Novel therapeutic approaches beyond the serotonin receptor

Traditional Chinese herbal formula, Fuzi-Lizhong pill, produces antidepressant-like effects in chronic restraint stress mice through systemic pharmacology

ETHNOPHARMACOLOGICAL RELEVANCE

Fuzi-Lizhong pill (FLP) is a well-validated traditional Chinese medicine (TCM) formula that has long been used in China for gastrointestinal disease and adjunctive therapy for depression. In our previous study, we reported that the principal herb of FLP, Aconitum carmichaelii Debx. (Fuzi), exhibits antidepressant-like effects. However, there have been no reports on whether FLP produces antidepressant-like effects and its potential molecular mechanisms.

AIM OF THE STUDY

We aim to demonstrate the antidepressant-like effects of FLP in chronic restraint stress (CRS) mice and to explore the associated molecular mechanisms.

MATERIALS AND METHODS

The active components and probable molecular targets of FLP, as well as the targets related to depression, were identified through network pharmacology. A protein-protein interaction (PPI) network was generated using the overlapping targets, followed by the visualization as well as identification of the core targets associated with the antidepressant-like action of FLP. Subsequently, KEGG and GO enrichment analyses were conducted. UHPLC-MS/MS was employed to further detect the active compounds in FLP. Molecular docking was applied to assess the connections between the active components as well as the core targets. The efficacy of FLP in treating depression and its molecular mechanisms were examined using western blotting, ELISA, 16S rRNA sequencing, HE staining, Nissl staining, and Golgi-Cox staining in a CRS-induced mouse model.

RESULTS

Network pharmacology and UHPLC-MS/MS analyses indicated that the active compounds of FLP comprised taraxerol, songorine, neokadsuranic acid B, ginkgetin, hispaglabridin B, quercetin, benzoylmesaconine and liquiritin. KEGG pathway analysis implicated that the PI3K/Akt/mTOR as well as MAPK signaling pathways are closely related to the therapeutic effects of FLP on depression. Molecular docking analysis demonstrated that the main components of FLP bind to PI3K, AKT, mTOR, BDNF and MAPK. FLP significantly decreased immobility in mice that were elevated by CRS in the FST and the TST. FLP also significantly increased sucrose preference in mice after CRS in the SPT. FLP upregulated proteins associated with BDNF-TrkB and PI3K/Akt/mTOR signaling and downregulated proteins associated with MAPK signaling. Serum levels of CORT, IL-6, IL-1β, and TNF-α in CRS mice were significantly decreased following treatment with FLP. In addition, FLP ameliorated CRS-induced gut microbiota dysbiosis as demonstrated by 16S rRNA sequencing analysis. FLP ameliorated CRS-induced intestinal inflammation and neuronal damage. Finally, antidepressant-like effects and concomitant increases in dendritic spine density induced by FLP administration were also reduced after rapamycin treatment.

CONCLUSION

These results demonstrate that FLP has antidepressant-like effects in mice exposed to CRS that involve activation of the PI3K/Akt/mTOR signaling pathway, increase in spinogenesis, inhibition of the MAPK signaling pathway, decrease in inflammation, and amelioration of gut microbiota dysbiosis. These findings provide novel evidence for the clinical application of FLP on depression.

Enhancing Fear Extinction: Pharmacological Approaches

Extinction is the process by which the memory of a learned conditioned association decreases over time and with introduction of new associations. It is a vital part of fear learning, and it is critical to recovery in multiple fear-related disorders, including Specific and Social Phobias, Panic Disorder, Obsessive Compulsive Disorder (OCD), and Posttraumatic Stress Disorder (PTSD). The process of extinction is also the underlying mechanism for recovery in gold-standard therapies for PTSD, including prolonged exposure, cognitive processing therapy, eye movement desensitization and procession, as well as other empirically-based paradigms. Pharmacological modulators of extinction are thus promising targets for treatment of fear-related disorders. We focus here on emerging psychopharmacological treatments to facilitate extinction: D-cycloserine, scopolamine, losartan, ketamine, and 3,4-methylenedioxymethamphetamine. We also provide an overview of recent advances in molecular pathways that show promise as targets for extincion and inhibitory learning, including pathways related to cannabinoid, brain-derived neurotrophic factor, hypothalamic-pituitary-adrenal signaling, and promising work in neurosteroid compounds.

New Avenues for the Treatment of Huntington's Disease

Huntington’s disease (HD) is a neurodegenerative disorder caused by a CAG expansion in the HD gene. The disease is characterized by neurodegeneration, particularly in the striatum and cortex. The first symptoms usually appear in mid-life and include cognitive deficits and motor disturbances that progress over time. Despite being a genetic disorder with a known cause, several mechanisms are thought to contribute to neurodegeneration in HD, and numerous pre-clinical and clinical studies have been conducted and are currently underway to test the efficacy of therapeutic approaches targeting some of these mechanisms with varying degrees of success. Although current clinical trials may lead to the identification or refinement of treatments that are likely to improve the quality of life of those living with HD, major efforts continue to be invested at the pre-clinical level, with numerous studies testing novel approaches that show promise as disease-modifying strategies. This review offers a detailed overview of the currently approved treatment options for HD and the clinical trials for this neurodegenerative disorder that are underway and concludes by discussing potential disease-modifying treatments that have shown promise in pre-clinical studies, including increasing neurotropic support, modulating autophagy, epigenetic and genetic manipulations, and the use of nanocarriers and stem cells.

Ketamine and the Future of Rapid-Acting Antidepressants

The therapeutic onset of traditional antidepressants is delayed by several weeks and many depressed patients fail to respond to treatment altogether. In contrast, subanesthetic ketamine can rapidly alleviate symptoms of depression within hours of a single administration, even in patients who are considered treatment-resistant. Ketamine is thought to exert these effects by restoring the integrity of neural circuits that are compromised in depression. This hypothesis stems in part from preclinical observations that ketamine can strengthen synaptic connections by increasing glutamate-mediated neurotransmission and promoting rapid neurotrophic factor release. An improved understanding of how ketamine, and other novel rapid-acting antidepressants, give rise to these processes will help foster future therapeutic innovation. Here, we review the history of antidepressant treatment advances that preceded the ketamine discovery, critically examine mechanistic hypotheses for how ketamine may exert its antidepressant effects, and discuss the impact this knowledge has had on ongoing drug discovery efforts.

