HDAC-mediated control of ERK- and PI3K-dependent TGF-β-induced extracellular matrix-regulating genes

HDAC3 genetic and pharmacologic inhibition radiosensitizes fusion positive rhabdomyosarcoma by promoting DNA double-strand breaks

Radiotherapy (RT) plays a critical role in the management of rhabdomyosarcoma (RMS), the prevalent soft tissue sarcoma in childhood. The high risk PAX3-FOXO1 fusion-positive subtype (FP-RMS) is often resistant to RT. We have recently demonstrated that inhibition of class-I histone deacetylases (HDACs) radiosensitizes FP-RMS both in vitro and in vivo. However, HDAC inhibitors exhibited limited success on solid tumors in human clinical trials, at least in part due to the presence of off-target effects. Hence, identifying specific HDAC isoforms that can be targeted to radiosensitize FP-RMS is imperative. We, here, found that only HDAC3 silencing, among all class-I HDACs screened by siRNA, radiosensitizes FP-RMS cells by inhibiting colony formation. Thus, we dissected the effects of HDAC3 depletion using CRISPR/Cas9-dependent HDAC3 knock-out (KO) in FP-RMS cells, which resulted in Endoplasmatic Reticulum Stress activation, ERK inactivation, PARP1- and caspase-dependent apoptosis and reduced stemness when combined with irradiation compared to single treatments. HDAC3 loss-of-function increased DNA damage in irradiated cells augmenting H2AX phosphorylation and DNA double-strand breaks (DSBs) and counteracting irradiation-dependent activation of ATM and DNA-Pkcs as well as Rad51 protein induction. Moreover, HDAC3 depletion hampers FP-RMS tumor growth in vivo and maximally inhibits the growth of irradiated tumors compared to single approaches. We, then, developed a new HDAC3 inhibitor, MC4448, which showed specific cell anti-tumor effects and mirrors the radiosensitizing effects of HDAC3 depletion in vitro synergizing with ERKs inhibition. Overall, our findings dissect the pro-survival role of HDAC3 in FP-RMS and suggest HDAC3 genetic or pharmacologic inhibition as a new promising strategy to overcome radioresistance in this tumor.

A novel HDAC8 inhibitor H7E exerts retinoprotective effects against glaucomatous injury via ameliorating aberrant Müller glia activation and oxidative stress

Glaucoma is considered a neurodegenerative disease characterized by progressive visual field defects that may lead to blindness. Although controlling intraocular pressure (IOP) is the mainstay of glaucoma treatment, some glaucoma patients have unmet needs due to unclear pathogenic mechanisms. Recently, there has been growing evidence that neuroinflammation is a potential target for the development of novel antiglaucoma agents. In this study, we investigated the protective effects and cellular mechanisms of H7E, a novel small molecule inhibits HDAC8, using in vitro and in vivo glaucoma-like models. Importantly, H7E mitigated extracellular MMP-9 activity and MCP-1 levels in glutamate- or S100B-stimulated reactive Müller glia. In addition, H7E inhibited the upregulation of inflammation- and proliferation-related signaling pathways, particularly the ERK and JNK MAPK pathways. Under conditions of oxidative damage, H7E prevents retinal cell death and reduces extracellular glutamate released from stressed Müller glia. In a mouse model of NMDA-induced retinal degeneration, H7E alleviated functional and structural defects within the inner retina as assessed by electroretinography and optical coherence tomography. Our results demonstrated that the newly identified compound H7E protects against glaucoma damage by specifically targeting HDAC8 activity in the retina. This protective effect is attributed to the inhibition of Müller glial activation and the prevention of retinal cell death caused by oxidative stress.

Histone H1.0 couples cellular mechanical behaviors to chromatin structure

Tuning of genome structure and function is accomplished by chromatin-binding proteins, which determine the transcriptome and phenotype of the cell. Here we investigate how communication between extracellular stress and chromatin structure may regulate cellular mechanical behaviors. We demonstrate that histone H1.0, which compacts nucleosomes into higher-order chromatin fibers, controls genome organization and cellular stress response. We show that histone H1.0 has privileged expression in fibroblasts across tissue types and that its expression is necessary and sufficient to induce myofibroblast activation. Depletion of histone H1.0 prevents cytokine-induced fibroblast contraction, proliferation and migration via inhibition of a transcriptome comprising extracellular matrix, cytoskeletal and contractile genes, through a process that involves locus-specific H3K27 acetylation. Transient depletion of histone H1.0 in vivo prevents fibrosis in cardiac muscle. These findings identify an unexpected role of linker histones to orchestrate cellular mechanical behaviors, directly coupling force generation, nuclear organization and gene transcription.

Epigenetic Regulation of EMP/EMT-Dependent Fibrosis

Fibrosis represents a process characterized by excessive deposition of extracellular matrix (ECM) proteins. It often represents the evolution of pathological conditions, causes organ failure, and can, in extreme cases, compromise the functionality of organs to the point of causing death. In recent years, considerable efforts have been made to understand the molecular mechanisms underlying fibrotic evolution and to identify possible therapeutic strategies. Great interest has been aroused by the discovery of a molecular association between epithelial to mesenchymal plasticity (EMP), in particular epithelial to mesenchymal transition (EMT), and fibrogenesis, which has led to the identification of complex molecular mechanisms closely interconnected with each other, which could explain EMT-dependent fibrosis. However, the result remains unsatisfactory from a therapeutic point of view. In recent years, advances in epigenetics, based on chromatin remodeling through various histone modifications or through the intervention of non-coding RNAs (ncRNAs), have provided more information on the fibrotic process, and this could represent a promising path forward for the identification of innovative therapeutic strategies for organ fibrosis. In this review, we summarize current research on epigenetic mechanisms involved in organ fibrosis, with a focus on epigenetic regulation of EMP/EMT-dependent fibrosis.

Pyroptosis-related signatures predict immune characteristics and prognosis in IPF

The purpose of this work was to use integrated bioinformatics analysis to screen for pyroptosis-related genes (PRGs) and possible immunological phenotypes linked to the development and course of IPF. Transcriptome sequencing datasets GSE70866, GSE47460 and GSE150910 were obtained from GEO database. From the GSE70866 database, 34 PRGs with differential expression were found in IPF as compared to healthy controls. In addition, a diagnostic model containing 4 genes PRGs (CAMP, MKI67, TCEA3 and USP24) was constructed based on LASSO logistic regression. The diagnostic model showed good predictive ability to differentiate between IPF and healthy, with ROC-AUC ranging from 0.910 to 0.997 in GSE70866 and GSE150910 datasets. Moreover, based on a combined cohort of the Freiburg and the Siena cohorts from GSE70866 dataset, we identified ten PRGs that might predict prognosis for IPF. We constructed a prognostic model that included eight PRGs (CLEC5A, TREM2, MMP1, IRF2, SEZ6L2, ADORA3, NOS2, USP24) by LASSO Cox regression and validated it in the Leuven cohort. The risk model divided IPF patients from the combined cohort into high-risk and low-risk subgroups. There were significant differences between the two subgroups in terms of IPF survival and GAP stage. There is a close correlation between leukocyte migration, plasma membrane junction, and poor prognosis in a high-risk subgroup. Furthermore, a high-risk score was associated with more plasma cells, activated NK cells, monocytes, and activated mast cells. Additionally, we identified HDAC inhibitors in the cMAP database that might be therapeutic for IPF. To summarize, pyroptosis and its underlying immunological features are to blame for the onset and progression of IPF. PRG-based predictive models and drugs may offer new treatment options for IPF.

HDAC5 inhibition attenuates ventricular remodeling and cardiac dysfunction

BACKGROUND

This study aimed to investigate the role of histone deacetylase 5 (HDAC5) in ventricular remodeling and explore the therapeutic potential of the HDAC5 inhibitor LMK235.

METHODS

A transverse aortic constriction (TAC) mouse model and angiotensin II (Ang II)-treated H9C2 cells were used to evaluate the effects of HDAC5 inhibition with LMK235 on ventricular remodeling and cardiac dysfunction. Additionally, the involvement of the extracellular signal-regulated kinase (ERK)/early growth response protein 1 (EGR1) signaling pathway in regulating myocyte enhancer factor 2 A (MEF2A) expression was assessed.

RESULTS

HDAC5 was upregulated in TAC mice and Ang II-treated H9C2 cells, suggesting its involvement in ventricular remodeling and cardiac dysfunction. LMK235 treatment significantly improved cardiac function in TAC mice and attenuated TAC-induced ventricular remodeling and Ang II-induced H9C2 cell hypertrophy. Mechanically, HDAC5 inhibition activated the ERK/EGR1 signaling pathway.

