Iduna在Aβ诱导大鼠星型胶质细胞损伤中的作用

目的:脑组织β-淀粉样蛋白(Aβ)沉积是阿尔茨海默病重要的病理特征。传统认为Aβ沉积能够诱导神经元凋亡。最近发现Aβ沉积同样能够诱导星型胶质细胞凋亡。Iduna是新近发现的内源性神经保护基因。本文的研究目的是探索Iduna在Aβ所致星型胶质细胞损伤机制中的作用。方法:采用大鼠神经胶质瘤细胞株C6进行细胞培养,细胞密度达到80%时传代培养。细胞随机分为对照组和Aβ组,经MTT法、比色法、Western Blot等实验方法,检测Aβ所致C6细胞损伤时细胞培养上清中的超氧化物歧化酶(SOD)活性、丙二醛(MDA)含量和C6细胞中聚腺苷酸二磷酸核糖转移酶-1(PARP1)通路内的Iduna蛋白的表达。结果:与对照组比较,Aβ组中Aβ能够增加C6细胞培养上清液中MDA含量,降低SOD活性;同时,Aβ可下调C6细胞中PARP1通路内的Iduna蛋白的表达。结论:Aβ引起星型胶质细胞损伤可能与神经保护因子Iduna下调从而引起PARP1死亡通路激活有关。     

星型胶质细胞对神经元调控的研究进展

神经系统的细胞主要由神经元和神经胶质细胞组成。人脑中神经元的总数约为1010~1012个。在脑内,神经元被神经胶质细胞紧紧包围,神经胶质细胞数量是神经元的10~50倍,约占据脑体积的一半,其中主要是星型胶质细胞(astrocytes,AS)。在视皮层,AS占整个神经胶质细胞的61·5%;在丘脑占     

DXM对大鼠星型胶质细胞P53和Bax表达的影响

目的探讨DXM(地塞米松dexamethasone)引起体外纯化培养的大鼠大脑皮质星型胶质细胞凋亡的机制。方法出生1～2 d的新生Wistar大鼠,在无菌条件下取脑,胰蛋白酶消化数分钟,制备星形胶质细胞悬液,以神经胶质纤维酸性蛋白(GFAP)鉴定星形胶质细胞;用不同浓度的DXM(浓度为10-5、10-4、10-3 mol/L)与纯化培养的大鼠大脑皮质星形胶质细胞共同孵育24 h后,用免疫细胞化学方法检测P53、Bax在星型胶质细胞内的表达情况,表达的强弱用平均光密度表示。结果星形胶质细胞的纯度达95%以上,P53和Bax的表达随着DXM浓度的升高而增强,与对照组比较各组均有极显著性差异(P0.01)。结论上述结果提示P53和Bax的表达增强可能是大剂量DXM引起星型胶质细胞凋亡的主要因素。     

姜黄素对缺氧下大鼠星型胶质细胞的影响及机制研究

目的：探讨姜黄素对缺氧条件下大鼠星型胶质细胞活力、细胞凋亡率及JAK2/STAT3信号通路的影响。方法：从大鼠大脑皮层分离培养星形胶质细胞,姜黄素干预缺氧条件星形胶质细胞,AG490作为JAK2/STAT3信号通路抑制剂,细胞缺氧处理24 h后,通过MTT法检测各组细胞活力;流式细胞术检测细胞凋亡率;Western blot检测凋亡蛋白B细胞淋巴瘤/白血病-2（Bcl-2）、Bcl-2相关X蛋白(Bax)、JAK2/STAT3信号通路磷酸化的蛋白酪氨酸激酶2（p-JAK2）及磷酸化的信号转导与转录因子3(p-STAT3)的蛋白表达。结果：与对照组比较,缺氧组细胞活力显著升高,凋亡率显著升高,Bcl-2蛋白表达显著降低,Bax、p-JAK2和p-STAT3的蛋白表达显著升高（P<0.05）;与缺氧组比较,缺氧+姜黄素组胞活力显著降低,凋亡率显著降低,Bcl-2蛋白表达显著升高,Bax、p-JAK2和p-STAT3的蛋白表达显著降低（P<0.05）;与缺氧+姜黄素组比较,缺氧+姜黄素组+AG490组细胞活力显著降低,细胞凋亡率显著降低,Bcl-2蛋白表达显著升高,Bax、p-JAK2和p-STAT3的蛋白表达显著降低（P<0.05）。结论：姜黄素可降低缺氧下大鼠星型胶质细胞活力,抑制细胞凋亡,其机制与JAK2/STAT3信号通路有关。     

