Fas/Fas配体系统及其下游信号转导通路的激活促进酒精性肝炎及酒精性肝纤维化的进展

目的 探明Fas/Fas配体(FasL)系统及其主导信号转导通路在酒精性肝炎和肝纤维化发生、发展中的作用及其机制. 方法 C57BL/6J小鼠以含4％(V/V)乙醇的Lieber-DeCarli液体饲料喂养4周,自第5周起联合微量CCl4腹腔注射至第8周,分别建立酒精性肝炎和肝纤维化模型.脱氧核糖核苷酸末端转移酶介导的缺口末端标记法(TUNEL)检测肝细胞凋亡.分别采用逆转录-聚合酶链反应、westem blot及免疫组织化学染色检测肝组织Fas、FasL、天冬氨酸特异性半胱氨酸蛋白酶3(caspase3)及细胞色素P450 2E1(CYP 2E1)的mRNA及蛋白质表达.多组样本均数间差异比较用单因素方差分析或Kruskal-Wallis H检验,组间比较用LSD-t检验或Mann-Whitney U检验. 结果 应用含4％(V/V)乙醇的Lieber-DeCarli液体饲料联合微量CCl4腹腔注射可快速建立小鼠酒精性肝炎和肝纤维化模型.肝细胞凋亡数随肝脏炎症及纤维化的加重而增高,并伴有凋亡相关基因表达增强.对照组、酒精性肝炎组、酒精性肝纤维化组小鼠细胞凋亡相关基因表达水平依次升高:Fas mRNA的相对表达量分别为0.50±0.05、0.61±0.10、0.76±0.03(H=12.137 P＜0.05),Fas蛋白的相对表达量分别为0.52±0.14、0.86±0.10、0.99±0.09(F=12.758P＜0.01);FasL mRNA相对表达量分别为0.31±0.03、0.53±0.02、1.02±0.04(F=153.260 P＜0.01);caspase3mRNA对表达量分别为0.86±0.11、0.85±0.05、1.33±0.16(F=8.740,P＜0.01),caspase 3蛋白相对表达量分别为0.40±0.03、0.69±0.06、1.02±0.10(F=90.785,P＜0.01);CYP 2E1 mRNA相对表达量分别为0.72±0.14、1.00±0.15、1.30±0.20(H=4.713,P＜ 0.01);各组间比较,P值均＜0.05.免疫组织化学染色结果显示,FasL及CYP 2E1的蛋白与mRNA的表达趋势一致. 结论 Fas/FasL系统及其下游信号转导通路的激活可能是酒精性肝病中诱导肝细胞凋亡的主导因素,可进一步促进酒精性肝炎和肝纤维化的发生与进展.     

福辛普利对实验性心力衰竭大鼠心肌细胞凋亡和Fas、Fas配体基因表达的影响

目的:探讨实验性心力衰竭大鼠心肌细胞凋亡和心肌组织Fas、Fas配体(FasL)蛋白及其信使核糖核酸(mRNA)表达的变化及血管紧张素转换酶抑制剂(ACEI)干预的影响及意义.方法:将30只健康Wistar大鼠,随机分为假手术组(n=10)、慢性心力衰竭组(n=10)和福辛普利组(n=10).通过缩窄Wistar大鼠腹主动脉建立慢性心力衰竭模型,以福辛普利进行干预,对照观察血流动力学、心肌细胞凋亡、心肌组织Fas、FasL蛋白及其mRNA表达的变化.结果:与假手术组相比,慢性心力衰竭组左心室舒张末压、心率显著升高(P＜0.01);收缩压、舒张压、平均压、左心室收缩压、左心室内压最大收缩率、左心室内压最大舒张率显著降低(P＜0.01).福辛普利组舒张压、左心室收缩压、左心室舒张末压、心率显著低于慢性心力衰竭组(P＜0.01),左心室内压最大收缩率、左心室内压最大舒张率显著高于慢性心力衰竭组(P＜0.01).慢性心力衰竭组心肌细胞凋亡指数、心肌组织Fas、FasL蛋白及其mRNA表达水平显著高于假手术组(P＜0.05),福辛普利组心肌细胞凋亡指数、心肌组织Fas、FasL蛋白及其mRNA表达水平显著低于慢性心力衰竭组(P＜0.05).结论:慢性心力衰竭的发生、发展过程中有心肌细胞凋亡的变化及Fas/FasL系统的参与;心力衰竭大鼠心肌细胞凋亡指数、心肌组织Fas、FasL蛋白及其mRNA表达水平增高,福辛普利长期干预慢性心力衰竭,能够降低细胞凋亡及Fas、FasL基因的表达,可能与其减少Fas/FasL系统介导的细胞凋亡的发生、改善心肌功能有关.     

