High-mobility group box 1 inhibition protects against hepatic ischemia-reperfusion injury

Abstract

Introduction. Hepatic ischemia followed by reperfusion (I/R) occurs in the settings of trauma, transplantation, and elective liver resections. The mechanisms that account for local organ damage are only partially understood. High-mobility group box 1 (HMGB1) has been identified as a late mediator of lethality in sepsis and is released by damaged tissues where it could also act as a mediator of inflammation and organ injury. We hypothesized that HMGB1 would contribute to organ injury following hepatic I/R. Methods. HMGB1 protein expression and hepatocellular secretion were determined in rat hepatocytes subjected to hypoxia (1% O 2) versus normoxic cells. The role of HMGB1 in mediating hepatic I/R injury was examined in C57Bl/6 mice that underwent 90 min of partial I/R injury. These mice were pretreated with neutralizing HMGB1 antibody (600 μg) or control normal saline 1 h prior to ischemia. Results. Basal HMGB1 expression was observed in normoxic hepatocytes and was dramatically up regulated 12–24 h after hypoxia. This corresponded to increased HMGB1 secretion 18–24 h after hypoxia. In mice undergoing partial warm liver I/R injury, HMGB1 protein expression is increased as early as 1 h after reperfusion and then increases in a time-dependent manner up to 24 h. Inhibition of HMGB1 activity with neutralizing antibody significantly decreased liver damage after warm ischemia compared to control animals. TABLE—ABSTRACT 81 Group ALT-1 h ALT-6 h ALT-24h Sham 67 ± 24 57 ± 8 51 ± 2 Control 3101 ± 1167 8140 ± 1656 905 ± 65 Anti-HMGB1 662 ± 120 ∗ 2382 ± 687 ∗ 265 ± 16 ∗ Note. Data are mean ± SEM, n = 3–4 per group; ∗ indicates P < 0.05 versus control. Conclusion. This study demonstrates that HMGB1 is up regulated in hepatocytes by simple hypoxia. The same was seen to occur in vivo in liver I/R as early as 1 h. The reduction in liver damage by a neutralizing antibody shows that HMGB1 is a key mediator in the pathways that lead to organ damage in warm liver I/R. Thus, unlike sepsis where HMGB1 is late mediator, this danger protein appears to be an early mediator in I/R.