bims-microg 2024-12-08 papers

bims-microg

Biomed News

on Microglia in health and disease

Issue of 2024–12–08
thirty papers selected by
Marcus Karlstetter, Universität zu Köln

Myeloid cell-specific loss of NPC1 in mice recapitulates microgliosis and neurodegeneration in patients with Niemann-Pick type C disease.
Homeostatic microglia initially seed and activated microglia later reshape amyloid plaques in Alzheimer's Disease.
Ketogenic diet modulates immune cell transcriptional landscape and ameliorates experimental autoimmune uveitis in mice.
Efficacy and safety of minocycline in retinitis pigmentosa: a prospective, open-label, single-arm trial.
Selenoprotein P is a target for regulating extracellular vesicle biogenesis and secretion from activated microglia in vivo.
Metformin attenuates central sensitization by regulating neuroinflammation through the TREM2-SYK signaling pathway in a mouse model of chronic migraine.
The FGFR inhibitor Rogaratinib reduces microglia reactivity and synaptic loss in TBI.
CD22 blockade exacerbates neuroinflammation in Neuromyelitis optica spectrum disorder.
Forced MyD88 signaling in microglia impacts the production and survival of regenerated retinal neurons.
Ageing-related changes in the regulation of microglia and their interaction with neurons.
Spinal AT1R contributes to neuroinflammation and neuropathic pain via NOX2-dependent redox signaling in microglia.
An acute microglial metabolic response controls metabolism and improves memory.
Th22 cells promote the transition from homeostatic to reactive microglia in diabetic encephalopathy.
Tumor-Associated Microglia Secrete Extracellular ATP to Support Glioblastoma Progression.
USP22 Inhibits Microglial M1 Polarization by Regulating the PU.1/NLRP3 Inflammasome Pathway.
Neuropathological and cerebrospinal fluid correlates of choroid plexus inflammation in progressive multiple sclerosis.
Siglecs-mediated immune regulation in neurological disorders.
Exerkines mitigating Alzheimer's disease progression by regulating inflammation: Focusing on macrophage/microglial NLRP3 inflammasome pathway.
Protocol for immunofluorescence staining and large-scale analysis to quantify microglial cell morphology at single-cell resolution in mice.
Peptide discovery across the spectrum of neuroinflammation; microglia and astrocyte phenotypical targeting, mediation, and mechanistic understanding.
Association of ten VEGF family genes with Alzheimer's disease endophenotypes at single cell resolution.
Long-term exposure of sucralose induces neuroinflammation and ferroptosis in human microglia cells via SIRT1/NLRP3/IL-1β/GPx4 signaling pathways.
Time-dependent phenotypical changes of microglia drive alterations in hippocampal synaptic transmission in acute slices.
Hypothyroidism promotes microglia M1 polarization by inhibiting BDNF-promoted PI3K-Akt signaling pathway.
Blocking of Tim-3 Ameliorates Spinal Cord Ischemia-Reperfusion Injury Through Inhibiting Neuroinflammation and Promoting M1-to-M2 Phenotypic Polarization of Microglia.
Single-microglia transcriptomic transition network-based prediction and real-world patient data validation identifies ketorolac as a repurposable drug for Alzheimer's disease.
Circular RNA circ_0061183 regulates microglial polarization induced by airborne ultrafine particles in HMC3 cells via sponging miR-98-5p.
ICU patient-on-a-chip emulating orchestration of mast cells and cerebral organoids in neuroinflammation.
Regulation of STING G-quadruplex for rescuing cellular senescence and Aβ phagocytic capacity of microglia.
Chemoproteomic profiling by bioorthogonal probes to reveal the novel targets of acrylamide in microglia.

Sci Transl Med. 2024 Dec 04. 16(776): eadl4616

Myeloid cell-specific loss of NPC1 in mice recapitulates microgliosis and neurodegeneration in patients with Niemann-Pick type C disease.

Lina Dinkel, Selina Hummel, Valerio Zenatti, Mariagiovanna Malara, Yannik Tillmann, Alessio Colombo, Laura Sebastian Monasor, Jung H Suh, Todd Logan, Stefan Roth, Lars Paeger, Patricia Hoffelner, Oliver Bludau, Andree Schmidt, Stephan A Müller, Martina Schifferer, Brigitte Nuscher, Jasenka Rudan Njavro, Matthias Prestel, Laura M Bartos, Karin Wind-Mark, Luna Slemann, Leonie Hoermann, Sebastian T Kunte, Johannes Gnörich, Simon Lindner, Mikael Simons, Jochen Herms, Dominik Paquet, Stefan F Lichtenthaler, Peter Bartenstein, Nicolai Franzmeier, Arthur Liesz, Antje Grosche, Tatiana Bremova-Ertl, Claudia Catarino, Skadi Beblo, Caroline Bergner, Susanne A Schneider, Michael Strupp, Gilbert Di Paolo, Matthias Brendel, Sabina Tahirovic.

Niemann-Pick type C (NPC) disease is an inherited lysosomal storage disorder mainly driven by mutations in the NPC1 gene, causing lipid accumulation within late endosomes/lysosomes and resulting in progressive neurodegeneration. Although microglial activation precedes neuronal loss, it remains elusive whether loss of the membrane protein NPC1 in microglia actively contributes to NPC pathology. In a mouse model with depletion of NPC1 in myeloid cells, we report severe alterations in microglial lipidomic profiles, including the enrichment of bis(monoacylglycero)phosphate, increased cholesterol, and a decrease in cholesteryl esters. Lipid dyshomeostasis was associated with microglial hyperactivity, marked by an increase in translocator protein 18 kDa (TSPO). These hyperactive microglia initiated a pathological cascade resembling NPC-like phenotypes, including a shortened life span, motor impairments, astrogliosis, neuroaxonal pathology, and increased neurofilament light chain (NF-L), a neuronal injury biomarker. As observed in the mouse model, patients with NPC showed increased NF-L in the blood and microglial hyperactivity, as visualized by TSPO-PET imaging. Reduced TSPO expression in blood-derived macrophages of patients with NPC was measured after N-acetyl-l-leucine treatment, which has been recently shown to have beneficial effects in patients with NPC, suggesting that TSPO is a potential marker to monitor therapeutic interventions for NPC. Conclusively, these results demonstrate that myeloid dysfunction, driven by the loss of NPC1, contributes to NPC disease and should be further investigated for therapeutic targeting and disease monitoring.

DOI: https://doi.org/10.1126/scitranslmed.adl4616
Nat Commun. 2024 Dec 05. 15(1): 10634

Homeostatic microglia initially seed and activated microglia later reshape amyloid plaques in Alzheimer's Disease.

Nóra Baligács, Giulia Albertini, Sarah C Borrie, Lutgarde Serneels, Clare Pridans, Sriram Balusu, Bart De Strooper.

The role of microglia in the amyloid cascade of Alzheimer's disease (AD) is debated due to conflicting findings. Using a genetic and a pharmacological approach we demonstrate that depletion of microglia before amyloid-β (Aβ) plaque deposition, leads to a reduction in plaque numbers and neuritic dystrophy, confirming their role in plaque initiation. Transplanting human microglia restores Aβ plaque formation. While microglia depletion reduces insoluble Aβ levels, soluble Aβ concentrations stay consistent, challenging the view that microglia clear Aβ. In later stages, microglial depletion decreases plaque compaction and increases neuritic dystrophy, suggesting a protective role. Human microglia with the TREM2R47H/R47H mutation exacerbate plaque pathology, emphasizing the importance of non-reactive microglia in the initiation of the amyloid cascade. Adaptive immune depletion (Rag2-/-) does not affect microglia's impact on plaque formation. These findings clarify conflicting reports, identifying microglia as key drivers of amyloid pathology, and raise questions about optimal therapeutic strategies for AD.

DOI: https://doi.org/10.1038/s41467-024-54779-w
J Neuroinflammation. 2024 Dec 03. 21(1): 319

Ketogenic diet modulates immune cell transcriptional landscape and ameliorates experimental autoimmune uveitis in mice.

Runping Duan, Tianfu Wang, Zhaohuai Li, Loujing Jiang, Xiaoyang Yu, Daquan He, Tianyu Tao, Xiuxing Liu, Zhaohao Huang, Lei Feng, Wenru Su.

