Glycogen synthase kinase-3: a putative molecular target for lithium mimetic drugs

Glycogen synthase kinase 3 (GSK3) inhibition: a potential therapeutic strategy for Alzheimer's disease

Alzheimer's disease (AD), the most common type of dementia among older adults, is a chronic neurodegenerative pathology that causes a progressive loss of cognitive functioning with a decline of rational skills. It is well known that AD is multifactorial, so there are many different pharmacological targets that can be pursued. According to estimates from the World Health Organization (WHO), 18 million individuals worldwide suffer from AD. Major initiatives to identify risk factors, enhance care giving, and conduct basic research to delay the beginning of AD were started by the USA, France, Germany, France, and various other nations. Widely recognized as a key player in the development and subsequent progression of AD pathogenesis, glycogen synthase kinase-3 (GSK-3) controls a number of crucial targets associated with neuronal degeneration. GSK-3 inhibition has been linked to reduced tau hyperphosphorylation, β-amyloid formation, and neuroprotective benefits in Alzheimer's disease. Lithium, the very first inhibitor of GSK-3β that was used therapeutically, has been successfully used for many years with remarkable results. A great variety of structurally varied strong GSK-3β blockers have been identified in recent years. The purpose of this thorough review is to cover the biological and structural elements of glycogen synthase kinase, as well as the medicinal chemistry aspects of GSK inhibitors that have been produced in recent years.

Lithium, Inflammation and Neuroinflammation with Emphasis on Bipolar Disorder-A Narrative Review

This narrative review examines lithium's effects on immune function, inflammation and cell survival, particularly in bipolar disorder (BD) in in vitro studies, animal models and clinical studies. In vitro studies show that high lithium concentrations (5 mM, beyond the therapeutic window) reduce interleukin (IL)-1β production in monocytes and enhance T-lymphocyte resistance, suggesting a protective role against cell death. Lithium modulates oxidative stress in lipopolysaccharide (LPS)-activated macrophages by inhibiting nuclear factor (NF)-ƙB activity and reducing nitric oxide production. At therapeutically relevant levels, lithium increased both pro-inflammatory [interferon (INF)-γ, IL-8 and tumor necrosis factor (TNF)-α)] and anti-inflammatory (IL-10) cytokines on whole blood supernatant culture in healthy volunteers, influencing the balance of pro- and anti-inflammatory responses. Animal models reveal lithium's potential to alleviate inflammatory diseases by reducing pro-inflammatory cytokines and enhancing anti-inflammatory responses. It also induces selective macrophage death in atherosclerotic plaques without harming other cells. In primary rat cerebellum cultures (ex vivo), lithium prevents neuronal loss and inhibits astroglial growth, impacting astrocytes and microglia. Clinical studies show that lithium alters cytokine profiles and reduces neuroinflammatory markers in BD patients. Chronic treatment decreases IL-2, IL-6, IL-10 and IFN-γ secretion from peripheral blood leukocytes. Lithium response correlates with TNF-α levels, with poor responders showing higher TNF-α. Overall, these findings elucidate lithium's diverse mechanisms in modulating immune responses, reducing inflammation and promoting cell survival, with significant implications for managing BD and other inflammation-related conditions. Yet, to better understand the drug's impact in BD and other inflammatory/neuroinflammatory conditions, further research is warranted to appreciate lithium's therapeutic potential and its role in immune regulation.

Jnk1 and downstream signalling hubs regulate anxiety-like behaviours in a zebrafish larvae phenotypic screen

Current treatments for anxiety and depression show limited efficacy in many patients, indicating the need for further research into the underlying mechanisms. JNK1 has been shown to regulate anxiety- and depressive-like behaviours in mice, however the effectors downstream of JNK1 are not known. Here we compare the phosphoproteomes from wild-type and Jnk1-/- mouse brains and identify JNK1-regulated signalling hubs. We next employ a zebrafish (Danio rerio) larvae behavioural assay to identify an antidepressant- and anxiolytic-like (AA) phenotype based on 2759 measured stereotypic responses to clinically proven antidepressant and anxiolytic (AA) drugs. Employing machine learning, we classify an AA phenotype from extracted features measured during and after a startle battery in fish exposed to AA drugs. Using this classifier, we demonstrate that structurally independent JNK inhibitors replicate the AA phenotype with high accuracy, consistent with findings in mice. Furthermore, pharmacological targeting of JNK1-regulated signalling hubs identifies AKT, GSK-3, 14-3-3 ζ/ε and PKCε as downstream hubs that phenocopy clinically proven AA drugs. This study identifies AKT and related signalling molecules as mediators of JNK1-regulated antidepressant- and anxiolytic-like behaviours. Moreover, the assay shows promise for early phase screening of compounds with anti-stress-axis properties and for mode of action analysis.

GSK3β-driven SOX2 overexpression is a targetable vulnerability in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is one of the deadliest forms of human malignancy that currently lacks approved targeted therapeutics. Accumulating evidence suggests that SOX2 overexpression is a key driving factor for ESCC and various squamous cell carcinoma. Here, through screening a small-molecule kinase inhibitor library, we identified GSK3β as a kinase that is critically required for robust SOX2 expression in ESCC cells. GSK3β did not promote SOX2 transcriptionally but was required for SOX2 protein stability. We demonstrated that GSK3β interacts with and phosphorylates SOX2 at residue S251, which blocks SOX2 from ubiquitination and proteasome-dependent degradation instigated by ubiquitin E3 ligase CUL4ADET1-COP1. Pharmacological inhibition or knockdown of GSK3β by RNA interference selectively impaired SOX2-positive ESCC cell proliferation, cancer stemness, and tumor growth in mouse xenograft model, suggesting that GSK3β promotes ESCC tumorigenesis primarily by driving SOX2 overexpression. GSK3β was found to be frequently overexpressed in clinical esophageal tumors, and there was a positive correlation between GSK3β and SOX2 protein levels. Notably, we found that SOX2 enhanced GSK3β expression transcriptionally, suggesting the existence of a vicious cycle that drives a coordinated GSK3β and SOX2 overexpression in ESCC cells. Finally, we demonstrated in tumor xenograft model that GSK3β inhibitor AR-A014418 was effective in suppressing SOX2-positive ESCC tumor progression and inhibited tumor progression cooperatively with chemotherapeutic agent carboplatin. In conclusion, we uncovered a novel role for GSK3β in driving SOX2 overexpression and tumorigenesis and provided evidence that targeting GSK3β may hold promise for the treatment of recalcitrant ESCCs.

Insulin Signaling Pathway Model in Adipocyte Cells

BACKGROUND

Worldwide, type 2 diabetes mellitus (T2DM) is one of the most pervasive and fastgrowing disorders, bringing long-term adverse effects. T2DM arises from pancreatic β-cells deficiency to produce enough insulin or when the body cannot effectively use the insulin produced by such cells. Accordingly, early diagnosis will decrease the long-term effects and high-healthcare costs of diabetes.

OBJECTIVE

The objective is developing an integrated mathematical model of the insulin signaling network based on Brännmark's model, which can simulate the signaling events more comprehensively with the added key components.

METHODS

In this study, a thorough mathematical model of the insulin signaling network was developed by expanding the previously validated model and incorporating the glycogen synthesis module. Parameters (69 parameters) of the integrated model were evaluated by a genetic algorithm by fitting the model predictions to eighty percent of experimental data from the literature. Twenty percent of the experimental data were used to evaluate the final optimized model.

RESULTS

The time-response curves indicate that the GS phosphorylation reaches its maximum in response to 10^-7 M insulin after 4 min, while the maximum phosphorylated GSK3 is attained within ~50 min. The doseresponse curves for the GSP and GSK3 of the insulin signaling intermediaries in response to the increased concentration of insulin, after 10 min, in the input from 0-100 nM exhibits a decreasing trend, whereas an increasing trend was observed for the GS and GSK3P. The GSK and GS phosphorylation sensitivity was enhanced by increasing the initial insulin concentration level from 0.001 to 100 nM. However, the sensitivity of GSK3 to insulin concentration changes (from 0.001 to 100 nM) was 3-fold higher than GS sensitivity.

