苦马豆素诱导人喉癌Hep-2细胞凋亡研究

苦马豆素具有广泛的抗肿瘤作用和免疫调节作用。本研究对苦马豆素诱导人喉癌Hep-2细胞凋亡的作用及其机制进行研究。通过不同浓度的苦马豆素处理Hep-2细胞24 h后,采用MTT法检测细胞活性;荧光显微镜观察细胞形态;Annexin V-FITC/PI双标记检测细胞凋亡;JC-1检测线粒体膜电位;实时荧光定量PCR和Western blot分别检测Bax和XIAP基因mRNA和蛋白质表达水平。在一定浓度范围内,苦马豆素抑制Hep-2细胞增殖,且呈剂量依赖性;荧光显微镜下细胞发生形态改变,并呈现典型的凋亡细胞特征;磷脂酰丝氨酸外翻加剧;线粒体膜电位逐渐下降;Bax的mRNA和蛋白质表达水平上升,XIAP的mRNA和蛋白质表达水平下降。苦马豆素通过调节细胞内Bax和XIAP的表达,并经线粒体信号途径诱导Hep-2细胞凋亡。     

PDCD5在类风湿关节炎成纤维样滑膜细胞凋亡中表达上调

为了研究程序化细胞死亡因子5(PDCD5)在类风湿关节炎成纤维样滑膜细胞凋亡中的作用,在不同的时间加入有效剂量100 nmol/L雷公藤内醇酯（triptolide）后,采用实时定量PCR、RT-PCR、Western 印迹和直接免疫荧光染色方法检测体外分离培养的类风湿关节炎成纤维样滑膜细胞中PDCD5在mRNA和蛋白水平的表达及蛋白表达特征.在雷公藤内醇酯诱导类风湿关节炎成纤维样滑膜细胞凋亡的过程中,PDCD5mRNA表达水平明显地渐次增加,呈现一种明确的时间依赖性递增表达模式,而PDCD5蛋白有时间依赖性表达上调持续16 h,并维持在相对恒定水平.直接免疫荧光染色结果显示,在正常体外培养的类风湿关节炎成纤维样滑膜细胞中,PDCD5蛋白的表达较弱,且主要分布在细胞浆.经雷公藤内醇酯处理4 h后,大多数细胞有PDCD5蛋白的聚集,直至12 h,细胞核周围PDCD5蛋白聚集显著增强.36 h后,PDCD5蛋白以核固缩的形式存在于凋亡的RA FLS中,细胞核染色质明显浓缩,片段化并出现了凋亡小体.上述结果表明,在类风湿关节炎成纤维样滑膜细胞凋亡的过程中,PDCD5表达上调并在凋亡早期出现核转位,PDCD5蛋白核转位要早于凋亡小体形成.PDCD5蛋白核转位是类风湿关节炎成纤维样滑膜细胞凋亡的早期事件,PDCD5不仅参与了类风湿关节炎成纤维样滑膜细胞的凋亡过程,而且在类风湿关节炎滑膜增生的凋亡调节中起到重要调节作用.     

HPV18-E6基因SiRNA对喉癌细胞的生长抑制作用

目的：探讨小分子干扰RNA（SiRNA）对喉癌细胞系Hep-2细胞中人乳头状瘤病毒HPV18型E6基因mRNA表达的干扰作用。方法：用Ambion公司pSilencer4,1CMV构建针对HPV18-E6基因的SiRNA真核表达载体,以携带HPV18-E6基因的人喉癌Hep-2细胞系为靶细胞,通过阳离子脂质体法转染SiRNA表达载体。RT-PCR分析转染后细胞HPV18-E6基因表达：Westernblot试验观察干涉后HPV18-E6蛋白的表达;流式细胞仪分析细胞增殖周期的改变。结果：成功构建了人HPV18-E6基因的RNA干涉真核表达载体psil-svvE6,并在Hep-2细胞中有效地发挥了对HPV18-E6基因表达的干涉作用。细胞周期阻滞于G0／G1期,并诱导细胞凋亡。结论：HPV18-E6基因在喉癌细胞Hep-2生长中可能起到非常重要的作用,有望成为逆转喉癌细胞永生化的靶点。     

