RESUMO
Anxiety is an emotional state that affects the quality of human life. Several neurotransmitters are involved in the regulation of anxiety, including glutamate. The major actions of glutamate are mediated by N-methyl-d-aspartate receptors (NMDARs) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs). The present study performed a behavioral and neurochemical analysis of Carioca High-conditioned Freezing (CHF) and Carioca Low-conditioned Freezing (CLF) rats compared with control rats. We evaluated thermal nociception, anxiety-like behavior, depressive-like behavior, spatial memory, habituation memory, and the content and localization of different glutamatergic receptor subunits and postsynaptic density-95 (PSD-95), a postsynaptic protein. The CHF group exhibited an anxious-like phenotype, impairments in habituation and spatial memory, and a depressive-like phenotype compared with the control group. In the ventral hippocampus, an increase in the PSD-95, GluN1 and GluA1 subunits and a decrease in the GluN2A subunit of glutamatergic receptors. The CLF group exhibited a less anxious-like phenotype, hyperlocomotion and habituation impairments. Also, CLF animals, presented, in the ventral hippocampus, an increase in the PSD-95, GluN1 and GluA2 subunits and a decrease in the GluN2B subunit. These results suggest that the differential composition of NMDAR and AMPAR subunits may be related to the modulation of different phenotypes in CHF and CLF rats, which may help identify new targets for therapeutic interventions for anxiety disorders and other comorbidities.
Assuntos
Hipocampo , Receptores de N-Metil-D-Aspartato , Animais , Ansiedade , Ácido Glutâmico , Hipocampo/metabolismo , Ratos , Receptores de N-Metil-D-Aspartato/genética , Receptores de N-Metil-D-Aspartato/metabolismo , Memória Espacial , Ácido alfa-Amino-3-hidroxi-5-metil-4-isoxazol PropiônicoRESUMO
OBJECTIVE: Interleukin 4 (IL-4) is an anti-inflammatory cytokine related to different aspects of central nervous system development such as survival, proliferation, and differentiation, among others. Our goals were to investigate the effect of intravitreous treatment with IL-4 on the activation of downstream signaling pathways in the retina and the distribution of retinal axons within the superior colliculus (SC). MATERIAL AND METHODS: Lister hooded rats were submitted to an intravitreous injection of either IL-4 (5 U/µL) or PBS (vehicle) at postnatal day 10 (PND10). At PND11 or PND14, retinas were processed for Western blot or immunohistochemistry. At PND13, a group of animals received an intraocular injection of an anterograde tracer in the left (untreated) eye in order to label the uncrossed retinotectal axons. RESULTS: Our data revealed that intravitreous treatment with IL-4 at PND10 leads to a decrease in GFAP content and a sustained increase in the phosphorylation of STAT6 and ERK levels in the retina. IL-4 also increases retinal axonal arbors within the SC, compared to control groups. CONCLUSIONS: These data suggest that a single in vivo treatment with IL-4 during the early stages of development modulates signaling pathways in the retina, resulting in altered binocular subcortical visual connectivity.
Assuntos
Interleucina-4/administração & dosagem , Sistema de Sinalização das MAP Quinases/fisiologia , Rede Nervosa/metabolismo , Retina/metabolismo , Fator de Transcrição STAT6/metabolismo , Vias Visuais/metabolismo , Animais , Injeções Intravítreas , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , Rede Nervosa/efeitos dos fármacos , Fosforilação/efeitos dos fármacos , Fosforilação/fisiologia , Ratos , Retina/efeitos dos fármacos , Roedores , Vias Visuais/efeitos dos fármacosRESUMO
BACKGROUND: Multiple sclerosis (MS) is an inflammatory demyelinating disease classically associated with axonal damage and loss; more recently, however, synaptic changes have been recognized as additional contributing factors. An anatomical area commonly affected in MS is the visual pathway; yet, changes other than those associated with inflammatory demyelination of the optic nerve, i.e., optic neuritis, have not been described in detail. METHODS: Adult mice were subjected to a diet containing cuprizone to mimic certain aspects of inflammatory demyelination as seen in MS. Demyelination and inflammation were assessed by real-time polymerase chain reaction and immunohistochemistry. Synaptic changes associated with inflammatory demyelination in the dorsal lateral geniculate nucleus (dLGN) were determined by immunohistochemistry, Western blot analysis, and electrophysiological field potential recordings. RESULTS: In the cuprizone model, demyelination was observed in retinorecipient regions of the subcortical visual system, in particular the dLGN, where it was found accompanied by microglia activation and astrogliosis. In contrast, anterior parts of the pathway, i.e., the optic nerve and tract, appeared largely unaffected. Under the inflammatory demyelinating conditions, as seen in the dLGN of cuprizone-treated mice, there was an overall decrease in excitatory synaptic inputs from retinal ganglion cells. At the same time, the number of synaptic complexes arising from gamma-aminobutyric acid (GABA)-generating inhibitory neurons was found increased, as were the synapses that contain the N-methyl-D-aspartate receptor (NMDAR) subunit GluN2B and converge onto inhibitory neurons. These synaptic changes were functionally found associated with a shift toward an overall increase in network inhibition. CONCLUSIONS: Using the cuprizone model of inflammatory demyelination, our data reveal a novel form of synaptic (mal)adaption in the CNS that is characterized by a shift of the excitation/inhibition balance toward inhibitory network activity associated with an increase in GABAergic inhibitory synapses and a possible increase in excitatory input onto inhibitory interneurons. In addition, our data recognize the cuprizone model as a suitable tool in which to assess the effects of inflammatory demyelination on subcortical retinorecipient regions of the visual system, such as the dLGN, in the absence of overt optic neuritis.
