Effect of antipsychotic drugs on gene expression in the prefrontal cortex and nucleus accumbens in the spontaneously hypertensive rat (SHR)

Risperidone Induced DNA Methylation Changes in Dopamine Receptor and Stathmin Genes in Mice Exposed to Social Defeat Stress

Objective

Methods

Results

Conclusion

Molecular phenotypes associated with antipsychotic drugs in the human caudate nucleus

Antipsychotic drugs are the current first-line of treatment for schizophrenia and other psychotic conditions. However, their molecular effects on the human brain are poorly studied, due to difficulty of tissue access and confounders associated with disease status. Here we examine differences in gene expression and DNA methylation associated with positive antipsychotic drug toxicology status in the human caudate nucleus. We find no genome-wide significant differences in DNA methylation, but abundant differences in gene expression. These gene expression differences are overall quite similar to gene expression differences between schizophrenia cases and controls. Interestingly, gene expression differences based on antipsychotic toxicology are different between brain regions, potentially due to affected cell type differences. We finally assess similarities with effects in a mouse model, which finds some overlapping effects but many differences as well. As a first look at the molecular effects of antipsychotics in the human brain, the lack of epigenetic effects is unexpected, possibly because long term treatment effects may be relatively stable for extended periods.

Hippocampal subfield transcriptome analysis in schizophrenia psychosis

We have previously demonstrated functional and molecular changes in hippocampal subfields in individuals with schizophrenia (SZ) psychosis associated with hippocampal excitability. In this study, we use RNA-seq and assess global transcriptome changes in the hippocampal subfields, DG, CA3, and CA1 from individuals with SZ psychosis and controls to elucidate subfield-relevant molecular changes. We also examine changes in gene expression due to antipsychotic medication in the hippocampal subfields from our SZ ON- and OFF-antipsychotic medication cohort. We identify unique subfield-specific molecular profiles in schizophrenia postmortem samples compared with controls, implicating astrocytes in DG, immune mechanisms in CA3, and synaptic scaling in CA1. We show a unique pattern of subfield-specific effects by antipsychotic medication on gene expression levels with scant overlap of genes differentially expressed by SZ disease effect versus medication effect. These hippocampal subfield changes serve to confirm and extend our previous model of SZ and can explain the lack of full efficacy of conventional antipsychotic medication on SZ symptomatology. With future characterization using single-cell studies, the identified distinct molecular profiles of the DG, CA3, and CA1 in SZ psychosis may serve to identify further potential hippocampal-based therapeutic targets.

Profile of the Nicotinic Cholinergic Receptor Alpha 7 Subunit Gene Expression is Associated with Response to Varenicline Treatment

INTRODUCTION

Smoking is considered the leading cause of preventable morbidity and mortality worldwide. Studies have sought to identify predictors of response to smoking cessation treatments. The aim of this study was to analyze a possible association of target gene expression for smoking cessation with varenicline.

METHODS

We included 74 smokers starting treatment with varenicline. Gene expression analysis was performed through the custom RT² Profiler qPCR array assay, including 17 genes. Times for sample collection were before the start of therapy (T0) and two weeks (T2) and four weeks (T4) after the start of treatment.

RESULTS

For gene expression analysis, we selected 14 patients who had success and 13 patients resistant to varenicline treatment. Success was considered to be when a patient achieved tobacco abstinence until the fourth week of treatment and resistant was when a patient had not stopped smoking as of the fourth week of treatment. We observed a significant difference for CHRNA7 gene expression: in the resistant group, samples from T2 and T4 had lower expression compared with T0 (fold change: 0.38, P = 0.007; fold change: 0.67, P = 0.004; respectively).

CONCLUSION

This exploratory clinical study, searching for a possible predictor of effectiveness for varenicline, reaffirmed the association of the α7 nAChR subunit for nicotine dependence and smoking therapy effectiveness with varenicline.

