MPP对培养中脑多巴胺能神经元的影响

目的:通过观察MPP+对体外培养的中脑多巴胺能神经元多巴胺及胆碱摄取能力、多巴胺含量变化及细胞形态的改变等,研究MPP+对中脑多巴胺能神经元功能的影响,探讨利用MPP+建立体外PD细胞模型的可能性及实际意义.方法:用孕14天Wistar大鼠,氯胺酮麻醉后取胚胎,按本室常规方法分离培养中脑多巴胺能神经元,培养至第7天后将不同浓度的MPP+加入培养有神经元的培养基中,使其终浓度分别为0.1μM,1μM,10μM.分别测定不同时相点[3H]多巴胺和[3H]胆碱摄取能力及细胞内多巴胺含量变化,并进行TH免疫细胞化学染色.结果:MPP+浓度为0.1μM、1μM和10μM时,其[3H]多巴胺摄取力分别是为6.2±0.7、5.9±0.5、5.4±04,较之对照组100±1.7的结果看,MPP+对中脑多巴胺能神经元多巴胺摄取力有明显抑制作用(P＜0.05);而[3H]胆碱摄取力其值为98±3.1,较之对照组100±2.4,差异不显著,说明MPP+对多巴胺能神经元胆碱摄取力无抑制作用(P＞0.05).另一个有趣的结果是胶质细胞的存在对MPP+的作用有明显影响,未抑制胶质细胞组其作用明显强于抑制胶质细胞组(P＜0.05);同时MPP+使中脑多巴胺能神经元细胞内多巴胺含量明显减少(P＜0.05);TH阳性细胞明显减少(P＜0.05).结论:MPP+对体外培养的中脑多巴胺能神经元多巴胺摄取力有明显的抑制作用,不仅使多巴胺的摄取降低,而且细胞内的多巴胺含量也显著减少,TH免疫组化染色结果也支持这一结果.MPP+对多巴胺能神经元胆碱摄取能力无明显抑制作用.     

MPP+对培养中脑多巴胺能神经元的影响

目的通过观察MPP+对体外培养的中脑多巴胺能神经元多巴胺及胆碱摄取能力、多巴胺含量变化及细胞形态的改变等,研究MPP+对中脑多巴胺能神经元功能的影响,探讨利用MPP+建立体外PD细胞模型的可能性及实际意义.方法用孕14天Wistar大鼠,氯胺酮麻醉后取胚胎,按本室常规方法分离培养中脑多巴胺能神经元,培养至第7天后将不同浓度的MPP+加入培养有神经元的培养基中,使其终浓度分别为0.1μM,1μM,10μM.分别测定不同时相点[3H]多巴胺和[3H]胆碱摄取能力及细胞内多巴胺含量变化,并进行TH免疫细胞化学染色.结果MPP+浓度为0.1μM、1μM和10μM时,其[3H]多巴胺摄取力分别是为6.2±0.7、5.9±0.5、5.4±04,较之对照组100±1.7的结果看,MPP+对中脑多巴胺能神经元多巴胺摄取力有明显抑制作用(P＜0.05);而[3H]胆碱摄取力其值为98±3.1,较之对照组100±2.4,差异不显著,说明MPP+对多巴胺能神经元胆碱摄取力无抑制作用(P＞0.05).另一个有趣的结果是胶质细胞的存在对MPP+的作用有明显影响,未抑制胶质细胞组其作用明显强于抑制胶质细胞组(P＜0.05);同时MPP+使中脑多巴胺能神经元细胞内多巴胺含量明显减少(P＜0.05);TH阳性细胞明显减少(P＜0.05).结论MPP+对体外培养的中脑多巴胺能神经元多巴胺摄取力有明显的抑制作用,不仅使多巴胺的摄取降低,而且细胞内的多巴胺含量也显著减少,TH免疫组化染色结果也支持这一结果.MPP+对多巴胺能神经元胆碱摄取能力无明显抑制作用.     

