Antidepressant-like effect of valproic acid-Possible involvement of PI3K/Akt/mTOR pathway

Genetic ablation of the isoform γ of PI3K decreases antidepressant efficacy of ketamine in male mice

About one-third of major depressive disorder (MDD) patients demonstrate unresponsiveness to classic antidepressants, and even the clinical efficacy of fast-acting drugs such as ketamine varies significantly among patients with treatment-resistant depression. Nevertheless, the lack of suitable animal models that mimic a possible ketamine-resistant phenotype challenges the understanding of resistance to drug treatment. In this study, we showed that PI3Kγ knock-out (KO) mice do not respond to classical doses of ketamine and classical antidepressants. PI3Kγ KO mice were unresponsive to both the rapid and sustained antidepressant-like effects of a single dose of ketamine in the forced swimming test. Additionally, they were unresponsive to the antidepressant-like effects induced by the tricyclic antidepressant imipramine and the selective serotonin reuptake inhibitor fluoxetine. However, acute pharmacological inhibition of PI3Kγ did not block the antidepressant-like effect of ketamine, showing that a chronic deficiency of the PI3Kγ-mediated pathway is necessary for the effects of classic doses of ketamine and antidepressants. Therefore, we propose that PI3Kγ participates in the antidepressant activity and is likely implicated in the neurobiology and phenotype observed in patients with MDD who demonstrate treatment resistance.

Epigenetic mechanisms of rapid-acting antidepressants

BACKGROUND

Rapid-acting antidepressants (RAADs), including dissociative anesthetics, psychedelics, and empathogens, elicit rapid and sustained therapeutic improvements in psychiatric disorders by purportedly modulating neuroplasticity, neurotransmission, and immunity. These outcomes may be mediated by, or result in, an acute and/or sustained entrainment of epigenetic processes, which remodel chromatin structure and alter DNA accessibility to regulate gene expression.

METHODS

In this perspective, we present an overview of the known mechanisms, knowledge gaps, and future directions surrounding the epigenetic effects of RAADs, with a focus on the regulation of stress-responsive DNA and brain regions, and on the comparison with conventional antidepressants.

MAIN BODY

Preliminary correlative evidence indicates that administration of RAADs is accompanied by epigenetic effects which are similar to those elicited by conventional antidepressants. These include changes in DNA methylation, post-translational modifications of histones, and differential regulation of non-coding RNAs in stress-responsive chromatin areas involved in neurotrophism, neurotransmission, and immunomodulation, in stress-responsive brain regions. Whether these epigenetic changes causally contribute to the therapeutic effects of RAADs, are a consequence thereof, or are unrelated, remains unknown. Moreover, the potential cell type-specificity and mechanisms involved are yet to be fully elucidated. Candidate mechanisms include neuronal activity- and serotonin and Tropomyosine Receptor Kinase B (TRKB) signaling-mediated epigenetic changes, and direct interaction with DNA, histones, or chromatin remodeling complexes.

CONCLUSION

Correlative evidence suggests that epigenetic changes induced by RAADs accompany therapeutic and side effects, although causation, mechanisms, and cell type-specificity remain largely unknown. Addressing these research gaps may lead to the development of novel neuroepigenetics-based precision therapeutics.

Molecular signatures of premature aging in Major Depression and Substance Use Disorders

Major depressive disorder (MDD) and substance-use disorders (SUDs) often lead to premature aging, increasing vulnerability to cognitive decline and other forms of dementia. This study utilized advanced systems bioinformatics to identify aging "signatures" in MDD and SUDs and evaluated the potential for known lifespan-extending drugs to target and reverse these signatures. The results suggest that inhibiting the transcriptional activation of FOS gene family members holds promise in mitigating premature aging in MDD and SUDs. Conversely, antidepressant drugs activating the PI3K/Akt/mTOR pathway, a common mechanism in rapid-acting antidepressants, may accelerate aging in MDD patients, making them unsuitable for those with comorbid aging-related conditions like dementia and Alzheimer's disease. Additionally, this innovative approach identifies potential anti-aging interventions for MDD patients, such as Deferoxamine, Resveratrol, Estradiol valerate, and natural compounds like zinc acetate, genistein, and ascorbic acid, regardless of comorbid anxiety disorders. These findings illuminate the premature aging effects of MDD and SUDs and offer insights into treatment strategies for patients with comorbid aging-related conditions, including dementia and Alzheimer's disease.

Human Wharton's jelly-derived mesenchymal stromal stem cells preconditioned with valproic acid promote cell migration and reduce renal inflammation in ischemia/reperfusion injury by activating the AKT/P13K and SDF1/CXCR4 pathways

OBJECTIVE

To determine whether WJ-MSCs pretreated with VPA would enhance their migration to improve functional recovery of renal IRI in rats.

