RESUMO
Nakamura et al. examined the evidence, using a discovery and a validation database, that amyloid-ß precursor protein (APP)669-711/amyloid-ß (Aß)1-42 and Aß1-40/Aß1-42 ratios, and composites based on traditional statistics; they concluded that these may be useful as biomarkers of Alzheimer's Disease (AD). We reexamined the same datasets, each of which included cognitively normal individuals (CN), individuals with mild cognitive impairment (MCI) and individuals with AD. We used fractal self-similar analyses and reexamined their data from (1) the Japanese National Center for Geriatrics and Gerontology (NCGG) (discovery database) and (2) the Australian Imaging, Biomarker and Lifestyle Study of Ageing (AIBL) cohort (validation database). Results: Using our methods, the three groups of individuals were found to be self-similar, i.e., they could not be differentiated quantitatively, in contrast to the findings of Nakamura et al. Conclusion: Appropriate biomarkers need further study. Our results suggest that APP669-711/Aß1-42 and Aß1-40/Aß1-42 ratios and their composites may not be valid biomarkers of AD, when reexamined using fractal methods for comparing biomarkers across populations.
Assuntos
Doença de Alzheimer , Biomarcadores , Doença de Alzheimer/diagnóstico , Peptídeos beta-Amiloides , HumanosRESUMO
Luongo et al. found that the mitochondrial Na+/Ca2+ exchanger (NCLX) was essential for Ca2+ homeostasis and viability. Here, we re-analyze their data in terms of fractal self-similarity and quantitative difference (QD). We calculated the 7-dimension data from NCLX conditional loss-of-function mouse models, and the 9-dimension data from NCLX overexpression (NCLX-Tg) models. RESULTS: The 9-dimension data of the NCLX-Tg and its tTA control were partially self-similar to each other, while the 7-dimension data in NCLX knockout models were not. CONCLUSION: The NCLX may be necessary but is not sufficient for Ca2+ homeostasis and viability.
Assuntos
Cálcio/metabolismo , Sobrevivência Celular/fisiologia , Homeostase/fisiologia , Modelos Teóricos , Trocador de Sódio e Cálcio/metabolismo , Algoritmos , Animais , Sinalização do Cálcio/fisiologia , Camundongos , Mitocôndrias/metabolismoRESUMO
Exercise is essential in regulating energy metabolism. Exercise activates cellular, molecular, and biochemical pathways with regulatory roles in training response adaptation. Among them, endurance/strength training of an individual has been shown to activate its respective signal transduction pathways in skeletal muscle. This was further studied from the viewpoint of quantitative difference (QD). For the mean values, [Formula: see text], of two sets of data, their QD is defined as [Formula: see text] ([Formula: see text]). The function-specific homeostasis (FSH) of a function of a biosystem is a negative-feedback response of the biosystem to maintain the function-specific conditions inside the biosystem so that the function is perfectly performed. A function in/far from its FSH is called a normal/dysfunctional function. A cellular normal function can resist the activation of other signal transduction pathways so that there are normal function-specific signal transduction pathways which full activation maintains the normal function. RESULTS: An acute endurance/strength training may be dysfunctional, but its regular training may be normal. The normal endurance/strength training of an individual may resist the activation of other signal transduction pathways in skeletal muscle so that there may be normal endurance/strength training-specific signal transduction pathways (NEPs/NSPs) in skeletal muscle. The endurance/strength training may activate NSPs/NEPs, but the QD from the control is smaller than 0.80. The simultaneous activation of both NSPs and NEPs may enhance their respective activation, and the QD from the control is larger than 0.80. The low level laser irradiation pretreatment of rats may promote the activation of NSPs in endurance training skeletal muscle. CONCLUSION: There may be NEPs/NSPs in skeletal muscle trained by normal endurance/strength training.
Assuntos
Exercício Físico/fisiologia , Resistência Física/fisiologia , Transdução de Sinais , Adaptação Fisiológica/fisiologia , Metabolismo Energético/fisiologia , Humanos , Força Muscular/fisiologia , Músculo Esquelético/fisiologia , Treinamento ResistidoRESUMO
Oligodendrocytes are the predominant cell type in white matter and are highly vulnerable to ischemic injury. The role of oligodendrocyte dysfunction in ischemic brain injury is unknown. In this study, we used a 24-amino acid peptide S14G-Humanin (HNG) to examine oligodendrogenesis and neurological functional recovery in a hypoxic/ischemic (H/I) neonatal model. Intraperitoneal HNG pre-treatment decreased infarct volume following H/I injury. Delayed HNG treatment 24 h after H/I injury did not reduce infarct volume but did decrease neurological deficits and brain atrophy. Delayed HNG treatment did not attenuate axonal demyelination at 48 h after H/I injury. However, at 14 d after H/I injury, delayed HNG treatment increased axonal remyelination, the thickness of corpus callosum at the midline, the number of Olig2(+) /BrdU(+) cells, and levels of brain-derived neurotrophic factor (BDNF). Our results suggest that targeting oligodendrogenesis via delayed HNG treatment may represent a promising approach for the treatment of stroke.
