The effects of clozapine on the GSK-3-mediated signaling pathway

Dynamic Foraging Behavior Performance Is Not Affected by Scn2a Haploinsufficiency

Dysfunction in the gene SCN2A, which encodes the voltage-gated sodium channel Nav1.2, is strongly associated with neurodevelopmental disorders including autism spectrum disorder and intellectual disability (ASD/ID). This dysfunction typically manifests in these disorders as a haploinsufficiency, where loss of one copy of a gene cannot be compensated for by the other allele. Scn2a haploinsufficiency affects a range of cells and circuits across the brain, including associative neocortical circuits that are important for cognitive flexibility and decision-making behaviors. Here, we tested whether Scn2a haploinsufficiency has any effect on a dynamic foraging task that engages such circuits. Scn2a +/- mice and wild-type (WT) littermates were trained on a choice behavior where the probability of reward between two options varied dynamically across trials and where the location of the high reward underwent uncued reversals. Despite impairments in Scn2a-related neuronal excitability, we found that both male and female Scn2a +/- mice performed these tasks as well as wild-type littermates, with no behavioral difference across genotypes in learning or performance parameters. Varying the number of trials between reversals or probabilities of receiving reward did not result in an observable behavioral difference, either. These data suggest that, despite heterozygous loss of Scn2a, mice can perform relatively complex foraging tasks that make use of higher-order neuronal circuits.

Neurotoxic/Neuroprotective Effects of Clozapine and the Positive Allosteric Modulator of mGluR2 JNJ-46356479 in Human Neuroblastoma Cell Cultures

Current antipsychotics (APs) effectively control positive psychotic symptoms, mainly by blocking dopamine (DA) D2 receptors, but have little effect on negative and cognitive symptoms. Increased glutamate (GLU) release would trigger neurotoxicity, leading to apoptosis and synaptic pruning, which is involved in the pathophysiology of schizophrenia. New pharmacological strategies are being developed such as positive allosteric modulators (PAMs) of the metabotropic GLU receptor 2 (mGluR2) that inhibit the presynaptic release of GLU. We previously reported that treatment of adult mice with JNJ-46356479 (JNJ), a recently developed mGluR2 PAM, partially improved neuropathological deficits and schizophrenia-like behavior in a postnatal ketamine mouse model. In the present study, we evaluated, for the first time, the putative neuroprotective and antiapoptotic activity of JNJ in a human neuroblastoma cell line and compared it with the effect of clozapine (CLZ) as a clinical AP with the highest efficacy and with apparent utility in managing negative symptoms. Specifically, we measured changes in cell viability, caspase 3 activity and apoptosis, as well as in the expression of key genes involved in survival and cell death, produced by CLZ and JNJ alone and in combination with a high DA or GLU concentration as apoptosis inducers. Our results suggest that JNJ is not neurotoxic and attenuates apoptosis, particularly by decreasing the caspase 3 activation induced by DA and GLU, as well as increasing and decreasing the number of viable and apoptotic cells, respectively, only when cultures were exposed to GLU. Its effects seem to be less neurotoxic and more neuroprotective than those observed with CLZ. Moreover, JNJ partially normalized altered expression levels of glycolytic genes, which could act as a protective factor and be related to its putative neuroprotective effect. More studies are needed to define the mechanisms of action of this GLU modulator and its potential to become a novel therapeutic agent for schizophrenia.

Deletion of Schizophrenia Susceptibility Gene Ulk4 Leads to Abnormal Cognitive Behaviors via Akt-GSK-3 Signaling Pathway in Mice

OBJECTIVES

Despite of strenuous research in the past decades, the etiology of schizophrenia (SCZ) still remains incredibly controversial. Previous genetic analysis has uncovered a close association of Unc-51 like kinase 4 (ULK4), a family member of Unc-51-like serine/threonine kinase, with SCZ. However, animal behavior data which may connect Ulk4 deficiency with psychiatric disorders, particularly SCZ are still missing.

METHODS

We generated Emx1-Cre:Ulk4flox/flox conditional knockout (CKO) mice, in which Ulk4 was deleted in the excitatory neurons of cerebral cortex and hippocampus.

RESULTS

The cerebral cellular architecture was maintained but the spine density of pyramidal neurons was reduced in Ulk4 CKO mice. CKO mice showed deficits in the spatial and working memories and sensorimotor gating. Levels of p-Akt and p-GSK-3α/β were markedly reduced in the CKO mice indicating an elevation of GSK-3 signaling. Mechanistically, Ulk4 may regulate the GSK-3 signaling via putative protein complex comprising of two phosphatases, protein phosphatase 2A (PP2A) and 1α (PP1α). Indeed, the reduction of p-Akt and p-GSK-3α/β was rescued by administration of inhibitor acting on PP2A and PP1α in CKO mice.

CONCLUSIONS

Our data identified potential downstream signaling pathway of Ulk4, which plays important roles in the cognitive functions and when defective, may promote SCZ-like pathogenesis and behavioral phenotypes in mice.

Antipsychotics preserve telomere length in peripheral blood mononuclear cells after acute oxidative stress injury

Antipsychotics may prolong or retain telomere length, affect mitochondrial function, and then affect the metabolism of nerve cells. To validate the hypothesis that antipsychotics can prolong telomere length after oxidative stress injury, leukocytes from healthy volunteers were extracted using Ficoll-Histopaque density gradient. The mononuclear cells layer was resuspended in cell culture medium. Oxidative stress was induced with hydrogen peroxide in cultured leukocytes. Four days later, leukocytes were treated with aripiprazole, haloperidol or clozapine for 7 days. Real-time PCR revealed that treatments with aripiprazole and haloperidol increased the telomere length by 23% and 20% in peripheral blood mononuclear cells after acute oxidative stress injury. These results suggest that haloperidol and aripiprazole can reduce the damage to telomeres induced by oxidative stress. The experiment procedure was approved by the Ethics Committee of Faculty of Medicine of the University of São Paulo (FMUSP/CAAE approval No. 52622616.8.0000.0065).

Challenges in Prescribing Clozapine in the Era of COVID-19: A Review Focused on Immunological Implications

The global COVID-19 pandemic has disrupted every aspect of the healthcare system. Apart from the issues surrounding COVID-19 itself, care for existing patients has met many challenges. One such challenge is caring for patients who are on clozapine treatment and have been confirmed positive for COVID-19. Schizophrenia has been considered to have a deep connection with the immune system, and clozapine can induce further changes in this system. COVID-19 can ravage the compromised immune system and aggravate tissue damage. The intricate relations between schizophrenia, clozapine, and COVID-19 make it difficult to predict the clinical course of COVID-19 in clozapine-treated patients. However, the rigid prohibition on using clozapine if COVID-19 is confirmed may harm patients. Patients who have to use clozapine are often refractory cases with no alternatives. Therefore, the decision to maintain or stop clozapine must be made after a comprehensive review of the patient’s unique situation. To do this, theoretical and practical issues surrounding the use of clozapine in COVID-19 should be reviewed and discussed. In this review, we gather useful information surrounding this issue and present an overview. Focusing on the immune system, various theoretical possibilities that could arise from schizophrenia, clozapine, and COVID-19 were carefully examined, and practical checklists for the care of these patients were explored. It is hoped that this review will convince many clinicians to pay attention to this momentous issue and facilitate more active sharing of clinical experiences.

The GSK3-NRF2 Axis in Suicide

Mutations in the genes coding for tryptophan-hydrolase-2 and the scaffold protein FKBP5 are associated with an increased risk of suicide. The mutation in both cases enhances the enzymatic activity of glycogen synthase kinase-3 (GSK3). Conversely, anti-suicidal medications, such as lithium, clozapine, and ketamine, indirectly inhibit the activity of GSK3. When GSK3 is active, it promotes the metabolic removal of the transcription factor NRF2 (nuclear factor erythroid 2-related factor-2), which suppresses the transcription of multiple genes that encode anti-oxidative and anti-inflammatory proteins. Notably, several suicide-biomarkers bear witness to an ongoing inflammatory process. Moreover, alterations in serum lipid levels measured in suicidal individuals are mirrored by data obtained in mice with genetic deletion of the NRF2 gene. Inflammation is presumably causally related to both dysphoria and anger, two factors relevant for suicide ideation and attempt. Preventing the catabolism of NRF2 could be a strategy to obtain novel suicide-prophylactic medications. Possible candidates are minocycline and nicotinic-α7 agonists. The antibiotic minocycline indirectly activates NRF2-transcriptional activity, whereas the activation of nicotinic-α7 receptors indirectly inhibits GSK3.

