JNK/AP-1信号通路在As_2O_3诱导乳腺癌细胞凋亡中的作用

目的探讨c-Jun N端激酶（JNK）信号通路在As2O3诱导乳腺癌细胞凋亡中的作用。方法体外培养MCF7细胞,以As2O3为刺激源,溴化丙锭（PI）染色结合流式细胞术方法检测细胞周期及细胞凋亡;双荧光素酶报告基因法检测MCF7细胞中AP-1的诱导活化;Western印迹法检测JNK、c-Jun的诱导活化及Fra-1的蛋白表达。结果 As2O3可显著诱导MCF7细胞凋亡并导致细胞周期行进阻滞;As2O3可诱导JNK持续性高强度表达,转录因子AP-1的转录激活活性上调;As2O3可诱导c-Jun活化并诱导Fra-1表达;转染c-Jun显性负性突变体TAM67或Fra-1shRNA可有效降低As2O3诱导的乳腺癌细胞凋亡。结论 JNK/AP-1途径是介导As2O3诱导乳腺癌细胞凋亡反应的重要信号通路。     

MAPK和SAPK信号途径的不同激活决定辐射的细胞效应

不同的细胞外刺激因素通过细胞内的信号转导途径传到细胞内的靶分子产生相应的细胞效应。辐射作为一种特殊的贯穿性损伤因子,它的信号转导有其特殊性。辐射既能激活SAPK/JNK(应激活化蛋白激酶/c-Jun NH₂末端激酶)信号途径介导细胞凋亡,又能激活MAPK/ERK(有丝分裂原活化激酶/细胞外相关激酶)信号途径促进细胞增殖、分化或保护细胞受到应激刺激而导致的损伤性效应,这两条通路的不同激活,决定了受辐射细胞的命运。     

低浓度乙醇诱导与紫外线照射对HepG2细胞周期及p53/p21蛋白表达的影响

目的观察低浓度乙醇诱导与紫外线照射导致HepG2肝癌细胞损伤的分子路径。方法选用HepG2肝癌细胞株，分别给予低浓度乙醇诱导与紫外线照射处理，观察两种损伤因素作用后细胞周期分布的差异，细胞中p53蛋白和p21蛋白表达的改变，分析蛋白表达与细胞周期改变的关系。结果紫外线照射后细胞中p53、p21蛋白表达均明显增强，出现G0～G1／G2～M期阻滞；低浓度乙醇诱导后主要出现G2～M期阻滞与p21蛋白表达的增强，p53蛋白表达改变不明显；两种损伤因素均能导致细胞凋亡率的增加。结论低浓度乙醇诱导与紫外线照射通过激活细胞内不同的分子事件，导致细胞周期与细胞凋亡的改变。     

Fas系统与辐射所致细胞凋亡

Ｆａｓ系统在辐射所致的细胞凋亡中起重要作用，其作用过程可能是：ＤＮＡ损伤激活Ｆａｓ系统的表达；Ｆａｓ与ＦａｓＬ结合启动凋亡信号并传递；通过神经鞘磷脂酶的活化，洋生神经酰胺，激活一系列蛋白激酶，启动胞内磷酸化过程，导致ＤＮＡ降解和细胞凋亡，癌基因参与正负调控，使Ｆａｓ系统在生理和病理活动中起调节作用。     

Caspase8、3蛋白在PUVA诱导K562细胞凋亡时的变化

目的研究Caspase8、3蛋白在补骨脂素(PSO)加长波紫外线(UVA)光化学疗法(PUVA)诱导人白血病K562细胞凋亡时的变化。方法用不同浓度的中药补骨脂中提取的PSO和(或)不同照射时间、波长为360nm的UVA作用于K562细胞,检测细胞凋亡率、在电镜下细胞超微结构改变及Caspase8、3蛋白的表达,用多因素方差分析法对定量资料进行统计分析。结果PSO、UVA照射及PUVA均可使细胞凋亡率增加,后两者上调Caspase8、3蛋白的表达,PUVA的作用显著强于前两者;PUVA处理后的K562细胞超微结构出现明显的凋亡形态学改变。结论PUVA可通过激活Caspase8、3基因诱导K562细胞凋亡。     

