锰对PC12 细胞的增殖抑制与凋亡研究

目的:研究锰作用下PC12细胞的增殖抑制作用与凋亡相关的形态学、生化指标改变。方法:用200,400,600,800μmol/LMnCl2的培养液,分别作用对数生长期PC12细胞1,2,3,4d后,用MTT筛选锰的细胞毒性剂量;透射电镜观察细胞形态学变化;琼脂糖凝胶电泳检测MnCl2对PC12细胞基因组DNA的影响。结果:MTT实验显示200-800μmol/L MnCl2作用4天对PC12有显著的抑制作用,呈剂量和时间依赖趋势,600μmol/L MnCl2作用4d对PC12的抑制率可达50%以上。600μmol/L MnCl2作用4d电镜可见细胞凋亡,同样条件下细胞DNA碎片化。结论:PC12细胞在锰作用下发生增殖抑制,原因是锰诱导PC12细胞凋亡。     

二烯丙基二硫诱导人白血病K562 细胞凋亡及其对Bax、Bag-1 表达的影响

目的:探讨二烯丙基二硫(Diallyl disulfide)诱导白血病K562细胞凋亡的作用及其机制。方法:采用吖啶橙/溴化乙啶(AO/EB)染色法观察细胞凋亡形态学变化;DNA琼脂糖凝胶电泳测定DNA梯度带;RT-PCR法检测BAG-1、BAX基因的mRNA表达变化。结果:DADS可诱导K562细胞凋亡。其对K562细胞的凋亡效用与药物浓度、有明显依赖关系;DNA琼脂糖凝胶电泳示:40mg/LDADS作用K562细胞48小时后能够产生明显的梯形电泳图谱(DNA ladder):DADS作用48h后,BAX mRNA表达水平较对照组上调;BAG-1 mRNA较对照组下调(差异具有统计学意义,P<0.05)。结论:DADS能够诱导K562细胞凋亡,其凋亡机制可能与上调BAX,下调BAG-1有关。     

参杞合剂对人鼻咽癌细胞CNE细胞周期及凋亡的影响

目的研究参杞合剂(SQ)在体外对CNE细胞周期及凋亡的影响。方法应用MTT法观察参杞合剂对细胞的抑制作用,流式细胞术观察不同浓度参杞合剂作用不同时间后CNE细胞周期的改变,电镜结合DNA电泳分析参杞合剂诱导凋亡的作用。结果SQ对CNE细胞生长有明显抑制作用,且其作用强度呈现出对浓度和时间的依赖性。CNE细胞在SQ作用下随着时间的延长和浓度的增加,G0/G1期比率下降,S期比率升高,出现S期阻滞。0.0625 g.生药/ml的SQ作用48 h后诱导出凋亡,凋亡率随着浓度的增加、时间的延长而增加,电镜下可见典型凋亡小体。琼脂糖凝胶电泳呈现出凋亡特征性的DNA条带。结论参杞合剂可直接杀伤肿瘤细胞,其机制可能通过阻滞细胞周期S期,诱导肿瘤细胞凋亡实现的。     

细胞周期特异性细胞凋亡的形态学观察

目的观察喜树碱诱导Molt-4细胞凋亡形态的细胞周期时相性变化,建立一种新的细胞周期特异性细胞凋亡分析方法.方法以凋亡诱导剂喜树碱(终浓度为0.15μmol/L)影响下的Molt-4细胞为检测对象,应用流式细胞术分析细胞凋亡及细胞周期的变化;用琼脂糖凝胶电泳的方法探测断裂的DNA片段存在,进一步证实细胞凋亡的存在;碘化丙啶(PI)染色后,再应用流式分选术结合激光扫描共聚焦显微镜(laser scanning confocal microsope, LSCM)观察各期细胞形态从而对已凋亡细胞进行形态学确认.结果①琼脂糖凝胶电泳可见清晰的DNA梯形条带(DNA ladder); ②喜树碱导致Molt-4细胞周期的S期水平明显下降,并伴随有一明显的细胞凋亡峰; ③只在S期细胞中可见到已凋亡细胞.以上说明喜树碱可以诱导Molt-4细胞凋亡,并细胞凋亡发生在细胞周期中的S期,与传统的结论一致.结论通过DNA直方图分选后细胞凋亡形态学分析可以对细胞凋亡的细胞周期特异性进行检测.这种方法使细胞周期特异性凋亡的分析更加可靠全面.     

