P300/CBP associated factor regulates nitroglycerin-dependent arterial relaxation by N(ε)-lysine acetylation of contractile proteins

Recent advances on the development of NO-releasing molecules (NORMs) for biomedical applications

Nitric oxide (NO) is an important biological messenger as well as a signaling molecule that participates in a broad range of physiological events and therapeutic applications in biological systems. However, due to its very short half-life in physiological conditions, its therapeutic applications are restricted. Efforts have been made to develop an enormous number of NO-releasing molecules (NORMs) and motifs for NO delivery to the target tissues. These NORMs involve organic nitrate, nitrite, nitro compounds, transition metal nitrosyls, and several nanomaterials. The controlled release of NO from these NORMs to the specific site requires several external stimuli like light, sound, pH, heat, enzyme, etc. Herein, we have provided a comprehensive review of the biochemistry of nitric oxide, recent advancements in NO-releasing materials with the appropriate stimuli of NO release, and their biomedical applications in cancer and other disease control.

The hydroxamic acid derivative YPX-C-05 alleviates hypertension and vascular dysfunction through the PI3K/Akt/eNOS pathway

BACKGROUND

Hypertension is a prevalent cardiovascular disease characterized by elevated blood pressure and increased vascular resistance. HDAC inhibitors have emerged as potential therapeutic agents due to their ability to modulate gene expression and cellular processes. YPX-C-05, a novel hydroxamic acid-based HDAC inhibitor, shows promise in its vasodilatory effects and potential targets for hypertension treatment. In this study, we aimed to elucidate the mechanisms underlying YPX-C-05's vasodilatory effects and explore its therapeutic potential in hypertension.

METHODS

To determine the ex vivo vasodilatory effects of YPX-C-05, isolated aortic rings precontracted with phenylephrine were used. We assessed YPX-C-05's inhibitory effects on HDACs and its impact on histone H4 deacetylation levels in endothelial cells. Network pharmacology analysis was employed to predict putative targets of YPX-C-05 for hypertension treatment. To investigate the involvement of the PI3K/Akt/eNOS pathway, we employed enzyme-linked immunosorbent assay and to assess the levels of NO, ET-1, BH2, and BH4 in human umbilical vein endothelial cells. And we also analyzed the mRNA expression of eNOS and ET-1. Furthermore, Western blotting was conducted to quantify the phosphorylated and total Akt and eNOS levels in human umbilical vein endothelial cell lysates following treatment with YPX-C-05. In order to elucidate the vasodilatory mechanism of YPX-C-05, we employed pharmacological inhibitors for evaluation purposes. Furthermore, we evaluated the chronic antihypertensive effects of YPX-C-05 on N-omega-nitro-L-arginine-induced hypertensive mice in an in vivo model. Vascular remodeling was assessed through histological analysis.

RESULTS

Our findings demonstrated that YPX-C-05 exerts significant vasodilatory effects in isolated aortic rings precontracted with phenylephrine. Furthermore, YPX-C-05 exhibited inhibitory effects on HDACs and increased histone H4 acetylation in endothelial cells. Network pharmacology analysis predicted YPX-C-05 might activate endothelial eNOS via PI3K/Akt signaling pathway. Inhibition of the PI3K/Akt/eNOS pathway attenuated the vasodilatory effects of YPX-C-05, as evidenced by reduced levels of phosphorylated Akt and eNOS in human umbilical vein endothelial cell lysates. The chronic administration of YPX-C-05 in N-omega-nitro-L-arginine-induced hypertensive mice resulted in significant antihypertensive effects. Histological analysis demonstrated a reduction in vascular remodeling, further supporting the therapeutic potential of YPX-C-05 in hypertension.

CONCLUSION

This study demonstrates for the first time that the novel hydroxamic acid-based HDAC inhibitor YPX-C-05 produces significant antihypertensive and vasodilatory effects through the PI3K/Akt/eNOS pathway. Our findings support the developing prospect of YPX-C-05 as a novel antihypertensive drug.