CONCLUSIONS

Our findings demonstrate that HDAC5 may suppress the activation of ERK/EGR1 signaling to regulate MEF2A expression and therefore participate in cardiac pathophysiology.

Molecular pathogenesis and treatment of cavernous nerve injury-induced erectile dysfunction: A narrative review

Introduction: Erectile dysfunction (ED) is a common complication after radical prostatectomy (RP), and it seriously affects the quality of life in patients and their partners. The primary trigger of postoperative ED is surgical injury to the cavernous nerves that control penile erection and run along the anterolateral aspect of the prostate. Despite the introduction and ongoing innovation of nerve-sparing techniques, a significant number of patients still suffer from moderate cavernous nerve injury (CNI), which is thought to be transient and reversible. Therefore, early postoperative penile rehabilitation therapy may salvage patients’ erectile function by promoting cavernous nerve regeneration and preventing penile structural alterations.

Aims: To present a comprehensive overview of the current molecular pathogenesis of CNI-induced ED, as well as novel therapeutic strategies and their potential mechanisms.

Methods: A literature search was performed using PubMed. Search terms included erectile dysfunction, cavernous nerve injury, pathogenesis, pathway, and treatment.

Results: The NOS/NO pathway, oxidative stress-related pathway, RhoA/ROCK pathway, transforming growth factor-β (TGF-β), sonic hedgehog (Shh), and hydrogen sulfide (H2S) are involved in the molecular pathogenesis of CNI-induced ED. Multiple neurotrophins, including brain-derived nerve growth factor (BDNF), glial cell line-derived neurotrophic factor (GDNF), and neurturin (NTN), were found to promote cavernous nerve regeneration. Emerging therapeutic approaches can be roughly summarized into four categories, namely small molecule and drug, stem cell-based therapy (SCT), micro-energy therapy and platelet-rich plasma (PRP) therapy.

Conclusion: These pathways collectively lead to the irreversible damage to the penile structure after CNI. The combined early rehabilitation strategies of promoting upstream nerve regeneration and recovering abnormal molecular signals of downstream penis are presumed to save patients’ erectile function after RP. In future studies, the cross-talk between these molecular pathways needs to be further clarified, and the questions of how denervation injury induces the molecular alterations in the penis also need to be addressed.

Targeting Histone Deacetylases in Idiopathic Pulmonary Fibrosis: A Future Therapeutic Option

Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal lung disease with limited therapeutic options, and there is a huge unmet need for new therapies. A growing body of evidence suggests that the histone deacetylase (HDAC) family of transcriptional corepressors has emerged as crucial mediators of IPF pathogenesis. HDACs deacetylate histones and result in chromatin condensation and epigenetic repression of gene transcription. HDACs also catalyse the deacetylation of many non-histone proteins, including transcription factors, thus also leading to changes in the transcriptome and cellular signalling. Increased HDAC expression is associated with cell proliferation, cell growth and anti-apoptosis and is, thus, a salient feature of many cancers. In IPF, induction and abnormal upregulation of Class I and Class II HDAC enzymes in myofibroblast foci, as well as aberrant bronchiolar epithelium, is an eminent observation, whereas type-II alveolar epithelial cells (AECII) of IPF lungs indicate a significant depletion of many HDACs. We thus suggest that the significant imbalance of HDAC activity in IPF lungs, with a “cancer-like” increase in fibroblastic and bronchial cells versus a lack in AECII, promotes and perpetuates fibrosis. This review focuses on the mechanisms by which Class I and Class II HDACs mediate fibrogenesis and on the mechanisms by which various HDAC inhibitors reverse the deregulated epigenetic responses in IPF, supporting HDAC inhibition as promising IPF therapy.

The Interaction Between Pulmonary Fibrosis and COVID-19 and the Application of Related Anti-Fibrotic Drugs

COVID-19 is a highly contagious respiratory disease, which mainly affects the lungs. Critically ill patients are easily complicated by cytokine storms, acute respiratory distress syndrome (ARDS), and respiratory failure, which seriously threaten their lives. Pulmonary fibrosis (PF) is a common interstitial lung disease, and its pathogenesis may involve the participation of a variety of immune cells and inflammatory factors. Current studies have shown that patients with COVID-19 may be complicated by pulmonary fibrosis, and patients with pulmonary fibrosis may also be at higher risk of contracting COVID-19 than healthy people. Pulmonary fibrosis is an important risk factor leading to the aggravation of COVID-19 disease. COVID-19 complicated by cytokine storm and ARDS mechanism pathways are similar to the pathogenesis of pulmonary fibrosis. The potential interaction between pulmonary fibrosis and COVID-19 can cause acute exacerbation of the patient’s condition, but the potential mechanism between the two has not been fully elucidated. Most of the drug treatment programs for COVID-19-related pulmonary fibrosis are currently formulated about the relevant guidelines for idiopathic pulmonary fibrosis (IPF), and there is no clear drug treatment program recommendation. This article aims to summarize the relevant mechanism pathways of COVID-19 and pulmonary fibrosis, explore the interrelationships and possible mechanisms, and discuss the value and risks of existing and potential COVID-19-related pulmonary fibrosis treatment drugs, to provide reference for anti-fibrosis treatment for patients.

Inflammation, Fibrosis and Cancer: Mechanisms, Therapeutic Options and Challenges

Uncontrolled inflammation is a salient factor in multiple chronic inflammatory diseases and cancers. In this review, we provided an in-depth analysis of the relationships and distinctions between uncontrolled inflammation, fibrosis and cancers, while emphasizing the challenges and opportunities of developing novel therapies for the treatment and/or management of these diseases. We described how drug delivery systems, combination therapy and the integration of tissue-targeted and/or pathways selective strategies could overcome the challenges of current agents for managing and/or treating chronic inflammatory diseases and cancers. We also recognized the value of the re-evaluation of the disease-specific roles of multiple pathways implicated in the pathophysiology of chronic inflammatory diseases and cancers-as well as the application of data from single-cell RNA sequencing in the success of future drug discovery endeavors.

Histone deacetylase inhibition by suberoylanilide hydroxamic acid: a therapeutic approach to treat human uterine leiomyoma

OBJECTIVE

To evaluate the effect of inhibition of histone deacetylases (HDACs) by suberoylanilide hydroxamic acid (SAHA) treatment of human uterine leiomyoma primary (HULP) cells in vitro on cell proliferation, cell cycle, extracellular matrix (ECM) formation, and transforming growth factor β3 (TGF-β3) signaling.

DESIGN

Prospective study comparing uterine leiomyoma (UL) vs. adjacent myometrium (MM) tissue and cells with or without SAHA treatment.

SETTING

Hospital and university laboratories.

PATIENT(S)

Women with UL without any hormone treatment.

INTERVENTION(S)

Myomectomy or hysterectomy surgery in women for leiomyoma disease.

MAIN OUTCOME MEASURE(S)

HDAC activity was assessed by enzyme-linked immunosorbent assay, and gene expression was assessed by quantitative real-time polymerase chain reaction. Effects of SAHA on HULP cells were analyzed by CellTiter (Promega, Madison, Wisconsin), Western blot, and quantitative real-time polymerase chain reaction.

RESULT(S)

The expression of HDAC genes (HDAC1, fold change [FC] = 1.65; HDAC3, FC = 2.08; HDAC6, FC = 2.42) and activity (0.56 vs. 0.10 optical density [OD]/h/mg) was significantly increased in UL vs. MM tissue. SAHA decreased HDAC activity in HULP cells but not in MM cells. Cell viability significantly decreased in HULP cells (81.68% at 5 μM SAHA, 73.46% at 10 μM SAHA), but not in MM cells. Proliferating cell nuclear antigen expression was significantly inhibited in SAHA-treated HULP cells (5 μM SAHA, FC = 0.556; 10 μM SAHA, FC = 0.622). Cell cycle markers, including C-MYC (5 μM SAHA, FC = 0.828) and CCND1 (5 μM SAHA, FC = 0.583; 10 μM SAHA, FC = 0.482), were significantly down-regulated after SAHA treatment. SAHA significantly inhibited ECM protein expression, including FIBRONECTIN (5 μM SAHA, FC = 0.815; 10 μM SAHA, FC = 0.673) and COLLAGEN I (5 μM SAHA, FC = 0.599; 10 μM SAHA, FC = 0.635), in HULP cells. TGFβ3 and MMP9 gene expression was also significantly down-regulated by 10 μM SAHA (TGFβ3, FC = 0.596; MMP9, FC = 0.677).

