The role of Akt-GSK-3beta signaling and synaptic strength in phencyclidine-induced neurodegeneration

Progress in The Research of Lactate Metabolism Disruption And Astrocyte-Neuron Lactate Shuttle Impairment in Schizophrenia: A Comprehensive Review

Schizophrenia (SCZ) is a complex neuropsychiatric disorder widely recognized for its impaired bioenergy utilization. The astrocyte-neuron lactate shuttle (ANLS) plays a critical role in brain energy supply. Recent studies have revealed abnormal lactate metabolism in SCZ, which is associated with mitochondrial dysfunction, tissue hypoxia, gastric acid retention, oxidative stress, neuroinflammation, abnormal brain iron metabolism, cerebral white matter hypermetabolic activity, and genetic susceptibility. Furthermore, astrocytes, neurons, and glutamate abnormalities are prevalent in SCZ with abnormal lactate metabolism, which are essential components for maintaining ANLS in the brain. Therefore, an in-depth study of the pathophysiological mechanisms of ANLS in SCZ with abnormal lactate metabolism will contribute to a better understanding of the pathogenesis of SCZ and provide new ideas and approaches for the diagnosis and treatment of SCZ.

Particulate matter (PM10) exacerbates on MK-801-induced schizophrenia-like behaviors through the inhibition of ERK-CREB-BDNF signaling pathway

Particulate matter (PM), released into the air by a variety of natural and human activities, is a key indicator of air pollution. Although PM is known as the extensive health hazard to affect a variety of illness, few studies have specifically investigated the effects of PM10 exposure on schizophrenic development. In the present study, we aimed to investigate the impact of PM10 on MK-801, N-methyl-D-aspartate (NMDA) receptor antagonist, induced schizophrenia-like behaviors in C57BL/6 mouse. Preadolescent mice were exposed PM10 to 3.2 mg/m3 concentration for 4 h/day for 2 weeks through a compartmentalized whole-body inhalation chamber. After PM10 exposure, we conducted behavioral tests during adolescence and adulthood to investigate longitudinal development of schizophrenia. We found that PM10 exacerbated schizophrenia-like behavior, such as psychomotor agitation, social interaction deficits and cognitive deficits at adulthood in MK-801-induced schizophrenia animal model. Furthermore, the reduced expression levels of brain-derived neurotrophic factor (BDNF) and the phosphorylation of BDNF related signaling molecules, extracellular signal-regulated kinase (ERK) and cAMP response element-binding protein (CREB), were exacerbated by PM10 exposure in the adult hippocampus of MK-801-treated mice. Thus, our present study demonstrates that exposure to PM10 in preadolescence exacerbates the cognitive impairment in animal model of schizophrenia, which are considered to be facilitated by the decreased level of BDNF through reduced ERK-CREB expression.

ACTN1 promotes HNSCC tumorigenesis and cisplatin resistance by enhancing MYH9-dependent degradation of GSK-3β and integrin β1-mediated phosphorylation of FAK

BACKGROUND

Head and neck squamous cell carcinoma (HNSCC) is one of the most common malignant tumors globally. Understanding the molecular basis of tumor progression and drug resistance can offer innovative strategies to enhance clinical outcomes for HNSCC patients.

METHODS

The cytoskeletal remodeling genes associated with cisplatin resistance were screened using a PCR array. The role of alpha-actinin 1 (ACTN1) in modulating cisplatin resistance and tumorigenesis in HNSCC was evaluated both in vitro and in vivo. Co-immunoprecipitation (Co-IP), IP-mass spectrometry (MS), western blotting, dual-luciferase assay, and bioinformatics analysis were performed to elucidate the underlying mechanisms involved.

RESULTS

Our study identifies ACTN1 as a crucial contributor to cisplatin resistance and tumorigenesis in HNSCC, as evidenced across cellular, animal, and patient-derived xenograft models. From a clinical perspective, overexpression of ACTN1 significantly correlates with a suboptimal response to neoadjuvant chemotherapy and reduced overall survival in HNSCC patients. Mechanistically, ACTN1 predominantly activates β-catenin-mediated signaling by promoting the interaction between myosin heavy chain 9 (MYH9) and GSK-3β, leading to the ubiquitin-dependent degradation of GSK-3β. ACTN1 also interacts with integrin β1, subsequently activating the FAK/PI3K/AKT pathway, providing an additional avenue for the activation of β-catenin signaling. Our study also unveils that the β-catenin/c-Myc axis transcriptionally regulates ACTN1, thereby creating a positive feedback loop promoting HNSCC tumorigenesis and drug resistance.

CONCLUSIONS

These insights underscore the novel mechanisms that highlight ACTN1's pivotal role in driving HNSCC progression and resistance to chemotherapy, suggesting ACTN1 as a promising therapeutic target in HNSCC management.

Alfaxalone Alleviates Neurotoxicity and Cognitive Impairment Induced by Isoflurane Anesthesia in Offspring Rats

BACKGROUND

The anesthetic isoflurane can cause neurotoxicity in fetuses and offspring of rats, affecting their neurodevelopment. However, the underlying mechanisms and therapeutic targets of isoflurane-induced neurotoxicity remain to be identified. Alfaxalone (ALF) is a steroid anesthetic. Steroids have been reported to have neuroprotective effects. This study aimed to investigate whether ALF could alleviate the isoflurane-induced neurotoxicity in fetuses and offspring of rats.

METHODS

On gestation day 15 (G15), the pregnant SD rats were randomly assigned to 4 groups: control 1 (CTL1) + control 2 (CTL2), isoflurane (ISO) + CTL2, CTL1 + ALF, and ISO + ALF. To analyze the changes in the expression levels of inflammatory cytokines, apoptotic factors, and synaptophysin, the brain tissues from the G15 fetuses and offspring at postnatal day 7 (P7), postnatal day 14 (P14), and postnatal day 31 (P31) were collected. The newborn neurons in the rats' offspring at P7, P14, and P31 were counted using immunofluorescence techniques. The Morris water maze (MWM) test was performed to assess the learning and memory abilities of P31 offspring rats.

RESULTS

ALF significantly alleviated the isoflurane-induced increase in the expression levels of inflammatory cytokines and apoptotic factors, such as interleukin (IL)-6 (ISO + CTL2 versus ISO + ALF: 5.133 ± 0.739 versus 1.093 ± 0.213, P < .001) and Caspase-3 (6.457 ± 0.6 versus 1.062 ± 0.1, P < .001) in the G15 fetuses. In P31 offspring rats, the expression levels of synaptophysin (0.719 ± 0.04 versus 1.068 ± 0.072, P < .001) and the number of newborn neurons in the dentate gyrus of the hippocampus were significantly lower in the ISO + CTL2 group as compared to those in the ISO + ALF group (118 ± 6 versus 140 ± 7, P < .001). These changes also occurred in the rat offspring at P7 and P14. In the MWM test, the escape latency of CTL1 + ALF group rats was significantly lower than that of ISO + ALF group rats (41 ± 6 versus 31 ± 7, P < .001) at P31.

CONCLUSIONS

Based on these findings, this study suggested that isoflurane exposure during pregnancy in rats could cause neuroinflammation and death of embryos as well as impairment of cognitive function in the offspring rats. ALF can be used to counteract the negative effects of isoflurane.

Tetramethylpyrazine protects neural stem cells against sevoflurane-induced toxicity through Akt/GSK-3β pathway

Sevoflurane, a commonly used anesthetic, has been found to cause neural stem cell (NSC) injury, thereby contributing to neurocognitive impairment following general anesthesia. Tetramethylpyrazine (TMP), one of the most widely used medicinal compounds isolated from a traditional Chinese herb, possess neuroprotective activity. However, its effect on sevoflurane-induced NSC injury remains unclear. NSCs were pretreated with indicated concentrations of TMP for 2 h and then exposed to sevoflurane for 6 h. Cell injury was measured using lactate dehydrogenase (LDH) release assay. Cell viability and proliferation were detected by cell counting kit-8 (CCK-8) assay and 5-bromo-2'-deoxyuridine (BrdU) labeling, respectively. Apoptotic cells were detected using terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. The levels of cleaved caspase-3, phosphorylated protein kinase B (Akt) and phosphorylated glycogen synthase kinase-3β (GSK-3β) were detected by western blotting. Our results showed exposure to sevoflurane decreased the viability and proliferation of NSCs, while TMP preserved NSC viability and proliferation after sevoflurane exposure. In addition, the expression of cleaved caspase-3 and TUNEL positive cells were markedly decreased in TMP-treated NSCs compared with the control. Furthermore, pretreatment with TMP significantly increased the levels of phosphorylated Akt and GSK-3β in sevoflurane-injured NSCs. However, an upstream inhibitor of Akt, LY294002 abolished the protective of TMP on the cell viability of NSCs. In conclusion, these findings indicate that TMP protects NSCs from sevoflurane-induced toxicity through Akt/GSK-3β pathway.