His452Tyr polymorphism in the human 5-HT2A receptor affects clozapine-induced signaling networks revealed by quantitative phosphoproteomics

Antipsychotic drugs remain the current standard for schizophrenia treatment. Although they directly recognize the orthosteric binding site of numerous monoaminergic G protein-coupled receptors (GPCRs), these drugs, and particularly second-generation antipsychotics such as clozapine, all have in common a very high affinity for the serotonin 5-HT_2A receptor (5-HT_2AR). Using classical pharmacology and targeted signaling pathway assays, previous findings suggest that clozapine and other atypical antipsychotics behave principally as 5-HT_2AR neutral antagonists and/or inverse agonists. However, more recent findings showed that antipsychotics may also behave as pathway-specific agonists. Reversible phosphorylation is a common element in multiple signaling networks. Combining a quantitative phosphoproteomic method with signaling network analysis, we tested the effect of clozapine treatment on the overall level of protein phosphorylation and signal transduction cascades in vitro in mammalian cell lines induced to express either the human 5-HT_2AR or the H452Y variant of the gene encoding the 5-HT_2AR receptor. This naturally occurring variation within the 5-HT_2AR gene was selected because it has been repeatedly associated with schizophrenia patients who do not respond to clozapine treatment. Our data show that short time exposure (5 or 10 min) to clozapine (10^-5 M) led to phosphorylation of numerous signaling components of pathways involved in processes such as endocytosis, ErbB signaling, insulin signaling or estrogen signaling. Cells induced to express the H452Y variant showed a different basal phosphoproteome, with increases in the phosphorylation of mTOR signaling components as a translationally relevant example. However, the effect of clozapine on the functional landscape of the phosphoproteome was significantly reduced in cells expressing the 5-HT_2AR-H452Y construct. Together, these findings suggest that clozapine behaves as an agonist inducing phosphorylation of numerous pathways downstream of the 5-HT_2AR, and that the single nucleotide polymorphism encoding 5-HT_2AR-H452Y affects these clozapine-induced phosphorylation-dependent signaling networks.

Clozapine Induced Disturbances in Hepatic Glucose Metabolism: The Potential Role of PGRMC1 Signaling

Newly emerging evidence has implicated that progesterone receptor component 1 (PGRMC1) plays a novel role not only in the lipid disturbance induced by atypical antipsychotic drugs (AAPD) but also in the deterioration of glucose homoeostasis induced by clozapine (CLZ) treatment. The present study aimed to investigate the role of PGRMC1 signaling on hepatic gluconeogenesis and glycogenesis in male rats following CLZ treatment (20 mg/kg daily for 4 weeks). Recombinant adeno-associated viruses (AAV) were constructed for the knockdown or overexpression of hepatic PGRMC1. Meanwhile, AG205, the specific inhibitor of PGRMC1 was also used for functional validation of PGRMC1. Hepatic protein expressions were measured by western blotting. Meanwhile, plasma glucose, insulin and glucagon, HbA1c and hepatic glycogen were also determined by assay kits. Additionally, concentrations of progesterone (PROG) in plasma, liver and adrenal gland were measured by a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. Our study demonstrated that CLZ promoted the process of gluconeogenesis and repressed glycogenesis, respectively mediated by PI3K-Akt-FOXO1 and GSK3β signaling via inhibition of PGRMC1-EGFR/GLP1R in rat liver, along with an increase in fasting blood glucose, HbA1c levels and a decrease in insulin and hepatic glycogen levels. Furthermore, through PGRMC1-EGFR/GLP1R-PI3K-Akt pathway, knockdown or inhibition (by AG205) of PGRMC1 mimics, whereas its overexpression moderately alleviates CLZ-induced glucose disturbances. Potentially, the PGRMC1 target may be regarded as a novel therapeutic strategy for AAPD-induced hepatic glucose metabolism disorder.

Putative hormetic mechanisms and effects of atypical antipsychotic agents: Implications for study design and clinical psychopharmacotherapeutics

This paper addresses a novel putative mechanism by which atypical antipsychotic agents induce clinically significant neuroprotective effects that may be viable in the treatment of schizophrenia - and perhaps other neuropsychiatric disorders. Based upon experimental studies with multiple in vitro models (i.e., PC 12 cells, NSC-34 hybrid cells, SH-SY5Y cells, the immune cell line U-937) and several rodent in vivo models, six atypical antipsychotic drugs, within direct experimental comparisons and/or preconditioning protocol studies with six different stressor/toxic agents (i.e. rotenone, hydrogen peroxide, MPP+, serum withdrawal, beta-amyloid, and corticosterone) were demonstrated to induce neuroprotective effects with consistently hormetic dose response patterns. These findings suggest that some of the reported neuroprotective effects of atypical human antipsychotic agents are likely to be mediated by hormetic mechanisms. These findings may have important implications for both experimental study design and clinical therapeutics.

Oral quetiapine treatment results in time-dependent alterations of recognition memory and brain-derived neurotrophic factor-related signaling molecules in the hippocampus of rats

Antipsychotic drugs (APDs) have a variety of important therapeutic applications for neuropsychiatric disorders. However, they are routinely prescribed off-label across all age categories, a controversial practice given their potential for producing metabolic and extrapyramidal side effects. Evidence also suggests that chronic treatment with some APDs may lead to impairments in cognition and decreases in brain volume, although these findings are controversial. The purpose of the studies described here was to evaluate one of the most commonly prescribed APDs, quetiapine, for chronic effects on recognition memory, brain-derived neurotrophic factor (BDNF), its precursor proBDNF, as well as relevant downstream signaling molecules that are known to influence neuronal plasticity and cognition. Multiple cohorts of adult rats were treated with quetiapine (25.0 mg/kg/day) for 30 or 90 days in their drinking water then evaluated for drug effects on motor function in a catalepsy assessment, recognition memory in a spontaneous novel object recognition (NOR) task, and BDNF-related signaling molecules in the post mortem hippocampus via Western Blot. The results indicated that oral quetiapine at a dose that did not induce catalepsy, led to time-dependent impairments in NOR performance, increases in the proBDNF/BDNF ratio, and decreases in Akt and CREB phosphorylation in the hippocampus. These results indicate that chronic treatment with quetiapine has the potential to adversely affect recognition memory and neurotrophin-related signaling molecules that support synaptic plasticity and cognitive function. Given the widespread use this APD across multiple conditions and patient populations, such long-term effects observed in animals should be considered.

Decreases in ganglion cell layer and inner plexiform layer volumes correlate better with disease severity in schizophrenia patients than retinal nerve fiber layer thickness: Findings from spectral optic coherence tomography

Background

Optic coherence tomography (OCT) is a new, contactless and fast neuroimaging method. Previous studies have observed thinning of the retinal nerve fibre layer (RNFL) in many neurodegenerative diseases, and researchers have suggested that correlations exist between the thinning of the RNFL and the neurodegeneration detected with other imaging methods or the severity of illness. More recently, OCT has been used in patients with schizophrenia. RNFL thinning has also been detected in these patients. With more sophisticated devices, segmentation of the retina and measurements of the ganglion cell layer (GCL) and internal plexiform layer (IPL) can be performed.

Methods

We measured the RNFL thickness and the GCL and IPL volumes in 40 treatment refractory patients with schizophrenia, 41 treatment responsive refractory patients and 41 controls using spectral-OCT, and we evaluated the correlations between the disease severity and OCT measurements.

Results

The global RNFL thickness and GCL and IPL volumes were decreased in the patients with schizophrenia compared with the controls. In addition, the GCL and IPL volumes were lower in the treatment refractory patients with schizophrenia compared to the treatment responsive patients. Using parameters such as the Positive and Negative Syndrome Scale (PANSS) and Clinical Global Impression (CGI) scores, the disease duration and number of hospitalizations, correlations between the GCL and IPL volumes and disease severity were stronger than the correlations between the RNFL and the disease parameters.

