Activation of Histone Deacetylase 2 by Inducible Heat Shock Protein 70 in Cardiac Hypertrophy

Role of histone deacetylase inhibitors in non-neoplastic diseases

Background

Epigenetic dysregulation has been implicated in the development and progression of a variety of human diseases, but epigenetic changes are reversible, and epigenetic enzymes and regulatory proteins can be targeted using small molecules. Histone deacetylase inhibitors (HDACis), as a class of epigenetic drugs, are widely used to treat various cancers and other diseases involving abnormal gene expression.

Results

Specially, HDACis have emerged as a promising strategy to enhance the therapeutic effect of non-neoplastic conditions, including neurological disorders, cardiovascular diseases, renal diseases, autoimmune diseases, inflammatory diseases, infectious diseases and rare diseases, along with their related mechanisms. However, their clinical efficacy has been limited by drug resistance and toxicity.

Conclusions

To date, most clinical trials of HDAC inhibitors have been related to the treatment of cancer rather than the treatment of non-cancer diseases, for which experimental studies are gradually underway. Discussions regarding non-neoplastic diseases often concentrate on specific disease types. Therefore, this review highlights the development of HDACis and their potential therapeutic applications in non-neoplastic diseases, either as monotherapy or in combination with other drugs or therapies.

Class I and II Histone Deacetylase Inhibitors as Therapeutic Modulators of Dilated Cardiac Tissue-Derived Mesenchymal Stem/Stromal Cells

The prevalence of dilated cardiomyopathy (DCM) is increasing globally, highlighting the need for innovative therapeutic approaches to prevent its onset. In this study, we examined the energetic and epigenetic distinctions between dilated and non-dilated human myocardium-derived mesenchymal stem/stromal cells (hmMSCs) and assessed the effects of class I and II HDAC inhibitors (HDACi) on these cells and their cardiomyogenic differentiation. Cells were isolated from myocardium biopsies using explant outgrowth methods. Mitochondrial and histone deacetylase activities, ATP levels, cardiac transcription factors, and structural proteins were assessed using flow cytometry, PCR, chemiluminescence, Western blotting, and immunohistochemistry. The data suggest that the tested HDAC inhibitors improved acetylation and enhanced the energetic status of both types of cells, with significant effects observed in dilated myocardium-derived hmMSCs. Additionally, the HDAC inhibitors activated the cardiac transcription factors Nkx2-5, HOPX, GATA4, and Mef2C, and upregulated structural proteins such as cardiac troponin T and alpha cardiac actin at both the protein and gene levels. In conclusion, our findings suggest that HDACi may serve as potential modulators of the energetic status and cardiomyogenic differentiation of human heart hmMSCs. This avenue of exploration could broaden the search for novel therapeutic interventions for dilated cardiomyopathy, ultimately leading to improvements in heart function.

Zinc-Dependent Histone Deacetylases in Lung Endothelial Pathobiology

A monolayer of endothelial cells (ECs) lines the lumen of blood vessels and, as such, provides a semi-selective barrier between the blood and the interstitial space. Compromise of the lung EC barrier due to inflammatory or toxic events may result in pulmonary edema, which is a cardinal feature of acute lung injury (ALI) and its more severe form, acute respiratory distress syndrome (ARDS). The EC functions are controlled, at least in part, via epigenetic mechanisms mediated by histone deacetylases (HDACs). Zinc-dependent HDACs represent the largest group of HDACs and are activated by Zn2+. Members of this HDAC group are involved in epigenetic regulation primarily by modifying the structure of chromatin upon removal of acetyl groups from histones. In addition, they can deacetylate many non-histone histone proteins, including those located in extranuclear compartments. Recently, the therapeutic potential of inhibiting zinc-dependent HDACs for EC barrier preservation has gained momentum. However, the role of specific HDAC subtypes in EC barrier regulation remains largely unknown. This review aims to provide an update on the role of zinc-dependent HDACs in endothelial dysfunction and its related diseases. We will broadly focus on biological contributions, signaling pathways and transcriptional roles of HDACs in endothelial pathobiology associated mainly with lung diseases, and we will discuss the potential of their inhibitors for lung injury prevention.

Epigenetic Network in Immunometabolic Disease

Although a large amount of data consistently shows that genes affect immunometabolic characteristics and outcomes, epigenetic mechanisms are also heavily implicated. Epigenetic changes, including DNA methylation, histone modification, and noncoding RNA, determine gene activity by altering the accessibility of chromatin to transcription factors. Various factors influence these alterations, including genetics, lifestyle, and environmental cues. Moreover, acquired epigenetic signals can be transmitted across generations, thus contributing to early disease traits in the offspring. A closer investigation is critical in this aspect as it can help to understand the underlying molecular mechanisms further and gain insights into potential therapeutic targets for preventing and treating diseases arising from immuno-metabolic dysregulation. In this review, the role of chromatin alterations in the transcriptional modulation of genes involved in insulin resistance, systemic inflammation, macrophage polarization, endothelial dysfunction, metabolic cardiomyopathy, and nonalcoholic fatty liver disease (NAFLD), is discussed. An overview of emerging chromatin-modifying drugs and the importance of the individual epigenetic profile for personalized therapeutic approaches in patients with immuno-metabolic disorders is also presented.

Insulin augments angiotensin II-induced myocardial fibrosis via the MEK/STAT3 pathway

Regular insulin therapy is significantly related to worse cardiovascular outcomes in patients with type 2 diabetes and heart failure. However, the mechanisms of the causal relationship remain unclear. In this study, we observed the effect of insulin on cardiac structure and function and found that insulin dramatically augmented angiotensin II (Ang II)-induced cardiac dysfunction, as well as the proliferation and collagen production of primary cardiac fibroblasts. Total STAT3 expression, but not activation was stimulated by insulin; the effect of insulin on Ang II-induced fibrosis disappeared when STAT3 was blocked and could be entirely suppressed by the MEK inhibitor PD0325901. Our findings suggest a noninsulin-dependent glucose-lowering regimen for patients with type 2 diabetes (T2DM) and heart failure (HF).

Targeting histone deacetylases for heart diseases

Histone deacetylases (HDACs) are responsible for the deacetylation of lysine residues in histone or non-histone substrates, leading to the regulation of many biological functions, such as gene transcription, translation and remodeling chromatin. Targeting HDACs for drug development is a promising way for human diseases, including cancers and heart diseases. In particular, numerous HDAC inhibitors have revealed potential clinical value for the treatment of cardiac diseases in recent years. In this review, we systematically summarize the therapeutic roles of HDAC inhibitors with different chemotypes on heart diseases. Additionally, we discuss the opportunities and challenges in developing HDAC inhibitors for the treatment of cardiac diseases.

The role of histone deacetylases in cardiac energy metabolism in heart diseases

Heart diseases are associated with substantial morbidity and mortality worldwide. The underlying mechanisms and pathological changes associated with cardiac diseases are exceptionally complex. Highly active cardiomyocytes require sufficient energy metabolism to maintain their function. Under physiological conditions, the choice of fuel is a delicate process that depends on the whole body and organs to support the normal function of heart tissues. However, disordered cardiac metabolism has been discovered to play a key role in many forms of heart diseases, including ischemic heart disease, cardiac hypertrophy, heart failure, and cardiac injury induced by diabetes or sepsis. Regulation of cardiac metabolism has recently emerged as a novel approach to treat heart diseases. However, little is known about cardiac energy metabolic regulators. Histone deacetylases (HDACs), a class of epigenetic regulatory enzymes, are involved in the pathogenesis of heart diseases, as reported in previous studies. Notably, the effects of HDACs on cardiac energy metabolism are gradually being explored. Our knowledge in this respect would facilitate the development of novel therapeutic strategies for heart diseases. The present review is based on the synthesis of our current knowledge concerning the role of HDAC regulation in cardiac energy metabolism in heart diseases. In addition, the role of HDACs in different models is discussed through the examples of myocardial ischemia, ischemia/reperfusion, cardiac hypertrophy, heart failure, diabetic cardiomyopathy, and diabetes- or sepsis-induced cardiac injury. Finally, we discuss the application of HDAC inhibitors in heart diseases and further prospects, thus providing insights into new treatment possibilities for different heart diseases.

