The role of microRNAs in synaptic plasticity, major affective disorders and suicidal behavior

Chronic Adolescent Restraint Stress Downregulates miRNA-200a Expression in Male and Female C57BL/6J and BALB/cJ Mice

Adolescence is a critical developmental period when the brain is plastic, and stress exposure can have lasting physiological consequences. One mechanism through which adolescent stress may have lasting effects is by altering microRNAs (miRNAs), leading to wide-scale gene expression changes. Three prior independent studies used unbiased approaches (RNA sequencing or microarray) to identify miRNAs differentially expressed by chronic variable stress in male rodents. In all three studies, miRNA-200a was differentially expressed in areas of the brain associated with emotion regulation. The current study extends this research to determine if chronic non-variable adolescent stress downregulates miRNA-200a expression by looking at two strains (BALB/cJ and C57BL/6J) of male and female mice. We utilized a 14-day (2 h/day) restraint stress protocol and verified stress effects on adolescent body weight gain and circulating corticosterone concentrations relative to non-restraint controls. Mice were then left undisturbed until they were euthanized in adulthood, at which time brains were collected to measure miRNA-200a in the ventral hippocampus. Three weeks after adolescent stress ended, differences in body weight between groups were no longer significant; however, animals exposed to stress had less miRNA-200a expression in the ventral hippocampus than control animals. These data implicate miRNA-200a expression as a potential mechanism by which adolescent stress can have persistent impacts on multiple outcomes in both male and female mice.

Early life stress enhances the susceptibility to depression and interferes with neuroplasticity in the hippocampus of adolescent mice via regulating miR-34c-5p/SYT1 axis

Early life events are major risk factors for the onset of depression and have long-term effects on the neurobiological changes and behavioral development of rodents. However, little is known about the specific mechanisms of early life adversity in the susceptibility to subsequent stress exposure in adolescence. This study characterized the effect of maternal separation (MS), an animal model of early life adversity, on the behavioral responses to restraint stress in mice during adolescence and investigated the molecular mechanism underlying behavioral vulnerability to chronic stress induced by MS. Our results showed that MS exposure could further reinforce the depressive vulnerability to restraint stress in adolescent mice. In addition, miR-34c-5p expression was obviously up-regulated in the hippocampi of MS mice at postnatal day (P) 14 and P42. Further, synaptotagmin-1 (SYT1) was deemed as a target gene candidate of miR-34c-5p on the basis of dual luciferase assay. It was found that the downregulation of miR-34c-5p expression in the hippocampi of MS mice could ameliorate dysfunction of synaptic plasticity by targeting molecule SYT1, effects which were accompanied by alleviation of depressive and anxious behaviors in these mice. The results demonstrated that the miR-34c-5p/SYT1 pathway was involved in the susceptibility to depression induced by MS via regulating neuroplasticity in the hippocampi of mice.

The neurotrophic activities of brain-derived neurotrophic factor are potentiated by binding with apigenin, a common flavone in vegetables, in stimulating the receptor signaling

AIMS

We aimed to identify the neurotrophic activities of apigenin (4',5,7-trihydroxyflavone) via its coordination with brain-derived neurotrophic factor (BNDF) and an elevated signaling of tyrosine kinase receptor B (Trk B receptor).

METHODS

The direct binding of apigenin to BDNF was validated by ultrafiltration and biacore assay. Neurogenesis, triggered by apigenin and/or BDNF, was determined in cultured SH-SY5Y cells and rat cortical neurons. The amyloid-beta (Aβ)25-35 -induced cellular stress was revealed by propidium iodide staining, mitochondrial membrane potential, bioenergetic analysis, and formation of reactive oxygen species levels. Activation of Trk B signaling was tested by western blotting.

RESULTS

Apigenin and BDNF synergistically maintained the cell viability and promoted neurite outgrowth of cultured neurons. In addition, the BDNF-induced neurogenesis of cultured neurons was markedly potentiated by applied apigenin, including the induced expressions of neurofilaments, PSD-95 and synaptotagmin. Moreover, the synergy of apigenin and BDNF alleviated the (Aβ)25-35 -induced cytotoxicity and mitochondrial dysfunction. The synergy could be accounted by phosphorylation of Trk B receptor, and which was fully blocked by a Trk inhibitor K252a.

CONCLUSION

Apigenin potentiates the neurotrophic activities of BDNF through direct binding, which may serve as a possible treatment for its curative efficiency in neurodegenerative diseases and depression.

Analysis of self-healing of depression by helping others in adolescents from the perspective of constructivism

Purpose

This study aims to explore the mechanism of psychological qualities constructed in helping others with depression and guide adolescents to actively participate in the practical activities of helping others to prevent and self-heal depression.

Method

Symptom self-rating scale, trait coping style questionnaire, and self-administered helper scale were employed. A total of 1,086 valid on-site questionnaires were collected from adolescents.

Result

The depression levels of adolescents were negatively correlated with helping beliefs, behaviors and total scores (r = -0.500, -0.401, and -0.530). Helping others had a significantly negative predictive effect on depression, effectively inhibiting depression levels. Although the positive coping style had an inhibitory effect on depression, it exerted no predictive effects on depression under the influence of helping others. In contrast, the negative coping style had a significantly positive predictive effect on depression.

Conclusion

Proactively participating in helping others is an important way to prevent and eliminate depression in adolescents. They should be instructed to give full play to their initiatives to participate in social practice and assist others actively, thus constructing positive psychological qualities, improving mental health, and achieving self-healing of depression and self-help through helping others.

miR-124 Exacerbates depressive-like behavior by targeting Ezh2 to induce autophagy

On the basis of our previous research, miR-124 and autophagy have been shown to be associated with depression and antidepressant treatment, respectively. However, whether miR-124 is involved in depressive-like behavior and antidepressant efficacy through regulating autophagy remains poorly understood. The chronic unpredictable mild stress (CUMS) depression model in mice was established, and then intraperitoneal fluoxetine injections (10 mg/kg) were administered for a duration of 4 weeks. The behavioral changes induced by CUMS were evaluated by the tail suspension test, open field test, sucrose preference test, and elevated plus maze test. Quantitative real-time PCR was used to detect expression levels of miR-124 and its three precursor genes in hippocampus of mice. Western blotting was used to detect the expressions of Ezh2 and autophagy proteins (P62, Atg3, Atg7, LC3-I, and LC3- II) in hippocampus of mice. Depression-like behaviors were successfully induced in CUMS models and reversed by SSRI treatments. The expression levels of miR-124 and its precursor gene ( miR-124-3 ) were significantly increased in the hippocampus of CUMS mice, while the expression levels were significantly decreased after 4 weeks of fluoxetine treatment. The mRNA and protein expressions of Ezh2, a validated target of miR-124, were decreased in the hippocampus of CUMS mice, and the fluoxetine treatment could reverse the expressions. A correlation analysis suggested that miR-124 had a significant negative correlation with Ezh2 mRNA expression. The protein levels of LC3-II/I, P62, and Atg7, which were found to be regulated by Ezh2, were increased in the hippocampus of CUMS mice and decreased after fluoxetine treatment. We speculated that autophagy was enhanced in the CUMS model of depression and might be mediated by miR-124 targeting Ezh2.

