDirect, Google Scholar, China National Knowledge Infrastructure (CNKI) and Web of Science. All eligible studies are analyzed and summarized in this review.

RESULTS

The pharmacological activities and therapeutic potentials of dioscin and diosgenin in cardiac diseases are similar, can effectively improve hypertrophic cardiomyopathy, arrhythmia, myocardial I/R injury and cardiotoxicity caused by doxorubicin. But the bioavailability of dioscin and diosgenin may be too low as a result of poor absorption and slow metabolism, which hinders their development and utilization.

CONCLUSION

Dioscin and diosgenin need further in-depth experimental research, clinical transformation and structural modification or research of new preparations before they can be expected to be developed into new therapeutic drugs in the field of cardiac disease.

Hypertrophy-Reduced Autophagy Causes Cardiac Dysfunction by Directly Impacting Cardiomyocyte Contractility

Cardiac remodeling and contractile dysfunction are leading causes in hypertrophy-associated heart failure (HF), increasing with a population's rising age. A hallmark of aged and diseased hearts is the accumulation of modified proteins caused by an impaired autophagy-lysosomal-pathway. Although, autophagy inducer rapamycin has been described to exert cardioprotective effects, it remains to be shown whether these effects can be attributed to improved cardiomyocyte autophagy and contractility. In vivo hypertrophy was induced by transverse aortic constriction (TAC), with mice receiving daily rapamycin injections beginning six weeks after surgery for four weeks. Echocardiographic analysis demonstrated TAC-induced HF and protein analyses showed abundance of modified proteins in TAC-hearts after 10 weeks, both reduced by rapamycin. In vitro, cardiomyocyte hypertrophy was mimicked by endothelin 1 (ET-1) and autophagy manipulated by silencing Atg5 in neonatal cardiomyocytes. ET-1 and siAtg5 decreased Atg5-Atg12 and LC3-II, increased natriuretic peptides, and decreased amplitude and early phase of contraction in cardiomyocytes, the latter two evaluated using ImageJ macro Myocyter recently developed by us. ET-1 further decreased cell contractility in control but not in siAtg5 cells. In conclusion, ET-1 decreased autophagy and cardiomyocyte contractility, in line with siAtg5-treated cells and the results of TAC-mice demonstrating a crucial role for autophagy in cardiomyocyte contractility and cardiac performance.

Current trends and future perspectives for heart failure treatment leveraging cGMP modifiers and the practical effector PKG

Cyclic guanosine monophosphate (cGMP), an intracellular second messenger molecule synthesized by guanylated cyclases (GCs), controls various myocardial properties, including cell growth and survival, interstitial fibrosis, endothelial permeability, cardiac contractility, and cardiovascular remodeling. These processes are mediated by the main cGMP effector protein kinase G (PKG) activation of which exerts intrinsic protective responses against the adverse effects of neurohormonal stimulation and pathological cardiac stress. Therapeutic strategies that enhance cGMP levels and PKG activation have been used for heart failure, which can be executed by reducing natriuretic peptide (NP) proteolysis, enhancing cGMP synthesis, or blocking cGMP hydrolysis. Among these, reducing NP clearance with neprilysin inhibitor combined with angiotensin receptor blocker has been shown to greatly improve the prognosis of patients with heart failure with reduced ejection fraction (HFrEF) compared to the prognosis of patients on standard therapy using angiotensin-converting enzyme inhibitors. Moreover, in a recent phase III clinical trial, soluble GC-derived cGMP generation was shown to have potential efficacy in the management of HFrEF. Despite the clinical significance of cGMP/PKG signaling activated by either soluble or particulate GCs in heart failure, the differential signaling events downstream of intracellular cGMP, which are precisely controlled not only by PKG activation but also by the changes in its targeting and compartmentalization depending on the pathophysiology of heart disease, are not yet completely understood. Hitherto, the importance of the latter PKG regulatory mechanisms in developing therapeutic strategies has not been elucidated. Further investigation of redox-based PKG modulation will aid in the successful development of clinical therapies and could also lead to the establishment of improved personalized treatments for patients with heart failure.

Myocardial Impact of NHE1 Regulation by Sildenafil

The cardiac Na⁺/H⁺ exchanger (NHE1) is a membrane glycoprotein fundamental for proper cell functioning due its multiple housekeeping tasks, including regulation of intracellular pH, Na⁺ concentration, and cell volume. In the heart, hyperactivation of NHE1 has been linked to the development of different pathologies. Several studies in animal models that reproduce the deleterious effects of ischemia/reperfusion injury or cardiac hypertrophy have conclusively demonstrated that NHE1 inhibition provides cardioprotection. Unfortunately, NHE1 inhibitors failed to reproduce these effects in the clinical arena. The reasons for those discrepancies are not apparent yet. However, a reasonable clue to consider would be that drugs that completely abolish the exchanger activity, including that its essential housekeeping function may not be the best therapeutic approach. Therefore, interventions tending to specifically reduce its hyperactive state without affecting its basal activity emerge as a novel potential gold standard. In this regard, a promising goal seems to be the modulation of the phosphorylation state of the cytosolic tail of the exchanger. Recent own experiments demonstrated that Sildenafil, a phosphodiesterase 5A inhibitor drug that has been widely used for the treatment of erectile dysfunction is able to decrease NHE1 phosphorylation, and hence reduce its hyperactivity. In connection, growing evidence demonstrates cardioprotective properties of Sildenafil against different cardiac pathologies, with the distinctive characteristic of directly affecting cardiac tissue without altering blood pressure. This mini-review was aimed to focus on the regulation of NHE1 activity by Sildenafil. For this purpose, experimental data reporting Sildenafil effects in different animal models of heart disease will be discussed.

