bims-microg 2024-12-01 papers

bims-microg

Biomed News

on Microglia in health and disease

Issue of 2024–12–01
29 papers selected by
Marcus Karlstetter, Universität zu Köln

Tlr7 drives sex differences in age- and Alzheimer's disease-related demyelination.
Microglial APOE3 Christchurch protects neurons from Tau pathology in a human iPSC-based model of Alzheimer's disease.
Haploinsufficiency at the CX3CR1 locus of hematopoietic stem cells favors the appearance of microglia-like cells in the central nervous system of transplant recipients.
Microglia regulate motor neuron plasticity via reciprocal fractalkine and adenosine signaling.
Accumulation of Bioactive Lipid Species in LPS-Induced Neuroinflammation Models Analysed with Multi-Modal Mass Spectrometry Imaging.
Imaging the eye as a window to brain health: frontier approaches and future directions.
P2Y6R Inhibition Induces Microglial M2 Polarization by Promoting PINK1/Parkin-Dependent Mitophagy After Spinal Cord Injury.
Modulation of Urea Transport Attenuates TLR2-Mediated Microglial Activation and Upregulates Microglial Metabolism In Vitro.
Elevated expression of the retrotransposon LINE-1 drives Alzheimer's disease-associated microglial dysfunction.
CRISPRi-based screen of Autism Spectrum Disorder risk genes in microglia uncovers roles of ADNP in microglia endocytosis and synaptic pruning.
Human VCP mutant ALS/FTD microglia display immune and lysosomal phenotypes independently of GPNMB.
Glioblastoma Drives Protease-Independent Extracellular Matrix Invasion of Microglia.
N-acetylaspartate mitigates pro-inflammatory responses in microglial cells by intersecting lipid metabolism and acetylation processes.
Serpina3n in neonatal microglia mediates its protective role for damaged adult microglia by alleviating extracellular matrix remodeling-induced tunneling nanotubes degradation in a cell model of traumatic brain injury.
M1 Microglia-Derived Exosomes Promote A1 Astrocyte Activation and Aggravate Ischemic Injury via circSTRN3/miR-331-5p/MAVS/NF-κB Pathway.
The IRE1-XBP1 Axis Regulates NLRP3 Inflammasome-Mediated Microglia Activation in Hypoxic Ischemic Encephalopathy.
Brain organoid models for studying the function of iPSC-derived microglia in neurodegeneration and brain tumours.
Single-cell transcriptomic landscape of the neuroimmune compartment in amyotrophic lateral sclerosis brain and spinal cord.
Mechanisms driving epigenetic and transcriptional responses of microglia in a neurodegenerative lysosomal storage disorder model.
Tau accumulation induces microglial state alterations in Alzheimer's disease model mice.
IL-1β-induced pericyte dysfunction with a secretory phenotype exacerbates retinal microenvironment inflammation via Hes1/STAT3 signaling pathway.
Purinergic-associated immune responses in neurodegenerative diseases.
Inhibition of Glycolysis Alleviates Chronic Unpredictable Mild Stress Induced Neuroinflammation and Depression-like Behavior.
Adolescent social isolation decreases colonic goblet cells and impairs spatial cognition through the reduction of cystine.
The effect of a dominant kinase-dead Csf1r mutation associated with adult-onset leukoencephalopathy on brain development and neuropathology.
Microglial cannabinoid receptor type II stimulation improves cognitive impairment and neuroinflammation in Alzheimer's disease mice by controlling astrocyte activation.
Engrailed-2 and inflammation convergently and independently impinge on cerebellar Purkinje cell differentiation.
Exploring the feasibility of using mice as a substitute model for investigating microglia in aging and Alzheimer's disease though single cell analysis.
Unique N-glycosylation signatures in Aβ oligomer- and lipopolysaccharide-activated human iPSC-derived microglia.

Science. 2024 Nov 29. 386(6725): eadk7844

Tlr7 drives sex differences in age- and Alzheimer's disease-related demyelination.

Chloe Lopez-Lee, Lay Kodama, Li Fan, Daphne Zhu, Jingjie Zhu, Man Ying Wong, Pearly Ye, Kendra Norman, Nessa R Foxe, Laraib Ijaz, Fangmin Yu, Hao Chen, Gillian K Carling, Eileen R Torres, Rachel D Kim, Dena B Dubal, Shane A Liddelow, Subhash C Sinha, Wenjie Luo, Li Gan.

Alzheimer's disease (AD) and other age-related disorders associated with demyelination exhibit sex differences. In this work, we used single-nuclei transcriptomics to dissect the contributions of sex chromosomes and gonads in demyelination and AD. In a mouse model of demyelination, we identified the roles of sex chromosomes and gonads in modifying microglia and oligodendrocyte responses before and after myelin loss. In an AD-related mouse model expressing APOE4, XY sex chromosomes heightened interferon (IFN) response and tau-induced demyelination. The X-linked gene, Toll-like receptor 7 (Tlr7), regulated sex-specific IFN response to myelin. Deletion of Tlr7 dampened sex differences while protecting against demyelination. Administering TLR7 inhibitor mitigated tau-induced motor impairment and demyelination in male mice, indicating that Tlr7 plays a role in the male-biased type I Interferon IFN response in aging- and AD-related demyelination.

DOI: https://doi.org/10.1126/science.adk7844
Cell Rep. 2024 Nov 28. pii: S2211-1247(24)01333-0. [Epub ahead of print]43(12): 114982

Microglial APOE3 Christchurch protects neurons from Tau pathology in a human iPSC-based model of Alzheimer's disease.

Guoqiang George Sun, Cheng Wang, Randall C Mazzarino, Paula Andrea Perez-Corredor, Hayk Davtyan, Mathew Blurton-Jones, Francisco Lopera, Joseph F Arboleda-Velasquez, Yanhong Shi.

  Alzheimer's disease (AD) is the most prevalent neurodegenerative disorder characterized by extracellular amyloid plaques and neuronal Tau tangles. A recent study found that the APOE3 Christchurch (APOECh) variant could delay AD progression. However, the underlying mechanisms remain unclear. In this study, we established neuron-microglia co-cultures and neuroimmune organoids using isogenic APOE3 and APOECh microglia derived from human induced pluripotent stem cells (hiPSCs) with PSEN1 mutant neurons or brain organoids. We show that APOECh microglia are resistant to Aβ-induced lipid peroxidation and ferroptosis and therefore preserve the phagocytic activity and promote pTau clearance, providing mechanistic insights into the neuroprotective role of APOE3Ch microglia. Moreover, we show that an APOE mimetic peptide can mimic the protective effects of APOECh microglia. These findings demonstrate that the APOECh microglia plays a causal role in microglial neuroprotection, which can be exploited for therapeutic development for AD.

Keywords:  APOE Christchurch; CP: Neuroscience; Tau; brain organoids; ferroptosis; iPSCs; induced pluripotent stem cells; lipid droplet; lipid peroxidation; microglia; phagocytosis; presenilin; resilience

DOI:  https://doi.org/10.1016/j.celrep.2024.114982
Nat Commun. 2024 Nov 25. 15(1): 10192

Haploinsufficiency at the CX3CR1 locus of hematopoietic stem cells favors the appearance of microglia-like cells in the central nervous system of transplant recipients.

Annita Montepeloso, Davide Mattioli, Danilo Pellin, Marco Peviani, Pietro Genovese, Alessandra Biffi.

