Epigenetic Modifications of Major Depressive Disorder

Integrating mitoepigenetics into research in mood disorders: a state-of-the-art review

Mood disorders, including major depressive disorder and bipolar disorder, are highly prevalent and stand among the leading causes of disability. Despite the largely elusive nature of the molecular mechanisms underpinning these disorders, two pivotal contributors-mitochondrial dysfunctions and epigenetic alterations-have emerged as significant players in their pathogenesis. This state-of-the-art review aims to present existing data on epigenetic alterations in the mitochondrial genome in mood disorders, laying the groundwork for future research into their pathogenesis. Associations between abnormalities in mitochondrial function and mood disorders have been observed, with evidence pointing to notable changes in mitochondrial DNA (mtDNA). These changes encompass variations in copy number and oxidative damage. However, information on additional epigenetic alterations in the mitochondrial genome remains limited. Recent studies have delved into alterations in mtDNA and regulations in the mitochondrial genome, giving rise to the burgeoning field of mitochondrial epigenetics. Mitochondrial epigenetics encompasses three main categories of modifications: mtDNA methylation/hydroxymethylation, modifications of mitochondrial nucleoids, and mitochondrial RNA alterations. The epigenetic modulation of mitochondrial nucleoids, lacking histones, may impact mtDNA function. Additionally, mitochondrial RNAs, including non-coding RNAs, present a complex landscape influencing interactions between the mitochondria and the nucleus. The exploration of mitochondrial epigenetics offers valuable perspectives on how these alterations impact neurodegenerative diseases, presenting an intriguing avenue for research on mood disorders. Investigations into post-translational modifications and the role of mitochondrial non-coding RNAs hold promise to unravel the dynamics of mitoepigenetics in mood disorders, providing crucial insights for future therapeutic interventions.

Molecular mechanisms underlying major depressive disorder and post-stroke affective disorders

Two of the most common and incapacitating mental health disorders around the world are major depressive disorder (MDD) and post-stroke depression (PSD). MDD is thought to result from abnormal connectivity between the monoaminergic, glutamatergic, GABAergic, and/or cholinergic pathways. Additional factors include the roles of hormonal, immune, ageing, as well as the influence of cellular, molecular, and epigenetics in the development of mood disorders. This complexity of factors has been anticipated by the Swiss psychiatrists Paul Kielholz and Jules Angst who introduced a multimodal treatment of MDD. Depression is the predominant mood disorder, impacting around one-third of individuals who have experienced a stroke. MDD and PSD share common underlying biological mechanisms related to the disruption of monoaminergic pathways. The major contributor to PSD is the stroke lesion location, which can involve the disruption of the serotoninergic, dopaminergic, glutamatergic, GABAergic, or cholinergic pathways. Additionally, various other disorders such as mania, bipolar disorder, anxiety disorder, and apathy might occur post-stroke, although their prevalence is considerably lower. However, there are differences in the onset of MDD among mood disorders. Some mood disorders develop gradually and can persist for a lifetime, potentially culminating in suicide. In contrast, PSD has a rapid onset because of the severe disruption of neural pathways essential for mood behavior caused by the lesion. However, PSD might also spontaneously resolve several months after a stroke, though it is associated with higher mortality. This review also provides a brief overview of the treatments currently available in medical practice.

Mitochondrial DNA oxidation, methylation, and copy number alterations in major and bipolar depression

Background

Mood disorders are common disabling psychiatric disorders caused by both genetic and environmental factors. Mitochondrial DNA (mtDNA) modifications and epigenetics are promising areas of research in depression since mitochondrial dysfunction has been associated with depression. In this study we aimed to investigate the mtDNA changes in depressive disorder (MDD) and bipolar disorder (BD).

Methods

Displacement loop methylation (D-loop-met), relative mtDNA copy number (mtDNA-cn) and mtDNA oxidation (mtDNA-oxi) were investigated in DNA samples of individuals with MDD (n = 34), BD (n = 23), and healthy controls (HC; n = 40) using the Real-Time Polymerase Chain Reaction (RT-PCR). Blood samples were obtained from a subset of individuals with MDD (n = 15) during a depressive episode (baseline) and after remission (8th week).

Results

The study groups exhibited significant differences in D-loop-met (p = 0.020), while relative mtDNA-cn and mtDNA-oxi showed comparable results. During the remission phase (8th week), there were lower levels of relative mtDNA-cn (Z = -2.783, p = 0.005) and D-loop-met (Z = -3.180, p = 0.001) compared to the acute MDD baseline, with no significant change in mtDNA-oxi levels (Z = -1.193, p = 0.233).

Conclusion

Our findings indicate significantly increased D-loop methylation in MDD compared to BD and HCs, suggesting distinct mtDNA modifications in these conditions. Moreover, the observed alterations in relative mtDNA-cn and D-loop-met during remission suggest a potential role of mtDNA alterations in the pathophysiology of MDD. Future studies may provide valuable insights into the dynamics of mtDNA modifications in both disorders and their response to treatment.

Research on Xiaoyao Powder in the treatment of depression based on epigenetics and quality markers

Depression has become one of the most common public health issues around the world, and the incidence has been increasing in recent years. A large amount of clinical investigations have proven that the treatment of depression is difficult. The prognosis is poor, and the fatality rate is high. At present, western medicine is the preferred treatment for depression, but it often causes adverse clinical reactions such as dry mouth, blurred vision, and memory loss, etc. The herbal compound Xiaoyao Powder is a traditional medicine for soothing the liver and relieving depression, strengthening the spleen, and nourishing the blood. It can reduce adverse reactions. It is effective in treating depression. In this study, we elucidate the function of Xiaoyao Powder in anti-depression from the perspective of clinical application and pharmacological mechanisms such as regulating epigenetic and chemical quality markers to provide empirical and experimental theoretical results that contribute to developing future depression therapy with Xiaoyao Powder.

Antidepressant and Anxiolytic Effects of L-Methionine in the WAG/Rij Rat Model of Depression Comorbid with Absence Epilepsy

Depression is a severe and widespread psychiatric disease that often accompanies epilepsy. Antidepressant treatment of depression comorbid with epilepsy is a major concern due to the risk of seizure aggravation. SAMe, a universal methyl donor for DNA methylation and the synthesis of brain monoamines, is known to have high antidepressant activity. This study aimed to find out whether L-methionine (L-MET), a precursor of SAMe, can have antidepressant and/or anxiolytic effects in the WAG/Rij rat model of depression comorbid with absence epilepsy. The results indicate that L-MET reduces the level of anxiety and depression in WAG/Rij rats and suppresses associated epileptic seizures, in contrast to conventional antidepressant imipramine, which aggravates absence seizures. The antidepressant effect of L-MET was comparable with that of the conventional antidepressants imipramine and fluoxetine. However, the antidepressant profile of L-MET was more similar to imipramine than to fluoxetine. Taken together, our findings suggest that L-MET could serve as a promising new antidepressant drug with anxiolytic properties for the treatment of depression comorbid with absence epilepsy. Increases in the level of monoamines and their metabolites-DA, DOPAC, HVA, NA, and MHPG-in several brain structures, is suggested to be a neurochemical mechanism of the beneficial phenotypic effect of L-MET.

