6-羟基-1H-吲唑抑制Tau磷酸化对MPP~+诱导凋亡的SH-SY5Y细胞保护作用的研究

目的研究6-羟基-1H-吲唑通过抑制Tau磷酸化对MPP+诱导凋亡的SH-SY5Y细胞的保护作用。方法体外培养人神经母细胞瘤细胞SH-SY5Y,以MPP+诱导SH-SY5Y细胞凋亡作为帕金森病的细胞模型。MTT分析法检测提前2 h加入6-羟基-1H-吲唑对细胞的保护作用;Hoechst 33258荧光染色法检测神经元凋亡情况;免疫细胞化学方法检测多巴胺能神经元内Tau的磷酸化水平。结果 200μmol·L-1MPP+可以使SH-SY5Y细胞存活率下降至(47.80±0.84)%(P<0.01),并且升高Tau磷酸化水平,出现典型的凋亡。而6-羟基-1H-吲唑抑制MPP+对SH-SY5Y细胞的毒性,并通过抑制Tau蛋白过度磷酸化而减少神经元凋亡,使TH-阳性细胞数目增加。结论 6-羟基-1H-吲唑可以通过抑制Tau磷酸化而对MPP+诱导凋亡的SH-SY5Y细胞发挥保护作用,提示Tau蛋白可能可以作为药物治疗帕金森等神经退行性疾病的新靶点。     

5-羟基-1-氢-吲唑对SH-SY5Y细胞的保护作用及其机制研究

目的研究5-羟基-1-氢-吲唑对1-甲基-4-苯基-吡啶离子(MPP~+)诱导凋亡的SH-SY5Y神经细胞的保护作用及其可能的作用机制。方法以MPP~+诱导SH-SY5Y细胞凋亡建立体外帕金森病细胞模型,以MTT法筛选药物有效保护浓度;以免疫化学染色以及Hoechst 33258核染研究药物的神经保护作用以及抗凋亡作用;以Western blot法检测与神经元凋亡密切相关的磷酸化tau蛋白及其上游激酶磷酸化糖原合成激酶(P-GSK-3β)和周期依赖性蛋白激酶5(cyclin dependent kinase,CDK5)的表达。结果 MPP+可引起GSK-3β的活化以及CDK5活性升高,诱导tau的异常磷酸化和神经细胞凋亡;而5-羟基-1-氢-吲唑可下调GSK-3β与CDK5的活性,降低磷酸化tau的水平和抑制MPP+导致的SH-SY5Y细胞的凋亡。结论 5-羟基-1-氢-吲唑可抑制MPP+引起的SH-SY5Y神经细胞凋亡,作用机制可能是通过同时抑制GSK-3β和CDK5两条信号传导通路,而降低tau蛋白的磷酸化水平,进一步发挥神经元保护作用。     

抗氧化作用可能是人参皂甙Rg1抗细胞凋亡的机制

目的 :探讨人参皂甙Rg1对MPP+诱导SHSY5Y细胞凋亡的保护作用及其可能的机制。方法 :用吖啶橙溴化乙锭染色观察SHSY5Y细胞凋亡率 ,流式细胞仪检测线粒体跨膜电位及细胞内活性氧 (ROS)水平 ,WesternBlot法检测bcl 2、bax蛋白表达水平。结果 :经 10 μmol·L- 1Rg1预处理后 ,MPP+诱导的SHSY5Y细胞凋亡受到明显的抑制 ,虽然线粒体跨膜电位无明显改变 ,但细胞内ROS下降 ,而bcl 2蛋白表达水平增加 ,bax蛋白表达水平减少。结论 :Rg1可抑制MPP+诱导的SHSY5Y细胞凋亡 ,其作用机制可能是通过清除ROS、调节bcl 2、bax蛋白表达水平起作用。     

