microRNA-124: a putative therapeutic target and biomarker for major depression

MicroRNA-124 influenced depressive symptoms via large-scale brain connectivity in major depressive disorder patients

This study aimed to investigate the neurobiological mechanisms by which microRNA 124 (miR-124) is involved in major depressive disorder (MDD). We enrolled 53 untreated MDD patients and 38 healthy control (HC) subjects who completed behavior assessments and resting-state functional MRI (rs-fMRI) scans. MiR-124 expression levels were detected in the peripheral blood of all participants. We determined that miR-124 levels could influence depressive symptoms via disrupted large-scale intrinsic intra- and internetwork connectivity, including the default mode network (DMN)-DMN, dorsal attention network (DAN)-salience network (SN), and DAN-cingulo-opercular network (CON). This study deepens our understanding of how miR-124 dysregulation contributes to depression.

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.

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.

Detection of micro-RNA by a combination of nucleic acid sequence-based amplification and a novel chemiluminescent pyrophosphate assay

Micro-RNA has attracted much attention as a biomarker for disease progression and malignancy. A compact, simple, rapid, and highly sensitive method is required to perform simple genetic analyses, such as point-of-care testing (POCT), at the clinic or bedside. Nucleic acid sequence-based amplification (NASBA) is a specific amplification method for a single-stranded RNA fragment that is useful for the highly sensitive detection of miRNAs. In this work, we developed a novel miRNA analytical system for POCT by combining the NASBA and chemiluminescence methods. Because the NASBA reaction is conducted at a constant temperature (41 °C) and detection by chemiluminescence reaction does not require a light source, these methods could be combined to amplify 100 ng/assay miRNA. This combined miRNA detection method could be useful for the future development of compact POCT systems.

A Systematic Review of Circulatory microRNAs in Major Depressive Disorder: Potential Biomarkers for Disease Prognosis

Major depressive disorder (MDD) is a neuropsychiatric disorder, which remains challenging to diagnose and manage due to its complex endophenotype. In this aspect, circulatory microRNAs (cimiRNAs) offer great potential as biomarkers and may provide new insights for MDD diagnosis. Therefore, we systemically reviewed the literature to explore various cimiRNAs contributing to MDD diagnosis and underlying molecular pathways. A comprehensive literature survey was conducted, employing four databases from 2012 to January 2021. Out of 1004 records, 157 reports were accessed for eligibility criteria, and 32 reports meeting our inclusion criteria were considered for in-silico analysis. This study identified 99 dysregulated cimiRNAs in MDD patients, out of which 20 cimiRNAs found in multiple reports were selected for in-silico analysis. KEGG pathway analysis indicated activation of ALS, MAPK, p53, and P13K-Akt signaling pathways, while gene ontology analysis demonstrated that most protein targets were associated with transcription. In addition, chromosomal location analysis showed clustering of dysregulated cimiRNAs at proximity 3p22-p21, 9q22.32, and 17q11.2, proposing their coregulation with specific transcription factors primarily involved in MDD physiology. Further analysis of transcription factor sites revealed the existence of HIF-1, REST, and TAL1 in most cimiRNAs. These transcription factors are proposed to target genes linked with MDD, hypothesizing that first-wave cimiRNA dysregulation may trigger the second wave of transcription-wide changes, altering the protein expressions of MDD-affected cells. Overall, this systematic review presented a list of dysregulated cimiRNAs in MDD, notably miR-24-3p, let 7a-5p, miR-26a-5p, miR135a, miR-425-3p, miR-132, miR-124 and miR-16-5p as the most prominent cimiRNAs. However, various constraints did not permit us to make firm conclusions on the clinical significance of these cimiRNAs, suggesting the need for more research on single blood compartment to identify the biomarker potential of consistently dysregulated cimiRNAs in MDD, as well as the therapeutic implications of these in-silico insights.

