Transcription factors in heart: promising therapeutic targets in cardiac hypertrophy

In vivo CRISPR/Cas9-mediated screen reveals a critical function of TFDP1 and E2F4 transcription factors in hematopoiesis

Hematopoiesis is a continuous process of blood cell production driven by hematopoietic stem and progenitor cells (HSPCs) in the bone marrow. Proliferation and differentiation of HSPCs are regulated by complex transcriptional networks. In order to identify transcription factors with key roles in HSPC-mediated hematopoietic reconstitution, we developed an efficient and robust CRISPR/Cas9-based in vivo genetic screen. Using this experimental system, we identified the TFDP1 transcription factor to be essential for HSPC proliferation and post-transplant hematopoiesis. We further discovered that E2F4, an E2F transcription factor, serves as a binding partner of TFDP1 and is required for HSPC proliferation. Deletion of TFDP1 caused downregulation of genes associated with the cell cycle, with around 50% of these genes being identified as direct targets of TFDP1 and E2F4. Thus, our study expands the transcriptional network governing hematopoietic development through an in vivo CRISPR/Cas9-based genetic screen and identifies TFDP1/E2F4 as positive regulators of cell cycle genes in HSPCs.

The essential role of MED27 in stabilizing the mediator complex for cardiac development and function

AIM

Transcriptional regulation of gene expression plays a crucial role in orchestrating complex morphogenetic and molecular events during heart development and function. Mediator complex is an essential multi-subunit protein complex that governs gene expression in eukaryotic cells. Although Mediator subunits (MEDs) work integrally in the complex, individual MED component displays specialized functions. MED27, categorized as an Upper Tail subunit, possesses an as-yet-uncharacterized function. In this study, we aimed to investigate the physiological role of MED27 in cardiomyocytes.

MATERIALS AND METHODS

we generated a Med27 floxed mouse line, which was further used to generate constitutive (cKO) and inducible (icKO) cardiomyocyte-specific Med27 knockout mouse models. Morphological, histological analysis and cardiac physiological studies were performed in Med27 cKO and icKO mutants. Transcriptional profiles were determined by RNA sequencing (RNAseq) analysis.

KEY FUNDINGS

Ablation of MED27 in developing mouse cardiomyocytes results in embryonic lethality, while its deletion in adult cardiomyocytes leads to heart failure and mortality. Similar to the ablation of another Upper Tail subunit, MED30 in cardiomyocytes, deletion of MED27 leads to decreased protein levels of most MEDs in cardiomyocytes. Interestingly, overexpression of MED30 fails to restore the protein levels of Mediator subunits in MED27-deficient cardiomyocytes, demonstrating that the role of MED27 in maintaining the integrity and stability of the Mediator complex is independent of MED30.

SIGNIFICANCE

Our results revealed an essential role of MED27 in cardiac development and function by maintaining the stability of the Mediator core.

CRISPR perfect adaptation for robust control of cellular immune and apoptotic responses

A central challenge in the quest for precise gene regulation within mammalian cells is the development of regulatory networks that can achieve perfect adaptation-where outputs consistently return to a set baseline post-stimulus. Here, we present such a system that leverages the CRISPR activation (CRISPRa) and anti-CRISPR proteins as two antithetic elements to establish perfect adaptation in mammalian cells and dynamically regulate gene expression. We demonstrate that this system can maintain stable expression levels of target genes in the face of external perturbations, thus providing a robust platform for biological applications. The versatility of our system is further showcased through its integration with endogenous regulatory mechanisms in T cells, such as the NF-κB-mediated immune response, and its ability to program apoptosis responses for precise spatial and temporal control of cellular growth and death. This study not only advances our understanding of gene regulation in mammalian cells but also opens new avenues for therapeutic intervention, particularly in diseases characterized by dysregulated gene expression.

Modeling cardiomyocyte signaling and metabolism predicts genotype-to-phenotype mechanisms in hypertrophic cardiomyopathy

Familial hypertrophic cardiomyopathy (HCM) is a significant precursor of heart failure and sudden cardiac death, primarily caused by mutations in sarcomeric and structural proteins. Despite the extensive research on the HCM genotype, the complex and context-specific nature of many signaling and metabolic pathways linking the HCM genotype to phenotype has hindered therapeutic advancements for patients. Here, we have developed a computational model of HCM encompassing cardiomyocyte signaling and metabolic networks and their associated interactions. Utilizing a stochastic logic-based ODE approach, we linked cardiomyocyte signaling to the metabolic network through a gene regulatory network and post-translational modifications. We validated the model against published data on activities of signaling species in the HCM context and transcriptomes of two HCM mouse models (i.e., R403Q-αMyHC and R92W-TnT). Our model predicts that HCM mutation induces changes in metabolic functions such as ATP synthase deficiency and a transition from fatty acids to carbohydrate metabolism. The model indicated major shifts in glutamine-related metabolism and increased apoptosis after HCM-induced ATP synthase deficiency. We predicted that the transcription factors STAT, SRF, GATA4, TP53, and FoxO are the key regulators of cardiomyocyte hypertrophy and apoptosis in HCM in alignment with experiments. Moreover, we identified shared (e.g., activation of PGC1α by AMPK, and FHL1 by titin) and context-specific mechanisms (e.g., regulation of Ca2+ sensitivity by titin in HCM patients) that may control genotype-to-phenotype transition in HCM across different species or mutations. We also predicted potential combination drug targets for HCM (e.g., mavacamten plus ROS inhibitors) preventing or reversing HCM phenotype (i.e., hypertrophic growth, apoptosis, and metabolic remodeling) in cardiomyocytes. This study provides new insights into mechanisms linking genotype to phenotype in familial hypertrophic cardiomyopathy and offers a framework for assessing new treatments and exploring variations in HCM experimental models.

Affinity chromatography reveals direct binding of the GATA4-NKX2-5 interaction inhibitor (3i-1000) with GATA4

Heart failure is a serious medical condition with a poor prognosis. Current treatments can only help manage the symptoms and slow the progression of heart failure. However, there is currently no cure to prevent and reverse cardiac remodeling. Transcription factors are in a central role in various cellular processes, and in the heart, GATA4 and NKX2-5 transcription factors mediate hypertrophic responses and remodeling. We have identified compounds that modulate the synergistic interaction of GATA4 and NKX2-5 and shown that the most promising compound (1, 3i-1000) is cardioprotective in vitro and in vivo. However, direct evidence of its binding site and mechanism of action has not been available. Due to the disordered nature of transcription factors, classical target engagement approaches cannot be utilized. Here, we synthesized a small-molecule ligand-binding pulldown probe of compound 1 to utilize affinity chromatography alongside CETSA, AlphaScreen, and molecular modeling to study ligand binding. These results provide the first evidence of direct physical binding of compound 1 selectively to GATA4. While developing drugs that target transcription factors presents challenges, advances in technologies and knowledge of intrinsically disordered proteins enable the identification of small molecules that can selectively target transcription factors.

Polypyrrole-based structures for activation of cellular functions under electrical stimulation

Polypyrrole (Ppy) is an electroconductive polymer used in various applications, including in vitro experiments with cell cultures under electrical stimulation (ES). Ppy can be applied in various forms and most importantly, it is biocompatible with cells. Ppy specifically directs ES to cells, which makes Ppy a potential polymer for the development of novel technologies for targeted tissue regeneration. The high potential of ES in combination with different Ppy-based systems, such as hydrogels, scaffolds, or Ppy-layers is advantageous to stimulate cellular differentiation towards neurogenic, cardiac, muscle, and osteogenic lineages. Different in-house devices and the principles of ES application used to stimulate cellular functions are reviewed and summarized. The focus of this review is to observe the most relevant studies and their in-house techniques regarding the application of Ppy-based materials for the use of bone, neural, cardiac, and muscle tissue regeneration under ES. Different types of Ppy materials, such as Ppy particles, layers/films, membranes, and 3D-shaped synthetic and natural scaffolds, as well as combining Ppy with different active molecules are reviewed.

Keeping the Heart Healthy: The Role of Exercise in Cardiac Repair and Regeneration

Significance: Heart failure is often accompanied by a decrease in the number of cardiomyocytes. Although the adult mammalian hearts have limited regenerative capacity, the rate of regeneration is extremely low and decreases with age. Exercise is an effective means to improve cardiovascular function and prevent cardiovascular diseases. However, the molecular mechanisms of how exercise acts on cardiomyocytes are still not fully elucidated. Therefore, it is important to explore the role of exercise in cardiomyocytes and cardiac regeneration. Recent Advances: Recent advances have shown that the effects of exercise on cardiomyocytes are critical for cardiac repair and regeneration. Exercise can induce cardiomyocyte growth by increasing the size and number. It can induce physiological cardiomyocyte hypertrophy, inhibit cardiomyocyte apoptosis, and promote cardiomyocyte proliferation. In this review, we have discussed the molecular mechanisms and recent studies of exercise-induced cardiac regeneration, with a focus on its effects on cardiomyocytes. Critical Issues: There is no effective way to promote cardiac regeneration. Moderate exercise can keep the heart healthy by encouraging adult cardiomyocytes to survive and regenerate. Therefore, exercise could be a promising tool for stimulating the regenerative capability of the heart and keeping the heart healthy. Future Directions: Although exercise is an important measure to promote cardiomyocyte growth and subsequent cardiac regeneration, more studies are needed on how to do beneficial exercise and what factors are involved in cardiac repair and regeneration. Thus, it is important to clarify the mechanisms, pathways, and other critical factors involved in the exercise-mediated cardiac repair and regeneration. Antioxid. Redox Signal. 39, 1088-1107.

