Activation of proprotein convertase in the mouse habenula causes depressive-like behaviors through remodeling of extracellular matrix

Neuron-non-neuron electrical coupling networks are involved in chronic stress-induced electrophysiological changes in lateral habenular neurons

The lateral habenula (LHb) is a key brain structure that receives input from higher brain regions and regulates monoaminergic activity. LHb hyperactivity has been implicated in the pathophysiology of depression, but the electrophysiological mechanisms underlying this hyperactivity remain poorly understood. To address this issue, we investigated how chronic stress alters the firing properties of LHb neurons in a mouse model of chronic social defeat. Whole-cell recordings were conducted from LHb neurons in the mouse acute brain slices. LHb neurons exhibited two types of rebound depolarizing potentials (RDPs) after the offset of hyperpolarization: short-RDPs (lasting <400 ms) and long-RDPs (order of seconds). Stress-susceptible mice showed a significantly reduced occurrence of long-RDPs, whereas spike firing in response to depolarizing current injections remained unchanged. Both short- and long-RDPs were triggered by T-type voltage-dependent Ca2+ channels and shortened by small-conductance Ca2+-activated K+ (SK) channels. The prolonged depolarizing phase of long-RDPs was mediated by cyclic nucleotide-gated (CNG) channels, which were activated via electrical coupling formed between neurons and non-neuronal cells. Whole-cell recording using an internal solution including a gap junction-permeable dye revealed that neurons formed dye coupling with non-neuronal cells, including oligodendrocytes and/or oligodendrocyte precursor cells. RNA-sequencing and genome editing experiments suggested that Cnga4, a CNG channel subtype, was the primary candidate for the long depolarizing phase of long-RDP, and its expression was decreased in the stress-susceptible mice. These findings suggest that stress-dependent changes in the firing activity of neurons are regulated by neuron-non-neuron networks formed in the LHb. KEY POINTS: Mouse lateral habenular (LHb) neurons exhibit short (<400 ms) rebound depolarizing potentials (short-RDPs) or long-RDPs (order of seconds) (long-RDPs) after the offset of hyperpolarization. The incidence of long-RDP neurons is significantly reduced in mice susceptible to chronic social defeat stress. The long depolarizing phase of long-RDPs is mediated by cyclic nucleotide-gated (CNG) channels, which are activated in non-neuronal cells via gap junctions. The expression of Cnga4, the gene encoding a subtype of the CNG channel, is decreased in the stress-susceptible mice. These results help us understand the mechanisms underlying stress-induced electrophysiological changes in LHb neurons and the functional roles of neuron-non-neuron networks for these neurons.

The disappointment centre of the brain gets exciting: a systematic review of habenula dysfunction in depression

BACKGROUND

The habenula is an epithalamic brain structure that acts as a neuroanatomical hub connecting the limbic forebrain to the major monoamine centres. Abnormal habenula activity is increasingly implicated in depression, with a surge in publications on this topic in the last 5 years. Direct activation of the habenula is sufficient to induce a depressive phenotype in rodents, suggesting a causative role in depression. However, the molecular basis of habenula dysfunction in depression remains elusive and it is unclear how the preclinical advancements translate to the clinical field.

METHODS

A systematic literature search was conducted following the PRISMA guidelines. The two search terms depress* and habenula* were applied across Scopus, Web of Science and PubMed databases. Studies eligible for inclusion must have examined the habenula in clinical cases of depression or preclinical models of depression and compared their measures to an appropriate control.

RESULTS

Preclinical studies (n = 63) measured markers of habenula activity (n = 16) and neuronal firing (n = 22), largely implicating habenula hyperactivity in depression. Neurotransmission was briefly explored (n = 15), suggesting imbalances within excitatory and inhibitory habenula signalling. Additional preclinical studies reported neuroconnectivity (n = 1), inflammatory (n = 3), genomic (n = 3) and circadian rhythm (n = 3) abnormalities. Seven preclinical studies (11%) included both males and females. From these, 5 studies (71%) reported a significant difference between the sexes in at least one habenula measure taken. Clinical studies (n = 24) reported abnormalities in habenula connectivity (n = 15), volume (n = 6) and molecular markers (n = 3). Clinical studies generally included male and female subjects (n = 16), however, few of these studies examined sex as a biological variable (n = 6).

