Molecular mechanisms underlying the transition of cardiac hypertrophy to heart failure

Exosomes: current knowledge and future perspectives

Exosomes are membrane-bound micro-vesicles that possess endless therapeutic potential for treatment of numerous pathologies including autoimmune, cardiovascular, ocular, and nervous disorders. Despite considerable knowledge about exosome biogenesis and secretion, still, there is a lack of information regarding exosome uptake by cell types and internal signaling pathways through which these exosomes process cellular response. Exosomes are key components of cell signaling and intercellular communication. In central nervous system (CNS), exosomes can penetrate BBB and maintain homeostasis by myelin sheath regulation and the waste products elimination. Therefore, the current review summarizes role of exosomes and their use as biomarkers in cardiovascular, nervous and ocular disorders. This aspect of exosomes provides positive hope to monitor disease development and enable early diagnosis and treatment optimization. In this review, we have summarized recent findings on physiological and therapeutic effects of exosomes and also attempt to provide insights about stress-preconditioned exosomes and stem cell-derived exosomes.

Gene therapy for heart failure: A novel treatment for the age old disease

Across the globe, cardiovascular disease (CVD) is the leading cause of mortality. According to reports, around 6.2 million people in the United states have heart failure. Current standards of care for heart failure can delay but not prevent progression of disease. Gene therapy is one of the novel treatment modalities that promises to fill this limitation in the current standard of care for Heart Failure. In this paper we performed an extensive search of the literature on various advances made in gene therapy for heart failure till date. We review the delivery methods, targets, current applications, trials, limitations and feasibility of gene therapy for heart failure. Various methods have been employed till date for administering gene therapies including but not limited to arterial and venous infusion, direct myocardial injection and pericardial injection. Various strategies such as AC6 expression, S100A1 protein upregulation, VEGF-B and SDF-1 gene therapy have shown promise in recent preclinical trials. Furthermore, few studies even show that stimulation of cardiomyocyte proliferation such as through cyclin A2 overexpression is a realistic avenue. However, a considerable number of obstacles need to be overcome for gene therapy to be part of standard treatment of care such as definitive choice of gene, gene delivery systems and a suitable method for preclinical trials and clinical trials on patients. Considering the challenges and taking into account the recent advances in gene therapy research, there are encouraging signs to indicate gene therapy for heart failure to be a promising treatment modality for the future. However, the time and feasibility of this option remains in a situation of balance.

Hypoxia-induced signaling in the cardiovascular system: pathogenesis and therapeutic targets

Hypoxia, characterized by reduced oxygen concentration, is a significant stressor that affects the survival of aerobic species and plays a prominent role in cardiovascular diseases. From the research history and milestone events related to hypoxia in cardiovascular development and diseases, The "hypoxia-inducible factors (HIFs) switch" can be observed from both temporal and spatial perspectives, encompassing the occurrence and progression of hypoxia (gradual decline in oxygen concentration), the acute and chronic manifestations of hypoxia, and the geographical characteristics of hypoxia (natural selection at high altitudes). Furthermore, hypoxia signaling pathways are associated with natural rhythms, such as diurnal and hibernation processes. In addition to innate factors and natural selection, it has been found that epigenetics, as a postnatal factor, profoundly influences the hypoxic response and progression within the cardiovascular system. Within this intricate process, interactions between different tissues and organs within the cardiovascular system and other systems in the context of hypoxia signaling pathways have been established. Thus, it is the time to summarize and to construct a multi-level regulatory framework of hypoxia signaling and mechanisms in cardiovascular diseases for developing more therapeutic targets and make reasonable advancements in clinical research, including FDA-approved drugs and ongoing clinical trials, to guide future clinical practice in the field of hypoxia signaling in cardiovascular diseases.

PCSK9: A emerging participant in heart failure

Heart failure (HF) is a complex clinical syndrome caused by various cardiovascular diseases. Its main pathogenesis includes cardiomyocyte loss, myocardial energy metabolism disorder, and activation of cardiac inflammation. Due to the clinically unsatisfactory treatment of heart failure, different mechanisms need to be explored to provide new targets for the treatment of this disease. Proprotein convertase subtilisin/kexin type 9 (PCSK9), a gene mainly related to familial hypercholesterolemia, was discovered in 2003. Aside from regulating lipid metabolism, PCSK9 may be involved in other biological processes such as apoptosis, autophagy, pyroptosis, inflammation, and tumor immunity and related to diabetes and neurodegenerative diseases. Recently, clinical data have shown that the circulating PCSK9 level is significantly increased in patients with heart failure, and it is related to the prognosis for heart failure. Furthermore, in animal models and patients with myocardial infarction, PCSK9 in the infarct margin area was also found to be significantly increased, which further suggested that PCSK9 might be closely related to heart failure. However, the specific mechanism of how PCSK9 participates in heart failure remains to be further explored. The purpose of this review is to summarize the potential mechanism of PCSK9's involvement in heart failure, thereby providing a new treatment strategy for heart failure.

Metoprolol Protects Against Arginine Vasopressin-Induced Cellular Senescence in H9C2 Cardiomyocytes by Regulating the Sirt1/p53/p21 Axis

Cardiomyocyte senescence is involved in the pathological mechanism of cardiac diseases. Metoprolol is a β1 receptor blocker used for the treatment of hypertension. Recent studies show that Metoprolol can protect cardiomyocytes against ischemia injury. The present study aims to investigate the protective effects of Metoprolol against arginine vasopressin (AVP)-induced cellular senescence in cultured cardiomyocytes. The cell proliferation assay and cytotoxicity lactate dehydrogenase assay showed that the highest tolerated dosage of Metoprolol in H9C2 cardiomyocytes was optimized as 10 µM. The enzyme-linked immunosorbent assay showed that Metoprolol significantly ameliorated the elevated level of the DNA oxidation product 8-hydroxy-2 deoxyguanosine. Metoprolol also decreased the percentage of senescence-associated β-galactosidase positive cells and improved the telomerase activity under AVP exposure. Moreover, treatment with Metoprolol ameliorated the decreased intracellular nicotinamide phosphoribosyltransferase activity, nicotinamide adenine dinucleotide/nicotinamide adenine dinucleotide phosphate (NAD⁺/NADPH) ratio, and Sirtuin1 activity in cardiomyocytes by AVP. Finally, Metoprolol was able to downregulate the AVP-induced expression of acetylated p53 and p21. Taken together, our data reveal that Metoprolol protected the cardiomyocytes from AVP-induced senescence.

Ethnic similarities in genetic polymorphisms associated with atrial fibrillation: Far East Asian vs European populations

BACKGROUND

In European ancestry, 111 genetic loci were identified as associated with atrial fibrillation (AF). We explored the reproducibility of those single nucleotide polymorphisms (SNPs) in a genome-wide association study (GWAS) meta-analysis of Far East Asian populations.

METHODS

We performed a meta-analysis of the Korean AF network and Japanese AF data sets (9118 cases and 33 467 controls) by an inverse-variance fixed-effects model. We compared the results with 111 previously reported SNPs proven in Europeans after excluding 36 missing loci and a locus with a minor allelic frequency (MAF) < 0.01 in the European population.

RESULTS

Among remaining 74 loci, 29 loci were replicated at a P < .05, and 17 of those loci were newly found in the Far East Asian population: 3 loci with a P < 5×10^-8 (METTL11B at 1q24, KCNN2 at 5q22 and LRMDA at 10q22), 4 loci at the threshold of the Bonferroni correction of P = 4.5 × 10^-4  ~ 5×10^-8 (KIF3C at 2p23, REEP3, NRBF2 at 10q21, SIRT1, MYPN at 10q21 and CFL2 at 14q13) and 10 SNPs with a P = .05 ~ 4.5 × 10^-4 . Among 18 AF loci with a MAF< 0.01 in the Far East Asian populations, 2 loci (GATA4 at 8q23 and SGCG at 13q12) were replicated after a fine mapping. Twenty-seven AF loci, including a locus, which had a sufficient sample size to get a power of over 80% (with a type 1 error α = 4.5 × 10^-4 ), were not replicated in the Far East Asian populations.