Fas/FasL途径在氟致人神经母细胞瘤SH-SY5Y细胞凋亡中的作用

目的 探讨Fas/FasL途径在氟致人神经母细胞瘤SH-SY5Y细胞凋亡中的作用.方法 用不同剂量氟化钠[NaF,0(对照)、20、40、80 mg/L].SH-SY5Y细胞进行染毒,24 h后检测细胞存活率、凋亡率和Fas、FasL mRNA表达;选择40 mg/L NaF组,观察在Fas受体激动剂(CH11)或拮抗剂(ZB4)作用下细胞凋亡率及Fas、FasL mRNA表达水平的改变.结果 40、80 mg/L组细胞存活率[(84.63±2.57)%、(69.04±5.63)%]明显低于对照组(100.00%),组间比较差异有统计学意义(P<0.01);细胞凋亡率随染毒剂量的升高呈上升趋势.40、80 mg/L组细胞凋亡率[(8.54±1.95)%、(17.94±2.71)%]明显高于对照组[(3.32±1.33)%],组间比较差异有统计学意义(Jp<0.05);NaF能不同程度地上调Fas、FasL mRNA表达,使Fas/β-actin[40mg/L组(0.94±0.51)、80 mg/L组(0.99±0.12)]和FasL/β-actin[40 mg/L组(0.96±0.42)、80 mg/L组(0.99±0.24)]比值增加.与对照组[Fas/β-actin(0.50±0.33)、FasL/β-actin(0.58±0.23)]比较,差异均有统计学意义(P<0.05).在对细胞凋亡率和Fas、FasL mRNA表达水平的影响中,NaF与CH11之间存在协同作用(,值分别为32.89、18.46、14.69,P<0.01),NaF与ZB4之间存在拈抗作用(F值分别为5.73、24.26、10.17,P<0.05或<0.01).结论 NaF可诱导SH-SY5Y细胞凋亡,Fas/FasL途径在NaF诱导SH-SY5Y细胞凋亡中起重要作用.     

乙型肝炎病毒X基因下调miR-192对人肝癌细胞株HepG2凋亡的影响

目的 探讨乙型肝炎病毒X基因(HBx)通过调节人肝癌细胞株HepG2中miR-192的表达而抑制其凋亡的机制.方法 设立3个细胞组:稳定转染HBx基因的HepG2细胞(HepG2/HBx),稳定转染空载体pcDNA3.1的HepG2细胞(HepG2/pcDNA3.1)以及未作转染的HepG2细胞.用流式细胞术分析3个细胞组的凋亡率差异,用Taqman探针荧光定量PCR检测3组细胞中miR-192的表达水平.转染miR-192后,用流式细胞术检测HepG2细胞凋亡率的变化,同时用SYBR Green荧光定量PCR和Western blot检测细胞中p53、PUMA表达的变化.计量资料均数的比较用单因素方差分析.结果 HepG2/HBx细胞的凋亡率为2.37％±0.35％,较HepG2/pcDNA3.1、HepG2细胞(11.46％±0.69％、12.50％±0.66％)明显降低(F=171.722,P＜0.01).miR-192表达在HepG2/HBx细胞中为49.1％±5.9％,较HepG2/pcDNA3.1、HepG2细胞(98.0％±8.9％,100％)也明显下调(F=14.319,P＜ 0.05).转染miR-192后HepG2细胞的凋亡率(15.74％±1.17％)较转染相应阴性对照的HepG2细胞的凋亡率(10.74％±1.15％)显著升高(F=18.415,P＜0.05),同时,p53、PUMA基因在mRNA (953:1.68±0.12比0.90±0.09,F=43.115,P＜0.05 ; PUMA:1.66±0.10比0.98±0.06,F=22.541,P＜0.05)和蛋白质水平(p53:3.07比1,PUMA:2.13比1)的表达均显著上升.结论 miR-192促进HepG2细胞凋亡,HBx通过下调miR-192抑制HepG2细胞凋亡.     

