bims-microg 2025-08-17 papers

bims-microg

Biomed News

on Microglia in health and disease

Issue of 2025–08–17
twenty papers selected by
Marcus Karlstetter, Universität zu Köln

Astrocyte priming enhances microglial Aβ clearance and is compromised by APOE4.
HAPLN2 forms aggregates and promotes microglial inflammation during brain aging in mice.
Inhibition of astrocyte signaling leads to sex-specific changes in microglia phenotypes in a diet-based model of cerebral small vessel disease.
Abstinence from cocaine self-administration promotes microglial pruning of astrocytes, which drives cocaine-seeking behavior.
Microglial States Are Susceptible to Senescence and Cholesterol Dysregulation in Alzheimer's Disease.
Transcriptional profiling uncovers microglial HIF-1α signaling as a therapeutic target of radiation-induced brain injury.
Calcineurin/NFAT1/Smad2 signaling regulates microglial autophagy that contributes to neuroinflammation and cognitive deficit in mice with sepsis-associated encephalopathy.
Programmed cell death signatures-driven microglial transformation in Alzheimer's disease: single-cell transcriptomics and functional validation.
RORα-activated mitophagy attenuating hypoxic-ischemic encephalopathy via suppression of microglial cGAS-STING axis.
Microglia-mediated inflammation and synaptic pruning contribute to sleep deprivation-induced mania in a sex-specific manner.
NADPH acts as an endogenous P2X7 receptor modulator to gate neuroinflammatory responses of microglia.
LRRK2-mutant microglia and neuromelanin synergize to drive dopaminergic neurodegeneration in an iPSC-based Parkinson's disease model.
GM1 Oligosaccharide Modulates Microglial Activation and α-Synuclein Clearance in a Human In Vitro Model.
Induced Microglial-like Cells Derived from Familial and Sporadic Alzheimer's Disease Peripheral Blood Monocytes Show Abnormal Phagocytosis and Inflammatory Response to PSEN1 E280A Cholinergic-like Neurons.
Transcriptional Regulation of Microglial Metabolic and Activation States by P2RY12.
Retinoid-X-Receptor as a Mediator of Post-Stroke Recovery by Reversing Age-Associated Phenotypes of Microglia/Hematogenous Macrophages.
Beta-hydroxybutyrate (BHB) elicits concentration-dependent anti-inflammatory effects on microglial cells which are reversible by blocking its monocarboxylate (MCT) importer.
Building a potent TREM2 agonistic, biparatopic, common light chain antibody.
Dectin-1 Drives Diabetic Retinopathy via Inducing Microglia-Mediated Inflammation and Blood-Retinal Barrier Breakdown.
Neural organoids incorporating microglia to assess neuroinflammation and toxicities induced by known developmental neurotoxins.

Nat Commun. 2025 Aug 14. 16(1): 7551

Astrocyte priming enhances microglial Aβ clearance and is compromised by APOE4.

Se-In Lee, Jichang Yu, Hyein Lee, Buyun Kim, Min Jun Jang, Hyeonbin Jo, Na Yeon Kim, Malk Eun Pak, Jae Kwang Kim, Sukhee Cho, Hong-Hee Won, Min Soo Kim, Fan Gao, Younghoon Go, Jinsoo Seo.

The innate immune system can develop a form of memory called priming, where prior exposure to a stimulus enhances subsequent responses. While well-characterized in peripheral immunity, its function in brain-resident cells such as astrocytes under non-disease conditions remains unclear. Here we show that human astrocytes derived from the induced pluripotent stem cells of healthy female donors, but not microglia, acquire a primed state following transient immune stimulations. Upon subsequent exposure to amyloid-β (Aβ), these astrocytes secrete elevated levels of cytokines and promote microglial Aβ uptake. In contrast, astrocytes carrying the Alzheimer's disease (AD) risk allele APOE4 exhibit reduced priming and fail to support microglial phagocytosis. These findings are validated in astrocyte-microglial co-cultures, cerebral organoids, and male mice, where astrocyte priming enhances Aβ clearance in an APOE4-sensitive manner. Our findings identify astrocytic immune memory as a modulator of microglial function and Aβ pathology, providing insights into how early protective responses in AD may be disrupted by genetic risk factors.

DOI: https://doi.org/10.1038/s41467-025-62995-1
PLoS Biol. 2025 Aug 14. 23(8): e3003006

HAPLN2 forms aggregates and promotes microglial inflammation during brain aging in mice.

Ayaka Watanabe, Shoshiro Hirayama, Itsuki Kominato, Sybille Marchese, Pietro Esposito, Vanya Metodieva, Taeko Kimura, Hiroshi Kameda, Terunori Sano, Masaki Takao, Sho Takatori, Masato Koike, Juan Alberto Varela, Taisuke Tomita, Shigeo Murata.

Protein aggregation is a hallmark of neurodegenerative diseases and is also observed in the brains of elderly individuals without such conditions, suggesting that aging drives the accumulation of protein aggregates. However, the comprehensive understanding of age-dependent protein aggregates involved in brain aging remains unclear. Here, we investigated proteins that become sarkosyl-insoluble with age and identified hyaluronan and proteoglycan link protein 2 (HAPLN2), a hyaluronic acid-binding protein of the extracellular matrix at the nodes of Ranvier, as an age-dependent aggregating protein in mouse brains. Elevated hyaluronic acid levels and impaired microglial function reduced the clearance of HAPLN2, leading to its accumulation. HAPLN2 oligomers induced microglial inflammatory responses both in vitro and in vivo. Furthermore, age-associated HAPLN2 aggregation was also observed in the human cerebellum. These findings suggest that HAPLN2 aggregation results from age-related decline in brain homeostasis and may exacerbate the brain environment by activating microglia. This study provides new insights into the mechanisms underlying cerebellar aging and highlights the role of HAPLN2 in age-associated changes in the brain.

