MPP+重新启动多巴胺能神经元细胞周期的作用及机制

目的研究1-甲基-4-苯基吡啶离子(MPP )重新启动多巴胺能神经元细胞周期的作用及机制。方法使用MPP 处理神经元样分化的PC12细胞,采用四甲基偶氮唑盐(MTT)法检测细胞活力,流式细胞仪检测早期凋亡细胞和细胞周期分布,免疫细胞化学检测ERK/MAPK通路活化水平。结果经MPP 处理后,细胞活力呈浓度依赖性下降,经25、50、75、100、150 mmol/L MPP 处理24 h后细胞存活率分别下降至对照组的(97.32±2.41)%(、67.69±3.03)%、(56.00±3.12)%、(47.23±2.55)%、(40.00±2.46)%,与对照组相比差异均有统计学意义(P<0.01)。经75 mmol/L MPP 处理后出现早期凋亡细胞,随处理时间延长,细胞凋亡率逐渐增加,其处理4、8、16和24 h后细胞凋亡率分别为(7.26±3.43)%、(8.34±3.55)%(、20.04±2.64)%和(28.46±2.35)%(P<0.01)。同时细胞周期中G0/G1期细胞减少,S期和G2/M期细胞增多(P<0.01),细胞内ERK1/2通路活化。结论MPP 可通过活化ERK1/2通路重新启动多巴胺神经元的细胞周期,并诱导多巴胺能神经元凋亡。     

MPP~+重新启动多巴胺能神经元细胞周期的作用及机制

目的研究1-甲基-4-苯基吡啶离子(MPP+)重新启动多巴胺能神经元细胞周期的作用及机制。方法使用MPP+处理神经元样分化的PC12细胞,采用四甲基偶氮唑盐(MTT)法检测细胞活力,流式细胞仪检测早期凋亡细胞和细胞周期分布,免疫细胞化学检测ERK/MAPK通路活化水平。结果经MPP+处理后,细胞活力呈浓度依赖性下降,经25、50、75、100、150 mmol/L MPP+处理24 h后细胞存活率分别下降至对照组的(97.32±2.41)%(、67.69±3.03)%、(56.00±3.12)%、(47.23±2.55)%、(40.00±2.46)%,与对照组相比差异均有统计学意义(P<0.01)。经75 mmol/L MPP+处理后出现早期凋亡细胞,随处理时间延长,细胞凋亡率逐渐增加,其处理4、8、16和24 h后细胞凋亡率分别为(7.26±3.43)%、(8.34±3.55)%(、20.04±2.64)%和(28.46±2.35)%(P<0.01)。同时细胞周期中G0/G1期细胞减少,S期和G2/M期细胞增多(P<0.01),细胞内ERK1/2通路活化。结论MPP+可通过活化ERK1/2通路重新启动多巴胺神经元的细胞周期,并诱导多巴胺能神经元凋亡。     

泛素羧基末端水解酶-1抑制剂对多巴胺能神经元的神经毒性作用

目的 利用人神经母细胞瘤SK-N-SH细胞观察泛素羧基末端水解酶-1(OCH-L1)抑制剂对多巴胺能神经元的毒性作用并探讨其可能的毒性机制. 方法 用不同浓度(5、10、25、50、75、100 μmol/L)的UCH-L1抑制剂作用SK-N-SH细胞24h,MTT法检测细胞活力、Hoechst染色检测凋亡的细胞核及Western blot检测UCH-L1蛋白、单个泛素分子及多聚化泛素蛋白的表达、荧光检测泛素蛋白酶体系统(UPS)的功能. 结果经UCH-L1抑制剂处理24 h后SK-N-SH细胞突起样结构消失,细胞体积变小、形态变圆;随着UCH-L1抑制剂浓度的增加,细胞活性进一步下降;与对照组比较,细胞活力在抑制剂浓度为50μmol/L时.作用24h后即出现明显下降,差异有统计学意义(P<0.05);Hoechst染色可见凋亡细胞碎裂的细胞核;Western blot检测到细胞内UCH-L1蛋白表达没有变化、单个泛素分子水平下降、多聚泛素化蛋白增加;荧光检测显示UPS功能下降.结论 UCH-L1抑制剂在体外对多巴胺能神经元有毒性作用,可诱导细胞凋亡.在凋亡过程中,UPS功能下降、细胞内多聚泛素化蛋白堆积可能发挥了作用.     

