The primary mechanism of secondary injury after cerebral ischemia may be the brain inflammation that emerges after an ischemic stroke, which promotes neuronal death and inhibits nerve tissue regeneration. As the first immune cells to be activated after an ischemic stroke, microglia play an important immunomodulatory role in the progression of the condition. After an ischemic stroke, peripheral blood immune cells (mainly T cells) are recruited to the central nervous system by chemokines secreted by immune cells in the brain, where they interact with central nervous system cells (mainly microglia) to trigger a secondary neuroimmune response. This review summarizes the interactions between T cells and microglia in the immune-inflammatory processes of ischemic stroke. We found that, during ischemic stroke, T cells and microglia demonstrate a more pronounced synergistic effect. Th1, Th17, and M1 microglia can co-secrete pro-inflammatory factors, such as interferon-γ, tumor necrosis factor-α, and interleukin-1β, to promote neuroinflammation and exacerbate brain injury. Th2, Treg, and M2 microglia jointly secrete anti-inflammatory factors, such as interleukin-4, interleukin-10, and transforming growth factor-β, to inhibit the progression of neuroinflammation, as well as growth factors such as brain-derived neurotrophic factor to promote nerve regeneration and repair brain injury. Immune interactions between microglia and T cells influence the direction of the subsequent neuroinflammation, which in turn determines the prognosis of ischemic stroke patients. Clinical trials have been conducted on the ways to modulate the interactions between T cells and microglia toward anti-inflammatory communication using the immunosuppressant fingolimod or overdosing with Treg cells to promote neural tissue repair and reduce the damage caused by ischemic stroke. However, such studies have been relatively infrequent, and clinical experience is still insufficient. In summary, in ischemic stroke, T cell subsets and activated microglia act synergistically to regulate inflammatory progression, mainly by secreting inflammatory factors. In the future, a key research direction for ischemic stroke treatment could be rooted in the enhancement of anti-inflammatory factor secretion by promoting the generation of Th2 and Treg cells, along with the activation of M2-type microglia. These approaches may alleviate neuroinflammation and facilitate the repair of neural tissues.

Chronic stress can affect brain function through various mechanisms, leading to the development of anxiety disorders. The chronic unpredictable mild stress (CUMS) is a classic model of chronic stress. This study evaluated the effects of different durations of CUMS on anxiety-like behavior, inflammation, and tryptophan metabolism in C57BL/6N mice. The results of behavioral assessments showed that after 3 and 4 weeks of CUMS exposure, the mice exhibited significant decreases in open arms ratio and time ratio in the elevated plus maze (EPM), prolonged latency in the novelty-suppressed feeding test (NSFT), and reduced transitions in the light/dark box (LDB), all indicative of anxiety-like behavior. The inflammatory factors expressions were quantified using qPCR, showing that pro-inflammatory and anti-inflammatory markers began to rise following 1-2 weeks of CUMS exposure. After 3 weeks of stress, TNF-α significantly increased, TGF-β levels started to decrease, and by 4 weeks of CUMS, Arg-1 expression also declined. In terms of tryptophan metabolism, 5-HT content in the hippocampus of the mice began to decrease after 3 weeks of CUMS, while the levels of neuroprotective kynurenic acid (KYNA) continued to rise. Concurrently, neurotoxic substances, including 3-hydroxykynurenine (3-HK) and quinolinic acid (QA), accumulated; after 4 weeks of CUMS, the KYNA content also started to decline. In conclusion, CUMS exposure for 3-4 weeks in male C57BL/6 N mice induces anxiety-like behavior alongside the occurrence of inflammatory responses and disturbances in tryptophan metabolism. These findings highlight the complex interplay between stress, inflammation, and metabolic pathways in the etiology of anxiety-related behaviors.

Neuroinflammation is defined as a process that includes cellular responses designed to protect the central nervous system from external influences, and it initiates in cases of extreme deviations from homeostasis. While it serves a protective role, excessive immune activation can lead to the release of neurotoxic factors, worsening disease progression. Histone deacetylases (HDACs) have been shown to modulate the expression of inflammatory genes by remodeling chromatin through the process of histone deacetylation. HDAC inhibitors (HDACi) alter histone acetylation and affect the transcription of genes involved in inflammatory pathways, making them promising therapeutic tools for the modulation of a variety of inflammatory diseases. However, their use is limited due to non-specific targeting and contradictory results. This study aimed to reconcile conflicting results and share insights on relevant HDACi in the inflammatory response induced by lipopolysaccharide (LPS), considering different exposure scenarios, cellular models, and associated molecular pathways. Specifically, the study evaluated the dose-dependent effects of two broad-spectrum HDACi, Trichostatin A (TSA) and Suberoylanilide Hydroxamic Acid (SAHA, Vorinostat), alongside selective inhibitors-MS-275 (Entinostat, class I), and MC1568 (class II)-on the expression and release of pro- and anti-inflammatory cytokines. Broad-spectrum HDAC inhibitors TSA and SAHA exhibited dose-dependent modulation of LPS-induced cytokine release. Co-treatment with TSA and LPS enhanced pro-inflammatory cytokines (TNF-α, IL-1β) and decreased IL10 in a dose-dependent manner at lower doses (≤ 10 nM), while high concentrations (100 nM) induced the anti-inflammatory IL-10. Pre-treatment with TSA led to a reduction in TNF-α levels induced by LPS, without affecting IL-1β or IL-10 levels. In contrast, the presence of TSA in LPS-triggered alveolar macrophages resulted in a decline in the production of both pro- and anti-inflammatory cytokine, irrespective of the TSA concentration. SAHA exhibited dual effects, enhancing TNF-α and IL-1β at nanomolar levels but suppressing TNF-α at micromolar doses in co-treated glial cells with LPS. Class-selective inhibitors highlighted distinct HDAC roles on LPS modulation: MS-275 reduced, while MC1568 enhanced, TNF-α release, alongside varied IL-1β and IL-10 modulation. To better understand the dual effects of SAHA, transcriptomic analysis of glial cells was conducted in the presence of LPS and low and high SAHA concentrations (100 nM or 5 µM). This analysis revealed a dose-dependent alteration in gene expression and pathway enrichment associated with cytokine signaling and immune regulation (e.g., JAK-STAT). Altogether, these findings reveal insights on the subtle, dose- and context-dependent role of HDACi in modulating glia inflammation.

The progression of traumatic brain injury (TBI) pathology is significantly influenced by age and involves a complex interplay of glial cells. However, the influence of age on the glial dynamics and their TBI responses remains mostly unexplored. Here, we obtain a comprehensive single-cell transcriptome atlas of three major glial types under the physiological and TBI conditions across four post-embryonic life stages in the zebrafish midbrain optic tectum. We identify a library of glial subtypes and states with specific age-dependent patterns that respond distinctly to TBI. Combining the glial interactome analysis and CRISPR-Cas9-mediated gene disruption, we reveal the essential roles of dla-notch3 and cxcl12a-cxcr4b interactions in the early-larval-stage-specific unresponsiveness of radial astrocytes to TBI and the TBI-induced age-independent recruitment of microglia to injury sites, respectively. Overall, our findings provide the molecular and cellular framework of TBI-induced age-related glial dynamics in vertebrate brains.