   BACKGROUND: Uveitis manifests as immune-mediated inflammatory disorders within the eye, posing a serious threat to vision. The ketogenic diet (KD) has emerged as a promising dietary intervention, yet its impact on the immune microenvironments and role in uveitis remains unclear.
METHODS: Utilizing single-cell RNA sequencing (scRNA-seq) data from lymph node and retina of mice, we conduct a comprehensive investigation into the effects of KD on immune microenvironments. Flow cytometry is conducted to verify the potential mechanisms.
RESULTS: This study demonstrates that KD alters the composition and function of immune profiles. Specifically, KD promotes the differentiation of Treg cells and elevates its proportion in heathy mice. In response to experimental autoimmune uveitis challenges, KD alleviates the inflammatory symptoms, lowers CD4+ T cell pathogenicity, and corrects the Th17/Treg imbalance. Additionally, KD decreases the proportion of Th17 cell and increases Treg cells in the retina. Analysis of combined retinal and CDLN immune cells reveals that retinal immune cells, particularly CD4+ T cells, exhibit heightened inflammatory responses, which KD partially reverses.
CONCLUSIONS: The KD induces inhibitory structural and functional alterations in immune cells from lymph nodes to retina, suggesting its potential as a therapy for uveitis.

Keywords:  Experimental autoimmune uveitis (EAU); Immune microenvironment; Ketogenic diet (KD); Uveitis

DOI:  https://doi.org/10.1186/s12974-024-03308-z
Signal Transduct Target Ther. 2024 Dec 04. 9(1): 339

Efficacy and safety of minocycline in retinitis pigmentosa: a prospective, open-label, single-arm trial.

Yuxi Chen, Yuan Pan, Yanyan Xie, Yuxun Shi, Yao Lu, Yiwen Xia, Wenru Su, Xiaoqing Chen, Zuoyi Li, Minzhen Wang, Siyu Miao, Yating Yang, Chenjin Jin, Guangwei Luo, Shixian Long, Hui Xiao, Chuangxin Huang, Jian Zhang, Dan Liang.

Retinitis pigmentosa (RP) is characterized by progressive photoreceptor cells death accelerated by the proliferation and activation of microglia pathologically. No consensus exists on the treatment. Minocycline is recognized as a microglia inhibitor with great anti-inflammatory and neuro-protective functions. However, efficacy of minocycline in RP patients is lacking. We conducted a prospective, open-label, and single-arm trial, in which daily oral minocycline of 100 mg was administered for 12 months in RP patients with light-adapted 30 Hz flicker electroretinography (ERG) amplitude >0 µV in at least one eye (NCT04068207). The primary outcome was the proportion of participants with improvement in the ERG amplitude at month 12. The secondary outcomes included improvements of the following items: other ERGs amplitudes, visual field, best-corrected visual acuity, contrast sensitivity, color vision, and NEI-VFQ-25. 35 of 288 patients met inclusive criteria were enrolled (median [IQR] age, 36 [31-45] years; 17 female [48.6%]). 32 participants completed all examinations, while 3 participants completed the 12-month online visit via conducting NEI-VFQ-25. The primary outcome showed improvement was 34.3% (12 of 35 [95% CI 19.1-52.2]). Similarly, all secondary outcomes showed improvements. Adverse events were reported in 22 participants (62.9%) and were all resolved without extra medication during the study period. No severe adverse events were recorded. Our findings identified daily oral minocycline of 100 mg for 12 months was beneficial in improving the visual function of RP patients with good safety. This study indicates minocycline may be a promising therapy for RP, but a randomized controlled trial is still needed of further exploration.

DOI: https://doi.org/10.1038/s41392-024-02037-2
Cell Rep. 2024 Nov 30. pii: S2211-1247(24)01376-7. [Epub ahead of print]43(12): 115025

Selenoprotein P is a target for regulating extracellular vesicle biogenesis and secretion from activated microglia in vivo.

Victor Bodart-Santos, Zhi Ruan, Bridgette C Melvin, Ikshu Pandey, Seiko Ikezu, Tsuneya Ikezu.

  Microglia, brain innate immune cells, participate in the spread of inflammatory signals and aggregated proteins through secretion of extracellular vesicles (EVs). Selenoprotein P (Sepp1) is a potential regulator of microglial EV secretion. Here, we investigate the effect of Sepp1 silencing on microglial transcriptomics to elucidate the Sepp1 regulatory mechanism of EV secretion and validate this effect in APPNL-G-F knockin mice. Silencing of Sepp1 significantly reduces EV secretion and CD63 loading to EVs from BV-2 microglia, as determined by single-vesicle flow cytometry and super-resolution microscopy. Sepp1 deficiency downregulates EV biogenesis machinery, accompanied by increased lysosomal activity and lipid metabolism. Silencing of Sepp1 in astrocytes but not neurons suppresses EV secretion in vitro. Finally, Sepp1 silencing reduces EV secretion from activated neurodegenerative microglia associated with amyloid plaques in APPNL-G-F mouse brains in vivo. Sepp1 is thus an emerging therapeutic target for ameliorating microglia-mediated disease spread through EV secretion in neurodegenerative disorders.

Keywords:  Alzheimer’s disease; CD63; CD9; CP: Cell biology; CP: Neuroscience; animal model; exosome; extracellular vesicles; lysosome; microglia; selenoprotein P; transcriptome

DOI:  https://doi.org/10.1016/j.celrep.2024.115025
J Neuroinflammation. 2024 Dec 03. 21(1): 318

Metformin attenuates central sensitization by regulating neuroinflammation through the TREM2-SYK signaling pathway in a mouse model of chronic migraine.

Zhenzhen Fan, Dandan Su, Zi Chao Li, Songtang Sun, Zhaoming Ge.

   BACKGROUND: Chronic migraine (CM) is a serious neurological disorder. Central sensitization is one of the important pathophysiological mechanisms underlying CM, and microglia-induced neuroinflammation conduces to central sensitization. Triggering receptor expressed on myeloid cells 2 (TREM2) is presented solely in microglia residing within the central nervous system and plays a key role in neuroinflammation. Metformin has been shown to regulate inflammatory responses and exert analgesic effects, but its relationship with CM remains unclear. In the study, we investigated whether metformin modulates TREM2 to improve central sensitization of CM and clarified the potential molecular mechanisms.
METHODS: A CM mouse model was induced by administration of nitroglycerin (NTG). Behavioral evaluations were conducted using von Frey filaments and hot plate experiments. Western blot and immunofluorescence techniques were employed to investigate the molecular mechanisms. Metformin and the SYK inhibitor R406 were administered to mice to assess their regulatory effects on neuroinflammation and central sensitization. To explore the role of TREM2-SYK in regulating neuroinflammation with metformin, a lentivirus encoding TREM2 was injected into the trigeminal nucleus caudalis (TNC). In vitro experiments were conducted to evaluate the regulation of TREM2-SYK by metformin, involving interventions with LPS, metformin, R406, siTREM2, and TREM2 plasmids.
RESULTS: Metformin and R406 pretreatment can effectively improve hyperalgesia in CM mice. Both metformin and R406 significantly inhibit c-fos and CGRP expression in CM mice, effectively suppressing the activation of microglia and NLRP3 inflammasome induced by NTG. With the administration of NTG, TREM2 expression gradually increased in TNC microglia. Additionally, we observed that metformin significantly inhibits TREM2 and SYK expression in CM mice. Lv-TREM2 attenuated metformin-mediated anti-inflammatory responses. In vitro experiments, knockdown of TREM2 inhibited LPS-induced SYK pathway activation and alleviated inflammatory responses. After the sole overexpression of TREM2, the SYK signaling pathway is activated, resulting in the activation of the NLRP3 inflammasome and an increased expression of pro-inflammatory cytokines; nevertheless, this consequence can be reversed by R406. The overexpression of TREM2 attenuates the inhibition of SYK activity mediated by metformin, and this effect can be reversed by R406.
CONCLUSIONS: Our findings suggest that metformin attenuates central sensitization in CM by regulating the activation of microglia and NLRP3 inflammasome through the TREM2-SYK pathway.

Keywords:  Central sensitization; Chronic migraine; Metformin; Microglia; SYK; TREM2

DOI:  https://doi.org/10.1186/s12974-024-03313-2
Front Immunol. 2024 ;15 1443940

The FGFR inhibitor Rogaratinib reduces microglia reactivity and synaptic loss in TBI.

Rida Rehman, Albrecht Froehlich, Florian Olde Heuvel, Lobna Elsayed, Tobias Boeckers, Markus Huber-Lang, Cristina Morganti-Kossmann, Francesco Roselli.