An insight into the sprawling microverse of microRNAs in depression pathophysiology and treatment response

Stress-related neuropathologies are pivotal in developing major depressive disorder (MDD) and are often governed by gene-regulatory changes. Being a stress-responsive gene-regulatory factor, microRNAs (miRNAs) have tremendous biomolecular potential to define an altered gene-regulatory landscape in the MDD brain. MiRNAs' regulatory roles in the MDD brain are closely aligned with changes in plasticity, neurogenesis, and stress-axis functions. MiRNAs act at the epigenetic interface between stress-induced environmental stimuli and cellular pathologies by triggering large-scale gene expression changes in a highly coordinated fashion. The parallel changes in peripheral circulation may provide an excellent opportunity for miRNA to devise more effective treatment strategies and help explore their potential as biomarkers in treatment response. This review discusses the role of miRNAs as epigenetic modifiers in the etiopathogenesis of MDD. Concurrently, key research is highlighted to show the progress in using miRNAs as predictive biomarkers for treatment response.

Dissecting early life stress-induced adolescent depression through epigenomic approach

Early life stress (ELS), such as abuse and neglect during childhood, can lead to psychiatric disorders in later life. Previous studies have suggested that ELS can cause profound changes in gene expression through epigenetic mechanisms, which can lead to psychiatric disorders in adulthood; however, studies on epigenetic modifications associated with ELS and psychiatric disorders in adolescents are limited. Moreover, how these epigenetic modifications can lead to psychiatric disorders in adolescents is not fully understood. Commonly, DNA methylation, histone modification, and the regulation of noncoding RNAs have been attributed to the reprogramming of epigenetic profiling associated with ELS. Although only a few studies have attempted to examine epigenetic modifications in adolescents with ELS, existing evidence suggests that there are commonalities and differences in epigenetic profiling between adolescents and adults. In addition, epigenetic modifications are sex-dependent and are influenced by the type of ELS. In this review, we have critically evaluated the current evidence on epigenetic modifications in adolescents with ELS, particularly DNA methylation and the expression of microRNAs in both preclinical models and humans. We have also clarified the impact of ELS on psychiatric disorders in adolescents to predict the development of neuropsychiatric disorders and to prevent and recover these disorders through personalized medicine.

M6A RNA Methylation-Based Epitranscriptomic Modifications in Plasticity-Related Genes via miR-124-C/EBPα-FTO-Transcriptional Axis in the Hippocampus of Learned Helplessness Rats

BACKGROUND

Impaired synaptic plasticity has been linked to dynamic gene regulatory network changes. Recently, gene regulation has been introduced with the emerging concept of unique N6-methyladenosine (m6A)-based reversible transcript methylation. In this study, we tested whether m6A RNA methylation may potentially serve as a link between the stressful insults and altered expression of plasticity-related genes.

METHODS

Expression of plasticity genes Nr3c1, Creb1, Ntrk2; m6A-modifying enzymes Fto, methyltransferase like (Mettl)-3 and 14; DNA methylation enzymes Dnmt1, Dnmt3a; transcription factor C/ebp-α; and miRNA-124-3p were determined by quantitative polymerase chain reaction (qPCR) in the hippocampus of rats that showed susceptibility to develop stress-induced depression (learned helplessness). M6A methylation of plasticity-related genes was determined following m6A mRNA immunoprecipitation. Chromatin immunoprecipitation was used to examine the endogenous binding of C/EBP-α to the Fto promoter. MiR-124-mediated post-transcriptional inhibition of Fto via C/EBPα was determined using an in vitro model.

RESULTS

Hippocampus of learned helplessness rats showed downregulation of Nr3c1, Creb1, and Ntrk2 along with enrichment in their m6A methylation. A downregulation in demethylating enzyme Fto and upregulation in methylating enzyme Mettl3 were also noted. The Fto promoter was hypomethylated due to the lower expression of Dnmt1 and Dnmt3a. At the same time, there was a lower occupancy of transcription factor C/EBPα on the Fto promoter. Conversely, C/ebp-α transcript was downregulated via induced miR-124-3p expression.

CONCLUSIONS

Our study mechanistically linked defective C/EBP-α-FTO-axis, epigenetically influenced by induced expression of miR-124-3p, in modifying m6A enrichment in plasticity-related genes. This could potentially be linked with abnormal neuronal plasticity in depression.

Association of Polymorphic Variants in Argonaute Genes with Depression Risk in a Polish Population

Argonaute (AGO) proteins, through their key role in the regulation of gene expression, participate in many biological processes, including cell differentiation, proliferation, death and DNA repair. Accurate regulation of gene expression appears to be important for the proper development of complex neural circuits. Loss of AGO proteins is known to lead to early embryonic mortality in mice with various malformations, including anomalies of the central nervous system. Single-nucleotide polymorphisms (SNPs) of AGO genes can lead to deregulation of the processes in which AGO proteins are involved. The contribution of different SNPs in depression has been extensively studied. However, there are hardly any studies on the contribution of AGO genes. The aim of our research was to assess the relationship between the occurrence of depression and the presence of SNPs in genes AGO1 (rs636882) and AGO2 (rs4961280; rs2292779; rs2977490) in a Polish population. One hundred and one subjects in the study group were diagnosed with recurrent depressive disorder by a psychiatrist. The control group comprised 117 healthy subjects. Study participants performed the HDRS (Hamilton Depression Scale) test to confirm or exclude depression and assess severity. The frequency of polymorphic variants of genes AGO1 (rs636882) and AGO2 (rs4961280; rs2292779; rs2977490) was determined using TaqMan SNP genotyping assays and the TaqMan universal PCR master mix, no AmpErase UNG. The rs4961280/AGO2 polymorphism was associated with a decrease in depression occurrence in the codominant (OR = 0.51, p = 0.034), dominant (OR = 0.49, p = 0.01), and overdominant (OR = 0.58, p = 0.049) models. Based on the obtained results, we found that the studied patients demonstrated a lower risk of depression with the presence of the polymorphic variant of the rs4961280/AGO2 gene—genotype C/A and C/A-A/A.

Synaptic plasticity and depression: the role of miRNAs dysregulation

BACKGROUND

MicroRNAs (miRNAs) have been recently shown to exert several functional roles in the development and function of neurons. Moreover, numerous miRNAs are present in high abundance in presynaptic and postsynaptic sites regulating synaptic plasticity and activity through different mechanisms.

METHODS

We searched PubMed and Google Scholar databases with key words "Synaptic plasticity", "miRNA" and "major depressive disorder.

RESULTS

Synaptic plasticity has an essential role in the ability of the brain to integrate transitory experiences into constant memory traces. Thus, it participates in the development of neuropsychiatric diseases such as major depressive disorder (MDD). Most notably, MDD-related alterations in synaptic function have been found to be closely related with abnormal expression of miRNAs.

CONCLUSIONS

Several miRNAs such as miR-9-5p, miR-204-5p, miR-128-3, miR-26a-3p, miR-218, miR-22-3p, miR-124-3p, miR-136-3p, miR-154-5p, miR-323a-3p, miR-425-5p, miR-34a, miR-137, miR-204-5p, miR-99a, miR-134, miR-124-3p and miR-3130-5p have been shown to be involved in the regulation of synaptic plasticity in the context of MDD. In the current review, we elaborate the role of miRNAs in regulation of this important neuronal feature in MDD.