Conclusion

Our findings suggest that OCT can be used to detect neurodegeneration in schizophrenia and that the GCL and IPL volumes can also be used to monitor the progression of neurodegeneration.

Clozapine Prevents Poly (I:C) Induced Inflammation by Modulating NLRP3 Pathway in Microglial Cells

Schizophrenia is a complex psychiatric disorder that exhibits an interconnection between the immune system and the brain. Experimental and clinical studies have suggested the presence of neuroinflammation in schizophrenia. In the present study, the effect of antipsychotic drugs, including clozapine, risperidone, and haloperidol (10, 20 and 20 μM, respectively), on the production of IL-1α, IL-1β, IL-2, IL-4, IL-5, IL-6, IL-10, IL-17, IL-18, INF-γ, and TNF-α was investigated in the unstimulated and polyriboinosinic-polyribocytidilic acid [poly (I:C)]-stimulated primary microglial cell cultures. In the unstimulated cultures, clozapine, risperidone, and haloperidol did not influence the cytokine levels. Nevertheless, in cell cultures under strong inflammatory activation by poly (I:C), clozapine reduced the levels of IL-1α, IL-1β, IL-2, and IL-17. Risperidone and haloperidol both reduced the levels of IL-1α, IL-1β, IL-2, and IL-17, and increased the levels of IL-6, IL-10, INF-γ, and TNF-α. Based on the results that were obtained with the antipsychotic drugs and observing that clozapine presented with a more significant anti-inflammatory effect, clozapine was selected for the subsequent experiments. We compared the profile of cytokine suppression obtained with the use of NLRP3 inflammasome inhibitor, CRID3 to that obtained with clozapine, to test our hypothesis that clozapine inhibits the NLRP3 inflammasome. Clozapine and CRID3 both reduced the IL-1α, IL-1β, IL-2, and IL-17 levels. Clozapine reduced the level of poly (I:C)-activated NLRP3 expression by 57%, which was higher than the reduction thay was seen with CRID3 treatment (45%). These results suggest that clozapine might exhibit anti-inflammatory effects by inhibiting NLRP3 inflammasome and this activity is not typical with the use of other antipsychotic drugs under the conditions of strong microglial activation.

Chronic oral treatment with risperidone impairs recognition memory and alters brain-derived neurotrophic factor and related signaling molecules in rats

Antipsychotic drugs (APDs) are essential for the treatment of schizophrenia and other neuropsychiatric illnesses such as bipolar disease. However, they are also extensively prescribed off-label for many other conditions, a practice that is controversial given their potential for long-term side effects. There is clinical and preclinical evidence that chronic treatment with some APDs may lead to impairments in cognition and decreases in brain volume, although the molecular mechanisms of these effects are unknown. The purpose of the rodent studies described here was to evaluate a commonly prescribed APD, risperidone, for chronic effects on recognition memory, brain-derived neurotrophic factor (BDNF), its precursor proBDNF, as well as relevant downstream signaling molecules that are known to influence neuronal plasticity and cognition. Multiple cohorts of adult rats were treated with risperidone (2.5 mg/kg/day) or vehicle (dilute acetic acid solution) in their drinking water for 30 or 90 days. Subjects were then evaluated for drug effects on recognition memory in a spontaneous novel object recognition task and protein levels of BDNF-related signaling molecules in the hippocampus and prefrontal cortex. The results indicated that depending on the treatment period, a therapeutically relevant daily dose of risperidone impaired recognition memory and increased the proBDNF/BDNF ratio in the hippocampus and prefrontal cortex. Risperidone treatment also led to a decrease in Akt and CREB phosphorylation in the prefrontal cortex. These results indicate that chronic treatment with a commonly prescribed APD, risperidone, has the potential to adversely affect recognition memory and neurotrophin-related signaling molecules that support synaptic plasticity and cognitive function.

Psychosocial Stress Induces Schizophrenia-Like Behavior in Mice With Reduced MMP-9 Activity

Understanding gene-environment interactions in the pathogenesis of schizophrenia remains a major research challenge. Matrix metalloproteinase-9 (MMP-9) has been previously implicated in the pathophysiology of schizophrenia. In the present study, adolescent Mmp-9 heterozygous mice, with a genetically lower level of MMP-9, were subjected to resident-intruder psychosocial stress for 3 weeks and then examined in behavioral tests that evaluated cognitive deficits and positive- and negative-like symptoms of schizophrenia. Cognitive and positive symptoms in unstressed Mmp-9 heterozygous mice were unaffected by stress exposure, whereas negative symptoms were manifested only after stress exposure. Interestingly, negative symptoms were ameliorated by treatment with the antipsychotic drug clozapine. We describe a novel gene × environment interaction mouse model of schizophrenia. Lower MMP-9 levels in the brain might be a risk factor for schizophrenia that, in combination with environmental factors (e.g., psychosocial stress), may evoke schizophrenia-like symptoms that are sensitive to antipsychotic treatment.

Comparative psychopharmacology of autism and psychotic-affective disorders suggests new targets for treatment

The first treatments showing effectiveness for some psychiatric disorders, such as lithium for bipolar disorder and chlorpromazine for schizophrenia, were discovered by accident. Currently, psychiatric drug design is seen as a scientific enterprise, limited though it remains by the complexity of brain development and function. Relatively few novel and effective drugs have, however, been developed for many years. The purpose of this article is to demonstrate how evolutionary biology can provide a useful framework for psychiatric drug development. The framework is based on a diametrical nature of autism, compared with psychotic-affective disorders (mainly schizophrenia, bipolar disorder and depression). This paradigm follows from two inferences: (i) risks and phenotypes of human psychiatric disorders derive from phenotypes that have evolved along the human lineage and (ii) biological variation is bidirectional (e.g. higher vs lower, faster vs slower, etc.), such that dysregulation of psychological traits varies in two opposite ways. In this context, the author review the evidence salient to the hypothesis that autism and psychotic-affective disorders represent diametrical disorders in terms of current, proposed and potential psychopharmacological treatments. Studies of brain-derived neurotrophic factor, the PI3K pathway, the NMDA receptor, kynurenic acid metabolism, agmatine metabolism, levels of the endocannabinoid anandamide, antidepressants, anticonvulsants, antipsychotics, and other treatments, demonstrate evidence of diametric effects in autism spectrum disorders and phenotypes compared with psychotic-affective disorders and phenotypes. These findings yield insights into treatment mechanisms and the development of new pharmacological therapies, as well as providing an explanation for the longstanding puzzle of antagonism between epilepsy and psychosis. Lay Summary: Consideration of autism and schizophrenia as caused by opposite alterations to brain development and function leads to novel suggestions for pharmacological treatments.

Clozapine-dependent inhibition of EGF/neuregulin receptor (ErbB) kinases

Clozapine is an antipsychotic agent prescribed to psychotic patients exhibiting tolerance and/or resistance to the conventional antipsychotic medications that mainly drive monoamine antagonism. As the pharmacological fundamentals of its unique antipsychotic profile have been unrevealed, here, we attempted to obtain hints at this question. Here, we found that clozapine directly acts on ErbB kinases to downregulate epidermal growth factor (EGF)/neuregulin signaling. In cultured cell lines and cortical neurons, EGF-triggered ErbB1 phosphorylation was diminished by 30 μM clozapine, but not haloperidol, risperidone, or olanzapine. The neuregulin-1-triggered ErbB4 phosphorylation was attenuated by 10 μM clozapine and 30 μM haloperidol. We assumed that clozapine may directly interact with the ErbB tyrosine kinases and affect their enzyme activity. To test this assumption, we performed in vitro kinase assays using recombinant truncated ErbB kinases. Clozapine (3-30 μM) significantly decreased the enzyme activity of the truncated ErbB1, B2, and B4 kinases. Acute in vivo administration of clozapine (20 mg/kg) to adult rats significantly suppressed the basal phosphorylation levels of ErbB4 in the brain, although we failed to detect effects on basal ErbB1 phosphorylation. Altogether with the previous findings that quinazoline inhibitors for ErbB kinases harbor antipsychotic potential in animal models for schizophrenia, our present observations suggest the possibility that the micromolar concentrations of clozapine can attenuate the activity of ErbB receptor kinases, which might illustrate a part of its unique antipsychotic psychopharmacology.

