RESUMO
Traumatic brain injury (TBI) has reached epidemic proportions around the world and is a major public health concern in the United States. Approximately 2.8 million individuals sustain a traumatic brain injury and are treated in an Emergency Department yearly in the U.S., and about 50,000 of them die. Persistent symptoms develop in 10-15% of the cases including neuropsychiatric disorders. Anxiety is the second most common neuropsychiatric disorder that develops in those with persistent neuropsychiatric symptoms after TBI. Abnormalities or atrophy in the temporal lobe has been shown in the overwhelming number of TBI cases. The basolateral amygdala (BLA), a temporal lobe structure that consolidates, stores and generates fear and anxiety-based behavioral outputs, is a critical brain region in the anxiety circuitry. In this review, we sought to capture studies that characterized the relationship between human post-traumatic anxiety and structural/functional alterations in the amygdala. We compared the human findings with results obtained with a reproducible mild TBI animal model that demonstrated a direct relationship between the alterations in the BLA and an anxiety-like phenotype. From this analysis, both preliminary insights, and gaps in knowledge, have emerged which may open new directions for the development of rational and more efficacious treatments.
Assuntos
Complexo Nuclear Basolateral da Amígdala , Lesões Encefálicas Traumáticas , Animais , Ansiedade , Encéfalo , HumanosRESUMO
Nerve agents are organophosphate (OP) compounds and among the most powerful poisons known to man. A terrorist attack on civilian or military populations causing mass casualties is a real threat. The OP nerve agents include soman, sarin, cyclosarin, tabun, and VX. The major mechanism of acute toxicity is the irreversible inhibition of acetylcholinesterase. Acetylcholinesterase inhibition results in the accumulation of excessive acetylcholine levels in synapses, leading to progression of toxic signs including hypersecretions, tremors, status epilepticus, respiratory distress, and death. Miosis and rhinorrhea are the most common clinical findings in those individuals acutely exposed to OP nerve agents. Prolonged seizures are responsible for the neuropathology. The brain region that shows the most severe damage is the amygdala, followed by the piriform cortex, hippocampus, cortex, thalamus, and caudate/putamen. Current medical countermeasures are only modestly effective in attenuating the seizures and neuropathology. Anticonvulsants such as benzodiazepines decrease seizure activity and improve outcome, but their efficacy depends upon the administration time after exposure to the nerve agent. Administration of benzodiazepines may increase the risk for seizure recurrence. Recent studies document long-term neurologic and behavior deficits, and technological advances demonstrate structural brain changes on magnetic resonance imaging.
Assuntos
Encéfalo/efeitos dos fármacos , Agentes Neurotóxicos/toxicidade , Acetilcolina/metabolismo , Acetilcolinesterase/metabolismo , Encéfalo/metabolismo , Humanos , Miose/tratamento farmacológico , Miose/etiologia , Transtornos Respiratórios/induzido quimicamente , Transtornos Respiratórios/tratamento farmacológico , Estado Epiléptico/induzido quimicamente , Estado Epiléptico/tratamento farmacológico , Fatores de TempoRESUMO
α-Linolenic acid (ALA) is a nutraceutical found in vegetable products such as flax and walnuts. The pleiotropic properties of ALA target endogenous neuroprotective and neurorestorative pathways in brain and involve the transcription factor nuclear factor kappa B (NF-κB), brain-derived neurotrophic factor (BDNF), a major neuroprotective protein in brain, and downstream signaling pathways likely mediated via activation of TrkB, the cognate receptor of BDNF. In this review, we discuss possible mechanisms of ALA efficacy against the highly toxic OP nerve agent soman. Organophosphate (OP) nerve agents are highly toxic chemical warfare agents and a threat to military and civilian populations. Once considered only for battlefield use, these agents are now used by terrorists to inflict mass casualties. OP nerve agents inhibit the critical enzyme acetylcholinesterase (AChE) that rapidly leads to a cholinergic crisis involving multiple organs. Status epilepticus results from the excessive accumulation of synaptic acetylcholine which in turn leads to the overactivation of muscarinic receptors; prolonged seizures cause the neuropathology and long-term consequences in survivors. Current countermeasures mitigate symptoms and signs as well as reduce brain damage, but must be given within minutes after exposure to OP nerve agents supporting interest in newer and more effective therapies. The pleiotropic properties of ALA result in a coordinated molecular and cellular program to restore neuronal networks and improve cognitive function in soman-exposed animals. Collectively, ALA should be brought to the clinic to treat the long-term consequences of nerve agents in survivors. ALA may be an effective therapy for other acute and chronic neurodegenerative disorders.
