cDNA array reveals differential gene expression following chronic neuroleptic administration: implications of synapsin II in haloperidol treatment

Risperidone-induced changes in DNA methylation in peripheral blood from first-episode schizophrenia patients parallel changes in neuroimaging and cognitive phenotypes

BACKGROUND

Second generation antipsychotics such as risperidone are first-line pharmacotherapy treatment choices for schizophrenia. However, our ability to reliably predict and monitor treatment reaction is impeded by the lack of relevant biomarkers. As a biomarker for the susceptibility of schizophrenia and clozapine treatment response, DNA methylation (DNAm) has been studied, but the impact of antipsychotics on DNAm has not been explored in drug-naïve patients.

OBJECTIVE

The aim of the present study was to examine changes of DNAm after short-term antipsychotic therapy in first-episode drug-naïve schizophrenia (FES) to identify the beneficial and adverse effect of risperidone on DNAm and their relation to treatment outcome.

METHODS

Thirty-eight never treated schizophrenia patients and 38 demographically matched individuals (healthy controls) were assessed at baseline and at 8-week follow-up with symptom ratings, and cognitive and functional imaging procedures, at which time a blood draw for DNAm studies was performed. During the 8-week period, patients received treatment with risperidone monotherapy. An independent data set was used as replication.

RESULTS

We identified brain related pathways enriched in 4,888 FES-associated CpG sites relative to controls. Risperidone administration in patients altered DNAm in 5,979 CpG sites relative to baseline. Significant group differences in DNAm at follow-up were seen in FES patients at 6,760 CpG sites versus healthy controls. Through comparison of effect size, we found 87.54% out of the risperidone-associated changes in DNAm showed possible beneficial effect, while only 12.46% showed potential adverse effect. There were 580 DNAm sites in which changes shifted methylation levels to be indistinguishable from controls after risperidone treatment. The DNAm changes of some sites that normalized after treatment were correlated with treatment-related changes in symptom severity, spontaneous neurophysiological activity, and cognition. We replicated our results in an independent data set.

CONCLUSION

The normalizing effect of risperidone monotherapy on gene DNAm, and its correlation with clinically relevant phenotypes, indicates that risperidone therapy is associated with DNAm changes that are related to changes in brain physiology, cognition and symptom severity.

Analysis of the caudate nucleus transcriptome in individuals with schizophrenia highlights effects of antipsychotics and new risk genes

Most studies of gene expression in the brains of individuals with schizophrenia have focused on cortical regions, but subcortical nuclei such as the striatum are prominently implicated in the disease, and current antipsychotic drugs target the striatum's dense dopaminergic innervation. Here, we performed a comprehensive analysis of the genetic and transcriptional landscape of schizophrenia in the postmortem caudate nucleus of the striatum of 443 individuals (245 neurotypical individuals, 154 individuals with schizophrenia and 44 individuals with bipolar disorder), 210 from African and 233 from European ancestries. Integrating expression quantitative trait loci analysis, Mendelian randomization with the latest schizophrenia genome-wide association study, transcriptome-wide association study and differential expression analysis, we identified many genes associated with schizophrenia risk, including potentially the dopamine D2 receptor short isoform. We found that antipsychotic medication has an extensive influence on caudate gene expression. We constructed caudate nucleus gene expression networks that highlight interactions involving schizophrenia risk. These analyses provide a resource for the study of schizophrenia and insights into risk mechanisms and potential therapeutic targets.

Reduced expression of synapsin II in a chronic phencyclidine preclinical rat model of schizophrenia

Schizophrenia is a mental disorder characterized by positive symptoms, negative symptoms, and cognitive dysfunction. Phencyclidine (PCP)-a N-methyl-D-aspartate (NMDA) receptor antagonist-induces symptoms indistinguishable from those of schizophrenia. A reduction of the phosphoprotein synapsin II has also been implicated in schizophrenia and has a well-known role in the maintenance of the presynaptic reserve pool and vesicle mobilization. This study assessed the behavioral and biochemical outcomes of chronic NMDA receptor antagonism in rodents and its implications for the pathophysiology of schizophrenia. Sprague Dawley rats received saline or chronic PCP (5 mg/kg/day) for 14 days via surgically implanted Alzet® osmotic mini-pumps. Following the treatment period, rats were tested with a series of behavioral paradigms, including locomotor activity, social interaction, and sensorimotor gating. Following behavioral assessment, the medial prefrontal cortex (mPFC) of all rats was isolated for synapsin II protein analysis. Chronic PCP treatment yielded a hyper-locomotive state (p = 0.0256), reduced social interaction (p = 0.0005), and reduced pre-pulse inhibition (p < 0.0001) in comparison to saline-treated controls. Synapsin IIa (p < 0.0001) and IIb (p < 0.0071) levels in the mPFC of chronically treated PCP rats were reduced in comparison to the saline group. Study results confirm that rats subject to chronic PCP treatment display behavioral phenotypes similar to established preclinical animal models of schizophrenia. Reduction of synapsin II expression in this context implicates the role of this protein in the pathophysiology of schizophrenia and sheds light on the longer-term consequences of NMDA receptor antagonism facilitated by chronic PCP treatment.

Differential Expression of Synapsin I and II upon Treatment by Lithium and Valproic Acid in Various Brain Regions

INTRODUCTION

Due to the heterogeneity of psychiatric illnesses and overlapping mechanisms, patients with psychosis are differentially responsive to pharmaceutical drugs. In addition to having therapeutic effects for schizophrenia and bipolar disorder, antipsychotics and mood stabilizers have many clinical applications and are used unconventionally due to their direct and indirect effects on neurotransmitters. Synapsins, a family of neuronal phosphoproteins, play a key regulatory role in neurotransmitter release at synapses. In this study, we investigated the effects of mood stabilizers, lithium, and valproic acid on synapsin gene expression in the rat brain.

METHODS

Intraperitoneal injections of saline, lithium, and valproic acid were administered to male Sprague Dawley rats twice daily for 14 d, corresponding to their treatment group. Following decapitation and brain tissue isolation, mRNA was extracted from various brain regions including the hippocampus, striatum, prefrontal cortex, and frontal cortex.

RESULTS

Biochemical analysis revealed that lithium significantly increased gene expression of synapsin I in the striatum, synapsin IIa in the hippocampus and prefrontal cortex, and synapsin IIb in the hippocampus and striatum. Valproic acid significantly increased synapsin IIa in the hippocampus and prefrontal cortex, as well as synapsin IIb in the hippocampus and striatum.

CONCLUSION

These significant changes in synapsin I and II expression may implicate a common transcription factor, early growth response 1, in its mechanistic pathway. Overall, these results elucidate mechanisms through which lithium and valproic acid act on downstream targets compared with antipsychotics and provide deeper insight on the involvement of synaptic proteins in treating neuropsychiatric illnesses.

Changed frontal pole gene expression suggest altered interplay between neurotransmitter, developmental, and inflammatory pathways in schizophrenia

Schizophrenia (Sz) probably occurs after genetically susceptible individuals encounter a deleterious environmental factor that triggers epigenetic mechanisms to change CNS gene expression. To determine if omnibus changes in CNS gene expression are present in Sz, we compared mRNA levels in the frontal pole (Brodmann’s area (BA) 10), the dorsolateral prefrontal cortex (BA 9) and cingulate cortex (BA 33) from 15 subjects with Sz and 15 controls using the Affymetrix™ Human Exon 1.0 ST Array. Differences in mRNA levels (±≥20%; p < 0.01) were identified (JMP Genomics 5.1) and used to predict pathways and gene x gene interactions that would be affected by the changes in gene expression using Ingenuity Pathway Analysis. There was significant variation in mRNA levels with diagnoses for 566 genes in BA 10, 65 genes in BA 9 and 40 genes in BA 33. In Sz, there was an over-representation of genes with changed expression involved in inflammation and development in BA 10, cell morphology in BA 9 and amino acid metabolism and small molecule biochemistry in BA 33. Using 94 genes with altered levels of expression in BA 10 from subjects with Sz, it was possible to construct an interactome of proven direct gene x gene interactions that was enriched for genes in inflammatory, developmental, oestrogen, serotonergic, cholinergic and NRG1 regulated pathways. Our data shows complex, regionally specific changes in cortical gene expression in Sz that are predicted to affect homeostasis between biochemical pathways already proposed to be important in the pathophysiology of the disorder.

