miR-214-3p Targets β-Catenin to Regulate Depressive-like Behaviors Induced by Chronic Social Defeat Stress in Mice

Epigenetic mechanisms in depression: Implications for pathogenesis and treatment

The risk of depression is influenced by both genetic and environmental factors. It has been suggested that epigenetic mechanisms may mediate the risk of depression following exposure to adverse life events. Epigenetics encompasses stable alterations in gene expression that are controlled through transcriptional, post-transcriptional, translational, or post-translational processes, including DNA modifications, chromatin remodeling, histone modifications, RNA modifications, and non-coding RNA (ncRNA) regulation, without any changes in the DNA sequence. In this review, we explore recent research advancements in the realm of epigenetics concerning depression. Furthermore, we evaluate the potential of epigenetic changes as diagnostic and therapeutic biomarkers for depression.

Brain-specific Pd1 deficiency leads to cortical neurogenesis defects and depressive-like behaviors in mice

Embryonic neurogenesis is tightly regulated by multiple factors to ensure the precise development of the cortex. Deficiency in neurogenesis may result in behavioral abnormalities. Pd1 is a well-known inhibitory immune molecule, but its function in brain development remains unknown. Here, we find brain specific deletion of Pd1 results in abnormal cortical neurogenesis, including enhanced proliferation of neural progenitors and reduced neuronal differentiation. In addition, neurons in Pd1 knockout mice exhibit abnormal morphology, both the total length and the number of primary dendrites were reduced. Moreover, Pd1cKO mice exhibit depressive-like behaviors, including immobility, despair, and anhedonia. Mechanistically, Pd1 regulates embryonic neurogenesis by targeting Pax3 through the β-catenin signaling pathway. The constitutive expression of Pax3 partly rescues the deficiency of neurogenesis in the Pd1 deleted embryonic brain. Besides, the administration of β-catenin inhibitor, XAV939, not only rescues abnormal brain development but also ameliorates depressive-like behaviors in Pd1cKO mice. Simultaneously, Pd1 plays a similar role in human neural progenitor cells (hNPCs) proliferation and differentiation. Taken together, our findings reveal the critical role and regulatory mechanism of Pd1 in embryonic neurogenesis and behavioral modulation, which could contribute to understanding immune molecules in brain development.

Enriched Environment Induces Sex-Specific Changes in the Adult Neurogenesis, Cytokine and miRNA Expression in Rat Hippocampus

An enriched environment stimulates adult hippocampal plasticity, but the exact cellular and molecular mechanisms are complex, and thus a matter of debate. We studied the behavior and hippocampal neurogenesis in adult male and female Wistar rats that were housed in an enriched environment (EE) for two months. Both EE males and females performed better than control animals in a Barnes maze, meaning that EE enhances spatial memory. However, the expression levels of neurogenesis markers KI67, DCX, Nestin, and Syn1 increased only in EE females, while in EE males only KI67 and BDNF were higher than in the corresponding control. The number of DCX+ neurons on brain slices increased in the dentate gyrus of EE females only, i.e., the level of adult hippocampal neurogenesis was increased in female but not in male rats. The level of anti-inflammatory IL-10 and signaling pathway components was upregulated in EE females. Of 84 miRNAs tested, in the hippocampi of EE female rats we detected upregulation in the expression levels of 12 miRNAs related to neuronal differentiation and morphogenesis, while in EE males four miRNAs were upregulated and involved in the regulation of cell proliferation/differentiation, and one was downregulated and associated with the stimulation of proliferation. Taken altogether, our results point to sex-specific differences in adult hippocampal plasticity, IL-10 expression, and miRNA profiles induced by an enriched environment.

Thrombospondin1 mimics rapidly relieve depression via Shank3 dependent uncoupling between dopamine D1 and D2 receptors

Deficits in astrocyte function contribute to major depressive disorder (MDD) and suicide, but the therapeutic effect of directly reactivating astrocytes for depression remains unclear. Here, specific gains and losses of astrocytic cell functions in the medial prefrontal cortex (mPFC) bidirectionally regulate depression-like symptoms. Remarkably, recombinant human Thrombospondin-1 (rhTSP1), an astrocyte-secreted protein, exerted rapidly antidepressant-like actions through tyrosine hydroxylase (Th)/dopamine (DA)/dopamine D2 receptors (D2Rs) pathways, but not dopamine D1 receptors (D1Rs), which was dependent on SH3 and multiple ankyrin repeat domains 3 (Shank3) in the mPFC. TSP1 in the mPFC might have potential as a target for treating clinical depression.