Amniotic Fluid Mesenchymal Stromal Cells Derived from Fetuses with Isolated Cardiac Defects Exhibit Decreased Proliferation and Cardiomyogenic Potential

Amniotic fluid mesenchymal stromal cells (AF-MSCs) represent an autologous cell source to ameliorate congenital heart defects (CHDs) in children. The AF-MSCs, having cardiomyogenic potential and being of fetal origin, may reflect the physiological and pathological changes in the fetal heart during embryogenesis. Hence, the study of defects in the functional properties of these stem cells during fetal heart development will help obtain a better understanding of the cause of neonatal CHDs. Therefore, in the present study, we compared the proliferative and cardiomyogenic potential of AF-MSCs derived from ICHD fetuses (ICHD AF-MSCs) with AF-MSCs from structurally normal fetuses (normal AF-MSCs). Compared to normal AF-MSCs, the ICHD AF-MSCs showed comparable immunophenotypic MSC marker expression and adipogenic and chondrogenic differentiation potential, with decreased proliferation, higher senescence, increased expression of DNA-damaged genes, and osteogenic differentiation potential. Furthermore, the expression of cardiac progenitor markers (PDGFR-α, VEGFR-2, and SSEA-1), cardiac transcription factors (GATA-4, NKx 2-5, ISL-1, TBX-5, TBX-18, and MeF-2C), and cardiovascular markers (cTNT, CD31, and α-SMA) were significantly reduced in ICHD AF-MSCs. Overall, these results suggest that the AF-MSCs of ICHD fetuses have proliferation defects with significantly decreased cardiomyogenic differentiation potential. Thus, these defects in ICHD AF-MSCs highlight that the impaired heart development in ICHD fetuses may be due to defects in the stem cells associated with heart development during embryogenesis.

Global profiling of protein lysine malonylation in mouse cardiac hypertrophy

Lysine malonylation, a novel identified protein posttranslational modification (PTM), is conservative and present in both eukaryotic and prokaryotic cells. Previous studies have reported that malonylation plays an important role in inflammation, angiogenesis, and diabetes. However, its potential role in cardiac remodeling remains unknown. Here, we observed a reduced lysine malonylation in hypertrophic mice hearts created by transverse aortic constriction (TAC) for 8 weeks. We also detected a decreased lysine malonylation in hypertrophic H9C2 cardiomyocytes induced by angiotensin II for 48 h. Using a proteomic method based on affinity purification and LC-MS/MS, we identified total 679 malonylated sites in 330 proteins in the hearts of sham mice and TAC mice. Bioinformatic analysis of the proteomic data revealed enrichment of malonylated proteins involved in cardiac structure and contraction, cGMP-PKG pathway, and metabolism. Specifically, we detected a decreased lysine malonylation in myocardial isocitrate dehydrogenase 2 (IDH2) by immunoprecipitation coupled with Western blotting both in vivo and in vitro. Together, our work suggests an important role and implication of protein lysine malonylation in cardiac hypertrophy, especially the IDH2. SIGNIFICANCE: Heart failure is the terminal stage of cardiac hypertrophy, which imposes an enormous clinical and economic burden worldwide. Despite our knowledge on the pathophysiology of the disease, current therapeutic approaches are still largely limited. Cardiac hypertrophy can be regulated at post-translational modifications (PTMs), and several PTMs have been reported in cardiac hypertrrophy and heart failure. In our study, we first reported a novel PTMs, lysine malonylation, in cardiac hypertophy. we found a reduced lysine malonylation in hypertrophic mice hearts in vivo and H9C2 cardiomyocytes after stimulating with angiotensinII for 48 h in vitro. Using affinity purification and LC-MS/MS, we identified 679 malonylated sites in 330 proteins in the hearts of sham and TAC mice. Compared to the sham group, 5 sites in 2 proteins were quantified as downregulated targets using a 2-fold threshold (downregulation <0.5-fold, P < 0.05). Functional analysis showed a significant enrichment in cardiac structure and contraction, cGMP-PKG pathway and metabolism. Notably, we identified a decreased Kmal level in isocitrate dehydrogenase 2 (IDH2), but the protein level of IDH2 has no changed in cardiac hypertrophy, These results highlight that lysine malonylation is associated with cardiac hypertrophy, and may be a new therapeutic target of the disease.

Evolutionarily conserved transcription factors as regulators of longevity and targets for geroprotection

Aging is the single largest risk factor for many debilitating conditions, including heart diseases, stroke, cancer, diabetes, and neurodegenerative disorders. While far from understood in its full complexity, it is scientifically well-established that aging is influenced by genetic and environmental factors, and can be modulated by various interventions. One of aging's early hallmarks are aberrations in transcriptional networks, controlling for example metabolic homeostasis or the response to stress. Evidence in different model organisms abounds that a number of evolutionarily conserved transcription factors, which control such networks, can affect lifespan and healthspan across species. These transcription factors thus potentially represent conserved regulators of longevity and are emerging as important targets in the challenging quest to develop treatments to mitigate age-related diseases, and possibly even to slow aging itself. This review provides an overview of evolutionarily conserved transcription factors that impact longevity or age-related diseases in at least one multicellular model organism (nematodes, flies, or mice), and/or are tentatively linked to human aging. Discussed is the general evidence for transcriptional regulation of aging and disease, followed by a more detailed look at selected transcription factor families, the common metabolic pathways involved, and the targeting of transcription factors as a strategy for geroprotective interventions.

Tripartite motif 27 promotes cardiac hypertrophy via PTEN/Akt/mTOR signal pathways

Tripartite motif-containing 27 (Trim27) is highly expressed in tumor cells and regulates natural immunity and apoptosis. However, the effects of Trim27 in cardiac hypertrophy are not fully elucidated. In this study, we tried to explore the potential role of Trim27 in pressure overload-induced cardiac hypertrophy and the underlying mechanism. The results indicated that compared to sham operation (Sham) group, transverse aortic constriction (TAC) group showed significantly up-regulated Trim27 protein expression (P < 0.05). The neonatal rat cardiomyocytes (NRCMs) were isolated and stimulated with PBS, angiotensin (AngII) and phenylephrine (PE). NRCMs were collected to detect the protein expression of Trim27. The results were consistent with the results in vivo. Compared to PBS treatment, the expression of Trim27 protein in NRCMs was significantly increased after PE or AngII stimulation (P < 0.05, respectively). Knockout of Trim27 can reduce the size of cardiomyocytes and reduce the proteins expression of ANP, BNP, and β-MHC, improve cardiac function, and reverse myocardial hypertrophy (P < 0.05). Trim27 may be involved in regulating the development of cardiac hypertrophy. Further results showed that Trim27 can increase the protein expression of phosphorylation of Akt, GSK3β, mTOR, and P70s6k by interacting with PTEN (phosphatase tensin homolog). These findings revealed that Trim27 can promote cardiac hypertrophy by activating PTEN/Akt/GSK3β/mTOR signaling pathway.

Understanding the molecular basis of cardiomyopathy

Inherited cardiomyopathies are a major cause of mortality and morbidity worldwide and can be caused by mutations in a wide range of proteins located in different cellular compartments. The present review is based on Dr. Ju Chen's 2021 Robert M. Berne Distinguished Lectureship of the American Physiological Society Cardiovascular Section, in which he provided an overview of the current knowledge on the cardiomyopathy-associated proteins that have been studied in his laboratory. The review provides a general summary of the proteins in different compartments of cardiomyocytes associated with cardiomyopathies, with specific focus on the proteins that have been studied in Dr. Chen's laboratory.