The role of the lateral septum in neuropsychiatric disease

The lateral septum (LS) is a structure in the midline of the brain that is interconnected with areas associated with stress and feeding. This review highlights the role of the LS in anxiety, depression, and eating disorders and their comorbidity. There is a prevailing view that the LS is anxiolytic. This review finds that the LS is both anxiolytic and anxiogenic. Furthermore, the LS can promote and inhibit feeding. Given these shared roles, the LS represents a common site for the comorbidity of neuropsychiatric disorders, and therefore a potential pharmacological target. This is crucial since currently available treatments are not always effective. Corticotrophin-releasing factor 2 antagonists are potential drugs for the treatment of anxiety and anorexia and require further research. Furthermore, other drugs currently in trials for binge eating, such as alpha-adrenergic agonists, may in fact promote food intake. It is hoped that the advancements in chemo- and optogenetic techniques will allow future studies to profile the specific neural connections of the LS and their function. This information could facilitate our understanding of the underlying mechanisms, and therefore pharmacological targets, of these psychiatric conditions.

Suicide and Changes in Expression of Neuronal miRNA Predicted by an Algorithm Search through miRNA Databases

Suicide is multifactorial and polygenic phenotype, affected by environmental and genetic factors. Among epigenetic mechanisms, miRNAs have been studied, but so far no very concise results exist. To overcome limitations of candidate miRNA and whole genome sequencing approaches, we created an in silico analysis algorithm that would help select the best suitable miRNAs that target the most interesting genes associated with suicidality. We used databases/web algorithms DIANA microT, miRDB, miRmap, miRWalk, and TargetScan and candidate genes SLC6A4, HTR1A, BDNF, NR3C1, ZNF714, and NRIP3. Based on a prediction algorithm, we have chosen miRNAs that are targeting regulation of the genes listed, and are at the same time being expressed in the brain. The highest ranking scores were obtained for hsa-miR-4516, hsa-miR-3135b, hsa-miR-124-3p, hsa-miR-129-5p, hsa-miR-27b-3p, hsa-miR-381-3p, hsa-miR-4286. Expression of these miRNAs was tested in the brain tissue of 40 suicide completers and controls, and hsa-miR-4516 and hsa-miR-381-3p showed a trend for statistical significance. We also checked the expression of the target genes of these miRNAs, and for NR3C1 expression was lower in suicide completers compared to controls, which is in accordance with the available literature results. To determine the miRNAs that are most suitable for further suicidality research, more studies, combining in silico analysis and wet lab experiments, should be performed.

Efficacy and safety of repeated esketamine intravenous infusion in the treatment of treatment-resistant depression: A case series

Repeated intravenous administration of esketamine may increase and prolong the treatment efficacy of depressive patients. Firstly, the patient received esketamine (0.4 mg/kg intravenous over 40 min) infusion every other day, and totally 6 times infusion. If the patient's symptoms cannot improve, they got another 6 times esketamine injection (one time per day, 0.4 mg/kg intravenous over 40 min). Our study reported that 12 times intravenous esketamine infusion adjunctive with oral antidepressants sustained the efficacy for 6 months at least. These cases provide evidence of the safety and longtime efficacy of repeated intravenous esketamine for the treatment of treatment resistant depression.

Functional neuroanatomy of mania

Mania, the diagnostic hallmark of bipolar disorder, is an episodic disturbance of mood, sleep, behavior, and perception. Improved understanding of the neurobiology of mania is expected to allow for novel avenues to address current challenges in its diagnosis and treatment. Previous research focusing on the impairment of functional neuronal circuits and brain networks has resulted in heterogenous findings, possibly due to a focus on bipolar disorder and its several phases, rather than on the unique context of mania. Here we present a comprehensive overview of the evidence regarding the functional neuroanatomy of mania. Our interpretation of the best available evidence is consistent with a convergent model of lateralized circuit dysfunction in mania, with hypoactivity of the ventral prefrontal cortex in the right hemisphere, and hyperactivity of the amygdala, basal ganglia, and anterior cingulate cortex in the left hemisphere of the brain. Clarification of dysfunctional neuroanatomic substrates of mania may contribute not only to improve understanding of the neurobiology of bipolar disorder overall, but also highlights potential avenues for new circuit-based therapeutic approaches in the treatment of mania.

Childhood traumatic events and the dopaminergic theory of psychosis: A mini-review of studies investigating gene – environment interactions

There is great body of evidence showing a relationship between childhood adversity and psychosis onset. Genetic factors moderate the association between childhood adversity and psychosis risk potentially by influencing biological and/or psychological reaction following exposure to adversity. In this review, we discuss studies identifying the specific genetic variants known to affect dopamine levels involved in this interaction. Our review shows that the catechol-O-methyltransferase (COMT), dopamine D2 receptor (DRD2), AKT1 gene play a key role in mediating the relationship between childhood adversity and development of psychosis. We have also found conflicting findings on the impact of dopamine genes on the relationship between childhood adversity and development of psychosis, suggesting that other genetic and environmental factors should be taken into account. We here discuss the implications of our findings and future directions.

The Effect of Adding Transcranial Direct Current Stimulation to Hyperbaric Oxygen Therapy in Patients With Delayed Encephalopathy After Carbon Monoxide Poisoning: A Randomised Controlled Trial

Objective: To investigate the effect of transcranial direct current stimulation (tDCS) combined with hyperbaric oxygen therapy (HBOT) in patients with delayed encephalopathy after carbon monoxide poisoning (DEACMP).

Design: A parallel-group, open-label randomised controlled study.

Setting: Hyperbaric Oxygen Therapy Room of the Second Hospital of Hebei Medical University.

Subjects: A total of 40 patients were recruited for the current study. Patients were randomly divided into a treatment group and a control group (20 cases/group).

Interventions: Control group: conventional, individualised rehabilitation therapy. Treatment group: conventional, individualised rehabilitation therapy and tDCS.

Main Measures: cognitive function of patients, the Barthel Index (BI).

Results: After treatment, significantly higher MMSE and BI scores, as well as a greater reduction in P300 latency and an increase in P300 amplitude, were observed in the treatment group compared to the control group (MMSE: 13 ± 7 vs. 9 ± 5; P300 latency: 342 ± 29 vs. 363 ± 17 ms; P300 amplitude: 7.0 ± 3.3 vs. 5.1 ± 2.7 μV; all P < 0.05). In both groups, however, MMSE and BI scores, in addition to P300 amplitude, were significantly improved; in contrast, there was a decrease in P300 latency in both groups after treatment compared to before treatment (all P < 0.05).

Conclusion: Combined with HBOT, tDCS can help improve cognitive function and ADL in patients with DEACMP. This combination therapy might be a helpful method to enhance the recovery of patients with DEACMP.

Is there a causal relationship between stress and migraine? Current evidence and implications for management

Background

The purpose of this narrative review is to examine the literature investigating a causal relationship between stress and migraine and evaluate its implications for managing migraine.

Methods

PubMed, PsycINFO and CINAHL were searched from 1988 to August 2021, identifying 2223 records evaluating the relationship between stress and migraine. Records were systematically screened. All potentially relevant records were thematically categorized into six mechanistic groups. Within each group the most recent reports providing new insights were cited.

