Targeting the correct HDAC(s) to treat cognitive disorders

Epigenetic differences at the HTR2A locus in progressive multiple sclerosis patients

The pathology of progressive multiple sclerosis (MS) is poorly understood. We have previously assessed DNA methylation in the CD4⁺ T cells of relapsing–remitting (RR) MS patients compared to healthy controls and identified differentially methylated regions (DMRs) in HLA-DRB1 and RNF39. This study aimed to investigate the DNA methylation profiles of the CD4⁺ T cells of progressive MS patients. DNA methylation was measured in two separate case/control cohorts using the Illumina 450K/EPIC arrays and data was analysed with the Chip Analysis Methylation Pipeline (ChAMP). Single nucleotide polymorphisms (SNPs) were assessed using the Illumina Human OmniExpress24 arrays and analysed using PLINK. Expression was assessed using the Illumina HT12 array and analysed in R using a combination of Limma and Illuminaio. We identified three DMRs at HTR2A, SLC17A9 and HDAC4 that were consistent across both cohorts. The DMR at HTR2A is located within the bounds of a haplotype block; however, the DMR remained significant after accounting for SNPs in the region. No expression changes were detected in any DMRs. HTR2A is differentially methylated in progressive MS independent of genotype. This differential methylation is not evident in RRMS, making it a potential biomarker of progressive disease.

Effects of exercise and pharmacological inhibition of histone deacetylases (HDACs) on epigenetic regulations and gene expressions crucial for neuronal plasticity in the motor cortex

The objective of this study was to examine the effect of epigenetic treatment using an histone deacetylases (HDAC) inhibitor in addition to aerobic exercise on the epigenetic markers and neurotrophic gene expressions in the motor cortex, to find a more enriched brain pre-conditioning for motor learning in neurorehabilitation. ICR mice were divided into four groups based on two factors: HDAC inhibition and exercise. Intraperitoneal administration of an HDAC inhibitor (1.2 g/kg sodium butyrate, NaB) and treadmill exercise (approximately at 10 m/min for 60 min) were conducted five days a week for four weeks. NaB administration inhibited total HDAC activity and enhanced acetylation level of histones specifically in histone H4, accompanying the increase of transcription levels of immediate-early genes (IEGs) (c-fos and Arc) and neurotrophins (BDNF and NT-4) crucial for neuroplasticity in the motor cortex. However, exercise enhanced HDAC activity and acetylation level of histone H4 and H3 without the modification of transcription levels. In addition, there were no synergic effects between HDAC inhibition and the exercise regime on the gene expressions. This study showed that HDAC inhibition could present more enriched condition for neuroplasticity to the motor cortex. However, exercise-induced neurotrophic gene expressions could depend on exercise regimen based on the intensity, the term etc. Therefore, this study has a novelty suggesting that pharmacological HDAC inhibition could be an alternative potent approach to present a neuronal platform with enriched neuroplasticity for motor learning and motor recovery, however, an appropriate exercise regimen is expected in this approach.

Myricitrin ameliorates cognitive deficits in MCAO cerebral stroke rats via histone acetylation-induced alterations of brain-derived neurotrophic factor

The present study screened the effect of Myricitrin on cognitive deficits post-cerebral ischemic stroke and the involved mechanism. The rats were submitted to middle cerebral artery occlusion (MCAO) and were treated with sodium butyrate or Myricitrin (15 and 30 mg/kg) for 28 days. The spatial memory was studied by Morris water maze (MWM). After 4 weeks, the rats were euthanized and hippocampus region was utilized for neurochemical and biochemical changes. The extent of histone acetylation was studied by ELISA. Protein levels were analyzed by Western blot analysis. The mRNA levels were analyzed by polymerase chain reaction (PCR). In silico bioinformatics docking studies were done for target confirmation of Myricitrin. The treatment of Myricitrin showed improved memory in MWM compared to rats treated with vehicle, and the effects of Myricitrin were similar to sodium butyrate-treated rats. At a dose of 30 mg/kg Myricitrin, the histone deacetylase content was decreased, the expression levels of BDNF were increased, the levels of acetylated H3 and H4 along with Syn-I in the hippocampus region were over-expressed compared to control vehicle-treated rats. However, at low dose, i.e., 15 mg/kg Myricitrin failed to show alterations in biochemical as well as neurochemical markers. Docking studies suggested the BDNF and Sun-I as potential target proteins of Myricitrin. The cognitive ameliorating effect of Myricitrin post-cerebral ischemia stroke can be attributed to increased expression of BDNF and Syn-I and modulation of histone acetylation.

Inhibition of Histone Methyltransferases EHMT1/2 Reverses Amyloid-β-Induced Loss of AMPAR Currents in Human Stem Cell-Derived Cortical Neurons

Emerging evidence suggests that epigenetic dysregulation of gene expression is one of the key molecular mechanisms of neurodegeneration and Alzheimer's disease (AD). However, little is known about the role of epigenetic dysregulation on synaptic dysfunction in humans, because of the difficulties of obtaining live human neurons. Here we generated mature human cortical neurons differentiated from human embryonic stem cells, and exposed them to amyloid-β (Aβ). We found that the histone methyltransferase, EHMT1, which catalyzes histone lysine 9 dimethylation (H3K9me2, a mark for gene repression), was significantly elevated in Aβ-treated human stem cell-derived neurons. Aβ treatment led to a significant reduction of AMPAR-mediated whole-cell current and excitatory postsynaptic current. Application of BIX01294, a selective inhibitor of EHMT1/2, restored AMPAR currents and glutamatergic synaptic transmission in Aβ-treated human cortical neurons. These results suggest that inhibition of the aberrant histone methylation is a novel approach to reverse Aβ-induced synaptic deficits in human neurons.

Oleuropein Improved Post Cerebral Stroke Cognitive Function by Promoting Histone Acetylation and Phosphorylation of cAMP Response Element-Binding Protein in MCAO Rats

Background:

Post-stroke cognitive impairment (PSCI) is commonest clinical disorder in which peripheral cholinergic activity is important. Oleuropein (OLP) is polyphenol is present in olive oil. Here we evaluated the effect of OLP in cognitive dysfunction rats in post cerebral stroke model.

Methods:

The post cerebral stroke cognitive dysfunction PSD rat model was created by occlusion of transient middle cerebral artery. The rats were divided into 6 groups named, Sham + Vehicle, Sham + OLP (50 mg/kg), PSD rats + Vehicle, PSD rats + OLP (20, 50 or 100 mg/kg). The spatial learning was assessed by Morris water maze (MWM). The expression of choline acetyltransferase (ChAT), acetylcholine (ACH), extent of histone acetylation and phosphorylation of cAMP response element-binding protein (CREB) were evaluated by Western blot assay and immunofluorescence staining.

