高钾诱导培养的小脑颗粒神经元凋亡

采用四唑盐比色、琼脂糖凝胶电泳、乙二酸荧光素染色和Hoechst33258 染色等方法研究高钾对原代培养的大鼠小脑颗粒神经元的毒性作用及其机制。结果发现：①高钾诱导神经元死亡呈剂量（50－100mmol/L）和时间依赖性;②神经元死亡呈现明显的凋亡特征：胞体缩小,染色质浓缩,DNA“梯形”条带形成和蛋白质合成抑制剂（cycloheximide,1.0mg/L)可阻断其毒性等;③MK－801（2μmol/L)、尼莫地平（10μmol/L）、硫酸镁（20μmol/L）可阻断高钾的大部分毒性作用。结果提示：高钾可能通过刺激内源性谷氨酸释放从而诱导小脑颗料神经元凋亡。     

磷酸化C-JUN不参与谷氨酸诱导的小脑颗粒神经元凋亡

观察磷酸化C-JUN与谷氨酸诱导的小脑颗粒神经元凋亡的关系.在培养的小脑颗粒神经元建立谷氨酸凋亡模型;采用MTT法分析细胞存活率,相差显微镜观察形态学,DNA凝胶电泳法分析细胞凋亡和原位细胞荧光免疫组织化学法检测磷酸化C-JUN.结果显示,谷氨酸诱导大鼠小脑颗粒神经元细胞体积缩小,突触断裂、消失,DNA电泳呈典型的"梯状"条带;谷氨酸处理24 h后细胞存活率为28.6 %±5.2 %.神经元在谷氨酸处理5,30 min及1,2,4,8,16和24 h后均未检测到有磷酸化C-JUN阳性细胞,与去极化组(25 mmol/L KCl)相同.而复极化组(5 mmol/L KCl)则在30 min检测到大量的磷酸化C-JUN阳性细胞,4 h荧光最强并持续.处理4 h后,400 倍荧光显微镜下,复极化组、去极化组和谷氨酸组的磷酸化C-JUN阳性细胞数分别为124 ±17,8±3,5±3.上述结果提示,谷氨酸诱导小脑颗粒神经元凋亡,磷酸化C-JUN不参与谷氨酸诱导的大鼠小脑颗粒神经元凋亡.     

磷酸化C—JUN不参与谷氨酸诱导的小脑颗粒神经元凋亡

观察磷酸化 C- JUN与谷氨酸诱导的小脑颗粒神经元凋亡的关系。在培养的小脑颗粒神经元建立谷氨酸凋亡模型 ;采用 MTT法分析细胞存活率 ,相差显微镜观察形态学 ,DNA凝胶电泳法分析细胞凋亡和原位细胞荧光免疫组织化学法检测磷酸化 C- JUN。结果显示 ,谷氨酸诱导大鼠小脑颗粒神经元细胞体积缩小 ,突触断裂、消失 ,DNA电泳呈典型的“梯状”条带 ;谷氨酸处理 2 4 h后细胞存活率为 2 8.6%± 5.2 %。神经元在谷氨酸处理 5,30 min及 1 ,2 ,4,8,1 6和 2 4 h后均未检测到有磷酸化 C- JUN阳性细胞 ,与去极化组 ( 2 5mmol/L KCl)相同。而复极化组 ( 5mmol/L KCl)则在 30 min检测到大量的磷酸化 C- JUN阳性细胞 ,4h荧光最强并持续。处理 4h后 ,40 0倍荧光显微镜下 ,复极化组、去极化组和谷氨酸组的磷酸化 C- JUN阳性细胞数分别为 1 2 4± 1 7,8± 3,5± 3。上述结果提示 ,谷氨酸诱导小脑颗粒神经元凋亡 ,磷酸化 C- JUN不参与谷氨酸诱导的大鼠小脑颗粒神经元凋亡。     

