ABSTRACT
Cerebral amyloid ß (Aß) accumulation is pathogenically associated with sporadic Alzheimer's disease (SAD). BACE-1 is involved in Aß generation while insulin-degrading enzyme (IDE) partakes in Aß proteolytic clearance. Vulnerable regions in AD brains show increased BACE-1 protein levels and enzymatic activity while the opposite occurs with IDE. Another common feature in SAD brains is Notch1 overexpression. Here we demonstrate an increase in mRNA levels of Hey-1, a Notch target gene, and a decrease of IDE transcripts in the hippocampus of SAD brains as compared to controls. Transient transfection of Notch intracellular domain (NICD) in N2aSW cells, mouse neuroblastoma cells (N2a) stably expressing human amyloid precursor protein (APP) Swedish mutation, reduce IDE mRNA levels, promoting extracellular Aß accumulation. Also, NICD, HES-1 and Hey-1 overexpression result in decreased IDE proximal promoter activity. This effect was mediated by 2 functional sites located at -379/-372 and -310-303 from the first translation start site in the -575/-19 (556 bp) fragment of IDE proximal promoter. By site-directed mutagenesis of the IDE promoter region we reverted the inhibitory effect mediated by NICD transfection suggesting that these sites are indeed responsible for the Notch-mediated inhibition of the IDE gene expression. Intracranial injection of the Notch ligand JAG-1 in Tg2576 mice, expressing the Swedish mutation in human APP, induced overexpression of HES-1 and Hey-1 and reduction of IDE mRNA levels, respectively. Our results support our theory that a Notch-dependent IDE transcriptional modulation may impact on Aß metabolism providing a functional link between Notch signaling and the amyloidogenic pathway in SAD.
Subject(s)
Amyloid beta-Protein Precursor/metabolism , Basic Helix-Loop-Helix Transcription Factors/metabolism , Cell Cycle Proteins/metabolism , Homeodomain Proteins/metabolism , Insulysin/metabolism , Promoter Regions, Genetic , Signal Transduction/physiology , Transcription, Genetic , Amyloid Precursor Protein Secretases/metabolism , Amyloid beta-Protein Precursor/genetics , Animals , Aspartic Acid Endopeptidases/metabolism , Basic Helix-Loop-Helix Transcription Factors/genetics , Cell Cycle Proteins/genetics , Cell Line , Hippocampus/metabolism , Homeodomain Proteins/genetics , Humans , Insulysin/genetics , Mice , Protein Binding , Receptors, Notch/genetics , Receptors, Notch/metabolism , Transcription Factor HES-1ABSTRACT
Peripheral inflammation triggers exacerbation in the central brain's ongoing damage in several neurodegenerative diseases. Systemic inflammatory stimulus induce a general response known as sickness behaviour, indicating that a peripheral stimulus can induce the synthesis of cytokines in the brain. In Parkinson's disease (PD), inflammation was mainly associated with microglia activation that can underlie the neurodegeneration of neurons in the substantia nigra (SN). Peripheral inflammation can transform the "primed" microglia into an "active" state, which can trigger stronger responses dealing with neurodegenerative processes. Numerous evidences show that systemic inflammatory processes exacerbate ongoing neurodegeneration in PD patient and animal models. Anti-inflammatory treatment in PD patients exerts a neuroprotective effect. In the present paper, we analyse the effect of peripheral infections in the etiology and progression in PD patients and animal models, suggesting that these peripheral immune challenges can exacerbate the symptoms in the disease.
ABSTRACT
Parkinson's disease is a neurodegenerative disorder with uncertain aetiology and ill-defined pathophysiology. Activated microglial cells in the substantia nigra (SN) are found in all animal models of Parkinson's disease and patients with the illness. Microglia may, however, have detrimental and protective functions in this disease. In this study, we tested the hypothesis that a sub-toxic dose of an inflammogen (lipopolysaccharide) can shift microglia to a pro-inflammatory state and exacerbate disease progression in an animal model of Parkinson's disease. Central lipopolysaccharide injection in a degenerating SN exacerbated neurodegeneration, accelerated and increased motor signs and shifted microglial activation towards a pro-inflammatory phenotype with increased interleukin-1beta (IL-1beta) secretion. Glucocorticoid treatment and specific IL-1 inhibition reversed these effects. Importantly, chronic systemic expression of IL-1 also exacerbated neurodegeneration and microglial activation in the SN. In vitro, IL-1 directly exacerbated 6-OHDA-triggered dopaminergic toxicity. In vivo, we found that nitric oxide was a downstream molecule of IL-1 action and partially responsible for the exacerbation of neurodegeneration observed. Thus, IL-1 exerts its exacerbating effect on degenerating dopaminergic neurons by direct and indirect mechanisms. This work demonstrates an unequivocal association between IL-1 overproduction and increased disease progression, pointing to inflammation as a risk factor for Parkinson's disease and suggesting that inflammation should be efficiently handled in patients to slow disease progression.