Anterior brain regions exhibit significant amounts of differentially-expressed genes which might cause dysfunction in schizophrenia. It’s thought that schizophrenia occurs when environmental factors trigger gene expression changes and downstream effects in the human brain, though this is not fully understood. An Australian research group led by Brian Dean, from the Florey Institute of Neuroscience and Mental Health, conducted a post-mortem human brain study in which they compared gene expression between 15 schizophrenia patients and 15 controls. They found 566 instances of altered gene expression in the most frontal part of the brain, Brodmann Area 10, and fewer changes in proximal regions. These are brain areas known to mediate schizophrenia-related traits and the changes in gene expression in these areas will affect a range of essential biological pathways. The group also found 97 differentially-expressed genes that have been shown to directly interact with each. This study paints a complex picture of the causes of schizophrenia but suggests modern technologies can help unravel these complexities.

Role of presynaptic phosphoprotein synapsin II in schizophrenia

Synapsin II is a member of the neuronal phosphoprotein family. These phosphoproteins are evolutionarily conserved across many organisms and are important in a variety of synaptic functions, including synaptogenesis and the regulation of neurotransmitter release. A number of genome-wide scans, meta-analyses, and genetic susceptibility studies have implicated the synapsin II gene (3p25) in the etiology of schizophrenia (SZ) and other psychiatric disorders. Further studies have found a reduction of synapsin II mRNA and protein in the prefrontal cortex in post-mortem samples from schizophrenic patients. Disruptions in the expression of this gene may cause synaptic dysfunction, which can result in neurotransmitter imbalances, likely contributing to the pathogenesis of SZ. SZ is a costly, debilitating psychiatric illness affecting approximately 1.1% of the world’s population, amounting to 51 million people today. The disorder is characterized by positive (hallucinations, paranoia), negative (social withdrawal, lack of motivation), and cognitive (memory impairments, attention deficits) symptoms. This review provides a comprehensive summary of the structure, function, and involvement of the synapsin family, specifically synapsin II, in the pathophysiology of SZ and possible target for therapeutic intervention/implications.

Change in expression of vesicular protein synapsin II by chronic treatment with D2 allosteric modulator PAOPA

The hallmark symptoms of schizophrenia include profound disturbances in thought, perception, cognition etc., which negatively impacts an individual's quality of life. Current antipsychotic drugs are not effective in treating all symptoms of this disorder, and often cause severe movement and metabolic side effects. Consequently, there remains a strong impetus to develop safer and more efficacious therapeutics for patients, as well as elucidating the etiology of schizophrenia. Previous work in our lab has introduced a novel candidate for the treatment of this disease: the dopamine D2 receptor (D2R) allosteric modulator, 3(R)-[(2(S)-pyrrolidinylcarbonyl)amino]-2-oxo-1-pyrrolidineacetamide (PAOPA). We have previously shown that PAOPA, by selectively modulating D2R, can ameliorate schizophrenia-like symptoms in animal models, although the precise mechanism is presently not understood. Synapsin II is a presynaptic vesicular protein which has been strongly implicated in schizophrenia, as it is reduced in the prefrontal cortex of patients, and knockdown of this protein elicits schizophrenia-like phenotypes in animal models. Given the therapeutic effects of PAOPA and the role of synapsin II in schizophrenia, the objective of this study was to investigate the effect of chronic administration of PAOPA (45 days) on neuronal synapsin II protein expression in rodents. Immunoblot results revealed that the synapsin IIa, but not the IIb isoform, was increased in the dopaminergic regions of the striatum, nucleus accumbens, and medial prefrontal cortex. The results of this study implicate a role for modulation of synapsin II as a possible therapeutic mechanism of action for potential antipsychotic drug PAOPA.

Effect of chronic antipsychotic treatment on striatal phosphodiesterase 10A levels: a [¹¹C]MP-10 PET rodent imaging study with ex vivo confirmation

A number of phosphodiesterase 10A (PDE10) inhibitors are about to undergo clinical evaluation for their efficacy in treating schizophrenia. As phosphodiesterases are in the same signalling pathway as dopamine D2 receptors, it is possible that prior antipsychotic treatment could influence these enzyme systems in patients. Chronic, in contrast to acute, antipsychotic treatment has been reported to increase brain PDE10A levels in rodents. The aim of this study was to confirm these findings in a manner that can be translated to human imaging studies to understand its consequences. Positron emission tomography (PET) scanning was used to evaluate PDE10A enzyme availability, after chronic haloperidol administration, using a specific PDE10A ligand ([(11)C]MP-10). The binding of [(11)C]MP-10 in the striatum and the cerebellum was measured in rodents and a simplified reference tissue model (SRTM) with cerebellum as the reference region was used to determine the binding potential (BPND). In rats treated chronically with haloperidol (2 mg kg(-1) per day), there was no significant difference in PDE10A levels compared with the vehicle-treated group (BPND±s.d.: 3.57 ± 0.64 versus 2.86 ± 0.71). Following PET scans, ex vivo analysis of striatal brain tissue for PDE10A mRNA (Pde10a) and PDE10A enzyme activity showed no significant difference. Similarly, the PDE10A protein content determined by western blot analysis was similar between the two groups, contrary to an earlier finding. The results of the study indicate that prior exposure to antipsychotic medication in rodents does not alter PDE10A levels.

Elevated gliadin antibody levels in individuals with schizophrenia

OBJECTIVES

We aimed to replicate, in a larger sample and in a different geographical location, the previously reported elevation of anti-gliadin IgG antibodies in schizophrenia.

METHODS

A total of 950 adults with schizophrenia (severity assessed by PANSS) and 1000 healthy controls were recruited in the Munich metropolitan area. Anti-gliadin IgG antibodies were analyzed with ELISA. χ(2)-tests and logistic regression were used to analyze the association of schizophrenia with elevated anti-gliadin IgG. A multivariable general linear model was used to compare anti-gliadin IgG levels between patients and controls.

RESULTS

The odds ratio of having elevated anti-gliadin IgG antibodies in the schizophrenia group was 2.13 (95% CI 1.57 to 2.91, p < 0.0001). Mean anti-gliadin IgG levels were higher in schizophrenia patients (0.81 ± 0.79 vs. 0.52 ± 0.56, t = 9.529, df = 1,697, p < 0.0001) and the difference persisted after adjusting for potential confounders.

CONCLUSIONS

Our study, limited by its cross sectional design, confirmed an association between anti-gliadin IgG antibodies and schizophrenia. Replication in longitudinal studies, clinical trials of gluten free diet and mechanistic investigation could lead to novel treatment targets, preventive and therapeutic considerations in schizophrenia.

Effects of the dopamine D2 allosteric modulator, PAOPA, on the expression of GRK2, arrestin-3, ERK1/2, and on receptor internalization

The activity of G protein-coupled receptors (GPCRs) is intricately regulated by a range of intracellular proteins, including G protein-coupled kinases (GRKs) and arrestins. Understanding the effects of ligands on these signaling pathways could provide insights into disease pathophysiologies and treatment. The dopamine D2 receptor is a GPCR strongly implicated in the pathophysiology of a range of neurological and neuropsychiatric disorders, particularly schizophrenia. Previous studies from our lab have shown the preclinical efficacy of a novel allosteric drug, 3(R)- [(2(S)-pyrrolidinylcarbonyl)amino]-2-oxo-1-pyrrolidineacetamide (PAOPA), in attenuating schizophrenia-like behavioural abnormalities in rodent models of the disease. As an allosteric modulator, PAOPA binds to a site on the D2 receptor, which is distinct from the endogenous ligand-binding site, in order to modulate the binding of the D2 receptor ligand, dopamine. The exact signaling pathways affected by this allosteric modulator are currently unknown. The objectives of this study were to decipher the in vivo effects, in rats, of chronic PAOPA administration on D2 receptor regulatory and downstream molecules, including GRK2, arrestin-3 and extracellular receptor kinase (ERK) 1/2. Additionally, an in vitro cellular model was also used to study PAOPA’s effects on D2 receptor internalization. Results from western immunoblots showed that chronic PAOPA treatment increased the striatal expression of GRK2 by 41%, arrestin-3 by 34%, phospho-ERK1 by 51% and phospho-ERK2 by 36%. Results also showed that the addition of PAOPA to agonist treatment in cells increased D2 receptor internalization by 33%. This study provides the foundational evidence of putative signaling pathways, and changes in receptor localization, affected by treatment with PAOPA. It improves our understanding on the diverse mechanisms of action of allosteric modulators, while advancing PAOPA’s development into a novel drug for the improved treatment of schizophrenia.

