Altered synaptic connectivity and brain function in mice lacking microglial adapter protein Iba1

TAMing Gliomas: Unraveling the Roles of Iba1 and CD163 in Glioblastoma

Gliomas, the most common type of primary brain tumor, are a significant cause of morbidity and mortality worldwide. Glioblastoma, a highly malignant subtype, is particularly common, aggressive, and resistant to treatment. The tumor microenvironment (TME) of gliomas, especially glioblastomas, is characterized by a distinct presence of tumor-associated macrophages (TAMs), which densely infiltrate glioblastomas, a hallmark of these tumors. This macrophage population comprises both tissue-resident microglia as well as macrophages derived from the walls of blood vessels and the blood stream. Ionized calcium-binding adapter molecule 1 (Iba1) and CD163 are established cellular markers that enable the identification and functional characterization of these cells within the TME. This review provides an in-depth examination of the roles of Iba1 and CD163 in malignant gliomas, with a focus on TAM activation, migration, and immunomodulatory functions. Additionally, we will discuss how recent advances in AI-enhanced cell identification and visualization techniques have begun to transform the analysis of TAMs, promising unprecedented precision in their characterization and providing new insights into their roles within the TME. Iba1 and CD163 appear to have both unique and shared roles in glioma pathobiology, and both have the potential to be targeted through different molecular and cellular mechanisms. We discuss the therapeutic potential of Iba1 and CD163 based on available preclinical (experimental) and clinical (human tissue-based) evidence.

Shuanglu tongnao formula alleviates cerebral ischemia/reperfusion injury by rebuilding inflammatory microenvironment after cerebral ischemia

ETHNOPHARMACOLOGICAL SIGNIFICANCE

Shuanglu tongnao formula (SLTNF) has been clinically proven to have significant efficacy in the treatment of Ischemic stroke (IS), and is a promising formula for IS treatment. Still, the underlying mechanism is not clear. Whether SLTNF ameliorates ischemic brain injury by reversing the pro-inflammatory microenvironment after IS is an interesting field of investigation.

AIM OF THE STUDY

Based on the result of network pharmacology and single-cell RNA sequencing (scRNA-seq), whether SLTNF mitigates cerebral ischemia/reperfusion (I/R) injury by reversing the pro-inflammatory microenvironment was investigated in vivo for the first time.

MATERIALS AND METHODS

The mice middle cerebral artery occlusion (MCAO) model was established to induce focal cerebral I/R. Subsequently, the remission effects of SLTNF treatment for cerebral I/R injury were evaluated in the MCAO model. scRNA-seq data was used to analyze the immune microenvironment after IS in mice. scRNA-seq and Network pharmacology were applied to predict the mechanism of the treatment of IS by SLTNF. Western blot (WB) and immunofluorescence techniques were employed to validate the potential mechanism.

RESULTS

The experimental results demonstrated that SLTNF dosage-dependently attenuated the infarct volume, neurobehavioral, cell morphology and Nissl bodies damage, and inhibited the apoptosis in cerebral I/R mice. Moreover, scRNA-seq results revealed that the number of NK cells, neutrophils, monocytes, astrocytes and microglia significantly increased after IS. The cell-cell interactions dominated by microglia after IS, the cell-cell interactions between microglia and other immune cells significantly heightened. Furthermore, SLTNF promoted the transition of M1 microglia to M2 type, eventually reversing the pro-inflammatory microenvironment. Combined analysis of scRNA-seq and Network pharmacology results predicted that AGE-RAGE signaling pathway could involve in the regulation of microglia polarization by SLTNF. WB results revealed that SLTNF significantly inhibited the protein expression of CCND1, IL-1β and p-STAT3, which belong to crucial targets of SLTNF and AGE-RAGE signaling pathway.

CONCLUSION

SLTNF attenuated cerebral I/R injury by reversing the pro-inflammatory microenvironment via the AGE-RAGE signaling pathway in mice.

Immune Dysregulation in Depression and Anxiety: A Review of the Immune Response in Disease and Treatment

Rates of depression and anxiety have increased significantly in recent decades, with many patients experiencing treatment-resistant symptoms. Beyond psychiatric manifestations, these conditions are associated with heightened risks of suicide, cardiovascular disease, chronic pain, and fatigue. Emerging research suggests that neuroinflammation, immune dysregulation, and hypothalamic-pituitary-adrenal axis dysfunction contribute to their pathophysiology, often interacting bidirectionally with stress. While current first-line treatments primarily target neurotransmitter imbalances, many patients do not achieve symptom resolution, highlighting the need for novel approaches. This review explores the role of immune dysfunction, cytokine activity, and neurotransmitter interactions in depression and anxiety. Additionally, we examine how existing pharmacological and non-pharmacological interventions influence inflammation and immune responses. Understanding these mechanisms may pave the way for more integrative treatment strategies that combine immune modulation with traditional psychiatric therapies.

The transcription factor MEF2C restrains microglial overactivation by inhibiting kinase CDK2

Microglial intrinsic immune checkpoints are essential safeguards to maintain immune homeostasis by preventing microglial overactivation, a process that substantially influences neurological disorders such as autism spectrum disorder (ASD). MEF2C is a crucial immune checkpoint that regulates microglial activation, but the mechanism remains unclear. We found that MEF2C-deficient (MEF2C-/-) induced microglia-like cells (iMGLs) derived from human pluripotent stem cells (hPSCs) exhibited overactivation following lipopolysaccharide stimulation, mimicking patterns observed in various neuroinflammatory disorders. High-throughput screening identified BMS265246, a cyclin-dependent kinase 2 (CDK2) inhibitor, which suppressed overactivation of MEF2C-/- iMGLs and normalized their inflammatory responses. Mechanistically, MEF2C transcriptionally upregulated p21 to inhibit CDK2 activation-mediated retinoblastoma protein (RB) degradation, thereby preventing transcription factor nuclear factor κB (NFκB) nuclear translocation and consequent microglial overactivation. BMS265246 treatment substantially ameliorated microglial overactivation and ASD-like behaviors in Mef2c-deficient mice. Our findings identify the MEF2C-p21-CDK2-RB-NFκB axis as a critical pathway to maintain microglial homeostasis and highlight CDK2 as a potential therapeutic target for neuroinflammation.

Traditional pediatric massage exerted an antidepressant effect and activated IGF-1/Nrf2 pathway in CUMS-exposed adolescent rats

The activation of insulin-like growth factor-1 (IGF-1)/nuclear factor-erythroid 2 related factor 2 (Nrf2) pathway contributes to enhance anti-inflammatory M2 microglia polarization and inhibit proinflammatory M1 microglia polarization, which is essential to resist neuroinflammation and thus resist depression. The prevalence of depression is high in adolescents, who are hypersensitive to chronic stress. Traditional pediatric massage (TPM) can effectively relieve depression. In this study, we investigated the action mechanism of TPM on preventing depression-like behaviors in adolescent rats exposed to chronic unpredictable mild stress (CUMS). In this investigation, we employed several behavioral tests and detections, including western blotting, immunofluorescence staining and RT-qPCR. The findings of this study demonstrated that TPM had an effectively antidepressant effect, maintained microglia polarization homeostasis and resisted neuroinflammation in the hippocampus in CUMS-exposed adolescent rats. With the treatment of picropodophyllin, the inhibitor of IGF-1 receptor, the antidepressant effect of TPM was blocked, along with inhibited IGF-1/Nrf2 pathway which were closely related with anti-inflammatory and anti-ferroptosis actions. The results suggest that TPM enhanced the resilience of adolescent rats to CUMS and exerted an antidepressant effect partially via activating IGF-1/Nrf2 pathway.

