HDAC inhibition attenuates inflammatory, hypertrophic, and hypertensive responses in spontaneously hypertensive rats

Epigenetic Metalloenzymes

Epigenetics controls the expression of genes and is responsible for cellular phenotypes. The fundamental basis of these mechanisms involves in part the post-translational modifications (PTMs) of DNA and proteins, in particular, the nuclear histones. DNA can be methylated or demethylated on cytosine. Histones are marked by several modifications including acetylation and/or methylation, and of particular importance are the covalent modifications of lysine. There exists a balance between addition and removal of these PTMs, leading to three groups of enzymes involved in these processes: the writers adding marks, the erasers removing them, and the readers able to detect these marks and participating in the recruitment of transcription factors. The stimulation or the repression in the expression of genes is thus the result of a subtle equilibrium between all the possibilities coming from the combinations of these PTMs. Indeed, these mechanisms can be deregulated and then participate in the appearance, development and maintenance of various human diseases, including cancers, neurological and metabolic disorders. Some of the key players in epigenetics are metalloenzymes, belonging mostly to the group of erasers: the zinc-dependent histone deacetylases (HDACs), the iron-dependent lysine demethylases of the Jumonji family (JMJ or KDM) and for DNA the iron-dependent ten-eleven-translocation enzymes (TET) responsible for the oxidation of methylcytosine prior to the demethylation of DNA. This review presents these metalloenzymes, their importance in human disease and their inhibitors.

Histone deacetylase inhibition has cardiac and vascular protective effects in rats with pressure overload cardiac hypertrophy

Histone deacetylase (HDAC) inhibitors have shown beneficial effects in animal models of cardiovascular diseases. We hypothesized that HDAC inhibitor, sodium valproate (VPA), has cardiac and vascular protective effects in rats with pressure overload cardiac hypertrophy induced by transverse aortic constriction (TAC). Sections of the heart were visualized after hematoxylin and eosin staining, picrosirius red staining and immunohistochemistry. The expression of genes related to cardiac hypertrophy, fibrosis, and oxidative stress was determined by quantitative real-time polymerase chain reaction. The aortic ring tension analysis was conducted using both the ascending aorta and descending thoracic aorta. TAC increased the expression of hypertrophic, fibrotic, and oxidative stress genes, which was attenuated by VPA. In the ascending aorta with intact endothelium, there was a significant decrease in the relaxation response, which was recovered by VPA treatment. These results indicate that VPA has cardiac and vascular protective effects in rats with pressure overload cardiac hypertrophy.

HDAC4 regulates vascular inflammation via activation of autophagy

Aims

Angiotensin II (Ang II) causes vascular inflammation, leading to vascular endothelial cell dysfunction, and is associated with the development of cardiovascular diseases. Therefore, interventions in inflammation may contribute to the reduction of cardiovascular diseases. Here, we aim to demonstrate that HDAC4, one of class IIa family histone de-acetylases (HDACs) members, promotes autophagy-dependent vascular inflammation.

Methods and results

By loss-of-function approaches, our study provides the first evidence that HDAC4 mediates Ang II-induced vascular inflammation in vitro and in vivo. In response to the Ang II, HDAC4 expression is up-regulated rapidly, with increased autophagic flux and inflammatory mediators in vascular endothelial cells (VECs). In turn, HDAC4 deficiency suppresses activation of autophagy, leading to reduced inflammation in Ang II-induced VECs. Consistently, using autophagy inhibitor or silencing LC3-II also alleviates vascular inflammation. Furthermore, HDAC4 regulates autophagy via facilitating transcription factor forkhead box O3a (FoxO3a) de-acetylation, thereby to increase its transcriptional activity. Loss of HDAC4 in VECs results in inhibition of FoxO3a de-acetylation to block its transcriptional activity, leading to downregulation of the downstream FoxO3a target, and hence reduces autophagy and vascular inflammation. FoxO3a silencing using siRNA approach significantly inhibits activation of autophagy. Finally, knockdown of HDAC4 in Ang II-infused mouse models ameliorates vascular inflammation, suggesting that inhibitor of HDAC4 may be potential therapeutics for vascular diseases associated with inflammation.

Conclusion

These results suggest that HDAC4-mediated FoxO3a acetylation regulates Ang II-induced autophagy activation, which in turn plays an essential role in causing vascular inflammation.

Ellagic acid inhibits proliferation and migration of cardiac fibroblasts by down-regulating expression of HDAC1

Cardiac fibroblasts (CFs) could be activated after myocardial infarction (MI). Thus, it is necessary to explore effective drugs to suppress the activation of CFs following MI. This study was designed to investigate the impacts of ellagic acid on CFs and the underlying mechanisms. The expression of histone deacetylases (HDACs) and fibrosis-related genes was detected by qRT-PCR and western blot. The Masson's Trichrome Staining assay was used to evaluate the area of cardiac fibrosis. The proliferation and migration of CFs were measured by CCK8 Kit and Transwell assay, respectively. Our results showed that ellagic acid significantly reduced protein expression of HDAC1, mRNA expression of collagen I, collagen III, MMP-2 and MMP-9 and the area of cardiac fibrosis in MI rats. In Ang II-stimulated CFs, ellagic acid (60 μmol/L) decreased the protein expression of HDAC1, collagen I, collagen III, MMP-2 and MMP-9, and inhibited cell proliferation and migration. Further, HDAC1 over-expression reversed the inhibitor effects of ellagic acid on proteins expression (collagen I, collagen III, MMP-2 and MMP-9) and proliferation and migration of CFs. The present results suggested that ellagic acid suppressed proliferation and migration of CFs by down-regulating expression of HDAC1.

Epigenetics and vascular diseases

Cardiovascular disease remains the number one cause of death and disability worldwide despite significant improvements in diagnosis, prevention, and early intervention efforts. There is an urgent need for improved understanding of cardiovascular processes responsible for disease development in order to develop more effective therapeutic strategies. Recent knowledge gleaned from the study of epigenetic mechanisms in the vasculature has uncovered new potential targets for intervention. Herein, we provide an overview of epigenetic mechanism, and review recent findings related to epigenetics in vascular diseases, highlighting classical epigenetic mechanism such as DNA methylation and histone modification as well as the newly discovered non-coding RNA mechanisms.