Assuntos
Suplementos Nutricionais , Agentes Neurotóxicos/efeitos adversos , Neuroproteção/efeitos dos fármacos , Fármacos Neuroprotetores/farmacologia , Organofosfatos/efeitos adversos , Transdução de Sinais/efeitos dos fármacos , Ácido alfa-Linolênico/farmacologia , Animais , Antidepressivos/farmacologia , Antidepressivos/uso terapêutico , Encéfalo/efeitos dos fármacos , Encéfalo/metabolismo , Cognição/efeitos dos fármacos , Transtornos Cognitivos/tratamento farmacológico , Transtornos Cognitivos/etiologia , Transtornos Cognitivos/metabolismo , Humanos , Modelos Animais , Doenças do Sistema Nervoso/induzido quimicamente , Doenças do Sistema Nervoso/tratamento farmacológico , Doenças do Sistema Nervoso/metabolismo , Doenças Neurodegenerativas/tratamento farmacológico , Doenças Neurodegenerativas/etiologia , Doenças Neurodegenerativas/metabolismo , Neuropatologia , Fármacos Neuroprotetores/uso terapêutico , Receptores de N-Metil-D-Aspartato/metabolismo , Ácido alfa-Linolênico/uso terapêuticoRESUMO
Traumatic brain injury (TBI) is a highly prevalent medical condition for which no medications specific for the prophylaxis or treatment of the condition as a whole exist. The spectrum of symptoms includes coma, headache, seizures, cognitive impairment, depression, and anxiety. Although it has been known for years that the inhibitory neurotransmitter γ-amino-butyric acid (GABA) is involved in TBI, no novel therapeutics based upon this mechanism have been introduced into clinical practice. We review the neuroanatomical, neurophysiological, neurochemical, and neuropharmacological relationships of GABA neurotransmission to TBI with a view toward new potential GABA-based medicines. The long-standing idea that excitatory and inhibitory (GABA and others) balances are disrupted by TBI is supported by the experimental data but has failed to invent novel methods of restoring this balance. The slow progress in advancing new treatments is due to the complexity of the disorder that encompasses multiple dynamically interacting biological processes including hemodynamic and metabolic systems, neurodegeneration and neurogenesis, major disruptions in neural networks and axons, frank brain lesions, and a multitude of symptoms that have differential neuronal and neurohormonal regulatory mechanisms. Although the current and ongoing clinical studies include GABAergic drugs, no novel GABA compounds are being explored. It is suggested that filling the gap in understanding the roles played by specific GABAA receptor configurations within specific neuronal circuits could help define new therapeutic approaches. Further research into the temporal and spatial delivery of GABA modulators should also be useful. Along with GABA modulation, research into the sequencing of GABA and non-GABA treatments will be needed.
Assuntos
Lesões Encefálicas Traumáticas , Humanos , Lesões Encefálicas Traumáticas/tratamento farmacológico , Lesões Encefálicas Traumáticas/metabolismo , Ácido gama-Aminobutírico/metabolismo , Convulsões/metabolismo , Transmissão Sináptica/fisiologia , Neurônios/metabolismoRESUMO
Nearly all of the American horses exported to Mexico and Canada are slaughtered for human consumption, and their meat is either exported around the world or consumed locally. Previous work showed that 18 Thoroughbred racehorses purchased by rescues that would have otherwise been sold for export for the sole purpose of slaughter to produce meat for human consumption were administered phenylbutazone. We report the number of American horses exported to Canada and Mexico from 2016 to 2021, the presence of contaminated horsemeat from Canadian slaughterhouses, and the human use and idiosyncratic effects of veterinary phenylbutazone and side effects of clenbuterol, 2 of the drugs that were found in contaminated Canadian horsemeat. The number of live American horses exported to Canada declined precipitously from 2016 to 2017, and a second decline occurred in 2020. All food-producing animals are under strict regulatory control to prevent animals administered banned drugs to enter the food chain. A major principle of this program is zero tolerance for banned drugs and testing for compliance. No regulatory process is in place to remove horses administered banned drugs such as phenylbutazone. The efficacy lasts for more than 24 hours as a result of the irreversible binding to cyclooxygenase, slow elimination, and long elimination half-life of its metabolite oxyphenbutazone. High or frequent doses of phenylbutazone result in disproportionately increased plasma concentrations, which result in the residual presence in tissues. It is this fact that underlies the ban of this drug in food-producing animals. No human clinical surveillance program is in place to monitor individuals on the possible short- and long-term consequences of banned drugs in contaminated horsemeat. If the United States is unable to put in place a regulatory program to remove horses administered banned drugs as exists for all food-producing animals, the exportation of American horses across both borders for the sole purpose of slaughter for human consumption must end.
