RESUMO
To explore how gene products, required for the initiation of synaptic growth, move from the cell body of the sensory neuron to its presynaptic terminals, and from the cell body of the motor neuron to its postsynaptic dendritic spines, we have investigated the anterograde transport machinery in both the sensory and motor neurons of the gill-withdrawal reflex of Aplysia. We found that the induction of long-term facilitation (LTF) by repeated applications of serotonin, a modulatory transmitter released during learning in Aplysia, requires upregulation of kinesin heavy chain (KHC) in both pre- and postsynaptic neurons. Indeed, upregulation of KHC in the presynaptic neurons alone is sufficient for the induction of LTF. However, KHC is not required for the persistence of LTF. Thus, in addition to transcriptional activation in the nucleus and local protein synthesis at the synapse, our studies have identified a third component critical for long-term learning-related plasticity: the coordinated upregulation of kinesin-mediated transport.
Assuntos
Aplysia/fisiologia , Cinesinas/fisiologia , Neurônios/fisiologia , Animais , Brânquias/fisiologia , Plasticidade Neuronal , Sinapses/fisiologia , Regulação para CimaRESUMO
Convergent lines of evidence have recently highlighted ß3-adrenoreceptors (ARs) as a potentially critical target in the regulation of nervous and behavioral functions, including memory consolidation, anxiety, and depression. Nevertheless, the role of ß3-ARs in the cerebellum has been never investigated. To address this issue, we first examined the effects of pharmacological manipulation of ß3-ARs on motor learning in mice. We found that blockade of ß3-ARs by SR 59230A impaired the acquisition of the rotarod task with no effect on general locomotion. Since the parallel fiber-Purkinje cell (PF-PC) synapse is considered to be the main cerebellar locus of motor learning, we assessed ß3-AR modulatory action on this synapse as well as its expression in cerebellar slices. We demonstrate, for the first time, a strong expression of ß3-ARs on Purkinje cell soma and dendrites. In addition, whole-cell patch-clamp recordings revealed that bath application of ß3-AR agonist CL316,243 depressed the PF-PC excitatory postsynaptic currents via a postsynaptic mechanism mediated by the PI3K signaling pathway. Application of CL316,243 also interfered with the expression of PF long-term potentiation, whereas SR 59230A prevented the induction of LTD at PF-PC synapse. These results underline the critical role of ß3-AR on cerebellar synaptic transmission and plasticity and provide a new mechanism for adrenergic modulation of motor learning.
Assuntos
Córtex Cerebelar/fisiologia , Receptores Adrenérgicos beta 3/fisiologia , Transmissão Sináptica/fisiologia , Animais , Córtex Cerebelar/metabolismo , Potenciais Pós-Sinápticos Excitadores , Feminino , Potenciação de Longa Duração , Depressão Sináptica de Longo Prazo , Masculino , Camundongos , Plasticidade Neuronal/fisiologia , Técnicas de Patch-Clamp , Fosfatidilinositol 3-Quinases/metabolismo , Células de Purkinje/metabolismo , Receptores Adrenérgicos beta 3/metabolismo , Teste de Desempenho do Rota-Rod , Sinapses/fisiologiaRESUMO
G-protein-coupled inwardly rectifying potassium (GIRK) channels contribute to the resting membrane potential of many neurons and play an important role in controlling neuronal excitability. Although previous studies have revealed a high expression of GIRK subunits in the cerebellum, their functional role has never been clearly described. Using patch-clamp recordings in mice cerebellar slices, we examined the properties of the GIRK currents in Purkinje cells (PCs) and investigated the effects of a selective agonist of GIRK1-containing channels, ML297 (ML), on PC firing and synaptic plasticity. We demonstrated that GIRK channel activation decreases the PC excitability by inhibiting both sodium and calcium spikes and, in addition, modulates the complex spike response evoked by climbing fiber stimulation. Our results indicate that GIRK channels have also a marked effect on synaptic plasticity of the parallel fiber-PC synapse, as the application of ML297 increased the expression of LTP while preventing LTD. We, therefore, propose that the recruitment of GIRK channels represents a crucial mechanism by which neuromodulators can control synaptic strength and membrane conductance for proper refinement of the neural network involved in memory storage and higher cognitive functions.
