Histone Deacetylase Inhibitors: A Novel Strategy for Neuroprotection and Cardioprotection Following Ischemia/Reperfusion Injury

Ischemia/reperfusion injury is a complex molecular cascade that causes deleterious cellular damage and organ dysfunction. Stroke, sudden cardiac arrest, and acute myocardial infarction are the most common causes of ischemia/reperfusion injury without effective pharmacologic therapies. Existing preclinical evidence suggests that histone deacetylase inhibitors may be an efficacious, affordable, and clinically feasible therapy that can improve neurologic and cardiac outcomes following ischemia/reperfusion injury. In this review, we discuss the pathophysiology and epigenetic modulations of ischemia/reperfusion injury and focus on the neuroprotective and cardioprotective effects of histone deacetylase inhibitors. We also summarize the protective effects of histone deacetylase inhibitors for other vital organs and highlight the key research priorities for their successful translation to the bedside.

Extracellular Endothelial Cell-Derived Vesicles: Emerging Role in Cardiac and Vascular Remodeling in Heart Failure

Extracellular vesicles play a pivotal role in numerous physiological (immune response, cell-to-cell cooperation, angiogenesis) and pathological (reparation, inflammation, thrombosis/coagulation, atherosclerosis, endothelial dysfunction) processes. The development of heart failure is strongly associated with endothelial dysfunction, microvascular inflammation, alteration in tissue repair, and cardiac and vascular remodeling. It has been postulated that activated endothelial cell-derived vesicles are not just transfer forms of several active molecules (such as regulatory peptides, coagulation factors, growth factors, active molecules, hormones that are embedded onto angiogenesis, tissue reparation, proliferation, and even prevention from ischemia/hypoxia), but are instead involved in direct myocardial and vascular damage due to regulation of epigenetic responses of the tissue. These responses are controlled by several factors, such as micro-RNAs, that are transferred inside extracellular vesicles from mother cells to acceptor cells and are transductors of epigenetic signals. Finally, it is not a uniform opinion whether different phenotypes of heart failure are the result of altered cardiac and vascular reparation due to certain epigenetic responses, which are yielded by co-morbidities, such as diabetes mellitus and obesity. The aim of the review is to summarize knowledge regarding the role of various types of extracellular endothelial cell-derived vesicles in the regulation of cardiac and vascular remodeling in heart failure.

Therapeutic approaches targeting Apolipoprotein E function in Alzheimer's disease

One of the primary genetic risk factors for Alzheimer’s disease (AD) is the presence of the Ɛ4 allele of apolipoprotein E (APOE). APOE is a polymorphic lipoprotein that is a major cholesterol carrier in the brain. It is also involved in various cellular functions such as neuronal signaling, neuroinflammation and glucose metabolism. Humans predominantly possess three different allelic variants of APOE, termed E2, E3, and E4, with the E3 allele being the most common. The presence of the E4 allele is associated with increased risk of AD whereas E2 reduces the risk. To understand the molecular mechanisms that underlie APOE-related genetic risk, considerable effort has been devoted towards developing cellular and animal models. Data from these models indicate that APOE4 exacerbates amyloid β plaque burden in a dose-dependent manner. and may also enhance tau pathogenesis in an isoform-dependent manner. Other studies have suggested APOE4 increases the risk of AD by mechanisms that are distinct from modulation of Aβ or tau pathology. Further, whether plasma APOE, by influencing systemic metabolic pathways, can also possibly alter CNS function indirectly is not complete;y understood. Collectively, the available studies suggest that APOE may impact multiple signaling pathways and thus investigators have sought therapeutics that would disrupt pathological functions of APOE while preserving or enhancing beneficial functions. This review will highlight some of the therapeutic strategies that are currently being pursued to target APOE4 towards preventing or treating AD and we will discuss additional strategies that holds promise for the future.

Emodin and emodin-rich rhubarb inhibits histone deacetylase (HDAC) activity and cardiac myocyte hypertrophy

Pathological cardiac hypertrophy is a classical hallmark of heart failure. At the molecular level, inhibition of histone deacetylase (HDAC) enzymes attenuate pathological cardiac hypertrophy in vitro and in vivo. Emodin is an anthraquinone that has been implicated in cardiac protection. However, it is not known if the cardio-protective actions for emodin are mediated through HDAC-dependent regulation of gene expression. Therefore, we hypothesized that emodin would attenuate pathological cardiac hypertrophy via inhibition of HDACs, and that these actions would be reflected in an emodin-rich food like rhubarb. In this study, we demonstrate that emodin and Turkish rhubarb containing emodin inhibit HDAC activity in vitro, with fast-on, slow-off kinetics. Moreover, we show that emodin increased histone acetylation in cardiomyocytes concomitant to global changes in gene expression; gene expression changes were similar to the well-established pan-HDAC inhibitor trichostatin A (TSA). We additionally present evidence that emodin inhibited phenylephrine (PE) and phorbol myristate acetate (PMA)-induced hypertrophy in neonatal rat ventricular myocytes (NRVMs). Lastly, we demonstrate that the cardioprotective actions of emodin are translated to an angiotensin II (Ang) mouse model of cardiac hypertrophy and fibrosis and are linked to HDAC inhibition. These data suggest that emodin blocked pathological cardiac hypertrophy, in part, by inhibiting HDAC-dependent gene expression changes.

HDAC inhibition improves cardiopulmonary function in a feline model of diastolic dysfunction

Heart failure with preserved ejection fraction (HFpEF) is a major health problem without effective therapies. This study assessed the effects of histone deacetylase (HDAC) inhibition on cardiopulmonary structure, function, and metabolism in a large mammalian model of pressure overload recapitulating features of diastolic dysfunction common to human HFpEF. Male domestic short-hair felines (n = 31, aged 2 months) underwent a sham procedure (n = 10) or loose aortic banding (n = 21), resulting in slow-progressive pressure overload. Two months after banding, animals were treated daily with suberoylanilide hydroxamic acid (b + SAHA, 10 mg/kg, n = 8), a Food and Drug Administration-approved pan-HDAC inhibitor, or vehicle (b + veh, n = 8) for 2 months. Echocardiography at 4 months after banding revealed that b + SAHA animals had significantly reduced left ventricular hypertrophy (LVH) (P < 0.0001) and left atrium size (P < 0.0001) versus b + veh animals. Left ventricular (LV) end-diastolic pressure and mean pulmonary arterial pressure were significantly reduced in b + SAHA (P < 0.01) versus b + veh. SAHA increased myofibril relaxation ex vivo, which correlated with in vivo improvements of LV relaxation. Furthermore, SAHA treatment preserved lung structure, compliance, blood oxygenation, and reduced perivascular fluid cuffs around extra-alveolar vessels, suggesting attenuated alveolar capillary stress failure. Acetylation proteomics revealed that SAHA altered lysine acetylation of mitochondrial metabolic enzymes. These results suggest that acetylation defects in hypertrophic stress can be reversed by HDAC inhibitors, with implications for improving cardiac structure and function in patients.

Up-regulation of HDACs, a harbinger of uraemic endothelial dysfunction, is prevented by defibrotide

Endothelial dysfunction is an earlier contributor to the development of atherosclerosis in chronic kidney disease (CKD), in which the role of epigenetic triggers cannot be ruled out. Endothelial protective strategies, such as defibrotide (DF), may be useful in this scenario. We evaluated changes induced by CKD on endothelial cell proteome and explored the effect of DF and the mechanisms involved. Human umbilical cord vein endothelial cells were exposed to sera from healthy donors (n = 20) and patients with end-stage renal disease on haemodialysis (n = 20). Differential protein expression was investigated by using a proteomic approach, Western blot and immunofluorescence. HDAC1 and HDAC2 overexpression was detected. Increased HDAC1 expression occurred at both cytoplasm and nucleus. These effects were dose-dependently inhibited by DF. Both the HDACs inhibitor trichostatin A and DF prevented the up-regulation of the endothelial dysfunction markers induced by the uraemic milieu: intercellular adhesion molecule-1, surface Toll-like receptor-4, von Willebrand Factor and reactive oxygen species. Moreover, DF down-regulated HDACs expression through the PI3/AKT signalling pathway. HDACs appear as key modulators of the CKD-induced endothelial dysfunction as specific blockade by trichostatin A or by DF prevents endothelial dysfunction responses to the CKD insult. Moreover, DF exerts its endothelial protective effect by inhibiting HDAC up-regulation likely through PI3K/AKT.