CONCLUSION

Considerably, the trends of all signaling components simulated by the expanded model shows high compatibility with experimental data (R2 ≥ 0.9), which approves the accuracy of the proposed model. The proposed mathematical model can be used in many biological systems and combined with the whole-body model of the blood glucose regulation system for a better understanding of the causes and potential treatment of type 2 diabetes. Although, this model is not a complete description of insulin signaling, yet it can make profound contributions to improvements regarding other important components and signaling branches such as epidermal growth factor (EGF) signaling, as well as signaling in other cell types in the model structure of future works.

Characterisation of Deficits and Sex Differences in Verbal and Visual Memory/Learning in Bipolar Disorder

OBJECTIVE

Cognitive impairment is consistently reported in bipolar disorder (BD), but few studies have characterised which memory component processes are affected. Further, it is unknown whether the component processes underlying memory impairment are moderated by sex. The present study examined diagnosis and sex differences in both verbal and visual memory/learning domains in patients with BD and psychiatrically healthy controls.

METHOD

Verbal and visual memory/learning were measured using the Hopkins Verbal Learning Test-Revised (HVLT-R) and Brief Visuospatial Memory Test-Revised (BVMT-R). 114 patients with BD (n = 50 males, n = 64 females), were compared to 105 psychiatrically healthy controls (n = 42 males, n = 63 females).

RESULTS

Patients with BD had worse performance in verbal and visual immediate and total recall, verbal and visual delayed free recall, and verbal recognition discrimination scores, but there were no group differences in learning slopes and cumulative learning index scores. There were trends for BD females to outperform BD males in visual memory/learning free recall and cumulative learning, but these results did not survive multiple testing correction. These findings did not change in a secondary sensitivity analysis comparing only strictly euthymic BD patients to controls (n = 64).

CONCLUSION

The present study found trait-like verbal and visual memory/learning impairment in BD that was attributable to deficient encoding and/or consolidation processes rather than deficits in learning. We did not find marked sex differences in either visual or verbal memory/learning measures, although some trend level effects were apparent and deserve exploration in future studies.

Ketamine modulates neural stem cell differentiation by regulating TRPC3 expression through the GSK3β/β-catenin pathway

Ketamine, a popular anesthetic, is often abused by people for its hallucinogenic effect. Thus, the safety of ketamine in pediatric populations has been called into question for potential neurotoxic effects. However, ketamine also has neuroprotective effects in many brain injury models. The differentiation of neural stem cells (NSCs) was influenced significantly by ketamine, but the molecular mechanism is still unclear. NSCs were extracted from the hippocampi of postnatal day 1 rats and treated with ketamine to induce NSCs differentiation. Our results found that ketamine promoted neuronal differentiation of NSCs dose-dependently in a small dose range (P < 0.001). The main types of neurons from NSCs were cholinergic (51 ± 4 %; 95 % CI: 41-61 %) and glutamatergic neurons (34 ± 3 %; 95 % CI: 27-42 %). Furthermore, we performed RNA sequencing to promise a more comprehensive understanding of the molecules regulated by ketamine. Finally, we combined bioimaging and multiple molecular biology techniques to clarify that ketamine influences NSC differentiation by regulating transient receptor potential canonical 3 (TRPC3) expressions. Ketamine dramatically repressed TRPC3 expression (MD [95 % CI]=0.67 [0.40-0.95], P < 0.001) with a significant increase of phosphorylated glycogen synthase kinase 3β (p-GSK3β; MD [95 % CI]=1.00 [0.74-1.27], P < 0.001) and a decrease of β-catenin protein expression (MD [95 % CI]=0.60 [0.32-0.89], P = 0.001), thereby promoting the differentiation of NSCs into neurons and inhibiting their differentiation into astrocytes. These results suggest that TRPC3 is necessary for ketamine to modulate NSC differentiation, which occurs partly via regulation of the GSK3β/β-catenin pathway.

Effects of Risperidone and Prenatal Poly I:C Exposure on GABAA Receptors and AKT-GSK3β Pathway in the Ventral Tegmental Area of Female Juvenile Rats

The ventral tegmental area (VTA) in the ventral midbrain is the origin of the dopaminergic neurotransmission pathways. Although GABA_A receptors and AKT-GSK3β signaling are involved in the pathophysiology of mental disorders and are modulated by antipsychotics, an unmet task is to reveal the pathological changes in these biomarkers and antipsychotic modulations in the VTA. Using a juvenile polyriboinosinic-polyribocytidylic acid (Poly I:C) psychiatric rat model, this study investigated the effects of adolescent risperidone treatment on GABA_A receptors and AKT/GSK3β in the VTA. Pregnant female Sprague-Dawley rats were administered Poly I:C (5mg/kg; i.p) or saline at gestational day 15. Juvenile female offspring received risperidone (0.9 mg/kg, twice per day) or a vehicle from postnatal day 35 for 25 days. Poly I:C offspring had significantly decreased mRNA expression of GABA_A receptor β3 subunits and glutamic acid decarboxylase (GAD2) in the VTA, while risperidone partially reversed the decreased GAD2 expression. Prenatal Poly I:C exposure led to increased expression of AKT2 and GSK3β. Risperidone decreased GABA_A receptor β2/3, but increased AKT2 mRNA expression in the VTA of healthy rats. This study suggests that Poly I:C-elicited maternal immune activation and risperidone differentially modulate GABAergic neurotransmission and AKT-GSK3β signaling in the VTA of adolescent rats.

Dynamic insulin-stimulated mTOR/GSK3 signaling in peripheral immune cells: Preliminary evidence for an association with lithium response in bipolar disorder

INTRODUCTION

A key mechanism of lithium is the inhibition of glycogen synthase kinase-3β (GSK3β) and activation of mammalian target of rapamycin (mTOR), two contributors to insulin signaling. We explored the relationship between these markers and clinical response to lithium in bipolar disorder (BD).

METHODS

Thirty-four subjects with BD who had been taking lithium for ≥2 years and had a maintenance lithium Alda score defined as either high (≥7; n = 20) or low (≤2; n = 14) were included in the study. Baseline protein expression of GSK3β and mTOR (total and phosphorylated (p)) was obtained from a buffy coat. Peripheral blood mononuclear cells (PBMCs) from a subset of each group (n = 11) were stimulated with insulin (10 µg) and change in protein expression was determined using Western blot.

RESULTS

In buffy coat samples, significantly higher levels of pmTOR were present in subjects with an Alda score ≤2 (lithium non-responsive), relative to those with scores ≥7 (lithium-responsive). No differences were observed for pGSK3β. In contrast, functional PBMC responses to 5 min of insulin stimulation demonstrated robust increases in pGSK3β (87.05 ± 43.41%) and pmTOR (105.7 ± 66.48%) in the lithium responsive group only. This contrasted observed decreases in pGSK3β (34.08 ± 16.12%) and pmTOR (37.84 ± 14.39%) 5 mins post-insulin in non-responders.

CONCLUSIONS

Dynamic increases in pmTOR and pGSK3β post-insulin stimulation may reflect an immunometabolic state that facilitates lithium response. Further prospective analyses are needed to replicate and extend these preliminary findings and further investigate the role of insulin signaling in lithium response in BD.

Effect of Lithium Drug on Binding Affinities of Glycogen Synthase Kinase-3 β to Its Network Partners: A New Computational Approach

Finding new methods to study the effect of small molecules on protein interaction networks provides us with invaluable tools in the fields of pharmacodynamics and drug design. Lithium is an antimanic drug that has been used for the treatment of bipolar disorder for more than 60 years. Here, we utilized a new approach to study the effect of lithium as a drug on the protein interaction network of GSK-3β as a hub protein and computed the affinities of GSK-3β to its partners in the presence of lithium or sodium ions. For this purpose, ensembles of GSK-3β protein structures were created in the presence of either lithium or sodium ions using adaptive tempering molecular dynamics simulations. The protein binding patches of GSK-3β for its partners were determined, and finally, the affinity of each binding patch to the related partner was computed for structures of ensembles using a monomer-based approach. Besides, by comparing structural dynamics of GSK-3β during MD simulations in the presence of LiCl and NaCl, we suggested a new mechanism for the inhibitory effect of lithium on GSK-3β.

