RESUMO
Genetic studies have highlighted microglia as pivotal in orchestrating Alzheimer's disease (AD). Microglia that adhere to Aß plaques acquire a transcriptional signature, "disease-associated microglia" (DAM), which largely emanates from the TREM2-DAP12 receptor complex that transmits intracellular signals through the protein tyrosine kinase SYK. The human TREM2R47H variant associated with high AD risk fails to activate microglia via SYK. We found that SYK-deficient microglia cannot encase Aß plaques, accelerating brain pathology and behavioral deficits. SYK deficiency impaired the PI3K-AKT-GSK-3ß-mTOR pathway, incapacitating anabolic support required for attaining the DAM profile. However, SYK-deficient microglia proliferated and advanced to an Apoe-expressing prodromal stage of DAM; this pathway relied on the adapter DAP10, which also binds TREM2. Thus, microglial responses to Aß involve non-redundant SYK- and DAP10-pathways. Systemic administration of an antibody against CLEC7A, a receptor that directly activates SYK, rescued microglia activation in mice expressing the TREM2R47H allele, unveiling new options for AD immunotherapy.
Assuntos
Doença de Alzheimer , Microglia , Animais , Camundongos , Humanos , Microglia/metabolismo , Glicogênio Sintase Quinase 3 beta/metabolismo , Fosfatidilinositol 3-Quinases/metabolismo , Peptídeos beta-Amiloides/metabolismo , Doença de Alzheimer/patologia , Placa Amiloide/metabolismo , Encéfalo/metabolismo , Modelos Animais de Doenças , Quinase Syk/metabolismo , Glicoproteínas de Membrana/genética , Glicoproteínas de Membrana/metabolismo , Receptores Imunológicos/metabolismoRESUMO
Checkpoint immunotherapy unleashes T cell control of tumors, but is undermined by immunosuppressive myeloid cells. TREM2 is a myeloid receptor that transmits intracellular signals that sustain microglial responses during Alzheimer's disease. TREM2 is also expressed by tumor-infiltrating macrophages. Here, we found that Trem2-/- mice are more resistant to growth of various cancers than wild-type mice and are more responsive to anti-PD-1 immunotherapy. Furthermore, treatment with anti-TREM2 mAb curbed tumor growth and fostered regression when combined with anti-PD-1. scRNA-seq revealed that both TREM2 deletion and anti-TREM2 are associated with scant MRC1+ and CX3CR1+ macrophages in the tumor infiltrate, paralleled by expansion of myeloid subsets expressing immunostimulatory molecules that promote improved T cell responses. TREM2 was expressed in tumor macrophages in over 200 human cancer cases and inversely correlated with prolonged survival for two types of cancer. Thus, TREM2 might be targeted to modify tumor myeloid infiltrates and augment checkpoint immunotherapy.
Assuntos
Imunoterapia , Glicoproteínas de Membrana/metabolismo , Neoplasias/terapia , Receptor de Morte Celular Programada 1/imunologia , Receptores Imunológicos/metabolismo , Animais , Anticorpos Monoclonais/uso terapêutico , Receptor 1 de Quimiocina CX3C/metabolismo , Linhagem Celular Tumoral , Modelos Animais de Doenças , Humanos , Linfócitos do Interstício Tumoral/citologia , Linfócitos do Interstício Tumoral/metabolismo , Glicoproteínas de Membrana/deficiência , Glicoproteínas de Membrana/genética , Metilcolantreno/toxicidade , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Neoplasias/induzido quimicamente , Neoplasias/patologia , Prognóstico , Receptor de Morte Celular Programada 1/metabolismo , Receptores Imunológicos/deficiência , Receptores Imunológicos/genética , Microambiente TumoralRESUMO
Recent single-cell RNA sequencing studies have revealed distinct microglial states in development and disease. These include proliferative-region-associated microglia (PAMs) in developing white matter and disease-associated microglia (DAMs) prevalent in various neurodegenerative conditions. PAMs and DAMs share a similar core gene signature. However, the extent of the dynamism and plasticity of these microglial states, as well as their functional significance, remains elusive, partly due to the lack of specific tools. Here, we generated an inducible Cre driver line, Clec7a-CreERT2, that targets PAMs and DAMs in the brain parenchyma. Utilizing this tool, we profiled labeled cells during development and in several disease models, uncovering convergence and context-dependent differences in PAM and DAM gene expression. Through long-term tracking, we demonstrated microglial state plasticity. Lastly, we specifically depleted DAMs in demyelination, revealing their roles in disease recovery. Together, we provide a versatile genetic tool to characterize microglial states in CNS development and disease.