   Background: Traumatic brain injury (TBI) induces an acute reactive state of microglia, which contribute to secondary injury processes through phagocytic activity and release of cytokines. Several receptor tyrosine kinases (RTK) are activated in microglia upon TBI, and their blockade may reduce the acute inflammation and decrease the secondary loss of neurons; thus, RTKs are potential therapeutic targets. We have previously demonstrated that several members of the Fibroblast Growth Factor Receptor (FGFR) family are transiently phosporylated upon TBI; the availability for drug repurposing of FGFR inhibitors makes worthwhile the elucidation of the role of FGFR in the acute phases of the response to TBI and the effect of FGFR inhibition.
Methods: A closed, blunt, weight-drop mild TBI protocol was employed. The pan-FGFR inhibitor Rogaratinib was administered to mice 30min after the TBI and daily up to 7 days post injury. Phosphor-RTK Arrays and proteomic antibody arrays were used to determine target engagement and large-scale impact of the FGFR inhibitor. pFGFR1 and pFGFR3 immunostaining were employed for validation. As outcome parameters of the TBI injury immunostainings for NeuN, VGLUT1, VGAT at 7dpi were considered.
Results: Inhibition of FGFR during TBI restricted phosphorylation of FGFR1, FGFR3, FGFR4 and ErbB4. Phosphorylation of FGFR1 and FGFR3 during TBI was traced back to Iba1+ microglia. Rogaratinib substantially dowregulated the proteomic signature of the neuroimmunological response to trauma, including the expression of CD40L, CXCR3, CCL4, CCR4, ILR6, MMP3 and OPG. Prolonged Rogaratinib treatment reduced neuronal loss upon TBI and prevented the loss of excitatory (vGLUT+) synapses.
Conclusion: The FGFR family is involved in the early induction of reactive microglia in TBI. FGFR inhibition selectively prevented FGFR phosphorylation in the microglia, dampened the overall neuroimmunological response and enhanced the preservation of neuronal and synaptic integrity. Thus, FGFR inhibitors may be relevant targets for drug repurposing aimed at modulating microglial reactivity in TBI.

Keywords:  proteomics; reactive microglia; receptor tyrosine kinase; synapses; traumatic brain injury

DOI:  https://doi.org/10.3389/fimmu.2024.1443940
J Neuroinflammation. 2024 Nov 30. 21(1): 313

CD22 blockade exacerbates neuroinflammation in Neuromyelitis optica spectrum disorder.

Wenjun Zhang, Yali Han, Huachen Huang, Yue Su, Honglei Ren, Caiyun Qi, Jinyi Li, Huaijin Yang, Jing Xu, Guoqiang Chang, Wenjin Qiu, Qiang Liu, Ting Chang.

   BACKGROUND: Neuromyelitis optica spectrum disorder (NMOSD) is an autoantibody-triggered central nervous system (CNS) demyelinating disease that primarily affects the spinal cord, optic nerves and brainstem. Among the first responders to CNS injury, microglia are prominent players that drive NMOSD lesion formation. However, the key molecular switches controlling the detrimental activity of microglia in NMOSD are poorly understood. CD22 governs the activity of innate and adaptive immunity. In this study, we investigated to what extent and by what mechanisms CD22 may modulate microglial activity, neuroinflammation and CNS lesion formation.
METHODS: To determine the expression profile of CD22 in NMOSD, we performed single-cell sequencing and flow cytometry analysis of immune cells from human peripheral blood. We investigated the potential effects and mechanisms of CD22 blockade on microglial activity, leukocyte infiltration and CNS demyelination in a mouse model of NMOSD induced by injection of NMOSD patient serum-derived AQP4-IgG and human complement.
RESULTS: Single-cell sequencing and flow cytometry analysis revealed that CD22 was expressed in B cells, neutrophils, monocytes and microglia-derived exosomes in human peripheral blood from NMOSD patients and controls (n = 5 per group). In a mouse model of NMOSD, CD22 was expressed in B cells, neutrophils, monocytes and microglia (n = 8 per group). In NMOSD mice, CD22 blockade significantly increased the number of CNS lesions, astrocyte loss and demyelination, accompanied by increased inflammatory activity and phagocytosis in microglia. Furthermore, the detrimental effects of CD22 blockade were significantly alleviated in NMOSD mice subjected to depletion of microglia or Gr-1+ myeloid cells, suggesting the involvement of microglia and peripheral Gr-1+ myeloid cells. Additionally, CD22 blockade also led to significantly reduced phosphorylation of SYK and GSK3β in NMOSD. Notably, the detrimental effects of CD22 blockade were greatly diminished in NMOSD mice receiving the phosphorylated SYK inhibitor R406.
CONCLUSIONS: Our findings revealed a previously unrecognized role of CD22 as a key molecular switch that governs the detrimental effects of microglia and Gr-1+ myeloid cells in NMOSD, which paves the way for the future design of immune therapies for NMOSD.

Keywords:  CD22; Demyelination; Microglia; Neuroinflammation; Neuromyelitis optica spectrum disorder

DOI:  https://doi.org/10.1186/s12974-024-03305-2
Front Cell Dev Biol. 2024 ;12 1495586

Forced MyD88 signaling in microglia impacts the production and survival of regenerated retinal neurons.

Jordan E Rumford, Ailis Grieshaber, Samantha Lewiston, Jordan L Reed, Samuel S Long, Diana M Mitchell.

  Inflammation and microglia appear to be key factors influencing the outcome of retinal regeneration following acute retinal damage. Despite such findings, direct connection of microglia-specific inflammatory factors as drivers of regenerative responses in the retina are still not defined, and intracellular pathways activated to stimulate such signals from microglia are currently unknown. We became interested in MyD88 regulation in microglia because transcriptomic datasets suggest myd88 could be regulated temporally in zebrafish microglia responding to damage in the central nervous system. MyD88 is an intracellular molecular adaptor that initiates signaling cascades downstream of several innate immune receptors, and probably most well-known for inducing gene expression of pro-inflammatory factors. Using zebrafish, which spontaneously regenerate retinal neurons after acute retinal damage, we studied the effects of overactivation of MyD88 signaling in microglia and macrophages on the Müller glia-mediated regenerative response. Our results indicate that increased MyD88 signaling in microglia/macrophages impacts the initial response of Müller glia entering a regenerative response after acute, neurotoxin-induced retinal damage to inner retinal neurons. In addition, increased MyD88 signaling in microglia/macrophages resulted in reduced survival of inner retinal neurons in regenerated retinas. This work supports the idea that temporal control of inflammatory signaling is a key component in the production of MG-derived progenitors yet further indicates that such control is important for differentiation and survival of regenerated neurons.

Keywords:  MyD88; Müller glia; NFkB; inflammation; microglia; regeneration; retina; zebrafish

DOI:  https://doi.org/10.3389/fcell.2024.1495586
Neuropharmacology. 2024 Nov 29. pii: S0028-3908(24)00410-6. [Epub ahead of print] 110241

Ageing-related changes in the regulation of microglia and their interaction with neurons.

Rommy von Bernhardi, Jaime Eugenín.

  Ageing is one of the most important risk factors for chronic health conditions, including neurodegenerative diseases. Inflammation is a feature of ageing, as well as a key pathophysiological mechanism for degenerative diseases. Microglia play multiple roles in the central nervous system; their states entail a complex assemblage of responses reflecting the multiplicity of functions they fulfil both under homeostatic basal conditions and in response to stimuli. Whereas glial cells can promote neuronal homeostasis and limit neurodegeneration, age-related inflammation (i.e. inflammaging) leads to the functional impairment of microglia and astrocytes, exacerbating their response to stimuli. Thus, microglia are key mediators for age-dependent changes of the nervous system, participating in the generation of a less supportive or even hostile environment for neurons. Whereas multiple changes of ageing microglia have been described, here we will focus on the neuron-microglia regulatory crosstalk through fractalkine (CX3CL1) and CD200, and the regulatory cytokine Transforming Growth Factor β1 (TGFβ1), which is involved in immunomodulation and neuroprotection. Ageing results in a dysregulated activation of microglia, affecting neuronal survival, and function. The apparent unresponsiveness of aged microglia to regulatory signals could reflect a restriction in the mechanisms underlying their homeostatic and reactive states. The spectrum of functions, required to respond to life-long needs for brain maintenance and in response to disease, would progressively narrow, preventing microglia from maintaining their protective functions.

