Stress granules inhibit endoplasmic reticulum stress-mediated apoptosis during hypoxia-induced injury in acute liver failure

ARTICLE HIGHLIGHTS

Research background

There is no relevant report on the relationship between stress granules (SGs), endoplasmic reticulum stress (ERS) and hepatocyte apoptosis in the process of hepatocyte ischemia and hypoxia for acute liver failure (ALF).

Research motivation

This paper provides potential targets and ideas for clinical treatment of ALF.

Research objectives

This study was to investigate whether SGs could protect hepatocytes from hypoxia-induced damage during ALF by reducing ERS mediated apoptosis.

Research methods

The agonist of SGs, arsenite (Ars) was used to intervene hypoxia-induced hepatocyte injury cellular model and ALF mice models. Further, the siRNA of ATF4 and SGs inhibitor anisomycin was then used to intervene in cell models.

Research results

In the in vitro study, we firstly observed how the levels of SGs, ERS and apoptosis changed over time. With the prolongation of hypoxia time, the levels of ERS and apoptosis in hepatocytes increased. The level of SGs increased at 4h and then decreased. Therefore, hepatocyte treated with hypoxia for 12 h were used as cell models for subsequent research. This suggested that SGs were stress-increased in the early stage of hepatocyte hypoxia to protect cells from damage. However, with the prolongation of hypoxia time, the production of SGs would decrease, and the effect of protecting hepatocytes will be weakened. Then the effects of SGs on ERS and apoptosis in hepatocyte hypoxia model was observed. Compared with the Hypoxia group, the apoptosis rate and ERS level decreased in SGs hepatocyte Ars treated group. However, Ars could elevate the level of SGs. In the next, it was verified the effect of SGs on apoptosis level of hepatocyte hypoxia model through ERS. It was verified the intervention effect of siRNA-ATF4. Compared with the normal group, the level of ATF4 mRNA in the siRNA-ATF4 group was decreased significantly. Compared with the Hypoxia group, the apoptosis rate, HIF-1α and lactate dehydrogenase (LDH) contents in cells, the level of ERS was decreased in the siRNA-ATF4 treatment group. Moreover, on the basis of siRNA-ATF4 intervention group, it was found that the apoptosis rate, HIF-1α and LDH contents in cells, the level of ERS was decreased. In the in vivo experiment, it was first detected whether the ALF mouse model was successfully established. HE staining showed that the liver tissue structure of mice in the normal group was regular, and the liver cells were neatly arranged in the hepatic lobules. No necrosis of liver cells and inflammatory cell infiltration. The liver lobule structure of the ALF model group was destroyed by LPS combined with D-Gal, accompanied by a large number of necrotic liver cells and infiltrating inflammatory cells. Compared with normal group, alanine aminotransferase (ALT), aspartate aminotransferase (AST) and total bilirubin (TBIL) levels in serum of model group were increased. The above studies indicate that the mouse model of ALF has been successfully constructed in this study, which is consistent with previous reports. After Ars intervention, the degree of infiltration of necrotic liver cells and inflammatory cells in mouse liver tissue was reduced, and the levels of ALT, AST and TBIL in serum were decreased.

Research conclusions

Hepatocytes were damaged by hypoxia and ischemia injury in the process of ALF. At this time, the content of HIF-1α in cells increased, which inhibited the formation of SGs mediated by G3BP1 and promoted the expression of ERS marker molecules ATF4 and CHOP. The activated ERS pathway further promotes hepatocyte apoptosis. Promoting SGs synthesis can inhibit the level of hepatocyte apoptosis by inhibiting the ATF4-mediated ERS pathway.

Research perspectives

SGs could protect hepatocytes from hypoxia-induced damage during ALF by reducing ERS-mediated apoptosis.