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

Background

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

Methods

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

Results

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

Conclusions

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

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

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

Pathological mechanisms and therapeutic outlooks for arthrofibrosis

Arthrofibrosis is a fibrotic joint disorder that begins with an inflammatory reaction to insults such as injury, surgery and infection. Excessive extracellular matrix and adhesions contract pouches, bursae and tendons, cause pain and prevent a normal range of joint motion, with devastating consequences for patient quality of life. Arthrofibrosis affects people of all ages, with published rates varying. The risk factors and best management strategies are largely unknown due to a poor understanding of the pathology and lack of diagnostic biomarkers. However, current research into the pathogenesis of fibrosis in organs now informs the understanding of arthrofibrosis. The process begins when stress signals stimulate immune cells. The resulting cascade of cytokines and mediators drives fibroblasts to differentiate into myofibroblasts, which secrete fibrillar collagens and transforming growth factor-β (TGF-β). Positive feedback networks then dysregulate processes that normally terminate healing processes. We propose two subtypes of arthrofibrosis occur: active arthrofibrosis and residual arthrofibrosis. In the latter the fibrogenic processes have resolved but the joint remains stiff. The best therapeutic approach for each subtype may differ significantly. Treatment typically involves surgery, however, a pharmacological approach to correct dysregulated cell signalling could be more effective. Recent research shows that myofibroblasts are capable of reversing differentiation, and understanding the mechanisms of pathogenesis and resolution will be essential for the development of cell-based treatments. Therapies with significant promise are currently available, with more in development, including those that inhibit TGF-β signalling and epigenetic modifications. This review focuses on pathogenesis of sterile arthrofibrosis and therapeutic treatments.

Class I histone deacetylase inhibitor MS-275 attenuates vasoconstriction and inflammation in angiotensin II-induced hypertension

Objective

Non-selective histone deacetylase (HDAC) inhibitors are known to improve hypertension. Here, we investigated the therapeutic effect and regulatory mechanism of the class I HDAC selective inhibitors, MS-275 and RGFP966, in angiotensin (Ang) II-induced hypertensive mice.

Methods and results

MS-275 inhibited the activity of HDAC1, HDAC2, and HDAC3, while RGFP966 weakly inhibited that of HDAC3 in a cell-free system. MS-275 and RGFP966 treatment reduced systolic blood pressure and thickness of the aorta wall in Ang II-induced hypertensive mice. MS-275 treatment reduced aorta collagen deposition, as determined by Masson’s trichrome staining. MS-275 decreased the components of the renin angiotensin system and increased vascular relaxation of rat aortic rings via the nitric oxide (NO) pathway. NO levels reduced by Ang II were restored by MS-275 treatment in vascular smooth muscle cells (VSMCs). However, MS-275 dose (3 mg·kg^-1·day^-1) was not enough to induce NO production in vivo. In addition, MS-275 did not prevent endothelial nitric oxide synthase (eNOS) uncoupling in the aorta of Ang II-induced mice. Treatment with MS-275 failed to inhibit Ang II-induced expression of NADPH oxidase (Nox)1, Nox2, and p47phox. MS-275 treatment reduced proinflammatory cytokines such as tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and monocyte chemoattractant protein (MCP)-1, as well as adhesion molecules. Histological analysis showed that Ang II-induced macrophage infiltration was reduced by MS-275 and RGFP966 administration.

Conclusions

Our results indicate that class I HDAC selective inhibitors may be good therapeutic agents for the treatment of hypertension through the regulation of vascular remodeling and vasoconstriction, as well as inflammation.

Histone deacetylase inhibitor LMK235 attenuates vascular constriction and aortic remodelling in hypertension

Here, we report that LMK235, a class I and histone deacetylase (HDAC6)‐preferential HDAC inhibitor, reduces hypertension via inhibition of vascular contraction and vessel hypertrophy. Angiotensin II‐infusion mice and spontaneously hypertensive rats (SHRs) were used to test the anti‐hypertensive effect of LMK235. Daily injection of LMK235 lowered angiotensin II‐induced systolic blood pressure (BP). A reduction in systolic BP in SHRs was observed on the second day when SHRs were treated with 3 mg/kg LMK235 every 3 days. However, LMK235 treatment did not affect angiotensin‐converting enzyme 1 and angiotensin II receptor mRNA expression in either hypertensive model. LMK235, acting via the nitric oxide pathway, facilitated the relaxing of vascular contractions induced by a thromboxane A2 agonist in the rat aortic and mesenteric artery ring test. In addition, LMK235 increased nitric oxide production in HUVECs and inhibited the increasing of aortic wall thickness in both animal hypertensive models. LMK235 decreased the enhanced cell cycle‐related genes cyclin D1 and E2F3 in angiotensin II‐infusion mice and restored the decreased p21 expression. In addition, LMK235 suppressed calcium calmodulin‐dependent protein kinase II (CaMKII) α, which is related to vascular smooth muscle cell proliferation. Inhibition or knockdown of HDAC5 blocked the CaMKIIα‐induced cell cycle gene expression. Immunoprecipitation demonstrated that class I HDACs were involved in the inhibition of CaMKII α‐induced HDAC4/5 by LMK235. We suggest that LMK235 should be further investigated for its use in the development of new therapeutic options to treat hypertension via reducing vascular hyperplasia or vasoconstriction.

Renoprotective Effect of the Histone Deacetylase Inhibitor CG200745 in DOCA-Salt Hypertensive Rats

The novel histone deacetylase inhibitor CG200745 was initially developed to treat various hematological and solid cancers. We investigated the molecular mechanisms associated with the renoprotective effects of CG200745 using deoxycorticosterone acetate (DOCA)-salt hypertensive (DSH) rats. DOCA strips (200 mg/kg) were implanted into rats one week after unilateral nephrectomy. Two weeks after DOCA implantation, DSH rats were randomly divided into two groups that received either physiological saline or CG200745 (5 mg/kg/day) for another two weeks. The extent of glomerulosclerosis and tubulointerstitial fibrosis was determined by Masson's trichrome staining. The renal expression of fibrosis and inflammatory markers was detected by semiquantitative immunoblotting, a polymerase chain reaction, and immunohistochemistry. Pathological signs such as glomerulosclerosis, tubulointerstitial fibrosis, increased systolic blood pressure, decreased creatinine clearance, and increased albumin-to-creatinine ratios in DSH rats were alleviated by CG200745 treatment compared to those manifestations in positive control animals. Furthermore, this treatment counteracted the increased expression of αSMA, TGF-β1, and Bax, and the decreased expression of Bcl-2 in the kidneys of DSH rats. It also attenuated the increase in the number of apoptotic cells in DSH rats. Thus, CG200745 can effectively prevent the progression of renal injury in DSH rats by exerting anti-inflammatory, anti-fibrotic, and anti-apoptotic effects.

