Suberoylanilide hydroxamic acid, a histone deacetylase inhibitor, ameliorates motor deficits in a mouse model of Huntington's disease

Identification of a histone deacetylase inhibitor as a therapeutic candidate for congenital central hypoventilation syndrome

Congenital central hypoventilation syndrome (CCHS), a rare genetic disease caused by heterozygous PHOX2B mutations, is characterized by life-threatening breathing deficiencies. PHOX2B is a transcription factor required for the specification of the autonomic nervous system, which contains, in particular, brainstem respiratory centers. In CCHS, PHOX2B mutations lead to cytoplasmic PHOX2B protein aggregations, thus compromising its transcriptional capability. Currently, the only available treatment for CCHS is assisted mechanical ventilation. Therefore, identifying molecules with alleviating effects on CCHS-related breathing impairments is of primary importance. A transcriptomic analysis of cells transfected with different PHOX2B constructs was used to identify compounds of interest with the CMap tool. Using fluorescence microscopy and luciferase assay, the selected molecules were further tested in vitro for their ability to restore the nuclear location and function of PHOX2B. Finally, an electrophysiological approach was used to investigate ex vivo the effects of the most promising molecule on respiratory activities of PHOX2B-mutant mouse isolated brainstem. The histone deacetylase inhibitor SAHA was found to have low toxicity in vitro, to restore the proper location and function of PHOX2B protein, and to improve respiratory rhythm-related parameters ex vivo. Thus, our results identify SAHA as a promising agent to treat CCHS-associated breathing deficiencies.

Cyclodextrin-Containing Drug Delivery Systems and Their Applications in Neurodegenerative Disorders

Cyclodextrins (CDs) are ubiquitous excipients, constituted of cyclic glucopyranose units, and possess a unique dual nature, that of a hydrophobic interior and a hydrophilic exterior. This enables their interaction with lipid-affinitive compounds and hydrophilic compounds, thereby augmenting their application in pharmaceutical formulations as agents for improving solubility, as well as fundamental elements of advanced drug delivery systems. Additionally, CDs, upon suitable modification, can strategically participate in the interaction with cellular components and physical barriers, such as the blood-brain barrier, where their intricate and multifunctional engagement leads to various biological impacts. This review consolidates the crucial features of CDs and their derivatives, and summarizes the applications of them as drug delivery systems in neurodegenerative disorders, emphasizing their notable potentials.

Effect of vorinostat on protein expression in vitro and in vivo following mRNA lipoplex administration

Previously, we demonstrated that cationic liposomes comprised of N-hexadecyl-N,N-dimethylhexadecan-1-aminium bromide, 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine and poly(ethylene glycol) cholesteryl ether induced substantial protein expression both in vitro and in vivo following the administration of mRNA/cationic liposome complexes (mRNA lipoplexes). The present study evaluated the effect of vorinostat, a histone deacetylase inhibitor, on protein expression levels in vitro and in vivo following the administration of mRNA lipoplexes. The half-maximal inhibitory concentration (IC50) values of vorinostat for human cervical carcinoma HeLa and human liver cancer HepG2 cells were determined to be 7.8 and 2.6 µM, respectively, following a 24 h incubation period. Treatment with 1 µM vorinostat resulted in a 2.7-fold increase in luciferase (Luc) activity for HeLa cells and a 1.6-fold increase for HepG2 cells at 24 h post-transfection with firefly Luc (FLuc) mRNA lipoplexes compared with untreated cells. However, treatment with 10 µM vorinostat decreased Luc activity compared with treatment with 1 µM vorinostat. Intravenous injection of Cy5-labeled mRNA lipoplexes into mice resulted in mRNA accumulation primarily in the lungs; however, co-injection with vorinostat at doses of 5 or 25 mg/kg resulted in mRNA accumulation in both the lungs and liver. Furthermore, intravenous injection of FLuc mRNA lipoplexes resulted in high Luc activity in both the lungs and spleen. Nevertheless, co-injection with vorinostat slightly decreased Luc activity in the lungs but not in the spleen. These findings indicated that vorinostat enhances in vitro protein expression from transfected mRNA after treatment with a lower concentration of IC50; however, it does not largely affect in vivo protein expression from the transfected mRNA.

The Mendelian disorders of chromatin machinery: Harnessing metabolic pathways and therapies for treatment

The Mendelian disorders of chromatin machinery (MDCMs) represent a distinct subgroup of disorders that present with neurodevelopmental disability. The chromatin machinery regulates gene expression by a range of mechanisms, including by post-translational modification of histones, responding to histone marks, and remodelling nucleosomes. Some of the MDCMs that impact on histone modification may have potential therapeutic interventions. Two potential treatment strategies are to enhance the intracellular pool of metabolites that can act as substrates for histone modifiers and the use of medications that may inhibit or promote the modification of histone residues to influence gene expression. In this article we discuss the influence and potential treatments of histone modifications involving histone acetylation and histone methylation. Genomic technologies are facilitating earlier diagnosis of many Mendelian disorders, providing potential opportunities for early treatment from infancy. This has parallels with how inborn errors of metabolism have been afforded early treatment with newborn screening. Before this promise can be fulfilled, we require greater understanding of the biochemical fingerprint of these conditions, which may provide opportunities to supplement metabolites that can act as substrates for chromatin modifying enzymes. Importantly, understanding the metabolomic profile of affected individuals may also provide disorder-specific biomarkers that will be critical for demonstrating efficacy of treatment, as treatment response may not be able to be accurately assessed by clinical measures.

Unlocking the epigenetic symphony: histone acetylation's impact on neurobehavioral change in neurodegenerative disorders

Recent genomics and epigenetic advances have empowered the exploration of DNA/RNA methylation and histone modifications crucial for gene expression in response to stress, aging and disease. Interest in understanding neuronal plasticity's epigenetic mechanisms, influencing brain rewiring amid development, aging and neurodegenerative disorders, continues to grow. Histone acetylation dysregulation, a commonality in diverse brain disorders, has become a therapeutic focus. Histone acetyltransferases and histone deacetylases have emerged as promising targets for neurodegenerative disorder treatment. This review delves into histone acetylation regulation, potential therapies and future perspectives for disorders like Alzheimer's, Parkinson's and Huntington's. Exploring genetic-environmental interplay through models and studies reveals molecular changes, behavioral insights and early intervention possibilities targeting the epigenome in at-risk individuals.

Treatment with sodium butyrate induces autophagy resulting in therapeutic benefits for spinocerebellar ataxia type 3

Spinocerebellar ataxia type 3 (SCA3, also known as Machado Joseph disease) is a fatal neurodegenerative disease caused by the expansion of the trinucleotide repeat region within the ATXN3/MJD gene. Mutation of ATXN3 causes formation of ataxin-3 protein aggregates, neurodegeneration, and motor deficits. Here we investigated the therapeutic potential and mechanistic activity of sodium butyrate (SB), the sodium salt of butyric acid, a metabolite naturally produced by gut microbiota, on cultured SH-SY5Y cells and transgenic zebrafish expressing human ataxin-3 containing 84 glutamine (Q) residues to model SCA3. SCA3 SH-SY5Y cells were found to contain high molecular weight ataxin-3 species and detergent-insoluble protein aggregates. Treatment with SB increased the activity of the autophagy protein quality control pathway in the SCA3 cells, decreased the presence of ataxin-3 aggregates and presence of high molecular weight ataxin-3 in an autophagy-dependent manner. Treatment with SB was also beneficial in vivo, improving swimming performance, increasing activity of the autophagy pathway, and decreasing the presence of insoluble ataxin-3 protein species in the transgenic SCA3 zebrafish. Co-treating the SCA3 zebrafish with SB and chloroquine, an autophagy inhibitor, prevented the beneficial effects of SB on zebrafish swimming, indicating that the improved swimming performance was autophagy-dependent. To understand the mechanism by which SB induces autophagy we performed proteomic analysis of protein lysates from the SB-treated and untreated SCA3 SH-SY5Y cells. We found that SB treatment had increased activity of Protein Kinase A and AMPK signaling, with immunoblot analysis confirming that SB treatment had increased levels of AMPK protein and its substrates. Together our findings indicate that treatment with SB can increase activity of the autophagy pathway process and that this has beneficial effects in vitro and in vivo. While our results suggested that this activity may involve activity of a PKA/AMPK-dependent process, this requires further confirmation. We propose that treatment with sodium butyrate warrants further investigation as a potential treatment for neurodegenerative diseases underpinned by mechanisms relating to protein aggregation including SCA3.

