依达拉奉对朊粒蛋白106-126诱导分化后PC12细胞凋亡的保护作用

目的 从细胞凋亡改变程度观察自由基清除剂--依达拉奉对朊粒蛋白(PrP)106-126诱导的分化PC12细胞损伤的保护作用,从而寻找更有效的朊粒病治疗方法.方法 应用膜联蛋白V/碘化丙啶双标记法检测细胞凋亡.激光共聚焦、显微镜观察线粒体膜电位,免疫组织化学法检测Bcl-2、Bax表达,caspase-3/CPP32细胞凋亡检测试剂盒和Western印迹检测Caspase-3活性.不同剂量依达拉奉组和各对照组同一时间点采用t检验.不同组间比较采用单因素方差分析.结果 在空白对照组中,94.5%为正常细胞;经100μmol/L PrP106-126处理后.损伤细胞达82.1%,其中早期凋亡细胞比例占21.2%,晚期凋亡细胞和坏死细胞占60.9%;给予30及60μmol/L依达拉奉处理后,凋亡、坏死细胞分别下降至31.8%和15.2%.当分化后的PC12细胞经PrP106-126肽段处理72 h后,线粒体膜电位下降36.1%.而加依达拉奉则抑制线粒体膜电位下降,且效应呈剂量依赖性;15、30、45和60μmol/L依达拉奉作用下,线粒体膜电位分别为对照组的47.3%、73.3%、94.1%和97.3%.依达拉奉能增强Bcl-2的表达,但抑制Bax的表达.PrP106-126肽段感染分化后的PCI2细胞,Caspase-3活性增至空白对照组的(397.21±5.63)%,15、30和60 μmol/L依达拉奉处理后,Caspase-3活性分别降至(170.12±5.01)%、(120.67±6.02)%和(100.21±8.04)%;Western印迹也证实依达拉奉呈剂量依赖性地抑制Caspase-3活性.结论 依达拉奉对PrP106-126诱导的分化PC12细胞具有抗氧化损伤作用,其机制可能是减轻细胞凋亡.     

aFGF对Aβ25-35诱导的PC12细胞凋亡的保护作用

目的 探讨酸性成纤维细胞生长因子(aFGF)对β淀粉样肽25-35(Aβ25-35)诱导凋亡PC12细胞凋亡的保护作用.方法 采用MTT比色法分析细胞存活率,Hoechst 332582-PI荧光染色法检测细胞凋亡,RT-PCR方法 检测PC12细胞Bax和Bcl-2基因mRNA的表达,Western印迹检测PC12细胞Bax和Bcl-2蛋白表达.结果 不同剂量(10、20、30 mg/L)aFGF预处理PC12细胞1 h可剂量依赖性对抗Aβ25-35引起的细胞凋亡,提高PC12细胞的存活率,减少Aβ25-35引起的PC12细胞核固缩、凝聚和碎裂,降低Bax基因mRNA表达及蛋白表达,增加bcl-2基因mRNA表达及蛋白表达.结论 aFGF可剂量依赖性对抗Aβ25-35对PC12细胞的毒性作用,其机制可能与下调凋亡基因Bax和上调抗凋亡基因Bcl-2表达有关.     

PrP 106-126肽段在朊蛋白病模型中的应用

朊蛋白病是一种人畜共患的具有传染性的中枢神经系统变性疾病,近年对朊蛋白病研究取得的进展与朊蛋白病模型的应用有着重要的关系,其中朊蛋白106-126肽段(PrP106-126)在朊蛋白病细胞模型中的应用受到人们越来越多的关注,现对其综述如下。1 PrP106-126的基本生物学特征朊蛋白是生物体正常存在的蛋白质,当正常朊蛋白转变为异常朊蛋白时其一级结构即氨基酸的排列顺序不发生变化,而二级结构发生了明显的变化,出现了较多的β折叠。由于构象改变,机体内的蛋白酶不能在原来的位点降解朊蛋白,使其在细胞中逐渐沉积增多,最终导致细胞死亡〔1〕。Pr…     