Mediator complex proximal Tail subunit MED30 is critical for Mediator core stability and cardiomyocyte transcriptional network

Dysregulation of cardiac transcription programs has been identified in patients and families with heart failure, as well as those with morphological and functional forms of congenital heart defects. Mediator is a multi-subunit complex that plays a central role in transcription initiation by integrating regulatory signals from gene-specific transcriptional activators to RNA polymerase II (Pol II). Recently, Mediator subunit 30 (MED30), a metazoan specific Mediator subunit, has been associated with Langer-Giedion syndrome (LGS) Type II and Cornelia de Lange syndrome-4 (CDLS4), characterized by several abnormalities including congenital heart defects. A point mutation in MED30 has been identified in mouse and is associated with mitochondrial cardiomyopathy. Very recent structural analyses of Mediator revealed that MED30 localizes to the proximal Tail, anchoring Head and Tail modules, thus potentially influencing stability of the Mediator core. However, in vivo cellular and physiological roles of MED30 in maintaining Mediator core integrity remain to be tested. Here, we report that deletion of MED30 in embryonic or adult cardiomyocytes caused rapid development of cardiac defects and lethality. Importantly, cardiomyocyte specific ablation of MED30 destabilized Mediator core subunits, while the kinase module was preserved, demonstrating an essential role of MED30 in stability of the overall Mediator complex. RNAseq analyses of constitutive cardiomyocyte specific Med30 knockout (cKO) embryonic hearts and inducible cardiomyocyte specific Med30 knockout (icKO) adult cardiomyocytes further revealed critical transcription networks in cardiomyocytes controlled by Mediator. Taken together, our results demonstrated that MED30 is essential for Mediator stability and transcriptional networks in both developing and adult cardiomyocytes. Our results affirm the key role of proximal Tail modular subunits in maintaining core Mediator stability in vivo.

Integrated Quantitative Phosphoproteomics and Cell-based Functional Screening Reveals Specific Pathological Cardiac Hypertrophy-related Phosphorylation Sites

Cardiac hypertrophic signaling cascades resulting in heart failure diseases are mediated by protein phosphorylation. Recent developments in mass spectrometry-based phosphoproteomics have led to the identification of thousands of differentially phosphorylated proteins and their phosphorylation sites. However, functional studies of these differentially phosphorylated proteins have not been conducted in a large-scale or high-throughput manner due to a lack of methods capable of revealing the functional relevance of each phosphorylation site. In this study, an integrated approach combining quantitative phosphoproteomics and cell-based functional screening using phosphorylation competition peptides was developed. A pathological cardiac hypertrophy model, junctate-1 transgenic mice and control mice, were analyzed using label-free quantitative phosphoproteomics to identify differentially phosphorylated proteins and sites. A cell-based functional assay system measuring hypertrophic cell growth of neonatal rat ventricle cardiomyocytes (NRVMs) following phenylephrine treatment was applied, and changes in phosphorylation of individual differentially phosphorylated sites were induced by incorporation of phosphorylation competition peptides conjugated with cell-penetrating peptides. Cell-based functional screening against 18 selected phosphorylation sites identified three phosphorylation sites (Ser-98, Ser-179 of Ldb3, and Ser-1146 of palladin) displaying near-complete inhibition of cardiac hypertrophic growth of NRVMs. Changes in phosphorylation levels of Ser-98 and Ser-179 in Ldb3 were further confirmed in NRVMs and other pathological/physiological hypertrophy models, including transverse aortic constriction and swimming models, using site-specific phospho-antibodies. Our integrated approach can be used to identify functionally important phosphorylation sites among differentially phosphorylated sites, and unlike conventional approaches, it is easily applicable for large-scale and/or high-throughput analyses.

AAV-mediated expression of NFAT decoy oligonucleotides protects from cardiac hypertrophy and heart failure

Previous studies have underlined the substantial role of nuclear factor of activated T cells (NFAT) in hypertension-induced myocardial hypertrophy ultimately leading to heart failure. Here, we aimed at neutralizing four members of the NFAT family of transcription factors as a therapeutic strategy for myocardial hypertrophy transiting to heart failure through AAV-mediated cardiac expression of a RNA-based decoy oligonucleotide (dON) targeting NFATc1-c4. AAV-mediated dON expression markedly decreased endothelin-1 induced cardiomyocyte hypertrophy in vitro and resulted in efficient expression of these dONs in the heart of adult mice as evidenced by fluorescent in situ hybridization. Cardiomyocyte-specific dON expression both before and after induction of transverse aortic constriction protected mice from development of cardiac hypertrophy, cardiac remodeling, and heart failure. Singular systemic administration of AAVs enabling a cell-specific expression of dONs for selective neutralization of a given transcription factor may thus represent a novel and powerful therapeutic approach.

Advances in targeting 'undruggable' transcription factors with small molecules

Transcription factors (TFs) represent key biological players in diseases including cancer, autoimmunity, diabetes and cardiovascular disease. However, outside nuclear receptors, TFs have traditionally been considered 'undruggable' by small-molecule ligands due to significant structural disorder and lack of defined small-molecule binding pockets. Renewed interest in the field has been ignited by significant progress in chemical biology approaches to ligand discovery and optimization, especially the advent of targeted protein degradation approaches, along with increasing appreciation of the critical role a limited number of collaborators play in the regulation of key TF effector genes. Here, we review current understanding of TF-mediated gene regulation, discuss successful targeting strategies and highlight ongoing challenges and emerging approaches to address them.

Mitochondrial ROS and mitochondria-targeted antioxidants in the aged heart

Excessive mitochondrial ROS production has been causally linked to the pathophysiology of aging in the heart and other organs, and plays a deleterious role in several age-related cardiac pathologies, including myocardial ischemia-reperfusion injury and heart failure, the two worldwide leading causes of death and disability in the elderly. However, ROS generation is also a fundamental mitochondrial function that orchestrates several signaling pathways, some of them exerting cardioprotective effects. In cardiac myocytes, mitochondria are particularly abundant and are specialized in subcellular populations, in part determined by their relationships with other organelles and their cyclic calcium handling activity necessary for adequate myocardial contraction/relaxation and redox balance. Depending on their subcellular location, mitochondria can themselves be differentially targeted by ROS and display distinct age-dependent functional decline. Thus, precise mitochondria-targeted therapies aimed at counteracting unregulated ROS production are expected to have therapeutic benefits in certain aging-related heart conditions. However, for an adequate design of such therapies, it is necessary to unravel the complex and dynamic interactions between mitochondria and other cellular processes.

Anti-inflammatory Effects of S. cumini Seed Extract on Gelatinase-B (MMP-9) Regulation against Hyperglycemic Cardiomyocyte Stress

Black berry (Syzygium cumini) fruit is useful in curing diabetic complications; however, its role in diabetes-induced cardiomyopathy is not yet known. In this study, we investigated the regulation of gelatinase-B (MMP-9) by S. cumini methanol seed extract (MSE) in diabetic cardiomyopathy using real-time PCR, RT-PCR, immunocytochemistry, gel diffusion assay, and substrate zymography. The regulatory effects of MSE on NF-κB, TNF-α, and IL-6 were also examined. Identification and estimation of polyphenol constituents present in S. cumini extract were carried out using reverse-phase HPLC. Further, in silico docking studies of identified polyphenols with gelatinase-B were performed to elucidate molecular level interaction in the active site of gelatinase-B. Docking studies showed strong interaction of S. cumini polyphenols with gelatinase-B. Our findings indicate that MSE significantly suppresses gelatinase-B expression and activity in high-glucose- (HG-) stimulated cardiomyopathy. Further, HG-induced activation of NF-κB, TNF-α, and IL-6 was also remarkably reduced by MSE. Our results suggest that S. cumini MSE may be useful as an effective functional food and dietary supplement to regulate HG-induced cardiac stress through gelatinase.

Heart malformation is an early response to valproic acid in developing zebrafish

Valproic acid (VPA) is a branched short-chain fatty acid primarily used in epilepsy, but is also used in bipolar disorder, migraine, and psychotic disorders. Despite its wide range of use, it is a teratogen resulting in various congenital abnormalities. Although a large number of scientific studies evidenced the teratogenic effects, there are limited data on embryonic exposure to VPA at specific or different stages of early embryogenesis. Based on this, the present study was planned to investigate the embryonic exposure to VPA at specific and different hours post fertilization (hpf) in zebrafish embryonic model. In first set of experiments, embryos from spawning groups of adult zebrafish were exposed to different molar concentrations of VPA at 2.5 hpf, and in the second set of experiments, embryos were exposed to VPA 100 μM at 24 hpf, 36 hpf, 48 hpf, 72 hpf, and 96 hpf. The parameters examined were hatching rate, mortality, morphology, body length, pericardial sac size, heartrate, anatomical changes in heart, skeletal and notochord till 120 hpf. It was observed that the embryos exposed to VPA at 2.5 hpf suffered from cardiac abnormalities including heart malformation, bradycardia, circulatory failure, and pericardial sac enlargement which was more apparent in embryos exposed to 100 μM VPA. In the second set of experiments, embryos exposed to VPA 100 μM at 24 hpf and 36 hpf suffered from heart malformations, but there was no incidence of cardiac malformation in embryos exposed to VPA at 48 hpf, 72 hpf, and 96 hpf. From the results, it was evident that exposure to VPA at early developmental stage of embryogenesis produced congenital cardiac abnormalities. Since VPA is a selective HDAC inhibitor, histone acetylation with aberrant gene expression during cardiogenesis might be the underlying cause of cardiac malformation.