Promoter Hypomethylation of miR-124 Gene Is Associated With Major Depressive Disorder

Based on our previous studies and other evidence, miR-124 is an important biomarker and therapeutic target for major depressive disorder (MDD). The aim of this study was to clarify the role of miR-124 methylation in MDD and antidepressant effects from the perspective of epigenetics. MethylTarget™ was used to detect methylation levels of the three miR-124 precursor genes (MIR124-1, MIR124-2, and MIR124-3) in 33 pre- and post-treatment MDD patients and 33 healthy controls. A total of 11 cytosine-phosphate-guanine (CpG) islands in the three miR-124 precursor genes, including 222 CpG sites, were detected. All CpG islands were hypomethylated in MDD patients when compared to healthy controls and seven CpG regions were still identified with a statistically significant difference after Bonferroni correction. In addition, 137 of 222 CpG sites were found a statistical difference between MDD patients and controls, and 40 CpG sites were still statistically significant after Bonferroni correction. After performing the LASSO regression model, seven biomarkers with differential methylation among 40 CpG sites were identified. Mean methylation score was lower in MDD patients (z = -5.84, p = 5.16E-9). The AUC value reached 0.917 (95% CI: 0.854-0.981) to discriminate MDD and controls. No changes in methylation of the three miR-124 precursor genes were found in MDD patients following antidepressant treatment. The methylation of miR-124 could be a promising diagnostic biomarker for MDD.

MicroRNAs as Critical Biomarkers of Major Depressive Disorder: A Comprehensive Perspective

Major Depressive Disorder (MDD) represents a major global health concern, a body-mind malady of rising prevalence worldwide nowadays. The complex network of mechanisms involved in MDD pathophysiology is subjected to epigenetic changes modulated by microRNAs (miRNAs). Serum free or vesicles loaded miRNAs have starred numerous publications, denoting a key role in cell-cell communication, systematically and in brain structure and neuronal morphogenesis, activity and plasticity. Upregulated or downregulated expression of these signaling molecules may imply the impairment of genes implicated in pathways of MDD etiopathogenesis (neuroinflammation, brain-derived neurotrophic factor (BDNF), neurotransmitters, hypothalamic-pituitary-adrenal (HPA) axis, oxidative stress, circadian rhythms...). In addition, these miRNAs could serve as potential biomarkers with diagnostic, prognostic and predictive value, allowing to classify severity of the disease or to make decisions in clinical management. They have been considered as promising therapy targets as well and may interfere with available antidepressant treatments. As epigenetic malleable regulators, we also conclude emphasizing lifestyle interventions with physical activity, mindfulness and diet, opening the door to new clinical management considerations.

Circulating microRNAs and Molecular Oxidative Stress in Older Adults with Neuroprogression Disorders

BACKGROUND

circulating microRNAs are potential blood biomarkers differentially expressed in many diseases including neuro depression disorders. It controls the expression of human genes and associated cellular and physiological processes in normal and diseased cells. We aimed to evaluate the potential role of circulating miRNAs and their association with both stress hormones and cellular oxidative stress in neuro depression disorders occurred among older adults.

METHODS

a total of 70 healthy subjects were included in this study. Based upon the profile of mood states (POMS-32 score), the participants classified into two groups; healthy subjects (n =30) and depression (n =40). The expression of microRNAs; miR-124, miR-34a-5p, miR-135, and miR-451-a and their correlation with cellular oxidative stress parameters; cellular NO, genes of SOD2, CAT and iNOS, and hormones; cortisol and serotonin were estimated by a quantitative real-time RT-PCR, high-performance liquid chromatography, and ELISA Immunoassay techniques, respectively.

RESULTS

depression was reported in 57.14% of the participants. The results showed a significant increase (p =0.01) in the total mood scores, and relative depression domains in older adults with depression compared to healthy controls. The relative expression levels of miR-124, miR-34a-5p significantly increased and the expression levels of miR-135, and miR-451-a significantly decreased in older adults with depression compared to healthy controls. In addition, the levels of cortisol significantly increased and serotonin (5HT) significantly reduced in all participants with depression. Cellular oxidative stress analysis for depressed subjects showed that serum NO levels and the expression of iNO gene significantly increased conversely with a decline in the molecular expression antioxidative genes; SOD2, CAT, respectively. The results showed that cellular oxidative stress parameters correlated positively with depression scores, cortisol, and negatively with cellular serotonin levels. In depressed subjects, the relative expression of microRNAs correlated positively with depression score, NO, iNOS, cortisol, and negatively associated with SOD2, CAT, and serotonin.

CONCLUSION

The combination of cellular oxidative stress and hormonal levels strongly supports a role for circulating miRNAs; miR-124, miR-34a-5p, miR-135, and miR-451-a in the regulation of depression and mood disorders among older adults. The expressed microRNAs with their related association to cellular oxidative stress and adrenal hormones are a step towards understanding the role of these small RNA molecules in the progression of depression among older adults. Thus, cellular miRNAs might have a prognostic role in the diagnosis and as a target for treatment strategies in depressed subjects.

