Effects of nerve growth factor (NGF), fluoxetine, and amitriptyline on gene expression profiles in rat brain

Neurotrophic basis to the pathogenesis of depression and phytotherapy

Depression is a major neuropsychiatric disease that considerably impacts individuals’ psychosocial function and life quality. Neurotrophic factors are now connected to the pathogenesis of depression, while the definitive neurotrophic basis remains elusive. Besides, phytotherapy is alternative to conventional antidepressants that may minimize undesirable adverse reactions. Thus, further research into the interaction between neurotrophic factors and depression and phytochemicals that repair neurotrophic factors deficit is highly required. This review highlighted the implication of neurotrophic factors in depression, with a focus on the brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF), vascular endothelial growth factor (VEGF), and nerve growth factor (NGF), and detailed the antidepressant activities of various phytochemicals targeting neurotrophic factors. Additionally, we presented future opportunities for novel diagnostic and therapeutic strategies for depression and provided solutions to challenges in this area to accelerate the clinical translation of neurotrophic factors for the treatment of depression.

Fluoxetine and environmental enrichment similarly reverse chronic social stress-related depression- and anxiety-like behavior, but have differential effects on amygdala gene expression

The adverse effects of stress on brain and behavior have long been known and well-studied, with abundant evidence linking stress to, among other things, mood and anxiety disorders. Likewise, many have investigated potential treatments for stress-related mood and anxiety phenotypes and demonstrated good response to standard antidepressant medications like selective serotonin reuptake inhibitors (SSRIs), as well as environmental manipulations like exercise or enrichment. However, the extent to which stress and various treatments act on overlapping pathways in the brain is less well understood. Here, we used a widely studied social defeat stress paradigm to induce a robust depression- and anxiety-like phenotype and chronic corticosterone elevation that persisted for at least 4 weeks in wild type male mice. When mice were treated with either the SSRI fluoxetine or an enriched environment, both led to similar behavioral recovery from social defeat. We then focused on the amygdala and assessed the effects of social defeat, fluoxetine, and enrichment on 168 genes broadly related to synaptic plasticity or oxidative stress. We found 24 differentially expressed genes in response to social defeat stress. Interestingly, fluoxetine led to broad normalization of the stress-induced expression pattern while enrichment led to expression changes in a separate set of genes. Together, this study provides additional insight into the chronic effects of social defeat stress on behavior and gene expression in the amygdala. The findings also suggest that, for a subset of genes assessed, fluoxetine and environmental enrichment have strikingly divergent effects on expression in the amygdala, despite leading to similar behavioral outcomes.

Evaluation of stress status using the stress map for guide dog candidates in the training stage using variations in the serum cortisol with nerve growth factor and magnesium ions

Most studies on guide dogs for the blind were conducted to investigate the appropriateness of the animals, including in terms of their breeding, constitution, and temperament. However, research to comprehend the stress status of guide dog candidates in response to their training has been unclear. In this study, the levels of serum cortisol, nerve growth factor (NGF), and magnesium ion (Mg²⁺) levels of guide dog candidates during the three training stages-the elementary, intermediate, and advanced classes-were examined. Dogs were classified based on the contents of the classes and period during the training in which they were subjected. Since the dogs in the elementary class had the lowest serum NGF and Mg²⁺ levels, they were understood to be under mental stress and to be unfamiliar with their new surroundings. In contrast, the serum NGF and Mg²⁺ levels were high in the dogs in the advanced class, though they were demonstrated to be mentally stable and acclimated to their environment. Additionally, they were almost free from the stress caused by daily life, since they had the lowest serum cortisol levels. The status of each dog was plotted on a map consisting of 2 axes representing the serum NGF and Mg²⁺ levels with high or low cortisol levels. Plots could be divided into three domains corresponding to the elementary, intermediate, and advanced classes. Therefore, for working dogs, serum NGF and Mg²⁺ levels in addition to serum cortisol levels may be important factors to comprehend the type of stress situation that each dog was in.

Direct and indirect evidences of BDNF and NGF as key modulators in depression: role of antidepressants treatment

PURPOSE

Depression is one of the most prevalent, recurrent and life-threatening mental illnesses. However, the precise mechanism underlying the disorder is not yet clearly understood. It is therefore, essential to identify the novel biomarkers which may help in the development of effective treatment.