Results:

Treatment of OLP at various doses showed higher number of spontaneous and rewarded alterations and lesser percentage bias compared to vehicle treated PSD rats. OLP resulted in decreased levels of ChAT and ACH, whereas the degree of histone acetylation and phosphorylation of CREB improved in dose dependent pattern.

Conclusion:

treatment of OLP improved PSCI via increasing the phosphorylation of CREB and histone acetylation, thus attenuating cholinergic activity.

Glutamate in schizophrenia: Neurodevelopmental perspectives and drug development

Research into the neurobiological processes that may lead to the onset of schizophrenia places growing emphasis on the glutamatergic system and brain development. Preclinical studies have shown that neurodevelopmental, genetic, and environmental factors contribute to glutamatergic dysfunction and schizophrenia-related phenotypes. Clinical research has suggested that altered brain glutamate levels may be present before the onset of psychosis and relate to outcome in those at clinical high risk. After psychosis onset, glutamate dysfunction may also relate to the degree of antipsychotic response and clinical outcome. These findings support ongoing efforts to develop pharmacological interventions that target the glutamate system and could suggest that glutamatergic compounds may be more effective in specific patient subgroups or illness stages. In this review, we consider the updated glutamate hypothesis of schizophrenia, from a neurodevelopmental perspective, by reviewing recent preclinical and clinical evidence, and discuss the potential implications for novel therapeutics.

Novel therapeutic targets for amyotrophic lateral sclerosis: ribonucleoproteins and cellular autonomy

INTRODUCTION

Amyotrophic lateral sclerosis (ALS) is a devastating disease with a lifetime risk of approximately 1:400. It is incurable and invariably fatal. Average survival is between 3 and 5 years and patients become increasingly paralyzed, losing the ability to speak, eat, and breathe. Therapies in development either (i) target specific familial forms of ALS (comprising a minority of around 10% of cases) or ii) emanate from (over)reliance on animal models or non-human/non-neuronal cell models. There is a desperate and unmet clinical need for effective treatments. Deciphering the primacy and relative contributions of defective protein homeostasis and RNA metabolism in ALS across different model systems will facilitate the identification of putative therapeutic targets.

AREAS COVERED

This review examines the putative common primary molecular events that lead to ALS pathogenesis. We focus on deregulated RNA metabolism, protein mislocalization/pathological aggregation and the role of glia in ALS-related motor neuron degeneration. Finally, we describe promising targets for therapeutic evaluation.

EXPERT OPINION

Moving forward, an effective strategy could be achieved by a poly-therapeutic approach which targets both deregulated RNA metabolism and protein dyshomeostasis in the relevant cell types, at the appropriate phase of disease.

A Review of epigenetics in psychiatry: focus on environmental risk factors

Epigenetic modifications play a key role in development and cell type specificity. These modifications seem to be particularly critical for brain development, where mutations in epigenetic enzymes have been associated with neurodevelopmental disorders as well as with the function of post-mitotic neurons. Epigenetic modifications can be influenced by genetic and environmental factors, both known major risk factors for psychiatric disorders. Epigenetic modifications may thus be an important mediator of the effects of genetic and environmental risk factors on cell function.

This review summarizes the different types of epigenetic regulation and then focuses on the mechanisms transducing environmental signals, especially adverse life events that are major risk factors for psychiatric disorders, into lasting epigenetic changes. This is followed by examples of how the environment can induce epigenetic changes that relate to the risk of psychiatric disorders.

HDAC1 dysregulation induces aberrant cell cycle and DNA damage in progress of TDP-43 proteinopathies

TAR DNA-binding protein 43 (TDP-43) has been implicated in frontotemporal lobar degeneration with ubiquitin-positive inclusions (FTLD-TDP) and amyotrophic lateral sclerosis. Histone deacetylase 1 (HDAC1) is involved in DNA repair and neuroprotection in numerous neurodegenerative diseases. However, the pathological mechanisms of FTLD-TDP underlying TDP-43 proteinopathies are unclear, and the role of HDAC1 is also poorly understood. Here, we found that aberrant cell cycle activity and DNA damage are important pathogenic factors in FTLD-TDP transgenic (Tg) mice, and we further identified these pathological features in the frontal cortices of patients with FTLD-TDP. TDP-43 proteinopathies contributed to pathogenesis by inducing cytosolic mislocalization of HDAC1 and reducing its activity. Pharmacological recovery of HDAC1 activity in FTLD-TDP Tg mice ameliorated their cognitive and motor impairments, normalized their aberrant cell cycle activity, and attenuated their DNA damage and neuronal loss. Thus, HDAC1 deregulation is involved in the pathogenesis of TDP-43 proteinopathies, and HDAC1 is a potential target for therapeutic interventions in FTLD-TDP.

Neuroendocrine, epigenetic, and intergenerational effects of general anesthetics

The progress of modern medicine would be impossible without the use of general anesthetics (GAs). Despite advancements in refining anesthesia approaches, the effects of GAs are not fully reversible upon GA withdrawal. Neurocognitive deficiencies attributed to GA exposure may persist in neonates or endure for weeks to years in the elderly. Human studies on the mechanisms of the long-term adverse effects of GAs are needed to improve the safety of general anesthesia but they are hampered not only by ethical limitations specific to human research, but also by a lack of specific biological markers that can be used in human studies to safely and objectively study such effects. The latter can primarily be attributed to an insufficient understanding of the full range of the biological effects induced by GAs and the molecular mechanisms mediating such effects even in rodents, which are far more extensively studied than any other species. Our most recent experimental findings in rodents suggest that GAs may adversely affect many more people than is currently anticipated. Specifically, we have shown that anesthesia with the commonly used GA sevoflurane induces in exposed animals not only neuroendocrine abnormalities (somatic effects), but also epigenetic reprogramming of germ cells (germ cell effects). The latter may pass the neurobehavioral effects of parental sevoflurane exposure to the offspring, who may be affected even at levels of anesthesia that are not harmful to the exposed parents. The large number of patients who require general anesthesia, the even larger number of their future unexposed offspring whose health may be affected, and a growing number of neurodevelopmental disorders of unknown etiology underscore the translational importance of investigating the intergenerational effects of GAs. In this mini review, we discuss emerging experimental findings on neuroendocrine, epigenetic, and intergenerational effects of GAs.

