Heterogeneity and individuality: microRNAs in mental disorders

MicroRNAs as Diagnostic Biomarkers and Predictors of Antidepressant Response in Major Depressive Disorder: A Systematic Review

Despite the hardships of major depressive disorder (MDD), biomarkers for the diagnosis and pharmacological management of this condition are lacking. MicroRNAs are epigenetic mechanisms that could provide promising MDD biomarkers. Our aim was to summarize the findings and provide validation for the selection and use of specific microRNAs as biomarkers in the diagnosis and treatment of MDD. A systematic review was conducted using the PubMed/Medline, Cochrane, PsycINFO, Embase, and LILACS databases from March 2022 to November 2023, with clusters of terms based on "microRNA" and "antidepressant". Studies involving human subjects, animal models, and cell cultures were included, whereas those that evaluated herbal medicines, non-pharmacological therapies, or epigenetic mechanisms other than miRNA were excluded. The review revealed differences in the expression of various microRNAs when considering the time of assessment (before or after antidepressant treatment) and the population studied. However, due to the heterogeneity of the microRNAs investigated, the limited size of the samples, and the wide variety of antidepressants used, few conclusions could be made. Despite the observed heterogeneity, the following microRNAs were determined to be important factors in MDD and the antidepressant response: mir-1202, mir-135, mir-124, and mir-16. The findings indicate the potential for the use of microRNAs as biomarkers for the diagnosis and treatment of MDD; however, more homogeneous studies are needed.

The role of epigenetics in anxiety disorders

Anxiety disorders (ADs) are extremely common psychiatric conditions that frequently co-occur with other physical and mental disorders. The pathophysiology of ADs is multifaceted and involves intricate connections among biological elements, environmental stimuli, and psychological mechanisms. Recent discoveries have highlighted the significance of epigenetics in bridging the gap between multiple risk factors that contribute to ADs and expanding our understanding of the pathomechanisms underlying ADs. Epigenetics is the study of how changes in the environment and behavior can have an impact on gene function. Indeed, researchers have found that epigenetic mechanisms can affect how genes are activated or inactivated, as well as whether they are expressed. Such mechanisms may also affect how ADs form and are protected. That is, the bulk of pharmacological trials evaluating epigenetic treatments for the treatment of ADs have used histone deacetylase inhibitors (HDACi), yielding promising outcomes in both preclinical and clinical studies. This review will provide an outline of how epigenetic pathways can be used to treat ADs or lessen their risk. It will also present the findings from preclinical and clinical trials that are currently available on the use of epigenetic drugs to treat ADs.

The long-lasting effects of early life adversities are sex dependent: The signature of miR-34a

BACKGROUND

Exposure to early life adversities (ELA) can influence a plethora of biological mechanisms leading to stress-related disorders later in life through epigenetic mechanisms, such as microRNAs (miRs). MiR-34 is a critical modulator of stress response and stress-induced pathologies and a link between ELA and miR-34a has been reported.

METHODS

Here using our well-established model of ELA (Repeated Cross Fostering) we investigate the behavioral long-term effects of ELA in male and female mice. We also assess basal and ELA-induced miR-34a expression in adult mice and investigate whether ELA affects the later miR-34a response to adult acute stress exposure across brain areas (medial preFrontal Cortex, Dorsal Raphe Nuclei) and peripheral organs (heart, plasma) in animals from both sexes. Finally, based on our previous data demonstrating the critical role of Dorsal Raphe Nuclei miR-34a expression in serotonin (5-HT) transmission, we also investigated prefrontal-accumbal 5-HT outflow induced by acute stress exposure in ELA and Control females by in vivo intracerebral microdialysis.

RESULTS

ELA not just induces a depressive-like state as well as enduring changes in miR-34a expression, but also alters miR-34a expression in response to adult acute stress exclusively in females. Finally, altered DRN miR-34a expression is associated with prefrontal-accumbal 5-HT release under acute stress exposure in females.

LIMITATIONS

Translational study on humans is necessary to verify the results obtained in our animal models of ELA-induced depression.

CONCLUSIONS

This is the first evidence showing long-lasting sex related effects of ELA on brain and peripheral miR-34a expression levels in an animal model of depression-like phenotype.

Polymorphisms in MicroRNA Genes Associated with Schizophrenia Susceptibility but Not with Effectiveness of MECT

Schizophrenia (SCZ) is a common and complex psychiatric disease associated with hereditary and environmental risk factors. MicroRNAs (miRNAs or miRs) are small, noncoding RNA molecules that endogenously regulate gene expression. Single nucleotide polymorphisms (SNPs) in related miRNA genes are associated with susceptibility of the disorder. We wonder if the SNPs have influence on the effectiveness of modified electroconvulsive therapy (MECT) for SCZ. rs1625579 within miR-137, rs6577555 within miR-34, and rs2296616 within miR-107 were sequenced in 150 cases and 150 controls to check the potential association between the SNPs and SCZ. Our results showed that allele G in rs1625579 (p = 0.005, adjusted OR = 1.379, 95%CI = 1.108 - 1.634), allele A in rs6577555 (p = 0.014, adjusted OR = 1.246, 95%CI = 1.045 - 1.463), allele G in rs2296616 (p < 0.001, adjusted OR = 1.646, 95%CI = 1.374 - 1.879) are positively associated with the disorder risk. MECT courses did significantly decrease the level of the miRNAs, except for the variant of rs2296616 with the AA genotype. Schizophrenic phenotypes assessed by the positive and negative syndrome scale (PANSS) were improved after MECT, and there was no significant relevance observed between the effectiveness of MECT and the variants of these loci. Thus, our findings indicate that polymorphisms within the loci may be involved in the pathogenesis of SCZ, and MECT is effective and unbiased for patients harboring different genotypes of the loci.