Assuntos
Cuprizona/toxicidade , Doenças Desmielinizantes/induzido quimicamente , Doenças Desmielinizantes/patologia , Corpos Geniculados/patologia , Vias Visuais/patologia , Animais , Quelantes/toxicidade , Corpo Caloso/efeitos dos fármacos , Corpo Caloso/patologia , Corpos Geniculados/efeitos dos fármacos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Vias Visuais/efeitos dos fármacosRESUMO
OBJECTIVE: The development of retinotectal pathways form precise topographical maps is usually completed by the third postnatal week. Cytokines participate in the development and plasticity of the nervous system. We have previously shown that in vivo treatment with interleukin 2 disrupts the retinocollicular topographical order in early stages of development. Therefore, we decided to study the effect of a single intravitreous injection of IL-6 upon retinotectal circuitry in neonates and juvenile rats. MATERIALS AND METHODS: Lister Hooded rats received an intravitreous injection of IL-6 (50 ng/ml) or vehicle (PBS) at either postnatal day (PND)10 or PND30 and the ipsilateral retinotectal pathway was evaluated 4 or 8 days later, respectively. RESULTS: Our data showed that, at different stages of development, a single IL-6 intravitreous treatment did not produce an inflammatory response and increased retinal axon innervation throughout the visual layers of the superior colliculus. CONCLUSIONS: Taken together, our data provide the first evidence that a single intravitreous injection with IL-6 leads to sprouting in the subcortical visual connections and suggest that small changes in IL-6 levels might be sufficient to impair the correct neuronal circuitry fine-tuning during brain development.
Assuntos
Interleucina-6/administração & dosagem , Retina/crescimento & desenvolvimento , Colículos Superiores/crescimento & desenvolvimento , Vias Visuais/crescimento & desenvolvimento , Animais , Animais Recém-Nascidos , Injeções Intravítreas , Plasticidade Neuronal/efeitos dos fármacos , Plasticidade Neuronal/fisiologia , Ratos , Retina/citologia , Retina/efeitos dos fármacos , Colículos Superiores/citologia , Colículos Superiores/efeitos dos fármacos , Vias Visuais/citologia , Vias Visuais/efeitos dos fármacosRESUMO
Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by selective dopaminergic loss. Non dopaminergic neurotransmitters such as glutamate are also involved in PD progression. NMDA receptor/postsynaptic density protein 95 (PSD-95)/neuronal nitric oxide synthase (nNOS) activation is involved in neuronal excitability in PD. Here, we are focusing on the evaluating these post-synaptic protein levels in the 6-OHDA model of PD. Adult male C57BL/6 mice subjected to unilateral striatal injury with 6-OHDA were assessed at 1-, 2-, or 4-weeks post-lesion. Animals were subjected to an apomorphine-induced rotation test followed by the analysis of protein content, synaptic structure, and NOx production. All biochemical analysis was performed comparing the control versus lesioned sides of the same animal. 6-OHDA mice exhibited contralateral rotation activity, difficulties in coordinating movements, and changes in Iba-1 and glial fibrillary acidic protein (GFAP) expression during the whole period. At one week of survival, the mice showed a shift in NMDA composition, favoring the GluN2A subunit and increased PSD95 and nNOS expression and NOx formation. After two-weeks, a decrease in the total number of synapses was observed in the lesioned side. However, the number of excitatory synapses was increased with a higher content of GluN1 subunit and PSD95. After four weeks, NMDA receptor subunits restored to control levels. Interestingly, NOx formation in the serum increased. This study reveals, for the first time, the temporal course of behavioral deficits and glutamatergic synaptic plasticity through NMDAr subunit shift. Together, these data demonstrate that dopamine depletion leads to a fine adaptive response over time, which can be used for further studies of therapeutic management adjustments with the progression of PD.
