A role for MAP kinase signaling in behavioral models of depression and antidepressant treatment

Emerging Perspectives on Neuroprotection

Neuroprotection aims to safeguard neurons from damage caused by various factors like stress, potentially leading to the rescue, recovery, or regeneration of the nervous system and its functions [J Clin Neurosci. 2002;9(1):4-8]. Conversely, neuroplasticity refers to the brain's ability to adapt and change throughout life, involving structural and functional alterations in cells and synaptic transmission [Neural Plast. 2014;2014:541870]. Neuroprotection is a broad and multidisciplinary field encompassing various approaches and strategies aimed at preserving and promoting neuronal health. It is a critical area of research in neuroscience and neurology, with the potential to lead to new therapies for a wide range of neurological disorders and conditions. Neuroprotection can take various forms and may involve pharmacological agents, lifestyle modifications, or behavioral interventions. Accordingly, also the perspective and the meaning of neuroprotection differs due to different angles of interpretation. The primary interpretation is from the pharmacological point of view since the most consistent data come from this field. In addition, we will discuss also alternative, yet less considered, perspectives on neuroprotection, focusing on specific neuroprotective targets, interactions with surrounding microglia, different levels of neuroprotective effects, the reversive/adaptative dimension, and its use as anticipatory/prophylactic intervention.

Immunometabolic Blood Biomarkers of Developmental Trajectories of Depressive Symptoms: Findings From the ALSPAC Birth Cohort

Studies of longitudinal trends of depressive symptoms in young people could provide insight into aetiologic mechanism, heterogeneity and origin of common cardiometabolic comorbidities for depression. Depression is associated with immunological and metabolic alterations, but immunometabolic characteristics of developmental trajectories of depressive symptoms remain unclear. Using depressive symptoms scores measured on 10 occasions between ages 10 and 25 years in the Avon Longitudinal Study of Parents and Children (n=7302), we identified four distinct trajectories: low-stable (70% of the sample), adolescent-limited (13%), adulthood-onset (10%) and adolescent-persistent (7%). We examined associations of these trajectories with: i) anthropometric, cardiometabolic and psychiatric phenotypes using multivariable regression (n=1709-3410); ii) 67 blood immunological proteins and 57 metabolomic features using empirical Bayes moderated linear models (n=2059 and n=2240 respectively); and iii) 28 blood cell counts and biochemical measures using multivariable regression (n=2256). Relative to the low-stable group, risk of depression and anxiety in adulthood was higher for all other groups, especially in the adolescent-persistent (ORdepression=22.80, 95% CI 15.25-34.37; ORGAD=19.32, 95% CI 12.86-29.22) and adulthood-onset (ORdepression=7.68, 95% CI 5.31-11.17; ORGAD=5.39, 95% CI 3.65-7.94) groups. The three depression-related trajectories vary in their immunometabolic profile, with evidence of little or no alterations in the adolescent-limited group. The adulthood-onset group shows widespread classical immunometabolic changes (e.g., increased immune cell counts and insulin resistance), while the adolescent-persistent group is characterised by higher BMI both in childhood and adulthood with few other immunometabolic changes. These findings point to distinct mechanisms and intervention opportunities for adverse cardiometabolic profile in different groups of young people with depression.

Levomilnacipran Improves Lipopolysaccharide-Induced Dysregulation of Synaptic Plasticity and Depression-Like Behaviors via Activating BDNF/TrkB Mediated PI3K/Akt/mTOR Signaling Pathway

Depression is a common psychological disease with high morbidity and mortality. Recently, the involvement of synaptic plasticity in the pathogenesis of depression has shed light on the direction of developing novel antidepressants. Levomilnacipran is a newly approved medication for the treatment of adult major depressive disorder. However, the detailed mechanisms underlying its antidepressant-like effects have yet to be illuminated. In this study, we aimed to investigate the role of levomilnacipran in regulating synaptic plasticity and explore the possible molecular mechanisms of its antidepressant effects using a rat model of depression induced by lipopolysaccharide (LPS). The results demonstrated that levomilnacipran (30 mg/kg, i.p.) significantly ameliorated depression-like behaviors in rats, alleviated the dysregulation of synaptic plasticity, and suppressed neuroinflammation within hippocampus induced by LPS-treatment. Levomilnacipran increased the expression of postsynaptic dense 95 (PSD-95) and synaptophysin (Syn) and reversed the imbalance between pro- and anti-inflammatory cytokines within hippocampus of depressed rats. Additionally, levomilnacipran elevated expression level of brain-derived neurotrophic factor (BDNF), accompanied by increased tyrosine kinase B (TrkB), phosphorylated phosphatidylinositol 3-kinase (PI3K), phosphorylated protein kinase B (p-Akt), and phosphorylated mammalian target of rapamycin (p-mTOR). Taken together, these results suggest that levomilnacipran may exert antidepressant effects via upregulating BDNF/TrkB mediated PI3K/Akt/mTOR signaling pathway to improve synaptic plasticity. These findings reveal potential mechanisms for the antidepressant effects of levomilnacipran and offer new insights into the treatments for depression.

Effects of nitrous oxide and ketamine on electrophysiological and molecular responses in the prefrontal cortex of mice: A comparative study

Nitrous oxide (N2O; laughing gas) has recently reported to produce rapid antidepressant effects, but little is known about the underlying mechanisms. We performed transcriptomics, in situ hybridization, and electrophysiological studies to examine the potential shared signatures induced by 1 h inhalation of 50% N2O and a single subanesthetic dose of ketamine (10 mg/kg, i.p.) in the medial prefrontal cortex (mPFC) in adult mice. Both treatments similarly affected the transcription of several negative regulators of mitogen-activated protein kinases (MAPKs), namely, dual specificity phosphatases (DUSPs). The effects were primarily located in the pyramidal cells. Notably, the overall effects of N2O on mRNA expression were much more prominent and widespread compared to ketamine. Ketamine caused an elevation of the spiking frequency of putative pyramidal neurons and increased gamma activity (30-100 Hz) of cortical local field potentials. However, N2O produced no such effects. Spiking amplitudes and spike-to-local field potential phase locking of putative pyramidal neurons and interneurons in this brain area showed no uniform changes across treatments. Our findings suggest that N2O and subanesthetic-dose ketamine target MAPK pathway in the mPFC but produce varying acute electrophysiological responses.

LHPP in Glutamatergic Neurons of the Ventral Hippocampus Mediates Depression-like Behavior by Dephosphorylating CaMKIIα and ERK

BACKGROUND

LHPP was recently shown to be a risk gene for major depressive disorder. LHPP has been proven to dephosphorylate the residues of histidine, serine, threonine, and tyrosine. However, much remains unknown about how LHPP contributes to depression.

METHODS

In the current study, we addressed this issue by integrating approaches of genetics, molecular biology, behavioral testing, and electrophysiology.

RESULTS

We found that levels of LHPP were upregulated in glutamatergic neurons of the ventral hippocampus in mice that displayed stress-induced depression-like behaviors. Knockout of LHPP in glutamatergic neurons of the brain improved the spontaneous activity of LHPPflox/flox·CaMKIIαCre+ (conditional knockout) mice. Adeno-associated virus-mediated LHPP knockdown in the ventral hippocampus enhanced resistance against chronic social defeat stress in mice. Manipulations of LHPP levels impacted the density of dendritic spines and excitability of CA1 pyramidal neurons by mediating the expressions of BDNF (brain-derived neurotrophic factor) and PSD95 via the modulation of the dephosphorylation of CaMKIIα and ERK. Notably, compared with wild-type LHPP, human mutant LHPP (E56K, S57L) significantly increased the activity of the CaMKIIα/ERK-BDNF/PSD95 signaling pathway. Finally, esketamine, not fluoxetine, markedly alleviated the LHPP upregulation-induced depression-like behaviors.

CONCLUSIONS

These findings provide evidence that LHPP contributes to the pathogenesis of depression via threonine and serine hydrolases, thereby identifying LHPP as a potential therapeutic target in treating patients with major depressive disorder.

In silico analysis of the Val66Met mutation in BDNF protein: implications for psychological stress

The brain-derived neurotrophic factor (BDNF) involves stress regulation and psychiatric disorders. The Val66Met polymorphism in the BDNF gene has been linked to altered protein function and susceptibility to stress-related conditions. This in silico analysis aimed to predict and analyze the consequences of the Val66Met mutation in the BDNF gene of stressed individuals. Computational techniques, including ab initio, comparative, and I-TASSER modeling, were used to evaluate the functional and stability effects of the Val66Met mutation in BDNF. The accuracy and reliability of the models were validated. Sequence alignment and secondary structure analysis compared amino acid residues and structural components. The phylogenetic analysis assessed the conservation of the mutation site. Functional and stability prediction analyses provided mixed results, suggesting potential effects on protein function and stability. Structural models revealed the importance of BDNF in key biological processes. Sequence alignment analysis showed the conservation of amino acid residues across species. Secondary structure analysis indicated minor differences between the wild-type and mutant forms. Phylogenetic analysis supported the evolutionary conservation of the mutation site. This computational study suggests that the Val66Met mutation in BDNF may have implications for protein stability, structural conformation, and function. Further experimental validation is needed to confirm these findings and elucidate the precise effects of this mutation on stress-related disorders.

