RESUMO
Myelin Basic Protein (MBP) is essential for both elaboration and maintenance of CNS myelin, and its reduced accumulation results in hypomyelination. How different Mbp mRNA levels affect myelin dimensions across the lifespan and how resident glial cells may respond to such changes are unknown. Here, to investigate these questions, we used enhancer-edited mouse lines that accumulate Mbp mRNA levels ranging from 8% to 160% of wild type. In young mice, reduced Mbp mRNA levels resulted in corresponding decreases in Mbp protein accumulation and myelin sheath thickness, confirming the previously demonstrated rate-limiting role of Mbp transcription in the control of initial myelin synthesis. However, despite maintaining lower line specific Mbp mRNA levels into old age, both MBP protein levels and myelin thickness improved or fully normalized at rates defined by the relative Mbp mRNA level. Sheath length, in contrast, was affected only when mRNA levels were very low, demonstrating that sheath thickness and length are not equally coupled to Mbp mRNA level. Striking abnormalities in sheath structure also emerged with reduced mRNA levels. Unexpectedly, an increase in the density of all glial cell types arose in response to reduced Mbp mRNA levels. This investigation extends understanding of the role MBP plays in myelin sheath elaboration, architecture, and plasticity across the mouse lifespan and illuminates a novel axis of glial cell crosstalk.
Assuntos
Proteína Básica da Mielina , Bainha de Mielina , Neuroglia , RNA Mensageiro , Animais , Proteína Básica da Mielina/metabolismo , Proteína Básica da Mielina/genética , Bainha de Mielina/metabolismo , Bainha de Mielina/genética , RNA Mensageiro/metabolismo , Neuroglia/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , MasculinoRESUMO
Regulation of neuroinflammation is critical for maintaining central nervous system (CNS) homeostasis and holds therapeutic promise in autoimmune diseases such as multiple sclerosis (MS). Previous studies have highlighted the significance of selective innate signaling in triggering anti-inflammatory mechanisms, which play a protective role in an MS-like disease, experimental autoimmune encephalomyelitis (EAE). However, the individual intra-CNS administration of specific innate receptor ligands or agonists, such as for toll-like receptor 7 (TLR7) and nucleotide-binding oligomerization-domain-containing protein 2 (NOD2), failed to elicit the desired anti-inflammatory response in EAE. In this study, we investigated the potential synergistic effect of targeting both TLR7 and NOD2 simultaneously to prevent EAE progression. Our findings demonstrate that simultaneous intrathecal administration of NOD2- and TLR7-agonists led to synergistic induction of Type I IFN (IFN I) and effectively suppressed EAE in an IFN I-dependent manner. Suppression of EAE was correlated with a significant decrease in the infiltration of monocytes, granulocytes, and natural killer cells, reduced demyelination, and downregulation of IL-1ß, CCL2, and IFNγ gene expression in the spinal cord. These results underscore the therapeutic promise of concurrently targeting the TLR7 and NOD2 pathways in alleviating neuroinflammation associated with MS, paving the way for novel and more efficacious treatment strategies.
Assuntos
Encefalomielite Autoimune Experimental , Esclerose Múltipla , Proteína Adaptadora de Sinalização NOD2 , Receptor 7 Toll-Like , Animais , Receptor 7 Toll-Like/metabolismo , Receptor 7 Toll-Like/agonistas , Proteína Adaptadora de Sinalização NOD2/metabolismo , Proteína Adaptadora de Sinalização NOD2/genética , Encefalomielite Autoimune Experimental/tratamento farmacológico , Encefalomielite Autoimune Experimental/metabolismo , Encefalomielite Autoimune Experimental/imunologia , Encefalomielite Autoimune Experimental/patologia , Esclerose Múltipla/tratamento farmacológico , Esclerose Múltipla/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Imunidade Inata/efeitos dos fármacos , Feminino , Medula Espinal/metabolismo , Medula Espinal/patologia , Medula Espinal/efeitos dos fármacos , Glicoproteínas de Membrana/metabolismo , Interferon Tipo I/metabolismo , Transdução de Sinais/efeitos dos fármacosRESUMO
Type I interferons (IFN), including IFNß, play a protective role in multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE). Type I IFNs are induced by the stimulation of innate signaling, including via cytoplasmic RIG-I-like receptors. In the present study, we investigated the potential effect of a chimeric protein containing the key domain of RIG-I signaling in the production of CNS endogenous IFNß and asked whether this would exert a therapeutic effect against EAE. We intrathecally administered an adeno-associated virus vector (AAV) encoding a fusion protein comprising RIG-I 2CARD domains (C) and the first 200 amino acids of mitochondrial antiviral-signaling protein (MAVS) (M) (AAV-CM). In vivo imaging in IFNß/luciferase reporter mice revealed that a single intrathecal injection of AAV-CM resulted in dose-dependent and sustained IFNß expression within the CNS. IFNß expression was significantly increased for 7 days. Immunofluorescent staining in IFNß-YFP reporter mice revealed extraparenchymal CD45+ cells, choroid plexus, and astrocytes as sources of IFNß. Moreover, intrathecal administration of AAV-CM at the onset of EAE induced the suppression of EAE, which was IFN-I-dependent. These findings suggest that accessing the signaling pathway downstream of RIG-I represents a promising therapeutic strategy for inflammatory CNS diseases, such as MS.