Non-histone protein acetylation by the evolutionarily conserved GCN5 and PCAF acetyltransferases

GCN5, conserved from yeast to humans, and the vertebrate specific PCAF, are lysine acetyltransferase enzymes found in large protein complexes. Both enzymes have well documented roles in the histone acetylation and the concomitant regulation of transcription. However, these enzymes also acetylate non-histone substrates to impact diverse aspects of cell physiology. Here, I review our current understanding of non-histone acetylation by GCN5 and PCAF across eukaryotes, from target identification to molecular mechanism and regulation. I focus mainly on budding yeast, where Gcn5 was first discovered, and mammalian systems, where the bulk of non-histone substrates have been characterized. I end the review by defining critical caveats and open questions that apply to all models.

Misconceptions in acute heart failure diagnosis and Management in the Emergency Department

INTRODUCTION

Acute heart failure (AHF) accounts for a significant number of emergency department (ED) visits, and the disease may present along a spectrum with a variety of syndromes.

OBJECTIVE

This review evaluates several misconceptions concerning heart failure evaluation and management in the ED, followed by several pearls.

DISCUSSION

AHF is a heterogeneous syndrome with a variety of presentations. Physicians often rely on natriuretic peptides, but the evidence behind their use is controversial, and these should not be used in isolation. Chest radiograph is often considered the most reliable imaging test, but bedside ultrasound (US) provides a more sensitive and specific evaluation for AHF. Diuretics are a foundation of AHF management, but in pulmonary edema, these medications should only be provided after vasodilator administration, such as nitroglycerin. Nitroglycerin administered in high doses for pulmonary edema is safe and effective in reducing the need for intensive care unit admission. Though classically dopamine is the first vasopressor utilized in patients with hypotensive cardiogenic shock, norepinephrine is associated with improved outcomes and lower mortality. Disposition is complex in patients with AHF, and risk stratification tools in conjunction with other assessments allow physicians to discharge patients safely with follow up.

CONCLUSION

A variety of misconceptions surround the evaluation and management of heart failure including clinical assessment, natriuretic peptide use, chest radiograph and US use, nitroglycerin and diuretics, vasopressor choice, and disposition. This review evaluates these misconceptions while providing physicians with updates in evaluation and management of AHF.

The Role of Nitroglycerin and Other Nitrogen Oxides in Cardiovascular Therapeutics

The use of nitroglycerin in the treatment of angina pectoris began not long after its original synthesis in 1847. Since then, the discovery of nitric oxide as a biological effector and better understanding of its roles in vasodilation, cell permeability, platelet function, inflammation, and other vascular processes have advanced our knowledge of the hemodynamic (mostly mediated through vasodilation of capacitance and conductance arteries) and nonhemodynamic effects of organic nitrate therapy, via both nitric oxide-dependent and -independent mechanisms. Nitrates are rapidly absorbed from mucous membranes, the gastrointestinal tract, and the skin; thus, nitroglycerin is available in a number of preparations for delivery via several routes: oral tablets, sublingual tablets, buccal tablets, sublingual spray, transdermal ointment, and transdermal patch, as well as intravenous formulations. Organic nitrates are commonly used in the treatment of cardiovascular disease, but clinical data limit their use mostly to the treatment of angina. They are also used in the treatment of subsets of patients with heart failure and pulmonary hypertension. One major limitation of the use of nitrates is the development of tolerance. Although several agents have been studied for use in the prevention of nitrate tolerance, none are currently recommended owing to a paucity of supportive clinical data. Only 1 method of preventing nitrate tolerance remains widely accepted: the use of a dosing strategy that provides an interval of no or low nitrate exposure during each 24-h period. Nitric oxide's important role in several cardiovascular disease mechanisms continues to drive research toward finding novel ways to affect both endogenous and exogenous sources of this key molecular mediator.

Histone Deacetylase Inhibitors Relax Mouse Aorta Partly through Their Inhibitory Action on L-Type Ca2+ Channels