Assuntos
Hipóxia-Isquemia Encefálica/tratamento farmacológico , Peptídeos e Proteínas de Sinalização Intracelular/farmacologia , Neurogênese/efeitos dos fármacos , Oligodendroglia/efeitos dos fármacos , Recuperação de Função Fisiológica/efeitos dos fármacos , Animais , Animais Recém-Nascidos , Atrofia/patologia , Axônios/efeitos dos fármacos , Axônios/patologia , Fator Neurotrófico Derivado do Encéfalo/efeitos dos fármacos , Infarto Cerebral/tratamento farmacológico , Infarto Cerebral/patologia , Infarto Cerebral/fisiopatologia , Modelos Animais de Doenças , Hipóxia-Isquemia Encefálica/patologia , Hipóxia-Isquemia Encefálica/fisiopatologia , Peptídeos e Proteínas de Sinalização Intracelular/administração & dosagem , Distribuição Aleatória , Ratos , Ratos Sprague-DawleyRESUMO
Females who enter menopause prematurely via bilateral ovariectomy (surgical menopause) have a significantly increased risk for cognitive decline and dementia. To help elucidate the mechanisms underlying this phenomenon, we used an animal model of surgical menopause, long-term (10-week) bilateral ovariectomy in female rats. Herein, we demonstrate that long-term oestrogen deprivation dramatically increases sensitivity of the normally resistant hippocampal CA3 region to ischaemic stress, an effect that was gender-specific, as it was not observed in long-term orchiectomized males. Furthermore, the enhanced damage to the CA3 region correlated with a worse cognitive outcome after ischaemic stress. Long-term ovariectomized rats also displayed a robust hyperinduction of Alzheimer's disease-related proteins in the CA3 region and a switch in amyloid precursor protein processing from non-amyloidogenic to amyloidogenic following ischaemic stress CA3 hypersensitivity also extended to an Alzheimer's disease-relevant insult, as the CA3 region of long-term ovariectomized rats was profoundly hypersensitive to the neurotoxic effects of amyloid-ß1-42, the most amyloidogenic form of the amyloid-ß peptide. Additional studies revealed that CA3 region hypersensitivity, Alzheimer's disease-related protein induction, and amyloidogenesis are mediated by a NADPH oxidase/superoxide/c-Jun N-terminal kinase/c-Jun signalling pathway, involving both transcriptional and post-translational mechanisms. In addition, while 17ß-oestradiol replacement at the end of the long-term oestrogen deprivation period could not prevent CA3 hypersensitivity and amyloidogenesis, if 17ß-oestradiol was initiated at the time of ovariectomy and maintained throughout the 10-week oestrogen deprivation period, it completely prevented these events, providing support for the 'critical window' hypothesis for oestrogen replacement therapy benefit. Collectively, these findings may help explain the increased risk of cognitive decline and dementia observed in women following surgical menopause, and they provide increased support that early 17ß-oestradiol replacement is critical in preventing the negative neural effects associated with bilateral ovariectomy.
Assuntos
Peptídeos beta-Amiloides/biossíntese , Peptídeos beta-Amiloides/toxicidade , Região CA3 Hipocampal/metabolismo , Menopausa/metabolismo , Degeneração Neural/metabolismo , Ovariectomia , Fragmentos de Peptídeos/biossíntese , Fragmentos de Peptídeos/toxicidade , Estresse Fisiológico/fisiologia , Peptídeos beta-Amiloides/metabolismo , Animais , Região CA3 Hipocampal/patologia , Feminino , Masculino , Modelos Animais , Degeneração Neural/patologia , Ovariectomia/efeitos adversos , Fragmentos de Peptídeos/metabolismo , Ratos , Ratos Sprague-DawleyRESUMO
Recent work suggests that timing of 17ß-estradiol (E2) therapy may be critical for observing a beneficial neural effect. Along these lines, E2 neuroprotection, but not its uterotropic effect, was shown to be lost following long-term E2 deprivation (LTED), and this effect was associated with a significant decrease of estrogen receptor-α (ERα) in the hippocampus but not the uterus. The purpose of the current study was to determine the mechanism underlying the ERα decrease and to determine whether aging leads to a similar loss of hippocampal ERα and E2 sensitivity. The results of the study show that ERα in the rat hippocampal CA1 region but not the uterus undergoes enhanced interaction with the E3 ubiquitin ligase C terminus of heat shock cognate protein 70 (Hsc70)-interacting protein (CHIP) that leads to its ubiquitination/proteasomal degradation following LTED (10-wk ovariectomy). E2 treatment initiated before but not after LTED prevented the enhanced ERα-CHIP interaction and ERα ubiquitination/degradation and was fully neuroprotective against global cerebral ischemia. Administration of a proteasomal inhibitor or CHIP antisense oligonucleotides to knock down CHIP reversed the LTED-induced down-regulation of ERα. Further work showed that these observations extended to natural aging, because aged rats showed enhanced CHIP interaction; ubiquitination and degradation of both hippocampal ERα and ERß; and, importantly, a correlated loss of E2 neuroprotection against global cerebral ischemia. In contrast, E2 administration to middle-aged rats was still capable of exerting neuroprotection. As a whole, the study provides support for a "critical period" for E2 neuroprotection of the hippocampus and provides important insight into the mechanism underlying the critical period.
