RESUMO
Parkinson's disease is a progressive neurodegenerative disorder characterized by altered striatal dopaminergic signalling that leads to motor and cognitive deficits. Parkinson's disease is also characterized by abnormal presence of soluble toxic forms of α-synuclein that, when clustered into Lewy bodies, represents one of the pathological hallmarks of the disease. However, α-synuclein oligomers might also directly affect synaptic transmission and plasticity in Parkinson's disease models. Accordingly, by combining electrophysiological, optogenetic, immunofluorescence, molecular and behavioural analyses, here we report that α-synuclein reduces N-methyl-d-aspartate (NMDA) receptor-mediated synaptic currents and impairs corticostriatal long-term potentiation of striatal spiny projection neurons, of both direct (D1-positive) and indirect (putative D2-positive) pathways. Intrastriatal injections of α-synuclein produce deficits in visuospatial learning associated with reduced function of GluN2A NMDA receptor subunit indicating that this protein selectively targets this subunit both in vitro and ex vivo. Interestingly, this effect is observed in spiny projection neurons activated by optical stimulation of either cortical or thalamic glutamatergic afferents. We also found that treatment of striatal slices with antibodies targeting α-synuclein prevents the α-synuclein-induced loss of long-term potentiation and the reduced synaptic localization of GluN2A NMDA receptor subunit suggesting that this strategy might counteract synaptic dysfunction occurring in Parkinson's disease.
Assuntos
Corpo Estriado/metabolismo , Receptores de N-Metil-D-Aspartato/metabolismo , Memória Espacial/fisiologia , Sinapses/fisiologia , Percepção Visual/fisiologia , alfa-Sinucleína/toxicidade , Animais , Corpo Estriado/efeitos dos fármacos , Corpo Estriado/patologia , Humanos , Potenciação de Longa Duração/efeitos dos fármacos , Potenciação de Longa Duração/fisiologia , Masculino , Camundongos , Camundongos Transgênicos , Técnicas de Cultura de Órgãos , Subunidades Proteicas/antagonistas & inibidores , Subunidades Proteicas/metabolismo , Ratos , Ratos Wistar , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores , Memória Espacial/efeitos dos fármacos , Sinapses/efeitos dos fármacos , Percepção Visual/efeitos dos fármacos , alfa-Sinucleína/administração & dosagemRESUMO
OBJECTIVE: Spreading depolarization (SD) is a transient self-propagating wave of neuronal and glial depolarization coupled with large membrane ionic changes and a subsequent depression of neuronal activity. Spreading depolarization in the cortex is implicated in migraine, stroke, and epilepsy. Conversely, spreading depolarization in the striatum, a brain structure deeply involved in motor control and in Parkinson's disease (PD) pathophysiology, has been poorly investigated. METHODS: We characterized the participation of glutamatergic and dopaminergic transmission in the induction of striatal spreading depolarization by using a novel approach combining optical imaging, measurements of endogenous DA levels, and pharmacological and molecular analyses. RESULTS: We found that striatal spreading depolarization requires the concomitant activation of D1-like DA and N-methyl-d-aspartate receptors, and it is reduced in experimental PD. Chronic l-dopa treatment, inducing dyskinesia in the parkinsonian condition, increases the occurrence and speed of propagation of striatal spreading depolarization, which has a direct impact on one of the signaling pathways downstream from the activation of D1 receptors. CONCLUSION: Striatal spreading depolarization might contribute to abnormal basal ganglia activity in the dyskinetic condition and represents a possible therapeutic target. © 2019 International Parkinson and Movement Disorder Society.
