5-甲基胞嘧啶与化学致癌

5-甲基胞嘧啶是DNA的正常组份在哺乳类细胞DNA中的碱基,除了腺嘌呤、鸟嘌呤、胸腺嘧啶与胞嘧啶以外,还有一种碱基就是5-甲基胞嘧啶(5~mC),这5-甲基胞嘧啶只占全部胞嘧啶的3％左右,在人类DNA5~mC是3.5～4.4％.在它的3＇侧常与鸟嘌呤为邻,90％以上的5~C是以5＇-5~mCG-3＇的顺序排在DNA中,因为5~mC与G相邻,对侧股按5＇→3＇方向也是5＇-5~mCG-3＇,故5~mCG在DNA中是对称的。     

5-氮杂胞苷对结肠癌细胞CHD5基因表达及细胞增殖活性的影响

目的研究甲基化转移酶抑制剂5-氮杂-2-脱氧胞苷(5-氮杂胞苷,AZA)对人肿瘤相关基因CHD5(染色质解旋酶DNA结合蛋白5)在结肠癌细胞中的基因转录的诱导作用以及其对细胞增殖的影响。方法 5μmol/L 5-氮杂胞苷分别作用于Lovo和SW480细胞,连续作用72 h后,用荧光定量PCR(qPCR)检测两种结肠癌细胞系中CHD5mRNA的表达,重亚硫酸盐测序(BSP)法分析启动子区的甲基化状况,MTT法分析5-氮杂胞苷对Lovo和SW480细胞增殖的影响。结果 5μmol/L 5-氮杂胞苷处理Lovo和SW480细胞72 h后,Lovo和SW480细胞中CHD5基因的发生了去甲基化,其mRNA重新表达,细胞生长受到抑制。结论 5-氮杂胞苷能够反转CHD5基因的甲基化状态,调控CHD5 mRNA表达,并能有效地抑制结肠癌细胞的增殖。     

内质网应激参与低浓度DNA加成性损伤剂诱发的细胞应答反应

目的：研究内质网应激在DNA损伤剂/致癌物诱发的细胞应答反应中的作用。 方法: 选择3种引起不同DNA损伤类型的DNA损伤剂/致癌物，烷化性DNA损伤剂N-甲基-N’-硝基-N-亚硝基胍（MNNG），大块加成性DNA损伤剂苯并［a］芘-7,8-9-二氢二醇-9,10-环氧化物（BPDE，环境致癌物苯并［a］芘在体内代谢形成的终致癌物）以及交联性DNA损伤剂丝裂霉素C（MMC）对人羊膜细胞FL系内质网应激反应的影响。采用SDS－PAGE 和免疫印迹法检测内质网应激蛋白GRP78/BiP, GADD153/CHOP的表达改变和定位于内质网的半胱天冬酶-12(caspase-12)的激活。 结果： 低浓度MNNG（0.25 μmol/L和1 μmol/L）和BPDE（5 nmol/L和50 nmol/L）均能引起FL细胞中GRP78/BiP和GADD153/CHOP的上调和caspase-12的激活；3种浓度的MMC（5 μmol/L、50 μmol/L和500 μmol/L）均引起GRP78/BiP的下调，不伴有GADD153/CHOP水平的改变和caspase-12的激活，更低浓度的MMC（5 nmol/L 和50 nmol/L）对此并无影响。 结论： 低浓度MNNG和BPDE可诱发暴露细胞的内质网应激，而MMC则导致在内质网应激反应诱发过程中起介导作用的GRP78/BiP蛋白的下调，从而可能改变细胞对内质网应激原的反应性。内质网应激在DNA损伤剂/致癌剂诱发的细胞应答反应中有一定作用。     