HDAC (Histone Deacetylase) Inhibitor Valproic Acid Attenuates Atrial Remodeling and Delays the Onset of Atrial Fibrillation in Mice

Supplemental Digital Content is available in the text.

Background:

A structural, electrical and metabolic atrial remodeling is central in the development of atrial fibrillation (AF) contributing to its initiation and perpetuation. In the heart, HDACs (histone deacetylases) control remodeling associated processes like hypertrophy, fibrosis, and energy metabolism. Here, we analyzed, whether the HDAC class I/IIa inhibitor valproic acid (VPA) is able to attenuate atrial remodeling in CREM-IbΔC-X (cAMP responsive element modulator isoform IbΔC-X) transgenic mice, a mouse model of extensive atrial remodeling with age-dependent progression from spontaneous atrial ectopy to paroxysmal and finally long-lasting AF.

Methods:

VPA was administered for 7 or 25 weeks to transgenic and control mice. Atria were analyzed macroscopically and using widefield and electron microscopy. Action potentials were recorded from atrial cardiomyocytes using patch-clamp technique. ECG recordings documented the onset of AF. A proteome analysis with consecutive pathway mapping identified VPA-mediated proteomic changes and related pathways.

Results:

VPA attenuated many components of atrial remodeling that are present in transgenic mice, animal AF models, and human AF. VPA significantly (P<0.05) reduced atrial dilatation, cardiomyocyte enlargement, atrial fibrosis, and the disorganization of myocyte’s ultrastructure. It significantly reduced the occurrence of atrial thrombi, reversed action potential alterations, and finally delayed the onset of AF by 4 to 8 weeks. Increased histone H4-acetylation in atria from VPA-treated transgenic mice verified effective in vivo HDAC inhibition. Cardiomyocyte-specific genetic inactivation of HDAC2 in transgenic mice attenuated the ultrastructural disorganization of myocytes comparable to VPA. Finally, VPA restrained dysregulation of proteins in transgenic mice that are involved in a multitude of AF relevant pathways like oxidative phosphorylation or RhoA (Ras homolog gene family, member A) signaling and disease functions like cardiac fibrosis and apoptosis of muscle cells.

Conclusions:

Our results suggest that VPA, clinically available, well-tolerated, and prescribed to many patients for years, has the therapeutic potential to delay the development of atrial remodeling and the onset of AF in patients at risk.

CD47 Deficiency Attenuates Isoproterenol-Induced Cardiac Remodeling in Mice

In this study, we investigated whether CD47 deficiency attenuates isoproterenol- (ISO-) induced cardiac remodeling in mice. Cardiac remodeling was induced by intraperitoneal (i.p.) injection of ISO (60 mg·kg⁻¹·d⁻¹ in 100 μl of sterile normal saline) daily for 14 days and was confirmed by increased levels of lactate dehydrogenase (LDH) and creatine kinase MB (CK-MB), increased heart weight to body weight (HW/BW) ratios, and visible cardiac fibrosis. Apoptosis was evaluated by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining. Levels of malondialdehyde (MDA) and reactive oxygen species (ROS) were found to be significantly higher in the ISO group than in the control group, while superoxide dismutase (SOD) levels were suppressed in the ISO group. However, CD47 knockout significantly limited ISO-induced increases in LDH, CK-MB, and HW/BW ratios, cardiac fibrosis, oxidative stress, and apoptosis in the heart. In addition, CD47 deficiency also increased p-AMPK and LAMP2 expression and decreased HDAC3, cleaved Caspase-3, cleaved Caspase-9, LC3II, and p62 expression in cardiac tissues. In conclusion, CD47 deficiency reduced i.p. ISO-induced cardiac remodeling probably by inhibiting the HDAC3 pathway, improving AMPK signaling and autophagy flux, and rescuing autophagic clearance.

Epigenetic Modifications in Cardiovascular Aging and Diseases

Aging is associated with a progressive decline in cardiovascular structure and function. Accumulating evidence links cardiovascular aging to epigenetic alterations encompassing a complex interplay of DNA methylation, histone posttranslational modifications, and dynamic nucleosome occupancy governed by numerous epigenetic factors. Advances in genomics technology have led to a profound understanding of chromatin reorganization in both cardiovascular aging and diseases. This review summarizes recent discoveries in epigenetic mechanisms involved in cardiovascular aging and diseases and discusses potential therapeutic strategies to retard cardiovascular aging and conquer related diseases through the rejuvenation of epigenetic signatures to a young state.

Histone deacetylase activity governs diastolic dysfunction through a nongenomic mechanism

There are no approved drugs for the treatment of heart failure with preserved ejection fraction (HFpEF), which is characterized by left ventricular (LV) diastolic dysfunction. We demonstrate that ITF2357 (givinostat), a clinical-stage inhibitor of histone deacetylase (HDAC) catalytic activity, is efficacious in two distinct murine models of diastolic dysfunction with preserved EF. ITF2357 blocked LV diastolic dysfunction due to hypertension in Dahl salt-sensitive (DSS) rats and suppressed aging-induced diastolic dysfunction in normotensive mice. HDAC inhibitor-mediated efficacy was not due to lowering blood pressure or inhibiting cellular and molecular events commonly associated with diastolic dysfunction, including cardiac fibrosis, cardiac hypertrophy, or changes in cardiac titin and myosin isoform expression. Instead, ex vivo studies revealed impairment of cardiac myofibril relaxation as a previously unrecognized, myocyte-autonomous mechanism for diastolic dysfunction, which can be ameliorated by HDAC inhibition. Translating these findings to humans, cardiac myofibrils from patients with diastolic dysfunction and preserved EF also exhibited compromised relaxation. These data suggest that agents such as HDAC inhibitors, which potentiate cardiac myofibril relaxation, hold promise for the treatment of HFpEF in humans.

Epigenetics and Mechanobiology in Heart Development and Congenital Heart Disease

: Congenital heart disease (CHD) is the most common birth defect worldwide and the number one killer of live-born infants in the United States. Heart development occurs early in embryogenesis and involves complex interactions between multiple cell populations, limiting the understanding and consequent treatment of CHD. Furthermore, genome sequencing has largely failed to predict or yield therapeutics for CHD. In addition to the underlying genome, epigenetics and mechanobiology both drive heart development. A growing body of evidence implicates the aberrant regulation of these two extra-genomic systems in the pathogenesis of CHD. In this review, we describe the stages of human heart development and the heart defects known to manifest at each stage. Next, we discuss the distinct and overlapping roles of epigenetics and mechanobiology in normal development and in the pathogenesis of CHD. Finally, we highlight recent advances in the identification of novel epigenetic biomarkers and environmental risk factors that may be useful for improved diagnosis and further elucidation of CHD etiology.

Selective inhibition of histone deacetylase 8 improves vascular hypertrophy, relaxation, and inflammation in angiotensin II hypertensive mice

Background

The dysregulation of histone deacetylase (HDAC) protein expression or its enzyme activity is implicated in a variety of diseases. Cardiac HDAC6 and HDAC8 enzyme activity induced by deoxycorticosterone acetate (DOCA) hypertension was attenuated by sodium valproate, a pan-HDAC inhibitor. However, the HDAC6-selective inhibitor, tubastatin A, did not attenuate angiotensin II-induced hypertension. The purpose of this study was to investigate whether PCI34051, an HDAC8-selective inhibitor, can modulate angiotensin II-induced hypertension and its regulatory mechanism.

