Brain derived neurotrophic factor: Epigenetic regulation in psychiatric disorders

Antidepressant-Like Effects of Acupuncture-Insights From DNA Methylation and Histone Modifications of Brain-Derived Neurotrophic Factor

Sensitive and stable biomarkers that facilitate depression detection and monitor the antidepressant efficiency are currently unavailable. Thus, the objective is to investigate the potential of DNA methylation and histone modifications of brain-derived neurotrophic factor (BDNF) in monitoring severity and antidepressive effects of acupuncture. The depression rat model was imitated by social isolation and chronic unpredicted mild stress (CUMS). The expression of serum BDNF was detected by enzyme-linked immunosorbent assay (ELISA), the hippocampal BDNF, acetylation levels in histone H3 lysine 9 (acH3K9), and HDAC2 by Western blot, the hippocampal mRNA of BDNF by RT-polymerase chain reaction (PCR). The DNA methylation patterns of the promoter I of BDNF was detected by MS-PCR. We investigated that the expression of BDNF in serum and hippocampus were significantly downregulated compared with controls. The same trend was found in mRNA of BDNF. Notably, acupuncture reversed the downregulation of BDNF in serum and hippocampus and mRNA of BDNF compared with model group. Acupuncture reversed the CUMS-induced downregulation of hippocampal acH3K9. On the contrary, the CUMS-induced upregulation of hippocampal HDAC2 in model group was significantly reversed by acupuncture. Collectively, the antidepressant effect of acupuncture might be mediated by regulating the DNA methylation and histone modifications of BDNF, which may represent novel biomaker for detection of depression and monitoring severity and antidepressive effects.

Alleviative effects of fluoxetine on depressive-like behaviors by epigenetic regulation of BDNF gene transcription in mouse model of post-stroke depression

Fluoxetine, one of the selective serotonin reuptake inhibitor (SSRI) antidepressants, has been thought to be effective for treating post-stroke depression (PSD). Recent work has shown that fluoxetine may exert an antidepressive effect through increasing the level of brain-derived neurotrophic factor (BDNF), but the underlying mechanism still remains unclear. In the present study, we successfully established the PSD model using male C57BL/6 J mice by photothrombosis of the left anterior cortex combined with isolatied-housing conditions. In the process, we confirmed that fluoxetine could improve the depression-like behaviors of PSD mice and upregulate the expression of BDNF in the hippocampus. However, depletion of BDNF by transfecting lentivirus-derived shBDNF in hippocampus suppressed the effect of fluoxetine. Furthermore, we demonstrated the epigenetic mechanisms involved in regulation of BDNF expression induced by fluoxetine. We found a statistically significant increase in DNA methylation at specific CpG sites (loci 2) of Bdnf promoter IV in the hippocampus of PSD mice. We also found that fluoxetine treatment could disassociate the MeCP2-CREB-Bdnf promoter IV complex via phosphorylation of MeCP2 at Ser421 by Protein Kinase A (PKA). Our research highlighted the importance of fluoxetine in regulating BDNF expression which could represent a potential strategy for preventing PSD.

The histone demethylase JMJD2A regulates the expression of BDNF and mediates neuropathic pain in mice

JMJD2A is a JmjC histone demethylase that catalyzes the demethylation of di- and trimethylated Lys9 and Lys36 in histone H3 (H3K9me2/3 and H3K36me2/3). The role of spinal JMJD2A-dependent histone demethylation in nociception hypersensitivity development remains elusive. Here we reported that the JMJD2A responded to neuropathic pain and participated in the maintenance of neuropathic pain. The mRNA and protein levels of Jmjd2a were significantly increased in the neurons of mouse undergoing neuropathic pain induced by sciatic nerve chronic constrictive injury (CCI) or unilateral spared nerve injury (SNI). Jmjd2a responded to 5-hydroxytryptamine (5-HT) and promoted the expression of the brain-derived neurotrophic factor (Bdnf), which is a protein critically involved in neuropathic pain. JMJD2A bound to the promoter of Bdnf and demethylated H3K9me3 and H3K36me3 at Bdnf promoter to promote the expression of Bdnf. Finally, we showed that JMJD2A promoted the expression of Bdnf during neuropathic pain and neuron-specific knockout of Jmjd2a blocked the hypersensitivity of mice undergoing chronic neuropathic pain induced by CCI and SNI. Taken together, our findings demonstrate that up-regulation of JMJD2A promotes neuropathic pain and it may serve as a promising target for treatment of chronic neuropathic pain.

Expression and methylation of BDNF in the human brain in schizophrenia

OBJECTIVES

To examine the combined effect of the BDNF Val66Met (rs6265) polymorphism and BDNF DNA methylation on transcriptional regulation of the BDNF gene.

METHODS

DNA methylation profiles were generated for CpG sites proximal to Val66Met, within BDNF promoter I and exon V for prefrontal cortex samples from 25 schizophrenia and 25 control subjects. Val66Met genotypes and BDNF mRNA expression data were generated by transcriptome sequencing. Expression, methylation and genotype data were correlated and examined for association with schizophrenia.

