GJ-4对冈田酸诱发小鼠学习记忆障碍的神经保护作用和机制研究

GJ-4是从中药栀子中提取出的藏红花色素类活性成分,前期研究发现GJ-4对Aβ诱发的小鼠学习记忆障碍具有明显的改善作用。本实验采用小鼠侧脑室注射冈田酸(okadaic acid, OA)建立记忆损伤模型(实验中所有操作均获得中国医学科学院北京协和医学院实验动物伦理委员会的批准,批准号:00000318),探讨GJ-4对Tau蛋白过度磷酸化引起神经元病变的改善作用及其机制。小鼠OA侧脑室注射后,连续16天灌胃给予GJ-4。结果显示, GJ-4可显著改善OA诱发的小鼠学习记忆障碍,同时减少小鼠海马区神经元尼氏小体的丢失。GJ-4可提高蛋白磷酸酶2A (protein phosphatase 2A, PP2A)活性并抑制糖原合成酶激酶-3β (glycogen synthase kinase-3β, GSK-3β)表达,进而降低Tau蛋白Ser396、Thr231和Ser404位点的磷酸化水平。进一步研究发现, GJ-4还可降低OA小鼠脑内氧化应激水平和海马星形胶质细胞活化介导的神经炎症而抑制神经元凋亡,最终发挥改善小鼠学习记忆障碍的作用。以上研究表明, GJ-4具有开发成为治疗阿尔茨海默症...     

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。     

褪黑素对冈田酸致NG108-15和SH-sY5Y细胞活性减弱的影响

目的观察褪黑素对冈田酸(okadaic acid,OA)致细胞活性减弱的影响。方法以光学显微镜和M TT法观察OA对细胞形态和活性的影响及M LT的拮抗作用。结果OA作用后细胞形态改变明显,突起回缩,细胞活性明显减弱,M LT作用后细胞活性显著提高。结论褪黑素可对抗OA致AD样细胞形态改变和活性减弱。     

喹啉酸致学习记忆障碍模型相关因素的探讨

目的本课题旨在从神经生化、神经病理和行为学三方面,对喹啉酸损伤所致的学习记忆障碍模型进行研究。方法应用微量注射方法,将喹啉酸注入大鼠双侧海马CA1区,建立大鼠学习记忆障碍模型,从行为学和病理形态学方面观察模型大鼠的改变。结果QA损伤所致的学习记忆障碍模型的大鼠,其行为学和海马的组织病理学有显著改变,同时海马神经元中的TH、TPH、ChAT和Glu的阳性细胞数量减少,并且NA、DA和5-HT的含量也有所下降。提示该模型可能是通过损伤Glu能神经系统和胆碱能神经系统造成了大鼠学习记忆的障碍。另外,QA也可能通过影响单胺类神经递质的代谢,而影响大鼠学习记忆的能力。结论此动物模型可作为学习记忆障碍模型的探讨,也可用于AD病发病机制的研究。     

氯化锂对冈田酸所致SK-N-SH神经元突触萎缩的保护作用

目的考察氯化锂(LiCl)对蛋白磷酸酶抑制剂冈田酸(OA)诱导的SK-N-SH细胞分化神经元损伤的保护作用和tau蛋白Ser-~(262)位点磷酸化水平的影响。方法利用全反式维甲酸(ATRA)诱导SK-N-SH细胞分化为成熟的神经元细胞;采用OA诱导成熟神经元细胞建立AD模型;采用磺酰罗丹明B(SRB)比色法考察LiCl对成熟的神经元细胞增殖的抑制作用;Giemsa染色观察SK-N-SH细胞形态学变化;并采用Image-Proplus软件测定神经元细胞的突触长度;采用Western blot检测synaptophysin蛋白和tau蛋白Ser-~(262)位点磷酸化水平。结果 10μmol·L~(-1)ATRA连续处理7 d,可诱导SK-N-SH细胞突触生长和synaptophysin蛋白表达等典型分化神经元的特征。20~100 nmol·L~(-1)OA作用于分化神经元,可浓度和时间依赖性抑制细胞增殖,同时致分化神经元突触萎缩,tau蛋白Ser-~(262)位点磷酸化水平也明显升高。10 mmol·L~(-1)LiCl预处理可维持synaptophysin蛋白高表达,抑制tau蛋白Ser-~(262)位点磷酸化水平(P<0.01)。结论LiCl能够改善OA所致分化神经元的突触损伤,并伴随着synaptophysin表达的升高、tau蛋白Ser-~(262)位点异常磷酸化水平的降低。     