Neurodegenerative Diseases: New Hopes and Perspectives

Alzheimer's disease, Parkinson's disease, Amyotrophic lateral sclerosis, Huntington's disease, and Friedrich ataxia are all incurable neurodegenerative diseases defined by the continuous progressive loss of distinct neuronal subtypes. Despite their rising prevalence among the world's ageing population, fewer advances have been made in the concurrent massive efforts to develop newer drugs. Recently, there has been a shift in research focus towards the discovery of new therapeutic agents for neurodegenerative diseases. In this review, we have summarized the recently developed therapies and their status in the management of neurodegenerative diseases.

Recombinant cellular model system for human muscle-type nicotinic acetylcholine receptor α12β1δε

The human muscle-type nicotinic acetylcholine receptor α12β1δε (nAChR) is a complex transmembrane receptor needed for drug screening for disorders like congenital myasthenic syndromes and multiple pterygium syndrome. Until today, most models are still using the nAChR from Torpedo californica electric ray. A simple reproducible cellular system expressing functional human muscle-type nAChR is still missing. This study addressed this issue and further tested the hypothesis that different chaperones, both biological and chemical, and posttranslational modification supporting substances as well as hypothermic incubation are able to increase the nAChR yield. Therefore, Gibson cloning was used to generate transfer plasmids carrying the sequence of nAChR or chosen biological chaperones to support the nAChR folding in the cellular host. Viral transduction was used for stable integration of these transgenes in Chinese hamster ovary cells (CHO). Proteins were detected with Western blot, in-cell and on-cell Western, and the function of the receptor with voltage clamp analysis. We show that the internalization of nAChR into plasma membranes was sufficient for detection and function. Additional transgenic overexpression of biological chaperones did result in a reduced nAChR expression. Chemical chaperones, posttranslational modification supporting substances, and hypothermic conditions are well-suited supporting applications to increase the protein levels of different subunits. This study presents a stable and functional cell line that expresses human muscle-type nAChR and yields can be further increased using the chemical chaperone nicotine without affecting cell viability. The simplified access to this model system should enable numerous applications beyond drug development. Graphical abstract created with http://biorender.com.

The Lysine Demethylase KDM7A Regulates Immediate Early Genes in Neurons

Lysine demethylase KDM7A removes histone modifications H3K9me1/2 and H3K27me1/2. KDM7A plays critical roles in gene expression and contribute to biological processes including tumorigenesis, metabolism, and embryonic development. However, the functions of KDM7A in mammalian nervous system are still poorly explored. In this study, functional roles of KDM7A are comprehensively investigated in neuronal cells by applying CUT&Tag-seq, RNA-seq and mice models. Knockdown of Kdm7a in N2A cells result in the alteration of histone modifications near transcription start sites (TSSs) and the expression changes of a large number of genes. In particular, the expression of immediate early genes (IEGs), a series of genes maintaining the function of the nervous system and associating with neurological disorders, are significantly decreased upon Kdm7a knockdown. Furthermore, in vivo knockdown of Kdm7a in dentate gyrus (DG) neuron of mice hippocampus, via Adeno-associated virus (AAV)-based stereotaxic microinjection, led to a significant decrease of the expression of c-Fos, a marker of neuron activity. Behavior assays in mice further revealed that Kdm7a knockdown in hippocampus repress neuron activity, which leading to impairment of emotion and memory. Collectively, the study reveals that KDM7A affects neuron functions by regulating IEGs, which may provide new clues for understanding epigenetic mechanisms in neurological disorders.

Enhancing Transcriptional Reprogramming of Mesenchymal Glioblastoma with Grainyhead-like 2 and HDAC Inhibitors Leads to Apoptosis and Cell-Cycle Dysregulation

Glioblastoma (GBM) tumor cells exhibit mesenchymal properties which are thought to play significant roles in therapeutic resistance and tumor recurrence. An important question is whether impairment of the mesenchymal state of GBM can sensitize these tumors to therapeutic intervention. HDAC inhibitors (HDACi) are being tested in GBM for their ability promote mesenchymal-to-epithelial transcriptional (MET) reprogramming, and for their cancer-specific ability to dysregulate the cell cycle and induce apoptosis. We set out to enhance the transcriptional reprogramming and apoptotic effects of HDACi in GBM by introducing an epithelial transcription factor, Grainyhead-like 2 (GRHL2), to specifically counter the mesenchymal state. GRHL2 significantly enhanced HDACi-mediated MET reprogramming. Surprisingly, we found that inducing GRHL2 in glioma stem cells (GSCs) altered cell-cycle drivers and promoted aneuploidy. Mass spectrometry analysis of GRHL2 interacting proteins revealed association with several key mitotic factors, suggesting their exogenous expression disrupted the established mitotic program in GBM. Associated with this cell-cycle dysregulation, the combination of GRHL2 and HDACi induced elevated levels of apoptosis. The key implication of our study is that although genetic strategies to repress the mesenchymal properties of glioblastoma may be effective, biological interactions of epithelial factors in mesenchymal cancer cells may dysregulate normal homeostatic cellular mechanisms.

Glioma Stem Cells Are Sensitized to BCL-2 Family Inhibition by Compromising Histone Deacetylases

Glioblastoma (GBM) remains an incurable disease with an extremely high five-year recurrence rate. We studied apoptosis in glioma stem cells (GSCs) in response to HDAC inhibition (HDACi) combined with MEK1/2 inhibition (MEKi) or BCL-2 family inhibitors. MEKi effectively combined with HDACi to suppress growth, induce cell cycle defects, and apoptosis, as well as to rescue the expression of the pro-apoptotic BH3-only proteins BIM and BMF. A RNAseq analysis of GSCs revealed that HDACi repressed the pro-survival BCL-2 family genes MCL1 and BCL-XL. We therefore replaced MEKi with BCL-2 family inhibitors and observed enhanced apoptosis. Conversely, a ligand for the cancer stem cell receptor CD44 led to reductions in BMF, BIM, and apoptosis. Our data strongly support further testing of HDACi in combination with MEKi or BCL-2 family inhibitors in glioma.

Suberoylanilide Hydroxamic Acid (SAHA) Is a Driver Molecule of Neuroplasticity: Implication for Neurological Diseases

Neuroplasticity is a crucial property of the central nervous system to change its activity in response to intrinsic or extrinsic stimuli. This is mainly achieved through the promotion of changes in the epigenome. One of the epi-drivers priming this process is suberoylanilide hydroxamic acid (SAHA or Vorinostat), a pan-histone deacetylase inhibitor that modulates and promotes neuroplasticity in healthy and disease conditions. Knowledge of the specific molecular changes induced by this epidrug is an important area of neuro-epigenetics for the identification of new compounds to treat cognition impairment and/or epilepsy. In this review, we summarize the findings obtained in cellular and animal models of various brain disorders, highlighting the multiple mechanisms activated by SAHA, such as improvement of memory, learning and behavior, and correction of faulty neuronal functioning. Supporting this evidence, in vitro and in vivo data underline how SAHA positively regulates the expression of neuronal genes and microtubule dynamics, induces neurite outgrowth and spine density, and enhances synaptic transmission and potentiation. In particular, we outline studies regarding neurodevelopmental disorders with pharmaco-resistant seizures and/or severe cognitive impairment that to date lack effective drug treatments in which SAHA could ameliorate defective neuroplasticity.