Casein kinase 1 epsilon and circadian misalignment impact affective behaviours in mice

Affective behaviours and mental health are profoundly affected by disturbances in circadian rhythms. Casein kinase 1 epsilon (CSNK1E) is a core component of the circadian clock. Mice with tau or null mutation of this gene have shortened and lengthened circadian period respectively. Here, we examined anxiety-like, fear, and despair behaviours in both male and female mice of these two different mutants. Compared with wild-type mice, we found reductions in fear and anxiety-like behaviours in both mutant lines and in both sexes, with the tau mutants exhibiting the greatest phenotypic changes. However, the behavioural despair had distinct phenotypic patterns, with markedly less behavioural despair in female null mutants, but not in tau mutants of either sex. To determine whether abnormal light entrainment of tau mutants to 24-h light-dark cycles contributes to these phenotypic differences, we also examined these behaviours in tau mutants on a 20-h light-dark cycle close to their endogenous circadian period. The normalized entrainment restored more wild-type-like behaviours for fear and anxiety, but it induced behavioural despair in tau mutant females. These data show that both mutations of Csnk1e broadly affect fear and anxiety-like behaviours, while the effects on behavioural despair vary with genetics, photoperiod, and sex, suggesting that the mechanisms by which Csnk1e affects fear and anxiety-like behaviours may be similar, but distinct from those affecting behavioural despair. Our study also provides experimental evidence in support of the hypothesis of beneficial outcomes from properly entrained circadian rhythms in terms of the anxiety-like and fear behaviours.

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.

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

BACKGROUND

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

METHODS

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

RESULTS

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

DISCUSSION

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

Lithium toxicity and the kidney with special focus on nephrotic syndrome associated with the acute kidney injury: A case-based systematic analysis

Despite the progress made in treating bipolar and unipolar affective disorders, lithium carbonate is still a common drug in psychiatric practice. Lithium-related renal side effects include nephrogenic diabetes insipidus, chronic tubulointerstitial nephropathy, and acute kidney injury (AKI). Nephrotic syndrome (NS) is an uncommon but severe complication of lithium treatment. We present a 49-year-old female treated with lithium carbonate due to a recurrent depressive disorder who developed NS during this therapy. NS spontaneously remitted after the drug withdrawal. Since her lithium serum levels were within the recommended values, we performed a retrospective analysis of lithium-induced NS cases trying to determine causes predisposing to the NS development, underlying histopathology, and preservation or irreversible loss of kidney function. This analysis revealed that in lithium-induced NS with AKI, lithium serum level was the key determinant of AKI development (the β coefficient = 0.8499 with a confidence interval ranging from 0.7452 to 0.9546 and p value < 0.0001). In these cases, the underlying pathology was mainly minimal change disease (MCD), which was quickly reversible upon the drug withdrawal. The development of chronic kidney disease (CKD) seemed to be associated with lithium therapy duration. However, the multiple regression analysis for CKD as the dependent variable showed that the decisive factor was focal segmental glomerulosclerosis (FSGS) as the underlying pathology (the β coefficient = 0.7866 with a confidence interval ranging from 0.600 to 0.9704 and the p value < 0.0001). Thus, we conclude that in lithium-induced NS/AKI, serum lithium levels contribute to these complications, while FSGS lesions are responsible for CKD's disease progression.

Mitochondria-targeting therapeutic strategies in the treatment of depression

Depression is an affective disease with a complex clinical picture that is characterized by mood and emotional disturbances. It is known that several factors contribute to the risk of developing depression. The concept that mitochondrial dysfunction is one of the causes of depression is supported by a wide range of studies on cell cultures, animal models, and clinical research. An understanding the relationship between mitochondrial processes and central nervous system abnormalities that occur in the course of depression can guide the development of novel mitochondrial targeted therapeutic strategies as well as the usage of currently available antidepressants in a new context. This brief review aims to summarize recent findings on mitochondria dysfunction in depression, provide insight into therapeutic strategies targeting mitochondrial pathways, allude to future promising therapies, and discuss factors that can be used to improve treatment outcomes. The main focus is on new aspects (the effects of nutraceuticals and physical activity on brain metabolism), which can be combined with the available treatment options [monoamine oxidase inhibitors (MAOIs), tricyclic antidepressants (TCAs), selective serotonin reuptake inhibitors (SSRIs) and atypical drugs] to enhance their therapeutic effects.

Mitochondrial dysfunction as a critical event in the pathophysiology of bipolar disorder

The understanding of the pathophysiology of bipolar disorder (BD) remains modest, despite recent advances in neurobiological research. The mitochondrial dysfunction hypothesis of bipolar disorder has been corroborated by several studies involving postmortem brain analysis, neuroimaging, and specific biomarkers in both rodent models and humans. Evidence suggests that BD might be related to abnormal mitochondrial morphology and dynamics, neuroimmune dysfunction, and atypical mitochondrial metabolism and oxidative stress pathways. Mitochondrial dysfunction in mood disorders is also associated with abnormal Ca2+ levels, glutamate excitotoxicity, an imbalance between pro- and antiapoptotic proteins towards apoptosis, abnormal gene expression of electron transport chain complexes, and decreased ATP synthesis. This paper aims to review and discuss the implications of mitochondrial dysfunction in BD etiology and to explore mitochondria as a potential target for novel therapeutic agents.

Advances toward precision medicine for bipolar disorder: mechanisms & molecules

Given its chronicity, contribution to disability and morbidity, and prevalence of more than 2%, the effective treatment, and prevention of bipolar disorder represents an area of significant unmet medical need. While more than half a century has passed since the introduction of lithium into widespread use at the birth of modern psychopharmacology, that medication remains a mainstay for the acute treatment and prevention of recurrent mania/hypomania and depression that characterize bipolar disorder. However, the continued limited understanding of how lithium modulates affective behavior and lack of validated cellular and animal models have resulted in obstacles to discovering more effective mood stabilizers with fewer adverse side effects. In particular, while there has been progress in developing new pharmacotherapy for mania, developing effective treatments for acute bipolar depression remain inadequate. Recent large-scale human genetic studies have confirmed the complex, polygenic nature of the risk architecture of bipolar disorder, and its overlap with other major neuropsychiatric disorders. Such discoveries have begun to shed light on the pathophysiology of bipolar disorder. Coupled with broader advances in human neurobiology, neuropharmacology, noninvasive neuromodulation, and clinical trial design, we can envision novel therapeutic strategies informed by defined molecular mechanisms and neural circuits and targeted to the root cause of the pathophysiology. Here, we review recent advances toward the goal of better treatments for bipolar disorder, and we outline major challenges for the field of translational neuroscience that necessitate continued focus on fundamental research and discovery.

Doxycycline reverses cognitive impairment, neuroinflammation and oxidative imbalance induced by D-amphetamine mania model in mice: A promising drug repurposing for bipolar disorder treatment?

Immune-inflammatory mechanisms are involved in the pathophysiology of bipolar disorder. Tetracyclines present neuroprotective actions based on their anti-inflammatory and microglia suppressant effects. Doxycycline (DOXY) is a tetracycline that demonstrates a better usage profile with protective actions against inflammation and CNS injury. Here, we investigated the effects of DOXY against behavioral, neuroinflammatory, and pro-oxidative changes induced by the d-amphetamine mania model. Adult mice were given d-amphetamine 2.0 mg/kg or saline for 14 days. Between days 8 and 14, received lithium, DOXY (25 or 50 mg/kg), or their combination (lithium+DOXY) on both doses. We collected the brain areas prefrontal cortex (PFC), hippocampus, and amygdala to evaluate inflammatory and oxidative alterations. D-amphetamine induced hyperlocomotion and impairment in recognition and working memory. Lithium reversed hyperlocomotion but could not restore cognitive alterations. DOXY alone (at both doses) or combined with lithium reversed d-amphetamine-induced cognitive changes. DOXY, better than lithium, reversed the d-amphetamine-induced rise in TNFα, MPO, and lipid peroxidation. DOXY reduced the hippocampal expression of Iba1 (a marker of microglial activation), inducible nitric oxide synthase (iNOS), and nitrite. Combined with lithium, DOXY increased the phosphorylated (inactivated) form of GSK3β (Ser9). Therefore, DOXY alone or combined with lithium reversed cognitive impairment and neuroinflammation induced by the mice's d-amphetamine model. This study points to DOXY as a promising adjunctive tool for bipolar disorder treatment focused on cognition and neuroimmune changes. Our data provide the first rationale for clinical trials investigating DOXY therapeutic actions in bipolar disorder mania.