CONCLUSIONS

Both preclinical and clinical evidence suggest the habenula is disrupted in depression. However, there are opportunities for sex-specific analyses across both areas. Preclinical evidence consistently suggests habenula hyperactivity as a primary driver for the development of depressive symptoms. Clinical studies support gross habenula abnormalities such as altered activation, connectivity, and volume, with emerging evidence of blood brain barrier dysfunction, however, progress is limited by a lack of detailed molecular analyses and limited imaging resolution.

Deciphering the role of siRNA in anxiety and depression

Anxiety and depression are central nervous system illnesses that are among the most prevalent medical concerns of the twenty-first century. Patients with this condition and their families bear psychological, financial, and societal hardship. There are currently restrictions when utilizing the conventional course of treatment. RNA interference is expected to become an essential approach in anxiety and depression due to its potent and targeted gene silencing. Silencing of genes by post-transcriptional modification is the mechanism of action of small interfering RNA (siRNA). The suppression of genes linked to disease is typically accomplished by siRNA molecules in an efficient and targeted manner. Unfavourable immune responses, off-target effects, naked siRNA instability, nuclease vulnerability, and the requirement to create an appropriate delivery method are some of the challenges facing the clinical application of siRNA. This review focuses on the use of siRNA in the treatment of anxiety and depression.

Hyperibone J exerts antidepressant effects by targeting ADK to inhibit microglial P2X7R/TLR4-mediated neuroinflammation

INTRODUCTION

The antidepressant properties of Hypericum species are known. Hyperibone J, a principal component found in the flowers of Hypericum bellum, exhibited in vitro anti-inflammatory effects. However, the antidepressant effects and mechanisms of Hyperibone J remain to be elucidated. Adenosine kinase (ADK) is upregulated in epilepsy and depression and has been implicated in promoting neuroinflammation.

OBJECTIVES

This study aimed to explore the impact of Hyperibone J on neuroinflammation-mediated depression and the mechanism underlying this impact.

METHODS

This study employed acute and chronic in vivo depression models and an in vitro LPS-induced depression model using BV-2 microglia. The in vivo antidepressant efficacy of Hyperibone J was assessed through behavioral assays. Techniques such as RNA-seq, western blot, qPCR and ELISA were utilized to elucidate the direct target and mechanism of action of Hyperibone J.

RESULTS

Compared with the model group, depression-like behaviors were significantly alleviated in the Hyperibone J group. Furthermore, Hyperibone J mitigated hippocampal neuroinflammation and neuronal damage. RNA-seq suggested that Hyperibone J predominantly influenced inflammation-related pathways. In vitro experiments revealed that Hyperibone J reversed the LPS-induced overexpression and release of inflammatory factors. Network pharmacology and various molecular biology experiments revealed that the potential binding of Hyperibone J at the ASN-312 site of ADK diminished the stability and protein expression of ADK. Mechanistic studies revealed that Hyperibone J attenuated the ADK/ATP/P2X7R/Caspase-1-mediated maturation and release of IL-1β. The study also revealed a significant correlation between Tlr4 expression and depression-like behaviors in mice. Hyperibone J downregulated ADK, inhibiting Tlr4 transcription, which in turn reduced the phosphorylation of NF-κB and the subsequent transcription of Nlrp3, Il-1b, Tnf, and Il-6.

CONCLUSION

Hyperibone J exerted antineuroinflammatory and antidepressant effects by binding to ADK in microglia, reducing its expression and thereby inhibiting the ATP/P2X7R/Caspase-1 and TLR4/NF-κB pathways. This study provides experimental evidence for the therapeutic potential of Hypericum bellum.

A risk estimation method for depression based on the dysbiosis of intestinal microbiota in Japanese patients

Introduction

Early detection of depression is important for preventing depression-related suicides and reducing the risk of recurrence. This study explored the association between depression and intestinal microbiota and developed a depression risk-estimation method based on this.