microRNA-21靶向PDCD4/PTEN对大鼠ADSCs凋亡的抑制作用

该研究探究miR-21对大鼠ADSCs凋亡的影响,为提高ADSCs移植存活率提供依据。该研究建立大鼠ADSCs体外凋亡模型,采用qRT-PCR检测miR-21的表达。在ADSCs中采用Lipofectamine 2000转染miR-21 mimics,qRT-PCR检测miR-21 mimics转染效率。CCK-8、Hoechst 33258检测大鼠ADSCs过表达miR-21对细胞存活率的影响;Western blot检测大鼠ADSCs过表达miR-21后凋亡相关蛋白表达量。结果显示H_2O_2诱导细胞凋亡后,miR-21在ADSCs中的表达明显下调。大鼠ADSCs转染miR-21 mimics后,ADSCs中miR-21的表达量较对照组显著提高了7.4倍。与miR-21 scramble组相比,ADSCs过表达miR-21后,ADSCs存活率显著升高,促凋亡蛋白Caspase-3和Bax的表达量显著降低,而抗凋亡蛋白Bcl-2的表达水平明显升高。与对照组相比,miR-21过表达后,PDCD4和PTEN mRNA无显著变化,但PDCD4和PTEN蛋白表达明显下调。利用PDCD4 siRNA和Phen阻断PDCD4和PTEN的表达后,Caspase-3、Bax的表达水平显著降低,Bcl-2的表达水平显著升高。该研究得出miR-21通过靶向PDCD4/PTEN增强大鼠ADSCs对凋亡的抑制作用。     

土贝母苷甲经miR-21/ PDCD4 途径诱导胶质瘤U251细胞凋亡

目的:研究土贝母苷甲(TBMS I)对胶质瘤U251细胞的抗肿瘤作用以及探究土贝母苷甲对miR-21及其靶基因PDCD4基因表达的影响。方法:U251细胞在体外进行培养,四甲基偶氮唑盐(MTT)法检测不同浓度的土贝母苷甲对细胞增殖的影响;Hoechst33258染色观察细胞核形态的变化;实时荧光定量PCR检测miR-21和PDCD4基因的表达情况;Western blot检测PDCD4蛋白的表达情况。结果:土贝母苷甲能够显著抑制U251细胞的增殖,其抑制作用呈剂量和时间依赖性。Hoechst33258染色观察到土贝母苷甲处理组细胞的细胞核形态表现出典型的凋亡特征。PCR结果显示:随着土贝母苷甲浓度增加,miR-21的表达逐渐降低(P0.05),PDCD4基因表达显著增加(P0.05)。Western blot结果提示:与阴性对照组相比,15、30μg/mL土贝母苷甲显著上调了PDCD4蛋白的表达(P0.05)。结论:土贝母苷甲能够显著抑制人胶质瘤U251细胞的增殖并诱导细胞发生凋亡,其机制可能与下调miR-21的表达和上调PDCD4的表达有关。     