Histone deacetylase (HDAC) inhibitors modulate acetylation/deacetylation of histone and nonhistone proteins. They have been widely used for cancer treatment. However, there have been only a few studies investigating the effect of HDAC inhibitors on vascular tone regulation, most of which employed chronic treatment with HDAC inhibitors. In the present study, we found that two hydroxamate-based pan-HDAC inhibitors, suberoylanilide hydroxamic acid (SAHA) and trichostatin A (TSA), could partially but acutely relax high extracellular K⁺-contracted mouse aortas. SAHA and TSA also attenuated the high extracellular K⁺-induced cytosolic Ca²⁺ rise and inhibited L-type Ca²⁺ channel current in whole-cell patch-clamp. These data demonstrate that SAHA could inhibit L-type Ca²⁺ channels to cause vascular relaxation. In addition, SAHA and TSA dose dependently relaxed the arteries precontracted with phenylephrine. The relaxant effect of SAHA and TSA was greater in phenylephrine-precontracted arteries than in high K⁺-contracted arteries. Although part of the relaxant effect of SAHA and TSA on phenylephrine-precontracted arteries was related to L-type Ca²⁺ channels, both agents could also induce relaxation via a mechanism independent of L-type Ca²⁺ channels. Taken together, HDAC inhibitors SAHA and TSA can acutely relax blood vessels via their inhibitory action on L-type Ca²⁺ channels and via another L-type Ca²⁺ channel-independent mechanism.

Phenylephrine-induced cardiac hypertrophy is attenuated by a histone acetylase inhibitor anacardic acid in mice

Cardiac hypertrophy is a complex process involving highly coordinated but tight regulation of multiple elements, such as in epigenetics, which make an important contribution to myocardium remodeling and cardiac hypertrophy. Epigenetic regulations, particularly histone acetylation, have been implicated in cardiac hypertrophy, however, the exact mechanism is still largely unknown. In the present study, we explored the potential attenuating effects of Chinese herbal extract anacardic acid on phenylephrine-induced cardiac hypertrophy and the underlying mechanism. The mouse cardiac hypertrophy model was established and the hearts were collected from C57BL/6 mice for further analyses. The data showed that anacardic acid modulated the cardiac genes expression and attenuated the phenylephrine-induced cardiac hypertrophy via the suppression of histone acetylases activity and downstream cardiac genes. In addition, anacardic acid abrogated histone and MEF2A acetylation and DNA-binding activity by blocking p300-HAT and PCAF-HAT activities. In addition, anacardic acid normalized the cardiac hypertrophy-related genes expressions (ANP, BNP, cTnT, cTnI, β-MHC, and Cx43) induced by phenylephrine at the level of transcription and translation. In addition, anacardic acid did not affect the blood routine index, hepatic function, renal function, and myocardial enzymes. Therefore, anacardic acid may prove to be a candidate drug to cure hypertrophic cardiomyopathy.

Effect of Shenmai injection on preventing the development of nitroglycerin-induced tolerance in rats

Long-term nitroglycerin (NTG) therapy causes tolerance to its effects attributing to increased oxidative stress and endothelial dysfunction. Shenmai injection (SMI), which is clinically used to treat cardiovascular diseases, consists of two herbal medicines, Ginseng Rubra and Ophiopogonjaponicas, and is reported to have antioxidant effects. The present study was designed to investigate the potential preventive effects of Shenmai injection on development of nitroglycerin-induced tolerance. The present study involves both in vivo and in vitro experiments to investigate nitroglycerin-induced tolerance. We examined the effect of Shenmai injection on the cardiovascular oxidative stress by measuring the serum levels of malondialdehyde (MDA) and superoxide dismutase (SOD). Endothelial dysfunction was determined by an endothelium-dependent vasorelaxation method in aortic rings and NOS activity. Inhibition of the cGMP/cGK-I signalling pathway was determined from released serum levels of cGMP and the protein expression levels of sGC, cGK-I, PDE1A and P-VASP by western blot. Here, we showed that SMI ameliorated the decrease in AV Peak Vel, the attenuation in the vasodilation response to nitroglycerin and endothelial dysfunction. SMI also reduced the cardiovascular oxidative stress by reducing the release of MDA and increasing the activity of SOD. Shenmai injection further ameliorated inhibition of the cGMP/cGK-I signalling pathway triggered by nitroglycerin-induced tolerance through up-regulating the protein expression of sGC, cGK-I, and P-VASP and down- regulating the proteins expression of PDE1A. In vitro studies showed that Shenmai injection could recover the attenuated vasodilation response to nitroglycerin following incubation (of aortic rings) with nitroglycerin via activating the enzymes of sGC and cGK-I. Therefore, we conclude that Shenmai injection could prevent NTG nitroglycerin-induced tolerance at least in part by decreasing the cardiovascular oxidative stress, meliorating the endothelial dysfunction and ameliorating the inhibition of the cGMP/cGK-I signalling pathway. These findings indicate the potential of Shenmai injection (SMI) as a promising medicine for preventing the development of nitroglycerin-induced tolerance.