Serotonergic Drugs Inhibit Chikungunya Virus Infection at Different Stages of the Cell Entry Pathway

Chikungunya virus (CHIKV) is an important reemerging human pathogen transmitted by mosquitoes. The virus causes an acute febrile illness, chikungunya fever, which is characterized by headache, rash, and debilitating (poly)arthralgia that can reside for months to years after infection. Currently, effective antiviral therapies and vaccines are lacking. Due to the high morbidity and economic burden in the countries affected by CHIKV, there is a strong need for new strategies to inhibit CHIKV replication. The serotonergic drug 5-nonyloxytryptamine (5-NT) was previously identified as a potential host-directed inhibitor for CHIKV infection. In this study, we determined the mechanism of action by which the serotonin receptor agonist 5-NT controls CHIKV infection. Using time-of-addition and entry bypass assays, we found that 5-NT predominantly inhibits CHIKV in the early phases of the replication cycle, at a step prior to RNA translation and genome replication. Intriguingly, however, no effect was seen during virus-cell binding, internalization, membrane fusion and genomic RNA (gRNA) release into the cell cytosol. In addition, we show that the serotonin receptor antagonist methiothepin mesylate (MM) also has antiviral properties toward CHIKV and specifically interferes with the cell entry process and/or membrane fusion. Taken together, pharmacological targeting of 5-HT receptors may represent a potent way to limit viral spread and disease severity.IMPORTANCE The rapid spread of mosquito-borne viral diseases in humans puts a huge economic burden on developing countries. For many of these infections, including those caused by chikungunya virus (CHIKV), there are no specific treatment possibilities to alleviate disease symptoms. Understanding the virus-host interactions that are involved in the viral replication cycle is imperative for the rational design of therapeutic strategies. In this study, we discovered an antiviral compound, elucidated its mechanism of action, and propose serotonergic drugs as potential host-directed antivirals for CHIKV.

Effects of Acupuncture on Alzheimer's Disease: Evidence from Neuroimaging Studies

As the worldwide population ages, the prevalence of Alzheimer's disease (AD) increases. However, the results of promising medications have been unsatisfactory. Chinese acupuncture has a long history of treating dementia, but lack of evidence from well-designed randomized controlled trials that validate its efficacy and safety, as well as its lack of clear underlying mechanisms, contribute to its limited application in clinical practice. In recent years, brain imaging technologies, such as functional magnetic resonance imaging and positron emission tomography, have been used to assess brain responses to acupuncture in a dynamic, visual, and objective way. These techniques are frequently used to explore neurological mechanisms of responses to acupuncture in AD and provide neuroimaging evidence as well as starting points to elucidate the possible mechanisms. This review summarizes the existing brain imaging evidence that explains the effects of acupuncture for AD and analyzes brain responses to acupuncture at cognitive-related acupoints [Baihui (GV 20), Shenmen (HT 7), Zusanli (ST 36), Neiguan (PC 6), and Taixi (KI 3)] from perspectives of acupoint specificity and acupoint combinations. Key issues and directions to consider in future studies are also put forward. This review should deepen our understanding of how brain imaging studies can be used to explore the underlying mechanisms of acupuncture in AD.

Maprotiline inhibits COX2 and iNOS gene expression in lipopolysaccharide-stimulated U937 macrophages and carrageenan-induced paw edema in rats

Maprotiline, a tetracyclic antidepressant, is used for the management of mental disorders and various types of chronic pain. In our previous work, we found the inhibitory effect of maprotiline on inflammatory mediator’s expression like tumor necrosis factor α (TNF-α and interleukin 1β (IL-1β. As part of that study, we sought to evaluate the effect of maprotiline on the expression of some inflammatory mediators such as cyclooxygenases 2 (COX2) and inducible nitric oxide synthase (iNOS). For this reason we used an in vitro model system of lipopolysaccharide (LPS)-stimulated human U937 macrophages and also an in vivo model of carrageenan-induced paw edema in rats. We measured the expression of these genes by quantitative RT-real time PCR. The expression of COX2 and iNOS significantly decreased by maprotiline in U937 macrophages and carrageenan-induced paw inflammation in rats. Our finding also confirmed that intraperitoneal (i.p.) injection of maprotiline inhibited carrageenan-induced paw edema. Moreover, maprotiline significantly decreased the migration of polymorphonuclear (PMN) leukocytes to the site of inflammation. The results of the present study provide further evidence for the anti-inflammatory effect of maprotiline. This effect appears to be mediated by down regulation of inflammatory genes. Further studies are needed to evaluate the complex cellular and molecular mechanisms of maprotiline.

Evaluation of the Effect of Antidepressant Drug, Fluvoxamine, on Cyclooxygenase-2 Protein Expression in Lipopolysaccharide-stimulated Macrophages

Background:

Fluvoxamine, a well-known selective serotonin reuptake inhibitor, is used for the management of mental disorders and various types of chronic pain. In our previous study, we found the inhibitory effect of fluvoxamine on inflammatory mediator‘s expression. In the line of the indicated study, we sought to evaluate the effect of fluvoxamine on the expression of some inflammatory mediators such as cyclooxygenase-2 (COX-2).

Materials and Methods:

An in vitro model system of lipopolysaccharide-stimulated human U937 macrophages was used. The expression of COX-2 protein was measured by flow cytometry.

Results:

The expression of COX-2 significantly decreased by fluvoxamine in U937 macrophages.

Conclusion:

The results of the present study provide further evidence for the anti-inflammatory effect of fluvoxamine. This effect appears to be mediated by the downregulation of inflammatory genes. Further studies are needed to evaluate the complex cellular and molecular mechanisms of fluvoxamine.