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.

Early life and adult stress promote sex dependent changes in hypothalamic miRNAs and environmental enrichment prevents stress-induced miRNA and gene expression changes in rats

BACKGROUND

The hypothalamus plays a key role in the stress response. While early life stress (ELS) increases susceptibility to psychiatric disorders including major depressive disorder (MDD), acute stress during adulthood can also precipitate MDD after ELS.

AIM

Here, we tested the expression of miRNAs following ELS and susceptibility to depression-like behavior and whether sex or acute stress exacerbates this response. We also tested whether environmental enrichment (Enr) promotes early life and adult behavioral stress resilience and its effect on hypothalamic miRNA and gene expression. Following rat maternal separation (MS) as an ELS model, Enr from weaning through adulthood, and restraint (RS) as acute adult stress, we tested both animal behavior and miRNA expression in the hypothalamus. Target genes and their enrichment and ontology were analyzed using bioinformatic tools. Target gene expression changes were tested using qPCR, and miRNA promoter methylation was studied using methylated-DNA immunoprecipitation qPCR.

RESULTS

MS, Enr, RS, and sex altered hypothalamic miRNAs, including several previously reported in MS literature: miRs-29, - 124, - 132, - 144, - 504. Sex had a significant effect on the greatest number of miRNAs. Also, Enr reversed downregulation of miR-29b-1-5p and -301b-3p in MS. qPCR showed that MAPK6 and MMP19, targets of miR-301b-3p, were upregulated in MS and reversed by Enr. Additionally, miR-219a was hypermethylated in MS coinciding with decreased miR-219a expression.

CONCLUSIONS

This study found that sex plays a critical role in the hypothalamic miRNA response to both ELS and acute stress, with males expressing greater changes following postnatal stress. Moreover, enrichment significantly altered behavior as well as hypothalamic miRNA expression and their gene targets. Because of its role as the initiator of the autonomic stress response and connection to hedonic and motivational behavior, the hypothalamic miRNA landscape may significantly alter both the short and long-term behavioral response to stress.

Early Life Irradiation-Induced Hypoplasia and Impairment of Neurogenesis in the Dentate Gyrus and Adult Depression Are Mediated by MicroRNA- 34a-5p/T-Cell Intracytoplasmic Antigen-1 Pathway

Early life radiation exposure causes abnormal brain development, leading to adult depression. However, few studies have been conducted to explore pre- or post-natal irradiation-induced depression-related neuropathological changes. Relevant molecular mechanisms are also poorly understood. We induced adult depression by irradiation of mice at postnatal day 3 (P3) to reveal hippocampal neuropathological changes and investigate their molecular mechanism, focusing on MicroRNA (miR) and its target mRNA and protein. P3 mice were irradiated by γ-rays with 5Gy, and euthanized at 1, 7 and 120 days after irradiation. A behavioral test was conducted before the animals were euthanized at 120 days after irradiation. The animal brains were used for different studies including immunohistochemistry, CAP-miRSeq, Real-Time Quantitative Reverse Transcription PCR (qRT-PCR) and western blotting. The interaction of miR-34a-5p and its target T-cell intracytoplasmic antigen-1 (Tia1) was confirmed by luciferase reporter assay. Overexpression of Tia1 in a neural stem cell (NSC) model was used to further validate findings from the mouse model. Irradiation with 5 Gy at P3 induced depression in adult mice. Animal hippocampal pathological changes included hypoplasia of the infrapyramidal blade of the stratum granulosum, aberrant and impaired cell division, and neurogenesis in the dentate gyrus. At the molecular level, upregulation of miR-34a-5p and downregulation of Tia1 mRNA were observed in both animal and neural stem cell models. The luciferase reporter assay and gene transfection studies further confirmed a direct interaction between miR-43a-5p and Tia1. Our results indicate that the early life γ-radiation-activated miR-43a-5p/Tia1 pathway is involved in the pathogenesis of adult depression. This novel finding may provide a new therapeutic target by inhibiting the miR-43a-5p/Tia1 pathway to prevent radiation-induced pathogenesis of depression.