HDAC Inhibitors Alleviate Uric Acid-Induced Vascular Endothelial Cell Injury by Way of the HDAC6/FGF21/PI3K/AKT Pathway

ABSTRACT

Uric acid (UA) accumulation triggers endothelial dysfunction, oxidative stress, and inflammation. Histone deacetylase (HDAC) plays a vital role in regulating the pathological processes of various diseases. However, the influence of HDAC inhibitor on UA-induced vascular endothelial cell injury (VECI) remains undefined. Hence, this study aimed to investigate the effect of HDACs inhibition on UA-induced vascular endothelial cell dysfunction and its detailed mechanism. UA was used to induce human umbilical vein endothelial cell (HUVEC) injury. Meanwhile, potassium oxonate-induced and hypoxanthine-induced hyperuricemia mouse models were also constructed. A broad-spectrum HDAC inhibitor trichostatin A (TSA) or selective HDAC6 inhibitor TubastatinA (TubA) was given to HUVECs or mice to determine whether HDACs can affect UA-induced VECI. The results showed pretreatment of HUVECs with TSA or HDAC6 knockdown-attenuated UA-induced VECI and increased FGF21 expression and phosphorylation of AKT, eNOS, and FoxO3a. These effects could be reversed by FGF21 knockdown. In vivo, both TSA and TubA reduced inflammation and tissue injury while increased FGF21 expression and phosphorylation of AKT, eNOS, and FoxO3a in the aortic and renal tissues of hyperuricemia mice. Therefore, HDACs, especially HDAC6 inhibitor, alleviated UA-induced VECI through upregulating FGF21 expression and then activating the PI3K/AKT pathway. This suggests that HDAC6 may serve as a novel therapeutic target for treating UA-induced endothelial dysfunction.

Critical Functions of Histone Deacetylases (HDACs) in Modulating Inflammation Associated with Cardiovascular Diseases

Histone deacetylases (HDACs) are a superfamily of enzymes that catalyze the removal of acetyl functional groups from lysine residues of histone and non-histone proteins. There are 18 mammalian HDACs, which are classified into four classes based on the primary homology with yeast HDACs. Among these groups, Class I and II HDACs play a major role in lysine deacetylation of the N-terminal histone tails. In mammals, HDACs play a pivotal role in the regulation of gene transcription, cell growth, survival, and proliferation. HDACs regulate the expression of inflammatory genes, as evidenced by the potent anti-inflammatory activity of pan-HDAC inhibitors, which were implicated in several pathophysiologic states in the inflammation process. However, it is unclear how each of the 18 HDAC proteins specifically contributes to the inflammatory gene expression. It is firmly established that inflammation and its inability to converge are central mechanisms in the pathogenesis of several cardiovascular diseases (CVDs). Emerging evidence supports the hypothesis that several different pro-inflammatory cytokines regulated by HDACs are associated with various CVDs. Based on this hypothesis, the potential for the treatment of CVDs with HDAC inhibitors has recently begun to attract attention. In this review, we will briefly discuss (1) pathophysiology of inflammation in cardiovascular disease, (2) the function of HDACs in the regulation of atherosclerosis and cardiovascular diseases, and (3) the possible therapeutic implications of HDAC inhibitors in cardiovascular diseases. Recent studies reveal that histone deacetylase contributes critically to mediating the pathophysiology of inflammation in cardiovascular disease. HDACs are also recognized as one of the major mechanisms in the regulation of inflammation and cardiovascular function. HDACs show promise in developing potential therapeutic implications of HDAC inhibitors in cardiovascular and inflammatory diseases.

Systemic study of selected histone deacetylase inhibitors in cardiac complications associated with cancer cachexia

Cancer cachexia is mainly characterized by wasting of skeletal muscles and fat and body weight loss, along with severe complications of major organs like liver, heart, brain and bone. There can be diminishing performance of these major organs as cancer cachexia progresses, one such drastic effect on the cardiac system. In the present study, differential effect of histone deacetylase inhibitors (HDACi) on cardiac complications associated with cancer cachexia is studied. Two models were used to induce cancer cachexia: B16F1 induced metastatic cancer cachexia and Lewis lung carcinoma cell - induced cancer cachexia. Potential of Class I HDACi entinostat, Class II HDACi MC1568, and nonspecific HDACi sodium butyrate on cardiac complications were evaluated using the cardiac hypertrophy markers, hemodynamic markers, and cardiac markers along with histopathological evaluation of heart sections by Periodic acid-Schiff staining, Masson's trichrome staining, Picro-sirius red staining, and haematoxylin and eosin staining. Immunohistochemistry evaluation by vimentin and caspase 3 protein expression was evaluated. Entinostat showed promising results by attenuating the cardiac complications, and MC1568 treatment further exacerbated the cardiac complications, while non-conclusive effect were recorded after treatment with sodium butyrate. This study will be helpful in evaluating other HDACi for potential in cardiac complications associated with cancer cachexia.

Honokiol Ameliorates Post-Myocardial Infarction Heart Failure Through Ucp3-Mediated Reactive Oxygen Species Inhibition

Post-myocardial infarction heart failure (post-MI HF) is one of the leading global causes of death, and current prevention and treatment methods still cannot avoid the increasing incidence. Honokiol (HK) has previously been reported to improve myocardial ischemia/reperfusion injury and reverse myocardial hypertrophy by activating Sirt1 and Sirt3. We suspect that HK may also have a therapeutic effect on post-MI HF. In this study, we aimed to investigate the efficacy and mechanism of HK in the treatment of post-MI HF. We found that HK inhibited myocardial reactive oxygen species (ROS) production, reduced myocardial fibrosis, and improved cardiac function in mice after MI. HK also reduced the abnormality of mitochondrial membrane potential (MMP) and apoptosis of cardiomyocytes caused by peroxide in neonatal cardiomyocytes. RNAseq results revealed that HK restored the transcriptome changes to a certain extent and significantly enhanced the expression of mitochondrial inner membrane uncoupling protein isoform 3 (Ucp3), a protein that inhibits the production of mitochondrial ROS, protects cardiomyocytes, and relieves heart failure after myocardial infarction (MI). In cardiomyocytes with impaired Ucp3 expression, HK cannot protect against the damage caused by peroxide. More importantly, in Ucp3 knockout mice, HK did not change the increase in the ROS level and cardiac function damage after MI. Taken together, our results suggest that HK can increase the expression of the cardioprotective protein Ucp3 and maintain MMP, thereby inhibiting the production of ROS after MI and ameliorating heart failure.

Hdac8 Inhibitor Alleviates Transverse Aortic Constriction-Induced Heart Failure in Mice by Downregulating Ace1

Background

Heart failure is characterized by activation of the renin-angiotensin-aldosterone system, which is involved in the regulation of cardiac hypertrophy and hypertension. Recently, we reported that Hdac8 inhibition alleviates isoproterenol-induced and angiotensin II-induced cardiac hypertrophy or hypertension in mice. Here, the effect and regulatory mechanisms of the Hdac8 selective inhibitor PCI34051 on pressure overload-induced heart failure were examined.

Methods and Results

At week 6 posttransverse aortic constriction (TAC), mice were administered with PCI34051 (3, 10, or 30 mg/kg bodyweight/day) for 2 weeks. The therapeutic effects of PCI34051 on TAC-induced cardiac and lung hypertrophy were determined by examining the heart weight-to-bodyweight and lung weight-to-bodyweight ratios and the cross-sectional cardiomyocyte area. Echocardiography analysis revealed that PCI34051 mitigated TAC-induced decreased ejection fraction and fractional shortening. Additionally, the expression of Hdac8 was upregulated in the cardiac and pulmonary tissues of TAC mice. The expression levels of Ace1 and Agtr1 were upregulated, whereas those of Ace2 and Agtr2 were downregulated in TAC mice. PCI34051 treatment or Hdac8 knockdown alleviated inflammation as evidenced by Rela downregulation and Nfkbia upregulation in mice, as well as in cardiomyocytes, but not in cardiac fibroblasts. Hdac8 overexpression-induced Rela pathway activation was downregulated in Ace1 knockdown cells. Picrosirius red staining, real-time polymerase chain reaction, and western blotting analyses revealed that PCI34051 alleviated fibrosis and downregulated fibrosis-related genes. Moreover, PCI34051 or Hdac8 knockdown in rat cardiac fibroblasts alleviated cardiac fibrosis through the Tgfb1-Smad2/3 pathway. The results of overexpression and knockdown experiments revealed that Hdac8 and Ace1 promote inflammation and fibrosis.

