High mobility group box chromosomal protein 1 in acute-on-chronic liver failure patients and mice with ConA-induced acute liver injury

High mobility group box chromosomal protein 1 (HMGB1) is an important proinflammatory molecule in many inflammatory disorders, but little is known about its role in acute-on-chronic liver failure (ACLF). Here, we investigated the relationship between the expression of HMGB1 and the disease onset and severity of ACLF patients and mice with acute liver injury/failure induced by concanavalin A (ConA). Peripheral blood mononuclear cells (PBMCs) and serum from ACLF patients were collected, and a mouse model of acute liver injury/failure was induced by ConA. HMGB1 mRNA expression in patient PBMCs or in murine livers and serum HMGB1 protein in ACLF patients and mice were assayed by RT-PCR and Western blotting, respectively. HMGB1 translocation in hepatocytes of ConA-treated mice was assessed by immunohistochemical staining. Up-regulated HMGB1 mRNA levels in PBMCs and accumulated protein in serum were both correlated with disease severity in ACLF patients. In the animal model, HMGB1 levels increased at 4 h and reached its peak value at 8–12 h after challenge with ConA, which suggests that HMGB1 is a relatively late proinflammatory cytokine compared with TNF-α. Translocation of HMGB1 from the nucleus to the cytoplasm in hepatocytes was correlated with the severity of liver injury in mice. While specific anti-HMGB1 antibodies and nicotine protected mice from acute liver injury/failure by reducing mortality and improving liver tissue injury, treatment with recombinant HMGB1 led to an increased mortality due to ConA challenge. Thus, the data from the present study suggest that HMGB1 plays a critical role in the systemic inflammation of ACLF and could be a potential therapeutic target in the treatment of ACLF.