Prenatal immune challenges pose significant risks to human embryonic brain and eye development. However, our knowledge about the safe usage of anti-inflammatory drugs during pregnancy is still limited. While human induced pluripotent stem cells (hIPSC)-derived brain organoid models have started to explore functional consequences upon viral stimulation, these models commonly lack microglia, which are susceptible to and promote inflammation. Furthermore, microglia are actively involved in neuronal development. Here, we generate hIPSC-derived microglia precursor cells and assemble them into retinal organoids. Once the outer plexiform layer forms, these hIPSC-derived microglia (iMG) fully integrate into the retinal organoids. Since the ganglion cell survival declines by this time in 3D-retinal organoids, we adapted the model into 2D and identify that the improved ganglion cell number significantly decreases only with iMG presence. In parallel, we applied the immunostimulant POLY(I:C) to mimic a fetal viral infection. While POLY(I:C) exposure alters the iMG phenotype, it does not hinder their interaction with ganglion cells. Furthermore, iMG significantly enhance the supernatant's inflammatory secretome and increase retinal cell proliferation. Simultaneous exposure with the non-steroidal anti-inflammatory drug (NSAID) ibuprofen dampens POLY(I:C)-mediated changes of the iMG phenotype and ameliorates cell proliferation. Remarkably, while POLY(I:C) disrupts neuronal calcium dynamics independent of iMG, ibuprofen rescues this effect only if iMG are present. Mechanistically, ibuprofen targets the enzymes cyclooxygenase 1 and 2 (COX1/PTGS1 and COX2/PTGS2) simultaneously, from which iMG mainly express COX1. Selective COX1 blockage fails to restore the calcium peak amplitude upon POLY(I:C) stimulation, suggesting ibuprofen's beneficial effect depends on the presence and interplay of COX1 and COX2. These findings underscore the importance of microglia in the context of prenatal immune challenges and provide insight into the mechanisms by which ibuprofen exerts its protective effects during embryonic development.

Neonatal hypoxic-ischemic brain injury (HIBI) can lead to white matter damage, which significantly contributes to cognitive dysfunction, emotional disorders, and sensorimotor impairments. Although dexmedetomidine enhances neurobehavioral outcomes, its impact on oligodendrocyte genesis and myelination following hypoxic-ischemic events, as well as the underlying mechanisms, remain poorly understood. Dexmedetomidine was administered 15 min post-HIBI. We assessed neurobehavioral deficits using various tests: surface righting, negative geotaxis, forelimb grip strength, cliff avoidance, sensory reflexes, novel object recognition, T-maze, and three-chamber social interaction. We also investigated the relationship between myelination and neurobehavioral outcomes. Measurements included oligodendrocyte precursor cell (OPC) proliferation and survival 24 h post-injury, early myelination, and oligodendrocyte differentiation by postnatal day 14. Furthermore, we evaluated microglial activation towards the M2 phenotype and the extent of neuroinflammation during the acute phase. Dexmedetomidine significantly ameliorated long-term neurological deficits caused by HIBI. Pearson linear regression analysis revealed a strong correlation between long-term neurological outcomes and myelin maturity. The treatment notably mitigated the long-term deterioration of myelin formation and maturation following HIBI. This protective effect was primarily due to enhanced OPC proliferation and survival post-HIBI during the acute phase and, to a lesser extent, to the modulation of microglial activity towards the M2 phenotype and a reduction in neuroinflammation. Dexmedetomidine offers substantial protection against long-term neurobehavioral disabilities induced by HIBI, primarily by revitalizing the impaired survival and maturation of oligodendrocyte progenitor cells and promoting myelination.

Neuropathic pain is triggered by nerve damage or disease and involves chronic neuroinflammation driven by activated microglia releasing pro-inflammatory cytokines. PANoptosis, a complex cell death program encompassing apoptosis, pyroptosis, and necroptosis, has emerged as a key player in neuroinflammation. While individual PANoptosis pathway have been linked to pain, its systemic role in neuropathic pain remains unclear. This study explored the involvement of PANoptosis in microglia under neuropathic pain and its potential therapeutic targeting. After spinal nerve ligation (SNL), robust microglia activation and pro-inflammatory cytokines were increased in spinal dorsal horn. To figure out the major PANoptosis under neuropathic pain, bioinformatic analysis and protein analysis were explored by using spinal dorsal horn on 14 days of post injury. The results supported that pyroptosis was the dominant pathway after injury, and we further investigated pyroptosis-related markers on microglia specifically. Notably, pyroptosis marker (caspase-1) was elevated in microglia compared to apoptosis (cleaved caspase-3) and necroptosis (p-RIPK3) markers. This finding highlights microglia pyroptosis as a key driver of neuropathic pain development. To harness this knowledge therapeutically, we employed intrathecal injection of NLRP3 siRNA nanoparticles. NLRP3, a crucial component of the inflammasome complex triggering pyroptosis, served as our target. Strikingly, this intervention effectively alleviated mechanical allodynia, a hallmark of neuropathic pain, alongside reducing microgliosis and dampening microglial pyroptosis. Our findings reveal that microglia pyroptosis plays a key role in neuropathic pain and suggest NLRP3 siRNA nanoparticles as a promising therapeutic avenue for pain management.

Demyelinating disorders, characterizing by the loss of myelin integrity, present significant challenges due to their impact on neurological function and lack of effective treatments. Understanding the mechanisms underlying myelin damage is crucial for developing therapeutic strategies. Triggering receptor expressed on myeloid cells 2 (TREM2), a pivotal immune receptor predominantly found on microglial cells, plays essential roles in phagocytosis and lipid metabolism, vital processes in neuroinflammation and immune regulation. Emerging evidence indicates a close relationship between TREM2 and various aspects of myelin sheath dynamics, including maintenance, response to damage, and regeneration. This review provides a comprehensive discussion of TREM2's influence on myelin physiology and pathology, highlighting its therapeutic potential and putative mechanisms in the progression of demyelinating disorders.

Alzheimer's and Parkinson's disease are the most common neurodegenerative diseases, significantly affecting the elderly with no current cure available. With the rapidly aging global population, advancing research on these diseases becomes increasingly critical. Both disorders are often studied using model organisms, which enable researchers to investigate disease phenotypes and their underlying molecular mechanisms. In this review, we critically discuss the strengths and limitations of using Drosophila, zebrafish, and mice as models for Alzheimer's and Parkinson's research. A focus is the application of single-cell RNA sequencing, which has revolutionized the field by providing novel insights into the cellular and transcriptomic landscapes characterizing these diseases. We assess how combining animal disease modeling with high-throughput sequencing and computational approaches has advanced the field of Alzheimer's and Parkinson's disease research. Thereby, we highlight the importance of integrative multidisciplinary approaches to further our understanding of disease mechanisms and thus accelerating the development of successful therapeutic interventions.