Methods

An angiotensin II-regulated mouse model was used in this study. Animals received vehicle or PCI34051 (3 mg·kg - ¹·day- ¹) via intraperitoneal injection. Systolic blood pressure was measured by the tail-cuff method. Blood vessel thickness was measured following hematoxylin and eosin staining, VCAM-1 immunohistochemistry was performed in the aortas, and mRNA expression of renin-angiotensin system components, inflammation markers, and NADPH oxidase (Nox) was determined by RT-PCR. The effect of PCI34051 on vasorelaxation was studied in rat aortic rings, and its effect on nitric oxide (NO) production was determined using DAF-FM DA, a fluorescent dye, in human umbilical vascular endothelial cells (HUVECs).

Results

PCI34051 administration reduced systolic blood pressure via downregulation of angiotensin II receptor type 1 (AT1) mRNA expression. PCI34051 treatment attenuated vascular hypertrophy by decreasing E2F3 and GATA6 mRNA expression. Vascular relaxation after PCI34051 treatment was more dependent on vascular endothelial cells and it was blocked by an NO synthase (NOS) inhibitor. In addition, NO production increased in HUVECs after PCI34051 treatment; this was decreased by the NOS inhibitor. The expression of inflammatory molecules and adhesion molecules VCAM-1 and ICAM-1 decreased in the aortas of angiotensin II-infused mice after PCI34051 administration. However, PCI34051 did not affect Nox or its regulatory subunits.

Conclusions

PCI34051 lowered high blood pressure through modulation of arterial remodeling, vasoconstriction, and inflammation in an angiotensin II-induced hypertension model. We suggest that HDAC8 could be a potential therapeutic target for hypertension.

Harnessing the HDAC-histone deacetylase enzymes, inhibitors and how these can be utilised in tissue engineering

There are large knowledge gaps regarding how to control stem cells growth and differentiation. The limitations of currently available technologies, such as growth factors and/or gene therapies has led to the search of alternatives. We explore here how a cell's epigenome influences determination of cell type, and potential applications in tissue engineering. A prevalent epigenetic modification is the acetylation of DNA core histone proteins. Acetylation levels heavily influence gene transcription. Histone deacetylase (HDAC) enzymes can remove these acetyl groups, leading to the formation of a condensed and more transcriptionally silenced chromatin. Histone deacetylase inhibitors (HDACis) can inhibit these enzymes, resulting in the increased acetylation of histones, thereby affecting gene expression. There is strong evidence to suggest that HDACis can be utilised in stem cell therapies and tissue engineering, potentially providing novel tools to control stem cell fate. This review introduces the structure/function of HDAC enzymes and their links to different tissue types (specifically bone, cardiac, neural tissues), including the history, current status and future perspectives of using HDACis for stem cell research and tissue engineering, with particular attention paid to how different HDAC isoforms may be integral to this field.

The nonepigenetic role for small molecule histone deacetylase inhibitors in the regulation of cardiac function

Eight million US adults are projected to suffer from heart failure (HF) by 2030. Of concern, 5-year mortality rates following HF diagnosis approximate 40%. Small molecule histone deacetylase (HDAC) inhibitors have demonstrated efficacy for the treatment and reversal of HF. Historically, HDACs were studied as regulators of nucleosomal histones, in which lysine deacetylation on histone tails changed DNA-histone protein electrostatic interactions, leading to chromatin condensation and changes in gene expression. However, recent proteomics studies have demonstrated that approximately 4500 proteins can be acetylated in various tissues; the function of most of these remains unknown. This Review will focus on the nonepigenetic role for lysine acetylation in the heart, with a focus on nonepigenetic actions for HDAC inhibitors on cardiac function.

Drugging transcription in heart failure

Advances in our understanding of the basic biology and biochemistry of chromatin structure and function at genome scales has led to tremendous growth in the fields of epigenomics and transcriptional biology. While it has long been appreciated that transcriptional pathways are dysregulated in failing hearts, only recently has the idea of disrupting altered transcription by targeting chromatin-associated proteins been explored. Here, we provide a brief overview of efforts to drug transcription in the context of heart failure, focusing on the bromo- and extra-terminal domain (BET) family of chromatin co-activator proteins.

Epigenetic therapies in heart failure

Heart failure (HF) is a dominant cause of morbidity and mortality in the developed world, with available pharmacotherapies limited by high rates of residual mortality and a failure to directly target the changes in cell state that drive adverse cardiac remodeling. Pathologic cardiac remodeling is driven by stress-activated cardiac signaling cascades that converge on defined components of the chromatin regulatory apparatus in the nucleus, triggering broad shifts in transcription and cell state. Thus, studies focusing on how cytosolic signaling pathways couple to the nuclear gene control machinery has been an area of therapeutic interest in HF. In this review, we discuss current concepts pertaining to the role of chromatin regulators in HF pathogenesis, with a focus on specific proteins and RNA-containing macromolecular complexes that have shown promise as druggable targets in the experimental setting.

Structure-Based Drug Designing Recommends HDAC6 Inhibitors To Attenuate Microtubule-Associated Tau-Pathogenesis

Protein acetylation and deacetylation play vital roles in the structural and physiological behavior of target proteins. Histone deacetylase 6 (HDAC6) remains a key therapeutic target in several chronic diseases such as cancer, neurodegenerative, and hematological diseases. In tau-pathogenesis, HDAC6 tightly regulates microtubule-associated tau physiology, and its inhibition suppresses Alzheimer's phenotype. To this end, the current study has identified novel HDAC6 inhibitors by structure-based drug designing method. A pharmacophore was generated from HDAC6 in complex with trichostatin A. The selected pharmacophore had five features including two hydrogen bond donors, one hydrogen bond acceptor, and two hydrophobic features. Pharmacophore validation obtained the highest GH score of 0.80. By applying Lipinski's rule of five and ADMET Descriptors, a drug-like database of 29 183 molecules was generated from the Zinc Natural Product Database. The validated pharmacophore screened 841 drug-like molecules and was subsequently subjected to molecular docking in the active site of HDAC6. Molecular docking identified 11 hits, where they showed the highest ChemPLP score (>90.00), stable conformation, and hydrogen-bond interactions with catalytic residues of HDAC6. Finally, molecular dynamics simulation identified three molecules as potent HDAC6 inhibitors with stable root-mean-square deviation and the highest number of hydrogen bonds with the catalytic residues of HDAC6. Overall, we recommend three novel inhibitors of HDAC6, capable of suppressing the microtubule-associated tau-pathogenesis.

Differential localizations of protein phosphatase 1 isoforms determine their physiological function in the heart

Protein phosphatase 1 isoforms α, β, and γ (PP1α, PP1β, and PP1γ) are highly homologous in the catalytic domains but have distinct subcellular localizations. In this study, we utilized both primary cell culture and knockout mice to investigate the isoform-specific roles of PP1s in the heart. In both neonatal and adult cardiac myocytes, PP1β was mainly localized in the nucleus, compared to the predominant presence of PP1α and PP1γ in the cytoplasm. Adenovirus-mediated overexpression of PP1α led to decreased phosphorylation of phospholamban, which was not influenced by overexpression of either PP1β or PP1γ. Interestingly, only cardiac-specific knockout of PP1β resulted in increased HDAC7 phosphorylation, consistent with the predominant nuclear localization of PP1β. Functionally, deletion of either PP1 isoform resulted in reduced fractional shortening in aging mice, however only PP1β deletion resulted in interstitial fibrosis in mice as early as 3 weeks of age. Deletion of neither PP1 isoform had any effect on pathological cardiac hypertrophy induced by 2 weeks of pressure overload stimulation. Together, our data suggest that PP1 isoforms have differential localizations to regulate the phosphorylation of their specific substrates for the physiological function in the heart.

HDAC inhibition as a therapeutic strategy in myocardial ischemia/reperfusion injury

Reperfusion injury during myocardial infarction accounts for approximately half of final infarct size. Whereas this has been known for decades, efficacious therapy targeting reperfusion injury remains elusive. Many proteins are subject to reversible acetylation, and drugs targeting enzymes that govern these events have emerged in oncology. Among these, small molecules targeting protein deacetylating enzymes, so-called histone deacetylases (HDACs), are approved for human use in rare cancers. Now, work emerging from multiple laboratories, and in both mice and large animals, has documented that HDAC inhibition using compounds approved for clinical use confers robust cardioprotection when delivered at the time of myocardial reperfusion. Here, we summarize the key underpinnings of this science, discuss potential mechanisms, and provide a framework for a first-in-human clinical trial.