3-硝基丙酸多次预处理上调神经凋亡抑制蛋白表达保护多巴胺能神经元的研究

目的研究3-硝基丙酸(3-nitropropionic acid,3-NPA)多次预处理对多巴胺能神经元的保护机制.方法应用MPTP在C57BL小鼠上制作帕金森病模型,应用爬杆、悬挂实验检测小鼠协调运动能力;应用免疫组化检测中脑黑质酪氨酸羟化酶(TH)及神经凋亡抑制蛋白(NAIP)的表达.结果在MPTP组小鼠爬杆、悬挂实验评分降低,TH表达明显减少,无NAIP表达;3-硝基丙酸单次预处理后评分增加,TH、NAIP表达增多;多次预处理后TH、NAIP表达及评分增加更明显.结论3-NPA多次预处理对多巴胺能神经元的保护机制与上调NAIP表达有关.     

美满霉素对帕金森病细胞凋亡模型保护作用的研究

目的探讨美满霉素(MC)对1甲基4苯基吡啶离子(MPP+)诱导的帕金森病细胞凋亡模型保护作用的机制。方法将不同浓度(10、50、250、500μmol/L)MPP+加入培养的PC12细胞中,选择最适当浓度的MPP+建立多巴胺神经元凋亡模型(MPP+组);通过四甲基偶氮唑盐法(MTT法)检测经不同浓度(0、10、50、100、200μmol/L)MC预处理后多巴胺神经元凋亡模型的活性,以此筛选出具有最佳保护作用MC浓度建立MC+MPP+组;用电泳法、流式细胞术和逆转录聚合酶链式反应分别检测MPP+组、MC+MPP+组细胞的凋亡率,以及此2组细胞caspase3mRNA的表达,并与空白对照组比较。结果(1)在MPP+为10μmol/L时可见细胞凋亡最典型的梯状DNA条带,以此浓度建立多巴胺神经元凋亡模型(MPP+组);用100μmol/LMC预处理的MPP+组细胞活性最高(P<0.05),以此作为此后实验用MC浓度。(2)MC+MPP+组细胞凋亡率及caspase3mRNA的灰度比值分别为(22.83±2.10)%及68.08±1.14,极显著低于MPP+组的(45.89±2.28)%及86.50±1.43(均P<0.01),但仍明显高于空白对照组的(11.05±1.02)%及53.75±1.23(均P<0.05)。结论MC可能通过下调caspase3mRNA表达保护MPP+诱导的PC12细胞凋亡。     

1-甲基-4-苯基吡啶离子调控线粒体自噬对线粒体氧化应激损伤的影响

目的 探讨1-甲基-4-苯基吡啶离子(MPP+)诱导线粒体自噬在帕金森病(PD)发病机制中的作用.方法 将细胞分为MPP+(0 mmol/L)对照组、MPP+(1 mmol/L)处理组和MPP+ (2 mmol/L)处理组,共同转染EGFP-LC3和RFP-MI-TO后加入MPP+处理48 h.Western blot检测细胞自噬水平的变化,甲丹磺酸尸胺(MDC)检测自噬空泡聚集,免疫荧光法检测EGFP-LC3和RFP-MITO亚细胞共定位,流式技术检测线粒体膜电位及活性氧.结果 MPP+1 mmol/L及MPP+2 mmol/L组LAMP2A、Beclin1和LC3-Ⅱ/LC3-Ⅰ的灰度值与对照组相比均上调,差异有统计学意义(P＜0.05).与对照组相比,MPP+处理组自噬水平增加,自噬空泡增加,外源性LC3表达上调,EGFP-LC3和RFP-MITO存在亚细胞共定位.MPP+1 mmol/L及MPP+2 mmol/L组线粒体膜电位较对照组降低;MPP+1 mmol/L及MPP+2 mmol/L组线粒体活性氧较对照组增加,差异均有统计学意义(P＜0.05).结论 MPP+通过调控线粒体自噬水平致线粒体氧化应激损伤.     