Assuntos
Plasticidade Celular , Microglia , Remielinização , Microglia/fisiologia , Animais , Camundongos , Plasticidade Celular/genética , Doenças Desmielinizantes/genética , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Modelos Animais de Doenças , Encéfalo , Bainha de Mielina/metabolismo , Substância Branca/patologiaRESUMO
Genetic tools to target microglia specifically and efficiently from the early stages of embryonic development are lacking. We generated a constitutive Cre line controlled by the microglia signature gene Crybb1 that produced nearly complete recombination in embryonic brain macrophages (microglia and border-associated macrophages [BAMs]) by the perinatal period, with limited recombination in peripheral myeloid cells. Using this tool in combination with Flt3-Cre lineage tracer, single-cell RNA-sequencing analysis, and confocal imaging, we resolved embryonic-derived versus monocyte-derived BAMs in the mouse cortex. Deletion of the transcription factor SMAD4 in microglia and embryonic-derived BAMs using Crybb1-Cre caused a developmental arrest of microglia, which instead acquired a BAM specification signature. By contrast, the development of genuine BAMs remained unaffected. Our results reveal that SMAD4 drives a transcriptional and epigenetic program that is indispensable for the commitment of brain macrophages to the microglia fate and highlight Crybb1-Cre as a tool for targeting embryonic brain macrophages.
Assuntos
Macrófagos , Microglia , Camundongos , Animais , Microglia/metabolismo , Macrófagos/metabolismo , Integrases/genética , Integrases/metabolismo , Encéfalo/metabolismoRESUMO
Systematic understanding of immune aging on a whole-body scale is currently lacking. We characterized age-associated alterations in immune cells across multiple mouse organs using single-cell RNA and antigen receptor sequencing and flow cytometry-based validation. We defined organ-specific and common immune alterations and identified a subpopulation of age-associated granzyme K (GZMK)-expressing CD8+ T (Taa) cells that are distinct from T effector memory (Tem) cells. Taa cells were highly clonal, had specific epigenetic and transcriptional signatures, developed in response to an aged host environment, and expressed markers of exhaustion and tissue homing. Activated Taa cells were the primary source of GZMK, which enhanced inflammatory functions of non-immune cells. In humans, proportions of the circulating GZMK+CD8+ T cell population that shares transcriptional and epigenetic signatures with mouse Taa cells increased during healthy aging. These results identify GZMK+ Taa cells as a potential target to address age-associated dysfunctions of the immune system.
Assuntos
Envelhecimento/fisiologia , Linfócitos T CD8-Positivos/fisiologia , Sistema Imunitário/fisiologia , Inflamação/imunologia , Receptores de Antígenos de Linfócitos B/genética , Receptores de Antígenos de Linfócitos T/genética , Animais , Células Cultivadas , Células Clonais , Citotoxicidade Imunológica , Feminino , Perfilação da Expressão Gênica , Granzimas/metabolismo , Humanos , Memória Imunológica , Camundongos , Camundongos Endogâmicos C57BL , Análise de Sequência de RNA , Análise de Célula Única , TranscriptomaRESUMO
CD4+ T cells can either enhance or inhibit tumour immunity. Although regulatory T cells have long been known to impede antitumour responses1-5, other CD4+ T cells have recently been implicated in inhibiting this response6,7. Yet, the nature and function of the latter remain unclear. Here, using vaccines containing MHC class I (MHC-I) neoantigens (neoAgs) and different doses of tumour-derived MHC-II neoAgs, we discovered that whereas the inclusion of vaccines with low doses of MHC-II-restricted peptides (LDVax) promoted tumour rejection, vaccines containing high doses of the same MHC-II neoAgs (HDVax) inhibited rejection. Characterization of the inhibitory cells induced by HDVax identified them as type 1 regulatory T (Tr1) cells expressing IL-10, granzyme B, perforin, CCL5 and LILRB4. Tumour-specific Tr1 cells suppressed tumour rejection induced by anti-PD1, LDVax or adoptively transferred tumour-specific effector T cells. Mechanistically, HDVax-induced Tr1 cells selectively killed MHC-II tumour antigen-presenting type 1 conventional dendritic cells (cDC1s), leading to low numbers of cDC1s in tumours. We then documented modalities to overcome this inhibition, specifically via anti-LILRB4 blockade, using a CD8-directed IL-2 mutein, or targeted loss of cDC2/monocytes. Collectively, these data show that cytotoxic Tr1 cells, which maintain peripheral tolerance, also inhibit antitumour responses and thereby function to impede immune control of cancer.