CONCLUSIONS

We newly replicated 19 AF-associated genetic loci in the European descent among the Far East Asian populations. It highlights the extensive sharing of AF genetic risks across Far East Asian populations.

CELF1 promotes vascular endothelial growth factor degradation resulting in impaired microvasculature in heart failure

Vascular rarefaction due to impaired angiogenesis is associated with contractile dysfunction and the transition from compensation to decompensation and heart failure. The regulatory mechanism controlling vascular rarefaction during the transition remains elusive. Increased expression of a nuclear RNA-binding protein CUGBP Elav-like family member 1 (CELF1) in the adult heart is associated with the transition from compensated hypertrophy to decompensated heart failure. Elevated CELF1 level resulted in degradation of the major cardiac gap junction protein, connexin 43, in dilated cardiomyopathy (DCM), the most common cause of heart failure. In the present study, we investigated the role of increased CELF1 expression in causing vascular rarefaction in DCM. CELF1 overexpression (CELF1-OE) in cardiomyocytes resulted in reduced capillary density. CELF1-OE mice administered hypoxyprobe showed immunoreactivity and increased mRNA levels of HIF1α, Glut-1, and Pdk-1, which suggested the association of a reduced capillary density-induced hypoxic condition with CELF1 overexpression. Vegfa mRNA level was downregulated in mouse hearts exhibiting DCM, including CELF1-OE and infarcted hearts. Vegfa mRNA level was also downregulated to a similar extent in cardiomyocytes isolated from infarcted hearts by Langendorff preparation, which suggested cardiomyocyte-derived Vegfa expression mediated by CELF1. Cardiomyocyte-specific depletion of CELF1 preserved the capillary density and Vegfa mRNA level in infarcted mouse hearts. Also, CELF1 bound to Vegfa mRNA and regulated Vegfa mRNA stability via the 3' untranslated region. These results suggest that elevated CELF1 level has dual effects on impairing the functions of cardiomyocytes and microvasculature in DCM.

Application of mesenchymal stem cell therapy for aging frailty: from mechanisms to therapeutics

Aging frailty is a complex geriatric syndrome that becomes more prevalent with advancing age. It constitutes a major health problem due to frequent adverse outcomes. Frailty is characterized by disruption of physiological homeostasis and progressive decline of health status. Multiple factors contribute to development of frailty with advancing age, including genome instability, DNA damage, epigenetic alternations, stem cell exhaustion, among others. These interrelated factors comprehensively result in loss of tissue homeostasis and diminished reserve capacity in frailty. Therefore, the aged organism gradually represents symptoms of frailty with decline in physiological functions of organs. Notably, the brain, cardiovascular system, skeletal muscle, and endocrine system are intrinsically interrelated to frailty. The patients with frailty may display the diminished reserves capacity of organ systems. Due to the complex pathophysiology, no specific treatments have been approved for prevention of this syndrome. At such, effective strategies for intervening in pathogenic process to improve health status of frail patients are highly needed. Recent progress in cell-based therapy has greatly contributed to the amelioration of degenerative diseases related to age. Mesenchymal stem cells (MSCs) can exert regenerative effects and possess anti-inflammatory properties. Transplantation of MSCs represents as a promising therapeutic strategy to address the pathophysiologic problems of frail syndrome. Currently, MSC therapy have undergone the phase I and II trials in human subjects that have endorsed the safety and efficacy of MSCs for aging frailty. However, despite these positive results, caution is still needed with regard to potential to form tumors, and further large-scale studies are warranted to confirm the therapeutic efficacy of MSC therapy.

Extracellular vesicle interplay in cardiovascular pathophysiology

Extracellular vesicles (EVs) are nanosized lipid bilayer-delimited particles released from cells that mediate intercellular communications and play a pivotal role in various physiological and pathological processes. Subtypes of EVs may include plasma membrane ectosomes or microvesicles and endosomal origin exosomes, although functional distinctions remain unclear. EVs carry cargo proteins, nucleic acids (RNA and DNA), lipids, and metabolites. By presenting or transferring this cargo to recipient cells, EVs can trigger cellular responses. We summarize contemporary understanding of EV biogenesis, composition, and function, with an emphasis on the role of EVs in the cardiovascular system. In addition, we outline the functional relevance of EVs in cardiovascular pathophysiology, further highlighting their potential for diagnostic and therapeutic applications.

Scoparone alleviates Ang II-induced pathological myocardial hypertrophy in mice by inhibiting oxidative stress

Long‐term poorly controlled myocardial hypertrophy often leads to heart failure and sudden death. Activation of ras‐related C3 botulinum toxin substrate 1 (RAC1) by angiotensin II (Ang II) plays a pivotal role in myocardial hypertrophy. Previous studies have demonstrated that scoparone (SCO) has beneficial effects on hypertension and extracellular matrix remodelling. However, the function of SCO on Ang II‐mediated myocardial hypertrophy remains unknown. In our study, a mouse model of myocardial hypertrophy was established by Ang II infusion (2 mg/kg/day) for 4 weeks, and SCO (60 mg/kg bodyweight) was administered by gavage daily. In vitro experiments were also performed. Our results showed that SCO could alleviate Ang II infusion‐induced cardiac hypertrophy and fibrosis in mice. In vitro, SCO treatment blocks Ang II‐induced cardiomyocyte hypertrophy, cardiac fibroblast collagen synthesis and differentiation to myofibroblasts. Meanwhile, we found that SCO treatment blocked Ang II‐induced oxidative stress in cardiomyocytes and cardiac fibroblasts by inhibiting RAC1‐GTP and total RAC1 in vivo and in vitro. Furthermore, reactive oxygen species (ROS) burst by overexpression of RAC1 completely abolished SCO‐mediated protection in cardiomyocytes and cardiac fibroblasts in vitro. In conclusion, SCO, an antioxidant, may attenuate Ang II‐induced myocardial hypertrophy by suppressing of RAC1 mediated oxidative stress.

Capillary Rarefaction in Obesity and Metabolic Diseases-Organ-Specificity and Possible Mechanisms

Obesity and its comorbidities like diabetes, hypertension and other cardiovascular disorders are the leading causes of death and disability worldwide. Metabolic diseases cause vascular dysfunction and loss of capillaries termed capillary rarefaction. Interestingly, obesity seems to affect capillary beds in an organ-specific manner, causing morphological and functional changes in some tissues but not in others. Accordingly, treatment strategies targeting capillary rarefaction result in distinct outcomes depending on the organ. In recent years, organ-specific vasculature and endothelial heterogeneity have been in the spotlight in the field of vascular biology since specialized vascular systems have been shown to contribute to organ function by secreting varying autocrine and paracrine factors and by providing niches for stem cells. This review summarizes the recent literature covering studies on organ-specific capillary rarefaction observed in obesity and metabolic diseases and explores the underlying mechanisms, with multiple modes of action proposed. It also provides a glimpse of the reported therapeutic perspectives targeting capillary rarefaction. Further studies should address the reasons for such organ-specificity of capillary rarefaction, investigate strategies for its prevention and reversibility and examine potential signaling pathways that can be exploited to target it.

