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1.
J Neurosci ; 44(19)2024 May 08.
Artigo em Inglês | MEDLINE | ID: mdl-38565288

RESUMO

Excitotoxicity and the concurrent loss of inhibition are well-defined mechanisms driving acute elevation in excitatory/inhibitory (E/I) balance and neuronal cell death following an ischemic insult to the brain. Despite the high prevalence of long-term disability in survivors of global cerebral ischemia (GCI) as a consequence of cardiac arrest, it remains unclear whether E/I imbalance persists beyond the acute phase and negatively affects functional recovery. We previously demonstrated sustained impairment of long-term potentiation (LTP) in hippocampal CA1 neurons correlating with deficits in learning and memory tasks in a murine model of cardiac arrest/cardiopulmonary resuscitation (CA/CPR). Here, we use CA/CPR and an in vitro ischemia model to elucidate mechanisms by which E/I imbalance contributes to ongoing hippocampal dysfunction in male mice. We reveal increased postsynaptic GABAA receptor (GABAAR) clustering and function in the CA1 region of the hippocampus that reduces the E/I ratio. Importantly, reduced GABAAR clustering observed in the first 24 h rebounds to an elevation of GABAergic clustering by 3 d postischemia. This increase in GABAergic inhibition required activation of the Ca2+-permeable ion channel transient receptor potential melastatin-2 (TRPM2), previously implicated in persistent LTP and memory deficits following CA/CPR. Furthermore, we find Ca2+-signaling, likely downstream of TRPM2 activation, upregulates Ca2+/calmodulin-dependent protein kinase II (CaMKII) activity, thereby driving the elevation of postsynaptic inhibitory function. Thus, we propose a novel mechanism by which inhibitory synaptic strength is upregulated in the context of ischemia and identify TRPM2 and CaMKII as potential pharmacological targets to restore perturbed synaptic plasticity and ameliorate cognitive function.


Assuntos
Proteína Quinase Tipo 2 Dependente de Cálcio-Calmodulina , Transdução de Sinais , Canais de Cátion TRPM , Animais , Masculino , Camundongos , Isquemia Encefálica/metabolismo , Região CA1 Hipocampal/metabolismo , Proteína Quinase Tipo 2 Dependente de Cálcio-Calmodulina/metabolismo , Neurônios GABAérgicos/metabolismo , Parada Cardíaca/complicações , Parada Cardíaca/metabolismo , Hipocampo/metabolismo , Camundongos Endogâmicos C57BL , Inibição Neural/fisiologia , Receptores de GABA-A/metabolismo , Canais de Cátion TRPM/metabolismo
2.
J Biol Chem ; 299(5): 104693, 2023 05.
Artigo em Inglês | MEDLINE | ID: mdl-37037305

RESUMO

The Ca2+/calmodulin-dependent protein kinase II (CaMKII) is a central regulator of learning and memory, which poses a problem for targeting it therapeutically. Indeed, our study supports prior conclusions that long-term interference with CaMKII signaling can erase pre-formed memories. By contrast, short-term pharmacological CaMKII inhibition with the neuroprotective peptide tatCN19o interfered with learning in mice only mildly and transiently (for less than 1 h) and did not at all reverse pre-formed memories. These results were obtained with ≥500-fold of the dose that protected hippocampal neurons from cell death after a highly clinically relevant pig model of transient global cerebral ischemia: ventricular fibrillation followed by advanced life support and electrical defibrillation to induce the return of spontaneous circulation. Of additional importance for therapy development, our preliminary cardiovascular safety studies in mice and pig did not indicate any concerns with acute tatCN19o injection. Taken together, although prolonged interference with CaMKII signaling can erase memory, acute short-term CaMKII inhibition with tatCN19o did not cause such retrograde amnesia that would pose a contraindication for therapy.


Assuntos
Proteína Quinase Tipo 2 Dependente de Cálcio-Calmodulina , Memória , Animais , Camundongos , Proteína Quinase Tipo 2 Dependente de Cálcio-Calmodulina/antagonistas & inibidores , Proteína Quinase Tipo 2 Dependente de Cálcio-Calmodulina/metabolismo , Hipocampo/metabolismo , Memória/efeitos dos fármacos , Memória/fisiologia , Neurônios/metabolismo , Fosforilação/fisiologia , Suínos , Peptídeos/farmacologia
3.
Glia ; 71(6): 1429-1450, 2023 06.
Artigo em Inglês | MEDLINE | ID: mdl-36794545