miR-340-5p及PDCD4在过表达乙肝病毒X蛋白的足细胞中的表达及生物学意义

乙肝病毒X蛋白(HBx)引起足细胞损伤与乙型肝炎相关性肾小球肾炎的发病有关,但具体的机制尚不清楚。miR‐340‐5p是受到HBx调控的miR,能够靶向细胞程序性死亡基因4(PDCD4)基因发挥神经元保护作用。本研究观察了过表达HBx的足细胞中miR‐340‐5p及PDCD4表达的变化及生物学意义。培养小鼠足细胞系MPC5后转染HBx质粒、miR‐340‐5p、si‐PDCD4,MTS法检测细胞增殖活力OD₄₉₀、TUNEL法检测细胞凋亡率、荧光定量PCR检测miR‐340‐5p的表达、Western blot检测PDCD4的表达、双荧光素酶报告基因实验验证miR‐340‐5p靶向PDCD4基因3’UTR。结果显示,与对照组比较,HBx组细胞中miR‐340‐5p的表达、OD₄₉₀水平降低,PDCD4的表达、凋亡率增加;与HBx组比较,HBx+miR‐340‐5p组细胞中miR‐340‐5p的表达、OD₄₉₀水平增加,PDCD4的表达、凋亡率降低,HBx+si‐PDCD4组细胞中OD₄₉₀水平增加,...     

蛋白激酶CK2α在人喉癌细胞Hep-2中的表达及意义

目的研究蛋白激酶CK2α(Protein kinase CK2α,PK-CK2α)在人喉癌细胞Hep-2中的表达,探讨其与喉癌之间的关系。方法体外培养Hep-2细胞和Hacat细胞,应用半定量逆转录-聚合酶链反应(RT-PCR)技术分别检测蛋白激酶CK2αmRNA在Hep-2细胞和Hacat细胞中的表达;应用免疫细胞化学技术分别检测蛋白激酶CK2α蛋白在Hep-2细胞和Hacat细胞中的表达。结果蛋白激酶CK2αmRNA在Hep-2细胞中高表达,在Hacat细胞中低表达,差异有统计学意义(P<0.01)。蛋白激酶CK2α蛋白在Hep-2细胞中高表达,在Hacat细胞中低表达,差异有统计学意义(P<0.01)。结论蛋白激酶CK2α过表达可能与喉癌的发生和发展有关。     

干扰素-γ对喉癌Hep-2细胞增殖和凋亡的影响

体外培养的人喉癌细胞系Hep-2细胞用10 ng/ml干扰素-γ处理不同时间后,利用细胞计数、细胞凋亡-DNA Ladder分析及半定量RT-PCR方法,探讨干扰素-γ对Hep-2细胞增殖及凋亡的影响并初步分析其作用分子机制。结果显示,与不处理对照细胞相比,干扰素-γ处理后第2天起Hep-2细胞增殖明显变慢;细胞凋亡分析显示,干扰素-γ处理后Hep-2细胞基因组DNA电泳图谱呈梯状分布;半定量RT-PCR分析显示,干扰素-γ处理诱导Hep-2细胞IFI16基因表达。结果表明,干扰素-γ抑制Hep-2细胞增殖诱导Hep-2细胞凋亡,其机制可能与干扰素-γ诱导IFI16基因表达有关。     

姜黄素光动力疗法下调人喉癌细胞中STAT3信号传导通路相关调控蛋白水平

目的利用激光照射含有姜黄素的喉癌细胞,探讨在激光的作用下姜黄素对人喉癌Hep-2细胞系增殖、凋亡及STAT3信号传导通路调控蛋白p-Stat3、cyclin Dl、Bcl-2水平的影响,为揭示姜黄素作为光敏剂的光动力疗法的抗癌机制提供实验依据。方法体外培养人喉鳞状细胞癌Hep-2细胞株,姜黄素光动力作用于喉癌细胞。实验分为以下4组:既不加光敏剂又不照光的空白对照组(A组),不加光敏剂的单纯照光对照组(B组)、只加光敏剂不照光的光敏剂对照组(C组)和光敏剂处理实验组(D组)。流式细胞技术检测不同实验组的细胞凋亡情况,及不同实验组P-STAT3及其靶基因产物cyclin Dl和Bcl-2蛋白表达水平。结果在激光的作用下,姜黄素抑制喉癌细胞增殖,促进细胞凋亡,下调STAT3信号传导通路蛋白p-STAT3、cyclin Dl和Bcl-2水平。结论受激发后的姜黄素可能通过降低STAT3相关调控蛋白的表达而抑制喉癌细胞增殖,促进其凋亡。     

