BACKGROUND: Liver failure in chronic hepatitis B (CHB) patients is a severe, life-threatening condition. Intestinal endotoxemia plays a significant role in the progress to liver failure. High mobility group box-1 (HMGB1) protein is involved in the process of endotoxemia. Regulatory T (Treg) cells maintain immune tolerance and contribute to the immunological hyporesponsiveness against HBV infection. However, the roles of HMGB1 and Treg cells in the pathogenesis of liver failure in CHB patients, and whether HMGB1 affects the immune activity of Treg cells are poorly known at present, and so were explored in this study.
METHODS: The levels of HMGB1 expression were detected by ELISA, real-time RT-PCR, and Western blotting, and the percentage of CD4⁺CD25⁺CD127^low Treg cells among CD4⁺ cells was detected by flow cytometry in liver failure patients with chronic HBV infection, CHB patients, and healthy controls. Then, CD4⁺CD25⁺CD127^low Treg cells isolated from the peripheral blood mononuclear cells from CHB patients were stimulated with HMGB1 at different concentrations or at various intervals. The effect of HMGB1 on the immune activity of Treg cells was assessed by a suppression assay of the allogeneic mixed lymphocyte response. The levels of forkhead box P3 (Foxp3) expression in Treg cells treated with HMGB1 were detected by RT-PCR and Western blotting.
RESULTS: A higher level of HMGB1 expression and a lower percentage of Treg cells within the population of CD4⁺ cells were found in liver failure patients than in CHB patients (82.6±20.1 µg/L vs. 34.2±13.7 µg/L; 4.55±1.34% vs. 9.52±3.89%, respectively). The immune activity of Treg cells was significantly weakened and the levels of Foxp3 expression were reduced in a dose- or time-dependent manner when Treg cells were stimulated with HMGB1 in vitro.
CONCLUSIONS: The high level of HMGB1 and the low percentage of Treg cells play an important role in the pathogenesis of liver failure in patients with chronic HBV infection. Moreover, HMGB1 can weaken the immune activity of Treg cells. It is suggested that effectively inhibiting HMGB1 expression could be a feasible way to treat liver failure by suppressing endotoxemia and enhancing Treg cell activity.