MiR-129-5p prevents depressive-like behaviors by targeting MAPK1 to suppress inflammation

Depression is a complex etiological disease with limited effective treatments. Previous studies have indicated the involvement of miRNAs in the pathophysiology of mood disorders. In this study, we focused on the role and mechanisms of miR-129-5p in depression by successfully constructing mice models of depressive-like behavior via chronic unpredictable mild stress (CUMS) exposure. Herein, miR-129-5p expression was decreased in the hippocampus of CUMS mice model. Upregulation of miR-129-5p reduced depressive-like behaviors of CUMS mice, as revealed in sucrose preference test, novelty suppressed feeding test, forced swim test, tail suspension test, social interaction test. MiR-129-5p upregulation decreased the concentrations and protein levels of proinflammatory cytokines (IL-6, IL-1β and TNF-α), indicating the inhibitory role of miR-129-5p in inflammation. Furthermore, miR-129-5p was identified to target MAPK1. MAPK1 was negatively regulated by miR-129-5p, and silencing of MAPK1 attenuated depressive-like behaviors in CUMS mice. Moreover, MAPK1 downregulation decreased inflammation in the hippocampus of CUMS mice. Upregulation of MAPK1 reversed the suppressive effects of miR-129-5p upregulation on depressive-like behaviors and inflammation in CUMS mice. In conclusion, the current study identified that miR-129-5p reduces depressive-like behaviors and suppresses inflammation by targeting MAPK1 in CUMS mice, offering a novel molecular interpretation for depression prevention.

Oligonucleotides as therapeutic tools for brain disorders: Focus on major depressive disorder and Parkinson's disease

Remarkable advances in understanding the role of RNA in health and disease have expanded considerably in the last decade. RNA is becoming an increasingly important target for therapeutic intervention; therefore, it is critical to develop strategies for therapeutic modulation of RNA function. Oligonucleotides, including antisense oligonucleotide (ASO), small interfering RNA (siRNA), microRNA mimic (miRNA), and anti-microRNA (antagomir) are perhaps the most direct therapeutic strategies for addressing RNA. Among other mechanisms, most oligonucleotide designs involve the formation of a hybrid with RNA that promotes its degradation by activation of endogenous enzymes such as RNase-H (e.g., ASO) or the RISC complex (e.g. RNA interference - RNAi for siRNA and miRNA). However, the use of oligonucleotides for the treatment of brain disorders is seriously compromised by two main limitations: i) how to deliver oligonucleotides to the brain compartment, avoiding the action of peripheral RNAses? and once there, ii) how to target specific neuronal populations? We review the main molecular pathways in major depressive disorder (MDD) and Parkinson's disease (PD), and discuss the challenges associated with the development of novel oligonucleotide therapeutics. We pay special attention to the use of conjugated ligand-oligonucleotide approach in which the oligonucleotide sequence is covalently bound to monoamine transporter inhibitors (e.g. sertraline, reboxetine, indatraline). This strategy allows their selective accumulation in the monoamine neurons of mice and monkeys after their intranasal or intracerebroventricular administration, evoking preclinical changes predictive of a clinical therapeutic action after knocking-down disease-related genes. In addition, recent advances in oligonucleotide therapeutic clinical trials are also reviewed.

Elevated peripheral inflammation is associated with attenuated striatal reward anticipation in major depressive disorder

BACKGROUND

Major depressive disorder (MDD) is the leading cause of years lived with disability worldwide, and up to 40% of individuals with MDD do not respond to current treatments. Studies suggest that peripheral inflammation plays an important role in the striatal mesolimbic dopamine pathway and corticostriatal reward circuitry in MDD. Although MDD patients show blunted striatal responses to reward, the link between degree of inflammation and attenuation of reward processing is unclear. We investigated whether MDD patients with elevated peripheral inflammation exhibit attenuated reward responses to enhance our understanding of MDD pathophysiology and develop more effective treatments for current non-responders.

METHODS

MDD subjects varying on serum C-reactive protein (CRP) concentrations (MDD-High CRP, >3 mg/L, n = 44; MDD-Low CRP, <3 mg/L, n = 44) and healthy comparisons (HC, n = 44) completed a monetary incentive delay (MID) task and provided blood samples to measure inflammation-related markers. MDD-High and MDD-Low were propensity score-matched on age, sex, body mass index (BMI), smoking status, exercise and MID task head motion. Percent change in blood oxygen level-dependent (BOLD) signal during anticipation of wins and losses was extracted from bilateral nucleus accumbens, dorsal caudate and dorsolateral putamen regions of interest (ROIs). A linear mixed-effects model was used to test group (MDD-High, MDD-Low and HC), condition (large-win, small-win and no win), and their interaction for these ROIs as well as whole-brain voxelwise data. Analyses also tested group differences in inflammatory mediators. Correlations were used to explore the relationship between inflammatory mediators and brain regions showing differences between MDD-High and MDD-Low.