RESUMO
Diabetic patients are more affected by depression than non-diabetics, and this is related to greater treatment resistance and associated with poorer outcomes. This increase in the prevalence of depression in diabetics is also related to hyperglycemia and hypercortisolism. In diabetics, the hyperactivity of the HPA axis occurs in parallel to gut dysbiosis, weakness of the intestinal permeability barrier, and high bacterial-product translocation into the bloodstream. Diabetes also induces an increase in the permeability of the blood-brain barrier (BBB) and Toll-like receptor 4 (TLR4) expression in the hippocampus. Furthermore, lipopolysaccharide (LPS)-induced depression behaviors and neuroinflammation are exacerbated in diabetic mice. In this context, we propose here that hypercortisolism, in association with gut dysbiosis, leads to an exacerbation of hippocampal neuroinflammation, glutamatergic transmission, and neuronal apoptosis, leading to the development and aggravation of depression and to resistance to treatment of this mood disorder in diabetic patients.
Assuntos
Síndrome de Cushing , Transtorno Depressivo , Diabetes Mellitus Experimental , Humanos , Camundongos , Animais , Eixo Encéfalo-Intestino , Sistema Hipotálamo-Hipofisário/fisiologia , Doenças Neuroinflamatórias , Disbiose , Sistema Hipófise-Suprarrenal/fisiologiaRESUMO
The retinotectal topography of rats develops within the first three postnatal weeks during the critical period. Previous studies have shown that monocular enucleation results in plasticity of the intact retinotectal pathway in a time-dependent manner. Glial fibrillary acidic protein (GFAP), an astrocyte marker, is up-regulated after central nervous system injury. Adenosine is a neuromodulator involved in the development and plasticity of the visual system acting through the inhibitory A1 and excitatory A2a receptor activities. Herein, we examined whether adenosine receptors and astrocytes are crucial for monocular enucleation (ME)-induced plasticity. We also investigate whether A2a blockade alters retinotectal plasticity in an astrocyte-dependent manner. Lister Hooded rats were submitted to monocular enucleation at postnatal day 10 (PND10) or PND21 and, after different survival times, were processed for immunohistochemistry or western blotting assays. Another group underwent subpial implantation of ELVAX containing vehicle (DMSO) or SCH58261 (1 µM - an A2a receptor antagonist), simultaneously with ME at PND10. After a 72 h survival, GFAP content and the retinotectal plasticity were evaluated. Our data show that monocular enucleation leads to an upregulation in GFAP expression in the contralateral superior colliculus. At PND10, a slight increase in GFAP labeling was observed at 72 h post-enucleation, while at PND21 GFAP increase was detected in the deafferented superior colliculus after 1 to 3 weeks of survival. The content of adenosine receptors also varies in the contralateral target after ME. A transient increase in A1 receptors is observed in the early periods of plasticity, while A2a receptors are upregulated later. Interestingly, the local blockade of A2a receptors abolished the increase in GFAP and the retinotectal reorganization induced by monocular enucleation during the critical period. Taken together these results suggest a correlation between astrocytes and A2a adenosine receptors in the subcortical visual plasticity.
Assuntos
Astrócitos , Colículos Superiores , Animais , Ratos , Astrócitos/metabolismo , Enucleação Ocular , Colículos Superiores/metabolismo , Receptores Purinérgicos P1/metabolismo , Imuno-Histoquímica , Receptor A2A de Adenosina/metabolismoRESUMO
Enteric glial cells (EGCs) constitute the majority of the neural population of the enteric nervous system and are found in all layers of the gastrointestinal tract. It is active in enteric functions such as immunomodulation, participating in inflammation and intestinal epithelial barrier (IEB) regulation. Both EGCs and IEB have been described as altered in Parkinson's disease (PD). Using an animal model of PD induced by 6-hydroxydopamine (6-OHDA), we investigated the effect of ongoing neurodegeneration on EGCs and inflammatory response during short periods after model induction. C57Bl/6 male mice were unilaterally injected with 6-OHDA in the striatum. Compared to the control group, 6-OHDA animals showed decreased relative water content in their feces from 1 w after model induction. Moreover, at 1 and 2 w post-induction, groups showed histopathological changes indicative of intestinal inflammation. We identified an increase in IBA1 and GFAP levels in the intestinal mucosa. At an earlier survival of 48 h, we detected an increase in GFAP in the neuromuscular layer, suggesting that it was a primary event for the upregulation of GDNF, TNF-α, and occludin in the intestinal mucosa observed after 1 w. Within 2 w, we identified a decrease in the expression of occludin barrier proteins. Thus, EGCs modulation may be an early enteric signal induced by parkinsonian neurodegeneration, followed by inflammatory and dysmotility signs besides IEB modification.