Assuntos
Potenciais Pós-Sinápticos Excitadores/fisiologia , Canais de Potássio Corretores do Fluxo de Internalização Acoplados a Proteínas G/fisiologia , Plasticidade Neuronal/fisiologia , Neurotransmissores/farmacologia , Células de Purkinje/fisiologia , Potenciais de Ação/efeitos dos fármacos , Potenciais de Ação/fisiologia , Animais , Animais Recém-Nascidos , Potenciais Pós-Sinápticos Excitadores/efeitos dos fármacos , Feminino , Canais de Potássio Corretores do Fluxo de Internalização Acoplados a Proteínas G/agonistas , Masculino , Camundongos , Plasticidade Neuronal/efeitos dos fármacos , Compostos de Fenilureia/farmacologia , Células de Purkinje/efeitos dos fármacos , Pirazóis/farmacologiaRESUMO
Alzheimer's disease (AD) is a common form of dementia mainly characterized by the deposition of neurofibrillary tangles and ß-amyloid (Aß) peptides in the brain. Additionally, increasing evidence demonstrates that a neuro-inflammatory state plays a key role in the development of this disease. Beside synthetic drugs, the use of natural compounds represents an alternative for the development of new potential drugs for the treatment of AD. Among these, the root of Salvia miltiorhiza Bunge (also known as Danshen) used for the treatment of cardiovascular, cerebrovascular disease and CNS functional decline in Chinese traditional medicine is one of the most representative examples. We therefore evaluated the effects of tanshinone IIA (TIIA) and cryptotanshinone (CRY) (the two major lipophilic compounds of Danshen) in a non-genetic mouse model of ß-amyloid (Aß)-induced AD, which is mainly characterized by reactive gliosis and neuro-inflammation in the brain. To this aim, mice were injected intracerebroventricularly (i.c.v.) with Aß1-42 peptide (3µg/3µl) and after with TIIA and CRY (1, 3, or 10mg/kg) intraperitoneally (i.p.) 3 times weekly for 21days following the induction of experimental AD. Spatial working memory was assessed as a measure of short-term memory in mice, whereas the level of GFAP, S100ß, COX-2, iNOS and NF-kBp65 monitored by western blot and ELISA assay, were selected as markers of reactive gliosis and neuro-inflammation. Finally, by docking studies, the modulation of key pro-inflammatory enzymes and pathways involved in the AD-related neuro-inflammation were also investigated. Results indicate that TIIA and CRY alleviate memory decline in Aß1-42-injected mice, in a dose dependent manner. Moreover, the analysis of gliosis-related and neuro-inflammatory markers in the hippocampal tissues reveal a remarkable reduction in the expression of GFAP, S100ß, COX-2, iNOS and NF-kBp65 after CRY (10mg/kg) treatment. These effects were less evident, but still significant, after TIIA (10mg/kg). Finally, in silico analysis also revealed that both compounds were able to interact with the binding sites of NF-kBp65 endorsing the data from biochemical analysis. We conclude that TIIA and CRY display anti-inflammatory and neuroprotective effect in a non-genetic mouse model of AD, thus playing a role in slowing down the course and onset of AD.
Assuntos
Abietanos/uso terapêutico , Doença de Alzheimer/tratamento farmacológico , Anti-Inflamatórios/uso terapêutico , Fármacos Neuroprotetores/uso terapêutico , Fenantrenos/uso terapêutico , Peptídeos beta-Amiloides , Animais , Modelos Animais de Doenças , Masculino , Memória/efeitos dos fármacos , Camundongos , Fragmentos de PeptídeosRESUMO
The formation of the complex cerebellar cortical circuits follows different phases, with initial synaptogenesis and subsequent processes of refinement guided by a variety of mechanisms. The regularity of the cellular and synaptic organization of the cerebellar cortex allowed detailed studies of the structural plasticity mechanisms underlying the formation of new synapses and retraction of redundant ones. For the attainment of the monoinnervation of the Purkinje cell by a single climbing fiber, several signals are involved, including electrical activity, contact signals, homosynaptic and heterosynaptic interaction, calcium transients, postsynaptic receptors, and transduction pathways. An important role in this developmental program is played by serotonergic projections that, acting on temporally and spatially regulated postsynaptic receptors, induce and modulate the phases of synaptic formation and maturation. In the adult cerebellar cortex, many developmental mechanisms persist but play different roles, such as supporting synaptic plasticity during learning and formation of cerebellar memory traces. A dysfunction at any stage of this process can lead to disorders of cerebellar origin, which include autism spectrum disorders but are not limited to motor deficits. Recent evidence in animal models links impairment of Purkinje cell function with autism-like symptoms including sociability deficits, stereotyped movements, and interspecific communication by vocalization.