Subject(s)
Interleukin-1/physiology , Parkinson Disease/physiopathology , Animals , Cells, Cultured , Dexamethasone/pharmacology , Disease Models, Animal , Disease Progression , Enzyme-Linked Immunosorbent Assay/methods , Glucocorticoids/pharmacology , Interleukin-1/antagonists & inhibitors , Interleukin-1/biosynthesis , Interleukin-1/pharmacology , Lipopolysaccharides/pharmacology , Male , Microglia/drug effects , Microglia/physiology , Nerve Degeneration/pathology , Nerve Degeneration/physiopathology , Nitric Oxide/physiology , Oxidopamine/pharmacology , Parkinson Disease/pathology , Psychomotor Performance , Rats , Rats, Wistar , Reverse Transcriptase Polymerase Chain Reaction/methods , Substantia Nigra/drug effects , Substantia Nigra/pathologyABSTRACT
The functional role of the long-lasting inflammation found in the substantia nigra (SN) of Parkinson's disease (PD) patients and animal models is unclear. Proinflammatory cytokines such as interleukin-1beta (IL-1beta) could be involved in mediating neuronal demise. However, it is unknown whether the chronic expression of cytokines such as IL-1beta in the SN can alter neuronal vitality. The aim of this study was to investigate the effects of the chronic expression of IL-1beta in the adult rat SN using a recombinant adenovirus expressing IL-1beta. The chronic expression of IL-1beta for 60 days induced dopaminergic cell death in the SN and unilateral akinesia starting only at 21 days post-injection. Microglial cell activation and inflammatory cell infiltrate were associated with dopaminergic cell death and motor disabilities. Astrocytic activation was delayed and associated with scar formation. The chronic expression of a single proinflammatory cytokine as IL-1beta in the SN elicited most of the characteristics of PD, including progressive dopaminergic cell death, akinesia and glial activation. Our data suggest that IL-1beta per se is able to mediate inflammatory-mediated toxic effects in the SN if its expression is sustained. This model will be helpful to identify possible therapeutic targets related to inflammation-derived neurodegeneration in the SN.
Subject(s)
Interleukin-1/biosynthesis , Movement Disorders/genetics , Movement Disorders/pathology , Nerve Degeneration/genetics , Nerve Degeneration/pathology , Substantia Nigra/metabolism , Substantia Nigra/pathology , Adenoviridae/genetics , Animals , Astrocytes/metabolism , Astrocytes/pathology , Cell Death/drug effects , Cytokines/biosynthesis , Cytokines/genetics , Dopamine/physiology , Genetic Vectors , Glial Fibrillary Acidic Protein/biosynthesis , Glial Fibrillary Acidic Protein/genetics , Interleukin-1/genetics , Macrophage Activation/genetics , Macrophage Activation/physiology , Macrophages/metabolism , Macrophages/pathology , Male , Microglia/metabolism , Microglia/pathology , Motor Activity/physiology , Neuroglia/drug effects , Neuroglia/physiology , Neurons/drug effects , Neurons/physiology , Parkinson Disease, Secondary/genetics , Parkinson Disease, Secondary/pathology , Rats , Rats, WistarABSTRACT
An appropriate inflammatory response is crucial for the maintenance of tissue homeostasis. The inflammatory responses seen in the brain parenchyma differ from those elicited in the periphery, ventricles and meninges. However, although an inflammatory component has been associated with many CNS diseases, the differences among parenchymal inflammatory responses in different brain regions have not yet been fully elucidated. Here, we performed a systematic comparison of the effects of a common pro-inflammatory stimulus, IL-1beta, on the hippocampus, substantia nigra, striatum and cortex. We determined various responses, including cytokine mRNA induction, glial activation, immune cell infiltration and changes in neuronal integrity, in both injected and adjacent regions 1 and 6 days after the injection of IL-1beta. We found that the mRNA for TGF-beta was up-regulated in a region-specific manner after IL-1beta administration. Contrary to its response in the periphery, IL-1alpha showed no detectable induction in the tested parenchymal regions. In addition, cytokine induction was also sometimes observed in regions distant from the site of injection. Interestingly, IL-1beta-mediated neurodegeneration was observed in the dentate gyrus of the hippocampus, but not in the other tested regions. The cellular recruitment mediated by IL-1 beta injection consisted mainly of polymorphonuclear cells (PMN), which correlated with IL-1betamRNA induction even in regions far from the injection site. These results indicate that various parenchymal regions show different inflammatory responses and neurodegeneration in response to IL-1beta. Taken together, our results provide a more precise picture of regional inflammation in the brain and should provide a basis for differential interpretation of results based on regional inflammatory differences.
Subject(s)
Brain/drug effects , Cytokines/metabolism , Interleukin-1/pharmacology , Neuroglia/drug effects , Animals , Brain/cytology , Cytokines/genetics , Ectodysplasins , Enzyme Activation/drug effects , Fluorescent Antibody Technique/methods , Functional Laterality , Glial Fibrillary Acidic Protein/metabolism , Lectins/metabolism , Male , Membrane Proteins/metabolism , Neurotoxicity Syndromes , Neutrophils/metabolism , Phosphopyruvate Hydratase/metabolism , RNA, Messenger/biosynthesis , Rats , Rats, Wistar , Reverse Transcriptase Polymerase Chain Reaction/methods , Time Factors , Tumor Necrosis Factors/metabolismABSTRACT
Los objetivos del trabajo fueron determinar en un modelo porcino los aspectos biologicos y estructurales de la integracion del ligamento cruzado anterior enaloinjertos de femur distal y evaluar la incorporacion del ADN de los fibroblastos del receptor sobre el tejido donante (resumen truncado)
Subject(s)
Animals , Anterior Cruciate Ligament , Bone Transplantation , Argentina , Swine , Transplantation, HomologousABSTRACT
Los objetivos del trabajo fueron determinar en un modelo porcino los aspectos biologicos y estructurales de la integracion del ligamento cruzado anterior enaloinjertos de femur distal y evaluar la incorporacion del ADN de los fibroblastos del receptor sobre el tejido donante (resumen truncado)