From Pathogenesis to Therapeutics: A Review of 150 Years of Huntington's Disease Research

Huntington's disease (HD) is a debilitating neurodegenerative genetic disorder caused by an expanded polyglutamine-coding (CAG) trinucleotide repeat in the huntingtin (HTT) gene. HD behaves as a highly penetrant dominant disorder likely acting through a toxic gain of function by the mutant huntingtin protein. Widespread cellular degeneration of the medium spiny neurons of the caudate nucleus and putamen are responsible for the onset of symptomology that encompasses motor, cognitive, and behavioural abnormalities. Over the past 150 years of HD research since George Huntington published his description, a plethora of pathogenic mechanisms have been proposed with key themes including excitotoxicity, dopaminergic imbalance, mitochondrial dysfunction, metabolic defects, disruption of proteostasis, transcriptional dysregulation, and neuroinflammation. Despite the identification and characterisation of the causative gene and mutation and significant advances in our understanding of the cellular pathology in recent years, a disease-modifying intervention has not yet been clinically approved. This review includes an overview of Huntington's disease, from its genetic aetiology to clinical presentation and its pathogenic manifestation. An updated view of molecular mechanisms and the latest therapeutic developments will also be discussed.

Nuclear compression regulates YAP spatiotemporal fluctuations in living cells

Yes-associated protein (YAP) is a key mechanotransduction protein in diverse physiological and pathological processes; however, a ubiquitous YAP activity regulatory mechanism in living cells has remained elusive. Here, we show that YAP nuclear translocation is highly dynamic during cell movement and is driven by nuclear compression arising from cell contractile work. We resolve the mechanistic role of cytoskeletal contractility in nuclear compression by manipulation of nuclear mechanics. Disrupting the linker of nucleoskeleton and cytoskeleton complex reduces nuclear compression for a given contractility and correspondingly decreases YAP localization. Conversely, decreasing nuclear stiffness via silencing of lamin A/C increases nuclear compression and YAP nuclear localization. Finally, using osmotic pressure, we demonstrated that nuclear compression even without active myosin or filamentous actin regulates YAP localization. The relationship between nuclear compression and YAP localization captures a universal mechanism for YAP regulation with broad implications in health and biology.

Histone deacetylase 7: a signalling hub controlling development, inflammation, metabolism and disease

Histone deacetylases (HDACs) catalyse removal of acetyl groups from lysine residues on both histone and non-histone proteins to control numerous cellular processes. Of the 11 zinc-dependent classical HDACs, HDAC4, 5, 7 and 9 are class IIa HDAC enzymes that regulate cellular and developmental processes through both enzymatic and non-enzymatic mechanisms. Over the last two decades, HDAC7 has been associated with key roles in numerous physiological and pathological processes. Molecular, cellular, in vivo and disease association studies have revealed that HDAC7 acts through multiple mechanisms to control biological processes in immune cells, osteoclasts, muscle, the endothelium and epithelium. This HDAC protein regulates gene expression, cell proliferation, cell differentiation and cell survival and consequently controls development, angiogenesis, immune functions, inflammation and metabolism. This review focuses on the cell biology of HDAC7, including the regulation of its cellular localisation and molecular mechanisms of action, as well as its associative and causal links with cancer and inflammatory, metabolic and fibrotic diseases. We also review the development status of small molecule inhibitors targeting HDAC7 and their potential for intervention in different disease contexts.

Assessment of suberoylanilide hydroxamic acid on a Alzheimer's disease model induced by β-amyloid(1-42) in aged female mice: Neuromodulatory and epigenetic effect

Alzheimer's disease (AD) is a neurodegenerative disease that affects several elderly people per years. AD is a pathology of multifactorial etiology, resulting from multiple environmental and genetic determinants. However, there is no effective pharmacological alternative for the treatment of this illness. In this sense, the purpose of current study was to characterize the mechanisms by which Aβ_1-42 injection via intracerebroventricular induces neurobehavioral changes in a time-course curve. In addition, suberoylanilide hydroxamic acid (SAHA) inhibitor of histone deacetylase (HDAC) was used to investigate the involvement of epigenetic modifications Aβ_1-42-caused in aged female mice. In general manner, Aβ_1-42 injection induced a major neurochemical disturbance in hippocampus and prefrontal cortex of animals and a serious impairment of memory. Overall, SAHA treatment attenuated neurobehavioral changes caused by Aβ_1-42 injection in aged female mice. The subchronic effects presented of SAHA were through modulation of HDAC activity, regulation of brain-derived neurotrophic factor (BDNF) levels and expression of BDNF mRNA, accompanied by unlocking cAMP/PKA/pCREB pathway in hippocampus and prefrontal cortex of animals.

The Transcription Factor NRF2 Has Epigenetic Regulatory Functions Modulating HDACs, DNMTs, and miRNA Biogenesis

The epigenetic regulation of gene expression is a complex and tightly regulated process that defines cellular identity and is associated with health and disease processes. Oxidative stress is capable of inducing epigenetic modifications. The transcription factor NRF2 (nuclear factor erythroid-derived 2-like 2) is a master regulator of cellular homeostasis, regulating genes bearing antioxidant response elements (AREs) in their promoters. Here, we report the identification of ARE sequences in the promoter regions of genes encoding several epigenetic regulatory factors, such as histone deacetylases (HDACs), DNA methyltransferases (DNMTs), and proteins involved in microRNA biogenesis. In this research, we study this possibility by integrating bioinformatic, genetic, pharmacological, and molecular approaches. We found ARE sequences in the promoter regions of genes encoding several HDACs, DNMTs, and proteins involved in miRNA biogenesis. We confirmed that NRF2 regulates the production of these genes by studying NRF2-deficient cells and cells treated with dimethyl fumarate (DMF), an inducer of the NRF2 signaling pathway. In addition, we found that NRF2 could be involved in the target RNA-dependent microRNA degradation (TDMD) of miR-155-5p through its interaction with Nfe2l2 mRNA. Our data indicate that NRF2 has an epigenetic regulatory function, complementing its traditional function and expanding the regulatory dimensions that should be considered when developing NRF2-centered therapeutic strategies.

Bromodomain and Extra-Terminal Proteins in Brain Physiology and Pathology: BET-ing on Epigenetic Regulation

BET proteins function as histone code readers of acetylated lysins that determine the positive regulation in transcription of genes involved in cell cycle progression, differentiation, inflammation, and many other pathways. In recent years, thanks to the development of BET inhibitors, interest in this protein family has risen for its relevance in brain development and function. For example, experimental evidence has shown that BET modulation affects neuronal activity and the expression of genes involved in learning and memory. In addition, BET inhibition strongly suppresses molecular pathways related to neuroinflammation. These observations suggest that BET modulation may play a critical role in the onset and during the development of diverse neurodegenerative and neuropsychiatric disorders, such as Alzheimer’s disease, fragile X syndrome, and Rett syndrome. In this review article, we summarize the most recent evidence regarding the involvement of BET proteins in brain physiology and pathology, as well as their pharmacological potential as targets for therapeutic purposes.

Suberoylanilide hydroxamic acid (SAHA) attenuates memory impairment in the offspring of rats exposed to sevoflurane anesthesia

BACKGROUND

SAHA was reported to enhance the expression of miR-129-5p, which was predicted to bind to 3' UTR of CASP-6, a gene playing crucial roles in the pathogenesis of memory impairment. Whether SAHA/miR-129-5p/CASP-6 is involved in the pathogenesis of prenatal exposure to sevoflurane remains to be explored.

METHODS

Morris water maze test was performed to evaluate the functional parameters of learning and memory. Quantitative real-time qPCR was carried out to analyze the expression of miRNAs and CASP-6 mRNA under different conditions.

RESULTS

Sevoflurane exposure of pregnant rats and SAHA treatment of the offspring had no effect on the blood gases, litter size, survival rate and weight. SAHA administration remarkably reversed the learning and memory impairment in prenatal rats caused by sevoflurane exposure. Mechanistically, the abnormal expression of miR-129-5p and CASP-6 in the offspring of pregnant rats exposed to sevoflurane was effectively restored by SAHA treatment. The luciferase activity of CASP-6 vector was effectively inhibited by miR-129-5p in primary neuron cells of rats. Moreover, the expression of CASP-6 mRNA and protein was significantly suppressed by miR-129-5p and SAHA treatment in a dose-dependent manner.