Assuntos
Encefalomielite Autoimune Experimental , Interferon Tipo I , Aminoácidos , Animais , Antivirais , Encefalomielite Autoimune Experimental/tratamento farmacológico , Interferon Tipo I/metabolismo , Interferon beta/genética , Interferon beta/metabolismo , Camundongos , Proteínas Recombinantes de Fusão , Transdução de SinaisRESUMO
Recently, the protective and/or pathological role of virus-specific T cells in SARS-CoV-2 infection has been the focus of many studies. We investigated the anti-spike IgG levels and SARS-CoV-2-specific T cells in 125 donors (90 vaccinated with four different vaccine platforms, 16 individuals with a previous natural infection, and 19 not vaccinated donors who did not report previous SARS-CoV-2 infections). Our data show that anti-spike IgG titers were similar between naturally infected subjects and those vaccinated with adenoviral vector vaccines. Of note, all immunized donors produced memory CD4+ and/or CD8+ T cells. A sustained polyfunctionality of SARS-CoV-2-specific T cells in all immunized donors was also demonstrated. Altogether, our data suggest that the natural infection produces an overall response like that induced by vaccination. Therefore, this detailed immunological evaluation may be relevant for other vaccine efforts especially for the monitoring of novel vaccines effective against emerging virus variants.
Assuntos
COVID-19 , Vacinas Virais , Anticorpos Antivirais , Linfócitos T CD8-Positivos , COVID-19/prevenção & controle , Humanos , Imunoglobulina G , SARS-CoV-2 , VacinaçãoRESUMO
Neuromyelitis optica (NMO) is an inflammatory disease of the central nervous system (CNS) most frequently mediated by serum autoantibodies against the water channel aquaporin 4, expressed on CNS astrocytes, resulting in primary astrocytopathy. There is no cure for NMO, and treatment with Type I interferon (IFNI)-IFNß is ineffective or even detrimental. We have previously shown that both NMO lesions and associated microglial activation were reduced in mice lacking the receptor for IFNß. However, the role of microglia in NMO is not well understood. In this study, we clarify the pathomechanism for IFNI dependence of and the role of microglia in experimental NMO. Transcriptome analysis showed a strong IFNI footprint in affected CNS tissue as well as in microglial subpopulations. Treatment with IFNß led to exacerbated pathology and further microglial activation as evidenced by expansion of a CD11c+ subset of microglia. Importantly, depletion of microglia led to suppression of pathology and decrease of IFNI signature genes. Our data show a pro-pathologic role for IFNI-activated microglia in NMO and open new perspectives for microglia-targeted therapies.
Assuntos
Interferon Tipo I , Neuromielite Óptica , Animais , Aquaporina 4 , Astrócitos , Camundongos , Microglia , Neuromielite Óptica/tratamento farmacológicoRESUMO
Microglia are resident macrophages of the central nervous system that contribute to homeostasis and neuroinflammation. Although known to play an important role in brain development, their exact function has not been fully described. Here, we show that in contrast to healthy adult and inflammation-activated cells, neonatal microglia show a unique myelinogenic and neurogenic phenotype. A CD11c+ microglial subset that predominates in primary myelinating areas of the developing brain expresses genes for neuronal and glial survival, migration, and differentiation. These cells are the major source of insulin-like growth factor 1, and its selective depletion from CD11c+ microglia leads to impairment of primary myelination. CD11c-targeted toxin regimens induced a selective transcriptional response in neonates, distinct from adult microglia. CD11c+ microglia are also found in clusters of repopulating microglia after experimental ablation and in neuroinflammation in adult mice, but despite some similarities, they do not recapitulate neonatal microglial characteristics. We therefore identify a unique phenotype of neonatal microglia that deliver signals necessary for myelination and neurogenesis.