Cell-free protein synthesis and purification of human dopamine D2 receptor long isoform

The human dopamine D2 receptor long isoform (D2L) has significant implications in neurological and neuropsychiatric disorders such as Parkinson's disease and schizophrenia. Detailed structural knowledge of this receptor is limited owing to its highly hydrophobic nature, which leads to protein aggregation and host toxicity when expressed in cellular systems. The newly emerging field of cell-free protein expression presents numerous advantages to overcome these challenges. This system utilizes protein synthesis machinery and exogenous DNA to synthesize functional proteins outside of intact cells. This study utilizes two different cell-free systems for the synthesis of human dopamine D2L receptor. These include the Escherichia coli lysate-based system and the wheat-germ lysate-based system. The bacterial cell-free method used pET 100/D-TOPO vector to synthesize hexa-histidine-tagged D2L receptor using a dialysis bag system; the resulting protein was purified using nickel-nitrilotriacetic acid affinity resin. The wheat germ system used pEU-glutathione-S-transferase (GST) vector to synthesize GST-tagged D2L receptor using a bilayer translation method; the resulting protein was purified using a GST affinity resin. The presence and binding capacity of the synthesized D2L receptor was confirmed by immunoblotting and radioligand competition assays, respectively. Additionally, in-gel protein sequencing via Nano LC-MS/MS was used to confirm protein synthesis via the wheat germ system. The results showed both systems to synthesize microgram quantities of the receptor. Improved expression of this highly challenging protein can improve research and understanding of the human dopamine D2L receptor.

Synapsin II gene expression in the dorsolateral prefrontal cortex of brain specimens from patients with schizophrenia and bipolar disorder: effect of lifetime intake of antipsychotic drugs

Synapsins are neuronal phosphoproteins crucial to regulating the processes required for normal neurotransmitter release. Synapsin II, in particular, has been implied as a candidate gene for schizophrenia. This study investigated synapsin II mRNA expression, using Real Time RT-PCR, in coded dorsolateral prefrontal cortical samples provided by the Stanley Foundation Neuropathology Consortium. Synapsin IIa was decreased in patients with schizophrenia when compared to both healthy subjects and patients with bipolar disorder, whereas the synapsin IIb was only significantly reduced in patients with schizophrenia when compared to healthy subjects, but not patients with bipolar disorder. Furthermore, lifetime antipsychotic drug use was positively associated with synapsin IIa expression in patients with schizophrenia. Results suggest that impairment of synaptic transmission by synapsin II reduction may contribute to dysregulated convergent molecular mechanisms which result in aberrant neural circuits that characterize schizophrenia, while implicating involvement of synapsin II in therapeutic mechanisms of currently prescribed antipsychotic drugs.

Gene-microRNA interactions associated with antipsychotic mechanisms and the metabolic side effects of olanzapine

RATIONALE

Changes in the cortical expression of small non-coding microRNA (miRNA) have been observed in postmortem analysis of psychotic disorders. Antipsychotic drugs (APDs) are the most effective treatment option for these disorders and have been associated with changes in gene expression. MicroRNA regulate numerous genes involved in brain development and function. It is therefore plausible to question whether miRNA expression is also altered and hence whether they take part in the neuroleptic mechanism of action.

OBJECTIVES

We sought to investigate whether treatment with APDs induces changes in miRNA expression and query the functional implications of such changes. Furthermore, we investigated the possible functional interplay of miRNA-gene regulatory interactions.

METHOD

High-throughput miRNA profiling of the whole brain of C57BL/6 mice treated with haloperidol, olanzapine or clozapine for 7 days was performed. Functional analysis was conducted on the putative targets of altered microRNA. Significant miRNA-gene regulatory interactions were evaluated by the integration of genome-wide mRNA expression analysis using the Bayesian networks with splitting-averaging strategy and functional analysis conducted.

RESULTS

Small subsets of miRNA were altered with each treatment with potential neurologically relevant influence. Metabolic pathways were enriched in olanzapine and clozapine treatments, possibly associated with their weight gain side effects. Neurologically and metabolically relevant miRNA-gene interaction networks were identified in the olanzapine treatment group.

CONCLUSION

This study is the first to suggest a role for miRNA in the mechanism of APD action and the metabolic side effects of the atypical ADPs, and adds support for their consideration in pharmacogenomics.

A gene expression and systems pathway analysis of the effects of clozapine compared to haloperidol in the mouse brain implicates susceptibility genes for schizophrenia

Clozapine has markedly superior clinical properties compared to other antipsychotic drugs but the side effects of agranulocytosis, weight gain and diabetes limit its use. The reason why clozapine is more effective is not well understood. We studied messenger RNA (mRNA) gene expression in the mouse brain to identify pathways changed by clozapine compared to those changed by haloperidol so that we could identify which changes were specific to clozapine. Data interpretation was performed using an over-representation analysis (ORA) of gene ontology (GO), pathways and gene-by-gene differences. Clozapine significantly changed gene expression in pathways related to neuronal growth and differentiation to a greater extent than haloperidol; including the microtubule-associated protein kinase (MAPK) signalling and GO terms related to axonogenesis and neuroblast proliferation. Several genes implicated genetically or functionally in schizophrenia such as frizzled homolog 3 (FZD3), U2AF homology motif kinase 1 (UHMK1), pericentriolar material 1 (PCM1) and brain-derived neurotrophic factor (BDNF) were changed by clozapine but not by haloperidol. Furthermore, when compared to untreated controls clozapine specifically regulated transcripts related to the glutamate system, microtubule function, presynaptic proteins and pathways associated with synaptic transmission such as clathrin cage assembly. Compared to untreated controls haloperidol modulated expression of neurotoxic and apoptotic responses such as NF-kappa B and caspase pathways, whilst clozapine did not. Pathways involving lipid and carbohydrate metabolism and appetite regulation were also more affected by clozapine than by haloperidol.

Convergent functional genomics of schizophrenia: from comprehensive understanding to genetic risk prediction

We have used a translational convergent functional genomics (CFG) approach to identify and prioritize genes involved in schizophrenia, by gene-level integration of genome-wide association study data with other genetic and gene expression studies in humans and animal models. Using this polyevidence scoring and pathway analyses, we identify top genes (DISC1, TCF4, MBP, MOBP, NCAM1, NRCAM, NDUFV2, RAB18, as well as ADCYAP1, BDNF, CNR1, COMT, DRD2, DTNBP1, GAD1, GRIA1, GRIN2B, HTR2A, NRG1, RELN, SNAP-25, TNIK), brain development, myelination, cell adhesion, glutamate receptor signaling, G-protein-coupled receptor signaling and cAMP-mediated signaling as key to pathophysiology and as targets for therapeutic intervention. Overall, the data are consistent with a model of disrupted connectivity in schizophrenia, resulting from the effects of neurodevelopmental environmental stress on a background of genetic vulnerability. In addition, we show how the top candidate genes identified by CFG can be used to generate a genetic risk prediction score (GRPS) to aid schizophrenia diagnostics, with predictive ability in independent cohorts. The GRPS also differentiates classic age of onset schizophrenia from early onset and late-onset disease. We also show, in three independent cohorts, two European American and one African American, increasing overlap, reproducibility and consistency of findings from single-nucleotide polymorphisms to genes, then genes prioritized by CFG, and ultimately at the level of biological pathways and mechanisms. Finally, we compared our top candidate genes for schizophrenia from this analysis with top candidate genes for bipolar disorder and anxiety disorders from previous CFG analyses conducted by us, as well as findings from the fields of autism and Alzheimer. Overall, our work maps the genomic and biological landscape for schizophrenia, providing leads towards a better understanding of illness, diagnostics and therapeutics. It also reveals the significant genetic overlap with other major psychiatric disorder domains, suggesting the need for improved nosology.