METHODS

150 Sprague-Dawley rats were distributed into 5 groups; Sham, IRI, WJ-MSC, VPA, and WJ-MSCs + VPA. 10 rats were sacrificed after 3, 5, and 7 days. Role of WJ-MSCs pretreated with VPA was evaluated by assessment of renal function, antioxidant enzymes together with renal histopathological and immunohistopathological analyses and finally by molecular studies.

RESULTS

WJ-MSCs and VPA significantly improved renal function and increased antioxidants compared to IRI group. Regarding gene expression, WJ-MSCs and VPA decreased BAX and TGF-β1, up-regulated Akt, PI3K, BCL2, SDF1α, and CXCR4 related to IRI. Additionally, WJ-MSCs pretreated with VPA improved the measured parameters more than either treatment alone.

CONCLUSION

WJ-MSCs isolated from the umbilical cord and pretreated with VPA defended the kidney against IRI by more easily homing to the site of injury.

Interplay of G-proteins and Serotonin in the Neuroimmunoinflammatory Model of Chronic Stress and Depression: A Narrative Review

INTRODUCTION

This narrative review addresses the clinical challenges in stress-related disorders such as depression, focusing on the interplay between neuron-specific and pro-inflammatory mechanisms at the cellular, cerebral, and systemic levels.

OBJECTIVE

We aim to elucidate the molecular mechanisms linking chronic psychological stress with low-grade neuroinflammation in key brain regions, particularly focusing on the roles of G proteins and serotonin (5-HT) receptors.

METHODS

This comprehensive review of the literature employs systematic, narrative, and scoping review methodologies, combined with systemic approaches to general pathology. It synthesizes current research on shared signaling pathways involved in stress responses and neuroinflammation, including calcium-dependent mechanisms, mitogen-activated protein kinases, and key transcription factors like NF-κB and p53. The review also focuses on the role of G protein-coupled neurotransmitter receptors (GPCRs) in immune and pro-inflammatory responses, with a detailed analysis of how 13 of 14 types of human 5-HT receptors contribute to depression and neuroinflammation.

RESULTS

The review reveals a complex interaction between neurotransmitter signals and immunoinflammatory responses in stress-related pathologies. It highlights the role of GPCRs and canonical inflammatory mediators in influencing both pathological and physiological processes in nervous tissue.

CONCLUSION

The proposed Neuroimmunoinflammatory Stress Model (NIIS Model) suggests that proinflammatory signaling pathways, mediated by metabotropic and ionotropic neurotransmitter receptors, are crucial for maintaining neuronal homeostasis. Chronic mental stress can disrupt this balance, leading to increased pro-inflammatory states in the brain and contributing to neuropsychiatric and psychosomatic disorders, including depression. This model integrates traditional theories on depression pathogenesis, offering a comprehensive understanding of the multifaceted nature of the condition.

Inhibition of Microglial GSK3β Activity Is Common to Different Kinds of Antidepressants: A Proposal for an In Vitro Screen to Detect Novel Antidepressant Principles

Depression is a major public health concern. Unfortunately, the present antidepressants often are insufficiently effective, whilst the discovery of more effective antidepressants has been extremely sluggish. The objective of this review was to combine the literature on depression with the pharmacology of antidepressant compounds, in order to formulate a conceivable pathophysiological process, allowing proposals how to accelerate the discovery process. Risk factors for depression initiate an infection-like inflammation in the brain that involves activation microglial Toll-like receptors and glycogen synthase kinase-3β (GSK3β). GSK3β activity alters the balance between two competing transcription factors, the pro-inflammatory/pro-oxidative transcription factor NFκB and the neuroprotective, anti-inflammatory and anti-oxidative transcription factor NRF2. The antidepressant activity of tricyclic antidepressants is assumed to involve activation of GS-coupled microglial receptors, raising intracellular cAMP levels and activation of protein kinase A (PKA). PKA and similar kinases inhibit the enzyme activity of GSK3β. Experimental antidepressant principles, including cannabinoid receptor-2 activation, opioid μ receptor agonists, 5HT2 agonists, valproate, ketamine and electrical stimulation of the Vagus nerve, all activate microglial pathways that result in GSK3β-inhibition. An in vitro screen for NRF2-activation in microglial cells with TLR-activated GSK3β activity, might therefore lead to the detection of totally novel antidepressant principles with, hopefully, an improved therapeutic efficacy.

Baicalin Ameliorates Corticosterone-Induced Depression by Promoting Neurodevelopment of Hippocampal via mTOR/GSK3 β Pathway

OBJECTIVE

To investigate the role of hippocampal neurodevelopment in the antidepressant effect of baicalin.