Anti-Depressant Fluoxetine Reveals its Therapeutic Effect Via Astrocytes

Although psychotropic drugs act on neurons and glial cells, how glia respond, and whether glial responses are involved in therapeutic effects are poorly understood. Here, we show that fluoxetine (FLX), an anti-depressant, mediates its anti-depressive effect by increasing the gliotransmission of ATP. FLX increased ATP exocytosis via vesicular nucleotide transporter (VNUT). FLX-induced anti-depressive behavior was decreased in astrocyte-selective VNUT-knockout mice or when VNUT was deleted in mice, but it was increased when astrocyte-selective VNUT was overexpressed in mice. This suggests that VNUT-dependent astrocytic ATP exocytosis has a critical role in the therapeutic effect of FLX. Released ATP and its metabolite adenosine act on P2Y₁₁ and adenosine A2b receptors expressed by astrocytes, causing an increase in brain-derived neurotrophic factor in astrocytes. These findings suggest that in addition to neurons, FLX acts on astrocytes and mediates its therapeutic effects by increasing ATP gliotransmission.

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Anti-depressant FLX acts on astrocytes and increases VNUT-dependent ATP exocytosis.

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Such astrocytic responses are responsible for the FLX-induced therapeutic effects.

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Astrocytic ATP and its metabolite adenosine increase BDNF in astrocytes, and reveal the therapeutic effects.

Kinoshita et al. demonstrated that astrocytes are a therapeutic target of the antidepressant, fluoxetine (FLX). They found that FLX stimulates VNUT-dependent ATP release from astrocytes leading to a BDNF-mediated anti-depressive effect. This study demonstrated the astrocytic regulation of this anti-depressive effect, which complements the previously described conventional mechanism of FLX. Because the involvement of astrocytes in the pathogenesis of depression is of current interest, this new insight into the role of astrocytes in anti-depressive effects should support the establishment of novel therapeutic strategies for depression.

Effect of Fluoxetine on the Hippocampus of Wistar Albino Rats in Cold Restraint Stress Model

INTRODUCTION

Stress has been known to be a potential modulator of learning and memory. Long term stress can lead to depression. Fluoxetine is a selective serotonin reuptake inhibitor group of drug used in the treatment of depression.

AIM

The present study was conducted to evaluate the potential of Fluoxetine on cold restraint induced stress in the hippocampus of Wistar rats.

MATERIALS AND METHODS

A total of 18 male wistar albino rats were divided randomly into three groups (n=6). Group 1 was the control group which were kept in normal laboratory conditions. Group 2 was the negative control group which were given cold restraint stress for period of four weeks. Group 3 was the experimental group, where the animals were pretreated with fluoxetine 10 mg/kg for a period of one week followed by cold restraint stress for 30 minutes and cotreated with fluoxetine 10 mg/kg for a period of four weeks. The whole study was done for a period of five weeks followed by behavioural studies and subsequently sacrificed with removal of brain for various histological, Immunohistochemical (IHC), neurochemical and antioxidant analysis. The values were expressed as Mean±SEM. One-way analysis of variance followed by Tukey's multiple comparisons test was used for the comparison of means. A probability of 0.05 and less was taken as statistically significant using Prism Graphpad software version 6.01.

RESULTS

The results show there was significant improvement in the Morris water maze test after treatment with fluoxetine in Group 2. Similar results were also noted in the levels of neurotransmitters and antioxidant levels in brain and also in the number of cells counted in IHC and histological studies by H&E when Group 3 was compared with Group 2. The treatment reversed the damage in Group 2 which was comparable with the control group.

CONCLUSION

The results revealed that administration of fluoxetine 10 mg/kg given orally has a potential antistressor effect by improving the neurogenic and neuroprotective effect on the cold restraint stress induced hippocampal damage.

Human cells involved in atherosclerosis have a sex

The influence of sex has been largely described in cardiovascular diseases. Atherosclerosis is a complex process that involves many cell types such as vessel cells, immune cells and endothelial progenitor cells; however, many, if not all, studies do not report the sex of the cells. This review focuses on sex differences in human cells involved in the atherosclerotic process, emphasizing the role of sex hormones. Furthermore, we report sex differences and issues related to the processes that determine the fate of the cells such as apoptotic and autophagic mechanisms. The analysis of the data reveals that there are still many gaps in our knowledge regarding sex influences in atherosclerosis, largely for the cell types that have not been well studied, stressing the urgent need for a clear definition of experimental conditions and the inclusion of both sexes in preclinical studies.

Gender differences in platelet brain derived neurotrophic factor in patients with cardiovascular disease and depression

Women have a higher prevalence of depression compared to men. Serum levels of Brain-derived neurotrophic factor (BDNF) are decreased in depression. BDNF may also have a protective role in the pathogenesis of coronary artery disease (CAD) or events. We examined whether there are gender differences in BDNF levels in patients with stable CAD and comorbid depression. We enrolled 37 patients (17 women) with stable CAD with and without depression from a single medical center. All patients had depression assessment with the Beck Depression Inventory-II questionnaire. Both plasma and platelet BDNF were measured in all patients using a standard ELISA method. Platelet BDNF levels were higher than plasma BDNF levels in the entire group (5903.9 ± 1915.6 vs 848.5 ± 460.5 pg/ml, p < 0.001). Women had higher platelet BDNF levels than men (6954.2 ± 1685.6 vs. 5011.2 ± 1653.5 pg/ml, p < 0.001). Women without depression (BDI-II < 5, n = 8) had higher platelet BDNF than men without depression (n = 8, 7382.8 ± 1633.1 vs 4811.7 ± 1642.3 pg/ml, p = 0.007). Women with no or minimal depression (BDI < 14, n = 14) had higher platelet BDNF levels than men with no or minimal depression (n = 18, 6900.2 ± 1486.6 vs 4972.9 ± 1568.9 pg/ml, p = 0.001). The plasma BDNF levels were similar between men and women in all categories of depression. In conclusion, women with stable CAD have increased platelet BDNF levels when compared to men with stable CAD regardless of their level of depression. Sex specific differences in BDNF could possibly indicate differences in factors linking platelet activation and depression in men and women.