Assuntos
Fenilbutazona , Saúde Pública , Cavalos , Humanos , Animais , Estados Unidos , Canadá , OxifenilbutazonaRESUMO
Hyperexcitability is a major mechanism implicated in several neuropsychiatric disorders, such as organophosphate-induced status epilepticus (SE), primary epilepsy, stroke, spinal cord injury, traumatic brain injury, schizophrenia, and autism spectrum disorders. Underlying mechanisms are diverse, but a functional impairment and loss of GABAergic inhibitory neurons are common features in many of these disorders. While novel therapies abound to correct for the loss of GABAergic inhibitory neurons, it has been difficult at best to improve the activities of daily living for the majority of patients. Alpha-linolenic acid (ALA) is an essential omega-3 polyunsaturated fatty acid found in plants. ALA exerts pleiotropic effects in the brain that attenuate injury in chronic and acute brain disease models. However, the effect of ALA on GABAergic neurotransmission in hyperexcitable brain regions involved in neuropsychiatric disorders, such as the basolateral amygdala (BLA) and CA1 subfield of the hippocampus, is unknown. Administration of a single dose of ALA (1500 nmol/kg) subcutaneously increased the charge transfer of inhibitory postsynaptic potential currents mediated by GABAA receptors in pyramidal neurons by 52% in the BLA and by 92% in the CA1 compared to vehicle animals a day later. Similar results were obtained in pyramidal neurons from the BLA and CA1 when ALA was bath-applied in slices from naïve animals. Importantly, pretreatment with the high-affinity, selective TrkB inhibitor, k252, completely abolished the ALA-induced increase in GABAergic neurotransmission in the BLA and CA1, suggesting a brain-derived neurotrophic factor (BDNF)-mediated mechanism. Addition of mature BDNF (20 ng/mL) significantly increased GABAA receptor inhibitory activity in the BLA and CA1 pyramidal neurons similar to the results obtained with ALA. ALA may be an effective treatment for neuropsychiatric disorders where hyperexcitability is a major feature.
Assuntos
Complexo Nuclear Basolateral da Amígdala , Ratos , Humanos , Animais , Complexo Nuclear Basolateral da Amígdala/metabolismo , Ácido alfa-Linolênico/farmacologia , Fator Neurotrófico Derivado do Encéfalo , Ratos Sprague-Dawley , Atividades Cotidianas , Transmissão Sináptica/fisiologia , Receptores de GABA-A/metabolismoRESUMO
Transcriptional regulation of the gene encoding brain-derived neurotrophic factor (BDNF) has been widely studied. However, an understanding of mechanisms modifying chromatin, events that are essential for controlling transcription, is rudimentary. We focused on two activation-dependent regions of the Bdnf gene physically linked to known transcription sites for exons 1 and 4. Using chromatin immunoprecipitation assays, we determined that N-methyl-D-aspartate (NMDA) receptor activation derepressed promoters 1 and 4-mediated transcription. This derepression correlated with reduced occupancy by histone deacetylase 1 and methyl cytosine-binding protein 2 of each promoter region near known transcription start sites in cultured hippocampal neurons. These changes did not occur at all sites upstream of transcription initiation. Taken together, these findings suggest that histone and other DNA-binding proteins are involved in remodeling of chromatin at some, but not all sites, within Bdnf promoters 1 and 4 and are associated with NMDA receptor-dependent increases in transcription.
Assuntos
Fator Neurotrófico Derivado do Encéfalo/genética , Epigênese Genética , Hipocampo/efeitos dos fármacos , Hipocampo/metabolismo , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Regiões Promotoras Genéticas/efeitos dos fármacos , Receptores de N-Metil-D-Aspartato/fisiologia , Animais , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Células Cultivadas , Proteínas de Ligação a DNA/metabolismo , Relação Dose-Resposta a Droga , Embrião de Mamíferos , Éxons , Regulação da Expressão Gênica/efeitos dos fármacos , Hipocampo/citologia , Histona Desacetilase 1/antagonistas & inibidores , Histona Desacetilase 1/metabolismo , Inibidores de Histona Desacetilases/farmacologia , Ácidos Hidroxâmicos/farmacologia , Proteína 2 de Ligação a Metil-CpG/metabolismo , N-Metilaspartato/farmacologia , RNA Mensageiro/metabolismo , Ratos , Ratos Sprague-Dawley , Fatores de Tempo , Sítio de Iniciação de Transcrição , Transcrição Gênica/efeitos dos fármacosRESUMO
Traumatic brain injury (TBI) is a major public health concern in the USA. There are approximately 2.5 million brain injuries annually, 90% of which may be classified as mild since these individuals do not display clear morphological abnormalities following injury on imaging. The majority of individuals develop neurocognitive deficits such as learning and memory impairment and recovery occurs over 3 to 6 months after mild TBI (mTBI). The hippocampus is highly susceptible to injury from mTBI due to the anatomic localization and has been implicated in the neurocognitive impairments after mTBI. Here, we investigated whether the mTBI-induced morphological and pathophysiological alterations of GABAergic interneurons in the CA1 subfield of the hippocampus recovers after 30 days in the controlled cortical impact (CCI) model of TBI. Design-based stereology shows a significant reduction in the number of GABAergic interneurons 7 days after CCI. However, the number of GABAergic interneurons is not significantly reduced at 30 days after CCI. The total number of neurons is not altered over the course of 30 days. GABAergic inhibitory currents in the CA1 subfield also show that, although there is a significant reduction in the CCI group at 7 days, the currents are not significantly different from sham controls at 30 days. We suggest that the recovery of GABAergic function in the CA1 subfield of the hippocampus observed 30 days after CCI is one of the mechanisms associated with the recovery of memory after mTBI.
