过表达apoA-I可缓解BEL-7402细胞中衣霉素诱导的内质网应激

内质网应激（endoplasmic reticulum stress，ER stress）对非酒精性脂肪性肝病（non alcoholic fatty liver disease，NAFLD）的发生发展具有十分重要的作用。本实验室前期结果证实，载脂蛋白A1（apolipoprotein A-I，apoA-I）可以通过减少肝细胞脂质堆积来减轻蛋氨酸胆碱缺乏饲料造成的非酒精性肝炎(non-alcoholic steatohepatitis，NASH)，但相关机制仍不十分清楚。为探索apoA I对内质网应激的影响，本研究采用衣霉素处理人肝癌BEL-7402细胞。Western印迹结果证实,衣霉素确实可以诱导BEL-7402细胞内质网应激，并具有时间和剂量依赖性。通过将apoA-I表达载体及其对照载体转染到BEL-7402细胞，再加入衣霉素处理，结果显示，与对照组相比,过表达apoA-I的细胞内质网应激标志分子表达明显减轻，同时与脂质合成相关的固醇调节元件结合蛋白1、脂肪酸合成酶和乙酰辅酶A羧化酶1蛋白质水平明显降低。脂质检测结果表明，细胞内甘油三酯和游离胆固醇水平也明显降低（P<0.05）。上述结果表明，apoA-I能够减轻衣霉素引起的内质网应激，可能机制是通过调控固醇调节元件结合蛋白1减少肝细胞的脂质堆积。

Overexpression of Apolipoprotein A-I Alleviates Endoplasmic Reticulum #br# Stress Induced by Tunicamycin in BEL-7402 Cells

Endoplasmic reticulum stress plays an important role in the development of non alcoholic fatty liver disease. Although apolipoprotein A-I (apoA-I) was demonstrated to alleviate non-alcoholic steatohepatitis by decreasing lipid storage in hepatocytes, the underlying mechanism remains largely unknown. To elucidate the effect of apoA-I on endoplasmic reticulum (ER) stress, tunicamycin was adopted for the induction of ER stress in BEL-7402 cells. Both dose- and time-dependent changes in Western blot were observed, when cells were transfected with apoA-I-expressing or control plasmids and treated for 24 hours with tunicamycin. The results showed that apoA-I overexpression decreased the protein levels of ER stress markers, as well as lipogenic gene products, including sterol regulatory element binding protein 1 (SREBP-1), fatty acid synthase, and acetyl CoA carboxylase 1. The cellular levels of triglycerides and free cholesterol were also decreased comparing with the control group (P<0.05). Our data suggested that apoA-I reduced ER stress by moderating SREBP 1 protein and reducing lipid accumulation.