RESUMO

Neonatal stroke is common and causes life-long motor and cognitive sequelae. Because neonates with stroke are not diagnosed until days-months after the injury, chronic targets for repair are needed. We evaluated oligodendrocyte maturity and myelination and assessed oligodendrocyte gene expression changes using single cell RNA sequencing (scRNA seq) at chronic timepoints in a mouse model of neonatal arterial ischemic stroke. Mice underwent 60 min of transient right middle cerebral artery occlusion (MCAO) on postnatal day 10 (p10) and received 5-ethynyl-2'-deoxyuridine (EdU) on post-MCAO days 3-7 to label dividing cells. Animals were sacrificed 14 and 28-30 days post-MCAO for immunohistochemistry and electron microscopy. Oligodendrocytes were isolated from striatum 14 days post-MCAO for scRNA seq and differential gene expression analysis. The density of Olig2+ EdU+ cells was significantly increased in ipsilateral striatum 14 days post-MCAO and the majority of oligodendrocytes were immature. Density of Olig2+ EdU+ cells declined significantly between 14 and 28 days post-MCAO without a concurrent increase in mature Olig2+ EdU+ cells. By 28 days post-MCAO there were significantly fewer myelinated axons in ipsilateral striatum. scRNA seq identified a cluster of "disease associated oligodendrocytes (DOLs)" specific to the ischemic striatum, with increased expression of MHC class I genes. Gene ontology analysis suggested decreased enrichment of pathways involved in myelin production in the reactive cluster. Oligodendrocytes proliferate 3-7 days post-MCAO and persist at 14 days, but fail to mature by 28 days. MCAO induces a subset of oligodendrocytes with reactive phenotype, which may be a therapeutic target to promote white matter repair.


Assuntos
Infarto da Artéria Cerebral Média , Acidente Vascular Cerebral , Camundongos , Animais , Infarto da Artéria Cerebral Média/complicações , Animais Recém-Nascidos , Acidente Vascular Cerebral/complicações , Oligodendroglia , Bainha de Mielina
4.
Neurobiol Dis ; 175: 105923, 2022 12.
Artigo em Inglês | MEDLINE | ID: mdl-36371060

RESUMO

Preclinical models demonstrate that nearly all anesthetics cause widespread neuroapoptosis in the developing brains of infant rodents and non-human primates. Anesthesia-induced developmental apoptosis is succeeded by prolonged neuropathology in the surviving neurons and lasting cognitive impairments, suggesting that anesthetics interfere with the normal developmental trajectory of the brain. However, little is known about effects of anesthetics on stereotyped axonal pruning, an important developmental algorithm that sculpts neural circuits for proper function. Here, we proposed that neonatal ketamine exposure may interfere with stereotyped axonal pruning of the infrapyramidal bundle (IPB) of the hippocampal mossy fiber system and that impaired pruning may be associated with alterations in the synaptic transmission of CA3 neurons. To test this hypothesis, we injected postnatal day 7 (PND7) mouse pups with ketamine or vehicle over 6 h and then studied them at different developmental stages corresponding to IPB pruning (PND20-40). Immunohistochemistry with synaptoporin (a marker of mossy fibers) revealed that in juvenile mice treated with ketamine at PND7, but not in vehicle-treated controls, positive IPB fibers extended farther into the stratum pyramidale of CA3 region. Furthermore, immunofluorescent double labeling for synaptoporin and PSD-95 strongly suggested that the unpruned IPB caused by neonatal ketamine exposure makes functional synapses. Importantly, patch-clamp electrophysiology for miniature excitatory postsynaptic currents (mEPSCs) in acute brain slices ex vivo revealed increased frequency and amplitudes of mEPSCs in hippocampal CA3 neurons in ketamine-treated groups when compared to vehicle controls. We conclude that neonatal ketamine exposure interferes with normal neural circuit development and that this interference leads to lasting increase in excitatory synaptic transmission in hippocampus.


Assuntos
Anestésicos , Ketamina , Camundongos , Animais , Ketamina/toxicidade , Transmissão Sináptica/fisiologia , Hipocampo , Sinapses/fisiologia , Fibras Musgosas Hipocampais , Anestésicos/farmacologia
5.
Neurobiol Dis ; 168: 105701, 2022 06 15.
Artigo em Inglês | MEDLINE | ID: mdl-35337949

RESUMO

Neurological symptoms following cerebellar stroke can range from motor to cognitive-affective impairments. Topographic imaging studies from patients with lesions confined to the cerebellum have shown evidence linking anterior cerebellar lobules with motor function and posterior lobules with cognitive function. Damage to the cerebellum can disrupt functional connectivity in cerebellar stroke patients, as it is highly interconnected with forebrain motor and cognitive areas. The hippocampus plays a key role in memory acquisition, a cognitive domain that is negatively impacted by posterior cerebellar stroke, and there is increasing evidence that the cerebellum can affect hippocampal function in health and disease. To study these topographical dissociations, we developed a mouse photo-thrombosis model to produce unilateral strokes in anterior (lobules III-V) or posterior (lobules VI-VIII) cerebellar cortex to examine hippocampal plasticity and behavior. Histological and MRI data demonstrate reproducible injury that is confined to the targeted lobules. We then measured hippocampal long-term potentiation (LTP) ex-vivo with extracellular field recording experiments in acute brain slices obtained from mice 7 days post-cerebellar stroke. Interestingly, we found that a unilateral posterior stroke resulted in a contralateral hippocampal impairment, matching the cerebellothalamic pathway trajectory, while LTP was intact in both hippocampi of mice with anterior strokes. We also assessed motor coordination and memory function at 7 days post-stroke using a balance beam, contextual and delay fear conditioning (CFC and DFC), and novel object recognition (NOR) tasks. Mice with anterior strokes showed lack of coordination evaluated as an increased number of missteps, while mice with posterior strokes did not. Mice with anterior or posterior cerebellar strokes demonstrated similar freezing behavior to shams in CFC and DFC, while only posterior stroke mice displayed a reduced discrimination index in the NOR task. These data suggest that a unilateral LTP impairment observed in mice with posterior strokes produces a mild memory impairment. Our results demonstrate that our model recapitulates aspects of clinical lesion-symptom mapping, with anterior cerebellar strokes producing impaired motor coordination and posterior cerebellar strokes producing an object-recognition memory impairment. Further studies are warranted to interrogate other motor and cognitive-affective behaviors and brain region specific alterations following focal cerebellar stroke. The novel model presented herein will allow for future preclinical translational studies to improve neurological deficits after cerebellar stroke.


