RESUMO
Immune-inflammatory activation impacts extracellular vesicles (EVs), including their miRNA cargo. There is evidence for changes in the EV miRNome in inflammation-associated neuropsychiatric disorders. This mouse study investigated: (1) effects of systemic lipopolysaccharide (LPS) and chronic social stress (CSS) on plasma EV miRNome; and (2) physiological, transcriptional, and behavioural effects of peripheral or central delivered LPS-activated EVs in recipient mice. LPS or CSS effects on the plasma EV miRNome were assessed by using microRNA sequencing. Recipient mice received plasma EVs isolated from LPS-treated or SAL-treated donor mice or vehicle only, either intravenously or into the nucleus accumbens (NAc), on three consecutive days. Bodyweight, spleen or NAc transcriptome and reward (sucrose) motivation were assessed. LPS and CSS increased the expression of 122 and decreased expression of 20 plasma EV miRNAs, respectively. Peripheral LPS-EVs reduced bodyweight, and both LPS-EVs and SAL-EVs increased spleen expression of immune-relevant genes. NAc-infused LPS-EVs increased the expression of 10 immune-inflammatory genes. Whereas motivation increased similarly across test days in all groups, the effect of test days was more pronounced in mice that received peripheral or central LPS-EVs compared with other groups. This study provides causal evidence that increased EV levels impact physiological and behavioural processes and are of potential relevance to neuropsychiatric disorders.
Assuntos
Vesículas Extracelulares/genética , Perfilação da Expressão Gênica/métodos , Lipopolissacarídeos/efeitos adversos , MicroRNAs/genética , Estresse Psicológico/genética , Animais , Vesículas Extracelulares/efeitos dos fármacos , Regulação da Expressão Gênica/efeitos dos fármacos , Masculino , Camundongos , Tamanho do Órgão/efeitos dos fármacos , Projetos Piloto , Análise de Sequência de RNA , Baço/efeitos dos fármacos , Baço/metabolismo , Estresse Psicológico/psicologiaRESUMO
Multiple sclerosis (MS) is a chronic inflammatory autoimmune disease of the central nervous system (CNS). Its first clinical presentation (clinically isolated syndrome, CIS) is often followed by the development of relapsing-remitting MS (RRMS). The periphery-to-CNS transmission of inflammatory molecules is a major pathophysiological pathway in MS. This could include signalling via extracellular vesicle (EV) microRNAs (miRNAs). In this study, we investigated the serum EV miRNome in CIS and RRMS patients and matched controls, with the aims to identify MS stage-specific differentially expressed miRNAs and investigate their biomarker potential and pathophysiological relevance. miRNA sequencing was conducted on serum EVs from CIS-remission, RRMS-relapse, and viral inflammatory CNS disorder patients, as well as from healthy and hospitalized controls. Differential expression analysis was conducted, followed by predictive power and target-pathway analysis. A moderate number of dysregulated serum EV miRNAs were identified in CIS-remission and RRMS-relapse patients, especially relative to healthy controls. Some of these miRNAs were also differentially expressed between the two MS stages and had biomarker potential for patient-control and CIS-RRMS separations. For the mRNA targets of the RRMS-relapse-specific EV miRNAs, biological processes inherent to MS pathophysiology were identified using in silico analysis. Study findings demonstrate that specific serum EV miRNAs have MS stage-specific biomarker potential and contribute to the identification of potential targets for novel, efficacious therapies.
Assuntos
Vesículas Extracelulares/metabolismo , Perfilação da Expressão Gênica , Regulação da Expressão Gênica , MicroRNAs/sangue , Esclerose Múltipla Recidivante-Remitente/sangue , Adolescente , Adulto , Idoso , Biomarcadores/sangue , Feminino , Humanos , Masculino , Pessoa de Meia-IdadeRESUMO
Despite the broad implications of the cannabinoid type 2 receptor (CB2) in neuroinflammatory processes, a suitable CB2-targeted probe is currently lacking in clinical routine. In this work, we synthesized 15 fluorinated pyridine derivatives and tested their binding affinities toward CB2 and CB1. With a sub-nanomolar affinity (Ki for CB2) of 0.8 nM and a remarkable selectivity factor of >12,000 over CB1, RoSMA-18-d6 exhibited outstanding in vitro performance characteristics and was radiofluorinated with an average radiochemical yield of 10.6 ± 3.8% (n = 16) and molar activities ranging from 52 to 65 GBq/µmol (radiochemical purity > 99%). [18F]RoSMA-18-d6 showed exceptional CB2 attributes as demonstrated by in vitro autoradiography, ex vivo biodistribution, and positron emission tomography (PET). Further, [18F]RoSMA-18-d6 was used to detect CB2 upregulation on postmortem human ALS spinal cord tissues. Overall, these results suggest that [18F]RoSMA-18-d6 is a promising CB2 PET radioligand for clinical translation.