Behavioral effects of non-viral mediated RNA interference of synapsin II in the medial prefrontal cortex of the rat

Synapsin II is a synaptic vesicle-associated phosphoprotein that has been implicated in the pathophysiology of schizophrenia. Researchers have demonstrated reductions in synapsin II mRNA and protein in post-mortem prefrontal cortex and hippocampus samples from patients with schizophrenia. Synapsin II protein expression has been shown to be regulated by dopamine D(1) and D(2) receptor activation. Furthermore, behavioral testing of the synapsin II knockout mouse has revealed a schizophrenic-like behavioral phenotype in this mutant strain, suggesting a relationship between dysregulated and/or reduced synapsin II and schizophrenia. However, it remains unknown the specific regions of the brain of which perturbations in synapsin II play a role in the pathophysiology of this disease. The aim of this project was to evaluate animals with a selective knock-down of synapsin II in the medial prefrontal cortex through the use of siRNA technology. Two weeks after continuous infusion of synapsin II siRNAs, animals were examined for the presence of a schizophrenic-like behavioral phenotype. Our results reveal that rats with selective reductions in medial prefrontal cortical synapsin II demonstrate deficits in sensorimotor gating (prepulse inhibition), hyperlocomotion, and reduced social behavior. These results implicate a role for decreased medial prefrontal cortical synapsin II levels in the pathophysiology of schizophrenia and the mechanisms of aberrant prefrontal cortical circuitry, and suggest that increasing synapsin II levels in the medial prefrontal cortex may potentially serve as a novel therapeutic target for this devastating disorder.

Genetic models of sensorimotor gating: relevance to neuropsychiatric disorders

Sensorimotor gating, or the ability of a sensory event to suppress a motor response, can be measured operationally via prepulse inhibition (PPI) of the startle response. PPI is deficient in schizophrenia patients as well as other neuropsychiatric disorders, can be measured across species, and has been used widely as a translational tool in preclinical neuropharmacological and genetic research. First developed to assess drug effects in pharmacological and developmental models, PPI has become one of the standard behavioral measures in genetic models of schizophrenia and other neuropsychiatric disorders that exhibit PPI deficits. In this chapter we review the literature on genetic models of sensorimotor gating and discuss the utility of PPI as a tool in phenotyping mutant mouse models. We highlight the approaches to genetic mouse models of neuropsychiatric disease, discuss some of the important caveats to these approaches, and provide a comprehensive table covering the more recent genetic models that have evaluated PPI.

Medial prefrontal cortical synapsin II knock-down induces behavioral abnormalities in the rat: examining synapsin II in the pathophysiology of schizophrenia

Synapsin II is a synaptic vesicle-associated phosphoprotein that has been implicated in the pathophysiology of schizophrenia. Studies have demonstrated reductions in synapsin II mRNA and protein in medial prefrontal cortical post-mortem samples from patients with schizophrenia, genetic associations between synapsin II and schizophrenia, and synapsin II protein regulation by dopamine receptor activation. Collectively, this research indicates a relationship between synapsin II dysregulation and schizophrenia; however, it remains unknown whether perturbations in synapsin II play a role in the pathophysiology of this disease. The aim of this project was to evaluate animals with selective knock-down of synapsin II in the medial prefrontal cortex. After continuous infusion of synapsin II antisense sequences, animals were examined for the presence of schizophrenic-like behavioral phenotypes and assessed on the response to clinically relevant antipsychotic drugs. Our results indicate that rats with selective reductions in medial prefrontal cortical synapsin II demonstrate deficits in sensorimotor gating (prepulse inhibition), reduced social behavior, and hyperlocomotion, which are corrected by the atypical antipsychotic drug olanzapine. Additionally, synapsin II knock-down disrupts serial search efficiency. These behavioral changes are accompanied by reductions in vesicular neurotransmitter transporter protein concentrations for glutamate (VGLUT1 and VGLUT2) and GABA (VGAT), without affecting dopamine (VMAT2). These results implicate a causal role for decreased synapsin II in the medial prefrontal cortex in the pathophysiology of schizophrenia and the mechanisms of aberrant prefrontal cortical circuitry, and suggest that synapsin II may potentially serve as a novel therapeutic target for this disorder.

Alpha-phenyl-N-tert-butylnitrone prevents oxidative stress in a haloperidol-induced animal model of tardive dyskinesia: investigating the behavioural and biochemical changes

Haloperidol (HP) is a widely prescribed antipsychotic drug used for the treatment of mental disorders. However, while providing therapeutic benefits, this drug also causes serious extrapyramidal side effects, such as tardive dyskinesia (TD). Upon chronic administration, HP causes behavioural supersensitivity to dopamine D2 receptor agonists, as well as the development of vacuous chewing movements (VCMs), in an animal model of human TD. Currently, a prevailing hypothesis to account for these behavioural abnormalities implicates oxidative stress. This study was undertaken to examine whether the free radical trapping agent, α-phenyl-N-tert-butylnitrone (PBN), can prevent the development of behavioural supersensitivity to dopamine D2 receptor agonists and the development of VCMs. Additionally, the study examined whether increased synthesis of apoptosis inducing factor (AIF) can result from HP-induced oxidative stress. Male Sprague-Dawley rats were treated with HP in conjunction with PBN, or its vehicle, for 4weeks. After a 24-hour washout period, behavioural observations were recorded along with the estimation of lipid peroxidation and antioxidant enzyme activities. The free radical trapping agent, PBN, prevented the development of behavioural supersensitivity, reduced lipid peroxidation and prevented the reduction of antioxidant enzyme activities. AIF concentrations at the mRNA and protein levels remained unchanged; therefore increased AIF gene expression is unlikely to be involved in HP-induced oxidative stress. The findings of the present study suggest the involvement of striatal free radicals in the development of behavioural supersensitivity, and free radical trapping agents, such as PBN, as possible options for the treatment of extrapyramidal side effects in humans.

Antipsychotic-induced gene regulation in multiple brain regions

The molecular mechanism of action of antipsychotic drugs is not well understood. Their complex receptor affinity profiles indicate that their action could extend beyond dopamine receptor blockade. Single gene expression studies and high-throughput gene profiling have shown the induction of genes from several molecular classes and functional categories. Using a focused microarray approach, we investigated gene regulation in rat striatum, frontal cortex, and hippocampus after chronic administration of haloperidol or olanzapine. Regulated genes were validated by in situ hybridization, real-time PCR, and immunohistochemistry. Only limited overlap was observed in genes regulated by haloperidol and olanzapine. Both drugs elicited maximal gene regulation in the striatum and least in the hippocampus. Striatal gene induction by haloperidol was predominantly in neurotransmitter signaling, G-protein coupled receptors, and transcription factors. Olanzapine prominently induced retinoic acid and trophic factor signaling genes in the frontal cortex. The data also revealed the induction of several genes that could be targeted in future drug development efforts. The study uncovered the induction of several novel genes, including somatostatin receptors and metabotropic glutamate receptors. The results demonstrating the regulation of multiple receptors and transcription factors suggests that both typical and atypical antipsychotics could possess a complex molecular mechanism of action.

Role of AP-2alpha transcription factor in the regulation of synapsin II gene expression by dopamine D1 and D2 receptors

Synapsins are a family of neuron-specific phosphoproteins involved in synaptic vesicle docking, synaptogenesis, and synaptic plasticity. Previous studies have reported an increase in synapsin II protein by dopaminergic agents in the striatum, medial prefrontal cortex, and nucleus accumbens. This study investigated the mechanistic pathway involved in synapsin II regulation by dopaminergic drugs using primary midbrain neurons to determine which of several transcription factors regulates synapsin II expression. Protein kinase A (PKA) participation in the signaling pathway was examined using selective PKA inhibitors, which reduced synapsin II expression in cell cultures while dopaminergic agents were unable to increase synapsin II in the presence of the PKA inhibitor. Transcription factor involvement was further investigated using separate cultures treated with antisense deoxyoligonucleotides (ADONs) against the following transcription factors: activating protein 2 alpha (AP-2alpha), early growth response factor 1 (EGR-1), or polyoma enhancer activator-3 (PEA-3). Selective knockdown of AP-2alpha by ADONs reduced synapsin II levels, whereas treatment with EGR-1 and PEA-3 ADONs did not affect synapsin II expression. Furthermore, dopaminergic agents were no longer able to influence synapsin II concentrations following AP-2alpha knockdown. Collectively, these results indicate that a cyclic adenosine-3',5'-monophosphate/PKA-dependent mechanism involving the AP-2alpha transcription factor is likely responsible for the increase in neuronal synapsin II following dopamine D1 receptor stimulation or dopamine D2 receptor inhibition.

