Reduced GSK-3? mRNA levels in postmortem dorsolateral prefrontal cortex of schizophrenic patients

Function of GSK‑3 signaling in spinal cord injury (Review)

Spinal cord injury (SCI) is a major social problem with a heavy burden on patient physiology and psychology. Glial scar formation and irreversible neuron loss are the two key points during SCI progression. During the acute phase of spinal cord injury, glial scars form, limiting the progression of inflammation. However, in the subacute or chronic phase, glial scarring inhibits axon regeneration. Following spinal cord injury, irreversible loss of neurons leads to further aggravation of spinal cord injury. Several therapies have been developed to improve either glial scar or neuron loss; however, few therapies reach the stage of clinical trials and there are no mainstream therapies for SCI. Exploring the key mechanism of SCI is crucial for finding further treatments. Glycogen synthase kinase-3 (GSK-3) is a widely expressed kinase with important physiological and pathophysiological functions in vivo. Dysfunction of the GSK-3 signaling pathway during SCI has been widely discussed for controlling neurite growth in vitro and in vivo, improving the proliferation and neuronal differentiation of endogenous neural stem cells and functional recovery from spinal cord injury. SCI can decrease the phosphorylated (p)/total (t)-GSK-3β ratio, which leads to an increase in apoptosis, whereas treatment with GSK-3 inhibitors can promote neurogenesis. In addition, several therapies for the treatment of SCI involve signaling pathways associated with GSK-3. Furthermore, signaling pathways associated with GSK-3 also participate in the pathological process of neuropathic pain that remains following SCI. The present review summarized the roles of GSK-3 signaling in SCI to aid in the understanding of GSK-3 signaling during the pathological processes of SCI and to provide evidence for the development of comprehensive treatments.

Possible involvement of Interleukin-17A in the deterioration of prepulse inhibition on acoustic startle response in mice

AIM

Proinflammatory cytokines such as interleukin-6 (IL-6) and IL-17A have been implicated in the pathophysiology of schizophrenia which often shows sensorimotor gating abnormalities. This study aimed to examine whether a proinflammatory cytokine, IL-17A, induces impairment in sensorimotor gating in mice. We also examined whether IL-17A administration affects GSK3α/β protein level or phosphorylation in the striatum.

METHODS

Recombinant mouse IL-17A (low-dose: 0.5 ng/mL and high-dose: 50 ng/mL with 10 μL/g mouse body weight, respectively) or vehicle was intraperitoneally administered into C57BL/6 male mice 10 times in 3 weeks (sub-chronic administration). Prepulse inhibition test using acoustic startle stimulus was conducted 4 weeks after the final IL-17A administration. We evaluated the effect of IL-17A administration on protein level or phosphorylation of GSK3α/β in the striatum by using Western blot analysis.

RESULTS

Administration of IL-17A induced significant PPI deterioration. Low-dose of IL-17A administration significantly decreased both GSK3α (Ser21) and GSK3β (Ser9) phosphorylation in mouse striatum. There was no significant alteration of GSK3α/β protein levels except for GSK3α in low-dose IL-17A administration group.

CONCLUSION

We demonstrated for the first time that sub-chronic IL-17A administration induced PPI disruption and that IL-17A administration resulted in decreased phosphorylation of GSKα/β at the striatum. These results suggest that IL-17A could be a target molecule in the prevention and treatment of sensorimotor gating abnormalities observed in schizophrenia.

Changes in cytokine and cytokine receptor levels during postnatal development of the human dorsolateral prefrontal cortex

In addition to their traditional roles in immune cell communication, cytokines regulate brain development. Cytokines are known to influence neural cell generation, differentiation, maturation, and survival. However, most work on the role of cytokines in brain development investigates rodents or focuses on prenatal events. Here, we investigate how mRNA and protein levels of key cytokines and cytokine receptors change during postnatal development of the human prefrontal cortex. We find that most cytokine transcripts investigated (IL1B, IL18, IL6, TNF, IL13) are lowest at birth and increase between 1.5 and 5 years old. After 5 years old, transcriptional patterns proceeded in one of two directions: decreased expression in teens and young adults (IL1B, p = 0.002; and IL18, p = 0.004) or increased mean expression with maturation, particularly in teenagers (IL6, p = 0.004; TNF, p = 0.002; IL13, p < 0.001). In contrast, cytokine proteins tended to remain elevated after peaking significantly around 3 years of age (IL1B, p = 0.012; IL18, p = 0.026; IL6, p = 0.039; TNF, p < 0.001), with TNF protein being highest in teenagers. An mRNA-only analysis of cytokine receptor transcripts found that early developmental increases in cytokines were paralleled by increases in their ligand-binding receptor subunits, such as IL1R1 (p = 0.033) and IL6R (p < 0.001) transcripts. In contrast, cytokine receptor-associated signaling subunits, IL1RAP and IL6ST, did not change significantly between age groups. Of the two TNF receptors, the 'pro-death' TNFRSF1A and 'pro-survival' TNFRSF1B, only TNFRSF1B was significantly changed (p = 0.028), increasing first in toddlers and again in young adults. Finally, the cytokine inhibitor, IL13, was elevated first in toddlers (p = 0.006) and again in young adults (p = 0.053). While the mean expression of interleukin-1 receptor antagonist (IL1RN) was highest in toddlers, this increase was not statistically significant. The fluctuations in cytokine expression reported here support a role for increases in specific cytokines at two different stages of human cortical development. The first is during the toddler/preschool period (IL1B, IL18, and IL13), and the other occurs at adolescence/young adult maturation (IL6, TNF and IL13).

Effects of Glycogen Synthase Kinase-3 Beta Gene Polymorphisms on the Plasma Concentration of Aripiprazole in Chinese Patients with Schizophrenia: A Preliminary Study

This study explored the differences in glycogen synthase kinase-3 beta (GSK3β) gene polymorphisms between patients with schizophrenia and healthy controls and investigated the association between gene polymorphisms and plasma concentration of aripiprazole. We enrolled 127 patients with schizophrenia and 125 healthy controls from southern Fujian. The genotypes of the rs6438552, rs12630592, and rs3732361 loci of GSK3β were evaluated by sequencing with amplified polymerase chain reaction, and the plasma concentration of aripiprazole was determined by high-performance liquid chromatography-tandem mass spectrometry. All three loci of GSK3β had three genotypes each. The genotype distribution in each locus was not significantly different, but there was a significant difference in the allele frequency between the schizophrenia and control groups within each locus. Linkage disequilibrium analyses of the three single-nucleotide polymorphisms (SNPs) revealed strong linkage. The haplotype analysis results showed two haplotypes in the three SNPs of GSK3β. The plasma concentrations, dose-corrected concentrations, and normalized concentrations of aripiprazole were significantly different among the different genotypes of the three SNPs. In conclusion, the rs6438552, rs12630592, and rs3732361 loci of GSK3β may be involved in schizophrenia, and GSK3β gene polymorphism may be correlated with the plasma concentration of aripiprazole.

Developmental effects of early-life stress on dopamine D2 receptor and proteins involved in noncanonical D2 dopamine receptor signaling pathway in the prefrontal cortex of male rats

OBJECTIVES

Dopamine neurotransmission is implicated in multiple neuropsychiatric disorders, most strikingly in Parkinson's disease, bipolar disorder, attention-deficit hyperactivity disorder and schizophrenia. In addition to canonical pathway, D2-receptor (D2R) exerts some of its biological actions through regulating the activity of Akt and GSK3, which in turn were found to be altered in several psychiatric illnesses. The present study examined the impacts of maternal separation, an early-life stress model which has been associated with disturbed neurodevelopment and appearance of many psychiatric disorders, on developmental changes in dopamine concentration and the expression of D2Rs, Akt and GSK-3β in the medial prefrontal cortex (PFC; a key target of stress) in adolescent and young adult male rats.

METHODS

Maternal separation was performed 3 h per day from postnatal days 2 to 11. The PFC protein and dopamine contents were determined using western blotting analysis and Eliza, respectively.

RESULTS

Results indicated long-term increases in the prefrontal dopamine levels in stressed adolescent and young adult male rats, accompanied by significant downregulation of D2R as well as upregulation of p-Akt and GSK-3β contents in stressed adolescence compared to controls, with all protein levels that returned to control values in stressed adult rats.

CONCLUSIONS

Our findings suggest that early-life stress differentially modulates prefrontal D2R/Akt/GSK-3β levels during development. Since adolescence period is susceptible to the onset of specific mental illnesses, disruption of noncanonical components of D2R signaling during this critical period may have an important role in programming neurobehavioral phenotypes in adulthood and manipulations influencing Akt/GSK-3β pathway may improve the expression of specific dopamine-related behaviors and the effects of dopaminergic drugs.