Assuntos
Transtorno Autístico/patologia , Córtex Cerebelar/crescimento & desenvolvimento , Rede Nervosa/crescimento & desenvolvimento , Serotonina/metabolismo , Animais , Transtorno Autístico/metabolismo , Córtex Cerebelar/metabolismo , Córtex Cerebelar/patologia , Modelos Animais de Doenças , Humanos , Camundongos , Rede Nervosa/metabolismo , Rede Nervosa/patologia , Plasticidade Neuronal/fisiologia , Neurônios/metabolismo , Neurônios/patologia , Sinapses/fisiologiaRESUMO
The c-Jun N-terminal kinase (JNK) is part of a stress signalling pathway strongly activated by NMDA-stimulation and involved in synaptic plasticity. Many studies have been focused on the post-synaptic mechanism of JNK action, and less is known about JNK presynaptic localization and its physiological role at this site. Here we examined whether JNK is present at the presynaptic site and its activity after presynaptic NMDA receptors stimulation. By using N-SIM Structured Super Resolution Microscopy as well as biochemical approaches, we demonstrated that presynaptic fractions contained significant amount of JNK protein and its activated form. By means of modelling design, we found that JNK, via the JBD domain, acts as a physiological effector on T-SNARE proteins; then using biochemical approaches we demonstrated the interaction between Syntaxin-1-JNK, Syntaxin-2-JNK, and Snap25-JNK. In addition, taking advance of the specific JNK inhibitor peptide, D-JNKI1, we defined JNK action on the SNARE complex formation. Finally, electrophysiological recordings confirmed the role of JNK in the presynaptic modulation of vesicle release. These data suggest that JNK-dependent phosphorylation of T-SNARE proteins may have an important functional role in synaptic plasticity.
Assuntos
Córtex Cerebral/metabolismo , Proteínas Quinases JNK Ativadas por Mitógeno/metabolismo , Terminações Pré-Sinápticas/enzimologia , Receptores de N-Metil-D-Aspartato/metabolismo , Proteínas SNARE/metabolismo , Animais , Córtex Cerebral/fisiologia , Agonistas de Aminoácidos Excitatórios/farmacologia , Potenciais Pós-Sinápticos Excitadores , Feminino , Glicina/farmacologia , Masculino , Camundongos , Proteína Quinase 10 Ativada por Mitógeno/metabolismo , Proteína Quinase 9 Ativada por Mitógeno/metabolismo , N-Metilaspartato/farmacologia , Sinaptossomos/metabolismoRESUMO
L-cysteine is currently recognized as a conditionally essential sulphur amino acid. Besides contributing to many biological pathways, cysteine is a key component of the keratin protein by its ability to form disulfide bridges that confer strength and rigidity to the protein. In addition to cysteine, iron represents another critical factor in regulating keratins expression in epidermal tissues, as well as in hair follicle growth and maturation. By focusing on human keratinocytes, the aim of this study was to evaluate the effect of cysteine supplementation as nutraceutical on keratin biosynthesis, as well as to get an insight on the interplay of cysteine availability and cellular iron status in regulating keratins expression in vitro. Herein we demonstrate that cysteine promotes a significant up-regulation of keratins expression as a result of de novo protein synthesis, while the lack of iron impairs keratin expression. Interestingly, cysteine supplementation counteracts the adverse effect of iron deficiency on cellular keratin expression. This effect was likely mediated by the up-regulation of transferrin receptor and ferritin, the main cellular proteins involved in iron homeostasis, at last affecting the labile iron pool. In this manner, cysteine may also enhance the metabolic iron availability for DNA synthesis without creating a detrimental condition of iron overload. To the best of our knowledge, this is one of the first study in an in vitro keratinocyte model providing evidence that cysteine and iron cooperate for keratins expression, indicative of their central role in maintaining healthy epithelia.