Abnormal expression and role of MicroRNA-214-3p/SLC8A1 in neonatal Hypoxic-Ischaemic encephalopathy

Neonatal hypoxic-ischaemic encephalopathy (HIE) refers to brain damage caused by intra-uterine distress and asphyxia/hypoxia during the perinatal and neonatal periods. MicroRNA (MiR)-214-3p plays a critical role in cell growth and apoptosis. The aim of this study was to investigate the expression and role of miR-214-3p in neonatal HIE development, and to explore the underlying mechanisms. The expression of miR-214-3p was significantly down-regulated, while that of Slc8a1, a direct target of miR-214-3p, was significantly up-regulated, in the brain tissue of neonatal HIE rats. The over-expression of miR-214-3p promoted the proliferation and inhibited the apoptosis of neurones, while its down-regulation had the opposite effect. Our results indicate that miR-214-3p expression was down-regulated in neonatal HIE rats, and the up-regulation of miR-214-3p expression protected against HIE development by inhibiting neuronal apoptosis.

A thalamic circuit facilitates stress susceptibility via melanocortin 4 receptor-mediated activation of nucleus accumbens shell

AIMS

Central melanocortin 4 receptor (MC4R) has been reported to induce anhedonia via eliciting dysfunction of excitatory synapses. It is evident that metabolic signals are closely related to chronic stress-induced depression. Here, we investigated that a neural circuit is involved in melanocortin signaling contributing to susceptibility to stress.

METHODS

Chronic social defeat stress (CSDS) was used to develop depressive-like behavior. Electrophysiologic and chemogenetic approaches were performed to evaluate the role of paraventricular thalamus (PVT) glutamatergic to nucleus accumbens shell (NAcsh) circuit in stress susceptibility. Pharmacological and genetic manipulations were applied to investigate the molecular mechanisms of melanocortin signaling in the circuit.

RESULTS

CSDS increases the excitatory neurotransmission in NAcsh through MC4R signaling. The enhanced excitatory synaptic input in NAcsh is projected from PVT glutamatergic neurons. Moreover, chemogenetic manipulation of PVT^Glu -NAcsh projection mediates the susceptibility to stress, which is dependent on MC4R signaling. Overall, these results reveal that the strengthened excitatory neurotransmission in NAcsh originates from PVT glutamatergic neurons, facilitating the susceptibility to stress through melanocortin signaling.

CONCLUSIONS

Our results make a strong case for harnessing a thalamic circuit to reorganize excitatory synaptic transmission in relieving stress susceptibility and provide insights gained on metabolic underpinnings of protection against stress-induced depressive-like behavior.

Long noncoding RNA Gm2694 drives depressive-like behaviors in male mice by interacting with GRP78 to disrupt endoplasmic reticulum homeostasis

Long noncoding RNAs (lncRNAs) are involved in various biological processes and implicated in the regulation of neuronal activity, but the potential role of lncRNAs in depression remains largely unknown. Here, we identified that lncRNA Gm2694 was increased in the medial prefrontal cortex (mPFC) of male mice subjected to chronic social defeat stress (CSDS). The down-regulation of Gm2694 in the mPFC alleviated CSDS-induced depressive-like behaviors through enhanced excitatory synaptic transmission. Furthermore, we found that Gm2694 preferentially interacted with the carboxyl-terminal domain of 78-kilodalton glucose-regulated protein (GRP78), which abrogated GRP78 function and disrupted endoplasmic reticulum homeostasis, resulting in a reduction of the surface expression of AMPA receptors (AMPARs). Overexpression of GRP78 in the mPFC promoted the surface expression of AMPARs and attenuated the CSDS-induced depressive-like behaviors of mice. Together, our results unraveled a previously unknown role of Gm2694 in regulating endoplasmic reticulum homeostasis and excitatory synaptic transmission in depression.

Synaptic plasticity and depression: the role of miRNAs dysregulation

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

A New Player in Depression: MiRNAs as Modulators of Altered Synaptic Plasticity

Depression is a psychiatric disorder that presents with a persistent depressed mood as the main clinical feature and is accompanied by cognitive impairment. Changes in neuroplasticity and neurogenesis greatly affect depression. Without genetic changes, epigenetic mechanisms have been shown to function by regulating gene expression during the body’s adaptation to stress. Studies in recent years have shown that as important regulatory factors in epigenetic mechanisms, microRNAs (miRNAs) play important roles in the development and progression of depression through the regulation of protein expression. Herein, we review the mechanisms of miRNA-mediated neuroplasticity in depression and discus synaptic structural plasticity, synaptic functional plasticity, and neurogenesis. Furthermore, we found that miRNAs regulate neuroplasticity through several signalling pathways to affect cognitive functions. However, these pathways do not work independently. Therefore, we try to identify synergistic correlations between miRNAs and multiple signalling pathways to broaden the potential pathogenesis of depression. In addition, in the future, dual-function miRNAs (protection/injury) are promising candidate biomarkers for the diagnosis of depression, and their regulated genes can potentially be used as target genes for the treatment of depression.