Aberrant Histone Modification of TNFAIP3, TLR4, TNIP2, miR-146a, and miR-155 in Major Depressive Disorder

Activated toll-like receptor (TLR) signaling has been well investigated in major depressive disorder (MDD). We previously reported that TNFAIP3, TLR4, TNIP2, miR-146a, and miR-155 play important roles in regulating the toll-like receptor 4 (TLR4) signaling pathway and may serve as novel targets in the pathogenesis of MDD. Recently, aberrant histone modification has been implicated in several psychiatric disorders, including schizophrenia and mood disorder; the most thoroughly studied modification is histone 3 lysine 4 tri-methylation (H3K4me3). In this work, we aimed to explore H3K4me3 differences in the promotors of genes encoding the abovementioned factors in patients with MDD, and whether they were altered after antidepressant treatment. A total of 30 MDD patients and 28 healthy controls were recruited. Peripheral blood mononuclear cells (PBMCs) were collected. The levels of H3K4me3 in the promoters of TNFAIP3, TLR4, TNIP2, miR-146a, and miR-155 were measured through chromatin immunoprecipitation (ChIP) followed by DNA methylation assay. Analysis of covariance was used to evaluate between-group differences after adjusting for age, sex, BMI, and smoking. In comparison with healthy controls, patients with MDD showed significantly lower H3K4me3 levels in the promoters of TNFAIP3, TLR4, TNIP2, miR-146a, and miR-155 in PBMCs. These levels were not significantly altered after completion of a 4-week antidepressant treatment. To explore the association between depression severity and H3K4me3 levels, a multiple linear regression model was generated. The results revealed that levels of H3K4me3 in the TNIP2 promoters a negative correlation with the 17-item Hamilton Depression Rating Scale (HAND-17) score, whereas that of TLR4 had a positive correlation with this score. The present results suggest that decreased H3K4me3 levels in the promoters of the genes encoding TNFAIP3, TLR4, miR-146a, miR-155, and TNIP2 are involved in psychopathology of major depressive disorder.

DNA Methylation in Depression and Depressive-Like Phenotype: Biomarker or Target of Pharmacological Intervention?

Major depressive disorder (MDD) is a debilitating psychiatric disorder, the third leading global cause of disability. Regarding aetiopathogenetic mechanisms involved in the onset of depressive disorders, the interaction between genetic vulnerability traits and environmental factors is believed to play a major role. Although much is still to be elucidated about the mechanisms through which the environment can interact with genetic background shaping the disease risk, there is a general agreement about a key role of epigenetic marking. In this narrative review, we focused on the association between changes in DNA methylation patterns and MDD or depressive-like phenotype in animal models, as well as mechanisms of response to antidepressant drugs. We discussed studies presenting DNA methylation changes at specific genes of interest and profiling analyses in both patients and animal models of depression. Overall, we collected evidence showing that DNA methylation could not only be considered as a promising epigenetic biomarker of pathology but could also help in predicting antidepressant treatment efficacy. Finally, we discussed the hypothesis that specific changes in DNA methylation signature could play a role in aetiopathogenetic processes as well as in the induction of antidepressant effect.

Epigenetic and Neuronal Activity Markers Suggest the Recruitment of the Prefrontal Cortex and Hippocampus in the Three-Hit Model of Depression in Male PACAP Heterozygous Mice

Depression and its increasing prevalence challenge patients, the healthcare system, and the economy. We recently created a mouse model based on the three-hit concept of depression. As genetic predisposition (first hit), we applied pituitary adenylate cyclase-activating polypeptide heterozygous mice on CD1 background. Maternal deprivation modeled the epigenetic factor (second hit), and the chronic variable mild stress was the environmental factor (third hit). Fluoxetine treatment was applied to test the predictive validity of our model. We aimed to examine the dynamics of the epigenetic marker acetyl-lysine 9 H3 histone (H3K9ac) and the neuronal activity marker FOSB in the prefrontal cortex (PFC) and hippocampus. Fluoxetine decreased H3K9ac in PFC in non-deprived animals, but a history of maternal deprivation abolished the effect of stress and SSRI treatment on H3K9ac immunoreactivity. In the hippocampus, stress decreased, while SSRI increased H3K9ac immunosignal, unlike in the deprived mice, where the opposite effect was detected. FOSB in stress was stimulated by fluoxetine in the PFC, while it was inhibited in the hippocampus. The FOSB immunoreactivity was almost completely abolished in the hippocampus of the deprived mice. This study showed that FOSB and H3K9ac were modulated in a territory-specific manner by early life adversities and later life stress interacting with the effect of fluoxetine therapy supporting the reliability of our model.

RPS6KA5 methylation predict response to 6-week treatment for adolescent MDD patients

OBJECTIVE

We aimed to investigate the effect of differentially methylated genes and chronic childhood stress on the development of depressive symptoms in Chinese adolescents, as well as to test whether methylation at baseline can be used as a predictor of remission at follow-up after six weeks of treatment.

METHODS

After recruiting 87 MDD patients and 53 healthy controls, we compared demographic and baseline clinical characteristics. The Childhood Chronic Stress Questionnaire was used to assess stress caused by early-life events. MDD patients underwent six weeks of treatment, and response to treatment was assessed using the Beck Depression Inventory-II. In addition, four MDD patients and five controls were randomly chosen for genome-wide methylation analysis.

RESULTS

The gene RPS6KA5 showed significant methylation differences between the two groups. Severity of chronic childhood stress was significantly associated with increased risk of depression in adolescents, but not with treatment response. Baseline RPS6KA5 methylation can predict remission after six weeks of treatment. We did not observe any interaction between RPS6KA5 methylation and chronic childhood stress.

CONCLUSIONS

Our results suggest that RPS6KA5 methylation can be used as a predictor of response to treatment in adolescent MDD patients. Here we offer new evidence for the role of epigenetics in early response to treatment of depression.

TRIAL REGISTRATION

ChiCTR, ChiCTR2000033402, 31/05/2020, http://www.chictr.org.cn/index.aspx.

Synergic action of L-acetylcarnitine and L-methylfolate in Mouse Models of Stress-Related Disorders and Human iPSC-Derived Dopaminergic Neurons

The epigenetic agents, L-acetylcarnitine (LAC) and L-methylfolate (MF) are putative candidates as add-on drugs in depression. We evaluated the effect of a combined treatment with LAC and MF in two different paradigms of chronic stress in mice and in human inducible pluripotent stem cells (hiPSCs) differentiated into dopaminergic neurons. Two groups of mice were exposed to chronic unpredictable stress (CUS) for 28 days or chronic restraint stress (CRS) for 21 day, and LAC (30 or 100 mg/kg) and/or MF (0.75 or 3 mg/kg) were administered i.p. once a day for 14 days, starting from the last week of stress. In both stress paradigms, LAC and MF acted synergistically in reducing the immobility time in the forced swim test and enhancing BDNF protein levels in the frontal cortex and hippocampus. In addition, LAC and MF acted synergistically in enhancing type-2 metabotropic glutamate receptor (mGlu2) protein levels in the hippocampus of mice exposed to CRS. Interestingly, CRS mice treated with MF showed an up-regulation of NFκB p65, which is a substrate for LAC-induced acetylation. We could also demonstrate a synergism between LAC and MF in cultured hiPSCs differentiated into dopamine neurons, by measuring dendrite length and number, and area of the cell soma after 3 days of drug exposure. These findings support the combined use of LAC and MF in the treatment of MDD and other stress-related disorders.

Genetic and epigenetic factors associated with depression: an updated overview

Depression is a complex psychiatric disturbance involving many environmental, genetic, and epigenetic factors. Until now, genetic, and non-genetic studies are still on the way to understanding the complex mechanism of this disease, and there are still many questions that have not yet been answered. Depression includes a large spectrum of heterogeneous symptoms correlated to the deficit of a range of psychological, cognitive, and emotional processes, and it affects various age groups. It is classified into several types according to the severity of symptoms, time of occurrence, and time. Following the World Health Organization (WHO), depression attacks near 350 million persons globally. Several factors overlap in causing depression, including genetic and epigenetic factors, environmental conditions, various stresses, lack of some nutrients to which people are exposed, and excessive stress and abuse in childhood. This study included conducting surveys on depression and new treatment trends based on epigenetic factors associated with the occurrence of the disease. Epigenetic factors provide a completely novel dimension to therapeutic approaches as most diseases are not monogenic, and it is likely that the environment has a significant contribution. Epigenetic inheritance is included in many mental and psychiatric disorders such as depression. In general, epigenetic modifications could be summarized in 3 major points: DNA methylation, histone modification, and non-mediated regulation of RNA (ncRNA). This study also describes some genes associated with one of the depressive disorders using bioinformatics tools and gene bank and had the genes: SLC6A4, COMT, TPH2, FKBP5, MDD1, HTR2A, and MDD2. As in this study, the awareness of Saudi society about depression and its genetic and non-genetic causes was estimated. The results showed that an encouraging percentage of more than half of the research sample possessed correct information about this disorder.