人参皂苷对蛋白磷酸酶抑制剂冈田酸拟阿尔采末病细胞模型的影响

目的探讨人参皂苷(ginsenoside,GS)对蛋白磷酸酶抑制剂冈田酸(OA)诱导拟Alzheimer病(AD)细胞模型神经细胞tau蛋白的磷酸化、微管、细胞凋亡和凋亡调节因子的影响。方法GS与人神经母细胞瘤细胞系SK-N-SH细胞预孵育24h,弃去培养基,然后用OA10nmol·L-1与SK-N-SH细胞共孵育6h;用倒置显微镜观察细胞形态的变化,激光共聚焦显微镜观察微管变化,Western blot方法观察磷酸化tau蛋白、凋亡因子Bcl-2、Bax和Caspase-3的表达,用TUNEL法观察凋亡细胞的变化。结果正常SK-N-SH神经细胞铺展良好,OA模型组细胞突起断裂,GS显示了细胞保护作用。通过激光共聚焦显微镜观察,正常SK-N-SH细胞微管粗壮、连续,而OA模型组微管断裂、消失;GS能够减少OA引起的微管破坏作用。OA模型组tau蛋白Ser-199/202和Ser-404位点磷酸化水平较正常对照组明显增高,非磷酸化水平较正常对照组明显下降;GS 50mg·L-1和100mg·L-1组使神经细胞tau蛋白Ser-199/202和Ser-404位点磷酸化水平较OA模型组明显下降,GS 50mg·L-1和100mg·L-1组的tau蛋白Ser202非磷酸化水平较模型组则明显升高;正常对照组未见凋亡细胞;OA模型组凋亡细胞明显增多,Bax和Caspase-3表达水平较正常对照组明显增高,Bcl-2水平明显下降;GS能够明显抑制OA诱导的细胞凋亡,减少Bax和Caspase-3表达。结论人参皂苷对蛋白磷酸酶抑制剂OA所致的神经细胞病理变化有明显的保护作用,可能是通过抑制tau蛋白过度磷酸化,防止细胞凋亡来发挥作用的,提示该药在防治AD方面可能具有良好的应用前景。     

冈田酸诱导NG108-15细胞tau蛋白过度磷酸化过程中PTEN蛋白水平的变化

目的探讨冈田酸(OA)诱导NG108-15细胞tau蛋白过度磷酸化过程中PTEN蛋白水平的变化。方法20 nmol.L-1OA孵育NG108-15细胞不同时间(0,3,6,12,18,24,36,48 h),倒置显微镜观察细胞形态的变化,免疫印迹法观测各时间点Ser396位点磷酸化tau蛋白及PTEN蛋白水平的变化。结果NG108-15细胞随OA孵育时间的延长逐渐出现细胞胞体变圆,突起回缩,悬浮生长。细胞Ser396位点磷酸化tau蛋白水平于OA作用6 h后显著升高,18 h达高峰,之后逐渐下降,但48 h仍高于基础水平;PTEN蛋白水平于3 h开始上升,18h达高峰,之后逐渐下降,12、18、24 h 3个时间点PTEN蛋白水平显著高于基础水平,36、48 h时间点PTEN蛋白水平与基础值比较差异无显著性。结论OA诱导NG108-15细胞AD样发生中,PTEN蛋白水平可能升高。     