谷氨酸影响星形胶质细胞表达神经生长因子的实验研究

本文利用双向ＥＬＩＳＡ 法定量检测体外培养乳鼠大脑皮质星形胶质细胞在不同浓度的谷氨酸条件培养基中ＮＧＦ的表达分泌量,观察谷氨酸的调节作用,并利用氯胺酮或ＥＧＴＡ 限制谷氨酸ＮＭ ＤＡ 型受体介导的钙离子内流,观察谷氨酸调节作用的改变。结果表明：体外培养的星状胶质细胞２４ ｈ 能表达分泌ＮＧＦ ３．１２３ ｐｇ／１０５ 细胞;１０ μｍ ｏｌ／Ｌ～１ ｍ ｍ ｏｌ／Ｌ的谷氨酸能显著促进ＮＧＦ表达,其中以１００ μｍ ｏｌ／Ｌ的谷氨酸作用为最强,而１０ ｍ ｍ ｏｌ／Ｌ 的谷氨酸反而起抑制作用;限制谷氨酸ＮＭＤＡ 型受体介导的钙离子内流,能消除谷氨酸的这种调节作用。结果提示：谷氨酸可因其浓度不同促进或抑制星形胶质细胞表达ＮＧＦ,这种调节作用可能通过其ＮＭ ＤＡ 受体介导的钙离子内流来实现。     

多巴胺通过mTOR-EAAT2通路影响星形胶质细胞谷氨酸摄取能力

目的:研究多巴胺(dopamine,DA)对星形胶质细胞谷氨酸(glutamate,Glu)摄取能力的影响,以及DA通过哺乳动物雷帕霉素靶蛋白(m TOR)-兴奋性氨基酸转运体2(EAAT2)信号通路对星形胶质细胞Glu摄取能力的影响。方法:采用Amplex Red谷氨酸测定试剂盒检测经过干预的原代皮层星形胶质细胞对Glu摄取含量的变化,RT-q PCR、Western blot和免疫荧光染色等检测EAAT2和m TOR mRNA和蛋白质相对表达量,m TOR拮抗剂雷帕霉素或m TOR兴奋剂MHY1485干预在DA中共培养的星形胶质细胞,检测m TOR和EAAT2的表达情况,以及培养上清液Glu的含量。结果:DA干预的原代星形胶质细胞中m TOR表达下调,EAAT2表达下调,培养上清液Glu水平上升;雷帕霉素干预后,EAAT2表达下调,培养上清液中Glu的含量增加;MHY1485干预后,EAAT2表达上调,培养上清液中Glu的含量下降。结论:DA通过与星形胶质细胞m TOR-EAAT2通路相互作用,减弱星形胶质细胞摄取Glu的能力,引起细胞外Glu蓄积,最终损伤星形胶质细胞的功能。     

