Neuroinflammation and Depression: Microglia Activation, Extracellular Microvesicles and microRNA Dysregulation

Microglial cannabinoid receptor 2 and epigenetic regulation: Implications for the treatment of depression

Depression, often stress-induced, is closely related to neuroinflammation, in which microglia, the brain's immune cells, are the leading players. Microglia shift between a quiescent and an active state, promoting both pro- and anti-inflammatory responses. Cannabinoid type 2 (CB2) receptor encoded by the CNR2 gene is a key player to modulate inflammatory activity. CB2 receptor is highly controlled at the epigenetic level, especially in response to stressful stimuli, positioning it between stress, neuroinflammation, and depression. The following review addresses how epigenetic regulation of CNR2 expression affects depression and the dissection, further, of molecular pathways driving neuroinflammation-related depressive states. The present study emphasizes the therapeutic potential of CB2 receptor agonists that selectively interact with activated microglia and opens a new avenue for the treatment of depression associated with neuroinflammation. The review, therefore, provides a framework of underlying mechanisms for developing novel therapeutic strategies that focus on relieving symptoms by modulating the neuroinflammatory response. Finally, this review underlines the possibilities of therapeutic interventions taking into account CB2 receptors in combating depression.

Probiotic Bactolac alleviates depression-like behaviors by modulating BDNF, NLRP3 and MC4R levels, reducing neuroinflammation and promoting neural repair in rat model

Depression, a prevalent psychiatric disorder, exerts severe and debilitating impacts on an individual's mental and physical well-being, and it is considered a chronic mental illness. Chronic stress plays an important role in the pathophysiology of depression. Lactobacillus plantarum and Streptococcus thermophilus are psychobiotic bacteria and synthesize some neurotransmitters that play a role in the pathogenesis of depression. In this study, we aimed to investigate the therapeutic effects of Bactolac (Lactobacillus plantarum NBIMCC 8767  + Streptococcus thermophilus NBIMCC 8258) on chronic stress-induced depression in rats. Behavioral tests, including the sucrose preference test, elevated plus maze test, forced swim test, and three-chamber sociability test, were employed to assess depressive and anxiety-like behaviors. The expression level of the 5-HT1A, DRD1, ADRA-2A, GABA-A α1, CNR1, NR3C2, NOD1, NLRP3 and MC4R; BDNF levels, glial activity and intestinal permeability were determined in chronic stress-induced depression in rats. In conclusions, chronic stress decreased the expression levels of 5-HT1A, DRD1, ADRA-2A, GABA-A α1, CNR1, NR3C2, NOD1 and BDNF level; increased the expression levels of NLRP3 and MC4R, caused neurodegeneration and glial activity, ultimately led to depressive effects. Bactolac was effective in reducing depressive-like behaviors according to the results of behavioral tests. Bactolac treatment provided high neuronal survival rate increasing BDNF level, prevented the excessive release of pro-inflammatory cytokines by reducing the expression levels of NLRP3 and MC4R, therefore, prevented the excessive activation of the hypothalamus-pituitary-adrenal (HPA) axis and accordingly, reduced neurodegeneration and glial cell activation in depressed rats. We can suggest that Bactolac supplementation may be beneficial in coping with stress, alleviate the effects of chronic stress and help to protect mental health.

L1CAM+ extracellular vesicles derived from the serum of adolescents with major depressive disorder induce depression-like phenotypes in adolescent mice

BACKGROUND

It has been reported that L1 cell adhesion molecule (L1CAM) antibody can capture neuron-derived extracellular vesicles (NDEVs) derived from peripheral blood. This antibody is significantly associated with occurrence of adult psychiatric disorders. However, the role and mechanism of L1CAM+ EVs (L1+ EVs) in adolescent with major depressive disorder (AMDD) is not well understood. This research aimed to explore the function and potential mechanism of L1+ EVs and miRNAs genes in AMDD.

METHODS

L1+ EVs derived from the serum of AMDD and healthy controls (HC) were transplanted into adolescent mice via tail vein. Their effects were explored using behavioral tests, hippocampal Nissl staining, and whole genome mRNA sequencing. MiRNAs expression in L1+ EVs was evaluated by whole-genome sequencing and qRT-PCR. Bioinformatics analysis was employed to explore the possible pathogenic molecular mechanisms of these miRNAs in AMDD.

RESULTS

Transplantation of L1+ EVs from AMDD induced depression-like behavior and hippocampal neuronal damage in adolescent mice and aberrant expression of 298 mRNA genes. The molecular signals related to MDD were enriched in the top pathways of the differentially expressed genes. Compared with HC, miR-375-3p and miR-200a-3p were upregulated in L1+ EVs from AMDD, miR-375-3p was also increased in the hippocampus of AMDD serum L1+ EVs-recipient mice. Bioinformatics analysis revealed that miR-375-3p might modulate the network of molecules associated with the MAPK pathway via protein interaction involving hippocampal differential genes Cadm2, Cacna2d1, and Casz1.

CONCLUSION

MiR-375-3p might contribute to L1+ EVs-induced AMDD. L1+ EVs miR-375-3p and miR-200a-3p could potentially serve as potential biomarkers for AMDD.

Cyclophilin A and C are the Main Components of Extracellular Vesicles in Response to Hyperglycemia in BV2 Microglial Cells

Cyclophilins (Cyps) and CD147 receptor play a crucial role in the inflammatory responses. Chronic inflammation causes tissue damage and is a common condition of several inflammation-based pathologies as diabetes or Alzheimer´s disease. Under high glucose (HG) conditions, microglia is activated and releases inflammatory mediators. In this process the role of Cyps is unknown, so this study was aimed to investigate the profile of Cyps in microglia and their release through extracellular vesicles (EVs) under hyperglycemia. An increase in reactive oxygen species (ROS) and nitric oxide (NO) levels was observed when BV2 glia cells were incubated with HG concentration. These effects were mitigated by the Cyps inhibitor cyclosporine A (CsA), suggesting the implication of Cyps in BV2 activation. In these conditions the intracellular expression of CypA, B, C and D, as well as the membrane expression of CD147 receptor was increased. In addition, only CypA and CypC were detected in the extracellular medium. Then, the presence of Cyps inside EVs was explored as an alternative secretion route. Interestingly, under HG treatment, an increase in the levels of the four Cyps in EVs was observed. When neurons were treated with EVs derived from HG-treated glia cells, their viability was reduced and EVs were detected in cytosol neurons pointing to an EVs-Cyps neurotoxic effect. These findings provide novel insights into the relationship between Cyps and EVs in neuroinflammation in hyperglycemia conditions. The current results strengthen the role of Cyps in cell communication and its potential role in brain function under pathological conditions.

Differences in symptom clusters based on multidimensional symptom experience and symptom burden in stroke patients

In the study of stroke symptoms, a significant unresolved issue remains: What are the similarities and differences in the use of three symptom dimensions-occurrence, severity, and distress-and symptom burden to identify symptom clusters, and which level is recommended for constructing symptom clusters? This study aimed to identify the number and types of symptom clusters in stroke patients on the basis of these dimensions and to determine the most suitable dimension for extracting symptom clusters. Data were collected from 656 stroke patients via a convenience sampling method at a tertiary-level hospital in Wuhan, China, between August 2023 and March 2024. Exploratory factor analysis was conducted to extract symptom clusters on the basis of the three dimensions of the symptom experience scale and symptom burden. Four similar symptom clusters were identified: the mood disturbance symptom cluster, the physical symptom cluster, the cognitive dysfunction symptom cluster, and the slurred speech and choking cough symptom cluster. The symptom of "fatigue" within the physical symptom cluster was not identified only in the dimension of distress (with a percentage agreement of 83.3%), whereas the symptom composition of other clusters remained consistent across all three symptom dimensions (with a percentage agreement of 100%). Moreover, all four symptom clusters exhibited high consistency in terms of both occurrence and symptom burden, regardless of whether the symptom with the highest factor loading or the overall symptom composition was considered. The use of symptom occurrence and symptom burden is recommended for identifying symptom clusters in stroke patients. Subsequently, trajectory studies of symptom clusters and symptom network analyses should be conducted on the basis of these two dimensions to establish a solid theoretical foundation for future clinical interventions and related scientific research.

Extracellular vesicles derived from mesenchymal stem cells alleviate depressive-like behavior in a rat model of chronic stress

Depression is a prevalent chronic psychiatric disorder with a growing impact on global health. Current treatments often fail to achieve full remission, highlighting the need for alternative therapeutic strategies. Mesenchymal stem cells (MSCs) have attracted significant interest for their therapeutic potential in neuropsychiatric disorders, primarily due to their capacity to target neuroinflammation. This study aimed to investigate if extracellular vesicles derived from human umbilical MSCs (hucMSCs) promote behavioral beneficial actions in a rat model of chronic unpredictable mild stress (CUMS). We show that a single dose of hucMSCs or their derived EVs (hucMSC-EVs) via the tail vein alleviated depressive-like behavior in rats, reduced markers of neuroinflammation, reduced pro-inflammatory cytokines (IL-1β and TNF-α), and increased the number and dendritic complexity of DCX-positive cells in the dentate gyrus. Proteomic analysis of EVs revealed the presence of proteins involved in modulation of inflammatory processes and cell activation. Our study demonstrates EVs derived from hucMSCs can effectively mitigate depressive symptoms by modulating neuroinflammatory pathways and enhancing neurogenesis. These findings support further exploration of MSC-derived EVs as a novel therapeutic option for neuropsychiatric disorders.