It takes two to tango: Widening our understanding of the onset of schizophrenia from a neuro-angiogenic perspective

Schizophrenia is a chronic debilitating mental disorder characterized by perturbations in thinking, perception, and behavior, along with brain connectivity deficiencies, neurotransmitter dysfunctions, and loss of gray brain matter. To date, schizophrenia has no cure and pharmacological treatments are only partially efficacious, with about 30% of patients describing little to no improvement after treatment. As in most neurological disorders, the main descriptions of schizophrenia physiopathology have been focused on neural network deficiencies. However, to sustain proper neural activity in the brain, another, no less important network is operating: the vast, complex and fascinating vascular network. Increasing research has characterized schizophrenia as a systemic disease where vascular involvement is important. Several neuro-angiogenic pathway disturbances have been related to schizophrenia. Alterations, ranging from genetic polymorphisms, mRNA, and protein alterations to microRNA and abnormal metabolite processing, have been evaluated in plasma, post-mortem brain, animal models, and patient-derived induced pluripotent stem cell (hiPSC) models. During embryonic brain development, the coordinated formation of blood vessels parallels neuro/gliogenesis and results in the structuration of the neurovascular niche, which brings together physical and molecular signals from both systems conforming to the Blood-Brain barrier. In this review, we offer an upfront perspective on distinctive angiogenic and neurogenic signaling pathways that might be involved in the biological causality of schizophrenia. We analyze the role of pivotal angiogenic-related pathways such as Vascular Endothelial Growth Factor and HIF signaling related to hypoxia and oxidative stress events; classic developmental pathways such as the NOTCH pathway, metabolic pathways such as the mTOR/AKT cascade; emerging neuroinflammation, and neurodegenerative processes such as UPR, and also discuss non-canonic angiogenic/axonal guidance factor signaling. Considering that all of the mentioned above pathways converge at the Blood-Brain barrier, reported neurovascular alterations could have deleterious repercussions on overall brain functioning in schizophrenia.

Chronic N-Acetylcysteine Treatment Prevents Amphetamine-Induced Hyperactivity in Heterozygous Disc1 Mutant Mice, a Putative Prodromal Schizophrenia Animal Model

Symptoms of schizophrenia (SZ) typically emerge during adolescence to young adulthood, which gives a window before full-blown psychosis for early intervention. Strategies for preventing the conversion from the prodromal phase to the psychotic phase are warranted. Heterozygous (Het) Disc1 mutant mice are considered a prodromal model of SZ, suitable for studying psychotic conversion. We evaluated the preventive effect of chronic N-acetylcysteine (NAC) administration, covering the prenatal era to adulthood, on the reaction following the Amph challenge, which mimics the outbreak or conversion of psychosis, in adult Het Disc1 mice. Biochemical and morphological features were examined in the striatum of NAC-treated mice. Chronic NAC treatment normalized the Amph-induced activity in the Het Disc1 mice. Furthermore, the striatal phenotypes of Het Disc1 mice were rescued by NAC including dopamine receptors, the expression of GSK3s, MSN dendritic impairments, and striatal PV density. The current study demonstrated a potent preventive effect of chronic NAC treatment in Disc1 Het mice on the acute Amph test, which mimics the outbreak of psychosis. Our findings not only support the benefit of NAC as a dietary supplement for SZ prodromes, but also advance our knowledge of striatal dopamine receptors, PV neurons, and GSK3 signaling pathways as therapeutic targets for treating or preventing the pathogenesis of mental disorders.

mTOR kinase activity disrupts a phosphorylation signaling network in schizophrenia brain

The AKT-mTOR signaling transduction pathway plays an important role in neurodevelopment and synaptic plasticity. mTOR is a serine/threonine kinase that modulates signals from multiple neurotransmitters and phosphorylates specific proteins to regulate protein synthesis and cytoskeletal organization. There is substantial evidence demonstrating abnormalities in AKT expression and activity in different schizophrenia (SZ) models. However, direct evidence for dysregulated mTOR kinase activity and its consequences on downstream effector proteins in SZ pathophysiology is lacking. Recently, we reported reduced phosphorylation of mTOR at an activating site and abnormal mTOR complex formation in the SZ dorsolateral prefrontal cortex (DLPFC). Here, we expand on our hypothesis of disrupted mTOR signaling in the SZ brain and studied the expression and activity of downstream effector proteins of mTOR complexes and the kinase activity profiles of SZ subjects. We found that S6RP phosphorylation, downstream of mTOR complex I, is reduced, whereas PKCα phosphorylation, downstream of mTOR complex II, is increased in SZ DLPFC. In rats chronically treated with haloperidol, we showed that S6RP phosphorylation is increased in the rat frontal cortex, suggesting a potential novel mechanism of action for antipsychotics. We also demonstrated key differences in kinase signaling networks between SZ and comparison subjects for both males and females using kinome peptide arrays. We further investigated the role of mTOR kinase activity by inhibiting it with rapamycin in postmortem tissue and compared the impact of mTOR inhibition in SZ and comparison subjects using kinome arrays. We found that SZ subjects are globally more sensitive to rapamycin treatment and AMP-activated protein kinase (AMPK) contributes to this differential kinase activity. Together, our findings provide new insights into the role of mTOR as a master regulator of kinase activity in SZ and suggest potential targets for therapeutic intervention.

Treating cognitive impairment in schizophrenia with GLP-1RAs: an overview of their therapeutic potential

INTRODUCTION

Schizophrenia is a neuropsychiatric disorder that affects approximately 1% of individuals worldwide. There are no available medications to treat cognitive impairment in this patient population currently. Preclinical evidence suggests that glucagon-like peptide-1 receptor agonists (GLP-1 RAs) improve cognitive function. There is a need to evaluate how GLP-1 RAs alter specific domains of cognition and whether they will be of therapeutic benefit in individuals with schizophrenia.

AREAS COVERED

This paper summarizes the effects of GLP-1 RAs on metabolic processes in the brain and how these mechanisms relate to improved cognitive function. We provide an overview of preclinical studies that demonstrate GLP-1 RAs improve cognition and comment on their potential therapeutic benefit in individuals with schizophrenia.

EXPERT OPINION

To understand the benefits of GLP-1 RAs in individuals with schizophrenia, further preclinical research with rodent models relevant to schizophrenia symptomology are needed. Moreover, preclinical studies must focus on using a wider range of behavioral assays to understand whether important aspects of cognition such as executive function, attention, and goal-directed behavior are improved using GLP-1 RAs. Further research into the specific mechanisms of how GLP-1 RAs affect cognitive function and their interactions with antipsychotic medication commonly prescribed is necessary.

Evidence of an interaction between FXR1 and GSK3β polymorphisms on levels of Negative Symptoms of Schizophrenia and their response to antipsychotics

BACKGROUND

Genome-Wide Association Studies (GWASs) have identified several genes associated with Schizophrenia (SCZ) and exponentially increased knowledge on the genetic basis of the disease. In addition, products of GWAS genes interact with neuronal factors coded by genes lacking association, such that this interaction may confer risk for specific phenotypes of this brain disorder. In this regard, fragile X mental retardation syndrome-related 1 (FXR1) gene has been GWAS associated with SCZ. FXR1 protein is regulated by glycogen synthase kinase-3β (GSK3β), which has been implicated in pathophysiology of SCZ and response to antipsychotics (APs). rs496250 and rs12630592, two eQTLs (Expression Quantitative Trait Loci) of FXR1 and GSK3β, respectively, interact on emotion stability and amygdala/prefrontal cortex activity during emotion processing. These two phenotypes are associated with Negative Symptoms (NSs) of SCZ suggesting that the interaction between these SNPs may also affect NS severity and responsiveness to medication.

METHODS

To test this hypothesis, in two independent samples of patients with SCZ, we investigated rs496250 by rs12630592 interaction on NS severity and response to APs. We also tested a putative link between APs administration and FXR1 expression, as already reported for GSK3β expression.

RESULTS

We found that rs496250 and rs12630592 interact on NS severity. We also found evidence suggesting interaction of these polymorphisms also on response to APs. This interaction was not present when looking at positive and general psychopathology scores. Furthermore, chronic olanzapine administration led to a reduction of FXR1 expression in mouse frontal cortex.

DISCUSSION

Our findings suggest that, like GSK3β, FXR1 is affected by APs while shedding new light on the role of the FXR1/GSK3β pathway for NSs of SCZ.

Expression of GSK3β, PICK1, NEFL, C4, NKCC1 and Synaptophysin in peripheral blood mononuclear cells of the first-episode schizophrenia patients

Schizophrenia (SZ) is a severe neurodevelopmental disease with unknown pathogenic mechanisms characterized with impaired cognitive function. The disturbed synaptic plasticity and synaptic loss have been widely reported in SZ. In this study, 41 first-episode schizophrenia (FES) patients and 44 healthy controls (HC) were recruited and the expression of six genes commonly relevant to synaptic functions was examined in the peripheral blood mononuclear cells (PBMCs). These genes were glycogen synthase kinase 3β (GSK3β), protein interacting with C-kinase 1 (PICK1), synaptophysin (SYP), neurofilament light (NEFL), complement component 4 (C4) and Na⁺-K^--2Cl^- cotransporter 1 (NKCC1). Real-time quantitative polymerase chain reaction (qPCR) was performed to determine the quantity of individual mRNA template. Compared to HC, the expression of PICK1 and NKCC1 genes in FES patients was relatively lower whereas the expression of NEFL was higher. No difference for the mRNA expression of GSK3β, SYP and C4 genes was detected between FES patients and HC, nor was the gender difference; Interestingly, the mRNA expression of PICK1 in female FES patients was significantly decreased compared to female HC, but not in males; and the NEFL gene was up-regulated in male FES patients but not in females. Our findings support an abnormal expression profile of synapse-related genes in the PBMCs of FES patients.

