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布雷菲德菌素A (Brefeldin A, BFA)被认为是一种新型抗癌药物,属真菌合成的大环内酯类抗生素[1-3],是青霉属、蓝青霉、棒曲霉等多种菌株的代谢产物。研究发现,BFA在前列腺癌、乳腺癌等细胞株的体外实验中表现出抗肿瘤活性[4-5],且其抗肿瘤机制与凋亡诱导作用相关。因此BFA作为一种新型抗肿瘤候选药物正引起越来越多人们的注意。
随着我国工业的发展,环境污染物如重金属和难降解有机污染物污染成为我国肝癌发病率居高不下的主要原因。研究表明,长期、低剂量摄入微囊藻毒素[6]、幽门螺杆菌感染[7]、环境中农药暴露[8]、苯并芘暴露[9]、砷暴露[10]以及氯化消毒副产物的暴露[11]等都与肝癌发生发展相关。有研究发现,BFA处理可引起HepG2发生明显而持久的内质网应激反应[12]。与内质网应激相关的蛋白激活转录因子4(ATF4)、C/EBP同源蛋白(CHOP)可通过自噬调控过程发挥抗肿瘤作用[13-14]。研究表明,ATF4介导的CHOP激活也可以诱导自噬相关蛋白5 (Atg5),Atg5对于自噬进程中的泛素化过程是必需的,它促进了Atg5-Atg12-Atg16L复合物的组装以及LC3从LC3-Ⅰ(自由形式)到LC3-Ⅱ(膜结合形式)的转化[15-16]。适度的自噬增加,可促进细胞进行物质更新,帮助细胞应对饥饿、低氧等不利的环境条件,而自噬水平的显著上调会大量消耗细胞中的细胞器,同时产生大量的空泡,最终导致细胞死亡,即自噬性细胞死亡(ACD)。那么BFA能否通过ATF4/CHOP通路激活HepG2细胞内的自噬水平并引起细胞死亡呢?为此,本实验室以人肝母细胞瘤细胞株HepG2细胞作为模型,探讨BFA对HepG2细胞内相关分子的影响,为进一步探讨BFA的抗肿瘤作用奠定基础。
布雷菲德菌素A对HepG2细胞自噬的诱导作用
Study of brefeldin a on induction of autophagy in HepG2 Cells
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摘要: 为探讨新型抗癌药物布雷菲德菌素A(BFA)诱导肝癌细胞发生自噬性死亡的作用机制,以HepG2细胞作为研究对象,将细胞分成阴性对照组、不同浓度BFA组和阳性对照组(雷帕霉素),采用MTT法测定HepG2细胞活性;采用免疫荧光法检测细胞内自噬标志蛋白LC3的表达和细胞核形态学改变;采用Western Blot法检测细胞内激活转录因子4(ATF4)、C/EBP同源蛋白(CHOP)、聚(腺苷二磷酸-核糖)多聚酶(PARP)、增殖细胞核抗原(PCNA)、微管相关蛋白1轻链3(LC3)、自噬相关蛋白5(Atg5)、自噬相关蛋白6(Atg6/Beclin-1)的表达水平。结果表明,BFA可引起HepG2细胞内自噬特征蛋白LC3-Ⅱ、Atg5、Beclin-1的蛋白表达水平明显增加;同时引起HepG2细胞活性降低、细胞数量减少、细胞核固缩和变形。说明BFA可能引起HepG2细胞发生自噬性细胞死亡。进一步探讨自噬诱导途径发现,BFA引起HepG2细胞内ATF4、CHOP的蛋白表达水平增加。BFA可能通过诱导ATF4和CHOP的过表达引起HepG2细胞发生自噬性细胞死亡。Abstract: To investigate the mechanism of the new anticancer drug Brefeldin A (BFA) induced autophagic cell death in HepG2 cells. MTT assay was used to measure the activity of HepG2 cells. The immunofluorescence method was used to observed the expression of LC3 and nuclear morphological changes. Measurement of activating transcription factor 4 (ATF4), C/EBP homologous protein (CHOP), poly ADP-ribose polymerase (PARP), proliferating cell nuclear antigen (PCNA), microtubule-associated protein 1 light chain 3 (LC3), autophagy related 5 homolog (Atg5), autophagy related 6 homolog (Atg6/Beclin-1) by Western blot. The results showed that BFA could significantly increase the expression levels of autophagy characteristic proteins LC3-Ⅱ, Atg5 and Beclin-1 in HepG2 cells; At the same time, it caused the decrease of HepG2 cell activity, cell number reduction, nucleus pyknosis and deformation. These results suggest that BFA may cause autophagic cell death in HepG2 cells. Further exploration of the autophagy induction pathway found that BFA caused an increase in the protein expression levels of ATF4 and CHOP in HepG2 cells. The above results suggest that BFA may induce autophagic cell death in HepG2 cells by inducing the overexpression of ATF4 and CHOP.
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表 1 抗体信息
Table 1. Information of Antibody
名称
Name公司
Company编号
No.稀释比
Dilution ratioMouse anti-human β-actin BOSTER, Wuhan BM0005 1∶2000 Rabbit anti-human LC3 Protein Tech, China 14600-1-AP 1∶1000 Mouse anti-human PCNA BOSTER, Wuhan BM0104 1∶1000 Mouse anti-human BECN1 BBI Life Sciences, China D190707 1∶1000 Rabbit anti-human PARP CST, America 9542 1∶1000 Mouse anti-human ATG5 Protein Tech, China 66744-1-lg 1∶1000 Rabbit anti-human CHOP Protein Tech, China 15204-1-AP 1∶500 Rabbit anti-human ATF4 Protein Tech, China 10835-1-AP 1∶1000 Anti-rabbit IgG (H+L), F(ab')2 Fragment (Alexa Fluor® 488 Conjugate) CST, America 4412 1∶2000 HRP-conjugated Goat anti-rabbit IgG BOSTER, Wuhan BA1054 1∶5000 HRP-conjugated Goat anti-mouse IgG BOSTER, Wuhan BA1050 1∶5000 表 2 BFA对HepG2细胞活性的影响(
, n=6)$\bar x \pm s $ Table 2. Effect of BFA on the activity of HepG2 cells (
, n=6)$\bar x \pm s $ 组别
Group细胞活性/% Activity 6 h 24 h 48 h CON 100 100 100 0.1% DMSO 112.43 94.99 105.63 0.09 μmol·L-1 BFA 110.42 91.66* 98.84 0.36 μmol·L-1 BFA 107.39 75.34*# 64.34*# 0.9 μmol·L-1 BFA 103.03 72.31*# 54.30*# 1.8 μmol·L-1 BFA 106.55 68.87*# 54.19*# 3.6 μmol·L-1 BFA 101.16 67.15*# 51.10*# 9.0 μmol·L-1 BFA 109.56 63.53*# 39.30*# F 1.217 154.142 144.577 P 0.316 <0.001 <0.001 注:*,与阴性对照组相比,P<0.05;#,与0.1% DMSO组相比,P<0.05.
Note: *,Compared with negative control group, P < 0.05;#,Compared with 0.1% DMSO group, P < 0.05. -
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