Identification of Potentially Relevant Genes for Excessive Exercise-Induced Pathological Cardiac Hypertrophy in Zebrafish

Exercise-induced cardiac remodeling has aroused public concern for some time, as sudden cardiac death is known to occur in athletes; however, little is known about the underlying mechanism of exercise-induced cardiac injury. In the present study, we established an excessive exercise-induced pathologic cardiac hypertrophy model in zebrafish with increased myocardial fibrosis, myofibril disassembly, mitochondrial degradation, upregulated expression of the pathological hypertrophy marker genes in the heart, contractile impairment, and cardiopulmonary function impairment. High-throughput RNA-seq analysis revealed that the differentially expressed genes were enriched in the regulation of autophagy, protein folding, and degradation, myofibril development, angiogenesis, metabolic reprogramming, and insulin and FoxO signaling pathways. FOXO proteins may be the core mediator of the regulatory network needed to promote the pathological response. Further, PPI network analysis showed that pik3c3, gapdh, fbox32, fzr1, ubox5, lmo7a, kctd7, fbxo9, lonrf1l, fbxl4, nhpb2l1b, nhp2, fbl, hsp90aa1.1, snrpd3l, dhx15, mrto4, ruvbl1, hspa8b, and faub are the hub genes that correlate with the pathogenesis of pathological cardiac hypertrophy. The underlying regulatory pathways and cardiac pressure-responsive molecules identified in the present study will provide valuable insights for the supervision and clinical treatment of pathological cardiac hypertrophy induced by excessive exercise.

LCZ696 Ameliorates Oxidative Stress and Pressure Overload-Induced Pathological Cardiac Remodeling by Regulating the Sirt3/MnSOD Pathway

Aims

We aimed to investigate whether LCZ696 protects against pathological cardiac hypertrophy by regulating the Sirt3/MnSOD pathway.

Methods

In vivo, we established a transverse aortic constriction animal model to establish pressure overload-induced heart failure. Subsequently, the mice were given LCZ696 by oral gavage for 4 weeks. After that, the mice underwent transthoracic echocardiography before they were sacrificed. In vitro, we introduced phenylephrine to prime neonatal rat cardiomyocytes and small-interfering RNA to knock down Sirt3 expression.

Results

Pathological hypertrophic stimuli caused cardiac hypertrophy and fibrosis and reduced the expression levels of Sirt3 and MnSOD. LCZ696 alleviated the accumulation of oxidative reactive oxygen species (ROS) and cardiomyocyte apoptosis. Furthermore, Sirt3 deficiency abolished the protective effect of LCZ696 on cardiomyocyte hypertrophy, indicating that LCZ696 induced the upregulation of MnSOD and phosphorylation of AMPK through a Sirt3-dependent pathway.

Conclusions

LCZ696 may mitigate myocardium oxidative stress and apoptosis in pressure overload-induced heart failure by regulating the Sirt3/MnSOD pathway.

Genome-wide translational reprogramming of genes important for myocyte functions in overload-induced heart failure

Genome-wide changes in gene translational efficiency during the development of heart failure are poorly understood. We tested the hypothesis that aberrant changes in translational efficiency of cardiac genes are associated with the development of myocyte decompensation in response to persistent stress stimuli. We demonstrated that chronic pressure overload in mice resulted in a genome-wide reprogramming of translational efficiency, with >50% of the translatome exhibiting decreased translational efficiencies during the transition from myocardial compensation to decompensation. Importantly, these translationally repressed genes included those involved in angiogenesis and energy metabolism. Moreover, we showed that the stress-induced translational reprogramming was accompanied by persistent activation of the eukaryotic initiation factor 2α (eIF2α)-mediated stress response pathway. Counteracting the endogenous eIF2α functions by cardiac-specific overexpression of an eIF2α-S51A mutant ameliorated the development of myocyte decompensation, with concomitant improvements in translation of cardiac functional genes and increases in angiogenic responses. These data suggest that the mismatch between transcription and translation of the cardiac genes with essential functions may represent a novel molecular mechanism underlying the development of myocyte decompensation in response to chronic stress stimuli, and the eIF2α pathway may be a viable therapeutic target for recovering the optimal translation of the repressed cardiac genes.

Clinical findings of gadolinium-enhanced cardiac magnetic resonance in Fabry patients

BACKGROUND

Fabry disease is one of the causes of left ventricular hypertrophy (LVH) and can be treated with enzyme replacement therapy or pharmacological chaperone therapy. Late gadolinium enhancement (LGE) in cardiac magnetic resonance (CMR) can identify myocardial fibrosis and be used for the stratification in LVH. However, the details of the prevalence and characteristics of LGE in Japanese Fabry patients have not been reported.

METHODS

We evaluated myocardial involvement in 26 Fabry patients (10 males, 16 females) using gadolinium-enhanced CMR. LGE areas were analyzed using the previously reported scoring method. Echocardiography was also performed to evaluate the left ventricular function and left ventricular mass.

RESULTS

LGE on CMR images was positive in 5 out of 26 patients, and all patients with LGE-positive findings suffered from LVH (2 out of 5 male patients and 3 out of 4 female patients with LVH on echocardiography). LGE was specifically localized at the mid-wall in the infero-lateral area of the left ventricle. LGE-positive patients seemed to be older, and tended to have a larger left ventricular mass index and higher B-type natriuretic peptide level than LGE-negative patients.

CONCLUSIONS

These results revealed that specific localization of LGE was present in Fabry patients.

Overview of the 83rd Annual Scientific Meeting of the Japanese Circulation Society - Renaissance of Cardiology for the Creation of Future Medicine

The 83^rdAnnual Scientific Meeting of the Japanese Circulation Society was held in Yokohama, Japan, on March 29-31, 2019, just as the cherry blossoms came into full bloom. Because the environment around cardiovascular healthcare is rapidly changing, it becomes highly important to make a breakthrough at the dawn of a new era. The main theme of this meeting was "Renaissance of Cardiology for the Creation of Future Medicine". The meeting benefited from the participation of 18,825 people, and there were in-depth and extensive discussions at every session, focusing on topics covering clinical and basic research, medical care provision system, human resource development, and public awareness in cardiovascular medicine. The meeting was completed with great success, and we greatly appreciate the tremendous cooperation and support from all affiliates.

Obesity and its cardiovascular effects

Obesity is described in terms of body fat percentage or body mass index (BMI), despite the fact that these measures do not give full insight about the body fat distribution. It is presently a consistently growing universal challenge since it has tripled in the last 10 years, killing approximately 28 million people each year. In this review, we aim to clarify the different results of obesity on the working and physiology of the cardiovascular system and to reveal changes in the obesity "paradox"-a variety of cardiovascular outcomes in typical/overweight people. Central fat build-up in ordinary/overweight populaces has been related to expanded occurrences of myocardial infarction, heart failure, or all-cause mortality when contrasted with the obese populace. These discoveries are additionally clarified as the abundance and prolonged vulnerability to free fatty acids (FFAs) in obesity. This has been believed to cause the myocardial substrate to move from glucose to FFAs digestion, which causes lipid gathering in cardiomyocytes, spilling over to other lean tissues, and prompting a general atherogenic impact. This cardiomyocyte lipid aggregation has been demonstrated to cause insulin resistance and cardiovascular hypertrophy, and to lessen the heart functions in general. There is a proof backing the fact that fat tissue is not only an energy reservoir, it also coordinates hormones and proinflammatory cytokines and deals with the energy transition of the body by putting away abundant lipids in diverse tissues.

Circulating endostatin as a risk factor for cardiovascular events in patients with stable coronary heart disease: A CLARICOR trial sub-study

BACKGROUND AND AIMS

Raised levels of serum endostatin, a biologically active fragment of collagen XVIII, have been observed in patients with ischemic heart disease but association with incident cardiovascular events in patients with stable coronary heart disease is uncertain.