神经酰胺上调bax表达诱导人内皮细胞凋亡

目的观察外源性神经酰胺（C2-ceramide）对内皮细胞凋亡及相关基因bax表达变化的影响。方法原代培养人脐静脉血管内皮细胞,用不同浓度的ceramide干预内皮细胞24h,并用同一浓度的ceramide作用内皮细胞不同时间后,采用TUNEL法检测细胞凋亡,逆转录聚合酶链反应（RT—PCR）、Westernblot技术对baxmRNA及蛋白表达分析。结果神经酰胺处理组内皮细胞的凋亡阳性率显著高于对照组（P〈0．05）,且具有时间和剂量依赖性;对照组和5、12．5、25、50μmol／L神经酰胺处理24h后,各组细胞凋亡率随干预剂量的加大逐渐上升;终浓度25μmol／L的神经酰胺处理6、24、48h后,细胞凋亡率随时间延长而逐渐升高;神经酰胺处理组baxmRNA及蛋白的表达较对照组显著升高（P〈0．01～0．05）。结论外源性神经酰胺能通过上调bax表达诱导内皮细胞凋亡。     

Fas系统与辐射所致细胞凋亡

Ｆａｓ系统在辐射所致的细胞凋亡中起重要作用，其作用过程可能是：ＤＮＡ损伤激活Ｆａｓ系统的表达；Ｆａｓ与ＦａｓＬ结合启动凋亡信号并传递：通过神经鞘磷脂酶的活化，产生神经酰胺，激活一系列蛋白激酶，启动胞内磷酸化过程，导致ＤＮＡ降解和细胞凋亡，癌基因参与正负调控，使Ｆａｓ系统在生理和病理活动中起调节作用     

神经酰胺与辐射诱导细胞凋亡

神经酰胺作为神经鞘脂类的主要成员之一,是一个主要调节细胞活动的第二信使以转导细胞凋亡等细胞生长抑制活动信号为主,研究表明,神经酰胺通路不同水平的功能性变化直接影响细胞的药敏感性和辐射敏感性,肿瘤细胞神经酰胺缺陷可导致肿瘤细胞对药物和电射的敏感性下降。     

神经酰胺与辐射诱导细胞凋亡

神经酰胺作为神经鞘脂类的主要成员之一,是一个主要调节细胞活动的第二信使,以转导细胞凋亡等细胞生长抑制活动信号为主。研究表明,神经酰胺通路不同水平的功能性变化直接影响细胞的药敏感性和辐射敏感性,肿瘤细胞神经酰胺缺陷可导致肿瘤细胞对药物和电射的敏感性下降。     

辐射联合外源性野生型p53基因对不同p53状态的黑色素瘤细胞系的生物学效应

目的研究辐射结合腺病毒（Ad CMV）载体介导的p53基因转导对不同p53状态的人黑色素瘤细胞系基因转移效率、凋亡和辐射敏感性的影响。方法用复制缺陷的重组腺病毒载体（AdCMV-p53）介导入p53基因转导1Gy X射线预照射的黑色素瘤细胞系A375（wt p53）和WM983a（mu p53），RT-PCR检测mRNA水平，流式细胞仪测定细胞周期阻滞及外源性P53蛋白表达情况，Tunel法检测细胞凋亡，克隆形成率测定辐射后细胞存活率。用携带报道基因的复制缺陷重组腺病毒载体AdCMV-GFP作为对照。结果1Gy X射线照射可较高地增加AdCMV-p53对A375和WM983a细胞系的基因转导效率，转导的外源性野生型p53可在两种细胞中高效表达，并诱导细胞周期G1期阻滞；单纯转导p53对A375（wt p53）细胞无明显诱导凋亡和生长抑制效应，但可部分诱导WM983a（mu p53）细胞凋亡；而转导p53基因48h后给予X射线辐射，两种细胞的克隆存活率较其对照组均明显减低，外源性p53基因对WM983a（mu p53）细胞的辐射增敏作用较A375（wt p53）细胞明显。结论外源性野生型p53基因过表达可增加黑色素瘤细胞系A375和WM983a的辐射敏感性，但对WM983a细胞系的辐射增敏作用高于A375细胞系。表明p53是基因治疗黑色素瘤较好的候选基因。     