METHODS

Forty male Institute of Cancer Research mice were divided into control, corticosterone (CORT, 40 mg/kg), CORT+baicalin-L (25 mg/kg), CORT+baicalin-H (50 mg/kg), and CORT+fluoxetine (10 mg/kg) groups according to a random number table. An animal model of depression was established by chronic CORT exposure. Behavioral tests were used to assess the reliability of depression model and the antidepressant effect of baicalin. In addition, Nissl staining and immunofluorescence were used to evaluate the effect of baicalin on hippocampal neurodevelopment in mice. The protein and mRNA expression levels of neurodevelopment-related factors were detected by Western blot analysis and real-time polymerase chain reaction, respectively.

RESULTS

Baicalin significantly ameliorated the depressive-like behavior of mice resulting from CORT exposure and promoted the development of dentate gyrus in hippocampus, thereby reversing the depressive-like pathological changes in hippocampal neurons caused by CORT neurotoxicity. Moreover, baicalin significantly decreased the protein and mRNA expression levels of glycogen synthase kinase 3 β (GSK3 β), and upregulated the expression levels of cell cycle protein D1, p-mammalian target of rapamycin (mTOR), doublecortin, and brain-derived neurotrophic factor (all P<0.01). There were no significant differences between baicalin and fluoxetine groups (P>0.05).

CONCLUSION

Baicalin can promote the development of hippocampal neurons via mTOR/GSK3 β signaling pathway, thus protect mice against CORT-induced neurotoxicity and play an antidepressant role.

Are the epigenetic changes predictive of therapeutic efficacy for psychiatric disorders? A translational approach towards novel drug targets

The etiopathogenesis of mental disorders is not fully understood and accumulating evidence support that clinical symptomatology cannot be assigned to a single gene mutation, but it involves several genetic factors. More specifically, a tight association between genes and environmental risk factors, which could be mediated by epigenetic mechanisms, may play a role in the development of mental disorders. Several data suggest that epigenetic modifications such as DNA methylation, post-translational histone modification and interference of microRNA (miRNA) or long non-coding RNA (lncRNA) may modify the severity of the disease and the outcome of the therapy. Indeed, the study of these mechanisms may help to identify patients particularly vulnerable to mental disorders and may have potential utility as biomarkers to facilitate diagnosis and treatment of psychiatric disorders. This article summarizes the most relevant preclinical and human data showing how epigenetic modifications can be central to the therapeutic efficacy of antidepressant and/or antipsychotic agents, as possible predictor of drugs response.

KW-2449 and VPA exert therapeutic effects on human neurons and cerebral organoids derived from MECP2-null hESCs

BACKGROUND

Rett syndrome (RTT), mainly caused by mutations in methyl-CpG binding protein 2 (MECP2), is one of the most prevalent neurodevelopmental disorders in girls. However, the underlying mechanism of MECP2 remains largely unknown and currently there is no effective treatment available for RTT.

METHODS

We generated MECP2-KO human embryonic stem cells (hESCs), and differentiated them into neurons and cerebral organoids to investigate phenotypes of MECP2 loss-of-function, potential therapeutic agents, and the underlying mechanism by transcriptome sequencing.

RESULTS

We found that MECP2 deletion caused reduced number of hESCs-derived neurons and simplified dendritic morphology. Moreover, MECP2-KO cortical organoids exhibited fewer neural progenitor cells and neurons at day 60. Electrophysiological recordings showed that MECP2 deletion altered synaptic activity in organoids. Transcriptome analysis of organoids identified many genes in the PI3K-AKT pathway downregulated following MECP2 deletion. Treatment with either KW-2449 or VPA, small molecules for the activation of PI3K-AKT signaling pathway, alleviated neuronal deficits and transcriptome changes in MECP2-KO human neuronal models.

CONCLUSIONS

These findings suggest that KW-2449 and VPA might be promising drugs for RTT treatment.

Valproic Acid-Induced Anxiety and Depression Behaviors are Ameliorated in p39 Cdk5 Activator-Deficient Mice

Valproic acid (VPA) is a drug used for the treatment of epilepsy, seizures, migraines, and bipolar disorders. Cyclin-dependent kinase 5 (Cdk5) is a Ser/Thr kinase activated by p35 or p39 in neurons and plays a role in a variety of neuronal functions, including psychiatric behaviors. We previously reported that VPA suppressed Cdk5 activity by reducing the expression of p35 in cultured cortical neurons, leaving p39 unchanged. In this study, we asked for the role of Cdk5 in VPA-induced anxiety and depression behaviors. Wild-type (WT) mice displayed increased anxiety and depression after chronic administration of VPA for 14 days, when the expression of p35 was decreased. To clarify their relationship, we used p39 knockout (KO) mice, in which p35 is the only Cdk5 activator. When p39 KO mice were treated chronically with VPA, unexpectedly, they exhibited fewer anxiety and depression behaviors than WT mice. The effects were p39 cdk5r2 gene-dosage dependent. Together, these results indicate that Cdk5-p39 plays a specific role in VPA-induced anxiety and depression behaviors.