Exercise Pills for Drug Addiction: Forced Moderate Endurance Exercise Inhibits Methamphetamine-Induced Hyperactivity through the Striatal Glutamatergic Signaling Pathway in Male Sprague Dawley Rats

Physical exercise reduces the extent, duration, and frequency of drug use in drug addicts during the drug initiation phase, as well as during prolonged addiction, withdrawal, and recurrence. However, information about exercise-induced neurobiological changes is limited. This study aimed to investigate the effects of forced moderate endurance exercise training on methamphetamine (METH)-induced behavior and the associated neurobiological changes. Male Sprague Dawley rats were subjected to the administration of METH (1 mg/kg/day, i.p.) and/or forced moderate endurance exercise (treadmill running, 21 m/min, 60 min/day) for 2 weeks. Over the two weeks, endurance exercise training significantly reduced METH-induced hyperactivity. METH and/or exercise treatment increased striatal dopamine (DA) levels, decreased p(Thr308)-Akt expression, and increased p(Tyr216)-GSK-3β expression. However, the phosphorylation levels of Ser9-GSK-3β were significantly increased in the exercise group. METH administration significantly increased the expression of NMDAr1, CaMKK2, MAPKs, and PP1 in the striatum, and exercise treatment significantly decreased the expression of these molecules. Therefore, it is apparent that endurance exercise inhibited the METH-induced hyperactivity due to the decrease in GSK-3β activation by the regulation of the striatal glutamate signaling pathway.

Immunomodulatory Effects of Dopamine in Inflammatory Diseases

Dopamine (DA) receptor, a significant G protein-coupled receptor, is classified into two families: D1-like (D1 and D5) and D2-like (D2, D3, and D4) receptor families, with further formation of homodimers, heteromers, and receptor mosaic. Increasing evidence suggests that the immune system can be affected by the nervous system and neurotransmitters, such as dopamine. Recently, the role of the DA receptor in inflammation has been widely studied, mainly focusing on NLRP3 inflammasome, NF-κB pathway, and immune cells. This article provides a brief review of the structures, functions, and signaling pathways of DA receptors and their relationships with inflammation. With detailed descriptions of their roles in Parkinson disease, inflammatory bowel disease, rheumatoid arthritis, systemic lupus erythematosus, and multiple sclerosis, this article provides a theoretical basis for drug development targeting DA receptors in inflammatory diseases.

Akt and calcium-permeable AMPA receptor are involved in the effect of pinoresinol on amyloid β-induced synaptic plasticity and memory deficits

Alzheimer's disease (AD) is one of the most prevalent neurodegenerative disorders characterized by memory deficits. Although no drug has given promising results, synaptic dysfunction-modulating agents might be considered potential candidates for alleviating this disorder. Pinoresinol, a lignan found in Forsythia suspensa, is a memory-enhancing agent with excitatory synaptic activation. In the present study, we tested whether pinoresinol reduces learning and memory and excitatory synaptic deficits in an amyloid β (Aβ)-induced AD-like mouse model. Pinoresinol enhanced hippocampal long-term potentiation (LTP) through calcium-permeable AMPA receptor, which was mediated by Akt activation. Moreover, pinoresinol ameliorated LTP deficits in amyloid β (Aβ)-treated hippocampal slices via Akt signaling. Oral administration of pinoresinol ameliorated Aβ-induced memory deficits without sensory dysfunction. Moreover, AD-like pathology, including neuroinflammation and synaptic deficit, were ameliorated by pinoresinol administration. Collectively, pinoresinol may be a good candidate for AD therapy by modulating synaptic functions.

Synergistic Interplay of Covalent and Non-Covalent Interactions in Reactive Polymer Nanoassembly Facilitates Intracellular Delivery of Antibodies

The primary impediments in developing large antibodies as drugs against intracellular targets involve their low transfection efficiency and suitable reversible encapsulation strategies for intracellular delivery with retention of biological activity. To address this, we outline an electrostatics-enhanced covalent self-assembly strategy to generate polymer-protein/antibody nanoassemblies. Through structure-activity studies, we down-select the best performing self-immolative pentafluorophenyl containing activated carbonate polymer for bioconjugation. With the help of an electrostatics-aided covalent self-assembly approach, we demonstrate efficient encapsulation of medium to large proteins (HRP, 44 kDa and β-gal, 465 kDa) and antibodies (ca. 150 kDa). The designed polymeric nanoassemblies are shown to successfully traffic functional antibodies (anti-NPC and anti-pAkt) to cytosol to elicit their bioactivity towards binding intracellular protein epitopes and inducing apoptosis.

Cannabidiol attenuates methamphetamine-induced conditioned place preference via the Sigma1R/AKT/GSK-3β/CREB signaling pathway in rats

Methamphetamine (METH) is a highly addictive psychostimulant. Cannabidiol (CBD) is an exogenous cannabinoid without psychostimulating activity, which has potential therapeutic effects on opioid addiction. However, it is unclear whether CBD has therapeutic effects on METH-induced motivational effects. The present study examines whether CBD has a protective effect on METH-induced conditioned place preference (CPP) in rats by regulating the Sigma1R and AKT-GSK3β-CREB signaling pathway. Seventy rats were equally and randomly divided into seven groups. The rat CPP model was established via the intraperitoneal injection (IP) of 2 mg/kg of METH. Next, the intraperitoneal injection of 10, 20, 40, and 80 mg/kg CBD was performed 1 h prior to the injection of saline or METH. The protein expression levels of Sigma1R, AKT, p-AKT, GSK-3β, p-GSK-3β, CREB, and p-CREB in the rats' prefrontal cortex, nucleus accumbens, and hippocampus and ventral tegmental were detected using western blot analysis. CBD was found to inhibit METH-induced CPP in a dose-dependent fashion. The expression levels of Sigma1R, p-AKT, p-GSK3β, and p-CREB increased significantly in the METH-induced CPP model. Treatment involving different doses of CBD caused differential inhibitory responses in the cellular protein abundance of Sigma1R, p-AKT, p-GSK3β, and p-CREB across various brain regions. The present study found that METH can induce CPP in rats. When a pretreatment of CBD is applied, the CBD can weaken CPP in METH-induced rats by regulating the SigmaR1/AKT/GSK-3β/CREB signaling pathway. The results of this study indicate that CBD has a potential therapeutic effect on METH-induced rewarding effects.

DL0410 ameliorates cognitive deficits in APP/PS1 transgenic mice by promoting synaptic transmission and reducing neuronal loss

At present, few available drugs can be used to either improve pathological features or prevent the progression of Alzheimer's disease (AD). DL0410 ((1,1'-([1,1'-biphenyl]-4,4'-diyl) bis (3-(piperidin-1-yl) propan-1-one) dihydrochloride) is a multiple-target small molecule that has been found to reverse cognitive impairment in different animal models of AD. In this study we evaluated the cognition-improving effects of DL0410 in APP/PS1 transgenic mice and explored the underlying mechanisms. APP/PS1 transgenic mice were administered DL0410 (3, 10, 30 mg· kg-1· d-1, ig) for 2 months. We found that DL0410 administration significantly ameliorated cognitive deficits in both the nest-building and Morris water maze tests. In electrophysiological analysis of hippocampal slices, we showed that DL0410 administration significantly enhanced the field EPSP slope and HFS-induced LTP in CA1 area. Furthermore, we revealed that DL0410 administration significantly increased the phosphorylation of AKT and the activity of GSK-3β in the hippocampus and cortex. Moreover, DL0410 administration dose-dependently increased the expression level of phosphorylated ERK1/2 in the hippocampus and cortex. In addition, DL0410 dose-dependently decreased the neuronal loss by decreasing the production of Aβ deposition, inhibited glial overactivation, and the production of inflammatory cytokines such as TNF-α, IL-1β, and IL-6. We conclude that DL0410 ameliorates cognitive deficits in APP/PS1 transgenic mice by promoting synaptic transmission via activating the AKT/GSK-3β and MAPK/ERK signaling pathway and reducing neuronal loss. DL0410 may be an effective agent for AD treatment in the future.