Dysfunction of Glutamatergic Synaptic Transmission in Depression: Focus on AMPA Receptor Trafficking

Pharmacological and anatomical evidence suggests that abnormal glutamatergic neurotransmission may be associated with the pathophysiology of depression. Compounds that act as NMDA receptor antagonists may be a potential treatment for depression, notably the rapid-acting agent ketamine. The rapid-acting and sustained antidepressant effects of ketamine rely on the activation of AMPA receptors (AMPARs). As the key elements of fast excitatory neurotransmission in the brain, AMPARs are crucially involved in synaptic plasticity and memory. Recent efforts have been directed toward investigating the bidirectional dysregulation of AMPAR-mediated synaptic transmission in depression. Here, we summarize the published evidence relevant to the dysfunction of AMPAR in stress conditions and review the recent progress toward the understanding of the involvement of AMPAR trafficking in the pathophysiology of depression, focusing on the roles of AMPAR auxiliary subunits, key AMPAR-interacting proteins, and posttranslational regulation of AMPARs. We also discuss new prospects for the development of improved therapeutics for depression.

Loss of monocarboxylate transporter 1 aggravates white matter injury after experimental subarachnoid hemorrhage in rats

Monocarboxylic acid transporter 1 (MCT1) maintains axonal function by transferring lactic acid from oligodendrocytes to axons. Subarachnoid hemorrhage (SAH) induces white matter injury, but the involvement of MCT1 is unclear. In this study, the SAH model of adult male Sprague-Dawley rats was used to explore the role of MCT1 in white matter injury after SAH. At 48 h after SAH, oligodendrocyte MCT1 was significantly reduced, and the exogenous overexpression of MCT1 significantly improved white matter integrity and long-term cognitive function. Motor training after SAH significantly increased the number of ITPR2⁺SOX10⁺ oligodendrocytes and upregulated the level of MCT1, which was positively correlated with the behavioral ability of rats. In addition, miR-29b and miR-124 levels were significantly increased in SAH rats compared with non-SAH rats. Further intervention experiments showed that miR-29b and miR-124 could negatively regulate the level of MCT1. This study confirmed that the loss of MCT1 may be one of the mechanisms of white matter damage after SAH and may be caused by the negative regulation of miR-29b and miR-124. MCT1 may be involved in the neurological improvement of rehabilitation training after SAH.

miR-98-5p plays a critical role in depression and antidepressant effect of ketamine

Ketamine has been demonstrated to be a rapid-onset and long-lasting antidepressant, but its underlying molecular mechanisms remain unclear. Recent studies have emerged microRNAs as important modulators for depression treatment. In this study, we report that miR-98-5p is downregulated in the prefrontal cortex and hippocampus of mice subjected to chronic social stress, while overexpressing it by its agonist alleviates depression-like behaviors. More importantly, we demonstrate that miR-98-5p is upregulated by ketamine administration, while inhibition of it by its antagonist blocks the antidepressant effect of ketamine. Our data implicate a novel molecular mechanism underlying the antidepressant effect of ketamine, and that therapeutic strategies targeting miR-98-5p could exert beneficial effects for depression treatment.

MicroRNAs, Multiple Sclerosis, and Depression

Multiple sclerosis (MS) is a chronic disease of the central nervous system that affects the brain and spinal cord. There are several disease courses in MS including relapsing–remitting MS (RRMS), primary progressive MS (PPMS), and secondary progressive MS (SPMS). Up to 50% of MS patients experience depressive disorders. Major depression (MD) is a serious comorbidity of MS. Many dysfunctions including neuroinflammation, peripheral inflammation, gut dysbiosis, chronic oxidative and nitrosative stress, and neuroendocrine and mitochondrial abnormalities may contribute to the comorbidity between MS and MD. In addition to these actions, medical treatment and microRNA (miRNA) regulation may also be involved in the mechanisms of the comorbidity between MS and MD. In the study, I review many common miRNA biomarkers for both diseases. These common miRNA biomarkers may help further explore the association between MS and MD.

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.

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

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

Transcription Factor TWIST1 Integrates Dendritic Remodeling and Chronic Stress to Promote Depressive-like Behaviors

BACKGROUND

Deficiency in neuronal structural plasticity is involved in the development of major depressive disorder. TWIST1, a helix-loop-helix transcription factor that is essential for morphogenesis and organogenesis, is normally expressed at low levels in mature neurons. However, it is poorly understood what role TWIST1 plays in the brain and whether it is involved in the pathophysiology of depression.

METHODS

Depressive-like behaviors in C57BL/6J mice were developed by chronic social defeat stress. Genetic and pharmacological approaches were used to investigate the role of the TWIST1-miR-214-PPAR-δ signaling pathway in depressive-like behaviors. Molecular biological and morphological studies were performed to define the molecular mechanisms downstream of TWIST1.