Conclusions

Treatment with PCI34051 enhanced cardiac and lung functions in the TAC-induced heart failure mouse model. These data suggest that HDAC8 is a potential novel therapeutic target for heart failure accompanied by pathological lung diseases.

Overexpression of Heat Shock Protein 70 Improves Cardiac Remodeling and Survival in Protein Phosphatase 2A-Expressing Transgenic Mice with Chronic Heart Failure

Heat shock protein (HSP) 70 is a molecular chaperone that regulates protein structure in response to thermal stress. In addition, HSP70 is involved in post-translational modification and is related to the severity of some diseases. Here, we tested the functional relevance of long-lasting HSP70 expression in a model of nonischemic heart failure using protein phosphatase 2 catalytic subunit A (PP2CA)-expressing transgenic mice. These transgenic mice, with cardiac-specific overexpression of PP2CA, abruptly died after 12 weeks of postnatal life. Serial echocardiograms to assess cardiac function revealed that the ejection fraction (EF) was gradually decreased in transgenic PP2CA (TgPP2CA) mice. In addition, PP2CA expression exacerbated systolic dysfunction and LV dilatation, with free wall thinning, which are indicators of fatal dilated cardiomyopathy. Interestingly, simultaneous expression of HSP70 in double transgenic mice (dTg) significantly improved the dilated cardiomyopathy phenotype of TgPP2CA mice. We observed better survival, preserved EF, reduced chamber enlargement, and suppression of free wall thinning. In the proposed molecular mechanism, HSP70 preferentially regulates the phosphorylation of AKT. Phosphorylation of AKT was significantly reduced in TgPP2CA mice but was not significantly lower in dTg mice. Signal crosstalk between AKT and its substrates, in association with HSP70, might be a useful intervention for patients with nonischemic heart failure to suppress cardiac remodeling and improve survival.

Relationship between HSPA1A-regulated gene expression and alternative splicing in mouse cardiomyocytes and cardiac hypertrophy

Background

Cardiac hypertrophy may be classified as either physiological or pathological. Pathological hypertrophy has a complex etiology and is genetically regulated. In this study, we used a mouse model of cardiac hypertrophy to explore the mechanisms of gene regulation, in particular, modulation of the expression of target genes through transcription factor activity, regulation of immune and inflammation-associated genes and regulation of the alternative splicing of transcription factors.

Methods

Mouse models of pathological cardiac hypertrophy were established by transverse aortic constriction (TAC). We overexpressed HSPA1A in mouse cardiac HL-1 cells. GO and KEGG pathway annotation database was used to analyze all DEGs.

Results

The expression of HSPA1A differed significantly between TAC + dantrolene vs. sham + dantrolene (Sham was the non-TAC group, and DMSO was the contrast agent), and TAC + DMSO vs. sham + DMSO. The RNA-binding protein Zfp36 was found to be differentially expressed between both TAC + dantrolene vs. sham + dantrolene and TAC + DMSO vs. sham + DMSO. The expression of mki67 and gm5619 was significantly different between TAC + dantrolene and TAC + DMSO. HSPA1A was found to selectively regulate the expression of non-coding RNAs related to cardiac hypertrophy, including Rn7sk and RMRP. The downregulated genes were mainly related to inflammation and the immune response. HSPA1A negatively regulated alternative splicing of Asxl2 and positively regulated alternative splicing of Runx1.

Conclusions

HSPA1A was closely related to cardiac hypertrophy. Zfp36 was also related to cardiac hypertrophy. Dantrolene may delay cardiac hypertrophy and ventricular remodeling by regulating the expression of the RNA-binding protein genes mki67 and gm5619. HSPA1A positively regulated the expression of the non-coding RNAs RN7SK and RMRP while negatively regulating the expression of inflammation- and immune response-related genes. HSPA1A can play a role in cardiac hypertrophy by regulating the alternative splicing of asxl2 and runx1.

P300/CBP-Associated Factor Activates Cardiac Fibroblasts by SMAD2 Acetylation

Various heart diseases cause cardiac remodeling, which in turn leads to ineffective contraction. Although it is an adaptive response to injury, cardiac fibrosis contributes to this remodeling, for which the reactivation of quiescent myofibroblasts is a key feature. In the present study, we investigated the role of the p300/CBP-associated factor (PCAF), a histone acetyltransferase, in the activation of cardiac fibroblasts. An intraperitoneal (i.p.) injection of a high dose (160 mg/kg) of isoproterenol (ISP) induced cardiac fibrosis and reduced the amount of the PCAF in cardiac fibroblasts in the mouse heart. However, the PCAF activity was significantly increased in cardiac fibroblasts, but not in cardiomyocytes, obtained from ISP-administered mice. An in vitro study using human cardiac fibroblast cells recapitulated the in vivo results; an treatment with transforming growth factor-β1 (TGF-β1) reduced the PCAF, whereas it activated the PCAF in the fibroblasts. PCAF siRNA attenuated the TGF-β1-induced increase in and translocation of fibrosis marker proteins. PCAF siRNA blocked TGF-β1-mediated gel contraction and cell migration. The PCAF directly interacted with and acetylated mothers against decapentaplegic homolog 2 (SMAD2). PCAF siRNA prevented TGF-β1-induced phosphorylation and the nuclear localization of SMAD2. These results suggest that the increase in PCAF activity during cardiac fibrosis may participate in SMAD2 acetylation and thereby in its activation.

Function of histone methylation and acetylation modifiers in cardiac hypertrophy

Cardiac hypertrophy is an adaptive response of the heart to increased workload induced by various physiological or pathological stimuli. It is a common pathological process in multiple cardiovascular diseases, and it ultimately leads to heart failure. The development of cardiac hypertrophy is accompanied by gene expression reprogramming, a process that is largely dependent on epigenetic regulation. Histone modifications such as methylation and acetylation are dynamically regulated under cardiac stress. These consequently contribute to the pathogenesis of cardiac hypertrophy via compensatory or maladaptive transcriptome reprogramming. Histone methylation and acetylation modifiers play crucial roles in epigenetic remodeling during the pathogenesis of cardiac hypertrophy. Regulation of histone methylation and acetylation modifiers serves as a bridge between signal transduction and downstream gene reprogramming. Exploring the role of histone modifiers in cardiac hypertrophy provides novel therapeutic strategies to treat cardiac hypertrophy and heart failure. In this review, we summarize the recent advancements in functional histone methylation and acetylation modifiers in cardiac hypertrophy, with an emphasis on the underlying mechanisms and the therapeutic potential.

Histone deacetylase 2 selective inhibitors: A versatile therapeutic strategy as next generation drug target in cancer therapy

Acetylation and deacetylation of histone and several non-histone proteins are the two important processes amongst the different modes of epigenetic modulation that are involved in regulating cancer initiation and development. Abnormal expression of histone deacetylases (HDACs) is often reported in various types of cancers. Few pan HDAC inhibitors have been approved for use as therapeutic interventions for cancer treatment including vorinostat, belinostat and panobinostat. However, not all the HDAC isoforms are abnormally expressed in certain cancers, such as in the case of, ovarian cancer where overexpression of HDAC1-3, lung cancer where overexpression of HDAC 1 and 3 and gastric cancer where overexpression of HDAC2 is seen. Therefore, pan-inhibition of HDAC is not an efficient way to combat cancer via HDAC inhibition. Hence, isoform-selective HDAC inhibition can be one of the best therapeutic strategies in the treatment of cancer. In this context since aberrant expression of HDAC2 largely contributes to cancer progression by silencing pro-apoptotic protein expressions such as NOXA and APAF1 (caspase 9-activating proteins) and inactivation of tumor suppressor p53, HDAC2 specific inhibitors may help to develop not only the direct targets but also indirect targets that are crucial for tumor development. However, to develop a HDAC2 specific and potent inhibitor, extensive knowledge of its structure and specific functions is essential. The present review updates details on the structural features, physiological functions, and roles of HDAC2 in different types of cancer, emphasizing the challenges and status of the development of HDAC2 selective inhibitors against various types of cancer.

Capsular Contracture in Breast Implant Surgery: Where Are We Now and Where Are We Going?