Major Depressive Disorder: Existing Hypotheses about Pathophysiological Mechanisms and New Genetic Findings

Major depressive disorder (MDD) is a common mental disorder generally characterized by symptoms associated with mood, pleasure and effectiveness in daily life activities. MDD is ranked as a major contributor to worldwide disability. The complex pathogenesis of MDD is not yet understood, and this is a major cause of failure to develop new therapies and MDD recurrence. Here we summarize the literature on existing hypotheses about the pathophysiological mechanisms of MDD. We describe the different approaches undertaken to understand the molecular mechanism of MDD using genetic data. Hundreds of loci have now been identified by large genome-wide association studies (GWAS). We describe these studies and how they have provided information on the biological processes, cell types, tissues and druggable targets that are enriched for MDD risk genes. We detail our understanding of the genetic correlations and causal relationships between MDD and many psychiatric and non-psychiatric disorders and traits. We highlight the challenges associated with genetic studies, including the complexity of MDD genetics in diverse populations and the need for a study of rare variants and new studies of gene-environment interactions.

Epigenetic studies in suicidal ideation and behavior

Most psychiatric disorders are associated with an elevated risk of suicide. Suicidal behavior is the product of the interaction of many risk factors, such as genetics and environmental factors. Hence, epigenetics research may help to understand the mechanisms leading to suicidal ideation and behavior. This review will discuss epigenetic studies in both suicidal ideation and behavior. Epigenetic modifications are likely to be important in both suicidal ideation and behavior. Most of the reviewed studies found significant epigenetic modifications linked with suicidal behavior rather than ideation. Although sizable research has been carried out on this topic, most studies have been done on small-scale samples, and future research is required in larger samples with better clinical characterization of suicide phenotypes to investigate these epigenetic modifications further.

Epigenetics of Schizophrenia

Schizophrenia (SCZ) is a chronic psychotic disorder that contributes significantly to disability, affecting behavior, thought, and cognition. It has long been known that there is a heritable component to schizophrenia; studies in both the pre-genomic and post-genomic era, however, have failed to elucidate fully the genetic basis for this complex disease. Epigenetic processes - broadly, those which contribute to changes in gene expression without altering the genetic code itself - may help to understand better the mechanisms leading to development of SCZ. The objective of this review is to synthesize current knowledge of the epigenetic mechanisms involved in schizophrenia. Specifically, DNA methylation studies in both peripheral and post-mortem brain samples in SCZ are reviewed, as are epigenetic mechanisms including histone modification. The promising role of non-coding RNA including micro-RNA (miRNA) and its role as a potential diagnostic and therapeutic biomarker is outlined, as are epigenetic age acceleration and telomere shortening. Finally, we discuss limitations in current knowledge and propose future research directions.

Uncovering the Roles of MicroRNAs in Major Depressive Disorder: From Candidate Diagnostic Biomarkers to Treatment Response Indicators

Major depressive disorder (MDD) is a recurrent debilitating illness that represents a major health burden due to its increasing worldwide prevalence, unclear pathological mechanism, nonresponsive treatment, and lack of reliable and specific diagnostic biomarkers. Recently, microRNA species (miRs) have gained particular interest because they have the ability to post-transcriptionally regulate gene expression by modulating mRNA stability and translation in a cohesive fashion. By regulating entire genetic circuitries, miRs have been shown to have dysregulated expression levels in blood samples from MDD patients, when compared to healthy subjects. In addition, antidepressant treatment (AD) also appears to alter the expression pattern of several miRs. Therefore, we critically and systematically reviewed herein the studies assessing the potential biomarker role of several candidate miRs for MDD, as well as treatment response monitoring indicators, in order to enrich the current knowledge and facilitate possible diagnostic biomarker development for MDD, which could aid in reducing both patients' burden and open novel avenues toward a better understanding of MDD neurobiology.

Histone deacetylase in neuropathology

Neuroepigenetics, a new branch of epigenetics, plays an important role in the regulation of gene expression. Neuroepigenetics is associated with holistic neuronal function and helps in formation and maintenance of memory and learning processes. This includes neurodevelopment and neurodegenerative defects in which histone modification enzymes appear to play a crucial role. These modifications, carried out by acetyltransferases and deacetylases, regulate biologic and cellular processes such as apoptosis and autophagy, inflammatory response, mitochondrial dysfunction, cell-cycle progression and oxidative stress. Alterations in acetylation status of histone as well as non-histone substrates lead to transcriptional deregulation. Histone deacetylase decreases acetylation status and causes transcriptional repression of regulatory genes involved in neural plasticity, synaptogenesis, synaptic and neural plasticity, cognition and memory, and neural differentiation. Transcriptional deactivation in the brain results in development of neurodevelopmental and neurodegenerative disorders. Mounting evidence implicates histone deacetylase inhibitors as potential therapeutic targets to combat neurologic disorders. Recent studies have targeted naturally-occurring biomolecules and micro-RNAs to improve cognitive defects and memory. Multi-target drug ligands targeting HDAC have been developed and used in cell-culture and animal-models of neurologic disorders to ameliorate synaptic and cognitive dysfunction. Herein, we focus on the implications of histone deacetylase enzymes in neuropathology, their regulation of brain function and plausible involvement in the pathogenesis of neurologic defects.

Prenatal and Early Postnatal Behavioural Programming in Laying Hens, With Possible Implications for the Development of Injurious Pecking

Injurious pecking (IP) represents a serious concern for the welfare of laying hens (Gallus gallus domesticus). The risk of IP among hens with intact beaks in cage-free housing prompts a need for solutions based on an understanding of underlying mechanisms. In this review, we explore how behavioural programming via prenatal and early postnatal environmental conditions could influence the development of IP in laying hens. The possible roles of early life adversity and mismatch between early life programming and subsequent environmental conditions are considered. We review the role of maternal stress, egg conditions, incubation settings (temperature, light, sound, odour) and chick brooding conditions on behavioural programming that could be linked to IP. Brain and behavioural development can be programmed by prenatal and postnatal environmental conditions, which if suboptimal could lead to a tendency to develop IP later in life, as we illustrate with a Jenga tower that could fall over if not built solidly. If so, steps taken to optimise the environmental conditions of previous generations and incubation conditions, reduce stress around hatching, and guide the early learning of chicks will aid in prevention of IP in commercial laying hen flocks.

Epigenetics: A Missing Link Between Early Life Stress and Depression

Exposure to early life stress (ELS) represents a major risk factor for the development of psychiatric disorders, including depression. The susceptibility associated with ELS may result from persistent changes in gene transcription, which can occur through epigenetic mechanisms, such as DNA methylation, histone modifications, and microRNA expression. Animal models and reports in humans described that negative stimuli can alter the neurodevelopment of an individual, affecting their behavior and cognitive development. It is currently hypothesized that levels of environmental adversity in this early developmental period are able to shape the experience-dependent maturation of stress-regulating pathways leading to long-lasting alterations in stress responsivity during adulthood. Here, we review key findings from animal and clinical studies examining the effects of prenatal and postnatal environment in shaping development of the neuroendocrine regulation of stress and the role of epigenetic mechanisms in the predisposition of depression.