Glycogen synthase kinase-3: The missing link to aberrant circuit function in disorders of cognitive dysfunction?

Elevated GSK-3 activity has been implicated in cognitive dysfunction associated with various disorders including Alzheimer's disease, schizophrenia, type 2 diabetes, traumatic brain injury, major depressive disorder and bipolar disorder. Further, aberrant neural oscillatory activity in, and between, cortical regions and the hippocampus is consistently present within these same cognitive disorders. In this review, we will put forth the idea that increased GSK-3 activity serves as a pathological convergence point across cognitive disorders, inducing similar consequent impacts on downstream signaling mechanisms implicated in the maintenance of processes critical to brain systems communication and normal cognitive functioning. In this regard we suggest that increased activation of GSK-3 and neuronal oscillatory dysfunction are early pathological changes that may be functionally linked. Mechanistic commonalities between these disorders of cognitive dysfunction will be discussed and potential downstream targets of GSK-3 that may contribute to neuronal oscillatory dysfunction identified.

A comprehensive analysis of GSK3B variation for schizophrenia in Han Chinese individuals

Glycogen synthase kinase-3B (GSK-3B) is thought to be involved in numerous neuronal functions and is implicated in the pathophysiology of schizophrenia. Interestingly, a functional polymorphism, rs3755557, in the GSK3B promoter region has been consistently reported to be a risk factor for schizophrenia in southwestern and northwestern Han Chinese individuals. In this study, we carried out a comprehensive analysis of the association of the rs3755557 polymorphism within GSK3B and schizophrenia in Han Chinese individuals. We recruited 782 patients with schizophrenia and 807 healthy controls from eastern China. In total, 143 drug-naïve patients with first-episode schizophrenia were enrolled for the evaluation of clinical features. We did not observe significant differences in genotype or allele distribution of the rs3755557 polymorphism between the schizophrenia and control groups in eastern Chinese individuals. After pooling these data of 2188 subjects with schizophrenia and 2885 healthy controls, we observed a significant difference in the A allele distribution of the rs3755557 polymorphism between schizophrenia patients and controls (Z = 4.13 P < 0.01). We further examined the relationship between the rs3755557 polymorphism and the clinical features of schizophrenia by comparing scores of the The Positive and Negative Syndrome Scale (PANSS) and The Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) with the genotypes of the rs3755557 polymorphism. There were significant differences in the scores of RBANS attention, delayed memory and total scores between the patients with the A allele and those without the A allele (P = 0.03, 0.01 and 0.01 after Bonferroni correction, respectively). Our eQTL analysis showed a significant association between the rs3755557 polymorphism and GSK3B expression in the hippocampus (P = 0.027). Our findings indicated that the rs3755557 polymorphism may confer susceptibility to schizophrenia and cognitive dysfunction in Han Chinese individuals.

Cannabidiol Counteracts the Psychotropic Side-Effects of Δ-9-Tetrahydrocannabinol in the Ventral Hippocampus through Bidirectional Control of ERK1-2 Phosphorylation

Evidence suggests that the phytocannabinoids Δ-9-tetrahydrocannabinol (THC) and cannabidiol (CBD) differentially regulate salience attribution and psychiatric risk. The ventral hippocampus (vHipp) relays emotional salience via control of dopamine (DA) neuronal activity states, which are dysregulated in psychosis and schizophrenia. Using in vivo electrophysiology in male Sprague Dawley rats, we demonstrate that intra-vHipp THC strongly increases ventral tegmental area (VTA) DA neuronal frequency and bursting rates, decreases GABA frequency, and amplifies VTA beta, gamma and ε oscillatory magnitudes via modulation of local extracellular signal-regulated kinase phosphorylation (pERK1-2). Remarkably, whereas intra-vHipp THC also potentiates salience attribution in morphine place-preference and fear conditioning assays, CBD coadministration reverses these changes by downregulating pERK1-2 signaling, as pharmacological reactivation of pERK1-2 blocked the inhibitory properties of CBD. These results identify vHipp pERK1-2 signaling as a critical neural nexus point mediating THC-induced affective disturbances and suggest a potential mechanism by which CBD may counteract the psychotomimetic and psychotropic side effects of THC.SIGNIFICANCE STATEMENT Strains of marijuana with high levels of delta-9-tetrahydrocannabinol (THC) and low levels of cannabidiol (CBD) have been shown to underlie neuropsychiatric risks associated with high-potency cannabis use. However, the mechanisms by which CBD mitigates the side effects of THC have not been identified. We demonstrate that THC induces cognitive and affective abnormalities resembling neuropsychiatric symptoms directly in the hippocampus, while dysregulating dopamine activity states and amplifying oscillatory frequencies in the ventral tegmental area via modulation of the extracellular signal-regulated kinase (ERK) signaling pathway. In contrast, CBD coadministration blocked THC-induced ERK phosphorylation, and prevented THC-induced behavioral and neural abnormalities. These findings identify a novel molecular mechanism that may account for how CBD functionally mitigates the neuropsychiatric side effects of THC.

Brain insulin resistance and altered brain glucose are related to memory impairments in schizophrenia

Memory is robustly impaired in schizophrenia (SZ) and related to functional outcome. Memory dysfunction has been shown to be related to altered brain glucose metabolism and brain insulin resistance in animal models and human studies of Alzheimer's disease. In this study, differences in brain glucose using magnetic resonance spectroscopy (MRS) and blood Extracellular Vesicle (EV) biomarkers of neuronal insulin resistance (i.e. Akt and signaling effectors) between SZ and controls were investigated, as well as whether these measures were related to memory impairments. Neuronal insulin resistance biomarkers showed a trend for being lower in SZ compared to controls, and memory measures were lower in SZ compared to controls. Occipital cortex glucose was higher in SZ compared to controls indicating lower brain glucose utilization. Linear regression analyses revealed significant relationships between neuronal insulin resistance biomarkers, memory measures, and brain glucose. More specifically, p70S6K, an insulin signaling effector, was related to verbal learning and brain MRS glucose in the SZ group. For the first time, we show that memory impairments in SZ may be related to brain glucose and brain insulin resistance. These data suggest that brain insulin resistance may play a role in the pathophysiology of learning and memory dysfunction in SZ.

Involvement of IL-6 and GSK3β in impaired sensorimotor gating induced by high-fat diet

Increased levels of proinflammatory cytokines have been implicated in schizophrenia; however, their pathophysiological roles in abnormal brain dysfunctions remain unclear. We evaluated the effect of proinflammatory cytokines on a high-fat diet (HFD)-induced prepulse inhibition (PPI) deficits in the acoustic startle response. Eight-week-old male C57BL/6J mice were fed a HFD for 3 weeks and then PPI was examined. HFD significantly induced PPI deficits and increased plasma IL-6, but not TNFα, levels. Interestingly, MR16-1 administration during the HFD period ameliorated PPI deficits. Further, in the striatum of HFD-fed mice, phosphorylation of GSK3β, but not GSK3α, was significantly increased; this increase was attenuated by MR16-1, although the protein levels of GSK3α and β were not altered. There were no significant differences in either phosphorylation or protein levels of GSK3α, β in the PFC during the HFD period. These results suggest that increased IL-6 levels during HFD may induce sensorimotor gating deficits, likely through the alteration of striatal GSK3β phosphorylation. MR16-1 might have a beneficial effect on such HFD-induced sensorimotor gating deficits.

Targeting GSK3 signaling as a potential therapy of neurodegenerative diseases and aging

INTRODUCTION

Glycogen synthase kinase 3 (GSK3) is at the center of cellular signaling and controls various aspects of brain functions, including development of the nervous system, neuronal plasticity and onset of neurodegenerative disorders. Areas covered: In this review, recent efforts in elucidating the roles of GSK3 in neuronal plasticity and development of brain pathologies; Alzheimer's and Parkinson's disease, schizophrenia, and age-related neurodegeneration are described. The effect of microglia and astrocytes on development of the pathological states is also discussed. Expert opinion: GSK3β and its signaling pathway partners hold great promise as therapeutic target(s) for a multitude of neurological disorders. Activity of the kinase is often elevated in brain disorders. However, due to the wide range of GSK3 cellular targets, global inhibition of the kinase leads to severe side-effects and GSK3 inhibitors rarely reach Phase-2 clinical trials. Thus, a selective modulation of a specific cellular pool of GSK3 or specific down- or upstream partners of the kinase might provide more efficient anti-neurodegenerative therapies.