Role of matrix metalloproteinases and histone deacetylase in oxidative stress-induced degradation of the endothelial glycocalyx

The glycocalyx is crucial for normal endothelial function. It also tethers extracellular superoxide dismutase (SOD3), which protects the endothelium against oxidative damage. Proteolytic enzymes [matrix metalloproteinases (MMPs)] are capable of disrupting endothelial cell surface proteins, such as syndecans, resulting in derangements of the endothelial glycocalyx. We sought to test the role of MMPs in oxidative stress-mediated disruption of the endothelial glycocalyx and examine the effect of pharmacological inhibition of MMPs on mitigating this detrimental effect. We also examined the role of histone deacetylase (HDAC) in the oxidative stress-mediated MMP induction and glycocalyx remodeling. Oxidative stress was experimentally induced in human adipose microvascular endothelial cells using H₂O₂ and buthionine sulfoximine in the presence and absence of potent MMP and HDAC inhibitors. H₂O₂ and buthionine sulfoximine resulted in a notable loss of the endothelial glycocalyx; they also increased the expression and proteolytic activity of MMP-2 and MMP-9 and subsequently increased the shedding of syndecan-1 and SOD3 from the endothelial cell surface. MMP upregulation was accompanied by a decline in mRNA and protein levels of their inhibitors, tissue inhibitors of metalloproteinase (TIMPs; TIMP-1 and TIMP-3). Furthermore, oxidative stress induced HDAC activity. Inhibition of MMPs and HDAC reversed syndecan-1 and SOD3 shedding and maintained endothelial glycocalyx integrity. HDAC inhibition increased TIMP expression and reduced MMP expression and activity in endothelial cells. Our findings shed light on MMPs and HDAC as therapeutically targetable mechanisms in oxidative stress-induced glycocalyx remodeling. NEW & NOTEWORTHY Oxidative stress, a hallmark of many diseases, damages the endothelial glycocalyx, resulting in vascular dysfunction. Studying the mechanistic link between oxidative stress and endothelial glycocalyx derangements might help discover new therapeutic targets to preserve vascular function. In this study, we investigated the involvement of matrix metalloproteinases and histone deacetylase in oxidative stress-induced endothelial glycocalyx degradation.

Epigenetics in Cardiac Fibrosis: Emphasis on Inflammation and Fibroblast Activation

Chemical modifications to nucleosomal DNA and histone tails greatly influence transcription of adjacent and distant genes, a mode of gene regulation referred to as epigenetic control. Here, the authors summarize recent findings that have illustrated crucial roles for epigenetic regulatory enzymes and reader proteins in the control of cardiac fibrosis. Particular emphasis is placed on epigenetic regulation of stress-induced inflammation and fibroblast activation in the heart. The potential of developing innovative small molecule "epigenetic therapies" to combat cardiac fibrosis is highlighted.

Repression of Transcriptional Activity of Forkhead Box O1 by Histone Deacetylase Inhibitors Ameliorates Hyperglycemia in Type 2 Diabetic Rats

Type 2 diabetes mellitus (T2DM) is a chronic disease manifested by hyperglycemia. It is essential to effectively control hyperglycemia to prevent complications of T2DM. Here, we hypothesize that repression of transcriptional activity of forkhead box O1 (FoxO1) via histone deacetylase inhibitors (HDACi) ameliorates hyperglycemia in T2DM rats. Methods: Male Long-Evans Tokushima Otsuka (LETO) and Otsuka Long-Evans Tokushima Fatty (OLETF) rats aged 14 weeks were administered sodium valproate (VPA, 0.71% w/v) dissolved in water for 20 weeks. Electrophoretic mobility shift assay (EMSA) and luciferase assay were performed for elucidation of transcriptional regulation through acetylation of FoxO1 by HDACi. Results: VPA attenuated blood glucose levels in accordance with a decrease in the expression of gluconeogenic genes in hyperglycemic OLETF rats. It has been shown that HDAC class I-specific and HDAC class IIa-specific inhibitors, as well as pan-HDAC inhibitors decrease FoxO1 enrichment at the cis-element of target gene promoters. Mutations in FoxO1 prevent its acetylation, thereby increasing its transcriptional activity. HDAC3 and HDAC4 interact with FoxO1, and knockdown of HDAC3, HDAC4, or their combination increases FoxO1 acetylation, thereby decreasing the expression of gluconeogenic genes. Conclusions: These results indicate that HDACi attenuates the transcriptional activity of FoxO1 by impeding deacetylation, thereby ameliorating hyperglycemia in T2DM rats.

Histone deacetylase inhibition attenuates atrial arrhythmogenesis in sterile pericarditis

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

Epigenetic processing in cardiometabolic disease

Albeit a consistent body of evidence supports the notion that genes influence cardiometabolic features and outcomes, the "non-genetic regulation" of this process is gaining increasing attention. Plastic chemical changes of DNA/histone complexes - known as epigenetic changes - critically determine gene activity by rapidly modifying chromatin accessibility to transcription factors. In this review, we describe the emerging role of chromatin modifications as fine tuners of gene transcription in adipogenesis, insulin resistance, macrophage polarization, immuno-metabolism, endothelial dysfunction and metabolic cardiomyopathy. Epigenetic processing participates in the dynamic interplay among different organs in the cardiometabolic patient. DNA methylation and post-translational histone modifications in both visceral and subcutaneous adipose tissue enable the transcription of genes implicated in lipo- and adipogenesis, inflammation and insulin resistance. Along the same line, complex networks of chromatin modifying enzymes are responsible for impaired nitric oxide bioavailability and defective insulin signalling in the vasculature, thus leading to reduced capillary recruitment and insulin delivery in the liver, skeletal muscle and adipose tissue. Furthermore, changes in methylation status of IL-4, IFNγ and Forkhead box P3 (Foxp3) gene loci are crucial for the polarization of immune cells, thus leading to adipose tissue inflammation and atherosclerosis. Cell-specific epigenetic information could advance our understanding of cardiometabolic processes, thus leading to individualized risk assessment and personalized therapeutic approaches in patients with cardiometabolic disturbances. The development of new chromatin modifying drugs indicates that targeting epigenetic changes is a promising approach to reduce the burden of cardiovascular disease in this setting.

β-adrenergic Receptor Stimulation Revealed a Novel Regulatory Pathway via Suppressing Histone Deacetylase 3 to Induce Uncoupling Protein 1 Expression in Mice Beige Adipocyte

Browning of adipose tissue has been prescribed as a potential way to treat obesity, marked by the upregulation of uncoupling protein 1 (Ucp1). Several reports have suggested that histone deacetylase (HDAC) might regulate Ucp1 by remodelling chromatin structure, although the mechanism remains unclear. Herein, we investigate the effect of β-adrenergic receptor (β-AR) activation on the chromatin state of beige adipocyte. β-AR-stimulated Ucp1 expression via cold (in vivo) and isoproterenol (in vitro) resulted in acetylation of histone activation mark H3K27. H3K27 acetylation was also seen within Ucp1 promoter upon isoproterenol addition, favouring open chromatin for Ucp1 transcriptional activation. This result was found to be associated with the downregulation of class I HDAC mRNA, particularly Hdac3 and Hdac8. Further investigation showed that although HDAC8 activity decreased, Ucp1 expression was not altered when HDAC8 was activated or inhibited. In contrast, HDAC3 mRNA and protein levels were simultaneously downregulated upon isoproterenol addition, resulting in reduced recruitment of HDAC3 to the Ucp1 enhancer region, causing an increased H3K27 acetylation for Ucp1 upregulation. The importance of HDAC3 inhibition was confirmed through the enhanced Ucp1 expression when the cells were treated with HDAC3 inhibitor. This study highlights the novel mechanism of HDAC3-regulated Ucp1 expression during β-AR stimulation.