Methods

The intestinal microbiota of Japanese patients with depression (33 males and 35 females) and disease-free controls (246 males and 384 females) in their 20's to 60's were compared by sex using 16S rRNA gene amplicon sequencing. A depression-risk estimation method was developed using structural equation modeling.

Results

Intestinal bacteria taxa that differed between depression and control groups were identified based on effect size (absolute value greater than 0.2). Neglecta was more abundant, while Coprobacter, Butyricimonas, Clostridium_XlVb, and Romboutsia were less abundant in the male depression group compared to the male control group. In the female depression group, Massilimicrobiota, Merdimonas, and Sellimonas were more abundant, whereas Dorea and Agathobacter were less abundant compared to the female control group. Several of the intestinal bacterial taxa that were less abundant in depression were associated with butyrate or hydrogen production. Using these depression-associated intestinal bacteria as indicators, risk-estimation models using structural equation modeling for depression were developed. In the risk-estimation models for males and females, the areas under the receiver operating characteristic curve were 0.72 and 0.70, respectively, indicating that these models can distinguish between individuals with and without depression.

Conclusions

This study provides insights into depression etiology and aids in its early detection and treatment.

Chronic non-discriminatory social defeat stress during the perinatal period induces depressive-like outcomes in female mice

Depression is more prevalent in women than in men. Perinatal stress is one of the main risk factors for depression in women. However, there is no suitable female model for perinatal depression that uses the social defeat stress (SDS) paradigm. The standard chronic SDS protocol, which is the most useful method for developing a depression-like model, is effective only in male mice. Thus, this study aimed to characterize a novel SDS method for producing a perinatal depression-like model mouse. We induced chronic SDS in perinatal female mice, wherein chronic non-discriminatory SDS (ND-SDS) was used to induce substantial stress in female mice. The female mice were placed in aggressive ICR mouse cages with sentinel male mice under ND-SDS conditions. Stressed female mice subjected to ND-SDS during the perinatal period efficiently exhibited stress-susceptible phenotypes, such as a social avoidance phenotype and anhedonic behavior, whereas stressed female mice subjected to SDS did not show depressive-like behaviors. These results indicate that chronic ND-SDS in perinatal females could be used to develop a female perinatal depression-like model that can be used to study women's health.

Apoptotic exosome-like vesicles transfer specific and functional mRNAs to endothelial cells by phosphatidylserine-dependent macropinocytosis

Apoptosis of endothelial cells prompts the release of apoptotic exosome-like vesicles (ApoExos), subtype extracellular vesicles secreted by apoptotic cells after caspase-3 activation. ApoExos are different from both apoptotic bodies and classical exosomes in their protein and nucleic acid contents and functions. In contrast to classical apoptotic bodies, ApoExos induce immunogenic responses that can be maladaptive when not tightly regulated. In the present study, we elucidated the mechanisms by which ApoExos are internalized by endothelial cells, which leads to shared specific and functional mRNAs of importance to endothelial function. Using flow cytometry and confocal microscopy, we revealed that ApoExos were actively internalized by endothelial cells. SiRNA-induced inhibition of classical endocytosis pathways with pharmacological inhibitors showed that ApoExos were internalized via phosphatidylserine-dependent macropinocytosis independently of classical endocytosis pathways. An electron microscopy analysis revealed that ApoExos increased the macropinocytosis rate in endothelial cells, setting in motion a positive feedback loop that increased the amount of internalized ApoExos. Deep sequencing of total RNA revealed that ApoExos possessed a unique protein-coding RNA profile, with PCSK5 being the most abundant mRNA. Internalization of ApoExos by cells led to the transfer of this RNA content from the ApoExos to cells. Specifically, PCSK5 mRNA was transferred to cells that had taken up ApoExos, and these cells subsequently expressed PCSK5. Collectively, our findings suggest that macropinocytosis is an effective entry pathway for the delivery of RNAs carried by ApoExos and that these RNAs are functionally expressed by the endothelial cells that internalize them. As ApoExos express a specific mRNA signature, these results suggest new avenues to understand how ApoExos produced at sites of vascular injury impact vascular function.

