松树皮中原花青素对荷瘤小鼠S_(180)肿瘤细胞抗氧化酶系的影响

目的研究松树皮中原花青素的体内抗肿瘤作用.方法采用小鼠移植性肿瘤模型S180肉瘤考察松树皮原花青素对荷瘤小鼠瘤重的抑制作用,紫外分光光度法测定原花青素对肿瘤细胞CuZn-SOD、GSH-PX活性以及MDA含量的影响,流式细胞仪检测原花青素对肿瘤细胞中活性氧含量的影响.结果松树皮原花青素对肿瘤细胞有较强的抑制作用,120mg·kg-1的剂量能显著抑制荷瘤小鼠S180肉瘤的生长,抑瘤率达49.73%;对S180肿瘤细胞中CuZn-SOD、GSH-PX活性有一定的作用,其中高剂量能够显著性的提高其活性;能够降低肿瘤细胞中MDA的含量,防止脂质过氧化的发生.结论松树皮原花青素通过抑制肿瘤的生长,保护正常细胞,减少自由基对正常细胞的伤害而达到抗肿瘤作用.     

骆驼蓬种子提取物及其β咔保啉生物碱对DNA拓扑异构酶Ⅱ活性的抑制作用

目的探讨去氢骆驼蓬碱、骆驼蓬碱、骆驼蓬总碱及哈尔满碱(止咳药用植物)对DNA拓扑异构酶Ⅱ活性的抑制作用。方法从体外培养的Q3肝癌细胞中,提取分离DNA拓扑异构酶Ⅱ;以阿霉素为阳性对照,用琼脂糖凝胶电泳法检测药物对DNA拓扑异构酶Ⅱ的作用。结果骆驼蓬总碱、去氢骆驼蓬碱、骆驼蓬碱及哈尔满碱对DNA拓扑异构酶Ⅱ活性均有一定的抑制作用。结论对DNA拓扑异构酶Ⅱ活性的抑制作用是骆驼蓬总碱、去氢骆驼蓬碱、骆驼蓬碱等生物碱抗癌作用和细胞毒作用的机制之一。     

黄癸素对拓扑异构酶的影响及联合羟喜树碱的抗肿瘤作用

观察黄癸素联合应用羟喜树碱对肿瘤细胞的协同抑制作用,并探讨黄癸素对拓扑异构酶的影响。采用MTT法检测黄癸素联合应用羟喜树碱对体外培养肿瘤细胞增殖的抑制作用,计算IC50和联合指数(CI值)判断药物协同作用效果;通过琼脂糖凝胶电泳法测定黄癸素对SW480细胞DNA拓扑异构酶活性的影响。结果显示,与两药单用比较,黄癸素联用羟喜树碱对SW480、SGC-7901、SW1116细胞的抑制作用更显著,IC50显著降低,两药联用对各种人癌细胞株的CI值均小于1,HepG2、SW480、SGC-7901、SW1116细胞的CI值最低分别达0.447、0.626、0.161和0.178,表现为较显著的协同效果。琼脂糖凝胶电泳法结果显示,经黄癸素(2.0～8.0 mg·L-1)处理的SW480细胞拓扑异构酶Ⅰ、Ⅱ的活性均有所降低。研究表明,黄癸素可抑制拓扑异构酶的活性,与典型的TopoⅠ抑制剂羟喜树碱合用具有良好的协同抑制肿瘤细胞增殖作用,该结果可能与两药在作用机制方面的协同有关。     

海南哥纳香醇甲GHM-10对L1210细胞DNA分子结构及拓扑异构酶II活性的影响

目的： 研究海南哥纳香醇甲（GHM-10）抑癌细胞DNA合成的作用机制。 方法： 用单细胞凝胶电泳法检测GHM-10对L1210细胞DNA分子的损伤,碱洗脱法测定GHM-10对L1210细胞DNA单链长度的影响,用GHM-10对超螺旋pUC18 DNA的解旋能力测定它对DNA拓扑异构酶II活性的影响。 结果： L1210细胞用GHM-10 (4～10) μg.ml^-1处理4.5 h后,DNA分子受损,表现为电泳后在荧光显微镜下可见彗星状拖尾。GHM-10 (4～25) μg.ml^-1处理L1210细胞5 h, 可引起DNA单链断裂。 L1210细胞或从L1210细胞分离的蛋白质在用GHM-10处理后,DNA拓扑异构酶II的活性均被抑制。结论： GHM-10可引起L1210细胞DNA分子损伤; 无论在细胞内还是细胞外,GHM-10可抑制拓扑异构酶II的活性。     