Epigenetic marks in suicide: a review

Suicide is a complex phenomenon and a global public health problem that involves several biological factors that could contribute to the pathophysiology of suicide. There is evidence that epigenetic factors influence some psychiatric disorders, suggesting a predisposition to suicide or suicidal behavior. Here, we review studies of molecular mechanisms of suicide in an epigenetic perspective in the postmortem brain of suicide completers and peripheral blood cells of suicide attempters. Besides, we include studies of gene-specific DNA methylation, epigenome-wide association, histone modification, and interfering RNAs as epigenetic factors. This review provides an overview of the epigenetic mechanisms described in different biological systems related to suicide, contributing to an understanding of the genetic regulation in suicide. We conclude that epigenetic marks are potential biomarkers in suicide, and they could become attractive therapeutic targets due to their reversibility and importance in regulating gene expression.

MicroRNA-542-3p Regulates P-glycoprotein Expression in Rat Epilepsy via the Toll-like Receptor 4/Nuclear Factor-kappaB Signaling Pathway

BACKGROUND

The function of microRNA-542-3p (miR-542-3p) in rat epilepsy is still unclear.

METHODS

The levels of miR-542-3p and toll-like receptor 4 (TLR4) were determined through quantitative real-time PCR. The protein levels were examined via the western blot analysis. The relationship between miR-542-3p and TLR4 was confirmed through luciferase assay. Pathological changes were analyzed via Hematoxylin-eosin (HE) and Nissl staining.

RESULTS

The rats and hippocampal cells were treated with kainic acid (KA) in vivo and in vitro. miR-542-3p was low in KA-treated rats, hippocampal cells and cerebrospinal fluid of patients with epilepsy. Further functional analysis showed that miR-542-3p overexpression inhibited KAinduced average seizure frequency, damage of hippocampal neuron and cell apoptosis, leading to the alleviation of the brain injury in epilepsy rats. miR-542-3p was determined to downregulate TLR4 expression. The relationship between miR-542-3p and TLR4 was confirmed. TLR4 knockdown reduced KA-induced nuclear factor-kappa B p65 (NF-κB p65), multidrug resistance 1 (MDR1), P-glycoprotein (P-gp) and apoptosis-associated protein levels. Further, for NF-κB p65, MDR1, P-gp and apoptosis-associated protein levels detection, miR-542-3p mimic showed a suppressive effect on these KA-induced protein levels, whereas TLR4 overexpression ameliorated the miR-542-3p-induced these protein levels in KA-treated epilepsy rats.

CONCLUSION

We identified that miR-542-3p attenuated seizure-induced brain injury and the expression of P-gp in epilepsy rats through inhibiting TLR4/NF-κB signaling pathway, which might contribute to improved epilepsy therapy.

Improving Bioinformatics Prediction of microRNA Targets by Ranks Aggregation

microRNAs are noncoding RNAs which downregulate a large number of target mRNAs and modulate cell activity. Despite continued progress, bioinformatics prediction of microRNA targets remains a challenge since available software still suffer from a lack of accuracy and sensitivity. Moreover, these tools show fairly inconsistent results from one another. Thus, in an attempt to circumvent these difficulties, we aggregated all human results of four important prediction algorithms (miRanda, PITA, SVmicrO, and TargetScan) showing additional characteristics in order to rerank them into a single list. Instead of deciding which prediction tool to use, our method clearly helps biologists getting the best microRNA target predictions from all aggregated databases. The resulting database is freely available through a webtool called miRabel¹ which can take either a list of miRNAs, genes, or signaling pathways as search inputs. Receiver operating characteristic curves and precision-recall curves analysis carried out using experimentally validated data and very large data sets show that miRabel significantly improves the prediction of miRNA targets compared to the four algorithms used separately. Moreover, using the same analytical methods, miRabel shows significantly better predictions than other popular algorithms such as MBSTAR, miRWalk, ExprTarget and miRMap. Interestingly, an F-score analysis revealed that miRabel also significantly improves the relevance of the top results. The aggregation of results from different databases is therefore a powerful and generalizable approach to many other species to improve miRNA target predictions. Thus, miRabel is an efficient tool to guide biologists in their search for miRNA targets and integrate them into a biological context.

Role of MicroRNAs in Anxiety and Anxiety-Related Disorders

MicroRNAs as critical regulators of gene expression important for functions including neuronal development, synapse formation, and synaptic plasticity have been linked with the regulation of neurobiological systems that underlie anxiety processing in the brain. In this chapter, we give an update on associative evidence linking regulation of microRNAs with anxiety- and trauma-related disorders. Moving beyond correlative research, functional studies have emerged recently that explore causal relationships between microRNA expression and anxiety-like behavior. It has been demonstrated that experimental up- or downregulation of the candidate microRNAs in important nodes of the anxiety neurocircuitry can indeed modulate anxiety-related behavior in animal models. Improved methodologies for assessing microRNA-mediated modulation have aided such functional studies, revealing a number of anxiety-regulating microRNAs including miR-15a, miR-17-92, miR-34, miR-101, miR-124, miR-135, and miR-155. Important functional target genes of these identified microRNAs are associated with specific neurotransmitter/neuromodulator signaling, neurotrophin (e.g., BDNF) expression and other aspects of synaptic plasticity, as well as with stress-regulatory/hypothalamic-pituitary-axis function. Furthermore, microRNAs have been revealed that are regulated in distinct brain regions following various anxiety-attenuating strategies. These include pharmacological treatments such as antidepressants and other drugs, as well as non-pharmacological interventions such as fear extinction/exposure therapy or positive stimuli such as exposure to environmental enrichment. These are first indications for a role for microRNAs in the mechanism of action of anxiolytic treatments. As research continues, there is much hope that a deeper understanding of the microRNA-mediated mechanisms underlying anxiety-related disorders could open up possibilities for future novel biomarker and treatment strategies.