利噜唑拮抗左旋多巴和多巴胺对中脑原代细胞的毒性作用

目的:研究左旋多巴(L-DOPA)和多巴胺(DA)对大鼠胚胎中脑原代细胞的毒性损害以及利噜唑拮抗L-DOPA和DA的毒性作用。方法:通过体外大鼠胚胎中脑原代细胞培养,采用MTT细胞活性和[~3H]DA摄取率检测中脑原代细胞的存活数和DA能神经元的[~3H]DA摄取功能。结果:当L-DOPA和DA浓度增至500 μmol·L~(-1)时,细胞存活率明显下降(P<0.05),均呈剂量依赖性。当L-DOPA和DA浓度分别增至1mmol·L~(-1)和200μmol·L~(-1)时,[~3H]DA摄取率明显下降(P<0.05),均呈剂量依赖性。利噜唑2～10μmol·L~(-1)能抑制L-DOPA和DA对细胞存活率和[~3H]DA摄取率的影响(P<0.05)。结论:大剂量L-DOPA和DA(≥500 μmol·L~(-1))对中脑原代细胞产生毒性损害,利噜唑能拮抗L-DOPA和DA对中脑原代细胞的毒性效应,具有神经保护作用。     

1-甲基-4-苯基-吡啶盐致多巴胺能细胞系MES23.5死亡机制的研究

帕金森病 (Parkinson’sdisease,PD)是常见的老年神经系统变性病 ,其主要病理特征是黑质多巴胺能神经元的选择性丢失。Longston等发现 1 甲基 4 苯基 吡啶 (MPTP)能对多巴胺能神经元造成选择性损害 ,产生与PD类似的临床特点及病理改变 ,而MPTP的神经毒性是通过其代谢产物 1 甲基 4 苯基 吡啶盐 (MPP+ )起作用的。方法、结果和讨论 :本研究应用多巴胺能神经细胞系MES2 3 5 ,观察在MPP+ 作用下 ,细胞的存活率、线粒体膜电位以及氧化应激指标的改变 ,以期能了解MPP+ 对多巴胺能细胞的毒性作用机制。培养的MES2 3 5细胞经MPP+(…     

化学预处理对大鼠海马脑片缺氧耐受性的影响及其与线粒体ATP敏感性钾通道的关系

目的:探讨3-硝基丙酸(3-NPA)预处理对海马脑片缺氧损伤的保护作用及线粒体内膜ATP敏感性钾(Mi-toK_(ATP))通道在预处理脑保护机制中的作用。方法:采用Nissl染色和透射电镜观察缺氧后大鼠海马CA_1区神经元密度、锥体细胞和亚细胞结构在预处理前后的变化,以及MitoK_(ATP)拮抗剂5-羟基癸酸盐(5-HD)孵育海马脑片对预处理效果的影响。结果:3-NPA组大鼠缺氧后海马CA_1区神经元密度(86.69±4.87)高于对照组(53.85±3.13,P<0.05),锥体细胞超微结构受损程度较对照组明显减轻。预处理大鼠海马脑片经100μmol/L 5-HD孵育后CA_1区神经元密度(57.31±7.89)较未孵育脑片降低(P<0.05),超微结构受损加重。结论:3-NPA预处理可提高海马脑片缺氧耐受能力,这种保护作用可能与MitoK_(ATP)通道开放有关。     

表没食子儿茶素没食子酸酯通过激活核因子相关因子2保护MPP+诱导的PC12细胞氧化损伤

目的 观察表没食子儿茶素没食子酸酯(EGCG)对MPP+诱导PC12细胞氧化损伤的保护作用及其与核因子相关因子-2(NRF2)之间的关系.方法 以不同浓度EGCG预处理MPP+诱导的PC12细胞,选用细胞外调节蛋白激酶(ERK)抑制剂U120作为干预药物,噻唑蓝(MTT)法检测细胞活性;Western blot检测细胞内NRF2表达量及核内外分布;实时荧光定量PCR检测NRF2下游抗氧化酶血红素氧合成酶-1(HO-1)和醌氧化还原酶1(NQ01)在转录水平的变化.结果 MTT法显示MPP+明显降低细胞生存率,具有浓度依赖效应,而EGCG预处理能明显抑制MPP+对细胞的损伤作用;Westem blot结果显示MPP+模型组NRF2表达量为对照组的148％±5％ (t=6.102,P＜0.01),EGCG预处理组NRF2表达量为对照组的188％±6％(t=11.172,P＜0.01),U120则能抑制EGCG诱导NRF2表达增加的效应,为对照组的148％±15％(t=6.118,P＜0.01);EGCG预处理组NRF2核内蛋白量的增加更加明显,为对照组的258％±2％(t=21.995,P＜0.01),U120+ EGCG+ MPP+组核内NRF2蛋白量较EGCG预处理组明显减低,为对照组的158％±1％(f=8.058,P＜0.01).与NRF2的变化一致,实时荧光定量PCR显示EGCG预处理组抗氧化酶HO-1、NQO1 mRNA水平较其余各组明显增高,U120也可抑制EGCG对HO-1和NQO1 mRNA的诱导效应.结论 EGCG能保护MPP+诱导的PC12细胞氧化损伤,其保护作用可能与通过激活ERK-NRF2途径,诱导下游HO-1、NQO1等抗氧化酶表达有关.     