尼莫地平诱导小脑颗粒神经元凋亡及机制研究

目的探讨尼莫地平能否诱导小脑颗粒神经元凋亡及可能机制。方法取Sprague-Dawley(SD)大鼠小脑颗粒神经元,体外培养7d,用含10μM尼莫地平培养基处理神经元24h,对照组为含1‰二甲亚砜(DMSO)培养基处理细胞。Hoechst33258染胞核检测凋亡率。Westernblot检测c-Fos和c-Jun蛋白的表达水平;腺病毒作载体过表达c-Fos和负显性c-Jun突变体阻断c-Jun功能,检测能否抑制尼莫地平诱导的神经元凋亡,免疫细胞化学方法检测腺病毒感染率。结果对照组神经元的凋亡率为(10±4)%,尼莫地平处理6、12、24h后神经元的凋亡率分别为(13±4)%、(28±5)%、(45±3)%。尼莫地平处理使c-Fos表达下调,但c-Jun表达水平上调。腺病毒Ad-c-Fos和Ad-c-JunDN(负显性c-Jun突变体)对神经元感染率为85%以上,过表达c-Fos或负显性c-Jun突变体使尼莫地平诱导的神经元凋亡率从(42±6)%减少到(28±6)%或(20±3)%。结论尼莫地平通过下调c-Fos和上调c-Jun表达诱导小脑颗粒神经元凋亡。     

渗透性应激诱导神经元凋亡

目的 :研究渗透性应激对神经元凋亡的诱导。方法 :体外原代培养鸡胚端脑神经元 ,以 1mol·L-1山梨醇处理神经元 1h ,换正常营养液 ,1h后行倒置显微镜、透射电镜形态学观察 ,MTT(噻唑蓝 )细胞活性分析以及DNA琼脂糖凝胶电泳。结果 :神经元活性明显下降 ,DNA电泳及形态学观察显示神经元以凋亡的形式死亡。结论 :渗透性应激可以诱导体外原代培养鸡胚端脑神经元凋亡     

一氧化氮及谷氨酸在内皮素-1诱导神经元凋亡中的作用

目的　观察一氧化氮 (NO)和谷氨酸在内皮素 (ET) 1诱导培养神经元凋亡中的作用。方法　神经元培养取自新生SD大鼠大脑皮质。培养 5天后分 4组 :对照组、ET 1组 (2 0nM)、ET 1 L NAME(N 硝基左旋精氨酸甲酯 ,NO合酶抑制剂 ,1 0 0mM)组和ET 1 APV组 (N 甲基 D 天冬氨酸型受体拮抗剂 ,1 0 0 μM)。培养 2 4h后 ,收集细胞用流式细胞仪定量检测凋亡率。上清液中NO水平通过硝酸还原酶法检测亚硝酸盐浓度反映 ,谷氨酸浓度测定用高压液相法。结果　 2 0nMET 1处理后 2 4h,培养神经元凋亡率较对照组显著增高 (P <0 0 0 1 )。L NAME和APV分别明显阻断ET 1诱导神经元凋亡的作用 ,与ET 1组比较 ,凋亡率降幅分别为 40 % (P<0 0 5)和 80 % (P <0 0 0 1 )。ET 1作用 2 4h后。神经元培养液中NO和谷氨酸浓度较对照组显著增高 (P <0 0 0 1 ) ,L NAME完全抑制了ET 1引起的培养液中NO的升高。结论　NO和谷氨酸参与了ET 1诱导培养大鼠大脑神经元凋亡过程 ,其中谷氨酸更为重要     

溶血磷脂酸诱导小脑颗粒细胞氧化性损伤与凋亡

目的研究溶血磷脂酸(LPA)对原代培养大鼠小脑颗粒细胞的细胞毒性作用及其损伤机制.方法将原代培养的大鼠小脑颗粒细胞暴露于不同剂量LPA中,测定噻唑蓝(MTT);应用流式细胞仪、透射电镜、激光共聚焦显微镜等技术观察细胞的凋亡率、凋亡细胞的核形态及细胞质和线粒体内活性氧(ROS)的形成.结果LPA对小脑颗粒细胞的损伤呈剂量依赖效应.经50μmol/LLPA作用后细胞生存率为正常细胞的(54.8±11.5)%,细胞凋亡率达(40.5±2.3)%,细胞染色质发生浓缩和形成凋亡小体,细胞质和线粒体内ROS形成增加,而经四甲基吡嗪(TMP)预处理后细胞生存率升至(84.7±8.8)%,细胞凋亡率减至(16.7±5.8)%,细胞核形态无明显改变,细胞质和线粒体内ROS形成被抑制.结论LPA具有神经毒性作用.通过增加线粒体内ROS形成,继而诱导神经元凋亡可能是其损伤机制之一.能减少内源性ROS形成的抗氧化剂可对抗LPA诱导的神经元凋亡.     