RESULTS

There was 43% more of the BDNF V-VIII-IX transcript in schizophrenia samples. BDNF mRNA expression and DNA methylation of seven CpG sites were not associated with schizophrenia after accounting for age and PMI effects. BDNF mRNA expression and DNA methylation were not altered by Val66Met after accounting for age and PMI effects. DNA methylation of one CpG site had a marginally significant positive correlation with mRNA expression in schizophrenia subjects.

CONCLUSIONS

Schizophrenia risk was not associated with differential BDNF mRNA expression and DNA methylation. A larger age-matched cohort with comprehensive clinical history is required to accurately identify the effects of genotype, mRNA expression and DNA methylation on schizophrenia risk.

HIV-1 gp120 Upregulates Brain-Derived Neurotrophic Factor (BDNF) Expression in BV2 Cells via the Wnt/β-Catenin Signaling Pathway

HIV-1 gp120 plays a critical role in the pathogenesis of HIV-associated pain, but the underlying molecular mechanisms are incompletely understood. This study aims to determine the effect and possible mechanism of HIV-1 gp120 on BDNF expression in BV2 cells (a murine-derived microglial cell line). We observed that gp120 (10 ng/ml) activated BV2 cells in cultures and upregulated proBDNF/mBDNF. Furthermore, gp120-treated BV2 also accumulated Wnt3a and β-catenin, suggesting the activation of the Wnt/β-catenin pathway. We demonstrated that activation of the pathway by Wnt3a upregulated BDNF expression. In contrast, inhibition of the Wnt/β-catenin pathway by either DKK1 or IWR-1 attenuated BDNF upregulation induced by gp120 or Wnt3a. These findings collectively suggest that gp120 stimulates BDNF expression in BV2 cells via the Wnt/β-catenin signaling pathway.

[Implication of human endogenous retroviruses in schizophrenia and bipolar disorder]

Schizophrenia and bipolar disorder are neuropsychiatric disorders of unknown origin. It seems that these two disorders share some common etiopathogenic mechanisms including genetic, environmental and inflammatory ones. Reactivation of the human endogenous retrovirus type W (HERV-W) can be a shared element in the pathophysiology of schizophrenia and bipolar disorder, linked to immuno-genetic and environment risk factors. We will present studies that have highlighted the presence of HERV-W in schizophrenic and bipolar disorder patients. We will then describe a two-hit model which could explain the common pathophysiological mechanism of affective and non-affective psychosis. Identification of immuno-inflammatory mediated subgroup of schizophrenia and bipolar disorder associated to HERV-W reactivation might open the way for the development of diagnostic biomarker and more targeted treatments. These new tools pave the way towards personalized psychiatry for a better care of patients.

Therapeutic Effects of Phytochemicals and Medicinal Herbs on Depression

Background. Depression is a recurrent, common, and potentially life-threatening psychiatric disease related to multiple assignable causes. Although conventional antidepressant therapy can help relieve symptoms of depression and prevent relapse of the illness, complementary therapies are required due to disadvantage of the current therapy such as adverse effects. Moreover, a number of studies have researched adjunctive therapeutic approaches to improve outcomes for depression patients. Purpose. One potential complementary method with conventional antidepressants involves the use of medicinal herbs and phytochemicals that provide therapeutic benefits. Studies have revealed beneficial effects of medical herbs and phytochemicals on depression and their central nervous system mechanism. Here, we summarize the current knowledge of the therapeutic benefits of phytochemicals and medicinal herbs against depression and describe their detailed mechanisms. Sections. There are two sections, phytochemicals against depression and medical herbs against depression, in this review. Conclusion. Use of phytomedicine may be an alternative option for the treatment of depression in case conventional drugs are not applicable due to their side effects, low effectiveness, or inaccessibility. However, the efficacy and safety of these phytomedicine treatments for depression have to be supported by clinical studies.

Does genetic BDNF deficiency in rats interact with neurotransmitter control of prepulse inhibition? Implications for schizophrenia

Several studies have suggested a role of BDNF in the development of schizophrenia. For example, post-mortem studies have shown significantly reduced levels of BDNF protein expression in the brain of schizophrenia patients. We investigated the relationship between reduced levels of BDNF in the brain and the regulation of prepulse inhibition (PPI), a behavioral endophenotype of schizophrenia. We used BDNF heterozygous mutant rats which display a 50% decrease of mature BDNF protein levels. Previously, we observed normal baseline PPI and responses to the dopamine D1/D2 receptor agonist, apomorphine, in these rats. Here, we focused on the effects of the NMDA receptor antagonist, MK-801, its interaction with mGluR2/3 and mGluR5 receptors, and the PPI response to serotonergic drugs. MK-801 administration caused a dose-dependent reduction of PPI and increase of startle amplitudes. Baseline PPI and the effect of 0.02-0.1mg/kg of MK-801 were not significantly altered in male or female BDNF heterozygous rats, although the MK-801-induced increase in startle levels was reduced. Co-treatment with the mGluR2/3 agonist, LY379,268, or the mGluR5 antagonist, MPEP, did not alter the effect of MK-801 on PPI in controls or BDNF mutant rats. Treatment with the serotonin-1A receptor agonist, 8-OH-DPAT, the serotonin-2A receptor agonist, DOI, or the serotonin releaser, fenfluramine, induced differential effects on PPI and startle but these effects were not different between the genotypes. These results show that a significant decrease of BDNF protein expression does not lead to reduced PPI at baseline or changes in the regulation of PPI via NMDA receptors or serotonergic mechanisms. These findings in a genetic rat model of BDNF deficiency do not support a role for similar reductions of BDNF levels in schizophrenia in the disruption of PPI, widely reported as an endophenotype of the illness. The potential implications of these results for our understanding of changes in PPI and BDNF expression in schizophrenia are discussed.