Mitochondria under the spotlight: On the implications of mitochondrial dysfunction and its connectivity to neuropsychiatric disorders

Neuropsychiatric disorders (NPDs) such as bipolar disorder (BD), schizophrenia (SZ) and mood disorder (MD) are hard to manage due to overlapping symptoms and lack of biomarkers. Risk alleles of BD/SZ/MD are emerging, with evidence suggesting mitochondrial (mt) dysfunction as a critical factor for disease onset and progression. Mood stabilizing treatments for these disorders are scarce, revealing the need for biomarker discovery and artificial intelligence approaches to design synthetically accessible novel therapeutics. Here, we show mt involvement in NPDs by associating 245 mt proteins to BD/SZ/MD, with 7 common players in these disease categories. Analysis of over 650 publications suggests that 245 NPD-linked mt proteins are associated with 800 other mt proteins, with mt impairment likely to rewire these interactions. High dosage of mood stabilizers is known to alleviate manic episodes, but which compounds target mt pathways is another gap in the field that we address through mood stabilizer-gene interaction analysis of 37 prescriptions and over-the-counter psychotropic treatments, which we have refined to 15 mood-stabilizing agents. We show 26 of the 245 NPD-linked mt proteins are uniquely or commonly targeted by one or more of these mood stabilizers. Further, induced pluripotent stem cell-derived patient neurons and three-dimensional human brain organoids as reliable BD/SZ/MD models are outlined, along with multiomics methods and machine learning-based decision making tools for biomarker discovery, which remains a bottleneck for precision psychiatry medicine.

Identification of antisense lncRNAs targeting GSK3β as a regulator in major depressive disorder

Aim: To identify lncRNAs targeting GSK3β in MDD. Materials & methods: The levels of GSK3β and its three targeting lncRNAs (gsk3β antisense AS1, AS2 and AS3) were detected in 52 patients with major depressive disorder (MDD) before and after 8 weeks of escitalopram treatment. The functional study was evaluated using the silence of lncR-gsk3βAS2/3. The correlation between lncRNA-gsk3β and 89 MDD patients was analyzed. Human neuron progenitor cells were used to investigate the functional role of lncRNA-gsk3β in MDD. Results: All three lncRNAs were downregulated in MDD patients but upregulated after treatment. Inhibition of gsk3βAS2/3 reduced GSK3β expression and its phosphorylation levels in the neuron progenitor cells. Conclusion: Our findings suggest that lncRNA-gsk3βAS3 regulates GSK3β activity in MDD and has potential as a novel therapeutic target.

Mesocortical BDNF signaling mediates antidepressive-like effects of lithium

Lithium has been used to treat major depressive disorder, yet the neural circuit mechanisms underlying this therapeutic effect remain unknown. Here, we demonstrated that the ventral tegmental area (VTA) dopamine (DA) neurons that project to the medial prefrontal cortex (mPFC), but not to nucleus accumbens (NAc), contributed to the antidepressive-like effects of lithium. Projection-specific electrophysiological recordings revealed that high concentrations of lithium increased firing rates in mPFC-, but not NAc-, projecting VTA DA neurons in mice treated with chronic unpredictable mild stress (CMS). In parallel, chronic administration of high-dose lithium in CMS mice restored the firing properties of mPFC-projecting DA neurons, and also rescued CMS-induced depressive-like behaviors. Nevertheless, chronic lithium treatment was insufficient to change the basal firing rates in NAc-projecting VTA DA neurons. Furthermore, chemogenetic activation of mPFC-, but not NAc-, projecting VTA DA neurons mimicked the antidepressive-like effects of lithium in CMS mice. Chemogenetic downregulation of VTA-mPFC DA neurons' firing activity abolished the antidepressive-like effects of lithium in CMS mice. Finally, we found that the antidepressant-like effects induced by high-dose lithium were mediated by BNDF signaling in the mesocortical DA circuit. Together, these results demonstrated the role of mesocortical DA projection in antidepressive-like effects of lithium and established a circuit foundation for lithium-based antidepressive treatment.

Antidepressant-relevant behavioral and synaptic molecular effects of long-term fasudil treatment in chronically stressed male rats

Several lines of evidence suggest that antidepressant drugs may act by modulating neuroplasticity pathways in key brain areas like the hippocampus. We have reported that chronic treatment with fasudil, a Rho-associated protein kinase inhibitor, prevents both chronic stress-induced depressive-like behavior and morphological changes in CA1 area. Here, we examined the ability of fasudil to (i) prevent stress-altered behaviors, (ii) influence the levels/phosphorylation of glutamatergic receptors and (iii) modulate signaling pathways relevant to antidepressant actions. 89 adult male Sprague-Dawley rats received intraperitoneal fasudil injections (10 mg/kg/day) or saline vehicle for 18 days. Some of these animals were daily restraint-stressed from day 5–18 (2.5 h/day). 24 hr after treatments, rats were either evaluated for behavioral tests (active avoidance, anxiety-like behavior and object location) or euthanized for western blot analyses of hippocampal whole extract and synaptoneurosome-enriched fractions. We report that fasudil prevents stress-induced impairments in active avoidance, anxiety-like behavior and novel location preference, with no effect in unstressed rats. Chronic stress reduced phosphorylations of ERK-2 and CREB, and decreased levels of GluA1 and GluN2A in whole hippocampus, without any effect of fasudil. However, fasudil decreased synaptic GluA1 Ser831 phosphorylation in stressed animals. Additionally, fasudil prevented stress-decreased phosphorylation of GSK-3β at Ser9, in parallel with an activation of the mTORC1/4E-BP1 axis, both in hippocampal synaptoneurosomes, suggesting the activation of the AKT pathway. Our study provides evidence that chronic fasudil treatment prevents chronic stress-altered behaviors, which correlated with molecular modifications of antidepressant-relevant signaling pathways in hippocampal synaptoneurosomes.

GPR56/ADGRG1 is associated with response to antidepressant treatment

It remains unclear why many patients with depression do not respond to antidepressant treatment. In three cohorts of individuals with depression and treated with serotonin-norepinephrine reuptake inhibitor (N = 424) we show that responders, but not non-responders, display an increase of GPR56 mRNA in the blood. In a small group of subjects we also show that GPR56 is downregulated in the PFC of individuals with depression that died by suicide. In mice, we show that chronic stress-induced Gpr56 downregulation in the blood and prefrontal cortex (PFC), which is accompanied by depression-like behavior, and can be reversed by antidepressant treatment. Gpr56 knockdown in mouse PFC is associated with depressive-like behaviors, executive dysfunction and poor response to antidepressant treatment. GPR56 peptide agonists have antidepressant-like effects and upregulated AKT/GSK3/EIF4 pathways. Our findings uncover a potential role of GPR56 in antidepressant response.

Survival genes expression analysis following ionizing radiation to LiCl treated KG1a cells

Purpose: Lithium chloride (LiCl) is clinically used for manic disorders. Its role has been shown in improving cell survival by decreasing Bax and p53 expression and increasing Bcl-2 concentration in the cell. This potential of LiCl is responsible for reducing irradiated cell death. In this study, we have explored the role of LiCl as a radioprotectant affecting survival genes.Materials and methods: To find out the cellular response upon LiCl pretreatment to radiation-exposed KG1a cells; viability, clonogenic assay and microarray studies were performed. This was followed by the detection of transcription factor binding motif in coregulated genes. These results were confirmed by reverse transcription-polymerase chain reaction (RT-PCR) and chromatin immunoprecipitation (CHIP).Results: LiCl improved irradiated KG1a cell survival and its clonogenicity at 2 mM concentration (clinically used). Microarray data analysis showed differential expression of cell-protecting genes playing an important role in apoptosis, cell cycle, adhesion and inflammation, etc. The coregulation analysis revealed genes involved in bile acid biosynthesis were also affected by LiCl treatment, these genes are likely to be responsible for radiation-induced gastrointestinal (GI) syndrome through bile production.Conclusions: This is the first study with respect to global genetic expression upon LiCl treatment to radiation-exposed cells. Our results suggest considering repurposing of LiCl as a protective agent for radiation injury.