高糖诱导大鼠海马神经元细胞模型建立及细胞凋亡的影响

目的通过不同葡萄糖浓度和不同作用时间诱导SD大鼠海马神经元,建立稳定的糖尿病脑病细胞模型,探讨高糖对海马神经元凋亡情况的影响。方法 (1)海马神经元的原代培养及纯度鉴定。(2)最适高糖浓度探索:CCK-8法检测海马神经元各组细胞活性。(3)最适浓度下高糖作用时间的探索:Western blot检测海马神经元细胞Bcl-2、Bax的表达情况。(4)最适浓度和作用时间下,流式细胞术检测细胞的凋亡率。结果 (1)成功培养海马神经元,神经元细胞经鉴定纯度达85%以上。(2) 45 mmol/L组海马神经元存活率均 80%。(3) 45 mmol/L-48 h为最适作用时间组,细胞内Bcl-2表达下降、Bax表达升高(P 0. 01)。(4)最适高糖组细胞凋亡率显著升高(P 0. 01)。结论高糖浓度为45 mmol/L、作用时间48 h为理想的糖尿病脑病细胞模型,且高糖通过影响Bcl-2、Bax的表达导致海马神经元凋亡率升高。     

内皮素-1诱导培养大鼠大脑皮质神经元凋亡的初步研究

目的观察内皮素(endothelin,ET)-1有无直接诱导原代培养神经元凋亡的作用,以及其作用通过的ET受体亚型。方法神经元培养取自新生SD大鼠大脑皮质。培养5 d后分别加入0.2 nmol/L,20 nmol/L ET-1处理24 h,用Annexin V、Hoechst 33258染色半定量测定细胞凋亡。再用流式细胞仪分别定量检测ET受体A拮抗剂(BQ123)或ET受体B拮抗剂(BQ788)对20 nmol/L ET-1诱导神经元凋亡的效果。结果0.2 nmol/L ET-1未显示诱导培养神经元凋亡的作用;20 nmol/L ET-1处理后24 h,培养神经元凋亡率明显高于对照组(P<0.01);BQ123和BQ788分别部分阻断了20 nmol/L ET-1诱导神经元凋亡的作用(P<0.01),但阻断效果不完全。结论20 nmol/L ET-1可直接诱导培养大鼠大脑皮质神经元凋亡,其作用可能是通过其A受体和B受体亚型共同实现的。     

Effect of potassium and N-methyl-D-aspartate on the aspartate aminotransferase activity in cultured cerebellar granule cells.

The effect of potassium depolarization and N-methyl-D-aspartate (NMDA) on the activity of aspartate aminotransferase (AAT; EC 2.6.1.1), an enzyme suggested to be involved in neurotransmitter glutamate synthesis, was studied in cultured cerebellar granule neurons. Both KCl and NMDA increased AAT activity in a dose-dependent manner. When cells were treated 48-72 hr with 40 mM KCl or 150 microM NMDA the AAT was enhanced about 65-75%. The EC50 for NMDA and KCl were 25 microM and 17 mM, respectively. The effect of NMDA and KCl was specific for AAT without affecting the activity of other enzymes like lactate dehydrogenase or protein content and it was observed only in granule cells but not in astrocytes or cortical neurons. The effect of KCl was not mediated by an activation of excitatory amino acid receptors and was Ca(++)-dependent. The effect of NMDA was completely blocked by Mg++ and NMDA antagonists. The increase of AAT induced by AAT and KCl was blocked by cycloheximide and actinomycin D, suggesting an involvement of de novo synthesis of proteins and RNA. Kainic acid and quinolinic acid were also effective in increasing the AAT activity. The action of kainate was less effective than that of NMDA and it was observed only at relatively low concentrations (10 microM). Quinolinic acid raised the activity of AAT about 45% at a concentration of 500 microM. Other non-NMDA agonists did not modify the AAT activity. From these findings we can conclude that NMDA and KCl exert a trophic action on cerebellar granular neurons.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cell volume regulation in cultured cerebellar granule neurons

Cultured rat cerebellar granule neurons exposed to solutions of reduced osmolarity, responded initially by swelling followed by a regulatory volume decrease (RVD) which is completed within 15 min. Increasing external osmolarity lead to cell shrinking but no evidence of volume regulation was observed within 1 hr. Replacing Na⁺ by choline did not affect RVD whereas N-methyl-D-glucamine accelerated the volume recovery and K⁺ suppressed it completely. The blockade of RVD in high extracellular K⁺ was only observed when chloride and nitrate but not sulfate or gluconate were the accompanying anions. Replacing intracellular Cl^?, by long incubations with gluconate, markedly inhibited RVD. Removal of extracellular Ca²⁺ or addition of dantrolene which blocks Ca²⁺ released from intracellular stores had no effect on RVD. Increasing extracellular taurine prevented RVD. These results indicate that membrane permeability to K⁺, Cl^?, and taurine is increased by hyposmolarity and suggest the involvement of these molecules in RVD in granule neurons. © 1993 Wiley-Liss, Inc.     