Assuntos
Sistema Nervoso Entérico , Doença de Parkinson , Animais , Modelos Animais de Doenças , Sistema Nervoso Entérico/metabolismo , Inflamação/metabolismo , Masculino , Camundongos , Neuroglia/metabolismo , Ocludina/metabolismo , Oxidopamina/metabolismo , Oxidopamina/toxicidade , Doença de Parkinson/metabolismoRESUMO
Monocular eye enucleation (ME) is a classical paradigm to induce neural plasticity in retinal ganglion cells (RGCs) axons from the intact eye, especially when performed within the critical period of visual system development. However, the precise mechanisms underlying the axonal sprouting and synaptogenesis seen in this model remain poorly understood. In the present work, we investigated the temporal alterations in phosphorylation of three kinases related to axonal growth and synaptogenesis-GSK3ß (an important repressor of axonal outgrowth), AKT, and ERK-in superior colliculus of rats submitted to ME during early postnatal development. Western blotting analysis showed an increase in pGSK3ß, the inactive form of this enzyme, 24 and 48 hr after ME. Accordingly, an increase in pERK levels was detected 24 hr after ME, indicating that phosphorylation of these enzymes might be related to axonal reorganization induced by ME. Interestingly, AKT phosphorylation was increased just 1 week after ME, suggesting it may be involved in the stabilization of newly formed synapses, rising from the axonal reorganization of remaining eye. A better understanding of how signaling pathways are modulated in a model of intense axonal sprouting can highlight possible therapeutic targets in RGCs injuries in adult individuals, where axonal regrowth is nearly absent.
Assuntos
Enucleação Ocular , Plasticidade Neuronal/fisiologia , Transdução de Sinais/fisiologia , Colículos Superiores/metabolismo , Animais , Feminino , Glicogênio Sintase Quinase 3 beta/metabolismo , Masculino , Fosforilação , Proteínas Proto-Oncogênicas c-akt/metabolismo , RatosRESUMO
The NMDA receptor is crucial to several functions in CNS physiology and some of its effects are mediated by promoting nitric oxide production from L-arginine and activation of signaling pathways and the transcription factor CREB. Our previous work demonstrated in retinal cells that increasing intracellular free L-arginine levels directly correlates to nitric oxide (NO) generation and can be promoted by protein synthesis inhibition and increase of free L-arginine concentration. Eukaryotic elongation factor 2 kinase (eEF2K), a calcium/calmodulin-dependent kinase, is also known to be activated by NMDA receptors leading to protein synthesis inhibition. Here we explored how does eEF2K participate in NMDA-induced NO signaling. We found that when this enzyme is inhibited, NMDA loses its ability to promote NO synthesis. On the other hand, when NO synthesis is increased by protein synthesis inhibition with cycloheximide or addition of exogenous L-arginine, eEF2K has no participation, showcasing a specific link between this enzyme and NMDA-induced NO signaling. We have previously shown that inhibition of the canonical NO signaling pathway (guanylyl cyclase/cGMP/cGK) blocks CREB activation by glutamate in retinal cells. Interestingly, pharmacological inhibition of eEF2K fully prevents CREB activation by NMDA, once again demonstrating the importance of eEF2K in NMDA receptor signaling. In summary, we demonstrated here a new role for eEF2K, directly controlling NMDA-dependent nitrergic signaling and modulating L-arginine availability in neurons, which can potentially be a new target for the study of physiological and pathological processes involving NMDA receptors in the central nervous system.
Assuntos
Sistema Nervoso Central/metabolismo , Proteína de Ligação ao Elemento de Resposta ao AMP Cíclico/metabolismo , Quinase do Fator 2 de Elongação/metabolismo , N-Metilaspartato/farmacologia , Óxido Nítrico/biossíntese , Animais , Arginina/farmacologia , Galinhas , Cicloeximida/farmacologia , Quinase do Fator 2 de Elongação/antagonistas & inibidores , Indazóis/farmacologia , Masculino , Fosforilação/efeitos dos fármacos , Piridinas/farmacologia , Pirimidinas/farmacologia , RatosRESUMO
Although the photoreceptors cell death is the main cause of some retinopathies diseases, the mechanisms involved in this process are poorly understood. The neuroprotective effects of interleukin-4 (IL-4) have been shown in several tissues, including retina. We demonstrate that treatment of rat retinal explants with IL-4 completely inhibited the thapsigargin-induced rod photoreceptor cell death after 24 hr in culture. We also showed that IL-4 receptor alpha subunit (IL-4Ralpha) is abundantly present in retina. Colocalization of IL-4Ralpha and rhodopsin indicate a direct effect of this cytokine in rod photoreceptor cells. Moreover, IL-4 increased the intracellular levels of cAMP in 7.4-fold, indicating that the neuroprotective effect of this cytokine was completely blocked by RpcAMP, an inhibitor of protein kinase (PKA). Our data demonstrate, for the first time, the neuroprotective effect of IL-4 through cAMP/PKA pathway in thapsigargin-induced photoreceptor cell death.