Assuntos
Antígenos de Neoplasias , Linfócitos T CD4-Positivos , Citotoxicidade Imunológica , Imunoterapia , Neoplasias , Linfócitos T Reguladores , Animais , Feminino , Humanos , Masculino , Camundongos , Antígenos de Neoplasias/imunologia , Vacinas Anticâncer/imunologia , Vacinas Anticâncer/uso terapêutico , Linfócitos T CD4-Positivos/imunologia , Linfócitos T CD4-Positivos/metabolismo , Linhagem Celular Tumoral , Quimiocina CCL5/metabolismo , Células Dendríticas/imunologia , Granzimas/metabolismo , Antígenos de Histocompatibilidade Classe I/imunologia , Antígenos de Histocompatibilidade Classe II/imunologia , Interleucina-10/metabolismo , Interleucina-10/imunologia , Camundongos Endogâmicos C57BL , Neoplasias/imunologia , Neoplasias/terapia , Linfócitos T Reguladores/imunologia , Receptores Imunológicos/antagonistas & inibidores , Glicoproteínas de Membrana/antagonistas & inibidores , Tolerância Imunológica , Linfócitos T CD8-Positivos/imunologiaRESUMO
Recent studies have characterized various mouse antigen-presenting cells (APCs) expressing the lymphoid-lineage transcription factor RORγt (Retinoid-related orphan receptor gamma t), which exhibit distinct phenotypic features and are implicated in the induction of peripheral regulatory T cells (Tregs) and immune tolerance to microbiota and self-antigens. These APCs encompass Janus cells and Thetis cell subsets, some of which express the AutoImmune REgulator (AIRE). RORγt+ MHCII+ type 3 innate lymphoid cells (ILC3) have also been implicated in the instruction of microbiota-specific Tregs. While RORγt+ APCs have been actively investigated in mice, the identity and function of these cell subsets in humans remain elusive. Herein, we identify a rare subset of RORγt+ cells with dendritic cell (DC) features through integrated single-cell RNA sequencing and single-cell ATAC sequencing. These cells, which we term RORγt+ DC-like cells (R-DC-like), exhibit DC morphology, express the MHC class II machinery, and are distinct from all previously reported DC and ILC3 subsets, but share transcriptional and epigenetic similarities with DC2 and ILC3. We have developed procedures to isolate and expand them in vitro, enabling their functional characterization. R-DC-like cells proliferate in vitro, continue to express RORγt, and differentiate into CD1c+ DC2-like cells. They stimulate the proliferation of allogeneic T cells. The identification of human R-DC-like cells with proliferative potential and plasticity toward CD1c+ DC2-like cells will prompt further investigation into their impact on immune homeostasis, inflammation, and autoimmunity.