Understanding the Antidepressant Mechanisms of Acupuncture: Targeting Hippocampal Neuroinflammation, Oxidative Stress, Neuroplasticity, and Apoptosis in CUMS Rats

Depression is recognized globally as one of the most intractable diseases, and its complexity and diversity make treatment extremely challenging. Acupuncture has demonstrated beneficial effects in various psychiatric disorders. However, the underlying mechanisms of acupuncture's antidepressant action, particularly in depression, remain elusive. Therefore, this study aimed to investigate the effects of acupuncture on chronic unpredictability stress (CUMS)-induced depressive symptoms in rats and to further elucidate its underlying molecular mechanisms. All rats were exposed to CUMS of two stressors every day for 28 days, except for the control group. One hour before CUMS, rats were given a treatment with acupuncture, electroacupuncture, sham-acupuncture, or fluoxetine (2.1 mg/kg). Behavioral tests and biological detection methods were conducted in sequence to evaluate depression-like phenotype in rats. The findings of this study demonstrate that acupuncture therapy effectively ameliorated depression-like behavior induced by CUMS in rats. Additionally, acupuncture exerted a restorative effect on the alterations induced by CUMS in the levels of malondialdehyde (MDA), catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), interleukin-1β (IL-1β), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), brain-derived neurotrophic factor (BDNF), cyclic AMP response element-binding protein (CREB), postsynaptic density95 (PSD95), gamma-aminobutyric acid (GABA), and acetylcholine (ACh). Additionally, our findings indicate that acupuncture also modulates the ERK and Caspase-3 apoptotic pathways in the hippocampus of CUMS rats. This study suggests that acupuncture may play a potential preventive role by regulating hippocampal neuroinflammatory response, levels of oxidative stress, apoptotic processes, and enhancing synaptic plasticity.

Exosomes enriched with miR-124-3p show therapeutic potential in a new microfluidic triculture model that recapitulates neuron-glia crosstalk in Alzheimer's disease

Background

Alzheimer's disease (AD), a complex neurodegenerative disease associated with ageing, is the leading cause of dementia. Few people with early AD are eligible for the novel Food and Drug Administration (FDA)-approved drug treatments. Accordingly, new tools and early diagnosis markers are required to predict subtypes, individual stages, and the most suitable personalized treatment. We previously demonstrated that the regulation of microRNA (miR)-124 is crucial for proper neuronal function and microglia reshaping in human AD cell models.

Objective

The aim of this study was to develop an efficient miR-124-3p-loaded exosome strategy and validate its therapeutic potential in using a multi-compartment microfluidic device of neuron-glia that recapitulates age-AD pathological features.

Methods and results

Using cortical microglia from mouse pups, separated from glial mixed cultures and maintained for 2 days in vitro (stressed microglia), we tested the effects of SH-SY5Y-derived exosomes loaded with miR-124-3p mimic either by their direct transfection with Exo-Fect™ (ET124) or by their isolation from the secretome of miR-124 transfected cells (CT124). ET124 revealed better delivery effciency and higher potent effects in improving the stressed microglia status than CT124. Tricultures of human SH-SY5Y neuroblastoma cells (SH-WT) were established in the presence of the human microglia cell line (HMC3) and immortalized human astrocytes (IM-HA) in tricompartmentalized microfluidic devices. Replacement of SH-WT cells with those transfected with APP695 (SH-SWE) in the tricultures and addition of low doses of hydrogen peroxide were used to simulate late-onset AD. The system mimicked AD-associated neurodegeneration and neuroinflammation processes. Notably, ET124 exhibited neuroprotective properties across the three cell types in the AD model by preventing neuronal apoptosis and neurite deficits, redirecting microglial profiles towards a steady state, and attenuating the inflammatory and miRNA fingerprints associated with astrocyte reactivity.

Conclusion

To the best of our knowledge, this is the first study supporting the neuro- and immunoprotective properties of miR-124-engineered exosomes in a microfluidic triculture platform, recapitulating age-related susceptibility to AD. Our system offers potential to develop personalized medicines in AD patient subtypes.

Prenatal amoxicillin exposure induces depressive-like behavior in offspring via gut microbiota and myristic acid-mediated modulation of the STING pathway

Amoxicillin is a widely used antibiotic globally, and its pervasive environmental presence poses significant risks to human health and ecosystems. Notably, prenatal amoxicillin exposure (PAmE) may have long-term neurodevelopmental toxicity for offspring. In this study, we investigated the lasting effects of PAmE on depressive-like behaviors in offspring rats, emphasizing the biological mechanisms mediated by changes in gut microbiota and its metabolite, myristic acid. Our results showed that PAmE significantly disrupted the gut microbiota composition in offspring, particularly through the reduction of Lachnospiraceae, leading to decreased levels of myristic acid. This disruption hindered the N-myristoylation of ADP-ribosylation factor 1 (ARF1), impaired the normal degradation of the stimulator of interferon genes protein, inhibited autophagic processes, and promoted M1 polarization of microglia, ultimately leading to depressive-like behaviors in the offspring. Remarkably, supplementation with Lachnospira or myristic acid effectively reversed the PAmE-induced neurodevelopmental and behavioral abnormalities, alleviating depressive-like symptoms. This study reveals how PAmE affects offspring neurodevelopment and behavior through gut microbiota and myristic acid, highlighting the crucial role of the gut-brain axis in the modulation of depressive symptoms. Supplementing Lachnospira or myristic acid could represent a novel strategy to mitigate PAmE-induced fetal-originated depression, providing new biological evidence and potential therapeutic avenues.

Exploring the active components and potential mechanisms of Zhimu-Huangbai herb-pair in the treatment of depression

BACKGROUND

The Zhimu-Huangbai herb-pair (ZB) is commonly used to treat depression. Previous research has verified that ZB is effective as an antidepressant. Nevertheless, its active components and potential mechanism still require further elucidation.

PURPOSE

This study aims to analyze the compounds of ZB penetrating into the brain using UPLC-MS and investigate the potential mechanisms of ZB in the treatment of depression through in vivo and in vitro experiments.

METHODS

The compounds of ZB that penetrate into the brain were identified using the UPLC-MS method. Network pharmacology analysis was employed to predict the therapeutic targets and mechanisms of the compounds of ZB in the brain for the treatment of depression. Subsequently, the molecular docking method was used to analyze the binding between active compounds and target proteins. Rat depression models induced by CUMS were used to investigate the impact of ZB on depression. Finally, the mechanism of ZB treatment for depression was investigated using the LPS-induced BV2 cell inflammation model.

RESULTS

A total of 17 compounds were identified in ZB that crossed the blood-brain barrier (BBB). The network pharmacological analysis showed that the anti-depressant mechanism of ZB is closely related to inflammatory cytokines, including TNF and IL-6. Furthermore, KEGG and PPI analyses demonstrated that ZB regulates the microglia M1/M2 phenotypic polarization by modulating inflammation-related pathways. ZB was found to improve depression-like behavior in vivo. The molecular docking indicated that the compounds in ZB that penetrate into the brain have a strong binding ability to RELA and PPAR-γ. ZB inhibited the expression of p-p65 and increased the expression of PPAR-γ in the mPFC. By rebalancing the ratio of pro-inflammatory/anti-inflammatory cytokines, ZB was able to reduce neuroinflammation in the mPFC and hippocampus regions. The immunofluorescence results showed that ZB-containing serum reduced M1 polarization induced by LPS in BV2 cells.

CONCLUSION

This study reveals that ZB effectively alleviates depression by regulating the M1/M2 phenotypic polarization of microglial cells. The mechanism may be that the active compounds of ZB reduce M1 phenotypic polarization by inhibiting P65 and increase M2 phenotypic polarization by promoting PPARγ.

Non-pharmacological therapeutic paradigms in stress-induced depression: from novel therapeutic perspective with focus on cell-based strategies

Major depressive disorder (MDD) is considered a psychiatric disorder and have a relationship with stressful events. Although the common therapeutic approaches against MDD are diverse, a large number of patients do not present an adequate response to antidepressant treatments. On the other hand, effective non-pharmacological treatments for MDD and their tolerability are addressed. Several affective treatments for MDD are used but non-pharmacological strategies for decreasing the common depression-related drugs side effects have been focused recently. However, the potential of extracellular vesicles (EVs) derived from mesenchymal stem cells (MSCs), microRNAs (miRNAs) as cell-based therapeutic paradigms, besides other non-pharmacological strategies including mitochondrial transfer, plasma, transcranial direct current stimulation (tDCS), transcranial magnetic stimulation (TMS), and exercise therapy needs to further study. This review explores the therapeutic potential of cell-based therapeutic non-pharmacological paradigms for MDD treatment. In addition, plasma therapy, mitotherapy, and exercise therapy in several in vitro and in vivo conditions in experimental disease models along with tDCS and TMS will be discussed as novel non-pharmacological promising therapeutic approaches.

Ectopic expression of the cation-chloride cotransporter KCC2 in blood exosomes as a biomarker for functional rehabilitation

Background

Traumatic brain injury (TBI) is a major cause of disabilities in industrialized countries. Cognitive decline typically occurs in the chronic phase of the condition, following cellular and molecular processes. In this study, we described the use of KCC2, a neuronal-specific potassium-chloride cotransporter, as a potent biomarker to predict cognitive dysfunction after TBI.

Methods

Using neuronal and total exosome collections from the blood serum of the controls and patients with TBI, we were able to anticipate the decline in cognitive performance.

Results

After TBI, we observed a significant and persistent loss of KCC2 expression in the blood exosomes, which was correlated with the changes in the network activity and cellular processes such as secondary neurogenesis. Furthermore, we established a correlation between this decrease in KCC2 expression and the long-term consequences of brain trauma and identified a link between the loss of KCC2 expression and the emergence of depressive-like behavior observed in the mice.

Conclusion

We successfully validated our previous findings, supporting the potential therapeutic benefits of bumetanide in mitigating post-traumatic depression (PTD) following TBI. This effect was correlated with the recovery of KCC2 expression in the blood exosomes, the prevention of extensive neuronal loss among the interneurons, and changes in secondary neurogenesis.