Acute and chronic effects of oral administration of a medium-chain fatty acid, capric acid, on locomotor activity and anxiety-like and depression-related behaviors in adult male C57BL/6J mice

Aim

Capric acid (also known as decanoic acid or C10) is one of the fatty acids in the medium‐chain triglycerides (MCTs) commonly found in dietary fats. Although dietary treatment with MCTs is recently of great interest for the potential therapeutic effects on neuropsychiatric disorders, the effects of oral administration of C10 on behavior remain to be examined. This study investigated acute and chronic effects of oral administration of C10 on locomotor activity and anxiety‐like and depression‐related behaviors in adult male C57BL/6J mice.

Methods

To explore the acute effects of C10 administration, mice were subjected to a series of behavioral tests in the following order: light/dark transition, open field, elevated plus maze, Porsolt forced swim, and tail suspension tests, 30 minutes after oral gavage of either vehicle or C10 solution (30 mmol/kg dose in Experiment 1; 0.1, 0.3, 1.0, 3.0 mmol/kg doses in Experiment 2). Next, to examine chronic effects of C10, mice repeatedly administered with either vehicle or C10 solution (0.3, 3.0 mmol/kg doses per day, for 21 days, in Experiment 3) were subjected to behavioral tests without oral administration immediately before each test.

Results

The mice administrated with the high dose of C10 (30 mmol/kg) showed lower body weights, shorter distance traveled, and more anxiety‐like behavior than vehicle‐treated mice, and the results reached study‐wide statistical significance. The C10 administration at a lower dose of 0.3 mmol/kg had no significant effects on body weights and induced nominally significantly longer distance traveled than vehicle administration. Repeated administration of C10 at a dose of 3.0 mmol/kg for more than 21 days caused lower body weights and decreased depression‐related behavior, although the behavioral differences did not reach study‐wide significance.

Conclusions

Although these results suggest dose‐dependent effects of oral administration of capric acid on locomotor activity and anxiety‐like and depression‐related behaviors, further study will be needed to replicate the findings and explore the underlying brain mechanisms.

Repeated oral administration of the medium‐chain fatty acid, capric acid, decreased depression‐related behavior in C57BL/6J mice. This study suggests that capric acid exerts an antidepressant effect.

Uncovering the active components, prospective targets, and molecular mechanism of Baihe Zhimu decoction for treating depression using network pharmacology-based analysis

ETHNOPHARMACOLOGICAL RELEVANCE

Baihe Zhimu decoction (BZD) is a classical traditional Chinese medicinal herbal formula. It consists of two herbal medicines, Rhizoma Anemarrhenae (Zhimu), the rhizomes of Anemarrhena asphodeloides Bge. (Liliaceae), and Bulbus Lilii (Baihe), the bulbs of Lilium brownii var. Viridulum Baker (Liliaceae). BZD has been widely used in China to treat depression and verified to be effective without evident side effects.

AIM OF THE STUDY

The aim of this study was to elucidate the active components, potential targets, and molecular mechanism of Baihe Zhimu decoction for treating depression.

MATERIALS AND METHODS

In this research, a chronic unpredictable mild stress (CUMS) mice was first established to evaluate the pharmacological effects of BZD for treating depression. A component database was then constructed for BZD. High-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (HPLC-QTOF-MS) technique was used to identify the components in BZD and blood-absorbed components. Further screening and validation of protein targets were performed by molecule docking. The component-target binding affinity was validated by surface plasmon resonance analysis (SPR) assay. The related pathways were predicted by Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis. Relative proteins in the predicted pathways were finally assessed by Western blot.

RESULTS

The pharmacology evaluation experiment demonstrated that BZD could improve depressive-like behavior, inhibit the hippocampal secretion of pro-inflammatory cytokines and reduce neuronal apoptosis in CUMS mice model. A component database containing 163 components and a target database covering 1286 proteins were constructed. HPLC-QTOF-MS assay identified twenty-six components from BZD and ten components absorbed into rat plasma after an intragastric treatment with BZD. Next, 56 underlying targets were screened out by a virtual high-throughput screening approach. Twenty-seven of them were further screened out and confirmed by molecular docking. Afterward, a component-target network was established, and the component-protein binding affinities were validated by SPR assays. By KEGG pathway enrichment analysis, two signaling pathways PI3K/Akt and MAPK were predicted as the potential signaling cascades. Finally, Western blot showed that BZD dramatically reversed the suppression of PI3K/Akt/GSK-3β pathway and the activation of MAPK pathway in CUMS mice model.