Exploring the Potential Molecular Mechanism of the Shugan Jieyu Capsule in the Treatment of Depression through Network Pharmacology, Molecular Docking, and Molecular Dynamics Simulation

BACKGROUND

Shugan Jieyu Capsule (SJC) is a pure Chinese medicine compound prepared with Hypericum perforatum and Acanthopanacis senticosi. SJC has been approved for the clinical treatment of depression, but the mechanism of action is still unclear.

OBJECTIVES

Network pharmacology, molecular docking, and molecular dynamics simulation (MDS) were applied in the present study to explore the potential mechanism of SJC in the treatment of depression.

METHODS

TCMSP, BATMAN-TCM, and HERB databases were used, and related literature was reviewed to screen the effective active ingredients of Hypericum perforatum and Acanthopanacis senticosi. TCMSP, BATMAN-TCM, HERB, and STITCH databases were used to predict the potential targets of effective active ingredients. GeneCards database, DisGeNET database, and GEO data set were used to obtain depression targets and clarify the intersection targets of SJC and depression. STRING database and Cytoscape software were used to build a protein-protein interaction (PPI) network of intersection targets and screen the core targets. The enrichment analysis on the intersection targets was conducted. Then the receiver operator characteristic (ROC) curve was constructed to verify the core targets. The pharmacokinetic characteristics of core active ingredients were predicted by SwissADME and pkCSM. Molecular docking was performed to verify the docking activity of the core active ingredients and core targets, and molecular dynamics simulations were performed to evaluate the accuracy of the docking complex.

RESULTS

We obtained 15 active ingredients and 308 potential drug targets with quercetin, kaempferol, luteolin, and hyperforin as the core active ingredients. We obtained 3598 targets of depression and 193 intersection targets of SJC and depression. A total of 9 core targets (AKT1, TNF, IL6, IL1B, VEGFA, JUN, CASP3, MAPK3, PTGS2) were screened with Cytoscape 3.8.2 software. A total of 442 GO entries and 165 KEGG pathways (p <0.01) were obtained from the enrichment analysis of the intersection targets, mainly enriched in IL-17, TNF, and MAPK signaling pathways. The pharmacokinetic characteristics of the 4 core active ingredients indicated that they could play a role in SJC antidepressants with fewer side effects. Molecular docking showed that the 4 core active components could effectively bind to the 8 core targets (AKT1, TNF, IL6, IL1B, VEGFA, JUN, CASP3, MAPK3, PTGS2), which were related to depression by the ROC curve. MDS showed that the docking complex was stable.

CONCLUSION

SJC may treat depression by using active ingredients such as quercetin, kaempferol, luteolin, and hyperforin to regulate targets such as PTGS2 and CASP3 and signaling pathways such as IL-17, TNF, and MAPK, and participate in immune inflammation, oxidative stress, apoptosis, neurogenesis, etc.

Effects of Artemisia annua L. on postmenopausal syndrome in ovariectomized mice

ETHNOPHARMACOLOGICAL RELEVANCE

Artemisia annua L. (Asteraceae) has been used as an antipyretic and anti-parasitic drug in traditional medicine for more than 2000 years. It has also been prescribed to treat symptoms caused by deficiency of Yin, which might be observed in menopausal state from the point of view of traditional medicine.

AIM OF THE STUDY

We hypothesized that A. annua might be useful for treating menopausal disorders with less adverse effects than hormone replacement therapy. Thus, the aim of the present study was to investigate effects of A. annua on postmenopausal symptoms of ovariectomized (OVX) mice.

MATERIALS AND METHODS

OVX mice were employed as a model for postmenopausal disorders. Mice were treated with a water extract of A. annua (EAA; 30, 100 or 300 mg/kg, p.o.) or 17β-estradiol (E2; 0.5 mg/kg, s.c.) for 8 weeks. Open field test (OFT), novel object recognition task (NOR), Y-maze test, elevated plus maze test (EPM), splash test and tail suspension test (TST) were conducted to determine whether EAA could ameliorate postmenopausal symptoms. Phosphorylated levels of extracellular signal-regulated kinase (ERK), protein kinase B (Akt), and glycogen synthase kinase-3β (GSK-3β), β-catenin and expression level of synaptophysin in the cortex and hippocampus were evaluated by Western blot analysis.

RESULTS

EAA treatment significantly increased the discrimination index in NOR, decreased the time in closed arm than in open arm in EPM, increased grooming time in splash test, and decreased immobility time in TST, as did E2 treatment. In addition, decreased phosphorylation levels of ERK, Akt, GSK-3β, and β-catenin and expression levels of synaptophysin in the cortex and hippocampus after OVX were reversed by administration of EAA and E2.

CONCLUSION

These results suggest that A. annua can ameliorate postmenopausal symptoms such as cognitive dysfunction, anxiety, anhedonia, and depression by activating ERK, Akt, and GSK-3β/β-catenin signaling pathway and hippocampal synaptic plasticity, and that A. annua would be a novel treatment for postmenopausal symptoms.

Long noncoding RNA NONHSAG045500 regulates serotonin transporter to ameliorate depressive-like behavior via the cAMP-PKA-CREB signaling pathway in a model of perinatal depression

OBJECTIVE

Perinatal depression (PND) is the most common complication of childbirth and negatively affects the mother. Long noncoding RNA (lncRNA) NONHSAG045500 inhibits the expression of 5-hydroxytryptamine (5-HT) transporter (i.e. serotonin transporter [SERT]) and produces an antidepressant effect. This study aimed to identify a link between the lncRNA NONHSAG045500 and the pathogenesis of PND.

METHODS

Female C57BL/6 J mice were divided into normal control group (control group, n = 15), chronic unpredictable stress (CUS) model group (PND group, n = 15), lncRNA NONHSAG045500-overexpressed group (LNC group, sublingual intravenous injection of NONHSAG045500 overexpression cells for 7 days, n = 15), and escitalopram treatment group (i.e. the selective serotonin reuptake inhibitor [SSRI] group, with escitalopram administered from the 10th day after pregnancy to the 10th day after delivery, n = 15). Control group mice were conceived normally, whereas, in the other groups, a CUS model was established before mice were conceived. Depressive-like behaviour was assessed via sucrose preference, forced swimming, and open-field tests. The expression levels of 5-HT, SERT, and cAMP-PKA-CREB pathway-related proteins in the prefrontal cortex were detected on the 10th day after delivery.

RESULTS

Mice in the PND group exhibited significant depressive-like behaviours compared with those in the control group, indicating that the PND model was successfully established. The expression of lncRNA NONHSAG045500 was markedly decreased in the PND group compared with that in the control group. After treatment, both LNC and SSRI groups showed a significant improvement in depression-like behaviour, and the expression of 5-HT in the prefrontal cortex was increased in these groups compared with that in the PND group. In addition, the LNC group displayed lower expression of SERT and higher expression of cAMP, PKA, and CREB when in comparison to PND group.

CONCLUSION

NONHSAG045500 mediates the development of PND mainly by activating the cAMP-PKA-CREB pathway, increasing the level of 5-HT, and decreasing the expression of SERT.

HnRNPK is involved in stress-induced depression-like behavior via ERK-BDNF pathway in mice

As a ubiquitous RNA-binding protein, heterogeneous nuclear ribonucleoprotein K (hnRNPK) interacts with numerous nucleic acids and proteins and is involved in various cellular functions. Available literature indicates that it can regulate dendritic spine density through the extracellular signal-regulating kinase (ERK) - brain-derived neurotrophic factor (BDNF) pathway, which is crucial to retain the synaptic plasticity in patients with major depressive disorder (MDD) and mouse depression models. However, ERK upstream regulatory kinase has not been fully elucidated. Furthermore, it remains unexplored whether hnRNPK may impact the depressive condition via the ERK pathway. The present study addressed this issue by integrating approaches of genetics, molecular biology, behavioral testing. We found that hnRNPK in the brain was mainly distributed in the hippocampal neurons; that it was significantly downregulated in mice that displayed stress-induced depression-like behaviors; and that the level of hnRNPK markedly decreased in MDD patients from the GEO database. Further in vivo and in vitro analyses revealed that the changes in the expressions of BDNF and PSD95 and in the phosphorylation of ERK (Thr202/Tyr204) paralleled the variation of hnRNPK levels in the ventral hippocampal neurons in mice with depression-like behaviors. Finally, esketamine treatment significantly increased the level of hnRNPK in mice. These findings evidence that hnRNPK involved in the pathogenesis of depression via the ERK-BDNF pathway, pinpointing hnRNPK as a potential therapeutic target in treating MDD patients.

