CREB, neurogenesis and depression

Molecular mechanisms of Schisandra chinensis in treating depression-neuropathic pain comorbidity by network pharmacology and molecular docking analysis

This study utilized network pharmacology and docking analyses to explore a groundbreaking therapeutic approach for managing the neuropathic pain and depressive disorder (NP/DD) comorbidity. Schisandra chinensis (SC), a common Chinese medicine, has demonstrated numerous beneficial effects in treating neuropsychological disorders. The main objective of this study was to identify potential bioactive components of SC and investigate their interactions with relevant target genes associated with NP/DD. To gain insights into the underlying molecular mechanisms, GO and KEGG analyses were conducted. Furthermore, molecular docking analysis was employed to validate the therapeutic relevance of SC's active ingredients. Seven bioactive components of SC, namely Longikaurin A, Deoxyharringtonine, Angeloylgomisin O, Schisandrin B, Gomisin A, Gomisin G, and Gomisin R, exhibited effectiveness in the treatment of NP/DD. From this list, the first five components were selected for further analysis. The analyses revealed a complex network of interactions between the targets of SC and NP/DD, providing valuable information about the molecular mechanisms involved in the treatment of NP/DD with SC. SC components demonstrated the ability to regulate pathways involving tumor necrosis factor (TNF), vascular endothelial growth factor (VEGF), and other growth hormones (GH). Overall, this study contributes to our understanding of the molecular mechanisms underlying the effects of SC in treating NP/DD. Further investigation is necessary to explore the therapeutic potential of SC as a viable strategy for NP/DD comorbidity. These findings lay a solid foundation for future research endeavors in this field, holding potential implications for the development of novel therapeutic interventions targeting NP/DD.

Indirect influence on the BDNF/TrkB receptor signaling pathway via GPCRs, an emerging strategy in the treatment of neurodegenerative disorders

Neuronal survival depends on neurotrophins and their receptors. There are two types of neurotrophin receptors: a nonenzymatic, trans-membrane protein of the tumor necrosis factor receptor (TNFR) family-p75 receptor and the tyrosine kinase receptors (TrkR) A, B, and C. Activation of the TrkBR by brain-derived neurotrophic factor (BDNF) or neurotrophin 4/5 (NT-4/5) promotes neuronal survival, differentiation, and synaptic function. It is shown that in the pathogenesis of several neurodegenerative conditions (Alzheimer's disease, Parkinson's disease, Huntington's disease) the BDNF/TrkBR signaling pathway is impaired. Since it is known that GPCRs and TrkR are regulating several cell functions by interacting with each other and generating a cross-communication in this review we have focused on the interaction between different GPCRs and their ligands on BDNF/TrkBR signaling pathway.

Transcriptomic analyses of rats exposed to chronic mild stress: Modulation by chronic treatment with the antipsychotic drug lurasidone

Exposure to stressful experiences accounts for almost half of the risk for mental disorders. Hence, stress-induced alterations represent a key target for pharmacological interventions aimed at restoring brain function in affected individuals. We have previously demonstrated that lurasidone, a multi-receptor antipsychotic drug approved for the treatment of schizophrenia and bipolar depression, can normalize the functional and molecular impairments induced by stress exposure, representing a valuable tool for the treatment of stress-induced mental illnesses. However, the mechanisms that may contribute to the therapeutic effects of lurasidone are still poorly understood. Here, we performed a transcriptomic analysis on the prefrontal cortex (PFC) of adult male rats exposed to the chronic mild stress (CMS) paradigm and we investigated the impact of chronic lurasidone treatment on such changes. We found that CMS exposure leads to an anhedonic phenotype associated with a down-regulation of different pathways associated to neuronal guidance and synaptic plasticity within the PFC. Interestingly, a significant part of these alterations (around 25%) were counteracted by lurasidone treatment. In summary, we provided new insights on the transcriptional changes relevant for the therapeutic intervention with lurasidone, which may ultimately promote resilience.

A study of roflumilast treatment on functional and structural changes in hippocampus in depressed Adult male Wistar rats

Depression is a common stress disability disorder that affects higher mental functions including emotion, cognition, and behavior. It may be mediated by inflammatory cytokines that interfere with neuroendocrine function, and synaptic plasticity. Therefore, reductions in inflammation might contribute to treatment response. The current study aims to evaluate the role of Protein Kinase (PKA)- cAMP response element-binding protein (CREB)- brain derived neurotropic factor (BDNF) signaling pathway in depression and the effects of roflumilast (PDE4 inhibitor) as potential antidepressant on the activity of the PKA-CREB-BDNF signaling pathway, histology, and pro-inflammatory cytokine production. Forty Adult male Wistar rats were divided into 4 groups: Control group, Positive Control group: similar to the controls but received Roflumilast (3 mg / kg / day) by oral gavage for the last 4 weeks of the experiment, Depressed group which were exposed to chronic stress for 6 weeks, and Roflumilast-treated group which were exposed to chronic stress for 6 weeks and treated by Roflumilast (3 mg / kg / day) by oral gavage for the last 4 weeks of the experiment. The depressed group showed significant increase in immobility time with significant decrease in swimming and struggling times, significant decrease in hippocampal PKA, CERB, BDNF, Dopamine, Cortisone, and Superoxide dismutase while hippocampal Phosphodiesterase-E4, Interleukin-6, and Malondialdhyde levels were significantly elevated. These findings were significantly reversed upon Roflumilast treatment. Therefore, it could be concluded that depression is a neurodegenerative inflammatory disease and oxidative stress plays a key role in depression. Roflumilast treatment attenuated the depression behavior in rats denoting its neuroprotective, and anti-inflammatory effects.

Niuhuang Qingxin Wan ameliorates depressive-like behaviors and improves hippocampal neurogenesis through modulating TrkB/ERK/CREB signaling pathway in chronic restraint stress or corticosterone challenge mice

Introduction: Chronic stress-associated hormonal imbalance impairs hippocampal neurogenesis, contributing to depressive and anxiety behaviors. Targeting neurogenesis is thus a promising antidepressant therapeutic strategy. Niuhuang Qingxin Wan (NHQXW) is an herbal formula for mental disorders in Traditional Chinese Medicine (TCM) practice, but its anti-depressant efficacies and mechanisms remain unverified. Methods: In the present study, we tested the hypothesis that NHQXW could ameliorate depressive-like behaviors and improve hippocampal neurogenesis by modulating the TrkB/ERK/CREB signaling pathway by utilizing two depression mouse models including a chronic restraint stress (CRS) mouse model and a chronic corticosterone (CORT) stress (CCS) induced mouse model. The depression-like mouse models were orally treated with NHQXW whereas fluoxetine was used as the positive control group. We evaluated the effects of NHQXW on depressive- and anxiety-like behaviors and determined the effects of NHQXW on inducing hippocampal neurogenesis. Results: NHQXW treatment significantly ameliorated depressive-like behaviors in those chronic stress mouse models. NHQXW significantly improved hippocampal neurogenesis in the CRS mice and CCS mice. The potential neurogenic mechanism of NHQXW was identified by regulating the expression levels of BDNF, TrkB, p-ERK (T202/T204), p-MEK1/2 (S217/221), and p-CREB (S133) in the hippocampus area of the CCS mice. NHQXW revealed its antidepressant and neurogenic effects that were similar to fluoxetine. Moreover, NHQXW treatment revealed long-term effects on preventing withdrawal-associated rebound symptoms in the CCS mice. Furthermore, in a bioactivity-guided quality control study, liquiritin was identified as one of the bioactive compounds of NHQXW with the bioactivities of neurogenesis-promoting effects. Discussion: Taken together, NHQXW could be a promising TCM formula to attenuate depressive- and anxiety-like behaviors against chronic stress and depression. The underlying anti-depressant mechanisms could be correlated with its neurogenic activities by stimulating the TrkB/ERK/CREB signaling pathway.

The Pleiotropic Face of CREB Family Transcription Factors

cAMP responsive element-binding protein (CREB) is one of the most intensively studied phosphorylation-dependent transcription factors that provide evolutionarily conserved mechanisms of differential gene expression in vertebrates and invertebrates. Many cellular protein kinases that function downstream of distinct cell surface receptors are responsible for the activation of CREB. Upon functional dimerization of the activated CREB to cis-acting cAMP responsive elements within the promoters of target genes, it facilitates signal-dependent gene expression. From the discovery of CREB, which is ubiquitously expressed, it has been proven to be involved in a variety of cellular processes that include cell proliferation, adaptation, survival, differentiation, and physiology, through the control of target gene expression. In this review, we highlight the essential roles of CREB proteins in the nervous system, the immune system, cancer development, hepatic physiology, and cardiovascular function and further discuss a wide range of CREB-associated diseases and molecular mechanisms underlying the pathogenesis of these diseases.

Maternal nicotine intoxication before pregnancy induces depressive- and anxiety-like behaviors as well as cognitive deficits in male offspring and correlates with neurobiological changes

INTRODUCTION

Maternal nicotine use has been suggested to affect the behavior of children and is linked to changes in neurological systems; however, the specific mechanism is yet to be understood.

METHODS

Mice were used to establish a maternal nicotine intoxication model. At postnatal day 60 (adolescent stage), male offspring were tested for behavioral tasks including sucrose preference, open field, elevated plus maze, light/dark box, object recognition, Morris water maze (MWM), and forced swimming. Enzyme-linked immunoassays were used to measure plasma concentrations of neurotransmitters including norepinephrine, dopamine, serotonin, and corticosterone. Serotonin transporter (Sert), brain-derived neurotrophic factor (Bdnf), cAMP response element binding protein (Creb), and phosphorylated (p)Creb mRNA levels were measured using quantitative real-time polymerase chain reaction.