RESULTS

The expression of TWIST1 was positively correlated with depressive behaviors in humans and mice. Chronic stress elevated TWIST1 expression in the medial prefrontal cortex of mice, which was reversed by fluoxetine treatment. While the overexpression of TWIST1 increased susceptibility to stress, the knockdown of TWIST1 prevented the defective morphogenesis of dendrites of pyramidal neurons in layer II/III of the medial prefrontal cortex and alleviated depressive-like behaviors. Mechanistically, this prodepressant property of TWIST1 was mediated, at least in part, through the repression of miR-214-PPAR-δ signaling and mitochondrial function, which was also mimicked by genetic and pharmacological inhibition of PPAR-δ.

CONCLUSIONS

These results suggest that TWIST1 in the medial prefrontal cortex mediates chronic stress-induced dendritic remodeling and facilitates the occurrence of depressive-like behavior, providing new information for developing drug targets for depression therapy.

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

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

Sex-Specific Role for SLIT1 in Regulating Stress Susceptibility

BACKGROUND

Major depressive disorder is a pervasive and debilitating syndrome characterized by mood disturbances, anhedonia, and alterations in cognition. While the prevalence of major depressive disorder is twice as high for women as men, little is known about the molecular mechanisms that drive sex differences in depression susceptibility.

METHODS

We discovered that SLIT1, a secreted protein essential for axonal navigation and molecular guidance during development, is downregulated in the adult ventromedial prefrontal cortex (vmPFC) of women with depression compared with healthy control subjects, but not in men with depression. This sex-specific downregulation of Slit1 was also observed in the vmPFC of mice exposed to chronic variable stress. To identify a causal, sex-specific role for SLIT1 in depression-related behavioral abnormalities, we performed knockdown (KD) of Slit1 expression in the vmPFC of male and female mice.

RESULTS

When combined with stress exposure, vmPFC Slit1 KD reflected the human condition by inducing a sex-specific increase in anxiety- and depression-related behaviors. Furthermore, we found that vmPFC Slit1 KD decreased the dendritic arborization of vmPFC pyramidal neurons and decreased the excitability of the neurons in female mice, effects not observed in males. RNA sequencing analysis of the vmPFC after Slit1 KD in female mice revealed an augmented transcriptional stress signature.

CONCLUSIONS

Together, our findings establish a crucial role for SLIT1 in regulating neurophysiological and transcriptional responses to stress within the female vmPFC and provide mechanistic insight into novel signaling pathways and molecular factors influencing sex differences in depression susceptibility.

Immune function of miR-214 and its application prospects as molecular marker

MicroRNAs are a class of evolutionary conserved non-coding small RNAs that play key regulatory roles at the post-transcriptional level. In recent years, studies have shown that miR-214 plays an important role in regulating several biological processes such as cell proliferation and differentiation, tumorigenesis, inflammation and immunity, and it has become a hotspot in the miRNA field. In this review, the regulatory functions of miR-214 in the proliferation, differentiation and functional activities of immune-related cells, such as dendritic cells, T cells and NK cells, were briefly reviewed. Also, the mechanisms of miR-214 involved in tumor immunity, inflammatory regulation and antivirus were discussed. Finally, the value and application prospects of miR-214 as a molecular marker in inflammation and tumor related diseases were analyzed briefly. We hope it can provide reference for further study on the mechanism and application of miR-214.

Disruption of microRNA-214 during general anaesthesia prevents brain injury and maintains mitochondrial fusion by promoting Mfn2 interaction with Pkm2

Duration of surgical general anaesthesia is associated with severe brain injury and neurological deficits. The specific mechanisms underlying post-general anaesthesia brain injury, however, still remain to be elucidated. Herein, we explore the role of microRNA-214 (miR-214) in the occurrence of brain injury after general anaesthesia and its underlying mechanism. Hippocampal tissues and neurons were isolated from rats exposed to 2% sevoflurane. TUNEL stains reflect hippocampal neuron apoptosis. Cultured hippocampal neurons stained with JC-1 and MitoTracker dyes were imaged by fluorescence microscope to visualize changes of mitochondrial membrane potential and mitochondrial fusion. Mitochondrial function was evaluated. Mitofusin 2 (Mfn2) binding to miR-214 or pyruvate kinase M2 (Pkm2) was confirmed by co-immunoprecipitation, immunofluorescence, dual luciferase reporter gene and RNA immunoprecipitation assays. After exposure to 2% sevoflurane, up-regulated miR-214 expression and impaired interaction between Mfn2 and Pkm2 were found in rat hippocampal tissues. Rats exposed to 2% sevoflurane also experienced neuronal injury, mitochondrial defects and deficits in the brain-derived neurotrophic factor (Bdnf) signalling. miR-214 was shown to target Mfn2 by impairing its binding with Pkm2. Inhibiting miR-214 expression using its specific inhibitor improved mitochondrial membrane potential, enhanced mitochondrial fusion, maintained mitochondrial function, restored interaction between Mfn2 and Pkm2, and activated the Bdnf signalling in cultured hippocampal neurons. Adenovirus infection of miR-214 inhibitor reduced neuron apoptosis and maintained mitochondrial function in the hippocampus of rats exposed to 2% sevoflurane. Taken together, the study demonstrates inhibition of miR-214 is cerebral protective against brain injury following general anaesthesia.