Assuntos
Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , AMP Cíclico/metabolismo , Interleucina-4/farmacologia , Fármacos Neuroprotetores/farmacologia , Células Fotorreceptoras Retinianas Bastonetes/efeitos dos fármacos , Animais , Morte Celular/efeitos dos fármacos , Morte Celular/fisiologia , AMP Cíclico/análogos & derivados , Citoproteção/efeitos dos fármacos , Citoproteção/fisiologia , Inibidores Enzimáticos/toxicidade , Interleucina-4/metabolismo , Degeneração Neural/induzido quimicamente , Degeneração Neural/tratamento farmacológico , Degeneração Neural/prevenção & controle , Fármacos Neuroprotetores/metabolismo , Técnicas de Cultura de Órgãos , Ratos , Receptores de Interleucina-4/efeitos dos fármacos , Receptores de Interleucina-4/metabolismo , Degeneração Retiniana/tratamento farmacológico , Degeneração Retiniana/metabolismo , Degeneração Retiniana/fisiopatologia , Células Fotorreceptoras Retinianas Bastonetes/metabolismo , Células Fotorreceptoras Retinianas Bastonetes/patologia , Rodopsina/metabolismo , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/fisiologia , Tapsigargina/toxicidade , Regulação para Cima/efeitos dos fármacos , Regulação para Cima/fisiologiaRESUMO
Interleukin-6 (IL-6) is involved in different processes of the central nervous system. Our aims were to investigate the effect of IL-6 on retinotectal topography and on different signaling pathways. Rats were submitted to an intravitreous injection of either IL-6 (50 ng/ml) or PBS (vehicle) at postnatal day 10 (PND10). At PND11 or PND14, different groups were processed for western blot, histochemistry or immunofluorescence analysis. IL-6 treatment leads to an increase in pSTAT-3 levels in the retina and a disruption in the retinotectal topographic map, suggesting that a transient increase in interleukin-6 levels may impact neural circuitry development.
Assuntos
Interleucina-6/farmacologia , Vias Visuais/crescimento & desenvolvimento , Animais , Interleucina-6/administração & dosagem , Interleucina-6/fisiologia , Injeções Intravítreas , Fosforilação , Ratos , Retina/efeitos dos fármacos , Retina/crescimento & desenvolvimento , Retina/metabolismo , Fator de Transcrição STAT3/metabolismo , Transdução de Sinais , Colículos Superiores/efeitos dos fármacos , Colículos Superiores/crescimento & desenvolvimento , Colículos Superiores/fisiologia , Vias Visuais/efeitos dos fármacos , Vias Visuais/fisiologiaRESUMO
Lesions in the central nervous system (CNS) can often induce structural reorganization within intact circuits of the brain. Several studies show advances in the understanding of mechanisms of brain plasticity and the role of the immune system activation. Microglia, a myeloid derived cell population colonizes the CNS during early phases of embryonic development. In the present study, we evaluated the role of microglial activation in the sprouting of intact axons following lesions of the visual pathways. We evaluated the temporal course of microglial activation in the superior colliculus following a contralateral monocular enucleation (ME) and the possible involvement of microglial cells in the plastic reorganization of the intact, uncrossed, retinotectal pathway from the remaining eye. Lister Hooded rats were enucleated at PND 10 and submitted to systemic treatment with inhibitors of microglial activation: cyclosporine A and minocycline. The use of neuroanatomical tracers allowed us to evaluate the time course of structural axonal plasticity. Immunofluorescence and western blot techniques were used to observe the expression of microglial marker, Iba-1 and the morphology of microglial cells. Following a ME, Iba-1 immunoreactivity showed a progressive increase of microglial activation in the contralateral SC at 24â¯h, peaking at 72â¯h after the lesion. Treatment with inhibitors of microglial activation blocked both the structural plasticity of intact uncrossed retinotectal axons and microglial activation as seen by the decrease of Iba-1 immunoreactivity. The local blockade of TNF-α with a neutralizing antibody was also able to block axonal plasticity of the intact eye following a ME. The data support the hypothesis that microglial activation is a necessary step for the regulation of neuroplasticity induced by lesions during early brain development.