Alterations in leukocyte transcriptional control pathway activity associated with major depressive disorder and antidepressant treatment

Major depressive disorder (MDD) is associated with a significantly elevated risk of developing serious medical illnesses such as cardiovascular disease, immune impairments, infection, dementia and premature death. Previous work has demonstrated immune dysregulation in subjects with MDD. Using genome-wide transcriptional profiling and promoter-based bioinformatic strategies, we assessed leukocyte transcription factor (TF) activity in leukocytes from 20 unmedicated MDD subjects versus 20 age-, sex- and ethnicity-matched healthy controls, before initiation of antidepressant therapy, and in 17 of the MDD subjects after 8 weeks of sertraline treatment. In leukocytes from unmedicated MDD subjects, bioinformatic analysis of transcription control pathway activity indicated an increased transcriptional activity of cAMP response element-binding/activating TF (CREB/ATF) and increased activity of TFs associated with cellular responses to oxidative stress (nuclear factor erythroid-derived 2-like 2, NFE2l2 or NRF2). Eight weeks of antidepressant therapy was associated with significant reductions in Hamilton Depression Rating Scale scores and reduced activity of NRF2, but not in CREB/ATF activity. Several other transcriptional regulation pathways, including the glucocorticoid receptor (GR), nuclear factor kappa-B cells (NF-κB), early growth response proteins 1-4 (EGR1-4) and interferon-responsive TFs, showed either no significant differences as a function of disease or treatment, or activities that were opposite to those previously hypothesized to be involved in the etiology of MDD or effective treatment. Our results suggest that CREB/ATF and NRF2 signaling may contribute to MDD by activating immune cell transcriptome dynamics that ultimately influence central nervous system (CNS) motivational and affective processes via circulating mediators.

The role of GSK-3 in treatment-resistant depression and links with the pharmacological effects of lithium and ketamine: A review of the literature

BACKGROUND

Since the discovery of antidepressants, new treatments have emerged with fewer side effects but no greater efficacy. Glycogen synthase kinase 3 β (GSK-3β), a kinase known for its activity on glycogen synthesis, has in the last few years raised growing interest in biological psychiatry. Several efficient treatments in major depression have an inhibitory effect on this kinase, which could be targeted in new mood disorder treatments.

METHODS

The aim of this review is to summarize findings concerning the intracellular pharmacologic effects of GSK-3β inhibitors on mood. After a brief description of the intracellular transduction pathways implicated in both GSK-3β and mood disorders, we reviewed the results demonstrating GSK-3β involvement in the effects of lithium and ketamine.

RESULTS

GSK-3β can be inhibited through several mechanisms such as serine phosphorylation or binding in a proteic scaffold and others. Its inhibition is implicated in numerous cellular pathways of interest involved in neuronal growth and architecture, cell survival, neurogenesis or synaptic plasticity. This inhibition appears to be both efficient and sufficient in improving mood in animal models. In human beings, several levels of evidence show GSK-3β inhibition with antidepressant use. Crucially, strong inhibition has been shown with lithium via the proteic scaffold PP2A/β-arrestin/AKT, and with the rapid antidepressant effect of ketamine via p70S6K.

CONCLUSION

Our review focuses on mechanisms whereby the GSK-3β pathway has a part in the antidepressant effect of lithium and ketamine. This article highlights the importance of translational research from cell and animal models to the clinical setting in order to develop innovative therapeutic targets.

Integrating the monoamine, neurotrophin and cytokine hypotheses of depression--a central role for the serotonin transporter?

Monoamine, in particular serotonergic neurotransmission has long been recognized as an important factor in the aetiology of depression. The serotonin transporter (SERT) is the primary regulator of serotonin levels in the brain and a key target for widely used antidepressant drugs, such as selective serotonin reuptake inhibitors (SSRIs). In realising the limitations of current antidepressant therapy, depression research has branched out to encompass other areas such as synaptic plasticity, neurogenesis and brain structural remodelling as factors which influence mood and behaviour. More recently, the immune system has been implicated in the development of depression and various intriguing observations have inspired the cytokine hypothesis of depression. Over the past two decades evidence of in vitro and in vivo regulation of SERT function by pro-inflammatory cytokines as well as by mechanisms of synaptic plasticity has been accumulating, offering a mechanistic link between the monoamine, neurotrophin and cytokine theories of depression. This review will focus firstly on the interconnected roles of serotonin and neurotrophins in depression and antidepressant therapy, secondly on the impact of the immune system on serotonin transporter regulation and neurotrophin signalling and finally we propose a model of reciprocal regulation of serotonin and neurotrophin signalling in the context of inflammation-induced depression.

Neuroimmunomodulation in depression: a review of inflammatory cytokines involved in this process

Depression is a debilitating mental disease that affects a large number of people globally; however the pathophysiological mechanisms of this disease remain incompletely understood. Some studies have shown that depression is associated with inflammatory activity, and the mode of action of several antidepressants appears to involve immunomodulation. In this case, the induction of a pro-inflammatory state in healthy or depressive subjects induces a 'sickness behaviour' resembling depressive symptomatology. Potential mechanisms of pro-inflammatory cytokines are effects on monoamine levels, disruption of the hypothalamic-pituitary-adrenal axis, activation of the pathological microglial cells, such as the macrophages and alterations in neuroplasticity and brain functions. Thus, this review will highlight the role of inflammation in depression, the possible mechanisms involved, and also explore effective treatments that act on the immune system.

Genotype variant associated with add-on memantine in bipolar II disorder

Memantine is a non-competitive N-methyl-d-asparate (NMDA) receptor antagonist with a mood-stabilizing effect. We investigated whether using valproic acid (VPA) plus add-on memantine to treat bipolar II disorder (BP-II) is more effective than using VPA alone (VPA + Pbo). We also evaluated, in BP-II patients, the association between the brain-derived neurotrophic factor (BDNF) Val66Met polymorphism with treatment response to VPA + add-on memantine and to VPA + Pbo. In this randomized, double-blind, controlled 12 wk study, BP-II patients undergoing regular VPA treatments were randomly assigned to a group: VPA + Memantine (5 mg/day) (n = 115) or VPA + Pbo (n = 117). The Hamilton Depression Rating Scale (HDRS) and Young Mania Rating Scale (YMRS) were used to evaluate clinical response during week 0, 1, 2, 4, 8 and 12. The genotypes of the BDNF Val66Met polymorphisms were determined using polymerase chain reactions plus restriction fragment length polymorphism analysis. To adjust within-subject dependence over repeated assessments, multiple linear regression with generalized estimating equation methods was used to analyze the effects of the BDNF Val66Met polymorphism on the clinical performance of memantine. Both groups showed significantly decreased YMRS and HDRS scores after 12 wk of treatment; the differences between groups were non-significant. When stratified by the BDNF Val66Met genotypes, significantly greater decreases in HDRS scores were found in the VPA + memantine group in patients with the Val Met genotype (p = 0.004). We conclude that the BDNF Val66Met polymorphism influenced responses to add-on memantine by decreasing depressive symptoms in patients with BP-II.