Assuntos
Doenças Cerebelares , Acidente Vascular Cerebral , Animais , Doenças Cerebelares/patologia , Doenças Cerebelares/psicologia , Cerebelo/patologia , Hipocampo/diagnóstico por imagem , Hipocampo/patologia , Humanos , Imageamento por Ressonância Magnética/métodos , Camundongos , Acidente Vascular Cerebral/complicações , Acidente Vascular Cerebral/diagnóstico por imagem , Acidente Vascular Cerebral/patologia
6.
Br J Anaesth ; 129(4): 555-566, 2022 10.
Artigo em Inglês | MEDLINE | ID: mdl-35701270

RESUMO

BACKGROUND: General anaesthesia in the neonatal period has detrimental effects on the developing mammalian brain. The impact of underlying inflammation on anaesthesia-induced developmental neurotoxicity remains largely unknown. METHODS: Postnatal day 7 (PND7) rats were randomly assigned to receive sevoflurane (3 vol% for 3 h) or carrier gas 12 h after bacterial lipopolysaccharide (LPS; 1 µg g-1) or vehicle injection. Pharmacological inhibition of caspase-1 by Vx-765 (two doses of 50 µg g-1 body weight) was used to investigate mechanistic pathways of neuronal injury. Histomorphological injury and molecular changes were quantified 2 h after the end of anaesthesia. Long-term functional deficits were tested at 5-8 weeks of age using a battery of behavioural tests in the memory and anxiety domains. RESULTS: Sevoflurane or LPS treatment increased activated caspase-3 and caspase-9 expression in the hippocampal subiculum and CA1, which was greater when sevoflurane was administered in the setting of LPS-induced inflammation. Neuronal injury induced by LPS+sevoflurane treatment resulted in sex-specific behavioural outcomes when rats were tested at 5-8 weeks of age, including learning and memory deficits in males and heightened anxiety-related behaviour in females. Hippocampal caspase-1 and NLRP1 (NLR family pyrin domain containing 1), but not NLRP3, were upregulated by LPS or LPS+sevoflurane treatment, along with related proinflammatory cytokines, interleukin (IL)-1ß, and IL-18. Pretreatment with Vx-765, a selective caspase-1 inhibitor, led to reduced IL-1ß in LPS and LPS+sevoflurane groups. Caspase-1 inhibition by Vx-765 significantly decreased activated caspase-3 and caspase-9 immunoreactivity in the subiculum. CONCLUSIONS: Systemic inflammation promotes developmental neurotoxicity by worsening anaesthesia-induced neuronal damage with sex-specific behavioural outcomes. This highlights the importance of studying anaesthesia-induced neurotoxicity in more clinically relevant settings.


Assuntos
Lipopolissacarídeos , Síndromes Neurotóxicas , Animais , Animais Recém-Nascidos , Caspase 1 , Caspase 3/metabolismo , Caspase 9/metabolismo , Citocinas/metabolismo , Inflamação/induzido quimicamente , Interleucina-18/metabolismo , Lipopolissacarídeos/toxicidade , Masculino , Mamíferos/metabolismo , Síndromes Neurotóxicas/etiologia , Ratos , Sevoflurano/toxicidade
7.
Int J Mol Sci ; 23(3)2022 Jan 20.
Artigo em Inglês | MEDLINE | ID: mdl-35163060

RESUMO

Since its invention, general anesthesia has been an indispensable component of modern surgery. While traditionally considered safe and beneficial in many pathological settings, hundreds of preclinical studies in various animal species have raised concerns about the detrimental and long-lasting consequences that general anesthetics may cause to the developing brain. Clinical evidence of anesthetic neurotoxicity in humans continues to mount as we continue to contemplate how to move forward. Notwithstanding the alarming evidence, millions of children are being anesthetized each year, setting the stage for substantial healthcare burdens in the future. Hence, furthering our knowledge of the molecular underpinnings of anesthesia-induced developmental neurotoxicity is crucially important and should enable us to develop protective strategies so that currently available general anesthetics could be safely used during critical stages of brain development. In this mini-review, we provide a summary of select strategies with primary focus on the mechanisms of neuroprotection and potential for clinical applicability. First, we summarize a diverse group of chemicals with the emphasis on intracellular targets and signal-transduction pathways. We then discuss epigenetic and transgenerational effects of general anesthetics and potential remedies, and also anesthesia-sparing or anesthesia-delaying approaches. Finally, we present evidence of a novel class of anesthetics with a distinct mechanism of action and a promising safety profile.