An update of cyclic nucleotide phosphodiesterase as a target for cardiac diseases

INTRODUCTION

Cyclic nucleotides, cAMP, and cGMP, are important second messengers of intracellular signaling and play crucial roles in cardiovascular biology and diseases. Cyclic nucleotide phosphodiesterases (PDEs) control the duration, magnitude, and compartmentalization of cyclic nucleotide signaling by catalyzing the hydrolysis of cyclic nucleotides. Individual PDEs modulate distinct signaling pathways and biological functions in the cell, making it a potential therapeutic target for the treatment of different cardiovascular disorders. The clinical success of several PDE inhibitors has ignited continued interest in PDE inhibitors and in PDE-target therapeutic strategies.

AREAS COVERED

This review concentrates on recent research advances of different PDE isoforms with regard to their expression patterns and biological functions in the heart. The limitations of current research and future directions are then discussed. The current and future development of PDE inhibitors is also covered.

EXPERT OPINION

Despite the therapeutic success of several marketed PDE inhibitors, the use of PDE inhibitors can be limited by their side effects, lack of efficacy, and lack of isoform selectivity. Advances in our understanding of the mechanisms by which cellular functions are changed through PDEs may enable the development of new approaches to achieve effective and specific PDE inhibition for various cardiac therapies.

Novel Insights Regarding Nitric Oxide and Cardiovascular Diseases

Nitric oxide (NO) is a powerful mediator with biological activities such as vasodilation and prevention of vascular smooth muscle cell proliferation as well as functional regulation of cardiac cells. Thus, impaired production or reduced bioavailability of NO predisposes to the onset of different cardiovascular (CV) diseases. Alterations in the redox balance associated with excitation-contraction coupling have been identified in heart failure (HF), thus contributing to contractile abnormalities and arrhythmias. For its ability to influence cell proliferation and angiogenesis, NO may be considered a therapeutic option for the management of several CV diseases. Several clinical studies and trials investigated therapeutic NO strategies for systemic hypertension, atherosclerosis, and/or prevention of in stent restenosis, coronary heart disease (CHD), pulmonary arterial hypertension (PAH), and HF, although with mixed results in long-term treatment and effective dose administered in selected groups of patients. Tadalafil, sildenafil, and cinaguat were evaluated for the treatment of PAH, whereas vericiguat was investigated in the treatment of HF patients with reduced ejection fraction. Furthermore, supplementation with hydrogen sulfide, tetrahydrobiopterin, and nitrite/nitrate has shown beneficial effects at the vascular level.

The long and winding road of designing phosphodiesterase inhibitors for the treatment of heart failure

Cyclic nucleotide phosphodiesterases (PDEs) are a superfamily of enzymes known to play a critical role in the indirect regulation of several intracellular metabolism pathways through the selective hydrolysis of the phosphodiester bonds of specific second messenger substrates such as cAMP (3',5'-cyclic adenosine monophosphate) and cGMP (3',5'-cyclic guanosine monophosphate), influencing the hypertrophy, contractility, apoptosis and fibroses in the cardiovascular system. The expression and/or activity of multiple PDEs is altered during heart failure (HF), which leads to changes in levels of cyclic nucleotides and function of cardiac muscle. Within the cardiovascular system, PDEs 1-5, 8 and 9 are expressed and are interesting targets for the HF treatment. In this comprehensive review we will present a briefly description of the biochemical importance of each cardiovascular related PDE to the HF, and cover almost all the "long and winding road" of designing and discovering ligands, hits, lead compounds, clinical candidates and drugs as PDE inhibitors in the last decade.

Melatonin alleviates angiotensin-II-induced cardiac hypertrophy via activating MICU1 pathway

Mitochondrial calcium uptake 1 (MICU1) is a pivotal molecule in maintaining mitochondrial homeostasis under stress conditions. However, it is unclear whether MICU1 attenuates mitochondrial stress in angiotensin II (Ang-II)-induced cardiac hypertrophy or if it has a role in the function of melatonin. Here, small-interfering RNAs against MICU1 or adenovirus-based plasmids encoding MICU1 were delivered into left ventricles of mice or incubated with neonatal murine ventricular myocytes (NMVMs) for 48 h. MICU1 expression was depressed in hypertrophic myocardia and MICU1 knockdown aggravated Ang-II-induced cardiac hypertrophy in vivo and in vitro. In contrast, MICU1 upregulation decreased cardiomyocyte susceptibility to hypertrophic stress. Ang-II administration, particularly in NMVMs with MICU1 knockdown, led to significantly increased reactive oxygen species (ROS) overload, altered mitochondrial morphology, and suppressed mitochondrial function, all of which were reversed by MICU1 supplementation. Moreover, peroxisome proliferator-activated receptor gamma coactivator 1-α (PGC-1α)/MICU1 expression in hypertrophic myocardia increased with melatonin. Melatonin ameliorated excessive ROS generation, promoted mitochondrial function, and attenuated cardiac hypertrophy in control but not MICU1 knockdown NMVMs or mice. Collectively, our results demonstrate that MICU1 attenuates Ang-II-induced cardiac hypertrophy by inhibiting mitochondria-derived oxidative stress. MICU1 activation may be the mechanism underlying melatonin-induced protection against myocardial hypertrophy.

Systolic overload-induced pulmonary inflammation, fibrosis, oxidative stress and heart failure progression through interleukin-1β

Chronic heart failure is associated with increased interleukin-1β (IL-1β), leukocyte infiltration, and fibrosis in the heart and lungs. Here we further studied the role of IL-1β in the transition from left heart failure to pulmonary hypertension and right ventricular hypertrophy in mice with existing left heart failure produced by transverse aortic constriction. We demonstrated that transverse aortic constriction-induced heart failure was associated with increased lung inflammation and cleaved IL-1β, and inhibition of IL-1β signaling using blocking antibodies of clone B122 effectively attenuated further decrease of left ventricular systolic function in mice with existing heart failure. We found that inhibition of IL-1β attenuated lung inflammation, inflammasome activation, fibrosis, oxidative stress, and right ventricular hypertrophy. IL-1β blocking antibodies of clone B122 also significantly attenuated lung T cell activation. Together, these data indicate that IL-1β signaling exerts a causal role for heart failure progression, or the transition from left heart failure to lung remodeling and right heart hypertrophy.