RESULTS

Male offspring of nicotine-intoxicated dams had significantly reduced sucrose preference, mobility time in the forced swimming test, and locomotor and exploratory activities. Offspring in the maternal nicotine intoxication group showed increased signs of depressive- and anxiety-like behavior. Recognition memory in the MWM was compromised in these animals. The hippocampal and prefrontal cortical regions showed significant changes in Bdnf, pCreb, and Sert gene expression, whereas CREB mRNA levels were unaffected. Moreover, compared to the controls, neurogenesis and neuronal viability were also reduced in these animals.

CONCLUSION

Prenatal nicotine exposure might affect the hypothalamic-pituitary-adrenal axis and reduce neurogenesis, potentially leading to depressive-like behaviors and cognitive deficiencies in male offspring.

4-F-PCP, a Novel PCP Analog Ameliorates the Depressive-Like Behavior of Chronic Social Defeat Stress Mice via NMDA Receptor Antagonism

Major depressive disorder is a leading cause of disability in more than 280 million people worldwide. Monoamine-based antidepressants are currently used to treat depression, but delays in treatment effects and lack of responses are major reasons for the need to develop faster and more efficient antidepressants. Studies show that ketamine (KET), a PCP analog, produces antidepressant effects within a few hours of administration that lasts up to a week. However, the use of KET has raised concerns about side effects, as well as the risk of abuse. 4 -F-PCP analog is a novel PCP analog that is also an NMDA receptor antagonist, structurally similar to KET, and might potentially elicit similar antidepressant effects, however, there has been no study on this subject yet. Herein, we investigate whether 4-F-PCP displays antidepressant effects and explored their potential therapeutic mechanisms. 4-F-PCP at 3 and 10 mg/kg doses showed antidepressant-like effects and repeated treatments maintained its effects. Furthermore, treatment with 4-F-PCP rescued the decreased expression of proteins most likely involved in depression and synaptic plasticity. Changes in the excitatory amino acid transporters (EAAT2, EAAT3, EAAT4) were also seen following drug treatment. Lastly, we assessed the possible side effects of 4-F-PCP after long-term treatment (up to 21 days). Results show that 4-F-PCP at 3 mg/kg dose did not alter the cognitive function of mice. Overall, current findings provide significant implications for future research not only with PCP analogs but also on the next generation of different types of antidepressants.

Immune transcriptional profiles in mothers with clinically elevated depression and anxiety symptoms several years post-delivery

BACKGROUND

Most research on maternal mental health focuses on the perinatal period and does not extend beyond 12 months postpartum. However, emerging evidence suggests that for some women (30%-50%), psychological symptoms may persist beyond the first year postpartum or even emerge later increasing the risk of chronic mood and anxiety symptoms. Despite the high prevalence rates and devastating maternal-child consequences, studies examining maternal depression, anxiety, and post-traumatic stress disorder (PTSD) beyond the first year postpartum are rare and our understanding of the underlying biological mechanisms is incomplete. Inflammatory processes are thought to be involved in the pathophysiology of depression, anxiety, & PTSD outside of the postpartum period. Therefore, the purpose of the current investigation was to examine the relationship between depression, anxiety, and PTSD two to three years post-delivery, and transcriptional control pathways relevant to inflammatory and antiviral processes.

METHODS

Women over 18 years of age enrolled in ongoing research studies at Cedars Sinai Medical Center who were 2-3 years postpartum were invited to participate in the current study. Women (N = 33) reported on their levels of depression, anxiety, and PTSD and provided a blood sample approximately 2-3 years post-delivery. Bioinformatic analyses of differential gene expression (DGEs) to infer transcription factor activity were used. Gene expression was assayed by RNA sequencing and TELiS bioinformatics analysis of transcription factor-binding motifs in the promoters of differentially expressed genes.

RESULTS

DGE analyses revealed that women with clinically elevated symptoms of depression, anxiety and PTSD (n = 16) showed upregulation of genes activated by transcription control pathways associated with inflammation (NF-_Κ B, p = 0.004; JUN, p = 0.02), including ꞵ-adrenergic responsive CREB (p = 0.01) and reduced activation of genes associated with the antiviral response (IRFs, p = 0.02) and the glucocorticoid signaling pathway (GR, p = 0.02) compared to women without clinical symptoms (n = 17).

CONCLUSIONS

This is one of the first investigations into the immune signaling pathways involved in depression, anxiety, and PTSD two to three years post-delivery. The results of this study suggest that clinically elevated symptoms of depression, anxiety, and PTSD two to three years post-delivery are associated with a gene expression profile characterized by upregulated expression of pro-inflammatory genes and downregulated expression of antiviral genes. The data also point to two potential stress responsive pathways linking symptoms to increased inflammatory signaling in immune cells: sympathetic nervous system mediated ꞵ-adrenergic signaling and reduced hypothalamic pituitary adrenal axis activity. Together, these findings highlight the need for investigations into maternal mental health beyond the first year postpartum. This article is protected by copyright. All rights reserved.

Exposure to chronic stress impairs the ability to cope with an acute challenge: Modulation by lurasidone treatment

Chronic stress represents a major contributor for the development of mental illness. This study aimed to investigate how animals exposed to chronic mild stress (CMS) responded to an acute stress (AS), as a vulnerability's challenge, and to establish the potential effects of the antipsychotic drug lurasidone on such mechanisms. Adult male Wistar rats were exposed or not (controls) to a CMS paradigm for 7 weeks. Starting from the end of week 2, animals were randomized to receive vehicle or lurasidone for 5 weeks. Sucrose intake was used to measure anhedonia. At the end, half of the animals were exposed to an acute stress before sacrifice. Exposure to CMS produced a significant reduction in sucrose consumption, whereas lurasidone progressively normalized such alteration. We found that exposure to AS produced an upregulation of Brain derived neurotrophic factor (Bdnf) in the prefrontal cortex of controls animals. This response was impaired in CMS rats and restored by lurasidone treatment. While in control animals, AS-induced increase of Bdnf mRNA levels was specific for Parvalbumin cells, CMS rats treated with lurasidone show a significant upregulation of Bdnf in pyramidal cells. Furthermore, when investigating the activation of different brain regions, CMS rats showed an impairment in the global response to the acute stressor, that was largely restored by lurasidone treatment. Our results suggest that lurasidone treatment in CMS rats may regulate specific circuits and mechanisms, which will ultimately contribute to boost resilience under stressful challenges.

Naringin Mediates Adult Hippocampal Neurogenesis for Antidepression via Activating CREB Signaling

The brain-derived neurotrophic factor/tropomyosin receptor kinase B/cAMP response element-binding protein (BDNF/TrkB/CREB) signaling pathway is a critical therapeutic target for inducing adult hippocampal neurogenesis and antidepressant therapy. In this study, we tested the hypothesis that naringin, a natural medicinal compound, could promote adult hippocampal neurogenesis and improve depression-like behaviors via regulating the BDNF/TrkB/CREB signaling pathway. We first investigated the effects of naringin on promoting adult hippocampal neurogenesis in both normal and chronic corticosterone (CORT)-induced depressive mice. Under physiological condition, naringin treatment enhanced the proliferation of neural stem/progenitor cells (NSPCs) and accelerated neuronal differentiation. In CORT-induced depression mouse model, naringin treatment promoted neuronal differentiation and maturation of NSPCs for hippocampal neurogenesis. Forced swim test, tail suspension test, and open field test confirmed the antidepressant and anxiolytic effects of naringin. Co-treatment of temozolomide (TMZ), a neurogenic inhibitor, abolished these antidepressant and anxiolytic effects. Meanwhile, naringin treatment increased phosphorylation of cAMP response element binding protein (CREB) but had no effect on the expression of brain-derived neurotrophic factor and phosphorylation of TrkB in the hippocampus of CORT-induced depressive mice. Co-treatment of CREB inhibitor 666-15, rather than TrkB inhibitor Cyc-B, abolished the neurogenesis-promoting and antidepressant effects of naringin. Taken together, naringin has antidepressant and anxiolytic effects, and the underlying mechanisms could be attributed to enhance hippocampal neurogenesis via activating CREB signaling.

Exploring the mechanisms of action of Cordyceps sinensis for the treatment of depression using network pharmacology and molecular docking

Background

Depression is the most common type of psychological disorder, with continuous, prolonged, and persistent bad moods as the main clinical feature. Cordyceps sinensis is a complex consisting of the ascospores and bodies of insect larvae from the Hepialidae family that have been parasitized by Cordyceps sinensis militaris. Previous studies have reported that this herb has antidepressant activity. The present study used network pharmacology and molecular docking techniques to investigate the potential antidepressant mechanisms of Cordyceps sinensis.

Methods

The active ingredients of Cordycepssinensis were identified using the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform (TCMSP) and the potential targets were predicted using the PharmMapper platform. The GeneCards database was then used to obtain sub-targets for depression. Common targets were screened and enrichment analyses were performed using the Metascape platform. Finally, the relationship between the active ingredients and the core targets were verified by molecular docking.

Results

Through network pharmacological analysis, 7 active ingredients in Cordyceps sinensis and 41 common targets of drugs and diseases were identified. The active ingredients of Cordyceps sinensis may exert antidepressant effects by acting on important targets such as catalase (CAT), CREB binding protein (CREBBP), epidermal growth factor (EGF), and E1A binding protein P300 (EP300), and by modulating the signaling pathways in which these targets are involved. Subsequently, the core targets were docked to the active ingredients and good binding was observed.