Assuntos
Encéfalo/citologia , Encéfalo/embriologia , Microglia/metabolismo , Bainha de Mielina/metabolismo , Neurogênese , Envelhecimento/genética , Animais , Animais Recém-Nascidos , Biomarcadores/metabolismo , Encéfalo/ultraestrutura , Antígeno CD11c/metabolismo , Agregação Celular , Encefalomielite Autoimune Experimental/genética , Encefalomielite Autoimune Experimental/patologia , Feminino , Perfilação da Expressão Gênica , Regulação da Expressão Gênica no Desenvolvimento , Fator de Crescimento Insulin-Like I/metabolismo , Camundongos Endogâmicos C57BL , Placa Neural/metabolismo , Regulação para Cima/genéticaRESUMO
Diffusion kurtosis imaging (DKI) is an imaging modality that yields novel disease biomarkers and in combination with nervous tissue modeling, provides access to microstructural parameters. Recently, DKI and subsequent estimation of microstructural model parameters has been used for assessment of tissue changes in neurodegenerative diseases and associated animal models. In this study, mouse spinal cords from the experimental autoimmune encephalomyelitis (EAE) model of multiple sclerosis (MS) were investigated for the first time using DKI in combination with biophysical modeling to study the relationship between microstructural metrics and degree of animal dysfunction. Thirteen spinal cords were extracted from animals with varied grades of disability and scanned in a high-field MRI scanner along with five control specimen. Diffusion weighted data were acquired together with high resolution T2* images. Diffusion data were fit to estimate diffusion and kurtosis tensors and white matter modeling parameters, which were all used for subsequent statistical analysis using a linear mixed effects model. T2* images were used to delineate focal demyelination/inflammation. Our results reveal a strong relationship between disability and measured microstructural parameters in normal appearing white matter and gray matter. Relationships between disability and mean of the kurtosis tensor, radial kurtosis, radial diffusivity were similar to what has been found in other hypomyelinating MS models, and in patients. However, the changes in biophysical modeling parameters and in particular in extra-axonal axial diffusivity were clearly different from previous studies employing other animal models of MS. In conclusion, our data suggest that DKI and microstructural modeling can provide a unique contrast capable of detecting EAE-specific changes correlating with clinical disability.
Assuntos
Encefalomielite Autoimune Experimental/diagnóstico por imagem , Substância Cinzenta/diagnóstico por imagem , Esclerose Múltipla/diagnóstico por imagem , Medula Espinal/diagnóstico por imagem , Substância Branca/diagnóstico por imagem , Animais , Imagem de Difusão por Ressonância Magnética , Encefalomielite Autoimune Experimental/patologia , Encefalomielite Autoimune Experimental/fisiopatologia , Feminino , Substância Cinzenta/patologia , Camundongos , Camundongos Endogâmicos C57BL , Modelos Biológicos , Esclerose Múltipla/patologia , Esclerose Múltipla/fisiopatologia , Medula Espinal/patologia , Substância Branca/patologiaRESUMO
Myeloid cells represent the major cellular component of innate immune responses. Myeloid cells include monocytes and macrophages, granulocytes (neutrophils, basophils and eosinophils) and dendritic cells (DC). The role of myeloid cells has been broadly described both in physiological and in pathological conditions. All tissues or organs are equipped with resident myeloid cells, such as parenchymal microglia in the brain, which contribute to maintaining homeostasis. Moreover, in case of infection or tissue damage, other myeloid cells such as monocytes or granulocytes (especially neutrophils) can be recruited from the circulation, at first to promote inflammation and later to participate in repair and regeneration. This review aims to address the regulatory roles of myeloid cells in inflammatory diseases of the central nervous system (CNS), with a particular focus on recent work showing induction of suppressive function via stimulation of innate signalling in multiple sclerosis (MS) and its animal model experimental autoimmune encephalomyelitis (EAE).
Assuntos
Sistema Nervoso Central/imunologia , Células Dendríticas/imunologia , Granulócitos/imunologia , Inflamação/imunologia , Macrófagos/imunologia , Células Mieloides/imunologia , Animais , Sistema Nervoso Central/patologia , Encefalomielite Autoimune Experimental/imunologia , Encefalomielite Autoimune Experimental/patologia , Humanos , Esclerose Múltipla/imunologia , Esclerose Múltipla/patologiaRESUMO
BACKGROUND: Neuromyelitis optica spectrum disorder (NMOSD) is a relapsing inflammatory central nervous system (CNS) disease for which there is no cure. Immunoglobulin G autoantibodies specific for the water channel aquaporin-4 are a serum biomarker, believed to induce complement-dependent astrocyte damage with secondary demyelination. OBJECTIVE: To investigate the effect of angiotensin AT2 receptor (AT2R) stimulation on NMOSD-like pathology and its underlying mechanism. METHODS: NMOSD-like pathology was induced in mice by intracerebral injection of immunoglobulin-G isolated from NMOSD patient serum, with complement. This mouse model produces the characteristic histological features of NMOSD. A specific AT2R agonist, Compound 21 (C21), was given intracerebrally at day 0 and by intrathecal injection at day 2. RESULTS: Loss of aquaporin-4 and glial fibrillary acidic protein was attenuated by treatment with C21. Administration of C21 induced mRNA for interleukin-10 in the brain. NMOSD-like pathology was exacerbated in interleukin-10-deficient mice, suggesting a protective role. C21 treatment did not attenuate NMOSD-like pathology in interleukin-10-deficient mice, indicating that the protective effect of AT2R stimulation was dependent on interleukin-10. CONCLUSION: Our findings identify AT2R as a novel potential therapeutic target for the treatment of NMOSD. Interleukin-10 signaling is an essential part of the protective mechanism counteracting NMOSD pathology.