Brain metastases (BMs) are a relatively common and severe complication in advanced non-small cell lung cancer (NSCLC), significantly affecting patient prognosis. Metastatic tumor cells can alter the brain tumor microenvironment (TME) to promote an immunosuppressive state, characterized by reduced infiltration of tumor-infiltrating lymphocytes (TILs), diminished expression of programmed death-ligand 1 (PD-L1), and changes in other proinflammatory factors and immune cell populations. Microglia, the resident macrophages of the brain, play a pivotal role in modulating the central nervous system (CNS) microenvironment through interactions with metastatic cancer cells, astrocytes, and infiltrating T cells. The M2 phenotype of microglia contributes to immunosuppression in BM via the activation of signaling pathways such as STAT3 and PI3K-AKT-mTOR. Recent advances have enhanced our understanding of the immune landscape of BMs in NSCLC, particularly regarding immune evasion within the CNS. Current immunotherapeutic strategies, including immune checkpoint inhibitors, have shown promise for NSCLC patients with BM, demonstrating intracranial activity and manageable safety profiles. Future research is warranted to further explore the molecular and immune mechanisms underlying BM, aiming to develop more effective treatments.

Neurosyphilis, a neurological manifestation of syphilis, is closely related to neuroinflammation. Autophagy, a fundamental cellular mechanism that mediates the degradation of intracellular components, plays a crucial role in immune regulation and inflammation. Microglia, resident immune cells in the brain, are central to these processes. However, the interplay between autophagy and neuroinflammation in the context of neurosyphilis remains poorly understood. In this research, the recombinant Treponema pallidum flagellin, FlaB3, was constructed to treat human microglia clone 3 (HMC3) cells and HMC3 cells in which TLR4 (Toll-like receptor 4) had been knocked down. We discovered that FlaB3 promotes IL-6 and IL-8 secretion through the TLR4 pathway. We also observed that FlaB3 regulates the expression of autophagy-related proteins Beclin1, LC3B, and P62 via the TLR4/PI3K/AKT/mTOR pathway, thereby inhibiting autophagy and autophagic flux in HMC3 cells. Subsequently, we discovered that the concentration of soluble amyloid β1-42 (Aβ1-42) was decreased in the cerebrospinal fluid of neurosyphilis patients. Immunofluorescence analysis further revealed that FlaB3 suppresses the degradation of Aβ by autophagosomes in HMC3 cells. Additionally, treatment with the autophagy activators Rapamycin and LY294002 decreased the levels of IL-6 and IL-8 secretion, indicating that autophagy modulates inflammation in HMC3 cells. In summary, our study demonstrates that FlaB3 promotes inflammation in HMC3 cells by inhibiting autophagy. This inhibition also impedes Aβ degradation, providing new insights into the pathogenesis of neurosyphilis.

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease characterized by the loss of motor neurons, leading to escalating muscle weakness, atrophy, and eventually paralysis. While neurons are the most visibly affected, emerging data highlight microglia-the brain's resident immune cells-as key contributors to disease onset and progression. Rather than existing in a simple beneficial or harmful duality, microglia can adopt multiple functional states shaped by internal and external factors, including those in ALS. Collectively, these disease-specific forms are called disease-associated microglia (DAM). Research using rodent models, patient-derived cells, and human postmortem tissue shows that microglia can transition into DAM phenotypes, driving inflammation and neuronal injury. However, these cells can also fulfill protective roles under certain conditions, revealing their adaptable nature. This review explores recent discoveries regarding the multifaceted behavior of microglia in ALS, highlights important findings that link these immune cells to motor neuron deterioration, and discusses emerging therapies-some already used in clinical trials-that aim to recalibrate microglial functions and potentially slow disease progression.

Though the etiology of autism spectrum disorder (ASD) is complex and not fully understood, it is believed that genetic risk factors, coupled with early life inflammation may predispose individuals to develop ASD. Maternal immune activation (MIA) is associated with increased incidence of ASD in offspring; however, not all mothers who experience inflammation during pregnancy have children with autism, suggesting that MIA may act as a disease primer that results in ASD pathology when paired with additional inflammatory insults. Here, we tested the hypothesis that MIA is a disease primer by using a two-hit model that combined MIA with a secondary immune stimulation in early life. C57BL/6J mouse dams were treated with polyinosinic-polycytidylic acid (Poly(I:C)) at embyronic day 12.5, and a subset of litters were then treated with the endotoxin lipopolysaccharide (LPS) four days after birth. Offspring were assessed in young adulthood for changes in behavior including sociability, repetitive-like behaviors, and anxiety-like behaviors. Flow cytometry was performed in adulthood to assess changes in immune cell populations in the periphery and in the brain. MIA increased repetitive-like behaviors in male mice and decreased sociability in both sexes. Unexpectedly, the secondary immune stimulation with LPS did not exacerbate changes in social and repetitive-like behaviors in either sex. MIA also altered distribution of cytotoxic CD8 + T cell populations in the periphery and brain of both sexes: CD8 + T cells were elevated in thymus but reduced in spleen, lymph, and brain. Additionally, MIA altered microglia activity in a region-specific manner in male mice, which was also not exacerbated but rather ameliorated when combined with LPS. Our results demonstrate that changes in repetitive-like and social behaviors that are induced by MIA in male mice are not exacerbated by subsequent inflammatory challenge and highlights the importance of considering the timing of stressors in the appearance of developmental pathology.

Translocator protein (TSPO) is a mitochondrial outer membrane protein expressed on a variety of immune cells, including macrophages, dendritic cells, and T cells, in addition to neurons and steroid-producing cells. Previous studies of TSPO ligands have suggested that TSPO is involved in multiple cellular functions, including steroidogenesis, immunomodulation, and cell proliferation. Currently, there are limited reports on the effects of TSPO or TSPO ligands on T cell-mediated immune responses. Here, we investigated the involvement of TSPO/TSPO ligand in T cell responses using a 2,4-dinitro-1-fluorobenzene (DNFB)-induced contact hypersensitivity (CH) model. Treatment with Ro5-4864, a TSPO ligand, during DNFB sensitization reduced the number and activation status of CD4+ and CD8+ T cells in draining lymph nodes and alleviated skin inflammation after DNFB challenge. Adoptive transfer of Ro5-4864-treated mouse-derived DNFB-sensitized T cells to naive mice inhibited CH responses after DNFB challenge. Ro5-4864-treated sensitized T cells showed lower proliferative responses when stimulated with DNFB-pulsed antigen-presenting cells compared to control-treated sensitized T cells. Ro5-4864 also suppressed cell proliferation, as well as adenosine triphosphate and lactate production, during T cell activation. Moreover, the inhibitory effects of Ro5-4864 on T cell responses were conserved in TSPO-deficient cells. Our results suggest that Ro5-4864 inhibits CH responses by suppressing energy metabolism, at least via glycolysis, to reduce the T cell primary response in a TSPO-independent manner.

