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1.
Neurobiol Dis ; 198: 106558, 2024 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-38852754

RESUMO

Periventricular nodular heterotopia (PNH), the most common brain malformation diagnosed in adulthood, is characterized by the presence of neuronal nodules along the ventricular walls. PNH is mainly associated with mutations in the FLNA gene - encoding an actin-binding protein - and patients often develop epilepsy. However, the molecular mechanisms underlying the neuronal failure still remain elusive. It has been hypothesized that dysfunctional cortical circuitry, rather than ectopic neurons, may explain the clinical manifestations. To address this issue, we depleted FLNA from cortical pyramidal neurons of a conditional Flnaflox/flox mice by timed in utero electroporation of Cre recombinase. We found that FLNA regulates dendritogenesis and spinogenesis thus promoting an appropriate excitatory/inhibitory inputs balance. We demonstrated that FLNA modulates RAC1 and cofilin activity through its interaction with the Rho-GTPase Activating Protein 24 (ARHGAP24). Collectively, we disclose an uncharacterized role of FLNA and provide strong support for neural circuit dysfunction being a consequence of FLNA mutations.


Assuntos
Córtex Cerebral , Filaminas , Proteínas rac1 de Ligação ao GTP , Animais , Camundongos , Fatores de Despolimerização de Actina/metabolismo , Córtex Cerebral/metabolismo , Filaminas/metabolismo , Filaminas/genética , Proteínas Ativadoras de GTPase/metabolismo , Proteínas Ativadoras de GTPase/genética , Camundongos Transgênicos , Neurogênese/fisiologia , Neurônios/metabolismo , Neuropeptídeos/metabolismo , Neuropeptídeos/genética , Heterotopia Nodular Periventricular/genética , Heterotopia Nodular Periventricular/metabolismo , Heterotopia Nodular Periventricular/patologia , Células Piramidais/metabolismo , Proteínas rac1 de Ligação ao GTP/metabolismo , Proteínas rac1 de Ligação ao GTP/genética
2.
Neurobiol Dis ; 145: 105043, 2020 11.
Artigo em Inglês | MEDLINE | ID: mdl-32798727

RESUMO

Rett syndrome (RTT; OMIM#312750) is mainly caused by mutations in the X-linked MECP2 gene (methyl-CpG-binding protein 2 gene; OMIM*300005), which leads to impairments in the brain-derived neurotrophic factor (BDNF) signalling. The boost of BDNF mediated effects would be a significant breakthrough but it has been hampered by the difficulty to administer BDNF to the central nervous system. Adenosine, an endogenous neuromodulator, may accomplish that role since through A2AR it potentiates BDNF synaptic actions in healthy animals. We thus characterized several hallmarks of the adenosinergic and BDNF signalling in RTT and explored whether A2AR activation could boost BDNF actions. For this study, the RTT animal model, the Mecp2 knockout (Mecp2-/y) (B6.129P2 (C)-Mecp2tm1.1Bird/J) mouse was used. Whenever possible, parallel data was also obtained from post-mortem brain samples from one RTT patient. Ex vivo extracellular recordings of field excitatory post-synaptic potentials in CA1 hippocampal area were performed to evaluate synaptic transmission and long-term potentiation (LTP). RT-PCR was used to assess mRNA levels and Western Blot or radioligand binding assays were performed to evaluate protein levels. Changes in cortical and hippocampal adenosine content were assessed by liquid chromatography with diode array detection (LC/DAD). Hippocampal ex vivo experiments revealed that the facilitatory actions of BDNF upon LTP is absent in Mecp2-/y mice and that TrkB full-length (TrkB-FL) receptor levels are significantly decreased. Extracts of the hippocampus and cortex of Mecp2-/y mice revealed less adenosine amount as well as less A2AR protein levels when compared to WT littermates, which may partially explain the deficits in adenosinergic tonus in these animals. Remarkably, the lack of BDNF effect on hippocampal LTP in Mecp2-/y mice was overcome by selective activation of A2AR with CGS21680. Overall, in Mecp2-/y mice there is an impairment on adenosinergic system and BDNF signalling. These findings set the stage for adenosine-based pharmacological therapeutic strategies for RTT, highlighting A2AR as a therapeutic target in this devastating pathology.


Assuntos
Fator Neurotrófico Derivado do Encéfalo/metabolismo , Receptor A1 de Adenosina/metabolismo , Receptor A2A de Adenosina/metabolismo , Síndrome de Rett/metabolismo , Transdução de Sinais/fisiologia , Animais , Hipocampo/metabolismo , Proteína 2 de Ligação a Metil-CpG , Camundongos , Camundongos Knockout , Receptor trkB/metabolismo , Síndrome de Rett/genética
3.
J Neurosci ; 36(48): 12117-12128, 2016 11 30.
Artigo em Inglês | MEDLINE | ID: mdl-27903722