大鼠空间辨别性学习记忆时海马ACh和ACh能纤维的变化

目的观察大鼠在空间辨别性学习记忆时海马乙酰胆碱(ACh)和ACh能纤维的变化,以探讨中枢ACh与学习记忆的关系。方法以水迷宫法建立大鼠学习记忆动物模型,用碱性羟胺比色法测定海马ACh含量,以及乙酰胆碱酯酶(AChE)的组织化学检测海马CA2、CA4区AChE。结果具有学习记忆能力的大鼠海马ACh含量和ACh能纤维的密度均比对照组增加(P<0.05)。结论中枢ACh参与空间辨别性学习记忆的过程,并与记忆的巩固有关。     

山茱萸环烯醚萜苷对蛋白磷酸酶抑制剂冈田酸拟阿尔采末病细胞模型的作用

目的探讨中药山茱萸环烯醚萜苷(COIG)对蛋白磷酸酶2A和1(PP2A和PP1)抑制剂冈田酸(okadaicacid,OA)拟阿尔采末病细胞模型tau蛋白过度磷酸化水平和细胞微管的影响。方法COIG与人神经母细胞瘤细胞系SKNSH细胞预孵育24h,再用OA10nmol·L-1与SKNSH细胞共孵育6h,在显微镜下观测细胞形态变化,用Westernblot方法观察磷酸化和非磷酸化tau蛋白表达,用间接免疫荧光法观察神经细胞微管的变化。结果正常SKNSH细胞铺展良好,OA模型组细胞变圆,突起断裂;OA模型组tau蛋白ser199/202和ser404位点磷酸化水平较正常对照组明显增高,非磷酸化水平下降;OA模型组细胞微管平均面积较正常对照组明显减少。COIG(100和200mg·L-1)给药组细胞形态基本恢复正常,tau蛋白ser199/202和ser404位点磷酸化水平较OA模型组明显下降、非磷酸化水平升高,细胞微管平均面积比模型组明显增大。结论山茱萸环烯醚萜苷能够抑制神经细胞tau蛋白过度磷酸化,保护细胞微管结构,因此可能具有治疗AD的应用前景。     

腹侧海马GABAA受体部分介导丙泊酚致大鼠空间学习记忆障碍

目的确定丙泊酚（propofol,Pro）致大鼠空间学习记忆障碍与腹侧海马γ-氨基丁酸A（GABAA）受体之间的关系。方法 112只SD大鼠随机分为14组,每组8只。采用Y迷宫法、以所需电击次数作为空间学习、记忆成绩指标,建立腹腔注射（i.p）Pro大鼠空间学习记忆障碍模型。大鼠海马置管后,腹侧海马内微量注射GABAA受体特异性拮抗剂荷包牡丹碱（bicuculline,Bic）,观察不同剂量Bic（0.125,0.25,0.5mmol&#183;L-1,1μL）对Pro所致空间学习记忆障碍的改善作用。结果 20mg&#183;kg-1Pro可导致大鼠空间学习记忆障碍,与0.9%氯化钠溶液、脂肪乳、5mg&#183;kg-1、10mg&#183;kg-1Pro组比较差异有极显著性（P〈0.01）。随着海马内注射Bic剂量的增加（0.125,0.25,0.5mmol&#183;L-1,1μL）,20mg&#183;kg-1Pro大鼠学习及记忆成绩有所改善（P〈0.05）,但最大剂量Bic组（即0.5mmol&#183;L-1,1μL）,仍无法达到溶媒对照组（与脂肪乳＋人工脑脊液组比,P〈0.05）水平。结论 Pro部分通过腹侧海马的GABAA受体导致大鼠空间学习记忆障碍。     