Inhibition of Histone Deacetylase Reinstates Hippocampus-Dependent Long-Term Synaptic Plasticity and Associative Memory in Sleep-Deprived Mice

Sleep plays an important role in the establishment of long-term memory; as such, lack of sleep severely impacts domains of our health including cognitive function. Epigenetic mechanisms regulate gene transcription and protein synthesis, playing a critical role in the modulation of long-term synaptic plasticity and memory. Recent evidences indicate that transcriptional dysregulation as a result of sleep deprivation (SD) may contribute to deficits in plasticity and memory function. The histone deacetylase inhibitor suberoylanilide hydroxamic acid (SAHA), also known as Vorinostat, a clinically approved drug for human use, has been shown to ameliorate cognitive deficits in several neurological disease models. To further explore the therapeutic effect of SAHA, we have examined its potential role in improving the SD-mediated impairments in long-term plasticity, associative plasticity, and associative memory. Here we show that SAHA preserves long-term plasticity, associative plasticity, and associative memory in SD hippocampus. Furthermore, we find that SAHA prevents SD-mediated epigenetic changes by upregulating histone acetylation, hence preserving the ERK-cAMP-responsive element-binding protein (CREB)/CREB-binding protein-brain-derived neurotrophic factor pathway in the hippocampus. These data demonstrate that modifying epigenetic mechanisms via SAHA can prevent or reverse impairments in long-term plasticity and memory that result from sleep loss. Thus, SAHA could be a potential therapeutic agent in improving SD-related memory deficits.

Transcriptional corepressor SIN3A regulates hippocampal synaptic plasticity via Homer1/mGluR5 signaling

Long-term memory depends on the control of activity-dependent neuronal gene expression, which is regulated by epigenetic modifications. The epigenetic modification of histones is orchestrated by the opposing activities of 2 classes of regulatory complexes: permissive coactivators and silencing corepressors. Much work has focused on coactivator complexes, but little is known about the corepressor complexes that suppress the expression of plasticity-related genes. Here, we define a critical role for the corepressor SIN3A in memory and synaptic plasticity, showing that postnatal neuronal deletion of Sin3a enhances hippocampal long-term potentiation and long-term contextual fear memory. SIN3A regulates the expression of genes encoding proteins in the postsynaptic density. Loss of SIN3A increases expression of the synaptic scaffold Homer1, alters the metabotropic glutamate receptor 1α (mGluR1α) and mGluR5 dependence of long-term potentiation, and increases activation of ERK in the hippocampus after learning. Our studies define a critical role for corepressors in modulating neural plasticity and memory consolidation and reveal that Homer1/mGluR signaling pathways may be central molecular mechanisms for memory enhancement.

Motor Transitions' Peculiarity of Heterozygous DAT Rats When Offspring of an Unconventional KOxWT Mating

Causal factors of psychiatric diseases are unclear, due to gene × environment interactions. Evaluation of consequences, after a dopamine-transporter (DAT) gene knock-out (DAT-KO), has enhanced our understanding into the pathological dynamics of several brain disorders, such as Attention-Deficit/Hyperactivity and Bipolar-Affective disorders. Recently, our attention has shifted to DAT hypo-functional (heterozygous, HET) rodents: HET dams display less maternal care and HET females display marked hypo-locomotion if cared by HET dams (Mariano et al., 2019). We assessed phenotypes of male DAT-heterozygous rats as a function of their parents: we compared "maternal" origin (MAT-HET, obtained by breeding KO-male rats with WT-female dams) to "mixed" origin (MIX-HET, obtained by classical breeding, both heterozygous parents) of the allele. MAT-HET subjects had significantly longer rhythms of daily locomotor activity than MIX-HET and WT-control subjects. Furthermore, acute methylphenidate (MPH: 0, 1, 2 mg/kg) revealed elevated threshold for locomotor stimulation in MAT-HETs, with no response to the lower dose. Finally, by Porsolt-Test, MAT-HETs showed enhanced escape-seeking (diving) with more transitions towards behavioral despair (floating). When comparing both MAT- and MIX-HET to WT-control rats, decreased levels of DAT and HDAC4 were evident in the ventral-striatum; moreover, with respect to MIX-HET subjects, MAT-HET ones displayed increased DAT density in dorsal-striatum. MAT-HET rats displayed region-specific changes in DAT expression, compared to "classical" MIX-HET subjects: greater DAT availability may elevate threshold for dopamine action. Further behavioral and epigenetic characterizations of MAT-HETs, together with deeper characterization of maternal roles, could help to explore parent-of-origin mechanisms for such a peculiar phenotype.

NMDA receptor hypofunction for schizophrenia revisited: Perspectives from epigenetic mechanisms

Schizophrenia (SZ) is a neurodevelopmental disorder with cognitive deficits manifesting during early stages of the disease. Evidence suggests that genetic factors in combination with environmental insults lead to complex changes to glutamatergic, GABAergic, and dopaminergic systems. In particular, the N-methyl-d-aspartate receptor (NMDAR), a major glutamate receptor subtype, is implicated in both the disease progression and symptoms of SZ. NMDARs are critical for synaptic plasticity and cortical maturation, as well as learning and memory processes. In fact, any deviation from normal NMDAR expression and function can have devastating consequences. Surprisingly, there is little evidence from human patients that direct mutations of NMDAR genes contribute to SZ. One intriguing hypothesis is that epigenetic changes, which could result from early insults, alter protein expression and contribute to the NMDAR hypofunction found in SZ. Epigenetics is referred to as modifications that alter gene transcription without changing the DNA sequence itself. In this review, we first discuss how epigenetic changes to NMDAR genes could contribute to NMDAR hypofunction. We then explore how NMDAR hypofunction may contribute to epigenetic changes in other proteins or genes that lead to synaptic dysfunction and symptoms in SZ. We argue that NMDAR hypofunction occurs in early stage of the disease, and it may consequentially initiate GABA and dopamine deficits. Therefore, targeting NMDAR dysfunction during the early stages would be a promising avenue for prevention and therapeutic intervention of cognitive and social deficits that remain untreatable. Finally, we discuss potential questions regarding the epigenetic of SZ and future directions for research.

When function follows form: Nuclear compartment structure and the epigenetic landscape of the aging neuron

The human brain is affected by cellular aging. Neurons are primarily generated during embryogenesis and early life with a limited capacity for renewal and replacement, making them some of the oldest cells in the human body. Our present understanding of neurodegenerative diseases points towards advanced neuronal age as a prerequisite for the development of these disorders. While significant progress has been made in understanding the relationship between aging and neurological disease, it will be essential to delve further into the molecular mechanisms of neuronal aging in order to develop therapeutic interventions targeting age-related brain dysfunction. In this mini review, we highlight recent findings on the relationship between the aging of nuclear structures and changes in the epigenetic landscape during neuronal aging and disease.

An integrative analysis of genome-wide association study and regulatory SNP annotation datasets identified candidate genes for bipolar disorder

Background

Bipolar disorder (BD) is a complex mood disorder. The genetic mechanism of BD remains largely unknown.

