Identification of a protective microglial state mediated by miR-155 and interferon-γ signaling in a mouse model of Alzheimer's disease

Nature neuroscience

2023 Jun 08

Yin, Z;Herron, S;Silveira, S;Kleemann, K;Gauthier, C;Mallah, D;Cheng, Y;Margeta, MA;Pitts, KM;Barry, JL;Subramanian, A;Shorey, H;Brandao, W;Durao, A;Delpech, JC;Madore, C;Jedrychowski, M;Ajay, AK;Murugaiyan, G;Hersh, SW;Ikezu, S;Ikezu, T;Butovsky, O;
PMID: 37291336 | DOI: 10.1038/s41593-023-01355-y

Microglia play a critical role in brain homeostasis and disease progression. In neurodegenerative conditions, microglia acquire the neurodegenerative phenotype (MGnD), whose function is poorly understood. MicroRNA-155 (miR-155), enriched in immune cells, critically regulates MGnD. However, its role in Alzheimer's disease (AD) pathogenesis remains unclear. Here, we report that microglial deletion of miR-155 induces a pre-MGnD activation state via interferon-γ (IFN-γ) signaling, and blocking IFN-γ signaling attenuates MGnD induction and microglial phagocytosis. Single-cell RNA-sequencing analysis of microglia from an AD mouse model identifies Stat1 and Clec2d as pre-MGnD markers. This phenotypic transition enhances amyloid plaque compaction, reduces dystrophic neurites, attenuates plaque-associated synaptic degradation and improves cognition. Our study demonstrates a miR-155-mediated regulatory mechanism of MGnD and the beneficial role of IFN-γ-responsive pre-MGnD in restricting neurodegenerative pathology and preserving cognitive function in an AD mouse model, highlighting miR-155 and IFN-γ as potential therapeutic targets for AD.

Peripheral monocyte-derived cells counter amyloid plaque pathogenesis in a mouse model of Alzheimer's disease

The Journal of clinical investigation

2022 Jun 01

Yan, P;Kim, KW;Xiao, Q;Ma, X;Czerniewski, LR;Liu, H;Rawnsley, DR;Yan, Y;Randolph, GJ;Epelman, S;Lee, JM;Diwan, A;
PMID: 35511433 | DOI: 10.1172/JCI152565

Microglia, the parenchymal tissue macrophages in the brain, surround amyloid plaques in brains of individuals with Alzheimer's disease (AD) but are ineffective at clearing amyloid to mitigate disease progression. Recent studies in mice indicate that microglia are derived exclusively from primitive yolk sac hematopoiesis and self-renew without contribution from ontogenically distinct monocytes/macrophages of definitive adult hematopoietic origin. Using a genetic fate-mapping approach to label cells of definitive hematopoietic origin throughout life span, we discovered that circulating monocytes contribute 6% of plaque-associated macrophages in aged AD mice. Moreover, peripheral monocytes contributed to a higher fraction of macrophages in the choroid plexus, meninges, and perivascular spaces of aged AD mice versus WT control mice, indicating enrichment at potential sites for entry into the brain parenchyma. Splenectomy, which markedly reduced circulating Ly6Chi monocytes, also reduced abundance of plaque-associated macrophages of definitive hematopoietic origin, resulting in increased amyloid plaque load. Together, these results indicate that peripherally derived monocytes invade the brain parenchyma, targeting amyloid plaques to reduce plaque load.