特异性p38 MAPK抑制剂SB203580对乳鼠小脑颗粒神经元的保护作用

目的　研究p38丝裂原激活蛋白激酶（MAPK）选择性抑制剂SB203580对乳鼠小脑颗粒神经元凋亡的保护作用。方法　SD乳鼠小脑颗粒神经元培养,琼脂糖凝胶电泳,SAPK/JNK分析试剂盒作激酶分析。结果　PI-3-K的特异性抑制剂LY294002诱导小脑颗粒神经元凋亡,但SB203580通过抑制细胞凋亡而促进小脑颗粒神经元的存活,且有浓度依赖性。LY294002诱导凋亡的颗粒神经元中c-Jun的表达量和磷酸化水平均升高,JNK被激活。但是,当小脑颗粒神经元生长在含SB203580的高钾培养基中,c-Jun的表达量、磷酸化水平和JNK的活性都明显的降低。结论　SB203580通过抑制JNK的活性,降低c-Jun的表达和磷酸化水平,对小脑颗粒神经元产生保护作用。     

人参皂甙Rb1通过提高PP2A活性抑制冈田酸诱导的大鼠海马神经元Tau蛋白AD样异常磷酸化

目的 研究人参皂甙Rb1对冈田酸诱导的海马神经元Tau蛋白过度磷酸化的抑制作用及其可能机制。方法用不同浓度的Rb1预处理大鼠后，向海马背侧一次性注射适量OA，建立Tau蛋白过度磷酸化的大鼠模型。通过Bieschowski’s染色、免疫组化和western-blot观察大鼠海马神经元突起和Tau蛋白磷酸化水平的变化；检测蛋白磷酸酯酶PP2A和胆碱乙酰转移酶(T-chE)活性，探讨Rb1作用的可能机制。结果模型组大鼠海马神经元神经原纤维排列紊乱，轴突断裂；Tau蛋白磷酸化水平和总Tau含量增多，PP2A活性明显受抑制，但T-chE活性无改变；Rb1预处理的大鼠，神经原纤维走行规则，轴突较完整，Tau磷酸化和总Tau水平比模型鼠下降，PP2A活性明显增高，但T—chE活性无明显改变。结论。Rb1可以减轻OA诱导的大鼠海马神经元Tau蛋白过度磷酸化，其机制可能主要与提高PP2A活性有关；Rb1对T-chE则无明显影响。     

银杏叶提取物对损伤后中脑多巴胺能神经细胞活性的影响

目的探讨银杏叶提取物(EGB761)对1-甲基-4-苯基吡啶离子(MPP+)及脂多糖(LPS)损伤后的中脑多巴胺能神经细胞是否具有保护作用。方法采用胚胎大鼠中脑原代细胞培养法,分离培养中脑神经细胞,培养细胞随机分为空白对照组、MPP+组、MPP++EGB761组、MPP++LPS组、MPP++EGB761+LPS组;给予MPP+、EGB761和LPS进行配组干预,然后观察细胞生长状况;通过3-(4,5-二甲基噻唑-2)-2,5-二苯基四氮唑溴盐(MTT)微量比色法检测细胞活性;酪氨酸羟化酶(TH)免疫荧光法(FITC),比较各组阳性神经元的变化,了解多巴胺能神经元的表达情况;同时硝酸还原法检测培养细胞中一氧化氮(NO)的表达情况。结果空白对照组、MPP++EGB761组:细胞生长旺盛,轴突延长明显;MPP++EGB761+LPS组:细胞生长受抑制,轴突较短MPP+组、MPP++LPS组细胞数量少,仅少数细胞稍有突起,大多数细胞无轴突。MTT法测得细胞吸光度值(A值)、免疫荧光TH阳性细胞表达及培养细胞NO的表达:空白对照组、MPP++EGB761组NO含量与MPP++EGB761+LPS组、MPP+组、MPP++LPS组比较差异有统计学意义(P<0.05)。MPP++EGB761+LPS组NO含量与MPP+组、MPP++LPS组比较差异有统计学意义(P<0.05),MPP+组与MPP++LPS组比较差异亦有统计学意义(P<0.05,见表1)。结论 LPS可加重MPP+对多巴胺能神经元的损伤作用,小胶质的活化及其释放的NO有可能参与该细胞凋亡过程。EGB761对损伤后的胚胎大鼠中脑原代培养细胞具有保护作用,此作用可能通过抑制小胶质的活化完成。     