Assuntos
Anestésicos/toxicidade , Desenvolvimento Infantil/efeitos dos fármacos , Síndromes Neurotóxicas/prevenção & controle , Animais , Criança , Epigênese Genética , Humanos , Mitocôndrias/metabolismo , Síndromes Neurotóxicas/metabolismo
8.
Int J Mol Sci ; 23(3)2022 Feb 08.
Artigo em Inglês | MEDLINE | ID: mdl-35163810

RESUMO

Over the past three decades, we have been grappling with rapidly accumulating evidence that general anesthetics (GAs) may not be as innocuous for the young brain as we previously believed. The growing realization comes from hundreds of animal studies in numerous species, from nematodes to higher mammals. These studies argue that early exposure to commonly used GAs causes widespread apoptotic neurodegeneration in brain regions critical to cognition and socio-emotional development, kills a substantial number of neurons in the young brain, and, importantly, results in lasting disturbances in neuronal synaptic communication within the remaining neuronal networks. Notably, these outcomes are often associated with long-term impairments in multiple cognitive-affective domains. Not only do preclinical studies clearly demonstrate GA-induced neurotoxicity when the exposures occur in early life, but there is a growing body of clinical literature reporting similar cognitive-affective abnormalities in young children who require GAs. The need to consider alternative GAs led us to focus on synthetic neuroactive steroid analogues that have emerged as effective hypnotics, and analgesics that are apparently devoid of neurotoxic effects and long-term cognitive impairments. This would suggest that certain steroid analogues with different cellular targets and mechanisms of action may be safe alternatives to currently used GAs. Herein we summarize our current knowledge of neuroactive steroids as promising novel GAs.


Assuntos
Anestésicos Gerais/efeitos adversos , Rede Nervosa/efeitos dos fármacos , Transtornos Neurocognitivos/induzido quimicamente , Animais , Criança , Modelos Animais de Doenças , Humanos , Transtornos Neurocognitivos/psicologia
9.
Neural Plast ; 2021: 8774663, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34659399

RESUMO

Hippocampal cell death and cognitive dysfunction are common following global cerebral ischemia across all ages, including children. Most research has focused on preventing neuronal death. Restoration of neuronal function after cell death is an alternative approach (neurorestoration). We previously identified transient receptor potential M2 (TRPM2) ion channels as a potential target for acute neuroprotection and delayed neurorestoration in an adult CA/CPR mouse model. Cardiac arrest/cardiopulmonary resuscitation (CA/CPR) in juvenile (p20-25) mice was used to investigate the role of ion TRPM2 channels in neuroprotection and ischemia-induced synaptic dysfunction in the developing brain. Our novel TRPM2 inhibitor, tatM2NX, did not confer protection against CA1 pyramidal cell death but attenuated synaptic plasticity (long-term plasticity (LTP)) deficits in both sexes. Further, in vivo administration of tatM2NX two weeks after CA/CPR reduced LTP impairments and restored memory function. These data provide evidence that pharmacological synaptic restoration of the surviving hippocampal network can occur independent of neuroprotection via inhibition of TRPM2 channels, providing a novel strategy to improve cognitive recovery in children following cerebral ischemia. Importantly, these data underscore the importance of age-appropriate models in disease research.


Assuntos
Isquemia Encefálica/tratamento farmacológico , Fragmentos de Peptídeos/farmacologia , Fragmentos de Peptídeos/uso terapêutico , Recuperação de Função Fisiológica/fisiologia , Canais de Cátion TRPM/antagonistas & inibidores , Canais de Cátion TRPM/fisiologia , Fatores Etários , Animais , Isquemia Encefálica/fisiopatologia , Reanimação Cardiopulmonar/métodos , Feminino , Parada Cardíaca/tratamento farmacológico , Parada Cardíaca/fisiopatologia , Hipocampo/efeitos dos fármacos , Hipocampo/fisiologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Rede Nervosa/efeitos dos fármacos , Rede Nervosa/fisiologia , Técnicas de Cultura de Órgãos , Recuperação de Função Fisiológica/efeitos dos fármacos
10.
Br J Anaesth ; 124(3): e81-e91, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-31980157

RESUMO

Exposure to anaesthetic drugs during the fetal or neonatal period induces widespread neuronal apoptosis in the brains of rodents and non-human primates. Hundreds of published preclinical studies and nearly 20 clinical studies have documented cognitive and behavioural deficits many months or years later, raising the spectre that early life anaesthesia exposure is a long-term, perhaps permanent, insult that might affect the quality of life of millions of humans. Although the phenomenon of anaesthesia-induced developmental neurotoxicity is well characterised, there are important and lingering questions pertaining to sex differences and neurodevelopmental sequelae that might occur differentially in females and males. We review the relevant literature on sex differences in the field of anaesthesia-induced developmental neurotoxicity, and present an emerging pattern of potential sex-dependent neurodevelopmental abnormalities in rodent models of human infant anaesthesia exposure.