Targeting autophagy in cardiac ischemia/reperfusion injury: A novel therapeutic strategy

Acute myocardial infarction (AMI) is one of the leading causes of morbidity worldwide. Myocardial reperfusion is known as an effective therapeutic choice against AMI. However, reperfusion of blood flow induces ischemia/reperfusion (I/R) injury through different complex processes including ion accumulation, disruption of mitochondrial membrane potential, the formation of reactive oxygen species, and so forth. One of the processes that gets activated in response to I/R injury is autophagy. Indeed, autophagy acts as a "double-edged sword" in the pathology of myocardial I/R injury and there is a controversy about autophagy being beneficial or detrimental. On the basis of the autophagy effect and regulation on myocardial I/R injury, many studies targeted it as a therapeutic strategy. In this review, we discuss the role of autophagy in I/R injury and its targeting as a therapeutic strategy.

Synthesis and Biological Evaluation of Novel Thiazolyl-Coumarin Derivatives as Potent Histone Deacetylase Inhibitors with Antifibrotic Activity

New histone deacetylases (HDAC) inhibitors with low toxicity to non-cancerous cells, are a prevalent issue at present because these enzymes are actively involved in fibrotic diseases. We designed and synthesized a novel series of thiazolyl-coumarins, substituted at position 6 (R = H, Br, OCH₃), linked to classic zinc binding groups, such as hydroxamic and carboxylic acid moieties and alternative zinc binding groups such as disulfide and catechol. Their in vitro inhibitory activities against HDACs were evaluated. Disulfide and hydroxamic acid derivatives were the most potent ones. Assays with neonatal rat cardiac fibroblasts demonstrated low cytotoxic effects for all compounds. Regarding the parameters associated to cardiac fibrosis development, the compounds showed antiproliferative effects, and triggered a strong decrease on the expression levels of both α-SMA and procollagen I. In conclusion, the new thiazolyl-coumarin derivatives inhibit HDAC activity and decrease profibrotic effects on cardiac fibroblasts.

HDAC inhibitor valproic acid protects heart function through Foxm1 pathway after acute myocardial infarction

BACKGROUND

Epigenetic histone acetylation is a major event controlling cell functions, such as metabolism, differentiation and repair. Here, we aim to determine whether Valproic acid (VPA), a FDA approved inhibitor of histone deacetylation for bipolar disease, could protect heart against myocardial infarction (MI) injury and elucidate key molecular pathways.

METHODS

VPA was administrated to MI rats at different time points, onset and after MI injury. Echocardiography, histology, serum biology assays, and gene expression, inhibition, and over-expression were performed to characterize the systolic function, infarct size, gene and signaling pathways.

FINDINGS

VPA treatment reduced the infarct size by ~50% and preserved the systolic function of heart after acute MI in rats. Even 60 min after infarction, VPA treatment significantly decreased infarct size. Furthermore, long-term treatment of VPA markedly improved myocardial performance. VPA regulated gene expression essential for cell survival and anti-inflammatory response. Consequently, oxidative stress and cell death were notably reduced after VPA treatment. Moreover, Foxm1 was identified as a potential key target of VPA. Overexpression of Foxm1 provided similar heart protective effect to VPA treatment. Particularly, both VPA treatment and Foxm1 over-expression repressed inflammatory response after MI for heart protection. In contrast, inhibition of Foxm1 activity abolished the cardiac protective effect of VPA. VPA mediated CM protection through Foxm1 upregulation was also identified in a human ESC derived CM hypoxia/reperfusion system.

INTERPRETATION

VPA treatments significantly reduce cardiac damage after MI and the cardioprotective effect of VPA is likely mediated via Foxm1 pathway. FUND: This work was mainly supported by 1R01HL109054.

The Crosstalk between Acetylation and Phosphorylation: Emerging New Roles for HDAC Inhibitors in the Heart

Approximately five million United States (U.S.) adults are diagnosed with heart failure (HF), with eight million U.S. adults projected to suffer from HF by 2030. With five-year mortality rates following HF diagnosis approximating 50%, novel therapeutic treatments are needed for HF patients. Pre-clinical animal models of HF have highlighted histone deacetylase (HDAC) inhibitors as efficacious therapeutics that can stop and potentially reverse cardiac remodeling and dysfunction linked with HF development. HDACs remove acetyl groups from nucleosomal histones, altering DNA-histone protein electrostatic interactions in the regulation of gene expression. However, HDACs also remove acetyl groups from non-histone proteins in various tissues. Changes in histone and non-histone protein acetylation plays a key role in protein structure and function that can alter other post translational modifications (PTMs), including protein phosphorylation. Protein phosphorylation is a well described PTM that is important for cardiac signal transduction, protein activity and gene expression, yet the functional role for acetylation-phosphorylation cross-talk in the myocardium remains less clear. This review will focus on the regulation and function for acetylation-phosphorylation cross-talk in the heart, with a focus on the role for HDACs and HDAC inhibitors as regulators of acetyl-phosphorylation cross-talk in the control of cardiac function.

Epigenetics and precision medicine in cardiovascular patients: from basic concepts to the clinical arena

Cardiovascular diseases (CVDs) remain the leading cause of mortality worldwide and also inflict major burdens on morbidity, quality of life, and societal costs. Considering that CVD preventive medications improve vascular outcomes in less than half of patients (often relative risk reductions range from 12% to 20% compared with placebo), precision medicine offers an attractive approach to refine the targeting of CVD medications to responsive individuals in a population and thus allocate resources more wisely and effectively. New tools furnished by advances in basic science and translational medicine could help achieve this goal. This approach could reach beyond the practitioners 'eyeball' assessment or venerable markers derived from the physical examination and standard laboratory evaluation. Advances in genetics have identified novel pathways and targets that operate in numerous diseases, paving the way for 'precision medicine'. Yet the inherited genome determines only part of an individual's risk profile. Indeed, standard genomic approaches do not take into account the world of regulation of gene expression by modifications of the 'epi'genome. Epigenetic modifications defined as 'heritable changes to the genome that do not involve changes in DNA sequence' have emerged as a new layer of biological regulation in CVD and could advance individualized risk assessment as well as devising and deploying tailored therapies. This review, therefore, aims to acquaint the cardiovascular community with the rapidly advancing and evolving field of epigenetics and its implications in cardiovascular precision medicine.

Disruption of cardiac Med1 inhibits RNA polymerase II promoter occupancy and promotes chromatin remodeling

The Mediator coactivator complex directs gene-specific expression by binding distal enhancer-bound transcription factors through its Med1 subunit while bridging to RNA polymerase II (Pol II) at gene promoters. In addition, Mediator scaffolds epigenetic modifying enzymes that determine local DNA accessibility. Previously, we found that deletion of Med1 in cardiomyocytes deregulates more than 5,000 genes and promotes acute heart failure. Therefore, we hypothesized that Med1 deficiency disrupts enhancer-promoter coupling. Using chromatin immunoprecipitation-coupled deep sequencing (ChIP-seq; n = 3/ChIP assay), we found that the Pol II pausing index is increased in Med1 knockout versus floxed control mouse hearts primarily due to a decrease in Pol II occupancy at the majority of transcriptional start sites without a corresponding increase in elongating species. Parallel ChIP-seq assays reveal that Med1-dependent gene expression correlates strongly with histone H3 K27 acetylation, which is indicative of open and active chromatin at transcriptional start sites, whereas H3 K27 trimethylated levels, representing condensed and repressed DNA, are broadly increased and inversely correlate with absolute expression levels. Furthermore, Med1 deletion leads to dynamic changes in acetyl-K27 associated superenhancer regions and their enriched transcription factor-binding motifs that are consistent with altered gene expression. Our findings suggest that Med1 is important in establishing enhancer-promoter coupling in the heart and supports the proposed role of Mediator in establishing preinitiation complex formation. We also found that Med1 determines chromatin accessibility within genes and enhancer regions and propose that the composition of transcription factors associated with superenhancer changes to direct gene-specific expression. NEW & NOTEWORTHY Based on our previous findings that transcriptional homeostasis and cardiac function are disturbed by cardiomyocyte deletion of the Mediator coactivator Med1 subunit, we investigated potential underlying changes in RNA polymerase II localization and global chromatin accessibility. Using chromatin immunoprecipitation sequencing, we found that disrupted transcription arises from a deficit in RNA polymerase II recruitment to gene promoters. Furthermore, active versus repressive chromatin marks are redistributed within gene loci and at enhancer regions correlated with gene expression changes.