Organic cation transporter 2 contributes to SSRI antidepressant efficacy by controlling tryptophan availability in the brain

Selective serotonin reuptake inhibitors (SSRI) are common first-line treatments for major depression. However, a significant number of depressed patients do not respond adequately to these pharmacological treatments. In the present preclinical study, we demonstrate that organic cation transporter 2 (OCT2), an atypical monoamine transporter, contributes to the effects of SSRI by regulating the routing of the essential amino acid tryptophan to the brain. Contrarily to wild-type mice, OCT2-invalidated mice failed to respond to prolonged fluoxetine treatment in a chronic depression model induced by corticosterone exposure recapitulating core symptoms of depression, i.e., anhedonia, social withdrawal, anxiety, and memory impairment. After corticosterone and fluoxetine treatment, the levels of tryptophan and its metabolites serotonin and kynurenine were decreased in the brain of OCT2 mutant mice compared to wild-type mice and reciprocally tryptophan and kynurenine levels were increased in mutants' plasma. OCT2 was detected by immunofluorescence in several structures at the blood-cerebrospinal fluid (CSF) or brain-CSF interface. Tryptophan supplementation during fluoxetine treatment increased brain concentrations of tryptophan and, more discreetly, of 5-HT in wild-type and OCT2 mutant mice. Importantly, tryptophan supplementation improved the sensitivity to fluoxetine treatment of OCT2 mutant mice, impacting chiefly anhedonia and short-term memory. Western blot analysis showed that glycogen synthase kinase-3β (GSK3β) and mammalian/mechanistic target of rapamycin (mTOR) intracellular signaling was impaired in OCT2 mutant mice brain after corticosterone and fluoxetine treatment and, conversely, tryptophan supplementation recruited selectively the mTOR protein complex 2. This study provides the first evidence of the physiological relevance of OCT2-mediated tryptophan transport, and its biological consequences on serotonin homeostasis in the brain and SSRI efficacy.

Astrocyte metabolism and signaling pathways in the CNS

Astrocytes comprise half of the cells in the central nervous system and play a critical role in maintaining metabolic homeostasis. Metabolic dysfunction in astrocytes has been indicated as the primary cause of neurological diseases, such as depression, Alzheimer's disease, and epilepsy. Although the metabolic functionalities of astrocytes are well known, their relationship to neurological disorders is poorly understood. The ways in which astrocytes regulate the metabolism of glucose, amino acids, and lipids have all been implicated in neurological diseases. Metabolism in astrocytes has also exhibited a significant influence on neuron functionality and the brain's neuro-network. In this review, we focused on metabolic processes present in astrocytes, most notably the glucose metabolic pathway, the fatty acid metabolic pathway, and the amino-acid metabolic pathway. For glucose metabolism, we focused on the glycolysis pathway, pentose-phosphate pathway, and oxidative phosphorylation pathway. In fatty acid metabolism, we followed fatty acid oxidation, ketone body metabolism, and sphingolipid metabolism. For amino acid metabolism, we summarized neurotransmitter metabolism and the serine and kynurenine metabolic pathways. This review will provide an overview of functional changes in astrocyte metabolism and provide an overall perspective of current treatment and therapy for neurological disorders.

Ginsenoside-Rg1 synergized with voluntary running exercise protects against glial activation and dysregulation of neuronal plasticity in depression

Depression is a common psychological disease accompanied by mental disorders and somatic symptoms. However, the underlying mechanisms regarding the pathogenesis of depression are still not clear. Neuronal damage resulting from inflammation is considered to be one of the important risk factors for depression. Ginsenoside-Rg1, a sterol extract extracted from ginseng herbs, has been shown to have neuroprotective effects against neurodegenerative diseases. Moreover, running exercise, a simple behavioral therapy, has been recently shown to have antidepressant effects. However, whether these two synergized strategies are more efficient in depression treatment, especially the neural mechanisms underlying this practical and interesting treatment is unknown. In this study, we have shown that ginsenoside-Rg1 synergized with voluntary running exercise exerts more efficiency on suppressing neuroinflammation, up-regulating expression of neurotrophic factors, and synaptic-related proteins, ameliorating neuronal structural damages than that of ginsenoside-Rg1 or voluntary exercise alone, suggesting its better neuroprotective effects. More importantly, the antidepressant-like effect of this synergistic treatment was also significantly better than either of these two treatments. These results suggest that ginsenoside-Rg1, synergized with voluntary running, may have higher efficacy in the treatment of depression through anti-inflammation and the improvement of neuroplasticity. These findings may provide a new perspective for the development of a therapeutic strategy for depression.

Chronic salmon calcitonin exerts an antidepressant effect via modulating the p38 MAPK signaling pathway

Depression is a common recurrent psychiatric disorder with a high lifetime prevalence and suicide rate. At present, although several traditional clinical drugs such as fluoxetine and ketamine, are widely used, medications with a high efficiency and reduced side effects are of urgent need. Our group has recently reported that a single administration of salmon calcitonin (sCT) could ameliorate a depressive-like phenotype via the amylin signaling pathway in a mouse model established by chronic restraint stress (CRS). However, the molecular mechanism underlying the antidepressant effect needs to be addressed. In this study, we investigated the antidepressant potential of sCT applied chronically and its underlying mechanism. In addition, using transcriptomics, we found the MAPK signaling pathway was upregulated in the hippocampus of CRS-treated mice. Further phosphorylation levels of ERK/p38/JNK kinases were also enhanced, and sCT treatment was able only to downregulate the phosphorylation level of p38/JNK, with phosphorylated ERK level unaffected. Finally, we found that the antidepressant effect of sCT was blocked by p38 agonists rather than JNK agonists. These results provide a mechanistic explanation of the antidepressant effect of sCT, suggesting its potential for treating the depressive disorder in the clinic.

Phytochemicals That Act on Synaptic Plasticity as Potential Prophylaxis against Stress-Induced Depressive Disorder

Depression is a neuropsychiatric disorder associated with persistent stress and disruption of neuronal function. Persistent stress causes neuronal atrophy, including loss of synapses and reduced size of the hippocampus and prefrontal cortex. These alterations are associated with neural dysfunction, including mood disturbances, cognitive impairment, and behavioral changes. Synaptic plasticity is the fundamental function of neural networks in response to various stimuli and acts by reorganizing neuronal structure, function, and connections from the molecular to the behavioral level. In this review, we describe the alterations in synaptic plasticity as underlying pathological mechanisms for depression in animal models and humans. We further elaborate on the significance of phytochemicals as bioactive agents that can positively modulate stress-induced, aberrant synaptic activity. Bioactive agents, including flavonoids, terpenes, saponins, and lignans, have been reported to upregulate brain-derived neurotrophic factor expression and release, suppress neuronal loss, and activate the relevant signaling pathways, including TrkB, ERK, Akt, and mTOR pathways, resulting in increased spine maturation and synaptic numbers in the neuronal cells and in the brains of stressed animals. In clinical trials, phytochemical usage is regarded as safe and well-tolerated for suppressing stress-related parameters in patients with depression. Thus, intake of phytochemicals with safe and active effects on synaptic plasticity may be a strategy for preventing neuronal damage and alleviating depression in a stressful life.

Role of neurotrophic and growth factors in the rapid and sustained antidepressant actions of ketamine

The neurotrophic hypothesis of depression proposes that reduced levels of brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGF) contribute to neuronal atrophy or loss in the prefrontal cortex (PFC) and hippocampus and impaired hippocampal adult neurogenesis, which are associated with depressive symptoms. Chronic, but acute, treatment with typical monoaminergic antidepressants can at least partially reverse these deficits, in part via induction of BDNF and/or VEGF expression, consistent with their delayed onset of action. Ketamine, an N-methyl-d-aspartate receptor antagonist, exerts rapid and sustained antidepressant effects. Rodent studies have revealed that ketamine rapidly increases BDNF and VEGF release and/or expression in the PFC and hippocampus, which in turn increases the number and function of spine synapses in the PFC and hippocampal neurogenesis. Ketamine also induces the persistent release of insulin-like growth factor 1 (IGF-1) in the PFC of male mice. These neurotrophic effects of ketamine are associated with its rapid and sustained antidepressant effects. In this review, we first provide an overview of the neurotrophic hypothesis of depression and then discuss the role of BDNF, VEGF, IGF-1, and other growth factors (IGF-2 and transforming growth factor-β1) in the antidepressant effects of ketamine and its enantiomers. This article is part of the Special Issue on 'Ketamine and its Metabolites'.

Yomogin, Isolated from Artemisia iwayomogi, Inhibits Neuroinflammation Stimulated by Lipopolysaccharide via Regulating MAPK Pathway

Neuroinflammation causes various neurological disorders, including depression and neurodegenerative diseases. Therefore, regulation of neuroinflammation is a promising therapeutic strategy for inflammation-related neurological disorders. This study aimed to investigate whether yomogin, isolated from Artemisia iwayomogi, has anti-neuroinflammatory effects. First, we evaluated the effects of yomogin by assessing pro-inflammatory mediators and cytokines in lipopolysaccharide (LPS)-stimulated BV2 microglial cells. The results showed that yomogin inhibited the increase in neuroinflammatory factors, including nitric oxide, inducible nitric oxide synthase, cyclooxygenase-2, interleukin-6, and tumor necrosis factor-α, and suppressed phosphorylation of c-Jun N-terminal kinase, extracellular signal-regulated kinase and p38, which participate in the mitogen-activated protein kinase (MAPK) pathway. To confirm these effects in vivo, we measured the activation of astrocyte and microglia in LPS-injected mouse brains. Results showed that yomogin treatment decreased astrocyte and microglia activations. Collectively, these results suggest that yomogin suppresses neuroinflammation by regulating the MAPK pathway and it could be a potential candidate for inflammation-mediated neurological diseases.