An experimental model for hypertensive crises emergencies: Long-term high-fat diet followed by acute vasoconstriction stress on spontaneously hypertensive rats

Currently, the prevention and treatment of hypertensive crises especially when it occurs with serious adverse outcomes have led to worldwide controversy. Despite of clinical possibilities of multiple agents, clinical failures still occur frequently. Therefore, early evaluations and observations of different therapies on appropriate animals should be emphasized. In the present study, an animal model for hypertensive crises emergencies was firstly established and experimentally testified. Five-month-male spontaneously hypertensive rat was consecutively fed with 60%-Kcal fat diet for four, six, and eight weeks with body weight and blood pressure monitored every two weeks, and then followed by an acute vasoconstriction stress of 5-min ice-bath treatment in the 4-h time interval of two adrenaline injections (0.8 mg/kg). Forty-four biochemical parameters were detected, covering hepatic and renal function, blood glucose and lipid levels, myocardial enzymes and energy metabolisms, blood coagulative and anti-coagulative system, oxidative stress and anti-inflammatory cytokine, blood viscosity, and RAAS system. Six tissues including heart, brain, liver, kidney, coronary arteries, and mesenteries were removed for pathological observations with hematoxylin-eosin staining. As a result, multi-organ dysfunctions in the heart, brain, liver, kidney, vascular endothelium, and blood system were testified in the modeling rats at weeks 6 and 8. In conclusion, severe consequences of this animal model were highly similar to those in hypertensive crises emergencies, which could be further utilized in the early intervention of hypertensive crises emergencies including the possible risk factors control and efficient therapies assessment. Impact statement In the late 90s, numerous reports predicted that 1-2% of hypertensive individuals would undergo hypertensive crises (HPC) and figures reached as high as 7% when no antihypertensive therapies were administrated. Currently, clinical failures appear frequently due to the improper or excessive medication regimen instead of the illness itself. Therefore, early evaluations and observations of HPC on appropriate animal models ahead of patients should be discussed and emphasized more widely. In the present study, an appropriate animal model for HPC emergencies was firstly established, in which the consequences of long-term high-fat diet feeding followed by an acute vasoconstriction stress on the spontaneously hypertensive rats were experimentally testified. The proposed model would have a wide application prospects in early intervention of HPC emergencies including the controls of possible risk factors and assessments of efficient therapies.

Histone deacetylase inhibition ameliorates hypertension and hyperglycemia in a model of Cushing's syndrome

Cushing's syndrome (CS) caused by hypercortisolism is occasionally accompanied by metabolic disorders such as hypertension, diabetes mellitus (DM), dyslipidemia, and central obesity. Thus morbidity and mortality, observed in cardiovascular disease, are elevated in patients with CS. We hypothesized that HDAC inhibition (HDACi) decreased transcriptional activity of glucocorticoid receptor (GR), which ameliorates hypertension and hyperglycemia in patients with CS. To establish an animal model of hypercortisolism, Sprague-Dawley rats were infused with adrenocorticotropic hormone (ACTH, 40 ng/day) or dexamethasone (Dex, 10 μg/day) via osmotic minipumps for 4 wk. Expression of GR target genes was determined by quantitative real-time PCR (qRT-PCR). GR enrichment on specific loci, and across the whole genome, was analyzed by chromatin immunoprecipitation (ChIP) and ChIPseq, respectively. HDACi decreased blood pressure and expression of ion regulators in the kidneys of ACTH-infused rats. Additionally, HDACi reduced deposition of polysaccharide, fasting blood glucose level, glucose intolerance, and expression of gluconeogenesis genes in the livers and kidneys of ACTH- and Dex-infused rats. Among class I HDACs, HDAC1 and HDAC3 interacted with GR. HDAC1 knockdown resulted in increased level of acetylation and decreased transcriptional activity of GR. GR recruitment on the promoters of 2,754 genes, which include ion transporters, channels, and gluconeogenic genes, was significantly decreased by MS-275, a class I HDAC inhibitor. These results indicate that HDACi ameliorates hypertension and hyperglycemia in a model of CS by decreasing the transcriptional activity of GR via elevating its level of acetylation.

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

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

Histone deacetylase inhibition, but not a mineralocorticoid receptor antagonist spironolactone, attenuates atypical transcription by an activating mutant MR (MRS 810L )

A mutation in the mineralocorticoid receptor (MRS 810L ) leads to early-onset hypertension, which is markedly exacerbated during pregnancy. The mutation causes progesterone and even the MR antagonist spironolactone to become potent agonists. Thus, it is hard to control hypertension in patients harbouring this mutation. We hypothesized that histone deacetylase inhibition (HDACi), but not the MR antagonist spironolactone, attenuates atypical transcriptional activity of activating mutant MR (MRS 810L ). We established HEK293T cells overexpressing wild-type MR (MRWT ) or MRS 810L and determined their transcriptional activities by luciferase assay. Expression of MR target genes was measured by quantitative real-time PCR (qRT-PCR). Treatment with aldosterone increased the expression of MR target genes as well as the transcriptional activities in HEK293T cells transfected either with MRWT or MRS 810L . Treatment with either spironolactone or progesterone also increased the expression of MR target genes as well as transcriptional activity, but only in HEK293T cells transfected with MRS 810L . Spironolactone abolished the promoter activity stimulated by aldosterone in HEK293T cells transfected with MRWT . Treatment with HDAC inhibitors attenuated the transcriptional activity as well as the expression of MR target genes induced by aldosterone, spironolactone, or progesterone whether HEK293T cells were transfected with either MRWT or MRS 810L . These results indicate that HDACi, but not an MR antagonist spironolactone, attenuates atypical transcriptional activity of an activating mutant MR (MRS 810L ).

Sodium butyrate suppresses angiotensin II-induced hypertension by inhibition of renal (pro)renin receptor and intrarenal renin-angiotensin system

OBJECTIVES

Butyrate, a short-chain fatty acid, is the end product of the fermentation of complex carbohydrates by the gut microbiota. Recently, sodium butyrate (NaBu) has been found to play a protective role in a number of chronic diseases. However, it is still unclear whether NaBu has a therapeutic potential in hypertension. The present study was aimed to investigate the role of NaBu in angiotensin II (Ang II)-induced hypertension and to further explore the underlying mechanism.

METHODS

Ang II was infused into uninephrectomized Sprague-Dawley rats with or without intramedullary infusion of NaBu for 14 days. Mean arterial blood pressure was recorded by the telemetry system. Renal tissues, serum samples, and 24-h urine samples were collected to examine renal injury and the regulation of the (pro)renin receptor (PRR) and renin.