β-arrestin 2对多巴胺能神经元的保护作用及机制研究

目的探讨β-arrestin 2对多巴胺能神经元的保护作用及机制。方法分离并培养原代小鼠中脑小胶质细胞,脂多糖(LPS)处理后采用实时定量PCR检测炎性细胞因子IL-6、IL-1β和TNF-α的转录水平,ELISA检测上述因子的表达水平;将原代小鼠中脑小胶质细胞和多巴胺能神经元Transwell共培养(细胞数2∶1),LPS处理后TUNEL法检测多巴胺能神经元凋亡,酪氨酸羟化酶(TH)免疫组织化学法检测多巴胺能神经元。结果原代小胶质细胞经LPS处理后IL-6、IL-1β和TNF-α的转录水平及表达水平均较对照组显著升高,而β-arrestin 2高表达能抑制这种炎症反应;β-arrestin 2高表达能显著抑制LPS处理所致的多巴胺能神经元凋亡,抑制多巴胺能神经元数目的减少。结论β-arrestin 2可能通过抑制小胶质细胞炎性细胞因子的产生,从而对多巴胺能神经元发挥神经保护作用。     

CDNF在多巴胺能神经元变性中对自噬调控的研究

目的探讨CDNF对多巴胺能神经元变性的作用及其对自噬的调控。方法通过蛋白酶体抑制剂Lactacysin诱导PC12细胞变性前和后分别施加200nM的脑源性神经营养因子(cerebral dopamine neurotrophic factor,CDNF),利用MTT法检测PC12细胞生存率、RT-PCR和Western-blotting检测alpha-共核蛋白(synuclein)mRNA和蛋白表达;利用Western-blotting检测p62、Beclin-1和LCI/II蛋白表达。结果经Lactacystin诱导后PC12细胞生存率为0.374±0.086、α-共核蛋白mRNA和蛋白表达分别为5.766±0.052和0.434±0.077,诱导前/后施加200nM的CDNF后PC12细胞生存率分别上升至(0.594±0.121和0.542±0.097)、α-共核蛋白mRNA和蛋白表达分别下降为(0.275±0.047、0.242±0.087和0.325±0.086、0.267±0.075);Beclin-1和p62分别下降为(0.728±0.143、0.235±0.096和0423±0.108、0.258±0.065),而LC3-I/II分别上升为(0.638±0.097和0.601±0.085)。结论 CDNF可能通过负向调控自噬对多巴胺能神经元发挥神经保护和逆转作用。     

蛋白酶体抑制剂对神经细胞的双重作用

目的探索蛋白酶体抑制剂在不同浓度时对多巴胺能神经元的作用及原因。方法用6-羟多巴(6-OHDA)50uM处理的人SH-SY5Y细胞作为细胞受损伤的模型,加用不同浓度的蛋白酶体抑制剂lactacystin,镜下细胞计数和SRB法测定细胞活力,平行对照组测定蛋白酶体活性。用选择性MEKl/2抑制剂PD98059验证蛋白酶体抑制剂是否通过MAPK途径起作用。结果蛋白酶体抑制剂lactacystin在0.1、0.25、0.5uM浓度时提高细胞存活率,在2、5uM时降低细胞存活率,相应的蛋白酶体活性分别是对照组的83.43%、73.84%、66.14%、24.11%、12.36%,加用PD98059后,0.25、0.5uMlactacystin的保护作用被阻断。结论蛋白酶体抑制剂在低浓度时对多巴胺能神经元有保护作用,高浓度时对多巴胺能神经元有毒性作用,这种不同作用的原因可能与蛋白酶体抑制的程度有关。蛋白酶体抑制剂的保护作用可能通过MAPK途径起作用。     

蛋白酶体功能与帕金森病相关性实验研究

目的 观察蛋白酶体抑制剂诱导大鼠黑质多巴胺能神经元α-突触核蛋白（α-synuclein，α-Syn）的表达及聚集．探讨蛋白酶体功能在帕金森病（PD）发病中的作用机制。方法采用立体定向将蛋白酶体抑制剂Lactacystin注射至大鼠黑质部位。以免疫荧光法观察黑质区多巴胺能神经元变性缺失，并应用免疫荧光双标法观察多巴胺能神经元内蛋白聚集的包涵体及其主要成分α-Syn的表达．然后通过原位杂交分析α-Syn mRNA表达及Western印迹法检测黑质α-Syn表达量改变。结果注射Lactacystin第7天大鼠开始出现自发性活动减少．阿扑吗啡尚可诱导出旋转行为；3周后患侧黑质部位酪氨酸羟化酶（TH）阳性细胞明显减少。TH与硫磺素、硫磺素与α-Syn复合染色呈阳性。α-Syn mRNA表达量升高，蛋白表达水平增加。结论Lactacystin诱导大鼠黑质细胞α-Syn表达升高并出现蛋白聚集可能是导致PD发病的机制之一。     