Results

First, studies have demonstrated an association of uncertain causality between high stress loads from stressful life events, daily hassles or other sources, and the incidence of new-onset migraine. Second, major stressful life events seem to precede the transformation from episodic to chronic migraine. Third, there is some evidence for changes in levels of stress as a risk factor for migraine attacks. Research also suggests there may be a reversed causality or that stress-trigger patterns are too individually heterogeneous for any generalized causality. Fourth, migraine symptom burden seems to increase in a setting of stress, partially driven by psychiatric comorbidity. Fifth, stress may induce sensitization and altered cortical excitability, partially explaining attack triggering, development of chronic migraine, and increased symptom burden including interictal symptom burden such as allodynia, photophobia or anxiety. Finally, behavioral interventions and forecasting models including stress variables seem to be useful in managing migraine.

Conclusion

The exact causal relationships in which stress causes incidence, chronification, migraine attacks, or increased burden of migraine remains unclear. Several individuals benefit from stress-oriented therapies, and such therapies should be offered as an adjuvant to conventional treatment and to those with a preference. Further understanding the relationship between stress, migraine and effective therapeutic options is likely to be improved by characterizing individual patterns of stress and migraine, and may in turn improve therapeutics.

Cathodal transcranial direct current stimulation on the prefrontal cortex applied after reactivation attenuates fear memories and prevent reinstatement after extinction

BACKGROUND

In the last decade, pharmacological strategies targeting reconsolidation after memory retrieval have shown promising efforts to attenuate persistent memories and overcome fear recovery. However, most reconsolidation inhibiting agents have not been approved for human testing. While non-invasive neuromodulation can be considered an alternative approach to pharmacological treatments, there is a lack of evidence about the efficacy of these technologies when modifying memory traces via reactivation/reconsolidation mechanism.

OBJECTIVE

In this study, we evaluate the effect of cathodal (c-tDCS) and anodal (a-DCS) transcranial direct current stimulation applied after memory reactivation and extinction in rats.

METHODS

Male Wistar rats were randomly assigned into three groups: one sham group, one anodal tDCS group, and one cathodal tDCS group (500 μA, 20 min). Reconsolidation and extinction of fear memories were evaluated using a contextual fear conditioning.

RESULTS

Our results showed that c-tDCS and a-tDCS after memory reactivation can attenuate mild fear memories. However, only c-tDCS stimulation prevented both fear expression under strong fear learning and fear recovery after a reinstatement protocol without modification of learning rate or extinction retrieval. Nevertheless, the remote memories were resistant to modification through this type of neuromodulation. Our results are discussed considering the interaction between intrinsic excitability promoted by learning and memory retrieval and the electric field applied during tDCS.

CONCLUSION

These results point out some of the boundary conditions influencing the efficacy of tDCS in fear attenuation and open new ways for the development of noninvasive interventions aimed to control fear-related disorders via reconsolidation.

Functional Constructivism Approach to Multilevel Nature of Bio-Behavioral Diversity

Attempts to revise the existing classifications of psychiatric disorders (DSM and ICD) continue and highlight a crucial need for the identification of biomarkers underlying symptoms of psychopathology. The present review highlights the benefits of using a Functional Constructivism approach in the analysis of the functionality of the main neurotransmitters. This approach explores the idea that behavior is neither reactive nor pro-active, but constructive and generative, being a transient selection of multiple degrees of freedom in perception and actions. This review briefly describes main consensus points in neuroscience related to the functionality of eight neurochemical ensembles, summarized as a part of the neurochemical model Functional Ensemble of Temperament (FET). None of the FET components is represented by a single neurotransmitter; all neurochemical teams have specific functionality in selection of behavioral degrees of freedom and stages of action construction. The review demonstrates the possibility of unifying taxonomies of temperament and classifications of psychiatric disorders and presenting these taxonomies formally and systematically. The paper also highlights the multi-level nature of regulation of consistent bio-behavioral individual differences, in line with the concepts of diagonal evolution (proposed earlier) and Specialized Extended Phenotype.

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.

Non-coding RNAs in depression: Promising diagnostic and therapeutic biomarkers

Non-coding RNAs (ncRNAs), including microRNAs, circular RNAs, and long non-coding RNAs, are important regulators of normal biological processes and their abnormal expression may be involved in the pathogenesis of human diseases including depression. Multiple studies have demonstrated a significantly increased or reduced ncRNAs expression in depressed patients compared with healthy subjects and that antidepressant therapy can alter the aberrant expression of ncRNAs in depressed patients. Although the existing evidence is important, it is also mixed and a comprehensive review to guide an effective clinical translation is lacking. Focused on human research, this review summarizes clinical findings of ncRNAs in depression, including those in brain tissues and peripheral samples. We outlined the characteristics and functions of ncRNAs and highlighted their performance in the diagnosis and treatment of depression. Although their precise roles in depression remain uncertain, ncRNAs have shown potential value as biomarkers for diagnosis and therapy in depressed patients.

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.

Nicotine abolishes memory-related synaptic strengthening and promotes synaptic depression in the neurogenic dentate gyrus of miR-132/212 knockout mice

Micro-RNAs (miRNAs) are highly evolutionarily conserved short-length/noncoding RNA molecules that modulate a wide range of cellular functions in many cell types by regulating the expression of a variety of targeted genes. miRNAs have also recently emerged as key regulators of neuronal genes mediating the effects of psychostimulant drugs and memory-related neuroplasticity processes. Smoking is a predominant addictive behaviour associated with millions of deaths worldwide, and nicotine is a potent natural psychoactive agonist of cholinergic receptors, highly abundant in cigarettes. The influence of miRNAs modulation on cholinergic signalling in the nervous system remains however poorly explored. Using miRNA knockout mice and biochemical, electrophysiological and pharmacological approaches, we examined the effects of miR-132/212 gene disruption on the levels of hippocampal nicotinic acetylcholine receptors, total ERK and phosphorylated ERK (pERK) and MeCP2 protein levels, and studied the impact of nicotine stimulation on hippocampal synaptic transmission and synaptic depression and strengthening. miR-132/212 deletion significantly altered α7-nAChR and pERK protein levels, but not total ERK or MeCP2, and resulted in both exacerbated synaptic depression and virtually abolished memory-related synaptic strengthening upon nicotine stimulation. These observations reveal a functional miRNAs/nicotinergic signalling interplay critical for nicotinic-receptor expression and neuroplasticity in brain structures relevant for drug addiction and learning and memory functions.

Severe Encephalatrophy and Related Disorders From Long-Term Ketamine Abuse: A Case Report and Literature Review

Ketamine is a glutamate N-methyl D-aspartate receptor antagonist and an anaesthetic agent that has been effectively used to treat depression. However, ketamine has also been increasingly used for recreational purposes. The dissociative side-effects of ketamine use, such as hallucinations, are the reason for abuse. Additionally, long-term ketamine abuse has been highly associated with liver-gallbladder and urinary symptoms. The present study reports the case of a 28-year-old young male adult with an 8-year history of daily inhalation of ketamine. We investigated the association between ketamine abuse and the mechanism of its adverse effects, particularly encephalatrophy, and attempted to find a link between these disorders. These results would help us to better understand ketamine usage, ketamine abuse effects and the addictive mechanism. To the best of our knowledge, the present case is the first report of severe brain atrophy related to ketamine abuse. Details of the patient are presented and the mechanism of the encephalatropy-associated ketamine abuse is discussed. Furthermore, organ dysfunction following chronic ketamine abuse may indicate that the side effects are the result of comprehensive action on multiple regions in the brain.

