白介素-6保护小脑颗粒神经元抗谷氨酸的神经毒性作用

目的：探讨白介素-6（IL-6）对谷氨酸诱导的神经元损伤的防治作用及其作用机制。方法：用IL-6慢性预处理培养的小脑颗粒神经元,然后后用谷氨酸急性刺激小脑颗粒神经元。用噻唑兰（MTT）比色法和末端脱氧核苷酸转移酶介导的原位缺口末端标记（TUNEL）法分别观察神经元的功能和凋亡的变化;用激光扫描共聚焦显微镜（LSCM）和逆转录聚合酶链式反应（RT—PCR）法分别检测神经元内Ca^2＋浓度的动态变化和IL-6信号转导蛋白gp130 mRNA的表达。结果：IL-6（2．5、5和10ng／ml）慢性预处理培养的小脑颗粒神经元,可浓度依赖性地改善谷氨酸诱导的神经元活性降低;并可明显减少谷氨酸诱导的神经元凋亡;还可显著抑制谷氨酸激发的神经元内Ca^2＋超载。此外。经IL-6慢性预处理的小脑颗粒神经元表达gp130mRNA明显低于未经IL-6预处理的神经元。结论：IL-6能保护神经元抵抗由谷氨酸诱导的兴奋毒性作用,IL-6的这种神经保护机制可能与它抑制神经元内Ca^2＋超载密切相关,而且可能由gp130细胞内信号转导途径介导。     

活性氧在谷氨酸兴奋性神经毒性中的作用

活性氧在谷氨酸兴奋性神经毒性中的作用易永杨祥良徐辉碧（华中理工大学化学系,武汉４３００７４）关键词谷氨酸兴奋性毒性活性氧作为神经递质的谷氨酸贮存于神经末梢突触囊泡内,随神经冲动由钙内流介导释放到突触间隙,尔后作用于突触后膜的谷氨酸受体,在中枢神经系统...     

EPC—K1防止ONOO^—诱导的小脑颗粒神经元凋亡

荧光显微镜观察及ＥＬＩＳＡ分析表明１０μｍｏｌ／Ｌ过氧化亚硝基可诱导原代培养的大鼠小脑颗粒神经元凋亡。应用ＥＳＲ自旋标记技术研究了这一过程中细胞膜生物物理特性的变化,结果表明神经细胞经过氧化亚硝基处理后,细胞膜表层及深层流动性均显著下降,膜蛋白巯基强弱固定化比值增加,维生素Ｃ、维生素Ｅ的衍生物Ｌ－抗坏血酸２－（３,４－二氢－２,５,７,８－四甲基－２－（４,８,１２－三甲基十三烷基）－２Ｈ－１－苯     

LINGO-1-Fc蛋白对低钾诱导小脑颗粒神经元凋亡的保护作用

髓鞘抑制因子Nogo-A、MAG和OMgp通过共同的受体信号复合物NgR/p75NTR(或者TROY)发挥对中枢神经纤维再生的抑制作用.新近克隆的跨膜蛋白LINGO-1是该信号途径的另一个重要组成成分和调节分子.LINGO-1特异表达于中枢神经系统,神经元上的LINGO-1被证明参与调节中枢神经再生的抑制信号,而少突胶质细胞表达的LINGO-1分子参与负调节少突胶质细胞的髓鞘化过程.为探讨LINGO-1分子在神经元凋亡过程中的作用,利用包含LINGO-1分子胞外段LRR和IgC2结构域的Fc融合蛋白作为功能性拮抗剂,研究LINGO-1对低钾诱导的小脑颗粒神经元凋亡的保护作用.利用成熟的Hoechst标记凋亡细胞的方法,观察到经LINGO-1-Fc蛋白预处理2h能够显著阻止小脑颗粒神经元的凋亡.仅包括LRR结构域的GST-LINGO-1与LINGO-1-Fc蛋白,虽同样具有与颗粒神经元的结合活性,但是GST-LINGO-1不能有效地阻止低钾诱导的细胞凋亡.这些结果提示,LINGO-1-Fc蛋白能够阻止低钾诱导的小脑颗粒神经元凋亡,并且这种作用可能是IgC2结构域依赖的.     