METHODS

The CLARICOR-trial is a randomized, placebo-controlled trial of stable coronary heart disease patients evaluating 14-day treatment with clarithromycin. The primary outcome was a composite of acute myocardial infarction, unstable angina pectoris, cerebrovascular disease or all-cause mortality. In the present sub-study using 10-year follow-up data, we investigated associations between serum endostatin at entry (randomization) and the composite outcome and its components during follow-up. The placebo group was used as discovery sample (1204 events, n = 1998) and the clarithromycin-treated group as replication sample (1220 events, n = 1979).

RESULTS

In Cox regression models adjusting for cardiovascular risk factors, glomerular filtration rate, and current pharmacological treatment, higher serum endostatin was associated with an increased risk of the composite outcome in the discovery sample (hazard ratio per standard deviation increase 1.11, 95% CI 1.03-1.19, p = 0.004), but slightly weaker and not statistically significant in the replication sample (hazard ratio 1.06, 95% CI 1.00-1.14, p = 0.06). In contrast, strong and consistent associations were found between endostatin and cardiovascular and all-cause mortality in all multivariable models and sub-samples. Addition of endostatin to a model with established cardiovascular risk factors provided no substantial improvement of risk prediction (<1%).

CONCLUSIONS

Raised levels of serum endostatin might be associated with cardiovascular events in patients with stable coronary heart disease. The clinical utility of endostatin measurements remains to be established.

The association between circulating endostatin levels and incident myocardial infarction

OBJECTIVE

Increased levels of circulating endostatin have been observed in patients with prevalent ischemic heart disease. However, the association between circulating endostatin, and incident myocardial infarction (MI) is less studied. Our main aim was to study the association between circulating endostatin and incident MI in the community adjusted for established cardiovascular risk factors in men and women.

DESIGN

Circulating endostatin was measured in a nested case control study based on three large community-based Swedish cohorts, including 533 MI cases, and 1003 age-, sex- and cohort-matched controls. Odds ratios (OR) with 95% confidence intervals (CI) were calculated with adjustments for established cardiovascular risk factors.

RESULTS

Higher endostatin was associated with a higher incidence of MI independently of established cardiovascular risk factors (OR 1.19, 95% CI 1.03-1.37, p = .02), but this association was abolished after additional adjustment for C-reactive protein. Sex-stratified analyses suggest that the association was substantially stronger in women as compared to men.

CONCLUSIONS

In our community based sample, higher endostatin predicted incident myocardial infarction predominantly in women but not independently of CRP. Thus, our findings do not support a broad utility of endostatin measurements for the prediction of incident myocardial infarction in clinical practice.

From pediatrics to geriatrics: Mechanisms of heart failure across the life-course

Heart failure (HF) is a significant public health problem and a disease with high 5-year mortality. Although age is the primary risk factor for development of HF, it is a disease which impacts patients of all ages. Historically, HF has been studied as a one-size fits all strategy- with the majority of both clinical and basic science investigations employing adult male subjects or adult male pre-clinical animal models. We postulate that inclusion of biological variables in HF studies is necessary to improve our understanding of mechanisms of HF and improve outcomes. In this review, we will discuss age-specific differences in HF patients, particularly focusing on the pediatric and geriatric age groups. In addition, we will also discuss the biological variable of sex. Characterizing and understanding the mechanistic differences in these distinct HF populations can provide insights that will benefit and personalize therapeutic interventions. Further, we propose that future investigations into the cellular mechanisms involved in the developing and juvenile heart may provide valuable insights for targets that would be beneficial in aging patients.

Interplay of N acetyl cysteine and melatonin in regulating oxidative stress-induced cardiac hypertrophic factors and microRNAs

Early and specific diagnosis of oxidative stress linked diseases as cardiac heart diseases remains a major dilemma for researchers and clinicians. MicroRNAs may serve as a better tool for specific early diagnostics and propose their utilization in future molecular medicines. We aimed to measure the microRNAs expressions in oxidative stress linked cardiac hypertrophic condition induced through stimulants as Endothelin and Isoproterenol. Cardiac hypertrophic animal models were confirmed by BNP, GATA4 expression, histological assays, and increased cell surface area. High oxidative stress (ROS level) and decreased antioxidant activities were assessed in hypertrophied groups. Enhanced expression of miR-152, miR-212/132 while decreased miR-142-3p expression was observed in hypertrophic condition. Similar pattern of these microRNAs was detected in HL-1 cells treated with H₂O₂. Upon administration of antioxidants, the miRNAs expression pattern altered from that of the cardiac hypertrophied model. Present investigation suggests that oxidative stress generated during the cardiac pathology may directly or indirectly regulate anti-hypertrophy pathway elements through microRNAs including antioxidant enzymes, which need further investigation. The down-regulation of free radical scavengers make it easier for the oxidative stress to play a key role in disease progression.

Estrogen receptor beta maintains expression of KLF15 to prevent cardiac myocyte hypertrophy in female rodents

Maintaining a healthy, anti-hypertrophic state in the heart prevents progression to cardiac failure. In humans, angiotensin II (AngII) indirectly and directly stimulates hypertrophy and progression, while estrogens acting through estrogen receptor beta (ERβ) inhibit these AngII actions. The KLF15 transcription factor has been purported to provide anti-hypertrophic action. In cultured neonatal rat cardiomyocytes, we found AngII inhibited KLF1 expression and nuclear localization, substantially prevented by estradiol (E2) or β-LGND2 (β-LGND2), an ERβ agonist. AngII stimulation of transforming growth factor beta expression in the myocytes activated p38α kinase via TAK1 kinase, inhibiting KLF15 expression. All was comparably reduced by E2 or β-LGND2. Knockdown of KLF15 in the myocytes induced myocyte hypertrophy and limited the anti-hypertrophic actions of E2 and β-LGND2. Key aspects were confirmed in an in-vivo model of cardiac hypertrophy. Our findings define additional anti-hypertrophic effects of ERβ supporting testing specific receptor agonists in humans to prevent progression of cardiac disease.

Circulating endostatin and the incidence of heart failure

OBJECTIVE

Circulating levels of endostatin are elevated in many underlying conditions leading to heart failure such as hypertension, diabetes, chronic kidney disease and ischemic heart disease. Yet, the association between endostatin and the incidence of heart failure has not been reported previously in the community.

DESIGN

We investigated the longitudinal association between serum endostatin levels and incident heart failure in two community-based cohorts of elderly: Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS, n = 966; mean age 70 years, 51% women, 81 events, mean follow-up 10 years) and Uppsala Longitudinal Study of Adult Men (ULSAM, n = 747 men; mean age 78 years, 98 heart failure events, mean follow-up 8 years). We also investigated the cross-sectional association between endostatin and echocardiographic left ventricular systolic function and diastolic function (ejection fraction and E/A-ratio, respectively).

RESULTS

Higher serum endostatin was associated with an increased risk for heart failure in both cohorts after adjustment for established heart failure risk factors, glomerular filtration rate and N-terminal pro-brain natriuretic peptide (NT-proBNP) (PIVUS: multivariable hazard ratio (HR) per 1-standard deviation (SD) increase, HR 1.46 (95%CI, 1.17-1.82, p < .001); ULSAM: HR 1.29 (95%CI, 1.00-1.68, p < .05). In cross-sectional analyses at baseline, higher endostatin was significantly associated with both worsened left ventricular systolic and diastolic function in both cohorts. Conclusion Higher serum endostatin was associated with left ventricular dysfunction and an increased heart failure risk in two community-based cohorts of elderly. Our findings encourage further experimental studies that investigate the role of endostatin in the development of heart failure.