Sustained Trem2 stabilization accelerates microglia heterogeneity and Aβ pathology in a mouse model of Alzheimer's disease

Cell reports

2022 May 31

Dhandapani, R;Neri, M;Bernhard, M;Brzak, I;Schweizer, T;Rudin, S;Joller, S;Berth, R;Kernen, J;Neuhaus, A;Waldt, A;Cuttat, R;Naumann, U;Keller, CG;Roma, G;Feuerbach, D;Shimshek, DR;Neumann, U;Gasparini, F;Galimberti, I;
PMID: 35649351 | DOI: 10.1016/j.celrep.2022.110883

TREM2 is a transmembrane protein expressed exclusively in microglia in the brain that regulates inflammatory responses to pathological conditions. Proteolytic cleavage of membrane TREM2 affects microglial function and is associated with Alzheimer's disease, but the consequence of reduced TREM2 proteolytic cleavage has not been determined. Here, we generate a transgenic mouse model of reduced Trem2 shedding (Trem2-Ile-Pro-Asp [IPD]) through amino-acid substitution of an ADAM-protease recognition site. We show that Trem2-IPD mice display increased Trem2 cell-surface-receptor load, survival, and function in myeloid cells. Using single-cell transcriptomic profiling of mouse cortex, we show that sustained Trem2 stabilization induces a shift of fate in microglial maturation and accelerates microglial responses to Aβ pathology in a mouse model of Alzheimer's disease. Our data indicate that reduction of Trem2 proteolytic cleavage aggravates neuroinflammation during the course of Alzheimer's disease pathology, suggesting that TREM2 shedding is a critical regulator of microglial activity in pathological states.

TREM2 splice isoforms generate soluble TREM2 species that disrupt long-term potentiation

Genome medicine

2023 Feb 20

Moutinho, M;Coronel, I;Tsai, AP;Di Prisco, GV;Pennington, T;Atwood, BK;Puntambekar, SS;Smith, DC;Martinez, P;Han, S;Lee, Y;Lasagna-Reeves, CA;Lamb, BT;Bissel, SJ;Nho, K;Landreth, GE;
PMID: 36805764 | DOI: 10.1186/s13073-023-01160-z

TREM2 is a transmembrane receptor expressed by myeloid cells and acts to regulate their immune response. TREM2 governs the response of microglia to amyloid and tau pathologies in the Alzheimer's disease (AD) brain. TREM2 is also present in a soluble form (sTREM2), and its CSF levels fluctuate as a function of AD progression. Analysis of stroke and AD mouse models revealed that sTREM2 proteins bind to neurons, which suggests sTREM2 may act in a non-cell autonomous manner to influence neuronal function. sTREM2 arises from the proteolytic cleavage of the membrane-associated receptor. However, alternatively spliced TREM2 species lacking a transmembrane domain have been postulated to contribute to the pool of sTREM2. Thus, both the source of sTREM2 species and its actions in the brain remain unclear.The expression of TREM2 isoforms in the AD brain was assessed through the analysis of the Accelerating Medicines Partnership for Alzheimer's Disease Consortium transcriptomics data, as well as qPCR analysis using post-mortem samples of AD patients and of the AD mouse model 5xFAD. TREM2 cleavage and secretion were studied in vitro using HEK-293T and HMC3 cell lines. Synaptic plasticity, as evaluated by induction of LTP in hippocampal brain slices, was employed as a measure of sTREM2 actions.Three distinct TREM2 transcripts, namely ENST00000373113 (TREM2230), which encodes the full-length transmembrane receptor, and the alternatively spliced isoforms ENST00000373122 (TREM2222) and ENST00000338469 (TREM2219), are moderately increased in specific brain regions of patients with AD. We provide experimental evidence that TREM2 alternatively spliced isoforms are translated and secreted as sTREM2. Furthermore, our functional analysis reveals that all sTREM2 species inhibit LTP induction, and this effect is abolished by the GABAA receptor antagonist picrotoxin.TREM2 transcripts can give rise to a heterogeneous pool of sTREM2 which acts to inhibit LTP. These results provide novel insight into the generation, regulation, and function of sTREM2 which fits into the complex biology of TREM2 and its role in human health and disease. Given that sTREM2 levels are linked to AD pathogenesis and progression, our finding that sTREM2 species interfere with LTP furthers our understanding about the role of TREM2 in AD.