Hematopoietic Stem Cell Transcription Factors in Cardiovascular Pathology

Transcription factors as multifaceted modulators of gene expression that play a central role in cell proliferation, differentiation, lineage commitment, and disease progression. They interact among themselves and create complex spatiotemporal gene regulatory networks that modulate hematopoiesis, cardiogenesis, and conditional differentiation of hematopoietic stem cells into cells of cardiovascular lineage. Additionally, bone marrow-derived stem cells potentially contribute to the cardiovascular cell population and have shown potential as a therapeutic approach to treat cardiovascular diseases. However, the underlying regulatory mechanisms are currently debatable. This review focuses on some key transcription factors and associated epigenetic modifications that modulate the maintenance and differentiation of hematopoietic stem cells and cardiac progenitor cells. In addition to this, we aim to summarize different potential clinical therapeutic approaches in cardiac regeneration therapy and recent discoveries in stem cell-based transplantation.

Network integration and modelling of dynamic drug responses at multi-omics levels

Uncovering cellular responses from heterogeneous genomic data is crucial for molecular medicine in particular for drug safety. This can be realized by integrating the molecular activities in networks of interacting proteins. As proof-of-concept we challenge network modeling with time-resolved proteome, transcriptome and methylome measurements in iPSC-derived human 3D cardiac microtissues to elucidate adverse mechanisms of anthracycline cardiotoxicity measured with four different drugs (doxorubicin, epirubicin, idarubicin and daunorubicin). Dynamic molecular analysis at in vivo drug exposure levels reveal a network of 175 disease-associated proteins and identify common modules of anthracycline cardiotoxicity in vitro, related to mitochondrial and sarcomere function as well as remodeling of extracellular matrix. These in vitro-identified modules are transferable and are evaluated with biopsies of cardiomyopathy patients. This to our knowledge most comprehensive study on anthracycline cardiotoxicity demonstrates a reproducible workflow for molecular medicine and serves as a template for detecting adverse drug responses from complex omics data.

Using a network propagation approach with integrated multi-omic data, Selevsek et al. develop a reproducible workflow for identifying drug toxicity effects in cellular systems. This is demonstrated with the analysis of anthracycline cardiotoxicity in cardiac microtissues under the effect of multiple drugs.

The regulatory effect of bromocriptine on cardiac hypertrophy by prolactin and D2 receptor modulation

BACKGROUND

Bromocriptine, a dopamine agonist, used for the treatment of hyperprolactinemia, type 2 diabetes, ovarian hyper-stimulation syndrome, has also effects on the cardiac remodeling process, but the mechanism of action is unknown. The aim of this work was to determinate the effect during hypertrophic process through molecular mechanisms that include prolactin receptor (Prlr) and receptor of dopamine 2 (D2 r) expression.

METHODS

We used a model of cardiac hypertrophy induced by an aortocaval fistula (ACF) surgery in rats. Protein concentrations of D2 r and Prlr were determined by western blotting. The treatment consisted in water (control), captopril (50 mg/kg/day), bromocriptine (3 mg/kg/day), and ACF group (n = 6 per group).

RESULTS

Our results showed that bromocriptine treatment decreases the hypertrophy index. Treatment with bromocriptine increases the protein expression of Prlr and D2 r in the cardiac tissue of rats with cardiac hypertrophy.

CONCLUSIONS

We concluded that bromocriptine has a protective effect on cardiac hypertrophy, and due to this effect, it may modulate the expression of Prlr and D2 r, which are involved in the development of cardiac hypertrophy.

Oncogenic Gene-Expression Programs in Leiomyosarcoma and Characterization of Conventional, Inflammatory, and Uterogenic Subtypes

Leiomyosarcoma (LMS) is a mesenchymal neoplasm with complex copy-number alterations and characteristic loss of tumor suppressor genes without known recurrent activating mutations. Clinical management of advanced LMS relies on chemotherapy and complementary palliative approaches, and research efforts to date have had limited success identifying clinically actionable biomarkers or targeted therapeutic vulnerabilities. To explore the biological underpinning of LMS, we evaluated gene-expression patterns of this disease in comparison with diverse sarcomas, nonmesenchymal neoplasms, and normal myogenic tissues. We identified a recurrent gene-expression program in LMS, with evidence of oncogenic evolution of an underlying smooth-muscle lineage-derived program characterized by activation of E2F1 and downstream effectors. Recurrently amplified or highly expressed genes in LMS were identified, including IGF1R and genes involved in retinoid signaling pathways. Though the majority of expressed transcripts were conserved across LMS samples, three separate subtypes were identified that were enriched for muscle-associated transcripts (conventional LMS), immune markers (inflammatory LMS), or a uterine-like gene-expression program (uterogenic LMS). Each of these subtypes expresses a unique subset of genes that may be useful in the management of LMS: IGF1R was enriched in conventional LMS, worse disease-specific survival was observed in inflammatory LMS, and prolactin was elaborated by uterogenic LMS. These results extend our understanding of LMS biology and identify several strategies and challenges for further translational investigation. IMPLICATIONS: LMS has a recurrent oncogenic transcriptional program and consists of molecular subtypes with biological and possible clinical implications.

Epigenomes of Human Hearts Reveal New Genetic Variants Relevant for Cardiac Disease and Phenotype

RATIONALE

Identifying genetic markers for heterogeneous complex diseases such as heart failure is challenging and requires prohibitively large cohort sizes in genome-wide association studies to meet the stringent threshold of genome-wide statistical significance. On the other hand, chromatin quantitative trait loci, elucidated by direct epigenetic profiling of specific human tissues, may contribute toward prioritizing subthreshold variants for disease association.

OBJECTIVE

Here, we captured noncoding genetic variants by performing epigenetic profiling for enhancer H3K27ac chromatin immunoprecipitation followed by sequencing in 70 human control and end-stage failing hearts.

METHODS AND RESULTS

We have mapped a comprehensive catalog of 47 321 putative human heart enhancers and promoters. Three thousand eight hundred ninety-seven differential acetylation peaks (FDR [false discovery rate], 5%) pointed to pathways altered in heart failure. To identify cardiac histone acetylation quantitative trait loci (haQTLs), we regressed out confounding factors including heart failure disease status and used the G-SCI (Genotype-independent Signal Correlation and Imbalance) test1 to call out 1680 haQTLs (FDR, 10%). RNA sequencing performed on the same heart samples proved a subset of haQTLs to have significant association also to gene expression (expression quantitative trait loci), either in cis (180) or through long-range interactions (81), identified by Hi-C (high-throughput chromatin conformation assay) and HiChIP (high-throughput protein centric chromatin) performed on a subset of hearts. Furthermore, a concordant relationship between the gain or disruption of TF (transcription factor)-binding motifs, inferred from alternative alleles at the haQTLs, implied a surprising direct association between these specific TF and local histone acetylation in human hearts. Finally, 62 unique loci were identified by colocalization of haQTLs with the subthreshold loci of heart-related genome-wide association studies datasets.

CONCLUSIONS

Disease and phenotype association for 62 unique loci are now implicated. These loci may indeed mediate their effect through modification of enhancer H3K27 acetylation enrichment and their corresponding gene expression differences (bioRxiv: https://doi.org/10.1101/536763). Graphical Abstract: A graphical abstract is available for this article.

Sustained Activation of AMPK Enhances Differentiation of Human iPSC-Derived Cardiomyocytes via Sirtuin Activation

Recent studies suggest that metabolic regulation may improve differentiation of cardiomyocytes derived from induced pluripotent stem cells (iPSCs). AMP-activated protein kinase (AMPK) is a master regulator of metabolic activities. We investigated whether AMPK participates in iPSC-derived cardiomyocyte differentiation. We observed that AMPK phosphorylation at Thr172 increased at day 9 but then decreased after day 11 of differentiation to cardiomyocytes. Inhibition of AMPK with compound C significantly reduced mRNA and protein expression of cardiac troponins TNNT2 and TNNI3. Moreover, sustained AMPK activation using AICAR from days 9 to 14 of differentiation increased mRNA and protein expression of both TNNT2 and TNNI3. AICAR decreased acetylation of histone 3 at Lys9 and 56 and histone 4 at Lys16 (known target sites for nuclear-localized sirtuins [SIRT1, SIRT6]), suggesting that AMPK activation enhances sirtuin activity. Sustained AMPK activation during days 9–14 of differentiation induces sirtuin-mediated histone deacetylation and may enhance cardiomyocyte differentiation from iPSCs.

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iPSC-derived cardiomyocytes transiently increased AMPK phosphorylation at Thr172

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Chemical inhibition of AMPK with compound C decreased TNNI3 and TNNT2 expression

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Sustained activation of AMPK using AICAR increased expression of TNNT2 and TNNI3

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AICAR decreased acetylation of histones H3 (at Lys9 and Lys56) and H4 (at Lys16).