Rac1 relieves neuronal injury induced by oxygenglucose deprivation and re-oxygenation via regulation of mitochondrial biogenesis and function

Certain microRNAs (miRNAs) can function as neuroprotective factors after reperfusion/ischemia brain injury. miRNA-142-3p can participate in the occurrence and development of tumors and myocardial ischemic injury by negatively regulating the activity of Rac1, but it remains unclear whether miRNA-142-3p also participates in cerebral ischemia/reperfusion injury. In this study, a model of oxygen-glucose deprivation/re-oxygenation in primary cortical neurons was established and the neurons were transfected with miR-142-3p agomirs or miR-142-3p antagomirs. miR-142-3p expression was down-regulated in neurons when exposed to oxygen-glucose deprivation/re-oxygenation. Over-expression of miR-142-3p using its agomir remarkably promoted cell death and apoptosis induced by oxygen-glucose deprivation/re-oxygenation and improved mitochondrial biogenesis and function, including the expression of peroxisome proliferator-activated receptor-γ coactivator-1α, mitochondrial transcription factor A, and nuclear respiratory factor 1. However, the opposite effects were produced if miR-142-3p was inhibited. Luciferase reporter assays verified that Rac Family Small GTPase 1 (Rac1) was a target gene of miR-142-3p. Over-expressed miR-142-3p inhibited NOX2 activity and expression of Rac1 and Rac1-GTPase (its activated form). miR-142-3p antagomirs had opposite effects after oxygen-glucose deprivation/re-oxygenation. Our results indicate that miR-142-3p down-regulates the expression and activation of Rac1, regulates mitochondrial biogenesis and function, and inhibits oxygen-glucose deprivation damage, thus exerting a neuroprotective effect. The experiments were approved by the Committee of Experimental Animal Use and Care of Central South University, China (approval No. 201703346) on March 7, 2017.

The Computational Analysis Conducted on miRNA Target Sites in Association with SNPs at 3'UTR of ADHD-implicated Genes

Background: Attention-deficit/hyperactivity disorder (ADHD) is a frequent chronic neuropsychiatric disorder in which different factors including environmental, genetic, and epigenetic factors play an important role in its pathogenesis. One of the effective epigenetic factors is recognized as MicroRNAs (miRNAs). On the other hand, it has been indicated that the single nucleotide polymorphism (SNPs) present within 3'UTR (3' untranslated region) of mRNAs can influence the regulation of miRNA-mediated gene and susceptibility to a diversity of human diseases.

Methods: The purpose of this study was to analyze the SNPs within the 3'UTR of miRNA target genes associated with ADHD . 3'UTR genetic variants were identified in all genes associated with ADHD using DisGeNET, dbGaP, Ovid, DAVID, Web of knowledge, and SNPs databases. miRNA's target prediction databases were applied in order to predict the miRNA binding sites. 124 SNPs with MAF>0.05 were identified located in the binding site of the miRNA of 35 genes amongst 51 genes associated with ADHD.

Results: Bioinformatics analysis predicted 81 MRE (miRNA recognition elements)-creating SNPs, 101 MRE-breaking SNPs, 61 MRE-enhancing SNPs, and finally predicted 41 MRE-decreasing SNPs in the 3'UTR of ADHD-implicated genes. These candidate SNPs within these genes miRNA binding sites can alter the miRNAs binding, and consequently, lead to mRNA gene regulation.

Conclusion: Therefore, these miRNA and MRE-SNPs may play important roles in ADHD, and because of that, they would be valuable for further investigation in the field of functional verification.

mirDIP 4.1-integrative database of human microRNA target predictions

MicroRNAs are important regulators of gene expression, achieved by binding to the gene to be regulated. Even with modern high-throughput technologies, it is laborious and expensive to detect all possible microRNA targets. For this reason, several computational microRNA-target prediction tools have been developed, each with its own strengths and limitations. Integration of different tools has been a successful approach to minimize the shortcomings of individual databases. Here, we present mirDIP v4.1, providing nearly 152 million human microRNA-target predictions, which were collected across 30 different resources. We also introduce an integrative score, which was statistically inferred from the obtained predictions, and was assigned to each unique microRNA-target interaction to provide a unified measure of confidence. We demonstrate that integrating predictions across multiple resources does not cumulate prediction bias toward biological processes or pathways. mirDIP v4.1 is freely available at http://ophid.utoronto.ca/mirDIP/.

