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1.
Front Cell Neurosci ; 16: 838419, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35966206

RESUMO

Homeostatic plasticity encompasses the mechanisms by which neurons stabilize their synaptic strength and excitability in response to prolonged and destabilizing changes in their network activity. Prolonged activity blockade leads to homeostatic scaling of action potential (AP) firing rate in hippocampal neurons in part by decreased activity of N-Methyl-D-Aspartate receptors and subsequent transcriptional down-regulation of potassium channel genes including KCNQ3 which encodes Kv7.3. Neuronal Kv7 channels are mostly heterotetramers of Kv7.2 and Kv7.3 subunits and are highly enriched at the axon initial segment (AIS) where their current potently inhibits repetitive and burst firing of APs. However, whether a decrease in Kv7.3 expression occurs at the AIS during homeostatic scaling of intrinsic excitability and what signaling pathway reduces KCNQ3 transcript upon prolonged activity blockade remain unknown. Here, we report that prolonged activity blockade in cultured hippocampal neurons reduces the activity of extracellular signal-regulated kinase 1/2 (ERK1/2) followed by a decrease in the activation of brain-derived neurotrophic factor (BDNF) receptor, Tropomyosin receptor kinase B (TrkB). Furthermore, both prolonged activity blockade and prolonged pharmacological inhibition of ERK1/2 decrease KCNQ3 and BDNF transcripts as well as the density of Kv7.3 and ankyrin-G at the AIS. Collectively, our findings suggest that a reduction in the ERK1/2 activity and subsequent transcriptional down-regulation may serve as a potential signaling pathway that links prolonged activity blockade to homeostatic control of BDNF-TrkB signaling and Kv7.3 density at the AIS during homeostatic scaling of AP firing rate.

2.
Epilepsia ; 63(5): 1211-1224, 2022 05.
Artigo em Inglês | MEDLINE | ID: mdl-35188269

RESUMO

OBJECTIVE: STriatal-Enriched protein tyrosine Phosphatase (STEP) is a brain-specific tyrosine phosphatase. Membrane-bound STEP61 is the only isoform expressed in hippocampus and cortex. Genetic deletion of STEP enhances excitatory synaptic currents and long-term potentiation in the hippocampus. However, whether STEP61 affects seizure susceptibility is unclear. Here we investigated the effects of STEP inhibitor TC-2153 on seizure propensity in a murine model displaying kainic acid (KA)-induced status epilepticus and its effect on hippocampal excitability. METHODS: Adult male and female C57BL/6J mice received intraperitoneal injection of either vehicle (2.8% dimethylsulfoxide [DMSO] in saline) or TC-2153 (10 mg/kg) and then either saline or KA (30 mg/kg) 3 h later before being monitored for behavioral seizures. A subset of female mice was ovariectomized (OVX). Acute hippocampal slices from Thy1-GCaMP6s mice were treated with either DMSO or TC-2153 (10 µM) for 1 h, and then incubated in artificial cerebrospinal fluid (ACSF) and potassium chloride (15 mM) for 2 min prior to live calcium imaging. Pyramidal neurons in dissociated rat hippocampal culture (DIV 8-10) were pre-treated with DMSO or TC-2153 (10 µM) for 1 h before whole-cell patch-clamp recording. RESULTS: TC-2153 treatment significantly reduced KA-induced seizure severity, with greater trend seen in female mice. OVX abolished this TC-2153-induced decrease in seizure severity in female mice. TC-2153 application significantly decreased overall excitability of acute hippocampal slices from both sexes. Surprisingly, TC-2153 treatment hyperpolarized resting membrane potential and decreased firing rate, sag voltage, and hyperpolarization-induced current (Ih ) of cultured hippocampal pyramidal neurons. SIGNIFICANCE: This study is the first to demonstrate that pharmacological inhibition of STEP with TC-2153 decreases seizure severity and hippocampal activity in both sexes, and dampens hippocampal neuronal excitability and Ih . We propose that the antiseizure effects of TC-2153 are mediated by its unexpected action on suppressing neuronal intrinsic excitability.


Assuntos
Dimetil Sulfóxido , Hipocampo , Animais , Benzotiepinas , Dimetil Sulfóxido/efeitos adversos , Dimetil Sulfóxido/metabolismo , Feminino , Ácido Caínico/farmacologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Ratos , Convulsões/induzido quimicamente , Convulsões/metabolismo
3.
Front Physiol ; 11: 568667, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33071824

RESUMO

Activity-dependent persistent changes in neuronal intrinsic excitability and synaptic strength are widely thought to underlie learning and memory. Voltage-gated KCNQ/Kv7 potassium channels have been of great interest as the potential targets for memory disorders due to the beneficial effects of their antagonists in cognition. Importantly, de novo dominant mutations in their neuronal subunits KCNQ2/Kv7.2 and KCNQ3/Kv7.3 are associated with epilepsy and neurodevelopmental disorder characterized by developmental delay and intellectual disability. The role of Kv7 channels in neuronal excitability and epilepsy has been extensively studied. However, their functional significance in neural plasticity, learning, and memory remains largely unknown. Here, we review recent studies that support the emerging roles of Kv7 channels in intrinsic and synaptic plasticity, and their contributions to cognition and behavior.