Therapeutic Implications of microRNAs in Depressive Disorders: A Review

MicroRNAs are hidden players in complex psychophysical phenomena such as depression and anxiety related disorders though the activation and deactivation of multiple proteins in signaling cascades. Depression is classified as a mood disorder and described as feelings of sadness, loss, or anger that interfere with a person’s everyday activities. In this review, we have focused on exploration of the significant role of miRNAs in depression by affecting associated target proteins (cellular and synaptic) and their signaling pathways which can be controlled by the attachment of miRNAs at transcriptional and translational levels. Moreover, miRNAs have potential role as biomarkers and may help to cure depression through involvement and interactions with multiple pharmacological and physiological therapies. Taken together, miRNAs might be considered as promising novel therapy targets themselves and may interfere with currently available antidepressant treatments.

BDNF receptor TrkB as the mediator of the antidepressant drug action

Brain-derived neurotrophic factor (BDNF) signaling through its receptor TrkB has for a long time been recognized as a critical mediator of the antidepressant drug action, but BDNF signaling has been considered to be activated indirectly through the action of typical and rapid-acting antidepressants through monoamine transporters and glutamate NMDA receptors, respectively. However, recent findings demonstrate that both typical and the fast-acting antidepressants directly bind to TrkB and thereby allosterically potentiate BDNF signaling, suggesting that TrkB is the direct target for antidepressant drugs. Increased TrkB signaling particularly in the parvalbumin-expressing interneurons orchestrates iPlasticity, a state of juvenile-like enhanced plasticity in the adult brain. iPlasticity sensitizes neuronal networks to environmental influences, enabling rewiring of networks miswired by adverse experiences. These findings have dramatically changed the position of TrkB in the antidepressant effects and they propose a new end-to-end model of the antidepressant drug action. This model emphasizes the enabling role of antidepressant treatment and the active participation of the patient in the process of recovery from mood disorders.

Chaigui granule exerts anti-depressant effects by regulating the synthesis of Estradiol and the downstream of CYP19A1-E2-ERKs signaling pathway in CUMS-induced depressed rats

Background: There is a significant gender difference in the prevalence of depression. Recent studies have shown that estrogen plays a crucial role in depression. Therefore, studying the specific mechanism of estrogen's role in depression can provide new ideas to address the treatment of depression. Chaigui granule has been shown to have exact antidepressant efficacy, and the contents of saikosaponin (a, b1, b2, d) and paeoniflorin in Chaigui granule are about 0.737% and 0.641%, respectively. Some studies have found that they can improve depression-induced decrease in testosterone (T) levels (∼36.99% decrease compared to control). However, whether Chaigui granule can exert antidepressant efficacy by regulating estrogen is still unclear. This study aimed to elucidate the regulation of estrogen levels by Chaigui granule and the underlying mechanism of its anti-depressant effect. Methods: Eighty-four male Sprague-Dawley (SD) rats were modeled using a chronic unpredictable mild stress (CUMS) procedure. The administration method was traditional oral gavage administration, and behavioral indicators were used to evaluate the anti-depressant effect of Chaigui granule. Enzyme-linked immunosorbent assay (ELISA) was adopted to assess the modulating impact of Chaigui granule on sex hormones. Then, reverse transcription-quantitative PCR (RT-qPCR), and Western blot (WB) techniques were employed to detect extracellular regulated protein kinases (ERK) signaling-related molecules downstream of estradiol in the hippocampus tissue. Results: The administration of Chaigui granule significantly alleviated the desperate behavior of CUMS-induced depressed rats. According to the results, we found that Chaigui granule could upregulate the level of estradiol (E2) in the serum (∼46.56% increase compared to model) and hippocampus (∼26.03% increase compared to model) of CUMS rats and increase the levels of CYP19A1 gene and protein, which was the key enzyme regulating the synthesis of T into E2 in the hippocampus. Chaigui granule was also found to have a significant back-regulatory effect on the gene and protein levels of ERβ, ERK1, and ERK2. Conclusion: Chaigui granule can increase the synthesis of E2 in the hippocampus of CUMS-induced depressed rats and further exert antidepressant effects by activating the CYP19A1-E2-ERKs signaling pathway.

Janus-Faced Fluorescence Imaging Agent for Malondialdehyde and Formaldehyde in Brains

Carbonyl stress caused by reactive carbonyl species (RCS) is closely related to various brain diseases. As the highly reactive, highly toxic, and lipophilic RCS, malondialdehyde (MDA) and formaldehyde (FA) could easily cross the blood-brain barrier (BBB) and induce protein dysfunction or cross-linking in the brain. Do MDA and FA coordinately regulate the physio-pathological processes of the brain? To answer the question, first of all, powerful identification and sensing tools are needed. However, competent probes for simultaneously analyzing MDA and FA in living brains are lacking, which originates from the following three challenges: (1) MDA and FA are difficult to distinguish due to their great similarity in structure and reactivity; (2) to achieve simultaneous and discriminable imaging, same excitation and different emissions are preferable; and (3) the detection of MDA and FA in living brains require the materials to pass through the BBB. Thus, we created a two-photon fluorescent agent, TFCH, for MDA/FA. The hydrazine group in TFCH could successfully differentiate MDA/FA at 440/510 nm under same excitation. Moreover, the lipophilic trifluoromethyl group (-CF₃) in TFCH prompts it to traverse the BBB, thereby realizing the coinstantaneous visualization of MDA and FA in the living brain. Using TFCH, we observed the excessive production of MDA and FA in living PC12 cells under carbonyl stress and oxidative stress. Notably, for the first time, two-photon fluorescence imaging indicated the synchronous increase of MDA and FA in living brains of mice with depression. Altogether, this work provides a promising tool for revealing the carbonyl stress-related molecular mechanism involved in brain diseases.

Mangiferin Alleviates Postpartum Depression-Like Behaviors by Inhibiting MAPK Signaling in Microglia

Postpartum depression (PPD), a severe mental health disorder, is closely associated with decreased gonadal hormone levels during the postpartum period. Mangiferin (MGF) possesses a wide range of pharmacological activities, including anti-inflammation. Growing evidence has suggested that neuroinflammation is involved in the development of depression. However, the role of MGF in the development of PPD is largely unknown. In the present study, by establishing a hormone-simulated pregnancy PPD mouse model, we found that the administration of MGF significantly alleviated PPD-like behaviors. Mechanistically, MGF treatment inhibited microglial activation and neuroinflammation. Moreover, we found that MGF treatment inhibited mitogen-activated protein kinase (MAPK) signaling in vivo and in vitro. Together, these results highlight an important role of MGF in microglial activation and thus give insights into the potential therapeutic strategy for PPD treatment.

An integrative approach to predict severity in nonketotic hyperglycinemia

OBJECTIVE

Glycine encephalopathy, also known as nonketotic hyperglycinemia (NKH), is an inherited neurometabolic disorder with variable clinical course and severity, ranging from infantile epileptic encephalopathy to psychiatric disorders. A precise phenotypic characterization and an evaluation of predictive approaches are needed.

METHODS

Longitudinal clinical and biochemical data of 25 individuals with NKH from the patient registry of International Working Group on Neurotransmitter related Disorders were studied with in silico analyses, pathogenicity scores and molecular modeling of GLDC and AMT variants.

RESULTS

Symptom onset (p<0_· 01) and diagnosis occur earlier in life in severe NKH (p<0_· 01). Presenting symptoms affect the age at diagnosis. Psychiatric problems occur predominantly in attenuated NKH. Onset-age ≥3 months (66% specificity, 100% sensitivity, AUC = 0·87) and cerebrospinal fluid (CSF)/plasma glycine ratio ≤0_· 09 (57% specificity, 100% sensitivity, AUC = 0·88) are sensitive indicators for attenuated NKH while CSF glycine concentration ≥116_· 5 μmol/L (100% specificity, 93% sensitivity, AUC = 0·97) and CSF/plasma glycine ratio ≥0_· 15 (100% specificity, 64% sensitivity, AUC = 0·88) are specific for severe forms. A ratio threshold of 0_· 128 discriminates the overlapping range. We present ten new GLDC variants. Two mild variants resulted in attenuated, while two severe variants or one mild and one severe variant lead to severe phenotype. Based on clinical, biochemical and genetic parameter we propose a severity prediction model.

INTERPRETATION

This study widens the phenotypic spectrum of attenuated NKH and expands the number of pathogenic variants. The multiparametric approach provides a promising tool to predict disease severity, helping to improve clinical management strategies. This article is protected by copyright. All rights reserved.

Bupleurum chinense DC improves CUMS-induced depressive symptoms in rats through upregulation of the cAMP/PKA/CREB signalling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Bupleurum chinense DC. (B. chinense) is the dried root of B. chinense, belonging to the Umbelliferae family. B. chinense has been reported since ancient times for its effect of soothing the liver and relieving depression. Additionally, its important role in treating depression, depressed mood disorders and anti-inflammation has been proven in previous studies. However, its specific mechanism of action remains unknown.

AIM OF THE STUDY

The key targets and metabolites of the antidepressant effect of B. chinense were investigated based on the cAMP signalling pathway. The study examined the mechanism for the antidepressant effect of B. chinense by target prediction, analysis of related metabolites and potential metabolic pathways.