Conclusions

The active ingredients of Cordycepssinensis may exert antidepressant effects by regulating the CREB binding protein and anti-oxidative stress effects. The foxo signaling pathway (hsa04068), hypoxia-inducible factor 1 (HIF-1) signaling pathway (hsa04066), and Huntington’s disease (hsa05016) may be involved in the underlying mechanisms of Cordycepssinensis. The joint application of network pharmacology and molecular docking provides a new approach to study the mechanisms of action of traditional Chinese medicine. Cordyceps sinensis may play an important role in the future treatment of patients with depression.

Hippocampal MSK1 regulates the behavioral and biological responses of mice to chronic social defeat stress: Involving of the BDNF-CREB signaling and neurogenesis

Depression is one of the most common psychiatric diseases in the 21st century, while its pathogenesis is not yet fully understood. Currently, besides to the monoaminergic system, the brain-derived neurotrophic factor (BDNF)-cAMP response element-binding protein (CREB) signaling is one of the most attractive signaling pathways for treating depression. Mitogen and stress-activated kinase (MSK) 1 and 2 are nuclear proteins activated downstream of the ERK1/2 or p38 MAPK pathways, and it has been demonstrated that MSKs are involved in the BDNF-CREB signaling. Here we assumed that MSKs may play a role in depression, and various methods including the chronic social defeat stress (CSDS) model of depression, western blotting, immunofluorescence and virus-mediated gene transfer were used together. It was found that CSDS fully enhanced the expression of both phosphorylated MSK1 and total MSK1 in the hippocampus but not the medial prefrontal cortex (mPFC). CSDS did not influence the expression of phosphorylated MSK2 and total MSK2 in the two brain regions. Genetic over-expression of hippocampal MSK1 fully prevented not only the CSDS-induced depressive-like behaviors but also the CSDS-induced dysfunction in the hippocampal BDNF-CREB signaling and neurogenesis in mice, while genetic knockdown of hippocampal MSK1 aggravated the CSDS-induced depressive-like symptomatology in mice. Our results collectively suggest that although CSDS evidently enhances the activity of hippocampal MSK1, it is not a contributor to the CSDS-induced dysfunction in the brain but a defensive feedback regulator which protects against CSDS. Therefore, hippocampal MSK1 participates in the pathogenesis of depression and is a feasible and potential antidepressant target.

A Duet Between Histamine and Oleoylethanolamide in the Control of Homeostatic and Cognitive Processes

In ballet, a pas de deux (in French it means "step of two") is a duet in which the two dancers perform ballet steps together. The suite of dances shares a common theme of partnership. How could we better describe the fine interplay between oleoylethanolamide (OEA) and histamine, two phylogenetically ancient molecules controlling metabolic, homeostatic and cognitive processes? Contrary to the pas de deux though, the two dancers presumably never embrace each other as a dancing pair but execute their "virtuoso solo" constantly exchanging interoceptive messages presumably via vagal afferents, the blood stream, the neuroenteric system. With one exception, which is in the control of liver ketogenesis, as in hepatocytes, OEA biosynthesis strictly depends on the activation of histaminergic H₁ receptors. In this review, we recapitulate our main findings that evidence the interplay of histamine and OEA in the control of food consumption and eating behaviour, in the consolidation of emotional memory and mood, and finally, in the synthesis of ketone bodies. We will also summarise some of the putative underlying mechanisms for each scenario.

1,3-Dicaffeoylquinic Acid as an Active Compound of Arctium lappa Root Extract Ameliorates Depressive-Like Behavior by Regulating Hippocampal Nitric Oxide Synthesis in Ovariectomized Mice

Menopause is a risk factor for depression. Although 1,3-dicaffeoylquinic acid (1,3-diCQA), a phenolic compound in Arctium lappa (A. lappa) root, has various health benefits, its effects on menopausal depression remain to be determined. Therefore, this study investigates the antidepressant-like effects of 1,3-diCQA from an A. lappa root extract (AE) and the associated molecular mechanisms. Ovariectomized (OVX) mice were orally administered AE for 20 weeks, following which depression-like behaviors were assessed. Although the mice exhibited depression-like behaviors, AE administration mitigated these symptoms by activating the ERK–CREB–BDNF pathway and increasing nNOS levels in the hippocampus. Similarly, a significant increase in nNOS-derived NO production and activation of the ERK–CREB–BDNF pathway was observed in the primary hippocampal neurons. Although this stimulatory effect of 1,3-diCQA was not significantly affected by treatment with estrogen receptor agonist or antagonist, it was inhibited by 7-NI, an nNOS inhibitor. Moreover, mice treated with 1,3-diCQA exhibited a marked improvement in their forced swimming test and tail suspension test immobility, while pretreatment with 7-NI reversed the antidepressant-like effects of 1,3-diCQA. Our results suggest that 1,3-diCQA regulates nNOS in an estrogen recepters-independent manner to increase NO production in OVX mice.

Xanthoceraside administration produces significant antidepressant effects in mice through activation of the hippocampal BDNF signaling pathway

Current available antidepressants have various adverse reactions and slow pharmacodynamics, so it is necessary to find novel antidepressants for effective treatment. Xanthoceraside (XAN), a novel triterpenoid saponin extracted from the fruit husks of Xanthoceras sorbifolium Bunge, has anti-amnesic and neuroprotective properties. The purpose and significance of this study is to assess whether XAN has antidepressant effects in mice using the forced swim test (FST), tail suspension test (TST) and chronic unpredictable mild stress (CUMS) model of depression. The effects of XAN treatment on the hippocampal brain-derived neurotrophic factor (BDNF) signaling pathway and neurogenesis were examined. The antidepressant mechanism of XAN was explored using a BDNF inhibitor (K252a) and an anti-BDNF antibody. It was found that XAN administration significantly reversed the depressive-like behaviors of CUMS-treated mice. XAN treatment also significantly prevented the decreasing effects of CUMS on the hippocampal BDNF signaling and neurogenesis. The antidepressant effects of XAN in mice were blocked by both administration of K252a and anti-BDNF antibody. Collectively, these findings indicate that XAN possesses antidepressant effects in mice which are mediated by activation of hippocampal BDNF signaling pathway, thus providing the first evidence that XAN can be a potential antidepressant candidate.

Astrocyte Intracellular Ca2+and TrkB Signaling in the Hippocampus Could Be Involved in the Beneficial Behavioral Effects of Antidepressant Treatment

Although monoaminergic-based antidepressant drugs are largely used to treat major depressive disorder (MDD), their mechanisms are still incompletely understood. Intracellular Ca²⁺ (iCa²⁺) and Calmodulin 1(CaM-1) homeostasis have been proposed to participate in the therapeutic effects of these compounds. We investigated whether intra-hippocampal inhibition of CaM-1 would modulate the behavioral responses to chronic treatment with imipramine (IMI) or 7-nitroindazole (7-NI), a selective inhibitor of the neuronal nitric oxide synthase 1 (NOS1) enzyme that shows antidepressant-like effects. We also investigated the interactions of IMI and CaM-1 on transient astrocyte iCa²⁺ evoked by glutamate stimuli. Intra-hippocampal microinjection of the lentiviral delivered (LV) short hairpin iRNA-driven against the CaM-1 mRNA (LV-shRNA-CaM-1) or the CaM-1 inhibitor N-(6-aminohexyl)-5-chloro-1-naphthalene sulphonamide (W-7) blocked the antidepressant-like effect of chronic treatment with IMI or 7-NI. The shRNA also inhibited the mRNA expression of the tropomyosin receptor kinase B (TrkB) in the microinjection region. The iCa²⁺ in ex vivo hippocampus slices stained with fluorescent Ca²⁺indicator Oregon Green 488 BAPTA-1 revealed that IMI increased the intensity and duration of iCa²⁺ oscillation and reduced the number of events evoked by glutamate stimuli, evaluated by using CCD imaging and the % ΔF/Fo parameters. The pre-treatment with W-7 fully antagonized this effect. The present results indicate that the behavioral benefits of chronic antidepressant treatment might be associated with astrocyte intracellular Ca²⁺dynamics and TrkB mRNA expression in the hippocampus.

Resveratrol and organic selenium-rich fermented milk reduces D-galactose-induced cognitive dysfunction in mice

Recently, dietary intervention has been considered as a prospective strategy in treating age-related cognitive dysfunction and brain plasticity degeneration. In this study, we developed a kind of functional fermented milk rich in resveratrol and organic selenium, and explored the effects on cognitive behavior, hippocampal neurogenesis and the neurotrophic signaling pathway in d-galactose model mice. Behavioral tests showed that the functional fermented milk significantly reversed spatial memory loss and showed a recognition behavior reduction in a novel object recognition task. Immunohistochemistry analysis demonstrated that the functional fermented milk significantly increased hippocampal neurogenesis. Moreover, walnut diets with dairy products reserved a d-galactose induced decrease of hippocampal p-ERK/ERK, p-CREB/CREB, and BDNF expression in the protein level. These findings confirmed that dietary treatment with the functional fermented milk could ameliorate cognitive dysfunction in d-galactose model mice, and yoghurt rich in resveratrol and organic selenium has the potential in treating age-related diseases.