Activation of signaling pathways downstream of the brain-derived neurotrophic factor receptor, TrkB, in the rat brain by vagal nerve stimulation and antidepressant drugs

Vagal nerve stimulation (VNS) has been approved for treatment resistant depression (TRD) by the Food and Drug Administration (FDA) since 2005. However, the cellular and molecular targets responsible for its effects are still not characterized. Previously, chronic administration of VNS to rats was found to phosphorylate tyrosine 515 on TrkB, the neurotrophin receptor, whereas traditional antidepressants did not do this. In the present study, Western blot analysis was used to characterize activation due to phosphorylation in the hippocampus of down-stream pathways linked to specific key tyrosine residues on TrkB (namely Y816 and Y515) after either acute or chronic administration of VNS and traditional antidepressant drugs. Chronic administration of VNS caused phosphorylation of effectors linked to Y 515; namely Akt, ERK and p70S6 kinase, but this was not produced by either desipramine or sertraline. All the treatments, when given chronically, caused phosphorylation of the transcription factor, CREB. Acute administration of all the treatments also caused phosphorylation of PLCγ1 but this was not maintained with chronic treatment. Further research is required to determine what role, if any, activation of down-stream targets of Y515 plays in the behavioural effects of VNS.

Neuronal-glial mechanisms of exercise-evoked stress robustness

Stress robustness by definition, incorporates both stress resistance (organisms endure greater stressor intensity or duration before suffering negative consequences) and stress resilience (organisms recover faster after suffering negative consequences). Factors that influence stress robustness include the nature of the stressor, (i.e., controllability, intensity, chronicity) and features of the organism (i.e., age, genetics, sex, and physical activity status). Here we present a novel hypothesis for how physically active versus sedentary living promotes stress robustness in the face of intense uncontrollable stress. Advances in neurobiology have established microglia as an active player in the regulation of synaptic activity, and recent work has revealed mechanisms for modulating glial function, including cross talk between neurons and glia. This chapter presents supporting evidence that the physical activity status of an organism may modulate stress-evoked neuronal-glial responses by changing the CX3CL1-CX3CR1 axis. Specifically, we propose that sedentary animals respond to an intense acute uncontrollable stressor with excessive serotonin (5-HT) and noradrenergic (NE) activity and/or prolonged down-regulation of the CX3CL1-CX3CR1 axis resulting in activation and proliferation of hippocampal microglia in the absence of pathogenic signals and consequent hippocampal-dependent memory deficits and reduced neurogenesis. In contrast, physically active animals respond to the same stressor with constrained 5-HT and NE activity and rapidly recovering CX3CL1-CX3CR1 axis responses resulting in the quieting of microglia, and protection from negative cognitive and neurobiological effects of stress.

Key regions of the cerebral network are altered after electroacupuncture at the Baihui (GV20) and Yintang acupuncture points in healthy volunteers: an analysis based on resting fcMRI

OBJECTIVE

To identify the key cerebral functional region affected by acupuncture point needling by examining cerebral networks using functional connectivity MRI (fcMRI) and analysing changes in the key regions of these brain networks at different time points after needle removal.

METHODS

Twelve healthy volunteers received 30 min of electroacupuncture (EA) at the Baihui (GV20) and Yintang acupuncture points and then underwent two fMRI scans, one each at 5 and 15 min after needle removal. Related brain networks were analysed centred at different 'seeds', centres which functionally connect the other cerebral regions in an organised network, such as the anterior frontal lobe, anterior cingulate gyrus, parahippocampal gyrus, amygdala, hypothalamus, head of the caudate nucleus and anterior lobe of the cerebellum. Networks were analysed based on the resting cerebral functional connection, and the differences in the activities of the brain networks between the two time points were compared.

RESULTS

At 5 min after needle removal, 12 brain functional regions were involved in organising the network centred at the caudate nucleus 'seed.' This number was greater than the number of related brain networks centred at the other 'seeds'. At 15 min after needle removal, 15 and 14 brain functional regions were involved in organised networks centred at the parahippocampal and hypothalamus 'seeds', respectively; these numbers were greater than the numbers of other related brain networks centred at the other 'seeds'.

CONCLUSIONS

A brain network composed of a large number of cerebral functional regions was found after EA at GV20 and Yintang in healthy volunteers. The key brain 'seed' supporting the largest brain network changed between 5 and 15 min after needle removal.

Ketamine, magnesium and major depression--from pharmacology to pathophysiology and back

The glutamatergic mechanism of antidepressant treatments is now in the center of research to overcome the limitations of monoamine-based approaches. There are several unresolved issues. For the action of the model compound, ketamine, NMDA-receptor block, AMPA-receptor activation and BDNF release appear to be involved in a mechanism, which leads to synaptic sprouting and strengthened synaptic connections. The link to the pathophysiology of depression is not clear. An overlooked connection is the role of magnesium, which acts as physiological NMDA-receptor antagonist: 1. There is overlap between the actions of ketamine with that of high doses of magnesium in animal models, finally leading to synaptic sprouting. 2. Magnesium and ketamine lead to synaptic strengthening, as measured by an increase in slow wave sleep in humans. 3. Pathophysiological mechanisms, which have been identified as risk factors for depression, lead to a reduction of (intracellular) magnesium. These are neuroendocrine changes (increased cortisol and aldosterone) and diabetes mellitus as well as Mg(2+) deficiency. 4. Patients with therapy refractory depression appear to have lower CNS Mg(2+) levels in comparison to health controls. 5. Experimental Mg(2+) depletion leads to depression- and anxiety like behavior in animal models. 6. Ketamine, directly or indirectly via non-NMDA glutamate receptor activation, acts to increase brain Mg(2+) levels. Similar effects have been observed with other classes of antidepressants. 7. Depressed patients with low Mg(2+) levels tend to be therapy refractory. Accordingly, administration of Mg(2+) either alone or in combination with standard antidepressants acts synergistically on depression like behavior in animal models.