Embryonic exposure to 6:2 fluorotelomer alcohol mediates autism spectrum disorder-like behavior by dysfunctional microbe-gut-brain axis in mice

6:2 fluorotelomer alcohol (6:2 FTOH) is considered an emerging contaminant as a substitute for perfluoroalkyl and polyfluoroalkyl substances. Autism spectrum disorder (ASD) is a highly heterogeneous childhood neurodevelopmental disorder, the prevalence of which has been significantly increasing globally, possibly due to rising exposure to environmental pollutants. Additionally, the microbe-gut-brain axis plays a crucial role in the development of ASD. The purpose of study was to investigate the impact of embryonic 6:2 FTOH exposure on neurological development in mice and explore the potential involvement of the microbe-gut-brain. Pregnant mice were orally administered 6:2 FTOH from gestation day 8.5 until delivery, and follow-up testing was performed on day 22 post-delivery. The findings revealed that embryonic exposure to 6:2 FTOH led to ASD-like symptoms, cortical neuron apoptosis, glial cell activation, and abnormal synapse formation in mice. Furthermore, impairment of colonic barrier function, inflammatory response, and dysbiosis in gut microbiota were observed. Interestingly, supplementation with Lactobacillus rhamnosus GG during embryonic development mitigated these adverse outcomes. This study enhances our understanding of how environmental pollutants can impact neurological development in children and provides valuable insights for clinical prevention, diagnosis, and treatment strategies for non-genetic ASD.

Cocaine-Induced Microglial Impairment and Its Rehabilitation by PLX-PAD Cell Therapy

Chronic cocaine use triggers inflammatory and oxidative processes in the central nervous system, resulting in impaired microglia. Mesenchymal stem cells, known for their immunomodulatory properties, have shown promise in reducing inflammation and enhancing neuronal survival. The study employed the cocaine self-administration model, focusing on ionized calcium-binding adaptor protein 1 (Iba-1) and cell morphology as markers for microglial impairment and PLX-PAD cells as a treatment for attenuating cocaine craving. The results revealed an addiction-stage and region-specific impairment in microglia following chronic cocaine exposure, with deficits observed in the Nucleus Accumbens (NAc) during the maintenance stage and in both the NAc and Dentate Gyrus (DG) during the extinction and reinstatement stages. Furthermore, PLX-PAD cell therapy demonstrated a significant reduction in cocaine craving and seeking behavior, interestingly accompanied by the prevention of Iba-1 level decrease and restoration of microglial activity in the NAc and DG. These findings highlight the unique role of microglia in modulating cocaine addiction behaviors through their influence on synaptic plasticity and neuronal remodeling associated with memory formation. They also suggest that PLX-PAD therapy may mitigate the detrimental effects of chronic cocaine exposure on microglia, underscoring the importance of incorporating microglia in comprehensive addiction rehabilitation strategies.

NEK7 induces lactylation in Alzheimer's disease to promote pyroptosis in BV-2 cells

Alzheimer's disease (AD), an age-related neurodegenerative disorder, is characterized by irreversible brain tissue degeneration. The amyloid-β (Aβ) cascade hypothesis stands as the predominant paradigm explaining AD pathogenesis. This study aimed to elucidate the mechanisms underlying Aβ-induced pyroptosis in AD. AD models were established using amyloid precursor protein/presenilin 1 (APP/PS1) transgenic mice and Aβ-treated BV-2 cells (5 µM, 24 h). NEK7 expression was evaluated in vitro and in vivo. Cell pyroptosis was assessed before and after NEK7 expression was inhibited in BV-2 cells. Adeno-associated virus (AAV) vectors carrying short hairpin RNA (shRNA) against NEK7 (AAV-sh-NEK7) were administered to mice to knockdown NEK7 in vivo. Spatial learning and memory abilities were evaluated using the Morris water maze test. The interaction between NEK7 and histone H4 lysine 12 lactylation (H4K12la) were then investigated. The results suggested that NEK7 expression was markedly elevated in both in vitro and in vivo AD models. Treatment with Aβ significantly reduced cell viability and enhanced pyroptosis in BV-2 cells; these effects were reversed by inhibiting NEK7. Furthermore, AD mice with NEK7 knockdown exhibited shorter escape latencies and increased time spent in the target quadrant, suggesting that NEK7 inhibition improved cognitive function and memory retention. Mechanistically, Aβ treatment induced histone lactylation in BV-2 cells, and suppression of lactylation attenuated NEK7 transcriptional activity and mRNA levels. In summary, elevated NEK7 expression promoted histone lactylation in BV-2 cells, thereby facilitating pyroptosis. Inhibition of NEK7 conferred protection against Aβ-induced cellular damage and enhanced cognitive performance and memory retention in AD model mice. Collectively, targeting NEK7 represents a potential therapeutic strategy for alleviating AD symptoms.

Activation of the Gut-Brain Interaction by Urolithin A and Its Molecular Basis

Background: Urolithin A (Uro-A), a type of polyphenol derived from pomegranate, is known to improve memory function when ingested, in addition to its direct effect on the skin epidermal cells through the activation of longevity gene SIRT1. However, the molI ecular mechanism by which orally ingested Uro-A inhibits cognitive decline via the intestine remains unexplored. Objectives: This study aimed to evaluate the role of Uro-A in improving cognitive function via improved intestinal function and the effect of Uro-A on the inflammation levels and gene expression in hippocampus. Methods: Research to clarify the molecular basis of the functionality of Uro-A was also conducted. Results: The results demonstrated that Uro-A suppressed age-related memory impairment in Aged mice (C57BL/6J Jcl, male, 83 weeks old) by reducing inflammation and altering hippocampal gene expression. Furthermore, exosomes derived from intestinal cells treated with Uro-A and from the serum of Aged mice fed with Uro-A both activated neuronal cells, suggesting that exosomes are promising candidates as mediators of the Uro-A-induced activation of gut-brain interactions. Additionally, neurotrophic factors secreted from intestinal cells may contribute to the Uro-A-induced activation of gut-brain interactions. Conclusions: This study suggests that Uro-A suppresses age-related cognitive decline and that exosomes and other secreted factors may contribute to the activation of the gut-brain interaction. These findings provide new insights into the therapeutic potential of Uro-A for cognitive health.

Co-localization and co-expression of Olfml3 with Iba1 in brain of mice

Olfml3 is a microglia-specific protein whose role in neuroinflammation is elusive. In silico analysis was conducted to characterize the Olfml3 protein, followed by molecular docking and MD simulation to check possible interaction with Iba1. Further, expression and co-localization analysis was performed in the LPS-induced neuroinflammatory mice brains. Results suggest that Olfml3 physically interacts with Iba1. Olfml3 and Iba1 expression increases during neuroinflammation in mice brains. Olfml3 was observed to co-localize with Iba1, and the number of Olfml3 and Iba1 dual-positive cells increased in the brain of the neuroinflammatory mice model. Thus, Olfml3 could potentially participate in microglia functions by interacting with Iba1.

Synaptic Pruning by Microglia: Lessons from Genetic Studies in Mice

BACKGROUND

Neural circuits are subjected to refinement throughout life. The dynamic addition and elimination (pruning) of synapses are necessary for maturation of neural circuits and synaptic plasticity. Due to their phagocytic nature, microglia have been considered as the primary mediators of synaptic pruning. Synaptic pruning can strengthen an active synapse by removing excess weaker synapses during development. Inappropriate synaptic pruning can often influence a disease outcome or an injury response.

SUMMARY

This review offers a focused discussion on microglial roles in synaptic pruning, based on the evidence gathered from genetic manipulations in mice. Genetically labeled microglia and synapses often allow assessment of their interactions in real time. Further manipulations involving synaptically localized molecules, neuronally or glial-derived diffusible factors, and their respective cognate receptors in microglia provide critical evidence in support of a direct role of microglia in synaptic pruning.