雷公藤红素对C6胶质瘤细胞凋亡及细胞周期阻滞的影响

目的 探讨雷公藤红素对体外C6胶质瘤细胞凋亡及细胞周期阻滞的影响及机制.方法 雷公藤红素处理体外培养的C6胶质瘤细胞,MTT法检测细胞增殖,Hochest33342染色荧光显微镜观察以及锇铀铅染色透射电镜观察胶质瘤细胞形态变化,流式细胞术分析细胞凋亡率及细胞周期改变.蛋白印迹分析检测凋亡相关蛋白及细胞周期调控蛋白的表达变化.结果 雷公藤红素对C6胶质瘤细胞的增殖抑制作用呈浓度和时间依赖性;2.56 μmol/L雷公藤红素处理C6胶质瘤细胞24h后,荧光显微镜、透射电镜下均可见凋亡形态学改变.流式细胞术检查显示,凋亡细胞比例由1.32％升高到19.34％;并且,处于G0/G1期的细胞比例由76.42％降低到54.52％,G2/M期细胞比例由9.29％升高到30.50％.蛋白印迹分析显示,雷公藤红素降低了Bcl -2及XIAP蛋白表达,促进了Bax及Caspase -3的表达以及PARP的剪切;雷公藤红素在诱导细胞周期调控蛋白p21、p27及cyclin B1蛋白表达增加的同时抑制了cdk2蛋白的表达.结论 雷公藤红素能够通过调节凋亡相关蛋白及细胞周期相关因子的表达影响C6胶质瘤细胞的凋亡及细胞周期阻滞.     

热休克蛋白对多巴胺能神经细胞的保护作用研究

目的探讨热休克蛋白(HSP)对蛋白酶体抑制剂处理的多巴胺能神经细胞的活力以及细胞内包涵体形成的影响。方法将PC12细胞进行热处理,免疫印迹法鉴定热休克蛋白表达,并确定最佳热处理条件;再应用高选择性的蛋白酶体抑制剂Lactacystin处理PC12细胞。MTT方法检测细胞活力,免疫荧光细胞化学染色观察细胞内包涵体形成的变化。结果免疫印迹法证实PC12细胞热处理2h后HSP70水平即开始迅速升高,一直持续至24h,其中4h的HSP70水平表达较高,故选其为最佳观察条件。未经热处理的对照组经5μM、10μM、15μM和20μMLactacystin处理24h后,PC12细胞的活力显著降低,呈剂量依赖性;热处理组的细胞活力比对照组显著升高,两者有显著性差异(P<0.01)。免疫荧光染色显示对照组细胞的胞浆内包涵体明显增多,而热处理组胞浆内包涵体明显减少。结论热休克蛋白能显著增强细胞活力,减少细胞内包涵体形成,对多巴胺能神经元可能有一定的保护作用。     

钙蛋白酶在MPP~+诱导的多巴胺能神经元损伤中的作用

目的观察钙蛋白酶在MPP+诱导的多巴胺能神经元损伤中的作用,探讨帕金森病的发病机制。方法使用神经生长因子诱导PC12细胞神经元样分化,然后使用MPP+处理神经元样分化的PC12细胞,制作帕金森病细胞模型。使用免疫印迹法检测细胞内总钙蛋白酶和活化的钙蛋白酶的表达水平,使用钙蛋白酶活性检测试剂盒观察钙蛋白酶活化水平,使用钙蛋白酶抑制剂ALLN和MDL28170抑制钙蛋白酶活性后采用MTT法检测其对细胞活性的影响,用流式细胞术观察细胞凋亡变化。结果神经元样分化的PC12细胞经MPP+处理后总的钙蛋白酶水平保持稳定,但活化的钙蛋白酶表达水平逐渐增高,钙蛋白酶活性也逐渐增高,MPP+处理12 h后达到高峰。ALLN和MDL28170能够显著抑制钙蛋白酶活性,并减轻MPP+诱导的PC12细胞损伤。钙蛋白酶抑制剂也能够明显抑制MPP+诱导的细胞凋亡。结论钙蛋白酶参与MPP+诱导的多巴胺能神经元损伤,可能是帕金森病新的治疗靶点。     

The Contribution of Cdc2 in Rotenone-Induced G2/M Arrest and Caspase-3-Dependent Apoptosis