Phytocannabinoids modulate emotional memory processing through interactions with the ventral hippocampus and mesolimbic dopamine system: implications for neuropsychiatric pathology

Growing clinical and preclinical evidence suggests a potential role for the phytocannabinoid cannabidiol (CBD) as a pharmacotherapy for various neuropsychiatric disorders. In contrast, delta-9-tetrahydrocannabinol (THC), the primary psychoactive component in cannabis, is associated with acute and neurodevelopmental propsychotic side effects through its interaction with central cannabinoid type 1 receptors (CB1Rs). CB1R stimulation in the ventral hippocampus (VHipp) potentiates affective memory formation through inputs to the mesolimbic dopamine (DA) system, thereby altering emotional salience attribution. These changes in DA activity and salience attribution, evoked by dysfunctional VHipp regulatory actions and THC exposure, could predispose susceptible individuals to psychotic symptoms. Although THC can accelerate the onset of schizophrenia, CBD displays antipsychotic properties, can prevent the acquisition of emotionally irrelevant memories, and reverses amphetamine-induced neuronal sensitization through selective phosphorylation of the mechanistic target of rapamycin (mTOR) molecular signaling pathway. This review summarizes clinical and preclinical evidence demonstrating that distinct phytocannabinoids act within the VHipp and associated corticolimbic structures to modulate emotional memory processing through changes in mesolimbic DA activity states, salience attribution, and signal transduction pathways associated with schizophrenia-related pathology.

Wnt Signaling in the Central Nervous System: New Insights in Health and Disease

Since its discovery, Wnt signaling has been shown to be one of the most crucial morphogens in development and during the maturation of central nervous system. Its action is relevant during the establishment and maintenance of synaptic structure and neuronal function. In this chapter, we will discuss the most recent evidence on these aspects, and we will explore the evidence that involves Wnt signaling on other less known functions, such as in adult neurogenesis, in the generation of oscillatory neural rhythms, and in adult behavior. The dysfunction of Wnt signaling at different levels will be also discussed, in particular in those aspects that have been found to be linked with several neurodegenerative diseases and neurological disorders. Finally, we will address the possibility of Wnt signaling manipulation to treat those pathophysiological aspects.

Topiramate via NMDA, AMPA/kainate, GABAA and Alpha2 receptors and by modulation of CREB/BDNF and Akt/GSK3 signaling pathway exerts neuroprotective effects against methylphenidate-induced neurotoxicity in rats

Chronic abuse of methylphenidate (MPH) often causes neuronal cell death. Topiramate (TPM) carries neuroprotective effects, but its exact mechanism of action remains unclear. In the present study, the role of various doses of TPM and its possible mechanisms, receptors and signaling pathways involved against MPH-induced hippocampal neurodegeneration were evaluated in vivo. Thus, domoic acid (DOM) was used as AMPA/kainate receptor agonist, bicuculline (BIC) as GABA_A receptor antagonist, ketamine (KET) as NMDA receptor antagonist, yohimbine (YOH) as α₂ adrenergic receptor antagonist and haloperidol (HAL) was used as dopamine D₂ receptor antagonist. Open field test (OFT) was used to investigate the disturbances in motor activity. Hippocampal neurodegenerative parameters were evaluated. Protein expressions of CREB/BDNF and Akt/GSK3 signaling pathways were also evaluated. Cresyl violet staining was performed to show and confirm the changes in the shape of the cells. TPM (70 and 100 mg/kg) reduced MPH-induced rise in lipid peroxidation, oxidized form of glutathione (GSSG), IL-1β and TNF-α levels, Bax expression and motor activity disturbances. In addition, TPM treatment increased Bcl-2 expression, the level of reduced form of glutathione (GSH) and the levels and activities of superoxide dismutase, glutathione peroxidase and glutathione reductase enzymes. TPM also inhibited MPH-induced hippocampal degeneration. Pretreatment of animals with DOM, BIC, KET and YOH inhibited TPM-induced neuroprotection and increased oxidative stress, neuroinflammation, neuroapoptosis and neurodegeneration while reducing CREB, BDNF and Akt protein expressions. Also pretreatment with DOM, BIC, KET and YOH inhibited TPM-induced decreases in GSK3. It can be concluded that the mentioned receptors by modulation of CREB/BDNF and Akt/GSK3 pathways, are involved in neuroprotection of TPM against MPH-induced neurodegeneration.

The involvement of BDNF-CREB signaling pathways in the pharmacological mechanism of combined SSRI- antipsychotic treatment in schizophrenia

Previous studies into the mechanism of SSRI-antipsychotic synergism in our laboratory identified unique changes in the brain, particularly in the γ-aminobutyric acid (GABA)-A receptor and its modulators. This study examined the role of brain derived neurotrophic factor (BDNF)-cAMP response element binding (CREB) protein signaling pathways, including protein kinase B (AKT), glycogen synthase kinase (GSK)-3β and related molecules in the molecular response to haloperidol, fluvoxamine, combined haloperidol+fluvoxamine and clozapine treatments in rat frontal cortex, hippocampus and primary cortical neuronal cultures. The effect of fluvoxamine augmentation on BDNF-CREB pathways in peripheral mononuclear cells (PMC׳s) of medicated schizophrenia patients was also studied. Chronic haloperidol (1mg/kg) +fluvoxamine (10mg/kg) treatment increased TrkB receptor and BDNF expression levels, and the phosphorylation of AKT/CREB/GSK-3β, compared to the individual drugs in rat brain. In addition, haloperidol+fluvoxamine treatment improved cognitive functions in rats, indicating that the molecular changes may have a role in behavioral improvement. In primary neuronal cell cultures, pretreatment with a selective PI3K inhibitor abolished the haloperidol+fluvoxamine-induced phosphorylation of AKT and GSK-3β, but did not affect the upregulation of CREB phosphorylation. In the clinic, PMC׳s of treated patients showed upregulation of mRNA expression and protein levels of BDNF, CREB and AKT after addition of fluvoxamine. Analyses of PMC genes and proteins showed significant inter-correlations and some gene changes correlated with improvement in negative and cognitive symptoms. Our study provides new knowledge of the molecular mechanisms of symptom amelioration in schizophrenia and may advance development of new drugs for this disease and other neuropsychiatric disorders.

PDE7B, NMBR and EPM2A Variants and Schizophrenia: A Case-Control and Pharmacogenetics Study

BACKGROUND

We investigated phosphodiesterase 7B (PDE7B), neuromedin B receptor (NMBR) and epilepsy progressive myoclonus type 2A (EPM2A) genes in schizophrenia (SCZ). To the best of our knowledge, these genes have been poorly investigated in studies of SCZ.

METHODS

Five hundred and seventy-three SCZ inpatients of Korean ethnicity and 560 healthy controls were genotyped for 2 PDE7B, 3 NMBR and 3 EPM2A polymorphisms. Differences in the allelic and genetic frequencies among healthy subjects and patients were calculated using the x03C7;2 statistics. Repeated-measure ANOVA was used to test possible influences of single-nucleotide polymorphisms on treatment efficacy. In case of positive findings, clinical and demographic variables were added as covariates, in order to investigate possible stratixFB01;cation bias.

RESULTS

The rs2717 and rs6926279 within the NMBR gene and rs702304 and rs2235481 within the EPM2A gene were associated with SCZ liability. rs1415744 was also associated with Positive and Negative Symptom Scale negative clinical improvement. The results remained the same after inclusion of the covariates and were partially confirmed in the allelic and haplotype analyses.

CONCLUSION

Our preliminary findings suggest a possible role of NMBR and EPM2A genes in SCZ susceptibility and, for the second one, also in antipsychotic pharmacogenetics. Nonetheless, further research is needed to conxFB01;rm our findings.

Neuronal and molecular effects of cannabidiol on the mesolimbic dopamine system: Implications for novel schizophrenia treatments

Growing clinical and pre-clinical evidence points to a critical role for cannabidiol (CBD), the largest phytochemical component of cannabis, as a potential pharmacotherapy for various neuropsychiatric disorders. In contrast to delta-9-tetrahydrocannabinol (THC), which is associated with acute and neurodevelopmental pro-psychotic side-effects, CBD possesses no known psychoactive or dependence-producing properties. However, evidence has demonstrated that CBD strongly modulates the mesolimbic dopamine (DA) system and may possess promising anti-psychotic properties. Despite the psychotropic differences between CBD and THC, little is known regarding their molecular and neuronal effects on the mesolimbic DA system, nor how these differential effects may relate to their potential pro vs. anti-psychotic properties. This review summarizes clinical and pre-clinical evidence demonstrating CBD's modulatory effects on DA activity states within the mesolimbic pathway, functional interactions with the serotonin 5-HT_1A receptor system, and their downstream molecular signaling effects. Together with clinical evidence showing that CBD may normalize affective and cognitive deficits associated with schizophrenia, CBD may represent a promising treatment for schizophrenia, acting through novel molecular and neuronal mesolimbic substrates.