N-甲基-N''''-硝基-N-亚硝基胍诱发的vero细胞JNK/SAPK通路的激活

目的和方法 :为了研究DNA损伤剂N -甲基 -N -硝基 -N -亚硝基胍 (MNNG)诱发vero细胞非定标性突变发生的信号转导机制 ,我们观察了MNNG诱发vero细胞c -JunNH2 -terminalkinase/stressactivatedproteinkinase(JNK/SAPK)通路激活的情况 :分别用Western印迹法和固相激酶活性测定法检测JNK1磷酸化和JNKs激酶活性。结果 :发现用 0 2 μmol/LMNNG和 1mg/L放线菌素酮 (CHM )分别处理vero细胞 2 5h和 1h后 ,都引起细胞抽提液中磷酸化JNK1的比例明显增高。同时通过测定JNKs的底物c -Jun的磷酸化程度 ,发现这两种处理也都可引起JNKs激酶活性显著增高 (分别增高 6 7和 3 0倍 )。结论 :证明 0 2 μmol/LMNNG和 1mg/LCHM分别处理vero细胞 2 5h和 1h都可引起vero细胞内JNK/SAPK通路被激活。     

5-氮杂-2'-脱氧胞苷对肝癌DNA甲基转移酶1及上皮钙黏附素表达的影响

目的:研究5-氮杂-2-脱氧胞苷(5-Aza-CdR)对肝癌细胞中DNA甲基转移酶1(DNMT1)及上皮钙黏附素(E-cadherin)表达的影响.方法:免疫组织化学检测上皮钙黏附素在肝癌(26例)及癌旁组织(20例)中的表达.用终浓度10μmol/L的5-Aza-CdR处理培养的肝癌细胞株GQY-7703作为实验组,未处理细胞为对照组;DNMT1基因和上皮钙黏附素基因(CDH1)的转录产物及表达蛋白分别使用半定量RT-PCR和免疫印迹法检测;CDH1的甲基化状态使用甲基化特异性PCR(MSP)检测.结果:相比较癌旁组织,肝癌组织中上皮钙黏附素表达显著下调.5-Aza-CdR降低了GQY-7703细胞中DNMT1在转录水平和翻译水平的表达CDH1 CpG岛的甲基化水平降低;上皮钙黏附素mRNA和蛋白表达量明显增高,对电泳条带的半定量分析显示实验组和对照组之间的差异具有统计学意义.结论:5-Aza-CdR通过抑制DNMT1的表达,改变了CDH1基因的异常甲基化状态,进而恢复上皮钙黏附素的表达.     

5-aza-cdR对神经细胞NG108-15细胞周期的影响

目的:观察DNA甲基转移酶(DNA methyltransferase,DNMT)抑制剂5-氮-2'脱氧胞苷(5-aza-2'deoxycytidine,5-aza-cdR)对神经细胞系NG108-15细胞周期的作用,并探讨相关的机制。方法:NG108-15细胞用10μmol/L 5-aza-cdR处理,RTCA分析细胞指数,流式细胞仪检测细胞周期和细胞凋亡,8-PCR检测DNMTs及细胞周期相关基因CCND1和CCND2 mRNA的表达。结果:5-aza-cdR能抑制NG108-15细胞的增殖,5-aza-cdR处理细胞后使细胞周期发生变化,同时使DNMT1的表达降低(P0.05)而DNMT3A和DNMT3B mRNA表达不变,并且CCND1和CCND2 mRNA表达也不变。结论:10μmol/L 5-aza-cdR可以抑制NG08-15细胞的增殖,其抑制作用可能是通过降低DNMT1表达实现的,这种抑制作用不影响CCND1和CCND2的表达。     