CONCLUSION(S)

SAHA treatment inhibits cell proliferation, cell cycle, ECM formation, and TGF-β3 signaling in HULP cells, suggesting that histone deacetylation may be useful for treatment of UL.

Backstage players of fibrosis: NOX4, mTOR, HDAC, and S1P; companions of TGF-β

The fibrotic process could be easily defined as a pathological excess of extracellular matrix deposition, leading to disruption of tissue architecture and eventually loss of function; however, this process involves a complex network of several signal transduction pathways. Virtually almost all organs could be affected by fibrosis, the most affected are the liver, lung, skin, kidney, heart, and eyes; in all of them, the transforming growth factor-beta (TGF-β) has a central role. The canonical and non-canonical signal pathways of TGF-β impact the fibrotic process at the cellular and molecular levels, inducing the epithelial-mesenchymal transition (EMT) and the induction of profibrotic gene expression with the consequent increase in proteins such as alpha-smooth actin (α-SMA), fibronectin, collagen, and other extracellular matrix proteins. Recently, it has been reported that some molecules that have not been typically associated with the fibrotic process, such as nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 4 (NOX4), mammalian target of rapamycin (mTOR), histone deacetylases (HDAC), and sphingosine-1 phosphate (S1P); are critical in its development. In this review, we describe and discuss the role of these new players of fibrosis and the convergence with TGF-β signaling pathways, unveiling new insights into the panorama of fibrosis that could be useful for future therapeutic targets.

The Epigenetic Regulation of Microenvironment in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a highly lethal and complex malignancy strongly influenced by the surrounding tumor microenvironment. The HCC microenvironment comprises hepatic stellate cells (HSCs), tumor-associated macrophages (TAMs), stromal and endothelial cells, and the underlying extracellular matrix (ECM). Emerging evidence demonstrates that epigenetic regulation plays a crucial role in altering numerous components of the HCC tumor microenvironment. In this review, we summarize the current understanding of the mechanisms of epigenetic regulation of the microenvironment in HCC. We review recent studies demonstrating how specific epigenetic mechanisms (DNA methylation, histone regulation, and non-coding RNAs mediated regulation) in HSCs, TAMs, and ECM, and how they contribute to HCC development, so as to gain new insights into the treatment of HCC via regulating epigenetic regulation in the tumor microenvironment.

Repurposing of histone deacetylase inhibitors: A promising strategy to combat pulmonary fibrosis promoted by TGF-β signalling in COVID-19 survivors

Coronavirus disease 2019 (COVID-19) has rapidly spread around the world causing global public health emergency. In the last twenty years, we have witnessed several viral epidemics such as severe acute respiratory syndrome coronavirus (SARS-CoV), Influenza A virus subtype H1N1 and most recently Middle East respiratory syndrome coronavirus (MERS-CoV). There were tremendous efforts endeavoured globally by scientists to combat these viral diseases and now for SARS-CoV-2. Several drugs such as chloroquine, arbidol, remdesivir, favipiravir and dexamethasone are adopted for use against COVID-19 and currently clinical studies are underway to test their safety and efficacy for treating COVID-19 patients. As per World Health Organization reports, so far more than 16 million people are affected by COVID-19 with a recovery of close to 10 million and deaths at 600,000 globally.

SARS-CoV-2 infection is reported to cause extensive pulmonary damages in affected people. Given the large number of recoveries, it is important to follow-up the recovered patients for apparent lung function abnormalities. In this review, we discuss our understanding about the development of long-term pulmonary abnormalities such as lung fibrosis observed in patients recovered from coronavirus infections (SARS-CoV and MERS-CoV) and probable epigenetic therapeutic strategy to prevent the development of similar pulmonary abnormalities in SARS-CoV-2 recovered patients. In this regard, we address the use of U.S. Food and Drug Administration (FDA) approved histone deacetylase (HDAC) inhibitors therapy to manage pulmonary fibrosis and their underlying molecular mechanisms in managing the pathologic processes in COVID-19 recovered patients.

Inhibition of histone deacetylases is the major pathway mediated by astaxanthin to antagonize LPS-induced inflammatory responses in mammary epithelial cells

Mastitis is a major inflammatory response of the mammary gland due to various pathogenic invasions and is a serious disease that affects the production yield and health status of cows. Astaxanthin (AST), a xanthophyll carotenoid, is a secondary metabolite synthesized by microalgae and yeasts that has been reported to suppress various inflammatory responses. However, the protective effect of AST on lipopolysaccharide (LPS)-induced mammary epithelial cells has not yet been reported. The present study results indicated that AST treatment markedly attenuated the oxidative stress markers and nitric oxide (NO) while improving the anti-oxidant enzymes in LPS exposed cells. On the other hand, LPS-exposed cells showed nuclear translocation of nuclear factor-κB (NF-κB) with the activation of inflammatory cytokines such as monocyte chemoattractant protein-1, tumor necrosis factor-α, interferon-γ, and interleukin-6 (IL-6). In addition, mRNA expression analysis revealed that the histone deacetylase (HDAC) -1, -2, -3, -6, -7 and pentraxin 3 (PTX3) expressions were increased in the LPS group. Furthermore, the activity of HDAC was increased to 2-fold with a significant reduction in the histone acetyltransferase activity in cells exposed to LPS. However, AST was able to inhibit the nuclear translocation of NF-κB with attenuated HDAC activity. Intriguingly, HDAC inhibition studies demonstrated that the cytokines such as IL-4, IL-8, granulocyte-mcrophage colony stimulating factor, C-reactive protein, IL-17A, and IL-22 were significantly suppressed which were upregulated in LPS treatment; while AST was found acting by improving the anti-inflammatory cytokine IL-10, and thioredoxin reductase levels. Collectively, these findings provide novel insights into the role of HDACs in regulating cellular processes involved in the pathogenesis of LPS-induced mastitis as well as the potential use of AST as a therapeutic in treatment for controlling disease progression.

TGFβ-induced fibroblast activation requires persistent and targeted HDAC-mediated gene repression

Tissue fibrosis is a chronic disease driven by persistent fibroblast activation that has recently been linked to epigenetic modifications. Here, we screened a small library of epigenetic small-molecule modulators to identify compounds capable of inhibiting or reversing TGFβ-mediated fibroblast activation. We identified pracinostat, an HDAC inhibitor, as a potent attenuator of lung fibroblast activation and confirmed its efficacy in patient-derived fibroblasts isolated from fibrotic lung tissue. Mechanistically, we found that HDAC-dependent transcriptional repression was an early and essential event in TGFβ-mediated fibroblast activation. Treatment of lung fibroblasts with pracinostat broadly attenuated TGFβ-mediated epigenetic repression and promoted fibroblast quiescence. We confirmed a specific role for HDAC-dependent histone deacetylation in the promoter region of the anti-fibrotic gene PPARGC1A (PGC1α) in response to TGFβ stimulation. Finally, we identified HDAC7 as a key factor whose siRNA-mediated knockdown attenuates fibroblast activation without altering global histone acetylation. Together, these results provide novel mechanistic insight into the essential role HDACs play in TGFβ-mediated fibroblast activation via targeted gene repression.

Circulating Relaxin-1 Level Is a Surrogate Marker of Myocardial Fibrosis in HFrEF

Introduction: Relaxin-1 (RLN1) has emerged as a possible therapeutic target in myocardial fibrosis due to its anti-fibrotic effects. Previous randomized clinical trials investigated therapeutic role of exogenous relaxin in patients with acute-on-chronic heart failure (HF) and failed to meet clinical endpoints. Here, we aimed to assess endogenous, circulating RLN1 levels in patients with heart failure with reduced ejection fraction (HFrEF) of ischemic origin. Furthermore, we analyzed relation of RLN1 and left ventricular diastolic function, left and right ventricular fibrosis, and invasive hemodynamic measurements. Unique feature of our study is the availability of ex vivo human myocardial tissue.

Methods: Human myocardial samples were available from the Transplantation Biobank of the Heart and Vascular Center at Semmelweis University after local ethical approval and informed consent of all participants (n = 47). Tissue was collected immediately after heart explantations; peripheral blood was collected before induction of anesthesia. Myocardial sections were stained for Masson’s trichrome and Picrosirius red staining to quantify fibrosis. Medical records were analyzed (ECG, anthropometry, blood tests, medication, echocardiography, and invasive hemodynamic measurements).