美满霉素对MPP+诱导的PC12细胞凋亡的保护作用

目的在离体细胞培养中探讨美满霉素(Minocycline,MC)对1-甲基-4-苯基吡啶离子(MPP )诱导的帕金森病细胞凋亡模型的保护作用.方法将MC或MPP 加入培养的PC12细胞中,建立多巴胺神经元凋亡模型,四甲基偶氮唑盐法(MTT法)检测细胞代谢活性,电泳法检测细胞凋亡,流式细胞术检测细胞凋亡率.结果MPP 浓度为10μmol/L时建立多胺神经元凋亡模型;MC 100 μmol/L预处理可明显升高MPP 处理的PC12细胞活性;MC MPP 组细胞凋亡率显著低于MPP 组(P＜0.01),但仍明显高于阴性对照组(P＜0.05).结论MC对MPP 诱导的细胞凋亡有一定的保护作用.     

Protection from 1-methyl-4-phenylpyridinium (MPP) toxicity and stimulation of regrowth of MPP-damaged dopaminergic fibers by treatment of mesencephalic cultures with EGF and basic FGF

Several peptide growth factors can maintain survival or promote recovery of injured central neurons. In the present study, the effects of epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF) on the toxicity produced by the dopaminergic neurotoxin, 1-methyl-4-phenylpyridinium (MPP+), were investigated in rat mesencephalic dopaminergic neurons in culture. High affinity [3H]DA uptake and morphometric analyses of tyrosine hydroxylase immunostained neurons were used to assess the extent of MPP+ toxicity, dopaminergic neuronal survival and growth of neurites. Consistent with previous reports, EGF and bFGF treatments stimulated neuritic outgrowth in dopaminergic neurons, increased DA uptake and enhanced their long-term survival in vitro. These growth factors also stimulated proliferation of astrocytes. The time course of EGF and bFGF effects on dopaminergic neurons coincided with the increase in glial cell density, suggesting that proliferation of glia mediates their trophic effects. Several findings from our study support this possibility. When MPP+ was applied to cultures at 4 days in vitro, before glial cells had proliferated, the damage to dopaminergic neurons was not affected by EGF or bFGF pretreatments. However, when cultures maintained in the presence of the growth factors for 10 days were exposed to MPP+, after they had become confluent with dividing glial cells, the MPP(+)-induced decreases in DA uptake and cell survival were significantly attenuated. Furthermore, when glial cell proliferation was inhibited by 5-fluoro-2'-deoxyuridine, the protective effects of EGF and bFGF against MPP+ toxicity were abolished. Continuous treatment of MPP(+)-exposed cultures with EGF or bFGF resulted in the stimulation of process regrowth of damaged dopaminergic neurons with concomitant recovery of DA uptake, suggesting that the injured neurons are able to respond to the trophic effects of EGF and bFGF. In summary, our study shows that the trophic effects of EGF and bFGF on mesencephalic dopaminergic neurons include protection from the toxicity produced by MPP+ and promotion of recovery of MPP(+)-damaged neurons. Stimulation of glial cell proliferation is necessary for these effects.     