CONCLUSIONS

BZD demonstrated a substantial pharmacological effect on CUMS mice model. Network pharmacology-based analysis predicted that ten blood-absorbed components can act on 27 target proteins. KEGG and Western blotting analysis suggested that BZD could exert antidepressant effects by regulating the PI3K/Akt and MAPK signaling pathways.

Valproate reverses mania-like behaviors in mice via preferential targeting of HDAC2

Valproate (VPA) has been used in the treatment of bipolar disorder since the 1990s. However, the therapeutic targets of VPA have remained elusive. Here we employ a preclinical model to identify the therapeutic targets of VPA. We find compounds that inhibit histone deacetylase proteins (HDACs) are effective in normalizing manic-like behavior, and that class I HDACs (e.g., HDAC1 and HDAC2) are most important in this response. Using an RNAi approach, we find that HDAC2, but not HDAC1, inhibition in the ventral tegmental area (VTA) is sufficient to normalize behavior. Furthermore, HDAC2 overexpression in the VTA prevents the actions of VPA. We used RNA sequencing in both mice and human induced pluripotent stem cells (iPSCs) derived from bipolar patients to further identify important molecular targets. Together, these studies identify HDAC2 and downstream targets for the development of novel therapeutics for bipolar mania.

Drug Repurposing for the Management of Depression: Where Do We Stand Currently?

A slow rate of new drug discovery and higher costs of new drug development attracted the attention of scientists and physicians for the repurposing and repositioning of old medications. Experimental studies and off-label use of drugs have helped drive data for further studies of approving these medications. A deeper understanding of the pathogenesis of depression encourages novel discoveries through drug repurposing and drug repositioning to treat depression. In addition to reducing neurotransmitters like epinephrine and serotonin, other mechanisms such as inflammation, insufficient blood supply, and neurotoxicants are now considered as the possible involved mechanisms. Considering the mentioned mechanisms has resulted in repurposed medications to treat treatment-resistant depression (TRD) as alternative approaches. This review aims to discuss the available treatments and their progress way during repositioning. Neurotransmitters’ antagonists, atypical antipsychotics, and CNS stimulants have been studied for the repurposing aims. However, they need proper studies in terms of formulation, matching with regulatory standards, and efficacy.

Epigenetic histone acetylation and Bdnf dysregulation in the hippocampus of rats exposed to repeated, low-dose diisopropylfluorophosphate

AIMS

Deployment-related exposures to organophosphate (OP) compounds are implicated for Gulf War Illness (GWI) development in First GW veterans. However, reasons for the persistence of GWI are not fully understood. Epigenetic modifications to chromatin are regulatory mechanisms that can adaptively or maladaptively respond to external stimuli. These include DNA methylation and histone acetylation. DNA methylation changes have been reported in GWI but the role of histone acetylation in GWI has been less explored, despite its importance as an epigenetic mechanism for neurological disorders.

MAIN METHODS

Male Sprague-Dawley rats were exposed to OP diisopropyl fluorophosphate (DFP, 0.5 mg/kg s.c., 5-d) and 6-m later brains were dissected for hippocampus. Western blotting, activity assays and chromatin immunoprecipitation (ChIP) were utilized for epigenetic analyses. Behavior was assessed using the Forced Swim Test (FST) and the Elevated Plus Maze (EPM).

KEY FINDINGS

We observed a significant upregulation in HDAC1 protein along with a significant increase in HDAC enzyme activity in the hippocampus of DFP rats. A locus-specific ChIP study revealed decreases in H3K9ac at the brain derived neurotrophic factor (Bdnf) promoter IV coupled with a significant decrease in BDNF protein in DFP rat hippocampus. Treatment with HDAC inhibitor valproic acid reduced HDAC activity and decreased the FST immobility time in DFP rats.

SIGNIFICANCE

Our research suggests that epigenetic alterations to histone acetylation pathways and decreased BDNF expression could represent novel mechanisms for GWI symptomatology and may provide new targets for developing effective drugs for GWI treatment.

Effects of different drying methods on the chemical constituents of Lilium lancifolium Thunb. based on UHPLC-MS analysis and antidepressant activity of the main chemical component regaloside A

The Lilium lancifolium Thunb. is a herb with multiple functions in both medicine and food in China, and its extracts have shown antidepressant effects. In this study, fresh bulbs of Lilium lancifolium Thunb. were processed to study the effects of different drying processes on changes in its main chemical components. We found that different drying methods can affect the chemical constituents of the herb. Among these components, Regaloside A has been found as the characteristic component. Here, Cell Counting Kit-8 assay, and Western blotting were used to evaluate the neuroprotective antidepressant effects of Regaloside A. The results showed the cell survival rate was improved, the phosphorylation levels of brain-derived neurotrophic factor, tyrosine kinase receptor B, phosphatidylinositol 3 kinase, protein kinase B, and mammalian target of rapamycin were increased after Regaloside A treatment. In general, different drying methods have a significant influence on the chemical composition of the herb, and Regaloside A may be the main chemical component of the herb. It can alleviate the damage of corticosterone in SH-SY5Y cells, and phosphatidylinositol-3-kinase/protein kinase B/mammalian target of rapamycin signaling mediated by brain-derived neurotrophic factor/tyrosine kinase receptor B may play an important role in the neuroprotective antidepressant effects of Regaloside A.