氧气葡萄糖剥夺诱导原代培养的星形胶质细胞释放谷氨酸

目的观察氧气葡萄糖剥夺(OGD)对原代培养的星形胶质细胞谷氨酸释放的影响,并探讨其释放机制。方法原代培养SD大鼠海马区星形胶质细胞,将其分为OGD组和对照组。OGD组的细胞置于不含糖和氧的培养基,37℃,950 mL/L N2和50 mL/L CO2,饱和湿度的培养环境下培养,而对照组细胞则正常培养。缺糖缺氧刺激时长分别为0、15、30、60、90、120 min,采用高效液相色谱,测定细胞外液的谷氨酸浓度。分别选用连接子蛋白43(Cx43)特异性反义寡核苷酸(Cx43-ASODN)和Cx43半通道的阻断剂Gap26预处理星形胶质细胞,采用高效液相色谱,测定细胞外液谷氨酸浓度,观察OGD对其谷氨酸释放的影响。结果与对照组相比较,OGD刺激后,细胞外液谷氨酸浓度升高,并在刺激90 min后,达到峰值,为(5.00±0.30)nmol/mL,显著高于对照组的(2.36±0.15)nmol/mL(P0.05);而OGD条件下,Cx43-ASODN或Cx43半通道阻断剂均可抑制细胞外液谷氨酸浓度的升高,刺激90 min后,细胞外液谷氨酸浓度分别为(4.02±0.18)nmol/mL和(3.93±0.32)nmol/mL,显著低于单纯OGD刺激组(P0.05)。结论 OGD可以诱导星形胶质细胞通过Cx43半通道释放谷氨酸。     

缺氧缺血性脑损伤后谷氨酸水平变化对少突胶质细胞的损伤

谷氨酸是哺乳动物中枢神经系统主要的兴奋性氨基酸,生理状态时,对中枢神经系统各种细胞的发育成熟具有重要作用。但在新生儿缺氧缺血性脑损伤(Hypoxic-Ischemic Brain Damage,HIBD)等病理情况下,脑室周围谷氨酸浓度升高,过度激活少突胶质细胞上的谷氨酸受体,导致少突胶质细胞损伤、死亡,继而使脑室周围白质软化,进一步引起HIBD患儿髓鞘化障碍,造成认知能力下降和远期行为学异常。本文主要综述谷氨酸对生理状态少突胶质细胞迁徙分化的影响及病理情况谷氨酸受体过度激活介导的少突胶质细胞损伤及机制。     

活化的星型胶质细胞生成Aβ对阿尔茨海默病的影响

在阿尔茨海默病(AD)发病机制中,Aβ起着中心作用。尽管神经元是大脑中Aβ的主要来源,但星型胶质细胞的数量至少是神经元的5倍,因此在AD中星型胶质细胞产生的Aβ,即使是低水平的,也起着重大的作用。此外,活化的星型胶质细胞可使Aβ生成明显增加。位点APP裂解酶1(BACE1)裂解APP导致发Aβ的生成。为了探索是否促炎症细胞因子或者Aβ42     

激活的星形胶质细胞分泌的TNF-α对大鼠离子型谷氨酸受体1表达的影响

目的探讨星形胶质细胞在癫痫发病中的作用。方法选用肿瘤坏死因子TNF-α(TNF-α)刺激及TNF-α反义寡核苷酸阻断后马桑内酯(CL)刺激纯化培养的海马星形胶质细胞,将这两种条件培养基提取液(ACM)10μl分别注入正常大鼠侧脑室,观察动物行为与脑电图的变化;用免疫细胞化学方法检测大脑皮质与海马中离子型谷氨酸受体(NMDARI)表达水平的改变,并做显微图像分析。结果1．侧脑室注射肿瘤坏死因子TNF-α刺激后的条件培养基提取液可引起大鼠Ⅲ级癫痫样发作及典型的尖波、棘波、棘-慢波癫痫样脑电图表现,大脑前梨状皮质和海马CA1区NMDAR1免疫反应阳性神经元数和平均光密度值均明显高于对照组;2．侧脑室注射TNF-α反义寡核苷酸阻断后由马桑内酯刺激的条件培养基提取液,大鼠无癫痫样行为发生,大脑前梨状皮质和海马CA1区NMDAR1免疫反应阳性神经元数和平均光密度值与对照组无显著性差异。结论1．激活的星形胶质细胞分泌的TNF-α可诱导大鼠癫痫发作。2．NMDAR1表达的变化可能与癫痫发作有关。     

Amyloid-beta peptide decreases glutamate uptake in cultured astrocytes: involvement of oxidative stress and mitogen-activated protein kinase cascades

