Inhibition of histone deacetylases in rats self-administering cocaine regulates lissencephaly gene-1 and reelin gene expression, as revealed by microarray technique

Epigenetic Effects of Addictive Drugs in the Nucleus Accumbens

Substance use induces long-lasting behavioral changes and drug craving. Increasing evidence suggests that epigenetic gene regulation contributes to the development and expression of these long-lasting behavioral alterations. Here we systematically review extensive evidence from rodent models of drug-induced changes in epigenetic regulation and epigenetic regulator proteins. We focus on histone acetylation and histone methylation in a brain region important for drug-related behaviors: the nucleus accumbens. We also discuss how experimentally altering these epigenetic regulators via systemically administered compounds or nucleus accumbens-specific manipulations demonstrate the importance of these proteins in the behavioral effects of drugs and suggest potential therapeutic value to treat people with substance use disorder. Finally, we discuss limitations and future directions for the field of epigenetic studies in the behavioral effects of addictive drugs and suggest how to use these insights to develop efficacious treatments.

Evidence for Modulation of Substance Use Disorders by the Gut Microbiome: Hidden in Plain Sight

The gut microbiome modulates neurochemical function and behavior and has been implicated in numerous central nervous system (CNS) diseases, including developmental, neurodegenerative, and psychiatric disorders. Substance use disorders (SUDs) remain a serious threat to the public well-being, yet gut microbiome involvement in drug abuse has received very little attention. Studies of the mechanisms underlying SUDs have naturally focused on CNS reward circuits. However, a significant body of research has accumulated over the past decade that has unwittingly provided strong support for gut microbiome participation in drug reward. β-Lactam antibiotics have been employed to increase glutamate transporter expression to reverse relapse-induced release of glutamate. Sodium butyrate has been used as a histone deacetylase inhibitor to prevent drug-induced epigenetic alterations. High-fat diets have been used to alter drug reward because of the extensive overlap of the circuitry mediating them. This review article casts these approaches in a different light and makes a compelling case for gut microbiome modulation of SUDs. Few factors alter the structure and composition of the gut microbiome more than antibiotics and a high-fat diet, and butyrate is an endogenous product of bacterial fermentation. Drugs such as cocaine, alcohol, opiates, and psychostimulants also modify the gut microbiome. Therefore, their effects must be viewed on a complex background of cotreatment-induced dysbiosis. Consideration of the gut microbiome in SUDs should have the beneficial effects of expanding the understanding of SUDs and aiding in the design of new therapies based on opposing the effects of abused drugs on the host's commensal bacterial community. SIGNIFICANCE STATEMENT: Proposed mechanisms underlying substance use disorders fail to acknowledge the impact of drugs of abuse on the gut microbiome. β-Lactam antibiotics, sodium butyrate, and high-fat diets are used to modify drug seeking and reward, overlooking the notable capacity of these treatments to alter the gut microbiome. This review aims to stimulate research on substance abuse-gut microbiome interactions by illustrating how drugs of abuse share with antibiotics, sodium butyrate, and fat-laden diets the ability to modify the host microbial community.

Histone deacetylase inhibition differentially attenuates cue-induced reinstatement: An interaction of environment and acH3K9 expression in the dorsal striatum

Substance use disorder is driven by complex gene-environment interactions. Epigenetic histone regulation is a significant contributor to several behavioral phenotypes of drug abuse. The primary epigenetic mechanisms that drive drug taking and drug seeking are still being investigated, and it is unclear how environmental conditions alter epigenetic histone acetylation to change behaviors geared toward drug reward. This study examined the effects of environmental condition on amphetamine self-administration, and whether drug-taking and drug-seeking behaviors could be influenced through inhibition of an epigenetic regulator, histone deacetylase (HDAC). Male rats reared for 30 days in enriched (EC), isolated (IC), or standard conditions (SC) prior to amphetamine (0.03, 0.05, 0.1 mg/kg/infusion, IV) self-administration, extinction, and reinstatement sessions. The HDAC inhibitor, Trichostatin A (TsA; 0.3 mg/kg, IV), was injected 30 min prior to operant sessions. After amphetamine-induced reinstatement (0.25 mg/kg, subcutaneous [s.c.]), tissue was extracted for Western blot analyses of acetylated histone H3 lysine 9 (acH3K9) in the nucleus accumbens (NAc) and dorsal striatum (DSt). While TsA did not significantly affect amphetamine self-administration or extinction, TsA decreased cue-, but not drug-induced reinstatement in IC rats only. In the DSt, but not in the NAc, IC rats exhibited significantly less acH3K9 expression than EC and SC rats, irrespective of TsA treatment. HDAC inhibition decreases cue-induced reinstatement of amphetamine seeking in IC rats. While IC rats exhibit less acH3K9 expression in the DSt, future studies are needed to elucidate the critical epigenetic factors that drive substance abuse, particularly in vulnerable populations. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Increased histone deacetylase activity in peripheral blood mononuclear cells of patients with schizophrenia

This study investigates the association between histone deacetylase (HDAC) activity in human peripheral blood mononuclear cells (PBMCs) and schizophrenia. Data were derived from a case-control association study of 19 unrelated adult patients with schizophrenia and 21 matched healthy controls. HDAC activity was measured with a HDAC activity colorimetric assay kit. Our findings suggest that HDAC activity in PBMCs is higher in patients with schizophrenia than in healthy people.