KEY MESSAGE

We discuss microglial contact-dependent "eat-me," "don't-eat-me," and "find-me" signals, as well as recently identified noncontact pruning, under the contexts of neural circuit, brain region, developmental window, and an injury or a disease state.

Suppression of the host antiviral response by non-infectious varicella zoster virus extracellular vesicles

Varicella zoster virus (VZV) reactivates from ganglionic sensory neurons to produce herpes zoster (shingles) in a unilateral dermatomal distribution, typically in the thoracic region. Reactivation not only heightens the risk of stroke and other neurological complications but also increases susceptibility to co-infections with various viral and bacterial pathogens at sites distant from the original infection. The mechanism by which VZV results in complications remote from the initial foci remains unclear. Small extracellular vesicles (sEVs) are membranous signaling structures that can deliver proteins and nucleic acids to modify the function of distal cells and tissues during normal physiological conditions. Although viruses have been documented to exploit the sEV machinery to propagate infection, the role of non-infectious sEVs released from VZV-infected neurons in viral spread and disease has not been studied. Using multi-omic approaches, we characterized the content of sEVs released from VZV-infected human sensory neurons (VZV sEVs). One viral protein was detected (immediate-early 62), as well as numerous immunosuppressive and vascular disease-associated host proteins and miRNAs that were absent in sEVs from uninfected neurons. Notably, VZV sEVs are non-infectious yet transcriptionally altered primary human cells, suppressing the antiviral type 1 interferon response and promoting neuroinvasion of a secondary pathogen in vivo. These results challenge our understanding of VZV infection, proposing that the virus may contribute to distant pathologies through non-infectious sEVs beyond the primary infection site. Furthermore, this study provides a previously undescribed immune-evasion mechanism induced by VZV that highlights the significance of non-infectious sEVs in early VZV pathogenesis.

IMPORTANCE

Varicella zoster virus (VZV) is a ubiquitous human virus that predominantly spreads by direct cell-cell contact and requires efficient and immediate host immune evasion strategies to spread. The mechanisms of immune evasion prior to virion entry have not been fully elucidated and represent a critical gap in our complete understanding of VZV pathogenesis. This study describes a previously unreported antiviral evasion strategy employed by VZV through the exploitation of the infected host cell's small extracellular vesicle (sEV) machinery. These findings suggest that non-infectious VZV sEVs could travel throughout the body, affecting cells remote from the site of infection and challenging the current understanding of VZV clinical disease, which has focused on local effects and direct infection. The significance of these sEVs in early VZV pathogenesis highlights the importance of further investigating their role in viral spread and secondary disease development to reduce systemic complications following VZV infections.

Accumulation of extracellular elastin-derived peptides disturbed neuronal morphology and neuron-microglia crosstalk in aged brain

Extracellular elastin-derived peptides (EDPs) accumulate in the aging brain and have been associated with vascular dementia and Alzheimer's disease (AD). The activation of inflammatory processes in glial cells with EDP treatment has received attention, but not in neurons. To properly understand EDPs' pathogenic significance, the impact on neuronal function and neuron-microglia crosstalk was explored further. Among the EDP molecules, Val-Gly-Val-Ala-Pro-Gly (VGVAPG) is a typical repeating hexapeptide. Here, we observed that EDPs-VGVAPG influenced neuronal survival and morphology in a dose-dependent manner. High concentrations of VGVAPG induced synapse loss and microglia hyperactivation in vivo and in vitro. Following EDP incubation, galectin 3 (Gal-3) released by neurons served as a chemokine, attracting microglial engulfment. Blocking Gal-3 and EDP binding remedied synapse loss in neurons and phagocytosis in microglia. In response to the accumulation of EDPs, proteomics in matrix remodeling and cytoskeleton dynamics, such as a disintegrin and metalloproteinase (ADAM) family, were engaged. These findings in extracellular EDPs provided more evidence for the relationship between aging and neuron dysfunction, increasing the insight of neuroinflammatory responses and the development of new specialized extracellular matrix remolding-targeted therapy options for dementia or other neurodegenerative disease.

Mir155hg Accelerates Hippocampal Neuron Injury in Convulsive Status Epilepticus by Inhibiting Microglial Phagocytosis

Convulsive status epilepticus (CSE) is a common critical neurological condition that can lead to irreversible hippocampal neuron damage and cognitive dysfunction. Multiple studies have demonstrated the critical roles that long non-coding RNA Mir155hg plays in a variety of diseases. However, less is known about the function and mechanism of Mir155hg in CSE. Here we investigate and elucidate the mechanism underlying the contribution of Mir155hg to CSE-induced hippocampal neuron injury. By applying high-throughput sequencing, we examined the expression of differentially expressed genes in normal and CSE rats. Subsequent RT-qPCR enabled us to measure the level of Mir155hg in rat hippocampal tissue. Targeted knockdown of Mir155hg was achieved by the AAV9 virus. Additionally, we utilized HE and Tunel staining to evaluate neuronal injury. Immunofluorescence (IF), Golgi staining, and brain path clamping were also used to detect the synaptic plasticity of hippocampal neurons. Finally, through IF staining and Sholl analysis, we assessed the degree of microglial phagocytic function. It was found that the expression of Mir155hg was elevated in CSE rats. HE and Tunel staining results showed that Mir155hg knockdown suppressed the hippocampal neuron loss and apoptosis followed CSE. IF, Golgi staining and brain path clamp data found that Mir155hg knockdown enhanced neuronal synaptic plasticity. The results from IF staining and Sholl analysis showed that Mir155hg knockdown enhanced microglial phagocytosis. Our findings suggest that Mir155hg promotes CSE-induced hippocampal neuron injury by inhibiting microglial phagocytosis.

Sex-specific impacts of prenatal bisphenol A exposure on genes associated with cortical development, social behaviors, and autism in the offspring's prefrontal cortex

BACKGROUND

Recent studies have shown that prenatal BPA exposure altered the transcriptome profiles of autism-related genes in the offspring's hippocampus, disrupting hippocampal neuritogenesis and causing male-specific deficits in learning. However, the sex differences in the effects of prenatal BPA exposure on the developing prefrontal cortex, which is another brain region highly implicated in autism spectrum disorder (ASD), have not been investigated.

METHODS

We obtained transcriptome data from RNA sequencing analysis of the prefrontal cortex of male and female rat pups prenatally exposed to BPA or control and reanalyzed. BPA-responsive genes associated with cortical development and social behaviors were selected for confirmation by qRT-PCR analysis. Neuritogenesis of primary cells from the prefrontal cortex of pups prenatally exposed to BPA or control was examined. The social behaviors of the pups were assessed using the two-trial and three-chamber tests. The male-specific impact of the downregulation of a selected BPA-responsive gene (i.e., Sema5a) on cortical development in vivo was interrogated using siRNA-mediated knockdown by an in utero electroporation technique.

RESULTS

Genes disrupted by prenatal BPA exposure were associated with ASD and showed sex-specific dysregulation. Sema5a and Slc9a9, which were involved in neuritogenesis and social behaviors, were downregulated only in males, while Anxa2 and Junb, which were also linked to neuritogenesis and social behaviors, were suppressed only in females. Neuritogenesis was increased in males and showed a strong inverse correlation with Sema5a and Slc9a9 expression levels, whereas, in the females, neuritogenesis was decreased and correlated with Anxa2 and Junb levels. The siRNA-mediated knockdown of Sema5a in males also impaired cortical development in utero. Consistent with Anxa2 and Junb downregulations, deficits in social novelty were observed only in female offspring but not in males.

