RESUMO
Parkinson's disease is a pervasive, ageing-related neurodegenerative disease the cardinal motor symptoms of which reflect the loss of a small group of neurons, the dopaminergic neurons in the substantia nigra pars compacta (SNc). Mitochondrial oxidant stress is widely viewed as being responsible for this loss, but why these particular neurons should be stressed is a mystery. Here we show, using transgenic mice that expressed a redox-sensitive variant of green fluorescent protein targeted to the mitochondrial matrix, that the engagement of plasma membrane L-type calcium channels during normal autonomous pacemaking created an oxidant stress that was specific to vulnerable SNc dopaminergic neurons. The oxidant stress engaged defences that induced transient, mild mitochondrial depolarization or uncoupling. The mild uncoupling was not affected by deletion of cyclophilin D, which is a component of the permeability transition pore, but was attenuated by genipin and purine nucleotides, which are antagonists of cloned uncoupling proteins. Knocking out DJ-1 (also known as PARK7 in humans and Park7 in mice), which is a gene associated with an early-onset form of Parkinson's disease, downregulated the expression of two uncoupling proteins (UCP4 (SLC25A27) and UCP5 (SLC25A14)), compromised calcium-induced uncoupling and increased oxidation of matrix proteins specifically in SNc dopaminergic neurons. Because drugs approved for human use can antagonize calcium entry through L-type channels, these results point to a novel neuroprotective strategy for both idiopathic and familial forms of Parkinson's disease.
Assuntos
Relógios Biológicos/fisiologia , Dopamina/metabolismo , Neurônios/metabolismo , Proteínas Oncogênicas/metabolismo , Estresse Oxidativo , Animais , Encéfalo/citologia , Encéfalo/metabolismo , Cálcio/metabolismo , Bloqueadores dos Canais de Cálcio/farmacologia , Canais de Cálcio Tipo L/metabolismo , Canais de Cálcio Tipo L/farmacologia , Sinalização do Cálcio , Peptidil-Prolil Isomerase F , Ciclofilinas/metabolismo , Di-Hidropiridinas/farmacologia , Deleção de Genes , Canais Iônicos/antagonistas & inibidores , Canais Iônicos/metabolismo , Glicosídeos Iridoides/farmacologia , Iridoides , Masculino , Camundongos , Camundongos Transgênicos , Mitocôndrias/metabolismo , Proteínas Mitocondriais/antagonistas & inibidores , Proteínas Mitocondriais/metabolismo , Neurônios/citologia , Proteínas Oncogênicas/deficiência , Proteínas Oncogênicas/genética , Doença de Parkinson/metabolismo , Doença de Parkinson/patologia , Doença de Parkinson/prevenção & controle , Peroxirredoxinas , Proteína Desglicase DJ-1 , Purinas/farmacologia , Superóxidos/metabolismo , Proteína Desacopladora 1RESUMO
Alveolar hypoxia elicits increases in mitochondrial reactive oxygen species (ROS) signaling in pulmonary arterial (PA) smooth muscle cells (PASMCs), triggering hypoxic pulmonary vasoconstriction. Mice deficient in sirtuin (Sirt) 3, a nicotinamide adenine dinucleotide-dependent mitochondrial deacetylase, demonstrate enhanced left ventricular hypertrophy after aortic banding, whereas cells from these mice reportedly exhibit augmented hypoxia-induced ROS signaling and hypoxia-inducible factor (HIF)-1 activation. We therefore tested whether deletion of Sirt3 would augment hypoxia-induced ROS signaling in PASMCs, thereby exacerbating the development of pulmonary hypertension (PH) and right ventricular hypertrophy. In PASMCs from Sirt3 knockout (Sirt3(-/-)) mice in the C57BL/6 background, we observed that acute hypoxia (1.5% O2; 30 min)-induced changes in ROS signaling, detected using targeted redox-sensitive, ratiometric fluorescent protein sensors (roGFP) in the mitochondrial matrix, intermembrane space, and the cytosol, were indistinguishable from Sirt3(+/+) cells. Acute hypoxia-induced cytosolic calcium signaling in Sirt3(-/-) PASMCs was also indistinguishable from Sirt3(+/+) cells. During sustained hypoxia (1.5% O2; 16 h), Sirt3 deletion augmented mitochondrial matrix oxidant stress, but this did not correspond to an augmentation of intermembrane space or cytosolic oxidant signaling. Sirt3 deletion did not affect HIF-1α stabilization under normoxia, nor did it augment HIF-1α stabilization during sustained hypoxia (1.5% O2; 4 h). Sirt3(-/-) mice housed in chronic hypoxia (10% O2; 30 d) developed PH, PA wall remodeling, and right ventricular hypertrophy that was indistinguishable from Sirt3(+/+) littermates. Thus, Sirt3 deletion does not augment hypoxia-induced ROS signaling or its consequences in the cytosol of PASMCs, or the development of PH. These findings suggest that Sirt3 responses may be cell type specific, or restricted to certain genetic backgrounds.