Aging compromises oligodendrocyte precursor cell maturation and efficient remyelination in the monkey brain

GeroScience

2022 Aug 05

Dimovasili, C;Fair, AE;Garza, IR;Batterman, KV;Mortazavi, F;Moore, TL;Rosene, DL;
PMID: 35930094 | DOI: 10.1007/s11357-022-00621-4

Age-associated cognitive decline is common among otherwise healthy elderly people, even in the absence of Alzheimer's disease and neuron loss. Instead, white matter loss and myelin damage are strongly associated with cognitive decline. Myelin is subject to lifelong oxidative stress that damages the myelin sheath, which is repaired by cells of the oligodendrocyte lineage. This process is mediated by oligodendrocyte precursor cells (OPCs) that sense the damage and respond by proliferating locally and migrating to the region, where they differentiate into mature myelinating oligodendrocytes. In aging, extensive myelin damage, in combination with inefficient remyelination, leads to chronically damaged myelin and loss of efficient neuronal conduction. This study used the rhesus monkey model of normal aging to examine how myelin regeneration capacity is affected by age. Results show that older subjects have reduced numbers of new BCAS1 + myelinating oligodendrocytes, which are newly formed cells, and that this reduction is associated with poorer cognitive performance. Interestingly, this does not result from limited proliferation of progenitor OPCs. Instead, the transcription factor NKX2.2, which regulates OPCs differentiation, is significantly decreased in aged OPCs. This suggests that these OPCs have a diminished potential for differentiation into mature oligodendrocytes. In addition, mature oligodendrocytes have reduced RNA expression of two essential myelin protein markers, MBP and PLP. These data collectively suggest that in the normal aging brain, there is a reduction in regenerative OPCs as well as myelin production that impairs the capacity for remyelination.

Microglial INPP5D limits plaque formation and glial reactivity in the PSAPP mouse model of Alzheimer's disease

Alzheimer's & dementia : the journal of the Alzheimer's Association

2022 Nov 30

Castranio, EL;Hasel, P;Haure-Mirande, JV;Ramirez Jimenez, AV;Hamilton, BW;Kim, RD;Glabe, CG;Wang, M;Zhang, B;Gandy, S;Liddelow, SA;Ehrlich, ME;
PMID: 36448627 | DOI: 10.1002/alz.12821

The inositol polyphosphate-5-phosphatase D (INPP5D) gene encodes a dual-specificity phosphatase that can dephosphorylate both phospholipids and phosphoproteins. Single nucleotide polymorphisms in INPP5D impact risk for developing late onset sporadic Alzheimer's disease (LOAD).To assess the consequences of inducible Inpp5d knockdown in microglia of APPKM670/671NL /PSEN1Δexon9 (PSAPP) mice, we injected 3-month-old Inpp5dfl/fl /Cx3cr1CreER/+ and PSAPP/Inpp5dfl/fl /Cx3cr1CreER/+ mice with either tamoxifen (TAM) or corn oil (CO) to induce recombination.At age 6 months, we found that the percent area of 6E10+ deposits and plaque-associated microglia in Inpp5d knockdown mice were increased compared to controls. Spatial transcriptomics identified a plaque-specific expression profile that was extensively altered by Inpp5d knockdown.These results demonstrate that conditional Inpp5d downregulation in the PSAPP mouse increases plaque burden and recruitment of microglia to plaques. Spatial transcriptomics highlighted an extended gene expression signature associated with plaques and identified CST7 (cystatin F) as a novel marker of plaques.Inpp5d knockdown increases plaque burden and plaque-associated microglia number. Spatial transcriptomics identifies an expanded plaque-specific gene expression profile. Plaque-induced gene expression is altered by Inpp5d knockdown in microglia. Our plaque-associated gene signature overlaps with human Alzheimer's disease gene networks.