Intracellular mechanisms and behavioral changes in mouse model of attention deficit hyperactivity disorder: Importance of age-specific NMDA receptor blockade

Exposure of NMDA receptor antagonists during developmental stages leads to behavioral consequences like attention deficit hyperactivity disorder (ADHD). However, the underlying molecular mechanisms have remained poorly understood. Herein, we studied the phosphorylated Akt (pAkt) and caspase-3, the key regulators of neuronal cell survival/death, as the probable downstream targets of MK-801 often used to engender ADHD-like condition. Swiss albino mice at postnatal days (PND) 7, 14 or 21 were injected with a single dose of MK-801 and evaluated for hyperactivity (open field test) and memory deficit at adolescence (PND 30) and adult stages (PND 60). PND 7 or 14 treatment groups (but not PND 21) consistently showed hyperactivity at the adolescence stage. A significant increase in working and reference memory errors in radial arm maze was noted at the adolescence age. PND 7 group continued to display the symptoms even in adulthood. All the treatment groups showed a significant decrease in the percent alterations (Y-maze) and discrimination index (novel object recognition test) at adolescence age. A significant increase in caspase-3 expression was noted in the prefrontal cortex (PFC) and hippocampus, whereas increased pAkt was noticed only in the hippocampus, following a single injection of MK-801 at PND 7. Concurrently, PND 7 treatment group showed significantly decreased neuronal nuclei (NeuN) expression (a marker for mature neurons) in the dentate gyrus, cornu ammonis-3 and PFC, but not in cornu ammonis-1, at adolescence age. We suggest that the observed symptoms of ADHD at adolescence and adulthood stages may be linked to alteration in pAkt and caspase-3 followed MK-801 treatment at PND 7.

Famotidine has a neuroprotective effect on MK-801 induced toxicity via the Akt/GSK-3β/β-catenin signaling pathway in the SH-SY5Y cell line

Schizophrenia cannot be treated sufficiently with existing antipsychotic drugs. Taken into account that increased Glycogen Synthase Kinase 3 Beta (GSK-3β) activity is associated with schizophrenia pathophysiology and certain antipsychotics can be able to decrease GSK3β activity, inhibition of GSK-3β activity could be a novel approach for the treatment of schizophrenia. In the present study MK-801, a widely used chemical for the in vivo/in vitro modeling of schizophrenia was selected to evoke a detrimental effect on cellular survival via GSK3β and related proteins. A limited number of studies have reported the curative effects of famotidine, an antiulcer drug, in schizophrenic patients. To the best of our knowledge, no study investigated the molecular mechanism of the beneficial effect of famotidine in the patients. A recent study based on computerized drug modeling software (docking) indicated that famotidine might inhibit the GSK3β activity due to its chemical structure independent from histaminergic receptors. In this study, we aimed to investigate the effects of famotidine on the Akt/GSK-3β/β-catenin signaling pathway on SH-SY5Y neuroblastoma cells in the presence of MK-801. We investigated the effects of famotidine, olanzapine (an antipsychotic drug), and SB 415286 (specific GSK-3β inhibitor), on the basal cellular survival and MK-801 induced neuronal death beside of Akt/GSK-3β/β-catenin protein and gene expressions in SH-SY5Y cells. Cell viability, protein and gene expressions were determined by the real-time cell analysis (xCELLigence) system, western blotting and real-time polymerase chain reactions (Rt-PCR), respectively. Our findings suggested that MK-801 administration decreased cell survival probably via the increasing GSK-3β gene expression and activity in the SH-SY5Y cells. Pre-treatments with famotidine, olanzapine, and SB 415286 prevented MK-801 induced cell death via inhibitory effects on the MK-801 induced GSK-3β activity. Overall, the present results suggest that famotidine has a neuroprotective effect against MK-801 via modulation of the Akt/GSK-3β/β-catenin signaling pathway, an important mechanism in schizophrenia neurobiology.

The effects of donepezil on phencyclidine-induced cognitive deficits in a mouse model of schizophrenia

Donepezil is the first-line of treatment for Alzheimer's disease (AD), which improves cognitive impairment effectively, but whether it has an impact on cognitive impairment in schizophrenia remains unknown. In this study, we evaluated the effects and mechanisms of donepezil on schizophrenia-like cognitive deficits induced by phencyclidine (PCP). The cognitive deficits model of schizophrenia was established by injecting PCP into mice. Risperidone, an atypical antipsychotic drug, served as positive control drug. Three behavioral tests including novel object recognition (NOR) test, Morris Water Maze (MWM) and passive avoidance (PA) test were performed to evaluate the effect of donepezil on PCP-induced cognitive deficits. Furthermore, the content of BDNF and NGF in the hippocampus and cortex of mice was determined using ELISA. Expressions of p-GSK-3β/GSK-3β, p-Akt/Akt, Bcl-2/Bax and Caspase-3 in the hippocampus and cortex were detected by Western blot. Results revealed that donepezil has a protective effect on PCP-induced cognitive dysfunction. Moreover, donepezil can also improve PCP-induced schizophrenia-like cognitive deficits by inhibiting neuronal apoptosis and regulating synaptic plasticity, which was possible through the up-regulation of p-Akt, p-GSK-3β, Bcl-2 and the down-regulation of Bax, Caspase-3. The results indicated that donepezil might exhibit a beneficial effect on the treatment of cognitive dysfunction in schizophrenia.

Biochemical Properties of Human D-amino Acid Oxidase Variants and Their Potential Significance in Pathologies

The stereoselective flavoenzyme D-amino acid oxidase (DAAO) catalyzes the oxidative deamination of neutral and polar D-amino acids producing the corresponding α-keto acids, ammonia, and hydrogen peroxide. Despite its peculiar and atypical substrates, DAAO is widespread expressed in most eukaryotic organisms. In mammals (and humans in particular), DAAO is involved in relevant physiological processes ranging from D-amino acid detoxification in kidney to neurotransmission in the central nervous system, where DAAO is responsible of the catabolism of D-serine, a key endogenous co-agonist of N-methyl-D-aspartate receptors. Recently, structural and functional studies have brought to the fore the distinctive biochemical properties of human DAAO (hDAAO). It appears to have evolved to allow a strict regulation of its activity, so that the enzyme can finely control the concentration of substrates (such as D-serine in the brain) without yielding to an excessive production of hydrogen peroxide, a potentially toxic reactive oxygen species (ROS). Indeed, dysregulation in D-serine metabolism, likely resulting from altered levels of hDAAO expression and activity, has been implicated in several pathologies, ranging from renal disease to neurological, neurodegenerative, and psychiatric disorders. Only one mutation in DAO gene was unequivocally associated to a human disease. However, several single nucleotide polymorphisms (SNPs) are reported in the database and the biochemical characterization of the corresponding recombinant hDAAO variants is of great interest for investigating the effect of mutations. Here we reviewed recently published data focusing on the modifications of the structural and functional properties induced by amino acid substitutions encoded by confirmed SNPs and on their effect on D-serine cellular levels. The potential significance of the different hDAAO variants in human pathologies will be also discussed.

Neurosteroid pregnenolone sulfate, alone, and as augmentation of lurasidone or tandospirone, rescues phencyclidine-induced deficits in cognitive function and social interaction

BACKGROUND

Pregnenolone sulfate (PregS), an endogenous neurosteroid, which negatively and positively modulates gamma amino butyric acid subunit A (GABA_A) and N-methyl D-aspartate (NMDA) receptors (R) respectively, among other potential neuroplastic changes on synaptic processes, has shown some beneficial effects on treating cognitive impairment associated with schizophrenia (CIAS) and negative symptoms. Lurasidone (Lur), an atypical antipsychotic drug (AAPD), and tandospirone (Tan), a 5-HT_1A R partial agonist, have also been reported to improve cognitive or negative symptoms, or both, in some schizophrenia patients.

METHODS

We tested whether PregS, by itself, and in combination with Lur or Tan could rescue persistent deficits produced by subchronic treatment with the NMDAR antagonist, phencyclidine (PCP)-in episodic memory, executive functioning, and social behavior, using novel object recognition (NOR), operant reversal learning (ORL), and social interaction (SI) tasks, in male C57BL/6 J mice.

RESULTS

PregS (10, but not 3 mg/kg) significantly rescued subchronic PCP-induced NOR and SI deficits. Co-administration of sub-effective doses (SEDs) of PregS (3 mg/kg) + Lur (0.1 mg/kg) or Tan (0.03 mg/kg) rescued scPCP-induced NOR and SI deficits. Further, PregS (30, but not 10 mg/kg) rescued PCP-induced ORL deficit, as did the combination of SED PregS (10 mg/kg) +SED Lur (1 mg/kg) or Tan (1 mg/kg).

CONCLUSION

PregS was effective alone and as adjunctive treatment for treating two types of cognitive impairments and negative symptoms in this schizophrenia model. Further study of the mechanisms by which PregS alone and in combination with AAPDs and 5-HT_1A R partial agonists, rescues the deficits in cognition and SI in this preclinical model is indicated.