Methods

We conducted an integrative analysis of genome-wide association study (GWAS) and regulatory SNP (rSNP) annotation datasets, including transcription factor binding regions (TFBRs), chromatin interactive regions (CIRs), mature microRNA regions (miRNAs), long non-coding RNA regions (lncRNAs), topologically associated domains (TADs) and circular RNAs (circRNAs). Firstly, GWAS dataset 1 of BD (including 20,352 cases and 31,358 controls) and GWAS dataset 2 of BD (including 7481 BD patients and 9250 controls) were integrated with rSNP annotation database to obtain BD associated SNP regulatory elements and SNP regulatory element-target gene (E–G) pairs, respectively. Secondly, a comparative analysis of the two datasets results was conducted to identify the common rSNPs and also their target genes. Then, gene sets enrichment analysis (FUMA GWAS) and HumanNet-XC analysis were conducted to explore the functional relevance of identified target genes with BD.

Results

After the integrative analysis, we identified 52 TFBRs target genes, 44 TADs target genes, 55 CIRs target genes and 21 lncRNAs target genes for BD, such as ITIH4 (P_dataset1 = 6.68 × 10⁻⁸, P_dataset2 = 6.64 × 10⁻⁷), ITIH3 (P_dataset1 = 1.09 × 10⁻⁸, P_dataset2 = 2.00 × 10⁻⁷), SYNE1 (P_dataset1 = 1.80 × 10⁻⁶, P_dataset2 = 4.33 × 10⁻⁹) and OPRM1 (P_dataset1 = 1.80 × 10⁻⁶, P_dataset2 = 4.33 × 10⁻⁹).

Conclusion

We conducted a large-scale integrative analysis of GWAS and 6 common rSNP information datasets to explore the potential roles of rSNPs in the genetic mechanism of BD. We identified multiple candidate genes for BD, supporting the importance of rSNP in the development of BD.

Glial Cells-The Strategic Targets in Amyotrophic Lateral Sclerosis Treatment

Amyotrophic lateral sclerosis (ALS) is a fatal neurological disease, which is characterized by the degeneration of motor neurons in the motor cortex and the spinal cord and subsequently by muscle atrophy. To date, numerous gene mutations have been linked to both sporadic and familial ALS, but the effort of many experimental groups to develop a suitable therapy has not, as of yet, proven successful. The original focus was on the degenerating motor neurons, when researchers tried to understand the pathological mechanisms that cause their slow death. However, it was soon discovered that ALS is a complicated and diverse pathology, where not only neurons, but also other cell types, play a crucial role via the so-called non-cell autonomous effect, which strongly deteriorates neuronal conditions. Subsequently, variable glia-based in vitro and in vivo models of ALS were established and used for brand-new experimental and clinical approaches. Such a shift towards glia soon bore its fruit in the form of several clinical studies, which more or less successfully tried to ward the unfavourable prognosis of ALS progression off. In this review, we aimed to summarize current knowledge regarding the involvement of each glial cell type in the progression of ALS, currently available treatments, and to provide an overview of diverse clinical trials covering pharmacological approaches, gene, and cell therapies.

Pharmacological intervention of histone deacetylase enzymes in the neurodegenerative disorders

Reversal of aging symptoms and related disorders are the challenging task where epigenetic is a crucial player that includes DNA methylation, histone modification; chromatin remodeling and regulation that are linked to the progression of various neurodegenerative disorders (NDDs). Overexpression of various histone deacetylase (HDACs) can activate Glycogen synthase kinase 3 which promotes the hyperphosphorylation of tau and inhibits its degradation. While HDAC is important for maintaining the neuronal morphology and brain homeostasis, at the same time, these enzymes are promoting neurodegeneration, if it is deregulated. Different experimental models have also confirmed the neuroprotective effects caused by HDAC enzymes through the regulation of neuronal apoptosis, inflammatory response, DNA damage, cell cycle regulation, and metabolic dysfunction. Apart from transcriptional regulation, protein-protein interaction, histone post-translational modifications, deacetylation mechanism of non-histone protein and direct association with disease proteins have been linked to neuronal imbalance. Histone deacetylases inhibitors (HDACi) can be able to alter gene expression and shown its efficacy on experimental models, and in clinical trials for NDD's and found to be a very promising therapeutic agent with certain limitation, for instance, non-specific target effect, isoform-selectivity, specificity, and limited number of predicted biomarkers. Herein, we discussed (i) the catalytic mechanism of the deacetylation process of various HDAC's in in vivo and in vitro experimental models, (ii) how HDACs are participating in neuroprotection as well as in neurodegeneration, (iii) a comprehensive role of HDACi in maintaining neuronal homeostasis and (iv) therapeutic role of biomolecules to modulate HDACs.

Neuron-Specific Menin Deletion Leads to Synaptic Dysfunction and Cognitive Impairment by Modulating p35 Expression

Menin (MEN1) is a critical modulator of tissue development and maintenance. As such, MEN1 mutations are associated with multiple endocrine neoplasia type 1 (MEN1) syndrome. Although menin is abundantly expressed in the nervous system, little is known with regard to its function in the adult brain. Here, we demonstrate that neuron-specific deletion of Men1 (CcKO) affects dendritic branching and spine formation, resulting in defects in synaptic function, learning, and memory. Furthermore, we find that menin binds to the p35 promoter region to facilitate p35 transcription. As a primary Cdk5 activator, p35 is expressed mainly in neurons and is critical for brain development and synaptic plasticity. Restoration of p35 expression in the hippocampus and cortex of Men1 CcKO mice rescues synaptic and cognitive deficits associated with Men1 deletion. These results reveal a critical role for menin in synaptic and cognitive function by modulating the p35-Cdk5 pathway.

Protective effects of 10,11-dihydro-5H-dibenzo[b,f]azepine hydroxamates on vascular cognitive impairment

A series of 10,11-dihydro-5H-dibenzo [b,f]azepine hydroxamates (4-15) were synthesized, behaving as histone deacetylase inhibitors, and examined for their influence on vascular cognitive impairment (VCI), which correlated with dementia. The results revealed that (E)-3-(4-(((3-(3-chloro-10,11-dihydro-5H-dibenzo [b,f]azepin-5-yl)propyl)amino)methyl)phenyl)-N-hydroxy-acrylamide (13) increases cerebral blood flow (CBF), attenuates cognitive impairment, and improves hippocampal atrophy in in vivo study. It is also able to increase the level of histone acetylation (H3K14 or H4K5) in the cortex and hippocampus of chronic cerebral hypoperfusion (CCH) mice; as a result, it could be a potential HDAC inhibitor for the treatment of vascular cognitive impairment.