Bromodomain inhibitors and cancer therapy: From structures to applications

Aberrations in the epigenetic landscape are a hallmark of cancer. Alterations in enzymes that are “writers,” “erasers,” or “readers” of histone modification marks are common. Bromodomains are “readers” that bind acetylated lysines in histone tails. Their most important function is the regulation of gene transcription by the recruitment of different molecular partners. Moreover, proteins containing bromodomains are also epigenetic regulators, although little is known about the specific function of these domains. In recent years, there has been increasing interest in developing small molecules that can target specific bromodomains. First, this has helped clarify biological functions of bromodomain-containing proteins. Secondly, it opens a new front for combatting cancer. In this review we will describe the structures and mechanisms associated with Bromodomain and Extra-Terminal motif (BET) inhibitors and non-BET inhibitors, their current status of development, and their promising role as anti-cancer agents.

Histone acetyltransferases: challenges in targeting bi-substrate enzymes

Histone acetyltransferases (HATs) are epigenetic enzymes that install acetyl groups onto lysine residues of cellular proteins such as histones, transcription factors, nuclear receptors, and enzymes. HATs have been shown to play a role in diseases ranging from cancer and inflammatory diseases to neurological disorders, both through acetylations of histone proteins and non-histone proteins. Several HAT inhibitors, like bi-substrate inhibitors, natural product derivatives, small molecules, and protein–protein interaction inhibitors, have been developed. Despite their potential, a large gap remains between the biological activity of inhibitors in in vitro studies and their potential use as therapeutic agents. To bridge this gap, new potent HAT inhibitors with improved properties need to be developed. However, several challenges have been encountered in the investigation of HATs and HAT inhibitors that hinder the development of new HAT inhibitors. HATs have been shown to function in complexes consisting of many proteins. These complexes play a role in the activity and target specificity of HATs, which limits the translation of in vitro to in vivo experiments. The current HAT inhibitors suffer from undesired properties like anti-oxidant activity, reactivity, instability, low potency, or lack of selectivity between HAT subtypes and other enzymes. A characteristic feature of HATs is that they are bi-substrate enzymes that catalyze reactions between two substrates: the cofactor acetyl coenzyme A (Ac-CoA) and a lysine-containing substrate. This has important—but frequently overlooked—consequences for the determination of the inhibitory potency of small molecule HAT inhibitors and the reproducibility of enzyme inhibition experiments. We envision that a careful characterization of molecular aspects of HATs and HAT inhibitors, such as the HAT catalytic mechanism and the enzyme kinetics of small molecule HAT inhibitors, will greatly improve the development of potent and selective HAT inhibitors and provide validated starting points for further development towards therapeutic agents.

Nitrates as a Treatment of Acute Heart Failure

The purpose of this article is to review the clinical efficacy and safety of nitrates in acute heart failure (AHF) by examining various trials on nitrates in AHF. Management of AHF can be challenging due to the lack of objective clinical evidence guiding optimal management. There have been many articles suggesting that, despite a benefit, nitrates are underused in clinical practice. Nitrates, when appropriately dosed, have a favourable effect on symptoms, blood pressure, intubation rates, mortality and other parameters.

Organic Nitrate Therapy, Nitrate Tolerance, and Nitrate-Induced Endothelial Dysfunction: Emphasis on Redox Biology and Oxidative Stress

Organic nitrates, such as nitroglycerin (GTN), isosorbide-5-mononitrate and isosorbide dinitrate, and pentaerithrityl tetranitrate (PETN), when given acutely, have potent vasodilator effects improving symptoms in patients with acute and chronic congestive heart failure, stable coronary artery disease, acute coronary syndromes, or arterial hypertension. The mechanisms underlying vasodilation include the release of •NO or a related compound in response to intracellular bioactivation (for GTN, the mitochondrial aldehyde dehydrogenase [ALDH-2]) and activation of the enzyme, soluble guanylyl cyclase. Increasing cyclic guanosine-3',-5'-monophosphate (cGMP) levels lead to an activation of the cGMP-dependent kinase I, thereby causing the relaxation of the vascular smooth muscle by decreasing intracellular calcium concentrations. The hemodynamic and anti-ischemic effects of organic nitrates are rapidly lost upon long-term (low-dose) administration due to the rapid development of tolerance and endothelial dysfunction, which is in most cases linked to increased intracellular oxidative stress. Enzymatic sources of reactive oxygen species under nitrate therapy include mitochondria, NADPH oxidases, and an uncoupled •NO synthase. Acute high-dose challenges with organic nitrates cause a similar loss of potency (tachyphylaxis), but with distinct pathomechanism. The differences among organic nitrates are highlighted regarding their potency to induce oxidative stress and subsequent tolerance and endothelial dysfunction. We also address pleiotropic effects of organic nitrates, for example, their capacity to stimulate antioxidant pathways like those demonstrated for PETN, all of which may prevent adverse effects in response to long-term therapy. Based on these considerations, we will discuss and present some preclinical data on how the nitrate of the future should be designed.

