铜过量负荷导致肝细胞凋亡及其对Bax Bcl-2基因表达的影响

Excessive copper induces hepatocyte apoptosis and affects Bax and Bcl-2 expression in rat liver

摘要:

目的：建立肝豆状核变性铜过量负荷大鼠模型，并研究肝铜沉积对肝细胞凋亡及Bax，Bcl-2基因表达的影响。方法：建立铜过量负荷大鼠模型，检测肝脏和血清铜以及血清丙氨酸氨基转移酶（ALT）含量；用末端脱氧核苷酸转移酶介导生物素标记(TUNEL)技术、RT-PCR和免疫组织化学方法分别检测铜过量负荷大鼠肝细胞凋亡、凋亡相关基因Bax，Bcl-2的mRNA和蛋白表达水平，并利用图像分析系统观察阳性细胞的变化规律。结果：随着铜负荷时间的延长，铜过量负荷大鼠肝组织铜含量、血清ALT水平逐渐升高，同时肝细胞的凋亡也逐渐增多，凋亡指数（AI）逐步升高。铜过量负荷大鼠肝组织Bax基因的表达水平明显高于对照组，且随着铜负荷时间的延长有升高趋势；Bcl-2基因的表达水平高于对照组，且随着铜负荷时间的延长也有升高趋势，但升高幅度低于Bax，故Bcl-2与Bax的比值（Bcl-2/Bax）随着铜负荷时间的延长而降低。结论：成功建立肝豆状核变性铜过量负荷大鼠模型，铜过量负荷通过相对上调促凋亡基因Bax表达水平来诱导肝细胞的凋亡。

Abstract:

OBJECTIVE: To establish a hepatolenticular degeneration rat model with excessive copper, and investigate the effects of excessive copper deposits in the liver on hepatocyte apoptosis and Bax and Bcl-2 expression. METHODS: Rat model of hepatolenticular degeneration was established by administering forages containing 1g/kg of copper sulfate and drinking water containing 0.185% copper sulfate. Copper level in the liver and serum and alanine aminotransferase (ALT) level in serum were measured using an atomic absorption spectrophotometer. The terminal deoxynucleotidyl transferase-mediated deoxyuridine 5-triphosphate nick-end labeling (TUNEL) method was used to detect hepatocyte apoptosis. Bax and Bcl-2 expression was observed by RT-PCR and imunohistochemistry staining. Quantification of positive cells was performed by image analyzer. RESULTS: With more prolonged excessive copper ingestion, copper level in the liver and serum as well as ALT level in serum rose, and more apoptosis cells appeared in the liver. Bax and Bcl-2 expression increased significantly compared with controls fed a normal diet and progressively increased with more prolonged excessive copper ingestion. The progressively increased extent of Bcl-2 expression was lower than that of Bax expression, so the ratio of Bcl-2/Bax decreased with increasing excessive copper ingestion time. CONCLUSIONS: Excessive copper deposits in the liver can induce hepatocyte apoptosis through an up-regulation of Bax expression.