CONCLUSION

This is the first study to show that prenatal BPA exposure dysregulated the expression of ASD-related genes and functions, including cortical neuritogenesis and development and social behaviors, in a sex-dependent manner. Our findings suggest that, besides the hippocampus, BPA could also exert its adverse effects through sex-specific molecular mechanisms in the offspring's prefrontal cortex, which in turn would lead to sex differences in ASD-related neuropathology and clinical manifestations, which deserves further investigation.

Neonatal microglia transplantation at early stage but not late stage after traumatic brain injury shows protective effects in mice

The transplantation of neonatal microglia suppresses neuroinflammation caused by traumatic brain injury (TBI). This research aimed to explore the optimal time point of neonatal microglia transplantation for the best effect on the improvement of long-term cognitive function and inflammatory response in mouse models. qPCR and immunoblotting showed that the level of Iba1 gradually increased to the highest on day 7 and then gradually declined in TBI mice. Furthermore, it was observed that the level of CD86 and TNF-α increased to the highest after 7 days and subsequently was maintained until day 21, whereas the level of CD206 and IL-10 increased to the highest after 24 h and subsequently decreased until day 21 by qPCR and enzyme-linked immunosorbent assay. Afterward, it was shown that the neonatal microglia transplantation within 1 h significantly attenuated anxiety-like behavior and improved cognitive impairments in TBI mice. Mechanism exploration showed that the neonatal microglia could significantly decrease the level of cleaved caspase-3, M1/M2 polarization, and inflammatory cytokine (TNF-α) while increasing the level of anti-inflammatory factor IL-10 in TBI mice after transplantation within 1 h. Here, our findings demonstrated that neonatal microglia transplantation within 1 h significantly attenuated anxiety-like behavior and cognitive impairments caused by TBI.NEW & NOTEWORTHY The study demonstrated that neonatal microglia transplantation within 1 h significantly inhibited the pathogenesis of traumatic brain injury (TBI) in mouse models through inhibition of M1 polarization and promotion of M2 polarization.

Effects of Exercise Training and L-Arginine Loaded Chitosan Nanoparticles on Hippocampus Histopathology, β-Secretase Enzyme Function, APP, Tau, Iba1and APOE-4 mRNA in Aging Rats

The objective of this study was to evaluate the combined and independent effects of exercise training and L-Arginine loaded chitosan nanoparticles (LA CNPs) supplementation on hippocampal Tau, App, Iba1, and ApoE gene expression, oxidative stress, β-secretase enzyme activity, and hippocampus histopathology in aging rats. Thirty-five male Wistar rats were randomly assigned to five groups (n = 7 in each): Young (8 weeks old), Old (20 months old), old + L-arginine supplementation (Old Sup), old + exercise (Old Exe) and old + L-arginine supplementation + exercise (Old Sup + Exe). LA CNPs were administered to the supplement groups through gavage at a dosage of 500 mg/kg/day for 6-weeks. Exercise groups were subjected to a swimming exercise program five days/week for the same duration. Upon the completion of their interventions, the animals underwent behavioral and open-field task tests and were subsequently sacrificed for hippocampus genetic and histopathological evaluation. For histopathological analysis of brain, Cresyl violet staining was used. Congo Red staining was employed to confirm amyloid plaques in the hippocampus. Expressions of Tau, App, Iba1, and ApoE genes were determined by real-time PCR. In contrast to the Old group, Old Exe and Old Sup + Exe groups spent more time in the central space in the open field task (p < 0.05) and have more live cells in the hippocampus. Old rats (Old, Old Sup and Old Exe groups) exhibited a significant Aβ peptide accumulation and increases in APP, Tau, Iba1, APOE-4 mRNA and MDA, along with decreases in SOD compared to the young group (p < 0.05). However, LA CNPs supplementation, exercise, and their combination (Old Sup, Old Exe and Old Sup + Exe) significantly reduced MDA, Aβ plaque as well as APP, Tau, Iba1, and APOE-4 mRNA compared to the Old group (p < 0.05). Consequently, the administration of LA CNPs supplements and exercise might regulate the risk factors of hippocampus cell and tissue.

Established and emerging techniques for the study of microglia: visualization, depletion, and fate mapping

The central nervous system (CNS) is an essential hub for neuronal communication. As a major component of the CNS, glial cells are vital in the maintenance and regulation of neuronal network dynamics. Research on microglia, the resident innate immune cells of the CNS, has advanced considerably in recent years, and our understanding of their diverse functions continues to grow. Microglia play critical roles in the formation and regulation of neuronal synapses, myelination, responses to injury, neurogenesis, inflammation, and many other physiological processes. In parallel with advances in microglial biology, cutting-edge techniques for the characterization of microglial properties have emerged with increasing depth and precision. Labeling tools and reporter models are important for the study of microglial morphology, ultrastructure, and dynamics, but also for microglial isolation, which is required to glean key phenotypic information through single-cell transcriptomics and other emerging approaches. Strategies for selective microglial depletion and modulation can provide novel insights into microglia-targeted treatment strategies in models of neuropsychiatric and neurodegenerative conditions, cancer, and autoimmunity. Finally, fate mapping has emerged as an important tool to answer fundamental questions about microglial biology, including their origin, migration, and proliferation throughout the lifetime of an organism. This review aims to provide a comprehensive discussion of these established and emerging techniques, with applications to the study of microglia in development, homeostasis, and CNS pathologies.

Behavioral as well as hippocampal transcriptomic and microglial responses differ across sexes in adult mouse offspring exposed to a dual genetic and environmental challenge

INTRODUCTION

A wide range of positive, negative, and cognitive symptoms compose the clinical presentation of schizophrenia. Schizophrenia is a multifactorial disorder in which genetic and environmental risk factors interact for a full emergence of the disorder. Infectious challenges during pregnancy are a well-known environmental risk factor for schizophrenia. Also, genetic variants affecting the function of fractalkine signaling between neurons and microglia were linked to schizophrenia. Translational animal models recapitulating these complex gene-environment associations have a great potential to untangle schizophrenia neurobiology and propose new therapeutic strategies.

METHODS

Given that genetic variants affecting the function of fractalkine signaling between neurons and microglia were linked to schizophrenia, we compared the outcomes of a well-characterized model of maternal immune activation induced using the viral mimetic polyinosinic:polycytidylic acid (Poly I:C) in wild-type versus fractalkine receptor knockout mice. Possible behavioral and immune alterations were assessed in male and female offspring during adulthood. Considering the role of the hippocampus in schizophrenia, microglial analyses and bulk RNA sequencing were performed within this region to assess the neuroimmune dynamics at play. Males and females were examined separately.

RESULTS

Offspring exposed to the dual challenge paradigm exhibited symptoms relevant to schizophrenia and unpredictably to mood disorders. Males displayed social and cognitive deficits related to schizophrenia, while females mainly presented anxiety-like behaviors related to mood disorders. Hippocampal microglia in females exposed to the dual challenge were hypertrophic, indicative of an increased surveillance, whereas those in males showed on the other end of the spectrum blunted morphologies with a reduced phagocytosis. Hippocampal bulk-RNA sequencing further revealed a downregulation in females of genes related to GABAergic transmission, which represents one of the main proposed causes of mood disorders.

CONCLUSIONS

Building on previous results, we identified in the current study distinctive behavioral phenotypes in female mice exposed to a dual genetic and environmental challenge, thus proposing a new model of neurodevelopmentally-associated mood and affective symptoms. This paves the way to future sex-specific investigations into the susceptibility to developmental challenges using animal models based on genetic and immune vulnerability as presented here.