RESULTS

Intramedullary infusion of NaBu in Sprague-Dawley rats lowered the Ang II-induced mean arterial pressure from 129 ± 6 mmHg to 108 ± 4 mmHg (P < 0.01). This corresponded with an improvement in Ang II-induced renal injury, including urinary albumin, glomerulosclerosis, and renal fibrosis, as well as the expression of inflammatory mediators tumor necrosis factor α, interleukin 6. The renal expression of PRR, angiotensinogen, angiotensin I-converting enzyme and the urinary excretion of soluble PRR, renin, and angiotensinogen were all increased by Ang II infusion but decreased by NaBu treatment. In cultured innermedullary collecting duct cells, NaBu treatment attenuated Ang II-induced expression of PRR and renin.

CONCLUSION

These results demonstrate that NaBu exerts an antihypertensive action, likely by suppressing the PRR-mediated intrarenal renin-angiotensin system.

Histone deacetylase and GATA-binding factor 6 regulate arterial remodeling in angiotensin II-induced hypertension

OBJECTIVE

Histone deacetylase (HDAC) inhibitors have been reported to improve essential and secondary hypertension. However, the specific HDAC that might serve as a therapeutic target and the associated upstream and downstream molecules involved in regulating hypertension remain unknown. Our study was aimed at investigating whether a selective inhibitor of class II HDAC (MC1568) modulates hypertension, elucidating the underlying mechanism.

METHODS

Hypertension was established by administering angiotensin II (Ang II) to mice before treatment with MC1568. SBP was measured.

RESULTS

Treatment with MC1568 reduced elevated SBP; attenuated arterial remodeling in the kidney's small arteries and thoracic aorta; and inhibited cell cycle regulatory gene expression, vascular smooth muscle cell (VSMC) proliferation, DNA synthesis, and VSMC hypertrophy in vivo and in vitro. Ang II enhanced the expression of phosphorylated HDAC4 and GATA-binding factor 6 (GATA6) proteins, which were specifically localized in the cytoplasm of cells in the arteries of kidneys and in aortas. Forced expression and knockdown of HDAC4 increased and decreased, respectively, the proliferation and expression of cell cycle genes in VSMCs. GATA6, a newly described binding partner of HDAC4, markedly enhanced the size and number of VSMCs. Calcium/calmodulin-dependent kinase IIα (CaMKIIα), but not HDAC4, translocated from the nucleus to the cytoplasm in response to Ang II. CaMKIIα and protein kinase D1 were associated with VSMC hypertrophy and hyperplasia via direct interaction with HDAC4. MC1568 treatment weakened the association between HDAC4 and CaMKIIα.

CONCLUSION

These results suggest that class II HDAC inhibition attenuates hypertension by negatively regulating VSMC hypertrophy and hyperplasia via the CaMKIIα/protein kinase D1/HDAC4/GATA6 pathway.

Trichostatin A attenuates oxidative stress-mediated myocardial injury through the FoxO3a signaling pathway

Trichostatin A (TSA), a histone deacetylase inhibitor, is widely used as an anticancer drug. Recently, TSA has been shown to exert a protective effect on ischemia/reperfusion (I/R) injury; however, the underlying mechanisms remain unclear. Forkhead box O3a (FoxO3a), a unique FoxO family member, has been shown to attenuate myocardial injury by increasing resistance to oxidative stress in mice. The present study aimed to investigate whether TSA exerts its cardioprotective effects through the FoxO3a signaling pathway. For this purpose, healthy male Wistar rats were pre-treated with TSA for 5 days before they were subjected to ligation/relaxation of the left anterior descending branch of the coronary artery and to 30 min of ischemia, followed by 24 h of reperfusion. The activities of creatine kinase (CK), lactate dehydrogenase (LDH), aspartate aminotransferase (AST) and superoxide diamutase (SOD), as well as the malondialdehyde (MDA) levels were examined. The H9c2 rat myocardial cell line was cultured in 10% FBS-containing DMEM for 24 h. The cells were incubated with/without TSA (50 nmol/l) for 1 h and then incubated with/without H₂O₂ (400 µM) for 2 h. Reactive oxygen species (ROS) and mitochondrial membrane potential (Δψm) were measured by probe staining in the H9c2 cells. The expression of FoxO3a, mitochondrial SOD2 and catalase was quantified by western blot analysis. The levels of H3 and H4 acetylation of the FoxO3a promoter region were examined by chromatin immunoprecipitation assay. TSA significantly reduced the myocardial infarct size and the activities of serum LDH, AST and CK in the rats. TSA also decreased the levels of MDA and increased the activities of SOD in the myocardial tissue of the rats. Consistent with the reduced injury to the TSA-treated rats, TSA significantly reduced the H₂O₂-induced levels of ROS and increased Δψm. In addition, TSA increased the expression of FoxO3a, SOD2 and catalase, which may be related to increasing the level of H4 acetylation of the FoxO3a promoter region. Our results thus revealed that TSA protected the myocardium from oxidative stress-mediated damage by increasing H4 acetylation of the FoxO3a promoter region, and the expression of FoxO3a, SOD2 and catalase.

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.

Histone 3 modifications and blood pressure in the Beijing Truck Driver Air Pollution Study

CONTEXT

Histone modifications regulate gene expression; dysregulation has been linked with cardiovascular diseases. Associations between histone modification levels and blood pressure in humans are unclear.

OBJECTIVE

We examine the relationship between global histone concentrations and various markers of blood pressure.

MATERIALS AND METHODS

Using the Beijing Truck Driver Air Pollution Study, we investigated global peripheral white blood cell histone modifications (H3K9ac, H3K9me3, H3K27me3, and H3K36me3) associations with pre- and post-work measurements of systolic (SBP) and diastolic (DBP) blood pressure, mean arterial pressure (MAP), and pulse pressure (PP) using multivariable mixed-effect models.

RESULTS

H3K9ac was negatively associated with pre-work SBP and MAP; H3K9me3 was negatively associated with pre-work SBP, DBP, and MAP; and H3K27me3 was negatively associated with pre-work SBP. Among office workers, H3K9me3 was negatively associated with pre-work SBP, DBP, and MAP. Among truck drivers, H3K9ac and H3K27me were negatively associated with pre-work SBP, and H3K27me3 was positively associated with post-work PP.

DISCUSSION AND CONCLUSION

Epigenome-wide H3K9ac, H3K9me3, and H3K27me3 were negatively associated with multiple pre-work blood pressure measures. These associations substantially changed during the day, suggesting an influence of daily activities. Blood-based histone modification biomarkers are potential candidates for studies requiring estimations of morning/pre-work blood pressure.

Role of the histone deacetylase inhibitor valproic acid in high-fat diet-induced hypertension via inhibition of HDAC1/angiotensin II axis

BACKGROUND

Obesity is known as an epidemic worldwide because of consumption of westernized high-fat diets and one of the major risk factors of hypertension. Histone deacetylases (HDACs) control gene expression by regulating histone/non-histone protein deacetylation. HDAC inhibitors exert anti-cancer and anti-inflammatory effects and play a protective role in cardiovascular diseases. In the present study, we tested the effect of an FDA-approved pan-HDAC inhibitor valproic acid (VPA) on high-fat diet (HFD)-induced hypertension in mice. Furthermore, we examined the mechanism of VPA-induced prevention of hypertension.