Assuntos
Cisteína/farmacologia , Ferro/metabolismo , Queratinócitos/metabolismo , Queratinas/biossíntese , Linhagem Celular , Homeostase , Humanos , Queratinócitos/efeitos dos fármacos , Biossíntese de Proteínas/efeitos dos fármacos , Regulação para CimaRESUMO
Signaling through mammalian target of rapamycin (mTOR) has been shown to play a central role in the regulation of skeletal muscle growth induced by a wide range of stimuli either mechanical or metabolic, such as growth factors and amino acids. Here, we demonstrate that mTOR and its downstream target, the ribosomal S6 kinase (p70(S6K)), are activated in L6 myocytes by a short-term glucose deprivation. Such response is specific of skeletal muscle and is likely responsible for the increased rate of protein synthesis and expression of the muscle-specific proteins during recovery from glucose deprivation. Nitric oxide and phosphatidylinositol-3-kinase (PI3K) are upstream positive regulators of mTOR since their pharmacological inhibition prevents the activation of p70(S6K) in response to glucose deprivation. We therefore propose a model of response to a brief period of glucose deprivation that may occur in skeletal muscle cells during resistance exercise and that may lead to protein accretion when blood flow recovers and all nutrients are again available.
Assuntos
Glucose/deficiência , Mioblastos Esqueléticos/metabolismo , Biossíntese de Proteínas , Transdução de Sinais , Serina-Treonina Quinases TOR/metabolismo , Animais , Células CACO-2 , Glucose/metabolismo , Células HEK293 , Humanos , Contração Muscular , Mioblastos Esqueléticos/fisiologia , Óxido Nítrico/metabolismo , Fosfatidilinositol 3-Quinases/metabolismo , Ratos , Proteínas Quinases S6 Ribossômicas/metabolismoRESUMO
The memory reconsolidation hypothesis suggests that a memory trace becomes labile after retrieval and needs to be reconsolidated before it can be stabilized. However, it is unclear from earlier studies whether the same synapses involved in encoding the memory trace are those that are destabilized and restabilized after the synaptic reactivation that accompanies memory retrieval, or whether new and different synapses are recruited. To address this issue, we studied a simple nonassociative form of memory, long-term sensitization of the gill- and siphon-withdrawal reflex in Aplysia, and its cellular analog, long-term facilitation at the sensory-to-motor neuron synapse. We found that after memory retrieval, behavioral long-term sensitization in Aplysia becomes labile via ubiquitin/proteasome-dependent protein degradation and is reconsolidated by means of de novo protein synthesis. In parallel, we found that on the cellular level, long-term facilitation at the sensory-to-motor neuron synapse that mediates long-term sensitization is also destabilized by protein degradation and is restabilized by protein synthesis after synaptic reactivation, a procedure that parallels memory retrieval or retraining evident on the behavioral level. These results provide direct evidence that the same synapses that store the long-term memory trace encoded by changes in the strength of synaptic connections critical for sensitization are disrupted and reconstructed after signal retrieval.
Assuntos
Memória/fisiologia , Neurônios Motores/fisiologia , Células Receptoras Sensoriais/fisiologia , Sinapses/fisiologia , Animais , Aplysia , Comportamento Animal/fisiologia , Células Cultivadas , Técnicas de Cocultura , Eletrochoque , Potenciais Pós-Sinápticos Excitadores/fisiologia , Medo/fisiologia , Brânquias/inervação , Memória/efeitos dos fármacos , Modelos Animais , Neurônios Motores/citologia , Proteínas do Tecido Nervoso/biossíntese , Plasticidade Neuronal/efeitos dos fármacos , Plasticidade Neuronal/fisiologia , Reflexo/fisiologia , Células Receptoras Sensoriais/citologia , Serotonina/farmacologia , Agonistas do Receptor de Serotonina/farmacologiaRESUMO
Functional ß3-adrenoceptors have been found in skeletal muscle where they mediate metabolic oxidation and glucose utilization. Whether ß3-adrenoceptors (ARs) also play any role in muscle protein metabolism still remains uncertain. By using rat L6 myocyte cultures, we found that CL316,243, a ß3-AR selective agonist, at the concentration of 10(-6) M for 24 h, induced a significant increase of skeletal muscle constitutive proteins such as H- and L-myosin and ß-actin. Such effect was correlated to an increased expression of phosphorylated p70(S6K) that was significantly inhibited by ß3-AR antagonist, SR 59230A, but not by ß2-AR antagonist, ICI-118,551. The CL316,243-induced activation of p70(S6K) was markedly inhibited by wortmannin, a PI3K inhibitor, and rapamycin, a specific inhibitor of mTOR, suggesting a critical involvement of the PI3K-mTOR-p70(S6K) signaling cascade in the anabolic response of L6 cells to ß3-AR agonist. Taken together, these results suggest that stimulation of ß3-AR in skeletal muscle cells activates a specific signaling pathway leading to protein synthesis and, eventually, muscle growth.