Results: Average RLN1 levels in HFrEF population were significantly higher than measured in age and gender matched healthy control human subjects (702 ± 283 pg/ml in HFrEF vs. 44 ± 27 pg/ml in control n = 47). We found a moderate inverse correlation between RLN1 levels and degree of myocardial fibrosis in both ventricles (r = −0.357, p = 0.014 in the right ventricle vs. r = −0.321, p = 0.028 in the left ventricle with Masson’s trichrome staining). Parallel, a moderate positive correlation was found in left ventricular diastolic function (echocardiography, E/A wave values) and RLN1 levels (r = 0.456, p = 0.003); a negative correlation with RLN1 levels and left ventricular end-systolic diameter (r = −0.373, p = 0.023), and diastolic pulmonary artery pressure (r = −0.894, p < 0.001). RLN1 levels showed moderate correlation with RLN2 levels (r = 0.453, p = 0.0003).

Conclusion: Increased RLN1 levels were accompanied by lower myocardial fibrosis rate, which is a novel finding in our patient population with coronary artery disease and HFrEF. RLN1 can have a biomarker role in ventricular fibrosis; furthermore, it may influence hemodynamic and vasomotor activity via neurohormonal mechanisms of action. Given these valuable findings, RLN1 may be targeted in anti-fibrotic therapeutics and in perioperative care of heart transplantation.

Epigenetic Mechanisms in Hepatic Stellate Cell Activation During Liver Fibrosis and Carcinogenesis

Liver fibrosis is an essential component of chronic liver disease (CLD) and hepatocarcinogenesis. The fibrotic stroma is a consequence of sustained liver damage combined with exacerbated extracellular matrix (ECM) accumulation. In this context, activation of hepatic stellate cells (HSCs) plays a key role in both initiation and perpetuation of fibrogenesis. These cells suffer profound remodeling of gene expression in this process. This review is focused on the epigenetic alterations participating in the transdifferentiation of HSCs from the quiescent to activated state. Recent advances in the field of DNA methylation and post-translational modifications (PTM) of histones (acetylation and methylation) patterns are discussed here, together with altered expression and activity of epigenetic remodelers. We also consider recent advances in translational approaches, including the use of epigenetic marks as biomarkers and the promising antifibrotic properties of epigenetic drugs that are currently being used in patients.

Protein kinase B/AKT mediates insulin-like growth factor 1-induced phosphorylation and nuclear export of histone deacetylase 5 via NADPH oxidase 4 activation in vascular smooth muscle cells

Insulin-like growth factor 1 (IGF-1) mediates the generation of reactive oxygen species (ROS) and the activation of growth promoting signaling pathways. Histone deacetylases (HDACs) regulate gene transcription by deacetylating lysine residues in histone and nonhistone proteins and a heightened HDAC activation, notably of HDAC5, is associated with vascular disorders, such as atherosclerosis. Although the contribution of IGF-1 in these pathologies is well documented, its role in HDAC phosphorylation and activation remains unexplored. Here, we examined the effect of IGF-1 on HDAC5 phosphorylation in vascular smooth muscle cells (VSMCs) and identified the signaling pathways involved in controlling HDAC5 phosphorylation and nuclear export. Treatment of A10 VSMCs with IGF-1 enhanced HDAC5 phosphorylation. Blockade of the IGF-1 receptor tyrosine kinase (TK) activity with the specific pharmacological inhibitor, AG1024, significantly inhibited IGF-1-induced HDAC5 phosphorylation, whereas the epidermal growth factor receptor (EGFR) TK antagonist, AG1478, had no effect. Inhibition of the mitogen-activated protein kinase pathway with U0126, SP600125, or SB203580, did not affect HDAC5 phosphorylation, whereas two inhibitors of the phosphoinositide 3-kinase (PI3K)/AKT pathways, wortmannin and SC66, almost completely attenuated IGF-1-induced responses as confirmed by immunoblotting of phospho-HDAC5 and by small interfering RNA (siRNA)-induced AKT silencing. Moreover, the NAD(P)H oxidase (Nox) inhibitor, diphenyleneiodonium (DPI), and Nox4 siRNA, attenuated IGF-1-induced phosphorylation of HDAC5 and AKT. The HDAC5 phosphorylation resulted in its nuclear export, which was reversed by SC66 and DPI. Our results indicate that IGF-1-induced phosphorylation and nuclear export of HDAC5 involve Nox4-dependent ROS generation and PI3K/AKT signaling pathways.

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.

Up-regulation of HO-1 promotes resistance of B-cell acute lymphocytic leukemia cells to HDAC4/5 inhibitor LMK-235 via the Smad7 pathway

PURPOSE

HDAC4/5 and Smad7 are potential therapeutic targets for the onset and progression of B-cell acute lymphocytic leukemia (B-ALL) and indices for clinical prognosis. In contrast, HO-1 (heat shock protein 32) plays a key role in protecting tumor cells from apoptosis.

METHODS

HDAC4/5, HO-1 and Smad7 expressions in 34 newly diagnosed B-ALL cases were detected by real-time PCR and Western blot. Lentivirus and small interference RNA were used to transfect B-ALL cells. The expression of Smad7 was detected after treatment with LMK-235 or Hemin and ZnPP. Apoptosis and proliferation were evaluated by flow cytometry, CCK-8 assay and Western blot.

RESULTS

HDAC4/5 was overexpressed in B-ALL patients with high HO-1 levels. Increasing the concentration of HDAC4/5 inhibitor LMK-235 induced the decrease of Smad7 and HO-1 expressions and the apoptosis of B-ALL cells by suppressing the phosphorylation of AKT (Protein kinase B). Up-regulating HO-1 alleviated the decrease of Smad7 expression and enhanced B-ALL resistance to LMK-235 by activating p-AKT which reduced the apoptosis of B-ALL cells and influenced the survival of leukemia patients. Silencing Smad7 also augmented the apoptosis rate of B-ALL cells by suppressing p-AKT.

CONCLUSION

HO-1 played a key role in protecting tumor cells from apoptosis, and HDAC4/5 were related with the apoptosis of B-ALL cells. LMK-235 may be able to improve the poor survival of leukemia patients.

Suppression of TGFβ-mediated conversion of endothelial cells and fibroblasts into cancer associated (myo)fibroblasts via HDAC inhibition

Background

Cancer-associated fibroblasts (CAFs) support tumour progression and invasion, and they secrete abundant extracellular matrix (ECM) that may shield tumour cells from immune checkpoint or kinase inhibitors. Targeting CAFs using drugs that revert their differentiation, or inhibit their tumour-supportive functions, has been considered as an anti-cancer strategy.

Methods

We have used human and murine cell culture models, atomic force microscopy (AFM), microarray analyses, CAF/tumour cell spheroid co-cultures and transgenic fibroblast reporter mice to study how targeting HDACs using small molecule inhibitors or siRNAs re-directs CAF differentiation and function in vitro and in vivo.

Results

From a small molecule screen, we identified Scriptaid, a selective inhibitor of HDACs 1/3/8, as a repressor of TGFβ-mediated CAF differentiation. Scriptaid inhibits ECM secretion, reduces cellular contraction and stiffness, and impairs collective cell invasion in CAF/tumour cell spheroid co-cultures. Scriptaid also reduces CAF abundance and delays tumour growth in vivo.

Conclusions

Scriptaid is a well-tolerated and effective HDACi that reverses many of the functional and phenotypic properties of CAFs. Impeding or reversing CAF activation/function by altering the cellular epigenetic regulatory machinery could control tumour growth and invasion, and be beneficial in combination with additional therapies that target cancer cells or immune cells directly.

Trichostatin A Restores Expression of Adherens and Tight Junction Proteins during Transforming Growth Factor β-Mediated Epithelial-to-Mesenchymal Transition

Purpose:

Adherens junctions and polarity markers play an important role in maintaining epithelial phenotype but get altered during the epithelial-mesenchymal transition (EMT). Alterations of these markers during EMT of lens epithelial cell (LEC) can lead to vision compromising conditions. The aim of this study was to examine if Trichostatin-A (TSA), a histone deacetylase inhibitor, can prevent EMT by restoring the adherens junction complex in LEC.