Type 5 phosphodiesterase (PDE5) and the vascular tree: From embryogenesis to aging and disease

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Vascular development depends on the timely differentiation of endothelial and smooth muscle cells.

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Vascular aging and vascular disease are influenced by endothelial and vascular smooth muscle cell compartments.

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A survey of the literature on the role of PDE5 in vascular development, aging and disease is reported.

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The role of PDE5 on vascular development, aging and disease needs to be further investigated by its genetic ablation.

Vascular tree development depends on the timely differentiation of endothelial and vascular smooth muscle cells. These latter are key players in the formation of the vascular scaffold that offers resistance to the blood flow. This review aims at providing an overview on the role of PDE5, the cGMP-specific phosphodiesterase that historically attracted much attention for its involvement in male impotence, in the regulation of vascular smooth muscle cell function. The overall goal is to underscore the importance of PDE5 expression and activity in this cell type in the context of the organs where its function has been extensively studied.

Sildenafil Recovers Burn-Induced Cardiomyopathy

Background: Severe burn injury initiates a feedback cycle of inflammation, fibrosis, oxidative stress and cardiac mitochondrial damage via the PDE5A-cGMP-PKG pathway. Aim: To test if the PDE5A-cGMP-PKG pathway may contribute to burn-induced heart dysfunction. Methods: Sprague–Dawley rats were divided four groups: sham; sham/sildenafil; 24 h post burn (60% total body surface area scald burn, harvested at 24 h post burn); and 24 h post burn/sildenafil. We monitored heart function and oxidative adducts, as well as cardiac inflammatory, cardiac fibrosis and cardiac remodeling responses in vivo. Results: Sildenafil inhibited the burn-induced PDE5A mRNA level and increased the cGMP level and PKG activity, leading to the normalization of PKG down-regulated genes (IRAG, PLB, RGS2, RhoA and MYTP), a decreased ROS level (H2O2), decreased oxidatively modified adducts (malonyldialdehyde [MDA], carbonyls), attenuated fibrogenesis as well as fibrosis gene expression (ANP, BNP, COL1A2, COL3A2, αSMA and αsk-Actin), and reduced inflammation and related gene expression (RELA, IL-18 and TGF-β) after the burn. Additionally, sildenafil treatment preserved left ventricular heart function (CO, EF, SV, LVvol at systolic, LVPW at diastolic and FS) and recovered the oxidant/antioxidant balance (total antioxidant, total SOD activity and Cu,ZnSOD activity). Conclusions: The PDE5A-cGMP-PKG pathway mediates burn-induced heart dysfunction. Sildenafil treatment recovers burn-induced cardiac dysfunction.

Sildenafil Recovers Burn-Induced Cardiomyopathy

Background: Severe burn injury initiates a feedback cycle of inflammation, fibrosis, oxidative stress and cardiac mitochondrial damage via the PDE5A-cGMP-PKG pathway. Aim: To test if the PDE5A-cGMP-PKG pathway may contribute to burn-induced heart dysfunction. Methods: Sprague–Dawley rats were divided four groups: sham; sham/sildenafil; 24 h post burn (60% total body surface area scald burn, harvested at 24 h post burn); and 24 h post burn/sildenafil. We monitored heart function and oxidative adducts, as well as cardiac inflammatory, cardiac fibrosis and cardiac remodeling responses in vivo. Results: Sildenafil inhibited the burn-induced PDE5A mRNA level and increased the cGMP level and PKG activity, leading to the normalization of PKG down-regulated genes (IRAG, PLB, RGS2, RhoA and MYTP), a decreased ROS level (H2O2), decreased oxidatively modified adducts (malonyldialdehyde [MDA], carbonyls), attenuated fibrogenesis as well as fibrosis gene expression (ANP, BNP, COL1A2, COL3A2, αSMA and αsk-Actin), and reduced inflammation and related gene expression (RELA, IL-18 and TGF-β) after the burn. Additionally, sildenafil treatment preserved left ventricular heart function (CO, EF, SV, LVvol at systolic, LVPW at diastolic and FS) and recovered the oxidant/antioxidant balance (total antioxidant, total SOD activity and Cu,ZnSOD activity). Conclusions: The PDE5A-cGMP-PKG pathway mediates burn-induced heart dysfunction. Sildenafil treatment recovers burn-induced cardiac dysfunction.

Various subtypes of phosphodiesterase inhibitors differentially regulate pulmonary vein and sinoatrial node electrical activities

Phosphodiesterase (PDE)3-5 are expressed in cardiac tissue and play critical roles in the pathogenesis of heart failure and atrial fibrillation. PDE inhibitors are widely used in the clinic, but their effects on the electrical activity of the heart are not well understood. The aim of the present study was to examine the effects of various PDE inhibitors on spontaneous cardiac activity and compare those effects between sinoatrial nodes (SANs) and pulmonary veins (PVs). Conventional microelectrodes were used to record action potentials in isolated rabbit SAN and PV tissue preparations, before and after administration of different concentrations (0.1, 1 and 10 µM) of milrinone (PDE3 inhibitor), rolipram (PDE4 inhibitor) and sildenafil (PDE5 inhibitor), with or without the application of isoproterenol (cAMP and PKA activator), KT5823 (PKG inhibitor) or H89 (PKA inhibitor). Milrinone (1 and 10 µM) increased the spontaneous activity in PVs by 10.6±4.9 and 16.7±5.3% and in SANs by 9.3±4.3 and 20.7±4.6%, respectively. In addition, milrinone (1 and 10 µM) induced the occurrence of triggered activity (0/8 vs. 5/8; P<0.005) in PVs. Rolipram increased PV spontaneous activity by 7.5±1.3-9.5±4.0%, although this was not significant, and did not alter SAN spontaneous activity. Sildenafil reduced spontaneous activity in PVs to a greater extent than that seen in SANs. Both KT5823 and H89 suppressed milrinone-increased PV spontaneous activity. In the presence of isoproterenol, milrinone did not alter isoproterenol-induced PV arrhythmogenesis, suggesting that the effects of PDE3 are mediated by the protein kinase G and protein kinase A signaling pathways. In conclusion, inhibitors of different PDE subtypes exert diverse electrophysiological effects on PV and SAN activities.