MATERIALS AND METHODS

A network pharmacology approach was used to predict the antidepressant targets and pathways of B. chinense. A depression rat model was established through the CUMS (chronic unpredictable mild stress) procedure. The depression model was assessed by body weight, sugar-water preference, water maze and enzyme-linked immunosorbent assay (ELISA) indicators (5hydroxytryptamine, etc.). The key metabolic pathways were screened by correlations between metabolites and key targets. Finally, a quantitative analysis of key targets and metabolites was experimentally validated.

RESULTS

B. chinense significantly ameliorated the reduction in body weight, sugar-water preference rate and cognitive performance in the water maze experiment in rats with depression induced by CUMS. ELISA, Western blotting (WB) and reverse transcription-polymerase chain reaction (RT-PCR) assays showed that B. chinense significantly improves the expression of protein kinase cyclic adenylic acid (cAMP)-activated catalytic subunit alpha (PRKACA), cAMP-response element-binding protein (CREB) and cAMP activation in the rat brain induced by CUMS. According to metabolic pathway analysis, B. chinense shows an antidepressant effect primarily by regulating the cAMP metabolic pathway.

CONCLUSION

B. chinense upregulated PRKACA and CREB expression and the level of the key metabolite cAMP in the cAMP/PKA/CREB pathway while reducing the inflammatory response to depression treatment. These new findings support future research on the antidepressant effects of B. chinense.

Impact of 5-HT7 receptor inverse agonism of lurasidone on monoaminergic tripartite synaptic transmission and pathophysiology of lower risk of weight gain

A part of atypical antipsychotics exert mood-stabilising effects via modulation of various monoamine receptors and intracellular signalling. Recent pharmacodynamic studies suggested that tripartite-synaptic transmission can be involved in pathophysiology of mood-disorders, schizophrenia, their associated cognitive impairments, and several adverse-reactions to atypical antipsychotics. Therefore, to explore mechanisms underlying antidepressive mood-stabilising and antipsychotic effects of lurasidone, we determined concentration-dependent effects of acute and subchronic lurasidone administrations on astroglial L-glutamate release, and expression of connexin43, ERK, AKT, adenosine monophosphate activated protein kinase (AMPK), 5-HT1A (5-HT1AR) and 5-HT7 (5-HT7R) receptors in cultured astrocytes using ultra-high-pressure liquid-chromatography with mass-spectrometry and capillary-immunoblotting systems. Therapeutically-relevant lurasidone concentration suppressed astroglial L-glutamate release through activated connexin43-containing hemichannel by decreasing connexin43 expression in plasma-membrane. Subchronic lurasidone administration downregulated 5-HT1AR and 5-HT7R in astroglial plasma-membrane concentration-dependently. Subchronic lurasidone administration attenuated ERK and AMPK signallings concentration-dependently without affecting AKT signalling. These results suggest that effects of subchronic lurasidone administration on astroglial L-glutamate release, 5-HT receptor, and intracellular signalling are similar to vortioxetine and different from mood-stabilising atypical antipsychotics, clozapine. Therefore, inhibitory effects of subchronic lurasidone administration on astroglial L-glutamate release through activated connexin43-containing hemichannel probably contribute to pathophysiology of antidepressive mood-stabilising effects of lurasidone. Furthermore, inhibitory effects of subchronic lurasidone administration on ERK and AMPK activities (without affecting AKT activity) induced by downregulation of 5-HT7R could result in clinical advantages of lurasidone, lower risk of weight gain.

Brain-derived neurotrophic factor and inflammation in depression: Pathogenic partners in crime?

Major depressive disorder is a debilitating disorder affecting millions of people each year. Brain-derived neurotrophic factor (BDNF) and inflammation are two prominent biologic risk factors in the pathogenesis of depression that have received considerable attention. Many clinical and animal studies have highlighted associations between low levels of BDNF or high levels of inflammatory markers and the development of behavioral symptoms of depression. However, less is known about potential interaction between BDNF and inflammation, particularly within the central nervous system. Emerging evidence suggests that there is bidirectional regulation between these factors with important implications for the development of depressive symptoms and anti-depressant response. Elevated levels of inflammatory mediators have been shown to reduce expression of BDNF, and BDNF may play an important negative regulatory role on inflammation within the brain. Understanding this interaction more fully within the context of neuropsychiatric disease is important for both developing a fuller understanding of biological pathogenesis of depression and for identifying novel therapeutic opportunities. Here we review these two prominent risk factors for depression with a particular focus on pathogenic implications of their interaction.

Evaluation of animal model congruence to human depression based on large-scale gene expression patterns of the CNS

Depression is a complex mental health disorder that is difficult to study. A wide range of animal models exist and for many of these data on large-scale gene expression patterns in the CNS are available. The goal of this study was to evaluate how well animal models match human depression by evaluating congruence and discordance of large-scale gene expression patterns in the CNS between almost 300 animal models and a portrait of human depression created from male and female datasets. Multiple approaches were used, including a hypergeometric based scoring system that rewards common gene expression patterns (e.g., up-up or down-down in both model and human depression), but penalizes opposing gene expression patterns. RRHO heat maps, Uniform Manifold Approximation Plot (UMAP), and machine learning were used to evaluate matching of models to depression. The top ranked model was a histone deacetylase (HDAC2) conditional knockout in forebrain neurons. Also highly ranked were various models for Alzheimer’s, including APPsa knock-in (2nd overall), APP knockout, and an APP/PS1 humanized double mutant. Other top models were the mitochondrial gene HTRA2 knockout (that is lethal in adulthood), a modified acetylcholinesterase, a Huntington’s disease model, and the CRTC1 knockout. Over 30 stress related models were evaluated and while some matched highly with depression, others did not. In most of the top models, a consistent dysregulation of MAP kinase pathway was identified and the genes NR4A1, BDNF, ARC, EGR2, and PDE7B were consistently downregulated as in humans with depression. Separate male and female portraits of depression were also evaluated to identify potential sex specific depression matches with models. Individual human depression datasets were also evaluated to allow for comparisons across the same brain regions. Heatmap, UMAP, and machine learning results supported the hypergeometric ranking findings. Together, this study provides new insights into how large-scale gene expression patterns may be similarly dysregulated in some animals models and humans with depression that may provide new avenues for understanding and treating depression.

Prophylactic treatment of curcumin in a rat model of depression by attenuating hippocampal synaptic loss

Curcumin is a polyphenol substance considered to be effective in the treatment of a number of neurodegenerative diseases. However, details regarding the exact mechanisms for the protective effects of curcumin in neuropsychiatric disorders, like depression, remain unknown. In the pathogenesis of major depressive disorder (MDD) it appears that dysregulation of oxidative stress and immune systems, particularly within the hippocampal region, may play a critical role. Here, we show that pre-treatment with curcumin (40 mg kg^-1) alleviates depression-like behaviors in a LPS-induced rat model of depression, effects which were accompanied with suppression of oxidative stress and inflammation and an inhibition of neuronal apoptosis in the hippocampal CA1 region, and results from ultramicrostructure electrophysiological experiments revealed that the curcumin pre-treatment significantly prevented excessive synaptic loss and enhanced synaptic functioning in this LPS-induced rat model. In addition, curcumin attenuated the increases in levels of miR-146a-5p and decreases in the expression of p-ERK signaling that would normally occur within CA1 regions of these depressed rats. Taken together, these results demonstrated that curcumin exerts neuroprotective and antidepressant activities by suppressing oxidative stress, neural inflammation and their related effects upon synaptic dysregulation. One of the mechanisms for these beneficial effects of curcumin appears to involve the miR-146a-5p/ERK signaling pathway within the hippocampal CA1 region. These findings not only elucidated some of the mechanisms underlying the neuroprotective/antidepressant effects of curcumin, but also suggested a role of curcumin as a potential therapeutic strategy for depression.

ERK/MAPK signalling in the developing brain: Perturbations and consequences

The extracellular regulated kinase/microtubule-associated protein kinase (ERK/MAPK) signalling pathway transduces signals that cause an alteration in the ongoing metabolic pathways and modifies gene expression patterns; thus, influencing cellular behaviour. ERK/MAPK signalling is essential for the proper development of the nervous system from neural progenitor cells derived from the embryonic mesoderm. Several signalling molecules that regulate the well-coordinated process of neurodevelopment transduce developmental information through the ERK/MAPK signalling pathway. The ERK/MAPK is a potential novel therapeutic target in several neurodevelopmental disorders, however, despite years of study, there is still significant uncertainty about the exact mechanism by which the ERK/MAPK signalling pathway elicits specific responses in neurodevelopment. Here, we will review the evidence highlighting the role of ERK/MAPK signalling in neurodevelopment. We will also discuss the structural implication and behavioural deficits associated with perturbed ERK/MAPK signalling pathway in cortical development, whilst examining its contribution to the neuropathology of several neurodevelopmental disorders, such as Autism Spectrum Disorder, Schizophrenia, Fragile X, and Attention Deficit Hyperactive Disorder.

Polymorphic variants in genes related to stress coping are associated with the awake bruxism

BACKGROUND

Chronic stress is one of the leading predisposing factors in bruxism aetiology, but the influence of genetic factors is also suggested. We aimed to study whether sequence variants in genes involved in stress regulation pathways: NTRK2 and BDNF, may be associated with awake bruxism susceptibility, clinical presentation, and patients' perceived stress level.