Assuntos
Hipertensão Pulmonar/etiologia , Hipertensão Pulmonar/metabolismo , Hipóxia/complicações , Hipóxia/metabolismo , Sirtuína 3/deficiência , Animais , Sinalização do Cálcio , Feminino , Hipertensão Pulmonar/patologia , Hipertrofia Ventricular Direita/etiologia , Hipertrofia Ventricular Direita/metabolismo , Hipertrofia Ventricular Direita/patologia , Subunidade alfa do Fator 1 Induzível por Hipóxia/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Mitocôndrias Musculares/metabolismo , Miócitos de Músculo Liso/metabolismo , Miócitos de Músculo Liso/patologia , Artéria Pulmonar/metabolismo , Artéria Pulmonar/patologia , Espécies Reativas de Oxigênio/metabolismo , Sirtuína 3/genética , Sirtuína 3/fisiologia , Vasoconstrição/fisiologiaRESUMO
Huntington's disease (HD) is a progressive, neurodegenerative disease caused by a CAG triplet expansion in huntingtin. Although corticostriatal dysfunction has long been implicated in HD, the determinants and pathway specificity of this pathophysiology are not fully understood. Here, using a male zQ175+/- knock-in mouse model of HD we carry out optogenetic interrogation of intratelencephalic and pyramidal tract synapses with principal striatal spiny projection neurons (SPNs). These studies reveal that the connectivity of intratelencephalic, but not pyramidal tract, neurons with direct and indirect pathway SPNs increased in early symptomatic zQ175+/- HD mice. This enhancement was attributable to reduced pre-synaptic inhibitory control of intratelencephalic terminals by striatal cholinergic interneurons. Lowering mutant huntingtin selectively in striatal cholinergic interneurons with a virally-delivered zinc finger repressor protein normalized striatal acetylcholine release and intratelencephalic functional connectivity, revealing a node in the network underlying corticostriatal pathophysiology in a HD mouse model.
Assuntos
Doença de Huntington , Doenças Neurodegenerativas , Camundongos , Masculino , Animais , Doença de Huntington/metabolismo , Doenças Neurodegenerativas/metabolismo , Corpo Estriado/metabolismo , Neostriado/metabolismo , Colinérgicos/metabolismo , Modelos Animais de Doenças , Camundongos Transgênicos , Proteína Huntingtina/genética , Proteína Huntingtina/metabolismoRESUMO
To clarify the relationship between reactive oxygen species (ROS) and cell death during ischemia-reperfusion (I/R), we studied cell death mechanisms in a cellular model of I/R. Oxidant stress during simulated ischemia was detected in the mitochondrial matrix using mito-roGFP, a ratiometric redox sensor, and by Mito-Sox Red oxidation. Reperfusion-induced death was attenuated by over-expression of Mn-superoxide dismutase (Mn-SOD) or mitochondrial phospholipid hydroperoxide glutathione peroxidase (mito-PHGPx), but not by catalase, mitochondria-targeted catalase, or Cu,Zn-SOD. Protection was also conferred by chemically distinct antioxidant compounds, and mito-roGFP oxidation was attenuated by NAC, or by scavenging of residual O(2) during the ischemia (anoxic ischemia). Mitochondrial permeability transition pore (mPTP) oscillation/opening was monitored by real-time imaging of mitochondrial calcein fluorescence. Oxidant stress caused release of calcein to the cytosol during ischemia, a response that was inhibited by chemically diverse antioxidants, anoxia, or over-expression of Mn-SOD or mito-PHGPx. These findings suggest that mitochondrial oxidant stress causes oscillation of the mPTP prior to reperfusion. Cytochrome c release from mitochondria to the cytosol was not detected until after reperfusion, and was inhibited by anoxic ischemia or antioxidant administration during ischemia. Although DNA fragmentation was detected after I/R, no evidence of Bax activation was detected. Over-expression of the anti-apoptotic protein Bcl-X(L) in cardiomyocytes did not confer protection against I/R-induced cell death. Moreover, murine embryonic fibroblasts with genetic depletion of Bax and Bak, or over-expression of Bcl-X(L), failed to show protection against I/R. These findings indicate that mitochondrial ROS during ischemia triggers mPTP activation, mitochondrial depolarization, and cell death during reperfusion through a Bax/Bak-independent cell death pathway. Therefore, mitochondrial apoptosis appears to represent a redundant death pathway in this model of simulated I/R. This article is part of a Special Issue entitled: Mitochondria and Cardioprotection.