Screening of schizophrenia associated miRNAs and the regulation of miR-320a-3p on integrin β1

Schizophrenia is one of the most severe chronic psychiatric disorders, which lacks of objective and effective diagnosis and observation indicators.In this work, the serum miRNA profiles of schizophrenic patients were analyzed. Targets of abnormal miRNAs, and their regulatory mechanisms were studied. A miRNA array was used to analyze the serum from 3 schizophrenic patients without treatment, 3 clinically cured patients and 3 healthy controls. The findings from the array were confirmed by real-time PCR in a larger cohort, including 59 patients and 60 healthy controls. The candidate miRNAs were analyzed using bioinformatics tools. Their potential targets were studied through in vitro cellular experiments.MiR-320a-3p and miR-320b were found to be down-regulated in patients compared with cured patients and controls in the miRNA array, which was also confirmed by real-time PCR in the larger cohort. Integrin β1 (ITG β1) was found to be one of the targets of miR-320a-3p. An enzyme-linked immune sorbent assay demonstrated that the ITG β1 concentration increased significantly in the patients' serum, and the in vitro study confirmed that miR-320a-3p targeted the 3' UTR of ITG β1 mRNA and reduced its expression.Our results demonstrated that the regulatory effect of miR-320a-3p on its target ITG β1 might play an important role in schizophrenia pathogenesis, which could be a potential pathway for schizophrenia diagnosis and therapy.

MicroRNAs as Immunotherapy Targets for Treating Gastroenterological Cancers

Gastroenterological cancers are the most common cancers categorized by systems and are estimated to comprise 18.4% of all cancers in the United States in 2017. Gastroenterological cancers are estimated to contribute 26.2% of cancer-related death in 2017. Gastroenterological cancers are characterized by late diagnosis, metastasis, high recurrence, and being refractory to current therapies. Since the current targeted therapies provide limited benefit to the overall response and survival, there is an urgent need for developing novel therapeutic strategy to improve the outcome of gastroenterological cancers. Immunotherapy has been developed and underwent clinical trials, but displayed limited therapeutic benefit. Since aberrant expressions of miRNAs are found in gastroenterological cancers and miRNAs have been shown to regulate antitumor immunity, the combination therapy combining the traditional antibody-based immunotherapy and novel miRNA-based immunotherapy is promising for achieving clinical success. This review summarizes the current knowledge about the miRNAs and long noncoding RNAs that exhibit immunoregulatory roles in gastroenterological cancers and precancerous diseases of digestive system, as well as the miRNA-based clinical trials for gastroenterological cancers. This review also analyzes the ongoing challenge of identifying appropriate therapy candidates for complex and dynamic tumor microenvironment, ensuring efficient and targeted delivery to specific cancer tissues, and developing strategy for avoiding off-target effect.

Turing Revisited: Decoding the microRNA Messages in Brain Extracellular Vesicles for Early Detection of Neurodevelopmental Disorders

The prevention of neurodevelopmental disorders (NDD) of prenatal origin suffers from the lack of objective tools for early detection of susceptible individuals and the long time lag, usually in years, between the neurotoxic exposure and the diagnosis of mental dysfunction. Human data on the effects of alcohol, lead, and mercury and experimental data from animals on developmental neurotoxins and their long-term behavioral effects have achieved a critical mass, leading to the concept of the Developmental Origin of Health and Disease (DOHaD). However, there is currently no way to evaluate the degree of brain damage early after birth. We propose that extracellular vesicles (EVs) and particularly exosomes, released by brain cells into the fetal blood, may offer us a non-invasive means of assessing brain damage by neurotoxins. We are inspired by the strategy applied by Alan Turing (a cryptanalyst working for the British government), who created a first computer to decrypt German intelligence communications during World War II. Given the growing evidence that microRNAs (miRNAs), which are among the molecules carried by EVs, are involved in cell-cell communication, we propose that decrypting messages from EVs can allow us to detect damage thus offering an opportunity to cure, reverse, or prevent the development of NDD. This review summarizes recent findings on miRNAs associated with selected environmental toxicants known to be involved in the pathophysiology of NDD.

Association of MIR137 With Symptom Severity and Cognitive Functioning in Belarusian Schizophrenia Patients

MicroRNA-137 (miRNA-137; miR-137) is one of the important post-transcriptional regulators of the nervous system development, and its MIR137 gene rs1625579 polymorphism was reported to be a potential regulator for schizophrenia susceptibility. However, schizophrenia characteristics controlled by MIR137 rs1625579 polymorphism are still insufficiently understood. There were 3 groups included in the study: (a) subjects with diagnosis of schizophrenia (n = 150; 81-females, 69-males), (b) mentally healthy people (control group; n = 102; 66-females, 36-males) and (c) Belarusian indigenous male group (n = 295). Associations of rs1625579 with schizophrenia, symptom's severity and cognitive performance [by using Positive and Negative Syndrome Scale (PANSS) and Wisconsin Card Sorting Test (WCST), respectively] were studied, when compared to controls. Allele and genotype frequencies were investigated in Belarusian indigenous males. Rs1625579 displayed no association with schizophrenia in Belarusian population. Significant "symptom severity-genotype" interactions were revealed for schizophrenia patients. Patients with T/G genotype displayed lower severity of positive symptoms and general psychopathology compared to homozygous subjects. T/T genotype was associated with the highest symptom's severity. The negative symptom scores and the total PANSS-score were significantly higher in females carrying genotype T/T vs. T/G+G/G; no significant gene-phenotype associations were found in males. WCST parameters did not show any association with rs1625579 polymorphism. MIR137 rs1625579 polymorphism might be an important sex-dependent factor influencing severity of schizophrenia psychopathological manifestations. These findings also contribute to the knowledge on candidate gene effects on characteristics related to schizophrenia phenotype. As miR 137 is considered to be cancer therapeutic target, miR-137 may also explain the lower incidence of cancer in schizophrenia patients. Further studies with larger sample size are needed to confirm these novel findings.