3-硝基丙酸多次化学预处理对多巴胺能神经元的保护作用

目的探讨3-硝基丙酸（3-NP）多次化学预处理对多巴胺能神经元的保护作用及可能机制。方法应用MPTP（30mg／kg）在C57BL小鼠上复制帕金森病模型，以3-NP（20mg／kg）行预处理，检测小鼠中脑黑质凋亡率和转录因子c-Jun的阳性细胞数量及c-Jun的蛋白水平；应用MPP^＋（0．25mmol／L）在SH—SY5Y细胞制作帕金森病模型，以3-NP（0．2mmol／L）进行预处理，并将携带显性突变体c—JuncDNA片段的真核表达载体质粒pcDNA3（HA）-Jun—dn转染SH—SY5Y细胞，检测各组细胞的c-Jun表达水平及凋亡率。结果小鼠中脑黑质凋亡率：MPTP组较对照组明显升高（P〈0.01），3-NP单次、多次预处理后均明显降低（P〈0．05，P〈0．01）；c—Jun阳性细胞数：MPTP组较对照组明显增加（P〈0．05），3-NP单次预处理组与MPTP组比较无明显差异，3-NP多次预处理后明显降低（P〈0．05）；c—Jun蛋白水平：与其阳性细胞数变化一致；细胞凋亡率：MPP^＋组较对照组明显升高，3-NP单次、多次预处理组细胞凋亡率明显降低（P〈0.05，P〈0．01）；c-Jun蛋白水平变化与中脑黑质一致；经pcDNA3（HA）-Jundn转染的细胞，其c-Jun的表达较未转染细胞明显降低（P〈0．01），其凋亡率也下降（P〈0．01）。结论3-NP单次、多次预处理对多巴胺能神经元确有保护作用，多次预处理保护效果更强，其机制与抑制转录因子c-Jun的表达，降低其蛋白水平有关。     

Terminally differentiated SH-SY5Y cells provide a model system for studying neuroprotective effects of dopamine agonists

We characterized undifferentiated (UN) and three differentiation conditions of the SH-SY5Y neuroblastoma cell line for phenotypic markers of dopaminergic cells, sensitivity to the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridinium ion (MPP+), the requirement to utilize the dopamine (DA) transporter (DAT) for MPP+ toxicity, and the neuroprotective effects of pramipexole. Cells were differentiated with retinoic acid (RA), 12-O-tetradecanoyl-phorbol-13-acetate (TPA), and RA followed by TPA (RA/TPA). RA/TPA treated cells exhibited the highest levels of tyrosine hydroxylase and DAT but lower levels of vesicular monoamine transporter. The kinetics of [3H]DA uptake and [3H]MPP+ uptake to DAT in RA/TPA differentiated cells were similar to that of rat and mouse caudate-putamen synaptosomes. RA/TPA differentiated cells evidenced high sensitivity to the neurotoxic effects of MPP+ (0.03 to 3.0 mM), and the neurotoxic effects of MPP+ were blocked with the DAT inhibitor 1-(2-[bis(4-fluorophenyl)methoxy]ethyl)-4-(3-phenylpropyl)piperazine (GBR 12909). DA-induced cell death was not more sensitive in RA vs RA/TPA differentiated cells and was not inhibited by transporter inhibitors. RA/TPA differentiated cells exhibited 3-fold and 6-fold higher levels, respectively, of DA D2 and D3 receptors than UN or RA differentiated cells. Pretreatment with pramipexole was protective against MPP+ in the RA/TPA differentiated cells but not in undifferentiated or RA differentiated cells. The neuroprotective effect of pramipexole was concentration-dependent and dopamine D2/D3 receptor dependent. In contrast, protection by pramipexole against DA was not DA receptor dependent. Further characterization of the neuroprotective effects of DA agonists in this model system can provide unique information about DA receptor dependent and independent mechanisms of neuroprotection.     