Assuntos
Mitocôndrias Cardíacas/metabolismo , Proteínas de Transporte da Membrana Mitocondrial/metabolismo , Traumatismo por Reperfusão Miocárdica/metabolismo , Traumatismo por Reperfusão Miocárdica/patologia , Miócitos Cardíacos/metabolismo , Animais , Antioxidantes/farmacologia , Apoptose , Hipóxia Celular , Células Cultivadas , Embrião de Galinha , Citocromos c/metabolismo , Fluoresceínas , Técnicas de Inativação de Genes , Potencial da Membrana Mitocondrial , Camundongos , Camundongos Transgênicos , Mitocôndrias Cardíacas/ultraestrutura , Poro de Transição de Permeabilidade Mitocondrial , Miócitos Cardíacos/patologia , Estresse Oxidativo , Propídio/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Superóxido Dismutase/genética , Superóxido Dismutase/metabolismo , Proteína Killer-Antagonista Homóloga a bcl-2/genética , Proteína X Associada a bcl-2/genéticaRESUMO
How do neurons match generation of adenosine triphosphate by mitochondria to the bioenergetic demands of regenerative activity? Although the subject of speculation, this coupling is still poorly understood, particularly in neurons that are tonically active. To help fill this gap, pacemaking substantia nigra dopaminergic neurons were studied using a combination of optical, electrophysiological, and molecular approaches. In these neurons, spike-activated calcium (Ca2+) entry through Cav1 channels triggered Ca2+ release from the endoplasmic reticulum, which stimulated mitochondrial oxidative phosphorylation through two complementary Ca2+-dependent mechanisms: one mediated by the mitochondrial uniporter and another by the malate-aspartate shuttle. Disrupting either mechanism impaired the ability of dopaminergic neurons to sustain spike activity. While this feedforward control helps dopaminergic neurons meet the bioenergetic demands associated with sustained spiking, it is also responsible for their elevated oxidant stress and possibly to their decline with aging and disease.
Assuntos
Cálcio , Neurônios Dopaminérgicos , Trifosfato de Adenosina/metabolismo , Ácido Aspártico , Cálcio/metabolismo , Neurônios Dopaminérgicos/metabolismo , Malatos/metabolismo , Malatos/farmacologia , Mitocôndrias/metabolismo , Oxidantes , Substância Negra/metabolismoRESUMO
The circuit mechanisms underlying fear-induced suppression of feeding are poorly understood. To help fill this gap, mice were fear conditioned, and the resulting changes in synaptic connectivity among the locus coeruleus (LC), the parabrachial nucleus (PBN), and the central nucleus of amygdala (CeA)-all of which are implicated in fear and feeding-were studied. LC neurons co-released noradrenaline and glutamate to excite PBN neurons and suppress feeding. LC neurons also suppressed inhibitory input to PBN neurons by inducing heterosynaptic, endocannabinoid-dependent, long-term depression of CeA synapses. Blocking or knocking down endocannabinoid receptors in CeA neurons prevented fear-induced depression of CeA synaptic transmission and fear-induced suppression of feeding. Altogether, these studies demonstrate that LC neurons play a pivotal role in modulating the circuitry that underlies fear-induced suppression of feeding, pointing to new ways of alleviating stress-induced eating disorders.