Assuntos
Axônios/metabolismo , Encéfalo/crescimento & desenvolvimento , Encéfalo/metabolismo , Microglia/metabolismo , Plasticidade Neuronal/fisiologia , Vias Visuais/metabolismo , Animais , Animais Recém-Nascidos , Axônios/química , Química Encefálica/fisiologia , Enucleação Ocular/efeitos adversos , Enucleação Ocular/tendências , Microglia/química , Ratos , Fatores de Tempo , Vias Visuais/química , Vias Visuais/patologiaRESUMO
Interleukin-4 (IL-4), an anti-inflammatory cytokine, has been related to the differentiation of the rodent retina in vitro, but constitutive presence of either IL-4 or of IL-4 receptor in the retina has not been reported. In this work we examined the expression of IL-4 and its specific receptor alpha subunit (IL-4Ralpha). IL-4Ralpha is expressed both in neural retina and non-neural ocular tissue, while IL-4 was found mainly in non-neural tissue. We characterized a novel trophic effect of IL-4 upon the retina. We showed that IL-4 can inhibit the proliferation of retinal cells (approximately 40%) through the cAMP-PKA pathway and associated with a reduction of cyclin D1 and increase of p27(kip1). IL-4 also promotes the differentiation of rod photoreceptors. Activation of tyrosine kinases, protein kinase C, and mitogen-activated kinases of the Erk family were required for IL-4-induced rod photoreceptor differentiation, independent of the release of other trophic factors in culture. Taken together, our results show, for the first time, that IL-4 directly modulates proliferation of retinal cells and rod photoreceptor differentiation, through distinct signaling pathways.
Assuntos
Diferenciação Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Interleucina-4/farmacologia , Retina/citologia , Células Fotorreceptoras Retinianas Bastonetes/efeitos dos fármacos , Transdução de Sinais/efeitos dos fármacos , Células-Tronco/efeitos dos fármacos , Análise de Variância , Animais , Animais Recém-Nascidos , Antígenos CD/metabolismo , Células Cultivadas , AMP Cíclico/metabolismo , Relação Dose-Resposta a Droga , Ativadores de Enzimas/farmacologia , Inibidores Enzimáticos/farmacologia , Camundongos , Camundongos Endogâmicos C57BL , Proteínas Quinases/metabolismo , Receptores de Superfície Celular/metabolismo , Retina/efeitos dos fármacos , Rodopsina/metabolismo , Transdução de Sinais/fisiologia , Baço/citologia , Timidina/metabolismo , Fatores de TempoRESUMO
Tryptophan is an essential amino acid and metabolic precursor of serotonin. Serotonin is both a classical neurotransmitter and a signaling molecule that plays crucial roles in the development of neural circuits and plasticity. The specification of neural circuits in rodents occurs during the postnatal period with conspicuous influence of environmental factors including the nutritional status. Sensory, motor and cognitive systems develop during a critical period, a time window that is crucial to the use-dependent organization of neuronal circuits. This review presents recent experimental findings that disclose some mechanism of tryptophan- and serotonin-dependent plasticity in the developing and adult brain.
Assuntos
Encéfalo/crescimento & desenvolvimento , Plasticidade Neuronal/fisiologia , Serotonina/biossíntese , Triptofano/deficiência , Vias Visuais/crescimento & desenvolvimento , Envelhecimento/metabolismo , Animais , Encéfalo/metabolismo , Deficiências do Desenvolvimento/etiologia , Deficiências do Desenvolvimento/metabolismo , Deficiências do Desenvolvimento/fisiopatologia , Humanos , Lactente , Transtornos da Nutrição do Lactente/complicações , Transtornos da Nutrição do Lactente/metabolismo , Transtornos da Nutrição do Lactente/fisiopatologia , Roedores/crescimento & desenvolvimento , Roedores/metabolismo , Vias Visuais/metabolismoRESUMO
The serotonin transporter (5-HTT) regulates serotonin homeostasis and has been used as a target for different drugs in depression treatment. Although the serotonergic system has received a lot of attention, little is known about the effects of these drugs over serotonin transporters. In this work, we investigated the expression pattern of 5-HTT during development of the visual system and the influence of fluoxetine on different signaling pathways. Our data showed that the expression of 5-HTT has a gradual increase from postnatal day 0 until 42 and decrease afterwards. Moreover, chronic fluoxetine treatment both in childhood and adolescence induces down regulation of 5-HTT expression and phosphorylation of ERK and AKT signaling pathways. Together these data suggest that the levels of 5-HTT protein could be important for the development of the central nervous system and suggest that the ERK and AKT are involved in the molecular pathways of antidepressants drugs, acting in concert to improve serotonergic signaling.