Brain insulin action: Implications for the treatment of schizophrenia

Insulin action in the central nervous system is a major regulator of energy balance and cognitive processes. The development of central insulin resistance is associated with alterations in dopaminergic reward systems and homeostatic signals affecting food intake, glucose metabolism, body weight and cognitive performance. Emerging evidence has highlighted a role for antipsychotics (APs) to modulate central insulin-mediated pathways. Although APs remain the cornerstone treatment for schizophrenia they are associated with severe metabolic complications and fail to address premorbid cognitive deficits, which characterize the disorder of schizophrenia. In this review, we first explore how the hypothesized association between schizophrenia and CNS insulin dysregulation aligns with the use of APs. We then investigate the proposed relationship between CNS insulin action and AP-mediated effects on metabolic homeostasis, and different domains of psychopathology, including cognition. We briefly discuss a potential role of CNS insulin signaling to explain the hypothesized, but somewhat controversial association between therapeutic efficacy and metabolic side effects of APs. Finally, we propose how this knowledge might inform novel treatment strategies to target difficult to treat domains of schizophrenia. This article is part of the issue entitled 'Special Issue on Antipsychotics'.

The role of striatum and prefrontal cortex in the prevention of amphetamine-induced schizophrenia-like effects mediated by nitric oxide compounds

Pharmacological manipulation of nitric oxide (NO) has been suggested as a promising treatment for schizophrenia symptoms. A single infusion of sodium nitroprusside, a NO donor with short half-life, was found to improve schizophrenia symptoms. However, an increasing number of preclinical studies have demonstrated the potential beneficial effects of both NO donors and inhibitors. We investigated the potential synergistic effect of sub-effective doses of the NO donor sodium nitroprusside or the NO inhibitor 7-Nitroindazole (7NI) combined with clozapine, a standard atypical antipsychotic, on counteracting amphetamine or MK-801-induced psychosis-like behaviors. The impact of sodium nitroprusside and 7NI on cAMP regulation in the prefrontal cortex and striatum was also evaluated. Confirming previous results, we found that both NO donors and inhibitors prevented amphetamine-induced effects (prepulse inhibition [PPI] disruption and hyperlocomotion). In addition, we observed a synergistic effect of sodium nitroprusside and clozapine on antagonizing the disruptive effects of amphetamine, but not MK-801, in the PPI test. The sub-effective dose of 7NI tested did not prevent amphetamine or MK-induced PPI effects when combined with clozapine. Interestingly, cAMP levels were significantly decreased in the prefrontal cortex after treatment with sodium nitroprusside. In the striatum, both sodium nitroprusside and 7NI blocked the amphetamine-induced increase of cAMP. Our data corroborate previous findings on the dopaminergic mechanisms involved in the action of sodium nitroprusside. It is likely that the differential effects of sodium nitroprusside are related to its ability to modify cAMP levels in the prefrontal cortex.

Increased platelet glycogen sysnthase kinase 3beta in first-episode psychosis

Past studies have linked intracellular pathways related to psychotic disorders to the GSK3B enzyme. This study aimed to investigate GSK3B protein expression and phosphorylation in drug-naïve first-episode psychosis patients (n=43) at baseline and following symptom remission, and in healthy controls (n=77). At baseline GSK3B total level was higher in patients (p<0.001). In schizophrenia spectrum patients (n=25) GSK3B total and phosphorylated levels were higher than in controls and patients with other non-affective psychotic disorders (n=18) (p<0.001; p=0.027; p=0.05 respectively). No enzyme changes were found after clinical remission. The implication of this finding for the biology of psychoses warrants further studies to clarify whether increased GSK3B may be useful as a biomarker for psychosis in general, and schizophrenia in particular.

Clozapine reduces Toll-like receptor 4/NF-κB-mediated inflammatory responses through inhibition of calcium/calmodulin-dependent Akt activation in microglia

Clozapine is an atypical antipsychotic agent used in the treatment of schizophrenia and severe mood disorders. Accumulating evidence suggests that neuroinflammation is closely associated with the pathogenesis of various neurodegenerative diseases and psychiatric disorders. Clozapine exerts anti-inflammatory activity. However, the molecular mechanism underlying the anti-inflammatory activity of clozapine is poorly understood. In this study, we found that clozapine suppressed lipopolysaccharide (LPS)-induced phosphorylation of IκBα at Ser-32 and of p65/RelA at Ser-468, as well as nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB)-dependent transcriptional activity in microglial cells. Clozapine downregulated LPS-induced Akt phosphorylation at Ser-473. Pharmacological Akt inhibitors ameliorated LPS-induced NF-κB activation. Removal of extracellular Ca²⁺ by EGTA or sequestration of intracellular Ca²⁺ by BAPTA-AM attenuated LPS-induced Akt phosphorylation. Treatment with calmodulin (CaM) antagonists and the CaM kinase inhibitor, KN-93, also prevented LPS-induced Akt and NF-κB activation, suggesting that Ca²⁺/CaM-dependent Akt activation is critical in LPS-induced NF-κB activation in microglia. These results suggest that clozapine exhibits anti-inflammatory activity through the inhibition of Ca²⁺/CaM/Akt-mediated NF-κB activation.

GSK3β negatively regulates TRAX, a scaffold protein implicated in mental disorders, for NHEJ-mediated DNA repair in neurons

Translin-associated protein X (TRAX) is a scaffold protein with various functions and has been associated with mental illnesses, including schizophrenia. We have previously demonstrated that TRAX interacts with a Gsα protein-coupled receptor, the A_2A adenosine receptor (A_2AR), and mediates the function of this receptor in neuritogenesis. In addition, stimulation of the A_2AR markedly ameliorates DNA damage evoked by elevated oxidative stress in neurons derived from induced pluripotent stem cells (iPSCs). Here, we report that glycogen synthase kinase 3 beta (GSK3β) and disrupted-in-schizophrenia 1 (DISC1) are two novel interacting proteins of TRAX. We present evidence to suggest that the stimulation of A_2AR markedly facilitated DNA repair through the TRAX/DISC1/GSK3β complex in a rat neuronal cell line (PC12), primary mouse neurons, and human medium spiny neurons derived from iPSCs. A_2AR stimulation led to the inhibition of GSK3β, thus dissociating the TRAX/DISC1/GSK3β complex and facilitating the non-homologous end-joining pathway (NHEJ) by enhancing the activation of a DNA-dependent protein kinase via phosphorylation at Thr²⁶⁰⁹. Similarly, pharmacological inhibition of GSK3β by SB216763 also facilitated the TRAX-mediated repair of oxidative DNA damage. Collectively, GSK3β binds with TRAX and negatively affects its ability to facilitate NHEJ repair. The suppression of GSK3β by A_2AR activation or a GSK3β inhibitor releases TRAX for the repair of oxidative DNA damage. Our findings shed new light on the molecular mechanisms underlying diseases associated with DNA damage and provides a novel target (i.e., the TRAX/DISC1/GSK3β complex) for future therapeutic development for mental disorders.

Amelioration of experimental autoimmune encephalomyelitis by clozapine is not associated with defective CD4 T cell responses

Atypical antipsychotic agents, such as clozapine, are used for treating psychosis and depression and have recently been found to modulate neuroinflammation. We have shown previously that treatment of mice with the atypical antipsychotic agents, clozapine or risperidone, attenuates disease severity in experimental autoimmune encephalomyelitis (EAE); however, the mechanism by which they are protective is unknown. In this study, we investigated the effects of clozapine on CD4⁺ T cell responses and found that clozapine did not significantly affect the expansion of myelin-specific T cells, their differentiation into pathogenic subsets, or their encephalitogenic capacity to induce EAE. Interestingly, although clozapine enhanced differentiation of regulatory T (Treg) cells, in vivo neutralization of Tregs indicated that Tregs were not responsible for the protective effects of clozapine during the induction and effector phase of EAE. Taken together, our studies indicate that clozapine does not mediate its protective effects by directly altering CD4 T cells.

