miR-132/212 is induced by stress and its dysregulation triggers anxiety-related behavior

Regulation of hippocampal miRNA expression by intestinal flora in anxiety-like mice

This study investigated the possible interaction between gut flora and miRNAs and the effect of both on anxiety disorders. The model group was induced with chronic restraint stress (CRS) and each group was tested for anxiety-like behaviour by open field test and elevated plus maze test. Meanwhile, the gut flora was analysed by 16S rRNA high-throughput sequencing. The miRNAs in hippocampus were analysed by high-throughput sequencing, and the key miRNAs were obtained by using the method of bioinformatics analysis. PCR was used to verify the significantly related key miRNAs. Spearman correlation analysis was used to explore the correlation between behaviour, key miRNAs and differential gut microbiota. The 16S rRNA high-throughput sequencing result showed that the gut flora was dysregulated in the model group. In particular, Verrucomicrobia, Akkermansia, Anaerostipes, Ralstonia, Burkholderia and Anaeroplasma were correlated with behaviour. The results of miRNA high-throughput sequencing analysis and bioinformatics analysis showed that 7 key miRNAs influenced the pathogenesis of anxiety, and qRT-PCR results were consistent with the high-throughput sequencing results. Mmu-miR-543-3p and mmu-miR-26a-5p were positively correlated with Verrucomicrobia, Akkermansia and Anaerostipes. Therefore, we infer that chronic stress caused the decrease of Akkermansia abundance, which may aggravate the decrease of mmu-miR-543-3p and mmu-miR-26a-5p expression, leading to the increase of SLC1A2 expression. In conclusion, gut flora has played an important influence on anxiety with changes in miRNAs.

Analysis of microRNAs and the microRNA-messengerRNA regulatory network in chronic alcohol exposure

Introduction: Chronic alcoholism is one of the most common neurological diseases in modern society. However, the key mechanisms underlying learning and memory impairments caused by chronic alcohol exposure remain unclear. In this study, a microRNA-messenger RNA (miRNA-mRNA) network was constructed to explore the potential function of key genes in chronic alcohol exposure, their effects on the hippocampus, and their mechanisms which facilitate brain injury in mice. Methods: The Morris water maze test was used to assess the learning ability of mice in each group. Mitochondrial ATPase activity and H2S levels in the hippocampi of mice were determined. Differentially expressed miRNAs and mRNAs in the mouse hippocampus were identified using second-generation sequencing. Using the TargetScan, miRTarBase, and miRDB databases, we predicted miRNA target genes and constructed a miRNA-mRNA regulatory network. Furthermore, using the Gene Ontology and KEGG databases we performed functional enrichment and protein-protein interaction analyses. Real-time quantitative polymerase chain reaction (qPCR) and other methods were employed to verify the mRNA expression of related genes. Results: The Morris water maze test revealed that mice exposed to chronic alcohol exhibited a significantly reduced learning ability compared to the control group (p < 0.05). Compared with the control group, the activity of mitochondrial ATPase in the hippocampal tissue of alcohol-treated mice was significantly decreased (p < 0.01), suggesting brain injury. In the model group, H2S significantly increased in the mice hippocampi (p < 0.01), indicating that chronic alcohol exposure could activate cystathionineβ-synthase (CBS) and catalyze the mass formation of H2S, suggesting brain injury. A total of 208 differentially expressed miRNAs and 377 differentially expressed mRNAs were screened through bioinformatic analysis. Enrichment analysis indicated that the main pathways were involved in neurodegeneration and regulation of the Wnt signaling pathway. The PCR detected a significant downregulation in the expressions of FOS and EGR1 genes. Discussion: Consequently, chronic alcohol exposure may regulate the expression of FOS and EGR1 in the hippocampus through miR-222-3p, miR-132-3p, miR-212-3p, and miR-191-5p, reduce the activity of hippocampal mitochondrial ATPase, activate CBS, catalyze the large amount of H2S formation, and destroy the mitochondrial structure, resulting in decreased learning ability. Our findings revealed valuable genes and miRNAs for the study of chronic alcohol exposure.

Functional involvement of septal miR-132 in extinction and oxytocin-mediated reversal of social fear

Social interactions are critical for mammalian survival and evolution. Dysregulation of social behavior often leads to psychopathologies such as social anxiety disorder, denoted by intense fear and avoidance of social situations. Using the social fear conditioning (SFC) paradigm, we analyzed expression levels of miR-132-3p and miR-124-3p within the septum, a brain region essential for social preference and avoidance behavior, after acquisition and extinction of social fear. Here, we found that SFC dynamically altered both microRNAs. Functional in vivo approaches using pharmacological strategies, inhibition of miR-132-3p, viral overexpression of miR-132-3p, and shRNA-mediated knockdown of miR-132-3p specifically within oxytocin receptor-positive neurons confirmed septal miR-132-3p to be critically involved not only in social fear extinction, but also in oxytocin-induced reversal of social fear. Moreover, Argonaute-RNA-co-immunoprecipitation-microarray analysis and further in vitro and in vivo quantification of target mRNA and protein, revealed growth differentiation factor-5 (Gdf-5) as a target of miR-132-3p. Septal application of GDF-5 impaired social fear extinction suggesting its functional involvement in the reversal of social fear. In summary, we show that septal miR-132-3p and its downstream target Gdf-5 regulate social fear expression and potentially mediate oxytocin-induced reversal of social fear.