足叶苦素抑制胰岛素样生长因子Ⅰ受体表达对肝癌细胞增殖与运动的影响

目的 观察足叶苦素(PPP)抑制胰岛素样生长因子Ⅰ受体(IGF-IR)后对肝癌细胞增殖和运动的影响. 方法 体外培养肝细胞L02和肝癌细胞(Bel-7404、Bel-7402、HepG2和Huh-7),以Western blot分析IGF-IR表达,以磺酰罗丹明B法分析细胞活性;在PPP抑制IGF-IR后,以流式细胞术分析细胞周期,以AnnexinV-FITC法分析细胞凋亡;在z-VAD-FMK抑制caspases后,以均质发光法检测caspase-3/7活性;划痕试验分析细胞运动能力.对数据进行析因设计方差分析,采用t检验或one-way ANOVA法进行组间比较.结果 肝细胞L02中几乎检测不到IGF-IR,各肝癌细胞中IGF-IR呈不同程度表达.PPP抑制肝癌细胞增殖呈时间和剂量依赖性,经1.0μmol/L PPP处理HepG2细胞24h,G1、S期和G2/M期细胞比例分别为2.1％±0.4％、11.0％±0.7％和87.1％±0.6％,且划痕不愈合;caspase-3/7活性显著增加(t=11.83,P＜0.01);HepG2细胞凋亡率为16.4％±0.4％,明显高于对照组的5.8％±0.2％ (t=14.05,P＜ 0.01);z-VAD-FMK抑制caspases表达,HepG2细胞凋亡率为11.3％±0.7％,明显高于对照组的5.8％±0.2％ (t=11.83,P＜0.01). 结论 IGF-IR表达与肝癌细胞增殖、运动和凋亡相关,可能是肝癌分子靶向治疗的有效靶点.     

HDV/HBV感染树鼩肝组织Fas/FasL表达与肝细胞凋亡

目的 探讨HDV感染树鼩肝组织中Fas/FasL表达与HDV感染之间的关系,以及Fas/FasL在丁型肝炎肝细胞凋亡中的作用。 方法 采用免疫组化和原位杂交技术对45份HDV感染树鼩肝组织中HDAg,Fas/FasL和Fas/FasL mRNA的表达进行了检测;应用原位末端标记技术对肝细胞凋亡进行了检测;并应用免疫组化双重染色对HDAg,Fas/FasL的表达以及肝细胞凋亡进行了检测。 结果 45份肝组织中有39份可检出Fas/FasL(阳性率87％),有41份可检出凋亡细胞(阳性率91％),HDAg表达与Fas/FasL表达之间有显著相关性(X_1~2=29.2,X_2~2=27.9,P<0.05),HDAg表达越强,Fas和FasL表达也越强,凋亡在HDAg阳性和阴性细胞中均可发生,以HDAg阳性细胞发生为主,Fas/FasL表达与肝细胞凋亡之间有显著相关性(X_1~2=35.1,X_2~2=40.2,p<0.05),Fas和FasL表达越强,凋亡阳性细胞越多。 结论 丁型肝炎病毒感染和未感染的肝细胞均可发生凋亡,但凋亡只在少数细胞发生;肝细胞内的病毒抗原表达可诱导Fas/FasL的表达;Fas/FasL肝细胞凋亡中起重要作用。     