谷氨酸对原代培养海马神经元的兴奋特性

目的:探索谷氨酸对培养大鼠海马神经元的兴奋特性.方法:分离及培养1日龄SD大鼠海马神经元,第9～15 d用膜片钳检测不同浓度谷氨酸对神经元兴奋特性,包括细胞膜电位、去极化/动作电位的影响.结果:谷氨酸降低海马神经元静息膜电位,诱发去极化/动作电位,高浓度谷氨酸处理组神经元的静息膜电位比低浓度组降低显著;100μmol/L谷氨酸长时间处理组的神经细胞膜电位显著低于短时间处理组.结论:谷氨酸对海马神经元兴奋性有浓度和时间依赖性.     

地塞米松对大白鼠海马兴奋性神经元和抑制性神经元的影响

为了探讨糖皮质激素对海马兴奋性神经元和抑制性神经元的作用,本实验将地塞米松注入大白鼠侧脑室,２ｈ 后经Ｎｉｓｓｌ染色法、免疫组织化学方法和细胞计数法观察了海马谷氨酸免疫反应性（ＧｌｕＩＲ）神经元和γ氨基丁酸免疫反应性（ＧＡＢＡＩＲ）神经元的变化。结果显示：（１）ＣＡ１、ＣＡ３ 和ＳＧ区的ＧｌｕＩＲ神经元明显增多,特别是ＣＡ１ 区。经细胞计数统计分析表明,与对照组相比ＣＡ１ 有极显著性差异（Ｐ＜ ０００１）,ＣＡ３区有显著性差异（００１＜ Ｐ＜ ００５）,ＳＧ处无明显差异（Ｐ＞ ００５）。（２）与对照组相比,ＧＡＢＡＩＲ神经元无明显变化。结果表明,糖皮质激素有增加海马谷氨酸能神经元的作用。尽管γ氨基丁酸能神经元无明显变化,并不表明糖皮质激素对其无影响     

人体小脑神经元发育的定量观察

目的:研究人体小脑神经元的发育过程。方法:应用体视学方法,对18例不同时期人体小脑组织Golgi染色后进行观察,观测小脑皮质分层出现的时间,观测并计算神经元的数密度、体密度和表面积密度。结果:6月龄时,小脑皮质出现较明显的分子层、蒲肯野细胞层和颗粒层;星形细胞、篮状细胞、蒲肯野细胞、颗粒细胞和高尔基细胞的的数密度随月龄/年龄的增长而减少,体密度和表面积密度随月龄/年龄的增长而增加,但这些减小和增大是不等速的,6-8月龄变化最明显。结论:人体小脑神经元的发育呈现快慢交替、不均速发展,6～8月是小脑神经元发育的重要时期。     

人体小脑神经元发育的定量观察

目的：研究人体小脑神经元的发育过程。方法：应用体视学方法,对18例不同时期人体小脑组织Golgi染色后进行观察,观测小脑皮质分层出现的时间,观测并计算神经元的数密度、体密度和表面积密度。结果：6月龄时,小脑皮质出现较明显的分子层、蒲肯野细胞层和颗粒层;星形细胞、篮状细胞、蒲肯野细胞、颗粒细胞和高尔基细胞的的数密度随月龄／年龄的增长而减少,体密度和表面积密度随月龄／年龄的增长而增加,但这些减小和增大是不等速的,6-8月龄变化最明显。结论：人体小脑神经元的发育呈现快慢交替、不均速发展,6～8月是小脑神经元发育的重要时期。     

Induction of Ornithine Decarboxylase by N-Methyl-D-Aspartate Receptor Activation Is Unrelated to Potentiation of Glutamate Excitotoxicity by Polyamines in Cerebellar Granule Neurons

Abstract: Polyamines positively modulate the activity of the N -methyl- d -aspartate (NMDA)-sensitive glutamate receptors. The concentration of polyamines in the brain increases in certain pathological conditions, such as ischemia and brain trauma, and these compounds have been postulated to play a role in excitotoxic neuronal death. In primary cultures of rat cerebellar granule neurons, exogenous application of the polyamines spermidine and spermine (but not putrescine) potentiated the delayed neurotoxicity elicited by NMDA receptor stimulation with glutamate. Furthermore, both toxic and nontoxic concentrations of glutamate stimulated the activity of ornithine decarboxylase (ODC)—the key regulatory enzyme in polyamine synthesis—and increased the concentration of ODC mRNA in cerebellar granule neurons but not in glial cells. Glutamate-induced ODC activation but not neurotoxicity was blocked by the ODC inhibitor difluoromethylornithine. Thus, high extracellular polyamine concentrations potentiate glutamate-triggered neuronal death, but the glutamate-induced increase in neuronal ODC activity may not play a determinant role in the cascade of intracellular events responsible for delayed excitotoxicity.     