Prefrontal cortex miR-874-3p prevents lipopolysaccharide-induced depression-like behavior through inhibition of indoleamine 2,3-dioxygenase 1 expression in mice

Indoleamine 2,3-dioxygenase 1 (IDO1) is the first rate-limiting enzyme that metabolizes tryptophan to the kynurenine pathway. Its activity is highly inducible by pro-inflammatory cytokines and correlates with the severity of major depressive disorder (MDD). MicroRNAs (miRNAs) are involved in gene regulation and the development of neuropsychiatric disorders including MDD. However, the role of miRNAs in targeting IDO1 in the pathophysiology of MDD is still unknown. In this study, we investigated the role of novel miRNAs in the regulation of IDO1 activity and its effect on lipopolysaccharide (LPS)-induced depression-like behavior in mice. LPS up-regulated miR-874-3p concomitantly with increase in IDO1 expression in the prefrontal cortex (PFC), increase in immobility in the forced swimming test as depression-like behavior and decrease in locomotor activity as sickness behavior without motor dysfunction. The miR-874-3p increased in both neuron and microglia after LPS. Its mimic significantly suppressed LPS-induced IDO1 expression in the PFC. Infusion of IDO1 inhibitor (1-methyl-l-tryptophan) and miR-874-3p into PFC prevented an increase in immobility in the forced swimming test, but did not decrease in locomotor activity induced by LPS. These results suggest that miR-874-3p may play an important role in preventing the LPS-induced depression-like behavior through inhibition of IDO1 expression. This may also serve as a novel potential target molecule for the treatment of MDD.

miR-218 in Adolescence Predicts and Mediates Vulnerability to Stress

BACKGROUND

Adolescence is a period of increased vulnerability to psychiatric disorders, including depression. Discovering novel biomarkers to identify individuals who are at high risk is very much needed. Our previous work shows that the microRNA miR-218 mediates susceptibility to stress and depression in adulthood by targeting the netrin-1 guidance cue receptor gene Dcc in the medial prefrontal cortex (mPFC).

METHODS

Here, we investigated whether miR-218 regulates Dcc expression in adolescence and could serve as an early predictor of lifetime stress vulnerability in male mice.

RESULTS

miR-218 expression in the mPFC increases from early adolescence to adulthood and correlates negatively with Dcc levels. In blood, postnatal miR-218 expression parallels changes occurring in the mPFC. Notably, circulating miR-218 levels in adolescence associate with vulnerability to social defeat stress in adulthood, with high levels associated with social avoidance severity. Indeed, downregulation of miR-218 in the mPFC in adolescence promotes resilience to stress in adulthood.

CONCLUSIONS

miR-218 expression in adolescence may serve both as a marker of risk and as a target for early interventions.

Differential activation of Gsk-3β in the cortex and the hippocampus induces cognitive and behavioural impairments in middle-aged ovariectomized rat

Glycogen synthase kinase-3 (Gsk-3β) aberration act as a crucial pathogenic factor in several neurological conditions. However its role in menopause associated behavioural impairments is still not unclear. The present study was designed to understand the role of Gsk-3β in the progression of neurobehavioural impairments in middle-aged ovariectomized (ovx) rats. The animals showed a significant impairment in spatial and recognition memory, along with anxiety and depression-like behaviour following 22 weeks of ovx. The genomic expression of ERα, ERβ, Nrf2, HO-1, TNFα, and IL-6 was altered in both the cortex and the hippocampus of ovx rats. Protein expression of p-Gsk-3β(Ser⁹) was significantly downregulated in the cortex after ovx. However, the hippocampus showed a surprisingly opposite trend in the levels of p-Gsk-3β(Ser⁹) as that of the cortex. Differential activation of Gsk-3β and its downstream proteins such as β-catenin and p-mTOR were also altered following ovx. The study concluded that differential activation of Gsk-3β, along with oxidative stress and neuroinflammation in the cortex and the hippocampus, leads to the induction of cognitive and behaviour impairments in ovx rats.

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Cognitive and behaviour impairment was displayed by rats after ovariectomy (ovx).

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Estrogen receptors differentially expressed in the cortex and the hippocampus region of ovx rats.

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Differential activation of Gsk-3β was observed in the cortex and the hippocampus after ovx.