LINE-1 hypomethylation is associated with poor risperidone response in a first episode of psychosis cohort

Aim: We investigated the DNA methylation profile over LINE-1 in antipsychotic-naive, first-episode psychosis-patients (n = 69) before and after 2 months of risperidone treatment and in healthy controls (n = 62). Materials & methods: Patients were evaluated using standardized scales and classified as responders and nonresponders. DNA from blood was bisulfite converted and LINE-1 fragments were amplified and pyrosequencing was performed. Results: Lower LINE-1 methylation was observed in antipsychotic-naive first-episode psychosis patients than in healthy controls. Lower DNA methylation levels before treatment were associated with poor risperidone responses. A positive correlation was observed between LINE-1 methylation levels and positive symptoms response. Conclusion: Our study brings new insight regarding how epigenomic studies and clinical correlation studies can supplement psychosis treatment.

Gene expression over the course of schizophrenia: from clinical high-risk for psychosis to chronic stages

The study of patients with schizophrenia (SZ) at different clinical stages may help clarify what effects could be due to the disease itself, to the pharmacological treatment, or to the disease progression. We compared expression levels of targeted genes in blood from individuals in different stages of SZ: clinical high risk for psychosis (CHR), first episode of psychosis (FEP), and chronic SZ (CSZ). Then, we further verified whether single-nucleotide polymorphisms (SNPs) could be related to gene expression differences. We investigated 12 genes in 394 individuals (27 individuals with CHR, 70 antipsychotic-naive individuals with FEP, 157 CSZ patients, and 140 healthy controls (HCs)). For a subsample, genotype data were also available, and we extracted SNPs that were previously associated with the expression of selected genes in whole blood or brain tissue. We generated a mediation model in which a putative cause (SNP) is related to a presumed effect (disorder) via an intermediate variable (gene expression). MBP and NDEL1 were upregulated in FEP compared to all other groups; DGCR8 was downregulated in FEP compared to HC and CHR; DGCR2 was downregulated in CSZ compared to FEP and HCs; DISC1 was upregulated in schizophrenia compared to controls or FEP, possibly induced by the rs3738398 and rs10864693 genotypes, which were associated with DISC1 expression; and UFD1 was upregulated in CSZ and CHR compared to FEP and HC. Our results indicated changes in gene expression profiles throughout the different clinical stages of SZ, reinforcing the need for staging approaches to better capture SZ heterogeneity.

Dimensional Traits of Schizotypy Associated With Glycine Receptor GLRA1 Polymorphism: An Exploratory Candidate-Gene Association Study

Schizotypy captures the underlying genetic vulnerability to schizophrenia. However, the genetic underpinnings of schizotypy remain unexplored. The authors examined the relationship between single nucleotide poly-morphisms (SNPs) and schizotypy. A sample of 137 subjects (43 healthy controls, 34 subjects with schizotypal personality disorder [SPD], 32 with borderline personality disorder, and 25 with other personality disorders) completed the Schizotypal Personality Questionnaire (SPQ). Subjects were genotyped using a custom array chip. Principal component analysis was used to cluster SPQ variables. Linear regression tested for associations between dimensional schizotypy and SNPs. Logistic regression tested for associations between SNPs and SPD diagnosis. There were significant associations between the minor alleles of three SNPs within the glycine receptor alpha 1 subunit (GLRA1) and the disorganized schizotypy dimension, even after Bonferroni correction. There were no significant associations between any SNPs and the categorical SPD diagnosis. Glycine receptor pathways may have an impact on dimensional traits of psychosis.

DNA methylation and antipsychotic treatment mechanisms in schizophrenia: Progress and future directions

Antipsychotic response in schizophrenia is a complex, multifactorial trait influenced by pharmacogenetic factors. With genetic studies thus far providing little biological insight or clinical utility, the field of pharmacoepigenomics has emerged to tackle the so-called "missing heritability" of drug response in disease. Research on psychiatric disorders has only recently started to assess the link between epigenetic alterations and treatment outcomes. DNA methylation, the best characterised epigenetic mechanism to date, is discussed here in the context of schizophrenia and antipsychotic treatment outcomes. The majority of published studies have assessed the influence of antipsychotics on methylation levels in specific neurotransmitter-associated candidate genes or at the genome-wide level. While these studies illustrate the epigenetic modifications associated with antipsychotics, very few have assessed clinical outcomes and the potential of differential DNA methylation profiles as predictors of antipsychotic response. Results from other psychiatric disorder studies, such as depression and bipolar disorder, provide insight into what may be achieved by schizophrenia pharmacoepigenomics. Other aspects that should be addressed in future research include methodological challenges, such as tissue specificity, and the influence of genetic variation on differential methylation patterns.