Assuntos
Medo/fisiologia , Comportamento Alimentar/fisiologia , Locus Cerúleo/fisiologia , Neurônios/fisiologia , Animais , Núcleo Central da Amígdala/fisiologia , Condicionamento Clássico , Feminino , Ácido Glutâmico/fisiologia , Masculino , Camundongos Endogâmicos C57BL , Vias Neurais/fisiologia , Norepinefrina/fisiologia , Núcleos Parabraquiais/fisiologia , Transmissão SinápticaRESUMO
Ca2+ channels with a CaV1.3 pore-forming α1 subunit have been implicated in both neurodegenerative and neuropsychiatric disorders, motivating the development of selective and potent inhibitors of CaV1.3 versus CaV1.2 channels, the calcium channels implicated in hypertensive disorders. We have previously identified pyrimidine-2,4,6-triones (PYTs) that preferentially inhibit CaV1.3 channels, but the structural determinants of their interaction with the channel have not been identified, impeding their development into drugs. By a combination of biochemical, computational, and molecular biological approaches, it was found that PYTs bind to the dihydropyridine (DHP) binding pocket of the CaV1.3 subunit, establishing them as negative allosteric modulators of channel gating. Site-directed mutagenesis, based on homology models of CaV1.3 and CaV1.2 channels, revealed that a single amino acid residue within the DHP binding pocket (M1078) is responsible for the selectivity of PYTs for CaV1.3 over CaV1.2. In addition to providing direction for chemical optimization, these results suggest that, like dihydropyridines, PYTs have pharmacological features that could make them of broad clinical utility.
Assuntos
Bloqueadores dos Canais de Cálcio/metabolismo , Canais de Cálcio Tipo L/metabolismo , Pirimidinonas/metabolismo , Regulação Alostérica , Sítio Alostérico , Animais , Cálcio/metabolismo , Canais de Cálcio Tipo L/química , Canais de Cálcio Tipo L/genética , Neurônios Dopaminérgicos/efeitos dos fármacos , Células HEK293 , Humanos , Camundongos , Simulação de Acoplamento Molecular , Mutagênese Sítio-Dirigida , Mutação , Ligação Proteica , Coelhos , RatosRESUMO
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
RESUMO
Monoamine oxidase (MAO) metabolizes cytosolic dopamine (DA), thereby limiting auto-oxidation, but is also thought to generate cytosolic hydrogen peroxide (H2O2). We show that MAO metabolism of DA does not increase cytosolic H2O2 but leads to mitochondrial electron transport chain (ETC) activity. This is dependent upon MAO anchoring to the outer mitochondrial membrane and shuttling electrons through the intermembrane space to support the bioenergetic demands of phasic DA release.
Assuntos
Dopamina/metabolismo , Neurônios Dopaminérgicos/metabolismo , Transporte de Elétrons/fisiologia , Metabolismo Energético/fisiologia , Monoaminoxidase/metabolismo , Animais , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Mitocôndrias/metabolismo , OxirreduçãoRESUMO
The motor symptoms of Parkinson's disease (PD) are thought to stem from an imbalance in the activity of striatal direct- and indirect-pathway spiny projection neurons (SPNs). Disease-induced alterations in the activity of networks controlling SPNs could contribute to this imbalance. One of these networks is anchored by the parafascicular nucleus (PFn) of the thalamus. To determine the role of the PFn in striatal PD pathophysiology, optogenetic, chemogenetic, and electrophysiological tools were used in ex vivo slices from transgenic mice with region-specific Cre recombinase expression. These studies revealed that in parkinsonian mice, the functional connectivity of PFn neurons with indirect pathway SPNs (iSPNs) was selectively enhanced by cholinergic interneurons acting through presynaptic nicotinic acetylcholine receptors (nAChRs) on PFn terminals. Attenuating this network adaptation by chemogenetic or genetic strategies alleviated motor-learning deficits in parkinsonian mice, pointing to a potential new therapeutic strategy for PD patients.