Differential Dynamical Pattern of Regional Homogeneity in Bipolar and Unipolar Depression: A Preliminary Resting-State fMRI Study

Background: Bipolar depression (BD) and unipolar depression (UD) are both characterized by depressive moods, which are difficult to distinguish in clinical practice. Human brain activity is time-varying and dynamic. Investigating dynamical pattern alterations of depressed brains can provide deep insights into the pathophysiological features of depression. This study aimed to explore similar and different abnormal dynamic patterns between BD and UD. Methods: Brain resting-state functional magnetic resonance imaging data were acquired from 36 patients with BD type I (BD-I), 38 patients with UD, and 42 healthy controls (HCs). Analysis of covariance was adopted to examine the differential pattern of the dynamical regional homogeneity (dReHo) temporal variability across 3 groups, with gender, age, and education level as covariates. Post-hoc analyses were employed to obtain the different dynamic characteristics between any 2 groups. We further applied the machine-learning methods to classify BD-I from UD by using the detected distinct dReHo pattern. Results: Compared with patients with UD, patients with BD-I demonstrated decreased dReHo variability in the right postcentral gyrus and right parahippocampal gyrus. By using the dReHo variability pattern of these two regions as features, we achieved the 91.89% accuracy and 0.92 area under curve in classifying BD-I from UD. Relative to HCs, patients with UD showed increased dReHo variability in the right postcentral gyrus, while there were no dReHo variability differences in patients with BD-I. Conclusions: The results of this study mainly report the differential dynamic pattern of the regional activity between BD-I and UD, particular in the mesolimbic system, and show its promising potential in assisting the diagnosis of these two depression groups.

Biomarkers for suicidal behavior: miRNAs and their potential for diagnostics through liquid biopsy - a systematic review

Background: Given that approximately 70% of miRNAs in the body are neuronal, we critically assessed current studies on miRNAs and suicidal behavior. Materials & Methods: To further define the role of miRNAs in suicide, we searched for studies on extracellular vesicles (exosomes) because miRNAs are particularly enriched in exosomes. miRNAs also have important physiological roles, and they can cross the blood-brain barrier and participate in cell-to-cell communication with both nearby and distant cells. Results & Conclusion: This critical assessment suggests that several miRNAs can be closely related to neurophysiology, suicidal behavior, and psychiatric disorders. However, clear overlap is poor due to either different methodologies applied or to molecular differences between suicidal behaviors and studied psychiatric disorders.

Voluntary wheel running promotes improvements in biomarkers associated with neurogenic activity in adult male rats

In rodents, hippocampal neurogenesis and synaptogenesis phenomena are affected by exercise. However, the role of exercise parameters such as intensity, duration, and mode on molecular mechanisms involved in these processes has not been elucidated. In this study, we evaluated the effects of different intensities and modes of running on the expression of genes contributing to neuronal differentiation and synapse formation in the hippocampus of adult male rats. Adult male Wistar rats (n = 24) were randomly divided into control, low-intensity running (LIR), high-intensity running (HIR), and the voluntary wheel running (WR) conditions. Changes in the expression of microRNA-124 (miR-124), microRNA-132 (miR-132), and their respective targets, were analyzed using quantitative RT-PCR and Western blotting techniques. Our results showed that WR compared to treadmill running increased miR-124 and miR-132 expression, while reducing the expression of their respective targets, glucocorticoid receptor (GR), SRY-Box 9 (SOX9), and GTP-activated protein P250 (P250GAP). Differences in expression levels were statistically significant (ps < 0.05), except for the expression of GR in HIR (P = 0.09). Moreover, the expression level of gene coding for the transcription factor cAMP-response element binding protein (CREB) was significantly higher in the WR group compared to the treadmill running groups (P = 0.001). Western blotting techniques indicated that the level of the CREB protein was higher in WR compared to the other groups qualitatively. These findings demonstrated a more dramatic effect for voluntary running on biomarkers that are associated with stimulating neurogenesis and synapse formation in the hippocampus of male rats compared with forced treadmill running. In addition, greater positive effects were observed for lower-intensity treadmill running as compared with high-intensity running.

The molecular effect of a polymorphic microRNA binding site of Wolfram syndrome 1 gene in dogs

Background

Although the molecular function of wolframin remains unclear, the lack of this protein is known to cause stress in the endoplasmic reticulum. Some variants in the Wolfram Syndrome 1 gene (WFS1) were associated with various neuropsychiatric disorders in humans, such as aggressiveness, impulsivity and anxiety.

Results

Here we present an in silico study predicting a single nucleotide polymorphism (rs852850348) in the canine WFS1 gene which was verified by direct sequencing and was genotyped by a PCR-based technique. We found that the rs852850348 polymorphism is located in a putative microRNA (cfa-miR-8834a and cfa-miR-1838) binding site. Therefore, the molecular effect of allelic variants was studied in a luciferase reporter system that allowed assessing gene expression. We demonstrated that the variant reduced the activity of the reporter protein expression in an allele-specific manner. Additionally, we performed a behavioral experiment and investigated the association with this locus to different performance in this test. Association was found between food possessivity and the studied WFS1 gene polymorphism in the Border collie breed.

Conclusions

Based on our findings, the rs852850348 locus might contribute to the genetic risk of possessivity behavior of dogs in at least one breed and might influence the regulation of wolframin expression.

Calcium-binding proteins are altered in the cerebellum in schizophrenia

Alterations in the cortico-cerebellar-thalamic-cortical circuit might underlie the diversity of symptoms in schizophrenia. However, molecular changes in cerebellar neuronal circuits, part of this network, have not yet been fully determined. Using LC-MS/MS, we screened altered candidates in pooled grey matter of cerebellum from schizophrenia subjects who committed suicide (n = 4) and healthy individuals (n = 4). Further validation by immunoblotting of three selected candidates was performed in two cohorts comprising schizophrenia (n = 20), non-schizophrenia suicide (n = 6) and healthy controls (n = 21). We found 99 significantly altered proteins, 31 of them previously reported in other brain areas by proteomic studies. Transport function was the most enriched category, while cell communication was the most prevalent function. For validation, we selected the vacuolar proton pump subunit 1 (VPP1), from transport, and two EF-hand calcium-binding proteins, calmodulin and parvalbumin, from cell communication. All candidates showed significant changes in schizophrenia (n = 7) compared to controls (n = 7). VPP1 was altered in the non-schizophrenia suicide group and increased levels of parvalbumin were linked to antipsychotics. Further validation in an independent cohort of non-suicidal chronic schizophrenia subjects (n = 13) and non-psychiatric controls (n = 14) showed that parvalbumin was increased, while calmodulin was decreased in schizophrenia. Our findings provide evidence of calcium-binding protein dysregulation in the cerebellum in schizophrenia, suggesting an impact on normal calcium-dependent synaptic functioning of cerebellar circuits. Our study also links VPP1 to suicide behaviours, suggesting a possible impairment in vesicle neurotransmitter refilling and release in these phenotypes.

Commentary on the study of Roy et al. Amygdala Based Altered mir-128-3p in Conferring Susceptibility to Depression-like Behavior via Wnt Signalling

The study of Roy and colleagues recently accepted for publication in International Journal of Neuropsychopharmacology is a very interesting report investigating the role of specific microRNAs (miRNAs) in vulnerability or resistance to major depressive disorder in a specific brain region (e.g., amygdala). MiRNAs may act as a mega-controller of gene expression being involved in the pathogenesis of major neuropsychiatric conditions. Interestingly, some of the altered miRNAs (e.g., hsa-miR-425-3p, miR-425, miR-674-3p, and miR-873-3p) identified in this study were found to be dysregulated even in existing studies, but several methodological issues may hamper the translation of basic research findings in clinical studies. MiRNAs are proposed as possible biomarkers of disease and treatment response to disentangle the biological complexity underlying major affective disorders. The main implications regarding the present findings are discussed.