Assuntos
Fluoxetina/farmacologia , Plasticidade Neuronal/efeitos dos fármacos , Proteínas Proto-Oncogênicas c-akt/efeitos dos fármacos , Inibidores Seletivos de Recaptação de Serotonina/farmacologia , Proteínas da Membrana Plasmática de Transporte de Serotonina/efeitos dos fármacos , Transdução de Sinais/efeitos dos fármacos , Colículos Superiores/efeitos dos fármacos , Animais , Animais Recém-Nascidos , Fluoxetina/administração & dosagem , Humanos , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , Ratos , Inibidores Seletivos de Recaptação de Serotonina/administração & dosagemRESUMO
Amyloid precursor protein (APP) is essential to physiological processes such as synapse formation and neural plasticity. Sequential proteolysis of APP by beta- and gamma-secretases generates amyloid-beta peptide (Aß), the main component of senile plaques in Alzheimer Disease. Alternative APP cleavage by alpha-secretase occurs within Aß domain, releasing soluble α-APP (sAPPα), a neurotrophic fragment. Among other functions, sAPPα is important to synaptogenesis, neural survival and axonal growth. APP and sAPPα levels are increased in models of neuroplasticity, which suggests an important role for APP and its metabolites, especially sAPPα, in the rearranging brain. In this work we analyzed the effects of monocular enucleation (ME), a classical model of lesion-induced plasticity, upon APP content, processing and also in secretases levels. Besides, we addressed whether α-secretase activity is crucial for retinotectal remodeling after ME. Our results showed that ME induced a transient reduction in total APP content. We also detected an increase in α-secretase expression and in sAPP production concomitant with a reduction in Aß and ß-secretase contents. These data suggest that ME facilitates APP processing by the non-amyloidogenic pathway, increasing sAPPα levels. Indeed, the pharmacological inhibition of α-secretase activity reduced the axonal sprouting of ipsilateral retinocollicular projections from the intact eye after ME, suggesting that sAPPα is necessary for synaptic structural rearrangement. Understanding how APP processing is regulated under lesion conditions may provide new insights into APP physiological role on neural plasticity.
Assuntos
Secretases da Proteína Precursora do Amiloide/metabolismo , Precursor de Proteína beta-Amiloide/metabolismo , Enucleação Ocular , Plasticidade Neuronal/fisiologia , Visão Monocular/fisiologia , Córtex Visual/fisiologia , Vias Visuais/fisiologia , Animais , Denervação , Ratos , Córtex Visual/cirurgia , Vias Visuais/cirurgiaRESUMO
Nitric oxide (NO) is a very reactive molecule, and its short half-life would make it virtually invisible until its discovery. NO activates soluble guanylyl cyclase (sGC), increasing 3',5'-cyclic guanosine monophosphate levels to activate PKGs. Although NO triggers several phosphorylation cascades due to its ability to react with Fe II in heme-containing proteins such as sGC, it also promotes a selective posttranslational modification in cysteine residues by S-nitrosylation, impacting on protein function, stability, and allocation. In the central nervous system (CNS), NO synthesis usually requires a functional coupling of nitric oxide synthase I (NOS I) and proteins such as NMDA receptors or carboxyl-terminal PDZ ligand of NOS (CAPON), which is critical for specificity and triggering of selected pathways. NO also modulates CREB (cAMP-responsive element-binding protein), ERK, AKT, and Src, with important implications for nerve cell survival and differentiation. Differences in the regulation of neuronal death or survival by NO may be explained by several mechanisms involving localization of NOS isoforms, amount of NO being produced or protein sets being modulated. A number of studies show that NO regulates neurotransmitter release and different aspects of synaptic dynamics, such as differentiation of synaptic specializations, microtubule dynamics, architecture of synaptic protein organization, and modulation of synaptic efficacy. NO has also been associated with synaptogenesis or synapse elimination, and it is required for long-term synaptic modifications taking place in axons or dendrites. In spite of tremendous advances in the knowledge of NO biological effects, a full description of its role in the CNS is far from being completely elucidated.