Assuntos
Anestésicos/efeitos adversos , Transtornos do Neurodesenvolvimento/induzido quimicamente , Animais , Ansiedade/induzido quimicamente , Apoptose/efeitos dos fármacos , Transtorno do Deficit de Atenção com Hiperatividade/induzido quimicamente , Transtornos Cognitivos/induzido quimicamente , Metilação de DNA , Feminino , Humanos , Masculino , Síndromes Neurotóxicas/etiologia , Caracteres Sexuais
11.
Br J Anaesth ; 124(5): 603-613, 2020 05.
Artigo em Inglês | MEDLINE | ID: mdl-32151384

RESUMO

BACKGROUND: The most currently used general anaesthetics are potent potentiators of γ-aminobutyric acid A (GABAA) receptors and are invariably neurotoxic during the early stages of brain development in preclinical animal models. As causality between GABAA potentiation and anaesthetic-induced developmental neurotoxicity has not been established, the question remains whether GABAergic activity is crucial for promoting/enhancing neurotoxicity. Using the neurosteroid analogue, (3α,5α)-3-hydroxy-13,24-cyclo-18,21-dinorchol-22-en-24-ol (CDNC24), which potentiates recombinant GABAA receptors, we examined whether this potentiation is the driving force in inducing neurotoxicity during development. METHODS: The neurotoxic potential of CDNC24 was examined vis-à-vis propofol (2,6-diisopropylphenol) and alphaxalone (5α-pregnan-3α-ol-11,20-dione) at the peak of rat synaptogenesis. In addition to the morphological neurotoxicity studies of the subiculum and medial prefrontal cortex (mPFC), we assessed the extra-, pre-, and postsynaptic effects of these agents on GABAergic neurotransmission in acute subicular slices from rat pups. RESULTS: CDNC24, like alphaxalone and propofol, caused dose-dependent hypnosis in vivo, with a higher therapeutic index. CDNC24 and alphaxalone, unlike propofol, did not cause developmental neuroapoptosis in the subiculum and mPFC. Propofol potentiated post- and extrasynaptic GABAA currents as evidenced by increased spontaneous inhibitory postsynaptic current (sIPSC) decay time and prominent tonic currents, respectively. CDNC24 and alphaxalone had a similar postsynaptic effect, but also displayed a strong presynaptic effect as evidenced by decreased frequency of sIPSCs and induced moderate tonic currents. CONCLUSIONS: The lack of neurotoxicity of CDNC24 and alphaxalone may be at least partly related to suppression of presynaptic GABA release in the developing brain.


Assuntos
Encéfalo/efeitos dos fármacos , Hipnóticos e Sedativos/toxicidade , Pregnanodionas/toxicidade , Esteroides/toxicidade , Animais , Apoptose/efeitos dos fármacos , Encéfalo/metabolismo , Encéfalo/patologia , Relação Dose-Resposta a Droga , Agonistas de Receptores de GABA-A/administração & dosagem , Agonistas de Receptores de GABA-A/farmacologia , Agonistas de Receptores de GABA-A/toxicidade , Hipocampo/efeitos dos fármacos , Hipocampo/crescimento & desenvolvimento , Hipocampo/metabolismo , Hipocampo/patologia , Hipnóticos e Sedativos/administração & dosagem , Hipnóticos e Sedativos/farmacologia , Potenciais Pós-Sinápticos Inibidores/efeitos dos fármacos , Síndromes Neurotóxicas/etiologia , Síndromes Neurotóxicas/patologia , Córtex Pré-Frontal/efeitos dos fármacos , Córtex Pré-Frontal/crescimento & desenvolvimento , Córtex Pré-Frontal/patologia , Pregnanodionas/administração & dosagem , Pregnanodionas/farmacologia , Propofol/administração & dosagem , Propofol/farmacologia , Propofol/toxicidade , Ratos Sprague-Dawley , Receptores de GABA-A/metabolismo , Esteroides/administração & dosagem , Esteroides/farmacologia , Sinapses/efeitos dos fármacos , Sinapses/fisiologia
12.
Neural Plast ; 2018: 9275239, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29853851

RESUMO

Ischemic long-term potentiation (iLTP) is a form of synaptic plasticity that occurs in acute brain slices following oxygen-glucose deprivation. In vitro, iLTP can occlude physiological LTP (pLTP) through saturation of plasticity mechanisms. We used our murine cardiac arrest and cardiopulmonary resuscitation (CA/CPR) model to produce global brain ischemia and assess whether iLTP is induced in vivo, contributing to the functionally relevant impairment of pLTP. Adult male mice were subjected to CA/CPR, and slice electrophysiology was performed in the hippocampal CA1 region 7 or 30 days later. We observed increased miniature excitatory postsynaptic current amplitudes, suggesting a potentiation of postsynaptic AMPA receptor function after CA/CPR. We also observed increased phosphorylated GluR1 in the postsynaptic density of hippocampi after CA/CPR. These data support the in vivo induction of ischemia-induced plasticity. Application of a low-frequency stimulus (LFS) to CA1 inputs reduced excitatory postsynaptic potentials in slices from mice subjected to CA/CPR, while having no effects in sham controls. These results are consistent with a reversal, or depotentiation, of iLTP. Further, depotentiation with LFS partially restored induction of pLTP with theta burst stimulation. These data provide evidence for iLTP following in vivo ischemia, which occludes pLTP and likely contributes to network disruptions that underlie memory impairments.