Keywords:  Ageing; CD200/CD200R; CX3CL1/CX3CR1; Fractalkine; Glial cells; Homeostatic and reactive microglia states; Neurodegenerative diseases; Neuron-microglia regulation; Transforming Growth Factor β (TGFβ)

DOI:  https://doi.org/10.1016/j.neuropharm.2024.110241
Free Radic Biol Med. 2024 Dec 03. pii: S0891-5849(24)01102-X. [Epub ahead of print]

Spinal AT1R contributes to neuroinflammation and neuropathic pain via NOX2-dependent redox signaling in microglia.

Wencui Zhang, Bo Jiao, Shangchen Yu, Kaiwen Zhang, Jiaoli Sun, Baowen Liu, Xianwei Zhang.

  Microglia-mediated neuroinflammation demonstrates a crucial act in the progression of neuropathic pain. Oxidative damage induced by reactive oxygen species (ROS) derived from NADPH oxidase (NOX) in microglia drives proinflammatory microglia activation. Recent evidence points to the central renin angiotensin system (RAS) is involved in oxidative stress and neuroinflammation, with the angiotensin converting enzyme/angiotensin II/angiotensin receptor-1 (ACE/Ang II/AT1R) axis promoting inflammation through increased ROS production, counteracted by the ACE2/Ang (1-7)/ Mas receptor (MasR) axis. While interventions targeting spinal AT1R have been shown to alleviate nociceptive hypersensitivity; yet the mechanisms remain elusive. Here, we discovered that spared nerve injury (SNI)-induced mechanical allodynia in rats were associated with M1-like microglia activation, oxidative stress and overactivity of ACE/Ang II/AT1R axis in the spinal cord. Increased AT1R and NOX2 expression were observed in activated dorsal horn microglia following SNI. Blockade of AT1R with losartan potassium (LOP) suppressed NOX2-mediated oxidative stress, and promoted a shift in microglia from the proinflammatory M1 phenotype to the anti-inflammatory M2 phenotype in LPS-treated BV-2 cells. Additionally, NOX2 overexpression triggered the activation of the high-mobility group box 1/ nuclear factor-kappa B (HMGB1/NF-κB) signaling pathway. Intrathecal administration of LOP effectively inhibited SNI-induced NOX2 overactivation in microglia and suppressed the HMGB1/NF-kB pathway, reducing oxidative stress and shifting the microglia polarization from M1 to M2 in the spinal cord, thereby attenuating neuroinflammation and pain hypersensitivity. Collectively, these findings underscore the neuroimmune-modulating effects of spinal AT1R in neuropathic pain, highlighting the regulation of redox homeostasis in microglia via a NOX2 dependent mechanism.

Keywords:  Microglia; NADPH oxidase; Neuroinflammation; Reactive oxygen species; Renin-angiotensinogen system

DOI:  https://doi.org/10.1016/j.freeradbiomed.2024.12.004
Elife. 2024 Dec 03. pii: RP87120. [Epub ahead of print]12

An acute microglial metabolic response controls metabolism and improves memory.

Anne Drougard, Eric H Ma, Vanessa Wegert, Ryan Sheldon, Ilaria Panzeri, Naman Vatsa, Stefanos Apostle, Luca Fagnocchi, Judith Schaf, Klaus Gossens, Josephine Völker, Shengru Pang, Anna Bremser, Erez Dror, Francesca Giacona, Sagar Sagar, Michael X Henderson, Marco Prinz, Russell G Jones, John Andrew Pospisilik.

  Chronic high-fat feeding triggers metabolic dysfunction including obesity, insulin resistance, and diabetes. How high-fat intake first triggers these pathophysiological states remains unknown. Here, we identify an acute microglial metabolic response that rapidly translates intake of high-fat diet (HFD) to a surprisingly beneficial effect on metabolism and spatial/learning memory. High-fat intake rapidly increases palmitate levels in cerebrospinal fluid and triggers a wave of microglial metabolic activation characterized by mitochondrial membrane activation and fission as well as metabolic skewing toward aerobic glycolysis. These effects are detectable throughout the brain and can be detected within as little as 12 hr of HFD exposure. In vivo, microglial ablation and conditional DRP1 deletion show that the microglial metabolic response is necessary for the acute effects of HFD. 13C-tracing experiments reveal that in addition to processing via β-oxidation, microglia shunt a substantial fraction of palmitate toward anaplerosis and re-release of bioenergetic carbons into the extracellular milieu in the form of lactate, glutamate, succinate, and intriguingly, the neuroprotective metabolite itaconate. Together, these data identify microglia as a critical nutrient regulatory node in the brain, metabolizing away harmful fatty acids and liberating the same carbons as alternate bioenergetic and protective substrates for surrounding cells. The data identify a surprisingly beneficial effect of short-term HFD on learning and memory.

Keywords:  cell biology; diabetes; inflammation; memory; metabolism; microglia; mitochondria; mouse; neuroscience

DOI:  https://doi.org/10.7554/eLife.87120
Acta Diabetol. 2024 Dec 04.

Th22 cells promote the transition from homeostatic to reactive microglia in diabetic encephalopathy.

Sheng-Xue Yu, Hong Dan Yu, Yu-Fei Wang, Tie-Feng Yao, Song-Ze Lv, Yan-Chuan Wang, Jun-Qi Li, Wen-Qiang Liu, Jia-Yuan Ding, Xue-Zheng Liu, Zhong-Fu Zuo, Wan-Peng Liu.

   BACKGROUND: Diabetic encephalopathy (DE) is one of the most serious complications of diabetes mellitus (DM), and its pathogenesis has not yet been clarified. Th22 cells are a newly discovered class of CD4+ T cells that play important roles in inflammatory, autoimmune and infectious diseases. However, it is unclear whether Th22 cells are involved in the pathogenesis of DE.
METHODS: We established a T2DM mouse model in vivo and cocultured Th22 cells with microglia under high glucose (HG) conditions in vitro. Cognitive dysfunction was evaluated using the Morris water maze (MWM) test; blood‒brain barrier (BBB) integrity was evaluated using the Evans blue (EB) extravasation assay; Th22 cells and IL-22 receptors were detected by immunofluorescence; and IL-1β, TNF-α, iNOS, CD86, Arg-1, and CD206 protein expression was measured by Western Blot (WB) analysis.
RESULTS: Th22 cells passed through the BBB into the hippocampus and secreted interleukin-22 (IL-22), and the mice subsequently exhibited decreased learning and memory abilities. In the DE model, IL-22 promoted the transformation of homeostatic microglia into reactive microglia as well as the inflammatory response. Additionally, coculture of Th22 cells with BV2 microglia cultured under HG conditions increased the production of proinflammatory cytokines, and the microglia showed reactive changes. Mechanistically, IL-22Rα1 acted as a ligand, and IL-22 bound to IL-22Rα1 on microglia to drive primary microglia-induced inflammatory responses. Interestingly, interleukin-22 binding protein (IL-22BP) directly binds to IL-22Rα1 on microglia to inhibit the proinflammatory effects of IL-22.
CONCLUSION: Th22 cells secrete IL-22 after passing through the BBB into the hippocampus and promote the transformation of homeostatic microglia into reactive microglia, which induces an inflammatory response, exacerbates learning and memory impairment and cognitive deficits, and contributes to and accelerates the development of DE.

Keywords:  Diabetic encephalopathy; IL-22; Microglia; Th22

DOI:  https://doi.org/10.1007/s00592-024-02384-0
Cancer Res. 2024 Dec 02. 84(23): 4017-4030

Tumor-Associated Microglia Secrete Extracellular ATP to Support Glioblastoma Progression.

Caren Yu-Ju Wu, Yiyun Chen, Ya-Jui Lin, Kuo-Chen Wei, Kwang-Yu Chang, Li-Ying Feng, Ko-Ting Chen, Gordon Li, Alexander Liang Ren, Ryan Takeo Nitta, Janet Yuling Wu, Kwang Bog Cho, Ayush Pant, John Choi, Crystal L Mackall, Lily H Kim, An-Chih Wu, Jian-Ying Chuang, Chiung-Yin Huang, Christopher M Jackson, Pin-Yuan Chen, Michael Lim.