Transcriptomic Analysis Shows Decreased Cortical Expression of NR4A1, NR4A2 and RXRB in Schizophrenia and Provides Evidence for Nuclear Receptor Dysregulation

Many genes are differentially expressed in the cortex of people with schizophrenia, implicating factors that control transcription more generally. Hormone nuclear receptors dimerize to coordinate context-dependent changes in gene expression. We hypothesized that members of two families of nuclear receptors (NR4As), and retinoid receptors (RARs and RXRs), are altered in the dorsal lateral prefrontal cortex (DLPFC) of people with schizophrenia. We used next generation sequencing and then qPCR analysis to test for changes in mRNA levels for transcripts encoding nuclear receptors: orphan nuclear receptors (3 in the NR4A, 3 in the RAR, 3 in the RXR families and KLF4) in total RNA extracted from the DLPFC from people with schizophrenia compared to controls (n = 74). We also correlated mRNA levels with demographic factors and with estimates of antipsychotic drug exposure (schizophrenia group only). We tested for correlations between levels of transcription factor family members and levels of genes putatively regulated by these transcription factors. We found significantly down regulated expression of NR4A1 (Nurr 77) and KLF4 mRNAs in people with schizophrenia compared to controls, by both NGS and qPCR (p = or <0.01). We also detected decreases in NR4A2 (Nurr1) and RXRB mRNAs by using qPCR in the larger cohort (p<0.05 and p<0.01, respectively). We detected decreased expression of RARG and NR4A2 mRNAs in females with schizophrenia (p<0.05). The mRNA levels of NR4A1, NR4A2 and NR4A3 were all negative correlated with lifetime estimates of antipsychotic exposure. These novel findings, which may be influenced by antipsychotic drug exposure, implicate the orphan and retinoid nuclear receptors in the cortical pathology found in schizophrenia. Genes down stream of these receptors can be dysregulated as well, but the direction of change is not immediately predictable based on the putative transcription factor changes.

Altered neural signaling and immune pathways in peripheral blood mononuclear cells of schizophrenia patients with cognitive impairment: A transcriptome analysis

Cognitive deficits are a core feature of schizophrenia and contribute significantly to functional disability. We investigated the molecular pathways associated with schizophrenia (SZ; n=47) cases representing both 'cognitive deficit' (CD; n=22) and 'cognitively spared' (CS; n=25) subtypes of schizophrenia (based on latent class analysis of 9 cognitive performance indicators), compared with 49 healthy controls displaying 'normal' cognition. This was accomplished using gene-set analysis of transcriptome data derived from peripheral blood mononuclear cells (PBMCs). We detected 27 significantly altered pathways (19 pathways up-regulated and 8 down-regulated) in the combined SZ group and a further 6 pathways up-regulated in the CS group and 5 altered pathways (4 down-regulated and 1 up-regulated) in the CD group. The transcriptome profiling in SZ and cognitive subtypes were characterized by the up-regulated pathways involved in immune dysfunction (e.g., antigen presentation in SZ), energy metabolism (e.g., oxidative phosphorylation), and down-regulation of the pathways involved in neuronal signaling (e.g., WNT in SZ/CD and ERBB in SZ). When we looked for pathways that differentiated the two cognitive subtypes we found that the WNT signaling was significantly down-regulated (FDR<0.05) in the CD group in accordance with the combined SZ cohort, whereas it was unaffected in the CS group. This suggested suppression of WNT signaling was a defining feature of cognitive decline in schizophrenia. The WNT pathway plays a role in both the development/function of the central nervous system and peripheral tissues, therefore its alteration in PBMCs may be indicative of an important genomic axis relevant to cognition in the neuropathology of schizophrenia.

Alterations of Dopamine D2 Receptors and Related Receptor-Interacting Proteins in Schizophrenia: The Pivotal Position of Dopamine Supersensitivity Psychosis in Treatment-Resistant Schizophrenia

Although the dopamine D2 receptor (DRD2) has been a main target of antipsychotic pharmacotherapy for the treatment of schizophrenia, the standard treatment does not offer sufficient relief of symptoms to 20%-30% of patients suffering from this disorder. Moreover, over 80% of patients experience relapsed psychotic episodes within five years following treatment initiation. These data strongly suggest that the continuous blockade of DRD2 by antipsychotic(s) could eventually fail to control the psychosis in some point during long-term treatment, even if such treatment has successfully provided symptomatic improvement for the first-episode psychosis, or stability for the subsequent chronic stage. Dopamine supersensitivity psychosis (DSP) is historically known as a by-product of antipsychotic treatment in the manner of tardive dyskinesia or transient rebound psychosis. Numerous data in psychopharmacological studies suggest that the up-regulation of DRD2, caused by antipsychotic(s), is likely the mechanism underlying the development of the dopamine supersensitivity state. However, regardless of evolving notions of dopamine signaling, particularly dopamine release, signal transduction, and receptor recycling, most of this research has been conducted and discussed from the standpoint of disease etiology or action mechanism of the antipsychotic, not of DSP. Hence, the mechanism of the DRD2 up-regulation or mechanism evoking clinical DSP, both of which are caused by pharmacotherapy, remains unknown. Once patients experience a DSP episode, they become increasingly difficult to treat. Light was recently shed on a new aspect of DSP as a treatment-resistant factor. Clarification of the detailed mechanism of DSP is therefore crucial, and a preventive treatment strategy for DSP or treatment-resistant schizophrenia is urgently needed.

Effects of antipsychotic drugs on the expression of synapse-associated proteins in the frontal cortex of rats subjected to immobilization stress

The present study examined the effects of antipsychotic drugs on the expression of synapse-associated proteins in the frontal cortex of rats with and without immobilization stress. Rats were subjected to immobilization stress 6h/day for 3 weeks. The effects of atypical antipsychotic drugs, olanzapine and aripiprazole, on expression of serine(9)-phosphorylated GSK-3β, β-catenin, BDNF, PSD-95, and synaptophysin were determined by Western blotting. A typical antipsychotic drug, haloperidol, was used for comparison. Immobilization stress significantly decreased the expression of these proteins in the frontal cortex. Chronic administration of olanzapine and aripiprazole significantly attenuated the immobilization stress-induced decrease in the levels of these proteins, whereas haloperidol had no such effect. Additionally, olanzapine and aripiprazole significantly increased levels of phosphorylated GSK-3β under normal conditions without stress, and aripiprazole also increased BDNF levels under this condition. These results indicate that olanzapine and aripiprazole, and, haloperidol, differentially regulate the levels of synapse-associated proteins in the rat frontal cortex. These findings may contribute to explain the neurobiological basis of how olanzapine and aripiprazole up-regulated synapse-associated proteins.

The GSK3B gene confers risk for both major depressive disorder and schizophrenia in the Han Chinese population

BACKGROUND

Glycogen synthease kinase-3B is a key gene encoding a protein kinase which is abundant in brain, and is involved in signal transduction cascades of neuronal cell development and energy metabolism. Previous researches proposed GSK3B as a potential region for schizophrenia.

METHOD

To validate the susceptibility of GSK3B to major depressive disorder, and to investigate the overlapping risk conferred by GSK3B for mental disorders, we performed a large-scale case-control study, analyzed 6 tag single nucleotide polymorphisms using TaqMan® technology in 1,045 major depressive disorder patients, 1,235 schizophrenia patients and 1,235 normal controls of Han Chinese origin.

RESULTS

We found rs334535 (Pallele=2.79E-03, Pgenotype=5.00E-03, OR=1.429) and rs2199503 (Pallele=0.020, Pgenotype= 0.040, OR=1.157) showed association with major depressive disorder before Bonferroni correction. rs6771023 (adjusted Pallele=1.64E-03, adjusted Pgenotype=6.00E-03, OR=0.701) and rs2199503 (adjusted Pallele=0.001, adjusted Pgenotype=0.002, OR=1.251) showed significant association with schizophrenia after Bonferroni correction. rs2199503 (adjusted Pallele=1.70E-03, adjusted Pgenotype=0.006, OR=1.208) remained to be significant in the combined cases of major depressive disorder and schizophrenia after Bonferroni correction.

LIMITATIONS

Further validations of our findings in samples with larger scale are suggested, and functional genomic study is needed to elucidate the role of GSK3B in signal pathway and psychiatric disorders.

CONCLUSIONS

Our results provide evidence that the GSK3B gene could be a promising region which contains genetic risk for both major depressive disorder and schizophrenia in the Han Chinese population. The study on variants conferring overlapping risk for multiple psychiatric disorders could be tangible pathogenesis support and clinical or diagnostic references.

Glycogen synthase kinase-3 as a therapeutic target for cognitive dysfunction in neuropsychiatric disorders

The serine/threonine kinase glycogen synthase kinase-3 (GSK-3) is involved in a broad range of cellular processes including cell proliferation, apoptosis and inflammation. It is now also increasingly acknowledged as having a role to play in cognitive-related processes such as neurogenesis, synaptic plasticity and neural cell survival. Cognitive impairment represents a major debilitating feature of many neurodegenerative and psychiatric disorders, including Alzheimer's disease, mood disorders, schizophrenia and fragile X syndrome, as well as being a result of traumatic brain injury or cranial irradiation. Accordingly, GSK-3 has been identified as an important therapeutic target for cognitive impairment, and recent preclinical studies have yielded important evidence demonstrating that GSK-3 inhibitors may be useful therapeutic interventions for restoring cognitive function in some of these brain disorders. The current review summarises the role of GSK-3 as a regulator of cognitive-dependent functions, examines current preclinical and clinical evidence of the potential of GSK-3 inhibitors as therapeutic agents for cognitive impairments in neuropsychiatric disorders, and offers some insight into the current obstacles that are impeding the clinical use of selective GSK-3 inhibitors in the treatment of cognitive impairment.