Substance P Administered after Myocardial Infarction Upregulates Microphthalmia-Associated Transcription Factor, GATA4, and the Expansion of c-Kit+ Cells

Microphthalmia-associated transcription factor (MITF), a basic helix-loop-helix leucine zipper transcription factor, can govern gene expression by binding to E box elements in the promoter region of its target gene. Although high levels of MITF have been observed in cardiomyocytes and the heart, the role of MITF after myocardial infarction (MI) remains unclear. We investigated the association between substance P (SP)/neurokinin-1 receptor (NK₁R) signaling and MITF expression after MI. Male Sprague-Dawley rats (8 weeks) were randomly divided in two groups: ischemia/reperfusion injury (I/R) and SP injection (5 nmol/kg, SP+I/R). At the end of 7 days, the left ventricle (LV; LV^7daysI/R, LV^7daysSP+I/R) and infarct-related areas (IA; IA^7daysI/R, IA^7daysSP+I/R) from the hearts were collected. Immunofluorescence staining demonstrated that the LV^7daysSP+I/R had a larger population of c-Kit⁺ GATA4^high cells, which markedly upregulated MITF, c-Kit, and GATA4. c-Kit⁺ cells in the explant-derived cells (EDCs) derived from IA^7daysSP+I/R migrated more widely than EDCs IA^7daysI/R. Immunofluorescence staining, western blot analysis, and qRT-PCR assay showed that SP-treated c-Kit⁺ cells exhibited a high expression of c-Kit, GATA4, and MITF. FTY720 (a MITF inhibitor), RP67580 (NK₁R inhibitor), or both inhibited the migration and proliferation of c-Kit⁺ cells increased by SP and blocked the upregulation of c-Kit, GATA4, and MITF. Overall, we suggest that MITF might be a potential regulator in SP-mediated c-Kit⁺ cell expansion post-MI via c-Kit and GATA4.

Loss of nuclear ARC contributes to the development of cardiac hypertrophy in rats

AIM

Cardiac hypertrophy and myocardial apoptosis are two major factors in heart failure. As a classical regulator of apoptosis, apoptosis repressor with caspase recruitment domain (ARC) has recently also been found to have a protective effect against hypertrophy. However, the mechanism underlying this effect is still not fully understood.

METHODS

In the present study, we established animal and cellular models to monitor the changes in total and nuclear ARC during cardiac hypertrophic processes. The preventive effects of nuclear ARC in cellular hypertrophy were verified by ARC regulation and nuclear export inhibition. To further explore the mechanism for nuclear ARC superficially, we analysed proteins that interact with ARC in the nucleus via Co-IP and mass spectrometry.

RESULTS

The expression of total ARC in hypertrophic myocardial tissue and H9C2 cells remained invariant, while the level of nuclear ARC decreased dramatically. By altering the content of ARC in H9C2 cells, we found that both nuclear ARC transfection and nuclear ARC export blockade attenuated norepinephrine or angiotensin II-induced hypertrophy, while ARC knockdown had an inverse effect. Co-IP data showed that ARC interacted with prohibitin (PHB) in the nucleus and might participate in maintaining the level of PHB in cells.

CONCLUSIONS

These findings suggest a novel mechanism for ARC in cardiac hypertrophy prevention and also indicate that the anti-hypertrophic roles of ARC are probably associated with its localization in nucleus, which imply the nuclear ARC as a potential therapeutic target for cardiac hypertrophy.

Specific Upregulation of TRPC1 and TRPC5 Channels by Mineralocorticoid Pathway in Adult Rat Ventricular Cardiomyocytes

Whereas cardiac TRPC (transient receptor potential canonical) channels and the associated store-operated Ca²⁺ entry (SOCE) are abnormally elevated during cardiac hypertrophy and heart failure, the mechanism of this upregulation is not fully elucidated but might be related to the activation of the mineralocorticoid pathway. Using a combination of biochemical, Ca²⁺ imaging, and electrophysiological techniques, we determined the effect of 24-h aldosterone treatment on the TRPCs/Orai-dependent SOCE in adult rat ventricular cardiomyocytes (ARVMs). The 24-h aldosterone treatment (from 100 nM to 1 µM) enhanced depletion-induced Ca²⁺ entry in ARVMs, as assessed by a faster reduction of Fura-2 fluorescence decay upon the addition of Mn²⁺ and increased Fluo-4/AM fluorescence following Ca²⁺ store depletion. These effects were prevented by co-treatment with a specific mineralocorticoid receptor (MR) antagonist, RU-28318, and they are associated with the enhanced depletion-induced N-[4-[3,5-Bis(trifluoromethyl)-1H-pyrazol-1-yl]phenyl]-4-methyl-1,2,3-thiadiazole-5-carboxamide (BTP2)-sensitive macroscopic current recorded by patch-clamp experiments. Molecular screening by qRT-PCR and Western blot showed a specific upregulation of TRPC1, TRPC5, and STIM1 expression at the messenger RNA (mRNA) and protein levels upon 24-h aldosterone treatment of ARVMs, corroborated by immunostaining. Our study provides evidence that the mineralocorticoid pathway specifically promotes TRPC1/TRPC5-mediated SOCE in adult rat cardiomyocytes.

Nuclear receptor corepressor 1 represses cardiac hypertrophy

The function of nuclear receptor corepressor 1 (NCoR1) in cardiomyocytes is unclear, and its physiological and pathological implications are unknown. Here, we found that cardiomyocyte‐specific NCoR1 knockout (CMNKO) mice manifested cardiac hypertrophy at baseline and had more severe cardiac hypertrophy and dysfunction after pressure overload. Knockdown of NCoR1 exacerbated whereas overexpression mitigated phenylephrine‐induced cardiomyocyte hypertrophy. Mechanistic studies revealed that myocyte enhancer factor 2a (MEF2a) and MEF2d mediated the effects of NCoR1 on cardiomyocyte hypertrophy. The receptor interaction domains (RIDs) of NCoR1 interacted with MEF2a to repress its transcriptional activity. Furthermore, NCoR1 formed a complex with MEF2a and class IIa histone deacetylases (HDACs) to suppress hypertrophy‐related genes. Finally, overexpression of RIDs of NCoR1 in the heart attenuated cardiac hypertrophy and dysfunction induced by pressure overload. In conclusion, NCoR1 cooperates with MEF2 and HDACs to repress cardiac hypertrophy. Targeting NCoR1 and the MEF2/HDACs complex may be an attractive therapeutic strategy to tackle pathological cardiac hypertrophy.

MicroRNA-19a/b-3p protect the heart from hypertension-induced pathological cardiac hypertrophy through PDE5A

AIM

PDE5A is a leading factor contributing to cGMP signaling and cardiac hypertrophy. However, microRNA-mediated posttranscriptional regulation of PDE5A has not been reported. The aim of this study is to screen the microRNAs that are able to regulate PDE5A and explore the function of the microRNAs in cardiac hypertrophy and remodeling.

METHODS AND RESULTS

Although miR-19a/b-3p (microRNA-19a-3p and microRNA-19b-3p) have been reported to be differentially expressed during cardiac hypertrophy, the direct targets and the functions of this microRNA family for regulation of cardiac hypertrophy have not yet been investigated. The present study identified some direct targets and the underlying functions of miR-19a/b-3p by using bioinformatics tools and gene manipulations within mouse neonatal cardiomyocytes. Transfection of miR-19a/b-3p down-regulated endogenous expressions of PDE5A at both mRNA and protein levels with real-time PCR and western blot. Luciferase reporter assays showed that PDE5A was a direct target of miR-19a/b-3p. In mouse models of cardiac hypertrophy, we found that miR-19a/b-3p was expressed in cardiomyocytes and that its expression was reduced in pressure overload-induced hypertrophic hearts. miR-19a/b-3p transgenic mice prevented the progress of cardiac hypertrophy and cardiac remodeling in response to angiotensin II infusion with echocardiographic assessment and pressure-volume relation analysis.

CONCLUSION

Our study elucidates that PDE5A is a novel direct target of miR-19a/b-3p, and demonstrates that antihypertrophic roles of the miR-19a/b-3p family in Ang II-induced hypertrophy and cardiac remodeling, suggests that endogenous miR-19a/b-3p might have clinical potential to suppress cardiac hypertrophy and heart failure.