Ketamine: A tale of two enantiomers

The discovery of the rapid antidepressant effects of the dissociative anaesthetic ketamine, an uncompetitive N-Methyl-D-Aspartate receptor antagonist, is arguably the most important breakthrough in depression research in the last 50 years. Ketamine remains an off-label treatment for treatment-resistant depression with factors that limit widespread use including its dissociative effects and abuse potential. Ketamine is a racemic mixture, composed of equal amounts of (S)-ketamine and (R)-ketamine. An (S)-ketamine nasal spray has been developed and approved for use in treatment-resistant depression in the United States and Europe; however, some concerns regarding efficacy and side effects remain. Although (R)-ketamine is a less potent N-Methyl-D-Aspartate receptor antagonist than (S)-ketamine, increasing preclinical evidence suggests (R)-ketamine may have more potent and longer lasting antidepressant effects than (S)-ketamine, alongside fewer side effects. Furthermore, a recent pilot trial of (R)-ketamine has demonstrated rapid-acting and sustained antidepressant effects in individuals with treatment-resistant depression. Research is ongoing to determine the specific cellular and molecular mechanisms underlying the antidepressant actions of ketamine and its component enantiomers in an effort to develop future rapid-acting antidepressants that lack undesirable effects. Here, we briefly review findings regarding the antidepressant effects of ketamine and its enantiomers before considering underlying mechanisms including N-Methyl-D-Aspartate receptor antagonism, γ-aminobutyric acid-ergic interneuron inhibition, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic receptor activation, brain-derived neurotrophic factor and tropomyosin kinase B signalling, mammalian target of rapamycin complex 1 and extracellular signal-regulated kinase signalling, inhibition of glycogen synthase kinase-3 and inhibition of lateral habenula bursting, alongside potential roles of the monoaminergic and opioid receptor systems.

MTORC1 signaling as a biomarker in major depressive disorder and its pharmacological modulation by novel rapid-acting antidepressants

Major depressive disorder (MDD) is a multifactorial psychiatric disorder with obscure pathophysiology. A biomarker-based approach in combination with standardized interview-based instruments is needed to identify MDD subtypes and novel therapeutic targets. Recent findings support the impairment of the mammalian target of rapamycin complex 1 (mTORC1) in MDD. No well-established biomarkers of mTORC1 disease- and treatment-modulated activity are currently available for use in early phase antidepressant drug (AD) development. This review aims to summarize biomarkers of mTORC1 activity in MDD and to suggest how these could be implemented in future early clinical trials on mTORC1 modulating ADs. Therefore, a PubMed-based narrative literature review of the mTORC1 involvement in MDD was performed. We have summarized recent pre-clinical and clinical findings linking the MDD to the impaired activity of several key biomarkers related to mTORC1. Also, cases of restoration of these impairments by classical ADs and novel fast-acting investigational ADs are summarized. The presented biomarkers may be used to monitor pharmacological effects by novel rapid-acting mTORC1-targeting ADs. Based on findings in the peripheral blood mononuclear cells, we argue that those may serve as an ex vivo model for evaluation of mTORC1 activity and propose the use of the summarized biomarkers for this purpose. This could both facilitate the selection of a pharmacodynamically active dose and guide future early clinical efficacy studies in MDD. In conclusion, this review provides a blueprint for the rational development of rapid-acting mTORC1-targeting ADs.

Anti-depressant effect of cerebrolysin in reserpine-induced depression in rats: Behavioral, biochemical, molecular and immunohistochemical evidence

Depression is a major psychological disorder that contributes to global health problem. This study aimed to evaluate the anti-depressant effect of Cerebrolysin (CBL) in Reserpine-induced depressed rats, its effect on oxidative stress, inflammation, regulatory cyclic AMP-dependent response element binding protein (CREB)/brain derived neurotropic factor (BDNF) signaling pathways, brain monoamines and histopathological changes was assessed. Rats received either the vehicle or Reserpine (0.5 mg/kg, i.p.) for 14 days. The other three groups were pretreated with CBL (2.5, 5 ml/kg; i.p.) or fluoxetine (FLU) (5 mg/kg, p.o.), respectively for 14 days, 30 min before reserpine injection. Then analyses were conducted. CBL reversed Reserpine-induced reduction in latency to immobility and prolongation of immobility time in the forced swimming test (FST), reduced malondialdehyde (MDA), elevated reduced glutathione (GSH), reduced tumor necrosis factor-alpha (TNF-ɑ), and elevated BDNF cortical and hippocampal brain contents. CBL elevated protein kinase A (PKA) and nuclear factor kappa-B (NF-κB) cortical and hippocampal protein expressions. CBL also ameliorated alterations in mRNA expressions of protein kinase B (AKT), CREB and BDNF in the cortical and hippocampal tissues. CBL elevated nor-epinephrine (NE), serotonin (5-HT), and dopamine (DA) and reduced 5-Hydroxyindoleacetic acid (5-HTAA), 3,4-Dihydroxyphenylacetic acid (DOPAC), and homovanillic acid (HVA) cortical and hippocampal contents. CBL effects were in parallel to those observed with the standard anti-depressant drug, FLU. This study shows that CBL exerted anti-depressant effect evidenced by attenuation of oxidative stress and inflammation as well as enhancement of neurogenesis, amelioration of monoaminergic system and histopathological changes.

Imipramine exerts antidepressant-like effects in chronic stress models of depression by promoting CRTC1 expression in the mPFC

Recent studies have suggested that CREB-regulated transcription coactivator 1 (CRTC1) plays a role in the pathophysiology of depression. Although imipramine is thought to prevent the reuptake of synaptic serotonin and norepinephrine, its antidepressant-like mechanisms remain elusive. In this study, the effects of imipramine on CRTC1 were studied in several models of depression, including the chronic restraint stress (CRS), chronic unpredictable mild stress (CUMS) and chronic social defeat stress (CSDS) models. We examined whether repeated imipramine administration can reverse the effects of CRS, CUMS and CSDS on CRTC1 expression in both the hippocampus and medial prefrontal cortex (mPFC). Furthermore, genetic knockdown of CRTC1 by CRTC1-shRNA was used to determine whether CRTC1 is necessary for the antidepressant-like effects of imipramine in mice. Our results showed that imipramine reversed the down-regulating effects of CRS, CUMS and CSDS on CRTC1 expression in the mPFC but not the hippocampus, and that CRTC1-shRNA fully abolished the antidepressant-like actions of imipramine in mice. In conclusion, CRTC1 in the mPFC is involved in the antidepressant mechanism of imipramine.

Neuroprotective effects of Camellia nitidissima Chi leaf extract in hydrogen peroxide-treated human neuroblastoma cells and its molecule mechanisms

Camellia nitidissima Chi (CNC) is a famous medicinal and edible plant with the name of "Tea for Longevity" in Guangxi province of China. In present study, we determined the protective effect of extract from CNC leaves on H2O2-induced cell injury and its underlying mechanisms in human neuroblastoma (SH-SY5Y) cells. The ethyl acetate fraction of CNC leaves (CLE, 50-200 μg/ml) treatment significantly increased the cell viability of H2O2-treated SH-SY5Y cells and reduced the leakage of LDH in a reversed "U"-shape manner. It was confirmed by Hoechst 33,342 staining that CLE attenuated H2O2-induced apoptosis in SH-SY5Y cells. The CLE (100 and 150 μg/ml) treatment significantly relieved H2O2-induced oxidative stress by decreasing intracellular ROS level, and increasing the activities of superoxide dismutase (SOD) and catalase (CAT). Western blot analysis demonstrated that the CLE treatment reserved H2O2-induced decrease of pCREB (Ser133) expression, and its downstream protein BDNF. In addition, 37 phenolic compounds in CLE were identified by UPLC-TOF MS/MS, and the main active phytochemicals seemed to be catechins, quercetin, kaempferol, and their derivatives. In conclusion, the data analysis showed that the neuroprotective effect of CNC leaves might be achieved via synergistically boosting endogenous antioxidant defenses and neurotrophic signaling pathway. These results suggest that CNC leaves are valuable resources for functional foods and beverages.

The epigenetic modulation of alcohol/ethanol and cannabis exposure/co-exposure during different stages