Assuntos
Neurônios Colinérgicos/fisiologia , Corpo Estriado/fisiopatologia , Potenciais Pós-Sinápticos Excitadores , Interneurônios/fisiologia , Doença de Parkinson/fisiopatologia , Tálamo/fisiopatologia , Animais , Neurônios Colinérgicos/metabolismo , Corpo Estriado/citologia , Ácido Glutâmico/metabolismo , Interneurônios/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Doença de Parkinson/metabolismo , Receptores Nicotínicos/metabolismo , Tálamo/citologiaRESUMO
Abnormal subthalamic nucleus (STN) activity is linked to impaired movement in Parkinson's disease (PD). The autonomous firing of STN neurons, which contributes to their tonic excitation of the extrastriatal basal ganglia and shapes their integration of synaptic input, is downregulated in PD models. Using electrophysiological, chemogenetic, genetic, and optical approaches, we find that chemogenetic activation of indirect pathway striatopallidal neurons downregulates intrinsic STN activity in normal mice but this effect is occluded in Parkinsonian mice. Loss of autonomous spiking in PD mice is prevented by STN N-methyl-D-aspartate receptor (NMDAR) knockdown and reversed by reactive oxygen species breakdown or KATP channel inhibition. Chemogenetic activation of hM3D(Gq) in STN neurons in Parkinsonian mice rescues their intrinsic activity, modifies their synaptic integration, and ameliorates motor dysfunction. Together these data argue that in PD mice increased indirect pathway activity leads to disinhibition of the STN, which triggers maladaptive NMDAR-dependent downregulation of autonomous firing.
Assuntos
Neurônios Dopaminérgicos/patologia , Regulação para Baixo , Mesencéfalo/patologia , Núcleo Subtalâmico/patologia , Animais , Neurônios Dopaminérgicos/efeitos dos fármacos , Regulação para Baixo/efeitos dos fármacos , Peróxido de Hidrogênio/toxicidade , Ativação do Canal Iônico/efeitos dos fármacos , Canais KATP/metabolismo , Masculino , Mesencéfalo/efeitos dos fármacos , Mesencéfalo/fisiopatologia , Camundongos Endogâmicos C57BL , Mitocôndrias/efeitos dos fármacos , Mitocôndrias/metabolismo , Atividade Motora/efeitos dos fármacos , Estresse Oxidativo/efeitos dos fármacos , Oxidopamina , Doença de Parkinson/patologia , Doença de Parkinson/fisiopatologia , Receptores de N-Metil-D-Aspartato/metabolismo , Núcleo Subtalâmico/efeitos dos fármacos , Núcleo Subtalâmico/fisiopatologiaRESUMO
Huntington's disease (HD) is initially characterized by an inability to suppress unwanted movements, a deficit attributable to impaired synaptic activation of striatal indirect pathway spiny projection neurons (iSPNs). To better understand the mechanisms underlying this deficit, striatal neurons in ex vivo brain slices from mouse genetic models of HD were studied using electrophysiological, optical and biochemical approaches. Distal dendrites of iSPNs from symptomatic HD mice were hypoexcitable, a change that was attributable to increased association of dendritic Kv4 potassium channels with auxiliary KChIP subunits. This association was negatively modulated by TrkB receptor signaling. Dendritic excitability of HD iSPNs was rescued by knocking-down expression of Kv4 channels, by disrupting KChIP binding, by restoring TrkB receptor signaling or by lowering mutant-Htt (mHtt) levels with a zinc finger protein. Collectively, these studies demonstrate that mHtt induces reversible alterations in the dendritic excitability of iSPNs that could contribute to the motor symptoms of HD.