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

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

Non-oxidizable HMGB1 induces cardiac fibroblasts migration via CXCR4 in a CXCL12-independent manner and worsens tissue remodeling after myocardial infarction

Myocardial infarction (MI) is a major health burden worldwide. Extracellular High mobility group box 1 (HMGB1) regulates tissue healing after injuries. The reduced form of HMGB1 (fr-HMGB1) exerts chemotactic activity by binding CXCL12 through CXCR4, while the disulfide form, (ds-HMGB1), induces cytokines expression by TLR4. Here, we assessed the role of HMGB1 redox forms and the non-oxidizable mutant (3S) on human cardiac fibroblast (hcFbs) functions and cardiac remodeling after infarction. Among HMGB1 receptors, hcFbs express CXCR4. Fr-HMGB1 and 3S, but not ds-HMGB1, promote hcFbs migration through Src activation, while none of HMGB1 redox forms induces proliferation or inflammatory mediators. 3S is more effective than fr-HMGB1 in stimulating hcFbs migration and Src phosphorylation being active at lower concentrations and in oxidizing conditions. Notably, chemotaxis toward both proteins is CXCR4-dependent but, in contrast to fr-HMGB1, 3S does not require CXCL12 since hcFbs migration persists in the presence of the CXCL12/CXCR4 inhibitor AMD3100 or an anti-CXCL12 antibody. Interestingly, 3S interacts with CXCR4 and induces a different receptor conformation than CXCL12. Mice undergoing MI and receiving 3S exhibit adverse LV remodeling owing to an excessive collagen deposition promoted by a higher number of myofibroblasts. On the contrary, fr-HMGB1 ameliorates cardiac performance enhancing neoangiogenesis and reducing the infarcted area and fibrosis. Altogether, our results demonstrate that non-oxidizable HMGB1 induce a sustained cardiac fibroblasts migration despite the redox state of the environment and by altering CXCL12/CXCR4 axis. This affects proper cardiac remodeling after an infarction.

Hemopexin counteracts systolic dysfunction induced by heme-driven oxidative stress

Heart failure is a leading cause of morbidity and mortality in patients affected by different disorders associated to intravascular hemolysis. The leading factor is the presence of pathologic amount of pro-oxidant free heme in the bloodstream, due to the exhaustion of the natural heme scavenger Hemopexin (Hx). Here, we evaluated whether free heme directly affects cardiac function, and tested the therapeutic potential of replenishing serum Hx for increasing serum heme buffering capacity. The effect of heme on cardiac function was assessed in vitro, on primary cardiomyocytes and H9c2 myoblast cell line, and in vivo, in Hx^-/- mice and in genetic and acquired mouse models of intravascular hemolysis. Purified Hx or anti-oxidants N-Acetyl-L-cysteine and α-tocopherol were used to counteract heme cardiotoxicity. In mice, Hx loss/depletion resulted in heme accumulation and enhanced reactive oxygen species (ROS) production in the heart, which ultimately led to severe systolic dysfunction. Similarly, high ROS reduced systolic Ca²⁺ transient amplitudes and fractional shortening in primary cardiomyocytes exposed to free heme. In keeping with these Ca²⁺ handling alterations, oxidation and CaMKII-dependent phosphorylation of Ryanodine Receptor 2 were higher in Hx^-/- hearts than in controls. Administration of anti-oxidants prevented systolic failure both in vitro and in vivo. Intriguingly, Hx rescued contraction defects of heme-treated cardiomyocytes and preserved cardiac function in hemolytic mice. We show that heme-mediated oxidative stress perturbs cardiac Ca²⁺ homeostasis and promotes contractile dysfunction. Scavenging heme, Hx counteracts cardiac heme toxicity and preserves left ventricular function. Our data generate the rationale to consider the therapeutic use of Hx to limit the cardiotoxicity of free heme in hemolytic disorders.

Cardiac telomere length in heart development, function, and disease

Telomeres are repetitive nucleoprotein structures at chromosome ends, and a decrease in the number of these repeats, known as a reduction in telomere length (TL), triggers cellular senescence and apoptosis. Heart disease, the worldwide leading cause of death, often results from the loss of cardiac cells, which could be explained by decreases in TL. Due to the cell-specific regulation of TL, this review focuses on studies that have measured telomeres in heart cells and critically assesses the relationship between cardiac TL and heart function. There are several lines of evidence that have identified rapid changes in cardiac TL during the onset and progression of heart disease as well as at critical stages of development. There are also many factors, such as the loss of telomeric proteins, oxidative stress, and hypoxia, that decrease cardiac TL and heart function. In contrast, antioxidants, calorie restriction, and exercise can prevent both cardiac telomere attrition and the progression of heart disease. TL in the heart is also indicative of proliferative potential and could facilitate the identification of cells suitable for cardiac rejuvenation. Although these findings highlight the involvement of TL in heart function, there are important questions regarding the validity of animal models, as well as several confounding factors, that need to be considered when interpreting results and planning future research. With these in mind, elucidating the telomeric mechanisms involved in heart development and the transition to disease holds promise to prevent cardiac dysfunction and potentiate regeneration after injury.

The Emerging Role of Metabolomics in the Diagnosis and Prognosis of Cardiovascular Disease

Perturbations in cardiac energy metabolism are major contributors to a number of cardiovascular pathologies. In addition, comorbidities associated with cardiovascular disease (CVD) can alter systemic and myocardial metabolism, often contributing to the worsening of cardiac function and health outcomes. State-of-the-art metabolomic technologies give us the ability to measure thousands of metabolites in biological fluids or biopsies, providing us with a metabolic fingerprint of individual patients. These metabolic profiles may serve as diagnostic and/or prognostic tools that have the potential to significantly alter the management of CVD. Herein, the authors review how metabolomics can assist in the interpretation of perturbed metabolic processes, and how this has improved our ability to understand the pathology of ischemic heart disease, atherosclerosis, and heart failure. Taken together, the integration of metabolomics with other "omics" platforms will allow us to gain insight into pathophysiological interactions of metabolites, proteins, genes, and disease states, while advancing personalized medicine.

Cardiac damage in athlete’s heart: When the “supernormal” heart fails!

Intense exercise may cause heart remodeling to compensate increases in blood pressure or volume by increasing muscle mass. Cardiac changes do not involve only the left ventricle, but all heart chambers. Physiological cardiac modeling in athletes is associated with normal or enhanced cardiac function, but recent studies have documented decrements in left ventricular function during intense exercise and the release of cardiac markers of necrosis in athlete’s blood of uncertain significance. Furthermore, cardiac remodeling may predispose athletes to heart disease and result in electrical remodeling, responsible for arrhythmias. Athlete’s heart is a physiological condition and does not require a specific treatment. In some conditions, it is important to differentiate the physiological adaptations from pathological conditions, such as hypertrophic cardiomyopathy, arrhythmogenic dysplasia of the right ventricle, and non-compaction myocardium, for the greater risk of sudden cardiac death of these conditions. Moreover, some drugs and performance-enhancing drugs can cause structural alterations and arrhythmias, therefore, their use should be excluded.

Let-7a Is an Antihypertrophic Regulator in the Heart via Targeting Calmodulin

Background: MicroRNAs (miRNAs) have been emerged as important regulator in a multiple of cardiovascular disease, including arrhythmia, cardiac hypertrophy and fibrosis, and myocardial infarction. The aim of this study was to investigate whether miRNA let-7a has antihypertrophic effects in angiotensin II (AngII)-induced cardiac hypertrophy.

Methods: Neonatal rat ventricular myocytes (NRVMs) were exposed to AngII for 36 h as a cellular model of hypertrophy; subcutaneous injection of AngII for 2 weeks was used to establish a mouse model of cardiac hypertrophy in vivo study. Cell surface area (CSA) was measured by immunofluorescence cytochemistry; expression of hypertrophy-related genes ANP, BNP, β-MHC was detected by Real-time PCR; luciferase activity assay was performed to confirm the miRNA's binding site in the calmodulin (CaM) gene; CaM protein was detected by Western blot; the hypertrophy parameters were measured by echocardiographic assessment.