Assuntos
Estradiol/farmacologia , Receptor alfa de Estrogênio/metabolismo , Hipocampo/metabolismo , Fármacos Neuroprotetores/farmacologia , Ubiquitina-Proteína Ligases/fisiologia , Envelhecimento/metabolismo , Animais , Feminino , Complexo de Endopeptidases do Proteassoma/fisiologia , Inibidores de Proteassoma , Ratos , Ratos Endogâmicos F344 , Ratos Sprague-Dawley , UbiquitinaçãoRESUMO
17ß-Estradiol (estradiol or E2) is implicated as a neuroprotective factor in a variety of neurodegenerative disorders. This review focuses on the mechanisms underlying E2 neuroprotection in cerebral ischemia, as well as emerging evidence from basic science and clinical studies, which suggests that there is a "critical period" for estradiol's beneficial effect in the brain. Potential mechanisms underlying the critical period are discussed, as are the neurological consequences of long-term E2 deprivation (LTED) in animals and in humans after natural menopause or surgical menopause. We also summarize the major clinical trials concerning postmenopausal hormone therapy (HT), comparing their outcomes with respect to cardiovascular and neurological disease and discussing their relevance to the critical period hypothesis. Finally, potential caveats, controversies and future directions for the field are highlighted and discussed throughout the review.
Assuntos
Isquemia Encefálica/prevenção & controle , Estradiol/uso terapêutico , Doenças Neurodegenerativas/prevenção & controle , Fármacos Neuroprotetores/uso terapêutico , Animais , Período Crítico Psicológico , Receptor alfa de Estrogênio/fisiologia , Terapia de Reposição de Estrogênios , Feminino , Humanos , Menopausa , Camundongos , Estresse Oxidativo/efeitos dos fármacos , Ratos , Receptores de Estrogênio , Receptores Acoplados a Proteínas G/fisiologiaRESUMO
The goal of this study was to elucidate the mechanisms of 17beta-estradiol (E(2)) antioxidant and neuroprotective actions in stroke. The results reveal a novel extranuclear receptor-mediated antioxidant mechanism for E(2) during stroke, as well as a hypersensitivity of the CA3/CA4 region to ischemic injury after prolonged hypoestrogenicity. E(2) neuroprotection was shown to involve a profound attenuation of NADPH oxidase activation and superoxide production in hippocampal CA1 pyramidal neurons after stroke, an effect mediated by extranuclear estrogen receptor alpha (ERalpha)-mediated nongenomic signaling, involving Akt activation and subsequent phosphorylation/inactivation of Rac1, a factor critical for activation of NOX2 NADPH oxidase. Intriguingly, E(2) nongenomic signaling, antioxidant action, and neuroprotection in the CA1 region were lost after long-term E(2) deprivation, and this loss was tissue specific because the uterus remained responsive to E(2). Correspondingly, a remarkable loss of ERalpha, but not ERbeta, was observed in the CA1 after long-term E(2) deprivation, with no change observed in the uterus. As a whole, the study reveals a novel, membrane-mediated antioxidant mechanism in neurons by E(2) provides support and mechanistic insights for a "critical period" of E(2) replacement in the hippocampus and demonstrates a heretofore unknown hypersensitivity of the CA3/CA4 to ischemic injury after prolonged hypoestrogenicity.
Assuntos
Isquemia Encefálica/enzimologia , Receptor alfa de Estrogênio/fisiologia , Estrogênios/uso terapêutico , NADPH Oxidases/antagonistas & inibidores , NADPH Oxidases/metabolismo , Estresse Oxidativo/fisiologia , Animais , Antioxidantes/uso terapêutico , Isquemia Encefálica/prevenção & controle , Morte Celular/efeitos dos fármacos , Morte Celular/fisiologia , Ativação Enzimática/efeitos dos fármacos , Ativação Enzimática/fisiologia , Estrogênios/farmacologia , Feminino , Estresse Oxidativo/efeitos dos fármacos , Ratos , Ratos Sprague-Dawley , Transdução de Sinais/genéticaRESUMO
alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) are responsible for excitotoxicity induced by ischemic injury in hippocampal CA1 neurons, whereas the molecular mechanisms responsible for their neurotrophic activities are much less studied. Here, we examined the neuroprotective effect of positive modeulation of AMPARs by coapplication of AMPA with PEPA, an allosteric potentiator of AMPARs. We showed that coapplication of AMPA with PEPA protected hippocampal CA1 neurons from brain ischemia-induced death. Coapplication of AMPA with PEPA could prevent downregulated expression of GluR2 subunit caused by ischemia and increase BDNF expression via Lyn-ERK1/2-CREB signaling. Furthermore, TrkB receptor-mediated PI3K/Akt signal pathway was activated after coapplication of AMPA with PEPA, which was related to MAPK pathway and protected CA1 neurons against ischemic insults through depression of JNK3 activity, release of cytochrome c to cytosol and depression of capase-3 activity. Our results revealed that positive modulation of AMPARs could exert neuroprotective effects and the possible signaling pathways underlied.