Assuntos
Piridinas/farmacologia , Compostos Radiofarmacêuticos/farmacologia , Receptor CB2 de Canabinoide/metabolismo , Animais , Encéfalo/diagnóstico por imagem , Radioisótopos de Flúor/química , Humanos , Ligantes , Masculino , Simulação de Acoplamento Molecular , Estrutura Molecular , Tomografia por Emissão de Pósitrons , Piridinas/síntese química , Piridinas/farmacocinética , Compostos Radiofarmacêuticos/síntese química , Compostos Radiofarmacêuticos/farmacocinética , Ratos Wistar , Medula Espinal/diagnóstico por imagem , Baço/diagnóstico por imagem , Relação Estrutura-Atividade , Trítio/químicaRESUMO
The cannabinoid type 2 (CB2) receptor has emerged as a valuable target for therapy and imaging of immune-mediated pathologies. With the aim to find a suitable radiofluorinated analogue of the previously reported CB2 positron emission tomography (PET) radioligand [11C]RSR-056, 38 fluorinated derivatives were synthesized and tested by in vitro binding assays. With a Ki (hCB2) of 6 nM and a selectivity factor of nearly 700 over cannabinoid type 1 receptors, target compound 3 exhibited optimal in vitro properties and was selected for evaluation as a PET radioligand. [18F]3 was obtained in an average radiochemical yield of 11 ± 4% and molar activities between 33 and 114 GBq/µmol. Specific binding of [18F]3 to CB2 was demonstrated by in vitro autoradiography and in vivo PET experiments using the CB2 ligand GW-405â¯833. Metabolite analysis revealed only intact [18F]3 in the rat brain. [18F]3 detected CB2 upregulation in human amyotrophic lateral sclerosis spinal cord tissue and may thus become a candidate for diagnostic use in humans.
Assuntos
Encéfalo/metabolismo , Radioisótopos de Flúor/metabolismo , Neuroimagem/métodos , Tomografia por Emissão de Pósitrons/métodos , Piridinas/química , Compostos Radiofarmacêuticos/metabolismo , Receptor CB2 de Canabinoide/metabolismo , Animais , Encéfalo/diagnóstico por imagem , AMP Cíclico/metabolismo , Radioisótopos de Flúor/química , Hepatócitos/metabolismo , Humanos , Ligantes , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Estrutura Molecular , Conformação Proteica , Radioquímica , Compostos Radiofarmacêuticos/química , Ratos , Ratos Wistar , Receptor CB2 de Canabinoide/química , Relação Estrutura-AtividadeRESUMO
Oligodendrocyte pathology is increasingly implicated in neurodegenerative diseases as oligodendrocytes both myelinate and provide metabolic support to axons. In multiple sclerosis (MS), demyelination in the central nervous system thus leads to neurodegeneration, but the severity of MS between patients is very variable. Disability does not correlate well with the extent of demyelination1, which suggests that other factors contribute to this variability. One such factor may be oligodendrocyte heterogeneity. Not all oligodendrocytes are the same-those from the mouse spinal cord inherently produce longer myelin sheaths than those from the cortex2, and single-cell analysis of the mouse central nervous system identified further differences3,4. However, the extent of human oligodendrocyte heterogeneity and its possible contribution to MS pathology remain unknown. Here we performed single-nucleus RNA sequencing from white matter areas of post-mortem human brain from patients with MS and from unaffected controls. We identified subclusters of oligodendroglia in control human white matter, some with similarities to mouse, and defined new markers for these cell states. Notably, some subclusters were underrepresented in MS tissue, whereas others were more prevalent. These differences in mature oligodendrocyte subclusters may indicate different functional states of oligodendrocytes in MS lesions. We found similar changes in normal-appearing white matter, showing that MS is a more diffuse disease than its focal demyelination suggests. Our findings of an altered oligodendroglial heterogeneity in MS may be important for understanding disease progression and developing therapeutic approaches.