Multitarget Approach for the Treatment of Alzheimer's Disease: Inhibition of Phosphodiesterase 9 (PDE9) and Histone Deacetylases (HDACs) Covering Diverse Selectivity Profiles

Here, we present a series of dual-target phosphodiesterase 9 (PDE9) and histone deacetylase (HDAC) inhibitors devised as pharmacological tool compounds for assessing the implications of these two targets in Alzheimer's disease (AD). These novel inhibitors were designed taking into account the key pharmacophoric features of known selective PDE9 inhibitors as well as privileged chemical structures, bearing zinc binding groups (hydroxamic acids and ortho-amino anilides) that hit HDAC targets. These substituents were selected according to rational criteria and previous knowledge from our group to explore diverse HDAC selectivity profiles (pan-HDAC, HDAC6 selective, and class I selective) that were confirmed in biochemical screens. Their functional response in inducing acetylation of histone and tubulin and phosphorylation of cAMP response element binding (CREB) was measured as a requisite for further progression into complete in vitro absorption, distribution, metabolism and excretion (ADME) and in vivo brain penetration profiling. Compound 31b, a selective HDAC6 inhibitor with acceptable brain permeability, was chosen for assessing in vivo efficacy of these first-in-class inhibitors, as well as studying their mode of action (MoA).

From molecular promise to preclinical results: HDAC inhibitors in the race for healthy aging drugs

Reversing or slowing the aging process brings great promise to treat or prevent age‐related disease, and targeting the hallmarks of aging is a strategy to achieve this. Epigenetics affects several if not all of the hallmarks of aging and has therefore emerged as a central target for intervention. One component of epigenetic regulation involves histone deacetylases (HDAC), which include the “classical” histone deacetylases (of class I, II, and IV) and sirtuin deacetylases (of class III). While targeting sirtuins for healthy aging has been extensively reviewed elsewhere, this review focuses on pharmacologically inhibiting the classical HDACs to promote health and longevity. We describe the theories of how classical HDAC inhibitors may operate to increase lifespan, supported by studies in model organisms. Furthermore, we explore potential mechanisms of how HDAC inhibitors may have such a strong grasp on health and longevity, summarizing their links to other hallmarks of aging. Finally, we show the wide range of age‐related preclinical disease models, ranging from neurodegeneration to heart disease, diabetes to sarcopenia, which show improvement upon HDAC inhibition.

Effects of Histone Deacetylase Inhibitors on the Development of Epilepsy and Psychiatric Comorbidity in WAG/Rij Rats

Epigenetic mechanisms, such as alterations in histone acetylation based on histone deacetylases (HDACs) activity, have been linked not only to normal brain function but also to several brain disorders including epilepsy and the epileptogenic process. In WAG/Rij rats, a genetic model of absence epilepsy, epileptogenesis and mild-depression comorbidity, we investigated the effects of two HDAC inhibitors (HDACi), namely sodium butyrate (NaB), valproic acid (VPA) and their co-administration, on the development of absence seizures and related psychiatric/neurologic comorbidities following two different experimental paradigms. Treatment effects have been evaluated by EEG recordings (EEG) and behavioural tests at different time points. Prolonged and daily VPA and NaB treatment, started before absence seizure onset (P30), significantly reduced the development of absence epilepsy showing antiepileptogenic effects. These effects were enhanced by NaB/VPA co-administration. Furthermore, early-chronic HDACi treatment improved depressive-like behaviour and cognitive performance 1 month after treatment withdrawal. WAG/Rij rats of 7 months of age showed reduced acetylated levels of histone H3 and H4, analysed by Western Blotting of homogenized brain, in comparison to WAG/Rij before seizure onset (P30). The brain histone acetylation increased significantly during treatment with NaB or VPA alone and more markedly during co-administration. We also observed decreased expression of both HDAC1 and 3 following HDACi treatment compared to control group. Our results suggest that histone modifications may have a crucial role in the development of epilepsy and early treatment with HDACi might be a possible strategy for preventing epileptogenesis also affecting behavioural comorbidities.

Therapeutic exercise accompanied by neuronal modulation to enhance neurotrophic factors in the brain with central nervous system disorders

Exercise is a primary therapeutic regimen in physical therapy to rehabilitate the motor function of patients with central nervous system (CNS) disorders such as cerebrovascular accident (CVA). Furthermore, exercise positively contributes to cognitive function related to neuroplasticity and neuroprotection in the hippocampus. Neurotrophins play a crucial role in neuroplasticity, neurogenesis, and neuroprotection in the CNS. Exercise enhances the expression of neurotrophins in the brain. Thus, novel regimens for kinesiotherapy in CNS disorders to further enhance exercise-induced expression are expected. In this review, we described three novel regimens for kinesiotherapy in CNS disorders based on the interaction between exercise and pharmacological treatment with the idea of "inhibition of inhibition" in the CNS.

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.

Regulation of HDAC1 and HDAC2 during consolidation and extinction of fear memory

Histone deacetylases (HDACs) regulate gene expression epigenetically through synchronized removal of acetyl groups from histones required towards memory consolidation. Moreover, dysregulated epigenetic machinery during fear or extinction learning may result in altered expression of some of these genes and result in Post Traumatic Stress Disorder (PTSD). In the present study, region-specific expression of Histone deacetylase 1 (HDAC1) and Histone deacetylase 2 (HDAC2) was correlated to the acetylation of histones H3 and H4 and the resultant conditioned response, in rats undergone fear and extinction learning. The neuronal activation, histone acetylation at H3/H4 and expression of HDAC1/HDAC2 in centrolateral amygdala (CeL) and centromedial amygdala (CeM) of central Amygdala (CeA) and prelimbic (PL) and infralimbic (IL) of Prefrontal cortex (PFC) were found to be associated in a differential manner following fear and extinction learning. Moreover in CeM, the main output of the fear circuitry, the level of HDAC1 was down-regulated following conditioning and up-regulated following extinction as opposed to which HDAC2 was down-regulated in CeM following conditioning but not following extinction. Furthermore, in CeL the HDAC1 was upregulated and HDAC2 was downregulated following conditioning and extinction. This has important implications in speculating of the role of HDACs in fear memory consolidation and its extinction.