Neurodevelopmental Perspectives on Wnt Signaling in Psychiatry

Mounting evidence indicates that Wnt signaling is relevant to pathophysiology of diverse mental illnesses including schizophrenia, bipolar disorder, and autism spectrum disorder. In the 35 years since Wnt ligands were first described, animal studies have richly explored how downstream Wnt signaling pathways affect an array of neurodevelopmental processes and how their disruption can lead to both neurological and behavioral phenotypes. Recently, human induced pluripotent stem cell (hiPSC) models have begun to contribute to this literature while pushing it in increasingly translational directions. Simultaneously, large-scale human genomic studies are providing evidence that sequence variation in Wnt signal pathway genes contributes to pathogenesis in several psychiatric disorders. This article reviews neurodevelopmental and postneurodevelopmental functions of Wnt signaling, highlighting mechanisms, whereby its disruption might contribute to psychiatric illness, and then reviews the most reliable recent genetic evidence supporting that mutations in Wnt pathway genes contribute to psychiatric illness. We are proponents of the notion that studies in animal and hiPSC models informed by the human genetic data combined with the deep knowledge base and tool kits generated over the last several decades of basic neurodevelopmental research will yield near-term tangible advances in neuropsychiatry.

Trace amine-associated receptor 1 activation silences GSK3β signaling of TAAR1 and D2R heteromers

Trace amine-associated receptor 1 (TAAR1) activation by selective endogenous agonists modulates dopaminergic neurotransmission. This results in antipsychotic-like behavior in vivo which might be initiated by an interaction of TAAR1 and dopamine D2L receptor (D2R). Here we analyzed the functional link between TAAR1 and D2R using highly potent and selective TAAR1 agonists, and newly generated tools such as TAAR1 knock-out and TAAR1 overexpressing rats as well as specific anti-rat TAAR1 antibodies. We provide data from co-immunoprecipitation experiments supporting a functional interaction of the two receptors in heterologous cells and in brain tissue. Interaction of TAAR1 with D2R altered the subcellular localization of TAAR1 and increased D2R agonist binding affinity. Using specific β-arrestin 2 (βArr2) complementation assays we show that the interaction of TAAR1 with D2R reduced βArr2 recruitment to D2R. In addition, we report that besides Gαs-protein signaling TAAR1 also signals via βArr2. In the presence of D2R, cAMP signaling of TAAR1 was reduced while its βArr2 signaling was enhanced, resulting in reduced GSK3β activation. These results demonstrate that βArr2 signaling may be an important pathway for TAAR1 function and that the activation of the TAAR1-D2R complex negatively modulates GSK3β signaling. Given that patients with schizophrenia or bipolar disorder show increased GSK3β signaling, such a reduction of GSK3β signaling triggered by the interaction of D2R with activated TAAR1 further supports TAAR1 as a target for the treatment of psychiatric disorders.

Unique Effects of Acute Aripiprazole Treatment on the Dopamine D2 Receptor Downstream cAMP-PKA and Akt-GSK3β Signalling Pathways in Rats

Aripiprazole is a wide-used antipsychotic drug with therapeutic effects on both positive and negative symptoms of schizophrenia, and reduced side-effects. Although aripiprazole was developed as a dopamine D₂ receptor (D₂R) partial agonist, all other D₂R partial agonists that aimed to mimic aripiprazole failed to exert therapeutic effects in clinic. The present in vivo study aimed to investigate the effects of aripiprazole on the D₂R downstream cAMP-PKA and Akt-GSK3β signalling pathways in comparison with a D₂R antagonist – haloperidol and a D₂R partial agonist – bifeprunox. Rats were injected once with aripiprazole (0.75mg/kg, i.p.), bifeprunox (0.8mg/kg, i.p.), haloperidol (0.1mg/kg, i.p.) or vehicle. Five brain regions – the prefrontal cortex (PFC), nucleus accumbens (NAc), caudate putamen (CPu), ventral tegmental area (VTA) and substantia nigra (SN) were collected. The protein levels of PKA, Akt and GSK3β were measured by Western Blotting; the cAMP levels were examined by ELISA tests. The results showed that aripiprazole presented similar acute effects on PKA expression to haloperidol, but not bifeprunox, in the CPU and VTA. Additionally, aripiprazole was able to increase the phosphorylation of GSK3β in the PFC, NAc, CPu and SN, respectively, which cannot be achieved by bifeprunox and haloperidol. These results suggested that acute treatment of aripiprazole had differential effects on the cAMP-PKA and Akt-GSK3β signalling pathways from haloperidol and bifeprunox in these brain areas. This study further indicated that, by comparison with bifeprunox, the unique pharmacological profile of aripiprazole may be attributed to the relatively lower intrinsic activity at D₂R.

The activation of the Akt/PKB signalling pathway in the brains of clozapine-exposed rats is linked to hyperinsulinemia and not a direct drug effect

The second generation antipsychotic drug clozapine is a much more effective therapy for schizophrenia than first generation compounds, but the reasons for this are poorly understood. We have previously shown that one distinguishing feature of clozapine is its ability to raise glucagon levels in animal models and thus causes prolonged hyperinsulinemia without inducing hypoglycaemia. Previous studies have provided evidence that defects in Akt/PKB and GSK3 signalling can contribute to development of psychiatric diseases. Clozapine is known to activate Akt/PKB in the brain, and some studies have indicated that this is due to a direct effect of the drug on the neurons. However, we provide strong evidence that elevated insulin levels induced by clozapine are in fact the real cause of the drug's effects on Akt/PKB and GSK3 in the brain. This suggests that the elevated levels of insulin induced by clozapine may contribute to this drug's therapeutic efficacy.

Potential molecular and cellular mechanism of psychotropic drugs

Psychiatric disorders are among the most debilitating of all medical illnesses. Whilst there are drugs that can be used to treat these disorders, they give sub-optimal recovery in many people and a significant number of individuals do not respond to any treatments and remain treatment resistant. Surprisingly, the mechanism by which psychotropic drugs cause their therapeutic benefits remain unknown but likely involves the underlying molecular pathways affected by the drugs. Hence, in this review, we have focused on recent findings on the molecular mechanism affected by antipsychotic, mood stabilizing and antidepressant drugs at the levels of epigenetics, intracellular signalling cascades and microRNAs. We posit that understanding these important interactions will result in a better understanding of how these drugs act which in turn may aid in considering how to develop drugs with better efficacy or increased therapeutic reach.

Redox-sensitive glycogen synthase kinase 3β-directed control of mitochondrial permeability transition: rheostatic regulation of acute kidney injury

Mitochondrial dysfunction plays a pivotal role in necroapoptotic cell death and in the development of acute kidney injury (AKI). Evidence suggests that glycogen synthase kinase (GSK) 3β resides at the nexus of multiple signaling pathways implicated in the regulation of mitochondrial permeability transition (MPT). In cultured renal tubular epithelial cells, a discrete pool of GSK3β was detected in mitochondria. Coimmunoprecipitation assay confirmed that GSK3β physically interacts with cyclophilin F and voltage-dependent anion channel (VDAC), key MPT regulators that possess multiple GSK3β phosphorylation consensus motifs, suggesting that GSK3β has a direct control of MPT. Upon a strong burst of reactive oxygen species elicited by the pro-oxidant herbicide paraquat, the activity of the redox-sensitive GSK3β was drastically enhanced. This was accompanied by augmented phosphorylation of cyclophilin F and VDAC, associated with MPT and cell death. Inhibition of GSK3β by either the selective inhibitor 4-Benzyl-2-methyl-1,2,4-thiadiazolidine-3,5-dione (TDZD-8) or forced expression of a kinase-dead mutant obliterated paraquat-induced phosphorylation of cyclophilin F and VDAC, prevented MPT, and improved cellular viability. Conversely, ectopic expression of a constitutively active GSK3β amplified the effect of paraquat on cyclophilin F and VDAC phosphorylation and sensitized cells to paraquat-induced MPT and death. In vivo, paraquat injection elicited marked oxidant stress in the kidney and resulted in acute kidney dysfunction and massive tubular apoptosis and necrosis. Consistent with in vitro findings, the activity of GSK3β was augmented in the kidney after paraquat injury, associated with increased phosphorylation of cyclophilin F and VDAC and sensitized MPT. TDZD-8 blocked GSK3β activity in the kidney, intercepted cyclophilin F and VDAC phosphorylation, prevented MPT, attenuated tubular cell death, and ameliorated paraquat-induced AKI. Our data suggest that the redox-sensitive GSK3β regulates renal tubular injury in AKI by controlling the activity of MPT regulators.