Alzheimer's disease (AD) is a progressive neurodegenerative disorder primarily characterized by excessive deposition of amyloid-beta (Abeta) peptides in the brain. One of the earliest neuropathological changes in AD is the presence of a high number of reactive astrocytes at sites of Abeta deposition. Disturbance of glutamatergic neurotransmission and consequent excitotoxicity is also believed as implicated in the progression of this dementia. Therefore, the study of astrocyte responses to Abeta, the main cellular type involved in the maintenance of synaptic glutamate concentrations, is crucial for understanding the pathogenesis of AD. This study aims to investigate the effect of Abeta on the astrocytic glutamate transporters, glutamate transporter-1 (GLT-1) and glutamate-aspartate transporter (GLAST), and their relative participation to glutamate clearance. In addition we have also investigated the involvement of mitogen-activated protein (MAP) kinases in the modulation of GLT-1 and GLAST levels and activity and the putative contribution of oxidative stress induced by Abeta to the astrocytic glutamate transport function. Therefore, we used primary cultures of rat brain astrocytes exposed to Abeta synthetic peptides. The data obtained show that Abeta(1-40) peptide decreased astroglial glutamate uptake capacity in a non-competitive mode of inhibition, assessed in terms of tritium radiolabeled d-aspartate (d-[(3)H]aspartate) transport. The activity of GLT-1 seemed to be more affected than that of GLAST, and the levels of both transporters were decreased in Abeta(1-40)-treated astrocytes. We demonstrated that MAP kinases, extracellular signal-regulated kinase (ERK), p38 and c-Jun N-terminal kinase, were activated in an early phase of Abeta(1-40) treatment and the whole pathways differentially modulated the glutamate transporters activity/levels. Moreover it was shown that oxidative stress induced by Abeta(1-40) may lead to the glutamate uptake impairment observed. Taken together, our results suggest that Abeta peptide downregulates the astrocytic glutamate uptake capacity and this effect may be in part mediated by oxidative stress and the differential activity and complex balance between the MAP kinase signaling pathways.     

Protective effect of epidermal growth factor on glutamate neurotoxicity in cultured cerebellar neurons.

The effects of epidermal growth factor (EGF) on glutamate-induced neuronal death were investigated in primary cultures of dissociated cerebellar neurons from fetal rats. Addition of an excess concentration of L-glutamate (5 mM) to the culture medium greatly decreased the number of surviving neurons 24 h later. When EGF was added to the culture medium 20 h prior to exposure to glutamate, glutamate-induced neuronal death was significantly reduced. The protective effects of EGF on glutamate neurotoxicity were concentration-dependent in the range of 0.01-10 ng/ml. When EGF was added 1 h prior to exposure to glutamate, it did not prevent glutamate-induced neuronal death, indicating that a longer exposure period is required for EGF to exert its protective effects. Furthermore, the protective effects of EGF on glutamate neurotoxicity disappeared in the presence of cycloheximide (0.1 microM), a protein synthesis inhibitor. These results suggest that EGF can protect brain neurons against glutamate toxicity through some protein synthesis.     

Glutamate transporter blockade affects Ca(2+) responses in astrocytes

Brief pretreatment of astrocytes in culture with glutamate (500 microM for 20 min), was earlier shown to significantly enhance the Ca(2+) responses to a depolarizing pulse. It is known that malfunction of glutamate transporters increases extracellular glutamate concentration. We hypothesized that pretreatment of astrocytes with glutamate in conditions where the glutamate transporter activity is blocked should cause further elevation of the Ca(2+) responses to a depolarizing pulse. To test the hypothesis we pretreated astrocytes in culture (primary rat astrocyte cultures) with glutamate (500 microM) and glutamate transport inhibitor, threo-beta-hydroxy-aspartate (200 microM, TBHA) or glutamate (500 microM) in Na(+) free extracellular solution for 20 min. The Ca(2+) responses were elicited by depolarization of the astrocyte to evoke voltage-gated Ca(2+) currents. Paradoxical attenuation of the Ca(2+) transients was observed when the glutamate pretreatment was done in conditions that blocked glutamate transport, accompanied by faster rise and decay times. When the experiments were done on astrocyte pairs that were pretreated with glutamate and TBHA, we observed attenuated Ca(2+) responses in the adjoining cell when compared with the depolarized cell. The results were contrary to our earlier observation of heightened responses in the adjoining cell of the astrocyte pair, in cells pretreated with glutamate alone. The attenuated Ca(2+) responses in astrocytes would imply decrease in the vesicular release of glutamate and ATP. Extracellular glutamate concentration dependent regulation of the Ca(2+) signaling mechanism thus seems to operate in astrocytes, which may be important in regulating the neurotoxic accumulation of glutamate in the extracellular space and the synapse.     