CONCLUSION

Our work demonstrated that the administration of SAHA suppressed the expression of CASP-6 via modulating the expression of miR-129-5p, and SAHA may rescue the apoptosis of neurons caused by exposure to sevoflurane. The underlying mechanism might be the ability of SAHA to relieve learning and memory impairment in the offspring of the pregnant rats exposed to sevoflurane.

Epigenetic modulation: Research progress on histone acetylation levels in major depressive disorders

Depression is a serious mental illness and a prevalent condition with multiple aetiologies. The impact of the current therapeutic strategies is limited and the pathogenesis of the illness is not well understood. According to previous studies, depression onset is influenced by a variety of environmental and genetic factors, including chronic stress, aberrant changes in gene expression, and hereditary predisposition. Transcriptional regulation in eukaryotes is closely related to chromosome packing and is controlled by histone post-translational modifications. The development of new antidepressants may proceed along a new path with medications that target epigenetics. Histone deacetylase inhibitors (HDACis) are a class of compounds that interfere with the function of histone deacetylases (HDACs). This review explores the relationship between HDACs and depression and focuses on the current knowledge on their regulatory mechanism in depression and the potential therapeutic use of HDACis with antidepressant efficacy in preclinical research. Future research on inhibitors is also proposed and discussed.

Small molecule modulators of chromatin remodeling: from neurodevelopment to neurodegeneration

The dynamic changes in chromatin conformation alter the organization and structure of the genome and further regulate gene transcription. Basically, the chromatin structure is controlled by reversible, enzyme-catalyzed covalent modifications to chromatin components and by noncovalent ATP-dependent modifications via chromatin remodeling complexes, including switch/sucrose nonfermentable (SWI/SNF), inositol-requiring 80 (INO80), imitation switch (ISWI) and chromodomain-helicase DNA-binding protein (CHD) complexes. Recent studies have shown that chromatin remodeling is essential in different stages of postnatal and adult neurogenesis. Chromatin deregulation, which leads to defects in epigenetic gene regulation and further pathological gene expression programs, often causes a wide range of pathologies. This review first gives an overview of the regulatory mechanisms of chromatin remodeling. We then focus mainly on discussing the physiological functions of chromatin remodeling, particularly histone and DNA modifications and the four classes of ATP-dependent chromatin-remodeling enzymes, in the central and peripheral nervous systems under healthy and pathological conditions, that is, in neurodegenerative disorders. Finally, we provide an update on the development of potent and selective small molecule modulators targeting various chromatin-modifying proteins commonly associated with neurodegenerative diseases and their potential clinical applications.

The role of altered protein acetylation in neurodegenerative disease

Acetylation is a key post-translational modification (PTM) involved in the regulation of both histone and non-histone proteins. It controls cellular processes such as DNA transcription, RNA modifications, proteostasis, aging, autophagy, regulation of cytoskeletal structures, and metabolism. Acetylation is essential to maintain neuronal plasticity and therefore essential for memory and learning. Homeostasis of acetylation is maintained through the activities of histone acetyltransferases (HAT) and histone deacetylase (HDAC) enzymes, with alterations to these tightly regulated processes reported in several neurodegenerative diseases including Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and amyotrophic lateral sclerosis (ALS). Both hyperacetylation and hypoacetylation can impair neuronal physiological homeostasis and increase the accumulation of pathophysiological proteins such as tau, α-synuclein, and Huntingtin protein implicated in AD, PD, and HD, respectively. Additionally, dysregulation of acetylation is linked to impaired axonal transport, a key pathological mechanism in ALS. This review article will discuss the physiological roles of protein acetylation and examine the current literature that describes altered protein acetylation in neurodegenerative disorders.

Therapeutic Efficacy of Novel HDAC Inhibitors SPA3052 and SPA3074 against Intestinal Inflammation in a Murine Model of Colitis

Inflammatory bowel diseases (IBD) are digestive tract disorders that involve chronic inflammation with frequent recurrences. This study aimed to evaluate the efficacy of two novel histone deacetylase 8 (HDAC8) inhibitors, namely, SPA3052 and SPA3074, against dextran sulfate sodium (DSS)-induced experimental colitis. Male C57BL/6N mice were subjected to two cycles of 1.5% DSS followed by treatment with suberoylanilide hydroxamic acid (SAHA), SPA3052, or SPA3074 for 14 days. Our results showed that SPA3074 administration increased (>50%) the expression of occludin, a tight junction protein, which was significantly decreased (>100%) after DSS treatment. Moreover, SPA3074 upregulated suppressor of cytokine signaling 1 (SOCS1) protein expression, which is known to be a key suppressor of T-helper cell differentiation and pro-inflammatory cytokines expression. Furthermore, we observed a decrease in SOCS1-associated Akt phosphorylation and an increase in lower extracellular signal-regulated kinase 1 and 2 phosphorylation, which contributed to lower nuclear factor-kappa B activation. Th2 effector cytokines, especially interleukin-13, were also downregulated by SPA3074 treatment. This study suggests that HDAC8 might be a promising novel target for the development of IBD treatments and that the novel HDAC8 inhibitor SPA3074 is a new candidate for IBD therapeutics.

Acetylation State of Lysine 14 of Histone H3.3 Affects Mutant Huntingtin Induced Pathogenesis

Huntington's Disease (HD) is a fatal neurodegenerative disorder caused by the expansion of a polyglutamine-coding CAG repeat in the Huntingtin gene. One of the main causes of neurodegeneration in HD is transcriptional dysregulation that, in part, is caused by the inhibition of histone acetyltransferase (HAT) enzymes. HD pathology can be alleviated by increasing the activity of specific HATs or by inhibiting histone deacetylase (HDAC) enzymes. To determine which histone's post-translational modifications (PTMs) might play crucial roles in HD pathology, we investigated the phenotype-modifying effects of PTM mimetic mutations of variant histone H3.3 in a Drosophila model of HD. Specifically, we studied the mutations (K→Q: acetylated; K→R: non-modified; and K→M: methylated) of lysine residues K9, K14, and K27 of transgenic H3.3. In the case of H3.3K14Q modification, we observed the amelioration of all tested phenotypes (viability, longevity, neurodegeneration, motor activity, and circadian rhythm defects), while H3.3K14R had the opposite effect. H3.3K14Q expression prevented the negative effects of reduced Gcn5 (a HAT acting on H3K14) on HD pathology, while it only partially hindered the positive effects of heterozygous Sirt1 (an HDAC acting on H3K14). Thus, we conclude that the Gcn5-dependent acetylation of H3.3K14 might be an important epigenetic contributor to HD pathology.

Pathogenesis and potential therapeutic application of stem cells transplantation in Huntington’s disease

Huntington's disease (HD) is a progressive neurodegenerative disorder which is caused due to repetitive CAG or glutamine expression along the coding region of the Huntington gene. This disease results in certain movement abnormalities, affective disturbances, dementia and cognitive impairments. To this date, there is no proper cure for this rare and fatal neurological condition but there have been certain advancements in the field of genetic animal model research studies to elucidate the understanding of the pathogenesis of this condition. Currently, HD follows a certain therapeutic approach which just relieves the symptoms but doesn't cure the underlying cause of the disease. Stem cell therapy can be a breakthrough in developing a potential cure for this condition. In this review, we have discussed the pathogenesis and the efficacy and clinical practicality of the therapeutic application of stem cell transplantation in Huntington's disease. The application of this groundbreaking therapy on genetically altered animal models has been listed and analyzed in brief.

Pathogenesis of Huntington's Disease: An Emphasis on Molecular Pathways and Prevention by Natural Remedies

BACKGROUND

Huntington's disease is an inherited autosomal dominant trait neuro-degenerative disorder caused by changes (mutations) of a gene called huntingtin (htt) that is located on the short arm (p) of chromosome 4, CAG expansion mutation. It is characterized by unusual movements, cognitive and psychiatric disorders.

OBJECTIVE

This review was undertaken to apprehend biological pathways of Huntington's disease (HD) pathogenesis and its management by nature-derived products. Natural products can be lucrative for the management of HD as it shows protection against HD in pre-clinical trials. Advanced research is still required to assess the therapeutic effectiveness of the known organic products and their isolated compounds in HD experimental models.