Interpretation of Neurodegenerative GWAS Risk Alleles in Microglia and their Interplay with Other Cell Types

Microglia have been implicated in numerous neurodegenerative and neuroinflammatory disorders; however, the causal contribution of this immune cell type is frequently debated. Genetic studies offer a unique vantage point in that they infer causality over a secondary consequence. Genome-wide association studies (GWASs) have identified hundreds of loci in the genome that are associated with susceptibility to neurodegenerative disorders. GWAS studies implicate microglia in the pathogenesis of Alzheimer's disease (AD), Parkinson's disease (PD), multiple sclerosis (MS), and to a lesser degree suggest a role for microglia in vascular dementia (VaD), frontotemporal dementia (FTD), and amyotrophic lateral sclerosis (ALS), and other neurodegenerative and neuropsychiatric disorders. The contribution and function of GWAS risk loci on disease progression is an ongoing field of study, in which large genomic datasets, and an extensive framework of computational tools, have proven to be crucial. Several GWAS risk loci are shared between disorders, pointing towards common pleiotropic mechanisms. In this chapter, we introduce key concepts in GWAS and post-GWAS interpretation of neurodegenerative disorders, with a focus on GWAS risk genes implicated in microglia, their interplay with other cell types and shared convergence of GWAS risk loci on microglia.

Contactomics of Microglia and Intercellular Communication

Microglia represent the main immunocompetent cell type in the parenchyma of the brain and the spinal cord, with roles extending way beyond their immune functions. While emerging data show the pivotal role of microglia in brain development, brain health and brain diseases, the exact mechanisms through which microglia contribute to complex neuroimmune interactions are still largely unclear. Understanding the communication between microglia and other cells represents an important cornerstone of these interactions, which may provide novel opportunities for therapeutic interventions in neurological or psychiatric disorders. As such, in line with studying the effects of the numerous soluble mediators that influence neuroimmune processes, attention on physical interactions between microglia and other cells in the CNS has increased substantially in recent years. In this chapter, we briefly summarize the latest literature on "microglial contactomics" and its functional implications in health and disease.

Using focused ultrasound to modulate microglial structure and function

Transcranial focused ultrasound (FUS) has the unique ability to target regions of the brain with high spatial precision, in a minimally invasive manner. Neuromodulation studies have shown that FUS can excite or inhibit neuronal activity, demonstrating its tremendous potential to improve the outcome of neurological diseases. Recent evidence has also shed light on the emerging promise that FUS has, with and without the use of intravenously injected microbubbles, in modulating the blood-brain barrier and the immune cells of the brain. As the resident immune cells of the central nervous system, microglia are at the forefront of the brain's maintenance and immune defense. Notably, microglia are highly dynamic and continuously survey the brain parenchyma by extending and retracting their processes. This surveillance activity aids microglia in performing key physiological functions required for brain activity and plasticity. In response to stressors, microglia rapidly alter their cellular and molecular profile to help facilitate a return to homeostasis. While the underlying mechanisms by which both FUS and FUS + microbubbles modify microglial structure and function remain largely unknown, several studies in adult mice have reported changes in the expression of the microglia/macrophage marker ionized calcium binding adaptor molecule 1, and in their phagocytosis, notably of protein aggregates, such as amyloid beta. In this review, we discuss the demonstrated and putative biological effects of FUS and FUS + microbubbles in modulating microglial activities, with an emphasis on the key cellular and molecular changes observed in vitro and in vivo across models of brain health and disease. Understanding how this innovative technology can modulate microglia paves the way for future therapeutic strategies aimed to promote beneficial physiological microglial roles, and prevent or treat maladaptive responses.

Molecular mapping of a core transcriptional signature of microglia-specific genes in schizophrenia

Besides playing a central role in neuroinflammation, microglia regulate synaptic development and is involved in plasticity. Converging lines of evidence suggest that these different processes play a critical role in schizophrenia. Furthermore, previous studies reported altered transcription of microglia genes in schizophrenia, while microglia itself seems to be involved in the etiopathology of the disease. However, the regional specificity of these brain transcriptional abnormalities remains unclear. Moreover, it is unknown whether brain and peripheral expression of microglia genes are related. Thus, we investigated the expression of a pre-registered list of 10 genes from a core signature of human microglia both at brain and peripheral levels. We included 9 independent Gene Expression Omnibus datasets (764 samples obtained from 266 individuals with schizophrenia and 237 healthy controls) from 8 different brain regions and 3 peripheral tissues. We report evidence of a widespread transcriptional alteration of microglia genes both in brain tissues (we observed a decreased expression in the cerebellum, associative striatum, hippocampus, and parietal cortex of individuals with schizophrenia compared with healthy controls) and whole blood (characterized by a mixed altered expression pattern). Our results suggest that brain underexpression of microglia genes may represent a candidate transcriptional signature for schizophrenia. Moreover, the dual brain-whole blood transcriptional alterations of microglia/macrophage genes identified support the model of schizophrenia as a whole-body disorder and lend weight to the use of blood samples as a potential source of biological peripheral biomarkers.

Microbiota-indole 3-propionic acid-brain axis mediates abnormal synaptic pruning of hippocampal microglia and susceptibility to ASD in IUGR offspring

BACKGROUND

Autism spectrum disorder (ASD) has been associated with intrauterine growth restriction (IUGR), but the underlying mechanisms are unclear.

RESULTS

We found that the IUGR rat model induced by prenatal caffeine exposure (PCE) showed ASD-like symptoms, accompanied by altered gut microbiota and reduced production of indole 3-propionic acid (IPA), a microbiota-specific metabolite and a ligand of aryl hydrocarbon receptor (AHR). IUGR children also had a reduced serum IPA level consistent with the animal model. We demonstrated that the dysregulated IPA/AHR/NF-κB signaling caused by disturbed gut microbiota mediated the hippocampal microglia hyperactivation and neuronal synapse over-pruning in the PCE-induced IUGR rats. Moreover, postnatal IPA supplementation restored the ASD-like symptoms and the underlying hippocampal lesions in the IUGR rats.

CONCLUSIONS

This study suggests that the microbiota-IPA-brain axis regulates ASD susceptibility in PCE-induced IUGR offspring, and supplementation of microbiota-derived IPA might be a promising interventional strategy for ASD with a fetal origin. Video Abstract.

Application of mesenchymal stem cells for anti-senescence and clinical challenges

Senescence is a hot topic nowadays, which shows the accumulation of senescent cells and inflammatory factors, leading to the occurrence of various senescence-related diseases. Although some methods have been identified to partly delay senescence, such as strengthening exercise, restricting diet, and some drugs, these only slow down the process of senescence and cannot fundamentally delay or even reverse senescence. Stem cell-based therapy is expected to be a potential effective way to alleviate or cure senescence-related disorders in the coming future. Mesenchymal stromal cells (MSCs) are the most widely used cell type in treating various diseases due to their potentials of self-replication and multidirectional differentiation, paracrine action, and immunoregulatory effects. Some biological characteristics of MSCs can be well targeted at the pathological features of aging. Therefore, MSC-based therapy is also a promising strategy to combat senescence-related diseases. Here we review the recent progresses of MSC-based therapies in the research of age-related diseases and the challenges in clinical application, proving further insight and reference for broad application prospects of MSCs in effectively combating senesce in the future.