Antidepressant effects of valproic acid in an animal model of depression

Valproic acid, beside its anticonvulsant action, is widely used as a mood stabilizer in the therapy of bipolar disorder. The potential antidepressant action of valproic acid has not been sufficiently characterized so far. The aim of the present study was to evaluate the antidepressant effect of valproic acid in an aldosterone model of depression. Subchronic treatment with valproic acid resulted in a reduction of the time spent in immobility in the forced swim test. In conclusion, the present study provides evidence on antidepressant effects of valproic acid using a classical behavioral approach for testing the efficacy of antidepressant drug in animal models.

Abnormal expression of rno_circRNA_014900 and rno_circRNA_005442 induced by ketamine in the rat hippocampus

BACKGROUND

Recent studies have shown that circular RNA (circRNA) is rich in microRNA (miRNA) binding sites. We have previously demonstrated that the antidepressant effect of ketamine is related to the abnormal expression of various miRNAs in the brain. This study determined the expression profile of circRNAs in the hippocampus of rats treated with ketamine.

METHODS

The aberrantly expressed circRNAs in rat hippocampus after ketamine injection were analyzed by microarray chip, and we further validated these circRNAs by quantitative reverse-transcription PCR (qRT-PCR). The target genes of the different circRNAs were predicted using bioinformatic analyses, and the functions and signal pathways of these target genes were investigated by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses.

RESULTS

Microarray analysis showed that five circRNAs were aberrantly expressed in rat hippocampus after ketamine injection (fold change > 2.0, p < 0.05). The results from the qRT-PCR showed that one of the circRNAs was significantly increased (rno_circRNA_014900; fold change = 2.37; p = 0.03), while one was significantly reduced (rno_circRNA_005442; fold change = 0.37; p = 0.01). We discovered a significant enrichment in several GO terms and pathways associated with depression.

CONCLUSION

Our findings showed the abnormal expression of ketamine-induced hippocampal circRNAs in rats.

Potential link between the RagA-mTOR-p70S6K axis and depressive-behaviors during bacterial liposaccharide challenge

BACKGROUND

Bacterial infection is a potential risk factor for depression. However, little is known about the mechanistic link between bacterial endotoxin and depressive-like behaviors. The aim of the present study was to clarify whether liposaccharide (LPS) could induce depressive-like behaviors in mice via sequentially activating small GTPase RagA, mammalian target of rapamycin (mTOR), and p70S6K.

METHODS

C57BL/6 N mice were treated with 0.83 mg/kg LPS by intraperitoneal injection for 24 h. The animals were assessed for depressive-like behaviors by forced swim test and tail suspension test. The expression levels of RagA, mTOR, and p70S6K were determined in mice, primary cortical neurons, neural stem cells, and PC12 cells.

RESULTS

LPS effectively induced depressive-like behaviors in mice. Biochemical examination revealed that LPS not only upregulated RagA expression but also activated mTOR/p70S6K pathway in mouse brains. LPS challenge also achieved a similar effect in primary cortical neurons, neural stem cells, and PC12 cells. Following the silencing of RagA expression with specific siRNA, LPS failed to induce mTORC1 translocation to the lysosomal membranes in PC12 cells. These results suggested that LPS might sequentially upregulate RagA and activate mTOR and p70S6K pathways in mice and neural stem cells.

CONCLUSIONS

This study for the first time demonstrated that LPS might induce depressive-like behaviors in mice via the upregulation of RagA and subsequent activation of mTOR/p70S6K pathway. Such information may highlight the RagA-mTOR-p70S6K signaling cascade as a novel therapeutic target for the development of new anti-depressant therapeutics.