A concise review of recent advances in anti-heart failure targets and its small molecules inhibitors in recent years

Heart failure is a disease with high mortality and the risk of heart failure increases in magnitude with age. The patients of heart failure is increasing year by year. Hence, Pharmaceutical researchers have to develop new drugs with better pharmacological effects to coping with this phenomenon. In this article, we reviewed the small molecule compounds for heart failure that have been marketed in recent years or are promising to enter clinical research. We also reviewed the SAR (structure activity relationship) of these molecules, such as renin inhibitors, ROMK inhibitors, a kind of new diuretics, and some dual-targets inhibitors. These small molecules proven to be beneficial effect on heart failure patients. Which may provide ideas for the design of novel anti-heart failure therapeutic drugs.

Therapies that enhance pulmonary vascular NO-signaling in the neonate

There are several pulmonary hypertensive diseases that affect the neonatal population, including persistent pulmonary hypertension of the newborn (PPHN) and bronchopulmonary dysplasia (BPD)-associated pulmonary hypertension (PH). While the indication for inhaled nitric oxide (iNO) use is for late-preterm and term neonates with PPHN, there is a suboptimal response to this pulmonary vasodilator in ~40% of patients. Additionally, there are no FDA-approved treatments for BPD-associated PH or for preterm infants with PH. Therefore, investigating mechanisms that alter the nitric oxide-signaling pathway has been at the forefront of pulmonary vascular biology research. In this review, we will discuss the various mechanistic pathways that have been targets in neonatal PH, including NO precursors, soluble guanylate cyclase modulators, phosphodiesterase inhibitors and antioxidants. We will review their role in enhancing NO-signaling at the bench, in animal models, as well as highlight their role in the treatment of neonates with PH.

Swimming exercise inhibits myocardial ER stress in the hearts of aged mice by enhancing cGMP‑PKG signaling

The purpose of the present study was to explore aging‑associated cardiac dysfunction and the possible mechanism by which swimming exercise modulates cardiac dysfunction in aged mice. Aged mice were divided into two groups: i) Aged mice; and ii) aged mice subjected to swimming exercises. Another cohort of 4‑month‑old male mice served as the control group. Cardiac structure and function in mice were analyzed using hematoxylin and eosin staining, and echocardiography. The levels of oxidative stress were determined by measuring the levels of superoxide dismutase, malondialdehyde and reactive oxygen species (ROS). Levels of the endoplasmic reticulum (ER) stress‑related protein PKR‑like ER kinase, glucose‑regulated protein 78 and C/EBP homologous protein were determined to evaluate the level of ER stress. The aged group exhibited an abnormal cardiac structure and decreased cardiac function, both of which were ameliorated by swimming exercise. The hearts of the aged mice exhibited pronounced oxidative and ER stress, which were ameliorated by exercise, and was accompanied by the reactivation of myocardial cGMP and suppression of cGMP‑specific phosphodiesterase type 5 (PDE5). The inhibition of PDE5 attenuated age‑induced cardiac dysfunction, blocked ROS production and suppressed ER stress. An ER stress inducer abolished the beneficial effects of the swimming exercise on cardiac function and increased ROS production. The present study suggested that exercise restored cardiac function in mice with age‑induced cardiac dysfunction by inhibiting oxidative stress and ER stress, and increasing cGMP‑protein kinase G signaling.

The role of cathepsin D in the pathophysiology of heart failure and its potentially beneficial properties: a translational approach

Aims

Cathepsin D is a ubiquitous lysosomal protease that is primarily secreted due to oxidative stress. The role of circulating cathepsin D in heart failure (HF) is unknown. The aim of this study is to determine the association between circulating cathepsin D levels and clinical outcomes in patients with HF and to investigate the biological settings that induce the release of cathepsin D in HF.

Methods and results

Cathepsin D levels were studied in 2174 patients with HF from the BIOSTAT‐CHF index study. Results were validated in 1700 HF patients from the BIOSTAT‐CHF validation cohort. The primary combined outcome was all‐cause mortality and/or HF hospitalizations. Human pluripotent stem cell‐derived cardiomyocytes were subjected to hypoxic, pro‐inflammatory signalling and stretch conditions. Additionally, cathepsin D expression was inhibited by targeted short hairpin RNAs (shRNA). Higher levels of cathepsin D were independently associated with diabetes mellitus, renal failure and higher levels of interleukin‐6 and N‐terminal pro‐B‐type natriuretic peptide (P < 0.001 for all). Cathepsin D levels were independently associated with the primary combined outcome [hazard ratio (HR) per standard deviation (SD): 1.12; 95% confidence interval (CI) 1.02–1.23], which was validated in an independent cohort (HR per SD: 1.23, 95% CI 1.09–1.40). In vitro experiments demonstrated that human stem cell‐derived cardiomyocytes released cathepsin D and troponin T in response to mechanical stretch. ShRNA‐mediated silencing of cathepsin D resulted in increased necrosis, abrogated autophagy, increased stress‐induced metabolism, and increased release of troponin T from human stem cell‐derived cardiomyocytes under stress.

Conclusions

Circulating cathepsin D levels are associated with HF severity and poorer outcome, and reduced levels of cathepsin D may have detrimental effects with therapeutic potential in HF.