Assuntos
Lesões Encefálicas Traumáticas/fisiopatologia , Região CA1 Hipocampal/fisiopatologia , Hipocampo/fisiopatologia , Potenciais Pós-Sinápticos Inibidores/fisiologia , Animais , Lesões Encefálicas/complicações , Lesões Encefálicas/fisiopatologia , Lesões Encefálicas Traumáticas/complicações , Modelos Animais de Doenças , Neurônios GABAérgicos , Interneurônios/metabolismo , Masculino , Memória/fisiologia , Transtornos da Memória/complicações , Ratos Sprague-DawleyRESUMO
Brain-derived neurotrophic factor (BDNF), via activation of TrkB receptors, mediates vital physiological functions in the brain, ranging from neuronal survival to synaptic plasticity, and has been implicated in the pathophysiology of neurodegenerative disorders. Although transcriptional regulation of the BDNF gene (Bdnf) has been extensively studied, much remains to be understood. We discovered a sequence within Bdnf promoter 4 that binds the basic helix-loop-helix protein BHLHB2 and is a target for BHLHB2-mediated transcriptional repression. NMDA receptor activation de-repressed promoter 4-mediated transcription and correlated with reduced occupancy of the promoter by BHLHB2 in cultured hippocampal neurons. Bhlhb2 gene -/- mice showed increased hippocampal exon 4-specific Bdnf mRNA levels compared with +/+ littermates under basal and activity-dependent conditions. Bhlhb2 knock-out mice also showed increased status epilepticus susceptibility, suggesting that BHLHB2 alters neuronal excitability. Together, these results support a role for BHLHB2 as a new modulator of Bdnf transcription and neuronal excitability.
Assuntos
Fatores de Transcrição Hélice-Alça-Hélice Básicos/fisiologia , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Proteínas de Homeodomínio/fisiologia , Neurônios/fisiologia , Regiões Promotoras Genéticas/fisiologia , Animais , Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Fator Neurotrófico Derivado do Encéfalo/genética , Células Cultivadas , Feminino , Proteínas de Homeodomínio/genética , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , Células NIH 3T3 , Neurônios/metabolismo , Regiões Promotoras Genéticas/genética , RatosRESUMO
To determine the epigenetic events associated with NMDA receptor-mediated activation of brain-derived neurotrophic factor gene (Bdnf) promoter 1 by hippocampal neurons in culture, we screened 12 loci across 4.5 kb of genomic DNA 5' of the transcription start site (TSS) of rat Bdnf for specific changes in histone modification and transcription factor binding following NMDA receptor stimulation. Chromatin immunoprecipitation (ChIP) assays showed that NMDA receptor stimulation produced a durable, time-dependent decrease in histone H3 at lysine 9 dimethylation (H3K9me2), within 3 h after NMDA treatment across multiple loci. Concomitant increases in H3K4me2 and H3K9/14 acetylation (H3AcK9/14) were associated with transcriptional activation, but occurred at fewer sites within the promoter. The decrease in H3K9me2 was associated with release of HDAC1, MBD1, MeCP2, and REST from specific locations within promoter 1, although with different kinetics. In addition, occupancy of sites proximal to and distal to the TSS by the transcription factors NF-kappaB, CREB-binding protein (CBP), and cAMP-response element-binding protein were correlated with increased occupancy of RNA polymerase II at two loci proximal to the TSS following NMDA receptor stimulation. These temporal changes in promoter occupancy could occur thousands of base pairs 5' of the TSS, suggesting a mechanism that produces waves of Bdnf transcription.