Respiration in Primary Cultured Cerebellar Granule Neurons and Cerebral Cortical Neurons

Respiration was measured polarographically in primary cultures enriched with cerebellar granule neurons or cerebral cortical neurons. The basal respiratory rate, measured on the sixth day after culturing, was 12.00 natom equiv. O/mg protein/min for the cortical neurons and 12.70 natom equiv. O/mg protein/min for the granule neurons. Maximal stimulation by 2,4-dinitrophenol produced a 20-40% increase over the basal rate for both neuronal types. Oligomycin inhibited neuronal basal respiration by 45%. These respiratory rates in neurons from primary culture are markedly lower than those measured in astrocytes grown under similar conditions.     

ROS Produced by NOX2 Controls In Vitro Development of Cerebellar Granule Neurons Development

Reactive oxygen species (ROS) act as signaling molecules that regulate nervous system physiology. ROS have been related to neural differentiation, neuritogenesis, and programmed cell death. Nevertheless, little is known about the mechanisms involved in the regulation of ROS during neuronal development. In this study, we evaluated the mechanisms by which ROS are regulated during neuronal development and the implications of these molecules in this process. Primary cultures of cerebellar granule neurons (CGN) were used to address these issues. Our results show that during the first 3 days of CGN development in vitro (days in vitro; DIV), the levels of ROS increased, reaching a peak at 2 and 3 DIV under depolarizing (25 mM KCl) and nondepolarizing (5 mM KCl) conditions. Subsequently, under depolarizing conditions, the ROS levels markedly decreased, but in nondepolarizing conditions, the ROS levels increased gradually. This correlated with the extent of CGN maturation. Also, antioxidants and NADPH-oxidases (NOX) inhibitors reduced the expression of Tau and MAP2. On the other hand, the levels of glutathione markedly increased at 1 DIV. We inferred that the ROS increase at this time is critical for cell survival because glutathione depletion leads to axonal degeneration and CGN death only at 2 DIV. During the first 3 DIV, NOX2 was upregulated and expressed in filopodia and growth cones, which correlated with the hydrogen peroxide (H₂O₂) distribution in the cell. Finally, NOX2 KO CGN showed shorter neurites than wild-type CGN. Taken together, these results suggest that the regulation of ROS is critical during the early stages of CGN development.     

Lysophosphatidylcholine Potentiates BDNF-Induced TrkB Phosphorylation and Downstream Signals in Cerebellar Granule Neurons

We found that brain-derived neurotrophic factor (BDNF)-induced phosphorylation of mitogen-activated protein kinase (MAPK) and Akt in cerebellar granule neurons was specifically potentiated by LPC. LPC also augmented the BDNF-induced phosphorylation of TrkB, the receptor for BDNF. In TrkB-transfected CHO-K1 cells, LPC potentiated BDNF-induced MAPK phosphorylation. These results suggest that LPC plays a role in BDNF-TrkB signaling by regulating the activation of TrkB.     

Death of Cerebellar Granule Neurons Induced by Piperine Is Distinct from that Induced by Low Potassium Medium

We compared neurotoxicity of piperine and low K⁺on cultured cerebellar granule neurons. As considered from lactate dehydrogenase release and 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyl tetrazolium bromide reduction, both piperine and shifting from high K⁺(25 mM) to low K⁺(5.4 mM) were cytotoxic to cerebellar granule neurons. Protein synthesis inhibitors, cycloheximide and anisomycin, and an endonuclease inhibitor, aurintricarboxylic acid, were protective against low K⁺-induced neuronal death whereas they were ineffective against that induced by piperine. D--tocopherol, trolox, and a spin trap 3,3,5,5-tetramethyl-l-pyrroline-l-oxide were protective against piperine neurotoxicity whereas they had no effect on that induced by low K⁺. These results suggest that piperine and low K⁺may exert neurotoxic effects on cerebellar granule neurons through different mechanisms. Death of cerebellar granule neurons induced by piperine may be mediated by non-apoptotic mechanisms and may involve membrane lipid peroxidation and/or free radical generation.     