Assuntos
Neuromielite Óptica , Animais , Aquaporina 4/genética , Autoanticorpos , Humanos , Interleucina-10 , Camundongos , Recidiva Local de Neoplasia , Neuromielite Óptica/tratamento farmacológico , Receptor Tipo 2 de AngiotensinaRESUMO
BACKGROUND: Encounter of autoantibodies with specific antigens can lead to hypersensitivity reactions and pathology. In multiple sclerosis and neuromyelitis optica spectrum disease (NMOSD), immunoglobulin-G (IgG) deposition has been observed in pathological lesions in the central nervous system. The paradigmatic autoantibodies in NMOSD are specific for the water channel aquaporin-4, localized to astrocytic end-feet at the blood-brain barrier and ependymal cells at the cerebrospinal fluid-brain barrier. We have previously observed that IgG antibodies from NMO patients (NMO-IgG) access brain parenchyma from the cerebrospinal fluid and induce subpial and periventricular NMO-like lesions and blood-brain barrier breakdown, in a complement-dependent manner. OBJECTIVE: To investigate how IgG trafficking from cerebrospinal fluid to brain parenchyma can be influenced by injury. METHODS: IgG from healthy donors was intrathecally injected into the cerebrospinal fluid via cisterna magna at 1, 2, 4, or 7 days after a distal stereotactic sterile needle insertion to the striatum. RESULTS: Antibody deposition, detected by staining for human IgG, peaked 1 day after the intrathecal injection and was selectively seen close to the needle insertion. When NMO-IgG was intrathecally injected, we observed complement-dependent NMO-like pathology (loss of aquaporin-4 and glial fibrillary acidic protein) proximal to the insertion site, with similar kinetics. A fluorescent tracer did not show the same distribution indicating IgG-selective localization. CONCLUSION: These findings suggest that IgG from cerebrospinal fluid localize selectively in brain parenchyma at the site of injury and pathogenic NMO-IgG induce astrocyte pathology at the same location.
Assuntos
Sistema Nervoso Central/metabolismo , Imunoglobulina G/líquido cefalorraquidiano , Tecido Parenquimatoso/metabolismo , Animais , Aquaporina 4/imunologia , Aquaporina 4/metabolismo , Sistema Nervoso Central/anatomia & histologia , Citocinas/genética , Citocinas/metabolismo , Dextranos/metabolismo , Feminino , Proteína Glial Fibrilar Ácida/metabolismo , Humanos , Imunoglobulina G/administração & dosagem , Camundongos , Camundongos Endogâmicos C57BL , Neuromielite Óptica/metabolismo , Neuromielite Óptica/patologia , Transporte Proteico/efeitos dos fármacos , Transporte Proteico/fisiologia , RNA Mensageiro/metabolismo , Fatores de TempoRESUMO
BACKGROUND: Antibodies with specificity for myelin oligodendrocyte glycoprotein (MOG) are implicated in multiple sclerosis and related diseases. The pathogenic importance of anti-MOG antibody in primary demyelinating pathology remains poorly characterized. OBJECTIVE: The objective of this study is to investigate whether administration of anti-MOG antibody would be sufficient for demyelination and to determine if type I interferon (IFN) signaling plays a similar role in anti-MOG antibody-mediated pathology, as has been shown for neuromyelitis optica-like pathology. METHODS: Purified IgG2a monoclonal anti-MOG antibody and mouse complement were stereotactically injected into the corpus callosum of wild-type and type I IFN receptor deficient mice (IFNAR1-KO) with and without pre-established experimental autoimmune encephalomyelitis (EAE). RESULTS: Anti-MOG induced complement-dependent demyelination in the corpus callosum of wild-type mice and did not occur in mice that received control IgG2a. Deposition of activated complement coincided with demyelination, and this was significantly reduced in IFNAR1-KO mice. Co-injection of anti-MOG and complement at onset of symptoms of EAE induced similar levels of callosal demyelination in wild-type and IFNAR1-KO mice. CONCLUSIONS: Anti-MOG antibody and complement was sufficient to induce callosal demyelination, and pathology was dependent on type I IFN. Induction of EAE in IFNAR1-KO mice overcame the dependence on type I IFN for anti-MOG and complement-mediated demyelination.