Monoamine Oxidase: A Potential Link in Papez Circuit to Generalized Anxiety Disorders

Anxiety is a common mental illness that affects a large number of people around the world, and its treatment is often based on the use of pharmacological substances such as benzodiazepines, serotonin, and 5-hydroxytyrosine (MAO) neurotransmitters. MAO neurotransmitters levels are deciding factors in the biological effects. This review summarizes the current understanding of the MAO system and its role in the modulation of anxiety-related brain circuits and behavior. The MAO-A polymorphisms have been implicated in the susceptibility to generalized anxiety disorder (GAD) in several investigations. The 5-HT system is involved in a wide range of physiological and behavioral processes, involving anxiety, aggressiveness, stress reactions, and other elements of emotional intensity. Among these, 5-HT, NA, and DA are the traditional 5-HT neurons that govern a range of biological activities, including sleep, alertness, eating, thermoregulation, pains, emotion, and memory, as anticipated considering their broad projection distribution in distinct brain locations. The DNMTs (DNA methyltransferase) protein family, which increasingly leads a prominent role in epigenetics, is connected with lower transcriptional activity and activates DNA methylation. In this paper, we provide an overview of the current state of the art in the elucidation of the brain's complex functions in the regulation of anxiety.

Stress, microRNAs, and stress-related psychiatric disorders: an overview

Stress is a major risk factor for psychiatric disorders. During and after exposure to stressors, the stress response may have pro- or maladaptive consequences, depending on several factors related to the individual response and nature of the stressor. However, the mechanisms mediating the long-term effects of exposure to stress, which may ultimately lead to the development of stress-related disorders, are still largely unknown. Epigenetic mechanisms have been shown to mediate the effects of the environment on brain gene expression and behavior. MicroRNAs, small non-coding RNAs estimated to control the expression of about 60% of all genes by post-transcriptional regulation, are a fundamental epigenetic mechanism. Many microRNAs are expressed in the brain, where they work as fine-tuners of gene expression, with a key role in the regulation of homeostatic balance, and a likely influence on pro- or maladaptive brain changes. Here we have selected a number of microRNAs, which have been strongly implicated as mediators of the effects of stress in the brain and in the development of stress-related psychiatric disorders. For all of them recent evidence is reported, obtained from rodent stress models, manipulation of microRNAs levels with related behavioral changes, and clinical studies of stress-related psychiatric disorders. Moreover, we have performed a bioinformatic analysis of the predicted brain-expressed target genes of the microRNAs discussed, and found a central role for mechanisms involved in the regulation of synaptic function. The complex regulatory role of microRNAs has suggested their use as biomarkers for diagnosis and treatment response, as well as possible therapeutic drugs. While, microRNA-based diagnostics have registered advancements, particularly in oncology and other fields, and many biotech companies have launched miRNA therapeutics in their development pipeline, the development of microRNA-based tests and drugs for brain disorders is comparatively slower.

Inversely Regulated Inflammation-Related Processes Mediate Anxiety-Obesity Links in Zebrafish Larvae and Adults

Anxiety and metabolic impairments are often inter-related, but the underlying mechanisms are unknown. To seek RNAs involved in the anxiety disorder-metabolic disorder link, we subjected zebrafish larvae to caffeine-induced anxiety or high-fat diet (HFD)-induced obesity followed by RNA sequencing and analyses. Notably, differentially expressed (DE) transcripts in these larval models and an adult zebrafish caffeine-induced anxiety model, as well as the transcript profiles of inherently anxious versus less anxious zebrafish strains and high-fat diet-fed versus standard diet-fed adult zebrafish, revealed inversely regulated DE transcripts. In both larval anxiety and obesity models, these included long noncoding RNAs and transfer RNA fragments, with the overrepresented immune system and inflammation pathways, e.g., the "interleukin signaling pathway" and "inflammation mediated by chemokine and cytokine signaling pathway". In adulthood, overrepresented immune system processes included "T cell activation", "leukocyte cell-cell adhesion", and "antigen processing and presentation". Furthermore, unlike adult zebrafish, obesity in larvae was not accompanied by anxiety-like behavior. Together, these results may reflect an antagonistic pleiotropic phenomenon involving a re-adjusted modulation of the anxiety-metabolic links with an occurrence of the acquired immune system. Furthermore, the HFD potential to normalize anxiety-upregulated immune-related genes may reflect the high-fat diet protection of anxiety and neurodegeneration reported by others.

miRNA-132/212 Deficiency Disrupts Selective Corticosterone Modulation of Dorsal vs. Ventral Hippocampal Metaplasticity