SUMMARY

Degeneration of neurons in Huntington's disease is distinguished by progressive loss of motor coordination and muscle function. This is due to the expansion of CAG trinucleotide in the first exon of the htt gene responsible for neuronal death and neuronal network degeneration in the brain. It is believed that the factors such as molecular genetics, oxidative stress, excitotoxicity, mitochondrial dysfunction, neuroglia dysfunction, protein aggregation, and altered UPS leads to HD. The defensive effect of the natural product provides therapeutic efficacy against HD. Recent reports on natural drugs have enlightened the protective role against HD via antioxidant, anti-inflammatory, antiapoptotic, and neurofunctional regulation.

Modifier pathways in polyglutamine (PolyQ) diseases: from genetic screens to drug targets

Polyglutamine (PolyQ) diseases include a group of inherited neurodegenerative disorders caused by unstable expansions of CAG trinucleotide repeats in the coding region of specific genes. Such genetic alterations produce abnormal proteins containing an unusually long PolyQ tract that renders them more prone to aggregate and cause toxicity. Although research in the field in the last years has contributed significantly to the knowledge of the biological mechanisms implicated in these diseases, effective treatments are still lacking. In this review, we revisit work performed in models of PolyQ diseases, namely the yeast Saccharomyces cerevisiae, the nematode worm Caenorhabditis elegans and the fruit fly Drosophila melanogaster, and provide a critical overview of the high-throughput unbiased genetic screens that have been performed using these systems to identify novel genetic modifiers of PolyQ diseases. These approaches have revealed a wide variety of cellular processes that modulate the toxicity and aggregation of mutant PolyQ proteins, reflecting the complexity of these disorders and demonstrating how challenging the development of therapeutic strategies can be. In addition to the unbiased large-scale genetic screenings in non-vertebrate models, complementary studies in mammalian systems, closer to humans, have contributed with novel genetic modifiers of PolyQ diseases, revealing neuronal function and inflammation as key disease modulators. A pathway enrichment analysis, using the human orthologues of genetic modifiers of PolyQ diseases clustered modifier genes into major themes translatable to the human disease context, such as protein folding and transport as well as transcription regulation. Innovative genetic strategies of genetic manipulation, together with significant advances in genomics and bioinformatics, are taking modifier genetic studies to more realistic disease contexts. The characterization of PolyQ disease modifier pathways is of extreme relevance to reveal novel therapeutic possibilities to delay disease onset and progression in patients.

MicroRNA editing patterns in Huntington's disease

Huntington's disease (HD) is a neurodegenerative disease. MicroRNAs (miRNAs) are small non-coding RNAs that mediate post-transcriptional regulation of target genes. Although miRNAs are extensively edited in human brains, the editome of miRNAs in brains of HD patients is largely unknown. By analyzing the small RNA sequencing profiles of brain tissues of 28 HD patients and 83 normal controls, 1182 miRNA editing sites with significant editing levels were identified. In addition to 27 A-to-I editing sites, we identified 3 conserved C-to-U editing sites in miRNAs of HD patients. 30 SNPs in the miRNAs of HD patients were also identified. Furthermore, 129 miRNA editing events demonstrated significantly different editing levels in prefrontal cortex samples of HD patients (HD-PC) when compared to those of healthy controls. We found that hsa-mir-10b-5p was edited to have an additional cytosine at 5'-end in HD-PC, and the edited hsa-mir-10b repressed GTPBP10 that was often downregulated in HD. The down-regulation of GTPBP10 might contribute to the progression of HD by causing gradual loss of function of mitochondrial. These results provide the first endeavor to characterize the miRNA editing events in HD and their potential functions.

Vorinostat Corrects Cognitive and Non-Cognitive Symptoms in a Mouse Model of Fragile X Syndrome

BACKGROUND

Fragile X syndrome (FXS) is caused by mutations in the FMR1 gene. It is a form of heritable intellectual disability and autism. Despite recent advance in elucidating disease mechanisms, there is no efficacious medication. Because de novo drug development is a lengthy process, repurposing the existing FDA-approved drugs offers an opportunity to advance clinical intervention for FXS. Our previous study with transcriptome analysis predicts potential therapeutic effects of vorinostat on FXS.

METHODS

We analyzed the vorinostat-induced transcriptome changes and confirmed its similarity to that induced by trifluoperazine, which was previously shown to correct pathological outcomes associated with FXS. To validate the therapeutic efficacy, we examined vorinostat's effect on correcting the key behavioral and cellular symptoms in a mouse model of FXS.

RESULTS

We found that vorinostat restores object location memory and passive avoidance memory in the Fmr1 knockout mice. For the non-cognitive behavioral symptoms, vorinostat corrected the autism-associated alterations, including repetitive behavior and social interaction deficits. In the open field test, vorinostat dampened hyperactivity in the center area of the arena. Surprisingly, vorinostat did not correct the abnormally elevated protein synthesis in cultured Fmr1 knockout hippocampal neurons, suggesting that different aspects of pathological outcomes may respond differently to a specific therapeutic intervention.

CONCLUSIONS

We used the drug-induced transcriptome signature to predict new application of existing drugs. Our data reveal the therapeutic effects of the FDA-approved drug vorinostat in a mouse model of FXS.

Discovery of HDAC6-Selective Inhibitor NN-390 with in Vitro Efficacy in Group 3 Medulloblastoma

Histone deacetylase 6 (HDAC6) has been targeted in clinical studies for anticancer effects due to its role in oncogenic transformation and metastasis. Through a second-generation structure-activity relationship (SAR) study, the design, and biological evaluation of the selective HDAC6 inhibitor NN-390 is reported. With nanomolar HDAC6 potency, >200-550-fold selectivity for HDAC6 in analogous HDAC isoform functional assays, potent intracellular target engagement, and robust cellular efficacy in cancer cell lines, NN-390 is the first HDAC6-selective inhibitor to show therapeutic potential in metastatic Group 3 medulloblastoma (MB), an aggressive pediatric brain tumor often associated with leptomeningeal metastases and therapy resistance. MB stem cells contribute to these patients' poor clinical outcomes. NN-390 selectively targets this cell population with a 44.3-fold therapeutic margin between patient-derived Group 3 MB cells in comparison to healthy neural stem cells. NN-390 demonstrated a 45-fold increased potency over HDAC6-selective clinical candidate citarinostat. In summary, HDAC6-selective molecules demonstrated in vitro therapeutic potential against Group 3 MB.

Modulation of SETDB1 activity by APQ ameliorates heterochromatin condensation, motor function, and neuropathology in a Huntington's disease mouse model

The present study describes evaluation of epigenetic regulation by a small molecule as the therapeutic potential for treatment of Huntington's disease (HD). We identified 5-allyloxy-2-(pyrrolidin-1-yl)quinoline (APQ) as a novel SETDB1/ESET inhibitor using a combined in silico and in vitro cell based screening system. APQ reduced SETDB1 activity and H3K9me3 levels in a HD cell line model. In particular, not only APQ reduced H3K9me3 levels in the striatum but it also improved motor function and neuropathological symptoms such as neuronal size and activity in HD transgenic (YAC128) mice with minimal toxicity. Using H3K9me3-ChIP and genome-wide sequencing, we also confirmed that APQ modulates H3K9me3-landscaped epigenomes in YAC128 mice. These data provide that APQ, a novel small molecule SETDB1 inhibitor, coordinates H3K9me-dependent heterochromatin remodelling and can be an epigenetic drug for treating HD, leading with hope in clinical trials of HD.