Lysine acetyltransfer supports platelet function

BACKGROUND AND OBJECTIVES

The reversible acetylation of protein lysine ε-amino groups, catalyzed by lysine acetyltransferases and deacetylases, serves as a molecular switch in the orchestration of diverse cellular activities. Here, we aimed to investigate the role of lysine acetyltransfer in platelet function.

METHODS AND RESULTS

Proteomics methods identified 552 acetyllysine (acK) modifications on 273 platelet proteins that serve as candidate substrates for lysine acetyltransferases. Bioinformatics analyses of the identified acK-modified platelet proteins supported roles for the lysine acetyltransferase p300 in the regulation of actin-mediated platelet processes. Biochemical experiments showed that platelets express p300, which is activated in an Src kinase-dependent manner upon platelet stimulation with the platelet glycoprotein VI agonist collagen-related peptide (CRP). Inhibition of platelet p300 abrogated CRP-stimulated lysine acetylation of actin, filamin, and cortactin, as well as F-actin polymerization, integrin activation, and platelet aggregation. Super-resolution visualization of platelet actin-rich adhesion structures revealed abundant acK protein colocalized with platelet actin cytoskeletal proteins. Inhibition of p300 blocked platelet filopodium formation and the spreading of platelets on fibrinogen and collagen surfaces. In whole blood, p300 inhibition prevented the formation of platelet aggregates under shear, suggesting a physiologic role for lysine acetyltransferase activity in platelet function.

CONCLUSION

Together, our findings reveal lysine acetyltransfer to be a potential regulator of platelet actin dynamics, and potential roles for lysine acetylation in the molecular coordination of platelet activation and function.

Trichostatin A Modulates Angiotensin II-induced Vasoconstriction and Blood Pressure Via Inhibition of p66shc Activation

Histone deacetylase (HDAC) has been recognized as a potentially useful therapeutic target for cardiovascular disorders. However, the effect of the HDAC inhibitor, trichostatin A (TSA), on vasoreactivity and hypertension remains unknown. We performed aortic coarctation at the inter-renal level in rats in order to create a hypertensive rat model. Hypertension induced by abdominal aortic coarctation was significantly suppressed by chronic treatment with TSA (0.5 mg/kg/day for 7 days). Nicotinamide adenine dinucleotide phosphate-driven reactive oxygen species production was also reduced in the aortas of TSA-treated aortic coarctation rats. The vasoconstriction induced by angiotensin II (Ang II, 100 nM) was inhibited by TSA in both endothelium-intact and endothelium-denuded rat aortas, suggesting that TSA has mainly acted in vascular smooth muscle cells (VSMCs). In cultured rat aortic VSMCs, Ang II increased p66shc phosphorylation, which was inhibited by the Ang II receptor type I (AT1R) inhibitor, valsartan (10 µM), but not by the AT2R inhibitor, PD123319. TSA (1~10 µM) inhibited Ang II-induced p66shc phosphorylation in VSMCs and in HEK293T cells expressing AT1R. Taken together, these results suggest that TSA treatment inhibited vasoconstriction and hypertension via inhibition of Ang II-induced phosphorylation of p66shc through AT1R.