Assuntos
Isquemia Encefálica/fisiopatologia , Região CA1 Hipocampal/fisiopatologia , Parada Cardíaca/fisiopatologia , Potenciação de Longa Duração , Neurônios/fisiologia , Animais , Isquemia Encefálica/complicações , Parada Cardíaca/complicações , Depressão Sináptica de Longo Prazo , Masculino , Camundongos Endogâmicos C57BL , Receptores de AMPA/fisiologia
13.
Matrix Biol ; 125: 88-99, 2024 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-38135163

RESUMO

Traumatic brain injury (TBI) is the leading cause of death and disability due to injury worldwide. Extracellular matrix (ECM) remodeling is known to significantly contribute to TBI pathophysiology. Glycosaminoglycans, which are long-chain, variably sulfated polysaccharides abundant within the ECM, have previously been shown to be substantially altered after TBI. In this study, we sought to delineate the dynamics of glycosaminoglycan alterations after TBI and discover the precise biologic processes responsible for observed glycosaminoglycan changes after injury. We performed state-of-the art mass spectrometry on brain tissues isolated from mice after TBI or craniotomy-alone. We observed dynamic changes in glycosaminoglycans at Day 1 and 7 post-TBI, with heparan sulfate, chondroitin sulfate, and hyaluronan remaining significantly increased after a week vis-à-vis craniotomy-alone tissues. We did not observe appreciable changes in circulating glycosaminoglycans in mice after experimental TBI compared to craniotomy-alone nor in patients with TBI and severe polytrauma compared to control patients with mild injuries, suggesting increases in injury site glycosaminoglycans are driven by local synthesis. We subsequently performed an unbiased whole genome transcriptomics analysis on mouse brain tissues 7 days post-TBI and discovered a significant induction of hyaluronan synthase 2, glypican-3, and decorin. The functional role of decorin after injury was further examined through multimodal behavioral testing comparing wild-type and Dcn-/- mice. We discovered that genetic ablation of Dcn led to an overall negative effect of TBI on function, exacerbating motor impairments after TBI. Collectively, our results provide a spatiotemporal characterization of post-TBI glycosaminoglycan alterations in the brain ECM and support an important adaptive role for decorin upregulation after TBI.


Assuntos
Lesões Encefálicas Traumáticas , Glicosaminoglicanos , Animais , Humanos , Camundongos , Lesões Encefálicas Traumáticas/genética , Sulfatos de Condroitina , Decorina/genética , Proteínas da Matriz Extracelular , Glicosaminoglicanos/química
14.
Stroke ; 44(3): 759-63, 2013 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-23349190

RESUMO

BACKGROUND AND PURPOSE: Pediatric stroke, birth to 18 years, is a significant cause of long-term disability in the United States; however, there is currently little experimental data on the pathophysiology of childhood stroke owing to lack of animal models. We developed a novel mouse model of experimental childhood-onset arterial ischemic stroke to characterize the sex-specific response of the adolescent brain to cerebral ischemia and assess the neuroprotective effect of estrogen at this developmental stage. METHODS: Postnatal day 20 to 25 mice were subjected to 90 minutes experimental stroke via the intraluminal filament middle cerebral artery occlusion model and ischemic damage assessed 22 hours after reperfusion. Real-time quantitative real-time polymerase chain reaction was performed 22 hours after middle cerebral artery occlusion to determine the effects of ischemia and estrogen treatment on the proapoptotic gene Bax. RESULTS: Ischemic injury did not differ between male and female juvenile (postnatal day 20-25) mice after middle cerebral artery occlusion. However, estrogen reduced ischemic injury in female mice, whereas having no effect in juvenile males. No differences in estrogen receptor expression were observed on postnatal day between 20 males and females. In contrast, estrogen minimized the ischemia-induced increase in the proapoptotic gene Bax in female mice, whereas having no effect on Bax induction in the male brain. CONCLUSIONS: Focal ischemia has fundamentally different effects in the juvenile brain compared with the adult, as evidenced by the lack of sex difference in ischemic injury in the murine postnatal day 20 to 25 middle cerebral artery occlusion model and the sexually dimorphic response to estrogen neuroprotection.


Assuntos
Envelhecimento/fisiologia , Estrogênios/fisiologia , Modelos Animais , Caracteres Sexuais , Transdução de Sinais/fisiologia , Acidente Vascular Cerebral/fisiopatologia , Animais , Encéfalo/efeitos dos fármacos , Encéfalo/metabolismo , Encéfalo/fisiopatologia , Estrogênios/farmacologia , Feminino , Regulação da Expressão Gênica no Desenvolvimento/efeitos dos fármacos , Infarto da Artéria Cerebral Média/complicações , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Fármacos Neuroprotetores/farmacologia , Transdução de Sinais/efeitos dos fármacos , Acidente Vascular Cerebral/etiologia , Acidente Vascular Cerebral/prevenção & controle , Proteína X Associada a bcl-2/metabolismo
15.
Eur J Neurosci ; 37(4): 555-63, 2013 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-23176253

RESUMO

Cerebellar Purkinje cells (PCs) are particularly sensitive to cerebral ischemia, and decreased GABA(A) receptor function following injury is thought to contribute to PC sensitivity to ischemia-induced excitotoxicity. Here we examined the functional properties of the GABA(A) receptors that are spared following ischemia in cultured Purkinje cells from rat and in vivo ischemia in mouse. Using subunit-specific positive modulators of GABA(A) receptors, we observed that oxygen and glucose deprivation (OGD) and cardiac arrest-induced cerebral ischemia cause a decrease in sensitivity to the ß(2/3) -subunit-preferring compound, etomidate. However, sensitivity to propofol, a ß-subunit-acting compound that modulates ß(1-3) -subunits, was not affected by OGD. The α/γ-subunit-acting compounds, diazepam and zolpidem, were also unaffected by OGD. We performed single-cell reverse transcription-polymerase chain reaction on isolated PCs from acutely dissociated cerebellar tissue and observed that PCs expressed the ß(1) -subunit, contrary to previous reports examining GABA(A) receptor subunit expression in PCs. GABA(A) receptor ß(1) -subunit protein was also detected in cultured PCs by western blot and by immunohistochemistry in the adult mouse cerebellum and levels remained unaffected by ischemia. High concentrations of loreclezole (30 µm) inhibited PC GABA-mediated currents, as previously demonstrated with ß(1) -subunit-containing GABA(A) receptors expressed in heterologous systems. From our data we conclude that PCs express the ß(1) -subunit and that there is a greater contribution of ß(1) -subunit-containing GABA(A) receptors following OGD.