Neuronal cell cycle reentry maintained in a G2-like state before cell death, has been confirmed in dopaminergic neurons of patients with Parkinson's disease (PD). Caspase-3 is a final effector in apoptotic dopaminergic neurons in patients. The association of aberrant G2/M regulation with caspase-3 dependent apoptosis remains to be elucidated. Cell division cycle protein 2 (Cdc2) is a key player in G2/M transition in mitotic cells. Although the deregulation of Cdc2 correlated with the control of apoptosis in neurons, the molecular pathway by which Cdc2 involves in apoptosis is not clear. In a rotenone-based cell model of PD, we demonstrated that rotenone arrested cell cycle at G2/M phase and activated caspase-3 both in cytoplasm and nucleus. The decreased activity of Cdc2 by roscovitine or rotenone enhanced G2/M arrest. The increased cells in G2/M arrest by rotenone upregulated the expression of Cdc2. Suppression of Cdc2 expression downregulated cleaved caspase-3/9 and delayed cell apoptosis. Used together, the upregulation of Cdc2 contributes to rotenone-induced caspase-3/9-dependent apoptosis, which is associated with the enhancement of G2/M arrest. Our results suggest the deregulation of Cdc2 as a transition between cell cycle arrest and cell death.     

Potassium-induced apoptosis in rat cerebellar granule cells involves cell-cycle blockade at the G1/S transition

The role of regulators controlling the G1/S transition of the cell cycle was analyzed during neuronal apoptosis in post-mitotic cerebellar granule cells in an attempt to identify common mechanisms of control with transformed cells. Cyclin D1 and its associated kinase activity CDK4 (cyclin-dependent kinase 4) are major regulators of the G1/S transition. Whereas cyclin D1 is the regulatory subunit of the complex, CDK4 represents the catalytic domain that, once activated, will phosphorylate downstream targets such as the retinoblastoma protein, allowing cell-cycle progression. Apoptosis was induced in rat cerebellar granule cells by depleting potassium in presence of serum. Western-blot analyses were performed and protein kinase activities were measured. As apoptosis proceeded, loss in cell viability was coincident with a significant increase in cyclin D1 protein levels, whereas CDK4 expression remained essentially constant. Synchronized to cyclin D1 accumulation, cyclin-dependent kinase inhibitor p27Kip1 drastically dropped to 20% normal values. Cyclin D1/CDK4-dependent kinase activity increased early during apoptosis, reaching a maximum at 9-12 h and decreasing to very low levels by 48 h. Cyclin E, a major downstream target of cyclin D1, decreased concomitantly to the reduction in cyclin D1/CDK4-dependent kinase activity. We suggest that neuronal apoptosis takes place through functional alteration of proteins involved in the control of the G1/S transition of the cell cycle. Thus, apoptosis in post-mitotic neurons could result from a failed attempt to re-enter cell cycle in response to extracellular conditions affecting cell viability and it could involve mechanisms similar to those that promote proliferation in transformed cells.     

环氧化酶-2抑制剂塞来昔布对C6胶质瘤细胞增殖和凋亡的影响

目的探讨选择性环氧化酶-2抑制剂塞来昔布对体外培养的C6胶质瘤细胞增殖和凋亡的影响。方法以不同浓度塞来昔布分别作用于C6胶质瘤细胞不同时间段,采用甲基噻唑蓝比色法检测细胞活性,流式细胞仪检测细胞周期和细胞凋亡,并用光镜及透射电镜观察细胞形态学和超微结构的变化。结果经不同浓度塞来昔布作用后,C6胶质瘤细胞活性受到抑制,且呈剂量时间依赖性,实验组与对照组之间以及实验组各亚组之间均有显著性差异（P〈0.05）。细胞周期检测发现实验组S期细胞减少,G2期细胞显著增加,与对照组比较有显著性差异（P〈0.05）;同时,塞来昔布还可诱导C6胶质瘤细胞凋亡,凋亡率在实验组与对照组之间有显著性差异（P〈0.05）。结论选择性环氧化酶-2抑制剂塞来昔布可抑制C6胶质瘤细胞增殖,诱导C6胶质瘤细胞凋亡。     

Nuclear factor-kappaB-dependent cyclin D1 induction and DNA replication associated with N-methyl-D-aspartate receptor-mediated apoptosis in rat striatum