Some molecular effectors of antidepressant action of quetiapine revealed by DNA microarray in the frontal cortex of anhedonic rats

OBJECTIVES AND METHODS

We have previously demonstrated that quetiapine (QTP) had antidepressant-like action by using the chronic mild stress (CMS) paradigm, an animal model of human depression. The aim of this study was to investigate the molecular mechanism(s) of QTP antidepressant effect by coupling the CMS protocol with Affymetrix microarray technology to screen the entire rat genome for gene changes in the frontal cortex.

RESULTS

The genes regulated by the administration of CMS whose transcription was reversed by chronic QTP treatment (2 mg/kg/day) were 42 (23 upregulated and 19 downregulated). The transcripts that showed no significant altered expression levels in anhedonic rats but were regulated by the administration of QTP were 19 (nine upregulated and 10 downregulated). On the whole, the action of QTP prevented the stress-induced impairment of some processes involved in central nervous system development or having a crucial role for viability of neural cells and cell-cell communications, like regulation of signal transduction, inorganic cation transport, membrane organization, and neurite morphogenesis. For 11 genes (Ptgs2, Gad1, Plcb1, Camk2a, Homer1, Senp2, Junb, Nfib, Hes5, Capon, and Marcks), significant differential expressions were confirmed by real-time reverse-transcriptase polymerase chain reaction.

CONCLUSION

We have shown that chronic QTP treatment prevented anhedonia and reversed, at least in part, the changes of gene expression induced by CMS in the rat frontal cortex. We have also identified and confirmed by two different methods that 11 genes, representing molecular targets of QTP, are presumably the effectors of its clinical efficacy.

Behavioral abnormalities in synapsin II knockout mice implicate a causal factor in schizophrenia

Recent studies on the phosphoprotein synapsin II have revealed reduced expression in postmortem medial prefrontal cortex tissues from subjects with schizophrenia, and chronic antipsychotic drug treatment has resulted in concurrent increases in synapsin II mRNA and protein levels. Collectively, this research suggests a role of synapsin II in the pathophysiology of schizophrenia; however, whether synapsin II plays a causal role in this disease process still remains unclear. Therefore, the goal of this investigation was to examine whether synapsin II knockout mice display behavioral abnormalities commonly expressed in preclinical animal models of schizophrenia, namely deficits in prepulse inhibition (PPI), decreased social behavior, and locomotor hyperactivity. Results indicate that mice with knockout of the synapsin II gene demonstrate deficits in PPI at three prepulse intensities (67, 70, and 73 dB), along with deficits in habituation to startle to a 110 dB acoustic pulse. Knockout animals also expressed decreased social behavior and increased locomotor activity when compared to wildtype and heterozygous populations. Complete knockout of the synapsin II gene was confirmed in postmortem brain tissues via immunoblotting. In conclusion, these results confirm that synapsin II knockout mice display behavioral endophenotypes similar to established preclinical animal models of schizophrenia, and lend support to the notion that abnormalities in synapsin II expression may play a causal role in the underlying pathophysiological mechanisms of schizophrenia.

Coregulation of genes in the mouse brain following treatment with clozapine, haloperidol, or olanzapine implicates altered potassium channel subunit expression in the mechanism of antipsychotic drug action

BACKGROUND

Antipsychotic drugs are the most effective treatment for the psychotic symptoms of schizophrenia, yet their mechanism of action remains largely unknown.

OBJECTIVES

Earlier studies have shown gene expression changes in rodent brains after treatment with antipsychotic drugs. We aimed to further characterize these changes using whole-genome transcript profiling to explore coregulation of genes after multiple antipsychotic drug treatment studies.

METHODS

This study involved transcript profile analysis after 7-day treatment of inbred C57BL/6 mice with conventional (haloperidol) or atypical (clozapine or olanzapine) antipsychotic drugs. Microarray analysis was undertaken using whole-brain mRNA on Affymetrix 430v2 arrays, with quantitative reverse transcriptase-PCR used to confirm gene expression changes. Western blotting was also used to explore translation of gene dysregulation to protein changes and to explore anatomical specificity of such changes.

MAIN RESULTS

Thirteen genes showed verified regulation by multiple antipsychotic drugs - three genes significantly upregulated and 10 genes significantly downregulated by treatment. These genes encode proteins that function in various biological processes including neurogenesis, cell adhesion, and four genes are involved in voltage-gated ion channels: neural precursor cell developmentally downregulated gene 4 (Nedd4), Kv channel interacting protein 3 (KChip3), potassium voltage-gated channel, shaker-related subfamily, alpha1 (Kcna1) encoding Kv1.1 protein and beta1 (Kcnab1) encoding Kvbeta1 protein. The translation of these gene expression changes to protein dysregulation for Kv1.1, KCHIP3, and NEDD4 was confirmed by western blot, with regional protein analyses undertaken for Kv1.1 and KCHIP3.

CONCLUSION

These results suggest that transcriptional regulation of ion channels, crucial for neurotransmission, may play a role in mediating antipsychotic drug effects.

Chronic treatment with aripiprazole induces differential gene expression in the rat frontal cortex

Chronic treatment of antipsychotic drugs can modulate gene expression in the brain, which may underscore their clinical efficacy. Aripiprazole is the first approved antipsychotic drug of the class of dopamine D2 receptor partial agonist, which has been shown to have similar efficacy and favourable side-effects profile compared to other antipsychotic drugs. This study aimed to identify differential gene expression induced by chronic treatment of aripiprazole. We used microarray-based gene expression profiling technology, real-time quantitative PCR and Western blot analysis to identify differentially expressed genes in the frontal cortex of rats under 4 wk treatment of aripiprazole (10 mg/kg). We were able to detect ten up-regulated genes, including early growth response gene 1, 2, 4 (Egr1, Egr2, Egr4), chromobox homolog 7 (Cbx7), cannabinoid receptor (Cnr1), catechol-O-methyltransferase (Comt), protein phosphatase 2c, magnesium dependent (Ppm2c), tachykinin receptor 3 (Tacr3), Wiscott-Aldrich syndrome-like gene (Wasl) and DNA methyltransferase 3a (Dnmt3a). Our data indicate that chronic administration of aripiprazole can induce differential expression of genes involved in transcriptional regulation and chromatin remodelling and genes implicated in the pathogenesis of psychosis.

Association of synapsin 2 with schizophrenia in families of Northern European ancestry

The synapsin 2 (Syn2) gene (3p25) is implicated in synaptogenesis, neurotransmitter release, and the localization of nitric oxide synthase to the proximity of its targets. In this study we investigated linkage and association between the Syn2 locus and schizophrenia. 37 pedigrees of Northern European ancestry from the NIMH Human Genetics Initiative collection were used. Four microsatellites and twenty SNPs were genotyped. Linkage (FASTLINK) and association (TRANSMIT, PDTPHASE) between markers and schizophrenia were evaluated. A maximum heterogeneity LOD of 1.93 was observed at marker D3S3434 with a recessive mode of inheritance. Significant results were obtained for association with schizophrenia using TRANSMIT (minimum nominal p=0.0000005) and PDTPHASE (minimum nominal p=0.014) using single marker analyses. Haplotype analysis using markers in introns 5 and 6 of Syn2 provided a single haplotype that is significantly associated with schizophrenia using TRANSMIT (nominal p<0.00000001) and PDTPHASE (nominal p=0.02). Simulation studies confirm the global significance of these results, but demonstrate that the small p-values generated by the bootstrap routine of TRANSMIT can be consistently anticonservative. Review of the literature suggests that Syn2 is likely to be involved in the etiology or pathogenesis of schizophrenia.