Terminally differentiated SH-SY5Y cells provide a model system for studying neuroprotective effects of dopamine agonists

We characterized undifferentiated (UN) and three differentiation conditions of the SH-SY5Y neuroblastoma cell line for phenotypic markers of dopaminergic cells, sensitivity to the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridinium ion (MPP), the requirement to utilize the dopamine (DA) transporter (DAT) for MPP toxicity, and the neuroprotective effects of pramipexole. Cells were differentiated with retinoic acid (RA), 12-O-tetradecanoly-phorbol-13-acetate (TPA), and RA followed by TPA (RA/TPA). RA/TPA treated cells exhibited the highest levels of tyrosine hydroxylase and DAT but lower levels of vesicular monoamine transporter. The kinetics of [³H]DA uptake and [³H]MPP uptake to DAT in RA/TPA differentiated cells were similar to that of rat and mouse caudate-putamen synaptosomes. RA/TPA differentiated cells evidenced high sensitivity to the neurotoxic effects of MPP (0.03 to 3.0 mM), and the neurotoxic effects of MPP were blocked with the DAT inhibitor 1-(2-[bis(4-fluorophenyl)methoxy]ethyl)-4-(3-phenylpropyl)piperazine (GBR 12909). DA-induced cell death was not more sensitive in RA vs RA/TPA differentiated cells and was not inhibited by transporter inhibitors. RA/TPA differentiated cells exhibited 3- fold and 6-fold higher levels, respectively, of DA D₂ and D₃ receptors than UN or RA differentiated cells. Pretreatment with pramipexole was protective against MPP in the RA/TPA differentiated cells but not in undifferentiated or RA differentiated cells. The neuroprotective effect of pramipexole was concentration-dependent and dopamine D₂/D₃ receptor dependent. In contrast, protection by pramipexole against DA was not DA receptor dependent. Further characterization of the neuroprotective effects of DA agonists in this model system can provide unique information about DA receptor dependent and independent mechanisms of neuroprotection.     

Local support cells promote survival of substantia nigra dopaminergic neurons in culture.

Recent studies suggest that brain neurons require extracellular signals for continued survival during maturity as well as development. However, factors underlying the survival of specific populations of central neurons remain to be defined. To examine the regulation of neuronal survival, we have studied the substantia nigra (SN) dopaminergic (DA) system, in dissociated cell culture. DA neuron number was monitored immunocytochemically with antibody to tyrosine hydroxylase (TH), the DA biosynthetic enzyme. Initially, mixed cultures were grown at low, medium, and high densities in serum-containing media. After 7 days, the number of neuron-specific enolase (NSE)-positive cells, a measure of total neuron number, was proportional to cell plating density. In contrast, high density culture elicited a marked, disproportionate increase in TH-immunopositive cells, suggesting that high density conditions selectively enhanced the DA subpopulation. To define the role of cellular interactions in the selective increase in DA cells, virtually pure neuron cultures were compared to support cell-neuron cocultures, in fully defined medium. In support cell-neuron cocultures, SN support cells evoked a four-fold increase in TH cells, while NSE number did not differ from controls. Moreover, local support cells elicited a greater increase in TH cell number than support cells derived from other brain regions. To determine whether increased TH cell number reflected enhanced survival, or possibly expression of TH by new populations, we monitored the time course of this effect. TH cell number remained constant after 3 days in cocultures, while declining fourfold in controls. In parallel studies, support cells were added to SN dissociates at zero time or after 3 days.(ABSTRACT TRUNCATED AT 250 WORDS)     

Neuroprotective effect of a neurotoxin, 3-nitropropionic acid, against hypoxic damage to the gerbil hippocampus: neuroprotection after the onset of hypoxic depolarization]

Ischemic/hypoxic tolerance induced by a subtoxic dose of neurotoxin, 3-nitropropionic acid(3-NPA), was recently reported as "chemical preconditioning". We previously showed that the neuroprotective effect by chemical preconditioning with 3-NPA was induced by prolonging the delay to hypoxic depolarization (HD) via activating adenosine receptors. In this study, we electrophysiologically assessed whether the protective effect of chemical preconditioning was potent after the onset of HD. An in vitro hippocampal slice model from adult gerbils was used to study the delay to HD during hypoxia and the recovery of synaptic responses after hypoxia. Hypoxia was sustained until a fixed period(8 min) following HD. These responses were examined in control slices and slices pretreated with subtoxic dose of 3-NPA(4 mg/kg) intraperitoneally at 3 hours prior to slice preparation. The delay to hypoxic depolarization in 3-NPA treated slices was significantly prolonged(p < 0.05). The field excitatory postsynaptic potential recovery after a fixed period of hypoxia under HD was also significantly improved in the 3-NPA treated group(48.6 +/- 23.8%) compared with the control group(29.2 +/- 12.2%) (p < 0.05). This finding indicates that chemical preconditioning with 3-NPA induces the neuroprotective effect against hypoxic damage after as well as before the onset of HD to the hippocampus.     