Assuntos
Isquemia Encefálica/metabolismo , Oxigênio/metabolismo , Células de Purkinje/metabolismo , Receptores de GABA-A/metabolismo , Animais , Western Blotting , Modelos Animais de Doenças , Glucose/deficiência , Imuno-Histoquímica , Masculino , Camundongos , Técnicas de Patch-Clamp , Reação em Cadeia da Polimerase , Ratos , Ratos Sprague-Dawley
16.
bioRxiv ; 2023 May 26.
Artigo em Inglês | MEDLINE | ID: mdl-37292810

RESUMO

Thalamocortical (TC) neurons within the ventrolateral thalamus (VL) receive projections from the cerebellum and the basal ganglia (BG) to facilitate motor and non-motor functions. Tonic and rebound firing patterns in response to excitatory cerebellar and inhibitory BG inputs, respectively, are a canonical feature of TC neurons and plays a key role in signal processing. The intrinsic excitability of TC neurons has a strong influence on how they respond to synaptic inputs, however, it is unknown whether their afferents influence their firing properties. Understanding the input-specific firing patterns could shed light into movement disorders with cerebellar or BG involvement. Here, we used whole-cell electrophysiology in brain slices from C57BL/6 mice to investigate the firing of TC neurons with optogenetic confirmation of cerebellar or BG afferents. TC neurons with cerebellar afferents exhibited higher tonic and rebound firing rates than those with BG afferents. This increased firing was associated with faster action potential depolarization kinetics and a smaller afterhyperpolarization potential. We also found differences in the passive membrane properties and sag currents during hyperpolarization. Despite higher rebound firing in TC neurons with cerebellar afferents, there were no differences in T-type calcium channel function compared to those with BG inputs. These data suggest input-specific differences in sodium and SK, but not T-type calcium channels, impact firing properties in TC populations. Altogether, we showed that the pronounced divergence observed in TC neuron firing properties correlate with its heterogeneous anatomical connectivity, which could signify a distinct signal integration and processing by these neurons. Keypoints: Thalamocortical neurons in the VL with cerebellar afferents have higher intrinsic tonic and rebound firing properties than those with basal ganglia afferents.Membrane resistance and action potential depolarization slope were different based on the presence of cerebellar afferents.Despite elevated rebound burst firing, T-type mediated currents did not correlate with increased firing in neurons with cerebellar afferents.

17.
iScience ; 26(10): 108061, 2023 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-37860758

RESUMO

Synaptic inhibition is critical for controlling neuronal excitability and function. During global cerebral ischemia (GCI), inhibitory synapses are rapidly eliminated, causing hyper-excitability which contributes to cell-death and the pathophysiology of disease. Sequential disassembly of inhibitory synapses begins within minutes of ischemia onset: GABAARs are rapidly trafficked away from the synapse, the gephyrin scaffold is removed, followed by loss of the presynaptic terminal. GABAARs are endocytosed during GCI, but how this process accompanies synapse disassembly remains unclear. Here, we define the precise trafficking itinerary of GABAARs during the initial stages of GCI, placing them in the context of rapid synapse elimination. Ischemia-induced GABAAR internalization quickly follows their initial dispersal from the synapse, and is controlled by PP1α signaling. During reperfusion injury, GABAARs are then trafficked to lysosomes for degradation, leading to permanent removal of synaptic GABAARs and contributing to the profound reduction in synaptic inhibition observed hours following ischemia onset.

18.
Exp Biol Med (Maywood) ; 248(7): 641-655, 2023 04.
Artigo em Inglês | MEDLINE | ID: mdl-37309741

RESUMO

General anesthetics are potent neurotoxins when given during early development, causing apoptotic deletion of substantial number of neurons and persistent neurocognitive and behavioral deficits in animals and humans. The period of intense synaptogenesis coincides with the peak of susceptibility to deleterious effects of anesthetics, a phenomenon particularly pronounced in vulnerable brain regions such as subiculum. With steadily accumulating evidence confirming that clinical doses and durations of anesthetics may permanently alter the physiological trajectory of brain development, we set out to investigate the long-term consequences on dendritic morphology of subicular pyramidal neurons and expression on genes regulating the complex neural processes such as neuronal connectivity, learning, and memory. Using a well-established model of anesthetic neurotoxicity in rats and mice neonatally exposed to sevoflurane, a volatile general anesthetic commonly used in pediatric anesthesia, we report that a single 6 h of continuous anesthesia administered at postnatal day (PND) 7 resulted in lasting dysregulation in subicular mRNA levels of cAMP responsive element modulator (Crem), cAMP responsive element-binding protein 1 (Creb1), and Protein phosphatase 3 catalytic subunit alpha, a subunit of calcineurin (Ppp3ca) (calcineurin) when examined during juvenile period at PND28. Given the critical role of these genes in synaptic development and neuronal plasticity, we deployed a set of histological measurements to investigate the implications of anesthesia-induced dysregulation of gene expression on morphology and complexity of surviving subicular pyramidal neurons. Our results indicate that neonatal exposure to sevoflurane induced lasting rearrangement of subicular dendrites, resulting in higher orders of complexity and increased branching with no significant effects on the soma of pyramidal neurons. Correspondingly, changes in dendritic complexity were paralleled by the increased spine density on apical dendrites, further highlighting the scope of anesthesia-induced dysregulation of synaptic development. We conclude that neonatal sevoflurane induced persistent genetic and morphological dysregulation in juvenile rodents, which could indicate heightened susceptibility toward cognitive and behavioral disorders we are beginning to recognize as sequelae of early-in-life anesthesia.