基于PI3K/AKT/NF-κB信号通路调控细胞凋亡探讨扶正解毒化瘀方抗人呼吸道合胞病毒的作用机制

观察扶正解毒化瘀方对人呼吸道合胞病毒(Human respiratory syncytial virus,HRSV)感染相关细胞凋亡的影响,探究其抗病毒作用机制。体外实验确定扶正解毒化瘀方对人喉癌上皮细胞(Hep-2)的细胞毒作用,选取最大无毒浓度(TC₀)进行干预实验;以HRSV A亚型感染Hep-2细胞,设细胞对照组、病毒对照组、利巴韦林药物对照组及扶正解毒化瘀方组,显微镜下观察细胞病变,通过酶联免疫吸附测定(ELISA)检测炎性因子调节的正常T细胞表达和分泌(RANTES)水平,Western Blot检测磷脂酰肌醇3-激酶(PI3K)/苏氨酸激酶(AKT)/核因子κB(NF-κB)通路相关蛋白表达,反转录聚合酶链反应(RT-PCR)检测凋亡相关蛋白的mRNA相对水平。与细胞对照组相比,病毒对照组细胞病变明显,细胞上清RANTES水平升高,细胞PI3K/AKT/NF-κB通路相关蛋白AKT、糖原合成酶激酶-3(GSK-3β)、NF-κBp65表达增加,凋亡相关蛋白Fas、Bax、TRAIL的mRNA水平升高,两组间差异具有统计学意义(P<0.05)。而...     

过氧化氢预处理对H9c2心肌细胞氧化应激损伤的保护作用

目的：活性氧介导的氧化损伤是缺血再灌注损伤的重要机制,本研究通过观察H2O2预处理对氧化损伤的H9c2心肌细胞存活率和细胞凋亡的影响,探讨其保护H9c2心肌细胞的作用机制。方法：体外培养H9c2心肌细胞,取对数生长期细胞用于实验研究。建立H2O2预处理抵抗高浓度H：O：诱导的细胞氧化损伤模型,实验分组如下：（1）正常对照组（CTL）;（2）损伤组（INJURY）;（3）预处理组十损伤组（PC）。应用CCK8法检测细胞存活率;试剂盒检测胞内MDA水平和T．sOD活性;Hoechst33258染色观察凋亡形态;Annexin-V／PI双染与流式细胞术检测细胞凋亡率。结果：25vLmol／L的H202预处理90rain能明显地保护H9c2心肌细胞抵抗400μmol／LH2O2诱导的氧化损伤,提高细胞存活率,下调MDA水平,上调SOD活性,抑制细胞凋亡,降低细胞凋亡率。结论：低浓度H2O2预处理能减轻H9c2心肌细胞的氧化损伤,抑制氧化损伤诱导的心肌细胞凋亡,具有很好的抗氧化损伤和抗心肌细胞凋亡的保护作用,其作用机制可能与细胞SOD活性上调有关。H2O2预处理为临床治疗心肌缺血／再灌注损伤提供了一项新策略。     