Elevated expression of unfolded protein response genes in the prefrontal cortex of depressed subjects: Effect of suicide

BACKGROUND

Major Depressive Disorder (MDD) is a leading cause of mental disability worldwide. Despite many studies, the pathophysiology associated with MDD brain is not very clear. It is reported that cellular stress is related to depressive symptoms. Under stressful conditions, intracellular homeostasis processes can be disrupted, which can induce a process of unfolded protein response (UPR) in the subcellular lumen of endoplasmic reticulum (ER). The purpose of this study is to elucidate whether UPR is active in the depressed brain.

METHODS

The dorsolateral prefrontal cortex (dlPFC) was used from 23 non-psychiatric controls and 43 MDD subjects. The expression levels of UPR associated genes (GRP78, GRP94, XBP-1, CHOP, ATF4C, and ATF6C) were measured by qRT-PCR.

RESULTS

The level of mRNA expression in MDD subjects was significantly higher for GRP78 (p = 0.008), GRP94 (p = 0.018), and ATF4C (p = 0.03) compared to non-psychiatric controls. Further analysis suggested that changes in the expression of these genes were specifically higher only in those MDD subjects who died by suicide but not in those who died by causes other than suicide when compared with non-psychiatric controls (GRP78, p = 0.007; GRP94, p = 0.041; ATF4C, p = 0.037).

LIMITATIONS

This study was performed only in MDD subjects who had died by suicide. Suicide subjects with other psychiatric illnesses need to be included.

CONCLUSIONS

Given that UPR is involved in many physiological processes in the brain, including inflammatory response as well as apoptosis, increased expression of UPR genes indicates that ER stress and mediated UPR may be critical factors in suicidality among depressed patients.

MicroRNA mediators of early life stress vulnerability to depression and suicidal behavior

Childhood environment can have a profound impact on brain structure and function. Epigenetic mechanisms have been shown to play a critical role in adaptive and maladaptive processes by regulating gene expression without changing the genome. Over the past few years, early life stress (ELS) has been established as a major risk factor for major depression and suicidal behavior along with other psychiatric illnesses in adulthood. In recent years, the emergence of small noncoding RNAs as a mega controller of gene expression has gained attention for their role in various disease processes. Among various noncoding RNAs, microRNAs (miRNAs) are the most studied and well characterized and have emerged as a major regulator of neural plasticity and higher brain functioning. More recently, although limited in number, studies are focusing on how miRNAs can play a role in the maladaptive processes associated with ELS both at adolescent and adult age and whether these processes are critical in developing depression and suicidal behavior. In this review, we critically evaluate how postnatal ELS relates to abnormalities in miRNA expression and functions from both animal and human literature and draw connections from these findings to depression and suicidal behavior later in life.

SSTR4, Childhood Adversity, Self-efficacy and Suicide Risk in Alcoholics

Background

Patients with alcohol dependence (AD) are known to develop poor social skills, to report a higher number of adverse childhood experiences (ACEs) and to attempt suicide more frequently than the general population. The background for the association between ACEs and a higher risk of suicide still remains understudied. SSTR4 rs2567608 is a functional polymorphism of the gene for somatostatin receptor subtype 4, predominantly found in the CA1 hippocampus area and involved in memory formation. We hypothesize that the functional polymorphism SSTR4 rs2567608, general self-efficacy, and adverse childhood experiences influence the risk of suicide attempt in patients with AD.

Methodology

176 patients with AD and 127 healthy controls were interviewed regarding 13 categories of ACEs and assessed with the General Self-Efficacy Scale. Genotyping for the SSTR4 rs2567608 polymorphism was performed according to the manufacturer’s standard PCR protocol.

Results

Patients with AD and the controls did not differ significantly according to the SSTR4 rs2567608 genotype and allele frequencies. Lower general self-efficacy, higher number of ACEs, and the SSTR4 rs2567608 TT genotype increased the risk of suicide attempt in patients with AD, and it persisted significant only in male patients with AD.

Conclusions

Our study supports previous findings on ACEs and general self-efficacy association with a risk for suicide. Additionally, we suggest that patients with AD of the SSTR4 rs2567608 TT genotype may be more vulnerable to ACEs and at a higher risk of suicide attempt.

Expressions of miR-132, miR-134, and miR-485 in rat primary motor cortex during transhemispheric functional reorganization after contralateral seventh cervical spinal nerve root transfer following brachial plexus avulsion injuries

The transfer of a contralateral healthy seventh cervical spinal nerve root (cC7) to the recipient nerve in the injured side is considered a promising procedure for restoration of the physiological functions of an injured hand after brachial plexus root avulsion injury (BPAI). Growing evidence shows that transhemispheric cortical reorganization plays an important role in the functional recovery of the injured arm after cC7 nerve transfer surgery. However, the molecular mechanism underlying the transhemispheric cortical reorganization after cC7 transfer remains elusive. In the present study, we investigated the expression of miR-132, miR-134, and miR-485 in the rat primary motor cortex after cC7 transfer following BPAI by quantitative PCR. The results demonstrated the dynamic alteration in the expression of miR-132, miR-134, and miR-485 in the primary motor cortex of rats after cC7 transfer following BPAI. It indicates that microRNAs are involved in the dynamic transhemispheric functional reorganization after cC7 root transfer following BPAI. Together, this study is the first to provide evidence for the involvement of microRNAs during dynamic transhemispheric functional reorganization after cC7 transfer following BPAI. The results are useful for understanding the mechanism underlying transhemispheric functional reorganization after contralateral seventh cervical spinal nerve root transfer following BPAI.

Molecular Mechanism of Adult Neurogenesis and its Association with Human Brain Diseases

Recent advances in neuroscience challenge the old dogma that neurogenesis occurs only during embryonic development. Mounting evidence suggests that functional neurogenesis occurs throughout adulthood. This review article discusses molecular factors that affect adult neurogenesis, including morphogens, growth factors, neurotransmitters, transcription factors, and epigenetic factors. Furthermore, we summarize and compare current evidence of associations between adult neurogenesis and human brain diseases such as Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, and brain tumors.

Conservation in Mammals of Genes Associated with Aggression-Related Behavioral Phenotypes in Honey Bees

The emerging field of sociogenomics explores the relations between social behavior and genome structure and function. An important question is the extent to which associations between social behavior and gene expression are conserved among the Metazoa. Prior experimental work in an invertebrate model of social behavior, the honey bee, revealed distinct brain gene expression patterns in African and European honey bees, and within European honey bees with different behavioral phenotypes. The present work is a computational study of these previous findings in which we analyze, by orthology determination, the extent to which genes that are socially regulated in honey bees are conserved across the Metazoa. We found that the differentially expressed gene sets associated with alarm pheromone response, the difference between old and young bees, and the colony influence on soldier bees, are enriched in widely conserved genes, indicating that these differences have genomic bases shared with many other metazoans. By contrast, the sets of differentially expressed genes associated with the differences between African and European forager and guard bees are depleted in widely conserved genes, indicating that the genomic basis for this social behavior is relatively specific to honey bees. For the alarm pheromone response gene set, we found a particularly high degree of conservation with mammals, even though the alarm pheromone itself is bee-specific. Gene Ontology identification of human orthologs to the strongly conserved honey bee genes associated with the alarm pheromone response shows overrepresentation of protein metabolism, regulation of protein complex formation, and protein folding, perhaps associated with remodeling of critical neural circuits in response to alarm pheromone. We hypothesize that such remodeling may be an adaptation of social animals to process and respond appropriately to the complex patterns of conspecific communication essential for social organization.