银杏叶提取物对损伤后中脑多巴胺能神经细胞活性的影响

目的 探讨银杏叶提取物(EGB761)对1-甲基-4-苯基吡啶离子(MPP+)及脂多糖(LPS)损伤后的中脑多巴胺能神经细胞是否具有保护作用.方法 采用胚胎大鼠中脑原代细胞培养法,分离培养中脑神经细胞,培养细胞随机分为空白对照组、MPP+组、MPP++EGB761组、MPP++LPS组、MPP++EGB761+LPS组;给予MPP+、EGB761和LPS进行配组干预,然后观察细胞生长状况;通过3-(4,5-二甲基噻唑-2)-2,5-二苯基四氮唑溴盐(MTT)微量比色法检测细胞活性;酪氨酸羟化酶(TH)免疫荧光法(FITC),比较各组阳性神经元的变化,了解多巴胺能神经元的表达情况;同时硝酸还原法检测培养细胞中一氧化氮(NO)的表达情况.结果 空白对照组、MPP++EGB761组:细胞生长旺盛,轴突延长明显;MPP++EGB761+LPS组:细胞生长受抑制,轴突较短 MPP+组、MPP++LPS组细胞数量少,仅少数细胞稍有突起,大多数细胞无轴突.MTT法测得细胞吸光度值(A值)、免疫荧光TH阳性细胞表达及培养细胞NO的表达:空白对照组、MPP++EGB761组NO含量与MPP++EGB761+LPS组、MPP+组、MPP++LPS组比较差异有统计学意义(P＜0.05).MPP++EGB761+LPS组NO含量与MPP+组、MPP++LPS组比较差异有统计学意义(P＜0.05),MPP+组与MPP++LPS组比较差异亦有统计学意义(P＜0.05,见表1).结论 LPS可加重MPP+对多巴胺能神经元的损伤作用,小胶质的活化及其释放的NO有可能参与该细胞凋亡过程.EGB761对损伤后的胚胎大鼠中脑原代培养细胞具有保护作用,此作用可能通过抑制小胶质的活化完成.     

咖啡因对LY294002诱导的小脑颗粒神经元凋亡的保护作用

目的:研究咖啡因对LY294002 诱导的小脑颗粒神经元凋亡的保护作用。方法:DNA 断裂分析采用琼脂糖凝胶电泳法,[Ca²⁺]i 测定采用Fura-2 荧光技术,磷酸化c-Jun 分析采用免疫荧光法,c-Jun 含量和JNK 活性分析采用Western blot 法。结果:咖啡因对LY294002 诱导小脑颗粒神经元凋亡具浓度依赖性的保护作用,这种保护作用不依赖[Ca²⁺]i 的升高或cAMP的生物效应。咖啡因可抑制c-Jun 氨基末端激酶(JNK) 的活性,降低细胞内磷酸化c-Jun 的含量和c-Jun 的表达。结论:咖啡因可抑制JNK 活性,阻断c Jun 磷酸化及其介导的细胞凋亡信号转导系统,从而对LY294002 诱导小脑颗粒神经元凋亡具有保护作用。     

人参皂苷Rg1可能通过丝裂素活化蛋白激酶途径抑制细胞凋亡

目的探讨人参皂苷Rg1对MPP+诱导细胞凋亡保护作用的可能信号传导途径.方法用吖啶橙-溴化乙锭染色观察SHSY5Y细胞凋亡率,流式细胞仪检测细胞内活性氧ROS水平,Western Blotting法检测JNK(c-jun NH2-terminal kinase)激酶活性,免疫细胞化学染色法检测裂解的Caspase-3阳性细胞的表达率.结果经10 μmol*L-1 Rg1或2.5 mmol*L-1 N-乙酰半胱氨酸预处理后,MPP+诱导的SHSY5Y细胞凋亡受到明显抑制,同时细胞内ROS下降,JNK激酶的活性减弱,裂解的Caspase-3阳性细胞表达率下降.结论 Rg1可抑制MPP+诱导的SHSY5Y细胞凋亡,其作用机制可能是通过清除ROS、减弱JNK激酶的活性,从而减少Caspase-3的激活.     