4.
Nat Commun ; 10(1): 909, 2019 02 22.
Artigo em Inglês | MEDLINE | ID: mdl-30796217

RESUMO

The distribution of single-cell properties across a population of cells can be measured using diverse tools, but no technology directly quantifies the biochemical stimulation events regulating these properties. Here we report digital counting of growth factors in single cells using fluorescent quantum dots and calibrated three-dimensional deconvolution microscopy (QDC-3DM) to reveal physiologically relevant cell stimulation distributions. We calibrate the fluorescence intensities of individual compact quantum dots labeled with epidermal growth factor (EGF) and demonstrate the necessity of near-infrared emission to overcome intrinsic cellular autofluoresence at the single-molecule level. When applied to human triple-negative breast cancer cells, we observe proportionality between stimulation and both receptor internalization and inhibitor response, reflecting stimulation heterogeneity contributions to intrinsic variability. We anticipate that QDC-3DM can be applied to analyze any peptidic ligand to reveal single-cell correlations between external stimulation and phenotypic variability, cell fate, and drug response.


Assuntos
Fator de Crescimento Epidérmico/química , Receptores ErbB/química , Pontos Quânticos/química , Análise de Célula Única/métodos , Neoplasias de Mama Triplo Negativas/metabolismo , Linhagem Celular Tumoral , Fator de Crescimento Epidérmico/antagonistas & inibidores , Fluorescência , Corantes Fluorescentes , Humanos , Imageamento Tridimensional , Microscopia de Fluorescência/métodos
5.
Sci Rep ; 7(1): 12313, 2017 09 26.
Artigo em Inglês | MEDLINE | ID: mdl-28951616

RESUMO

Recurrent high-frequency epileptic seizures cause progressive hippocampal sclerosis, which is associated with caspase-3 activation and NMDA receptor-dependent excitotoxicity. However, the identity of caspase-3 substrates that contribute to seizure-induced hippocampal atrophy remains largely unknown. Here, we show that prolonged high-frequency epileptiform discharges in cultured hippocampal neurons leads to caspase-dependent cleavage of GIRK1 and GIRK2, the major subunits of neuronal G protein-activated inwardly rectifying potassium (GIRK) channels that mediate membrane hyperpolarization and synaptic inhibition in the brain. We have identified caspase-3 cleavage sites in GIRK1 (387ECLD390) and GIRK2 (349YEVD352). The YEVD motif is highly conserved in GIRK2-4, and located within their C-terminal binding sites for Gßγ proteins that mediate membrane-delimited GIRK activation. Indeed, the cleaved GIRK2 displays reduced binding to Gßγ and cannot coassemble with GIRK1. Loss of an ER export motif upon cleavage of GIRK2 abolishes surface and current expression of GIRK2 homotetramic channels. Lastly, kainate-induced status epilepticus causes GIRK1 and GIRK2 cleavage in the hippocampus in vivo. Our findings are the first to show direct cleavage of GIRK1 and GIRK2 subunits by caspase-3, and suggest the possible role of caspase-3 mediated down-regulation of GIRK channel function and expression in hippocampal neuronal injury during prolonged epileptic seizures.


Assuntos
Caspase 3/metabolismo , Canais de Potássio Corretores do Fluxo de Internalização Acoplados a Proteínas G/metabolismo , Hipocampo/patologia , Estado Epiléptico/complicações , Animais , Atrofia/etiologia , Atrofia/patologia , Células Cultivadas , Modelos Animais de Doenças , Hipocampo/citologia , Humanos , Ácido Caínico/toxicidade , Masculino , Neurônios/patologia , Canais de Potássio Corretores do Fluxo de Internalização/metabolismo , Cultura Primária de Células , Ratos , Ratos Sprague-Dawley , Estado Epiléptico/induzido quimicamente , Estado Epiléptico/patologia
6.
J Neuroinflammation ; 12: 160, 2015 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-26337952