HnRNP K mislocalisation in neurons of the dentate nucleus is a novel neuropathological feature of neurodegenerative disease and ageing

Neuropathology and applied neurobiology

2022 Jun 01

Sidhu, R;Gatt, A;Fratta, P;Lashley, T;Bampton, A;
PMID: 35064577 | DOI: 10.1111/nan.12793

Nuclear depletion and cytoplasmic mislocalisation of the RNA-binding protein heterogeneous ribonucleoprotein K (hnRNP K) within pyramidal neurons of the frontal cortex have been shown to be a common neuropathological feature in frontotemporal lobar degeneration (FTLD) and elderly control brain. Here, we describe a second neuronal subtype vulnerable to mislocalisation within the dentate nucleus of the cerebellum. In contrast to neurons within the cerebellar cortex that typically exhibited normal, nuclear staining, many neurons of the dentate nucleus exhibited striking mislocalisation of hnRNP K to the cytoplasm within neurodegenerative disease brain. Mislocalisation frequency in this region was found to be significantly higher in both FTLD-TDP A and Alzheimer's disease (AD) brain than in age-matched controls. However, within control (but not disease) subjects, mislocalisation frequency was significantly associated with age-at-death with more elderly controls typically exhibiting greater levels of the pathology. This study provides further evidence for hnRNP K mislocalisation being a more anatomically diverse pathology than previously thought and suggests that potential dysfunction of the protein may be more broadly relevant to the fields of neurodegeneration and ageing.

Elevating microglia TREM2 reduces amyloid seeding and suppresses disease-associated microglia

The Journal of experimental medicine

2022 Dec 05

Zhao, N;Qiao, W;Li, F;Ren, Y;Zheng, J;Martens, YA;Wang, X;Li, L;Liu, CC;Chen, K;Zhu, Y;Ikezu, TC;Li, Z;Meneses, AD;Jin, Y;Knight, JA;Chen, Y;Bastea, L;Linares, C;Sonustun, B;Job, L;Smith, ML;Xie, M;Liu, YU;Umpierre, AD;Haruwaka, K;Quicksall, ZS;Storz, P;Asmann, YW;Wu, LJ;Bu, G;
PMID: 36107206 | DOI: 10.1084/jem.20212479

TREM2 is exclusively expressed by microglia in the brain and is strongly linked to the risk for Alzheimer's disease (AD). As microglial responses modulated by TREM2 are central to AD pathogenesis, enhancing TREM2 signaling has been explored as an AD therapeutic strategy. However, the effective therapeutic window targeting TREM2 is unclear. Here, by using microglia-specific inducible mouse models overexpressing human wild-type TREM2 (TREM2-WT) or R47H risk variant (TREM2-R47H), we show that TREM2-WT expression reduces amyloid deposition and neuritic dystrophy only during the early amyloid seeding stage, whereas TREM2-R47H exacerbates amyloid burden during the middle amyloid rapid growth stage. Single-cell RNA sequencing reveals suppressed disease-associated microglia (DAM) signature and reduced DAM population upon TREM2-WT expression in the early stage, whereas upregulated antigen presentation pathway is detected with TREM2-R47H expression in the middle stage. Together, our findings highlight the dynamic effects of TREM2 in modulating AD pathogenesis and emphasize the beneficial effect of enhancing TREM2 function in the early stage of AD development.

Attenuation of Alzheimer's brain pathology in 5XFAD mice by PTH1-34, a peptide of parathyroid hormone

Alzheimer's research & therapy

2023 Mar 14

Chen, L;Xiong, L;Yao, L;Pan, J;Arzola, E;Zhu, X;Mei, L;Xiong, WC;
PMID: 36918976 | DOI: 10.1186/s13195-023-01202-z