PK15细胞凋亡过程中角蛋白中间纤维的变化

用放线菌素D诱导上皮型猪肾细胞PK15（Porcrne Kidney-15)发生凋亡,细胞在凋亡诱导过程中经历了从铺展、皱缩变圆至脱落的形态变化。凝胶电泳证明被诱导细胞的DNA发生降解,形成明显的DNAladder。免疫荧光显示凋亡过程中细胞角蛋白网状结构发生改变;应用选择性抽提结合整装电镜技术,观察到凋亡细胞中仍有中间纤维网络存在,这一现象前人未曾报道,免疫印迹反应进一步证明,凋亡细胞中部分Ⅱ型角蛋白发生降解。而Ⅰ型角蛋白则无降解现象。     

胡桃楸提取液诱导Hela细胞凋亡的研究

目的：初步探讨胡桃揪提取液对Hela细胞的凋亡诱导作用。方法：通过形态学观察,琼脂糖凝胶电泳及流式细胞术（FCM）检测凋亡细胞。结果：形态学观察发现核固缩、出现凋亡小体。琼脂糖凝胶电泳可见DNA ladder条带。流式细胞仪检测有凋亡峰。结论：胡桃揪提取液可诱导Hela细胞凋亡。     

5-烯丙基-7-二氟亚甲基白杨素（C19H14O4F2）诱导人卵巢癌CoC1细胞凋亡

目的 观察5-烯丙基-7-二氟亚甲基白杨素（ADFMChR）诱导人卵巢癌（CoCl）细胞凋亡的作用。方法 以体外培养的人卵巢癌CoCl为研究对象。采用软琼脂克隆测定ADFMChR对细胞集落的影响;流式细胞术（FCM）检测ADFMChR诱导细胞凋亡率;凝胶电泳观察ADFMChR诱导基因DNA梯形条带。Westernblot分析ADFMChR对CoCl细胞PPARγ,NF-κB,Bcl-2,Bax蛋白表达的影响。结果软琼脂克隆显示ADFMChR呈剂量依赖性抑制细胞集落形成;FCM分析发现ADFMChR呈剂量依赖性诱导细胞凋亡;ADFMChR（30μmol／L）孵育CoCl细胞48h后,DNA琼脂糖凝胶电泳呈现典型梯形条带。Westernblot分析结果表明ADFMChR以剂量依赖方式上调CoCl细胞PPARγ和Bax蛋白表达,下调NF-κB和Bcl-2蛋白表达。结论 ADFMChR诱导人卵巢癌CoCl细胞凋亡与其活化PPARγ,抑制NF-κB表达和提高Bax／Bcl-2比值有关。     

镉诱导HEK293细胞凋亡及其线粒体凋亡途径

本课题研究了氯化镉(CdCl_2)诱导HEK293细胞(人胚胎肾细胞系)的凋亡,初步探讨了凋亡过程中Caspase-3、Bcl-2的变化和凋亡诱导因子(AIF)的转移以及它们的意义。MTT法检测CdCl_2对HEK293细胞增殖的抑制作用;通过倒置显微镜、电镜、琼脂糖凝胶电泳、流式细胞术、激光共聚焦观察细胞凋亡;应用Western blot法和荧光免疫法测定Caspase-3酶原、Bcl-2蛋白的变化以及检测AIF蛋白在细胞中的定位。结果显示:CdCl_2对HEK293细胞具有显著的生长抑制作用,并呈明显的剂量和时间依赖性。在琼脂糖凝胶电泳中,显示有凋亡细胞特有的DNA梯状条带,其中30μmol/L作用6-9h梯状条带最为清晰,时间过长或浓度过高则梯状条带逐渐模糊,表明镉浓度过高或处理时间过长,细胞有坏死。流式细胞仪检测也印证了这一结果。形态学观察可见明显的细胞凋亡特征。同时线粒体膜电位明显下降,发现Caspase-3酶原蛋白、Bcl-2蛋白含量减少,并具有时间依赖性;另外检测到线粒体AIF向细胞核转移。而Bcl-2转染后有一定的抑制凋亡作用。实验结果提示,CdCl_2能够诱导HEK293细胞凋亡,线粒体损伤导致AIF转移与细胞色素c释放,从而引发的非Caspases与Caspases凋亡途径可能在镉引发的细胞凋亡过程中起重要作用,而Caspase-3, Bcl-2起着重要的调控作用。     