拓扑异构酶抑制剂——一种新型的抗肿瘤药物

拓扑异构酶控制、维持和修饰DNA拓扑结构。拓扑异构酶抑制剂通过作用于拓扑异构酶 ,对很多肿瘤发挥抑制活性。论述了拓扑异构酶抑制剂的作用机理、杀伤肿瘤细胞的机制及耐药性问题。     

思文霉素对胞外DNA拓扑异构酶介导产生的断裂和松驰反应的影响

思文霉素（Siwenmycin）是最先从我国土壤中的链霉菌培养物中提取的一个新型蒽环类抗生素。研究表明该药是DNA拓扑异构酶抑制剂，以ATP依赖性pBR322 DNA断裂松驰反应，观察思文霉素对从哺乳动物细胞中提取的DNA拓扑异构酶Ⅱ活性的抑制作用后发现该药对此酶的最大抑制浓度为25mmol/L。用思文霉素处理Bel 7402细胞后，从中提取的DNA拓扑异构酶Ⅱ所介导的DNA断裂松驰反应活性比对照组增加5倍，研究还发现，思文霉素可抑制胞外DNA拓扑异构酶Ⅰ活性，碱性洗脱实验证明该药可引起DNA单链断裂。     

恶性胶质瘤DNA拓扑异构酶的表达

目的从细胞分子生物学角度探讨DNA拓扑异构酶(TopoII)在恶性胶质瘤多药耐药中的作用。方法应用流式细胞仪对20例原发与20例复发恶性胶质瘤术后标本中DNA拓扑异构酶进行测定,对照研究。结果20例复发恶性胶质瘤中DNA拓扑异构酶的表达量较20例原发者明显减少(P<0.05)。结论恶性胶质瘤在治疗过程中获得多药耐药性可能是由于DNA拓扑异构酶数量的减少或活性降低造成的。     

松树皮中原花青素对荷S180肉瘤小鼠抗肿瘤作用的研究

目的 研究松树皮原花青素小鼠体内抗肿瘤作用。方法 采用小鼠移植性肿瘤模型考察松树皮原花青素对荷瘤小鼠S180肉瘤抑制作用;流式细胞仪检测原花青素对肿瘤细胞周期的影响;ATPase试剂盒检测原花青素对肿瘤细胞中钙泵活性的影响;激光共聚焦显微镜观察原花青素对肿瘤细胞中钙离子含量的影响。结果 松树皮原花青素抑制荷瘤小鼠S180肉瘤的生长;抑制肿瘤细胞中钙泵活性,升高钙离子的含量并使肿瘤细胞G0/G1期比例降低,S期细胞的比例增加。结论 松树皮原花青素体内对S180肿瘤细胞具有一定的抗肿瘤作用。     

原花青素对人冠状动脉平滑肌细胞增殖和凋亡的影响

目的研究原花青素对人冠状动脉平滑肌细胞增殖和凋亡的影响。方法采用MTT实验检测原花青素对体外培养的人冠状动脉平滑肌细胞增殖的影响,运用流式细胞术、基因组DNA电泳观察凋亡特征性＂梯状＂条带检测细胞凋亡,采用Caspase活性定量检测试剂盒分析Caspase-9、Caspase-3的活性。结果原花青素对人冠状动脉平滑肌细胞具有明显的抑制作用,且其作用有剂量依赖性。流式细胞仪检测显示原花青素可以显著诱导人冠状动脉平滑肌细胞凋亡,DNA电泳显示原花青素作用于人冠状动脉平滑肌细胞后出现凋亡细胞特有的DNA阶梯状条带。原花青素作用后人冠状动脉平滑肌细胞Caspase-9、Caspase-3活性明显升高。结论原花青素可能通过线粒体信号通路抑制人冠状动脉平滑肌细胞的生长并诱导其凋亡。     