Neuroinflammation and Depression: Microglia Activation, Extracellular Microvesicles and microRNA Dysregulation

Patients with chronic inflammation are often associated with the emergence of depression symptoms, while diagnosed depressed patients show increased levels of circulating cytokines. Further studies revealed the activation of the brain immune cell microglia in depressed patients with a greater magnitude in individuals that committed suicide, indicating a crucial role for neuroinflammation in depression brain pathogenesis. Rapid advances in the understanding of microglial and astrocytic neurobiology were obtained in the past 15–20 years. Indeed, recent data reveal that microglia play an important role in managing neuronal cell death, neurogenesis, and synaptic interactions, besides their involvement in immune-response generating cytokines. The communication between microglia and neurons is essential to synchronize these diverse functions with brain activity. Evidence is accumulating that secreted extracellular vesicles (EVs), comprising ectosomes and exosomes with a size ranging from 0.1–1 μm, are key players in intercellular signaling. These EVs may carry specific proteins, mRNAs and microRNAs (miRNAs). Transfer of exosomes to neurons was shown to be mediated by oligodendrocytes, microglia and astrocytes that may either be supportive to neurons, or instead disseminate the disease. Interestingly, several recent reports have identified changes in miRNAs in depressed patients, which target not only crucial pathways associated with synaptic plasticity, learning and memory but also the production of neurotrophic factors and immune cell modulation. In this article, we discuss the role of neuroinflammation in the emergence of depression, namely dynamic alterations in the status of microglia response to stimulation, and how their activation phenotypes may have an etiological role in neurodegeneneration, in particular in depressive-like behavior. We will overview the involvement of miRNAs, exosomes, ectosomes and microglia in regulating critical pathways associated with depression and how they may contribute to other brain disorders including amyotrophic lateral sclerosis (ALS), Alzheimer’s disease (AD) and Parkinson’s disease (PD), which share several neuroinflammatory-associated processes. Specific reference will be made to EVs as potential biomarkers and disease monitoring approaches, focusing on their potentialities as drug delivery vehicles, and on putative therapeutic strategies using autologous exosome-based delivery systems to treat neurodegenerative and psychiatric disorders.

Association of human microRNAs miR-22 and miR-491 polymorphisms with panic disorder with or without agoraphobia in a Korean population

BACKGROUND

The possible involvement of microRNAs (miRNA) in psychiatric disorders has been recently recognized. Several miRNA polymorphisms have been found to be associated with panic disorder (PD) in European populations. However, the association of miRNA polymorphisms on PD has not been reported in Asian populations. We evaluated the effect of miR-22 and miR-491 polymorphisms on susceptibility to PD in a Korean population.

METHODS

Genotyping for four polymorphic variants of the primary miRNA (pri-miRNA) regions of miR-22 (rs8076112 and rs6502892) and miR-491 (rs4977831 and rs2039391) was performed using blood samples of 341 Korean patients with PD and 229 healthy control subjects. To evaluate PD phenotypes, the Panic Disorder Severity Scale (PDSS) and Anxiety Sensitivity Inventory-Revised (ASI-R) were administered.

RESULTS

Three single-nucleotide polymorphisms (SNPs) were found to be associated with PD: rs8076112 miR-22 and rs4977831 and miR-491 rs2039391. The rs8076112C/rs6502892C haplotypes of miR-22 and rs4977831G/rs2039391G and rs4977831A/rs2039391A haplotypes of miR-491 were significantly overrepresented in patients with PD than in healthy control subjects. In combination analysis, miR-22 rs8076112AC/rs6502892CC and rs8076112CC/rs6502892CC and miR-491 rs4977831AG/rs2039391AA were more frequent in patients with PD. Among the phenotype assessments, ASI-R scores were significantly associated with miR-22 rs6502892 in the subgroup with the agoraphobic phenotype.

LIMITATIONS

The results should be considered preliminary due to the relatively small sample size and the selection of only four SNPs.

CONCLUSIONS

This is the first report to show possible associations of miR-22 and miR-491 with genetic susceptibility to PD in a Korean population.

Network analysis of microRNA and mRNA seasonal dynamics in a highly plastic sensorimotor neural circuit

Background

Adult neurogenesis and the incorporation of adult-born neurons into functional circuits requires precise spatiotemporal coordination across molecular networks regulating a wide array of processes, including cell proliferation, apoptosis, neurotrophin signaling, and electrical activity. MicroRNAs (miRs) - short, non-coding RNA sequences that alter gene expression by post-transcriptional inhibition or degradation of mRNA sequences - may be involved in the global coordination of such diverse biological processes. To test the hypothesis that miRs related to adult neurogenesis and related cellular processes are functionally regulated in the nuclei of the avian song control circuit, we used microarray analyses to quantify changes in expression of miRs and predicted target mRNAs in the telencephalic nuclei HVC, the robust nucleus of arcopallium (RA), and the basal ganglia homologue Area X in breeding and nonbreeding Gambel’s white-crowned sparrows (Zonotrichia leucophrys gambelli).

Results

We identified 46 different miRs that were differentially expressed across seasons in the song nuclei. miR-132 and miR-210 showed the highest differential expression in HVC and Area X, respectively. Analyzing predicted mRNA targets of miR-132 identified 33 candidate target genes that regulate processes including cell cycle control, calcium signaling, and neuregulin signaling in HVC. Likewise, miR-210 was predicted to target 14 mRNAs differentially expressed across seasons that regulate serotonin, GABA, and dopamine receptor signaling and inflammation.

Conclusions

Our results identify potential miR–mRNA regulatory networks related to adult neurogenesis and provide opportunities to discover novel genetic control of the diverse biological processes and factors related to the functional incorporation of new neurons to the adult brain.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-2175-z) contains supplementary material, which is available to authorized users.

Possible scenarios of the influence of low-dose ionizing radiation on neural functioning

Possible scenarios of the influence of ionizing radiation on neural functioning and the CNS are suggested. We argue that the radiation-induced bystander mechanisms associated with Ca(2+) flows, reactive nitrogen and oxygen species, and cytokines might lead to modulation of certain neuronal signaling pathways. The considered scenarios of conjugation of the bystander signaling and the neuronal signaling might result in modulation of certain synaptic receptors, neurogenesis, neurotransmission, channel conductance, synaptic signaling, different forms of neural plasticity, memory formation and storage, and learning. On this basis, corresponding new possible strategies for treating neurodegenerative deceases and mental disorders are proposed. The mechanisms considered might also be associated with neuronal survival and relevant to the treatment for brain injuries. At the same time, these mechanisms might be associated with detrimental effects and might facilitate the development of some neurological and psychiatric disorders.

The influence of inflammatory cytokines in physiopathology of suicidal behavior

BACKGROUND

Based on the urgent need for reliable biomarkers in relation to suicide risk both for more accurate prediction as well as for new therapeutic opportunities, several researchers have been studied evidences of the potential participation of inflammatory processes in the brain, in particular cytokines, in suicide. The purpose of this review was to analyze the associations between inflammation markers and suicide.