METHODS

In this milieu, the profile of the brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) were considered as biomarkers in the light of pathophysiology of depression and its treatment.

RESULTS

Previously, we have reported that BDNF level in the postmortem brain of suicide victims was significantly lower than those of normal controls. We also found decreased BDNF levels in the specific brain regions of the learned helplessness model of depression in rat, and was found to increase normal level following chronic fluoxetine hydrochloride treatment. NGF is another important member of neurotrophin, which is dysregulated in the pathophysiology of depression in some models of peripheral nerve damage and stress. The results shown evidences of the effect of antidepressants on modulating depression via the NGF in preclinical and clinical models of depression, but conflicted, therefore make it currently difficult to affirm the therapeutic role of antidepressants.

CONCLUSIONS

Here, we review some of the preclinical and clinical studies aimed at disclosing the role of BDNF and NGF mediated pathophysiological mechanisms of depression and the new therapeutic approaches targeting those key molecules. In addition, an important link between BDNF, NGF and depression has been discussed in the light of current existing knowledge.

[Effects of 15-day chronic stress on behavior and neurological changes in the hippocampus of ICR mice]

  Numerous rodent models of depression have been reported, most requiring a long experimental period and significant effort. We explored a new potential mouse model for depression by investigating whether exposure to a 15-day chronic stress paradigm could induce depression-like behavior in ICR mice. Animals in the stress-exposed groups were subjected to 3 h of restraint while immersed in a 28°C water bath daily for 15 consecutive days. Immobility time in the forced swim test was increased in the chronic stress-exposed mice compared with the controls. Serum corticosterone levels were also much higher in the stressed mice than in the control mice. Hippocampal cell survival (BrdU-positive cells) and neurotrophic factor (NGF, TrkA) mRNA levels were significantly decreased in the chronic stress-exposed mice compared with controls. Administration of the anti-depressant drugs clomipramine (20 mg/kg/d) or imipramine (30 mg/kg/d) did not change the immobility time in the forced swim test, but treatment with lithium (100 mg/kg/d) did result in slight improvement. These results suggest that this 15-day chronic stress paradigm can induce depression-like behavior and neurological changes, in a short time and with minimal effort, facilitating the assessment of treatments for depression.

Prediction of new drug indications based on clinical data and network modularity

Drug repositioning is commonly done within the drug discovery process in order to adjust or expand the application line of an active molecule. Previous computational methods in this domain mainly focused on shared genes or correlations between genes to construct new drug-disease associations. We propose a method that can not only handle drugs or diseases with or without related genes but consider the network modularity. Our method firstly constructs a drug network and a disease network based on side effects and symptoms respectively. Because similar drugs imply similar diseases, we then cluster the two networks to identify drug and disease modules, and connect all possible drug-disease module pairs. Further, based on known drug-disease associations in CTD and using local connectivity of modules, we predict potential drug-disease associations. Our predictions are validated by testing their overlaps with drug indications reported in published literatures and CTD, and KEGG enrichment analysis are also made on their related genes. The experimental results demonstrate that our approach can complement the current computational approaches and its predictions can provide new clues for the candidate discovery of drug repositioning.

Growth factors as clinical biomarkers of prognosis and diagnosis in psychiatric disorders

The psychiatric disorders are one of the most disabling illnesses in the world and represent a major problem for public health. These disorders are characterized by neuroanatomical or biochemical changes and it has been suggested that such changes may be due to inadequate neurodevelopment. Diverse alterations in the gene expression and/or serum level of specific growth factors have been implicated in the etiology, symptoms and progression of some psychiatric disorders. Herein, we summarize the latest information regarding the role of brain-derived neurotrophic factor (BDNF), epidermal growth factor (EGF), fibroblast growth factor (FGF), Insulin-like growth factor (IGF-1), neuroregulin-1 (NGR-1), erythropoietin (EPO), vascular growth factor (VEGF), transforming growth factor beta (TGF-β), nerve growth factor (NGF) and others cytokines in the pathogenesis of schizophrenia, depression, bipolar and anxiety disorders. Focusing on the role of these growth factors and their relationship with the main impairments (cognitive, emotional and social) of these pathologies. Some of these signaling molecules may be suitable biological markers for diagnosis and prognosis in cognitive, mood and social disabilities across different mental disorders.