Assuntos
Agonistas de Receptores Adrenérgicos beta 3/farmacologia , Dioxóis/farmacologia , Fibras Musculares Esqueléticas/metabolismo , Biossíntese de Proteínas/efeitos dos fármacos , Proteínas Quinases S6 Ribossômicas 70-kDa/metabolismo , Transdução de Sinais/efeitos dos fármacos , Serina-Treonina Quinases TOR/metabolismo , Actinas/genética , Actinas/metabolismo , Antagonistas Adrenérgicos beta/farmacologia , Androstadienos/farmacologia , Animais , Células Cultivadas , Expressão Gênica/efeitos dos fármacos , Fibras Musculares Esqueléticas/efeitos dos fármacos , Fibras Musculares Esqueléticas/enzimologia , Fosfatidilinositol 3-Quinases/metabolismo , Inibidores de Fosfoinositídeo-3 Quinase , Fosforilação , Propanolaminas/farmacologia , Ratos , Proteínas Quinases S6 Ribossômicas 70-kDa/genética , Sirolimo/farmacologia , Miosinas de Músculo Esquelético/genética , Miosinas de Músculo Esquelético/metabolismo , Serina-Treonina Quinases TOR/antagonistas & inibidores , Serina-Treonina Quinases TOR/genética , WortmaninaRESUMO
The modulation of dopamine release from midbrain projections to the striatum has long been demonstrated in reward-based learning, but the synaptic basis of aversive learning is far less characterized. The cerebellum receives axonal projections from the locus coeruleus, and norepinephrine release is implicated in states of arousal and stress, but whether aversive learning relies on plastic changes in norepinephrine release in the cerebellum is unknown. Here we report that in mice, norepinephrine is released in the cerebellum following an unpredicted noxious event (a foot-shock) and that this norepinephrine release is potentiated powerfully with fear acquisition as animals learn that a previously neutral stimulus (tone) predicts the aversive event. Importantly, both chemogenetic and optogenetic inhibition of the locus coeruleus-cerebellum pathway block fear memory without impairing motor function. Thus, norepinephrine release in the cerebellum is modulated by experience and underlies aversive learning.
Assuntos
Aprendizagem da Esquiva , Norepinefrina , Camundongos , Animais , Aprendizagem da Esquiva/fisiologia , Norepinefrina/metabolismo , Locus Cerúleo/fisiologia , Cerebelo/metabolismo , Mesencéfalo/metabolismoRESUMO
Loss of the Fragile X mental retardation protein (FMRP) is associated with presumed postsynaptic deficits in mouse models of Fragile X syndrome. However, the possible presynaptic roles of FMRP in learning-related plasticity have received little attention. As a result, the mechanisms whereby FMRP influences synaptic function remain poorly understood. To investigate the cellular locus of the effects of FMRP on synaptic plasticity, we cloned the Aplysia homolog of FMRP and find it to be highly expressed in neurons. By selectively down-regulating FMRP in individual Aplysia neurons at the sensory-to-motor neuron synapse reconstituted in co-cultures, we demonstrate that FMRP functions both pre- and postsynaptically to constrain the expression of long-term synaptic depression induced by repeated pulses of FMRF-amide. In contrast, FMRP has little to no effect on long-term synaptic facilitation induced by repeated pulses of serotonin. Since other components of signaling pathways involved in plasticity appear to be conserved between Aplysia and mammalian neurons, our findings suggest that FMRP can participate in both pre- and postsynaptic regulation of enduring synaptic plasticity that underlies the storage of certain types of long-term memory.