Effects of antipsychotic drugs on neurites relevant to schizophrenia treatment

Although antipsychotic drugs are mainly used for treating schizophrenia, they are widely used for treating various psychiatric diseases in adults, the elderly, adolescents and even children. Today, about 1.2% of the worldwide population suffers from psychosis and related disorders, which translates to about 7.5 million subjects potentially targeted by antipsychotic drugs. Neurites project from the cell body of neurons and connect neurons to each other to form neural networks. Deficits in neurite outgrowth and integrity are implicated in psychiatric diseases including schizophrenia. Neurite deficits contribute to altered brain development, neural networking and connectivity as well as symptoms including psychosis and altered cognitive function. This review revealed that (1) antipsychotic drugs could have profound effects on neurites, synaptic spines and synapse, by which they may influence and regulate neural networking and plasticity; (2) antipsychotic drugs target not only neurotransmitter receptors but also intracellular signaling molecules regulating the signaling pathways responsible for neurite outgrowth and maintenance; (3) high doses and chronic administration of antipsychotic drugs may cause some loss of neurites, synaptic spines, or synapsis in the cortical structures. In addition, confounding effects causing neurite deficits may include elevated inflammatory cytokines and antipsychotic drug-induced metabolic side effects in patients on chronic antipsychotic therapy. Unraveling how antipsychotic drugs affect neurites and neural connectivity is essential for improving therapeutic outcomes and preventing aversive effects for patients on antipsychotic drug treatment.

Inhibition of GSK-3beta Signaling Pathway Rescues Ketamine-Induced Neurotoxicity in Neural Stem Cell-Derived Neurons

Clinical application of anesthetic reagent, ketamine (Keta), may induce irreversible neurotoxicity in central nervous system. In this work, we utilized an in vitro model of neural stem cells-derived neurons (nSCNs) to evaluate the role of GSK-3 signaling pathway in Keta-induced neurotoxicity. Embryonic mouse-brain neural stem cells were differentiated into neurons in vitro. Keta (50 μM)-induced neurotoxicity in cultured nSCNs was monitored by apoptosis, immunohistochemical and western blot assays, respectively. GSK-3 signaling pathways, including GSK-3α and GSK-3β, were inhibited by siRNA in the culture. The subsequent effects of GSK-3α or GSK-3β downregulation on Keta-induced neurotoxicity, including apoptosis and neurite loss, were then evaluated in nSCNs. Finally, caspase and Akt/ERK signal pathways were further examined by western blot to evaluate the regulatory effect of GSK-3 signaling pathways on Keta-induced neural injury. Keta (50 μM) caused markedly nSCN apoptosis and neurite degeneration in vitro. Keta decreased GSK-3β phosphorylation, but had no effect on GSK-3α phosphorylation. SiRNA-induced GSK-3β downregulation rescued Keta-induced neurotoxicity in nSCNs by reducing neuronal apoptosis and preventing neurite degeneration. On the other hand, GSK-3α downregulation had no effect on Keta-induced neurotoxicity. Western blot showed that, in Keta-injured nSCNs, GSK-3β downregulation reduced Caspase-1/3 proteins, but left phosphorylated Akt/ERK unchanged. GSK-3β, not GSK-3α, was specifically involved in the process of Keta-induced neurotoxicity in nSCNs. Inhibiting GSK-3β may be an effective approach to counter toxic effect of ketamine on central neurons in clinical and experimental applications.

Postnatal Administration of Dizocilpine Inhibits Neuronal Excitability in PFC and Induces Social Deficits Detected by MiceProfiler

Schizophrenia is a devastating mental disease with social deficit as its core component of negative symptoms, which could be induced in rodents by dizocilpine (MK-801), a noncompetitive NMDA receptor antagonist. NMDA receptors are highly expressed during the postnatal period. However, less attention has been paid to the effects of postnatal MK-801 administration on social interaction. In this study, we evaluated the effects of postnatal administration of MK-801 on social interaction and explored the possible mechanisms. Postnatal day-7 mice were intraperitoneally injected with MK-801 twice daily for 5 days, and their social interaction repertoire was monitored by a computerized video in the 10th week. The contact event, relative position event, stop-state, and dynamic event were analyzed with MiceProfiler automatic idTracker system. The results showed that MK-801 reduced the number of the contact events, relative position events, and stop-states, while increased the number and duration of dynamic events. These changes implied that MK-801-injected mice had indifference and lower motivation in social interaction and could be a useful model for studies on the social deficit of schizophrenia. The prefrontal cortex is the key region for social interaction behaviors. Slice patch clamp was performed to analyze the cellular excitability of prefrontal cortical neurons after postnatal treatment with MK-801 in mice. The results demonstrated that MK-801 injection reduced the frequency and amplitude of action potentials, but increased the frequency of miniature inhibitory postsynaptic currents. These data illustrated that the excitability of neurons in the prefrontal cortex was inhibited. Finally, immunoblotting data demonstrated that MK-801 significantly decreased the levels of sirtuin 1 (SIRT1) and phosphorylated protein kinase B (p-PKB) in the prefrontal cortex (both P < 0.05). Taken together, our results indicated that administration of MK-801 to postnatal mice induces social interaction deficits possibly due to inhibiting the neuronal excitability and decreasing the levels of SIRT1 and p-PKB in the prefrontal cortex.

Proteomic systems evaluation of the molecular validity of preclinical psychosis models compared to schizophrenia brain pathology

Pharmacological and genetic rodent models of schizophrenia play an important role in the drug discovery pipeline, but quantifying the molecular similarity of such models with the underlying human pathophysiology has proved difficult. We developed a novel systems biology methodology for the direct comparison of anterior prefrontal cortex tissue from four established glutamatergic rodent models and schizophrenia patients, enabling the evaluation of which model displays the greatest similarity to schizophrenia across different pathophysiological characteristics of the disease. Liquid chromatography coupled tandem mass spectrometry (LC-MS^E) proteomic profiling was applied comparing healthy and "disease state" in human post-mortem samples and rodent brain tissue samples derived from models based on acute and chronic phencyclidine (PCP) treatment, ketamine treatment or NMDA receptor knockdown. Protein-protein interaction networks were constructed from significant abundance changes and enrichment analyses enabled the identification of five functional domains of the disease such as "development and differentiation", which were represented across all four rodent models and were thus subsequently used for cross-species comparison. Kernel-based machine learning techniques quantified that the chronic PCP model represented schizophrenia brain changes most closely for four of these functional domains. This is the first study aiming to quantify which rodent model recapitulates the neuropathological features of schizophrenia most closely, providing an indication of face validity as well as potential guidance in the refinement of construct and predictive validity. The methodology and findings presented here support recent efforts to overcome translational hurdles of preclinical psychiatric research by associating functional dimensions of behaviour with distinct biological processes.

Baicalin Attenuates Ketamine-Induced Neurotoxicity in the Developing Rats: Involvement of PI3K/Akt and CREB/BDNF/Bcl-2 Pathways

Ketamine is widely used as an anesthetic in pediatric clinical practice. However, numerous studies have reported that exposure to ketamine during the developmental period induces neurotoxicity. Here we investigate the neuroprotective effects of baicalin, a natural flavonoid compound, against ketamine-induced apoptotic neurotoxicity in the cortex and hippocampus of the Sprague-Dawley postnatal day 7 (PND7) rat pups. Our results revealed that five continuous injections of ketamine (20 mg/kg) at 90-min intervals over 6 h induced obvious morphological damages of neuron by Nissl staining and apoptosis by TUNEL assays in the prefrontal cortex and hippocampus of PND7 rat pups. Baicalin (100 mg/kg) pretreatment alleviated ketamine-induced morphological change and apoptosis. Caspase-3 activity and caspase-3 mRNA expression increase induced by ketamine were also inhibited by baicalin treatment. LY294002, an inhibitor of PI3K, abrogated the effect of baicalin against ketamine-induced caspase-3 activity and caspase-3 mRNA expression increase. In addition, Western blot studies indicated that baicalin not only inhibited ketamine-induced p-Akt and p-GSK-3β decrease, but also relieved ketamine-induced p-CREB and BDNF expression decrease. Baicalin also attenuated ketamine-induced Bcl-2/Bax decrease and caspase-3 expression increase. Further in vitro experiments proved that baicalin mitigated ketamine-induced cell viability decrease in the MTT assay, morphological change by Rosenfeld's staining, and caspase-3 expression increase by Western blot in the primary neuron-glia mixed cultures. LY294002 abrogated the protective effect of baicalin. These data demonstrate that baicalin exerts neuroprotective effect against ketamine-induced neuronal apoptosis by activating the PI3K/Akt and its downstream CREB/BDNF/Bcl-2 signaling pathways. Therefore, baicalin appears to be a promising agent in preventing or reversing ketamine's apoptotic neurotoxicity at an early developmental stage.