Cortisol is a potent human steroid hormone that plays key roles in the central nervous system, influencing processes such as brain neuronal synaptic plasticity and regulating the expression of emotional and behavioral responses. The relevance of cortisol stands out in the disease, as its dysregulation is associated with debilitating conditions such as Alzheimer's Disease, chronic stress, anxiety and depression. Among other brain regions, cortisol importantly influences the function of the hippocampus, a structure central for memory and emotional information processing. The mechanisms fine-tuning the different synaptic responses of the hippocampus to steroid hormone signaling remain, however, poorly understood. Using ex vivo electrophysiology and wild type (WT) and miR-132/miR-212 microRNAs knockout (miRNA-132/212-/-) mice, we examined the effects of corticosterone (the rodent's equivalent to cortisol in humans) on the synaptic properties of the dorsal and ventral hippocampus. In WT mice, corticosterone predominantly inhibited metaplasticity in the dorsal WT hippocampi, whereas it significantly dysregulated both synaptic transmission and metaplasticity at dorsal and ventral regions of miR-132/212-/- hippocampi. Western blotting further revealed significantly augmented levels of endogenous CREB and a significant CREB reduction in response to corticosterone only in miR-132/212-/- hippocampi. Sirt1 levels were also endogenously enhanced in the miR-132/212-/- hippocampi but unaltered by corticosterone, whereas the levels of phospo-MSK1 were only reduced by corticosterone in WT, not in miR-132/212-/- hippocampi. In behavioral studies using the elevated plus maze, miRNA-132/212-/- mice further showed reduced anxiety-like behavior. These observations propose miRNA-132/212 as potential region-selective regulators of the effects of steroid hormones on hippocampal functions, thus likely fine-tuning hippocampus-dependent memory and emotional processing.

Chronic Stress Impairs the Structure and Function of Astrocyte Networks in an Animal Model of Depression

Now astrocytes appear to be the key contributors to the pathophysiology of major depression. Evidence in rodents shows that chronic stress is associated with a decreased expression of astrocytic GFAP-immunoreactivity within the cortex in addition to changes in the complexity and length of astrocyte processes. Furthermore, postmortem brains of individuals with depression have revealed a decrease in astrocyte density. Notably, astrocytes are extensively coupled to one another through gap junctions to form a network, or syncytium, and we have previously demonstrated that syncytial isopotentiality is a mechanism by which astrocytes function as an efficient system with respect to brain homeostasis. Interestingly, the question of how astrocyte network function changes following chronic stress is yet to be elucidated. Here, we sought to examine the effects of chronic stress on network-level astrocyte (dys)function. Using a transgenic aldh1l1-eGFP astrocyte reporter mouse, a six-week unpredictable chronic mild stress (UCMS) paradigm as a rodent model of major depression, and immunohistochemical approaches, we show that the morphology of individual astrocytes is altered by chronic stress exposure. Additionally, in astrocyte syncytial isopotentiality measurement, we found that UCMS impairs the syncytial coupling strength of astrocytes within the hippocampus and prefrontal cortex-two brain regions that have been implicated in the regulation of mood. Together, these findings reveal that chronic stress leads to astrocyte atrophy and impaired gap junction coupling, raising the prospect that both individual and network-level astrocyte functionality are important in the etiology of major depression and other neuropsychiatric disorders.

MAPK Is a Mutual Pathway Targeted by Anxiety-Related miRNAs, and E2F5 Is a Putative Target for Anxiolytic miRNAs

Anxiety-related disorders (ARDs) are chronic neuropsychological diseases and the sixth leading cause of disability in the world. As dysregulation of microRNAs (miRs) are observed in the pathological course of neuropsychiatric disorders, the present study aimed to introduce miRs that underlie anxiety processing in the brain. First, we collected the experimentally confirmed anxiety-related miRNAs (ARmiRs), predicted their target transcripts, and introduced critical cellular pathways with key commune hub genes. As a result, we have found nine anxiolytic and ten anxiogenic ARmiRs. The anxiolytic miRs frequently target the mRNA of Acyl-CoA synthetase long-chain family member 4 (Acsl4), AFF4-AF4/FMR2 family member 4 (Aff4), and Krüppel like transcription factor 4 (Klf4) genes, where miR-34b-5p and miR-34c-5p interact with all of them. Moreover, the anxiogenic miRs frequently target the mRNA of nine genes; among them, only two miR (miR-142-5p and miR-218-5p) have no interaction with the mRNA of trinucleotide repeat-containing adaptor 6B (Tnrc6b), and miR-124-3p interacts with all of them where MAPK is the main signaling pathway affected by both anxiolytic and anxiogenic miR. In addition, the anxiolytic miR commonly target E2F transcription factor 5 (E2F5) in the TGF-β signaling pathway, and the anxiogenic miR commonly target Ataxin 1 (Atxn1), WASP-like actin nucleation promoting factor (Wasl), and Solute Carrier Family 17 Member 6 (Slc17a6) genes in the notch signaling, adherence junction, and synaptic vesicle cycle pathways, respectively. Taken together, we conclude that the most important anxiolytic (miR-34c, Let-7d, and miR-17) and anxiogenic (miR-19b, miR-92a, and 218) miR, as hub epigenetic modulators, potentially influence the pathophysiology of anxiety, primarily via interaction with the MAPK signaling pathway. Moreover, the role of E2F5 as a novel putative target for anxiolytic miRNAs in ARDs disorders deserves further exploration.