神经生长因子对谷氨酸介导的基底核神经元损伤的保护作用

本研究的目的是观察神经生长因子(nerve growth factor,NGF)对谷氨酸诱导的基底核神经元损伤的保护作用。取出生后1d乳鼠前脑基底核神经元培养,随机分为正常对照组、模型组(谷氨酸损伤组)和NGF保护组。用倒置相差显微镜进行活细胞观察,采用RT-PCR技术检测前脑基底核神经元的神经生长相关蛋白-43(growth associated protein-43,GAP-43)的表达。结果显示谷氨酸损伤组神经元胞体回缩,突起消失或断裂。NGF保护组的神经元绝大多数胞体饱满,突起明显,细胞间的网络联系仍清晰可见,接近于正常对照组;NGF保护组神经元内GAP-43mRNA表达比谷氨酸损伤组高,两者比较有统计学意义(P<0.05)。结果提示,NGF能保护基底核神经元免受谷氨酸兴奋性毒性的损伤。     

Synaptic modulation by astrocytes via Ca2+-dependent glutamate release

In the past 15 years the classical view that astrocytes play a relatively passive role in brain function has been overturned and it has become increasingly clear that signaling between neurons and astrocytes may play a crucial role in the information processing that the brain carries out. This new view stems from two seminal observations made in the early 1990s: 1. astrocytes respond to neurotransmitters released during synaptic activity with elevation of their intracellular Ca2+ concentration ([Ca2+]i); 2. astrocytes release chemical transmitters, including glutamate, in response to [Ca2+]i elevations. The simultaneous recognition that astrocytes sense neuronal activity and release neuroactive agents has been instrumental for understanding previously unknown roles of these cells in the control of synapse formation, function and plasticity. These findings open a conceptual revolution, leading to rethink how brain communication works, as they imply that information travels (and is processed) not just in the neuronal circuitry but in an expanded neuron-glia network. In this review we critically discuss the available information concerning: 1. the characteristics of the astrocytic Ca2+ responses to synaptic activity; 2. the basis of Ca2+-dependent glutamate exocytosis from astrocytes; 3. the modes of action of astrocytic glutamate on synaptic function.     

Protective effect of serofendic acid on glutamate-induced neurotoxicity in rat cultured motor neurons

We have previously reported that a sulfur-containing neuroprotective substance named serofendic acid was purified and isolated from lipophilic extract of fetal calf serum (FCS). In the present study, we investigated the effect of serofendic acid on glutamate neurotoxicity using embryonic rat spinal cord culture. When cultures were exposed to glutamate (20 microM) with a glutamate transporter inhibitor L-trans-pyrrolidine-2,4-decarboxylate (PDC; 40 microM) for 24 h, motor neurons were injured through both N-methyl-D-aspartate and alpha-amino-3-hydroxy-5-methylisoxazole/kainate receptors. This glutamate neurotoxicity was attenuated by nitric oxide (NO) synthase inhibitors. Serofendic acid (0.1-5 microM) prevented glutamate neurotoxicity in a concentration-dependent manner. S-Nitrosocysteine (SNOC; 10 microM), an NO donor, induced motor neuronal death. Serofendic acid (5 microM) also prevented SNOC-induced neurotoxicity. These results indicate that serofendic acid protects cultured motor neurons from glutamate neurotoxicity by reducing the cytotoxic action of NO.     