Although inflammation and oxidative stress have been increasingly recognised as components of Alzheimer's disease (AD) and Parkinson's disease (PD) pathologies. Few studies have investigated peripheral inflammation, and none have examined oxidative stress in Dementia with Lewy bodies (DLB). The purpose of our study was to characterize and compare those biomarkers in DLB with those in AD and amnestic mild cognitive impairment (aMCI). Plasma samples were obtained from Chinese patients with DLB (n = 50), AD (n = 59), and aMCI (n = 30), and healthy controls (HCs) (n = 54). Peripheral inflammatory biomarkers, including interferon-gamma (IFN-γ), interleukins (IL-1β, IL-2, IL-4, IL-6, IL-10, IL-12p70, IL-17A), tumor necrosis factor-alpha (TNF-α), and C-reactive protein (CRP). Oxidative stress markers, such as superoxide dismutase (SOD), malondialdehyde (MDA), and glutathione peroxidase (GSH-Px), were also assessed. The findings revealed that DLB patients had higher IL-6 levels than AD and HCs and elevated IL-10 and IL-17A levels compared to HCs. In terms of oxidative stress, the levels of SOD were significantly lower and MDA were significantly higher in the DLB and AD compared with HCs. Significant positive correlations were found between Unified Parkinson's Disease Rating Scale (UPDRS) scores and CRP levels. Our study identifies a unique peripheral immune and oxidative stress profile in DLB, characterized by elevated IL-6, MDA, and reduced SOD levels, distinguishing it from AD. These findings, linked to α-synuclein (α-Syn) pathology, provide novel insights into DLB mechanisms and highlight potential biomarkers for disease monitoring, targeted therapies, and future clinical trials.

Cerebral ischemia‒reperfusion injury (CIRI) is a type of secondary brain damage caused by reperfusion after ischemic stroke due to vascular obstruction. In this study, a CIRI diagnostic model was established by identifying hypoxia-related differentially expressed genes (HRDEGs) in patients with CIRI. The ischemia‒reperfusion injury (IRI)-related datasets were downloaded from the Gene Expression Omnibus (GEO) database ( http://www.ncbi.nlm.nih.gov/geo ), and hypoxia-related genes in the Gene Cards database were identified. After the datasets were combined, hypoxia-related differentially expressed genes (HRDEGs) expressed in CIRI patients were identified. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses of the HRDEGs were performed using online tools. Gene set enrichment analysis (GSEA) and gene set variation analysis (GSVA) were performed with the combined gene dataset. CIRI diagnostic models based on HRDEGs were constructed via least absolute shrinkage and selection operator (LASSO) regression analysis and a support vector machine (SVM) algorithm. The efficacy of the 9 identified hub genes for CIRI diagnosis was evaluated via mRNA‒microRNA (miRNA) interaction, mRNA-RNA-binding protein (RBP) network interaction, immune cell infiltration, and receiver operating characteristic (ROC) curve analyses. We then performed logistic regression analysis and constructed logistic regression models based on the expression of the 9 HRDEGs. We next established a nomogram and calibrated the prediction data. Finally, the clinical utility of the constructed logistic regression model was evaluated via decision curve analysis (DCA). This study revealed 9 critical genes with high diagnostic value, offering new insights into the diagnosis and selection of therapeutic targets for patients with CIRI. : Not applicable.

Microglia, the resident immune cells of the central nervous system, play a critical role in maintaining neuronal health, but are often overlooked in traditional neuron-focused in vitro models.

In this study, we developed a novel co-culture system of human pluripotent stem cell (hPSC)-derived microglia and neurons to investigate how hPSC-derived microglia influence neuronal morphology and network activity. Using high-content morphological analysis and multi-electrode arrays (MEA), we demonstrate that these microglia successfully incorporate into neuronal networks and modulate key aspects of neuronal function.

hPSC-derived microglia significantly reduced cellular debris and altered neuronal morphology by decreasing axonal and dendritic segments and reducing synapse density. Interestingly, despite the decrease in synapse density, neuronal network activity increased.

Our findings underscore the importance of including hPSC-derived microglia in in vitro models to better simulate in vivo neuroglial interactions and provide a platform for investigating neuron-glia dynamics in health and disease.

Alzheimer's disease (AD), the most common type of dementia among older adults, is a chronic neurodegenerative pathology that causes a progressive loss of cognitive functioning with a decline of rational skills. It is well known that AD is multifactorial, so there are many different pharmacological targets that can be pursued. According to estimates from the World Health Organization (WHO), 18 million individuals worldwide suffer from AD. Major initiatives to identify risk factors, enhance care giving, and conduct basic research to delay the beginning of AD were started by the USA, France, Germany, France, and various other nations. Widely recognized as a key player in the development and subsequent progression of AD pathogenesis, glycogen synthase kinase-3 (GSK-3) controls a number of crucial targets associated with neuronal degeneration. GSK-3 inhibition has been linked to reduced tau hyperphosphorylation, β-amyloid formation, and neuroprotective benefits in Alzheimer's disease. Lithium, the very first inhibitor of GSK-3β that was used therapeutically, has been successfully used for many years with remarkable results. A great variety of structurally varied strong GSK-3β blockers have been identified in recent years. The purpose of this thorough review is to cover the biological and structural elements of glycogen synthase kinase, as well as the medicinal chemistry aspects of GSK inhibitors that have been produced in recent years.

Chemotherapy-related cognitive impairment (CRCI) significantly impacts cancer survivors. Due to unclear mechanisms, effective treatments for cognitive deficits are lacking. Here, we examined if microglia-mediated deficits in synaptic plasticity drive CRCI. Adult male mice were treated with the chemotherapeutic drugs 5-fluorouracil and leucovorin (5-Fu/LV, intraperitoneal injection, I.P.) on Days 1, 8, and 15 at a dosage of 50 mg/kg for 5-Fu and 90 mg/kg for LV for 3 weeks. Cognitive function was assessed using a novel object recognition (NOR) test 4 weeks after completion of 5-Fu/LV treatment. Compared with vehicle treatment, 5-Fu/LV treatment reduced the preference for exploring novel objects in the NOR test. Treatment with 5-Fu/LV increased the numbers of Iba1-positive microglial and CD68-positive/Iba1-positive microglia with shortened process lengths and diminished endpoints but decreased the number of phagocytotic (≤ 1 FITC-labeled beads) Iba1-positive microglia. Furthermore, 5-Fu/LV treatment reduced the long-term potentiation (LTP) recorded in the hippocampal CA1 region in response to a theta burst stimulation of the CA3-CA1 pathway and decreased the evoked N-methyl-D-aspartic acid receptor (NMDAR)-excitatory postsynaptic currents (NMDAR-EPSCs) in CA1 neurons. Cotreatment with the microglial inhibitor minocycline (33 mg/kg, daily for 3 weeks) restored cognitive deficits and microglial ramification, decreased the number of CD68-positive microglia, and reversed the reductions in LTP and the amplitude of NMDAR-EPSCs in 5-Fu/LV-treated mice. Our data suggest that microglial dysfunction and related synaptic dysfunction contribute to 5-Fu/LV-induced cognitive impairment.