DOI: https://doi.org/10.1371/journal.pbio.3003006
J Neuroinflammation. 2025 Aug 09. 22(1): 202

Inhibition of astrocyte signaling leads to sex-specific changes in microglia phenotypes in a diet-based model of cerebral small vessel disease.

Jenna L Gollihue, Khine Zin Aung, Colin B Rogers, Leopoldine B Galopin, Nicholas A Wright, Pradoldej Sompol, Erica M Weekman, Yuriko Katsumata, Josh M Morganti, Christopher M Norris.

  Hyperhomocysteinemia (HHcy)-inducing diets recapitulate cerebral small vessel disease phenotypes in mice including cerebrovascular pathology/dysfunction, neuroinflammation, synaptic deficits, and cognitive decline. We recently showed that astrocyte signaling through calcineurin(CN)/nuclear factor of activated T cells (NFATs) plays a causative role in these phenotypes. Here, we assessed the impact of astrocytic signaling on microglia, which set the inflammatory tone in brain. Seven-to-eight-week-old male and female C57BL/6 J mice received intrahippocampal injections of adeno-associated virus (AAV) expressing EGFP (AAV2/5-Gfa2-EGFP) or AAV expressing the NFAT inhibitor VIVIT (i.e., AAV2/5-Gfa2-VIVIT-EGFP). Mice were then fed with control chow (CT) or B-vitamin-deficient chow for 12 weeks to induce HHcy. Immunohistochemistry and Western blot analyses suggested that expression of the homeostatic microglial marker, P2RY12, responded differently to AAV treatments depending on diet and sex. We next conducted single-cell RNA sequencing (scRNA-seq) to determine if microglial genes and/or clustering patterns were differentially sensitive to diet and AAV, depending on sex. In males, disease-associated microglial genes and subclusters were overrepresented in HHcy-treated mice, while VIVIT promoted the appearance of homeostatic microglial genes and clusters. In contrast, microglial genes in females were less sensitive to diet and AAV treatments, though disease-like patterns were also observed in the HHcy condition. Very few of the HHcy-sensitive microglial genes in females were affected by VIVIT. Though based on small sample sizes, the results suggest a sexually dimorphic influence of astrocyte signaling on microglial transcriptional phenotypes in the context of HHcy and small cerebral vessel disease. However, these interpretations will need to be bolstered with additional biological replicates and more stringent statistical analyses.

Keywords:  Astrocyte reactivity; Calcium; Microglia; Neuroinflammation; Vascular

DOI:  https://doi.org/10.1186/s12974-025-03523-2
Cell Rep. 2025 Aug 12. pii: S2211-1247(25)00908-8. [Epub ahead of print]44(8): 116137

Abstinence from cocaine self-administration promotes microglial pruning of astrocytes, which drives cocaine-seeking behavior.

Anze Testen, Jonathan W VanRyzin, Tania J Bellinger, Ronald Kim, Han Wang, Matthew J Gastinger, Emily A Witt, Janay P Franklin, Haley A Vecchiarelli, Katherine Picard, Michael D Scofield, Marie-Ève Tremblay, Kathryn J Reissner.

  Rodent drug self-administration leads to a compromised ability of nucleus accumbens astrocytes to maintain glutamate homeostasis as well as to reductions in surface area, volume, and synaptic colocalization of astrocyte membranes. However, the mechanisms driving astrocyte responses to drug administration are unknown. Here, we report that long-access rat cocaine self-administration followed by prolonged home cage abstinence results in decreased branching complexity of nucleus accumbens astrocytes, characterized by the loss of peripheral processes. Using a combination of confocal fluorescence microscopy and immunoelectron microscopy, we show that these alterations in astrocyte structural features are driven by microglial phagocytosis, as virally labeled astrocyte membranes are found within microglial phagolysosomes. Inhibition of complement C3-mediated phagocytosis using the neutrophil inhibitory peptide (NIF) rescued astrocyte structure and decreased cocaine-seeking behavior following cocaine self-administration and abstinence. Collectively, these results provide evidence for microglial pruning of nucleus accumbens astrocytes across cocaine abstinence, which mediates cocaine craving.

Keywords:  CP: Neuroscience; astrocytes; cocaine; drug seeking; microglia; nucleus accumbens; phagocytosis; relapse

DOI:  https://doi.org/10.1016/j.celrep.2025.116137
Aging Cell. 2025 Aug 11. e70189

Microglial States Are Susceptible to Senescence and Cholesterol Dysregulation in Alzheimer's Disease.

Boyang Li, Shaowei Wang, Bilal Kerman, Cristelle Hugo, E Keats Shwab, Chang Shu, Ornit Chiba-Falek, Zoe Arvanitakis, Hussein N Yassine.

  Cellular senescence is a major contributor to aging-related degenerative diseases, including Alzheimer's disease (AD), but much less is known about the key cell types and pathways driving senescence mechanisms in the brain. We hypothesized that dysregulated cholesterol metabolism is central to cellular senescence in AD. We analyzed single-cell RNA-seq data from the ROSMAP and SEA-AD cohorts to uncover cell type-specific senescence pathologies. In ROSMAP snRNA-seq data (982,384 nuclei from postmortem prefrontal cortex), microglia emerged as central contributors to AD-associated senescence phenotypes among non-neuronal cells. Homeostatic, inflammatory, phagocytic, lipid-processing, and neuronal-surveillance microglial states were associated with AD-related senescence in both ROSMAP (152,459 microglia nuclei from six brain regions) and SEA-AD (82,486 microglia nuclei) via integrative analysis. We assessed top senescence-associated bioprocesses and demonstrated that senescent microglia exhibit altered cholesterol-related processes and dysregulated cholesterol metabolism. We identified three gene co-expression modules representing cholesterol-related senescence signatures in postmortem brains. To validate these findings, we applied these signatures to snRNA-seq data from iPSC-derived microglia（iMGs) exposed to myelin, Aβ, apoptotic neurons, and synaptosomes. Treatment with AD-related substrates altered cholesterol-associated senescence signatures in iMGs. This study provides the first human evidence that dysregulated cholesterol metabolism in microglia drives cellular senescence in AD. Targeting cholesterol pathways in senescent microglia is an attractive strategy to attenuate AD progression.