Assuntos
Corpo Estriado/fisiopatologia , Neurônios Dopaminérgicos/fisiologia , Discinesia Induzida por Medicamentos/fisiopatologia , Levodopa/farmacologia , Neurônios/fisiologia , Transtornos Parkinsonianos/fisiopatologia , Transmissão Sináptica/fisiologia , Animais , Protocolos de Quimioterapia Combinada Antineoplásica/metabolismo , Antiparkinsonianos/farmacologia , Corpo Estriado/efeitos dos fármacos , Compostos de Mostarda Nitrogenada/metabolismo , Prednisolona/metabolismo , Procarbazina/metabolismo , Ratos , Ratos Wistar , Vincristina/metabolismoRESUMO
Among genetic abnormalities identified in Parkinson's disease (PD), mutations of the leucine-rich repeat kinase2 (LRRK2) gene, such as the G2019S missense mutation linked to enhanced kinase activity, are the most common. While the complex role of LRRK2 has not been fully elucidated, evidence that mutated kinase activity affects synaptic transmission has been reported. Thus, our aim was to explore possible early alterations of neurotransmission produced by the G2019S LRRK2 mutation in PD. We performed electrophysiological patch-clamp recordings of striatal spiny projection neurons (SPNs) in the G2019S-Lrrk2 knock-in (KI) mouse model of PD, in D1994S kinase-dead (KD), Lrrk2 knock-out (KO) and wild-type (WT) mice. In G2019S Lrrk2 KI mice, basal spontaneous glutamatergic transmission, synaptic facilitation, and NMDA/AMPA ratios were unchanged, whereas the stimulation of dopamine (DA) D2 receptor by quinpirole reduced the spontaneous and evoked excitatory postsynaptic currents (EPSC). Quinpirole reduced the EPSC amplitude of SPNs in KI but not in KD, KO and WT mice, suggesting that the enhanced LRRK2 kinase activity induced by the G2019S mutation is associated with the observed functional alteration of SPNs synaptic transmission. The effect of quinpirole was mediated by a phospholipase C (PLC)-dependent release of endocannabinoid, with subsequent activation of presynaptic cannabinoid receptor 1 and reduced release of glutamate. The key role of DA D2 receptor in reducing glutamatergic output in our LRRK2 genetic model of PD further supports the use of DA agonists in the treatment of early PD patients with LRRK2 mutations to counteract the disease progression.
Assuntos
Corpo Estriado/metabolismo , Ácido Glutâmico/metabolismo , Serina-Treonina Proteína Quinase-2 com Repetições Ricas em Leucina/genética , Transtornos Parkinsonianos/genética , Transtornos Parkinsonianos/metabolismo , Receptores de Dopamina D2/metabolismo , Animais , Corpo Estriado/efeitos dos fármacos , Agonistas de Dopamina/farmacologia , Agonistas de Dopamina/uso terapêutico , Potenciais Pós-Sinápticos Excitadores/efeitos dos fármacos , Potenciais Pós-Sinápticos Excitadores/fisiologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , Transtornos Parkinsonianos/tratamento farmacológico , Quimpirol/farmacologia , Quimpirol/uso terapêutico , Receptores de Dopamina D2/agonistas , Transmissão Sináptica/efeitos dos fármacos , Transmissão Sináptica/fisiologiaRESUMO
During multiple sclerosis (MS), a close link has been demonstrated to occur between inflammation and neuro-axonal degeneration, leading to the hypothesis that immune mechanisms may promote neurodegeneration, leading to irreversible disease progression. Energy deficits and inflammation-driven mitochondrial dysfunction seem to be involved in this process. In this work we investigated, by the use of striatal electrophysiological field-potential recordings, if the inflammatory process associated with experimental autoimmune encephalomyelitis (EAE) is able to influence neuronal vulnerability to the blockade of mitochondrial complex IV, a crucial component for mitochondrial activity responsible of about 90% of total cellular oxygen consumption. We showed that during the acute relapsing phase of EAE, neuronal susceptibility to mitochondrial complex IV inhibition is markedly enhanced. This detrimental effect was counteracted by the pharmacological inhibition of microglia, of nitric oxide (NO) synthesis and its intracellular pathway (involving soluble guanylyl cyclase, sGC, and protein kinase G, PKG). The obtained results suggest that mitochondrial complex IV exerts an important role in maintaining neuronal energetic homeostasis during EAE. The pathological processes associated with experimental MS, and in particular the activation of microglia and of the NO pathway, lead to an increased neuronal vulnerability to mitochondrial complex IV inhibition, representing promising pharmacological targets.