Transplantation of engineered hematopoietic stem/progenitor cells (HSPCs) showed curative potential in patients affected by neurometabolic diseases treated in early stage. Favoring the engraftment and maturation of the engineered HSPCs in the central nervous system (CNS) could allow enhancing further the therapeutic potential of this approach. Here we unveil that HSPCs haplo-insufficient at the Cx3cr1 (Cx3cr1-/+) locus are favored in central nervous system (CNS) engraftment and generation of microglia-like progeny cells (MLCs) as compared to wild type (Cx3cr1+/+) HSPCs upon transplantation in mice. Based on this evidence, we have developed a CRISPR-based targeted gene addition strategy at the human CX3CR1 locus resulting in an enhanced ability of the edited human HSPCs to generate mature MLCs upon transplantation in immunodeficient mice, and in lineage specific, regulated and robust transgene expression. This approach, which benefits from the modulation of pathways involved in microglia maturation and migration in haplo-insufficient cells, may broaden the application of HSPC gene therapy to a larger spectrum of neurometabolic and neurodegenerative diseases.

DOI: https://doi.org/10.1038/s41467-024-54515-4
Nat Commun. 2024 Nov 28. 15(1): 10349

Microglia regulate motor neuron plasticity via reciprocal fractalkine and adenosine signaling.

Alexandria B Marciante, Arash Tadjalli, Maria Nikodemova, Kayla A Burrowes, Jose Oberto, Edward K Luca, Yasin B Seven, Jyoti J Watters, Tracy L Baker, Gordon S Mitchell.

We report an important role for microglia in regulating neuroplasticity within phrenic motor neurons. Brief episodes of low oxygen (acute intermittent hypoxia; AIH) elicit a form of respiratory motor plasticity known as phrenic long-term facilitation (pLTF) that is regulated by the balance of competing serotonin vs adenosine-initiated cellular mechanisms. Serotonin arises from brainstem raphe neurons, but the source of adenosine is unknown. We tested if hypoxic episodes initiate phrenic motor neuron to microglia fractalkine signaling that evokes extracellular adenosine formation using a well-defined neurophysiology preparation in male rats. With moderate AIH, phrenic motor neuron adenosine 2A receptor activation undermines serotonin-dominant pLTF whereas severe AIH induces pLTF by the adenosine-dependent mechanism. Consequently, phrenic motor neuron fractalkine knockdown, microglial fractalkine receptor inhibition, and microglial ablation enhance moderate AIH, but suppress severe AIH-induced pLTF. We conclude, microglia play important roles in healthy spinal cords, regulating plasticity in motor neurons responsible for breathing.

DOI: https://doi.org/10.1038/s41467-024-54619-x
Int J Mol Sci. 2024 Nov 08. pii: 12032. [Epub ahead of print]25(22):

Accumulation of Bioactive Lipid Species in LPS-Induced Neuroinflammation Models Analysed with Multi-Modal Mass Spectrometry Imaging.

Irma Berrueta Razo, Kerry Shea, Tiffany-Jayne Allen, Hervé Boutin, Adam McMahon, Nicholas Lockyer, Philippa J Hart.

  Neuroinflammation is a complex biological process related to a variety of pathologies, often requiring better understanding in order to develop new, targeted therapeutic interventions. Within this context, multimodal Mass Spectrometry Imaging (MSI) has been used to characterise molecular changes in neuroinflammation for biomarker discovery not possible to other techniques. In this study, molecules including bioactive lipids were detected across inflamed regions of the brain in rats treated with lipopolysaccharide (LPS). The detected lipids may be acting as inflammatory mediators of the immune response. We identified that N-acyl-phosphatidylethanolamine (NAPE) species accumulated in the inflamed area. The presence of these lipids could be related to the endocannabinoid (eCB) signalling system, mediating an anti-inflammatory response from microglial cells at the site of injury to balance pro-inflammation and support neuronal protection. In addition, polyunsaturated fatty acids (PUFAs), specifically n-3 and n-6 species, were observed to accumulate in the area where LPS was injected. PUFAs are directly linked to anti-inflammatory mediators resolving inflammation. Finally, acylcarnitine species accumulated around the inflammation region. Accumulation of these molecules could be due to a deficient β-oxidation cycle.

Keywords:  DESI; MALDI; TOF-SIMS; mass spectrometry imaging; neuroinflammation

DOI:  https://doi.org/10.3390/ijms252212032
J Neuroinflammation. 2024 Nov 29. 21(1): 309

Imaging the eye as a window to brain health: frontier approaches and future directions.

Hasan U Banna, Mary Slayo, James A Armitage, Blanca Del Rosal, Loretta Vocale, Sarah J Spencer.

Recent years have seen significant advances in diagnostic testing of central nervous system (CNS) function and disease. However, there remain challenges in developing a comprehensive suite of non- or minimally invasive assays of neural health and disease progression. Due to the direct connection with the CNS, structural changes in the neural retina, retinal vasculature and morphological changes in retinal immune cells can occur in parallel with disease conditions in the brain. The retina can also, uniquely, be assessed directly and non-invasively. For these reasons, the retina may prove to be an important "window" for revealing and understanding brain disease. In this review, we discuss the gross anatomy of the eye, focusing on the sensory and non-sensory cells of the retina, especially microglia, that lend themselves to diagnosing brain disease by imaging the retina. We include a history of ocular imaging to describe the different imaging approaches undertaken in the past and outline current and emerging technologies including retinal autofluorescence imaging, Raman spectroscopy, and artificial intelligence image analysis. These new technologies show promising potential for retinal imaging to be used as a tool for the diagnosis of brain disorders such as Alzheimer's disease and others and the assessment of treatment success.

DOI: https://doi.org/10.1186/s12974-024-03304-3
Mol Neurobiol. 2024 Nov 28.

P2Y6R Inhibition Induces Microglial M2 Polarization by Promoting PINK1/Parkin-Dependent Mitophagy After Spinal Cord Injury.

Jiezhao Lin, Yuanfang Sun, Haoran Huang, Cheng Yu, Wenhao Kuang, Yihan Wang, Lixin Zhu.

  Secondary injury presents a significant hurdle to neural regeneration following spinal cord injury (SCI), primarily driven by inflammation in which microglial cells play a crucial role. Despite the growing interest in mitophagy, studies on its occurrence post-spinal cord injury, particularly within microglial cells, are scarce. While P2Y6R has been implicated in inflammation regulation in various neurological conditions, its specific role in SCI remains uncertain. Our study revealed an upregulation of P2Y6R expression following SCI notably in microglial cells. Treatment with the P2Y6R-specific inhibitor, MRS2578, in mice facilitated M2 polarization of microglial cells and alleviated secondary damage, ultimately enhancing neural regeneration and functional recovery. In an in vitro BV2 inflammation model, our findings indicate that P2Y6R inhibition induced M2 polarization of BV2 cells and reduced neuroinflammation through PINK/Parkin-dependent mitophagy activation. In summary, our results underscore the potential of P2Y6R inhibition in promoting mitophagy-induced M2 polarization of microglial cells, thereby ameliorating secondary injury following spinal cord injury.

Keywords:  M2 polarization; Microglial; Mitophagy; P2Y6R; Spinal cord injury

DOI:  https://doi.org/10.1007/s12035-024-04631-5
Metabolites. 2024 Nov 17. pii: 634. [Epub ahead of print]14(11):

Modulation of Urea Transport Attenuates TLR2-Mediated Microglial Activation and Upregulates Microglial Metabolism In Vitro.

Najlaa A Al-Thani, Dylan Zinck, Gavin S Stewart, Derek A Costello.