Pharmacogenetics and pharmacogenomics of schizophrenia: a review of last decade of research

The last decade of research into the pharmacogenetics of antipsychotics has seen the development of genetic tests to determine the patients' metabolic status and the first attempts at personalization of antipsychotic treatment. The most significant results are the association between drug metabolic polymorphisms, mainly in cytochrome P450 genes, with variations in drug metabolic rates and side effects. Patients with genetically determined CYP2D6 poor metabolizer (PMs) status may require lower doses of antipsychotic. Alternatively, CYP2D6 ultrarapid matabolizers (UMs) will need increased drug dosage to obtain therapeutic response. Additionally, polymorphisms in dopamine and serotonin receptor genes are repeatedly found associated with response phenotypes, probably reflecting the strong affinities that most antipsychotics display for these receptors. In particular, there is important evidence suggesting association between dopamine 2 receptor (D2) polymorphisms (Taq I and -141-C Ins/Del) and a dopamine 3 receptor (D3) polymorphism (Ser9Gly) with antipsychotic response and drug-induced tardive dyskinesia. Additionally, there is accumulating evidence indicating the influence of a 5-HT2C polymorphism (-759-T/C) in antipsychotic-induced weight gain. Application of this knowledge to clinical practice is slowly gathering pace, with pretreatment determination of individual's drug metabolic rates, via CYP genotyping, leading the field. Genetic determination of patients' metabolic status is expected to bring clinical benefits by helping to adjust therapeutic doses and reduce adverse reactions. Genetic tests for the pretreatment prediction of antipsychotic response, although still in its infancy, have obvious implications for the selection and improvement of antipsychotic treatment. These developments can be considered as successes, but the objectives of bringing pharmacogenetic and pharmacogenomic research in psychiatric clinical practice are far from being realized. Further development of genetic tests is required before the concept of tailored treatment can be applied to psychopharmatherapy. This review aims to summarize the key findings from the last decade of research in the field. Current knowledge on genetic prediction of drug metabolic status, general response and drug-induced side effects will be reviewed and future pharmacogenomic and epigenetic research will be discussed.

Reduction of synapsin III in the prefrontal cortex of individuals with schizophrenia

We analyzed the expression of a presynaptic protein, synapsin III, in individuals with schizophrenia. Since levels of synapsin III were previously found to be significantly reduced in the hippocampus of individuals with schizophrenia, we examined another brain region believed to be a major locus of dysfunction in schizophrenia, the dorsolateral prefrontal cortex (DLPFC). Western blot analyses using tissue obtained from the Stanley Foundation Neuropathology Consortium revealed that synapsin III levels were significantly decreased in the DLPFC of individuals with schizophrenia compared to controls. These findings are consistent with growing evidence of presynaptic abnormalities and prefrontal cortical dysfunction in schizophrenia.

Dopamine and serotonin metabolism in response to chronic administration of fluvoxamine and haloperidol combined treatment

Treating primary 'negative symptoms' of schizophrenia with a combination of a typical antipsychotic and a selective serotonin reuptake inhibitor, is more effective than with antipsychotic alone and is similar to the effect of the atypical antipsychotic, clozapine. The mechanism of this treatment combination is unknown and may involve changes in dopaminergic and serotonin systems. We studied dopamine and serotonin metabolism in different rat brain areas at 1.5 and 24 h after the last dosage of chronic treatment (30 days), with haloperidol plus fluvoxamine, each drug alone, and clozapine. Haloperidol-fluvoxamine combination, haloperidol, and clozapine treatments increased striatal and frontal cortex dopamine turnover and reduced striatal tyrosine hydroxylase activity at 1.5 h. At 24 h both dopamine turnover and tyrosine hydroxylase activity were reduced. Thus, in chronically treated animals, release of striatal dopamine increases following a drug pulse and returns to baseline by 24 h. Serotonin and 5-hydroxyindoleacetic acid concentrations were decreased at 1.5 h in haloperidol-fluvoxamine and clozapine groups and returned to normal levels by 24 h. A limited behavioral assessment showed that treatment with haloperidol plus fluvoxamine reduced motor activity compared to haloperidol, and increased sniffing compared to haloperidol, fluvoxamine and clozapine. These findings indicate that combining antipsychotic with SSRI results in specific changes in dopaminergic and serotonergic systems and in behavior. The possibility that these may be relevant to the mechanism underlying the clinical effectiveness of augmentation treatment warrant further study.

Molecular profiling of antipsychotic drug function: convergent mechanisms in the pathology and treatment of psychiatric disorders

Despite great progress in antipsychotic drug research, the molecular mechanisms by which these drugs work have remained elusive. High-throughput gene profiling methods have advanced this field by allowing the simultaneous investigation of hundreds to thousands of genes. However, different methodologies, choice of brain region, and drugs studied have made comparisons across different studies difficult. Because of the complexity of gene expression changes caused by drugs, teasing out the most relevant expression differences is a challenging task. One approach is to focus on gene expression changes that converge on the same systems that were previously deemed important to the pathology of psychiatric disorders. From the microarray studies performed on human postmortem brain samples from schizophrenics, the systems most implicated to be dysfunctional are synaptic machinery, oligodendrocyte/myelin function, and mitochondrial/ubiquitin metabolism. Drugs may act directly or indirectly to compensate for underlying pathological deficits in schizophrenia or via other mechanisms that converge on these pathways. Side effects, consisting of motor and metabolic dysfunction (which occur with typical and atypical drugs, respectively), also may be mediated by gene expression changes that have been reported in these studies. This article surveys both the convergent antipsychotic mechanisms and the genes that may be responsible for other effects elicited by antipsychotic drugs.

Chronic haloperidol treatment results in a decrease in the expression of myelin/oligodendrocyte-related genes in the mouse brain

Schizophrenia is a complex psychiatric illness that manifests as a combination of positive symptoms, negative symptoms, and cognitive deficits. Antipsychotic drugs, such as haloperidol, attenuate dopamine receptor signaling in neurons and constitute the frontline treatment for the positive symptoms of schizophrenia. However, haloperidol treatment has also been reported to exacerbate preexisting negative symptoms/cognitive deficits and the severity of these deficits has been correlated with white matter pathology in schizophrenia. Indeed, several studies implicate oligodendrocyte function in the pathophysiology of schizophrenia, but it is unknown whether these effects are related to drug treatment. It is well established that haloperidol alters gene expression in neurons. However, its effect on oligodendrocytes is unknown. In this study, we investigate the effects of chronic haloperidol treatment on the expression of eight genes known to play critical roles in myelin/oligodendrocyte function. We treated male mice with haloperidol (2 mg/kg/day) for 30 days and measured gene expression changes by using in situ hybridization analysis and quantitative densitometry. Haloperidol caused a decrease in the expression of these genes in several white matter regions of the mouse CNS. In contrast, clozapine (10 mg/kg/day) had no effect on the expression of a subset of these genes. This has important implications for both disease pathology and the consideration of treatment options for patients.

Chronic olanzapine treatment causes differential expression of genes in frontal cortex of rats as revealed by DNA microarray technique

Recent emerging biochemical data indicate that several important neuroregulatory genes and proteins may be involved in the etiology of schizophrenia and bipolar disorder. Additionally, the same genes appear to be targets of several psychotropic medications that are used to treat these disorders. Recent DNA microarray studies show that genes involved in synaptic neurotransmission, signal transduction, and glutamate/GABA regulation may be differentially regulated in brains of subjects with schizophrenia. We hypothesized that chronic administration of olanzapine to rats would alter expression of various genes that may be involved in the etiology of schizophrenia and mood disorders. Rats were administered olanzapine (N=20, 2 mg/kg/day) or sterile saline intraperitoneally (N=20) daily for 21 days. Control and olanzapine-treated frontal cortices were analyzed using cDNA microarray technology. The results showed significant downregulation of 31 genes and upregulation of 38 genes by greater than two-fold in the drug-treated brains vs controls. Our results provide evidence for altered regulation of genes involved with signal transduction and cell communication, metabolism and energy pathways, transport, immune response, nucleic acid metabolism, and neuronal growth factors. Real-time quantitative RT-PCR analysis verified the direction and magnitude of change in six genes of interest: calbindin 3, homer 1, regulator of G-protein signaling (RGS) 2, pyruvate kinase, Reelin and insulin 2. Western blotting showed significant upregulation in protein products for Reelin 410 and Reelin 180 kDa and downregulation for NMDA3B and RGS2. Our results show for the first time that olanzapine causes changes in levels of several important genes that may be involved in the etiology and treatment of schizophrenia and other psychiatric disorders.

Critical appraisal of DNA microarrays in psychiatric genomics

Transcriptome profiling using DNA microarrays are data-driven approaches with the potential to uncover unanticipated relationships between gene expression alterations and psychiatric disorders. Studies to date have yielded both convergent and divergent findings. Differences may be explained, at least in part, by the use of a variety of microarray platforms and analytical approaches. Consistent findings across studies suggest, however, that important relationships may exist between altered gene expression and genetic susceptibility to psychiatric disorders. For example, GAD67, RGS4, DTNBP1, NRG1, and GABRAB2 show expression alterations in the postmortem brain of subjects with schizophrenia, and these genes have been also implicated as putative, heritable schizophrenia susceptibility genes. Thus, we propose that for some genes, altered expression in the postmortem human brain may have a dual origin: polymorphisms in the candidate genes themselves or upstream genetic-environmental factors that converge to alter their expression level. We hypothesize that certain gene products, which function as "molecular hubs," commonly show altered expression in psychiatric disorders and confer genetic susceptibility for one or more diseases. Microarray gene expression studies are ideally suited to reveal these putative disease-associated molecular hubs and to identify promising candidates for genetic association studies.