Harm avoidance involved in mediating the association between nerve growth factor (NGF) gene polymorphisms and antidepressant efficacy in patients with major depressive disorder

BACKGROUND

Antidepressants have variable efficacies in subjects with major depressive disorder (MDD). Nerve growth factor (NGF) has been suggested to play an important role in the pathogenesis of depressive symptoms and the response to antidepressant therapy. The aim of this study was to examine whether NGF gene polymorphisms are associated with the antidepressant therapeutic efficacy in subjects with MDD.

METHODS

A naturalistic follow-up study was carried out on 557 subjects with MDD. Of the enrolled patients, 304 completed the 8-week open-label antidepressant treatment. Seven single-nucleotide polymorphisms (SNPs) of the NGF gene were genotyped. The 21-item Hamilton Depression Rating Scale was used to assess depressive severity from baseline to endpoint. Tridimensional Personality Questionnaire was used to assess baseline personality traits. Single marker and haplotype analyses were conducted. Binary logistic regression was used to calculate odds ratios of remission. Structural equation modeling was used to analyze the predicted mediation effect.

RESULTS

A significant difference in genotype frequencies between remitters and non-remitters was observed in three NGF SNPs (rs12760036, rs7523654, and rs17033692). The haplotype analysis revealed that the CCC haplotype (rs2254527-rs6678788-rs12760036) was associated with a higher remission rate, while the CCA haplotype was associated with a lower remission rate. The harm avoidance psychological factor partially mediated the effect of NGF variants on antidepressant efficacy.

LIMITATIONS

The selected SNPs may not cover whole NGF gene.

CONCLUSIONS

NGF variants are associated with remission rates after 8-week antidepressant treatment, and harm avoidance partially mediated the effect of NGF variants on treatment outcomes.

Time Course of Behavioral Alteration and mRNA Levels of Neurotrophic Factor Following Stress Exposure in Mouse

Stress is known to affect neurotrophic factor expression, which induces depression-like behavior. However, whether there are time-dependent changes in neurotrophic factor mRNA expression following stress remains unclear. In the present study, we tested whether chronic stress exposure induces long-term changes in depression-related behavior, serum corticosterone, and hippocampal proliferation as well as neurotrophic factor family mRNA levels, such as brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), neurotrophin-3 (NT-3), and ciliary neurotrophic factor (CNTF), in the mouse hippocampus. The mRNA level of neurotrophic factors (BDNF, NGF, NT-3, and CNTF) was measured using the real-time PCR. The serum corticosterone level was evaluated by enzyme-linked immunosorbent assay, and, for each subject, the hippocampal proliferation was examined by 5-bromo-2-deoxyuridine immunostaining. Mice exhibited depression-like behavior in the forced-swim test (FST) and decreased BDNF mRNA and hippocampal proliferation in the middle of the stress exposure. After 15 days of stress exposure, we observed increased immobility in the FST, serum corticosterone levels, and BDNF mRNA levels and degenerated hippocampal proliferation, maintained for at least 2 weeks. Anhedonia-like behavior in the sucrose preference test and NGF mRNA levels were decreased following 15 days of stress. NGF mRNA levels were significantly higher 1 week after stress exposure. The current data demonstrate that chronic stress exposure induces prolonged BDNF and NGF mRNA changes and increases corticosterone levels and depression-like behavior in the FST, but does not alter other neurotrophic factors or performance in the sucrose preference test.

The nerve growth factor signaling and its potential as therapeutic target for glaucoma

Neuroprotective therapies which focus on factors leading to retinal ganglion cells (RGCs) degeneration have been drawing more and more attention. The beneficial effects of nerve growth factor (NGF) on the glaucoma have been recently suggested, but its effects on eye tissue are complex and controversial in various studies. Recent clinical trials of systemically and topically administrated NGF demonstrate that NGF is effective in treating several ocular diseases, including glaucoma. NGF has two receptors named high affinity NGF tyrosine kinase receptor TrkA and low affinity receptor p75NTR. Both receptors exist in cells in retina like RGC (expressing TrkA) and glia cells (expressing p75NTR). NGF functions by binding to TrkA or p75NTR alone or both together. The binding of NGF to TrkA alone in RGC promotes RGC's survival and proliferation through activation of TrkA and several prosurvival pathways. In contrast, the binding of NGF to p75NTR leads to apoptosis although it also promotes survival in some cases. Binding of NGF to both TrkA and p75NTR at the same time leads to survival in which p75NTR functions as a TrkA helping receptor. This review discusses the current understanding of the NGF signaling in retina and the therapeutic implications in the treatment of glaucoma.