Nobiletin-rich kososan, a Kampo formula, prevents the onset of apathy-like behavior and neuroinflammation in sickness behavior mouse model induced by increasing doses of lipopolysaccharide

Infectious diseases are often concomitant with symptoms of lassitude and emotional disturbances, including depression, the so-called sickness behavior. Kososan, a Kampo (traditional Japanese herbal) formula, has been clinically used for depressive mood, with demonstrated efficacy in stress-induced depressive-like behavior mouse models. Additionally, our previous study has shown that nobiletin-rich kososan (NKS) prevents aging-related depressive-like behaviors and neuroinflammation in mice. Here, we examined whether NKS alleviates depressive-like behavior and neuroinflammation in a mouse model of sickness behavior induced by lipopolysaccharide (LPS). Repeated oral administration of NKS and the positive control antidepressant paroxetine (Paro) significantly prevented this behavior. NKS and Paro significantly increased the anti-inflammatory milieu in the hippocampus and prefrontal cortex (PFC), as well as brain microglia, of LPS-injected mice. The expression of the vascular tight junction protein claudin-5 was also significantly increased by the treatment with NKS, but not with Paro, in the hippocampus and PFC of LPS-injected mice. In vitro analysis using brain microvascular endothelial cells (BMVECs) showed that incubation with 5% serum derived from mice orally administered NKS resulted in a significant increase in the expression of anti-inflammatory heme oxygenase 1 as well as autophagic flux markers. Moreover, the claudin-5 levels in BMVECs were also increased under LPS-stimulated conditions. These results suggest that NKS exerts prophylactic effects against the LPS-induced apathy-like behavior, partly mediated by the increase in the anti-inflammatory milieu and in the levels of tight junction proteins in the brain. This study provides scientific evidence supporting the potential efficacy of NKS in preventing post-infection depression.

MicroRNA-specific targets for neuronal plasticity, neurotransmitters, neurotrophic factors, and gut microbes in the pathogenesis and therapeutics of depression

Depression is of great concern because of the huge burden, and it is impacted by various epigenetic modifications, e.g., histone modification, covalent modifications in DNA, and silencing mechanisms of non-coding protein genes, e.g., microRNAs (miRNAs). MiRNAs are a class of endogenous non-coding RNAs. Alternations in specific miRNAs have been observed both in depressive patients and experimental animals. Also, miRNAs are highly expressed in the central nervous system and can be delivered to different tissues via tissue-specific exosomes. However, the mechanism of miRNAs' involvement in the pathological process of depression is not well understood. Therefore, we summarized and discussed the role of miRNAs in depression. Conclusively, miRNAs are involved in the pathology of depression by causing structural and functional changes in synapses, mediating neuronal regeneration, differentiation, and apoptosis, regulating the gut microbes and the expression of various neurotransmitters and BDNF, and mediating inflammatory and immune responses. Moreover, miRNAs can predict the efficacy of antidepressant medications and explain the mechanism of action of antidepressant drugs and aerobic exercise to prevent and assist in treating depression.

A Cross-Sectional Trait Versus State Biomarker Analysis of Inflammatory Cytokines and miRNAs in Patients with Major Depressive Disorder

Background

Inflammatory cytokines are associated with the pathophysiology of major depressive disorder (MDD). Nevertheless, whether they are trait or state biomarkers remains unclear. We aimed to assess and compare selected cytokines, miRNAs, and oxidative stress biomarker levels between patients with MDD, first-degree relatives (FDRs), and unrelated healthy controls (UHCs).

Methods

Using a cross-sectional design, we recruited patients with MDD, their FDRs and age, gender, body mass index-matched UHCs. Serum levels of IL-6, IL-1β, TNF-α, hs-CRP, and IL-10 were evaluated using the Enzyme-Linked Immunosorbent Assay (ELISA) method. We quantified the gene expressions of plasma miR-16, miR-132, and miR-1202 using Quantitative Real Time-Polymerase Chain Reaction (qRT-PCR). We estimated the total oxidant status and total antioxidant status levels in the serum by ELISA. We used sequential multiple linear regression analysis to find the association between MDD vs. UHCs (model 1), FDRs vs. UHCs (model 2), and MDD vs. FDRs (model 3) after adjusting for age, gender, and BMI as covariates.

Results

The study involved 50 patients with MDD (mean age = 34.7 ± 10.1 years), 31 FDRs (mean age = 32.7 ± 12.2 years), and 50 UHCs (mean age = 34.1 ± 10.3 years). Patients with MDD had higher levels IL-6 (β = 6.04; 95% CI; 1.60 to 10.49; p = 0.008) and downregulated miR-1202 (β = -0.38; 95% CI: -0.70 to -0.06; p = 0.02) compared to FDRs with statistically significant differences.

Conclusion

The higher levels of serum IL-6 and downregulated plasma miR-1202 expression in patients with MDD compared to FDRs may be a state biomarkers in MDD. However, an adequately powered study can answer these questions with certainty.

Therapeutic effects of exercise on depression: The role of microglia

Major depressive disorderadversely affects mental health. Traditional therapeutic approaches, including medication, psychological intervention, and physical therapy, exert beneficial effects on depression. However, these approaches are associated with some limitations, such as high cost, adverse reactions, recurrent episodes, and low patient adherence. Previous studies have demonstrated that exercise therapy can effectively mitigate depressive symptoms, although the underlying mechanism has not been elucidated. Recent studies have suggested that depression is a microglial disease. Microglia regulate the inflammatory response, synaptic plasticity, neurogenesis, kynurenine pathway and the activation of hypothalamic-pituitary-adrenal axis, all of which affect depression. Exercise therapy is reported to shift the balance of microglial M1/M2 polarization in the hippocampus, frontal lobe, and striatum, suppressing the release of pro-inflammatory factors and consequently alleviating behavioral deficits in animal models of depression. Further studies are needed to examine the specific effects of different exercise regimens on microglia to identify the exercise regimen with the best therapeutic effect.

Research progress on astrocyte-derived extracellular vesicles in the pathogenesis and treatment of neurodegenerative diseases

Neurodegenerative disorders, including Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), and Huntington's disease (HD), pose significant global health risks and represent a substantial public health concern in the contemporary era. A primary factor in the pathophysiology of these disorders is aberrant accumulation and aggregation of pathogenic proteins within the brain and spinal cord. Recent investigations have identified extracellular vesicles (EVs) in the central nervous system (CNS) as potential carriers for intercellular transport of misfolded proteins associated with neurodegenerative diseases. EVs are involved in pathological processes that contribute to various brain disorders including neurodegenerative disorders. Proteins linked to neurodegenerative disorders are secreted and distributed from cell to cell via EVs, serving as a mechanism for direct intercellular communication through the transfer of biomolecules. Astrocytes, as active participants in CNS intercellular communication, release astrocyte-derived extracellular vesicles (ADEVs) that are capable of interacting with diverse target cells. This review primarily focuses on the involvement of ADEVs in the development of neurological disorders and explores their potential dual roles - both advantageous and disadvantageous in the context of neurological disorders. Furthermore, this review examines the current studies investigating ADEVs as potential biomarkers for the diagnosis and treatment of neurodegenerative diseases. The prospects and challenges associated with the application of ADEVs in clinical settings were also comprehensively reviewed.

Hypothyroidism Promotes Microglia M1 Polarization by Inhibiting BDNF-Promoted PI3K-Akt Signaling Pathway

INTRODUCTION

Hypothyroidism and its induced neurological-associated disorders greatly affect the health-related quality of patients' life. Meanwhile, microglia in brain have essential regulatory functions on neurodegeneration, but the underlying link between hypothyroidism and microglia function is largely ambiguous.

METHODS

We deciphered how hypothyroidism modulates the polarization of microglia by constructing methimazole-induced mice model and checking the expression pattern of biomarkers of microglia M1 polarization. Then, we used lipopolysaccharide (LPS)-treated BV2 cells to explore the effecting factors on microglia M1 polarization. Finally, global transcriptome sequencing (RNA-seq) was utilized to identify the underlying regulatory mechanisms.

RESULTS

We detected that biomarkers of microglia M1 polarization and pro-inflammatory cytokines were significantly increased in hypothyroidism mice brain; hypothyroidism could also repress the expression of BDNF and TrkB, and the anti-inflammatory cytokine such as IL-10. In BV2 cells, LPS treatment decreased expression of BDNF, IL-10, and Arg1, while BDNF overexpression (BDNF-OE) significantly reversed the inflammation induced by LPS. BDNF-OE significantly repressed expression of iNOS and TNF-α, but increased expression of IL-10 and Arg1. For mechanism, RNA-seq analysis demonstrated that BDNF-OE could globally regulate transcriptome profile by affecting gene expression. In LPS-treated BV2 cells, BDNF-OE significantly altered expression pattern of genes involved in PI3K-Akt signaling pathway, including Thbs3, Myc, Gdnf, Thbs1, and Ccnd1 as upregulated genes, and Gnb4, Fgf22, Pik3r3, Pgf, Cdkn1a, and Pdgfra as downregulated genes. Myc, Gdnf, Thbs1, and Ccnd1 showed much higher expression levels than other genes in PI3K-Akt signaling pathway and could be promising targets of BDNF in reversing microglia M1 polarization.

CONCLUSION

Our study demonstrated a sound conclusion that hypothyroidism promotes microglia M1 polarization by inhibiting BDNF expression in brain; BDNF could inhibit the M1 polarization of microglia by activating PI3K-Akt signaling pathway, which could serve as a promising therapeutic target for microglia-induced neurodegenerative or emotional disorders in future.

INTRODUCTION

Hypothyroidism and its induced neurological-associated disorders greatly affect the health-related quality of patients' life. Meanwhile, microglia in brain have essential regulatory functions on neurodegeneration, but the underlying link between hypothyroidism and microglia function is largely ambiguous.