METHODS

Nine-week-old male C57BL/6 mice were fed either a normal diet (ND) or HFD. When the HFD group reached a pre-hypertensive phase (130-140 mm Hg systolic blood pressure), VPA was administered for 6 days (300 mg kg^-1 per day). Body weights and blood pressure (BP), expression of renin-angiotensin system (RAS) components and HDAC1 were determined. The direct role of HDAC1 in the expression of RAS components was investigated using gene silencing.

RESULTS

HFD accelerated the increase in body weight from 22.4±1.3 to 31.9±3.0 compared to in the ND group from 22.7±0.9 to 26.0±1.7 (P=0.0134 ND vs HFD), systolic BP from 118.5±5.7 to 145.0±3.0 (P<0.001), and diastolic BP from 91.0±13.6 to 121.0±5.0 (P=0.006); BP was not altered in the ND group. HFD increased RAS components and HDAC1 in the kidneys as well as leptin in the plasma. VPA administration prevented the progression of hypertension and inhibited the increase in expression of HDAC1 and RAS components. VPA did not affect plasma leptin level. Knockdown of HDAC1 in MDCK cells decreased the expression of angiotensinogen and type 1 angiotensin II receptor.

CONCLUSIONS

VPA prevented HFD-induced hypertension by downregulating angiotensin II and its receptor via inhibition of HDAC1, offering a novel therapeutic option for HFD-induced hypertension.

Early transcriptional alteration of histone deacetylases in a murine model of doxorubicin-induced cardiomyopathy

Doxorubicin is a potent chemotherapeutic agent that is widely-used to treat a variety of cancers but causes acute and chronic cardiac injury, severely limiting its use. Clinically, the acute side effects of doxorubicin are mostly manageable, whereas the delayed consequences can lead to life-threatening heart failure, even decades after cancer treatment. The cardiotoxicity of doxorubicin is subject to a critical cumulative dose and so dosage limitation is considered to be the best way to reduce these effects. Hence, a number of studies have defined a "safe dose" of the drug, both in animal models and clinical settings, with the aim of avoiding long-term cardiac effects. Here we show that a dose generally considered as safe in a mouse model can induce harmful changes in the myocardium, as early as 2 weeks after infusion. The adverse changes include the development of fibrotic lesions, disarray of cardiomyocytes and a major transcription dysregulation. Importantly, low-dose doxorubicin caused specific changes in the transcriptional profile of several histone deacetylases (HDACs) which are epigenetic regulators of cardiac remodelling. This suggests that cardioprotective therapies, aimed at modulating HDACs during doxorubicin treatment, deserve further exploration.

HDAC9 is an epigenetic repressor of kidney angiotensinogen establishing a sex difference

Background

Sexual difference has been shown in the pathogenesis of chronic kidney disease induced by hypertension. Females are protected from hypertension and related end-organ damage. Augmentation of renal proximal tubular angiotensinogen (AGT) expression can promote intrarenal angiotensin formation and the development of associated hypertension and kidney injury. Female rodents exhibit lower intrarenal AGT levels than males under normal conditions, suggesting that the suppressed intrarenal AGT production by programmed mechanisms in females may provide protection from these diseases. This study was performed to examine whether epigenetic mechanisms serve as repressors of AGT.

Methods

Male and female Sprague Dawley rats were used to investigate sex differences of systemic, hepatic, and intrarenal AGT levels. All histone deacetylase (HDAC) mRNA levels in the kidneys were determined using a PCR array. HDAC9 protein expression in the kidneys and cultured renal proximal tubular cells (PTC) was analyzed by Western blot analysis and immunohistochemistry. The effects of HDAC9 on AGT expression were evaluated by using an inhibitor and siRNA. ChIP assay was performed to investigate the interaction between the AGT promoter and HDAC9.

Results

Plasma and liver AGT levels did not show differences between male and female Sprague-Dawley rats. In contrast, females exhibited lower AGT levels than males in the renal cortex and urine. In the absence of supplemented sex hormones, primary cultured renal cortical cells isolated from female rats sustained lower AGT levels than those from males, suggesting that the kidneys have a unique mechanism of AGT regulation controlled by epigenetic factors rather than sex hormones. HDAC9 mRNA and protein levels were higher in the renal cortex of female rats versus male rats (7.09 ± 0.88, ratio to male) while other HDACs did not exhibit a sex difference. HDAC9 expression was localized in PTC which are the primary source of intrarenal AGT. Importantly, HDAC9 knockdown augmented AGT mRNA (1.92 ± 0.35-fold) and protein (2.25 ± 0.50-fold) levels, similar to an HDAC9 inhibitor. Furthermore, an interaction between HDAC9 and a distal 5’ flanking region of AGT via a histone complex containing H3 and H4 was demonstrated.

Conclusions

These results indicate that HDAC9 is a novel suppressing factor involved in AGT regulation in PTC, leading to low levels of intrarenal AGT in females. These findings will help to delineate mechanisms underlying sex differences in the development of hypertension and renin-angiotensin system (RAS) associated kidney injury.

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.

Selective inhibition of HDAC2 by magnesium valproate attenuates cardiac hypertrophy

The regulatory paradigm in cardiac hypertrophy involves alterations in gene expression that is mediated by chromatin remodeling. Various data suggest that class I and class II histone deacetylases (HDACs) play opposing roles in the regulation of hypertrophic pathways. To address this, we tested the effect of magnesium valproate (MgV), an HDAC inhibitor with 5 times more potency on class I HDACs. Cardiac hypertrophy was induced by partial abdominal aortic constriction in Wistar rats, and at the end of 6 weeks, we evaluated hypertrophic, hemodynamic, and oxidative stress parameters, and mitochondrial DNA concentration. Treatment with MgV prevented cardiac hypertrophy, improved hemodynamic functions, prevented oxidative stress, and increased mitochondrial DNA concentration. MgV treatment also increased the survival rate of the animals as depicted by the Kaplan-Meier curve. Improvement in hypertrophy due to HDAC inhibition was further confirmed by HDAC mRNA expression studies, which revealed that MgV decreases expression of pro-hypertrophic HDAC (i.e., HDAC2) without altering the expression of anti-hypertrophic HDAC5. Selective class I HDAC inhibition is required for controlling cardiac hypertrophy. Newer HDAC inhibitors that are class I inhibitors and class II promoters can be designed to obtain "pan" or "dual" natural HDAC "regulators".

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".