溃疡性结肠炎中Fas/FasL介导的结肠上皮

目的探讨Fas/FasL介导的结肠上皮细胞凋亡在溃疡性结肠炎(UC)发病机制中的作用.方法按Powell-Tuck评分系统对UC患者疾病活动性进行评分.免疫组化法检测35例UC和15例对照标本Fas、FasL表达,M30Cytodeath特异性检测结肠上皮细胞凋亡,图像分析仪定量分析.结果UC组表达Fas、FasL的水平平均为(27.1±2.9)%、(16.5±3.2)%,凋亡指数平均为(3.5±1.0)%,均比对照组明显增高[分别为(11.6±3.1)%、(5.3±2.4)%及(0.3±0.1)%,P＜0.01];UC表达Fas、FasL的水平与疾病活动性评分有正相关性(r=0.42和r=0.38,P＜0.05),而与组织学分级没有相关性(P＞0.05);组织学分级与疾病活动性评分呈显著正相关(r=0.848,P＜0.01).Fas与M30可共同表达且具有相关性.结论Fas/FasL介导的结肠上皮细胞大量凋亡可能是UC上皮层破坏的机制之一.     

过氧化物酶体增殖活化受体-α激活对HepG2细胞脂肪变性及血红素加氧酶-1表达的影响

目的 研究过氧化物酶体增殖活化受体-α(PPAR-α)激活对油酸诱导的HepG2细胞脂肪变性及血红素加氧酶-1 (HO-1)表达的影响.方法 以油酸(OA)诱导人肝癌HepG2细胞脂肪变性为模型组,采用不同浓度的PPAR-α激动剂非诺贝特(FF)处理HepG2细胞24h,油红O染色观察细胞内脂滴数量,甘油-3-磷酸氧化酶法检测细胞内甘油三酯(TG)含量,采用实时荧光定量PCR检测各组HepG2细胞PPAR-α、HO-1 mRNA水平,采用免疫细胞化学法检测PPAR-α与HO-1蛋白表达.采用SPSS13.0软件,采用单因素方差分析及Pearaon直线相关进行相关分析.结果 (1)模型组HepG2细胞内TG含量为(379.98±23.19) mg/g,对照组为(185.03±12.68) mg/g,模型组HepG2细胞内TG含量明显增加,t=24.385,P＜0.01.PPAR-α的mRNA及蛋白相对表达水平模型组分别为0.42±0.38和0.47±0.14,对照组分别为1.00±0.00和1.85±0.12,模型组明显降低,t=0.583和1.382P值均＜0.01.HO-1的mRNA及蛋白相对表达水平模型组分别为0.36±0.66和0.26±0.10,对照组分别为1.00±0.00和1.22±0.12,模型组明显降低,t=0.637和t=0.967,P值均＜0.01;(2)FF浓度在5、10、50μmol/L时,HepG2细胞内TG值分别为(294.00±19.80) mg/g、(250.33±9.96)mg/g和(196.99±9.14) mg/g,t值分别为10.747、16.200和22.873, F=148.555;P值均＜0.01 ;PPAR-α的mRNA相对表达量分别为0.55±0.65,0.85±0.61,1.31±0.36,t值分别为0.137、0.430和0.893,F=177.637,P值均＜0.01;PPAR-α蛋白累积光密度值分别为0.82±0.11、1.31±0.16和1.75±0.13,t值分别为0.352,0.840,1.280,F=120.764,P值均＜0.01;HO-1的mRNA相对表达量分别为0.62±0.05、0.84±0.07和1.30±0.11,t值分别为0.257,0.480,0.937,F=74.768,P值均＜0.01;HO-1蛋白累积光密度值分别为0.44±0.08、0.81±0.08和1.20±0.10,t值分别为0.180,0.553,0.943,F=119.903,P值均＜0.01.结论 PPAR-α的激活可以抑制HepG2细胞脂肪变性,HO-1可能是其重要下游因子.     