Cell cycle reentry has been found during apoptosis of postmitotic neurons under certain pathological conditions. To evaluate whether nuclear factor-kappaB (NF-kappaB) activation promotes cell cycle entry and neuronal apoptosis, we studied the relation among NF-kappaB-mediated cyclin induction, bromodeoxyuridine (BrdU) incorporation, and apoptosis initiation in rat striatal neurons following excitotoxic insult. Intrastriatally injected N-methyl-D-aspartate receptor agonist quinolinic acid (QA, 60 nmol) elicited a rise in cyclin D1 mRNA and protein levels (P<0.05). QA-induced NF-kappaB activation occurred in striatal neurons and nonneuronal cells and partially colocalized with elevated cyclin D1 immunoreactivity and TUNEL-positive nuclei. QA triggered DNA replication as evidenced by BrdU incorporation; some striatal BrdU-positive cells were identified as neurons by colocalization with NeuN. Blockade of NF-kappaB nuclear translocation with the recombinant peptide NF-kappaB SN50 attenuated the QA-induced elevation in cyclin D1 and BrdU incorporation. QA-induced internucleosomal DNA fragmentation was blunted by G(1)/S-phase cell cycle inhibitors. These findings suggest that NF-kappaB activation stimulates cyclin D1 expression and triggers DNA replication in striatal neurons. Excitotoxin-induced neuronal apoptosis may thus result from, at least partially, a failed cell cycle attempt.     

戊四氮致惊厥大鼠海马神经元Cyclin D_1表达改变和意义

目的　探讨戊四氮致惊厥大鼠海马细胞周期素 Cyclin D1 与神经细胞凋亡的关系。方法　利用寡核苷酸探针原位组织杂交技术观察各组海马 Cyclin D1 m RNA的表达水平 ,同时采用 TUNEL原位末端标记方法观察神经元凋亡。结果　戊四氮致惊厥后 6 h,大鼠海马内 Cyclin D1 m RNA表达开始增强 ,12 h达到高峰 ,2 4h开始回落。同时 ,观察到戊四氮致惊厥大鼠海马神经元凋亡数量有类似改变。结论　 Cyclin D1 m RNA表达水平的增高可能表明戊四氮致惊厥大鼠海马神经元重新进入细胞周期 ,可能与神经细胞凋亡有关。     

Gene expression profiling in the midbrain of striatal 6-hydroxydopamine-injected mice

In order to clarify mechanisms underlying dopaminergic neuronal death in Parkinson's disease (PD), a gene expression profiling study was performed in a rodent model of PD. In this model, mice are intrastriatally injected with 6-hydroxydopamine (6-OHDA) and dopaminergic neurons in the substantia nigra (SN) gradually die by retrograde degeneration. The SN were removed 2 h, 24 h, or 14 days after 6-OHDA administration. Levels of mRNAs related to cell death or survival were quantified using adaptor-tagged competitive PCR (ATAC-PCR). The cyclin D1 gene showed an immediate increase in mRNA expression. After 24 h, when dopaminergic neurons were under intense degeneration, levels of caspase 8 mRNA and p53 apoptosis effecter related to pmp 22 (PERP) mRNA increased and, conversely, FAS mRNA decreased. After 14 days, when the degeneration was attenuated, levels of PERP mRNA and serum- and glucocorticoid-regulated kinase (SGK) mRNA still increased. SGK has a similarity to AKT, which is an important molecule involved in nerve growth factor signal transduction. AKT mRNA levels are low in dopaminergic neurons. These results suggest that an increase in cyclin D1 mRNA triggers dopaminergic neurons to enter an abnormal cell cycle, which leads to neuronal degeneration and cell death, possibly induced by PERP and caspase 8. In addition to cell death-related genes, several survival-related genes are activated. SGK might function as a key enzyme for the survival of dopaminergic neurons.     

IRE1-TNAF2信号转导通路在Hcy诱导PC12细胞凋亡中的作用

目的探讨内质网应激(ERS)IRE1-TNAF2信号转导通路在同型半胱氨酸(Hcy)致大鼠嗜铬细胞瘤(PC12)细胞凋亡中的作用。方法 Hcy作用于神经生长因子诱导的PC12细胞。MTT检测5mmol.L-1Hcy不同时间作用的PC12细胞活性;流式细胞仪检测不同浓度Hcy作用24h后细胞凋亡率;RT-PCR观察IRE1、TNAF2及caspase-12 mRNA表达水平变化。结果经Hcy处理后PC12细胞发生凋亡,并呈浓度和时间依赖性。与对照组相比,IRE1 mRNA和TRAF2 mRNA表达水平增加(P<0.05),Caspase-12 mRNA表达也相应增高(P<0.05)。结论 Hcy可诱导PC12细胞凋亡,IRE1-TNAF2信号转导通路的激活在其中起重要作用。