Methods:

Fetal human lens epithelial cell line (FHL124) was used. Cells were treated with 10 ng/ml TGF-β2 in the presence or absence of TSA. Real time-PCR and western blotting were carried out for HDAC1, HDAC2, CDH1 (E-cad), TJP1 (ZO-1) and CTNNB1 (β-cat). Level of histone acetylation was analyzed by western blotting. Chromatin Immunoprecipitation was carried out to study the level of acetylated histone H4 and HDAC2 at the promoter regions of CDH1, TJP1, and CTNNB1. E-cad, ZO-1, and β-cat were localized using immunofluorescence. Kruskal-Wallis test was used for statistical analysis.

Results:

TSA down-regulated HDAC1 and HDAC2 and led to an increase in global acetylation. The mRNA and protein levels of E-cad, ZO-1, and β-cat decreased during EMT but were up-regulated by TSA treatment. TSA also helped in stabilizing these proteins at cell-cell junctions during EMT. TSA decreases association of HDAC2 at the promoter regions of adherens junction genes while increasing histone H4 acetylation status.

Conclusion:

TSA increases histone acetylation and restores the adherens junction complex in LECs. TSA helps in preventing EMT and thus shows potential against lens fibrosis and vision compromising conditions.

Neuroprotective and Nerve Regenerative Approaches for Treatment of Erectile Dysfunction after Cavernous Nerve Injury

Erectile dysfunction (ED) is a significant cause of reduced quality of life in men and their partners. Cavernous nerve injury (CNI) during pelvic surgery results in ED in greater than 50% of patients, regardless of additional patient factors. ED related to CNI is difficult to treat and typically poorly responsive to first- and second-line therapeutic options. Recently, a significant amount of research has been devoted to exploring neuroprotective and neuroregenerative approaches to salvage erectile function in patients with CNI. In addition, therapeutic options such as neuregulins, immunophilin ligands, gene therapy, stem cell therapy and novel surgical strategies, have shown benefit in pre-clinical, and limited clinical studies. In the era of personalized medicine, these new therapeutic technologies will be the future of ED treatment and are described in this review.

Inhibition of HDAC3 prevents diabetic cardiomyopathy in OVE26 mice via epigenetic regulation of DUSP5-ERK1/2 pathway

Inhibition of total histone deacetylases (HDACs) was phenomenally associated with the prevention of diabetic cardiomyopathy (DCM). However, which specific HDAC plays the key role in DCM remains unclear. The present study was designed to determine whether DCM can be prevented by specific inhibition of HDAC3 and to elucidate the mechanisms by which inhibition of HDAC3 prevents DCM. Type 1 diabetes OVE26 and age-matched wild-type (WT) mice were given the selective HDAC3 inhibitor RGFP966 or vehicle for 3 months. These mice were then killed immediately or 3 months later for cardiac function and pathological examination. HDAC3 activity was significantly increased in the heart of diabetic mice. Administration of RGFP966 significantly prevented DCM, as evidenced by improved diabetes-induced cardiac dysfunction, hypertrophy, and fibrosis, along with diminished cardiac oxidative stress, inflammation, and insulin resistance, not only in the mice killed immediately or 3 months later following the 3-month treatment. Furthermore, phosphorylated extracellular signal-regulated kinases (ERK) 1/2, a well-known initiator of cardiac hypertrophy, was significantly increased, while dual specificity phosphatase 5 (DUSP5), an ERK1/2 nuclear phosphatase, was substantially decreased in diabetic hearts. Both of these changes were prevented by RGFP966. Chromatin immunoprecipitation (ChIP) assay showed that HDAC3 inhibition elevated histone H3 acetylation on the DUSP5 gene promoter at both two time points. These findings suggest that diabetes-activated HDAC3 inhibits DUSP5 expression through deacetylating histone H3 on the primer region of DUSP5 gene, leading to the derepression of ERK1/2 and the initiation of DCM. The present study indicates the potential application of HDAC3 inhibitor for the prevention of DCM.

Epigenetic regulation of TGF-β1 signalling in dilative aortopathy of the thoracic ascending aorta

The term 'epigenetics' refers to heritable, reversible DNA or histone modifications that affect gene expression without modifying the DNA sequence. Epigenetic modulation of gene expression also includes the RNA interference mechanism. Epigenetic regulation of gene expression is fundamental during development and throughout life, also playing a central role in disease progression. The transforming growth factor β1 (TGF-β1) and its downstream effectors are key players in tissue repair and fibrosis, extracellular matrix remodelling, inflammation, cell proliferation and migration. TGF-β1 can also induce cell switch in epithelial-to-mesenchymal transition, leading to myofibroblast transdifferentiation. Cellular pathways triggered by TGF-β1 in thoracic ascending aorta dilatation have relevant roles to play in remodelling of the vascular wall by virtue of their association with monogenic syndromes that implicate an aortic aneurysm, including Loeys-Dietz and Marfan's syndromes. Several studies and reviews have focused on the progression of aneurysms in the abdominal aorta, but research efforts are now increasingly being focused on pathogenic mechanisms of thoracic ascending aorta dilatation. The present review summarizes the most recent findings concerning the epigenetic regulation of effectors of TGF-β1 pathways, triggered by sporadic dilative aortopathy of the thoracic ascending aorta in the presence of a tricuspid or bicuspid aortic valve, a congenital malformation occurring in 0.5-2% of the general population. A more in-depth comprehension of the epigenetic alterations associated with TGF-β1 canonical and non-canonical pathways in dilatation of the ascending aorta could be helpful to clarify its pathogenesis, identify early potential biomarkers of disease, and, possibly, develop preventive and therapeutic strategies.

Crosstalk between Smad2/3 and specific isoforms of ERK in TGF-β1-induced TIMP-3 expression in rat chondrocytes

This study investigated the roles of ERK1 and ERK2 in transforming growth factor‐β1 (TGF‐β1)‐induced tissue inhibitor of metalloproteinases‐3 (TIMP‐3) expression in rat chondrocytes, and the specific roles of ERK1 and ERK2 in crosstalk with Smad2/3 were investigated to demonstrate the molecular mechanism of ERK1/2 regulation of TGF‐β1 signalling. To examine the interaction of specific isoforms of ERK and the Smad2/3 signalling pathway, chondrocytes were infected with LV expressing either ERK1 or ERK2 siRNA and stimulated with or without TGF‐β1. At indicated time‐points, TIMP‐3 expression was determined by real‐time PCR and Western blotting; p‐Smad3, nuclear p‐Smad3, Smad2/3, p‐ERK1/2 and ERK1/2 levels were assessed. And then, aggrecan, type II collagen and the intensity of matrix were examined. TGF‐β1‐induced TIMP‐3 expression was significantly inhibited by ERK1 knock‐down, and the decrease in TIMP‐3 expression was accompanied by a reduction of p‐Smad3 in ERK1 knock‐down cells. Knock‐down of ERK2 had no effect on neither TGF‐β1‐induced TIMP‐3 expression nor the quantity of p‐Smad3. Moreover, aggrecan, type II collagen expression and the intensity of matrix were significantly suppressed by ERK1 knock‐down instead of ERK2 knock‐down. Taken together, ERK1 and ERK2 have different roles in TGF‐β1‐induced TIMP‐3 expression in rat chondrocytes. ERK1 instead of ERK2 can regulate TGF‐β/Smad signalling, which may be the mechanism through which ERK1 regulates TGF‐β1‐induced TIMP‐3 expression.

The histone 3 lysine 9 methyltransferase inhibitor chaetocin improves prognosis in a rat model of high salt diet-induced heart failure

Histone acetylation has been linked to cardiac hypertrophy and heart failure. However, the pathological implications of changes in histone methylation and the effects of interventions with histone methyltransferase inhibitors for heart failure have not been fully clarified. Here, we focused on H3K9me3 status in the heart and investigated the effects of the histone H3K9 methyltransferase inhibitor chaetocin on prognoses in Dahl salt-sensitive rats, an animal model of chronic heart failure. Chaetocin prolonged survival and restored mitochondrial dysfunction. ChIP-seq analysis demonstrated that chronic stress to the heart induced H3K9me3 elevation in thousands of repetitive elements, including intronic regions of mitochondria-related genes, such as the gene encoding peroxisome proliferator-activated receptor-gamma coactivator 1 alpha. Furthermore, chaetocin reversed this effect on these repetitive loci. These data suggested that excessive heterochromatinization of repetitive elements of mitochondrial genes in the failing heart may lead to the silencing of genes and impair heart function. Thus, chaetocin may be a potential therapeutic agent for chronic heart failure.