高糖诱导人肾小球系膜细胞CTGF启动子去甲基化及基因表达

目的:观察高糖刺激和甲基化抑制剂5-氮杂-2-脱氧胞苷(5-aza-dCyd)对人肾小球系膜细胞(HMCs)结缔组织生长因子(CTGF)基因启动子的甲基化水平和基因表达的影响.方法:用不同终浓度的5-aza-dCyd(0、1、2、5、10 μmol/L)刺激HMCs,于48h提取细胞基因组DNA、总RNA和蛋白质;用不同浓度的葡萄糖(5 mmol/L、30 mmol/L)刺激细胞,于0、24、48、72 h收集细胞;应用甲基化特异性PCR(MSP)检测细胞CTGF基因启动子甲基化状态,RT-PCR检测CTGFmRNA表达,Western blot检测 CTGF 蛋白表达.结果:不同浓度5-aza-dCyd处理HMCs 48 h后,0、1、2、5 μmol/L 5-azadcyd组CTGF基因启动子呈半甲基化状态,均有微量CTGFmRNA和蛋白的表达,差异无统计学意义(均P＞0.05);10 μmol/L 5-aza-dCyd组甲基化条带阴性,呈完全去甲基化状态,CTGF mRNA和蛋白表达均增加,与0 μmol/L组比较差异有统计学意义(P＜0.01).5 mmol/L葡萄糖组HMCs各时间点CTGF基因启动子均呈半甲基化状态,表达微量CTGFmRNA和蛋白质,差异无统计学意义(均P＞0.05);30 mmol/L葡萄糖组CTGF启动子在0 h呈半甲基化状态,甲基化条带较强;24 h甲基化条带减弱,48 h甲基化条带阴性,呈完全去甲基化状态,24 h、48 h、72 h CTGF mRNA和蛋白质表达均增加,与5 mmol/L组相应时间点比较差异有统计学意义(均P＜0.05).结论:高糖和甲基化抑制剂5-aza-dCyd均可诱导人肾小球系膜细胞CTGF基因启动子的去甲基化并增加CTGF的表达,提示DNA甲基化可能参与了人肾小球系膜细胞CTGF基因表达的调控.     

用高通量实时荧光PCR技术研究低浓度MNNG诱发的细胞基因应答反应

目的：研究低浓度 N-甲基-N'-硝基-N-甲基亚硝基胍对人羊膜FL细胞部分基因表达的影响，以助于阐明MNNG引起细胞应答反应的基因及其调控机制。方法：用ABI公司的高通量实时荧光定量PCR方法，检测FL细胞在0.2 μmol/L MNNG处理后基因表达发生的改变。数据用ABI公司的SDS 2.1软件分析。结果：MNNG处理后，在检测的95个基因中，29个基因表达发生改变，其中14个基因下调2倍以上，15个基因下调在1.5-2倍之间；其中有4个基因与细胞周期相关，6个基因与信号转导相关，6个基因与转录调节相关。结论：在低浓度 MNNG攻击后，FL细胞的基因表达发生了显著的变化。     

miR-30a抑制Ang2诱导的大鼠心肌细胞系H9c2自噬

目的 探索miR-30a对血管紧张素2(Ang2)诱导的大鼠心肌细胞自噬的影响.方法 1)将H9c2细胞分为对照组(control)、Ang2处理组(Ang22×10-6 mol/L)、去甲肾上腺素阳性对照组(NE 5×10-6 mol/L).处理细胞48 h,RT-qPCR检测miR-30a表达;Western bl...     

小鼠神经母细胞瘤N2a细胞脑啡肽酶基因的表达与启动子区甲基化和组蛋白修饰相关

目的研究小鼠神经母细胞瘤Neuro-2a(N2a)细胞中脑啡肽酶(NEP)基因表达的表观调控机制,探讨DNA甲基化与组蛋白乙酰化之间的相互作用。方法体外培养N2a细胞,以3μmol/L、5μmol/L DNA甲基化酶抑制5-氮杂脱氧胞苷(5-Aza-dc)及(300、500、700)nmol/L组蛋白去乙酰化酶抑制剂曲古抑菌素A(TSA)分别处理N2a细胞48 h和24 h。采用逆转录PCR(RT-PCR)、Western blot法分别检测NEP的mRNA、蛋白表达;亚硫酸氢盐测序聚合酶链反应(BSP)法检测NEP基因启动子区DNA的甲基化水平;染色质免疫共沉淀(ChIP)法检测NEP基因启动子区组蛋白H3的乙酰化水平。结果 5-Aza-dc和TSA均能剂量依赖地提高NEP基因的表达(P0.01);5-Aza-dc可诱导NEP基因去甲基化(P0.01);TSA可增高NEP组蛋白H3乙酰化水平(P0.05),但不能明显改变NEP基因DNA的甲基化水平(P0.05)。结论在小鼠神经母细胞瘤N2a细胞中NEP基因的表达受DNA甲基化及组蛋白乙酰化的调控,组蛋白乙酰化水平并不影响DNA甲基化状态。     