Assuntos
Sistema Nervoso Central/fisiologia , Óxido Nítrico/metabolismo , Transdução de Sinais/fisiologia , Animais , Sistema Nervoso Central/crescimento & desenvolvimento , Plasticidade Neuronal/fisiologia , Neurônios/fisiologia , Neurotransmissores/fisiologiaRESUMO
Alzheimer's disease (AD) and type 2 diabetes appear to share similar pathogenic mechanisms. dsRNA-dependent protein kinase (PKR) underlies peripheral insulin resistance in metabolic disorders. PKR phosphorylates eukaryotic translation initiation factor 2α (eIF2α-P), and AD brains exhibit elevated phospho-PKR and eIF2α-P levels. Whether and how PKR and eIF2α-P participate in defective brain insulin signaling and cognitive impairment in AD are unknown. We report that ß-amyloid oligomers, AD-associated toxins, activate PKR in a tumor necrosis factor α (TNF-α)-dependent manner, resulting in eIF2α-P, neuronal insulin receptor substrate (IRS-1) inhibition, synapse loss, and memory impairment. Brain phospho-PKR and eIF2α-P were elevated in AD animal models, including monkeys given intracerebroventricular oligomer infusions. Oligomers failed to trigger eIF2α-P and cognitive impairment in PKR(-/-) and TNFR1(-/-) mice. Bolstering insulin signaling rescued phospho-PKR and eIF2α-P. Results reveal pathogenic mechanisms shared by AD and diabetes and establish that proinflammatory signaling mediates oligomer-induced IRS-1 inhibition and PKR-dependent synapse and memory loss.
Assuntos
Peptídeos beta-Amiloides/toxicidade , Encéfalo/efeitos dos fármacos , Proteínas Substratos do Receptor de Insulina/metabolismo , Polímeros/toxicidade , Fator de Necrose Tumoral alfa/metabolismo , eIF-2 Quinase/metabolismo , Doença de Alzheimer/metabolismo , Doença de Alzheimer/patologia , Peptídeos beta-Amiloides/química , Animais , Encéfalo/metabolismo , Modelos Animais de Doenças , Haplorrinos/metabolismo , Hipoglicemiantes/farmacologia , Proteínas Substratos do Receptor de Insulina/antagonistas & inibidores , Transtornos da Memória/metabolismo , Transtornos da Memória/patologia , Camundongos , Camundongos Knockout , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Fosforilação/efeitos dos fármacos , Polímeros/química , Receptores Tipo I de Fatores de Necrose Tumoral/deficiência , Receptores Tipo I de Fatores de Necrose Tumoral/genética , Receptores Tipo I de Fatores de Necrose Tumoral/metabolismo , Transdução de Sinais/efeitos dos fármacos , Sinapses/efeitos dos fármacos , Sinapses/metabolismo , Fator de Necrose Tumoral alfa/antagonistas & inibidores , eIF-2 Quinase/deficiência , eIF-2 Quinase/genéticaRESUMO
The development and maturation of sensory systems depends on the correct pattern of connections which occurs during a critical period when axonal elimination and synaptic plasticity are involved in the formation of topographical maps. Among the mechanisms involved in synaptic stabilization, essential fatty acids (EFAs), available only through diet, appear as precursors of signaling molecules involved in modulation of gene expression and neurotransmitter release. Omega-3 fatty acids, such as docosahexaenoic acid (DHA), are considered EFAs and are accumulated in the brain during fetal period and neonatal development. In this study, we demonstrated the effect of omega-3/DHA nutritional restriction in the long-term stabilization of connections in the visual system. Female rats were fed 5 weeks before mating with either a control (soy oil) or a restricted (coconut oil) diet. Litters were fed until postnatal day 13 (PND13), PND28 or PND42 with the same diets when they received an intraocular injection of HRP. Another group received a single retinal lesion at the temporal periphery at PND21. Omega-3 restriction induced an increase in the optical density in the superficial layers of the SC, as a result of axonal sprouting outside the main terminal zones. This effect was observed throughout the SGS, including the ventral and intermediate sub-layers at PND13 and also at PND28 and PND42. The quantification of optical densities strongly suggests a delay in axonal elimination in the omega3(-) groups. The supplementation with fish oil (DHA) was able to completely reverse the abnormal expansion of the retinocollicular projection. The same pattern of expanded terminal fields was also observed in the ipsilateral retinogeniculate pathway. The critical period window was studied in lesion experiments in either control or omega-3/DHA restricted groups. DHA restriction induced an increased sprouting of intact, ipsilateral axons at the deafferented region of the superior colliculus compared to the control group, revealing an abnormal extension of the critical period. Finally, in omega-3 restricted group we observed in the collicular visual layers normal levels of GAP-43 with decreased levels of its phosphorylated form, p-GAP-43, consistent with a reduction in synaptic stabilization. The data indicate, therefore, that chronic dietary restriction of omega-3 results in a reduction in DHA levels which delays axonal elimination and critical period closure, interfering with the maintenance of terminal fields in the visual system.