COMT, 5-HTR2A, and SLC6A4 mRNA Expressions in First-Episode Antipsychotic-Naïve Schizophrenia and Association With Treatment Outcomes

Background: Dopaminergic and serotonergic systems play crucial roles in the pathophysiology of schizophrenia and modulate response to antipsychotic treatment. However, previous studies of dopaminergic and serotonergic genes expression are sparse, and their results have been inconsistent. In this longitudinal study, we aim to investigate the expressions of Catechol-O-methyltransferase (COMT), serotonin 2A receptor (5-HTR2A), and serotonin transporter gene (SLC6A4) mRNA in first-episode antipsychotic-naïve schizophrenia and to test if these mRNA expressions are associated with cognitive deficits and treatment outcomes or not. Method: We measured COMT, 5-HTR2A, and SLC6A4 mRNA expressions in 45 drug-naive first-episode schizophrenia patients and 38 health controls at baseline, and repeated mRNA measurements in all patients at the 8-week follow up. Furthermore, we also assessed antipsychotic response and cognitive improvement after 8 weeks of risperidone monotherapy. Results: Patients were divided into responders (N = 20) and non-responders groups (N = 25) according to the Remission criteria of the Schizophrenia Working Group. Both patient groups have significantly higher COMT mRNA expression and lower SLC6A4 mRNA expression when compared with healthy controls. Interestingly, responder patients have significantly higher levels of COMT and 5-HTR2A mRNA expressions than non-responder patients at baseline. However, antipsychotic treatment has no significant effect on the expressions of COMT, 5-HTR2A, and SLC6A4 mRNA over 8-week follow up. Conclusion: Our findings suggest that dysregulated COMT and SLC6A4 mRNA expressions may implicate in the pathophysiology of schizophrenia, and that COMT and 5-HTR2A mRNA may be potential biomarkers to predict antipsychotic response.

Gene expression elucidates functional impact of polygenic risk for schizophrenia

Over 100 genetic loci harbor schizophrenia-associated variants, yet how these variants confer liability is uncertain. The CommonMind Consortium sequenced RNA from dorsolateral prefrontal cortex of people with schizophrenia (N = 258) and control subjects (N = 279), creating a resource of gene expression and its genetic regulation. Using this resource, ∼20% of schizophrenia loci have variants that could contribute to altered gene expression and liability. In five loci, only a single gene was involved: FURIN, TSNARE1, CNTN4, CLCN3 or SNAP91. Altering expression of FURIN, TSNARE1 or CNTN4 changed neurodevelopment in zebrafish; knockdown of FURIN in human neural progenitor cells yielded abnormal migration. Of 693 genes showing significant case-versus-control differential expression, their fold changes were ≤ 1.33, and an independent cohort yielded similar results. Gene co-expression implicates a network relevant for schizophrenia. Our findings show that schizophrenia is polygenic and highlight the utility of this resource for mechanistic interpretations of genetic liability for brain diseases.

Gene expression alterations related to mania and psychosis in peripheral blood of patients with a first episode of psychosis

Psychotic disorders affect ~3% of the general population and are among the most severe forms of mental diseases. In early stages of psychosis, clinical aspects may be difficult to distinguish from one another. Undifferentiated psychopathology at the first-episode of psychosis (FEP) highlights the need for biomarkers that can improve and refine differential diagnosis. We investigated gene expression differences between patients with FEP-schizophrenia spectrum (SCZ; N=53) or FEP-Mania (BD; N=16) and healthy controls (N=73). We also verified whether gene expression was correlated to severity of psychotic, manic, depressive symptoms and/or functional impairment. All participants were antipsychotic-naive. After the psychiatric interview, blood samples were collected and the expression of 12 psychotic-disorder-related genes was evaluated by quantitative PCR. AKT1 and DICER1 expression levels were higher in BD patients compared with that in SCZ patients and healthy controls, suggesting that expression of these genes is associated more specifically to manic features. Furthermore, MBP and NDEL1 expression levels were higher in SCZ and BD patients than in healthy controls, indicating that these genes are psychosis related (independent of diagnosis). No correlation was found between gene expression and severity of symptoms or functional impairment. Our findings suggest that genes related to neurodevelopment are altered in psychotic disorders, and some might support the differential diagnosis between schizophrenia and bipolar disorder, with a potential impact on the treatment of these disorders.