Potential epigenomic co-management in rare diseases and epigenetic therapy

The purpose of this review is to highlight the impact of the alternative splicing process on human disease. Epigenetic regulation determines not only what parts of the genome are expressed but also how they are spliced. The recent progress in the field of epigenetics has important implications for the study of rare diseases. The role of epigenetics in rare diseases is a key issue in molecular physiology and medicine because not only rare diseases can benefit from epigenetic research, but can also provide useful principles for other common and complex disorders such as cancer, cardiovascular, type 2 diabetes, obesity, and neurological diseases. Predominantly, epigenetic modifications include DNA methylation, histone modification, and RNA-associated silencing. These modifications in the genome regulate numerous cellular activities. Disruption of epigenetic regulation process can contribute to the etiology of numerous diseases during both prenatal and postnatal life. Here, I discuss current knowledge about this matter including some current epigenetic therapies and future directions in the field by emphasizing on the RNA-based therapy via antisense oligonucleotides to correct splicing defects.

Panobinostat, a histone deacetylase inhibitor, rescues the angiogenic potential of endothelial colony-forming cells in moyamoya disease

PURPOSE

Moyamoya disease (MMD) is one of the most common causes of pediatric stroke. We found defective angiogenic function and downregulation of retinaldehyde dehydrogenase 2 (RALDH2) in MMD endothelial colony-forming cells (ECFCs). Downregulation of RALDH2 mRNA was caused by decreased binding of acetyl-histone H3 (Ac-H3) to the RALDH2 promoter. In this study, we evaluated the feasibility of using a histone deacetylase (HDAC) inhibitor, panobinostat, to upregulate RALDH2 expression and restore the angiogenic potential of MMD ECFCs.

METHODS

ECFCs from healthy normal controls and patients with MMD were isolated and characterized. After panobinostat treatment, western blot, tube formation, and chromatin immunoprecipitation (ChIP) assays were conducted in vitro. A matrigel plug assay was performed in vivo.

RESULTS

Panobinostat increased the levels of Ac-H3 and Ac-H4 in both normal and MMD ECFCs but was much more effective in MMD ECFCs. Increased expression of RALDH2 by panobinostat was observed only in MMD ECFCs. Panobinostat increased the tube formation of both normal and MMD ECFCs in vitro and in vivo, but the effect was greater with MMD ECFCs.

CONCLUSIONS

We demonstrated that panobinostat increases the angiogenic ability of MMD ECFCs by regulating RALDH2 acetylation. Our results suggest that panobinostat might be a potent therapeutic option for MMD patients.

Inhibition of EHMT1/2 rescues synaptic and cognitive functions for Alzheimer's disease

Epigenetic dysregulation, which leads to the alteration of gene expression in the brain, is suggested as one of the key pathophysiological bases of ageing and neurodegeneration. Here we found that, in the late-stage familial Alzheimer's disease (FAD) mouse model, repressive histone H3 dimethylation at lysine 9 (H3K9me2) and euchromatic histone methyltransferases EHMT1 and EHMT2 were significantly elevated in the prefrontal cortex, a key cognitive region affected in Alzheimer's disease. Elevated levels of H3K9me2 were also detected in the prefrontal cortex region of post-mortem tissues from human patients with Alzheimer's disease. Concomitantly, H3K9me2 at glutamate receptors was increased in prefrontal cortex of aged FAD mice, which was linked to the diminished transcription, expression and function of AMPA and NMDA receptors. Treatment of FAD mice with specific EHMT1/2 inhibitors reversed histone hyper-methylation and led to the recovery of glutamate receptor expression and excitatory synaptic function in prefrontal cortex and hippocampus. Chromatin immunoprecipitation-sequencing (ChIP-seq) data indicated that FAD mice exhibited genome-wide increase of H3K9me2 enrichment at genes involved in neuronal signalling (including glutamate receptors), which was reversed by EHMT1/2 inhibition. Moreover, the impaired recognition memory, working memory, and spatial memory in aged FAD mice were rescued by the treatment with EHMT1/2 inhibitors. These results suggest that disrupted epigenetic regulation of glutamate receptor transcription underlies the synaptic and cognitive deficits in Alzheimer's disease, and targeting histone methylation enzymes may represent a novel therapeutic strategy for this prevalent neurodegenerative disorder.

[Environment and epigenetics]

Environmental factors are among the strongest risk factors for psychiatric disorders. Differences in exposure to such environments have been associated with lasting biological changes. In recent years epigenetic mechanisms have been brought to the forefront as central in mediating a lasting embedding of environmental risk factors. This article first summarizes the different levels of epigenetic regulation and then focuses on mechanisms transducing environmental signals into lasting epigenetic changes. This is followed by examples of how environmentally induced epigenetic changes relate to risk and resilience to psychiatric disorders and their treatment.

PET neuroimaging reveals histone deacetylase dysregulation in schizophrenia

BACKGROUND

Patients with schizophrenia (SCZ) experience chronic cognitive deficits. Histone deacetylases (HDACs) are enzymes that regulate cognitive circuitry; however, the role of HDACs in cognitive disorders, including SCZ, remains unknown in humans. We previously determined that HDAC2 mRNA levels were lower in dorsolateral prefrontal cortex (DLPFC) tissue from donors with SCZ compared with controls. Here we investigated the relationship between in vivo HDAC expression and cognitive impairment in patients with SCZ and matched healthy controls using [11C]Martinostat positron emission tomography (PET).

METHODS

In a case-control study, relative [11C]Martinostat uptake was compared between 14 patients with SCZ or schizoaffective disorder (SCZ/SAD) and 17 controls using hypothesis-driven region-of-interest analysis and unbiased whole brain voxel-wise approaches. Clinical measures, including the MATRICS consensus cognitive battery, were administered.

RESULTS

Relative HDAC expression was lower in the DLPFC of patients with SCZ/SAD compared with controls, and HDAC expression positively correlated with cognitive performance scores across groups. Patients with SCZ/SAD also showed lower relative HDAC expression in the dorsomedial prefrontal cortex and orbitofrontal gyrus, and higher relative HDAC expression in the cerebral white matter, pons, and cerebellum compared with controls.

CONCLUSIONS

These findings provide in vivo evidence of HDAC dysregulation in patients with SCZ and suggest that altered HDAC expression may impact cognitive function in humans.

FUNDING

National Institute of Mental Health (NIMH), Brain and Behavior Foundation, Massachusetts General Hospital (MGH), Athinoula A. Martinos Center for Biomedical Imaging, National Institute of Biomedical Imaging and Bioengineering (NIBIB), NIH Shared Instrumentation Grant Program.

Enhancer function regulated by combinations of transcription factors and cofactors

Regulation of the expression of diverse genes is essential for making possible the complexity of higher organisms, and the temporal and spatial regulation of gene expression allows for the alteration of cell types and growth patterns. A critical component of this regulation is the DNA sequence-specific binding of transcription factors (TFs). However, most TFs do not independently participate in gene transcriptional regulation, because they lack an effector function. Instead, TFs are thought to work by recruiting cofactors, including Mediator complex (Mediator), chromatin-remodeling complexes (CRCs), and histone-modifying complexes (HMCs). Mediator associates with the majority of transcribed genes and acts as an integrator of multiple signals. On the other hand, CRCs and HMCs are selectively recruited by TFs. Although all the pairings between TFs and CRCs or HMCs are not fully known, there are a growing number of established TF-CRC and TF-HMC combinations. In this review, we focused on the most important of these pairings and discuss how they control gene expression.