Keywords:  Alzheimer's; cellular senescence; cholesterol; microglia

DOI:  https://doi.org/10.1111/acel.70189
Free Radic Biol Med. 2025 Aug 08. pii: S0891-5849(25)00883-4. [Epub ahead of print]239 552-564

Transcriptional profiling uncovers microglial HIF-1α signaling as a therapeutic target of radiation-induced brain injury.

Yoonsoo Choi, Joong-Sun Kim, Changjong Moon, Ja-Hyun Baik, Hae-June Lee, Yeonghoon Son.

  Cranial irradiation is a widely used therapeutic modality for brain tumors but is frequently associated with long-term neurological complications, including cognitive deficits and mood disturbances. Despite its clinical relevance, the cellular and molecular mechanisms underlying radiation-induced brain injury (RIBI) remain poorly understood. In this study, we employed single-cell RNA sequencing to elucidate cell-type-specific transcriptional changes following cranial irradiation in mice. Irradiated animals exhibited marked microglial alterations, including a dynamic shift toward a pathologically activated state, alongside significant impairments in hippocampus-dependent cognitive dysfunction. Notably, we identified a radiation-induced upregulation of hypoxia-inducible factor-1 alpha (HIF-1α) signaling specifically within microglial populations, which was not detectable using conventional bulk analyses. Pharmacological inhibition of HIF-1α with 2-methoxyestradiol led to partial recovery of cognitive function and selectively suppressed the expression of Ccl2, a key HIF-1α-associated chemokine implicated in neuroinflammatory signaling. These findings highlight the subtype-specific vulnerability of microglia to radiation and underscore the central role of HIF-1α-mediated transcriptional changes in RIBI. Targeting the microglial HIF-1α-Ccl2 axis may thus offer a promising strategy to mitigate late-onset cognitive dysfunction following cranial irradiation.

Keywords:  2-Methoxyestradiol; HIF-1α signaling; Microglia; Radiation-induced brain injury; Single-cell RNA sequencing

DOI:  https://doi.org/10.1016/j.freeradbiomed.2025.08.014
Free Radic Biol Med. 2025 Aug 08. pii: S0891-5849(25)00877-9. [Epub ahead of print]240 15-28

Calcineurin/NFAT1/Smad2 signaling regulates microglial autophagy that contributes to neuroinflammation and cognitive deficit in mice with sepsis-associated encephalopathy.

Rui Ding, Nanbin Hu, Xinlong Zhang, Fan Jiang, Yue Feng, Zhixiang Li, Siruo Tang, Wanlin Li, Hongwei Shi, Yanna Si.

   OBJECTIVE: Sepsis-induced encephalopathy is a critical determinant of mortality, driven by microglial activation and excessive autophagy. However, the underlying mechanisms remain unclear.
METHODS: Sepsis was induced in wild-type and nuclear factor of activated T cells (NFAT) 1-deficient mice via cecal ligation and puncture. Hippocampal morphology, microglial autophagy, polarization, and inflammatory cytokine expressions were analyzed. Cognitive function was evaluated using the Morris water maze and fear conditioning tests. In vitro, BV2 microglia were stimulated with lipopolysaccharide (LPS), followed by genetic manipulation of calcineurin, NFAT1 or Smad2 to investigate underlying mechanisms.
RESULTS: In wild-type mice, sepsis induced microglial autophagy, M1 polarization and neuroinflammation, resulting in cognitive impairment. These changes were accompanied by upregulated NFAT1 and elevated phosphorylation of Smad2 in hippocampal microglia. Notably, the sepsis-induced effects were attenuated by either pharmacological inhibition of autophagy (using 3-methyladenine) or genetic NFAT1 deficiency. Smad2 overexpression in NFAT1-deficient mice reversed sepsis-induced pathological phenotype, suggesting a functional dependency on Smad2 downstream of NFAT1. Corroborating the in vivo findings, in vitro experiments demonstrated that knockdown of calcineurin, NFAT1 or Smad2 suppressed LPS-induced autophagy and inflammatory responses in microglial cells. Furthermore, Smad2 overexpression rescued the effects of NFAT1 knockdown on LPS-exposure cells.
CONCLUSION: The calcineurin/NFAT1 pathway may interact with Smad2 signaling promotes microglial autophagy during sepsis, exacerbating neuroinflammation and cognitive impairment. These findings support targeting this pathway for treating or even preventing sepsis-induced encephalopathy.

Keywords:  Autophagy; Cognitive impairment; NFAT1; Sepsis-associated encephalopathy; Smad2

DOI:  https://doi.org/10.1016/j.freeradbiomed.2025.08.008
Front Immunol. 2025 ;16 1610717

Programmed cell death signatures-driven microglial transformation in Alzheimer's disease: single-cell transcriptomics and functional validation.

Mi-Mi Li, Ying-Xia Yang, Ya-Li Huang, Shu-Juan Wu, Wan-Li Huang, Li-Chao Ye, Ying-Ying Xu.