Theranostic Biomarkers for Schizophrenia

Schizophrenia is a highly heritable, chronic, severe, disabling neurodevelopmental brain disorder with a heterogeneous genetic and neurobiological background, which is still poorly understood. To allow better diagnostic procedures and therapeutic strategies in schizophrenia patients, use of easy accessible biomarkers is suggested. The most frequently used biomarkers in schizophrenia are those associated with the neuroimmune and neuroendocrine system, metabolism, different neurotransmitter systems and neurotrophic factors. However, there are still no validated and reliable biomarkers in clinical use for schizophrenia. This review will address potential biomarkers in schizophrenia. It will discuss biomarkers in schizophrenia and propose the use of specific blood-based panels that will include a set of markers associated with immune processes, metabolic disorders, and neuroendocrine/neurotrophin/neurotransmitter alterations. The combination of different markers, or complex multi-marker panels, might help in the discrimination of patients with different underlying pathologies and in the better classification of the more homogenous groups. Therefore, the development of the diagnostic, prognostic and theranostic biomarkers is an urgent and an unmet need in psychiatry, with the aim of improving diagnosis, therapy monitoring, prediction of treatment outcome and focus on the personal medicine approach in order to improve the quality of life in patients with schizophrenia and decrease health costs worldwide.

Elevated methylation and decreased serum concentrations of BDNF in patients in levomethadone compared to diamorphine maintenance treatment

Brain-derived neurotrophic factor (BDNF) appears to play a crucial role in the reward response to drugs such as heroin. The primary objective of the present study was to examine epigenetic changes and serum levels of BDNF in patients undergoing different opiate-based maintenance treatments. We compared patients receiving treatment with either levomethadone (n = 55) or diamorphine (n = 28) with a healthy control group (n = 51). When comparing all subjects (patients and controls), BDNF serum levels showed a negative correlation with the BDNF IV promoter methylation rate (r = -0.177, p = 0.048). Furthermore, BDNF serum levels negatively correlated with Beck's Depression Inventory measurements (r = -0.177, p < 0.001). Patients receiving diamorphine maintenance treatment showed slightly decreased BDNF serum levels compared to healthy controls, whereas patients on levomethadone maintenance treatment with or without heroine co-use showed a pronounced decrease (analysis of covariance: control vs. levomethadone with and without heroine co-use: p < 0.0001, diamorphine vs. levomethadone with heroine co-use: p = 0.043, diamorphine vs. levomethadone without heroine co-use: p < 0.0001). According to these findings, methylation of the BDNF IV promoter showed the highest level in patients receiving levomethadone without heroine co-use (linear mixed model: control vs. levomethadone group without heroine co-use: p = 0.008, with heroin co-use: p = 0.050, diamorphine vs. levomethadone group with heroine co-use: p = 0.077 and without heroine co-use: p = 0.015.). For the first time, we show an epigenetic mechanism that may provide an explanation for mood destabilization in levomethadone maintenance treatment.

Brain-derived neurotrophic factor and schizophrenia

Schizophrenia is a severe disorder affecting approximately 1% of the population. Historically, alterations of dopaminergic function were considered the primary cause of schizophrenia. However, for many patients, drugs that alter dopaminergic function do not consistently lead to resolution of the symptoms of schizophrenia. Thus, there is an increased interest in pathophysiologic processes that result in altered neurodevelopment and plasticity associated with schizophrenia. Brain-derived neurotrophic factor (BDNF) is a neurotrophin involved in neurogenesis, synaptic plasticity, cognition, and neurotransmission. Genetic polymorphism, expression, and function of BDNF have been implicated in psychiatric diseases, including schizophrenia. This review discusses BDNF, its role in neurologic processes, and the evidence implicating BDNF in schizophrenia.

The human BDNF gene: peripheral gene expression and protein levels as biomarkers for psychiatric disorders

Brain-derived neurotrophic factor (BDNF) regulates the survival and growth of neurons, and influences synaptic efficiency and plasticity. The human BDNF gene consists of 11 exons, and distinct BDNF transcripts are produced through the use of alternative promoters and splicing events. The majority of the BDNF transcripts can be detected not only in the brain but also in the blood cells, although no study has yet investigated the differential expression of BDNF transcripts at the peripheral level. This review provides a description of the human BDNF gene structure as well as a summary of clinical and preclinical evidence supporting the role of BDNF in the pathogenesis of psychiatric disorders. We will discuss several mechanisms as possibly underlying BDNF modulation, including epigenetic mechanisms. We will also discuss the potential use of peripheral BDNF as a biomarker for psychiatric disorders, focusing on the factors that can influence BDNF gene expression and protein levels. Within this context, we have also characterized, for we believe the first time, the expression of BDNF transcripts in the blood, with the aim to provide novel insights into the molecular mechanisms and signaling that may regulate peripheral BDNF gene expression levels.