Distribution of microRNAs associated with major depressive disorder among blood compartments

OBJECTIVE

Major depressive disorder (MDD) is a recurrent disorder with an increasing incidence. Alterations in key signaling pathways of the nervous system, such as the Wnt and MAPK pathways, mediated through microRNAs (miRNAs) provide crucial information regarding the etiopathology of MDD. We aimed to analyze whether the heterogeneity of literature findings regarding differential expression of miRNAs in the blood could arise from their different distributions among blood compartments.

METHODS

We performed a pilot study analyzing the differential expression of miR-26a, miR-494, miR-30c, miR-93, and miR-101 and investigated their levels in white blood cells, total plasma (TP), exosomes from plasma, and exosome depleted plasma (EDP) in patients with MDD before and after antidepressant treatment with escitalopram and in healthy controls.

RESULTS

MiR-494 was more abundant in EDP, and miR-26a and miR-30c were predominantly more abundant in TP relative to other blood compartments. Moreover, miR-30c, miR-101, and miR-26a, were significantly downregulated in TP of patients with MDD compared with controls. After antidepressant treatment, only miR-494 was significantly differently expressed in EDP.

CONCLUSIONS

This proof-of-principle study suggests that identifying the miRNA abundance in different blood compartments is crucial for biomarker development and could enrich the current knowledge regarding MDD pathophysiology.

The Importance of Epigenetics in Diagnostics and Treatment of Major Depressive Disorder

Recent studies imply that there is a tight association between epigenetics and a molecular mechanism of major depressive disorder (MDD). Epigenetic modifications, i.e., DNA methylation, post-translational histone modification and interference of microRNA (miRNA) or long non-coding RNA (lncRNA), are able to influence the severity of the disease and the outcome of the therapy. This article summarizes the most recent literature data on this topic, i.e., usage of histone deacetylases as therapeutic agents with an antidepressant effect and miRNAs or lncRNAs as markers of depression. Due to the noteworthy potential of the role of epigenetics in MDD diagnostics and therapy, we have gathered the most relevant data in this area.

Fluoxetine regulates eEF2 activity (phosphorylation) via HDAC1 inhibitory mechanism in an LPS-induced mouse model of depression

BACKGROUND

Selective serotonin reuptaker inhibitors, including fluoxetine, are widely studied and prescribed antidepressants, while their exact molecular and cellular mechanism are yet to be defined. We investigated the involvement of HDAC1 and eEF2 in the antidepressant mechanisms of fluoxetine using a lipopolysaccharide (LPS)-induced depression-like behavior model.

METHODS

For in vivo analysis, mice were treated with LPS (2 mg/kg BW), fluoxetine (20 mg/kg BW), HDAC1 activator (Exifone: 54 mg/kg BW) and NH125 (1 mg/kg BW). Depressive-like behaviors were confirmed via behavior tests including OFT, FST, SPT, and TST. Cytokines were measured by ELISA while Iba-1 and GFAP expression were determined by immunofluorescence. Further, the desired gene expression was measured by immunoblotting. For in vitro analysis, BV2 cell lines were cultured; treated with LPS, exifone, and fluoxetine; collected; and analyzed.

RESULTS

Mice treated with LPS displayed depression-like behaviors, pronounced neuroinflammation, increased HDAC1 expression, and reduced eEF2 activity, as accompanied by altered synaptogenic factors including BDNF, SNAP25, and PSD95. Fluoxetine treatment exhibited antidepressant effects and ameliorated the molecular changes induced by LPS. Exifone, a selective HDAC1 activator, reversed the antidepressant and anti-inflammatory effects of fluoxetine both in vivo and in vitro, supporting a causing role of HDAC1 in neuroinflammation allied depression. Further molecular mechanisms underlying HDAC1 were explored with NH125, an eEF2K inhibitor, whose treatment reduced immobility time, altered pro-inflammatory cytokines, and NLRP3 expression. Moreover, NH125 treatment enhanced eEF2 and GSK3β activities, BDNF, SNAP25, and PSD95 expression, but had no effects on HDAC1.

CONCLUSIONS

Our results showed that the antidepressant effects of fluoxetine may involve HDAC1-eEF2 related neuroinflammation and synaptogenesis.

Antidepressant treatment is associated with epigenetic alterations of Homer1 promoter in a mouse model of chronic depression

BACKGROUND

Understanding the neurobiology of depression and the mechanism of action of therapeutic measures is currently a research priority. We have shown that the expression of the synaptic protein Homer1a correlates with depression-like behavior and its induction is a common mechanism of action of different antidepressant treatments. However, the mechanism of Homer1a regulation is still unknown.

METHODS

We combined the chronic despair mouse model (CDM) of chronic depression with different antidepressant treatments. Depression-like behavior was characterized by forced swim and tail suspension tests, and via automatic measurement of sucrose preference in IntelliCage. The Homer1 mRNA expression and promoter DNA methylation were analyzed in cortex and peripheral blood by qRT-PCR and pyrosequencing.

RESULTS

CDM mice show decreased Homer1a and Homer1b/c mRNA expression in cortex and blood samples, while chronic treatment with imipramine and fluoxetine or acute ketamine application increases their level only in the cortex. The quantitative analyses of the methylation of 7 CpG sites, located on the Homer1 promoter region containing several CRE binding sites, show a significant increase in DNA methylation in the cortex of CDM mice. In contrast, antidepressant treatments reduce the methylation level.

LIMITATIONS

Homer1 expression and promotor methylation were not analyzed in different blood cell types. Other CpG sites of Homer1 promoter should be investigated in future studies. Our experimental approach does not distinguish between methylation and hydroxymethylation.

CONCLUSIONS

We demonstrate that stress-induced depression-like behavior and antidepressant treatments are associated with epigenetic alterations of Homer1 promoter, providing new insights into the mechanism of antidepressant treatment.

Alterations observed in the interferon α and β signaling pathway in MDD patients are marginally influenced by cis-acting alleles

Major depressive disorder (MDD) is a common psychiatric disorder with a multifactorial aetiology determined by the interaction between genetic and environmental risk factors. Pieces of evidence indicate that inflammation and immune activation may contribute to the onset of MDD playing a role in the pathogenetic mechanism. To date, it is not known to which extent the association between MDD and inflammation is shaped by the genetic background or by the presence of environmental factors. To clarify this issue, we analyzed genotype and blood RNA profiles of 463 MDD cases and 459 controls (NIMH-Study 88/Site621) estimating the Genetic and Environmental Regulated eXpression component of gene expression (GReX and EReX respectively). Both components were tested for association with MDD. Many genes belonging to the α/β interferon signaling pathway showed an association between MDD and EReX, only two between MDD and GReX. Also other MDD differentially expressed genes were more influenced by the EReX than by GReX. These results suggest that impact of the genetic background on MDD blood gene expression alterations is much lower than the contribution of environmental factors and almost absent for the genes of the interferon pathway.

Children With Disruptive Mood Dysregulation Disorder and Psychopathological Risk in Their Mothers: The Function of Global DNA Methylation

Epigenetic mechanisms, in particular DNA methylation, have been implicated in the etiopathogenesis of psychopathologies in adulthood. The significance of this mechanism in child psychopathologies, however, is much less recognized. Here, we examined whether global DNA methylation alteration was associated with the presence of disruptive mood dysregulation disorder (DMDD) in children. Moreover, in light of the relevance of the interplay between children and parents for the onset and maintaining of psychopathology during development, we measured the association between psychological symptoms, attachment styles, and global DNA methylation levels in healthy and DMDD mother-child dyads (mothers: N = 126, age = 38.3 ± 2.5 years; children: N = 150, age = 8.2 ± 0.9 years, gender ratio [f/m] = 72/78). We did not observe any significant differences in global DNA methylation levels in DMDD children when compared with healthy peers, and children's symptoms did not correlate with variations in this parameter. The mothers showed different levels of psychological symptomatology. Notably, mothers with high psychological symptomatology showed the lowest levels of global DNA methylation. Maternal global DNA methylation levels were associated with maternal hostility, interpersonal sensitivity, psychoticism, and general severity index. Moreover, we found an effect of maternal mental health on the severity of children's symptoms, independently from both maternal and child DNA methylation levels. Despite here DNA methylation does not appear to be involved in the maternal inheritance of vulnerability to depression, this biological link could still arise in later stages of the child's development.