   Background: This study aims to develop and validate a programmed cell death signature (PCDS) for predicting and classifying Alzheimer's disease (AD) using an integrated machine learning framework. We further explore the role of S100A4 in AD pathogenesis, particularly in microglia.
Methods: A total of one single-cell RNA sequencing (scRNA-seq) and four bulk RNA-seq datasets from multiple GEO datasets were analyzed. Weighted Gene Co-expression Network Analysis (WGCNA) was utilized to identify PCD-related genes. An integrated machine learning framework, combining 12 algorithms was used to construct a PCDS model. The performance of PCDS was validated using multiple independent cohorts. In vitro experiments using BV2 microglia were conducted to validate the role of S100A4 in AD, including siRNA transfection, Western blot, qRT-PCR, cell viability and cytotoxicity assay, flow cytometry, and immunofluorescence.
Results: ScRNA-seq analysis revealed higher PCD levels in microglia from AD patients. Seventy-seven PCD-related genes were identified, with 70 genes used to construct the PCDS model. The optimal model, combining Stepglm and Random Forest, achieved an average AUC of 0.832 across five cohorts. High PCDS correlated with upregulated pathways related to inflammation and immune response, while low PCDS associated with protective pathways. In vitro, S100A4 knockdown in AbetaO-treated BV2 microglia improved cell viability, reduced LDH release, and partially alleviated apoptosis. S100A4 inhibition attenuated pro-inflammatory responses, as evidenced by the reduced expression of pro-inflammatory mediators (IL-6, iNOS, TNF-α) and promoted an anti-inflammatory state, indicated by increased expression of markers such as IL-10, ARG1, and YM1/2. Furthermore, S100A4 knockdown mitigated oxidative stress, restoring mitochondrial function and decreasing ROS levels.
Conclusion: This study developed a robust PCDS model for AD prediction and identified S100A4 as a potential therapeutic target. The findings highlight the importance of PCD pathways in AD pathogenesis and provide new insights for early diagnosis and intervention.

Keywords:  Alzheimer’s disease; machine learning; microglia; programmed cell death; single-cell

DOI:  https://doi.org/10.3389/fimmu.2025.1610717
Front Immunol. 2025 ;16 1592737

RORα-activated mitophagy attenuating hypoxic-ischemic encephalopathy via suppression of microglial cGAS-STING axis.

Lei Song, Haiyan Shen, Fei Hong, Weiyan Zhang, Hongyi Lu.

   Introduction: Hypoxic-ischemic encephalopathy (HIE) involves neuroinflammation driven by microglial activation, yet regulatory mechanisms remain poorly defined. This study investigates how Retinoic Acid Receptor-Related Orphan Receptor Alpha (RORα) modulates mitophagy to suppress mtDNA-cGAS-STING-NLRP3 signaling in aging microglia, offering therapeutic potential for HIE.
Methods: A multi-omics approach combining single-cell RNA sequencing (scRNA-seq) of an HIE rat model, Weighted Gene Co-Expression Network Analysis (WGCNA), and LASSO regression identified RORα as a pivotal regulator. In vivo and in vitro HIE models with RORα overexpression were assessed via behavioral tests (morris water maze, tail suspension), reactive oxygen species (ROS) quantification, and molecular profiling (RT-qPCR, Western Blot, ELISA). Mitophagy inhibitor 3-MA was used to validate pathway dependence.
Results: Multi-omics integration revealed RORα as a hub gene linked to inflammatory and metabolic pathways. RORα activation enhanced mitophagy, reducing mtDNA leakage by 43% and cGAS-STING activity by 68%, which suppressed NLRP3 inflammasome activation (p < 0.01). This correlated with improved cognitive/motor function in HIE rats (p < 0.05) and attenuated ROS/IL-1β levels. Critically, 3-MA reversed RORα's anti-inflammatory effects, confirming mitophagy dependence.
Conclusion: RORα alleviates HIE by resolving microglial neuroinflammation through mitophagic inhibition of mtDNA-cGAS-STING-NLRP3 signaling. These findings position RORα as a novel therapeutic target for HIE, bridging mitochondrial quality control and neuroimmunology.

Keywords:  NLRP3 inflammasome; RORα; cGAS-STING pathway; hypoxic-ischemic encephalopathy; mitophagy; neuroinflammation; scRNA-seq

DOI:  https://doi.org/10.3389/fimmu.2025.1592737
Transl Psychiatry. 2025 Aug 15. 15(1): 285

Microglia-mediated inflammation and synaptic pruning contribute to sleep deprivation-induced mania in a sex-specific manner.

Rong-Jun Ni, Wei-Jun Yuan, Yi-Yan Wang, Xiao Yang, Jin-Xue Wei, Lian-Sheng Zhao, Qiang Wang, Xiang-Dong Tang, Xiao-Hong Ma.

Sleep loss is a key trigger for a manic episode of bipolar disorder (BD), but the underlying microglial and molecular mechanisms remain unclear. Sleep loss induces microglial and inflammatory responses. Microglia, resident macrophages in the central nervous system, regulate synaptic pruning by engulfing dendritic spines. Here, we introduce a modified paradoxical sleep deprivation (SD) paradigm as a BD mouse model. After intermittent 16-h daily SD for 4 days, the mice showed mania-like behavior, reduced cytokine/chemokine production, mitochondrial damage, microglial loss, decreased synaptic engulfment by microglia, and synaptic gain. Single-nucleus RNA sequencing (snRNA-seq) revealed cell-type-specific inflammation- and synapse-related gene expression profiles in the prefrontal cortex (PFC) and hippocampus of SD-treated male mice. Interestingly, much more differentially expressed genes were observed in SD-treated female versus male mouse brain, especially in the PFC. Pharmacological depletion of microglia by colony stimulating factor-1 receptor (CSF1R) inhibitor PLX3397 blocked SD-induced inflammation-related and senescence-associated abnormalities in a sex-specific manner. Microglial elimination reversed SD-induced synapse gain and mania-like behavior in males but not in females. However, microglial inhibition by minocycline had no effect on SD-induced behaviors in a sex-independent manner. These findings demonstrate that microglia-mediated neuroinflammation and synaptic pruning contribute to SD-induced mania-like behavior in a mouse model of BD in a sex-specific manner.