Assuntos
Isquemia Encefálica/metabolismo , Proteína de Ligação ao Elemento de Resposta ao AMP Cíclico/metabolismo , MAP Quinases Reguladas por Sinal Extracelular/metabolismo , Receptores de AMPA/metabolismo , Quinases da Família src/metabolismo , Animais , Região CA1 Hipocampal/metabolismo , Regulação da Expressão Gênica , Sistema de Sinalização das MAP Quinases , Masculino , Proteína Quinase 1 Ativada por Mitógeno/metabolismo , Proteína Quinase 3 Ativada por Mitógeno/metabolismo , Neurônios/metabolismo , RNA Mensageiro/metabolismo , Ratos , Ratos Endogâmicos , Receptores de AMPA/genética , Transdução de SinaisRESUMO
17beta-Estradiol (E2) has been implicated to be neuroprotective in a variety of neurodegenerative disorders, although the mechanism remains poorly understood. The current study sheds light on this issue by demonstrating that low physiological levels of E2 protects the hippocampus CA1 against global cerebral ischemia by preventing elevation of dickkopf-1 (Dkk1), an antagonist of the Wnt/beta-catenin signaling pathway, which is a principal mediator of neurodegeneration in cerebral ischemia and Alzheimer's disease. E2 inhibition of Dkk1 elevation correlated with a reduction of phospho-beta-catenin and elevation of nuclear beta-catenin levels, as well as enhancement of Wnt-3, suggesting E2 activation of the Wnt/beta-catenin signaling pathway. In agreement, the beta-catenin downstream prosurvival factor, survivin, was induced by E2 at 24 and 48 h after cerebral ischemia, an effect observed only in surviving neurons because degenerating neurons lacked survivin expression. E2 suppression of Dkk1 elevation was found to be caused by attenuation of upstream c-Jun N-terminal protein kinase (JNK)/c-Jun signaling, as E2 attenuation of JNK/c-Jun activation and a JNK inhibitor significantly blocked Dkk1 induction. Tau hyperphosphorylation has been implicated to have a prodeath role in Alzheimer's disease and cerebral ischemia, and E2 attenuates tau hyperphosphorylation. Our study demonstrates that tau hyperphosphorylation is strongly induced after global cerebral ischemia, and that E2 inhibits tau hyperphosphorylation by suppressing activation of the JNK/c-Jun/Dkk1 signaling pathway. Finally, exogenous Dkk1 replacement via intracerebroventricular administration completely reversed E2-induced neuroprotection, nuclear beta-catenin induction, and phospho-tau attenuation, further suggesting that E2 inhibition of Dkk1 is a critical mechanism underlying its neuroprotective and phospho-tau regulatory effects after cerebral ischemia.
Assuntos
Isquemia Encefálica/metabolismo , Estradiol/farmacologia , Peptídeos e Proteínas de Sinalização Intercelular/metabolismo , Fármacos Neuroprotetores/farmacologia , Proteínas tau/metabolismo , Animais , Isquemia Encefálica/patologia , Isquemia Encefálica/fisiopatologia , Morte Celular/efeitos dos fármacos , Regulação para Baixo/efeitos dos fármacos , Feminino , Hipocampo/metabolismo , Hipocampo/patologia , Hipocampo/fisiopatologia , Injeções Intraventriculares , Peptídeos e Proteínas de Sinalização Intercelular/administração & dosagem , Peptídeos e Proteínas de Sinalização Intercelular/farmacologia , Proteínas Quinases JNK Ativadas por Mitógeno/metabolismo , Proteínas Associadas aos Microtúbulos/metabolismo , Neurônios/efeitos dos fármacos , Neurônios/patologia , Fosforilação/efeitos dos fármacos , Proteínas Proto-Oncogênicas c-jun/metabolismo , Ratos , Ratos Sprague-Dawley , Proteínas Recombinantes/administração & dosagem , Proteínas Recombinantes/farmacologia , Transdução de Sinais/efeitos dos fármacos , Survivina , Regulação para Cima , Proteínas Wnt/metabolismo , beta Catenina/metabolismoRESUMO
Previous work has demonstrated that ischemic preconditioning neuroprotection is associated with inhibition of JNK pathway activation. The present study was designed to examine the hypothesis that the suppression of JNK3 activation by preconditioning is mediated by NMDA receptors and crosstalk between ERK1/2 and JNK3. Preconditioning (3 min ischemia) 2 days before global cerebral ischemia (8-min) markedly decreased neuronal degeneration in hippocampus CA1, an effect abolished by pretreatment with the NMDA receptor antagonist, MK-801. Furthermore, preconditioning abolished cerebral ischemia-induced JNK3 activation and enhanced ERK1/2 activation, an effect reversed by MK-801. Due to the inverse relationship between ERK1/2 and JNK3 activation following preconditioning, we hypothesized that ERK1/2 may regulate JNK3 activation following preconditioning. In support of this contention, pretreatment with the MEK inhibitor, PD98059 significantly attenuated preconditioning-induced ERK1/2 phosphorylation, and strongly reversed preconditioning down-regulation of JNK3 phosphorylation. This finding suggests that ERK1/2 signaling is responsible for preconditioning-induced down-regulation of JNK3 activation. Western blot analysis and immunohistochemistry further demonstrated that preconditioning, in an NMDA-dependent manner, enhanced activation of the pro-survival factors, p-CREB and Bcl-2, while attenuating activation of putative pro-death factors, p-c-Jun and Fas-L in the hippocampus CA1. As a whole, the study demonstrates that preconditioning attenuation of pro-death JNK3 in the hippocampus CA1 following global cerebral ischemia is mediated by NMDA receptor-induced crosstalk between ERK1/2 and JNK3. The ERK1/2-mediated reduction of JNK3 activation leads to enhanced pro-survival signaling (P-CREB and Bcl-2 induction) and attenuation of pro-death signaling (p-c-Jun and Fas-L), with subsequent induction of ischemic tolerance.