Sex-dependent factors of alcohol and neuroimmune mechanisms

Excessive alcohol use disrupts neuroimmune signaling across various cell types, including neurons, microglia, and astrocytes. The present review focuses on recent, albeit limited, evidence of sex differences in biological factors that mediate neuroimmune responses to alcohol and underlying neuroimmune systems that may influence alcohol drinking behaviors. Females are more vulnerable than males to the neurotoxic and negative consequences of chronic alcohol drinking, reflected by elevations of pro-inflammatory cytokines and inflammatory mediators. Differences in cytokine, microglial, astrocytic, genomic, and transcriptomic evidence suggest females are more reactive than males to neuroinflammatory changes after chronic alcohol exposure. The growing body of evidence supports that innate immune factors modulate synaptic transmission, providing a mechanistic framework to examine sex differences across neurocircuitry. Targeting neuroimmune signaling may be a viable strategy for treating AUD, but more research is needed to understand sex-specific differences in alcohol drinking and neuroimmune mechanisms.

Ginsenoside Rb1 inhibits ferroptosis to ameliorate hypoxic-ischemic brain damage in neonatal rats

Hypoxic ischemic encephalopathy (HIE) is among the leading causes of neonatal mortality, and currently there is no effective treatment. Ginsenoside Rb1 (GsRb1) is one of the principal active components of ginseng, and has protective benefits against oxidative stress, inflammation, hypoxic injury, and so on. However, the role and underlying mechanism of GsRb1 on HIE are unclear. Here, we established the neonatal rat hypoxic-ischemic brain damage (HIBD) model in vivo and the PC12 cell oxygen-glucose deprivation (OGD) model in vitro to investigate the neuroprotective effects of GsRb1 on HIE, and illuminate the potential mechanism. Our results showed that GsRb1 and the ferroptosis inhibitor liproxstatin-1 (Lip-1) could significantly restore System Xc activity and antioxidant levels as well as inhibit lipid oxidation levels and inflammatory index levels of HIBD and OGD models. Taken together, GsRb1 might inhibit ferroptosis to exert neuroprotective effects on HIE through alleviating oxidative stress and inflammation, which will set the foundation for future research on ferroptosis by reducing hypoxic-ischemic brain injury and suggest that GsRb1 might be a promising therapeutic agent for HIE.

Association between APOE genotype and microglial cell morphology

APOE is the largest genetic risk factor for late-onset Alzheimer disease (AD) with E4 conferring an increased risk for AD compared to E3. The ApoE protein can impact diverse pathways in the brain including neuroinflammation but the precise impact of ApoE isoforms on inflammation remains unknown. As microglia are a primary source of neuroinflammation, this study determined whether ApoE isoforms have an impact on microglial morphology and activation using immunohistochemistry and digital analyses. Analysis of ionized calcium-binding adaptor molecule 1 (Iba1) immunoreactivity indicated greater microglial activation in both the hippocampus and superior and middle temporal gyrus (SMTG) in dementia participants versus non-demented controls. Further, only an increase in activation was seen in E3-Dementia participants in the entire SMTG, whereas in the grey matter of the SMTG, only a diagnosis of dementia impacted activation. Specific microglial morphologies showed a reduction in ramified microglia in the dementia group. For rod microglia, a reduction was seen in E4-Control patients in the hippocampus whereas in the SMTG an increase was seen in E4-Dementia patients. These findings suggest an association between ApoE isoforms and microglial morphologies and highlight the importance of considering ApoE isoforms in studies of AD pathology.

Lactoferrin alleviates Western diet-induced cognitive impairment through the microbiome-gut-brain axis

Lactoferrin (Lf) has been shown to benefit cognitive function in several animal models. To elucidate the underlying mechanisms, male C57BL/6J mice were randomly divided into the control (CON), Western-style diets (WD), lactoferrin (Lf), and Lf + antibiotics (AB) groups. The Lf group was intragastrically administered with Lf, and the Lf + AB group additionally drank a solution with antibiotics. After 16 weeks of intervention, Lf improved the cognitive function as indicated by behavioral tests. Lf also increased the length and curvature of postsynaptic density and upregulated the related protein expression, suggesting improved hippocampal neurons and synapses. Lf suppressed microglia activation and proliferation as revealed by immunofluorescence analysis. Lf decreased the serum levels of pro-inflammatory cytokines and downregulated their protein expressions in the hippocampus region. Lf also inhibited the activation of NF-κB/NLRP3 inflammasomes in the hippocampus. Meanwhile, Lf upregulated the expression of tight junction proteins, and increased the abundance of Bacteroidetes at phylum and Roseburia at genus, which are beneficial for gut barrier and cognitive function. The antibiotics eliminated the effects of long-term Lf intervention on cognitive impairment in the Lf + AB group, suggesting that gut microbiota participated in Lf action. Short-term Lf intervention (2 weeks) prevented WD-induced gut microbiota alteration without inducing behavioral changes, supporting the timing sequence of gut microbiota to the brain. Thus, Lf intervention alleviated cognitive impairment by inhibiting microglial activation and neuroinflammation through the microbiome-gut-brain axis.

Cognitive Impairments, Neuroinflammation and Blood-Brain Barrier Permeability in Mice Exposed to Chronic Sleep Fragmentation during the Daylight Period

Obstructive sleep apnea (OSA) is a chronic condition characterized by intermittent hypoxia (IH) and sleep fragmentation (SF). In murine models, chronic SF can impair endothelial function and induce cognitive declines. These deficits are likely mediated, at least in part, by alterations in Blood-brain barrier (BBB) integrity. Male C57Bl/6J mice were randomly assigned to SF or sleep control (SC) conditions for 4 or 9 weeks and in a subset 2 or 6 weeks of normal sleep recovery. The presence of inflammation and microglia activation were evaluated. Explicit memory function was assessed with the novel object recognition (NOR) test, while BBB permeability was determined by systemic dextran-4kDA-FITC injection and Claudin 5 expression. SF exposures resulted in decreased NOR performance and in increased inflammatory markers and microglial activation, as well as enhanced BBB permeability. Explicit memory and BBB permeability were significantly associated. BBB permeability remained elevated after 2 weeks of sleep recovery (p < 0.01) and returned to baseline values only after 6 weeks. Chronic SF exposures mimicking the fragmentation of sleep that characterizes patients with OSA elicits evidence of inflammation in brain regions and explicit memory impairments in mice. Similarly, SF is also associated with increased BBB permeability, the magnitude of which is closely associated with cognitive functional losses. Despite the normalization of sleep patterns, BBB functional recovery is a protracted process that merits further investigation.

Emerging non-proinflammatory roles of microglia in healthy and diseased brains

Microglia, the resident myeloid cells of the central nervous system, are the first line of defense against foreign pathogens, thereby confining the extent of brain injury. However, the role of microglia is not limited to macrophage-like functions. In addition to proinflammatory response mediation, microglia are involved in neurodevelopmental remodeling and homeostatic maintenance in the absence of disease. An increasing number of studies have also elucidated microglia-mediated regulation of tumor growth and neural repair in diseased brains. Here, we review the non-proinflammatory roles of microglia, with the aim of promoting a deeper understanding of the functions of microglia in healthy and diseased brains and contributing to the development of novel therapeutics that target microglia in neurological disorders.

Morphologic Findings in the Cerebral Cortex in COVID-19: Association of Microglial Changes with Clinical and Demographic Variables

Despite the enormous interest in COVID-19, there is no clear understanding of the mechanisms underlying the neurological symptoms in COVID-19. Microglia have been hypothesized to be a potential mediator of the neurological manifestations associated with COVID-19. In most existing studies to date, morphological changes in internal organs, including the brain, are considered in isolation from clinical data and defined as a consequence of COVID-19. We performed histological immunohistochemical (IHC) studies of brain autopsy materials of 18 patients who had died from COVID-19. We evaluated the relationship of microglial changes with the clinical and demographic characteristics of the patients. The results revealed neuronal alterations and circulatory disturbances. We found an inverse correlation between the integral density Iba-1 (microglia/macrophage-specific marker) IHC staining and the duration of the disease (R = -0.81, p = 0.001), which may indicate a reduced activity of microglia and do not exclude their damage in the long-term course of COVID-19. The integral density of Iba-1 IHC staining was not associated with other clinical and demographic factors. We observed a significantly higher number of microglial cells in close contact with neurons in female patients, which confirms gender differences in the course of the disease, indicating the need to study the disease from the standpoint of personalized medicine.