Glioblastoma (GBM) is a highly aggressive brain tumor with poor prognosis and high recurrence rates. The complex immune microenvironment of GBM is highly infiltrated by tumor-associated microglia and macrophages (TAM). TAMs are known to be heterogeneous in their functional and metabolic states and can transmit either protumoral or antitumoral signals to glioma cells. Here, we performed bulk RNA sequencing and single-cell RNA sequencing on samples from patients with GBM, which revealed increased ATP synthase expression and oxidative phosphorylation activity in TAMs located in the tumor core relative to the tumor periphery. Both in vitro and in vivo models displayed similar trends of augmented TAM mitochondrial activity, along with elevated mitochondrial fission, glucose uptake, mitochondrial membrane potential, and extracellular ATP (eATP) production by TAMs in the presence of GBM cells. Tumor-secreted factors, including GM-CSF, induced the increase in TAM eATP production. Elevated eATP in the GBM microenvironment promoted glioma growth and invasion by activating the P2X purinoceptor 7 (P2X7R) on glioma cells. Inhibition of the eATP-P2X7R axis attenuated tumor cell viability in vitro and reduced tumor size and prolonged survival in glioma-bearing mouse models. Overall, this study revealed elevated TAM-derived eATP in GBM and provided the basis for targeting the eATP-P2X7R signaling axis as a therapeutic strategy in GBM. Significance: Glioblastoma-mediated metabolic reprogramming in tumor-associated microglia increases ATP secretion that supports cancer cell proliferation and invasion by activating P2X7R, which can be inhibited to attenuate tumor growth.

DOI: https://doi.org/10.1158/0008-5472.CAN-24-0018
Brain Res Bull. 2024 Dec 02. pii: S0361-9230(24)00291-0. [Epub ahead of print] 111157

USP22 Inhibits Microglial M1 Polarization by Regulating the PU.1/NLRP3 Inflammasome Pathway.

Ming-Chen Yu, Xiao-Lin Li, Ming-Liang Ning, Zhen-Zhong Yan, Wan-Tao Yu.

   OBJECTIVE: This study aimed to investigate the effect of Ubiquitin-Specific Peptidase 22 (USP22) on the inflammatory response mediated by BV-2 mouse microglia and explore the role of the PU box binding protein 1 (PU.1)/NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome in the USP22-induced polarization of BV-2 cells.
METHODS: The BV-2 mouse microglia line was cultured in vitro, and plasmid and siRNA transfection was performed to overexpress or knockdown USP22. Subsequently, BV-2 cells were treated with lipopolysaccharide (LPS) and interferon-gamma (IFN-γ) and interleukin (IL)-4 to induce M1 and M2 polarization, respectively. Western blot was used to detect the expression levels of USP22, PU.1, M1 polarization markers [inducible nitric oxide synthase (iNOS), and cluster of differentiation (CD) 86], M2 polarization markers [arginase 1 (Arg1), and CD206], in BV-2 cells from different treatment groups. Additionally, measurement was performed on the inflammasome NLRP3, and its activation-related proteins [NIMA-related kinase7 (NEK7), cleaved-caspase 1, apoptosis-associated speck-like protein containing a CARD (ASC)]. Enzyme-linked immunosorbent (ELISA) assay was employed to determine the levels of inflammatory cytokines tumor necrosis factor-alpha (TNF-α), IL-1 β, and IL-10 in the cells. Furthermore, immunofluorescence was utilized to analyze the levels of iNOS and Arg1-positive BV-2 cells in different treatment groups. Moreover, the ubiquitination level of PU.1 was detected using immunoprecipitation.
RESULTS: The protein expression level of USP22 was significantly down-regulated in BV-2 cells treated with M1 polarization. Overexpression of USP22 remarkably reduced the protein levels of iNOS and CD86, but markedly increased the protein levels of Arg1 and CD206 in cells. Besides, there was a notable reduction in the levels of TNF-α and IL-1 β in the cell culture medium, while a remarkable increase was observed in the level of IL-10. Additionally, the level of iNOS-positive cells was significantly decreased, while the level of Arg1-positive cells was considerably increased. However, up-regulation of PU.1 expression could reverse the above results and promoted the expression of NLRP3 and its activation-related proteins. Notably, overexpression of USP22 significantly down-regulated the protein expression and ubiquitination level of PU.1.
CONCLUSION: USP22 inhibits the M1 polarization of BV-2 mouse microglia. The PU.1/NLRP3 inflammasome pathway may be a critical regulatory pathway of USP22 in BV-2 cell polarization.

Keywords:  M1 polarization; NLRP3; PU.1; USP22; inflammasome; microglia

DOI:  https://doi.org/10.1016/j.brainresbull.2024.111157
Brain Pathol. 2024 Dec 01. e13322

Neuropathological and cerebrospinal fluid correlates of choroid plexus inflammation in progressive multiple sclerosis.

R Magliozzi, S Hametner, M Mastantuono, A Mensi, M Karimian, L Griffiths, L M Watkins, A Poli, G M Berti, E Barusolo, B Bellini, S Rossi, D Gveric, J A Stratton, K Akassoglou, S Magon, R Nicholas, R Reynolds, O W Howell, S Monaco.

  Among the intrathecal inflammatory niches where compartmentalized inflammation persists and plays a pivotal role in progressive multiple sclerosis (MS), choroid plexus (CP) has recently received renewed attention. To better characterize the neuropathological/molecular correlates of CP in progressive MS and its potential link with other brain inflammatory compartments, such as perivascular spaces and leptomeninges, the levels, composition and phenotype of CP immune infiltration in lateral ventricles of the hippocampus were examined in 40 post-mortem pathologically confirmed MS and 10 healthy donors, using immunochemistry/immunofluorescence and in-situ sequencing. Significant inflammation was detected in the CP of 21 out of the 40 MS cases (52%). The degree of CP inflammation was found correlated with: number of CP macrophages (R: 0.878, p = 1.012 x 10-13) and high frequency of innate immune cells expressing the markers MHC-class II, CD163, CD209, CD11c, TREM2 and TSPO; perivascular inflammation (R: 0.509, p = 7.921 x 10-4), and less with meningeal inflammation (R: 0.365, p = 0.021); number of active lesions (R: 0.51, p: 3.524 x 10-5). However, it did not significantly correlate with any clinical/demographic characteristics of the examined population. In-situ sequencing analysis of gene expression in the CP of 3 representative MS cases and 3 controls revealed regulation of inflammatory pathways mainly related to 'type 2 immune response', 'defense to infections', 'antigen processing/presentation'. Analysis of 78 inflammatory molecules in paired post-mortem CSF, the levels of fibrinogen (R: 0.640, p = 8.752 x 10-6), PDGF-bb (R: 0.470, p = 0.002), CXCL13 (R: 0.428, p = 0.006) and IL15 (R: 0.327, p = 0.040) were correlated with extent of CP inflammation. Elevated fibrinogen and complement deposition were found in CP and in underlying subependymal periventricular areas, according to "surface-in" gradient associated with concomitant prominent microglia activation. CP inflammation, predominantly characterized by innate immunity, represents another key determinant of intrathecal, compartmentalised inflammation persisting in progressive MS, which may be possibly activated by fibrinogen and influence periventricular pathology, even without substantial association with clinical features.

Keywords:  choroid plexus; gradient; inflammation; multiple sclerosis

DOI:  https://doi.org/10.1111/bpa.13322
Pharmacol Res. 2024 Nov 29. pii: S1043-6618(24)00476-6. [Epub ahead of print]210 107531

Siglecs-mediated immune regulation in neurological disorders.

Huifang Tu, Limei Yuan, Bo Ni, Yufeng Lin, Kaiyuan Wang.

  The surfaces of various immune cells are rich in glycan chains, including the sialic-acid-binding immunoglobulin-like lectins (Siglecs) family. As an emerging glyco-immune checkpoint, Siglecs have the ability to bind and interact with various glycoproteins, thereby eliciting a series of downstream reactions to modulate the immune response. The impact of Siglecs has been extensively studied in tumor immunotherapy. However, research in neurological disorders and neurological diseases is very limited, and therapeutic options involving Siglecs need further exploration. Siglecs play a crucial role in the development, homeostasis, and repair processes of the nervous system, especially in degenerative diseases. This review summarizes studies on the immunomodulatory role mediated by Siglecs expressed on different immune cells in various neurological disorders, elucidates how dysregulated sialic acid contributes to several psychiatric disorders, and discusses the progress and limitations of research on the treatment of neurological disorders.

Keywords:  Innate immunity; Microglia; Neurological disorder; Sialic acid; Siglecs

DOI:  https://doi.org/10.1016/j.phrs.2024.107531
Alzheimers Dement. 2024 Dec 06.

Exerkines mitigating Alzheimer's disease progression by regulating inflammation: Focusing on macrophage/microglial NLRP3 inflammasome pathway.