Prefrontal inefficiency is associated with polygenic risk for schizophrenia

Considering the diverse clinical presentation and likely polygenic etiology of schizophrenia, this investigation examined the effect of polygenic risk on a well-established intermediate phenotype for schizophrenia. We hypothesized that a measure of cumulative genetic risk based on additive effects of many genetic susceptibility loci for schizophrenia would predict prefrontal cortical inefficiency during working memory, a brain-based biomarker for the disorder. The present study combined imaging, genetic and behavioral data obtained by the Mind Clinical Imaging Consortium study of schizophrenia (n = 255). For each participant, we derived a polygenic risk score (PGRS), which was based on over 600 nominally significant single nucleotide polymorphisms, associated with schizophrenia in a separate discovery sample comprising 3322 schizophrenia patients and 3587 control participants. Increased polygenic risk for schizophrenia was associated with neural inefficiency in the left dorsolateral prefrontal cortex after covarying for the effects of acquisition site, diagnosis, and population stratification. We also provide additional supporting evidence for our original findings using scores based on results from the Psychiatric Genomics Consortium study. Gene ontology analysis of the PGRS highlighted genetic loci involved in brain development and several other processes possibly contributing to disease etiology. Our study permits new insights into the additive effect of hundreds of genetic susceptibility loci on a brain-based intermediate phenotype for schizophrenia. The combined impact of many common genetic variants of small effect are likely to better reveal etiologic mechanisms of the disorder than the study of single common genetic variants.

Paliperidone protects SK-N-SH cells against glutamate toxicity via Akt1/GSK3β signaling pathway

Schizophrenia is a heterogeneous psychotic illness and its etiology remains poorly understood. Recent studies have suggested that neurodegeneration is a component of schizophrenia pathology and some atypical antipsychotics appear to slow progressive morphological brain changes. In addition, the atypical antipsychotics were reported to have a superior therapeutic efficacy in treating schizophrenia and have a low incidence of extrapyramidal side effects (EPS) compared to typical antipsychotics. However, the mechanisms of atypical antipsychotics in treating schizophrenia and the basis for differences in their clinical effects were still totally unknown. In the present study, we investigated whether paliperidone shows protective effects on SK-N-SH cells from cell toxicity induced by exposure to glutamate. We examined the effects of the drugs on cell viability (measured by MTT metabolism assay and lactate dehydrogenase (LDH) activity assay), apoptosis rate, ROS levels and gene expression and phosphorylation of Akt1 and GSK3β. The results showed that paliperidone significantly increases the cell viability by MTT and LDH assays (p<0.05), in contrast to the typical antipsychotic (haloperidol), which had little neuroprotective activity. Moreover, paliperidone retarded the glutamate-mediated promotion of ROS and the rate of apoptosis (p<0.05). In addition, paliperidone also effectively reversed glutamate-induced decreases of gene expression and phosphorylation of Akt1 and GSK3β (both p<0.05). Our results demonstrated that paliperidone could effectively protect SK-N-SH cells from glutamate-induced damages via Akt1/GSK3β signaling pathway.

Neurodevelopment in schizophrenia: the role of the wnt pathways

OBJECTIVES

To review the role of Wnt pathways in the neurodevelopment of schizophrenia.

METHODS

SYSTEMATIC PUBMED SEARCH, USING AS KEYWORDS ALL THE TERMS RELATED TO THE WNT PATHWAYS AND CROSSING THEM WITH EACH OF THE FOLLOWING AREAS: normal neurodevelopment and physiology, neurodevelopmental theory of schizophrenia, schizophrenia, and antipsychotic drug action.

RESULTS

Neurodevelopmental, behavioural, genetic, and psychopharmacological data point to the possible involvement of Wnt systems, especially the canonical pathway, in the pathophysiology of schizophrenia and in the mechanism of antipsychotic drug action. The molecules most consistently found to be associated with abnormalities or in antipsychotic drug action are Akt1, glycogen synthase kinase3beta, and beta-catenin. However, the extent to which they contribute to the pathophysiology of schizophrenia or to antipsychotic action remains to be established.

CONCLUSIONS

The study of the involvement of Wnt pathway abnormalities in schizophrenia may help in understanding this multifaceted clinical entity; the development of Wnt-related pharmacological targets must await the collection of more data.

Paliperidone protects prefrontal cortical neurons from damages caused by MK-801 via Akt1/GSK3β signaling pathway

Recent studies have suggested that neurodegeneration is involved in the pathogenesis of schizophrenia, and some atypical antipsychotics appear to prevent or retard progressive morphological brain changes. However, the underlying molecular mechanisms are largely unknown. Whether changes in intracellular signaling pathways are related to their neuroprotective effects remains undefined. In the present study, we used mouse embryonic prefrontal cortical neurons to examine the neuroprotection of paliperidone against the neuronal damage induced by exposure to the NMDA receptor antagonist, MK-801. Paliperidone inhibited MK-801 induced neurotoxicity both in MTT metabolism assay (p<0.01) and in lactate dehydrogenase (LDH) activity assay (p<0.01). Time course studies revealed that paliperidone effectively attenuated the elevation of intracellular free calcium concentration ([Ca(2+)]i) induced by exposure to MK-801 (p<0.01). Moreover, paliperidone could significantly retard MK-801-mediated inhibition of neurite outgrowth (p<0.01) and reverse MK-801-induced decreases of gene expression and phosphorylation of Akt1 and GSK3β (both p<0.01). Furthermore, these protective effects of paliperidone were blocked by pretreatment with a PI3K inhibitor LY294002. Taking together, our results demonstrated that paliperidone could protect prefrontal cortical neurons from MK-801-induced damages via Akt1/GSK3β signaling pathway.

ABCA8 stimulates sphingomyelin production in oligodendrocytes

Members of the ABCA (ATP-binding cassette subfamily A) family are characterized by their ability to transport lipids across cellular membranes and regulate lipid homoeostasis in the brain and peripheral tissues. ABCA8 is a little-known member of this subfamily that was originally cloned from human brain libraries and has no known function. In an effort to elucidate the role of ABCA8 in the brain we first undertook a comprehensive analysis of its expression in the human brain. ABCA8 was differentially expressed in multiple regions of adult human brains with significantly higher expression in oligodendrocyte-enriched white matter regions compared with grey matter cortical regions. We then assessed the impact of ABCA8 on sphingomyelin production in oligodendrocyte and showed that ABCA8 was able to significantly stimulate both sphingomyelin synthase 1 expression and sphingomyelin production. Furthermore, ABCA8 expression in the prefrontal cortex across the human life span correlated strongly with age-associated myelination, and the myelinating gene p25α was significantly up-regulated with ABCA8. The present study represents the first extensive expression and functional study of ABCA8 in the human brain and the results strongly suggest that ABCA8 regulates lipid metabolism in oligodendrocytes and potentially plays a role in myelin formation and maintenance.

Potential application as screening and drug designing tools of cytoarchitectural deficiencies present in three animal models of schizophrenia

BACKGROUND

The development of new treatment alternatives for schizophrenia has been prevented by the unknown etiology of the illness and the divergence of results in the field. However, consistent neuropathological findings are emerging from anatomical areas known to be at the core of schizophrenia. If these deficiencies are replicated in animal models then such anomalies could become the target for a new generation of drugs.

OBJECTIVE

To determine if the methylazoxymethanol acetate (MAM) model, the heterozygote reeler mouse (HRM) and NMDA-antagonists treated rats replicate neuropathological deficits encountered in patients with schizophrenia and to establish if such changes could lead the search for developing novel treatment alternatives.

METHODS

Databases including MEDLINE, Cochrane and Ovid were searched; search terms included neuropathology, schizophrenia and animal models.

RESULTS/CONCLUSIONS

NMDA-antagonist treated animals partially replicate schizophrenia anomalies in parvalbumin positive interneurons. In contrast, neuroanatomical deficiencies replicated by the MAM model and the HRM in the hippocampus and the prefrontal cortex seem promising targets for future pharmacological research in schizophrenia. Such neuroanatomical findings along with evidence from molecules and genes associated with schizophrenia suggest new drugs should aim to correct deficits in the formation of dendrites and axons that seems to be implicated in this illness pathophysiology.