Nuclear receptor subfamily 4 group A member 2 inhibits activation of ERK signaling and cell growth in response to β-adrenergic stimulation in adult rat cardiomyocytes

Sustained elevation of sympathetic activity is an important contributor to pathological cardiac hypertrophy, ventricular arrhythmias, and left ventricular contractile dysfunction in chronic heart failure. The orphan nuclear receptor NR4A2 is an immediate early-response gene activated in the heart under β-adrenergic stimulation. The goal of this study was to identify the transcriptional remodeling events induced by increased NR4A2 expression in cardiomyocytes and their impact on the physiological response of those cells to sustained β-adrenergic stimulation. Treatment of adult rat ventricular myocytes with isoproterenol induced a rapid (<4 h) increase in NR4A2 levels that was accompanied by a transient (<24 h) increase in nuclear localization of the transcription factor. Adenovirus-mediated overexpression of NR4A2 to similar levels modulated the expression of genes linked to adrenoceptor signaling, calcium signaling, cell growth and proliferation and counteracted the increase in protein synthesis rate and cell surface area mediated by chronic isoproterenol stimulation. Consistent with those findings, NR4A2 overexpression also blocked the phosphorylative activation of growth-related kinases ERK1/2, Akt, and p70 S6 kinase. Prominent among the transcriptional changes induced by NR4A2 was the upregulation of the dual-specificity phosphatases DUSP2 and DUSP14, two known inhibitors of ERK1/2. Pretreatment of NR4A2-overexpressing cardiomyocytes with the DUSP inhibitor BCI [(E)-2-benzylidene-3-(cyclohexylamino)-2,3-dihydro-1H-inden-1-one] prevented the inhibition of ERK1/2 following isoproterenol stimulation. In conclusion, our results suggest that NR4A2 acts as a novel negative feedback regulator of the β-adrenergic receptor-mediated growth response in cardiomyocytes and this at least partly through DUSP-mediated inhibition of ERK1/2 signaling.

High-intensity interval training increase GATA4, CITED4 and c-Kit and decreases C/EBPβ in rats after myocardial infarction

AIM

Myocardial infarction (MI), an important cause of morbidity and mortality, can be followed by left ventricular dysfunction and cardiomyocyte loss. Cardiac repair mechanisms may subsequently improve left ventricular function. Exercise training has been suggested to have cardioprotective effects against MI damage, but detailed knowledge is lacking on the effects of different types and intensities of exercise training on molecular targets of cardiomyocyte regeneration.

MAIN METHODS

MI was induced in male Wistar rats by ligating the left anterior descending coronary artery. After MI induction, the rats were randomly assigned to one of five groups: sham operated, and experimental MI followed by no exercise, or low, moderate or high intensity exercise Cardiac function and infarct size were assessed by echocardiography and Evans blue/TTC staining, respectively. The expression of mRNA markers and proteins associated with myocardial regeneration was measured with RT-PCR and western blotting.

KEY FINDINGS

Exercise training at different intensities improved cardiac function and levels of stem cell and cardiomyocyte markers, and reduced infarct size. mRNA levels of GATA4, Nkx2.5 and c-Kit and protein expression of Nkx2.5 and c-Kit were significantly increased in all MI-exercise groups. The high-intensity exercise group had greater increases than the low and moderate intensity exercise groups. In the high-intensity exercise group, Sca-1 and CITED4 increased more than in the low-intensity exercise group. C/EBPβ mRNA and protein levels decreased after exercise training, with greater reductions in the high-intensity exercise group than the low- or moderate-intensity groups.

SIGNIFICANCE

The findings suggest that by targeting cardiogenesis, high-intensity training can exert cardioprotective effects against cardiac dysfunction in an experimental model of MI.

Role of microRNAs in doxorubicin-induced cardiotoxicity: an overview of preclinical models and cancer patients

Cardiotoxicity is a well-known side effect of doxorubicin (DOX), but the mechanisms leading to this phenomenon are still not completely clear. Prediction of drug-induced dysfunction onset is difficult and is still largely based on detection of cardiac troponin (cTn), a circulating marker of heart damage. In the last years, several investigations focused on the possible involvement of microRNAs (miRNAs) in DOX-induced toxicity in vitro, with contrasting results. Recently, several groups employed animal models to mimic patient’s condition, investigate the biological pathways perturbed by DOX, and identify diagnostic markers of cardiotoxicity. We reviewed the results from several studies investigating cardiac miRNAs expression in rodent models of DOX-treatment. We also discussed the data from two publications indicating the possible use of circulating miRNA as biomarkers of DOX-induced cardiotoxicity. Unfortunately, limited information was derived from these studies, as selection methods of candidate-miRNAs and heterogeneity in cardiotoxicity assessment greatly hampered the novelty and robustness of the findings. Nevertheless, at least one circulating miRNA, miR-1, showed a good potential as early biomarker of drug-mediated cardiac dysfunction onset. The use of animal models to investigate DOX-induced cardiotoxicity surely helps narrowing the gap between basic research and clinical practice. Despite this, several issues, including selection of relevant miRNAs and less-than-optimal assessment of cardiotoxicity, greatly limited the results obtained so far. Nonetheless, the association of patients-based studies with the use of preclinical models may be the key to address the many unanswered questions regarding the pathophysiology and early detection of cardiotoxicity.

Possible mechanism of GATA4 inhibiting myocardin activity during cardiac hypertrophy

Myocardin is an important factor that regulates cardiac hypertrophy, and its activity can be regulated by GATA4. However, the molecular mechanism of the above process remains unclear. This paper presents three kinds of possible molecular mechanisms of GATA4 inhibiting myocardin activity in the process of cardiac hypertrophy. First, a competitive combination of GATA4 and SRF with myocardin could reduce the formation of the myocardin-SRF-CarG box complex when GATA4 was overexpressed. Second, overexpression of GATA4 could inhibit the combination of myocardin and p300 and downregulate acetylated myocardin levels. Finally, GATA4 could upregulate the phosphorylation of myocardin protein upon activation of the ERK pathway. These findings may provide insight into the function of GATA4 and myocardin in the occurrence and development of cardiac hypertrophy.

Semantic Multi-Classifier Systems Identify Predictive Processes in Heart Failure Models across Species

Genetic model organisms have the potential of removing blind spots from the underlying gene regulatory networks of human diseases. Allowing analyses under experimental conditions they complement the insights gained from observational data. An inevitable requirement for a successful trans-species transfer is an abstract but precise high-level characterization of experimental findings. In this work, we provide a large-scale analysis of seven weak contractility/heart failure genotypes of the model organism zebrafish which all share a weak contractility phenotype. In supervised classification experiments, we screen for discriminative patterns that distinguish between observable phenotypes (homozygous mutant individuals) as well as wild-type (homozygous wild-types) and carriers (heterozygous individuals). As the method of choice we use semantic multi-classifier systems, a knowledge-based approach which constructs hypotheses from a predefined vocabulary of high-level terms (e.g., Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways or Gene Ontology (GO) terms). Evaluating these models leads to a compact description of the underlying processes and guides the screening for new molecular markers of heart failure. Furthermore, we were able to independently corroborate the identified processes in Wistar rats.

Role of Overexpressed Transcription Factor FOXO1 in Fatal Cardiovascular Septal Defects in Patau Syndrome: Molecular and Therapeutic Strategies

Patau Syndrome (PS), characterized as a lethal disease, allows less than 15% survival over the first year of life. Most deaths owe to brain and heart disorders, more so due to septal defects because of altered gene regulations. We ascertained the cytogenetic basis of PS first, followed by molecular analysis and docking studies. Thirty-seven PS cases were referred from the Department of Pediatrics, King Abdulaziz University Hospital to the Center of Excellence in Genomic Medicine Research, Jeddah during 2008 to 2018. Cytogenetic analyses were performed by standard G-band method and trisomy13 were found in all the PS cases. Studies have suggested that genes of chromosome 13 and other chromosomes are associated with PS. We, therefore, did molecular pathway analysis, gene interaction, and ontology studies to identify their associations. Genomic analysis revealed important chr13 genes such as FOXO1, Col4A1, HMGBB1, FLT1, EFNB2, EDNRB, GAS6, TNFSF1, STARD13, TRPC4, TUBA3C, and TUBA3D, and their regulatory partners on other chromosomes associated with cardiovascular disorders, atrial and ventricular septal defects. There is strong indication of involving FOXO1 (Forkhead Box O1) gene-a strong transcription factor present on chr13, interacting with many septal defects link genes. The study was extended using molecular docking to find a potential drug lead for overexpressed FOXO1 inhibition. The phenothiazine and trifluoperazine showed efficiency to inhibit overexpressed FOXO1 protein, and could be potential drugs for PS/trisomy13 after validation.

Network-based predictions of in vivo cardiac hypertrophy

Cardiac hypertrophy is a common response of cardiac myocytes to stress and a predictor of heart failure. While in vitro cell culture studies have identified numerous molecular mechanisms driving hypertrophy, it is unclear to what extent these mechanisms can be integrated into a consistent framework predictive of in vivo phenotypes. To address this question, we investigate the degree to which an in vitro-based, manually curated computational model of the hypertrophy signaling network is able to predict in vivo hypertrophy of 52 cardiac-specific transgenic mice. After minor revisions motivated by in vivo literature, the model concordantly predicts the qualitative responses of 78% of output species and 69% of signaling intermediates within the network model. Analysis of four double-transgenic mouse models reveals that the computational model robustly predicts hypertrophic responses in mice subjected to multiple, simultaneous perturbations. Thus the model provides a framework with which to mechanistically integrate data from multiple laboratories and experimental systems to predict molecular regulation of cardiac hypertrophy.