CONCLUSION

On the basis of the potential pathophysiological role of Mg(2+)-regulation, it may be possible to predict the action of ketamine and of related compounds based on Mg(2+) levels. Furthermore, screening for compounds to increase neuronal Mg(2+) concentration could be a promising instrument to identify new classes of antidepressants. Overall, any discussion of the glutamatergic system in affective disorders should consider the role of Mg(2+).

Platelets and depression in cardiovascular disease: A brief review of the current literature

Major depression is an independent risk factor for cardiovascular mortality and morbidity. The exact mechanisms linking depression and increased cardiovascular risk remain poorly understood. Several mechanisms have been proposed including increased platelet reactivity. This review focuses on the current literature that examines the platelet hypothesis of depression. To date studies show increased serotonin response, increased platelet serotonin receptor density, decreased serotonin transporter binding, and decreased platelet serotonin levels in individuals with depression. However other studies have shown no change in serotonin uptake. In addition to platelet serotonin specific pathways, other platelet pathways that have shown significant changes in depressed individuals include blunting of the platelet adenosine response, increased platelet thrombin response, increased glycoprotein Ib expression, increased P-selectin, β thromboglobulin, and platelet factor four, as well as decreased platelet brain derived neurotrophic factor. However there are other studies that show conflicting evidence of increased platelet activation as measured by integrin receptor α_2bβ₃. Other conflicting data include α adrenergic density and platelet response to augmented serotonin. The direction of future research in platelet functional changes in depression and coronary artery disease should continue to focus on serotonin specific pathways with emphasis on potential mechanisms of specific pathway changes.

The fibroblast growth factor family: neuromodulation of affective behavior

In this review, we propose a broader view of the role of the fibroblast growth factor (FGF) family in modulating brain function. We suggest that some of the FGF ligands together with the FGF receptors are altered in individuals with affective disorder and modulate emotionality in animal models. Thus, we propose that members of the FGF family may be genetic predisposing factors for anxiety, depression, or substance abuse; that they play a key organizing role during early development but continue to play a central role in neuroplasticity in adulthood; and that they work not only over extended time frames, but also via rapid signaling mechanisms, allowing them to exert an "on-line" influence on behavior. Therefore, the FGF family appears to be a prototype of "switch genes" that are endowed with organizational and modulatory properties across the lifespan, and that may represent molecular candidates as biomarkers and treatment targets for affective and addictive disorders.

Interaction of the DRD3 and BDNF gene variants in subtyped bipolar disorder

OBJECTIVES

Bipolar disorder is a severe mental disorder with prominent genetic etiologic factors. Dopaminergic dysfunction has been implicated in the pathogenesis of bipolar disorder, which suggests that the dopamine D3 receptor gene (DRD3) is a strong candidate gene. The brain-derived neurotrophic factor (BDNF) gene has been implicated in the etiology of bipolar disorder. We examined the association between the BDNF Val66Met and DRD3 Ser9Gly polymorphisms with two subtypes of bipolar disorder: bipolar-I and -II. Because BDNF regulates DRD3 expression (1), we also examined possible interactions between these genes.

METHODS

We recruited 964 participants: 268 with bipolar-I, 436 with bipolar-II, and 260 healthy controls. The genotypes of the BDNF Val66Met and DRD3 Ser9Gly polymorphisms were determined using polymerase chain reactions plus restriction fragment length polymorphism analysis.

RESULTS

Logistic regression analysis showed a significant main effect for the Val/Val genotype of the BDNF Val66Met polymorphism (P=0.020), which predicted bipolar-II patients. Significant interaction effects for the BDNF Val66Met Val/Val genotype and both DRD3 Ser9Gly Ser/Ser and Ser/Gly genotypes were found only in bipolar-II patients (P=0.027 and 0.006, respectively).

CONCLUSION

We provide initial evidence that the BDNF Val66Met and DRD3 Ser9Gly genotypes interact only in bipolar-II disorder and that bipolar-I and bipolar-II may be genetically distinct.

A critical review of the mechanism of action for the selective serotonin reuptake inhibitors: do these drugs possess anti-inflammatory properties and how relevant is this in the treatment of depression?

The selective serotonin reuptake inhibitors (SSRIs) are the most widely prescribed pharmacological treatment for depression. Since their introduction many have considered the primary mechanism by which the SSRIs produced therapeutic improvement in depression is their effect on monoaminergic signalling. In recent years, however, the credibility of the monoamine theory and the therapeutic efficacy of these compounds in the treatment of depression has been extensively criticized. In the current review the legitimacy of these criticisms is critically examined, in many instances the evidence base used to support these criticisms is found to be weak. Nevertheless, the apparent 'failure' of the monoamine theory has been of benefit in motivating research into alternative mechanisms through which the SSRIs may act. Given research demonstrating that depressive symptoms are intimately linked with disturbances in pro-inflammatory signalling, perhaps the most promising discovery has been the realisation that SSRIs posses significant anti-inflammatory properties. These recent findings are discussed and contextualised with respect to the neurogenic, neurotrophic and gluatamatergic effects that these drugs also possess.

COMT and BDNF interacted in bipolar II disorder not comorbid with anxiety disorder

Bipolar disorder (BP), especially bipolar II disorder (BP-II), is highly comorbid with anxiety disorder (AD). Monoaminergic dysfunction has been implicated in the pathogenesis of BP, it may be important to investigate genes such as the catechol-O-methyltransferase (COMT), involved in monoamine metabolism and brain-derived neurotrophic factor (BDNF) genes, modulating the monoamine system. We therefore examined the association of the COMT Val158Met and BDNF Val66Met polymorphisms with BP-II with and without comorbidity of AD, and possible interactions between these genes. Seven hundred and seventy-one participants were recruited: 314 with bipolar-II without AD, 117 with bipolar-II with AD, and 340 healthy controls. The genotypes of the COMT and BDNF polymorphisms were determined using polymerase chain reactions plus restriction fragment length polymorphism analysis. Logistic regression analysis showed a significant effect of the COMT and the BDNF polymorphisms, and a significant interaction effect for the Val/Val genotypes of the BDNF Val66Met polymorphism and the COMsT Val158Met Val/Met and Met/Met genotypes (P=0.007, 0.048) discriminated between BP-II without AD patients and controls. Our findings provide initial evidence that the COMT and BDNF genes interact in bipolar-II without AD. Our findings suggest the involvement of dopaminergic pathway in the pathogenesis of bipolar-II.