Increased expression of NDEL1 and MBP genes in the peripheral blood of antipsychotic-naïve patients with first-episode psychosis

Schizophrenia is a multifactorial neurodevelopmental disorder with high heritability. First-episode psychosis (FEP) is a critical period for determining the disease prognosis and is especially helpful for identifying potential biomarkers associated with the onset and progression of the disorder. We investigated the mRNA expression of 12 schizophrenia-related genes in the blood of antipsychotic-naïve FEP patients (N=73) and healthy controls (N=73). To evaluate the influences of antipsychotic treatment and progression of the disorder, we compared the gene expression within patients before and after two months of treatment with risperidone (N=64). We observed a significantly increased myelin basic protein (MBP) and nuclear distribution protein nudE-like 1 (NDEL1) mRNA levels in FEP patients compared with controls. Comparing FEP before and after risperidone treatment, no significant differences were identified; however; a trend of relatively low NDEL1 expression was observed after risperidone treatment. Animals chronically treated with saline or risperidone exhibited no significant change in Ndel1 expression levels in the blood or the prefrontal cortex (PFC), suggesting that the trend of low NDEL1 expression observed in FEP patients after treatment is likely due to factors other than risperidone treatment (i.e., disease progression). In addition to the recognized association with schizophrenia, MBP and NDEL1 gene products also play an essential role in the functions that are deregulated in schizophrenia, such as neurodevelopment. Our data strengthen the importance of these biological processes in psychotic disorders, indicating that these changes can be detected peripherally and potentially represent putative novel blood biomarkers of susceptibility and disorder progression.

Low expression of Gria1 and Grin1 glutamate receptors in the nucleus accumbens of Spontaneously Hypertensive Rats (SHR)

The Spontaneously Hypertensive Rat (SHR) strain is a classical animal model for the study of essential hypertension. Recently, our group suggested that this strain could be a useful animal model for schizophrenia, which is a severe mental illness with involvement of glutamatergic system. The aim of this study is to investigate glutamatergic receptors (Gria1 and Grin1) and glycine transporter (Glyt1) gene expression in the prefrontal cortex (PFC) and nucleus accumbens (NAcc) of SHR animals. The effects in gene expression of a chronic treatment with antipsychotic drugs (risperidone, haloperidol and clozapine) were also analyzed. Animals were treated daily for 30 days, and euthanized for brain tissue collection. The expression pattern was evaluated by Real Time Reverse-Transcriptase (RT) PCR technique. In comparison to control rats, SHR animals present a lower expression of both NMDA (Grin1) and AMPA (Gria1) gene receptors in the NAcc. Antipsychotic treatments were not able to change gene expressions in any of the regions evaluated. These findings provide evidence for the role of glutamatergic changes in schizophrenia-like phenotype of the SHR strain.

DNA methylation in psychosis: insights into etiology and treatment

Evidence for involvement of DNA methylation in psychosis forms the focus of this perspective. Of interest are results from two independent sets of experiments including rats treated with antipsychotic drugs and monozygotic twins discordant for schizophrenia. The results show that DNA methylation is increased in rats treated with antipsychotic drugs, reflecting the global effect of the drugs. Some of these changes are also seen in affected schizophrenic twins that were treated with antipsychotics. The genes and pathways identified in the unrelated experiments are relevant to neurodevelopment and psychiatric disorders. The common cause is hypothesized to be aberrations resulting from medication use. However, this needs to be established by future studies that address the origin of methylation changes in psychosis.