Localization of 5-HT2A, 5-HT3, 5-HT5A and 5-HT7 receptor-like immunoreactivity in the rat cerebellum

Although serotonin (5-hydroxytryptamine, 5-HT) is known to exert a modulatory action on cerebellar function, our current knowledge of the nature of receptor subtypes mediating serotonergic activity in this part of the brain remains fragmentary. In this study, we report the presence and distribution of 5-HT3, 5-HT5A and 5-HT7 receptor-like immunoreactivity in the rat cerebellum using immunofluorescence histochemistry. 5-HT3 immunoreactivity was found in fibers sparsely distributed throughout the cerebellum. Most of them were seen in the cerebellar cortex as fine varicose 5-HT3-positive axonal processes. 5-HT5A immunoreactivity, on the other hand, was observed in neuronal somata of the cerebellar cortex and deep cerebellar nuclei. Based upon cell morphology and the use of cell-specific markers, Purkinje cells, molecular layer interneurons and Golgi cells were found to be 5-HT5A immunopositive. In addition, the use of cell-specific markers allowed us to identify previously reported large 5-HT2A-positive cells in the granular layer as being Golgi cells. Finally, 5-HT7 immunoreactivity was observed only in Purkinje cells. Corroborating previous radioligand-binding, in situ hybridization and immunohistochemical studies, our data relate serotonin receptor subtypes to specific cerebellar cell types and may consequently contribute to the elucidation of serotonergic actions in the cerebellum.     

Case 5

A 53-year-old man with a heavy exposure to asbestos 25 years earlier was admitted to the East Orange Veterans Administration Medical Center with a rapidly enlarging chest wall mass of 4-5 weeks duration.

The mass, overlying the ninth and tenth ribs in the infraaxillary area, was firm. On X-ray the ribs appeared eroded and the mass was seen to extend into the pleural space. A chest wall resection was performed, and the tumor was sharply dissected from the diaphragm to which it was firmly adherent. Grossly, it measured 7.5 X 5.0 X 3.0 cm and was yellow-tan with homogeneous and nodular areas The inferior aspect of the ninth rib was obviously involved and the tumor extended between the pleura and intercostal muscle.

The patient did not receive further therapy and was asymptomatic 7 months after surgery.     

Case 5

A 53-year-old man with a heavy exposure to asbestos 25 years earlier was admitted to the East Orange Veterans Administration Medical Center with a rapidly enlarging chest wall mass of 4-5 weeks duration.

The mass, overlying the ninth and tenth ribs in the infraaxillary area, was firm. On X-ray the ribs appeared eroded and the mass was seen to extend into the pleural space. A chest wall resection was performed, and the tumor was sharply dissected from the diaphragm to which it was firmly adherent. Grossly, it measured 7.5 X 5.0 X 3.0 cm and was yellow-tan with homogeneous and nodular areas The inferior aspect of the ninth rib was obviously involved and the tumor extended between the pleura and intercostal muscle.

The patient did not receive further therapy and was asymptomatic 7 months after surgery.     