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Expression of β-catenin and p-mTOR also altered in both the regions of the rat brain.

Chaperone Sigma1R and Antidepressant Effect

This review analyzes the current scientific literature on the role of the Sigma1R chaperone in the pathogenesis of depressive disorders and pharmacodynamics of antidepressants. As a result of ligand activation, Sigma1R is capable of intracellular translocation from the endoplasmic reticulum (ER) into the region of nuclear and cellular membranes, where it interacts with resident proteins. This unique property of Sigma1R provides regulation of various receptors, ion channels, enzymes, and transcriptional factors. The current review demonstrates the contribution of the Sigma1R chaperone to the regulation of molecular mechanisms involved in the antidepressant effect.

MiR-218: a molecular switch and potential biomarker of susceptibility to stress

Low miR-218 expression in the medial prefrontal cortex (mPFC) is a consistent trait of depression. Here we assessed whether miR-218 in the mPFC confers resilience or susceptibility to depression-like behaviors in adult mice, using the chronic social defeat stress (CSDS) model of depression. We also investigated whether stress-induced variations of miR-218 expression in the mPFC can be detected in blood. We find that downregulation of miR-218 in the mPFC increases susceptibility to a single session of social defeat, whereas overexpression of miR-218 selectively in mPFC pyramidal neurons promotes resilience to CSDS and prevents stress-induced morphological alterations to those neurons. After CSDS, susceptible mice have low levels of miR-218 in blood, as compared with control or resilient groups. We show further that upregulation and downregulation of miR-218 levels specifically in the mPFC correlate with miR-218 expression in blood. Our results suggest that miR-218 in the adult mPFC might function as a molecular switch that determines susceptibility vs. resilience to chronic stress, and that stress-induced variations in mPFC levels of miR-218 could be detected in blood. We propose that blood expression of miR-218 might serve as potential readout of vulnerability to stress and as a proxy of mPFC function.

Serum Level of miR-1 and miR-155 as Potential Biomarkers of Stress-Resilience of NET-KO and SWR/J Mice

In the present study, we used three strains of mice with various susceptibility to stress: mice with knock-out of the gene encoding norepinephrine transporter (NET-KO), which are well characterized as displaying a stress-resistant phenotype, as well as two strains of mice displaying two different stress-coping strategies, i.e., C57BL/6J (WT in the present study) and SWR/J. The procedure of restraint stress (RS, 4 h) was applied, and the following behavioral experiments (the forced swim test and sucrose preference test) indicated that NET-KO and SWR/J mice were less sensitive to RS than WT mice. Then, we aimed to find the miRNAs which changed in similar ways in the serum of NET-KO and SWR/J mice subjected to RS, being at the same time different from the miRNAs found in the serum of WT mice. Using Custom TaqMan Array MicroRNA Cards, with primers for majority of miRNAs expressed in the serum (based on a preliminary experiment using the TaqMan Array Rodent MicroRNA A + B Cards Set v3.0, Thermo Fisher Scientific, Waltham, MA, USA) allowed the identification of 21 such miRNAs. Our further analysis focused on miR-1 and miR-155 and their targets—these two miRNAs are involved in the regulation of BDNF expression and can be regarded as biomarkers of stress-resilience.

Plasma MicroRNA Expression Profiles in Psoriasis

Background

Psoriasis is an immune-mediated inflammatory chronic skin disease characterized by chronic inflammation in the dermis, parakeratosis, and excessive epidermal growth. MicroRNAs (miRNAs) are key regulators of immune responses. Although differential expression of miRNAs has been reported in certain inflammatory autoimmune diseases, their role in psoriasis has not been fully illuminated. Our aims were to confirm plasma miRNA expression signatures in psoriasis and to examine their potential influence on psoriasis pathogenesis.

Methods

A miRNome PCR array was used to analyse the plasma of psoriasis patients and healthy donors. We performed miRNA pathway enrichment and target gene network analyses on psoriasis plasma samples.

Results

We found several specific plasma miRNA signatures relevant to psoriasis. The miRNAs targeted pathways associated with psoriasis, such as the VEGF, MAPK, and WNT signaling pathways. Network analysis revealed pivotal deregulated plasma miRNAs and their relevant target genes and pathways regulating psoriasis pathogenesis.

Conclusions

This study analysed the expression of plasma miRNAs and their target pathways, elucidating the pathogenesis of psoriasis; these results may be used to design novel therapeutic strategies and to identify diagnostic biomarkers for psoriasis.