Assuntos
Autoanticorpos/metabolismo , Doenças Desmielinizantes/metabolismo , Interferon Tipo I/metabolismo , Glicoproteína Mielina-Oligodendrócito/metabolismo , Animais , Autoanticorpos/imunologia , Corpo Caloso/imunologia , Corpo Caloso/metabolismo , Corpo Caloso/patologia , Doenças Desmielinizantes/imunologia , Doenças Desmielinizantes/patologia , Interferon Tipo I/imunologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Glicoproteína Mielina-Oligodendrócito/imunologiaRESUMO
BACKGROUND: Autoreactive Th1 and Th17 cells are believed to mediate the pathology of multiple sclerosis in the central nervous system (CNS). Their interaction with microglia and astrocytes in the CNS is crucial for the regulation of the neuroinflammation. Previously, we have shown that only Th1 but not Th17 effectors activate microglia. However, it is not clear which cells are targets of Th17 effectors in the CNS. METHODS: To understand the effects driven by Th17 cells in the CNS, we induced experimental autoimmune encephalomyelitis in wild-type mice and CD4+ T cell-specific integrin α4-deficient mice where trafficking of Th1 cells into the CNS was affected. We compared microglial and astrocyte response in the brain and spinal cord of these mice. We further treated astrocytes with supernatants from highly pure Th1 and Th17 cultures and assessed the messenger RNA expression of neurotrophic factors, cytokines and chemokines, using real-time PCR. Data obtained was analyzed using the Kruskal-Wallis test. RESULTS: We observed in α4-deficient mice weak microglial activation but comparable astrogliosis to that of wild-type mice in the regions of the brain populated with Th17 infiltrates, suggesting that Th17 cells target astrocytes and not microglia. In vitro, in response to supernatants from Th1 and Th17 cultures, astrocytes showed altered expression of neurotrophic factors, pro-inflammatory cytokines and chemokines. Furthermore, increased expression of chemokines in Th1- and Th17-treated astrocytes enhanced recruitment of microglia and transendothelial migration of Th17 cells in vitro. CONCLUSION: Our results demonstrate the delicate interaction between T cell subsets and glial cells and how they communicate to mediate their effects. Effectors of Th1 act on both microglia and astrocytes whereas Th17 effectors preferentially target astrocytes to promote neuroinflammation.
Assuntos
Astrócitos/metabolismo , Encefalomielite Autoimune Experimental/metabolismo , Gliose/metabolismo , Mediadores da Inflamação/metabolismo , Células Th1/metabolismo , Células Th17/metabolismo , Animais , Astrócitos/patologia , Movimento Celular/fisiologia , Células Cultivadas , Citocinas/metabolismo , Encefalomielite Autoimune Experimental/patologia , Gliose/patologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , Células Th1/patologia , Células Th17/patologiaRESUMO
The Type I interferons (IFN), beta (IFN-ß) and the alpha family (IFN-α), act through a common receptor and have anti-inflammatory effects. IFN-ß is used to treat multiple sclerosis (MS) and is effective against experimental autoimmune encephalomyelitis (EAE), an animal model for MS. Mice with EAE show elevated levels of Type I IFNs in the central nervous system (CNS), suggesting a role for endogenous Type I IFN during inflammation. However, the therapeutic benefit of Type I IFN produced in the CNS remains to be established. The aim of this study was to examine whether experimentally induced CNS-endogenous Type I IFN influences EAE. Using IFN-ß reporter mice, we showed that direct administration of polyinosinic-polycytidylic acid (poly I:C), a potent inducer of IFN-ß, into the cerebrospinal fluid induced increased leukocyte numbers and transient upregulation of IFN-ß in CD45/CD11b-positive cells located in the meninges and choroid plexus, as well as enhanced IFN-ß expression by parenchymal microglial cells. Intrathecal injection of poly I:C to mice showing first symptoms of EAE substantially increased the normal disease-associated expression of IFN-α, IFN-ß, interferon regulatory factor-7 and IL-10 in CNS, and disease worsening was prevented for as long as IFN-α/ß was expressed. In contrast, there was no therapeutic effect on EAE in poly I:C-treated IFN receptor-deficient mice. IFN-dependent microglial and astrocyte response included production of the chemokine CXCL10. These results show that Type I IFN induced within the CNS can play a protective role in EAE and highlight the role of endogenous type I IFN in mediating neuroprotection.