Postoperative cognitive dysfunction (POCD) is common in the aged population and associated with poor clinical outcomes. Irisin, an endogenous molecule that mediates the beneficial effects of exercise, has shown neuroprotective potential in several models of neurological diseases. Here we show that preoperative serum level of irisin is reduced in dementia patients over the age of 70. Comprehensive proteomics analysis reveals that deletion of irisin affects the nervous and immune systems, and reduces the expression of complement proteins. Systemically administered irisin penetrates the blood-brain barrier in mice, targets the microglial integrin αVβ5 receptor, activates signal transducer and activator of transcription 6 (STAT6), induces microglia reprogramming to the M2 phenotype, and improves immune microenvironment in LPS-induced neuroinflammatory mice. Finally, prophylactic administration of irisin prevents POCD-like behavior, particularly early cognitive dysfunction. Our findings provide new insights into the direct regulation of the immune microenvironment by irisin, and reveal that recombinant irisin holds great promise as a novel therapy for preventing POCD and other neuroinflammatory disorders. SUMMARY: Our findings reveal molecular and cellular mechanisms of irisin on neuroinflammation, and show that prophylactic administration of irisin prevents POCD-like behavior, particularly early cognitive dysfunction.

Perioperative neurocognitive disorders (PND) is one of the most common postoperative complications, which can lead to a harmful impact on self-dependence, longer hospital stays, increased medical costs, morbidity, and mortality amongst older adults. Microglia can modulate synapse elimination involved in the complement component protein 1q (C1q) pathway to induce cognitive dysfunction, which is significantly improved by short chain fatty acids (SCFAs) treatment. Here we investigate the effects of SCFAs treatment on PND via mediating C1q complement pathway. High-throughput sequencing of 16S rDNA from fecal samples of male SD rats was applied to assess the changes in gut microbiota. Fecal microbiota transplantation (FMT) was performed to investigate whether gut microbiota from PND rats could alter cognitive impairment. The blood from the rat tail vein was collected to measure the SCFAs concentrations. Hippocampal and brain tissue samples were obtained to perform Western blots, Golgi and immunofluorescence staining. Primary microglia treated with SCFAs or Histone deacetylase inhibitor were cultured to measure microglial activation states and the expression of acetylated histone. The 16S rDNA sequencing results showed that PND rats had the significant changes in the species diversity of the gut microbiota and the metabolite of specifc species. Gut microbiota from PND rats could alter spatial learning and memory, and meanwhile, the changed SCFAs concentrations in plasma were involved. The synapse elimination in PND rats was strikingly reversed by SCFAs treatment involved in modulation complement C1q via suppressing neuroinflammation. This suggests that a link between gut microbiota dysbiosis and cognitive function impairment is involved in synapse elimination via mediating complement C1q pathway. SCFAs treatment can alleviate PND, the mechanisms of which may be associated with regulating complement C1q pathway.

Ischemic stroke is a cerebrovascular disease associated with high mortality and disability rates. Since the inflammation and immune response play a central role in driving ischemic damage, it becomes essential to modulate excessive inflammatory reactions to promote cell survival and facilitate tissue repair around the injury site. Various cell types are involved in the inflammatory response, including microglia, astrocytes, and neutrophils, each exhibiting distinct phenotypic profiles upon stimulation. They display either proinflammatory or anti-inflammatory states, a phenomenon known as 'cell polarization.' There are two cell polarization therapy strategies. The first involves inducing cells into a neuroprotective phenotype in vitro, then reintroducing them autologously. The second approach utilizes small molecular substances to directly affect cells in vivo. In this review, we elucidate the polarization dynamics of the three reactive cell populations (microglia, astrocytes, and neutrophils) in the context of ischemic stroke, and provide a comprehensive summary of the molecular mechanisms involved in their phenotypic switching. By unraveling the complexity of cell polarization, we hope to offer insights for future research on neuroinflammation and novel therapeutic strategies for ischemic stroke.

Autophagy, a regulator of inflammation, has been implicated in various central nervous system pathologies. Despite this, the role and mechanisms of autophagy in lipopolysaccharide (LPS)-induced neuroinflammation are not clear. This study investigated whether autophagy can play a neuroprotective role in LPS-induced neuroinflammation.

Primary microglial cells and male C57BL/6 J mice were treated with LPS, autophagy inhibitors (3-methyladenine, 3-MA), or autophagy activators (rapamycin). Cell viability, NF-κB pathway activation, pro-inflammatory cytokine expression, M1 polarization, autophagy markers, and neuronal damage were evaluated via various techniques including CCK-8 assay, Western blot analysis, ELISA, immunohistochemistry, and histological staining.

LPS (1 μg/mL) effectively inhibited cell viability, stimulated the expression of IκB-α and NF-κB, and simultaneously suppressed autophagy protein expression. The pro-inflammatory cytokines IL-1β and IL-6 showed a significant increase. Contrary to the effect of 3-MA, the rapamycin treatment inhibited the polarization of microglia cells to the M1 type in the various groups of microglia cells after LPS stimulation. This was evidenced by decreased expression of cytokines IL-1β, IL-6, and CD86, and increased expression of Arg-1, IL-10, and CD206. In vivo experiments found that mice with injections of LPS and 3-MA in the lateral ventricle showed significantly increased expression of IκB-α and NF-κB in brain tissues, elevated levels of pro-inflammatory cytokines, decreased autophagy levels, and increased necrotic neurons. There was increased aggregation of microglia cells and increased neuronophagocytosis. Conversely, mice injected with rapamycin showed enhanced neuronal cell autophagy, decreased expression of pro-inflammatory cytokines and apoptosis, and reduced neuronophagocytosis.

Enhancing autophagy can effectively mitigate LPS-induced neuroinflammation by inhibiting microglial M1 polarization and neuronophagocytosis, thereby protecting neuronal integrity. These findings suggest potential therapeutic strategies targeting autophagy in neuroinflammatory conditions.

Exosomes, which are small extracellular vesicles (sEVs), serve as versatile regulators of intercellular communication in the progression of various diseases, including neurological disorders. Among the diverse array of cargo they carry, non-coding RNAs (ncRNAs) play key regulatory roles in various pathophysiological processes. Exosomal ncRNAs derived from distinct cells modulate their reciprocal crosstalk locally or remotely, thereby mediating neurological diseases. Nevertheless, the emerging role of exosomal ncRNAsin microglia-mediated phenotypes remains largely unexplored. This review aims to summarise the biological functions of exosomal ncRNAs and the molecular mechanisms that underlie their impact on microglia-mediated intercellular communication, modulating neuroinflammation and synaptic functions within the landscape of neurological disorders. Furthermore, this review comprehensively described the potential applications of exosomal ncRNAs as diagnostic and prognostic biomarkers, as well as innovative therapeutic targets for the treatment of neurological diseases.