Design of Diarylheptanoid Derivatives as Dual Inhibitors Against Class IIa Histone Deacetylase and β-amyloid Aggregation

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder with multiple etiologies. Beta-amyloid (Aβ) self-aggregation and overexpression of class IIa histone deacetylases (HDACs) are strongly implicated with AD pathogenesis. In this study, a series of novel diarylheptanoid derivatives were designed, synthesized and evaluated for use as dual Aβ self-aggregation and class IIa HDAC inhibitors. Among these compounds, 4j, 5c, and 5e displayed effective inhibitions for Aβ self-aggregation, HDAC5 activity and HDAC7 activity with IC₅₀ values of <10 μM. The compounds contain three common features: (1) a catechol or pyrogallol moiety, (2) a carbonyl linker and (3) an aromatic ring that can function as an HDAC cap and create hydrophobic interactions with Aβ_1-42. Furthermore, compounds 4j, 5c, and 5e showed no significant cytotoxicity to human neuroblastoma SH-SY5Y cells and also exhibited neuroprotective effect against H₂O₂-induced toxicity. Overall, these promising in vitro data highlighted compounds 4j, 5c, and 5e as lead compounds that are worthy for further investigation.

Histone deacetylase inhibitor MS-275 restores social and synaptic function in a Shank3-deficient mouse model of autism

Autism is a neurodevelopmental disorder characterized by social deficits and repetitive behaviors. Genetic screening has identified synaptic, transcriptional, and chromatin genes disrupted in autistic patients. Haploinsufficiency of Shank3, which encodes a scaffold protein at glutamatergic synapses, is causally linked to autism. Using a Shank3-deficient mouse model that exhibits prominent autism-like phenotypes, we have found that histone acetylation in the prefrontal cortex (PFC) is abnormally low, which can be reversed by MS-275 (also known as Entinostat, SNDX-275), a class I histone deacetylase (HDAC) inhibitor that is selectively potent in PFC. A brief (3-day) treatment with MS-275 (i.p.) led to the sustained (11 days) rescue of autistic social preference deficits in Shank3-deficient mice, without altering locomotion, motor coordination, anxiety, or the increased grooming. MS-275 treatment also rescued the diminished NMDAR surface expression and NMDAR function induced by Shank3 deficiency. Moreover, F-actin at synapses was restored and the transcription of actin regulators was elevated by MS-275 treatment of Shank3-deficient mice, which may contribute to the recovery of actin-based NMDAR synaptic delivery. Taken together, these results suggest that MS-275 treatment could normalize the aberrant epigenetic regulation of genes, leading to the amelioration of synaptic and social deficits associated with autism.

Abnormal modification of histone acetylation involved in depression-like behaviors of rats induced by chronically unpredicted stress

Depression is a complex multifactorial mental disorder. Its etiology involves many factors such as social environments, genetics, and psychology. Recent studies have shown that epigenetic modification may be associated with depression. Histone acetylation is one of the main mechanisms of epigenetic modification and plays an important role in genetic expression. In this study, we investigated the role of histone acetylation in the depression-like behaviors of rats undergoing chronically unpredicted stress (CUS) by detecting the mRNA and protein expression of histone deacetylase 5, cAMP-response element-binding protein, and the level of histone acetylated modification of H3K14, H3K23, and H4K16 in the prefrontal cortex and hippocampus of the rats. The results showed that significantly increasing depression-like behaviors were observed with a decreasing histone acetylated modification level, especially on acytelated-H3K14, acytelated-H3K23, and acytelated-H4K16, upregulating histone deacetylase 5 expression and downregulating cAMP-response element-binding protein expression in CUS rats, compared with control rats. The results indicate that the decrease in the histone acetylation modification level may be partly involved in the mechanism of depression-like behaviors of rats induced by CUS.

Biophenols: Enzymes (β-secretase, Cholinesterases, histone deacetylase and tyrosinase) inhibitors from olive (Olea europaea L.)

The focus of this study was on inhibition of enzymes involved in the pathogenesis Alzheimer's disease (AD) including prime amyloid beta (Aβ) producing enzyme (β-secretase: BACE-1) and disease progression enzymes including acetylcholinesterase (AChE), butyrylcholinesterase (BChE), histone deacetylase (HDAC), and tyrosinase along with the catecholamine L-DOPA, by using olive biophenols. Here we report the strongest inhibition of BACE-1 from rutin (IC₅₀: 3.8 nM) followed by verbascoside (IC₅₀: 6.3 nM) and olive fruit extract (IC₅₀: 18 ng), respectively. Olive biophenol, quercetin exhibited strongest enzyme inhibitory activity against tyrosinase (IC₅₀: 10.73 μM), BChE (IC₅₀: 19.08 μM), AChE (IC₅₀: 55.44 μM), and HDAC (IC₅₀: 105.1 μM) enzymes. Furthermore, olive biophenol verbascoside (IC₅₀: 188.6 μM), and hydroxytyrosol extreme extract (IC₅₀: 66.22 μg) were showed the highest levels of inhibition against the HDAC enzyme. Neuroprotective capacity against levodopa-induced toxicity in neuroblastoma (SH-SY5Y) cells of olive biophenols were assessed, where rutin indicated the highest neuroprotection (74%), followed by caffeic acid (73%), and extract hydroxytyrosol extreme (97%), respectively. To the best of our knowledge, this is the first in vitro report on the enzymes inhibitory activity of olive biophenols. Taken together, our in vitro results data suggest that olive biophenols could be a promising natural inhibitor, which may reduce the enzyme-induced toxicity associated with the oxidative stress involved in the progression of AD.

CHEMICAL COMPOUNDS USED IN THE STUDY

Acetylthiocholine iodide (PubChem CID: 74629); S-Butyrylthiocholine chloride (PubChem CID: 3015121); Caffeic acid (PubChem CID: 689043); Dimethyl sulfoxide (DMSO) (PubChem: 679); L-3,4-Dihydroxyphenylalanine (L-DOPA) (PubChem CID: 6047); 5,5'-Dithiobis (2-nitrobenzoic acid) (DTNB) (PubChem CID: 6254); Epigallocatechin gallate (EGCG) (PubChem CID: 65064); Ethylenediamine tetraacetic acid (EDTA) (PubChem CID: 6049); Galantamine hydrobromide (PubChem CID: 121587); l-Glutamine (PubChem CID: 5961); Hydroxytyrosol (PubChem CID: 82755); Kojic acid (PubChem CID: 3840); Luteolin (PubChem CID: 5280445); Oleuropein (PubChem CID: 5281544); Penicillin-streptomycin (PubChem CID: 131715954); Quercetin (PubChem CID: 5280343); Rutin (PubChem CID: 5280805); Tris-HCl buffer (PubChem: 93573); Trypan blue (PubChem: 9562061).