Transgenerational effects of paternal heroin addiction on anxiety and aggression behavior in male offspring

BACKGROUND

Heroin addiction is a growing concern, affecting the socioeconomic development of many countries. Little is known about transgenerational effects on phenotype changes due to heroin addiction. This study aims to investigate changes in level of anxiety and aggression up to four different generations of adult male rats due to paternal exposure to heroin.

METHODS

Male Sprague-Dawley rats were exposed with heroin intraperitoneally (i.p.) twice-daily for 14 days with increasing dosage regimen (F0-heroin). Male Sprague-Dawley rats (6-weeks-old) were divided into: (1) heroin exposed group (F0-heroin) and (2) control group treated with saline solution (F0-control). The dosage regime started with the lowest dose of 3 mg/kg per day of heroin followed by 1.5 mg/kg increments per day to a final dose of 13.5 mg/kg per day. Offspring were weaned on postnatal day 21. The adult male offspring from each generation were then mated with female-naïve rats after 2 weeks of heroin absence. Open field test and elevated plus maze test were used to study the anxiety level, whereas resident intruder test was used to evaluate aggression level in the addicted male rats and their offspring.

RESULTS

Heroin exposure in male rats had resulted in smaller sizes of the litters compared to the control. We observed a higher anxiety level in the F1 and F2 progenies sired by the heroin exposed rats (F0) as compared to the control rats. Paternal heroin exposure also caused significantly more aggressive offspring in F1 compared to the control. The same pattern was also observed in the F2.

CONCLUSION

Our results demonstrated that the progenies of F1 and F2 sustained higher levels of anxiety and aggression which are due to paternal heroin exposure.

Epigenetic Manipulation of Brain-derived Neurotrophic Factor Improves Memory Deficiency Induced by Neonatal Anesthesia in Rats

BACKGROUND

Although neonatal exposure to anesthetic drugs is associated with memory deficiency in rodent models and possibly in pediatric patients, the underlying mechanisms remain elusive. The authors tested their hypothesis that exposure of the developing brain to anesthesia triggers epigenetic modification, involving the enhanced interaction among transcription factors (histone deacetylase 2, methyl-cytosine-phosphate-guanine-binding protein 2, and DNA methyltransferase 1) in Bdnf promoter region(s) that inhibit brain-derived neurotrophic factor (BDNF) expression, resulting in insufficient drive for local translation of synaptic mRNAs. The authors further hypothesized that noninvasive environmental enrichment (EE) will attenuate anesthesia-induced epigenetic inhibition of BDNF signaling and memory loss in rodent models.

METHODS

Seven days after birth (P7), neonatal rats were randomly assigned to receive either isoflurane anesthesia for 6 h or sham anesthesia. On P21, pups were weaned, and animals were randomly assigned to EE or a standard cage environment (no EE). Behavioral, molecular, and electrophysiological studies were performed on rats on P65.

RESULTS

The authors found a substantial reduction of hippocampal BDNF (n = 6 to 7) resulting from the transcriptional factors-mediated epigenetic modification in the promoter region of Bdnf exon IV in rats exposed postnatally to anesthetic drugs. This BDNF reduction led to the insufficient drive for the synthesis of synaptic proteins (n = 6 to 8), thus contributing to the hippocampal synaptic (n = 8 to 11) and cognitive dysfunction (n = 10) induced by neonatal anesthesia. These effects were mitigated by the exposure to an enriched environment.

CONCLUSIONS

The findings of this study elucidated the epigenetic mechanism underlying memory deficiency induced by neonatal anesthesia and propose EE as a potential therapeutic approach.

Inhibition of DNA Methylation in the Developing Rat Brain Disrupts Sexually Dimorphic Neurobehavioral Phenotypes in Adulthood

Accumulating evidence indicates a critical implication of DNA methylation in the brain development. We aim to determine whether the disruption of DNA methylation patterns in the developing brain adversely affects neurobehavioral phenotypes later in life in a sex-dependent manner. 5-Aza-2'-deoxycytidine (5-Aza), a DNA methylation inhibitor, was administered in newborn rats from postnatal day 1 to 3. Neurobehavioral outcomes were analyzed at 3 months of age. 5-Aza treatment significantly inhibited DNA methyltransferase activity and decreased global DNA methylation levels in neonatal rat brains, resulting in asymmetric growth restriction with the increased brain to body weight ratio in both male and female rats at 14 days and 3 months of age. Compared with the saline control, 5-Aza treatment significantly improved performance of male rats on the rotarod test, and 5-Aza-treated female rats demonstrated less anxiety, less depression-like behaviors, and enhanced spatial learning performance. Of importance, neonatal 5-Aza treatment eliminated the sexually dimorphic differences in several neurobehavioral tests in adult rats. In addition, 5-Aza treatment decreased promoter methylation of brain-derived neurotrophic factor (BDNF) gene and significantly increased BDNF mRNA and protein abundance in the prefrontal cortex and hippocampus of female rats in a sex-dependent manner. Thus, brain DNA methylation appears to be essential for sexual differentiations of the brain and neurobehavioral functions. Inhibition of DNA methylation in the developing brain of early life induces aberrant neurobehavioral profiles and disrupts sexually dimorphic neurobehavioral phenotypes in adulthood, of which altered BDNF signaling pathway may be an important mediator.