Redox regulation of genome stability by effects on gene expression, epigenetic pathways and DNA damage/repair

Reactive oxygen and nitrogen species (e.g. H2O2, nitric oxide) confer redox regulation of essential cellular signaling pathways such as cell differentiation, proliferation, migration and apoptosis. In addition, classical regulation of gene expression or activity, including gene transcription to RNA followed by translation to the protein level, by transcription factors (e.g. NF-κB, HIF-1α) and mRNA binding proteins (e.g. GAPDH, HuR) is subject to redox regulation. This review will give an update of recent discoveries in this field, and specifically highlight the impact of reactive oxygen and nitrogen species on DNA repair systems that contribute to genomic stability. Emphasis will be placed on the emerging role of redox mechanisms regulating epigenetic pathways (e.g. miRNA, DNA methylation and histone modifications). By providing clinical correlations we discuss how oxidative stress can impact on gene regulation/activity and vise versa, how epigenetic processes, other gene regulatory mechanisms and DNA repair can influence the cellular redox state and contribute or prevent development or progression of disease.

A novel cell-permeable, selective, and noncompetitive inhibitor of KAT3 histone acetyltransferases from a combined molecular pruning/classical isosterism approach

Selective inhibitors of the two paralogue KAT3 acetyltransferases (CBP and p300) may serve not only as precious chemical tools to investigate the role of these enzymes in physiopathological mechanisms but also as lead structures for the development of further antitumor agents. After the application of a molecular pruning approach to the hardly optimizable and not very cell-permeable garcinol core structure, we prepared many analogues that were screened for their inhibitory effects using biochemical and biophysical (SPR) assays. Further optimization led to the discovery of the benzylidenebarbituric acid derivative 7h (EML425) as a potent and selective reversible inhibitor of CBP/p300, noncompetitive versus both acetyl-CoA and a histone H3 peptide, and endowed with good cell permeability. Furthermore, in human leukemia U937 cells, it induced a marked and time-dependent reduction in the acetylation of lysine H4K5 and H3K9, a marked arrest in the G0/G1 phase and a significant increase in the hypodiploid nuclei percentage.

Identification of structural features of 2-alkylidene-1,3-dicarbonyl derivatives that induce inhibition and/or activation of histone acetyltransferases KAT3B/p300 and KAT2B/PCAF

Dysregulation of the activity of lysine acetyltransferases (KATs) is related to a variety of diseases and/or pathological cellular states; however, their role remains unclear. Therefore, the development of selective modulators of these enzymes is of paramount importance, because these molecules could be invaluable tools for assessing the importance of KATs in several pathologies. We recently found that diethyl pentadecylidenemalonate (SPV106) possesses a previously unobserved inhibitor/activator activity profile against protein acetyltransferases. Herein, we report that manipulation of the carbonyl functions of a series of analogues of SPV106 yielded different activity profiles against KAT2B and KAT3B (pure KAT2B activator, pan-inhibitor, or mixed KAT2B activator/KAT3B inhibitor). Among the novel compounds, a few derivatives may be useful chemical tools for studying the mechanism of lysine acetylation and its implications in physiological and/or pathological processes.

Organic nitrates: update on mechanisms underlying vasodilation, tolerance and endothelial dysfunction

Given acutely, organic nitrates, such as nitroglycerin (GTN), isosorbide mono- and dinitrates (ISMN, ISDN), and pentaerythrityl tetranitrate (PETN), have potent vasodilator and anti-ischemic effects in patients with acute coronary syndromes, acute and chronic congestive heart failure and arterial hypertension. During long-term treatment, however, side effects such as nitrate tolerance and endothelial dysfunction occur, and therapeutic efficacy of these drugs rapidly vanishes. Recent experimental and clinical studies have revealed that organic nitrates per se are not just nitric oxide (NO) donors, but rather a quite heterogeneous group of drugs considerably differing for mechanisms underlying vasodilation and the development of endothelial dysfunction and tolerance. Based on this, we propose that the term nitrate tolerance should be avoided and more specifically the terms of GTN, ISMN and ISDN tolerance should be used. The present review summarizes preclinical and clinical data concerning organic nitrates. Here we also emphasize the consequences of chronic nitrate therapy on the supersensitivity of the vasculature to vasoconstriction and on the increased autocrine expression of endothelin. We believe that these so far rather neglected and underestimated side effects of chronic therapy with at least GTN and ISMN are clinically important.