3-硝基丙酸预处理保护多巴胺神经元机制研究

目的 研究3-硝基丙酸（3-NPA）多次预处理保护多巴胺神经元的作用及其可能机制。方法使用MPP+在分泌多巴胺的人神经纤维瘤细胞SH SY5Y上制作帕金森病细胞模型,在模型制作前分别1或5次加入3-NPA（0.2 mmol·L 1）进行预处理,分别应用液闪烁仪检测［3H］DA摄取率,双波长分光光度仪检测细胞内游离钙离子（Ca2+）浓度的改变,观察3 NPA预处理保护多巴胺神经元的作用。结果MPP+可降低［3H］DA摄取率,升高细胞内游离钙离子浓度,3-NPA预处理可提高［3H］DA摄取率,降低胞内游离钙离子浓度,3 NPA多次预处理较3-NPA单次预处理的作用更好。结论3-NPA预处理对多巴胺神经元有明显的保护作用,可能与其降低胞内游离钙离子浓度有关。     

芍药苷对MPP~+所致大鼠黑质脑片多巴胺能神经元损伤的保护作用

目的研究芍药苷(paeoniflorin,PF)对MPP+所致大鼠黑质脑片多巴胺能神经元损伤的保护作用,并观察PF对α-synuclein(α-syn)mRNA表达水平的影响。方法离体培养SD大鼠黑质器官型脑片,培养的d10给予不同浓度的MPP+(0.1、0.5、1.0mmol·L-1)处理24h,并在0.5mmol.L-1MPP+处理的基础上,给予1μmol·L-1或10μmol·L-1的PF进行干预。免疫组化法计数黑质致密部酪氨酸羟化酶(tyrosine hydroxylase,TH)阳性细胞数,定量RT-PCR法检测α-syn mRNA的表达丰度。结果MPP+(0.1、0.5、1.0mmol.L-1)处理导致黑质致密部TH+细胞数较正常对照组减少,差异均有统计学意义(P<0.05或P<0.01);MPP+(0.5mmol.L-1)使α-syn mRNA的表达水平明显升高(P<0.01)。PF(10μmol·L-1)有效增加了TH+细胞的数量(P<0.01),并明显下调了α-syn mRNA的表达(P<0.05)。结论PF能有效拮抗MPP+导致的多巴胺能神经元受损死亡,其机制可能与下调α-syn的表达有关。     

氯化锂抑制β-淀粉样蛋白诱导细胞Tau蛋白磷酸化

目的探讨GSK-3β抑制剂氯化锂(LiCl)在β-淀粉样蛋白25～35片断(Aβ25-35)诱导的细胞Tau蛋白磷酸化中的作用及机制。方法MTT法观察不同浓度的LiCl(1、5、10、20mmol.L-1)单独作用24h,对SH-SY5Y细胞存活率的影响;20μmol.L-1的凝聚态Aβ25-35作用于SH-SY5Y细胞不同时间点,蛋白免疫印迹法研究Tau蛋白磷酸化位点(Ser199、Ser396及Tau1)水平的变化;LiCl(20mmol.L-1)预处理细胞1h后,观察Aβ的作用有无变化及可能的作用机制。结果不同浓度的LiCl作用24h后,MTT法示细胞存活率无明显变化(P>0.05);20μmol.L-1Aβ25-35作用不同时间点后,Tau蛋白在Ser396、Ser199位点的磷酸化水平在3h逐渐增加,6h达到最高峰,12h后又逐渐下降,在这3个时间点的增加量均具有统计学意义(P<0.05),而对非磷酸化Tau1没有影响(P>0.05);LiCl预处理可抑制Aβ25-35的作用(P<0.05),并可诱导失活形式的GSK-3β在Ser9位点的磷酸化(p-GSK-3βSer9)表达增高。结论GSK-3β参与了Aβ25-35诱导细胞Tau蛋白磷酸化的作用,LiCl可通过诱导失活形式的p-GSK-3βSer9表达增高而抑制GSK-3β的活性,进而抑制Aβ诱导的细胞Tau蛋白磷酸化。该实验为研究AD的发病机制及探索有效治疗药物提供了重要的理论基础。     