METHODS

The study group included 104 patients with probable awake bruxism and 191 population controls. Patients underwent dental examination concerning the symptoms of bruxism and psychological testing. Genotyping was performed using HRMA and sequencing. Statistical analyses were conducted, and P values below 0.05 were considered statistically significant.

RESULTS

We observed a positive correlation of measured stress level and pathological teeth attrition in the anterior segment (r = 0.45, P < 0.001), enamel attritions (r = 0.44, P < 0.001), tongue impressions (r = 0.50, P < 0.001) and posterior teeth attrition (r = 0.27, P = 0.005). Moreover, the c.196A variant (p.66Met) of the BDNF gene and c.1397-31392G allele of the NTRK2 gene were present with elevated frequency, comparing to controls.

CONCLUSIONS

This study hence the thesis that perceived stress level is a substantial contributing factor to awake bruxism occurrence and its clinical manifestations. Moreover, sequence variants in genes related to stress coping may be correlated with awake bruxism's susceptibility via elevated perceived stress level.

LGI1 governs neuritin-mediated resilience to chronic stress

Depression is accompanied by neuronal atrophy and decreased neuroplasticity. Leucine-rich glioma-inactivated protein 1 (LGI1), a metastasis suppressor, plays an important role in the development of CNS synapses. We found that LGI1 expression was reduced in the hippocampi of mice that underwent chronic unpredictable stress (CUS), and could be rescued by the antidepressant, fluoxetine. Recombinant soluble neuritin, an endogenous protein previously implicated in antidepressant-like behaviors, elevated hippocampal LGI1 expression in a manner dependent on histone deacetylase 5 (HDAC5) phosphorylation. Accordingly, Nrn1 ^flox/flox ;Pomc-cre (Nrn1 cOE) mice, which conditionally overexpress neuritin, displayed increases in hippocampal LGI1 level under CUS and exhibited resilience to CUS that were blocked by hippocampal depletion of LGI1. Interestingly, neuritin-mediated LGI1 expression was inhibited by HNMPA-(AM)₃, an insulin receptor inhibitor, as was neuritin-mediated HDAC5 phosphorylation. We thus establish hippocampal LGI1 as an effector of neurite outgrowth and stress resilience, and suggest that HDAC5-LGI1 plays a critical role in ameliorating pathological depression.

MicroRNA-26a-3p rescues depression-like behaviors in male rats via preventing hippocampal neuronal anomalies

Depression is a neuropsychiatric disease associated with neuronal anomalies within specific brain regions. In the present study, we screened microRNA (miRNA) expression profiles in the dentate gyrus (DG) of the hippocampus and found that miR-26a-3p was markedly downregulated in a rat model of depression, whereas upregulation of miR-26a-3p within DG regions rescued the neuronal deterioration and depression-like phenotypes resulting from stress exposure, effects that appear to be mediated by the PTEN pathway. The knockdown of miR-26a-3p in DG regions of normal control rats induced depression-like behaviors, effects that were accompanied by activation of the PTEN/PI3K/Akt signaling pathway and neuronal deterioration via suppression of autophagy, impairments in synaptic plasticity, and promotion of neuronal apoptosis. In conclusion, these results suggest that miR-26a-3p deficits within the hippocampal DG mediated the neuronal anomalies contributing to the display of depression-like behaviors. This miRNA may serve as a potential therapeutic target for the treatment of depression.

TGF-β/Smad Signalling in Neurogenesis: Implications for Neuropsychiatric Diseases

TGF-β/Smad signalling has been the subject of extensive research due to its role in the cell cycle and carcinogenesis. Modifications to the TGF-β/Smad signalling pathway have been found to produce disparate effects on neurogenesis. We review the current research on canonical and non-canonical TGF-β/Smad signalling pathways and their functions in neurogenesis. We also examine the observed role of neurogenesis in neuropsychiatric disorders and the relationship between TGF-β/Smad signalling and neurogenesis in response to stressors. Overlapping mechanisms of cell proliferation, neurogenesis, and the development of mood disorders in response to stressors suggest that TGF-β/Smad signalling is an important regulator of stress response and is implicated in the behavioural outcomes of mood disorders.

Hippocampal miR-211-5p regulates neurogenesis and depression-like behaviors in the rat

Emerging evidence has shown that microRNAs (miRNAs) contribute to the pathogenesis of depression, a potentially life-threatening and disabling mental disorder caused by the interaction of genetic and environmental factors. However, the specific miRNAs and their underlying molecular mechanisms as involved in the pathogenesis and development of depression remain largely unknown. In the present study, we screened miRNA expression profiles and found that miR-211-5p was significantly down-regulated within the dentate gyrus (DG) hippocampus in the chronic unpredictable mild stress (CUMS) induced rat model of depression. Deficits in miR-211-5p were accompanied with reductions in neurogenesis and increased apoptosis in these CUMS rats. In contrast, an up-regulation of miR-211-5p within the DG area in CUMS rats promoted neuronal neurogenesis, reduced neuronal apoptosis via suppression of the Dyrk1A/STAT3 signaling pathway and relieved depression-like behaviors in these CUMS rats. In rats subjected to a knock-down of miR-211-5p in the DG there was an increase in neuronal apoptosis and a decrease in neuronal regeneration, effects which were accompanied with an induction of depression-like behaviors. Taken together, the results of our study reveal that altered levels of miR-211-5p in the hippocampal DG area exert a significant impact on neurogenesis, apoptosis and thus depression-like behaviors in rats. These findings suggest that the miR-211-5p/Dyrk1A pathway plays an important role in the pathogenesis of depression and may serve as a potential therapeutic target for the treatment of depression.

Bioinformatics analysis of a TF-miRNA-lncRNA regulatory network in major depressive disorder

Major depressive disorder (MDD) is a highly prevalent disease and one of the main causes of disability worldwide. Although many studies have partially revealed the occurrence and development process of MDD, the pathogeny and molecular mechanisms are not fully understood. Weighted gene coexpression network analysis (WGCNA) was used to explore the co-expression modules and hub genes in MDD. A protein-protein interaction (PPI) network of the most significant module and a TF-miRNA-lncRNA regulatory network of MDD were constructed using bioinformatics analysis tools. A KEGG pathway and gene ontology (GO) functional enrichment analysis of the genes in the significant module was performed using DAVID. Five hub genes in the PPI network and 10 genes in the TF-miRNA-lncRNA regulatory network with high degree values were identified, which may provide new insights for the investigation of key pathways, diagnostic bio-markers, and therapeutic targets of MDD. This study brings a novel perspective and provides valuable information to explore the molecular mechanism of MDD.

Rapamycin attenuates depression and anxiety-like behaviors through modulation of the NLRP3 pathway in pentylenetetrazole-kindled male Wistar rats

BACKGROUND

There is cumulative evidence that shows the effect of epilepsy on behavioral conditions like anxiety and depression.

OBJECTIVES

The effects of rapamycin on anxiety and depression caused by pentylenetetrazole (PTZ) in the rat and possible underlying mechanisms were evaluated.

METHODS

Male Wistar rats were divided into experimental and control groups. The experimental groups were treated with intraperitoneal (i.p.) injection of 0.5, 1, and 2 mg/kg of rapamycin, while the control group received normal saline only. Kindling was induced by sub-threshold dose (35 mg/kg, i.p.) of PTZ for one month. When the kindling procedure was done, the seizure behaviors and the behavioral function were evaluated. For anxiety parameters, the elevated plus maze (EPM) was used. The forced swim test was employed to assess the antidepressant potential. At the end of the experiment, rats were euthanized and the blood serum and brain samples were isolated for respective measurement of oxidative stress and gene expression parameters.

RESULTS

Rapamycin delayed the development of kindling and the onset time of seizures. Rapamycin administration reduced immobility time in the FST, exerting antidepressant-like activity. In the EPM test, rapamycin produced an anxiolytic-like effect. In addition, rapamycin increased the catalase and superoxide dismutase levels in the serum and significantly decreased the gene expression of I11b and Nlrp3 compared to the PTZ group.

CONCLUSION

Our results showed that the inhibitory effect of mTOR inhibitor (rapamycin) on reactive oxygen species production during NLRP3 inflammasome activation could bring about behavioral alterations in anxiety and depression.

Neuronal activity regulated pentraxin (narp) and GluA4 subunit of AMPA receptor may be targets for fluoxetine modulation

Fluoxetine is the foremost prescribed antidepressant. Drugs acting on monoaminergic system may also regulate glutamatergic system. Indeed, the investigation of proteins associated with this system, such as Narp (neuronal activity-dependent pentraxin) and GluA4 subunit of AMPA receptor may reveal poorly explored modulations triggered by conventional antidepressants. This study aimed to uncover neurochemical mechanisms underlying the chronic fluoxetine treatment, mainly by evaluating these protein targets in the prefrontal cortex and in the hippocampus. Mice received a daily administration of fluoxetine (0.1, 1 or 10 mg/kg, p.o.) or potable water (vehicle group) for 21 days. These animals were submitted to the forced swim test (FST) to verify antidepressant-like responses and the open-field test (OFT) to assess locomotor activity. Modulation of signaling proteins was analyzed by western blot. Chronic treatment with fluoxetine (1 and 10 mg/kg) was effective, since it reduced the immobility time in the FST, without altering locomotor activity. Fluoxetine 10 mg/kg increased CREB phosphorylation and BDNF expression in the prefrontal cortex and hippocampus. Noteworthy, in the hippocampus fluoxetine also promoted Akt activation and augmented Narp expression. In the prefrontal cortex, a significant decrease in the expression of the GluA4 subunit and Narp were observed following fluoxetine administration (10 mg/kg). The results provide evidence of novel molecular targets potentially involved in the antidepressant effects of fluoxetine, since in mature rodents Narp and GluA4 are mainly expressed in the GABAergic parvalbumin-positive (PV+) interneurons. This may bring new insights into the molecular elements involved in the mechanisms underlying the antidepressant effects of fluoxetine.