METHODS

We deciphered how hypothyroidism modulates the polarization of microglia by constructing methimazole-induced mice model and checking the expression pattern of biomarkers of microglia M1 polarization. Then, we used lipopolysaccharide (LPS)-treated BV2 cells to explore the effecting factors on microglia M1 polarization. Finally, global transcriptome sequencing (RNA-seq) was utilized to identify the underlying regulatory mechanisms.

RESULTS

We detected that biomarkers of microglia M1 polarization and pro-inflammatory cytokines were significantly increased in hypothyroidism mice brain; hypothyroidism could also repress the expression of BDNF and TrkB, and the anti-inflammatory cytokine such as IL-10. In BV2 cells, LPS treatment decreased expression of BDNF, IL-10, and Arg1, while BDNF overexpression (BDNF-OE) significantly reversed the inflammation induced by LPS. BDNF-OE significantly repressed expression of iNOS and TNF-α, but increased expression of IL-10 and Arg1. For mechanism, RNA-seq analysis demonstrated that BDNF-OE could globally regulate transcriptome profile by affecting gene expression. In LPS-treated BV2 cells, BDNF-OE significantly altered expression pattern of genes involved in PI3K-Akt signaling pathway, including Thbs3, Myc, Gdnf, Thbs1, and Ccnd1 as upregulated genes, and Gnb4, Fgf22, Pik3r3, Pgf, Cdkn1a, and Pdgfra as downregulated genes. Myc, Gdnf, Thbs1, and Ccnd1 showed much higher expression levels than other genes in PI3K-Akt signaling pathway and could be promising targets of BDNF in reversing microglia M1 polarization.

CONCLUSION

Our study demonstrated a sound conclusion that hypothyroidism promotes microglia M1 polarization by inhibiting BDNF expression in brain; BDNF could inhibit the M1 polarization of microglia by activating PI3K-Akt signaling pathway, which could serve as a promising therapeutic target for microglia-induced neurodegenerative or emotional disorders in future.

The Role of Extracellular Vesicles and Microparticles in Central Nervous System Disorders: Mechanisms, Biomarkers, and Therapeutic Potential

Microscopic, membranous vesicles known as extracellular vesicles (EVs) have been proposed to play a role in the mechanisms underlying central nervous system (CNS) diseases. EVs are secreted by a variety of cells, including myeloid, endothelial, microglial, oligodendroglial, and mesenchymal stem cells (MSCs). Body fluids such as plasma, urine, and cerebrospinal fluid (CSF) contain microparticles (MPs). The detection of MPs in CSF may indicate genetic or environmental susceptibility to conditions such as schizophrenia, schizoaffective disorder, and bipolar disorder. MPs of different origins can exhibit changes in specific biomarkers at various stages of the disease, aiding in the diagnosis and monitoring of neurological conditions. However, understanding the role and clinical applications of MPs is complicated by challenges such as their isolation and dual roles within the CNS. In this review, we discuss the history, characteristics, and roles of MPs in CNS diseases. We also provide practical insights for future research and highlight the challenges that obscure the therapeutic potential of MPs.

Association of HHV‑6 reactivation and SLC6A3 (C>T, rs40184), BDNF (C>T, rs6265), and JARID2 (G>A, rs9383046) single nucleotide polymorphisms in depression

Major depressive disorder (MDD) is a global health concern with a complex etiology involving genetic, environmental and infectious factors. The exact cause of MDD remains unknown. The present study explored the association between genetic factors, human herpesvirus 6 (HHV-6) and MDD. The present study analyzed single nucleotide polymorphisms (SNPs) and HHV-6 viral load in oral buccal samples from patients with MDD (with and without blood relatives with MDD) and healthy controls. The study used high-resolution melt analysis to examine rs40184 (C>T) in the solute carrier family 6 member 3 (SLC6A31) gene, rs6265 (C>T) in the brain-derived neurotrophic factor (BDNF) gene and rs9383046 (G>A) in the jumonji and AT-rich interaction domain-containing 2 (JARID2) gene. HHV-6 infection and viral load was assessed using the quantitative PCR. Whole-exome sequencing was used to examine SNPs. The variant alleles of SNPs rs40184 [18/40 (45.00) vs. 29/238 (12.55%)] and rs6265 [30/54 (55.46) vs. 117/292 (40.06%)] were significantly more common in patients with MDD than in healthy controls, indicating they may be probable hereditary risk factors for MDD. HHV-6 positivity was significantly more common in carriers of the G/A genotype (12/15, 80%) than carriers of the G/G genotype (75/363, 20.7%) for rs9383046, implying that genetic variations may affect HHV-6 risk and MDD onset. Similarly, HHV-6 viral loads were significantly higher in carriers of the G/A genotype (99,990.85±118,392.64 copies/ng DNA) than carriers of the G/G genotype (48,249.30±101,216.28 copies/ng DNA) for rs9383046. Whole-exome sequencing identified two SNPs in JARID2 (rs11757092 and rs9383050) associated with MDD, highlighting its genetic complexity. The present study helps explain the complex interactions between HHV-6 infection, genetics and MDD onset, improving understanding of how SNPs in JARID2 contribute to HHV-6 infection and MDD onset; these findings may impact future approaches to diagnosing and treating MDD.

Understanding Aβ25-35 peptide altered exosomal proteome and associated pathways linked with the Alzheimer's disease pathogenesis using human neuroblastoma SH-SY5Y Cells

The central nervous system (CNS) involves a complex interplay of communications between the neurons and various glial cells, which is crucial for brain functions. The major interactomes are exosomes that transmit sundry molecules (DNA, miRNAs, and proteins) between the cells and thus alter cell physiology. Exosomes can act as neuroprotective or neurodegenerative agents depending on the microenvironment of cells secreting them. Therefore, revealing exosome proteome becomes important to understand donor cells' physiology and its effect on the recipient cell. In this study, oxidative stress was induced by Aβ25-35 in the human neuroblastoma SH-SY5Y cells and the protective effects of phytochemical ferulic acid (FA) were evaluated alone and in combination with Aβ25-35 (pre-treated for 3 h before Aβ25-35 exposure) and proteome of their secreted exosomes was analyzed, which was carried out via a high-resolution LC-MS Triple-ToF and further network-based analysis has been carried out using various bioinformatics tools. The proteomic profiling enlightened the multiple roles of exosomes as proteins associated with the various pathways advocate that exosomes can mediate a wide range of effects, from normal physiological processes like synaptic plasticity, neuronal metabolic support, nerve regeneration, DNA repair, axon guidance, and long-term potentiation (LTP) to abnormal pathological processes like inflammatory responses, oxidative stress, apoptosis, and formation of neutrophil extracellular traps (NETs). On comparison, treatment with Aβ25-35 resulted in a significant modulation of the exosomal proteome, promoting pathways associated with neurodegeneration. Conversely, the phytochemical FA displayed a protective effect by effectively countering Aβ25-35-induced oxidative stress responses linked with neurodegeneration, as seen in Alzheimer's disease (AD). Taken together, this study highlights the dual role of exosomes in physiological and pathophysiological neurodegenerative AD, which intricately depend on the particular cellular milieu.

Milk derived extracellular vesicle uptake in human microglia regulates the DNA methylation machinery : Short title: milk-derived extracellular vesicles and the epigenetic machinery

Mammalian milk contains milk-derived extracellular vesicles (MEVs), a group of biological nanovesicles that transport macromolecules. Their ability to cross the blood brain barrier and the presence of cargo capable of modifying gene function have led to the hypothesis that MEVs may play a role in brain function and development. Here, we investigated the uptake of MEVs by human microglia cells in vitro and explored the functional outcomes of MEV uptake. We examined the expression of the miR-148/152 family, highly abundant MEV microRNAs, that directly suppress the translation of DNA methyltransferase (DNMT) enzymes crucial for catalyzing DNA methylation modifications. We also measured phenotypic and inflammatory gene expression in baseline homeostatic and IFN-γ primed microglia to determine if MEVs induce anti-inflammatory effects. We found that MEVs are taken up and localize in baseline and primed microglia. In baseline microglia, MEV supplementation reduced miR-148a-5P levels, increased DNMT1 transcript, protein abundance, and enzymatic activity, compared to cells that did not receive MEVs. In primed microglia, MEV supplementation decreased miR-148a-5P levels and increased DNMT1 protein abundance, but DNMT1 transcript and enzymatic levels remained unchanged. Contrary to predictions, MEV supplementation failed to attenuate pro-inflammatory IL1β expression in primed microglia. This study provides the first evidence of MEV uptake by a brain macrophage, suggesting a potential role in regulating epigenetic machinery and neuroimmune modulation.

The Yin and Yang of Microglia-Derived Extracellular Vesicles in CNS Injury and Diseases

Microglia, the resident immune cells of the central nervous system (CNS), play a crucial role in maintaining neural homeostasis but can also contribute to disease and injury when this state is disrupted or conversely play a pivotal role in neurorepair. One way that microglia exert their effects is through the secretion of small vesicles, microglia-derived exosomes (MGEVs). Exosomes facilitate intercellular communication through transported cargoes of proteins, lipids, RNA, and other bioactive molecules that can alter the behavior of the cells that internalize them. Under normal physiological conditions, MGEVs are essential to homeostasis, whereas the dysregulation of their production and/or alterations in their cargoes have been implicated in the pathogenesis of numerous neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's disease (PD), multiple sclerosis (MS), spinal cord injury (SCI), and traumatic brain injury (TBI). In contrast, MGEVs may also offer therapeutic potential by reversing inflammation or being amenable to engineering for the delivery of beneficial biologics or drugs. The effects of MGEVs are determined by the phenotypic state of the parent microglia. Exosomes from anti-inflammatory or pro-regenerative microglia support neurorepair and cell survival by delivering neurotrophic factors, anti-inflammatory mediators, and molecular chaperones. Further, MGEVs can also deliver components like mitochondrial DNA (mtDNA) and proteins to damaged neurons to enhance cellular metabolism and resilience. MGEVs derived from pro-inflammatory microglia can have detrimental effects on neural health. Their cargo often contains pro-inflammatory cytokines, molecules involved in oxidative stress, and neurotoxic proteins, which can exacerbate neuroinflammation, contribute to neuronal damage, and impair synaptic function, hindering neurorepair processes. The role of MGEVs in neurodegeneration and injury-whether beneficial or harmful-largely depends on how they modulate inflammation through the pro- and anti-inflammatory factors in their cargo, including cytokines and microRNAs. In addition, through the propagation of pathological proteins, such as amyloid-beta and alpha-synuclein, MGEVs can also contribute to disease progression in disorders such as AD and PD, or by the transfer of apoptotic or necrotic factors, they can induce neuron toxicity or trigger glial scarring during neurological injury. In this review, we have provided a comprehensive and up-to-date understanding of the molecular mechanisms underlying the multifaceted role of MGEVs in neurological injury and disease. In particular, the role that specific exosome cargoes play in various pathological conditions, either in disease progression or recovery, will be discussed. The therapeutic potential of MGEVs has been highlighted including potential engineering methodologies that have been employed to alter their cargoes or cell-selective targeting. Understanding the factors that influence the balance between beneficial and detrimental exosome signaling in the CNS is crucial for developing new therapeutic strategies for neurodegenerative diseases and neurotrauma.

