Open AccessBaicalin promoted site‐2 protease and not site‐1 protease in endoplasmic reticulum stress‐induced apoptosis of human hepatocellular carcinoma cells
Author(s) -
Yu Zhe,
Luo Xin,
Wang Chen,
Ye Jianhong,
Liu Shourong,
Xie Lei,
Wang Fei,
Bao Jianfeng
Publication year - 2016
Publication title -
febs open bio
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.718
H-Index - 31
ISSN - 2211-5463
DOI - 10.1002/2211-5463.12130
Subject(s) - endoplasmic reticulum , protease , apoptosis , hepatocellular carcinoma , chemistry , unfolded protein response , microbiology and biotechnology , biochemistry , cancer research , enzyme , biology
Baicalin (5,6‐dihydroxy‐7‐ o ‐glucuronide flavone) is an extract from the roots of Chinese herb Huang Qin ( Scutellaria baicalensis Georgi) and is reported to have antioxidative, antiproliferative, anti‐inflammatory, and anticancer activities. This study aimed to investigate the inhibitory effect of baicalin on human hepatocellular carcinoma ( HCC ) cells and the involvement of endoplasmic reticulum stress‐induced cell apoptosis. Two human HCC cell lines, HepG2 and SMMC 7221, were used in this study. The cells were incubated with baicalin solutions at various concentrations. A 3‐(4,5‐Dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) assay was used to assess cell proliferation inhibition; a TUNEL assay was used to evaluate cell apoptosis; small RNA interference was applied to silence IRE 1, ATF 6, and protein kinase R‐like ER kinase ( PERK ), which are transmembrane proteins inducing cell apoptosis, and two proteases (S1P and S2P) which cleave ATF 6. Real‐time PCR was used to evaluate the silencing effects of specific si RNA . Expression levels of specific proteins were analyzed by western blotting. Baicalin was found to inhibit the proliferation of HCC cells by inducing apoptosis in a concentration‐dependent manner. Elevated expression levels of GRP 78, CHOP , p50‐ ATF 6, and caspase12 were found after baicalin incubation. Compared with IRE 1 and PERK silencing, ATF 6 knockdown dramatically impaired baicalin's apoptosis‐inducing activity. Furthermore, S2P silencing, rather than S1P silencing, was also found to impair baicalin‐induced HCC cell apoptosis significantly. In conclusion, (a) baicalin inhibits human HCC cells by inducing apoptosis; (b) baicalin induces cell apoptosis by activating ATF 6 signaling pathway in endoplasmic reticulum ( ER ) stress; (c) S2P, rather than S1P is the molecular target for baicalin in inducing ER stress‐mediated HCC cell apoptosis.