BDNF DNA methylation changes as a biomarker of psychiatric disorders: literature review and open access database analysis

Brain-derived neurotrophic factor (BDNF) plays an important role in nervous system development and function and it is well established that BDNF is involved in the pathogenesis of a wide range of psychiatric disorders. Recently, numerous studies have associated the DNA methylation level of BDNF promoters with certain psychiatric phenotypes. In this review, we summarize data from current literature as well as from our own analysis with respect to the correlation of BDNF methylation changes with psychiatric disorders and address questions about whether DNA methylation related to the BDNF can be useful as biomarker for specific neuropsychiatric disorders.

Maternal n-3 polyunsaturated fatty acid deprivation during pregnancy and lactation affects neurogenesis and apoptosis in adult offspring: associated with DNA methylation of brain-derived neurotrophic factor transcripts

In this study, we hypothesized that n-3 polyunsaturated fatty acid (PUFA) deficiency during pregnancy and lactation will make a lasting impact on brain neurogenesis and apoptosis of the adult offspring and that these harmful effects cannot be reversed by n-3 PUFA supplementation after weaning. Moreover, the underlying mechanisms may be attributable to the epigenetic changes of brain-derived neurotrophic factor (BDNF). C57BL/6J female mice were fed with n-3 PUFA-deficient diet (n-3 def) or n-3 PUFA-adequate diet (n-3 adq) throughout pregnancy and lactation. At postnatal 21 days, equal numbers of male pups from both groups were fed the opposite diet, and the remaining male pups were fed with the same diets as their mothers until 3 months of age. Feeding the n-3 adq diet to pups from the maternal n-3 def group significantly increased the n-3 PUFA concentration but did not change expressions of calretinin, Bcl2, and Bax in the hippocampus. Feeding the n-3 def diet to pups from the maternal n-3 adq group significantly reduced the n-3 PUFA concentration but did not reduce expressions of calretinin and Bcl2. Similarly, BDNF levels, especially mRNA expressions of BDNF transcripts IV and IX, were also reduced by maternal n-3 def and not reversed by n-3 PUFA supplementation after weaning. The decrease in BDNF expression by maternal n-3 def diet was associated with greater DNA methylation at special CpG sites. These results suggested that the maternal n-3 PUFA deficiency during pregnancy and lactation imprints long-term changes of brain development in adult offspring.

Maternal separation prior to neonatal hypoxia-ischemia: Impact on emotional aspects of behavior and markers of synaptic plasticity in hippocampus

Exposure to early-life stress is associated with long-term alterations in brain and behavior, and may aggravate the outcome of neurological insults. This study aimed at investigating the possible interaction between maternal separation, a model of early stress, and subsequent neonatal hypoxia-ischemia on emotional behavior and markers of synaptic plasticity in hippocampus. Therefore, rat pups (N=60) were maternally separated for a prolonged (MS 180min) or a brief (MS 15min) period during the first six postnatal days, while a control group was left undisturbed. Hypoxia-ischemia was applied to a subgroup of each rearing condition on postnatal day 7. Emotional behavior was examined at three months of age and included assessments of anxiety (elevated plus maze), depression-like behavior (forced swimming) and spontaneous exploration (open field). Synaptic plasticity was evaluated based on BDNF and synaptophysin expression in CA3 and dentate gyrus hippocampal regions. We found that neonatal hypoxia-ischemia caused increased levels of anxiety, depression-like behavior and locomotor activity (ambulation). Higher anxiety levels were also seen in maternally separated rats (MS180min) compared to non-maternally separated rats, but prolonged maternal separation prior to HI did not potentiate the HI-associated effect. No differences among the three rearing conditions were found regarding depression-like behavior or ambulation. Immunohistochemical evaluation of synaptophysin revealed that both prolonged maternal separation (MS180min) and neonatal hypoxia-ischemia significantly reduced its expression in the CA3 and dentate gyrus. Decreases in synaptophysin expression in these areas were not exacerbated in rats that were maternally separated for a prolonged period prior to HI. Regarding BDNF expression, we found a significant decrease in immunoreactivity only in the hypoxic-ischemic rats that were subjected to the prolonged maternal separation paradigm. The above findings suggest that early-life stress prior to neonatal hypoxia-ischemia leads to significant alterations in synaptic plasticity of the dorsal hippocampus during adulthood, but does not exacerbate HI-related changes in emotional behavior.