凋亡相关基因Fas/Fasl在非小细胞肺癌中的表达及临床意义

目的探讨Fas/FasL在非小细胞肺癌(NSCLC)中的表达与临床意义。方法采用免疫组化(S-P法)检测Fas、FasL在60例NSCLC和20例癌旁正常组织中的表达。采用TUNEL法检测凋亡细胞。结果 Fas在NSCLC中阳性率为46.7%(28/60),在正常肺组织阳性率为100%(20/20),差异性有统计学意义(χ2=14.359,P=0.000);高分化组中的阳性率为78.6%,在中、低分化组阳性率为37.0%,差异有统计学意义(χ2=7.468,P=0.006);TNM分期Ⅰ、Ⅱ期的阳性率为57.5%,Ⅲ、Ⅳ期的阳性率为25%,差异有统计学意义(χ2=5.658,P=0.017);FasL在NSCLC中阳性率为68.23%(41/60),在正常肺组织中阳性率为15%(3/20),差异有统计学意义(χ2=17.239,P=0.000);伴有淋巴结转移者表达的阳性率为85.3%,不伴淋巴结转移者中的表达阳性率为53.8%,差异有统计学意义(χ2=10.431,P=0.001)。FasL与凋亡指数(AI)呈负相关(r=-0.702,P=0.000),Fas与AI呈正相关(r=0.732,P=0.000)。结论 Fas及FasL的表达与NSCLC的发生、发展关系密切;监测Fas/FasL可能有助于NSCLC分化程度、TNM分期及淋巴结转移的判断。     

新生期小鼠胰岛细胞凋亡及其机制的研究

目的 观察新生期小鼠胰岛细胞凋亡的变化特点并分析细胞凋亡相关基因的表达差异,初步探讨相关机制.方法 采用胶原酶消化法分离纯化第1、3和8周小鼠胰岛细胞,以磷脂结合蛋白V-绿色荧光素/碘化丙啶双染法流式细胞术检测细胞凋亡率.透射电镜观察胰岛细胞凋亡形态,原位末端脱氧核苷酸转移酶标记（Tunel）/胰岛素免疫荧光双染法检测凋亡.采用实时定量PCR技术检测凋亡相关基因mRNA的表达.采用Western blotting技术检测促凋亡基因和抗凋亡基因的表达.多组间统计数据比较采用单因素方差分析.结果 （1）新生期小鼠胰岛细胞凋亡率在3周时显著增加,明显高于1周和8周[分别为（10.53±2.61）％、（1.80±0.69）％、（3.26±0.94）％,F=32.09,P＜0.01].透射电镜结果显示新生第3周小鼠胰岛细胞核出现凋亡早期改变.3周时Tunel/胰岛素双阳性细胞数明显高于1周和8周.（2）新生期小鼠胰岛细胞凋亡相关基因的表达呈动态变化,3周时,促凋亡基因Fas和FasL的mRNA表达均明显高于1周和8周（分别为1.53±0.21、1.00±0.00、0.46±0.24,F=24.85,P＜0.01;2.63±0.56比1.00±0.00、0.52±0.14,F=32.77,P＜0.01）,抗凋亡基因Bcl-2 mRNA表达明显低于1周和8周（分别为0.30±0.23、1.00±0.00、1.71±0.00,F=78.06,P＜0.01）.（3）3周时,Fas、FasL和裂解的Caspase-3蛋白表达均明显高于1周和8周（分别为2.05±0.16、1.00±0.00、0.59±0.24,F=61.47,P＜0.01;3.54±0.86、1.00±0.00、0.72±0.26,F=27.04,P＜0.01;5.74±0.59比1.00±0.00、3.11±0.20,F=128.79,P＜0.01）;Bcl-2蛋白表达明显低于1周和8周（0.62±0.13比1.00±0.00、1.90±0.10,F=151.08,P＜0.01）.结论 Fas/FasL以及Bc1-2介导的细胞凋亡信号通路可能参与新生期小鼠胰岛细胞凋亡的调控.     

Fas and Fas ligand-mediated apoptosis and its role in autoimmune diabetes

The relationship between Fas-mediated apoptosis and Type 1 diabetes is currently under investigation. Fas/Fas ligand interaction could be involved both in the insulitis process and in β-cell death. Nevertheless, different mechanisms appear to be involved in human Type 1 diabetes and in NOD mice. In the present work, we review recent evidence of the role of the Fas/Fas ligand system in human and NOD mouse diabetes, describing possible hypotheses for its involvement in the pathogenesis of the disease, with possible implications for therapy and islet transplantation. Copyright © 1998 John Wiley & Sons, Ltd.     