Studies have reported the significant economic impact of smoking cannabis and drinking alcohol In the USA. It was estimated that the costs of cannabis-related treatment, hospitalization and loss of work-related pay have amounted to $200 billion. (Andersen AM, Dogan MV, Beach SRH, Philibert RA. 2015 Genes 6, 991-1022. ( doi:10.3390/genes6040991 )). Data from the National Epidemiologic Survey on Alcohol and Related Conditions showed that individuals with general anxiety disorder and substance use disorder (GAD-SUD) have higher psychiatric comorbidity rates than those without substance use disorder (Alegría AA, Hasin DS, Nunes EV, Liu SM, Davies C, Grant BF, Blanco C. 2010 J. Clin. Psychiatry 71, 1187-1195. ( doi:10.4088/JCP.09m05328gry )). Moreover, the criminal justice system is significantly impacted by this cost (Andersen AM, Dogan MV, Beach SRH, Philibert RA. 2015 Genes 6, 991-1022. ( doi:10.3390/genes6040991 )). Despite the increasing use of cannabis, there are still too many obscure facts. One of the new areas that scientific evidence shows is impacted negatively by cannabis use is the epigenome, which is an understudied area that we are still learning about. In addition, over the past few decades, we have seen various social and healthcare changes that have raised critical questions about their ongoing roles in regulating marijuana and alcohol use. This is important because of the increasing popularity and usage across various ages especially young adults and teenagers. More than 97.5 million Americans over 12 years old have used cannabis for non-medical use despite the significant side effects, with 1 in 10 users developing cannabis dependence (Crean RD, Crane NA, Mason BJ. 2011 J. Addict. Med. 5, 1-8. ( doi:10.1097/ADM.0b013e31820c23fa ), Office of Applied Studies. 2006 Substance Abuse and Mental Health Services Administration, USA.). It was reported that 16% of substance abuse admissions in the USA were for cannabis-related symptoms, which is second only to alcohol-related disorders (Agalioti T, Lomvardas S, Parekh B, Yie J, Maniatis T, Thanos D. 2000 Cell 103, 667-678. ( doi:10.1016/S0092-8674(00)00169-0 ), Soutoglou E, Talianidis I. 2002 Science 295, 1901-1904. ( doi:10.1126/science.1068356 )). Today there are thirty-one states and the District of Columbia that currently have legalized marijuana for either medical or recreational use. Data about marijuana use from NIAAA's National Epidemiologic Survey on Alcohol and Related Conditions (NESARC) indicates that 'in total, 79 000 people were interviewed on alcohol and drug use. When examined by age young adults (ages 18-21) were found to be at highest risk for marijuana use and marijuana use disorder, with use increasing from 10.5 to 21.2% and disorder increasing from 4.4 to 7.5%'. 'Given these facts, George Koob, PhD, director of NIAAA stated the importance for the scientific community to convey this information to the public about the potential hazards of marijuana and it's use'. On the other hand, according to the National Institute on Alcohol Abuse and Alcoholism, 16 million adults suffer from alcohol use disorders. To the best of our knowledge, epigenetic mechanisms have been previously studied in alcohol and cannabis abuse separately. Recent studies highlighted the molecular mechanisms that are linked with drug-induced transcriptional regulation, behavioural abnormalities and neurodegeneration, which has emphasized the role of chromatin modification/remodelling in the generation of drug activation of certain genes and the disabling of others, and the effect of that on addiction (Maze I, Nestler EJ. 2011 Ann. N. Y. Acad. Sci. 1216, 99-113. ( doi:10.1111/j.1749-6632.2010.05893.x ); Renthal W, Nestler EJ. 2008 Trends Mol. Med. 14, 341-350. ( doi:10.1016/j.molmed.2008.06.004 )). In this review, we will give an overview of epigenome science relevant to cannabis/the endocannabinoid system and the potential of epigenetic overlap between alcohol and cannabinergic activity at different stages, to aid further investigations that could bring more treatment options to our horizon.

NMDAR-independent, cAMP-dependent antidepressant actions of ketamine

Ketamine produces rapid and robust antidepressant effects in depressed patients within hours of administration, often when traditional antidepressant compounds have failed to alleviate symptoms. We hypothesized that ketamine would translocate Gα_s from lipid rafts to non-raft microdomains, similarly to other antidepressants but with a distinct, abbreviated treatment duration. C6 glioma cells were treated with 10 µM ketamine for 15 min, which translocated Gα_s from lipid raft domains to non-raft domains. Other NMDA antagonist did not translocate Gα_s from lipid raft to non-raft domains. The ketamine-induced Gα_s plasma membrane redistribution allows increased functional coupling of Gα_s and adenylyl cyclase to increase intracellular cyclic adenosine monophosphate (cAMP). Moreover, increased intracellular cAMP increased phosphorylation of cAMP response element-binding protein (CREB), which, in turn, increased BDNF expression. The ketamine-induced increase in intracellular cAMP persisted after knocking out the NMDA receptor indicating an NMDA receptor-independent effect. Furthermore, 10 µM of the ketamine metabolite (2R,6R)-hydroxynorketamine (HNK) also induced Gα_s redistribution and increased cAMP. These results reveal a novel antidepressant mechanism mediated by acute ketamine treatment that may contribute to ketamine's powerful antidepressant effect. They also suggest that the translocation of Gα_s from lipid rafts is a reliable hallmark of antidepressant action that might be exploited for diagnosis or drug development.

CREB deletion increases resilience to stress and downregulates inflammatory gene expression in the hippocampus

The transcription factor CREB (cyclic AMP response element (CRE)-binding protein) is implicated in the pathophysiology and treatment of depression. Structural and functional studies in both animals and humans suggest that abnormalities of the hippocampus may play a role in depression. CREB regulates thousands of genes, yet to date, only a handful that mediate depression or antidepressant response have been identified as relevant CREB targets. In order to comprehensively identify genes regulated by CREB in the hippocampus, we employed translating ribosome affinity purification (TRAP) to detect actively translating mRNAs in wild type and CREB-deficient mice. Using Creb^loxP/loxP; Rosa^LSL-GFP-L10a mice, we conducted whole genome sequencing to identify transcripts only in cells that lack CREB, as introduction of Cre-recombinase simultaneously deleted CREB and expressed GFP-tagged L10a ribosomes that enabled TRAP. We identified over 200 downregulated genes predominantly associated with inflammation and the immune system, including toll-like receptor 1 (TLR1). To determine if baseline disruption in gene expression in the hippocampus of CREB-deficient mice can modulate behavior, we used unpredictable chronic mild stress (UCMS) to produce a set of behavioral alterations with strong validity for depression. We found that CREB-deficient mice demonstrated resilience to the physiological effects of UCMS and also showed changes in affective behaviors specifically in the presence of stress. TLR1 expression was increased following UCMS in control but not in CREB-deficient mice. The results suggest that CREB-mediated regulation of immune system and inflammatory factors may provide additional targets for the treatment of depression.

Hippocampal Salt-Inducible Kinase 2 Plays a Role in Depression via the CREB-Regulated Transcription Coactivator 1-cAMP Response Element Binding-Brain-Derived Neurotrophic Factor Pathway

BACKGROUND

Developing novel pharmacological targets beyond monoaminergic systems is now a popular strategy for finding new ways to treat depression. Salt-inducible kinase (SIK) is a kinase that regulates the nuclear translocation of cyclic adenosine monophosphate response element binding protein (CREB)-regulated transcription coactivator (CRTC) by phosphorylation. Here, we hypothesize that dysfunction of the central SIK-CRTC system may contribute to the pathogenesis of depression.

METHODS

Chronic social defeat stress (CSDS) and chronic unpredictable mild stress (CUMS) models of depression, various behavioral tests, viral-mediated gene transfer, Western blotting, coimmunoprecipitation, quantitative real-time reverse transcription polymerase chain reaction, and immunohistochemistry were used in this study (for in vivo studies, n = 10; for in vitro studies, n = 5).

RESULTS

Both CSDS and CUMS markedly increased the expression of hippocampal SIK2, which reduced CRTC1 nuclear translocation and binding of CRTC1 and CREB in the hippocampus. Genetic overexpression of hippocampal SIK2 in naïve mice simulated chronic stress, inducing depressive-like behaviors in the forced swim test, tail suspension test, sucrose preference test, and social interaction test, as well as decreasing the brain-derived neurotrophic factor signaling cascade and neurogenesis in the hippocampus. In contrast, genetic knockdown and knockout of hippocampal SIK2 protected against CSDS and CUMS, exerting significant antidepressant-like effects that were mediated via the downstream CRTC1-CREB-brain-derived neurotrophic factor pathway. Moreover, fluoxetine, venlafaxine, and mirtazapine all significantly restored the effects of CSDS and CUMS on the hippocampal SIK2-CRTC1 pathway, which was necessary for their antidepressant actions.

CONCLUSIONS

The hippocampal SIK2-CRTC1 pathway is involved in the pathogenesis of depression, and hippocampal SIK2 could be a novel target for the development of antidepressants.

Transcriptomic predictors of inflammation-induced depressed mood

Inflammation plays a significant role in the pathophysiology of depression. However, not all individuals exposed to inflammatory challenge develop depression, and identifying those at risk is necessary to develop targeted monitoring, prevention, and treatment strategies. Within a randomized double-blind placebo-controlled study (n = 115), we examined whether leukocyte transcriptome profiles predicted inflammation-induced depressed mood in volunteers who received low-dose intravenous endotoxin (n = 58; aged 18-50). At baseline, transcription factor (TF) activities were assessed using genome-wide transcriptional profiling of peripheral blood mononuclear cells and promoter-based bioinformatic analyses. Then, participants were administered endotoxin. Self-reported depressed mood was assessed using the Profile of Mood States. Based on extant studies linking transcriptional profiles to depressive disorder, we examined whether post-endotoxin depressed mood is predicted by baseline activity of TFs related to immune activation, sympathetic activation, and glucocorticoid insensitivity: respectively, nuclear factor kappa B (NF-kB), cAMP response element-binding protein (CREB), and glucocorticoid receptor (GR). Twenty-one participants (36%) experienced an increase in depressed mood from baseline to 2 h post endotoxin, when depressive response peaks. Bioinformatics analyses controlling for age, sex, ethnicity, body mass index, and physical sickness response revealed that post-endotoxin depressed mood was predicted by increased baseline activity of TFs related to inflammation (NF-kB) and beta-adrenergic signaling (CREB) and by decreased activity of GR-related TFs (P's < 0.001). Inflammation-induced depressed mood is predicted by peripheral transcriptome profiles related to immune activation, sympathetic activation, and glucocorticoid insensitivity. With further replication, these stress-related molecular profiles could be used for a novel genomic approach for identifying individuals at high-risk for the inflammatory subtype of depression.

Social defeat stress before pregnancy induces depressive-like behaviours and cognitive deficits in adult male offspring: correlation with neurobiological changes

BACKGROUND

Epidemiological surveys and studies with animal models have established a relationship between maternal stress and affective disorders in their offspring. However, whether maternal depression before pregnancy influences behaviour and related neurobiological mechanisms in the offspring has not been studied.