山茱萸环烯醚萜苷对冈田酸拟阿尔茨海默病细胞模型的抗凋亡作用研究

目的:研究山茱萸环烯醚萜苷(CIG)对蛋白磷酸酶抑制剂冈田酸(OA)拟阿尔茨海默病(AD)细胞模型中神经细胞凋亡的影响及其作用机制。方法:CIG与人神经母细胞瘤细胞系SK-N-SH细胞预孵育24h,再用OA10nmol与神经细胞共孵育6h,用TUNEL法观察凋亡细胞的变化,用蛋白免疫印记法观察凋亡因子B细胞淋巴瘤(Bcl-2)、Bcl-2相关X蛋白(Bax)和细胞凋亡蛋白酶(Caspase-3)的表达。结果:正常对照细胞铺展良好,未出现凋亡细胞;OA模型组凋亡细胞显著增多,Bax和Cas-pase-3的表达水平显著增高,Bcl-2的表达水平显著下降;CIG(100和200μg.mL-1)给药组凋亡细胞较OA模型组显著减少,Bax和Caspase-3表达水平显著降低,Bcl-2表达显著增高。结论:CIG能通过影响凋亡调节因子而抑制神经细胞凋亡,提示该药可能具有治疗AD的良好应用前景。     

Okadaic acid modulates exocytotic and transporter-dependent release of dopamine in bovine retina in vitro

Bovine retinas were isolated for the study of the modulation of exocytotic and transporter-dependent release of dopamine (DA) in vitro. Endogenous DA was measured in the medium using HPLC with electrochemical detection under successive incubations with transfers in fresh medium every 30 min.As expected, potassium caused a calcium-dependent exocytotic liberation of DA. Amphetamine or tyramine induced a calcium-independent release by reversing DA transport across the plasma membrane. Okadaic acid, a specific inhibitor of phosphatases 1 and 2A, induced a slight but significant DA release in the absence of calcium. Furthermore, the toxin increased potassium-, amphetamine-or tyramine-induced DA release independently of extracellular calcium. In addition, okadaic acid completely annulled the ability of a calcium-free extracellular environment to inhibit the potassium-induced DA release. Finally, the toxin prevented the time-dependent decline in the efficacies of amphetamine or tyramine to release DA.In agreement with proposed schemes described for rat striatum, the results of the present study confirmed the existence of distinct release modes of DA in bovine retina. The results obtained with okadaic acid suggest that phosphatase 1 and/or phosphatase 2A constitute part of a direct or indirect mechanism to inhibit both exocytotic and transporter-dependent DA release.     

Cromoglycate drugs suppress eicosanoid generation in U937 cells by promoting the release of Anx-A1

Using biochemical, epifluorescence and electron microscopic techniques in a U937 model system, we investigated the effect of anti-allergic drugs di-sodium cromoglycate and sodium nedocromil on the trafficking and release of the anti-inflammatory protein Annexin-A1 (Anx-A1) when this was triggered by glucocorticoid (GC) treatment. GCs alone produced a rapid (within 5 min) concentration-dependent activation of PKCα/β (Protein Kinase C; EC 2.7.11.13) and phosphorylation of Anx-A1 on Ser²⁷. Both phosphoproteins accumulated at the plasma membrane and Anx-A1 was subsequently externalised thereby inhibiting thromboxane (Tx) B₂ generation. When administered alone, cromoglycate or nedocromil had little effect on this pathway however, in the presence of a fixed sub-maximal concentration of GCs, increasing amounts of the cromoglycate-like drugs caused a striking concentration-dependent enhancement of Anx-A1 and PKCα/β phosphorylation, membrane recruitment and Anx-A1 release from cells resulting in greatly enhanced inhibition of TxB₂ generation. GCs also stimulated phosphatase accumulation at the plasma membrane of U937 cells. Both cromoglycate and nedocromil inhibited this enzymatic activity as well as that of a highly purified PP2A phosphatase preparation. We conclude that stimulation by the cromoglycate-like drugs of intracellular Anx-A1 trafficking and release (hence inhibition of eicosanoid release) is secondary to inhibition of a phosphatase PP2A (phosphoprotein phosphatase; EC 3.1.3.16), which probably forms part of a control loop to limit Anx-A1 release. These experiments provide a basis for a novel mechanism of action for the cromolyns, a group of drugs that have long puzzled investigators.     