Assuntos
Encefalomielite Autoimune Experimental/tratamento farmacológico , Interferon-alfa/metabolismo , Interferon beta/metabolismo , Fármacos Neuroprotetores/farmacologia , Poli I-C/farmacologia , Animais , Astrócitos/efeitos dos fármacos , Astrócitos/imunologia , Astrócitos/patologia , Encéfalo/efeitos dos fármacos , Encéfalo/imunologia , Encéfalo/patologia , Quimiocina CXCL10/metabolismo , Encefalomielite Autoimune Experimental/imunologia , Encefalomielite Autoimune Experimental/patologia , Interferon-alfa/genética , Interferon beta/genética , Leucócitos/efeitos dos fármacos , Leucócitos/patologia , Leucócitos/fisiologia , Meninges/efeitos dos fármacos , Meninges/imunologia , Meninges/patologia , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Microglia/efeitos dos fármacos , Microglia/patologia , Microglia/fisiologia , Distribuição Aleatória , Receptor de Interferon alfa e beta/genética , Receptor de Interferon alfa e beta/metabolismo , Medula Espinal/efeitos dos fármacos , Medula Espinal/imunologia , Medula Espinal/patologiaRESUMO
Microglia most likely appeared early in evolution as they are not only present in vertebrates, but are also found in nervous systems of various nonvertebrate organisms. Mammalian microglia are derived from a specific embryonic, self-renewable myeloid cell population that is throughout lifetime not replaced by peripheral myeloid cells. These phylogenic and ontogenic features suggest that microglia serve vital functions. Yet, microglia often are described as neurotoxic cells, that actively kill (healthy) neurons. Since it is from an evolutionary point of view difficult to understand why an important and vulnerable organ like the brain should host numerous potential killers, we here review the concept of microglia neurotoxicity. On one hand it is discussed that most of our understanding about how microglia kill neurons is based on in vitro experiments or correlative staining studies that suffer from the difficulty to discriminate microglia and peripheral myeloid cells in the diseased brain. On the other hand it is described that a more functional approach by mutating, inactivating or deleting microglia is seldom associated with a beneficial outcome in an acute injury situation, suggesting that microglia are normally important protective elements in the brain. This might change in chronic disease or the aged brain, where; however, it remains to be established whether microglia simply lose their protective capacities or whether microglia become truly neurotoxic cells.
Assuntos
Encéfalo/patologia , Microglia/patologia , Doenças do Sistema Nervoso/patologia , Neurônios/patologia , Envelhecimento/metabolismo , Envelhecimento/patologia , Animais , Encéfalo/metabolismo , Humanos , Microglia/química , Microglia/metabolismo , Doenças do Sistema Nervoso/metabolismo , Doenças do Sistema Nervoso/prevenção & controle , Neurônios/metabolismoRESUMO
Interferons (IFNs) are implicated as an important component of the innate immune system influencing viral infections, inflammation, and immune surveillance. We review here the complex biological activity of IFNs in the central nervous system (CNS) and associated glialimmune interactions, with focus specifically on the Type I IFNs in physiological and pathological conditions. IFN-α and IFN-ß are the predominant Type I IFNs in the CNS. They are produced in the CNS by glial cells, mostly microglia and astrocytes, as well as by neurons. A variety of mechanisms stimulate IFN production in glial cells, including innate stimuli from Toll-like and other receptors, which can recognize endogenous entities, as well as pathogens. We will review evidence that differential signaling by IFN-α versus IFN-ß through the common heterodimeric receptor IFNAR is the basis for CNS-selective Type I IFN response, and the capacity of CNS glial cells to produce and respond to Type I IFN. Differential signaling outcomes of IFN-α and IFN-ß, which have been ascribed to differential affinity for IFNAR1 and IFNAR2, determine whether Type I IFN exert pathogenic or protective roles in the CNS. These points will be discussed with reference to selected neurological diseases, and effects of Type I IFN on the integrity of the bloodbrain barrier.
Assuntos
Sistema Nervoso Central , Sistema Imunitário/fisiologia , Interferons/metabolismo , Neuroglia/fisiologia , Animais , Sistema Nervoso Central/citologia , Sistema Nervoso Central/imunologia , Sistema Nervoso Central/metabolismo , Humanos , Interferons/uso terapêutico , Doenças do Sistema Nervoso/tratamento farmacológico , Doenças do Sistema Nervoso/imunologiaRESUMO
BACKGROUND: Tissue-resident antigen-presenting cells (APC) exert a major influence on the local immune environment. Microglia are resident myeloid cells in the central nervous system (CNS), deriving from early post-embryonic precursors, distinct from adult hematopoietic lineages. Dendritic cells (DC) and macrophages infiltrate the CNS during experimental autoimmune encephalomyelitis (EAE). Microglia are not considered to be as effective APC as DC or macrophages. METHODS: In this work we compared the antigen presenting capacity of CD11c⺠and CD11câ» microglia subsets with infiltrating CD11c⺠APC, which include DC. The microglial subpopulations (CD11câ» CD45dim CD11b⺠and CD11c⺠CD45dim CD11bâº) as well as infiltrating CD11c⺠CD45high cells were sorted from CNS of C57BL/6 mice with EAE. Sorted cells were characterised by flow cytometry for surface phenotype and by quantitative real-time PCR for cytokine expression. They were co-cultured with primed T cells to measure induction of T cell proliferation and cytokine response. RESULTS: The number of CD11c⺠microglia cells increased dramatically in EAE. They expressed equivalent levels of major histocompatibility complex and co-stimulatory ligands CD80 and CD86 as those expressed by CD11c⺠cells infiltrating from blood. CD11c⺠microglia differed significantly from blood-derived CD11c⺠cells in their cytokine profile, expressing no detectable IL-6, IL-12 or IL-23, and low levels of IL-1ß. By contrast, CD11câ» microglia expressed low but detectable levels of all these cytokines. Transforming growth factor ß expression was similar in all three populations. Although CNS-resident and blood-derived CD11c⺠cells showed equivalent ability to induce proliferation of myelin oligodendrocyte glycoprotein-immunised CD4⺠T cells, CD11c⺠microglia induced lower levels of T helper (Th)1 and Th17 cytokines, and did not induce Th2 cytokines. CONCLUSIONS: Our findings show distinct subtypes of APC in the inflamed CNS, with a hierarchy of functional competence for induction of CD4⺠T cell responses.
