Annals of Hepatology (Jan 2020)
Phosphorylation of eIF2α mitigates endoplasmic reticulum stress and hepatocyte necroptosis in acute liver injury
Abstract
Introduction and objectives: Necroptosis and endoplasmic reticulum (ER) stress has been implicated in acute and chronic liver injury. Activated eukaryotic initiation factor 2 alpha (eIF2α) attenuates protein synthesis and relieves the load of protein folding in the ER. In this study, we aimed to analyze the impact of eIF2α phosphorylation on hepatocyte necroptosis in acute liver injury. Materials and methods: Male BALB/c mice were injected with tunicamycin or d-galactosamine, and LO2 cells were incubated with tunicamycin to induce acute liver injury. 4-Phenylbutyric acid (PBA) and salubrinal were used to inhibit ER stress and eIF2α dephosphorylation, respectively. We analyzed the eIF2α phosphorylation, ER stress, and hepatocyte necroptosis in mice and cells model. Results: Tunicamycin or d-galactosamine significantly induced ER stress and necroptosis, as well as eIF2α phosphorylation, in mice and LO2 cells (p < 0.05). ER stress aggravated tunicamycin-induced hepatocyte necroptosis in mice and LO2 cells (p < 0.05). Elevated eIF2α phosphorylation significantly mitigated hepatocyte ER stress (p < 0.05) and hepatocyte necroptosis in mice (34.37 ± 3.39% vs 22.53 ± 2.18%; p < 0.05) and LO2 cells (1 ± 0.11 vs 0.33 ± 0.05; p < 0.05). Interestingly, tumor necrosis factor receptor (TNFR) 1 protein levels were not completely synchronized with necroptosis. TNFR1 expression was reduced in d-galactosamine-treated mice (p < 0.05) and cells incubated with tunicamycin for 12 and 24 h (p < 0.05). ER stress partially restored TNFR1 expression and increased necroptosis in tunicamycin-incubated cells (p < 0.05). Conclusions: These results imply that ER stress can mediate hepatocyte necroptosis independent of TNFR1 signaling and elevated eIF2α phosphorylation can mitigate ER stress during acute liver injury.