Assuntos
Isquemia Encefálica/prevenção & controle , Precondicionamento Isquêmico , Proteína Quinase 10 Ativada por Mitógeno/metabolismo , Proteína Quinase 3 Ativada por Mitógeno/metabolismo , Receptores de N-Metil-D-Aspartato/metabolismo , Análise de Variância , Animais , Isquemia Encefálica/patologia , Proteína de Ligação a CREB/metabolismo , Modelos Animais de Doenças , Maleato de Dizocilpina/farmacologia , Regulação para Baixo , Ativação Enzimática , Flavonoides/farmacologia , Regulação Enzimológica da Expressão Gênica/efeitos dos fármacos , Hipocampo/efeitos dos fármacos , Hipocampo/metabolismo , Marcação In Situ das Extremidades Cortadas/métodos , Masculino , Proteína Quinase 10 Ativada por Mitógeno/antagonistas & inibidores , Proteína Quinase 3 Ativada por Mitógeno/antagonistas & inibidores , Proteínas Proto-Oncogênicas c-bcl-2/metabolismo , Ratos , Ratos Sprague-Dawley , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/fisiologia , Fatores de TempoRESUMO
The purpose of this study was to enhance our understanding of the mechanisms of neuronal death after focal cerebral ischemia and the neuroprotective effects of tamoxifen (TMX). The phosphorylation state of 31 protein kinases/signaling proteins and superoxide anion (O(2)(-)) production in the contralateral and ipsilateral cortex was measured after permanent middle cerebral artery occlusion (pMCAO) in ovariectomized rats treated with placebo or TMX. The study revealed that pMCAO modulated the phosphorylation of a number of kinases/proteins in the penumbra at 2 h after pMCAO. Of significant interest, phospho-ERK1/2 (pERK1/2) was elevated significantly after pMCAO. TMX attenuated the elevation of pERK1/2, an effect correlated with reduced infarct size. In situ detection of O(2)(-) production showed a significant elevation at 1-2 h after pMCAO in the ischemic cortex with enhanced oxidative damage detected at 24 h. ERK activation may be downstream of free radicals, a suggestion supported by the findings that cells positive for O(2)(-) had high pERK activation and that a superoxide dismutase (SOD) mimetic, tempol, significantly attenuated pERK activation after MCAO. TMX treatment significantly reduced the MCAO-induced elevation of O(2)(-) production, oxidative damage, and proapoptotic caspase-3 activation. Additionally, pMCAO induced a significant reduction in the levels of manganese SOD (MnSOD), which scavenge O(2)(-), an effect largely prevented by TMX treatment, thus providing a potential mechanistic basis for the antioxidant effects of TMX. As a whole, these studies suggest that TMX neuroprotection may be achieved via an antioxidant mechanism that involves enhancement of primarily MnSOD levels, with a corresponding reduction of O(2)(-) production, and downstream kinase and caspase-3 activation.
Assuntos
Isquemia Encefálica/tratamento farmacológico , Isquemia Encefálica/metabolismo , Fosfotransferases/metabolismo , Superóxido Dismutase/metabolismo , Superóxidos/metabolismo , Tamoxifeno/farmacologia , Tamoxifeno/uso terapêutico , Animais , Encéfalo/efeitos dos fármacos , Encéfalo/enzimologia , Encéfalo/metabolismo , Isquemia Encefálica/patologia , Caspase 3/metabolismo , Citoproteção/efeitos dos fármacos , Dano ao DNA/efeitos dos fármacos , Ativação Enzimática/efeitos dos fármacos , Feminino , Infarto da Artéria Cerebral Média/patologia , Peroxidação de Lipídeos/efeitos dos fármacos , Mitocôndrias/enzimologia , Fármacos Neuroprotetores/farmacologia , Fármacos Neuroprotetores/uso terapêutico , Estresse Oxidativo/efeitos dos fármacos , Ratos , Ratos Sprague-DawleyRESUMO
In this study, we investigated whether the increase of inhibitory gamma-amino butyric acid (GABA) signal suppresses the excitatory glutamate signal induced by cerebral ischemia and the underlying mechanisms. In global cerebral ischemia, focal cerebral ischemia and oxygen-glucose deprivation, application of muscimol and baclofen, agonists of GABA(A) receptor and GABA(B) receptor, exerted neuroprotection. The agonists inhibited the increased assembly of the GluR6-PSD-95-MLK3 module induced by cerebral ischemia and the activation of the MLK3-MKK4/7-JNK3 cascade. Our results suggest that stimulation of the inhibitory GABA receptors can attenuate the excitatory JNK3 apoptotic signaling pathway via inhibiting the increased assembly of the GluR6-PSD-95-MLK3 signaling module in cerebral ischemia.