Effects of β-Arrestin-Biased Dopamine D2 Receptor Ligands on Schizophrenia-Like Behavior in Hypoglutamatergic Mice

Current antipsychotic drugs (APDs) show efficacy with positive symptoms, but are limited in treating negative or cognitive features of schizophrenia. Whereas all currently FDA-approved medications target primarily the dopamine D2 receptor (D2R) to inhibit G(i/o)-mediated adenylyl cyclase, a recent study has shown that many APDs affect not only G(i/o)- but they can also influence β-arrestin- (βArr)-mediated signaling. The ability of ligands to differentially affect signaling through these pathways is termed functional selectivity. We have developed ligands that are devoid of D2R-mediated G(i/o) protein signaling, but are simultaneously partial agonists for D2R/βArr interactions. The purpose of this study was to test the effectiveness of UNC9975 or UNC9994 on schizophrenia-like behaviors in phencyclidine-treated or NR1-knockdown hypoglutamatergic mice. We have found the UNC compounds reduce hyperlocomotion in the open field, restore PPI, improve novel object recognition memory, partially normalize social behavior, decrease conditioned avoidance responding, and elicit a much lower level of catalepsy than haloperidol. These preclinical results suggest that exploitation of functional selectivity may provide unique opportunities to develop drugs with fewer side effects, greater therapeutic selectivity, and enhanced efficacy for treating schizophrenia and related conditions than medications that are currently available.

Global quantitative analysis of phosphorylation underlying phencyclidine signaling and sensorimotor gating in the prefrontal cortex

Prepulse inhibition (PPI) is an example of sensorimotor gating and deficits in PPI have been demonstrated in schizophrenia patients. Phencyclidine (PCP) suppression of PPI in animals has been studied to elucidate the pathological elements of schizophrenia. However, the molecular mechanisms underlying PCP treatment or PPI in the brain are still poorly understood. In this study, quantitative phosphoproteomic analysis was performed on the prefrontal cortex from rats that were subjected to PPI after being systemically injected with PCP or saline. PCP downregulated phosphorylation events were significantly enriched in proteins associated with long-term potentiation (LTP). Importantly, this data set identifies functionally novel phosphorylation sites on known LTP-associated signaling molecules. In addition, mutagenesis of a significantly altered phosphorylation site on xCT (SLC7A11), the light chain of system xc-, the cystine/glutamate antiporter, suggests that PCP also regulates the activity of this protein. Finally, new insights were also derived on PPI signaling independent of PCP treatment. This is the first quantitative phosphorylation proteomic analysis providing new molecular insights into sensorimotor gating.

Olanzapine Prevents the PCP-induced Reduction in the Neurite Outgrowth of Prefrontal Cortical Neurons via NRG1

Accumulating evidence suggests that reducing neurite outgrowth and synaptic plasticity plays a critical role in the pathology of cognitive deficits in schizophrenia. The N-methyl-D-aspartate receptor antagonist phencyclidine (PCP) can induce symptoms of schizophrenia as well as reduce dendritic spine density and neurite growth. The antipsychotic drug olanzapine may improve these deficits. This study aimed to investigate: (1) if olanzapine prevents PCP-induced suppression of neurite outgrowth and synaptic protein expression; (2) if olanzapine affects the Akt-GSK3 signaling pathway; and (3) the role of neuregulin 1 (NRG1) in this process. Immunofluorescence revealed that PCP treatment for 24 hours reduces both neurite length (28.5%) and the number of neurite branches (35.6%) in primary prefrontal cortical neuron cultures. PCP reduced protein and mRNA expressions of synaptophysin (24.9% and 23.2%, respectively) and PSD95 (31.5% and 21.4%, respectively), and the protein expression of p-Akt (26.7%) and p-GSK3β (35.2%). Olanzapine co-treatment prevented these PCP-induced effects in normal neurons but not in neurons from NRG1-knockout mice. These results indicate that NRG1 mediates the preventive effects of olanzapine on the PCP-induced impairment of neurite outgrowth and synaptic protein expression. This study provides potential targets for interventions on improving the efficacy of olanzapine on preventing cognitive deficits in schizophrenia.

Hippocampal Proteomic and Metabonomic Abnormalities in Neurotransmission, Oxidative Stress, and Apoptotic Pathways in a Chronic Phencyclidine Rat Model

Schizophrenia is a neuropsychiatric disorder affecting 1% of the world's population. Due to both a broad range of symptoms and disease heterogeneity, current therapeutic approaches to treat schizophrenia fail to address all symptomatic manifestations of the disease. Therefore, disease models that reproduce core pathological features of schizophrenia are needed for the elucidation of pathological disease mechanisms. Here, we employ a comprehensive global label-free liquid chromatography-mass spectrometry proteomic (LC-MS(E)) and metabonomic (LC-MS) profiling analysis combined with the targeted proteomics (selected reaction monitoring and multiplex immunoassay) of serum and brain tissues to investigate a chronic phencyclidine (PCP) rat model in which glutamatergic hypofunction is induced through noncompetitive NMDAR-receptor antagonism. Using a multiplex immunoassay, we identified alterations in the levels of several cytokines (IL-5, IL-2, and IL-1β) and fibroblast growth factor-2. Extensive proteomic and metabonomic brain tissue profiling revealed a more prominent effect of chronic PCP treatment on both the hippocampal proteome and metabonome compared to the effect on the frontal cortex. Bioinformatic pathway analysis confirmed prominent abnormalities in NMDA-receptor-associated pathways in both brain regions, as well as alterations in other neurotransmitter systems such as kainate, AMPA, and GABAergic signaling in the hippocampus and in proteins associated with neurodegeneration. We further identified abundance changes in the level of the superoxide dismutase enzyme (SODC) in both the frontal cortex and hippocampus, which indicates alterations in oxidative stress and substantiates the apoptotic pathway alterations. The present study could lead to an increased understanding of how perturbed glutamate receptor signaling affects other relevant biological pathways in schizophrenia and, therefore, support drug discovery efforts for the improved treatment of patients suffering from this debilitating psychiatric disorder.

Pregnenolone sulfate normalizes schizophrenia-like behaviors in dopamine transporter knockout mice through the AKT/GSK3β pathway

Pregnenolone sulfate, an endogenous neurosteroid in the central nervous system, is a positive allosteric modulator of the NMDA receptor, and plays a role in the modulation of learning and memory. Here, we study the actions of pregnenolone sulfate using the dopamine transporter knockout (DAT-KO) mice, which exhibit endophenotypes that recapitulate certain symptoms of schizophrenia, including the psychomotor agitation, stereotypy, prepulse inhibition (PPI) deficits and cognitive impairments. We found that acute treatment with pregnenolone sulfate normalized the hyperlocomotion and stereotypic bouts, and rescued the PPI deficits of DAT-KO mice. In addition, long-term treatment with pregnenolone sulfate rescued the cognitive deficits of DAT-KO mice in the novel object recognition and social transmission of food preference tests. We also showed that pregnenolone sulfate normalized behavioral abnormalities in MK801-treated wild-type mice, whereas pregnenolone, its precursor, only partially rescued MK801-induced behavioral abnormalities. This indicates that there are distinct mechanisms of action between pregnenolone sulfate and pregnenolone, and the involvement of NMDA receptor signaling in the action of pregnenolone sulfate. Moreover, we found that acute treatment with pregnenolone sulfate increased the phosphorylation levels of striatal AKT and GSK3β in DAT-KO mice, and that long-term treatment with pregnenolone sulfate increased expression levels of NR1 subunit of the NMDA receptor in hippocampus. Thus, pregnenolone sulfate was able to rescue the behavioral anomalies of DAT-KO mice through the NMDA receptor-mediated, AKT/GSK3β signaling pathway.

Chronic phencyclidine induces inflammatory responses and activates GSK3β in mice

Use of phencyclidine (PCP) in rodents can mimic some aspects of schizophrenia. However, the underlying mechanism is still unclear. Growing evidence indicates that neuroinflammation plays a significant role in the pathophysiology of schizophrenia. In this study, we focused on inflammatory responses as target of PCP for inducing schizophrenia-like symptoms. 3-month-old C57BL/6J mice received daily injections of PCP (20 mg/kg, i.p.) or saline for one week. PCP-injected mice produced schizophrenia-like behaviours including impaired spatial short-term memory assessed by the Y-maze task and sensorimotor gating deficits in a prepulse inhibition task. Simultaneously, chronic PCP administration induced astrocyte and microglial activation in both the cortex and hippocampus. Additionally, the proinflammatory cytokine interleukin-1β was significantly up-regulated in PCP administrated mice. Furthermore, PCP treatment decreased ratio of the phospho-Ser9 epitope of glycogen synthase kinase-3β (GSK3β) over total GSK3β, which is indicative of increased GSK3β activity. These data demonstrate that chronic PCP in mouse produces inflammatory responses and GSK3β activation.