Histone deacetylase inhibitors regulate vitamin C transporter functional expression in intestinal epithelial cells

Intestinal absorption of vitamin C in humans is mediated via the sodium-dependent vitamin C transporters (hSVCT1 and hSVCT2). hSVCT1 and hSVCT2 are localized at the apical and basolateral membranes, respectively, of polarized intestinal epithelia. Studies have identified low plasma levels of vitamin C and decreased expression of hSVCT1 in patients with several inflammatory conditions including inflammatory bowel disease (IBD). Investigating the underlying mechanisms responsible for regulating hSVCT1 expression are critical for understanding vitamin C homeostasis, particularly in conditions where suboptimal vitamin C levels detrimentally affect human health. Previous research has shown that hSVCT1 expression is regulated at the transcriptional level, however, little is known about epigenetic regulatory pathways that modulate hSVCT1 expression in the intestine. In this study, we found that hSVCT1 expression and function were significantly decreased in intestinal epithelial cells by the histone deacetylase inhibitors (HDACi), valproic acid (VPA), and sodium butyrate (NaB). Further, expression of transcription factor HNF1α, which is critical for SLC23A1 promoter activity, was significantly down regulated in VPA-treated cells. Chromatin immunoprecipitation (ChIP) assays showed significantly increased enrichment of tetra-acetylated histone H3 and H4 within the SLC23A1 promoter following VPA treatment. In addition, knockdown of HDAC isoforms two, and three significantly decreased hSVCT1 functional expression. Following VPA administration to mice, functional expression of SVCT1 in the jejunum was significantly decreased. Collectively, these in vitro and in vivo studies demonstrate epigenetic regulation of SVCT1 expression in intestinal epithelia partly mediated through HDAC isoforms two and three.

Zebrafish an experimental model of Huntington's disease: molecular aspects, therapeutic targets and current challenges

Huntington disease (HD) is a lethal autosomal dominant neurodegenerative disease whose exact causative mechanism is still unknown. It can transform from one generation to another generation. The CAG triplet expansion on polyglutamine (PolyQ) tract on Huntingtin protein primarily contributes in HD pathogenesis. Apart from this some another molecular mechanisms are also involved in HD pathology such as loss of Brain derived neurotrophic factor in medium spiny neurons, mitochondrial dysfunction, and alterations in synaptic plasticity are briefly discussed in this review. However, several chemicals (3-nitropropionic acid, and Quinolinic acid) and genetic (mHTT-ΔN17-97Q over expression) experimental models are used to explore the exact pathogenic mechanism and finding of new drug targets for the development of novel therapeutic approaches. The zebrafish (Danio rerio) is widely used in in-vivo screening of several central nervous system (CNS) diseases such as HD, Alzheimer's disease (AD), Parkinson's disease (PD), and in memory deficits. Thus, this makes zebrafish as an excellent animal model for the development of new therapeutic strategies against various CNS disorders. We had reviewed several publications utilizing zebrafish and rodents to explore the disease pathology. Studies suggested that zebrafish genes and their human homologues have conserved functions. Zebrafish advantages and their characteristics over the other experimental animals make it an excellent tool for the disease study. This review explains the possible pathogenic mechanism of HD and also discusses about possible treatment therapies, apart from this we also discussed about possible potential therapeutic targets which will helps in designing of novel therapeutic approaches to overcome the disease progression.  Diagrammatic depiction shows prevention of HD pathogenesis through attenuation of various biochemical alterations.

Histone deacetylase in neuropathology

Neuroepigenetics, a new branch of epigenetics, plays an important role in the regulation of gene expression. Neuroepigenetics is associated with holistic neuronal function and helps in formation and maintenance of memory and learning processes. This includes neurodevelopment and neurodegenerative defects in which histone modification enzymes appear to play a crucial role. These modifications, carried out by acetyltransferases and deacetylases, regulate biologic and cellular processes such as apoptosis and autophagy, inflammatory response, mitochondrial dysfunction, cell-cycle progression and oxidative stress. Alterations in acetylation status of histone as well as non-histone substrates lead to transcriptional deregulation. Histone deacetylase decreases acetylation status and causes transcriptional repression of regulatory genes involved in neural plasticity, synaptogenesis, synaptic and neural plasticity, cognition and memory, and neural differentiation. Transcriptional deactivation in the brain results in development of neurodevelopmental and neurodegenerative disorders. Mounting evidence implicates histone deacetylase inhibitors as potential therapeutic targets to combat neurologic disorders. Recent studies have targeted naturally-occurring biomolecules and micro-RNAs to improve cognitive defects and memory. Multi-target drug ligands targeting HDAC have been developed and used in cell-culture and animal-models of neurologic disorders to ameliorate synaptic and cognitive dysfunction. Herein, we focus on the implications of histone deacetylase enzymes in neuropathology, their regulation of brain function and plausible involvement in the pathogenesis of neurologic defects.

Improved HDAC Inhibition, Stronger Cytotoxic Effect and Higher Selectivity against Leukemias and Lymphomas of Novel, Tricyclic Vorinostat Analogues

Histone deacetylase (HDAC) inhibitors are a class of drugs used in the cancer treatment. Here, we developed a library of 19 analogues of Vorinostat, an HDAC inhibitor used in lymphomas treatment. In Vorinostat, we replaced the hydrophobic phenyl group with various tricyclic 'caps' possessing a central, eight-membered, heterocyclic ring, and investigated the HDAC activity and cytotoxic effect on the cancer and normal cell lines. We found that 3 out of the 19 compounds, based on dibenzo[b,f]azocin-6(5H)-one, 11,12-dihydrodibenzo[b,f]azocin-6(5H)-one, and benzo[b]naphtho[2,3-f][1,5]diazocine-6,14(5H,13H)-dione scaffolds, showed better HDACs inhibition than the referenced Vorinostat. In leukemic cell line MV4-11 and in the lymphoma cell line Daudi, three compounds showed lower IC50 values than Vorinostat. These compounds had higher activity and selectivity against MV4-11 and Daudi cell lines than reference Vorinostat. We also observed a strong correlation between HDACs inhibition and the cytotoxic effect. Cell lines derived from solid tumours: A549 (lung carcinoma) and MCF-7 (breast adenocarcinoma) as well as reference BALB/3T3 (normal murine fibroblasts) were less susceptible to compounds tested. Developed derivatives show improved properties than Vorinostat, thus they could be considered as possible agents for leukemia and lymphoma treatment.

The Essential Role of Epigenetic Modifications in Neurodegenerative Diseases with Dyskinesia

Epigenetics play an essential role in the occurrence and improvement of many diseases. Evidence shows that epigenetic modifications are crucial to the regulation of gene expression. DNA methylation is closely linked to embryonic development in mammalian. In recent years, epigenetic drugs have shown unexpected therapeutic effects on neurological diseases, leading to the study of the epigenetic mechanism in neurodegenerative diseases. Unlike genetics, epigenetics modify the genome without changing the DNA sequence. Research shows that epigenetics is involved in all aspects of neurodegenerative diseases. The study of epigenetic will provide valuable insights into the molecular mechanism of neurodegenerative diseases, which may lead to new treatments and diagnoses. This article reviews the role of epigenetic modifications neurodegenerative diseases with dyskinesia, and discusses the therapeutic potential of epigenetic drugs in neurodegenerative diseases.

Chromatin Alterations in Neurological Disorders and Strategies of (Epi)Genome Rescue

Neurological disorders (NDs) comprise a heterogeneous group of conditions that affect the function of the nervous system. Often incurable, NDs have profound and detrimental consequences on the affected individuals' lives. NDs have complex etiologies but commonly feature altered gene expression and dysfunctions of the essential chromatin-modifying factors. Hence, compounds that target DNA and histone modification pathways, the so-called epidrugs, constitute promising tools to treat NDs. Yet, targeting the entire epigenome might reveal insufficient to modify a chosen gene expression or even unnecessary and detrimental to the patients' health. New technologies hold a promise to expand the clinical toolkit in the fight against NDs. (Epi)genome engineering using designer nucleases, including CRISPR-Cas9 and TALENs, can potentially help restore the correct gene expression patterns by targeting a defined gene or pathway, both genetically and epigenetically, with minimal off-target activity. Here, we review the implication of epigenetic machinery in NDs. We outline syndromes caused by mutations in chromatin-modifying enzymes and discuss the functional consequences of mutations in regulatory DNA in NDs. We review the approaches that allow modifying the (epi)genome, including tools based on TALENs and CRISPR-Cas9 technologies, and we highlight how these new strategies could potentially change clinical practices in the treatment of NDs.