  Background: Alzheimer's disease (AD) is a neurodegenerative disorder traditionally characterised by the presence of amyloid beta (Aβ) plaques and neurofibrillary tau tangles in the brain. However, emerging research has highlighted additional metabolic hallmarks of AD pathology. These include the metabolic reprogramming of microglia in favour of glycolysis over oxidative phosphorylation. This shift is attributed to an 'M1'-like pro-inflammatory phenotype, which exacerbates neuroinflammation and contributes to neuronal damage. The urea cycle also presents as an altered metabolic pathway in AD, due to elevated urea levels and altered expression of urea cycle enzymes, metabolites, and transporters in the brain. However, to date, these changes remain largely unexplored. Methods: This study focuses on understanding the effects of extracellular urea and urea transporter-B (UT-B) inhibition on inflammatory changes in lipoteichoic acid (LTA)-stimulated BV2 microglia and on the viability of SH-SY5Y neuronal cells under oxidative stress and neurotoxic conditions. Results: In BV2 microglia, UT-B inhibition demonstrated a notable anti-inflammatory effect by reducing the formation of nitric oxide (NO) and the expression of tumour necrosis factor α (TNFα) and CCL2 in response to stimulation with the toll-like receptor (TLR)2 agonist, lipoteichoic acid (LTA). This was accompanied by a reduction in extracellular urea and upregulation of UT-B expression. The application of exogenous urea was also shown to mediate the inflammatory profile of BV2 cells in a similar manner but had only a modest impact on UT-B expression. While exposure to LTA alone did not alter the microglial metabolic profile, inhibition of UT-B upregulated the expression of genes associated with both glycolysis and fatty acid oxidation. Conversely, neither increased extracellular urea nor UT-B inhibition had a significant impact on cell viability or cytotoxicity in SH-SY5Y neurones exposed to oxidative stressors tert-butyl hydroperoxide (t-BHP) and 6-hydroxydopamine (6-OHDA). Conclusions: This study further highlights the involvement of urea transport in regulating the neuroinflammation associated with AD. Moreover, we reveal a novel role for UT-B in maintaining microglial metabolic homeostasis. Taken together, these findings contribute supporting evidence to the regulation of UT-B as a therapeutic target for intervention into neuroinflammatory and neurodegenerative disease.

Keywords:  6-OHDA; UT-B; lipoteichoic acid; neuroinflammation; nitric oxide; oxidative stress; tBHP; urea

DOI:  https://doi.org/10.3390/metabo14110634
Acta Neuropathol. 2024 Nov 27. 148(1): 75

Elevated expression of the retrotransposon LINE-1 drives Alzheimer's disease-associated microglial dysfunction.

Nainika Roy, Imdadul Haq, Jason C Ngo, David A Bennett, Andrew F Teich, Philip L De Jager, Marta Olah, Falak Sher.

  Aberrant activity of the retrotransposable element long interspersed nuclear element-1 (LINE-1) has been hypothesized to contribute to cellular dysfunction in age-related disorders, including late-onset Alzheimer's disease (LOAD). However, whether LINE-1 is differentially expressed in cell types of the LOAD brain, and whether these changes contribute to disease pathology is largely unknown. Here, we examined patterns of LINE-1 expression across neurons, astrocytes, oligodendrocytes, and microglia in human postmortem prefrontal cortex tissue from LOAD patients and cognitively normal, age-matched controls. We report elevated immunoreactivity of the open reading frame 1 protein (ORF1p) encoded by LINE-1 in microglia from LOAD patients and find that this immunoreactivity correlates positively with disease-associated microglial morphology. In human iPSC-derived microglia (iMG), we found that CRISPR-mediated transcriptional activation of LINE-1 drives changes in microglial morphology and cytokine secretion and impairs the phagocytosis of amyloid beta (Aβ). We also find LINE-1 upregulation in iMG induces transcriptomic changes genes associated with antigen presentation and lipid metabolism as well as impacting the expression of many AD-relevant genes. Our data posit that heightened LINE-1 expression may trigger microglial dysregulation in LOAD and that these changes may contribute to disease pathogenesis, suggesting a central role for LINE-1 activity in human LOAD.

Keywords:  Alzheimer’s disease; LINE-1; Microglia; Neuroinflammation; Retrotransposons; Transposable elements

DOI:  https://doi.org/10.1007/s00401-024-02835-6
bioRxiv. 2024 Nov 17. pii: 2024.06.01.596962. [Epub ahead of print]

CRISPRi-based screen of Autism Spectrum Disorder risk genes in microglia uncovers roles of ADNP in microglia endocytosis and synaptic pruning.

Olivia M Teter, Amanda McQuade, Venus Hagan, Weiwei Liang, Nina M Dräger, Sydney M Sattler, Brandon B Holmes, Vincent Cele Castillo, Vasileios Papakis, Kun Leng, Steven Boggess, Tomasz J Nowakowski, James Wells, Martin Kampmann.

Autism Spectrum Disorders (ASD) are a set of neurodevelopmental disorders with complex biology. The identification of ASD risk genes from exome-wide association studies and de novo variation analyses has enabled mechanistic investigations into how ASD-risk genes alter development. Most functional genomics studies have focused on the role of these genes in neurons and neural progenitor cells. However, roles for ASD risk genes in other cell types are largely uncharacterized. There is evidence from postmortem tissue that microglia, the resident immune cells of the brain, appear activated in ASD. Here, we used CRISPRi-based functional genomics to systematically assess the impact of ASD risk gene knockdown on microglia activation and phagocytosis. We developed an iPSC-derived microglia-neuron coculture system and high-throughput flow cytometry readout for synaptic pruning to enable parallel CRISPRi-based screening of phagocytosis of beads, synaptosomes, and synaptic pruning. Our screen identified ADNP , a high-confidence ASD risk genes, as a modifier of microglial synaptic pruning. We found that microglia with ADNP loss have altered endocytic trafficking, remodeled proteomes, and increased motility in coculture.

DOI: https://doi.org/10.1101/2024.06.01.596962
Mol Neurodegener. 2024 Nov 26. 19(1): 90

Human VCP mutant ALS/FTD microglia display immune and lysosomal phenotypes independently of GPNMB.

Benjamin E Clarke, Oliver J Ziff, Giulia Tyzack, Marija Petrić Howe, Yiran Wang, Pierre Klein, Claudia A Smith, Cameron A Hall, Adel Helmy, Michael Howell, Gavin Kelly, Rickie Patani.

BACKGROUND: Microglia play crucial roles in maintaining neuronal homeostasis but have been implicated in contributing to amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). However, the role of microglia in ALS/FTD remains incompletely understood.
METHODS: Here, we generated highly enriched cultures of VCP mutant microglia derived from human induced pluripotent stem cells (hiPSCs) to investigate their cell autonomous and non-cell autonomous roles in ALS pathogenesis. We used RNA-sequencing, proteomics and functional assays to study hiPSC derived VCP mutant microglia and their effects on hiPSC derived motor neurons and astrocytes.
RESULTS: Transcriptomic, proteomic and functional analyses revealed immune and lysosomal dysfunction in VCP mutant microglia. Stimulating healthy microglia with the inflammatory inducer lipopolysaccharide (LPS) showed partial overlap with VCP mutant microglia in their reactive transformation. LPS-stimulated VCP mutant microglia displayed differential activation of inflammatory pathways compared with LPS-stimulated healthy microglia. Conserved gene expression changes were identified between VCP mutant microglia, SOD1 mutant mice microglia, and postmortem ALS spinal cord microglial signatures, including increased expression of the transmembrane glycoprotein GPNMB. While knockdown of GPNMB affected inflammatory and phagocytosis processes in microglia, this was not sufficient to ameliorate cell autonomous phenotypes in VCP mutant microglia. Secreted factors from VCP mutant microglia were sufficient to activate the JAK-STAT pathway in hiPSC derived motor neurons and astrocytes.
CONCLUSIONS: VCP mutant microglia undergo cell autonomous reactive transformation involving immune and lysosomal dysfunction that partially recapitulate key phenotypes of microglia from other ALS models and post mortem tissue. These phenotypes occur independently of GPNMB. Additionally, VCP mutant microglia elicit non cell autonomous responses in motor neurons and astrocytes involving the JAK-STAT pathway.