The Role of ERK1/2 in the Development of Diabetic Cardiomyopathy

Diabetes mellitus is a chronic metabolic condition that affects carbohydrate, lipid and protein metabolism and may impair numerous organs and functions of the organism. Cardiac dysfunction afflicts many patients who experience the oxidative stress of the heart. Diabetic cardiomyopathy (DCM) is one of the major complications that accounts for more than half of diabetes-related morbidity and mortality cases. Chronic hyperglycemia and hyperlipidemia from diabetes mellitus cause cardiac oxidative stress, endothelial dysfunction, impaired cellular calcium handling, mitochondrial dysfunction, metabolic disturbances, and remodeling of the extracellular matrix, which ultimately lead to DCM. Although many studies have explored the mechanisms leading to DCM, the pathophysiology of DCM has not yet been fully clarified. In fact, as a potential mechanism, the associations between DCM development and mitogen-activated protein kinase (MAPK) activation have been the subjects of tremendous interest. Nonetheless, much remains to be investigated, such as tissue- and cell-specific processes of selection of MAPK activation between pro-apoptotic vs. pro-survival fate, as well as their relation with the pathogenesis of diabetes and associated complications. In general, it turns out that MAPK signaling pathways, such as extracellular signal-regulated kinase 1/2 (ERK1/2), c-Jun N-terminal protein kinase (JNK) and p38 MAP kinase, are demonstrated to be actively involved in myocardial dysfunction, hypertrophy, fibrosis and heart failure. As one of MAPK family members, the activation of ERK1/2 has also been known to be involved in cardiac hypertrophy and dysfunction. However, many recent studies have demonstrated that ERK1/2 signaling activation also plays a crucial role in FGF21 signaling and exerts a protective environment of glucose and lipid metabolism, therefore preventing abnormal healing and cardiac dysfunction. The duration, extent, and subcellular compartment of ERK1/2 activation are vital to differential biological effects of ERK1/2. Moreover, many intracellular events, including mitochondrial signaling and protein kinases, manipulate signaling upstream and downstream of MAPK, to influence myocardial survival or death. In this review, we will summarize the roles of ERK1/2 pathways in DCM development by the evidence from current studies and will present novel opinions on "differential influence of ERK1/2 action in cardiac dysfunction, and protection against myocardial ischemia-reperfusion injury".

Histone deacetylases 3 deletion restrains PM2.5-induced mice lung injury by regulating NF-κB and TGF-β/Smad2/3 signaling pathways

Acute lung injury (ALI) as a serious disease with high mortality has been emphasized as a threat to human health and life. Accumulating studies demonstrated that PM2.5 plays a significant role in metabolic and lung diseases. Histone deacetylases 3 (HDAC3) is an important regulator in control of gene transcription, required in up-regulation of inflammation-related signaling, and has been known as a key hotpot in treating a lot of chronic inflammatory diseases. TGF-β/Smad signaling pathway has been proven to be of significance in fibrosis development. Our results found that PM2.5 induced lung function injury in WT mice with a inflammatory responses through the activation of TGF-β/Smad signaling pathways, resulting in lung injury. Of note, HDAC3-deficient mice after PM2.5 administration further promoted TGF-β/Smad signaling pathways activation. In addition, TLR4, p-NF-κB and p-IκBα indicated that HDAC3 knockout mice have a higher inflammation-related signals expression in lung tissue than WT mice after PM2.5 administration, resulting in pro-inflammatory cytokines releasing. Moreover, in vitro experiment of lung epithelial cells challenged with PM2.5, further indicated that TGF-β/Smad2/3 was involved in fibrosis development, leading to inflammation response. Also, the activation of TLR4/NF-κB could be observed in PM2.5-induced lung epithelial cells, leading to inflammation infiltration. These results indicate a new therapeutic target to protect against lung injury caused by PM2.5.

Therapeutic activity of the histone deacetylase inhibitor SB939 on renal fibrosis

Fibrosis is the final pathological outcome of many chronic kidney diseases and is quite common. Thus, development of effective anti-fibrotic agents is urgently needed. Although histone deacetylases (HDACs) have been reported to be involved in renal fibrosis, current HDAC inhibitors are unsatisfactory anti-fibrosis drugs. Therefore, more potentially relevant anti-renal fibrosis HDAC inhibitors are needed. We initially found that non-cytotoxic concentrations of SB939 (pracinostat) had strong anti-fibrotic activity, drastically decreasing TGF-β1-induced alpha smooth muscle actin (α-SMA) expression in the NRK renal fibroblast cell line. Similar anti-fibrotic activity of SB939 on epithelial-to-mesenchymal transition (EMT) was confirmed using the HK-2 human renal proximal tubular epithelial cell line. SB939 inhibited Smad-independent TGF-β signaling involving the MAPK and PI3K/AKT pathways. To evaluate in vivo anti-fibrotic activity, we administered SB939 in a unilateral ureteric obstruction (UUO) model. SB939 treatment markedly inhibited the accumulation of α-SMA and tissue injury. Inflammatory and pro-fibrotic cytokines in the obstructed kidney were also significantly decreased by SB939 treatment. Our results suggest that SB939 might be a promising therapeutic drug for preventing renal fibrosis.

Epigenetic regulation in heart failure: part II DNA and chromatin

Epigenetic regulatory mechanisms play key roles in cardiac development, differentiation, homeostasis, response to stress and injury, and disease. Human heart failure (HF) epigenetic regulatory mechanisms have not been deciphered to date. This 2-part review distills the rapidly evolving research focused on human HF epigenetic regulatory mechanisms. Part I, which was published in the September/October issue, focused on epigenetic regulatory mechanisms involving RNA, specifically the role of short, intermediate, and long noncoding RNAs (lncRNAs) and endogenous competing RNA regulatory networks. Part II, now in the November/December issue, focuses on the epigenetic regulatory mechanisms involving DNA, including DNA methylation, histone modifications, and chromatin conformational changes. Part II concludes with 2 examples of well-studied integrated epigenetic regulatory mechanisms: the structural and functional roles of the Mediator complex in regulating transcription and the epigenetic networked "cross-talk" regulating atrial natriuretic peptide and brain natriuretic peptide promoter activation.

Histone deacetylase inhibitors restore IL-10 expression in lipopolysaccharide-induced cell inflammation and reduce IL-1β and IL-6 production in breast silicone implant in C57BL/6J wild-type murine model

Among epigenetic enzymes, histone deacetylases (HDACs) are responsible for regulating the expression of an extensive array of genes by reversible deacetylation of nuclear histones as well as a large number of non-histone proteins. Initially proposed for cancer therapy, recently the interest for HDAC inhibitors (HDACi) as orally active, safe, and anti-inflammatory agents is rising due to their ability in reducing the severity of inflammatory and autoimmune diseases. In particular, selective HDAC3, HDAC6, and HDAC8 inhibitors have been described to downregulate the expression of pro-inflammatory cytokines (TNF-α, TGF-β, IL-1β, and IL-6). Herein, using KB31, C2C12, and 3T3-J2 cell lines, we demonstrated that, under lipopolysaccharide-induced in vitro inflammation, HDAC3/6/8 inhibitor MC2625 and HDAC6-selective inhibitor MC2780 were effective at a concentration of 30 ng/mL to downregulate mRNA expression of pro-inflammatory cytokines (IL-1β and IL-6) and to promote the transcription of IL-10 gene, without affecting the cell viability. Afterwards, we investigated by immunohistochemistry the activity of MC2625 and MC2780 at a concentration of 60 ng/kg animal weight to regulate silicone-triggered immune response in C57BL/6J female mice. Our findings evidenced the ability of such inhibitors to reduce host inflammation in silicone implants promoting a thickness reduction of peri-implant fibrous capsule, upregulating IL-10 expression, and reducing the production of both IL-1β and IL-6. These results underline the potential application of MC2625 and MC2780 in inflammation-related diseases.

Targeting histone deacetylases: A novel therapeutic strategy for atrial fibrillation

Atrial fibrillation (AF) is a common cardiac arrhythmia associated with high mortality and morbidity. Current treatments of AF have limited efficacy and considerable side effects. Histone deacetylases (HDACs) play critical roles in the pathophysiology of cardiovascular diseases and contribute to the genesis of AF. Therefore, HDAC inhibition may prove a novel therapeutic strategy for AF through upstream therapy and modifications of AF electrical and structural remodeling. In this review, we provide an update of the knowledge of the effects of HDACs and HDAC inhibitors on AF, and dissect potential underlying mechanisms.