A Comprehensive Analysis of Unique and Recurrent Copy Number Variations in Alzheimer's Disease and its Related Disorders

BACKGROUND

Copy number variations (CNVs) play an important role in the genetic etiology of various neurological disorders, including Alzheimer's disease (AD). Type 2 diabetes mellitus (T2DM) and major depressive disorder (MDD) were shown to have share mechanisms and signaling pathways with AD.

OBJECTIVE

We aimed to assess CNVs regions that may harbor genes contributing to AD, T2DM, and MDD in 67 Saudi familial and sporadic AD patients, with no alterations in the known genes of AD and genotyped previously for APOE.

METHODS

DNA was analyzed using the CytoScan-HD array. Two layers of filtering criteria were applied. All the identified CNVs were checked in the Database of Genomic Variants (DGV).

RESULTS

A total of 1086 CNVs (565 gains and 521 losses) were identified in our study. We found 73 CNVs harboring genes that may be associated with AD, T2DM or MDD. Nineteen CNVs were novel. Most importantly, 42 CNVs were unique in our studied cohort existing only in one patient. Two large gains on chromosomes 1 and 13 harbored genes implicated in the studied disorders. We identified CNVs in genes that encode proteins involved in the metabolism of amyloid-β peptide (AGRN, APBA2, CR1, CR2, IGF2R, KIAA0125, MBP, RER1, RTN4R, VDR and WISPI) or Tau proteins (CACNAIC, CELF2, DUSP22, HTRA1 and SLC2A14).

CONCLUSION

The present work provided information on the presence of CNVs related to AD, T2DM, and MDD in Saudi Alzheimer's patients.

Dissecting major depression: The role of blood biomarkers and adverse childhood experiences in distinguishing clinical subgroups

BACKGROUND

The syndromic diagnosis of major depressive disorder (MDD) is associated with individual differences in prognosis, course, treatment response, and outcome. There is evidence that patients with a history to adverse childhood experiences (ACEs) may belong to a distinct clinical subgroup. The combination of data on ACEs and blood biomarkers could allow the identification of diagnostic MDD subgroups.

METHODS

We selected several blood markers (global DNA methylation, and VEGF-a, TOLLIP, SIRT1, miR-34a genes) among factors that contribute to the pathogenetic mechanisms of MDD. We examined their level in 37 MDD patients and 30 healthy subjects. ACEs were measured by the Parental Bonding Instrument and the Childhood Trauma Questionnaire.

RESULTS

We found significant differences between patients and healthy subjects in three biomarkers (TOLLIP, VEGF-a, and global DNA methylation), independently from the confounding effect of parental care received. By contrast, SIRT1 differences were modulated by quality of parental care. The lowest levels of SIRT1 were recorded in patients with active symptoms and low maternal/paternal care. miR-34a and SIRT1 levels were associated with MDD symptoms especially in early-life stressed patients.

LIMITATIONS

Small sample size, no information on personality comorbidity and suicidal history, cross-sectional definition of remission, and lack of follow-up.

CONCLUSIONS

Our findings suggest that the levels of global DNA methylation, TOLLIP, and VEGF-a reflect pathophysiological changes associated with MDD that are independent from the long-term effects of low parental care. This study also suggests that SIRT1 may be an additional variable distinguishing the ecophenotype that includes MDD patients with exposure to ACEs.

Epigenetic marks and their relationship with BDNF in the brain of suicide victims

Background

Suicide is a common phenomenon affecting people of all ages. There is a strong relationship between suicidal ideation and depressive disorders. Increasing number of studies suggest that epigenetic modifications in certain brain areas are the main mechanism through which environmental and genetic factors interact with each other contributing to the development of mental disorders. To verify this hypothesis, some epigenetic marks: H3K9/14ac, HDAC2/3, H3K27me2 and Sin3a, as well as p-S421-MeCP2/MeCP2 were examined. On the other hand, BDNF protein level were studied.

Materials and methods

Western blot analysis were performed in the frontal cortex (FCx) and hippocampus (HP) of suicide victims (n = 14) and non-suicidal controls (n = 8). The differences between groups and correlations between selected proteins were evaluated using Mann-Whitney U-test and Spearman’s rank correlation.

Results

Statistically significant decrease in H3K9/14ac (FCx:↓~23%;HP:↓~33%) combined with increase in HDAC3 (FCx:↑~103%;HP:↑~85% in HP) protein levels in suicides compared to the controls was shown. These alterations were accompanied by an increase in H3K27me2 (FCx:↑45%;HP:↑~59%) and Sin3a (HP:↑50%) levels and decrease in p-S421-MeCP2/MeCP2 protein ratio (HP:↓~55%;FCx:↓~27%). Moreover, reduced BDNF protein level (FCx:↓~43%;HP:↓~28%) in suicides was observed. On the other hand, some significant correlations (e.g. between H3K9/14ac and HDAC2 or between BDNF and p-S421-MeCP2/MeCP2) were demonstrated.

Conclusions

Our findings confirm the role of epigenetic component and BDNF protein in suicidal behavior. Lowered BDNF protein level in suicides is probably due to decrease in histone acetylation and increased level of factors related with deacetylation and methylation processes, including MeCP2 factor, which may operate bidirectionally (an activator or inhibitor of transcription).

The Epigenetic Overlap between Obesity and Mood Disorders: A Systematic Review

(1) Background: Obesity and mood disorders are considered as the most prevalent morbidities in many countries. We suppose that epigenetic mechanisms may induce higher rates of obesity in subjects who suffer from mood disorders. In this systematic review, we focused on the potential roles of DNA methylation on mood disorders and obesity development. (2) Methods: This systematic review was conducted in accordance with the PRISMA statement and registered in Prospero. A systematic search was conducted in MEDLINE, Scopus, Web of Science, Cochrane Central database, EMBASE, and CINHAL. We also conducted a Grey literature search, such as Google Scholar. (3) Results: After deduplication, we identified 198 potentially related citations. Finally, ten unique studies met our inclusion criteria. We have found three overlap genes that show significant DNA methylation changes, both in obesity and depression. Pathway analysis interaction for TAPBP, BDNF, and SORBS2 confirmed the relation of these genes in both obesity and mood disorders. (4) Conclusions: While mechanisms linking both obesity and mood disorders to epigenetic response are still unknown, we have already known chronic inflammation induces a novel epigenetic program. As the results of gene enrichment, pathways analysis showed that TAPBP, BDNF, and SORBS2 linked together by inflammatory pathways. Hypermethylation in these genes might play a crucial rule in the co-occurrence of obesity and mood disorders.

Proposed Neuroimmune Roles of Dimethyl Fumarate, Bupropion, S-Adenosylmethionine, and Vitamin D3 in Affording a Chronically Ill Patient Sustained Relief from Inflammation and Major Depression

We had discussed earlier that, after most of the primary author's multiple sclerosis (MS) symptoms were lessened by prior neuroimmune therapies, use of dimethyl fumarate (DMF) gradually subdued his asthma and urticaria symptoms, as well as his MS-related intercostal cramping; and bupropion supplemented with S-adenosylmethionine (SAMe) and vitamin D3 (vit-D3) helped remit major depression (MD). Furthermore, the same cocktail (bupropion plus supplements), along with previously discussed routines (yoga, meditation, physical exercises, and timely use of medications for other illnesses), continued to subdue MD during new difficulties with craniopharyngioma, which caused bitemporal vision loss; sphenoid sinus infections, which caused cranial nerve-VI (CN6) palsy and diplopia; and through their treatments. Impressed by the benefit the four compounds provided, in this manuscript, we focus on explaining current neuroimmune literature proposals on how: (1) DMF impedes inflammation, oxidative stress, and cell death in CNS and peripheral tissues; (2) Bupropion curbs anxiety, MD, and enhances alertness, libido, and moods; (3) SAMe silences oxidative stress and depression by multiple mechanisms; and (4) Vit-D3 helps brain development and functioning and subdues inflammation. we realize that herein we have reviewed proposed mechanisms of remedies we discovered by literature searches and physician assisted auto-experimentation; and our methods might not work with other patients. We present our experiences so readers are heartened to reflect upon their own observations in peer-reviewed forums and make available a wide body of information for the chronically ill and their physicians to benefit from.