The histone acetylase activator pentadecylidenemalonate 1b rescues proliferation and differentiation in the human cardiac mesenchymal cells of type 2 diabetic patients

This study investigates the diabetes-associated alterations present in cardiac mesenchymal cells (CMSC) obtained from normoglycemic (ND-CMSC) and type 2 diabetic patients (D-CMSC), identifying the histone acetylase (HAT) activator pentadecylidenemalonate 1b (SPV106) as a potential pharmacological intervention to restore cellular function. D-CMSC were characterized by a reduced proliferation rate, diminished phosphorylation at histone H3 serine 10 (H3S10P), decreased differentiation potential, and premature cellular senescence. A global histone code profiling of D-CMSC revealed that acetylation on histone H3 lysine 9 (H3K9Ac) and lysine 14 (H3K14Ac) was decreased, whereas the trimethylation of H3K9Ac and lysine 27 significantly increased. These observations were paralleled by a downregulation of the GCN5-related N-acetyltransferases (GNAT) p300/CBP-associated factor and its isoform 5-α general control of amino acid synthesis (GCN5a), determining a relative decrease in total HAT activity. DNA CpG island hypermethylation was detected at promoters of genes involved in cell growth control and genomic stability. Remarkably, treatment with the GNAT proactivator SPV106 restored normal levels of H3K9Ac and H3K14Ac, reduced DNA CpG hypermethylation, and recovered D-CMSC proliferation and differentiation. These results suggest that epigenetic interventions may reverse alterations in human CMSC obtained from diabetic patients.

Evaluation of a large library of (thiazol-2-yl)hydrazones and analogues as histone acetyltransferase inhibitors: enzyme and cellular studies

Recently we described some (thiazol-2-yl)hydrazones as antiprotozoal, antifungal and anti-MAO agents as well as Gcn5 HAT inhibitors. Among these last compounds, CPTH2 and CPTH6 showed HAT inhibition in cells and broad anticancer properties. With the aim to identify HAT inhibitors more potent than the two prototypes, we synthesized several new (thiazol-2-yl)hydrazones including some related thiazolidines and pyrimidin-4(3H)-ones, and we tested the whole library existing in our lab against human p300 and PCAF HAT enzymes. Some compounds (1x, 1c', 1d', 1i' and 2m) were more efficient than CPTH2 and CPTH6 in inhibiting the p300 HAT enzyme. When tested in human leukemia U937 and colon carcinoma HCT116 cells (100 μM, 30 h), 1x, 1i' and 2m gave higher (U937 cells) or similar (HCT116 cells) apoptosis than CPTH6, and were more potent than CPTH6 in inducing cytodifferentiation (U937 cells).

Quinoline-based p300 histone acetyltransferase inhibitors with pro-apoptotic activity in human leukemia U937 cells

Chemical manipulations performed on 2-methyl-3-carbethoxyquinoline (1), a histone acetyltransferase inhibitor previously identified by our research group and active at the sub-millimolar/millimolar level, led to compounds bearing higher alkyl groups at the C2-quinoline or additional side chains at the C6-quinoline positions. Such compounds displayed at least threefold improved inhibitory potency toward p300 protein lysine acetyltransferase activity; some of them decreased histone H3 and H4 acetylation levels in U937 cells and induced high degrees of apoptosis (three compounds >10-fold higher than compound 1) after treatment of U937 cells.

Lysine deacetylase inhibition promotes relaxation of arterial tone and C-terminal acetylation of HSPB6 (Hsp20) in vascular smooth muscle cells

There is increasing interest in establishing the roles that lysine acetylation of non nuclear proteins may exert in modulating cell function. Lysine deacetylase 8 (KDAC8), for example, has been suggested to interact with α-actin and control the differentiation of smooth muscle cells. However, a direct role of smooth muscle non nuclear protein acetylation in regulating tone is unresolved. We sought to define the actions of two separate KDAC inhibitors on arterial tone and identify filament-interacting protein targets of acetylation and association with KDAC8. Compound 2 (a specific KDAC8 inhibitor) or Trichostatin A (TSA, a broad-spectrum KDAC inhibitor) inhibited rat arterial contractions induced by phenylephrine (PE) or high potassium solution. In contrast to the predominantly nuclear localization of KDAC1 and KDAC2, KDAC8 was positioned in extranuclear areas of native vascular smooth muscle cells. Several filament-associated proteins identified as putative acetylation targets colocalized with KDAC8 by immunoprecipitation (IP): cortactin, α-actin, tropomyosin, HSPB1 (Hsp27) and HSPB6 (Hsp20). Use of anti-acetylated lysine antibodies showed that KDAC inhibition increased acetylation of each protein. A custom-made antibody targeting the C-terminal acetylated lysine of human HSPB6 identified this as a novel target of acetylation that was increased by KDAC inhibition. HSPB6 phosphorylation, a known vasodilatory modification, was concomitantly increased. Interrogation of publicly available mass spectrometry data identified 50 other proteins with an acetylated C-terminal lysine. These novel data, in alliance with other recent studies, alert us to the importance of elucidating the mechanistic links between changes in myofilament-associated protein acetylation, in conjunction with other posttranslational modifications, and the regulation of arterial tone.

