HDAC2 as a new target to improve schizophrenia treatment

Assessment of Protective Effects of Carvacrol on Haloperidol-Induced Oxidative Stress and Genotoxicity in Human Peripheral Blood Lymphocytes

Haloperidol is a first-generation antipsychotic drug that has several indications in a wide range of mental conditions. The extensive prescription of haloperidol is correlated with some less-known adverse effects such as genotoxicity. Carvacrol is a monoterpenoid mainly found in oregano and thyme. It has the potential to scavenge free radicals in addition to increasing antioxidant defense enzyme activities and glutathione levels. In this study, we attempted to explore the possible potential of haloperidol in inducing genotoxicity in human peripheral lymphocytes as well as the protective role of carvacrol against this effect. The lymphocytes were divided into separate groups as follows: control group (cosolvent and NS); carvacrol group (5 μM); haloperidol group (25, 50, and 100 ng/ml); haloperidol (25, 50, and 100 ng/ml) + carvacrol (5 μM); positive control (0.8 μg/ml Cisplatin). After 24 hours of treatment, we conducted a cytokinesis-Block micronucleus test and an alkaline comet assay in order to determine genetic damage. Additionally, we measured glutathione and MDA levels as the biomarkers associated with oxidative stress. Significant increases in the levels of genotoxicity biomarkers (micronucleus frequency, DNA percentage in tail and tail moment) were observed in haloperidol-treated cells. The result of our oxidative stress tests also demonstrated that haloperidol had the potential to induce oxidative stress via reducing the levels of glutathione and increasing lipid peroxidation. Treatment with carvacrol significantly decreased the genotoxic events. It can be presumed that the induction of oxidative stress by haloperidol is the critical event associated with haloperidol-mediated genotoxicity. Therefore, using carvacrol as a natural antioxidant protected human lymphocytes against haloperidol genetic damage.

Comprehensive DNA Methylation Analysis of Human Neuroblastoma Cells Treated With Haloperidol and Risperidone

Accumulating evidence suggests that the epigenetic alterations induced by antipsychotics contribute to the therapeutic efficacy. However, global and site-specific epigenetic changes by antipsychotics and those shared by different classes of antipsychotics remain poorly understood. We conducted a comprehensive DNA methylation analysis of human neuroblastoma cells cultured with antipsychotics. The cells were cultured with low and high concentrations of haloperidol or risperidone for 8 days. DNA methylation assay was performed with the Illumina HumanMethylation450 BeadChip. We found that both haloperidol and risperidone tended to cause hypermethylation changes and showed similar DNA methylation changes closely related to neuronal functions. A total of 294 differentially methylated probes (DMPs), including 197 hypermethylated and 97 hypomethylated DMPs, were identified with both haloperidol and risperidone treatment. Gene ontology analysis of the hypermethylated probe-associated genes showed enrichment of genes related to the regulation of neurotransmitter receptor activity and lipoprotein lipase activity. Pathway analysis identified that among the DMP-associated genes, SHANK1 and SHANK2 were the major genes in the neuropsychiatric disorder-related pathways. Our data would be valuable for understanding the mechanisms of action of antipsychotics from an epigenetic viewpoint.

Cognitive Deficit in Schizophrenia: From Etiology to Novel Treatments

Schizophrenia is a major mental illness characterized by positive and negative symptoms, and by cognitive deficit. Although cognitive impairment is disabling for patients, it has been largely neglected in the treatment of schizophrenia. There are several reasons for this lack of treatments for cognitive deficit, but the complexity of its etiology-in which neuroanatomic, biochemical and genetic factors concur-has contributed to the lack of effective treatments. In the last few years, there have been several attempts to develop novel drugs for the treatment of cognitive impairment in schizophrenia. Despite these efforts, little progress has been made. The latest findings point to the importance of developing personalized treatments for schizophrenia which enhance neuroplasticity, and of combining pharmacological treatments with non-pharmacological measures.

A BRD's (BiRD's) eye view of BET and BRPF bromodomains in neurological diseases

Neurological disorders (NLDs) are among the top leading causes for disability worldwide. Dramatic changes in the epigenetic topography of the brain and nervous system have been found in many NLDs. Histone lysine acetylation has prevailed as one of the well characterised epigenetic modifications in these diseases. Two instrumental components of the acetylation machinery are the evolutionarily conserved Bromodomain and PHD finger containing (BRPF) and Bromo and Extra terminal domain (BET) family of proteins, also referred to as acetylation 'readers'. Several reasons, including their distinct mechanisms of modulation of gene expression and their property of being highly tractable small molecule targets, have increased their translational relevance. Thus, compounds which demonstrated promising results in targeting these proteins have advanced to clinical trials. They have been established as key role players in pathologies of cancer, cardiac diseases, renal diseases and rheumatic diseases. In addition, studies implicating the role of these bromodomains in NLDs are gaining pace. In this review, we highlight the findings of these studies, and reason for the plausible roles of all BET and BRPF members in NLDs. A comprehensive understanding of their multifaceted functions would be radical in the development of therapeutic interventions.