AIF1: Function and Connection with Inflammatory Diseases

Macrophages are a type of immune cell distributed throughout all tissues of an organism. Allograft inflammatory factor 1 (AIF1) is a calcium-binding protein linked to the activation of macrophages. AIF1 is a key intracellular signaling molecule that participates in phagocytosis, membrane ruffling and F-actin polymerization. Moreover, it has several cell type-specific functions. AIF1 plays important roles in the development of several diseases: kidney disease, rheumatoid arthritis, cancer, cardiovascular diseases, metabolic diseases and neurological disorders, and in transplants. In this review, we present a comprehensive review of the known structure, functions and role of AIF1 in inflammatory diseases.

Origin and Emergence of Microglia in the CNS-An Interesting (Hi)story of an Eccentric Cell

Microglia belong to tissue-resident macrophages of the central nervous system (CNS), representing the primary innate immune cells. This cell type constitutes ~7% of non-neuronal cells in the mammalian brain and has a variety of biological roles integral to homeostasis and pathophysiology from the late embryonic to adult brain. Its unique identity that distinguishes its "glial" features from tissue-resident macrophages resides in the fact that once entering the CNS, it is perennially exposed to a unique environment following the formation of the blood-brain barrier. Additionally, tissue-resident macrophage progenies derive from various peripheral sites that exhibit hematopoietic potential, and this has resulted in interpretation issues surrounding their origin. Intensive research endeavors have intended to track microglial progenitors during development and disease. The current review provides a corpus of recent evidence in an attempt to disentangle the birthplace of microglia from the progenitor state and underlies the molecular elements that drive microgliogenesis. Furthermore, it caters towards tracking the lineage spatiotemporally during embryonic development and outlining microglial repopulation in the mature CNS. This collection of data can potentially shed light on the therapeutic potential of microglia for CNS perturbations across various levels of severity.

Endothelial progenitor cell transplantation attenuates synaptic loss associated with enhancing complement receptor 3-dependent microglial/macrophage phagocytosis in ischemic mice

Endothelial progenitor cell (EPC) transplantation has therapeutic effects in cerebral ischemia. However, how EPCs modulate microglial activity remains unclear. In the study, we explored whether EPCs modulated microglial/macrophage activity and facilitated injured brain repair. Adult male mice (n = 184) underwent transient middle cerebral artery occlusion, and EPCs were transplanted into the brain immediately after ischemia. Microglial/macrophage activity and complement receptor 3 (CR3) expression were evaluated in ischemic brains and cultured microglia. CR3 agonist leukadherin-1 was administrated into mice immediately after ischemia to imitate the effects of EPCs. Synaptophysin and postsynaptic density protein 95 (PSD-95) expressions were detected in EPC- and leukadherin-1 treated mice. We found that EPC transplantation increased the number of M2 microglia/macrophage-phagocytizing apoptotic cells and CR3 expression in ischemic brains at 3 days after ischemia (p < 0.05). EPC-conditional medium or cultured EPCs increased microglial migration and phagocytosis and upregulated CR3 expression in cultured microglia under oxygen-glucose deprivation condition (p < 0.05). Leukadherin-1 reduced brain atrophy volume and neurological deficits at 14 days after ischemia (p < 0.05). Both EPC transplantation and leukadherin-1 increased synaptophysin and PSD-95 expression at 14 days after ischemia (p < 0.05). EPC transplantation promoted CR3-mediated microglial/macrophage phagocytosis and subsequently attenuated synaptic loss. Our study provided a novel therapeutic mechanism for EPCs.

Inhibiting mitochondrial inflammation through Drp1/HK1/NLRP3 pathway: A mechanism of alpinetin attenuated aging-associated cognitive impairment

Mitochondrial inflammation triggered by abnormal mitochondrial division and regulated by the Drp1/HK1/NLRP3 pathway is correlated with the progression of aging-associated cognitive impairment (AACI). Alpinetin is a novel flavonoid derived from Zingiberaceae that has many bioactivities such as antiinflammation and anti-oxidation. However, whether alpinetin alleviates AACI by suppressing Drp1/HK1/NLRP3 pathway-inhibited mitochondrial inflammation is still unknown. In the present study, D-galactose (D-gal)-induced aging mice and BV-2 cells were used, and the effects of alpinetin on learning and memory function, neuroprotection and activation of the Drp1/HK1/NLRP3 pathway were investigated. Our data indicated that alpinetin significantly alleviated cognitive dysfunction and neuronal damage in the CA1 and CA3 regions of D-gal-treated mice. Moreover, D-gal-induced microglial activation was markedly reduced by alpinetin by inhibiting the Drp1/HK1/NLRP3 pathway-suppressed mitochondrial inflammation, down-regulating the levels of p-Drp1 (s616), VDAC, NLRP3, ASC, Cleaved-caspase 1, IL-18, and IL-1β, and up-regulating the expression of HK1. Furthermore, after Drp1 inhibition by Mdivi-1 in vitro, the inhibitory effect of alpinetin on Drp1/HK1/NLRP3 pathway was more evident. In summary, the current results implied that alpinetin attenuated aging-related cognitive deficits by inhibiting the Drp1/HK1/NLRP3 pathway and suppressing mitochondrial inflammation, suggesting that the inhibition of the Drp1/HK1/NLRP3 pathway is one of the mechanisms by which alpinetin attenuates AACI.

Increased adipose catecholamine levels and protection from obesity with loss of Allograft Inflammatory Factor-1

Recent studies implicate macrophages in regulation of thermogenic, sympathetic neuron-mediated norepinephrine (NE) signaling in adipose tissues, but understanding of such non-classical macrophage activities is incomplete. Here we show that male mice lacking the allograft inflammatory factor-1 (AIF1) protein resist high fat diet (HFD)-induced obesity and hyperglycemia. We link this phenotype to higher adipose NE levels that stem from decreased monoamine oxidase A (MAOA) expression and NE clearance by AIF1-deficient macrophages, and find through reciprocal bone marrow transplantation that donor Aif1-/- vs WT genotype confers the obesity phenotype in mice. Interestingly, human sequence variants near the AIF1 locus associate with obesity and diabetes; in adipose samples from participants with obesity, we observe direct correlation of AIF1 and MAOA transcript levels. These findings identify AIF1 as a regulator of MAOA expression in macrophages and catecholamine activity in adipose tissues - limiting energy expenditure and promoting energy storage - and suggest how it might contribute to human obesity.

Toxicologic Pathology Forum Opinion: Interpretation of Gliosis in the Brain and Spinal Cord Observed During Nonclinical Safety Studies

Gliosis, defined as a nonneoplastic reaction (hypertrophy and/or proliferation) of astrocytes and/or microglial cells, is a frequent finding in the central nervous system (CNS [brain and/or spinal cord]) in nonclinical safety studies. Gliosis in rodents and nonrodents occurs at low incidence as a spontaneous finding and is induced by various test articles (e.g., biomolecules, cell and gene therapies, small molecules) delivered centrally (i.e., by injection or infusion into cerebrospinal fluid or neural tissue) or systemically. Several CNS gliosis patterns occur in nonclinical species. First, gliosis may accompany degeneration and/or necrosis of cells (mainly neurons) or neural parenchyma (neuron processes and myelin). Second, gliosis often follows inflammation (i.e., leukocyte accumulation causing parenchymal damage) or neoplasm formation. Third, gliosis may appear as variably sized, randomly scattered foci of reactive glial cells in the absence of visible parenchymal damage or inflammation. In interpreting test article-related CNS gliosis, adversity is indicated by parenchymal injury (e.g., degeneration, necrosis, or inflammation) and not the mere existence of a glial reaction. In the absence of clear structural damage to the parenchyma, gliosis as a standalone CNS finding should be interpreted as a nonadverse reaction to regional alterations in microenvironmental conditions rather than as evidence of a glial reaction associated with neurotoxicity.