Assuntos
Fator Neurotrófico Derivado do Encéfalo/genética , Montagem e Desmontagem da Cromatina/fisiologia , Hipocampo/citologia , Neurônios/metabolismo , Regiões Promotoras Genéticas/fisiologia , Receptores de N-Metil-D-Aspartato/metabolismo , Acetilação/efeitos dos fármacos , Análise de Variância , Animais , Azacitidina/análogos & derivados , Azacitidina/farmacologia , Montagem e Desmontagem da Cromatina/efeitos dos fármacos , Imunoprecipitação da Cromatina/métodos , Proteínas de Ligação a DNA/metabolismo , Embrião de Mamíferos , Inibidores Enzimáticos/farmacologia , Éxons/fisiologia , Histona Desacetilase 1 , Histona Desacetilases/metabolismo , Histonas/metabolismo , Ácidos Hidroxâmicos/farmacologia , Técnicas In Vitro , Lisina/metabolismo , Proteína 2 de Ligação a Metil-CpG/metabolismo , Metilação/efeitos dos fármacos , N-Metilaspartato/farmacologia , Neurônios/efeitos dos fármacos , Regiões Promotoras Genéticas/efeitos dos fármacos , RNA Mensageiro/metabolismo , Ratos , Ratos Sprague-Dawley , Receptores de N-Metil-D-Aspartato/efeitos dos fármacos , Proteínas Repressoras/metabolismo , Fatores de Tempo , Fatores de Transcrição/metabolismoRESUMO
The brain developed adaptive mechanisms in the face of changing environments and stresses imposed on the nervous system. The addition of glutamate as the major excitatory amino acid neurotransmitter to the brain's complement of amino acids and peptides dictated a coordinated transcriptional and translational program to meet the demands of excitatory neurotransmission. One such program is the ability of neurons to sustain and maintain their survival given the nature of glutamate-mediated receptor activation. The unique development of endogenous neuronal pathways activated by glutamate receptors transformed neurons and allowed them to survive under conditions of high energy demands. These same endogenous survival pathways also mediate plastic responses to meet another demand of the brain, adaptation. An endogenous protein that plays a central role in glutamate receptor-mediated survival pathways is brain-derived neurotrophic factor (BDNF). Intermittent but frequent synaptic ionotropic glutamate receptor activation ensures neuronal survival through a BDNF autocrine loop. In sharp contrast, overactivation of ionotropic glutamate receptors leads to neuronal cell death. Thus, innovative strategies that induce endogenous neuronal survival pathways through low-level activation of ionotropic glutamate receptors or those that bypass receptor activation but upregulate endogenous survival pathways may not only prevent neurodegenerative disorders that involve glutamate as a final common pathway that kills neurons, but may also provide treatment alternatives critical for neurons to survive stressful conditions such as stroke, status epilepticus and hypoglycemic-induced neuronal cell death.
Assuntos
Doenças Neurodegenerativas/tratamento farmacológico , Transdução de Sinais/fisiologia , Animais , Fator Neurotrófico Derivado do Encéfalo/fisiologia , Proteína de Ligação ao Elemento de Resposta ao AMP Cíclico/fisiologia , MAP Quinases Reguladas por Sinal Extracelular/genética , MAP Quinases Reguladas por Sinal Extracelular/fisiologia , Ácido Glutâmico/fisiologia , Humanos , NF-kappa B/fisiologia , Fosfatidilinositol 3-Quinases/fisiologia , Receptores de N-Metil-D-Aspartato/efeitos dos fármacos , Receptores de N-Metil-D-Aspartato/fisiologia , Transdução de Sinais/efeitos dos fármacosRESUMO
Approximately, 1.7 million Americans suffer a TBI annually and TBI is a major cause of death and disability. The majority of the TBI cases are of the mild type and while most patients recover completely from mild TBI (mTBI) about 10% result in persistent symptoms and some result in lifelong disability. Anxiety disorders are the second most common diagnosis post-TBI. Of note, TBI-induced anxiety disorders are difficult to treat and remain a chronic condition suggesting that new therapies are needed. Previous work from our laboratory demonstrated that a mild TBI induced an anxiety-like phenotype, a key feature of the human condition, associated with loss of GABAergic interneurons and hyperexcitability in the basolateral amygdala (BLA) in rodents 7 and 30 days after a controlled cortical impact (CCI) injury. We now confirm that animals display significantly increased anxiety-like behavior 30 days after CCI. The anxiety-like behavior was associated with a significant loss of GABAergic interneurons and significant reductions in the frequency and amplitude of spontaneous and miniature GABAA-receptor-mediated inhibitory postsynaptic currents (IPSCs) in the BLA. Significantly, subchronic treatment with alpha-linolenic acid (ALA) after CCI prevents the development of anxiety-like behavior, the loss of GABAergic interneurons, hyperexcitability in the BLA and reduces the impact injury. Taken together, administration of ALA after CCI is a potent therapy against the neuropathology and pathophysiological effects of mTBI in the BLA.