PP2A Inhibition Assay Using Recombinant Enzyme for Rapid Detection of Okadaic Acid and Its Analogs in Shellfish

Okadaic acid and its analogs (OAs) responsible for diarrhetic shellfish poisoning (DSP) strongly inhibit protein phosphatase 2A (PP2A) and thus are quantifiable by measuring the extent of the enzyme inhibition. In this study, we evaluated the suitability of the catalytic subunit of recombinant human PP2A (rhPP2Ac) for use in a microplate OA assay. OA, dinophysistoxin-1(DTX1), and hydrolyzate of 7-O-palmitoyl-OA strongly inhibited rhPP2Ac activity with IC(50) values of 0.095, 0.104, and 0.135 nM, respectively. The limits of detection and quantitation for OA in the digestive gland of scallops and mussels were 0.0348 μg/g and 0.0611 μg/g respectively, and, when converted to the whole meat basis, are well below the regulation level proposed by EU (0.16 μg/g whole meat). A good correlation with LC-MS data was demonstrated, the correlation coefficient being 0.996 with the regression slope of 1.097.     

Inhibitors of ser/thr phosphatases 1 and 2A induce apoptosis in pituitary GH3 cells

Two structurally different inhibitors of ser/thr phosphatases 1 and 2A, okadaic acid and calyculin A, time- and concentration-dependently stimulated and inhibited cell-specific function (hormone gene expression) in pituitary GH₃ cells. The negative effect was associated with the appearance of apoptotic cell death. Nanomolar concentrations of both agents produced the characteristic morphological alterations and a DNA fragmentation ladder. Calyculin A treatment resulted in comparable changes with 10fold lower concentrations than okadaic acid. Observations with derivatives of okadaic acid with no or lower phosphatase inhibitory potency supported the conclusion that apoptosis induction is related to inhibition of ser/thr phosphatases, presumably types 1 and 2A. Membrane damage as measured by lactate dehydrogenase liberation into medium was significantly lower in apoptotic vs. necrotic cells. DNA fragmentation could be reduced by the addition of zinc but not by removal of extracellular calcium with EGTA. Apoptotic changes were reduced by the concomitant activation of protein kinase A by a membrane permeable cAMP analogue. Incubation of cells for 4 months in successively increased concentrations of okadaic acid resulted in a population that proliferated at the initially lethal concentration of 30 nM. Received: 6 February 1997 / Accepted: 1 April 1997     

Mechanisms of the spatial memory deficits induced by injection of okadaic acid into the Meynert nucleus basalis of rats

We previously reported that the injection of okadaic acid (OA) into the Meynert nucleus basalis of rats induced spatial memory deficits. The present study was designed to further explore the underlying mechanisms. We found that the level of acetylcholine (Ach) in the hippocampus significantly decreased 24 h after injection of OA into the Meynert nucleus basalis of rats. Simultaneously, spatial memory deficit, PP-2A inhibition and tau hyperphosphorylation at Ser-198/Ser-199/Ser-202 (Tau-1 epitope) and Ser-396/Ser-404 (PHF-1 epitope) were observed. With the restoration of hippocampus Ach to normal levels at 48 and 72 h after the injection, the spatial memory deficits, PP-2A inhibition and tau hyperphosphorylation were reversed. It is suggested that injection of OA into the Meynert nucleus basalis of rats may impair the hippocampus-dependent spatial memory through damaging the cholinergic projection between the Meynert nucleus basalis and the hippocampus and the selective inhibition of PP-2A and tau hyperphosphorylation may be at least part of the underlying mechanisms.     