姜黄素对人食管癌EC9706细胞凋亡的诱导作用

目的:应用姜黄素处理人食管癌EC9706细胞,研究姜黄素对人食管癌EC9706细胞凋亡的诱导作用。方法:应用细胞计数、流式细胞仪、琼脂糖凝胶电泳、Hoechst染色、H.E染色和透射电镜检测经姜黄素诱导处理后人食管癌EC9706细胞的凋亡。结果:经姜黄素诱导处理后,人食管癌EC9706细胞生长抑制率达69.9%;细胞周期检测出现亚二倍体(亚G1期)细胞峰值,细胞凋亡率达23%;琼脂糖凝胶电泳显示出细胞凋亡典型的180-200 bp及其倍体的DNA"梯状"条带;Hoechst染色显示细胞核内出现浓染致密的固缩形态或颗粒状荧光;光镜和电镜下可见典型的细胞凋亡特征:细胞体积缩小,染色体凝集,可见有成群或单独存在的凋亡细胞,电镜下可见凋亡小体存在。结论:姜黄素能够有效诱导人食管癌EC9706细胞的凋亡,从而进一步为食管癌等恶性肿瘤疾病的治疗和凋亡机理的研究提供重要基础和科学依据.     

姜黄素诱导沉默MDR1基因的SGC7901/ADM细胞凋亡

为探讨MDR1基因沉默对姜黄素诱导人胃癌SGC7901/ADM细胞凋亡的影响,将已构建的靶向MDR1基因的RNAi表达载体转染SGC7901/ADM细胞,建立转染细胞单克隆,流式细胞术检测细胞外排功能。姜黄素处理SGC7901/ADM细胞48 h后,通过激光共聚焦显微镜下观察细胞形态结构,琼脂糖凝胶电泳检测DNA片段化。结果显示,各干扰载体转染组细胞内Rho-123荧光强度不同程度增强,细胞经姜黄素处理48 h后,激光共聚焦显微镜下呈明显的凋亡形态结构,DNA琼脂糖凝胶电泳呈梯状条带,说明MDR1基因沉默能促进姜黄素诱导SGC7901/ADM细胞凋亡。     

Cell nucleus and DNA fragmentation are not required for apoptosis

Apoptosis is the predominant form of cell death and occurs under a variety of physiological and pathological conditions. Cells undergoing apoptotic cell death reveal a characteristic sequence of cytological alterations including membrane blebbing and nuclear and cytoplasmic condensation. Activation of an endonuclease which cleaves genomic DNA into internucleosomal DNA fragments is considered to be the hallmark of apoptosis. However, no clear evidence exists that DNA degradation plays a primary and causative role in apoptotic cell death. Here we show that cells enucleated with cytochalasin B still undergo apoptosis induced either by treatment with menadione, an oxidant quinone compound, or by triggering APO-1/Fas, a cell surface molecule involved in physiological cell death. Incubation of enucleated cells with the agonistic monoclonal anti-APO-1 antibody revealed the key morphological features of apoptosis. Moreover, in non-enucleated cells inhibitors of endonuclease blocked DNA fragmentation, but not cell death induced by anti-APO-1. These data suggest that DNA degradation and nuclear signaling are not required for induction of apoptotic cell death.     