Assuntos
Ansiedade/prevenção & controle , Lesões Encefálicas Traumáticas/tratamento farmacológico , Contusões/tratamento farmacológico , Ácido alfa-Linolênico/uso terapêutico , Animais , Ansiedade/etiologia , Ansiedade/fisiopatologia , Lesões Encefálicas Traumáticas/complicações , Lesões Encefálicas Traumáticas/fisiopatologia , Contusões/etiologia , Contusões/fisiopatologia , Potenciais Pós-Sinápticos Inibidores/efeitos dos fármacos , Potenciais Pós-Sinápticos Inibidores/fisiologia , Masculino , Ratos , Ratos Sprague-Dawley , Resultado do Tratamento , Ácido alfa-Linolênico/farmacologiaRESUMO
Domoic acid (DOM) is an excitatory amino acid analog of kainic acid (KA) that acts through glutamic acid (GLU) receptors, inducing a fast and potent neurotoxic response. Here, we present evidence for an enhancement of excitotoxicity following exposure of cultured cerebellar granule cells to DOM in the presence of lower than physiological Na+ concentrations. The concentration of DOM that reduced by 50% neuronal survival was approximately 3 µM in Na+-free conditions and 16 µM in presence of a physiological concentration of extracellular Na+. The enhanced neurotoxic effect of DOM was fully prevented by AMPA/KA receptor antagonist, while N-methyl-D-aspartate-receptor-mediated neurotoxicity did not seem to be involved, as the absence of extracellular Na+ failed to potentiate GLU excitotoxicity under the same experimental conditions. Lowering of extracellular Na+ concentration to 60 mM eliminated extracellular recording of spontaneous electrophysiological activity from cultured neurons grown on a multi electrode array and prevented DOM stimulation of the electrical activity. Although changes in the extracellular Na+ concentration did not alter the magnitude of the rapid increase in intracellular Ca2+ levels associated to DOM exposure, they did change significantly the contribution of voltage-sensitive calcium channels (VScaCs) and the recovery time to baseline. The prevention of Ca2+ influx via VSCaCs by nifedipine failed to prevent DOM toxicity at any extracellular Na+ concentration, while the reduction of extracellular Ca2+ concentration ameliorated DOM toxicity only in the absence of extracellular Na+, enhancing it in physiological conditions. Our data suggest a crucial role for extracellular Na+ concentration in determining excitotoxicity by DOM.
Assuntos
Cerebelo/efeitos dos fármacos , Neurônios GABAérgicos/efeitos dos fármacos , Ácido Caínico/análogos & derivados , Neurotoxinas/toxicidade , Sódio/metabolismo , Animais , Células Cultivadas , Cerebelo/citologia , Cerebelo/metabolismo , Espaço Extracelular , Neurônios GABAérgicos/metabolismo , Ácido Caínico/toxicidade , Camundongos , Cultura Primária de Células , Ratos , Receptores de GlutamatoRESUMO
Neurotrophins are critical to the development and maintenance of the mammalian central nervous system. Among them is brain-derived neurotrophic factor (BDNF), whose synthesis and release is targeted by activation of glutamate receptors. Perturbation of this process probably underlies neurodegenerative and psychiatric disorders. A naturally occurring variation in humans, in the form of a common single-nucleotide polymorphism in the pro region of the polypeptide at codon 66 (Val66-->Met), affects processing of the pro-BDNF polypeptide and its activation-dependent release. This variant is associated with differences in the volume of the hippocampal formation and with anxiety and depression-related phenotypes. Convergent findings supporting a role for BDNF in alterations to hippocampal structure and behavior are found in a "humanized" BDNF transgenic mouse. Also, recent human genetic studies have supported a role of BDNF signaling in addictive behaviors by allele-, genotype-, and haplotype-based association of the TrkB gene, which encodes the cognate receptor for BDNF, with alcohol dependence. A better understanding of the influence of BDNF-mediated pathways in cell survival and plasticity will aid in developing new approaches to restoring normal function in disease states.
Assuntos
Sintomas Comportamentais , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Plasticidade Neuronal/fisiologia , Neurônios/fisiologia , Sintomas Comportamentais/genética , Sintomas Comportamentais/patologia , Sintomas Comportamentais/fisiopatologia , Fator Neurotrófico Derivado do Encéfalo/genética , Sobrevivência Celular/fisiologia , Humanos , Memória/fisiologia , Mutação , Plasticidade Neuronal/genética , Neurônios/patologiaRESUMO
Paraoxon, the active metabolite of parathion, is an acetylcholinesterases (AChE) inhibitor that kills cultured cerebellar granule cell neurons via an apoptotic mechanism. Protein kinase C is an enzyme with diverse functions but its role in paraoxon-induced cell death is unknown. We show that a neurotoxic concentration of paraoxon increases PKC phosphorylation. We tested whether PKC is involved in paraoxon-induced neuronal cell death by using the PKC activator, phorbol 12-myristate 13-acetate (TPA). TPA increases PKC activity and enhances the neurotoxic effect of paraoxon by 28%. In sharp contrast, addition of the PKC inhibitor Ro-31-8220 protects more than 30% neurons that would otherwise die from paraoxon-induced neuronal cell death in either a pretreatment or post-treatment paradigm and markedly reduces phospho-PKC pan levels. We also show that the pretreatment of Ro-31-8220 blocks paraoxon-induced caspase-3 activity completely. These results suggest that activation of protein kinase C is required for paraoxon neurotoxicity.