Phase 1/2 Trial of Vorinostat and Radiation and Maintenance Vorinostat in Children with Diffuse Intrinsic Pontine Glioma: A Children's Oncology Group Report

BACKGROUND

A phase 1/2 trial of vorinostat (suberoylanilide hydroxamic acid), an oral histone deacetylase (HDAC) inhibitor, was conducted in children with newly-diagnosed diffuse intrinsic pontine glioma (DIPG) through the Children's Oncology Group (COG) to: 1) determine the recommended phase 2 dose (RP2D) of vorinostat given concurrently with radiation therapy; 2) document the toxicities of continuing vorinostat as maintenance therapy after radiation; and 3) to determine the efficacy of this regimen by comparing the risk of progression or death with an historical model from past COG trials.

METHODS

Vorinostat was given once daily, Monday through Friday, during radiation therapy (54 Gy in 30 fractions), and then continued at 230 mg/m 2 daily for a maximum of twelve 28-day cycles.

RESULTS

Twelve patients enrolled on the phase 1 study; the RP2D of vorinostat given concurrently with radiation was 230 mg/m 2/day, Monday through Friday weekly. The six patients enrolled at the RP2D and an additional 64 patients enrolled onto the phase 2 study contributed to the efficacy assessment. Although vorinostat was well-tolerated, did not interrupt radiation therapy, and was permanently discontinued in only 8.6% of patients due to toxicities, risk for EFS-event was not significantly reduced compared with the target risk derived from historical COG data (p = 0.32; 1-sided). The 1-year EFS was 5.85% (95% CI 1.89 - 13.1%) and 1-year OS was 39.2% (27.8 - 50.5%).

CONCLUSIONS

Vorinostat given concurrently with radiation followed by vorinostat monotherapy was well tolerated in children with newly-diagnosed DIPG but failed to improve outcome.

New Avenues for the Treatment of Huntington's Disease

Huntington’s disease (HD) is a neurodegenerative disorder caused by a CAG expansion in the HD gene. The disease is characterized by neurodegeneration, particularly in the striatum and cortex. The first symptoms usually appear in mid-life and include cognitive deficits and motor disturbances that progress over time. Despite being a genetic disorder with a known cause, several mechanisms are thought to contribute to neurodegeneration in HD, and numerous pre-clinical and clinical studies have been conducted and are currently underway to test the efficacy of therapeutic approaches targeting some of these mechanisms with varying degrees of success. Although current clinical trials may lead to the identification or refinement of treatments that are likely to improve the quality of life of those living with HD, major efforts continue to be invested at the pre-clinical level, with numerous studies testing novel approaches that show promise as disease-modifying strategies. This review offers a detailed overview of the currently approved treatment options for HD and the clinical trials for this neurodegenerative disorder that are underway and concludes by discussing potential disease-modifying treatments that have shown promise in pre-clinical studies, including increasing neurotropic support, modulating autophagy, epigenetic and genetic manipulations, and the use of nanocarriers and stem cells.

Valproate reverses mania-like behaviors in mice via preferential targeting of HDAC2

Valproate (VPA) has been used in the treatment of bipolar disorder since the 1990s. However, the therapeutic targets of VPA have remained elusive. Here we employ a preclinical model to identify the therapeutic targets of VPA. We find compounds that inhibit histone deacetylase proteins (HDACs) are effective in normalizing manic-like behavior, and that class I HDACs (e.g., HDAC1 and HDAC2) are most important in this response. Using an RNAi approach, we find that HDAC2, but not HDAC1, inhibition in the ventral tegmental area (VTA) is sufficient to normalize behavior. Furthermore, HDAC2 overexpression in the VTA prevents the actions of VPA. We used RNA sequencing in both mice and human induced pluripotent stem cells (iPSCs) derived from bipolar patients to further identify important molecular targets. Together, these studies identify HDAC2 and downstream targets for the development of novel therapeutics for bipolar mania.

NLRP3 inflammasome inhibition by histone acetylation ameliorates sevoflurane-induced cognitive impairment in aged mice by activating the autophagy pathway

Age-related cognitive impairment is associated with diminished autophagy and progressively increased neuroinflammation. Histone acetylation has been shown to be a key process in sevoflurane-induced neurobehavioral abnormalities. Here, we investigated whether histone acetylation regulates the interaction between autophagy and the NLRP3 inflammasome in models of sevoflurane-induced cognitive impairment and explored the underlying molecular mechanisms. Aged C57BL/6 J mice and cultured primary hippocampal neurons were exposed to 3% sevoflurane for 2 h. Hippocampal tissue samples and hippocampal neurons were harvested. The processes of histone acetylation and autophagy and the activation of the NLRP3 inflammasome were observed using western blotting, immunofluorescence staining, and transmission electron microscopy. Suberoylanilide hydroxamic acid (SAHA), an inhibitor of histone deacetylases, increased histone H3 and H4 acetylation in both the mouse hippocampus and primary neurons. Concomitantly, sevoflurane upregulated components of the NLRP3 inflammasome (NLRP3, cleaved caspase-1, and IL-1β) by promoting autophagic degradation in the aging brain. Cognitive deficits and inadequate autophagy induced by sevoflurane were reversed and NLRP3 inflammasome activation was inhibited by SAHA. Treatment with 3-MA, an autophagy inhibitor, eliminated the neuroprotective effects of SAHA on improving cognition in mice, activating autophagy and downregulating the NLRP3 inflammasome. Based on these results, histone acetylation activates autophagy plays an important role in inhibiting the activation of the NLRP3 inflammasome to protect the host from excessive neuroinflammation and sevoflurane-induced cognitive dysfunction in the aging brain.

Development of HDAC Inhibitors Exhibiting Therapeutic Potential in T-Cell Prolymphocytic Leukemia

Epigenetic targeting has emerged as an efficacious therapy for hematological cancers. The rare and incurable T-cell prolymphocytic leukemia (T-PLL) is known for its aggressive clinical course. Current epigenetic agents such as histone deacetylase (HDAC) inhibitors are increasingly used for targeted therapy. Through a structure-activity relationship (SAR) study, we developed an HDAC6 inhibitor KT-531, which exhibited higher potency in T-PLL compared to other hematological cancers. KT-531 displayed strong HDAC6 inhibitory potency and selectivity, on-target biological activity, and a safe therapeutic window in nontransformed cell lines. In primary T-PLL patient cells, where HDAC6 was found to be overexpressed, KT-531 exhibited strong biological responses, and safety in healthy donor samples. Notably, combination studies in T-PLL patient samples demonstrated KT-531 synergizes with approved cancer drugs, bendamustine, idasanutlin, and venetoclax. Our work suggests HDAC inhibition in T-PLL could afford sufficient therapeutic windows to achieve durable remission either as stand-alone or in combination with targeted drugs.

Ameliorative Role of Nutraceuticals on Neurodegenerative Diseases Using the Drosophila melanogaster as a Discovery Model to Define Bioefficacy

Neurodegeneration is the destruction of neurons, and once the neurons degenerate they can't revive. This is one of the most concerned health conditions among aged population, more than ∼70% of the elderly people are suffering from neurodegeneration. Among all of the neurodegenerative diseases, Alzheimer's disease (AD), Parkinson's disease (PD) and Poly-glutamine disease (Poly-Q) are the major one and affecting most of the people around the world and posing excessive burden on the society. In order to understand this disease in non-human animal models it is pertinent to examine in model organism and various animal model are being used for such diseases like rat, mice and non-vertebrate model like Drosophila. Drosophila melanogaster is one of the best animal proven by several eminent scientist and had received several Nobel prizes for uncovering mechanism of human related genes and highly efficient model for studying neurodegenerative diseases due to its great affinity with human disease-related genes. Another factor is also employed to act as therapeutic or preventive method that is nutraceuticals. Nutraceuticals are functional natural compounds with antioxidant properties and had extensively showed the neuroprotective effect in different organisms. These nutraceuticals having antioxidant properties act through scavenging free radicals or by increasing endogenous cellular antioxidant defense molecules. For the best benefit, we are trying to utilize these nutraceuticals, which will have no or negligible side effects. In this review, we are dealing with various types of such nutraceuticals which have potent value in the prevention and curing of the diseases related to neurodegeneration.HighlightsNeurodegeneration is the silently progressing disease which shows its symptoms when it is well rooted.Many chemical drugs (almost all) have only symptomatic relief with side effects.Potent mechanism of neurodegeneration and improvement effect by nutraceuticals is proposed.Based on the Indian Cuisine scientists are trying to find the medicine from the food or food components having antioxidant properties.The best model to study the neurodegenerative diseases is Drosophila melanogaster.Many nutraceuticals having antioxidant properties have been studied and attenuated various diseases are discussed.