Epigenomic regulation of heart failure: integrating histone marks, long noncoding RNAs, and chromatin architecture

Epigenetic processes are known to have powerful roles in organ development across biology. It has recently been found that some of the chromatin modulatory machinery essential for proper development plays a previously unappreciated role in the pathogenesis of cardiac disease in adults. Investigations using genetic and pharmacologic gain- and loss-of-function approaches have interrogated the function of distinct epigenetic regulators, while the increased deployment of the suite of next-generation sequencing technologies have fundamentally altered our understanding of the genomic targets of these chromatin modifiers. Here, we review recent developments in basic and translational research that have provided tantalizing clues that may be used to unlock the therapeutic potential of the epigenome in heart failure. Additionally, we provide a hypothesis to explain how signal-induced crosstalk between histone tail modifications and long non-coding RNAs triggers chromatin architectural remodeling and culminates in cardiac hypertrophy and fibrosis.

Converse role of class I and class IIa HDACs in the progression of atrial fibrillation

Atrial fibrillation (AF), the most common persistent clinical tachyarrhythmia, is associated with altered gene transcription which underlies cardiomyocyte dysfunction, AF susceptibility and progression. Recent research showed class I and class IIa histone deacetylases (HDACs) to regulate pathological and fetal gene expression, and thereby induce hypertrophy and cardiac contractile dysfunction. Whether class I and class IIa HDACs are involved in AF promotion is unknown. We aim to elucidate the role of class I and class IIa HDACs in tachypacing-induced contractile dysfunction in experimental model systems for AF and clinical AF. METHODS AND RESULTS: Class I and IIa HDACs were overexpressed in HL-1 cardiomyocytes followed by calcium transient (CaT) measurements. Overexpression of class I HDACs, HDAC1 or HDAC3, significantly reduced CaT amplitude in control normal-paced (1 Hz) cardiomyocytes, which was further reduced by tachypacing (5 Hz) in HDAC3 overexpressing cardiomyocytes. HDAC3 inhibition by shRNA or by the specific inhibitor, RGFP966, prevented contractile dysfunction in both tachypaced HL-1 cardiomyocytes and Drosophila prepupae. Conversely, overexpression of class IIa HDACs (HDAC4, HDAC5, HDAC7 or HDAC9) did not affect CaT in controls, with HDAC5 and HDAC7 overexpression even protecting against tachypacing-induced CaT loss. Notably, the protective effect of HDAC5 and HDAC7 was abolished in cardiomyocytes overexpressing a dominant negative HDAC5 or HDAC7 mutant, bearing a mutation in the binding domain for myosin enhancer factor 2 (MEF2). Furthermore, tachypacing induced phosphorylation of HDAC5 and promoted its translocation from the nucleus to cytoplasm, leading to up-regulation of MEF2-related fetal gene expression (β-MHC, BNP). In accord, boosting nuclear localization of HDAC5 by MC1568 or Go6983 attenuated CaT loss in tachypaced HL-1 cardiomyocytes and preserved contractile function in Drosophila prepupae. Findings were expanded to clinical AF. Here, patients with AF showed a significant increase in expression levels and activity of HDAC3, phosphorylated HDAC5 and fetal genes (β-MHC, BNP) in atrial tissue compared to controls in sinus rhythm. CONCLUSION: Class I and class IIa HDACs display converse roles in AF progression. Whereas overexpression of Class I HDAC3 induces cardiomyocyte dysfunction, class IIa HDAC5 overexpression reveals protective properties. Accordingly, HDAC3 inhibitors and HDAC5 nuclear boosters show protection from tachypacing-induced changes and therefore may represent interesting therapeutic options in clinical AF.

Transgenic overexpression of active HDAC4 in the heart attenuates cardiac function and exacerbates remodeling in infarcted myocardium

Histone deacetylases (HDACs) play a critical role in modulating cardiac function and ischemic injury. HDAC4 was found to be elevated and activated in response to injury. However, whether HDAC4 mediates cardiac function is currently unknown. In this study, we created myocyte-specific activated HDAC4 transgenic mice to examine the role of HDAC4 in mediating cardiac function during development and response to infarction. There are no differences in cardiac function and gross phenotype between wild-type and cardiomyocyte-specific HDAC4 transgenic mice at 1 mo of age. However, cardiac dysfunction and vascular growth deficiency were displayed in 6-mo-old HDAC4-transgenic mice compared with wild-type mice. Activation of HDAC4 increased heart and myocyte size, hypertrophic proteins, and interstitial fibrosis in 6-mo-old mice but not in 1-mo-old mice. To further define whether activated HDAC4 in the heart could impact myocardial function and remodeling, myocardial infarction was created in both wild-type and cardiomyocyte-specific HDAC4-transgenic mice. In myocardial infarction, the overexpression of activated HDAC4 exacerbated cardiac dysfunction and augmented cardiac remodeling and interstitial fibrosis, which was associated with the reduction of cardiokines in the heart. These results indicate the activation of HDAC4 as a crucial regulator for cardiac function in development and myocardial infarction. NEW & NOTEWORTHY We created myocyte-specific activated HDAC4-transgenic mice to examine the function of HDAC4 in mediating cardiac function. HDAC4 overexpression led to cardiac dysfunction, which was associated with increased hypertrophy and myocardial fibrosis. Furthermore, the overexpression of activated HDAC4 exacerbated cardiac dysfunction, augmented remodeling, and increased apoptosis in the infarcted heart. This is the first demonstration that transgenic overexpression of HDAC4 is crucial for modulation of cardiac function and remodeling.

Histone deacetylase inhibition attenuates atrial arrhythmogenesis in sterile pericarditis

Cardiac surgery is complicated with atrial fibrillation (AF). Histone deacetylase (HDAC) inhibition reduces AF occurrence. In pericarditis, HDAC inhibition may modulate AF trigger and substrate. We recorded electrocardiograms in control and pericardiotomic (op) rabbits without and with an intraperitoneal injection of MPT0E014 (HDAC inhibitor). Conventional microelectrodes recorded action potentials (APs) in pulmonary veins (PVs), the right and left atrium (LA). Masson's trichrome was used to identify collagen fibers in PVs and the LA. Electrocardiograms showed frequent atrial premature contractions in op rabbits, but not in the other 3 groups. The beating rates in PVs and opPVs were decreased by MPT0E014 treatment. Spontaneous burst firings occurred in opPVs (36.4%), but not in control PVs. H₂O₂ induced greater burst firings in opPVs (72.7%) than in control PVs (11.1%), MPT0E014-treated PVs (16.7%), and MPT0E014-treated opPVs (12.5%). The AP duration at a repolarization extent of 90% (APD₉₀) was shorter in the opLA than that in the control LA. In the presence of isoproterenol (1 μM), rapid atrial pacing (RAP, 20 Hz) induced a higher incidence of burst firings in the opLA (90%) than in the other groups. In contrast, acetylcholine (5 mM) and RAP induced a lower incidence of burst firing in the MPT0E014-treated LA (33.3%) than in the other groups. Fibrosis prevailed in opPVs and the opLA compared to the respective control PVs and LA, which was attenuated in those that received MPT0E014. In conclusion, a pericardiotomy increased fibrosis and arrhythmogenesis in PVs and the LA, which were prevented by HDAC inhibition.