原花青素对β-淀粉样肽(25-35)诱导的PC12细胞凋亡的保护作用

目的 探讨原花青素(pmcyanidins，PC)对β-淀粉样肽(25-35)[βamyloid pepfide-(25-35)，Aβ25-35]诱导PC12细胞凋亡的保护作用。方法 采用MTT比色法分析细胞存活率，Hoechst 33258-PI荧光染色法检测凋亡，流式细胞仪检测分析细胞凋亡率变化情况。结果 不同剂量PC预处理PC12细胞1h可剂量依赖性对抗Aβ25-35引起的PC12细胞凋亡，提高细胞的存活率，减少Aβ25-35引起的核固缩、凝聚和碎裂，降低细胞凋亡率。结论 PC可剂量依赖性对抗Aβ25-35对PC12细胞的毒性作用。     

aFGF对Aβ25-5诱导的PC12细胞凋亡的保护作用

目的探讨酸性成纤维细胞生长因子（aFGF）对β淀粉样肽25-35（AB25-35）诱导凋亡PC12细胞凋亡的保护作用。方法采用MTT比色法分析细胞存括率，Hoechst 332582-PI荧光染色法检测细胞凋亡，RT-PCR方法检测PCI2细胞Bax和Bcl-2基因mRNA的表达，Western印迹检测PC12细胞Bax和Bcl-2蛋白表达。结果不同剂量（10、20、30mg／L）aFGF预处理PC12细胞1h可剂量依赖性对抗AB25-35引起的细胞凋亡，提高PC12细胞的存括率，减少Aβ25-35引起的PC12细胞核固缩、凝聚和碎裂，降低Bax基因mRNA表达及蛋白表达，增加bcl-2基因mRNA表达及蛋白表达。结论aFGF可剂量依赖性对抗Aβ25-35对PC12细胞的毒性作用，其机制可能与下调凋亡基因Bax和上调抗凋亡基因Bcl-2表达有关。     

CyPA对β淀粉样蛋白诱导PC12细胞凋亡的保护作用

用亲环素A(CyPA)进行预处理PC12细胞,再加入β淀粉样蛋白(Aβ)25-35>继续培养,采用MTT法分析细胞存活率,HE染色法观察细胞形态,流式细胞仪检测细胞凋亡,应用2,7-二氯荧光素二乙酸酯(DCFH-DA)检测细胞内ROS含量.发现CyPA可提高细胞的存活率,减少Aβ25-35>引起的细胞凋亡,减少细胞内活性氧簇(ROS)的产生.提示CyPA可抵抗Aβ25-35>对PC12细胞的毒性作用,其机制可能与减少细胞内ROS的产生有关.     

羊膜上皮细胞对6-OHDA所致PC12细胞损伤的保护作用

目的 探讨羊膜上皮细胞（HAEC）对6-羟基多巴胺（6-OHDA）所致PC12细胞损伤的保护作用机制.方法 采用MTT检测、AO活体荧光素标记和流式细胞仪检测技术,观察加入终浓度分别为30、40、50 μmol/L的6-OHDA 24 h后,HAEC培养液上清对6-OHDA所致的P C 12细胞损伤的保护作用.结果 随着6-OHDA浓度的增大,PC12细胞活力逐渐降低,受损伤细胞的数量逐渐增加,终浓度为50 μmol/L的6-OHDA损害组可见细胞凋亡样改变;HAEC培养液上清可明显拮抗6-OHDA的毒性作用,使PC12细胞的存活率增加,受损伤细胞的数量降低.结论 HAEC培养液上清能拮抗6-OHDA所致的PC12 细胞损伤.     

IGF-1对Aβ25-35致PC12细胞损伤的保护作用及其机制的探讨

目的探讨胰岛素样生长因子1(IGF-1)对β样淀粉蛋白(Aβ25-35)引起的PC12细胞凋亡及tau蛋白磷酸化的保护作用及其机制。方法采用MTT,TUNEL等检测磷酸化Akt、Akt水平及Tau蛋白磷酸化水平,观察IGF-1对Aβ25-35致PC12细胞的损伤保护作用。结果MTT分析法表明IGF-1保护组的细胞活性显著高于Aβ损伤组(P<0.01),TUNEL法检测结果显示IGF-1保护组凋亡指数低于Aβ损伤组(P<0.01),IGF-1保护组能使被Aβ下调的磷酸化Akt水平恢复至与对照组相近的水平,总Akt水平基本维持不变。IGF-1保护组tau蛋白在Ser396,Ser202位点的磷酸化水平和总tau蛋白水平均明显低于Aβ损伤组。结论IGF-1能降低Aβ的细胞毒性,抑制Aβ25-35诱导的PC12细胞的凋亡和tau蛋白磷酸化,这一作用机制是通过PI3K/Akt信号传导途径来实现的。     