DOI: https://doi.org/10.1038/s41398-025-03525-x
Acta Pharmacol Sin. 2025 Aug 11.

NADPH acts as an endogenous P2X7 receptor modulator to gate neuroinflammatory responses of microglia.

Yu-Jie Mou, Feng-Min Li, Jun-Tong Lou, Hai-Yue Tu, Yi Zhu, Rui Sheng, Zhong-Ling Zhang, Yu-Zheng Zhao, Fu-Hai Ji, Jun-Chao Wu, Zheng-Hong Qin.

  Reduced nicotinamide adenine dinucleotide phosphate (NADPH) is an important coenzyme involved in cellular biosynthetic and redox metabolism. It has been recognized for its role in regulating neuroinflammation through coordinating redox reactions. Whether there are new actions other than redox regulation remain unclear. In this study we investigated a novel mechanism by which NADPH regulated microglia-mediated neuroinflammation. We showed that NADPH application significantly alleviated NLRP3 inflammasome activation in microglia and exerted neuroprotective effects both in vitro and in vivo neuroinflammation models. With P2X7R knockdown microglial cells and P2X7RcKO mice, we demonstrated that P2X7R was a crucial mediator of the anti-inflammatory effects for the supplemented NADPH. We conducted whole-cell recording from murine microglial cell line BV2 cells, and found that application of ATP (1 mM) elicited an inward current, which was reduced by co-application of P2X7R antagonist A-438079 (20 μM) or NADPH (1 mM). By performing a drug affinity responsive targets stability (DARTS) assay, we revealed that NADPH (not NADP+ or NADH), like the P2X7R agonist ATP, bound to the extracellular domain of P2X7R, leading to the suppression of ATP-induced P2X7R activation. Our research provides the first evidence of NADPH as an endogenous inhibitor of P2X7R in modulation of microglia-mediated neuroinflammation. This study expands the biological functions of NADPH and offers a novel target for NADPH-based therapies in neuroimmune-related diseases.

Keywords:  NADPH; NLRP3 inflammation; P2X7 receptor; microglia; neuroinflammation.

DOI:  https://doi.org/10.1038/s41401-025-01638-z
Commun Biol. 2025 Aug 12. 8(1): 1203

LRRK2-mutant microglia and neuromelanin synergize to drive dopaminergic neurodegeneration in an iPSC-based Parkinson's disease model.

Lucas Blasco-Agell, Meritxell Pons-Espinal, Veronica Testa, Gerard Roch, Jara Montero-Muñoz, Irene Fernandez-Carasa, Valentina Baruffi, Marta Gonzalez-Sepulveda, Yvonne Richaud-Patin, Senda Jimenez, Thais Cuadros, Joana M Cladera-Sastre, Joan Compte, Zoe Manglano-Artuñedo, Salvador Ventura, Manel Juan, Eduardo Tolosa, Angel Raya, Miquel Vila, Antonella Consiglio.

Parkinson's disease (PD) is a progressive, incurable neurodegenerative disorder characterized by the loss of neuromelanin (NM)-containing dopamine neurons (DAn) in the substantia nigra of the midbrain. Non-neuronal cells are increasingly recognized as contributors to PD. We generated human microglia-like cells (hMG) from induced pluripotent stem cells (iPSC) derived from patients with LRRK2 PD-causing mutations, gene-corrected isogenic controls, and healthy donors. While neither genotype induced neurodegeneration in healthy DAn, LRRK2 hMG become hyperreactive to LPS stimulation, exhibiting increased cytokine expression, reactive oxygen species, and phagocytosis. When exposed to NM-containing particles, but not α-synuclein fibrils, LRRK2 hMG trigger DAn degeneration, in a process that is prevented by pre-treatment with the immunomodulatory drug ivermectin. Finally, post-mortem analysis of midbrain tissue of LRRK2-PD patients show increased microglia activation around NM-containing neurons, confirming our in vitro findings. Overall, our work highlights NM-activated microglia's role in PD progression, and provides a model for testing therapeutic targets.

DOI: https://doi.org/10.1038/s42003-025-08544-4
Int J Mol Sci. 2025 Aug 07. pii: 7634. [Epub ahead of print]26(15):

GM1 Oligosaccharide Modulates Microglial Activation and α-Synuclein Clearance in a Human In Vitro Model.

Giulia Lunghi, Carola Pedroli, Maria Grazia Ciampa, Laura Mauri, Laura Rouvière, Alexandre Henriques, Noelle Callizot, Benedetta Savino, Maria Fazzari.

  Neuroinflammation driven by microglial activation and α-synuclein (αSyn) aggregation is one of the central features driving Parkinson's disease (PD) pathogenesis. GM1 ganglioside's oligosaccharide moiety (OligoGM1) has shown neuroprotective potential in PD neuronal models, but its direct effects on inflammation remain poorly defined. This study investigated the ability of OligoGM1 to modulate microglial activation and αSyn handling in a human in vitro model. Human embryonic microglial (HMC3) cells were exposed to αSyn pre-formed fibrils (PFFs) in the presence or absence of OligoGM1. Microglial activation markers, intracellular αSyn accumulation, and cytokine release were assessed by immunofluorescence and ELISA. OligoGM1 had no effect on microglial morphology or cytokine release under basal conditions. Upon αSyn challenge, cells exhibited increased amounts of ionized calcium-binding adaptor molecule 1 (Iba1), triggered receptor expressed on myeloid cells 2 (TREM2), elevated αSyn accumulation, and secreted pro-inflammatory cytokines. OligoGM1 pre-treatment significantly reduced the number and area of Iba1(+) cells, the intracellular αSyn burden in TREM2(+) microglia, and the release of interleukin 6 (IL-6). OligoGM1 selectively attenuated αSyn-induced microglial activation and enhanced αSyn clearance without compromising basal immune function. These findings confirm and support the potential of OligoGM1 as a multitarget therapeutic candidate for PD that is capable of modulating glial reactivity and neuroinflammatory responses.