RESULTS

A social defeat stress (SDS) maternal rat model was established using the resident-intruder paradigm with female specific pathogen-free Wistar rats and evaluated with behavioural tests. SDS maternal rats showed a significant reduction in sucrose preference and locomotor and exploratory activities after 4 weeks of stress. In the third week of the experiment, a reduction in body weight gain was observed in SDS animals. Sucrose preference, open field, the elevated-plus maze, light-dark box, object recognition, the Morris water maze, and forced swimming tests were performed using the 2-month-old male offspring of the female SDS rats. Offspring subjected to pre-gestational SDS displayed enhanced anxiety-like behaviours, reduced exploratory behaviours, reduced sucrose preference, and atypical despair behaviours. With regard to cognition, the offspring showed significant impairments in the retention phase of the object recognition test, but no effect was observed in the acquisition phase. These animals also showed impairments in recognition memory, as the discrimination index in the Morris water maze test in this group was significantly lower for both 1 h and 24 h memory retention compared to controls. Corticosterone, adrenocorticotropic hormone, and monoamine neurotransmitters levels were determined using enzyme immunoassays or radioimmunoassays in plasma, hypothalamus, left hippocampus, and left prefrontal cortex samples from the offspring of the SDS rats. These markers of hypothalamic-pituitary-adrenal axis responsiveness and the monoaminergic system were significantly altered in pre-gestationally stressed offspring. Brain-derived neurotrophic factor (BDNF), cyclic adenosine monophosphate response element binding protein (CREB), phosphorylated CREB (pCREB), and serotonin transporter (SERT) protein levels were evaluated using western blotting with right hippocampus and right prefrontal cortex samples. Expression levels of BDNF, pCREB, and SERT in the offspring were also altered in the hippocampus and in the prefrontal cortex; however, there was no effect on CREB.

CONCLUSION

We conclude that SDS before pregnancy might induce depressive-like behaviours, cognitive deficits, and neurobiological alterations in the offspring.

Selective Depletion of CREB in Serotonergic Neurons Affects the Upregulation of Brain-Derived Neurotrophic Factor Evoked by Chronic Fluoxetine Treatment

Neurotrophic factors are regarded as crucial regulatory components in neuronal plasticity and are postulated to play an important role in depression pathology. The abundant expression of brain-derived neurotrophic factor (BDNF) in various brain structures seems to be of particular interest in this context, as downregulation of BDNF is postulated to be correlated with depression and its upregulation is often observed after chronic treatment with common antidepressants. It is well-known that BDNF expression is regulated by cyclic AMP response element-binding protein (CREB). In our previous study using mice lacking CREB in serotonergic neurons (Creb1^TPH2CreERT2 mice), we showed that selective CREB ablation in these particular neuronal populations is crucial for drug-resistant phenotypes in the tail suspension test observed after fluoxetine administration in Creb1^TPH2CreERT2 mice. The aim of this study was to investigate the molecular changes in the expression of neurotrophins in Creb1^TPH2CreERT2 mice after chronic fluoxetine treatment, restricted to the brain structures implicated in depression pathology with profound serotonergic innervation including the prefrontal cortex (PFC) and hippocampus. Here, we show for the first time that BDNF upregulation observed after fluoxetine in the hippocampus or PFC might be dependent on the transcription factor CREB residing, not within these particular structures targeted by serotonergic projections, but exclusively in serotonergic neurons. This observation may shed new light on the neurotrophic hypothesis of depression, where the effects of BDNF observed after antidepressants in the hippocampus and other brain structures were rather thought to be regulated by CREB residing within the same brain structures. Overall, these results provide further evidence for the pivotal role of CREB in serotonergic neurons in maintaining mechanisms of antidepressant drug action by regulation of BDNF levels.

Walnut diets up-regulate the decreased hippocampal neurogenesis and age-related cognitive dysfunction in d-galactose induced aged rats

Recently, dietary intervention has been considered as a prospective strategy in delaying age-related cognitive dysfunction and brain plasticity degeneration. This study explored the effect of walnut diets (6% and 9%, 8 weeks) on cognitive behavior, hippocampal neurogenesis and the neurotrophic signaling pathway in d-galactose (d-gal) model rats. Behavioral tests showed that walnut diets significantly reversed spatial memory loss in the Morris water test, locomotor activity deficiency in an open field test, and a recognition behavior reduction in a novel object recognition task. Immunohistochemistry analysis demonstrated walnut diets significantly increased the hippocampal neurogenesis in d-gal model rats. Moreover, western blot results indicated that walnut diets reserved a d-gal induced decrease of hippocampal pCREB (Ser133) and BDNF expression, two crucial intracellular molecules involved in hippocampal neurogenesis. These findings confirmed that chronic walnut-rich diets could ameliorate cognitive dysfunction in d-gal model rats, and the up-regulation of neurogenesis, as well as the expression of pCREB and BDNF in hippocampus, may be one of the molecular and cellular mechanisms underlying these effects.

Depression and adult neurogenesis: Positive effects of the antidepressant fluoxetine and of physical exercise

Of wide interest for health is the relation existing between depression, a very common psychological illness, accompanied by anxiety and reduced ability to concentrate, and adult neurogenesis. We will focus on two neurogenic stimuli, fluoxetine and physical exercise, both endowed with the ability to activate adult neurogenesis in the dentate gyrus of the hippocampus, known to be required for learning and memory, and both able to counteract depression. Fluoxetine belongs to the class of selective serotonin reuptake inhibitor (SSRI) antidepressants, which represent the most used pharmacological therapy; physical exercise has also been shown to effectively counteract depression symptoms in rodents as well as in humans. While there is evidence that the antidepressant effect of fluoxetine requires its pro-neurogenic action, exerted by promoting proliferation, differentiation and survival of progenitor cells of the hippocampus, on the other hand fluoxetine exerts also neurogenesis-independent antidepressant effects by influencing the plasticity of the new neurons generated. Similarly, the antidepressant action of running also correlates with an increase of hippocampal neurogenesis and plasticity, although the gene pathways involved are only partially coincident with those of fluoxetine, such as those involved in serotonin metabolism and synapse formation. We further discuss how extra-neurogenic actions are also suggested by the fact that, unlike running, fluoxetine is unable to stimulate neurogenesis during aging, but still displays antidepressant effects. Moreover, in specific conditions, fluoxetine or running activate not only progenitor but also stem cells, which normally are not stimulated; this fact reveals how stem cells have a long-term, hidden ability to self-renew and, more generally, that neurogenesis is subject to complex controls that may play a role in depression, such as the type of neurogenic stimulus or the state of the local niche. Finally, we discuss how fluoxetine or running are effective in counteracting depression originated from stress or neurodegenerative diseases.

Social defeat stress: Mechanisms underlying the increase in rewarding effects of drugs of abuse

Social interaction is known to be the main source of stress in human beings, which explains the translational importance of this research in animals. Evidence reported over the last decade has revealed that, when exposed to social defeat experiences (brief episodes of social confrontations during adolescence and adulthood), the rodent brain undergoes remodeling and functional modifications, which in turn lead to an increase in the rewarding and reinstating effects of different drugs of abuse. The mechanisms by which social stress cause changes in the brain and behavior are unknown, and so the objective of this review is to contemplate how social defeat stress induces long-lasting consequences that modify the reward system. First of all, we will describe the most characteristic results of the short- and long-term consequences of social defeat stress on the rewarding effects of drugs of abuse such as psychostimulants and alcohol. Secondly, and throughout the review, we will carefully assess the neurobiological mechanisms underlying these effects, including changes in the dopaminergic system, corticotrophin releasing factor signaling, epigenetic modifications and the neuroinflammatory response. To conclude, we will consider the advantages and disadvantages and the translational value of the social defeat stress model, and will discuss challenges and future directions.

cAMP Response Element-Binding Protein (CREB): A Possible Signaling Molecule Link in the Pathophysiology of Schizophrenia

Dopamine is a brain neurotransmitter involved in the pathology of schizophrenia. The dopamine hypothesis states that, in schizophrenia, dopaminergic signal transduction is hyperactive. The cAMP-response element binding protein (CREB) is an intracellular protein that regulates the expression of genes that are important in dopaminergic neurons. Dopamine affects the phosphorylation of CREB via G protein-coupled receptors. Neurotrophins, such as brain derived growth factor (BDNF), are critical regulators during neurodevelopment and synaptic plasticity. The CREB is one of the major regulators of neurotrophin responses since phosphorylated CREB binds to a specific sequence in the promoter of BDNF and regulates its transcription. Moreover, susceptibility genes associated with schizophrenia also target and stimulate the activity of CREB. Abnormalities of CREB expression is observed in the brain of individuals suffering from schizophrenia, and two variants (-933T to C and -413G to A) were found only in schizophrenic patients. The CREB was also involved in the therapy of animal models of schizophrenia. Collectively, these findings suggest a link between CREB and the pathophysiology of schizophrenia. This review provides an overview of CREB structure, expression, and biological functions in the brain and its interaction with dopamine signaling, neurotrophins, and susceptibility genes for schizophrenia. Animal models in which CREB function is modulated, by either overexpression of the protein or knocked down through gene deletion/mutation, implicating CREB in schizophrenia and antipsychotic drugs efficacy are also discussed. Targeting research and drug development on CREB could potentially accelerate the development of novel medications against schizophrenia.