自噬及凋亡相关蛋白在PC12细胞缺糖缺氧过程中的表达及其意义

目的 探讨自噬及凋亡相关蛋白在PC12细胞缺糖缺氧(OGD)过程中的表达及其意义.方法 将PC12 细胞分为正常对照组、缺糖缺氧1、4和12 h组.MTT法检测细胞存活率,Western印迹法检测各组PC12细胞中BECN1、Bcl-2及Bax蛋白的表达水平.结果 与正常对照组相比,OGD 1及4 h组PC12细胞存活率下降(均P<0.05),BECN1蛋白表达升高,且Bcl-2/Bax比值升高;而与缺糖缺氧1和4 h组相比,OGD 12 h组细胞存活率明显下降(P<0.01),BECN1蛋白表达及Bcl-2/Bax比值亦明显降低.结论 自噬蛋白BECN1及凋亡相关蛋白Bcl-2、Bax参与了PC12细胞OGD损伤过程.在OGD早期,自噬起主要作用,并对OGD PC12细胞起一定的保护作用,随着OGD时间的延长,凋亡在其中占主导地位,促进凋亡蛋白表达,引起PC12细胞的死亡.     

银杏叶内酯N对PC12细胞凋亡的保护作用

目的探讨银杏内酯N对过氧化氢(H2O2)诱导的PC12细胞凋亡的保护作用。方法用H2O2诱导PC12细胞损伤,刺激其凋亡,给予不同剂量的受试药物干预。用MTT法检测细胞存活率;用吖啶橙染色检测银杏内酯N对PC12细胞凋亡的作用;用流式细胞术检测银杏内酯N对PC12细胞活性氧(ROS)的影响,荧光定量RT-PCR法、Western印迹法分别检测Bcl-2、Bax mRNA和相应蛋白的表达。结果银杏内酯N可对抗H2O2诱导的PC12损伤,提高存活率和抑制凋亡,降低PC12细胞ROS水平,与模型组比较均有显著差异(P<0.05);Bcl-2蛋白及mRNA表达量升高,而Bax mRNA和Bax蛋白及表达量降低,与模型组比较均有显著差异(P<0.05),且呈一定的量效关系。结论银杏内酯N可对抗H2O2的神经毒性,其机制与调节凋亡相关基因及蛋白的表达有关。     

NMR-detected hydrogen exchange and molecular dynamics simulations provide structural insight into fibril formation of prion protein fragment 106-126

PrP106-126, a peptide corresponding to residues 107-127 of the human prion protein, induces neuronal cell death by apoptosis and causes proliferation and hypertrophy of glia, reproducing the main neuropathological features of prion-related transmissible spongiform encephalopathies, such as bovine spongiform encephalopathy and Creutzfeldt-Jakob disease. Although PrP106-126 has been shown to form amyloid-like fibrils in vitro, their structural properties have not been elucidated. Here, we investigate the conformational characteristics of a fibril-forming fragment of the mouse prion protein, MoPrP106-126, by using electron microscopy, CD spectroscopy, NMR-detected hydrogen-deuterium exchange measurements, and molecular dynamics simulations. The fibrils contain approximately 50% beta-sheet structure, and strong amide exchange protection is limited to the central portion of the peptide spanning the palindromic sequence VAGAAAAGAV. Molecular dynamics simulations indicate that MoPrP106-126 in water assumes a stable structure consisting of two four-stranded parallel beta-sheets that are tightly packed against each other by methyl-methyl interactions. Fibril formation involving polyalanine stacking is consistent with the experimental observations.     

Polyanion induced fibril growth enables the development of a reproducible assay in solution for the screening of fibril interfering compounds, and the investigation of the prion nucleation site.

The misfolded conformer of the prion protein (PrP) that aggregates into fibrils is believed to be the pathogenic agent in transmissible spongiform encephalopathies. In order to find fibril interfering compounds a screening assay in solution would be the preferred format to approximate more closely to physical conditions and enable the performance of kinetic studies. However, such an assay is hampered by the high irreproducibility because of the stochastic nature of the fibril formation process. According to published fibril models, the fibrillar core may be composed of stacked parallel beta-strands. In these models positive charge repulsion may reduce the chance of favorable stacking and cause the irreproducibility in the fibril formation. This study shows that the charge compensation by polyanions induced a very strong fibril growth which made it possible to develop a highly reproducible fibril interference assay. The stimulating effect of the polyanions depended on the presence of the basic residues Lys(106), Lys(110) and His(111). The assay was validated by comparison of the 50% fibril inhibition levels of peptide huPrP106-126 by six tetracyclic compounds. With this new assay, the fibrillogenic core (GAAAAGAVVG) of peptide huPrP106-126 was determined and for the first time it was possible to test the inhibition potentials of peptide analogues. Also it was found that variants of peptide huPrP106-126 with proline substitutions at positions Ala(115), Ala(120), or Val(122) inhibited the fibril formation of huPrP106-126.     