Ketamine affects the neurogenesis of rat fetal neural stem progenitor cells via the PI3K/Akt-p27 signaling pathway

Ketamine is widely used as an anesthetic, analgesic, or sedative in pediatric patients. We reported that ketamine alters the normal neurogenesis of rat fetal neural stem progenitor cells (NSPCs) in the developing brain, but the underlying mechanisms remain unknown. The PI3K-PKB/Akt (phosphatidylinositide 3-kinase/protein kinase B) signaling pathway plays many important roles in cell survival, apoptosis, and proliferation. We hypothesized that PI3K-PKB/Akt signaling may be involved in ketamine-altered neurogenesis of cultured NSPCs in vitro. NSPCs were isolated from Sprague-Dawley rat fetuses on gestational day 17. 5-bromo-2'-deoxyuridine (BrdU) incorporation, Ki67 staining, and differentiation tests were utilized to identify primary cultured NSPCs. Immunofluorescent staining was used to detect Akt expression, whereas Western blots measured phosphorylated Akt and p27 expression in NSPCs exposed to different treatments. We report that cultured NSPCs had properties of neurogenesis: proliferation and neural differentiation. PKB/Akt was expressed in cultured rat fetal cortical NSPCs. Ketamine inhibited the phosphorylation of Akt and further enhanced p27 expression in cultured NSPCs. All ketamine-induced PI3K/Akt signaling changes could be recovered by N-methyl-d-aspartate (NMDA) receptor agonist, NMDA. These data suggest that the inhibition of PI3K/Akt-p27 signaling may be involved in ketamine-induced neurotoxicity in the developing brain, whereas excitatory NMDA receptor activation may reverse these effects.

α-amino-3-hydroxy-5-methyl-4-isoxazoleproprionic acid receptor activation protects against phencyclidine-induced caspase-3 activity by activating voltage-gated calcium channels

Phencyclidine (PCP) is a noncompetitive, open channel blocker of the N-methyl-D-aspartate (NMDA) receptor-ion channel complex. When administered to immature animals, it is known to cause apoptotic neurodegeneration in several regions, and this is followed by olanzapine-sensitive, schizophrenia-like behaviors in late adolescence and adulthood. Clarification of its mechanism of action could yield data that would help to inform the treatment of schizophrenia. In our initial experiments, we found that α-amino-3-hydroxy-5-methyl-4-isoxazoleproprionic acid (AMPA) inhibited PCP-induced apoptosis in organotypic neonatal rat brain slices in a concentration-dependent and 6-cyano-7-nitroquinoxaline-2,3-dione-sensitive manner. Calcium signaling pathways are widely implicated in apoptosis, and PCP prevents calcium influx through NMDA receptor channels. We therefore hypothesized that AMPA could protect against this effect by activation of voltage-dependent calcium channels (VDCCs). In support of this hypothesis, pretreatment with the calcium channel blocker cadmium chloride eliminated AMPA-mediated protection against PCP. Furthermore, the L-type VDCC inhibitor nifedipine (10 µM) fully abrogated the effects of AMPA, suggesting that L-type VDCCs are required for AMPA-mediated protection against PCP-induced neurotoxicity. Whereas the P/Q-type inhibitor ω-agatoxin TK (200 nM) reduced AMPA protection by 51.7%, the N-type VDCC inhibitor ω-conotoxin (2 µM) had no effect. Decreased AMPA-mediated protection following cotreatment with K252a, a TrkB inhibitor, suggests that brain-derived neurotrophic factor signaling plays an important role. By analogy, these results suggest that activation of L-type, and to a lesser extent P/Q-type, VDCCs might be advantageous in treating conditions associated with diminished NMDAergic activity during early development.

Drug discovery based on genetic and metabolic findings in schizophrenia

Recent progress in the genetics of schizophrenia provides the rationale for re-evaluating causative factors and therapeutic strategies for this disease. Here, we review the major candidate susceptibility genes and relate the aberrant function of these genes to defective regulation of energy metabolism in the schizophrenic brain. Disturbances in energy metabolism potentially lead to neurodevelopmental deficits, impaired function of the mature nervous system and failure to maintain neurites/dendrites and synaptic connections. Current antipsychotic drugs do not specifically address these underlying deficits; therefore, a new generation of more effective medications is urgently needed. Novel targets for future drug discovery are identified in this review. The coordinated application of structure-based drug design, systems biology and research on model organisms may greatly facilitate the search for next-generation antipsychotic drugs.

The AKT/mTOR pathway mediates neuronal protective effects of erythropoietin in sepsis

Sepsis is one of the most common causes of mortality in intensive care units. Although sepsis-associated encephalopathy (SAE) is reported to be a leading manifestation of sepsis, its pathogenesis remains to be elucidated. In this study, we investigated whether exogenous recombinant human erythropoietin (rhEPO) could protect brain from neuronal apoptosis in the model of SAE. We showed that application of rhEPO enhanced Bcl-2, decreased Bad in lipopolysaccharide treated neuronal cultures, and improved neuronal apoptosis in hippocampus of cecal ligation and peroration rats. We also found that rhEPO increased the expression of phosphorylated AKT, and the antiapoptotic role of rhEPO could be abolished by phosphoinositide 3-kinase (PI3K)/AKT inhibitor LY294002 or SH-5. In addition, systemic sepsis inhibited the hippocampal-phosphorylated mammalian target of rapamycin (mTOR) and p70S6K (downstream substrates of PKB/AKT signaling), which were restored by administration of exogenous rhEPO. Moreover, treatment with mTOR-signaling inhibitor rapamycin or transfection of mTOR siRNA reversed the neuronal protective effects of rhEPO. Finally, exogenous rhEPO rescued the emotional and spatial cognitive defects without any influence on locomotive activity. These results illustrated that exogenous rhEPO improves brain dysfunction by reducing neuronal apoptosis, and AKT/mTOR signaling is likely to be involved in this process. Application of rhEPO may serve as a potential therapy for the treatment of SAE.

Erythropoietin attenuates 6-hydroxydopamine-induced apoptosis via glycogen synthase kinase 3β-mediated mitochondrial translocation of Bax in PC12 cells

The aim of this study was to determine the mechanism by which erythropoietin (EPO) suppressed 6-hydroxydopamine (6-OHDA)-induced apoptosis. Our results showed that 6-OHDA remarkably decreased phosphorylation of glycogen synthase kinase 3β (GSK3β) as well as enhanced the level of Bax in the mitochondria. Besides, 6-OHDA decreased the mitochondrial expression of Bcl-2 without altering the cytoplasmic expression of Bcl-2. In line with these results, 6-OHDA treatment enhanced the apoptosis and caspase 3 activity in PC12 cells. These findings indicated that mitochondrial dysfunction was involved in the neurotoxicity of 6-OHDA and GSK3β might act upstream of Bax/Bcl-2 and the caspase 3 pathways in 6-OHDA-treated PC12 cells. Furthermore, EPO reduced 6-OHDA-induced growth inhibition. Western blot exhibited that GSK3β inhibitor 4-benzyl-2-methyl-1, 2,4-thiadiazolidine-3, 5-dione (TDZD8) and EPO not only increased the phosphorylation of GSK3β but also inhibited the mitochondrial translocation of Bax. In agreement with these results, EPO and TDZD8 obviously increased the mitochondrial expression of Bcl-2. Finally, TDZD-8 and EPO significantly suppressed the enhanced apoptosis and activity of caspase 3 induced by 6-OHDA. Taken together, GSK3β-mediated mitochondrial cell death pathway is involved in the neuroprotective effect of EPO against 6-OHDA-induced apoptosis.

NMDA Neurotransmission Dysfunction in Behavioral and Psychological Symptoms of Alzheimer's Disease

Dementia has become an all-important disease because the population is aging rapidly and the cost of health care associated with dementia is ever increasing. In addition to cognitive function impairment, associated behavioral and psychological symptoms of dementia (BPSD) worsen patient’s quality of life and increase caregiver’s burden. Alzheimer’s disease is the most common type of dementia and both behavioral disturbance and cognitive impairment of Alzheimer’s disease are thought to be associated with the N-methyl-D-aspartate (NMDA) dysfunction as increasing evidence of dysfunctional glutamatergic neurotransmission had been reported in behavioral changes and cognitive decline in Alzheimer’s disease. We review the literature regarding dementia (especially Alzheimer’s disease), BPSD and relevant findings on glutamatergic and NMDA neurotransmission, including the effects of memantine, a NMDA receptor antagonist, and NMDA-enhancing agents, such as D-serine and D-cycloserine. Literatures suggest that behavioral disturbance and cognitive impairment of Alzheimer’s disease may be associated with excitatory neurotoxic effects which result in impairment of neuronal plasticity and degenerative processes. Memantine shows benefits in improving cognition, function, agitation/aggression and delusion in Alzheimer’s disease. On the other hand, some NMDA modulators which enhance NMDA function through the co-agonist binding site can also improve cognitive function and psychotic symptoms. We propose that modulating NMDA neurotransmission is effective in treating behavioral and psychological symptoms of Alzheimer’s disease. Prospective study using NMDA enhancers in patients with Alzheimer’s disease and associated behavioral disturbance is needed to verify this hypothesis.