DOI: https://doi.org/10.1186/s13024-024-00773-1
bioRxiv. 2024 Nov 11. pii: 2024.11.08.622715. [Epub ahead of print]

Glioblastoma Drives Protease-Independent Extracellular Matrix Invasion of Microglia.

Chia-Wen Chang, Ashwin Bale, Rohit Bhargava, Brendan A C Harley.

Glioblastoma (GBM) is the most common and lethal form of primary brain cancer. Microglia infiltration into the tumor microenvironment is associated with immunosuppression and poor prognosis. Improved physicochemical understanding of microglia activation and invasion may provide novel GBM therapeutic strategies essential for improving long-term treatment efficacy. Here, we combine microfluidic systems with 3-D collagen hydrogels to systematically investigate microglia activation, invasion, contractility and cytokine secretion in response of GBM-microglia crosstalk. GBM inflammatory biomolecules significantly promote activation and 3D invasion of microglia. Interestingly, microglia invasion is not significantly affected by inhibitors of MMP activity or cellular glycolysis. In contrast, ROCK-pathway inhibition significantly impedes microglia invasion. Infrared microscopy analyses show that GBM co-culture does not significantly alter microglia lipid content. Further, GBM conditioned media resulted in significantly increased collagen hydrogel contraction, suggesting the importance of microglia contractility to physically remodel the local extracellular matrix (ECM). We also identify a panel of soluble proteins that may contribute to microglia chemotaxis, such as TIMP-1 and CXCL12. Taken together, this study suggests that the presence of GBM cells can enhance microglia invasion via increased cellular contractility, independent of MMP activity and cellular glycolysis.

DOI: https://doi.org/10.1101/2024.11.08.622715
Cell Commun Signal. 2024 Nov 25. 22(1): 564

N-acetylaspartate mitigates pro-inflammatory responses in microglial cells by intersecting lipid metabolism and acetylation processes.

Federica Felice, Pamela De Falco, Martina Milani, Serena Castelli, Antonella Ragnini-Wilson, Giacomo Lazzarino, Nadia D'Ambrosi, Fabio Ciccarone, Maria Rosa Ciriolo.

   BACKGROUND: Microglia play a crucial role in brain development and repair by facilitating processes such as synaptic pruning and debris clearance. They can be activated in response to various stimuli, leading to either pro-inflammatory or anti-inflammatory responses associated with specific metabolic alterations. The imbalances between microglia activation states contribute to chronic neuroinflammation, a hallmark of neurodegenerative diseases. N-acetylaspartate (NAA) is a brain metabolite predominantly produced by neurons and is crucial for central nervous system health. Alterations in NAA metabolism are observed in disorders such as Multiple Sclerosis and Canavan disease. While NAA's role in oligodendrocytes and astrocytes has been investigated, its impact on microglial function remains less understood.
METHODS: The murine BV2 microglial cell line and primary microglia were used as experimental models. Cells were treated with exogenous NAA and stimulated with LPS/IFN-γ to reproduce the pro-inflammatory phenomenon. HPLC and immunofluorescence analysis were used to study lipid metabolism following NAA treatment. Automated fluorescence microscopy was used to analyze phagocytic activity. The effects on the pro-inflammatory response were evaluated by analysis of protein/mRNA expression and ChIP assay of typical inflammatory markers.
RESULTS: NAA treatment promotes an increase in both lipid synthesis and degradation, and enhances the phagocytic activity of BV2 cells, thus fostering surveillant microglia characteristics. Importantly, NAA decreases the pro-inflammatory state induced by LPS/IFN-γ via the activation of histone deacetylases (HDACs). These findings were validated in primary microglial cells, highlighting the impact on cellular metabolism and inflammatory responses.
CONCLUSIONS: The study highlighted the role of NAA in reinforcing the oxidative metabolism of surveillant microglial cells and, most importantly, in buffering the inflammatory processes characterizing reactive microglia. These results suggest that the decreased levels of NAA observed in neurodegenerative disorders can contribute to chronic neuroinflammation.

Keywords:  Anti-inflammatory response; Histone deacetylases; Lipid turnover; Microglial polarization; NAA; Oxidative metabolism

DOI:  https://doi.org/10.1186/s12964-024-01947-6
Neuroscience. 2024 Nov 27. pii: S0306-4522(24)00655-9. [Epub ahead of print]

Serpina3n in neonatal microglia mediates its protective role for damaged adult microglia by alleviating extracellular matrix remodeling-induced tunneling nanotubes degradation in a cell model of traumatic brain injury.

Gengfan Ye, Zhigang Wang, Pandi Chen, Junyi Ye, Shiwei Li, Maosong Chen, Jiugeng Feng, Hongcai Wang, Wei Chen.

  Traumatic brain injury (TBI) induces significant neuroinflammation, primarily driven by microglia. Neonatal microglia (NMG) may have therapeutic potential by modulating the inflammatory response of damaged adult microglia (AMG). This study investigates the influence of NMG on AMG function through extracellular matrix (ECM) remodeling and the formation of tunneling nanotubes (TnTs), with a focus on the role of Serpina3n. We established an in vitro TBI model using a 3D Transwell system, co-culturing damaged AMG with NMG. Viral vector transfection was employed to manipulate Serpina3n expression in NMG. Quantitative real-time PCR, Western blotting, and ELISA were utilized to assess inflammatory markers, ECM remodeling proteins, and TnTs-related proteins. Co-culturing with NMG significantly inhibited M1 polarization of AMG and reduced the release of pro-inflammatory cytokines while promoting M2 polarization and increasing the production of anti-inflammatory cytokines. NMG expressed higher levels of Serpina3n, which played a crucial role in reducing Granzyme B, matrix metalloproteinase (MMP) 2 and MMP9 expression, thereby mitigating ECM remodeling. Inhibition of Serpina3n in NMG increased pro-inflammatory markers and decreased TnTs formation proteins, whereas overexpression of M-sec in AMG counteracted these effects. This highlights the importance of TnTs in maintaining microglial function and promoting an anti-inflammatory environment. In conclusion, NMG improve the function of damaged AMG by modulating ECM remodeling and promoting TnTs formation through the action of Serpina3n.

Keywords:  ECM; Neonatal Microglia; Serpina3n; TBI; Tunneling Nanotubes

DOI:  https://doi.org/10.1016/j.neuroscience.2024.11.066
J Inflamm Res. 2024 ;17 9285-9305

M1 Microglia-Derived Exosomes Promote A1 Astrocyte Activation and Aggravate Ischemic Injury via circSTRN3/miR-331-5p/MAVS/NF-κB Pathway.

Zhongyuan Li, Pengfei Xu, Yang Deng, Rui Duan, Qiang Peng, Shiyao Wang, Zhaohan Xu, Ye Hong, Yingdong Zhang.

   Background: After ischemic stroke (IS), microglia and astrocytes undergo polarization, transforming into a pro-inflammatory phenotype (M1 or A1). According to previous studies, exosomes might play an important role in the interplay between M1 microglia and A1 astrocytes after IS.
Methods: We used the microglial oxygen-glucose deprivation/reperfusion (OGD/R) model and ultracentrifugation to extract M1 microglial exosomes (M1-exos). Subsequently, we identified circSTRN3 enriched in exosomes through RNA sequencing and detected the role of circSTRN3 in astrocyte activation based on bioinformatics analysis, immunofluorescence, Western blotting, and polymerase chain reaction analysis. We validated these findings in the middle cerebral artery occlusion/reperfusion (MCAO/R) model of adult male C57BL/6J mice. Finally, we confirmed the correlation among circSTRN3, miR-331-5p, and stroke severity score in exosomes isolated from peripheral blood of IS patients.
Results: Our findings revealed that M1-exos promoted A1 astrocyte activation. CircSTRN3 was abundant in M1-exos, which could sponge miR-331-5p to affect mitochondrial antiviral signaling protein (MAVS), activate NF-κB pathway, and participate in A1 astrocyte activation. In addition, overexpressed circSTRN3 augmented the infarct size and neurological dysfunction in MCAO/R models, while miR-331-5p mimics reversed the effect. Furthermore, circSTRN3 in IS patients was positively correlated with stroke severity score (R 2 = 0.83, P < 0.001), while miR-331-5p demonstrated a negative correlation with the same score (R 2 = 0.81, P < 0.001).
Conclusion: Taken together, our research indicated that circSTRN3 from M1-exos could promote A1 astrocyte activation and exacerbate ischemic brain injury via miR331-5p/MAVS/NF-κB axis.

