Search Results (105)

Lafora disease (LD) is a fatal neurodegenerative disorder caused by mutations in the EPM2A or EPM2B/NHLRC1 genes, encoding Laforin and Malin, respectively. While the Laforin/Malin E3-ubiquitin ligase complex is a known regulator of canonical autophagy and glycogen metabolism, its role in non-canonical autophagy pathways remains unexplored. Given that neuroinflammation is a hallmark of LD, we investigated the relationship between the Laforin/Malin complex and Rubicon, a critical regulator of LC3-associated phagocytosis (LAP) and LC3-associated endocytosis (LANDO). In this work, we identify Rubicon as a novel substrate and binding partner of the Laforin/Malin complex. Co-immunoprecipitation and confocal microscopy assays in HEK293 and U2OS cells demonstrated that Malin physically interacts with Rubicon, promoting its K63-linked polyubiquitination. This post-translational modification adds another layer of control to the regulation of Rubicon in specific cellular contexts. To determine the functional relevance of this interaction in LD, we assessed LAP and LANDO in primary astrocytes from Malin-deficient mice. Using flow cytometry, we quantified the engulfment and degradation of Zymosan particles and microglial debris (LAP), as well as EGF receptor internalization (LANDO). Surprisingly, no significant functional impairments were observed in Malin-deficient astrocytes compared to WT controls. These findings suggest that while the Laforin/Malin complex regulates Rubicon via K63-linked ubiquitination, redundant signaling nodes may preserve non-canonical autophagy output in Malin-deficient astrocytes. Full article

Background: Progesterone (P4) is used as an antiseizure medication (ASM) to treat catamenial epilepsy, refractory to first-line drugs. P4 and other neurosteroids (NSs) are important regulators of multiple nervous system functions, including neuronal excitability and synaptic plasticity. In addition to their antiseizure properties, P4 and other NSs are also anti-inflammatory agents. Neuroinflammation is an important pathophysiological mechanism of epilepsy refractory to ASMs. Accordingly, we evaluated the ability of P4 to modulate neuroinflammation, using human microglia activated by lipopolysaccharide (LPS). Methods: Human microglia (HMC3) were stimulated for 3 h with LPS in the absence or presence of various concentrations of P4. Thereafter, levels of (i) toll-like receptor 4 (TLR4), (ii) the NLRP3 inflammasome, and (iii) pro-inflammatory cytokines were quantitated by real-time PCR and Western blot analyses. Phagocytic activity was also assessed using a phagocytosis assay employing fluorescent beads. Results: P4 treatment significantly reduced the microglial inflammatory state induced by LPS, which was mediated by upregulation of the TLR4- and NLRP3-axes. The protective effects of P4 were mediated by inhibition of Nuclear Factor kappa-light-chain-enhancer of activated B cells (NFκB) phosphorylation and reduced activation of Mitogen-Activated Protein Kinases (MAPK). The effects of P4 included a significant reduction in mRNA levels of the main pro-inflammatory cytokines and a reduction in phagocytic activity of HMC3. Conclusions: P4 is endowed with significant anti-inflammatory properties, which may be involved in the beneficial effects reported for drug-resistant catamenial epilepsy. Further research is required to clarify P4 post-receptor mechanisms of action and to explore the roles of other P4-derived NSs. Full article

Intracerebral hemorrhage induces severe secondary brain injury characterized by excessive neuroinflammation and inefficient hematoma clearance, processes largely governed by microglial polarization and phagocytic activity. The immunoproteasome, an inducible proteasome isoform involved in immune regulation, has been implicated in inflammatory neurological disorders, but its role in microglial responses after ICH remains unclear. In this study, rat models of common hemorrhage, severe hemorrhage, and severe hemorrhage with hematoma aspiration were used to represent graded injury severity and post-evacuation recovery. Transcriptomic profiling at day 3 post-injury identified immunoproteasome-associated gene networks, while expression of the catalytic subunits LMP2 and LMP7, microglial polarization markers, and phagocytic receptors was analyzed by Western blotting and immunofluorescence. Severe hemorrhage markedly induced LMP2 and LMP7 expression, predominantly in Iba1⁺ microglia, accompanied by enhanced ER stress, NF-κB signaling, and M1-like polarization and reduced phagocytic marker expression. Hematoma aspiration attenuated immunoproteasome expression and restored M2-associated and phagocytic signatures. Consistently, pharmacological inhibition of immunoproteasomes in primary microglia enhanced erythrophagocytosis and promoted a reparative phenotype in vitro. These findings indicate that immunoproteasome activation links hemorrhagic severity to maladaptive microglial polarization and impaired hematoma clearance after ICH, and that reducing immunoproteasome expression may help rebalance inflammatory and phagocytic microglial functions. Full article