The glutamate antagonist, MK-801, does not prevent dopaminergic cell death induced by the 1-methyl-4-phenylpyridinium ion (MPP) in rat dissociated mesencephalic cultures

The neuroprotective effects of MK-801, a non-competitive antagonist of the N-methyl-D-aspartate (NMDA) receptor/channel, were assessed in a culture model which reproduces in vitro the selective degeneration of mesencephalic dopaminergic neurons seen in parkinsonian brains. Dissociated mesencephalic cells derived from rat embryonic brains were subjected for 24 h to intoxication by the 1-methyl-4-phenylpyridinium (MPP+), the active metabolite of the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). MPP+ at 3 and 10 microM produced selective and dose-dependent damages to dopaminergic neurons as quantified by the loss of the number of TH immunoreactive cells and the loss of [3H]DA uptake whereas other cell types remained unaffected. MK-801 at 3 and 10 microM failed to rescue degenerating dopaminergic neurons in presence of MPP+. At 50 microM, i.e. the highest concentration that is not toxic by itself in this culture system, MK-801 was also found ineffective. Furthermore, degree of dopaminergic cell damage was not reduced when repeated additions of the glutamate antagonist (10 microM/6 h for 24 h) were performed during exposure to MPP+ or when mesencephalic cultures were left after intoxication for up to 2 days in a culture medium still supplemented with MK-801 but free of toxin. In accordance with these results, MK-801 did not affect significantly the uptake of [3H]DA in control cultures, thereby suggesting that this compound cannot prevent intracellular accumulation of MPP+ within dopaminergic neurons. At higher concentrations of MPP+ (100 microM) tested, toxic effects were seen toward dopaminergic neurons and non-dopaminergic cells as quantified by Trypan blue dye accumulation and loss of [3H]GABA uptake.(ABSTRACT TRUNCATED AT 250 WORDS)     

Prevention of 1-methyl-4-phenylpyridinium- and 6-hydroxydopamine-induced nitration of tyrosine hydroxylase and neurotoxicity by EUK-134, a superoxide dismutase and catalase mimetic, in cultured dopaminergic neurons

Oxidative stress has been implicated in the selective degeneration of dopaminergic (DAergic) neurons in Parkinson's disease (PD). In this study, we tested the efficacy of EUK-134, a superoxide dismutase (SOD) and catalase mimetic, on the nitration of tyrosine hydroxylase (TH), a marker of oxidative stress, and neurotoxicity produced by 1-methyl-4-phenylpyridinium (MPP(+)) and 6-hydroxydopamine (6-OHDA) in primary DAergic neuron cultures. Exposure of cultures to 10 microM MPP(+) reduced dopamine (DA) uptake and the number of tyrosine hydroxylase immunoreactive (THir) neurons to 56 and 52% of control, while exposure to 30 microM 6-OHDA reduced DA uptake and the number of THir neurons to 58 and 59% of control, respectively. Pretreatment of cultures with 0.5 microM EUK-134 completely protected DAergic neurons against MPP(+)- and 6-OHDA-induced neurotoxicity. Exposure of primary neuron cultures to either MPP(+) or 6-OHDA produced nitration of tyrosine residues in TH. Pretreatment of cultures with 0.5 microM EUK-134 completely prevented MPP(+)- or 6-OHDA-induced nitration of tyrosine residues in TH. Taken together, these results support the idea that reactive oxygen species (ROS) are critically involved in MPP(+)- and 6-OHDA-induced neurotoxicity and suggest a potential therapeutic role for synthetic catalytic scavengers of ROS, such as EUK-134, in the treatment of PD.