Assuntos
Encéfalo/metabolismo , Encéfalo/patologia , Esclerose Múltipla/patologia , Oligodendroglia/patologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Animais , Autopsia , Biomarcadores , Estudos de Casos e Controles , Progressão da Doença , Feminino , Perfilação da Expressão Gênica , Regulação da Expressão Gênica/genética , Humanos , Masculino , Camundongos , Pessoa de Meia-Idade , Esclerose Múltipla/genética , Bainha de Mielina/genética , Bainha de Mielina/metabolismo , Bainha de Mielina/patologia , Oligodendroglia/metabolismo , Remielinização/genética , Análise de Sequência de RNA , Transcrição Gênica , Substância Branca/citologia , Substância Branca/metabolismo , Substância Branca/patologiaRESUMO
Maternal immune activation (mIA) in rodents is rapidly emerging as a key model for neurodevelopmental disorders such as autism spectrum disorder (ASD) and schizophrenia. Here, we optimise a mIA model in rats, aiming to address certain limitations of current work in this field. Specifically, the lack of clear evidence for methodology chosen, identification of successful induction of mIA in the dams and investigation of male offspring only. We focus on gestational and early juvenile changes in offspring following mIA, as detailed information on these critical early developmental time points is sparse. Following strain (Wistar, Lister Hooded, Sprague Dawley) comparison and selection, and polyriboinosinic-polyribocytidylic acid (poly I:C) dose selection (2.5-15â¯mg/kg single or once daily for 5â¯days), mIA was induced in pregnant Wistar rats with 10â¯mg/kg poly I:C i.p. on gestational day (GD) 15. Early morphometric analysis was conducted in male and female offspring at GD21 and postnatal day (PD) 21, eight dams for each treatment at each time point were used, 32 in total. Subsequent microglia analysis was conducted at PD21 in a small group of offspring. Poly I:C at 10â¯mg/kg i.p. induced a robust, but variable, plasma IL-6 response 3â¯h post-injection and reduced body weight at 6â¯h and 24â¯h post-injection in two separate cohorts of Wistar rats at GD15. Plasma IL-6 was not elevated at PD21 in offspring or dams. Poly I:C-induced mIA did not affect litter numbers, but resulted in PD21 pup, and GD21 placenta growth restriction. Poly I:C significantly increased microglial activation at PD21 in male hippocampi. We have identified 10â¯mg/kg poly I:C i.p on GD15 as a robust experimental approach for inducing mIA in Wistar rats and used this to identify early neurodevelopmental changes. This work provides a framework to study the developmental trajectory of disease-relevant, sex-specific phenotypic changes in rats.
Assuntos
Imunidade Ativa/fisiologia , Ativação Linfocitária/imunologia , Efeitos Tardios da Exposição Pré-Natal/imunologia , Animais , Comportamento Animal/fisiologia , Citocinas/imunologia , Modelos Animais de Doenças , Feminino , Hipocampo/efeitos dos fármacos , Imunidade Ativa/imunologia , Interleucina-6/metabolismo , Ativação Linfocitária/fisiologia , Masculino , Modelos Animais , Atividade Motora/efeitos dos fármacos , Transtornos do Neurodesenvolvimento , Placenta/metabolismo , Poli I-C/farmacologia , Gravidez , Ratos , Ratos Wistar , Esquizofrenia/imunologia , Linfócitos T/imunologiaRESUMO
Aberrant epileptic activity is detectable at early disease stages in Alzheimer's disease (AD) patients and in AD mouse models. Here, we investigated in young ArcticAß mice whether AD-like pathology renders neuronal networks more susceptible to the development of acquired epilepsy induced by unilateral intrahippocampal injection of kainic acid (IHK). In this temporal lobe epilepsy model, IHK induces a status epilepticus followed after two weeks by spontaneous recurrent seizures (SRS). ArcticAß mice exhibited more severe status epilepticus and early onset of SRS. This hyperexcitable phenotype was characterized in CA1 neurons by decreased synaptic strength, increased kainic acid-induced LTP and reduced frequency of spontaneous inhibitory currents. However, no difference in neurodegeneration, neuroinflammation, axonal reorganization or adult neurogenesis was observed in ArcticAß mice compared to wild-type littermates following IHK-induced epileptogenesis. Neuropeptide Y (NPY) expression was reduced at baseline and its IHK-induced elevation in mossy fibres and granule cells was attenuated. However, although this alteration might underlie premature seizure onset, neutralization of soluble Aß species by intracerebroventricular Aß-specific antibody application mitigated the hyperexcitable phenotype of ArcticAß mice and prevented early SRS onset. Therefore, the development of seizures at early stages of AD is mediated primarily by Aß species causing widespread changes in synaptic function.
Assuntos
Doença de Alzheimer , Peptídeos beta-Amiloides , Epilepsia do Lobo Temporal , Hipocampo , Plasticidade Neuronal , Convulsões , Doença de Alzheimer/metabolismo , Doença de Alzheimer/fisiopatologia , Peptídeos beta-Amiloides/metabolismo , Animais , Região CA1 Hipocampal/metabolismo , Região CA1 Hipocampal/fisiopatologia , Giro Denteado/metabolismo , Giro Denteado/fisiopatologia , Modelos Animais de Doenças , Eletroencefalografia , Epilepsia do Lobo Temporal/metabolismo , Epilepsia do Lobo Temporal/fisiopatologia , Agonistas de Aminoácidos Excitatórios/farmacologia , Hipocampo/metabolismo , Hipocampo/fisiopatologia , Ácido Caínico/farmacologia , Masculino , Camundongos , Camundongos Transgênicos , Plasticidade Neuronal/fisiologia , Convulsões/metabolismo , Convulsões/fisiopatologia , Estado Epiléptico/metabolismo , Estado Epiléptico/fisiopatologiaRESUMO
Triggering receptor expressed on myeloid cells-2 (TREM-2), a transmembrane receptor expressed by macrophages, microglia, and osteoclasts (OCs), plays a protective role in late-onset Alzheimer Disease (AD). To validate TREM-2 as a therapeutic target in AD, its potential secondary parallel effect on bone homeostasis should be clarified. However, animal models and monolayer cultures of human cells were shown poorly predictive of TREM-2 function in human. Therefore, this study aimed to engineer a tridimensional in vitro model using human progenitors differentiated into osteoblasts and OCs, recapitulating physiological bone homeostasis. Human bone marrow-derived mesenchymal cells were seeded and cultured under perfusion inside a collagen type I scaffold for 3 weeks, generating osteoblasts and mineralized matrix. Human peripheral blood-derived CD14+ monocytes were subsequently seeded through the generated tissue, thanks to perfusion flow, and further cultured for up to 3 weeks with an inductive medium, generating mature OCs. This culture system supported collagenous matrix deposition and resorption, allowing for the investigation of kinetic of soluble TREM-2 over the coculture time. Agonistic activation of TREM-2 in this model had no effect on OC activity or on mineralized matrix turnover. In conclusion, the engineered culture system represents a tridimensional, in vitro human bone model for drug testing and suggested no effect of TREM-2 agonist on bone resorption.