可溶性Fas,可溶性Fas配体与细胞因子在1型糖尿病发病中的意义

目的　研究可溶性Fas(sFas)和可溶性Fas配体(sFasL)与细胞因子在1型糖尿病发病中的作用。方法　32名1型糖尿病患者和20名正常人的血清,采用夹心BAS-ELISA法分别检测sFas,sFasL,γ干扰素(IFN-γ)及白细胞介素-1(IL-1)含量。结果　1型糖尿病血清中sFas,IFN-γ及IL-1含量分别为(1　　546±685,1　　074±451与1　　406±721)ng/L,显著高于正常组;sFasL为(211±73)mg/L,低于正常组但差异无显著性。在1型糖尿病患者中高浓度sFas伴高IFN-γ者共12例,低浓度sFas伴低IFN-γ者共9例。结论　1型糖尿病患者血清中的sFas,IFN-γ及IL-1高于正常人,sFas与IFN-γ浓度呈正相关(r=0.79,P＜0.05)。对1型糖尿病患者血清进行sFas,IFN-γ及IL-1等检测可作为反映胰岛细胞病变的辅助指标,有助于对疾病的诊断与治疗。     

The signaling pathways by which the Fas/FasL system accelerates oocyte aging

In spite of great efforts, the mechanisms for postovulatory oocyte aging are not fully understood. Although our previous work showed that the FasL/Fas signaling facilitated oocyte aging, the intra-oocyte signaling pathways are unknown. Furthermore, the mechanisms by which oxidative stress facilitates oocyte aging and the causal relationship between Ca²⁺ rises and caspase-3 activation and between the cell cycle and apoptosis during oocyte aging need detailed investigations. Our aim was to address these issues by studying the intra-oocyte signaling pathways for Fas/FasL to accelerate oocyte aging. The results indicated that sFasL released by cumulus cells activated Fas on the oocyte by increasing reactive oxygen species via activating NADPH oxidase. The activated Fas triggered Ca²⁺ release from the endoplasmic reticulum by activating phospholipase C-γ pathway and cytochrome c pathway. The cytoplasmic Ca²⁺ rises activated calcium/calmodulin-dependent protein kinase II (CaMKII) and caspase-3. While activated CaMKII increased oocyte susceptibility to activation by inactivating maturation-promoting factor (MPF) through cyclin B degradation, the activated caspase-3 facilitated further Ca²⁺ releasing that activates more caspase-3 leading to oocyte fragmentation. Furthermore, caspase-3 activation and fragmentation were prevented in oocytes with a high MPF activity, suggesting that an oocyte must be in interphase to undergo apoptosis.     

Fa基因多态性与自身免疫性肝病的相关性

自身免疫性肝炎(AIH)和原发性胆汁性肝硬化(PBC)均是由免疫介导的病因不明的慢性肝脏炎症性疾病,表现为严重的肝脏病变,并可以进展为肝硬化Ⅲ.为探寻自身免疫性肝病的遗传易感性,我们分析了自身免疫性肝病患者的Fas基因多态性.     

Cholangiocarcinomas express Fas ligand and disable the Fas receptor

Cholangiocarcinoma is a highly-malignant adenocarcinoma originating from cholangiocytes. Current concepts support escape from immune surveillance using aberrant expression of Fas ligand (FasL) and dysregulation of receptor (FasR) signaling as a potential mechanism for tumor progression. Our aims were to determine if altered expression of FasR and FasL or changes in expression of FLICE inhibitor (I-FLICE) allow cholangiocarcinoma cells to escape immune surveillance. Human cholangiocarcinoma cell lines were evaluated for the functional expression of FasR and FasL by (1) quantitating apoptosis after incubation of cells with agonistic antibodies and (2) an in vitro cell death assay involving coculture of cholangiocarcinoma cells with Fas-sensitive thymocytes. I-FLICE antisense treatment was performed by stable transfection with complementary DNA (cDNA) for I-FLICE in the reverse orientation. We found that normal cholangiocytes in vivo express FasL. Human cholangiocarcinoma cell lines express both FasL and FasR and I-FLICE. FasL expressed by cholangiocarcinomas in vitro induced lymphocyte cell death (70% after 24 hours). Despite the expression of FasR, exposure of the cells to agonistic antibodies (500 ng/mL) induced only minimal apoptosis in the Jurkat cells. Antisense treatment of cholangiocarcinomas in vitro with I-FLICE reduced protein expression of I-FLICE by 90% to 95% and increased Fas-mediated apoptosis 2-fold. We concluded that cholangiocarcinomas escape immune surveillance either by disabling FasR signaling through the expression of I-FLICE and/or increased FasL expression to induce apoptosis of invading T cells. Reduction of I-FLICE expression in cholangiocarcinoma cells restored Fas-mediated apoptosis. Therapeutic maneuvers to inhibit expression of I-FLICE may aid in the treatment of cholangiocarcinoma.     