Jaehwan Cheon, Soonyong Kwon, Mikyung Kim.

  Recent research highlights the critical role of inflammation in accelerating amyloid beta and phosphorylated tubulin-associated protein tau cascade and Alzheimer's disease (AD) progression. Emerging evidence suggests that exercise influences AD by modulating inflammatory responses. We conducted a comprehensive search across multiple online databases. Our approach focused on previous and recent studies exploring the links among inflammation, AD, and the effects of exercise, specifically targeting research articles and books published in English. We pointed out that inflammation extends from the periphery to the central nervous system, facilitated by macrophage/microglial NLRP3 (nucleotide-binding domain, leucine rich-containing family, pyrin domain-containing protein 3) inflammasome signaling, which exacerbates classical AD mechanisms. Moreover, we provided further insights into the modulation of inflammasome signaling through exercise and exerkines, which may contribute to mitigating AD development. These insights deepen our understanding of AD mechanisms and offer the potential for identifying key therapeutic targets and biomarkers crucial for effective disease management and treatment. HIGHLIGHTS: Inflammation is potentially linked to the acceleration of classical Alzheimer's disease (AD) pathogenesis, including the pathways involving amyloid beta and phosphorylated tau, mediated by pro-inflammatory cytokines. Inflammation, initiated by the nucleotide-binding domain, leucine rich-containing family, pyrin domain-containing protein 3 (NLRP3) inflammasome signaling pathway within M1-type macrophages/microglia, may contribute to neuroinflammation and AD progression. Exercise has the potential to reduce inflammation and the development of AD by influencing NLRP3 inflammasome signaling via exerkines.

Keywords:  Alzheimer's disease; NLRP3; exercise; exerkines; inflammasome; inflammation; macrophage; microglia

DOI:  https://doi.org/10.1002/alz.14432
STAR Protoc. 2024 Dec 04. pii: S2666-1667(24)00632-4. [Epub ahead of print]5(4): 103467

Protocol for immunofluorescence staining and large-scale analysis to quantify microglial cell morphology at single-cell resolution in mice.

Frida Lind-Holm Mogensen, Corrado Ameli, Alexander Skupin, Alessandro Michelucci.

  Here, we present a protocol for quantifying microglial cell morphology at the single-cell level in mice. We provide comprehensive details, starting from optimal mouse brain dissection to computational analyses of up to 350 microglial cells per brain slice. Analyzing the morphology of microglial cells is essential for understanding their functional and activation states in different conditions, including during disease development and progression, as well as for assessing the effect of therapeutic interventions. For complete details on the use and execution of this protocol, please refer to Lind-Holm Mogensen et al.1 and Fixemer et al.2.

Keywords:  bioinformatics; cell biology; immunology; neuroscience

DOI:  https://doi.org/10.1016/j.xpro.2024.103467
Front Mol Neurosci. 2024 ;17 1443985

Peptide discovery across the spectrum of neuroinflammation; microglia and astrocyte phenotypical targeting, mediation, and mechanistic understanding.

Benjamin A Benita, Kyle M Koss.

  Uncontrolled and chronic inflammatory states in the Central Nervous System (CNS) are the hallmark of neurodegenerative pathology and every injury or stroke-related insult. The key mediators of these neuroinflammatory states are glial cells known as microglia, the resident immune cell at the core of the inflammatory event, and astroglia, which encapsulate inflammatory insults in proteoglycan-rich scar tissue. Since the majority of neuroinflammation is exclusively based on the responses of said glia, their phenotypes have been identified to be on an inflammatory spectrum encompassing developmental, homeostatic, and reparative behaviors as opposed to their ability to affect devastating cell death cascades and scar tissue formation. Recently, research groups have focused on peptide discovery to identify these phenotypes, find novel mechanisms, and mediate or re-engineer their actions. Peptides retain the diverse function of proteins but significantly reduce the activity dependence on delicate 3D structures. Several peptides targeting unique phenotypes of microglia and astroglia have been identified, along with several capable of mediating deleterious behaviors or promoting beneficial outcomes in the context of neuroinflammation. A comprehensive review of the peptides unique to microglia and astroglia will be provided along with their primary discovery methodologies, including top-down approaches using known biomolecules and naïve strategies using peptide and phage libraries.

Keywords:  astrocytes; glia; microglia; neuroinflammation; peptide

DOI:  https://doi.org/10.3389/fnmol.2024.1443985
Alzheimers Dement. 2024 Dec 06.

Association of ten VEGF family genes with Alzheimer's disease endophenotypes at single cell resolution.

Yiyang Wu, Julia B Libby, Logan C Dumitrescu, Philip L De Jager, Vilas Menon, Julie A Schneider, David A Bennett, Timothy J Hohman.

   INTRODUCTION: Using a single-nucleus transcriptome derived from the dorsolateral prefrontal cortex of 424 Religious Orders Study and the Rush Memory and Aging Project (ROS/MAP) participants, we investigated the cell type-specific effect of ten vascular endothelial growth factor (VEGF) genes on Alzheimer's disease (AD) endophenotypes.
METHODS: Negative binomial mixed models were used for differential gene expression and association analysis with AD endophenotypes. VEGF-associated intercellular communication was also profiled.
RESULTS: Higher microglia FLT1, endothelial FLT4, and oligodendrocyte VEGFB are associated with greater amyloid beta (Aβ) load, whereas higher VEGFB expression in inhibitory neurons is associated with lower Aβ load. Higher astrocyte NRP1 is associated with lower tau density. Higher microglia and endothelial FLT1 are associated with worse cognition performance. Endothelial and microglial FLT1 expression was upregulated in clinical AD patients compared to cognitively normal controls. Finally, AD cells showed a significant reduction in VEGF signaling compared to controls.
DISCUSSION: Our results highlight key changes in VEGF receptor expression in endothelial and microglial cells during AD, and the potential protective role of VEGFB in neurons.
HIGHLIGHTS: The prefrontal cortical expression of FLT1 and FLT4 was associated with worse cross-sectional global cognitive function, longitudinal cognitive trajectories, and more Alzheimer's disease (AD) neuropathology. The associations between FLT1 or FLT4 and AD endophenotypes appear to be driven by endothelial and microglial cells. VEGFB expression seems to have opposing effects on the Aβ burden in AD depending on cell types, highlighting its potential protective role in neurons.

Keywords:  Alzheimer's disease; association analysis; dementia; signaling pathway; single cell; single‐nucleus RNA sequencing; transcriptome; vascular endothelial growth factor

DOI:  https://doi.org/10.1002/alz.14419
Food Sci Nutr. 2024 Nov;12(11): 9094-9107

Long-term exposure of sucralose induces neuroinflammation and ferroptosis in human microglia cells via SIRT1/NLRP3/IL-1β/GPx4 signaling pathways.

Ceyhan Hacioglu.

  Microglia serve as the primary defense mechanism in the brain. Artificial sweeteners are widely used as dietary supplements, though their long-term effects remain uncertain. In this study, we investigated the effects of sucralose on microglia during prolonged exposure via the neuroinflammatory and ferroptosis pathways. Initially, human microglial clone 3 (HMC3) cells were exposed to sucralose (0-50 mM) for 24, 48, and 72 h to investigate the short-term effects. Subsequently, HMC3 cells were treated with 1 mM sucralose for 7, 14, and 21 days to examine long-term effects. We measured levels of interleukin-1β (IL-1β), NOD-like receptor protein 3 (NLRP3), 8-hydroxydeoxyguanosine (8-OHdG), Sirtuin-1 (SIRT1), glutathione peroxidase-4 (GPx4), reduced glutathione (GSH), malondialdehyde (MDA), ferrous iron (Fe2+), and caspase 3/7. Additionally, we analyzed the impact of sucralose on cell morphology, migration, and expression levels of IL-1β, NLRP3, SIRT1, and GPx4. Sucralose inhibited cell viability and proliferation in HMC3 cells in a concentration- and time-dependent manner and induced membrane and nuclear abnormalities. Moreover, sucralose significantly reduced the cell migration rate. Long-term sucralose treatment decreased Fe2+, GPx4, GSH, and SIRT1 levels in HMC3 cells while increasing IL-1β, MDA, NLRP3, 8-OHdG, and caspase 3/7 activity. Sucralose treatment also enhanced microglial activation and neuroinflammation by upregulating IL-1β and NLRP3 and downregulating SIRT1 and GPx4, thereby inducing ferroptosis and suppressing cell viability. Consequently, high concentrations or long-term sucralose treatment may induce neuroinflammation and ferroptosis by targeting the SIRT1/NLRP3/IL-1β/GPx4 pathway in HMC3 cells.