RESUMO

BACKGROUND: Fetal alcohol exposure is a leading cause of preventable birth defects, yet drinking during pregnancy remains prevalent worldwide. Studies suggest that activation of the neuroimmune system plays a role in the effects of alcohol exposure during the rodent equivalent to the third trimester of human pregnancy (i.e., first week of neonatal life), particularly by contributing to neuronal loss. Here, we performed a comprehensive study investigating differences in the neuroimmune response in the cerebellum and hippocampus, which are important targets of third trimester-equivalent alcohol exposure. METHODS: To model heavy, binge-like alcohol exposure during this period, we exposed rats to alcohol vapor inhalation during postnatal days (P)3-5 (blood alcohol concentration = 0.5 g/dL). The cerebellar vermis and hippocampus of rat pups were analyzed for signs of glial cell activation and neuronal loss by immunohistochemistry at different developmental stages. Cytokine production was measured by reverse transcriptase polymerase chain reaction during peak blood alcohol concentration and withdrawal periods. Additionally, adolescent offspring were assessed for alterations in gait and spatial memory. RESULTS: We found that this paradigm causes Purkinje cell degeneration in the cerebellar vermis at P6 and P45; however, no signs of neuronal loss were found in the hippocampus. Significant increases in pro-inflammatory cytokines were observed in both brain regions during alcohol withdrawal periods. Although astrocyte activation occurred in both the hippocampus and cerebellar vermis, microglial activation was observed primarily in the latter. CONCLUSIONS: These findings suggest that heavy, binge-like third trimester-equivalent alcohol exposure has time- and brain region-dependent effects on cytokine levels, morphological activation of microglia and astrocytes, and neuronal survival.


Assuntos
Depressores do Sistema Nervoso Central/toxicidade , Cerebelo/patologia , Encefalite/induzido quimicamente , Etanol/toxicidade , Hipocampo/patologia , Neurônios/patologia , Fatores Etários , Análise de Variância , Animais , Animais Recém-Nascidos , Condicionamento Psicológico/efeitos dos fármacos , Citocinas/genética , Citocinas/metabolismo , Encefalite/patologia , Encefalite/fisiopatologia , Medo , Lateralidade Funcional/efeitos dos fármacos , Marcha/efeitos dos fármacos , Proteína Glial Fibrilar Ácida/genética , Proteína Glial Fibrilar Ácida/metabolismo , Marcação In Situ das Extremidades Cortadas , Masculino , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , RNA Mensageiro , Ratos
7.
Pharmacol Biochem Behav ; 137: 78-85, 2015 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-26284742

RESUMO

Ethanol consumption during pregnancy produces a wide range of morphological and behavioral alterations known as fetal alcohol spectrum disorder (FASD). Among the behavioral deficits associated with FASD is an increased probability of developing anxiety disorders. Studies with animal models of FASD have demonstrated that ethanol exposure during the equivalent to the 1(st) and 2(nd) trimesters of human pregnancy increases anxiety-like behavior. Here, we examined the impact on this type of behavior of exposure to high doses of ethanol in vapor inhalation chambers during the rat equivalent to the human 3rd trimester of pregnancy (i.e., neonatal period in these animals). We evaluated anxiety-like behavior with the elevated plus maze. Using whole-cell patch-clamp electrophysiological techniques in brain slices, we also characterized glutamatergic and GABAergic synaptic transmission in the basolateral amygdala, a brain region that has been implicated to play a role in emotional behavior. We found that ethanol-exposed adolescent offspring preferred the closed arms over the open arms in the elevated plus maze and displayed lower head dipping activity than controls. Electrophysiological measurements showed an increase in the frequency of spontaneous and miniature excitatory postsynaptic currents in pyramidal neurons from the ethanol group. These findings suggest that high-dose ethanol exposure during the equivalent to the last trimester of human pregnancy can persistently increase excitatory synaptic inputs to principal neurons in the basolateral amygdala, leading to an increase in anxiety-like behaviors.


Assuntos
Ansiedade/induzido quimicamente , Complexo Nuclear Basolateral da Amígdala/efeitos dos fármacos , Etanol/administração & dosagem , Ácido Glutâmico , Terceiro Trimestre da Gravidez/efeitos dos fármacos , Efeitos Tardios da Exposição Pré-Natal/induzido quimicamente , Animais , Animais Recém-Nascidos , Ansiedade/metabolismo , Ansiedade/psicologia , Complexo Nuclear Basolateral da Amígdala/metabolismo , Etanol/toxicidade , Potenciais Pós-Sinápticos Excitadores/efeitos dos fármacos , Potenciais Pós-Sinápticos Excitadores/fisiologia , Feminino , Ácido Glutâmico/metabolismo , Exposição por Inalação , Masculino , Aprendizagem em Labirinto/efeitos dos fármacos , Aprendizagem em Labirinto/fisiologia , Técnicas de Cultura de Órgãos , Gravidez , Terceiro Trimestre da Gravidez/metabolismo , Efeitos Tardios da Exposição Pré-Natal/metabolismo , Efeitos Tardios da Exposição Pré-Natal/psicologia , Ratos , Ratos Sprague-Dawley
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