METHODS

To achieve this goal, a systematic review of literature was conducted via electronic database Scopus using the Medical Subject Headings (MeSH) terms: "cytokines", "suicide" and "inflammation". Through this search it was found 54 articles. After analyzing them 15 met the eligibility criteria and were included in the final sample.

RESULTS

One of the most mentioned inflammatory markers was Interferon-α (IFN-α), a pro-inflammatory cytokine which has been shown to increase serum concentrations of pro-inflammatory cytokines such as interleukin (IL)-1, IL-6, tumor necrosis factor-a (TNF- α) and IFN-ϒ, which are factors increased suicide victims and attempters. In this line, IL-6 is not only found to be elevated in the cerebrospinal fluid of suicide attempters, even its levels in the peripheral blood have been proposed as a biological suicide marker. Another study stated that increased levels of IL-4 and IL-13 transcription in the orbitofrontal cortex of suicides suggest that these cytokines may affect neurobehavioral processes relevant to suicide.

LIMITATIONS

A lack of studies and great amount of cross-sectional studies.

CONCLUSION

Inflammation may play an important role in the pathophysiology of suicide, especially, levels of some specific inflammatory cytokines.

Epigenetic studies of suicidal behavior

Recent studies have shown an association between gene alterations by epigenetic mechanisms and suicidal behavior. These epigenetic mechanisms are mitotically, and in some cases meiotically, heritable changes in the genome through non-DNA sequence coding processes that alter gene expression as a result of variable changes in environmental stimuli. Genome-wide association studies have been inconsistent in elucidating the association between genes and suicidal behavior, thereby making the heritability of suicidal behavior is unclear. However, recent epigenetic studies have provided evidence that epigenetic mechanisms could deliver the missing link between the heritability of suicidal behavior and the interaction between environment and the genome. The present review provides an in-depth discussion of epigenetic mechanisms that may regulate gene expression in suicidal behavior. The findings of current epigenetic studies on suicidal behavior will also be discussed considering future epigenome-wide association studies on elucidating the contributions of environment and genome on suicidal behavior.

Emerging role of microRNAs in major depressive disorder: diagnosis and therapeutic implications

Major depressive disorder (MDD) is a major public health concern. Despite tremendous advances, the pathogenic mechanisms associated with MDD are still unclear. Moreover, a significant number of MDD subjects do not respond to the currently available medication. MicroRNAs (miRNAs) are a class of small noncoding RNAs that control gene expression by modulating translation, messenger RNA (mRNA) degradation, or stability of mRNA targets. The role of miRNAs in disease pathophysiology is emerging rapidly. Recent studies demonstrating the involvement of miRNAs in several aspects of neural plasticity, neurogenesis, and stress response, and more direct studies in human postmortem brain provide strong evidence that miRNAs can not only play a critical role in MDD pathogenesis, but can also open up new avenues for the development of therapeutic targets. Circulating miRNAs are now being considered as possible biomarkers in disease pathogenesis and in monitoring therapeutic responses because of the presence and/or release of miRNAs in blood cells as well as in other peripheral tissues. In this review, these aspects are discussed in a comprehensive and critical manner.

The role of ketamine in treatment-resistant depression: a systematic review

Background:

At least 10-20% of the patients suffering from depression meet criteria for treatment-resistant depression (TRD). In the last decades, an important role of glutamate in mood modulation has been hypothesized and ketamine, a non noncompetitive antagonist of the N-methyl-D-aspartate (NMDA) receptors, has been demonstrated to be effective in both MDD and TRD. However, concerns emerged about the optimal dosage, and frequency of administration of this treatment.

Methods:

aiming to systematically review the current literature focusing on the main pharmacological properties and impact of ketamine in TRD, a detailed literature search in PubMed/Medline and ScienceDirect databases was conducted. Twenty-four manuscripts including a total of 416 patients fulfilled inclusion criteria.

Results:

Most studies demonstrated that the NMDA antagonist ketamine has rapid antidepressant effects in TRD patients, confirming the active role of glutamate in the pathophysiology of this complex condition. Ketamine has been demonstrated to be rapidly effective and was associated with a significant clinical improvement in depressive symptoms within hours after administration. Also, ketamine was also found to be effective in reducing suicidality in TRD samples.

Limitations:

The long-term efficacy of ketamine has not been investigated by most studies. The psychotomimetic properties may complicate the application of this pharmacological agent.

Conclusions:

Ketamine may be considered a valid and intriguing antidepressant option for the treatment of TRD. Further studies are needed to evaluate its long-term antidepressant efficacy in patients with TRD.

Identification of circulating microRNAs as potential biomarkers for detecting acute ischemic stroke

MicroRNAs (miRNAs) are present in serum and have the potential to serve as disease biomarkers. As such, it is important to explore the clinical value of miRNAs in serum as biomarkers for ischemic stroke (IS) and cast light on the pathogenesis of IS. In this study, we screened differentially expressed serum miRNAs from IS and normal people by miRNA microarray analysis, and validated the expression of candidate miRNAs using quantitative reverse-transcriptase polymerase chain reaction assays. Furthermore, we performed gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) pathway analyses to disclose functional enrichment of genes predicted to be regulated by the differentially expressed miRNAs. Notably, our results revealed that 115 miRNAs were differentially expressed in IS, among which miR-32-3p, miR-106-5p, and miR-532-5p were first found to be associated with IS. In addition, GO and KEGG pathway analyses showed that genes predicted to be regulated by differentially expressed miRNAs were significantly enriched in several related biological process and pathways, including axon guidance, glioma, MAPK signaling, mammalian target of rapamycin signaling, and ErbB-signaling pathway. In conclusion, we identified the changed expression pattern of miRNAs in IS. Serum miR-32-3p, miR-106-5p, miR-1246, and miR-532-5p may serve as potential diagnostic biomarkers for IS. Our results also demonstrate a novel role for miRNAs in the pathogenesis of IS.

Heterogeneity and individuality: microRNAs in mental disorders

MicroRNAs are about 22 nucleotide long single-stranded RNA molecules, negatively regulating gene expression of a single gene or a gene network. In neural tissues, they have been implicated in developmental and neuroplasticity-related processes, such as neurogenesis, differentiation, apoptosis and long-term potentiation. Their molecular mode of action is reminiscent of findings of genome-wide association studies in mental disorders, unable to attribute the risk of disease to a specific gene, but rather to multiple genes, gene-networks and gene-environment interaction. As such, microRNAs are an attractive target for research. Here, we review clinical studies conducted in humans on microRNAs in mental disorders with a particular focus on schizophrenia, bipolar disorder, major depressive disorder and anxiety disorders. The majority of clinical studies have focused on schizophrenia. The most robust finding has been reported for rs1625579 located in MIR137HG, which was associated with schizophrenia on a genome-wide level. Concerning bipolar disorder, major depression and anxiety disorders, promising results have been published, but only a considerably smaller number of clinical studies is available and genome-wide association studies did not suggest a direct link to microRNAs so far. Expression of microRNAs as biomarkers of mental disorders and treatment response is currently emerging with preliminary results. Larger-scaled genetic and functional studies along with translational research are needed to enhance our understanding of microRNAs in mental disorders. These studies will aid in disentangling the complex genetic nature of these disorders and possibly contribute to the development of novel, individualized diagnostic and therapeutic approaches.