GABAergic inhibitory neurons as therapeutic targets for cognitive impairment in schizophrenia

Schizophrenia is considered primarily as a cognitive disorder. However, functional outcomes in schizophrenia are limited by the lack of effective pharmacological and psychosocial interventions for cognitive impairment. GABA (gamma-aminobutyric acid) interneurons are the main inhibitory neurons in the central nervous system (CNS), and they play a critical role in a variety of pathophysiological processes including modulation of cortical and hippocampal neural circuitry and activity, cognitive function-related neural oscillations (eg, gamma oscillations) and information integration and processing. Dysfunctional GABA interneuron activity can disrupt the excitatory/inhibitory (E/I) balance in the cortex, which could represent a core pathophysiological mechanism underlying cognitive dysfunction in schizophrenia. Recent research suggests that selective modulation of the GABAergic system is a promising intervention for the treatment of schizophrenia-associated cognitive defects. In this review, we summarized evidence from postmortem and animal studies for abnormal GABAergic neurotransmission in schizophrenia, and how altered GABA interneurons could disrupt neuronal oscillations. Next, we systemically reviewed a variety of up-to-date subtype-selective agonists, antagonists, positive and negative allosteric modulators (including dual allosteric modulators) for α5/α3/α2 GABA_A and GABA_B receptors, and summarized their pro-cognitive effects in animal behavioral tests and clinical trials. Finally, we also discuss various representative histone deacetylases (HDAC) inhibitors that target GABA system through epigenetic modulations, GABA prodrug and presynaptic GABA transporter inhibitors. This review provides important information on current potential GABA-associated therapies and future insights for development of more effective treatments.

Restoring Tip60 HAT/HDAC2 Balance in the Neurodegenerative Brain Relieves Epigenetic Transcriptional Repression and Reinstates Cognition

Cognitive decline is a debilitating hallmark during preclinical stages of Alzheimer's disease (AD), yet the causes remain unclear. Because histone acetylation homeostasis is critical for mediating epigenetic gene control throughout neuronal development, we postulated that its misregulation contributes to cognitive impairment preceding AD pathology. Here, we show that disruption of Tip60 histone acetlytransferase (HAT)/histone deacetylase 2 (HDAC2) homeostasis occurs early in the brain of an AD-associated amyloid precursor protein (APP) Drosophila model and triggers epigenetic repression of neuroplasticity genes well before Aβ plaques form in male and female larvae. Repressed genes display enhanced HDAC2 binding and reduced Tip60 and histone acetylation enrichment. Increasing Tip60 in the AD-associated APP brain restores Tip60 HAT/HDAC2 balance by decreasing HDAC2 levels, reverses neuroepigenetic alterations to activate synaptic plasticity genes, and reinstates brain morphology and cognition. Such Drosophila neuroplasticity gene epigenetic signatures are conserved in male and female mouse hippocampus and their expression and Tip60 function is compromised in hippocampus from AD patients. We suggest that Tip60 HAT/HDAC2-mediated epigenetic gene disruption is a critical initial step in AD that is reversed by restoring Tip60 in the brain.SIGNIFICANCE STATEMENT Mild cognitive impairment is a debilitating hallmark during preclinical stages of Alzheimer's disease (AD), yet its causes remain unclear. Although recent findings support elevated histone deacetylase 2 (HDAC2) as a cause for epigenetic repression of synaptic genes that contribute to cognitive deficits, whether alterations in histone acetlytransferase (HAT) levels that counterbalance HDAC2 repressor action occur and the identity of these HATs remain unknown. We demonstrate that disruption of Tip60 HAT/HDAC2 homeostasis occurs early in the AD Drosophila brain and triggers epigenetic repression of neuroplasticity genes before Aβ plaques form. Increasing Tip60 in the AD brain restores Tip60 HAT/HDAC2 balance, reverses neuroepigenetic alterations to activate synaptic genes, and reinstates brain morphology and cognition. Our data suggest that disruption of the Tip60 HAT/HDAC2 balance is a critical initial step in AD.

Design, synthesis, biological evaluation and in vivo testing of dual phosphodiesterase 5 (PDE5) and histone deacetylase 6 (HDAC6)-selective inhibitors for the treatment of Alzheimer's disease

We have identified chemical probes that act as dual phosphodiesterase 5 (PDE5) and histone deacetylase 6 (HDAC6)-selective inhibitors (>1 log unit difference versus class I HDACs) to decipher the contribution of HDAC isoforms to the positive impact of dual-acting PDE5 and HDAC inhibitors on mouse models of Alzheimer's disease (AD) and fine-tune this systems therapeutics approach. Structure- and knowledge-based approaches led to the design of first-in-class molecules with the desired target compound profile: dual PDE5 and HDAC6-selective inhibitors. Compound 44b, which fulfilled the biochemical, functional and ADME-Tox profiling requirements and exhibited adequate pharmacokinetic properties, was selected as pharmacological tool compound and tested in a mouse model of AD (Tg2576) in vivo.

Social deficits in Shank3-deficient mouse models of autism are rescued by histone deacetylase (HDAC) inhibition

Haploinsufficiency of the SHANK3 gene is causally linked to autism spectrum disorder (ASD), and ASD-associated genes are also enriched for chromatin remodelers. Here we found that brief treatment with romidepsin, a highly potent class I histone deacetylase (HDAC) inhibitor, alleviated social deficits in Shank3-deficient mice, which persisted for ~3 weeks. HDAC2 transcription was upregulated in these mice, and knockdown of HDAC2 in prefrontal cortex also rescued their social deficits. Nuclear localization of β-catenin, a Shank3-binding protein that regulates cell adhesion and transcription, was increased in Shank3-deficient mice, which induced HDAC2 upregulation and social deficits. At the downstream molecular level, romidepsin treatment elevated the expression and histone acetylation of Grin2a and actin-regulatory genes and restored NMDA-receptor function and actin filaments in Shank3-deficient mice. Taken together, these findings highlight an epigenetic mechanism underlying social deficits linked to Shank3 deficiency, which may suggest potential therapeutic strategies for ASD patients bearing SHANK3 mutations.