Search for common targets of lithium and valproic acid identifies novel epigenetic effects of lithium on the rat leptin receptor gene

Epigenetics may have an important role in mood stabilizer action. Valproic acid (VPA) is a histone deacetylase inhibitor, and lithium (Li) may have downstream epigenetic actions. To identify genes commonly affected by both mood stabilizers and to assess potential epigenetic mechanisms that may be involved in their mechanism of action, we administered Li (N = 12), VPA (N = 12), and normal chow (N = 12) to Brown Norway rats for 30 days. Genomic DNA and mRNA were extracted from the hippocampus. We used the mRNA to perform gene expression analysis on Affymetrix microarray chips, and for genes commonly regulated by both Li and VPA, we validated expression levels using quantitative real-time PCR. To identify potential mechanisms underlying expression changes, genomic DNA was bisulfite treated for pyrosequencing of key CpG island 'shores' and promoter regions, and chromatin was prepared from both hippocampal tissue and a hippocampal-derived cell line to assess modifications of histones. For most genes, we found little evidence of DNA methylation changes in response to the medications. However, we detected histone H3 methylation and acetylation in the leptin receptor gene, Lepr, following treatment with both drugs. VPA-mediated effects on histones are well established, whereas the Li effects constitute a novel mechanism of transcriptional derepression for this drug. These data support several shared transcriptional targets of Li and VPA, and provide evidence suggesting leptin signaling as an epigenetic target of two mood stabilizers. Additional work could help clarify whether leptin signaling in the brain has a role in the therapeutic action of Li and VPA in bipolar disorder.

Ameliorative effects of baicalein in MPTP-induced mouse model of Parkinson's disease: A microarray study

Baicalein, a flavonoid from Scutellaria baicalensis Georgi, has been shown to possess neuroprotective properties. The purpose of this study was to explore the effects of baicalein on motor behavioral deficits and gene expression in N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced mice model of Parkinson's disease (PD). The behavioral results showed that baicalein significantly improves the abnormal behaviors in MPTP-induced mice model of PD, as manifested by shortening the total time for climbing down the pole, prolonging the latent periods of rotarod, and increasing the vertical movements. Using cDNA microarray and subsequent bioinformatic analyses, it was found that baicalein significantly promotes the biological processes including neurogenesis, neuroblast proliferation, neurotrophin signaling pathway, walking and locomotor behaviors, and inhibits dopamine metabolic process through regulation of gene expressions. Based on analysis of gene co-expression networks, the results indicated that the regulation of genes such as LIMK1, SNCA and GLRA1 by baicalein might play central roles in the network. Our results provide experimental evidence for the potential use of baicalein in the treatment of PD, and revealed gene expression profiles, biological processes and pathways influenced by baicalein in MPTP-treated mice.

Long-term effects of combined neonatal and adolescent stress on brain-derived neurotrophic factor and dopamine receptor expression in the rat forebrain

Altered brain-derived neurotrophic factor (BDNF) signalling and dopaminergic neurotransmission have been shown in the forebrain in schizophrenia. The 'two hit' hypothesis proposes that two major disruptions during development are involved in the pathophysiology of this illness. We therefore used a 'two hit' rat model of combined neonatal and young-adult stress to assess effects on BDNF signalling and dopamine receptor expression. Wistar rats were exposed to neonatal maternal separation (MS) stress and/or adolescent/young-adult corticosterone (CORT) treatment. At adulthood the medial prefrontal cortex (mPFC), caudate putamen (CPu) and nucleus accumbens (NAc) were analysed by qPCR and Western blot. The 'two hit' combination of MS and CORT treatment caused significant increases in BDNF mRNA and protein levels in the mPFC of male, but not female rats. BDNF mRNA expression was unchanged in the CPu but was significantly reduced by CORT in the NAc. DR3 and DR2 mRNA were significantly up-regulated in the mPFC of two-hit rats and a positive correlation was found between BDNF and DR3 expression in male, but not female rats. DR2 and DR3 expression were significantly increased following CORT treatment in the NAc and a significant negative correlation between BDNF and DR3 and DR2 mRNA levels was found. Our data demonstrate male-specific two-hit effects of developmental stress on BDNF and DR3 expression in the mPFC. Furthermore, following chronic adolescent CORT treatment, the relationship between BDNF and dopamine receptor expression was significantly altered in the NAc. These results elucidate the long-term effects of 'two hit' developmental stress on behaviour.