Luteolin (Ltn), a natural flavonoid, effectively inhibits microglial activation in Alzheimer’s disease (AD) with promising therapeutic potential, but its efficacy is severely limited by the blood–brain barrier (BBB). To overcome this obstacle, this study prepared poly (lactic-co-glycolic acid) (PLGA) nanoparticles (NPs)—designated as TGN/RAP12-RBC-NPs@Ltn—which were coated with red blood cell membranes (RBCm) functionalized with two peptides, TGN (TGNYKALHPHN) and RAP12 (EAKIEKHNHYQK). The results demonstrated that TGN significantly enhanced BBB permeability, while RAP12 enabled effective targeting and delivery of TGN/RAP12-RBC-NPs@Ltn to microglial mitochondria in the brain. In addition, the presence of RBCm significantly inhibited the phagocytosis of NPs by macrophages, exerting a notable role in immune evasion. Meanwhile, the study confirmed that encapsulating Ltn within NPs significantly enhanced cognitive function in APP/PS1 mice, modulated the expression of key mitochondrial metabolic enzymes—pyruvate dehydrogenase (PDH) and its phosphorylated forms (pS232PDH, pS293PDH, pS300PDH)—in microglia, thereby ameliorating mitochondrial dysfunction and effectively regulating the neuroinflammatory environment in the mouse brain, and ultimately contributed to therapeutic efficacy. From this, it could be seen that TGN/RAP12-RBC-NPs@Ltn could significantly enhance the therapeutic effect of Ltn on AD, providing an effective treatment strategy for delaying the progression of AD. Full article

Microglia perform surveillance and phagocytosis to maintain the homeostasis of the central nervous system (CNS). These processes are energetically demanding, and given the critical roles of mitochondria in providing ATP, the characteristics of the mitochondrial network can modulate microglial behavior. Although the Ca²⁺-permeable Transient Receptor Potential Vanilloid 4 (TRPV4) is known for regulating microglial morphology and migration, and it is implicated in mitochondrial calcium uptake, it is unknown whether TRPV4 affects the mitochondrial network in microglia. Our study provides evidence that TRPV4 plays a role in the integrity and complexity of the mitochondrial network in microglia. Quantification of the Mitochondrial Fragmentation and Complexity Index (MFCI) and increased pDrp1 (Ser616) showed a shift towards mitochondrial network fragmentation, and lowered complexity in Trpv4 knockout versus wild-type primary murine microglia in vitro. The distribution of mitochondria within microglia showed significant differences in density at 10–32 µm away from the nucleus. Furthermore, acute pharmacological TRPV4 inhibition with GSK2193874 did not induce significant mitochondria network fragmentation. Our findings establish TRPV4 as a regulator of mitochondrial dynamics and adaptive responses, highlighting its importance for maintaining homeostasis in microglia and the entire CNS. Full article

Intracerebral hemorrhage (ICH) is the deadliest subtype of stroke, and its primary harm to the human body arises from the formation of brain hematomas. Promoting microglial-mediated endogenous hematoma clearance has become a key focus in current ICH treatment strategies. Semaphorin 3s (Sema3s) are molecular signals involved in the regulation of the central nervous system, angiogenesis, and microenvironment homeostasis, and they are closely associated with various central nervous system diseases. Hematoma clearance and inflammation regulation are crucial to the role of microglia, yet the mechanisms by which Sema3s regulate microglia after ICH remain unclear. Here, using high-throughput RNA sequencing of a mouse ICH model, we identified that neuron-derived Sema3B is downregulated after ICH. Further mechanistic studies revealed that Sema3B can bind to PlexinA1 on microglia, activating NRF2 to promote the expression of the phagocytic receptor TREM2 and the key hematoma clearance molecule HO-1. Furthermore, Sema3B enhances the interaction between PlexinA1 and TREM2, cooperatively boosting microglial phagocytosis of the hematoma after ICH. Furthermore, Sema3B regulates the M2 polarization of microglia, exerting an anti-inflammatory effect. Our findings suggest that manipulating microglial phagocytosis of hematoma and inflammation suppression via regulation of Sema3B may be a potential strategy for treating patients with ICH. Full article