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.

Intracellular pathways of antipsychotic combined therapies: implication for psychiatric disorders treatment

Dysfunctions in the interplay among multiple neurotransmitter systems have been implicated in the wide range of behavioral, emotional and cognitive symptoms displayed by major psychiatric disorders, such as schizophrenia, bipolar disorder or major depression. The complex clinical presentation of these pathologies often needs the use of multiple pharmacological treatments, in particular (1) when monotherapy provides insufficient improvement of the core symptoms; (2) when there are concurrent additional symptoms requiring more than one class of medication and (3) in order to improve tolerability, by using two compounds below their individual dose thresholds to limit side effects. To date, the choice of drug combinations is based on empirical paradigm guided by clinical response. Nonetheless, several preclinical studies have demonstrated that drugs commonly used to treat psychiatric disorders may impact common intracellular target molecules (e.g. Akt/GSK-3 pathway, MAP kinases pathway, postsynaptic density proteins). These findings support the hypothesis that convergence at crucial steps of transductional pathways could be responsible for synergistic effects obtained in clinical practice by the co-administration of those apparently heterogeneous pharmacological compounds. Here we review the most recent evidence on the molecular crossroads in antipsychotic combined therapies with antidepressants, mood stabilizers, and benzodiazepines, as well as with antipsychotics. We first discuss clinical clues and efficacy of such combinations. Then we focus on the pharmacodynamics and on the intracellular pathways underpinning the synergistic, or concurrent, effects of each therapeutic add-on strategy, as well as we also critically appraise how pharmacological research may provide new insights on the putative molecular mechanisms underlying major psychiatric disorders.

Altered Wnt signalling in the teenage suicide brain: focus on glycogen synthase kinase-3β and β-catenin

Glycogen synthase kinase (GSK)-3β and β-catenin are important components of the Wnt signalling pathway, which is involved in numerous physiological functions such as cognition, brain development and cell survival. Their abnormalities have been implicated in mood disorders and schizophrenia. Teenage suicide is a major public health concern; however, very little is known about its neurobiology. In order to examine if abnormalities of GSK-3β and β-catenin are associated with teenage suicide, we determined the gene and protein expression of GSK-3β and β-catenin in the prefrontal cortex (PFC) and hippocampus obtained from 24 teenage suicide victims and 24 normal control subjects. Protein expression was determined using Western blot with specific antibodies and gene expression (mRNA levels) was determined using the real-time polymerase chain reaction method. No significant change was observed in the GSK-3β protein levels either in the PFC or hippocampus of suicide victims compared to controls. However, protein levels of pGSK-3β-ser(9) were significantly decreased in the PFC and hippocampus of suicide victims compared to normal controls. We also found that GSK-3β mRNA levels were significantly decreased in the PFC but not in the hippocampus of teenage suicide victims compared to controls. Mean protein and mRNA levels of β-catenin were significantly decreased in both the PFC and hippocampus of teenage suicide group compared to controls. The observation that there is a decrease in β-catenin and pGSK-3β-ser(9) in the PFC and hippocampus of teenage suicide victims does indicate a disturbance in the Wnt signalling pathway in teenage suicide.

The AKT1 gene is associated with attention and brain morphology in schizophrenia

OBJECTIVES

A meta-analysis of the associations between genetic variants in the AKT1 gene and schizophrenia found that a single nucleotide polymorphism (SNP5; rs2494732) was associated with schizophrenia in Asian populations.

METHODS

In this study, we investigated the effects of this SNP on memory and attentional performance and brain structure using magnetic resonance imaging in a Japanese population (117 patients with schizophrenia and 189 healthy subjects).

RESULTS

The memory performance, particularly attention/concentration score, measured by the Wechsler Memory Scale-Revised in A carriers of SNP5, which was found to be enriched in patients with schizophrenia, was lower than that in individuals with the G/G genotype. We confirmed the association of the SNP with attentional performance using the Continuous Performance Test, which assessed sustained attention and vigilance of attentional function. Patients with A allele demonstrated lower attentional performance than patients with the G/G genotype. Patients with the A allele had smaller gray matter volumes in the right inferior parietal lobule related to attentional processes and in the frontostriatal region related to different SNPs in AKT1 than patients with the G/G genotype.

CONCLUSIONS

Our results suggest that a genetic variant of AKT1 might be associated with attentional deficits and brain morphological vulnerability in patients with schizophrenia.

Examination of methylphenidate-mediated behavior regulation by glycogen synthase kinase-3 in mice

Abnormalities in dopaminergic activity have been implicated in psychiatric diseases, such as attention deficit hyperactivity disorder (ADHD), and are treated with therapeutic stimulants, commonly methylphenidate or amphetamine. Amphetamine administration increases glycogen synthase kinase-3 (GSK3) activation, which is necessary for certain acute behavioral responses to amphetamine, including increased locomotor activity and impaired sensorimotor gating. Here, we tested if modulating GSK3 by administration of the GSK3 inhibitor lithium or expression of constitutively active GSK3 altered behavioral responses to methylphenidate administered to mice acutely or daily for 8 days. Methylphenidate or amphetamine was administered to mice intraperitoneally for 1 or 8 days. Open-field activity and pre-pulse inhibition (PPI) were measured. In contrast to lithium's blockade of acute amphetamine-induced locomotor hyperactivity, lithium treatment did not significantly reduce methylphenidate-induced locomotor hyperactivity in wild-type mice after acute or 8 days of repeated methylphenidate administration. Lithium treatment significantly increased the impairment in PPI caused by methylphenidate, but significantly reduced the amphetamine-induced PPI deficit. In GSK3 knockin mice, expression of constitutively active GSK3β, but not GSK3α, significantly increased locomotor hyperactivity after acute methylphenidate treatment, and significantly impaired PPI, preventing further methylphenidate-induced impairment of PPI that was evident in wild-type mice and GSK3α knockin mice. Lithium does not counteract locomotor activity and PPI responses to methylphenidate as it does these responses to amphetamine, indicating that different mechanisms mediate these behavioral responses to methylphenidate and amphetamine. Only active GSK3β, not GSK3α, modulates behavioral responses to MPH, indicating selectivity in the actions of GSK3 isoforms.

The wnt pathway in mood disorders

OBJECTIVES

To review the evidence of the involvement of the Wnt signalling pathway in mood disorders and in the action of drugs used to treat these disorders.

METHODS

We performed a careful PubMed search using as keywords all possible terms relevant to the Wnt pathway and crossing them with each of four areas, i.e., developmental effects, behavioural effects, mood disorders, and drugs used in their treatment. Papers were selected on the basis of their content and their data used for discussion.

RESULTS

Neurodevelopmental and behavioural data point to the possibility of involvement of the Wnt pathway in the pathophysiology of mood disorders. Clinical and post-mortem data are not sufficient to corroborate a definite role for Wnt alterations in any mood disorder. Combining genetic and pharmacological data, we may state that glycogen synthase kinase is the key molecule in bipolar disorder, as it is connected with many other signalling pathways that were shown to be involved in mood disorders, while Wnt molecules in the hippocampus appear to be mainly involved in depressive disorders.

CONCLUSIONS

Altered Wnt signalling may play a role in the pathophysiology of mood disorders, although not a central one. It is premature to draw conclusions regarding the possible usefulness of Wnt manipulations in the treatment of mood disorders.

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.