Keywords:  astrocyte; circSTRN3; exosome; ischemic stroke; miR-331-5p; microglia

DOI:  https://doi.org/10.2147/JIR.S485252
Crit Rev Immunol. 2025 ;45(1): 55-64

The IRE1-XBP1 Axis Regulates NLRP3 Inflammasome-Mediated Microglia Activation in Hypoxic Ischemic Encephalopathy.

Qun Cai, Liyuan Shen, Xiaoqun Zhang, Zhijun Zhang, Ting Wang.

Hypoxic-ischemic encephalopathy (HIE) is a perinatal injury caused by cerebral hypoxia and reduced blood perfusion. Microglia activation-induced neuroinflammatory injury is a leading cause of neuron loss and brain injury. Efficient treatment strategies are still required further investigation. Our study is aimed to investigate the role of IRE1-XBP1 inhibitor 4μ8С in HIE. Rat pups (7 d) were used to establish HIE model using unilateral carotid artery ligation and hypoxia. A series of experiments including Western blot, Morris water maze test, TTC staining, RT-qPCR, TUNEL staining, and immunofluorescence staining were operated to evaluate the role of 4μ8С in HIE. 4μ8С treatment effectively reduced phosphorylated IRElα and XBP1 protein levels. 4μ8С treatment improves cognition and learning abilities of HIE rats. 4μ8С treatment alleviated brain infarction and cell apoptosis in HIE rats. 4μ8С treatment inhibited NLRP3 inflammasome activation-mediated microglia activation and inflammatory response. In conclusion, 4μ8С suppressed microglia and NLRP3 inflammasome activation by inactivating IRE1/XBP1 axis during HIE development, which revealed IRE1α inhibition as a novel mechanism for neuron protection.

DOI: https://doi.org/10.1615/CritRevImmunol.2024053554
Neurobiol Dis. 2024 Nov 22. pii: S0969-9961(24)00344-9. [Epub ahead of print]203 106742

Brain organoid models for studying the function of iPSC-derived microglia in neurodegeneration and brain tumours.

Angelica Maria Sabogal-Guaqueta, Teresa Mitchell-Garcia, Jasmijn Hunneman, Daniëlle Voshart, Arun Thiruvalluvan, Floris Foijer, Frank Kruyt, Marina Trombetta-Lima, Bart J L Eggen, Erik Boddeke, Lara Barazzuol, Amalia M Dolga.

  Microglia represent the main resident immune cells of the brain. The interplay between microglia and other cells in the central nervous system, such as neurons or other glial cells, influences the function and ability of microglia to respond to various stimuli. These cellular communications, when disrupted, can affect the structure and function of the brain, and the initiation and progression of neurodegenerative diseases including Alzheimer's disease and Parkinson's disease, as well as the progression of other brain diseases like glioblastoma. Due to the difficult access to patient brain tissue and the differences reported in the murine models, the available models to study the role of microglia in disease progression are limited. Pluripotent stem cell technology has facilitated the generation of highly complex models, allowing the study of control and patient-derived microglia in vitro. Moreover, the ability to generate brain organoids that can mimic the 3D tissue environment and intercellular interactions in the brain provide powerful tools to study cellular pathways under homeostatic conditions and various disease pathologies. In this review, we summarise the most recent developments in modelling degenerative diseases and glioblastoma, with a focus on brain organoids with integrated microglia. We provide an overview of the most relevant research on intercellular interactions of microglia to evaluate their potential to study brain pathologies.

Keywords:  Glioblastoma; Microglia; Neurodegenerative diseases; Organoids; iPSC

DOI:  https://doi.org/10.1016/j.nbd.2024.106742
bioRxiv. 2024 Nov 14. pii: 2024.11.12.623183. [Epub ahead of print]

Single-cell transcriptomic landscape of the neuroimmune compartment in amyotrophic lateral sclerosis brain and spinal cord.

John F Tuddenham, Masashi Fujita, Anthony Khairallah, Claire Harbison, Xena E Flowers, Guillermo Coronas-Samano, Silas Maniatis, Aidan Daly, Julie A Schneider, Andrew F Teich, Jean Paul G Vonsattel, Peter A Sims, Wassim Elyaman, Elizabeth M Bradshaw, Hemali Phatnani, Neil Shneider, David A Bennett, Philip L De Jager, Serge Przedborski, Vilas Menon, Marta Olah.

Development of therapeutic approaches that target specific microglia responses in amyotrophic lateral sclerosis (ALS) is crucial due to the involvement of microglia in ALS progression. Our study identifies the predominant microglia subset in human ALS primary motor cortex and spinal cord as an undifferentiated phenotype with dysregulated respiratory electron transport. Moreover, we find that the interferon response microglia subset is enriched in donors with aggressive disease progression, while a previously described potentially protective microglia phenotype is depleted in ALS. Additionally, we observe an enrichment of non-microglial immune cell, mainly NK/T cells, in ALS central nervous system, primarily in the spinal cord. These findings pave the way for the development of microglia subset-specific therapeutic interventions to slow or even stop ALS progression.

DOI: https://doi.org/10.1101/2024.11.12.623183
bioRxiv. 2024 Nov 14. pii: 2024.11.12.623296. [Epub ahead of print]

Mechanisms driving epigenetic and transcriptional responses of microglia in a neurodegenerative lysosomal storage disorder model.

Christopher D Balak, Johannes C M Schlachetzki, Addison J Lana, Elizabeth West, Christine Hong, Jordan DuGal, Yi Zhou, Benjamin Li, Payam Saisan, Nathanael J Spann, Vishal Sarsani, Martina P Pasillas, Sydney O'Brien, Philip Gordts, Beth Stevens, Fredrik Kamme, Christopher K Glass.

Lysosomal dysfunction is causally linked to neurodegeneration in many lysosomal storage disorders (LSDs) and is associated with various age-related neurodegenerative diseases 1,2 , but there is limited understanding of the mechanisms by which altered lysosomal function leads to changes in gene expression that drive pathogenic cellular phenotypes. To investigate this question, we performed systematic imaging, transcriptomic, and epigenetic studies of major brain cell types in Sgsh null (KO) mice, a preclinical mouse model for Sanfilippo syndrome (Mucopolysaccharidosis Type IIIA, MPS-IIIA) 3,4 . MPS-IIIA is a neurodegenerative LSD caused by homozygous loss-of-function (LoF) mutations in SGSH which results in severe early-onset developmental, behavioral, and neurocognitive impairment 5-15 . Electron microscopy, immunohistochemistry, and single-nucleus RNA-sequencing analysis revealed microglia as the cell type exhibiting the most dramatic phenotypic alterations in Sgsh KO mice. Further temporal analysis of microglia gene expression showed dysregulation of genes associated with lysosomal function and immune signaling pathways beginning early in the course of the disease. Sgsh deficiency similarly resulted in increases in open chromatin and histone acetylation at thousands of putative microglia-specific enhancers associated with upregulated genes but had much less impact on the epigenetic landscapes of neurons or oligodendrocytes. We provide evidence for dominant and context-dependent roles of members of the MITF/TFE family as major drivers of microglia-specific epigenetic and transcriptional changes resulting from lysosomal stress that are dependent on collaborative interactions with PU.1/ETS and C/EBP transcription factors. Lastly, we show that features of the transcriptomic and epigenetic alterations observed in murine Sgsh deficiency are also observed in microglia derived from mouse models of age-related neurodegeneration and in human Alzheimer's disease patients, revealing common and disease-specific transcriptional mechanisms associated with disease-associated microglia phenotypes.