Oxidant and Inflammatory Mechanisms and Targeted Therapy in Atrial Fibrillation: An Update

Atrial fibrillation (AF) is an important cause of stroke and risk factor for heart failure and death. Current pharmacologic treatments for AF have limited efficacy, and treatments that more directly target the underlying causes of AF are needed. Oxidant stress and inflammatory activation are interrelated pathways that promote atrial electrical and structural remodeling, leading to atrial ectopy, interstitial fibrosis, and increased stroke risk. This review evaluates the impact of common stressors on atrial oxidant stress and inflammatory activation and the contribution of these pathways to atrial remodeling. Recent studies suggest that integrated efforts to target the underlying risk factors, rather than the AF per se, may have a greater impact on health and outcomes than isolated efforts focused on the electrical abnormalities.

Histone deacetylase inhibitor, CG200745, attenuates cardiac hypertrophy and fibrosis in DOCA-induced hypertensive rats

CG200745 is a novel inhibitor of histone deacetylases (HDACs), initially developed for treatment of various hematological and solid cancers. Because it is water-soluble, it can be administered orally. We hypothesized that the HDAC inhibitor, CG200745, attenuates cardiac hypertrophy and fibrosis in deoxycorticosterone acetate (DOCA)-induced hypertensive rats. For establishment of hypertension, 40 mg/kg of DOCA was subcutaneously injected four times weekly into Sprague-Dawley rats. All the rats used in this study including those in the sham group had been unilaterally nephrectomized and allowed free access to drinking water containing 1% NaCl. Systolic blood pressure was measured by the tail-cuff method. Blood chemistry including sodium, potassium, glucose, triglyceride, and cholesterol levels was analyzed. Sections of the heart were visualized after trichrome and hematoxylin and eosin stain. The expression of hypertrophic genes such as atrial natriuretic peptide A (Nppa) and atrial natriuretic peptide B (Nppb) in addition to fibrotic genes such as Collagen-1, Collagen-3, connective tissue growth factor (Ctgf), and Fibronectin were measured by quantitative real-time PCR (qRT-PCR). Injection of DOCA increased systolic blood pressure, heart weight, and cardiac fibrosis, which was attenuated by CG200745. Neither DOCA nor CG200745 affected body weight, vascular contraction and relaxation responses, and blood chemistry. Injection of DOCA increased expression of both hypertrophic and fibrotic genes, which was abrogated by CG200745. These results indicate that CG200745 attenuates cardiac hypertrophy and fibrosis in DOCA-induced hypertensive rats.

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.

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.

Mechanisms of Vascular Smooth Muscle Contraction and the Basis for Pharmacologic Treatment of Smooth Muscle Disorders

The smooth muscle cell directly drives the contraction of the vascular wall and hence regulates the size of the blood vessel lumen. We review here the current understanding of the molecular mechanisms by which agonists, therapeutics, and diseases regulate contractility of the vascular smooth muscle cell and we place this within the context of whole body function. We also discuss the implications for personalized medicine and highlight specific potential target molecules that may provide opportunities for the future development of new therapeutics to regulate vascular function.

Lysine acetyltransferases cyclic adenosine monophosphate response element-binding binding protein and acetyltransferase p300 attenuate transcriptional activity of the mineralocorticoid receptor through its acetylation

Acetylation of the mineralocorticoid receptor (MR) by inhibition of lysine deacetylases attenuates MR's transcriptional activity. However, the specific lysine acetyltransferases that are responsible for acetylation of the MR remain unknown. We hypothesized that the acetyltransferases cyclic adenosine monophosphate response element-binding binding protein (CBP) and acetyltransferase p300 (p300) attenuate transcriptional activity of the MR through its acetylation. Expression of MR target genes was measured by quantitative real-time polymerase chain reaction. Recruitment of MR and RNA polymerase II (Pol II) on promoters of target genes was analysed by chromatin immunoprecipitation. Acetylation of the MR was determined by western blot with an anti-acetyl-lysine antibody after immunoprecipitation with an anti-MR antibody. In human embryonic kidney (HEK) 293 cells, overexpression of CBP or p300, but not p300/CBP-associated factor, increased MR acetylation and decreased expression of MR target genes. The downregulation of target genes coincided with a decrease in the recruitment of MR and Pol II to specific hormone response elements. These results demonstrate that overexpression of CBP or p300 attenuates the transcriptional activity of the MR through its acetylation in HEK 293 cells. Our data provide strong evidence identifying CBP and p300 as lysine acetyltransferases responsible for the regulation of MR that may provide new therapeutic targets for the treatment of hypertension.

Human GRK4γ142V Variant Promotes Angiotensin II Type I Receptor-Mediated Hypertension via Renal Histone Deacetylase Type 1 Inhibition

The influence of a single gene on the pathogenesis of essential hypertension may be difficult to ascertain, unless the gene interacts with other genes that are germane to blood pressure regulation. G-protein-coupled receptor kinase type 4 (GRK4) is one such gene. We have reported that the expression of its variant hGRK4γ(142V) in mice results in hypertension because of impaired dopamine D1 receptor. Signaling through dopamine D1 receptor and angiotensin II type I receptor (AT1R) reciprocally modulates renal sodium excretion and blood pressure. Here, we demonstrate the ability of the hGRK4γ(142V) to increase the expression and activity of the AT1R. We show that hGRK4γ(142V) phosphorylates histone deacetylase type 1 and promotes its nuclear export to the cytoplasm, resulting in increased AT1R expression and greater pressor response to angiotensin II. AT1R blockade and the deletion of the Agtr1a gene normalize the hypertension in hGRK4γ(142V) mice. These findings illustrate the unique role of GRK4 by targeting receptors with opposite physiological activity for the same goal of maintaining blood pressure homeostasis, and thus making the GRK4 a relevant therapeutic target to control blood pressure.

MRI and serum high-sensitivity C reactive protein predict long-term mortality in non-ischaemic cardiomyopathy

Objective

Myocardial fibrosis related to non-specific inflammation can be detected using late gadolinium-enhancement cardiovascular MR (LGE-CMR), which is an important prognostic indicator for dilated cardiomyopathy (DCM). The aims of this study were to define the prognostic factors for DCM with LGE-CMR, and to evaluate the impact of the prognostic factors on adverse effects.

Methods

We performed a retrospective analysis of a prospectively maintained single centre registry. We analysed the data from 76 patients with DCM who had been admitted for acute heart failure. The primary combined end point was defined as all-cause mortality and rehospitalisation.

Results

LGE-CMR was present in 39 patients (51%), and the mean follow-up period was 813±54 days. The primary end point occurred in 20 patients (5 (13.5%) patients without LGE-CMR and 15 (38.5%) patients with LGE-CMR, p=0.006). Sixteen of 39 patients with LGE-CMR exhibited elevated high-sensitivity C reactive protein (hs-CRP >0.3 mg/dL). Patients with elevated hs-CRP and LGE-CMR had a significantly higher incidence of the primary end point compared with patients with normal hs-CRP and LGE-CMR (62.5%; 10 patients, 22.7%; 5 patients, respectively, p=0.001). Elevated hs-CRP was significantly associated with the primary end point (HR: 4.04; 95% CI 1.67 to 9.76; p=0.002). After elevated hs-CRP was adjusted for known predictors of DCM, it was still associated with the primary end point (HR: 2.91; 95% CI 1.19 to 7.15; p=0.02).