Activity-dependent survival and enhanced turnover of calcium in cultured rat cerebellar granule neurons

Neurons survive when their activity is maintained. An influential hypothesis on the cellular mechanism underlying this phenomenon is that there is an appropriate range of intracellular Ca²⁺ concentration ([Ca²⁺]i) for survival. The rat cerebellar granule neuron in culture serves as the most often used model system for the analysis of activity-dependent survival, since it does not survive unless an excitant (KCl or glutamate) is added to the culture medium. Against the above-mentioned hypothesis, we found in our previous examination no difference between steady-state [Ca²⁺]i in granule neurons cultured under high KCl (i.e., survival) and low KCl (i.e., death) conditions. In this report, we present the quantitative background of unchanged [Ca²⁺]i between the two culture conditions. Influx of Ca²⁺ due predominantly to L-type voltage-dependent calcium channels was higher in high KCl cultures than in low KCl cultures. At the same time, efflux of Ca²⁺ due to the activity of Ca²⁺/Na⁺ antiport was also higher in high KCl cultures. Additionally, we found that the endocytotic activity was greater in high KCl cultures than in low KCl cultures, as monitored by the rate of uptake of horseradish peroxidase added to medium. Since the uptake was blocked by an internal Ca²⁺ chelator, the increased endocytotic activity in high KCl cultures might be a consequence of the enhanced Ca²⁺ turnover.     

Agmatine induces glutamate release and cell death in cultured rat cerebellar granule neurons

We investigated the effect of agmatine on cell viability of rat cerebellar granule neurons in a high-K+ (27.5 mM) medium. Exposure of cultured rat cerebellar granule neurons to agmatine (200-800 microM) resulted in a significant decrease in cell viability. Agmatine-induced neuronal death began to occur 6-12 h after addition, and gradually progressed. The agmatine neurotoxicity was attenuated by N-methyl-D-aspartate (NMDA) receptor antagonists and by enzymatic degradation of L-glutamate with glutamic pyruvic transaminase. Furthermore, a significant increase in extracellular L-glutamate concentration was detected before cell death occurred. In addition, agmatine-induced glutamate release and cell death were both blocked by pretreatment with botulinum toxin C, which is known to specifically inhibit the exocytosis. The agmatine neurotoxicity was not observed when extracellular K+ concentration was lower (10 mM). These results suggest that agmatine induces glutamate release through the exocytosis and thereby causes NMDA receptor-mediated neuronal death in conditions in which extracellular K+ concentrations are elevated.     

NOX2 mediates apoptotic death induced by staurosporine but not by potassium deprivation in cerebellar granule neurons

Neuronal apoptotic death involves the participation of reactive oxygen species (ROS), but their sources have not been completely elucidated. Previous studies have demonstrated that the ROS‐producing enzyme NADPH oxidase is present in neuronal cells and that this enzyme could participate in the apoptotic neuronal death. Cerebellar granule neurons (CGN) undergo apoptosis when cells are transferred from a medium with 25 mM KCl (K25) to a 5 mM KCl (K5) medium or when they are treated with staurosporine (ST). Under these conditions, apoptotic death of CGN is dependent on ROS production. In this study, we evaluated the role of NOX2, an NADPH oxidase homolog, in the apoptotic death of CGN induced by two different conditions. In CGN from NOX2‐deficient (ko) mice, a significantly lower rate of apoptotic death occurs compared with wild‐type (wt) CGN. Also, caspase‐3 activation, NADPH oxidase activity, and superoxide anion production induced by ST were markedly lower in ko neurons than in wt CGN. In contrast to the case with ST, when CGN were treated with K5, no differences were observed between ko and wt cells in any of the parameters measured. However, all NADPH oxidase inhibitors tested noticeably reduced cell death and apoptotic parameters induced by K5 in both wt and ko CGN. These results suggest that NOX2 could be necessary for apoptotic death induced by ST, but not by K5, which could require other member of the NOX family in the apoptotic process. © 2009 Wiley‐Liss, Inc.     