Alzheimer's disease (AD) and osteoporosis are two distinct diseases but often occur in the same patient. Their relationship remains poorly understood. Studies using Tg2576 AD animal model demonstrate bone deficits, which precede the brain phenotypes by several months, arguing for the independence of bone deficits on brain degeneration and raising a question if the bone deficits contribute to the AD development. To address this question, we investigated the effects of PTH1-34, a peptide of parathyroid hormone analog and a well-recognized effective anabolic therapy drug for patients with osteoporosis, on 5XFAD animal model.5XFAD mice, an early onset β-amyloid (Aβ)-based AD mouse model, were treated with PTH1-34 intermittently [once daily injection of hPTH1-34 (50 μg/Kg), 5 days/week, starting at 2-month old (MO) for 2-3 month]. Wild type mice (C57BL/6) were used as control. The bone phenotypes were examined by microCT and evaluated by measuring serum bone formation and resorption markers. The AD relevant brain pathology (e.g., Aβ and glial activation) and behaviors were assessed by a combination of immunohistochemical staining analysis, western blots, and behavior tests. Additionally, systemic and brain inflammation were evaluated by serum cytokine array, real-time PCR (qPCR), and RNAscope.A reduced trabecular, but not cortical, bone mass, accompanied with a decrease in bone formation and an increase in bone resorption, was detected in 5XFAD mice at age of 5/6-month old (MO). Upon PTH1-34 treatments, not only these bone deficits but also Aβ-associated brain pathologies, including Aβ and Aβ deposition levels, dystrophic neurites, glial cell activation, and brain inflammatory cytokines, were all diminished; and the cognitive function was improved. Further studies suggest that PTH1-34 acts on not only osteoblasts in the bone but also astrocytes in the brain, suppressing astrocyte senescence and expression of inflammatory cytokines in 5XFAD mice.These results suggest that PTH1-34 may act as a senolytic-like drug, reducing systemic and brain inflammation and improving cognitive function, and implicate PTH1-34's therapeutic potential for patients with not only osteoporosis but also AD.

Single-cell transcriptomic atlas of Alzheimer's disease middle temporal gyrus reveals region, cell type and sex specificity of gene expression with novel genetic risk for MERTK in female

medRxiv : the preprint server for health sciences

2023 Feb 23

Zhang, L;He, CH;Coffey, S;Yin, D;Hsu, IU;Su, C;Ye, Y;Zhang, C;Spurrier, J;Nicholson, L;Rothlin, CV;Ghosh, S;Gopal, PP;Hafler, DA;Zhao, H;Strittmatter, SM;
PMID: 36865305 | DOI: 10.1101/2023.02.18.23286037

Alzheimer's disease, the most common age-related neurodegenerative disease, is closely associated with both amyloid-ß plaque and neuroinflammation. Two thirds of Alzheimer's disease patients are females and they have a higher disease risk. Moreover, women with Alzheimer's disease have more extensive brain histological changes than men along with more severe cognitive symptoms and neurodegeneration. To identify how sex difference induces structural brain changes, we performed unbiased massively parallel single nucleus RNA sequencing on Alzheimer's disease and control brains focusing on the middle temporal gyrus, a brain region strongly affected by the disease but not previously studied with these methods. We identified a subpopulation of selectively vulnerable layer 2/3 excitatory neurons that that were RORB-negative and CDH9-expressing. This vulnerability differs from that reported for other brain regions, but there was no detectable difference between male and female patterns in middle temporal gyrus samples. Disease-associated, but sex-independent, reactive astrocyte signatures were also present. In clear contrast, the microglia signatures of diseased brains differed between males and females. Combining single cell transcriptomic data with results from genome-wide association studies (GWAS), we identified MERTK genetic variation as a risk factor for Alzheimer's disease selectively in females. Taken together, our single cell dataset revealed a unique cellular-level view of sex-specific transcriptional changes in Alzheimer's disease, illuminating GWAS identification of sex-specific Alzheimer's risk genes. These data serve as a rich resource for interrogation of the molecular and cellular basis of Alzheimer's disease.