Genetic risk scores to predict the prognosis of chronic heart failure patients in Chinese Han

Chronic heart failure (CHF) has poor prognosis and polygenic heritability, and the genetic risk score (GRS) to predict CHF outcome has not yet been researched comprehensively. In this study, we sought to establish GRS to predict the outcomes of CHF. We re-analysed the proteomics data of failing human heart and combined them to filter the data of high-throughput sequencing in 1000 Chinese CHF cohort. Cox hazards models were used based on single nucleotide polymorphisms (SNPs) to estimate the association of GRS with the prognosis of CHF, and to analyse the difference between individual SNPs and tertiles of genetic risk. In the cohort study, GRS encompassing eight SNPs harboured in seven genes were significantly associated with the prognosis of CHF (P = 2.19 × 10^-10 after adjustment). GRS was used in stratifying individuals into significantly different CHF risk, with those in the top tertiles of GRS distribution having HR of 3.68 (95% CI: 2.40-5.65 P = 2.47 × 10^-10 ) compared with those in the bottom. We developed GRS and demonstrated its association with first event of heart failure endpoint. GRS might be used to stratify individuals for CHF prognostic risk and to predict the outcomes of genomic screening as a complement to conventional risk and NT-proBNP.

P66Shc Deletion Ameliorates Oxidative Stress and Cardiac Dysfunction in Pressure Overload-Induced Heart Failure

OBJECTIVE

p66Shc is a redox enzyme that plays an important role in the response of oxidative stress and the p53-dependent apoptosis. The expression level of p66Shc has a negative correlation with the resistance of oxidative stress in vivo and in vitro. We aim to demonstrate the function of p66Shc in pressure overload-induced heart failure.

METHODS AND RESULTS

The pressure overload-induced heart failure was induced in mice by transverse aortic constriction (TAC). Cardiac dysfunction was shown by transthoracic echocardiography. Western blot was used to check the protein levels of phosphodiesterase type 5 (PDE5) and ventricular oxidative stress markers. Superoxide dismutase (SOD) mimetic M40401 and PDE5 inhibitor sildenafil were used in the treatment of mice. The deletion of p66Shc attenuated cardiac dysfunction and oxidative stress in pressure overload-induced heart failure. p66Shc deletion also decreased the expression of ventricular oxidative stress markers and enhanced PKG signaling by promoting the expression of PDE5. M40401 and sildenafil attenuated the TAC-induced cardiac dysfunction and oxidative stress in p66Shc overexpression mice.

CONCLUSIONS

Our findings suggest that p66Shc participates in the regulation of cardiac dysfunction and oxidative stress in TAC-derived pressure overload-induced heart failure in mice, and SOD and PDE5 are molecules downstream of p66Shc in this regulatory process.

Isolevuglandin scavenger attenuates pressure overload-induced cardiac oxidative stress, cardiac hypertrophy, heart failure and lung remodeling

Increased levels of reactive isolevuglandins (IsoLGs) are associated with vascular inflammation and hypertension, two important factors affect heart failure (HF) development. The role of IsoLGs in HF development is unknown. Here we studied the role of IsoLG scavenger 2-hydroxybenzylamine (2-HOBA) in transverse aortic constriction (TAC) induced heart failure. We observed that TAC caused a significant increase of IsoLG protein adducts in cardiac and lung tissues in mice. Both IsoLG scavenger 2-hydroxybenzylamine (2-HOBA) and its less reactive isomer 4-hydroxybenzylamine (4-HOBA) significantly attenuated the left ventricular (LV) and lung IsoLGs in mice after TAC. 2-HOBA and 4-HOBA attenuated TAC-induced LV hypertrophy, heart failure, and the increase of lung weight in mice, and also improved TAC-induced LV dysfunction. Moreover, both 2-HOBA and 4-HOBA effectively attenuated LV cardiomyocyte hypertrophy, lung inflammation, lung fibrosis. These findings suggest that methods to reduce IsoLGs may be useful for HF therapy.

Protein Quality Control Activation and Microtubule Remodeling in Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is the most common inherited cardiac disorder. It is mainly caused by mutations in genes encoding sarcomere proteins. Mutant forms of these highly abundant proteins likely stress the protein quality control (PQC) system of cardiomyocytes. The PQC system, together with a functional microtubule network, maintains proteostasis. We compared left ventricular (LV) tissue of nine donors (controls) with 38 sarcomere mutation-positive (HCMSMP) and 14 sarcomere mutation-negative (HCMSMN) patients to define HCM and mutation-specific changes in PQC. Mutations in HCMSMP result in poison polypeptides or reduced protein levels (haploinsufficiency, HI). The main findings were 1) several key PQC players were more abundant in HCM compared to controls, 2) after correction for sex and age, stabilizing heat shock protein (HSP)B1, and refolding, HSPD1 and HSPA2 were increased in HCMSMP compared to controls, 3) α-tubulin and acetylated α-tubulin levels were higher in HCM compared to controls, especially in HCMHI, 4) myosin-binding protein-C (cMyBP-C) levels were inversely correlated with α-tubulin, and 5) α-tubulin levels correlated with acetylated α-tubulin and HSPs. Overall, carrying a mutation affects PQC and α-tubulin acetylation. The haploinsufficiency of cMyBP-C may trigger HSPs and α-tubulin acetylation. Our study indicates that proliferation of the microtubular network may represent a novel pathomechanism in cMyBP-C haploinsufficiency-mediated HCM.

FNDC5/Irisin inhibits pathological cardiac hypertrophy

Cardiac hypertrophy is a common pathophysiological process in various cardiovascular diseases, which still has no effective therapies. Irisin is a novel myokine mainly secreted by skeletal muscle and is believed to be involved in the regulation of energy metabolism. In the present study, we found that irisin expression was elevated in hypertrophic murine hearts and serum. Moreover, angiotension II-induced cardiomyocyte hypertrophy was attenuated after irisin administration and aggravated after irisin knockdown in vitro. Next, we generated transverse aortic constriction (TAC)-induced cardiac hypertrophy murine model and found that cardiac hypertrophy and fibrosis were significantly attenuated with improved cardiac function assessed by echocardiography after irisin treatment. Mechanistically, we demonstrated that FNDC5 was cleaved into irisin, at least partially, in a disintegrin and metalloproteinase (ADAM) family-dependent manner. ADAM10 was the candidate enzyme responsible for the cleavage. Further, we found irisin treatment activated AMPK and subsequently inhibited activation of mTOR. AMPK inhibition ablated the protective role of irisin administration. In conclusion, we find irisin is secreted in an ADAM family-dependent manner, and irisin treatment improves cardiac function and attenuates pressure overload-induced cardiac hypertrophy and fibrosis mainly through regulating AMPK-mTOR signaling.

