Toxic bile salts induce rodent hepatocyte apoptosis via direct activation of Fas
Toxic bile salts induce rodent hepatocyte apoptosis via direct activation of Fas
复制标题
DOI：
10.1172/jci4765
复制
发表时间：
1999-01-01
影响因子：
15.9
通讯作者：
Gores, GJ
中科院分区：
文献类型：
--
作者：
Faubion, WA;Guicciardi, ME;Gores, GJ
胆汁淤积性肝损伤似乎是由甘氨酸鹅去氧胆酸盐(GCDC)等有毒胆盐诱导肝细胞凋亡所致。本实验室以往的研究表明，组织蛋白酶B是肝细胞凋亡过程中的下游效应蛋白酶。由于半胱氨酸天冬氨酸酶可以启动细胞凋亡，本研究旨在确定半胱氨酸蛋白酶在组织蛋白酶B激活中的作用。GCDC处理的McNtcp.24肝癌细胞的免疫印迹显示，聚(ADP-核糖)聚合酶和Iamin B-1被切割成表明效应半胱氨酸酶激活的片段。Caspase 8抑制剂CrmA可抑制GCDC诱导的组织蛋白酶B激活和细胞凋亡。与这些结果一致的是，在GCDC处理的细胞中观察到caspase 8样活性的增加。对GCDC诱导的caspase 8激活机制的研究表明，显性负性FADD抑制了细胞的凋亡，从Fas缺陷的淋巴组织增殖性小鼠分离的肝细胞对GCDC诱导的细胞凋亡具有抵抗力。GCDC处理后，免疫沉淀实验显示Fas寡聚，共聚焦显微镜观察到Delta FADD-GFP(Fas相关死亡结构域-绿色荧光蛋白)聚集，在没有检测到Fas配体mRNA的情况下。总之，这些数据表明，GCDC诱导的肝细胞凋亡涉及Fas的配体非依赖性寡聚，FADD的募集，caspase 8的激活，以及随后效应蛋白酶的激活，包括下游的caspase和组织蛋白B。
Cholestatic liver injury appears to result from the induction of hepatocyte apoptosis by toxic bile salts such as glycochenodeoxycholate (GCDC). Previous studies from this laboratory indicate that cathepsin B is a downstream effector protease during the hepatocyte apoptotic process. Because caspases can initiate apoptosis, the present studies were undertaken to determine the role of caspases in cathepsin B activation. Immunoblotting of GCDC-treated McNtcp.24 hepatoma cells demonstrated cleavage of poly(ADP-ribose) polymerase and Iamin B-1 to fragments that indicate activation of effector caspases. Transfection with CrmA, an inhibitor of caspase 8, prevented GCDC-induced cathepsin B activation and apoptosis. Consistent with these results, an increase in caspase 8-like activity was observed in GCDC-treated cells. Examination of the mechanism of GCDC-induced caspase 8 activation revealed that dominant-negative FADD inhibited apoptosis and that hepatocytes isolated from Fas-deficient lymphoproliferative mice were resistant to GCDC-induced apoptosis. After GCDC treatment, immunoprecipitation experiments demonstrated Fas oligomerization, and confocal microscopy demonstrated Delta FADD-GFP (Fas-associated death domain-green fluorescent protein, aggregation in the absence of detectable Fas Ligand mRNA. Collectively, these data suggest that GCDC-induced hepatocyte apoptosis involves ligand-independent oligomerization of Fas, recruitment of FADD, activation of caspase 8, and subsequent activation of effector proteases, including downstream caspases and cathepsin B.