Conclusions

Among patients with DCM, LGE-CMR and elevated hs-CRP are associated with a higher incidence of the long-term combined end point of all-cause mortality and hospitalisation.

Trial registration number:

UMIN000001171.

Histone deacetylase inhibitors modulate KATP subunit transcription in HL-1 cardiomyocytes through effects on cholesterol homeostasis

Histone deacetylase inhibitors (HDIs) are under investigation for the treatment of a number of human health problems. HDIs have proven therapeutic value in refractory cases of cutaneous T-cell lymphoma. Electrocardiographic ST segment morphological changes associated with HDIs were observed during development. Because ST segment morphology is typically linked to changes in ATP sensitive potassium (K_ATP) channel activity, we tested the hypothesis that HDIs affect cardiac K_ATP channel subunit expression. Two different HDIs, romidepsin and trichostatin A, caused ~20-fold increase in SUR2 (Abcc9) subunit mRNA expression in HL-1 cardiomyocytes. The effect was specific for the SUR2 subunit as neither compound causes a marked change in SUR1 (Abcc8) expression. Moreover, the effect was cell specific as neither HDI markedly altered K_ATP subunit expression in MIN6 pancreatic β-cells. We observe significant enrichment of the H3K9Ac histone mark specifically at the SUR2 promoter consistent with the conclusion that chromatin remodeling at this locus plays a role in increasing SUR2 gene expression. Unexpectedly, however, we also discovered that HDI-dependent depletion of cellular cholesterol is required for the observed effects on SUR2 expression. Taken together, the data in the present study demonstrate that K_ATP subunit expression can be epigenetically regulated in cardiomyocytes, defines a role for cholesterol homeostasis in mediating epigenetic regulation and suggests a potential molecular basis for the cardiac effects of the HDIs.

Histone Deacetylases and Cardiometabolic Diseases

Cardiometabolic disease, emerging as a worldwide epidemic, is a combination of metabolic derangements leading to type 2 diabetes mellitus and cardiovascular disease. Genetic and environmental factors are linked through epigenetic mechanisms to the pathogenesis of cardiometabolic disease. Post-translational modifications of histone tails, including acetylation and deacetylation, epigenetically alter chromatin structure and dictate cell-specific gene expression patterns. The histone deacetylase family comprises 18 members that regulate gene expression by altering the acetylation status of nucleosomal histones and by functioning as nuclear transcriptional corepressors. Histone deacetylases regulate key aspects of metabolism, inflammation, and vascular function pertinent to cardiometabolic disease in a cell- and tissue-specific manner. Histone deacetylases also likely play a role in the metabolic memory of diabetes mellitus, an important clinical aspect of the disease. Understanding the molecular, cellular, and physiological functions of histone deacetylases in cardiometabolic disease is expected to provide insight into disease pathogenesis, risk factor control, and therapeutic development.

Epigenetic mechanisms in heart development and disease

Suboptimal intrauterine development has been linked to predisposition to cardiovascular disease in adulthood, a concept termed 'developmental origins of health and disease'. Although the exact mechanisms underlying this developmental programming are unknown, a growing body of evidence supports the involvement of epigenetic regulation. Epigenetic mechanisms such as DNA methylation, histone modifications and micro-RNA confer added levels of gene regulation without altering DNA sequences. These modifications are relatively stable signals, offering possible insight into the mechanisms underlying developmental origins of health and disease. This review will discuss the role of epigenetic mechanisms in heart development as well as aberrant epigenetic regulation contributing to cardiovascular disease. Additionally, we will address recent advances targeting epigenetic mechanisms as potential therapeutic approaches to cardiovascular disease.

Non-sirtuin histone deacetylases in the control of cardiac aging

Histone deacetylases (HDACs) catalyze the removal of acetyl-groups from lysine residues within nucelosomal histone tails and thousands of non-histone proteins. The 18 mammalian HDACs are grouped into four classes. Classes I, II and IV HDACs employ zinc as a co-factor for catalytic activity, while class III HDACs (also known as sirtuins) require NAD+ for enzymatic function. Small molecule inhibitors of zinc-dependent HDACs are efficacious in multiple pre-clinical models of pressure overload and ischemic cardiomyopathy, reducing pathological hypertrophy and fibrosis, and improving contractile function. Emerging data have revealed numerous mechanisms by which HDAC inhibitors benefit the heart, including suppression of oxidative stress and inflammation, inhibition of MAP kinase signaling, and enhancement of cardiac protein aggregate clearance and autophagic flux. Here, we summarize recent findings with zinc-dependent HDACs and HDAC inhibitors in the heart, focusing on newly described functions for distinct HDAC isoforms (e.g. HDAC2, HDAC3 and HDAC6). Potential for pharmacological HDAC inhibition as a means of treating age-related cardiac dysfunction is also discussed. This article is part of a Special Issue entitled: CV Aging.

Angiotensin II-induced hypertensive renal inflammation is mediated through HMGB1-TLR4 signaling in rat tubulo-epithelial cells

BACKGROUND AND PURPOSE

Angiotensin II is a vaso-constrictive peptide that regulates blood pressure homeostasis. Even though the inflammatory effects of AngII in renal pathophysiology have been studied, there still exists a paucity of data with regard to the mechanism of action of AngII-mediated kidney injury. The objective of this study was to elucidate the mechanistic role of HMGB1-TLR4 signaling in AngII-induced inflammation in the kidney.

EXPERIMENTAL APPROACH

Rat tubular epithelial cells (NRK52E) were treated with AngII over a preset time-course. In another set of experiments, HMGB1 was neutralized and TLR4 was knocked down using small interfering RNA targeting TLR4. Cell extracts were subjected to RT-PCR, immunoblotting, flow cytometry, and ELISA.

KEY RESULTS

AngII-induced inflammation in NRK52E cells increased gene and protein expression of TLR4, HMGB1 and key proinflammatory cytokines (TNFα and IL1β). Pretreatment with Losartan (an AT1 receptor blocker) attenuated the AngII-induced expression of TLR4 and inflammatory cytokines. TLR4 silencing was used to elucidate the specific role played by TLR4 in AngII-induced inflammation. TLR4siRNA treatment in these cells significantly decreased the AngII-induced inflammatory effect. Consistent observations were made when the Ang II treated cells were pretreated with anti-HMGB1. Downstream activation of NFκB and rate of generation of ROS was also decreased on gene silencing of TLR4 and exposure to anti-HMGB1.

CONCLUSIONS AND IMPLICATIONS

These results indicate a key role for HMGB1-TLR4 signaling in AngII-mediated inflammation in the renal epithelial cells. Our data also reveal that AngII-induced effects could be alleviated by HMGB1-TLR4 inhibition, suggesting this pathway as a potential therapeutic target for hypertensive renal dysfunctions.