Assuntos
Inibidores da Colinesterase/farmacologia , Regulação da Expressão Gênica/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Paraoxon/farmacologia , Proteína Quinase C/metabolismo , Análise de Variância , Animais , Animais Recém-Nascidos , Contagem de Células/métodos , Morte Celular/efeitos dos fármacos , Células Cultivadas , Cerebelo/citologia , Relação Dose-Resposta a Droga , Interações Medicamentosas , Inibidores Enzimáticos/farmacologia , Ratos , Ratos Sprague-Dawley , Fatores de TempoRESUMO
The dietary intake of ω-3 polyunsaturated fatty acids has been linked to a reduction in the incidence of aging-associated disease including cardiovascular disease and stroke. Additionally, long-lived Caenorhabditis elegans glp-1 germ line-less mutant animals show a number of changes in lipid metabolism including the increased production of the ω-3 fatty acid, α-linolenic acid (ALA). Here, we show that the treatment of C. elegans with ALA produces a dose-dependent increase in lifespan. The increased longevity of the glp-1 mutant animals is known to be dependent on both the NHR-49/PPARα and SKN-1/Nrf2 transcription factors, although the mechanisms involved are incompletely understood. We find that ALA treatment increased the lifespan of wild-type worms and that these effects required both of these transcription factors. Specifically, NHR-49 was activated by ALA to promote the expression of genes involved in the ß-oxidation of lipids, whereas SKN-1 is not directly activated by ALA, but instead, the exposure of ALA to air results in the oxidation of ALA to a group of compounds termed oxylipins. At least one of the oxylipins activates SKN-1 and enhances the increased longevity resulting from ALA treatment. The results show that ω-3 fatty acids inhibit aging and that these effects could reflect the combined effects of the ω-3 fatty acid and the oxylipin metabolites. The benefits of ω-3 fatty acid consumption on human health may similarly involve the production of oxylipins, and differences in oxylipin conversion could account for at least part of the variability found between observational vs. interventional clinical trials.
Assuntos
Proteínas de Caenorhabditis elegans/genética , Caenorhabditis elegans/efeitos dos fármacos , Longevidade/efeitos dos fármacos , Oxilipinas/metabolismo , PPAR alfa/genética , Receptores Citoplasmáticos e Nucleares/genética , Ácido alfa-Linolênico/farmacologia , Animais , Biotransformação , Caenorhabditis elegans/genética , Caenorhabditis elegans/crescimento & desenvolvimento , Caenorhabditis elegans/metabolismo , Proteínas de Caenorhabditis elegans/metabolismo , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Relação Dose-Resposta a Droga , Regulação da Expressão Gênica no Desenvolvimento , Metabolismo dos Lipídeos , Longevidade/genética , Fator 2 Relacionado a NF-E2/genética , Fator 2 Relacionado a NF-E2/metabolismo , Oxirredução , PPAR alfa/metabolismo , Receptores Citoplasmáticos e Nucleares/metabolismo , Transdução de Sinais , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Ácido alfa-Linolênico/metabolismoRESUMO
The brain-derived neurotrophic factor (BDNF) gene is critical for neuronal function and survival, and is likely to be important in psychiatric disorders. In this study, we used single-nucleotide polymorphism (SNP) discovery, functional analyses, and genetic association studies to better understand the potential role of BDNF sequence variation in behavior. Screening 480 unrelated individuals for SNPs and genotyping was performed in US Caucasian, American Indian, and African American populations. Lifetime DSM-III-R psychiatric diagnoses were assigned and the Tridimensional Personality Questionnaire (TPQ) was administered to measure anxious temperament (harm avoidance (HA)) and novelty seeking (NS). A novel SNP (-281 C>A) in promoter 1 was discovered that had decreased DNA binding in vitro and decreased basal reporter gene activity in transfected rat hippocampal neurons. The frequency of the -281 A allele was 0.03 in a Caucasian sample, but was virtually absent in other populations. Association analyses in a community-based sample showed that individuals with the -281 A allele (13 heterozygotes) had lower TPQ HA (F=4.8, p<0.05). In contrast, the Met 66 allele was associated with increased HA (F=4.1, p=0.02) and was most abundant in individuals with both anxiety disorders and major depression (p<0.05). Among the Val66Val homozygotes, individuals who were -281 CA heterozygotes had significantly lower HA than the -281 CC homozygotes (p<0.01). Our results suggest that in this population, the low activity -281 A allele may be protective against anxiety and psychiatric morbidity, whereas Met 66 may be a risk allele.