Assuntos
Apoptose , Isquemia Encefálica/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , MAP Quinase Quinase Quinases/metabolismo , Proteínas de Membrana/metabolismo , Proteína Quinase 10 Ativada por Mitógeno/antagonistas & inibidores , Receptores de GABA/metabolismo , Receptores de Ácido Caínico/metabolismo , Traumatismo por Reperfusão/metabolismo , Transdução de Sinais , Animais , Baclofeno/farmacologia , Proteína 4 Homóloga a Disks-Large , Agonistas GABAérgicos/farmacologia , Imuno-Histoquímica , Masculino , Muscimol/farmacologia , Ratos , Ratos Sprague-Dawley , MAP Quinase Quinase Quinase 11 Ativada por Mitógeno , Receptor de GluK2 CainatoRESUMO
PELP1 (proline-, glutamic acid-, and leucine-rich protein-1) is a novel estrogen receptor (ER)-interacting protein that has been implicated to be important for mediation of both the genomic and nongenomic signaling of 17beta-estradiol (E2). PELP1 contains ten nuclear receptor-interacting boxes (LXXLL motifs), which allow it to interact with ER and other nuclear hormone receptors, a zinc finger, a glutamic acid-rich domain, and two proline-rich domains. The proline-rich regions contain several consensus PXXP motifs, which allow PELP1 to couple the ER with SH3 domain-containing kinase signaling proteins, such as Src and PI3K P85 regulatory subunit. PELP1 is expressed in many different brain regions, including the hippocampus, hypothalamus, and cerebral cortex. Further work has demonstrated that PELP1 is colocalized with ER-alpha in neurons in various brain regions. PELP1 is primarily expressed in neurons, with some expression also observed in glia. Subcellular localization studies revealed that PELP1 is highly localized in the cell nucleus of neurons, with some cytoplasm localization as well, and PELP1 is also localized at synaptic sites. Work in other tissues has demonstrated that PELP1 is critical for nongenomic and genomic signaling by E2, as PELP1 knockdown studies significantly attenuates E2-induced activation of ERK and Akt signaling pathways, and inhibits E2 genomic transcriptional effects on gene expression in breast cancer cells. Preliminary studies in the brain, suggests that similar roles may exist for PELP1 in the brain, but this remains to be established, and further work to characterize the precise roles and functions of PELP1 in the brain are needed.
Assuntos
Receptores de Estrogênio/metabolismo , Transativadores/metabolismo , Animais , Humanos , Ligação Proteica , Processamento de Proteína Pós-Traducional , Estrutura Terciária de Proteína , Transativadores/química , Transativadores/genéticaRESUMO
JNK signaling pathway is activated and involved in the selective neuronal death in the hippocampal CA1 subfield following cerebral ischemia. However, little is known about upstream partner controlling the pathway. Here we reported that ischemia/reperfusion significantly elevated Cdc42 activity, enhanced assembly of the Cdc42-MLK3 complex and activation of JNK pathway. Most importantly, knock-down endogenous Cdc42 selectively suppressed the MLK3/MKK7/JNK3 cascade, and subsequently blocked the phosphorylation of c-Jun and FasL expression. Meanwhile, Bcl-2 was inactivated and the release of cytochrome c was diminished. These alterations eventually perturbed the caspase-3 activation as well as post-ischemic neuronal cell death. Taken together, our findings strongly suggest that Cdc42 serves as an upstream activator and modulates JNK-mediated apoptosis machinery in vivo, which ultimately results in neuronal apoptosis via nuclear and non-nuclear pathways. Thus, Cdc42 may be a potential therapeutic target in ischemic brain injury.
Assuntos
Apoptose , Regulação para Baixo , Hipocampo/enzimologia , MAP Quinase Quinase Quinases/antagonistas & inibidores , Proteína Quinase 10 Ativada por Mitógeno/antagonistas & inibidores , Neurônios/citologia , Proteína cdc42 de Ligação ao GTP/genética , Animais , Apoptose/efeitos dos fármacos , Isquemia Encefálica/induzido quimicamente , Isquemia Encefálica/enzimologia , Caspase 3/metabolismo , Células Cultivadas , Citocromos c/metabolismo , Regulação para Baixo/efeitos dos fármacos , Ativação Enzimática/efeitos dos fármacos , Hipocampo/citologia , Hipocampo/efeitos dos fármacos , Masculino , Neurônios/efeitos dos fármacos , Neurônios/enzimologia , Neurônios/metabolismo , Oligonucleotídeos Antissenso/farmacologia , Fosforilação/efeitos dos fármacos , Ligação Proteica/efeitos dos fármacos , Proteínas Proto-Oncogênicas c-bcl-2/metabolismo , Ratos , Ratos Sprague-Dawley , Reperfusão , Proteína cdc42 de Ligação ao GTP/antagonistas & inibidores , Proteína cdc42 de Ligação ao GTP/deficiência , MAP Quinase Quinase Quinase 11 Ativada por MitógenoRESUMO
JNK pathway is an important pro-apoptotic kinase cascade mediating cell death in response to a variety of extracellular stimuli including excitotoxicity, which results in selective and delayed neuronal death in the hippocampal CA1. On the contrary, activation of the protein kinase Akt, which is controlled by the opposing actions of PI3K and PTEN, contributes to enhanced resistance to apoptosis through multiple mechanisms. We here demonstrate that the temporal pattern of Akt activation reversely correlates with JNK1/2 activation following various time points of ischemic reperfusion. However, the activation of JNK1/2 could be decreased by the elevation of Akt activation via increasing the tyrosine phosphorylation of PTEN by bpv(pic), a potent PTPases inhibitor for PTEN, or by intracerebroventricular infusion of PTEN antisense oligodeoxynucleotides (AS-ODNs). In contrast, JNK1/2 activation was significantly increased by preventing PTEN degradation after pretreatment with proteasome inhibitor. The neuroprotective effects of bpv(pic) and PTEN AS-ODNs were significant in the CA1 subfield after transient global ischemia. In conclusion, the present results clearly show that PTEN plays a key regulatory role in the cross-talk between cell survival PI3K/Akt pathway and pro-death JNK pathway, and raise a new possibility that agents targeting phosphatase PTEN may offer a great promise to expand the therapeutic options in protecting neurons form ischemic brain damage.