Results: The expression of let-7a was decreased in AngII-induced cardiac hypertrophy in vitro and in vivo. Overexpression of let-7a attenuated AngII-induced increase of cell surface area and repressed the increased mRNA levels of ANP, BNP and β-MHC. Dual-luciferase reporter assay showed that let-7a could bind to the 3'UTR of CaM 1 gene. Let-7a downregulated the expression of CaM protein. In vivo, let-7a produced inhibitory effects on cardiac hypertrophy, including the downregulation of cross-sectional area of cardiomyocytes in mouse heart, the reduction of IVSD and LVPWD, the suppression of hypertrophy marker genes ANP, BNP, β-MHC mRNA level, and the downregulation of CaM protein level.

Conclusions: let-7a possesses a prominent anti-hypertrophic property by targeting CaM genes. The findings provide new insight into molecular mechanism of cardiac hypertrophy.

Early transcriptional changes in cardiac mitochondria during chronic doxorubicin exposure and mitigation by dexrazoxane in mice

Identification of early biomarkers of cardiotoxicity could help initiate means to ameliorate the cardiotoxic actions of clinically useful drugs such as doxorubicin (DOX). Since DOX has been shown to target mitochondria, transcriptional levels of mitochondria-related genes were evaluated to identify early candidate biomarkers in hearts of male B6C3F1 mice given a weekly intravenous dose of 3mg/kg DOX or saline (SAL) for 2, 3, 4, 6, or 8 weeks (6, 9, 12, 18, or 24 mg/kg cumulative DOX doses, respectively). Also, a group of mice was pretreated (intraperitoneally) with the cardio-protectant, dexrazoxane (DXZ; 60 mg/kg) 30 min before each weekly dose of DOX or SAL. At necropsy a week after the last dose, increased plasma concentrations of cardiac troponin T (cTnT) were detected at 18 and 24 mg/kg cumulative DOX doses, whereas myocardial alterations were observed only at the 24 mg/kg dose. Of 1019 genes interrogated, 185, 109, 140, 184, and 451 genes were differentially expressed at 6, 9, 12, 18, and 24 mg/kg cumulative DOX doses, respectively, compared to concurrent SAL-treated controls. Of these, expression of 61 genes associated with energy metabolism and apoptosis was significantly altered before and after occurrence of myocardial injury, suggesting these as early genomics markers of cardiotoxicity. Much of these DOX-induced transcriptional changes were attenuated by pretreatment of mice with DXZ. Also, DXZ treatment significantly reduced plasma cTnT concentration and completely ameliorated cardiac alterations induced by 24 mg/kg cumulative DOX. This information on early transcriptional changes during DOX treatment may be useful in designing cardioprotective strategies targeting mitochondria.

HypoxamiRs: regulators of cardiac hypoxia and energy metabolism

Hypoxia and its intricate regulation are at the epicenter of cardiovascular research. Mediated by hypoxia-inducible factors as well as by several microRNAs, recently termed 'hypoxamiRs', hypoxia affects several cardiac pathophysiological processes. Hypoxia is the driving force behind the regulation of the characteristic metabolic switch from predominant fatty acid oxidation in the healthy heart to glucose utilization in the failing myocardium, but also instigates reactivation of the fetal gene program, induces the cardiac hypertrophy response, alters extracellular matrix composition, influences mitochondrial biogenesis, and impacts upon myocardial contractility. HypoxamiR regulation adds a new level of complexity to this multitude of hypoxia-mediated effects, rendering the understanding of the hypoxic response a fundamental piece in solving the cardiovascular disease puzzle.

The antioxidant compound tert-butylhydroquinone activates Akt in myocardium, suppresses apoptosis and ameliorates pressure overload-induced cardiac dysfunction

Tert-butylhydroquinone (TBHQ) is an antioxidant compound which shows multiple cytoprotective actions. We evaluated the effects of TBHQ on pathological cardiac remodeling and dysfunction induced by chronic overload. Pressure overload was created by transverse aortic constriction (TAC) in male C57BL/6 mice. TBHQ was incorporated in the diet and administered for 4 weeks. TBHQ treatment prevented left ventricular dilatation and cardiac dysfunction induced by TAC, and decreased the prevalence of myocardial apoptosis. The beneficial effects of TBHQ were associated with an increase in Akt activation, but not related to activations of Nrf2 or AMP-activated protein kinase. TBHQ-induced Akt activation was accompanied by increased phosphorylation of Bad, glycogen synthase kinase-3β (GSK-3β) and mammalian target of rapamycin (mTOR). Mechanistically, we showed that in cultured H9c2 cells and primary cardiac myocytes, TBHQ stimulated Akt phosphorylation and suppressed oxidant-induced apoptosis; this effect was abolished by wortmannin or an Akt inhibitor. Blockade of the Akt pathway in vivo accelerated cardiac dysfunction, and abrogated the protective effects of TBHQ. TBHQ also reduced the reactive aldehyde production and protein carbonylation in stressed myocardium. We suggest that TBHQ treatment may represent a novel strategy for timely activation of the cytoprotective Akt pathway in stressed myocardium.

Epigenetic regulation by histone demethylases in hypoxia

The response to hypoxia is primarily mediated by the hypoxia-inducible transcription factor (HIF). Levels of HIF are regulated by the oxygen-sensing HIF hydroxylases, members of the 2-oxoglutarate (2OG) dependent oxygenase family. JmjC-domain containing histone lysine demethylases (JmjC-KDMs), also members of the 2OG oxygenase family, are key epigenetic regulators that modulate the methylation levels of histone tails. Kinetic studies of the JmjC-KDMs indicate they could also act in an oxygen-sensitive manner. This may have important implications for epigenetic regulation in hypoxia. In this review we examine evidence that the levels and activity of JmjC-KDMs are sensitive to oxygen availability, and consider how this may influence their roles in early development and hypoxic disease states including cancer and cardiovascular disease.

Canopy 2 attenuates the transition from compensatory hypertrophy to dilated heart failure in hypertrophic cardiomyopathy

AIMS

A mismatch between adequate angiogenesis and overgrowth of myocytes may be a critical mechanism controlling the transition from adaptive hypertrophy to heart failure. Canopy 2 (CNPY2) was recently identified as a secreted, HIF-1α-regulated angiogenic growth factor. As angiogenic factors play important roles in the development of myocardial hypertrophy, we investigated the role of CNPY2 in molecular and functional changes during development of chronic heart failure using cardiac-specific transgenic (TG) mice that overexpress human CNPY2.

METHODS AND RESULTS

We generated TG mice that constitutively express CNPY2 in the myocardium. Cardiomyopathy was induced in TG and wild-type (WT) mice by transverse aortic constriction (TAC). WT mice developed significant ventricular hypertrophy at 4 weeks and severe dilatation and heart failure at 12 weeks after TAC. However, TG mice preserved much better cardiac structure and function, with less severe ventricular dilatation and markedly reduced cardiac apoptosis and fibrosis following TAC. Excess CNPY2 in TG mice prevented significant loss of vasculature up to 12 weeks after TAC injury, resulting in a better local myocardial environment that facilitated myocyte survival and prevented excessive matrix remodelling compared with WT mice. TG mice had less accumulation of endogenous tumor suppressor p53 after TAC, indicating intrinsic activation of the p53-mediated repression of HIF-1α, and Cnpy2 was diminished in TG mice compared with WT controls.