Capsular contracture is the leading complication after surgery with breast implants. A lot of progress has been made investigating this complication over the years, and knowledge has been gained on this complication. Currently, the exact cause for capsular contracture is still unclear. It has been hypothesized that immunobiological factors (i.e., immunological and bacterial factors) and several risk factors play a central role in its development. In this paper, we give an overview of the known immunological factors that have been investigated in contracted and non-contracted capsules, as well as the role of bacterial formation around breast implants. We also report on risk factors that might increase the risk of capsular development. Lastly, it provides the latest research on this matter and discusses future perspectives as follow-up research is needed to unravel the pathogenic process leading to capsular contracture. This knowledge is of interest to establish medical therapies in order to prevent such side effects. Overall, capsular contracture seems to be a multifactorial condition consisting of several risk factors. LEVEL OF EVIDENCE V: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Selective HDAC8 Inhibition Attenuates Isoproterenol-Induced Cardiac Hypertrophy and Fibrosis via p38 MAPK Pathway

Histone deacetylase (HDAC) expression and enzymatic activity are dysregulated in cardiovascular diseases. Among Class I HDACs, HDAC2 has been reported to play a key role in cardiac hypertrophy; however, the exact function of HDAC8 remains unknown. Here we investigated the role of HDAC8 in cardiac hypertrophy and fibrosis using the isoproterenol-induced cardiac hypertrophy model system.Isoproterenol-infused mice were injected with the HDAC8 selective inhibitor PCI34051 (30 mg kg⁻¹ body weight). Enlarged hearts were assessed by HW/BW ratio, cross-sectional area, and echocardiography. RT-PCR, western blotting, histological analysis, and cell size measurements were performed. To elucidate the role of HDAC8 in cardiac hypertrophy, HDAC8 knockdown and HDAC8 overexpression were also used. Isoproterenol induced HDAC8 mRNA and protein expression in mice and H9c2 cells, while PCI34051 treatment decreased cardiac hypertrophy in isoproterenol-treated mice and H9c2 cells. PCI34051 treatment also reduced the expression of cardiac hypertrophic markers (Nppa, Nppb, and Myh7), transcription factors (Sp1, Gata4, and Gata6), and fibrosis markers (collagen type I, fibronectin, and Ctgf) in isoproterenol-treated mice. HDAC8 overexpression stimulated cardiac hypertrophy in cells, whereas HDAC8 knockdown reversed those effects. HDAC8 selective inhibitor and HDAC8 knockdown reduced the isoproterenol-induced activation of p38 MAPK, whereas HDAC8 overexpression promoted p38 MAPK phosphorylation. Furthermore, p38 MAPK inhibitor SB203580 significantly decreased the levels of p38 MAPK phosphorylation, as well as ANP and BNP protein expression, induced by HDAC8 overexpression.Here we show that inhibition of HDAC8 activity or expression suppresses cardiac hypertrophy and fibrosis. These findings suggest that HDAC8 could be a promising target to treat cardiac hypertrophy and fibrosis by regulating p38 MAPK.

S-Nitrosylation of Histone Deacetylase 2 by Neuronal Nitric Oxide Synthase as a Mechanism of Diastolic Dysfunction

BACKGROUND

Although the clinical importance of heart failure with preserved ejection fraction has been extensively explored, most therapeutic regimens, including nitric oxide (NO) donors, lack therapeutic benefit. Although the clinical characteristics of heart failure with preserved ejection fraction are somewhat heterogeneous, diastolic dysfunction (DD) is one of the most important features. Here we report that neuronal NO synthase (nNOS) induces DD by S-nitrosylation of HDAC2 (histone deacetylase 2).

METHODS

Two animal models of DD-SAUNA (SAlty drinking water/Unilateral Nephrectomy/Aldosterone) and mild transverse aortic constriction mice-as well as human heart samples from patients with left ventricular hypertrophy were used. Genetically modified mice that were either nNOS-ablated or HDAC2 S-nitrosylation-resistant were also challenged. N(ω)-propyl-L-arginine, an nNOS selective inhibitor, and dimethyl fumarate, an NRF2 (nuclear factor erythroid 2-related factor 2) inducer, were used. Molecular events were further checked in human left ventricle specimens.

RESULTS

SAUNA or mild transverse aortic constriction stress impaired diastolic function and exercise tolerance without overt systolic failure. Among the posttranslational modifications tested, S-nitrosylation was most dramatically increased in both models. Utilizing heart samples from both mice and humans, we observed increases in nNOS expression and NO production. N(ω)-propyl-L-arginine alleviated the development of DD in vivo. Similarly, nNOS knockout mice were resistant to SAUNA stress. nNOS-induced S-nitrosylation of HDAC2 was relayed by transnitrosylation of GAPDH. HDAC2 S-nitrosylation was confirmed in both DD mouse and human left ventricular hypertrophy. S-nitrosylation of HDAC2 took place at C262 and C274. When DD was induced, HDAC2 S-nitrosylation was detected in wild-type mouse, but not in HDAC2 knock-in mouse heart that expressed HDAC2 C262A/C274A. In addition, HDAC2 C262A/C274A mice maintained normal diastolic function under DD stimuli. Gene delivery with adenovirus-associated virus 9 (AAV9)-NRF2, a putative denitrosylase of HDAC2, or pharmacological intervention by dimethyl fumarate successfully induced HDAC2 denitrosylation and mitigated DD in vivo.

CONCLUSIONS

Our observations are the first to demonstrate a new mechanism underlying DD pathophysiology. Our results provide theoretical and experimental evidence to explain the ineffectiveness of conventional NO enhancement trials for improving DD with heart failure symptoms. More important, our results suggest that reduction of NO or denitrosylation of HDAC2 may provide a new therapeutic platform for the treatment of refractory heart failure with preserved ejection fraction.

Ketogenic diets inhibit mitochondrial biogenesis and induce cardiac fibrosis

In addition to their use in relieving the symptoms of various diseases, ketogenic diets (KDs) have also been adopted by healthy individuals to prevent being overweight. Herein, we reported that prolonged KD exposure induced cardiac fibrosis. In rats, KD or frequent deep fasting decreased mitochondrial biogenesis, reduced cell respiration, and increased cardiomyocyte apoptosis and cardiac fibrosis. Mechanistically, increased levels of the ketone body β-hydroxybutyrate (β-OHB), an HDAC2 inhibitor, promoted histone acetylation of the Sirt7 promoter and activated Sirt7 transcription. This in turn inhibited the transcription of mitochondrial ribosome-encoding genes and mitochondrial biogenesis, leading to cardiomyocyte apoptosis and cardiac fibrosis. Exogenous β-OHB administration mimicked the effects of a KD in rats. Notably, increased β-OHB levels and SIRT7 expression, decreased mitochondrial biogenesis, and increased cardiac fibrosis were detected in human atrial fibrillation heart tissues. Our results highlighted the unknown detrimental effects of KDs and provided insights into strategies for preventing cardiac fibrosis in patients for whom KDs are medically necessary.

HDAC5 inhibition reduces angiotensin II-induced vascular contraction, hypertrophy, and oxidative stress in a mouse model

Non-specific histone deacetylase (HDAC) inhibition reduces high blood pressure in essential hypertensive animal models. However, the exact HDAC isoforms that play a critical role in controlling hypertension are not known. Here, we investigated the role of HDAC5 in vascular contraction, hypertrophy, and oxidative stress in the context of angiotensin II (Ang II)-induced hypertension. Genetic deletion of HDAC5 and treatment with class IIa HDAC inhibitors (TMP269 and TMP195) prevented Ang II-induced increases in blood pressure and arterial wall thickness. Hdac5-knockout mice were also resistant to the thromboxane A2 agonist (U46619)-induced vascular contractile response. Furthermore, the expression of Rho-associated protein kinase (ROCK) 2 was downregulated in the aortas of Ang II-treated Hdac5-knockout mice. Knockdown of HDAC5, RhoA, or ROCK2 reduced collagen gel contraction, whereas silencing of ROCK1 increased it. VSMC hypertrophy reduced on knocking down HDAC5, ROCK1, and ROCK2. Here we showed that genetic deletion of HDAC5 and pharmacological inhibition of class IIa HDACs ameliorated Ang II-induced ROS generation. Moreover, ROCK1 and ROCK2, the downstream targets of HDAC5, influenced ROS generation. The relative protein levels of HDAC5, ROCK1, and ROCK2 were increased both in the cytoplasm and nuclear fraction in response to Ang II stimulation in vascular smooth muscle cells. Inhibition of HDAC5 expression or activity reduced vascular hypertrophy, vasoconstriction, and oxidative stress in the Ang II-induced hypertension model. These findings indicate that HDAC5 may serve as a potential target in the treatment of hypertension.