Assuntos
Células Apresentadoras de Antígenos/metabolismo , Proliferação de Células , Sistema Nervoso Central/patologia , Citocinas/metabolismo , Encefalomielite Autoimune Experimental/patologia , Microglia/metabolismo , Linfócitos T/fisiologia , Animais , Antígenos CD/metabolismo , Antígeno CD11c/metabolismo , Sistema Nervoso Central/imunologia , Modelos Animais de Doenças , Encefalomielite Autoimune Experimental/imunologia , Feminino , Citometria de Fluxo , Complexo Principal de Histocompatibilidade/fisiologia , Camundongos , Camundongos Endogâmicos C57BLRESUMO
BACKGROUND: Myelin-specific T cells are implicated in multiple sclerosis (MS) and drive experimental autoimmune encephalomyelitis (EAE). EAE is commonly induced with short peptides, whereas in MS, whole myelin proteins are available for immune response. We asked whether immunization with the immunoglobulin-like domain of myelin oligodendrocyte glycoprotein (MOG(Igd), residues 1-125) might induce distinct CD4+ T-cell response and/or a stronger CD8+ T-cell response, compared to the 21 amino acid immunodominant MHC II-associating peptide (p35-55). OBJECTIVES: Compare both EAE and T-cell responses in C57BL/6 mice immunized with MOG(Igd) and MOG p35-55. METHODS: Cytokine production, and chemokine receptor expression by CD4+ and CD8+ T cells in the mouse central nervous system (CNS), were analyzed by flow cytometry. RESULTS: MOG(Igd) triggered progression to more severe EAE than MOG p35-55, despite similar time of onset and overall incidence. EAE in MOG(Igd)-immunized mice was characterized by an increased percentage of CXCR3+ interferon-γ-producing CD4+ T cells in CNS. The CD8+ T-cell response to both immunogens was similar. CONCLUSIONS: Increased incidence of severe disease following MOG(Igd) immunization, accompanied by an increased percentage of CD4+ T cells in the CNS expressing CXCR3 and producing interferon-γ, identifies a pathogenic role for interferon-γ that is not seen when disease is induced with a single Major Histocompatibility Complex (MHC) II-associating epitope.
Assuntos
Sistema Nervoso Central/imunologia , Encefalomielite Autoimune Experimental/imunologia , Glicoproteína Mielina-Oligodendrócito/imunologia , Fragmentos de Peptídeos/imunologia , Receptores CXCR3/imunologia , Células Th1/imunologia , Animais , Linfócitos T CD8-Positivos/imunologia , Linfócitos T CD8-Positivos/metabolismo , Sistema Nervoso Central/metabolismo , Progressão da Doença , Encefalomielite Autoimune Experimental/metabolismo , Epitopos , Feminino , Imunização , Interferon gama/imunologia , Interferon gama/metabolismo , Camundongos Endogâmicos C57BL , Glicoproteína Mielina-Oligodendrócito/administração & dosagem , Fragmentos de Peptídeos/administração & dosagem , Ratos , Receptores CXCR3/metabolismo , Índice de Gravidade de Doença , Células Th1/metabolismo , Células Th17/imunologia , Células Th17/metabolismo , Fatores de TempoRESUMO
Within the central nervous system, astrocytes and microglia are the primary responders to endogenous ligands released upon injury and stress, as well as to infectious pathogens. Toll-like receptors (TLRs) are implicated in recognition of both types of stimulus. Whether astrocytes respond as strongly as microglia to TLR agonists remains contentious. In this study, we have rigorously purified astrocytes to determine their capacity for autonomous TLR response, in absence of microglia. We used flow cytometry and differential adhesion as well as a myeloid lineage-specific suicide gene to purify astrocytes from mixed glial cultures and measured their response to TLR agonists. Our results show that the response of astrocytes to TLR2 and TLR3 agonists is greatly enhanced by, and response to TLR4 agonists is completely dependent on, the presence of functional microglia. In the case of the TLR4 response to lipopolysaccharide, microglia exert their effect on astrocytes at least partially through release of soluble mediators that directly activate or facilitate astrocyte responses. Our findings underline the contribution of glial crosstalk in CNS responses to injury or inflammation.