Ammonium induced dysfunction of 5-HT2B receptor in astrocytes

Previously we reported that gene expression of astrocytic 5-HT_2B receptors was decreased in brains of depressed animals exposed to chronic mild stress (CMS) (Li et al., 2012) and of Parkinson's disease (Song et al., 2018). Depression is also one of the psychiatric symptoms in hyperammonemia, and astrocyte is a primary target of ammonium in brain in vivo. In the present study, we have used preparations of the brains of urease-treated mice and ammonium-treated astrocytes in culture to study gene expression and function of 5-HT_2B receptors. The urease-treated mice showed depressive behaviour. Both mRNA and protein of 5-HT_2B receptors were increased in the brains of urease-treated mice and in ammonium-treated cultured astrocytes. Further study revealed that mRNA and protein expression of adenosine deaminase acting on RNA 2 (ADAR2), an enzyme catalyze RNA deamination of adenosine to inosine was increased in the brains of urease-treated mice and in ammonium-treated cultured astrocytes. This increase in ADAR2 induced RNA editing of 5-HT_2B receptors. Cultured astrocytes treated with ammonium lost 5-HT induced Ca²⁺ signalling and ERK_1/2 phosphorylation, indicating dysfunction of 5-HT_2B receptors. This is in agreement with our previous observation that edited 5-HT_2B receptors no longer respond to 5-HT (Hertz et al., 2014). Ammonium effects are inhibited by ADAR2 siRNA in cultured astrocytes, suggesting that increased gene expression and editing and loss of function of 5-HT_2B receptors are results of increased activity of ADAR2. In summary, we have demonstrated that functional malfunction of astrocytic 5-HT_2B receptors occurs in animal models of major depression, Parkinson depression and hepatic encephalopathy albeit via different mechanisms. Understanding the role of astrocytic 5-HT_2B receptors in different pathological contexts may instigate development of novel therapeutic strategies for treating disease-specific depressive behaviour.

Streptolysin S induces mitochondrial damage and macrophage death through inhibiting degradation of glycogen synthase kinase-3β in Streptococcus pyogenes infection

Group A Streptococcus (GAS) infection is associated with a variety of human diseases. Previous studies indicate GAS infection leads to RAW264.7 cell death, but the mechanism is unclear. Here, analyzing the timing of reactive oxygen species (ROS) production and using mitochondrial ROS scavenger, we found the wild type GAS-induced RAW264.7 cell death was associated with mitochondrial ROS. The wild type GAS infection could activate glycogen synthase kinase-3β (GSK-3β). Inhibition of GSK-3β activity by lithium chloride or decreasing GSK-3β expression by lentivirus-mediated short hairpin RNA for GSK-3β could not only decrease the wild type GAS-induced mitochondrial ROS generation, mitochondria damage and cell death, but also reduced GAS intracellular replication. Streptolysin S (SLS), a GAS toxin, played the important role on GAS-induced macrophage death. Compared to the wild type GAS with its isogenic sagB mutant (SLS mutant)-infected macrophages, we found sagB mutant infection caused less mitochondrial ROS generation and cell death than those of the wild type GAS-infected ones. Furthermore, the sagB mutant, but not the wild type or the sagB-complementary mutant, could induce GSK-3β degradation via a proteasome-dependent pathway. These results suggest that a new mechanism of SLS-induced macrophage death was through inhibiting GSK-3β degradation and further enhancing mitochondrial damage.

hif-1 plays a role in hypoxia-induced gustatory plasticity of Caenorhabditis elegans

Background: Hypoxia-inducible factor 1 (HIF-1) is a key transcription factor in the detection of low oxygen levels, inducing expression of genes involved in mediating the response to hypoxia to maintain cellular oxygen homeostasis. Caenorhabditis elegans is a soil nematode that has evolved specialized chemosensory neurons that detect changes in oxygen levels and guide its behaviour and responses to food. The role of the hif-1 gene in modifying chemosensory behaviour in response to chemical hypoxia however remains unclear. Furthermore, the role of epigenetic modifiers in mediating this behavioural response to hypoxia is unclear. Aims: Our study addresses two questions (a) Do hypoxia-mimetics modify worm behaviour and (b) Are these behaviours modulated by HIF-dependent expression of epigenetic regulators? Material and methods: This study used established behavioural paradigms in hif-1 mutant strains of C. elegans, to study responses to chemical hypoxia. Results: We show that exposure to the hypoxia-mimetic, sodium sulphite, changes the gustatory responses, chemotaxis, gustatory plasticity and associative conditioning behaviour. Longer-term exposure to hypoxia changes the behavioural response of wild type C. elegans, mediated by the HIF pathway. Epigenetic modifiers, lithium chloride and valproic acid, further modulate these behavioural responses.

Clinical Trials and Therapeutic Rationale for Drug Repurposing in Schizophrenia

There is a paucity of efficacious novel drugs to address high rates of treatment resistance and refractory symptoms in schizophrenia. The identification of novel therapeutic indications for approved drugs-drug repurposing-has the potential to expedite clinical trials and reduce the costly risk of failure which currently limits central nervous system drug discovery efforts. In the present Review we discuss the historical role of drug repurposing in schizophrenia drug discovery and review the main classes of repurposing candidates currently in clinical trials for schizophrenia in terms of their therapeutic rationale, mechanisms of action, and preliminary results from clinical trials. Subsequently we outline the challenges and limitations which face the clinical repurposing pipeline and how novel technologies might serve to address these.

High-fructose corn syrup consumption in adolescent rats causes bipolar-like behavioural phenotype with hyperexcitability in hippocampal CA3-CA1 synapses

BACKGROUND AND PURPOSE

Children and adolescents are the top consumers of high-fructose corn syrup (HFCS) sweetened beverages. Even though the cardiometabolic consequences of HFCS consumption in adolescents are well known, the neuropsychiatric consequences have yet to be determined.

EXPERIMENTAL APPROACH

Adolescent rats were fed for a month with 11% weight/volume carbohydrate containing HFCS solution, which is similar to the sugar-sweetened beverages of human consumption. The metabolic, behavioural and electrophysiological characteristics of HFCS-fed rats were determined. Furthermore, the effects of TDZD-8, a highly specific GSK-3B inhibitor, on the HFCS-induced alterations were further explored.

KEY RESULTS

HFCS-fed adolescent rats displayed bipolar-like behavioural phenotype with hyperexcitability in hippocampal CA3-CA1 synapses. This hyperexcitability was associated with increased presynaptic release probability and increased readily available pool of AMPA receptors to be incorporated into the postsynaptic membrane, due to decreased expression of the neuron-specific α3-subunit of Na⁺ /K⁺ -ATPase and an increased ser⁸⁴⁵ -phosphorylation of GluA1 subunits (AMPA receptor subunit) respectively. TDZD-8 treatment was found to restore behavioural and electrophysiological disturbances associated with HFCS consumption by inhibition of GSK-3B, the most probable mechanism of action of lithium for its mood-stabilizing effects.

CONCLUSION AND IMPLICATIONS

This study shows that HFCS consumption in adolescent rats led to a bipolar-like behavioural phenotype with neuronal hyperexcitability, which is known to be one of the earliest endophenotypic manifestations of bipolar disorder. Inhibition of GSK-3B with TDZD-8 attenuated hyperexcitability and restored HFCS-induced behavioural alterations.

Atopic diseases/diathesis and subsequent ischemic stroke among patients with bipolar disorder: A nationwide longitudinal study

INTRODUCTION

Previous studies have suggested that both bipolar disorder and atopy are associated with an increased risk of stroke. However, the role of atopic diseases/diathesis in the risk of stroke among patients with bipolar disorder remains unclear.