Histone methyltransferase Setdb1 mediates osteogenic differentiation by suppressing the expression of miR-212-3p under mechanical unloading

Emerging evidence indicates that multiple mechanisms are involved in bone loss induced by mechanical unloading. Thus far, few study has established the pathophysiological role of histone modification for osteogenic differentiation under mechanical unloading. Here we demonstrated that the histone H3 lysine 9 (H3K9) methyltransferase Setdb1, which was sensitive to mechanical unloading, was increased during osteogenic differentiation of MC3T3-E1 cells for the first time. Knockdown of Setdb1 significantly blocked osteoblast function in vivo and in vitro. Through bioinformatics analysis of candidate miRNAs regulated by H3K9me3, we further identified that Setdb1 inhibited the expression of miR-212-3p by regulating the formation of H3K9me3 in the promoter region. Mechanically, we revealed that miR-212-3p was upregulated under mechanical unloading and suppressed osteogenic differentiation by directly downregulating High mobility group box 1 protein (Hmgb1) expression. Furthermore, we verified the molecular mechanism of the SETDB1/miR-212-3p/HMGB1 pathway in hFOB cells under mechanical unloading. In summary, these data demonstrate the essential function of the Setdb1/miR-212-3p/Hmgb1 pathway in osteogenic differentiation under mechanical unloading, and present a potential protective strategies against bone loss induced by mechanical unloading.

Downregulated miRNAs associated with auditory deafferentation and compensatory neural plastic changes following single-sided deafness in the inferior colliculi of rats

BACKGROUND AND AIMS

Deafferentation and compensatory neural plastic changes in the inferior colliculus (IC) have been suggested following single-sided deafness (SSD). We explored related miRNA changes in the IC of SSD rats using miRNA microarray analyses.

METHODS

Eight-week-old rats were divided into control and SSD rats (n = 8 for each group). SSD rats underwent right-side cochlear ablation surgery, with the IC harvested two weeks post-surgery. miRNA microarray analysis was performed using GeneChip miRNA 4.0, microarray (Affymetrix Inc.). miRNAs whose expression levels differed between SSD and control rats with a fold-change ≥1.5 and P < 0.05 were examined using quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Target genes of differentially expressed miRNAs were predicted using TargetScan software. The pathways related to predicted target genes were analyzed. mRNA levels of predicted target genes were estimated using qRT-PCR.

RESULTS

The expression of miR-15b-5p, miR-202-5p, and miR-212-3p was lower in the contralateral (left) IC of SSD rats than that of control rats. In SSD rats, miRNA expression levels in the contralateral IC were 0.45-, 0.25-, and 0.50-fold lower for miR-15b-5p, miR-202-5p, and miR-212-3p, respectively (P < 0.05). The expression of predicted target genes (Spred1, Rasa1, Lsm11, and Srsf1) was higher in the contralateral IC of SSD rats than in control rats. The targets were predicted to be related with cleavage of growing transcripts in the termination region, mitogen-activated protein kinase family signaling cascades, RAF/AMP kinase cascade, regulation of RAS by GTPase activating proteins (GAPs), and RNA polymerase II transcription termination. For ipsilateral ICs, miR-425-3p, miR-199a-5p, and miR-134-3p showed lower expressions in SSD rats than in control rats, which were 0.55-, 0.61-, and 0.69-fold lower, respectively (P < 0.05). The expression of predicted target genes (Atp2b2, Grin2b, Foxp1, Ztbt20, Zfp91, and Strn) was higher in the ipsilateral IC of SSD rats; the regulation of synaptic plasticity, cAMP signaling pathway, metal ion binding, and calcium ion transport can be associated with these target genes.

CONCLUSION

Adult rats with unilateral auditory deprivation showed miRNA changes in the IC. The contralateral IC showed decreased miRNA expression predicted to be related to MAPK and RAS signaling, whereas the ipsilateral IC revealed decreased miRNA expression predicted to be associated with synaptic plasticity and calcium ion transport.