RESULTS

MDD-High exhibited: (a) lower BOLD signal change in dorsal caudate, thalamus, left insula and left precuneus during anticipation of small wins than MDD-Low; and (b) higher serum soluble intercellular adhesion molecule 1 (sICAM-1) and interleukin 6 (IL-6) concentrations than MDD-Low and HC. MDD as a whole, regardless of CRP-based inflammation, exhibited: (a) lower precuneus BOLD signal change to large wins than HC; and (b) higher Interleukin 1 receptor antagonist (IL-1ra), macrophage-derived chemokine (MDC) and macrophage inflammatory protein-1 alpha (MIP-1α) concentrations than HC. Higher serum sICAM-1 concentrations were associated with lower caudate BOLD signal change to small wins only within the MDD-High group.

CONCLUSION

Within MDD patients, high inflammation (CRP, sICAM-1) was linked to reduced striatal activation recruited to discriminate intermediate reward magnitudes. These findings support an association between levels of peripheral inflammation and the degree of reward-related activation in individuals with MDD.

REGISTRATION OF CLINICAL TRIALS

The ClinicalTrials.gov identifier for the clinical protocol associated with data published in this current paper is NCT02450240, "Latent Structure of Multi-level Assessments and Predictors of Outcomes in Psychiatric Disorders."

The important roles of microRNAs in depression: new research progress and future prospects

MicroRNAs (miRNAs) are non-encoding, single-stranded RNA molecules of about 22 nucleotides in length encoded by endogenous genes involved in posttranscriptional gene expression regulation. Studies have shown that miRNAs participate in a series of important pathophysiological processes, including the pathogenesis of depression. This article systematically summarized the research results published in the field of miRNAs and depression, which mainly involved three topics: circulating miRNAs as markers for diagnosis and prognosis of depression, the regulatory roles of miRNAs in the pathogenesis of depression, and the roles of miRNAs in the mechanisms of depression treatment. By summarizing and analyzing the research literature in recent years, we found that some circulating miRNAs can be potential biomarkers for the diagnosis and prognostic evaluation of depression. miRNAs that disorderly expressed during the disease play important roles in the depression pathogenesis, and miRNAs also play roles in the mechanisms of psychotherapy and drug therapy for depression. Elucidating the important roles of miRNAs in depression will bring people's understanding of the pathogenesis of depression to a new level. In addition, these miRNAs may be developed as new biomarkers for diagnosing depression, or as drug targets, or these molecules may be used as new drugs, which may provide new means for the treatment of depression. KEY MESSAGES: • The research results of miRNAs and depression are reviewed. • Circulating miRNAs can be potential biomarkers for depression. • MiRNAs play important roles in the depression pathogenesis. • MiRNAs play important roles in drug therapy for depression.

Neuronal Development-Related miRNAs as Biomarkers for Alzheimer's Disease, Depression, Schizophrenia and Ionizing Radiation Exposure

Radiation exposure may induce Alzheimer's disease (AD), depression or schizophrenia. A number of experimental and clinical studies suggest the involvement of miRNA in the development of these diseases, and also in the neuropathological changes after brain radiation exposure. The current literature review indicated the involvement of 65 miRNAs in neuronal development in the brain. In the brain tissue, blood, or cerebral spinal fluid (CSF), 11, 55, or 28 miRNAs are involved in the development of AD respectively, 89, 50, 19 miRNAs in depression, and 102, 35, 8 miRNAs in schizophrenia. We compared miRNAs regulating neuronal development to those involved in the genesis of AD, depression and schizophrenia and also those driving radiation-induced brain neuropathological changes by reviewing the available data. We found that 3, 11, or 8 neuronal developmentrelated miRNAs from the brain tissue, 13, 16 or 14 miRNAs from the blood of patient with AD, depression and schizophrenia respectively were also involved in radiation-induced brain pathological changes, suggesting a possibly specific involvement of these miRNAs in radiation-induced development of AD, depression and schizophrenia respectively. On the other hand, we noted that radiationinduced changes of two miRNAs, i.e., miR-132, miR-29 in the brain tissue, three miRNAs, i.e., miR- 29c-5p, miR-106b-5p, miR-34a-5p in the blood were also involved in the development of AD, depression and schizophrenia, thereby suggesting that these miRNAs may be involved in the common brain neuropathological changes, such as impairment of neurogenesis and reduced learning memory ability observed in these three diseases and also after radiation exposure.