Inhibiting the C5-C5a receptor axis

Activation of the complement system is a major pathogenic event that drives various inflammatory responses in numerous diseases. All pathways of complement activation lead to cleavage of the C5 molecule generating the anaphylatoxin C5a and, C5b that subsequently forms the terminal complement complex (C5b-9). C5a exerts a predominant pro-inflammatory activity through interactions with the classical G-protein coupled receptor C5aR (CD88) as well as with the non-G protein coupled receptor C5L2 (GPR77), expressed on various immune and non-immune cells. C5b-9 causes cytolysis through the formation of the membrane attack complex (MAC), and sub-lytic MAC and soluble C5b-9 also possess a multitude of non-cytolytic immune functions. These two complement effectors, C5a and C5b-9, generated from C5 cleavage, are key components of the complement system responsible for propagating and/or initiating pathology in different diseases, including paroxysmal nocturnal hemoglobinuria, rheumatoid arthritis, ischemia-reperfusion injuries and neurodegenerative diseases. Thus, the C5-C5a receptor axis represents an attractive target for drug development. This review provides a comprehensive analysis of different methods of inhibiting the generation of C5a and C5b-9 as well as the signalling cascade of C5a via its receptors. These include the inhibition of C5 cleavage through targeting of C5 convertases or via the C5 molecule itself, as well as blocking the activity of C5a by neutralizing antibodies and pharmacological inhibitors, or by targeting C5a receptors per se. Examples of drugs and naturally occurring compounds used are discussed in relation to disease models and clinical trials. To date, only one such compound has thus far made it to clinical medicine: the anti-C5 antibody eculizumab, for treating paroxysmal nocturnal hemoglobinuria. However, a number of drug candidates are rapidly emerging that are currently in early-phase clinical trials. The C5-C5a axis as a target for drug development is highly promising for the treatment of currently intractable major human diseases.     

Mast Cells and 5-HT: Uptake of labelled 5-hydroxytryptamine (5-HT) and 5-hydroxytryptophan in relation to storage of 5-HT in individual rat mast cells

The capacity of individual rat peritoneal mast cells to take up and concentrate radioactively labelled 5-hydroxytryptamine (5-HT) and 5-hydroxytryptophan (5-HTP) was studied by quantitative cyto-chemical methods. By means of consecutive application of microfluorometric, autoradiographic and microinterferometric methods, the following parameters could be determined for each cell: 1. Relative amount of endogenous 5-HT. 2. Concentration of accumulated isotopes. 3. Dry mass. 4. Concentration of endogenous 5-HT. 5. Total amount of accumulated isotopes. The calculated correlations of these variables to each other showed general heterogeneity of the population, variations between the different cells being very large. However, on the whole, increasing dry mass of the mast cells was accompanied by an increase in 5-HT content, but with a decrease in concentrations of endogenous 5-HT and accumulated radioactive 5-HTP. Similarly, cells having large stores of endogenous 5-HT showed a higher total uptake, but a lower cellular concentration of exogenous 5-HT and 5-HTP, than cells that were poor in endogenous 5-HT. The results indicated that the uptake of ³H-5-HTP was proportional to the total area of the cell membrane, while the degree of 3-HT uptake was determined by other factors. When the concentrations of radioactivity in the incubation medium was compared to that of the living mast cell, it was found that the averagr cell was able to concentrate exogenous 5-HTP and 5-HT around 4 and 30 times, respectively.     

Partial monosomy 5p and partial trisomy 5q due to paternal pericentric inversion of chromosome 5

Summary A male infant with partial monosomy 5p and partial trisomy 5q due to paternal pericentric inversion of chromosome 5 (46,XY,rec(5), dup q,inv(5)(p15.1q35.1)pat) is reported together with the oral findings. The phenotype was chiefly the cri-du-chat syndrome. Severe retardation of mental and motor development, microencephaly, cardiac malformation, crying and facial appearance unique to the cri-du-chat syndrome were observed. Perioral and intraoral findings included thin upper lip, downturning corners of mouth, micrognathia, shallow palate, and cleft of soft palate. Anterior deciduous teeth were small and canine deciduous teeth were conic. The row of deciduous teeth showed a flat arch-like shape that was very wide but short in length. No abnormality was noted in the number of deciduous teeth or the timing of eruption.