Upregulation of C/EBPβ and TSC2 by an HDAC inhibitor CG200745 protects heart from DOCA-induced hypertrophy

Histone deacetylases (HDACs) are a vast family divided into four major classes: class I (1, 2, 3, and 8), class II (4, 5, 6, 7, 9 and 10), class III (sirtuin family) and class IV (HDAC11). HDAC inhibition attenuates cardiac hypertrophy through suppression of the mechanistic target of rapamycin complex1 (mTORC1) signaling. HDAC inhibitors upregulate the expression of tuberous sclerosis complex 2 (TSC2), an mTORC1 inhibitor. However, the molecular mechanism underlying HDAC inhibitor-mediated upregulation of TSC2 is unclear. We hypothesized that an HDAC inhibitor, CG200745 (CG), ameliorates cardiac hypertrophy through the inhibition of mTORC1 signaling by upregulating of the CCAAT/enhancer-binding protein-β (C/EBP-β)/TSC2 pathway. To establish a cardiac hypertrophy model, deoxycorticosterone acetate (DOCA, 40 mg/kg/wk) was subcutaneously injected for 4 weeks into Sprague-Dawley rats. All rats were unilaterally nephrectomized and had free access to drinking water containing 1% NaCl with or without CG of different concentrations. The expression level of TSC2 and C/EBP-β was measured by quantitative real-time PCR (qRT-PCR) and western blot analysis. Acetylation of C/EBP-β was analyzed by immunoprecipitation. The recruitment of C/EBP-β and polymerase II (Pol II) on TSC2 promoter region was analyzed by chromatin immunoprecipitation (ChIP). CG treatment increased the expression of TSC2. In addition, CG treated rats showed an increased in the expression and acetylation of C/EBP-β, owing to the increase in the recruitment of C/EBP-β and Pol II at Tsc2 gene promoter. Thus, CG ameliorates cardiac hypertrophy through the inhibition of mTORC1 signaling via upregulation of the C/EBP-β/TSC2 pathway in DOCA-induced hypertensive rats.

HDAC1/2-mediated regulation of JNK and ERK phosphorylation in bovine mammary epithelial cells in response to TNF-α

Bovine mammary epithelial cells (MAC-Ts) are a common cell line for the study of mammary epithelial inflammation; these cells are used to mechanistically elucidate molecular underpinnings that contribute to bovine mastitis. Bovine mastitis is the most prevalent form of disease in dairy cattle that culminates in annual losses of two billion dollars for the US dairy industry. Thus, there is an urgent need for improved therapeutic strategies. Histone deacetylase (HDAC) inhibitors are efficacious in rodent models of inflammation, yet their role in bovine mammary cells remain unclear. HDACs have traditionally been studied in the regulation of nucleosomal DNA, in which deacetylation of histones impact chromatin accessibility and gene expression. Using MAC-T cells stimulated with tumor necrosis factor α (TNF-α) as a model for mammary cell inflammation, we report that inhibition of HDACs1 and 2 (HDAC1/2) attenuated TNF-α-mediated inflammatory gene expression. Of note, we report that HDAC1/2-mediated inflammatory gene expression was partly regulated by c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK) phosphorylation. Here, we report that HDAC1/2 inhibition attenuated JNK and ERK activation and thus inflammatory gene expression. These data suggest that HDACs1 and 2 regulate inflammatory gene expression via canonical (i.e., gene expression) and noncanonical (e.g., signaling dependent) mechanisms. Whereas, further studies using primary cell lines and animal models are needed. Our combined data suggest that HDAC1/2-specific inhibitors may prove efficacious for the treatment of bovine mastitis.

Food Bioactive HDAC Inhibitors in the Epigenetic Regulation of Heart Failure

Approximately 5.7 million U.S. adults have been diagnosed with heart failure (HF). More concerning is that one in nine U.S. deaths included HF as a contributing cause. Current HF drugs (e.g., β-blockers, ACEi) target intracellular signaling cascades downstream of cell surface receptors to prevent cardiac pump dysfunction. However, these drugs fail to target other redundant intracellular signaling pathways and, therefore, limit drug efficacy. As such, it has been postulated that compounds designed to target shared downstream mediators of these signaling pathways would be more efficacious for the treatment of HF. Histone deacetylation has been linked as a key pathogenetic element for the development of HF. Lysine residues undergo diverse and reversible post-translational modifications that include acetylation and have historically been studied as epigenetic modifiers of histone tails within chromatin that provide an important mechanism for regulating gene expression. Of recent, bioactive compounds within our diet have been linked to the regulation of gene expression, in part, through regulation of the epi-genome. It has been reported that food bioactives regulate histone acetylation via direct regulation of writer (histone acetyl transferases, HATs) and eraser (histone deacetylases, HDACs) proteins. Therefore, bioactive food compounds offer unique therapeutic strategies as epigenetic modifiers of heart failure. This review will highlight food bio-actives as modifiers of histone deacetylase activity in the heart.

Deacetylation of Histone H4 Accompanying Cardiomyogenesis is Weakened in HDAC1-Depleted ES Cells

Cell differentiation into cardiomyocytes requires activation of differentiation-specific genes and epigenetic factors that contribute to these physiological processes. This study is focused on the in vitro differentiation of mouse embryonic stem cells (mESCs) induced into cardiomyocytes. The effects of clinically promising inhibitors of histone deacetylases (HDACi) on mESC cardiomyogenesis and on explanted embryonic hearts were also analyzed. HDAC1 depletion caused early beating of cardiomyocytes compared with those of the wild-type (wt) counterpart. Moreover, the adherence of embryonic bodies (EBs) was reduced in HDAC1 double knockout (dn) mESCs. The most important finding was differentiation-specific H4 deacetylation observed during cardiomyocyte differentiation of wt mESCs, while H4 deacetylation was weakened in HDAC1-depleted cells induced to the cardiac pathway. Analysis of the effect of HDACi showed that Trichostatin A (TSA) is a strong hyperacetylating agent, especially in wt mESCs, but only SAHA reduced the size of the beating areas in EBs that originated from HDAC1 dn mESCs. Additionally, explanted embryonic hearts (e15) responded to treatment with HDACi: all of the tested HDACi (TSA, SAHA, VPA) increased the levels of H3K9ac, H4ac, H4K20ac, and pan-acetylated lysines in embryonic hearts. This observation shows that explanted tissue can be maintained in a hyperacetylation state several hours after excision, which appears to be useful information from the view of transplantation strategy and the maintenance of gene upregulation via acetylation in tissue intended for transplantation.

Myocyte-specific overexpressing HDAC4 promotes myocardial ischemia/reperfusion injury

Background

Histone deacetylases (HDACs) play a critical role in modulating myocardial protection and cardiomyocyte survivals. However, Specific HDAC isoforms in mediating myocardial ischemia/reperfusion injury remain currently unknown.

We used cardiomyocyte-specific overexpression of active HDAC4 to determine the functional role of activated HDAC4 in regulating myocardial ischemia and reperfusion in isovolumetric perfused hearts.

Methods

In this study, we created myocyte-specific active HDAC4 transgenic mice to examine the functional role of active HDAC4 in mediating myocardial I/R injury. Ventricular function was determined in the isovolumetric heart, and infarct size was determined using tetrazolium chloride staining.

Results

Myocyte-specific overexpressing activated HDAC4 in mice promoted myocardial I/R injury, as indicated by the increases in infarct size and reduction of ventricular functional recovery following I/R injury. Notably, active HDAC4 overexpression led to an increase in LC-3 and active caspase 3 and decrease in SOD-1 in myocardium. Delivery of chemical HDAC inhibitor attenuated the detrimental effects of active HDAC4 on I/R injury, revealing the pivotal role of active HDAC4 in response to myocardial I/R injury.

Conclusions

Taken together, these findings are the first to define that activated HDAC4 as a crucial regulator for myocardial ischemia and reperfusion injury.

Electronic supplementary material

The online version of this article (10.1186/s10020-018-0037-2) contains supplementary material, which is available to authorized users.