Assuntos
Imunidade Inata , Linfócitos , Humanos , Camundongos , Animais , Membro 3 do Grupo F da Subfamília 1 de Receptores Nucleares/metabolismo , Inflamação/metabolismo , Células DendríticasRESUMO
Triggering receptor expressed on myeloid cells 2 (TREM2) sustains microglia response to brain injury stimuli including apoptotic cells, myelin damage, and amyloid ß (Aß). Alzheimer's disease (AD) risk is associated with the TREM2R47H variant, which impairs ligand binding and consequently microglia responses to Aß pathology. Here, we show that TREM2 engagement by the mAb hT2AB as surrogate ligand activates microglia in 5XFAD transgenic mice that accumulate Aß and express either the common TREM2 variant (TREM2CV) or TREM2R47H scRNA-seq of microglia from TREM2CV-5XFAD mice treated once with control hIgG1 exposed four distinct trajectories of microglia activation leading to disease-associated (DAM), interferon-responsive (IFN-R), cycling (Cyc-M), and MHC-II expressing (MHC-II) microglia types. All of these were underrepresented in TREM2R47H-5XFAD mice, suggesting that TREM2 ligand engagement is required for microglia activation trajectories. Moreover, Cyc-M and IFN-R microglia were more abundant in female than male TREM2CV-5XFAD mice, likely due to greater Aß load in female 5XFAD mice. A single systemic injection of hT2AB replenished Cyc-M, IFN-R, and MHC-II pools in TREM2R47H-5XFAD mice. In TREM2CV-5XFAD mice, however, hT2AB brought the representation of male Cyc-M and IFN-R microglia closer to that of females, in which these trajectories had already reached maximum capacity. Moreover, hT2AB induced shifts in gene expression patterns in all microglial pools without affecting representation. Repeated treatment with a murinized hT2AB version over 10 d increased chemokines brain content in TREM2R47H-5XFAD mice, consistent with microglia expansion. Thus, the impact of hT2AB on microglia is shaped by the extent of TREM2 endogenous ligand engagement and basal microglia activation.
Assuntos
Doença de Alzheimer/genética , Encéfalo/metabolismo , Glicoproteínas de Membrana/genética , Microglia/metabolismo , Receptores Imunológicos/genética , Doença de Alzheimer/tratamento farmacológico , Doença de Alzheimer/metabolismo , Doença de Alzheimer/patologia , Peptídeos beta-Amiloides/genética , Peptídeos beta-Amiloides/metabolismo , Animais , Anticorpos Monoclonais/farmacologia , Anticorpos Neutralizantes/farmacologia , Encéfalo/efeitos dos fármacos , Encéfalo/patologia , Proliferação de Células , Quimiocinas/genética , Quimiocinas/metabolismo , Modelos Animais de Doenças , Feminino , Regulação da Expressão Gênica , Células HEK293 , Humanos , Cinética , Masculino , Glicoproteínas de Membrana/antagonistas & inibidores , Glicoproteínas de Membrana/metabolismo , Camundongos , Camundongos Transgênicos , Microglia/classificação , Microglia/efeitos dos fármacos , Microglia/patologia , Mutação , Ligação Proteica , Receptores Imunológicos/antagonistas & inibidores , Receptores Imunológicos/metabolismo , Fatores SexuaisRESUMO
A key pathological process in Parkinson's disease (PD) is the transneuronal spreading of α-synuclein. Alpha-synuclein (α-syn) is a presynaptic protein that, in PD, forms pathological inclusions. Other hallmarks of PD include neurodegeneration and microgliosis in susceptible brain regions. Whether it is primarily transneuronal spreading of α-syn particles, inclusion formation, or other mechanisms, such as inflammation, that cause neurodegeneration in PD is unclear. We used a model of spreading of α-syn induced by striatal injection of α-syn preformed fibrils into the mouse striatum to address this question. We performed quantitative analysis for α-syn inclusions, neurodegeneration, and microgliosis in different brain regions, and generated gene expression profiles of the ventral midbrain, at two different timepoints after disease induction. We observed significant neurodegeneration and microgliosis in brain regions not only with, but also without α-syn inclusions. We also observed prominent microgliosis in injured brain regions that did not correlate with neurodegeneration nor with inclusion load. Using longitudinal gene expression profiling, we observed early gene expression changes, linked to neuroinflammation, that preceded neurodegeneration, indicating an active role of microglia in this process. Altered gene pathways overlapped with those typical of PD. Our observations indicate that α-syn inclusion formation is not the major driver in the early phases of PD-like neurodegeneration, but that microglia, activated by diffusible, oligomeric α-syn, may play a key role in this process. Our findings uncover new features of α-syn induced pathologies, in particular microgliosis, and point to the necessity for a broader view of the process of α-syn spreading.