Fructus Arctii Mitigates Depressive Disorder via the Let-7e-Modulated Toll-Like Receptor (TLR) Signaling Pathway

BACKGROUND

Depressive disorder is a common and serious public health challenge globally. Fructus arctii is a traditional medicinal plant ingredient with diverse pharmacological effects. This study aimed to investigate the therapeutic potential of Fructus arctii in alleviating depressive-like behaviors.

MATERIALS AND METHODS

We established a chronic unpredictable mild stress (CUMS)-induced depression mouse model to assess the antidepressant effects of Fructus arctii. BV2 cells treated with lipopolysaccharide (LPS) were used to mimic neuronal damage. Behavioral tests, including the sucrose preference test, tail-suspension test, and forced swim test, were conducted to evaluate the impact of Fructus arctii on depressive-like behaviors. Let-7e expression was detected by RT-qPCR, and TLR4 signaling pathway activation was evaluated by western blot analysis, which also assessed the inflammatory response by measuring levels of IL-6, IL-1β, MCP-1, TNF-α, and iNOS. Immunohistological analysis was conducted to detect the expression of microglia markers. Luciferase reporter assays verified the interaction between let-7e and TLR4.

RESULTS

Fructus arctii administration effectively alleviated depressive-like behaviors induced by CUMS in mice, as evidenced by improved sucrose preference and reduced immobility time in behavioral tests. Mechanistically, Fructus arctii reversed the CUMS-induced downregulation of let-7e and upregulation of TLR4 and MyD88 protein levels in mice hippocampus tissues. In addition, Fructus arctii suppressed microglial activation and reduced the levels of inflammatory factors by upregulating let-7e. Let-7e was verified to bind to TLR4, thereby negatively regulating its expression. TLR4 overexpression reversed the suppressive effect of let-7e upregulation on inflammatory reactions and microglial activation. Furthermore, intracerebroventricular injection of let-7e agomiR alleviated depressive-like behavior and inhibited microglial activation in vivo.

CONCLUSION

In summary, Fructus arctii mitigates depression by regulating the let-7e/TLR4/MyD88 pathway, offering new insights into potential depression therapies.

Rehmannia glutinosa DC.-Lilium lancifolium Thunb. in the treatment of depression: a comprehensive review and perspectives

Background

In recent years, the incidence of depression, recognized as a serious psychological disorder, has escalated rapidly. Rehmannia glutinosa DC. (Scrophulariaceae; Rehmanniae Radix, Crude drug) and Lilium lancifolium Thunb. (Liliaceae; Lilii bulbus, Crude drug) constitute a classic anti-depressant combination, exhibiting pharmacological effects that include anti-depressive, anti-anxiety, and anti-inflammatory properties. Current clinical studies have demonstrated that Baihe Dihuang Decoction, a traditional Chinese herbal compound, is effective in treating depression. However, the majority of scholars have predominantly examined Rehmannia glutinosa and Lilium in isolation, and a comprehensive elucidation of their principal active metabolites and pharmacological mechanisms remains lacking.

Methods

A comprehensive literature search was conducted as of 29 September 2024, utilizing databases such as PubMed, CNKI, Wanfang Data, Baidu Scholar, and Google Scholar. Additionally, classical texts on Chinese herbal medicine, the Chinese Pharmacopoeia, as well as doctoral and master's theses, were included in the collected materials. The search employed specific terms including "R. glutinosa," "Lilium," "Baihe Dihuang decoction," "application of Baihe Dihuang decoction," "pathogenesis of depression," and "pharmacological action and mechanism of depression.

Results

This paper reviewed the traditional applications and dosages of the R. glutinosa-Lilium as documented in Chinese medical classics, thereby establishing a foundation for the contemporary development and clinical application of the classical formula Baihe Dihuang Decoction. Additionally, recent years have seen a comprehensive review of the pharmacological effects and mechanisms of R. glutinosa-Lilium and its principal metabolites in the context of depression.

Conclusion

This paper has reviewed the active metabolites of R. glutinosa-Lilium and demonstrated its efficacy in the treatment of depression, as well as its role in modulating the underlying mechanisms of the disorder. The findings aim to serve as a reference for further research into the mechanisms of depression, its clinical applications, and the development of novel therapeutic agents.

Omega-3 Fatty Acids and Neuroinflammation in Depression: Targeting Damage-Associated Molecular Patterns and Neural Biomarkers

Major Depressive Disorder (MDD) is a prevalent mental health condition with a complex pathophysiology involving neuroinflammation, neurodegeneration, and disruptions in neuronal and glial cell function. Microglia, the innate immune cells of the central nervous system, release inflammatory cytokines in response to pathological changes associated with MDD. Damage-associated molecular patterns (DAMPs) act as alarms, triggering microglial activation and subsequent inflammatory cytokine release. This review examines the cellular mechanisms underlying MDD pathophysiology, focusing on the lipid-mediated modulation of neuroinflammation. We explore the intricate roles of microglia and astrocytes in propagating inflammatory cascades and discuss how these processes affect neuronal integrity at the cellular level. Central to our analysis are three key molecules: High Mobility Group Box 1 (HMGB1) and S100 Calcium Binding Protein β (S100β) as alarmins, and Neuron-Specific Enolase (NSE) as an indicator of neuronal stress. We present evidence from in vitro and ex vivo studies demonstrating how these molecules reflect and contribute to the neuroinflammatory milieu characteristic of MDD. The review then explores the potential of omega-3 polyunsaturated fatty acids (ω-3 PUFAs) as neuroinflammation modulators, examining their effects on microglial activation, cytokine production, and neuronal resilience in cellular models of depression. We critically analyze experimental data on how ω-3 PUFA supplementation influences the expression and release of HMGB1, S100β, and NSE in neuronal and glial cultures. By integrating findings from lipidomic and cellular neurobiology, this review aims to elucidate the mechanisms by which ω-3 PUFAs may exert their antidepressant effects through modulation of neuroinflammatory markers. These insights contribute to our understanding of lipid-mediated neuroprotection in MDD and may inform the development of targeted, lipid-based therapies for both depression and neurodegenerative disorders.

Exosomes Derived from DPA-treated UCMSCs Attenuated Depression-like Behaviors and Neuroinflammation in a Model of Depression Induced by Chronic Stress

Depression is characterized by both neuroinflammation and neurodegeneration. Exosomes (Exo) have been shown to function as inhibitors of inflammation and promoters of neurogenesis. Omega-3 polyunsaturated fatty acids, such as eicosapentaenoic acid, can combat depression by increasing levels of docosapentaenoic acid (DPA). This study explored the effects of DPA on the therapeutic potential of Exo derived from human umbilical cord mesenchymal stem cells (hUCMSCs) in glia-induced neuroinflammation associated with depression. Exposure to chronic unpredictable mild stress (CUMS) over six weeks induced depression- and anxiety-like behaviors, while decreasing the levels of serotonin and dopamine. Molecularly, CUMS increased the concentrations of the microglial M1 markers Iba1, iNOS, and IL-1β, while reducing the M2 markers Arg1, CD206, and IL-10 in the prefrontal cortex and hippocampus. However, Exo therapy reversed these effects. Moreover, DPA treatment of Exo demonstrated superior efficacy in alleviating depressive behaviors, neurotransmitter deficiencies, and M1 microglial activation. In vitro, Exo suppressed LPS-stimulated BV2 cell viability and M1 microglial activation, while mitigating the SH-SY5Y cell apoptosis triggered by treatment with the conditioned medium from LPS-activated BV2 cells. Furthermore, administration of DPA enhanced this effect. Mechanically, DPA enhanced Exo function by upregulating miR125b-5p expression, thereby targeting the MyD88/TRAF6/NF-κB signaling pathway. In summary, Exo exhibited antidepressant effects by suppressing M1 microglial neuroinflammation, while DPA treatment provided a more potent therapeutic effect on depression-like changes through the upregulation of miR125b-5p targeting the MyD88/TRAF6/NF-κB pathway.