Large normal-range TBP and ATXN7 CAG repeat lengths are associated with increased lifetime risk of depression

Depression is one of the most prevalent and debilitating psychiatric disorders worldwide. Recently, we showed that both relatively short and relatively long cytosine-adenine-guanine (CAG) repeats in the huntingtin gene (HTT) are associated with an increased risk of lifetime depression. However, to what extent the variations in CAG repeat length in the other eight polyglutamine disease-associated genes (PDAGs) are associated with depression is still unknown. We determined the CAG repeat sizes of ATXN1, ATXN2, ATXN3, CACNA1A, ATXN7, TBP, ATN1 and AR in two well-characterized Dutch cohorts-the Netherlands Study of Depression and Anxiety and the Netherlands Study of Depression in Older Persons-including 2165 depressed and 1058 non-depressed individuals-aged 18-93 years. The association between PDAG CAG repeat size and the risk for depression was assessed via binary logistic regression. We found that the odds ratio (OR) for lifetime depression was significantly higher for individuals with >10, compared with subjects with ≤10, CAG repeats in both ATXN7 alleles (OR=1.90, confidence interval (CI) 1.26-2.85). For TBP we found a similar association: A CAG repeat length exceeding the median in both alleles was associated with an increased risk for lifetime depression (OR=1.33, CI 1.00-1.76). In conclusion, we observed that carriers of either ATXN7 or TBP alleles with relatively large CAG repeat sizes in both alleles had a substantially increased risk of lifetime depression. Our findings provide critical evidence for the notion that repeat polymorphisms can act as complex genetic modifiers of depression.

MicroRNAs as biomarkers for psychiatric disorders with a focus on autism spectrum disorder: Current progress in genetic association studies, expression profiling, and translational research

MicroRNAs (miRNAs) are a group of small noncoding RNA molecules, 18-25 nucleotides in length, which can negatively regulate gene expression at the post-transcriptional level by binding to messenger RNAs. About half of all identified miRNAs in humans are expressed in the brain and display regulatory functions important for many biological processes related to the development of the central nervous system (CNS). Disruptions in miRNA biogenesis and miRNA-target interaction have been related to CNS diseases, including psychiatric disorders. In this review, we focus on the role of miRNAs in autism spectrum disorder (ASD) and summarize recent findings about ASD-associated genetic variants in miRNA genes, in miRNA biogenesis genes, and miRNA targets. We discuss deregulation of miRNA expression in ASD and functional validation of ASD-related miRNAs in animal models. Including miRNAs in studies of ASD will contribute to our understanding of its etiology and pathogenesis and facilitate the discrimination between different disease subgroups. Autism Res 2017. © 2017 International Society for Autism Research, Wiley Periodicals, Inc. Autism Res 2017, 10: 1184-1203. © 2017 International Society for Autism Research, Wiley Periodicals, Inc.

Exacerbation of Mild Hypoxia on Acute Radiation Syndrome and Subsequent Mortality

Mild hypoxia induced by 20% hemorrhage results in increases in few cytokine concentrations and sclerostin levels in blood, but shows no changes in bone formation, bone marrow cellularity, and gastrointestinal (GI) integrity and no systemic bacterial infection as well as no subsequent mortality. On the other hand, severe hypoxia induced by 40% hemorrhage causes significant increases in most cytokine concentrations, GI injury, lung injury, systemic bacterial infection, cellular ATP reduction and subsequent mortality. The severe hypoxia drastically damages GI and lung morphology, elevates cytokine concentrations in blood and increases inducible nitric oxide synthase (iNOS) expression in cells that is mediated by transcription factors NF-κB/NF-IL6, subsequently producing free radicals that disrupt mitochondria. ATP depletion, p53 phosphorylation, and caspase-3 activation are found, suggesting cell apoptosis. As a result, mortality occurs. However, when mild hypoxia follows ionizing radiation, the mild hypoxia significantly enhances radiation-induced mortality and acute radiation syndrome, including injury of bone marrow, GI, kidney, and lung. The synergism also occurs at the molecular level, resulting in alteration of microRNAs, amplification of iNOS expression, cytokine increases, sepsis, and ATP depletion. This is the first demonstration of synergistic effects between mild hypoxia and ionizing radiation.

hsa-miR-4485 regulates mitochondrial functions and inhibits the tumorigenicity of breast cancer cells

The modulation of mitochondrial functions is important for maintaining cellular homeostasis. Mitochondria essentially depend on the import of RNAs and proteins encoded by the nuclear genome. MicroRNAs encoded in the nucleus can translocate to mitochondria and target the genome, affecting mitochondrial function. Here, we analyzed the role of miR-4485 in the regulation of mitochondrial functions. We showed that miR-4485 translocated to mitochondria where its levels varied in response to different stress conditions. A direct binding of miR-4485 to mitochondrial 16S rRNA was demonstrated. MiR-4485 regulated the processing of pre-rRNA at the 16S rRNA-ND1 junction and the translation of downstream transcripts. MiR-4485 modulated mitochondrial complex I activity, the production of ATP, ROS levels, caspase-3/7 activation, and apoptosis. Transfection of a miR-4485 mimic downregulated the expression of regulatory glycolytic pathway genes and reduced the clonogenic ability of breast cancer cells. Ectopic expression of miR-4485 in MDA-MB-231 breast carcinoma cells decreased the tumorigenicity in a nude mouse xenograft model. Furthermore, levels of both precursor and mature miR-4485 are decreased in tumor tissue of breast cancer patients. We conclude that the mitochondria-targeted miR-4485 may act as a tumor suppressor in breast carcinoma cells by negatively regulating mitochondrial RNA processing and mitochondrial functions.