Background and Objectives: SARS-CoV-2 produces potentially pathogenic molecules, such as single-stranded RNA and spike proteins, which can potentially activate microglial cells. In this study, we aimed to investigate whether SARS-CoV-2 spike protein S1 and mRNA vaccines can cause neurotoxicity directly or through microglial involvement. Materials and Methods: Primary cerebellar granule cell cultures isolated from Wistar rats and organotypic hippocampal slice cultures from transgenic C57BL/6J mice were used in the experiments. Imaging and quantitative analysis of cell viability, proliferation, and phagocytic activity were performed using light and fluorescence microscopy. Results: The exogenous SARS-CoV-2 S1 protein at 50 µg/mL concentration induced neuronal cell death in neuronal–glial co-cultures and stimulated microglial proliferation during the first 3 days of exposure without an effect on inflammatory cytokine secretion. Single application of Tozinameran/Riltozinameran and Original/Omicron BA. 4–5 vaccines did not affect neuronal viability and total neuronal number in cell co-cultures after 7 days of exposure. In contrast, three repeated treatments with mRNA vaccines at 6 ng/mL caused microglial proliferation without affecting microglial phagocytosis and TNF-α release. In organotypic brain slice cultures, only Tozinameran/Riltozinameran stimulated microglial cell proliferation in female brain slices, while male brain slices remained unaffected by both vaccines, indicating sex-dependent effects. Conclusions: The findings suggest that mRNA vaccines do not exert neurotoxic effects in primary neuronal–glial co-cultures, but induce microglial proliferation, particularly in female brains in the absence of inflammatory cytokine release. SARS-CoV-2 S1 protein at high concentrations directly induces neuronal death. Full article

Neurodegenerative disorders are characterized by progressive neuronal loss and dysfunction, yet increasing evidence indicates that glial cells are central mediators of both disease initiation and progression. Astrocytes, microglia, and oligodendrocyte lineage cells modulate neuronal survival by regulating neuroinflammation, metabolic support, synaptic maintenance, and proteostasis. However, dysregulated glial responses, including chronic microglial activation, impaired phagocytosis, altered cytokine production, and mitochondrial dysfunction, contribute to persistent inflammation and structural degeneration observed across Alzheimer’s disease, Parkinson’s disease, amyotrophic lateral sclerosis, Huntington’s disease and multiple sclerosis. Recent advances in single-cell and spatial omics have revealed extensive glial heterogeneity and dynamic shifts between neuroprotective and neurotoxic phenotypes, emphasizing the context-dependent nature of glial activity. This review summarizes current knowledge regarding the multifaceted involvement of glial cells in neurodegenerative disorders. Full article

The microglia, first identified by Pío del Río-Hortega, are resident macrophages in the CNS that aid in immune monitoring, synaptic remodeling, and tissue repair. Microglial biology’s dual functions in maintaining homeostasis and contributing to neurodegeneration are examined in this review, with a focus on neurodegenerative disease treatment targets. Methods: We reviewed microglial research using single-cell transcriptomics, molecular genetics, and neuroimmunology to analyze heterogeneity and activation states beyond the M1/M2 paradigm. Results: Microglia maintains homeostasis through phagocytosis, trophic factor production, and synaptic pruning. They acquire activated morphologies in pathological conditions, releasing proinflammatory cytokines and reactive oxygen species via NF-κB, MAPK, and NLRP3 signaling. Single-cell investigations show TREM2 and APOE-expressing disease-associated microglia (DAM) in neurodegenerative lesions. Microglial senescence, mitochondrial failure, and chronic inflammation result from Nrf2/Keap1 redox pathway malfunction in ageing. Microglial interactions with astrocytes via IL-1α, TNF-α, and C1q result in neurotoxic or neuroprotective A2 astrocytes, demonstrating linked glial responses. Microglial inflammatory or reparative responses are influenced by epigenetic and metabolic reprogramming, such as regulation of PGC-1α, SIRT1, and glycolytic flux. Microglia are essential to neuroprotection and neurodegeneration. TREM2 agonists, NLRP3 inhibitors, and epigenetic modulators can treat chronic neuroinflammation and restore CNS homeostasis in neurodegenerative illnesses by targeting microglial signaling pathways. Full article