RESUMO

Adenosine kinase (ADK) deficiency in human patients (OMIM:614300) disrupts the methionine cycle and triggers hypermethioninemia, hepatic encephalopathy, cognitive impairment, and seizures. To identify whether this neurological phenotype is intrinsically based on ADK deficiency in the brain or if it is secondary to liver dysfunction, we generated a mouse model with a brain-wide deletion of ADK by introducing a Nestin-Cre transgene into a line of conditional ADK deficient Adkfl/fl mice. These AdkΔbrain mice developed a progressive stress-induced seizure phenotype associated with spontaneous convulsive seizures and profound deficits in hippocampus-dependent learning and memory. Pharmacological, biochemical, and electrophysiological studies suggest enhanced adenosine levels around synapses resulting in an enhanced adenosine A1 receptor (A1R)-dependent protective tone despite lower expression levels of the receptor. Theta-burst-induced LTP was enhanced in the mutants and this was dependent on adenosine A2A receptor (A2AR) and tropomyosin-related kinase B signaling, suggesting increased activation of these receptors in synaptic plasticity phenomena. Accordingly, reducing adenosine A2A receptor activity in AdkΔbrain mice restored normal associative learning and contextual memory and attenuated seizure risk. We conclude that ADK deficiency in the brain triggers neuronal adaptation processes that lead to dysregulated synaptic plasticity, cognitive deficits, and increased seizure risk. Therefore, ADK mutations have an intrinsic effect on brain physiology and may present a genetic risk factor for the development of seizures and learning impairments. Furthermore, our data show that blocking A2AR activity therapeutically can attenuate neurological symptoms in ADK deficiency. SIGNIFICANCE STATEMENT: A novel human genetic condition (OMIM #614300) that is based on mutations in the adenosine kinase (Adk) gene has been discovered recently. Affected patients develop hepatic encephalopathy, seizures, and severe cognitive impairment. To model and understand the neurological phenotype of the human mutation, we generated a new conditional knock-out mouse with a brain-specific deletion of Adk (AdkΔbrain). Similar to ADK-deficient patients, AdkΔbrain mice develop seizures and cognitive deficits. We identified increased basal synaptic transmission and enhanced adenosine A2A receptor (A2AR)-dependent synaptic plasticity as the underlying mechanisms that govern these phenotypes. Our data show that neurological phenotypes in ADK-deficient patients are intrinsic to ADK deficiency in the brain and that blocking A2AR activity therapeutically can attenuate neurological symptoms in ADK deficiency.


Assuntos
Adenosina Quinase/deficiência , Adenosina/metabolismo , Encéfalo/fisiopatologia , Plasticidade Neuronal , Receptor A2A de Adenosina/metabolismo , Transmissão Sináptica , Adenosina Quinase/genética , Animais , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , Neurotransmissores/metabolismo , Sinapses/enzimologia
4.
Restor Neurol Neurosci ; 36(4): 485-501, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29889085

RESUMO

BACKGROUND: T-lymphocyte (T-cell) invasion into the brain parenchyma is a major consequence of traumatic brain injury (TBI). However, the role of T-cells in the post-TBI functional outcome and secondary inflammatory processes is unknown. We explored the dynamics of T-cell infiltration into the cortex after TBI to establish whether the infiltration relates to post-injury functional impairment/recovery and progression of the secondary injury. METHOD: TBI was induced in rats by lateral fluid-percussion injury, and the acute functional impairment was assessed using the neuroscore. Animals were killed between 1-90 d post-TBI for immunohistochemical analysis of T-cell infiltration (CD3), chronic macrophage/microglial reaction (CD68), blood-brain barrier (BBB) dysfunction (IgG), and endophenotype of the cortical injury. Furthermore, the occurrence of spontaneous seizures and spike-and-wave discharges were assessed using video-electroencephalography. RESULTS: The number of T-cells peaked at 2-d post-TBI, and then dramatically decreased by 7-d post-TBI (5% of 2-d value). Unexpectedly, chronic T-cell infiltration at 1 or 3 months post-TBI did not correlate with the severity of chronic inflammation (p > 0.05) or BBB dysfunction (p > 0.05). Multiple regression analysis indicated that inflammation and BBB dysfunction is associated with 48% of the perilesional T-cell infiltration even at the chronic time-point (r = 0.695, F = 6.54, p < 0.05). The magnitude of T-cell infiltration did not predict the pathologic endophenotype of cortical injury, but the higher the number of T-cells in the cortex, the poorer the recovery index based on the neuroscore (r = - 0.538, p < 0.05). T-cell infiltration was not associated with the number or duration of age-related spike-and-wave discharges (SWD). Nevertheless, the higher the number of SWD, the poorer the recovery index (r = - 0.767, p < 0.5). CONCLUSIONS: These findings suggest that acute infiltration of T-cells into the brain parenchyma after TBI is a contributing factor to poor post-injury recovery.


Assuntos
Córtex Motor/patologia , Recuperação de Função Fisiológica/fisiologia , Traumatismos da Medula Espinal/patologia , Traumatismos da Medula Espinal/fisiopatologia , Linfócitos T/fisiologia , Animais , Barreira Hematoencefálica/patologia , Citocinas/metabolismo , Modelos Animais de Doenças , Eletroencefalografia , Macrófagos/patologia , Masculino , Córtex Motor/fisiopatologia , Doenças do Sistema Nervoso/etiologia , Ratos , Ratos Sprague-Dawley , Traumatismos da Medula Espinal/mortalidade , Linfócitos T/patologia , Fatores de Tempo
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