Assuntos
Isquemia Encefálica/metabolismo , Proteína Quinase 8 Ativada por Mitógeno/metabolismo , Proteína Quinase 9 Ativada por Mitógeno/metabolismo , PTEN Fosfo-Hidrolase/metabolismo , Fosfatidilinositol 3-Quinases/metabolismo , Proteínas Proto-Oncogênicas c-akt/metabolismo , Animais , Sequência de Bases , Isquemia Encefálica/tratamento farmacológico , Isquemia Encefálica/genética , Isquemia Encefálica/patologia , Sobrevivência Celular/efeitos dos fármacos , Ativação Enzimática/efeitos dos fármacos , Hipocampo/efeitos dos fármacos , Hipocampo/metabolismo , Hipocampo/patologia , Masculino , Fármacos Neuroprotetores/farmacologia , Oligodesoxirribonucleotídeos Antissenso/genética , Oligodesoxirribonucleotídeos Antissenso/farmacologia , Compostos Organometálicos/farmacologia , PTEN Fosfo-Hidrolase/antagonistas & inibidores , PTEN Fosfo-Hidrolase/genética , Fosforilação , Inibidores de Proteases/farmacologia , Ratos , Ratos Sprague-Dawley , Transdução de SinaisRESUMO
Cerebral ischemia induces kainate receptor glutamate receptor 6 (GluR6) binding to the postsynaptic density protein 95 (PSD95), which in turn anchors mixed lineage kinase 3 (MLK3) via SH3 domain in rat brain. MLK3 subsequently activates c-Jun NH(2)-terminal kinase (JNK) via MAP kinase kinases (MKKs). In this study, we investigated the association of PSD95 with GluR6 and MLK3, the autophosphorylation of MLK3, the combination of MLK3 with JNK3, and the phosphorylation of JNK3 during cerebral ischemia in rat hippocampus CA1. Our results indicate that the GluR6-PSD95-MLK3 complex quickly enhanced at 5 min of ischemia and peaked at 10 min of ischemia, and then gradually reduced with the prolonged time of ischemia. Interestingly, the combination of MLK3 and JNK3 gradually increased from 5 min to 30 min of ischemia. JNK3 phosphorylation first increased and then attenuated in cytosol, suggesting the translocation of activated JNK3 to nucleus during ischemia. To further investigate the possible mechanism of JNK3 activation, antioxidant N-acetylcysteine (NAC) was given to the rats 20 min prior to ischemia. Results indicate that NAC distinctly inhibited the association of PSD95 with GluR6 and MLK3, the autophosphorylation of MLK3, the combination of MLK3 with JNK3 and JNK3 activation. Taken together, these finding indicate that ischemic stimulation results in JNK3 activation through the GluR6-PSD95-MLK3 signaling module, and that the activation of JNK3 is closely related to oxidative stress.
Assuntos
Acetilcisteína/farmacologia , Antioxidantes/farmacologia , Isquemia Encefálica/patologia , Hipocampo/efeitos dos fármacos , Proteína Quinase 10 Ativada por Mitógeno/metabolismo , Transdução de Sinais/efeitos dos fármacos , Acetilcisteína/uso terapêutico , Animais , Antioxidantes/uso terapêutico , Western Blotting , Isquemia Encefálica/tratamento farmacológico , Modelos Animais de Doenças , Proteína 4 Homóloga a Disks-Large , Ativação Enzimática/efeitos dos fármacos , Regulação da Expressão Gênica/efeitos dos fármacos , Humanos , Imunoprecipitação/métodos , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , MAP Quinase Quinase Quinases/metabolismo , Masculino , Proteínas de Membrana/metabolismo , Ratos , Ratos Sprague-Dawley , Receptores de Ácido Caínico/metabolismo , Fatores de Tempo , MAP Quinase Quinase Quinase 11 Ativada por Mitógeno , Receptor de GluK2 CainatoRESUMO
Over-activation of ionotropic glutamate receptors can cause an excessive influx of calcium ions into neurons, which subsequently triggers the degeneration and death of cells in a process known as excitotoxicity. Here, we examined the effects of modulating ionotropic glutamate receptors and L-type voltage-gated calcium channels (L-VGCC) on the expression and activation of c-Jun in hippocampus of SD rats after transient global ischemia. The total protein of c-Jun was altered by ischemia-reperfusion and reached its high levels at 3-6 h of reperfusion. However, the increased expression was prevented by pretreatment of ketamine (a non-competitive N-methyl-D-aspartate (NMDA) receptors antagonist) or nifedipine (a blocker of L-VGCC), but not by 6,7-dinitroquinoxaline-2,3(1H,4H)-dione (DNQX), an AMPA/KA receptor antagonist. On the other hand, c-Jun phosphorylation was significantly increased 3 h after reperfusion, which was inhibited by DNQX, but not ketamine or nifedipine. AP-1 binding activity reactions were also performed by electrophoretic mobility shift assay (EMSA), which detected similar results as those in Western blotting. Our results clearly showed that c-Jun expression is NMDA receptor/L-VGCC-dependent and c-Jun activation is AMPA/KA receptor-dependent, which expands our knowledge of the JNK-c-Jun signaling pathway in ischemic brain damage.