Opposite effects of lithium and valproic acid on trophic factor deprivation-induced glycogen synthase kinase-3 activation, c-Jun expression and neuronal cell death

Recent studies demonstrate that lithium and valproic acid (VPA), two commonly used mood-stabilizing drugs, have neuroprotective effects against a variety of insults. Inhibition of the proapoptotic enzyme, glycogen synthase kinase-3 (GSK-3), has been suggested to be the mechanism of action of neuroprotection for both drugs. In this study, we tested if lithium and VPA could protect cultured cerebellar granule neurons (CGNs) from GSK-3-mediated apoptosis induced by trophic factor withdrawal (serum/potassium deprivation). Both lithium and indirubin, a specific GSK-3 inhibitor, protected CGNs in a dose-dependent manner. In contrast, VPA did not provide any neuroprotection and even potentiated cell death. Immunoblot analysis revealed that lithium inhibited the trophic factor deprivation-induced activation of GSK-3 as well as the in vivo phosphorylation of the microtubule-associated protein Tau on Ser199, a specific target site for GSK-3. Under these same experimental conditions, however, VPA neither inhibited GSK-3 activation nor hindered GSK-3 mediated Tau phosphorylation. Furthermore, in accordance with their effects on neuronal survival, lithium prevented the induction of c-Jun expression in trophic factor-deprived CGNs, whereas VPA potentiated it. Collectively, these results show that VPA is not a universal inhibitor of neuronal GSK-3, and that instead of being neuroprotective, VPA can even exacerbate neuronal death under some conditions.     

The 28-day repeated arsenic exposure increases tau phosphorylation in the rat brain

Herein, we examined whether prolonged arsenic exposure altered tau phosphorylation in the brain of Sprague Dawley rats expressing endogenous wild-type tau. The results showed that daily intraperitoneal injections of 2.5 mg/kg BW sodium arsenite over 28 days caused arsenic accumulation in the rat brain. Interestingly, we found an increase in tau phosphorylation at the Tau 1 region (189−207) and S202 in the hippocampus, S404 in the cerebral cortex, and S396 and S404 in the cerebellum of arsenic-treated rats. Additionally, arsenic increased active ERK1/2 phosphorylation at T202/Y204 in the hippocampus, cerebral cortex, and cerebellum. Meanwhile, we detected increasing active JNK phosphorylation at T183/Y185 in the hippocampus and cerebellum. Moreover, p35, a neuron-specific activator of CDK5, was also elevated in the cerebellum of arsenic-treated rats, suggesting that CDK5 activity may be increased by arsenic. These results suggested that arsenic may induce tau phosphorylation through the activation of tau kinases, ERK1/2, JNK, and CDK5. Together, the findings from this study demonstrated that prolonged arsenic exposure is implicated in neurodegeneration by promoting tau phosphorylation in the rat brain and points toward a possible prevention strategy against neurodegeneration induced by environmental arsenic exposure.     