自噬抑制剂3-MA上调H2O2损伤的PC12细胞氧化应激水平

为探究自噬抑制剂6-氨基-3-甲基腺嘌呤（3-methyladenine,3-MA）对损伤细胞氧化应激水平的影响,将3-MA作用于H2O2诱导的PC12细胞损伤模型,以自噬增强剂雷帕霉素（rapamycin,Rap）作为对照,探讨自噬与氧化应激的关系。测定线粒体的膜电位和细胞内的活性氧（reactive oxygen species, ROS）与丙二醛(malondialdehyde, MDA)含量,以及超氧化物歧化酶(superoxide dismutase,SOD)和过氧化氢酶(catalase,CAT)活性,评价损伤细胞的氧化应激状态。单丹(磺)酰戊二胺（monodansylcadaverine,MDC）染色,观察损伤细胞的自噬情况。蛋白质印迹分析损伤细胞中的自噬相关蛋白质LC3-II/LC3-I比值变化。实验结果显示：与正常组相比,H2O2损伤细胞的ROS水平上升到正常组的141%,MDA含量增加(P<0.001);CAT与SOD酶活力显著降低(P<0.001),差异均有统计学意义,证明损伤细胞氧化应激水平增加;MDC染色结果表明,H2O2组自噬明显增加。Western印迹结果表明,LC3-II/LC3-I值显著升高（P<0.05）;与损伤组相比,3-MA组MDC染色结果表明,自噬水平降低。Western印迹结果表明,LC3-II/LC3-I值下降;细胞内ROS水平升高,增加到正常组的208%。MDA含量增加(P<0.001),CAT、SOD酶活力降低(P<0.001)。综上结果表明,自噬抑制剂可增加H2O2诱导的PC12细胞损伤模型的氧化应激水平,增加细胞凋亡。     

Physiological changes induced in four bacterial strains following oxidative stress

In order to study the behaviour and resistance of bacteria under extreme conditions, physiological changes associated with oxidative stress were monitored using flow cytometry. The study was conducted to assess the maintenance of membrane integrity and potential as well as the esterase activity, the intracellular pH and the production of superoxide anions in four bacterial strains (Ralstonia metallidurans, Escherichia coli, Shewanella oneidensis and Deinococcus radiodurans). The strains were chosen for their potential usefulness in bioremediation. Suspensions of R. metallidurans, E. coli, S. oneidensis and D. radiodurans were submitted to 1 h oxidative stress (H2O2 at various concentrations from 0 to 880 mM). Cell membrane permeability (propidium iodide) and potential (rhodamine-123, 3,3'-dihexyloxacarbocyanine iodide), intracellular esterase activity (fluorescein diacetate), intracellular reactive oxygen species concentration (hydroethidine) and intracellular pH (carboxyflurorescein diacetate succinimidyl ester (5(6)) were monitored to evaluate the physiological state and the overall fitness of individual bacterial cells under oxidative stress. The four bacterial strains exhibited varying sensitivities towards H2O2. However, for all bacterial strains, some physiological damage could already be observed from 13.25 mM H2O2 onwards, in particular with regard to their membrane permeability. Depending on the bacterial strains, moderate to high physiological damage could be observed between 13.25 mM and 220 mM H2O2. Membrane potential, esterase activity, intracellular pH and production of superoxide anion production were considerably modified at high H2O2 concentrations in all four strains. In conclusion, we show that a range of significant physiological alterations occurs when bacteria are challenged with H2O2 and fluorescent staining methods coupled with flow cytometry are useful for monitoring the changes induced not only by oxidative stress but also by other stresses like temperature, radiation, pressure, pH, etc....     

氧化胁迫对水稻幼苗抗冷力的影响

利用Ｈ２Ｏ２和甲基紫精（ＭＶ）对水稻幼苗作三种不同程度的氧化胁迫预处理。结果表明：轻度氧化胁迫预处理（１０ｕｍｏｌ／ＬＨ２Ｏ２或１０ｕｍｏｌ／ＬＭＶ处理４ｈ）提高了水稻幼苗的抗冷力,严重氧化胁迫预处理（１０ｕｍｏｌ／ＬＨ２Ｏ２或１０ｕｍｏｌ／ＬＭＶ分别处理１６ｈ和４０ｈ）则削弱水稻幼苗的抗冷力。氧化胁迫预处理刺激了水稻幼苗叶片抗氧化酶（ＳＯＤ,ＣＡＴ,ＰＯＸ和ＡＰＸ）的活性。经冷胁迫后,不同预处理苗的叶片抗氧化酶活性、膜脂过氧化和膜结构的变化趋势不同：轻度氧化胁迫预处理使幼苗仍保持较高的抗氧化酶活性,减轻了由冷胁迫引起的膜脂过氧化和细胞膜的渗漏程度,而严重氧化胁迫预处理则相反。因此,水稻幼苗对氧化胁迫感知并作出反应的机制（氧化应激机制）在水稻幼苗对低温反应和适应过程中起着很重要的调节作用。     