Morita therapy for schizophrenia: An updated meta-analysis

Morita therapy was developed for common mental problems, and our aim was to evaluate the clinical effect of Morita therapy on schizophrenia. The literature was searched in 10 databases, namely, PubMed, Chinese National Knowledge Infrastructure (CNKI), Sinomed, Wanfang, Cochrane Library, UpToDate, Web of Science, Medline, PsycINFO and Embase, from inception to September 4, 2019. Random-effects models were used. For continuous results, the standardized mean differences (SMDs) and 95% confidence intervals (CIs) were calculated to synthesize the effects. Thirty studies were included, with a total of 2651 patients with schizophrenia. Compared to pharmacotherapy alone and standard care alone, Morita therapy plus pharmacotherapy and Morita therapy plus standard care both had significant effects on mental state (pooled effect size = -1.09, 95% CI: -0.35, -0.83), social functioning (pooled effect size = -0.61, 95% CI: -2.30, -0.92) and behavior (pooled effect size = 1.13, 95% CI: 0.75, 1.51). Significant heterogeneity between studies was found for mental state (I² = 89%, p < 0.05) and social functioning (I² = 95%, p < 0.05), but no heterogeneity was found for behavior (I² = 0%, p = 0.84). Morita therapy has positive effects on mental state and social functioning among patients with schizophrenia, but it leads to some problems with behavior among these patients. Most included studies have unclear bias, and the forest plots show high heterogeneity among the results. Thus, Morita therapy cannot be implemented in clinical practice as a feasible strategy, the conclusion has yet to be confirmed, and new trials and future studies are desired.

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.

HDAC2-dependent Antipsychotic-like Effects of Chronic Treatment with the HDAC Inhibitor SAHA in Mice

Antipsychotic drugs, including both typical such as haloperidol and atypical such as clozapine, remain the current standard for schizophrenia treatment. These agents are relatively effective in treating hallucinations and delusions. However, cognitive deficits are at present essentially either persistent or exacerbated following chronic antipsychotic drug exposure. This underlines the need of new therapeutic approaches to improve cognition in treated schizophrenia patients. Our previous findings suggested that upregulation of histone deacetylase 2 (HDAC2) expression upon chronic antipsychotic treatment may lead to negative effects on cognition and cortical synaptic structure. Here we tested different phenotypes of psychosis, synaptic plasticity, cognition and antipsychotic drug action in HDAC2 conditional knockout (HDAC2-cKO) mice and controls. Conditional depletion of HDAC2 function in glutamatergic pyramidal neurons led to a protective phenotype against behavior models induced by psychedelic and dissociative drugs, such as DOI and MK801, respectively. Immunoreactivity toward synaptophysin, which labels presynaptic terminals of functional synapses, was decreased in the frontal cortex of control mice chronically treated with clozapine - an opposite effect occurred in HDAC2-cKO mice. Chronic treatment with the class I and class II HDAC inhibitor SAHA prevented via HDAC2 the disruptive effects of MK801 on recognition memory. Additionally, chronic SAHA treatment affected transcription of numerous plasticity-related genes in the frontal cortex of control mice, an effect that was not observed in HDAC2-cKO animals. Together, these findings suggest that HDAC2 may represent a novel target to improve synaptic plasticity and cognition in treated schizophrenia patients.

Differences in 5-HT2A and mGlu2 Receptor Expression Levels and Repressive Epigenetic Modifications at the 5-HT2A Promoter Region in the Roman Low- (RLA-I) and High- (RHA-I) Avoidance Rat Strains