Assuntos
Doença de Parkinson , alfa-Sinucleína/metabolismo , Animais , Modelos Animais de Doenças , Camundongos , Microglia/metabolismo , Doenças Neuroinflamatórias , Doença de Parkinson/genética , alfa-Sinucleína/genéticaRESUMO
Microglia are parenchymal macrophages of the CNS; as professional phagocytes they are important for maintenance of the brain's physiology. These cells are generated through primitive hematopoiesis in the yolk sac and migrate into the brain rudiment after establishment of embryonic circulation. Thereafter, microglia develop in a stepwise fashion, reaching complete maturity after birth. In the CNS, microglia self-renew without input from blood monocytes. Recent RNA-sequencing studies have defined a molecular signature for microglia under homeostasis. However, during disease, microglia undergo remarkable phenotypic changes, which reflect the acquisition of specialized functions tailored to the pathological context. In addition to microglia, the brain-border regions host populations of extraparenchymal macrophages with disparate origins and phenotypes that have recently been delineated. In this review we outline recent findings that provide a deeper understanding of both parenchymal microglia and extraparenchymal brain macrophages in homeostasis and during disease.
Assuntos
Encéfalo/citologia , Encéfalo/imunologia , Macrófagos , Microglia , Animais , Linhagem da Célula , Homeostase/imunologia , Humanos , Macrófagos/citologia , Macrófagos/imunologia , Microglia/citologia , Microglia/imunologiaRESUMO
Brain inflammation is a critical factor involved in neurodegeneration. Recently, the prostaglandin E2 (PGE2 ) downstream members were suggested to modulate neuroinflammatory responses accompanying neurodegenerative diseases. In this study, we investigated the protective effects of prostaglandin E2 receptor 2 (EP2 ) during TLR3 and TLR4-driven inflammatory response using in vitro primary microglia and ex vivo organotypic hippocampal slice cultures (OHSCs). Depletion of microglia from OHSCs differentially affected TLR3 and TLR4 receptor expression. Poly(I:C) induced the production of prostaglandin E2 in OHSCs by increasing cyclooxygenase (COX-2) and microsomal prostaglandin E synthase (mPGES)-1. Besides, stimulation of OHSCs and microglia with Poly(I:C) upregulated EP2 receptor expression. Co-stimulation of OHSCs and microglia with the EP2 agonist butaprost reduced inflammatory mediators induced by LPS and Poly(I:C). In Poly(I:C) challenged OHSCs, butaprost almost restored microglia ramified morphology and reduced Iba1 immunoreactivity. Importantly, microglia depletion prevented the induction of inflammatory mediators following Poly(I:C) or LPS challenge in OHSCs. Activation of EP2 receptor reversed the Poly(I:C)/LPS-induced phosphorylation of the mitogen activated protein kinases (MAPKs) ERK, p38 MAPK and c-Jun N-terminal kinase (JNK) in microglia. Collectively, these data identify an anti-inflammatory function for EP2 signaling in diverse innate immune responses, through a mechanism that involves the mitogen-activated protein kinases pathway.
Assuntos
Hipocampo/imunologia , Inflamação/metabolismo , Microglia/imunologia , Proteínas Quinases Ativadas por Mitógeno/metabolismo , Receptores de Prostaglandina E Subtipo EP2/metabolismo , Alprostadil/análogos & derivados , Alprostadil/farmacologia , Animais , Proteínas de Ligação ao Cálcio/metabolismo , Células Cultivadas , Córtex Cerebral/efeitos dos fármacos , Córtex Cerebral/imunologia , Córtex Cerebral/patologia , Hipocampo/efeitos dos fármacos , Hipocampo/patologia , Imunidade Inata/fisiologia , Fatores Imunológicos/farmacologia , Inflamação/tratamento farmacológico , Inflamação/patologia , Lipopolissacarídeos , Camundongos Endogâmicos C57BL , Proteínas dos Microfilamentos/metabolismo , Microglia/efeitos dos fármacos , Microglia/patologia , Poli I-C , Prostaglandina-Endoperóxido Sintases/metabolismo , Receptores de Prostaglandina E Subtipo EP2/agonistas , Técnicas de Cultura de Tecidos , Receptor 3 Toll-Like/metabolismo , Receptor 4 Toll-Like/metabolismoRESUMO
BACKGROUND: Amyloid ß (Aß) peptide aggregation is the main molecular mechanism underlying the development of Alzheimer's disease, the most widespread form of senile dementia worldwide. Increasing evidence suggests that the key factor leading to impaired neuronal function is accumulation of water-soluble Aß oligomers rather than formation of the senile plaques created by the deposition of large fibrillary aggregates of Aß. However, several questions remain about the preliminary steps and the progression of Aß oligomerization. METHODS: We show that the initial stages of the aggregation of fluorescently labeled Aß can be determined with a high degree of precision and at physiological (i.e., nanomolar) concentrations by using either steady-state fluorimetry or time-correlated single-photon counting. RESULTS: We study the dependence of the oligomerization extent and rate on the Aß concentration. We determine the chemical binding affinity of fluorescently labeled Aß for liposomes that have been recently shown to be pharmacologically active in vivo, reducing the Aß burden within the brain. We also probe their capacity to hinder the Aß oligomerization process in vitro. CONCLUSIONS: We introduced a fluorescence assay allowing investigation of the earliest steps of Aß oligomerization, the peptide involved in Alzheimer's disease. The assay proved to be sensitive even at Aß concentrations as low as those physiologically observed in the cerebrospinal fluid. GENERAL SIGNIFICANCE: This work represents an extensive and quantitative study on the initial events of Aß oligomerization at physiological concentration. It may enhance our comprehension of the molecular mechanisms leading to Alzheimer's disease, thus paving the way to novel therapeutic strategies.