Profound Increase of Lung Airway Resistance in Heart Failure: a Potential Important Contributor for Dyspnea

Dyspnea is a major symptom of heart failure (HF). Here, we have studied the lung remodeling and airway resistance in HF mice. We demonstrated that aortic banding-induced HF caused a dramatic decrease of lung compliance and an increase of lung airway resistance. The decrease of lung compliance was correlated with the increased lung weight in a linear fashion (γ² = 0.824). An HF-induced increase of lung airway resistance and a decrease of lung compliance were almost identical in anesthetized mice and in the isolated lungs from these mice. HF caused profound lung fibrosis in mice with increased lung weight. Moreover, HF patients of NYHA class III-IV showed increased lung density as revealed by high-resolution CT scanning. These data indicate that lung compliance and lung airway resistance may be useful in determining lung remodeling after HF, and lung structure changes may contribute to dyspnea in HF.

PKR: A Kinase to Remember

Aging is a major risk factor for many diseases including metabolic syndrome, cancer, inflammation, and neurodegeneration. Identifying mechanistic common denominators underlying the impact of aging is essential for our fundamental understanding of age-related diseases and the possibility to propose new ways to fight them. One can define aging biochemically as prolonged metabolic stress, the innate cellular and molecular programs responding to it, and the new stable or unstable state of equilibrium between the two. A candidate to play a role in the process is protein kinase R (PKR), first identified as a cellular protector against viral infection and today known as a major regulator of central cellular processes including mRNA translation, transcriptional control, regulation of apoptosis, and cell proliferation. Prolonged imbalance in PKR activation is both affected by biochemical and metabolic parameters and affects them in turn to create a feedforward loop. Here, we portray the central role of PKR in transferring metabolic information and regulating cellular function with a focus on cancer, inflammation, and brain function. Later, we integrate information from open data sources and discuss current knowledge and gaps in the literature about the signaling cascades upstream and downstream of PKR in different cell types and function. Finally, we summarize current major points and biological means to manipulate PKR expression and/or activation and propose PKR as a therapeutic target to shift age/metabolic-dependent undesired steady states.

GCN2 deficiency ameliorates cardiac dysfunction in diabetic mice by reducing lipotoxicity and oxidative stress

Excessive myocardial lipid accumulation is a major feature of diabetic cardiomyopathy (DCM). Although general control nonderepressible 2 (GCN2) has been identified as a sensor of amino acid availability, it also functions as an important regulator of hepatic lipid metabolism. Our previous studies have reported that GCN2 promotes pressure overload or doxorubicin-induced cardiac dysfunction by increasing cardiomyocyte apoptosis and myocardial oxidative stress. However, the impact of GCN2 on the development of DCM remains unclear. In this study, we investigated the effect of GCN2 on DCM in type 1 and type 2 diabetes animal models. After streptozotocin (STZ) or high-fat diet (HFD) plus low-dose STZ treatments, GCN2^-/- mice developed less cardiac dysfunction, hyperlipidemia, myocardial hypertrophy, fibrosis, lipid accumulation, oxidative stress, inflammation and apoptosis compared with wild-type (WT) mice. In diabetic hearts, GCN2 deficiency attenuated the upregulation of peroxisome proliferator-activated receptor alpha (PPARα) and gamma (PPARγ), the phosphorylation of eIF2α and the induction of activating transcription factor 4 (ATF4) and C/EBP homologous protein (CHOP), as well as the reduction of Bcl-2. Furthermore, we found that knockdown of GCN2 attenuated, whereas overexpression of GCN2 exacerbated, high glucose or palmitic acid-induced cell death, oxidative and endoplasmic reticulum stress and lipid accumulation in H9C2 cells. Collectively, our data provide evidence that GCN2 deficiency protects cardiac function by reducing lipid accumulation, oxidative stress and cell death. Our findings suggest that strategies to inhibit GCN2 activity in the heart may be novel approaches for DCM therapy.

Association between asymmetric dimethylarginine serum levels and left ventricular longitudinal deformation in patients with normal ejection fractions: a two-dimensional speckle-tracking echocardiography examination

OBJECTIVES

Nitric oxide is an endogenous substance that preserves the myocardial function in patients with heart failure. Asymmetric dimethylarginine (ADMA) is a competitive inhibitor of endogenous nitric oxide synthase. We sought to explore the association between the left ventricular (LV) function as assessed with two-dimensional echocardiography and the serum level of ADMA in nondiabetic patients without significant coronary artery disease.

PATIENTS AND METHODS

Eighty-seven consecutive patients with normal LV ejection fractions were included in this cross-sectional study. The ADMA serum level was measured, and the longitudinal deformation indices of the LV myocardium were evaluated using two-dimensional speckle-tracking echocardiography (2DSTE).

RESULTS

The systolic strain, the systolic strain rate, and the early and late diastolic strain rates as evaluated with 2DSTE were not statistically significantly different between the patients with normal ADMA serum levels and those with increased ADMA serum levels. The two study groups were also not significantly different in terms of the systolic and diastolic myocardial velocities obtained with tissue Doppler.

CONCLUSION

Our findings showed no statistically significant correlations between the serum ADMA level and the 2DSTE-derived indices of the longitudinal deformation of the LV myocardium in our nondiabetic patients without significant coronary artery stenosis and with normal LV ejection fractions.