DOI: https://doi.org/10.1101/2024.11.12.623296
eNeuro. 2024 Nov 26. pii: ENEURO.0260-24.2024. [Epub ahead of print]

Tau accumulation induces microglial state alterations in Alzheimer's disease model mice.

Kenichi Nagata, Shoko Hashimoto, Daisuke Joho, Ryo Fujioka, Yukio Matsuba, Misaki Sekiguchi, Naomi Mihira, Daisuke Motooka, Yu-Chen Liu, Daisuke Okuzaki, Masataka Kikuchi, Shigeo Murayama, Takaomi C Saido, Hiroshi Kiyama, Hiroki Sasaguri.

Unique microglial states have been identified in Alzheimer's disease (AD) model mice and postmortem AD brains. Although it has been well documented that amyloid-β accumulation induces the alteration of microglial states, the relationship between tau pathology and microglial states remains incompletely understood because of a lack of suitable AD models. In the present study, we generated a novel AD model mouse by the intracerebral administration of tau purified from human brains with primary age-related tauopathy into App knock-in mice with humanized tau. Immunohistochemical analyses revealed that Dectin-1-positive disease-associated microglia were increased in the AD model mice after tau accumulation in the brain. We then performed single-nucleus RNA sequencing on the AD model mice to evaluate the differences in microglial states with and without tau propagation and accumulation. By taking advantage of spatial transcriptomics and existing single-cell RNA sequencing datasets, we showed for the first time that tau propagation and accumulation induce a disease-associated microglial phenotype at the expense of an age-related non-homeostatic counterpart (namely, white matter-associated microglia) in an AD model mouse brain. Future work using spatial transcriptomics at single-cell resolution will pave the way for a more appropriate interpretation of microglial alterations in response to tau pathology in the AD brain.Significance Statement We generated a novel Alzheimer's disease model mouse showing humanized tau accumulation and propagation after amyloid beta accumulation. Immunohistochemical analyses revealed that disease-associated microglia were increased in the model mice after tau accumulation in the brain. Using single-cell RNA-seq and spatial transcriptomics, we showed for the first time that tau propagation and accumulation induce a disease-associated microglial phenotype at the expense of an age-related non-homeostatic counterpart in the model mouse brain.

DOI: https://doi.org/10.1523/ENEURO.0260-24.2024
Int Immunopharmacol. 2024 Nov 28. pii: S1567-5769(24)02133-7. [Epub ahead of print]144 113611

IL-1β-induced pericyte dysfunction with a secretory phenotype exacerbates retinal microenvironment inflammation via Hes1/STAT3 signaling pathway.

Caoxin Huang, Xiaofang Zhang, Menghua Wu, Chen Yang, Xilin Ge, Wenting Chen, Xuejun Li, Suhuan Liu, Shuyu Yang.

  Retinal pericytes are mural cells surrounding capillaries to maintain the integrity of blood-retina barrier and regulate vascular behaviors. Pericyte loss has been considered as the hallmark of diabetic retinopathy (DR), which is a major complication of diabetes and the leading cause of blindness in adults. However, the precise function of pericytes in regulating the retinal microenvironment and the underlying mechanism remains largely unknown. In this study, we observed a secretory phenotype of pericytes with elevated inflammatory cytokines in response to Interleukin-1β (IL-1β), a canonical inflammatory cytokine which significantly increases during the initial stages of diabetic retinopathy. This phenotype is also accompanied by reduced expression of adherent junction proteins and contractile proteins. Paracrine cytokines derived from pericytes further induce the chemotaxis of microglia cells and trigger detrimental changes in endothelial cells, including reduced expression of tight junction protein Occludin and increased apoptosis. Mechanically, the secretion potential in pericytes is partially mediated by Hes1/STAT3 signaling pathway. Moreover, co-injection of stattic, an inhibitor targeting STAT3 activation, could effectively attenuate IL-1β-induced retinal inflammation and microglial activation in retina tissues. Collectively, these findings demonstrate the potential of retinal pericytes as an initial inflammatory sensor prior to their anatomical pathological loss, via undergoing phenotypic changes and secreting paracrine factors to amplify local inflammation and damage endothelial cells in vitro. Furthermore, inhibition of STAT3 activation by inhibitors significantly ameliorates IL-1β-induced retinal inflammation, suggesting STAT3 in retinal pericytes as a promising target for alleviating DR and other IL-1β-induced ocular diseases.

Keywords:  Endothelial cells; Hes1; IL-1β; Inflammation; Microglial cells; Pericyte; Retina; STAT3

DOI:  https://doi.org/10.1016/j.intimp.2024.113611
Prog Neurobiol. 2024 Nov 22. pii: S0301-0082(24)00129-1. [Epub ahead of print]243 102693

Purinergic-associated immune responses in neurodegenerative diseases.

Sara Carracedo, Agathe Launay, Paul-Alexandre Dechelle-Marquet, Emilie Faivre, David Blum, Cécile Delarasse, Eric Boué-Grabot.

  The chronic activation of immune cells can participate in the development of pathological conditions such as neurodegenerative diseases including Alzheimer's disease (AD), Multiple Sclerosis (MS), Parkinson's disease (PD), Huntington's disease (HD) and Amyotrophic Lateral Sclerosis (ALS). In recent years, compelling evidence indicates that purinergic signaling plays a key role in neuro-immune cell functions. The extracellular release of adenosine 5'-triphosphate (ATP), and its breakdown products (ADP and adenosine) provide the versatile basis for complex purinergic signaling through the activation of several families of receptors. G-protein coupled adenosine A2A receptors, ionotropic P2X and G-protein coupled P2Y receptors for ATP and other nucleotides are abundant and widely distributed in neurons, microglia, and astrocytes of the central nervous system as well as in peripheral immune cells. These receptors are strongly linked to inflammation, with a functional interplay that may influence the intricate purinergic signaling involved in inflammatory responses. In the present review, we examine the roles of the purinergic receptors in neuro-immune cell functions with particular emphasis on A2AR, P2X4 and P2X7 and their possible relevance to specific neurodegenerative disorders. Understanding the molecular mechanisms governing purinergic receptor interaction will be crucial for advancing the development of effective immunotherapies targeting neurodegenerative diseases.

Keywords:  A2A; Adenosine signaling; Astrocytes; Immune responses; Microglia; Neurodegenerative disease; P2X; Purinergic signaling

DOI:  https://doi.org/10.1016/j.pneurobio.2024.102693
Brain Sci. 2024 Oct 30. pii: 1098. [Epub ahead of print]14(11):

Inhibition of Glycolysis Alleviates Chronic Unpredictable Mild Stress Induced Neuroinflammation and Depression-like Behavior.

Bing Liu, Ke Dong, Xiaobing Chen, Huafeng Dong, Yun Zhao, Xue Wang, Zhaowei Sun, Fang Xie, Lingjia Qian.