Assuntos
Corpo Estriado/patologia , Proteína Huntingtina/metabolismo , Doença de Huntington/patologia , Doença de Huntington/fisiopatologia , Proteínas Mutantes/metabolismo , Neurônios/metabolismo , Canais de Potássio Shal/metabolismo , Animais , Modelos Animais de Doenças , Proteína Huntingtina/genética , Camundongos , Proteínas Mutantes/genéticaRESUMO
Huntington's disease (HD) is a dominantly inherited neurodegenerative disorder caused by a CAG trinucleotide expansion in the huntingtin gene (HTT), which codes for the pathologic mutant HTT (mHTT) protein. Since normal HTT is thought to be important for brain function, we engineered zinc finger protein transcription factors (ZFP-TFs) to target the pathogenic CAG repeat and selectively lower mHTT as a therapeutic strategy. Using patient-derived fibroblasts and neurons, we demonstrate that ZFP-TFs selectively repress >99% of HD-causing alleles over a wide dose range while preserving expression of >86% of normal alleles. Other CAG-containing genes are minimally affected, and virally delivered ZFP-TFs are active and well tolerated in HD neurons beyond 100 days in culture and for at least nine months in the mouse brain. Using three HD mouse models, we demonstrate improvements in a range of molecular, histopathological, electrophysiological and functional endpoints. Our findings support the continued development of an allele-selective ZFP-TF for the treatment of HD.
Assuntos
Alelos , Proteína Huntingtina/genética , Doença de Huntington/terapia , Mutação , Transcrição Gênica , Dedos de Zinco , Animais , Células Cultivadas , Modelos Animais de Doenças , Feminino , Humanos , Doença de Huntington/genética , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos CBA , Neuroproteção , Repetições de TrinucleotídeosRESUMO
The ability of the Cav1 channel inhibitor isradipine to slow the loss of substantia nigra pars compacta (SNc) dopaminergic (DA) neurons and the progression of Parkinson's disease (PD) is being tested in a phase 3 human clinical trial. But it is unclear whether and how chronic isradipine treatment will benefit SNc DA neurons in vivo. To pursue this question, isradipine was given systemically to mice at doses that achieved low nanomolar concentrations in plasma, near those achieved in patients. This treatment diminished cytosolic Ca2+ oscillations in SNc DA neurons without altering autonomous spiking or expression of Ca2+ channels, an effect mimicked by selectively knocking down expression of Cav1.3 channel subunits. Treatment also lowered mitochondrial oxidant stress, reduced a high basal rate of mitophagy, and normalized mitochondrial mass - demonstrating that Cav1 channels drive mitochondrial oxidant stress and turnover in vivo. Thus, chronic isradipine treatment remodeled SNc DA neurons in a way that should not only diminish their vulnerability to mitochondrial challenges, but to autophagic stress as well.
Assuntos
Sinalização do Cálcio/efeitos dos fármacos , Neurônios Dopaminérgicos/metabolismo , Isradipino/farmacologia , Mitocôndrias/metabolismo , Mitofagia/efeitos dos fármacos , Estresse Oxidativo/efeitos dos fármacos , Animais , Caveolina 1/metabolismo , Neurônios Dopaminérgicos/patologia , Humanos , Masculino , Camundongos , Mitocôndrias/patologia , Doença de Parkinson/tratamento farmacológico , Doença de Parkinson/metabolismo , Doença de Parkinson/patologiaRESUMO
Parkinson's disease (PD) is a debilitating neurodegenerative disease characterized by a loss of dopaminergic neurons in the substantia nigra (SN). Although mitochondrial dysfunction and dysregulated α-synuclein (aSyn) expression are postulated to play a role in PD pathogenesis, it is still debated why neurons of the SN are targeted while neighboring dopaminergic neurons of the ventral tegmental area (VTA) are spared. Using electrochemical and imaging approaches, we investigated metabolic changes in cultured primary mouse midbrain dopaminergic neurons exposed to a parkinsonian neurotoxin, 1-methyl-4-phenylpyridinium (MPP+). We demonstrate that the higher level of neurotoxicity in SN than VTA neurons was due to SN neuron-specific toxin-induced increase in cytosolic dopamine (DA) and Ca2+, followed by an elevation of mitochondrial Ca2+, activation of nitric oxide synthase (NOS), and mitochondrial oxidation. The increase in cytosolic Ca2+ was not caused by MPP+-induced oxidative stress, but rather depended on the activity of both L-type calcium channels and aSyn expression, suggesting that these two established pathogenic factors in PD act in concert.