Advances in novel molecular targets for antidepressants

Depression is the most common psychiatric illness affecting numerous people world-wide. The currently available antidepressant treatment presents low response and remission rates. Thus, new effective antidepressants need to be developed or discovered. Aiming to give an overview of novel possible antidepressant drug targets, we summarized the molecular targets of antidepressants and the underlying neurobiology of depression. We have also addressed the multidimensional perspectives on the progress in the psychopharmacological treatment of depression and on the new potential approaches with effective drug discovery.

The Progress in Diagnosis and Treatment of Exosomes and MicroRNAs on Epileptic Comorbidity Depression

The occurrence of epilepsy can increase the incidence of depression, and the risk of epilepsy in the patients with depression is also high, both of which have an adverse effect on the life and the psychology of the patient, which is not conducive to the prognosis of the patients with epilepsy. With lucubrating the function of exosomes and microRNAs, some scholars found that the exosomes and its microRNAs have development prospect in the diagnosis and treatment of the disease. MicroRNAs are involved in the regulation of seizures and depression, as biomarkers, that can significantly improve the management of epileptic patients and play a preventive role in the occurrence of epilepsy and epilepsy depressive disorder. Moreover, due to its regulation to genes, appropriate application of microRNAs may have therapeutic effect on epilepsy and depression with the characteristics of long distance transmission and stability of exosomes, to a certain extent. This provides a great convenience for the diagnosis and treatment of epileptic comorbidity depression.

miR-138 Increases Depressive-Like Behaviors by Targeting SIRT1 in Hippocampus

BACKGROUND

Major depressive disorder (MDD) is a serious and common mood disorder with unknown etiology. Emerging evidence has demonstrated the critical roles of SIRT1 and microRNAs (miRNAs) in the progression of MDD. However, the underlying molecular mechanisms remain to be fully understood.

METHODS

In the present study, the expression level of miR-138 and SIRT1 were analyzed by RT-PCR or Western blotting in a chronic unpredictable mild stress (CUMS) model. The depressive-like behaviors were analyzed by forced swimming test (FST) and sucrose preference test (SPT) in mice injected with miR-138 and SIRT1 overexpression lentivirus. The luciferase reporter assay was used to assess the direct regulation of miR-138 on SIRT1 expression.

RESULTS

The upregulation of miR-138 was found in the hippocampus of the CUMS mice and correlated with decreased SIRT1 expression. C57BL/6J mice treated with SIRT1- and miR-138-expressing (miR-138) lentivirus showed increased depressive-like behaviors. In contrast, SIRT1 or si-miR-138 lentivirus treated C57BL/6J mice showed decreased depressive-like behaviors. Moreover, the Sirt1/PGC-1α/FNDC5/BDNF pathway was downregulated following miR-138 overexpression and increased upon miR-138 knockdown in hippocampus in CUMS mice and cultured primary neuronal cells. Mechanistically, luciferase reporter assay demonstrated that SIRT1 gene was a downstream transcriptional target of miR-138.

CONCLUSION

Our data demonstrated the regulation role of miR-138 on SIRT1 gene expression, miR-138 increased depressive-like behaviors by regulating SIRT1 expression in hippocampus.

MicroRNA-Based Biomarkers in the Diagnosis and Monitoring of Therapeutic Response in Patients with Depression

Depression is a debilitating mental illness that affects up to 120 million people worldwide; it is currently determined based on subjective diagnostic schemes that are limited by high uncertainty. Hence, there is an urgent need to identify effective and reliable biomarkers to increase diagnostic accuracy. MicroRNAs (miRNAs) constitute a recently discovered class of non-coding RNAs that play a key role in the regulation of gene expression by modulating translation, messenger RNA (mRNA) degradation, or stability of mRNA targets. Dysregulated expression of miRNAs is being investigated as a clinical biomarker for a variety of diseases, including depression. Accumulating evidence has shown that miRNAs participate in many aspects of neural plasticity, neurogenesis, and the stress response. This is supported by more direct studies based on human postmortem brain tissue that strongly indicate that miRNAs not only play a key role in the pathogenesis of major depressive disorder, but also present potential for the development of therapeutic targets. miRNAs in the peripheral and central nervous system are being considered as potential biomarkers in the diagnosis of depression and in monitoring the therapeutic response to antidepressants, owing to their stability, tissue-specificity, and disease-specific expression. In this review, we focus on various miRNAs in tissues and fluids that could be employed as diagnostic and therapeutic biomarkers in patients with depression.