Distinct mechanisms underlay DNA disintegration during apoptosis induced by genotoxic and nongenotoxic agents in neuroblastoma cells

Exposure of mouse NB-2a neuroblastoma cells to genotoxic (etoposide or cytosine arabinoside) or nongenotoxic challenges (serum deprivation or okadaic acid) resulted in progressive cell death with biochemical and morphological characteristics typical of apoptosis. Apoptotic cell death induced by nongenotoxic agents was associated with the disintegration of nuclear DNA into high molecular weight (HMW) and oligonucleosomal-DNA fragments, while the formation of HMW-DNA fragments, but not oligonucleosomal-DNA ladder accompanied apoptosis induced by genotoxic agents. Combination of genotoxic and nongenotoxic insults, i.e. incubation of etoposide-treated cells in the serum-free medium, resulted in an additive effect on the profile of DNA disintegration, which involved both HMW fragmentation pattern as in etoposide alone treated cells and the oligonucleosomal-DNA ladder observed with serum-deprived cells. On the other hand, incubation of serum-deprived cells in the presence of Zn²⁺-ions led to the abrogation of internucleosomal DNA fragmentation but accumulation of HMW-DNA fragments. Differences in the pattern of DNA fragmentation were reproducible in a cell free apoptotic system after treatment of isolated normal nuclei with cytosolic extracts prepared from the cells treated with genotoxic or nogenotoxic apoptotic inducers. Cell free experiments also revealed that activities responsible for the formation of HMW- and oligonucleosomal-DNA fragments are separable in cytosolic extract prepared from the serum-deprived cells. Finally, DNA fragmentation induced by nongenotoxic apoptotic inducers was effectively prevented by cycloheximide and suramin, while both cycloheximide and suramin had only a slight inhibitory effect on DNA fragmentation induced by genotoxic agents. The results presented suggest that distinct pathways underlay disintegration of nuclear DNA during apoptosis induced by genotoxic and nongenotoxic inducers, and that the formation of HMW- and oligonucleosomal-DNA fragments proceeds via separate mechanisms in NB-2a neuroblastoma cells.     

Apoptosis of human leukemic HL—60 cells induced to differentiate by treatment with RA or DMSO

In present study,we studied the effect of all-trans retinoic acid(ATRA)and dimethylsulfoxide(DMSO)on the induction of apoptosis in HL-60 cell line.Based on morphological changes by Hochest 33342 staining and identification of internuclesomal NDA celeavage by gel electrophoresis,we observed aberrant nuclear chromatin condensation and ladder-like pattern of DNA degradation. Using Flow Cytometric method.We found sub-G1 peak in RA-treated HL-60 cells starting 5 to 6d after the initiation of the treatment However,Such an obvious apoptotic peak was not identified in DMSO-differentiated cells.Combining the research accomplished before.our study approves further that apoptosis could be a common mode of death of terminally differentiated HL-60 cells.     

Analysis of aclarubicin-induced cell death in human fibroblasts

In the present study we investigated the mode of cell death induced by aclarubicin (ACL) in trisomic (BB) and normal (S-2) human fibroblasts. Cells were incubated with ACL for 2h and then cultured in drug-free medium for up to 96h. Using fluorescence microscopy, agarose gel electrophoresis and comet assay we demonstrate that ACL induced time-dependent morphological and biochemical changes in both cell types. The population of apoptotic cells, analysed by acridine orange and ethidium bromide nuclear staining reached its maximum at 24-48h. Prolonged post-treatment time progressively increased the level of necrotic cells. At 24-48h time points we also observed a significant increase in caspase-3 activity, oligonucleosomal DNA fragmentation and DNA strand breaks. Cotreatment of cells with the specific caspase-3 inhibitor Ac-DEVD-CHO partly reduced the extent of apoptosis and necrosis and DNA degradation. In conclusion, trisomic and normal fibroblasts demonstrate similar response to aclarubicin treatment. Drug induced the apoptotic and necrotic pathway of cell death that was mediated by caspase-3.     