Protective effect of metabotropic glutamate receptor inhibition on amyotrophic lateral sclerosis-cerebrospinal fluid toxicity in vitro

Conflicting results have been reported concerning the toxicity of cerebrospinal fluid from patients with amyotrophic lateral sclerosis (ALS-CSF) when added to neuronal cultures. The possible toxic factor(s) and the exact mode of action (e.g. requirement of glial cells) have not been identified so far. Glutamate is a potential candidate for this toxic effect, since antagonists of ionotropic glutamate receptors have been shown to attenuate ALS-CSF toxicity. We studied the effects of ALS-CSF on mixed and motoneuron-enriched chick embryonic spinal cord cultures. We found a toxic action of ALS-CSF in both culture types which could not be attenuated by 5 kDa-filtration or 15 min 90 degrees C heating. Nevertheless, the metabotropic glutamate receptor (mGluR) group I antagonist 1-aminoindan-1,5-dicarboxylic acid, but also the group I agonist (s)-3,5-dihydroxyphenylglycine (DHPG) exerted protective effects against ALS-CSF toxicity. In this experimental setting, DHPG may functionally act via a receptor blockade due to sustained activation. No protective effect was seen with the mGluR group III inhibitor (RS)-alpha-cyclopropyl-4-phosphonophenylglycine (CPPG). Addition of DHPG did not increase the protective action of the AMPA inhibitor 6-chloro-4-hydroxyquinoline-2-carboxylic acid (6-CKU). Addition of l-glutamate did not mimic these toxic ALS-CSF effects in motoneuron-enriched cultures. Our experiments demonstrate that ALS-CSF toxicity is mediated by a small heat-resistant molecule which may act directly on neurons. Since blockade of group I mGluRs exerts a protective effect, the possibility of targeting these mGluRs pharmacologically in motoneuron disease should be kept in mind.     

Role of protein kinase C in Ca2+ homeostasis disorders in cultured rat neurons during hyperstimulation of glutamate receptors

The primary culture of rat cerebellar neurons was used to study protein kinase C activity, intracellular variations in calcium concentration ([Ca²⁺]_i), changes in the mitochondrial potential, and neuronal death during hyperstimulation of glutamate receptors and after 24-h incubation with phorbol ester. Prolonged exposure of neurons to glutamate (100 μM, 45 min) was followed by the development of delayed calcium dysregulation. Protein kinase C activity depended on the time of cell incubation with glutamate. Protein kinase C activity increased in response to application of glutamate for 15 min. However, protein kinase C activity decreased after 45-min exposure to glutamate and development of delayed calcium dysregulation. Protein kinase C activity was nearly undetected after 24-h preincubation of neurons with phorbol ester. Under these conditions, delayed calcium dysregulation developed more slowly and was observed in a smaller number of neurons. Neuronal death decreased to 2±1%. Our results suggest that protein kinase C plays an important role in death of neurons, which exhibit delayed calcium dysregulation during glutamate treatment. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 145, No. 5, pp. 533–537, May, 2008     

Depolarization of cultured astrocytes by glutamate and aspartate

The excitatory transmitter substances glutamate and aspartate are known to have a depolarizing action on cultured CNS neurones, the depolarization being associated with an increase in membrane conductance. When the effects of these amino acids (at a concentration of 10^?4 M) were studied on the membrane potential and resistance of cultured glial cells, they also caused a depolarization of many astrocytes but without producing significant changes in membrane resistance. The majority of glial cells depolarized by glutamate and aspartate were lying in the vicinity of neurones in the dense zone of the cultures, whereas isolated astrocytes in the outgrowth zone were usually not affected by the amino acids. 4-Aminopyridine (5 mM), a substance known to block K⁺-conductance in various excitable membranes, reversibly reduced or abolished the depolarization caused by glutamate and aspartate on glial cells, but had no or only a small effect on the depolarization of neurones caused by these amino acids.These results suggest that the depolarization of glial cells by glutamate and aspartate is caused by an increase in the concentration of extracellular K⁺ which is released from neighbouring neurones during their activation by the amino acids.