Understanding the role of histone deacetylase and their inhibitors in neurodegenerative disorders: Current targets and future perspective

Neurodegenerative diseases are a group of pathological conditions that cause motor inc-ordination (jerking movements), cognitive and memory impairments result from degeneration of neurons in a specific area of the brain. Oxidative stress, mitochondrial dysfunction, excitotoxicity, neuroinflammation, neurochemical imbalance and histone deacetylase enzymes (HDAC) are known to play a crucial role in neurodegeneration. HDAC is classified into four categories (class I, II, III and class IV) depending upon their location and functions. HDAC1 and 2 are involved in neurodegeneration, while HDAC3-11 and class III HDACs are beneficial as neuroprotective. HDACs are localized in different parts of the brain- HDAC1 (hippocampus and cortex), HDAC2 (nucleus), HDAC3, 4, 5, 7 and 9 (nucleus and cytoplasm), HDAC6 & HDAC7 (cytoplasm) and HDAC11 (Nucleus, cornus ammonis 1 and spinal cord). In pathological conditions, HDAC up-regulates glutamate, phosphorylation of tau, and glial fibrillary acidic proteins while down-regulating BDNF, Heat shock protein 70 and Gelsolin. Class III HDACs are divided into seven sub-classes (SIRT1-SIRT7). Sirtuins are localized in the different parts of the brain and neuron -Sirt1 (nucleus), Sirt2 (cortex, striatum, hippocampus and spinal cord), Sirt3 (mitochondria and cytoplasm), Sirt4, Sirt5 & Sirt6 (mitochondria), Sirt7 (nucleus) and Sirt8 (nucleolus). SIRTs (1, 3, 4, and 6) are involved in neuronal survival, proliferation and modulating stress response, and SIRT2 is associated with Parkinsonism, Huntington’s disease and Alzheimer’s disease, whereas SIRT6 is only associated with Alzheimer’s disease. In this critical review, we have discussed the mechanisms and therapeutic targets of HDACs that would be beneficial for the management of neurodegenerative disorders.

Treatment with Histone Deacetylase Inhibitor Attenuates Peripheral Inflammation-Induced Cognitive Dysfunction and Microglial Activation: The Effect of SAHA as a Peripheral HDAC Inhibitor

It has been demonstrated that peripheral inflammation induces cognitive dysfunction. Several histone deacetylase (HDAC) inhibitors ameliorate cognitive dysfunction in animal models of not only peripheral inflammation but also Alzheimer's disease. However, it is not clear which HDAC expressed in the central nervous system or peripheral tissues is involved in the therapeutic effect of HDAC inhibition on cognitive dysfunction. Hence, the present study investigated the effect of peripheral HDAC inhibition on peripheral inflammation-induced cognitive dysfunction. Suberoylanilide hydroxamic acid (SAHA), a pan-HDAC inhibitor that is mainly distributed in peripheral tissues after intraperitoneal administration, was found to prevent peripheral inflammation-induced cognitive dysfunction. Moreover, pretreatment with SAHA dramatically increased mRNA expression of interleukin-10, an anti-inflammatory cytokine, in peripheral and central tissues and attenuated peripheral inflammation-induced microglial activation in the CA3 region of the hippocampus. Minocycline, a macrophage/microglia inhibitor, also ameliorated cognitive dysfunction. Furthermore, as a result of treatment with liposomal clodronate, depletion of peripheral macrophages partially ameliorated the peripheral inflammation-evoked cognitive dysfunction. Taken together, these findings demonstrate that inhibition of peripheral HDAC plays a critical role in preventing cognitive dysfunction induced by peripheral inflammation via the regulation of anti-inflammatory cytokine production and the inhibition of microglial functions in the hippocampus. Thus, these findings could provide support for inhibition of peripheral HDAC as a novel therapeutic strategy for inflammation-induced cognitive dysfunction.

Autophagy-targeted therapy to modulate age-related diseases: Success, pitfalls, and new directions

Autophagy is a critical metabolic process that supports homeostasis at a basal level and is dynamically regulated in response to various physiological and pathological processes. Autophagy has some etiologic implications that support certain pathological processes due to alterations in the lysosomal-degradative pathway. Some of the conditions related to autophagy play key roles in highly relevant human diseases, e.g., cardiovascular diseases (15.5%), malignant and other neoplasms (9.4%), and neurodegenerative conditions (3.7%). Despite advances in the discovery of new strategies to treat these age-related diseases, autophagy has emerged as a therapeutic option after preclinical and clinical studies. Here, we discuss the pitfalls and success in regulating autophagy initiation and its lysosome-dependent pathway to restore its homeostatic role and mediate therapeutic effects for cancer, neurodegenerative, and cardiac diseases. The main challenge for the development of autophagy regulators for clinical application is the lack of specificity of the repurposed drugs, due to the low pharmacological uniqueness of their target, including those that target the PI3K/AKT/mTOR and AMPK pathway. Then, future efforts must be conducted to deal with this scenery, including the disclosure of key components in the autophagy machinery that may intervene in its therapeutic regulation. Among all efforts, those focusing on the development of novel allosteric inhibitors against autophagy inducers, as well as those targeting autolysosomal function, and their integration into therapeutic regimens should remain a priority for the field.

Epigenetic regulation in Huntington's disease

Huntington's disease (HD) is a devastating and fatal monogenic neurodegenerative disorder characterized by progressive loss of selective neurons in the brain and is caused by an abnormal expansion of CAG trinucleotide repeats in a coding exon of the huntingtin (HTT) gene. Progressive gene expression changes that begin at premanifest stages are a prominent feature of HD and are thought to contribute to disease progression. Increasing evidence suggests the critical involvement of epigenetic mechanisms in abnormal transcription in HD. Genome-wide alterations of a number of epigenetic modifications, including DNA methylation and multiple histone modifications, are associated with HD, suggesting that mutant HTT causes complex epigenetic abnormalities and chromatin structural changes, which may represent an underlying pathogenic mechanism. The causal relationship of specific epigenetic changes to early transcriptional alterations and to disease pathogenesis require further investigation. In this article, we review recent studies on epigenetic regulation in HD with a focus on DNA and histone modifications. We also discuss the contribution of epigenetic modifications to HD pathogenesis as well as potential mechanisms linking mutant HTT and epigenetic alterations. Finally, we discuss the therapeutic potential of epigenetic-based treatments.

α-Synuclein A53T Binds to Transcriptional Adapter 2-Alpha and Blocks Histone H3 Acetylation

α-Synuclein (α-syn) is a hallmark amyloidogenic protein component of Lewy bodies in dopaminergic neurons affected by Parkinson’s disease (PD). Despite the multi-faceted gene regulation of α-syn in the nucleus, the mechanism underlying α-syn crosstalk in chromatin remodeling in PD pathogenesis remains elusive. Here, we identified transcriptional adapter 2-alpha (TADA2a) as a novel binding partner of α-syn using the BioID system. TADA2a is a component of the p300/CBP-associated factor and is related to histone H3/H4 acetylation. We found that α-syn A53T was more preferentially localized in the nucleus than the α-syn wild-type (WT), leading to a stronger disturbance of TADA2a. Indeed, α-syn A53T significantly reduced the level of histone H3 acetylation in SH-SY5Y cells; its reduction was also evident in the striatum (STR) and substantia nigra (SN) of mice that were stereotaxically injected with α-syn preformed fibrils (PFFs). Interestingly, α-syn PFF injection resulted in a decrease in TADA2a in the STR and SN of α-syn PFF-injected mice. Furthermore, the levels of TADA2a and acetylated histone H3 were significantly decreased in the SN of patients with PD. Therefore, histone modification through α-syn A53T-TADA2a interaction may be associated with α-syn-mediated neurotoxicity in PD pathology.