Differential Expression of miRNAs and Their Predicted Target Pathways in Cochlear Nucleus Following Chronic Noise Exposure in Rats

Several recent preclinical studies have reported that dynamic changes in miRNA expression contribute to hearing function. This study aims to investigate miRNA expression changes in the cochlear nuclei (CN) of rats following chronic noise exposure. Eight-week-old rats (n = 14) were exposed to noise for 4 weeks. The control rats (n = 14) were raised under identical conditions without noise. Two months after noise exposure, the auditory brainstem response (ABR) was examined, and the cochlea and CN were harvested. In the CN, the expression levels of arc, neurocan, and brevican were measured (n = 6 per group). Furthermore, the expression levels of miRNAs and their predicted target genes were measured in the CN (n = 8 per group). ABR thresholds were elevated after 4 weeks of noise exposure, which were maintained for 3 months. In CN, the protein expression of arc and brevican was higher in the noise-exposed group than in the control group (0.95 [standard deviation (SD) = 0.53] vs. 3.19 [SD = 1.00], p < 0.001 for arc and 1.02 [SD = 0.10] vs. 1.66 [SD = 0.24], p < 0.001 for brevican). The noise-exposed rats exhibited lower expression levels of miR-758-5p, miR-15b-5p, miR-212-3p, miR-199a-5p, and miR-134-3p than the control rats (all p < 0.001). The AMPK signaling pathway was predicted to be regulated by these miRNAs. The predicted target genes AKT3, SIRT1, and PRKAA1 were highly expressed in noise-exposed rats. In CN of noise-exposed rats, the miRNAs of miR-758-5p, miR-15b-5p, miR-212-3p, miR-199a-5p, and miR-134-3p were reduced and related to AMPK signaling including AKT3 and SIRT1 expression. These modulation of signaling pathways could mediate the increased expression of brevican in the CN of noise-exposed rats.

MicroRNAs miR-629-3p, miR-1202 and miR-1225-5p as potential diagnostic and surgery outcome biomarkers for mesial temporal lobe epilepsy with hippocampal sclerosis

BACKGROUND

Mesial temporal lobe epilepsy (MTLE) is a symptomatic epilepsy syndrome clinically characterized by high prevalence, pharmacoresistance, good surgical prognosis and hippocampal sclerosis (HS); however, no singular criteria can be considered sufficient for the MTLE-HS diagnosis. MicroRNAs (miRNAs) are small non-coding molecules that act as important gene-expression regulators at post-transcriptional level. Evidences on the involvement of miRNAs in epilepsy pathogenesis as well as their potential to be employed as biomarkers claim for investigations on miRNAs' applicability as epilepsy diagnosis and prognosis biomarkers. Consequently, the present study aimed to evaluate the applicability of three specific miRNAs as biomarkers of diagnosis and surgical outcomes in adult patients with MTLE-HS.

METHOD

Hippocampus, amygdala and blood samples from 20 patients with MTLE-HS were analyzed, 10 with favorable surgical prognosis (Engel I) and 10 with unfavorable surgical prognosis (Engel III-IV). For the control groups, hippocampus and amygdala from necropsy and blood samples from healthy individuals were adopted. The miRNAs expression analysis was performed using Real-Time Quantitative Polymerase Chain Reaction for miRNAs highlighted from microarray as being involved in GABAergic neurotransmission.

RESULTS

The miRNAs miR-629-3p, miR-1202 and miR-1225-5p were found to be hyperexpressed in MTLE-HS patients' blood.

CONCLUSIONS

Our data suggest the existence of three circulating miRNAs (miR-629-3p, miR-1202 and miR-1225-5p) that could possibly act as additional tools in the set of factors that contribute to MTLE-HS diagnose.

Overexpression of miR-132-3p contributes to neuronal protection in in vitro and in vivo models of Alzheimer's disease

One of the neuropathological hallmarks of Alzheimer's disease (AD) is accumulation and deposition of amyloid-beta (Aβ_1-42) plaques in the hippocampus. Recently, microRNAs (miRNAs), have been demonstrated to play an essential role in AD. We have previously demonstrated that miR-132-3p exerts neuroprotection via regulating histone deacetylase 3 (HDAC3) in a mouse model of AD. In the present study, we further unveiled neuroprotective roles of miR-132-3p in transgenic amyloid precursor protein/presenilin 1 (APP/PS1) mice compared with those in age-matched wild-type C57BL/6 mice. Lentiviral-mediated inhibition or overexpression of miR-132-3p in the hippocampus of APP/PS1 mice was used to explore the contributions of hippocampal miR-132-3p in spatial memory, amyloid burden, apoptosis, and the number of hippocampal cells in a mouse model of AD. Overexpression of hippocampal miR-132-3p ameliorated spatial memory deficits in the Morris water maze, reduced both Aβ_1-42 accumulation and apoptosis, and promoted the numbers of hippocampal cells in the brains of APP/PS1 mice. Furthermore, trichostatin A (TSA) promoted the expression of miR-132-3p in Aβ_1-42-burdened neurons while increasing the expression levels of synaptic proteins. Taken together, our results suggest that miR-132-3p may represent a promising therapeutic target for the treatment of AD.

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.