胰岛素对AD样小鼠学习记忆的影响及其机制

【摘要】目的 研究胰岛素对阿尔茨海默病（AD）样小鼠学习记忆能力的影响及其机制。方法 将21只小鼠随机分为对照(CON) 组、模型（链脲佐菌素,STZ）组和胰岛素治疗(INS) 组,每组7只,后2组小鼠脑室内注射STZ建立 AD模型,INS组小鼠皮下注射胰岛素持续30 d。Morris水迷宫检测小鼠学习记忆能力,Western blotting检测Tau和神经丝（NFs）蛋白的磷酸化水平,荧光染料Fluoro-Jade B（FJB）标记退化神经元。结果 与CON组相比,STZ组小鼠平均逃避潜伏期和路径长度明显增加(P < 0.05)、穿越隐匿平台次数明显减少(P < 0.05),小鼠脑内Tau蛋白在Ser199/ 202、Ser396/404、Thr212和Thr205位点的磷酸化水平以及NFs蛋白的磷酸化增加(P < 0.05),FJB标记的小鼠海马CA1 区平均累积光密度(IOD)较CON组明显增加(P < 0.001);与STZ组相比,INS组小鼠学习记忆改善,逃避潜伏期和路径长度明显减少(P < 0.05)、穿越隐匿平台次数明显增加(P < 0.05),Tau蛋白特异性位点和NFs蛋白的磷酸化作用明显降低(P < 0.05),FJB标记的小鼠海马CA1区平均累积分光密度(IOD)明显减少(P < 0.001)。结论 胰岛素能改善STZ脑室内注射的AD样小鼠学习记忆减退,可能与降低Tau和NFs蛋白的过度磷酸化和神经细胞退行性变有关。     

Novel neuroprotective mechanisms of pramipexole, an anti-Parkinson drug, against endogenous dopamine-mediated excitotoxicity

Parkinson disease is characterized by selective degeneration of mesencephalic dopaminergic neurons, and endogenous dopamine may play a pivotal role in the degenerative processes. Using primary cultured mesencephalic neurons, we found that glutamate, an excitotoxin, caused selective dopaminergic neuronal death depending on endogenous dopamine content. Pramipexole, a dopamine D2/D3 receptor agonist used clinically in the treatment of Parkinson disease, did not affect glutamate-induced calcium influx but blocked dopaminergic neuronal death induced by glutamate. Pramipexole reduced dopamine content but did not change the levels of total or phosphorylated tyrosine hydroxylase, a rate-limiting enzyme in dopamine synthesis. The neuroprotective effect of pramipexole was independent of dopamine receptor stimulation because it was not abrogated by domperidone, a dopamine D2-type receptor antagonist. Moreover, both active S(-)- and inactive R(+)-enantiomers of pramipexole as a dopamine D2-like receptor agonist equally suppressed dopaminergic neuronal death. These results suggest that pramipexole protects dopaminergic neurons from glutamate neurotoxicity by the reduction of intracellular dopamine content, independently of dopamine D2-like receptor activation.     

Neurofibrillary degeneration of the Alzheimer-type: an alternate pathway to neuronal apoptosis?

Neuronal death is a process which may be either physiological or pathological. Apoptosis and necrosis are two of these processes which are particularly studied. However, in neurodegenerative disorders, some neurons escape to these types of death and "agonize" in a process referred to as neurofibrillary degeneration. Neurofibrillary degeneration is characterized by the intraneuronal aggregation of abnormally phosphorylated microtubule-associated Tau proteins. A number of studies have reported a reactivation of the cell cycle in the neurofibrillary degeneration process. This reactivation of the cell cycle is reminiscent of the initiation of apoptosis in post-mitotic cells where G1/S markers including cyclin D1 and cdk4/6, are commonly found. However, in neurons exhibiting neurofibrillary degeneration, both G1/S and G2/M markers are found suggesting that they do not follow the classical apoptosis and an aberrant cell cycle occurs. This aberrant response leading to neurofibrillary degeneration may be triggered by the sequential combination of three partners: the complex Cdk5/p25 induces both apoptosis and the "abnormal mitotic Tau phosphorylation". These mitotic epitopes may allow for the nuclear depletion of Pin1. This latter may be responsible for escaping classical apoptosis in a subset of neurons. Since neurofibrillary degeneration is likely to be a third way to die, molecular mechanisms leading to changes in Tau phosphorylation including activation of kinases such as cdk5 or other regulators such as Pin1 could be important drug targets as they are possibly involved in early stages of neurodegeneration.     