Gene regulation and genetics in neurochemistry, past to future

Ask any neuroscientist to name the most profound discoveries in the field in the past 60 years, and at or near the top of the list will be a phenomenon or technique related to genes and their expression. Indeed, our understanding of genetics and gene regulation has ushered in whole new systems of knowledge and new empirical approaches, many of which could not have even been imagined prior to the molecular biology boon of recent decades. Neurochemistry, in the classic sense, intersects with these concepts in the manifestation of neuropeptides, obviously dependent upon the central dogma (the established rules by which DNA sequence is eventually converted into protein primary structure) not only for their conformation but also for their levels and locales of expression. But, expanding these considerations to non-peptide neurotransmitters illustrates how gene regulatory events impact neurochemistry in a much broader sense, extending beyond the neurochemicals that translate electrical signals into chemical ones in the synapse, to also include every aspect of neural development, structure, function, and pathology. From the beginning, the mutability - yet relative stability - of genes and their expression patterns were recognized as potential substrates for some of the most intriguing phenomena in neurobiology - those instances of plasticity required for learning and memory. Near-heretical speculation was offered in the idea that perhaps the very sequence of the genome was altered to encode memories. A fascinating component of the intervening progress includes evidence that the central dogma is not nearly as rigid and consistent as we once thought. And this mutability extends to the potential to manipulate that code for both experimental and clinical purposes. Astonishing progress has been made in the molecular biology of neurochemistry during the 60 years since this journal debuted. Many of the gains in conceptual understanding have been driven by methodological progress, from automated high-throughput sequencing instruments to recombinant-DNA vectors that can convey color-coded genetic modifications in the chromosomes of live adult animals. This review covers the highlights of these advances, both theoretical and technological, along with a brief window into the promising science ahead. This article is part of the 60th Anniversary special issue.

HDAC inhibitor-dependent transcriptome and memory reinstatement in cognitive decline models

Aging and increased amyloid burden are major risk factors for cognitive diseases such as Alzheimer's disease (AD). Effective therapies for these diseases are lacking. Here, we evaluated mouse models of age-associated memory impairment and amyloid deposition to study transcriptome and cell type-specific epigenome plasticity in the brain and peripheral organs. We determined that aging and amyloid pathology are associated with inflammation and impaired synaptic function in the hippocampal CA1 region as the result of epigenetic-dependent alterations in gene expression. In both amyloid and aging models, inflammation was associated with increased gene expression linked to a subset of transcription factors, while plasticity gene deregulation was differentially mediated. Amyloid pathology impaired histone acetylation and decreased expression of plasticity genes, while aging altered H4K12 acetylation-linked differential splicing at the intron-exon junction in neurons, but not nonneuronal cells. Furthermore, oral administration of the clinically approved histone deacetylase inhibitor vorinostat not only restored spatial memory, but also exerted antiinflammatory action and reinstated epigenetic balance and transcriptional homeostasis at the level of gene expression and exon usage. This study provides a systems-level investigation of transcriptome plasticity in the hippocampal CA1 region in aging and AD models and suggests that histone deacetylase inhibitors should be further explored as a cost-effective therapeutic strategy against age-associated cognitive decline.

The histone deacetylase inhibitor sodium butyrate decreases excessive ethanol intake in dependent animals

Converging evidence indicates that epigenetic mechanisms are involved in drug addiction, and that enzymes involved in chromatin remodeling may represent interesting targets in addiction treatment. No study has addressed whether histone deacetylase (HDAC) inhibitors (HDACi) can reduce excessive ethanol intake or prevent relapse in alcohol-dependent animals. Here, we assessed the effects of two HDACi, sodium butyrate (NaB) and MS-275, in the operant ethanol self-administration paradigm in dependent and non-dependent rats. To characterize some of the epigenetic mechanisms associated with alcohol dependence and NaB treatment, we measured the levels of histone H3 acetylation in different brain areas of dependent and non-dependent rats, submitted or not to NaB treatment. Our results demonstrated that (1) NaB and MS-275 strongly decreased excessive alcohol intake of dependent rats in the operant ethanol self-administration paradigm but not of non-dependent rats; (2) NaB reduced excessive drinking and prevented the escalation of ethanol intake in the intermittent access to 20% ethanol paradigm; and (3) NaB completely blocked the increase of ethanol consumption induced by an alcohol deprivation, thus demonstrating a preventive effect of NaB on relapse. The mapping of cerebral histone H3 acetylation revealed a hyperacetylation in the amygdala and cortical areas in dependent rats. Interestingly, NaB did not exacerbate the hyperacetylation observed in these regions, but instead restored it, specifically in cortical areas. Altogether, our results clearly demonstrated the efficacy of NaB in preventing excessive ethanol intake and relapse and support the hypothesis that HDACi may have a potential use in alcohol addiction treatment.