Relationship between ST8SIA2, polysialic acid and its binding molecules, and psychiatric disorders

Polysialic acid (polySia, PSA) is a unique and functionally important glycan, particularly in vertebrate brains. It is involved in higher brain functions such as learning, memory, and social behaviors. Recently, an association between several genetic variations and single nucleotide polymorphisms (SNPs) of ST8SIA2/STX, one of two polysialyltransferase genes in vertebrates, and psychiatric disorders, such as schizophrenia (SZ), bipolar disorder (BD), and autism spectrum disorder (ASD), was reported based on candidate gene approaches and genome-wide studies among normal and mental disorder patients. It is of critical importance to determine if the reported mutations and SNPs in ST8SIA2 lead to impairments of the structure and function of polySia, which is the final product of ST8SIA2. To date, however, only a few such forward-directed studies have been conducted. In addition, the molecular mechanisms underlying polySia-involved brain functions remain unknown, although polySia was shown to have an anti-adhesive effect. In this report, we review the relationships between psychiatric disorders and polySia and/or ST8SIA2, and describe a new function of polySia as a regulator of neurologically active molecules, such as brain-derived neurotrophic factor (BDNF) and dopamine, which are deeply involved in psychiatric disorders. This article is part of a Special Issue entitled "Glycans in personalised medicine" Guest Editor: Professor Gordan Lauc.

DNA Methylation of BDNF Gene in Schizophrenia

Background

Although genetic factors are risk factors for schizophrenia, some environmental factors are thought to be required for the manifestation of disease. Epigenetic mechanisms regulate gene functions without causing a change in the nucleotide sequence of DNA. Brain-derived neurotrophic factor (BDNF) is a neurotrophin that regulates synaptic transmission and plasticity. It has been suggested that BDNF may play a role in the pathophysiology of schizophrenia. It is established that methylation status of the BDNF gene is associated with fear learning, memory, and stressful social interactions. In this study, we aimed to investigate the DNA methylation status of BDNF gene in patients with schizophrenia.

Material/Methods

The study included 49 patients (33 male and 16 female) with schizophrenia and 65 unrelated healthy controls (46 male and 19 female). Determination of methylation pattern of CpG islands was based on the principle that bisulfite treatment of DNA results in conversion of unmethylated cytosine residues into uracil, whereas methylated cytosine residues remain unmodified. Methylation-specific PCR was performed with primers specific for either methylated or unmethylated DNA.

Results

There was no significant difference in methylated or un-methylated status for BDNF promoters between schizophrenia patients and controls. The mean duration of illness was significantly lower in the hemi-methylated group compared to the non-methylated group for BDNF gene CpG island-1 in schizophrenia patients.

Conclusions

Although there were no differences in BDNF gene methylation status between schizophrenia patients and healthy controls, there was an association between duration of illness and DNA methylation.

Serum BDNF levels in unaffected first-degree relatives of patients with bipolar disorder

Objective:

Unaffected relatives of bipolar disorder (BD) patients have been investigated for the identification of endophenotypes in an attempt to further elucidate the pathophysiology of the disease. Brain-derived neurotrophic factor (BDNF) is considered to be implicated in the pathophysiology of BD, but its role as an endophenotype has been poorly studied. We investigated abnormal serum BDNF levels in BD patients, in their unaffected relatives, and in healthy controls.

Methods:

BDNF levels were obtained from 25 DSM-IV bipolar I disorder patients, 23 unaffected relatives, and 27 healthy controls. All BD patients were in remission. The unaffected subjects were first-degree relatives of the proband who had no lifetime DSM-IV diagnosis of axis I disorder. BDNF serum levels were determined by sandwich ELISA using monoclonal BDNF-specific antibodies.

Results:

There were no statistical differences in BDNF levels among BD patients, relatives, and healthy controls.

Conclusion:

Serum BDNF levels may not indicate high genetic risk for BD, possibly acting as state markers rather than trait markers of the disease.

miR-182 (microRNA-182) suppression in the hippocampus evokes antidepressant-like effects in rats

Depression is a serious and potentially life-threatening mental disorder with unknown etiology. Emerging evidence shows that brain-derived neurotrophic factor (BDNF) and microRNAs (miRNAs) play critical roles in the etiology of depression. However, the molecular mechanisms are not fully understood. Expression of miR-182 and BDNF in the hippocampus were analyzed in a chronic unpredictable mild stress (CUMS) model. Male Wistar rats received bilateral intra-hippocampal infusions of BDNF- and miR-182-expressing (miR-182) or miR-182-silencers (si-miR-182) lentiviral vectors (LV). miR-182 upregulation was correlated with decreased BDNF expression in the hippocampus of a CUMS model. Accordingly, an anti-depressant like effect was observed when LV-BDNF or LV-si-miR-182 was injected into the hippocampus. Moreover, BDNF and its target gene cyclic AMP responsive element binding protein 1 (CREB1) decreased following LV-miR-182 injection and increased upon LV-si-miR-182 injection in rat hippocampus and cultured neuronal cells. In contrast, miR-182 overexpression exacerbated depression-like behaviors and decreased BDNF. Further, luciferase reporter evidence confirmed BDNF was a miR-182 target. Taken together, the current results reveal a potential molecular regulation of miR-182 on BDNF and the pronounced behavioral consequences of this regulation.

Transcranial direct current stimulation and neuroplasticity genes: implications for psychiatric disorders

BACKGROUND AND AIM

Transcranial direct current stimulation (tDCS) is a non-invasive and well-tolerated brain stimulation technique with promising efficacy as an add-on treatment for schizophrenia and for several other psychiatric disorders. tDCS modulates neuroplasticity; psychiatric disorders are established to be associated with neuroplasticity abnormalities. This review presents the summary of research on potential genetic basis of neuroplasticity-modulation mechanism underlying tDCS and its implications for treating various psychiatric disorders.