Synapse integrity and function: Dependence on protein synthesis and identification of potential failure points

Synaptic integrity and function depend on myriad proteins - labile molecules with finite lifetimes that need to be continually replaced with freshly synthesized copies. Here we describe experiments designed to expose synaptic (and neuronal) properties and functions that are particularly sensitive to disruptions in protein supply, identify proteins lost early upon such disruptions, and uncover potential, yet currently underappreciated failure points. We report here that acute suppressions of protein synthesis are followed within hours by reductions in spontaneous network activity levels, impaired oxidative phosphorylation and mitochondrial function, and, importantly, destabilization and loss of both excitatory and inhibitory postsynaptic specializations. Conversely, gross impairments in presynaptic vesicle recycling occur over longer time scales (days), as does overt cell death. Proteomic analysis identified groups of potentially essential 'early-lost' proteins including regulators of synapse stability, proteins related to bioenergetics, fatty acid and lipid metabolism, and, unexpectedly, numerous proteins involved in Alzheimer's disease pathology and amyloid beta processing. Collectively, these findings point to neuronal excitability, energy supply and synaptic stability as early-occurring failure points under conditions of compromised supply of newly synthesized protein copies.

Amentoflavone Exerts Anti-Neuroinflammatory Effects by Inhibiting TLR4/MyD88/NF-κB and Activating Nrf2/HO-1 Pathway in Lipopolysaccharide-Induced BV2 Microglia

Background

Amentoflavone, a natural biflavone, exerts anti-inflammation, antioxidation, and antiapoptosis effects on many diseases. However, the mechanism of amentoflavone on neuroinflammation-related diseases has not been comprehensively examined clearly.

Methods

BV2 microglial cells were treated with amentoflavone (10 μM), followed by lipopolysaccharide (LPS). Microglial activation and migration ability and the expression of proinflammatory cytokines and other signaling proteins were determined using immunohistochemistry, immunofluorescence, quantitative real-time polymerase chain reaction, Western blotting, enzyme-linked immunosorbent assay, and wound-healing assays.

Results

Amentoflavone restored LPS-induced microglia activation, migration, and inflammation response which depends on regulating toll-like receptor 4 (TLR4)/myeloid differentiation factor 88 (MyD88)/nuclear factor kappa B (NF-κB) pathway. In addition, amentoflavone also enhanced nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) levels in LPS-treated BV2 microglial cells.

Conclusions

Amentoflavone ameliorated LPS-induced neuroinflammatory response and oxidative stress in BV2 microglia. These data provide new insight into the mechanism of amentoflavone in the treatment of neuroinflammation-related diseases. Therefore, amentoflavone may be a potential therapeutic option for neurological disorders.

Oxytocin and microglia in the development of social behaviour

Oxytocin is a well-established regulator of social behaviour. Microglia, the resident immune cells of the central nervous system, regulate brain development and maintenance in health and disease. Oxytocin and microglia interact: microglia appear to regulate the oxytocin system and are, in turn, regulated by oxytocin, which appears to have anti-inflammatory effects. Both microglia and oxytocin are regulated in sex-specific ways. Oxytocin and microglia may work together to promote experience-dependent circuit refinement through multiple developmental-sensitive periods contributing to individual differences in social behaviour. This article is part of the theme issue 'Interplays between oxytocin and other neuromodulators in shaping complex social behaviours'.

Prenatal environmental stressors impair postnatal microglia function and adult behavior in males

Gestational exposure to environmental toxins and socioeconomic stressors is epidemiologically linked to neurodevelopmental disorders with strong male bias, such as autism. We model these prenatal risk factors in mice by co-exposing pregnant dams to an environmental pollutant and limited-resource stress, which robustly activates the maternal immune system. Only male offspring display long-lasting behavioral abnormalities and alterations in the activity of brain networks encoding social interactions. Cellularly, prenatal stressors diminish microglial function within the anterior cingulate cortex, a central node of the social coding network, in males during early postnatal development. Precise inhibition of microglial phagocytosis within the anterior cingulate cortex (ACC) of wild-type (WT) mice during the same critical period mimics the impact of prenatal stressors on a male-specific behavior, indicating that environmental stressors alter neural circuit formation in males via impairing microglia function during development.

Block et al. show that combined exposure to air pollution and maternal stress during pregnancy activates the maternal immune system and induces male-specific impairments in social behavior and circuit connectivity in offspring. Cellularly, prenatal stressors diminish microglia phagocytic function, and inhibition of microglia phagocytosis phenocopies behavioral deficits from prenatal stressors.

Dim Blue Light at Night Induces Spatial Memory Impairment in Mice by Hippocampal Neuroinflammation and Oxidative Stress

Light pollution is one of the most serious public problems, especially the night light. However, the effect of dim blue light at night (dLAN-BL) on cognitive function is unclear. In this study, we evaluated the effects of exposure to dLAN-BL in C57BL/6J mice for 4 consecutive weeks. Our results showed dLAN-BL significantly impaired spatial learning and memory and increased plasma corticosterone level in mice. Consistent with these changes, we observed dLAN-BL significantly increased the numbers and activation of microglia and the levels of oxidative stress product MDA in the hippocampus, decreased the levels of antioxidant enzymes Glutathione peroxidase (GSH-Px), Superoxide dismutase (SOD), Gluathione reductase (Gsr), total antioxidants (T-AOC) and the number of neurons in the hippocampus, up-regulated the mRNA expression levels of IL6, TNF-α and the protein expression levels of iNOS, COX2, TLR4, p-p65, Cleaved-Caspase3 and BAX, and down-regulated the mRNA expression levels of IL4, IL10, Psd95, Snap25, Sirt1, Dcx and the protein expression level of BCL2. In vitro results further showed corticosterone (10uM)-induced BV2 cell activation and up-regulated content of IL6, TNF-α in the cell supernatant and the protein expression levels of iNOS, COX2, p-p65 in BV2 cells. Our findings suggested dLAN-BL up-regulated plasma corticosterone level and hippocampal microglia activation, which in turn caused oxidative stress and neuroinflammation, leading to neuronal loss and synaptic dysfunction, ultimately leading to spatial learning and memory dysfunction in mice.

Microglia as a Hub for Suicide Neuropathology: Future Investigation and Prevention Targets

Suicide is a complex public health challenge associated worldwide with one death every 40 s. Research advances in the neuropathology of suicidal behaviors (SB) have defined discrete brain changes which may hold the key to suicide prevention. Physiological differences in microglia, the resident immune cells of the brain, are present in post-mortem tissue samples of individuals who died by suicide. Furthermore, microglia are mechanistically implicated in the outcomes of important risk factors for SB, including early-life adversity, stressful life events, and psychiatric disorders. SB risk factors result in inflammatory and oxidative stress activities which could converge to microglial synaptic remodeling affecting susceptibility or resistance to SB. To push further this perspective, in this Review we summarize current areas of opportunity that could untangle the functional participation of microglia in the context of suicide. Our discussion centers around microglial state diversity in respect to morphology, gene and protein expression, as well as function, depending on various factors, namely brain region, age, and sex.