Assuntos
Canais de Cálcio Tipo L/fisiologia , Hipocampo/metabolismo , Ataque Isquêmico Transitório/metabolismo , Proteínas Quinases JNK Ativadas por Mitógeno/metabolismo , Receptores de AMPA/fisiologia , Receptores de Ácido Caínico/fisiologia , Receptores de N-Metil-D-Aspartato/fisiologia , Animais , Bloqueadores dos Canais de Cálcio/farmacologia , Estenose das Carótidas/complicações , Ativação Enzimática , Ataque Isquêmico Transitório/etiologia , Proteínas Quinases JNK Ativadas por Mitógeno/biossíntese , Ketamina/farmacologia , Masculino , Nifedipino/farmacologia , Fosforilação , Ligação Proteica , Quinoxalinas/farmacologia , Ratos , Ratos Sprague-Dawley , Receptores de AMPA/antagonistas & inibidores , Receptores de Ácido Caínico/antagonistas & inibidores , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores , Reperfusão , Fator de Transcrição AP-1/metabolismoRESUMO
Post-ischemic activation of NMDA receptors (NMDARs) has been linked to NMDAR subunit-specific signaling that mediates pro-survival or pro-death activity. Although extensive studies have been performed to characterize the role of GluN2A and GluN2B following ischemia, there is less understanding regarding the regulation of GluN2C. Here, we show that GluN2C expression is increased in acute hippocampal slices in response to ischemia. Strikingly, GluN2C knockout mice, following global cerebral ischemia, exhibit greater neuronal death in the CA1 area of the hippocampus and reduced spatial working memory compared to wild-type mice. Moreover, we find that GluN2C-expressing hippocampal neurons show marked resistance to NMDA-induced toxicity and reduced calcium influx. Using both in vivo and in vitro experimental models of ischemia, we demonstrate a neuroprotective role of GluN2C, suggesting a mechanism by which GluN2C is upregulated to promote neuronal survival following ischemia. These results may provide insights into development of NMDAR subunit-specific therapeutic strategies to protect neurons from excitotoxicity.
Assuntos
Isquemia Encefálica/metabolismo , Sinalização do Cálcio , Regulação da Expressão Gênica , Hipocampo/metabolismo , Neurônios/metabolismo , Neuroproteção , Receptores de N-Metil-D-Aspartato/biossíntese , Animais , Isquemia Encefálica/genética , Isquemia Encefálica/patologia , Morte Celular , Hipocampo/patologia , Masculino , Camundongos , Camundongos Knockout , Neurônios/patologia , Ratos , Ratos Sprague-Dawley , Receptores de N-Metil-D-Aspartato/genéticaRESUMO
Current studies demonstrated that cell survival is determined by a balance among signaling cascades, including those that recruit the Akt and JNK pathways. In our present work, the relationship between Akt1 and JNK1/2 was evaluated after cerebral ischemia-reperfusion in the hippocampus in a four-vessel occlusion model of Sprague-Dawley rats. This paper was based on our present and previous studies. Firstly, Akt1 had one active peak during reperfusion following 15 min ischemia. Secondly, two peaks of JNK1/2 activation occurred during reperfusion, respectively. Thirdly, the phosphorylation of JNK substrates c-Jun and Bcl-2, and the activation of a key protease of caspase-3 were detected. They only had one active peak, respectively, during reperfusion. To clarify the mechanism of Akt1 activation and further define whether JNK1/2 activation could be regulated by Akt1 through PI3K pathway, LY294002 and insulin were, respectively, administrated to the rats prior to ischemia. Our research indicated that LY294002, a PI3K inhibitor, significantly suppressed Akt1 activation. Furthermore, LY294002 significantly strengthened both peaks of JNK1/2 activation, c-Jun activation, Bcl-2 phosphorylation, and the activation of caspase-3 during reperfusion. In contrast, insulin, a PI3K agonist, not only obviously activated Akt1 during early and later reperfusion, but also inhibited phosphorylation of JNK1/2, c-Jun, and Bcl-2 and attenuated the activation of caspase-3. In addition, pretreatment of insulin significantly increased the number of the surviving CA1 pyramidal cells at 5 days of reperfusion. Consequently, our results indicated that the cross-talk between Akt1 and JNK1/2 could be mediated by insulin receptor through PI3K in rat hippocampus during reperfusion. This signaling pathway might play a neuroprotective role against ischemic insults via inhibition of the JNK pathway, involving the death effector of caspase-3.