METHODS

Using Taiwan's National Health Insurance Research Database, we selected 55,593 patients with bipolar disorder between 2002 and 2008, divided them into patients with atopic diseases/diathesis (n = 21,050) and patients without atopic diseases/diathesis (n = 34,543), and observed them until the end of 2011. Patients who experienced a stroke during the follow-up period were identified.

RESULTS

Patients with bipolar disorder and atopic diseases/diathesis had an elevated risk of ischemic stroke (hazard ratio [HR]: 1.44, 95% confidence interval [CI]: 1.25-1.59) compared with patients with only bipolar disorder; a dose-dependent relationship was observed between the number of allergic comorbidities and the risk of ischemic stroke (1 atopic disease, HR: 1.30, 95% CI: 1.13-1.49; 2 atopic diseases, HR: 1.59, 95% CI: 1.33-1.91; ≥ 3 atopic diseases, HR: 2.09, 95% CI: 1.50-2.91).The role of atopic diseases in the risk of hemorrhagic stroke among patients with bipolar disorder was nonsignificant (HR: 0.84, 95% CI: 0.64-1.09).

CONCLUSIONS

Patients with bipolar disorder and atopic diseases/diathesis are more prone to ischemic stroke later in life than are those without atopic diseases/diathesis. Further study is required to investigate the underlying mechanism linking atopy, bipolar disorder, and stroke.

Effects of Magnesium Supplementation on Unipolar Depression: A Placebo-Controlled Study and Review of the Importance of Dosing and Magnesium Status in the Therapeutic Response

Animal studies using tests and models have demonstrated that magnesium exerts an antidepressant effect. The literature contains few studies in humans involving attempts to augment antidepressant therapy with magnesium ions. The purpose of our study was to assess the efficacy and safety of antidepressant treatment, in combination with magnesium ions. A total of 37 participants with recurrent depressive disorder who developed a depressive episode were included in this study. As part of this double-blind study, treatment with the antidepressant fluoxetine was accompanied with either magnesium ions (120 mg/day as magnesium aspartate) or placebo. During an 8-week treatment period, each patient was monitored for any clinical abnormalities. Moreover, serum fluoxetine and magnesium levels were measured, and pharmaco-electroencephalography was performed. The fluoxetine + magnesium and fluoxetine + placebo groups showed no significant differences in either Hamilton Depression Rating Scale (HDRS) scores or serum magnesium levels at any stage of treatment. Multivariate statistical analysis of the whole investigated group showed that the following parameters increased the odds of effective treatment: lower baseline HDRS scores, female gender, smoking, and treatment augmentation with magnesium. The parameters that increased the odds of remission were lower baseline HDRS scores, shorter history of disease, the presence of antidepressant-induced changes in the pharmaco-EEG profile at 6 h after treatment, and the fact of receiving treatment augmented with magnesium ions. The limitation of this study is a small sample size.

Ebselen has lithium-like effects on central 5-HT2A receptor function

BACKGROUND AND PURPOSE

Lithium's antidepressant action may be mediated by inhibition of inositol monophosphatase (IMPase), a key enzyme in G_q -protein coupled receptor signalling. Recently, the antioxidant agent ebselen was identified as an IMPase inhibitor. Here, we investigated both ebselen and lithium in models of the 5-HT_2A receptor, a G_q -protein coupled receptor involved in lithium's actions.

EXPERIMENTAL APPROACH

5-HT_2A receptor function was assessed in mice by measuring the behavioural (head-twitches, ear scratches) and molecular (cortical immediate early gene [IEG] mRNA; Arc, c-fos, Egr2) responses to 5-HT_2A receptor agonists. Ebselen and lithium were administered either acutely or repeatedly prior to assessment of 5-HT_2A receptor function. Because lithium and 5-HT_2A receptor antagonists augment the action of selective serotonin reuptake inhibitors (SSRIs), ebselen was tested for this activity by co-administration with the SSRI citalopram in microdialysis (extracellular 5-HT) experiments.

KEY RESULTS

Acute and repeated administration of ebselen inhibited behavioural and IEG responses to the 5-HT_2A receptor agonist DOI. Repeated lithium also inhibited DOI-evoked behavioural and IEG responses. In comparison, a selective IMPase inhibitor (L-690330) attenuated the behavioural response to DOI whereas glycogen synthase kinase inhibitor (AR-A014418) did not. Finally, ebselen enhanced the increase in extracellular 5-HT induced by citalopram, and also increased regional brain 5-HT synthesis.

CONCLUSIONS AND IMPLICATIONS

Our data demonstrated lithium-mimetic effects of ebselen in different experimental models of 5-HT_2A receptor function, probably mediated by IMPase inhibition. This evidence of lithium-like neuropharmacological effects of ebselen adds further support for the clinical testing of ebselen in mood disorders, including as an antidepressant augmenting agent.

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.

Astroglial 5-HT2B receptor in mood disorders

Introduction: Astroglia represent the main cellular homeostatic system of the central nervous system (CNS). Astrocytes are intimately involved in regulation and maintenance of neurotransmission by regulating neurotransmitters removal and turnover and by supplying neurons with neurotransmitters precursors. Astroglial cells are fundamental elements of monoaminergic transmission in the brain and in the spinal cord. Astrocytes receive monoaminergic inputs and control catabolism of monoamines through dedicated transporters and intracellular enzymatic pathways.Areas covered: Astroglial cells express serotonergic receptors; in this review, we provide an in-depth characterization of 5-HT_2B receptors. Activation of these receptors triggers numerous intracellular signaling cascades that regulate expression of multiple genes. Astroglial 5-HT_2B receptors are activated by serotonin-specific reuptake inhibitors, such as major anti-depressant fluoxetine. Expression of astroglial serotonin receptors undergoes remarkable changes in depression disorders, and these changes can be corrected by chronic treatment with anti-depressant drugs.Expert commentary: Depressive behaviors, which occur in rodents following chronic stress or in neurotoxic models of Parkinson disease, are associated with significant changes in the expression of astroglial, but not neuronal 5-HT_2B receptors; while therapy with anti-depressants normalizes both receptors expression and depressive behavioral phenotype. In summary, astroglial serotonin receptors are linked to mood disorders and may represent a novel target for cell- and molecule-specific therapies of depression and mood disorders.

Involvement of PKA/DARPP-32/PP1α and β- arrestin/Akt/GSK-3β Signaling in Cadmium-Induced DA-D2 Receptor-Mediated Motor Dysfunctions: Protective Role of Quercetin

Given increasing risk of cadmium-induced neurotoxicity, the study was conducted to delineate the molecular mechanisms associated with cadmium-induced motor dysfunctions and identify targets that govern dopaminergic signaling in the brain involving in vivo, in vitro, and in silico approaches. Selective decrease in dopamine (DA)-D2 receptors on cadmium exposure was evident which affected the post-synaptic PKA/DARPP-32/PP1α and β-arrestin/Akt/GSK-3β signaling concurrently in rat corpus striatum and PC12 cells. Pharmacological inhibition of PKA and Akt in vitro demonstrates that both pathways are independently modulated by DA-D2 receptors and associated with cadmium-induced motor deficits. Ultrastructural changes in the corpus striatum demonstrated neuronal degeneration and loss of synapse on cadmium exposure. Further, molecular docking provided interesting evidence that decrease in DA-D2 receptors may be due to direct binding of cadmium at the competitive site of dopamine on DA-D2 receptors. Treatment with quercetin resulted in the alleviation of cadmium-induced behavioral and neurochemical alterations. This is the first report demonstrating that cadmium-induced motor deficits are associated with alteration in postsynaptic dopaminergic signaling due to a decrease in DA-D2 receptors in the corpus striatum. The results further demonstrate that quercetin has the potential to alleviate cadmium-induced dopaminergic dysfunctions.

Anti-stress effects of a GSK-3β inhibitor, AR-A014418, in immobilization stress of variable duration in mice

BACKGROUND

The present study was designed to explore the anti-stress role of AR-A014418, a selective glycogen synthase kinase-3β inhibitor (GSK-3β), on changes provoked by immobilization stress of varying duration.

