N-乙酰半胱氨酸对内质网应激介导的HepG2细胞凋亡的作用

目的 了解N-乙酰半胱氨酸(NAC)对内质网氧化应激介导的肝细胞凋亡的阻抑作用,探讨其治疗肝细胞损伤的作用机制.方法 用过氧化氢(H2O2)诱导HepG2细胞,建立内质网氧化应激凋亡模型,用NAC进行干预.通过四甲基偶氮唑盐、DNA梯度分析,Western blot、流式细胞仪检测细胞凋亡率及活性氧(ROS)的产生等方法,了解NAC对H2O2诱导HepG2细胞的凋亡率、凋亡信号蛋白的表达以及ROS产生的影响.结果 用不同浓度H2O2(0、1、3,5 mmol/L)诱导HepG2细胞6 h后,发现随着H2O2浓度增加,细胞活力下降,凋亡率增加,分别为0.7%±0.5%、26.4%±1.8%、29.7%±1.2%、51.2%±9.4%;细胞凋亡信号蛋白表达增加,ROS产生增多,分别为14.0%±0.5%、95.2%±0.1%、97.5%±0.25%、98.3%±0.2%;在3 mmol/L时出现典型内质网氧化应激凋亡形态学改变.用NAC(10、20 mmol/L)干预后发现,NAC可明显提高细胞活力、细胞凋亡率由29.7%±1.2%降至23.3%±4.7%和14.3%±1.2%,细胞凋亡过程中凋亡信号蛋白的表达减少、细胞内ROS的产生率由97.5%±0.2%降至52.2%±0.8%和51.2%±2.9%.结论 NAC能对氧自由基反应有直接抑制作用,阻断内质网氧化应激介导的肝细胞凋亡,减轻肝细胞损伤.

The effect of N-acetyl-L-cysteine on endoplasmic reticulum stress mediated apoptosis of HepG2 cells

OBJECTIVE: To analyze the mechanisms of NAC on endoplasmic reticulum (ER) stress mediated cells apoptosis of HepG2 cells and to evaluate the potential role of NAC in the treatment of liver injury. METHODS: HepG2 cells were treated with H2O2 to make a model of oxidative ER stress mediated apoptosis. To evaluate the apoptosis, various methods such as MTT, DNA ladder, Western blot and flow cytometry were used. Then the optimal dosage and incubution time of NAC intervention in apoptosis were ascertained, and the differences between induction and intervention of apoptosis, including the percentage of apoptosis, the expression of apoptotic protein (GRP78, Caspase-12, PARP) and the production of reactive oxygen species (ROS) were compared. RESULTS: The activity of the cells decreased by H2O2 (0, 1, 3, 5 mmol/L) treatments in a dose-dependent manner. The ratio of apoptotic cells increased (0.7%+/-0.5%, 26.4%+/-1.8%, 29.7%+/-1.2% and 51.2%+/-9.4%, respectively) as did the production of ROS (14.0%+/-0.5%, 95.2%+/-0.1%, 97.5%+/-0.2% and 98.3%+/-0.2%, respectively). The HepG2 cells showed typical morphologic change of ER stress 6 hr after they were treated with 3 mmol/L H2O2. ER stress mediated-apoptosis was confirmed by Western blot. NAC (10 mmol/L and 20 mmol/L) protected cells from apoptosis. Typical features of ER stress apoptosis were seen accompanied by diminishing the ratio of apoptotic cells from 29.7%+/-1.2% to 23.3%+/-4.7% and 14.3%+/-1.2%. The production of ROS also decreased from 97.5%+/-0.2% to 52.2%+/-0.8% and 51.2%+/-2.9%. The effect was related to the concentration: 20 mmol/L NAC was more effective than 10 mmol/L. CONCLUSIONS: As an oxidizing agent, H2O2 may induce ROS in cells and induce oxidative stress, causing ER stress and apoptosis. NAC can inhibit the procession of ROS directly and prevent injuries to the hepatocytes. [Chinese FullText URL http://zhgz.chinajournal.net.cn].