Diagnostic and therapeutic potential of microRNAs in neuropsychiatric disorders: Past, present, and future

Neuropsychiatric disorders are common health problems affecting approximately 1% of the population. Twin, adoption, and family studies have displayed a strong genetic component for many of these disorders; however, the underlying pathophysiological mechanisms and neural substrates remain largely unknown. Given the critical need for new diagnostic markers and disease-modifying treatments, expanding the focus of genomic studies of neuropsychiatric disorders to include the role of non-coding RNAs (ncRNAs) is of growing interest. Of known types of ncRNAs, microRNAs (miRNAs) are 20-25-nucleotide, single-stranded, molecules that regulate gene expression through post-transcriptional mechanisms and have the potential to coordinately regulate complex regulatory networks. In this review, we summarize the current knowledge on miRNA alteration/dysregulation in neuropsychiatric disorders, with a special emphasis on schizophrenia (SCZ), bipolar disorder (BD), and major depressive disorder (MDD). With an eye toward the future, we also discuss the diagnostic and prognostic potential of miRNAs for neuropsychiatric disorders in the context of personalized treatments and network medicine.

Oxytocin and Anxiety Disorders

In the present chapter, we review the literature focusing on oxytocin (OT)-centered research in anxiety spectrum conditions, comprising separation anxiety disorder, specific phobias, social anxiety disorder (SAD), panic disorder, generalized anxiety disorder, and anxiety-related endophenotypes (e.g., trust behavior, behavioral inhibition, neuroticism, and state/trait anxiety). OT receptor gene (OXTR) polymorphisms have been implicated in gene-environment interactions with attachment style and childhood maltreatment and to influence clinical outcomes, including SAD intensity and limbic responsiveness. Epigenetic OXTR DNA methylation patterns have emerged as a link between categorical, dimensional, neuroendocrinological, and neuroimaging SAD correlates, highlighting them as potential peripheral surrogates of the central oxytocinergic tone. A pathophysiological framework of OT integrating the dynamic nature of epigenetic biomarkers and the summarized genetic and peripheral evidence is proposed. Finally, we emphasize opportunities and challenges of OT as a key network node of social interaction and fear learning in social contexts. In conjunction with multi-level investigations incorporating a dimensional understanding of social affiliation and avoidance in anxiety spectrum disorders, these concepts will help to promote research for diagnostic, state, and treatment response biomarkers of the OT system, advancing towards indicated preventive interventions and personalized treatment approaches.

MicroRNA expression profiles in chronic epilepsy rats and neuroprotection from seizures by targeting miR-344a

MicroRNA (miRNA) is believed to play a crucial role in the cause and treatment of epilepsy by controlling gene expression. However, it is still unclear how miRNA profiles change after multiple prolonged seizures and aggravation of brain injury in chronic epilepsy (CE). To investigate the role of miRNA in epilepsy, we utilized the CE rat models with pentylenetetrazol (PTZ) and miRNA profiles in the hippocampus. miRNA profiles were characterized using miRNA microarray analysis and were compared with the rats in the sham group, which received 0.9% physiological saline treatment at the same dose. Four up-regulated miRNAs (miR-139-3p, -770-5p, -127-5p, -331-3p) and 5 down-regulated miRNAs (miR-802-5p, -380-5p, -183-5p, -547-5p, -344a/-344a-5p) were found in the CE rats (fold change >1.5, P<0.05). Three of the dysregulated miRNAs were validated by quantitative real-time polymerase chain reaction, which revealed an outcome consistent with the initial results of the miRNA microarray analyses. Then, miR-344a agomir was intracerebroventricularly injected and followed by PTZ induction of CE models to investigate the effect of miR-344a in chronic neocortical epileptogenesis. After miRNA-344a agomir and scramble treatment, results showed a restoration of seizure behavior and a reduction in neuron damage in the cortex in miRNA-334a agomir treated rats. These data suggest that miRNA-344a might have a small modulatory effect on seizure-induced apoptosis signaling pathways in the cortex.

Two SNAP-25 genetic variants in the binding site of multiple microRNAs and susceptibility of ADHD: A meta-analysis

The aim of this meta-analysis is to assess the associations between two most widely investigated polymorphisms (rs3746544 and rs1051312) in the 3'UTR of the SNAP-25 gene and susceptibility of ADHD. Two investigators selected related studies and assessed methodological quality independently. Six studies were included in this meta-analysis for a total of 715 cases and 655 controls. There is no apparent association between rs3746544 polymorphisms and risk of ADHD. However, subgroup analysis based on ethnicity demonstrated a strong association between rs3746544 polymorphism and ADHD in the subset of Asian participants, but not among Caucasians. Compared to the T allele, the allele G was associated with a significantly decreased risk of developing ADHD in the Asian population (odds ratio (OR) = 0.70, 95% confidence interval (CI) = 0.52-0.95, p = 0.02). The association between the TT genotype and ADHD risk was also significantly increased as compared to G/T (OR = 1.56, 95% CI = 1.00-2.44, p = 0.05) and the dominant genetic model (GG + GT vs. TT: OR = 1.51, 95% CI = 1.07-2.13, p = 0.02). For the rs1051312 SNP, being homozygous for the minor allele (C/C) was associated with a 3.66 higher odds of ADHD as compared to cases homozygous for the major allele (T/T) (95% CI = 1.64-8.13, p = 0.001), and 3.57 higher odds as compared to heterozygous (C/T) carriers (95% CI = 2.01-12.90, p < 0.001). Our results suggest that the polymorphisms rs3746544 and rs1051312 may increase the odds of developing ADHD. Additional studies are needed to confirm these findings.