Astrocytes and microglia constitute nearly half of all central nervous system cells and are indispensable for its proper function. Both exhibit striking morphological and functional heterogeneity, adopting either neuroprotective (A2, M2) or proinflammatory (A1, M1) phenotypes in response to cytokines, pathogen-associated molecular patterns (PAMPs)/damage-associated molecular patterns (DAMPs), toll-like receptor 4 (TLR4) activation, and NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome signaling. Crucially, many of these phenotypic transitions arise during the earliest stages of neurodegeneration, when glial dysfunction precedes overt neuronal loss and may act as a primary driver of disease onset. This review critically examines glial-centered hypotheses of neurodegeneration, with emphasis on their roles in early disease phases: (i) microglial polarization from an M2 neuroprotective state to an M1 proinflammatory state; (ii) NLRP3 inflammasome assembly via P2X purinergic receptor 7 (P2X7R)-mediated K⁺ efflux; (iii) a self-amplifying astrocyte–microglia–neuron inflammatory feedback loop; (iv) impaired microglial phagocytosis and extracellular-vesicle–mediated propagation of β-amyloid (Aβ) and tau; (v) astrocytic scar formation driven by aquaporin-4 (AQP4), matrix metalloproteinase-9 (MMP-9), glial fibrillary acidic protein (GFAP)/vimentin, connexins, and janus kinase/signal transducer and activator of transcription 3 (JAK/STAT3) signaling; (vi) cellular reprogramming of astrocytes and NG2 glia into functional neurons; and (vii) mitochondrial dysfunction in glia, including Dynamin-related protein 1/Mitochondrial fission protein 1 (Drp1/Fis1) fission imbalance and dysregulation of the sirtuin 1/peroxisome proliferator-activated receptor gamma coactivator 1-alpha (Sirt1/PGC-1α) axis. Promising therapeutic strategies target pattern-recognition receptors (TLR4, NLRP3/caspase-1), cytokine modulators (interleukin-4 (IL-4), interleukin-10 (IL-10)), signaling cascades (JAK2–STAT, nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), phosphoinositide 3-kinase–protein kinase B (PI3K–AKT), adenosine monophosphate-activated protein kinase (AMPK)), microglial receptors (triggering receptor expressed on myeloid cells 2 (TREM2)/spleen tyrosine kinase (SYK)/ DNAX-activating protein 10 (DAP10), siglec-3 (CD33), chemokine C-X3-C motif ligand 1/ CX3C motif chemokine receptor 1 (CX3CL1/CX3CR1), Cluster of Differentiation 200/ Cluster of Differentiation 200 receptor 1 (CD200/CD200R), P2X7R), and mitochondrial biogenesis pathways, with a focus on normalizing glial phenotypes rather than simply suppressing pathology. Interventions that restore neuroglial homeostasis at the earliest stages of disease may hold the greatest potential to delay or prevent progression. Given the complexity of glial phenotypes and molecular isoform diversity, a comprehensive, multitargeted approach is essential for mitigating Alzheimer’s disease and related neurodegenerative disorders. This review not only synthesizes pathogenesis but also highlights therapeutic opportunities, offering what we believe to be the first concise overview of the principal hypotheses implicating glial cells in neurodegeneration. Rather than focusing on isolated mechanisms, our goal is a holistic perspective—integrating diverse glial processes to enable comparison across interconnected pathological conditions. Full article

Brain damage caused by hypoxia-ischemia is a serious complication for a newborn with possible life-long sequelae. To develop targeted neuroprotective strategies, it is essential to understand the mechanisms of injury, particularly the role of microglial phagocytosis, which may contribute to neuronal loss after hypoxia-ischemia. The aim was to evaluate neuronal cell death by phagocytosis in neonatal hypoxia-ischemia by investigating key signaling molecules and the effect of gene deletion of the phagocytic receptor Myeloid-epithelial-reproductive tyrosine kinase (MerTK) in a neonatal mouse model. MerTK, growth arrest–specific 6, and genes related to phagoptosis were regulated in the brain 6–72 h after hypoxic ischemia. Brain injury was reduced in MerTK knock-out vs. wild-type mice by 48% in gray matter (p = 0.002) and by 32% in white matter (p = 0.04). There was a near 40% reduction in NeuN immunoreactivity in microglia in MerTK knock-out mice vs. wild-type (p = 0.03) indicating attenuation of neuronal phagocytosis by microglia. In summary, the reduction in microglial neuronal engulfment and brain injury in MerTK-deficient mice strongly indicates that phagoptosis contributes to neuronal loss after neonatal hypoxia-ischemia. This insight suggests that targeting MerTK-mediated phagocytosis may represent a potential therapeutic approach in neonatal hypoxia-ischemic brain injury. Full article