Proteomic identification of the proteins related to cigarette smoke-induced cardiac hypertrophy in spontaneously hypertensive rats

Smoking increases the risk of cardiovascular diseases. The present study was designed to determine the effects of 2-month exposure to cigarette smoke (CS) on proteins in the left ventricles of spontaneously hypertensive rats (SHR) and to identify the molecular targets associated with the pathogenesis/progression of CS-induced cardiac hypertrophy. SHR and Wistar Kyoto rats (WKY) were exposed to CS at low (2 puffs/min for 40 min) or high dose (2 puffs/min for 120 min), 5 days a week for 2 months. Using the two-dimensional fluorescence difference gel electrophoresis combined with MALDI-TOF/TOF tandem mass spectrometry, we compared differences in the expression levels of proteins in the whole left ventricles induced by long-term smoking. High-dose CS mainly caused cardiac hypertrophy in SHR, but not WKY, but no change in blood pressure. Proteomic analysis identified 30 protein spots with significant alterations, with 14 up-regulated and 16 down-regulated proteins in the left ventricles of CS-exposed SHR, compared with control SHR. Among these proteins, two members of the heat shock proteins (HSP70 and HSP20) showed significant up-regulation in the left ventricles of CS high-dose SHR, and the results were confirmed by western blot analysis. Our findings suggested that HSPs play an important role in regulation of CS-induced cardiac hypertrophy.

Disentangling the epigenetic landscape in cardiovascular patients: a path toward personalized medicine

Despite significant advances in our understanding of cardiovascular disease (CVD) we are still far from having developed breakthrough strategies to combat coronary atherosclerosis and heart failure, which account for most of CV deaths worldwide. Available cardiovascular therapies have failed to show to be equally effective in all patients, suggesting that inter-individual diversity is an important factor when it comes to conceive and deliver effective personalized treatments. Genome mapping has proved useful in identifying patients who could benefit more from specific drugs depending on genetic variances; however, our genetic make-up determines only a limited part of an individual's risk profile. Recent studies have demonstrated that epigenetic changes - defined as dynamic changes of DNA and histones which do not affect DNA sequence - are key players in the pathophysiology of cardiovascular disease and may participate to delineate cardiovascular risk trajectories over the lifetime. Epigenetic modifications include changes in DNA methylation, histone modifications and non-coding RNAs and these epigenetic signals have shown to cooperate in modulating chromatin accessibility to transcription factors and gene expression. Environmental factors such as air pollution, smoking, psychosocial context, and unhealthy diet regimens have shown to significantly modify the epigenome thus leading to altered transcriptional programs and CVD phenotypes. Therefore, the integration of genetic and epigenetic information might be invaluable to build individual maps of cardiovascular risk and hence, could be employed for the design of customized diagnostic and therapeutic strategies. In the present review, we discuss the growing importance of epigenetic information and its putative implications in cardiovascular precision medicine.

Cardiac hypertrophy in a dish: a human stem cell based model

Cardiac hypertrophy is an important and independent risk factor for the development of heart failure. To better understand the mechanisms and regulatory pathways involved in cardiac hypertrophy, there is a need for improved in vitro models. In this study, we investigated how hypertrophic stimulation affected human induced pluripotent stem cell (iPSC)-derived cardiomyocytes (CMs). The cells were stimulated with endothelin-1 (ET-1) for 8, 24, 48, 72, or 96 h. Parameters including cell size, ANP-, proBNP-, and lactate concentration were analyzed. Moreover, transcriptional profiling using RNA-sequencing was performed to identify differentially expressed genes following ET-1 stimulation. The results show that the CMs increase in size by approximately 13% when exposed to ET-1 in parallel to increases in ANP and proBNP protein and mRNA levels. Furthermore, the lactate concentration in the media was increased indicating that the CMs consume more glucose, a hallmark of cardiac hypertrophy. Using RNA-seq, a hypertrophic gene expression pattern was also observed in the stimulated CMs. Taken together, these results show that hiPSC-derived CMs stimulated with ET-1 display a hypertrophic response. The results from this study also provide new molecular insights about the underlying mechanisms of cardiac hypertrophy and may help accelerate the development of new drugs against this condition.

Histone deacetylases in modulating cardiac disease and their clinical translational and therapeutic implications

Cardiovascular diseases are the leading cause of mortality and morbidity worldwide. Histone deacetylases (HDACs) play an important role in the epigenetic regulation of genetic transcription in response to stress or pathological conditions. HDACs interact with a complex co-regulatory network of transcriptional regulators, deacetylate histones or non-histone proteins, and modulate gene expression in the heart. The selective HDAC inhibitors have been considered to be a critical target for the treatment of cardiac disease, especially for ameliorating cardiac dysfunction. In this review, we discuss our current knowledge of the cellular and molecular basis of HDACs in mediating cardiac development and hypertrophy and related pharmacologic interventions in heart disease.

Isoform-specific characterization of class I histone deacetylases and their therapeutic modulation in pulmonary hypertension

Pharmacological modulation of class I histone deacetylases (HDAC) has been evaluated as a therapeutic strategy for pulmonary hypertension (PH) in experimental models of PH. However, information of their expression, regulation and transcriptional targets in human PH and the therapeutic potential of isoform-selective enzyme modulation are lacking. Comprehensive analysis of expression and regulation of class I HDACs (HDAC1, HDAC2, HDAC3 and HDAC8) was performed in cardiopulmonary tissues and adventitial fibroblasts isolated from pulmonary arteries (PAAF) of idiopathic pulmonary arterial hypertension (IPAH) patients and healthy donors. Cellular functions and transcriptional targets of HDAC enzymes were investigated. Therapeutic effects of pan-HDAC (Vorinostat), class-selective (VPA) and isoform-selective (CAY10398, Romidepsin, PCI34051) HDAC inhibitors were evaluated ex vivo (IPAH-PAAF, IPAH-PASMC) and in vivo (rat chronic hypoxia-induced PH and zebrafish angiogenesis). Our screening identifies dysregulation of class I HDAC isoforms in IPAH. Particularly, HDAC1 and HDAC8 were consistently increased in IPAH-PAs and IPAH-PAAFs, whereas HDAC2 and HDAC8 showed predominant localization with ACTA2-expressing cells in extensively remodeled IPAH-PAs. Hypoxia not only significantly modulated protein levels of deacetylase (HDAC8), but also significantly caused dynamic changes in the global histone lysine acetylation levels (H3K4ac, H3K9/K14ac and H3K27ac). Importantly, isoform-specific RNA-interference revealed that HDAC isoforms regulate distinct subset of transcriptome in IPAH-PAAFs. Reduced transcript levels of KLF2 in IPAH-PAAFs was augmented by HDAC8 siRNA and HDAC inhibitors, which also attenuated IPAH-associated hyperproliferation and apoptosis-resistance ex vivo, and mitigated chronic hypoxia-induced established PH in vivo, at variable degree. Class I HDAC isoforms are significantly dysregulated in human PAH. Isoform-selective HDAC inhibition is a viable approach to circumvent off-target effects.

Inhibition of heat shock protein 70 blocks the development of cardiac hypertrophy by modulating the phosphorylation of histone deacetylase 2

AIMS

Previously, we reported that phosphorylation of histone deacetylase 2 (HDAC2) and the resulting activation causes cardiac hypertrophy. Through further study of the specific binding partners of phosphorylated HDAC2 and their mechanism of regulation, we can better understand how cardiac hypertrophy develops. Thus, in the present study, we aimed to elucidate the function of one such binding partner, heat shock protein 70 (HSP70).