Polyanion induced fibril growth enables the development of a reproducible assay in solution for the screening of fibril interfering compounds,and the investigation of the prion nucleation site

The misfolded conformer of the prion protein (PrP) that aggregates into fibrils is believed to be the pathogenic agent in transmissible spongiform encephalopathies. In order to find fibril interfering compounds a screening assay in solution would be the preferred format to approximate more closely to physical conditions and enable the performance of kinetic studies. However, such an assay is hampered by the high irreproducibility because of the stochastic nature of the fibril formation process. According to published fibril models, the fibrillar core may be composed of stacked parallel β-strands. In these models positive charge repulsion may reduce the chance of favorable stacking and cause the irreproducibility in the fibril formation. This study shows that the charge compensation by polyanions induced a very strong fibril growth which made it possible to develop a highly reproducible fibril interference assay. The stimulating effect of the polyanions depended on the presence of the basic residues Lys¹⁰⁶, Lys¹¹⁰ and His¹¹¹. The assay was validated by comparison of the 50% fibril inhibition levels of peptide huPrP106-126 by six tetracyclic compounds. With this new assay, the fibrillogenic core (GAAAAGAVVG) of peptide huPrP106-126 was determined and for the first time it was possible to test the inhibition potentials of peptide analogues. Also it was found that variants of peptide huPrP106-126 with proline substitutions at positions Ala¹¹⁵, Ala¹²⁰, or Val¹²² inhibited the fibril formation of huPrP106-126.     

氯通道阻滞剂在β_(25-35)淀粉样多肽诱导PC12细胞凋亡的保护作用

目的探讨氯通道阻滞剂(DIDS)对β25-35淀粉样多肽(Aβ25-35)诱导PC12细胞凋亡的影响。方法PC12细胞按实验不同分为对照组(DMEM培养液)、Aβ25-35组(Aβ25-35 40μmol/L)、DIDS组(Aβ25-35 40μmol/L+DIDS 50μmol/L)。MTT法测细胞存活率,Hoechst 33258荧光染色观察细胞核形态学改变,流式细胞技术测细胞凋亡率。结果Aβ25-35组与对照组和DIDS组比较,PC12细胞的存活率明显降低(P<0.05),细胞凋亡率明显增高(P<0.05),不同DIDS浓度依赖性升高PC12细胞存活率,DIDS 50μmol/L能显著下调Aβ25-35诱导的细胞凋亡(P<0.05)。结论DIDS对Aβ25-35诱导PC12细胞损伤有保护作用。     

Inhibition of PC12 cell redox activity is a specific, early indicator of the mechanism of beta-amyloid-mediated cell death.

An in vitro tissue culture cell model system forinvestigating the biochemical mechanisms involved in the neurodegenerativeactions of beta-amyloid has been established. Using rat pheochromocytoma PC12cells, it was found that an early, specific response of cells to thebeta-amyloid protein or the beta-amyloid fragment 25-35 was a potent inhibitionof cellular redox activity, as measured by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) reduction. This inhibitory response wasrapid and occurred at nanomolar concentrations of peptide, concentrations atwhich no equivalent decreases in cell proliferation or cell survival wereobserved. The inhibition of PC12 cell MTT reduction was initially reversibleupon removal of the peptide; if sustained for several days, however, by repeatedpeptide application, it became associated with a dramatic reduction in cellsurvival. Inhibition of MTT reduction may, therefore, be an early indicator ofthe mechanism of beta-amyloid-mediated cell death.     

Synthetic peptides homologous to prion protein residues 106-147 form amyloid-like fibrils in vitro.

Gerstmann-Sträussler-Scheinker disease (GSS) is a prion-related encephalopathy pathologically characterized by massive deposition of prion protein (PrP) amyloid in the central nervous system. The major component of amyloid fibrils isolated from patients of the Indiana kindred of GSS (GSS-Ik) is an 11-kDa fragment of PrP spanning residues 58 to approximately 150. These patients carry a missense mutation of the PRNP gene, causing a Phe-->Ser substitution at codon 198. We investigated fibrillogenesis in vitro by using synthetic peptides homologous to consecutive segments of GSS-Ik amyloid protein (residues 57-64, 89-106, 106-126, and 127-147) as well as peptides from the PrP region with the GSS-Ik mutation (residues 191-205 and 181-205, both wild type and mutant). Peptide PrP-(106-126) formed straight fibrils similar to those extracted from GSS brains, whereas peptide PrP-(127-147) formed twisted fibrils resembling scrapie-associated fibrils isolated from subjects with transmissible spongiform encephalopathies. Congo red staining and x-ray fibril diffraction showed that both straight and twisted fibrils had tinctorial and conformational properties of native amyloid. Conversely, the other peptides did not form amyloid-like fibrils under similar conditions. These findings suggest that the sequence spanning residues 106-147 of PrP is central to amyloid fibril formation in GSS and related encephalopathies.     