HDAC11 deletion reduces fructose-induced cardiac dyslipidemia, apoptosis and inflammation by attenuating oxidative stress injury

Diabetes mellitus (DM) is a risk factor for abnormal heart development, but the molecular mechanism remains obscure. Histone deacetylase 11 (HDAC11), the most recently identified histone deacetylase, is the sole member of class IV HDACs. However, its role in diabetic cardiac injury is still poorly understood. In the present study, we attempted to explore the effects of HDAC11 on fructose (Fru)-induced cardiac injury using the wild type (HDAC11^+/+) and knockout (HDAC11^-/-) mice. The results indicated that HDAC11 was significantly expressed in human and mouse diabetic heart failure (DHF) hearts. HDAC11^-/- reduced the body weight, inguinal fat-pad mass, and elevated blood pressure in Fru-fed mice. Compared to HDAC11^+/+/Fru group, cardiac function was significantly improved in HDAC11^-/-/Fru mice. HDAC11^-/-/Fru mice exhibited reduced cardiac triacylglycerol (TG), total cholesterol (TC) and free fatty acid (FFA) levels, along with decreased mRNA levels of lipid synthesis-, lipid storage- and lipid oxidation-associated genes. In addition, HDAC11^-/- attenuated apoptosis, oxidative stress and inflammation in the heart of Fru-fed mice, as evidenced by the reduced cleavage of Caspase-3, nicotinamide adenine dinucleotide phosphate (NADPH), and xanthine oxidase (XOD) activity, enhanced superoxide dismutase (SOD) activity, as well as the decreased interleukin 1β (IL-1β) and tumor necrosis factor-α (TNF-α) levels, which was accompanied with down-regulated p-NF-κB. The results above were verified in Fru-treated primary cardiomyocytes isolated from HDAC11^+/+ or HDAC11^-/- mice. Intriguingly, suppressing the expressions of anti-oxidants using zinc protoporphyrin (ZnPP) or siNrf-2 siRNA markedly abolished the results that HDAC11 suppression-induced reduction of apoptosis, reactive oxygen species (ROS) production, inflammation, as well as the improvement of dyslipidemia in Fru-incubated primary cardiomyocytes. Thus, ROS production was responsible for HDAC11-modulated diabetic heart injury. These findings suggested that suppressing HDAC11 has therapeutic potential for treating diabetes mellitus-associated cardiac injury.

Inhibition of HDAC6 Activity Alleviates Myocardial Ischemia/Reperfusion Injury in Diabetic Rats: Potential Role of Peroxiredoxin 1 Acetylation and Redox Regulation

Patients with diabetes are more vulnerable to myocardial ischemia/reperfusion (MI/R) injury, which is associated with excessive reactive oxygen species (ROS) generation and decreased antioxidant defense. Histone deacetylase 6 (HDAC6), a regulator of the antioxidant protein peroxiredoxin 1 (Prdx1), is associated with several pathological conditions in the cardiovascular system. This study investigated whether tubastatin A (TubA), a highly selective HDAC6 inhibitor, could confer a protective effect by modulating Prdx1 acetylation in a rat model of MI/R and an in vitro model of hypoxia/reoxygenation (H/R). Here, we found that diabetic hearts with excessive HDAC6 activity and decreased acetylated-Prdx1 levels were more vulnerable to MI/R injury. TubA treatment robustly improved cardiac function, reduced cardiac infarction, attenuated ROS generation, and increased acetylated-Prdx1 levels in diabetic MI/R rats. These results were further confirmed by an in vitro study using H9c2 cells. Furthermore, a study using Prdx1 acetyl-silencing mutants (K197R) showed that TubA only slightly attenuated H/R-induced cell death and ROS generation in K197R-transfected H9c2 cells exposed to high glucose (HG), but these differences were not statistically significant. Taken together, these findings suggest that HDAC6 inhibition reduces ROS generation and confers a protective effect against MI/R or H/R injury by modulating Prdx1 acetylation at K197.

A Computational Systems Biology Approach for Identifying Candidate Drugs for Repositioning for Cardiovascular Disease

We report an in silico method to screen for receptors or pathways that could be targeted to elicit beneficial transcriptional changes in a cellular model of a disease of interest. In our method, we integrate: (1) a dataset of transcriptome responses of a cell line to a panel of drugs; (2) two sets of genes for the disease; and (3) mappings between drugs and the receptors or pathways that they target. We carried out a gene set enrichment analysis (GSEA) test for each of the two gene sets against a list of genes ordered by fold-change in response to a drug in a relevant cell line (HL60), with the overall score for a drug being the difference of the two enrichment scores. Next, we applied GSEA for drug targets based on drugs that have been ranked by their differential enrichment scores. The method ranks drugs by the degree of anti-correlation of their gene-level transcriptional effects on the cell line with the genes in the disease gene sets. We applied the method to data from (1) CMap 2.0; (2) gene sets from two transcriptome profiling studies of atherosclerosis; and (3) a combined dataset of drug/target information. Our analysis recapitulated known targets related to CVD (e.g., PPARγ; HMG-CoA reductase, HDACs) and novel targets (e.g., amine oxidase A, δ-opioid receptor). We conclude that combining disease-associated gene sets, drug-transcriptome-responses datasets and drug-target annotations can potentially be useful as a screening tool for diseases that lack an accepted cellular model for in vitro screening.

Activation of Class I histone deacetylases contributes to mitochondrial dysfunction in cardiomyocytes with altered complex activities

Histone deacetylases (HDACs) play vital roles in the pathophysiology of heart failure, which is associated with mitochondrial dysfunction. Tumor necrosis factor-α (TNF-α) contributes to the genesis of heart failure and impairs mitochondria. This study evaluated the role of HDACs in TNF-α-induced mitochondrial dysfunction and investigated their therapeutic potential and underlying mechanisms. We measured mitochondrial oxygen consumption rate (OCR) and ATP production using Seahorse XF24 extracellular flux analyzer and bioluminescent assay in control and TNF-α (10 ng/ml, 24 h)-treated HL-1 cells with or without HDAC inhibition. TNF-α increased Class I and II (but not Class IIa) HDAC activities (assessed by Luminescent) with enhanced expressions of Class I (HDAC1, HDAC2, HDAC3, and HDAC8) but not Class IIb HDAC (HDAC6 and HDAC10) proteins in HL-1 cells. TNF-α induced mitochondrial dysfunction with impaired basal, ATP-linked, and maximal respiration, decreased cellular ATP synthesis, and increased mitochondrial superoxide production (measured by MitoSOX red fluorescence), which were rescued by inhibiting HDACs with MPT0E014 (1 μM, a Class I and IIb inhibitor), or MS-275 (1 μM, a Class I inhibitor). MPT0E014 reduced TNF-α-decreased complex I and II enzyme (but not III or IV) activities (by enzyme activity microplate assays). Our results suggest that Class I HDAC actions contribute to TNF-α-induced mitochondrial dysfunction in cardiomyocytes with altered complex I and II enzyme regulation. HDAC inhibition improves dysfunctional mitochondrial bioenergetics with attenuation of TNF-α-induced oxidative stress, suggesting the therapeutic potential of HDAC inhibition in cardiac dysfunction.

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.

Givinostat reduces adverse cardiac remodeling through regulating fibroblasts activation

Cardiovascular diseases (CVDs) are a major burden on the healthcare system: indeed, over two million new cases are diagnosed every year worldwide. Unfortunately, important drawbacks for the treatment of these patients derive from our current inability to stop the structural alterations that lead to heart failure, the common endpoint of many CVDs. In this scenario, a better understanding of the role of epigenetics – hereditable changes of chromatin that do not alter the DNA sequence itself – is warranted. To date, hyperacetylation of histones has been reported in hypertension and myocardial infarction, but the use of inhibitors for treating CVDs remains limited. Here, we studied the effect of the histone deacetylase inhibitor Givinostat on a mouse model of acute myocardial infarction. We found that it contributes to decrease endothelial-to-mesenchymal transition and inflammation, reducing cardiac fibrosis and improving heart performance and protecting the blood vessels from apoptosis through the modulatory effect of cardiac fibroblasts on endothelial cells. Therefore, Givinostat may have potential for the treatment of CVDs.