METHODS AND RESULTS

Primary cultures of rat neonatal ventricular cardiomyocytes and H9c2 cardiomyoblasts were used for in vitro cellular experiments. HSP70 knockout (KO) mice and transgenic (Tg) mice that overexpress HSP70 in the heart were used for in vivo analysis. Peptide-precipitation and immunoprecipitation assay revealed that HSP70 preferentially binds to phosphorylated HDAC2 S394. Forced expression of HSP70 increased phosphorylation of HDAC2 S394 and its activation, but not that of S422/424, whereas knocking down of HSP70 reduced it. However, HSP70 failed to phosphorylate HDAC2 in the cell-free condition. Phosphorylation of HDAC2 S394 by casein kinase 2α1 enhanced the binding of HSP70 to HDAC2, whereas dephosphorylation induced by the catalytic subunit of protein phosphatase 2A (PP2CA) had the opposite effect. HSP70 prevented HDAC2 dephosphorylation by reducing the binding of HDAC2 to PP2CA. HSP70 KO mouse hearts failed to phosphorylate S394 HDAC2 in response to isoproterenol infusion, whereas Tg overexpression of HSP70 increased the phosphorylation and activation of HDAC2. 2-Phenylethynesulfonamide (PES), an HSP70 inhibitor, attenuated cardiac hypertrophy induced either by phenylephrine in neonatal ventricular cardiomyocytes or by aortic banding in mice. PES reduced HDAC2 S394 phosphorylation and its activation by interfering with the binding of HSP70 to HDAC2.

CONCLUSION

These results demonstrate that HSP70 specifically binds to S394-phosphorylated HDAC2 and maintains its phosphorylation status, which results in HDAC2 activation and the development of cardiac hypertrophy. Inhibition of HSP70 has possible application as a therapeutic.

Histone Deacetylase Inhibitor Suberoylanilide Hydroxamic Acid Improves Energetic Status and Cardiomyogenic Differentiation of Human Dilated Myocardium-Derived Primary Mesenchymal Cells

Background. In this study the effect of histone deacetylase (HDAC) inhibitor suberoylanilide hydroxamic acid (SAHA) on the energetic status and cardiomyogenic differentiation of human healthy and dilated myocardium-derived mesenchymal stromal cells (hmMSC) have been investigated. Methods. The hmMSC were isolated from the healthy and dilated post-operation heart biopsies by explant outgrowth method. Cell proliferation, HDAC activity, mitochondrial membrane potential, and level of adenosine triphosphate (ATP) were evaluated. The effect of SAHA on mitochondrial parameters has been investigated also by Seahorse XF analyzer and cardiomyogenic differentiation was confirmed by the expression of transcription factor NK2 Homeobox 5 (Nkx2.5), cardiac troponin T and alpha cardiac actin at gene and protein levels. Results. Dilated myocardium-derived hmMSC had almost 1.5 folds higher HDAC activity compared to the healthy cells and significantly lower mitochondrial membrane potential and ATP level. HDAC class I and II inhibitor SAHA improved energetic status of mitochondria in dilated myocardium-isolated hmMSC and increased expression of cardiac specific proteins during 14 days of exposure of cells to SAHA. Conclusions. HDAC inhibitor SAHA can be a promising therapeutic for dilated cardiomyopathy (DCM). Dilated hmMSC exposed to SAHA improved energetic status and, subsequently, cardiomyogenic differentiation. Data suggest that human dilated myocardium-derived MSC still have cardio tissue regenerative potential, which might be stimulated by HDAC inhibitors.

Come Together: Protein Assemblies, Aggregates and the Sarcostat at the Heart of Cardiac Myocyte Homeostasis

Homeostasis in vertebrate systems is contingent on normal cardiac function. This, in turn, depends on intricate protein-based cellular machinery, both for contractile function, as well as, durability of cardiac myocytes. The cardiac small heat shock protein (csHsp) chaperone system, highlighted by αB-crystallin (CRYAB), a small heat shock protein (sHsp) that forms ∼3–5% of total cardiac mass, plays critical roles in maintaining proteostatic function via formation of self-assembled multimeric chaperones. In this work, we review these ancient proteins, from the evolutionarily preserved role of homologs in protists, fungi and invertebrate systems, as well as, the role of sHsps and chaperones in maintaining cardiac myocyte structure and function. We propose the concept of the “sarcostat” as a protein quality control mechanism in the sarcomere. The roles of the proteasomal and lysosomal proteostatic network, as well as, the roles of the aggresome, self-assembling protein complexes and protein aggregation are discussed in the context of cardiac myocyte homeostasis. Finally, we will review the potential for targeting the csHsp system as a novel therapeutic approach to prevent and treat cardiomyopathy and heart failure.

Roles of Histone Acetylation Modifiers and Other Epigenetic Regulators in Vascular Calcification

Vascular calcification (VC) is characterized by calcium deposition inside arteries and is closely associated with the morbidity and mortality of atherosclerosis, chronic kidney disease, diabetes, and other cardiovascular diseases (CVDs). VC is now widely known to be an active process occurring in vascular smooth muscle cells (VSMCs) involving multiple mechanisms and factors. These mechanisms share features with the process of bone formation, since the phenotype switching from the contractile to the osteochondrogenic phenotype also occurs in VSMCs during VC. In addition, VC can be regulated by epigenetic factors, including DNA methylation, histone modification, and noncoding RNAs. Although VC is commonly observed in patients with chronic kidney disease and CVD, specific drugs for VC have not been developed. Thus, discovering novel therapeutic targets may be necessary. In this review, we summarize the current experimental evidence regarding the role of epigenetic regulators including histone deacetylases and propose the therapeutic implication of these regulators in the treatment of VC.

Epigenetic-sensitive pathways in personalized therapy of major cardiovascular diseases

The complex pathobiology underlying cardiovascular diseases (CVDs) has yet to be explained. Aberrant epigenetic changes may result from alterations in enzymatic activities, which are responsible for putting in and/or out the covalent groups, altering the epigenome and then modulating gene expression. The identification of novel individual epigenetic-sensitive trajectories at single cell level might provide additional opportunities to establish predictive, diagnostic and prognostic biomarkers as well as drug targets in CVDs. To date, most of studies investigated DNA methylation mechanism and miRNA regulation as epigenetics marks. During atherogenesis, big epigenetic changes in DNA methylation and different ncRNAs, such as miR-93, miR-340, miR-433, miR-765, CHROME, were identified into endothelial cells, smooth muscle cells, and macrophages. During man development, lipid metabolism, inflammation and homocysteine homeostasis, alter vascular transcriptional mechanism of fundamental genes such as ABCA1, SREBP2, NOS, HIF1. At histone level, increased HDAC9 was associated with matrix metalloproteinase 1 (MMP1) and MMP2 expression in pro-inflammatory macrophages of human carotid plaque other than to have a positive effect on toll like receptor signaling and innate immunity. HDAC9 deficiency promoted inflammation resolution and reverse cholesterol transport, which might block atherosclerosis progression and promote lesion regression. Here, we describe main human epigenetic mechanisms involved in atherosclerosis, coronary heart disease, ischemic stroke, peripheral artery disease; cardiomyopathy and heart failure. Different epigenetics mechanisms are activated, such as regulation by circular RNAs, as MICRA, and epitranscriptomics at RNA level. Moreover, in order to open new frontiers for precision medicine and personalized therapy, we offer a panoramic view on the most innovative bioinformatic tools designed to identify putative genes and molecular networks underlying CVDs in man.

Epigenetics in dilated cardiomyopathy

PURPOSE OF REVIEW

Characterized by enlarged ventricle and loss of systolic function, dilated cardiomyopathy (DCM) has the highest morbidity among all the cardiomyopathies. Although it is well established that DCM is typically caused by mutations in a large number of genes, there is an emerging appreciation for the contribution of epigenetic alteration in the development of DCM.

RECENT FINDINGS

We present some of the recent progress in the field of epigenetics in DCM by focusing on the four major epigenetic modifications, that is, DNA methylation, histone modification, chromatin remodeling as well as the noncoding RNAs. The major players involved in these DCM-related epigenetic reprogramming will be highlighted. Finally, the diagnostic and the therapeutic implications for DCM based on new knowledge of epigenetic regulation will also be discussed.

SUMMARY

As a rapidly expanding field, epigenetic studies in DCM have the promise to yield both novel mechanistic insights as well as potential new avenues for more effective treatment of the disease.