Assuntos
Proteínas Quinases Dependentes de GMP Cíclico/metabolismo , GMP Cíclico/metabolismo , Encefalomielite Autoimune Experimental/metabolismo , Microglia/metabolismo , Mitocôndrias/metabolismo , Óxido Nítrico/metabolismo , Animais , GMP Cíclico/antagonistas & inibidores , Proteínas Quinases Dependentes de GMP Cíclico/antagonistas & inibidores , Encefalomielite Autoimune Experimental/tratamento farmacológico , Encefalomielite Autoimune Experimental/patologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Microglia/efeitos dos fármacos , Microglia/patologia , Mitocôndrias/efeitos dos fármacos , Mitocôndrias/patologia , Esclerose Múltipla/tratamento farmacológico , Esclerose Múltipla/metabolismo , Esclerose Múltipla/patologia , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Neurônios/patologia , Óxido Nítrico/antagonistas & inibidores , Técnicas de Cultura de Órgãos , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/fisiologia , Azida Sódica/farmacologia , Azida Sódica/uso terapêuticoRESUMO
Cognitive impairment (CI) is a disabling concomitant of multiple sclerosis (MS) with a complex and controversial pathogenesis. The cytokine interleukin-17A (IL-17A) is involved in the immune pathogenesis of MS, but its possible effects on synaptic function and cognition are still largely unexplored. In this study, we show that the IL-17A receptor (IL-17RA) is highly expressed by hippocampal neurons in the CA1 area and that exposure to IL-17A dose-dependently disrupts hippocampal long-term potentiation (LTP) through the activation of its receptor and p38 mitogen-activated protein kinase (MAPK). During experimental autoimmune encephalomyelitis (EAE), IL-17A overexpression is paralleled by hippocampal LTP dysfunction. An in vivo behavioral analysis shows that visuo-spatial learning abilities are preserved when EAE is induced in mice lacking IL-17A. Overall, this study suggests a key role for the IL-17 axis in the neuro-immune cross-talk occurring in the hippocampal CA1 area and its potential involvement in synaptic dysfunction and MS-related CI.
Assuntos
Comportamento Animal , Região CA1 Hipocampal/metabolismo , Cognição , Encefalomielite Autoimune Experimental/metabolismo , Interleucina-17/metabolismo , Plasticidade Neuronal , Receptores de Interleucina-17/metabolismo , Sinapses/metabolismo , Animais , Região CA1 Hipocampal/patologia , Região CA1 Hipocampal/fisiopatologia , Encefalomielite Autoimune Experimental/patologia , Encefalomielite Autoimune Experimental/fisiopatologia , Encefalomielite Autoimune Experimental/psicologia , Interleucina-17/genética , Potenciação de Longa Duração , Masculino , Camundongos Biozzi , Camundongos Endogâmicos C57BL , Camundongos Knockout , Receptores de Interleucina-17/genética , Transdução de Sinais , Aprendizagem Espacial , Sinapses/patologia , Proteínas Quinases p38 Ativadas por MitógenoRESUMO
Neuroactive estrogenic and androgenic steroids influence synaptic transmission, finely modulating synaptic plasticity in several brain regions including the hippocampus. While estrogens facilitate long-term potentiation (LTP), androgens are involved in the induction of long-term depression (LTD) and depotentiation (DP) of synaptic transmission. To examine sex neurosteroid-dependent LTP and LTD in single cells, patch-clamp recordings from hippocampal CA1 pyramidal neurons of male rats and selective antagonists for estrogen receptors (ERs) and androgen (AR) receptors were used. LTP induced by high-frequency stimulation (HFS) depended on activation of ERs since it was prevented by the ER antagonist ICI 182,780 in most of the neurons. Application of the selective antagonists for ERα (MPP) or ERß (PHTPP) caused a reduction of the LTP amplitude, while these antagonists in combination, prevented LTP completely. LTP was never affected by blocking AR with the specific antagonist flutamide. Conversely, LTD and DP, elicited by low-frequency stimulation (LFS), were impeded by flutamide, but not by ICI 182,780, in most neurons. In few cells, LTD was even reverted to LTP by flutamide. Moreover, the combined application of both ER and AR antagonists completely prevented both LTP and LTD/DP in the same neuron. The current study demonstrates that the activation of ERs is necessary for inducing LTP in hippocampal pyramidal neurons, whereas the activation of ARs is required for LTD and DP. Moreover, both estrogen- and androgen-dependent LTP and LTD can be expressed in the same pyramidal neurons, suggesting that the activation of sex neurosteroids signaling pathways is responsible for bidirectional synaptic plasticity.