Biological markers for anxiety disorders, OCD and PTSD - a consensus statement. Part I: Neuroimaging and genetics

OBJECTIVES

Biomarkers are defined as anatomical, biochemical or physiological traits that are specific to certain disorders or syndromes. The objective of this paper is to summarise the current knowledge of biomarkers for anxiety disorders, obsessive-compulsive disorder (OCD) and post-traumatic stress disorder (PTSD).

METHODS

Findings in biomarker research were reviewed by a task force of international experts in the field, consisting of members of the World Federation of Societies for Biological Psychiatry Task Force on Biological Markers and of the European College of Neuropsychopharmacology Anxiety Disorders Research Network.

RESULTS

The present article (Part I) summarises findings on potential biomarkers in neuroimaging studies, including structural brain morphology, functional magnetic resonance imaging and techniques for measuring metabolic changes, including positron emission tomography and others. Furthermore, this review reports on the clinical and molecular genetic findings of family, twin, linkage, association and genome-wide association studies. Part II of the review focuses on neurochemistry, neurophysiology and neurocognition.

CONCLUSIONS

Although at present, none of the putative biomarkers is sufficient and specific as a diagnostic tool, an abundance of high-quality research has accumulated that will improve our understanding of the neurobiological causes of anxiety disorders, OCD and PTSD.

miRNAs in NMDA receptor-dependent synaptic plasticity and psychiatric disorders

The identification and functional delineation of miRNAs (a class of small non-coding RNAs) have added a new layer of complexity to our understanding of the molecular mechanisms underlying synaptic plasticity. Genome-wide association studies in conjunction with investigations in cellular and animal models, moreover, provide evidence that miRNAs are involved in psychiatric disorders. In the present review, we examine the current knowledge about the roles played by miRNAs in NMDA (N-methyl-D-aspartate) receptor-dependent synaptic plasticity and psychiatric disorders.

Sustained lentiviral-mediated overexpression of microRNA124a in the dentate gyrus exacerbates anxiety- and autism-like behaviors associated with neonatal isolation in rats

Autism spectrum disorders (ASD) are highly disabling psychiatric disorders. Despite a strong genetic etiology, there are no efficient therapeutic interventions that target the core symptoms of ASD. Emerging evidence suggests that dysfunction of microRNA (miR) machinery may contribute to the underlying molecular mechanisms involved in ASD. Here, we report a stress model demonstrating that neonatal isolation-induced long-lasting hippocampal elevation of miR124a was associated with reduced expression of its target BDNF mRNA. In addition, we investigated the impact of lentiviral-mediated overexpression of miR124a into the dentate gyrus (DG) on social interaction, repetitive- and anxiety-like behaviors in the neonatal isolation (Iso) model of autism. Rats isolated from the dams on PND 1 to PND 11 were assessed for their social interaction, marble burying test (MBT) and repetitive self-grooming behaviors as adults following miR124a overexpression. Also, anxiety-like behavior and locomotion were evaluated in the elevated plus maze (EPM) and open-field (OF) tests. Results show that, consistent with previously published reports, Iso rats displayed decreased social interaction contacts but increased repetitive- and anxiety-like behaviors. Interestingly, across both autism- and anxiety-like behavioral assays, miR124a overexpression in the DG significantly exacerbated repetitive behaviors, social impairments and anxiety with no effect on locomotor activity. Our novel findings attribute neonatal isolation-inducible cognitive impairments to induction of miR124a and consequently suppressed BDNF mRNA, opening venues for intercepting these miR124a-mediated damages. They also highlight the importance of studying microRNAs in the context of ASD and identify miR124a as a novel potential therapeutic target for improving mood disorders.

Pathogenetic and therapeutic applications of microRNAs in major depressive disorder

As a class of noncoding RNAs, microRNAs (miRNAs) regulate gene expression by inhibiting translation of messenger RNAs. These miRNAs have been shown to play a critical role in higher brain functioning and actively participate in synaptic plasticity. Pre-clinical evidence demonstrates that expression of miRNAs is differentially altered during stress. On the other hand, depressed individuals show marked changes in miRNA expression in brain. MiRNAs are also target of antidepressants and electroconvulsive therapy. Moreover, these miRNAs are present in circulating blood and can be easily detected. Profiling of miRNAs in blood plasma/serum provides evidence that determination of miRNAs in blood can be used as possible diagnostic and therapeutic tool. In this review article, these aspects are critically reviewed and the role of miRNAs in possible etiopathogenesis and therapeutic implications in the context of major depressive disorder is discussed.

Novel developments in genetic and epigenetic mechanisms of anxiety

PURPOSE OF REVIEW

The present review aims to deliver a systematic overview of current developments and trends in (epi)genetics of anxiety and to identify upcoming challenges and opportunities.