Brain macrophage development, diversity and dysregulation in health and disease

Cellular & molecular immunology

2023 Jun 26

Silvin, A;Qian, J;Ginhoux, F;
PMID: 37365324 | DOI: 10.1038/s41423-023-01053-6

Brain macrophages include microglia in the parenchyma, border-associated macrophages in the meningeal-choroid plexus-perivascular space, and monocyte-derived macrophages that infiltrate the brain under various disease conditions. The vast heterogeneity of these cells has been elucidated over the last decade using revolutionary multiomics technologies. As such, we can now start to define these various macrophage populations according to their ontogeny and their diverse functional programs during brain development, homeostasis and disease pathogenesis. In this review, we first outline the critical roles played by brain macrophages during development and healthy aging. We then discuss how brain macrophages might undergo reprogramming and contribute to neurodegenerative disorders, autoimmune diseases, and glioma. Finally, we speculate about the most recent and ongoing discoveries that are prompting translational attempts to leverage brain macrophages as prognostic markers or therapeutic targets for diseases that affect the brain.

Blood-brain barrier penetration of non-replicating SARS-CoV-2 and S1 Variants of Concern induce neuroinflammation which is accentuated in a mouse model of Alzheimer's disease

Brain, behavior, and immunity

2023 Jan 19

Erickson, MA;Logsdon, AF;Rhea, EM;Hansen, KM;Holden, SJ;Banks, WA;Smith, JL;German, C;Farr, SA;Morley, JE;Weaver, RR;Hirsch, AJ;Kovac, A;Kontsekova, E;Baumann, KK;Omer, MA;Raber, J;
PMID: 36682515 | DOI: 10.1016/j.bbi.2023.01.010

COVID-19 and especially Long COVID are associated with severe CNS symptoms and may place persons at risk to develop long-term cognitive impairments. Here, we show that two non-infective models of SARS-CoV-2 can cross the blood-brain barrier (BBB) and induce neuroinflammation, a major mechanism underpinning CNS and cognitive impairments, even in the absence of productive infection. The viral models cross the BBB by the mechanism of adsorptive transcytosis with the sugar N-acetylglucosamine being key. The delta and omicron variants cross the BBB faster than the other variants of concern, with peripheral tissue uptake rates also differing for the variants. Neuroinflammation induced by icv injection of S1 protein was greatly enhanced in young and especially in aged SAMP8 mice, a model of Alzheimer's disease, whereas sex and obesity had little effect.

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	Description
sense Example: Hs-LAG3-sense	Standard probes for RNA detection are in antisense. Sense probe is reverse complent to the corresponding antisense probe.
Intron# Example: Mm-Htt-intron2	Probe targets the indicated intron in the target gene, commonly used for pre-mRNA detection
Pool/Pan Example: Hs-CD3-pool (Hs-CD3D, Hs-CD3E, Hs-CD3G)	A mixture of multiple probe sets targeting multiple genes or transcripts
No-XSp Example: Hs-PDGFB-No-XMm	Does not cross detect with the species (Sp)
XSp Example: Rn-Pde9a-XMm	designed to cross detect with the species (Sp)
O# Example: Mm-Islr-O1	Alternative design targeting different regions of the same transcript or isoforms
CDS Example: Hs-SLC31A-CDS	Probe targets the protein-coding sequence only
EnEm	Probe targets exons n and m
En-Em	Probe targets region from exon n to exon m
Retired Nomenclature
tvn Example: Hs-LEPR-tv1	Designed to target transcript variant n
ORF Example: Hs-ACVRL1-ORF	Probe targets open reading frame
UTR Example: Hs-HTT-UTR-C3	Probe targets the untranslated region (non-protein-coding region) only
5UTR Example: Hs-GNRHR-5UTR	Probe targets the 5' untranslated region only
3UTR Example: Rn-Npy1r-3UTR	Probe targets the 3' untranslated region only
Pan Example: Pool	A mixture of multiple probe sets targeting multiple genes or transcripts

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