RESUMO
Interferons (IFNs) are widely expressed cytokines with antiviral and immune-modulating effects and have been utilised for the treatment of several human pathological conditions. In particular, the immune-modulatory drug IFN-ß is utilized in the treatment of multiple sclerosis (MS), a chronic autoimmune and neurodegenerative disorder of the central nervous system (CNS). Although the effects of IFN-ß on immune cells functions have been widely investigated, information about the ability of the drug to modulate neuronal transmission in the CNS is still largely lacking. The aim of this study was to investigate the ability of IFN-ß1a to modulate excitatory synaptic transmission in the CNS. Whole cell patch-clamp electrophysiological recordings were performed in the nucleus striatum, one of the CNS grey matter structures that is prone to degenerate during the course of MS. We demonstrate that the drug IFN-ß1a, independently from its known peripheral immune-modulating action, is able to directly modulate synaptic transmission. In particular, we demonstrated that IFN-ß1a reduces the amplitude of striatal excitatory post-synaptic currents, indicating an inhibitory effect on glutamate neurotransmission, and in particular on its NMDA component. The inhibitory effect of IFN-ß1a on striatal glutamate neurotransmission was found to be mediated by a novel post-synaptic mechanism requiring Ca(2+), CaMKII and the GluN2A subunit of the NMDA receptor, without the involvement of the classic STAT1 pathway. The evidence of a novel neuro-modulating effect of IFN-ß shed light on the mechanisms of action of the drug and on the complex bidirectional interaction occurring between the immune and the nervous system. This article is part of the Special Issue entitled 'Synaptopathy--from Biology to Therapy'.
Assuntos
Encéfalo/efeitos dos fármacos , Proteína Quinase Tipo 2 Dependente de Cálcio-Calmodulina/fisiologia , Potenciais Pós-Sinápticos Excitadores/efeitos dos fármacos , Ácido Glutâmico/fisiologia , Interferon beta/administração & dosagem , Neurônios/efeitos dos fármacos , Receptores de N-Metil-D-Aspartato/fisiologia , Potenciais de Ação/efeitos dos fármacos , Animais , Encéfalo/fisiologia , Camundongos Endogâmicos C57BL , Neurônios/fisiologia , Receptores de AMPA/fisiologiaRESUMO
Cognitive impairment is common in multiple sclerosis (MS). Unfortunately, the synaptic and molecular mechanisms underlying MS-associated cognitive dysfunction are largely unknown. We explored the presence and the underlying mechanism of cognitive and synaptic hippocampal dysfunction during the remission phase of experimental MS. Experiments were performed in a chronic-relapsing experimental autoimmune encephalomyelitis (EAE) model of MS, after the resolution of motor deficits. Immunohistochemistry and patch-clamp recordings were performed in the CA1 hippocampal area. The hole-board was utilized as cognitive/behavioural test. In the remission phase of experimental MS, hippocampal microglial cells showed signs of activation, CA1 hippocampal synapses presented an impaired long-term potentiation (LTP) and an alteration of spatial tests became evident. The activation of hippocampal microglia mediated synaptic and cognitive/behavioural alterations during EAE. Specifically, LTP blockade was found to be caused by the reactive oxygen species (ROS)-producing enzyme nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. We suggest that in the remission phase of experimental MS microglia remains activated, causing synaptic dysfunctions mediated by NADPH oxidase. Inhibition of microglial activation and NADPH oxidase may represent a promising strategy to prevent neuroplasticity impairment associated with active neuro-inflammation, with the aim to improve cognition and counteract MS disease progression.