CONCLUSION

Our study showed a correlation between downregulation of endogenous mouse Cnpy2 and p53-mediated HIF-1α inhibition during late-stage hypertrophic development. Additional CNPY2 attenuated the transition from compensatory hypertrophic response to maladaptive ventricular dilatation and heart failure.

Taxifolin protects against cardiac hypertrophy and fibrosis during biomechanical stress of pressure overload

Cardiac hypertrophy is a key pathophysiological component to biomechanical stress, which has been considered to be an independent and predictive risk factor for adverse cardiovascular events. Taxifolin (TAX) is a typical plant flavonoid, which has long been used clinically for treatment of cardiovascular and cerebrovascular diseases. However, very little is known about whether TAX can influence the development of cardiac hypertrophy. In vitro studies, we found that TAX concentration-dependently inhibited angiotensin II (Ang II) induced hypertrophy and protein synthesis in cardiac myocytes. Then we established a mouse model by transverse aortic constriction (TAC) to further confirm our findings. It was demonstrated that TAX prevented pressure overload induced cardiac hypertrophy in mice, as assessed by ventricular mass/body weight, echocardiographic parameters, myocyte cross-sectional area, and the expression of ANP, BNP and β-MHC. The excess production of reactive oxygen species (ROS) played critical role in the development of cardiac hypertrophy. TAX arrested oxidative stress and decreased the expression of 4-HNE induced by pressure overload. Moreover, TAX negatively modulated TAC-induced phosphorylation of ERK1/2 and JNK1/2. Further studies showed that TAX significantly attenuated left ventricular fibrosis and collagen synthesis through abrogating the phosphorylation of Smad2 and Smad2/3 nuclear translocation. These results demonstrated that TAX could inhibit cardiac hypertrophy and attenuate ventricular fibrosis after pressure overload. These beneficial effects were at least through the inhibition of the excess production of ROS, ERK1/2, JNK1/2 and Smad signaling pathways. Therefore, TAX might be a potential candidate for the treatment of cardiac hypertrophy and fibrosis.

miR-185 plays an anti-hypertrophic role in the heart via multiple targets in the calcium-signaling pathways

MicroRNA (miRNA) is an endogenous non-coding RNA species that either inhibits RNA translation or promotes degradation of target mRNAs. miRNAs often regulate cellular signaling by targeting multiple genes within the pathways. In the present study, using Gene Set Analysis, a useful bioinformatics tool to identify miRNAs with multiple target genes in the same pathways, we identified miR-185 as a key candidate regulator of cardiac hypertrophy. Using a mouse model, we found that miR-185 was significantly down-regulated in myocardial cells during cardiac hypertrophy induced by transverse aortic constriction. To confirm that miR-185 is an anti-hypertrophic miRNA, genetic manipulation studies such as overexpression and knock-down of miR-185 in neonatal rat ventricular myocytes were conducted. The results showed that up-regulation of miR-185 led to anti-hypertrophic effects, while down-regulation led to pro-hypertrophic effects, suggesting that miR-185 has an anti-hypertrophic role in the heart. Our study further identified Camk2d, Ncx1, and Nfatc3 as direct targets of miR-185. The activity of Nuclear Factor of Activated T-cell (NFAT) and calcium/calmodulin-dependent protein kinase II delta (CaMKIIδ) was negatively regulated by miR-185 as assessed by NFAT-luciferase activity and western blotting. The expression of phospho-phospholamban (Thr-17), a marker of CaMKIIδ activity, was also significantly reduced by miR-185. In conclusion, miR-185 effectively blocked cardiac hypertrophy signaling through multiple targets, rendering it a potential drug target for diseases such as heart failure.

The role of mAKAPβ in the process of cardiomyocyte hypertrophy induced by angiotensin II

Angiotensin II (AngII) is the central product of the renin-angiotensin system (RAS) and this octapeptide contributes to the pathophysiology of cardiac hypertrophy and remodeling. mAKAPβ is an A-kinase anchoring protein (AKAP) that has the function of binding to the regulatory subunit of protein kinase A (PKA) and confining the holoenzyme to discrete locations within the cell. In this study, we aimed to investigate the role of mAKAPβ in AngII‑induced cardiomyocyte hypertrophy and the possible mechanisms involved. Cultured cardiomyocytes from neonatal rats were treated with AngII. Subsequently, the morphology of the cardiomyocytes was observed and the expression of mAKAPβ and cardiomyocyte hypertrophic markers was measured. mAKAPβ‑shRNA was constructed for RNA interference; the expression of mAKAPβ and hypertrophic markers, the cell surface area and the [3H]Leucine incorporation rate in the AngII‑treated rat cardiomyocytes were detected following RNA interference. Simultaneously, changes in the expression levels of phosphorylated extracellular signal-regulated kinase (p-ERK)2 in the cardiomyocytes were assessed. The cell size of the AngII-treated cardiaomyocytes was significantly larger than that of the untreated cardiomyocytes. The expression of hypertrophic markers and p-ERK2, the cell surface area and the [3H]Leucine incorporation rate were all significantly increased in the AngII‑treated cells. However, the expression of mAKAPβ remained unaltered in this process. RNA interference simultaneously inhibited the protein expression of mAKAPβ and p‑ERK2, and the hypertrophy of the cardiomyocytes induced by AngII was attenuated. These results demonstrate that AngII induces hypertrophy in cardiomyocytes, and mAKAPβ is possibly involved in this process. The effects of mAKAPβ on AngII‑induced cardiomyocyte hypertrophy may be associated with p-ERK2 expression.

Pathologic function and therapeutic potential of exosomes in cardiovascular disease

The heart is a very complex conglomeration of organized interactions between various different cell types that all aid in facilitating myocardial function through contractility, sufficient perfusion, and cell-to-cell reception. In order to make sure that all features of the heart work effectively, it is imperative to have a well-controlled communication system among the different types of cells. One of the most important ways that the heart regulates itself is by the use of extracellular vesicles, more specifically, exosomes. Exosomes are types of nano-vesicles, naturally released from living cells. They are believed to play a critical role in intercellular communication through the means of certain mechanisms including direct cell-to-cell contact, long-range signals as well as electrical and extracellular chemical molecules. Exosomes contain many unique features like surface proteins/receptors, lipids, mRNAs, microRNAs, transcription factors and other proteins. Recent studies indicate that the exosomal contents are highly regulated by various stress and disease conditions, in turn reflective of the parent cell status. At present, exosomes are well appreciated to be involved in the process of tumor and infection disease. However, the research on cardiac exosomes is just emerging. In this review, we summarize recent findings on the pathologic effects of exosomes on cardiac remodeling under stress and disease conditions, including cardiac hypertrophy, peripartum cardiomyopathy, diabetic cardiomyopathy and sepsis-induced cardiovascular dysfunction. In addition, the cardio-protective effects of stress-preconditioned exosomes and stem cell-derived exosomes are also summarized. Finally, we discuss how to epigenetically reprogram exosome contents in host cells which makes them beneficial for the heart.

Cardiac fibroblast-derived microRNA passenger strand-enriched exosomes mediate cardiomyocyte hypertrophy

In response to stress, the heart undergoes extensive cardiac remodeling that results in cardiac fibrosis and pathological growth of cardiomyocytes (hypertrophy), which contribute to heart failure. Alterations in microRNA (miRNA) levels are associated with dysfunctional gene expression profiles associated with many cardiovascular disease conditions; however, miRNAs have emerged recently as paracrine signaling mediators. Thus, we investigated a potential paracrine miRNA crosstalk between cardiac fibroblasts and cardiomyocytes and found that cardiac fibroblasts secrete miRNA-enriched exosomes. Surprisingly, evaluation of the miRNA content of cardiac fibroblast-derived exosomes revealed a relatively high abundance of many miRNA passenger strands ("star" miRNAs), which normally undergo intracellular degradation. Using confocal imaging and coculture assays, we identified fibroblast exosomal-derived miR-21_3p (miR-21*) as a potent paracrine-acting RNA molecule that induces cardiomyocyte hypertrophy. Proteome profiling identified sorbin and SH3 domain-containing protein 2 (SORBS2) and PDZ and LIM domain 5 (PDLIM5) as miR-21* targets, and silencing SORBS2 or PDLIM5 in cardiomyocytes induced hypertrophy. Pharmacological inhibition of miR-21* in a mouse model of Ang II-induced cardiac hypertrophy attenuated pathology. These findings demonstrate that cardiac fibroblasts secrete star miRNA-enriched exosomes and identify fibroblast-derived miR-21* as a paracrine signaling mediator of cardiomyocyte hypertrophy that has potential as a therapeutic target.