Expression alteration of microRNAs in Nucleus Accumbens is associated with chronic stress and antidepressant treatment in rats

BACKGROUND

Nucleus Accumbens (NAc) is a vital brain region for the process of reward and stress, whereas microRNA plays a crucial role in depression pathology. However, the abnormality of NAc miRNA expression during the stress-induced depression and antidepressant treatment, as well as its biological significance, are still unknown.

METHODS

We performed the small RNA-sequencing in NAc of rats from three groups: control, chronic unpredictable mild stress (CUMS), and CUMS with an antidepressant, Escitalopram. We applied an integrative pipeline for analyzing the miRNA expression alternation in different model groups, including differential expression analysis, co-expression analysis, as well as a subsequent pathway/network analysis to discover both miRNA alteration pattern and its biological significance.

RESULT

A total of 423 miRNAs were included in analysis.18/8 differential expressing (DE) miRNA (adjusted p < 0.05, |log2FC| > 1) were observed in controls Vs. depression/depression Vs. treatment, 2 of which are overlapping. 78% (14/18) of these miRNAs showed opposite trends of alteration in stress and treatment. Two micro RNA, miR-10b-5p and miR-214-3p, appeared to be hubs in the regulation networks and also among the top findings in both differential analyses. Using co-expression analysis, we found a functional module that strongly correlated with stress (R = 0.96, P = 0.003), and another functional module with a moderate correlation with anhedonia (R = 0.89, P = 0.02). We also found that predicted targets of these miRNAs were significantly enriched in the Ras signaling pathway, which is associated with both depression, anhedonia, and antidepressant treatment.

CONCLUSION

Escitalopram treatment can significantly reverse NAc miRNA abnormality induced by chronic stress. However, the novel miRNA alteration that is absent in stress pathology also emerges, which means that antidepressant treatment is unlikely to bring miRNA expression back to the same level as the controls. Also, the Ras-signaling pathway may be involved in explaining the depression disease etiology, the clinical symptom, and treatment response of stress-induced depression.

Link between depression and cardiovascular diseases due to epigenomics and proteomics: Focus on energy metabolism

Major depression is the most common mental disorder and a leading cause of years lived with disability. In addition to the burden attributed to depressive symptoms and reduced daily life functioning, people with major depression are at increased risk of premature mortality, particularly due to cardiovascular diseases. Several studies point to a bi-directional relation between major depression and cardiovascular diseases, thereby indicating that both diseases may share common pathophysiological pathways. These include lifestyle factors (e.g. physical activity, smoking behavior), dysfunctions of endocrine systems (e.g. hypothalamus-pituitary adrenal axis), and a dysbalance of pro- and anti-inflammatory factors. Furthermore, recent research point to the role of epigenomic and proteomic factors, that are reviewed here with a particular focus on the mitochondrial energy metabolism.

MicroRNAs in depression and suicide: Recent insights and future perspectives

Suicide is a major public health concern. A significant proportion of depressed individuals show suicidal ideation. The currently available medications are not optimal and a large number of depressed/suicidal patients do not respond to these medications. Thus, there is an urgent need to fully understand the neurobiological mechanisms associated with depression and suicidal behavior and to find novel targets for therapeutic interventions. In this regard, microRNAs (miRNAs), member of small non-coding RNA family, have emerged as an invaluable tool not only to understand disease pathogenesis but also to precisely pinpoint the targets that can be developed as drugs. In this review, these aspects have been discussed in a comprehensive and critical manner.

Macrophage Migration Inhibitory Factor and microRNA-451a in Response to Mindfulness-based Therapy or Treatment as Usual in Patients with Depression, Anxiety, or Stress and Adjustment Disorders

BACKGROUND

Macrophage migration inhibitory factor is a proinflammatory cytokine that has been associated with various psychiatric disorders. MicroRNA-451a can directly target macrophage migration inhibitory factor and downregulate its expression in cells. However, the role of macrophage migration inhibitory factor and microRNA-451a in psychiatric patients treated with psychotherapeutic interventions is unknown. In this study, our aim was to investigate levels of macrophage migration inhibitory factor and its regulating microRNA-451a in patients with depression, anxiety, or stress and adjustment disorders who underwent mindfulness-based therapy or treatment as usual.