A comprehensive metabolomics investigation of hippocampus, serum, and feces affected by chronic fluoxetine treatment using the chronic unpredictable mild stress mouse model of depression

A metabolomic investigation of depression and chronic fluoxetine treatment was conducted using a chronic unpredictable mild stress model with C57BL/6N mice. Establishment of the depressive model was confirmed by body weight measurement and behavior tests including the forced swim test and the tail suspension test. Behavioral despair by depression was reversed by four week-treatment with fluoxetine. Hippocampus, serum, and feces samples collected from four groups (control + saline, control + fluoxetine, model + saline, and model + fluoxetine) were subjected to metabolomic profiling based on ultra-high performance liquid chromatography-quadrupole-time-of-flight mass spectrometry. Alterations in the metabolic patterns were evident in all sample types. The antidepressant effects of fluoxetine appeared to involve various metabolic pathways including energy metabolism, neurotransmitter synthesis, tryptophan metabolism, fatty acid metabolism, lipid metabolism, and bile acid metabolism. Predictive marker candidates of depression were identified, including β-citryl-L-glutamic acid (BCG) and docosahexaenoic acid (DHA) in serum and chenodeoxycholic acid and oleamide in feces. This study suggests that treatment effects of fluoxetine might be differentiated by altered levels of tyramine and BCG in serum, and that DHA is a potential serum marker for depression with positive association with hippocampal DHA. Collectively, our comprehensive study provides insights into the biochemical perturbations involved in depression and the antidepressant effects of fluoxetine.

Influence of the HDAC Inhibitor Valproic Acid on the Growth and Proliferation of Temsirolimus-Resistant Prostate Cancer Cells In Vitro

The mechanistic target of rapamycin (mTOR) is elevated in prostate cancer, making this protein attractive for tumor treatment. Unfortunately, resistance towards mTOR inhibitors develops and the tumor becomes reactivated. We determined whether epigenetic modulation by the histone deacetylase (HDAC) inhibitor, valproic acid (VPA), may counteract non-responsiveness to the mTOR inhibitor, temsirolimus, in prostate cancer (PCa) cells. Prostate cancer cells, sensitive (parental) and resistant to temsirolimus, were exposed to VPA, and tumor cell growth behavior compared. Temsirolimus resistance enhanced the number of tumor cells in the G2/M-phase, correlating with elevated cell proliferation and clonal growth. The cell cycling proteins cdk1 and cyclin B, along with Akt-mTOR signaling increased, whereas p19, p21 and p27 decreased, compared to the parental cells. VPA significantly reduced cell growth and up-regulated the acetylated histones H3 and H4. Cdk1 and cyclin B decreased, as did phosphorylated mTOR and the mTOR sub-complex Raptor. The mTOR sub-member Rictor and phosphorylated Akt increased under VPA. Knockdown of cdk1, cyclin B, or Raptor led to significant cell growth reduction. HDAC inhibition through VPA counteracts temsirolimus resistance, probably by down-regulating cdk1, cyclin B and Raptor. Enhanced Rictor and Akt, however, may represent an undesired feedback loop, which should be considered when designing future therapeutic regimens.

Schisantherin B Improves the Pathological Manifestations of Mice Caused by Behavior Desperation in Different Ages-Depression with Cognitive Impairment

Depression is a major mood disorder. Abnormal expression of glial glutamate transporter-1 (GLT-1) is associated with depression. Schisantherin B (STB) is one bioactive of lignans isolated from Schisandra chinensis (Turcz.) Baill which has been commonly used as a traditional herbal medicine for thousands of years. This paper was designed to investigate the effects of STB on depressive mice induced by forced swimming test (FST). Additionally, we also assessed the impairment of FST on cognitive function in mice with different ages. FST and open field test (OFT) were used for assessing depressive symptoms, and Y-maze was used for evaluating cognition processes. Our study showed that STB acting as an antidepressant, which increased GLT-1 levels by promoting PI3K/AKT/mTOR pathway. Although the damage is reversible, short-term learning and memory impairment caused by FST test is more serious in the aged mice, and STB also exerts cognition improvement ability in the meanwhile. Our findings suggested that STB might be a promising therapeutic agent of depression by regulating the GLT-1 restoration as well as activating PI3K/AKT/mTOR pathway.

Probiotics decrease depressive behaviors induced by constipation via activating the AKT signaling pathway

Chronic constipation is often accompanied by emotional disorders such as depression and anxiety. The aim of this study was to determine whether administration of a multispecies probiotic can decrease depressive behaviors through the gut-brain axis and identify any underlying mechanisms. A mouse model of constipation induced by loperamide (5 mg·kg^-1,i.p.) was used. For that purpose, 36 ICR male mice were divided into three groups: control, constipation and probiotic groups. The probiotic group received treatment with a probiotic once per day for 14 days via a gavage. All other groups were given an equal volume of normal saline. The fecal parameters and intestinal transit ratio were recorded. The forced swimming test and tail suspension test were used to detect changes in depressive behaviors. Total superoxide dismutase (T-SOD) activity and malondialdehyde (MDA) levels were measured by assay kits. We also detected neuronal survival, as well as phosphorylated Ser/Thr protein kinase (p-AKT), Bcl-2, Bcl-2 associated X protein (Bax) and cleaved caspase-3 levels in the hippocampus. The results showed that administration of a probiotic could ameliorate depressive behaviors and relieve neuronal cell injury in the hippocampal CA3 regions. Moreover, probiotic treatment decreased MDA levels and increased SOD activity. Furthermore, probiotic administration increased p-AKT and Bcl-2 levels in the hippocampus of the constipated mice, while decreasing the concentrations of Bax and cleaved caspase-3, so as to inhibit the neural apoptosis. In the present study, we confirm that probiotics can alleviate depression induced by constipation through protecting neuronal health via activation of the AKT signaling pathway.