RECENT FINDINGS

Genes related to peptide and hormone signaling have been suggested for anxiety-related phenotypes, e.g., the NPSR1 gene, which has been associated predominantly with panic disorder in women, and shown to interact with environmental factors and to influence psychometric, neurophysiological, and neuroimaging correlates of anxiety. Similar multi-level results have been reported for genetic and epigenetic variation in the OXTR gene, especially in social anxiety disorder (SAD), and for CRHR1 gene variation in women with panic disorder. Variants in RGS2 and ASIC1 genes were linked to panic disorder, with the latter also being implicated in SAD treatment response. Finally, monoaminergic 'risk' genes (SLC6A4, MAOA, HTR1A) were related to SAD, generalized anxiety disorder and women with panic disorder, anxiety traits and response to psychopharmacological and psychotherapeutic interventions.

SUMMARY

Converging evidence for potential genetic and epigenetic risk markers has been gathered and future studies call for independent replications and multi-level integration of dimensional approaches, environmental factors, and biological readouts, while considering sex-specific substratification. Particularly, epigenetic variation appears promising for disease course and treatment response predictions.

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.

Association between single nucleotide polymorphisms in MiR219-1 and MiR137 and susceptibility to schizophrenia in a Chinese population

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A case-control study investigated rs107822, rs1625579 and risk of schizophrenia.

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rs107822 was negatively associated with susceptibility to schizophrenia.

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No association was found between rs1625579 and the disorder.

Schizophrenia is one of the most common mental disorders to severely affect human health worldwide. Single nucleotide polymorphisms (SNPs) within related genes are candidate susceptible factors for the disorder. Rs107822 within MiR219-1 and rs1625579 within MiR137 were genotyped in 589 cases and 622 controls to investigate the possible association between the loci and schizophrenia in a Chinese population. Our results showed significant association between rs107822 and the disorder in allele (C vs. T: adjusted OR = 0.773, 95%CI = 0.655–0.912), co-dominant (TC vs. TT: adjusted OR = 0.734, 95%CI = 0.571–0.943; CC vs. TT: adjusted OR = 0.655, 95%CI = 0.459–0.936), dominant (TC + CC vs. TT: adjusted OR = 0.707, 95%CI = 0.559–0.895), and recessive (CC vs. TC + TT: adjusted OR = 0.724, 95%CI = 0.524–0.999) models, respectively. Meanwhile, negative associations were also observed between rs107822 and the disorder in male and female subgroups, and genotype CC of the locus was significantly associated with a lower positive symptom score of PANSS compared to genotype TT carrier in the cases group. However, we didn’t observe a significant association between rs1625579 and the disorder. These findings indicate that rs107822 within MiR219-1 might be involved in pathogenesis of schizophrenia and that genotypes TC, CC and allele C of the locus are protective factors for schizophrenia in a Chinese population.

Determining the role of microRNAs in psychiatric disorders

Recent studies have revealed that patients with psychiatric disorders have altered microRNA (miRNA) expression profiles in the circulation and brain. Furthermore, animal studies have shown that manipulating the levels of particular miRNAs in the brain can alter behaviour. Here, we review recent studies in humans, animal models, cellular systems and bioinformatics that have advanced our understanding of the contribution of brain miRNAs to the regulation of behaviour in the context of psychiatric conditions. These studies highlight the potential of miRNA levels to be used in the diagnosis of psychiatric disorders and suggest that brain miRNAs could become novel treatment targets for psychiatric disorders.

Learning from the past and looking to the future: Emerging perspectives for improving the treatment of psychiatric disorders

Modern neuropsychopharmacology commenced in the 1950s with the serendipitous discovery of first-generation antipsychotics and antidepressants which were therapeutically effective yet had marked adverse effects. Today, a broader palette of safer and better-tolerated agents is available for helping people that suffer from schizophrenia, depression and other psychiatric disorders, while complementary approaches like psychotherapy also have important roles to play in their treatment, both alone and in association with medication. Nonetheless, despite considerable efforts, current management is still only partially effective, and highly-prevalent psychiatric disorders of the brain continue to represent a huge personal and socio-economic burden. The lack of success in discovering more effective pharmacotherapy has contributed, together with many other factors, to a relative disengagement by pharmaceutical firms from neuropsychiatry. Nonetheless, interest remains high, and partnerships are proliferating with academic centres which are increasingly integrating drug discovery and translational research into their traditional activities. This is, then, a time of transition and an opportune moment to thoroughly survey the field. Accordingly, the present paper, first, chronicles the discovery and development of psychotropic agents, focusing in particular on their mechanisms of action and therapeutic utility, and how problems faced were eventually overcome. Second, it discusses the lessons learned from past successes and failures, and how they are being applied to promote future progress. Third, it comprehensively surveys emerging strategies that are (1), improving our understanding of the diagnosis and classification of psychiatric disorders; (2), deepening knowledge of their underlying risk factors and pathophysiological substrates; (3), refining cellular and animal models for discovery and validation of novel therapeutic agents; (4), improving the design and outcome of clinical trials; (5), moving towards reliable biomarkers of patient subpopulations and medication efficacy and (6), promoting collaborative approaches to innovation by uniting key partners from the regulators, industry and academia to patients. Notwithstanding the challenges ahead, the many changes and ideas articulated herein provide new hope and something of a framework for progress towards the improved prevention and relief of psychiatric and other CNS disorders, an urgent mission for our Century.