Ketamine-50 years in use: from anesthesia to rapid antidepressant effects and neurobiological mechanisms

Over the past 50 years, ketamine has solidified its position in both human and veterinary medicine as an important anesthetic with many uses. More recently, ketamine has been studied and used for several new indications, ranging from chronic pain to drug addiction and post-traumatic stress disorder. The discovery of the rapid-acting antidepressant effects of ketamine has resulted in a surge of interest towards understanding the precise mechanisms driving its effects. Indeed, ketamine may have had the largest impact for advancements in the research and treatment of psychiatric disorders in the past few decades. While intense research efforts have been aimed towards uncovering the molecular targets underlying ketamine's effects in treating depression, the underlying neurobiological mechanisms remain elusive. These efforts are made more difficult by ketamine's complex dose-dependent effects on molecular mechanisms, multiple pharmacologically active metabolites, and a mechanism of action associated with the facilitation of synaptic plasticity. This review aims to provide a brief overview of the different uses of ketamine, with an emphasis on examining ketamine's rapid antidepressant effects spanning molecular, cellular, and network levels. Another focus of the review is to offer a perspective on studies related to the different doses of ketamine used in antidepressant research. Finally, the review discusses some of the latest hypotheses concerning ketamine's action.

Creation of a gene expression portrait of depression and its application for identifying potential treatments

Depression is a complex mental health disorder and the goal here was to identify a consistent underlying portrait of expression that ranks all genes from most to least dysregulated and indicates direction of change relative to controls. Using large-scale neural gene expression depression datasets, a combined portrait (for men and women) was created along with one for men and one for women only. The depressed brain was characterized by a "hypo" state, that included downregulation of activity-related genes, including EGR1, FOS, and ARC, and indications of a lower brain temperature and sleep-like state. MAP kinase and BDNF pathways were enriched with overlapping genes. Expression patterns suggested decreased signaling for GABA and for neuropeptides, CRH, SST, and CCK. GWAS depression genes were among depression portrait genes and common genes of interest included SPRY2 and PSEN2. The portraits were used with the drug repurposing approach of signature matching to identify treatments that could reverse depression gene expression patterns. Exercise was identified as the top treatment for depression for the combined and male portraits. Other non-traditional treatments that scored well were: curcumin, creatine, and albiflorin. Fluoxetine scored best among typical antidepressants. The creation of the portraits of depression provides new insights into the complex landscape of depression and a novel platform for evaluating and identifying potential new treatments.

Hippocampal D1-but not D2-like dopamine receptors modulate the phosphorylation of ERK in food deprivation-induced reinstatement of morphine in extinguished rats

Reinstatement to drug abuse is the most challenging issue in the treatment of addiction. Thus, knowledge of the involved neurobiological mechanisms of reinstatement is a fundamental necessity. There is substantial and crucial evidence that dopamine is implicated in motivational processes such as relapse. Our behavioral results reported that the administration of dopamine receptor antagonists inhibited reinstatement of morphine in food-deprived rats. Previous studies have indicated that the ERK pathway plays a critical role in the cellular responses to stress and reward. Therefore, the purpose of the current study was to evaluate the effect of intra-dentate gyrus administration of dopamine receptor antagonists on the phosphorylation of hippocampal ERK in the reinstatement phase of morphine reward in food-deprived rats. All groups of animals passed conditioned place preference and were bilaterally given different doses of D1- or D2-like dopamine compounds (0.25, 1 and 4 μg/0.5 μl) into the dentate gyrus. Immediately after the reinstatement phase, each animal was euthanized, and the hippocampi were immediately dissected. Then, the p-ERK/ERK ratio was evaluated using Western blot analysis. The principal findings in this study demonstrated that intra-dentate gyrus administration of the highest dose of the D1-like receptor antagonist could enhance the hippocampal p-ERK/ERK ratio in food-deprived rats while the D2-Like receptor antagonist failed to change this ratio.

Effect of 5-HT6 Receptor Ligands Combined with Haloperidol or Risperidone on Antidepressant-/Anxiolytic-Like Behavior and BDNF Regulation in Hippocampus and Prefrontal Cortex of Rats

BACKGROUND

The presence of depressive and anxiety symptoms in patients with schizophrenia may have an important impact on treatment and compliance. Hence, interventions addressing such comorbidity in schizophrenia should be explored. One target may be a serotonergic 5-HT₆ receptor (5-HT₆R) since its ligands displayed antidepressant- and anxiolytic-like activities in preclinical experiments.

METHODS

Acute and chronic (21 days) administration of haloperidol or risperidone in combination with a selective 5-HT₆R agonist (WAY-181187) or antagonist (SB-742457) to rats was performed for detecting antidepressant- and anxiolytic-like behaviors. In addition, the level of brain-derived neurotrophic factor (BDNF) protein and its gene expression in hippocampus and prefrontal cortex were determined.

RESULTS

Both single and chronic administration of WAY-181187 with haloperidol produced antidepressant- and anxiolytic-like activities. SB-742457 did not provide full benefits in terms of improvement of haloperidol-induced adverse mood effects. However, the administration of SB-742457 with risperidone triggered its anxiolytic-like activity. Both 5-HT₆R ligands evoked no changes in haloperidol-induced effects on BDNF level. WAY-181187 induced repression of the BDNF gene while SB-742457 increased its expression in both structures. 5-HT₆R ligands, when combined with risperidone, did not change BDNF protein level and increased gene expression in the hippocampus, while they elevated BDNF level and potentiated gene expression in the prefrontal cortex.

CONCLUSION

The combined administration of WAY-181187 and haloperidol provided the greatest benefits, which were manifested by antidepressant-like effects and suppression of the anxiogenic-like properties. The combined administration of risperidone with both agonist and antagonist resulted only in an anxiolytic-like effect. It seems that the anxiolytic-like effects induced by haloperidol or risperidone with the addition of 5-HT₆R ligands are task-specific. The data on BDNF protein and gene expression did not fully correspond with the behavioral outcomes, and thus it appears that other factors/mechanisms are involved in the observed antidepressant- and/or anxiolytic-like effects.

Molecular and neuronal mechanisms underlying the effects of adolescent nicotine exposure on anxiety and mood disorders

Tobacco addiction is highly co-morbid with a variety of mental health conditions, including schizophrenia, mood and anxiety disorders. Nicotine, the primary psychoactive compound in tobacco-related products is known to functionally modulate brain circuits that are disturbed in these disorders. Nicotine can potently regulate the transmission of various neurochemicals, including dopamine (DA), γ-amino-butyric acid (GABA) and glutamate, within various mesocorticolimbic structures, such as the ventral tegmental area (VTA), nucleus accumbens (NAc) and prefrontal cortex (PFC), all of which show pathologies in these disorders. Many neuropsychiatric diseases have etiological origins during neurodevelopment, typically occurring during vulnerable periods of adolescent or pre-natal brain development. During these neurodevelopmental periods, exposure to extrinsic drug insults can induce enduring and long-term pathophysiological sequelae that ultimately increase the risk of developing chronic mental health disorders in later life. These vulnerability factors are of growing concern given rising rates of adolescent nicotine exposure via traditional tobacco use and the increasing use of alternative nicotine delivery formats such as vaping and e-cigarettes. A large body of clinical and pre-clinical evidence points to an important role for adolescent exposure to nicotine and increased vulnerability to developing mood and anxiety disorders in later life. This review will examine current clinical and pre-clinical evidence that pinpoints specific mechanisms within the mesocorticolimbic circuitry and molecular biomarkers linked to the association between adolescent nicotine exposure and increased risk of developing mood and anxiety-related disorders. This article is part of the special issue on 'Vulnerabilities to Substance Abuse'.