Keywords:  NLRP3; artificial sweeteners; ferroptosis; microglia; neuroinflammation; sirtuins; sucralose

DOI:  https://doi.org/10.1002/fsn3.4488
Front Cell Neurosci. 2024 ;18 1456974

Time-dependent phenotypical changes of microglia drive alterations in hippocampal synaptic transmission in acute slices.

Laura Ferrucci, Bernadette Basilico, Ingrid Reverte, Francesca Pagani, Giorgia Scaringi, Federica Cordella, Barbara Cortese, Gaia De Propris, Andrea Galeone, Letizia Mazzarella, Alessandro Mormino, Stefano Garofalo, Azka Khan, Valeria De Turris, Valentina Ferretti, Paola Bezzi, Cornelius Gross, Daniele Caprioli, Cristina Limatola, Silvia Di Angelantonio, Davide Ragozzino.

  It is widely acknowledged that microglia actively regulate synaptic function in the brain. Remarkably, much of our understanding regarding the role of microglia in synaptic regulation is derived from studies in acute brain slices. However, it is still uncertain to what extent the preparation and maintenance of acute slices can influence microglial function and whether microglial changes may affect synaptic transmission. In this study, we examined the impact of acute slice resting time on hippocampal CA1 microglia, by assessing morphological and functional parameters at two distinct time intervals. We report that after 4 h from slicing microglia undergo morphological, functional, and transcriptional changes, including a decrease in the number of branches and in their movement speed. Furthermore, microglia acquire a reactive phenotype, characterized by increased amplitude of outward rectifying K+ currents, increased expression of the pro-inflammatory cytokine Tnfα and altered expression of the microglial receptors Cx3cr1 and P2y12r. We also examined time-dependent changes of excitatory synaptic transmission in CA1 pyramidal neurons from acute hippocampal slices, reporting time-dependent decrease in both amplitude and frequency of postsynaptic currents (sEPSCs), along with a decrease in spine density. Noticeably, sEPSCs amplitude decrease was absent in slices prepared from PLX5622 microglia-depleted mice, suggesting that this time-dependent effect on synaptic transmission is microglia-dependent. Our findings highlight possible causal relation between microglia phenotypic changes in the hours following slice preparation and concomitant synaptic changes, pointing to the mechanisms of acute synaptic modulation, whose understanding is crucial for unraveling microglia-neurons interplay in nature. Furthermore, they emphasize the potential issues associated with experimental time windows in ex vivo samples.

Keywords:  acute slices; electrophysiology; microglia; microglia reactivity; synaptic transmission

DOI:  https://doi.org/10.3389/fncel.2024.1456974
Neuroendocrinology. 2024 Dec 04. 1-19

Hypothyroidism promotes microglia M1 polarization by inhibiting BDNF-promoted PI3K-Akt signaling pathway.

Yuan Zhan, Lang Lang, Fen Wang, Xian Wu, Haiwang Zhang, Yuelin Dong, Hao Yang, Defa Zhu.

Hypothyroidism greatly affects the health-related quality of patients' life, and microglia in brain have essential functions on neurodegeneration, but the underlying link between hypothyroidism and microglia function is largely ambiguous.
METHODS: Methimazole-induced mice was used to construct hypothyroidism model and explore the polarization of microglia. Lipopolysaccharide (LPS)-treated BV2 cells were used to investigate the effecting factors on microglia M1 polarization. Finally, global transcriptome sequencing (RNA-seq) was utilized to identify the underlying regulatory mechanisms.
RESULTS: The biomarkers of microglia M1 polarization and pro-inflammatory cytokines were significantly increased in hypothyroidism mice brain; hypothyroidism could also repress the expression of BDNF and TrkB, and the anti-inflammatory cytokine such as IL-10. In BV2 cells, LPS treatment decreased expression of BDNF, IL-10, and Arg1, while BDNF overexpression (BDNF-OE) significantly reversed the inflammation-induced by LPS by repressing iNOS and TNF-α, while increasing IL-10 and Arg1. RNA-seq analysis demonstrated that in LPS-treated BV2 cells, BDNF-OE significantly altered expression pattern of genes involved in PI3K-Akt signaling pathway, including the upregulated Thbs3, Myc, Gdnf, Thbs1, and Ccnd1, and the downregulated Gnb4, Fgf22, Pik3r3, Pgf, Cdkn1a, and Pdgfra. Myc, Gdnf, Thbs1, and Ccnd1 showed much higher expression levels than other genes in PI3K-Akt signaling pathway.
CONCLUSIONS: Our study demonstrated a sound conclusion that hypothyroidism promotes microglia M1 polarization by inhibiting BDNF-activated PI3K-Akt signaling pathway in brain, which could serve as a promising therapeutic target for microglia-induced neurodegenerative or emotional disorders in future.

DOI: https://doi.org/10.1159/000542858
Immun Inflamm Dis. 2024 Dec;12(12): e70084

Blocking of Tim-3 Ameliorates Spinal Cord Ischemia-Reperfusion Injury Through Inhibiting Neuroinflammation and Promoting M1-to-M2 Phenotypic Polarization of Microglia.

Zhenxing Li, Binbin Zhou, Guanghui Chen, Xiangyu Yang, Han Su, Bolin Li.

BACKGROUND: Blocking of Tim-3 exerts therapeutic effects in a series of ischemia-reperfusion injury (IRI).
METHODS: In this work, a cross-clamped aortic arch was conducted to establish SCIRI rat model. Besides, rat spinal microglia was subjected to OGD/R to mimic I/R-like conditions in vitro. The in vivo and in vitro therapeutic effects of Tim-3 antibody in SCIRI were investigated from these aspects: neuronal apoptosis, neuroinflammation, microglia activation, and polarization.
RESULTS: It was verified that Tim-3 was highly expressed in spinal cord tissues of SCIRI rats and blocking of Tim-3 attenuated SCIRI-induced pathological injury, neuronal apoptosis, neuroinflammation, and microglia activation (M1 polarization). In addition, it was verified that Tim-3 was highly expressed in OGD/R-treated rat spinal microglia and blocking of Tim-3 attenuated OGD/R-induced inflammation and spinal microglia activation (M1 polarization).
CONCLUSIONS: Tim-3 antibody can exert therapeutic effects in SCIRI through inhibiting neuroinflammation and promoting microglia polarization from M1 to M2 phenotype.

DOI: https://doi.org/10.1002/iid3.70084
Alzheimers Dement. 2024 Dec 06.

Single-microglia transcriptomic transition network-based prediction and real-world patient data validation identifies ketorolac as a repurposable drug for Alzheimer's disease.

Jielin Xu, Wenqiang Song, Zhenxing Xu, Michael M Danziger, Ehud Karavani, Chengxi Zang, Xin Chen, Yichen Li, Isabela M Rivera Paz, Dhruv Gohel, Chang Su, Yadi Zhou, Yuan Hou, Yishai Shimoni, Andrew A Pieper, Jianying Hu, Fei Wang, Michal Rosen-Zvi, James B Leverenz, Jeffrey Cummings, Feixiong Cheng.

   INTRODUCTION: High microglial heterogeneities hinder the development of microglia-targeted treatment for Alzheimer's disease (AD).
METHODS: We integrated 0.7 million single-nuclei RNA-sequencing transcriptomes from human brains using a variational autoencoder. We predicted AD-relevant microglial subtype-specific transition networks for disease-associated microglia (DAM), tau microglia, and neuroinflammation-like microglia (NIM). We prioritized drugs by specifically targeting microglia-specific transition networks and validated drugs using two independent real-world patient databases.
RESULTS: We identified putative AD molecular drivers (e.g., SYK, CTSB, and INPP5D) in transition networks of DAM and NIM. Via specifically targeting NIM, we identified that usage of ketorolac was associated with reduced AD incidence in both MarketScan (hazard ratio [HR] = 0.89) and INSIGHT (HR = 0.83) Clinical Research Network databases, mechanistically supported by ketorolac-treated transcriptomic data from AD patient induced pluripotent stem cell-derived microglia.
DISCUSSION: This study offers insights into the pathobiology of AD-relevant microglial subtypes and identifies ketorolac as a potential anti-inflammatory treatment for AD.
HIGHLIGHTS: An integrative analysis of ≈ 0.7 million single-nuclei RNA-sequencing transcriptomes from human brains identified Alzheimer's disease (AD)-relevant microglia subtypes. Network-based analysis identified putative molecular drivers (e.g., SYK, CTSB, INPP5D) of transition networks between disease-associated microglia (DAM) and neuroinflammation-like microglia (NIM). Via network-based prediction and population-based validation, we identified that usage of ketorolac (a US Food and Drug Administration-approved anti-inflammatory medicine) was associated with reduced AD incidence in two independent patient databases. Mechanistic observation showed that ketorolac treatment downregulated the Type-I interferon signaling in patient induced pluripotent stem cell-derived microglia, mechanistically supporting its protective effects in real-world patient databases.