Lactobacillus paracasei Supplementation Prevents Early Life Stress-Induced Anxiety and Depressive-Like Behavior in Maternal Separation Model-Possible Involvement of Microbiota-Gut-Brain Axis in Differential Regulation of MicroRNA124a/132 and Glutamate Receptors

This study was designed to investigate stressful social experience (SSE) in early life by examining how it can induce alterations in the microbiota-gut-brain axis. To test this, different experimental groups of pups experienced the presence of either a stranger (S) with mother (M+P+S) or without their mother (MS+S-M). Animals were assessed for anxiety-like behavior and high-throughput bacterial 16s rRNA sequencing was performed to analyze the structure of the gut microbiota. Our analysis revealed that early life SSE induced anxiety-like behavior and reduced the diversity and richness of gut microbiota. In the second experiment, all groups were supplemented with Lactobacillus paracasei HT6. The findings indicated that Lactobacillus supplementation had a significant beneficial effect on anxiety-like behavior in stressed rats (MS, M+P+S, and MS + S-M) accompanied by normalized levels of adrenocorticotropic hormone (ACTH), corticosterone (CORT), glucocorticoid receptor (GR), serotonin (5-HT), dopamine (DA), and noradrenaline (NA). Concomitantly, the expression of microRNA (miR)-124a was down-regulated and miR-132, caspase-3, glutamate receptors (GluR1, GluR 2; NR2A, and NR2B) were up-regulated in stressed groups but remained unchanged by Lactobacillus supplementation in stressed individuals. This indicates that stress-associated GluR1-GR altered interactions can be significantly prevented by Lactobacillus supplementation. Analysis of the fecal metabolite profile was undertaken to analyze the effect of Lactobacillus, revealing that five predicted neuroactive microbial metabolites were reduced by early life SSE. Our results showed a potential link between Lactobacillus supplementation and beneficial effects on anxiety-like behavior, the mechanism of which could be potentially mediated through stress hormones, neurotransmitters, and expression of miRNAs, glutamate receptors, and the microbiota-gut-brain axis.

MicroRNA-dependent control of neuroplasticity in affective disorders

Affective disorders are a group of neuropsychiatric disorders characterized by severe mood dysregulations accompanied by sleep, eating, cognitive, and attention disturbances, as well as recurring thoughts of suicide. Clinical studies consistently show that affective disorders are associated with reduced size of brain regions critical for mood and cognition, neuronal atrophy, and synaptic loss in these regions. However, the molecular mechanisms that mediate these changes and thereby increase the susceptibility to develop affective disorders remain poorly understood. MicroRNAs (miRNAs or miRs) are small regulatory RNAs that repress gene expression by binding to the 3'UTR of mRNAs. They have the ability to bind to hundreds of target mRNAs and to regulate entire gene networks and cellular pathways implicated in brain function and plasticity, many of them conserved in humans and other animals. In rodents, miRNAs regulate synaptic plasticity by controlling the morphology of dendrites and spines and the expression of neurotransmitter receptors. Furthermore, dysregulated miRNA expression is frequently observed in patients suffering from affective disorders. Together, multiple lines of evidence suggest a link between miRNA dysfunction and affective disorder pathology, providing a rationale to consider miRNAs as therapeutic tools or molecular biomarkers. This review aims to highlight the most recent and functionally relevant studies that contributed to a better understanding of miRNA function in the development and pathogenesis of affective disorders. We focused on in vivo functional studies, which demonstrate that miRNAs control higher brain functions, including mood and cognition, in rodents, and that their dysregulation causes disease-related behaviors.

miR-132 Regulates PTSD-like Behaviors in Rats Following Single-Prolonged Stress Through Fragile X-Related Protein 1

Fragile X-related protein 1 (FXR1) is a member of the fragile X family of RNA-binding proteins, which regulates a number of neurological and neuropsychiatric disorders such as fragile X syndrome, and is expected as a novel therapeutic target for some psychiatric diseases. However, it is unknown how FXR1 changes and functions in post-traumatic stress disorder (PTSD), a common mental disorder related to trauma and stressor. In this study, we characterized the expression pattern of FXR1 in the pathophysiological process of PTSD and further investigated the possible mechanism underlying these changes by finding an upstream regulator, namely miRNA-132 (miR-132). Furthermore, we verified whether miR-132 silence had an effect on the PTSD-like behaviors of single prolonged stress (SPS) rats through open field test, forced swimming test, and water maze test. At last, we examined the expression levels of PSD95 and synapsin I in the hippocampus, which was one of the key brain regions associated with PTSD. We showed that the levels of FXR1 and fragile X mental retardation protein (FMRP), an autosomal homolog of FXR1, were decreased in the hippocampus of PTSD rats, but the levels of PSD95 and synapsin I were increased, which could be reversed by downregulation of miR-132. The results revealed that miR-132 could modulate PTSD-like behaviors in rats following SPS through regulating FXR1 and FMRP.