Long-lasting antidepressant action of ketamine, but not glycogen synthase kinase-3 inhibitor SB216763, in the chronic mild stress model of mice

Background

Clinical studies demonstrate that the N-methyl-D-aspartate (NMDA) receptor antagonist, ketamine, induces rapid antidepressant effects in patients with refractive major depressive disorder and bipolar depression. This rapid onset of action makes ketamine a highly attractive drug for patients, particularly those who do not typically respond to therapy. A recent study suggested that glycogen synthase kinase (GSK)-3 may underlie the rapid antidepressant action of ketamine, although the precise mechanisms are unclear. In this study, we examined the effects of ketamine and GSK-3 inhibitor SB216763 in the unpredictable, chronic mild stress (CMS) mouse model of mice.

Methodology/Principal Findings

Adult C57/B6 male mice were divided into 2 groups, a non-stressed control group and the unpredictable CMS (35 days) group. Then, either vehicle, ketamine (10 mg/kg), or the established GSK-3 inhibitor, SB216763 (10 mg/kg), were administered into mice in the CMS group, while vehicle was administered to controls. In the open field test, there was no difference between the four groups (control+vehicle, CMS+vehicle, CMS+ketamine, CMS+SB216763). In the sucrose intake test, a 1% sucrose intake drop, seen in CMS mice, was significantly attenuated after a single dose of ketamine, but not SB216763. In the tail suspension test (TST) and forced swimming test (FST), the increased immobility time seen in CMS mice was significantly attenuated by a single dose of ketamine, but not SB216763. Interestingly, the ketamine-induced increase in the sucrose intake test persisted for 8 days after a single dose of ketamine. Furthermore, a single administration of ketamine, but not SB216763, significantly attenuated the immobility time of the TST and FST in the control (non-stressed) mice.

Conclusions/Significance

These findings suggest that a single administration of ketamine, but not GSK-3 inhibitor SB216763, produces a long-lasting antidepressant action in CMS model mice.

Network of brain protein level changes in glutaminase deficient fetal mice

Glutaminase is a multifunctional enzyme encoded by gene Gls involved in energy metabolism, ammonia trafficking and regeneration of neurotransmitter glutamate. To address the proteomic basis for the neurophenotypes of glutaminase-deficient mice, brain proteins from late gestation wild type, Gls+/- and Gls-/- male mice were subjected to two-dimensional gel electrophoresis, with subsequent identification by mass spectrometry using nano-LC-ESI-MS/MS. Protein spots that showed differential genotypic variation were quantified by immunoblotting. Differentially expressed proteins unambiguously identified by MS/MS included neurocalcin delta, retinol binding protein-1, reticulocalbin-3, cytoskeleton proteins fascin and tropomyosin alpha-4-chain, dihydropyrimidinase-related protein-5, apolipoprotein IV and proteins from protein metabolism proteasome subunits alpha type 2, type 7, heterogeneous nuclear ribonucleoprotein C1/C2 and H, voltage-gated anion-selective channel proteins 1 and 2, ATP synthase subunit β and transitional endoplasmic reticulum ATPase. An interaction network determined by Ingenuity Pathway Analysis revealed a link between glutaminase and calcium, Akt and retinol signaling, cytoskeletal elements, ATPases, ion channels, protein synthesis and the proteasome system, intermediary, nucleic acid and lipid metabolism, huntingtin, guidance cues, transforming growth factor beta-1 and hepatocyte nuclear factor 4-alpha. The network identified involves (a) cellular assembly and organization and (b) cell signaling and cell cycle, suggesting that Gls is crucial for neuronal maturation.

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.

Dual inhibitor of PDE7 and GSK-3-VP1.15 acts as antipsychotic and cognitive enhancer in C57BL/6J mice

Cognitive deficit is a core of schizophrenia and it is not effectively treated by the available antipsychotic drugs, hence new and more effective therapy is needed. Schizophrenia is considered as a pathway disorder where Disrupted-In-Schizophrenia-1 (DISC1) is important molecular player that regulates multiple cellular cascades. We recently reported synergistic action between phosphodiesterase-4 (PDE4) and glycogen synthase kinase-3 (GSK-3) as DISC1 interacting proteins. In the current study we characterized behavioural effects of a newly developed compound, VP1.15 that inhibits both PDE7 and GSK-3 with main focus on its antipsychotic and cognitive capacities. VP1.15 reduced ambulation in C57BL/6J mice in a dose-dependent manner (7.5 mg/kg and 3 mg/kg, respectively) and, hence, lower dose was chosen for the further analysis. VP1.1.5 facilitated pre-pulse inhibition (PPI), reversed amphetamine- but not MK-801-induced PPI deficit. The drug was able to ameliorate the disrupted latent inhibition (LI) induced by the increased number of conditioning trials and reversed amphetamine-induced LI deficit, supporting further its antipsychotic effects. The drug also significantly improved episodic memory in the spatial object recognition test, facilitated working memory in Y-maze and enhanced cued fear memory, but had no effect on executive function in the Puzzle box and contextual fear conditioning. Taken together, VP1.15 elicited antipsychotic effects and also facilitated cognitive domains in mice, suggesting that multitarget drugs, affecting molecular substrates from the same pathway, perhaps could be antipsychotics of new-generation that open a new possibilities in drug discoveries. This article is part of a Special Issue entitled 'Cognitive Enhancers'.

Perinatal phencyclidine treatment alters neuregulin 1/erbB4 expression and activation in later life

Schizophrenia is a complex and devastating mental disorder of unknown etiology. Hypofunction of N-methyl-D-aspartate (NMDA) receptors are implicated in the disorder, since phencyclidine (PCP) and other NMDA receptor antagonists mimic schizophrenia-like symptoms in humans and animals so well. Moreover, genetic linkage and post mortem studies strongly suggest a role for altered neuregulin 1 (Nrg1)/erbB4 signaling in schizophrenia pathology. This study investigated the relationship between the NMDA receptor and Nrg1 signaling pathways using the perinatal PCP animal model. Rats (n=5/group) were treated with PCP (10 mg/kg) or saline on postnatal days (PN) 7, 9 and 11 and were sacrificed on PN12, 5 weeks and 20 weeks for biochemical analyses. Western blotting was used to determine total and phosphorylated levels of proteins involved in NMDA receptor/Nrg1 signaling in the prefrontal cortex and hippocampus. In the cortex, PCP treatment altered Nrg1/erbB4 expression levels throughout development, including decreased Nrg1 and erbB4 at PN12 (-25-30%; p<0.05); increased erbB4 and p-erbB4 (+18-27%; p<0.01) at 5 weeks; and decreased erbB4 and p-erbB4 (-16-18%; p<0.05) along with increased Nrg1 (+33%; p<0.01) at 20 weeks. In the hippocampus, levels of Nrg1/erbB4 were largely unaffected apart from a significant decrease in p-erbB4 at 20 weeks (-13%; p<0.001); however NMDA receptor subunits and PSD-95 showed increases at PN12 and 5 weeks (+20-32%; p<0.05), and decreases at 20 weeks (-22-29%; p<0.05). This study shows that NMDA receptor antagonism early in development can have long term effects on Nrg1/erbB4 expression which could be important in understanding pathological processes which might be involved in schizophrenia.

Inhibition of glycogen synthase kinase-3 attenuates psychotomimetic effects of ketamine

N-methyl-D-aspartate (NMDA) glutamate receptors mediate fast neurotransmission and regulate synaptic plasticity in the brain. Disruption of NMDA receptor-mediated signaling by noncompetitive antagonists, such as PCP or ketamine, evokes psychotomimetic behaviors, although the cellular mechanisms by which hypofunctional NMDA receptor signaling drives behavioral pathology are still unclear. Activation of glycogen synthase kinase-3 (GSK-3) has been implicated in the cellular neurotoxicity of NMDA receptor antagonists. Accordingly, in the present study we examined the ability of GSK-3 inhibitors, SB216763 and 1-azakenpaullone, to reverse the behavioral aberrations induced by ketamine. Male NMRI mice received intracerebroventricular (i.c.v.) injection of the GSK-3 inhibitors, SB216763 and 1-azakenpaullone, 5 min prior to ketamine administration. Locomotor activity, rotarod performance, prepulse inhibition, novel object recognition, and duration of loss of righting reflex were monitored. GSK-3 inhibitors attenuated ketamine-induced locomotor hyperactivity, motor incoordination, sensorimotor impairment, and cognitive deficits, but did not affect ketamine anesthesia. These data support an important role of GSK-3 in the expression of behavioral aberrations associated with NMDA receptor hypofunction, and suggest that GSK-3 inhibitors may ameliorate certain behavioral and cognitive dysfunctions in patients with schizophrenia.