Characterization of the activation of glutaminase induced by N-methyl-D-aspartate and potassium in cerebellar granule cells

Chronic stimulation of cerebellar granule cells with N-methyl-D-aspartate (NMDA) or KCl induces a specific activation of the enzymes directly involved in glutamate neurotransmitter synthesis. Phosphate-activated glutaminase (PAG) activity is enhanced in cultured granule neurons incubated with 150 μM NMDA or 25 mM KCl. Other enzymes are not affected by this treatment like lactate dehydrogenase (LDH) and glutamate dehydrogenase (GLDH), which is also a mitochondrial enzyme but not directly involved in neurotransmitter synthesis. This effect is dependent on protein synthesis and is induced after 12 hr of NMDA or KCl stimulation. Kinetics of PAG activity showed that K_m values were unaffected, in contrast to V_max values that were increased approximately 70% and 215% over control by NMDA and KCl treatment, respectively. For GLDH, we found two isoforms that were affected differentially by the experimental conditions. Western blot analysis clearly evidenced an increase of approximately 120–180% in the amount of PAG in NMDA- and KCl-treated cells, whereas GLDH was not significantly modified. These results demonstrate that the NMDA- and KCl-induced activation of PAG are not due to the modification of the preexisting enzyme, but to an increase in the synthesis of this enzyme. This suggests that NMDA receptor stimulation during critical periods of the cerebellar granule cell development leads to the activation of gene expression involved in the process of cell differentiation. © 1996 Wiley-Liss, Inc.     

mGluR7-like metabotropic glutamate receptors inhibit NMDA-mediated excitotoxicity in cultured mouse cerebellar granule neurons

Glutamate-induced glutamate release may be involved in the delayed neuronal death induced by N-methyl-D-aspartate (NMDA). In order to examine a possible modulatory effect of the presynaptic group III mGluRs on glutamate excitotoxicity, the effect of L-2-amino-4-phosphonobutyrate (L-AP4) was examined on NMDA-induced delayed death of mouse cerebellar granule neurons in culture. We found that L-AP4, at high concentration (in the millimolar range), inhibited in a non-competitive manner the NMDA-induced toxicity. This effect was mimicked by high concentration of L-serine-o-phosphate (L-SOP), and was inhibited by pertussis toxin (PTX) indicating the involvement of a Gi/o protein. This suggests the involvement of mGluR7 in the L-AP4 effect, and this was consistent with the detection of both mGluR7 protein and mRNA in these cultured neurons. To examine the mechanism of the L-AP4-induced protection from excitotoxic damage, the effect of L-AP4 on glutamate release was examined. L-AP4 (> or = 1 mM) noncompetitively inhibited by more than 60% the glutamate release induced by NMDA during the insult. We also observed that the 10-min NMDA receptor stimulation resulted in a dramatic increase in the extracellular glutamate concentration reaching 6000% of the control value 24 h after the insult. This large increase was also inhibited when NMDA was applied in the presence of > or = 1 mM L-AP4. Part of the L-AP4-induced protection from excitotoxic damage of granule neurons may therefore result from the inhibition of the vicious cycle: dying cells release glutamate, glutamate induced cell death. The present results add to the hypothesis that presynaptic mGluRs, probably mGluR7, may be the targets of drugs decreasing glutamate release and then neuronal death observed in some pathological situations.     

Akt mediates the anti-apoptotic effect of NMDA but not that induced by potassium depolarization in cultured cerebellar granule cells

Apoptosis of cultured cerebellar granule neurons (CGNs) deprived of serum is prevented by K+ depolarization or moderate concentrations of N-methyl-d-aspartate (NMDA). Here, we have examined the role of the serine/threonine kinase Akt in these protective effects. The exposure of mouse CGNs to NMDA or K+ depolarization increased the phosphorylation of Akt, compared with that measured in cells incubated in a physiological K+ concentration. Only the NMDA-evoked response was reduced by inhibitors of phosphatidylinositol 3-kinase (wortmannin and LY294002) and mitogen-activated protein kinase (PD98059 and U0126). Similarly, the capacity of NMDA to inhibit apoptosis of CGNs deprived of serum was greatly reduced by these inhibitors as well as by the transfection of neurons with a catalytically inactive mutant of Akt, whereas the protective effect of K+ depolarization remained unaffected. These findings indicate that K+ depolarization and NMDA activate Akt through different signalling pathways in CGNs. Moreover, Akt mediates the anti-apoptotic effect of NMDA, but not that evoked by K+ depolarization.