SIRT7 protecting hepatocytes from LPS or D-GalN/LPS-induced apoptosis by attenuating endoplasmic reticulum stress via inactivation of GRP78 / 上海交通大学学报（医学版）

ABSTRACT

Objective:To investigate the effects of SIRT7 on acute liver injury induced by lipopolysaccharide (LPS) or D-galactosamine (D-GalN)/LPS and its mechanisms. Methods:Thirteen-week-old C57BL/6J mice were randomly divided into normal saline group (n=5), LPS group (n=7), and D-GalN/LPS group (n=8), which were respectively intraperitoneally injected with normal saline, LPS or D-GalN/LPS. The serum and livers of normal saline group and LPS group mice were collected 24 hours after the injection, and the samples of D-GalN/LPS group were collected 8 hours after the injection. Liver pathological changes were compared by using H-E staining, and serological indicators of the mice from three groups were also compared. Liver apoptosis and inflammatory cells infiltration were determined by TUNEL staining and F4/80 staining. Meanwhile, the mRNA levels of SIRT7 and inflammatory factors, including interleukin-1β (IL-1β), IL-6, and tumor necrosis factor α (TNF-α) in livers were detected by realtime-PCR. Western blotting was used to detect the protein levels of SIRT7, cleaved-caspase3 and the 78 kDa glucose regulated protein (GRP78) in mouse liver tissues. AML-12 cell line overexpressing SIRT7 was stimulated with LPS, and Western blotting was used to study the roles of SIRT7 in the endoplasmic reticulum (ER) stress induced by LPS in vitro. Results:LPS or D-GalN/LPS induced inflammatory cells infiltration, hyperemia and hepatocytes apoptosis in livers. Meanwhile, serum glutamic-pyruvic transaminase (GPT) and glutamic-oxalacetic transaminase (GOT) in the mice treated by LPS or D-GalN/LPS were significantly increased. Moreover, both liver SIRT7 mRNA and protein levels were down-regulated, while GRP78 protein in ER stress pathway was up-regulated. In AML-12 cells, SIRT7 overexpression inhibited LPS-induced up-regulation of GRP78. Conclusion:SIRT7 protects against LPS or D-GalN/LPS-induced hepatocytes apoptosis by attenuating ER stress via inactivating GRP78.