Post-viral neuroinflammatory syndromes, particularly those occurring after SARS-CoV-2 infection, have received increasing attention due to their complex and persistent neurological manifestations. The aim of this narrative review is to integrate current evidence on the molecular and cellular mechanisms underlying chronic neuroinflammation following viral infections, with a focus on dysregulated innate immune responses, macrophage–microglia interactions, oxidative–mitochondrial stress, and impaired inflammation resolution pathways. Our synthesis shows that prolonged activation of macrophages and glial cells promotes the continuous release of pro-inflammatory mediators, while defective phagocytosis and inadequate clearance of cellular debris maintain an inflammatory microenvironment. Mitochondrial dysfunction further amplifies immune activation by stimulating metabolic stress and reactive oxygen species production. In parallel, deficiencies in mediators specialized in inflammation resolution impede the transition from inflammation to resolution, allowing neuroimmune imbalance and nociceptive sensitization to persist long after virus clearance. Key conclusions indicate that these interconnected mechanisms collectively contribute to the long-term neurological symptoms observed in post-viral states, including cognitive impairment, neuropathic pain, and fatigue. Emerging therapeutic strategies targeting cytokine signaling, microglial reactivity, mitochondrial function, and resolution pathways are promising, but remain insufficiently validated in clinical practice. Overall, evidence suggests that post-viral neuroinflammation results from the convergence of sustained immune activation and failure of endogenous resolution mechanisms, highlighting the need for further mechanistic studies and targeted interventions. Full article

Microglia are the resident immune cells of the CNS, maintaining brain homeostasis partially through phagocytosis. In Alzheimer’s disease (AD), microglial phagocytosis is significantly impaired, contributing to the accumulation of pathological aggregates. Microglial phenotypes are dynamic and can shift depending on the disease stage and local environment. While some subpopulations retain or enhance phagocytic activity, especially under inflammatory conditions, others lose their capacity to clear toxic debris effectively. This variability underscores the need for a more nuanced understanding of microglial regulation and function. This paper explores the dual role of microglial phagocytosis in AD and discusses the emerging insights into microglial heterogeneity and how phenotypic shifts affect phagocytic capacity throughout disease progression. A comprehensive understanding of microglial phagocytosis and its dysregulation in AD is essential for designing targeted treatments. Modulating microglial activity to enhance their protective roles without triggering harmful inflammation represents a promising direction for therapeutic intervention in AD. Full article

Maternal immune activation (MIA) during pregnancy has been associated with increased risk of fetal loss and neurodevelopmental disorders in offspring. This review summarizes recent findings on the effects of MIA on fetal survival and microglial phenotype. Studies using polyinosinic–polycytidylic acid [poly(I:C)-induced MIA mouse models have revealed the crucial role of interleukin-17A (IL-17A) in mediating these effects. Overexpression of RORγt, a key transcription factor for IL-17A production, enhances poly(I: C)-induced fetal loss, possibly due to increased placental vulnerability. Intraventricular administration of IL-17A in fetal brains activates microglia and alters their localization, particularly in periventricular regions and the medial cortex. These activated microglia may contribute to abnormal synaptic pruning and excessive phagocytosis of neural progenitor cells, potentially leading to long-term neurodevelopmental abnormalities. The insights gained from MIA research have important clinical implications, including the potential for early identification of high-risk pregnancies and the development of novel preventive and therapeutic strategies. Future research should focus on elucidating the roles of other cytokines, determining critical periods of MIA susceptibility, and translating findings to human populations, while carefully considering ethical implications and the need for appropriate risk communication. Full article

Lipid droplets (LDs) are emerging as key regulators of metabolism and inflammation, with their buildup in microglia linked to aging and neurodegeneration. Perilipin-2 (Plin2) is a ubiquitously expressed LD-associated protein that stabilizes lipid stores; in peripheral tissues, its upregulation promotes lipid retention, inflammation, and metabolic dysfunction. Yet, its role in microglia remains unclear. Using CRISPR-engineered Plin2 knockout (KO) BV2 microglia, we examined how Plin2 contributes to lipid accumulation, bioenergetics, and immune function. Compared to wild-type (WT) cells, Plin2 KO microglia showed markedly reduced LD burden under basal and oleic acid-loaded conditions. Functionally, this was linked to enhanced phagocytosis of zymosan particles, even after lipid loading, indicating improved clearance capacity. Transcriptomics revealed genotype-specific responses to amyloid-β (Aβ), especially in mitochondrial metabolism pathways. Seahorse assays confirmed a distinct bioenergetic profile in KO cells, with reduced basal respiration and glycolysis but preserved mitochondrial capacity, increased spare reserve, and a blunted glycolytic response to Aβ. Together, these findings establish Plin2 as a regulator of microglial lipid storage and metabolic state, with its loss reducing lipid buildup, enhancing phagocytosis, and altering Aβ-induced metabolic reprogramming. Targeting Plin2 may represent a strategy to reprogram microglial metabolism and function in aging and neurodegeneration. Full article