Cytokine level in patients with mood disorder, alcohol use disorder and their comorbidity

OBJECTIVES

Because alcohol use disorder (AUD) is often accompanied by mood disorder (MD) and both alcoholism and depression result in activation of the immune system, this study compares serum cytokine levels in the presence of co-morbidity with those in either AUD or MD alone.

METHODS

In this naturalistic prospective study the levels of 15 different cytokines were measured in serum samples of patients with MD (n = 43), participants with combined AUD-MD (n = 44) and AUD without MD (n = 42). The levels were compared cross-sectionally among themselves and with those in 50 healthy volunteers.

RESULTS

Pro-inflammatory IFN-2α levels were consistently significantly higher and anti-inflammatory IL-1RA significantly lower in all study groups in comparison to healthy volunteers. In the MD only group we found increased IL-6 (p = 0.001), IL-7 (p = 0.001) and IL-13 (p = 0.006) levels, and decreased TNFα (p = 0.0001), IL-1RA (p = 0.012), IL-10 (p = 0.002) compared with group MD + AUD. Patients with AUD only showed elevated levels of IL-1β (p = 0.046), IL-2 (p = 0.004), IL-7 (p = 0.0001), IL-4 (p = 0.049) and IL-13 (p = 0.015) in contrast with MD + AUD group.

CONCLUSIONS

Because the interactions of alcohol with peripheral and cerebral immune systems are multifaceted, the pertinent connection to the mechanism how alcohol consumption contributes to the development of mood disorders cannot be properly explored.

Neuroinflammation mechanisms of neuromodulation therapies for anxiety and depression

Mood disorders are associated with elevated inflammation, and the reduction of symptoms after multiple treatments is often accompanied by pro-inflammation restoration. A variety of neuromodulation techniques that regulate regional brain activities have been used to treat refractory mood disorders. However, their efficacy varies from person to person and lack reliable indicator. This review summarizes clinical and animal studies on inflammation in neural circuits related to anxiety and depression and the evidence that neuromodulation therapies regulate neuroinflammation in the treatment of neurological diseases. Neuromodulation therapies, including transcranial magnetic stimulation (TMS), transcranial electrical stimulation (TES), electroconvulsive therapy (ECT), photobiomodulation (PBM), transcranial ultrasound stimulation (TUS), deep brain stimulation (DBS), and vagus nerve stimulation (VNS), all have been reported to attenuate neuroinflammation and reduce the release of pro-inflammatory factors, which may be one of the reasons for mood improvement. This review provides a better understanding of the effective mechanism of neuromodulation therapies and indicates that inflammatory biomarkers may serve as a reference for the assessment of pathological conditions and treatment options in anxiety and depression.

Circuits regulating pleasure and happiness - focus on potential biomarkers for circuitry including the habenuloid complex

INTRODUCTION

The multiplicity and complexity of the neuronal connections in the central nervous system make it difficult to disentangle circuits that play an essential role in the development or treatment of (neuro)psychiatric disorders. By choosing the evolutionary development of the forebrain as a starting point, a certain order in the connections can be created. The dorsal diencephalic connection (DDC) system can be applied for the development of biomarkers that can predict treatment response.

MATERIALS AND METHODS

After providing a brief introduction to the theory, we examined neuroanatomical publications on the connectivity of the DDC system. We then searched for neurochemical components that are specific for the habenula.

RESULTS AND DISCUSSION

The best strategy to find biomarkers that reflect the function of the habenular connection is to use genetic variants of receptors, transporters or enzymes specific to this complex. By activating these with probes and measuring the response in people with different functional genotypes, the usefulness of biomarkers can be assessed.

CONCLUSIONS

The most promising biomarkers in this respect are those linked to activation or inhibition of the nicotine receptor, dopamine D4 receptor, μ-opioid receptor and also those of the functioning of habenular glia cells (astrocytes and microglia).