METHODS

Acute stress of varying degree was induced by subjecting mice to immobilization stress of short duration (30 min) or long duration (120 min). Thereafter, these animals were exposed to the same stressor for 5 days to induce stress adaptation. The behavioral alterations were assessed using an actophotometer, a hole-board, and the open field and social interaction tests. The serum corticosterone levels were assessed as markers of the hypothalamic-pituitary-adrenal (HPA) axis activity. The levels of total GSK-3β and p-GSK-3β-S9 were determined in the prefrontal cortex.

RESULTS

A single exposure to short or long immobilization stress produced behavioral and biochemical changes and the levels of p-GSK-3β-S9 decreased without affecting the total GSK-3β levels in the brain. However, repeated exposure to both short and long stress reversed the behavioral and biochemical changes along with the normalization of p-GSK-3β-S9 levels. The administration of AR-A014418, a selective GSK-3β inhibitor, diminished acute stress-induced behavioral and biochemical changes. Furthermore, AR-A014418 normalized acute stress-induced alterations in p-GSK-3β-S9 levels without changing total GSK-3β levels.

CONCLUSIONS

Our study suggests that acute stress-induced decrease in p-GSK-3β-S9 levels in the brain contributes to the development of behavioral and biochemical alterations and the normalization of GSK-3β signaling may contribute to stress adaptive behavior in mice which have been subjected to repeated immobilization stress.

Progress in bipolar disorder drug design toward the development of novel therapeutic targets: a clinician's perspective

INTRODUCTION

Bipolar disorder (BD) is a considerable burden to the affected individual. The need for novel drug targets and improved drug design (DD) in BD is therefore clear. Areas covered: The following article provides a brief, narrative, clinician-oriented overview of the most promising novel pharmacological targets for BD along with a concise overview regarding the general DD process and the unmet needs relevant to BD. Expert opinion: A number of novel potential drug targets have been investigated. With the notable exception of the kynurenine pathway, available evidence is too scarce to highlight a definitive roadmap for forthcoming DD in BD. BD itself may present with different facets, as it is a polymorphic clinical spectrum. Therefore, promoting clinical-case stratification should be based on precision medicine, rather than on novel biological targets. Furthermore, the full release of raw study data to the scientific community and the development of uniform clinical trial standards (including more realistic outcomes) should be promoted to facilitate the DD process in BD.

Angiotensin II-triggered kinase signaling cascade in the central nervous system

Recent studies have projected the renin-angiotensin system as a central component of the physiological and pathological processes of assorted neurological disorders. Its primary effector hormone, angiotensin II (Ang II), not only mediates the physiological effects of vasoconstriction and blood pressure regulation in cardiovascular disease but is also implicated in a much wider range of neuronal activities and diseases, including Alzheimer's disease, neuronal injury, and cognitive disorders. Ang II produces different actions by acting on its two subtypes of receptors (AT1 and AT2); however, the well-known physiological actions of Ang II are mainly mediated through AT1 receptors. Moreover, recent studies also suggest the important functional role of AT2 receptor in the brain. Ang II acts on AT1 receptors and conducts its functions via MAP kinases (ERK1/2, JNK, and p38MAPK), glycogen synthase kinase, Rho/ROCK kinase, receptor tyrosine kinases (PDGF and EGFR), and nonreceptor tyrosine kinases (Src, Pyk2, and JAK/STAT). AT1R-mediated NADPH oxidase activation also leads to the generation of reactive oxygen species, widely implicated in neuroinflammation. These signaling cascades lead to glutamate excitotoxicity, apoptosis, cerebral infarction, astrocyte proliferation, nociception, neuroinflammation, and progression of other neurological disorders. The present review focuses on the Ang II-triggered signal transduction pathways in central nervous system.

Biphasic Regulation of Caveolin-1 Gene Expression by Fluoxetine in Astrocytes: Opposite Effects of PI3K/AKT and MAPK/ERK Signaling Pathways on c-fos

Previously, we reported that fluoxetine acts on 5-HT_2B receptor and induces epidermal growth factor receptor (EGFR) transactivation in astrocytes. Recently, we have found that chronic treatment with fluoxetine regulates Caveolin-1 (Cav-1)/PTEN/PI3K/AKT/glycogen synthase kinase 3β (GSK-3β) signaling pathway and glycogen content in primary cultures of astrocytes with bi-phasic concentration dependence. At low concentrations fluoxetine down-regulates Cav-1 gene expression, decreases membrane content of PTEN, increases PI3K activity and increases phosphorylation of GSK-3β and increases its activity; at high concentrations fluoxetine acts on PTEN/PI3K/AKT/GSK-3β in an inverse fashion. Here, we present the data indicating that acute treatment with fluoxetine at lower concentrations down-regulates c-Fos gene expression via PI3K/AKT signaling pathway; in contrast at higher concentrations fluoxetine up-regulates c-Fos gene expression via MAPK/extracellular-regulated kinase (ERK) signaling pathway. However, acute treatment with fluoxetine has no effect on Cav-1 protein content. Similarly, chronic effects of fluoxetine on Cav-1 gene expression are suppressed by inhibitor of PI3K at lower concentrations, but by inhibitor of MAPK at higher concentrations, indicating that the mechanism underlying bi-phasic regulation of Cav-1 gene expression by fluoxetine is opposing effects of PI3K/AKT and MAPK/ERK signal pathways on c-Fos gene expression. The effects of fluoxetine on Cav-1 gene expression at both lower and higher concentrations are abolished by AG1478, an inhibitor of EGFR, indicating the involvement of 5-HT_2B receptor induced EGFR transactivation as we reported previously. However, PP1, an inhibitor of Src only abolished the effect by lower concentrations, suggesting the relevance of Src with PI3K/AKT signal pathway during activation of EGFR.

Role of Dopamine D2 Receptor in Stress-Induced Myelin Loss

Dopaminergic systems play a major role in reward-related behavior and dysregulation of dopamine (DA) systems can cause several mental disorders, including depression. We previously reported that dopamine D2 receptor knockout (D2R^-/-) mice display increased anxiety and depression-like behaviors upon chronic stress. Here, we observed that chronic stress caused myelin loss in wild-type (WT) mice, while the myelin level in D2R^-/- mice, which was already lower than that in WT mice, was not affected upon stress. Fewer mature oligodendrocytes (OLs) were observed in the corpus callosum of stressed WT mice, while in D2R^-/- mice, both the control and stressed group displayed a decrease in the number of mature OLs. We observed a decrease in the number of active β-catenin (ABC)-expressing and TCF4-expressing cells among OL lineage cells in the corpus callosum of stressed WT mice, while such regulation was not found in D2R^-/- mice. Administration of lithium normalized the behavioral impairments and myelin damage induced by chronic stress in WT mice, and restored the number of ABC-positive and TCF4-positive OLs, while such effect was not found in D2R^-/- mice. Together, our findings indicate that chronic stress induces myelin loss through the Wnt/β-catenin signaling pathway in association with DA signaling through D2R.

Ras Activity Tunes the Period and Modulates the Entrainment of the Suprachiasmatic Clock

The small GTPase Ras is a universal eukaryotic cytoplasmic membrane-anchored protein, which regulates diverse downstream signal transduction pathways that play an important role in the proper functioning of neurons. Ras activity is a central regulator of structural and functional synaptic plasticity in the adult nervous system, where it channels neuronal responses to various extracellular cues allowing the organism to adapt to complex environmental stimuli. The suprachiasmatic nucleus (SCN) is the principle pacemaker of the circadian clock, and the circadian and photic regulation of Ras activity in the SCN is an important modulator of the clockwork. We have generated transgenic mouse expressing constitutively active V12-H-Ras selectively in neurons via a synapsin I promoter (synRas mice), which serves as a suitable model to study the role of neuronal Ras signaling. Modulation of Ras activity affects ERK1,2/CREB signaling and glycogen synthase kinase-3 beta expression in the SCN, which in turn modify the photoentrainment of the clock and the fine tuning the circadian period length. The main focus of this review is to offer an overview of the function of Ras signaling in the circadian rhythm and its potential role in learning and memory consolidation.