Mechanisms and Therapeutic Targets of Depression After Intracerebral Hemorrhage

The relationship between depression and intracerebral hemorrhage (ICH) is complicated. One of the most common neuropsychiatric comorbidities of hemorrhagic stroke is Post-ICH depression. Depression, as a neuropsychiatric symptom, also negatively impacts the outcome of ICH by enhancing morbidity, disability, and mortality. However, the ICH outcome can be improved by antidepressants such as the frequently-used selective serotonin reuptake inhibitors. This review therefore presents the mechanisms of post-ICH depression, we grouped the mechanisms according to inflammation, oxidative stress (OS), apoptosis and autophagy, and explained them through their several associated signaling pathways. Inflammation is mainly related to Toll-like receptors (TLRs), the NF-kB mediated signal pathway, the PPAR-γ-dependent pathway, as well as other signaling pathways. OS is associated to nuclear factor erythroid-2 related factor 2 (Nrf2), the PI3K/Akt pathway and the MAPK/P38 pathway. Moreover, autophagy is associated with the mTOR signaling cascade and the NF-kB mediated signal pathway, while apoptosis is correlated with the death receptor-mediated apoptosis pathway, mitochondrial apoptosis pathway, caspase-independent pathways and others. Furthermore, we found that neuroinflammation, oxidative stress, autophagy, and apoptosis experience interactions with one another. Additionally, it may provide several potential therapeutic targets for patients that might suffer from depression after ICH.

Loss of Microglia and Impaired Brain-Neurotrophic Factor Signaling Pathway in a Comorbid Model of Chronic Pain and Depression

Major depressive disorder (MDD) and chronic pain are two complex disorders that often coexist. The underlying basis for this comorbidity is unknown. In the current investigation, microglia and the brain-derived neurotrophic factor (BDNF)-cAMP response element-binding protein (CREB) pathway were investigated. A comorbidity model, with characteristics of both MDD and chronic pain, was developed by the administration of dextran sodium sulfate (DSS) and the induction of chronic unpredictable psychological stress (CUS). Mechanical threshold sensory testing and the visceromotor response (VMR) were employed to measure mechanical allodynia and visceral hypersensitivity, respectively. RT-qPCR and western blotting were used to assess mRNA and protein levels of ionized calcium-binding adaptor molecule 1 (Iba-1), nuclear factor-kappa B (NF-κB), nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor, alpha (IκBa), BDNF, and CREB. In comorbid animals, mechanical allodynia and visceral hypersensitivities were significant with increased mRNA and protein levels for NF-κB-p65 and IκBa. Furthermore, the comorbid animals had deceased mRNA and protein levels for Iba-1, BDNF, and CREB as well as a reduced number and density of microglia in the medial prefrontal cortex (mPFC). These results together suggest that DSS and CUS can induce the comorbidities of chronic pain and depression-like behavior. The pathology of this comorbidity involves loss of microglia within the mPFC with subsequent activation of NF-κB-p65 and down-regulation of BDNF/p-CREB signaling.

Drug repurposing may generate novel approaches to treating depression

Objectives

The breakthrough advancements in scientific medical research have greatly improved our understanding of the pathogenesis of depression, encouraging drug discoverers to take a shorter path than ever through drug repurposing to generate new antidepressant medications. In addition to reduced noradrenergic and serotonergic neurotransmission in the brain, other coincidence features such as glutamate neurotoxicity, inflammation and/or cerebrovascular insufficiency are implicated in the pathogenesis of major depressive disorder and late-life depression. This short review discusses the progress made in repurposing drugs for antidepressant actions.

Key findings

Drugs being repurposed as antidepressants act on novel drug targets, thereby treating resistant depression and improving remission rate. Drugs such as ketamine, dextromethorphan/quinidine and scopolamine are rapidly acting antidepressants targeting glutamate receptors. Nimodipine and quetiapine are efficient add-on therapy for late-life depression. Anti-inflammatory drugs, statins, insulin sensitizers, minocycline could remarkably contribute to treating refractory depression.

Summary

Drug repurposing represents an alternative approach to cope with major obstacles, including financial insufficiency and unavoidable long lag evaluation time, undermining the classical pathway of developing new hit compounds into clinically approved antidepressants.