Association between dietary fatty acids and depressive symptoms in Chinese haemodialysis patients: a cross-sectional study

Depression is highly prevalent in haemodialysis patients, and diet might play an important role. Therefore, we conducted this cross-sectional study to determine the association between dietary fatty acids (FA) consumption and the prevalence of depression in maintenance haemodialysis (MHD) patients. Dietary intake was assessed using a validated FFQ between December 2021 and January 2022. The daily intake of dietary FA was categorised into three groups, and the lowest tertile was used as the reference category. Depression was assessed using the Patient Health Questionnaire-9. Logistic regression and restricted cubic spline (RCS) models were applied to assess the relationship between dietary FA intake and the prevalence of depression. As a result, after adjustment for potential confounders, a higher intake of total FA [odds ratio (OR)T3 vs. T1 = 1·59, 95 % confidence interval (CI) = 1·04, 2·46] and saturated fatty acids (SFA) (ORT3 vs. T1 = 1·83, 95 % CI = 1·19, 2·84) was associated with a higher prevalence of depressive symptoms. Significant positive linear trends were also observed (P < 0·05) except for SFA intake. Similarly, the prevalence of depression in MHD patients increased by 20% (OR = 1.20, 95% CI = 1.01-1.43) for each standard deviation increment in SFA intake. RCS analysis indicated an inverse U-shaped correlation between SFA and depression (P nonlinear > 0·05). Additionally, the sensitivity analysis produced similar results. Furthermore, no statistically significant association was observed in the subgroup analysis with significant interaction. In conclusion, higher total dietary FA and SFA were positively associated with depressive symptoms among MHD patients. These findings inform future research exploring potential mechanism underlying the association between dietary FA and depressive symptoms in MHD patients.

Identification of molecular targets of Hypericum perforatum in blood for major depressive disorder: a machine-learning pharmacological study

BACKGROUND

Major depressive disorder (MDD) is one of the most common psychiatric disorders worldwide. Hypericum perforatum (HP) is a traditional herb that has been shown to have antidepressant effects, but its mechanism is unclear. This study aims to identify the molecular targets of HP for the treatment of MDD.

METHODS

We performed differential analysis and weighted gene co-expression network analysis (WGCNA) with blood mRNA expression cohort of MDD and healthy control to identify DEGs and significant module genes (gene list 1). Three databases, CTD, DisGeNET, and GeneCards, were used to retrieve MDD-related gene intersections to obtain MDD-predicted targets (gene list 2). The validated targets were retrieved from the TCMSP database (gene list 3). Based on these three gene lists, 13 key pathways were identified. The PPI network was constructed by extracting the intersection of genes and HP-validated targets on all key pathways. Key therapeutic targets were obtained using MCODE and machine learning (LASSO, SVM-RFE). Clinical diagnostic assessments (Nomogram, Correlation, Intergroup expression), and gene set enrichment analysis (GSEA) were performed for the key targets. In addition, immune cell analysis was performed on the blood mRNA expression cohort of MDD to explore the association between the key targets and immune cells. Finally, molecular docking prediction was performed for the targets of HP active ingredients on MDD.

RESULTS

Differential expression analysis and WGCNA module analysis yielded 933 potential targets for MDD. Three disease databases were intersected with 982 MDD-predicted targets. The TCMSP retrieved 275 valid targets for HP. Separate enrichment analysis intersected 13 key pathways. Five key targets (AKT1, MAPK1, MYC, EGF, HSP90AA1) were finally screened based on all enriched genes and HP valid targets. Combined with the signaling pathway and immune cell analysis suggested the effect of peripheral immunity on MDD and the important role of neutrophils in immune inflammation. Finally, the binding of HP active ingredients (quercetin, kaempferol, and luteolin) and all 5 key targets were predicted based on molecular docking.

CONCLUSIONS

The active constituents of Hypericum perforatum can act on MDD and key targets and pathways of this action were identified.

The Hidden Dangers of Sedentary Living: Insights into Molecular, Cellular, and Systemic Mechanisms

With the aging of the global population, neurodegenerative diseases are emerging as a major public health issue. The adoption of a less sedentary lifestyle has been shown to have a beneficial effect on cognitive decline, but the molecular mechanisms responsible are less clear. Here we provide a detailed analysis of the complex molecular, cellular, and systemic mechanisms underlying age-related cognitive decline and how lifestyle choices influence these processes. A review of the evidence from animal models, human studies, and postmortem analyses emphasizes the importance of integrating physical exercise with cognitive, multisensory, and motor stimulation as part of a multifaceted approach to mitigating cognitive decline. We highlight the potential of these non-pharmacological interventions to address key aging hallmarks, such as genomic instability, telomere attrition, and neuroinflammation, and underscore the need for comprehensive and personalized strategies to promote cognitive resilience and healthy aging.

Exosome-associated mitochondrial DNA in late-life depression: Implications for cognitive decline in older adults

BACKGROUND

Disrupted cellular communication, inflammatory responses and mitochondrial dysfunction are consistently observed in late-life depression (LLD). Exosomes (EXs) mediate cellular communication by transporting molecules, including mitochondrial DNA (EX-mtDNA), playing critical role in immunoregulation alongside tumor necrosis factor (TNF). Changes in EX-mtDNA are indicators of impaired mitochondrial function and might increase vulnerability to adverse health outcomes. Our study examined EX-mtDNA levels and integrity, exploring their associations with levels of TNF receptors I and II (TNFRI and TNFRII), and clinical outcomes in LLD.

METHODS

Ninety older adults (50 LLD and 40 controls (HC)) participated in the study. Blood was collected and exosomes were isolated using size-exclusion chromatography. DNA was extracted and EX-mtDNA levels and deletion were assessed using qPCR. Plasma TNFRI and TNFRII levels were quantified by multiplex immunoassay. Correlation analysis explored relationships between EX-mtDNA, clinical outcomes, and inflammatory markers.

RESULTS

Although no differences were observed in EX-mtDNA levels between groups, elevated levels correlated with poorer cognitive performance (r = -0.328, p = 0.002) and increased TNFRII levels (r = 0.367, p = 0.004). LLD exhibited higher deletion rates (F(83,1) = 4.402, p = 0.039), with a trend remaining after adjusting for covariates (p = 0.084). Deletion correlated with poorer cognitive performance (r = -0.335, p = 0.002). No other associations were found.

LIMITATION

Cross-sectional study with a small number of participants from a specialized geriatric psychiatry treatment center.

CONCLUSION

Our findings suggest that EX-mtDNA holds promise as an indicator of cognitive outcomes in LLD. Additional research is needed to further comprehend the role of EX-mtDNA levels/integrity in LLD, paving the way for its clinical application in the future.

Acute liver damage generates age independent microglia morphology changes in mice

Non-alcoholic fatty liver disease (NAFLD) has emerged as a silent global epidemic, frequently contributing to systemic inflammation. As the primary immune cells of the central nervous system (CNS), microglia undergo morphological changes that serve as critical indicators of CNS health. In this study, we aimed to quantify alterations in microglial morphology within the cortex of young and aged mice with liver damage. Our results demonstrated that hepatic dysfunction leads to a significant increase in total branch length in both young (285.79±68.23 μm) and aged animals (268.67±69.06 μm), compared to their respective controls (164.07±33.05 μm and 140.96±27.18 μm) (p<0.0001). Additionally, aged animals with liver damage exhibited a mean branch length of 5.84±0.66 μm, higher than 2.63±0.19 μm observed in those without liver injury. The number of primary branches in aged mice with liver damage decreased from 6.6±1.2 branches to 3.1±1.5 (p<0.0001). In addition, we have shown a decrease in the number of secondary branches in aged animals with liver damage. This suggests that microglia not only respond to CNS-specific injuries but also to chronic systemic pathologies like NAFLD. These findings highlight the importance of better understanding the liver-brain axis in order to better understand the neuroimmune consequences of systemic diseases.

miR-29a-5p rescues depressive-like behaviors in a CUMS-induced mouse model by facilitating microglia M2-polarization in the prefrontal cortex via TMEM33 suppression

BACKGROUND

Depression accounts for a high proportion of neuropsychiatric disorders and is associated with abnormal states of neurons in specific brain regions. Microglia play a pivotal role in the inflammatory state during depression development; however, the exact mechanism underlying chronic mood states remains unknown. Thus, the present study aimed to determine whether microRNAs (miRNAs) alleviate stress-induced depression-like behavior in mice by regulating the expression levels of their target genes, explore the role of neuroinflammation induced by microglial activation in the pathogenesis and progression of depression, and determine whether the role of the miR-29a-5p/transmembrane protein 33 (TMEM33) axis.

METHODS

In this study, chronic unpredictable mild stress (CUMS) mouse depression model, various behavioral tests, western blotting, dual-luciferase reporter assay, enzyme-linked immunosorbent assay, real-time quantitative reverse transcription PCR, immunofluorescence and lentivirus-mediated gene transfer were used.

RESULTS

After exposure to the CUMS paradigm, miR-29a-5p was significantly down-regulated. This downregulation subsequently promoted the polarization of microglia M1 by upregulating the expression of TMEM33, resulting in enhanced inflammatory chemokines affecting neurons. Conversely, the upregulation of miR-29a-5p within the prefrontal cortex (PFC) suppressed TMEM33 expression, facilitated microglia M2-polarization, and ameliorated depressive-like behavior.

LIMITATIONS

Only rodent models of depression were used, and human samples were not included.

CONCLUSIONS

The results of this study suggest that miR-29a-5p deficits within the PFC mediate microglial anomalies and contribute to depressive-like behaviors. miR-29a-5p and TMEM33 may, therefore, serve as potential therapeutic targets for the treatment of depression.

Emerging role of Jumonji domain-containing protein D3 in inflammatory diseases

Jumonji domain-containing protein D3 (JMJD3) is a 2-oxoglutarate-dependent dioxygenase that specifically removes transcriptional repression marks di- and tri-methylated groups from lysine 27 on histone 3 (H3K27me2/3). The erasure of these marks leads to the activation of some associated genes, thereby influencing various biological processes, such as development, differentiation, and immune response. However, comprehensive descriptions regarding the relationship between JMJD3 and inflammation are lacking. Here, we provide a comprehensive overview of JMJD3, including its structure, functions, and involvement in inflammatory pathways. In addition, we summarize the evidence supporting JMJD3's role in several inflammatory diseases, as well as the potential therapeutic applications of JMJD3 inhibitors. Additionally, we also discuss the challenges and opportunities associated with investigating the functions of JMJD3 and developing targeted inhibitors and propose feasible solutions to provide valuable insights into the functional exploration and discovery of potential drugs targeting JMJD3 for inflammatory diseases.