Translocation of AIF in the human and rat striatum following protracted haloperidol, but not clozapine treatment

Loss of mitochondrial membrane integrity and consequent release of apoptogenic factors may be involved in mediating striatal neurodegeneration after prolonged treatment with the typical antipsychotic drug haloperidol. Apoptosis-inducing factor (AIF), an intramitochondrial protein, may have a large influence on mediating haloperidol-induced striatal neuron destruction. Translocation of this protein from mitochondria to the nucleus promotes cell death independently of the caspase cascade. To examine how AIF may contribute to haloperidol-induced apoptosis, AIF translocation was observed in three haloperidol treatment paradigms. SH-SY5Y cells were treated with both haloperidol and clozapine and examined for AIF immunofluorescence. Immunohistochemistry was also performed on human striatal sections obtained from the Stanley Foundation Neuropathology Consortium and on rat brain sections following 28 days of antipsychotic drug treatment. In the cellular model haloperidol, but not clozapine treatment increased the nuclear AIF immunofluorescent signal and decreased cell viability. Corollary to these findings, striatal sections from patients who had taken haloperidol and rats who were administered haloperidol both had an elevated nuclear AIF signal. The results provide novel evidence implicating the involvement of AIF in haloperidol-associated apoptosis and its relevance to the development of typical antipsychotic drug-related adverse effects such as tardive dyskinesia.

Microarray analysis reveals distinct gene expression patterns in the mouse cortex following chronic neuroleptic and stimulant treatment: implications for body weight changes

Atypical neuroleptics are associated with clinical significant weight gain, whereas stimulants are used as anorexiant drugs. The aim of this study was to examine gene expression changes in the mouse frontal cortex following chronic oral treatment with antipsychotics and a stimulant by microarray assessments. Twenty 10-12-week-old male C57BL6 mice received daily for 31 days either the typical neuroleptic haloperidol (1 mg/kg), the atypical neuroleptic clozapine (10 mg/kg) or the stimulant phenylpropanolamine (3 mg/kg). We identified a set of genes that was differently expressed between the neuroleptic-treated groups and the stimulant-treated group. Importantly, we found in the majority of gene alterations down-regulation in genes involved in ATP biosynthesis and lipid metabolism following the stimulant treatment, suggesting these genes as candidates that may regulate body weight. We also identified remarkable expression patterns of genes that encode signalling molecules (e.g. insulin, mitochondrial uncoupling protein 1) that are implicated in the control of food intake and are differently expressed in the neuroleptic groups.

Dopamine-D1 and -D2 receptors differentially regulate synapsin II expression in the rat brain

We previously demonstrated that chronic treatment with the dopamine-D2 receptor antagonist, haloperidol, increases mRNA and protein content of the phosphoprotein, synapsin II, in the rat striatum. Since dopamine-D2 receptor antagonism and dopamine-D1 receptor blockade can have opposing effects on gene expression, the present investigation compared the effects of haloperidol with those of the dopamine-D1 receptor antagonist, R-[+]-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine (SCH23390), on the expression of synapsin II protein. Haloperidol and SCH23390 respectively elevated and reduced concentrations of the molecule in mouse primary midbrain cell cultures. Additional experiments revealed that the dopamine-D1 receptor agonist, R-[+]-1-phenyl-2,3,4,5-tetrahydro-(1H)-3-benzapezine-7,8-diol (SKF38393), upregulated the phosphoprotein in these cells. Furthermore, in vivo rat studies demonstrated that chronic haloperidol treatment increases synapsin II protein expression in the medial prefrontal cortex and nucleus accumbens, as was observed in the striatum. In contrast, chronic SCH23390 administration reduced concentrations of this protein in all of these regions, although the reductions seen in the medial prefrontal cortex were insignificant. Neither haloperidol nor the dopamine-D1 receptor antagonist affected synapsin I protein expression in any of the studied brain areas. Based on these findings, we propose dopamine receptors may specifically regulate synapsin II expression through a cyclic AMP-dependent pathway. Since synapsin II is involved in neurotransmitter release and synaptogenesis, and changes in synaptic efficacy and structure are suggested in schizophrenia as well as in haloperidol treatment, our findings offer insight into the mechanistic actions of the antipsychotic agent at the synaptic level.

Antipsychotic pathway genes with expression altered in opposite direction by antipsychotics and amphetamine

To develop a new strategy for identifying possible psychotic- or antipsychotic-related pathway genes, rats were treated with clinical doses of haloperidol and clozapine for 4 days, and the altered expression of genes was compared with the genes altered in expression after amphetamine sensitization. The objective was to identify genes with expression altered in the same direction by haloperidol and clozapine but in the opposite direction in the amphetamine-sensitized rat striatum. These criteria were met by 21 genes, consisting of 15 genes upregulated by amphetamine, and 6 genes downregulated by amphetamine. Of the 21 genes, 15 are not presently identified, and only 3 genes (cathepsin K, GRK6, and a gene with accession number AI177589) are located in chromosome regions known to be associated with schizophrenia.

cDNA array reveals increased expression of glucose-dependent insulinotropic polypeptide following chronic clozapine treatment: role in atypical antipsychotic drug-induced adverse metabolic effects

Clozapine is an atypical antipsychotic drug with unique pharmacological and therapeutic properties. Unlike the typical antipsychotic drug, haloperidol, clozapine does not cause extrapyramidal side effects; however, weight gain, dyslipidemia, and type II diabetes are commonly associated with the use of this drug in subjects with schizophrenia. The aim of this study was to profile gene expression in the rat striatum following clozapine treatment. Chronic treatment with clozapine revealed upregulation of several genes including the glucose-dependent insulinotropic polypeptide (GIP) gene by over 200% in the rat striatum. The cDNA array results for the GIP gene were confirmed by real-time RT-PCR as well as by radioimmunoassay. Expression of the GIP gene in the central nervous system is consistent with the results of retinal GIP gene expression as reported by other investigators. Taken together, these findings implicate the possible role of GIP as a neuromodulator in the central nervous system. GIP is an insulinotropic agent with stimulatory effects on insulin synthesis and release from the pancreas. However, changes in brain GIP levels are most likely unrelated to the metabolic adverse effects (dyslipidemia, type II diabetes, weight gain) associated with clozapine treatment. Therefore, we also measured GIP gene expression in the K-cell-rich regions, duodenum and jejunum (small intestine), and plasma GIP levels using radioimmunoassay following chronic treatment with clozapine. GIP mRNA levels in the small intestine and the plasma GIP at the protein level were significantly elevated in clozapine-treated subjects. Furthermore, as observed in humans, chronic clozapine treatment also caused weight gain, and increased levels of insulin, triglycerides and leptin in the plasma. These results suggest that adverse metabolic effects associated with clozapine treatment may be related to its ability to increase intestinal gene expression for GIP.

Antipsychotic drugs elevate mRNA levels of presynaptic proteins in the frontal cortex of the rat

BACKGROUND

Molecular adaptations are believed to contribute to the mechanism of action of antipsychotic drugs (APDs). We attempted to establish common gene regulation patterns induced by chronic treatment with APDs.

METHODS

Gene expression analysis was performed with the Affymetrix U34A array in the frontal cortex (FC) and the striatum of rats chronically treated with two concentrations of either clozapine or haloperidol. Key data were verified with real-time quantitative polymerase chain reaction.

RESULTS

Many genes in the FC affected by APD-treatment contribute to similar functions. mRNAs coding for synaptic vesicle docking- and microtubule-associated proteins were upregulated; mRNAs for serine-threonine protein phosphatases were downregulated, whereas the serine-threonine kinases protein kinase A, protein kinase C, and calcium/calmodulin kinase II alpha and IV were upregulated, indicating increased potential for protein phosphorylation. In the striatum, altered gene expression was less focused on genes of particular function or location, and the high concentration of haloperidol had a different gene expression profile than any of the other APD treatments.

CONCLUSION

We found an increase in the transcription of genes coding for proteins involved in synaptic plasticity and synaptic activity in the FC. We furthermore found that the gene expression profile of APDs is different between FC and striatum.