The possible role of the Akt signaling pathway in schizophrenia

Serine/threonine protein kinase v-akt murine thymoma viral oncogene homolog (Akt) is one of the survival kinases with multiple biological functions in the brain and throughout the body. Schizophrenia is one of the most devastating psychiatric disorders. Accumulating evidence has indicated the involvement of the Akt signaling pathway in the pathogenesis of this disorder. Genetic linkage and association studies have identified Akt-1 as a candidate susceptibility gene related for schizophrenia. The level of Akt-1 protein and its kinase activity decreased significantly both in white blood cells from schizophrenic patients and in postmortem brain tissue of schizophrenic patients. Consistent with these findings, alterations in the upstream and downstream pathways of Akt have also been found in many psychiatric disorders. Furthermore, both typical and atypical antipsychotic drugs modify the Akt signaling pathway in a variety of conditions relative to schizophrenia. In addition as a survival kinase, Akt participates in neurodevelopment, synaptic plasticity, protein synthesis and neurotransmission in the central nervous system. It is thought that reduced activity of phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway could at least partially explain the cognitive impairment, synaptic morphologic abnormality, neuronal atrophy and dysfunction of neurotransmitter signaling in schizophrenia. In addition, reduced levels of Akt may increase the effects of risk factors on neurodevelopment, attenuate the effects of growth factors on neurodevelopment and reduce the response of patients to antipsychotic agents. More recently, the role of Akt signaling in the functions of schizophrenia susceptibility genes such as disrupted-in-schizophrenia 1 (DISC-1), neuregulin-1 (NRG-1) and dysbindin-1 has been reported. Thus, Akt deficiency may create a context permissive for the expression of risk-gene effects in neuronal morphology and function. This paper reviews the role of Akt in the pathophysiology of schizophrenia and as a potential therapeutic strategy targeting Akt.

Type I interferons impair BDNF-induced cell signaling and neurotrophic activity in differentiated human SH-SY5Y neuroblastoma cells and mouse primary cortical neurons

Type I interferons (IFNs) have been shown to act on neurons and to cause neuronal damage through mechanisms not completely defined. Here, we investigated the effects of type I IFNs on brain-derived neurotrophic factor (BDNF)-induced TrkB receptor signaling and neurotrophic activity. In retinoic acid-treated human SH-SY5Y neuroblastoma cells and mouse primary cortical neurons, long-term exposure to IFNs curtailed BDNF-induced activation of phosphatidylinositol 3-kinase, phospholipase Cγ and extracellular-regulated kinases 1 and 2 signaling. Moreover, IFN-β inhibited BDNF-induced cell survival, neurite outgrowth, and expression of neuronal markers, such as neurofilament proteins, growth-associated protein-43 and glutamate α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor subunit GluR1. The IFN inhibitory effects were associated with down-regulation of TrkB and inhibition of TrkB autophosphorylation. In SH-SY5Y cells, blockade of either Janus kinase with pyridone 6 or signal transducer and activator of transcription (STAT) 1 with siRNA transfection attenuated IFN-β-induced TrkB down-regulation. Quantitative real time RT-PCR indicated that IFN-β significantly reduced TrkB mRNA levels. Moreover, blockade of protein kinase R counteracted IFN-β-induced inhibition of TrkB expression and signaling. These data indicate that in neuronal cells IFNs negatively regulate BDNF signaling and neurotrophic activity through inhibition of TrkB activation and Janus kinase/Signal transducer and activator of transcription-dependent down-regulation of TrkB.

Clozapine impairs insulin action by up-regulating Akt phosphorylation and Ped/Pea-15 protein abundance

Clinical and experimental evidence indicates that atypical antipsychotics impair glucose metabolism. We investigated whether clozapine may directly affect insulin action by analyzing insulin signaling in vitro and in vivo. Clozapine reduced insulin-stimulated glucose uptake in PC12 and in L6 cells, representative models of neuron and skeletal muscle, respectively. Consistently, clozapine reduced insulin effect on insulin receptor (IR) by 40% and on IR substrate-1 (IRS1) tyrosine phosphorylation by 60%. Insulin-stimulated Akt phosphorylation was also reduced by about 40%. Moreover, insulin-dependent phosphorylation of protein kinase C-ζ (PKC-ζ) was completely blunted in clozapine-treated cells. Interestingly, clozapine treatment was accompanied by an insulin-independent increase of Akt phosphorylation, with no change of IR, IRS1, and PKC-ζ basal phosphorylation. The cellular abundance of Ped/Pea-15, an Akt substrate and inducer of insulin resistance, was also increased following clozapine exposure, both in the absence and in the presence of cyclohexymide, a protein synthesis inhibitor. Similar as in cellular models, in the caudate-putamen and in the tibialis muscle of clozapine-treated C57/BL/KsJ mice, Akt phosphorylation and Ped/Pea-15 protein levels were increased and PKC-ζ phosphorylation was decreased. Thus, in these experimental models, clozapine deranged Akt function and up-regulated Ped/Pea-15, thereby inhibiting insulin stimulation of PKC-ζ and of glucose uptake.

Genetic overlap between schizophrenia and bipolar disorder: a study with AKT1 gene variants and clinical phenotypes

INTRODUCTION

A number of epidemiological and genetic studies suggests an overlap of Schizophrenia and Bipolar disorder across the traditional binary classification. AKT1 gene variants were previously shown to be associated with schizophrenia. In this study, our aim was to determine whether AKT1 gene variants are associated with particular phenotypes for schizophrenia (SCZ) and bipolar disorder (BPD).

METHODS

This study included 529 subjects of European ancestry: 364 patients suffering from SCZ, BPD or schizoaffective disorder and 165 healthy controls. BPD patients were additionally subdivided into two groups: BPD with or without psychosis. Six AKT1 variants were assessed in a case-control study and allelic associations were analyzed. Moreover, meta-analyses were performed for those variants found in case-control studies of schizophrenia and schizoaffective disorder.

RESULTS

Nominal associations were found for three AKT1 gene variants, namely rs3803300, rs2494732 and rs2498804, in the four phenotypes. Two SNP survived Bonferroni corrections for multiple testing: rs3803300 (p<0.001) and rs2498804 (p<0.03) in group 1 (BPD without psychosis). In group 2 (BPD with psychosis) and in group 4 (SCZ), rs3803300 was significant but did not survive multiple testing. While rs2494732 was associated with the presence of psychosis (group-2, 3 and 4), rs2498804 was associated with affective symptoms (groups-1, 2 and 3). One meta-analysis found a significant level of association between rs3803300 and schizophrenia in Asian subjects.

CONCLUSION

AKT1 gene variations appeared to impact the risk for a class of psychiatric symptoms, comprising SCZ and BPD. Our findings support the view that AKT1 genetic variants are shared by both BPD and SCZ.

Clozapine protects dopaminergic neurons from inflammation-induced damage by inhibiting microglial overactivation

Increasing evidence suggests a possible involvement of neuroinflammation in some psychiatric disorders, and also pharmacological reports indicate that anti-inflammatory effects are associated with therapeutic actions of psychoactive drugs, such as anti-depressants and antipsychotics. The purpose of this study was to explore whether clozapine, a widely used antipsychotic drugs, displays anti-inflammatory and neuroprotective effects. Using primary cortical and mesencephalic neuron-glia cultures, we found that clozapine was protective against inflammation-related neurodegeneration induced by lipopolysaccharide (LPS). Pretreatment of cortical or mesencephalic neuron-glia cultures with clozapine (0.1 or 1 μM) for 24 h attenuated LPS-induced neurotoxicity. Clozapine also protected neurons against 1-methyl-4-phenylpyridinium(+) (MPP(+))-induced neurotoxicity, but only in cultures containing microglia, indicating an indispensable role of microglia in clozapine-afforded neuroprotection. Further observation revealed attenuated LPS-induced microglial activation in primary neuron-glia cultures and in HAPI microglial cell line with clozapine pretreatment. Clozapine ameliorated the production of microglia-derived superoxide and intracellular reactive oxygen species (ROS), as well as the production of nitric oxide and TNF-α following LPS. In addition, the protective effect of clozapine was not observed in neuron-glia cultures from mice lacking functional NADPH oxidase (PHOX), a key enzyme for superoxide production in immune cells. Further mechanistic studies demonstrated that clozapine pretreatment inhibited LPS-induced translocation of cytosolic subunit p47(phox) to the membrane in microglia, which was most likely through inhibiting the phosphoinositide 3-kinase (PI3K) pathway. Taken together, this study demonstrates that clozapine exerts neuroprotective effect via the attenuation of microglia activation through inhibition of PHOX-generated ROS production and suggests potential use of antipsychotic drugs for neuroprotection.