Exploiting Circulating MicroRNAs as Biomarkers in Psychiatric Disorders

Non-invasive peripheral biomarkers play a significant role in both disease diagnosis and progression. In the past few years, microRNA (miRNA) expression changes in circulating peripheral tissues have been found to be correlative with changes in neuronal tissues from patients with neuropsychiatric disorders. This is a notable quality of a biomolecule to be considered as a biomarker for both prognosis and diagnosis of disease. miRNAs, members of the small non-coding RNA family, have recently gained significant attention due to their ability to epigenetically influence almost every aspect of brain functioning. Empirical evidence suggests that miRNA-associated changes in the brain are often translated into behavioral changes. Current clinical understanding further implicates their role in the management of major psychiatric conditions, including major depressive disorder (MDD), bipolar disorder (BD), and schizophrenia (SZ). This review aims to critically evaluate the potential advantages and disadvantages of miRNAs as diagnostic/prognostic biomarkers in psychiatric disorders as well as in treatment response.

Perioperative Considerations for Patients With Major Depressive Disorder Undergoing Surgery

In the United States, approximately 15% of adults suffer from major depressive disorder (MDD), which results in an annual cost of over $200 billion per year. In the perioperative setting, MDD is associated with increased morbidity and mortality. The exact causes of the increase in adverse outcomes are unknown. Major depression affects virtually all major systems in the human body, and most antidepressants affect dopamine, norepinephrine, and serotonin levels or alter their target receptors. Unfortunately, anesthesia and medications used in the perioperative period affect the same neurotransmitters. As a result, patients with MDD are at an increased risk for cardiovascular effects, altered thermoregulation, and postoperative cognitive dysfunction. To determine when to continue or hold antidepressants preoperatively and avoid potential drug interactions, perioperative providers must understand the pharmacological action of antidepressants. This article reviews the pathophysiology of MDD, mechanism of action of antidepressants, and perioperative considerations for patients on antidepressant medications.

Pathways Connecting Late-Life Depression and Dementia

Late-life depression is associated with significant cognitive impairment. Meta-analyses showed that depression is associated with an increased risk for Alzheimer’s disease (AD) and it might be an etiological factor for AD. Since late-life depression is often connected with cognitive impairment and dementia is usually associated with depressive symptoms, a simple diagnostic approach to distinguish between the disorders is challenging. Several overlapping pathophysiological substrates might explain the comorbidity of both syndromes. Firstly, a stress syndrome, i.e., elevated cortisol levels, has been observed in up to 70% of depressed patients and also in AD pathology. Stress conditions can cause hippocampal neuronal damage as well as cognitive impairment. Secondly, the development of a depression and dementia after the onset of vascular diseases, the profile of cerebrovascular risk factors in both disorders and the impairments depending on the location of cerebrovascular lesions, speak in favor of a vascular hypothesis as a common factor for both disorders. Thirdly, neuroinflammatory processes play a key role in the etiology of depression as well as in dementia. Increased activation of microglia, changes in Transforming-Growth-Factor beta1 (TGF-beta1) signaling, production of pro-inflammatory cytokines as well as reduction of anti-inflammatory molecules are examples of common pathways impaired in dementia and depression. Fourthly, the neurotrophin BDNF is highly expressed in the central nervous system, especially in the hippocampus, where it plays a key role in the proliferation, differentiation and the maintenance of neuronal integrity throughout lifespan. It has been associated not only with antidepressant properties but also a reduction of cognitive impairment and therefore could be involved also in AD. Another etiologic factor is amyloid accumulation, as plasma amyloid beta-42 independently predicts both late-onset depression and AD. Higher plasma amyloid beta-42 predicts the development of late onset depression and conversion to possible AD. However, clinical trials with antibodies against beta amyloid recently failed, i.e., Solanezumab, Aducanumab, and Crenezumab. An overproduction of amyloid-beta might simply reflect a form of synaptic plasticity to compensate for neuronal dysfunction in different kind of neurological and psychiatric diseases of multiple etiologies. The tau hypothesis, sex/gender specific differences, epigenetics and the gut microbiota-brain axis imply other potential common pathways connecting late-life depression and dementia. In conclusion, different potential pathophysiological links between dementia and depression highlight several specific synergistic and multifaceted treatment possibilities, depending on the individual risk profile of the patient.

Lifestyle and biological factors influence the relationship between mental health and low-grade inflammation

Mental health modulates the risk of common chronic conditions. Although inflammation is thought to partly explain this link, its relation with mental health is still unclear and largely unexplored. We investigated three scales assessing psychological resilience (CD-RISC), depression symptoms (PHQ9-6) and mental wellbeing (SF36-MCS) in an Italian adult population cohort (N_max = 16,952). This showed a slightly higher frequency of men, more educated and younger participants, compared to samples with incomplete questionnaires. We performed stepwise generalized linear models to test the association between each scale and INFLA-score, a composite blood-based inflammation index. At each step, a class of potential mediators was included in the model, namely health conditions, lifestyle factors, or both (full model). Full model analysis was also conducted on single blood markers involved in the inflammatory process. In the baseline model, we observed significant associations of PHQ9-6 (standardized β(SE) = 0.024(0.009), p = 8.9 × 10^-3) and SF36-MCS (β(SE) = -0.021(0.008), p = 7 × 10^-3) with INFLA-score. These associations survived adjustment for health conditions but not for lifestyle factors, which explained 81% and 17% of the association with PHQ9-6 and SF36-MCS. Significant associations (p < 4.2 × 10^-3) after mediator adjustment were observed for single low-grade inflammation markers, including platelet distribution width (with PHQ9-6 and CD-RISC), granulocyte- and neutrophil-to-lymphocyte ratios, monocyte and lymphocyte fractions (with SF36-MCS). After imputation of missing data, we observed substantially consistent associations. These findings suggest that the relationship between mental health and low-grade inflammation is largely influenced by lifestyle. However, the associations with specific biomarkers related to inflammation are partly independent and might be explained by biological factors.

Neuropsychological Disorders and their Nanocarriers

Neuropsychological disorders are now growing rapidly worldwide among the people of diverse backgrounds irrespective of age, gender, and geographical region. Such disorders not only disturb the normal life and functionality of an individual but also impact the social relationships of the patient and the people associated with them, and if not treated in time, it may also result in mortality in severe conditions. Various antipsychotic drugs have been developed but their use is often limited by issues related to effective drug delivery at the site of action i.e. brain, mainly because of the blood-brain barrier. To resolve these issues, researchers and scientists have been working to develop a more effective drug delivery system where drugs can cross the blood-brain barrier and reach the brain in more effective concentrations. Drugs have been modified and formulated into nano-carriers and experimental studies for efficient and targeted delivery of drugs have been conducted. This review focuses on certain common neuropsychological diseases and their nanocarriers developed for drug delivery in the brain and are discussed with a brief description of various experimental in vitro and in vivo studies. This review also focuses on the intranasal route for the delivery of antipsychotic drugs and constraints faced due to the blood-brain barrier by the drugs.