Neural ECM in addiction, schizophrenia, and mood disorder

The extracellular matrix (ECM) has a prominent role in brain development, maturation of neural circuits, and adult neuroplasticity. This multifactorial role of the ECM suggests that processes that affect composition or turnover of ECM in the brain could lead to altered brain function, possibly underlying conditions of impaired mental health, such as neuropsychiatric or neurodegenerative disease. In support of this, in the last two decades, clinical and preclinical research provided evidence of correlations and to some degree causal links, between aberrant ECM function and neuropsychiatric disorders, the most prominent being addiction and schizophrenia. Based on these initial observations of involvement of different classes of ECM molecules (laminin, reelin, and their integrin receptors, as well as tenascins and chondroitin sulfate proteoglycans), ECM targets have been suggested as a novel entry point in the treatment of neuropsychiatric disorders. Hence, understanding how ECM molecules contribute to proper neuronal functioning and how this is dysregulated in conditions of mental illness is of pivotal importance. In this chapter, we will review available literature that implicates the different classes of brain ECM molecules in psychiatric disorders, with a primary focus on addiction (opiates, psychostimulants, and alcohol), and we will compare these ECM adaptations with those implicated in schizophrenia and mood disorders.

Cocaine represses protein phosphatase-1Cβ through DNA methylation and Methyl-CpG Binding Protein-2 recruitment in adult rat brain

Repeated cocaine exposure induces epigenetic factors such as DNA methyl-binding proteins, indicating that resulting changes in gene expression are mediated by alterations in brain DNA methylation. While the activity of protein phosphatase type-1 (PP1) is involved in cocaine effects and in brain plasticity, the expression of the PP1Cβ catalytic subunit gene was identified here as modulated by cocaine. Its expression was induced together with that of PP1Cγ in the brain of Methyl-CpG Binding Protein-2 (Mecp2) mutant mice, whereas PP1Cα expression was not affected, illustrating a different regulation of PP1C isoforms. Repeated cocaine administration was found to increase DNA methylation at the PP1Cβ gene together with its binding to Mecp2 in rat caudate putamen, establishing a link between two genes involved in cocaine-related effects and in learning and memory processes. Cocaine also increased DNMT3 expression, resulting in PP1Cβ repression that did not occur in the presence of DNMT inhibitor. Cocaine-induced PP1Cβ repression was observed in several brain structures, as evaluated by RT-qPCR, immunohistochemistry and Western blot, but did not occur after a single cocaine injection. Our data demonstrate that PP1Cβ is a direct MeCP2-target gene in vivo. They suggest that its repression may participate to behavioral adaptations triggered by the drug.

Blockade of ethanol-induced behavioral sensitization by sodium butyrate: descriptive analysis of gene regulations in the striatum

BACKGROUND

Behavioral sensitization induced by repeated ethanol (EtOH) exposure may play a critical role in the development of alcohol dependence. Because recent data demonstrate that histone deacetylase inhibitor (HDACi) may be of interest in the treatment of addiction, we explored the effect of the HDACi sodium butyrate (NaB) on EtOH-induced behavioral sensitization (EIBS) in DBA/2J mice. We also investigated gene regulations in the striatum of sensitized mice using epigenetic- and signal transduction-related PCR arrays.

METHODS

Mice were injected with saline or EtOH (0.5 to 2.5 g/kg) once a day for 10 days. Mice received NaB (200 to 600 mg/kg) 30 minutes before each injection (prevention protocol) or once daily between days 11 and 16 (reversal protocol). At day 17, brains were removed 30 minutes after a saline or EtOH challenge to assess gene and proteins levels.

RESULTS

Only the intermediate EtOH doses (1.0 and 2.0 g/kg) were effective in inducing EIBS, and both doses were associated with specific gene regulations in the striatum. The induction of sensitization by 1.0 g/kg (but not 2.0 g/kg) EtOH was dose-dependently prevented or reversed by NaB. Among the 168 studied genes, EIBS blockade was associated with specific gene regulations (bcl-2, bdnf, hdac4, pak1, penk, tacr1, vip…) and changes in brain-derived neurotrophic factor in both striatum and prefrontal cortex.

CONCLUSIONS

These results indicate that EIBS is associated with specific gene regulations in the striatum depending on the EtOH dose and that NaB can be useful in blocking some long-lasting neuro-adaptations to repeated EtOH administrations.