Expression and localization of mitochondrial ferritin mRNA in Alzheimer's disease cerebral cortex

Mitochondrial ferritin (MtF) has been identified as a novel ferritin encoded by an intron-lacking gene with specific mitochondrial localization located on chromosome 5q23.1. MtF has been associated with neurodegenerative disorders such as Friedreich ataxia and restless leg syndrome. However, little information is available about MtF in Alzheimer's disease (AD). In this study, therefore, we investigated the expression and localization of MtF messenger RNA (mRNA) in the cerebral cortex of AD and control cases using real-time polymerase chain reaction (PCR) as well as in situ hybridization histochemistry. We also examined protein expression using western-blot assay. In addition, we used in vitro methods to further explore the effect of oxidative stress and β-amyloid peptide (Aβ) on MtF expression. To do this we examined MtF mRNA and protein expression changes in the human neuroblastoma cell line, IMR-32, after treatment with Aβ, H2O2, or both. The neuroprotective effect of MtF on oxidative stress induced by H(2)O(2) was measured by MTT assay. The in situ hybridization studies revealed that MtF mRNA was detected mainly in neurons to a lesser degree in glial cells in the cerebral cortex. The staining intensity and the number of positive cells were increased in the cerebral cortex of AD patients. Real-time PCR and western-blot confirmed that MtF expression levels in the cerebral cortex were significantly higher in AD cases than that in control cases at both the mRNA and the protein level. Cell culture experiments demonstrated that the expression of both MtF mRNA and protein were increased by treatment with H2O2 or a combination of Aβ and H2O2, but not with Aβ alone. Finally, MtF expression showed a significant neuroprotective effect against H2O2-induced oxidative stress (p<0.05). The present study suggests that MtF is involved in the pathology of AD and may play a neuroprotective role against oxidative stress.     

α-硫辛酸对H9c2细胞在H2O2导致的氧化应激损伤中的保护作用

缺血再灌注产生的氧自由基会导致心肌细胞凋亡. 近年研究发现, α-硫辛酸（α-lipoic acid, LA）具有抗氧化作用, 但LA是否能够对抗心肌细胞凋亡, 保护心脏功能的作用尚未明确. 本研究利用H2O2诱导的心肌细胞H9c2氧化应激模型, 分别用CCK 8方法检测细胞存活率、Hoechst33342染色观察细胞核的形态变化、流式细胞术检测细胞凋亡率、real time PCR法检测Bcl 2/Bax基因表达变化, 评价LA是否具有对抗氧化损伤引起的心肌细胞凋亡能力. 结果显示, LA能提高H2O2损伤的H9c2细胞存活率, 降低心肌细胞凋亡, 而且LA通过上调Bcl 2的表达而发挥抑制细胞凋亡的作用. 研究结果证实, LA对氧化应激损伤的心肌细胞具有较好的保护作用. 该研究为LA在临床上用于治疗氧化应激引起的心肌细胞凋亡提供了实验依据.     