Oral delivery of xenon for cardiovascular protection

Cardiac hypertrophy often causes impairment of cardiac function. Xenon (Xe), a naturally occurring noble gas, is known to provide neurological and myocardial protection without side effects. The conventional method of Xe delivery by inhalation is not feasible on a chronic basis. We have developed an orally deliverable, effective Xe formulation for long-term administration. We employed 2-hydroxypropyl)-β-cyclodextrin (HPCD), which was dissolved in water to increase the Xe concentration in solution. The beneficial effects of long-term oral administration of Xe-enriched solutions on cardiovascular function were evaluated in vivo. HPCD increased Xe solubility from 0.22 mM to 0.67 mM (3.8-fold). Aged ApoE knockout mice fed high-fat diet for 6 weeks developed hypertension, and myocardial hypertrophy with impaired cardiac function. Oral Xe prevented this ischemic damage, preserving normal blood pressure, while maintaining normal left ventricular mass and wall thickness. This novel formulation allows for gastrointestinal delivery and cardiovascular stabilization.

The anti-cancer drug doxorubicin induces substantial epigenetic changes in cultured cardiomyocytes

The anthracycline doxorubicin (DOX) is widely used in cancer therapy with the limitation of cardiotoxicity leading to the development of congestive heart failure. DOX-induced oxidative stress and changes of the phosphoproteome as well as epigenome were described but the exact mechanisms of the adverse long-term effects are still elusive. Here, we tested the impact of DOX treatment on cell death, oxidative stress parameters and expression profiles of proteins involved in epigenetic pathways in a cardiomyocyte cell culture model. Markers of oxidative stress, apoptosis and expression of proteins involved in epigenetic processes were assessed by immunoblotting in cultured rat myoblasts (H9c2) upon treatment with DOX (1 or 5 μM for 24 or 48 h) in adherent viable and detached apoptotic cells. The apoptosis markers cleaved caspase-3 and fractin as well as oxidative stress markers 3-nitrotyrosine and malondialdehyde were dose-dependently increased by DOX treatment. Histone deacetylases (SIRT1 and HDAC2), histone lysine demethylases (KDM3A and LSD1) and histone lysine methyltransferases (SET7 and SMYD1) were significantly regulated by DOX treatment with generation of cleaved protein fragments and posttranslational modifications. Overall, we found significant decrease in histone 3 acetylation in DOX-treated cells. DOX treatment of cultured cardiomyocyte precursor cells causes severe cell death by apoptosis associated with cellular oxidative stress. In addition, significant regulation of proteins involved in epigenetic processes and changes in global histone 3 acetylation were observed. However, the significance and clinical impact of these changes remain elusive.

Toll-Like Receptors (TLRs) Expression in Contracted Capsules Compared to Uncontracted Capsules

INTRODUCTION

The etiology of capsular contracture after surgical implantation of breast implants remains unclear, but an important role is seen for the immune system. Toll-like receptors are immune receptors recognizing both pathogen-associated molecular patterns and damage-associated molecular patterns. The former are present on bacteria such as Staphylococcus epidermidis (bacteria earlier associated with capsular contracture), and the latter are released after (mechanical) stress. The aim of this study was to investigate the expression of TLRs 1-10 in relation to capsular contracture.

MATERIALS AND METHODS

Fifty consecutive breast capsules were collected during implant removal or replacement. The extent of capsular contracture was scored according to the Baker score. A sample specimen (0.5 cm3) was obtained from all tissues. cDNA was synthesized from isolated mRNA from the collected specimens. PCR analyses were conducted to test for cDNA presence and to quantify concentration. TLR1-10 expression was measured for each of the Baker scores separately and compared to all Baker scores.

RESULTS

Expression of all TLRs in all Baker scores was seen. TLR2 and TLR6 were more often present in contracted samples (Baker 3 or 4) compared to uncontracted samples (Baker 1 or 2) [Baker 2 vs. 3 (p = 0.034) and Baker 2 vs. 3 (p = 0.003), respectively]. None of the TLRs displayed a significantly higher expression in contracted capsules compared to uncontracted capsules.

CONCLUSION

This study shows that TLR2 and TLR6 are more often expressed in contracted capsules compared to non-contracted capsules however not in higher concentrations.

LEVEL OF EVIDENCE III

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Protein Quality Control Activation and Microtubule Remodeling in Hypertrophic Cardiomyopathy

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

Effect of HDAC2/Inpp5f on neuropathic pain and cognitive function through regulating PI3K/Akt/GSK-3β signal pathway in rats with neuropathic pain

The effect of histone deacetylase (HDAC)2/Inositol polyphosphate-5-phosphatase F (Inpp5f) on neuropathic pain and cognitive dysfunction through regulating PI3K/Akt/GSK-3β signal pathway in rats with neuropathic pain was investigated. A total of 80 SPF mature male SD rats were averagely randomized into the sham operation group, the model group, the HDAC2 intervention group (group A) and the Inpp5f intervention group (group B). The rat models of neuropathic pain were established in the model group, and groups A and B. At the 15th day after modeling, rats in group A were transfected with the interference vector of HDAC2, and rats in group B were transfected with the overexpression vector of Inpp5f. Rats in the four groups were observed before modeling, after modeling/before intervention and 3 days after intervention in terms of paw thermal withdrawal latency (PWL), paw withdrawal mechanical threshold (PWT) and changes in cognitive function (Morris water maze and passive avoidance task). Then the rats were sacrificed. RT-qPCR and western blot analysis were used to detect the levels of HDAC2 mRNA, Inpp5f mRNA, phosphorylated PI3K (p-PI3K), phosphorylated AKT (p-AKT), phosphorylated GSK-3β (p-GSK-3β) in rat brain tissue. Correlation of HDAC2 mRNA with Inpp5f mRNA expression levels was detected by Pearsons correlation analysis. Compared with the sham operation group, PWL was significantly lower while PWT was higher in the other 3 groups (P<0.05). Three days after intervention, PWL was significantly higher while PWT was significantly lower (P<0.05). Inhibiting the expression of HDAC2 or promoting the expression of Inpp5f can effectively improve cognitive function in rats (P<0.05). After intervention, compared with the sham operation group, rats in the other 3 groups had higher HDAC2 mRNA level and lower Inpp5f mRNA level (P<0.05). In conclusion, neuropathic pain can cause an increase in HDAC2 expression level and a decrease in Inpp5f expression level, and activate the PI3K/Akt/GSK-3β signal pathway. Inhibition of HDAC2 expression can inhibit the activation of PI3K/Akt/GSK-3β signal pathway through increasing Inpp5f expression, thus improving the condition and cognitive disorder of rats with neuropathic pain.

Epigenetics, cardiovascular disease, and cellular reprogramming

Under the seeming disorder of "junk" sequences the last decade has seen developments in our understanding of non-coding RNA's (ncRNAs). It's a complex revised order and nowhere is this more relevant than in the developing heart whereby old rules have been set aside to make room for new ones. The development of the mammalian heart has been studied at the genetic and cellular level for several decades because these areas were considered ideal control points. As such, detailed mechanisms governing cell lineages are well described. Emerging evidence suggests a complex new order regulated by epigenetic mechanisms mark cardiac cell lineage. Indeed, molecular cardiologists are in the process of shedding light on the roles played by ncRNAs, nucleic acid methylation and histone/chromatin modifications in specific pathologies of the heart. The aim of this article is to discuss some of the recent advances in the field of cardiovascular epigenetics that are related to direct cell reprogramming and repair. As such, we explore ncRNAs as nodes regulating signaling networks and attempt to make sense of regulatory disorder by reinforcing the importance of epigenetic components in the developmental program.

Angiotensin II Signal Transduction: An Update on Mechanisms of Physiology and Pathophysiology

The renin-angiotensin-aldosterone system plays crucial roles in cardiovascular physiology and pathophysiology. However, many of the signaling mechanisms have been unclear. The angiotensin II (ANG II) type 1 receptor (AT₁R) is believed to mediate most functions of ANG II in the system. AT₁R utilizes various signal transduction cascades causing hypertension, cardiovascular remodeling, and end organ damage. Moreover, functional cross-talk between AT₁R signaling pathways and other signaling pathways have been recognized. Accumulating evidence reveals the complexity of ANG II signal transduction in pathophysiology of the vasculature, heart, kidney, and brain, as well as several pathophysiological features, including inflammation, metabolic dysfunction, and aging. In this review, we provide a comprehensive update of the ANG II receptor signaling events and their functional significances for potential translation into therapeutic strategies. AT₁R remains central to the system in mediating physiological and pathophysiological functions of ANG II, and participation of specific signaling pathways becomes much clearer. There are still certain limitations and many controversies, and several noteworthy new concepts require further support. However, it is expected that rigorous translational research of the ANG II signaling pathways including those in large animals and humans will contribute to establishing effective new therapies against various diseases.