Assuntos
Aplysia/fisiologia , Proteína do X Frágil da Deficiência Intelectual/metabolismo , Potenciação de Longa Duração/fisiologia , Neurônios Motores/fisiologia , Terminações Pré-Sinápticas/fisiologia , Células Receptoras Sensoriais/fisiologia , Animais , Aplysia/efeitos dos fármacos , Aplysia/genética , Aplysia/metabolismo , Células Cultivadas , Clonagem Molecular/métodos , Técnicas de Cocultura , Regulação para Baixo/efeitos dos fármacos , Regulação para Baixo/fisiologia , Estimulação Elétrica/métodos , Potenciais Pós-Sinápticos Excitadores/efeitos dos fármacos , Potenciais Pós-Sinápticos Excitadores/genética , FMRFamida/farmacologia , Proteína do X Frágil da Deficiência Intelectual/genética , Potenciação de Longa Duração/efeitos dos fármacos , Moduladores de Transporte de Membrana/farmacologia , Microscopia Confocal , Neurônios Motores/efeitos dos fármacos , Mutação/genética , Oligonucleotídeos Antissenso/farmacologia , Técnicas de Patch-Clamp/métodos , Terminações Pré-Sinápticas/efeitos dos fármacos , Células Receptoras Sensoriais/efeitos dos fármacos , Serotonina/farmacologiaRESUMO
The synaptic pathways in the striatum are central to basal ganglia functions including motor control, learning and organization, action selection, acquisition of motor skills, cognitive function, and emotion. Here, we review the role of the striatum and its connections in motor learning and performance. The development of new techniques to record neuronal activity and animal models of motor disorders using neurotoxin, pharmacological, and genetic manipulations are revealing pathways that underlie motor performance and motor learning, as well as how they are altered by pathophysiological mechanisms. We discuss approaches that can be used to analyze complex motor skills, particularly in rodents, and identify specific questions central to understanding how striatal circuits mediate motor learning.
Assuntos
Gânglios da Base , Corpo Estriado , Animais , Gânglios da Base/fisiologia , Corpo Estriado/fisiologiaRESUMO
Several studies indicate a relationship between maternal gut microbiota alteration and increased risk of autism spectrum disorders (ASD) in offspring. The possibility of compensating for such metabolic dysfunction at a very early stage of disease via maternal treatment has not been enough explored. Here, we examined in BTBR mouse model of ASD the effect of maternal treatment with the gut microbial metabolite butyrate (BUT) on the behavioral and synaptic plasticity deficits in juvenile and adult offspring. We show that BUT treatment of BTBR dams rescues the social and partially the repetitive behavior deficits in the offspring. In addition, maternal BUT implementation prevents the cerebellar cortex hypertrophy as well as the Purkinje cells firing and long-term synaptic plasticity deficits in BTBR mice. Our results demonstrate, for the first time, that maternal BUT treatment can improve ASD-like symptoms in offspring thus providing new directions for the early treatment of neurodevelopmental disorders.
Assuntos
Transtorno do Espectro Autista , Transtorno Autístico , Camundongos , Animais , Transtorno Autístico/tratamento farmacológico , Ácido Butírico/farmacologia , Comportamento Social , Transtorno do Espectro Autista/tratamento farmacológico , Transtorno do Espectro Autista/prevenção & controle , Transtorno do Espectro Autista/metabolismo , Camundongos Endogâmicos , Modelos Animais de Doenças , Camundongos Endogâmicos C57BL , Comportamento AnimalRESUMO
The ability to identify and avoid environmental stimuli that signal danger is essential to survival. Our understanding of how the brain encodes aversive behaviors has been primarily focused on roles for the amygdala, hippocampus (HIPP), prefrontal cortex, ventral midbrain, and ventral striatum. Relatively little attention has been paid to contributions from the dorsal striatum (DS) to aversive learning, despite its well-established role in stimulus-response learning. Here, we review studies exploring the role of DS in aversive learning, including different roles for the dorsomedial and dorsolateral striatum in Pavlovian fear conditioning as well as innate and inhibitory avoidance (IA) behaviors. We outline how future investigation might determine specific contributions from DS subregions, cell types, and connections that contribute to aversive behavior.