Phencyclidine-induced decrease of synaptic connectivity via inhibition of BDNF secretion in cultured cortical neurons

Repeated administration of phencyclidine (PCP), a noncompetitive N-methyl-D-aspartate (NMDA) receptor blocker, produces schizophrenia-like behaviors in humans and rodents. Although impairment of synaptic function has been implicated in the effect of PCP, the molecular mechanisms have not yet been elucidated. Considering that brain-derived neurotrophic factor (BDNF) plays an important role in synaptic plasticity, we examined whether exposure to PCP leads to impaired BDNF function in cultured cortical neurons. We found that PCP caused a transient increase in the level of intracellular BDNF within 3 h. Despite the increased intracellular amount of BDNF, activation of Trk receptors and downstream signaling cascades, including MAPK/ERK1/2 and PI3K/Akt pathways, were decreased. The number of synaptic sites and expression of synaptic proteins were decreased 48 h after PCP application without any impact on cell viability. Both electrophysiological and biochemical analyses revealed that PCP diminished glutamatergic neurotransmission. Furthermore, we found that the secretion of BDNF from cortical neurons was suppressed by PCP. We also confirmed that PCP-caused downregulation of Trk signalings and synaptic proteins were restored by exogenous BDNF application. It is possible that impaired secretion of BDNF and subsequent decreases in Trk signaling are responsible for the loss of synaptic connections caused by PCP.

Group II metabotropic glutamate receptor agonist ameliorates MK801-induced dysfunction of NMDA receptors via the Akt/GSK-3β pathway in adult rat prefrontal cortex

Pharmacological intervention targeting mGluRs has emerged as a potential treatment for schizophrenia, whereas the mechanisms involved remain elusive. We explored the antipsychotic effects of an mGluR2/3 agonist in the MK-801 model of schizophrenia in the rat prefrontal cortex. We found that the mGluR2/3 agonist LY379268 effectively recovered the disrupted expression of NMDA receptors induced by MK-801 administration. This effect was attributable to the direct regulatory action of LY379268 on NMDA receptors via activation of the Akt/GSK-3β signaling pathway. As occurs with the antipsychotic drug clozapine, acute treatment with LY379268 significantly increased the expression and phosphorylation of NMDA receptors, as well as Akt and GSK-3β. Physiologically, LY379268 significantly enhanced NMDA-induced current in prefrontal neurons and a GSK-3β inhibitor occluded this effect. In contrast to the widely proposed mechanism of modulating presynaptic glutamate release, our results strongly argue that mGluR2/3 agonists modulate the function of NMDA receptors through postsynaptic actions and reverse the MK-801-induced NMDA dysfunction via the Akt/GSK-3β pathway. This study provides novel evidence for postsynaptic mechanisms of mGluR2/3 in regulation of NMDA receptors and presents useful insights into the mechanistic actions of mGluR2/3 agonists as potential antipsychotic agents for treating schizophrenia.

Effects of neonatal MK-801 treatment on p70S6K-S6/eIF4B signal pathways and protein translation in the frontal cortex of the developing rat brain

Systemic injections of MK-801, a selective NMDAR antagonist, into neonatal rats induces long-term neurochemical and behavioural changes. It has been suggested that these changes form the neurodevelopmental basis for schizophrenia-like behaviour in rats. In this study, 7-d-old rats were treated with MK-801, and their frontal cortices were examined to investigate the effects on p70S6K-S6 signal pathway and on protein translation, which play crucial roles in the neurodevelopmental process. MK-801, in doses of 0.5 and 1.0 mg/kg, induced a decrease in phosphorylation of p70S6K and its substrates, S6 and eIF4B, in the first 8 h, and no change at 24 and 48 h. These effects were more prominent after two injections of MK-801 than one. Decreased S6 phosphorylation by MK-801 was evident in the prefrontal, cingulate, and insular cortex. In two representative upstream p70S6K-S6 pathways related to ERK1/2 and Akt, changes in ERK1/2-p90RSK phosphorylation were accompanied by changes of p70S6K-S6. Although two MK-801 injections induced a dose-dependent decrease in phosphorylation of Akt and mTOR at 4 and 8 h, a single injection did not produce a significant effect. Protein synthesis rate, measured by [3H]leucine incorporation in frontal cortical tissue, was reduced until 24 h after two MK-801 (1.0 mg/kg) injections. In summary, this study found that neonatal MK-801 treatment induced dysregulation in the p70S6K-S6/eIF4B pathway and protein translation in the frontal cortex of the developing rat brain, which may suggest an important role of protein translation machinery in the MK-801 neurodevelopmental animal model of schizophrenia.

Activation of glycogen synthase kinase-3 beta is required for hyperdopamine and D2 receptor-mediated inhibition of synaptic NMDA receptor function in the rat prefrontal cortex

The interactions between dopamine and glutamate systems play an essential role in normal brain functions and neuropsychiatric disorders. The mechanism of NMDA receptor regulation through high concentrations of dopamine, however, remains unclear. Here, we show the signaling pathways involved in hyperdopaminergic regulation of NMDA receptor functions in the prefrontal cortex by incubating cortical slices with high concentration of dopamine or administering dopamine reuptake inhibitor 1-(2-[bis-(4-fluorophenyl)methoxy]ethyl)- 4-(3-phenylpropyl)piperazine (GBR12909) in vivo. We found that, under both conditions, the synaptic NMDA receptor-mediated currents were significantly attenuated by excessive dopamine stimulation through activation of D(2) receptors. Furthermore, high dose of dopamine failed to affect NMDA receptor-mediated currents after blockade of NR2B subunits but triggered a dynamin-dependent endocytosis of NMDA receptors. The high-dose dopamine/D(2) receptor-mediated suppression of NMDA receptors was involved in the increase of glycogen synthase kinase-3beta (GSK-3beta) activity, which in turn phosphorylates beta-catenin and disrupts beta-catenin-NR2B interaction, but was dependent on neither Gq11 nor PLC (phospholipase C). Moreover, the hyperdopamine induced by GBR12909 significantly decreased the expression of both surface and intracellular NR2B proteins, as well as NR2B mRNA levels, suggesting an inhibition of protein synthesis. These effects were, however, completely reversed by administration of either GSK-3beta inhibitor or D(2) receptor antagonist. These results therefore suggest that GSK-3beta is required for the hyperdopamine/D(2) receptor-mediated inhibition of NMDA receptors in the prefrontal neurons and these actions may underlie D(2) receptor-mediated psychostimulant effects and hyperdopamine-dependent behaviors in the brain.

Brain-derived neurotrophic factor prevents phencyclidine-induced apoptosis in developing brain by parallel activation of both the ERK and PI-3K/Akt pathways

Phencyclidine is an N-methyl d-aspartate receptor (NMDAR) blocker that has been reported to induce neuronal apoptosis during development and schizophrenia-like behaviors in rats later in life. Brain-derived neurotrophic factor (BDNF) has been shown to prevent neuronal death caused by NMDAR blockade, but the precise mechanism is unknown. This study examined the role of the phosphatidylinositol-3 kinase (PI3K)/Akt and extracellular signal-regulated kinase (ERK) pathways in BDNF protection of PCP-induced apoptosis in corticostriatal organotypic cultures. It was observed that BDNF inhibited PCP-induced apoptosis in a concentration-dependent fashion. BDNF effectively prevented PCP-induced inhibition of the ERK and PI-3K/Akt pathways and suppressed GSK-3beta activation. Blockade of either PI-3K/Akt or ERK activation abolished BDNF protection. Western blot analysis revealed that the PI-3K inhibitor LY294002 prevented the stimulating effect of BDNF on the PI-3K/Akt pathway, but had no effect on the ERK pathway. Similarly, the ERK inhibitor PD98059 prevented the stimulating effect of BDNF on the ERK pathway, but not the PI-3K/Akt pathway. Co-application of LY294002 and PD98059 had no additional effect on BDNF-evoked activation of Akt or ERK. However, concurrent exposure to PD98059 and LY294002 caused much greater inhibition of BDNF-evoked phosphorylation of GSK-3beta at serine 9 than did LY294002 alone. Finally, either BDNF or GSK-3beta inhibition prevented PCP-induced suppression of cyclic-AMP response element binding protein (CREB) phosphorylation. These data demonstrate that the protective effect of BDNF against PCP-induced apoptosis is mediated by parallel activation of the PI-3K/Akt and ERK pathways, most likely involves inhibition of GSK-3beta and activation of CREB.