Assuntos
Astrócitos/metabolismo , Microglia/fisiologia , Receptor 2 Toll-Like/metabolismo , Receptor 3 Toll-Like/metabolismo , Receptor 4 Toll-Like/metabolismo , Animais , Animais Recém-Nascidos , Antígenos CD/metabolismo , Astrócitos/efeitos dos fármacos , Encéfalo/citologia , Antígeno CD11b/genética , Células Cultivadas , Quimiocina CCL2/metabolismo , Técnicas de Cocultura , Ensaio de Imunoadsorção Enzimática , Citometria de Fluxo , Proteína Glial Fibrilar Ácida/metabolismo , Glutamina/análogos & derivados , Glutamina/farmacologia , Indutores de Interferon/farmacologia , Interleucina-1beta/metabolismo , Macrófagos/efeitos dos fármacos , Macrófagos/fisiologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Microglia/efeitos dos fármacos , Compostos Organometálicos/farmacologia , Poli I-C/farmacologia , Polissacarídeos/farmacologia , Fator de Necrose Tumoral alfa/metabolismoRESUMO
In multiple sclerosis (MS), myelin-specific T cells are normally associated with destruction of myelin and axonal damage. However, in acute MS plaque, remyelination occurs concurrent with T-cell infiltration, which raises the question of whether T cells might stimulate myelin repair. We investigated the effect of myelin-specific T cells on oligodendrocyte formation at sites of axonal damage in the mouse hippocampal dentate gyrus. Infiltrating T cells specific for myelin proteolipid protein stimulated proliferation of chondroitin sulfate NG2-expressing oligodendrocyte precursor cells early after induction via axonal transection, resulting in a 25% increase in the numbers of oligodendrocytes. In contrast, T cells specific for ovalbumin did not stimulate the formation of new oligodendrocytes. In addition, infiltration of myelin-specific T cells enhanced the sprouting response of calretinergic associational/commissural fibers within the dentate gyrus. These results have implications for the perception of MS pathogenesis because they show that infiltrating myelin-specific T cells can stimulate oligodendrogenesis in the adult central nervous system.
Assuntos
Bainha de Mielina/imunologia , Bainha de Mielina/patologia , Neurogênese/imunologia , Oligodendroglia/imunologia , Oligodendroglia/patologia , Linfócitos T/imunologia , Envelhecimento , Animais , Axônios/metabolismo , Axônios/patologia , Calbindina 2 , Contagem de Células , Movimento Celular , Proliferação de Células , Citocinas/genética , Citocinas/metabolismo , Giro Denteado/metabolismo , Giro Denteado/patologia , Feminino , Camundongos , Proteína Proteolipídica de Mielina/metabolismo , Degeneração Neural/patologia , Neurônios Aferentes/metabolismo , Neurônios Aferentes/patologia , Especificidade de Órgãos/imunologia , Via Perfurante/metabolismo , Via Perfurante/patologia , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Proteína G de Ligação ao Cálcio S100/metabolismoRESUMO
Innate glial response is critical for the induction of inflammatory mediators and recruitment of leukocytes to sites of the injury in the CNS. We have examined the involvement of type I IFN signaling in the mouse hippocampus following sterile injury (transection of entorhinal afferents). Type I IFNs signal through a receptor (IFNAR), which involves activation of IFN regulatory factor (IRF)9, leading to the induction of IFN-stimulated genes including IRF7, that in turn enhances the induction of type I IFN. Axonal transection induced upregulation of IRF7 and IRF9 in hippocampus. Induction of IRF7 and IRF9 mRNAs was IFNAR dependent. Double-labeling immunofluorescence showed that IRF7 selectively was induced in Mac-1/CD11b(+) macrophages/microglia in hippocampus after axonal transection. IRF7 mRNA was also detected in microglia sorted by flow cytometry. Lack of type I IFN signaling resulted in increased leukocyte infiltration into the lesion-reactive hippocampus. Axonal lesion-induced CXCL10 gene expression was abrogated, whereas matrix metalloproteinase 9 mRNA was elevated in IFNAR-deficient mice. Our findings point to a role for type I IFN signaling in regulation of CNS response to sterile injury.