Role for non-homologous end-joining in the repair of UVA-induced DNA damage

PURPOSE: The biological significance of long-wavelength ultraviolet (UV) light, UVA, is increasingly realized, but the precise nature of the cellular damage responsible for the effects of this radiation is still not clear. It has been reported that UVA can induce double-strand breaks in DNA, but the biological significance of these is not known. We have therefore examined the UVA sensitivity of a cell line deficient in non-homologous end-joining, the major pathway for the repair of DNA double-strand breaks in mammalian cells in order to determine the biological importance of UVA-induced DSB. MATERIALS AND METHODS: Xrs-6, a Chinese hamster ovary cell line mutant for XRCC5 (Ku80) was compared with its parental CHO-K1 cell line for its sensitivity to UVA radiation (365 nm) using both a clonogenic assay and the micronucleus assay. RESULTS: Xrs-6 cells were sensitive to the cytotoxic effects of UVA. This resulted in the formation of chromosome damage, as measured by the micronucleus assay, which this cell line was unable to repair. CONCLUSIONS: Owing to the nature of the repair defect in these cells, these results imply that DNA double-strand breaks are produced in cells following UVA irradiation, that the non-homologous end-joining repair pathway is involved in their repair and that they are produced with sufficient frequency to have biological significance.     

ras-raf信号转导途径对受辐射细胞G_1期阻滞的调控作用

目的　探讨ras raf信号转导途径在受辐射KG 1细胞中对周期的调控作用方式。方法　通过转染DN ras阻断GM CSF的信号传递后 ,瞬间转染cyclinD1,观察cyclinD1对受辐射细胞周期阻滞的影响作用。结果　转染DN ras的受辐射KG 1细胞即使用GM CSF刺激亦不能跳出G1期阻滞 ;瞬间转染cyclinD1能促进受辐射细胞跳出周期阻滞。 结论　ras raf信号转导途径通过促进周期蛋白cyclinD1的表达而对受辐射细胞周期进行调控。     

Role for non-homologous end-joining in the repair of UVA-induced DNA damage

Purpose : The biological significance of long-wavelength ultraviolet (UV) light, UVA, is increasingly realized, but the precise nature of the cellular damage responsible for the effects of this radiation is still not clear. It has been reported that UVA can induce double-strand breaks in DNA, but the biological significance of these is not known. We have therefore examined the UVA sensitivity of a cell line deficient in non-homologous end-joining, the major pathway for the repair of DNA double-strand breaks in mammalian cells in order to determine the biological importance of UVA-induced DSB. Materials and methods : Xrs-6, a Chinese hamster ovary cell line mutant for XRCC5 (Ku80) was compared with its parental CHO-K1 cell line for its sensitivity to UVA radiation (365 nm) using both a clonogenic assay and the micronucleus assay. Results : Xrs-6 cells were sensitive to the cytotoxic effects of UVA. This resulted in the formation of chromosome damage, as measured by the micronucleus assay, which this cell line was unable to repair. Conclusions : Owing to the nature of the repair defect in these cells, these results imply that DNA double-strand breaks are produced in cells following UVA irradiation, that the non-homologous end-joining repair pathway is involved in their repair and that they are produced with sufficient frequency to have biological significance.     

电离辐射对EL-4细胞凋亡与坏死的影响

目的 研究不同剂量电离辐射对EL－4细胞凋亡和细胞坏死的影响。方法 采用PI和Hoechst 33342双染、流式细胞术检测。结果 实验结果表明：给予50－200mGy低剂量照射后6h,EL－4细胞凋亡和坏死较对照组没有升高,而给予1．0－8．0Gy大剂量X射线照射后6h,细胞凋亡较对照组有明显升高,4．0Gy以上剂量,细胞坏死显著升高。结论 一定剂量的电离辐射不仅可以诱导凋亡的产生,而且可直接导致细胞坏死,即细胞的死亡模式与受照剂量有关。     

Exposure to a 50-Hz magnetic field induced ceramide generation in cultured cells

Purpose To investigate the effects of a 50-Hz magnetic field (MF) exposure on ceramide metabolism, as well as the cascade downstream signaling pathways in human amniotic (FL) cells.

Materials and methods FL cells were exposed to MF at 0.4?mT for different durations (from 5–60?min). The ceramides levels were analyzed with high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). The activity of cathepsin D was assayed using a fluorometric assay kit, and the activity of protein phosphatase 2A (PP2A) was examined by Western blotting. After exposing to MF at 0.4?mT for 60?min with sequential culture for different durations (0, 3, 6, 12 or 36?h), the rate of cell apoptosis was assessed by flow cytometry.