Ischemic stroke is a serious clinical condition that is challenging to cure; therefore, slowing down the depletion of ATP is crucial to enhancing the tolerance of ischemic tissue through preconditioning. Electroacupuncture (EA) preconditioning induces tolerance to cerebral ischemia; however, the underlying mechanism remains unclear.

The P2×7 receptor (P2×7R) mediates the stimulation of microglial cells and is involved in the development of cerebral ischemia-reperfusion (I/R) damage. We hypothesized that the protective effect of EA preconditioning is associated with the downregulation of P2×7R expression.

We performed EA at the "Baihui" and "Fengfu" for 30 min before establishing a rat model of cerebral I/R induced based on the middle cerebral artery occlusion model (MCAO). MCAO rats were administered a ventricular injection of 2 '(3')-O-(4-benzoyl) adenosine triphosphate (BzATP), a P2×7R agonist, 30 min before EA. Neurologic scoring, infarction volume, and expression of cytokines, Bcl-2 and Bax, Iba1, P2×7R, p38, and phosphorylated p38 (p-p38) in ischemia penumbra were detected 24 h after cerebral I/R.

EA preconditioning ameliorated neurologic scoring, decreased infarction volume, and neuronal injury, and decreased cytokine release, while BzATP exacerbated cerebral I/R damage and inflammation events, unlike the favorable efficacy of EA. EA inhibited the expression of Iba-1, P2×7R, and p-p38/p38 in the ischemic penumbra, whereas BzATP reversed this effect.

EA could induce cerebral tolerance to I/R damage by suppressing P2×7R expression and release of inflammatory factors.

Microglia, the primary immune cells of the central nervous system (CNS), are crucial in maintaining brain homeostasis and responding to pathological changes. While they play protective roles, their activation can lead to neuroinflammation and the progression of neurodegenerative diseases. Metal nanoparticles (NPs), due to their unique ability to cross the blood-brain barrier (BBB), have emerged as promising agents for drug delivery to the CNS. In this way, we aim to review the dual role of metal-containing NPs, gold (AuNPs), silver (AgNPs), iron oxide (IONPs), zinc oxide (ZnONPs), cobalt (CoNPs), titanium dioxide (TiO2NPs), and silica (SiO2NPs) in modulating microglial activity. Some NPs promote anti-inflammatory effects, while others exacerbate neuroinflammation. We examine how these NPs influence microglial activation, focusing on their potential therapeutic benefits and risks. A deeper understanding of NP-microglia interactions is crucial for developing safe and efficient treatments for neuroinflammatory and neurodegenerative disorders.

Microglia are key immune cells in the central nervous system (CNS) and maintain hemostasis in physiological conditions. Microglial depletion leads to rapid repopulation, but the gene expression and signaling pathways related to repopulation remain unclear. Here, we used RNA sequencing (RNA-Seq) analysis to profile the transcriptome of microglia-depleted tissue by taking advantage of a conditional genetic microglial depletion model (CX3CR1CreER/+ system). Differential gene expression (DGE) sequencing analysis showed that 1226 genes were differentially up- and downregulated in both groups compared to control. Our data demonstrated that many microglial genes were highly regulated on day 3 after depletion but the numbers of differentially expressed genes were reduced by day 7. Gene ontology (GO) analysis categorized these differentially expressed genes on day 3 and day 7 to the specific biological processes, such as cell proliferation, cell activation, and cytokine and chemokine production. DGE analysis indicated that specific genes related to proliferation were regulated after depletion. Consistent with the changes in transcriptome, the histological analysis of transgenic mice revealed that the microglia after depletion undergo proliferation and activation from day 3 to day 7. Collectively, these results suggest that transcriptomic changes in microglial genes during depletion have a profound implication for the renewal and activation of microglia and may help to understand the regulatory mechanism of microglial activation in disease conditions.

Over the past two decades, microglia and astrocytes have emerged as critical mediators of neural circuit formation. Particularly during the postnatal period, both glial subtypes play essential roles in orchestrating nervous system development through communication with neurons. These functions include regulating synapse elimination, modulating neuronal density and activity, mediating synaptogenesis, facilitating axon guidance and organization, and actively promoting neuronal survival. Despite the vital roles of both microglia and astrocytes in ensuring homeostatic brain development, the extent to which the postnatal functions of these cells are regulated by sex and the manner in which these glial cells communicate with one another to coordinate nervous system development remain less well understood. Here, we review the critical functions of both microglia and astrocytes independently and synergistically in mediating neural circuit formation, focusing our exploration on the postnatal period from birth to early adulthood.

Monitoring the morphological and biochemical information of neurons and glial cells at high temporal resolution in three-dimensional (3D) volumes of in vivo is pivotal for understanding their structure and function, and quantifying the brain microenvironment. Conventional two-photon fluorescence lifetime volumetric imaging speed faces the acquisition speed challenges of slow serial focal tomographic scanning, complex post-processing procedures for lifetime images, and inherent trade-offs among contrast, signal-to-noise ratio, and speed. This study presents a two-photon fluorescence lifetime volumetric projection microscopy using an axially elongated Bessel focus and instant frequency-domain fluorescence lifetime technique, and integrating with a convolutional network to enhance the imaging speed for in vivo neurodynamics mapping. The proposed method is validated by monitoring intracellular Ca2+ concentration throughout whole volume, tracking microglia movement and microenvironmental changes following thermal injury in the zebrafish brain, analyzing structural and functional variations of gap junctions in astrocyte networks, and measuring the Ca2+ concentration in neurons in mouse brains. This innovative methodology enables quantitative in vivo visualization of neurodynamics and the cellular processes and interactions in the brain.

Neuroinflammation is a critical factor in the pathogenesis of various neurodegenerative and psychiatric disorders, including Alzheimer's disease, Parkinson's disease, and major depressive disorder. Psychedelics, such as psilocybin, lysergic acid diethylamide (LSD), and dimethyltryptamine (DMT), have demonstrated promising therapeutic effects on neuroinflammation, primarily through interactions with serotonin (5-HT) receptors, particularly the 5-HT2A receptor. Activation of these receptors by psychedelics modulates the production of pro-inflammatory cytokines, regulates microglial activity, and shifts the balance between neurotoxic and neuroprotective metabolites. Additionally, psychedelics affect critical signaling pathways, including the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), phosphatidylinositol-3-kinase/protein kinase B (PI3K/Akt), and mechanistic target of rapamycin (mTOR) pathways, promoting neuroplasticity and exerting anti-inflammatory effects. Beyond the serotonergic system, other neurotransmitter systems-including the glutamatergic, dopaminergic, noradrenergic, gamma-aminobutyric acid (GABAergic), and cholinergic systems-also play significant roles in mediating the effects of psychedelics. This review examines the intricate mechanisms by which psychedelics modulate neuroinflammation and underscores their potential as innovative therapeutic agents for treating neuroinflammatory and neuropsychiatric disorders.