METHOD

A systematic review highlighting the genes involved in neuroplasticity and their role in psychiatric disorders was carried out. The focus was on the established genetic findings of tDCS response relationship with BDNF and COMT gene polymorphisms.

RESULT

Synthesis of these preliminary observations suggests the potential influence of neuroplastic genes on tDCS treatment response. These include several animal models, pharmacological studies, mentally ill and healthy human subject trials.

CONCLUSION

Taking into account the rapidly unfolding understanding of tDCS and the role of synaptic plasticity disturbances in neuropsychiatric disorders, in-depth evaluation of the mechanism of action pertinent to neuroplasticity modulation with tDCS needs further systematic research. Genes such as NRG1, DISC1, as well as those linked with the glutamatergic receptor in the context of their direct role in the modulation of neuronal signalling related to neuroplasticity aberrations, are leading candidates for future research in this area. Such research studies might potentially unravel observations that might have potential translational implications in psychiatry.

BDNF polymorphisms are associated with schizophrenia onset and positive symptoms

Numerous studies have showed that brain-derived neurotrophic factor (BDNF) may be involved in the pathogenesis and pathophysiology of schizophrenia. The purposes of this study were to investigate the potential association of BDNF gene polymorphisms with susceptibility to schizophrenia and the psychopathological symptoms in patients with schizophrenia in a Han Chinese population. Four polymorphisms (rs6265, rs12273539, rs10835210 and rs2030324) of the BDNF gene were analyzed in a case-control study of 1887 Han Chinese individuals (844 patients and 1043 controls). We assessed 825 patients for psychopathology using the Positive and Negative Syndrome Scale. In single marker analyses the BDNF rs10835210 mutant A allele was significantly associated with schizophrenia. Haplotype analyses revealed higher frequencies of haplotypes containing the mutant A allele of the rs10835210 in schizophrenia than controls. We also found that this polymorphism rs10835210 was associated with positive symptoms, and the patients carrying the mutational allele A showed more positive symptoms. These findings suggest the role of these BDNF gene variants in both susceptibility to schizophrenia and in clinical symptom severity.

Karolinska Scales of Personality, cognition and psychotic symptoms in patients with schizophrenia and healthy controls

BACKGROUND

Studies on both personality dimensions and cognition in schizophrenia are scarce. The objective of the present study was to examine personality traits and the relation to cognitive function and psychotic symptoms in a sample of patients with schizophrenia and healthy controls.

METHOD

In total 23 patients with schizophrenia and 14 controls were assessed with the Karolinska Scales of Personality (KSP). A broad cognitive test programme was used, including the Wechsler Adult Intelligence Scales, the Finger-Tapping Test, the Trail Making Test, the Verbal Fluency Test, the Benton Visual Retention Test, the Wisconsin Card Sorting Test and Rey Auditory Verbal Learning Test .

RESULTS

Compared with controls, the patients exhibited prominent elevations on KSP scales measuring anxiety proneness and neuroticism (P = 0.000005-0.0001), on the Detachment scale (P < 0.00009) and lower value on the Socialization scale (P < 0.0002). The patients also scored higher on the Inhibition of Aggression, Suspicion, Guilt and Irritability scales (P = 0.002-0.03) while the remaining five scales did not differ between patients and controls. KSP anxiety-related scales correlated with the Positive and Negative Symptoms Scale (PANSS) general psychopathology subscale. Cognitive test results were uniformly lower in the patient group and correlated with PANSS negative symptoms subscale. There was no association between KSP scale scores and PANSS positive or negative symptoms.

CONCLUSION

The patients revealed a highly discriminative KSP test profile with elevated scores in neuroticism- and psychoticism-related scales as compared to controls. Results support previous findings utilizing other personality inventories in patients with schizophrenia. Cognitive test performance correlated inversely with negative symptoms.

Reversal of corticosterone-induced BDNF alterations by the natural antioxidant alpha-lipoic acid alone and combined with desvenlafaxine: Emphasis on the neurotrophic hypothesis of depression

Brain derived neurotrophic factor (BDNF) is linked to the pathophysiology of depression. We hypothesized that BDNF is one of the neurobiological pathways related to the augmentation effect of alpha-lipoic acid (ALA) when associated with antidepressants. Female mice were administered vehicle or CORT 20mg/kg during 14 days. From the 15th to 21st days the animals were divided in groups that were further administered: vehicle, desvenlafaxine (DVS) 10 or 20mg/kg, ALA 100 or 200mg/kg or the combinations of DVS10+ALA100, DVS20+ALA100, DVS10+ALA200 or DVS20+ALA200. ALA or DVS alone or in combination reversed CORT-induced increase in immobility time in the forced swimming test and decrease in sucrose preference, presenting, thus, an antidepressant-like effect. DVS10 alone reversed CORT-induced decrease in BDNF in the prefrontal cortex (PFC), hippocampus (HC) and striatum (ST). The same was observed in the HC and ST of ALA200 treated animals. The combination of DVS and ALA200 reversed CORT-induced alterations in BDNF and even, in some cases, increased the levels of this neurotrophin when compared to vehicle-treated animals in HC and ST. Taken together, these results suggest that the combination of the DVS+ALA may be valuable for treating conditions in which BDNF levels are decreased, such as depression.