Results Exposing cells to MF at 0.4?mT for different durations caused a significant increase in ceramide production via de novo synthesis and hydrolysis of sphingomyelin (SM), and the effect was different according to the exposure time. However, no significant change in cell apoptosis was detected after MF exposure for 60?min with sequentially culturing for up to 36?h. In addition, increase in ceramide did not activate its downstream signal molecules, cathepsin D and PP2A, which are usually closely related to apoptosis of cells.

Conclusions Exposure to a 50-Hz MF could raise ceramide levels but had no significant effect on apoptosis in cultured cells.     

大鼠大脑照射后海马区细胞凋亡与病理形态学变化的研究

目的　了解大鼠大脑受电离辐射后早期海马区细胞凋亡、bcl 2表达和病理形态学变化的情况。方法　用流式细胞仪测定凋亡细胞的比例与bcl 2蛋白的含量 ,用电镜和光镜分别作形态学变化的观察。结果　受 2 0Gy照射后第 1天起海马中就出现了凋亡细胞并逐步增加 ,至照射后3个月时恢复正常 ,而bcl 2蛋白的含量则呈相反的改变。在 3 0Gy照射后 3个月组中有坏死灶的存在 ,而其他组别中可以看到血管、胶质细胞和神经元等组织的形态学异常。结论　大鼠大脑受辐射后早期海马区可发生神经细胞凋亡、bcl 2表达的下降 ,以及各组织成分的病理形态学改变 ,这些变化的程度与照射剂量和观测时间有关。     

高能电子线皮肤辐射损伤动物模型的超微病理学研究

目的 通过动物模型研究高能电子线皮肤辐射损伤产生延迟性坏死和溃疡难以愈合的病理改变和机理,为进一步临床研究打下基础。方法 本实验以ＳＤ大鼠作为实验对象,以直线加速器产生的４ＭｅＶ的电子线照射臀部皮肤制作皮肤放射损伤模型。实验动物分５Ｇｙ、１５Ｇｙ、３０Ｇｙ、４５Ｇｙ４个剂量组,一次性照射后２个月作病理学肉眼、光镜、电镜观察。结果 ５Ｇｙ组光镜形态改变不明显,电镜下可见棘细胞肿胀,基底细胞核固缩,核膜下染色质边集,血管内皮细胞肿胀,部分细胞核固缩,管腔狭小,皮下胶原纤维断裂水肿：１５Ｇ６ｙ组棘细胞和基底细胞肿胀明显,基底细胞胞浆内张力微丝、桥粒、半桥粒显著减少,血管内皮和毛囊上皮细胞变性;３０Ｇｙ组电镜下棘细胞、基底细胞核固缩、水肿明显。ｙ组３周时可见皮肤溃疡形成,电镜见基底细胞层有凋亡细胞和凋亡小体形成,基底膜     

Ceramide induces activation of the mitochondrial/caspases pathway in Jurkat and SCC61 cells sensitive to γ-radiation but activation of this sequence is defective in radioresistant SQ20B cells

Purpose : To clarify the molecular mechanisms leading to radiation-induced apoptosis or resistance, the kinetics (1-48 h) and sequence of events triggered in response to 10 Gy irradiation were investigated in three cell lines displaying a gradient of sensitivity to γ-rays. Materials and methods : Ceramide levels were measured by high performance liquid chromatography (HPLC). Mitochondrial function was evaluated in terms of transmembrane potential (ΔΨm) , reactive oxygen species (ROS) and glutathione levels analysed by flow cytometry or HPLC. Caspase activation was assessed by immunoblotting, and apoptosis by flow cytometry. Results : In Jurkat radiosensitive cells and SCC61 adherent cells with intermediate radiosensitivity, the degree of delayed ceramide release was directly related to their propensity to undergo apoptosis. Transduction of the death signal was mediated by a drop in ΔΨm and glutathione levels, ROS accumulation and activation of effector caspases. Experiments conducted with caspase inhibitors, bongkrekic acid, or DL-PDMP indicated that ceramide triggers mitochondrial collapse, followed by the activation of caspases-9, -8 and -3, and poly(ADP-ribose)polymerase cleavage. In SQ20B radioresistant cells, γ-radiation did not induce ceramide generation or subsequent activation of the mitochondrial/caspase apoptotic pathway. Conclusions : Ceramide appears to be a determining factor in the commitment phase of radiation-induced apoptosis. When ceramide is not generated, the whole pathway is ineffective and resistance to apoptosis may result.