RESUMO
While protein synthesis in neurons is largely attributed to cell body and dendrites, the capability of synaptic regions to synthesize new proteins independently of the cell body has been widely demonstrated as an advantageous mechanism subserving synaptic plasticity. Thus, the contribution that local protein synthesis at synapses makes to physiology and pathology of brain plasticity may be more prevalent than initially thought. In this study, we tested if local protein synthesis at synapses is deregulated in the brains of TgCRND8 mice, an animal model for Alzheimer's disease (AD) overexpressing mutant human amyloid precursor protein (APP). To this end, we used synaptosomes as a model system to study the functionality of the synaptic regions in mouse brains. Our results showed that, while TgCRND8 mice exhibit early signs of brain inflammation and deficits in learning, the electrophoretic profile of newly synthesized proteins in their synaptosomes was subtly different from that of the control mice. Interestingly, APP itself was, in part, locally synthesized in the synaptosomes, underscoring the potential importance of local translation at synapses. More importantly, after the contextual fear conditioning, de novo synthesis of some individual proteins was significantly enhanced in the synaptosomes of control animals, but the TgCRND8 mice failed to display such synaptic modulation by training. Taken together, our results demonstrate that synaptic synthesis of proteins is impaired in the brain of a mouse model for AD, and raise the possibility that this deregulation may contribute to the early progression of the pathology.
Assuntos
Doença de Alzheimer/metabolismo , Encéfalo/metabolismo , Neurônios/metabolismo , Sinapses/metabolismo , Doença de Alzheimer/patologia , Peptídeos beta-Amiloides/metabolismo , Precursor de Proteína beta-Amiloide/metabolismo , Animais , Modelos Animais de Doenças , Transtornos da Memória/metabolismo , Camundongos Transgênicos , Placa Amiloide/patologia , Sinaptossomos/metabolismoRESUMO
BACKGROUND AND PURPOSE: Alzheimer's disease (AD) is a common neurodegenerative disease characterized by a neuroinflammatory state, and to date, there is no cure and its treatment represents a large unmet clinical need. The involvement of Th17 cells in the pathogenesis of AD-related neuroinflammation has been reported in several studies. However, the role of the cytokine, IL-17 has not been well addressed. Herein, we investigate the effects of IL-17 neutralizing antibody (IL-17Ab) injected by i.c.v. or intranasal (IN) routes on amyloid-ß (Aß)-induced neuroinflammation and memory impairment in mice. EXPERIMENTAL APPROACH: Aß1-42 was injected into cerebral ventricles of adult CD1 mice. These mice received IL-17Ab via i.c.v. either at 1 h prior to Aß1-42 injection or IN 5 and 12 days after Aß1-42 injection. After 7 and 14 days of Aß1-42 administration, we evaluated olfactory, spatial and working memory and performed biochemical analyses on whole brain and specific brain areas. KEY RESULTS: Pretreatment with IL-17Ab, given, i.c.v., markedly reduced Aß1-42 -induced neurodegeneration, improved memory function, and prevented the increase of pro-inflammatory mediators in a dose-dependent manner at 7 and 14 days. Similarly, the double IN administration of IL-17Ab after Aß1-42 injection reduced neurodegeneration, memory decline, and the levels of proinflammatory mediators and cytokines. CONCLUSION AND IMPLICATIONS: These findings suggest that the IL-17Ab reduced neuroinflammation and behavioural symptoms induced by Aß. The efficacy of IL-17Ab IN administration in reducing Aß1-42 neurodegeneration points to a possible future therapeutic approach in patients with AD. LINKED ARTICLES: This article is part of a themed section on Therapeutics for Dementia and Alzheimer's Disease: New Directions for Precision Medicine. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.18/issuetoc.