Keywords:  GM1 oligosaccharide; Parkinson’s disease; microglia; neurodegeneration; α-synuclein

DOI:  https://doi.org/10.3390/ijms26157634
Int J Mol Sci. 2025 Jul 24. pii: 7162. [Epub ahead of print]26(15):

Induced Microglial-like Cells Derived from Familial and Sporadic Alzheimer's Disease Peripheral Blood Monocytes Show Abnormal Phagocytosis and Inflammatory Response to PSEN1 E280A Cholinergic-like Neurons.

Viviana Soto-Mercado, Miguel Mendivil-Perez, Carlos Velez-Pardo, Marlene Jimenez-Del-Rio.

  In familial Alzheimer's disease (FAD), presenilin 1 (PSEN1) E280A cholinergic-like neurons (ChLNs) induce aberrant secretion of extracellular amyloid beta (eAβ). How PSEN1 E280A ChLNs-eAβ affects microglial activity is still unknown. We obtained induced microglia-like cells (iMG) from human peripheral blood cells (hPBCs) in a 15-day differentiation process to investigate the effect of bolus addition of Aβ42, PSEN1 E280A cholinergic-like neuron (ChLN)-derived culture supernatants, and PSEN1 E280A ChLNs on wild type (WT) iMG, PSEN1 E280A iMG, and sporadic Alzheimer's disease (SAD) iMG. We found that WT iMG cells, when challenged with non-cellular (e.g., lipopolysaccharide, LPS) or cellular (e.g., Aβ42, PSEN1 E280A ChLN-derived culture supernatants) microenvironments, closely resemble primary human microglia in terms of morphology (resembling an "amoeboid-like phenotype"), expression of surface markers (Ionized calcium-binding adapter molecule 1, IBA-1; transmembrane protein 119, TMEM119), phagocytic ability (high pHrodo™ Red E. coli BioParticles™ phagocytic activity), immune metabolism (i.e., high generation of reactive oxygen species, ROS), increase in mitochondrial membrane potential (ΔΨm), response to ATP-induced transient intracellular Ca2+ influx, cell polarization (cluster of differentiation 68 (CD68)/CD206 ratio: M1 phenotype), cell migration activity according to the scratch wound assay, and especially in their inflammatory response (secretion of cytokine interleukin-6, IL-6; Tumor necrosis factor alpha, TNF-α). We also found that PSEN1 E280A and SAD iMG are physiologically unresponsive to ATP-induced Ca2+ influx, have reduced phagocytic activity, and diminished expression of Triggering Receptor Expressed on Myeloid Cells 2 (TREM2) protein, but when co-cultured with PSEN1 E280A ChLNs, iMG shows an increase in pro-inflammatory phenotype (M1) and secretes high levels of cytokines IL-6 and TNF-α. As a result, PSEN1 E280A and SAD iMG induce apoptosis in PSEN1 E280A ChLNs as evidenced by abnormal phosphorylation of protein TAU at residue T205 and cleaved caspase 3 (CC3). Taken together, these results suggest that PSEN1 E280A ChLNs initiate a vicious cycle between damaged neurons and M1 phenotype microglia, resulting in excessive ChLN death. Our findings provide a suitable platform for the exploration of novel therapeutic approaches for the fight against FAD.

Keywords:  Alzheimer; cholinergic; familial; microglia; mutation; neurons; sporadic; variant

DOI:  https://doi.org/10.3390/ijms26157162
Glia. 2025 Aug 15.

Transcriptional Regulation of Microglial Metabolic and Activation States by P2RY12.

Aida Oryza Lopez-Ortiz, Madison Doceti, JaQuinta Thomas, Abigayle Duffy, Morgan Coburn, Akhabue K Okojie, Audrey Lee, Elizabeth Aidita Sou, Alban Gaultier, Ukpong B Eyo.

  Microglia are the resident immune cells of the CNS. Under homeostatic conditions, microglia play critical roles in orchestrating synaptic pruning, debris clearance, and dead cell removal. In disease, they are powerful mediators of neuroinflammation, as they rapidly respond to injury or infection within the CNS by altering their morphology, proliferating, and releasing cytokines and other signaling molecules. Understanding the molecular pathways involved in microglial function is pivotal for advancing neurobiological research and developing effective strategies for CNS disorders. In this context, P2RY12 is a G protein-coupled receptor (GPCR) that is uniquely enriched in microglia in the parenchyma and a canonical marker of homeostatic, ramified microglia. However, P2RY12 is downregulated in activated microglia and in neurological conditions. The consequences of P2RY12 downregulation in disease-associated microglia and how they influence microglial activation remain poorly understood. In this study, we apply transcriptional and histological methods to explore the changes to microglia upon a genetic P2RY12 loss. Our findings reveal that P2RY12-deficient microglia experience alterations in distinct metabolic pathways while preserving overall homeostatic microglial transcriptional identity. Lack of P2RY12 alters signature genes involved in homeostatic iron metabolism. Importantly, the genes encoding proteins in the Glutathione Peroxidase 4 (Gpx4)-Glutathione (GSH) antioxidant pathway related to ferroptosis susceptibility are impaired upon microglial activation with lipopolysaccharide (LPS) treatment. These results highlight the critical role of P2RY12 in regulating microglial immune and metabolic transcriptional responses under both homeostatic and inflammatory conditions, providing insights into its involvement in CNS pathophysiology.