Cardiac-enriched BAF chromatin-remodeling complex subunit Baf60c regulates gene expression programs essential for heart development and function

How chromatin-remodeling complexes modulate gene networks to control organ-specific properties is not well understood. For example, Baf60c (Smarcd3) encodes a cardiac-enriched subunit of the SWI/SNF-like BAF chromatin complex, but its role in heart development is not fully understood. We found that constitutive loss of Baf60c leads to embryonic cardiac hypoplasia and pronounced cardiac dysfunction. Conditional deletion of Baf60c in cardiomyocytes resulted in postnatal dilated cardiomyopathy with impaired contractile function. Baf60c regulates a gene expression program that includes genes encoding contractile proteins, modulators of sarcomere function, and cardiac metabolic genes. Many of the genes deregulated in Baf60c null embryos are targets of the MEF2/SRF co-factor Myocardin (MYOCD). In a yeast two-hybrid screen, we identified MYOCD as a BAF60c interacting factor; we showed that BAF60c and MYOCD directly and functionally interact. We conclude that Baf60c is essential for coordinating a program of gene expression that regulates the fundamental functional properties of cardiomyocytes.

Epigenetics in diabetic nephropathy, immunity and metabolism

When it comes to the epigenome, there is a fine line between clarity and confusion-walk that line and you will discover another fascinating level of transcription control. With the genetic code representing the cornerstone of rules for information that is encoded to proteins somewhere above the genome level there is a set of rules by which chemical information is also read. These epigenetic modifications show a different side of the genetic code that is diverse and regulated, hence modifying genetic transcription transiently, ranging from short- to long-term alterations. While this complexity brings exquisite control it also poses a formidable challenge to efforts to decode mechanisms underlying complex disease. Recent technological and computational advances have improved unbiased acquisition of epigenomic patterns to improve our understanding of the complex chromatin landscape. Key to resolving distinct chromatin signatures of diabetic complications is the identification of the true physiological targets of regulatory proteins, such as reader proteins that recognise, writer proteins that deposit and eraser proteins that remove specific chemical moieties. But how might a diverse group of proteins regulate the diabetic landscape from an epigenomic perspective? Drawing from an ever-expanding compendium of experimental and clinical studies, this review details the current state-of-play and provides a perspective of chromatin-dependent mechanisms implicated in diabetic complications, with a special focus on diabetic nephropathy. We hypothesise a codified signature of the diabetic epigenome and provide examples of prime candidates for chemical modification. As for the pharmacological control of epigenetic marks, we explore future strategies to expedite and refine the search for clinically relevant discoveries. We also consider the challenges associated with therapeutic strategies targeting epigenetic pathways.

HDAC1 localizes to the mitochondria of cardiac myocytes and contributes to early cardiac reperfusion injury

RATIONALE

Recent evidence indicates that histone deacetylase enzymes (HDACs) contribute to ischemia reperfusion (I/R) injury, and pan-HDAC inhibitors have been shown to be cardioprotective when administered either before an ischemic insult or during reperfusion. We have shown previously that selective inhibition of class I HDACs provides superior cardioprotection when compared to pan-HDAC inhibition in a pretreatment model, but selective class I HDAC inhibition has not been tested during reperfusion, and specific targets of class I HDACs in I/R injury have not been identified.

OBJECTIVE

We hypothesized that selective inhibition of class I HDACs with the drug MS-275 (entinostat) during reperfusion would improve recovery from I/R injury in the first hour of reperfusion.

METHODS AND RESULTS

Hearts from male Sprague-Dawley rats were subjected to ex vivo I/R injury±MS-275 class I HDAC inhibition during reperfusion alone. MS-275 significantly attenuated I/R injury, as indicated by improved LV function and tissue viability at the end of reperfusion. Unexpectedly, we observed that HDAC1 is present in the mitochondria of cardiac myocytes, but not fibroblasts or endothelial cells. We then designed mitochondria-restricted and mitochondria-excluded HDAC inhibitors, and tested both in our ex vivo I/R model. The selective inhibition of mitochondrial HDAC1 attenuated I/R injury to the same extent as MS-275, whereas the mitochondrial-excluded inhibitor did not. Further assays demonstrated that these effects are attributable to a decrease in SDHA activity and subsequent metabolic ROS production in reperfusion.

CONCLUSIONS

We demonstrate for the first time that HDAC1 is present within the mitochondria of cardiac myocytes, and mitochondrial HDAC1 contributes significantly to I/R injury within the first hour of reperfusion.

Effect of prehypertensive losartan therapy on AT1R and ATRAP methylation of adipose tissue in the later life of high‑fat‑fed spontaneously hypertensive rats

Hypertension is frequently associated with metabolic disorders. The present study was designed to investigate the long-term effect of prehypertensive losartan therapy on metabolic disorders in high-fat-fed spontaneously hypertensive rats (SHRs), and to examine the role of epigenetic regulation of angiotensin II type 1 receptor (AT1R) and AT1 receptor-associated protein (ATRAP) expression in adipose tissue. A total of 32 4-week-old male SHRs were divided into four groups (n=8 rats/group): Standard chow; standard chow + losartan; high-fat diet; and high-fat diet + losartan. At 10 weeks of age, treatment with losartan was discontinued. Rats were followed up until 26 weeks of age. Obesity, dyslipidemia, hyperglycemia, abnormal adipokine secretion, larger adipocytes and decreased expression of markers of adipocyte differentiation were present in high-fat-fed SHRs, and were attenuated in losartan-treated rats. The increased expression and promoter hypomethylation of AT1R subtype a (AT1aR) in the adipose tissue of high-fat-fed SHRs were reversed by treatment with losartan. No difference was observed in the expression and promoter methylation of AT1R subtype b (AT1bR) among the four groups. Decreased expression and promoter hypermethylation of ATRAP were demonstrated in the adipose tissue of high-fat-fed SHRs. However, losartan made no difference to the expression and promoter methylation of ATRAP. Prehypertensive losartan therapy may relieve metabolic disorders in the later life of high-fat-fed SHRs. Differential epigenetic regulation of AT1aR and ATRAP expression through DNA methylation in adipose tissue may be involved in the long-term beneficial effect.

Epigenetics for the pediatric cardiologist

A genetic basis of congenital heart disease (CHD) has been known for decades. In addition to the sequence of the genome, the contribution of epigenetics to pediatric cardiology is increasingly recognized. Multiple epigenetic mechanisms, including DNA methylation, histone modification, and RNA-based regulation, are known mediators of cardiovascular disease, including both development and progression of CHD and its sequelae. Basic understanding of the concepts of epigenetics will be essential to all pediatric cardiologists in order to understand mechanisms of pathophysiology, pharmacotherapeutic concepts, and to understand the role of epigenetics in precision medicine.

Histone deacetylase adaptation in single ventricle heart disease and a young animal model of right ventricular hypertrophy

BackgroundHistone deacetylase (HDAC) inhibitors are promising therapeutics for various forms of cardiac diseases. The purpose of this study was to assess cardiac HDAC catalytic activity and expression in children with single ventricle (SV) heart disease of right ventricular morphology, as well as in a rodent model of right ventricular hypertrophy (RVH).MethodsHomogenates of right ventricle (RV) explants from non-failing controls and children born with a SV were assayed for HDAC catalytic activity and HDAC isoform expression. Postnatal 1-day-old rat pups were placed in hypoxic conditions, and echocardiographic analysis, gene expression, HDAC catalytic activity, and isoform expression studies of the RV were performed.ResultsClass I, IIa, and IIb HDAC catalytic activity and protein expression were elevated in the hearts of children born with a SV. Hypoxic neonatal rats demonstrated RVH, abnormal gene expression, elevated class I and class IIb HDAC catalytic activity, and protein expression in the RV compared with those in the control.ConclusionsThese data suggest that myocardial HDAC adaptations occur in the SV heart and could represent a novel therapeutic target. Although further characterization of the hypoxic neonatal rat is needed, this animal model may be suitable for preclinical investigations of pediatric RV disease and could serve as a useful model for future mechanistic studies.