Assuntos
Anestésicos Inalatórios , Éteres Metílicos , Humanos , Criança , Animais , Ratos , Camundongos , Sevoflurano/toxicidade , Sevoflurano/metabolismo , Calcineurina/metabolismo , Calcineurina/farmacologia , Animais Recém-Nascidos , Anestésicos Inalatórios/toxicidade , Éteres Metílicos/toxicidade , Hipocampo/metabolismo
19.
J Cereb Blood Flow Metab ; 43(2_suppl): 66-77, 2023 11.
Artigo em Inglês | MEDLINE | ID: mdl-37150606

RESUMO

Post-stroke cognitive impairment and dementia (PSCID) affects many survivors of large vessel cerebral ischemia. The molecular pathways underlying PSCID are poorly defined but may overlap with neurodegenerative pathophysiology. Specifically, synaptic dysfunction after stroke may be directly mediated by alterations in the levels of amyloid beta (Aß), the peptide that accumulates in the brains of Alzheimer's disease (AD) patients. In this study, we use the transient middle cerebral artery occlusion (MCAo) model in young adult mice to evaluate if a large vessel stroke increases brain soluble Aß levels. We show that soluble Aß40 and Aß42 levels are increased in the ipsilateral hippocampus in MCAo mice 7 days after the injury. We also analyze the level and activity of ß-site amyloid precursor protein cleaving enzyme 1 (BACE1), an enzyme that generates Aß in the brain, and observe that BACE1 activity is increased in the ipsilateral hippocampus of the MCAo mice. Finally, we highlight that treatment of MCAo mice with a BACE1 inhibitor during the recovery period rescues stroke-induced deficits in hippocampal synaptic plasticity. These findings support a molecular pathway linking ischemia to alterations in BACE1-mediated production of Aß, and encourage future studies that evaluate whether targeting BACE1 activity improves the cognitive deficits seen with PSCID.


Assuntos
AVC Isquêmico , Acidente Vascular Cerebral , Humanos , Camundongos , Animais , Peptídeos beta-Amiloides/metabolismo , Secretases da Proteína Precursora do Amiloide/metabolismo , Precursor de Proteína beta-Amiloide/metabolismo , Ácido Aspártico Endopeptidases , AVC Isquêmico/metabolismo , Hipocampo/metabolismo , Modelos Teóricos
20.
Shock ; 60(4): 585-593, 2023 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-37548929

RESUMO

ABSTRACT: The Earth's population is aging, and by 2050, one of six people will be 65 years or older. Therefore, proper treatment of injuries that disproportionately impact people of advanced age will be more important. Clinical studies reveal people 65 years or older account for 16.5% of all burn injuries and experience higher morbidity, including neurocognitive decline, and mortality that we and others believe are mediated, in part, by heightened intestinal permeability. Herein, we used our clinically relevant model of scald burn injury in young and aged mice to determine whether age and burn injury cooperate to induce heightened colonic damage, alterations to the fecal microbiome, and whether resultant changes in the microbiome correlate with neuroinflammation. We found that aged, burn-injured mice have an increase in colonic lymphoid aggregates, inflammation, and proinflammatory chemokine expression when compared with young groups and sham-injured aged mice. We then performed fecal microbiota sequencing and found a striking reduction in gut protective bacterial taxa, including Akkermansia , in the aged burn group compared with all other groups. This reduction correlated with an increase in serum fluorescein isothiocyanate-Dextran administered by gavage, indicating heightened intestinal permeability. Furthermore, loss of Akkermansia was highly correlated with increased messenger RNA expression of neuroinflammatory markers in the brain, including chemokine ligand 2, TNF-α, CXC motif ligand 1, and S100 calcium-binding protein A8. Finally, we discovered that postburn alterations in the microbiome correlated with measures of strength in all treatment groups, and those that performed better on the rotarod and hanging wire tests had higher abundance of Akkermansia than those that performed worse. Taken together, these findings indicate that loss of protective bacteria after burn injury in aged mice contributes to alterations in the colon, gut leakiness, neuroinflammation, and strength. Therefore, supplementation of protective bacteria, such as Akkermansia , after burn injury in aged patients may have therapeutic benefit.


Assuntos
Queimaduras , Microbiota , Humanos , Idoso , Doenças Neuroinflamatórias , Disbiose/microbiologia , Ligantes , Queimaduras/microbiologia , Bactérias/genética , Quimiocinas , Colo
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