Neurotoxic/neuroprotective activity of haloperidol, risperidone and paliperidone in neuroblastoma cells

The neurotoxicity of antipsychotic (AP) drugs seems to be linked with neurological side effects like extrapyramidal symptoms (EPS). On the other hand, neuroprotective effects can mitigate or slow the progressive degenerative structural changes in the brain leading to improved outcome of schizophrenia. First and second-generation antipsychotics may differ in their neurotoxic and neuroprotective properties. The aim of this study was to compare the neurotoxic/neuroprotective activity of haloperidol, a first-generation antipsychotic, and risperidone, a second-generation one, with paliperidone, a relatively new second-generation antipsychotic, in SK-N-SH cells. Haloperidol, risperidone and paliperidone (10, 50, 100 μM) were administered, either alone or in combination with dopamine (100 μM), to human neuroblastoma SK-N-SH. We examined the effects of the drugs on cell viability (measured by alamarBlue®), caspase-3 activity (measured by fluorimetric assay) and cell death (by measuring the externalization of phosphatidylserine). Haloperidol significantly decreased cell viability and increased caspase-3 activity and cell death. Risperidone and paliperidone did not affect cell viability or cell death. Both second-generation APs decreased caspase-3 activity, especially paliperidone. In cells treated with dopamine in combination with antipsychotics, only paliperidone (10 μM) induced a slight improvement in cell viability. While haloperidol potentiated the dopamine-induced increase in caspase-3 activity, risperidone and paliperidone reduced this effect. The results indicate that haloperidol induces apoptosis, whereas risperidone and paliperidone may afford protection against it. Of the APs tested, paliperidone always showed the strongest neuroprotective effect. The different antipsychotic effects on survival and cell death might be related to differences in their capacity to induce EPS.

DISC1 Pathway in Brain Development: Exploring Therapeutic Targets for Major Psychiatric Disorders

Genetic risk factors for major psychiatric disorders play key roles in neurodevelopment. Thus, exploring the molecular pathways of risk genes is important not only for understanding the molecular mechanisms underlying brain development, but also to decipher how genetic disturbances affect brain maturation and functioning relevant to major mental illnesses. During the last decade, there has been significant progress in determining the mechanisms whereby risk genes impact brain development. Nonetheless, given that the majority of psychiatric disorders have etiological complexities encompassing multiple risk genes and environmental factors, the biological mechanisms of these diseases remain poorly understood. How can we move forward to our research for discovery of the biological markers and novel therapeutic targets for major mental disorders? Here we review recent progress in the neurobiology of disrupted in schizophrenia 1 (DISC1), a major risk gene for major mental disorders, with a particular focus on its roles in cerebral cortex development. Convergent findings implicate DISC1 as part of a large, multi-step pathway implicated in various cellular processes and signal transduction. We discuss links between the DISC1 pathway and environmental factors, such as immune/inflammatory responses, which may suggest novel therapeutic targets. Existing treatments for major mental disorders are hampered by a limited number of pharmacological targets. Consequently, elucidation of the DISC1 pathway, and its association with neuropsychiatric disorders, may offer hope for novel treatment interventions.

GSK-3: Functional Insights from Cell Biology and Animal Models

Glycogen synthase kinase-3 (GSK-3) is a widely expressed and highly conserved serine/threonine protein kinase encoded in mammals by two genes that generate two related proteins: GSK-3α and GSK-3β. GSK-3 is active in cells under resting conditions and is primarily regulated through inhibition or diversion of its activity. While GSK-3 is one of the few protein kinases that can be inactivated by phosphorylation, the mechanisms of GSK-3 regulation are more varied and not fully understood. Precise control appears to be achieved by a combination of phosphorylation, localization, and sequestration by a number of GSK-3-binding proteins. GSK-3 lies downstream of several major signaling pathways including the phosphatidylinositol 3′ kinase pathway, the Wnt pathway, Hedgehog signaling and Notch. Specific pools of GSK-3, which differ in intracellular localization, binding partner affinity, and relative amount are differentially sensitized to several distinct signaling pathways and these sequestration mechanisms contribute to pathway insulation and signal specificity. Dysregulation of signaling pathways involving GSK-3 is associated with the pathogenesis of numerous neurological and psychiatric disorders and there are data suggesting GSK-3 isoform-selective roles in several of these. Here, we review the current knowledge of GSK-3 regulation and targets and discuss the various animal models that have been employed to dissect the functions of GSK-3 in brain development and function through the use of conventional or conditional knockout mice as well as transgenic mice. These studies have revealed fundamental roles for these protein kinases in memory, behavior, and neuronal fate determination and provide insights into possible therapeutic interventions.

DISC1: Structure, Function, and Therapeutic Potential for Major Mental Illness

Disrupted in schizophrenia 1 (DISC1) is well established as a genetic risk factor across a spectrum of psychiatric disorders, a role supported by a growing body of biological studies, making the DISC1 protein interaction network an attractive therapeutic target. By contrast, there is a relative deficit of structural information to relate to the myriad biological functions of DISC1. Here, we critically appraise the available bioinformatics and biochemical analyses on DISC1 and key interacting proteins, and integrate this with the genetic and biological data. We review, analyze, and make predictions regarding the secondary structure and propensity for disordered regions within DISC1, its protein-interaction domains, subcellular localization motifs, and the structural and functional implications of common and ultrarare DISC1 variants associated with major mental illness. We discuss signaling pathways of high pharmacological potential wherein DISC1 participates, including those involving phosphodiesterase 4 (PDE4) and glycogen synthase kinase 3 (GSK3). These predictions and priority areas can inform future research in the translational and potentially guide the therapeutic processes.

G-Protein-Coupled Receptor-Mediated MAPK and PI3-Kinase Signaling Is Maintained in Chinese Hamster Ovary Cells after γ-Irradiation

To expedite G-protein-coupled receptor (GPCR) drug screening studies, cell lines amenable to transfection (e.g. CHO cells) have been widely used as cellular models. These cells can be frozen in a ready-to-use format, allowing screening of a single batch of cells and validation of the cellular material prior to the screening run. A common method used to deliver frozen cells to screening programs is to γ-irradiate the cells, abrogating cell division after thawing and ensuring consistency in the number of cells analyzed per well. With the recognition that signaling proteins such as ERK and Akt are important markers of GPCR activation, along with the availability of suitable assays for their measurement, these outputs have become important for GPCR screening programs. Here we show that several γ-irradiated and frozen CHO-K1 cell lines expressing transfected GPCRs, initially optimized for performing cAMP or AequoScreen calcium flux assays, can be used for the measurement of GPCR-mediated ERK and Akt phosphorylation. Furthermore, CHO-K1 cells transfected with NOP or GAL1 receptors show pharmacology for a number of agonists and antagonists that is consistent with non-irradiated cultured lines. These data indicate that γ-irradiated CHO-K1 cells can be reliably used for the measurement of GPCR-mediated kinase signaling outputs.

Antipsychotic drugs suppress the AKT/NF-κB pathway and regulate the differentiation of T-cell subsets

Antipsychotic drugs (APDs) are commonly used to ease the symptoms of schizophrenia; however, these same drugs also have an effect on the human immune system. Our previous studies have shown that risperidone and clozapine effectively decrease the production of IFN-γ for CD4(+) T-cells in PBMC. In contrast, haloperidol causes an increase in the production of IFN-γ for CD4(+) T-cells in PBMC. In this study we show that risperidone and clozapine can reduce Th1 cell differentiation and T-bet expression. The differentiation of Th1 cells was reduced in clozapine or risperidone treated PBMC by inhibiting the phosphorylation of AKT but not STAT-4. Typical APD, haloperidol, had the opposite effect in regulating T cell differentiation when compared with atypical APDs including risperidone and clozapine. Haloperidol decreased the expression of GATA-3, a Th2-related transcription factor, by inhibiting NF-κB activation rather than STAT-6 phosphorylation and thus decreased Th2 differentiation. In addition, chronic risperidone and clozapine treatment reduces the IFN-γ producing CD4(+) T-cell population within PBMC. In conclusion, this study suggests that APDs do indeed regulate the body's immune response and therefore all APDs should have their own patent in regulating immune responses.