Epigenetic Mechanisms in the Neurodevelopmental Theory of Depression

The genome (genes), epigenome, and environment work together from the earliest stages of human life to produce a phenotype of human health or disease. Epigenetic modifications, including among other things: DNA methylation, modifications of histones and chromatin structure, as well as functions of noncoding RNA, are coresponsible for specific patterns of gene expression. This refers also to mental disorders, including depressive disorders. Early childhood experiences accompanied by severe stressors (considered a risk factor for depression in adult life) are linked with changes in gene expression. They include genes involved in a response to stress (hypothalamic-pituitary-adrenal axis, HPA), associated with autonomic nervous system hyperactivity and with cortical, and subcortical processes of neuroplasticity and neurodegeneration. These are, among others: gene encoding glucocorticoid receptor, FK506 binding protein 5 gene (FKBP5), gene encoding arginine vasopressin and oestrogen receptor alpha, 5-hydroxy-tryptamine transporter gene (SLC6A4), and gene encoding brain-derived neurotrophic factor. How about personality? Can the experiences unique to every human being, the history of his or her development and gene-environment interactions, through epigenetic mechanisms, shape the features of our personality? Can we pass on these features to future generations? Hence, is the risk of depression inherent in our biological nature? Can we change our destiny?

Antidepressant mechanisms of venlafaxine involving increasing histone acetylation and modulating tyrosine hydroxylase and tryptophan hydroxylase expression in hippocampus of depressive rats

Venlafaxine (VEN) is a widely used antidepressant as a serotonin-reuptake and norepinephrine-reuptake inhibitor. It is used primarily in depression, especially with generalized anxiety disorder or chronic pain. This medicine is of interest because its mechanisms involved multiple aspects. In the current study, the antidepressant action of VEN was investigated by studying the histone acetylation and expression of tyrosine hydroxylase (TH) and tryptophan hydroxylase (TPH) in rats exposed to chronic unpredicted stress (CUS) for 28 days. Male Sprague-Dawley rats were divided into a control group, VEN-treated control group, CUS group, and VEN-treated CUS group. VEN (23.4 mg/kg once daily) was administered to rats by intragastric gavage, whereas the same volume of vehicle was given to rats in the control and model groups. Rat behaviors, acetylated H3 at lysine 9 (acH3K9), acetylated H3 at lysine 14 (acH3K14), acetylated H4 at lysine 12 (acH4K12), histone deacetylase 5, and TH and TPH expression in the hippocampus were determined. Chronic VEN treatment significantly relieved the anxiety- and depression-like behaviors, prevented the increase of histone deacetylase 5 expression and decrease of acH3K9 level, and promoted TH and TPH protein expression in the hippocampus of CUS rats. The results suggest that the preventive antidepressant mechanism of VEN is partly involved in the blocking effects on histone de-acetylated modification and then increasing TH, TPH expression.

Disease-discordant twin structural MRI studies on affective disorders

Magnetic resonance imaging (MRI) studies have identified neural structures implicated in the pathophysiology of mood disorders, especially bipolar disorder (BD) and major depressive disorder (MDD). However, the role of genetic and environmental influences on such brain deficits is still unclear. In this context, the present review summarizes the current evidence from structural MRI and Diffusion Tensor Imaging (DTI) studies on twin samples concordant or discordant for BD or MDD, with the aim of clarifying the role of genetic and environmental risk factors on brain alterations. Although the results showed a complex interplay between gene and environment in affective disorders, the evidence seem to underline that both genetic and environmental risk factors have an impact on brain areas and vulnerability to MDD and BD. However, the precise mechanism of action and the interaction between these factors still needs to be unveiled. Therefore, future larger studies on concordant or discordant twins should be encouraged, because this population provides a unique opportunity to probe separately genetic and environmental markers of disease vulnerability.

Association between epigenetic age acceleration and depressive symptoms in a prospective cohort study of urban-dwelling adults

OBJECTIVE

This study tests associations of DNA methylation-based (DNAm) measures of epigenetic age acceleration (EAA) with cross-sectional and longitudinal depressive symptoms in an urban sample of middle-aged adults.

METHODS

White and African-American adult participants in the Healthy Aging in Neighborhoods of Diversity across the Life Span study for whom DNA samples were analyzed (baseline age: 30-65 years) we included. We estimated three DNAm based EAA measures: (1) universal epigenetic age acceleration (AgeAccel); (2) intrinsic epigenetic age acceleration (IEAA); and (3) extrinsic epigenetic age acceleration (EEAA). Depressive symptoms were assessed using the 20-item Center for Epidemiological Studies-Depression scale total and sub-domain scores at baseline (2004-2009) and follow-up visits (2009-2013). Linear mixed-effects regression models were conducted, adjusting potentially confounding covariates, selection bias and multiple testing (N = 329 participants, ∼52% men, k = 1.9 observations/participant, mean follow-up time∼4.7 years).

RESULTS

None of the epigenetic age acceleration measures were associated with total depressive symptom scores at baseline or over time. IEAA - a measure of cellular epigenetic age acceleration irrespective of white blood cell composition - was cross-sectionally associated with decrement in "positive affect" in the total population (γ011± SE = -0.090 ± 0.030, P = 0.003, Cohen's D: -0.16) and among Whites (γ011 ± SE = -0.135 ± 0.048, P = 0.005, Cohen's D: -0.23), after correction for multiple testing. Baseline "positive affect" was similarly associated with AgeAccel.

LIMITATIONS

Limitations included small sample size, weak-moderate effects and measurement error.

CONCLUSIONS

IEAA and AgeAccel, two measures of EAA using Horvath algorithm, were linked to a reduced "positive affect", overall and among Whites. Future studies are needed to replicate our findings and test bi-directional relationships.

Effects of Histone Deacetylase Inhibitors on the Development of Epilepsy and Psychiatric Comorbidity in WAG/Rij Rats

Epigenetic mechanisms, such as alterations in histone acetylation based on histone deacetylases (HDACs) activity, have been linked not only to normal brain function but also to several brain disorders including epilepsy and the epileptogenic process. In WAG/Rij rats, a genetic model of absence epilepsy, epileptogenesis and mild-depression comorbidity, we investigated the effects of two HDAC inhibitors (HDACi), namely sodium butyrate (NaB), valproic acid (VPA) and their co-administration, on the development of absence seizures and related psychiatric/neurologic comorbidities following two different experimental paradigms. Treatment effects have been evaluated by EEG recordings (EEG) and behavioural tests at different time points. Prolonged and daily VPA and NaB treatment, started before absence seizure onset (P30), significantly reduced the development of absence epilepsy showing antiepileptogenic effects. These effects were enhanced by NaB/VPA co-administration. Furthermore, early-chronic HDACi treatment improved depressive-like behaviour and cognitive performance 1 month after treatment withdrawal. WAG/Rij rats of 7 months of age showed reduced acetylated levels of histone H3 and H4, analysed by Western Blotting of homogenized brain, in comparison to WAG/Rij before seizure onset (P30). The brain histone acetylation increased significantly during treatment with NaB or VPA alone and more markedly during co-administration. We also observed decreased expression of both HDAC1 and 3 following HDACi treatment compared to control group. Our results suggest that histone modifications may have a crucial role in the development of epilepsy and early treatment with HDACi might be a possible strategy for preventing epileptogenesis also affecting behavioural comorbidities.

Clinical epigenetics: seizing opportunities for translation

Biomarker discovery and validation are necessary for improving the prediction of clinical outcomes and patient monitoring. Despite considerable interest in biomarker discovery and development, improvements in the range and quality of biomarkers are still needed. The main challenge is how to integrate preclinical data to obtain a reliable biomarker that can be measured with acceptable costs in routine clinical practice. Epigenetic alterations are already being incorporated as valuable candidates in the biomarker field. Furthermore, their reversible nature offers a promising opportunity to ameliorate disease symptoms by using epigenetic-based therapy. Thus, beyond helping to understand disease biology, clinical epigenetics is being incorporated into patient management in oncology, as well as being explored for clinical applicability for other human pathologies such as neurological and infectious diseases and immune system disorders.