海岸松制剂Pycnogenol~疗牙斑形成和牙龈出血的临床试验

在欧洲和美国,Pycnogenol(?)是一种有专利权的饮食补充剂,系法国海岸松 Pinuspinaster Aiton 树皮提取物,主要活性成分是咖啡酸、桔酸、低聚原花青素、单体原花青素和前原花青素。药理试验、体内外动物试验和人体试验显示,海岸松树皮总提取物或部位在灌流器官中显示有很强的抗氧化活性,并证实它可以防止脂质过氧化、炎症和羟自由基引起的 DNA 损伤。此外,它还能通过减少     

Mirabijalone-B的抗肿瘤效应及对DNA拓扑异构酶的影响

目的研究化合物Mirabijalone-B(MB)的抗肿瘤活性及对DNA拓扑异构酶(TOPO)活性的影响。方法以5株人肿瘤细胞株为模型,采用改良MTT法检测化合物MB的体外抗肿瘤活性;以质粒pBR322超螺旋DNA为底物,采用凝胶电泳分别检测MB对TOPOⅠ、Ⅱ介导的pBR322DNA解旋反应的影响。结果化合物MB对5株人肿瘤细胞株K562、HL-60、A549、Bel-7402和SGC-7901生长增殖的半数抑制浓度(IC50)分别为8.73、1.26、4.44、1.93和3.55mg.L-1;MB在80和16mg·mL-1浓度时,分别完全抑制TOPOⅠ、Ⅱ介导的pBR322超螺旋DNA的解旋反应;但在无TO-PO存在的条件下,MB对pBR322超螺旋DNA的解旋反应无直接影响。结论化合物MB体外明显抑制人肿瘤细胞的生长增殖,对DNATOPO尤其是TOPOⅡ活性的抑制可能是其抗肿瘤作用的机制之一。     

原花青素抗促癌物诱发H_2O_2释放及脂质过氧化

目的　探讨葡萄原花青素抗氧化和肿瘤化学预防作用机制。方法　以大鼠多形核白细胞 (PMNs)为材料 ,利用酚红氧化原理比色测定了原花青素对巴豆油 (crotonoil)刺激PMNs生成H2 O2 的影响。结果　原花青素能显著性抑制巴豆油刺激PMNs生成H2 O2 ;以原花青素的大鼠含药血清代替反应系统中的药物 ,同样观察到原花青素具有抑制H2 O2 释放的作用 ,该作用在给药后 1h左右最强 ,且具有一定的时效关系和量效关系。对巴豆油诱发的小鼠肝线粒体脂质过氧化 ,原花青素具明显抑制作用 ,能明显提高肝线粒体SOD活力 ,减少MDA生成。结论　原花青素的抗氧化作用可能是其肿瘤化学预防作用的一个重要方面     

Studies on cytotoxic, hydroxyl radical scavenging and topoisomerase inhibitory activities of extracts of Tabernaemontana divaricata (L.) R.Br. ex Roem. and Schult

In the present investigation, the cytotoxic, hydroxyl radical scavenging and topoisomerase inhibition activities of Tabernaemontana divaricata (Apocynaceae) were evaluated. The extracts from leaves of the plant were prepared with different solvents viz. chloroform, methanol, ethyl acetate and hexane. In, in vitro cytotoxicity assay, with cell lines viz HCT-15 (Colon), HT-29 (Colon), 502713 (Colon), MCF-7 (Breast), PC- 3 (Prostrate), it was observed that the ethyl acetate extract was effective against only one colon cell line (502713) at the lowest dose i.e. 10 micro g/ml, whereas the chloroform extract was effective against all the three colon cancer cell lines, at 30 microg/ ml. In order to evaluate the mechanism of cytotoxicity of these extracts, they were assessed for their ability to scavenge hydroxyl radicals in plasmid nicking assay with pBR322. It was observed that all the extracts effectively inhibited the unwinding of supercoiled DNA except hexane extract, which showed the least effect. Since the expression of topo enzymes is linked with cell proliferation so the extracts were also checked for topo I and topo II inhibitory activities. It was noticed that ethyl acetate extract selectively showed inhibition of topo II in topoisomerase II relaxation assay.     