Assuntos
Osso e Ossos/citologia , Homeostase , Glicoproteínas de Membrana/metabolismo , Modelos Biológicos , Osteoclastos/citologia , Receptores Imunológicos/metabolismo , Engenharia Tecidual , Osso e Ossos/metabolismo , Células Cultivadas , Humanos , Técnicas In Vitro , Osteoclastos/metabolismoRESUMO
Astrocytes are involved in non-cell-autonomous pathogenic cascades in amyotrophic lateral sclerosis (ALS); however, their role is still debated. We show that astrocytic NF-κB activation drives microglial proliferation and leukocyte infiltration in the SOD1 (G93A) ALS model. This response prolongs the presymptomatic phase, delaying muscle denervation and decreasing disease burden, but turns detrimental in the symptomatic phase, accelerating disease progression. The transition corresponds to a shift in the microglial phenotype showing two effects that can be dissociated by temporally controlling NF-κB activation. While NF-κB activation in astrocytes induced a Wnt-dependent microglial proliferation in the presymptomatic phase with neuroprotective effects on motoneurons, in later stage, astrocyte NF-κB-dependent microglial activation caused an accelerated disease progression. Notably, suppression of the early microglial response by CB2R agonists had acute detrimental effects. These data identify astrocytes as important regulators of microglia expansion and immune response. Therefore, stage-dependent microglia modulation may be an effective therapeutic strategy in ALS.
Assuntos
Esclerose Lateral Amiotrófica/imunologia , Astrócitos/imunologia , NF-kappa B/imunologia , Esclerose Lateral Amiotrófica/genética , Esclerose Lateral Amiotrófica/patologia , Esclerose Lateral Amiotrófica/terapia , Animais , Astrócitos/patologia , Modelos Animais de Doenças , Camundongos , Camundongos Transgênicos , Microglia/imunologia , Microglia/patologia , Neurônios Motores/imunologia , Neurônios Motores/patologia , NF-kappa B/genética , Receptor CB2 de Canabinoide/agonistas , Receptor CB2 de Canabinoide/genética , Receptor CB2 de Canabinoide/imunologia , Superóxido Dismutase/genética , Superóxido Dismutase/imunologia , Superóxido Dismutase-1/genética , Superóxido Dismutase-1/imunologiaRESUMO
Genetic variants in the triggering receptor expressed on myeloid cells 2 (TREM2) increase the risk for several neurodegenerative diseases including Alzheimer's disease and frontotemporal dementia (FTD). Homozygous TREM2 missense mutations, such as p.T66M, lead to the FTD-like syndrome, but how they cause pathology is unknown. Using CRISPR/Cas9 genome editing, we generated a knock-in mouse model for the disease-associated Trem2 p.T66M mutation. Consistent with a loss-of-function mutation, we observe an intracellular accumulation of immature mutant Trem2 and reduced generation of soluble Trem2 similar to patients with the homozygous p.T66M mutation. Trem2 p.T66M knock-in mice show delayed resolution of inflammation upon in vivo lipopolysaccharide stimulation and cultured macrophages display significantly reduced phagocytic activity. Immunohistochemistry together with in vivo TSPO small animal positron emission tomography (µPET) demonstrates an age-dependent reduction in microglial activity. Surprisingly, perfusion magnetic resonance imaging and FDG-µPET imaging reveal a significant reduction in cerebral blood flow and brain glucose metabolism. Thus, we demonstrate that a TREM2 loss-of-function mutation causes brain-wide metabolic alterations pointing toward a possible function of microglia in regulating brain glucose metabolism.