Microarray analysis of differentially expressed genes in rat frontal cortex under chronic risperidone treatment

Long-term administration of antipsychotic drugs can induce differential expression of a variety of genes in the brain, which may underscore the molecular mechanism of the clinical efficacy and/or side effects of antipsychotic drugs. We used cDNA microarray analysis to screen differentially expressed genes in rat frontal cortex under 4 weeks' treatment of risperidone (1 mg/kg). Using real-time quantitative PCR, we were able to verify eight genes, whose expression were significantly upregulated in rat frontal cortex under chronic risperidone treatment when compared with control animals. These genes include receptor for activated protein kinase C, amida, cathepsin D, calpain 2, calcium-independent receptor for alpha-latrotoxin, monoamine oxidase B, polyubiquitin, and kinesin light chain. In view of the physiological function of these genes, the results of our study suggest that chronic risperidone treatment may affect the neurotransmission, synaptic plasticity, and proteolysis of brain cells. This study also demonstrates that cDNA microarray analysis is useful for uncovering genes that are regulated by chronic antipsychotic drugs treatment, which may help bring new insight into the molecular mechanism of antipsychotic drugs.

Dopamine D2-like antagonists induce chromatin remodeling in striatal neurons through cyclic AMP-protein kinase A and NMDA receptor signaling

Antipsychotic drugs regulate gene transcription in striatal neurons by blocking dopamine D2-like receptors. Little is known about the underlying changes in chromatin structure, including covalent modifications at histone N-terminal tails that are epigenetic regulators of gene expression. We show that treatment with D2-like antagonists rapidly induces the phosphorylation of histone H3 at serine 10 and the acetylation of H3-lysine 14 in bulk chromatin from striatum and in nuclei of striatal neurons. We find that, in vivo, D2-like antagonist-induced H3 phospho-acetylation is inhibited by the NMDA receptor antagonist MK-801 and by the protein kinase A (PKA) inhibitor Rp-adenosine 3c',5c'-cyclic monophosphorothioate triethylammonium salt but increased by the PKA activator Sp-adenosine 3c',5c'-cyclic monophosphorothioate triethylammonium salt. Furthermore, in dissociated striatal cultures which lack midbrain and cortical pre-synaptic inputs, H3 phospho-acetylation was induced by glutamate, L-type Ca2+ channel agonists and activators of cAMP-dependent PKA but inhibited by NMDA receptor antagonists or PKA antagonists. The dual modification, H3pS10-acK14, was enriched at genomic sites with active transcription and showed the kinetics of the early response. Together, these results suggest that histone modifications and chromatin structure in striatal neurons are dynamically regulated by dopaminergic and glutamatergic inputs converging on the cellular level. Blockade of D2-like receptors induces H3 phospho-acetylation, H3pS10-acK14, through cAMP-dependent PKA, and post-synaptic NMDA receptor signaling.

A rare polymorphism affects a mitogen-activated protein kinase site in synapsin III: possible relationship to schizophrenia

BACKGROUND

Synapsin III plays a role in neuronal plasticity and maps to chromosome 22q12-13, a region suggested to be linked to schizophrenia. To determine if synapsin III plays a role in this disease, we searched for polymorphisms in this gene in patients with schizophrenia and controls.

METHODS

The synapsin III gene was initially sequenced from 10 individuals with schizophrenia to identify polymorphisms. Association analysis was then performed using 118 individuals with schizophrenia and 330 population controls. Synapsin III expression was studied by immunoblot analyses, and phosphorylation sites were mapped by sequencing trypsin-digested synapsin III fragments phosphorylated with phosphorus-32.

RESULTS

A rare, missense polymorphism, S470N, was identified in the synapsin III gene and appeared more frequently in individuals with schizophrenia than in controls (p =.0048). The site affected by the polymorphism, Ser470, was determined to be a substrate for mitogen-activated protein kinase, a downstream effector of neurotrophin action. Phosphorylation at Ser470 was increased during neonatal development and in response to neurotrophin-3 in cultured hippocampal neurons.

CONCLUSIONS

Our observations suggest an association of a rare polymorphism in synapsin III with schizophrenia, but further studies will be required to clarify its role in this disease.

Antipsychotics increase microtubule-associated protein 2 mRNA but not spinophilin mRNA in rat hippocampus and cortex

Antipsychotic (neuroleptic) drugs induce structural alterations in synaptic terminals and changes in the expression of presynaptic protein genes. Whether there are also changes in corresponding postsynaptic (dendritic) markers has not been determined. We describe the effect of 14-day treatment with typical (haloperidol, chlorpromazine) or atypical (clozapine, olanzapine, risperidone) antipsychotics on the expression of two dendritic protein genes, microtubule-associated protein 2 (MAP2) and spinophilin, using in situ hybridization, in the rat hippocampus, retrosplenial, and occipitoparietal cortices. MAP2 mRNA was increased modestly in the dentate gyrus and retrosplenial cortex by chlorpromazine, risperidone, and olanzapine and in the occipitoparietal cortex by chlorpromazine, haloperidol, and risperidone. None of the antipsychotics affected spinophilin mRNA in any area. Overall, these results show a modulation of MAP2 gene expression, likely reflecting functional or structural changes in the dendritic tree in response to some typical and atypical antipsychotics. The lack of change in spinophilin mRNA suggests that dendritic spines are not affected selectively by the drugs. The data provide further evidence that antipsychotics regulate genes involved in synaptic structure and function. Such actions may underlie their long-term effects on neural plasticity in areas of the brain implicated in the pathology of schizophrenia.

Antipsychotic drug treatment alters expression of mRNAs encoding lipid metabolism-related proteins

Using an automated PCR-based genomics approach, TOtal Gene expression Analysis (TOGA), we have examined gene expression profiles of mouse striatum and frontal cortex in response to clozapine and haloperidol drug treatment. Of 17 315 mRNAs observed, TOGA identified several groups of related molecules that were regulated by drug treatment. The expression of some genes encoding proteins involved in neurotransmission, signal transduction, oxidative stress, cell adhesion, apoptosis and proteolysis were altered in the brains of both clozapine- and haloperidol-treated mice as recognized by TOGA. Most notable was the differential expression of those genes whose products are associated with lipid metabolism. These include apolipoprotein D (apoD), the mouse homolog of oxysterol-binding protein-like protein 8 (OSBPL8), a diacylglycerol receptor (n-chimerin), and lysophosphatidic acid (LPA) acyltransferase. Real-time PCR analysis confirmed increases in the RNA expression of apoD (1.6-2.2-fold) and OSBPL8 (1.7-2.6-fold), and decreases in the RNA expression of n-chimerin (1.5-2.2-fold) and LPA acyltransferase (1.5-fold) in response to haloperidol and/or clozapine treatment. Additional molecules related to calcium homeostasis and signal transduction, as well as four sequences of previously unidentified mRNAs, were also confirmed by real-time PCR to be regulated by drug treatment. While antipsychotic drugs may affect several metabolic pathways, lipid metabolism/signaling pathways may be of particular importance in the mechanisms of antipsychotic drug action and in the pathophysiology of psychiatric disorders.

Time-dependent changes in gene expression profiles of midbrain dopamine neurons following haloperidol administration

Antipsychotic drugs require a treatment regimen of several weeks before clinical efficacy is achieved in patient populations. While the biochemical mechanisms underlying the delayed temporal profile remain unclear, molecular adaptations in specific neuroanatomical loci are likely involved. Haloperidol-induced changes in gene expression in various brain regions have been observed; however, alterations in distinct neuronal populations have remained elusive. The present study examined changes in gene expression profiles of ventral tegmental area (VTA) and substantia nigra (SN) tyrosine hydroxylase immunopositive neurons following 1, 10 or 21 days of haloperidol administration (0.5 mg/kg/day). Macroarrays were used to study the expression of receptors, signaling proteins, transcription factors and pre- and post-synaptic proteins. Data were analyzed using conventional statistical procedures as well as self-organizing maps (SOM) to elucidate conserved patterns of expression changes. Results show statistically significant haloperidol-induced and time-dependent alterations in 17 genes in the VTA and 25 genes in the SN, including glutamate and GABA receptor subunits, signaling proteins and transcription factors. SOMs revealed distinct patterns of gene expression changes in response to haloperidol. Understanding how gene expression is altered over a clinically relevant time course of haloperidol administration may provide insight into the development of antipsychotic efficacy as well as the underlying pathology of schizophrenia.