Diminution of free radical induced DNA damage by extracts/fractions from bark of Schleichera oleosa (Lour.) Oken

The present study was undertaken to investigate the effect of extracts of Schleichera oleosa (Sapindaceae) for its cytotoxic and hydroxyl radical-scavenging activities. The bark of the tree was used to prepare extracts with different solvents (i.e., hexane, chloroform, ethyl acetate, methanol, and water). The extracts were initially assessed for their in vitro cytotoxicity potential in the sulforhodamine B dye assay against cell lines, such as 502713 (colon), SW-620 (colon), HCT-15 (colon), A-549 (lung), HEP-2 (liver), SK-NS-H (central nervous system), and IMR-32 (neuroblastoma). It was observed that the water extract was effective against all the three colon cancer cell lines, while only methanol and water extracts were effective against A-549 (lung) and HEP-2 (liver), respectively. As DNA damage is one of the hallmarks of cell death, so the extracts were assessed for their ability to scavenge hydroxyl radicals, in the deoxyribose degradation assay (site- and nonsite specific) as well as their protective effect against the hydroxyl radical–induced DNA damage in the plasmid nicking assay, using pBR322. It was observed that all the extracts, except chloroform and hexane, exhibited relatively greater antioxidant activity in the nonsite-specific than in the site-specific assay. Similarly, the extracts were also found to be effective in inhibiting the hydroxyl radical–induced unwinding of supercoiled DNA, which further confirmed the hydroxyl radical–scavenging ability of the extracts in the deoxyribose degradation method.     

低浓度N-甲基-N′-硝基-N-亚硝基胍对HeLa细胞DNA聚合酶及拓扑异构酶Ⅱα mRNA表达水平的影响

利用定量逆转录聚合酶链反应(RT-PCR)方法， 研究了低浓度甲基硝基亚硝基胍(MNNG)对HeLa细胞DNA聚合酶(Polα,β,δ,ε)及拓扑异构酶Ⅱα(TopⅡα) mRNA表达水平的影响. 发现经0.2 μmol·L^-1 MNNG 处理2.5 h后，HeLa细胞Polβ mRNA水平在6-24 h内升高约1倍，而Polα,δ,ε及TopIIα mRNA水平则无明显改变. 提示Polβ mRNA水平改变可能参与MNNG诱发细胞遗传不稳定的发生.     

Santamarin的抗肿瘤活性及对DNA拓扑异构酶的影响

目的研究Santamarin的体内外抗肿瘤活性及对DNA拓扑异构酶(TOPO)活性的影响。方法以7株人肿瘤细胞株为模型,采用改良MTT法检测Santamarin对肿瘤细胞增殖的影响;以小鼠移植性肉瘤S180和小鼠移植性肝癌H22为模型,检测Santamarin对在体肿瘤生长的影响;以pBR322 DNA为底物,采用琼脂糖凝胶电泳检测Santamarin对TOPO介导的pBR322 DNA解旋反应的影响,以及对pBR322 DNA是否具有直接断裂作用。结果Santamarin对7株人肿瘤细胞株的半数抑制浓度(IC50)在0.99~3.61mg·L-1之间;Santamarin30、90和270mg·kg-1剂量对S180生长的抑制率分别为51.44%、63.60%和56.37%;对H22生长的抑制率分别为40.77%、39.47%和46.73%。Santamarin在2g·L-1时完全抑制TOPOI、Ⅱ的活性,但对DNA无直接断裂作用。结论Santamarin具有较为明显的体内外抗肿瘤活性,对DNA TOPO活性的抑制可能是其作用机制之一。     