Assuntos
Encéfalo/patologia , Demência Frontotemporal/patologia , Glucose/metabolismo , Glicoproteínas de Membrana/genética , Microglia/fisiologia , Mutação de Sentido Incorreto , Perfusão , Receptores Imunológicos/genética , Animais , Modelos Animais de Doenças , Técnicas de Introdução de Genes , Humanos , Imuno-Histoquímica , Imageamento por Ressonância Magnética , Camundongos , Proteínas Mutantes/genética , Tomografia por Emissão de PósitronsRESUMO
Immunotherapeutic approaches are currently the most advanced treatments for Alzheimer's disease (AD). Antibodies against amyloid ß-peptide (Aß) bind to amyloid plaques and induce their clearance by microglia via Fc receptor-mediated phagocytosis. Dysfunctions of microglia may play a pivotal role in AD pathogenesis and could result in reduced efficacy of antibody-mediated Aß clearance. Recently, heterozygous mutations in the triggering receptor expressed on myeloid cells 2 (TREM2), a microglial gene involved in phagocytosis, were genetically linked to late onset AD Loss of TREM2 reduces the ability of microglia to engulf Aß. We have now investigated whether loss of TREM2 affects the efficacy of immunotherapeutic approaches. We show that anti-Aß antibodies stimulate Aß uptake and amyloid plaque clearance in a dose-dependent manner in the presence or absence of TREM2. However, TREM2-deficient N9 microglial cell lines, macrophages as well as primary microglia showed significantly reduced uptake of antibody-bound Aß and as a consequence reduced clearance of amyloid plaques. Titration experiments revealed that reduced efficacy of amyloid plaque clearance by Trem2 knockout cells can be compensated by elevating the concentration of therapeutic antibodies.
Assuntos
Amiloide/metabolismo , Glicoproteínas de Membrana/deficiência , Neuroglia/imunologia , Fagocitose , Receptores Imunológicos/deficiência , Animais , Células Cultivadas , Camundongos Endogâmicos C57BL , Camundongos Knockout , Neuroglia/fisiologiaRESUMO
The olfactory epithelium (OE) of mice deficient in cystic fibrosis transmembrane conductance regulator (CFTR) exhibits ion transport deficiencies reported in human CF airways, as well as progressive neuronal loss, suggesting defects in olfactory neuron homeostasis. Microvillar cells, a specialized OE cell-subtype, have been implicated in maintaining tissue homeostasis. These cells are endowed with a PLCß2/IP3 R3/TRPC6 signal transduction pathway modulating release of neuropeptide Y (NPY), which stimulates OE stem cell activity. It is unknown, however, whether microvillar cells also mediate the deficits observed in CFTR-null mice. Here we show that Cftr mRNA in mouse OE is exclusively localized in microvillar cells and CFTR immunofluorescence is coassociated with the scaffolding protein NHERF-1 and PLCß2 in microvilli. In CFTR-null mice, PLCß2 was undetectable, NHERF-1 mislocalized, and IP3 R3 more intensely stained, along with increased levels of NPY, suggesting profound alteration of the PLCß2/IP3 R3 signaling pathway. In addition, basal olfactory neuron homeostasis was altered, shown by increased progenitor cell proliferation, differentiation, and apoptosis and by reduced regenerative capacity following methimazole-induced neurodegeneration. The importance of CFTR in microvillar cells was further underscored by decreased thickness of the OE mucus layer and increased numbers of immune cells within this tissue in CFTR-KO mice. Finally, we observed enhanced immune responses to an acute viral-like infection, as well as hyper-responsiveness to chemical and physical stimuli applied intranasally. Taken together, these data strengthen the notion that microvillar cells in the OE play a key role in maintaining tissue homeostasis and identify several mechanisms underlying this regulation through the multiple functions of CFTR.
Assuntos
Regulador de Condutância Transmembrana em Fibrose Cística/metabolismo , Regulação da Expressão Gênica/genética , Homeostase/fisiologia , Neurônios/fisiologia , Bulbo Olfatório/citologia , Animais , Antígenos CD , Antitireóideos/farmacologia , Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Bromodesoxiuridina/metabolismo , Caspase 3/metabolismo , Regulador de Condutância Transmembrana em Fibrose Cística/genética , Epitélio/metabolismo , Regulação da Expressão Gênica/efeitos dos fármacos , Homeostase/efeitos dos fármacos , Homeostase/genética , Receptores de Inositol 1,4,5-Trifosfato/metabolismo , Antígeno Ki-67/metabolismo , Metimazol/farmacologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos CFTR , Camundongos Transgênicos , Neurônios/efeitos dos fármacos , Polinucleotídeos/farmacologiaRESUMO
Epidemiological studies have shown a clear association between maternal infection and schizophrenia or autism in the progeny. Animal models have revealed maternal immune activation (mIA) to be a profound risk factor for neurochemical and behavioural abnormalities in the offspring. Microglial priming has been proposed as a major consequence of mIA, and represents a critical link in a causal chain that leads to the wide spectrum of neuronal dysfunctions and behavioural phenotypes observed in the juvenile, adult or aged offspring. Such diversity of phenotypic outcomes in the mIA model are mirrored by recent clinical evidence suggesting that infectious exposure during pregnancy is also associated with epilepsy and, to a lesser extent, cerebral palsy in children. Preclinical research also suggests that mIA might precipitate the development of Alzheimer and Parkinson diseases. Here, we summarize and critically review the emerging evidence that mIA is a shared environmental risk factor across CNS disorders that varies as a function of interactions between genetic and additional environmental factors. We also review ongoing clinical trials targeting immune pathways affected by mIA that may play a part in disease manifestation. In addition, future directions and outstanding questions are discussed, including potential symptomatic, disease-modifying and preventive treatment strategies.