The serotonin 2A (5-HT_2A) and metabotropic glutamate 2 (mGlu2) receptors regulate each other and are associated with schizophrenia. The Roman high- (RHA-I) and the Roman low- (RLA-I) avoidance rat strains present well-differentiated behavioral profiles, with the RHA-I strain emerging as a putative genetic rat model of schizophrenia-related features. The RHA-I strain shows increased 5-HT_2A and decreased mGlu2 receptor binding levels in prefrontal cortex (PFC). Here, we looked for differences in gene expression and transcriptional regulation of these receptors. The striatum (STR) was included in the analysis. 5-HT_2A, 5-HT_1A, and mGlu2 mRNA and [³H]ketanserin binding levels were measured in brain homogenates. As expected, 5-HT_2A binding was significantly increased in PFC in the RHA-I rats, while no difference in binding was observed in STR. Surprisingly, 5-HT_2A gene expression was unchanged in PFC but significantly decreased in STR. mGlu2 receptor gene expression was significantly decreased in both PFC and STR. No differences were observed for the 5-HT_1A receptor. Chromatin immunoprecipitation assay revealed increased trimethylation of histone 3 at lysine 27 (H3K27me3) at the promoter region of the HTR2A gene in the STR. We further looked at the Akt/GSK3 signaling pathway, a downstream point of convergence of the serotonin and glutamate system, and found increased phosphorylation levels of GSK3β at tyrosine 216 and increased β-catenin levels in the PFC of the RHA-I rats. These results reveal region-specific regulation of the 5-HT_2A receptor in the RHA-I rats probably due to absence of mGlu2 receptor that may result in differential regulation of downstream pathways.

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.

Exploratory analysis for a targeted patient population responsive to the metabotropic glutamate 2/3 receptor agonist pomaglumetad methionil in schizophrenia

BACKGROUND

Accumulating evidence indicates that glutamatergic tone in schizophrenia may vary as a function of illness duration or medication history. We conducted an exploratory analysis of the existing clinical trial database of pomaglumetad methionil (pomaglumetad) to demonstrate treatment response in targeted patient populations.

METHODS

Results of the H8Y-MC-HBBM (HBBM) study and an integrated analysis based on five placebo-controlled trials were summarized. Patients with schizophrenia were randomly assigned to receive either pomaglumetad, 40 or 80 mg twice daily (BID), placebo, or risperidone, 2 mg BID, for up to 6 weeks. Patient subgroups were analyzed to determine the efficacy of pomaglumetad treatment in patients early-in-disease (≤3 years) and late-in-disease (≥10 years) (HBBM, 40 mg, n = 206, 80 mg, n = 198; integrated analysis, 40 mg, n = 382, 80 mg, n = 381) and in patients previously treated with central nervous system drugs with prominent serotonin 2A receptor antagonist activity (S2 group) or with predominant dopamine D2 receptor antagonist activity (D2 group; HBBM, 40 mg, n = 275, 80 mg, n = 269; integrated analysis, 40 mg, n = 590, 80 mg, n = 506).

RESULTS

In the HBBM study and integrated analysis, only patients early-in-disease or previously treated with D2 drugs exhibited significantly greater improvement relative to those receiving placebo, when treated with pomaglumetad, 40 mg (but not 80 mg) BID. Treatment response to risperidone did not appear to depend upon these patient subgroups.

CONCLUSIONS

Demonstration of antipsychotic efficacy of a potential glutamate-based pharmacotherapy for schizophrenia may require the identification of appropriate patient subgroups whose treatment responsiveness may be fundamentally related to dysregulation of central nervous system glutamatergic tone.

Epigenetic signaling in schizophrenia

Histone modifications and DNA methylation represent central dynamic and reversible processes that regulate gene expression and contribute to cellular phenotypes. These epigenetic marks have been shown to play fundamental roles in a diverse set of signaling and behavioral outcomes. Psychiatric disorders such as schizophrenia and depression are complex and heterogeneous diseases with multiple and independent factors that may contribute to their pathophysiology, making challenging to find a link between specific elements and the underlying mechanisms responsible for the disorder and its treatment. Growing evidences suggest that epigenetic modifications in certain brain regions and neural circuits represent a key mechanism through which environmental factors interact with individual's genetic constitution to affect risk of psychiatric conditions throughout life. This review focuses on recent advances that directly implicate epigenetic modifications in schizophrenia and antipsychotic drug action.

Epigenetic Mechanisms of Serotonin Signaling

Histone modifications and DNA methylation represent central dynamic and reversible processes that regulate gene expression and contribute to cellular phenotypes. These epigenetic marks have been shown to play fundamental roles in a diverse set of signaling and behavioral outcomes. Serotonin is a monoamine that regulates numerous physiological responses including those in the central nervous system. The cardinal signal transduction mechanisms via serotonin and its receptors are well established, but fundamental questions regarding complex interactions between the serotonin system and heritable epigenetic modifications that exert control on gene function remain a topic of intense research and debate. This review focuses on recent advances and contributions to our understanding of epigenetic mechanisms of serotonin receptor-dependent signaling, with focus on psychiatric disorders such as schizophrenia and depression.