Albaconol的抗肿瘤活性及对DNA拓扑异构酶Ⅱ的影响

目的　研究地花菌提取物Albaconol的体内外抗肿瘤活性及对DNA拓扑异构酶Ⅱ (TOPOⅡ )活性的影响。方法　以人白血病细胞株K5 6 2、人乳腺癌细胞株Bcap 37、人胃腺癌细胞株BGC 82 3和人非小细胞肺癌细胞株A5 4 9为模型 ,采用MTT法测试Albaconol对肿瘤细胞增殖的影响 ;以小鼠移植性肉瘤S180 和小鼠移植性肝癌H2 2 为模型 ,检测Al baconol静脉给药对肿瘤生长的影响 ;以 pBR32 2DNA为底物 ,采用琼脂糖凝胶电泳法测定Albaconol对肿瘤细胞DNATOPOⅡ活性的影响。结果　Albaconol对K5 6 2、Bcap 37、BGC 82 3、A5 4 9的半数抑制浓度 (IC50 )分别为 (2 4 2±1 77)、(1 88± 1 4 1)、(1 0 4± 0 6 4 )、(1 18± 1 10 )mg·L-1;Albaconol0 87、1 73、3 4 6mg·kg-1剂量组对S180 生长的抑制百分率 (抑瘤率 )分别为 2 8 2 %、4 3 2 %、4 7 4 % ;对H2 2 的抑瘤率分别为 15 6 %、2 2 4 %、37 8% ;Albaconol能明显影响DNATOPOⅡ的活性 ,表现为促进其介导的DNA解旋或断裂 ,并抑制其介导的DNA再连接反应。结论　Alba conol具有较强的体内、外抗肿瘤活性 ,DNATOPOⅡ是其抗肿瘤作用的细胞内靶点之一。     

DNA interaction and dual topoisomerase I and II inhibition properties of the anti-tumor drug prodigiosin.

Prodigiosin is a red pigment produced by Serratia marcescens with apoptotic activity. We examined the mechanism of action of this tripyrrole alkaloid, focusing on its interaction with DNA and its ability to inhibit both topoisomerase I and topoisomerase II. We also evaluated the DNA damage induced in cancer cell lines. Prodigiosin-DNA intercalation was analyzed using a competition dialysis assay with different DNA base sequences. Topoisomerase I and II inhibition was studied in vitro by a cleavage assay, and in cultured cells, by analysis of its ability to form covalent complexes. Furthermore, we analyzed DNA damage by pulse-field gel electrophoresis and by immunocytochemistry. Apoptosis inducing factor (AIF)/phospho-H2AX (p-H2AX) double labeling by confocal microscopy was performed to determine the possible implication of AIF in the prodigiosin-DNA damage. Finally, we studied the ability of this drug to induce copper-mediated DNA damage at different pH by a DNA cleavage assay. Our results demonstrate prodigiosin-DNA interaction in vitro and in cultured cells. It involves prodigiosin-DNA intercalation, with some preference for the alternating base pairs but with no discrimination between AT or CG sequences, dual abolition of topoisomerase I and II activity and, as consequence, DNA cleavage. Prodigiosin-DNA damage is independent of AIF. Furthermore, we found that copper-mediated cleavage activity is associated with pH (occurring at pH 6.8 rather than pH 7.4) and with the Cu(2+) ion concentration. These results indicate DNA a therapeutic target for prodigiosin and could explain the apoptosis mechanism of action induced by this antineoplastic drug.     

Protection of DNA and membrane from γ-radiation induced damage by the extract of Acorus calamus Linn.: An in vitro study

Acorus calamus, an ethnomedicinally important plant, was investigated for its protecting activity against radiation induced DNA and membrane damage. The in vitro free radical scavenging activity of the extract (water:ethanol, 1:1) of A. calamus was studied by parameters viz DPPH (1,1-diphenyl-2-picryl-hydrazyl) radical scavenging activity, hydroxyl radical scavenging activity, and superoxide radical scavenging activity. Membrane damage due to radiation exposure was measured as the peroxidation of lipids in terms of thiobarbituric acid reacting substance (TBARS). The in vitro DNA damage was monitored by assessing the radiation induced relaxation of supercoiled plasmid DNA (pBR322). Damage to cellular DNA induced by γ-radiation (6Gy) was monitored by alkaline single cell gel electrophoresis or comet assay in murine cells and human peripheral blood leukocytes. Enhancement of DNA repair mechanism was also monitored. The extract effectively scavenged free radicals in a concentration dependent manner. Presence of A. calamus extract during irradiation prevented peroxidation of membrane lipids in mouse liver homogenate. It helped to reduce the disappearance of the covalently closed circular (ccc) form of plasmid DNA following exposure to γ-radiation. Also the A. calamus extract effectively protected DNA from radiation induced strand breaks and enhanced the DNA repair process. Hence A. calamus extract can be used as a good source of natural radioprotecting agent.