Expression of NPAS3 in the human cortex and evidence of its posttranscriptional regulation by miR-17 during development, with implications for schizophrenia

NPAS3 is a developmentally important transcription factor that has been associated with psychiatric illness. Our aim is to better define the regulation of NPAS3 mRNA (messenger RNA) levels during normal human prefrontal cortical development and in schizophrenia. Utilizing postmortem tissue from 134 human brains, we assessed: 60 normal brains ranging in age from birth to adulthood, 37 chronic individuals with schizophrenia, and 37 matched controls. mRNA and microRNA (miRNA) expressions were measured by microarray and quantitative real-time PCR. Protein expression was measured by Western blotting. During human postnatal cortical development (neonate to adult), we found decreased NPAS3 mRNA yet increased NPAS3 protein expression, suggesting the involvement of posttranscriptional regulation. Through screening, we identified one NPAS-targeted miRNA (miR-17) that changed in a pattern consistent with the developmental regulation of NPAS3. Using luciferase reporter assays, we assessed the impact of miR-17 on NPAS3 translation and demonstrated that miR-17 alters NPAS3 biosynthesis by binding to the NPAS3 3'untranslated region (UTR). In schizophrenia prefrontal cortex, we found significant elevations in miR-17 expression. While NPAS3 mRNA was unaltered, reduced NPAS3 protein expression was detected in a subpopulation of people with schizophrenia. The reciprocal expression of NPAS3 mRNA and protein during postnatal development mediated by a schizophrenia-associated change in miR-17 suggests that there is complex control over NPAS3 synthesis in the human prefrontal cortex and that if NPAS3 is dysregulated in schizophrenia, it is not evident by large changes in NPAS3 expression. Further studies into how changes in NPAS3 or its miRNA regulator may influence the development of schizophrenia are warranted.

Increases in two truncated TrkB isoforms in the prefrontal cortex of people with schizophrenia

The truncated brain-derived neurotrophic factor (BDNF) receptors (truncated TrkB [TrkB-TK-] and sarc homology containing TrkB [TrkB-Shc]) are alternative transcripts of the full-length TrkB receptor (TrkB-TK+) that produce isoforms capable of binding to BDNF but not being able to mediate the classic neurotrophic response via tyrosine kinase signaling. We hypothesized that in the dorsolateral prefrontal cortex (DLPFC) of people with schizophrenia, truncated TrkB receptors (TK- and Shc) would be altered and may contribute to deficits in BDNF function. Using a large cohort of controls and schizophrenics (n = 72/72), we measured mRNA expression of the full-length TrkB receptor, TrkB-TK+ and the truncated TrkB receptors, TrkB-TK- and TrkB-Shc, by quantitative real-time polymerase chain reaction and protein expression by western blotting. We found highly significant increases in mRNA expression of both truncated TrkB receptor isoforms in people with schizophrenia. When we examined the full-length TrkB-TK+:truncated TrkB ratios, we observed significant decreases in schizophrenia both on the mRNA and protein level. We found a slight reduction in TrkB-TK+ mRNA and a significant reduction in TrkB-TK+ protein expression in schizophrenia, which was evident in females. No gender-specific changes were found for the truncated TrkB receptors. Diagnostic changes in TrkB-TK+ mRNA and protein may be subtle and/or gender-specific, whereas changes in TrkB-TK- and TrkB-Shc expression are robust and may generalize to both males and females with schizophrenia. Increased truncated TrkB receptors may contribute to reduced overall BDNF/tyrosine receptor kinase B (TrkB) signaling and lead to reduced neuronal plasticity in the DLPFC in schizophrenia suggesting that therapies aimed at ameliorating neurotrophin deficits may need to consider blocking excessive truncated TrkB function.

Estudos traducionais de neuropsiquiatria e esquizofrenia: modelos animais genéticos e de neurodesenvolvimento

Sintomas psiquiátricos são subjetivos por natureza e tendem a se sobrepor entre diferentes desordens. Sendo assim, a criação de modelos de uma desordem neuropsiquiátrica encontra desafios pela falta de conhecimento dos fundamentos da fisiopatologia e diagnósticos precisos. Modelos animais são usados para testar hipóteses de etiologia e para representar a condição humana tão próximo quanto possível para aumentar nosso entendimento da doença e avaliar novos alvos para a descoberta de drogas. Nesta revisão, modelos animais genéticos e de neurodesenvolvimento de esquizofrenia são discutidos com respeito a achados comportamentais e neurofisiológicos e sua associação com a condição clínica. Somente modelos animais específicos de esquizofrenia podem, em último caso, levar a novas abordagens diagnósticas e descoberta de drogas. Argumentamos que biomarcadores moleculares são importantes para aumentar a tradução de animais a humanos, já que faltam a especificidade e a fidelidade necessárias às leituras comportamentais para avaliar sintomas psiquiátricos humanos.

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.

The dopamine D2 receptor regulates Akt and GSK-3 via Dvl-3

The dopamine D2 receptor (D2DR) regulates Akt and may also target the Wnt pathway, two signalling cascades that inhibit glycogen synthase kinase-3 (GSK-3). This study examined whether the Wnt pathway is regulated by D2DR and the role of Akt and dishevelled-3 (Dvl-3) in regulating GSK-3 and the transcription factor β-catenin in the rat brain. Western blotting showed that subchronic treatment of raclopride (D2DR antagonist) increase phosphorylated Akt, Dvl-3, GSK-3, phosphorylated GSK-3 and β-catenin, whereas subchronic treatment of quinpirole (D2DR agonist) induced the opposite response. Co-immunopreciptations revealed an association between GSK-3 and the D2DR complex that was altered following raclopride and quinpirole, albeit in opposite directions. SCH23390 (D1DR antagonist) and nafadotride (D3DR antagonist) were also used to determine if the response was specific to the D2DR. Neither subchronic treatment affected Dvl-3, GSK-3, Akt nor β-catenin protein levels, although nafadotride altered the phosphorylation state of Akt and GSK-3. In addition, in-vitro experiments were conducted to manipulate Akt and Dvl-3 activity in SH-SY5Y cells to elucidate how the pattern of change observed following manipulation of D2DR developed. Results indicate that Akt affects the phosphorylation state of GSK-3 but has no effect on β-catenin levels. However, altering Dvl-3 levels resulted in changes in Akt and the Wnt pathway similar to what was observed following raclopride or quinpirole treatment. Collectively, the data suggests that the D2DR very specifically regulates Wnt and Akt signalling via Dvl-3.

Developmental trajectory of the endocannabinoid system in human dorsolateral prefrontal cortex

Background

Endocannabinoids provide control over cortical neurotransmission. We investigated the developmental expression of key genes in the endocannabinoid system across human postnatal life and determined whether they correspond to the development of markers for inhibitory interneurons, which shape cortical development. We used microarray with qPCR validation and in situ hybridisation to quantify mRNA for the central endocannabinoid receptor CB₁R, endocannabinoid synthetic enzymes (DAGLα for 2-arachidonylglycerol [2-AG] and NAPE-PLD for anandamide), and inactivating enzymes (MGL and ABHD6 for 2-AG and FAAH for anandamide) in human dorsolateral prefrontal cortex (39 days - 49 years).

Results

CB₁R mRNA decreases until adulthood, particularly in layer II, after peaking between neonates and toddlers. DAGLα mRNA expression is lowest in early life and adulthood, peaking between school age and young adulthood. MGL expression declines after peaking in infancy, while ABHD6 increases from neonatal age. NAPE-PLD and FAAH expression increase steadily after infancy, peaking in adulthood.

Conclusions

Stronger endocannabinoid regulation of presynaptic neurotransmission in both supragranular and infragranular cortical layers as indexed through higher CB₁R mRNA may occur within the first few years of human life. After adolescence, higher mRNA levels of the anandamide synthetic and inactivating enzymes NAPE-PLD and FAAH suggest that a late developmental switch may occur where anandamide is more strongly regulated after adolescence than earlier in life. Thus, expression of key genes in the endocannabinoid system changes with maturation of cortical function.

AKT/GSK3 signaling pathway and schizophrenia

Schizophrenia is a prevalent complex trait disorder manifested by severe neurocognitive dysfunctions and lifelong disability. During the past few years several studies have provided direct evidence for the involvement of different signaling pathways in schizophrenia. In this review, we mainly focus on AKT/GSK3 signaling pathway in schizophrenia. The original study on the involvement of this pathway in schizophrenia was published by Emamian et al. in 2004. This study reported convergent evidence for a decrease in AKT1 protein levels and levels of phosphorylation of GSK-3β in the peripheral lymphocytes and brains of individuals with schizophrenia; a significant association between schizophrenia and an AKT1 haplotype; and a greater sensitivity to the sensorimotor gating-disruptive effect of amphetamine, conferred by AKT1 deficiency. It also showed that haloperidol can induce a stepwise increase in regulatory phosphorylation of AKT1 in the brains of treated mice that could compensate for the impaired function of this signaling pathway in schizophrenia. Following this study, several independent studies were published that not only confirmed the association of this signaling pathway with schizophrenia across different populations, but also shed light on the mechanisms by which AKT/GSK3 pathway may contribute to the development of this complex disorder. In this review, following an introduction on the role of AKT in human diseases and its functions in neuronal and non-neuronal cells, a review on the results of studies published on AKT/GSK3 signaling pathway in schizophrenia after the original 2004 paper will be provided. A brief review on other signaling pathways involved in schizophrenia and the possible connections with AKT/GSK3 signaling pathway will be discussed. Moreover, some possible molecular mechanisms acting through this pathway will be discussed besides the mechanisms by which they may contribute to the pathogenesis of schizophrenia. Finally, different transcription factors related to schizophrenia will be reviewed to see how hypo-activity of AKT signaling pathway may impact such transcriptional mechanisms.

