Endotoxin tolerance alleviates experimental acute liver failure via inhibition of high mobility group box 1

Abstract

High mobility group box 1 (HMGB1) has been widely reported to mediate damage caused by inflammatory responses. The aim of our study is to investigate the role of HMGB1 in endotoxin tolerance (ET) alleviating inflammation of acute liver failure (ALF) rats and its possible signaling mechanism. To mimic ET, male Sprague-Dawley rats were pretreated with low dose of lipopolysaccharide (LPS) (0.1 mg/kg once a day intraperitoneally for consecutive five days) before subsequent ALF induction. ALF was induced by intraperitoneal administration of D-GalN/LPS. ET induced by LPS pretreatment significantly improved the survival rate of ALF rats. Moreover, after ALF induction, ET+ALF rats exhibited lower serum enzyme (ALT, AST and TBiL) levels, lower production of inflammatory cytokines (IL-6, TNF-a and HMGB1) and more minor liver histopathological damage than ALF rats. ET+ALF rats showed enhanced expression levels of HMGB1, decreased levels of STAT1 and p-STAT1, augmented expression of SOCS1 in liver tissues than ALF rats. These results indicated that ET induced by low-dose LPS pretreatment may alleviate inflammation and liver injury in experimental acute liver failure rats mainly through inhibition of hepatic HMGB1 translocation and release.

Keywords: Endotoxin tolerance; JAK/STAT1 signaling; acute liver failure; high mobility group box 1; lipopolysaccharide (LPS).

Figure 1

Significant difference in survival rates was found between ALF group and ET+ALF group by Kaplan-Meier survival analysis (P<0.01 by Log-rank Test).

Figure 2

Representative photographs of liver sections using H&E staining (original magnification: × 200). A. Liver sections from the control group; B. Liver sections from the ALF group; C. Liver sections from the ET+ALF group.

Figure 3

Effect of ET induced by LPS pretreatment on liver function and levels of serum cytokine in ALF rats. The serum levels of alanine aminotransferase (ALT) (A), aspartate aminotransferase (AST) (B) and total bilirubin (TBiL) (C) were assayed using an automated blood chemistry analyzer. The serum concentrations of TNF-a, IL-6 and HMGB1 in ALF group (D) and ET+ALF group (E) were detected by ELISA assay and compared with that in control group (F).

Figure 4

Effect of ET induced by low-dose LPS pretreatment on the changes of SOCS1 (B), STAT1 (C), p-STAT1 (D) and HMGB1 (E) protein expression in liver of ALF rats. (A) displays typical pictures of protein abundance in the liver. (B-E) shows the quantitative levels of SOCS1, STAT1, p-STAT1, and HMGB1 protein in the liver measured by Western blot respectively. Lane 1 represents rat liver of the control group; Lane 2-6 represent rat liver of ALF group at 2 h, 6 h, 12 h, 24 h, 48 h after ALF induction; Lane 7-11 represent rat liver of ET+ALF group at 2 h, 6 h, 12 h, 24 h, 48 h after ALF induction. Levels of SOCS1 (B), STAT1 (C), p-STAT1 (D) and P65 (E) were standardized to GAPDH content. All data were expressed as mean ± SD of six rats at every point of time. *Represents P<0.05 versus control group; #indicates P<0.05 versus ALF group.