Microglial NLRP3 inflammasome-mediated neuroinflammation and therapeutic strategies in depression

Previous studies have demonstrated a bidirectional relationship between inflammation and depression. Activation of the nucleotide-binding oligomerization domain, leucine-rich repeat, and NLR family pyrin domain-containing 3 (NLRP3) inflammasomes is closely related to the pathogenesis of various neurological diseases. In patients with major depressive disorder, NLRP3 inflammasome levels are significantly elevated. Understanding the role that NLRP3 inflammasome-mediated neuroinflammation plays in the pathogenesis of depression may be beneficial for future therapeutic strategies. In this review, we aimed to elucidate the mechanisms that lead to the activation of the NLRP3 inflammasome in depression as well as to provide insight into therapeutic strategies that target the NLRP3 inflammasome. Moreover, we outlined various therapeutic strategies that target the NLRP3 inflammasome, including NLRP3 inflammatory pathway inhibitors, natural compounds, and other therapeutic compounds that have been shown to be effective in treating depression. Additionally, we summarized the application of NLRP3 inflammasome inhibitors in clinical trials related to depression. Currently, there is a scarcity of clinical trials dedicated to investigating the applications of NLRP3 inflammasome inhibitors in depression treatment. The modulation of NLRP3 inflammasomes in microglia holds promise for the management of depression. Further investigations are necessary to ascertain the efficacy and safety of these therapeutic approaches as potential novel antidepressant treatments.

Insights into the Effect of Light Pollution on Mental Health: Focus on Affective Disorders-A Narrative Review

The presence of artificial light at night has emerged as an anthropogenic stressor in recent years. Various sources of light pollution have been shown to affect circadian physiology with serious consequences for metabolic pathways, possibly disrupting pineal melatonin production with multiple adverse health effects. The suppression of melatonin at night may also affect human mental health and contribute to the development or exacerbation of psychiatric disorders in vulnerable individuals. Due to the high burden of circadian disruption in affective disorders, it has been hypothesized that light pollution impacts mental health, mainly affecting mood regulation. Hence, the aim of this review was to critically summarize the evidence on the effects of light pollution on mood symptoms, with a particular focus on the role of circadian rhythms in mediating this relationship. We conducted a narrative review of the literature in the PubMed, Scopus, and Web of Science datasets. After the screening process, eighteen papers were eligible for inclusion. The results clearly indicate a link between light pollution and the development of affective symptoms, with a central role of sleep disturbances in the emergence of mood alterations. Risk perception also represents a crucial topic, possibly modulating the development of affective symptoms in response to light pollution. The results of this review should encourage a multidisciplinary approach to the design of healthier environments, including lighting conditions among the key determinants of human mental health.

Evidence for reduced anti-inflammatory microglial phagocytic response in late-life major depression

Major depressive disorder (MDD) is associated with Alzheimer's disease (AD) but the precise mechanisms underlying this relationship are not understood. While it is well established that cerebrospinal fluid (CSF) soluble levels of triggering receptor expressed on myeloid cells 2 (sTREM2) increase during early stages of AD, how sTREM2 levels behave in subjects with MDD is not known. In a longitudinal study, we measured CSF sTREM2 levels in 27 elderly cognitively intact individuals with late-life major depression (LLMD) and in 19 healthy controls. We tested the hypothesis that, similarly to what happens in early stages of AD, CSF sTREM2 would be elevated in MDD. In addition, we compared the associations of CSF sTREM2, pro- and anti- inflammatory, and AD biomarkers in LLMD and control subjects. Surprisingly, we found that mean CSF sTREM2 levels were significantly reduced in LLMD compared to controls. This reduction was no longer significant at the 3-year follow-up visit when depression severity improved. In addition, we found that CSF sTREM2 was associated with AD biomarkers and proinflammatory cytokines in controls but not in LLMD. These findings suggest that impaired microglia phagocytic response to AD pathology may be a novel link between MDD and AD.

Stress-Related Roles of Exosomes and Exosomal miRNAs in Common Neuropsychiatric Disorders

Exosomes, natural nanovesicles that contain a cargo of biologically active molecules such as lipids, proteins, and nucleic acids, are released from cells to the extracellular environment. They then act as autocrine, paracrine, or endocrine mediators of communication between cells by delivering their cargo into recipient cells and causing downstream effects. Exosomes are greatly enriched in miRNAs, which are small non-coding RNAs that act both as cytoplasmic post-transcriptional repression agents, modulating the translation of mRNAs into proteins, as well as nuclear transcriptional gene activators. Neuronal exosomal miRNAs have important physiologic functions in the central nervous system (CNS), including cell-to-cell communication, synaptic plasticity, and neurogenesis, as well as modulating stress and inflammatory responses. Stress-induced changes in exosomal functions include effects on neurogenesis and neuroinflammation, which can lead to the appearance of various neuropsychiatric disorders such as schizophrenia, major depression, bipolar disorder, and Alzheimer's and Huntington's diseases. The current knowledge regarding the roles of exosomes in the pathophysiology of common mental disorders is discussed in this review.

Interactions Between Extracellular Vesicles and Autophagy in Neuroimmune Disorders

Neuroimmune disorders, such as multiple sclerosis, neuromyelitis optica spectrum disorder, myasthenia gravis, and Guillain-Barré syndrome, are characterized by the dysfunction of both the immune system and the nervous system. Increasing evidence suggests that extracellular vesicles and autophagy are closely associated with the pathogenesis of these disorders. In this review, we summarize the current understanding of the interactions between extracellular vesicles and autophagy in neuroimmune disorders and discuss their potential diagnostic and therapeutic applications. Here we highlight the need for further research to fully understand the mechanisms underlying these disorders, and to develop new diagnostic and therapeutic strategies.

Extracellular Vesicles in Multiple Sclerosis: Their Significance in the Development and Possible Applications as Therapeutic Agents and Biomarkers

Extracellular vesicles (EVs) are "micro-shuttles" that play a role as mediators of intercellular communication. Cells release EVs into the extracellular environment in both physiological and pathological conditions and are involved in intercellular communication, due to their ability to transfer proteins, lipids, and nucleic acids, and in the modulation of the immune system and neuroinflammation. Because EVs can penetrate the blood-brain barrier and move from the central nervous system to the peripheral circulation, and vice versa, recent studies have shown a substantial role for EVs in several neurological diseases, including multiple sclerosis (MS). MS is a demyelinating disease where the main event is caused by T and B cells triggering an autoimmune reaction against myelin constituents. Recent research has elucidate the potential involvement of extracellular vesicles (EVs) in the pathophysiology of MS, although, to date, their potential role both as agents and therapeutic targets in MS is not fully defined. We present in this review a summary and comprehensive examination of EVs' involvement in the pathophysiology of multiple sclerosis, exploring their potential applications as biomarkers and indicators of therapy response.

Regulatory roles of microRNAs in modulating mitochondrial dynamics, amyloid beta fibrillation, microglial activation, and cholinergic signaling: Implications for alzheimer's disease pathogenesis

Alzheimer's Disease (AD) remains a formidable challenge due to its complex pathology, notably involving mitochondrial dysfunction and dysregulated microRNA (miRNA) signaling. This study delves into the underexplored realm of miRNAs' impact on mitochondrial dynamics and their interplay with amyloid-beta (Aβ) aggregation and tau pathology in AD. Addressing identified gaps, our research utilizes advanced molecular techniques and AD models, alongside patient miRNA profiles, to uncover miRNAs pivotal in mitochondrial regulation. We illuminate novel miRNAs influencing mitochondrial dynamics, Aβ, and tau, offering insights into their mechanistic roles in AD progression. Our findings not only enhance understanding of AD's molecular underpinnings but also spotlight miRNAs as promising therapeutic targets. By elucidating miRNAs' roles in mitochondrial dysfunction and their interactions with hallmark AD pathologies, our work proposes innovative strategies for AD therapy, aiming to mitigate disease progression through targeted miRNA modulation. This contribution marks a significant step toward novel AD treatments, emphasizing the potential of miRNAs in addressing this complex disease.

Role of Glial Cells in Neuronal Function, Mood Disorders, and Drug Addiction

Mood disorders and substance use disorder (SUD) are of immense medical and social concern. Although significant progress on neuronal involvement in mood and reward circuitries has been achieved, it is only relatively recently that the role of glia in these disorders has attracted attention. Detailed understanding of the glial functions in these devastating diseases could offer novel interventions. Here, following a brief review of circuitries involved in mood regulation and reward perception, the specific contributions of neurotrophic factors, neuroinflammation, and gut microbiota to these diseases are highlighted. In this context, the role of specific glial cells (e.g., microglia, astroglia, oligodendrocytes, and synantocytes) on phenotypic manifestation of mood disorders or SUD are emphasized. In addition, use of this knowledge in the potential development of novel therapeutics is touched upon.

Comparison of the Protective Effects of Casein Hydrolysate Containing Tyr-Pro-Val-Glu-Pro-Phe and Casein on the Behaviors and Peripheral and Brain Functions in Mice with Chronic-Stress-Induced Anxiety and Insomnia

Chronic stress is a major inducer of anxiety and insomnia. Milk casein has been studied for its stress-relieving effects. We previously prepared a casein hydrolysate (CP) rich in the sleep-enhancing peptide YPVEPF, and this study aims to systemically investigate the different protective effects of CP and casein on dysfunction and anxiety/insomnia behavior and its underlying mechanisms in chronically stressed mice. Behavioral results showed that CP ameliorated stress-induced insomnia and anxiety more effectively than milk casein, and this difference in amelioration was highly correlated with an increase in GABA, 5-HT, GABAA, 5-HT1A receptors, and BDNF and a decrease in IL-6 and NMDA receptors in stressed mice. Furthermore, CP restored these dysfunctions in the brain and colon by activating the HPA response, modulating the ERK/CREB-BDNF-TrκB signaling pathway, and alleviating inflammation. The abundant YPVEPF (1.20 ± 0.04%) and Tyr-based/Trp-containing peptides of CP may be the key reasons for its different effects compared to casein. Thus, this work revealed the main active structures of CP and provided a novel dietary intervention strategy for the prevention and treatment of chronic-stress-induced dysfunction and anxiety/insomnia behaviors.