Activation of G Proteins Bidirectionally Affects Apoptosis of Cultured Cerebellar Granule Neurons

Abstract: Cultured cerebellar granule neurons maintained in depolarizing concentrations of K⁺ (25 m M ) and then switched to physiological concentrations of K⁺ (5 m M ) undergo apoptosis. We now report that activation of specific G proteins robustly and bidirectionally affects apoptosis of cultured rat cerebellar granule neurons. Stimulation of G_s with cholera toxin completely blocks apoptosis induced by nondepolarizing concentrations of K⁺, whereas stimulation of G_o/G_i with the wasp venom peptide mastoparan induces apoptosis of cerebellar granule neurons even in high (depolarizing) concentrations of K⁺. Moreover, pretreatment of cerebellar granule neurons with cholera toxin attenuates neuronal death induced by mastoparan. By contrast, pertussis toxin, cell-permeable analogues of cyclic AMP, and activators of protein kinase A do not affect apoptosis of cultured cerebellar granule neurons. These data suggest that G proteins may function as key switches for controlling the programmed death of mammalian neurons, especially in the developing CNS.     

Novel Neuronal Effects of Midkine on Embryonic Cerebellar Neurons Examined Using a Defined Culture System

1. Midkine (MK) is known to be a member of a family of heparin-binding neurotrophic factors. We used a chemically defined culture system to examine neuronal activities of MK on embryonic rat cerebellar cells.2. In the culture system, a substrate surface was chemically modified either with amine or with laminin peptide to homogenize substrate conditions for culturing neurons.3. At the optimal concentration (2.5 ng/ml), MK moderately promoted survivability (1.3-fold) and accelerated neurite outgrowth (1.4-fold) of cerebellar cells, putatively granule neurons, grown on an amine-modified surface.4. Higher dosages (10 ng/ml or more) of MK, however, caused cellular fragmentation and detachment. Such degenerative effects were diminished by increasing the surface adhesiveness using laminin peptide, suggesting that the cellular degeneration might be caused by changes in the adhesive property of the neuron.5. Using this culture system, we have found that MK has a novel modulatory activity of neuronal adhesiveness on the cultured cerebellar granule cells. Together with the expression pattern of MK, our study supports the idea that MK may be involved in the developmental events of the cerebellum.     

Metabotropic Glutamate Receptors in Cultured Cerebellar Granule Cells: Developmental Profile

Abstract: Excitatory amino acid (EAA)-induced polyphosphoinositide (PPI) hydrolysis was studied during the development in culture of cerebellar granule cells. The developmental pattern was similar using metabotropic glutamate (Glu) receptor (mGluR) agonists, including L-Glu, quisqualate, and trans -(±)-1-amino-1,3-cyclopentanedicarboxylic acid: The stimulation of [³H]inositol monophosphate ([³H]-InsP) formation was low at 2 days in vitro (DIV), but the response increased steeply, reaching a peak at 4 DIV, followed by a progressive decline. In contrast, carbamylcholine-induced PPI hydrolysis exhibited a plateau after a pronounced increase during the first week in vitro. At 6 DIV, but not at 4 DIV, when the activity peaked, PPI hydrolysis elicited by Glu was reduced by the N -methyl- d -aspartate (NMDA) receptor antagonist MK-801, indicating that in cultured granule cells, NMDA receptors contribute to [³H]-InsP formation and that this component of the response develops relatively late. Accordingly, NMDA-induced [³H]-InsP formation, estimated under Mg²⁺-free conditions, increased markedly from very low values at 2 DIV to a plateau at 8–10 DIV. The developmental pattern of EAA-induced PPI hydrolysis was paralleled by changes in the level of an mRNA for a specific mGluR subtype ( mGluR1 mRNA). RNA blot analysis performed with the pmGR1 cDNA probe revealed that the hybridization signal in RNA extracts from cultures at 1 DIV was very weak, but mGluR mRNA levels increased dramatically between 1 and 3 DIV, followed by a progressive decrease, so that by 15 DIV the mRNA levels were only ∼10% of the values at 3 DIV. These observations indicate that the functional expression of the mGluR is subject to developmental regulation, which critically involves receptor mRNA levels.