Post-stimulation effect of electroacupuncture at Yintang (EX-HN3) and GV20 on cerebral functional regions in healthy volunteers: a resting functional MRI study

Objective The aim of the present work was to observe the activation/deactivation of cerebral functional regions after electroacupuncture (EA) at Yintang (EX-HN3) and GV20 by functional MRI (fMRI). Design A total of 12 healthy volunteers were stimulated by EA at Yintang and GV20 for 30 min. Resting-state fMRI scans were performed before EA, and at 5 and 15 min after needle removal. Statistical parametric mapping was used to preprocess initial data, and regional homogeneity (ReHo) and amplitude of low-frequency fluctuation (ALFF) were analysed. Results ReHo at 5 min post stimulation showed increases in the left temporal lobe and cerebellum and decreases in the left parietal lobe, occipital lobe and right precuneus. At 15 min post stimulation, ReHo showed increases in the left fusiform gyrus; lingual gyrus; middle temporal gyrus; postcentral gyrus; limbic lobe; cingulate gyrus; paracentral lobule; cerebellum, posterior lobe, declive; right cuneus and cerebellum, anterior lobe, culmen. It also showed decreases in the left frontal lobe, parietal lobe, right temporal lobe, frontal lobe, parietal lobe and right cingulate gyrus. ALFF at 5 min post stimulation showed increases in the right temporal lobe, but decreases in the right limbic lobe and posterior cingulate gyrus. At 15 min post stimulation ALFF showed increases in the left frontal lobe, parietal lobe, occipital lobe, right temporal lobe, parietal lobe, occipital lobe and cerebellum, but decreases in the left frontal lobe, anterior cingulate gyrus, right frontal lobe and posterior cingulate gyrus. Conclusions After EA stimulation at Yintang and GV20, which are associated with psychiatric disorder treatments, changes were localised in the frontal lobe, cingulate gyrus and cerebellum. Changes were higher in number and intensity at 15 min than at 5 min after needle removal, demonstrating lasting and strong after-effects of EA on cerebral functional regions.

The interaction between BDNF and DRD2 in bipolar II disorder but not in bipolar I disorder

Bipolar I (BP-I) and bipolar II (BP-II) disorders are the two most common subtypes of bipolar disorder. However, most studies have not differentiated bipolar disorder into BP-I and BP-II groups, for which the underlying etiology differentiating these two subtypes remains unclear. The genetic association between both subtypes is essential for improving our understanding. The dopamine D2 receptor/ankyrin repeat and kinase domain containing 1 (DRD2/ANKK1), one of the dopaminergic pathways, as well as the brain-derived neurotrophic factor (BDNF) gene, were reported as candidate genes in the etiology of bipolar disorder. Therefore, we examined the contribution of the BDNF and DRD2/ANKK1 genes and their interaction to the differentiation of BP-I and BP-II. Seven hundred ninety-two participants were recruited: 208 with BP-I, 329 with BP-II, and 255 healthy controls. The genotypes of the BDNF and DRD2/ANKK1 Taq1A polymorphisms were determined using polymerase chain reactions plus restriction fragment length polymorphism analysis. A significant main effect for the Val/Val genotype of the BDNF Val66Met polymorphism predicted BP-II patients. The significant interaction effect for the Val/Val genotype of the BDNF Val66Met polymorphism and A1/A2 genotype of DRD2/ANKK1 Taq1A polymorphism was found only in BP-II patients. We provide initial evidence that the BDNF Val66Me and DRD2/ANKK1 Taq1A polymorphisms interact only in BP-II disorder and that BP-I and BP-II are genetically distinct.

High-frequency rTMS treatment increases white matter FA in the left middle frontal gyrus in young patients with treatment-resistant depression

BACKGROUND

Repetitive transcranial magnetic stimulation (rTMS) is an effective treatment for treatment-resistant depression (TRD), but its therapeutic mechanisms are unclear. White matter abnormalities are thought to cause network dysfunction underlying TRD. Diffusion tensor imaging (DTI) is an ideal tool for examining neural connections and the integrity of white matter. Few studies have used DTI to investigate the impact of rTMS on alterations of whiter matter in TRD.

METHOD

30 young treatment-resistant unipolar depression patients (19 males and 11 females) were enrolled in a double-blind, randomized high-frequency (15 Hz) rTMS treatment study. Seventeen patients were treated with real stimulation, and 13 were treated with sham stimulation. White-matter fractional anisotropy (FA) was evaluated using voxel-based analysis (VBA) of FA maps derived from DTI before and after treatment. Twenty-five age- and gender-matched subjects were examined as a control group.

RESULTS

In an exploratory VBA method, clusters of fifty voxels or greater that survived a family-wise error (FWE)-corrected threshold of p<0.05 were considered significant. The results revealed significantly reduced FA in the left middle frontal gyrus, with peak coordinates [-18 46 -14] in TRD patients. This reduced FA was significantly improved after active rTMS treatment, but not sham stimulation. FA increases were correlated with decreased depressive symptoms.

LIMITATIONS

This study requires replication and further clarification in a larger patient population, and optimization of stimulation locations and methods.

CONCLUSIONS

These results suggest that the efficacy of rTMS on TRD is related to increased white-matter FA in the left middle frontal gyrus.