Dorsal root ganglion-derived exosomes deteriorate neuropathic pain by activating microglia via the microRNA-16-5p/HECTD1/HSP90 axis

BACKGROUND

The activated microglia have been reported as pillar factors in neuropathic pain (NP) pathology, but the molecules driving pain-inducible microglial activation require further exploration. In this study, we investigated the effect of dorsal root ganglion (DRG)-derived exosomes (Exo) on microglial activation and the related mechanism.

METHODS

A mouse model of NP was generated by spinal nerve ligation (SNL), and DRG-derived Exo were extracted. The effects of DRG-Exo on NP and microglial activation in SNL mice were evaluated using behavioral tests, HE staining, immunofluorescence, and western blot. Next, the differentially enriched microRNAs (miRNAs) in DRG-Exo-treated microglia were analyzed using microarrays. RT-qPCR, RNA pull-down, dual-luciferase reporter assay, and immunofluorescence were conducted to verify the binding relation between miR-16-5p and HECTD1. Finally, the effects of ubiquitination modification of HSP90 by HECTD1 on NP progression and microglial activation were investigated by Co-IP, western blot, immunofluorescence assays, and rescue experiments.

RESULTS

DRG-Exo aggravated NP resulting from SNL in mice, promoted the activation of microglia in DRG, and increased neuroinflammation. miR-16-5p knockdown in DRG-Exo alleviated the stimulating effects of DRG-Exo on NP and microglial activation. DRG-Exo regulated the ubiquitination of HSP90 through the interaction between miR-16-5p and HECTD1. Ubiquitination alteration of HSP90 was involved in microglial activation during NP.

CONCLUSIONS

miR-16-5p shuttled by DRG-Exo regulated the ubiquitination of HSP90 by interacting with HECTD1, thereby contributing to the microglial activation in NP.

Liraglutide and Naringenin relieve depressive symptoms in mice by enhancing Neurogenesis and reducing inflammation

Depression is a debilitating mental disease that negatively impacts individuals' lives and society. Novel hypotheses have been recently proposed to improve our understanding of depression pathogenesis. Impaired neuroplasticity and upregulated neuro-inflammation add-on to the disturbance in monoamine neurotransmitters and therefore require novel anti-depressants to target them simultaneously. Recent reports demonstrate the antidepressant effect of the anti-diabetic drug liraglutide. Similarly, the natural flavonoid naringenin has shown both anti-diabetic and anti-depressant effects. However, the neuro-pharmacological mechanisms underlying their actions remain understudied. The study aims to evaluate the antidepressant effects and neuroprotective mechanisms of liraglutide, naringenin or a combination of both. Depression was induced in mice by administering dexamethasone (32 mcg/kg) for seven consecutive days. Liraglutide (200 mcg/kg), naringenin (50 mg/kg) and a combination of both were administered either simultaneously or after induction of depression for twenty-eight days. Behavioral and molecular assays were used to assess the progression of depressive symptoms and biomarkers. Liraglutide and naringenin alone or in combination alleviated the depressive behavior in mice, manifested by decrease in anxiety, anhedonia, and despair. Mechanistically, liraglutide and naringenin improved neurogenesis, decreased neuroinflammation and comparably restored the monoamines levels to that of the reference drug escitalopram. The drugs protected mice from developing depression when given simultaneously with dexamethasone. Collectively, the results highlight the usability of liraglutide and naringenin in the treatment of depression in mice and emphasize the different pathways that contribute to the pathogenesis of depression.

miRNAs in treatment-resistant depression: a systematic review

BACKGROUND

Treatment-resistant depression (TRD) is a condition in a subset of depressed patients characterized by resistance to antidepressant medications. The global prevalence of TRD has been steadily increasing, yet significant advancements in its diagnosis and treatment remain elusive despite extensive research efforts. The precise underlying pathogenic mechanisms are still not fully understood. Epigenetic mechanisms play a vital role in a wide range of diseases. In recent years, investigators have increasingly focused on the regulatory roles of miRNAs in the onset and progression of TRD. miRNAs are a class of noncoding RNA molecules that regulate the translation and degradation of their target mRNAs via interaction, making the exploration of their functions in TRD essential for elucidating their pathogenic mechanisms.

METHODS AND RESULTS

A systematic search was conducted in four databases, namely PubMed, Web of Science, Cochrane Library, and Embase, focusing on studies related to treatment-resistant depression and miRNAs. The search was performed using terms individually or in combination, such as "treatment-resistant depression," "medication-resistant depression," and "miRNAs." The selected articles were reviewed and collated, covering the time period from the inception of each database to the end of February 2024. We found that miRNAs play a crucial role in the pathophysiology of TRD through three main aspects: 1) involvement in miRNA-mediated inflammatory responses (including miR-155, miR-345-5p, miR-146a, and miR-146a-5p); 2) influence on 5-HT transport processes (including miR-674,miR-708, and miR-133a); and 3) regulation of synaptic plasticity (including has-miR-335-5p,has-miR- 1292-3p, let-7b, and let-7c). Investigating the differential expression and interactions of these miRNAs could contribute to a deeper understanding of the molecular mechanisms underlying TRD.

CONCLUSIONS

miRNAs might play a pivotal role in the pathogenesis of TRD. Gaining a deeper understanding of the roles and interrelations of miRNAs in TRD will contribute to elucidating disease pathogenesis and potentially provide avenues for the development of novel diagnostic and therapeutic strategies.

Stress, pain, anxiety, and depression in endometriosis-Targeting glial activation and inflammation

Endometriosis (EM) is a gynecological inflammatory disease often accompanied by stress, chronic pelvic pain (CPP), anxiety, and depression, leading to a diminished quality of life. This review aims to discuss the relationship between systemic and local inflammatory responses in the central nervous system (CNS), focusing on glial dysfunctions (astrocytes and microglia) as in critical brain regions involved in emotion, cognition, pain processing, anxiety, and depression. The review presents that EM is connected to increased levels of pro-inflammatory cytokines in the circulation. Additionally, chronic stress and CPP as stressors may contribute to the dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis, depleting the production of inflammatory mediators in the circulatory system and the brain. The systemic cytokines cause blood-brain barrier (BBB) breakdown, activate microglia in the brain, and lead to neuroinflammation. Furthermore, CPP may induce neuronal morphological alterations in critical regions through central sensitization and the activation of glial cells. The activation of glial cells, particularly the polarization of microglia, leads to the activation of the NLRP3 inflammasome and the overproduction of inflammatory cytokines. These inflammatory cytokines interact with the signaling pathways involved in neural plasticity. Additionally, persistent inflammatory conditions in the brain lead to neuronal death, which is correlated with a reduced volume of key brain regions such as the hippocampus. This review highlights the involvement of glial cells in the pathogenesis of the mental comorbidities of EM (i.e., pain, anxiety, and depression) and to discuss potential therapeutic approaches for targeting the inflammation and activation of microglia in key brain regions.

Effect of General Anesthetic Agents on Microglia

The effects of general anesthetic agents (GAAs) on microglia and their potential neurotoxicity have attracted the attention of neuroscientists. Microglia play important roles in the inflammatory process and in neuromodulation of the central nervous system. Microglia-mediated neuroinflammation is a key mechanism of neurocognitive dysfunction during the perioperative period. Microglial activation by GAAs induces anti-inflammatory and pro-inflammatory effects in microglia, suggesting that GAAs play a dual role in the mechanism of postoperative cognitive dysfunction. Understanding of the mechanisms by which GAAs regulate microglia may help to reduce the incidence of postoperative adverse effects. Here, we review the actions of GAAs on microglia and the consequent changes in microglial function. We summarize clinical and animal studies associating microglia with general anesthesia and describe how GAAs interact with neurons via microglia to further explore the mechanisms of action of GAAs in the nervous system.

Acupuncture Ameliorates Depression-Like Behaviors Through Modulating the Neuroinflammation Mediated by TLR4 Signaling Pathway in Rats Exposed to Chronic Restraint Stress

Recently, emerging evidence has identified that stress-induced activation of neuroinflammation is considered to be one of the most prevalently precipitating factors in the pathogenesis of depression. Data from clinical trials and experimental findings has verified the efficacy and safety of acupuncture in the prevention and treatment of depression. However, the mechanism of the preventive effect of acupuncture for depression has not been fully elucidated. The current study aimed to investigate the preventive effect and mechanism of acupuncture through modulating the neuroinflammation mediated by toll-like receptor 4 (TLR4) signaling pathway in rats exposed to chronic restraint stress (CRS). All rats were subjected to CRS for 21 days, with the exception of rats in control group. One hour before CRS, rats in acupuncture group were exposed to acupuncture at Baihui (GV20) and Yintang (GV29). The depression-like behaviors were evaluated by body weight assessment and sucrose preference test at 0, 7, 14, and 21 days. The expression of activated microglia in hippocampus was detected by immunofluorescence. The expression of key proteins on TLR4 signaling pathway of TLR4, MyD88, TRAF6, NF-κB p65, TNF-α, and mRNA of TLR4 in the hippocampus was detected by western blot and real-time quantitative polymerase chain reaction to investigate the effect of acupuncture on stress-induced activation of neuroinflammation. The present study provided evidence that acupuncture exerted potential preventive effect that might be mediated in part by suppressing the neuroinflammation induced by TLR4 signaling pathway, which may be a promising treatment target to improve current treatments for depression.