Assuntos
1-Metil-4-fenilpiridínio/toxicidade , Neurônios Dopaminérgicos/efeitos dos fármacos , Doença de Parkinson/metabolismo , Substância Negra/metabolismo , Área Tegmentar Ventral/metabolismo , alfa-Sinucleína/metabolismo , Animais , Canais de Cálcio Tipo L/efeitos dos fármacos , Canais de Cálcio Tipo L/metabolismo , Sinalização do Cálcio/efeitos dos fármacos , Linhagem Celular , Neurônios Dopaminérgicos/metabolismo , CamundongosRESUMO
We examined adaptations in nucleus accumbens (NAc) neurons in mouse and rat peripheral nerve injury models of neuropathic pain. Injury selectively increased excitability of NAc shell indirect pathway spiny projection neurons (iSPNs) and altered their synaptic connectivity. Moreover, injury-induced tactile allodynia was reversed by inhibiting and exacerbated by exciting iSPNs, indicating that they not only participated in the central representation of pain, but gated activity in ascending nociceptive pathways.
Assuntos
Vias Neurais/fisiopatologia , Neuralgia/fisiopatologia , Núcleo Accumbens/anatomia & histologia , Núcleo Accumbens/fisiopatologia , Analgésicos/farmacologia , Animais , Anti-Inflamatórios não Esteroides/uso terapêutico , Potenciais Pós-Sinápticos Excitadores , Feminino , Técnicas In Vitro , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Naproxeno/farmacologia , Vias Neurais/metabolismo , Neuralgia/metabolismo , Neuralgia/psicologia , Neurônios/patologia , Núcleo Accumbens/metabolismo , Medição da Dor , Traumatismos dos Nervos Periféricos/fisiopatologia , Ratos , Ratos Sprague-Dawley , Comportamento Social , Sinapses/patologiaRESUMO
Loss of noradrenergic locus coeruleus (LC) neurons is a prominent feature of aging-related neurodegenerative diseases, such as Parkinson's disease (PD). The basis of this vulnerability is not understood. To explore possible physiological determinants, we studied LC neurons using electrophysiological and optical approaches in ex vivo mouse brain slices. We found that autonomous activity in LC neurons was accompanied by oscillations in dendritic Ca(2+) concentration that were attributable to the opening of L-type Ca(2+) channels. This oscillation elevated mitochondrial oxidant stress and was attenuated by inhibition of nitric oxide synthase. The relationship between activity and stress was malleable, as arousal and carbon dioxide increased the spike rate but differentially affected mitochondrial oxidant stress. Oxidant stress was also increased in an animal model of PD. Thus, our results point to activity-dependent Ca(2+) entry and a resulting mitochondrial oxidant stress as factors contributing to the vulnerability of LC neurons.
Assuntos
Dendritos/enzimologia , Locus Cerúleo/enzimologia , Mitocôndrias/enzimologia , Óxido Nítrico Sintase/fisiologia , Estresse Oxidativo/fisiologia , Animais , Canais de Cálcio Tipo L/fisiologia , Ativação Enzimática/fisiologia , Locus Cerúleo/citologia , Locus Cerúleo/metabolismo , Masculino , Potencial da Membrana Mitocondrial/fisiologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Mitocôndrias/metabolismoRESUMO
Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder. The debilitating choreic movements that plague HD patients have been attributed to striatal degeneration induced by the loss of cortically supplied brain-derived neurotrophic factor (BDNF). Here, we show that in mouse models of early symptomatic HD, BDNF delivery to the striatum and its activation of tyrosine-related kinase B (TrkB) receptors were normal. However, in striatal neurons responsible for movement suppression, TrkB receptors failed to properly engage postsynaptic signaling mechanisms controlling the induction of potentiation at corticostriatal synapses. Plasticity was rescued by inhibiting p75 neurotrophin receptor (p75NTR) signaling or its downstream target phosphatase-and-tensin-homolog-deleted-on-chromosome-10 (PTEN). Thus, corticostriatal synaptic dysfunction early in HD is attributable to a correctable defect in the response to BDNF, not its delivery.