Methylation analysis for postpartum depression: a case control study

BACKGROUND

Postpartum depression (PPD) is a major depressive disorder that occurs after childbirth. Objective diagnostic and predictive methods for PPD are important for early detection and appropriate intervention. DNA methylation has been recognized as a potential biomarker for major depressive disorder. In this study, we used methylation analysis and peripheral blood to search for biomarkers that could to lead to the development a predictive method for PPD.

METHODS

Study participants included 36 pregnant women (18 cases and 18 controls determined after childbirth). Genome-wide DNA methylation profiles were obtained by analysis with an Infinium Human Methylation 450BeadChip. The association of DNA methylation status at each DNA methylation site with PPD was assessed using linear regression analysis. We also conducted functional enrichment analysis of PPD using The Database for Annotation, Visualization and Integrated Discovery 6.8 to explore enriched functional-related gene groups for PPD.

RESULTS

In the analysis with postpartum depressed state as an independent variable, the difference in methylation frequency between the postpartum non-depressed group and the postpartum depressed group was small, and sites with genome-wide significant differences were not confirmed. After analysis by The Database for Annotation, Visualization and Integrated Discovery 6.8, we revealed four gene ontology terms, including axon guidance, related to postpartum depression.

CONCLUSIONS

These findings may help with the development of an objective predictive method for PPD.

Bridging Basic and Clinical Research in Early Life Adversity, DNA Methylation, and Major Depressive Disorder

Early life adversity (ELA)- including childhood physical, emotional, and sexual abuse, as well as childhood neglect- is an important predictive factor for negative psychopathology, including Major Depressive Disorder (MDD). ELA can epigenetically regulate key emotional and behavioral systems in ways that can stably persist into adulthood and contribute to the development of MDD and other psychopathology. DNA methylation has been one of the most investigated forms of epigenetic regulation in ELA to MDD pathway. From these studies, genes and sites associated with ELA/MDD have been identified and should be further investigated in order to identify potential avenues for intervention.

Gut Microbiota-Based Pharmacokinetics and the Antidepressant Mechanism of Paeoniflorin

Paeoniflorin, the main component of Xiaoyao Wan, presents low oral bioavailability and unclear antidepressant mechanism. To elucidate the potential reasons for the low bioavailability of paeoniflorin and explore its antidepressant mechanism from the perspective of the gut microbiota, here, a chronic unpredictable depression model and forced swimming test were firstly performed to examine the antidepressant effects of paeoniflorin. Then the pharmacokinetic study of paeoniflorin in rats was performed based on the gut microbiota; meanwhile, the gut microbiota incubated with paeoniflorin in vitro was used to identify the possible metabolites of paeoniflorin. Molecular virtual docking experiments together with the specific inhibitor tests were applied to investigate the mechanism of paeoniflorin metabolism by the gut microbiota. Finally, the intestinal microbiota composition was analyzed by 16S rRNA gene sequencing technology. The pharmacodynamics tests showed that paeoniflorin had significant antidepressant activity, but its oral bioavailability was 2.32%. Interestingly, we found paeoniflorin was converted into benzoic acid by the gut microbiota, and was mainly excreted through the urine with the gut metabolite benzoic acid as the prominent excreted form. Moreover, paeoniflorin could also regulate the composition of the gut microbiota by increasing the abundance of probiotics. Therefore, the metabolism effect of gut microbiota may be one of the main reasons for the low oral bioavailability of paeoniflorin. Additionally, paeoniflorin can be metabolized into benzoic acid via gut microbiota enzymes, which might exert antidepressant effects through the blood-brain barrier into the brain.

A cross comparison between Ayurvedic etiology of Major Depressive Disorder and bidirectional effect of gut dysregulation

Ayurveda, an Indian medical science has been practiced for thousands of years. What makes Ayurveda relevant today is its subtle understanding of the environment and its focus on the generation of good health through one's own lifestyle choices. The digestive system has long been an area of critical importance within the Ayurvedic system and is only now being acknowledged by modern science as a key component in the regulation of physical and mental well-being. The gut microbiome and enteric nervous system are two particular areas in which the onset of psychiatric disorders, such as depression, have been associated. There are some striking similarities between this biomedical understanding of the gastrointestinal system and the Ayurvedic perspective of disease development. Major Depressive Disorder (MDD) is becoming increasingly linked with gut dysregulation in contemporary literature and is a pathology explored within both the Ayurvedic and Western systems of medicine. This literature review seeks to draw parallels between these two areas of study and highlight the importance of the digestive system when diagnosing and treating MDD.

Parvalbumin Promoter Methylation Altered in Major Depressive Disorder

Aims: To determine the extent of DNA methylation of parvalbumin gene (PVALB) promoter in major depressive disorder (MDD) patients with and without suicide attempt in comparison with healthy controls. Methods: The extracted DNA from dried blood spots of MDD patients (n = 92) including non-suicidal MDD and suicidal-MDD subgroups (n = 45 and n = 47, respectively) and age-matched control subjects (n = 95) was used for DNA methylation analysis at four CpG sites in the promoter sequence of PVALB by pyrosequencing. Results: The PVALB methylation was significantly increased at CpG2 and decreased at CpG4 in the MDD group compared to the control group, while there was no difference between non-suicidal MDD and suicidal-MDD subgroups. A significant inverse correlation of severity of MDD was indicated only for CpG4. Conclusion: This study provides the first evidence of abnormalities of PVALB promoter methylation in MDD and its correlation with MDD severity indicating a role for epigenetics in this psychiatric disorder.

Neuropeptide and Small Transmitter Coexistence: Fundamental Studies and Relevance to Mental Illness

Neuropeptides are auxiliary messenger molecules that always co-exist in nerve cells with one or more small molecule (classic) neurotransmitters. Neuropeptides act both as transmitters and trophic factors, and play a role particularly when the nervous system is challenged, as by injury, pain or stress. Here neuropeptides and coexistence in mammals are reviewed, but with special focus on the 29/30 amino acid galanin and its three receptors GalR1, -R2 and -R3. In particular, galanin's role as a co-transmitter in both rodent and human noradrenergic locus coeruleus (LC) neurons is addressed. Extensive experimental animal data strongly suggest a role for the galanin system in depression-like behavior. The translational potential of these results was tested by studying the galanin system in postmortem human brains, first in normal brains, and then in a comparison of five regions of brains obtained from depressed people who committed suicide, and from matched controls. The distribution of galanin and the four galanin system transcripts in the normal human brain was determined, and selective and parallel changes in levels of transcripts and DNA methylation for galanin and its three receptors were assessed in depressed patients who committed suicide: upregulation of transcripts, e.g., for galanin and GalR3 in LC, paralleled by a decrease in DNA methylation, suggesting involvement of epigenetic mechanisms. It is hypothesized that, when exposed to severe stress, the noradrenergic LC neurons fire in bursts and release galanin from their soma/dendrites. Galanin then acts on somato-dendritic, inhibitory galanin autoreceptors, opening potassium channels and inhibiting firing. The purpose of these autoreceptors is to act as a 'brake' to prevent overexcitation, a brake that is also part of resilience to stress that protects against depression. Depression then arises when the inhibition is too strong and long lasting - a maladaption, allostatic load, leading to depletion of NA levels in the forebrain. It is suggested that disinhibition by a galanin antagonist may have antidepressant activity by restoring forebrain NA levels. A role of galanin in depression is also supported by a recent candidate gene study, showing that variants in genes for galanin and its three receptors confer increased risk of depression and anxiety in people who experienced childhood adversity or recent negative life events. In summary, galanin, a neuropeptide coexisting in LC neurons, may participate in the mechanism underlying resilience against a serious and common disorder, MDD. Existing and further results may lead to an increased understanding of how this illness develops, which in turn could provide a basis for its treatment.