PDE5 inhibitor protects the mitochondrial function of hypoxic myocardial cells

Protective effect of phosphodiesterase 5 (PDE5) inhibitor sildenafil on hypoxic injury of isolated myocardial cells and its mechanism of action were investigated. Myocardial cells of neonatal mice were isolated, cultured and divided into blank, control, and PDE5 inhibitor group. Cells in the control and the PDE5 inhibitor group were treated with hypoxia and serum deprivation for 6 h to simulate the myocardial ischemia process in vivo, while those in the PDE5 inhibitor group were treated with 1 µmol/l sildenafil. The cell viability was detected via Cell Counting kit-8 (CCK-8), the cytotoxicity was detected via lactate dehydrogenase release assay, and the apoptosis level was detected via flow cytometry, Hoechst staining and caspase-3 activity assay. Moreover, changes in mitochondrial membrane potential of myocardial cells were detected via JC-1 staining and flow cytometry, fluorescein adenosine triphosphate (ATP) assay kit was used to detect the production of ATP in myocardial cells, and reverse transcription-polymerase chain reaction (RT-PCR) was used to detect the level of Sirt3 messenger ribonucleic acid (mRNA) in myocardial cells. Finally, the expression and changes of Sirt3, peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) and acetylated PGC-1α were detected via western blot analysis. After hypoxia treatment, the cell viability was decreased, the cytotoxic effect was enhanced, the percentage of apoptosis was increased, the activity of apoptosis-related protein was increased, the mitochondrial membrane potential was decreased, the production of ATP was reduced, the expression of Sirt3 was decreased, and the acetylation level of PGC-1α was increased. However, after pretreatment with sildenafil, the damage to membrane potential of myocardial cells was significantly alleviated, and the production of ATP was increased. At the same time, myocardial cell apoptosis was decreased, Sirt3 expression was increased and PGC-1α acetylation was decreased. PDE5 inhibitor inhibits apoptosis of hypoxic myocardial cells through protecting mitochondrial function.

Inhibition of cardiac hypertrophy by aromadendrin through down-regulating NFAT and MAPKs pathways

Cardiac hypertrophy is a maladaptive response to pressure overload and it's an important risk factor for heart failure and other adverse cardiovascular events. Aromadendrin (ARO) has remarkable anti-lipid peroxidation efficacy and is a potential therapeutic medicine for the management of diabetes and cardiovascular diseases. In this study, we established the cardiac hypertrophy cell model in rat neonatal ventricular cardiomyocytes (RNVMs) with phenylephrine. The cell model was characterized by the increased protein synthesis and cardiomyocyte size, which can be normalized by ARO treatment in both concentration- and time-dependent manner. In transverse aortic constriction (TAC) induced cardiac hypertrophy model, ARO administration improved the impairment of cardiac function and alleviated the cardiac hypertrophy indicators, like ventricular mass/body weight, myocyte cross-sectional area, and the expression of ANP, BNP and Myh7. ARO treatment also suppressed the cardiac fibrosis and the correlated fibrogenic genes. Our further investigation revealed ARO could down-regulate pressure overload-induced Malondialdehyde (MDA) and 4-HNE expression, restore the decrease of GSH/GSSG ratio, meanwhile prevent nuclear translocation of NFAT and the activation of MAPKs pathways. Collectively, ARO has a protective effect against experimental cardiac hypertrophy in mice, suggesting its potential as a novel therapeutic drug for pathological cardiac hypertrophy.

Gentisic acid attenuates pressure overload-induced cardiac hypertrophy and fibrosis in mice through inhibition of the ERK1/2 pathway

We previously reported that gentisic acid (2,5‐dihydroxybenzoic acid) is the third most abundant phenolic component of Dendropanax morbifera branch extracts. Here, we investigated its effects on cardiac hypertrophy and fibrosis in a mouse model of pressure overload and compared them to those of the beta blocker bisoprolol and calcium channel blocker diltiazem. Cardiac hypertrophy was induced in mice by transverse aortic constriction (TAC). Beginning 2 weeks after this procedure, the mice were given daily intraperitoneal injections of gentisic acid (100 mg/kg/d), bisoprolol (5 mg/kg/d) or diltiazem (10 mg/kg/d) for 3 weeks. Cardiac hypertrophy was evaluated by the heart weight‐to‐body weight ratio, the cardiomyocyte cross‐sectional area after haematoxylin and eosin staining, and echocardiography. Markers of cardiac hypertrophy and fibrosis were tested by reverse transcription‐quantitative real‐time polymerase chain reaction, western blotting and Masson's trichrome staining. The suppressive effects of gentisic acid treatment on TAC‐induced cardiac hypertrophy and fibrosis were comparable to those of bisoprolol administration. Cardiac hypertrophy was reversed and left ventricular septum and posterior wall thickness were restored by gentisic acid, bisoprolol and diltiazem treatment. Cardiac hypertrophic marker gene expression and atrial and brain natriuretic peptide levels were decreased by gentisic acid and bisoprolol, as were cardiac (interstitial and perivascular) fibrosis and fibrosis‐related gene expression. Cardiac hypertrophy‐associated upregulation of the transcription factors GATA4 and Sp1 and activation of extracellular signal‐regulated kinase 1/2 were also negated by these drugs. These results suggest that gentisic acid could serve as a therapeutic agent for cardiac hypertrophy and fibrosis.