左旋丁苯酞对低灌注大鼠脑皮质Tau蛋白磷酸化的影响

目的通过观察左旋丁苯酞(1-NBP)对脑低灌注大鼠学习记忆的改善作用,并研究其皮质β-淀粉样肽(Aβ1-42)水平以及Tau蛋白磷酸化变化,以探讨1-NBP改善认识功能的作用机制。方法大鼠双侧颈总动脉结扎90d,制备脑低灌注模型。实验分假手术组,溶剂对照组,1-NBP 30、120mg/kg组。1-NBP治疗组连续给予45d后,用Morris水迷宫检测大鼠的空间学习和记忆能力,后取大鼠脑皮质组织,用酶联免疫吸附试验(ELISA)检测Aβ1-42含量,用蛋白印迹法检测Tau蛋白的磷酸化水平。结果在水迷宫空间探索实验中1-NBP明显增加脑低灌注大鼠在目标象限活动时间的百分比。1-NBP明显减少了大鼠皮质Aβ1-42含量,降低低灌注大鼠皮质Tau蛋白的磷酸化水平。结论 1-NBP改善了脑低灌注大鼠的学习记忆缺陷,可能是通过减少皮质Aβ1-42的水平,从而减轻Tau蛋白的磷酸化,最终保护了神经元免受损伤。     

渥曼青霉素在体诱导tau蛋白阿尔采末样磷酸化以及褪黑激素的拮抗作用

目的:研究渥曼青霉素能否在体诱导tau蛋白阿尔采末样磷酸化以及褪黑激素的对这种效应的拮抗作用.方法:采用立体定位技术向大鼠侧脑室注射渥曼青霉素和褪黑激素,免疫组织化学和免疫印迹技术观察磷酸化tau蛋白的分布及含量,电子显微镜观察轴突结构.结果:注射渥曼青霉素(10μmol·L~(-1))6h后,海马CAI锥体神经元tau蛋白的Ser-396/404位点被磷酸化,神经元轴突膨胀,部分髓鞘脱落.免疫印迹结果表明,渥曼青霉素注射后1h到6h,tau蛋白的Ser-396/404位点磷酸化逐渐增加,6h到24h逐渐减少,6h为tau蛋白的Ser-396/404磷酸化的峰值.提前12h注射褪黑激素(10μmol·L~(-1)和100μmol·L~(-1)),可部分对抗渥曼青霉素(10μmol·L~(-1))注射6h后诱导的tau蛋白Ser-396/404磷酸化.结论:在体注射渥曼青霉素可诱导大脑tau蛋白阿采末样磷酸化,褪黑激素可部分拮抗这一损伤效应.     

Neuronal response to radical stress

Glutamate and reactive oxygen species including nitric oxide (NO) and superoxide anion (O2.-) have been postulated to play pivotal roles in the pathogenesis of the neuronal cell loss that is associated with several neurological disease states including Parkinson's disease and amyotrophic lateral sclerosis. In mesencephalic cultures, nondopaminergic neurons but not dopaminergic neurons are susceptible to NO cytotoxicity, although both types of neurons are damaged by glutamate. Methylphenylpyridium ion (MPP+) selectively enhances glutamate and NO cytotoxicity against dopaminergic neurons of mesencephalic cultures. It is suggested that glutathione plays an important role in the expression of NO-mediated glutamate cytotoxicity in dopaminergic neurons. In cultured spinal neurons, glutamate coadministered with the glutamate transporter inhibitor selectively damages motor neurons. Motor neurons are injured by NO, whereas nonmotor neurons are protected by NO through the guanylyl cyclase-cGMP cascade. It is suggested that selective motor neuronal death caused by chronic low-level exposure to glutamate is mediated by the formation of NO in nonmotor neurons. It is possible that neurotoxicity induced by NO and O2.- associated with neurodegenerative disorders is regulated by intracellular defense systems such as glutathione and cGMP.