Assuntos
Peptídeos beta-Amiloides/química , Lipossomos/química , Fragmentos de Peptídeos/química , Agregação Patológica de Proteínas , Doença de Alzheimer/metabolismo , Peptídeos beta-Amiloides/metabolismo , Humanos , Fragmentos de Peptídeos/metabolismo , Espectrometria de FluorescênciaRESUMO
Platinum-containing molecules are widely used as anticancer drugs. These molecules exert cytotoxic effects by binding to DNA through various mechanisms. The binding between DNA and platinum-based drugs hinders the opening of DNA, and therefore, DNA duplication and transcription are severely hampered. Overall, impeding the above-mentioned important DNA mechanisms results in irreversible DNA damage and the induction of apoptosis. Several molecules, including multinuclear platinum compounds, belong to the family of platinum drugs, and there is a body of research devoted to developing more efficient and less toxic versions of these compounds. In this study, we combined different biophysical methods, including single-molecule assays (magnetic tweezers) and bulk experiments (ultraviolet absorption for thermal denaturation) to analyze the differential stability of double-stranded DNA in complex with either cisplatin or multinuclear platinum agents. Specifically, we analyzed how the binding of BBR3005 and BBR3464, two representative multinuclear platinum-based compounds, to DNA affects its stability as compared with cisplatin binding. Our results suggest that single-molecule approaches can provide insights into the drug-DNA interactions that underlie drug potency and provide information that is complementary to that generated from bulk analysis; thus, single-molecule approaches have the potential to facilitate the selection and design of optimized drug compounds. In particular, relevant differences in DNA stability at the single-molecule level are demonstrated by analyzing nanomechanically induced DNA denaturation. On the basis of the comparison between the single-molecule and bulk analyses, we suggest that transplatinated drugs are able to locally destabilize small portions of the DNA chain, whereas other regions are stabilized.
Assuntos
Antineoplásicos/farmacologia , DNA/efeitos dos fármacos , Compostos Organoplatínicos/farmacologia , Algoritmos , Cisplatino/farmacologia , DNA/metabolismo , Congelamento , Estrutura Molecular , Desnaturação de Ácido Nucleico/efeitos dos fármacos , Plasmídeos/genética , Análise EspectralRESUMO
Microglia are suggested to be involved in several neuropsychiatric diseases. Indeed changes in microglia morphology have been reported in different mouse models of depression. A crucial regulatory system for microglia function is the well-defined CX3C axis. Thus, we aimed to clarify the role of microglia and CX3CR1 in depressive behavior by subjecting CX3CR1-deficient mice to a particular chronic despair model (CDM) paradigm known to exhibit face validity to major depressive disorder. In wild-type mice we observed the development of chronic depressive-like behavior after 5days of repetitive swim stress. 3D-reconstructions of Iba-1-labeled microglia in the dentate molecular layer revealed that behavioral effects were associated with changes in microglia morphology towards a state of hyper-ramification. Chronic treatment with the anti-depressant venlafaxine ameliorated depression-like behavior and restored microglia morphology. In contrast, CX3CR1 deficient mice showed a clear resistance to either (i) stress-induced depressive-like behavior, (ii) changes in microglia morphology and (iii) antidepressant treatment. Our data point towards a role of hyper-ramified microglia in the etiology of chronic depression. The lack of effects in CX3CR1 deficient mice suggests that microglia hyper-ramification is controlled by neuron-microglia signaling via the CX3C axis. However, it remains to be elucidated how hyper-ramified microglia contribute to depressive-like behavior.