Distinction of apoptotic and necrotic cell death by in situ labelling of fragmented DNA

The occurrence and spatial distribution of intracellular DNA fragmentation was investigated by in situ 3 end labelling of DNA breaks in K562 cells treated in such a way to cause either apoptotic or necrotic cell death. The localisation of DNA breaks was examined by confocal laser microscopy and compared with the electron-microscopic appearance of the cells. In addition, the number of cells with fragmented DNA was counted and compared with the number of dead cells, as determined by the nigrosin dye exclusion test. Apoptosis was induced by cultivation of the cells in the presence of actinomycin D. Cells undergoing apoptosis were characterised by massive intracellular DNA fragmentation that was highly ordered into successive steps. Cells in early stages of the apoptotic process had DNA breaks diffusely distributed in the entire nucleus, except the nucleolus, with crescent-like accumulations beyond the nuclear membrane. In the more advanced stages, the nucleus was transformed into many round bodies with intense labelling. Intracellular accumulations of fragmented DNA corresponded exactly to electron-dense chromatin seen in the electron microscope, whereas diffuse DNA breaks had no morphological correlate at the ultrastructural level. In necrosis induced by ionomycin, NaN₃, or rapid freezing combined with thawing, no DNA fragmentation occurred at the onset of cell death, but appeared 24 h later. This fragmentation was not characterised by a unique morphology, but represented the breakdown of the chromatin in the configuration remaining after cell death. Therefore, apoptosis is characterised by DNA fragmentation that proceeds in a regular orderly sequence at the beginning of cell death, and can be detected by in situ 3end labelling of DNA breaks.     

Induced thermotolerance to apoptosis in a human T lymphocyte cell line.

A brief exposure to elevated temperatures elicits, in all organisms, a transient state of increased heat resistance known as thermotolerance. The mechanism for this thermotolerant state is unknown primarily because it is not clear how mild hyperthermia leads to cell death. The realization that cell death can occur through an active process of self destruction, known as apoptosis, led us to consider whether thermotolerance provides protection against this mode of cell death. Apoptosis is a common and essential form of cell death that occurs under both physiological and pathological conditions. This mode of cell death requires the active participation of the dying cell and in this way differs mechanistically from the alternative mode of cell death, necrosis. Here we show that mild hyperthermia induces apoptosis in a human leukemic T cell line. This is evidenced by chromatin condensation, nuclear fragmentation and the cleavage of DNA into oligonucleosome size units. DNA fragmentation is a biochemical hallmark of apoptosis and requires the activation of an endogenous endonuclease. The extent of DNA fragmentation was proportional to the severity of heat stress for cells heated at 43 degrees C from 30 to 90 minutes. A brief conditioning heat treatment induced a resistance to apoptosis. This was evident as a resistance to DNA fragmentation and a reduction in the number of apoptotic cells after a heat challenge. Resistance to DNA fragmentation developed during a recovery period at 37 degrees C and was correlated with enhanced heat shock protein (hsp) synthesis. This heat-induced resistance to apoptosis suggests that thermotolerant cells have gained the capacity to prevent the onset of this pathway of self-destruction. An examination of this process in heated cells should provide new insights into the molecular basis of cellular thermotolerance.     

Nuclear translocation of granzyme B in target cell apoptosis

Granzyme B is the prototypic member of a family of serine proteases localized to the cytolytic granules of cytotoxic lymphocytes. Together with another granule protein, perforin, granzyme B is capable of inducing all aspects of apoptotic death in target cells. A number of granzyme B substrates have been identified and it has been demonstrated that granzyme B is responsible, directly or indirectly, for the morphological nuclear changes observed in target cell apoptosis, including DNA fragmentation. In an earlier study, we showed that granzyme B binds to a nuclear protein in a manner dependent on its enzymatic activity. Here, we demonstrate that granzyme B is translocated rapidly to the nucleus in cells that have been induced to undergo apoptosis by a granzyme-dependent process, and that translocation is dependent on caspase activity. Appearance of granzyme B in the nucleus of target cells precedes the detection of DNA fragmentation. Although not directly responsible for DNA fragmentation, these data suggest a nuclear role for granzyme B in target cell apoptosis. c-Abl nuclear functions.     