Assuntos
Encéfalo/embriologia , Doenças do Sistema Nervoso Central/epidemiologia , Complicações Infecciosas na Gravidez/epidemiologia , Efeitos Tardios da Exposição Pré-Natal/epidemiologia , Doença de Alzheimer/epidemiologia , Doença de Alzheimer/imunologia , Animais , Encéfalo/imunologia , Doenças do Sistema Nervoso Central/imunologia , Paralisia Cerebral/epidemiologia , Paralisia Cerebral/imunologia , Transtornos Globais do Desenvolvimento Infantil/epidemiologia , Transtornos Globais do Desenvolvimento Infantil/imunologia , Feminino , Humanos , Doença de Parkinson/epidemiologia , Doença de Parkinson/imunologia , Gravidez , Complicações Infecciosas na Gravidez/imunologia , Efeitos Tardios da Exposição Pré-Natal/imunologia , Esquizofrenia/epidemiologia , Esquizofrenia/imunologiaRESUMO
For the last 20 years, the "amyloid cascade hypothesis" has dominated research aimed at understanding, preventing, and curing Alzheimer's disease (AD). During that time researchers have acquired an enormous amount of data and have been successful, more than 300 times, in curing the disease in animal model systems by treatments aimed at clearing amyloid deposits. However, to date similar strategies have not been successful in human AD patients. Hence, before rushing into further clinical trials with compounds that aim at lowering amyloid-beta (Aß) levels in increasingly younger people, it would be of highest priority to re-assess the initial assumption that accumulation of Aß in the brain is the primary pathological event driving AD. Here we question this assumption by highlighting experimental evidence in support of the alternative hypothesis suggesting that APP and Aß are part of a neuronal stress/injury system, which is up-regulated to counteract inflammation/oxidative stress-associated neurodegeneration that could be triggered by a brain injury, chronic infections, or a systemic disease. In AD, this protective program may be overridden by genetic and other risk factors, or its maintenance may become dysregulated during aging. Here, we provide a hypothetical example of a hypothesis-driven correlation between car accidents and airbag release in analogy to the evolution of the amyloid focus and as a way to offer a potential explanation for the failure of the AD field to translate the success of amyloid-related therapeutic strategies in experimental models to the clinic.
Assuntos
Doença de Alzheimer/fisiopatologia , Envelhecimento/fisiologia , Doença de Alzheimer/terapia , Peptídeos beta-Amiloides/metabolismo , Precursor de Proteína beta-Amiloide/metabolismo , Animais , Humanos , Neurônios/fisiologiaRESUMO
BACKGROUND: Reelin and its downstream signaling members are important modulators of actin and microtubule cytoskeleton dynamics, a fundamental prerequisite for proper neurodevelopment and adult neuronal functions. Reductions in Reelin levels have been suggested to contribute to Alzheimer's disease (AD) pathophysiology. We have previously reported an age-related reduction in Reelin levels and its accumulation in neuritic varicosities along the olfactory-limbic tracts, which correlated with cognitive impairments in aged mice. Here, we aimed to investigate whether a similar Reelin-associated neuropathology is observed in the aged human hippocampus and whether it correlated with dementia status. RESULTS: Our immunohistochemical stainings revealed the presence of N- and C-terminus-containing Reelin fragments in corpora amylacea (CAm), aging-associated spherical deposits. The density of these deposits was increased in the molecular layer of the subiculum of AD compared to non-demented individuals. Despite the limitation of a small sample size, our evaluation of several neuronal and glial markers indicates that the presence of Reelin in CAm might be related to aging-associated impairments in neuronal transport leading to accumulation of organelles and protein metabolites in neuritic varicosities, as previously suggested by the findings and discussions in rodents and primates. CONCLUSIONS: Our results indicate that aging- and disease-associated changes in Reelin levels and proteolytic processing might play a role in the formation of CAm by altering cytoskeletal dynamics. However, its presence may also be an indicator of a degenerative state of neuritic compartments.