Nucleation-dependent conformational conversion of the Y145Stop variant of human prion protein: structural clues for prion propagation

One of the most intriguing disease-related mutations in human prion protein (PrP) is the Tyr to Stop codon substitution at position 145. This mutation results in a Gerstmann-Straussler-Scheinker-like disease with extensive PrP amyloid deposits in the brain. Here, we provide evidence for a spontaneous conversion of the recombinant polypeptide corresponding to the Y145Stop variant (huPrP23-144) from a monomeric unordered state to a fibrillar form. This conversion is characterized by a protein concentration-dependent lag phase and has characteristics of a nucleation-dependent polymerization. Atomic force microscopy shows that huPrP23-144 fibrils are characterized by an apparent periodicity along the long axis, with an average period of 20 nm. Fourier-transform infrared spectra indicate that the conversion is associated with formation of beta-sheet structure. However, the infrared bands for huPrP23-144 are quite different from those for a synthetic peptide PrP106-126, suggesting conformational non-equivalence of beta-structures in the disease-associated Y145Stop variant and a frequently used short model peptide. To identify the region that is critical for the self-seeded assembly of huPrP23-144 amyloid, experiments were performed by using the recombinant polypeptides corresponding to prion protein fragments 23-114, 23-124, 23-134, 23-137, 23-139, and 23-141. Importantly, none of the fragments ending before residue 139 showed a propensity for conformational conversion to amyloid fibrils, indicating that residues within the 138-141 region are essential for this conversion.     

复方丹参注射液对H2O2诱导的PC12细胞凋亡的保护作用

目的　探讨复方丹参注射液 (ISM)对 H2 O2 诱导的 PC1 2细胞凋亡的保护作用机制。方法　在 H2 O2 诱导 PC1 2细胞凋亡模型的基础上 ,采用 MTT比色分析测定细胞存活率 ,Hoechst- PI荧光染色和流式细胞仪检测分析细胞凋亡情况 ,RT- PCR检测 par- 4和 caspase- 3基因 m RNA表达 ,Western blot检测 par- 4蛋白表达和 caspase- 3P2 0活性片段 ,比色法检测 caspase- 3相对活性。结果　不同剂量 ISM预处理 1 h可提高 PC1 2细胞存活率 ,降低 par- 4和 caspase- 3的 m RNA表达以及 Par- 4的蛋白表达 ,caspase- 3 P2 0活性片段和 caspase- 3相对活性减少 ,但变化不明显。结论　 ISM可剂量依赖性地对抗 H2 O2的神经毒性作用 ,其机制可能与凋亡基因 par- 4表达有关 ,与 caspase- 3的关系尚需进一步探讨。     

Melatonin-induced autophagy protects against human prion protein-mediated neurotoxicity

Melatonin has neuroprotective effects in the models of neurodegenerative disease including Alzheimer's and Parkinson's disease. Several studies have shown that melatonin prevents neurodegeneration by regulation of mitochondrial function. However, the protective action of melatonin has not been reported in prion disease. We investigated the influence of melatonin on prion-mediated neurotoxicity. Melatonin rescued neuronal cells from PrP(106-126)-induced neurotoxicity by prevention of mitochondrial dysfunction. Moreover, the protective effect of melatonin against mitochondrial dysfunction was related with autophagy activation. Melatonin-treated cells were dose-dependently increased in LC3-II, an autophagy marker. Melatonin-induced autophagy prevented a PrP(106-126)-induced reduction in mitochondrial potential and translocation of Bax to the mitochondria and cytochrome c release. On the other hand, downregulation of autophagy protein 5 with Atg5 siRNA or the autophagy blocker 3-methyladenine prevented the melatonin-mediated neuroprotective effects. This is the first report demonstrating that treatment with melatonin appears to protect against prion-mediated neurotoxicity and that the neuroprotection is induced by melatonin-mediated autophagy signals. The results of this study suggest that regulation of melatonin is a therapeutic strategy for prion peptide-induced apoptosis.