   BACKGROUND: Growing evidence suggests that glucose metabolism plays a crucial role in activated immune cells, significantly contributing to the occurrence and development of neuroinflammation and depression-like behaviors. Chronic stress has been reported to induce microglia activation and disturbances in glucose metabolism in the hippocampus.
AIMS: This study aims to investigate how chronic stress-mediated glycolysis promotes neuroinflammation and to assess the therapeutic potential of the glycolysis inhibitor, 2-deoxy-D-glucose (2-DG), in a model of chronic stress-induced neuroinflammation and depression-like behavior.
METHODS: In in vitro studies, we first explored the effects of 2-DG on the inflammatory response of microglia cells. The results showed that corticosterone (Cort) induced reactive oxygen species (ROS) production, increased glycolysis, and promoted the release of inflammatory mediators. However, these effects were reversed by intervention with 2-DG. Subsequently, we examined changes in depression-like behavior and hippocampal glycolysis in mice during chronic stress. The results indicated that chronic stress led to prolonged escape latency in the Morris water maze, increased platform-crossing frequency, reduced sucrose preference index, and extended immobility time in the forced swim test, all of which are indicative of depression-like behavior in mice. Additionally, we found that the expression of the key glycolytic enzyme hexokinase 2 (HK2) was upregulated in the hippocampus of stressed mice, along with an increased release of inflammatory factors. Further in vivo experiments investigated the effects of 2-DG on glycolysis and pro-inflammatory mediator production, as well as the therapeutic effects of 2-DG on chronic stress-induced depression-like behavior in mice. The results showed that 2-DG alleviated chronic stress-induced depression-like behaviors, such as improving escape latency and platform-crossing frequency in the Morris water maze, and increasing the time spent in the center of the open field. Additionally, 2-DG intervention reduced the level of glycolysis in the hippocampus and decreased the release of pro-inflammatory mediators.
CONCLUSIONS: These findings suggest that 2-DG can mitigate neuroinflammation and depressive behaviors by inhibiting glycolysis and inflammatory responses. Overall, our results highlight the potential of 2-DG as a therapeutic agent for alleviating chronic stress-induced neuroinflammation through the regulation of glycolysis.

Keywords:  2-DG; CUMS; glycolysis; microglia; neuroinflammation

DOI:  https://doi.org/10.3390/brainsci14111098
Mol Psychiatry. 2024 Nov 29.

Adolescent social isolation decreases colonic goblet cells and impairs spatial cognition through the reduction of cystine.

Moeka Tanabe, Kazuo Kunisawa, Imari Saito, Aika Kosuge, Hiroyuki Tezuka, Tomoki Kawai, Yuki Kon, Koyo Yoshidomi, Akari Kagami, Masaya Hasegawa, Hisayoshi Kubota, Haruto Ojika, Tadashi Fujii, Takumi Tochio, Yoshiki Hirooka, Kuniaki Saito, Toshitaka Nabeshima, Akihiro Mouri.

Negative experiences during adolescence, such as social isolation (SI), bullying, and abuse, increase the risk of psychiatric diseases in adulthood. However, the pathogenesis of psychiatric diseases induced by these factors remain poorly understood. In adolescents, stress affects the intestinal homeostasis in the gut-brain axis. This study determined whether adolescent SI induces behavioral abnormalities by disrupting colonic function. Adolescent mice exposed to SI exhibit spatial cognitive deficits and microglial activation in the hippocampus (HIP). SI decreased the differentiation of mucin-producing goblet cells, which was accompanied by alterations in the composition of the gut microbiota, particularly the depletion of mucin-feeding bacteria. Treatment with rebamipide, which promotes goblet cell differentiation in the colon, attenuated SI-induced spatial cognitive deficits and microglial activation in the HIP and decreased cystine, a downstream metabolite of homocysteine. Treatment with cystine ameliorated SI-induced spatial cognitive deficits and increased microglial C-C motif chemokine ligand 7 (CCL7) levels in the HIP. Inhibition of CCL7 receptors by antagonists of CC motif chemokine receptors 2 (CCR2) and 3 (CCR3) in the HIP prevented spatial cognitive deficits induced by SI. Infusion of CCL7 into the HIP following microglial ablation with clodronate liposome induced spatial cognitive deficits. These findings suggest that adolescent SI decreases serum cystine levels by damaging the colonic goblet cells, resulting in spatial cognitive deficits by triggering microglial activation in the HIP. Our results indicate that increased CCL7 expression in hippocampal microglia may contribute to spatial cognitive deficits by activating CCR2 and CCR3.

DOI: https://doi.org/10.1038/s41380-024-02826-9
Neurobiol Dis. 2024 Nov 22. pii: S0969-9961(24)00345-0. [Epub ahead of print]203 106743

The effect of a dominant kinase-dead Csf1r mutation associated with adult-onset leukoencephalopathy on brain development and neuropathology.

Jennifer Stables, Reiss Pal, Barry M Bradford, Dylan Carter-Cusack, Isis Taylor, Clare Pridans, Nemat Khan, Trent M Woodruff, Katharine M Irvine, Kim M Summers, Neil A Mabbott, David A Hume.

  Amino acid substitutions in the kinase domain of the human CSF1R protein are associated with autosomal dominant adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP). To model the human disease, we created a disease-associated mutation (Glu631Lys; E631K) in the mouse Csf1r locus. Previous analysis demonstrated that heterozygous mutation (Csf1rE631K/+) had a dominant inhibitory effect on CSF1R signaling in vitro and in vivo but did not recapitulate human disease pathology. We speculated that leukoencephalopathy in humans requires an environmental trigger and/or epistatic interaction with common neurodegenerative disease-associated alleles. Here we examine the Csf1rE631K/+ mutation impact on microglial phenotype, postnatal brain development, age-related changes in gene expression and on prion disease and experimental autoimmune encephalitis (EAE), two pathologies in which microgliosis is a prominent feature. The Csf1rE631K/+ mutation reduced microglial abundance and the expression of microglial-associated transcripts relative to wild-type controls at 12 and 43 weeks of age. There was no selective effect on homeostatic markers e.g. P2ry12, or age-related changes in gene expression in striatum and hippocampus. An epistatic interaction was demonstrated between Csf1rE631K/+ and Cx3cr1EGFP/+ genotypes leading to dysregulated microglial and neuronal gene expression in hippocampus and striatum. Heterozygous Csf1rE631K mutation reduced the microgliosis associated with both diseases. There was no significant impact on disease severity or progression in prion disease. In EAE, inflammation-associated transcripts in the hippocampus and striatum were suppressed in parallel with microglia-specific transcripts. The results support a dominant inhibitory model of CSF1R-related leukoencephalopathy and likely contributions of an environmental trigger and/or genetic background to neuropathology.

Keywords:  CSF1R; Kinase-dead; Leukoencephalopathy; Macrophage

DOI:  https://doi.org/10.1016/j.nbd.2024.106743
Cell Death Dis. 2024 Nov 26. 15(11): 858

Microglial cannabinoid receptor type II stimulation improves cognitive impairment and neuroinflammation in Alzheimer's disease mice by controlling astrocyte activation.

Akira Sobue, Okiru Komine, Fumito Endo, Chihiro Kakimi, Yuka Miyoshi, Noe Kawade, Seiji Watanabe, Yuko Saito, Shigeo Murayama, Takaomi C Saido, Takashi Saito, Koji Yamanaka.