Keywords:  Alzheimer's disease; disease‐associate microglia; drug repurposing; ketorolac molecular driver; neuroinflammation‐like microglia; protein–protein interactome

DOI:  https://doi.org/10.1002/alz.14373
J Hazard Mater. 2024 Nov 29. pii: S0304-3894(24)03300-4. [Epub ahead of print]484 136719

Circular RNA circ_0061183 regulates microglial polarization induced by airborne ultrafine particles in HMC3 cells via sponging miR-98-5p.

Hui-Xian Zeng, Shuang-Jian Qin, Qi-Zhen Wu, Qing-Guo Zeng, Jia-Hui Li, Anna Oudin, Katja M Kanninen, Mo Yang, Pasi Jalava, Guang-Hui Dong, Xiao-Wen Zeng.

  Airborne ultrafine particulate matter (PM0.1) can enter the brain, induce microglia activation, and promote the development of Alzheimer's disease (AD). Circular RNAs (circRNAs) are also involved in AD pathogenesis. However, the role of AD-related circRNAs in PM0.1-induced microglia activation remains unclear. Therefore, we explore cytotoxicity, microglia activation, and AD-associated circRNA expression in human microglial HMC3 cells treated with PM0.1, and further examined circRNA expression in mice and cognitively impaired individuals. The results revealed that PM0.1 exposure decreased cell viability, increased lactate dehydrogenase activity, caused microglia activation, elevated microglial M1 maker expression, downregulated microglial M2 maker expression, and reduced AD-related circ_0061183 expression in vitro. Functionally, circ_0061183 silencing enhanced microglia activation and microglial M1 polarization, but inhibited microglial M2 polarization. Mechanistically, circ_0061183 can bind to miR-98-5p to co-regulate M2 microglial-related IL10 expression, which may affect transforming growth factor-β signaling to regulate PM0.1-inhibited microglial M2 polarization. Moreover, circ_0061183 downregulation was observed in the brain of PM2.5-exposed mice and AD mice and in the blood of cognitively impaired individuals. Furthermore, circ_0061183 was positively related to mini-mental state examination scores and amyloid-β42 peptide expression in elderly individuals. Overall, the current work offers epigenetic insights into the regulatory mechanisms of circRNAs on microglial activation caused by environmental pollutants.

Keywords:  Alzheimer’s disease; Circular RNA; Microglia activation; Microglia polarization; Ultrafine particles

DOI:  https://doi.org/10.1016/j.jhazmat.2024.136719
Commun Biol. 2024 Dec 05. 7(1): 1627

ICU patient-on-a-chip emulating orchestration of mast cells and cerebral organoids in neuroinflammation.

Pelin Saglam-Metiner, Sena Yanasik, Yusuf Caglar Odabasi, Jennifer Modamio, Moritz Negwer, Cigir Biray-Avci, Ayse Guler, Ali Erturk, Ender Yildirim, Ozlem Yesil-Celiktas.

Propofol and midazolam are the current standard of care for prolonged sedation in Intensive Care Units (ICUs). However, the effects and mechanism of these sedatives in brain tissue are unclear. Herein, the development of an ICU patient-on-a-chip platform to elucidate those effects is reported. The humanized neural tissue compartment combines mast cells differentiated from human induced pluripotent stem cells (hiPSCs) with cerebral organoids in a three-dimensional (3D) matrix, which is covered with a membrane populated with human cerebral microvascular endothelial cells (hCMEC/D3) that separates the tissue chamber from the vascular lumen, where sedatives were infused for four days to evaluate neurotoxicity and cell-mediated immune responses. Subsequent to propofol administration, gene expressions of CD40 and TNF-α in mast cells, AIF1 in microglia and GFAP/S100B/OLIG2/MBP in macroglia were elevated, as well as NOS2, CD80, CD40, CD68, IL6 and TNF-α mediated proinflammation is noted in cerebral organoids, which resulted in higher expressions of GJB1, GABA-A and NMDAR1 in the tissue construct of the platform. Besides, midazolam administration stimulated expression of CD40 and CD203c+ reactivated mast cell proliferation and compromised BBB permeability and decreased TEER values with higher barrier disruption, whereas increased populations of CD11b+ microglia, higher expressions of GFAP/DLG4/GJB1 and GABA-A-/NMDAR1- identities, as well as glutamate related neurotoxicity and IL1B, IFNG, IFNA1, IL6 genes mediated proinflammation, resulting in increased apoptotic zones are observed in cerebral organoids. These results suggest that different sedatives cause variations in cell type activation that modulate different pathways related to neuroinflammation and neurotoxicity in the ICU patient-on-chip platform.

DOI: https://doi.org/10.1038/s42003-024-07313-z
Chem Sci. 2024 Nov 27.

Regulation of STING G-quadruplex for rescuing cellular senescence and Aβ phagocytic capacity of microglia.

Heying Yuan, Jie Yang, Geng Qin, Yue Sun, Chuanqi Zhao, Chunyu Wang, Jinsong Ren, Xiaogang Qu.

Alzheimer's disease (AD), the most common form of dementia, affects millions of people worldwide and its cause is very complicated. Besides the classical amyloid cascade hypothesis, oxidative stress, metal ion imbalance, cellular senescence and neuroinflammation are also considered crucial triggers of AD. Therefore, therapeutic strategies other than inhibiting Aβ deposition are very promising. As a crucial innate immune pathway, the abnormal activation of the cGAS-STING pathway in AD has attracted much attention and become a promising target for AD treatment. Here, we identify a highly conserved and stable G-quadruplex (G4) in the STING promoter region, and further verify its function in transcriptional inhibition of STING by using CRISPR technology to precisely target STING G4. Intriguingly, down-regulation of STING expression can alleviate cellular senescence and restore the Aβ phagocytic capacity of microglia. Our results highlight the compelling therapeutic potential of STING promoter G4 for regulation of the abnormal activation of the cGAS-STING pathway in AD. Different from the existing therapeutic strategies for AD, this work provides an alternative way of targeting the functional gene secondary structure, such as the STING promoter region, which may promote the design and synthesis of drug candidates for AD.

DOI: https://doi.org/10.1039/d4sc04453c
J Hazard Mater. 2024 Dec 04. pii: S0304-3894(24)03341-7. [Epub ahead of print]484 136760

Chemoproteomic profiling by bioorthogonal probes to reveal the novel targets of acrylamide in microglia.

Binru Zheng, Jia Shang, Yuanqing Wei, Qianqian Tao, Jizhou Yin, An Kang, Rui Liu, Hongzhen Lian, Shuying Han.

  Neurotoxicity studies caused by exposure to acrylamide (AA) are of wide interest, but the methods for direct analysis of AA targets in living neuronal cells by cysteine profiling are still lacking. To address this, we developed a specific bioorthogonal probe, AAPA-P2, for chemical proteomics analysis of AA covalent binding sites. AAPA-P2 captured 754 target proteins, increasing the number of identified target proteins by 20-fold. Further screening revealed 96 proteins that are both highly sensitive and heavily modified by AAPA-P2, with validation performed on some potential key targets and binding sites. AA was found to induce neurotoxicity by binding to newly identified targets, Proteasome 26S Subunit, non ATPase 9 (PSMD9) and NADH dehydrogenase (ubiquinone) 1 alpha subcomplex 5 (NDUFA5), interfering with the ubiquitin-proteasome system, and inducing mitochondria-dependent apoptosis. The present work provides an effective bioorthogonal probe tool for identifying covalent binding targets of acrylamide and offers new insights into the molecular mechanisms underlying acrylamide-induced neurotoxicity.

Keywords:  Acrylamide; Bioorthogonal probe; Covalent binding sites; Neurotoxicity

DOI:  https://doi.org/10.1016/j.jhazmat.2024.136760