The social ecology of childhood and early life adversity

An increasing prevalence of early childhood adversity has reached epidemic proportions, creating a public health crisis. Rather than focusing only on adverse childhood experiences (ACEs) as the main lens for understanding early childhood experiences, detailed assessments of a child's social ecology are required to assess "early life adversity." These should also include the role of positive experiences, social relationships, and resilience-promoting factors. Comprehensive assessments of a child's physical and social ecology not only require parent/caregiver surveys and clinical observations, but also include measurements of the child's physiology using biomarkers. We identify cortisol as a stress biomarker and posit that hair cortisol concentrations represent a summative and chronological record of children's exposure to adverse experiences and other contextual stressors. Future research should use a social-ecological approach to investigate the robust interactions among adverse conditions, protective factors, genetic and epigenetic influences, environmental exposures, and social policy, within the context of a child's developmental stages. These contribute to their physical health, psychiatric conditions, cognitive/executive, social, and psychological functions, lifestyle choices, and socioeconomic outcomes. Such studies must inform preventive measures, therapeutic interventions, advocacy efforts, social policy changes, and public awareness campaigns to address early life adversities and their enduring effects on human potential. IMPACT: Current research does not support the practice of using ACEs as the main lens for understanding early childhood experiences. The social ecology of early childhood provides a contextual framework for evaluating the long-term health consequences of early life adversity. Comprehensive assessments reinforced with physiological measures and/or selected biomarkers, such as hair cortisol concentrations to assess early life stress, may provide critical insights into the relationships between early adversity, stress axis regulation, and subsequent health outcomes.

miRNA regulation of social and anxiety-related behaviour

Neuropsychiatric disorders, including autism spectrum disorders (ASD) and anxiety disorders are characterized by a complex range of symptoms, including social behaviour and cognitive deficits, depression and repetitive behaviours. Although the mechanisms driving pathophysiology are complex and remain largely unknown, advances in the understanding of gene association and gene networks are providing significant clues to their aetiology. In recent years, small noncoding RNA molecules known as microRNA (miRNA) have emerged as a new gene regulatory layer in the pathophysiology of mental illness. These small RNAs can bind to the 3'-UTR of mRNA thereby negatively regulating gene expression at the post-transcriptional level. Their ability to regulate hundreds of target mRNAs simultaneously predestines them to control the activity of entire cellular pathways, with obvious implications for the regulation of complex processes such as animal behaviour. There is growing evidence to suggest that numerous miRNAs are dysregulated in pathophysiology of neuropsychiatric disorders, and there is strong genetic support for the association of miRNA genes and their targets with several of these conditions. This review attempts to cover the most relevant microRNAs for which an important contribution to the control of social and anxiety-related behaviour has been demonstrated by functional studies in animal models. In addition, it provides an overview of recent expression profiling and genetic association studies in human patient-derived samples in an attempt to highlight the most promising candidates for biomarker discovery and therapeutic intervention.

MicroRNAs as systemic biomarkers to assess distress in animal models for gastrointestinal diseases

Severity assessment of animal experiments is mainly conducted by using subjective parameters. A widely applicable biomarker to assess animal distress could contribute to an objective severity assessment in different animal models. Here, the distress of three murine animal models for gastrointestinal diseases was assessed by multiple behavioral and physiological parameters. To identify possible new biomarkers for distress 750 highly conserved microRNAs were measured in the blood plasma of mice before and after the induction of pancreatitis. Deregulated miRNA candidates were identified and further quantified in additional animal models for pancreatic cancer and cholestasis. MiR-375 and miR-203 were upregulated during pancreatitis and down regulated during cholestasis, whereas miR-132 was upregulated in all models. Correlation between miR-132 and plasma corticosterone concentrations resulted in the highest correlation coefficient, when compared to the analysis of miR-375, miR-203 and miR-30b. These results indicate that miR-132 might function as a general biomarker for distress, whereas the other miRNAs were altered in a disease specific manner. In conclusion, plasma miRNA profiling may help to better characterize the level of distress in mouse models for gastrointestinal diseases.

Angiotensin (1-7) through modulation of the NMDAR-nNOS-NO pathway and serotonergic metabolism exerts an anxiolytic-like effect in rats

Although recent studies have shown that angiotensin (1-7) (Ang [1-7]) exerts anti-stress and anxiolytic-like effects, the underlying mechanisms remain elusive. The ventral hippocampus (VH) is proposed to be a critical brain region for mood and stress management through the N-methyl-d-aspartate receptor (NMDAR) signaling pathway. However, the role of VH NMDAR signaling in the effects of Ang (1-7) remains unclear. In the present study, Ang (1-7) was injected into the bilateral VH of stressed rats, or in combination with a Fyn kinase inhibitor, NMDAR antagonist, neuronal nitric oxide synthase (nNOS) inhibitor, or nitric oxide (NO) scavenger. Anxiety-like behaviors were assessed using the open field test and elevated plus maze test, while alterations in NMDAR-nNOS-NO signaling and serotonergic metabolism were examined in the VH. After 21 days of chronic restraint stress, anxiety-like behaviors were evident. Levels of phosphorylated NR2B (a key NMDAR subunit), its upstream kinase Fyn, as well as activity of nNOS and monoamine oxidase (MAO) were markedly reduced. In contrast, levels of serotonin were increased. Bilateral VH infusion of Ang (1-7) recovered NMDAR-nNOS-NO signaling and MAO-mediated serotonin metabolism, as well as reducing anxiety-like behaviors in stressed rats. These effects were diminished by blockade of MasR (Ang [1-7]-specific receptor), Fyn kinase, NMDAR, nNOS, or NO production. Altogether, these findings indicate that Ang (1-7) exerts anxiolytic effects through modulation of the NMDAR-nNOS-NO pathway and serotonergic metabolism. Future translational research should focus on the relationship between Ang (1-7), glutamatergic neurotransmission, and serotonergic neurotransmission in the VH.