Stem cells are the most sensitive screening tool to identify toxicity of GATA4-targeted novel small-molecule compounds

Safety assessment of drug candidates in numerous in vitro and experimental animal models is expensive, time consuming and animal intensive. More thorough toxicity profiling already in the early drug discovery projects using human cell models, which more closely resemble the physiological cell types, would help to decrease drug development costs. In this study we aimed to compare different cardiac and stem cell models for in vitro toxicity testing and to elucidate structure–toxicity relationships of novel compounds targeting the cardiac transcription factor GATA4. By screening the effects of eight compounds at concentrations ranging from 10 nM up to 30 µM on the viability of eight different cell types, we identified significant cell type- and structure-dependent toxicity profiles. We further characterized two compounds in more detail using high-content analysis. The results highlight the importance of cell type selection for toxicity screening and indicate that stem cells represent the most sensitive screening model, which can detect toxicity that may otherwise remain unnoticed. Furthermore, our structure–toxicity analysis reveals a characteristic dihedral angle in the GATA4-targeted compounds that causes stem cell toxicity and thus helps to direct further drug development efforts towards non-toxic derivatives.

Salvia miltiorrhizaBurge (Danshen): a golden herbal medicine in cardiovascular therapeutics

Salvia miltiorrhiza Burge (Danshen) is an eminent medicinal herb that possesses broad cardiovascular and cerebrovascular protective actions and has been used in Asian countries for many centuries. Accumulating evidence suggests that Danshen and its components prevent vascular diseases, in particular, atherosclerosis and cardiac diseases, including myocardial infarction, myocardial ischemia/reperfusion injury, arrhythmia, cardiac hypertrophy and cardiac fibrosis. The published literature indicates that lipophilic constituents (tanshinone I, tanshinone IIa, tanshinone IIb, cryptotanshinone, dihydrotanshinone, etc) as well as hydrophilic constituents (danshensu, salvianolic acid A and B, protocatechuic aldehyde, etc) contribute to the cardiovascular protective actions of Danshen, suggesting a potential synergism among these constituents. Herein, we provide a systematic up-to-date review on the cardiovascular actions and therapeutic potential of major pharmacologically active constituents of Danshen. These bioactive compounds will serve as excellent drug candidates in small-molecule cardiovascular drug discovery. This article also provides a scientific rationale for understanding the traditional use of Danshen in cardiovascular therapeutics.

GATA4 regulates angiogenesis and persistence of inflammation in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by abnormal inflammation, angiogenesis, and cartilage destruction. In RA, neoangiogenesis is an early and crucial event to promote the formation of pannus, causing further inflammatory cell infiltration. The transcription factor GATA4 is a critical regulator of cardiac differentiation-specific gene expression. We find that a higher level of GATA4 exists in synovium of rheumatoid arthritis (RA) patients, but the function of GATA4 in RA remains unclear. In the present study, IL-1β induces inflammation in fibroblast-like synoviocytes (FLS) MH7A, which is accompanied with the increased expression of GATA4 and VEGF production. Through application of GATA4 loss-of-function assays, we confirm the requirement of GATA4 expression for inflammation induced by IL-1β in FLS. In addition, we demonstrate for the first time that GATA4 plays key roles in regulating VEGF secretion from RA FLS to promote cellular proliferation, induce cell migration, and angiogenic tube formation of endothelial cells. GATA4 induces the angiogenic factors VEGFA and VEGFC, by directly binding to the promoter and enhancing transcription. The knockdown of GATA4 attenuates the development of collagen-induced arthritis (CIA) and prevents RA-augmented angiogenesis in vivo, which are accompanied with decreased VEGF level. These results reveal a previously unrecognized function for GATA4 as a regulator of RA angiogenesis and we provide experimental data validating the therapeutic target of GATA4 in RA mice.

Cardiac Actions of a Small Molecule Inhibitor Targeting GATA4-NKX2-5 Interaction

Transcription factors are fundamental regulators of gene transcription, and many diseases, such as heart diseases, are associated with deregulation of transcriptional networks. In the adult heart, zinc-finger transcription factor GATA4 is a critical regulator of cardiac repair and remodelling. Previous studies also suggest that NKX2-5 plays function role as a cofactor of GATA4. We have recently reported the identification of small molecules that either inhibit or enhance the GATA4–NKX2-5 transcriptional synergy. Here, we examined the cardiac actions of a potent inhibitor (3i-1000) of GATA4–NKX2-5 interaction in experimental models of myocardial ischemic injury and pressure overload. In mice after myocardial infarction, 3i-1000 significantly improved left ventricular ejection fraction and fractional shortening, and attenuated myocardial structural changes. The compound also improved cardiac function in an experimental model of angiotensin II -mediated hypertension in rats. Furthermore, the up-regulation of cardiac gene expression induced by myocardial infarction and ischemia reduced with treatment of 3i-1000 or when micro- and nanoparticles loaded with 3i-1000 were injected intramyocardially or intravenously, respectively. The compound inhibited stretch- and phenylephrine-induced hypertrophic response in neonatal rat cardiomyocytes. These results indicate significant potential for small molecules targeting GATA4–NKX2-5 interaction to promote myocardial repair after myocardial infarction and other cardiac injuries.

Myocardial transcription factors in diastolic dysfunction: clues for model systems and disease

There are multiple intrinsic mechanisms for diastolic dysfunction ranging from molecular to structural derangements in ventricular myocardium. The molecular mechanisms regulating the progression from normal diastolic function to severe dysfunction still remain poorly understood. Recent studies suggest a potentially important role of core cardio-enriched transcription factors (TFs) in the control of cardiac diastolic function in health and disease through their ability to regulate the expression of target genes involved in the process of adaptive and maladaptive cardiac remodeling. The current relevant findings on the role of a variety of such TFs (TBX5, GATA-4/6, SRF, MYOCD, NRF2, and PITX2) in cardiac diastolic dysfunction and failure are updated, emphasizing their potential as promising targets for novel treatment strategies. In turn, the new animal models described here will be key tools in determining the underlying molecular mechanisms of disease. Since diastolic dysfunction is regulated by various TFs, which are also involved in cross talk with each other, there is a need for more in-depth research from a biomedical perspective in order to establish efficient therapeutic strategies.

Identifying Pri-miRNA Transcription Start Sites

MicroRNAs (miRNAs) are small non-coding RNAs that can regulate gene expression playing vital role in nearly all biological pathways. Even though miRNAs have been intensely studied for more than two decades, information regarding miRNA transcription regulation remains limited. The rapid cleavage of primary miRNA transcripts (pri-miRNAs) by Drosha in the nucleus hinders their identification with conventional RNA-seq approaches. Identifying the transcription start site (TSS) of miRNAs will enable genome-wide identification of their expression regulators, including transcription factors (TFs), other non-coding RNAs (ncRNAs) and epigenetic modifiers, providing significant breakthroughs in understanding the mechanisms underlying miRNA expression in development and disease. Here we present a protocol that utilizes microTSS, a versatile computational framework for accurate and single-nucleotide resolution miRNA TSS predictions as well as miRGen, a database of miRNA gene TSSs coupled with genome-wide maps of TF binding sites.

STAT3 Suppression Is Involved in the Protective Effect of SIRT6 Against Cardiomyocyte Hypertrophy

The activation of signal transducer and activator of transcription 3 (STAT3) is critical for the development of cardiac hypertrophy and heart failure. Sirtuin 6 (SIRT6) protects cardiomyocytes from hypertrophy. This study focused on the association between SIRT6 and STAT3 in the regulation of cardiomyocyte hypertrophy. In the phenylephrine (PE)-induced hypertrophic cardiomyocyte model and in the hearts of isoprenaline-induced cardiac hypertrophic rat model, the mRNA and protein expressions of STAT3 and its phosphorylated level at tyrosine 705 (P-STAT3) were significantly increased. By contrast, the deacetylation activity of SIRT6 was weakened without altering its protein expression. In addition, the nuclear localization of STAT3 and P-STAT3 was enhanced by PE, suggesting that STAT3 was activated in cardiomyocyte hypertrophy. Adenovirus infection-induced SIRT6 overexpression repressed the activation of STAT3 by decreasing its mRNA and protein levels, by suppressing its transcriptional activity, and by hindering the expressions of its target genes. Moreover, the effect of SIRT6 overexpression on eliminating PE-induced expressions of hypertrophic biomarkers, such as atrial natriuretic factor and brain natriuretic peptide, was reversed by STAT3 overexpression. Likewise, SIRT6 knockdown-induced upregulation of atrial natriuretic factor and brain natriuretic peptide was reversed by STAT3 silencing. These observations suggest that the antihypertrophic effect of SIRT6 involves STAT3 suppression. In conclusion, SIRT6 prevents PE-induced activation of STAT3 in cardiomyocyte hypertrophy; the inhibitory effect of SIRT6 on STAT3 contributes to cardiac protection.