Assuntos
Comportamento Animal/fisiologia , Quimiocina CX3CL1/deficiência , Transtorno Depressivo Maior/fisiopatologia , Microglia/patologia , Estresse Psicológico/complicações , Animais , Transtorno Depressivo Maior/etiologia , Modelos Animais de Doenças , Camundongos , Camundongos Endogâmicos C57BLRESUMO
Microglia help limit the progression of Alzheimer's disease (AD) by constraining amyloid-ß (Aß) pathology, effected through a balance of activating and inhibitory intracellular signals delivered by distinct cell surface receptors. Human leukocyte Ig-like receptor B4 (LILRB4) is an inhibitory receptor of the immunoglobulin (Ig) superfamily that is expressed on myeloid cells and recognizes apolipoprotein E (ApoE) among other ligands. Here, we find that LILRB4 is highly expressed in the microglia of patients with AD. Using mice that accumulate Aß and carry a transgene encompassing a portion of the LILR region that includes LILRB4, we corroborated abundant LILRB4 expression in microglia wrapping around Aß plaques. Systemic treatment of these mice with an anti-human LILRB4 monoclonal antibody (mAb) reduced Aß load, mitigated some Aß-related behavioral abnormalities, enhanced microglia activity, and attenuated expression of interferon-induced genes. In vitro binding experiments established that human LILRB4 binds both human and mouse ApoE and that anti-human LILRB4 mAb blocks such interaction. In silico modeling, biochemical, and mutagenesis analyses identified a loop between the two extracellular Ig domains of LILRB4 required for interaction with mouse ApoE and further indicated that anti-LILRB4 mAb may block LILRB4-mApoE by directly binding this loop. Thus, targeting LILRB4 may be a potential therapeutic avenue for AD.
Assuntos
Doença de Alzheimer , Microglia , Humanos , Camundongos , Animais , Microglia/metabolismo , Anticorpos/metabolismo , Receptores de Superfície Celular/metabolismo , Amiloide/metabolismo , Modelos Animais de Doenças , Doença de Alzheimer/patologia , Peptídeos beta-Amiloides/metabolismo , Apolipoproteínas E , Leucócitos/metabolismo , Camundongos Transgênicos , Glicoproteínas de Membrana/metabolismo , Receptores Imunológicos/metabolismoRESUMO
Tumor-associated macrophages (TAMs) represent a key component of the tumor microenvironment and are generally associated with immunosuppression and poor prognosis. TREM2 is a transmembrane receptor of the immunoglobulin superfamily expressed in myeloid cells. TREM2 has been extensively studied in microglia and neurodegenerative diseases and recently emerged as a marker of pro-tumorigenic macrophages. The accumulation of TREM2-expressing TAMs was reported across numerous cancer patients and tumor models. TREM2 genetic blockade or TREM2 targeting with antibodies resulted in improved tumor control, enhanced response to anti-PD1, and significant changes in the tumor immune landscape. Preclinical studies paved the way for an ongoing clinical trial with a TREM2 depleting antibody and inspired further exploration of TREM2 targeting therapies. Here, we review the current knowledge about the impact of TREM2 in cancer, with an emphasis on the TREM2+ macrophage signature across different cancer types, the contribution of TREM2 to TAM phenotype and function, and the promising effects of TREM2 modulation.
RESUMO
The meninges are a membranous structure enveloping the central nervous system (CNS) that host a rich repertoire of immune cells mediating CNS immune surveillance. Here, we report that the mouse meninges contain a pool of monocytes and neutrophils supplied not from the blood but by adjacent skull and vertebral bone marrow. Under pathological conditions, including spinal cord injury and neuroinflammation, CNS-infiltrating myeloid cells can originate from brain borders and display transcriptional signatures distinct from their blood-derived counterparts. Thus, CNS borders are populated by myeloid cells from adjacent bone marrow niches, strategically placed to supply innate immune cells under homeostatic and pathological conditions. These findings call for a reinterpretation of immune-cell infiltration into the CNS during injury and autoimmunity and may inform future therapeutic approaches that harness meningeal immune cells.