Activation of EphB2 in the basolateral amygdala promotes stress vulnerability of mice by increasing NMDA-dependent synaptic function

The occurrence of major depressive disorder (MDD) has been linked to an increased vulnerability to stress. The basolateral amygdala (BLA) is one of the critical brain areas that involved in the regulation of pathological reactivity to stress. Increasing evidence indicates that the EphB2 receptor (EphB2) plays a critical role in neuropsychiatric disorders, such as Alzheimer's disease, pain and anxiety. However, whether the EphB2 in the BLA is involved in stress vulnerability is unclear. Here, we identified EphB2 in the BLA as a key regulator contributed to the modulation of stress vulnerability in adult mice. We found that the expression of EphB2 in the BLA was significantly increased in the animal model induced by chronic social stress. Knockdown of EphB2 in the BLA produced antidepressant-like behavioral effects, whereas activation of EphB2 in the BLA increased the susceptibility to subthreshold social defeat stress. Furthermore, we demonstrated that the role of EphB2 in the stress vulnerability was mediated by modulating NMDA receptors, since the knockdown of EphB2 in the BLA prevented not only the increase in the amplitudes of both the miniature and the evoked NMDAR-mediated EPSC, but also the enhancement of surface expression of NMDARs in the defeated mice. Taken together, these results suggest that EphB2 in the BLA is a critical factor contributes to the vulnerability to stress, which may be a potential target for the treatment of depression.

The Role of Circular RNAs in Brain Injury

Circular RNAs are an increasingly important topic in non-coding RNA biology, drawing considerable attention in recent years. Accumulating evidence suggests a critical role for circular RNAs in both early and latent stages of disease pathogenesis. Circular RNAs are abundantly expressed in brain tissue, with significant implications for neural development and disease progression. Disruption of these processes, including those seen in response to brain injury, can have serious consequences such as hemiplegia, aphasia, coma, and death. In this review, we describe the role of circular RNAs in the context of brain injury and explore the potential connection between circular RNAs, brain hypoxic ischemic injury, ischemia-reperfusion injury, and traumatic injury.

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

BACKGROUND

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

METHODS

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

RESULT

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

CONCLUSION

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

Role of non-coding RNA in the pathogenesis of depression

Depression is increasingly threatening human health as a serious psychological problem. However, it is remarkable that the precise mechanism underlying depression remains unelucidated. Recent studies have clarified that non-coding RNA, including but not limited to microRNA, long non-coding RNA, and circular RNA, plays an important role in the pathogenesis of depression. The research results cited in this paper reveal the origin, expression, distribution, function, and mechanism of microRNA in the nervous system. MicroRNA is involved in regulation of life activities, including growth, immune reaction, haematopoiesis, and metabolism, which are significant for maintaining normal physiological functions. Moreover, microRNA plays an important role in cell death and proliferation, development of cancer, and disease prognosis. Here, we also introduce the general research status of long non-coding RNA and circular RNA. Next, descriptive study methods, including fluorescence quantitative polymerase chain reaction, northern blot, microarray technology, RNA-seq, and fluorescent in situ hybridization are discussed. Functional study methods are also summarized and divided into gain- and loss-of-function studies. Moreover, the roles of non-coding RNA in the pathogenesis of depression, including neurogenesis, synaptic plasticity, brain-derived neurotrophic factor expression, HPA axis regulation, neurotransmission, neuropeptide expression, neuro-inflammation, and polyamine synthesis are discussed. Nevertheless, many unknown associations between non-coding RNA and depression remain to be clarified.

Traumatic Stress Produces Delayed Alterations of Synaptic Plasticity in Basolateral Amygdala

Acute traumatic event exposure is a direct cause of post-traumatic stress disorder (PTSD). Amygdala is suggested to be associated with the development of PTSD. In our previous findings, different activation patterns of GABAergic neurons and glutamatergic neurons in early or late stages after stress were found. However, the neural plastic mechanism underlying the role of basolateral amygdala (BLA) in post-traumatic stress disorder remains unclear. Therefore, this study mainly aimed at investigating time-dependent morphologic and electrophysiological changes in BLA during the development of PTSD. We used single prolonged stress (SPS) procedure to establish PTSD model of rats. The rats showed no alterations in anxiety behavior as well as in dendritic spine density or synaptic transmission in BLA 1 day after SPS. However, 10 days after SPS, rats showed enhancement of anxiety behavior, and spine density and frequency of miniature excitatory and inhibitory postsynaptic currents in BLA. Our results suggested that after traumatic stress, BLA displayed delayed increase in both spinogenesis and synaptic transmission, which seemed to facilitate the development of PTSD.