Advanced paternal age as a risk factor for neurodevelopmental disorders: a translational study

Advanced paternal age (APA) is a risk factor for several neurodevelopmental disorders, including autism and schizophrenia. The potential mechanisms conferring this risk are poorly understood. Here, we show that the personality traits schizotypy and neuroticism correlated with paternal age in healthy subjects (N = 677). Paternal age was further positively associated with gray matter volume (VBM, N = 342) in the right prefrontal and the right medial temporal cortex. The integrity of fiber tracts (DTI, N = 222) connecting these two areas correlated positively with paternal age. Genome-wide methylation analysis in humans showed differential methylation in APA individuals, linking APA to epigenetic mechanisms. A corresponding phenotype was obtained in our rat model. APA rats displayed social-communication deficits and emitted fewer pro-social ultrasonic vocalizations compared to controls. They further showed repetitive and stereotyped patterns of behavior, together with higher anxiety during early development. At the neurobiological level, microRNAs miR-132 and miR-134 were both differentially regulated in rats and humans depending on APA. This study demonstrates associations between APA and social behaviors across species. They might be driven by changes in the expression of microRNAs and/or epigenetic changes regulating neuronal plasticity, leading to brain morphological changes and fronto-hippocampal connectivity, a network which has been implicated in social interaction.

MicroRNA-212 targets SIRT2 to influence lipogenesis in bovine mammary epithelial cell line

In this research paper we filter and verify miRNAs which may target silent information regulator homolog 2 (SIRT2) gene and then describe the mechanism whereby miRNA-212 might regulate lipogenic genes in mammary epithelial cell lines via targeting SIRT2. Bioinformatics analysis revealed that the bovine SIRT2 gene is regulated by three miRNAs: miR-212, miR-375 and miR-655. The three miRNAs were verified and screened by qRT-PCR, western blot, and luciferase multiplex verification techniques and only miR-212 was shown to have a targeting relationship with SIRT2. The results of co-transfecting miR-212 and silencing RNA (siRNA) showed that by targeting SIRT2, miR-212 can regulate the expression of fatty acid synthetase (FASN) and sterol regulatory element binding factor 1 (SREBP1) but not peroxisome proliferator-activated receptor gamma (PPARγ). Measurement of triglyceride (TAG) content showed that miR-212 increased the fat content of mammary epithelial cell lines. The study indicates that miR-212 could target and inhibit the expression of the SIRT2 gene to promote lipogenesis in mammary epithelial cell lines.

The Potential Role of Epigenetic Drugs in the Treatment of Anxiety Disorders

There is increasing evidence that abnormalities in epigenetic mechanisms of gene expression contribute to the pathogenesis of anxiety disorders (ADs). This article discusses the role of epigenetic mechanisms of gene expression in the pathogenesis of ADs. It also discusses the data so far obtained from preclinical and clinical trials on the use of epigenetic drugs for treating ADs. Most drug trials investigating the use of epigenetic drugs for treating ADs have used histone deacetylase inhibitors (HDACi). HDACi are showing favorable results in both preclinical and clinical drug trials for treating ADs. However, at present the mode of action of HDACi in ADs is not clear. More work needs to be done to elucidate how epigenetic dysregulation contributes to the pathogenesis of ADs. More work also needs to be done on the mode of action of HDACi in alleviating the signs and symptoms of ADs.

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.

Gene-Environment Interactions and Role of Epigenetics in Anxiety Disorders

Several environmental risk factors such as early adverse childhood experiences, stress, and stressful life events are associated with anxiety disorders. Current approaches such as epigenetics and gene-environment interactions were used to identify candidate biomarkers for anxiety disorders to assess determinants of disease. In this chapter, in relation to gene-environment interactions, a variety of association studies regarding anxiety disorders were surveyed. We then showed supporting results from recent association studies such as human studies and animal models in terms of the epigenetic contribution to disease susceptibility to anxiety disorders. At last, future directions and limitations are highlighted. With the advances in multi-omics technologies, innovative ideas regarding disease prevention and drug responsiveness in anxiety disorders require further research in epigenetics and gene-environment interactions.

Data highlighting the expression of two miR-132/212 target genes-Sirt1 and Pten-after chronic stress

The data presented here are related to our research article entitled “miR-132/212 is induced by stress and its dysregulation triggers anxiety-related behavior” (Aten et al., 2018). In this article, we utilize immunofluorescent techniques to examine the protein-level expression of two microRNA-132/212 target genes, Sirt1 and Pten, in miR-132 transgenic and miR-132/212 conditional knockout (cKO) mouse lines. Additionally, using immunohistochemistry, we detail the expression profile of Sirt1 and Pten in the hippocampus and amygdala of WT mice after a 15 day chronic restraint stress paradigm.