Assuntos
Ansiedade/genética , Fator Neurotrófico Derivado do Encéfalo/genética , Transtornos do Humor/genética , Polimorfismo de Nucleotídeo Único/fisiologia , Regiões Promotoras Genéticas , Adulto , Substituição de Aminoácidos , Animais , Células Cultivadas , Manual Diagnóstico e Estatístico de Transtornos Mentais , Ensaio de Desvio de Mobilidade Eletroforética/métodos , Embrião de Mamíferos , Feminino , Frequência do Gene , Variação Genética , Genótipo , Hipocampo/citologia , Humanos , Masculino , Metionina/genética , Pessoa de Meia-Idade , Transtornos do Humor/epidemiologia , Transtornos do Humor/etnologia , Neurônios/fisiologia , Inventário de Personalidade/estatística & dados numéricos , RNA Mensageiro/biossíntese , Ratos , Reação em Cadeia da Polimerase Via Transcriptase Reversa/métodos , Transfecção/métodos , Valina/genéticaRESUMO
The cerebellum is a brain region that is resistant to many of the neurodegenerative disorders such as stroke and Alzheimer's disease. In contrast, the neocortex (cerebrum, cerebral cortex) is vulnerable to these disorders. While there may be many reasons for the differences in vulnerability to acute and chronic neurodegenerative disorders, the cerebellum appears to be equipped with the tools necessary to protect itself against these types of insults. Over the last century, evidence has accumulated to suggest that the cerebellum is also involved in memory and higher cognitive function. We have discovered that intrinsic survival pathways exist in cerebellar granule cells that are regulated by low level stimulation of N-methyl-d-aspartate (NMDA) receptors. Activation of NMDA receptors protects vulnerable neurons against glutamate-mediated excitotoxicity acting on NMDA receptors. This report focuses on how modulation of neuronal survival by NMDA receptors through a brain-derived neurotrophic factor (BDNF)-mediated pathway may be incorporated into a network of cerebellar function, particularly in light of recent findings suggesting that the cerebellum plays a vital role in learning, memory, fear conditioning, and cognitive processing.
Assuntos
Córtex Cerebelar/patologia , Doenças Cerebelares/prevenção & controle , Fármacos Neuroprotetores/uso terapêutico , Animais , Doenças Cerebelares/patologia , Doenças Cerebelares/psicologia , Transtornos Cognitivos/etiologia , Transtornos Cognitivos/patologia , HumanosRESUMO
Alpha-linolenic acid (ALA) is plant-based essential omega-3 polyunsaturated fatty acids that must be obtained through the diet. This could explain in part why the severe deficiency in omega-3 intake pointed by numerous epidemiologic studies may increase the brain's vulnerability representing an important risk factor in the development and/or deterioration of certain cardio- and neuropathologies. The roles of ALA in neurological disorders remain unclear, especially in stroke that is a leading cause of death. We and others have identified ALA as a potential nutraceutical to protect the brain from stroke, characterized by its pleiotropic effects in neuroprotection, vasodilation of brain arteries, and neuroplasticity. This review highlights how chronic administration of ALA protects against rodent models of hypoxic-ischemic injury and exerts an anti-depressant-like activity, effects that likely involve multiple mechanisms in brain, and may be applied in stroke prevention. One major effect may be through an increase in mature brain-derived neurotrophic factor (BDNF), a widely expressed protein in brain that plays critical roles in neuronal maintenance, and learning and memory. Understanding the precise roles of ALA in neurological disorders will provide the underpinnings for the development of new therapies for patients and families who could be devastated by these disorders.
Assuntos
Ácidos Graxos Ômega-3/metabolismo , Fármacos Neuroprotetores/metabolismo , Acidente Vascular Cerebral/prevenção & controle , Ácido alfa-Linolênico/metabolismo , Animais , Encéfalo/metabolismo , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Humanos , Acidente Vascular Cerebral/metabolismoRESUMO
Exposure to organophosphorous (OP) nerve agents such as soman inhibits the critical enzyme acetylcholinesterase (AChE) leading to excessive acetylcholine accumulation in synapses, resulting in cholinergic crisis, status epilepticus and brain damage in survivors. The hippocampus is profoundly damaged after soman exposure leading to long-term memory deficits. We have previously shown that treatment with three sequential doses of alpha-linolenic acid, an essential omega-3 polyunsaturated fatty acid, increases brain plasticity in naïve animals. However, the effects of this dosing schedule administered after a brain insult and the underlying molecular mechanisms in the hippocampus are unknown. We now show that injection of three sequential doses of alpha-linolenic acid after soman exposure increases the endogenous expression of mature BDNF, activates Akt and the mammalian target of rapamycin complex 1 (mTORC1), increases neurogenesis in the subgranular zone of the dentate gyrus, increases retention latency in the passive avoidance task and increases animal survival. In sharp contrast, while soman exposure also increases mature BDNF, this increase did not activate downstream signaling pathways or neurogenesis. Administration of the inhibitor of mTORC1, rapamycin, blocked the alpha-linolenic acid-induced neurogenesis and the enhanced retention latency but did not affect animal survival. Our results suggest that alpha-linolenic acid induces a long-lasting neurorestorative effect that involves activation of mTORC1 possibly via a BDNF-TrkB-mediated mechanism.