Tumor necrosis factor alpha, but not Fas, mediates hepatocellular apoptosis in the murine ischemic liver.

BACKGROUND & AIMS: Apoptosis of hepatocytes is a central feature of ischemic injury in the liver. The aim of this study was to identify extracellular inducers of apoptosis in the murine ischemic liver. METHODS: Involvement of tumor necrosis factor (TNF)-alpha and Fas signaling was evaluated using various knockout mice (TNF-receptor 1 [TNF-R1]-/-, Fas[lpr]-/-, and Fas ligand[gld]-/-) and wild-type mice pretreated with pentoxifylline, an inhibitor of TNF-alpha synthesis. RESULTS: Expression of TNF-alpha was increased after ischemia and reperfusion in wild-type mice and TNF-R1-deficient mice when compared with sham-operated animals. Pentoxifylline prevented up-regulation of TNF-alpha expression. Inhibition of TNF-alpha resulted in significant decrease of serum aspartate aminotransferase levels and prolonged animal survival. Markers of apoptosis (terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling staining, cytochrome C release, and caspase 3 activity) were consistently decreased, and animal survival was prolonged after blocking TNF-alpha. In contrast, inhibition of Fas signaling did not alter parameters of tissue injury or apoptosis, and animal survival remained unchanged. CONCLUSIONS: We identify TNF-alpha as a crucial inducer of apoptotic cell death in the ischemic liver. A role for Fas could not be identified. These findings may lead to novel strategies to prevent ischemic injury of the liver.     

Suppression of P-gp induced multiple drug resistance in a drug resistant gastric cancer cell line by overexpression of Fas

AIM:To observe the drug sensitizing effect and related mechanisms of fas gene transduction on human drug-resistant gastric cancer cell SGC7901/VCR (resistant to Vincristine).METHODS:The cell cycle alteration was observed by FACS. The sensitivity of gastric cancer cells to apoptosis was determined by in vitro apoptosis assay. The drug sensitization of cells to several anti-tumor drugs was observed by MTT assay. Immunochemical method was used to show expression of P-gp and Topo II in gastric cancer cells.RESULTS:Comparing to SGC7901 and pBK-SGC7901/VCR, fas-SGC7901/VCR showed decreasing G2 cells and increasing S cells, the G2 phase fraction of pBK-SGC7901/VCR was about 3.0 times that of fas -SGC7901/VCR but S phase fraction of fas -SGC7901/VCR was about 1.9 times that of pBK-SGC7901/VCR, indicating S phase arrest of fas-SGC7901/VCR. FACS also suggested apoptosis of fas-SGC7901/VCR.fas-SGC7901/VCR was more sensitive to apoptosis inducing agent VM-26 than pBK-SGC7901/VCR. MTT assay showed increased sensitization of fas-SGC7901/VCR to DDP, MMC and 5-FU, but same sensitization to VCR according to pBK-SGC7901/VCR. SGC7901, PBK-SGC7901/VCR and fas -SGC7901/VCR had positively stained Topo II equally. P-gp staining in pBK-SGC7901/VCR was stronger than in SGC7901, but there was little staining of P-gp in fas-SGC7901/VCR.CONCLUSION:fas gene transduction could reverse the MDR of human drug-resistant gastric cancer cell SGC7901/VCR to a degree, possibly because of higher sensitization to apoptosis and decreased expression of P-gp.