Asymmetric dimethylarginine (ADMA) as an important risk factor for the increased cardiovascular diseases and heart failure in chronic kidney disease

Patients with chronic kidney disease have an increased cardiovascular morbidity and mortality. It has been recognized that the traditional cardiovascular risk factors could only partially explain the increased cardiovascular morbidity and mortality in patients with chronic kidney disease. Asymmetric dimethylarginine (ADMA) and N-monomethy l-arginine (L-NMMA) are endogenous inhibitors of nitric oxide synthases that attenuate nitric oxide production and enhance reactive oxidative specie generation. Increased plasma ADMA and/or L-NMMA are strong and independent risk factor for chronic kidney disease, and various cardiovascular diseases such as hypertension, coronary artery disease, atherosclerosis, diabetes, and heart failure. Both ADMA and L-NMMA are also eliminated from the body through either degradation by dimethylarginine dimethylaminohydrolase-1 (DDAH1) or urine excretion. This short review will exam the literature of ADMA and L-NMMA degradation and urine excretion, and the role of chronic kidney diseases in ADMA and L-NMMA accumulation and the increased cardiovascular disease risk. Based on all available data, it appears that the increased cardiovascular morbidity in chronic kidney disease may relate to the dramatic increase of systemic ADMA and L-NMMA after kidney failure.

Mitochondrial ROS Drive Sudden Cardiac Death and Chronic Proteome Remodeling in Heart Failure

RATIONALE

Despite increasing prevalence and incidence of heart failure (HF), therapeutic options remain limited. In early stages of HF, sudden cardiac death (SCD) from ventricular arrhythmias claims many lives. Reactive oxygen species (ROS) have been implicated in both arrhythmias and contractile dysfunction. However, little is known about how ROS in specific subcellular compartments contribute to HF or SCD pathophysiology. The role of ROS in chronic proteome remodeling has not been explored.

OBJECTIVE

We will test the hypothesis that elevated mitochondrial ROS (mROS) is a principal source of oxidative stress in HF and in vivo reduction of mROS mitigates SCD.

METHODS AND RESULTS

Using a unique guinea pig model of nonischemic HF that recapitulates important features of human HF, including prolonged QT interval and high incidence of spontaneous arrhythmic SCD, compartment-specific ROS sensors revealed increased mROS in resting and contracting left ventricular myocytes in failing hearts. Importantly, the mitochondrially targeted antioxidant (MitoTEMPO) normalized global cellular ROS. Further, in vivo MitoTEMPO treatment of HF animals prevented and reversed HF, eliminated SCD by decreasing dispersion of repolarization and ventricular arrhythmias, suppressed chronic HF-induced remodeling of the expression proteome, and prevented specific phosphoproteome alterations. Pathway analysis of mROS-sensitive networks indicated that increased mROS in HF disrupts the normal coupling between cytosolic signals and nuclear gene programs driving mitochondrial function, antioxidant enzymes, Ca²⁺ handling, and action potential repolarization, suggesting new targets for therapeutic intervention.

CONCLUSIONS

mROS drive both acute emergent events, such as electrical instability responsible for SCD, and those that mediate chronic HF remodeling, characterized by suppression or altered phosphorylation of metabolic, antioxidant, and ion transport protein networks. In vivo reduction of mROS prevents and reverses electrical instability, SCD, and HF. Our findings support the feasibility of targeting the mitochondria as a potential new therapy for HF and SCD while identifying new mROS-sensitive protein modifications.

Targeting Phosphodiesterase-5 by Vardenafil Improves Vascular Graft Function

OBJECTIVES

Ischaemia reperfusion (IR) injury occurs during vascular graft harvesting and implantation during vascular/cardiac surgery. Elevated intracellular cyclic guanosine monophosphate (cGMP) levels contribute to an effective endothelial protection in different pathophysiological conditions. The hypothesis that the phosphodiesterase-5 inhibitor vardenafil would protect vascular grafts against IR injury by upregulating the nitric oxide-cGMP pathway in the vessel wall of the bypass graft was investigated.

METHODS

Lewis rats (n = 6-7/group) were divided into Group 1, control; Group 2, donor rats received intravenous saline; Group 3, received intravenous vardenafil (30 μg/kg) 2 h before explantation. Whereas aortic arches of Group 1 were immediately mounted in an organ bath, aortic segments of Groups 2 and 3 were stored for 2 h in saline and transplanted into the abdominal aorta of the recipient. Two hours after transplantation, the implanted grafts were harvested. Endothelium dependent and independent vasorelaxations were investigated. TUNEL, CD-31, ICAM-1, VCAM-1, α-SMA, nitrotyrosine, dihydroethidium and cGMP immunochemistry were also performed.

RESULTS

Compared with the control, the saline group showed significantly attenuated endothelium dependent maximal relaxation (R_max) 2 h after reperfusion, which was significantly improved by vardenafil supplementation (R_max control, 91 ± 2%; saline 22 ± 2% vs. vardenafil 39 ± 4%, p < .001). Vardenafil pre-treatment significantly reduced DNA fragmentation (control 9 ± 1%, saline 66 ± 8% vs. vardenafil 13 ± 1%, p < .001), nitro-oxidative stress (control 0.8 ± 0.3, saline 7.6 ± 1.3 vs. vardenafil 3.8 ± 1, p = .036), reactive oxygen species level (vardenafil 36 ± 4, control 34 ± 2 vs. saline 43 ± 2, p = .049), prevented vascular smooth muscle cell damage (control 8.5 ± 0.7, saline 4.3 ± 0.6 vs. vardenafil 6.7 ± 0.6, p = .013), decreased ICAM-1 (control 4.1 ± 0.5, saline 7.0 ± 0.9 vs. vardenafil 4.4 ± 0.6, p = .031), and VCAM-1 score (control 4.4 ± 0.4, saline 7.3 ± 1.0 vs. vardenafil 5.2 ± 0.4, p = .046) and increased cGMP score in the aortic wall (control 11.2 ± 0.8, saline 6.5 ± 0.8 vs. vardenafil 8.9 ± 0.6, p = .016). The marker for endothelial integrity (CD-31) was also higher in the vardenafil group (control 74 ± 4%, saline 22 ± 2% vs. vardenafil 40 ± 3%, p = .008).

CONCLUSIONS

The results support the view that impairment of intracellular cGMP signalling plays a role in the pathogenesis of the endothelial dysfunction of an arterial graft after bypass surgery, which can effectively be prevented by vardenafil. Its clinical use as preconditioning drug could be a novel approach in vascular/cardiac surgery.