Neurotrophins in the ventral tegmental area: Role in social stress, mood disorders and drug abuse

This review discusses the impact of neurotrophins and other trophic factors, including fibroblast growth factor and glial cell line-derived neurotrophic factor, on mood disorders, weight regulation and drug abuse, with an emphasis on stress- and drug-induced changes in the ventral tegmental area (VTA). Neurotrophins, comprising nerve growth factor, brain-derived neurotrophic factor (BDNF), and neurotrophins 3 and 4/5 play important roles in neuronal plasticity and the development of different psychopathologies. In the VTA, most research has focused on the role of BDNF, because other neurotrophins are not found there in significant quantities. BDNF originating in the VTA provides trophic support to dopamine neurons. The diverse intracellular signaling pathways activated by BDNF may underlie precise physiological functions specific to the VTA. In general, VTA BDNF expression increases after psychostimulant exposures, and enhanced BDNF level in the VTA facilitates psychostimulant effects. The impact of VTA BDNF on the behavioral effects of psychostimulants relies primarily on its action within the mesocorticolimbic circuit. In the case of opiates, VTA BDNF expression and effects seem to be dependent on whether an animal is drug-naïve or has a history of drug use, only the latter of which is related to dopamine mechanisms. Social defeat stress that is continuous in mice or intermittent in rats increases VTA BDNF expression, and is associated with depressive and social avoidance behaviors. Intermittent social defeat stress induces persistent VTA BDNF expression that triggers psychostimulant cross-sensitization. Understanding the cellular and molecular substrates of neurotrophin effects may lead to novel therapeutic approaches for the prevention and treatment of substance use and mood disorders.

Decreased mRNA and Protein Expression of BDNF, NGF, and their Receptors in the Hippocampus from Suicide: An Analysis in Human Postmortem Brain

Despite the devastating effect of suicide on numerous lives, there is still a lack of knowledge concerning its neurochemical aspects. There is increasing evidence that brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) are involved in the pathophysiology and treatment of depression through binding and activating their cognate receptors TrkB and TrkA respectively. The present study was performed to examine whether the expression profiles of BDNF and/or TrkB as well as NGF and/or TrkA were altered in the hippocampus of postmortem brain of the participants, who had committed suicide and whether these alterations were associated with specific psychopathologic conditions. These studies were performed on the hippocampus of 21 suicide victims and 19 non-psychiatric control individuals. The protein and mRNA levels of BDNF, TrkB, NGF, and TrkA were determined by sandwich enzyme-linked immunosorbent assay, Western blot and reverse transcription-PCR. Given the importance of BDNF and NGF and their cognate receptors in mediating physiological functions, including cell survival and synaptic plasticity, our findings of reduced expression of BDNF, TrkB, NGF, and TrkA on both the protein and mRNA levels of postmortem brains of suicide victims suggest that these molecules may play an important role in the pathophysiological aspects of suicidal behavior.

Decreased mRNA and Protein Expression of BDNF, NGF, and their Receptors in the Hippocampus from Suicide: An Analysis in Human Postmortem Brain

Despite the devastating effect of suicide on numerous lives, there is still a lack of knowledge concerning its neurochemical aspects. There is increasing evidence that brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) are involved in the pathophysiology and treatment of depression through binding and activating their cognate receptors TrkB and TrkA respectively. The present study was performed to examine whether the expression profiles of BDNF and/or TrkB as well as NGF and/or TrkA were altered in the hippocampus of postmortem brain of the participants, who had committed suicide and whether these alterations were associated with specific psychopathologic conditions. These studies were performed on the hippocampus of 21 suicide victims and 19 non-psychiatric control individuals. The protein and mRNA levels of BDNF, TrkB, NGF, and TrkA were determined by sandwich enzyme-linked immunosorbent assay, Western blot and reverse transcription-PCR. Given the importance of BDNF and NGF and their cognate receptors in mediating physiological functions, including cell survival and synaptic plasticity, our findings of reduced expression of BDNF, TrkB, NGF, and TrkA on both the protein and mRNA levels of postmortem brains of suicide victims suggest that these molecules may play an important role in the pathophysiological aspects of suicidal behavior.