METHODS

A total of 168 patients with psychiatric disorders were included from a randomized controlled trial that compared mindfulness-based therapy with treatment as usual. Plasma levels of macrophage migration inhibitory factor and microRNA-451a were measured at baseline and after the 8-week follow-up using Luminex assay and qPCR.

RESULTS

Macrophage migration inhibitory factor levels decreased significantly in patients posttreatment, whereas microRNA-451a levels showed a nonsignificant change. Macrophage migration inhibitory factor levels were inversely associated with microRNA-451a expression levels at baseline (β=-0.04, P=.008). The change in macrophage migration inhibitory factor levels (follow-up levels minus baseline levels) was associated with the change in microRNA-451a (follow-up levels minus baseline levels) (β=-0.06, P < .0001). The change in either macrophage migration inhibitory factor or microRNA-451a was not associated with improvement in psychiatric symptoms.

CONCLUSION

We demonstrate that the levels of macrophage migration inhibitory factor decreased after psychotherapeutic interventions in patients with psychiatric disorders. However, this reduction was not associated with an improvement in psychiatric symptoms in response to the treatment. We also found an association between macrophage migration inhibitory factor and its regulating microRNA. However, this association needs to be further examined in future studies.

The role of microRNAs in glucocorticoid action

Glucocorticoids (GCs) are steroids with profound anti-inflammatory and immunomodulatory activities. Synthetic GCs are widely used for managing chronic inflammatory and autoimmune conditions, as immunosuppressants in transplantation, and as anti-tumor agents in certain hematological cancers. However, prolonged GC exposure can cause adverse effects. A detailed understanding of GCs' mechanisms of action may enable harnessing of their desirable actions while minimizing harmful effects. Here, we review the impact on the GC biology of microRNAs, small non-coding RNAs that post-transcriptionally regulate gene expression. Emerging evidence indicates that microRNAs modulate GC production by the adrenal glands and the cells' responses to GCs. Furthermore, GCs influence cell proliferation, survival, and function at least in part by regulating microRNA expression. We propose that the beneficial effects of GCs may be enhanced through combination with reagents targeting specific microRNAs.

Analysis of the association of MIR124-1 and its target gene RGS4 polymorphisms with major depressive disorder and antidepressant response

BACKGROUND

Increasing evidence has indicated that dysfunction of miR-124 and target gene regulator of G protein signaling 4 (RGS4) may be involved in the etiology and treatment of major depressive disorder (MDD). However, the molecular mechanisms are not fully understood. This study aimed to investigate whether common genetic variations in these two genes are associated with MDD and therapeutic response to antidepressants in the Chinese population.

METHODS

Three polymorphisms including rs531564 (a functional single-nucleotide polymorphism [SNP] in MIR124-1), rs10759 (a microRNA-binding site SNP in RGS4), and rs951436 (a promoter SNP in RGS4) were genotyped in 225 Chinese MDD patients and 436 controls. Among the MDD patients, 147 accepted antidepressant treatment for 8 weeks with therapeutic evaluation at baseline, week 2, week 4, week 6, and week 8 using the 17-item Hamilton Rating Scale for Depression. Multifactor dimensionality reduction (MDR) was used to identify gene-gene interactions.

RESULTS

No significant association with MDD was discovered in single-SNP analyses. However, by MDR analysis, the three-locus model of gene-gene interaction was the best for predicting MDD risk. In pharmacogenetic study, a significant association was found in genotypic frequencies of rs951436 between the remitter and non-remitter groups (p=0.026, correction p=0.078). For further analysis, the rs951436 heterozygote carriers had threefold probabilities of achieving clinical complete remission (odds ratio =3.00, 95% confidence interval =1.33-6.76, p=0.007, correction p=0.021) as compared with rs951436 homozygotes (AA+CC) after 8 weeks of treatment.

CONCLUSION

An interaction effect of MIR124-1 and RGS4 polymorphisms may play a more important role than individual factors for MDD development. Moreover, RGS4 gene polymorphisms may be associated with antidepressant response among the Han population.