Immunoregulatory potential of marine algal toxins yessotoxin and okadaic acid in mouse T lymphocyte cell line EL-4

We have studied the effects of the marine algal toxins yessotoxin (YTX) and okadaic acid (OA) on the T cell receptor complex (TCR) expression, an important mechanism by which T cell responsiveness is controlled. Immune system cells are relevant targets to study the immunoregulatory potential of marine toxins since the immune system has been reported as one of the targets of marine algal toxins. This study reports results from exposing the mouse T lymphocyte cell line EL-4 to increasing concentrations of YTX and OA for 72 h. We found that both YTX and OA affected TCR recycling kinetics and induced a specific and reversible TCR down-regulation in T lymphocyte EL-4 cells that was time and concentration dependent. Experiments using the potent protein kinase C (PKC) inhibitor stausporine indicated that YTX-induced TCR down-regulation was partially mediated by PKC activation. In contrast, OA-induced TCR down-regulation was mediated by the serine/threonine protein phophatase 2A (PP2A) inhibition. In summary, the results suggest that OA and YTX concentrations in a similar range than those detected in mice bloodstream after oral administration have the potential to adjust the T cell responsiveness during the initiation of T cell activation by affecting the TCR expression levels via PKC and PP2A activities.     

复方氨基酸注射液在临床应用中存在的问题

目的:了解我院临床中对复方氨基酸(COAA)注射液使用中存在的问题。方法:抽查我院近三年外科及部分其他科室病历580例、1450次医嘱(处方)作分析讨论。结果:主要存在的问题有:①用法不当与葡萄糖或脂肪乳的配合启用较晚;对使用非蛋白热卡与氮的比率重视不够,占全部医嘱(处方)的93％;②输入量不足:选用COAA注射液的种类不合理。结论:我院临床对COAA注射液的药理学、用法用量、组方各成份作用和在营养学中重要性的原理缺乏足够的了解。     

Subcellular Distribution and Protein Binding of Perfluorooctanoic Acid in Rat Liver and Kidney

Perfluorooctanoic acid (PFOA) is an organic fluorochemical, and its elimination in rats is markedly sex-dependent. Liver and kidney are two primary tissues of distribution of PFOA in rats. In this study, the subcellular distribution of PFOA in male and female rat liver and kidney was examined. The results demonstrated that PFOA content in the liver cytosol of the female rat was significantly higher (49 ± 6% of total radioactive residues, TRR) than in the male liver (26 ± 5% TRR), whereas PFOA distribution in the heavier subcellular fractions, especially the nuclei and cell debris fraction, was marginally higher in male rat liver. In rat kidney, more than 70% of PFOA was distributed in the cytosolic fraction, with no significant difference between sexes. The degree of protein binding of PFOA in rat liver and kidney cytosol was analyzed by two different chromatographic methods. The percentage of protein-bound PFOA in the liver cytosol was found to be approximately 55% in both male and female rats. In contrast, significantly more PFOA was bound to cytosolic proteins in the kidney of male rats (42 ± 6% TRR) than in females (17 ± 5% TRR). Ligand blotting analysis revealed that multiple proteins from the liver cytosol, nuclei, and mitochondria fractions were capable of specific binding to PFOA.     

Effects of the Nitric Oxide Synthase Inhibitor -NAME on Recognition and Spatial Memory Deficits Produced by Different NMDA Receptor Antagonists in the Rat

There is consistent experimental evidence that noncompetitive antagonists of the N-methyl--aspartate (NMDA) receptor, such as ketamine, MK-801, and phencyclidine (PCP), impair cognition and produce psychotomimetic effects in rodents. Nitric oxide (NO) is considered as an intracellular messenger in the brain. The implication of NO in learning and memory is well documented. This study was designed to investigate the ability of the NO synthase inhibitor -NAME to antagonize recognition and spatial memory deficits produced by the NMDA receptor antagonists, MK-801 and ketamine, in the rat. -NAME (1–3 mg/kg) counteracted MK-801- (0.1 mg/kg) and ketamine (3 mg/kg)-induced performance impairments in the novel object recognition task. -NAME (10 mg/kg) attenuated ketamine (15 mg/kg)-induced spatial working memory and retention deficits in the radial water maze paradigm. -NAME, applied at 3 mg/kg, however, disrupted rodents'' performance in this spatial memory task. The present findings indicate (1) that -NAME is sensitive to glutamate hypofunction produced by other than PCP NMDA antagonists such as MK-801 and ketamine and (2) that -NAME alone differentially affects rodents'' spatial memory.