Alzheimer's disease (AD) is the most common form of dementia and is characterized by the accumulation of amyloid β (Aβ) and phosphorylated tau. Neuroinflammation, mainly mediated by glial activation, plays an important role in AD progression. Although there is growing evidence for the anti-neuroinflammatory and neuroprotective effects of the cannabinoid system modulation, the detailed mechanism remains unclear. To address these issues, we analyzed the expression levels of cannabinoid receptor type II (Cnr2/Cb2) in AppNL-G-F/NL-G-F mice and human AD precuneus, which is vulnerable to amyloid deposition in AD, and the effects of JWH 133, a selective CB2 agonist, on neuroinflammation in primary glial cells and neuroinflammation and cognitive impairment in AppNL-G-F/NL-G-F mice. The levels of Cnr2/Cb2 were upregulated in microglia isolated from the cerebral cortex of AppNL-G-F/NL-G-F mice. CNR2 expression was also increased in RNAs derived from human precuneus with advanced AD pathology. Chronic oral administration of JWH 133 significantly ameliorated the cognitive impairment of AppNL-G-F/NL-G-F mice without neuropsychiatric side effects. Microglia and astrocyte mRNAs were directly isolated from the mouse cerebral cortex by magnetic-activated cell sorting, and the gene expression was determined by quantitative PCR. JWH 133 administration significantly decreased reactive astrocyte markers and microglial C1q, an inducer for the reactive astrocytes in AppNL-G-F/NL-G-F mice. In addition, JWH133 administration inhibited the expression of p-STAT3 (signal transducer and activator of transcription 3) in astrocytes in AppNL-G-F/NL-G-F mice. Furthermore, JWH 133 administration suppressed dystrophic presynaptic terminals surrounding amyloid plaques. In conclusion, stimulation of microglial CB2 ameliorates cognitive dysfunction in AppNL-G-F/NL-G-F mice by controlling astrocyte activation and inducing beneficial neuroinflammation, and our study has implications that CB2 may represent an attractive therapeutic target for the treatment of AD and perhaps other neurodegenerative diseases involving neuroinflammation.

DOI: https://doi.org/10.1038/s41419-024-07249-6
J Neuroinflammation. 2024 Nov 28. 21(1): 306

Engrailed-2 and inflammation convergently and independently impinge on cerebellar Purkinje cell differentiation.

Mohammed Bahaaeldin, Carolin Bülte, Fabienne Luelsberg, Sujeet Kumar, Joachim Kappler, Christof Völker, Karl Schilling, Stephan L Baader.

  Autism spectrum disorders (ASD) have a complex pathogenesis thought to include both genetic and extrinsic factors. Among the latter, inflammation of the developing brain has recently gained growing attention. However, how genetic predisposition and inflammation might converge to precipitate autistic behavior remains elusive. Cerebellar structure and function are well known to be affected in autism. We therefore used cerebellar slice cultures to probe whether inflammatory stimulation and (over)expression of the autism susceptibility gene Engrailed-2 interact in shaping differentiation of Purkinje cells, key organizers of cerebellar histogenesis and function. We show that lipopolysaccharide treatment reduces Purkinje cell dendritogenesis and that this effect is enhanced by over-expression of Engrailed-2 in these cells. The effects of lipopolysaccharide can be blocked by inhibiting microglia proliferation and also by blocking tumor necrosis factor alpha receptor signaling, suggesting microglia and tumor necrosis factor alpha are major players in this scenario. These findings identify Purkinje cells as a potential integrator of genetic and environmental signals that lead to an autism-associated morphology.

Keywords:  Autism; Cerebellum; Engrailed; Inflammation; LPS; Microglia; Purkinje cell differentiation; Slice culture; Tumor necrosis factor alpha

DOI:  https://doi.org/10.1186/s12974-024-03301-6
PLoS One. 2024 ;19(11): e0311374

Exploring the feasibility of using mice as a substitute model for investigating microglia in aging and Alzheimer's disease though single cell analysis.

Rong He, Qiang Zhang, Limei Wang, Yiwen Hu, Yue Qiu, Jia Liu, Dingyun You, Jishuai Cheng, Xue Cao.

OBJECTIVE: To guide animal experiments, we investigated the similarities and differences between humans and mice in aging and Alzheimer's disease (AD) at the single-nucleus RNA sequencing (snRNA-seq) or single-cell RNA sequencing (scRNA-seq) level.
METHODS: Microglia cells were extracted from dataset GSE198323 of human post-mortem hippocampus. The distributions and proportions of microglia subpopulation cell numbers related to AD or age were compared. This comparison was done between GSE198323 for humans and GSE127892 for mice, respectively. The Seurat R package and harmony R package were used for data analysis and batch effect correction. Differentially expressed genes (DEGs) were identified by FindMarkers function with MAST test. Comparative analyses were conducted on shared genes in DEGs associated with age and AD. The analyses were done between human and mouse using various bioinformatics techniques. The analysis of genes in DEGs related to age was conducted. Similarly, the analysis of genes in DEGs related to AD was performed. Cross-species analyses were conducted using orthologous genes. Comparative analyses of pseudotime between humans and mice were performed using Monocle2.
RESULTS: (1) Similarities: The proportion of microglial subpopulation Cell_APOE/Apoe shows consistent trends, whether in AD or normal control (NC) groups in both humans and mice. The proportion of Cell_CX3CR1/Cx3cr1, representing homeostatic microglia, remains stable with age in NC groups across species. Tuberculosis and Fc gamma R-mediated phagocytosis pathways are shared in microglia responses to age and AD across species, respectively. (2) Differences: IL1RAPL1 and SPP1 as marker genes are more identifiable in human microglia compared to their mouse counterparts. Most genes of DEGs associated with age or AD exhibit different trends between humans and mice. Pseudotime analyses demonstrate varying cell density trends in microglial subpopulations, depending on age or AD across species.
CONCLUSIONS: Mouse Apoe and Cell_Apoe maybe serve as proxies for studying human AD, while Cx3cr1 and Cell_Cx3cr1 are suitable for human aging studies. However, AD mouse models (App_NL_G_F) have limitations in studying human genes like IL1RAPL1 and SPP1 related to AD. Thus, mouse models cannot fully replace human samples for AD and aging research.

DOI: https://doi.org/10.1371/journal.pone.0311374
Res Sq. 2024 Nov 19. pii: rs.3.rs-5308977. [Epub ahead of print]

Unique N-glycosylation signatures in Aβ oligomer- and lipopolysaccharide-activated human iPSC-derived microglia.

Xinyu Tang, Ryan Schindler, Jacopo Lucente, Armin Oloumi, Jennyfer Tena, Danielle Harvey, Carlito Lebrilla, Angela Zivkovic, Lee-Way Jin, Izumi Maezawa.

Microglia are the immune cells in the central nervous system (CNS) and become pro-inflammatory/activated in Alzheimer's disease (AD). Cell surface glycosylation plays an important role in immune cells; however, the N-glycosylation and glycosphingolipid (GSL) signatures of activated microglia are poorly understood. Here, we study comprehensive combined transcriptomic and glycomic profiles using human induced pluripotent stem cells-derived microglia (hiMG). Distinct changes in N-glycosylation patterns in amyloid-β oligomer (AβO) and LPS-treated hiMG were observed. In AβO-treated cells, the relative abundance of bisecting N-acetylglucosamine (GlcNAc) N-glycans decreased, corresponding with a downregulation of MGAT3. The sialylation of N-glycans increased in response to AβO, accompanied by an upregulation of genes involved in N-glycan sialylation (ST3GAL4 and 6). Unlike AβO-induced hiMG, LPS-induced hiMG exhibited a decreased abundance of complex-type N-glycans, aligned with downregulation of mannosidase genes (MAN1A1, MAN2A2, and MAN1C1) and upregulation of ER degradation related-mannosidases (EDEM1-3). Fucosylation increased in LPS-induced hiMG, aligned with upregulated fucosyltransferase 4 (FUT4) and downregulated alpha-L-fucosidase 1 (FUCA1) gene expression, while sialofucosylation decreased, aligned with upregulated neuraminidase 4 (NEU4). Inhibition of sialyation and fucosylation in AβO- and LPS-induced hiMG alleviated pro-inflammatory responses. However, the GSL profile did not exhibit significant changes in response to AβO or LPS activation. AβO- and LPS- specific glycosylation changes could contribute to impaired microglia function, highlighting glycosylation pathways as potential therapeutic targets for AD.

DOI: https://doi.org/10.21203/rs.3.rs-5308977/v1