ABSTRACT
AIM:To investigate the effect of SET7/9 (SET domain containing 7/9) -mediated endoplasmic reticulum stress (ERS) on protein kinase R-like endoplasmic reticulum kinase (PERK) signaling pathway, and to explore the mechanisms of arsenic-induced hepatocyte apoptosis.METHODS:Human liver LO2 cells were divided into control group, arsenic poisoning model group, negative transfection group and SET7/9 siRNA transfection group.The apoptosis of the LO2 cells in each group was analyzed by flow cytometry.The protein levels of SET7/9, glucose-regulated protein 78 (GRP78) , PERK and p-PERK in the LO2 cells of each group were observed by Western blot.RESULTS:Inhibition of SET7/9 expression reduced the apoptotic rate of arsenic-induced LO2 cells.Arsenic exposure increased the expression of SET7/9 in the LO2 cells.Arsenic exposure increased the protein levels of GRP78 and p-PERK in the LO2 cells, but decreased the protein levels of GRP78 and p-PERK after transfection with SET7/9 siRNA (P<0.05).CONCLUSION:Arsenic exposure induces hepatocyte apoptosis by increasing SET7/9 to activate ERS by PERK signaling pathway.
ABSTRACT
AIM:To observe the changes of autophagy-related indexes during endoplasmic reticulum stress (ERS) induced by dithiothreitol (DTT) and its effect on apoptosis in human normal hepatocytes.METHODS:LO2 cells were treated with DTT at 2.0 mmol/L for 0, 6, 12 and 24 h to induce ERS.The expression of glucose-regulated protein 78 (GRP78) , protein kinase R-like endoplasmic reticulum kinase (PERK) , activating transcription factor 4 (ATF4) , C/EBP homologous protein (CHOP) , autophagy-related gene 12 (Atg12) , autophagy-related gene 5 (Atg5) and microtubule-associated protein 1 light chain 3 (LC3) at mRNA and protein levels was determined by real-time PCR and Western blot.The apoptosis was analyzed by flow cytometry.The formation of autophagosomes was observed under transmission electron microscope.After the LO2 cells were pretreated with rapamycin at 400 nmol/L for 1 h and treated with DTT at 2.0mmol/L for 24 h, the effect of rapamycin pretreatment on the apoptosis was analyzed by flow cytometry.RESULTS:After treatment with DTT at 2.0 mmol/L for 6, 12 and 24 h, the mRNA and protein levels of GRP78, PERK, ATF4, CHOP, Atg12, Atg5 and LC3 in the LO2 cells were significantly higher than those in 0 h group (P<0.05).At the same time, the ratio of LC3Ⅱ/LC3Ⅰwas also increased after DTT treatment (P<0.05).Observation under transmission electron microscope showed that autophagosomes were found in the LO2 cells treated with DTT for 6, 12 and 24 h.After DTT treatment for 6, 12 and 24 h, the apoptosis rate of LO2 cells was significantly higher than that in DTT 0 h group, while the apoptosis induced by DTT was significantly decreased after rapamycin pretreatment (P<0.05).CONCLUSION:ERS induces autophagy and rapamycin pretreatment alleviates the apoptosis of LO2 cells to some extent.