Histone Deacetylase-3/CAGE Axis Targets EGFR Signaling and Regulates the Response to Anti-Cancer Drugs

We have previously reported the role of miR-326-HDAC3 loop in anti-cancer drug-resistance. CAGE, a cancer/testis antigen, regulates the response to anti-cancer drug-resistance by forming a negative feedback loop with miR-200b. Studies investigating the relationship between CAGE and HDAC3 revealed that HDAC3 negatively regulated the expression of CAGE. ChIP assays demonstrated the binding of HDAC3 to the promoter sequences of CAGE. However, CAGE did not affect the expression of HDAC3. We also found that EGFR signaling regulated the expressions of HDAC3 and CAGE. Anti-cancer drug-resistant cancer cell lines show an increased expression of pEGFR(Y845). HDAC3 was found to negatively regulate the expression of pEGFR(Y845). CAGE showed an interaction and co-localization with EGFR. It was seen that miR-326, a negative regulator of HDAC3, regulated the expression of CAGE, pEGFR(Y845), and the interaction between CAGE and EGFR. miR-326 inhibitor induced the binding of HDAC3 to the promoter sequences in anti-cancer drug-resistant Malme3M(R) cells, decreasing the tumorigenic potential of Malme3M(R) cells in a manner associated with its effect on the expression of HDAC3, CAGE and pEGFR(Y845). The down-regulation of HDAC3 enhanced the tumorigenic, angiogenic and invasion potential of the anti-cancer drug-sensitive Malme3M cells in CAGE-dependent manner. Studies revealed that PKCδ was responsible for the increased expression of pEGFR(Y845) and CAGE in Malme3M(R) cells. CAGE showed an interaction with PKCδ in Malme3M(R) cells. Our results show that HDAC3-CAGE axis can be employed as a target for overcoming resistance to EGFR inhibitors.

Histone deacetylase 3 expression correlates with vasculogenic mimicry through the phosphoinositide3-kinase / ERK-MMP-laminin5γ2 signaling pathway

Vasculogenic mimicry (VM) refers to the process by which highly aggressive tumor cells mimic endothelial cells to form vessel-like structures that aid in supplying enough nutrients to rapidly growing tumors. Histone deacetylases (HDACs) regulate the expression and activity of numerous molecules involved in cancer initiation and progression. Notably, HDAC3 is overexpressed in the majority of carcinomas. However, thus far, no data are available to support the role of HDAC3 in VM. In this study, we subjected glioma specimens to immunohistochemical and histochemical double-staining methods and found that VM and HDAC3 expression were related to the pathological grade of gliomas. The presence of VM correlated with HDAC3 expression in glioma tissues. The formation of tubular structures, as determined by the tube formation assay to evaluate VM, was impaired in U87MG cells when transfected by siRNA or treated with an HDAC3 inhibitor. Importantly, the expression of VM-related molecules such as MMP-2/14 and laminin5γ2 was also affected when HDAC3 expression was altered. Furthermore, U87MG cells were treated with a phosphoinositide 3-kinase (PI3K) inhibitor or/and ERK inhibitor and found that the PI3K and ERK signaling pathways play key roles in VM; whereas, in VM, the two signaling pathways did not act upstream or downstream from each other. Taken together, our findings showed that HDAC3 contributed to VM in gliomas, possibly through the PI3K/ERK–MMPs–laminin5γ2 signaling pathway, which could potentially be a novel therapeutic target for gliomas.

Targeting histone deacetylases: perspectives for epigenetic-based therapy in cardio-cerebrovascular disease

Although the pathogenesis of cardio-cerebrovascular disease (CCVD) is multifactorial, an increasing number of experimental and clinical studies have highlighted the importance of histone deacetylase (HDAC)-mediated epigenetic processes in the development of cardio-cerebrovascular injury. HDACs are a family of enzymes to balance the acetylation activities of histone acetyltransferases on chromatin remodeling and play essential roles in regulating gene transcription. To date, 18 mammalian HDACs are identified and grouped into four classes based on similarity to yeast orthologs. The zinc-dependent HDAC family currently consists of 11 members divided into three classes (class I, II, and IV) on the basis of structure, sequence homology, and domain organization. In comparison, class III HDACs (also known as the sirtuins) are composed of a family of NAD⁺-dependent protein-modifying enzymes related to the Sir2 gene. HDAC inhibitors are a group of compounds that block HDAC activities typically by binding to the zinc-containing catalytic domain of HDACs and have displayed anti-inflammatory and antifibrotic effects in the cardio-cerebrovascular system. In this review, we summarize the current knowledge about classifications, functions of HDACs and their roles and regulatory mechanisms in the cardio-cerebrovascular system. Pharmacological targeting of HDAC-mediated epigenetic processes may open new therapeutic avenues for the treatment of CCVD.

Association of histone acetylation at the ACTA2 promoter region with epithelial mesenchymal transition of lens epithelial cells

PURPOSE

Epithelial mesenchymal transition (EMT) plays a central role in the development of fibrotic complications of the lens. The current study is designed to check whether EMT of lens epithelial cells (LECs) is regulated by epigenetic modifications and to evaluate the effect of Trichostatin-A (TSA) on the transforming growth factor-β (TGF-β)-induced EMT.

METHODS

Fetal human LECs (FHL124) were treated with TGF-β2 in the presence or absence of TSA. Levels of mRNA, protein, as well as localization of α-smooth muscle actin (αSMA) were studied along with migration of LECs. Acetylation of histone H4 was analyzed and chromatin immunoprecipitation (ChIP) was carried out to study the level of acetylated histone H4 at the promoter of αSMA gene (ACTA2). Student's t-test was used for statistical analysis.

RESULTS

TGF-β2 treatment resulted in myofibroblast-like changes and increased migratory capacity of FHL124. Protein and mRNA expression of αSMA increased, and immunofluorescence revealed presence of extensive stress fibers. TSA treatment preserved epithelial morphology, retarded cell migration, and abrogated an increase in αSMA levels. TSA led to the accumulation of acetylated histone H4 that was reduced on TGF-β2 treatment. However, increased level of histone H4 acetylation was found at the ACTA2 promoter region during TGF-β treatment.

CONCLUSIONS

The increased level of αSMA, a hallmark of EMT in LECs, is associated with increased level of histone H4 acetylation at its promoter region, and TSA helps in suppressing EMT by epigenetically reducing this level. TSA thus shows promising potential in management of fibrotic conditions of the lens.

Histone deacetylases and atherosclerosis

Atherosclerosis is the most common pathological process that leads to cardiovascular diseases, a disease of large- and medium-sized arteries that is characterized by a formation of atherosclerotic plaques consisting of necrotic cores, calcified regions, accumulated modified lipids, smooth muscle cells (SMCs), endothelial cells, leukocytes, and foam cells. Recently, the question about how to suppress the occurrence of atherosclerosis and alleviate the progress of cardiovascular disease becomes the hot topic. Accumulating evidence suggests that histone deacetylases(HDACs) play crucial roles in arteriosclerosis. This review summarizes the effect of HDACs and HDAC inhibitors(HDACi) on the progress of atherosclerosis.

Novel therapeutic targets in the management of atrial fibrillation

Atrial fibrillation (AF) is the most common cardiac arrhythmia, contributing to increased morbidity and reduced survival through its associations with stroke and heart failure. AF contributes to a four- to fivefold increase in the risk of stroke in the general population and is responsible for 10-15 % of all ischemic strokes. Diagnosis and treatment of AF require considerable health care resources. Current therapies to restore sinus rhythm in AF are suboptimal and are limited either by their pro-arrhythmic effects or by their procedure-related complications. These limitations have necessitated identification of newer therapeutic targets to expand the treatment options. There has been a considerable amount of research interest in investigating the mechanisms of initiation and propagation of AF. Despite extensive research focused on the pathogenesis of AF, a thorough understanding of various pathways mediating initiation and propagation of AF still remains limited. Research efforts focused on the identification of these pathways and molecular mediators have generated a great degree of interest for developing more targeted therapies. This review discusses the potential therapeutic targets and the results from experimental and clinical research investigating these targets.