Antidepressant-like Effects of p-Coumaric Acid on LPS-induced Depressive and Inflammatory Changes in Rats

Depression causes mental and physical changes which affect quality of life. It is estimated to become the second most prevalent disease, but despite its commonness, the pathophysiology of depression remains unclear and medicine is not sufficiently protective. p-Coumaric acid (p-CA) is a dietary phenolic acid which has been proven to have antifungal, anti-HIV, anti-melanogenic, antioxidant and anti-inflammatory effects. Considering these effects, we investigated whether p-CA can prevent depressive symptoms by reducing inflammatory cytokines in animals injected with lipopolysaccharide (LPS). Changes in despair-related behaviors, inflammatory cytokines, neurotrophic factors and synaptic activity were measured. In these animals, p-CA improved despair-related behavioral symptoms induced by LPS in the forced swim test (FST), tail suspension test (TST) and sucrose splash test (SST). p-CA also prevented the increase of inflammatory cytokines in the hippocampus such as cycloxigenase-2 and tumor necrosis factor-α due to LPS. Similarly, it prevented the reduction of brain-derived neurotrophic factor (BDNF) by LPS. Electrophysiologically, p-CA blocked the reduction of long-term depression in LPS-treated organotypic tissue slices. In conclusion, p-CA prevented LPS-induced depressive symptoms in animals, as determined by behavioral, biochemical and electrophysiological measures. These findings suggest the potential use of p-CA as a preventive and therapeutic medicine for depression.

Neurobiology and consequences of social isolation stress in animal model-A comprehensive review

The brain is a vital organ, susceptible to alterations under genetic influences and environmental experiences. Social isolation (SI) acts as a stressor which results in alterations in reactivity to stress, social behavior, function of neurochemical and neuroendocrine system, physiological, anatomical and behavioral changes in both animal and humans. During early stages of life, acute or chronic SIS has been proposed to show signs and symptoms of psychiatric and neurological disorders such as anxiety, depression, schizophrenia, epilepsy and memory loss. Exposure to social isolation stress induces a variety of endocrinological changes including the activation of hypothalamic-pituitary-adrenal (HPA) axis, culminating in the release of glucocorticoids (GCs), release of catecholamines, activation of the sympatho-adrenomedullary system, release of Oxytocin and vasopressin. In several regions of the central nervous system (CNS), SIS alters the level of neurotransmitter such as dopamine, serotonin, gamma aminobutyric acid (GABA), glutamate, nitrergic system and adrenaline as well as leads to alteration in receptor sensitivity of N-methyl-D-aspartate (NMDA) and opioid system. A change in the function of oxidative and nitrosative stress (O&NS) mediated mitochondrial dysfunction, inflammatory factors, neurotrophins and neurotrophicfactors (NTFs), early growth response transcription factor genes (Egr) and C-Fos expression are also involved as a pathophysiological consequences of SIS which induce neurological and psychiatric disorders.

Hippocampal PPARα is a novel therapeutic target for depression and mediates the antidepressant actions of fluoxetine in mice

BACKGROUND AND PURPOSE

Developing novel pharmacological targets beyond the monoaminergic system is now a popular strategy for treating depression. PPARα is a nuclear receptor protein that functions as a transcription factor,-regulating gene expression. We have previously reported that both WY14643 and fenofibrate, two pharmacological agonists of PPARα, have antidepressant-like effects in mice, implying that PPARα is a potential antidepressant target.

EXPERIMENTAL APPROACH

We first used various biotechnological methods to evaluate the effects of chronic stress and fluoxetine on hippocampal PPARα. The viral-mediated genetic approach was then employed to explore whether hippocampal PPARα was an antidepressant target. PPARα inhibitors, PPARα-knockout (KO) mice and PPARα-knockdown (KD) mice were further used to determine the role of PPARα in the antidepressant effects of fluoxetine.

KEY RESULTS

Chronic stress significantly decreased mRNA and protein levels of PPARα in the hippocampus, but not other regions, and also fully reduced the recruitment of hippocampal PPARα to the cAMP response element-binding (CREB) promoter. Genetic overexpression of hippocampal PPARα induced significant antidepressant-like actions in mice by promoting CREB-mediated biosynthesis of brain-derived neurotrophic factor. Moreover, fluoxetine notably restored the stress-induced negative effects on hippocampal PPARα. Using PPARα antagonists fully blocked the antidepressant effects of fluoxetine in mice, and similarly, both PPARα-KO and PPARα-KD abolished the effects of fluoxetine. Besides, PPARα-KO and PPARα-KD aggravated depression in mice.

CONCLUSIONS AND IMPLICATIONS

Hippocampal PPARα is a potential novel antidepressant target that mediates the antidepressant actions of fluoxetine in mice.

Hippocampal FXR plays a role in the pathogenesis of depression: A preliminary study based on lentiviral gene modulation

As a well-known bile acid receptor, the role of Farnesoid X receptor (FXR) in the digestive system and cardiovascular system has been widely explored. However, there are very few studies involving FXR in the central nervous system. In this study, we explored the role of FXR in the pathogenesis of depression, a serious and worldwide neuropsychiatric disease. It was found that chronic unpredictable mild stress (CUMS) fully enhanced the protein and mRNA expressions of FXR in hippocampus, but not medial prefrontal cortex (mPFC). Overexpression of hippocampal FXR induced notable depressive-like behaviors and decreased expression of brain-derived neurotrophic factor (BDNF) in naïve rats, while knockdown of hippocampal FXR fully prevented the effects of CUMS on rat behaviors and hippocampal BDNF expression. Taken together, our research extends the knowledge of FXR's role in the central nervous system, and may provide a potential and novel therapeutic target for treating depression.

Hippocampal astrocyte atrophy in a mouse depression model induced by corticosterone is reversed by fluoxetine instead of benzodiazepine diazepam

Astrocytes have become promising new agents against major depressive disorders (MDD) primarily due to the crucial role they play in the pathogenesis of such disorders. However, a simple and reliable animal model that can be used to screen for astrocyte-targeting antidepressants has not yet been developed. In this study, we utilized a repeated corticosterone (CORT) injection paradigm to develop a mouse depression model wherein we examined the occurrence of alterations in hippocampal astrocyte population by using two astrocytic markers, namely, glial fibrillary acidic protein (GFAP) and S100β. Moreover, we determined the effects of fluoxetine and diazepam on CORT-induced astrocytic alterations to assess the predictive validity. Results showed that repeated CORT injections showed no effects on the number of GFAP⁺ and S100β⁺ astrocytes, but they decreased the protrusion length of GFAP⁺ astrocytes and GFAP protein expression in the hippocampus. Furthermore, repeated CORT injections produced a sustained increase of S100β protein levels in the entire hippocampus of male mice. CORT-induced hippocampal astrocyte disruption was antagonized by chronic fluoxetine treatment. By contrast, the anxiolytic drug diazepam was ineffective in the same experimental setting. All these findings suggest that the repeated CORT injection paradigm produces the astrocytic alterations similar to those in MDD and can serve as a useful mouse model to screen antidepressants meant to target astrocytes. These observations can also help in further discussing the underlying mechanisms of CORT-induced astrocytic alterations.

Antidepressant-like actions by silencing of neuronal ELAV-like RNA-binding proteins HuB and HuC in a model of depression in male mice

Currently available antidepressant drugs often fail to achieve full remission and patients might evolve to treatment resistance, showing the need to achieve a better therapy of depressive disorders. Increasing evidence supports that post-transcriptional regulation of gene expression is important in neuronal development and survival and a relevant role is played by RNA binding proteins (RBP). To explore new therapeutic strategies, we investigated the role of the neuron-specific ELAV-like RBP (HuB, HuC, HuD) in a mouse model of depression. In this study, a 4-week unpredictable chronic mild stress (UCMS) protocol was applied to mice to induce a depressive-like phenotype. In the last 2 weeks of the UCMS regimen, silencing of HuB, HuC or HuD was performed by using specific antisense oligonucleotides (aODN). Treatment of UCMS-exposed mice with anti-HuB and anti-HuC aODN improved both anhedonia and behavioural despair, used as measures of depressive-like behaviour, without modifying the response of stressed mice to an anxiety-inducing environment. On the contrary, HuD silencing promoted an anxiolytic-like behaviour in UCMS-exposed mice without improving depressive-like behaviours. The antidepressant-like phenotype of anti-HuB and anti-HuC mice was not shown concurrently with the promotion of adult hippocampal neurogenesis in the dentate gyrus, and no increase in the BDNF and CREB content was detected. Conversely, in the CA3 hippocampal region, projection area of newly born neurons, HuB and HuC silencing increased the number of BrdU/NeuN positive cells. These results give the first indication of a role of nELAV in the modulation of emotional states in a mouse model of depression.

Antidepressant effects of aqueous extract of saffron and its effects on CREB, P-CREB, BDNF, and VGF proteins in rat cerebellum

Objective

The role of BDNF (brain-derived neurotrophic factor), CREB (cAMP response element binding) and VGF neuropeptide has been proved in antidepressant activity of long term saffron administration in the rat hippocampus. In this study we evaluated the role of these proteins in antidepressant activity of saffron in long term administration in the rat cerebellum.

Methods

Saffron aqueous extract (40 and 80 mg/kg/day) and imipramine (10 mg/kg/day) were administered intraperitoneally for 21 days to rats. At the end of experiment, animals were sacrificed and cerebellums were separated. The protein levels of BDNF, VGF, CREB and P- CREB in the rat cerebellum were evaluated using western blot analysis.

Results

Saffron aqueous extract (80mg/kg/day) caused significant increase in protein level of P-CREB in long term treatment in the rat cerebellum. The increases in the protein levels of VGF, CREB and BDNF were not significant.

Conclusion

In summary, our results showed that antidepressant effect of saffron in rat cerebellum might be due to the enhanced phosphorylation of CREB.