Assuntos
Comportamento Animal , Região CA1 Hipocampal , Cognição , Potenciação de Longa Duração , Microglia , Esclerose Múltipla , NADPH Oxidases/metabolismo , Animais , Região CA1 Hipocampal/enzimologia , Região CA1 Hipocampal/patologia , Região CA1 Hipocampal/fisiopatologia , Encefalomielite Autoimune Experimental/enzimologia , Encefalomielite Autoimune Experimental/patologia , Encefalomielite Autoimune Experimental/fisiopatologia , Ativação Enzimática , Feminino , Camundongos , Microglia/enzimologia , Microglia/patologia , Esclerose Múltipla/enzimologia , Esclerose Múltipla/patologia , Esclerose Múltipla/fisiopatologiaRESUMO
BACKGROUND: Advanced Parkinson's disease (PD) is characterized by massive degeneration of nigral dopaminergic neurons, dramatic motor and cognitive alterations, and presence of nigral Lewy bodies, whose main constituent is α-synuclein (α-syn). However, the synaptic mechanisms underlying behavioral and motor effects induced by early selective overexpression of nigral α-syn are still a matter of debate. METHODS: We performed behavioral, molecular, and immunohistochemical analyses in two transgenic models of PD, mice transgenic for truncated human α-synuclein 1-120 and rats injected with the adeno-associated viral vector carrying wild-type human α-synuclein. We also investigated striatal synaptic plasticity by electrophysiological recordings from spiny projection neurons and cholinergic interneurons. RESULTS: We found that overexpression of truncated or wild-type human α-syn causes partial reduction of striatal dopamine levels and selectively blocks the induction of long-term potentiation in striatal cholinergic interneurons, producing early memory and motor alterations. These effects were dependent on α-syn modulation of the GluN2D-expressing N-methyl-D-aspartate receptors in cholinergic interneurons. Acute in vitro application of human α-syn oligomers mimicked the synaptic effects observed ex vivo in PD models. CONCLUSIONS: We suggest that striatal cholinergic dysfunction, induced by a direct interaction between α-syn and GluN2D-expressing N-methyl-D-aspartate receptors, represents a precocious biological marker of the disease.
Assuntos
Neurônios Colinérgicos/efeitos dos fármacos , Dopamina/fisiologia , Doença de Parkinson/tratamento farmacológico , Receptores de N-Metil-D-Aspartato/genética , alfa-Sinucleína/genética , Animais , Animais Geneticamente Modificados , Dependovirus , Modelos Animais de Doenças , Feminino , Humanos , Potenciação de Longa Duração , Masculino , Camundongos , Camundongos Transgênicos , Neostriado/fisiologia , Ratos , Ratos Sprague-Dawley , Proteínas Recombinantes/genética , Transmissão SinápticaRESUMO
Structural and functional neuronal plasticity could play a crucial role during the course of multiple sclerosis (MS). The immune system and the central nervous system (CNS) strictly interact in physiologic conditions and during inflammation to modulate neuroplasticity and in particular the ability of the synapses to undergo long-term changes in the efficacy of synaptic transmission, such as long-term potentiation (LTP). During MS, neuro-inflammation might deeply influence the ability of neuronal networks to express physiologic plasticity, reducing the plastic reserve of the brain, with a negative impact on symptoms progression and cognitive performances. In this manuscript we review the evidence on synaptic plasticity alterations in experimental autoimmune encephalomyelitis (EAE), the most diffuse and widely utilized experimental model of MS, together with their potential underlying mechanisms and clinical relevance. This article is part of a Special Issue entitled SI: Brain and Memory.
Assuntos
Encéfalo/fisiopatologia , Encefalomielite Autoimune Experimental/fisiopatologia , Potenciação de Longa Duração , Depressão Sináptica de Longo Prazo/fisiologia , Esclerose Múltipla/fisiopatologia , Animais , Encéfalo/imunologia , Encefalomielite Autoimune Experimental/complicações , Hipocampo/imunologia , Hipocampo/fisiopatologia , Humanos , CamundongosRESUMO
17ß-estradiol (E2), a neurosteroid synthesized by P450-aromatase (ARO), modulates various brain functions. We characterized the role of the locally synthesized E2 on striatal long-term synaptic plasticity and explored possible interactions between E2 receptors (ERs) and dopamine (DA) receptors in the dorsal striatum of adult male rats. Inhibition of E2 synthesis or antagonism of ERs prevented the induction of long-term potentiation (LTP) in both medium spiny neurons (MSNs) and cholinergic interneurons (ChIs). Activation of a D1-like DA receptor/cAMP/PKA-dependent pathway restored LTP. In MSNs exogenous E2 reversed the effect of ARO inhibition. Also antagonism of M1 muscarinic receptors prevented the D1-like receptor-mediated restoration of LTP confirming a role for ChIs in controlling the E2-mediated LTP of MSNs. A novel striatal interaction, occurring between ERs and D1-like receptors in both MSNs and ChIs, might be critical to regulate basal ganglia physiology and to compensate synaptic alterations in Parkinson's disease.