Veratric acid inhibits iNOS expression through the regulation of PI3K activation and histone acetylation in LPS-stimulated RAW264.7 cells

In the present study, we investigated regulatory effects of veratric acid on the production of nitric oxide (NO) in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. NO production was significantly decreased by veratric acid in the LPS-stimulated RAW264.7 cells in a dose-dependent manner. The reduction in nitric oxide production was induced by the downregulation of inducible NO synthase (iNOS) expression. Veratric acid suppressed the LPS-induced effects on the regulatory and catalytic subunits of phosphoinositide 3-kinase (PI3K), comprised of p85, p110α, p110β and Akt. The acetylation of p300 and the phosphorylation of activating transcription factor 2 (ATF-2) induced by LPS were downregulated following treatment with veratric acid; similar effects were observed following treatment with LY294002, a specific inhibitor of PI3K/Akt. The LPS-induced expression of histone deacetylase (HDAC)3 decreased to basal levels following treatment with veratric acid, and its expression was also downregulated by LY294002. In the measurement of histone acetylation levels, the LPS-stimulated acetylation of histone H4 was significantly attenuated by veratric acid, and was also reduced following the inhibition of PI3K/Akt with LY294002. From our data, it can be concluded that veratric acid exerts a regulatory effect on LPS-induced iNOS expression. Our results suggest that veratric acid impedes the PI3K/Akt-mediated histone acetyl-transferase (HAT) activation and HDAC expression induced by LPS, thereby abrogating iNOS expression.

Effects of Trichostatin A on Cumulus Expansion during Mouse Oocyte Maturation

This study was conducted to investigate the effects of Trichostatin A (TSA) on cumulus expansion during mouse oocyte maturation. TSA treatment inhibited cumulus expansion and significantly reduced the cumulus expansion index (CEI) (p<0.05). To determine the underlying mechanism, the expression levels of several key factors that play crucial roles in cumulus expansion including components of extracellular matrix (ECM) (Has2, Ptgs2, Ptx3, and Tnfaip6) and Growth differentiation factor 9 (GDF9) were measured in control and TSA treated samples by real-time PCR. The effect of TSA on ERK phosphorylation (p-ERK1/2) in cumulus cells and GDF9 protein level in fully grown oocytes (FGOs) were detected by Western blotting. The expression levels of the ECM genes were significantly decreased (p<0.05) by TSA treatment while GDF9 expression did not response to TSA (p>0.05). TSA treatment blocked the activation of ERK1/2 (p<0.05) and had no significant effect on GDF9 protein expression (p>0.05). Collectively, these results suggested that TSA treatment altered ECM gene expression and blocked ERK1/2 activation to inhibit cumulus expansion in the mouse.

Targeting cardiac fibroblasts to treat fibrosis of the heart: focus on HDACs

Cardiac fibrosis is implicated in numerous physiologic and pathologic conditions, including scar formation, heart failure and cardiac arrhythmias. However the specific cells and signaling pathways mediating this process are poorly understood. Lysine acetylation of nucleosomal histone tails is an important mechanism for the regulation of gene expression. Additionally, proteomic studies have revealed that thousands of proteins in all cellular compartments are subject to reversible lysine acetylation, and thus it is becoming clear that this post-translational modification will rival phosphorylation in terms of biological import. Acetyl groups are conjugated to lysine by histone acetyltransferases (HATs) and removed from lysine by histone deacetylases (HDACs). Recent studies have shown that pharmacologic agents that alter lysine acetylation by targeting HDACs have the remarkable ability to block pathological fibrosis. Here, we review the current understanding of cardiac fibroblasts and the fibrogenic process with respect to the roles of lysine acetylation in the control of disease-related cardiac fibrosis. Potential for small molecule HDAC inhibitors as anti-fibrotic therapeutics that target cardiac fibroblasts is highlighted. This article is part of a Special Issue entitled "Myocyte-Fibroblast Signalling in Myocardium."

Histone deacetylase inhibitor reduces hypertrophic scarring in a rabbit ear model

BACKGROUND

Hypertrophic scars result from excessive collagen deposition at sites of healing dermal wounds and could be functionally and cosmetically problematic. The authors tested the ability of the histone deacetylase inhibitor trichostatin A to reduce hypertrophic scar formation in a rabbit ear model.

METHODS

The authors have developed a reliable rabbit model that results in hypertrophic scarring. Four 1-cm, full-thickness, circular wounds were made on each ear. After the wounds reepithelialized, 0.02% trichostatin A was injected intradermally into the wounds in the treatment group. Expression of collagen I and fibronectin was detected by reverse transcription polymerase chain reaction and Western blot analysis at postoperative day 23. Scar hypertrophy was quantified by measurement of the scar elevation index at postoperative day 45.

RESULTS

Compared with the control group, injection of trichostatin A led to much more normal-appearing scars in the rabbit ear. The scar elevation index at postoperative day 45 was significantly decreased after injection of trichostatin A compared with untreated scars. Furthermore, the authors confirmed the decreased expression of collagen I and fibronectin at postoperative day 23 (after the rabbits had been treated with trichostatin A for 1 week) in the treated scars compared with the control scars according to reverse transcription polymerase chain reaction and Western blot analysis.

CONCLUSIONS

The introduction of trichostatin A can result in the decreased formation of hypertrophic scars in a rabbit ear model, which is corroborated by evidence of decreased collagen I and fibronectin synthesis.

Signal-dependent repression of DUSP5 by class I HDACs controls nuclear ERK activity and cardiomyocyte hypertrophy

Cardiac hypertrophy is a strong predictor of morbidity and mortality in patients with heart failure. Small molecule histone deacetylase (HDAC) inhibitors have been shown to suppress cardiac hypertrophy through mechanisms that remain poorly understood. We report that class I HDACs function as signal-dependent repressors of cardiac hypertrophy via inhibition of the gene encoding dual-specificity phosphatase 5 (DUSP5) DUSP5, a nuclear phosphatase that negatively regulates prohypertrophic signaling by ERK1/2. Inhibition of DUSP5 by class I HDACs requires activity of the ERK kinase, mitogen-activated protein kinase kinase (MEK), revealing a self-reinforcing mechanism for promotion of cardiac ERK signaling. In cardiac myocytes treated with highly selective class I HDAC inhibitors, nuclear ERK1/2 signaling is suppressed in a manner that is absolutely dependent on DUSP5. In contrast, cytosolic ERK1/2 activation is maintained under these same conditions. Ectopic expression of DUSP5 in cardiomyocytes results in potent inhibition of agonist-dependent hypertrophy through a mechanism involving suppression of the gene program for hypertrophic growth. These findings define unique roles for class I HDACs and DUSP5 as integral components of a regulatory signaling circuit that controls cardiac hypertrophy.

Relaxin prevents cardiac fibroblast-myofibroblast transition via notch-1-mediated inhibition of TGF-β/Smad3 signaling

The hormone relaxin (RLX) is produced by the heart and has beneficial actions on the cardiovascular system. We previously demonstrated that RLX stimulates mouse neonatal cardiomyocyte growth, suggesting its involvement in endogenous mechanisms of myocardial histogenesis and regeneration. In the present study, we extended the experimentation by evaluating the effects of RLX on primary cultures of neonatal cardiac stromal cells. RLX inhibited TGF-β1-induced fibroblast-myofibroblast transition, as judged by its ability to down-regulate α-smooth muscle actin and type I collagen expression. We also found that the hormone up-regulated metalloprotease (MMP)-2 and MMP-9 expression and downregulated the tissue inhibitor of metalloproteinases (TIMP)-2 in TGF-β1-stimulated cells. Interestingly, the effects of RLX on cardiac fibroblasts involved the activation of Notch-1 pathway. Indeed, Notch-1 expression was significantly decreased in TGF-β1-stimulatedfibroblasts as compared to the unstimulated controls; this reduction was prevented by the addition of RLX to TGF-β1-stimulated cells. Moreover, pharmacological inhibition of endogenous Notch-1 signaling by N-3,5-difluorophenyl acetyl-L-alanyl-2-phenylglycine-1,1-dimethylethyl ester (DAPT), a γ-secretase specific inhibitor, as well as the silencing of Notch-1 ligand, Jagged-1, potentiated TGF-β1-induced myofibroblast differentiation and abrogated the inhibitory effects of RLX. Interestingly, RLX and Notch-1 exerted their inhibitory effects by interfering with TGF-β1 signaling, since the addition of RLX to TGF-β1-stimulated cells caused a significant decrease in Smad3 phosphorylation, a typical downstream event of TGF-β1 receptor activation, while the treatment with a prevented this effect. These data suggest that Notch signaling can down-regulate TGF-β1/Smad3-induced fibroblast-myofibroblast transition and that RLX could exert its well known anti-fibrotic action through the up-regulation of this pathway. In conclusion, the results of the present study beside supporting the role of RLX in the field of cardiac fibrosis, provide novel experimental evidence on the molecular mechanisms underlying its effects.