Impact of anger emotional stress before pregnancy on adult male offspring

Previous studies have reported that maternal chronic stress or depression is linked to an increased risk of affective disorders in progeny. However, the impact of maternal chronic stress before pregnancy on the progeny of animal models is unknown. We investigated the behaviors and the neurobiology of 60-day-old male offspring of female rats subjected to 21 days of resident-intruder stress before pregnancy. An anger stressed parental rat model was established using the resident-intruder paradigm and it was evaluated using behavioral tests. Anger stressed maternal rats showed a significant increase in locomotion and aggression but a reduction in sucrose preference. Offspring subjected to pre-gestational anger stress displayed enhanced aggressive behaviors, reduced anxiety, and sucrose preference. Further, offspring subjected to pre-gestational stress showed significant impairments in the recognition index (RI) on the object recognition test and the number of platform crossings in the Morris water maze test. The monoaminergic system was significantly altered in pre-gestationally stressed offspring, and the expression of phosphorylated cyclic adenosine monophosphate response element binding protein (P-CREB), brain-derived neurotrophic factor (BDNF), and serotonin transporter (SERT) levels in pre-gestational stressed offspring were altered in some brain regions. Fluoxetine was used to treat pre-gestational stressed maternal rats and it significantly reduced the changes caused by stress, as evidenced by both behaviors and neural biochemical indexes in the offspring in some but not all cases. These findings suggest that anger stress before pregnancy could induce aggressive behaviors, cognitive deficits, and neurobiological alterations in offspring.

Transgenic mice lacking CREB and CREM in noradrenergic and serotonergic neurons respond differently to common antidepressants on tail suspension test

Evidence exists that chronic antidepressant therapy enhances CREB levels and activity. Nevertheless, the data are not conclusive, as previous analysis of transgenic mouse models has suggested that CREB inactivation in fact contributes to antidepressant-like behavior. The aim of this study was to evaluate the role of CREB in this context by exploiting novel transgenic mouse models, characterized by selective ablation of CREB restricted to noradrenergic (Creb1^DBHCre/Crem−/−) or serotonergic (Creb1^TPH2CreERT2/Crem−/−) neurons in a CREM-deficient background to avoid possible compensatory effects of CREM. Selective and functional ablation of CREB affected antidepressant-like behavior in a tail suspension test (TST) after antidepressant treatment. Contrary to single Creb1^DBHCre mutants, Creb1^DBHCre/Crem−/− mice did not respond to acute desipramine administration (20 mg/kg) on the TST. On the other hand, single Creb1^TPH2CreERT2 mutants displayed reduced responses to fluoxetine (10 mg/kg) on the TST, while the effects in Creb1^TPH2CreERT2/Crem−/− mice differed by gender. Our results provide further evidence for the important role of CREM as a compensatory factor. Additionally, the results indicate that new models based on the functional ablation of CREB in select neuronal populations may represent a valuable tool for investigating the role of CREB in the mechanism of antidepressant therapy.

The effect of maternal forced exercise on offspring pain perception, motor activity and anxiety disorder: the role of 5-HT2 and D2 receptors and CREB gene expression

The effect of maternal forced exercise on central disorders in offsprings has been shown but the mechanism is still unclear. In this study, the role of 5-HT2 and D2 receptors in neuroprotective effects of maternal forced exercise on offspring neurodevelopment and neurobehavioral symptoms is evaluated. Sixty pregnant rats were trained by forced exercise and some behavioral and molecular aspects in their offspring were evaluated in presence of 5-HT2 and D2 receptors agonists and antagonists. The results showed that maternal forced exercise causes increase of pain tolerability and increase latency of pain perception in offspring in hot plate test, writhing test and tail flick test. Also maternal forced exercise causes decrease of depression and anxiety like behavior in offsprings. On the other hand, treatment of mothers by forced exercise in combination with 5-HT2 and D2 receptor antagonists inhibited the protective effects of forced exercise and cause disturbance in pain perception and tolerability and increase depression and anxiety in offsprings. Also expression of cyclic AMP response element binding protein (CREB) was changed in all experimental groups. In conclusion, our data suggested that maternal forced exercise causes neurobehavioral protective effect on offsprings and this effect might probably be mediated by 5-HT2 and D2 receptors and activation of CREB gene expression.

Nutrients, neurogenesis and brain ageing: From disease mechanisms to therapeutic opportunities

Appreciation of the physiological relevance of mammalian adult neurogenesis has in recent years rapidly expanded from a phenomenon of homeostatic cell replacement and brain repair to the current view of a complex process involved in high order cognitive functions. In parallel, an array of endogenous or exogenous triggers of neurogenesis has also been identified, among which metabolic and nutritional cues have drawn significant attention. Converging evidence from animal and in vitro studies points to nutrient sensing and energy metabolism as major physiological determinants of neural stem cell fate, and modulators of the whole neurogenic process. While the cellular and molecular circuitries underlying metabolic regulation of neurogenesis are still incompletely understood, the key role of mitochondrial activity and dynamics, and the importance of autophagy have begun to be fully appreciated; moreover, nutrient-sensitive pathways and transducers such as the insulin-IGF cascade, the AMPK/mTOR axis and the transcription regulators CREB and Sirt-1 have been included, beside more established "developmental" signals like Notch and Wnt, in the molecular networks that dictate neural-stem-cell self-renewal, migration and differentiation in response to local and systemic inputs. Many of these nutrient-related cascades are deregulated in the contest of metabolic diseases and in ageing, and may contribute to impaired neurogenesis and thus to cognition defects observed in these conditions. Importantly, accumulating knowledge on the metabolic control of neurogenesis provides a theoretical framework for the trial of new or repurposed drugs capable of interfering with nutrient sensing as enhancers of neurogenesis in the context of neurodegeneration and brain senescence.

Piper sarmentosum Roxb. produces antidepressant-like effects in rodents, associated with activation of the CREB-BDNF-ERK signaling pathway and reversal of HPA axis hyperactivity

ETHNOPHARMACOLOGICAL RELEVANCE

There are many plants of genus Piper which have been reported to induce antidepressant-like effects, Piper sarmentosum (PS) is one of them. PS is a Chinese herbal medicine and a traditional edible vegetable.

MATERIALS AND METHODS

In the present study, the antidepressant-like effects of PS extracts and the ethyl acetate fraction of PS extracts (PSY) were assessed using the open field test (OFT), forced swimming test (FST), and tail suspension test (TST) in mice. Furthermore, we applied a 4 consecutive weeks of chronic unpredictable mild stress (CUMS) as a model of depression in rats, followed by a sucrose preference test. Then we examined the possible mechanisms of this action. The activity of the hypothalamic-pituitary-adrenal (HPA) axis was evaluated by detecting the serum corticosterone (CORT) concentrations, and the protein expression levels of brain-derived neurotrophic factor (BDNF), the phosphorylated form CREB and ERK1/2 were detected by qRT-PCR or Western blot.

RESULTS

The results showed that PS extracts (100, 200mg/kg) and PSY (12.5, 25, 50mg/kg) treatment produced antidepressant-like effects in mice similar to fluoxetine (20mg/kg), indicated by the reduced immobility time in the FST and TST, while both had no influence on the locomotor activity in the OFT. PSY treatment significantly increased sucrose preference and reduced serum CORT levels in CUMS rats. Moreover, PSY up-regulated BDNF protein levels, and increased CREB and ERK phosphorylation levels in the hippocampus on CUMS rats.

CONCLUSIONS

These findings suggest that the antidepressant-like effects of PS extracts and PSY are mediated, at least in part, by modulating HPA axis, BDNF, CREB and ERK phosphorylation and expression in the hippocampus.

Z-Guggulsterone Produces Antidepressant-Like Effects in Mice through Activation of the BDNF Signaling Pathway

BACKGROUND

Z-guggulsterone, an active compound extracted from the gum resin of the tree Commiphora mukul, has been shown to improve animal memory deficits via activating the brain-derived neurotrophic factor signaling pathway. Here, we investigated the antidepressant-like effect of Z-guggulsterone in a chronic unpredictable stress mouse model of depression.

METHODS

The effects of Z-guggulsterone were assessed in mice with the tail suspension test and forced swimming test. Z-guggulsterone was also investigated in the chronic unpredictable stress model of depression with fluoxetine as the positive control. Changes in hippocampal neurogenesis as well as the brain-derived neurotrophic factor signaling pathway after chronic unpredictable stress/Z-guggulsterone treatment were investigated. The tryptophan hydroxylase inhibitor and the tyrosine kinase B inhibitor were also used to explore the antidepressant-like mechanisms of Z-guggulsterone.

RESULTS

Z-guggulsterone (10, 30 mg/kg) administration protected the mice against the chronic unpredictable stress-induced increases in the immobile time in the tail suspension test and forced swimming test and also reversed the reduction in sucrose intake in sucrose preference experiment. Z-guggulsterone (10, 30 mg/kg) administration prevented the reductions in brain-derived neurotrophic factor protein expression levels as well as the phosphorylation levels of cAMP response element binding protein, extracellular signal-regulated kinase 1/2, and protein kinase B in the hippocampus and cortex induced by chronic unpredictable stress. Z-guggulsterone (10, 30 mg/kg) treatment also improved hippocampal neurogenesis in chronic unpredictable stress-treated mice. Blockade of the brain-derived neurotrophic factor signal, but not the monoaminergic system, attenuated the antidepressant-like effects of Z-guggulsterone.

CONCLUSIONS

Z-guggulsterone exhibits antidepressant activity via activation of the brain-derived neurotrophic factor signaling pathway and upregulation of hippocampal neurogenesis.

Biological hypotheses and biomarkers of bipolar disorder

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