Understanding Key Mechanisms of Exercise-Induced Cardiac Protection to Mitigate Disease: Current Knowledge and Emerging Concepts

The benefits of exercise on the heart are well recognized, and clinical studies have demonstrated that exercise is an intervention that can improve cardiac function in heart failure patients. This has led to significant research into understanding the key mechanisms responsible for exercise-induced cardiac protection. Here, we summarize molecular mechanisms that regulate exercise-induced cardiac myocyte growth and proliferation. We discuss in detail the effects of exercise on other cardiac cells, organelles, and systems that have received less or little attention and require further investigation. This includes cardiac excitation and contraction, mitochondrial adaptations, cellular stress responses to promote survival (heat shock response, ubiquitin-proteasome system, autophagy-lysosomal system, endoplasmic reticulum unfolded protein response, DNA damage response), extracellular matrix, inflammatory response, and organ-to-organ crosstalk. We summarize therapeutic strategies targeting known regulators of exercise-induced protection and the challenges translating findings from bench to bedside. We conclude that technological advancements that allow for in-depth profiling of the genome, transcriptome, proteome and metabolome, combined with animal and human studies, provide new opportunities for comprehensively defining the signaling and regulatory aspects of cell/organelle functions that underpin the protective properties of exercise. This is likely to lead to the identification of novel biomarkers and therapeutic targets for heart disease.

HSP72 functionally inhibits the anti-neoplastic effects of HDAC inhibitors

BACKGROUND

The anticancer effects of histone deacetylase inhibitors (HDACi) vary between patients, and their molecular mechanisms remain poorly understood. Previously, we have identified heat shock 70 kDa protein 1A (HSPA1A, also known as HSP72) as the most overexpressed protein in valproic acid (VPA)-resistant cell lines. KNK437, an inhibitor of heat shock proteins, enhanced the cytotoxic effects of not only VPA but also vorinostat, another HDACi. However, the mechanisms underlying the role of HSP72 in resistance against HDACi remain largely unknown.

OBJECTIVE

The purpose of this study was to identify the mechanisms underlying the role of HSP72 in HDACi resistance.

METHODS

We established an HSP72-overexpressing Jurkat cell line and used it to assess the functional role of HSP72 following treatment with the HDACi vorinostat and VPA.

RESULTS

HDACi-induced apoptosis, assessed using annexin V assays, sub-G1 fraction analysis, and PARP cleavage, was significantly lower in HSP72-overexpressing cells than in control cells. The HDACi-induced upregulation in caspase-3, -8, and -9 activity, as well as the HDACi-induced reduction in mitochondrial membrane potential, were also suppressed following HSP72 overexpression. The basal expression levels of Bcl-2, phosphorylated Bad, and XIAP increased in HSP72-overexpressing cells, whereas HDACi-induced Bid truncation and the suppression of Bad expression. Furthermore, vorinostat-induced histone hyperacetylation was also diminished in HSP72-overexpressing cells.

CONCLUSION

These findings clearly demonstrate that HSP72 inhibits HDACi-induced apoptosis.

Sumoylation of histone deacetylase 1 regulates MyoD signaling during myogenesis

Sumoylation, the conjugation of a small ubiquitin-like modifier (SUMO) protein to a target, has diverse cellular effects. However, the functional roles of the SUMO modification during myogenesis have not been fully elucidated. Here, we report that basal sumoylation of histone deacetylase 1 (HDAC1) enhances the deacetylation of MyoD in undifferentiated myoblasts, whereas further sumoylation of HDAC1 contributes to switching its binding partners from MyoD to Rb to induce myocyte differentiation. Differentiation in C2C12 skeletal myoblasts induced new immunoblot bands above HDAC1 that were gradually enhanced during differentiation. Using SUMO inhibitors and sumoylation assays, we showed that the upper band was caused by sumoylation of HDAC1 during differentiation. Basal deacetylase activity was not altered in the SUMO modification-resistant mutant HDAC1 K444/476R (HDAC1 2R). Either differentiation or transfection of SUMO1 increased HDAC1 activity that was attenuated in HDAC1 2R. Furthermore, HDAC1 2R failed to deacetylate MyoD. Binding of HDAC1 to MyoD was attenuated by K444/476R. Binding of HDAC1 to MyoD was gradually reduced after 2 days of differentiation. Transfection of SUMO1 induced dissociation of HDAC1 from MyoD but potentiated its binding to Rb. SUMO1 transfection further attenuated HDAC1-induced inhibition of muscle creatine kinase luciferase activity that was reversed in HDAC1 2R. HDAC1 2R failed to inhibit myogenesis and muscle gene expression. In conclusion, HDAC1 sumoylation plays a dual role in MyoD signaling: enhancement of HDAC1 deacetylation of MyoD in the basally sumoylated state of undifferentiated myoblasts and dissociation of HDAC1 from MyoD during myogenesis.

New Aspects of Vascular Calcification: Histone Deacetylases and Beyond

Vascular calcification is a pathologic phenomenon in which calcium phosphate is ectopically deposited in the arteries. Previously, calcification was considered to be a passive process in response to metabolic diseases, vascular or valvular diseases, or even aging. However, now calcification is recognized as a highly-regulated consequence, like bone formation, and many clinical trials have been carried out to elucidate the correlation between vascular calcification and cardiovascular events and mortality. As a result, vascular calcification has been implicated as an independent risk factor in cardiovascular diseases. Many molecules are now known to be actively associated with this process. Recently, our laboratory found that posttranslational modification of histone deacetylase (HDAC) 1 is actively involved in the development of vascular calcification. In addition, we found that modulation of the activity of HDAC as well as its protein stability by MDM2, an HDAC1-E3 ligase, may be a therapeutic target in vascular calcification. In the present review, we overview the pathomechanism of vascular calcification and the involvement of posttranslational modification of epigenetic regulators.

Heart irradiation reduces microvascular density and accumulation of HSPA1 in mice

PURPOSE

Improvement of radiotherapy techniques reduces the exposure of normal tissues to ionizing radiation. However, the risk of radiation-related late effects remains elevated. In the present study, we investigated long-term effects of radiation on heart muscle morphology.

MATERIALS AND METHODS

We established a mouse model to study microvascular density (MVD), deposition of collagen fibers, and changes in accumulation of heat shock 70 kDa protein 1 (HSPA1) in irradiated heart tissue. Hearts of C57BL/6 mice received a single dose of X‑ray radiation in the range 0.2-16 Gy. Analyses were performed 20, 40, and 60 weeks after irradiation.

RESULTS

Reduction in MD was revealed as a long-term effect observed 20-60 weeks after irradiation. Moreover, a significant and dose-dependent increase in accumulation of HSPA1, both cytoplasmic and nuclear, was observed in heart tissues collected 20 weeks after irradiation. We also noticed an increase in collagen deposition in hearts treated with higher doses.

CONCLUSIONS

This study shows that some changes induced by radiation in the heart tissue, such as reduction in microvessel density, increase in collagen deposition, and accumulation of HSPA1, are observed as long-term effects which might be associated with late radiation cardiotoxicity.

Class I HDACs control a JIP1-dependent pathway for kinesin-microtubule binding in cardiomyocytes

Class I histone deacetylase (HDAC) inhibitors block hypertrophy and fibrosis of the heart by suppressing pathological signaling and gene expression programs in cardiac myocytes and fibroblasts. The impact of HDAC inhibition in unstressed cardiac cells remains poorly understood. Here, we demonstrate that treatment of cultured cardiomyocytes with small molecule HDAC inhibitors leads to dramatic induction of c-Jun amino-terminal kinase (JNK)-interacting protein-1 (JIP1) mRNA and protein expression. In contrast to prior findings, elevated levels of endogenous JIP1 in cardiomyocytes failed to significantly alter JNK signaling or cardiomyocyte hypertrophy. Instead, HDAC inhibitor-mediated induction of JIP1 was required to stimulate expression of the kinesin heavy chain family member, KIF5A. We provide evidence for an HDAC-dependent regulatory circuit that promotes formation of JIP1:KIF5A:microtubule complexes that regulate intracellular transport of cargo such as autophagosomes. These findings define a novel role for class I HDACs in the control of the JIP1/kinesin axis in cardiomyocytes, and suggest that HDAC inhibitors could be used to alter microtubule transport in the heart.