Assuntos
Doença de Alzheimer/metabolismo , Moléculas de Adesão Celular Neuronais/metabolismo , Proteínas da Matriz Extracelular/metabolismo , Hipocampo/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Neurônios/metabolismo , Serina Endopeptidases/metabolismo , Idoso de 80 Anos ou mais , Doença de Alzheimer/líquido cefalorraquidiano , Astrócitos/metabolismo , Western Blotting , Moléculas de Adesão Celular Neuronais/líquido cefalorraquidiano , Proteínas da Matriz Extracelular/líquido cefalorraquidiano , Feminino , Imunofluorescência , Humanos , Imuno-Histoquímica , Masculino , Microglia/metabolismo , Proteínas do Tecido Nervoso/líquido cefalorraquidiano , Proteína Reelina , Serina Endopeptidases/líquido cefalorraquidianoRESUMO
Magnetic resonance imaging (MRI) can be used to monitor pathological changes in Alzheimer's disease (AD). The objective of this longitudinal study was to assess the effects of progressive amyloid-related pathology on multiple MRI parameters in transgenic arcAß mice, a mouse model of cerebral amyloidosis. Diffusion-weighted imaging (DWI), T1-mapping and quantitative susceptibility mapping (QSM), a novel MRI based technique, were applied to monitor structural alterations and changes in tissue composition imposed by the pathology over time. Vascular function and integrity was studied by assessing blood-brain barrier integrity with dynamic contrast-enhanced MRI and cerebral microbleed (CMB) load with susceptibility weighted imaging and QSM. A linear mixed effects model was built for each MRI parameter to incorporate effects within and between groups (i.e. genotype) and to account for changes unrelated to the disease pathology. Linear mixed effects modelling revealed a strong association of all investigated MRI parameters with age. DWI and QSM in addition revealed differences between arcAß and wt mice over time. CMBs became apparent in arcAß mice with 9 month of age; and the CMB load reflected disease stage. This study demonstrates the benefits of linear mixed effects modelling of longitudinal imaging data. Moreover, the diagnostic utility of QSM and assessment of CMB load should be exploited further in studies of AD.
Assuntos
Encéfalo/irrigação sanguínea , Angiopatia Amiloide Cerebral/diagnóstico por imagem , Imagem de Difusão por Ressonância Magnética/métodos , Animais , Barreira Hematoencefálica , Encéfalo/diagnóstico por imagem , Angiopatia Amiloide Cerebral/genética , Modelos Animais de Doenças , Modelos Lineares , Estudos Longitudinais , Masculino , Camundongos , Camundongos TransgênicosRESUMO
As research into various aging-associated neurodegenerative disorders reveals their immense pathophysiological complexity, the focus is currently shifting from studying changes in an advanced disease state to investigations involving pre-symptomatic periods, possible aberrations in early life, and even abnormalities in brain development. Recent studies on the etiology of schizophrenia and autism spectrum disorders revealed a profound impact of neurodevelopmental disturbances on disease predisposition, onset and progression. Here, we discuss how a prenatal immune challenge can affect the developing brain-with a selective focus on the impact on microglia, the brain's immune cells-and the implications for brain aging and its associated risk of developing Alzheimer's disease.
Assuntos
Encéfalo/crescimento & desenvolvimento , Encéfalo/patologia , Doenças do Sistema Imunitário/patologia , Sistema Imunitário/fisiologia , Efeitos Tardios da Exposição Pré-Natal/imunologia , Envelhecimento/efeitos dos fármacos , Envelhecimento/imunologia , Envelhecimento/patologia , Animais , Encéfalo/efeitos dos fármacos , Encéfalo/imunologia , Feminino , Humanos , Sistema Imunitário/imunologia , Microglia/efeitos dos fármacos , Microglia/imunologia , Microglia/patologia , Poli I-C/farmacologia , Gravidez , Efeitos Tardios da Exposição Pré-Natal/patologiaRESUMO
Despite tremendous investments in understanding the complex molecular mechanisms underlying Alzheimer disease (AD), recent clinical trials have failed to show efficacy. A potential problem underlying these failures is the assumption that the molecular mechanism mediating the genetically determined form of the disease is identical to the one resulting in late-onset AD. Here, we integrate experimental evidence outside the 'spotlight' of the genetic drivers of amyloid-ß (Aß) generation published during the past two decades, and present a mechanistic explanation for the pathophysiological changes that characterize late-onset AD. We propose that chronic inflammatory conditions cause dysregulation of mechanisms to clear misfolded or damaged neuronal proteins that accumulate with age, and concomitantly lead to tau-associated impairments of axonal integrity and transport. Such changes have several neuropathological consequences: focal accumulation of mitochondria, resulting in metabolic impairments; induction of axonal swelling and leakage, followed by destabilization of synaptic contacts; deposition of amyloid precursor protein in swollen neurites, and generation of aggregation-prone peptides; further tau hyperphosphorylation, ultimately resulting in neurofibrillary tangle formation and neuronal death. The proposed sequence of events provides a link between Aß and tau-related neuropathology, and underscores the concept that degenerating neurites represent a cause rather than a consequence of Aß accumulation in late-onset AD.