N-Acetylcysteine Rescues Hippocampal Oxidative Stress-Induced Neuronal Injury via Suppression of p38/JNK Signaling in Depressed Rats

Progression of neuronal deterioration within specific brain regions is considered as one of the principal bases for the development of major depressive disorders. Therefore, protects and promotes the maintaining of normal structure and function of neurons might be a potential therapeutic strategy in the treatment of depression. Here, we report that the antioxidant, N-acetylcysteine (NAC), inhibited neuronal injury through its capacity to reduce oxidative stress and exerted antidepressant effects. Specifically, we show that antioxidant enzyme activity was significantly decreased in the hippocampal CA1 region of depressive rats, while treatment with NAC (300 mg/kg, i.p.) produced neuroprotective effects against mitochondrial oxidative stress injuries and oxidative DNA damage in CA1 neurons of these rats. Moreover, NAC treatment alleviated neuronal injury resulting from neuroinflammation and apoptosis in depressed rats, effects that were associated with reductions in dendritic spine atrophy, and synapse deficits. These effects appear to involve a down-regulation of p38 mitogen-activated protein kinase (MAPK)-JNK signaling along with an up-regulation of ERK signaling within the hippocampal CA1 region. Moreover, this NAC treatment significantly ameliorated depression-like behaviors as indicated by performance in the sucrose preference and forced swim tests (FST). Taken together, these results reveal the potential involvement of oxidative stress in the generation of depression. And, the antidepressant-like effects exerted by NAC may involve reductions in this oxidative stress that can result in neuronal deterioration. Such neuroprotective effects of NAC may indicate a potential therapeutic strategy for the treatment of stress-related depression.

Toll-like receptor 2 (TLR2)-deficiency impairs male mouse recovery from a depression-like state

Major depression is a prevalent, debilitating disease, yet therapeutic interventions for depression are frequently inadequate. Many clinical and pre-clinical studies have demonstrated that depression is associated with aberrant activation of the inflammatory system, raising the possibility that reducing inflammation may provide antidepressant effects. Using the learned helplessness mouse model, we tested if susceptibility or recovery were affected by deficiency in either of two receptors that initiate inflammatory signaling, Toll-like receptor-4 (TLR4) and TLR2, using knockout male mice. TLR4^-/- mice displayed a strong resistance to learned helplessness, confirming that blocking inflammatory signaling through TLR4 provides robust protection against this depression-like behavior. Surprisingly, TLR2^-/- mice displayed increased susceptibility to learned helplessness, indicating that TLR2-mediated signaling counteracts susceptibility. TLR2-mediated signaling also promotes recovery, as TLR2^-/- mice demonstrated a severe impairment in recovery from learned helplessness. That TLR2 actually protects from learned helplessness was further verified by the finding that administration of the TLR2 agonist Pam3CSK4 reduced susceptibility to learned helplessness. Treatment with Pam3CSK4 also reversed chronic restraint stress-induced impaired sociability and impaired learning in the novel object recognition paradigm, demonstrating that TLR2 stimulation can protect from multiple impairments caused by stress. In summary, these results demonstrate that TLR2-mediated signaling provides a counter-signal to oppose deleterious effects of stress that may be related to depression, and indicate that TLR2 and TLR4 act oppositely to balance mood-relevant responses to stress.

Childhood trauma, suicide risk and inflammatory phenotypes of depression: insights from monocyte gene expression

Circulating monocytes contribute to inflammatory processes. We here validate abnormal expression of inflammation-related genes in monocytes of a large and well-characterised group of MDD patients, and relate the outcomes to pertinent clinical characteristics. Thirty-two genes of a previously established inflammation-related gene signature were assessed in 197 patients with MDD, and 151 controls collected during the EU-MOODINFLAME project. Monocyte gene- expression data were related to age, sex, BMI, depression severity, childhood adversity (CA) and suicide risk (SR). Three distinct gene profiles were identified within the MDD group (downregulated, mixed upregulated and strongly upregulated genes). Patients in the merged upregulated groups had a significantly higher prevalence of CA and high SR. Using hierarchical clustering of the genes, we found a cluster of mainly cytokine (production)-related genes; patients with SR had a significantly higher expression of this cluster than patients without SR (particularly for IL-6, IL1A and IL1B). Such difference did not emerge for patients with and without CA. A downregulated gene profile was found for patients not exposed to CA and without SR (particularly for glucocorticoid-signalling genes NR3C1a and HSPA1/B). No inflammatory changes were observed for healthy controls exposed to CA. Our data show that inflammatory activation in MDD is not uniform, and that immunologically discernible phenotypes of depression can be linked to CA and high SR. The absence of monocyte inflammatory activation in healthy controls exposed to CA suggests an inflammatory involvement in MDD-prone individuals exposed to early stressors, but not healthy controls.

Antidepressant-like activity and safety profile evaluation of 1H-imidazo[2,1-f]purine-2,4(3H,8H)-dione derivatives as 5-HT1A receptor partial agonists

Current antidepressant therapy has several disadvantages related to the properties of antidepressants. Considering their unfavourable features, the process of searching for new antidepressant drugs with better safety and tolerability requires consistent efforts and many complementary studies. Serotonin 5-HT_1A receptor is considered as an interesting target of antidepressant therapy. In the present study, the intrinsic activity at different signaling pathways coupled to serotonin 5-HT_1A receptor, antidepressant-like and pharmacokinetic properties, and the safety profile of two novel imidazopurine-2,4-dione derivatives, namely compounds AZ-853 (8-(4-(4-(2-fluorophenyl)piperazin-1-yl)butyl)-1,3-dimethyl-1H- imidazo[2,1-f]purine-2,4(3H,8H)-dione) and AZ-861 (1,3-dimethyl-8-(4-(4-(3-(trifluoromethyl)phenyl)piperazin-1-yl)butyl)-1H-imidazo[2,1-f]purine-2,4(3H,8H)-dione), were studied in animal models through in vitro and in vivo experiments. We demonstrated that AZ-853 and AZ-861, which structurally differ by one substituent and its placement in the phenyl ring, showed varied functional, pharmacological, and pharmacokinetic properties as well as side effect profiles. AZ-861 exhibited stronger agonistic action in all functional assays. After acute and repeated administration in mice, both compounds showed antidepressant-like activity in the forced swim test, which was partially mediated by 5-HT_1A receptor activation. AZ-853 showed a more potent antidepressant-like effect, presumably due to its better penetration into brain structures. Both compounds did not show anticholinergic properties, but after repeated administration, they induced weak sedation and lipid metabolism disturbances without affecting serum glucose level. The stronger α₁-adrenolytic effect of AZ-853 is responsible for decreased systolic blood pressure, and in contrast to AZ-861, AZ-853 induced weight gain in mice. The interesting comparative pharmacological profiles of AZ-853 and AZ-861 encourage to conduct further experiments to fully understand their mechanisms and differences in action.

Inverse changes in telomere length between the blood and brain in depressive-like mice

BACKGROUND

Telomeres are nucleoprotein complexes located at the end of chromosomes. Previous studies have confirmed that telomere length is reduced in the peripheral blood of depression patients. However, studies regarding whether telomere length is altered in brain regions associated with depression are limited. It remains unclear whether the peripheral blood telomere length indicates telomere variation in the brain.

METHODS

Using quantitative PCR, we measured telomere length in five brain regions (prefrontal cortex, amygdala, nucleus accumbens, paraventricular nucleus, and hippocampus) from depressive-like mice and in peripheral blood from depressive-like mice and major depressive disorder (MDD) patients. We also examined the expression of telomerase- and alternative lengthening of telomere (ALT)-related genes in the prefrontal cortex and amygdala of depressive-like mice.

RESULTS

Telomeres were shortened in the peripheral blood of depressive-like mice and MDD patients, but were elongated in the prefrontal cortex and amygdala compared with healthy controls. We also observed that the expression of ALT-related genes increased in the prefrontal cortex and amygdala.

LIMITATIONS

The amount of human sample was limited. The mechanism of telomere lengthening in the brain of depressive-like mice was not well explained. Mice and humans have inherently different telomere and telomere maintenance systems.

CONCLUSION

These findings illustrate that the telomere length in the peripheral blood may not indicate the dynamics of telomere length in the brain. They offer a new perspective on variable telomere length in different brain regions affected in depression and provide a new basis for understanding the relationship between variable telomere length and MDD.

Brain-derived neurotrophic factor in 5-HT neurons regulates susceptibility to depression-related behaviors induced by subchronic unpredictable stress

Chronic stress is a major risk factor for the development of depression. Brain-derived neurotrophic factor (BDNF) plays an important role in neural functions and exhibits antidepressant effects. However, studies on depression-related behavioral response to BDNF have mainly focused on the limbic system, whereas other regions of the brain still require further exploration. Here, we report that exposure to chronic unpredictable stress (CUS) can induce depression-associated behaviors in mice. CUS could decrease total Bdnf mRNA and protein levels in the dorsal raphe nucleus (DRN), which correlated with depression-related behaviors. A corresponding reduction in exon-specific Bdnf mRNA was observed in the DRN of CUS mice. Bdnf was highly expressed in 5- Hydroxytryptamine (5-HT) neurons from the DRN. Selective deletion of Bdnf in 5-HT neurons alone could not induce anhedonia and behavioral despair in male or female mice, as indicated by the unchanged female urine sniffing time and preference for sucrose/saccharin. However, it could increase the latency to food in female mice, but not in male mice as shown by novelty-suppressed food test. Nevertheless, enhanced stress-induced susceptibility is observed in these male mice as suggested by the decrease in female urine sniffing time, and for female mice by the reduced sucrose preference and increased immobility in forced swim test. Furtherly, total Bdnf mRNA levels in DRN were correlated with depression-related behaviors of female, but not male 5-HT neurons specific Bdnf knockout mice. Our results indicate that BDNF might act on 5-HT neurons to regulate depression-related behaviors and stress vulnerability in a sex-dependent manner.