Roles of endoplasmic reticulum stress and autophagy on H2O2‑induced oxidative stress injury in HepG2 cells

Abstract

Endoplasmic reticulum stress (ERS) can be induced by a variety of physiological and pathological factors including oxidative stress, which triggers the unfolded protein response to deal with ERS. Autophagy has been hypothesized to be a means for tumor cells to increase cell survival under conditions of hypoxia, metabolic stress and even chemotherapy. Although they may function independently from each other, there are also interactions between responses to oxidative stress injury induced by pathologic and pharmacological factors. The aim of the present study was to investigate the effects of ERS and autophagy on H2O2-induced oxidative stress injury in human HepG2 hepatoblastoma cells. It was demonstrated that exposure of HepG2 cells to H2O2 decreased cell viability and increased reactive oxygen species (ROS) levels in a dosage-dependent manner. In addition, apoptosis and autophagy rates were elevated and reduced following cell exposure to H2O2 + the ERS inducer Tunicamycin (TM), and to H2O2 + the ERS inhibitor Salubrinal (SAL), compared with the cells treated with H2O2 alone, respectively. Further studies revealed that TM enhanced the expression of ERS-related genes including glucose-regulated protein-78/binding immunoglobulin protein, inositol-requiring kinase-I and activating transcription factor 6 and C/EBP-homologous protein 10, which were attenuated by SAL compared with cells exposed to H2O2 alone. The data from the present study also demonstrated that LC3II/LC3-I and p62, members of autophagy-related genes, were increased and decreased in cells treated with H2O2 + TM compared with cells treated with H2O2, respectively, indicating that autophagy was stimulated by ERS. Furthermore, a reduction in the levels of pro caspase-3 and pro caspase-9, and elevation level of caspase-12 were observed in cells exposed to H2O2 + TM compared with cells treated with H2O2, respectively, suggesting apoptosis induced by H2O2 was enhanced by ERS or autophagy triggered by H2O2. The above results suggest that the ERS inducer may be a potential target for pharmacological intervention targeted to ERS or autophagy to enhance oxidative stress injury of tumor cells induced by antitumor drugs.

Knockout of PRDX6 induces mitochondrial dysfunction and cell cycle arrest at G2/M in HepG2 hepatocarcinoma cells

“…It is well known that a complex connection exist between mitochondria and ER so that signals from damaged mitochondria may have stimulated the production of ROS from the ER surface with the involvement of NOX complexes [ 60 ]. HepG2 cells respond to H 2 O 2 -induced oxidative stress by activation of the unfolded protein response (UPR) and autophagy for survival [ 61 ]. However, the UPR was not activated in HepG2 PRDX6−/- cells despite mitochondrial damage and ER stress, as indicated by decreased levels of HSP5A/Bip, nor was apoptosis as evidenced by flow cytometry and because caspases were not induced.…”

Reduction of integrin alpha 4 activity through splice modulating antisense oligonucleotides

“…Polyclonal goat anti-rabbit immunoglobulins/HRP (Dako, cat. no P0448) 38 at a dilution of 1:10,000 and Luminata Crescendo western HRP substrate were used for immunodetection. The blots were exposed for a serial scan of 30 s using the Fusion FX system (Vilber Lourmat, Marne-la-Vallée, France) and the entire image was processed.…”

Zyflamend induces apoptosis in pancreatic cancer cells via modulation of the JNK pathway

“…Nonetheless, a considerable body of evidence also indicates that both autophagy and ER stress can lead to apoptosis in tumor cells. In addition to this, a growing body of literature supports existing crosstalk between the two pathways [39,40]. However, which pathway is upstream of the other is yet to be determined.…”