Assessment of apoptosis in xenobiotic-induced immunotoxicity.

Generation of immunity is a highly complex process in which proliferation and differentiation of immune-competent cells regulated by cytokines and cell-cell interactions play a major role. Reducing the number of immune-competent cells or altering the function, selection, and differentiation of lymphocytes after xenobiotic treatment may lead to serious adverse effects. Programmed cell death, or apoptosis, is a highly regulated process by which an organism eliminates unwanted cells without eliciting an inflammatory response. However, xenobiotics are also able to trigger unwanted apoptosis or to alter the regulation of programmed cell death. Cytological characteristics of apoptosis are generally different from those seen in acute pathological cell death resulting from cell injury. The morphological characteristics of apoptosis are unique including cell shrinkage, membrane blebbing, chromatin condensation, DNA fragmentation, disruption of the nuclear lamina, nuclear fragmentation, and emergence of apoptotic bodies. It is now established that apoptosis plays a critical role in both development and homeostasis of the immune system: thymic selection, cytotoxicity, deletion of autoreactive cells, and regulation of the size of the lymphoid compartment. Assessment of apoptosis relies on the morphological and biochemical modifications of the dying cells. As a rule, and because an apoptotic cell rarely displays all of the characteristic apoptotic features, several criteria should be monitored in parallel including morphological examination. The techniques described in this paper have been divided into five categories: analysis of cell morphology by microscopy, identification of DNA fragmentation, determination of mitochondrial membrane potential, detection of plasma membrane changes, analysis of caspase activation.     

Effects of ceramide, the Fas signal intermediate, on apoptosis and phospholipase D activity in mouse ovarian granulosa cells in vitro

Although recent studies have demonstrated that ovarian follicular atresia occurs by apoptosis of granulosa cells, the intracellular signaling pathways involved in apoptotic cell death are still poorly characterized. We examined the role of ceramide as a candidate intracellular mediator of Fas-mediated signaling in cultured granulosa cells. Expression of Fas antigen was demonstrated by Western blot of granulosa cell lysates and immunostaining of cultured granulosa cells. Exposure of granulosa cells to anti-Fas monoclonal antibody (anti-Fas mAb) resulted in significant sphingomyelin hydrolysis, which was accompanied by a progressive increase in endogenous levels of ceramide. The addition of exogenous C6-ceramide induced drastic morphological change, including nuclear fragmentation and typical apoptotic DNA degradation. Furthermore, both anti-Fas mAb and C6-ceramide decreased phospholipase D (PLD) activity and diacylglycerol (DAG) concentrations in a time- or a dose-dependent manner. In addition, treatment with phorbol 12-myristate 13-acetate completely attenuated the ceramide-induced inhibition of PLD activity and partially suppressed ceramide-induced apoptosis. These results indicate that the Fas/ceramide signaling pathway might play a role in granulosa cell apoptosis and suggest that the PLD/DAG pathway might be cross-linked to the Fas/ceramide pathway in apoptotic processes of granulosa cells.     

Apoptosis-inducing ability of silver(I) cyanide-phosphines useful for anti-cancer studies

Metal-based drugs have shown early promise as anticancer agents suggesting the potential application of silver(I) complexes as apoptosis-inducing agents. The ability of a silver(I) cyanide containing phosphine complex to induce cell death was evaluated in both a malignant (SNO esophageal cancer) and non-malignant (HDF-a skin and HEK293 kidney) cell lines. A dose-dependent decrease in cell viability was observed in the SNO cells. Light microscopy revealed morphological features indicative of apoptotic cell death. The mode of cell death was confirmed as apoptosis by phosphatidylserine externalization, DNA fragmentation and nuclear condensation. Furthermore, both the non-malignant cell lines showed morphological features indicative of apoptosis when exposed to complex 1. We propose the use of this silver(I) cyanide phosphine complex as an highly effective positive apoptosis control for use in anticancer studies of phosphine complexes.