Assuntos
Células da Medula Óssea/fisiologia , Doenças do Sistema Nervoso Central/imunologia , Sistema Nervoso Central/imunologia , Meninges/imunologia , Células Mieloides/fisiologia , Crânio/anatomia & histologia , Coluna Vertebral/anatomia & histologia , Animais , Medula Óssea/fisiologia , Encéfalo/citologia , Encéfalo/imunologia , Encéfalo/fisiologia , Movimento Celular , Sistema Nervoso Central/citologia , Doenças do Sistema Nervoso Central/patologia , Dura-Máter/citologia , Dura-Máter/imunologia , Dura-Máter/fisiologia , Encefalomielite Autoimune Experimental/imunologia , Encefalomielite Autoimune Experimental/patologia , Homeostase , Meninges/citologia , Meninges/fisiologia , Camundongos , Monócitos/fisiologia , Neutrófilos/fisiologia , Medula Espinal/citologia , Medula Espinal/imunologia , Medula Espinal/fisiologia , Traumatismos da Medula Espinal/imunologia , Traumatismos da Medula Espinal/patologiaRESUMO
The meninges contain adaptive immune cells that provide immunosurveillance of the central nervous system (CNS). These cells are thought to derive from the systemic circulation. Through single-cell analyses, confocal imaging, bone marrow chimeras, and parabiosis experiments, we show that meningeal B cells derive locally from the calvaria, which harbors a bone marrow niche for hematopoiesis. B cells reach the meninges from the calvaria through specialized vascular connections. This calvarial-meningeal path of B cell development may provide the CNS with a constant supply of B cells educated by CNS antigens. Conversely, we show that a subset of antigen-experienced B cells that populate the meninges in aging mice are blood-borne. These results identify a private source for meningeal B cells, which may help maintain immune privilege within the CNS.
Assuntos
Subpopulações de Linfócitos B/fisiologia , Linfócitos B/fisiologia , Células da Medula Óssea/fisiologia , Sistema Nervoso Central/imunologia , Dura-Máter/citologia , Linfopoese , Meninges/citologia , Meninges/imunologia , Crânio/anatomia & histologia , Envelhecimento , Animais , Subpopulações de Linfócitos B/imunologia , Movimento Celular , Sistema Nervoso Central/fisiologia , Dura-Máter/imunologia , Fibroblastos/fisiologia , Homeostase , Privilégio Imunológico , Camundongos , Plasmócitos/fisiologia , Análise de Célula ÚnicaRESUMO
A growing body of evidence indicates that microglia actively remove synapses in vivo, thereby playing a key role in synaptic refinement and modulation of brain connectivity. This phenomenon was mainly investigated in immunofluorescence staining and confocal microscopy. However, a quantification of synaptic material in microglia using these techniques is extremely time-consuming and labor-intensive. To address this issue, we aimed to quantify synaptic proteins in microglia using flow cytometry. With this approach, we first showed that microglia from the healthy adult mouse brain contain a detectable level of VGLUT1 protein. Next, we found more than two-fold increased VGLUT1 immunoreactivity in microglia from the developing brain (P15) as compared to adult microglia. These data indicate that microglia-mediated synaptic pruning mostly occurs during the brain developmental period. We then quantified the VGLUT1 staining in microglia in two transgenic models characterized by pathological microglia-mediated synaptic pruning. In the 5xFAD mouse model of Alzheimer's disease (AD) microglia exhibited a significant increase in VGLUT1 immunoreactivity before the onset of amyloid pathology. Moreover, conditional deletion of TDP-43 in microglia, which causes a hyper-phagocytic phenotype associated with synaptic loss, also resulted in increased VGLUT1 immunoreactivity within microglia. This work provides a quantitative assessment of synaptic proteins in microglia, under homeostasis, and in mouse models of disease.
RESUMO
Ongoing research is revealing multiple, previously unappreciated, facets of immunity in the central nervous system, and the recent studies on the meningeal lymphatic system represent an emblematic example. In this context, a paper from Louveau and colleagues (Nat. Neurosci. 2018;21:1380-1391), which we discuss here, elucidates the importance of the meningeal lymphatics for the drainage of macromolecules and immune cells from the cerebrospinal fluid, and their delivery into the cervical lymph nodes, especially during neuroinflammatory diseases.