Gallic Acid Reduces Blood Pressure and Attenuates Oxidative Stress and Cardiac Hypertrophy in Spontaneously Hypertensive Rats

Gallic acid (GA) has been reported to have beneficial effects on cancer, vascular calcification, and diabetes-induced myocardial dysfunction. We hypothesized that GA controls hypertension via oxidative stress response regulation in an animal model for essential hypertension. Spontaneously hypertensive rats (SHRs) were administered GA for 16 weeks. GA treatment lowered elevated systolic blood pressure in SHRs through the inhibition of vascular contractility and components of the renin-angiotensin II system. In addition, GA administration reduced aortic wall thickness and body weight in SHRs. In SHRs, GA attenuated left ventricular hypertrophy and reduced the expression of cardiac-specific transcription factors. NADPH oxidase 2 (Nox2) and GATA4 mRNA expression was induced in SHR hearts and angiotensin II-treated H9c2 cells; this expression was downregulated by GA treatment. Nox2 promoter activity was increased by the synergistic action of GATA4 and Nkx2-5. GA seems to regulate oxidative stress by inhibiting the DNA binding activity of GATA4 in the rat Nox2 promoter. GA reduced the GATA4-induced Nox activity in SHRs and angiotensin II-treated H9c2 cells. GA administration reduced the elevation of malondialdehyde levels in heart tissue obtained from SHRs. These findings suggest that GA is a potential therapeutic agent for treating cardiac hypertrophy and oxidative stress in SHRs.

Effects of moderate‑intensity endurance exercise on angiotensin II and angiotensin II type I receptors in the rat heart

The current study was aimed at examining the effects of moderate‑intensity endurance exercise on the expression of angiotensin II (AngII) and AngII type 1 receptor (AT1R) in the rat heart. Male Sprague‑Dawley rats were randomly divided into the control group (n=20) and moderate‑intensity endurance exercise group (n=20). Cardiac hypertrophy was induced by treadmill endurance training for 8 weeks. The mRNA expression of AngII and AT1R were assessed by reverse transcription‑quantitative polymerase chain reaction. The immune response positive area and optical density of AngII and AT1R was measured by immunohistochemistry. AngII was primarily expressed in the cytoplasm and membrane, however infrequently in coronary vascular wall smooth muscle cells. AT1R was primarily expressed in the coronary vessel wall smooth muscle, rarely in cardiac cells. The mRNA expression of cardiac AngII was significantly increased after the 8‑week exercise period, while AT1R was significantly decreased. Immunohistochemistry indicated a significant increase in the AngII immune‑positive area and optical density after the 8‑week exercise. The AT1R immune‑positive area and optical density was significantly reduced following the 8‑week exercise. In conclusion, subsequent to 8‑weeks endurance training, the AngII expression was increased and the AT1R expression was decreased. AT1R may expand the coronary artery, thereby increasing coronary blood flow and ensuring the energy supply of heart during exercise. The expression change in AngII does not reflect the character of cardiac hypertrophy. The exercise‑induced change in the expression of AngII and AT1R may be a protective mechanism to avoid cardiac pathological hypertrophy.

Developmental programming: Interaction between prenatal BPA and postnatal overfeeding on cardiac tissue gene expression in female sheep

Epidemiologic studies and studies in rodents point to potential risks from developmental exposure to BPA on cardiometabolic diseases. Furthermore, it is becoming increasingly evident that the manifestation and severity of adverse outcomes is the result of interaction between developmental insults and the prevailing environment. Consistent with this premise, recent studies in sheep found prenatal BPA treatment prevented the adverse effects of postnatal obesity in inducing hypertension. The gene networks underlying these complex interactions are not known. mRNA-seq of myocardium was performed on four groups of four female sheep to assess the effects of prenatal BPA exposure, postnatal overfeeding and their interaction on gene transcription, pathway perturbations and functional effects. The effects of prenatal exposure to BPA, postnatal overfeeding, and prenatal BPA with postnatal overfeeding all resulted in transcriptional changes (85-141 significant differentially expressed genes). Although the effects of prenatal BPA and postnatal overfeeding did not involve dysregulation of many of the same genes, they affected a remarkably similar set of biological pathways. Furthermore, an additive or synergistic effect was not found in the combined treatment group, but rather prenatal BPA treatment led to a partial reversal of the effects of overfeeding alone. Many genes previously known to be affected by BPA and involved in obesity, hypertension, or heart disease were altered following these treatments, and AP-1, EGR1, and EGFR were key hubs affected by BPA and/or overfeeding. Environ. Mol. Mutagen. 58:4-18, 2017. © 2016 Wiley Periodicals, Inc.

Developmental programming: Interaction between prenatal BPA and postnatal overfeeding on cardiac tissue gene expression in female sheep

Epidemiologic studies and studies in rodents point to potential risks from developmental exposure to BPA on cardiometabolic diseases. Furthermore, it is becoming increasingly evident that the manifestation and severity of adverse outcomes is the result of interaction between developmental insults and the prevailing environment. Consistent with this premise, recent studies in sheep found prenatal BPA treatment prevented the adverse effects of postnatal obesity in inducing hypertension. The gene networks underlying these complex interactions are not known. mRNA-seq of myocardium was performed on four groups of four female sheep to assess the effects of prenatal BPA exposure, postnatal overfeeding and their interaction on gene transcription, pathway perturbations and functional effects. The effects of prenatal exposure to BPA, postnatal overfeeding, and prenatal BPA with postnatal overfeeding all resulted in transcriptional changes (85-141 significant differentially expressed genes). Although the effects of prenatal BPA and postnatal overfeeding did not involve dysregulation of many of the same genes, they affected a remarkably similar set of biological pathways. Furthermore, an additive or synergistic effect was not found in the combined treatment group, but rather prenatal BPA treatment led to a partial reversal of the effects of overfeeding alone. Many genes previously known to be affected by BPA and involved in obesity, hypertension, or heart disease were altered following these treatments, and AP-1, EGR1, and EGFR were key hubs affected by BPA and/or overfeeding. Environ. Mol. Mutagen. 58:4-18, 2017. © 2016 Wiley Periodicals, Inc.

Naringin Mitigates Cardiac Hypertrophy by Reducing Oxidative Stress and Inactivating c-Jun Nuclear Kinase-1 Protein in Type I Diabetes

Cardiac hypertrophy (CH) in type 1 diabetes mellitus is attributed to increased oxidative stress-associated activation of c-Jun Nuclear Kinase (JNK). We investigated the effects of naringin on hyperglycemia-associated oxidative stress, activation of JNK-1, and CH. Male Sprague-Dawley rats (225-250 g) (n = 7) were divided into 6 groups. Groups I and II were orally treated with distilled water [3.0 mL/kg body weight/day (BW)] and naringin (50 mg/kg BW), respectively. Groups III-VI were rendered diabetic by a single intraperitoneal injection of 65 mg/kg BW of streptozotocin. Groups III, IV, and V were further treated with insulin (4.0 I.U, s.c, twice daily), naringin (50 mg/kg BW), and ramipril (3.0 mg/kg BW), respectively. After 56 days, the animals were sacrificed and then plasma and cardiac tissues obtained for further analysis. Naringin treatment of diabetic rats significantly reversed oxidative stress, lipid peroxidation, proteins oxidation, CH indices, and JNK protein activation compared with untreated diabetic animals. Our results do suggest that naringin mitigates CH by inhibiting oxidative stress leading to inactivation of JNK-1. Naringin supplements could therefore ameliorate CH in diabetic patients.

Gallic acid prevents isoproterenol-induced cardiac hypertrophy and fibrosis through regulation of JNK2 signaling and Smad3 binding activity

Gallic acid, a type of phenolic acid, has been shown to have beneficial effects in inflammation, vascular calcification, and metabolic diseases. The present study was aimed at determining the effect and regulatory mechanism of gallic acid in cardiac hypertrophy and fibrosis. Cardiac hypertrophy was induced by isoproterenol (ISP) in mice and primary neonatal cardiomyocytes. Gallic acid pretreatment attenuated concentric cardiac hypertrophy. It downregulated the expression of atrial natriuretic peptide, brain natriuretic peptide, and beta-myosin heavy chain in vivo and in vitro. Moreover, it prevented interstitial collagen deposition and expression of fibrosis-associated genes. Upregulation of collagen type I by Smad3 overexpression was observed in cardiac myoblast H9c2 cells but not in cardiac fibroblasts. Gallic acid reduced the DNA binding activity of phosphorylated Smad3 in Smad binding sites of collagen type I promoter in rat cardiac fibroblasts. Furthermore, it decreased the ISP-induced phosphorylation of c-Jun N-terminal kinase (JNK) and extracellular signal regulated kinase (ERK) protein in mice. JNK2 overexpression reduced collagen type I and Smad3 expression as well as GATA4 expression in H9c2 cells and cardiac fibroblasts. Gallic acid might be a novel therapeutic agent for the prevention of cardiac hypertrophy and fibrosis by regulating the JNK2 and Smad3 signaling pathway.