Current concepts of platelet activation: possibilities for therapeutic modulation of heterotypic vs. homotypic aggregation

Thrombogenic and inflammatory activity are two distinct aspects of platelet biology, which are sustained by the ability of activated platelets to interact with each other (homotypic aggregation) and to adhere to circulating leucocytes (heterotypic aggregation). These two events are regulated by distinct biomolecular mechanisms that are selectively activated in different pathophysiological settings. They can occur simultaneously, for example, as part of a pro-thrombotic/pro-inflammatory response induced by vascular damage, or independently, as in certain clinical conditions in which abnormal heterotypic aggregation has been observed in the absence of intravascular thrombosis. Current antiplatelet drugs have been developed to target specific molecular signalling pathways mainly implicated in thrombus formation, and their ever increasing clinical use has resulted in clear benefits in the treatment and prevention of arterial thrombotic events. However, the efficacy of currently available antiplatelet drugs remains suboptimal, most likely because their therapeutic action is limited to only few of the signalling pathways involved in platelet homotypic aggregation. In this context, modulation of heterotypic aggregation, which is believed to contribute importantly to acute thrombotic events, as well to the pathophysiology of atherosclerosis itself, may offer benefits over and above the classical antiplatelet approach. This review will focus on the distinct biomolecular pathways that, following platelet activation, underlie homotypic and heterotypic aggregation, aiming potentially to identify novel therapeutic targets.

Mechanism of acute tryptophan depletion: is it only serotonin?

The method of acute tryptophan depletion (ATD), which reduces the availability of the essential amino acid tryptophan (TRP), the dietary serotonin (5-hydroxytryptamine (5-HT)) precursor, has been applied in many experimental studies. ATD application leads to decreased availability of TRP in the brain and its synthesis into 5-HT. It is therefore assumed that a decrease in 5-HT release and subsequent blunted neurotransmission is the underlying mechanism for the behavioural effects of ATD. However, direct evidence that ATD decreases extracellular 5-HT concentrations is lacking. Furthermore, several studies provide support for alternative underlying mechanisms of ATD. This may question the utility of the method as a selective serotonergic challenge tool. As ATD is extensively used for investigating the role of 5-HT in cognitive functions and psychiatric disorders, the potential of alternative mechanisms and possible confounding factors should be taken into account. It is suggested that caution is required when interpreting ATD effects in terms of a selective serotonergic effect.

That dog is smarter than you know: advances in understanding canine learning, memory, and cognition

Tests of canine cognition are now receiving much deserved attention. Not only are dogs excellent models for human anxiety-related conditions and those involving brain aging, but how dogs learn and problem solve are interesting stand-alone topics. A number of factors can affect learning at the molecular level including stress or distress, factors that affect olfaction, effects of breed and nutritional factors including that may affect available brain energy. This review provides an overview of how these factors may affect baseline learning and brain aging.

The role of genetic variation of BDNF gene in antidepressant-induced mania in bipolar disorder

The occurrence of mania during antidepressant treatment is a key issue in the clinical management of bipolar disorder (BD). Brain-derived neurotrophic factor (BDNF) has been implicated in the pathogenesis of mood disorders. Moreover, antidepressants increase the expression of BDNF and its overactivity may be involved in the mechanism of development of the manic state. The aim of the present study was to test the influence of BDNF gene alterations in antidepressant-induced mania in bipolar patients. A case-control study was performed to analyse genotype and allele frequencies for the BDNF polymorphisms between two groups [37 patients with antidepressant-induced mania (AIM+) and 55 patients without antidepressant-induced mania (AIM-)]. No significant differences were found between AIM+ and AIM- groups. Our results did not support the BDNF gene link to antidepressant-induced mania, like a previous study with a smaller sample has already suggested.

High-frequency rTMS treatment increases left prefrontal myo-inositol in young patients with treatment-resistant depression

BACKGROUND

Neuroimaging studies suggest that the prefrontal cortex (PFC) is involved in the pathophysiology of major depression. Repetitive transcranial magnetic stimulation (rTMS) as an antidepressant intervention has increasingly been investigated in the last two decades. In this study metabolic changes within PFC of severely depressed patients before and after rTMS were evaluated by proton magnetic resonance spectroscopy (1H-MRS).

METHOD

Thirty-four young depressed patients with treatment-resistant unipolar depression were enrolled in a double-blind, randomized study active ((n=19) vs. sham(n=15)), and the PFC was investigated before and after high-frequency (15 Hz) rTMS using 3-tesla proton magnetic resonance spectroscopy. Response was defined as a 50% reduction of the Hamilton depression rating scale. The results were compared with 28 age- and gender-matched healthy controls.

RESULTS

In depressive patients a significant reduction in myo-inositol (m-Ino) was observed pre-rTMS (p<0.001). After successful treatment, m-Ino increased significantly in left PFC and the levels no longer differed from those of age-matched controls. In addition to a positive correlation between clinical improvement and an increment in m-Ino ratio, a correlation between clinical improvement and early age onset was observed.

CONCLUSIONS

Our results support the notion that major depressive disorder is accompanied by state-dependent metabolic alterations, especially in myo-inositol metabolism, which can be partly reversed by successful rTMS.

Early life stressors and genetic influences on the development of bipolar disorder: the roles of childhood abuse and brain-derived neurotrophic factor

OBJECTIVES

Although there is increasing research exploring the psychosocial influences and biological underpinnings of bipolar disorder, relatively few studies have specifically examined the interplay between these factors in the development of this illness. Social-biological models within a developmental psychopathology perspective are necessary to advance our understanding of the processes involved in the onset and course of bipolar disorder. This article presents a review of the empirical literature linking childhood abuse to bipolar disorder, the research to date on the possible role of brain-derived neurotrophic factor (BDNF) in the development of this disorder, followed by a discussion of how childhood abuse may interact with BDNF.

METHODS

A literature search was conducted using Psycinfo to identify relevant articles on childhood abuse, BDNF, and bipolar disorder.

RESULTS

The extant research implicates both childhood abuse and BDNF in the etiology of bipolar disorder. Specifically, there is growing evidence associating early abuse to the development of bipolar disorder. Similarly, the BDNF Val66 allele has been linked with increased susceptibility to bipolar disorder. Based on existing research, a genetic diathesis-transactional stress model is proposed incorporating childhood abuse and the BDNF gene in the pathogenesis of bipolar disorder.

CONCLUSIONS

Although there is some support for this model, the relatively modest amount of relevant literature highlights the need for further research. An integrative theoretical framework including both social and biological processes in bipolar disorder is important for the development of effective prevention and treatment strategies for this disorder.