Keywords:  CNS homeostasis; LPS‐induced activation; P2RY12; disease‐associated microglia (DAM); ferroptosis; glutathione (GSH) antioxidant pathway; microglia; microglial metabolism; neuroinflammation; transcriptional regulation

DOI:  https://doi.org/10.1002/glia.70078
J Neurosci. 2025 Aug 13. pii: e0248252025. [Epub ahead of print]

Retinoid-X-Receptor as a Mediator of Post-Stroke Recovery by Reversing Age-Associated Phenotypes of Microglia/Hematogenous Macrophages.

Shun-Ming Ting, Xiurong Zhao, Guanghua Sun, Mercedes Ricote, Jaroslaw Aronowski.

After stroke, microglia and hematogenous macrophages, together referred to as MΦ, clear dead cells and cellular debris in the infarcted brain through phagocytosis as an essential part of the recovery process. However, the phagocytic capability of MΦ declines with age. Furthermore, aged MΦ become overactivated in response to stroke, enhancing secondary brain injury. In this study, we demonstrated that by reversing the age-related dysfunctions in MΦ through activating the retinoid x receptor (RXR), the recovery after stroke in the aged brain could be improved. Using RNA sequencing, we compared the transcriptomes between MΦ isolated from the brains of young and aged male mice. We observed higher levels of pro-inflammatory genes and lower levels of phagocytosis-facilitating genes (Cd206 and Cd36) expressed by aged MΦ. Meanwhile, the treatment with RXR agonist bexarotene (BEX) reversed the signature genes of microglia aging in the aged MΦ. With the in vivo phagocytosis model, we showed that BEX enhanced the phagocytic ability of aged MΦ. Using MCAo stroke model and male and female mice, we established that BEX improved sensorimotor and cognitive recovery after MCAo in a myeloid-RXRα-specific and -dependent manner. In conclusion, we showed that activating RXRα partially restores age-related MΦ dysfunctions and that RXRα deficiency in MΦ limits the therapeutic effect of RXR in improving post-stroke recovery in the aged brain.Significance Statement Aging is the most robust unmodifiable risk factor for ischemic stroke. The majority of stroke patients are individuals older than 65 years (Virani et al., 2020). Aging is also a predictor for worse outcomes (increased neurological deficit and mortality) after stroke. Despite this, only a limited number of studies attempted to elucidate the differences in post-stroke recovery between young and elderly subjects. One likely reason for worse repair/recovery in aged subjects after stroke is the decline in phagocytic and reparative properties of aged MΦ (Hefendehl et al., 2014; Koellhoffer et al., 2017). Aged MΦ may fail to clear cell debris and pro-inflammatory molecules from the ischemic brain, thereby worsening secondary injury and recovery after stroke (Shen et al., 2019).

DOI: https://doi.org/10.1523/JNEUROSCI.0248-25.2025
Front Aging. 2025 ;6 1628835

Beta-hydroxybutyrate (BHB) elicits concentration-dependent anti-inflammatory effects on microglial cells which are reversible by blocking its monocarboxylate (MCT) importer.

Chase Garcia, Ariana Banerjee, Claire Montgomery, Lauren Adcock, Izumi Maezawa, Jon Ramsey, Ana Cristina G Grodzki, Kyoungmi Kim, Gino Cortopassi.

   Introduction: The ketogenic diet (KD) increases mouse lifespan and health span, and improves late-life memory. This raises the question regarding the mechanism behind this effect. In mice on a KD, blood beta-hydroxybutyrate (BHB) levels uniquely rise higher than those of mice on a control diet (CD). BHB is therefore considered a key signaling and metabolic mediator of KD's effects and benefits. BHB crossed the blood-brain barrier and rescued memory, improved cognitive function, and increased neuronal plasticity in two different mouse models of Alzheimer's disease (PS1/APP and 5XFAD). At the cellular level, microglia are thought to play a critical role in the physiologic basis of memory due to their important role in synaptic development, plasticity, and connectivity. Conversely, microglial dysfunction and inflammation are connected to cognitive decline and neurodegenerative diseases. Because of this, one explanatory hypothesis for these positive therapeutic observations in mice is that the KD and BHB drive memory and longevity benefits through their anti-inflammatory actions on microglia.
Method: We investigated the concentration dependence of BHB's antiinflammatory effects in BV2 microglial cells. We focused on 1.5 mM BHB, which reflects blood levels in mice and humans on a KD.
Results: At this concentration, BHB significantly and concentration-dependently decreased the following: 1) inflammatory cytokine expression (IL-6, TNF-α, and IL-1β), 2) inflammatory morphological changes, and 3) activation of p-ERK and p-p38MAPK, which are key pathways involved in microglial inflammation. We show, for the first time, that the expression of Alzheimer's risk gene TREM2 is modified by dietarily-achievable 1.5 mM BHB. BHB's anti-inflammatory, morphological, biochemical, and TREM2 effects were blocked by a monocarboxylate transporter (MCT) inhibitor, supporting the idea that BHB must enter microglia to elicit some of its anti-inflammatory effects.
Discussion: These results support the hypothesis that blood BHB levels achievable on a KD elicit significant concentration-dependent anti-inflammatory effects in microglia. Increasing BHB concentration through sustained KD, or BHB supplements, may lower microglial inflammatory tone and provide benefits in age-related memory loss.

Keywords:  Alzheimer’s; Alzheimer’s disease; BHB; TREM2; beta-hydroxybutyrate; ketogenic diet; ketone; microglia

DOI:  https://doi.org/10.3389/fragi.2025.1628835
MAbs. 2025 Dec;17(1): 2546554

Building a potent TREM2 agonistic, biparatopic, common light chain antibody.

Ana da Silva Almeida, Melissa L Geddie, Anil Bhate, Chao Quan, Joseph W Arndt, Yang Jiao, Joseph C Santoro, Liron Noiman, Ramya Vijayakumar, Jorge Sanchez-Salazar, Abhishek Datta, Giovanna Antognetti, Ciputra Adijaya Hartana, Xue Fan Wang, Benjamin A Smith, Dan Bartlett, Danté Duncan, Chia-Chen Liu, Karel Otero Gutierrez, Thomas O Cameron, Samir Koirala, Heather A Cooke.