不同活性氧胁迫下Bacillus sp. F26以抗氧化物酶合成为特征的应激响应

采用不同的活性氧发生源, 研究了· 、H2O2和OH·胁迫下Bacillus sp. F26以抗氧化物酶合成为特征的应激响应。结果表明, 细胞对氧胁迫的应激响应程度取决于活性氧种类、胁迫程度和形式(瞬时和持续)。Bacillus sp. F26对H2O2胁迫的响应程度最高, 过氧化氢酶的快速合成对细胞抵抗H2O2胁迫至关重要, 当细胞及时分解进入胞内的H2O2, 胁迫对细胞的氧化损伤程度并不高, 相反会刺激细胞的生长和底物消耗, 当胁迫超过过氧化氢酶的分解能力时, H2O2会迅速抑制细胞生长和过氧化氢酶合成; 由于 ·与细胞作用的方式和效果与H2O2不同, 超氧化物歧化酶和过氧化氢酶的快速合成并不能保证细胞及时有效地清除胞内的活性氧, 因此, 细胞对 ·胁迫的响应程度要低于H2O2胁迫; 在所考察的3种活性氧中, OH·胁迫(Fenton反应体系)对细胞的氧化损伤程度最大, 胁迫强烈地抑制了细胞生长和抗氧化物酶的合成。由此表明, 由于不同活性氧的化学性质有所不同, 细胞对不同种类、程度和形式的活性氧胁迫会表现出不同的生物学效应, 为了提高自身对氧胁迫的抵抗能力, 微生物会通过自身的代谢调节适应新的环境, 包括调整抗氧化物酶合成水平、改变生长速度以及底物消耗速率等。     

Protective effects of green tea polyphenol against reactive oxygen species-induced oxidative stress in cultured rat calvarial osteoblast

The injurious effects of reactive oxygen species on osteoblasts and the potential protective role played by green tea polyphenols (GtPP) were investigated using primarily cultured rat calvarial osteoblasts. Oxidative stress was induced in cultured osteoblasts, either by adding 100 mmol/L H2O2 or by the action of 40 U/L xanthine oxidase (XO) in the presence of xanthine (250 micromol/L). After incubation, the cellular viability, function and morphology were evaluated. Both treatments produced a significant reduction in osteoblast viability, as assessed by a two-colored fluorescence staining method combined with flow cytometric analysis and MTT assay. A significant reduction in the alkaline phosphatase activity was observed after H2O2 addition, whereas XO did not have the same effect. On the microscopic observations, the morphological changes and intracellular ultrastructural damages were remarkably induced by both treatments. The H2O2-induced alterations were prevented by pre-incubating the osteoblasts with 200 microg/ml GtPP for 1 h. When the oxidative stress was induced by XO, the cellular viability and morphology was also maintained at the same polyphenol concentration. These results demonstrate that GtPP can act as a biological antioxidant in a cell culture experimental model and protect cells from oxidative stress-induced toxicity.     

Glutathione is the antioxidant responsible for resistance to oxidative stress in V79 Chinese hamster fibroblasts rendered resistant to cadmium.

By manipulation of Cd and Zn concentrations in the medium, several phenotypes, differing in the contents of glutathione (GSH) and metallothionein (Mt), were derived from a parental clone of V79 Chinese hamster fibroblast. In some of these phenotypes, resistance to Cd and cross-resistance to oxidative stress was developed. The highest levels of GSH and Mt were found in cells which were rendered resistant to Cd by stepwise increases of Cd and Zn in the cell medium for over 50 passages. Upon removal of Cd/Zn from the medium of these cells or addition of Cd/Zn to the parental cell medium, changes of cellular GSH and Mt levels occurred to different extents. At the same time, changes in the resistance to Cd and H2O2 were observed. Good linear correlations were observed for Mt levels x resistance to Cd and for GSH levels x resistance to H2O2. Poor linear correlations were found for Mt levels x resistance to H2O2 or for GSH levels x resistance to Cd. Moreover, addition of Zn to the medium produced an increase in Mt content without affecting the GSH content. In this case no cross-resistance to oxidative stress was developed. Therefore, Mt which has been shown to be an excellent antioxidant in in vitro experiments, does not seem to play any major role against oxidative stress in Zn and Cd challenged cells. Most of the cross-resistance to oxidative stress in Cd challenged cells seems to be accounted for by the parallel increase in GSH.