Endoplasmic reticulum stress in hepatic stellate cells induced by tunicamycin promotes apoptosis and cell cycle arrest

Objective To investigate the effect of endoplasmic reticulum stress (ERS) induced by tunicamycin on proliferation, activation, and apoptosis of HSC-T6 rat hepatic stellate cells and its possible mechanism. Methods With the expression level of glucose regulated protein 78 (GRP78) as an indicator to explore the optimal concentration and time, a cell model of tunicamycin-induced ERS in HSC-T6 cells was established. HSC-T6 cells were randomized into control group, treatment group with 1 mL/L of dimethyl sulfoxide (DMSO), and treatment group with 1 μg/mL of tunicamycin, and the cells were treated for 12 h. MTT assay was used to detect cell proliferation, flow cytometry to detect apoptosis and cell cycle, and Western blot to detect the protein expressions of α-smooth muscle actin (α-SMA), C/EBP cAMP homologous protein (CHOP), caspase-12, and cyclin D1. Results The optimal dose of tunicamycin to induce ERS in HSC-T6 cells was 1 μg/mL and the optimal time was 12 hours. Compared with the control group and treatment group with DMSO, the treatment group with 1 μg/mL of tunicamycin had no significant change in cell proliferation, but the expression of α-SMA was up-regulated with the apoptosis increased, the proportion of G1 phase cells was significantly increased and that of S phase cells decreased, the ERS induced apoptosis related signal proteins CHOP and caspase-12 were significantly up-regulated, and the expression of cyclin D1 was significantly down-regulated. Conclusion Tunicamycin treatment of HSC-T6 cells for 12 hours induces significant ERS and activation of the cells. The insignificant change in the number of cells during the activation may be related to the increased apoptosis and the cell cycle arrest induced by the activation of the GRP78/CHOP/caspase-12 pathway.