Alzheimer's disease (AD), a prevalent neurodegenerative disorder, predominantly affects individuals over the age of 65 and poses significant challenges in terms of effective management and treatment. The disease's pathogenesis involves complex molecular pathways including misfolded proteins accumulation, neuroinflammation, and synaptic dysfunction. Recent insights have highlighted the role of microRNAs (miRNAs) as critical regulators within these pathways, where they influence gene expression and contribute to the pathophysiological landscape of AD. Notably, emerging research has demonstrated that polyphenols, including curcumin, might modulate miRNA activity, thus offering a novel approach to mitigate AD symptoms and progression. This review explores the potential mechanisms through which polyphenols regulate miRNA expression and activity, specifically focusing on autophagy enhancement and inflammation reduction in the context of AD. We provide a detailed examination of key studies linking miRNA dysregulation to AD pathogenesis and discuss how polyphenols might correct these aberrations. The findings presented here underscore the therapeutic potential of polyphenols in AD treatment via miRNA modulation, pointing to new directions in disease management strategies and highlighting the need for targeted research into miRNA-based interventions.

Background: Anxiety disorders are the most common mental illnesses. S. aureus is a Gram-positive opportunistic pathogen most commonly associated with anxiety-like behaviors. Minocycline ameliorates Gram-negative bacterial LPS-induced anxiety-like behaviors by suppressing microglia activation. However, the effects of minocycline on anxiety-like behaviors caused by S. aureus infections have received little attention. In this study, we aimed to investigate the molecular mechanism and effect of minocycline on anxiety-like behaviors caused by S. aureus infection. Methods: BV2 and N9 microglial cells were treated in vitro. The effects of minocycline on lipoteichoic acid (LTA)-stimulated inflammatory responses, STAT3 activation, and GLS1 expression were assessed using Western blotting, and cytokine secretion was determined using an ELISA. A mouse model was used to evaluate the capacity of minocycline to ameliorate anxiety-like behaviors caused by S. aureus infection. Results: We found that ≥100 μmol/L of minocycline remarkably attenuated LTA-induced TLR2 signaling pathway activation and proinflammatory cytokine expression in microglial cells. Minocycline prevented LTA-stimulated STAT3 activation and GLS1 expression in vitro. LTA-induced TLR2, TNF-α, IL-6, and GLS1 expression was markedly reduced by the inhibition of STAT3 phosphorylation. Mice were pretreated with 50 mg/kg of minocycline, significantly attenuating microglial activation and neuroinflammation. Minocycline also effectively alleviated the anxiety-like behaviors induced by S. aureus infection. Conclusions: Our findings indicate that minocycline alleviates S. aureus infection-induced anxiety-like behaviors by suppressing microglia activation.

The recent approval of lecanemab highlights that the amyloid beta (Aβ) protein is an important pathological target in Alzheimer's disease (AD) and further emphasizes the significance of neuroinflammatory pathways in regulating Aβ accumulation. Indeed, Aβ accumulation triggers microglia activation, which are key mediators in neuroinflammation. The inflammatory responses in this process can lead to neuronal damage and functional decline. Microglia secrete proinflammatory cytokines that accelerate neuronal death and release anti-inflammatory cytokines and growth factors contributing to neuronal recovery and protection. Thus, microglia play a dual role in neurodegeneration and neuroprotection, complicating their function in AD. Therefore, elucidating the complex interactions between Aβ protein, microglia, and neuroinflammation is essential for developing new strategies for treating AD. This review investigates the receptors and pathways involved in activating microglia and aims to enhance understanding of how these processes impact neuroinflammation in AD, as well as how they can be regulated. This review also analyzed studies reported in the existing literature and ongoing clinical trials. Overall, these studies will contribute to understanding the regulatory mechanisms of neuroinflammation and developing new therapies that can slow the pathological progression of AD.

Neuroinflammation and mitochondrial dysfunction are early events in Alzheimer's disease (AD) and contribute to neurodegeneration and cognitive impairment. Evidence suggests that the inflammatory axis mediated by macrophage migration inhibitory factor (MIF) binding to its receptor, CD74, plays an important role in many central nervous system (CNS) disorders such as AD. Our group has developed DRhQ, a novel CD74 binding construct which competitively inhibits MIF binding, blocks macrophage activation and migration into the CNS, enhances anti-inflammatory microglia cell numbers and reduces pro-inflammatory gene expression. Here, we evaluate its effects in amyloid-β (Aβ) overexpressing mice. 5xFAD mice and their wild type littermates were treated with DRhQ (100 µg) or vehicle for 4 weeks. DRhQ improved cognition and cortical mitochondrial function in both male and female 5xFAD mice. Aβ plaque burden in 5xFAD animals was not robustly impacted by DRhQ treatment in either the hippocampus or the cortex. Cortical microglial activation was similarly not apparently affected by DRhQ treatment, although in the hippocampus there was evidence of a reduction in activated microglia for female 5xFAD mice. Future studies are needed to confirm this possible sex-dependent response on microglial activation, as well as to optimize the dose and timing of DRhQ treatment and gain a better understanding of its mechanism of action in AD.

Persistent reactive oxygen species (ROS) and neuroinflammation contribute to the onset and progression of neurodegenerative diseases, underscoring the need for targeted therapeutic strategies to mitigate these effects. Extracellular vesicles (EVs) show promise in drug delivery due to their biocompatibility, ability to cross biological barriers, and specific interactions with cell and tissue receptors. In this study, we demonstrated that human plasma-derived EVs (pEVs) exhibit higher brain-targeting specificity, while adipose-derived mesenchymal stem cells EVs (ADMSC-EVs) offer regenerative and immunomodulatory properties. We further investigated the potential of these EVs as therapeutic carriers for brain-targeted drug delivery, using Donepezil (DNZ) as the model drug. DNZ, a cholinesterase inhibitor commonly used for Alzheimer's disease (AD), also has neuroprotective and anti-inflammatory properties. The size of EVs used ranged from 50 to 300 nm with a surface charge below -30 mV. Both formulations showed rapid cellular internalization, without toxicity, and the ability to cross the blood-brain barrier (BBB) in a zebrafish model. The have analyzed the anti-inflammatory and antioxidant actions of pEVs-DNZ and ADMSC-EVs-DNZ in the presence of lipopolysaccharide (LPS). ADMSC-EVs significantly reduced the inflammatory mediators released by HMC3 microglial cells while treatment with pEVs-DNZ and ADMSC-EVs-DNZ lowered both phagocytic activity and ROS levels in these cells. In vivo experiments using zebrafish larvae revealed that both EV formulations reduced microglial proliferation and exhibited antioxidant effects. Overall, this study highlights the potential of EVs loaded with DNZ as a novel approach for treating neuroinflammation underlying various neurodegenerative diseases.