Epigenetic regulation in vascular cells

PURPOSE OF REVIEW

This review summarizes recent findings in the epigenetics of vascular cells and discusses the new challenges for therapeutic strategies of cardiovascular diseases.

RECENT FINDINGS

There is emerging optimism that epigenetic mechanisms can provide the missing link to connect (epi)genomes with the cause of complex diseases. Environmental factors like intrauterine conditions during fetal development appear to preprogram humans for complex diseases. The purpose of this review is to summarize the newest results about the inheritable epigenetic features of cardiovascular diseases. Also, the recently discovered role of small RNAs in epigenetic gene regulation is discussed.

SUMMARY

Epigenetic mechanisms of gene regulation will likely become major determinants in the pathogenesis of complex diseases and may offer new opportunities for the treatment of these diseases.

More answers to the still unresolved question of nitrate tolerance

Organic nitrates are traditionally felt to be a safe adjuvant in the chronic therapy of patients with coronary artery disease. Despite their long use, progress in the understanding of the pharmacology and mechanism of action of these drugs has been achieved only in the last two decades, with the identification of the role of oxidative stress in the pathophysiology of nitrate tolerance, with, the discovery of the ancillary effects of nitrates, and with the demonstration that nitrate therapy has important chronic side effects that might modify patients' prognosis. These advances are however mostly confined to the molecular level or to studies in healthy volunteers, and the true impact of organic nitrates on clinical outcome remains unknown. Complicating this issue, evidence supports the existence of important differences among the different drugs belonging to the group, and there are reasons to believe that the nitrates should not be treated as a homogeneous class. As well, the understanding of the effects of alternative nitric oxide (NO) donors is currently being developed, and future studies will need to test whether the properties of these new medications may compensate and prevent the abnormalities imposed by chronic nitrate therapy. Intermittent therapy with nitroglycerin and isosorbide mononitrate is now established in clinical practice, but they should neither be considered a definitive solution to the problem of nitrate tolerance. Both these strategies are not deprived of complications, and should currently be seen as a compromise rather than a way fully to exploit the benefits of NO donor therapy.

A nitric oxide-dependent cross-talk between class I and III histone deacetylases accelerates skin repair

In a mouse model of skin repair we found that the class I-IIa histone deacetylase inhibitor trichostatin A accelerated tissue regeneration. Unexpectedly, this effect was suppressed by Sirtinol, a class III histone deacetylase (HDAC) (sirtuin)-selective inhibitor. The role of sirtuins (SIRTs) was then investigated by using resveratrol and a novel SIRT1-2-3 activator, the MC2562 compound we synthesized recently. Both resveratrol and MC2562 were effective in accelerating wound repair. The local administration of natural or synthetic SIRT activators, in fact, significantly accelerated skin regeneration by increasing keratinocyte proliferation. In vitro experiments revealed that the activation of SIRTs stimulated keratinocyte proliferation via endothelial NO synthase phosphorylation and NO production. In this condition, the class I member HDAC2 was found S-nitrosylated on cysteine, a post-transduction modification associated with loss of activity and DNA binding capacity. After deacetylase inhibitor or SIRT activator treatment, ChIP showed, in fact, a significant HDAC2 detachment from the promoter region of insulin growth factor I (IGF-I), fibroblast growth factor 10 (FGF-10), and Epithelial Growth Factor (EGF), which may be the final recipients and effectors of the SIRT-NO-HDAC signaling cascade. Consistently, the effect of SIRT activators was reduced in the presence of NG-nitro-L-arginine methyl ester (L-NAME), a general inhibitor of NO synthesis. In conclusion, the NO-dependent cross-talk among class III and I histone deacetylases suggests an unprecedented signaling pathway important for skin repair.