Developmental changes in human dopamine neurotransmission: cortical receptors and terminators

Background

Dopamine is integral to cognition, learning and memory, and dysfunctions of the frontal cortical dopamine system have been implicated in several developmental neuropsychiatric disorders. The dorsolateral prefrontal cortex (DLPFC) is critical for working memory which does not fully mature until the third decade of life. Few studies have reported on the normal development of the dopamine system in human DLPFC during postnatal life. We assessed pre- and postsynaptic components of the dopamine system including tyrosine hydroxylase, the dopamine receptors (D1, D2 short and D2 long isoforms, D4, D5), catechol-O-methyltransferase, and monoamine oxidase (A and B) in the developing human DLPFC (6 weeks -50 years).

Results

Gene expression was first analysed by microarray and then by quantitative real-time PCR. Protein expression was analysed by western blot. Protein levels for tyrosine hydroxylase peaked during the first year of life (p < 0.001) then gradually declined to adulthood. Similarly, mRNA levels of dopamine receptors D2S (p < 0.001) and D2L (p = 0.003) isoforms, monoamine oxidase A (p < 0.001) and catechol-O-methyltransferase (p = 0.024) were significantly higher in neonates and infants as was catechol-O-methyltransferase protein (32 kDa, p = 0.027). In contrast, dopamine D1 receptor mRNA correlated positively with age (p = 0.002) and dopamine D1 receptor protein expression increased throughout development (p < 0.001) with adults having the highest D1 protein levels (p ≤ 0.01). Monoamine oxidase B mRNA and protein (p < 0.001) levels also increased significantly throughout development. Interestingly, dopamine D5 receptor mRNA levels negatively correlated with age (r = -0.31, p = 0.018) in an expression profile opposite to that of the dopamine D1 receptor.

Conclusions

We find distinct developmental changes in key components of the dopamine system in DLPFC over postnatal life. Those genes that are highly expressed during the first year of postnatal life may influence and orchestrate the early development of cortical neural circuitry while genes portraying a pattern of increasing expression with age may indicate a role in DLPFC maturation and attainment of adult levels of cognitive function.

Genetic association and identification of a functional SNP at GSK3β for schizophrenia susceptibility

OBJECTIVE

GSK3β is a key gene in neurodevelopment, and also an important target of antipsychotics. Several lines of evidence including association and gene expression studies have suggested GSK3β as a susceptibility gene for schizophrenia, but the underlying genetic mechanism is still unknown. In this study, we test whether the genetic variants in GSK3β contribute to the risk of schizophrenia in Chinese population.

METHODS

We first conducted an association analysis of 9 representative SNPs spanning the entire genomic region of GSK3β in two independent Han Chinese case-control samples from southwestern China (the Kunming sample and the Yuxi sample, a total of 2550 subjects).Then using EMSA and reporter gene assays, we tested the functional impact of the identified risk SNP on transcriptional factor binding affinity and promoter activity.

RESULTS

We observed weak allelic associations of three GSK3β SNPs (rs3755557, rs7431209 and rs13320980) with schizophrenia in the combined Han Chinese samples. Further analysis using genotypes (under recessive genetic model) supported the association of rs3755557 (p = 0.01, corrected), which is located in the GSK3β promoter region. The functional assays demonstrated that the risk SNP (rs3755557) could influence the transcription factor binding affinities, resulting in a higher promoter activity of the risk allele.

CONCLUSION

Our findings suggest that GSK3β is likely a risk gene for schizophrenia, and its expression alteration caused by the risk SNP in the promoter region may contribute to the etiology of schizophrenia.

The effects of neuropsychiatric drugs on glycogen synthase kinase-3 signaling

Glycogen synthase kinase-3 (GSK-3) has been implicated in the action of antipsychotics, mood stabilizers, and antidepressants. Given that only antipsychotics are able to alleviate the positive symptoms of schizophrenia, the regulation of GSK-3 by antipsychotics would be expected to differ from other neuropsychiatric drugs if GSK-3 is involved in the alleviation of psychosis. Consequently, the current study examined the effects of antipsychotics (haloperidol and clozapine), mood stabilizers (lithium and valproic acid), and antidepressants (imipramine and fluoxetine) on GSK-3, as well as Akt and Wnt in the prefrontal cortex and striatum. Western blotting and co-immunoprecipitation experiments showed that only antipsychotic treatment increased Dvl-3, GSK-3, and β-catenin levels and enhanced the association of GSK-3 at the dopamine D2 receptor (D₂DR) complex in the rat prefrontal cortex. In the striatum, haloperidol had the same effect on Wnt signaling as observed in the prefrontal cortex, whereas clozapine did not affect Dvl-3, GSK-3 or β-catenin levels. All three classes of drugs were able to activate Akt signaling as shown by the increased phosphorylated Akt and phosphorylated GSK-3 protein levels in the prefrontal cortex and/or striatum. In conclusion, regulation of the Wnt pathway is specific to antipsychotics, whereas antipsychotics, mood stabilizers, and antidepressants all affect Akt.

Interactions of human truncated DISC1 proteins: implications for schizophrenia

Numerous genetic linkage and association reports have implicated the Disrupted-in-Schizophrenia (DISC1) gene in psychiatric illness. The Scottish family translocation, predicted to encode a C-terminus-truncated protein, suggests involvement of short isoforms in the pathophysiology of mental disorders. We recently reported complex alternative splicing patterns for the DISC1 gene and found that short isoforms are overexpressed in the brains of patients with schizophrenia and in carriers of risk-associated alleles. Investigation into the protein-protein interactions of alternative DISC1 isoforms may provide information about the functional consequences of overexpression of truncated forms in mental illness. Human embryonic kidney (HEK293) cells were transiently co-transfected with human epitope-tagged DISC1 variants and epitope-tagged NDEL1, FEZ1, GSK3β and PDE4B constructs. Co-immunoprecipitation assays demonstrated that all truncated DISC1 variants formed complexes with full-length DISC1. Short DISC1 splice variants LΔ78, LΔ3 and Esv1 showed reduced or no binding to NDEL1 and PDE4B proteins, but fully interacted with FEZ1 and GSK3β. The temporal expression pattern of GSK3β in the human postmortem tissue across the lifespan closely resembled that of the truncated DISC1 variants, suggesting the possibility of interactions between these proteins in the human brain. Our results suggest that complexes of full-length DISC1 with truncated DISC1 variants may result in cellular disturbances critical to DISC1 function.

Paranoid schizophrenia is characterized by increased CB1 receptor binding in the dorsolateral prefrontal cortex

A number of studies suggest a dysregulation of the endogenous cannabinoid system in schizophrenia (SCZ). In the present study, we examined cannabinoid CB(1) receptor (CB(1)R) binding and mRNA expression in the dorsolateral prefrontal cortex (DLPFC) (Brodmann's area 46) of SCZ patients and controls, post-mortem. Receptor density was investigated using autoradiography with the CB(1)R ligand [(3)H] CP 55,940 and CB(1)R mRNA expression was measured using quantitative RT-PCR in a cohort of 16 patients with paranoid SCZ, 21 patients with non-paranoid SCZ and 37 controls matched for age, post-mortem interval and pH. All cases were obtained from the University of Sydney Tissue Resource Centre. Results were analyzed using one-way analysis of variance (ANOVA) and post hoc Bonferroni tests and with analysis of covariance (ANCOVA) to control for demographic factors that would potentially influence CB(1)R expression. There was a main effect of diagnosis on [(3)H] CP 55,940 binding quantified across all layers of the DLPFC (F(2,71) = 3.740, p = 0.029). Post hoc tests indicated that this main effect was due to patients with paranoid SCZ having 22% higher levels of CB(1)R binding compared with the control group. When ANCOVA was employed, this effect was strengthened (F(2,67) = 6.048, p = 0.004) with paranoid SCZ patients differing significantly from the control (p = 0.004) and from the non-paranoid group (p = 0.016). In contrast, no significant differences were observed in mRNA expression between the different disease subtypes and the control group. Our findings confirm the existence of a CB(1)R dysregulation in SCZ and underline the need for further investigation of the role of this receptor particularly in those diagnosed with paranoid SCZ.

Expression of VGluT1 and VGAT mRNAs in human dorsolateral prefrontal cortex during development and in schizophrenia

A balance between excitatory and inhibitory neurotransmission is important in normal brain function, and in schizophrenia a deficit in γ-aminobutyric acid (GABA)ergic inhibitory neurotransmission has been indicated by postmortem studies. We examined the ratio of excitatory to inhibitory vesicular neurotransmitter transporter mRNAs (VGluT1 to VGAT) and their ratio in the dorsolateral prefrontal cortex during normal human development and in people with schizophrenia and controls by quantitative RT-PCR. The ratio of VGluT1/VGAT increased gradually in development to reach a peak at school age (5-12 years), after which levels remained fairly constant into adulthood. The VGluT1 mRNA/VGAT mRNA ratio was unchanged in schizophrenia, as was the ratio of complexin 2 mRNA to complexin 1 mRNA (related to synaptic vesicle fusion in excitatory and inhibitory terminals, respectively). This suggests that the excitatory/inhibitory balance is attained prior to adolescence and is maintained across the rest of the life-span and also indicates that in schizophrenia this balance is not greatly disturbed.