Assuntos
Doença de Alzheimer/diagnóstico , Doença de Alzheimer/genética , Idoso , Doença de Alzheimer/patologia , Doença de Alzheimer/fisiopatologia , Peptídeos beta-Amiloides/genética , Animais , Encéfalo/patologia , Encéfalo/fisiopatologia , Morte Celular/genética , Morte Celular/fisiologia , Modelos Animais de Doenças , Progressão da Doença , Humanos , Mediadores da Inflamação/sangue , Camundongos , Neuritos/patologia , Neuritos/fisiologia , Emaranhados Neurofibrilares/genética , Emaranhados Neurofibrilares/patologia , Emaranhados Neurofibrilares/fisiologia , Deficiências na Proteostase/diagnóstico , Deficiências na Proteostase/genética , Deficiências na Proteostase/patologia , Deficiências na Proteostase/fisiopatologia , Proteínas tau/genéticaRESUMO
The extracellular signaling protein Reelin, indispensable for proper neuronal migration and cortical layering during development, is also expressed in the adult brain where it modulates synaptic functions. It has been shown that proteolytic processing of Reelin decreases its signaling activity and promotes Reelin aggregation in vitro, and that proteolytic processing is affected in various neurological disorders, including Alzheimer's disease (AD). However, neither the pathophysiological significance of dysregulated Reelin cleavage, nor the involved proteases and their modulators are known. Here we identified the serine protease tissue plasminogen activator (tPA) and two matrix metalloproteinases, ADAMTS-4 and ADAMTS-5, as Reelin cleaving enzymes. Moreover, we assessed the influence of several endogenous protease inhibitors, including tissue inhibitors of metalloproteinases (TIMPs), α-2-Macroglobulin, and multiple serpins, as well as matrix metalloproteinase 9 (MMP-9) on Reelin cleavage, and described their complex interplay in the regulation of this process. Finally, we could demonstrate that in the murine hippocampus, the expression levels and localization of Reelin proteases largely overlap with that of Reelin. While this pattern remained stable during normal aging, changes in their protein levels coincided with accelerated Reelin aggregation in a mouse model of AD.
Assuntos
Proteínas ADAM/metabolismo , Moléculas de Adesão Celular Neuronais/metabolismo , Proteínas da Matriz Extracelular/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Pró-Colágeno N-Endopeptidase/metabolismo , Proteólise , Serina Endopeptidases/metabolismo , Ativador de Plasminogênio Tecidual/metabolismo , Proteína ADAMTS4 , Proteína ADAMTS5 , Animais , Moléculas de Adesão Celular Neuronais/química , Matriz Extracelular/metabolismo , Proteínas da Matriz Extracelular/química , Células HEK293 , Células HeLa , Hipocampo/citologia , Hipocampo/enzimologia , Humanos , Imuno-Histoquímica , Metaloproteinase 9 da Matriz/metabolismo , Camundongos , Camundongos Transgênicos , Proteínas do Tecido Nervoso/química , Processamento de Proteína Pós-Traducional , Transporte Proteico , Proteína Reelina , Serina Endopeptidases/químicaRESUMO
The main olfactory epithelium consists of 4 major cell types: sensory neurons, supporting cells, microvillar cells, and basal progenitor cells. Several populations of microvillar olfactory cells have been described, whose properties are not yet fully understood. In this study, we aimed to clarify the classification of microvillar cells by introducing a specific marker, CD73. Furthermore, we investigated the turnover of CD73-microvillar cells during adult life. Using direct and indirect immunofluorescence in adult main olfactory epithelium, we first demonstrate that ecto-5'-nucleotidase (CD73) is a reliable marker for microvillar cells reported previously to express phospholipase C ß2 (PLC ß2) along with type 3 IP(3) receptors (IP(3)R3) and transient receptor potential channels 6 (TRPC6), as well as for cells labeled by transgenic expression of tauGFP driven by the IP(3)R3 promoter. The ubiquitous CD73 immunoreactivity in the microvilli of these 2 cell populations indicates that they correspond to the same cell type (CD73-microvillar cell), endowed with a signal transduction cascade mobilizing Ca(++) from intracellular stores. These microvillar cells respond to odors, possess a basal process, and do not degenerate after bulbectomy, suggesting that they contribute to cellular homeostasis in the olfactory epithelium. Next, we examined whether CD73-microvillar cells undergo turnover in the adult olfactory epithelium. By combining CD73 immunofluorescence and BrdU pulse labeling, we show delayed BrdU incorporation in a small fraction of CD73-positive microvillar cells, which persists for several weeks after BrdU administration. These findings indicate that CD73-microvillar cells likely differentiate from proliferating progenitor cells and have a slow turnover despite their apical position in the olfactory epithelium. These combined properties are unique among olfactory cells, in line with the possibility that they might regulate cellular homeostasis driven by extracellular ATP and adenosine.