Clock Genes and Altered Sleep-Wake Rhythms: Their Role in the Development of Psychiatric Disorders

In mammals, the circadian clocks network (central and peripheral oscillators) controls circadian rhythms and orchestrates the expression of a range of downstream genes, allowing the organism to anticipate and adapt to environmental changes. Beyond their role in circadian rhythms, several studies have highlighted that circadian clock genes may have a more widespread physiological effect on cognition, mood, and reward-related behaviors. Furthermore, single nucleotide polymorphisms in core circadian clock genes have been associated with psychiatric disorders (such as autism spectrum disorder, schizophrenia, anxiety disorders, major depressive disorder, bipolar disorder, and attention deficit hyperactivity disorder). However, the underlying mechanisms of these associations remain to be ascertained and the cause–effect relationships are not clearly established. The objective of this article is to clarify the role of clock genes and altered sleep–wake rhythms in the development of psychiatric disorders (sleep problems are often observed at early onset of psychiatric disorders). First, the molecular mechanisms of circadian rhythms are described. Then, the relationships between disrupted circadian rhythms, including sleep–wake rhythms, and psychiatric disorders are discussed. Further research may open interesting perspectives with promising avenues for early detection and therapeutic intervention in psychiatric disorders.

Bi-phasic regulation of glycogen content in astrocytes via Cav-1/PTEN/PI3K/AKT/GSK-3β pathway by fluoxetine

OBJECTIVE

Here, we present the data indicating that chronic treatment with fluoxetine regulates Cav-1/PTEN/PI3K/AKT/GSK-3β signalling pathway and glycogen content in primary cultures of astrocytes with bi-phasic concentration dependence.

RESULTS

At lower concentrations, fluoxetine downregulates gene expression of Cav-1, decreases membrane content of PTEN, increases activity of PI3K/AKT, and elevates GSK-3β phosphorylation thus suppressing its activity. At higher concentrations, fluoxetine acts in an inverse fashion. As expected, fluoxetine at lower concentrations increased while at higher concentrations decreased glycogen content in astrocytes.

CONCLUSIONS

Our findings indicate that bi-phasic regulation of glycogen content via Cav-1/PTEN/PI3K/AKT/GSK-3β pathway by fluoxetine may be responsible for both therapeutic and side effects of the drug.

Clock-Enhancing Small Molecules and Potential Applications in Chronic Diseases and Aging

Normal physiological functions require a robust biological timer called the circadian clock. When clocks are dysregulated, misaligned, or dampened, pathological consequences ensue, leading to chronic diseases and accelerated aging. An emerging research area is the development of clock-targeting compounds that may serve as drug candidates to correct dysregulated rhythms and hence mitigate disease symptoms and age-related decline. In this review, we first present a concise view of the circadian oscillator, physiological networks, and regulatory mechanisms of circadian amplitude. Given a close association of circadian amplitude dampening and disease progression, clock-enhancing small molecules (CEMs) are of particular interest as candidate chronotherapeutics. A recent proof-of-principle study illustrated that the natural polymethoxylated flavonoid nobiletin directly targets the circadian oscillator and elicits robust metabolic improvements in mice. We describe mood disorders and aging as potential therapeutic targets of CEMs. Future studies of CEMs will shed important insight into the regulation and disease relevance of circadian clocks.

Biological hypotheses and biomarkers of bipolar disorder

The most common mood disorders are major depressive disorders and bipolar disorders (BD). The pathophysiology of BD is complex, multifactorial, and not fully understood. Creation of new hypotheses in the field gives impetus for studies and for finding new biomarkers for BD. Conversely, new biomarkers facilitate not only diagnosis of a disorder and monitoring of biological effects of treatment, but also formulation of new hypotheses about the causes and pathophysiology of the BD. BD is characterized by multiple associations between disturbed brain development, neuroplasticity, and chronobiology, caused by: genetic and environmental factors; defects in apoptotic, immune-inflammatory, neurotransmitter, neurotrophin, and calcium-signaling pathways; oxidative and nitrosative stress; cellular bioenergetics; and membrane or vesicular transport. Current biological hypotheses of BD are summarized, including related pathophysiological processes and key biomarkers, which have been associated with changes in genetics, systems of neurotransmitter and neurotrophic factors, neuroinflammation, autoimmunity, cytokines, stress axis activity, chronobiology, oxidative stress, and mitochondrial dysfunctions. Here we also discuss the therapeutic hypotheses and mechanisms of the switch between depressive and manic state.

Ketamine-Induced Glutamatergic Mechanisms of Sleep and Wakefulness: Insights for Developing Novel Treatments for Disturbed Sleep and Mood

Ketamine, a drug with rapid antidepressant effects and well-described effects on slow wave sleep (SWS), is a useful intervention for investigating sleep-wake mechanisms involved in novel therapeutics. The drug rapidly (within minutes to hours) reduces depressive symptoms in individuals with major depressive disorder (MDD) or bipolar disorder (BD), including those with treatment-resistant depression. Ketamine treatment elevates extracellular glutamate in the prefrontal cortex. Glutamate, in turn, plays a critical role as a proximal element in a ketamine-initiated molecular cascade that increases synaptic strength and plasticity, which ultimately results in rapidly improved mood. In MDD, rapid antidepressant response to ketamine is related to decreased waking as well as increased total sleep, SWS, slow wave activity (SWA), and rapid eye movement (REM) sleep. Ketamine also increases brain-derived neurotrophic factor (BDNF) levels. In individuals with MDD, clinical response to ketamine is predicted by low baseline delta sleep ratio, a measure of deficient early night production of SWS. Notably, there are important differences between MDD and BD that may be related to the effects of diagnosis or of mood stabilizers. Consistent with its effects on clock-associated molecules, ketamine alters the timing and amplitude of circadian activity patterns in rapid responders versus non-responders with MDD, suggesting that it affects mood-dependent central neural circuits. Molecular interactions between sleep homeostasis and clock genes may mediate the rapid and durable elements of clinical response to ketamine and its active metabolite.

Low-Dose Lithium Stabilizes Human Endothelial Barrier by Decreasing MLC Phosphorylation and Universally Augments Cholinergic Vasorelaxation Capacity in a Direct Manner

Lithium at serum concentrations up to 1 mmol/L has been used in patients suffering from bipolar disorder for decades and has recently been shown to reduce the risk for ischemic stroke in these patients. The risk for stroke and thromboembolism depend not only on cerebral but also on general endothelial function and health; the entire endothelium as an organ is therefore pathophysiologically relevant. Regardless, the knowledge about the direct impact of lithium on endothelial function remains poor. We conducted an experimental study using lithium as pharmacologic pretreatment for murine, porcine and human vascular endothelium. We predominantly investigated endothelial vasorelaxation capacities in addition to human basal and dynamic (thrombin-/PAR-1 receptor agonist-impaired) barrier functioning including myosin light chain (MLC) phosphorylation (MLC-P). Low-dose therapeutic lithium concentrations (0.4 mmol/L) significantly augment the cholinergic endothelium-dependent vasorelaxation capacities of cerebral and thoracic arteries, independently of central and autonomic nerve system influences. Similar concentrations of lithium (0.2–0.4 mmol/L) significantly stabilized the dynamic thrombin-induced and PAR-1 receptor agonist-induced permeability of human endothelium, while even the basal permeability appeared to be stabilized. The lithium-attenuated dynamic permeability was mediated by a reduced endothelial MLC-P known to be followed by a lessening of endothelial cell contraction and paracellular gap formation. The well-known lithium-associated inhibition of inositol monophosphatase/glycogen synthase kinase-3-β signaling-pathways involving intracellular calcium concentrations in neurons seems to similarly occur in endothelial cells, too, but with different down-stream effects such as MLC-P reduction. This is the first study discovering low-dose lithium as a drug directly stabilizing human endothelium and ubiquitously augmenting cholinergic endothelium-mediated vasorelaxation. Our findings have translational and potentially clinical impact on cardiovascular and cerebrovascular disease associated with inflammation explaining why lithium can reduce, e.g., the risk for stroke. However, further clinical studies are warranted.