Allicin ameliorates obesity comorbid depressive-like behaviors: involvement of the oxidative stress, mitochondrial function, autophagy, insulin resistance and NOX/Nrf2 imbalance in mice

The increased prevalence of obesity has been a major medical and public health problem in the past decades. In obese status, insulin resistance and sustained oxidative stress damage might give rise to behavioral deficits. The anti-obesity and anti-oxidant effects of allicin have been previously reported in peripheral tissues. In the present study, the functions and mechanisms of allicin involved in the prevention of high-fat diet (HFD)-induced depressive-like behaviors were investigated to better understand the pharmacological activities of allicin. Obese mice (five weeks of age) were treated with allicin (50, 100, and 200 mg/kg) by gavage for 15 weeks and behavioral test (sucrose preference, open field, and tail suspension) were performed. Furthermore, markers of oxidative stress, mitochondrial function, autophagy, and insulin resistance were measured in the hippocampal tissue. Finally, the levels of NADPH oxidase (NOX2, NOX4) and the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway were evaluated in the hippocampus. The body weight, metabolic disorders, and depressive-like behaviors in obese mice were ameliorated by allicin. The depressive-like behaviors presented in the obese mice were accompanied by remarkably excessive reactive oxygen species (ROS) production and oxidative stress, damaged mitochondrial function, imbalanced autophagy, and enhanced insulin resistance in the hippocampus. We found that allicin improved the above undesirable effects in the obese mice. Furthermore, allicin significantly decreased NOX2 and NOX4 levels and activated the Nrf2 pathway. Allicin attenuated depressive-like behaviors triggered by long-term HFD consumption by inhibiting ROS production and oxidative stress, improving mitochondrial function, regulating autophagy, and reducing insulin resistance in the hippocampus via optimization of NOX/Nrf2 imbalance.

MicroRNA-99a is a Potential Target for Regulating Hypothalamic Synaptic Plasticity in the Peri/Postmenopausal Depression Model

Accumulating evidence has demonstrated that there is a growing trend of menopausal women suffering from depression. However, the pathogenesis of menopausal depression still remains unclear. Hence, this paper aims to reveal the pathological mechanisms involved in postmenopausal depression by using a novel peri- to postmenopausal depression model induced by a two-step ovariectomy plus chronic mild stress (CMS). The results of metabolic chambers and serum hormone/cytokine determination revealed that peri/postmenopausal depressive mice exhibited endocrine and metabolic disorders. Electrophysiological recordings indicated that the hippocampal synaptic transmission was compromised. Compared to the sham group, the microRNA-99a (miR-99a) level decreased significantly in the hypothalamus, and its target FK506-binding protein 51 (FKBP51) enormously increased; in contrast, the nuclear translocation of the progesterone receptor (PR) decreased in hypothalamic paraventricular nucleus (PVN) in the peri/postmenopausal depression mouse model. Additionally, synaptic proteins, including postsynaptic density protein 95 (PSD-95) and synaptophysin (SYN), showed a similar decrease in the hypothalamus. Accordingly, the present work suggests that miR-99a may be involved in the regulation of hypothalamic synaptic plasticity and that it might be a potential therapeutic target for peri/postmenopausal depression.

Antidepressive effects of kaempferol mediated by reduction of oxidative stress, proinflammatory cytokines and up-regulation of AKT/β-catenin cascade

Kaempferol (KFL), the major constituent of various fruits and vegetables, could attenuate oxidaitve stress and inflammation. The aims of the present study were to explore the ameliorative abilities of KFL on the depressive-like behaviors in a chronic social defeat stress (CSDS) mouse model, and to determine the potential mechanisms on oxidative stress, neuroinflammation, and AKT/β-catenin signaling pathway. Three behavioral tests, sucrose preference test (SPT), social interaction test (SIT), and tail suspension test (TST), were used to evaluate the antidepressive effects of KFL in CSDS mice. Activity levels of antioxidant enzyme, superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT), glutathione s-transferase (GST), and concentrations of malonaldehyde (MDA) and protein carbonylation in the prefrontal cortex were assessed by commercial kits, respectively. Elisa was used to detect the levels of interleukin-1β (IL-1β) and tumor necrosis factor α (TNF-α). Q-PCR was used to determine the mRNA level of CD-11b. Furthermore, activity level of AKT/β-catenin signaling in the prefrontal cortex of CSDS mice was investigated by western blot. In addition, LY294002, a PI3-K inhibitor, was used to investigate the role of AKT/β-catenin signaling in the antidepressant effects of KFL. Social defeat stress reduced the bodyweights, sucrose consumptions, social interaction times, and the tail suspension mobility times in mice. CSDS mice were also exhibited remarkablely increased levels in oxidative stress markers, inflammatory mediators, and decreased activity of AKT/β-catenin cascade in the prefrontal cortex, which were reversed by treatment with KFL. Interestingly, LY294002 appeared to partly inhibit the overall KFL-mediated protective effects in the CSDS mice. These results confirmed that KFL exerted antidepressive effects, which might be mediated, at least in part, by enhanced antioxidant abilities and anti-inflammation effects via up-regulation AKT/β-catenin cascade activity in the prefrontal cortex of CSDS mice. Thus, KFL might be a promising, effective, and safe food medicine for depression treatment.