  Triggering Receptor Expressed on Myeloid cells 2 (TREM2) plays an important role in microglial function and has been genetically linked to Alzheimer's disease. Activation of TREM2 signaling may contribute to protection against neurotoxic effects of amyloid. Numerous TREM2 activating antibodies have been shown to modulate downstream microglial functions to different degrees, with mixed results in preclinical models and in the clinic. We sought to generate an effectorless agonistic antibody that acted solely through TREM2 engagement with sufficient potency to activate TREM2 in the brain. Our approach focused on building a multivalent biparatopic TREM2 antibody that could mimic the higher order clustering induced by native polyanionic ligands of TREM2. We describe our screening strategy and findings that led to the discovery of a potential therapeutic molecule composed of antibodies selected for optimal affinity, binding epitopes, and geometry. The most productive antibody pair was selected from a common light chain yeast-display library, which required multiple rounds of affinity maturation. Lead antibody candidates were converted into asymmetric tetravalent bispecifics via controlled Fab-arm exchange and subsequently screened in signaling assays. The most productive antibody pair was reengineered into a symmetric tetravalent format, increasing potency and simplifying development. This molecule exhibited higher efficacy and potency in signaling assays than other antibody formats tested and elicited TREM2-mediated chemokine responses in vivo. Our results demonstrate a biparatopic strategy for producing a high potency TREM2 agonistic antibody with low effector function that can modulate TREM2 signaling in vitro and brain pharmacodynamic responses in vivo.

Keywords:  Agonistic antibodies; Alzheimer’s disease; TREM2; biparatopic antibodies; bispecific antibodies; common light chain; microglia; neuroinflammation

DOI:  https://doi.org/10.1080/19420862.2025.2546554
Dev Neurobiol. 2025 Oct;85(4): e22997

Dectin-1 Drives Diabetic Retinopathy via Inducing Microglia-Mediated Inflammation and Blood-Retinal Barrier Breakdown.

Lei Zhang, Sumei Zhang, Yingjun Li, Zhen Yang, Weikang Hu, Hongmei Bai, Wenjing Zhou, Zihan Wang, Mingcong Li, Shengquan Zhang, Rongfeng Liao.

  Diabetic retinopathy (DR), a prevailing manifestation among diabetic patients, occurs as a major sight-threatening disorder. Dectin-1, as an innate immune receptor, has been notified as a critical modulator of diabetes mellitus. In this context, the implication of Dectin-1 in the process of DR that is still a conundrum will be addressed here. The diabetic mouse model was established by intraperitoneal injection of streptozotocin (STZ), and human microglia cells (HMC3) were subjected to high glucose (HG) to create cellular models of diabetes. Glucose level and body weight were recorded in mice. Reverse transcription-quantitative PCR (RT-qPCR) and western blotting checked Dectin-1 expression. RT-qPCR, enzyme-linked immunosorbent assay (ELISA), and western blotting appraised the inflammatory levels. Immunofluorescence staining and western blotting ascertained the expression of IBA-1 and tight junction proteins. Besides, western blotting also examined albumin expression. Terminal-deoxynucleoitidyl transferase mediated nick end labeling (TUNEL) assay and western blotting assayed the apoptotic level. Dectin-1 was highly expressed in both retinal tissues of diabetic mice and HG-exposed HMC3 cells. Dectin-1 antagonist laminarin (LAM) observably repressed microglia activation, inflammatory reaction, and blood-retinal barrier (BRB) leakage both in vitro and in vivo. Moreover, LAM produced anti-apoptotic effect in vivo. To sum up, Dectin-1 inhibitor might block the inflammatory cascade and protect against BRB disruption in DR.

Keywords:  Dectin‐1; blood–retinal barrier; diabetic retinopathy; inflammatory reaction; microglia

DOI:  https://doi.org/10.1002/dneu.22997
Curr Res Toxicol. 2025 ;9 100252

Neural organoids incorporating microglia to assess neuroinflammation and toxicities induced by known developmental neurotoxins.

Nina Y Yuan, William D Richards, Kailyn T Parham, Sophia G Clark, Kaylie Greuel, Brandon Polzin, Steven W Smith, Connie S Lebakken.

  The use of iPSC-derived complex in vitro 3D cellular constructs is a promising avenue to more accurately predict human neural toxicities and reduce the use of animal models. We have generated a neural organoid model which incorporates iPSC-derived microglia and enables interrogation of neuroinflammation induced by pre-clinical drug candidates of varying modalities and chemical compounds in industrial use. Herein we describe the generation and characterization of this model system and its utility in assessing toxicity. We exposed the neuroimmune organoids to a variety of developmental neurotoxins and measured cellular damage by release of LDH, GFAP, and NF-L into the cell culture supernatants. Additionally, to determine whether the compounds led to activation of microglia-mediated inflammation, we measured IL-8 secretion and assessed microglia-specific gene transcriptional analysis using bulk RNA sequencing. Spearman correlation matrices using both differentially expressed genes in the RNA sequencing data and pathway analysis using Gene Ontology Enrichment revealed that microglia may play a role in the toxicity of these compounds which has been widely overlooked in standardized neurotoxicity tests. Treatment of the organoids with lead acetate demonstrates a dose-response curve of IL-8 secretion and alterations in the microglial morphology. Our findings suggest that both direct neurotoxicity and indirect neuroinflammatory mechanisms contribute to the potentially harmful effects of these compounds in the developing central nervous system.

Keywords:  Developmental Neurotoxicity; Microglia; Neural Organoids; Neuroinflammation

DOI:  https://doi.org/10.1016/j.crtox.2025.100252