While widefield microscopy has long been constrained by out-of-focus scattering, advancements have generated a solution in the form of confocal laser scanning microscopy (cLSM) and optical sectioning microscopy using structured illumination (OSM). In this study, we aim to investigate, using microglia branching, if cLSM and OSM can produce images with comparable morphological characteristics.

By imaging the somatosensory microglia from a tissue slice of a 3-week-old mouse and establishing morphological parameters that characterizes the microglial branching pattern, we were able to show that there is no difference in total length of the branch tree, number of branches, mean branch length and number of primary to terminal branches. We did find that area-based parameters such as mean occupied area and mean surveillance area were bigger in cLSM isolated microglia compared to OSM ones. Additionally, by investigating the difference in acquisition time between techniques and personal costs we were able to establish that the amortization could be made in 6.11 ± 2.93 years in the case of countries with a Human Development Index (HDI) = 7-9 and 7.06 ± 3.13 years, respectably, for countries with HDI < 7. As such, OSM systems seem a valid option if one just wants basic histological evaluation, and cLSM should be considered for groups that demand higher resolution or volumetric images.

Repurposing drugs (DR) has become a viable approach to hasten the search for cures for neurodegenerative diseases (NDs). This review examines different off-target and on-target drug discovery techniques and how they might be used to find possible treatments for non-diagnostic depressions. Off-target strategies look at the known or unknown side effects of currently approved drugs for repositioning, whereas on-target strategies connect disease pathways to targets that can be treated with drugs. The review highlights the potential of experimental and computational methodologies, such as machine learning, proteomic techniques, network and genomics-based approaches, and in silico screening, in uncovering new drug-disease correlations. It also looks at difficulties and failed attempts at drug repurposing for NDs, highlighting the necessity of exact and standardised procedures to increase success rates. This review's objectives are to address the purpose of drug repurposing in human disorders, particularly neurological diseases, and to provide an overview of repurposing candidates that are presently undergoing clinical trials for neurological conditions, along with any possible causes and early findings. We then include a list of drug repurposing strategies, restrictions, and difficulties for upcoming research.

Retrotransposon Gag-like 4 (RTL4), a gene acquired from a retrovirus, is a causative gene in autism spectrum disorder. Its knockout mice exhibit increased impulsivity, impaired short-term spatial memory, failure to adapt to novel environments, and delayed noradrenaline (NA) recovery in the frontal cortex. However, due to its very low expression in the brain, it remains unknown which brain cells express RTL4 and its dynamics in relation to NA. We addressed these issues using knock-in mice carrying endogenous Rtl4 fused to Venus, which encodes a fluorescent protein. The RTL4-Venus fusion protein was detected as a secreted protein in the midbrain, hypothalamus, hippocampus and amygdala in the postnatal brain. Its signal intensity was high during critical periods of neonatal adaptation to novel environments. It was upregulated by various stimuli, including isoproterenol administration, whereas it was decreased by anesthesia but was maintained by milnacipran administration, suggesting its highly sensitive response to stressors, possible dependence on the arousal state and involvement in the NA reuptake process. In vitro mixed glial culture experiments demonstrated that Rtl4 is a microglial gene and suggested that RTL4 secretion responds rapidly to isoproterenol. Microglial RTL4 plays an important role in the NA response and possibly in the development of the NAergic neuronal network in the brain.

Neuropathic pain is a chronic pain condition that is primarily caused by underlying neurological damage and dysfunction. Recent studies have identified microRNAs (miRNAs) as a key factor in the treatment of neuropathic pain. To explore the effects of miR-133a-3p on neuroinflammation and neuropathic pain via GTP cyclohydrolase (GCH1), and its underlying mechanisms. In vitro models were constructed using BV-2 cells that had been treated with lipopolysaccharide, followed by treatment with either miR-133a-3p mimic or GCH1 viral knockdown/overexpression. The expression of miR-133a-3p and GCH1 in BV-2 cells was quantified by RT-qPCR. The degree of neuroinflammation was quantified using an enzyme-linked immunosorbent assay (ELISA). The targeting relationship between miR-133a-3p and GCH1 was confirmed by western blot and dual luciferase reporter assay. A chronic constriction injury model was employed to induce neuropathic pain in rats, and the mechanical withdrawal threshold (MWT) was quantified. Immunofluorescence was used to demonstrate alterations in microglial cells. The expression of miR-133a-3p was found to be decreased in lipopolysaccharide-induced BV-2 cells. The overexpression of miR-133a-3p was observed to inhibit the expression of IL-1β, IL-6, TNF-α and iNOS, which was attributed to a reduction in GCH1.Nevertheless, OE-GCH1 could partially reverse the downregulation by miR-133a-3p of the expression of inflammatory factors. In animal experiments, intrathecal injection of AVV-miR-133a-3p was observed to alleviate mechanical nociceptive abnormalities induced by activated microglia. Furthermore, miR-133a-3p ameliorated neuroinflammation in the spinal cord of chronic constriction injury rats. In summary, miR-133a-3p improves neuroinflammation and neuropathic pain by binding to GCH1. The binding of miR-133a-3p to GCH1 has been demonstrated to improve neuroinflammation and neuropathic pain.This insight will facilitate the development of new methods to effectively treat neuropathic pain.

Depression is a highly prevalent psychological disorder characterized by persistent dysphoria, psychomotor retardation, insomnia, anhedonia, suicidal ideation, and a remarkable decrease in overall well-being. Despite the prevalence of accessible antidepressant therapies, many individuals do not achieve substantial improvement. Understanding the multifactorial pathophysiology and the heterogeneous nature of the disorder could lead the way toward better outcomes. Recent findings have elucidated the substantial impact of compromised blood-brain barrier (BBB) integrity on the manifestation of depression. BBB functions as an indispensable defense mechanism, tightly overseeing the transport of molecules from the periphery to preserve the integrity of the brain parenchyma. The dysfunction of the BBB has been implicated in a multitude of neurological disorders, and its disruption and consequent brain alterations could potentially serve as important factors in the pathogenesis and progression of depression. In this review, we extensively examine the pathophysiological relevance of the BBB and delve into the specific modifications of its components that underlie the complexities of depression. A particular focus has been placed on examining the effects of peripheral inflammation on the BBB in depression and elucidating the intricate interactions between the gut, BBB, and brain. Furthermore, this review encompasses significant updates on the assessment of BBB integrity and permeability, providing a comprehensive overview of the topic. Finally, we outline the therapeutic relevance and strategies based on BBB in depression, including COVID-19-associated BBB disruption and neuropsychiatric implications. Understanding the comprehensive pathogenic cascade of depression is crucial for shaping the trajectory of future research endeavors.