Recent Advances in Nicotinic Receptor Signaling in Alcohol Abuse and Alcoholism

Alcohol is the most commonly abused legal substance and alcoholism is a serious public health problem. It is a leading cause of preventable death in the world. The cellular and molecular mechanisms of alcohol reward and addiction are still not well understood. Emerging evidence indicates that unlike other drugs of abuse, such as nicotine, cocaine, or opioids, alcohol targets numerous channel proteins, receptor molecules, and signaling pathways in the brain. Previously, research has identified brain nicotinic acetylcholine receptors (nAChRs), a heterogeneous family of pentameric ligand-gated cation channels expressed in the mammalian brain, as critical molecular targets for alcohol abuse and dependence. Genetic variations encoding nAChR subunits have been shown to increase the vulnerability to develop alcohol dependence. Here, we review recent insights into the rewarding effects of alcohol, as they pertain to different nAChR subtypes, associated signaling molecules, and pathways that contribute to the molecular mechanisms of alcoholism and/or comorbid brain disorders. Understanding these cellular changes and molecular underpinnings may be useful for the advancement of brain nicotinic-cholinergic mechanisms, and will lead to a better translational and therapeutic outcome for alcoholism and/or comorbid conditions.

Population difference in the association of BDNF promoter methylation with mild cognitive impairment in the Xinjiang Uygur and Han populations

BACKGROUND

Mild cognitive impairment (MCI) is a clinical transitional stage between normal aging and Alzheimer disease, which leads to memory loss and a reduction in cognitive function. Brain derived neurotrophic factor (BDNF) plays an important role in neuronal development and plasticity. The aim of this study was to explore the association between BDNF promoter methylation and MCI in the Xinjiang Uygur and Han populations.

METHODS

A DNA methylation assay using bisulfite pyrosequencing technology was performed on 96 Uygur and 96 Han Chinese individuals from Xinjiang province, China.

RESULTS

We found a significantly higher BDNF methylation level in Han MCI cases than in Uygur MCI cases in males from Xinjiang province (p=0.022). In addition, the methylation level was significantly higher in Xinjiang Han healthy Chinese individuals (Northwestern China) than in Ningbo Han healthy Chinese individuals (Southeastern China) (Female and Male: p=1.17E-05; Female: p=0.020; Male: p=1.37E-04). But our results showed no significant association of BDNF methylation with MCI in either the Uygur or Han Chinese populations (p>0.05). Further gender-based subgroup analyses did not find any significant results (p>0.05).

CONCLUSION

Our results indicate that different levels of BDNF methylation may be present in different populations and environments. This study also provides further information regarding the relationship between BDNF methylation levels and MCI in Xinjiang Uygur and Han ethnic groups.

Peripheral leukocyte expression of the potential biomarker proteins Bdnf, Sirt1, and Psen1 is not regulated by promoter methylation in Alzheimer's disease patients

The identification of Alzheimer's disease (AD) biomarkers is crucial to support drug discovery. Within putative biomarkers, peripheral Bdnf levels correlate with cognitive decline and AD, although conflicting findings are reported. Sirtuin 1 (Sirt1) serum levels are lower in AD patients and Presenilin 1 (Psen1) is expressed by blood cells. DNA methylation is altered in AD patients, suggesting that epigenetic mechanisms play a role in AD pathophysiology. The objective of this study was to investigate promoter methylation levels of potential biomarkers in AD cases and controls. Peripheral blood DNA methylation levels were analysed by methylation-specific primer real-time PCR. Bdnf promoter methylation levels did not differ between AD patients and controls. Similarly, Sirt1 promoter revealed minimal levels of methylation which did not display significant differences between groups. No significant difference was revealed between AD patients and controls also in Psen1 methylation, showing a large variability of values among subjects. Although peripheral Bdnf expression is associated with differential promoter methylation in psychiatric and neurological disorders, our results suggest that different mechanisms take place in AD. The finding that the control of Sirt1 protein levels in blood is not exerted through the repression of mRNA expression by promoter hypermethylation is in agreement with previous data. In contrast, other studies reported that Psen1 methylation may be increased or decreased in AD patients, suggesting that additional studies are required. In conclusion, this study shows that peripheral levels of the potential AD biomarker proteins Bdnf, Sirt1, and Psen1 are not regulated by different promoter methylation.

Epigenetic mechanisms in schizophrenia

Epigenetic modifications, including DNA methylation, histone modifications, and non-coding RNAs, have been implicated in a number of complex diseases. Schizophrenia and other major psychiatric and neurodevelopmental disorders are associated with abnormalities in multiple epigenetic mechanisms, resulting in altered gene expression during development and adulthood. Polymorphisms and copy number variants in schizophrenia risk genes contribute to the high heritability of the disease, but environmental factors that lead to epigenetic modifications may either reduce or exacerbate the expression of molecular and behavioral phenotypes associated with schizophrenia and related disorders. In the present paper, we will review the current understanding of molecular dysregulation in schizophrenia, including disruption of the dopamine, NMDA, and GABA signaling pathways, and discuss the role of epigenetic factors underlying disease pathology.