Whole-genome profiling highlights the molecular complexity underlying eccentric cardiac hypertrophy

OBJECTIVES

Heart failure is typically preceded by myocardial hypertrophy and remodeling, which can be concentric due to pressure overload (PO), or eccentric because of volume overload (VO). The molecular mechanisms that underlie these differing patterns of hypertrophy are distinct and have yet to be fully elucidated. Thus, the goal of this work is to identify novel therapeutic targets for cardiovascular conditions marked by hypertrophy that have previously been resistant to medical treatment, such as a pure VO.

METHODS

Concentric or eccentric hypertrophy was induced in rats for 2 weeks with transverse aortic constriction (TAC) or aortocaval fistula (ACF), respectively. Hemodynamic and echocardiographic analysis were used to assess the development of left ventricular (LV) hypertrophy and functional differences between groups. Changes in gene expression were determined by microarray and further characterized with Ingenuity Pathway Analysis.

RESULTS

Both models of hypertrophy increased LV mass. Rats with TAC demonstrated concentric LV remodeling while rats with ACF exhibited eccentric LV remodeling. Microarray analysis associated eccentric remodeling with a more extensive alteration of gene expression compared with concentric remodeling. Rats with VO had a marked activation of extracellular matrix genes, promotion of cell cycle genes, downregulation of genes associated with oxidative metabolism, and dysregulation of genes critical to cardiac contractile function. Rats with PO demonstrated similar categorical changes, but with the involvement of fewer individual genes.

CONCLUSIONS

Our results indicate that eccentric remodeling is a far more complex process than concentric remodeling. This study highlights the importance of several key biological functions early in the course of VO, including regulation of matrix, metabolism, cell proliferation, and contractile function. Thus, the results of this analysis will inform the ongoing search for new treatments to prevent the progression to heart failure in VO.

CD4+ T cells promote the transition from hypertrophy to heart failure during chronic pressure overload

BACKGROUND

The mechanisms by which the heart adapts to chronic pressure overload, producing compensated hypertrophy and eventually heart failure (HF), are still not well defined. We aimed to investigate the involvement of T cells in the progression to HF using a transverse aortic constriction (TAC) model.

METHODS AND RESULTS

Chronic HF was associated with accumulation of T lymphocytes and activated/effector CD4(+) T cells within cardiac tissue. After TAC, enlarged heart mediastinal draining lymph nodes showed a high density of both CD4(+) and CD8(+) T-cell subsets. To investigate the role of T cells in HF, TAC was performed on mice deficient for recombination activating gene 2 expression (RAG2KO) lacking B and T lymphocytes. Compared with wild-type TAC mice, RAG2KO mice did not develop cardiac dilation and showed improved contractile function and blunted adverse remodeling. Reconstitution of the T-cell compartment into RAG2KO mice before TAC enhanced contractile dysfunction, fibrosis, collagen accumulation, and cross-linking. To determine the involvement of a specific T-cell subset, we performed TAC on mice lacking CD4(+) (MHCIIKO) and CD8(+) T-cell subsets (CD8KO). In contrast to CD8KO mice, MHCIIKO mice did not develop ventricular dilation and dysfunction. MHCIIKO mice also displayed very low fibrosis, collagen accumulation, and cross-linking within cardiac tissue. Interestingly, mice with transgenic CD4(+) T-cell receptor specific for ovalbumin failed to develop HF and adverse remodeling.

CONCLUSIONS

These results demonstrate for the first time a crucial role of CD4(+) T cells and specific antigen recognition in the progression from compensated cardiac hypertrophy to HF.

Obesity is associated with lower coronary microvascular density

Background

Obesity is associated with diastolic dysfunction, lower maximal myocardial blood flow, impaired myocardial metabolism and increased risk of heart failure. We examined the association between obesity, left ventricular filling pressure and myocardial structure.

Methods

We performed histological analysis of non-ischemic myocardium from 57 patients (46 men and 11 women) undergoing coronary artery bypass graft surgery who did not have previous cardiac surgery, myocardial infarction, heart failure, atrial fibrillation or loop diuretic therapy.

Results

Non-obese (body mass index, BMI, ≤30 kg/m², n=33) and obese patients (BMI >30 kg/m², n=24) did not differ with respect to myocardial total, interstitial or perivascular fibrosis, arteriolar dimensions, or cardiomyocyte width. Obese patients had lower capillary length density (1145±239, mean±SD, vs. 1371±333 mm/mm³, P=0.007) and higher diffusion radius (16.9±1.5 vs. 15.6±2.0 μm, P=0.012), in comparison with non-obese patients. However, the diffusion radius/cardiomyocyte width ratio of obese patients (0.73±0.11 μm/μm) was not significantly different from that of non-obese patients (0.71±0.11 μm/μm), suggesting that differences in cardiomyocyte width explained in part the differences in capillary length density and diffusion radius between non-obese and obese patients. Increased BMI was associated with increased pulmonary capillary wedge pressure (PCWP, P<0.0001), and lower capillary length density was associated with both increased BMI (P=0.043) and increased PCWP (P=0.016).

Conclusions

Obesity and its accompanying increase in left ventricular filling pressure were associated with lower coronary microvascular density, which may contribute to the lower maximal myocardial blood flow, impaired myocardial metabolism, diastolic dysfunction and higher risk of heart failure in obese individuals.

Intrinsic-mediated caspase activation is essential for cardiomyocyte hypertrophy

Cardiomyocyte hypertrophy is the cellular response that mediates pathologic enlargement of the heart. This maladaptation is also characterized by cell behaviors that are typically associated with apoptosis, including cytoskeletal reorganization and disassembly, altered nuclear morphology, and enhanced protein synthesis/translation. Here, we investigated the requirement of apoptotic caspase pathways in mediating cardiomyocyte hypertrophy. Cardiomyocytes treated with hypertrophy agonists displayed rapid and transient activation of the intrinsic-mediated cell death pathway, characterized by elevated levels of caspase 9, followed by caspase 3 protease activity. Disruption of the intrinsic cell death pathway at multiple junctures led to a significant inhibition of cardiomyocyte hypertrophy during agonist stimulation, with a corresponding reduction in the expression of known hypertrophic markers (atrial natriuretic peptide) and transcription factor activity [myocyte enhancer factor-2, nuclear factor kappa B (NF-κB)]. Similarly, in vivo attenuation of caspase activity via adenoviral expression of the biologic effector caspase inhibitor p35 blunted cardiomyocyte hypertrophy in response to agonist stimulation. Treatment of cardiomyocytes with procaspase 3 activating compound 1, a small-molecule activator of caspase 3, resulted in a robust induction of the hypertrophy response in the absence of any agonist stimulation. These results suggest that caspase-dependent signaling is necessary and sufficient to promote cardiomyocyte hypertrophy. These results also confirm that cell death signal pathways behave as active remodeling agents in cardiomyocytes, independent of inducing an apoptosis response.