Assuntos
Anti-Inflamatórios/uso terapêutico , Anticorpos Neutralizantes/uso terapêutico , Interleucina-17/imunologia , Transtornos da Memória/tratamento farmacológico , Doenças Neurodegenerativas/tratamento farmacológico , Fármacos Neuroprotetores/uso terapêutico , Peptídeos beta-Amiloides , Animais , Comportamento Animal/efeitos dos fármacos , Encéfalo/efeitos dos fármacos , Encéfalo/metabolismo , Masculino , Aprendizagem em Labirinto/efeitos dos fármacos , Transtornos da Memória/metabolismo , Camundongos , Doenças Neurodegenerativas/metabolismo , Fragmentos de PeptídeosRESUMO
Egocentric (self-centered) and allocentric (viewpoint independent) representations of space are essential for spatial navigation and wayfinding. Deficits in spatial memory come with age-related cognitive decline, are marked in mild cognitive impairment (MCI) and Alzheimer's disease (AD), and are associated with cognitive deficits in autism. In most of these disorders, a change in the brain areas engaged in the spatial reference system processing has been documented. However, the spatial memory deficits observed during physiological and pathological aging are quite different. While patients with AD and MCI have a general spatial navigation impairment in both allocentric and egocentric strategies, healthy older adults are particularly limited in the allocentric navigation, but they can still count on egocentric navigation strategy to solve spatial tasks. Therefore, specific navigational tests should be considered for differential diagnosis between healthy and pathological aging conditions. Finally, more research is still needed to better understand the spatial abilities of autistic individuals.
RESUMO
Purkinje cell (PC) dysfunction or degeneration is the most frequent finding in animal models with ataxic symptoms. Mutations affecting intrinsic membrane properties can lead to ataxia by altering the firing rate of PCs or their firing pattern. However, the relationship between specific firing alterations and motor symptoms is not yet clear, and in some cases PC dysfunction precedes the onset of ataxic signs. Moreover, a great variety of ionic and synaptic mechanisms can affect PC signaling, resulting in different features of motor dysfunction. Mutations affecting Na+ channels (NaV1.1, NaV1.6, NaVß4, Fgf14 or Rer1) reduce the firing rate of PCs, mainly via an impairment of the Na+ resurgent current. Mutations that reduce Kv3 currents limit the firing rate frequency range. Mutations of Kv1 channels act mainly on inhibitory interneurons, generating excessive GABAergic signaling onto PCs, resulting in episodic ataxia. Kv4.3 mutations are responsible for a complex syndrome with several neurologic dysfunctions including ataxia. Mutations of either Cav or BK channels have similar consequences, consisting in a disruption of the firing pattern of PCs, with loss of precision, leading to ataxia. Another category of pathogenic mechanisms of ataxia regards alterations of synaptic signals arriving at the PC. At the parallel fiber (PF)-PC synapse, mutations of glutamate delta-2 (GluD2) or its ligand Crbl1 are responsible for the loss of synaptic contacts, abolishment of long-term depression (LTD) and motor deficits. At the same synapse, a correct function of metabotropic glutamate receptor 1 (mGlu1) receptors is necessary to avoid ataxia. Failure of climbing fiber (CF) maturation and establishment of PC mono-innervation occurs in a great number of mutant mice, including mGlu1 and its transduction pathway, GluD2, semaphorins and their receptors. All these models have in common the alteration of PC output signals, due to a variety of mechanisms affecting incoming synaptic signals or the way they are processed by the repertoire of ionic channels responsible for intrinsic membrane properties. Although the PC is a final common pathway of ataxia, the link between specific firing alterations and neurologic symptoms has not yet been systematically studied and the alterations of the cerebellar contribution to motor signals are still unknown.
RESUMO
The role of the cerebellum in Alzheimer's disease (AD) has been neglected for a long time. Recent studies carried out using transgenic mouse models have demonstrated that amyloid-ß (Aß) is deposited in the cerebellum and affects synaptic transmission and plasticity, sometimes before plaque formation. A wide variability of motor phenotype has been observed in the different murine models of AD, without a consistent correlation with the extent of cerebellar histopathological changes or with cognitive deficits. The loss of noradrenergic drive may contribute to the impairment of cerebellar synaptic function and motor learning observed in these mice. Furthermore, cerebellar neurons, particularly granule cells, have been used as in vitro model of Aß-induced neuronal damage. An unexpected conclusion is that the cerebellum, for a long time thought to be somehow protected from AD pathology, is actually considered as a region vulnerable to Aß toxic damage, even at the early stage of the disease, with consequences on motor performance.